CT Fluoroscopy Shielding: Decreases in Scattered Radiation for the Patient and Operator

PubMed Central

Neeman, Ziv; Dromi, Sergio A.; Sarin, Shawn; Wood, Bradford J.

2008-01-01

PURPOSE High-radiation exposure occurs during computed tomographic (CT) fluoroscopy. Patient and operator doses during thoracic and abdominal interventional procedures were studied in the present experiment, and a novel shielding device to reduce exposure to the patient and operator was evaluated. MATERIALS AND METHODS With a 16-slice CT scanner in CT fluoroscopy mode (120 kVp, 30 mA), surface dosimetry was performed on adult and pediatric phantoms. The shielding was composed of tungsten antimony in the form of a lightweight polymer sheet. Doses to the patient were measured with and without shielding for thoracic and abdominal procedures. Doses to the operator were recorded with and without phantom, gantry, and table shielding in place. Double-layer lead-free gloves were used by the operator during the procedures. RESULTS Tungsten antimony shielding adjacent to the scan plane resulted in a maximum dose reduction of 92.3% to the patient. Maximum 85.6%, 93.3%, and 85.1% dose reductions were observed for the operator’s torso, gonads, and hands, respectively. The use of double-layer lead-free gloves resulted in a maximum radiation dose reduction of 97%. CONCLUSIONS Methods to reduce exposure during CT fluoroscopy are effective and should be searched for. Significant reduction in radiation doses to the patient and operator can be accomplished with tungsten antimony shielding. PMID:17185699

Low Dose MDCT with Tube Current Modulation: Role in Detection of Urolithiasis and Patient Effective Dose Reduction

PubMed Central

Kakkar, Chandan; Sripathi, Smiti; Parakh, Anushri; Shrivastav, Rajendra

2016-01-01

Introduction Urolithiasis is one of the major, recurring problem in young individuals and CT being the commonest diagnostic modality used. In order to reduce the radiation dose to the patient who are young and as stone formation is a recurring process; one of the simplest way would be, low dose CT along with tube current modulation. Aim Aim of this study was to compare the sensitivity and specificity of low dose (70mAs) with standard dose (250mAs) protocol in detecting urolithiasis and to define the tube current and mean effective patient dose by these protocols. Materials and Methods A prospective study was conducted in 200 patients over a period of 2 years with acute flank pain presentation. CT was performed in 100 cases with standard dose and another 100 with low dose protocol using tube current modulation. Sensitivity and specificity for calculus detection, percentage reduction of dose and tube current with low dose protocol was calculated. Results Urolithiasis was detected in 138 patients, 67 were examined by high dose and 71 were by low dose protocol. Sensitivity and Specificity of low dose protocol was 97.1% and 96.4% with similar results found in high BMI patients. Tube current modulation resulted in reduction of effective tube current by 12.17%. The mean effective patient dose for standard dose was 10.33 mSv whereas 2.92 mSv for low dose with 51.13–53.8% reduction in low dose protocol. Conclusion The study has reinforced that low-dose CT with tube current modulation is appropriate for diagnosis of urolithiasis with significant reduction in tube current and patient effective dose. PMID:27437322

Urethra sparing - potential of combined Nickel-Titanium stent and intensity modulated radiation therapy in prostate cancer.

PubMed

Thomsen, Jakob Borup; Arp, Dennis Tideman; Carl, Jesper

2012-05-01

To investigate a novel method for sparing urethra in external beam radiotherapy of prostate cancer and to evaluate the efficacy of such a treatment in terms of tumour control using a mathematical model. This theoretical study includes 20 patients previously treated for prostate cancer using external beam radiotherapy. All patients had a Nickel-Titanium (Ni-Ti) stent inserted into the prostate part of urethra. The stent has been used during the treatment course as an internal marker for patient positioning prior to treatment. In this study the stent is used for delineating urethra while intensity modulated radiotherapy was used for lowering dose to urethra. Evaluation of the dose plans were performed using a tumour control probability model based on the concept of uniform equivalent dose. The feasibility of the urethra dose reduction method is validated and a reduction of about 17% is shown to be possible. Calculations suggest a nearly preserved tumour control probability. A new concept for urethra dose reduction is presented. The method relies on the use of a Ni-Ti stent as a fiducial marker combined with intensity modulated radiotherapy. Theoretical calculations suggest preserved tumour control. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

ANI/MAELU engineering inspection criteria 8.3 ALARA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, L.

1995-03-01

The purpose of this criteria section is to provide guidelines for programs whose intent is to achieve occupational doses and doses to members of the public that are as low as is reasonably achievable (ALARA). The success that has been achieved by applying ALARA concepts at nuclear power plants is clearly illustrated by the major reductions in the annual cumulative dose to workers at many sites over the last few years. This success is the combined result of the general maturity of the nuclear industry, the intensive study of dose reduction practices by industry groups, and the successful sharing ofmore » experience and practices among plants. Source term reduction should be used as a primary ALARA mechanism. Methods which should be considered include: satellite and cobalt reduction, chemistry control, decontamination, submicron filters, zinc addition, hot spot reduction and permanent or temporary shielding.« less

A study on the indirect urea dosing method in the Selective Catalytic Reduction system

NASA Astrophysics Data System (ADS)

Brzeżański, M.; Sala, R.

2016-09-01

This article presents the results of studies on concept solution of dosing urea in a gas phase in a selective catalytic reduction system. The idea of the concept was to heat-up and evaporate the water urea solution before introducing it into the exhaust gas stream. The aim was to enhance the processes of urea converting into ammonia, what is the target reductant for nitrogen oxides treatment. The study was conducted on a medium-duty Euro 5 diesel engine with exhaust line consisting of DOC catalyst, DPF filter and an SCR system with a changeable setup allowing to dose the urea in liquid phase (regular solution) and to dose it in a gas phase (concept solution). The main criteria was to assess the effect of physical state of urea dosed on the NOx conversion ratio in the SCR catalyst. In order to compare both urea dosing methods a special test procedure was developed which consisted of six test steps covering a wide temperature range of exhaust gas generated at steady state engine operation condition. Tests were conducted for different urea dosing quantities defined by the a equivalence ratio. Based on the obtained results, a remarkable improvement in NOx reduction was found for gas urea application in comparison to the standard liquid urea dosing. Measured results indicate a high potential to increase an efficiency of the SCR catalyst by using a gas phase urea and provide the basis for further scientific research on this type of concept.

Effect of leaded glasses and thyroid shielding on cone beam CT radiation dose in an adult female phantom

PubMed Central

Goren, AD; Prins, RD; Dauer, LT; Quinn, B; Al-Najjar, A; Faber, RD; Patchell, G; Branets, I; Colosi, DC

2013-01-01

Objectives: This study aims to demonstrate the effectiveness of leaded glasses in reducing the lens of eye dose and of lead thyroid collars in reducing the dose to the thyroid gland of an adult female from dental cone beam CT (CBCT). The effect of collimation on the radiation dose in head organs is also examined. Methods: Dose measurements were conducted by placing optically stimulated luminescent dosemeters in an anthropomorphic female phantom. Eye lens dose was measured by placing a dosemeter on the anterior surface of the phantom eye location. All exposures were performed on one commercially available dental CBCT machine, using selected collimation and exposure techniques. Each scan technique was performed without any lead shielding and then repeated with lead shielding in place. To calculate the percent reduction from lead shielding, the dose measured with lead shielding was divided by the dose measured without lead shielding. The percent reduction from collimation was calculated by comparing the dose measured with collimation to the dose measured without collimation. Results: The dose to the internal eye for one of the scans without leaded glasses or thyroid shield was 0.450 cGy and with glasses and thyroid shield was 0.116 cGy (a 74% reduction). The reduction to the lens of the eye was from 0.396 cGy to 0.153 cGy (a 61% reduction). Without glasses or thyroid shield, the thyroid dose was 0.158 cGy; and when both glasses and shield were used, the thyroid dose was reduced to 0.091 cGy (a 42% reduction). Conclusions: Collimation alone reduced the dose to the brain by up to 91%, with a similar reduction in other organs. Based on these data, leaded glasses, thyroid collars and collimation minimize the dose to organs outside the field of view. PMID:23412460

Ultralow dose computed tomography attenuation correction for pediatric PET CT using adaptive statistical iterative reconstruction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brady, Samuel L., E-mail: samuel.brady@stjude.org; Shulkin, Barry L.

2015-02-15

Purpose: To develop ultralow dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT). Methods: A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultralow doses (10–35 mA s). CT quantitation: noise, low-contrast resolution, and CT numbers for 11 tissue substitutes were analyzed in-phantom. CT quantitation was analyzed to a reduction of 90% volume computed tomography dose index (0.39/3.64; mGy) from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET imagesmore » were reconstructed with the lower-dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUV{sub bw}) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation dose and CTAC noise magnitude were compared for 140 patient examinations (76 post-ASiR implementation) to determine relative dose reduction and noise control. Results: CT numbers were constant to within 10% from the nondose reduced CTAC image for 90% dose reduction. No change in SUV{sub bw}, background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols was found down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62% and 86% (3.2/8.3–0.9/6.2). Noise magnitude in dose-reduced patient images increased but was not statistically different from predose-reduced patient images. Conclusions: Using ASiR allowed for aggressive reduction in CT dose with no change in PET reconstructed images while maintaining sufficient image quality for colocalization of hybrid CT anatomy and PET radioisotope uptake.« less

Magnetic resonance angiography: current status and future directions

PubMed Central

2011-01-01

With recent improvement in hardware and software techniques, magnetic resonance angiography (MRA) has undergone significant changes in technique and approach. The advent of 3.0 T magnets has allowed reduction in exogenous contrast dose without compromising overall image quality. The use of novel intravascular contrast agents substantially increases the image windows and decreases contrast dose. Additionally, the lower risk and cost in non-contrast enhanced (NCE) MRA has sparked renewed interest in these methods. This article discusses the current state of both contrast-enhanced (CE) and NCE-MRA. New CE-MRA methods take advantage of dose reduction at 3.0 T, novel contrast agents, and parallel imaging methods. The risks of gadolinium-based contrast media, and the NCE-MRA methods of time-of-flight, steady-state free precession, and phase contrast are discussed. PMID:21388544

SU-C-207-05: A Comparative Study of Noise-Reduction Algorithms for Low-Dose Cone-Beam Computed Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, S; Yao, W

2015-06-15

Purpose: To study different noise-reduction algorithms and to improve the image quality of low dose cone beam CT for patient positioning in radiation therapy. Methods: In low-dose cone-beam CT, the reconstructed image is contaminated with excessive quantum noise. In this study, three well-developed noise reduction algorithms namely, a) penalized weighted least square (PWLS) method, b) split-Bregman total variation (TV) method, and c) compressed sensing (CS) method were studied and applied to the images of a computer–simulated “Shepp-Logan” phantom and a physical CATPHAN phantom. Up to 20% additive Gaussian noise was added to the Shepp-Logan phantom. The CATPHAN phantom was scannedmore » by a Varian OBI system with 100 kVp, 4 ms and 20 mA. For comparing the performance of these algorithms, peak signal-to-noise ratio (PSNR) of the denoised images was computed. Results: The algorithms were shown to have the potential in reducing the noise level for low-dose CBCT images. For Shepp-Logan phantom, an improvement of PSNR of 2 dB, 3.1 dB and 4 dB was observed using PWLS, TV and CS respectively, while for CATPHAN, the improvement was 1.2 dB, 1.8 dB and 2.1 dB, respectively. Conclusion: Penalized weighted least square, total variation and compressed sensing methods were studied and compared for reducing the noise on a simulated phantom and a physical phantom scanned by low-dose CBCT. The techniques have shown promising results for noise reduction in terms of PSNR improvement. However, reducing the noise without compromising the smoothness and resolution of the image needs more extensive research.« less

Pediatric cT: Implementation of ASIR for Substantial Radiation Dose Reduction While Maintaining Pre-ASIR Image Noise1

PubMed Central

Brady, Samuel L.; Moore, Bria M.; Yee, Brian S.; Kaufman, Robert A.

2015-01-01

Purpose To determine a comprehensive method for the implementation of adaptive statistical iterative reconstruction (ASIR) for maximal radiation dose reduction in pediatric computed tomography (CT) without changing the magnitude of noise in the reconstructed image or the contrast-to-noise ratio (CNR) in the patient. Materials and Methods The institutional review board waived the need to obtain informed consent for this HIPAA-compliant quality analysis. Chest and abdominopelvic CT images obtained before ASIR implementation (183 patient examinations; mean patient age, 8.8 years ± 6.2 [standard deviation]; range, 1 month to 27 years) were analyzed for image noise and CNR. These measurements were used in conjunction with noise models derived from anthropomorphic phantoms to establish new beam current–modulated CT parameters to implement 40% ASIR at 120 and 100 kVp without changing noise texture or magnitude. Image noise was assessed in images obtained after ASIR implementation (492 patient examinations; mean patient age, 7.6 years ± 5.4; range, 2 months to 28 years) the same way it was assessed in the pre-ASIR analysis. Dose reduction was determined by comparing size-specific dose estimates in the pre- and post-ASIR patient cohorts. Data were analyzed with paired t tests. Results With 40% ASIR implementation, the average relative dose reduction for chest CT was 39% (2.7/4.4 mGy), with a maximum reduction of 72% (5.3/18.8 mGy). The average relative dose reduction for abdominopelvic CT was 29% (4.8/6.8 mGy), with a maximum reduction of 64% (7.6/20.9 mGy). Beam current modulation was unnecessary for patients weighing 40 kg or less. The difference between 0% and 40% ASIR noise magnitude was less than 1 HU, with statistically nonsignificant increases in patient CNR at 100 kVp of 8% (15.3/14.2; P = .41) for chest CT and 13% (7.8/6.8; P = .40) for abdominopelvic CT. Conclusion Radiation dose reduction at pediatric CT was achieved when 40% ASIR was implemented as a dose reduction tool only; no net change to the magnitude of noise in the reconstructed image or the patient CNR occurred. PMID:23901128

Efficacy of a Radiation Absorbing Shield in Reducing Dose to the Interventionalist During Peripheral Endovascular Procedures: A Single Centre Pilot Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Power, S.; Mirza, M.; Thakorlal, A.

PurposeThis prospective pilot study was undertaken to evaluate the feasibility and effectiveness of using a radiation absorbing shield to reduce operator dose from scatter during lower limb endovascular procedures.Materials and MethodsA commercially available bismuth shield system (RADPAD) was used. Sixty consecutive patients undergoing lower limb angioplasty were included. Thirty procedures were performed without the RADPAD (control group) and thirty with the RADPAD (study group). Two separate methods were used to measure dose to a single operator. Thermoluminescent dosimeter (TLD) badges were used to measure hand, eye, and unshielded body dose. A direct dosimeter with digital readout was also used tomore » measure eye and unshielded body dose. To allow for variation between control and study groups, dose per unit time was calculated.ResultsTLD results demonstrated a significant reduction in median body dose per unit time for the study group compared with controls (p = 0.001), corresponding to a mean dose reduction rate of 65 %. Median eye and hand dose per unit time were also reduced in the study group compared with control group, however, this was not statistically significant (p = 0.081 for eye, p = 0.628 for hand). Direct dosimeter readings also showed statistically significant reduction in median unshielded body dose rate for the study group compared with controls (p = 0.037). Eye dose rate was reduced for the study group but this was not statistically significant (p = 0.142).ConclusionInitial results are encouraging. Use of the shield resulted in a statistically significant reduction in unshielded dose to the operator’s body. Measured dose to the eye and hand of operator were also reduced but did not reach statistical significance in this pilot study.« less

Correlates of individual differences in compensatory nicotine self-administration in rats following a decrease in nicotine unit dose

PubMed Central

Harris, Andrew C.; Pentel, Paul R.; LeSage, Mark G.

2013-01-01

Rationale The ability of tobacco harm reduction strategies to produce significant reductions in toxin exposure is limited by compensatory increases in smoking behavior. Characterizing factors contributing to the marked individual variability in compensation may be useful for understanding this phenomenon and assessing the feasibility of harm reduction interventions. Objective To use an animal model of human compensatory smoking that involves a decrease in unit dose supporting nicotine self-administration (NSA) to examine potential contributors to individual differences in compensation. Methods Rats were trained for NSA during daily 23 hr sessions at a unit dose of 0.06 mg/kg/inf until responding was stable. The unit dose was then reduced to 0.03 mg/kg/inf for at least 10 sessions. Following reacquisition of NSA at the training dose and extinction, single-dose nicotine pharmacokinetic parameters were determined. Results Decreases in nicotine intake following dose reduction were proportionally less than the decrease in unit dose, indicating partial compensation. Compensatory increases in infusion rates were observed across the course of the 23 hr sessions. The magnitude of compensation differed considerably between rats. Rats exhibiting the highest baseline infusion rates exhibited the lowest levels of compensation. Nicotine pharmacokinetic parameters were not significantly correlated with compensation. Infusion rates immediately returned to pre-reduction levels when baseline conditions were restored. Conclusions These findings provide initial insights into correlates of individual differences in compensation following a reduction in nicotine unit dose. The present assay may be useful for characterizing mechanisms and potential consequences of the marked individual differences in compensatory smoking observed in humans. PMID:19475400

SU-F-J-39: Dose Reduction Strategy Using Attenuation-Based Tube Current Modulation Method in CBCT for IGRT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, K; Lee, H; Kim, C

2016-06-15

Purpose: To reduce radiation dose to the patients, tube current modulation (TCM) method has been actively used in diagnostic CT systems. However, TCM method has not yet been applied to a kV-CBCT system on a LINAC machine. The purpose of this study is to investigate whether the use of TCM method is desirable in kV-CBCT system for IGRT. We have developed an attenuation-based tube current modulation (a-TCM) method using the prior knowledge of treatment CT image of a patient. Methods: Patients go through a diagnostic CT scan for RT planning; therefore, using this prior information of CT images, one canmore » estimate the total attenuation of an x-ray through the patient body in a CBCT setting for radiation therapy. We performed a numerical study incorporating major factors into account such as polychromatic x-ray, scatter, noise, and bow-tie filter to demonstrate that a-TCM method can produce equivalent quality of images at reduced imaging radiation doses. Using the CT projector program, 680 projection images of the pediatric XCAT phantom were obtained both in conventional scanning condition, i.e., without modulating the tube current, and in the proposed a-TCM scanning condition. FDK reconstruction algorithm was used for image reconstruction, and the organ dose due to imaging radiation has been calculated in both cases and compared using GATE/Geant4 simulation toolkit. Results: Reconstructed CT images in the a-TCM method showed similar SSIM values and noise properties to the reference images acquired by the conventional CBCT. In addition, reduction of organ doses ranged from 12% to 27%. Conclusion: We have successfully demonstrated the feasibility and dosimetric merit of the a-TCM method for kV-CBCT, and envision that it can be a useful option of CBCT scanning that provides patient dose reduction without degrading image quality.« less

Dosimetric Evaluation of Metal Artefact Reduction using Metal Artefact Reduction (MAR) Algorithm and Dual-energy Computed Tomography (CT) Method

NASA Astrophysics Data System (ADS)

Laguda, Edcer Jerecho

Purpose: Computed Tomography (CT) is one of the standard diagnostic imaging modalities for the evaluation of a patient's medical condition. In comparison to other imaging modalities such as Magnetic Resonance Imaging (MRI), CT is a fast acquisition imaging device with higher spatial resolution and higher contrast-to-noise ratio (CNR) for bony structures. CT images are presented through a gray scale of independent values in Hounsfield units (HU). High HU-valued materials represent higher density. High density materials, such as metal, tend to erroneously increase the HU values around it due to reconstruction software limitations. This problem of increased HU values due to metal presence is referred to as metal artefacts. Hip prostheses, dental fillings, aneurysm clips, and spinal clips are a few examples of metal objects that are of clinical relevance. These implants create artefacts such as beam hardening and photon starvation that distort CT images and degrade image quality. This is of great significance because the distortions may cause improper evaluation of images and inaccurate dose calculation in the treatment planning system. Different algorithms are being developed to reduce these artefacts for better image quality for both diagnostic and therapeutic purposes. However, very limited information is available about the effect of artefact correction on dose calculation accuracy. This research study evaluates the dosimetric effect of metal artefact reduction algorithms on severe artefacts on CT images. This study uses Gemstone Spectral Imaging (GSI)-based MAR algorithm, projection-based Metal Artefact Reduction (MAR) algorithm, and the Dual-Energy method. Materials and Methods: The Gemstone Spectral Imaging (GSI)-based and SMART Metal Artefact Reduction (MAR) algorithms are metal artefact reduction protocols embedded in two different CT scanner models by General Electric (GE), and the Dual-Energy Imaging Method was developed at Duke University. All three approaches were applied in this research for dosimetric evaluation on CT images with severe metal artefacts. The first part of the research used a water phantom with four iodine syringes. Two sets of plans, multi-arc plans and single-arc plans, using the Volumetric Modulated Arc therapy (VMAT) technique were designed to avoid or minimize influences from high-density objects. The second part of the research used projection-based MAR Algorithm and the Dual-Energy Method. Calculated Doses (Mean, Minimum, and Maximum Doses) to the planning treatment volume (PTV) were compared and homogeneity index (HI) calculated. Results: (1) Without the GSI-based MAR application, a percent error between mean dose and the absolute dose ranging from 3.4-5.7% per fraction was observed. In contrast, the error was decreased to a range of 0.09-2.3% per fraction with the GSI-based MAR algorithm. There was a percent difference ranging from 1.7-4.2% per fraction between with and without using the GSI-based MAR algorithm. (2) A range of 0.1-3.2% difference was observed for the maximum dose values, 1.5-10.4% for minimum dose difference, and 1.4-1.7% difference on the mean doses. Homogeneity indexes (HI) ranging from 0.068-0.065 for dual-energy method and 0.063-0.141 with projection-based MAR algorithm were also calculated. Conclusion: (1) Percent error without using the GSI-based MAR algorithm may deviate as high as 5.7%. This error invalidates the goal of Radiation Therapy to provide a more precise treatment. Thus, GSI-based MAR algorithm was desirable due to its better dose calculation accuracy. (2) Based on direct numerical observation, there was no apparent deviation between the mean doses of different techniques but deviation was evident on the maximum and minimum doses. The HI for the dual-energy method almost achieved the desirable null values. In conclusion, the Dual-Energy method gave better dose calculation accuracy to the planning treatment volume (PTV) for images with metal artefacts than with or without GE MAR Algorithm.

Iterative methods for dose reduction and image enhancement in tomography

DOEpatents

Miao, Jianwei; Fahimian, Benjamin Pooya

2012-09-18

A system and method for creating a three dimensional cross sectional image of an object by the reconstruction of its projections that have been iteratively refined through modification in object space and Fourier space is disclosed. The invention provides systems and methods for use with any tomographic imaging system that reconstructs an object from its projections. In one embodiment, the invention presents a method to eliminate interpolations present in conventional tomography. The method has been experimentally shown to provide higher resolution and improved image quality parameters over existing approaches. A primary benefit of the method is radiation dose reduction since the invention can produce an image of a desired quality with a fewer number projections than seen with conventional methods.

Prospective ECG-Triggered Coronary CT Angiography: Clinical Value of Noise-Based Tube Current Reduction Method with Iterative Reconstruction

PubMed Central

Shen, Junlin; Du, Xiangying; Guo, Daode; Cao, Lizhen; Gao, Yan; Yang, Qi; Li, Pengyu; Liu, Jiabin; Li, Kuncheng

2013-01-01

Objectives To evaluate the clinical value of noise-based tube current reduction method with iterative reconstruction for obtaining consistent image quality with dose optimization in prospective electrocardiogram (ECG)-triggered coronary CT angiography (CCTA). Materials and Methods We performed a prospective randomized study evaluating 338 patients undergoing CCTA with prospective ECG-triggering. Patients were randomly assigned to fixed tube current with filtered back projection (Group 1, n = 113), noise-based tube current with filtered back projection (Group 2, n = 109) or with iterative reconstruction (Group 3, n = 116). Tube voltage was fixed at 120 kV. Qualitative image quality was rated on a 5-point scale (1 = impaired, to 5 = excellent, with 3–5 defined as diagnostic). Image noise and signal intensity were measured; signal-to-noise ratio was calculated; radiation dose parameters were recorded. Statistical analyses included one-way analysis of variance, chi-square test, Kruskal-Wallis test and multivariable linear regression. Results Image noise was maintained at the target value of 35HU with small interquartile range for Group 2 (35.00–35.03HU) and Group 3 (34.99–35.02HU), while from 28.73 to 37.87HU for Group 1. All images in the three groups were acceptable for diagnosis. A relative 20% and 51% reduction in effective dose for Group 2 (2.9 mSv) and Group 3 (1.8 mSv) were achieved compared with Group 1 (3.7 mSv). After adjustment for scan characteristics, iterative reconstruction was associated with 26% reduction in effective dose. Conclusion Noise-based tube current reduction method with iterative reconstruction maintains image noise precisely at the desired level and achieves consistent image quality. Meanwhile, effective dose can be reduced by more than 50%. PMID:23741444

Potential benefit of the CT adaptive statistical iterative reconstruction method for pediatric cardiac diagnosis

NASA Astrophysics Data System (ADS)

Miéville, Frédéric A.; Ayestaran, Paul; Argaud, Christophe; Rizzo, Elena; Ou, Phalla; Brunelle, Francis; Gudinchet, François; Bochud, François; Verdun, Francis R.

2010-04-01

Adaptive Statistical Iterative Reconstruction (ASIR) is a new imaging reconstruction technique recently introduced by General Electric (GE). This technique, when combined with a conventional filtered back-projection (FBP) approach, is able to improve the image noise reduction. To quantify the benefits provided on the image quality and the dose reduction by the ASIR method with respect to the pure FBP one, the standard deviation (SD), the modulation transfer function (MTF), the noise power spectrum (NPS), the image uniformity and the noise homogeneity were examined. Measurements were performed on a control quality phantom when varying the CT dose index (CTDIvol) and the reconstruction kernels. A 64-MDCT was employed and raw data were reconstructed with different percentages of ASIR on a CT console dedicated for ASIR reconstruction. Three radiologists also assessed a cardiac pediatric exam reconstructed with different ASIR percentages using the visual grading analysis (VGA) method. For the standard, soft and bone reconstruction kernels, the SD is reduced when the ASIR percentage increases up to 100% with a higher benefit for low CTDIvol. MTF medium frequencies were slightly enhanced and modifications of the NPS shape curve were observed. However for the pediatric cardiac CT exam, VGA scores indicate an upper limit of the ASIR benefit. 40% of ASIR was observed as the best trade-off between noise reduction and clinical realism of organ images. Using phantom results, 40% of ASIR corresponded to an estimated dose reduction of 30% under pediatric cardiac protocol conditions. In spite of this discrepancy between phantom and clinical results, the ASIR method is as an important option when considering the reduction of radiation dose, especially for pediatric patients.

Ultralow Dose MSCT Imaging in Dental Implantology

PubMed Central

Widmann, Gerlig; Al-Ekrish, Asma'a A.

2018-01-01

Introduction: The Council Directive 2013/59 Euratom has a clear commitment for keeping medical radiation exposure as low as reasonably achievable and demands a regular review and use of diagnostic reference levels. Methods: In dental implantology, the range of effective doses for cone beam computed tomography (CBCT) shows a broad overlap with multislice computed tomography (MSCT). More recently, ultralow dose imaging with new generations of MSCT scanners may impart radiation doses equal to or lower than CBCT. Dose reductions in MSCT have been further facilitated by the introduction of iterative image reconstruction technology (IRT), which provides substantial noise reduction over the current standard of filtered backward projection (FBP). Aim: The aim of this article is to review the available literature on ultralow dose CT imaging and IRTs in dental implantology imaging and to summarize their influence on spatial and contrast resolution, image noise, tissue density measurements, and validity of linear measurements of the jaws. Conclusion: Application of ultralow dose MSCT with IRT technology in dental implantology offers the potential for very large dose reductions compared with standard dose imaging. Yet, evaluation of various diagnostic tasks related to dental implantology is still needed to confirm the results obtained with various IRTs and ultra-low doses so far. PMID:29492174

A quantitative comparison of noise reduction across five commercial (hybrid and model-based) iterative reconstruction techniques: an anthropomorphic phantom study.

PubMed

Patino, Manuel; Fuentes, Jorge M; Hayano, Koichi; Kambadakone, Avinash R; Uyeda, Jennifer W; Sahani, Dushyant V

2015-02-01

OBJECTIVE. The objective of our study was to compare the performance of three hybrid iterative reconstruction techniques (IRTs) (ASiR, iDose4, SAFIRE) and their respective strengths for image noise reduction on low-dose CT examinations using filtered back projection (FBP) as the standard reference. Also, we compared the performance of these three hybrid IRTs with two model-based IRTs (Veo and IMR) for image noise reduction on low-dose examinations. MATERIALS AND METHODS. An anthropomorphic abdomen phantom was scanned at 100 and 120 kVp and different tube current-exposure time products (25-100 mAs) on three CT systems (for ASiR and Veo, Discovery CT750 HD; for iDose4 and IMR, Brilliance iCT; and for SAFIRE, Somatom Definition Flash). Images were reconstructed using FBP and using IRTs at various strengths. Nine noise measurements (mean ROI size, 423 mm(2)) on extracolonic fat for the different strengths of IRTs were recorded and compared with FBP using ANOVA. Radiation dose, which was measured as the volume CT dose index and dose-length product, was also compared. RESULTS. There were no significant differences in radiation dose and image noise among the scanners when FBP was used (p > 0.05). Gradual image noise reduction was observed with each increasing increment of hybrid IRT strength, with a maximum noise suppression of approximately 50% (48.2-53.9%). Similar noise reduction was achieved on the scanners by applying specific hybrid IRT strengths. Maximum noise reduction was higher on model-based IRTs (68.3-81.1%) than hybrid IRTs (48.2-53.9%) (p < 0.05). CONCLUSION. When constant scanning parameters are used, radiation dose and image noise on FBP are similar for CT scanners made by different manufacturers. Significant image noise reduction is achieved on low-dose CT examinations rendered with IRTs. The image noise on various scanners can be matched by applying specific hybrid IRT strengths. Model-based IRTs attain substantially higher noise reduction than hybrid IRTs irrespective of the radiation dose.

Achieving routine submillisievert CT scanning: report from the summit on management of radiation dose in CT.

PubMed

McCollough, Cynthia H; Chen, Guang Hong; Kalender, Willi; Leng, Shuai; Samei, Ehsan; Taguchi, Katsuyuki; Wang, Ge; Yu, Lifeng; Pettigrew, Roderic I

2012-08-01

This Special Report presents the consensus of the Summit on Management of Radiation Dose in Computed Tomography (CT) (held in February 2011), which brought together participants from academia, clinical practice, industry, and regulatory and funding agencies to identify the steps required to reduce the effective dose from routine CT examinations to less than 1 mSv. The most promising technologies and methods discussed at the summit include innovations and developments in x-ray sources; detectors; and image reconstruction, noise reduction, and postprocessing algorithms. Access to raw projection data and standard data sets for algorithm validation and optimization is a clear need, as is the need for new, clinically relevant metrics of image quality and diagnostic performance. Current commercially available techniques such as automatic exposure control, optimization of tube potential, beam-shaping filters, and dynamic z-axis collimators are important, and education to successfully implement these methods routinely is critically needed. Other methods that are just becoming widely available, such as iterative reconstruction, noise reduction, and postprocessing algorithms, will also have an important role. Together, these existing techniques can reduce dose by a factor of two to four. Technical advances that show considerable promise for additional dose reduction but are several years or more from commercial availability include compressed sensing, volume of interest and interior tomography techniques, and photon-counting detectors. This report offers a strategic roadmap for the CT user and research and manufacturer communities toward routinely achieving effective doses of less than 1 mSv, which is well below the average annual dose from naturally occurring sources of radiation.

Evaluation of an iterative model-based CT reconstruction algorithm by intra-patient comparison of standard and ultra-low-dose examinations.

PubMed

Noël, Peter B; Engels, Stephan; Köhler, Thomas; Muenzel, Daniela; Franz, Daniela; Rasper, Michael; Rummeny, Ernst J; Dobritz, Martin; Fingerle, Alexander A

2018-01-01

Background The explosive growth of computer tomography (CT) has led to a growing public health concern about patient and population radiation dose. A recently introduced technique for dose reduction, which can be combined with tube-current modulation, over-beam reduction, and organ-specific dose reduction, is iterative reconstruction (IR). Purpose To evaluate the quality, at different radiation dose levels, of three reconstruction algorithms for diagnostics of patients with proven liver metastases under tumor follow-up. Material and Methods A total of 40 thorax-abdomen-pelvis CT examinations acquired from 20 patients in a tumor follow-up were included. All patients were imaged using the standard-dose and a specific low-dose CT protocol. Reconstructed slices were generated by using three different reconstruction algorithms: a classical filtered back projection (FBP); a first-generation iterative noise-reduction algorithm (iDose4); and a next generation model-based IR algorithm (IMR). Results The overall detection of liver lesions tended to be higher with the IMR algorithm than with FBP or iDose4. The IMR dataset at standard dose yielded the highest overall detectability, while the low-dose FBP dataset showed the lowest detectability. For the low-dose protocols, a significantly improved detectability of the liver lesion can be reported compared to FBP or iDose 4 ( P = 0.01). The radiation dose decreased by an approximate factor of 5 between the standard-dose and the low-dose protocol. Conclusion The latest generation of IR algorithms significantly improved the diagnostic image quality and provided virtually noise-free images for ultra-low-dose CT imaging.

[Study of CT Automatic Exposure Control System (CT-AEC) Optimization in CT Angiography of Lower Extremity Artery by Considering Contrast-to-Noise Ratio].

PubMed

Inada, Satoshi; Masuda, Takanori; Maruyama, Naoya; Yamashita, Yukari; Sato, Tomoyasu; Imada, Naoyuki

2016-01-01

To evaluate the image quality and effect of radiation dose reduction by setting for computed tomography automatic exposure control system (CT-AEC) in computed tomographic angiography (CTA) of lower extremity artery. Two methods of setting were compared for CT-AEC [conventional and contrast-to-noise ratio (CNR) methods]. Conventional method was set noise index (NI): 14and tube current threshold: 10-750 mA. CNR method was set NI: 18, minimum tube current: (X+Y)/2 mA (X, Y: maximum X (Y)-axis tube current value of leg in NI: 14), and maximum tube current: 750 mA. The image quality was evaluated by CNR, and radiation dose reduction was evaluated by dose-length-product (DLP). In conventional method, mean CNRs for pelvis, femur, and leg were 19.9±4.8, 20.4±5.4, and 16.2±4.3, respectively. There was a significant difference between the CNRs of pelvis and leg (P<0.001), and between femur and leg (P<0.001). In CNR method, mean CNRs for pelvis, femur, and leg were 15.2±3.3, 15.3±3.2, and 15.3±3.1, respectively; no significant difference between pelvis, femur, and leg (P=0.973) in CNR method was observed. Mean DLPs were 1457±434 mGy⋅cm in conventional method, and 1049±434 mGy·cm in CNR method. There was a significant difference in the DLPs of conventional method and CNR method (P<0.001). CNR method gave equal CNRs for pelvis, femur, and leg, and was beneficial for radiation dose reduction in CTA of lower extremity artery.

Impact of view reduction in CT on radiation dose for patients

NASA Astrophysics Data System (ADS)

Parcero, E.; Flores, L.; Sánchez, M. G.; Vidal, V.; Verdú, G.

2017-08-01

Iterative methods have become a hot topic of research in computed tomography (CT) imaging because of their capacity to resolve the reconstruction problem from a limited number of projections. This allows the reduction of radiation exposure on patients during the data acquisition. The reconstruction time and the high radiation dose imposed on patients are the two major drawbacks in CT. To solve them effectively we adapted the method for sparse linear equations and sparse least squares (LSQR) with soft threshold filtering (STF) and the fast iterative shrinkage-thresholding algorithm (FISTA) to computed tomography reconstruction. The feasibility of the proposed methods is demonstrated numerically.

SU-G-IeP2-10: Lens Dose Reduction by Patient Position Modification During Neck CT Exams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mosher, E; Lee, C; Butman, J

Purpose: Irradiation of the lens during a neck CT may increase a patient’s risk of developing cataracts later in life. Radiologists and technologists at the National Institutes of Health Clinical Center (NIHCC) have developed new CT imaging protocols that include a reduction in scan range and modifying neck positioning using a head tilt. This study will evaluate the efficacy of this protocol in the reduction of lens dose. Methods: We retrieved CT images of five male patients who had two sets of CT images: before and after the implementation of the new protocol. The lens doses before the new protocolmore » were calculated using an in-house CT dose calculator, National Cancer Institute dosimetry system for CT (NCICT), where computational human phantoms with no head tilt are included. We also calculated the lens dose for the patient CT conducted after the new protocol by using an adult male computational phantom with the neck position deformed to match the angle of the head tilt. We also calculated the doses to other radiosensitive organs including the globes of the eye, brain, pituitary gland and salivary glands before and after head tilt. Results: Our dose calculations demonstrated that modifying neck position reduced dose to the lens by 89% on average (range: 86–96%). Globe, brain, pituitary and salivary gland doses also decreased by an average of 65% (51–95%), 38% (−8–66%), 34% (−43–84%) and 14% (13–14%), respectively. The new protocol resulted in a nearly ten-fold decrease in lens dose. Conclusion: The use of a head tilt and scan range reduction is an easy and effective method to reduce radiation exposure to the lens and other radiosensitive organs, while still allowing for the inclusion of critical neck structures in the CT image. We are expanding our study to a total of 10 males and 10 females.« less

Improvements to image quality using hybrid and model-based iterative reconstructions: a phantom study.

PubMed

Aurumskjöld, Marie-Louise; Ydström, Kristina; Tingberg, Anders; Söderberg, Marcus

2017-01-01

The number of computed tomography (CT) examinations is increasing and leading to an increase in total patient exposure. It is therefore important to optimize CT scan imaging conditions in order to reduce the radiation dose. The introduction of iterative reconstruction methods has enabled an improvement in image quality and a reduction in radiation dose. To investigate how image quality depends on reconstruction method and to discuss patient dose reduction resulting from the use of hybrid and model-based iterative reconstruction. An image quality phantom (Catphan® 600) and an anthropomorphic torso phantom were examined on a Philips Brilliance iCT. The image quality was evaluated in terms of CT numbers, noise, noise power spectra (NPS), contrast-to-noise ratio (CNR), low-contrast resolution, and spatial resolution for different scan parameters and dose levels. The images were reconstructed using filtered back projection (FBP) and different settings of hybrid (iDose 4 ) and model-based (IMR) iterative reconstruction methods. iDose 4 decreased the noise by 15-45% compared with FBP depending on the level of iDose 4 . The IMR reduced the noise even further, by 60-75% compared to FBP. The results are independent of dose. The NPS showed changes in the noise distribution for different reconstruction methods. The low-contrast resolution and CNR were improved with iDose 4 , and the improvement was even greater with IMR. There is great potential to reduce noise and thereby improve image quality by using hybrid or, in particular, model-based iterative reconstruction methods, or to lower radiation dose and maintain image quality. © The Foundation Acta Radiologica 2016.

Comparison of blood flow models and acquisitions for quantitative myocardial perfusion estimation from dynamic CT

NASA Astrophysics Data System (ADS)

Bindschadler, Michael; Modgil, Dimple; Branch, Kelley R.; La Riviere, Patrick J.; Alessio, Adam M.

2014-04-01

Myocardial blood flow (MBF) can be estimated from dynamic contrast enhanced (DCE) cardiac CT acquisitions, leading to quantitative assessment of regional perfusion. The need for low radiation dose and the lack of consensus on MBF estimation methods motivates this study to refine the selection of acquisition protocols and models for CT-derived MBF. DCE cardiac CT acquisitions were simulated for a range of flow states (MBF = 0.5, 1, 2, 3 ml (min g)-1, cardiac output = 3, 5, 8 L min-1). Patient kinetics were generated by a mathematical model of iodine exchange incorporating numerous physiological features including heterogenenous microvascular flow, permeability and capillary contrast gradients. CT acquisitions were simulated for multiple realizations of realistic x-ray flux levels. CT acquisitions that reduce radiation exposure were implemented by varying both temporal sampling (1, 2, and 3 s sampling intervals) and tube currents (140, 70, and 25 mAs). For all acquisitions, we compared three quantitative MBF estimation methods (two-compartment model, an axially-distributed model, and the adiabatic approximation to the tissue homogeneous model) and a qualitative slope-based method. In total, over 11 000 time attenuation curves were used to evaluate MBF estimation in multiple patient and imaging scenarios. After iodine-based beam hardening correction, the slope method consistently underestimated flow by on average 47.5% and the quantitative models provided estimates with less than 6.5% average bias and increasing variance with increasing dose reductions. The three quantitative models performed equally well, offering estimates with essentially identical root mean squared error (RMSE) for matched acquisitions. MBF estimates using the qualitative slope method were inferior in terms of bias and RMSE compared to the quantitative methods. MBF estimate error was equal at matched dose reductions for all quantitative methods and range of techniques evaluated. This suggests that there is no particular advantage between quantitative estimation methods nor to performing dose reduction via tube current reduction compared to temporal sampling reduction. These data are important for optimizing implementation of cardiac dynamic CT in clinical practice and in prospective CT MBF trials.

Using the benchmark dose (BMD) methodology to determine an appropriate reduction of certain ingredients in food products.

PubMed

Bi, Jian

2010-01-01

As the desire to promote health increases, reductions of certain ingredients, for example, sodium, sugar, and fat in food products, are widely requested. However, the reduction is not risk free in sensory and marketing aspects. Over reduction may change the taste and influence the flavor of a product and lead to a decrease in consumer's overall liking or purchase intent for the product. This article uses the benchmark dose (BMD) methodology to determine an appropriate reduction. Calculations of BMD and one-sided lower confidence limit of BMD are illustrated. The article also discusses how to calculate BMD and BMDL for over dispersed binary data in replicated testing based on a corrected beta-binomial model. USEPA Benchmark Dose Software (BMDS) were used and S-Plus programs were developed. The method discussed in the article is originally used to determine an appropriate reduction of certain ingredients, for example, sodium, sugar, and fat in food products, considering both health reason and sensory or marketing risk.

Quantitative Analysis of the Effect of Iterative Reconstruction Using a Phantom: Determining the Appropriate Blending Percentage

PubMed Central

Kim, Hyun Gi; Lee, Young Han; Choi, Jin-Young; Park, Mi-Suk; Kim, Myeong-Jin; Kim, Ki Whang

2015-01-01

Purpose To investigate the optimal blending percentage of adaptive statistical iterative reconstruction (ASIR) in a reduced radiation dose while preserving a degree of image quality and texture that is similar to that of standard-dose computed tomography (CT). Materials and Methods The CT performance phantom was scanned with standard and dose reduction protocols including reduced mAs or kVp. Image quality parameters including noise, spatial, and low-contrast resolution, as well as image texture, were quantitatively evaluated after applying various blending percentages of ASIR. The optimal blending percentage of ASIR that preserved image quality and texture compared to standard dose CT was investigated in each radiation dose reduction protocol. Results As the percentage of ASIR increased, noise and spatial-resolution decreased, whereas low-contrast resolution increased. In the texture analysis, an increasing percentage of ASIR resulted in an increase of angular second moment, inverse difference moment, and correlation and in a decrease of contrast and entropy. The 20% and 40% dose reduction protocols with 20% and 40% ASIR blending, respectively, resulted in an optimal quality of images with preservation of the image texture. Conclusion Blending the 40% ASIR to the 40% reduced tube-current product can maximize radiation dose reduction and preserve adequate image quality and texture. PMID:25510772

Preparation of metallic nanoparticles by irradiation in starch aqueous solution

NASA Astrophysics Data System (ADS)

NemÅ£anu, Monica R.; Braşoveanu, Mirela; Iacob, Nicuşor

2014-11-01

Colloidal silver nanoparticles (AgNPs) were synthesized in a single step by electron beam irradiation reduction of silver ions in aqueous solution containing starch. The nanoparticles were characterized by spectrophotocolorimetry and compared with those obtained by chemical (thermal) reduction method. The results showed that the smaller sizes of AgNPs were prepared with higher yields as the irradiation dose increased. The broadening of particle size distribution occurred by increasing of irradiation dose and dose rate. Chromatic parameters such as b* (yellow-blue coordinate), C* (chroma) and ΔEab (total color difference) could characterize the nanoparticles with respect of their concentration. Hue angle ho was correlated to the particle size distribution. Experimental data of the irradiated samples were also subjected to factor analysis using principal component extraction and varimax rotation in order to reveal the relation between dependent variables and independent variables and to reduce their number. The radiation-based method provided silver nanoparticles with higher concentration and narrower size distribution than those produced by chemical reduction method. Therefore, the electron beam irradiation is effective for preparation of silver nanoparticles using starch aqueous solution as dispersion medium.

SU-F-J-48: Effect of Scan Length On Magnitude of Imaging Dose in KV CBCT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deshpande, S; Naidu, S; Sutar, A

Purpose: To study effect of scan length on magnitude of imaging dose deposition in Varian kV CBCT for head & neck and pelvis CBCT. Methods: To study effect of scan length we measured imaging dose at depth of 8 cm for head and neck Cone Beam Computed Tomography (CBCT) acquisition ( X ray beam energy is used 100kV and 200 degree of gantry rotation) and at 16 cm depth for pelvis CBCT acquisition ( X ray beam energy used is 125 kV and 360 degree of gantry rotation) in specially designed phantom. We used farmer chamber which was calibrated inmore » kV X ray range for measurements .Dose was measured with default field size, and reducing field size along y direction to 10 cm and 5 cm. Results: As the energy of the beam decreases the scattered radiation increases and this contributes significantly to the dose deposited in the patient. By reducing the scan length to 10 Cm from default 20.6 cm we found a dose reduction of 14% for head and neck CBCT protocol and a reduction of 26% for pelvis CBCT protocol. Similarly for a scan length of 5cm compared to default the dose reduction in head and neck CBCT protocol is 36% while in the pelvis CBCT protocol the dose reduction is 50%. Conclusion: By limiting the scan length we can control the scatter radiation generated and hence the dose to the patient. However the variation in dose reduction for same length used in two protocols is because of the scan geometry. The pelvis CBCT protocol uses a full rotation and head and neck CBCT protocol uses partial rotation.« less

Achieving Routine Submillisievert CT Scanning: Report from the Summit on Management of Radiation Dose in CT

PubMed Central

Chen, Guang Hong; Kalender, Willi; Leng, Shuai; Samei, Ehsan; Taguchi, Katsuyuki; Wang, Ge; Yu, Lifeng; Pettigrew, Roderic I.

2012-01-01

This Special Report presents the consensus of the Summit on Management of Radiation Dose in Computed Tomography (CT) (held in February 2011), which brought together participants from academia, clinical practice, industry, and regulatory and funding agencies to identify the steps required to reduce the effective dose from routine CT examinations to less than 1 mSv. The most promising technologies and methods discussed at the summit include innovations and developments in x-ray sources; detectors; and image reconstruction, noise reduction, and postprocessing algorithms. Access to raw projection data and standard data sets for algorithm validation and optimization is a clear need, as is the need for new, clinically relevant metrics of image quality and diagnostic performance. Current commercially available techniques such as automatic exposure control, optimization of tube potential, beam-shaping filters, and dynamic z-axis collimators are important, and education to successfully implement these methods routinely is critically needed. Other methods that are just becoming widely available, such as iterative reconstruction, noise reduction, and postprocessing algorithms, will also have an important role. Together, these existing techniques can reduce dose by a factor of two to four. Technical advances that show considerable promise for additional dose reduction but are several years or more from commercial availability include compressed sensing, volume of interest and interior tomography techniques, and photon-counting detectors. This report offers a strategic roadmap for the CT user and research and manufacturer communities toward routinely achieving effective doses of less than 1 mSv, which is well below the average annual dose from naturally occurring sources of radiation. © RSNA, 2012 PMID:22692035

A simple method for low-contrast detectability, image quality and dose optimisation with CT iterative reconstruction algorithms and model observers.

PubMed

Bellesi, Luca; Wyttenbach, Rolf; Gaudino, Diego; Colleoni, Paolo; Pupillo, Francesco; Carrara, Mauro; Braghetti, Antonio; Puligheddu, Carla; Presilla, Stefano

2017-01-01

The aim of this work was to evaluate detection of low-contrast objects and image quality in computed tomography (CT) phantom images acquired at different tube loadings (i.e. mAs) and reconstructed with different algorithms, in order to find appropriate settings to reduce the dose to the patient without any image detriment. Images of supraslice low-contrast objects of a CT phantom were acquired using different mAs values. Images were reconstructed using filtered back projection (FBP), hybrid and iterative model-based methods. Image quality parameters were evaluated in terms of modulation transfer function; noise, and uniformity using two software resources. For the definition of low-contrast detectability, studies based on both human (i.e. four-alternative forced-choice test) and model observers were performed across the various images. Compared to FBP, image quality parameters were improved by using iterative reconstruction (IR) algorithms. In particular, IR model-based methods provided a 60% noise reduction and a 70% dose reduction, preserving image quality and low-contrast detectability for human radiological evaluation. According to the model observer, the diameters of the minimum detectable detail were around 2 mm (up to 100 mAs). Below 100 mAs, the model observer was unable to provide a result. IR methods improve CT protocol quality, providing a potential dose reduction while maintaining a good image detectability. Model observer can in principle be useful to assist human performance in CT low-contrast detection tasks and in dose optimisation.

A novel curvilinear approach for prostate seed implantation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podder, Tarun K.; Dicker, Adam P.; Hutapea, Parsaoran

Purpose: A new technique called ''curvilinear approach'' for prostate seed implantation has been proposed. The purpose of this study is to evaluate the dosimetric benefit of curvilinear distribution of seeds for low-dose-rate (LDR) prostate brachytherapy. Methods: Twenty LDR prostate brachytherapy cases planned intraoperatively with VariSeed planning system and I-125 seeds were randomly selected as reference rectilinear cases. All the cases were replanned by using curved-needle approach keeping the same individual source strength and the volume receiving 100% of prescribed dose 145 Gy (V{sub 100}). Parameters such as number of needles, seeds, and the dose coverage of the prostate (D{sub 90},more » V{sub 150}, V{sub 200}), urethra (D{sub 30}, D{sub 10}) and rectum (D{sub 5}, V{sub 100}) were compared for the rectilinear and the curvilinear methods. Statistical significance was assessed using two-tailed student's t-test. Results: Reduction of the required number of needles and seeds in curvilinear method were 30.5% (p < 0.001) and 11.8% (p < 0.49), respectively. Dose to the urethra was reduced significantly; D{sub 30} reduced by 10.1% (p < 0.01) and D{sub 10} reduced by 9.9% (p < 0.02). Reduction in rectum dose D{sub 5} was 18.5% (p < 0.03) and V{sub 100} was also reduced from 0.93 cc in rectilinear to 0.21 cc in curvilinear (p < 0.001). Also the V{sub 150} and V{sub 200} coverage of prostate reduced by 18.8% (p < 0.01) and 33.9% (p < 0.001), respectively. Conclusions: Significant improvement in the relevant dosimetric parameters was observed in curvilinear needle approach. Prostate dose homogeneity (V{sub 150}, V{sub 200}) improved while urethral dose was reduced, which might potentially result in better treatment outcome. Reduction in rectal dose could potentially reduce rectal toxicity and complications. Reduction in number of needles would minimize edema and thereby could improve postimplant urinary incontinence. This study indicates that the curvilinear implantation approach is dosimetrically superior to conventional rectilinear implantation technique.« less

Efficacy of a radiation absorbing shield in reducing dose to the interventionalist during peripheral endovascular procedures: a single centre pilot study.

PubMed

Power, S; Mirza, M; Thakorlal, A; Ganai, B; Gavagan, L D; Given, M F; Lee, M J

2015-06-01

This prospective pilot study was undertaken to evaluate the feasibility and effectiveness of using a radiation absorbing shield to reduce operator dose from scatter during lower limb endovascular procedures. A commercially available bismuth shield system (RADPAD) was used. Sixty consecutive patients undergoing lower limb angioplasty were included. Thirty procedures were performed without the RADPAD (control group) and thirty with the RADPAD (study group). Two separate methods were used to measure dose to a single operator. Thermoluminescent dosimeter (TLD) badges were used to measure hand, eye, and unshielded body dose. A direct dosimeter with digital readout was also used to measure eye and unshielded body dose. To allow for variation between control and study groups, dose per unit time was calculated. TLD results demonstrated a significant reduction in median body dose per unit time for the study group compared with controls (p = 0.001), corresponding to a mean dose reduction rate of 65 %. Median eye and hand dose per unit time were also reduced in the study group compared with control group, however, this was not statistically significant (p = 0.081 for eye, p = 0.628 for hand). Direct dosimeter readings also showed statistically significant reduction in median unshielded body dose rate for the study group compared with controls (p = 0.037). Eye dose rate was reduced for the study group but this was not statistically significant (p = 0.142). Initial results are encouraging. Use of the shield resulted in a statistically significant reduction in unshielded dose to the operator's body. Measured dose to the eye and hand of operator were also reduced but did not reach statistical significance in this pilot study.

Dose reduction assessment in dynamic CT myocardial perfusion imaging in a porcine balloon-induced-ischemia model

NASA Astrophysics Data System (ADS)

Fahmi, Rachid; Eck, Brendan L.; Vembar, Mani; Bezerra, Hiram G.; Wilson, David L.

2014-03-01

We investigated the use of an advanced hybrid iterative reconstruction (IR) technique (iDose4, Philips Health- care) for low dose dynamic myocardial CT perfusion (CTP) imaging. A porcine model was created to mimic coronary stenosis through partial occlusion of the left anterior descending (LAD) artery with a balloon catheter. The severity of LAD occlusion was adjusted with FFR measurements. Dynamic CT images were acquired at end-systole (45% R-R) using a multi-detector CT (MDCT) scanner. Various corrections were applied to the acquired scans to reduce motion and imaging artifacts. Absolute myocardial blood flow (MBF) was computed with a deconvolution-based approach using singular value decomposition (SVD). We compared a high and a low dose radiation protocol corresponding to two different tube-voltage/tube-current combinations (80kV p/100mAs and 120kV p/150mAs). The corresponding radiation doses for these protocols are 7.8mSv and 34.3mSV , respectively. The images were reconstructed using conventional FBP and three noise-reduction strengths of the IR method, iDose. Flow contrast-to-noise ratio, CNRf, as obtained from MBF maps, was used to quantitatively evaluate the effect of reconstruction on contrast between normal and ischemic myocardial tissue. Preliminary results showed that the use of iDose to reconstruct low dose images provide better or comparable CNRf to that of high dose images reconstructed with FBP, suggesting significant dose savings. CNRf was improved with the three used levels of iDose compared to FBP for both protocols. When using the entire 4D dynamic sequence for MBF computation, a 77% dose reduction was achieved, while considering only half the scans (i.e., every other heart cycle) allowed even further dose reduction while maintaining relatively higher CNRf.

Pediatric CT: implementation of ASIR for substantial radiation dose reduction while maintaining pre-ASIR image noise.

PubMed

Brady, Samuel L; Moore, Bria M; Yee, Brian S; Kaufman, Robert A

2014-01-01

To determine a comprehensive method for the implementation of adaptive statistical iterative reconstruction (ASIR) for maximal radiation dose reduction in pediatric computed tomography (CT) without changing the magnitude of noise in the reconstructed image or the contrast-to-noise ratio (CNR) in the patient. The institutional review board waived the need to obtain informed consent for this HIPAA-compliant quality analysis. Chest and abdominopelvic CT images obtained before ASIR implementation (183 patient examinations; mean patient age, 8.8 years ± 6.2 [standard deviation]; range, 1 month to 27 years) were analyzed for image noise and CNR. These measurements were used in conjunction with noise models derived from anthropomorphic phantoms to establish new beam current-modulated CT parameters to implement 40% ASIR at 120 and 100 kVp without changing noise texture or magnitude. Image noise was assessed in images obtained after ASIR implementation (492 patient examinations; mean patient age, 7.6 years ± 5.4; range, 2 months to 28 years) the same way it was assessed in the pre-ASIR analysis. Dose reduction was determined by comparing size-specific dose estimates in the pre- and post-ASIR patient cohorts. Data were analyzed with paired t tests. With 40% ASIR implementation, the average relative dose reduction for chest CT was 39% (2.7/4.4 mGy), with a maximum reduction of 72% (5.3/18.8 mGy). The average relative dose reduction for abdominopelvic CT was 29% (4.8/6.8 mGy), with a maximum reduction of 64% (7.6/20.9 mGy). Beam current modulation was unnecessary for patients weighing 40 kg or less. The difference between 0% and 40% ASIR noise magnitude was less than 1 HU, with statistically nonsignificant increases in patient CNR at 100 kVp of 8% (15.3/14.2; P = .41) for chest CT and 13% (7.8/6.8; P = .40) for abdominopelvic CT. Radiation dose reduction at pediatric CT was achieved when 40% ASIR was implemented as a dose reduction tool only; no net change to the magnitude of noise in the reconstructed image or the patient CNR occurred. © RSNA, 2013.

SU-C-BRF-01: Correlation of DIBH Breath Hold Amplitude with Dosimetric Sparing of Heart and Left Anterior Descending Artery in Left Breast Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Taeho; Reardon, Kelli; Sukovich, Kaitlyn

Purpose: A 7.4% increase in major coronary events per 1 Gy increase in mean heart dose has been reported from the population-based analysis of radiation-induced cardiac toxicity following treatment of left sided breast cancer. Deep inhalation breath-hold (DIBH) is clinically utilized to reduce radiation dose to heart and left anterior descending artery (LAD). We investigated the correlation of dose sparing in heart and LAD with internal DIBH amplitude to develop a quantitative predictive model for expected dose to heart and LAD based on internal breath hold amplitude. Methods: A treatment planning study (Prescription Dose = 50 Gy) was performed onmore » 50 left breast cancer patients underwent DIBH whole breast radiotherapy. Two CT datasets, free breathing (FB) and DIBH, were utilized for treatment planning and for determination of the internal anatomy DIBH amplitude (difference between sternum position at FB and DIBH). The heart and LAD dose between FB and DIBH plans was compared and dose to the heart and LAD as a function of breath hold amplitude was determined. Results: Average DIBH amplitude using internal anatomy was 13.9±4.2 mm. The DIBH amplitude-mean dose reduction correlation is 20%/5mm (0.3 Gy/5mm) for the heart and 18%/5mm (1.1 Gy/5mm) for LAD. The correlation with max dose reduction is 12%/5mm (3.8 Gy/5mm) for the heart and 16%/5mm (3.2 Gy/5mm) for LAD. We found that average dose reductions to LAD from 6.0±6.5 Gy to 2.0±1.6 Gy with DIBH (4.0 Gy reduction: -67%, p < 0.001) and average dose reduction to the heart from 1.3±0.7 Gy to 0.7±0.2 Gy with DIBH (0.6 Gy reduction: -46%, p < 0.001). That suggests using DIBH may reduce the risk of the major coronary event for left sided breast cancer patients. Conclusion: The correlation between breath hold amplitude and dosimetric sparing suggests that dose sparing linearly increases with internal DIBH amplitude.« less

Standard Pentostatin Dose Reductions in Renal Insufficiency are not Adequate: Selected Patients with Steroid-Refractory Acute Graft-versus-Host Disease

PubMed Central

Poi, Ming J.; Hofmeister, Craig C.; Johnston, Jeffrey S.; Edwards, Ryan B.; Jansak, Buffy S.; Lucas, David M.; Farag, Sherif S.; Dalton, James T.; Devine, Steven M.; Grever, Michael R.; Phelps, Mitch A.

2013-01-01

Background and Objective Pentostatin is an irreversible inhibitor of adenosine deaminase and has been used to prevent graft-versus-host disease (GVHD) and to treat both acute and chronic GVHD. Dose reduction equations for patients with renal insufficiency are based on few patients with limited pharmacokinetic and clinical results. This phase II study (NCT00201786) was conducted to assess pentostatin efficacy and infectious complications seen from our previous phase I study in steroid-refractory acute GVHD (aGVHD). Patients and Methods Hospitalized patients with steroid-refractory aGVHD were given pentostatin 1.5 mg/m2/day intravenously on days 1–3 of each 14 day cycle. Prior to each dose, dose modifications were based on Cockcroft-Gault estimated creatinine clearance (eCrCL) with 30–50 ml/min/1.73m2 leading to a 50% dose reduction and eCrCL< 30 ml/min/1.73m2 leading to study removal. Plasma pentostatin area under the concentration-time curve (AUC) and incidence of infectious complications were evaluated. Results Two of the eight patients treated demonstrated excessive pentostatin exposure as determined by measurement of AUC. One of these patients had renal impairment while the other patient demonstrated borderline renal function. Despite dose reduction to 0.75 mg/m2, AUCs were significantly increased compared to the other patients in this study. Seven of eight patients treated with pentostatin had cytomegalovirus (CMV) viremia after pentostatin treatment; however none developed proven CMV disease. Conclusion A 50% dose reduction in patients with eCrCL 30–50 ml/min/1.73m2 seems reasonable. However, the eCrCL should be interpreted with extreme cautions in patients who are critically ill and/or with poor performance status. Renal function assessment based on the Cockcroft-Gault method could be significantly overestimated thus risking pentostatin over-dosing. These results imply a need to closely monitor pentostatin exposure in patients with renal insufficiency. PMID:23588536

Towards tracer dose reduction in PET studies: Simulation of dose reduction by retrospective randomized undersampling of list-mode data.

PubMed

Gatidis, Sergios; Würslin, Christian; Seith, Ferdinand; Schäfer, Jürgen F; la Fougère, Christian; Nikolaou, Konstantin; Schwenzer, Nina F; Schmidt, Holger

2016-01-01

Optimization of tracer dose regimes in positron emission tomography (PET) imaging is a trade-off between diagnostic image quality and radiation exposure. The challenge lies in defining minimal tracer doses that still result in sufficient diagnostic image quality. In order to find such minimal doses, it would be useful to simulate tracer dose reduction as this would enable to study the effects of tracer dose reduction on image quality in single patients without repeated injections of different amounts of tracer. The aim of our study was to introduce and validate a method for simulation of low-dose PET images enabling direct comparison of different tracer doses in single patients and under constant influencing factors. (18)F-fluoride PET data were acquired on a combined PET/magnetic resonance imaging (MRI) scanner. PET data were stored together with the temporal information of the occurrence of single events (list-mode format). A predefined proportion of PET events were then randomly deleted resulting in undersampled PET data. These data sets were subsequently reconstructed resulting in simulated low-dose PET images (retrospective undersampling of list-mode data). This approach was validated in phantom experiments by visual inspection and by comparison of PET quality metrics contrast recovery coefficient (CRC), background-variability (BV) and signal-to-noise ratio (SNR) of measured and simulated PET images for different activity concentrations. In addition, reduced-dose PET images of a clinical (18)F-FDG PET dataset were simulated using the proposed approach. (18)F-PET image quality degraded with decreasing activity concentrations with comparable visual image characteristics in measured and in corresponding simulated PET images. This result was confirmed by quantification of image quality metrics. CRC, SNR and BV showed concordant behavior with decreasing activity concentrations for measured and for corresponding simulated PET images. Simulation of dose-reduced datasets based on clinical (18)F-FDG PET data demonstrated the clinical applicability of the proposed data. Simulation of PET tracer dose reduction is possible with retrospective undersampling of list-mode data. Resulting simulated low-dose images have equivalent characteristics with PET images actually measured at lower doses and can be used to derive optimal tracer dose regimes.

SU-F-I-09: Improvement of Image Registration Using Total-Variation Based Noise Reduction Algorithms for Low-Dose CBCT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, S; Farr, J; Merchant, T

Purpose: To study the effect of total-variation based noise reduction algorithms to improve the image registration of low-dose CBCT for patient positioning in radiation therapy. Methods: In low-dose CBCT, the reconstructed image is degraded by excessive quantum noise. In this study, we developed a total-variation based noise reduction algorithm and studied the effect of the algorithm on noise reduction and image registration accuracy. To study the effect of noise reduction, we have calculated the peak signal-to-noise ratio (PSNR). To study the improvement of image registration, we performed image registration between volumetric CT and MV- CBCT images of different head-and-neck patientsmore » and calculated the mutual information (MI) and Pearson correlation coefficient (PCC) as a similarity metric. The PSNR, MI and PCC were calculated for both the noisy and noise-reduced CBCT images. Results: The algorithms were shown to be effective in reducing the noise level and improving the MI and PCC for the low-dose CBCT images tested. For the different head-and-neck patients, a maximum improvement of PSNR of 10 dB with respect to the noisy image was calculated. The improvement of MI and PCC was 9% and 2% respectively. Conclusion: Total-variation based noise reduction algorithm was studied to improve the image registration between CT and low-dose CBCT. The algorithm had shown promising results in reducing the noise from low-dose CBCT images and improving the similarity metric in terms of MI and PCC.« less

Dose Reduction Study in Vaginal Balloon Packing Filled With Contrast for HDR Brachytherapy Treatment;HDR; Uterine cervix cancer; Vaginal balloon packing; Contrast; Monte Carlo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saini, Amarjit S.; Zhang, Geoffrey G., E-mail: geoffrey.zhang@moffitt.org; Finkelstein, Steven E.

2011-07-15

Purpose: Vaginal balloon packing is a means to displace organs at risk during high dose rate brachytherapy of the uterine cervix. We tested the hypothesis that contrast-filled vaginal balloon packing reduces radiation dose to organs at risk, such as the bladder and rectum, in comparison to water- or air-filled balloons. Methods and Materials: In a phantom study, semispherical vaginal packing balloons were filled with air, saline solution, and contrast agents. A high dose rate iridium-192 source was placed on the anterior surface of the balloon, and the diode detector was placed on the posterior surface. Dose ratios were taken withmore » each material in the balloon. Monte Carlo (MC) simulations, by use of the MC computer program DOSXYZnrc, were performed to study dose reduction vs. balloon size and contrast material, including commercially available iodine- and gadolinium-based contrast agents. Results: Measured dose ratios on the phantom with the balloon radius of 3.4 cm were 0.922 {+-} 0.002 for contrast/saline solution and 0.808 {+-} 0.001 for contrast/air. The corresponding ratios by MC simulations were 0.895 {+-} 0.010 and 0.781 {+-} 0.010. The iodine concentration in the contrast was 23.3% by weight. The dose reduction of contrast-filled balloon ranges from 6% to 15% compared with water-filled balloon and 11% to 26% compared with air-filled balloon, with a balloon size range between 1.4 and 3.8 cm, and iodine concentration in contrast of 24.9%. The dose reduction was proportional to the contrast agent concentration. The gadolinium-based contrast agents showed less dose reduction because of much lower concentrations in their solutions. Conclusions: The dose to the posterior wall of the bladder and the anterior wall of the rectum can be reduced if the vaginal balloon is filled with contrast agent in comparison to vaginal balloons filled with saline solution or air.« less

Stacked competitive networks for noise reduction in low-dose CT

PubMed Central

Du, Wenchao; Chen, Hu; Wu, Zhihong; Sun, Huaiqiang; Liao, Peixi

2017-01-01

Since absorption of X-ray radiation has the possibility of inducing cancerous, genetic and other diseases to patients, researches usually attempt to reduce the radiation dose. However, reduction of the radiation dose associated with CT scans will unavoidably increase the severity of noise and artifacts, which can seriously affect diagnostic confidence. Due to the outstanding performance of deep neural networks in image processing, in this paper, we proposed a Stacked Competitive Network (SCN) approach to noise reduction, which stacks several successive Competitive Blocks (CB). The carefully handcrafted design of the competitive blocks was inspired by the idea of multi-scale processing and improvement the network’s capacity. Qualitative and quantitative evaluations demonstrate the competitive performance of the proposed method in noise suppression, structural preservation, and lesion detection. PMID:29267360

Potential uncertainty reduction in model-averaged benchmark dose estimates informed by an additional dose study.

PubMed

Shao, Kan; Small, Mitchell J

2011-10-01

A methodology is presented for assessing the information value of an additional dosage experiment in existing bioassay studies. The analysis demonstrates the potential reduction in the uncertainty of toxicity metrics derived from expanded studies, providing insights for future studies. Bayesian methods are used to fit alternative dose-response models using Markov chain Monte Carlo (MCMC) simulation for parameter estimation and Bayesian model averaging (BMA) is used to compare and combine the alternative models. BMA predictions for benchmark dose (BMD) are developed, with uncertainty in these predictions used to derive the lower bound BMDL. The MCMC and BMA results provide a basis for a subsequent Monte Carlo analysis that backcasts the dosage where an additional test group would have been most beneficial in reducing the uncertainty in the BMD prediction, along with the magnitude of the expected uncertainty reduction. Uncertainty reductions are measured in terms of reduced interval widths of predicted BMD values and increases in BMDL values that occur as a result of this reduced uncertainty. The methodology is illustrated using two existing data sets for TCDD carcinogenicity, fitted with two alternative dose-response models (logistic and quantal-linear). The example shows that an additional dose at a relatively high value would have been most effective for reducing the uncertainty in BMA BMD estimates, with predicted reductions in the widths of uncertainty intervals of approximately 30%, and expected increases in BMDL values of 5-10%. The results demonstrate that dose selection for studies that subsequently inform dose-response models can benefit from consideration of how these models will be fit, combined, and interpreted. © 2011 Society for Risk Analysis.

Radiation dose reduction: comparative assessment of publication volume between interventional and diagnostic radiology

PubMed Central

Hansmann, Jan; Henzler, Thomas; Gaba, Ron C.; Morelli, John N.

2017-01-01

PURPOSE We aimed to quantify and compare awareness regarding radiation dose reduction within the interventional radiology and diagnostic radiology communities. METHODS Abstracts accepted to the annual meetings of the Society of Interventional Radiology (SIR), the Cardiovascular and Interventional Radiological Society of Europe (CIRSE), the Radiological Society of North America (RSNA), and the European Congress of Radiology (ECR) between 2005 and 2015 were analyzed using the search terms “interventional/computed tomography” and “radiation dose/radiation dose reduction.” A PubMed query using the above-mentioned search terms for the years of 2005–2015 was performed. RESULTS Between 2005 and 2015, a total of 14 520 abstracts (mean, 660±297 abstracts) and 80 614 abstracts (mean, 3664±1025 abstracts) were presented at interventional and diagnostic radiology meetings, respectively. Significantly fewer abstracts related to radiation dose were presented at the interventional radiology meetings compared with the diagnostic radiology meetings (162 abstracts [1% of total] vs. 2706 [3% of total]; P < 0.001). On average 15±7 interventional radiology abstracts (range, 6–27) and 246±105 diagnostic radiology abstracts (range, 112–389) pertaining to radiation dose were presented at each meeting. The PubMed query revealed an average of 124±39 publications (range, 79–187) and 1205±307 publications (range, 829–1672) related to interventional and diagnostic radiology dose reduction per year, respectively (P < 0.001). CONCLUSION The observed increase in the number of abstracts regarding radiation dose reduction in the interventional radiology community over the past 10 years has not mirrored the increased volume seen within diagnostic radiology, suggesting that increased education and discussion about this topic may be warranted. PMID:28287072

Preparation of metallic nanoparticles by irradiation in starch aqueous solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nemţanu, Monica R., E-mail: monica.nemtanu@inflpr.ro; Braşoveanu, Mirela, E-mail: monica.nemtanu@inflpr.ro; Iacob, Nicuşor, E-mail: monica.nemtanu@inflpr.ro

Colloidal silver nanoparticles (AgNPs) were synthesized in a single step by electron beam irradiation reduction of silver ions in aqueous solution containing starch. The nanoparticles were characterized by spectrophotocolorimetry and compared with those obtained by chemical (thermal) reduction method. The results showed that the smaller sizes of AgNPs were prepared with higher yields as the irradiation dose increased. The broadening of particle size distribution occurred by increasing of irradiation dose and dose rate. Chromatic parameters such as b* (yellow-blue coordinate), C* (chroma) and ΔE{sub ab} (total color difference) could characterize the nanoparticles with respect of their concentration. Hue angle h{supmore » o} was correlated to the particle size distribution. Experimental data of the irradiated samples were also subjected to factor analysis using principal component extraction and varimax rotation in order to reveal the relation between dependent variables and independent variables and to reduce their number. The radiation-based method provided silver nanoparticles with higher concentration and narrower size distribution than those produced by chemical reduction method. Therefore, the electron beam irradiation is effective for preparation of silver nanoparticles using starch aqueous solution as dispersion medium.« less

SU-E-I-49: The Evaluation of Usability of Multileaf Collimator for Diagnostic Radiation in Cephalometric Exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, S; Kim, K; Jung, H

Purpose: This study evaluated usability of Multileaf collimator (MLC) for diagnostic radiation in cephalometric exposure using optical stimulated luminance dosimeters (OSLDs) Methods: The MLC material was made alloy tool steel (SKD-11) and the density of it is 7.89g/m3 that is similar to it of steel (Fe, 7.85 g/m3) and the MLC was attached to general radiography unit (Rex-650R, Listem Inc, Korea) for cephalometric exposure. The OSLDs that used were nanoDotTM Dosimeter (Landauer Inc, Glenwood, USA) and we read out OSLDs with micro star system (Landauer Inc, Glenwood, USA). The Optical annealing system contained fluorescent lamps (Osram lumilux, 24 W, 280more » ∼780 nm). To measure absorbed dose using OSLDs, was carried out dosimetric characteristics of OSLDs. Based on these, we evaluated dose reduction of critical organ (Eyes, Thyroids) with MLC in cephalometric exposure Results: The dosimetric characteristics were following that batch homogeneity was 1.21% and reproducibility was 0.96% of the coefficient of variation The linearity was that the correlation of between dose and count was fitted by linear function (dose,mGy = 0.00029 × Count, R2 =0.997). The range of angular dependence was from −3.6% to 3.7% variation when each degree was normalized by zero degree. The organ dose of Rt. eye, Lt eye, thyroids were 77.8 μGy, 337.0 μGy, 323.1μGy, respectively in open field and the dose reduction of organ dose was 10.6%(8.3μGy), 12.4 %(42 μGy), 87.1%(281.4μGy) with MLC Conclusion: We certified dose reduction of organ dose in cephalometric exposure. The dose reduction of Eye was 11% because of reduction of field size and it of thyroids was 87% by primary beam shielding.« less

Prospective Evaluation of Prior Image Constrained Compressed Sensing (PICCS) Algorithm in Abdominal CT: A comparison of reduced dose with standard dose imaging

PubMed Central

Lubner, Meghan G.; Pickhardt, Perry J.; Kim, David H.; Tang, Jie; Munoz del Rio, Alejandro; Chen, Guang-Hong

2014-01-01

Purpose To prospectively study CT dose reduction using the “prior image constrained compressed sensing” (PICCS) reconstruction technique. Methods Immediately following routine standard dose (SD) abdominal MDCT, 50 patients (mean age, 57.7 years; mean BMI, 28.8) underwent a second reduced-dose (RD) scan (targeted dose reduction, 70-90%). DLP, CTDIvol and SSDE were compared. Several reconstruction algorithms (FBP, ASIR, and PICCS) were applied to the RD series. SD images with FBP served as reference standard. Two blinded readers evaluated each series for subjective image quality and focal lesion detection. Results Mean DLP, CTDIvol, and SSDE for RD series was 140.3 mGy*cm (median 79.4), 3.7 mGy (median 1.8), and 4.2 mGy (median 2.3) compared with 493.7 mGy*cm (median 345.8), 12.9 mGy (median 7.9 mGy) and 14.6 mGy (median 10.1) for SD series, respectively. Mean effective patient diameter was 30.1 cm (median 30), which translates to a mean SSDE reduction of 72% (p<0.001). RD-PICCS image quality score was 2.8±0.5, improved over the RD-FBP (1.7±0.7) and RD-ASIR(1.9±0.8)(p<0.001), but lower than SD (3.5±0.5)(p<0.001). Readers detected 81% (184/228) of focal lesions on RD-PICCS series, versus 67% (153/228) and 65% (149/228) for RD-FBP and RD-ASIR, respectively. Mean image noise was significantly reduced on RD-PICCS series (13.9 HU) compared with RD-FBP (57.2) and RD-ASIR (44.1) (p<0.001). Conclusion PICCS allows for marked dose reduction at abdominal CT with improved image quality and diagnostic performance over reduced-dose FBP and ASIR. Further study is needed to determine indication-specific dose reduction levels that preserve acceptable diagnostic accuracy relative to higher-dose protocols. PMID:24943136

A Comparative Evaluation of Normal Tissue Doses for Patients Receiving Radiation Therapy for Hodgkin Lymphoma on the Childhood Cancer Survivor Study and Recent Children's Oncology Group Trials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Rachel; Ng, Angela; Constine, Louis S.

Purpose: Survivors of pediatric Hodgkin lymphoma (HL) are recognized to have an increased risk of delayed adverse health outcomes related to radiation therapy (RT). However, the necessary latency required to observe these late effects means that the estimated risks apply to outdated treatments. We sought to compare the normal tissue dose received by children treated for HL and enrolled in the Childhood Cancer Survivor Study (CCSS) (diagnosed 1970-1986) with that of patients treated in recent Children's Oncology Group (COG) trials (enrolled 2002-2012). Methods and Materials: RT planning data were obtained for 50 HL survivors randomly sampled from the CCSS cohortmore » and applied to computed tomography planning data sets to reconstruct the normal tissue dosimetry. For comparison, the normal tissue dosimetry data were obtained for all 191 patients with full computed tomography–based volumetric RT planning on COG protocols AHOD0031 and AHOD0831. Results: For early-stage patients, the mean female breast dose in the COG patients was on average 83.5% lower than that for CCSS patients, with an absolute reduction of 15.5 Gy. For advanced-stage patients, the mean breast dose was decreased on average by 70% (11.6 Gy average absolute dose reduction). The mean heart dose decreased on average by 22.9 Gy (68.6%) and 17.6 Gy (56.8%) for early- and advanced-stage patients, respectively. All dose comparisons for breast, heart, lung, and thyroid were significantly lower for patients in the COG trials than for the CCSS participants. Reductions in the prescribed dose were a major contributor to these dose reductions. Conclusions: These are the first data quantifying the significant reduction in the normal tissue dose using actual, rather than hypothetical, treatment plans for children with HL. These findings provide useful information when counseling families regarding the risks of contemporary RT.« less

Cryoradiolytic reduction of heme proteins: Maximizing dose-dependent yield

NASA Astrophysics Data System (ADS)

Denisov, Ilia G.; Victoria, Doreen C.; Sligar, Stephen G.

2007-04-01

Radiolytic reduction in frozen solutions and crystals is a useful method for generation of trapped intermediates in protein-based radical reactions. In this communication we define the conditions which provide the maximum yield of one electron-reduced myoglobin at 77 K using 60Co γ-irradiation in aqueous glycerol glass. The yield reached 50% after 20 kGy, was almost complete at ˜160 kGy total dose, and does not depend on the protein concentration in the range 0.01-5 mM.

Potential of combining iterative reconstruction with noise efficient detector design: aggressive dose reduction in head CT

PubMed Central

Bender, B; Schabel, C; Fenchel, M; Ernemann, U; Korn, A

2015-01-01

Objective: With further increase of CT numbers and their dominant contribution to medical exposure, there is a recent quest for more effective dose control. While reintroduction of iterative reconstruction (IR) has proved its potential in many applications, a novel focus is placed on more noise efficient detectors. Our purpose was to assess the potential of IR in combination with an integrated circuit detector (ICD) for aggressive dose reduction in head CT. Methods: Non-contrast low-dose head CT [190 mAs; weighted volume CT dose index (CTDIvol), 33.2 mGy] was performed in 50 consecutive patients, using a new noise efficient detector and IR. Images were assessed in terms of quantitative and qualitative image quality and compared with standard dose acquisitions (320 mAs; CTDIvol, 59.7 mGy) using a conventional detector and filtered back projection. Results: By combining ICD and IR in low-dose examinations, the signal to noise was improved by about 13% above the baseline level in the standard-dose control group. Both, contrast-to-noise ratio (2.02 ± 0.6 vs 1.88 ± 0.4; p = 0.18) and objective measurements of image sharpness (695 ± 84 vs 705 ± 151 change in Hounsfield units per pixel; p = 0.79) were fully preserved in the low-dose group. Likewise, there was no significant difference in the grading of several subjective image quality parameters when both noise-reducing strategies were used in low-dose examinations. Conclusion: Combination of noise efficient detector with IR allows for meaningful dose reduction in head CT without compromise of standard image quality. Advances in knowledge: Our study demonstrates the feasibility of almost 50% dose reduction in head CT dose (1.1 mSv per scan) through combination of novel dose-reducing strategies. PMID:25827204

SU-G-IeP3-05: Effects of Image Receptor Technology and Dose Reduction Software On Radiation Dose Estimates for Fluoroscopically-Guided Interventional (FGI) Procedures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merritt, Z; Dave, J; Eschelman, D

Purpose: To investigate the effects of image receptor technology and dose reduction software on radiation dose estimates for most frequently performed fluoroscopically-guided interventional (FGI) procedures at a tertiary health care center. Methods: IRB approval was obtained for retrospective analysis of FGI procedures performed in the interventional radiology suites between January-2011 and December-2015. This included procedures performed using image-intensifier (II) based systems which were subsequently replaced, flat-panel-detector (FPD) based systems which were later upgraded with ClarityIQ dose reduction software (Philips Healthcare) and relatively new FPD system already equipped with ClarityIQ. Post procedure, technologists entered system-reported cumulative air kerma (CAK) and kerma-areamore » product (KAP; only KAP for II based systems) in RIS; these values were analyzed. Data pre-processing included correcting typographical errors and cross-verifying CAK and KAP. The most frequent high and low dose FGI procedures were identified and corresponding CAK and KAP values were compared. Results: Out of 27,251 procedures within this time period, most frequent high and low dose procedures were chemo/immuno-embolization (n=1967) and abscess drainage (n=1821). Mean KAP for embolization and abscess drainage procedures were 260,657, 310,304 and 94,908 mGycm{sup 2}, and 14,497, 15,040 and 6307 mGycm{sup 2} using II-, FPD- and FPD with ClarityIQ- based systems, respectively. Statistically significant differences were observed in KAP values for embolization procedures with respect to different systems but for abscess drainage procedures significant differences were only noted between systems with FPD and FPD with ClarityIQ (p<0.05). Mean CAK reduced significantly from 823 to 308 mGy and from 43 to 21 mGy for embolization and abscess drainage procedures, respectively, in transitioning to FPD systems with ClarityIQ (p<0.05). Conclusion: While transitioning from II- to FPD- based systems was not associated with dose reduction for the most frequently performed FGI procedures, substantial dose reduction was noted with relatively newer systems and dose reduction software.« less

A Monte Carlo study on quantifying the amount of dose reduction by shielding the superficial organs of an Iranian 11-year-old boy

PubMed Central

Akhlaghi, Parisa; Hoseinian-Azghadi, Elie; Miri-Hakimabad, Hashem; Rafat-Motavalli, Laleh

2016-01-01

A method for minimizing organ dose during computed tomography examinations is the use of shielding to protect superficial organs. There are some scientific reports that usage of shielding technique reduces the surface dose to patients with no appreciable loss in diagnostic quality. Therefore, in this Monte Carlo study based on the phantom of a 11-year-old Iranian boy, the effect of using an optimized shield on dose reduction to body organs was quantified. Based on the impact of shield on image quality, lead shields with thicknesses of 0.2 and 0.4 mm were considered for organs exposed directly and indirectly in the scan range, respectively. The results showed that there is 50%–62% reduction in amounts of dose for organs located fully or partly in the scan range at different tube voltages and modeling the true location of all organs in human anatomy, especially the ones located at the border of the scan, range affects the results up to 49%. PMID:28144117

Effectiveness of disinfectant treatments for inactivating Piscirickettsia salmonis.

PubMed

Muniesa, A; Escobar-Dodero, J; Silva, N; Henríquez, P; Bustos, P; Perez, A M; Mardones, F O

2018-03-08

This short communication investigated in vitro differences between commercial disinfectants types (n = 36), doses of application, and time of action in the elimination of Piscirickettsia salmonis, the most important bacterium affecting farmed salmon in Chile. Seven different treatments were examined, including active and inactive chlorine dioxides, glutaraldehyde, hypochlorite disinfectants and detergents, peracetic acid, peroxides and other miscellaneous methods A 3 replicate set of each of the sample groups was stored at 20 °C and 95% relative humidity and retested after 1, 5 and 30 min with varying doses (low, recommended and high doses). Multiple comparison tests were performed for the mean log CFU/ml among different disinfectant types, dose (ppm) and time of exposure (minutes) on the reduction of P. salmonis. Overall, disinfection using peracetic acid, peroxides, and both active and inactive chlorine dioxides caused significantly higher reduction of >7.5 log CFU/ml in samples, compared to other tested sanitizers. The lowest reduction was obtained after disinfection with hypochlorite detergents. As expected, as doses and time of action increase, there was a significant reduction of the overall counts of P. salmonis. However, at lowest doses, only use of paracetic acids resulted in zero counts. Implementation of effective protocols, making use of adequate disinfectants, may enhance biosecurity, and ultimately, mitigate the impact of P. salmonis in farmed salmon. Copyright © 2018. Published by Elsevier B.V.

A combination of spatial and recursive temporal filtering for noise reduction when using region of interest (ROI) fluoroscopy for patient dose reduction in image guided vascular interventions with significant anatomical motion

NASA Astrophysics Data System (ADS)

Setlur Nagesh, S. V.; Khobragade, P.; Ionita, C.; Bednarek, D. R.; Rudin, S.

2015-03-01

Because x-ray based image-guided vascular interventions are minimally invasive they are currently the most preferred method of treating disorders such as stroke, arterial stenosis, and aneurysms; however, the x-ray exposure to the patient during long image-guided interventional procedures could cause harmful effects such as cancer in the long run and even tissue damage in the short term. ROI fluoroscopy reduces patient dose by differentially attenuating the incident x-rays outside the region-of-interest. To reduce the noise in the dose-reduced regions previously recursive temporal filtering was successfully demonstrated for neurovascular interventions. However, in cardiac interventions, anatomical motion is significant and excessive recursive filtering could cause blur. In this work the effects of three noise-reduction schemes, including recursive temporal filtering, spatial mean filtering, and a combination of spatial and recursive temporal filtering, were investigated in a simulated ROI dose-reduced cardiac intervention. First a model to simulate the aortic arch and its movement was built. A coronary stent was used to simulate a bioprosthetic valve used in TAVR procedures and was deployed under dose-reduced ROI fluoroscopy during the simulated heart motion. The images were then retrospectively processed for noise reduction in the periphery, using recursive temporal filtering, spatial filtering and a combination of both. Quantitative metrics for all three noise reduction schemes are calculated and are presented as results. From these it can be concluded that with significant anatomical motion, a combination of spatial and recursive temporal filtering scheme is best suited for reducing the excess quantum noise in the periphery. This new noise-reduction technique in combination with ROI fluoroscopy has the potential for substantial patient-dose savings in cardiac interventions.

Variability in CT lung-nodule volumetry: Effects of dose reduction and reconstruction methods.

PubMed

Young, Stefano; Kim, Hyun J Grace; Ko, Moe Moe; Ko, War War; Flores, Carlos; McNitt-Gray, Michael F

2015-05-01

Measuring the size of nodules on chest CT is important for lung cancer staging and measuring therapy response. 3D volumetry has been proposed as a more robust alternative to 1D and 2D sizing methods. There have also been substantial advances in methods to reduce radiation dose in CT. The purpose of this work was to investigate the effect of dose reduction and reconstruction methods on variability in 3D lung-nodule volumetry. Reduced-dose CT scans were simulated by applying a noise-addition tool to the raw (sinogram) data from clinically indicated patient scans acquired on a multidetector-row CT scanner (Definition Flash, Siemens Healthcare). Scans were simulated at 25%, 10%, and 3% of the dose of their clinical protocol (CTDIvol of 20.9 mGy), corresponding to CTDIvol values of 5.2, 2.1, and 0.6 mGy. Simulated reduced-dose data were reconstructed with both conventional filtered backprojection (B45 kernel) and iterative reconstruction methods (SAFIRE: I44 strength 3 and I50 strength 3). Three lab technologist readers contoured "measurable" nodules in 33 patients under each of the different acquisition/reconstruction conditions in a blinded study design. Of the 33 measurable nodules, 17 were used to estimate repeatability with their clinical reference protocol, as well as interdose and inter-reconstruction-method reproducibilities. The authors compared the resulting distributions of proportional differences across dose and reconstruction methods by analyzing their means, standard deviations (SDs), and t-test and F-test results. The clinical-dose repeatability experiment yielded a mean proportional difference of 1.1% and SD of 5.5%. The interdose reproducibility experiments gave mean differences ranging from -5.6% to -1.7% and SDs ranging from 6.3% to 9.9%. The inter-reconstruction-method reproducibility experiments gave mean differences of 2.0% (I44 strength 3) and -0.3% (I50 strength 3), and SDs were identical at 7.3%. For the subset of repeatability cases, inter-reconstruction-method mean/SD pairs were (1.4%, 6.3%) and (-0.7%, 7.2%) for I44 strength 3 and I50 strength 3, respectively. Analysis of representative nodules confirmed that reader variability appeared unaffected by dose or reconstruction method. Lung-nodule volumetry was extremely robust to the radiation-dose level, down to the minimum scanner-supported dose settings. In addition, volumetry was robust to the reconstruction methods used in this study, which included both conventional filtered backprojection and iterative methods.

Edge enhancement algorithm for low-dose X-ray fluoroscopic imaging.

PubMed

Lee, Min Seok; Park, Chul Hee; Kang, Moon Gi

2017-12-01

Low-dose X-ray fluoroscopy has continually evolved to reduce radiation risk to patients during clinical diagnosis and surgery. However, the reduction in dose exposure causes quality degradation of the acquired images. In general, an X-ray device has a time-average pre-processor to remove the generated quantum noise. However, this pre-processor causes blurring and artifacts within the moving edge regions, and noise remains in the image. During high-pass filtering (HPF) to enhance edge detail, this noise in the image is amplified. In this study, a 2D edge enhancement algorithm comprising region adaptive HPF with the transient improvement (TI) method, as well as artifacts and noise reduction (ANR), was developed for degraded X-ray fluoroscopic images. The proposed method was applied in a static scene pre-processed by a low-dose X-ray fluoroscopy device. First, the sharpness of the X-ray image was improved using region adaptive HPF with the TI method, which facilitates sharpening of edge details without overshoot problems. Then, an ANR filter that uses an edge directional kernel was developed to remove the artifacts and noise that can occur during sharpening, while preserving edge details. The quantitative and qualitative results obtained by applying the developed method to low-dose X-ray fluoroscopic images and visually and numerically comparing the final images with images improved using conventional edge enhancement techniques indicate that the proposed method outperforms existing edge enhancement methods in terms of objective criteria and subjective visual perception of the actual X-ray fluoroscopic image. The developed edge enhancement algorithm performed well when applied to actual low-dose X-ray fluoroscopic images, not only by improving the sharpness, but also by removing artifacts and noise, including overshoot. Copyright © 2017 Elsevier B.V. All rights reserved.

Six steps to a successful dose-reduction strategy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, M.

1995-03-01

The increased importance of demonstrating achievement of the ALARA principle has helped produce a proliferation of dose-reduction ideas. Across a company there may be many dose-reduction items being pursued in a variety of areas. However, companies have a limited amount of resource and, therefore, to ensure funding is directed to those items which will produce the most benefit and that all areas apply a common policy, requires the presence of a dose-reduction strategy. Six steps were identified in formulating the dose-reduction strategy for Rolls-Royce and Associates (RRA): (1) collating the ideas; (2) quantitatively evaluating them on a common basis; (3)more » prioritizing the ideas in terms of cost benefit, (4) implementation of the highest priority items; (5) monitoring their success; (6) periodically reviewing the strategy. Inherent in producing the dose-reduction strategy has been a comprehensive dose database and the RRA-developed dose management computer code DOMAIN, which allows prediction of dose rates and dose. The database enabled high task dose items to be identified, assisted in evaluating dose benefits, and monitored dose trends once items had been implemented. The DOMAIN code was used both in quantifying some of the project dose benefits and its results, such as dose contours, used in some of the dose-reduction items themselves. In all, over fifty dose-reduction items were evaluated in the strategy process and the items which will give greatest benefit are being implemented. The strategy has been successful in giving renewed impetus and direction to dose-reduction management.« less

Image-based metal artifact reduction in x-ray computed tomography utilizing local anatomical similarity

NASA Astrophysics Data System (ADS)

Dong, Xue; Yang, Xiaofeng; Rosenfield, Jonathan; Elder, Eric; Dhabaan, Anees

2017-03-01

X-ray computed tomography (CT) is widely used in radiation therapy treatment planning in recent years. However, metal implants such as dental fillings and hip prostheses can cause severe bright and dark streaking artifacts in reconstructed CT images. These artifacts decrease image contrast and degrade HU accuracy, leading to inaccuracies in target delineation and dose calculation. In this work, a metal artifact reduction method is proposed based on the intrinsic anatomical similarity between neighboring CT slices. Neighboring CT slices from the same patient exhibit similar anatomical features. Exploiting this anatomical similarity, a gamma map is calculated as a weighted summation of relative HU error and distance error for each pixel in an artifact-corrupted CT image relative to a neighboring, artifactfree image. The minimum value in the gamma map for each pixel is used to identify an appropriate pixel from the artifact-free CT slice to replace the corresponding artifact-corrupted pixel. With the proposed method, the mean CT HU error was reduced from 360 HU and 460 HU to 24 HU and 34 HU on head and pelvis CT images, respectively. Dose calculation accuracy also improved, as the dose difference was reduced from greater than 20% to less than 4%. Using 3%/3mm criteria, the gamma analysis failure rate was reduced from 23.25% to 0.02%. An image-based metal artifact reduction method is proposed that replaces corrupted image pixels with pixels from neighboring CT slices free of metal artifacts. This method is shown to be capable of suppressing streaking artifacts, thereby improving HU and dose calculation accuracy.

Optimization of the scan protocols for CT-based material extraction in small animal PET/CT studies

NASA Astrophysics Data System (ADS)

Yang, Ching-Ching; Yu, Jhih-An; Yang, Bang-Hung; Wu, Tung-Hsin

2013-12-01

We investigated the effects of scan protocols on CT-based material extraction to minimize radiation dose while maintaining sufficient image information in small animal studies. The phantom simulation experiments were performed with the high dose (HD), medium dose (MD) and low dose (LD) protocols at 50, 70 and 80 kVp with varying mA s. The reconstructed CT images were segmented based on Hounsfield unit (HU)-physical density (ρ) calibration curves and the dual-energy CT-based (DECT) method. Compared to the (HU;ρ) method performed on CT images acquired with the 80 kVp HD protocol, a 2-fold improvement in segmentation accuracy and a 7.5-fold reduction in radiation dose were observed when the DECT method was performed on CT images acquired with the 50/80 kVp LD protocol, showing the possibility to reduce radiation dose while achieving high segmentation accuracy.

Behavioral and Psychological Predictors of Chemotherapy Adherence in Patients with Advanced Non-Small-Cell Lung Cancer

PubMed Central

Greer, Joseph A.; Pirl, William F.; Park, Elyse R.; Lynch, Thomas J.; Temel, Jennifer S.

2013-01-01

Objective Dose delays and reductions in chemotherapy due to hematologic toxicities are common among patients with advanced non-small-cell lung cancer (NSCLC). However, limited data exist on behavioral or psychological predictors of chemotherapy adherence. The goal of this study was to explore the frequency and clinical predictors of infusion dose delays and reductions in this patient population. Methods Fifty patients newly diagnosed with advanced NSCLC of high performance status (ECOG PS=0-1) completed baseline assessments on quality of life (FACT-L) and mood (HADS) within eight weeks of diagnosis. Participants were followed prospectively for six months. Chemotherapy dosing data came from medical chart review. Results All patients received chemotherapy during the course of the study, beginning with either a platinum-based doublet (74%), an oral epidermal growth factor receptor-tyrosine kinase inhibitor (14%), or a parenteral single agent (12%). Forty percent (N=20) of patients had either a dose delay (38%) and/or reduction (16%) in their scheduled infusions. Fisher’s exact tests showed that patients who experienced neutropenia, smoked at the time of diagnosis, or reported heightened baseline anxiety were significantly more likely to experience dose delays or reductions. There were no associations between chemotherapy adherence and patient demographics, performance status, or quality of life. Conclusion In this sample, over one-third of patients with advanced NSCLC experienced either a dose delay or reduction in prescribed chemotherapy regimens. Behavioral and psychological factors, such as tobacco use and anxiety symptoms, appear to play an important role in chemotherapy adherence, though further study is required to confirm these findings. PMID:19027443

Can use of adaptive statistical iterative reconstruction reduce radiation dose in unenhanced head CT? An analysis of qualitative and quantitative image quality

PubMed Central

Heggen, Kristin Livelten; Pedersen, Hans Kristian; Andersen, Hilde Kjernlie; Martinsen, Anne Catrine T

2016-01-01

Background Iterative reconstruction can reduce image noise and thereby facilitate dose reduction. Purpose To evaluate qualitative and quantitative image quality for full dose and dose reduced head computed tomography (CT) protocols reconstructed using filtered back projection (FBP) and adaptive statistical iterative reconstruction (ASIR). Material and Methods Fourteen patients undergoing follow-up head CT were included. All patients underwent full dose (FD) exam and subsequent 15% dose reduced (DR) exam, reconstructed using FBP and 30% ASIR. Qualitative image quality was assessed using visual grading characteristics. Quantitative image quality was assessed using ROI measurements in cerebrospinal fluid (CSF), white matter, peripheral and central gray matter. Additionally, quantitative image quality was measured in Catphan and vendor’s water phantom. Results There was no significant difference in qualitative image quality between FD FBP and DR ASIR. Comparing same scan FBP versus ASIR, a noise reduction of 28.6% in CSF and between −3.7 and 3.5% in brain parenchyma was observed. Comparing FD FBP versus DR ASIR, a noise reduction of 25.7% in CSF, and −7.5 and 6.3% in brain parenchyma was observed. Image contrast increased in ASIR reconstructions. Contrast-to-noise ratio was improved in DR ASIR compared to FD FBP. In phantoms, noise reduction was in the range of 3 to 28% with image content. Conclusion There was no significant difference in qualitative image quality between full dose FBP and dose reduced ASIR. CNR improved in DR ASIR compared to FD FBP mostly due to increased contrast, not reduced noise. Therefore, we recommend using caution if reducing dose and applying ASIR to maintain image quality. PMID:27583169

Influence of different treatment techniques on radiation dose to the LAD coronary artery

PubMed Central

Nieder, Carsten; Schill, Sabine; Kneschaurek, Peter; Molls, Michael

2007-01-01

Background The purpose of this proof-of-principle study was to test the ability of an intensity-modulated radiotherapy (IMRT) technique to reduce the radiation dose to the heart plus the left ventricle and a coronary artery. Radiation-induced heart disease might be a serious complication in long-term cancer survivors. Methods Planning CT scans from 6 female patients were available. They were part of a previous study of mediastinal IMRT for target volumes used in lymphoma treatment that included 8 patients and represent all cases where the left anterior descending coronary artery (LAD) could be contoured. We compared 6 MV AP/PA opposed fields to a 3D conformal 4-field technique and an optimised 7-field step-and-shoot IMRT technique and evaluated DVH's for several structures. The planning system was BrainSCAN 5.21 (BrainLAB, Heimstetten, Germany). Results IMRT maintained target volume coverage but resulted in better dose reduction to the heart, left ventricle and LAD than the other techniques. Selective dose reduction could be accomplished, although not to the degree initially attempted. The median LAD dose was approximately 50% lower with IMRT. In 5 out of 6 patients, IMRT was the best technique with regard to heart sparing. Conclusion IMRT techniques are able to reduce the radiation dose to the heart. In addition to dose reduction to whole heart, individualised dose distributions can be created, which spare, e.g., one ventricle plus one of the coronary arteries. Certain patients with well-defined vessel pathology might profit from an approach of general heart sparing with further selective dose reduction, accounting for the individual aspects of pre-existing damage. PMID:17547777

Radiation dose reduction in medical x-ray CT via Fourier-based iterative reconstruction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fahimian, Benjamin P.; Zhao Yunzhe; Huang Zhifeng

Purpose: A Fourier-based iterative reconstruction technique, termed Equally Sloped Tomography (EST), is developed in conjunction with advanced mathematical regularization to investigate radiation dose reduction in x-ray CT. The method is experimentally implemented on fan-beam CT and evaluated as a function of imaging dose on a series of image quality phantoms and anonymous pediatric patient data sets. Numerical simulation experiments are also performed to explore the extension of EST to helical cone-beam geometry. Methods: EST is a Fourier based iterative algorithm, which iterates back and forth between real and Fourier space utilizing the algebraically exact pseudopolar fast Fourier transform (PPFFT). Inmore » each iteration, physical constraints and mathematical regularization are applied in real space, while the measured data are enforced in Fourier space. The algorithm is automatically terminated when a proposed termination criterion is met. Experimentally, fan-beam projections were acquired by the Siemens z-flying focal spot technology, and subsequently interleaved and rebinned to a pseudopolar grid. Image quality phantoms were scanned at systematically varied mAs settings, reconstructed by EST and conventional reconstruction methods such as filtered back projection (FBP), and quantified using metrics including resolution, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs). Pediatric data sets were reconstructed at their original acquisition settings and additionally simulated to lower dose settings for comparison and evaluation of the potential for radiation dose reduction. Numerical experiments were conducted to quantify EST and other iterative methods in terms of image quality and computation time. The extension of EST to helical cone-beam CT was implemented by using the advanced single-slice rebinning (ASSR) method. Results: Based on the phantom and pediatric patient fan-beam CT data, it is demonstrated that EST reconstructions with the lowest scanner flux setting of 39 mAs produce comparable image quality, resolution, and contrast relative to FBP with the 140 mAs flux setting. Compared to the algebraic reconstruction technique and the expectation maximization statistical reconstruction algorithm, a significant reduction in computation time is achieved with EST. Finally, numerical experiments on helical cone-beam CT data suggest that the combination of EST and ASSR produces reconstructions with higher image quality and lower noise than the Feldkamp Davis and Kress (FDK) method and the conventional ASSR approach. Conclusions: A Fourier-based iterative method has been applied to the reconstruction of fan-bean CT data with reduced x-ray fluence. This method incorporates advantageous features in both real and Fourier space iterative schemes: using a fast and algebraically exact method to calculate forward projection, enforcing the measured data in Fourier space, and applying physical constraints and flexible regularization in real space. Our results suggest that EST can be utilized for radiation dose reduction in x-ray CT via the readily implementable technique of lowering mAs settings. Numerical experiments further indicate that EST requires less computation time than several other iterative algorithms and can, in principle, be extended to helical cone-beam geometry in combination with the ASSR method.« less

Radiation dose reduction in medical x-ray CT via Fourier-based iterative reconstruction

PubMed Central

Fahimian, Benjamin P.; Zhao, Yunzhe; Huang, Zhifeng; Fung, Russell; Mao, Yu; Zhu, Chun; Khatonabadi, Maryam; DeMarco, John J.; Osher, Stanley J.; McNitt-Gray, Michael F.; Miao, Jianwei

2013-01-01

Purpose: A Fourier-based iterative reconstruction technique, termed Equally Sloped Tomography (EST), is developed in conjunction with advanced mathematical regularization to investigate radiation dose reduction in x-ray CT. The method is experimentally implemented on fan-beam CT and evaluated as a function of imaging dose on a series of image quality phantoms and anonymous pediatric patient data sets. Numerical simulation experiments are also performed to explore the extension of EST to helical cone-beam geometry. Methods: EST is a Fourier based iterative algorithm, which iterates back and forth between real and Fourier space utilizing the algebraically exact pseudopolar fast Fourier transform (PPFFT). In each iteration, physical constraints and mathematical regularization are applied in real space, while the measured data are enforced in Fourier space. The algorithm is automatically terminated when a proposed termination criterion is met. Experimentally, fan-beam projections were acquired by the Siemens z-flying focal spot technology, and subsequently interleaved and rebinned to a pseudopolar grid. Image quality phantoms were scanned at systematically varied mAs settings, reconstructed by EST and conventional reconstruction methods such as filtered back projection (FBP), and quantified using metrics including resolution, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs). Pediatric data sets were reconstructed at their original acquisition settings and additionally simulated to lower dose settings for comparison and evaluation of the potential for radiation dose reduction. Numerical experiments were conducted to quantify EST and other iterative methods in terms of image quality and computation time. The extension of EST to helical cone-beam CT was implemented by using the advanced single-slice rebinning (ASSR) method. Results: Based on the phantom and pediatric patient fan-beam CT data, it is demonstrated that EST reconstructions with the lowest scanner flux setting of 39 mAs produce comparable image quality, resolution, and contrast relative to FBP with the 140 mAs flux setting. Compared to the algebraic reconstruction technique and the expectation maximization statistical reconstruction algorithm, a significant reduction in computation time is achieved with EST. Finally, numerical experiments on helical cone-beam CT data suggest that the combination of EST and ASSR produces reconstructions with higher image quality and lower noise than the Feldkamp Davis and Kress (FDK) method and the conventional ASSR approach. Conclusions: A Fourier-based iterative method has been applied to the reconstruction of fan-bean CT data with reduced x-ray fluence. This method incorporates advantageous features in both real and Fourier space iterative schemes: using a fast and algebraically exact method to calculate forward projection, enforcing the measured data in Fourier space, and applying physical constraints and flexible regularization in real space. Our results suggest that EST can be utilized for radiation dose reduction in x-ray CT via the readily implementable technique of lowering mAs settings. Numerical experiments further indicate that EST requires less computation time than several other iterative algorithms and can, in principle, be extended to helical cone-beam geometry in combination with the ASSR method. PMID:23464329

Dose tracking and dose auditing in a comprehensive computed tomography dose-reduction program.

PubMed

Duong, Phuong-Anh; Little, Brent P

2014-08-01

Implementation of a comprehensive computed tomography (CT) radiation dose-reduction program is a complex undertaking, requiring an assessment of baseline doses, an understanding of dose-saving techniques, and an ongoing appraisal of results. We describe the role of dose tracking in planning and executing a dose-reduction program and discuss the use of the American College of Radiology CT Dose Index Registry at our institution. We review the basics of dose-related CT scan parameters, the components of the dose report, and the dose-reduction techniques, showing how an understanding of each technique is important in effective auditing of "outlier" doses identified by dose tracking. Copyright © 2014 Elsevier Inc. All rights reserved.

Dosimetric evaluation of intrafractional tumor motion by means of a robot driven phantom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richter, Anne; Wilbert, Juergen; Flentje, Michael

2011-10-15

Purpose: The aim of the work was to investigate the influence of intrafractional tumor motion to the accumulated (absorbed) dose. The accumulated dose was determined by means of calculations and measurements with a robot driven motion phantom. Methods: Different motion scenarios and compensation techniques were realized in a phantom study to investigate the influence of motion on image acquisition, dose calculation, and dose measurement. The influence of motion on the accumulated dose was calculated by employing two methods (a model based and a voxel based method). Results: Tumor motion resulted in a blurring of steep dose gradients and a reductionmore » of dose at the periphery of the target. A systematic variation of motion parameters allowed the determination of the main influence parameters on the accumulated dose. The key parameters with the greatest influence on dose were the mean amplitude and the pattern of motion. Investigations on necessary safety margins to compensate for dose reduction have shown that smaller safety margins are sufficient, if the developed concept with optimized margins (OPT concept) was used instead of the standard internal target volume (ITV) concept. Both calculation methods were a reasonable approximation of the measured dose with the voxel based method being in better agreement with the measurements. Conclusions: Further evaluation of available systems and algorithms for dose accumulation are needed to create guidelines for the verification of the accumulated dose.« less

Half-Fan-Based Intensity-Weighted Region-of-Interest Imaging for Low-Dose Cone-Beam CT in Image-Guided Radiation Therapy.

PubMed

Yoo, Boyeol; Son, Kihong; Pua, Rizza; Kim, Jinsung; Solodov, Alexander; Cho, Seungryong

2016-10-01

With the increased use of computed tomography (CT) in clinics, dose reduction is the most important feature people seek when considering new CT techniques or applications. We developed an intensity-weighted region-of-interest (IWROI) imaging method in an exact half-fan geometry to reduce the imaging radiation dose to patients in cone-beam CT (CBCT) for image-guided radiation therapy (IGRT). While dose reduction is highly desirable, preserving the high-quality images of the ROI is also important for target localization in IGRT. An intensity-weighting (IW) filter made of copper was mounted in place of a bowtie filter on the X-ray tube unit of an on-board imager (OBI) system such that the filter can substantially reduce radiation exposure to the outer ROI. In addition to mounting the IW filter, the lead-blade collimation of the OBI was adjusted to produce an exact half-fan scanning geometry for a further reduction of the radiation dose. The chord-based rebinned backprojection-filtration (BPF) algorithm in circular CBCT was implemented for image reconstruction, and a humanoid pelvis phantom was used for the IWROI imaging experiment. The IWROI image of the phantom was successfully reconstructed after beam-quality correction, and it was registered to the reference image within an acceptable level of tolerance. Dosimetric measurements revealed that the dose is reduced by approximately 61% in the inner ROI and by 73% in the outer ROI compared to the conventional bowtie filter-based half-fan scan. The IWROI method substantially reduces the imaging radiation dose and provides reconstructed images with an acceptable level of quality for patient setup and target localization. The proposed half-fan-based IWROI imaging technique can add a valuable option to CBCT in IGRT applications.

Does dose matter in reducing gestational weight gain in exercise interventions? A systematic review of literature

PubMed Central

McDonald, Samantha M.; Liu, Jihong; Wilcox, Sara; Lau, Erica Y.; Archer, Edward

2015-01-01

Objective This purpose of this review was to examine the relationship between exercise dose and reductions in weight gain during pregnancy in exercise interventions. Design and Methods Four electronic research databases (PubMed, Web of Science, CINAHL, and Academic Search Premiere) were used to identify exercise interventions conducted with pregnant women. Eligible articles must have satisfied the following criteria: inclusion of a control condition, exercise as a major intervention component, weight gain measured and reported for each experimental condition, description of exercise dose (frequency, intensity and duration), and utilized an adequate number of control conditions to assess independent effects of exercise on weight gain. Results The literature search identified 4837 articles, of these, 174 abstracts were screened and 21 intervention studies (18 exercise-only, 3 exercise/diet) were eligible for review. Only 38% of the interventions achieved statistically significant reductions in weight gain during pregnancy. Successful interventions possessed higher adherence and lower attrition rates and were predominantly conducted among normal weight populations. No clear patterns or consistencies of exercise dose and weight gain were evident. Conclusions Adherence and retention rates were strong contributors to the success of exercise interventions on weight gain during pregnancy. However, an exercise dose associated with reductions in weight gain was unquantifiable among these interventions. It is strongly suggested that future researchers investigate methods to increase adherence and compliance, especially among overweight and obese women, and utilize objective measurement tools to accurately evaluate exercise dose performed by the participants and the impact on both body composition and weight gain. PMID:25846125

Poisson-Gaussian Noise Analysis and Estimation for Low-Dose X-ray Images in the NSCT Domain.

PubMed

Lee, Sangyoon; Lee, Min Seok; Kang, Moon Gi

2018-03-29

The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of each subband in the multiscale domain is the most important factor in performing noise reduction, with non-subsampled contourlet transform (NSCT) representing an effective method for scale and direction decomposition. In this study, we use artificially generated noise to analyze and estimate the Poisson-Gaussian noise of low-dose X-ray images in the NSCT domain. The noise distribution of the subband coefficients is analyzed using the noiseless low-band coefficients and the variance of the noisy subband coefficients. The noise-after-transform also follows a Poisson-Gaussian distribution, and the relationship between the noise parameters of the subband and the full-band image is identified. We then analyze noise of actual images to validate the theoretical analysis. Comparison of the proposed noise estimation method with an existing noise reduction method confirms that the proposed method outperforms traditional methods.

Poisson–Gaussian Noise Analysis and Estimation for Low-Dose X-ray Images in the NSCT Domain

PubMed Central

Lee, Sangyoon; Lee, Min Seok; Kang, Moon Gi

2018-01-01

The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of each subband in the multiscale domain is the most important factor in performing noise reduction, with non-subsampled contourlet transform (NSCT) representing an effective method for scale and direction decomposition. In this study, we use artificially generated noise to analyze and estimate the Poisson–Gaussian noise of low-dose X-ray images in the NSCT domain. The noise distribution of the subband coefficients is analyzed using the noiseless low-band coefficients and the variance of the noisy subband coefficients. The noise-after-transform also follows a Poisson–Gaussian distribution, and the relationship between the noise parameters of the subband and the full-band image is identified. We then analyze noise of actual images to validate the theoretical analysis. Comparison of the proposed noise estimation method with an existing noise reduction method confirms that the proposed method outperforms traditional methods. PMID:29596335

Optimization of spatiotemporally fractionated radiotherapy treatments with bounds on the achievable benefit

NASA Astrophysics Data System (ADS)

Gaddy, Melissa R.; Yıldız, Sercan; Unkelbach, Jan; Papp, Dávid

2018-01-01

Spatiotemporal fractionation schemes, that is, treatments delivering different dose distributions in different fractions, can potentially lower treatment side effects without compromising tumor control. This can be achieved by hypofractionating parts of the tumor while delivering approximately uniformly fractionated doses to the surrounding tissue. Plan optimization for such treatments is based on biologically effective dose (BED); however, this leads to computationally challenging nonconvex optimization problems. Optimization methods that are in current use yield only locally optimal solutions, and it has hitherto been unclear whether these plans are close to the global optimum. We present an optimization framework to compute rigorous bounds on the maximum achievable normal tissue BED reduction for spatiotemporal plans. The approach is demonstrated on liver tumors, where the primary goal is to reduce mean liver BED without compromising any other treatment objective. The BED-based treatment plan optimization problems are formulated as quadratically constrained quadratic programming (QCQP) problems. First, a conventional, uniformly fractionated reference plan is computed using convex optimization. Then, a second, nonconvex, QCQP model is solved to local optimality to compute a spatiotemporally fractionated plan that minimizes mean liver BED, subject to the constraints that the plan is no worse than the reference plan with respect to all other planning goals. Finally, we derive a convex relaxation of the second model in the form of a semidefinite programming problem, which provides a rigorous lower bound on the lowest achievable mean liver BED. The method is presented on five cases with distinct geometries. The computed spatiotemporal plans achieve 12-35% mean liver BED reduction over the optimal uniformly fractionated plans. This reduction corresponds to 79-97% of the gap between the mean liver BED of the uniform reference plans and our lower bounds on the lowest achievable mean liver BED. The results indicate that spatiotemporal treatments can achieve substantial reductions in normal tissue dose and BED, and that local optimization techniques provide high-quality plans that are close to realizing the maximum potential normal tissue dose reduction.

A comparison of mean parotid gland dose with measures of parotid gland function after radiotherapy for head-and-neck cancer: Implications for future trials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roesink, Judith M.; Schipper, Maria; Busschers, Wim

2005-11-15

Purpose: To determine the most adequate parameter to measure the consequences of reducing the parotid gland dose. Methods and Materials: One hundred eight patients treated with radiotherapy for various malignancies of the head and neck were prospectively evaluated using three methods. Parotid gland function was objectively determined by measuring stimulated parotid flow using Lashley cups and scintigraphy. To assess xerostomia-related quality of life, the head-and-neck cancer module European Organization for Research and Treatment of Cancer QLQ (Quality of Life Questionnaire) H and N35 was used. Measurements took place before radiotherapy and 6 weeks and 12 months after the completion ofmore » radiotherapy. Complication was defined for each method using cutoff values. The correlation between these complications and the mean parotid gland dose was investigated to find the best measure for parotid gland function. Results: For both flow and scintigraphy data, the best definition for objective parotid gland toxicity seemed to be reduction of stimulated parotid flow to {<=}25% of the preradiotherapy flow. Of all the subjective variables, only the single item dry mouth 6 weeks after radiotherapy was found to be significant. The best correlation with the mean parotid gland dose was found for the stimulated flow measurements. The predictive ability was the highest for the time point 1 year after radiotherapy. Subjective findings did not correlate with the mean parotid dose. Conclusions: Stimulated flow measurements using Lashley cups, with a complication defined as flow {<=}25% of the preradiotherapy output, correlated best with the mean parotid gland dose. When reduction of the mean dose to the parotid gland is intended, the stimulated flow measurement is the best method for evaluating parotid gland function.« less

A Highly Durable RNAi Therapeutic Inhibitor of PCSK9

PubMed Central

Fitzgerald, Kevin; White, Suellen; Borodovsky, Anna; Bettencourt, Brian R.; Strahs, Andrew; Clausen, Valerie; Wijngaard, Peter; Horton, Jay D.; Taubel, Jorg; Brooks, Ashley; Fernando, Chamikara; Kauffman, Robert S.; Kallend, David; Vaishnaw, Akshay; Simon, Amy

2018-01-01

BACKGROUND Inclisiran (ALN-PCSsc) is a long-acting RNA interference (RNAi) therapeutic agent that inhibits the synthesis of proprotein convertase subtilisin–kexin type 9 (PCSK9), a target for the lowering of low-density lipoprotein (LDL) cholesterol. METHODS In this phase 1 trial, we randomly assigned healthy volunteers with an LDL cholesterol level of at least 100 mg per deciliter in a 3:1 ratio to receive a subcutaneous injection of inclisiran or placebo in either a single-ascending-dose phase (at a dose of 25, 100, 300, 500, or 800 mg) or a multiple-dose phase (125 mg weekly for four doses, 250 mg every other week for two doses, or 300 or 500 mg monthly for two doses, with or without concurrent statin therapy); each dose cohort included four to eight participants. Safety, the side-effect profile, and pharmacodynamic measures (PCSK9 level, LDL cholesterol level, and exploratory lipid variables) were evaluated. RESULTS The most common adverse events were cough, musculoskeletal pain, nasopharyngitis, headache, back pain, and diarrhea. All the adverse events were mild or moderate in severity. There were no serious adverse events or discontinuations due to adverse events. There was one grade 3 elevation in the γ-glutamyltransferase level, which was considered by the investigator to be related to statin therapy. In the single-dose phase, inclisiran doses of 300 mg or more reduced the PCSK9 level (up to a least-squares mean reduction of 74.5% from baseline to day 84), and doses of 100 mg or more reduced the LDL cholesterol level (up to a least-squares mean reduction of 50.6% from baseline). Reductions in the levels of PCSK9 and LDL cholesterol were maintained at day 180 for doses of 300 mg or more. All multiple-dose regimens reduced the levels of PCSK9 (up to a least-squares mean reduction of 83.8% from baseline to day 84) and LDL cholesterol (up to a least-squares mean reduction of 59.7% from baseline to day 84). CONCLUSIONS In this phase 1 trial, no serious adverse events were observed with inclisiran. Doses of 300 mg or more (in single or multiple doses) significantly reduced levels of PCSK9 and LDL cholesterol for at least 6 months. (Funded by Alnylam Pharmaceuticals and the Medicines Company; ClinicalTrials.gov number, NCT02314442.) PMID:27959715

Radiation dose reduction in medical x-ray CT via Fourier-based iterative reconstruction.

PubMed

Fahimian, Benjamin P; Zhao, Yunzhe; Huang, Zhifeng; Fung, Russell; Mao, Yu; Zhu, Chun; Khatonabadi, Maryam; DeMarco, John J; Osher, Stanley J; McNitt-Gray, Michael F; Miao, Jianwei

2013-03-01

A Fourier-based iterative reconstruction technique, termed Equally Sloped Tomography (EST), is developed in conjunction with advanced mathematical regularization to investigate radiation dose reduction in x-ray CT. The method is experimentally implemented on fan-beam CT and evaluated as a function of imaging dose on a series of image quality phantoms and anonymous pediatric patient data sets. Numerical simulation experiments are also performed to explore the extension of EST to helical cone-beam geometry. EST is a Fourier based iterative algorithm, which iterates back and forth between real and Fourier space utilizing the algebraically exact pseudopolar fast Fourier transform (PPFFT). In each iteration, physical constraints and mathematical regularization are applied in real space, while the measured data are enforced in Fourier space. The algorithm is automatically terminated when a proposed termination criterion is met. Experimentally, fan-beam projections were acquired by the Siemens z-flying focal spot technology, and subsequently interleaved and rebinned to a pseudopolar grid. Image quality phantoms were scanned at systematically varied mAs settings, reconstructed by EST and conventional reconstruction methods such as filtered back projection (FBP), and quantified using metrics including resolution, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs). Pediatric data sets were reconstructed at their original acquisition settings and additionally simulated to lower dose settings for comparison and evaluation of the potential for radiation dose reduction. Numerical experiments were conducted to quantify EST and other iterative methods in terms of image quality and computation time. The extension of EST to helical cone-beam CT was implemented by using the advanced single-slice rebinning (ASSR) method. Based on the phantom and pediatric patient fan-beam CT data, it is demonstrated that EST reconstructions with the lowest scanner flux setting of 39 mAs produce comparable image quality, resolution, and contrast relative to FBP with the 140 mAs flux setting. Compared to the algebraic reconstruction technique and the expectation maximization statistical reconstruction algorithm, a significant reduction in computation time is achieved with EST. Finally, numerical experiments on helical cone-beam CT data suggest that the combination of EST and ASSR produces reconstructions with higher image quality and lower noise than the Feldkamp Davis and Kress (FDK) method and the conventional ASSR approach. A Fourier-based iterative method has been applied to the reconstruction of fan-bean CT data with reduced x-ray fluence. This method incorporates advantageous features in both real and Fourier space iterative schemes: using a fast and algebraically exact method to calculate forward projection, enforcing the measured data in Fourier space, and applying physical constraints and flexible regularization in real space. Our results suggest that EST can be utilized for radiation dose reduction in x-ray CT via the readily implementable technique of lowering mAs settings. Numerical experiments further indicate that EST requires less computation time than several other iterative algorithms and can, in principle, be extended to helical cone-beam geometry in combination with the ASSR method.

Adaptive statistical iterative reconstruction and bismuth shielding for evaluation of dose reduction to the eye and image quality during head CT

NASA Astrophysics Data System (ADS)

Kim, Myeong Seong; Choi, Jiwon; Kim, Sun Young; Kweon, Dae Cheol

2014-03-01

There is a concern regarding the adverse effects of increasing radiation doses due to repeated computed tomography (CT) scans, especially in radiosensitive organs and portions thereof, such as the lenses of the eyes. Bismuth shielding with an adaptive statistical iterative reconstruction (ASIR) algorithm was recently introduced in our clinic as a method to reduce the absorbed radiation dose. This technique was applied to the lens of the eye during CT scans. The purpose of this study was to evaluate the reduction in the absorbed radiation dose and to determine the noise level when using bismuth shielding and the ASIR algorithm with the GE DC 750 HD 64-channel CT scanner for CT of the head of a humanoid phantom. With the use of bismuth shielding, the noise level was higher in the beam-hardening artifact areas than in the revealed artifact areas. However, with the use of ASIR, the noise level was lower than that with the use of bismuth alone; it was also lower in the artifact areas. The reduction in the radiation dose with the use of bismuth was greatest at the surface of the phantom to a limited depth. In conclusion, it is possible to reduce the radiation level and slightly decrease the bismuth-induced noise level by using a combination of ASIR as an algorithm process and bismuth as an in-plane hardware-type shielding method.

SU-C-206-07: A Practical Sparse View Ultra-Low Dose CT Acquisition Scheme for PET Attenuation Correction in the Extended Scan Field-Of-View

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, J; Fan, J; Gopinatha Pillai, A

Purpose: To further reduce CT dose, a practical sparse-view acquisition scheme is proposed to provide the same attenuation estimation as higher dose for PET imaging in the extended scan field-of-view. Methods: CT scans are often used for PET attenuation correction and can be acquired at very low CT radiation dose. Low dose techniques often employ low tube voltage/current accompanied with a smooth filter before backprojection to reduce CT image noise. These techniques can introduce bias in the conversion from HU to attenuation values, especially in the extended CT scan field-of-view (FOV). In this work, we propose an ultra-low dose CTmore » technique for PET attenuation correction based on sparse-view acquisition. That is, instead of an acquisition of full amount of views, only a fraction of views are acquired. We tested this technique on a 64-slice GE CT scanner using multiple phantoms. CT scan FOV truncation completion was performed based on the published water-cylinder extrapolation algorithm. A number of continuous views per rotation: 984 (full), 246, 123, 82 and 62 have been tested, corresponding to a CT dose reduction of none, 4x, 8x, 12x and 16x. We also simulated sparse-view acquisition by skipping views from the fully-acquired view data. Results: FBP reconstruction with Q. AC filter on reduced views in the full extended scan field-of-view possesses similar image quality to the reconstruction on acquired full view data. The results showed a further potential for dose reduction compared to the full acquisition, without sacrificing any significant attenuation support to the PET. Conclusion: With the proposed sparse-view method, one can potential achieve at least 2x more CT dose reduction compared to the current Ultra-Low Dose (ULD) PET/CT protocol. A pre-scan based dose modulation scheme can be combined with the above sparse-view approaches, which can even further reduce the CT scan dose during a PET/CT exam.« less

EVALUATION OF CHITOSAN COAGULATION AS A SUSTAINABLE METHOD FOR POINT OF USE DRINKINGWATER TREATMENT IN DEVELOPING COUNTRIES

EPA Science Inventory

Chitosan A was found to remove up to 3.4 log₁₀ E. coli, a reduction of 99.96%. The removal was dose dependent; up to a point, removal of E. coli increases with increasing dose. Removal of E. coli ranged from 0% removal by a dose of 1g/L to...

SU-C-12A-07: Effect of Vertical Position On Dose Reduction Using X-Care

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silosky, M; Marsh, R

Purpose: Reduction of absorbed dose to radiosensitive tissues is an important goal in diagnostic radiology. Siemens Medical has introduced a technique (X-CARE) to lower CT dose to anterior anatomy by reducing the tube current during 80° of rotation over radiosensitive tissues. Phantom studies have shown 30-40% dose reduction when phantoms are positioned at isocenter. However, for CT face and sinus exams, the center of the head is commonly positioned below isocenter. This work investigated the effects of vertical patient positioning on dose reduction using X-CARE. Methods: A 16cm Computed Tomography Dose Index phantom was scanned on a Siemens Definition Flashmore » CT scanner using a routine head protocol, with the phantom positioned at scanner isocenter. Optically stimulated luminescent dosimeters were placed on the anterior and posterior sides of the phantom. The phantom was lowered in increments of 2cm and rescanned, up to 8cm below isocenter. The experiment was then repeated using the same scan parameters but adding the X-CARE technique. The mean dosimeter counts were determined for each phantom position, and the difference between XCARE and routine scans was plotted as a function of distance from isocenter. Results: With the phantom positioned at isocenter, using XCARE reduced dose to the anterior side of the phantom by 40%, compared to dose when X-CARE was not used. Positioned below isocenter, anterior dose was reduced by only 20-27%. Additionally, using X-CARE at isocenter reduced dose to the anterior portion of the phantom by 45.6% compared to scans performed without X-CARE 8cm below isocenter. Conclusion: While using X-CARE substantially reduced dose to the anterior side of the phantom, this effect was diminished when the phantom was positioned below isocenter, simulating common practice for face and sinus scans. This indicates that centering the head in the gantry will maximize the effect of X-CARE.« less

Full dose reduction potential of statistical iterative reconstruction for head CT protocols in a predominantly pediatric population

PubMed Central

Mirro, Amy E.; Brady, Samuel L.; Kaufman, Robert. A.

2016-01-01

Purpose To implement the maximum level of statistical iterative reconstruction that can be used to establish dose-reduced head CT protocols in a primarily pediatric population. Methods Select head examinations (brain, orbits, sinus, maxilla and temporal bones) were investigated. Dose-reduced head protocols using an adaptive statistical iterative reconstruction (ASiR) were compared for image quality with the original filtered back projection (FBP) reconstructed protocols in phantom using the following metrics: image noise frequency (change in perceived appearance of noise texture), image noise magnitude, contrast-to-noise ratio (CNR), and spatial resolution. Dose reduction estimates were based on computed tomography dose index (CTDIvol) values. Patient CTDIvol and image noise magnitude were assessed in 737 pre and post dose reduced examinations. Results Image noise texture was acceptable up to 60% ASiR for Soft reconstruction kernel (at both 100 and 120 kVp), and up to 40% ASiR for Standard reconstruction kernel. Implementation of 40% and 60% ASiR led to an average reduction in CTDIvol of 43% for brain, 41% for orbits, 30% maxilla, 43% for sinus, and 42% for temporal bone protocols for patients between 1 month and 26 years, while maintaining an average noise magnitude difference of 0.1% (range: −3% to 5%), improving CNR of low contrast soft tissue targets, and improving spatial resolution of high contrast bony anatomy, as compared to FBP. Conclusion The methodology in this study demonstrates a methodology for maximizing patient dose reduction and maintaining image quality using statistical iterative reconstruction for a primarily pediatric population undergoing head CT examination. PMID:27056425

SU-G-BRC-02: A Novel Multi-Criteria Optimization Approach to Generate Deliverable Intensity-Modulated Radiation Therapy (IMRT) Treatment Plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirlik, G; D’Souza, W; Zhang, H

2016-06-15

Purpose: To present a novel multi-criteria optimization (MCO) solution approach that generates treatment plans with deliverable apertures using column generation. Methods: We demonstrate our method with 10 locally advanced head-and-neck cancer cases retrospectively. In our MCO formulation, we defined an objective function for each structure in the treatment volume. This resulted in 9 objective functions, including 3 distinct objectives for primary target volume, high-risk and low-risk target volumes, 5 objectives for each of the organs-at-risk (OARs) (two parotid glands, spinal cord, brain stem and oral cavity), and one for the non-target non-OAR normal tissue. Conditional value-at-risk (CVaR) constraints were utilizedmore » to ensure at least certain fraction of the target volumes receiving the prescription doses. To directly generate deliverable plans, column generation algorithm was embedded within our MCO approach for aperture shape generation. Final dose distributions for all plans were generated using a Monte Carlo kernel-superposition dose calculation. We compared the MCO plans with the clinical plans, which were created by clinicians. Results: At least 95% target coverage was achieved by both MCO plans and clinical plans. However, the average conformity indices of clinical plans and the MCO plans were 1.95 and 1.35, respectively (31% reduction, p<0.01). Compared to the conventional clinical plan, the proposed MCO method achieved average reductions in left parotid mean dose of 5% (p=0.06), right parotid mean dose of 18% (p<0.01), oral cavity mean dose of 21% (p=0.03), spinal cord maximum dose of 20% (p<0.01), brain stem maximum dose of 61% (p<0.01), and normal tissue maximum dose of 5% (p<0.01), respectively. Conclusion: We demonstrated that the proposed MCO method was able to obtain deliverable IMRT treatment plans while achieving significant improvements in dosimetric plan quality.« less

SU-F-I-71: Fetal Protection During Fluoroscopy: To Shield Or Not to Shield?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, S; Vanderhoek, M

Purpose: Lead aprons are routinely used to shield the fetus from radiation during fluoroscopically guided interventions (FGI) involving pregnant patients. When placed in the primary beam, lead aprons often reduce image quality and increase fluoroscopic radiation output, which can adversely affect fetal dose. The purpose of this work is to identify an effective and practical method to reduce fetal dose without affecting image quality. Methods: A pregnant patient equivalent abdominal phantom is set on the table along with an image quality test object (CIRS model 903) representing patient anatomy of interest. An ion chamber is positioned at the x-ray beammore » entrance to the phantom, which is used to estimate the relative fetal dose. For three protective methods, image quality and fetal dose measurements are compared to baseline (no protection):1. Lead apron shielding the entire abdomen; 2. Lead apron shielding part of the abdomen, including the fetus; 3. Narrow collimation such that fetus is excluded from the primary beam. Results: With lead shielding the entire abdomen, the dose is reduced by 80% relative to baseline along with a drastic deterioration of image quality. With lead shielding only the fetus, the dose is reduced by 65% along with complete preservation of image quality, since the image quality test object is not shielded. However, narrow collimation results in 90% dose reduction and a slight improvement of image quality relative to baseline. Conclusion: The use of narrow collimation to protect the fetus during FGI is a simple and highly effective method that simultaneously reduces fetal dose and maintains sufficient image quality. Lead aprons are not as effective at fetal dose reduction, and if placed improperly, they can severely degrade image quality. Future work aims to investigate a wider variety of fluoroscopy systems to confirm these results across many different system geometries.« less

Estimate of the shielding effect on secondary cancer risk due to cone-beam CT in image-guided radiotherapy

NASA Astrophysics Data System (ADS)

Sung, Jiwon; Baek, Tae Seong; Yoon, Myonggeun; Kim, Dong Wook; Kim, Dong Hyun

2014-09-01

This study evaluated the effect of a simple shielding method using a thin lead sheet on the imaging dose caused by cone-beam computed tomography (CBCT) in image-guided radiation therapy (IGRT). Reduction of secondary doses from CBCT was measured using a radio-photoluminescence glass dosimeter (RPLGD) placed inside an anthropomorphic phantom. The entire body, except for the region scanned by using CBCT, was shielded by wrapping it with a 2-mm lead sheet. Changes in secondary cancer risk due to shielding were calculated using BEIR VII models. Doses to out-of-field organs for head-and-neck, chest, and pelvis scans were decreased 15 ~ 100%, 23 ~ 90%, and 23 ~ 98%, respectively, and the average reductions in lifetime secondary cancer risk due to the 2-mm lead shielding were 1.6, 11.5, and 12.7 persons per 100,000, respectively. These findings suggest that a simple, thin-lead-sheet-based shielding method can effectively decrease secondary doses to out-of-field regions for CBCT, which reduces the lifetime cancer risk on average by 9 per 100,000 patients.

Efficacy of alternate day versus daily dosing of rosuvastatin

PubMed Central

Dulay, Daisy; LaHaye, Stephen A; Lahey, Karen A; Day, Andrew G

2009-01-01

BACKGROUND: Compared with other statins, rosuvastatin has a relatively long half-life, which may allow for the administration of this medication on an alternate day basis. OBJECTIVE: To compare the efficacy of administering rosuvastatin on a daily basis versus on an alternate day basis for the treatment of dyslipidemia. METHODS: In the present crossover study, 45 patients with documented hypercholesterolemia requiring pharmacotherapy were administered either 20 mg of rosuvastatin on alternate days or 10 mg of rosuvastatin daily for six weeks. After a four-week washout period, patients were then switched to the other regimen for another six weeks. The primary end point was the percentage reduction of low-density lipoprotein cholesterol (LDL-C). RESULTS: LDL-C decreased by 48.5% versus 40.9% with daily and alternate day dosing, respectively. This represented an additional absolute reduction of LDL-C of 7.6% (95% CI 1.8% to 13.4%, P=0.012) with the daily dosing regimen. Both dosing regimens provided similar improvements in high-density lipoprotein cholesterol and triglycerides. CONCLUSIONS: Compared with alternate day dosing, daily dosing of rosuvastatin provides a statistically significant advantage in LDL-C reduction. However, the alternate day regimen may be a viable option for those patients in whom cost is a limitation to compliance. PMID:19214297

Gonad dose in AP pelvis radiography: Impact of anode heel orientation.

PubMed

Mraity, H A A B; England, A; Hogg, P

2017-02-01

For antero posterior (AP) pelvis radiographic examination, determine the impact of anode heel orientation on female/male gonad dose. High sensitivity thermo-luminescent dosimeters (TLDs) were used with an ATOM dosimetry phantom; the phantom was positioned for AP pelvis. TLDs were placed into the testes and ovaries. Radiation dose received by these organs was measured with the feet toward anode and feet toward the cathode. kVp, mAs and SID were manipulated to generate a range of exposures. A dose profile was also generated using Unfors Mult-O-Meter 401 along the long axis of the phantom. A decrease in dose from the central ray toward the anode was noted, with a marked increase toward the cathode. A significant reduction in dose was received by the testes with feet towards the anode compared with feet towards cathode (P˂0.001). No difference was seen for ovarian dose (P˃0.05). kVp, mAs and SID all have an effect on male and female gonad dose. For male pelvis imaging, placing feet towards the anode can be used as a simple dose reduction method. Copyright © 2016 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.

Evaluation and optimization of occupational eye lens dosimetry during positron emission tomography (PET) procedures.

PubMed

Guiu-Souto, Jacobo; Sánchez-García, Manuel; Vázquez-Vázquez, Rubén; Otero, Carlos; Luna, Victor; Mosquera, Javier; Busto, Ramón Lobato; Aguiar, Pablo; Ruibal, Álvaro; Pardo-Montero, Juan; Pombar-Cameán, Miguel

2016-06-01

The last recommendations of the International Commission on Radiological Protection for eye lens dose suggest an important reduction on the radiation limits associated with early and late tissue reactions. The aim of this work is to quantify and optimize the eye lens dose associated to nurse staff during positron emission tomography (PET) procedures. PET is one of the most important diagnostic methods of oncological and neurological cancer disease involving an important number of workers exposed to the high energy isotope F-18. We characterize the relevant stages as preparation and administration of monodose syringes in terms of occupational dose. A direct reading silicon dosimeter was used to measure the lens dose to staff. The highest dose of radiation was observed during preparation of the fluorodesoxyglucose (FDG) syringes. By optimizing a suitable vials' distribution of FDG we find an important reduction in occupational doses. Extrapolation of our data to other clinical scenarios indicates that, depending on the work load and/or syringes activity, safety limits of the dose might be exceeded.

TU-F-CAMPUS-J-04: Evaluation of Metal Artifact Reduction Technique for the Radiation Therapy Planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, K; Kuo, H; Ritter, J

Purpose: To evaluate the feasibility of using a metal artifact reduction technique in depleting metal artifact and its application in improving dose calculation in External Radiation Therapy Planning. Methods: CIRS electron density phantom was scanned with and without steel drill bits placed in some plug holes. Meta artifact reduction software with Metal Deletion Technique (MDT) was used to remove metal artifacts for scanned image with metal. Hounsfield units of electron density plugs from artifact free reference image and MDT processed images were compared. To test the dose calculation improvement after the MDT processed images, clinically approved head and neck planmore » with manual dental artifact correction was tested. Patient images were exported and processed with MDT and plan was recalculated with new MDT image without manual correction. Dose profiles near the metal artifacts were compared. Results: The MDT used in this study effectively reduced the metal artifact caused by beam hardening and scatter. The windmill around the metal drill was greatly improved with smooth rounded view. Difference of the mean HU in each density plug between reference and MDT images were less than 10 HU in most of the plugs. Dose difference between original plan and MDT images were minimal. Conclusion: Most metal artifact reduction methods were developed for diagnostic improvement purpose. Hence Hounsfield unit accuracy was not rigorously tested before. In our test, MDT effectively eliminated metal artifacts with good HU reproduciblity. However, it can introduce new mild artifacts so the MDT images should be checked with original images.« less

Statistical model based iterative reconstruction in clinical CT systems. Part III. Task-based kV/mAs optimization for radiation dose reduction

PubMed Central

Li, Ke; Gomez-Cardona, Daniel; Hsieh, Jiang; Lubner, Meghan G.; Pickhardt, Perry J.; Chen, Guang-Hong

2015-01-01

Purpose: For a given imaging task and patient size, the optimal selection of x-ray tube potential (kV) and tube current-rotation time product (mAs) is pivotal in achieving the maximal radiation dose reduction while maintaining the needed diagnostic performance. Although contrast-to-noise (CNR)-based strategies can be used to optimize kV/mAs for computed tomography (CT) imaging systems employing the linear filtered backprojection (FBP) reconstruction method, a more general framework needs to be developed for systems using the nonlinear statistical model-based iterative reconstruction (MBIR) method. The purpose of this paper is to present such a unified framework for the optimization of kV/mAs selection for both FBP- and MBIR-based CT systems. Methods: The optimal selection of kV and mAs was formulated as a constrained optimization problem to minimize the objective function, Dose(kV,mAs), under the constraint that the achievable detectability index d′(kV,mAs) is not lower than the prescribed value of d℞′ for a given imaging task. Since it is difficult to analytically model the dependence of d′ on kV and mAs for the highly nonlinear MBIR method, this constrained optimization problem is solved with comprehensive measurements of Dose(kV,mAs) and d′(kV,mAs) at a variety of kV–mAs combinations, after which the overlay of the dose contours and d′ contours is used to graphically determine the optimal kV–mAs combination to achieve the lowest dose while maintaining the needed detectability for the given imaging task. As an example, d′ for a 17 mm hypoattenuating liver lesion detection task was experimentally measured with an anthropomorphic abdominal phantom at four tube potentials (80, 100, 120, and 140 kV) and fifteen mA levels (25 and 50–700) with a sampling interval of 50 mA at a fixed rotation time of 0.5 s, which corresponded to a dose (CTDIvol) range of [0.6, 70] mGy. Using the proposed method, the optimal kV and mA that minimized dose for the prescribed detectability level of d℞′=16 were determined. As another example, the optimal kV and mA for an 8 mm hyperattenuating liver lesion detection task were also measured using the developed framework. Both an in vivo animal and human subject study were used as demonstrations of how the developed framework can be applied to the clinical work flow. Results: For the first task, the optimal kV and mAs were measured to be 100 and 500, respectively, for FBP, which corresponded to a dose level of 24 mGy. In comparison, the optimal kV and mAs for MBIR were 80 and 150, respectively, which corresponded to a dose level of 4 mGy. The topographies of the iso-d′ map and the iso-CNR map were the same for FBP; thus, the use of d′- and CNR-based optimization methods generated the same results for FBP. However, the topographies of the iso-d′ and iso-CNR map were significantly different in MBIR; the CNR-based method overestimated the performance of MBIR, predicting an overly aggressive dose reduction factor. For the second task, the developed framework generated the following optimization results: for FBP, kV = 140, mA = 350, dose = 37.5 mGy; for MBIR, kV = 120, mA = 250, dose = 18.8 mGy. Again, the CNR-based method overestimated the performance of MBIR. Results of the preliminary in vivo studies were consistent with those of the phantom experiments. Conclusions: A unified and task-driven kV/mAs optimization framework has been developed in this work. The framework is applicable to both linear and nonlinear CT systems such as those using the MBIR method. As expected, the developed framework can be reduced to the conventional CNR-based kV/mAs optimization frameworks if the system is linear. For MBIR-based nonlinear CT systems, however, the developed task-based kV/mAs optimization framework is needed to achieve the maximal dose reduction while maintaining the desired diagnostic performance. PMID:26328971

Fully Convolutional Architecture for Low-Dose CT Image Noise Reduction

NASA Astrophysics Data System (ADS)

Badretale, S.; Shaker, F.; Babyn, P.; Alirezaie, J.

2017-10-01

One of the critical topics in medical low-dose Computed Tomography (CT) imaging is how best to maintain image quality. As the quality of images decreases with lowering the X-ray radiation dose, improving image quality is extremely important and challenging. We have proposed a novel approach to denoise low-dose CT images. Our algorithm learns directly from an end-to-end mapping from the low-dose Computed Tomography images for denoising the normal-dose CT images. Our method is based on a deep convolutional neural network with rectified linear units. By learning various low-level to high-level features from a low-dose image the proposed algorithm is capable of creating a high-quality denoised image. We demonstrate the superiority of our technique by comparing the results with two other state-of-the-art methods in terms of the peak signal to noise ratio, root mean square error, and a structural similarity index.

Radiation dose reduction to the breast in thoracic CT: Comparison of bismuth shielding, organ-based tube current modulation, and use of a globally decreased tube current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Jia; Duan Xinhui; Christner, Jodie A.

2011-11-15

Purpose: The purpose of this work was to evaluate dose performance and image quality in thoracic CT using three techniques to reduce dose to the breast: bismuth shielding, organ-based tube current modulation (TCM) and global tube current reduction. Methods: Semi-anthropomorphic thorax phantoms of four different sizes (15, 30, 35, and 40 cm lateral width) were used for dose measurement and image quality assessment. Four scans were performed on each phantom using 100 or 120 kV with a clinical CT scanner: (1) reference scan; (2) scan with bismuth breast shield of an appropriate thickness; (3) scan with organ-based TCM; and (4)more » scan with a global reduction in tube current chosen to match the dose reduction from bismuth shielding. Dose to the breast was measured with an ion chamber on the surface of the phantom. Image quality was evaluated by measuring the mean and standard deviation of CT numbers within the lung and heart regions. Results: Compared to the reference scan, dose to the breast region was decreased by about 21% for the 15-cm phantom with a pediatric (2-ply) shield and by about 37% for the 30, 35, and 40-cm phantoms with adult (4-ply) shields. Organ-based TCM decreased the dose by 12% for the 15-cm phantom, and 34-39% for the 30, 35, and 40-cm phantoms. Global lowering of the tube current reduced breast dose by 23% for the 15-cm phantom and 39% for the 30, 35, and 40-cm phantoms. In phantoms of all four sizes, image noise was increased in both the lung and heart regions with bismuth shielding. No significant increase in noise was observed with organ-based TCM. Decreasing tube current globally led to similar noise increases as bismuth shielding. Streak and beam hardening artifacts, and a resulting artifactual increase in CT numbers, were observed for scans with bismuth shields, but not for organ-based TCM or global tube current reduction. Conclusions: Organ-based TCM produces dose reduction to the breast similar to that achieved with bismuth shielding for both pediatric and adult phantoms. However, organ-based TCM does not affect image noise or CT number accuracy, both of which are adversely affected by bismuth shielding. Alternatively, globally decreasing the tube current can produce the same dose reduction to the breast as bismuth shielding, with a similar noise increase, yet without the streak artifacts and CT number errors caused by the bismuth shields. Moreover, globally decreasing the tube current reduces the dose to all tissues scanned, not simply to the breast.« less

MO-F-CAMPUS-I-04: Patient Eye-Lens Dose Reduction in Routine Brain CT Examinations Using Organ-Based Tube Current Modulation and In-Plane Bismuth Shielding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Hui-Yu; Liao, Ying-Lan; Chang Gung University / Chang Gung Memorial Hospital, Taoyun, Taiwan

Purpose: The purpose of this study is to assess eye-lens dose for patients who underwent brain CT examinations using two dose reduction Methods: organ-based tube current modulation (OBTCM) and in-plane bismuth shielding method. Methods: This study received institutional review board approval; written informed consent to participate was obtained from all patients. Ninety patients who underwent the routine brain CT examination were randomly assigned to three groups, ie. routine, OBTCM, and bismuth shield. The OBTCM technique reduced the tube current when the X-ray tube rotates in front of patients’ eye-lens region. The patients in the bismuth shield group were covered one-plymore » bismuth shield in the eyes’ region. Eye-lens doses were measured using TLD-100H chips and the total effective doses were calculated using CT-Expo according to the CT scanning parameters. The surface doses for patients at off-center positions were assessed to evaluate the off-centering effect. Results: Phantom measurements indicates that OBTCM technique could reduced by 26% to 28% of the surface dose to the eye lens, and increased by 25% of the surface dose at the opposed incident direction at the angle of 180°. Patients’ eye-lens doses were reduced 16.9% and 30.5% dose of bismuth shield scan and OBTCM scan, respectively compared to the routine scan. The eye-lens doses were apparently increased when the table position was lower than isocenter. Conclusion: Reducing the dose to the radiosensitive organs, such as eye lens, during routine brain CT examinations could lower the radiation risks. The OBTCM technique and in-plane bismuth shielding could be used to reduce the eye-lens dose. The eye-lens dose could be effectively reduced using OBTCM scan without interfering the diagnostic image quality. Patient position relative the CT gantry also affects the dose level of the eye lens. This study was supported by the grants from the Ministry of Science and Technology of Taiwan (MOST103-2314-B-182-009-MY2), and Chang Gung Memorial Hospital (CMRPD1C0682)« less

Monte Carlo method for calculating the radiation skyshine produced by electron accelerators

NASA Astrophysics Data System (ADS)

Kong, Chaocheng; Li, Quanfeng; Chen, Huaibi; Du, Taibin; Cheng, Cheng; Tang, Chuanxiang; Zhu, Li; Zhang, Hui; Pei, Zhigang; Ming, Shenjin

2005-06-01

Using the MCNP4C Monte Carlo code, the X-ray skyshine produced by 9 MeV, 15 MeV and 21 MeV electron linear accelerators were calculated respectively with a new two-step method combined with the split and roulette variance reduction technique. Results of the Monte Carlo simulation, the empirical formulas used for skyshine calculation and the dose measurements were analyzed and compared. In conclusion, the skyshine dose measurements agreed reasonably with the results computed by the Monte Carlo method, but deviated from computational results given by empirical formulas. The effect on skyshine dose caused by different structures of accelerator head is also discussed in this paper.

FW-CADIS Method for Global and Semi-Global Variance Reduction of Monte Carlo Radiation Transport Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, John C; Peplow, Douglas E.; Mosher, Scott W

2014-01-01

This paper presents a new hybrid (Monte Carlo/deterministic) method for increasing the efficiency of Monte Carlo calculations of distributions, such as flux or dose rate distributions (e.g., mesh tallies), as well as responses at multiple localized detectors and spectra. This method, referred to as Forward-Weighted CADIS (FW-CADIS), is an extension of the Consistent Adjoint Driven Importance Sampling (CADIS) method, which has been used for more than a decade to very effectively improve the efficiency of Monte Carlo calculations of localized quantities, e.g., flux, dose, or reaction rate at a specific location. The basis of this method is the development ofmore » an importance function that represents the importance of particles to the objective of uniform Monte Carlo particle density in the desired tally regions. Implementation of this method utilizes the results from a forward deterministic calculation to develop a forward-weighted source for a deterministic adjoint calculation. The resulting adjoint function is then used to generate consistent space- and energy-dependent source biasing parameters and weight windows that are used in a forward Monte Carlo calculation to obtain more uniform statistical uncertainties in the desired tally regions. The FW-CADIS method has been implemented and demonstrated within the MAVRIC sequence of SCALE and the ADVANTG/MCNP framework. Application of the method to representative, real-world problems, including calculation of dose rate and energy dependent flux throughout the problem space, dose rates in specific areas, and energy spectra at multiple detectors, is presented and discussed. Results of the FW-CADIS method and other recently developed global variance reduction approaches are also compared, and the FW-CADIS method outperformed the other methods in all cases considered.« less

SU-F-T-325: On the Use of Bolus in Dosimetry and Dose Reduction for Pacemaker and Defibrillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, W; Kenneth, R; Higgins, S

Purpose: Special attention is required in planning and administering radiation therapy to patients with cardiac implantable electronic devices (CIEDs), such as pacemaker and defibrillator. The range of dose to CIEDs that can induce malfunction is very large among CIEDs. Significant defects have been reported at dose as low as 0.15Gy. Failures causing discomfort have been reported at dose as low as 0.05Gy. Therefore, accurate estimation of dose to CIED and dose reduction are both important even if the dose is expected to be less than the often-used 2Gy limit. We investigate the use of bolus in in vivo dosimetry formore » CIEDs. Methods: In our clinic, high-energy beams (>10MV) are not used for patients with CIED due to neutron production. Solid water phantom measurements of out-of-field dose for a 6MV beam were performed using parallel plate chamber at different depth with and without 2cm bolus covering the chamber. In vivo dosimetry at skin surface above the pacemaker was performed with and without bolus for 3 patients with pacemaker <5cm from the field edge. Results: Chamber measured dose at depth ∼1 to 1.5cm below the skin surface, where the CIED is normally located, was reduced by ∼6% – 20% with bolus. The dose reduction became smaller at deeper depth. In vivo dosimetry at skin surface also yielded ∼20% – 60% lower dose when using bolus for the 3 patients. In general, TPS calculation underestimated the dose. The dose measured with bolus is closer to the dose at the depth of the pacemaker and less affected by contaminant electrons and linac head leakage. Conclusion: In vivo CIED dose measurements should be performed with 1 to 2cm bolus covering the dosimeter on the skin above the CIED for more accurate CIED dose estimation. The use of bolus also reduces the dose delivered to CIED.« less

Dose reduction potential of iterative reconstruction algorithms in neck CTA-a simulation study.

PubMed

Ellmann, Stephan; Kammerer, Ferdinand; Allmendinger, Thomas; Brand, Michael; Janka, Rolf; Hammon, Matthias; Lell, Michael M; Uder, Michael; Kramer, Manuel

2016-10-01

This study aimed to determine the degree of radiation dose reduction in neck CT angiography (CTA) achievable with Sinogram-affirmed iterative reconstruction (SAFIRE) algorithms. 10 consecutive patients scheduled for neck CTA were included in this study. CTA images of the external carotid arteries either were reconstructed with filtered back projection (FBP) at full radiation dose level or underwent simulated dose reduction by proprietary reconstruction software. The dose-reduced images were reconstructed using either SAFIRE 3 or SAFIRE 5 and compared with full-dose FBP images in terms of vessel definition. 5 observers performed a total of 3000 pairwise comparisons. SAFIRE allowed substantial radiation dose reductions in neck CTA while maintaining vessel definition. The possible levels of radiation dose reduction ranged from approximately 34 to approximately 90% and depended on the SAFIRE algorithm strength and the size of the vessel of interest. In general, larger vessels permitted higher degrees of radiation dose reduction, especially with higher SAFIRE strength levels. With small vessels, the superiority of SAFIRE 5 over SAFIRE 3 was lost. Neck CTA can be performed with substantially less radiation dose when SAFIRE is applied. The exact degree of radiation dose reduction should be adapted to the clinical question, in particular to the smallest vessel needing excellent definition.

Radioiodine therapy of hyperfunctioning thyroid nodules: usefulness of an implemented dose calculation algorithm allowing reduction of radioiodine amount.

PubMed

Schiavo, M; Bagnara, M C; Pomposelli, E; Altrinetti, V; Calamia, I; Camerieri, L; Giusti, M; Pesce, G; Reitano, C; Bagnasco, M; Caputo, M

2013-09-01

Radioiodine is a common option for treatment of hyperfunctioning thyroid nodules. Due to the expected selective radioiodine uptake by adenoma, relatively high "fixed" activities are often used. Alternatively, the activity is individually calculated upon the prescription of a fixed value of target absorbed dose. We evaluated the use of an algorithm for personalized radioiodine activity calculation, which allows as a rule the administration of lower radioiodine activities. Seventy-five patients with single hyperfunctioning thyroid nodule eligible for 131I treatment were studied. The activities of 131I to be administered were estimated by the method described by Traino et al. and developed for Graves'disease, assuming selective and homogeneous 131I uptake by adenoma. The method takes into account 131I uptake and its effective half-life, target (adenoma) volume and its expected volume reduction during treatment. A comparison with the activities calculated by other dosimetric protocols, and the "fixed" activity method was performed. 131I uptake was measured by external counting, thyroid nodule volume by ultrasonography, thyroid hormones and TSH by ELISA. Remission of hyperthyroidism was observed in all but one patient; volume reduction of adenoma was closely similar to that assumed by our model. Effective half-life was highly variable in different patients, and critically affected dose calculation. The administered activities were clearly lower with respect to "fixed" activities and other protocols' prescription. The proposed algorithm proved to be effective also for single hyperfunctioning thyroid nodule treatment and allowed a significant reduction of administered 131I activities, without loss of clinical efficacy.

Does dose matter in reducing gestational weight gain in exercise interventions? A systematic review of literature.

PubMed

McDonald, Samantha M; Liu, Jihong; Wilcox, Sara; Lau, Erica Y; Archer, Edward

2016-04-01

The purpose of this review was to examine the relationship between exercise dose and reductions in weight gain during pregnancy in exercise interventions. Systematic literature review. Four electronic research databases (PubMed, Web of Science, CINAHL, and Academic Search Premiere) were used to identify exercise interventions conducted with pregnant women. Eligible articles must have satisfied the following criteria: inclusion of a control condition, exercise as a major intervention component, weight gain measured and reported for each experimental condition, description of exercise dose (frequency, intensity and duration), and utilized an adequate number of control conditions to assess independent effects of exercise on weight gain. The literature search identified 4837 articles. Of these, 174 abstracts were screened and 21 intervention studies (18 exercise-only, 3 exercise/diet) were eligible for review. Only 38% of the interventions achieved statistically significant reductions in gestational weight gain. Successful interventions possessed higher adherence and lower attrition rates and were predominantly conducted among normal weight populations. No clear patterns or consistencies of exercise dose and reductions in weight gain were evident. An exercise dose associated with reductions in weight gain was unquantifiable among these interventions. Adherence and retention rates were strong contributors to the success of exercise interventions on gestational weight gain. It is strongly suggested that future researchers investigate methods to increase adherence and compliance, especially among overweight and obese women, and utilize objective measurement tools to accurately evaluate exercise dose performed by the participants and the impact on body composition and weight gain. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Characterization of adaptive statistical iterative reconstruction algorithm for dose reduction in CT: A pediatric oncology perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brady, S. L.; Yee, B. S.; Kaufman, R. A.

Purpose: This study demonstrates a means of implementing an adaptive statistical iterative reconstruction (ASiR Trade-Mark-Sign ) technique for dose reduction in computed tomography (CT) while maintaining similar noise levels in the reconstructed image. The effects of image quality and noise texture were assessed at all implementation levels of ASiR Trade-Mark-Sign . Empirically derived dose reduction limits were established for ASiR Trade-Mark-Sign for imaging of the trunk for a pediatric oncology population ranging from 1 yr old through adolescence/adulthood. Methods: Image quality was assessed using metrics established by the American College of Radiology (ACR) CT accreditation program. Each image quality metricmore » was tested using the ACR CT phantom with 0%-100% ASiR Trade-Mark-Sign blended with filtered back projection (FBP) reconstructed images. Additionally, the noise power spectrum (NPS) was calculated for three common reconstruction filters of the trunk. The empirically derived limitations on ASiR Trade-Mark-Sign implementation for dose reduction were assessed using (1, 5, 10) yr old and adolescent/adult anthropomorphic phantoms. To assess dose reduction limits, the phantoms were scanned in increments of increased noise index (decrementing mA using automatic tube current modulation) balanced with ASiR Trade-Mark-Sign reconstruction to maintain noise equivalence of the 0% ASiR Trade-Mark-Sign image. Results: The ASiR Trade-Mark-Sign algorithm did not produce any unfavorable effects on image quality as assessed by ACR criteria. Conversely, low-contrast resolution was found to improve due to the reduction of noise in the reconstructed images. NPS calculations demonstrated that images with lower frequency noise had lower noise variance and coarser graininess at progressively higher percentages of ASiR Trade-Mark-Sign reconstruction; and in spite of the similar magnitudes of noise, the image reconstructed with 50% or more ASiR Trade-Mark-Sign presented a more smoothed appearance than the pre-ASiR Trade-Mark-Sign 100% FBP image. Finally, relative to non-ASiR Trade-Mark-Sign images with 100% of standard dose across the pediatric phantom age spectrum, similar noise levels were obtained in the images at a dose reduction of 48% with 40% ASIR Trade-Mark-Sign and a dose reduction of 82% with 100% ASIR Trade-Mark-Sign . Conclusions: The authors' work was conducted to identify the dose reduction limits of ASiR Trade-Mark-Sign for a pediatric oncology population using automatic tube current modulation. Improvements in noise levels from ASiR Trade-Mark-Sign reconstruction were adapted to provide lower radiation exposure (i.e., lower mA) instead of improved image quality. We have demonstrated for the image quality standards required at our institution, a maximum dose reduction of 82% can be achieved using 100% ASiR Trade-Mark-Sign ; however, to negate changes in the appearance of reconstructed images using ASiR Trade-Mark-Sign with a medium to low frequency noise preserving reconstruction filter (i.e., standard), 40% ASiR Trade-Mark-Sign was implemented in our clinic for 42%-48% dose reduction at all pediatric ages without a visually perceptible change in image quality or image noise.« less

Reduced dose to urethra and rectum with the use of variable needle spacing in prostate brachytherapy: a potential role for robotic technology

PubMed Central

Vyas, Shilpa; Le, Yi; Zhang, Zhe; Armour, Woody

2015-01-01

Purpose Several robotic delivery systems for prostate brachytherapy are under development or in pre-clinical testing. One of the features of robotic brachytherapy is the ability to vary spacing of needles at non-fixed intervals. This feature may play an important role in prostate brachytherapy, which is traditionally template-based with fixed needle spacing of 0.5 cm. We sought to quantify potential reductions in the dose to urethra and rectum by utilizing variable needle spacing, as compared to fixed needle spacing. Material and methods Transrectal ultrasound images from 10 patients were used by 3 experienced planners to create 120 treatment plans. Each planner created 4 plan variations per patient with respect to needle positions: 125I fixed spacing, 125I variable spacing, 103Pd fixed spacing, and 103Pd variable spacing. The primary planning objective was to achieve a prostate V100 of 100% while minimizing dose to urethra and rectum. Results All plans met the objective of achieving prostate V100 of 100%. Combined results for all plans show statistically significant improvements in all assessed dosimetric variables for urethra (Umax, Umean, D30, D5) and rectum (Rmax, Rmean, RV100) when using variable spacing. The dose reductions for mean and maximum urethra dose using variable spacing had p values of 0.011 and 0.024 with 103Pd, and 0.007 and 0.029 with 125I plans. Similarly dose reductions for mean and maximum rectal dose using variable spacing had p values of 0.007 and 0.052 with 103Pd, and 0.012 and 0.037 with 125I plans. Conclusions The variable needle spacing achievable by the use of robotics in prostate brachytherapy allows for reductions in both urethral and rectal planned doses while maintaining prostate dose coverage. Such dosimetric advantages have the potential in translating to significant clinical benefits with the use of robotic brachytherapy. PMID:26622227

SU-E-J-07: IGRT Gently: Evaluating Imaging Dose in Phantoms of Different Sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, B; Duggar, W; Stanford, J

Purpose: IGRT imaging procedures have emerged as a common method of patient position verification in radiotherapy, though imaging dose is generally neglected in the treatment plan. Consequently, evaluating and optimizing the dose from these procedures is worthwhile. This process is especially important for children, who are more radiosensitive than adults. The aim of this work was to gain some understanding of the relative doses involved with various XVI-preset parameters for an “adult” and “child” phantom set, with the hopes that imaging dose for a child can be reduced. Methods: 32 and 16cm CTDI-phantoms were used as surrogates for adult andmore » child torsos, respectively. Dose was measured in the central and peripheral chamber positions of the phantoms. CBCT scans were made for both phantoms using Elekta’s Chest-preset to establish a dose baseline. The child-phantom was then scanned using the Elekta Head and Neck (HN) preset. A modified HN-preset (named Peds Abd-pelvis) was also created with a doubled mAs to maintain a reduction in dose to the child-phantom (relative to the baseline), while providing clinically-usable image quality. Results: The baseline dose to the child-phantom from the Chest-preset was 310% that of the adult-phantom for the center chamber position and 150% at the periphery. An average dose reduction of 97% was obtained in the childphantom by switching from the Chest-preset to the HN-preset, while the Peds Abd-pelvis-preset similarly reduced the dose by an average of 92%. Conclusion: XVI-preset parameters significantly affect dose, and should be optimized to reduce dose, while ensuring clinically-usable image quality. Using a modified imaging preset (Peds Abd-pelvis-preset) greatly reduced the dose to the child-phantom compared to the dose for the Chest-preset for both the child and adult-phantoms. This outcome provides support for the development of child-specific protocols for IGRT imaging in pediatric patients.« less

Efficacy of sacubitril/valsartan vs. enalapril at lower than target doses in heart failure with reduced ejection fraction: the PARADIGM-HF trial.

PubMed

Vardeny, Orly; Claggett, Brian; Packer, Milton; Zile, Michael R; Rouleau, Jean; Swedberg, Karl; Teerlink, John R; Desai, Akshay S; Lefkowitz, Martin; Shi, Victor; McMurray, John J V; Solomon, Scott D

2016-10-01

In this analysis, we utilized data from PARADIGM-HF to test the hypothesis that participants who exhibited any dose reduction during the trial would have similar benefits from lower doses of sacubitril/valsartan relative to lower doses of enalapril. In a post-hoc analysis from PARADIGM-HF, we characterized patients by whether they received the maximal dose (200 mg sacubitril/valsartan or 10 mg enalapril twice daily) throughout the trial or had any dose reduction to lower doses (100/50/0 mg sacubitril/valsartan or 5/2.5/0 mg enalapril twice daily). The treatment effect for the primary outcome was estimated, stratified by dose level using time-updated Cox regression models. In the two treatment arms, participants with a dose reduction (43% of those randomized to enalapril and 42% of those randomized to sacubitril/valsartan) had similar baseline characteristics and similar baseline predictors of the need for dose reduction. In a time-updated analysis, any dose reduction was associated with a higher subsequent risk of the primary event [hazard ratio (HR) 2.5, 95% confidence interval (CI) 2.2-2.7]. However, the treatment benefit of sacubitril/valsartan over enalapril following a dose reduction was similar (HR 0.80, 95% CI 0.70-0.93, P < 0.001) to that observed in patients who had not experienced any dose reduction (HR 0.79, 95% CI 0.71-0.88, P < 0.001). In PARADIGM-HF, study medication dose reduction identified patients at higher risk of a major cardiovascular event. The magnitude of benefit for patients on lower doses of sacubitril/valsartan relative to those on lower doses of enalapril was similar to that of patients who remained on target doses of both drugs. © 2016 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology.

Paediatric cardiac CT examinations: impact of the iterative reconstruction method ASIR on image quality--preliminary findings.

PubMed

Miéville, Frédéric A; Gudinchet, François; Rizzo, Elena; Ou, Phalla; Brunelle, Francis; Bochud, François O; Verdun, Francis R

2011-09-01

Radiation dose exposure is of particular concern in children due to the possible harmful effects of ionizing radiation. The adaptive statistical iterative reconstruction (ASIR) method is a promising new technique that reduces image noise and produces better overall image quality compared with routine-dose contrast-enhanced methods. To assess the benefits of ASIR on the diagnostic image quality in paediatric cardiac CT examinations. Four paediatric radiologists based at two major hospitals evaluated ten low-dose paediatric cardiac examinations (80 kVp, CTDI(vol) 4.8-7.9 mGy, DLP 37.1-178.9 mGy·cm). The average age of the cohort studied was 2.6 years (range 1 day to 7 years). Acquisitions were performed on a 64-MDCT scanner. All images were reconstructed at various ASIR percentages (0-100%). For each examination, radiologists scored 19 anatomical structures using the relative visual grading analysis method. To estimate the potential for dose reduction, acquisitions were also performed on a Catphan phantom and a paediatric phantom. The best image quality for all clinical images was obtained with 20% and 40% ASIR (p < 0.001) whereas with ASIR above 50%, image quality significantly decreased (p < 0.001). With 100% ASIR, a strong noise-free appearance of the structures reduced image conspicuity. A potential for dose reduction of about 36% is predicted for a 2- to 3-year-old child when using 40% ASIR rather than the standard filtered back-projection method. Reconstruction including 20% to 40% ASIR slightly improved the conspicuity of various paediatric cardiac structures in newborns and children with respect to conventional reconstruction (filtered back-projection) alone.

The adaptive statistical iterative reconstruction-V technique for radiation dose reduction in abdominal CT: comparison with the adaptive statistical iterative reconstruction technique

PubMed Central

Cho, Jinhan; Oh, Jongyeong; Kim, Dongwon; Cho, Junghyun; Kim, Sanghyun; Lee, Sangyun; Lee, Jihyun

2015-01-01

Objective: To investigate whether reduced radiation dose abdominal CT images reconstructed with adaptive statistical iterative reconstruction V (ASIR-V) compromise the depiction of clinically competent features when compared with the currently used routine radiation dose CT images reconstructed with ASIR. Methods: 27 consecutive patients (mean body mass index: 23.55 kg m−2 underwent CT of the abdomen at two time points. At the first time point, abdominal CT was scanned at 21.45 noise index levels of automatic current modulation at 120 kV. Images were reconstructed with 40% ASIR, the routine protocol of Dong-A University Hospital. At the second time point, follow-up scans were performed at 30 noise index levels. Images were reconstructed with filtered back projection (FBP), 40% ASIR, 30% ASIR-V, 50% ASIR-V and 70% ASIR-V for the reduced radiation dose. Both quantitative and qualitative analyses of image quality were conducted. The CT dose index was also recorded. Results: At the follow-up study, the mean dose reduction relative to the currently used common radiation dose was 35.37% (range: 19–49%). The overall subjective image quality and diagnostic acceptability of the 50% ASIR-V scores at the reduced radiation dose were nearly identical to those recorded when using the initial routine-dose CT with 40% ASIR. Subjective ratings of the qualitative analysis revealed that of all reduced radiation dose CT series reconstructed, 30% ASIR-V and 50% ASIR-V were associated with higher image quality with lower noise and artefacts as well as good sharpness when compared with 40% ASIR and FBP. However, the sharpness score at 70% ASIR-V was considered to be worse than that at 40% ASIR. Objective image noise for 50% ASIR-V was 34.24% and 46.34% which was lower than 40% ASIR and FBP. Conclusion: Abdominal CT images reconstructed with ASIR-V facilitate radiation dose reductions of to 35% when compared with the ASIR. Advances in knowledge: This study represents the first clinical research experiment to use ASIR-V, the newest version of iterative reconstruction. Use of the ASIR-V algorithm decreased image noise and increased image quality when compared with the ASIR and FBP methods. These results suggest that high-quality low-dose CT may represent a new clinical option. PMID:26234823

SU-E-I-37: Low-Dose Real-Time Region-Of-Interest X-Ray Fluoroscopic Imaging with a GPU-Accelerated Spatially Different Bilateral Filtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, H; Lee, J; Pua, R

2014-06-01

Purpose: The purpose of our study is to reduce imaging radiation dose while maintaining image quality of region of interest (ROI) in X-ray fluoroscopy. A low-dose real-time ROI fluoroscopic imaging technique which includes graphics-processing-unit- (GPU-) accelerated image processing for brightness compensation and noise filtering was developed in this study. Methods: In our ROI fluoroscopic imaging, a copper filter is placed in front of the X-ray tube. The filter contains a round aperture to reduce radiation dose to outside of the aperture. To equalize the brightness difference between inner and outer ROI regions, brightness compensation was performed by use of amore » simple weighting method that applies selectively to the inner ROI, the outer ROI, and the boundary zone. A bilateral filtering was applied to the images to reduce relatively high noise in the outer ROI images. To speed up the calculation of our technique for real-time application, the GPU-acceleration was applied to the image processing algorithm. We performed a dosimetric measurement using an ion-chamber dosimeter to evaluate the amount of radiation dose reduction. The reduction of calculation time compared to a CPU-only computation was also measured, and the assessment of image quality in terms of image noise and spatial resolution was conducted. Results: More than 80% of dose was reduced by use of the ROI filter. The reduction rate depended on the thickness of the filter and the size of ROI aperture. The image noise outside the ROI was remarkably reduced by the bilateral filtering technique. The computation time for processing each frame image was reduced from 3.43 seconds with single CPU to 9.85 milliseconds with GPU-acceleration. Conclusion: The proposed technique for X-ray fluoroscopy can substantially reduce imaging radiation dose to the patient while maintaining image quality particularly in the ROI region in real-time.« less

Evaluation of energy in heated water vapor for the application of lung volume reduction in patients with severe emphysema.

PubMed

Henne, Erik; Kesten, Steven; Herth, Felix J F

2013-01-01

A method of achieving endoscopic lung volume reduction for emphysema has been developed that utilizes precise amounts of thermal energy in the form of water vapor to ablate lung tissue. This study evaluates the energy output and implications of the commercial InterVapor system and compares it to the clinical trial system. Two methods of evaluating the energy output of the vapor systems were used, a direct energy measurement and a quantification of resultant thermal profile in a lung model. Direct measurement of total energy and the component attributable to gas (vapor energy) was performed by condensing vapor in a water bath and measuring the temperature and mass changes. Infrared images of a lung model were taken after vapor delivery. The images were quantified to characterize the thermal profile. The total energy and vapor energy of the InterVapor system was measured at various dose levels and compared to the clinical trial system at a dose of 10.0 cal/g. An InterVapor dose of 8.5 cal/g was found to have the most similar vapor energy output with the smallest associated reduction in total energy. This was supported by characterization of the thermal profile in the lung model that demonstrated the profile of InterVapor at 8.5 cal/g to not exceed the profile of the clinical trial system. Considering both total energy and vapor energy is important during the development of clinical vapor applications. For InterVapor, a closer study of both energy types justified a reduced target vapor-dosing range for lung volume reduction. The clinical implication is a potential improvement for benefiting the risk profile. Copyright © 2013 S. Karger AG, Basel.

Neutron track length estimator for GATE Monte Carlo dose calculation in radiotherapy.

PubMed

Elazhar, H; Deschler, T; Létang, J M; Nourreddine, A; Arbor, N

2018-06-20

The out-of-field dose in radiation therapy is a growing concern in regards to the late side-effects and secondary cancer induction. In high-energy x-ray therapy, the secondary neutrons generated through photonuclear reactions in the accelerator are part of this secondary dose. The neutron dose is currently not estimated by the treatment planning system while it appears to be preponderant for distances greater than 50 cm from the isocenter. Monte Carlo simulation has become the gold standard for accurately calculating the neutron dose under specific treatment conditions but the method is also known for having a slow statistical convergence, which makes it difficult to be used on a clinical basis. The neutron track length estimator, a neutron variance reduction technique inspired by the track length estimator method has thus been developped for the first time in the Monte Carlo code GATE to allow a fast computation of the neutron dose in radiotherapy. The details of its implementation, as well as the comparison of its performances against the analog MC method, are presented here. A gain of time from 15 to 400 can be obtained by our method, with a mean difference in the dose calculation of about 1% in comparison with the analog MC method.

Sci-Thur PM – Brachytherapy 05: Surface Collimation Applied to Superficial Flap High Dose-Rate Brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Derek; Sabondjian, Eric; Lawrence, Kailin

Purpose: To apply surface collimation for superficial flap HDR skin brachytherapy utilizing common clinical resources and to demonstrate the potential for OAR dose reduction within a clinically relevant setting. Methods: Two phantom setups were used. 3 mm lead collimation was applied to a solid slab phantom to determine appropriate geometries relating to collimation and dwell activation. The same collimation was applied to the temple of an anthropomorphic head phantom to demonstrate lens dose reduction. Each setup was simulated and planned to deliver 400 cGy to a 3 cm circular target to 3 mm depth. The control and collimated irradiations weremore » sequentially measured using calibrated radiochromic films. Results: Collimation for the slab phantom attenuated the dose beyond the collimator opening, decreasing the fall-off distances by half and reducing the area of healthy skin irradiated. Target coverage can be negatively impacted by a tight collimation margin, with the required margin approximated by the primary beam geometric penumbra. Surface collimation applied to the head phantom similarly attenuated the surrounding normal tissue dose while reducing the lens dose from 84 to 68 cGy. To ensure consistent setup between simulation and treatment, additional QA was performed including collimator markup, accounting for collimator placement uncertainties, standoff distance verification, and in vivo dosimetry. Conclusions: Surface collimation was shown to reduce normal tissue dose without compromising target coverage. Lens dose reduction was demonstrated on an anthropomorphic phantom within a clinical setting. Additional QA is proposed to ensure treatment fidelity.« less

Ultrasound Evaluation of Thyroid Gland Pathologies After Radiation Therapy and Chemotherapy to Treat Malignancy During Childhood

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lollert, André, E-mail: andre.lollert@unimedizin-mainz.de; Gies, Christina; Laudemann, Katharina

Purpose: The purpose of this study was to evaluate correlations between treatment of malignancy by radiation therapy during childhood and the occurrence of thyroid gland pathologies detected by ultrasonography in follow-up examinations. Methods and Materials: Reductions of thyroid gland volume below 2 standard deviations of the weight-specific mean value, occurrence of ultrasonographically detectable thyroid gland pathologies, and hypothyroidism were retrospectively assessed in 103 children and adolescents 7 months to 20 years of age (median: 7 years of age) at baseline (1997-2013) treated with chemoradiation therapy (with the thyroid gland dose assessable) or with chemotherapy alone and followed by ultrasonography and laboratory examinations throughmore » 2014 (median follow-up time: 48 months). Results: A relevant reduction of thyroid gland volume was significantly correlated with thyroid gland dose in univariate (P<.001) and multivariate analyses for doses above 2 Gy. Odds ratios were 3.1 (95% confidence interval: 1.02-9.2; P=.046) for medium doses (2-25 Gy) and 14.8 (95% confidence interval: 1.4-160; P=.027) for high doses (>25 Gy). Thyroid gland dose was significantly higher in patients with thyroid gland pathologies during follow-up (P=.03). Univariate analysis revealed significant correlations between hypothyroidism and thyroid gland dose (P<.001). Conclusions: Ultrasonographically detectable changes, that is, volume reductions, pathologies, and hypothyroidism, after malignancy treatment during childhood are associated with thyroid gland dose. Both ultrasonography and laboratory follow-up examinations should be performed regularly after tumor therapy during childhood, especially if the treatment included radiation therapy.« less

Evaluation of surface and shallow depth dose reductions using a Superflab bolus during conventional and advanced external beam radiotherapy.

PubMed

Yoon, Jihyung; Xie, Yibo; Zhang, Rui

2018-03-01

The purpose of this study was to evaluate a methodology to reduce scatter and leakage radiations to patients' surface and shallow depths during conventional and advanced external beam radiotherapy. Superflab boluses of different thicknesses were placed on top of a stack of solid water phantoms, and the bolus effect on surface and shallow depth doses for both open and intensity-modulated radiotherapy (IMRT) beams was evaluated using thermoluminescent dosimeters and ion chamber measurements. Contralateral breast dose reduction caused by the bolus was evaluated by delivering clinical postmastectomy radiotherapy (PMRT) plans to an anthropomorphic phantom. For the solid water phantom measurements, surface dose reduction caused by the Superflab bolus was achieved only in out-of-field area and on the incident side of the beam, and the dose reduction increased with bolus thickness. The dose reduction caused by the bolus was more significant at closer distances from the beam. Most of the dose reductions occurred in the first 2-cm depth and stopped at 4-cm depth. For clinical PMRT treatment plans, surface dose reductions using a 1-cm Superflab bolus were up to 31% and 62% for volumetric-modulated arc therapy and 4-field IMRT, respectively, but there was no dose reduction for Tomotherapy. A Superflab bolus can be used to reduce surface and shallow depth doses during external beam radiotherapy when it is placed out of the beam and on the incident side of the beam. Although we only validated this dose reduction strategy for PMRT treatments, it is applicable to any external beam radiotherapy and can potentially reduce patients' risk of developing radiation-induced side effects. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Assessment of female breast dose for thoracic cone-beam CT using MOSFET dosimeters.

PubMed

Sun, Wenzhao; Wang, Bin; Qiu, Bo; Liang, Jian; Xie, Weihao; Deng, Xiaowu; Qi, Zhenyu

2017-03-21

To assess the breast dose during a routine thoracic cone-beam CT (CBCT) check with the efforts to explore the possible dose reduction strategy. Metal oxide semiconductor field-effect transistor (MOSFET) dosimeters were used to measure breast surface doses during a thorax kV CBCT scan in an anthropomorphic phantom. Breast doses for different scanning protocols and breast sizes were compared. Dose reduction was attempted by using partial arc CBCT scan with bowtie filter. The impact of this dose reduction strategy on image registration accuracy was investigated. The average breast surface doses were 20.02 mGy and 11.65 mGy for thoracic CBCT without filtration and with filtration, respectively. This indicates a dose reduction of 41.8% by use of bowtie filter. It was found 220° partial arc scanning significantly reduced the dose to contralateral breast (44.4% lower than ipsilateral breast), while the image registration accuracy was not compromised. Breast dose reduction can be achieved by using ipsilateral 220° partial arc scan with bowtie filter. This strategy also provides sufficient image quality for thorax image registration in daily patient positioning verification.

TU-G-BRA-01: Assessing Radiation-Induced Reductions in Regional Lung Perfusion Following Stereotactic Radiotherapy for Lung Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGurk, R; Green, R; Lawrence, M

2015-06-15

Purpose: The dose-dependent nature of radiation therapy (RT)-induced lung injury following hypo-fractionated stereotactic RT is unclear. We herein report preliminary results of a prospective study assessing the magnitude of RT-induced reductions in regional lung perfusion following hypo-fractionated stereotactic RT. Methods: Four patients undergoing hypo-fractionated stereotactic lung RT (SBRT: 12 Gy x 4 fractions or 10 Gy x 5 fractions) had a pre-treatment SPECT (single-photon emission computed tomography) perfusion scan providing a 3D map of regional lung perfusion. Scans were repeated 3–6 months post-treatment. Pre- and post SPECT scans were registered to the planning CT scan (and hence the 3D dosemore » data). Changes in regional perfusion (counts per cc on the pre-post scans) were computed in regions of the lung exposed to different doses of radiation (in 5 Gy intervals), thus defining a dose-response function. SPECT scans were internally normalized to the regions receiving <5 Gy. Results: At 3 months post-RT, the changes in perfusion are highly variable. At 6 months, there is a consistent dose-dependent reduction in regional perfusion. The average percent decline in regional perfusion was 10% at 15–20 Gy, 20% at 20–25 Gy, and 30% at 25–30 Gy representing a relatively linear dose response with an approximate 2% reduction per Gray for doses in excess of 10 Gy. There was a subtle increase in perfusion in the lung receiving <10 Gy. Conclusion: Hypo-fractionated stereotactic RT appears to cause a dose-dependent reduction in regional lung perfusion. There appears to be a threshold effect with no apparent perfusion loss at doses <10 Gy, though this might be in part due to the normalization technique used. Additional data is needed from a larger number of patients to better assess this issue. This sort of data can be used to assist optimizing RT treatment plans that minimize the risk of lung injury. Partly supported by the NIH (CA69579) and the Lance Armstrong Foundation.« less

Does Iterative Reconstruction Lower CT Radiation Dose: Evaluation of 15,000 Examinations

PubMed Central

Noël, Peter B.; Renger, Bernhard; Fiebich, Martin; Münzel, Daniela; Fingerle, Alexander A.; Rummeny, Ernst J.; Dobritz, Martin

2013-01-01

Purpose Evaluation of 15,000 computed tomography (CT) examinations to investigate if iterative reconstruction (IR) reduces sustainably radiation exposure. Method and Materials Information from 15,000 CT examinations was collected, including all aspects of the exams such as scan parameter, patient information, and reconstruction instructions. The examinations were acquired between January 2010 and December 2012, while after 15 months a first generation IR algorithm was installed. To collect the necessary information from PACS, RIS, MPPS and structured reports a Dose Monitoring System was developed. To harvest all possible information an optical character recognition system was integrated, for example to collect information from the screenshot CT-dose report. The tool transfers all data to a database for further processing such as the calculation of effective dose and organ doses. To evaluate if IR provides a sustainable dose reduction, the effective dose values were statistically analyzed with respect to protocol type, diagnostic indication, and patient population. Results IR has the potential to reduce radiation dose significantly. Before clinical introduction of IR the average effective dose was 10.1±7.8mSv and with IR 8.9±7.1mSv (p*=0.01). Especially in CTA, with the possibility to use kV reduction protocols, such as in aortic CTAs (before IR: average14.2±7.8mSv; median11.4mSv /with IR:average9.9±7.4mSv; median7.4mSv), or pulmonary CTAs (before IR: average9.7±6.2mSV; median7.7mSv /with IR: average6.4±4.7mSv; median4.8mSv) the dose reduction effect is significant(p*=0.01). On the contrary for unenhanced low-dose scans of the cranial (for example sinuses) the reduction is not significant (before IR:average6.6±5.8mSv; median3.9mSv/with IR:average6.0±3.1mSV; median3.2mSv). Conclusion The dose aspect remains a priority in CT research. Iterative reconstruction algorithms reduce sustainably and significantly radiation dose in the clinical routine. Our results illustrate that not only in studies with a limited number of patients but also in the clinical routine, IRs provide long-term dose saving. PMID:24303035

SU-F-T-424: Mitigation of Increased Surface Dose When Treating Through A Carbon Fiber Couch Top

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, E; Misgina, F

Purpose: To study the effect of the Varian carbon fiber couch top on surface dose for patients being treated using single PA beams in the supine position and to identify simple methods for surface dose reduction. Methods: Measurements of surface dose were obtained in Solid Water phantoms using both a parallel plate ionization chamber (PTW Advanced Markus) and EBT2 Radiochromic films for both 6 and 10MV photons. All measurements were referenced to a depth considered a typical for PA Spine fields. Techniques used to reduce the surface dose included introducing an air standoff using Styrofoam sheets to suspend the phantommore » surface above the couch top and by adding a thin high Z scattering foil on the table surface. Surface doses were evaluated for typical field sizes, standoff heights, and various scattering materials. Comparisons were made to the surface dose obtainable when treating through a Varian Mylar covered tennis racket style couch top. Results: Dependence on typical spine field sizes was relatively minor. Dependence on air gap was much more significant. Surface doses decreased exponentially with increases in air standoff distance. Surface doses were reduced by approximately 50% for an air gap of 10cm and 40% for a 15cm air gap. Surface doses were reduced by an additional 15% by the addition of a 1mm Tin scattering foil. Conclusion: Using simple techniques, it is possible to reduce the surface dose when treating single PA fields through the Varian carbon fiber couch top. Surface doses can be reduced to levels observed when treating though transparent Mylar tops by adding about 15 cm of air gap. Further reductions are possible by adding thin scattering foils, such as Tin or Lead, on the couch surface. This is a low cost approach to reduce surface dose when using the Varian carbon fiber couch top.« less

Schistosoma mansoni: is acquired immunity induced by highly x-irradiated cercariae dependent on the size of the challenging dose

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsue, S.Y.; Hsue, H.F.; Osborne, J.W.

1982-04-01

A high degree of immunity, as shown by a 91% reduction of the number of worms recovered was found in five groups of mice that were immunized five times with highly X-irradiated cercariae and then challenged with 10, 20, 50, 100, or 500 normal Schistosoma mansoni cercariae. The results indicated that there were no significant differences in worm reduction in immunized mice challenged with different numbers of cercariae; consequently the immunity induced by this immunization method did not appear to be challenge-dose-dependent. However, the results also showed that when immunized mice were challenged with 500, 100, 50, 20, and 10more » cercariae, 0, 13, 26, 56, and 68%, respectively, of the experimental animals were free of worms. Thus, the percentage of worm-negative cases increased as the number of challenge cercariae decreased. When viewed in this manner, the acquired immunity may be considered challenge-dose-dependent as well. If this method of vaccination is used for schistosomiasis control, we may anticipate that in both hypo- and hyperendemic areas, the intensity of infection and the severity of the disease will be reduced owing to a reduction in worms burdens, and in hypoendemic areas, there will be a number of worm-free cases.« less

EP3/FP dual receptor agonist ONO-9054 administered morning or evening to patients with open-angle glaucoma or ocular hypertension: results of a randomised crossover study

PubMed Central

Berlin, Michael S; Rowe-Rendleman, Cheryl; Ahmed, Ike; Ross, Douglas T; Fujii, Akifumi; Ouchi, Takafumi; Quach, Christine; Wood, Andrew; Ward, Caroline L

2016-01-01

Background/aims The novel prostaglandin E (EP) 3 and prostaglandin F (FP) receptor agonist ONO-9054 is effective in lowering intraocular pressure (IOP) in patients with ocular hypertension and open-angle glaucoma when administered once daily. This study compares the effects of morning (AM) versus evening (PM) dosing of ONO-9054 on tolerability and IOP lowering. Methods This was a single-centre, randomised, double-masked, two-sequence, placebo-controlled crossover study in 12 subjects with bilateral primary open-angle glaucoma or ocular hypertension. Two 14-day crossover regimens were separated by a 2-week washout: ONO-9054 (1 drop to each eye) in the morning (07:00) and vehicle in the evening (19:00) and vice versa. IOP was measured multiple times during select days. Ocular examinations also evaluated safety and tolerability. Results Mild ocular hyperaemia, reported by six subjects with PM dosing, was the most frequent adverse event. Mild to moderate dryness was also slightly more frequent after PM dosing. Maximum IOP reduction from baseline occurred on day 2 with decreases from baseline of −7.4 mm Hg (−30.8%) for AM dosing and −9.1 mm Hg, (−38.0%) for PM dosing; after 14 days, mean reduction in IOP was −6.8 mm Hg (−28.6%) for AM dosing and −7.5 mm Hg (−31.0%) for PM dosing. Conclusions PM dosing of ONO-0954 was associated with a slightly increased frequency of mild hyperaemia and mild to moderate dryness. Both dosing schedules provided sustained reduction in IOP. Trial registration number NCT01670266. PMID:26453641

Technical Note: Phantom study to evaluate the dose and image quality effects of a computed tomography organ-based tube current modulation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gandhi, Diksha; Schmidt, Taly Gilat, E-mail: taly.gilat-schmidt@marquette.edu; Crotty, Dominic J.

Purpose: This technical note quantifies the dose and image quality performance of a clinically available organ-dose-based tube current modulation (ODM) technique, using experimental and simulation phantom studies. The investigated ODM implementation reduces the tube current for the anterior source positions, without increasing current for posterior positions, although such an approach was also evaluated for comparison. Methods: Axial CT scans at 120 kV were performed on head and chest phantoms on an ODM-equipped scanner (Optima CT660, GE Healthcare, Chalfont St. Giles, England). Dosimeters quantified dose to breast, lung, heart, spine, eye lens, and brain regions for ODM and 3D-modulation (SmartmA) settings.more » Monte Carlo simulations, validated with experimental data, were performed on 28 voxelized head phantoms and 10 chest phantoms to quantify organ dose and noise standard deviation. The dose and noise effects of increasing the posterior tube current were also investigated. Results: ODM reduced the dose for all experimental dosimeters with respect to SmartmA, with average dose reductions across dosimeters of 31% (breast), 21% (lung), 24% (heart), 6% (spine), 19% (eye lens), and 11% (brain), with similar results for the simulation validation study. In the phantom library study, the average dose reduction across all phantoms was 34% (breast), 20% (lung), 8% (spine), 20% (eye lens), and 8% (brain). ODM increased the noise standard deviation in reconstructed images by 6%–20%, with generally greater noise increases in anterior regions. Increasing the posterior tube current provided similar dose reduction as ODM for breast and eye lens, increased dose to the spine, with noise effects ranging from 2% noise reduction to 16% noise increase. At noise equal to SmartmA, ODM increased the estimated effective dose by 4% and 8% for chest and head scans, respectively. Increasing the posterior tube current further increased the effective dose by 15% (chest) and 18% (head) relative to SmartmA. Conclusions: ODM reduced dose in all experimental and simulation studies over a range of phantoms, while increasing noise. The results suggest a net dose/noise benefit for breast and eye lens for all studied phantoms, negligible lung dose effects for two phantoms, increased lung dose and/or noise for eight phantoms, and increased dose and/or noise for brain and spine for all studied phantoms compared to the reference protocol.« less

Peak skin and eye lens radiation dose from brain perfusion CT based on Monte Carlo simulation.

PubMed

Zhang, Di; Cagnon, Chris H; Villablanca, J Pablo; McCollough, Cynthia H; Cody, Dianna D; Stevens, Donna M; Zankl, Maria; Demarco, John J; Turner, Adam C; Khatonabadi, Maryam; McNitt-Gray, Michael F

2012-02-01

The purpose of our study was to accurately estimate the radiation dose to skin and the eye lens from clinical CT brain perfusion studies, investigate how well scanner output (expressed as volume CT dose index [CTDI(vol)]) matches these estimated doses, and investigate the efficacy of eye lens dose reduction techniques. Peak skin dose and eye lens dose were estimated using Monte Carlo simulation methods on a voxelized patient model and 64-MDCT scanners from four major manufacturers. A range of clinical protocols was evaluated. CTDI(vol) for each scanner was obtained from the scanner console. Dose reduction to the eye lens was evaluated for various gantry tilt angles as well as scan locations. Peak skin dose and eye lens dose ranged from 81 mGy to 348 mGy, depending on the scanner and protocol used. Peak skin dose and eye lens dose were observed to be 66-79% and 59-63%, respectively, of the CTDI(vol) values reported by the scanners. The eye lens dose was significantly reduced when the eye lenses were not directly irradiated. CTDI(vol) should not be interpreted as patient dose; this study has shown it to overestimate dose to the skin or eye lens. These results may be used to provide more accurate estimates of actual dose to ensure that protocols are operated safely below thresholds. Tilting the gantry or moving the scanning region further away from the eyes are effective for reducing lens dose in clinical practice. These actions should be considered when they are consistent with the clinical task and patient anatomy.

Comparison of Chest Pain Protocols for Electrocardiography-Gated Dual-Source Cardiothoracic CT in Children and Adults: The Effect of Tube Current Saturation on Radiation Dose Reduction

PubMed Central

2018-01-01

Objective To compare radiation doses between conventional and chest pain protocols using dual-source retrospectively electrocardiography (ECG)-gated cardiothoracic computed tomography (CT) in children and adults and assess the effect of tube current saturation on radiation dose reduction. Materials and Methods This study included 104 patients (16.6 ± 7.7 years, range 5–48 years) that were divided into two groups: those with and those without tube current saturation. The estimated radiation doses of retrospectively ECG-gated spiral cardiothoracic CT were compared between conventional, uniphasic, and biphasic chest pain protocols acquired with the same imaging parameters in the same patients by using paired t tests. Dose reduction percentages, patient ages, volume CT dose index values, and tube current time products per rotation were compared between the two groups by using unpaired t tests. A p value < 0.05 was considered significant. Results The volume CT dose index values of the biphasic chest pain protocol (10.8 ± 3.9 mGy) were significantly lower than those of the conventional protocol (12.2 ± 4.7 mGy, p < 0.001) and those of the uniphasic chest pain protocol (12.9 ± 4.9 mGy, p < 0.001). The dose-saving effect of biphasic chest pain protocol was significantly less with a saturated tube current (4.5 ± 10.2%) than with unsaturated tube current method (14.8 ± 11.5%, p < 0.001). In 76 patients using 100 kVp, patient age showed no significant differences between the groups with and without tube current saturation in all protocols (p > 0.05); the groups with tube current saturation showed significantly higher volume CT dose index values (p < 0.01) and tube current time product per rotation (p < 0.001) than the groups without tube current saturation in all protocols. Conclusion The radiation dose of dual-source retrospectively ECG-gated spiral cardiothoracic CT can be reduced by approximately 15% by using the biphasic chest pain protocol instead of the conventional protocol in children and adults if radiation dose parameters are further optimized to avoid tube current saturation. PMID:29353996

Influence of scatter reduction method and monochromatic beams on image quality and dose in mammography.

PubMed

Moeckli, Raphaël; Verdun, Francis R; Fiedler, Stefan; Pachoud, Marc; Bulling, Shelley; Schnyder, Pierre; Valley, Jean-François

2003-12-01

In mammography, the image contrast and dose delivered to the patient are determined by the x-ray spectrum and the scatter to primary ratio S/P. Thus the quality of the mammographic procedure is highly dependent on the choice of anode and filter material and on the method used to reduce the amount of scattered radiation reaching the detector. Synchrotron radiation is a useful tool to study the effect of beam energy on the optimization of the mammographic process because it delivers a high flux of monochromatic photons. Moreover, because the beam is naturally flat collimated in one direction, a slot can be used instead of a grid for scatter reduction. We have measured the ratio S/P and the transmission factors for grids and slots for monoenergetic synchrotron radiation. In this way the effect of beam energy and scatter rejection method were separated, and their respective importance for image quality and dose analyzed. Our results show that conventional mammographic spectra are not far from optimum and that the use of a slot instead of a grid has an important effect on the optimization of the mammographic process. We propose a simple numerical model to quantify this effect.

TU-G-BRA-04: Changes in Regional Lung Function Measured by 4D-CT Ventilation Imaging for Thoracic Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakajima, Y; Kadoya, N; Kabus, S

Purpose: To test the hypothesis: 4D-CT ventilation imaging can show the known effects of radiotherapy on lung function: (1) radiation-induced ventilation reductions, and (2) ventilation increases caused by tumor regression. Methods: Repeat 4D-CT scans (pre-, mid- and/or post-treatment) were acquired prospectively for 11 thoracic cancer patients in an IRB-approved clinical trial. A ventilation image for each time point was created using deformable image registration and the Hounsfield unit (HU)-based or Jacobian-based metric. The 11 patients were divided into two subgroups based on tumor volume reduction using a threshold of 5 cm{sup 3}. To quantify radiation-induced ventilation reduction, six patients whomore » showed a small tumor volume reduction (<5 cm{sup 3}) were analyzed for dose-response relationships. To investigate ventilation increase caused by tumor regression, two of the other five patients were analyzed to compare ventilation changes in the lung lobes affected and unaffected by the tumor. The remaining three patients were excluded because there were no unaffected lobes. Results: Dose-dependent reductions of HU-based ventilation were observed in a majority of the patient-specific dose-response curves and in the population-based dose-response curve, whereas no clear relationship was seen for Jacobian-based ventilation. The post-treatment population-based dose-response curve of HU-based ventilation demonstrated the average ventilation reductions of 20.9±7.0% at 35–40 Gy (equivalent dose in 2-Gy fractions, EQD2), and 40.6±22.9% at 75–80 Gy EQD2. Remarkable ventilation increases in the affected lobes were observed for the two patients who showed an average tumor volume reduction of 37.1 cm{sup 3} and re-opening airways. The mid-treatment increase in HU-based ventilation of patient 3 was 100.4% in the affected lobes, which was considerably greater than 7.8% in the unaffected lobes. Conclusion: This study has demonstrated that 4D-CT ventilation imaging shows the known effects of radiotherapy on lung function: radiation-induced ventilation reduction and ventilation increase caused by tumor regression, providing validation for 4D-CT ventilation imaging. This study was supported in part by a National Lung Cancer Partnership Young Investigator Research grant.« less

Method for protection against genotoxic mutagenesis

DOEpatents

Grdina, David J.

1996-01-01

A method and pharmaceutical for protecting against genotoxic damage in irradiated cells. Reduction of mutations at the hypoxanthine-guanine phosphoribosyl transferase locus is accomplished by administering an effective dose of a compound having protected sulfhydryl groups which metabolize in vivo to produce both free sulfhydryl groups and disulfides.

Kilovoltage Imaging Doses in the Radiotherapy of Pediatric Cancer Patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng Jun, E-mail: jun.deng@yale.edu; Chen Zhe; Roberts, Kenneth B.

Purpose: To investigate doses induced by kilovoltage cone-beam computed tomography (kVCBCT) to pediatric cancer patients undergoing radiotherapy, as well as strategies for dose reduction. Methods and Materials: An EGS4 Monte Carlo code was used to calculate three-dimensional dose deposition due to kVCBCT on 4 pediatric cancer patients. Absorbed doses to various organs were analyzed for both half-fan and full-fan modes. Clinical conditions, such as distance from organ at risk (OAR) to CBCT field border, kV peak energy, and testicular shielding, were studied. Results: The mean doses induced by one CBCT scan operated at 125 kV in half-fan mode to testes,more » liver, kidneys, femoral heads, spinal cord, brain, eyes, lens, and optical nerves were 2.9, 4.7, 7.7, 10.5, 8.8, 7.6, 7.7, 7.8, and 7.2 cGy, respectively. Increasing the distances from OARs to CBCT field border greatly reduced the doses to OARs, ranging from 33% reduction for spinal cord to 2300% reduction for testes. As photon beam energy increased from 60 to 125 kV, the dose increase due to kVCBCT ranged from 170% for lens to 460% for brain and spinal cord. A testicular shielding made of 1-cm cerrobend could reduce CBCT doses down to 31%, 51%, 68%, and 82%, respectively, for 60, 80, 100, and 125 kV when the testes lay within the CBCT field. Conclusions: Generally speaking, kVCBCT deposits much larger doses to critical structures in children than in adults, usually by a factor of 2 to 3. Increasing the distances from OARs to CBCT field border greatly reduces doses to OARs. Depending on OARs, kVCBCT-induced doses increase linearly or exponentially with photon beam energy. Testicular shielding works more efficiently at lower kV energies. On the basis of our study, it is essential to choose an appropriate scanning protocol when kVCBCT is applied to pediatric cancer patients routinely.« less

Safety and dose modification for patients receiving niraparib.

PubMed

Berek, J S; Matulonis, U A; Peen, U; Ghatage, P; Mahner, S; Redondo, A; Lesoin, A; Colombo, N; Vergote, I; Rosengarten, O; Ledermann, J; Pineda, M; Ellard, S; Sehouli, J; Gonzalez-Martin, A; Berton-Rigaud, D; Madry, R; Reinthaller, A; Hazard, S; Guo, W; Mirza, M R

2018-05-14

Niraparib is a poly(ADP-ribose) polymerase (PARP) inhibitor approved in the United States and Europe for maintenance treatment of adult patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in complete or partial response to platinum-based chemotherapy. In the pivotal ENGOT-OV16/NOVA trial, the dose reduction rate due to TEAE was 68.9%, and the discontinuation rate due to TEAE was 14.7%, including 3.3% due to thrombocytopenia. A retrospective analysis was performed to identify clinical parameters that predict dose reductions. All analyses were performed on the safety population, comprising all patients who received at least one dose of study drug. Patients were analyzed according to the study drug consumed (ie, as treated). A predictive modeling method (decision trees) was used to identify important variables for predicting the likelihood of developing grade ≥3 thrombocytopenia within 30 days after the first dose of niraparib and determine cutoff points for chosen variables. Following dose modification, 200 mg was the most commonly administered dose in the ENGOT-OV16/NOVA trial. Baseline platelet count and baseline body weight were identified as risk factors for increased incidence of grade ≥3 thrombocytopenia. Patients with a baseline body weight <77 kg or a baseline platelet count <150,000/μL in effect received an average daily dose approximating 200 mg (median = 207 mg) due to dose interruption and reduction. Progression-free survival in patients who were dose reduced to either 200 mg or 100 mg was consistent with that of patients who remained at the 300 mg starting dose. The analysis presented suggests that patients with baseline body weight of < 77 kg or baseline platelets of < 150,000/μL may benefit from a starting dose of 200 mg per day. (ClinicalTrials.gov ID: NCT01847274).

Feasibility study of the neutron dose for real-time image-guided proton therapy: A Monte Carlo study

NASA Astrophysics Data System (ADS)

Kim, Jin Sung; Shin, Jung Suk; Kim, Daehyun; Shin, Eunhyuk; Chung, Kwangzoo; Cho, Sungkoo; Ahn, Sung Hwan; Ju, Sanggyu; Chung, Yoonsun; Jung, Sang Hoon; Han, Youngyih

2015-07-01

Two full rotating gantries with different nozzles (multipurpose nozzle with MLC, scanning dedicated nozzle) for a conventional cyclotron system are installed and being commissioned for various proton treatment options at Samsung Medical Center in Korea. The purpose of this study is to use Monte Carlo simulation to investigate the neutron dose equivalent per therapeutic dose, H/D, for X-ray imaging equipment under various treatment conditions. At first, we investigated the H/D for various modifications of the beamline devices (scattering, scanning, multi-leaf collimator, aperture, compensator) at the isocenter and at 20, 40 and 60 cm distances from the isocenter, and we compared our results with those of other research groups. Next, we investigated the neutron dose at the X-ray equipment used for real-time imaging under various treatment conditions. Our investigation showed doses of 0.07 ~ 0.19 mSv/Gy at the X-ray imaging equipment, depending on the treatment option and interestingly, the 50% neutron dose reduction was observed due to multileaf collimator during proton scanning treatment with the multipurpose nozzle. In future studies, we plan to measure the neutron dose experimentally and to validate the simulation data for X-ray imaging equipment for use as an additional neutron dose reduction method.

Influence of dose on particle size and optical properties of colloidal platinum nanoparticles.

PubMed

Gharibshahi, Elham; Saion, Elias

2012-11-12

Attempts to produce colloidal platinum nanoparticles by using steady absorption spectra with various chemical-based reduction methods often resulted in the fast disappearance of the absorption maxima leaving reduced platinum nanoparticles with little information on their optical properties. We synthesized colloidal platinum nanoparticles in an aqueous solution of polyvinyl pyrrolidone by gamma radiolytic reduction method, which produced steady absorption spectra of fully reduced and highly pure platinum nanoparticles free from by-product impurities or reducing agent contamination. The average particle size was found to be in the range of 3.4–5.3 nm and decreased with increasing dose due to the domination of nucleation over ion association in the formation of metal nanoparticles by the gamma radiolytic reduction method. The platinum nanoparticles exhibit optical absorption spectra with two absorption peaks centered at about 216 and 264 nm and the peaks blue shifted to lower wavelengths with decreasing particle size. The absorption spectra of platinum nanoparticles were also calculated using quantum mechanical treatment and coincidently a good agreement was obtained between the calculated and measured absorption peaks at various particle sizes. This indicates that the 216 and 264-nm absorption peaks of platinum nanoparticles conceivably originated from the intra-band transitions of conduction electrons of (n = 5, l = 2) and (n = 6, l = 0) energy states respectively to higher energy states. The absorption energies, i.e., conduction band energies of platinum nanoparticles derived from the absorption peaks increased with increasing dose and decreased with increasing particle size.

Influence of Dose on Particle Size and Optical Properties of Colloidal Platinum Nanoparticles

PubMed Central

Gharibshahi, Elham; Saion, Elias

2012-01-01

Attempts to produce colloidal platinum nanoparticles by using steady absorption spectra with various chemical-based reduction methods often resulted in the fast disappearance of the absorption maxima leaving reduced platinum nanoparticles with little information on their optical properties. We synthesized colloidal platinum nanoparticles in an aqueous solution of polyvinyl pyrrolidone by gamma radiolytic reduction method, which produced steady absorption spectra of fully reduced and highly pure platinum nanoparticles free from by-product impurities or reducing agent contamination. The average particle size was found to be in the range of 3.4–5.3 nm and decreased with increasing dose due to the domination of nucleation over ion association in the formation of metal nanoparticles by the gamma radiolytic reduction method. The platinum nanoparticles exhibit optical absorption spectra with two absorption peaks centered at about 216 and 264 nm and the peaks blue shifted to lower wavelengths with decreasing particle size. The absorption spectra of platinum nanoparticles were also calculated using quantum mechanical treatment and coincidently a good agreement was obtained between the calculated and measured absorption peaks at various particle sizes. This indicates that the 216 and 264-nm absorption peaks of platinum nanoparticles conceivably originated from the intra-band transitions of conduction electrons of (n = 5, l = 2) and (n = 6, l = 0) energy states respectively to higher energy states. The absorption energies, i.e., conduction band energies of platinum nanoparticles derived from the absorption peaks increased with increasing dose and decreased with increasing particle size. PMID:23203091

Statistical model based iterative reconstruction (MBIR) in clinical CT systems: Experimental assessment of noise performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ke; Tang, Jie; Chen, Guang-Hong, E-mail: gchen7@wisc.edu

Purpose: To reduce radiation dose in CT imaging, the statistical model based iterative reconstruction (MBIR) method has been introduced for clinical use. Based on the principle of MBIR and its nonlinear nature, the noise performance of MBIR is expected to be different from that of the well-understood filtered backprojection (FBP) reconstruction method. The purpose of this work is to experimentally assess the unique noise characteristics of MBIR using a state-of-the-art clinical CT system. Methods: Three physical phantoms, including a water cylinder and two pediatric head phantoms, were scanned in axial scanning mode using a 64-slice CT scanner (Discovery CT750 HD,more » GE Healthcare, Waukesha, WI) at seven different mAs levels (5, 12.5, 25, 50, 100, 200, 300). At each mAs level, each phantom was repeatedly scanned 50 times to generate an image ensemble for noise analysis. Both the FBP method with a standard kernel and the MBIR method (Veo{sup ®}, GE Healthcare, Waukesha, WI) were used for CT image reconstruction. Three-dimensional (3D) noise power spectrum (NPS), two-dimensional (2D) NPS, and zero-dimensional NPS (noise variance) were assessed both globally and locally. Noise magnitude, noise spatial correlation, noise spatial uniformity and their dose dependence were examined for the two reconstruction methods. Results: (1) At each dose level and at each frequency, the magnitude of the NPS of MBIR was smaller than that of FBP. (2) While the shape of the NPS of FBP was dose-independent, the shape of the NPS of MBIR was strongly dose-dependent; lower dose lead to a “redder” NPS with a lower mean frequency value. (3) The noise standard deviation (σ) of MBIR and dose were found to be related through a power law of σ ∝ (dose){sup −β} with the component β ≈ 0.25, which violated the classical σ ∝ (dose){sup −0.5} power law in FBP. (4) With MBIR, noise reduction was most prominent for thin image slices. (5) MBIR lead to better noise spatial uniformity when compared with FBP. (6) A composite image generated from two MBIR images acquired at two different dose levels (D1 and D2) demonstrated lower noise than that of an image acquired at a dose level of D1+D2. Conclusions: The noise characteristics of the MBIR method are significantly different from those of the FBP method. The well known tradeoff relationship between CT image noise and radiation dose has been modified by MBIR to establish a more gradual dependence of noise on dose. Additionally, some other CT noise properties that had been well understood based on the linear system theory have also been altered by MBIR. Clinical CT scan protocols that had been optimized based on the classical CT noise properties need to be carefully re-evaluated for systems equipped with MBIR in order to maximize the method's potential clinical benefits in dose reduction and/or in CT image quality improvement.« less

Evaluation of an iterative model-based reconstruction of pediatric abdominal CT with regard to image quality and radiation dose.

PubMed

Aurumskjöld, Marie-Louise; Söderberg, Marcus; Stålhammar, Fredrik; von Steyern, Kristina Vult; Tingberg, Anders; Ydström, Kristina

2018-06-01

Background In pediatric patients, computed tomography (CT) is important in the medical chain of diagnosing and monitoring various diseases. Because children are more radiosensitive than adults, they require minimal radiation exposure. One way to achieve this goal is to implement new technical solutions, like iterative reconstruction. Purpose To evaluate the potential of a new, iterative, model-based method for reconstructing (IMR) pediatric abdominal CT at a low radiation dose and determine whether it maintains or improves image quality, compared to the current reconstruction method. Material and Methods Forty pediatric patients underwent abdominal CT. Twenty patients were examined with the standard dose settings and 20 patients were examined with a 32% lower radiation dose. Images from the standard examination were reconstructed with a hybrid iterative reconstruction method (iDose 4 ), and images from the low-dose examinations were reconstructed with both iDose 4 and IMR. Image quality was evaluated subjectively by three observers, according to modified EU image quality criteria, and evaluated objectively based on the noise observed in liver images. Results Visual grading characteristics analyses showed no difference in image quality between the standard dose examination reconstructed with iDose 4 and the low dose examination reconstructed with IMR. IMR showed lower image noise in the liver compared to iDose 4 images. Inter- and intra-observer variance was low: the intraclass coefficient was 0.66 (95% confidence interval = 0.60-0.71) for the three observers. Conclusion IMR provided image quality equivalent or superior to the standard iDose 4 method for evaluating pediatric abdominal CT, even with a 32% dose reduction.

Effect of reduced agalsidase Beta dosage in fabry patients: the Australian experience.

PubMed

Ghali, Joanna; Nicholls, Kathy; Denaro, Charles; Sillence, David; Chapman, Ian; Goldblatt, Jack; Thomas, Mark; Fletcher, Janice

2012-01-01

In Australia, enzyme replacement therapy (ERT) for Fabry Disease (FD), both Agalsidase alfa (Replagal, Shire HGT) and beta (Fabrazyme, Genzyme), is funded and monitored through a specific government program. Agalsidase beta supply has been rationed by Genzyme since 2009 due to manufacturing issues. Consequently, the Australian Fabry Disease Advisory Committee has treated patients on Agalsidase beta at 50% of their usual dose from mid-2009, with a further reduction to 30% for some patients from late 2009. To determine the clinical effect of Agalsidase beta dose reduction in the Australian FD patient cohort. A questionnaire assessing FD symptoms was administered to 40 patients on long-term ERT. Clinical data from The Fabry Registry for patients receiving Agalsidase alfa or beta, for at least 2 years prior to the time of enforced Agalsidase beta dose reduction, were reviewed. Disease burden and quality of life (QOL) were graded using the Disease Severity Scoring System, Mainz Severity Score Index, Brief Pain Inventory and Short Form 36 Health Survey at 2 years before dose reduction, at the time of dose reduction and at the most recent clinical review following dose reduction. Disease severity and QOL scores did not change between the ERT groups. Males on Agalsidase beta reported lower energy levels after dose reduction, while no change was reported by females on either product or by males on a stable dose of Agalsidase alfa. This study suggests that energy levels in male patients worsen after dose reduction of Agalsidase beta.

Efficacy of radiation safety glasses in interventional radiology.

PubMed

van Rooijen, Bart D; de Haan, Michiel W; Das, Marco; Arnoldussen, Carsten W K P; de Graaf, R; van Zwam, Wim H; Backes, Walter H; Jeukens, Cécile R L P N

2014-10-01

This study was designed to evaluate the reduction of the eye lens dose when wearing protective eyewear in interventional radiology and to identify conditions that optimize the efficacy of radiation safety glasses. The dose reduction provided by different models of radiation safety glasses was measured on an anthropomorphic phantom head. The influence of the orientation of the phantom head on the dose reduction was studied in detail. The dose reduction in interventional radiological practice was assessed by dose measurements on radiologists wearing either leaded or no glasses or using a ceiling suspended screen. The different models of radiation safety glasses provided a dose reduction in the range of a factor of 7.9-10.0 for frontal exposure of the phantom. The dose reduction was strongly reduced when the head is turned to the side relative to the irradiated volume. The eye closest to the tube was better protected due to side shielding and eyewear curvature. In clinical practice, the mean dose reduction was a factor of 2.1. Using a ceiling suspended lead glass shield resulted in a mean dose reduction of a factor of 5.7. The efficacy of radiation protection glasses depends on the orientation of the operator's head relative to the irradiated volume. Glasses can offer good protection to the eye under clinically relevant conditions. However, the performance in clinical practice in our study was lower than expected. This is likely related to nonoptimized room geometry and training of the staff as well as measurement methodology.

Patient geometry-driven information retrieval for IMRT treatment plan quality control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu Binbin; Ricchetti, Francesco; Sanguineti, Giuseppe

Purpose: Intensity modulated radiation therapy (IMRT) treatment plan quality depends on the planner's level of experience and the amount of time the planner invests in developing the plan. Planners often unwittingly accept plans when further sparing of the organs at risk (OARs) is possible. The authors propose a method of IMRT treatment plan quality control that helps planners to evaluate the doses of the OARs upon completion of a new plan. Methods: It is achieved by comparing the geometric configurations of the OARs and targets of a new patient with those of prior patients, whose plans are maintained in amore » database. They introduce the concept of a shape relationship descriptor and, specifically, the overlap volume histogram (OVH) to describe the spatial configuration of an OAR with respect to a target. The OVH provides a way to infer the likely DVHs of the OARs by comparing the relative spatial configurations between patients. A database of prior patients is built to serve as an external reference. At the conclusion of a new plan, planners search through the database and identify related patients by comparing the OAR-target geometric relationships of the new patient with those of prior patients. The treatment plans of these related patients are retrieved from the database and guide planners in determining whether lower doses delivered to the OARs in the new plan are feasible. Results: Preliminary evaluation is promising. In this evaluation, they applied the analysis to the parotid DVHs of 32 prior head-and-neck patients, whose plans are maintained in a database. Each parotid was queried against the other 63 parotids to determine whether a lower dose was possible. The 17 parotids that promised the greatest reduction in D{sub 50} (DVH dose at 50% volume) were flagged. These 17 parotids came from 13 patients. The method also indicated that the doses of the other nine parotids of the 13 patients could not be reduced, so they were included in the replanning process as controls. Replanning with an effort to reduce D{sub 50} was conducted on these 26 parotids. After replanning, the average reductions for D{sub 50} of the 17 flagged parotids and nine unflagged parotids were 6.6 and 1.9 Gy, respectively. These results demonstrate that the quality control method has accurately identified not only the parotids that require dose reductions but also those for which dose reductions are marginal. Originally, 11 of out the 17 flagged parotids did not meet the Radiation Therapy Oncology Group sparing goal of V(30 Gy)<50%. Replanning reduced them to three. Additionally, PTV coverage and OAR sparing of the original plans were compared to those of the replans by using pairwise Wilcoxon p test. The statistical comparisons show that replanning compromised neither PTV coverage nor OAR sparing. Conclusions: This method provides an effective quality control mechanism for evaluating the DVHs of the OARs. Adoption of such a method will advance the quality of current IMRT planning, providing better treatment plan consistency.« less

Race differences: modeling the pharmacodynamics of rosuvastatin in Western and Asian hypercholesterolemia patients

PubMed Central

Yang, Juan; Li, Lu-jin; Wang, Kun; He, Ying-chun; Sheng, Yu-cheng; Xu, Ling; Huang, Xiao-hui; Guo, Feng; Zheng, Qing-shan

2011-01-01

Aim: To evaluate race differences in the pharmacodynamics of rosuvastatin in Western and Asian hypercholesterolemia patients using a population pharmacodynamic (PPD) model generated and validated using published clinical efficacy trials. Methods: Published studies randomized trials with rosuvastatin treatment for at least 4 weeks in hypercholesterolemia patients were used for model building and validation. Population pharmacodynamic analyses were performed to describe the dose-response relationship with the mean values of LDL-C reduction (%) from dose-ranging trials using NONMEM software. Baseline LDL-C and race were analyzed as the potential covariates. Model robustness was evaluated using the bootstrap method and the data-splitting method, and Monte Carlo simulation was performed to assess the predictive performance of the PPD model with the mean effects from the one-dose trials. Results: Of the 36 eligible trials, 14 dose-ranging trials were used in model development and 22 one-dose trials were used for model prediction. The dose-response of rosuvastatin was successfully described by a simple Emax model with a fixed E0, which provided a common Emax and an approximate twofold difference in ED50 for Westerners and Asians. The PPD model was demonstrated to be stable and predictive. Conclusion: The race differences in the pharmacodynamics of rosuvastatin are consistent with those observed in the pharmacokinetics of the drug, confirming that there is no significant difference in the exposure-response relationship for LDL-C reduction between Westerners and Asians. The study suggests that for a new compound with a mechanism of action similar to that of rosuvastatin, its efficacy in Western populations plus its pharmacokinetics in bridging studies in Asian populations may be used to support a registration of the new compound in Asian countries. PMID:21151159

Reducing statistical uncertainties in simulated organ doses of phantoms immersed in water

DOE PAGES

Hiller, Mauritius M.; Veinot, Kenneth G.; Easterly, Clay E.; ...

2016-08-13

In this study, methods are addressed to reduce the computational time to compute organ-dose rate coefficients using Monte Carlo techniques. Several variance reduction techniques are compared including the reciprocity method, importance sampling, weight windows and the use of the ADVANTG software package. For low-energy photons, the runtime was reduced by a factor of 10 5 when using the reciprocity method for kerma computation for immersion of a phantom in contaminated water. This is particularly significant since impractically long simulation times are required to achieve reasonable statistical uncertainties in organ dose for low-energy photons in this source medium and geometry. Althoughmore » the MCNP Monte Carlo code is used in this paper, the reciprocity technique can be used equally well with other Monte Carlo codes.« less

Benefits of adaptive radiation therapy in lung cancer as a function of replanning frequency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dial, Christian; Weiss, Elisabeth; Hugo, Geoffrey D., E-mail: gdhugo@vcu.edu

Purpose: To quantify the potential benefit associated with daily replanning in lung cancer in terms of normal tissue dose sparing and to characterize the tradeoff between adaptive benefit and replanning frequency. Methods: A set of synthetic images and contours, derived from weekly active breathing control images of 12 patients who underwent radiation therapy treatment for nonsmall cell lung cancer, is generated for each fraction of treatment using principal component analysis in a way that preserves temporal anatomical trends (e.g., tumor regression). Daily synthetic images and contours are used to simulate four different treatment scenarios: (1) a “no-adapt” scenario that simulatesmore » delivery of an initial plan throughout treatment, (2) a “midadapt” scenario that implements a single replan for fraction 18, (3) a “weekly adapt” scenario that simulates weekly adaptations, and (4) a “full-adapt” scenario that simulates daily replanning. An initial intensity modulated radiation therapy plan is created for each patient and replanning is carried out in an automated fashion by reoptimizing beam apertures and weights. Dose is calculated on each image and accumulated to the first in the series using deformable mappings utilized in synthetic image creation for comparison between simulated treatments. Results: Target coverage was maintained and cord tolerance was not exceeded for any of the adaptive simulations. Average reductions in mean lung dose (MLD) and volume of lung receiving 20 Gy or more (V20{sub lung}) were 65 ± 49 cGy (p = 0.000 01) and 1.1% ± 1.2% (p = 0.0006), respectively, for all patients. The largest reduction in MLD for a single patient was 162 cGy, which allowed an isotoxic escalation of the target dose of 1668 cGy. Average reductions in cord max dose, mean esophageal dose (MED), dose received by 66% of the heart (D66{sub heart}), and dose received by 33% of the heart (D33{sub heart}), were 158 ± 280, 117 ± 121, 37 ± 77, and 99 ± 120 cGy, respectively. Average incremental reductions in MLD for the midadapt, weekly adapt, and full-adapt treatments were 38, 18, and 8 cGy, respectively. Incremental reductions in MED for the same treatments were 57, 37, and 23 cGy. Reductions in MLD and MED for the full-adapt treatment were correlated with the absolute decrease in the planning target volume (r = 0.34 and r = 0.26). Conclusions: Adaptive radiation therapy for lung cancer yields clinically relevant reductions in normal tissue doses for frequencies of adaptation ranging from a single replan up to daily replanning. Increased frequencies of adaptation result in additional benefit while magnitude of benefit decreases.« less

Low-dose CT of postoperative pelvic fractures: a comparison with radiography.

PubMed

Eriksson, Thomas; Berg, Per; Olerud, Claes; Shalabi, Adel; Hänni, Mari

2018-01-01

Background Computed tomography (CT) is superior to conventional radiography (CR) for assessing internal fixation of pelvic fractures, but with a higher radiation exposure. Low-dose CT (LDCT) could possibly have a sufficient diagnostic accuracy but with a lower radiation dose. Purpose To compare postoperative diagnostic accuracy of LDCT and CR after open reduction and internal fixation of pelvic fracture. Material and Methods Twenty-one patients were examined with LDCT and CR 0-9 days after surgery. The examinations were reviewed by two musculoskeletal radiologists. Hardware, degree of fracture reduction, image quality, and reviewing time were assessed, and effective radiation dose was calculated. Inter-reader agreement was calculated. Results LDCT was significantly better than CR in determining whether hardware positioning was assessable ( P < 0.001). Acetabular congruence was assessable in all fractured patients with LDCT. In 12 of the 32 assessments with CR of patients with an acetabular fracture, joint congruence was not assessable due to overlapping hardware ( P = 0.001). Image quality was significantly higher for LDCT. Median time to review was 240 s for LDCT compared to 180 s for CR. Effective dose was 0.79 mSv for LDCT compared to 0.32 mSv for CR ( P < 0.001). Conclusion LDCT is more reliable than CR in assessing hardware position and fracture reduction. Joint congruency is sometimes not possible to assess with CR, due to overlapping hardware. The image quality is higher, but also the effective dose, with LDCT than with CR.

Method for protection against genotoxic mutagenesis

DOEpatents

Grdina, D.J.

1996-01-30

A method and pharmaceutical for protecting against genotoxic damage in irradiated cells are disclosed. Reduction of mutations at the hypoxanthine-guanine phosphoribosyl transferase locus is accomplished by administering an effective dose of a compound having protected sulfhydryl groups which metabolize in vivo to produce both free sulfhydryl groups and disulfides. 10 figs.

Radiation dose reduction efficiency of buildings after the accident at the Fukushima Daiichi Nuclear Power Station.

PubMed

Monzen, Satoru; Hosoda, Masahiro; Osanai, Minoru; Tokonami, Shinji

2014-01-01

Numerous radionuclides were released from the Fukushima Daiichi Nuclear Power Station (F1-NPS) in Japan following the magnitude 9.0 earthquake and tsunami on March 11, 2011. Local residents have been eager to calculate their individual radiation exposure. Thus, absorbed dose rates in the indoor and outdoor air at evacuation sites in the Fukushima Prefecture were measured using a gamma-ray measuring devices, and individual radiation exposure was calculated by assessing the radiation dose reduction efficiency (defined as the ratio of absorbed dose rate in the indoor air to the absorbed dose rate in the outdoor air) of wood, aluminum, and reinforced concrete buildings. Between March 2011 and July 2011, dose reduction efficiencies of wood, aluminum, and reinforced concrete buildings were 0.55 ± 0.04, 0.15 ± 0.02, and 0.19 ± 0.04, respectively. The reduction efficiency of wood structures was 1.4 times higher than that reported by the International Atomic Energy Agency. The efficiency of reinforced concrete was similar to previously reported values, whereas that of aluminum structures has not been previously reported. Dose reduction efficiency increased in proportion to the distance from F1-NPS at 8 of the 18 evacuation sites. Time variations did not reflect dose reduction efficiencies at evacuation sites although absorbed dose rates in the outdoor air decreased. These data suggest that dose reduction efficiency depends on structure types, levels of contamination, and evacuee behaviors at evacuation sites.

SU-C-18C-06: Radiation Dose Reduction in Body Interventional Radiology: Clinical Results Utilizing a New Imaging Acquisition and Processing Platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohlbrenner, R; Kolli, KP; Taylor, A

2014-06-01

Purpose: To quantify the patient radiation dose reduction achieved during transarterial chemoembolization (TACE) procedures performed in a body interventional radiology suite equipped with the Philips Allura Clarity imaging acquisition and processing platform, compared to TACE procedures performed in the same suite equipped with the Philips Allura Xper platform. Methods: Total fluoroscopy time, cumulative dose area product, and cumulative air kerma were recorded for the first 25 TACE procedures performed to treat hepatocellular carcinoma (HCC) in a Philips body interventional radiology suite equipped with Philips Allura Clarity. The same data were collected for the prior 85 TACE procedures performed to treatmore » HCC in the same suite equipped with Philips Allura Xper. Mean values from these cohorts were compared using two-tailed t tests. Results: Following installation of the Philips Allura Clarity platform, a 42.8% reduction in mean cumulative dose area product (3033.2 versus 1733.6 mGycm∧2, p < 0.0001) and a 31.2% reduction in mean cumulative air kerma (1445.4 versus 994.2 mGy, p < 0.001) was achieved compared to similar procedures performed in the same suite equipped with the Philips Allura Xper platform. Mean total fluoroscopy time was not significantly different between the two cohorts (1679.3 versus 1791.3 seconds, p = 0.41). Conclusion: This study demonstrates a significant patient radiation dose reduction during TACE procedures performed to treat HCC after a body interventional radiology suite was converted to the Philips Allura Clarity platform from the Philips Allura Xper platform. Future work will focus on evaluation of patient dose reduction in a larger cohort of patients across a broader range of procedures and in specific populations, including obese patients and pediatric patients, and comparison of image quality between the two platforms. Funding for this study was provided by Philips Healthcare, with 5% salary support provided to authors K. Pallav Kolli and Robert G. Gould for time devoted to the study. Data acquisition and analysis was performed by the authors independent of the funding source.« less

Case Example of Dose Optimization Using Data From Bortezomib Dose-Finding Clinical Trials

PubMed Central

Backenroth, Daniel; Cheung, Ying Kuen Ken; Hershman, Dawn L.; Vulih, Diana; Anderson, Barry; Ivy, Percy; Minasian, Lori

2016-01-01

Purpose The current dose-finding methodology for estimating the maximum tolerated dose of investigational anticancer agents is based on the cytotoxic chemotherapy paradigm. Molecularly targeted agents (MTAs) have different toxicity profiles, which may lead to more long-lasting mild or moderate toxicities as well as to late-onset and cumulative toxicities. Several approved MTAs have been poorly tolerated during long-term administration, leading to postmarketing dose optimization studies to re-evaluate the optimal treatment dose. Using data from completed bortezomib dose-finding trials, we explore its toxicity profile, optimize its dose, and examine the appropriateness of current designs for identifying an optimal dose. Patients and Methods We classified the toxicities captured from 481 patients in 14 bortezomib dose-finding studies conducted through the National Cancer Institute Cancer Therapy Evaluation Program, computed the incidence of late-onset toxicities, and compared the incidence of dose-limiting toxicities (DLTs) among groups of patients receiving different doses of bortezomib. Results A total of 13,008 toxicities were captured: 46% of patients’ first DLTs and 88% of dose reductions or discontinuations of treatment because of toxicity were observed after the first cycle. Moreover, for the approved dose of 1.3 mg/m2, the estimated cumulative incidence of DLT was > 50%, and the estimated cumulative incidence of dose reduction or treatment discontinuation because of toxicity was nearly 40%. Conclusions When considering the entire course of treatment, the approved bortezomib dose exceeds the conventional ceiling DLT rate of 20% to 33%. Retrospective analysis of trial data provides an opportunity for dose optimization of MTAs. Future dose-finding studies of MTAs should take into account late-onset toxicities to ensure that a tolerable dose is identified for future efficacy and comparative trials. PMID:26926682

TH-AB-BRA-08: Simulated Tumor Tracking in An MRI Linac for Lung Tumor Lesions Using the Monaco Treatment Planning System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Ward, S; Kim, A; McCann, C

2016-06-15

Purpose: To simulate tumor tracking in an Elekta MRI-linac (MRL) and to compare this tracking method with our current ITV approach in terms of OAR sparing for lung cancer patients. Methods: Five SABR-NSCLC patients with central lung tumors were selected for reasons of potential enhancement of tumor-tissue delineation using MRI. The Monaco TPS was used to compare the current clinical ITV approach to a simulated, novel tracking method which used a 7MV MRL beam in the presence of an orthogonal 1.5 T magnetic field (4D-MRL method). In the simulated tracking scenario, achieved using the virtual couch shift (VCS), the PTVmore » was defined using an isotropic 5mm margin applied to the GTV of each phase, as acquired from an 8-phase amplitude-binned 4DCT. These VCS plans were optimized and weighted on each phase. The dose weighting was performed using the patient-specific breathing traces. The doses were accumulated on the inhale phase. The two methods were compared by assessing the OAR DVHs. Results: The 4D-MRL method resulted in a reduced target volume (by an average of 29% over all patients). The benefits of using an MRL tracking system depended on the tumor motion amplitude and the relative OAR motion (ROM) to the target. The reduction in mean doses to parallel organs was up to 3 Gy for the heart and 2.1 Gy for the lung. The reductions in maximum doses to serial organs were up to 9.4 Gy, 5.6 Gy, and 8.7 Gy for the esophagus, spinal cord, and the trachea, respectively. Serial organs benefited from MRL tracking when the ROM was ≥ 0.3 cm despite small tumor motion amplitude in some cases. Conclusions: This work demonstrated the potential benefit for an MRL tracking system to spare OARs in SABR-NSCLC patients with central tumors. The benefits are embodied in the target volume reduction. This project was made possible with the financial support of Elekta.« less

Normal tissue complication probability modelling of tissue fibrosis following breast radiotherapy

NASA Astrophysics Data System (ADS)

Alexander, M. A. R.; Brooks, W. A.; Blake, S. W.

2007-04-01

Cosmetic late effects of radiotherapy such as tissue fibrosis are increasingly regarded as being of importance. It is generally considered that the complication probability of a radiotherapy plan is dependent on the dose uniformity, and can be reduced by using better compensation to remove dose hotspots. This work aimed to model the effects of improved dose homogeneity on complication probability. The Lyman and relative seriality NTCP models were fitted to clinical fibrosis data for the breast collated from the literature. Breast outlines were obtained from a commercially available Rando phantom using the Osiris system. Multislice breast treatment plans were produced using a variety of compensation methods. Dose-volume histograms (DVHs) obtained for each treatment plan were reduced to simple numerical parameters using the equivalent uniform dose and effective volume DVH reduction methods. These parameters were input into the models to obtain complication probability predictions. The fitted model parameters were consistent with a parallel tissue architecture. Conventional clinical plans generally showed reducing complication probabilities with increasing compensation sophistication. Extremely homogenous plans representing idealized IMRT treatments showed increased complication probabilities compared to conventional planning methods, as a result of increased dose to areas receiving sub-prescription doses using conventional techniques.

Clinical Evaluation of Normalized Metal Artifact Reduction in kVCT Using MVCT Prior Images (MVCT-NMAR) for Radiation Therapy Treatment Planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paudel, Moti Raj, E-mail: mpaudel@ualberta.ca; Mackenzie, Marc; Fallone, B. Gino

Purpose: To evaluate the metal artifacts in diagnostic kilovoltage computed tomography (kVCT) images of patients that are corrected by use of a normalized metal artifact reduction (NMAR) method with megavoltage CT (MVCT) prior images: MVCT-NMAR. Methods and Materials: MVCT-NMAR was applied to images from 5 patients: 3 with dual hip prostheses, 1 with a single hip prosthesis, and 1 with dental fillings. The corrected images were evaluated for visualization of tissue structures and their interfaces and for radiation therapy dose calculations. They were compared against the corresponding images corrected by the commercial orthopedic metal artifact reduction algorithm in a Phillipsmore » CT scanner. Results: The use of MVCT images for correcting kVCT images in the MVCT-NMAR technique greatly reduces metal artifacts, avoids secondary artifacts, and makes patient images more useful for correct dose calculation in radiation therapy. These improvements are significant, provided the MVCT and kVCT images are correctly registered. The remaining and the secondary artifacts (soft tissue blurring, eroded bones, false bones or air pockets, CT number cupping within the metal) present in orthopedic metal artifact reduction corrected images are removed in the MVCT-NMAR corrected images. A large dose reduction was possible outside the planning target volume (eg, 59.2 Gy to 52.5 Gy in pubic bone) when these MVCT-NMAR corrected images were used in TomoTherapy treatment plans without directional blocks for a prostate cancer patient. Conclusions: The use of MVCT-NMAR corrected images in radiation therapy treatment planning could improve the treatment plan quality for patients with metallic implants.« less

[Applying dose banding to the production of antineoplastic drugs: a narrative review of the literature].

PubMed

Pérez Huertas, Pablo; Cueto Sola, Margarita; Escobar Cava, Paloma; Borrell García, Carmela; Albert Marí, Asunción; López Briz, Eduardo; Poveda Andrés, José Luis

2015-07-01

The dosage of antineoplastic drugs has historically been based on individualized prescription and preparation according to body surface area or patient´s weight. Lack of resources and increased assistance workload in the areas where chemotherapy is made, are leading to the development of new systems to optimize the processing without reducing safety. One of the strategies that has been proposed is the elaboration by dose banding. This new approach standardizes the antineoplastic agents doses by making ranges or bands accepting a percentage of maximum variation. It aims to reduce processing time with the consequent reduction in waiting time for patients; to reduce errors in the manufacturing process and to promote the rational drug use. In conclusion, dose banding is a suitable method for optimizing the development of anticancer drugs, obtaining reductions in oncologic patients waiting time but without actually causing a favorable impact on direct or indirect costs. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

A pragmatic approach to determine the optimal kVp in cone beam CT: balancing contrast-to-noise ratio and radiation dose

PubMed Central

Silkosessak, O; Jacobs, R; Bogaerts, R; Bosmans, H; Panmekiate, S

2014-01-01

Objectives: To determine the optimal kVp setting for a particular cone beam CT (CBCT) device by maximizing technical image quality at a fixed radiation dose. Methods: The 3D Accuitomo 170 (J. Morita Mfg. Corp., Kyoto, Japan) CBCT was used. The radiation dose as a function of kVp was measured in a cylindrical polymethyl methacrylate (PMMA) phantom using a small-volume ion chamber. Contrast-to-noise ratio (CNR) was measured using a PMMA phantom containing four materials (air, aluminium, polytetrafluoroethylene and low-density polyethylene), which was scanned using 180 combinations of kVp/mA, ranging from 60/1 to 90/8. The CNR was measured for each material using PMMA as background material. The pure effect of kVp and mAs on the CNR values was analysed. Using a polynomial fit for CNR as a function of mA for each kVp value, the optimal kVp was determined at five dose levels. Results: Absorbed doses ranged between 0.034 mGy mAs−1 (14 × 10 cm, 60 kVp) and 0.108 mGy mAs−1 (14 × 10 cm, 90 kVp). The relation between kVp and dose was quasilinear (R2 > 0.99). The effect of mA and kVp on CNR could be modelled using a second-degree polynomial. At a fixed dose, there was a tendency for higher CNR values at increasing kVp values, especially at low dose levels. A dose reduction through mA was more efficient than an equivalent reduction through kVp in terms of image quality deterioration. Conclusions: For the investigated CBCT model, the most optimal contrast at a fixed dose was found at the highest available kVp setting. There is great potential for dose reduction through mA with a minimal loss in image quality. PMID:24708447

SU-E-I-57: Evaluation and Optimization of Effective-Dose Using Different Beam-Hardening Filters in Clinical Pediatric Shunt CT Protocol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gill, K; Aldoohan, S; Collier, J

Purpose: Study image optimization and radiation dose reduction in pediatric shunt CT scanning protocol through the use of different beam-hardening filters Methods: A 64-slice CT scanner at OU Childrens Hospital has been used to evaluate CT image contrast-to-noise ratio (CNR) and measure effective-doses based on the concept of CT dose index (CTDIvol) using the pediatric head shunt scanning protocol. The routine axial pediatric head shunt scanning protocol that has been optimized for the intrinsic x-ray tube filter has been used to evaluate CNR by acquiring images using the ACR approved CT-phantom and radiation dose CTphantom, which was used to measuremore » CTDIvol. These results were set as reference points to study and evaluate the effects of adding different filtering materials (i.e. Tungsten, Tantalum, Titanium, Nickel and Copper filters) to the existing filter on image quality and radiation dose. To ensure optimal image quality, the scanner routine air calibration was run for each added filter. The image CNR was evaluated for different kVps and wide range of mAs values using above mentioned beam-hardening filters. These scanning protocols were run under axial as well as under helical techniques. The CTDIvol and the effective-dose were measured and calculated for all scanning protocols and added filtration, including the intrinsic x-ray tube filter. Results: Beam-hardening filter shapes energy spectrum, which reduces the dose by 27%. No noticeable changes in image low contrast detectability Conclusion: Effective-dose is very much dependent on the CTDIVol, which is further very much dependent on beam-hardening filters. Substantial reduction in effective-dose is realized using beam-hardening filters as compare to the intrinsic filter. This phantom study showed that significant radiation dose reduction could be achieved in CT pediatric shunt scanning protocols without compromising in diagnostic value of image quality.« less

Reviewing long-term antidepressants can reduce drug burden: a prospective observational cohort study

PubMed Central

Johnson, Chris F; Macdonald, Hector J; Atkinson, Pauline; Buchanan, Alasdair I; Downes, Noreen; Dougall, Nadine

2012-01-01

Background Antidepressant prescribing continues to rise. Contributing factors are increased long-term prescribing and possibly the use of higher selective serotonin re-uptake inhibitor (SSRI) doses. Aim To review general practice patients prescribed the same antidepressant long-term (≥2 years) and evaluate prescribing and management pre and post-review. Design and setting Prospective observational cohort study using routine data from 78 urban general practices, Scotland. Method All patients prescribed antidepressants (excluding amitriptyline) for ≥2 years were identified from records November 2009 to March 2010. GPs selected patients for face-to-face review of clinical condition and medication, December 2009 to September 2010. Pre- and post-review data were collected; average antidepressant doses and changes in prescribed daily doses were calculated. Onward referral to support services was recorded. Results 8.6% (33 312/388 656) of all registered patients were prescribed an antidepressant, 47.1% (15 689) were defined as long-term users and 2849 (18.2%) were reviewed. 811 (28.5%) patients reviewed had a change in antidepressant therapy: 7.0% stopped, 12.8% reduced dose, 5.3% increased dose, and 3.4% changed antidepressant, resulting in 9.5% (95% CI = 9.1% to 9.8% P<0.001) reduction in prescribed daily dose and 8.1% reduction in prescribing costs. 6.3% were referred onwards, half to NHS Mental Health Services. Pre-review SSRI doses were 10–30% higher than previously reported. Conclusion Almost half of all people prescribed antidepressants were long-term users. Appropriate reductions in prescribing can be achieved by reviewing patients. Higher SSRI doses may be contributing to current antidepressant growth. PMID:23211181

Effective method of measuring the radioactivity of [ 131I]‐capsule prior to radioiodine therapy with significant reduction of the radiation exposure to the medical staff

PubMed Central

Lützen, Ulf; Zhao, Yi; Marx, Marlies; Imme, Thea; Assam, Isong; Siebert, Frank‐Andre; Culman, Juraj

2016-01-01

Radiation Protection in Radiology, Nuclear Medicine and Radio Oncology is of the utmost importance. Radioiodine therapy is a frequently used and effective method for the treatment of thyroid disease. Prior to each therapy the radioactivity of the [ 131I]‐capsule must be determined to prevent misadministration. This leads to a significant radiation exposure to the staff. We describe an alternative method, allowing a considerable reduction of the radiation exposure. Two [ 131I]‐capsules (A01=2818.5; A02=73.55.0 MBq) were measured multiple times in their own delivery lead containers — that is to say, [ 131I]‐capsules remain inside the containers during the measurements (shielded measurement) using a dose calibrator and a well‐type and a thyroid uptake probe. The results of the shielded measurements were correlated linearly with the [ 131I]‐capsules radioactivity to create calibration curves for the used devices. Additional radioactivity measurements of 50 [ 131I]‐capsules of different radioactivities were done to validate the shielded measuring method. The personal skin dose rate (HP(0.07)) was determined using calibrated thermo luminescent dosimeters. The determination coefficients for the calibration curves were R2>0.9980 for all devices. The relative uncertainty of the shielded measurement was <6.8%. At a distance of 10 cm from the unshielded capsule the HP(0.07) was 46.18 μSv/(GBq⋅s), and on the surface of the lead container containing the [ 131I]‐capsule the HP(0.07) was 2.99 and 0.27 μSv/(GBq⋅s) for the two used container sizes. The calculated reduction of the effective dose by using the shielded measuring method was, depending on the used container size, 74.0% and 97.4%, compared to the measurement of the unshielded [ 131I]‐capsule using a dose calibrator. The measured reduction of the effective radiation dose in the practice was 56.6% and 94.9 for size I and size II containers. The shielded [ 131I]‐capsule measurement reduces the radiation exposure to the staff significantly and offers the same accuracy of the unshielded measurement in the same amount of time. In order to maintain the consistency of the measuring method, monthly tests have to be done by measuring a [ 131I]‐capsule with known radioactivity. PACS number(s): 93.85.Np, 92.20.Td, 87.50.yk, 87.53.Bn PMID:27455475

Standard pentostatin dose reductions in renal insufficiency are not adequate: selected patients with steroid-refractory acute graft-versus-host disease.

PubMed

Poi, Ming J; Hofmeister, Craig C; Johnston, Jeffrey S; Edwards, Ryan B; Jansak, Buffy S; Lucas, David M; Farag, Sherif S; Dalton, James T; Devine, Steven M; Grever, Michael R; Phelps, Mitch A

2013-08-01

Pentostatin is an irreversible inhibitor of adenosine deaminase and has been used to prevent graft-versus-host disease (GVHD) and to treat both acute and chronic GVHD. Dose reduction equations for patients with renal insufficiency are based on few patients with limited pharmacokinetic and clinical results. This phase II study (NCT00201786) was conducted to assess pentostatin efficacy and infectious complications seen from our previous phase I study in steroid-refractory acute GVHD (aGVHD). Hospitalized patients with steroid-refractory aGVHD were given pentostatin 1.5 mg/m(2)/day intravenously on days 1-3 of each 14-day cycle. Prior to each dose, dose modifications were based on Cockcroft-Gault estimated creatinine clearance (eCrCL) with 30-50 mL/min/1.73 m(2) leading to a 50 % dose reduction and eCrCL less than 30 mL/min/1.73 m(2) leading to study removal. Plasma pentostatin area under the concentration-time curve (AUC) and incidence of infectious complications were evaluated. Two of the eight patients treated demonstrated excessive pentostatin exposure as determined by measurement of AUC. One of these patients had renal impairment, whereas the other patient demonstrated borderline renal function. Despite dose reduction to 0.75 mg/m(2), AUCs were significantly increased compared to the other patients in this study. Seven of eight patients treated with pentostatin had cytomegalovirus (CMV) viremia after pentostatin treatment; however none developed proven CMV disease. A 50 % dose reduction in patients with eCrCL 30-50 mL/min/1.73 m(2) seems reasonable. However, the eCrCL should be interpreted with extreme caution in patients who are critically ill and/or with poor performance status. Renal function assessment based on the Cockcroft-Gault method could be significantly overestimated thus risking pentostatin overdosing. These results imply a need to closely monitor pentostatin exposure in patients with renal insufficiency.

Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT.

PubMed

Chatterson, Leslie C; Leswick, David A; Fladeland, Derek A; Hunt, Megan M; Webster, Stephen; Lim, Hyun

2014-07-01

Custom bismuth-antimony shields were previously shown to reduce fetal dose by 53% on an 8DR (detector row) CT scanner without dynamic adaptive section collimation (DASC), automatic tube current modulation (ATCM) or adaptive statistical iterative reconstruction (ASiR). The purpose of this study is to compare the effective maternal and average fetal organ dose reduction both with and without bismuth-antimony shields on a 64DR CT scanner using DASC, ATCM and ASiR during maternal CTPA. A phantom with gravid prosthesis and a bismuth-antimony shield were used. Thermoluminescent dosimeters (TLDs) measured fetal radiation dose. The average fetal organ dose and effective maternal dose were determined using 100 kVp, scanning from the lung apices to the diaphragm utilizing DASC, ATCM and ASiR on a 64DR CT scanner with and without shielding in the first and third trimester. Isolated assessment of DASC was done via comparing a new 8DR scan without DASC to a similar scan on the 64DR with DASC. Average third trimester unshielded fetal dose was reduced from 0.22 mGy ± 0.02 on the 8DR to 0.13 mGy ± 0.03 with the conservative 64DR protocol that included 30% ASiR, DASC and ATCM (42% reduction, P<0.01). Use of a shield further reduced average third trimester fetal dose to 0.04 mGy ± 0.01 (69% reduction, P<0.01). The average fetal organ dose reduction attributable to DASC alone was modest (6% reduction from 0.17 mGy ± 0.02 to 0.16 mGy ± 0.02, P=0.014). First trimester fetal organ dose on the 8DR protocol was 0.07 mGy ± 0.03. This was reduced to 0.05 mGy ± 0.03 on the 64DR protocol without shielding (30% reduction, P=0.009). Shields further reduced this dose to below accurately detectable levels. Effective maternal dose was reduced from 4.0 mSv on the 8DR to 2.5 mSv on the 64DR scanner using the conservative protocol (38% dose reduction). ASiR, ATCM and DASC combined significantly reduce effective maternal and fetal organ dose during CTPA. Shields continue to be an effective means of fetal dose reduction. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Statistical model based iterative reconstruction (MBIR) in clinical CT systems: experimental assessment of noise performance.

PubMed

Li, Ke; Tang, Jie; Chen, Guang-Hong

2014-04-01

To reduce radiation dose in CT imaging, the statistical model based iterative reconstruction (MBIR) method has been introduced for clinical use. Based on the principle of MBIR and its nonlinear nature, the noise performance of MBIR is expected to be different from that of the well-understood filtered backprojection (FBP) reconstruction method. The purpose of this work is to experimentally assess the unique noise characteristics of MBIR using a state-of-the-art clinical CT system. Three physical phantoms, including a water cylinder and two pediatric head phantoms, were scanned in axial scanning mode using a 64-slice CT scanner (Discovery CT750 HD, GE Healthcare, Waukesha, WI) at seven different mAs levels (5, 12.5, 25, 50, 100, 200, 300). At each mAs level, each phantom was repeatedly scanned 50 times to generate an image ensemble for noise analysis. Both the FBP method with a standard kernel and the MBIR method (Veo(®), GE Healthcare, Waukesha, WI) were used for CT image reconstruction. Three-dimensional (3D) noise power spectrum (NPS), two-dimensional (2D) NPS, and zero-dimensional NPS (noise variance) were assessed both globally and locally. Noise magnitude, noise spatial correlation, noise spatial uniformity and their dose dependence were examined for the two reconstruction methods. (1) At each dose level and at each frequency, the magnitude of the NPS of MBIR was smaller than that of FBP. (2) While the shape of the NPS of FBP was dose-independent, the shape of the NPS of MBIR was strongly dose-dependent; lower dose lead to a "redder" NPS with a lower mean frequency value. (3) The noise standard deviation (σ) of MBIR and dose were found to be related through a power law of σ ∝ (dose)(-β) with the component β ≈ 0.25, which violated the classical σ ∝ (dose)(-0.5) power law in FBP. (4) With MBIR, noise reduction was most prominent for thin image slices. (5) MBIR lead to better noise spatial uniformity when compared with FBP. (6) A composite image generated from two MBIR images acquired at two different dose levels (D1 and D2) demonstrated lower noise than that of an image acquired at a dose level of D1+D2. The noise characteristics of the MBIR method are significantly different from those of the FBP method. The well known tradeoff relationship between CT image noise and radiation dose has been modified by MBIR to establish a more gradual dependence of noise on dose. Additionally, some other CT noise properties that had been well understood based on the linear system theory have also been altered by MBIR. Clinical CT scan protocols that had been optimized based on the classical CT noise properties need to be carefully re-evaluated for systems equipped with MBIR in order to maximize the method's potential clinical benefits in dose reduction and/or in CT image quality improvement. © 2014 American Association of Physicists in Medicine.

Use of a channelized Hotelling observer to assess CT image quality and optimize dose reduction for iteratively reconstructed images.

PubMed

Favazza, Christopher P; Ferrero, Andrea; Yu, Lifeng; Leng, Shuai; McMillan, Kyle L; McCollough, Cynthia H

2017-07-01

The use of iterative reconstruction (IR) algorithms in CT generally decreases image noise and enables dose reduction. However, the amount of dose reduction possible using IR without sacrificing diagnostic performance is difficult to assess with conventional image quality metrics. Through this investigation, achievable dose reduction using a commercially available IR algorithm without loss of low contrast spatial resolution was determined with a channelized Hotelling observer (CHO) model and used to optimize a clinical abdomen/pelvis exam protocol. A phantom containing 21 low contrast disks-three different contrast levels and seven different diameters-was imaged at different dose levels. Images were created with filtered backprojection (FBP) and IR. The CHO was tasked with detecting the low contrast disks. CHO performance indicated dose could be reduced by 22% to 25% without compromising low contrast detectability (as compared to full-dose FBP images) whereas 50% or more dose reduction significantly reduced detection performance. Importantly, default settings for the scanner and protocol investigated reduced dose by upward of 75%. Subsequently, CHO-based protocol changes to the default protocol yielded images of higher quality and doses more consistent with values from a larger, dose-optimized scanner fleet. CHO assessment provided objective data to successfully optimize a clinical CT acquisition protocol.

Low Dose MDCT with Tube Current Modulation: Role in Detection of Urolithiasis and Patient Effective Dose Reduction.

PubMed

Koteshwar, Prakashini; Kakkar, Chandan; Sripathi, Smiti; Parakh, Anushri; Shrivastav, Rajendra

2016-05-01

Urolithiasis is one of the major, recurring problem in young individuals and CT being the commonest diagnostic modality used. In order to reduce the radiation dose to the patient who are young and as stone formation is a recurring process; one of the simplest way would be, low dose CT along with tube current modulation. Aim of this study was to compare the sensitivity and specificity of low dose (70mAs) with standard dose (250mAs) protocol in detecting urolithiasis and to define the tube current and mean effective patient dose by these protocols. A prospective study was conducted in 200 patients over a period of 2 years with acute flank pain presentation. CT was performed in 100 cases with standard dose and another 100 with low dose protocol using tube current modulation. Sensitivity and specificity for calculus detection, percentage reduction of dose and tube current with low dose protocol was calculated. Urolithiasis was detected in 138 patients, 67 were examined by high dose and 71 were by low dose protocol. Sensitivity and Specificity of low dose protocol was 97.1% and 96.4% with similar results found in high BMI patients. Tube current modulation resulted in reduction of effective tube current by 12.17%. The mean effective patient dose for standard dose was 10.33 mSv whereas 2.92 mSv for low dose with 51.13-53.8% reduction in low dose protocol. The study has reinforced that low-dose CT with tube current modulation is appropriate for diagnosis of urolithiasis with significant reduction in tube current and patient effective dose.

Decolorization and COD reduction of dyeing wastewater from a cotton textile mill using thermolysis and coagulation.

PubMed

Kumar, Pradeep; Prasad, B; Mishra, I M; Chand, Shri

2008-05-01

The decolorization and reduction of COD of dyeing wastewater from a cotton textile mill was conducted using catalytic thermal treatment (thermolysis) accompanied with/without coagulation. Thermolysis in presence of a homogeneous copper sulphate catalyst was found to be the most effective in comparison to other catalysts (FeCl(3), FeSO(4), CuO, ZnO and PAC) used. A maximum reduction of chemical oxygen demand (COD) and color of dyeing wastewater of 66.85% and 71.4%, respectively, was observed with a catalyst concentration of 5 kg/m(3) at pH 8. Commercial alum was found most effective coagulant among various coagulants (aluminum potassium sulphate, PAC, FeCl(3) and FeSO(4)) tested during coagulation operations, resulting in 58.57% COD and 74% color reduction at pH 4 and coagulant dose of 5 kg/m(3). Coagulation of the clear fluid (supernatant) obtained after treatment by thermolysis at the conditions previously used resulted in an overall reduction of 89.91% COD and 94.4% color at pH 4 and a coagulant dose of 2 kg/m(3). The application of thermolysis followed by coagulation, thus, is the most effective treatment method in removing nearly 90% COD and 95% color at a lower dose of coagulant (2 kg/m(3)). The sludge thus produced would contain lower inorganic mass coagulant and, therefore, less amount of inorganic sludge.

Reduction of radiation dose and imaging costs in scoliosis radiography. Application of large-screen image intensifier photofluorography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manninen, H.; Kiekara, O.; Soimakallio, S.

1988-04-01

Photofluorography using a large-field image intensifier (Siemens Optilux 57) was applied to scoliosis radiography and compared with a full-size rare-earth screen/film technique. When scoliosis radiography (PA-projection) was performed on 25 adolescent patients, the photofluorographs were found to be of comparable diagnostic quality with full-size films. A close correspondence between the imaging techniques was found in the Cobb angle measurements as well as in the grading of rotation with the pedicle method. The use of photofluorography results in a radiation dose reduction of about one-half and considerable savings in direct imaging costs and archive space. In our opinion the method ismore » particularly well-suited for follow-up and screening evaluation of scoliosis, but in tall patients the image field size of 40 x 40 cm restricts its usefulness as initial examination.« less

The impact of low-Z and high-Z metal implants in IMRT: A Monte Carlo study of dose inaccuracies in commercial dose algorithms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spadea, Maria Francesca, E-mail: mfspadea@unicz.it; Verburg, Joost Mathias; Seco, Joao

2014-01-15

Purpose: The aim of the study was to evaluate the dosimetric impact of low-Z and high-Z metallic implants on IMRT plans. Methods: Computed tomography (CT) scans of three patients were analyzed to study effects due to the presence of Titanium (low-Z), Platinum and Gold (high-Z) inserts. To eliminate artifacts in CT images, a sinogram-based metal artifact reduction algorithm was applied. IMRT dose calculations were performed on both the uncorrected and corrected images using a commercial planning system (convolution/superposition algorithm) and an in-house Monte Carlo platform. Dose differences between uncorrected and corrected datasets were computed and analyzed using gamma index (Pγ{submore » <1}) and setting 2 mm and 2% as distance to agreement and dose difference criteria, respectively. Beam specific depth dose profiles across the metal were also examined. Results: Dose discrepancies between corrected and uncorrected datasets were not significant for low-Z material. High-Z materials caused under-dosage of 20%–25% in the region surrounding the metal and over dosage of 10%–15% downstream of the hardware. Gamma index test yielded Pγ{sub <1}>99% for all low-Z cases; while for high-Z cases it returned 91% < Pγ{sub <1}< 99%. Analysis of the depth dose curve of a single beam for low-Z cases revealed that, although the dose attenuation is altered inside the metal, it does not differ downstream of the insert. However, for high-Z metal implants the dose is increased up to 10%–12% around the insert. In addition, Monte Carlo method was more sensitive to the presence of metal inserts than superposition/convolution algorithm. Conclusions: The reduction in terms of dose of metal artifacts in CT images is relevant for high-Z implants. In this case, dose distribution should be calculated using Monte Carlo algorithms, given their superior accuracy in dose modeling in and around the metal. In addition, the knowledge of the composition of metal inserts improves the accuracy of the Monte Carlo dose calculation significantly.« less

Dose and risk in diagnostic radiology: How big How little Lecture Number 16

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webster, E.W.

1992-01-01

This lecture is divided into two parts: dose and risk. The dose segment is technical and noncontroversial since it deals with straightforward measurements or calculations which do not depend on unproven hypotheses. Some conflicting contributions of low dose epidemiological studies to the appraisal of risk are briefly presented. Attention is focused on the following: dose reduction in radiography; dose reduction in fluoroscopy; limitations of dose reduction; estimated radiation risks for diagnostic radiology examinations; excess breast cancer following X-ray examinations for scoliosis; dose-response relation for human mammary cancer; lung cancer from protracted X-irradiation; leukemia and diagnostic X-ray exposure; and thyroid cancermore » after diagnostic dose of I-131.« less

Disease activity guided dose reduction and withdrawal of adalimumab or etanercept compared with usual care in rheumatoid arthritis: open label, randomised controlled, non-inferiority trial.

PubMed

van Herwaarden, Noortje; van der Maas, Aatke; Minten, Michiel J M; van den Hoogen, Frank H J; Kievit, Wietske; van Vollenhoven, Ronald F; Bijlsma, Johannes W J; van den Bemt, Bart J F; den Broeder, Alfons A

2015-04-09

To evaluate whether a disease activity guided strategy of dose reduction of two tumour necrosis factor (TNF) inhibitors, adalimumab or etanercept, is non-inferior in maintaining disease control in patients with rheumatoid arthritis compared with usual care. Randomised controlled, open label, non-inferiority strategy trial. Two rheumatology outpatient clinics in the Netherlands, from December 2011 to May 2014. 180 patients with rheumatoid arthritis and low disease activity using adalimumab or etanercept; 121 allocated to the dose reduction strategy, 59 to usual care. Disease activity guided dose reduction (advice to stepwise increase the injection interval every three months, until flare of disease activity or discontinuation) or usual care (no dose reduction advice). Flare was defined as increase in DAS28-CRP (a composite score measuring disease activity) greater than 1.2, or increase greater than 0.6 and current score of at least 3.2. In the case of flare, TNF inhibitor use was restarted or escalated. Difference in proportions of patients with major flare (DAS28-CRP based flare longer than three months) between the two groups at 18 months, compared against a non-inferiority margin of 20%. Secondary outcomes included TNF inhibitor use at study end, functioning, quality of life, radiographic progression, and adverse events. Dose reduction of adalimumab or etanercept was non-inferior to usual care (proportion of patients with major flare at 18 months, 12% v 10%; difference 2%, 95% confidence interval -12% to 12%). In the dose reduction group, TNF inhibitor use could successfully be stopped in 20% (95% confidence interval 13% to 28%), the injection interval successfully increased in 43% (34% to 53%), but no dose reduction was possible in 37% (28% to 46%). Functional status, quality of life, relevant radiographic progression, and adverse events did not differ between the groups, although short lived flares (73% v 27%) and minimal radiographic progression (32% v 15%) were more frequent in dose reduction than usual care. A disease activity guided, dose reduction strategy of adalimumab or etanercept to treat rheumatoid arthritis is non-inferior to usual care with regard to major flaring, while resulting in the successful dose reduction or stopping in two thirds of patients.Trial registration Dutch trial register (www.trialregister.nl), NTR 3216. © van Herwaarden et al 2015.

A dose ranging study of ibuprofen suspension as an antipyretic.

PubMed Central

Marriott, S C; Stephenson, T J; Hull, D; Pownall, R; Smith, C M; Butler, A

1991-01-01

A double blind trial was conducted to determine the dose of ibuprofen suspension, which is effective in reducing the body temperature. The principal measure of efficacy was a reduction in axillary temperature of 1 degree C or more three hours after dosing. A second objective of the trial was to compare the incidence and severity of side effects and the palatability of a range of ibuprofen doses. Ninety three children were included in the analysis. All four doses of ibuprofen studied (0.625 mg/kg-5 mg/kg) were associated with temperature reduction and only the lowest dose failed to satisfy the principal measure of efficacy. The influence of dose on the magnitude of the body temperature reduction was significant and the 5 mg/kg dose achieved the largest mean reduction in body temperature (2 degrees C). The tolerability and palatability of all doses studied were excellent. These findings suggest that ibuprofen is a good alternative to paracetamol as an antipyretic. PMID:1929509

CT-guided brachytherapy of prostate cancer: reduction of effective dose from X-ray examination

NASA Astrophysics Data System (ADS)

Sanin, Dmitriy B.; Biryukov, Vitaliy A.; Rusetskiy, Sergey S.; Sviridov, Pavel V.; Volodina, Tatiana V.

2014-03-01

Computed tomography (CT) is one of the most effective and informative diagnostic method. Though the number of CT scans among all radiographic procedures in the USA and European countries is 11% and 4% respectively, CT makes the highest contribution to the collective effective dose from all radiographic procedures, it is 67% in the USA and 40% in European countries [1-5]. Therefore it is necessary to understand the significance of dose value from CT imaging to a patient . Though CT dose from multiple scans and potential risk is of great concern in pediatric patients, this applies to adults as well. In this connection it is very important to develop optimal approaches to dose reduction and optimization of CT examination. International Commission on Radiological Protection (ICRP) in its publications recommends radiologists to be aware that often CT image quality is higher than it is necessary for diagnostic confidence[6], and there is a potential to reduce the dose which patient gets from CT examination [7]. In recent years many procedures, such as minimally invasive surgery, biopsy, brachytherapy and different types of ablation are carried out under guidance of computed tomography [6;7], and during a procedures multiple CT scans focusing on a specific anatomic region are performed. At the Clinics of MRRC different types of treatment for patients with prostate cancer are used, incuding conformal CT-guided brachytherapy, implantation of microsources of I into the gland under guidance of spiral CT [8]. So, the purpose of the study is to choose optimal method to reduce radiation dose from CT during CT-guided prostate brachytherapy and to obtain the image of desired quality.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kieselmann, J; Bartzsch, S; Oelfke, U

Purpose: Microbeam Radiation Therapy is a preclinical method in radiation oncology that modulates radiation fields on a micrometre scale. Dose calculation is challenging due to arising dose gradients and therapeutically important dose ranges. Monte Carlo (MC) simulations, often used as gold standard, are computationally expensive and hence too slow for the optimisation of treatment parameters in future clinical applications. On the other hand, conventional kernel based dose calculation leads to inaccurate results close to material interfaces. The purpose of this work is to overcome these inaccuracies while keeping computation times low. Methods: A point kernel superposition algorithm is modified tomore » account for tissue inhomogeneities. Instead of conventional ray tracing approaches, methods from differential geometry are applied and the space around the primary photon interaction is locally warped. The performance of this approach is compared to MC simulations and a simple convolution algorithm (CA) for two different phantoms and photon spectra. Results: While peak doses of all dose calculation methods agreed within less than 4% deviations, the proposed approach surpassed a simple convolution algorithm in accuracy by a factor of up to 3 in the scatter dose. In a treatment geometry similar to possible future clinical situations differences between Monte Carlo and the differential geometry algorithm were less than 3%. At the same time the calculation time did not exceed 15 minutes. Conclusion: With the developed method it was possible to improve the dose calculation based on the CA method with respect to accuracy especially at sharp tissue boundaries. While the calculation is more extensive than for the CA method and depends on field size, the typical calculation time for a 20×20 mm{sup 2} field on a 3.4 GHz and 8 GByte RAM processor remained below 15 minutes. Parallelisation and optimisation of the algorithm could lead to further significant calculation time reductions.« less

Lack of association between dopaminergic antagonism and negative symptoms in schizophrenia: a positron emission tomography dopamine D2/3 receptor occupancy study

PubMed Central

Fervaha, Gagan; Caravaggio, Fernando; Mamo, David C.; Mulsant, Benoit H.; Pollock, Bruce G.; Nakajima, Shinichiro; Gerretsen, Philip; Rajji, Tarek K.; Mar, Wanna; Iwata, Yusuke; Plitman, Eric; Chung, Jun Ku; Remington, Gary; Graff-Guerrero, Ariel

2016-01-01

Rationale Several pre-clinical studies suggest that antipsychotic medications cause secondary negative symptoms. However, direct evidence for a relationship among antipsychotic medications, their direct effects on neurotransmitter systems, and negative symptoms in schizophrenia remains controversial. Objective The objective of this study was to examine the relationship between antipsychotic-related dopamine D2/3 receptor occupancy and negative symptoms in patients with schizophrenia. Methods Forty-one clinically stable outpatients with schizophrenia participated in this prospective dose reduction positron emission tomography (PET) study. Clinical assessments and [11C]-raclopride PET scans were performed before and after participants underwent gradual dose reduction of their antipsychotic medication by up to 40% from the baseline dose. Results No significant relationship was found between antipsychotic-related dopamine D2/3 receptor occupancy and negative symptom severity at baseline or follow-up. Similar null findings were found for subdomains of negative symptoms (amotivation and diminished expression). Occupancy was significantly lower following dose reduction; however, negative symptom severity did not change significantly, though a trend toward reduction was noted. Examination of change scores between these two variables revealed no systematic relationship. Conclusions Our cross-sectional and longitudinal results failed to find a significant dose-dependent relationship between severity of negative symptoms and antipsychotic-related dopaminergic antagonism in schizophrenia. These findings argue against the notion that antipsychotics necessarily cause secondary negative symptoms. Our results are also in contrast with the behavioural effects of dopaminergic antagonism routinely reported in pre-clinical investigations, suggesting that the role of this variable in the context of chronic treatment and schizophrenia needs to be re-examined. PMID:27557949

A lack of association between severity of nicotine withdrawal and individual differences in compensatory nicotine self-administration in rats

PubMed Central

Harris, Andrew C.; Pentel, Paul R.; Burroughs, Danielle; Staley, Mylissa D.; LeSage, Mark G.

2013-01-01

Rationale Compensatory smoking may represent an adverse consequence of smoking reduction or the use of reduced nicotine tobacco products. Factors contributing to individual variability in compensation are poorly understood. Objective To examine whether severity of nicotine withdrawal as measured by elevated intracranial self-stimulation (ICSS) thresholds is related to individual differences in compensatory nicotine self-administration (NSA) following unit dose reduction. Methods Rats were trained for ICSS and NSA (0.06 mg/kg/inf). After stabilization, effects of reducing the nicotine unit dose to 0.03 mg/kg/inf were examined. Following reacquisition of NSA (0.06 mg/kg/inf), effects of antagonist-precipitated withdrawal and saline extinction (spontaneous withdrawal) were examined. Results Reducing the NSA unit dose produced partial compensation as indicated by increased infusion rates but a 35% mean decrease in daily nicotine intake. Magnitude of compensation varied considerably among rats. Dose reduction did not elicit withdrawal in rats as a group, although there were substantial increases in ICSS thresholds in some animals. Intracranial self-stimulation thresholds were consistently elevated during precipitated and spontaneous withdrawal, confirming that rats were nicotine-dependent. Individual differences in compensation were not correlated with changes in ICSS thresholds during dose reduction, precipitated withdrawal, or spontaneous withdrawal. In a secondary analysis, greater precipitated withdrawal severity predicted greater initial nicotine-seeking during extinction. Conclusions Severity of nicotine withdrawal was not related to the degree of compensation in this protocol. These data do not support a role for nicotine withdrawal in individual differences in compensation during reduced nicotine exposure, but do suggest that withdrawal may contribute to nicotine-seeking during early abstinence. PMID:21494791

Soft-tissue imaging with C-arm cone-beam CT using statistical reconstruction

NASA Astrophysics Data System (ADS)

Wang, Adam S.; Webster Stayman, J.; Otake, Yoshito; Kleinszig, Gerhard; Vogt, Sebastian; Gallia, Gary L.; Khanna, A. Jay; Siewerdsen, Jeffrey H.

2014-02-01

The potential for statistical image reconstruction methods such as penalized-likelihood (PL) to improve C-arm cone-beam CT (CBCT) soft-tissue visualization for intraoperative imaging over conventional filtered backprojection (FBP) is assessed in this work by making a fair comparison in relation to soft-tissue performance. A prototype mobile C-arm was used to scan anthropomorphic head and abdomen phantoms as well as a cadaveric torso at doses substantially lower than typical values in diagnostic CT, and the effects of dose reduction via tube current reduction and sparse sampling were also compared. Matched spatial resolution between PL and FBP was determined by the edge spread function of low-contrast (˜40-80 HU) spheres in the phantoms, which were representative of soft-tissue imaging tasks. PL using the non-quadratic Huber penalty was found to substantially reduce noise relative to FBP, especially at lower spatial resolution where PL provides a contrast-to-noise ratio increase up to 1.4-2.2× over FBP at 50% dose reduction across all objects. Comparison of sampling strategies indicates that soft-tissue imaging benefits from fully sampled acquisitions at dose above ˜1.7 mGy and benefits from 50% sparsity at dose below ˜1.0 mGy. Therefore, an appropriate sampling strategy along with the improved low-contrast visualization offered by statistical reconstruction demonstrates the potential for extending intraoperative C-arm CBCT to applications in soft-tissue interventions in neurosurgery as well as thoracic and abdominal surgeries by overcoming conventional tradeoffs in noise, spatial resolution, and dose.

Developmental Exposure to Perchlorate Alters Synaptic Transmission in Hippocampus of the Adult Rat

PubMed Central

Gilbert, Mary E.; Sui, Li

2008-01-01

Background Perchlorate is an environmental contaminant that blocks iodine uptake into the thyroid gland and reduces thyroid hormones. This action of perchlorate raises significant concern over its effects on brain development. Objectives The purpose of this study was to evaluate neurologic function in rats after developmental exposure to perchlorate. Methods Pregnant rats were exposed to 0, 30, 300, or 1,000 ppm perchlorate in drinking water from gestational day 6 until weaning. Adult male offspring were evaluated on a series of behavioral tasks and neurophysiologic measures of synaptic function in the hippocampus. Results At the highest perchlorate dose, triiodothyronine (T3) and thyroxine (T4) were reduced in pups on postnatal day 21. T4 in dams was reduced relative to controls by 16%, 28%, and 60% in the 30-, 300-, and 1,000-ppm dose groups, respectively. Reductions in T4 were associated with increases in thyroid-stimulating hormone in the high-dose group. No changes were seen in serum T3. Perchlorate did not impair motor activity, spatial learning, or fear conditioning. However, significant reductions in baseline synaptic transmission were observed in hippocampal field potentials at all dose levels. Reductions in inhibitory function were evident at 300 and 1,000 ppm, and augmentations in long-term potentiation were observed in the population spike measure at the highest dose. Conclusions Dose-dependent deficits in hippocampal synaptic function were detectable with relatively minor perturbations of the thyroid axis, indicative of an irreversible impairment in synaptic transmission in response to developmental exposure to perchlorate. PMID:18560531

Radiation dose management in thoracic CT: an international survey.

PubMed

Molinari, Francesco; Tack, Denis M; Boiselle, Philip; Ngo, Long; Mueller-Mang, Christina; Litmanovich, Diana; Bankier, Alexander A

2013-01-01

We aimed to examine current practice patterns of international thoracic radiologists regarding radiation dose management in adult thoracic computed tomography (CT) examinations. An electronic questionnaire was sent to 800 members of five thoracic radiology societies in North America, Europe, Asia, and Latin America addressing radiation dose training and education, standard kVp and mAs settings for thoracic CT, dose reduction practices, clinical scenarios, and demographics. Of the 800 radiologists, 146 responded to our survey. Nearly half (66/146, 45% [95% confidence interval, 37%-53%]) had no formal training in dose reduction, with "self-study of the literature" being the most common form of training (54/146, 37% [29%-45%]). One hundred and seventeen (80% [74%-87%]) had automatic exposure control, and 76 (65% [56%-74%]) used it in all patients. Notably, most respondents (89% [84%-94%]) used a 120 to 125 kVp standard setting, whereas none used 140 kVp. The most common average dose-length-product (DLP) value was 150 to 249 mGy.cm (75/146, 51% [43%-59%]), and 59% (51%-67%) delivered less than 250 mGy.cm in a 70 kg patient. There was a tendency towards higher DLP values with multidetector-row CT. Age, gender, and pregnancy were associated more with dose reduction than weight and clinical indication. Efforts for reducing patient radiation dose are highly prevalent among thoracic radiologists. Areas for improvement include reduction of default tube current settings, reduction of anatomical scan coverage, greater use of automatic exposure control, and eventually, reduction of current reference dose values. Our study emphasizes the need for international guidelines to foster greater conformity in dose reduction by thoracic radiologists.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caillet, V; Colvill, E; Royal North Shore Hospital, Sydney, NSW

Purpose: The objective of this study was to investigate the dosimetric benefits of multi-leaf collimator (MLC) tracking for lung SABR treatments in end-to-end clinically realistic planning and delivery scenarios. Methods: The clinical benefits of MLC tracking were assessed using previously delivered treatment plans and physical experiments. The 10 most recent single lesion lung SABR patients were re-planned following a 4D-GTV-based real-time adaptive protocol (PTV defined as the end-of-exhalation GTV plus 5.0 mm margins). The plans were delivered on a Trilogy Varian linac. Electromagnetic transponders (Calypso, Varian Medical Systems, USA) were embedded into a programmable moving phantom (HexaMotion platform) tracked withmore » the Varian Calypso system. For each physical experiment, the MLC positions were collected and used as input for dose reconstruction. For both planned and physical experiments, the OAR dose metrics from the conventional and real-time adaptive SABR plans (Mean Lung Dose (MLD), V20 for lung, and near-maximum dose (D2%) for spine and heart) were statistically compared. The Wilcoxon test was used to compare plan and physical experiment dose metrics. Results: While maintaining target coverage, percentage reductions in dose metrics to the OARs were observed for both planned and physical experiments. Comparing the two plans showed MLD percentage reduction (MLDr) of 25.4% (absolute differences of 1.41 Gy) and 28.9% (1.29%) for the V20r. D2% percentage reduction for spine and heart were respectively 27.9% (0.3 Gy) and 20.2% (0.3 Gy). For the physical experiments, MLDr was 23.9% (1.3 Gy), and V20r 37.4% (1.6%). D2% reduction for spine and heart were respectively 27.3% (0.3 Gy) and 19.6% (0.3 Gy). For both plans and physical experiments, significant OAR dose differences (p<0.05) were found between the conventional SABR and real-time adaptive plans. Conclusion: Application of MLC tracking for lung SABR patients has the potential to reduce the dose to OARs during radiation therapy.« less

Improving Low-dose Cardiac CT Images based on 3D Sparse Representation

NASA Astrophysics Data System (ADS)

Shi, Luyao; Hu, Yining; Chen, Yang; Yin, Xindao; Shu, Huazhong; Luo, Limin; Coatrieux, Jean-Louis

2016-03-01

Cardiac computed tomography (CCT) is a reliable and accurate tool for diagnosis of coronary artery diseases and is also frequently used in surgery guidance. Low-dose scans should be considered in order to alleviate the harm to patients caused by X-ray radiation. However, low dose CT (LDCT) images tend to be degraded by quantum noise and streak artifacts. In order to improve the cardiac LDCT image quality, a 3D sparse representation-based processing (3D SR) is proposed by exploiting the sparsity and regularity of 3D anatomical features in CCT. The proposed method was evaluated by a clinical study of 14 patients. The performance of the proposed method was compared to the 2D spares representation-based processing (2D SR) and the state-of-the-art noise reduction algorithm BM4D. The visual assessment, quantitative assessment and qualitative assessment results show that the proposed approach can lead to effective noise/artifact suppression and detail preservation. Compared to the other two tested methods, 3D SR method can obtain results with image quality most close to the reference standard dose CT (SDCT) images.

Efficacy, Safety, and Feasibility of the Morphine Microdose Method in Community-Based Clinics.

PubMed

Wilkes, Denise M; Orillosa, Susan J; Hustak, Erik C; Williams, Courtney G; Doulatram, Gulshan R; Solanki, Daneshvari R; Garcia, Eduardo A; Huang, Li-Yen M

2017-06-13

The goal of this study was to assess the success of the morphine microdose method in a community pain clinic setting by monitoring follow-up frequency, dose escalation, and monotherapy/polytherapy ratio. The morphine microdose method involves a pretrial reduction or elimination of systemic opioids followed by a period of abstinence. Intrathecal (IT) morphine is then started at doses of less than 0.2 mg per day. Systemic opioid abstinence is then continued after pump implant and IT morphine monotherapy. Retrospective review of medical records. Private and academic pain clinic practices. Chronic noncancer pain patients. We reviewed the charts of 60 patients who had completed a microdose regimen and had an IT pump implanted between June 11, 2008, and October 11, 2014. During IT therapy, dose change over time, pain scores, side effects, max dose, and duration were recorded. The majority of patients (35/60, 58%) were successfully managed solely on morphine microdose monotherapy. These patients did not require additional oral therapy. There was a significant reduction in mean pain scores, from 7.4 ± 0.32 before microdose therapy to 4.8 ± 0.3 after microdose therapy. Microdose therapy achieved analgesia, improved safety, and avoided systemic side effects. The safety of IT therapy was increased by using a lower concentration (2 mg/mL) and lower daily doses (<3 mg/d) of morphine. Furthermore, microdose therapy was feasible, safe, and cost-effective in the outpatient setting. 2017 American Academy of Pain Medicine. This work is written by US Government employees and is in the public domain in the US.

[Examination of patient dose reduction in cardiovasucular X-ray systems with a metal filter].

PubMed

Yasuda, Mitsuyoshi; Kato, Kyouichi; Tanabe, Nobuaki; Sakiyama, Koushi; Uchiyama, Yushi; Suzuki, Yoshiaki; Suzuki, Hiroshi; Nakazawa, Yasuo

2012-01-01

In interventional X-ray for cardiology of flat panel digital detector (FPD), the phenomenon that exposure dose was suddenly increased when a subject thickness was thickened was recognized. At that time, variable metal built-in filters in FPD were all off. Therefore, we examined whether dose reduction was possible without affecting a clinical image using metal filter (filter) which we have been conventionally using for dose reduction. About 45% dose reduction was achieved when we measured an exposure dose at 30 cm of acrylic thickness in the presence of a filter. In addition, we measured signal to noise ratio/contrast to noise ratio/a resolution limit by the visual evaluation, and there was no influence by filter usage. In the clinical examination, visual evaluation of image quality of coronary angiography (40 cases) using a 5-point evaluation scale by a physician was performed. As a result, filter usage did not influence the image quality (p=NS). Therefore, reduction of sudden increase of exposure dose was achieved without influencing an image quality by adding filter to FPD.

Brachytherapy devices and methods employing americium-241

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, L. A.

1985-04-16

Sources and methods for radiation therapy, particularly brachytherapy, employing americium-241 (60 keV gamma emission and 433 year half-life) provide major advantages for radiotherapy, including simplified radiation protection, dose reduction to healthy tissue, increased dose to tumor, and improved dose distributions. A number of apparent drawbacks and unfavorable considerations including low gamma factor, high self-absorption, increased activity required and alpha-particle generation leading to helium gas pressure buildup and potential neutron contamination in the generated radiation are all effectively dealt with and overcome through recognition of subtle favorable factors unique to americium-241 among brachytherapy sources and through suitable constructional techniques. Due tomore » an additional amount of radiation, in the order of 50%, provided primarily to nearby regions as a result of Compton scatter in tissue and water, higher dose rates occur than would be predicted by conventional calculations.« less

A Projection Quality-Driven Tube Current Modulation Method in Cone-Beam CT for IGRT: Proof of Concept.

PubMed

Men, Kuo; Dai, Jianrong

2017-12-01

To develop a projection quality-driven tube current modulation method in cone-beam computed tomography for image-guided radiotherapy based on the prior attenuation information obtained by the planning computed tomography and then evaluate its effect on a reduction in the imaging dose. The QCKV-1 phantom with different thicknesses (0-400 mm) of solid water upon it was used to simulate different attenuation (μ). Projections were acquired with a series of tube current-exposure time product (mAs) settings, and a 2-dimensional contrast to noise ratio was analyzed for each projection to create a lookup table of mAs versus 2-dimensional contrast to noise ratio, μ. Before a patient underwent computed tomography, the maximum attenuation [Formula: see text] within the 95% range of each projection angle (θ) was estimated according to the planning computed tomography images. Then, a desired 2-dimensional contrast to noise ratio value was selected, and the mAs setting at θ was calculated with the lookup table of mAs versus 2-dimensional contrast to noise ratio,[Formula: see text]. Three-dimensional cone-beam computed tomography images were reconstructed using the projections acquired with the selected mAs. The imaging dose was evaluated with a polymethyl methacrylate dosimetry phantom in terms of volume computed tomography dose index. Image quality was analyzed using a Catphan 503 phantom with an oval body annulus and a pelvis phantom. For the Catphan 503 phantom, the cone-beam computed tomography image obtained by the projection quality-driven tube current modulation method had a similar quality to that of conventional cone-beam computed tomography . However, the proposed method could reduce the imaging dose by 16% to 33% to achieve an equivalent contrast to noise ratio value. For the pelvis phantom, the structural similarity index was 0.992 with a dose reduction of 39.7% for the projection quality-driven tube current modulation method. The proposed method could reduce the additional dose to the patient while not degrading the image quality for cone-beam computed tomography. The projection quality-driven tube current modulation method could be especially beneficial to patients who undergo cone-beam computed tomography frequently during a treatment course.

MO-C-18A-01: Advances in Model-Based 3D Image Reconstruction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, G; Pan, X; Stayman, J

2014-06-15

Recent years have seen the emergence of CT image reconstruction techniques that exploit physical models of the imaging system, photon statistics, and even the patient to achieve improved 3D image quality and/or reduction of radiation dose. With numerous advantages in comparison to conventional 3D filtered backprojection, such techniques bring a variety of challenges as well, including: a demanding computational load associated with sophisticated forward models and iterative optimization methods; nonlinearity and nonstationarity in image quality characteristics; a complex dependency on multiple free parameters; and the need to understand how best to incorporate prior information (including patient-specific prior images) within themore » reconstruction process. The advantages, however, are even greater – for example: improved image quality; reduced dose; robustness to noise and artifacts; task-specific reconstruction protocols; suitability to novel CT imaging platforms and noncircular orbits; and incorporation of known characteristics of the imager and patient that are conventionally discarded. This symposium features experts in 3D image reconstruction, image quality assessment, and the translation of such methods to emerging clinical applications. Dr. Chen will address novel methods for the incorporation of prior information in 3D and 4D CT reconstruction techniques. Dr. Pan will show recent advances in optimization-based reconstruction that enable potential reduction of dose and sampling requirements. Dr. Stayman will describe a “task-based imaging” approach that leverages models of the imaging system and patient in combination with a specification of the imaging task to optimize both the acquisition and reconstruction process. Dr. Samei will describe the development of methods for image quality assessment in such nonlinear reconstruction techniques and the use of these methods to characterize and optimize image quality and dose in a spectrum of clinical applications. Learning Objectives: Learn the general methodologies associated with model-based 3D image reconstruction. Learn the potential advantages in image quality and dose associated with model-based image reconstruction. Learn the challenges associated with computational load and image quality assessment for such reconstruction methods. Learn how imaging task can be incorporated as a means to drive optimal image acquisition and reconstruction techniques. Learn how model-based reconstruction methods can incorporate prior information to improve image quality, ease sampling requirements, and reduce dose.« less

Evaluation of the low dose cardiac CT imaging using ASIR technique

NASA Astrophysics Data System (ADS)

Fan, Jiahua; Hsieh, Jiang; Deubig, Amy; Sainath, Paavana; Crandall, Peter

2010-04-01

Today Cardiac imaging is one of the key driving forces for the research and development activities of Computed Tomography (CT) imaging. It requires high spatial and temporal resolution and is often associated with high radiation dose. The newly introduced ASIR technique presents an efficient method that offers the dose reduction benefits while maintaining image quality and providing fast reconstruction speed. This paper discusses the study of image quality of the ASIR technique for Cardiac CT imaging. Phantoms as well as clinical data have been evaluated to demonstrate the effectiveness of ASIR technique for Cardiac CT applications.

Patients with Fabry Disease after Enzyme Replacement Therapy Dose Reduction Versus Treatment Switch

PubMed Central

Krämer, Johannes; Duning, Thomas; Lenders, Malte; Canaan-Kühl, Sima; Krebs, Alice; González, Hans Guerrero; Sommer, Claudia; Üçeyler, Nurcan; Niemann, Markus; Störk, Stefan; Schelleckes, Michael; Reiermann, Stefanie; Stypmann, Jörg; Brand, Stefan-Martin; Wanner, Christoph; Brand, Eva

2014-01-01

Because of the shortage of agalsidase-beta in 2009, many patients with Fabry disease were treated with lower doses or were switched to agalsidase-alfa. This observational study assessed end-organ damage and clinical symptoms during dose reduction or switch to agalsidase-alfa. A total of 105 adult patients with Fabry disease who had received agalsidase-beta (1.0 mg/kg body weight) for ≥1 year were nonrandomly assigned to continue this treatment regimen (regular-dose group, n=38), receive a reduced dose of 0.3–0.5 mg/kg (dose-reduction group, n=29), or switch to 0.2 mg/kg agalsidase-alfa (switch group) and were followed prospectively for 1 year. We assessed clinical events (death, myocardial infarction, severe arrhythmia, stroke, progression to ESRD); changes in cardiac, renal, and neurologic function; and Fabry-related symptoms (neuropathic pain, hypohidrosis, diarrhea, and disease severity scores). Organ function and Fabry-related symptoms remained stable in the regular-dose group. In contrast, estimated GFR decreased by about 3 ml/min per 1.73 m2 (P=0.01) in the dose-reduction group, and the median albumin-to-creatinine ratio increased from 114 (0–606) mg/g to 216 (0–2062) mg/g (P=0.03) in the switch group. Furthermore, mean Mainz Severity Score Index scores and frequencies of pain attacks, chronic pain, gastrointestinal pain, and diarrhea increased significantly in the dose-reduction and switch groups. In conclusion, patients receiving regular agalsidase-beta dose had a stable disease course, but dose reduction led to worsening of renal function and symptoms. Switching to agalsidase-alfa is safe, but microalbuminuria may progress and Fabry-related symptoms may deteriorate. PMID:24556354

Patients with Fabry disease after enzyme replacement therapy dose reduction versus treatment switch.

PubMed

Weidemann, Frank; Krämer, Johannes; Duning, Thomas; Lenders, Malte; Canaan-Kühl, Sima; Krebs, Alice; Guerrero González, Hans; Sommer, Claudia; Üçeyler, Nurcan; Niemann, Markus; Störk, Stefan; Schelleckes, Michael; Reiermann, Stefanie; Stypmann, Jörg; Brand, Stefan-Martin; Wanner, Christoph; Brand, Eva

2014-04-01

Because of the shortage of agalsidase-beta in 2009, many patients with Fabry disease were treated with lower doses or were switched to agalsidase-alfa. This observational study assessed end-organ damage and clinical symptoms during dose reduction or switch to agalsidase-alfa. A total of 105 adult patients with Fabry disease who had received agalsidase-beta (1.0 mg/kg body weight) for ≥1 year were nonrandomly assigned to continue this treatment regimen (regular-dose group, n=38), receive a reduced dose of 0.3-0.5 mg/kg (dose-reduction group, n=29), or switch to 0.2 mg/kg agalsidase-alfa (switch group) and were followed prospectively for 1 year. We assessed clinical events (death, myocardial infarction, severe arrhythmia, stroke, progression to ESRD); changes in cardiac, renal, and neurologic function; and Fabry-related symptoms (neuropathic pain, hypohidrosis, diarrhea, and disease severity scores). Organ function and Fabry-related symptoms remained stable in the regular-dose group. In contrast, estimated GFR decreased by about 3 ml/min per 1.73 m(2) (P=0.01) in the dose-reduction group, and the median albumin-to-creatinine ratio increased from 114 (0-606) mg/g to 216 (0-2062) mg/g (P=0.03) in the switch group. Furthermore, mean Mainz Severity Score Index scores and frequencies of pain attacks, chronic pain, gastrointestinal pain, and diarrhea increased significantly in the dose-reduction and switch groups. In conclusion, patients receiving regular agalsidase-beta dose had a stable disease course, but dose reduction led to worsening of renal function and symptoms. Switching to agalsidase-alfa is safe, but microalbuminuria may progress and Fabry-related symptoms may deteriorate.

Relationship between radiation dose reduction and image quality change in photostimulable phosphor luminescence X-ray imaging systems.

PubMed

Sakurai, T; Kawamata, R; Kozai, Y; Kaku, Y; Nakamura, K; Saito, M; Wakao, H; Kashima, I

2010-05-01

The aim of the study was to clarify the change in image quality upon X-ray dose reduction and to re-analyse the possibility of X-ray dose reduction in photostimulable phosphor luminescence (PSPL) X-ray imaging systems. In addition, the study attempted to verify the usefulness of multiobjective frequency processing (MFP) and flexible noise control (FNC) for X-ray dose reduction. Three PSPL X-ray imaging systems were used in this study. Modulation transfer function (MTF), noise equivalent number of quanta (NEQ) and detective quantum efficiency (DQE) were evaluated to compare the basic physical performance of each system. Subjective visual evaluation of diagnostic ability for normal anatomical structures was performed. The NEQ, DQE and diagnostic ability were evaluated at base X-ray dose, and 1/3, 1/10 and 1/20 of the base X-ray dose. The MTF of the systems did not differ significantly. The NEQ and DQE did not necessarily depend on the pixel size of the system. The images from all three systems had a higher diagnostic utility compared with conventional film images at the base and 1/3 X-ray doses. The subjective image quality was better at the base X-ray dose than at 1/3 of the base dose in all systems. The MFP and FNC-processed images had a higher diagnostic utility than the images without MFP and FNC. The use of PSPL imaging systems may allow a reduction in the X-ray dose to one-third of that required for conventional film. It is suggested that MFP and FNC are useful for radiation dose reduction.

Reducing radiation dose to selected organs by selecting the tube start angle in MDCT helical scans: A Monte Carlo based study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Di; Zankl, Maria; DeMarco, John J.

Purpose: Previous work has demonstrated that there are significant dose variations with a sinusoidal pattern on the peripheral of a CTDI 32 cm phantom or on the surface of an anthropomorphic phantom when helical CT scanning is performed, resulting in the creation of ''hot'' spots or ''cold'' spots. The purpose of this work was to perform preliminary investigations into the feasibility of exploiting these variations to reduce dose to selected radiosensitive organs solely by varying the tube start angle in CT scans. Methods: Radiation dose to several radiosensitive organs (including breasts, thyroid, uterus, gonads, and eye lenses) resulting from MDCTmore » scans were estimated using Monte Carlo simulation methods on voxelized patient models, including GSF's Baby, Child, and Irene. Dose to fetus was also estimated using four pregnant female models based on CT images of the pregnant patients. Whole-body scans were simulated using 120 kVp, 300 mAs, both 28.8 and 40 mm nominal collimations, and pitch values of 1.5, 1.0, and 0.75 under a wide range of start angles (0 deg. - 340 deg. in 20 deg. increments). The relationship between tube start angle and organ dose was examined for each organ, and the potential dose reduction was calculated. Results: Some organs exhibit a strong dose variation, depending on the tube start angle. For small peripheral organs (e.g., the eye lenses of the Baby phantom at pitch 1.5 with 40 mm collimation), the minimum dose can be 41% lower than the maximum dose, depending on the tube start angle. In general, larger dose reductions occur for smaller peripheral organs in smaller patients when wider collimation is used. Pitch 1.5 and pitch 0.75 have different mechanisms of dose reduction. For pitch 1.5 scans, the dose is usually lowest when the tube start angle is such that the x-ray tube is posterior to the patient when it passes the longitudinal location of the organ. For pitch 0.75 scans, the dose is lowest when the tube start angle is such that the x-ray tube is anterior to the patient when it passes the longitudinal location of the organ. Conclusions: Helical MDCT scanning at pitch 1.5 and pitch 0.75 results in ''cold spots'' and ''hot spots'' that are created both at surface and in-depth locations within patients. For organs that have a relatively small longitudinal extent, dose can vary considerably with different start angles. While current MDCT systems do not provide the user with the ability to control the tube start angle, these results indicate that in these specific situations (pitch 1.5 or pitch 0.75, small organs and especially small patients), there could be significant dose savings to organs if that functionality would be provided.« less

Effectiveness of thyroid gland shielding in dental CBCT using a paediatric anthropomorphic phantom

PubMed Central

Davies, J; Horner, K; Theodorakou, C

2015-01-01

Objectives: The purpose of the study is to evaluate the effectiveness of thyroid shielding in dental CBCT examinations using a paediatric anthropomorphic phantom. Methods: An ATOM® 706-C anthropomorphic phantom (Computerized Imaging Reference Systems Inc., Norfolk, VA) representing a 10-year-old child was loaded with six thermoluminescent dosemeters positioned at the level of the thyroid gland. Absorbed doses to the thyroid were measured for five commercially available thyroid shields using a large field of view (FOV). Results: A statistically significant thyroid gland dose reduction was found using thyroid shielding for paediatric CBCT examinations for a large FOV. In addition, a statistically significant difference in thyroid gland doses was found depending on the position of the thyroid gland. There was little difference in the effectiveness of thyroid shielding when using a lead vs a lead-equivalent thyroid shield. Similar dose reduction was found using 0.25- and 0.50-mm lead-equivalent thyroid shields. Conclusions: Thyroid shields are to be recommended when undertaking large FOV CBCT examinations on young patients. PMID:25411710

Iterative reconstruction for x-ray computed tomography using prior-image induced nonlocal regularization.

PubMed

Zhang, Hua; Huang, Jing; Ma, Jianhua; Bian, Zhaoying; Feng, Qianjin; Lu, Hongbing; Liang, Zhengrong; Chen, Wufan

2014-09-01

Repeated X-ray computed tomography (CT) scans are often required in several specific applications such as perfusion imaging, image-guided biopsy needle, image-guided intervention, and radiotherapy with noticeable benefits. However, the associated cumulative radiation dose significantly increases as comparison with that used in the conventional CT scan, which has raised major concerns in patients. In this study, to realize radiation dose reduction by reducing the X-ray tube current and exposure time (mAs) in repeated CT scans, we propose a prior-image induced nonlocal (PINL) regularization for statistical iterative reconstruction via the penalized weighted least-squares (PWLS) criteria, which we refer to as "PWLS-PINL". Specifically, the PINL regularization utilizes the redundant information in the prior image and the weighted least-squares term considers a data-dependent variance estimation, aiming to improve current low-dose image quality. Subsequently, a modified iterative successive overrelaxation algorithm is adopted to optimize the associative objective function. Experimental results on both phantom and patient data show that the present PWLS-PINL method can achieve promising gains over the other existing methods in terms of the noise reduction, low-contrast object detection, and edge detail preservation.

Iterative Reconstruction for X-Ray Computed Tomography using Prior-Image Induced Nonlocal Regularization

PubMed Central

Ma, Jianhua; Bian, Zhaoying; Feng, Qianjin; Lu, Hongbing; Liang, Zhengrong; Chen, Wufan

2014-01-01

Repeated x-ray computed tomography (CT) scans are often required in several specific applications such as perfusion imaging, image-guided biopsy needle, image-guided intervention, and radiotherapy with noticeable benefits. However, the associated cumulative radiation dose significantly increases as comparison with that used in the conventional CT scan, which has raised major concerns in patients. In this study, to realize radiation dose reduction by reducing the x-ray tube current and exposure time (mAs) in repeated CT scans, we propose a prior-image induced nonlocal (PINL) regularization for statistical iterative reconstruction via the penalized weighted least-squares (PWLS) criteria, which we refer to as “PWLS-PINL”. Specifically, the PINL regularization utilizes the redundant information in the prior image and the weighted least-squares term considers a data-dependent variance estimation, aiming to improve current low-dose image quality. Subsequently, a modified iterative successive over-relaxation algorithm is adopted to optimize the associative objective function. Experimental results on both phantom and patient data show that the present PWLS-PINL method can achieve promising gains over the other existing methods in terms of the noise reduction, low-contrast object detection and edge detail preservation. PMID:24235272

Clinical analysis of speculum-based vaginal packing for high-dose-rate intracavitary tandem and ovoid brachytherapy in cervical cancer

PubMed Central

Sud, Shivani; Roth, Toni

2018-01-01

Purpose Intra-vaginal packing is used to fix the applicator and displace organs at risk (OAR) during high-dose-rate intracavitary tandem and ovoid brachytherapy (HDR-ICB). We retain the speculum from applicator placement as a dual-function bladder and rectum retractor during treatment. Our objective is to review salient techniques for OAR displacement, share our packing technique, and determine the reduction in dose to OAR and inter-fraction variability of dose to OAR, associated with speculum-based vaginal packing (SBVP) in comparison to conventional gauze packing during HDR-ICB. Material and methods We reviewed HDR-ICB treatment plans for 45 patients, including 10 who underwent both conventional gauze packing and SBVP. Due to institutional inter-provider practice differences, patients non-selectively received either packing procedure. Packing was performed under conscious sedation, followed by cone beam computed tomography used for dosimetric planning. Maximum absolute and percent-of-prescription dose to the International Commission of Radiation Units bladder and rectal points in addition to D0.1cc, D1.0cc, and D2.0cc volumes of the bladder and rectum were analyzed and compared for each packing method using an independent sample t-test. Results Of the 179 fractions included, 73% and 27% used SBVP and gauze packing, respectively. For patients prescribed 6 Gy to point A, SBVP was associated with reduced mean D0.1cc bladder dose, inter-fraction variability in D0.1cc bladder dose by 9.3% (p = 0.026) and 9.0%, respectively, and statistically equivalent rectal D0.1cc, D1.0cc, and D2.0cc. Patients prescribed 5.5 Gy or 5 Gy to point A after dose optimization, were less likely to benefit from SBVP. In the intra-patient comparison, 80% of patients had reduction in at least one rectum or bladder parameter. Conclusions In patients with conducive anatomy, SBVP is a cost-efficient packing method that is associated with improved bladder sparing and comparable rectal sparing relative to gauze packing during HDR-ICB without general anesthesia. PMID:29619054

TH-AB-207A-12: CT Lung Cancer Screening and the Effects of Further Dose Reduction On CAD Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, S; Lo, P; Hoffman, J

Purpose: CT lung screening is already performed at low doses. In this study, we investigated the effects of further dose reduction on a lung-nodule CAD detection algorithm. Methods: The original raw CT data and images from 348 patients were obtained from our local database of National Lung Screening Trial (NLST) cases. 61 patients (17.5%) had at least one nodule reported on the NLST reader forms. All scans were acquired with fixed mAs (25 for standard-sized patients, 40 for large patients) on a 64-slice scanner (Sensation 64, Siemens Healthcare). All images were reconstructed with 1-mm slice thickness, B50 kernel. Based onmore » a previously-published technique, we added noise to the raw data to simulate reduced-dose versions of each case at 50% and 25% of the original NLST dose (i.e. approximately 1.0 and 0.5 mGy CTDIvol). For each case at each dose level, a CAD detection algorithm was run and nodules greater than 4 mm in diameter were reported. These CAD results were compared to “truth”, defined as the approximate nodule centroids from the NLST forms. Sensitivities and false-positive rates (FPR) were calculated for each dose level, with a sub-analysis by nodule LungRADS category. Results: For larger category 4 nodules, median sensitivities were 100% at all three dose levels, and mean sensitivity decreased with dose. For the more challenging category 2 and 3 nodules, the dose dependence was less obvious. Overall, mean subject-level sensitivity varied from 38.5% at 100% dose to 40.4% at 50% dose, a difference of only 1.9%. However, median FPR quadrupled from 1 per case at 100% dose to 4 per case at 25% dose. Conclusions: Dose reduction affected nodule detectability differently depending on the LungRADS category, and FPR was very sensitive at sub-screening levels. Care should be taken to adapt CAD for the very challenging noise characteristics of screening. Funding support: NIH U01 CA181156; Disclosures (McNitt-Gray): Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics.« less

Lens dose in routine head CT: comparison of different optimization methods with anthropomorphic phantoms.

PubMed

Nikupaavo, Ulla; Kaasalainen, Touko; Reijonen, Vappu; Ahonen, Sanna-Mari; Kortesniemi, Mika

2015-01-01

The purpose of this study was to study different optimization methods for reducing eye lens dose in head CT. Two anthropomorphic phantoms were scanned with a routine head CT protocol for evaluation of the brain that included bismuth shielding, gantry tilting, organ-based tube current modulation, or combinations of these techniques. Highsensitivity metal oxide semiconductor field effect transistor dosimeters were used to measure local equivalent doses in the head region. The relative changes in image noise and contrast were determined by ROI analysis. The mean absorbed lens doses varied from 4.9 to 19.7 mGy and from 10.8 to 16.9 mGy in the two phantoms. The most efficient method for reducing lens dose was gantry tilting, which left the lenses outside the primary radiation beam, resulting in an approximately 75% decrease in lens dose. Image noise decreased, especially in the anterior part of the brain. The use of organ-based tube current modulation resulted in an approximately 30% decrease in lens dose. However, image noise increased as much as 30% in the posterior and central parts of the brain. With bismuth shields, it was possible to reduce lens dose as much as 25%. Our results indicate that gantry tilt, when possible, is an effective method for reducing exposure of the eye lenses in CT of the brain without compromising image quality. Measurements in two different phantoms showed how patient geometry affects the optimization. When lenses can only partially be cropped outside the primary beam, organ-based tube current modulation or bismuth shields can be useful in lens dose reduction.

Assessment of phase based dose modulation for improved dose efficiency in cardiac CT on an anthropomorphic motion phantom

NASA Astrophysics Data System (ADS)

Budde, Adam; Nilsen, Roy; Nett, Brian

2014-03-01

State of the art automatic exposure control modulates the tube current across view angle and Z based on patient anatomy for use in axial full scan reconstructions. Cardiac CT, however, uses a fundamentally different image reconstruction that applies a temporal weighting to reduce motion artifacts. This paper describes a phase based mA modulation that goes beyond axial and ECG modulation; it uses knowledge of the temporal view weighting applied within the reconstruction algorithm to improve dose efficiency in cardiac CT scanning. Using physical phantoms and synthetic noise emulation, we measure how knowledge of sinogram temporal weighting and the prescribed cardiac phase can be used to improve dose efficiency. First, we validated that a synthetic CT noise emulation method produced realistic image noise. Next, we used the CT noise emulation method to simulate mA modulation on scans of a physical anthropomorphic phantom where a motion profile corresponding to a heart rate of 60 beats per minute was used. The CT noise emulation method matched noise to lower dose scans across the image within 1.5% relative error. Using this noise emulation method to simulate modulating the mA while keeping the total dose constant, the image variance was reduced by an average of 11.9% on a scan with 50 msec padding, demonstrating improved dose efficiency. Radiation dose reduction in cardiac CT can be achieved while maintaining the same level of image noise through phase based dose modulation that incorporates knowledge of the cardiac reconstruction algorithm.

Real-time colour pictorial radiation monitoring during coronary angiography: effect on patient peak skin and total dose during coronary angiography.

PubMed

Wilson, Sharon M; Prasan, Ananth M; Virdi, Amy; Lassere, Marissa; Ison, Glenn; Ramsay, David R; Weaver, James C

2016-10-10

The aim of this study was to evaluate whether a real-time (RT) colour pictorial radiation dose monitoring system reduces patient skin and total radiation dose during coronary angiography and intervention. Patient demographics, procedural variables and radiation parameters were recorded before and after institution of the RT skin dose recording system. Peak skin dose as well as traditionally available measures of procedural radiation dose were compared. A total of 1,077 consecutive patients underwent coronary angiography, of whom 460 also had PCI. Institution of the RT skin dose recording system resulted in a 22% reduction in peak skin dose after accounting for confounding variables. Radiation dose reduction was most pronounced in those having PCI but was also seen over a range of subgroups including those with prior coronary artery bypass surgery, high BMI, and with radial arterial access. This was associated with a significant reduction in the number of patients placed at risk of skin damage. Similar reductions in parameters reflective of total radiation dose were also demonstrated after institution of RT radiation monitoring. Institution of an RT skin dose recording reduced patient peak skin and total radiation dose during coronary angiography and intervention. Consideration should be given to widespread adoption of this technology.

Comparison of filgrastim and pegfilgrastim to prevent neutropenia and maintain dose intensity of adjuvant chemotherapy in patients with breast cancer.

PubMed

Kourlaba, Georgia; Dimopoulos, Meletios A; Pectasides, Dimitrios; Skarlos, Dimosthenis V; Gogas, Helen; Pentheroudakis, George; Koutras, Angelos; Fountzilas, George; Maniadakis, Nikos

2015-07-01

The aim of this study was to compare the effectiveness of prophylactic single fixed dose of pegfilgrastim and daily administration of filgrastim on febrile neutropenia (FN), severe neutropenia, treatment delay, and dose reduction in patients with breast cancer receiving dose-dense adjuvant chemotherapy. A retrospective cohort study with 1058 breast cancer patients matched by age and chemotherapy was conducted. The primary endpoints were FN, severe (grade 3, 4) neutropenia, dose reduction (>10 % reduction of the dose planned), and treatment delay (dose given more than 2 days later). Eighteen episodes of FN (3.4%) in the filgrastim group and 23 (4.3%) in the pegfilgrastim group (p = 0.500) were recorded. More than half of the total episodes (27/41) occurred during the first 4 cycles of treatment. Patients who received filgrastim were almost three times more likely to experience a severe neutropenia episode and were significantly more likely to experience a dose reduction (18.5%) compared to those who received pegfilgrastim (10.8%) (p < 0.001). The percentage of patients, who received their planned dose on time, was significantly lower in patients receiving filgrastim (58%) compared to those receiving pegfilgrastim (72.4%, p < 0.001). No significant difference was detected on FN rate between daily administration of filgrastim and single administration of pegfilgrastim. However, patients receiving pegfilgrastim had a significantly lower rate of severe neutropenia, as well as dose reduction and treatment delay, thus, achieving a higher dose density.

Dose reduction and cost-benefit analysis at Japan`s Tokai No. 2 Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humamoto, Hisao; Suzuki, Seishiro; Taniguchi, Kazufumi

1995-03-01

In the Tokai No. 2 power plant of the Japan Atomic Power Company, about 80% of the annual dose equivalent is received during periodic maintenance outages. A project group for dose reduction was organized at the company`s headquarters in 1986; in 1988, they proposed a five-year program to reduce by half the collective dose of 4 person-Sv per normal outage work. To achieve the target dose value, some dose-reduction measures were undertaken, namely, permanent radiation shielding, decontamination, automatic, operating machines, and ALARA organization. As the result, the collective dose from normal outage work was 1.6 person-Sv in 1992, which wasmore » less than the initial target value.« less

The reduction methods of operator's radiation dose for portable dental X-ray machines.

PubMed

Cho, Jeong-Yeon; Han, Won-Jeong

2012-08-01

This study was aimed to investigate the methods to reduce operator's radiation dose when taking intraoral radiographs with portable dental X-ray machines. Two kinds of portable dental X-ray machines (DX3000, Dexcowin and Rextar, Posdion) were used. Operator's radiation dose was measured with an 1,800 cc ionization chamber (RadCal Corp.) at the hand level of X-ray tubehead and at the operator's chest and waist levels with and without the backscatter shield. The operator's radiation dose at the hand level was measured with and without lead gloves and with long and short cones. The backscatter shield reduced operator's radiation dose at the hand level of X-ray tubehead to 23 - 32%, the lead gloves to 26 - 31%, and long cone to 48 - 52%. And the backscatter shield reduced operator's radiation dose at the operator's chest and waist levels to 0.1 - 37%. When portable dental X-ray systems are used, it is recommended to select X-ray machine attached with a backscatter shield and a long cone and to wear the lead gloves.

Comparison of the Immunogenicity of Various Booster Doses of Inactivated Polio Vaccine Delivered Intradermally Versus Intramuscularly to HIV-Infected Adults

PubMed Central

Troy, Stephanie B.; Kouiavskaia, Diana; Siik, Julia; Kochba, Efrat; Beydoun, Hind; Mirochnitchenko, Olga; Levin, Yotam; Khardori, Nancy; Chumakov, Konstantin; Maldonado, Yvonne

2015-01-01

Background. Inactivated polio vaccine (IPV) is necessary for global polio eradication because oral polio vaccine can rarely cause poliomyelitis as it mutates and may fail to provide adequate immunity in immunocompromised populations. However, IPV is unaffordable for many developing countries. Intradermal IPV shows promise as a means to decrease the effective dose and cost of IPV, but prior studies, all using 20% of the standard dose used in intramuscular IPV, resulted in inferior antibody titers. Methods. We randomly assigned 231 adults with well-controlled human immunodeficiency virus infection at a ratio of 2:2:2:1 to receive 40% of the standard dose of IPV intradermally, 20% of the standard dose intradermally, the full standard dose intramuscularly, or 40% of the standard dose intramuscularly. Intradermal vaccination was done using the NanoPass MicronJet600 microneedle device. Results. Baseline immunity was 87%, 90%, and 66% against poliovirus serotypes 1, 2, and 3, respectively. After vaccination, antibody titers increased a median of 64-fold. Vaccine response to 40% of the standard dose administered intradermally was comparable to that of the standard dose of IPV administered intramuscularly and resulted in higher (although not significantly) antibody titers. Intradermal administration had higher a incidence of local side effects (redness and itching) but a similar incidence of systemic side effects and was preferred by study participants over intramuscular administration. Conclusions. A 60% reduction in the standard IPV dose without reduction in antibody titers is possible through intradermal administration. PMID:25567841

Initial apixaban dosing in patients with atrial fibrillation.

PubMed

Buchholz, Alexander; Ueberham, Laura; Gorczynska, Kaja; Dinov, Borislav; Hilbert, Sebastian; Dagres, Nikolaos; Husser, Daniela; Hindricks, Gerhard; Bollmann, Andreas

2018-05-01

Apixaban is a non-vitamin K oral anticoagulant approved for prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation (AF). Current labeling recommends dose reduction based on patient age, weight, and renal function. The aim of this study was to analyze adherence to current labeling instructions concerning initial apixaban dosing in clinical practice and identify factors associated with inappropriate dose reduction. Patients with AF initiated on apixaban in 2016 were identified in the Heart Center Leipzig database. Records were screened to identify patient characteristics, prescribed apixaban dose, renal function, and further dosing-relevant secondary diagnoses and co-medication. We identified 569 consecutive patients with AF initiated on apixaban. In 301 (52.9%) patients, apixaban was prescribed in standard dose (5 mg b.i.d.) and in 268 (47.1%) in a reduced dose (2.5 mg b.i.d.). Of 268 patients receiving a reduced dose, 163 (60.8%) did not meet labeling criteria for dose reduction. In univariate and multivariate regression analysis, age (OR: 0.736, 95% CI: 0.664-0.816, P < 0.0001), patient weight (OR: 1.120, 95% CI: 1.076-1.166, P < 0.0001), and serum creatinine level (OR: 0.910, 95% CI: 0.881-0.940, P < 0.0001) were independent predictors for apixaban underdosage. In clinical practice, apixaban dosing is frequently inconsistent with labeling. Factors associated with inappropriate dose reduction are age, patient weight, and serum creatinine level, the same factors used as criteria for dose adjustment. However, in underdosed patients, the 3 factors did not meet the criteria for dose reduction. © 2018 Wiley Periodicals, Inc.

Validation of no-reference image quality index for the assessment of digital mammographic images

NASA Astrophysics Data System (ADS)

de Oliveira, Helder C. R.; Barufaldi, Bruno; Borges, Lucas R.; Gabarda, Salvador; Bakic, Predrag R.; Maidment, Andrew D. A.; Schiabel, Homero; Vieira, Marcelo A. C.

2016-03-01

To ensure optimal clinical performance of digital mammography, it is necessary to obtain images with high spatial resolution and low noise, keeping radiation exposure as low as possible. These requirements directly affect the interpretation of radiologists. The quality of a digital image should be assessed using objective measurements. In general, these methods measure the similarity between a degraded image and an ideal image without degradation (ground-truth), used as a reference. These methods are called Full-Reference Image Quality Assessment (FR-IQA). However, for digital mammography, an image without degradation is not available in clinical practice; thus, an objective method to assess the quality of mammograms must be performed without reference. The purpose of this study is to present a Normalized Anisotropic Quality Index (NAQI), based on the Rényi entropy in the pseudo-Wigner domain, to assess mammography images in terms of spatial resolution and noise without any reference. The method was validated using synthetic images acquired through an anthropomorphic breast software phantom, and the clinical exposures on anthropomorphic breast physical phantoms and patient's mammograms. The results reported by this noreference index follow the same behavior as other well-established full-reference metrics, e.g., the peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM). Reductions of 50% on the radiation dose in phantom images were translated as a decrease of 4dB on the PSNR, 25% on the SSIM and 33% on the NAQI, evidencing that the proposed metric is sensitive to the noise resulted from dose reduction. The clinical results showed that images reduced to 53% and 30% of the standard radiation dose reported reductions of 15% and 25% on the NAQI, respectively. Thus, this index may be used in clinical practice as an image quality indicator to improve the quality assurance programs in mammography; hence, the proposed method reduces the subjectivity inter-observers in the reporting of image quality assessment.

Volume of interest CBCT and tube current modulation for image guidance using dynamic kV collimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, David, E-mail: david.parsons@dal.ca, E-mail: james.robar@nshealth.ca; Robar, James L., E-mail: david.parsons@dal.ca, E-mail: james.robar@nshealth.ca

2016-04-15

Purpose: The focus of this work is the development of a novel blade collimation system enabling volume of interest (VOI) CBCT with tube current modulation using the kV image guidance source on a linear accelerator. Advantages of the system are assessed, particularly with regard to reduction and localization of dose and improvement of image quality. Methods: A four blade dynamic kV collimator was developed to track a VOI during a CBCT acquisition. The current prototype is capable of tracking an arbitrary volume defined by the treatment planner for subsequent CBCT guidance. During gantry rotation, the collimator tracks the VOI withmore » adjustment of position and dimension. CBCT image quality was investigated as a function of collimator dimension, while maintaining the same dose to the VOI, for a 22.2 cm diameter cylindrical water phantom with a 9 mm diameter bone insert centered on isocenter. Dose distributions were modeled using a dynamic BEAMnrc library and DOSXYZnrc. The resulting VOI dose distributions were compared to full-field CBCT distributions to quantify dose reduction and localization to the target volume. A novel method of optimizing x-ray tube current during CBCT acquisition was developed and assessed with regard to contrast-to-noise ratio (CNR) and imaging dose. Results: Measurements show that the VOI CBCT method using the dynamic blade system yields an increase in contrast-to-noise ratio by a factor of approximately 2.2. Depending upon the anatomical site, dose was reduced to 15%–80% of the full-field CBCT value along the central axis plane and down to less than 1% out of plane. The use of tube current modulation allowed for specification of a desired SNR within projection data. For approximately the same dose to the VOI, CNR was further increased by a factor of 1.2 for modulated VOI CBCT, giving a combined improvement of 2.6 compared to full-field CBCT. Conclusions: The present dynamic blade system provides significant improvements in CNR for the same imaging dose and localization of imaging dose to a predefined volume of interest. The approach is compatible with tube current modulation, allowing optimization of the imaging protocol.« less

SU-F-18C-06: Prospective Patient Evaluation of Iterative Reconstruction in Radiation Oncology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, R; Vance, S; Cattaneo, R

2014-06-15

Purpose: This work incorporates iterative reconstruction (IR) into a dose reduction study to characterize image quality metrics, delineation, and dosimetric assessment, with the goal of reducing imaging dose in Radiation Oncology. Methods: Three-dimensional noise power spectrum (NPS) analysis characterized noise magnitude/texture (120 kVp, 50–200 mAs, IR levels 1–6 yielding noise reduction of 0.89–0.55 compared to filtered backprojection (FBP)). Task-specific Modulation Transfer Functions (MTFtask) were characterized across varied subject contrasts. A prospective dose reduction study (500 to 150 mAs) was conducted for 12 patients (43 inter-fraction CTs) for high-dose rate brachytherapy. Three physicians performed qualitative image assessment between full-dose FBP (FD-FBP,more » 500 mAs), low-dose FBP (LD-FBP, 150–250 mAs), and low-dose IRL5-6 (LD-IR) scans for image noise, cuff/bladder interface detectability, spatial resolution, texture, and segmentation confidence. Comparisons between LD-FBP and LD-IR were conducted for the following metrics: delineation (bladder and rectum evaluated via overlap indices (OI) and Dice similarity coefficients (DSC)), noise, boundary changes, dose calculation, and digitally reconstructed radiographs (DRRs). Results: NPS showed ∼50% reduction in noise magnitude and ∼0.1 1/mm spatial frequency shift with IRL6. The largest MTFtask decrease between FBP and IR was 0.08 A.U. Qualitative patient image evaluation revealed LD-IR was equivalent or slightly worse than FD-FBP, and superior to LD-FBP for all metrics except low contrast interface and texture. The largest CT number discrepancy from FBP occurred at a bone/tissue interface using IRL6 (−1.2 ± 4.9 HU (range: −17.6 – 12.5 HU)). No significant contour differences (OIs and DSCs = 0.85 – 0.95) and dose calculation discrepancy (<0.02%) were observed. DRRs preserved anatomical detail and demonstrated <2% difference in intensity between LD-FBP and LD-IRL6. Conclusion: While phantom analysis showed slight noise texture differences with IR, patient results revealed that image quality, contouring ability, and dosimetric parameters were not adversely affected, thus support integrating IR into treatment planning. Research supported in part by a grant from Philips HealthCare.« less

A Comparative Efficacy of Low-Dose Combined Oral Contraceptives Containing Desogestrel and Drospirenone in Premenstrual Symptoms

PubMed Central

Wichianpitaya, Jirath; Taneepanichskul, Surasak

2013-01-01

Objective. To compare the efficacy of low-dose COC containing desogestrel (DSG) with drospirenone (DRSP) in the changes of premenstrual symptoms. Methods. In an open-label randomized controlled trial, 90 women with premenstrual syndrome who required COC were randomly recruited and allocated equally to receive either 6 cycles of 20 micrograms ethinyl estradiol (EE)/150 micrograms DSG (DSG group) or 20 micrograms EE/3 mg DRSP (DRSP group) in 24/4 extended regimen. Analysis of covariance and repeated analysis of variance were used to determine the difference of mean Women's Health Assessment Questionnaire (WHAQ) scores changes between groups, within group, and in premenstrual, menstrual, and postmenstrual phases. Results. Baseline characteristics and WHAQ scores were comparable. At the ends of the 3rd and the 6th cycles, mean WHAQ scores of all the 3 phases in DRSP group showed significant reduction and were significantly lower than those in DSG group. DSG group showed significant reduction in both premenstrual and menstrual phases after the 6th cycle. Adverse effects were comparable in both groups. In conclusion, low-dose COC containing either DSG or DRSP reduced premenstrual symptoms, but the latter showed greater efficacy and earlier reduction. PMID:23577032

131I-tositumomab myeloablative radioimmunotherapy for non-Hodgkin’s lymphoma: radiation dose to the testes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hattori, Naoya; Gopal, Ajay K.; Shields, Andrew T.

Purpose: To investigate radiation doses to the testes delivered by a radiolabeled anti-CD20 antibody and its effects on male sex hormone levels. Materials and methods: Testicular uptake and retention of 131I-tositumomab were measured, and testicular absorbed doses were calculated for 67 male patients (54+/-11 years of age) with non-Hodgkin's lymphoma who had undergone myeloablative radioimmunotherapy (RIT) using 131I-tositumomab. Time-activity curves for the major organs, testes, and whole body were generated from planar imaging studies. In a subset of patients, male sex hormones were measured before and 1 year after the therapy. Results: The absorbed dose to the testes showed considerablemore » variability (range=4.4-70.2 Gy). Pretherapy levels of total testosterone were below the lower limit of the reference range, and post-therapy evaluation demonstrated further reduction [4.6+/-1.8 nmol/l (pre-RIT) vs. 3.8+/-2.9 nmol/l (post-RIT), P<0.05]. Patients receiving higher radiation doses to the testes (>=25 Gy) showed a greater reduction [4.7+/-1.6 nmol/l (pre-RIT) vs. 3.3+/-2.7 nmol/l (post-RIT), P<0.05] compared with patients receiving lower doses (<25 Gy), who showed no significant change in total testosterone levels. Conclusion: The testicular radiation absorbed dose varied highly among individual patients. Finally, patients receiving higher doses to the testes were more likely to show post-RIT suppression of testosterone levels.« less

SU-E-I-37: Eye Lens Dose Reduction From CT Scan Using Organ Based Tube Current Modulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H; Rensselaer Polytechnic Inst., Troy, NY; Liu, T

Purpose: To investigate the eye lens dose reduction by CT scan with organ based tube current modulation (OBTCM) using GPU Monte Carlo code ARCHER-CT. Methods: 36 X-ray sources and bowtie filters were placed around the patient head with the projection angle interval of 10° for one rotation of CT scan, each projection was simulated respectively. The voxel eye models with high resolution(0.1mm*0.1mm*0.1mm) were used in the simulation and different tube voltage including 80kVp, 100kVp, 120kVp and 140kVp were taken into consideration. Results: The radiation doses to the eye lens increased with the tube voltage raised from 80kVp to 140kVp, andmore » the dose results from 0° (AP) direction are much higher than those from 180° (PA) direction for all the 4 different tube voltage investigated. This 360° projection dose characteristic enables organ based TCM, which can reduce the eye lens dose by more than 55%. Conclusion: As the eye lens belongs to superficial tissues, its radiation dose to external exposure like CT is direction sensitive, and this characteristic feature makes organ based TCM to be an effective way to reduce the eye lens dose, so more clinical use of this technique were recommended. National Nature Science Foundation of China(No.11475047)« less

Weight-adapted iodinated contrast media administration in abdomino-pelvic CT: Can image quality be maintained?

PubMed

Perrin, E; Jackson, M; Grant, R; Lloyd, C; Chinaka, F; Goh, V

2018-02-01

In many centres, a fixed method of contrast-media administration is used for CT regardless of patient body habitus. The aim of this trial was to assess contrast enhancement of the aorta, portal vein, liver and spleen during abdomino-pelvic CT imaging using a weight-adapted contrast media protocol compared to the current fixed dose method. Thirty-nine oncology patients, who had previously undergone CT abdomino-pelvic imaging at the institution using a fixed contrast media dose, were prospectively imaged using a weight-adapted contrast media dose (1.4 ml/kg). The two sets of images were assessed for contrast enhancement levels (HU) at locations in the liver, aorta, portal vein and spleen during portal-venous enhancement phase. The t-test was used to compare the difference in results using a non-inferiority margin of 10 HU. When the contrast dose was tailored to patient weight, contrast enhancement levels were shown to be non-inferior to the fixed dose method (liver p < 0.001; portal vein p = 0.003; aorta p = 0.001; spleen p = 0.001). As a group, patients received a total contrast dose reduction of 165 ml using the weight-adapted method compared to the fixed dose method, with a mean cost per patient of £6.81 and £7.19 respectively. Using a weight-adapted method of contrast media administration was shown to be non-inferior to a fixed dose method of contrast media administration. Patients weighing 76 kg, or less, received a lower contrast dose which may have associated cost savings. A weight-adapted contrast media protocol should be implemented for portal-venous phase abdomino-pelvic CT for oncology patients with adequate renal function (>70 ml/min/1.73 m 2 ). Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Low tube voltage dual source computed tomography to reduce contrast media doses in adult abdomen examinations: A phantom study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thor, Daniel; Brismar, Torkel B., E-mail: torkel.brismar@gmail.com; Fischer, Michael A.

Purpose: To evaluate the potential of low tube voltage dual source (DS) single energy (SE) and dual energy (DE) computed tomography (CT) to reduce contrast media (CM) dose in adult abdominal examinations of various sizes while maintaining soft tissue and iodine contrast-to-noise ratio (CNR). Methods: Four abdominal phantoms simulating a body mass index of 16 to 35 kg/m{sup 2} with four inserted syringes of 0, 2, 4, and 8 mgI/ml CM were scanned using a 64-slice DS-CT scanner. Six imaging protocols were used; one single source (SS) reference protocol (120 kV, 180 reference mAs), four low kV SE protocols (70more » and 80 kV using both SS and DS), and one DE protocol at 80/140 kV. Potential CM reduction with unchanged CNRs relative to the 120 kV protocol was calculated along with the corresponding increase in radiation dose. Results: The potential contrast media reductions were determined to be approximately 53% for DS 70 kV, 51% for SS 70 kV, 44% for DS 80 kV, 40% for SS 80 kV, and 20% for DE (all differences were significant, P < 0.05). Constant CNR could be achieved by using DS 70 kV for small to medium phantom sizes (16–26 kg/m{sup 2}) and for all sizes (16–35 kg/m{sup 2}) when using DS 80 kV and DE. Corresponding radiation doses increased by 60%–107%, 23%–83%, and 6%–12%, respectively. Conclusions: DS single energy CT can be used to reduce CM dose by 44%–53% with maintained CNR in adult abdominal examinations at the cost of an increased radiation dose. DS dual-energy CT allows reduction of CM dose by 20% at similar radiation dose as compared to a standard 120 kV single source.« less

Radiation Dose Reduction via Sinogram Affirmed Iterative Reconstruction and Automatic Tube Voltage Modulation (CARE kV) in Abdominal CT

PubMed Central

Shin, Hyun Joo; Lee, Young Han; Choi, Jin-Young; Park, Mi-Suk; Kim, Myeong-Jin; Kim, Ki Whang

2013-01-01

Objective To evaluate the feasibility of sinogram-affirmed iterative reconstruction (SAFIRE) and automated kV modulation (CARE kV) in reducing radiation dose without increasing image noise for abdominal CT examination. Materials and Methods This retrospective study included 77 patients who received CT imaging with an application of CARE kV with or without SAFIRE and who had comparable previous CT images obtained without CARE kV or SAFIRE, using the standard dose (i.e., reference mAs of 240) on an identical CT scanner and reconstructed with filtered back projection (FBP) within 1 year. Patients were divided into two groups: group A (33 patients, CT scanned with CARE kV); and group B (44 patients, scanned after reducing the reference mAs from 240 to 170 and applying both CARE kV and SAFIRE). CT number, image noise for four organs and radiation dose were compared among the two groups. Results Image noise increased after CARE kV application (p < 0.001) and significantly decreased as SAFIRE strength increased (p < 0.001). Image noise with reduced-mAs scan (170 mAs) in group B became similar to that of standard-dose FBP images after applying CARE kV and SAFIRE strengths of 3 or 4 when measured in the aorta, liver or muscle (p ≥ 0.108). Effective doses decreased by 19.4% and 41.3% for groups A and B, respectively (all, p < 0.001) after application of CARE kV with or without SAFIRE. Conclusion Combining CARE kV, reduction of mAs from 240 to 170 mAs and noise reduction by applying SAFIRE strength 3 or 4 reduced the radiation dose by 41.3% without increasing image noise compared with the standard-dose FBP images. PMID:24265563

Effects of Surgery and Proton Therapy on Cerebral White Matter of Craniopharyngioma Patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uh, Jinsoo, E-mail: jinsoo.uh@stjude.org; Merchant, Thomas E.; Li, Yimei

Purpose: The purpose of this study was to determine radiation dose effect on the structural integrity of cerebral white matter in craniopharyngioma patients receiving surgery and proton therapy. Methods and Materials: Fifty-one patients (2.1-19.3 years of age) with craniopharyngioma underwent surgery and proton therapy in a prospective therapeutic trial. Anatomical magnetic resonance images acquired after surgery but before proton therapy were inspected to identify white matter structures intersected by surgical corridors and catheter tracks. Longitudinal diffusion tensor imaging (DTI) was performed to measure microstructural integrity changes in cerebral white matter. Fractional anisotropy (FA) derived from DTI was statistically analyzed for 51more » atlas-based white matter structures of the brain to determine radiation dose effect. FA in surgery-affected regions in the corpus callosum was compared to that in its intact counterpart to determine whether surgical defects affect radiation dose effect. Results: Surgical defects were seen most frequently in the corpus callosum because of transcallosal resection of tumors and insertion of ventricular or cyst catheters. Longitudinal DTI data indicated reductions in FA 3 months after therapy, which was followed by a recovery in most white matter structures. A greater FA reduction was correlated with a higher radiation dose in 20 white matter structures, indicating a radiation dose effect. The average FA in the surgery-affected regions before proton therapy was smaller (P=.0001) than that in their non–surgery-affected counterparts with more intensified subsequent reduction of FA (P=.0083) after therapy, suggesting that surgery accentuated the radiation dose effect. Conclusions: DTI data suggest that mild radiation dose effects occur in patients with craniopharyngioma receiving surgery and proton therapy. Surgical defects present at the time of proton therapy appear to accentuate the radiation dose effect longitudinally. This study supports consideration of pre-existing surgical defects and their locations in proton therapy planning and studies of treatment effect.« less

Estimation of breast dose reduction potential for organ-based tube current modulated CT with wide dose reduction arc

NASA Astrophysics Data System (ADS)

Fu, Wanyi; Sturgeon, Gregory M.; Agasthya, Greeshma; Segars, W. Paul; Kapadia, Anuj J.; Samei, Ehsan

2017-03-01

This study aimed to estimate the organ dose reduction potential for organ-dose-based tube current modulated (ODM) thoracic CT with wide dose reduction arc. Twenty-one computational anthropomorphic phantoms (XCAT, age range: 27- 75 years, weight range: 52.0-105.8 kg) were used to create a virtual patient population with clinical anatomic variations. For each phantom, two breast tissue compositions were simulated: 50/50 and 20/80 (glandular-to-adipose ratio). A validated Monte Carlo program was used to estimate the organ dose for standard tube current modulation (TCM) (SmartmA, GE Healthcare) and ODM (GE Healthcare) for a commercial CT scanner (Revolution, GE Healthcare) with explicitly modeled tube current modulation profile, scanner geometry, bowtie filtration, and source spectrum. Organ dose was determined using a typical clinical thoracic CT protocol. Both organ dose and CTDIvol-to-organ dose conversion coefficients (h factors) were compared between TCM and ODM. ODM significantly reduced all radiosensitive organ doses (p<0.01). The breast dose was reduced by 30+/-2%. For h factors, organs in the anterior region (e.g. thyroid, stomach) exhibited substantial decreases, and the medial, distributed, and posterior region either saw an increase or no significant change. The organ-dose-based tube current modulation significantly reduced organ doses especially for radiosensitive superficial anterior organs such as the breasts.

Effect of Study Design on Sample Size in Studies Intended to Evaluate Bioequivalence of Inhaled Short‐Acting β‐Agonist Formulations

PubMed Central

Zeng, Yaohui; Singh, Sachinkumar; Wang, Kai

2017-01-01

Abstract Pharmacodynamic studies that use methacholine challenge to assess bioequivalence of generic and innovator albuterol formulations are generally designed per published Food and Drug Administration guidance, with 3 reference doses and 1 test dose (3‐by‐1 design). These studies are challenging and expensive to conduct, typically requiring large sample sizes. We proposed 14 modified study designs as alternatives to the Food and Drug Administration–recommended 3‐by‐1 design, hypothesizing that adding reference and/or test doses would reduce sample size and cost. We used Monte Carlo simulation to estimate sample size. Simulation inputs were selected based on published studies and our own experience with this type of trial. We also estimated effects of these modified study designs on study cost. Most of these altered designs reduced sample size and cost relative to the 3‐by‐1 design, some decreasing cost by more than 40%. The most effective single study dose to add was 180 μg of test formulation, which resulted in an estimated 30% relative cost reduction. Adding a single test dose of 90 μg was less effective, producing only a 13% cost reduction. Adding a lone reference dose of either 180, 270, or 360 μg yielded little benefit (less than 10% cost reduction), whereas adding 720 μg resulted in a 19% cost reduction. Of the 14 study design modifications we evaluated, the most effective was addition of both a 90‐μg test dose and a 720‐μg reference dose (42% cost reduction). Combining a 180‐μg test dose and a 720‐μg reference dose produced an estimated 36% cost reduction. PMID:29281130

Race differences: modeling the pharmacodynamics of rosuvastatin in Western and Asian hypercholesterolemia patients.

PubMed

Yang, Juan; Li, Lu-jin; Wang, Kun; He, Ying-chun; Sheng, Yu-cheng; Xu, Ling; Huang, Xiao-hui; Guo, Feng; Zheng, Qing-shan

2011-01-01

To evaluate race differences in the pharmacodynamics of rosuvastatin in Western and Asian hypercholesterolemia patients using a population pharmacodynamic (PPD) model generated and validated using published clinical efficacy trials. Published studies randomized trials with rosuvastatin treatment for at least 4 weeks in hypercholesterolemia patients were used for model building and validation. Population pharmacodynamic analyses were performed to describe the dose-response relationship with the mean values of LDL-C reduction (%) from dose-ranging trials using NONMEM software. Baseline LDL-C and race were analyzed as the potential covariates. Model robustness was evaluated using the bootstrap method and the data-splitting method, and Monte Carlo simulation was performed to assess the predictive performance of the PPD model with the mean effects from the one-dose trials. Of the 36 eligible trials, 14 dose-ranging trials were used in model development and 22 one-dose trials were used for model prediction. The dose-response of rosuvastatin was successfully described by a simple E(max) model with a fixed E(0), which provided a common E(max) and an approximate twofold difference in ED(50) for Westerners and Asians. The PPD model was demonstrated to be stable and predictive. The race differences in the pharmacodynamics of rosuvastatin are consistent with those observed in the pharmacokinetics of the drug, confirming that there is no significant difference in the exposure-response relationship for LDL-C reduction between Westerners and Asians. The study suggests that for a new compound with a mechanism of action similar to that of rosuvastatin, its efficacy in Western populations plus its pharmacokinetics in bridging studies in Asian populations may be used to support a registration of the new compound in Asian countries.

SU-E-T-495: Influence of Reduced Target-To-Nozzle Distance On Secondary Neutron Dose Equivalent in Proton and Carbon Ion Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Y; Shahnazi, K; Wang, W

Purpose: Ion beams have an unavoidable lateral spread due to nuclear interactions interacting with the air and monitoring systems. To minimize this spread, the distance between the nozzle and the patient should be kept as small as possible.The purpose of this work was to determine the impact of the target-to-nozzle distance reduction on the secondary neutron dose equivalent in proton and carbon ion radiotherapy. Methods: In this study, abdominal and head phantoms were scanned with our CT scanner. Cubical targets with side lengths of 3 cm to 10 cm and 1 cm to 5 cm were drawn in the abdominalmore » and head phantoms respectively. Two intensity-modulated plans were made for each phantom and ion. The first of these plans placed the target at the isocenter while the other shifted the phantom 30 cm towards the nozzle. The plans at both phantom locations were optimized to provide identical dose coverage to the PTVs.Secondary neutron dose equivalent at 50 cm lateral to the center of target. Results: The neutron dose equivalent was higher for the larger field size from 0.25µSv per Gy (RBE) to 72µSv per Gy (RBE). The neutron dose equivalent was smaller when the phantom was placed at the upstream target location versus at the isocenter location by 8.9% to 10.4% and 11.0% to 22.1% for proton plans of the abdominal and head phantoms respectively. Differences for carbon plans with different target-to-nozzle locations were less than 3% for both phantoms. Conclusion: A reduction of target-to-nozzle distance can lead to benefits for proton radiotherapy. In this study, a reduction of secondary neutron dose equivalent was found for proton plans with a smaller target-to-nozzle distance. A greater impact was found for a head phantom with a smaller field size; however, a reduction of the target-to-nozzle distance had little effect for carbon therapy.« less

Effect of pill burden on dosing preferences, willingness to pay, and likely adherence among patients with type 2 diabetes

PubMed Central

Hauber, A Brett; Han, Steven; Yang, Jui-Chen; Gantz, Ira; Tunceli, Kaan; Gonzalez, Juan Marcos; Brodovicz, Kimberly; Alexander, Charles M; Davies, Michael; Iglay, Kristy; Zhang, Qiaoyi; Radican, Larry

2013-01-01

Purpose To quantify willingness-to-pay (WTP) for reducing pill burden and dosing frequency among patients with type 2 diabetes mellitus (T2DM), and to examine the effect of dosing frequency and pill burden on likely medication adherence. Patients and methods Participants were US adults with T2DM on oral antihyperglycemic therapy. Each patient completed an online discrete-choice experiment (DCE) with eight choice questions, each including a pair of hypothetical medication profiles. Each profile was defined by reduction in average glucose (AG), daily dosing, chance of mild-to-moderate stomach problems, frequency of hypoglycemia, weight change, incremental risk of congestive heart failure (CHF), and cost. Patients were asked to rate their likely adherence to the profiles presented in each question. Choice questions were based on a predetermined experimental design. Choice data were analyzed using random-parameters logit. Likely treatment adherence was analyzed using a Heckman two-stage model. Results Of the 1,114 patients who completed the survey, 90 had lower dosing burden (<5 pills/day taken once/day or as needed) for all medications, and 1,024 had higher dosing burden (≥5 pills/day or more than once/day). Reduction in AG was valued most highly by patients. Hypoglycemia, chance of mild-to-moderate stomach problems, weight change, incremental risk of CHF, and daily dosing were less valued. Patients with higher current dosing burden had lower WTP for more convenient dosing schedules than patients with lower current dosing burden. Changes in dosing and cost impacted likely adherence. The magnitude of the impact of dosing on likely adherence was higher for patients with lower current dosing burden than for patients with higher current dosing burden. Conclusion Patients with T2DM were willing to pay for improvements in efficacy, side effects, and dosing. Patients’ WTP for more convenient dosing depended on current dosing burden, as did the effect of these attributes on likely adherence. PMID:24086104

SU-F-T-441: Dose Calculation Accuracy in CT Images Reconstructed with Artifact Reduction Algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ng, C; Chan, S; Lee, F

Purpose: Accuracy of radiotherapy dose calculation in patients with surgical implants is complicated by two factors. First is the accuracy of CT number, second is the dose calculation accuracy. We compared measured dose with dose calculated on CT images reconstructed with FBP and an artifact reduction algorithm (OMAR, Philips) for a phantom with high density inserts. Dose calculation were done with Varian AAA and AcurosXB. Methods: A phantom was constructed with solid water in which 2 titanium or stainless steel rods could be inserted. The phantom was scanned with the Philips Brillance Big Bore CT. Image reconstruction was done withmore » FBP and OMAR. Two 6 MV single field photon plans were constructed for each phantom. Radiochromic films were placed at different locations to measure the dose deposited. One plan has normal incidence on the titanium/steel rods. In the second plan, the beam is at almost glancing incidence on the metal rods. Measurements were then compared with dose calculated with AAA and AcurosXB. Results: The use of OMAR images slightly improved the dose calculation accuracy. The agreement between measured and calculated dose was best with AXB and image reconstructed with OMAR. Dose calculated on titanium phantom has better agreement with measurement. Large discrepancies were seen at points directly above and below the high density inserts. Both AAA and AXB underestimated the dose directly above the metal surface, while overestimated the dose below the metal surface. Doses measured downstream of metal were all within 3% of calculated values. Conclusion: When doing treatment planning for patients with metal implants, care must be taken to acquire correct CT images to improve dose calculation accuracy. Moreover, great discrepancies in measured and calculated dose were observed at metal/tissue interface. Care must be taken in estimating the dose in critical structures that come into contact with metals.« less

Inactivation of antibiotic resistance genes in municipal wastewater by chlorination, ultraviolet, and ozonation disinfection.

PubMed

Zhuang, Yao; Ren, Hongqiang; Geng, Jinju; Zhang, Yingying; Zhang, Yan; Ding, Lili; Xu, Ke

2015-05-01

This study investigated the inactivation of two antibiotic resistance genes (ARGs)-sul1 and tetG, and the integrase gene of class 1 integrons-intI1 by chlorination, ultraviolet (UV), and ozonation disinfection. Inactivation of sul1, tetG, and intI1 underwent increased doses of three disinfectors, and chlorine disinfection achieved more inactivation of ARGs and intI1 genes (chlorine dose of 160 mg/L with contact time of 120 min for 2.98-3.24 log reductions of ARGs) than UV irradiation (UV dose of 12,477 mJ/cm(2) for 2.48-2.74 log reductions of ARGs) and ozonation disinfection (ozonation dose of 177.6 mg/L for 1.68-2.55 log reductions of ARGs). The 16S rDNA was more efficiently removed than ARGs by ozone disinfection. The relative abundance of selected genes (normalized to 16S rDNA) increased during ozonation and with low doses of UV and chlorine disinfection. Inactivation of sul1 and tetG showed strong positive correlations with the inactivation of intI1 genes (for sul1, R (2)  = 0.929 with p < 0.01; for tetG, R (2)  = 0.885 with p < 0.01). Compared to other technologies (ultraviolet disinfection, ozonation disinfection, Fenton oxidation, and coagulation), chlorination is an alternative method to remove ARGs from wastewater effluents. At a chlorine dose of 40 mg/L with 60 min contact time, the selected genes inactivation efficiency could reach 1.65-2.28 log, and the cost was estimated at 0.041 yuan/m(3).

Earlier therapeutic effects associated with high dose (2.0 mg) Ranibizumab for treatment of vascularized pigment epithelial detachments in age-related macular degeneration

PubMed Central

Chan, C K; Abraham, P; Sarraf, D; Nuthi, A S D; Lin, S G; McCannel, C A

2015-01-01

Summary statement Intravitreal high dose (2 mg) ranibizumab may lead to quicker resolution of choroidal neovascularization (CNV) and associated retinal pigment epithelial detachment in eyes with exudative age-related macular degeneration, although it may possibly correlate with RPE tears in certain cases. Purpose This prospective study compared the outcomes of 0.5 vs 2.0 mg intravitreal ranibizumab injections (RI) for treating vascularized pigment epithelial detachment (vPED) due to age-related macular degeneration. Methods Patients with vPED were randomized to receive 2.0 vs 0.5 mg RI monthly for 12 months or for 4 months and then repeated on a pro-re nata basis. Optical coherence tomography, fundus photography, and fluorescein and indocyanine-green angiography were obtained at baseline and subsequent specific intervals. Outcome measures were best-corrected standardized visual acuities, central 1-mm thickness, surface area (SA), greatest linear diameter (GLD), heights (PED and CNV), and amount of subretinal fluid (SRF) and cystoid macular edema (CME). Results Both groups yielded reductions of the central 1-mm thickness, PED and CNV SA and PED height and GLD, SRF, and CME. Vision improvement and reduction in SRF and PED height occurred earlier for eyes receiving the 2.0 mg dose. Cataract progression was similar but RPE tears developed more often with the 2.0 mg dose. Conclusions There were similar visual and anatomical outcomes at the end of the study; however, the higher dose yielded more rapid reductions and more complete resolution of the PED, although there was possible increased tendency for an RPE tear with the higher dose. PMID:25277305

The use of adaptive statistical iterative reconstruction (ASiR) technique in evaluation of patients with cervical spine trauma: impact on radiation dose reduction and image quality

PubMed Central

Sheikh, Adnan

2016-01-01

Objective: The aim of this study was to evaluate the impact of adaptive statistical iterative reconstruction (ASiR) technique on the image quality and radiation dose reduction. The comparison was made with the traditional filtered back projection (FBP) technique. Methods: We retrospectively reviewed 78 patients, who underwent cervical spine CT for blunt cervical trauma between 1 June 2010 and 30 November 2010. 48 patients were imaged using traditional FBP technique and the remaining 30 patients were imaged using the ASiR technique. The patient demographics, radiation dose, objective image signal and noise were recorded; while subjective noise, sharpness, diagnostic acceptability and artefacts were graded by two radiologists blinded to the techniques. Results: We found that the ASiR technique was able to reduce the volume CT dose index, dose–length product and effective dose by 36%, 36.5% and 36.5%, respectively, compared with the FBP technique. There was no significant difference in the image noise (p = 0.39), signal (p = 0.82) and signal-to-noise ratio (p = 0.56) between the groups. The subjective image quality was minimally better in the ASiR group but not statistically significant. There was excellent interobserver agreement on the subjective image quality and diagnostic acceptability for both groups. Conclusion: The use of ASiR technique allowed approximately 36% radiation dose reduction in the evaluation of cervical spine without degrading the image quality. Advances in knowledge: The present study highlights that the ASiR technique is extremely helpful in reducing the patient radiation exposure while maintaining the image quality. It is highly recommended to utilize this novel technique in CT imaging of different body regions. PMID:26882825

Regulation of steroid hormones and energy status with cysteamine and its effect on spermatogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yandi

Although it is well known that cysteamine is a potent chemical for treating many diseases including cystinosis and it has many adverse effects, the effect of cysteamine on spermatogenesis is as yet unknown. Therefore the objective of this investigation was to explore the effects of cysteamine on spermatogenesis and the underlying mechanisms. Sheep were treated with vehicle control, 10 mg/kg or 20 mg/kg cysteamine for six months. After that, the semen samples were collected to determine the spermatozoa motility by computer-assisted sperm assay method. Blood samples were collected to detect the levels of hormones and the activity of enzymes. Spermatozoamore » and testis samples were collected to study the mechanism of cysteamine's actions. It was found that the effects of cysteamine on spermatogenesis were dose dependent. A low dose (10 mg/kg) cysteamine treatment increased ovine spermatozoa motility; however, a higher dose (20 mg/kg) decreased both spermatozoa concentration and motility. This decrease might be due to a reduction in steroid hormone production by the testis, a reduction in energy in the testis and spermatozoa, a disruption in the blood-testis barrier, or a breakdown in the vital signaling pathways involved in spermatogenesis. The inhibitory effects of cysteamine on sheep spermatogenesis may be used to model its effects on young male patients with cystinosis or other diseases that are treated with this drug. Further studies on spermatogenesis that focus on patients treated with cysteamine during the peripubertal stage are warranted. - Highlights: • Dose dependent effects of cysteamine on spermatogenesis • A low dose (10 mg/kg) increased spermatozoa motility. • A higher dose (20 mg/kg) decreased both concentration and motility of spermatozoa. • Disruption in the blood-testis barrier caused reduction in concentration and motility.« less

Impact of the NTCP modeling on medical decision to select eligible patient for proton therapy: the usefulness of EUD as an indicator to rank modern photon vs proton treatment plans.

PubMed

Chaikh, Abdulhamid; Calugaru, Valentin; Bondiau, Pierre-Yves; Thariat, Juliette; Balosso, Jacques

2018-06-07

The aim of this study is to evaluate the impact of normal tissue complication probability (NTCP)-based radiobiological models on the estimated risk for late radiation lung damages. The second goal is to propose a medical decision-making approach to select the eligible patient for particle therapy. 14 pediatric patients undergoing cranio-spinal irradiation were evaluated. For each patient, two treatment plans were generated using photon and proton therapy with the same dose prescriptions. Late radiation damage to lung was estimated using three NTCP concepts: the Lyman-Kutcher-Burman, the equivalent uniform dose (EUD) and the mean lung dose according to the quantitative analysis of normal tissue effects in the clinic QUANTEC review. Wilcoxon paired test was used to calculate p-value. Proton therapy achieved lower lung EUD (Gy). The average NTCP values were significantly lower with proton plans, p < 0.05, using the three NTCP concepts. However, applying the same TD 50/5 using radiobiological models to compare NTCP from proton and photon therapy, the ΔNTCP was not a convincing method to measure the potential benefit of proton therapy. Late radiation pneumonitis estimated from the mean lung dose model correlated with QUANTEC data better. treatment effectiveness assessed on NTCP reduction depends on radiobiological predictions and parameters used as inputs for in silico evaluation. Since estimates of absolute NTCP values from LKB and GN models are imprecise due to EUD ≪ TD 50/5 , a reduction of the EUD value with proton plans would better predict a reduction of dose/toxicity. The EUD concept appears as a robust radiobiological surrogate of the dose distribution to select the optimal patient's plan.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paudel, M; currently at University of Toronto, Sunnybrook Health Sciences Center, Toronto, ON; MacKenzie, M

Purpose: To evaluate the metal artifacts in diagnostic kVCT images of patients that are corrected using a normalized metal artifact reduction method with MVCT prior images, MVCT-NMAR. Methods: An MVCTNMAR algorithm was developed and applied to five patients: three with bilateral hip prostheses, one with unilateral hip prosthesis and one with dental fillings. The corrected images were evaluated for visualization of tissue structures and their interfaces, and for radiotherapy dose calculations. They were also compared against the corresponding images corrected by a commercial metal artifact reduction technique, O-MAR, on a Phillips™ CT scanner. Results: The use of MVCT images formore » correcting kVCT images in the MVCT-NMAR technique greatly reduces metal artifacts, avoids secondary artifacts, and makes patient images more useful for correct dose calculation in radiotherapy. These improvements are significant over the commercial correction method, provided the MVCT and kVCT images are correctly registered. The remaining and the secondary artifacts (soft tissue blurring, eroded bones, false bones or air pockets, CT number cupping within the metal) present in O-MAR corrected images are removed in the MVCT-NMAR corrected images. Large dose reduction is possible outside the planning target volume (e.g., 59.2 Gy in comparison to 52.5 Gy in pubic bone) when these MVCT-NMAR corrected images are used in TomoTherapy™ treatment plans, as the corrected images no longer require directional blocks for prostate plans in order to avoid the image artifact regions. Conclusion: The use of MVCT-NMAR corrected images in radiotherapy treatment planning could improve the treatment plan quality for cancer patients with metallic implants. Moti Raj Paudel is supported by the Vanier Canada Graduate Scholarship, the Endowed Graduate Scholarship in Oncology and the Dissertation Fellowship at the University of Alberta. The authors acknowledge the CIHR operating grant number MOP 53254.« less

MO-PIS-Exhibit Hall-01: Imaging: CT Dose Optimization Technologies I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denison, K; Smith, S

Partners in Solutions is an exciting new program in which AAPM partners with our vendors to present practical “hands-on” information about the equipment and software systems that we use in our clinics. The imaging topic this year is CT scanner dose optimization capabilities. Note that the sessions are being held in a special purpose room built on the Exhibit Hall Floor, to encourage further interaction with the vendors. Dose Optimization Capabilities of GE Computed Tomography Scanners Presentation Time: 11:15 – 11:45 AM GE Healthcare is dedicated to the delivery of high quality clinical images through the development of technologies, whichmore » optimize the application of ionizing radiation. In computed tomography, dose management solutions fall into four categories: employs projection data and statistical modeling to decrease noise in the reconstructed image - creating an opportunity for mA reduction in the acquisition of diagnostic images. Veo represents true Model Based Iterative Reconstruction (MBiR). Using high-level algorithms in tandem with advanced computing power, Veo enables lower pixel noise standard deviation and improved spatial resolution within a single image. Advanced Adaptive Image Filters allow for maintenance of spatial resolution while reducing image noise. Examples of adaptive image space filters include Neuro 3-D filters and Cardiac Noise Reduction Filters. AutomA adjusts mA along the z-axis and is the CT equivalent of auto exposure control in conventional x-ray systems. Dynamic Z-axis Tracking offers an additional opportunity for dose reduction in helical acquisitions while SmartTrack Z-axis Tracking serves to ensure beam, collimator and detector alignment during tube rotation. SmartmA provides angular mA modulation. ECG Helical Modulation reduces mA during the systolic phase of the heart cycle. SmartBeam optimization uses bowtie beam-shaping hardware and software to filter off-axis x-rays - minimizing dose and reducing x-ray scatter. The DICOM Radiation Dose Structured Report (RDSR) generates a dose report at the conclusion of every examination. Dose Check preemptively notifies CT operators when scan parameters exceed user-defined dose thresholds. DoseWatch is an information technology application providing vendor-agnostic dose tracking and analysis for CT (and all other diagnostic x-ray modalities) SnapShot Pulse improves coronary CTA dose management. VolumeShuttle uses two acquisitions to increase coverage, decrease dose, and conserve on contrast administration. Color-Coding for Kids applies the Broselow-Luten Pediatric System to facilitate pediatric emergency care and reduce medical errors. FeatherLight achieves dose optimization through pediatric procedure-based protocols. Adventure Series scanners provide a child-friendly imaging environment promoting patient cooperation with resultant reduction in retakes and patient motion. Philips CT Dose Optimization Tools and Advanced Reconstruction Presentation Time: 11:45 ‘ 12:15 PM The first part of the talk will cover “Dose Reduction and Dose Optimization Technologies” present in Philips CT Scanners. The main Technologies to be presented include: DoseRight and tube current modulation (DoseRight, Z-DOM, 3D-DOM, DoseRight Cardiac) Special acquisition modes Beam filtration and beam shapers Eclipse collimator and ClearRay collimator NanoPanel detector DoseRight will cover automatic tube current selection that automatically adjusts the dose for the individual patient. The presentation will explore the modulation techniques currently employed in Philips CT scanners and will include the algorithmic concepts as well as illustrative examples. Modulation and current selection technologies to be covered include the Automatic Current Selection component of DoseRight, ZDOM longitudinal dose modulation, 3D-DOM (combination of longitudinal and rotational dose modulation), Cardiac Dose right (an ECG based dose modulation scheme), and the DoseRight Index (DRI) IQ index. The special acquisition modes covers acquisition techniques such as prospective gating that is designed to reduce exposure to the patient through the Cardiac Step and Shoot scan mode. This mode can substitute the much higher dose retrospective scan modes for certain types of cardiac imaging. The beam filtration and beam shaper portion will discuss the variety of filtration and beam shaping configurations available on Philips scanners. This topic includes the x-ray beam characteristics, tube filtration as well as dose compensator characteristics. The Eclipse collimator, ClearRay collimator and the NanoPanel detector portion will discuss additional technologies specific to wide coverage CT that address some of the unique challenges encountered and techniques employed to optimize image quality and optimize dose utilization. The Eclipse collimator reduces extraneous exposure by actively blocking the radiation tails at either end of helical scans that do not contribute to the image generation. The ClearRay collimator and the NanoPanel detector optimize the quality of the signal that reaches the detectors by addressing the increased scattered radiation present in wide coverage and the NanoPanel detector adds superior electronic noise characteristics valuable when imaging at a low dose level. The second part of the talk will present “Advanced Reconstruction Technologies” currently available on Philips CT Scanners. The talk will cover filtered back projection (FBP), iDose4 and Iterative Model Reconstruction (IMR). Each reconstruction method will include a discussion of the algorithm as well as similarities and differences between the algorithms. Examples illustrating the merits of each algorithm will be presented, and techniques and metrics to characterize the performance of each type of algorithm will be presented. The Filtered Back projection portion will discuss and provide a brief summary of relevant standard image reconstruction techniques in common use, and discuss the common tradeoffs when using the FBP algorithm. The iDose4 portion will present the algorithms used for iDose4 as well the different levels. The meaning of different levels of iDose4 available will be presented and quantified. Guidelines for selection iDose4 parameters based on the imaging need will be explained. The different image quality goals available with iDose4 and specifically how iDose4 enables noise reduction, spatial resolution improvement or both will be explained. The approaches to leveraging the benefits of iDose4 such as improved spatial resolution, decreased noise, and artifact prevention will be described and quantified; and measurements and metrics behind the improvements will be presented. The image quality benefits in specific imaging situations as well as how to best combine the technology with other dose reduction strategies to ensure the best image quality at a given dose level will be presented. Insight into the IMR algorithm as well as contrast to the iDose4 techniques and performance characteristics will be discussed. Metrics and techniques for characterizing this class of algorithm and IQ performance will be presented. The image quality benefits and the dose reduction capabilities of IMR will be explored. Illustrative examples of the noise reduction, spatial resolution improvement, and low contrast detectability improvements of the reconstruction method will be presented: clinical cases and phantom measurements demonstrating the benefits of IMR in the areas of low dose imaging, spatial resolution and low contrast resolution are discussed and the technical details behind the measurements will be presented compared to both iDose4 and traditional filtered back projection (FBP)« less

Effects of a radiation dose reduction strategy for computed tomography in severely injured trauma patients in the emergency department: an observational study.

PubMed

Kim, Soo Hyun; Jung, Seung Eun; Oh, Sang Hoon; Park, Kyu Nam; Youn, Chun Song

2011-11-03

Severely injured trauma patients are exposed to clinically significant radiation doses from computed tomography (CT) imaging in the emergency department. Moreover, this radiation exposure is associated with an increased risk of cancer. The purpose of this study was to determine some effects of a radiation dose reduction strategy for CT in severely injured trauma patients in the emergency department. We implemented the radiation dose reduction strategy in May 2009. A prospective observational study design was used to collect data from patients who met the inclusion criteria during this one year study (intervention group) from May 2009 to April 2010. The prospective data were compared with data collected retrospectively for one year prior to the implementation of the radiation dose reduction strategy (control group). By comparison of the cumulative effective dose and the number of CT examinations in the two groups, we evaluated effects of a radiation dose reduction strategy. All the patients met the institutional adult trauma team activation criteria. The radiation doses calculated by the CT scanner were converted to effective doses by multiplication by a conversion coefficient. A total of 118 patients were included in this study. Among them, 33 were admitted before May 2009 (control group), and 85 were admitted after May 2009 (intervention group). There were no significant differences between the two groups regarding baseline characteristics, such as injury severity and mortality. Additionally, there was no difference between the two groups in the mean number of total CT examinations per patient (4.8 vs. 4.5, respectively; p = 0.227). However, the mean effective dose of the total CT examinations per patient significantly decreased from 78.71 mSv to 29.50 mSv (p < 0.001). The radiation dose reduction strategy for CT in severely injured trauma patients effectively decreased the cumulative effective dose of the total CT examinations in the emergency department. But not effectively decreased the number of CT examinations.

Measuring radiation dose in computed tomography using elliptic phantom and free-in-air, and evaluating iterative metal artifact reduction algorithm

NASA Astrophysics Data System (ADS)

Morgan, Ashraf

The need for an accurate and reliable way for measuring patient dose in multi-row detector computed tomography (MDCT) has increased significantly. This research was focusing on the possibility of measuring CT dose in air to estimate Computed Tomography Dose Index (CTDI) for routine quality control purposes. New elliptic CTDI phantom that better represent human geometry was manufactured for investigating the effect of the subject shape on measured CTDI. Monte Carlo simulation was utilized in order to determine the dose distribution in comparison to the traditional cylindrical CTDI phantom. This research also investigated the effect of Siemens health care newly developed iMAR (iterative metal artifact reduction) algorithm, arthroplasty phantom was designed and manufactured that purpose. The design of new phantoms was part of the research as they mimic the human geometry more than the existing CTDI phantom. The standard CTDI phantom is a right cylinder that does not adequately represent the geometry of the majority of the patient population. Any dose reduction algorithm that is used during patient scan will not be utilized when scanning the CTDI phantom, so a better-designed phantom will allow the use of dose reduction algorithms when measuring dose, which leads to better dose estimation and/or better understanding of dose delivery. Doses from a standard CTDI phantom and the newly-designed phantoms were compared to doses measured in air. Iterative reconstruction is a promising technique in MDCT dose reduction and artifacts correction. Iterative reconstruction algorithms have been developed to address specific imaging tasks as is the case with Iterative Metal Artifact Reduction or iMAR which was developed by Siemens and is to be in use with the companys future computed tomography platform. The goal of iMAR is to reduce metal artifact when imaging patients with metal implants and recover CT number of tissues adjacent to the implant. This research evaluated iMAR capability of recovering CT numbers and reducing noise. Also, the use of iMAR should allow using lower tube voltage instead of 140 KVp which is used frequently to image patients with shoulder implants. The evaluations of image quality and dose reduction were carried out using an arthroplasty phantom.

Practical Advice on Calculating Confidence Intervals for Radioprotection Effects and Reducing Animal Numbers in Radiation Countermeasure Experiments

PubMed Central

Landes, Reid D.; Lensing, Shelly Y.; Kodell, Ralph L.; Hauer-Jensen, Martin

2014-01-01

The dose of a substance that causes death in P% of a population is called an LDP, where LD stands for lethal dose. In radiation research, a common LDP of interest is the radiation dose that kills 50% of the population by a specified time, i.e., lethal dose 50 or LD50. When comparing LD50 between two populations, relative potency is the parameter of interest. In radiation research, this is commonly known as the dose reduction factor (DRF). Unfortunately, statistical inference on dose reduction factor is seldom reported. We illustrate how to calculate confidence intervals for dose reduction factor, which may then be used for statistical inference. Further, most dose reduction factor experiments use hundreds, rather than tens of animals. Through better dosing strategies and the use of a recently available sample size formula, we also show how animal numbers may be reduced while maintaining high statistical power. The illustrations center on realistic examples comparing LD50 values between a radiation countermeasure group and a radiation-only control. We also provide easy-to-use spreadsheets for sample size calculations and confidence interval calculations, as well as SAS® and R code for the latter. PMID:24164553

Pharmacokinetic and pharmacodynamic drug interactions of carbamazepine and glibenclamide in healthy albino Wistar rats

PubMed Central

Prashanth, S.; Kumar, A. Anil; Madhu, B.; Rama, N.; Sagar, J. Vidya

2011-01-01

Aims: To find out the pharmacokinetic and pharmacodynamic drug interaction of carbamazepine, a protype drug used to treat painful diabetic neuropathy with glibenclamide in healthy albino Wistar rats following single and multiple dosage treatment. Materials and Methods: Therapeutic doses (TD) of glibenclamide and TD of carbamazepine were administered to the animals. The blood glucose levels were estimated by GOD/POD method and the plasma glibenclamide concentrations were estimated by a sensitive RP HPLC method to calculate pharmacokinetic parameters. Results: In single dose study the percentage reduction of blood glucose levels and glibenclamide concentrations of rats treated with both carbamazepine and glibenclamide were significantly increased when compared with glibenclamide alone treated rats and the mechanism behind this interaction may be due to inhibition of P-glycoprotein mediated transport of glibenclamide by carbamazepine, but in multiple dose study the percentage reduction of blood glucose levels and glibenclamide concentrations were reduced and it may be due to inhibition of P-glycoprotein mediated transport and induction of CYP2C9, the enzyme through which glibenclamide is metabolised. Conclusions: In the present study there is a pharmacokinetic and pharmacodynamic interaction between carbamazepine and glibenclamide was observed. The possible interaction involves both P-gp and CYP enzymes. To investigate this type of interactions pre-clinically are helpful to avoid drug-drug interactions in clinical situation. PMID:21701639

The value of thyroid shielding in intraoral radiography

PubMed Central

Hazenoot, Bart; Sanderink, Gerard C H; Berkhout, W Erwin R

2016-01-01

Objectives: To evaluate the utility of the application of a thyroid shield in intraoral radiography when using rectangular collimation. Methods: Experimental data were obtained by measuring the absorbed dose at the position of the thyroid gland in a RANDO® (The Phantom Laboratory, Salem, NY) male phantom with a dosemeter. Four protocols were tested: round collimation and rectangular collimation, both with and without thyroid shield. Five exposure positions were deployed: upper incisor (Isup), upper canine (Csup), upper premolar (Psup), upper molar (Msup) and posterior bitewing (BW). Exposures were made with 70 kV and 7 mA and were repeated 10 times. The exposure times were as recommended for the exposure positions for the respective collimator type by the manufacturer for digital imaging. The data were statistically analyzed with a three-way ANOVA test. Significance was set at p < 0.01. Results: The ANOVA test revealed that the differences between mean doses of all protocols and geometries were statistically significant, p < 0.001. For the Isup, thyroid dose levels were comparable with both collimators at a level indicating primary beam exposure. Thyroid shield reduced this dose with circa 75%. For the Csup position, round collimation also revealed primary beam exposure, and thyroid shield yield was 70%. In Csup with rectangular collimation, the thyroid dose was reduced with a factor 4 compared with round collimation and thyroid shield yielded an additional 42% dose reduction. The thyroid dose levels for the Csup, Psup, Msup and BW exposures were lower with rectangular collimation without thyroid shield than with round collimation with thyroid shield. With rectangular collimation, the thyroid shield in Psup, Msup and BW reduced the dose 10% or less, where dose levels were already low, implying no clinical significance. Conclusions: For the exposures in the upper anterior region, thyroid shield results in an important dose reduction for the thyroid. For the other exposures, thyroid shield augments little to the reduction achieved by rectangular collimation. The use of thyroid shield is to be advised, when performing upper anterior radiography. PMID:27008105

SU-G-TeP1-11: Predictors of Cardiac and Lung Dose Sparing in DIBH for Left Breast Treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, N; Kalet, A; Fang, L

Purpose: This retrospective study of left sided whole breast radiation therapy (RT) patients investigates possible predictive parameters correlating to cardiac and left lung dose sparing by deep inspiration breath-hold (DIBH) technique compared to free-breathing (FB). Methods: Thirty-one patients having both DIBH and FB CT scans were included in the study. All patients were planned with a standard step-and-shoot tangential technique using MV photons, with prescription of 50Gy or 50.4Gy. The displacement of the breath hold sternal mark during DIBH, the cardiac contact distances of the axial (CCDax) and parasagittal (CCDps) planes, and lateral-heart-to-chest (LHC) distance on FB CT scans weremore » measured. Lung volumes, mean dose and dose-volume histograms (V5, V10 and V20) were analyzed and compared for heart and left lung for both FB and DIBH techniques. Correlation analysis was performed to identify the predictors for heart and left lung dose sparing. Two-tailed Student’s t-test and linear regression were used for data analysis with significance level of P≤0.05. Results: All dosimetric metrics for the heart and left lung were significantly reduced (P<0.01) with DIBH. Breath hold sternal mark displacement ranged from 0.4–1.8 cm and correlated with mean (P=0.05) and V5 (P=0.02) of heart dose reduction by DIBH. FB lung volume showed correlation with mean lung dose reduction by DIBH (P<0.01). The FB-CCDps and FB-LHC distance had strong positive and negative correlation with FB mean heart dose (P<0.01) and mean heart dose reduction by DIBH (P<0.01), respectively. FB-CCDax showed no correlation with dosimetric changes. Conclusion: DIBH technique has been shown to reduce dose to the heart and left lung. In this patient cohort, FB-CCDps, FB-LHC distance, and FB lung volume served as significant predictors for heart and left lung. These parameters can be further investigated to be used as a tool to better select patients who will benefit from DIBH.« less

SU-F-P-45: Clinical Experience with Radiation Dose Reduction of CT Examinations Using Iterative Reconstruction Algorithms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weir, V; Zhang, J

2016-06-15

Purpose: Iterative reconstruction (IR) algorithms have been adopted by medical centers in the past several years. IR has a potential to substantially reduce patient dose while maintaining or improving image quality. This study characterizes dose reductions in clinical settings for CT examinations using IR. Methods: We retrospectively analyzed dose information from patients who underwent abdomen/pelvis CT examinations with and without contrast media in multiple locations of our Healthcare system. A total of 743 patients scanned with ASIR on 64 slice GE lightspeed VCTs at three sites, and 30 patients scanned with SAFIRE on a Siemens 128 slice Definition Flash inmore » one site was retrieved. For comparison, patient data (n=291) from a GE scanner and patient data (n=61) from two Siemens scanners where filtered back-projection (FBP) was used was collected retrospectively. 30% and 10% ASIR, and SAFIRE Level 2 was used. CTDIvol, Dose-length-product (DLP), weight and height from all patients was recorded. Body mass index (BMI) was calculated accordingly. To convert CTDIvol to SSDE, AP and lateral dimensions at the mid-liver level was measured for each patient. Results: Compared with FBP, 30% ASIR reduces dose by 44.1% (SSDE: 12.19mGy vs. 21.83mGy), while 10% ASIR reduced dose by 20.6% (SSDE 17.32mGy vs. 21.83). Use of SAFIRE reduced dose by 61.4% (SSDE: 8.77mGy vs. 22.7mGy). The geometric mean for patients scanned with ASIR was larger than for patients scanned with FBP (geometric mean is 297.48 mmm vs. 284.76 mm). The same trend was observed for the Siemens scanner where SAFIRE was used (geometric mean: 316 mm with SAFIRE vs. 239 mm with FBP). Patient size differences suggest that further dose reduction is possible. Conclusion: Our data confirmed that in clinical practice IR can significantly reduce dose to patients who undergo CT examinations, while meeting diagnostic requirements for image quality.« less

Esophageal Cancer Dose Escalation using a Simultaneous Integrated Boost Technique

PubMed Central

Welsh, James; Palmer, Matthew B.; Ajani, Jaffer A.; Liao, Zhongxing; Swisher, Steven G.; Hofstetter, Wayne L.; Allen, Pamela K.; Settle, Steven H.; Gomez, Daniel; Likhacheva, Anna; Cox, James D.; Komaki, Ritsuko

2014-01-01

Purpose We previously showed that 75% of radiation therapy (RT) failures in patients with unresectable esophageal cancer are in the gross tumor volume (GTV). We performed a planning study to evaluate if a simultaneous integrated boost (SIB) technique could selectively deliver a boost dose of radiation to the GTV in patients with esophageal cancer. Methods and Materials Treatment plans were generated using four different approaches (two-dimensional conformal RT [2D-CRT] to 50.4 Gy or 64.8 Gy, intensity-modulated RT [IMRT] to 50.4 Gy, and SIB-IMRT to 64.8 Gy) and optimized for 10 patients with distal esophageal cancer. All plans were constructed to deliver the target dose in 28 fractions using heterogeneity corrections. Isodose distributions were evaluated for target coverage and normal tissue exposure. Results The 50.4-Gy IMRT plan was associated with significant reductions in mean cardiac, pulmonary, and hepatic doses relative to the 50.4-Gy 2D-CRT plan. The 64.8-Gy SIB-IMRT plan produced a 28% increase in GTV dose and the same normal tissue doses as the 50.4-Gy IMRT plan; compared with the 50.4-Gy 2D-CRT plan, the 64.8-Gy SIB-IMRT produced significant dose reductions to all critical structures (heart, lung, liver, and spinal cord). Conclusions The use of SIB-IMRT allowed us to selectively increase the dose to the GTV, the area at highest risk of failure, while simultaneously reducing the dose to the normal heart, lung, and liver. Clinical implications warrant systematic evaluation. PMID:21123005

No compelling evidence that sibutramine prolongs life in rodents despite providing a dose-dependent reduction in body weight

PubMed Central

Smith, Daniel L.; Robertson, Henry; Desmond, Renee; Nagy, Tim R.; Allison, David B.

2010-01-01

Objective The health and longevity effects of body weight reduction resulting from exercise and caloric restriction in rodents are well known, but less is known about whether similar effects occur with weight reduction from the use of a pharmaceutical agent such as sibutramine, a serotonin-norepinephrine reuptake inhibitor. Results & Conclusion Using data from a two-year toxicology study of sibutramine in CD rats and CD-1 mice, despite a dose-dependent reduction in food intake and body weight in rats compared to controls, and a body weight reduction in mice at the highest dose, there was no compelling evidence for reductions in mortality rate. PMID:21079617

Human recombinant lactoferrin acts synergistically with antimicrobials commonly used in neonatal practice against coagulase-negative staphylococci and Candida albicans causing neonatal sepsis.

PubMed

Venkatesh, Mohan Pammi; Rong, Liang

2008-09-01

Neonatal sepsis causes significant mortality and morbidity. Coagulase-negative staphylococci (CoNS) and Candida frequently cause neonatal sepsis at >72 h of age. Lactoferrin, which is present in human milk, is a component of innate immunity and has broad-spectrum antimicrobial activity. The synergistic effects of lactoferrin with antibiotics against neonatal isolates have not been systematically evaluated. Here, eight clinical strains (seven neonatal) of CoNS and three strains (two neonatal) of Candida albicans were studied. MIC50 and MIC90 values of human recombinant lactoferrin (talactoferrin; TLF), vancomycin (VAN) and nafcillin (NAF) against CoNS, and of TLF, amphotericin B (AMB) and fluconazole (FLC) against C. albicans, were evaluated according to established guidelines. Antimicrobial combinations of TLF with NAF or VAN against CoNS, and TLF with AMB or FLC against C. albicans, were evaluated by a checkerboard method with serial twofold dilutions. Synergy was evaluated by the median effects principle, and combination indices and dose reduction indices were reported at 50, 75 and 90% inhibitory effect at several drug-dose ratios. It was found that TLF acted synergistically with NAF and VAN against CoNS, and with AMB and FLC against C. albicans, at multiple dose effects and drug-dose ratios with few exceptions. In synergistic combinations, drug reduction indices indicated a significant reduction in doses of antibiotics, which may be clinically relevant. Thus TLF acts synergistically with anti-staphylococcal and anti-Candida agents commonly used in neonatal practice and is a promising agent that needs to be evaluated in clinical studies.

Rectal artemisinins for malaria: a review of efficacy and safety from individual patient data in clinical studies

PubMed Central

Gomes, Melba; Ribeiro, Isabela; Warsame, Marian; Karunajeewa, Harin; Petzold, Max

2008-01-01

Background Rectal administration of artemisinin derivatives has potential for early treatment for severe malaria in remote settings where injectable antimalarial therapy may not be feasible. Preparations available include artesunate, artemisinin, artemether and dihydroartemisinin. However each may have different pharmacokinetic properties and more information is needed to determine optimal dose and comparative efficacy with each another and with conventional parenteral treatments for severe malaria. Methods Individual patient data from 1167 patients in 15 clinical trials of rectal artemisinin derivative therapy (artesunate, artemisinin and artemether) were pooled in order to compare the rapidity of clearance of Plasmodium falciparum parasitaemia and the incidence of reported adverse events with each treatment. Data from patients who received comparator treatment (parenteral artemisinin derivative or quinine) were also included. Primary endpoints included percentage reductions in parasitaemia at 12 and 24 hours. A parasite reduction of >90% at 24 hours was defined as parasitological success. Results Artemisinin and artesunate treatment cleared parasites more rapidly than parenteral quinine during the first 24 hours of treatment. A single higher dose of rectal artesunate treatment was five times more likely to achieve >90% parasite reductions at 24 hours than were multiple lower doses of rectal artesunate, or a single lower dose administration of rectal artemether. Conclusion Artemisinin and artesunate suppositories rapidly eliminate parasites and appear to be safe. There are less data on artemether and dihydroartemisinin suppositories. The more rapid parasite clearance of single high-dose regimens suggests that achieving immediate high drug concentrations may be the optimal strategy. PMID:18373841

Observer Performance in the Detection and Classification of Malignant Hepatic Nodules and Masses with CT Image-Space Denoising and Iterative Reconstruction

PubMed Central

Yu, Lifeng; Li, Zhoubo; Manduca, Armando; Blezek, Daniel J.; Hough, David M.; Venkatesh, Sudhakar K.; Brickner, Gregory C.; Cernigliaro, Joseph C.; Hara, Amy K.; Fidler, Jeff L.; Lake, David S.; Shiung, Maria; Lewis, David; Leng, Shuai; Augustine, Kurt E.; Carter, Rickey E.; Holmes, David R.; McCollough, Cynthia H.

2015-01-01

Purpose To determine if lower-dose computed tomographic (CT) scans obtained with adaptive image-based noise reduction (adaptive nonlocal means [ANLM]) or iterative reconstruction (sinogram-affirmed iterative reconstruction [SAFIRE]) result in reduced observer performance in the detection of malignant hepatic nodules and masses compared with routine-dose scans obtained with filtered back projection (FBP). Materials and Methods This study was approved by the institutional review board and was compliant with HIPAA. Informed consent was obtained from patients for the retrospective use of medical records for research purposes. CT projection data from 33 abdominal and 27 liver or pancreas CT examinations were collected (median volume CT dose index, 13.8 and 24.0 mGy, respectively). Hepatic malignancy was defined by progression or regression or with histopathologic findings. Lower-dose data were created by using a validated noise insertion method (10.4 mGy for abdominal CT and 14.6 mGy for liver or pancreas CT) and images reconstructed with FBP, ANLM, and SAFIRE. Four readers evaluated routine-dose FBP images and all lower-dose images, circumscribing liver lesions and selecting diagnosis. The jackknife free-response receiver operating characteristic figure of merit (FOM) was calculated on a per–malignant nodule or per-mass basis. Noninferiority was defined by the lower limit of the 95% confidence interval (CI) of the difference between lower-dose and routine-dose FOMs being less than −0.10. Results Twenty-nine patients had 62 malignant hepatic nodules and masses. Estimated FOM differences between lower-dose FBP and lower-dose ANLM versus routine-dose FBP were noninferior (difference: −0.041 [95% CI: −0.090, 0.009] and −0.003 [95% CI: −0.052, 0.047], respectively). In patients with dedicated liver scans, lower-dose ANLM images were noninferior (difference: +0.015 [95% CI: −0.077, 0.106]), whereas lower-dose FBP images were not (difference −0.049 [95% CI: −0.140, 0.043]). In 37 patients with SAFIRE reconstructions, the three lower-dose alternatives were found to be noninferior to the routine-dose FBP. Conclusion At moderate levels of dose reduction, lower-dose FBP images without ANLM or SAFIRE were noninferior to routine-dose images for abdominal CT but not for liver or pancreas CT. © RSNA, 2015 Online supplemental material is available for this article. PMID:26020436

Alternative methods for the median lethal dose (LD(50)) test: the up-and-down procedure for acute oral toxicity.

PubMed

Rispin, Amy; Farrar, David; Margosches, Elizabeth; Gupta, Kailash; Stitzel, Katherine; Carr, Gregory; Greene, Michael; Meyer, William; McCall, Deborah

2002-01-01

The authors have developed an improved version of the up-and-down procedure (UDP) as one of the replacements for the traditional acute oral toxicity test formerly used by the Organisation for Economic Co-operation and Development member nations to characterize industrial chemicals, pesticides, and their mixtures. This method improves the performance of acute testing for applications that use the median lethal dose (classic LD50) test while achieving significant reductions in animal use. It uses sequential dosing, together with sophisticated computer-assisted computational methods during the execution and calculation phases of the test. Staircase design, a form of sequential test design, can be applied to acute toxicity testing with its binary experimental endpoints (yes/no outcomes). The improved UDP provides a point estimate of the LD50 and approximate confidence intervals in addition to observed toxic signs for the substance tested. It does not provide information about the dose-response curve. Computer simulation was used to test performance of the UDP without the need for additional laboratory validation.

A simplified technique for delivering total body irradiation (TBI) with improved dose homogeneity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao Rui; Bernard, Damian; Turian, Julius

2012-04-15

Purpose: Total body irradiation (TBI) with megavoltage photon beams has been accepted as an important component of management for a number of hematologic malignancies, generally as part of bone marrow conditioning regimens. The purpose of this paper is to present and discuss the authors' TBI technique, which both simplifies the treatment process and improves the treatment quality. Methods: An AP/PA TBI treatment technique to produce uniform dose distributions using sequential collimator reductions during each fraction was implemented, and a sample calculation worksheet is presented. Using this methodology, the dosimetric characteristics of both 6 and 18 MV photon beams, including lungmore » dose under cerrobend blocks was investigated. A method of estimating midplane lung doses based on measured entrance and exit doses was proposed, and the estimated results were compared with measurements. Results: Whole body midplane dose uniformity of {+-}10% was achieved with no more than two collimator-based beam modulations. The proposed model predicted midplane lung doses 5% to 10% higher than the measured doses for 6 and 18 MV beams. The estimated total midplane doses were within {+-}5% of the prescribed midplane dose on average except for the lungs where the doses were 6% to 10% lower than the prescribed dose on average. Conclusions: The proposed TBI technique can achieve dose uniformity within {+-}10%. This technique is easy to implement and does not require complicated dosimetry and/or compensators.« less

A Multi-institutional Clinical Trial of Rectal Dose Reduction via Injected Polyethylene-Glycol Hydrogel During Intensity Modulated Radiation Therapy for Prostate Cancer: Analysis of Dosimetric Outcomes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Danny Y., E-mail: dsong2@jhmi.edu; Herfarth, Klaus K.; Uhl, Matthias

2013-09-01

Purpose: To characterize the effect of a prostate-rectum spacer on dose to rectum during external beam radiation therapy for prostate cancer and to assess for factors correlated with rectal dose reduction. Methods and Materials: Fifty-two patients at 4 institutions were enrolled into a prospective pilot clinical trial. Patients underwent baseline scans and then were injected with perirectal spacing hydrogel and rescanned. Intensity modulated radiation therapy plans were created on both scans for comparison. The objectives were to establish rates of creation of ≥7.5 mm of prostate-rectal separation, and decrease in rectal V70 of ≥25%. Multiple regression analysis was performed tomore » evaluate the associations between preinjection and postinjection changes in rectal V70 and changes in plan conformity, rectal volume, bladder volume, bladder V70, planning target volume (PTV), and postinjection midgland separation, gel volume, gel thickness, length of PTV/gel contact, and gel left-to-right symmetry. Results: Hydrogel resulted in ≥7.5-mm prostate-rectal separation in 95.8% of patients; 95.7% had decreased rectal V70 of ≥25%, with a mean reduction of 8.0 Gy. There were no significant differences in preinjection and postinjection prostate, PTV, rectal, and bladder volumes. Plan conformities were significantly different before versus after injection (P=.02); plans with worse conformity indexes after injection compared with before injection (n=13) still had improvements in rectal V70. In multiple regression analysis, greater postinjection reduction in V70 was associated with decreased relative postinjection plan conformity (P=.01). Reductions in V70 did not significantly vary by institution, despite significant interinstitutional variations in plan conformity. There were no significant relationships between reduction in V70 and the other characteristics analyzed. Conclusions: Injection of hydrogel into the prostate-rectal interface resulted in dose reductions to rectum for >90% of patients treated. Rectal sparing was statistically significant across a range of 10 to 75 Gy and was demonstrated within the presence of significant interinstitutional variability in plan conformity, target definitions, and injection results.« less

Radiation dose reduction in digital breast tomosynthesis (DBT) by means of deep-learning-based supervised image processing

NASA Astrophysics Data System (ADS)

Liu, Junchi; Zarshenas, Amin; Qadir, Ammar; Wei, Zheng; Yang, Limin; Fajardo, Laurie; Suzuki, Kenji

2018-03-01

To reduce cumulative radiation exposure and lifetime risks for radiation-induced cancer from breast cancer screening, we developed a deep-learning-based supervised image-processing technique called neural network convolution (NNC) for radiation dose reduction in DBT. NNC employed patched-based neural network regression in a convolutional manner to convert lower-dose (LD) to higher-dose (HD) tomosynthesis images. We trained our NNC with quarter-dose (25% of the standard dose: 12 mAs at 32 kVp) raw projection images and corresponding "teaching" higher-dose (HD) images (200% of the standard dose: 99 mAs at 32 kVp) of a breast cadaver phantom acquired with a DBT system (Selenia Dimensions, Hologic, CA). Once trained, NNC no longer requires HD images. It converts new LD images to images that look like HD images; thus the term "virtual" HD (VHD) images. We reconstructed tomosynthesis slices on a research DBT system. To determine a dose reduction rate, we acquired 4 studies of another test phantom at 4 different radiation doses (1.35, 2.7, 4.04, and 5.39 mGy entrance dose). Structural SIMilarity (SSIM) index was used to evaluate the image quality. For testing, we collected half-dose (50% of the standard dose: 32+/-14 mAs at 33+/-5 kVp) and full-dose (standard dose: 68+/-23 mAs at 33+/-5 kvp) images of 10 clinical cases with the DBT system at University of Iowa Hospitals and Clinics. NNC converted half-dose DBT images of 10 clinical cases to VHD DBT images that were equivalent to full dose DBT images. Our cadaver phantom experiment demonstrated 79% dose reduction.

Comparison of the efficacy and safety of intensive-dose and standard-dose statin treatment for stroke prevention

PubMed Central

Wang, Juan; Chen, Dan; Li, Da-Bing; Yu, Xin; Shi, Guo-Bing

2016-01-01

Abstract Background: Previous study indicated that high-dose statin treatment might increase the risk of hemorrhagic stroke and adverse reactions. We aim to compare the efficacy and safety of intensive-dose and standard-dose statin treatment for preventing stroke in high-risk patients. Methods: A thorough search was performed of multiple databases for publications from 1990 to June 2015. We selected the randomized clinical trials comparing standard-dose statin with placebo and intensive-dose statin with standard-dose statin or placebo for the prevention of stroke events in patients. Duplicate independent data extraction and bias assessments were performed. Data were pooled using a fixed-effects model or a random-effects model if significant heterogeneity was present. Results: For the all stroke incidences, intensive-dose statin treatment compared with placebo treatment and standard-dose statin treatment compared with placebo treatment showed a significant 21% reduction in relative risk (RR) (RR 0.79, 95% confidence interval (CI) [0.71, 0.87], P < 0.00001) and an 18% reduction in RR (RR 0.82, 95% CI [0.73, 0.93], P = 0.002) in the subgroup without renal transplant recipients and patients undergoing regular hemodialysis separately. For the fatal stroke incidences, intensive-dose statin treatment compared with standard dose or placebo was effective reducing fatal stroke (RR 0.61, 95% CI [0.39, 0.96], P = 0.03) and the RR was 1.01 (95% CI [0.85, 1.20], P = 0.90) in standard-dose statin treatment compared with placebo. Conclusion: The results of this meta-analysis suggest that intensive-dose statin treatment might be more favorable for reducing the incidences of all strokes than standard-dose statin treatment, especially for patients older than 65 years in reducing the incidences of all stroke incidences. PMID:27684837

Testosterone Dose Dependently Prevents Bone and Muscle Loss in Rodents after Spinal Cord Injury

PubMed Central

Conover, Christine F.; Beggs, Luke A.; Beck, Darren T.; Otzel, Dana M.; Balaez, Alexander; Combs, Sarah M.; Miller, Julie R.; Ye, Fan; Aguirre, J. Ignacio; Neuville, Kathleen G.; Williams, Alyssa A.; Conrad, Bryan P.; Gregory, Chris M.; Wronski, Thomas J.; Bose, Prodip K.; Borst, Stephen E.

2014-01-01

Abstract Androgen administration protects against musculoskeletal deficits in models of sex-steroid deficiency and injury/disuse. It remains unknown, however, whether testosterone prevents bone loss accompanying spinal cord injury (SCI), a condition that results in a near universal occurrence of osteoporosis. Our primary purpose was to determine whether testosterone-enanthate (TE) attenuates hindlimb bone loss in a rodent moderate/severe contusion SCI model. Forty (n=10/group), 14 week old male Sprague-Dawley rats were randomized to receive: (1) Sham surgery (T9 laminectomy), (2) moderate/severe (250 kdyne) SCI, (3) SCI+Low-dose TE (2.0 mg/week), or (4) SCI+High-dose TE (7.0 mg/week). Twenty-one days post-injury, SCI animals exhibited a 77–85% reduction in hindlimb cancellous bone volume at the distal femur (measured via μCT) and proximal tibia (measured via histomorphometry), characterized by a >70% reduction in trabecular number, 13–27% reduction in trabecular thickness, and increased trabecular separation. A 57% reduction in cancellous volumetric bone mineral density (vBMD) at the distal femur and a 20% reduction in vBMD at the femoral neck were also observed. TE dose dependently prevented hindlimb bone loss after SCI, with high-dose TE fully preserving cancellous bone structural characteristics and vBMD at all skeletal sites examined. Animals receiving SCI also exhibited a 35% reduction in hindlimb weight bearing (triceps surae) muscle mass and a 22% reduction in sublesional non-weight bearing (levator ani/bulbocavernosus [LABC]) muscle mass, and reduced prostate mass. Both TE doses fully preserved LABC mass, while only high-dose TE ameliorated hindlimb muscle losses. TE also dose dependently increased prostate mass. Our findings provide the first evidence indicating that high-dose TE fully prevents hindlimb cancellous bone loss and concomitantly ameliorates muscle loss after SCI, while low-dose TE produces much less profound musculoskeletal benefit. Testosterone-induced prostate enlargement, however, represents a potential barrier to the clinical implementation of high-dose TE as a means of preserving musculoskeletal tissue after SCI. PMID:24378197

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiller, Mauritius M.; Veinot, Kenneth G.; Easterly, Clay E.

In this study, methods are addressed to reduce the computational time to compute organ-dose rate coefficients using Monte Carlo techniques. Several variance reduction techniques are compared including the reciprocity method, importance sampling, weight windows and the use of the ADVANTG software package. For low-energy photons, the runtime was reduced by a factor of 10 5 when using the reciprocity method for kerma computation for immersion of a phantom in contaminated water. This is particularly significant since impractically long simulation times are required to achieve reasonable statistical uncertainties in organ dose for low-energy photons in this source medium and geometry. Althoughmore » the MCNP Monte Carlo code is used in this paper, the reciprocity technique can be used equally well with other Monte Carlo codes.« less

Improving Low-dose Cardiac CT Images based on 3D Sparse Representation

PubMed Central

Shi, Luyao; Hu, Yining; Chen, Yang; Yin, Xindao; Shu, Huazhong; Luo, Limin; Coatrieux, Jean-Louis

2016-01-01

Cardiac computed tomography (CCT) is a reliable and accurate tool for diagnosis of coronary artery diseases and is also frequently used in surgery guidance. Low-dose scans should be considered in order to alleviate the harm to patients caused by X-ray radiation. However, low dose CT (LDCT) images tend to be degraded by quantum noise and streak artifacts. In order to improve the cardiac LDCT image quality, a 3D sparse representation-based processing (3D SR) is proposed by exploiting the sparsity and regularity of 3D anatomical features in CCT. The proposed method was evaluated by a clinical study of 14 patients. The performance of the proposed method was compared to the 2D spares representation-based processing (2D SR) and the state-of-the-art noise reduction algorithm BM4D. The visual assessment, quantitative assessment and qualitative assessment results show that the proposed approach can lead to effective noise/artifact suppression and detail preservation. Compared to the other two tested methods, 3D SR method can obtain results with image quality most close to the reference standard dose CT (SDCT) images. PMID:26980176

Characterizing regional-scale temporal evolution of air dose rates after the Fukushima Daiichi Nuclear Power Plant accident.

PubMed

Wainwright, Haruko M; Seki, Akiyuki; Mikami, Satoshi; Saito, Kimiaki

2018-09-01

In this study, we quantify the temporal changes of air dose rates in the regional scale around the Fukushima Dai-ichi Nuclear Power Plant in Japan, and predict the spatial distribution of air dose rates in the future. We first apply the Bayesian geostatistical method developed by Wainwright et al. (2017) to integrate multiscale datasets including ground-based walk and car surveys, and airborne surveys, all of which have different scales, resolutions, spatial coverage, and accuracy. This method is based on geostatistics to represent spatial heterogeneous structures, and also on Bayesian hierarchical models to integrate multiscale, multi-type datasets in a consistent manner. We apply this method to the datasets from three years: 2014 to 2016. The temporal changes among the three integrated maps enables us to characterize the spatiotemporal dynamics of radiation air dose rates. The data-driven ecological decay model is then coupled with the integrated map to predict future dose rates. Results show that the air dose rates are decreasing consistently across the region. While slower in the forested region, the decrease is particularly significant in the town area. The decontamination has contributed to significant reduction of air dose rates. By 2026, the air dose rates will continue to decrease, and the area above 3.8 μSv/h will be almost fully contained within the non-residential forested zone. Copyright © 2018 Elsevier Ltd. All rights reserved.

Implementation of dual-energy technique for virtual monochromatic and linearly mixed CBCTs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Hao; Giles, William; Ren Lei

Purpose: To implement dual-energy imaging technique for virtual monochromatic (VM) and linearly mixed (LM) cone beam CTs (CBCTs) and to demonstrate their potential applications in metal artifact reduction and contrast enhancement in image-guided radiation therapy (IGRT). Methods: A bench-top CBCT system was used to acquire 80 kVp and 150 kVp projections, with an additional 0.8 mm tin filtration. To implement the VM technique, these projections were first decomposed into acrylic and aluminum basis material projections to synthesize VM projections, which were then used to reconstruct VM CBCTs. The effect of VM CBCT on the metal artifact reduction was evaluated withmore » an in-house titanium-BB phantom. The optimal VM energy to maximize contrast-to-noise ratio (CNR) for iodine contrast and minimize beam hardening in VM CBCT was determined using a water phantom containing two iodine concentrations. The LM technique was implemented by linearly combining the low-energy (80 kVp) and high-energy (150 kVp) CBCTs. The dose partitioning between low-energy and high-energy CBCTs was varied (20%, 40%, 60%, and 80% for low-energy) while keeping total dose approximately equal to single-energy CBCTs, measured using an ion chamber. Noise levels and CNRs for four tissue types were investigated for dual-energy LM CBCTs in comparison with single-energy CBCTs at 80, 100, 125, and 150 kVp. Results: The VM technique showed substantial reduction of metal artifacts at 100 keV with a 40% reduction in the background standard deviation compared to a 125 kVp single-energy scan of equal dose. The VM energy to maximize CNR for both iodine concentrations and minimize beam hardening in the metal-free object was 50 keV and 60 keV, respectively. The difference of average noise levels measured in the phantom background was 1.2% between dual-energy LM CBCTs and equivalent-dose single-energy CBCTs. CNR values in the LM CBCTs of any dose partitioning are better than those of 150 kVp single-energy CBCTs. The average CNR for four tissue types with 80% dose fraction at low-energy showed 9.0% and 4.1% improvement relative to 100 kVp and 125 kVp single-energy CBCTs, respectively. CNRs for low-contrast objects improved as dose partitioning was more heavily weighted toward low-energy (80 kVp) for LM CBCTs. Conclusions: Dual-energy CBCT imaging techniques were implemented to synthesize VM CBCT and LM CBCTs. VM CBCT was effective at achieving metal artifact reduction. Depending on the dose-partitioning scheme, LM CBCT demonstrated the potential to improve CNR for low contrast objects compared to single-energy CBCT acquired with equivalent dose.« less

SU-F-T-46: The Effect of Inter-Seed Attenuation and Tissue Composition in Prostate 125I Brachytherapy Dose Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamura, K; Araki, F; Ohno, T

Purpose: To investigate the difference of dose distributions with/without the effect of inter-seed attenuation and tissue compositions in prostate {sup 125}I brachytherapy dose calculations, using Monte Carlo simulations of Particle and Heavy Ion Transport code System (PHITS). Methods: The dose distributions in {sup 125}I prostate brachytherapy were calculated using PHITS for non-simultaneous and simultaneous alignments of STM1251 sources in water or prostate phantom for six patients. The PHITS input file was created from DICOM-RT file which includes source coordinates and structures for clinical target volume (CTV) and organs at risk (OARs) of urethra and rectum, using in-house Matlab software. Photonmore » and electron cutoff energies were set to 1 keV and 100 MeV, respectively. The dose distributions were calculated with the kerma approximation and the voxel size of 1 × 1 × 1 mm{sup 3}. The number of incident photon was set to be the statistical uncertainty (1σ) of less than 1%. The effect of inter-seed attenuation and prostate tissue compositions was evaluated from dose volume histograms (DVHs) for each structure, by comparing to results of the AAPM TG-43 dose calculation (without the effect of inter-seed attenuation and prostate tissue compositions). Results: The dose reduction due to the inter-seed attenuation by source capsules was approximately 2% for CTV and OARs compared to those of TG-43. In additions, by considering prostate tissue composition, the D{sub 90} and V{sub 100} of CTV reduced by 6% and 1%, respectively. Conclusion: It needs to consider the dose reduction due to the inter-seed attenuation and tissue composition in prostate {sup 125}I brachytherapy dose calculations.« less

Monte Carlo investigation of backscatter point spread function for x-ray imaging examinations

NASA Astrophysics Data System (ADS)

Xiong, Zhenyu; Vijayan, Sarath; Rudin, Stephen; Bednarek, Daniel R.

2017-03-01

X-ray imaging examinations, especially complex interventions, may result in relatively high doses to the patient's skin inducing skin injuries. A method was developed to determine the skin-dose distribution for non-uniform x-ray beams by convolving the backscatter point-spread-function (PSF) with the primary-dose distribution to generate the backscatter distribution that, when added to the primary dose, gives the total-dose distribution. This technique was incorporated in the dose-tracking system (DTS), which provides a real-time color-coded 3D-mapping of skin dose during fluoroscopic procedures. The aim of this work is to investigate the variation of the backscatter PSF with different parameters. A backscatter PSF of a 1-mm x-ray beam was generated by EGSnrc Monte-Carlo code for different x-ray beam energies, different soft-tissue thickness above bone, different bone thickness and different entrance-beam angles, as well as for different locations on the SK-150 anthropomorphic head phantom. The results show a reduction of the peak scatter to primary dose ratio of 48% when X-ray beam voltage is increased from 40 keV to 120 keV. The backscatter dose was reduced when bone was beneath the soft tissue layer and this reduction increased with thinner soft tissue and thicker bone layers. The backscatter factor increased about 21% as the angle of incidence of the beam with the entrance surface decreased from 90° (perpendicular) to 30°. The backscatter PSF differed for different locations on the SK-150 phantom by up to 15%. The results of this study can be used to improve the accuracy of dose calculation when using PSF convolution in the DTS.

WE-AB-202-01: Evaluating the Toxicity Reduction with CT-Ventilation Functional Avoidance Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinogradskiy, Y; Miyasaka, Y; Kadoya, N

Purpose: CT-ventilation is an exciting new imaging modality that uses 4DCTs to calculate lung ventilation. Studies have proposed to use 4DCT-ventilation imaging for functional avoidance radiotherapy which implies designing treatment plans to spare functional portions of the lung. Although retrospective studies have been performed to evaluate the dosimetric gains to functional lung; no work has been done to translate the dosimetric gains to an improvement in pulmonary toxicity. The purpose of our work was to evaluate the potential reduction in toxicity for 4DCT-ventilation based functional avoidance. Methods: 70 lung cancer patients with 4DCT imaging were used for the study. CT-ventilationmore » maps were calculated using the patient’s 4DCT, deformable image registrations, and a density-change-based algorithm. Radiation pneumonitis was graded using imaging and clinical information. Log-likelihood methods were used to fit a normal-tissue-complication-probability (NTCP) model predicting grade 2+ radiation pneumonitis as a function of doses (mean and V20) to functional lung (>15% ventilation). For 20 patients a functional plan was generated that reduced dose to functional lung while meeting RTOG 0617-based constraints. The NTCP model was applied to the functional plan to determine the reduction in toxicity with functional planning Results: The mean dose to functional lung was 16.8 and 17.7 Gy with the functional and clinical plans respectively. The corresponding grade 2+ pneumonitis probability was 26.9% with the clinically-used plan and 24.6% with the functional plan (8.5% reduction). The V20-based grade 2+ pneumonitis probability was 23.7% with the clinically-used plan and reduced to 19.6% with the functional plan (20.9% reduction). Conclusion: Our results revealed a reduction of 9–20% in complication probability with functional planning. To our knowledge this is the first study to apply complication probability to convert dosimetric results to toxicity improvement. The results presented in the current work provide seminal data for prospective clinical trials in functional avoidance. YV discloses funding from State of Colorado. TY discloses National Lung Cancer Partnership; Young Investigator Research grant.« less

SU-F-T-198: Dosimetric Comparison of Carbon and Proton Radiotherapy for Recurrent Nasopharynx Carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Y; Zhao, J; Wang, W

2016-06-15

Purpose: Various radiotherapy planning methods for locally recurrent nasopharynx carcinoma (R-NPC) have been proposed. The purpose of this study was to compare carbon and proton therapy for the treatment of R-NPC in terms of dose coverage for target volume and sparing for organs at risk (OARs). Methods: Six patients who were suffering from R-NPC and treated using carbon therapy were selected for this study. Treatment plans with a total dose of 57.5Gy (RBE) in 23 fractions were made using SIEMENS Syngo V11. An intensity-modulated radiotherapy optimization method was chosen for carbon plans (IMCT) while for proton plans both intensity-modulated radiotherapymore » (IMPT) and single beam optimization (proton-SBO) methods were chosen. Dose distributions, dose volume parameters, and selected dosimetric indices for target volumes and OARs were compared for all treatment plans. Results: All plans provided comparable PTV coverage. The volume covered by 95% of the prescribed dose was comparable for all three plans. The average values were 96.11%, 96.24% and 96.11% for IMCT, IMPT, and proton-SBO respectively. A significant reduction of the 80% and 50% dose volumes were observed for the IMCT plans compared to the IMPT and proton-SBO plans. Critical organs lateral to the target such as brain stem and spinal cord were better spared by IMPT than by proton-SBO, while IMCT spared those organs best. For organs in the beam path, such as parotid glands, the mean dose results were similar for all three plans. Conclusion: Carbon plans yielded better dose conformity than proton plans. They provided similar or better target coverage while significantly lowering the dose for normal tissues. Dose sparing for critical organs in IMPT plans was better than proton-SBO, however, IMPT is known to be more sensitive to range uncertainties. For proton plans it is essential to find a balance between the two optimization methods.« less

An adaptive algorithm for the detection of microcalcifications in simulated low-dose mammography.

PubMed

Treiber, O; Wanninger, F; Führ, H; Panzer, W; Regulla, D; Winkler, G

2003-02-21

This paper uses the task of microcalcification detection as a benchmark problem to assess the potential for dose reduction in x-ray mammography. We present the results of a newly developed algorithm for detection of microcalcifications as a case study for a typical commercial film-screen system (Kodak Min-R 2000/2190). The first part of the paper deals with the simulation of dose reduction for film-screen mammography based on a physical model of the imaging process. Use of a more sensitive film-screen system is expected to result in additional smoothing of the image. We introduce two different models of that behaviour, called moderate and strong smoothing. We then present an adaptive, model-based microcalcification detection algorithm. Comparing detection results with ground-truth images obtained under the supervision of an expert radiologist allows us to establish the soundness of the detection algorithm. We measure the performance on the dose-reduced images in order to assess the loss of information due to dose reduction. It turns out that the smoothing behaviour has a strong influence on detection rates. For moderate smoothing. a dose reduction by 25% has no serious influence on the detection results. whereas a dose reduction by 50% already entails a marked deterioration of the performance. Strong smoothing generally leads to an unacceptable loss of image quality. The test results emphasize the impact of the more sensitive film-screen system and its characteristics on the problem of assessing the potential for dose reduction in film-screen mammography. The general approach presented in the paper can be adapted to fully digital mammography.

An adaptive algorithm for the detection of microcalcifications in simulated low-dose mammography

NASA Astrophysics Data System (ADS)

Treiber, O.; Wanninger, F.; Führ, H.; Panzer, W.; Regulla, D.; Winkler, G.

2003-02-01

This paper uses the task of microcalcification detection as a benchmark problem to assess the potential for dose reduction in x-ray mammography. We present the results of a newly developed algorithm for detection of microcalcifications as a case study for a typical commercial film-screen system (Kodak Min-R 2000/2190). The first part of the paper deals with the simulation of dose reduction for film-screen mammography based on a physical model of the imaging process. Use of a more sensitive film-screen system is expected to result in additional smoothing of the image. We introduce two different models of that behaviour, called moderate and strong smoothing. We then present an adaptive, model-based microcalcification detection algorithm. Comparing detection results with ground-truth images obtained under the supervision of an expert radiologist allows us to establish the soundness of the detection algorithm. We measure the performance on the dose-reduced images in order to assess the loss of information due to dose reduction. It turns out that the smoothing behaviour has a strong influence on detection rates. For moderate smoothing, a dose reduction by 25% has no serious influence on the detection results, whereas a dose reduction by 50% already entails a marked deterioration of the performance. Strong smoothing generally leads to an unacceptable loss of image quality. The test results emphasize the impact of the more sensitive film-screen system and its characteristics on the problem of assessing the potential for dose reduction in film-screen mammography. The general approach presented in the paper can be adapted to fully digital mammography.

Analysis of esophageal-sparing treatment plans for patients with high-grade esophagitis.

PubMed

Niedzielski, Joshua; Bluett, Jaques B; Williamson, Ryan T; Liao, Zhongxing; Gomez, Daniel R; Court, Laurence E

2013-07-08

We retrospectively generated IMRT plans for 14 NSCLC patients who had experienced grade 2 or 3 esophagitis (CTCAE version 3.0). We generated 11-beam and reduced esophagus dose plan types to compare changes in the volume and length of esophagus receiving doses of 50, 55, 60, 65, and 70 Gy. Changes in planning target volume (PTV) dose coverage were also compared. If necessary, plans were renormalized to restore 95% PTV coverage. The critical organ doses examined were mean lung dose, mean heart dose, and volume of spinal cord receiving 50 Gy. The effect of interfractional motion was determined by applying a three-dimensional rigid shift to the dose grid. For the esophagus plan, the mean reduction in esophagus V50, V55, V60, V65, and V70 Gy was 2.8, 4.1, 5.9, 7.3, and 9.5 cm(3), respectively, compared with the clinical plan. The mean reductions in LE50, LE55, LE60, LE65, and LE70 Gy were 2.0, 3.0, 3.8, 4.0, and 4.6 cm, respectively. The mean heart and lung dose decreased 3.0 Gy and 2.4 Gy, respectively. The mean decreases in 90% and 95% PTV coverage were 1.7 Gy and 2.8 Gy, respectively. The normalized plans' mean reduction of esophagus V50, V55, V60, V65, and V70 Gy were 1.6, 2.0, 2.9, 3.9, and 5.5 cm(3), respectively, compared with the clinical plans. The normalized plans' mean reductions in LE50, LE55, LE60, LE65, and LE70 Gy were 4.9, 5.2, 5.4, 4.9, and 4.8 cm, respectively. The mean reduction in maximum esophagus dose with simulated interfractional motion was 3.0 Gy and 1.4 Gy for the clinical plan type and the esophagus plan type, respectively. In many cases, the esophagus dose can be greatly reduced while maintaining critical structure dose constraints. PTV coverage can be restored by increasing beam output, while still obtaining a dose reduction to the esophagus and maintaining dose constraints.

Analysis of esophageal‐sparing treatment plans for patients with high‐grade esophagitis

PubMed Central

Bluett, Jaques B.; Williamson, Ryan T.; Liao, Zhongxing; Gomez, Daniel R.; Court, Laurence E.

2013-01-01

We retrospectively generated IMRT plans for 14 NSCLC patients who had experienced grade 2 or 3 esophagitis (CTCAE version 3.0). We generated 11‐beam and reduced esophagus dose plan types to compare changes in the volume and length of esophagus receiving doses of 50, 55, 60, 65, and 70 Gy. Changes in planning target volume (PTV) dose coverage were also compared. If necessary, plans were renormalized to restore 95% PTV coverage. The critical organ doses examined were mean lung dose, mean heart dose, and volume of spinal cord receiving 50 Gy. The effect of interfractional motion was determined by applying a three‐dimensional rigid shift to the dose grid. For the esophagus plan, the mean reduction in esophagus V50, V55, V60, V65, and V70 Gy was 2.8, 4.1, 5.9, 7.3, and 9.5 cm3, respectively, compared with the clinical plan. The mean reductions in LE50, LE55, LE60, LE65, and LE70 Gy were 2.0, 3.0, 3.8, 4.0, and 4.6 cm, respectively. The mean heart and lung dose decreased 3.0 Gy and 2.4 Gy, respectively. The mean decreases in 90% and 95% PTV coverage were 1.7 Gy and 2.8 Gy, respectively. The normalized plans’ mean reduction of esophagus V50, V55, V60, V65, and V70 Gy were 1.6, 2.0, 2.9, 3.9, and 5.5 cm3, respectively, compared with the clinical plans. The normalized plans’ mean reductions in LE50, LE55, LE60, LE65, and LE70 Gy were 4.9, 5.2, 5.4, 4.9, and 4.8 cm, respectively. The mean reduction in maximum esophagus dose with simulated interfractional motion was 3.0 Gy and 1.4 Gy for the clinical plan type and the esophagus plan type, respectively. In many cases, the esophagus dose can be greatly reduced while maintaining critical structure dose constraints. PTV coverage can be restored by increasing beam output, while still obtaining a dose reduction to the esophagus and maintaining dose constraints. PACS number: 87.53 Tf PMID:23835390

Bladder–Rectum Spacer Balloon in High-Dose-Rate Brachytherapy in Cervix Carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rai, Bhavana; Patel, Firuza D., E-mail: firuzapatel@gmail.com; Chakraborty, Santam

2013-04-01

Purpose: To compare bladder and rectum doses with the use of a bladder–rectum spacer balloon (BRSB) versus standard gauze packing in the same patient receiving 2 high-dose-rate intracavitary brachytherapy fractions. Methods and Materials: This was a randomized study to compare the reduction in bladder and rectum doses with the use of a BRSB compared with standard gauze packing in patients with carcinoma of the cervix being treated with high-dose-rate intracavitary brachytherapy. The patients were randomized between 2 arms. In arm A, vaginal packing was done with standard gauze packing in the first application, and BRSB was used in the secondmore » application. Arm B was the reverse of arm A. The International Commission for Radiation Units and Measurement (ICRU) point doses and doses to 0.1-cm{sup 3}, 1-cm{sup 3}, 2-cm{sup 3}, 5-cm{sup 3}, and 10-cm{sup 3} volumes of bladder and rectum were compared. The patients were also subjectively assessed for the ease of application and the time taken for application. Statistical analysis was done using the paired t test. Results: A total of 43 patients were enrolled; however, 3 patients had to be excluded because the BRSB could not be inserted owing to unfavorable local anatomy. Thus 40 patients (80 plans) were evaluated. The application was difficult in 3 patients with BRSB, and in 2 patients with BRSB the application time was prolonged. There was no significant difference in bladder doses to 0.1 cm{sup 3}, 1 cm{sup 3}, 2 cm{sup 3}, 5 cm{sup 3}, and 10 cm{sup 3} and ICRU bladder point. Statistically significant dose reductions to 0.1-cm{sup 3}, 1-cm{sup 3}, and 2-cm{sup 3} volumes for rectum were observed with the BRSB. No significant differences in 5-cm{sup 3} and 10-cm{sup 3} volumes and ICRU rectum point were observed. Conclusion: A statistically significant dose reduction was observed for small high-dose volumes in rectum with the BRSB. The doses to bladder were comparable for BRSB and gauze packing. Transparent balloons of variable sizes are recommended for patients with a less spacious vaginal cavity.« less

The adaptive statistical iterative reconstruction-V technique for radiation dose reduction in abdominal CT: comparison with the adaptive statistical iterative reconstruction technique.

PubMed

Kwon, Heejin; Cho, Jinhan; Oh, Jongyeong; Kim, Dongwon; Cho, Junghyun; Kim, Sanghyun; Lee, Sangyun; Lee, Jihyun

2015-10-01

To investigate whether reduced radiation dose abdominal CT images reconstructed with adaptive statistical iterative reconstruction V (ASIR-V) compromise the depiction of clinically competent features when compared with the currently used routine radiation dose CT images reconstructed with ASIR. 27 consecutive patients (mean body mass index: 23.55 kg m(-2) underwent CT of the abdomen at two time points. At the first time point, abdominal CT was scanned at 21.45 noise index levels of automatic current modulation at 120 kV. Images were reconstructed with 40% ASIR, the routine protocol of Dong-A University Hospital. At the second time point, follow-up scans were performed at 30 noise index levels. Images were reconstructed with filtered back projection (FBP), 40% ASIR, 30% ASIR-V, 50% ASIR-V and 70% ASIR-V for the reduced radiation dose. Both quantitative and qualitative analyses of image quality were conducted. The CT dose index was also recorded. At the follow-up study, the mean dose reduction relative to the currently used common radiation dose was 35.37% (range: 19-49%). The overall subjective image quality and diagnostic acceptability of the 50% ASIR-V scores at the reduced radiation dose were nearly identical to those recorded when using the initial routine-dose CT with 40% ASIR. Subjective ratings of the qualitative analysis revealed that of all reduced radiation dose CT series reconstructed, 30% ASIR-V and 50% ASIR-V were associated with higher image quality with lower noise and artefacts as well as good sharpness when compared with 40% ASIR and FBP. However, the sharpness score at 70% ASIR-V was considered to be worse than that at 40% ASIR. Objective image noise for 50% ASIR-V was 34.24% and 46.34% which was lower than 40% ASIR and FBP. Abdominal CT images reconstructed with ASIR-V facilitate radiation dose reductions of to 35% when compared with the ASIR. This study represents the first clinical research experiment to use ASIR-V, the newest version of iterative reconstruction. Use of the ASIR-V algorithm decreased image noise and increased image quality when compared with the ASIR and FBP methods. These results suggest that high-quality low-dose CT may represent a new clinical option.

High-Dose Statin Pretreatment Decreases Periprocedural Myocardial Infarction and Cardiovascular Events in Patients Undergoing Elective Percutaneous Coronary Intervention: A Meta-Analysis of Twenty-Four Randomized Controlled Trials

PubMed Central

Wang, Le; Peng, Pingan; Zhang, Ou; Xu, Xiaohan; Yang, Shiwei; Zhao, Yingxin; Zhou, Yujie

2014-01-01

Background Evidence suggests that high-dose statin pretreatment may reduce the risk of periprocedural myocardial infarction (PMI) and major adverse cardiac events (MACE) for certain patients; however, previous analyses have not considered patients with a history of statin maintenance treatment. In this meta-analysis of randomized controlled trials (RCTs), we reevaluated the efficacy of short-term high-dose statin pretreatment to prevent PMI and MACE in an expanded set of patients undergoing elective percutaneous coronary intervention. Methods We searched the PubMed/Medline database for RCTs that compared high-dose statin pretreatment with no statin or low-dose statin pretreatment as a prevention of PMI and MACE. We evaluated the incidence of PMI and MACE, including death, spontaneous myocardial infarction, and target vessel revascularization at the longest follow-up for each study for subgroups stratified by disease classification and prior low-dose statin treatment. Results Twenty-four RCTs with a total of 5,526 patients were identified. High-dose statin pretreatment was associated with 59% relative reduction in PMI (odds ratio [OR]: 0.41; 95% confidence interval [CI]: 0.34–0.49; P<0.00001) and 39% relative reduction in MACE (OR: 0.61; 95% CI: 0.45–0.83; P = 0.002). The benefit of high-dose statin pretreatment on MACE was significant for statin-naive patients (OR: 0.69; 95% CI: 0.50–0.95; P = 0.02) and prior low dose statin-treated patients (OR: 0.28; 95% CI: 0.12–0.65; P = 0.003); and for patients with acute coronary syndrome (OR: 0.52; 95% CI: 0.34–0.79; P = 0.003), but not for patients with stable angina (OR: 0.71; 95% CI 0.45–1.10; P = 0.12). Long-term effects on survival were less obvious. Conclusions High-dose statin pretreatment can result in a significant reduction in PMI and MACE for patients undergoing elective PCI. The positive effect of high-dose statin pretreatment on PMI and MACE is significant for statin-naïve patients and patients with prior treatment. The positive effect of high-dose statin pretreatment on MACE is significant for patients with acute coronary syndrome. PMID:25473831

Radiation Dose to the Lens of the Eye from Computed Tomography Scans of the Head

NASA Astrophysics Data System (ADS)

Januzis, Natalie Ann

While it is well known that exposure to radiation can result in cataract formation, questions still remain about the presence of a dose threshold in radiation cataractogenesis. Since the exposure history from diagnostic CT exams is well documented in a patient's medical record, the population of patients chronically exposed to radiation from head CT exams may be an interesting area to explore for further research in this area. However, there are some challenges in estimating lens dose from head CT exams. An accurate lens dosimetry model would have to account for differences in imaging protocols, differences in head size, and the use of any dose reduction methods. The overall objective of this dissertation was to develop a comprehensive method to estimate radiation dose to the lens of the eye for patients receiving CT scans of the head. This research is comprised of a physics component, in which a lens dosimetry model was derived for head CT, and a clinical component, which involved the application of that dosimetry model to patient data. The physics component includes experiments related to the physical measurement of the radiation dose to the lens by various types of dosimeters placed within anthropomorphic phantoms. These dosimeters include high-sensitivity MOSFETs, TLDs, and radiochromic film. The six anthropomorphic phantoms used in these experiments range in age from newborn to adult. First, the lens dose from five clinically relevant head CT protocols was measured in the anthropomorphic phantoms with MOSFET dosimeters on two state-of-the-art CT scanners. The volume CT dose index (CTDIvol), which is a standard CT output index, was compared to the measured lens doses. Phantom age-specific CTDIvol-to-lens dose conversion factors were derived using linear regression analysis. Since head size can vary among individuals of the same age, a method was derived to estimate the CTDIvol-to-lens dose conversion factor using the effective head diameter. These conversion factors were derived for each scanner individually, but also were derived with the combined data from the two scanners as a means to investigate the feasibility of a scanner-independent method. Using the scanner-independent method to derive the CTDIvol-to-lens dose conversion factor from the effective head diameter, most of the fitted lens dose values fell within 10-15% of the measured values from the phantom study, suggesting that this is a fairly accurate method of estimating lens dose from the CTDIvol with knowledge of the patient's head size. Second, the dose reduction potential of organ-based tube current modulation (OB-TCM) and its effect on the CTDIvol-to-lens dose estimation method was investigated. The lens dose was measured with MOSFET dosimeters placed within the same six anthropomorphic phantoms. The phantoms were scanned with the five clinical head CT protocols with OB-TCM enabled on the one scanner model at our institution equipped with this software. The average decrease in lens dose with OB-TCM ranged from 13.5 to 26.0%. Using the size-specific method to derive the CTDIvol-to-lens dose conversion factor from the effective head diameter for protocols with OB-TCM, the majority of the fitted lens dose values fell within 15-18% of the measured values from the phantom study. Third, the effect of gantry angulation on lens dose was investigated by measuring the lens dose with TLDs placed within the six anthropomorphic phantoms. The 2-dimensional spatial distribution of dose within the areas of the phantoms containing the orbit was measured with radiochromic film. A method was derived to determine the CTDIvol-to-lens dose conversion factor based upon distance from the primary beam scan range to the lens. The average dose to the lens region decreased substantially for almost all the phantoms (ranging from 67 to 92%) when the orbit was exposed to scattered radiation compared to the primary beam. The effectiveness of this method to reduce lens dose is highly dependent upon the shape and size of the head, which influences whether or not the angled scan range coverage can include the entire brain volume and still avoid the orbit. The clinical component of this dissertation involved performing retrospective patient studies in the pediatric and adult populations, and reconstructing the lens doses from head CT examinations with the methods derived in the physics component. The cumulative lens doses in the patients selected for the retrospective study ranged from 40 to 1020 mGy in the pediatric group, and 53 to 2900 mGy in the adult group. This dissertation represents a comprehensive approach to lens of the eye dosimetry in CT imaging of the head. The collected data and derived formulas can be used in future studies on radiation-induced cataracts from repeated CT imaging of the head. Additionally, it can be used in the areas of personalized patient dose management, and protocol optimization and clinician training.

SU-D-209-03: Radiation Dose Reduction Using Real-Time Image Processing in Interventional Radiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanal, K; Moirano, J; Zamora, D

Purpose: To characterize changes in radiation dose after introducing a new real-time image processing technology in interventional radiology systems. Methods: Interventional radiology (IR) procedures are increasingly complex, at times requiring substantial time and radiation dose. The risk of inducing tissue reactions as well as long-term stochastic effects such as radiation-induced cancer is not trivial. To reduce this risk, IR systems are increasingly equipped with dose reduction technologies.Recently, ClarityIQ (Philips Healthcare) technology was installed in our existing neuroradiology IR (NIR) and vascular IR (VIR) suites respectively. ClarityIQ includes real-time image processing that reduces noise/artifacts, enhances images, and sharpens edges while alsomore » reducing radiation dose rates. We reviewed 412 NIR (175 pre- and 237 post-ClarityIQ) procedures and 329 VIR (156 preand 173 post-ClarityIQ) procedures performed at our institution pre- and post-ClarityIQ implementation. NIR procedures were primarily classified as interventional or diagnostic. VIR procedures included drain port, drain placement, tube change, mesenteric, and implanted venous procedures. Air Kerma (AK in units of mGy) was documented for all the cases using a commercial radiation exposure management system. Results: When considering all NIR procedures, median AK decreased from 1194 mGy to 561 mGy. When considering all VIR procedures, median AK decreased from 49 to 14 mGy. Both NIR and VIR exhibited a decrease in AK exceeding 50% after ClarityIQ implementation, a statistically significant (p<0.05) difference. Of the 5 most common VIR procedures, all median AK values decreased, but significance (p<0.05) was only reached in venous access (N=53), angio mesenteric (N=41), and drain placement procedures (N=31). Conclusion: ClarityIQ can reduce dose significantly for both NIR and VIR procedures. Image quality was not assessed in conjunction with the dose reduction.« less

Is Weight-Based Adjustment of Automatic Exposure Control Necessary for the Reduction of Chest CT Radiation Dose?

PubMed Central

Prakash, Priyanka; Gilman, Matthew D.; Shepard, Jo-Anne O.; Digumarthy, Subba R.

2010-01-01

Objective To assess the effects of radiation dose reduction in the chest CT using a weight-based adjustment of the automatic exposure control (AEC) technique. Materials and Methods With Institutional Review Board Approval, 60 patients (mean age, 59.1 years; M:F = 35:25) and 57 weight-matched patients (mean age, 52.3 years, M:F = 25:32) were scanned using a weight-adjusted AEC and non-weight-adjusted AEC, respectively on a 64-slice multidetector CT with a 0.984:1 pitch, 0.5 second rotation time, 40 mm table feed/rotation, and 2.5 mm section thickness. Patients were categorized into 3 weight categories; < 60 kg (n = 17), 60-90 kg (n = 52), and > 90 kg (n = 48). Patient weights, scanning parameters, CT dose index volumes (CTDIvol) and dose length product (DLP) were recorded, while effective dose (ED) was estimated. Image noise was measured in the descending thoracic aorta. Data were analyzed using a standard statistical package (SAS/STAT) (Version 9.1, SAS institute Inc, Cary, NC). Results Compared to the non-weight-adjusted AEC, the weight-adjusted AEC technique resulted in an average decrease of 29% in CTDIvol and a 27% effective dose reduction (p < 0.0001). With weight-adjusted AEC, the CTDIvol decreased to 15.8, 15.9, and 27.3 mGy for the < 60, 60-90 and > 91 kg weight groups, respectively, compared to 20.3, 27.9 and 32.8 mGy, with non-weight-adjusted AEC. No significant difference was observed for objective image noise between the chest CT acquired with the non-weight-adjusted (15.0 ± 3.1) and weight-adjusted (16.1 ± 5.6) AEC techniques (p > 0.05). Conclusion The results of this study suggest that AEC should be tailored according to patient weight. Without weight-based adjustment of AEC, patients are exposed to a 17 - 43% higher radiation-dose from a chest CT. PMID:20046494

Blood phenylalanine concentrations in patients with PAH-deficient hyperphenylalaninaemia off diet without and with three different single oral doses of tetrahydrobiopterin: assessing responsiveness in a model of statistical process control.

PubMed

Lindner, M; Gramer, G; Garbade, S F; Burgard, P

2009-08-01

Tetrahydrobiopterin (BH(4)) cofactor loading is a standard procedure to differentiate defects of BH(4) metabolism from phenylalanine hydroxylase (PAH) deficiency. BH(4) responsiveness also exists in PAH-deficient patients with high residual PAH activity. Unexpectedly, single cases with presumed nil residual PAH activity have been reported to be BH(4) responsive, too. BH(4) responsiveness has been defined either by a >or=30% reduction of blood Phe concentration after a single BH(4) dose or by a decline greater than the individual circadian Phe level variation. Since both methods have methodological disadvantages, we present a model of statistical process control (SPC) to assess BH(4) responsiveness. Phe levels in 17 adult PKU patients of three phenotypic groups off diet were compared without and with three different single oral dosages of BH(4) applied in a double-blind randomized cross-over design. Results are compared for >or=30% reduction and SPC. The effect of BH(4) by >or=30% reduction was significant for groups (p < 0.01) but not for dose (p = 0.064), with no interaction of group with dose (p = 0.24). SPC revealed significant effects for group (p < 0.01) and the interaction for group with dose (p < 0.05) but not for dose alone (p = 0.87). After one or more loadings, seven patients would be judged to be BH(4) responsive either by the 30% criterion or by the SPC model, but only three by both. Results for patients with identical PAH genotype were not very consistent within (for different BH(4) doses) and between the two models. We conclude that a comparison of protein loadings without and with BH(4) combined with a standardized procedure for data analysis and decision would increase the reliability of diagnostic results.

Dosimetric comparison of deep inspiration breath hold and free breathing technique in stereotactic body radiotherapy for localized lung tumor using Flattening Filter Free beam

NASA Astrophysics Data System (ADS)

Mani, Karthick Raj; Bhuiyan, Md. Anisuzzaman; Alam, Md. Mahbub; Ahmed, Sharif; Sumon, Mostafa Aziz; Sengupta, Ashim Kumar; Rahman, Md. Shakilur; Azharul Islam, Md. S. M.

2018-03-01

Aim: To compare the dosimetric advantage of stereotactic body radiotherapy (SBRT) for localized lung tumor between deep inspiration breath hold technique and free breathing technique. Materials and methods: We retrospectively included ten previously treated lung tumor patients in this dosimetric study. All the ten patients underwent CT simulation using 4D-CT free breathing (FB) and deep inspiration breath hold (DIBH) techniques. Plans were created using three coplanar full modulated arc using 6 MV flattening filter free (FFF) bream with a dose rate of 1400 MU/min. Same dose constraints for the target and the critical structures for a particular patient were used during the plan optimization process in DIBH and FB datasets. We intend to deliver 50 Gy in 5 fractions for all the patients. For standardization, all the plans were normalized at target mean of the planning target volume (PTV). Doses to the critical structures and targets were recorded from the dose volume histogram for evaluation. Results: The mean right and left lung volumes were inflated by 1.55 and 1.60 times in DIBH scans compared to the FB scans. The mean internal target volume (ITV) increased in the FB datasets by 1.45 times compared to the DIBH data sets. The mean dose followed by standard deviation (x¯ ± σx¯) of ipsilateral lung for DIBH-SBRT and FB-SBRT plans were 7.48 ± 3.57 (Gy) and 10.23 ± 4.58 (Gy) respectively, with a mean reduction of 36.84% in DIBH-SBRT plans. Ipsilateral lung were reduced to 36.84% in DIBH plans compared to FB plans. Conclusion: Significant dose reduction in ipsilateral lung due to the lung inflation and target motion restriction in DIBH-SBRT plans were observed compare to FB-SBRT. DIBH-SBRT plans demonstrate superior dose reduction to the normal tissues and other critical structures.

Cone beam computed tomography radiation dose and image quality assessments.

PubMed

Lofthag-Hansen, Sara

2010-01-01

Diagnostic radiology has undergone profound changes in the last 30 years. New technologies are available to the dental field, cone beam computed tomography (CBCT) as one of the most important. CBCT is a catch-all term for a technology comprising a variety of machines differing in many respects: patient positioning, volume size (FOV), radiation quality, image capturing and reconstruction, image resolution and radiation dose. When new technology is introduced one must make sure that diagnostic accuracy is better or at least as good as the one it can be expected to replace. The CBCT brand tested was two versions of Accuitomo (Morita, Japan): 3D Accuitomo with an image intensifier as detector, FOV 3 cm x 4 cm and 3D Accuitomo FPD with a flat panel detector, FOVs 4 cm x 4 cm and 6 cm x 6 cm. The 3D Accuitomo was compared with intra-oral radiography for endodontic diagnosis in 35 patients with 46 teeth analyzed, of which 41 were endodontically treated. Three observers assessed the images by consensus. The result showed that CBCT imaging was superior with a higher number of teeth diagnosed with periapical lesions (42 vs 32 teeth). When evaluating 3D Accuitomo examinations in the posterior mandible in 30 patients, visibility of marginal bone crest and mandibular canal, important anatomic structures for implant planning, was high with good observer agreement among seven observers. Radiographic techniques have to be evaluated concerning radiation dose, which requires well-defined and easy-to-use methods. Two methods: CT dose index (CTDI), prevailing method for CT units, and dose-area product (DAP) were evaluated for calculating effective dose (E) for both units. An asymmetric dose distribution was revealed when a clinical situation was simulated. Hence, the CTDI method was not applicable for these units with small FOVs. Based on DAP values from 90 patient examinations effective dose was estimated for three diagnostic tasks: implant planning in posterior mandible and examinations of impacted lower third molars and retained upper cuspids. It varied between 11-77 microSv. Radiation dose should be evaluated together with image quality. Images of a skull phantom were obtained with both units varying tube voltage, tube current, degree of rotation and FOVs. Seven observers assessed subjective image quality using a six-point rating scale for two diagnostic tasks: periapical diagnosis and implant planning in the posterior part of the jaws. Intra-observer agreement was good and inter-observer agreement moderate. Periapical diagnosis was found to, regardless of jaw, require higher exposure parameters compared to implant planning. Implant planning in the lower jaw required higher exposure parameters compared to upper jaw. Substantial dose reduction could be made without loss of diagnostic information by using a rotation of 180 degrees, in particular implant planning in upper jaw. CBCT with small FOVs was found to be well-suited for periapical diagnosis and implant planning. The CTDI method is not applicable estimating effective dose for these units. Based on DAP values effective dose varied between 11-77 microSv (ICRP 60, 1991) in a retrospectively selected patient material. Adaptation of exposure parameters to diagnostic task can give substantial dose reduction.

Computed Tomography Number Changes Observed During Computed Tomography–Guided Radiation Therapy for Head and Neck Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Mei; Department of Radiation Oncology, Sichuan Cancer Hospital, Chengdu; Yang, Cungeng

2015-04-01

Purpose: To investigate CT number (CTN) changes in gross tumor volume (GTV) and organ at risk (OAR) according to daily diagnostic-quality CT acquired during CT-guided intensity modulated radiation therapy for head and neck cancer (HNC) patients. Methods and Materials: Computed tomography scans acquired using a CT-on-rails during daily CT-guided intensity modulated radiation therapy for 15 patients with stage II to IVa squamous cell carcinoma of the head and neck were analyzed. The GTV, parotid glands, spinal cord, and nonspecified tissue were generated on each selected daily CT. The changes in CTN distributions and the mean and mode values were collected.more » Pearson analysis was used to assess the correlation between the CTN change, organ volume reduction, and delivered radiation dose. Results: Volume and CTN changes for GTV and parotid glands can be observed during radiation therapy delivery for HNC. The mean (±SD) CTNs in GTV and ipsi- and contralateral parotid glands were reduced by 6 ± 10, 8 ± 7, and 11 ± 10 Hounsfield units, respectively, for all patients studied. The mean CTN changes in both spinal cord and nonspecified tissue were almost invisible (<2 Hounsfield units). For 2 patients studied, the absolute mean CTN changes in GTV and parotid glands were strongly correlated with the dose delivered (P<.001 and P<.05, respectively). For the correlation between CTN reductions and delivered isodose bins for parotid glands, the Pearson coefficient varied from −0.98 (P<.001) in regions with low-dose bins to 0.96 (P<.001) in high-dose bins and were patient specific. Conclusions: The CTN can be reduced in tumor and parotid glands during the course of radiation therapy for HNC. There was a fair correlation between CTN reduction and radiation doses for a subset of patients, whereas the correlation between CTN reductions and volume reductions in GTV and parotid glands were weak. More studies are needed to understand the mechanism for the radiation-induced CTN changes.« less

Thyroid Dose During Neurointerventional Procedures: Does Lead Shielding Reduce the Dose?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shortt, C. P.; Fanning, N. F.; Malone, L.

2007-09-15

Purpose. To assess radiation dose to the thyroid in patients undergoing neurointerventional procedures and to evaluate dose reduction to the thyroid by lead shielding. Methods and Materials. A randomized patient study was undertaken to evaluate the dose reduction by thyroid lead shields and assess their practicality in a clinical setting. Sixty-five patients attending for endovascular treatment of arteriovenous malformations (AVMs) and aneurysms were randomized into one of 2 groups a) No Thyroid Shield and b) Thyroid Lead Shield. Two thermoluminescent dosimeters (TLDs) were placed over the thyroid gland (1 on each side) at constant positions on each patient in bothmore » groups. A thyroid lead shield (Pb eq. 0.5 mm) was placed around the neck of patients in the thyroid lead shield group after the neurointerventional radiologist had obtained satisfactory working access above the neck. The total dose-area-product (DAP) value, number and type of digital subtraction angiography (DSA) runs and fluoroscopy time were recorded for all patients. Results. Of the 72 patients who initially attended for neurointerventional procedures, 7 were excluded due to failure to consent or because of procedures involving access to the external carotid circulation. Of the remaining 65 who were randomized, a further 9 were excluded due to; procedureabandonment, unfeasible shield placement or shield interference with the procedure. Patient demographics included mean age of 47.9 yrs (15-74), F:M=1.4:1. Mean fluoroscopy time was 25.9 min. Mean DAP value was 13,134.8 cGy.cm{sup 2} and mean number of DSA runs was 13.4. The mean relative thyroid doses were significantly different (p< 0.001) between the unshielded (7.23 mSv/cGy2 x 105) and shielded groups (3.77 mSv/cGy2 x 105). A mean thyroid dose reduction of 48% was seen in the shielded group versus the unshielded group. Conclusion. Considerable doses to the thyroid are incurred during neurointerventional procedures, highlighting the need for increased awareness of patient radiation protection. Thyroid lead shielding yields significant radiation protection, is inexpensive and when not obscuring the field of view, should be used routinely.« less

SU-E-T-284: Dose Plan Optimization When Using Hydrogel Prostate-Rectum Spacer: A Single Institution Experience

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajecki, M; Thurber, A; Catalfamo, F

2015-06-15

Purpose: To describe rectal dose reduction achieved and techniques used to take advantage of the increased peri-rectal spacing provided by injected polyethylene-glycol. Methods: Thirty prostate cancer patents were 2:1 randomized during a clinical trial to evaluate the effectiveness of injected poly-ethylene glycol hydrogel (SpaceOAR System) in creating space between the prostate and the anterior rectal wall. All patients received a baseline CT/MR scan and baseline IMRT treatment plan. Patients were randomized to receive hydrogel injection (n=20) or Control (n=10), followed by another CT/MR scan and treatment plan (single arc VMAT, 6 MV photons, 79.2 Gy, 44 fractions). Additional optimization structuresmore » were employed to constrain the dose to the rectum; specifically an avoidance structure to limit V75 <15%, and a control structure to limit the maximum relative dose <105% in the interface region of the anterior rectal wall and the prostate planning target volume. Dose volumetric data was analyzed for rectal volumes receiving 60 through 80 Gy. Results: Rectal dose reduction was observed in all patients who received the hydrogel. Volumetric analysis indicates a median rectal volume and (reduction from baseline plan) following spacer application of 4.9% (8.9%) at V60Gy, 3.8% (8.1%) at V65Gy, 2.5% (7.2%) at V70Gy, 1.6% (5.8%) at V75Gy, and 0.5% (2.5%) at V80Gy. Conclusion: Relative to planning without spacers, rectal dose constraints of 5%, 4%, 3%, 2%, 1% for V60, V65, V70, V75, and V80, should be obtainable when peri-rectal spacers are used. The combined effect of increased peri-rectal space provided by the hydrogel, with strict optimization objectives, resulted in reduced dose to the rectum. To maximize benefit, strict optimization objectives and reduced rectal dose constraints should be employed when creating plans for patients with perirectal spacers. Clinical Trial for SpaceOAR product conducted by Augmenix,Inc. The research site was paid to be a participating site.« less

Dose reduction of scattered photons from concrete walls lined with lead: Implications for improvement in design of megavoltage radiation therapy facility mazes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Affan, I. A. M., E-mail: info@medphys-environment.co.uk; Hugtenburg, R. P.; Piliero, M.

Purpose: This study explores the possibility of using lead to cover part of the radiation therapy facility maze walls in order to absorb low energy photons and reduce the total dose at the maze entrance of radiation therapy rooms. Methods: Experiments and Monte Carlo simulations were utilized to establish the possibility of using high-Z materials to cover the concrete walls of the maze in order to reduce the dose of the scattered photons at the maze entrance. The dose of the backscattered photons from a concrete wall was measured for various scattering angles. The dose was also calculated by themore » FLUKA and EGSnrc Monte Carlo codes. The FLUKA code was also used to simulate an existing radiotherapy room to study the effect of multiple scattering when adding lead to cover the concrete walls of the maze. Monoenergetic photons were used to represent the main components of the x ray spectrum up to 10 MV. Results: It was observed that when the concrete wall was covered with just 2 mm of lead, the measured dose rate at all backscattering angles was reduced by 20% for photons of energy comparable to Co-60 emissions and 70% for Cs-137 emissions. The simulations with FLUKA and EGS showed that the reduction in the dose was potentially even higher when lead was added. One explanation for the reduction is the increased absorption of backscattered photons due to the photoelectric interaction in lead. The results also showed that adding 2 mm lead to the concrete walls and floor of the maze reduced the dose at the maze entrance by up to 90%. Conclusions: This novel proposal of covering part or the entire maze walls with a few millimeters of lead would have a direct implication for the design of radiation therapy facilities and would assist in upgrading the design of some mazes, especially those in facilities with limited space where the maze length cannot be extended to sufficiently reduce the dose.« less

Prospective Measurement of Patient Exposure to Radiation During Pediatric Ureteroscopy

PubMed Central

Kokorowski, Paul J.; Chow, Jeanne S.; Strauss, Keith; Pennison, Melanie; Routh, Jonathan C.; Nelson, Caleb P.

2013-01-01

Objective Little data have been reported regarding radiation exposure during pediatric endourologic procedures, including ureteroscopy (URS). We sought to measure radiation exposure during pediatric URS and identify opportunities for exposure reduction. Methods We prospectively observed URS procedures as part of a quality improvement initiative. Pre-operative patient characteristics, operative factors, fluoroscopy settings and radiation exposure were recorded. Our outcomes were entrance skin dose (ESD, in mGy) and midline dose (MLD, in mGy). Specific modifiable factors were identified as targets for potential quality improvement. Results Direct observation was performed on 56 consecutive URS procedures. Mean patient age was 14.8 ± 3.8 years (range 7.4 to 19.2); 9 children were under age 12 years. Mean ESD was 46.4 ± 48 mGy. Mean MLD was 6.2 ± 5.0 mGy. The most important major determinant of radiation dose was total fluoroscopy time (mean 2.68 ± 1.8 min) followed by dose rate setting, child anterior-posterior (AP) diameter, and source to skin distance (all p<0.01). The analysis of factors affecting exposure levels found that the use of ureteral access sheaths (p=0.01) and retrograde pyelography (p=0.04) were significantly associated with fluoroscopy time. We also found that dose rate settings were higher than recommended in up to 43% of cases and ideal C-arm positioning could have reduced exposure 14% (up to 49% in some cases). Conclusions Children receive biologically significant radiation doses during URS procedures. Several modifiable factors contribute to dose and could be targeted in efforts to implement dose reduction strategies. PMID:22341275

SU-F-J-45: Sparing Normal Tissue with Ultra-High Dose Rate in Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Y

Purpose: To spare normal tissue by reducing the location uncertainty of a moving target, we proposed an ultra-high dose rate system and evaluated. Methods: High energy electrons generated with a linear accelerator were injected into a storage ring to be accumulated. The number of the electrons in the ring was determined based on the prescribed radiation dose. The dose was delivered within a millisecond, when an online imaging system found that the target was in the position that was consistent with that in a treatment plan. In such a short time period, the displacement of the target was negligible. Themore » margin added to the clinical target volume (CTV) could be reduced that was evaluated by comparing of volumes between CTV and ITV in 14 cases of lung stereotactic body radiation therapy (SBRT) treatments. A design of the ultra-high dose rate system was evaluated based clinical needs and the recent developments of low energy (a few MeV) electron storage ring. Results: This design of ultra-high dose rate system was feasible based on the techniques currently available. The reduction of a target volume was significant by reducing the margin that accounted the motion of the target. ∼50% volume reduction of the internal target volume (ITV) could be achieved in lung SBRT treatments. Conclusion: With this innovation of ultra-high dose rate system, the margin of target is able to be significantly reduced. It will reduce treatment time of gating and allow precisely specified gating window to improve the accuracy of dose delivering.« less

SU-E-P-11: Comparison of Image Quality and Radiation Dose Between Different Scanner System in Routine Abdomen CT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, S; Wang, Y; Weng, H

Purpose To evaluate image quality and radiation dose of routine abdomen computed tomography exam with the automatic current modulation technique (ATCM) performed in two different brand 64-slice CT scanners in our site. Materials and Methods A retrospective review of routine abdomen CT exam performed with two scanners; scanner A and scanner B in our site. To calculate standard deviation of the portal hepatic level with a region of interest of 12.5 mm x 12.5mm represented to the image noise. The radiation dose was obtained from CT DICOM image information. Using Computed tomography dose index volume (CTDIv) to represented CT radiationmore » dose. The patient data in this study were with normal weight (about 65–75 Kg). Results The standard deviation of Scanner A was smaller than scanner B, the scanner A might with better image quality than scanner B. On the other hand, the radiation dose of scanner A was higher than scanner B(about higher 50–60%) with ATCM. Both of them, the radiation dose was under diagnostic reference level. Conclusion The ATCM systems in modern CT scanners can contribute a significant reduction in radiation dose to the patient. But the reduction by ATCM systems from different CT scanner manufacturers has slightly variation. Whatever CT scanner we use, it is necessary to find the acceptable threshold of image quality with the minimum possible radiation exposure to the patient in agreement with the ALARA principle.« less

Spatiotemporal Fractionation Schemes for Irradiating Large Cerebral Arteriovenous Malformations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unkelbach, Jan, E-mail: junkelbach@mgh.harvard.edu; Bussière, Marc R.; Chapman, Paul H.

2016-07-01

Purpose: To optimally exploit fractionation effects in the context of radiosurgery treatments of large cerebral arteriovenous malformations (AVMs). In current practice, fractionated treatments divide the dose evenly into several fractions, which generally leads to low obliteration rates. In this work, we investigate the potential benefit of delivering distinct dose distributions in different fractions. Methods and Materials: Five patients with large cerebral AVMs were reviewed and replanned for intensity modulated arc therapy delivered with conventional photon beams. Treatment plans allowing for different dose distributions in all fractions were obtained by performing treatment plan optimization based on the cumulative biologically effective dosemore » delivered at the end of treatment. Results: We show that distinct treatment plans can be designed for different fractions, such that high single-fraction doses are delivered to complementary parts of the AVM. All plans create a similar dose bath in the surrounding normal brain and thereby exploit the fractionation effect. This partial hypofractionation in the AVM along with fractionation in normal brain achieves a net improvement of the therapeutic ratio. We show that a biological dose reduction of approximately 10% in the healthy brain can be achieved compared with reference treatment schedules that deliver the same dose distribution in all fractions. Conclusions: Boosting complementary parts of the target volume in different fractions may provide a therapeutic advantage in fractionated radiosurgery treatments of large cerebral AVMs. The strategy allows for a mean dose reduction in normal brain that may be valuable for a patient population with an otherwise normal life expectancy.« less

Physical aspects of total-body irradiation at the Middlesex Hospital (UCL group of hospitals), London 1988-1993: II. In vivo planning and dosimetry.

PubMed

Planskoy, B; Tapper, P D; Bedford, A M; Davis, F M

1996-11-01

Part II of this paper gives the results of applying the TBI methods described in part I, to in vivo patient planning and dosimetry. Patients are planned on nine CT based body slices, five of which pass through the lungs. Planned doses are verified with ten silicon diodes applied bi-laterally to five body sites, at each treatment. LiF TLDs are applied to seven other body sites at the first treatment only. For 84 patients and at least 1016 measurements per body site with the diodes, the mean measured total doses agreed with planned doses within at most 2% except at lung levels, where the mean measured dose was 3% too low. Standard deviations of the measurements about the mean were between 2.4 and 3.1%. For the LiF TLDs, the mean measured doses for all seven body sites were with in +/- 5% of planned doses. A separate assessment of measured entrance and transmitted doses showed that the former agreed well with planned doses, but that the latter tended to be low, especially over the lungs, and that they had a wider dispersion. Possible reasons for this are discussed. These results show measurement uncertainties similar to those for non-TBI treatments of Nilsson et al, Leunens et al and Essers et al. An analysis of the treatment plans showed a mean dose inhomogeneity in the body (75 patients, nine slices) of 19 +/- 6.0% (1 s.d.) and in the lungs (40 patients, five slices) of 9.2 +/- 2.85% (1 s.d.). The conclusions are that, overall, the methods are reasonably satisfactory but that, with an extra effort, even closer agreement between measured and planned doses and a further limited reduction in the body dose inhomogeneity could be obtained. However, if it were thought desirable to make a substantial reduction in the dose inhomogeneity in the body and lungs, this could only be achieved with the available equipment by changing from lateral to anterior-posterior irradiation and any potential advantages of this change would have to be balanced against a likely deterioration in patient comfort and an increase in treatment set-up times.

Intraoral radiology in general dental practices - a comparison of digital and film-based X-ray systems with regard to radiation protection and dose reduction.

PubMed

Anissi, H D; Geibel, M A

2014-08-01

The purpose of this study was to gain insight into the distribution and application of digital intraoral radiographic techniques within general dental practices and to compare these with film-based systems in terms of patient dose reduction. 1100 questionnaires were handed out to general dental practitioners. Data was analyzed with respect to the type of system by using descriptive statistics and nonparametric tests, i.e. Kruskal-Wallis, Mann-Whitney and chi-square test (SPSS 20). 64% of the questioned dentists still use film-based radiology, 23% utilize storage phosphor plate (SPP) systems and 13% use a charge-coupled device (CCD). A strong correlation between the number of dentists working in a practice and the use of digital dental imaging was observed. Almost 3/4 of the film users work with E- or F-speed film. 45% of them refuse to change to a digital system. The use of lead aprons was popular, while only a minority preferred thyroid shields and rectangular collimators. A fourfold reduction of exposure time from D-speed film to CCD systems was observed. Due to detector size and positioning errors, users of CCD systems take significantly more single-tooth radiographs in total. Considering the number of radiographs per patient, there is only a slight tendency towards more X-rays with CCD systems. Up to image generation, digital systems seem to be as or even more difficult to handle than film-based systems, while their handling was favored after radiographic exposure. Despite a slight increase of radiographs taken with CCD systems, there is a significant dosage reduction. Corresponding to the decrease in exposure time, the patient dose for SPP systems is reduced to one half compared to film. The main issues in CCD technology are positioning errors and the size of the X-ray detectors which are difficult to eliminate. The usage of radiation protection measures still needs to be improved. ► Responsible use of digital intraoral radiology results in a significant dose reduction in everyday practice. ► The ALARA principle is only achieved by strict implementation of dose-reducing methods. ► The efforts to use dose-reducing devices must be increased. © Georg Thieme Verlag KG Stuttgart · New York.

Lowering the glycemic index of white bread using a white bean extract

PubMed Central

Udani, Jay K; Singh, Betsy B; Barrett, Marilyn L; Preuss, Harry G

2009-01-01

Background Phase 2® is a dietary supplement derived from the common white kidney bean (Phaseolus vulgaris). Phase 2 has been shown to inhibit alpha-amylase, the complex carbohydrate digesting enzyme, in vitro. The inhibition of alpha-amylase may result in the lowering of the effective Glycemic Index (GI) of certain foods. The objective of this study was to determine whether the addition of Phase 2 would lower the GI of a commercially available high glycemic food (white bread). Methods An open-label 6-arm crossover study was conducted with 13 randomized subjects. Standardized GI testing was performed on white bread with and without the addition of Phase 2 in capsule and powder form, each in dosages of 1500 mg, 2000 mg, and 3000 mg. Statistical analysis was performed by one-way ANOVA of all seven treatment groups using unadjusted multiple comparisons (t tests) to the white bread control. Results For the capsule formulation, the 1500 mg dose had no effect on the GI and the 2000 mg and 3000 mg capsule doses caused insignificant reductions in GI. For the powder, the 1500 mg and 2000 mg doses caused insignificant reductions in the GI, and the 3000 mg dose had a significant effect (-20.23 or 34.11%, p = 0.023) Conclusion Phase 2 white bean extract appears to be a novel and potentially effective method for reducing the GI of existing foods without modifying their ingredient profile. Trial Registration Trial Registration: ISRCTN50347345 PMID:19860922

Radiotherapy for gastric lymphoma: a planning study of 3D conformal radiotherapy, the half-beam method, and intensity-modulated radiotherapy.

PubMed

Inaba, Koji; Okamoto, Hiroyuki; Wakita, Akihisa; Nakamura, Satoshi; Kobayashi, Kazuma; Harada, Ken; Kitaguchi, Mayuka; Sekii, Shuhei; Takahashi, Kana; Yoshio, Kotaro; Murakami, Naoya; Morota, Madoka; Ito, Yoshinori; Sumi, Minako; Uno, Takashi; Itami, Jun

2014-11-01

During radiotherapy for gastric lymphoma, it is difficult to protect the liver and kidneys in cases where there is considerable overlap between these organs and the target volume. This study was conducted to compare the three radiotherapy planning techniques of four-fields 3D conformal radiotherapy (3DCRT), half-field radiotherapy (the half-beam method) and intensity-modulated radiotherapy (IMRT) used to treat primary gastric lymphoma in which the planning target volume (PTV) had a large overlap with the left kidney. A total of 17 patients with gastric diffuse large B-cell lymphoma (DLBCL) were included. In DLBCL, immunochemotherapy (Rituximab + CHOP) was followed by radiotherapy of 40 Gy to the whole stomach and peri-gastric lymph nodes. 3DCRT, the half-field method, and IMRT were compared with respect to the dose-volume histogram (DVH) parameters and generalized equivalent uniform dose (gEUD) to the kidneys, liver and PTV. The mean dose and gEUD for 3DCRT was higher than for IMRT and the half-beam method in the left kidney and both kidneys. The mean dose and gEUD of the left kidney was 2117 cGy and 2224 cGy for 3DCRT, 1520 cGy and 1637 cGy for IMRT, and 1100 cGy and 1357 cGy for the half-beam method, respectively. The mean dose and gEUD of both kidneys was 1335 cGy and 1559 cGy for 3DCRT, 1184 cGy and 1311 cGy for IMRT, and 700 cGy and 937 cGy for the half-beam method, respectively. Dose-volume histograms (DVHs) of the liver revealed a larger volume was irradiated in the dose range <25 Gy with 3DCRT, while the half-beam method irradiated a larger volume of liver with the higher dose range (>25 Gy). IMRT and the half-beam method had the advantages of dose reduction for the kidneys and liver. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Impact of Dose to the Bladder Trigone on Long-Term Urinary Function After High-Dose Intensity Modulated Radiation Therapy for Localized Prostate Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghadjar, Pirus; Zelefsky, Michael J.; Spratt, Daniel E.

2014-02-01

Purpose: To determine the potential association between genitourinary (GU) toxicity and planning dose–volume parameters for GU pelvic structures after high-dose intensity modulated radiation therapy in localized prostate cancer patients. Methods and Materials: A total of 268 patients who underwent intensity modulated radiation therapy to a prescribed dose of 86.4 Gy in 48 fractions during June 2004-December 2008 were evaluated with the International Prostate Symptom Score (IPSS) questionnaire. Dose–volume histograms of the whole bladder, bladder wall, urethra, and bladder trigone were analyzed. The primary endpoint for GU toxicity was an IPSS sum increase ≥10 points over baseline. Univariate and multivariate analysesmore » were done by the Kaplan-Meier method and Cox proportional hazard models, respectively. Results: Median follow-up was 5 years (range, 3-7.7 years). Thirty-nine patients experienced an IPSS sum increase ≥10 during follow-up; 84% remained event free at 5 years. After univariate analysis, lower baseline IPSS sum (P=.006), the V90 of the trigone (P=.006), and the maximal dose to the trigone (P=.003) were significantly associated with an IPSS sum increase ≥10. After multivariate analysis, lower baseline IPSS sum (P=.009) and increased maximal dose to the trigone (P=.005) remained significantly associated. Seventy-two patients had both a lower baseline IPSS sum and a higher maximal dose to the trigone and were defined as high risk, and 68 patients had both a higher baseline IPSS sum and a lower maximal dose to the trigone and were defined as low risk for development of an IPSS sum increase ≥10. Twenty-one of 72 high-risk patients (29%) and 5 of 68 low-risk patients (7%) experienced an IPSS sum increase ≥10 (P=.001; odds ratio 5.19). Conclusions: The application of hot spots to the bladder trigone was significantly associated with relevant changes in IPSS during follow-up. Reduction of radiation dose to the lower bladder and specifically the bladder trigone seems to be associated with a reduction in late GU toxicity.« less

Generation of the additional fluorescence radiation in the elastomeric shields used in computer tomography (CT).

PubMed

Szajerski, P; Zaborski, M; Bem, H; Baryn, W; Kusiak, E

Two commercially available (EP, Z) and eight new elastomeric composites (M1-M4, G1-G4, of thickness ≈1 mm) containing mixtures of differing proportions of heavy metal additives (Bi, W, Gd and Sb) have been synthesised and examined as protective shields. The intensity of the X-ray fluorescence radiation generated in the typical elastomeric shields for CT, containing Bi and other heavy metal additives influence on the practical shielding properties. A method for assessing the radiation shielding properties of elastomeric composites used in CT examination procedures via X-ray spectrometry has been proposed. To measure the radiation reduction ability of the protective shields, the dose reduction factor (DRF) has been determined. The lead equivalents for the examined composites were within the ranges of 0.046-0.128 and 0.048-0.130 mm for 122.1 and 136.5 keV photons, respectively. The proposed method, unlike to the common approach, includes a dose contribution from the induced X-ray fluorescence radiation of the heavy metal elements in the protective shields. The results clearly indicate that among the examined compositions, the highest values DRF have been achieved with preparations containing Bi+W, Bi+W+Gd and Bi+W+Sb mixtures with gradually decreasing content of heavy metal additives in the following order: Bi, W, Gd and Sb. The respective values of DRF obtained for the investigated composites were 21, 28 and 27 % dose reduction for a 1 mm thick shield and 39 and ~50 % for a 2 mm thick layer (M1-M4).

Effect of Study Design on Sample Size in Studies Intended to Evaluate Bioequivalence of Inhaled Short-Acting β-Agonist Formulations.

PubMed

Zeng, Yaohui; Singh, Sachinkumar; Wang, Kai; Ahrens, Richard C

2018-04-01

Pharmacodynamic studies that use methacholine challenge to assess bioequivalence of generic and innovator albuterol formulations are generally designed per published Food and Drug Administration guidance, with 3 reference doses and 1 test dose (3-by-1 design). These studies are challenging and expensive to conduct, typically requiring large sample sizes. We proposed 14 modified study designs as alternatives to the Food and Drug Administration-recommended 3-by-1 design, hypothesizing that adding reference and/or test doses would reduce sample size and cost. We used Monte Carlo simulation to estimate sample size. Simulation inputs were selected based on published studies and our own experience with this type of trial. We also estimated effects of these modified study designs on study cost. Most of these altered designs reduced sample size and cost relative to the 3-by-1 design, some decreasing cost by more than 40%. The most effective single study dose to add was 180 μg of test formulation, which resulted in an estimated 30% relative cost reduction. Adding a single test dose of 90 μg was less effective, producing only a 13% cost reduction. Adding a lone reference dose of either 180, 270, or 360 μg yielded little benefit (less than 10% cost reduction), whereas adding 720 μg resulted in a 19% cost reduction. Of the 14 study design modifications we evaluated, the most effective was addition of both a 90-μg test dose and a 720-μg reference dose (42% cost reduction). Combining a 180-μg test dose and a 720-μg reference dose produced an estimated 36% cost reduction. © 2017, The Authors. The Journal of Clinical Pharmacology published by Wiley Periodicals, Inc. on behalf of American College of Clinical Pharmacology.

Image guidance doses delivered during radiotherapy: Quantification, management, and reduction: Report of the AAPM Therapy Physics Committee Task Group 180.

PubMed

Ding, George X; Alaei, Parham; Curran, Bruce; Flynn, Ryan; Gossman, Michael; Mackie, T Rock; Miften, Moyed; Morin, Richard; Xu, X George; Zhu, Timothy C

2018-05-01

With radiotherapy having entered the era of image guidance, or image-guided radiation therapy (IGRT), imaging procedures are routinely performed for patient positioning and target localization. The imaging dose delivered may result in excessive dose to sensitive organs and potentially increase the chance of secondary cancers and, therefore, needs to be managed. This task group was charged with: a) providing an overview on imaging dose, including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV-CT, megavoltage cone-beam CT (MV-CBCT) and kilovoltage cone-beam CT (kV-CBCT), and b) providing general guidelines for commissioning dose calculation methods and managing imaging dose to patients. We briefly review the dose to radiotherapy (RT) patients resulting from different image guidance procedures and list typical organ doses resulting from MV and kV image acquisition procedures. We provide recommendations for managing the imaging dose, including different methods for its calculation, and techniques for reducing it. The recommended threshold beyond which imaging dose should be considered in the treatment planning process is 5% of the therapeutic target dose. Although the imaging dose resulting from current kV acquisition procedures is generally below this threshold, the ALARA principle should always be applied in practice. Medical physicists should make radiation oncologists aware of the imaging doses delivered to patients under their care. Balancing ALARA with the requirement for effective target localization requires that imaging dose be managed based on the consideration of weighing risks and benefits to the patient. © 2018 American Association of Physicists in Medicine.

CORK Study in Cystic Fibrosis: Sustained Improvements in Ultra-Low-Dose Chest CT Scores After CFTR Modulation With Ivacaftor.

PubMed

Ronan, Nicola J; Einarsson, Gisli G; Twomey, Maria; Mooney, Denver; Mullane, David; NiChroinin, Muireann; O'Callaghan, Grace; Shanahan, Fergus; Murphy, Desmond M; O'Connor, Owen J; Shortt, Cathy A; Tunney, Michael M; Eustace, Joseph A; Maher, Michael M; Elborn, J Stuart; Plant, Barry J

2018-02-01

Ivacaftor produces significant clinical benefit in patients with cystic fibrosis (CF) with the G551D mutation. Prevalence of this mutation at the Cork CF Centre is 23%. This study assessed the impact of cystic fibrosis transmembrane conductance regulator modulation on multiple modalities of patient assessment. Thirty-three patients with the G551D mutation were assessed at baseline and prospectively every 3 months for 1 year after initiation of ivacaftor. Change in ultra-low-dose chest CT scans, blood inflammatory mediators, and the sputum microbiome were assessed. Significant improvements in FEV 1 , BMI, and sweat chloride levels were observed post-ivacaftor treatment. Improvement in ultra-low-dose CT imaging scores were observed after treatment, with significant mean reductions in total Bhalla score (P < .01), peribronchial thickening (P = .035), and extent of mucous plugging (P < .001). Reductions in circulating inflammatory markers, including interleukin (IL)-1β, IL-6, and IL-8 were demonstrated. There was a 30% reduction in the relative abundance of Pseudomonas species and an increase in the relative abundance of bacteria associated with more stable community structures. Posttreatment community richness increased significantly (P = .03). Early and sustained improvements on ultra-low-dose CT scores suggest it may be a useful method of evaluating treatment response. It paralleled improvement in symptoms, circulating inflammatory markers, and changes in the lung microbiota. Copyright © 2017 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

Visual grading characteristics and ordinal regression analysis during optimisation of CT head examinations.

PubMed

Zarb, Francis; McEntee, Mark F; Rainford, Louise

2015-06-01

To evaluate visual grading characteristics (VGC) and ordinal regression analysis during head CT optimisation as a potential alternative to visual grading assessment (VGA), traditionally employed to score anatomical visualisation. Patient images (n = 66) were obtained using current and optimised imaging protocols from two CT suites: a 16-slice scanner at the national Maltese centre for trauma and a 64-slice scanner in a private centre. Local resident radiologists (n = 6) performed VGA followed by VGC and ordinal regression analysis. VGC alone indicated that optimised protocols had similar image quality as current protocols. Ordinal logistic regression analysis provided an in-depth evaluation, criterion by criterion allowing the selective implementation of the protocols. The local radiology review panel supported the implementation of optimised protocols for brain CT examinations (including trauma) in one centre, achieving radiation dose reductions ranging from 24 % to 36 %. In the second centre a 29 % reduction in radiation dose was achieved for follow-up cases. The combined use of VGC and ordinal logistic regression analysis led to clinical decisions being taken on the implementation of the optimised protocols. This improved method of image quality analysis provided the evidence to support imaging protocol optimisation, resulting in significant radiation dose savings. • There is need for scientifically based image quality evaluation during CT optimisation. • VGC and ordinal regression analysis in combination led to better informed clinical decisions. • VGC and ordinal regression analysis led to dose reductions without compromising diagnostic efficacy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y. M., E-mail: ymingy@gmail.com; Bednarz, B.; Svatos, M.

Purpose: The future of radiation therapy will require advanced inverse planning solutions to support single-arc, multiple-arc, and “4π” delivery modes, which present unique challenges in finding an optimal treatment plan over a vast search space, while still preserving dosimetric accuracy. The successful clinical implementation of such methods would benefit from Monte Carlo (MC) based dose calculation methods, which can offer improvements in dosimetric accuracy when compared to deterministic methods. The standard method for MC based treatment planning optimization leverages the accuracy of the MC dose calculation and efficiency of well-developed optimization methods, by precalculating the fluence to dose relationship withinmore » a patient with MC methods and subsequently optimizing the fluence weights. However, the sequential nature of this implementation is computationally time consuming and memory intensive. Methods to reduce the overhead of the MC precalculation have been explored in the past, demonstrating promising reductions of computational time overhead, but with limited impact on the memory overhead due to the sequential nature of the dose calculation and fluence optimization. The authors propose an entirely new form of “concurrent” Monte Carlo treat plan optimization: a platform which optimizes the fluence during the dose calculation, reduces wasted computation time being spent on beamlets that weakly contribute to the final dose distribution, and requires only a low memory footprint to function. In this initial investigation, the authors explore the key theoretical and practical considerations of optimizing fluence in such a manner. Methods: The authors present a novel derivation and implementation of a gradient descent algorithm that allows for optimization during MC particle transport, based on highly stochastic information generated through particle transport of very few histories. A gradient rescaling and renormalization algorithm, and the concept of momentum from stochastic gradient descent were used to address obstacles unique to performing gradient descent fluence optimization during MC particle transport. The authors have applied their method to two simple geometrical phantoms, and one clinical patient geometry to examine the capability of this platform to generate conformal plans as well as assess its computational scaling and efficiency, respectively. Results: The authors obtain a reduction of at least 50% in total histories transported in their investigation compared to a theoretical unweighted beamlet calculation and subsequent fluence optimization method, and observe a roughly fixed optimization time overhead consisting of ∼10% of the total computation time in all cases. Finally, the authors demonstrate a negligible increase in memory overhead of ∼7–8 MB to allow for optimization of a clinical patient geometry surrounded by 36 beams using their platform. Conclusions: This study demonstrates a fluence optimization approach, which could significantly improve the development of next generation radiation therapy solutions while incurring minimal additional computational overhead.« less

Concurrent Monte Carlo transport and fluence optimization with fluence adjusting scalable transport Monte Carlo

PubMed Central

Svatos, M.; Zankowski, C.; Bednarz, B.

2016-01-01

Purpose: The future of radiation therapy will require advanced inverse planning solutions to support single-arc, multiple-arc, and “4π” delivery modes, which present unique challenges in finding an optimal treatment plan over a vast search space, while still preserving dosimetric accuracy. The successful clinical implementation of such methods would benefit from Monte Carlo (MC) based dose calculation methods, which can offer improvements in dosimetric accuracy when compared to deterministic methods. The standard method for MC based treatment planning optimization leverages the accuracy of the MC dose calculation and efficiency of well-developed optimization methods, by precalculating the fluence to dose relationship within a patient with MC methods and subsequently optimizing the fluence weights. However, the sequential nature of this implementation is computationally time consuming and memory intensive. Methods to reduce the overhead of the MC precalculation have been explored in the past, demonstrating promising reductions of computational time overhead, but with limited impact on the memory overhead due to the sequential nature of the dose calculation and fluence optimization. The authors propose an entirely new form of “concurrent” Monte Carlo treat plan optimization: a platform which optimizes the fluence during the dose calculation, reduces wasted computation time being spent on beamlets that weakly contribute to the final dose distribution, and requires only a low memory footprint to function. In this initial investigation, the authors explore the key theoretical and practical considerations of optimizing fluence in such a manner. Methods: The authors present a novel derivation and implementation of a gradient descent algorithm that allows for optimization during MC particle transport, based on highly stochastic information generated through particle transport of very few histories. A gradient rescaling and renormalization algorithm, and the concept of momentum from stochastic gradient descent were used to address obstacles unique to performing gradient descent fluence optimization during MC particle transport. The authors have applied their method to two simple geometrical phantoms, and one clinical patient geometry to examine the capability of this platform to generate conformal plans as well as assess its computational scaling and efficiency, respectively. Results: The authors obtain a reduction of at least 50% in total histories transported in their investigation compared to a theoretical unweighted beamlet calculation and subsequent fluence optimization method, and observe a roughly fixed optimization time overhead consisting of ∼10% of the total computation time in all cases. Finally, the authors demonstrate a negligible increase in memory overhead of ∼7–8 MB to allow for optimization of a clinical patient geometry surrounded by 36 beams using their platform. Conclusions: This study demonstrates a fluence optimization approach, which could significantly improve the development of next generation radiation therapy solutions while incurring minimal additional computational overhead. PMID:27277051

High dose simvastatin exhibits enhanced lipid lowering effects relative to simvastatin/ezetimibe combination therapy

USDA-ARS?s Scientific Manuscript database

Technical Abstract: Background: Statins are the frontline in cholesterol reduction therapies; however use in combination with agents that possess complimentary mechanisms of action may achieve further reduce in LDL-C. Methods and Results: Thirty-nine patients were treated with either 80mg simvasta...

Canakinumab reduces the risk of acute gouty arthritis flares during initiation of allopurinol treatment: results of a double-blind, randomised study

PubMed Central

Schlesinger, Naomi; Mysler, Eduardo; Lin, Hsiao-Yi; De Meulemeester, Marc; Rovensky, Jozef; Arulmani, Udayasankar; Balfour, Alison; Krammer, Gerhard; Sallstig, Peter; So, Alexander

2011-01-01

Objective This study assessed the efficacy and safety of canakinumab, a fully human anti-interleukin 1β monoclonal antibody, for prophylaxis against acute gouty arthritis flares in patients initiating urate-lowering treatment. Methods In this double-blind, double-dummy, dose-ranging study, 432 patients with gouty arthritis initiating allopurinol treatment were randomised 1:1:1:1:1:1:2 to receive: a single dose of canakinumab, 25, 50, 100, 200, or 300 mg subcutaneously; 4×4-weekly doses of canakinumab (50+50+25+25 mg subcutaneously); or daily colchicine 0.5 mg orally for 16 weeks. Patients recorded details of flares in diaries. The study aimed to determine the canakinumab dose having equivalent efficacy to colchicine 0.5 mg at 16 weeks. Results A dose-response for canakinumab was not apparent with any of the four predefined dose-response models. The estimated canakinumab dose with equivalent efficacy to colchicine was below the range of doses tested. At 16 weeks, there was a 62% to 72% reduction in the mean number of flares per patient for canakinumab doses ≥50 mg versus colchicine based on a negative binomial model (rate ratio: 0.28–0.38, p≤0.0083), and the percentage of patients experiencing ≥1 flare was significantly lower for all canakinumab doses (15% to 27%) versus colchicine (44%, p<0.05). There was a 64% to 72% reduction in the risk of experiencing ≥1 flare for canakinumab doses ≥50 mg versus colchicine at 16 weeks (hazard ratio (HR): 0.28–0.36, p≤0.05). The incidence of adverse events was similar across treatment groups. Conclusions Single canakinumab doses ≥50 mg or four 4-weekly doses provided superior prophylaxis against flares compared with daily colchicine 0.5 mg. PMID:21540198

Innovations in Medication Preparation Safety and Wastage Reduction: Use of a Workflow Management System in a Pediatric Hospital.

PubMed

Davis, Stephen Jerome; Hurtado, Josephine; Nguyen, Rosemary; Huynh, Tran; Lindon, Ivan; Hudnall, Cedric; Bork, Sara

2017-01-01

Background: USP <797> regulatory requirements have mandated that pharmacies improve aseptic techniques and cleanliness of the medication preparation areas. In addition, the Institute for Safe Medication Practices (ISMP) recommends that technology and automation be used as much as possible for preparing and verifying compounded sterile products. Objective: To determine the benefits associated with the implementation of the workflow management system, such as reducing medication preparation and delivery errors, reducing quantity and frequency of medication errors, avoiding costs, and enhancing the organization's decision to move toward positive patient identification (PPID). Methods: At Texas Children's Hospital, data were collected and analyzed from January 2014 through August 2014 in the pharmacy areas in which the workflow management system would be implemented. Data were excluded for September 2014 during the workflow management system oral liquid implementation phase. Data were collected and analyzed from October 2014 through June 2015 to determine whether the implementation of the workflow management system reduced the quantity and frequency of reported medication errors. Data collected and analyzed during the study period included the quantity of doses prepared, number of incorrect medication scans, number of doses discontinued from the workflow management system queue, and the number of doses rejected. Data were collected and analyzed to identify patterns of incorrect medication scans, to determine reasons for rejected medication doses, and to determine the reduction in wasted medications. Results: During the 17-month study period, the pharmacy department dispensed 1,506,220 oral liquid and injectable medication doses. From October 2014 through June 2015, the pharmacy department dispensed 826,220 medication doses that were prepared and checked via the workflow management system. Of those 826,220 medication doses, there were 16 reported incorrect volume errors. The error rate after the implementation of the workflow management system averaged 8.4%, which was a 1.6% reduction. After the implementation of the workflow management system, the average number of reported oral liquid medication and injectable medication errors decreased to 0.4 and 0.2 times per week, respectively. Conclusion: The organization was able to achieve its purpose and goal of improving the provision of quality pharmacy care through optimal medication use and safety by reducing medication preparation errors. Error rates decreased and the workflow processes were streamlined, which has led to seamless operations within the pharmacy department. There has been significant cost avoidance and waste reduction and enhanced interdepartmental satisfaction due to the reduction of reported medication errors.

Progressive cone beam CT dose control in image-guided radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan Hao; Cervino, Laura; Jiang, Steve B.

2013-06-15

Purpose: Cone beam CT (CBCT) in image-guided radiotherapy (IGRT) offers a tremendous advantage for treatment guidance. The associated imaging dose is a clinical concern. One unique feature of CBCT-based IGRT is that the same patient is repeatedly scanned during a treatment course, and the contents of CBCT images at different fractions are similar. The authors propose a progressive dose control (PDC) scheme to utilize this temporal correlation for imaging dose reduction. Methods: A dynamic CBCT scan protocol, as opposed to the static one in the current clinical practice, is proposed to gradually reduce the imaging dose in each treatment fraction.more » The CBCT image from each fraction is processed by a prior-image based nonlocal means (PINLM) module to enhance its quality. The increasing amount of prior information from previous CBCT images prevents degradation of image quality due to the reduced imaging dose. Two proof-of-principle experiments have been conducted using measured phantom data and Monte Carlo simulated patient data with deformation. Results: In the measured phantom case, utilizing a prior image acquired at 0.4 mAs, PINLM is able to improve the image quality of a CBCT acquired at 0.2 mAs by reducing the noise level from 34.95 to 12.45 HU. In the synthetic patient case, acceptable image quality is maintained at four consecutive fractions with gradually decreasing exposure levels of 0.4, 0.1, 0.07, and 0.05 mAs. When compared with the standard low-dose protocol of 0.4 mAs for each fraction, an overall imaging dose reduction of more than 60% is achieved. Conclusions: PINLM-PDC is able to reduce CBCT imaging dose in IGRT utilizing the temporal correlations among the sequence of CBCT images while maintaining the quality.« less

Cardiac Dose Reduction with Deep-Inspiratory Breath Hold Technique of Radiotherapy for Left-Sided Breast Cancer

PubMed Central

Sripathi, Lalitha Kameshwari; Ahlawat, Parveen; Simson, David K; Khadanga, Chira Ranjan; Kamarsu, Lakshmipathi; Surana, Shital Kumar; Arasu, Kavi; Singh, Harpreet

2017-01-01

Introduction: Different techniques of radiation therapy have been studied to reduce the cardiac dose in left breast cancer. Aim: In this prospective dosimetric study, the doses to heart as well as other organs at risk (OAR) were compared between free-breathing (FB) and deep inspiratory breath hold (DIBH) techniques in intensity modulated radiotherapy (IMRT) and opposed-tangent three-dimensional radiotherapy (3DCRT) plans. Materials and Methods: Fifteen patients with left-sided breast cancer underwent computed tomography simulation and images were obtained in both FB and DIBH. Radiotherapy plans were generated with 3DCRT and IMRT techniques in FB and DIBH images in each patient. Target coverage, conformity index, homogeneity index, and mean dose to heart (Heart Dmean), left lung, left anterior descending artery (LAD) and right breast were compared between the four plans using the Wilcoxon signed rank test. Results: Target coverage was adequate with both 3DCRT and IMRT plans, but IMRT plans showed better conformity and homogeneity. A statistically significant dose reduction of all OARs was found with DIBH. 3DCRTDIBH decreased the Heart Dmean by 53.5% (7.1 vs. 3.3 Gy) and mean dose to LAD by 28% compared to 3DCRTFB. IMRT further lowered mean LAD dose by 18%. Heart Dmean was lower with 3DCRTDIBH over IMRTDIBH (3.3 vs. 10.2 Gy). Mean dose to the contralateral breast was also lower with 3DCRT over IMRT (0.32 vs. 3.35 Gy). Mean dose and the V20 of ipsilateral lung were lower with 3DCRTDIBH over IMRTDIBH (13.78 vs. 18.9 Gy) and (25.16 vs. 32.95%), respectively. Conclusions: 3DCRTDIBH provided excellent dosimetric results in patients with left-sided breast cancer without the need for IMRT. PMID:28974856

SU-E-T-797: Variations of Cardiac Dose at Different Respiratory Status in CyberKnife M6â„¢ Treatment Plans for Accelerated Partial Breast Irradiation (APBI)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, S; Shang, C; Evans, G

2015-06-15

Purpose: Cyberknife robotic assisted radiation delivery has become a choice for accelerated breast RT, while a slightly increased cardiac dose has been reported. The dose dynamics throughout the respiration cycle has scarcely been explored. This study was designed to investigate the dose changes at each respiratory phase or status during respiration cycle. Methods: Six patients with 4DCT studies and six patients with a pair of free-breathing and deep breath-hold CT sets were used for dosimetry comparisons. 4DCT sets were obtained by Siemens™ CT and its respiratory gating system, comprising of 8 phases. Standard APBI plan at 340 cGy was donemore » per fraction per NSABP B-39/RTOG 0413 and modulated with Cyberknife M6™ on MultiPlan™5.1.2. For the purpose of this study, the tumor volume was outlined in the media-lower quadrant of the left breast. Results: Except for D5cc in plans with 4DCT, cardiac doses are significantly different between respiratory phases in well inhaled breathing phases, and more significantly in plans with BH CT. Mean cardiac doses in 100% inhalation phase were often found to be 5–15% (p< 0.02) less than those in other phases. Conclusion: Although ineligible cardiac doses are noted in APBI plans using 4D free-breathing CT and instantaneous free breathing CT series, a reduction in cardiac dose was seen for the well-inhaled phases. This provides practical guidance for cardiac dose reduction applicable with CK M6 APBR.« less

Lung Volume Reduction After Stereotactic Ablative Radiation Therapy of Lung Tumors: Potential Application to Emphysema

DOE Office of Scientific and Technical Information (OSTI.GOV)

Binkley, Michael S.; Shrager, Joseph B.; Stanford Cancer Institute, Stanford University School of Medicine, Stanford, California

2014-09-01

Purpose: Lung volume reduction surgery (LVRS) improves dyspnea and other outcomes in selected patients with severe emphysema, but many have excessive surgical risk for LVRS. We analyzed the dose-volume relationship for lobar volume reduction after stereotactic ablative radiation therapy (SABR) of lung tumors, hypothesizing that SABR could achieve therapeutic volume reduction if applied in emphysema. Methods and Materials: We retrospectively identified patients treated from 2007 to 2011 who had SABR for 1 lung tumor, pre-SABR pulmonary function testing, and ≥6 months computed tomographic (CT) imaging follow-up. We contoured the treated lobe and untreated adjacent lobe(s) on CT before and after SABRmore » and calculated their volume changes relative to the contoured total (bilateral) lung volume (TLV). We correlated lobar volume reduction with the volume receiving high biologically effective doses (BED, α/β = 3). Results: 27 patients met the inclusion criteria, with a median CT follow-up time of 14 months. There was no grade ≥3 toxicity. The median volume reduction of the treated lobe was 4.4% of TLV (range, −0.4%-10.8%); the median expansion of the untreated adjacent lobe was 2.6% of TLV (range, −3.9%-11.6%). The volume reduction of the treated lobe was positively correlated with the volume receiving BED ≥60 Gy (r{sup 2}=0.45, P=.0001). This persisted in subgroups determined by high versus low pre-SABR forced expiratory volume in 1 second, treated lobe CT emphysema score, number of fractions, follow-up CT time, central versus peripheral location, and upper versus lower lobe location, with no significant differences in effect size between subgroups. Volume expansion of the untreated adjacent lobe(s) was positively correlated with volume reduction of the treated lobe (r{sup 2}=0.47, P<.0001). Conclusions: We identified a dose-volume response for treated lobe volume reduction and adjacent lobe compensatory expansion after lung tumor SABR, consistent across multiple clinical parameters. These data serve to inform our ongoing prospective trial of stereotactic ablative volume reduction (SAVR) for severe emphysema in poor candidates for LVRS.« less

Impact of dose reductions on efficacy outcome in heart transplant patients receiving enteric-coated mycophenolate sodium or mycophenolate mofetil at 12 months post-transplantation.

PubMed

Segovia, Javier; Gerosa, Gino; Almenar, Luis; Livi, Ugolino; Viganò, Mario; Arizón, Jose Maria; Yonan, Nizar; Di Salvo, Thomas G; Renlund, Dale G; Kobashigawa, Jon A

2008-01-01

Mycophenolic acid (MPA) dose reduction is associated with increased risk of rejection and graft loss in renal transplantation. This analysis investigated the impact of MPA dose changes with enteric-coated mycophenolate sodium (EC-MPS) or mycophenolate mofetil (MMF) in de novo heart transplant recipients. In a 12-month, single-blind trial, 154 patients (EC-MPS, 78; MMF, 76) were randomized to either EC-MPS (1080 mg bid) or MMF (1500 mg bid) in combination with cyclosporine and steroids. The primary efficacy variable was the incidence of treatment failure, comprising a composite of biopsy-proven (BPAR) and treated acute rejection, graft loss or death. Significantly fewer patients receiving EC-MPS required > or =2 dose reductions than patients on MMF (26.9% vs. 42.1% of patients, p = 0.048). Accordingly, the average daily dose of EC-MPS as a percentage of the recommended dose was significantly higher than for MMF (88.4% vs. 79.0%, p = 0.016). Among patients requiring > or =1 dose reduction, the incidence of treated BPAR grade > or =3A was significantly lower with EC-MPS compared with MMF (23.4% vs. 44.0%, p = 0.032). These data suggest that EC-MPS-treated heart transplant patients are less likely to require multiple dose reductions than those on MMF which may be associated with a significantly lower risk of treated BPAR > or =3A.

Evaluating the effect of increased pitch, iterative reconstruction and dual source CT on dose reduction and image quality.

PubMed

Gariani, Joanna; Martin, Steve P; Botsikas, Diomidis; Becker, Christoph D; Montet, Xavier

2018-06-14

To compare radiation dose and image quality of thoracoabdominal scans obtained with a high-pitch protocol (pitch 3.2) and iterative reconstruction (Sinogram Affirmed Iterative Reconstruction) in comparison to standard pitch reconstructed with filtered back projection (FBP) using dual source CT. 114 CT scans (Somatom Definition Flash, Siemens Healthineers, Erlangen, Germany), 39 thoracic scans, 54 thoracoabdominal scans and 21 abdominal scans were performed. Analysis of three protocols was undertaken; pitch of 1 reconstructed with FBP, pitch of 3.2 reconstructed with SAFIRE, pitch of 3.2 with stellar detectors reconstructed with SAFIRE. Objective and subjective image analysis were performed. Dose differences of the protocols used were compared. Dose was reduced when comparing scans with a pitch of 1 reconstructed with FBP to high-pitch scans with a pitch of 3.2 reconstructed with SAFIRE with a reduction of volume CT dose index of 75% for thoracic scans, 64% for thoracoabdominal scans and 67% for abdominal scans. There was a further reduction after the implementation of stellar detectors reflected in a reduction of 36% of the dose-length product for thoracic scans. This was not at the detriment of image quality, contrast-to-noise ratio, signal-to-noise ratio and the qualitative image analysis revealed a superior image quality in the high-pitch protocols. The combination of a high pitch protocol with iterative reconstruction allows significant dose reduction in routine chest and abdominal scans whilst maintaining or improving diagnostic image quality, with a further reduction in thoracic scans with stellar detectors. Advances in knowledge: High pitch imaging with iterative reconstruction is a tool that can be used to reduce dose without sacrificing image quality.

In Vivo Dosimetry for Single-Fraction Targeted Intraoperative Radiotherapy (TARGIT) for Breast Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eaton, David J., E-mail: davideaton@nhs.net; Best, Bronagh; Brew-Graves, Chris

Purpose: In vivo dosimetry provides an independent check of delivered dose and gives confidence in the introduction or consistency of radiotherapy techniques. Single-fraction intraoperative radiotherapy of the breast can be performed with the Intrabeam compact, mobile 50 kV x-ray source (Carl Zeiss Surgical, Oberkochen, Germany). Thermoluminescent dosimeters (TLDs) can be used to estimate skin doses during these treatments. Methods and Materials: Measurements of skin doses were taken using TLDs for 72 patients over 3 years of clinical treatments. Phantom studies were also undertaken to assess the uncertainties resulting from changes in beam quality and backscatter conditions in vivo. Results: Themore » mean measured skin dose was 2.9 {+-} 1.6 Gy, with 11% of readings higher than the prescription dose of 6 Gy, but none of these patients showed increased complications. Uncertainties due to beam hardening and backscatter reduction were small compared with overall accuracy. Conclusions: TLDs are a useful and effective method to measure in vivo skin doses in intraoperative radiotherapy and are recommended for the initial validation or any modification to the delivery of this technique. They are also an effective tool to show consistent and safe delivery on a more frequent basis or to determine doses to other critical structures as required.« less

Cargo and Container X-Ray Inspection with Intra-Pulse Multi-Energy Method for Material Discrimination

NASA Astrophysics Data System (ADS)

Saverskiy, Aleksandr Y.; Dinca, Dan-Cristian; Rommel, J. Martin

The Intra-Pulse Multi-Energy (IPME) method of material discrimination mitigates main disadvantages of the traditional "interlaced" approach: ambiguity caused by sampling different regions of cargo and reduction of effective scanning speed. A novel concept of creating multi-energy probing pulses using a standing-wave structure allows maintaining a constant energy spectrum while changing the time duration of each sub-pulse and thus enables adaptive cargo inspection. Depending on the cargo density, the dose delivered to the inspected object is optimized for best material discrimination, maximum material penetration, or lowest dose to cargo. A model based on Monte-Carlo simulation and experimental reference points were developed for the optimization of inspection conditions.

Toward computer-assisted image-guided congenital heart defect repair: an initial phantom analysis.

PubMed

Kwartowitz, David M; Mefleh, Fuad N; Baker, G Hamilton

2017-10-01

Radiation exposure in interventional cardiology is an important consideration, due to risk of cancer and other morbidity to the patient and clinical staff. Cardiac catheterizations rely heavily on fluoroscopic imaging exposing both patient and clinician to ionizing radiation. An image-guided surgery system capable of facilitating cardiac catheterizations was developed and tested to evaluate dose reduction. Several electromagnetically tracked tools were constructed specifically a 7-Fr catheter with five 5-degree-of-freedom magnetic seeds. Catheter guidance was accomplished using our image guidance system Kit for Navigation by Image-Focused Exploration and fluoroscopy alone. A cardiac phantom was designed and 3D printed to validate the image guidance procedure. In mock procedures, an expert clinician guided and deployed an occluder across the septal defect of the phantom heart. The image guidance method resulted in a dose of 1.26 mSv of radiation dose per procedure, while traditional guidance resulted in a dose of 3.33 mSv. Average overall dose savings for the image-guided method was nearly 2.07 mSv or 62 %. The work showed significant ([Formula: see text]) decrease in radiation dose with use of image guidance methods at the expense of a modest increase in procedure time. This study lays the groundwork for further exploration of image guidance applications in pediatric cardiology.

The effect of pomelo citrus (Citrus maxima var. Nambangan), vitamin C and lycopene towards the number reduction of mice (Mus musculus) apoptotic hepatocyte caused of ochratoxin A

NASA Astrophysics Data System (ADS)

Badriyah, Hastuti, Utami Sri

2017-06-01

Foods can contaminated by some mycotoxin produced by molds. Ochratoxin A is a sort of mycotoxin that cause structural damage on hepatocytes. Pomelo citrus (Citrus maxima var. Nambangan) contain vitamin C and lycopene that have antioxidant character. This research is done to: 1)examine the effect of pomelo citrus juice, vitamin C, and lycopene treatment towards the number reduction of mice apoptotic hepatocytes caused by ochratoxin A exposure, 2)examine the effect of vitamin C mixed with lycopene treatment towards the number reduction of mice apoptotic hepatocytes caused by ochratoxin A exposure. The experimental group used male mice strain BALB-C in the age of three month and bodyweight 20-30 grams devided in 4 experiment group and control group. The experiment group I were administered pomelo citrus juice 0,5 ml/30 grams BW/day orally during 2 weeks and then administered with ochratoxin in the dose of 1 mg/kg BW during 1 week. The experiment group II were administered with vitamin C in the dose of 5,85 µg/30g BW with the same methods. The experiment group III were administered with lycopene in the dose of 0,1025 µg/30 g BW with the same methods. The experiment group IV were administered with vitamin C mixed with lycopene with the same methods. The control group were administered with ochratoxin A in the dose of 1 mg/kg BW per oral during 1 week. The apoptotic hepatocyte number were count by microscopic observation of hepatocyte slides from experiment group as well as control group with cytochemical staining. The research result shows that: 1) the pomelo citrus juice, vitamin C as well as lycopene administration could reduce the mice apoptotic hepatocyte number caused by ochratoxin A exposure, compared with the mice apoptotic hepatocyte number caused by ochratoxin A exposure only; 2) the vitamin C mixed with lycopene could reduce the mice apoptotic hepatocyte number caused by ochratoxin A exposure compared with the mice apoptotic hepatocyte number caused by ochratoxin exposure only.

Benchmark studies of induced radioactivity produced in LHC materials, Part II: Remanent dose rates.

PubMed

Brugger, M; Khater, H; Mayer, S; Prinz, A; Roesler, S; Ulrici, L; Vincke, H

2005-01-01

A new method to estimate remanent dose rates, to be used with the Monte Carlo code FLUKA, was benchmarked against measurements from an experiment that was performed at the CERN-EU high-energy reference field facility. An extensive collection of samples of different materials were placed downstream of, and laterally to, a copper target, intercepting a positively charged mixed hadron beam with a momentum of 120 GeV c(-1). Emphasis was put on the reduction of uncertainties by taking measures such as careful monitoring of the irradiation parameters, using different instruments to measure dose rates, adopting detailed elemental analyses of the irradiated materials and making detailed simulations of the irradiation experiment. The measured and calculated dose rates are in good agreement.

PWR Facility Dose Modeling Using MCNP5 and the CADIS/ADVANTG Variance-Reduction Methodology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blakeman, Edward D; Peplow, Douglas E.; Wagner, John C

2007-09-01

The feasibility of modeling a pressurized-water-reactor (PWR) facility and calculating dose rates at all locations within the containment and adjoining structures using MCNP5 with mesh tallies is presented. Calculations of dose rates resulting from neutron and photon sources from the reactor (operating and shut down for various periods) and the spent fuel pool, as well as for the photon source from the primary coolant loop, were all of interest. Identification of the PWR facility, development of the MCNP-based model and automation of the run process, calculation of the various sources, and development of methods for visually examining mesh tally filesmore » and extracting dose rates were all a significant part of the project. Advanced variance reduction, which was required because of the size of the model and the large amount of shielding, was performed via the CADIS/ADVANTG approach. This methodology uses an automatically generated three-dimensional discrete ordinates model to calculate adjoint fluxes from which MCNP weight windows and source bias parameters are generated. Investigative calculations were performed using a simple block model and a simplified full-scale model of the PWR containment, in which the adjoint source was placed in various regions. In general, it was shown that placement of the adjoint source on the periphery of the model provided adequate results for regions reasonably close to the source (e.g., within the containment structure for the reactor source). A modification to the CADIS/ADVANTG methodology was also studied in which a global adjoint source is weighted by the reciprocal of the dose response calculated by an earlier forward discrete ordinates calculation. This method showed improved results over those using the standard CADIS/ADVANTG approach, and its further investigation is recommended for future efforts.« less

Dose and scatter characteristics of a novel cone beam CT system for musculoskeletal extremities

NASA Astrophysics Data System (ADS)

Zbijewski, W.; Sisniega, A.; Vaquero, J. J.; Muhit, A.; Packard, N.; Senn, R.; Yang, D.; Yorkston, J.; Carrino, J. A.; Siewerdsen, J. H.

2012-03-01

A novel cone-beam CT (CBCT) system has been developed with promising capabilities for musculoskeletal imaging (e.g., weight-bearing extremities and combined radiographic / volumetric imaging). The prototype system demonstrates diagnostic-quality imaging performance, while the compact geometry and short scan orbit raise new considerations for scatter management and dose characterization that challenge conventional methods. The compact geometry leads to elevated, heterogeneous x-ray scatter distributions - even for small anatomical sites (e.g., knee or wrist), and the short scan orbit results in a non-uniform dose distribution. These complex dose and scatter distributions were investigated via experimental measurements and GPU-accelerated Monte Carlo (MC) simulation. The combination provided a powerful basis for characterizing dose distributions in patient-specific anatomy, investigating the benefits of an antiscatter grid, and examining distinct contributions of coherent and incoherent scatter in artifact correction. Measurements with a 16 cm CTDI phantom show that the dose from the short-scan orbit (0.09 mGy/mAs at isocenter) varies from 0.16 to 0.05 mGy/mAs at various locations on the periphery (all obtained at 80 kVp). MC estimation agreed with dose measurements within 10-15%. Dose distribution in patient-specific anatomy was computed with MC, confirming such heterogeneity and highlighting the elevated energy deposition in bone (factor of ~5-10) compared to soft-tissue. Scatter-to-primary ratio (SPR) up to ~1.5-2 was evident in some regions of the knee. A 10:1 antiscatter grid was found earlier to result in significant improvement in soft-tissue imaging performance without increase in dose. The results of MC simulations elucidated the mechanism behind scatter reduction in the presence of a grid. A ~3-fold reduction in average SPR was found in the MC simulations; however, a linear grid was found to impart additional heterogeneity in the scatter distribution, mainly due to the increase in the contribution of coherent scatter with increased spatial variation. Scatter correction using MC-generated scatter distributions demonstrated significant improvement in cupping and streaks. Physical experimentation combined with GPU-accelerated MC simulation provided a sophisticated, yet practical approach in identifying low-dose acquisition techniques, optimizing scatter correction methods, and evaluating patientspecific dose.

Ultra-Low-Dose Fetal CT With Model-Based Iterative Reconstruction: A Prospective Pilot Study.

PubMed

Imai, Rumi; Miyazaki, Osamu; Horiuchi, Tetsuya; Asano, Keisuke; Nishimura, Gen; Sago, Haruhiko; Nosaka, Shunsuke

2017-06-01

Prenatal diagnosis of skeletal dysplasia by means of 3D skeletal CT examination is highly accurate. However, it carries a risk of fetal exposure to radiation. Model-based iterative reconstruction (MBIR) technology can reduce radiation exposure; however, to our knowledge, the lower limit of an optimal dose is currently unknown. The objectives of this study are to establish ultra-low-dose fetal CT as a method for prenatal diagnosis of skeletal dysplasia and to evaluate the appropriate radiation dose for ultra-low-dose fetal CT. Relationships between tube current and image noise in adaptive statistical iterative reconstruction and MBIR were examined using a 32-cm CT dose index (CTDI) phantom. On the basis of the results of this examination and the recommended methods for the MBIR option and the known relationship between noise and tube current for filtered back projection, as represented by the expression SD = (milliamperes) -0.5 , the lower limit of the optimal dose in ultra-low-dose fetal CT with MBIR was set. The diagnostic power of the CT images obtained using the aforementioned scanning conditions was evaluated, and the radiation exposure associated with ultra-low-dose fetal CT was compared with that noted in previous reports. Noise increased in nearly inverse proportion to the square root of the dose in adaptive statistical iterative reconstruction and in inverse proportion to the fourth root of the dose in MBIR. Ultra-low-dose fetal CT was found to have a volume CTDI of 0.5 mGy. Prenatal diagnosis was accurately performed on the basis of ultra-low-dose fetal CT images that were obtained using this protocol. The level of fetal exposure to radiation was 0.7 mSv. The use of ultra-low-dose fetal CT with MBIR led to a substantial reduction in radiation exposure, compared with the CT imaging method currently used at our institution, but it still enabled diagnosis of skeletal dysplasia without reducing diagnostic power.

REDUCTION OF DOSES IN DIAGNOSTIC USES OF RADIOISOTOPES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosain, F.

1960-03-01

> A moderately low-level counting technique with anticoincidence gas- flow counter was developed for use in metabolic and diagnostic tracer studies with radioisotopes. Several important experiments and results were reported which have been carried out with reduced doses of tracer isotopes. A reduction of the tracer dose of ahout 1/30th of the present conventional doses was achieved which helps to minimize the chances of radiation hazards. (auth)

Dose reduction of risperidone and olanzapine and estimated dopamine D₂ receptor occupancy in stable patients with schizophrenia: findings from an open-label, randomized, controlled study.

PubMed

Takeuchi, Hiroyoshi; Suzuki, Takefumi; Bies, Robert R; Remington, Gary; Watanabe, Koichiro; Mimura, Masaru; Uchida, Hiroyuki

2014-11-01

While acute-phase antipsychotic response has been attributed to 65%-80% dopamine D₂ receptor blockade, the degree of occupancy for relapse prevention in the maintenance treatment of schizophrenia remains unknown. In this secondary study of an open-label, 28-week, randomized, controlled trial conducted between April 2009 and August 2011, clinically stable patients with schizophrenia (DSM-IV) treated with risperidone or olanzapine were randomly assigned to the reduction group (dose reduced by 50%) or maintenance group (dose kept constant). Plasma antipsychotic concentrations at peak and trough before and after dose reduction were estimated with population pharmacokinetic techniques, using 2 collected plasma samples. Corresponding dopamine D₂ occupancy levels were then estimated using the model we developed. Relapse was defined as worsening in 4 Positive and Negative Syndrome Scale-Positive subscale items: delusion, conceptual disorganization, hallucinatory behavior, and suspiciousness. Plasma antipsychotic concentrations were available for 16 and 15 patients in the reduction and maintenance groups, respectively. Estimated dopamine D₂ occupancy (mean ± SD) decreased following dose reduction from 75.6% ± 4.9% to 66.8% ± 6.4% at peak and 72.3% ± 5.7% to 62.0% ± 6.8% at trough. In the reduction group, 10 patients (62.5%) did not demonstrate continuous D₂ receptor blockade above 65% (ie, < 65% at trough) after dose reduction; furthermore, 7 patients (43.8%) did not achieve a threshold of 65% occupancy even at peak. Nonetheless, only 1 patient met our relapse criteria after dose reduction during the 6 months of the study. The results suggest that the therapeutic threshold regarding dopamine D₂ occupancy may be lower for those who are stable in antipsychotic maintenance versus acute-phase treatment. Positron emission tomography studies are warranted to further test our preliminary findings. UMIN Clinical Trials Registry identifier: UMIN000001834. © Copyright 2014 Physicians Postgraduate Press, Inc.

SU-E-T-632: A Dosimetric Comparison of the 3D-CRT Planning of Chest Wall in Post-Mastectomy Breast Cancer Patients, with and Without Breast Board Setup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muzaffar, Ambreen; Masood, Asif; Ullah, Haseeb

2014-06-15

Purpose: Breast boards are used in breast radiation which increases normal lung and heart doses, when supraclavicular field is included. Therefore, in this study through dose volume histogram (DVHs), lung and heart doses comparison was done between two different setups i.e. with and without breast board, for the treatment of left chest wall and supraclavicular fossa in postmastectomy left breast cancer. Methods: In this study, CT-Simulation scans of ten breast cancer patients were done with and without breast board, at Shifa International Hospitals Islamabad, to investigate the differences between the two different setups of the irradiation of left chest wallmore » in terms of lung and heart doses. For immobilization, support under the neck, shoulders and arms was used. Precise PLAN 2.15 treatment planning system (TPS) was used for 3D-CRT planning. The total prescribed dose for both the plans was 5000 cGy/25 fractions. The chest wall was treated with a pair of tangential photon fields and the upper supraclavicular nodal regions were treated with an anterior photon field. A mono-isocentric technique was used to match the tangential fields with the anterior field at the isocentre. The dose volume histogram was used to compare the doses of heart and ipsilateral lung. Results: Both the plans of each patient were generated and compared. DVH results showed that for the same PTV dose coverage, plans without breast board resulted in a reduction of lung and heart doses compared with the plans with breast board. There was significant reductions in V20, V<25 and mean doses for lung and V<9 and mean doses for heart. Conclusion: In comparison of both the plans, setup without breast board significantly reduced the dose-volume of the ipsilateral lung and heart in left chest wall patients. Waived registration request has been submitted.« less

Metallic artifact mitigation and organ-constrained tissue assignment for Monte Carlo calculations of permanent implant lung brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutherland, J. G. H.; Miksys, N.; Thomson, R. M., E-mail: rthomson@physics.carleton.ca

2014-01-15

Purpose: To investigate methods of generating accurate patient-specific computational phantoms for the Monte Carlo calculation of lung brachytherapy patient dose distributions. Methods: Four metallic artifact mitigation methods are applied to six lung brachytherapy patient computed tomography (CT) images: simple threshold replacement (STR) identifies high CT values in the vicinity of the seeds and replaces them with estimated true values; fan beam virtual sinogram replaces artifact-affected values in a virtual sinogram and performs a filtered back-projection to generate a corrected image; 3D median filter replaces voxel values that differ from the median value in a region of interest surrounding the voxelmore » and then applies a second filter to reduce noise; and a combination of fan beam virtual sinogram and STR. Computational phantoms are generated from artifact-corrected and uncorrected images using several tissue assignment schemes: both lung-contour constrained and unconstrained global schemes are considered. Voxel mass densities are assigned based on voxel CT number or using the nominal tissue mass densities. Dose distributions are calculated using the EGSnrc user-code BrachyDose for{sup 125}I, {sup 103}Pd, and {sup 131}Cs seeds and are compared directly as well as through dose volume histograms and dose metrics for target volumes surrounding surgical sutures. Results: Metallic artifact mitigation techniques vary in ability to reduce artifacts while preserving tissue detail. Notably, images corrected with the fan beam virtual sinogram have reduced artifacts but residual artifacts near sources remain requiring additional use of STR; the 3D median filter removes artifacts but simultaneously removes detail in lung and bone. Doses vary considerably between computational phantoms with the largest differences arising from artifact-affected voxels assigned to bone in the vicinity of the seeds. Consequently, when metallic artifact reduction and constrained tissue assignment within lung contours are employed in generated phantoms, this erroneous assignment is reduced, generally resulting in higher doses. Lung-constrained tissue assignment also results in increased doses in regions of interest due to a reduction in the erroneous assignment of adipose to voxels within lung contours. Differences in dose metrics calculated for different computational phantoms are sensitive to radionuclide photon spectra with the largest differences for{sup 103}Pd seeds and smallest but still considerable differences for {sup 131}Cs seeds. Conclusions: Despite producing differences in CT images, dose metrics calculated using the STR, fan beam + STR, and 3D median filter techniques produce similar dose metrics. Results suggest that the accuracy of dose distributions for permanent implant lung brachytherapy is improved by applying lung-constrained tissue assignment schemes to metallic artifact corrected images.« less

Radiation exposure from Chest CT: Issues and Strategies

PubMed Central

Maher, Michael M.; Rizzo, Stefania; Kanarek, David; Shephard, Jo-Anne O.

2004-01-01

Concerns have been raised over alleged overuse of CT scanning and inappropriate selection of scanning methods, all of which expose patients to unnecessary radiation. Thus, it is important to identify clinical situations in which techniques with lower radiation dose such as plain radiography or no radiation such as MRI and occasionally ultrasonography can be chosen over CT scanning. This article proposes the arguments for radiation dose reduction in CT scanning of the chest and discusses recommended practices and studies that address means of reducing radiation exposure associated with CT scanning of the chest. PMID:15082885

[Detection of lung nodules. New opportunities in chest radiography].

PubMed

Pötter-Lang, S; Schalekamp, S; Schaefer-Prokop, C; Uffmann, M

2014-05-01

Chest radiography still represents the most commonly performed X-ray examination because it is readily available, requires low radiation doses and is relatively inexpensive. However, as previously published, many initially undetected lung nodules are retrospectively visible in chest radiographs. The great improvements in detector technology with the increasing dose efficiency and improved contrast resolution provide a better image quality and reduced dose needs. The dual energy acquisition technique and advanced image processing methods (e.g. digital bone subtraction and temporal subtraction) reduce the anatomical background noise by reduction of overlapping structures in chest radiography. Computer-aided detection (CAD) schemes increase the awareness of radiologists for suspicious areas. The advanced image processing methods show clear improvements for the detection of pulmonary lung nodules in chest radiography and strengthen the role of this method in comparison to 3D acquisition techniques, such as computed tomography (CT). Many of these methods will probably be integrated into standard clinical treatment in the near future. Digital software solutions offer advantages as they can be easily incorporated into radiology departments and are often more affordable as compared to hardware solutions.

Magnitudes of biomarker reductions in response to controlled reductions in cigarettes smoked per day: a one-week clinical confinement study.

PubMed

Theophilus, Eugenia H; Coggins, Christopher R E; Chen, Peter; Schmidt, Eckhardt; Borgerding, Michael F

2015-03-01

Tobacco toxicant-related exposure reduction is an important tool in harm reduction. Cigarette per day reduction (CPDR) occurs as smokers migrate from smoking cigarettes to using alternative tobacco/nicotine products, or quit smoking. Few reports characterize the dose-response relationships between CPDR and effects on exposure biomarkers, especially at the low end of CPD exposure (e.g., 5 CPD). We present data on CPDR by characterizing magnitudes of biomarker reductions. We present data from a well-controlled, one-week clinical confinement study in healthy smokers who were switched from smoking 19-25 CPD to smoking 20, 10, 5 or 0 CPD. Biomarkers were measured in blood, plasma, urine, and breath, and included smoke-related toxicants, urine mutagenicity, smoked cigarette filter analyses (mouth level exposure), and vital signs. Many of the biomarkers (e.g., plasma nicotine) showed strong CPDR dose-response reductions, while others (e.g., plasma thiocyanate) showed weaker dose-response reductions. Factors that lead to lower biomarker reductions include non-CPD related contributors to the measured response (e.g., other exposure sources from environment, life style, occupation; inter-individual variability). This study confirms CPDR dose-responsive biomarkers and suggests that a one-week design is appropriate for characterizing exposure reductions when smokers switch from cigarettes to new tobacco products. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Detection of calcification clusters in digital breast tomosynthesis slices at different dose levels utilizing a SRSAR reconstruction and JAFROC

NASA Astrophysics Data System (ADS)

Timberg, P.; Dustler, M.; Petersson, H.; Tingberg, A.; Zackrisson, S.

2015-03-01

Purpose: To investigate detection performance for calcification clusters in reconstructed digital breast tomosynthesis (DBT) slices at different dose levels using a Super Resolution and Statistical Artifact Reduction (SRSAR) reconstruction method. Method: Simulated calcifications with irregular profile (0.2 mm diameter) where combined to form clusters that were added to projection images (1-3 per abnormal image) acquired on a DBT system (Mammomat Inspiration, Siemens). The projection images were dose reduced by software to form 35 abnormal cases and 25 normal cases as if acquired at 100%, 75% and 50% dose level (AGD of approximately 1.6 mGy for a 53 mm standard breast, measured according to EUREF v0.15). A standard FBP and a SRSAR reconstruction method (utilizing IRIS (iterative reconstruction filters), and outlier detection using Maximum-Intensity Projections and Average-Intensity Projections) were used to reconstruct single central slices to be used in a Free-response task (60 images per observer and dose level). Six observers participated and their task was to detect the clusters and assign confidence rating in randomly presented images from the whole image set (balanced by dose level). Each trial was separated by one weeks to reduce possible memory bias. The outcome was analyzed for statistical differences using Jackknifed Alternative Free-response Receiver Operating Characteristics. Results: The results indicate that it is possible reduce the dose by 50% with SRSAR without jeopardizing cluster detection. Conclusions: The detection performance for clusters can be maintained at a lower dose level by using SRSAR reconstruction.

Mammographic film-processor temperature, development time, and chemistry: effect on dose, contrast, and noise.

PubMed

Kimme-Smith, C; Rothschild, P A; Bassett, L W; Gold, R H; Moler, C

1989-01-01

Six different combinations of film-processor temperature (33.3 degrees C, 35 degrees C), development time (22 sec, 44 sec), and chemistry (Du Pont medium contrast developer [MCD] and Kodak rapid process [RP] developer) were each evaluated by separate analyses with Hurter and Driffield curves, test images of plastic step wedges, noise variance analysis, and phantom images; each combination also was evaluated clinically. Du Pont MCD chemistry produced greater contrast than did Kodak RP chemistry. A change in temperature from 33.3 degrees C (92 degrees F) to 35 degrees C (95 degrees F) had the least effect on dose and image contrast. Temperatures of 36.7 degrees C (98 degrees F) and 38.3 degrees C (101 degrees F) also were tested with extended processing. The speed increased for 36.7 degrees C but decreased at 38.3 degrees C. Base plus fog increased, but contrast decreased for these higher temperatures. Increasing development time had the greatest effect on decreasing the dose required for equivalent film darkening when imaging BR12 breast equivalent test objects; ion chamber measurements showed a 32% reduction in dose when the development time was increased from 22 to 44 sec. Although noise variance doubled in images processed with the extended development time, diagnostic capability was not compromised. Extending the processing time for mammographic films was an effective method of dose reduction, whereas varying the processing temperature and chemicals had less effect on contrast and dose.

Characterization and implementation of OSL dosimeters for use in evaluating the efficacy of organ-based tube current modulation for CT scans of the face and orbits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsh, R. M.; Silosky, M., E-mail: michael.silosky@ucdenver.edu

Purpose: The purpose of this work was to characterize commercially available optically stimulated luminescent (OSL) dosimeters for general clinical applications and apply the results to the development of a method to evaluate the efficacy of a vendor-specific organ-based tube current modulation application for both phantom and clinical computed tomography (CT) scans of the face and orbits. Methods: This study consisted of three components: (1) thorough characterization of the dosimeters for CT scans in phantom, including evaluations of depletion, fading, angular dependence, and conversion from counts to absorbed dose; (2) evaluation of the efficacy of using plastic glasses to position themore » dosimeters over the eyes in both phantom and clinical studies; and (3) preliminary dosimetry measurements made using organ-based tube current modulation in computed tomography dose index (CTDI) and anthropomorphic phantom studies. Results: (1) Depletion effects were found to have a linear relationship with the output of the OSL dosimeters (R{sup 2} = 0.96). Fading was found to affect dosimeter readings during the first two hours following exposure but had no effect during the remaining 60-h period observed. No significant angular dependence was observed for the exposure conditions used in this study (with p-values ranging from 0.9 to 0.26 for all t-tests). Dosimeter counts varied linearly with absorbed dose when measured in the center and 12 o’clock positions of the CTDI phantoms. These linear models of counts versus absorbed dose had overlapping 95% confidence intervals for the intercepts but not for the slopes. (2) When dosimeters were positioned using safety glasses, there was no adverse effect on image quality, and there was no statistically significant difference between this placement and placement of the dosimeters directly on the eyes of the phantom (p = 0.24). (3) When using organ-based tube current modulation, the dose to the lens of the eye was reduced between 19% and 43%, depending on the scan protocol used and the positioning of the phantom. Furthermore, the amount of dose reduction was significantly affected by the vertical position of the phantom, with the largest reduction in dose seen when the phantom was centered in the gantry. Conclusions: (1) An appropriate correction factor, specific to CT scanning, was developed to account for depletion and fading characteristics of the dosimeters. Additionally, an equation to convert dosimeter counts to absorbed dose was established. (2) The use of plastic safety glasses was validated as an appropriate positioning device when measuring dose to the lens of the eye. (3) The use of organ-based tube current modulation can reduce dose to the lens of the eye during CT scanning. The amount of dose reduction, however, is largely influenced by the positioning of the anatomy in the gantry.« less

Effect of Edge-Preserving Adaptive Image Filter on Low-Contrast Detectability in CT Systems: Application of ROC Analysis

PubMed Central

Okumura, Miwa; Ota, Takamasa; Kainuma, Kazuhisa; Sayre, James W.; McNitt-Gray, Michael; Katada, Kazuhiro

2008-01-01

Objective. For the multislice CT (MSCT) systems with a larger number of detector rows, it is essential to employ dose-reduction techniques. As reported in previous studies, edge-preserving adaptive image filters, which selectively eliminate only the noise elements that are increased when the radiation dose is reduced without affecting the sharpness of images, have been developed. In the present study, we employed receiver operating characteristic (ROC) analysis to assess the effects of the quantum denoising system (QDS), which is an edge-preserving adaptive filter that we have developed, on low-contrast resolution, and to evaluate to what degree the radiation dose can be reduced while maintaining acceptable low-contrast resolution. Materials and Methods. The low-contrast phantoms (Catphan 412) were scanned at various tube current settings, and ROC analysis was then performed for the groups of images obtained with/without the use of QDS at each tube current to determine whether or not a target could be identified. The tube current settings for which the area under the ROC curve (Az value) was approximately 0.7 were determined for both groups of images with/without the use of QDS. Then, the radiation dose reduction ratio when QDS was used was calculated by converting the determined tube current to the radiation dose. Results. The use of the QDS edge-preserving adaptive image filter allowed the radiation dose to be reduced by up to 38%. Conclusion. The QDS was found to be useful for reducing the radiation dose without affecting the low-contrast resolution in MSCT studies. PMID:19043565

Does initial dosing of levothyroxine in infants with congenital hypothyroidism lead to frequent dose adjustments secondary to iatrogenic hyperthyroidism on follow-up?

PubMed

Craven, Meghan; Frank, Graeme R

2018-06-27

Congenital hypothyroidism (CH) is the most common preventable cause of intellectual disability. The recommended starting dose of levothyroxine (LT4) is between 10 and 15 μg/kg, an extremely wide range. We hypothesized that a sizable proportion of newborns treated for CH at the higher end of the dosage range become biochemically hyperthyroid at a follow-up visit. This study is a retrospective chart review of infants with CH between 2002 and 2012. Of the 104 patients included in this analysis, the average age at diagnosis was 11 days and the average starting dose of LT4 was 12±2.5 μg/kg. At follow-up, 36.5% required a dose reduction because of iatrogenic hyperthyroxinemia, 51% required no dose adjustment and 12.5% required a dose increase due to an elevated thyroid stimulating hormone (TSH). The starting doses of LT4 for those requiring a dose reduction, those not requiring an adjustment and those requiring an increase in the dose were 13.2±2.4, 11.5±2.1 and 10.3±2.6 μg/kg/day, respectively (p≤0.0001). Of the 34% of infants treated with an initial dose of >12.5 μg/day, 57.1% required a dose reduction at follow-up, compared to 26.1% of those whose initial starting dose was ≤12.5 μg/kg/day (p=0.007). Following the guidelines for initiating therapy for CH, 36.5% of the infants required a dose reduction for iatrogenic hyperthyroxinemia. These infants received a higher dose of LT4 than the infants who either required no adjustment or required an increase in the dose. A narrower range for initial dosing in CH may be appropriate.

Methods for Reducing Normal Tissue Complication Probabilities in Oropharyngeal Cancer: Dose Reduction or Planning Target Volume Elimination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samuels, Stuart E.; Eisbruch, Avraham; Vineberg, Karen

Purpose: Strategies to reduce the toxicities of head and neck radiation (ie, dysphagia [difficulty swallowing] and xerostomia [dry mouth]) are currently underway. However, the predicted benefit of dose and planning target volume (PTV) reduction strategies is unknown. The purpose of the present study was to compare the normal tissue complication probabilities (NTCP) for swallowing and salivary structures in standard plans (70 Gy [P70]), dose-reduced plans (60 Gy [P60]), and plans eliminating the PTV margin. Methods and Materials: A total of 38 oropharyngeal cancer (OPC) plans were analyzed. Standard organ-sparing volumetric modulated arc therapy plans (P70) were created and then modified by eliminatingmore » the PTVs and treating the clinical tumor volumes (CTVs) only (C70) or maintaining the PTV but reducing the dose to 60 Gy (P60). NTCP dose models for the pharyngeal constrictors, glottis/supraglottic larynx, parotid glands (PGs), and submandibular glands (SMGs) were analyzed. The minimal clinically important benefit was defined as a mean change in NTCP of >5%. The P70 NTCP thresholds and overlap percentages of the organs at risk with the PTVs (56-59 Gy, vPTV{sub 56}) were evaluated to identify the predictors for NTCP improvement. Results: With the P60 plans, only the ipsilateral PG (iPG) benefited (23.9% vs 16.2%; P<.01). With the C70 plans, only the iPG (23.9% vs 17.5%; P<.01) and contralateral SMG (cSMG) (NTCP 32.1% vs 22.9%; P<.01) benefited. An iPG NTCP threshold of 20% and 30% predicted NTCP benefits for the P60 and C70 plans, respectively (P<.001). A cSMG NTCP threshold of 30% predicted for an NTCP benefit with the C70 plans (P<.001). Furthermore, for the iPG, a vPTV{sub 56} >13% predicted benefit with P60 (P<.001) and C70 (P=.002). For the cSMG, a vPTV{sub 56} >22% predicted benefit with C70 (P<.01). Conclusions: PTV elimination and dose-reduction lowered the NTCP of the iPG, and PTV elimination lowered the NTCP of the cSMG. NTCP thresholds and the percentage of overlap of the PTV with organs at risk can predict which patients will benefit and inform future clinical trial design.« less

TU-AB-201-08: Rotating Shield High Dose Rate Brachytherapy with 153Gd and 75Se Isotopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renaud, M; Seuntjens, J; Enger, S

Purpose: To introduce rotating shield brachytherapy (RSBT) for different cancer sites with {sup 153}Gd and {sup 75}Se isotopes. RSBT is a form of intensity modulated brachytherapy, using shielded rotating catheters to provide a better dose distribution in the tumour while protecting healthy tissue. Methods: BrachySource, a Geant4-based Monte Carlo dose planning system was developed for investigation of RSBT with {sup 153}Gd and {sup 75}Se for different cancer sites. Dose distributions from {sup 153}Gd, {sup 75}Se and {sup 192}Ir isotopes were calculated in a 40 cm radius water phantom by using the microSelectron-v2 source model. The source was placed inside amore » cylindrical platinum shield with 1.3 mm diameter. An emission window coinciding with the active core of the source was created by removing half (180°) of the wall of the shield. Relative dose rate distributions of the three isotopes were simulated. As a proof of concept, a breast cancer patient originally treated with Mammosite was re-simulated with unshielded {sup 192}Ir and shielded {sup 153}Gd. Results: The source with the lowest energy, {sup 153}Gd, decreased the dose on the shielded side by 91%, followed by {sup 75}Se and {sup 192}Ir with 36% and 16% reduction at 1 cm from the source. The breast cancer patient simulation showed the ability of shielded {sup 153}Gd to spare the chest wall by a 90% dose reduction when only one emission window angle is considered. In this case, fully covering the PTV would require more delivery angles and the chest wall dose reduction would be less, however, the simulation demonstrates the potential of shielded {sup 153}Gd to selectively isolate organs at risk. Conclusion: Introducing {sup 153}Gd and {sup 75}Se sources combined with RSBT will allow escalation of dose in the target volume while maintaining low doses in radiation sensitive healthy tissue. Tailoring treatments to each individual patient by treating all parts of the tumour without over-irradiation of normal tissues will be possible. The author acknowledges partial support by the CREATE Medical Physics Research Training Network grant of the Natural Sciences and Engineering Research Council (Grant number: 432290), and the Quebec Fonds de recherche Nature et Technologies.« less

Comparison of cardiac and lung doses for breast cancer patients with free breathing and deep inspiration breath hold technique in 3 dimensional conformal radiotherapy - a dosimetric study

NASA Astrophysics Data System (ADS)

Raj Mani, Karthick; Poudel, Suresh; Maria Das, K. J.

2017-12-01

Purpose: To investigate the cardio-pulmonary doses between Deep Inspiration Breath Hold (DIBH) and Free Breathing (FB) technique in left sided breast irradiation. Materials & Methods: DIBH CT and FB CT were acquired for 10 left sided breast patients who underwent whole breast irradiation with or without nodal irradiation. Three fields single isocenter technique were used for patients with node positive patients along with two tangential conformal fields whereas only two tangential fields were used in node negative patients. All the critical structures like lungs, heart, esophagus, thyroid, etc., were delineated in both DIBH and FB scan. Both DIBH and FB scans were fused with the Dicom origin as they were acquired with the same Dicom coordinates. Plans were created in the DIBH scan for a dose range between 50 Gy in 25 fractions. Critical structures doses were recorded from the Dose Volume Histogram for both the DIBH and FB data set for evaluation. Results: The average mean heart dose in DIBH vs FB was 13.18 Gy vs 6.97 Gy, (p = 0.0063) significantly with DIBH as compared to FB technique. The relative reduction in average mean heart dose was 47.12%. The relative V5 reduced by 14.70% (i.e. 34.42% vs 19.72%, p = 0.0080), V10 reduced by 13.83% (i.e. 27.79 % vs 13.96%, p = 0.0073). V20 reduced by 13.19% (i.e. 24.54 % vs 11.35%, p = 0.0069), V30 reduced by 12.38% (i.e. 22.27 % vs 9.89 %, p = 0.0073) significantly with DIBH as compared to FB. The average mean left lung dose reduced marginally by 1.43 Gy (13.73 Gy vs 12.30 Gy, p = 0.4599) but insignificantly with DIBH as compared to FB. Other left lung parameters (V5, V10, V20 and V30) shows marginal decreases in DIBH plans compare to FB plans. Conclusion: DIBH shows a substantial reduction of cardiac doses but slight and insignificant reduction of pulmonary doses as compared with FB technique. Using the simple DIBH technique, we can effectively reduce the cardiac morbidity and at the same time radiation induced lung pneumonitis is unlikely to increase.

Treatment of BK virus-associated hemorrhagic cystitis with low-dose intravenous cidofovir in patients undergoing allogeneic hematopoietic cell transplantation

PubMed Central

Lee, Seung-Shin; Jung, Sung-Hoon; Ahn, Seo-Yeon; Kim, Jae-Yong; Jang, Hee-Chang; Kang, Seung-Ji; Jang, Mi-Ok; Yang, Deok-Hwan; Kim, Yeo-Kyeoung; Lee, Je-Jung; Kim, Hyeoung-Joon

2015-01-01

Background/Aims BK virus (BKV) has been associated with late-onset hemorrhagic cystitis (HC) in recipients of hematopoietic stem cell transplantation (HSCT). Cidofovir has been used at higher doses (3 to 5 mg/kg/wk) with probenecid prophylaxis; however, cidofovir may result in nephrotoxicity or cytopenia at high doses. Methods Allogeneic HSCT recipients with BKV-associated HC are treated with 1 mg/kg intravenous cidofovir weekly at our institution. A microbiological response was defined as at least a one log reduction in urinary BKV viral load, and a clinical response was defined as improvement in symptoms and stability or reduction in cystitis grade. Results Eight patients received a median of 4 weekly (range, 2 to 11) doses of cidofovir. HC occurred a median 69 days (range, 16 to 311) after allogeneic HSCT. A clinical response was detected in 7/8 patients (86%), and 4/5 (80%) had a measurable microbiological response. One patient died of uncontrolled graft-versus-host disease; therefore, we could not measure the clinical response to HC treatment. One microbiological non-responder had a stable BKV viral load with clinical improvement. Only three patients showed transient grade 2 serum creatinine toxicities, which resolved after completion of concomitant calcineurin inhibitor treatment. Conclusions Weekly intravenous low-dose cidofovir without probenecid appears to be a safe and effective treatment option for patients with BKV-associated HC. PMID:25750563

Optimizing Radiation Doses for Computed Tomography Across Institutions: Dose Auditing and Best Practices.

PubMed

Demb, Joshua; Chu, Philip; Nelson, Thomas; Hall, David; Seibert, Anthony; Lamba, Ramit; Boone, John; Krishnam, Mayil; Cagnon, Christopher; Bostani, Maryam; Gould, Robert; Miglioretti, Diana; Smith-Bindman, Rebecca

2017-06-01

Radiation doses for computed tomography (CT) vary substantially across institutions. To assess the impact of institutional-level audit and collaborative efforts to share best practices on CT radiation doses across 5 University of California (UC) medical centers. In this before/after interventional study, we prospectively collected radiation dose metrics on all diagnostic CT examinations performed between October 1, 2013, and December 31, 2014, at 5 medical centers. Using data from January to March (baseline), we created audit reports detailing the distribution of radiation dose metrics for chest, abdomen, and head CT scans. In April, we shared reports with the medical centers and invited radiology professionals from the centers to a 1.5-day in-person meeting to review reports and share best practices. We calculated changes in mean effective dose 12 weeks before and after the audits and meeting, excluding a 12-week implementation period when medical centers could make changes. We compared proportions of examinations exceeding previously published benchmarks at baseline and following the audit and meeting, and calculated changes in proportion of examinations exceeding benchmarks. Of 158 274 diagnostic CT scans performed in the study period, 29 594 CT scans were performed in the 3 months before and 32 839 CT scans were performed 12 to 24 weeks after the audit and meeting. Reductions in mean effective dose were considerable for chest and abdomen. Mean effective dose for chest CT decreased from 13.2 to 10.7 mSv (18.9% reduction; 95% CI, 18.0%-19.8%). Reductions at individual medical centers ranged from 3.8% to 23.5%. The mean effective dose for abdominal CT decreased from 20.0 to 15.0 mSv (25.0% reduction; 95% CI, 24.3%-25.8%). Reductions at individual medical centers ranged from 10.8% to 34.7%. The number of CT scans that had an effective dose measurement that exceeded benchmarks was reduced considerably by 48% and 54% for chest and abdomen, respectively. After the audit and meeting, head CT doses varied less, although some institutions increased and some decreased mean head CT doses and the proportion above benchmarks. Reviewing institutional doses and sharing dose-optimization best practices resulted in lower radiation doses for chest and abdominal CT and more consistent doses for head CT.

Is sympathetic neural vasoconstriction blunted in the vascular bed of exercising human muscle?

PubMed

Tschakovsky, Michael E; Sujirattanawimol, Kittiphong; Ruble, Stephen B; Valic, Zoran; Joyner, Michael J

2002-06-01

Sympathetic vasoconstriction of muscle vascular beds is important in the regulation of systemic blood pressure. However, vasoconstriction during exercise can also compromise blood flow support of muscle metabolism. This study tested the hypothesis that local factors in exercising muscle blunt vessel responsiveness to sympathetic vasoconstriction. We performed selective infusions of three doses of tyramine into the brachial artery (n = 8) to evoke endogenous release of noradrenaline (norepinephrine) at rest and during moderate and heavy rhythmic handgrip exercise. In separate experiments, tyramine was administered during two doses of adenosine infusion (n = 7) and two doses of sodium nitroprusside (SNP) infusion (n = 8). Vasoconstrictor effectiveness across conditions was assessed as the percentage reduction in forearm vascular conductance (FVC), calculated from invasive blood pressure and non-invasive Doppler ultrasound blood flow measurements at the brachial artery. Tyramine evoked a similar dose-dependent vasoconstriction at rest in all three groups, with the highest dose resulting in a 42-46 % reduction in FVC. This vasoconstriction was blunted with increasing exercise intensity (e.g. tyramine high dose percentage reduction in FVC; rest -43.4 +/- 3.7 %, moderate exercise -27.5 +/- 2.3 %, heavy exercise -16.7 +/- 3.6 %; P < 0.05). In contrast, tyramine infusion resulted in a greater percentage reduction in FVC during both doses of adenosine vs. rest (P < 0.05). Finally, percentage change in FVC was greater during low dose SNP infusion vs. rest (P < 0.05), but not different from rest at the high dose of SNP infusion (P = 0.507). A blunted percentage reduction in FVC during endogenous noradrenaline release in exercise but not vasodilator infusion indicates that sympathetic vasoconstriction is blunted in exercising muscle. This blunting appears to be exercise intensity-dependent.

Using lean "automation with a human touch" to improve medication safety: a step closer to the "perfect dose".

PubMed

Ching, Joan M; Williams, Barbara L; Idemoto, Lori M; Blackmore, C Craig

2014-08-01

Virginia Mason Medical Center (Seattle) employed the Lean concept of Jidoka (automation with a human touch) to plan for and deploy bar code medication administration (BCMA) to hospitalized patients. Integrating BCMA technology into the nursing work flow with minimal disruption was accomplished using three steps ofJidoka: (1) assigning work to humans and machines on the basis of their differing abilities, (2) adapting machines to the human work flow, and (3) monitoring the human-machine interaction. Effectiveness of BCMA to both reinforce safe administration practices and reduce medication errors was measured using the Collaborative Alliance for Nursing Outcomes (CALNOC) Medication Administration Accuracy Quality Study methodology. Trained nurses observed a total of 16,149 medication doses for 3,617 patients in a three-year period. Following BCMA implementation, the number of safe practice violations decreased from 54.8 violations/100 doses (January 2010-September 2011) to 29.0 violations/100 doses (October 2011-December 2012), resulting in an absolute risk reduction of 25.8 violations/100 doses (95% confidence interval [CI]: 23.7, 27.9, p < .001). The number of medication errors decreased from 5.9 errors/100 doses at baseline to 3.0 errors/100 doses after BCMA implementation (absolute risk reduction: 2.9 errors/100 doses [95% CI: 2.2, 3.6,p < .001]). The number of unsafe administration practices (estimate, -5.481; standard error 1.133; p < .001; 95% CI: -7.702, -3.260) also decreased. As more hospitals respond to health information technology meaningful use incentives, thoughtful, methodical, and well-managed approaches to technology deployment are crucial. This work illustrates how Jidoka offers opportunities for a smooth transition to new technology.

Evaluation of the brain anaesthesia response monitor during anaesthesia for cardiac surgery: a double-blind, randomised controlled trial using two doses of fentanyl.

PubMed

Shoushtarian, Mehrnaz; McGlade, Desmond P; Delacretaz, Louis J; Liley, David T J

2016-12-01

The brain anaesthesia response (BAR) monitor uses a method of EEG analysis, based on a model of brain electrical activity, to monitor the cerebral response to anaesthetic and sedative agents via two indices, composite cortical state (CCS) and cortical input (CI). It was hypothesised that CCS would respond to the hypnotic component of anaesthesia and CI would differentiate between two groups of patients receiving different doses of fentanyl. Twenty-five patients scheduled to undergo elective first-time coronary artery bypass graft surgery were randomised to receive a total fentanyl dose of either 12 μg/kg (fentanyl low dose, FLD) or 24 μg/kg (fentanyl moderate dose, FMD), both administered in two divided doses. Propofol was used for anaesthesia induction and pancuronium for intraoperative paralysis. Hemodynamic management was protocolised using vasoactive drugs. BIS, CCS and CI were simultaneously recorded. Response of the indices (CI, CCS and BIS) to propofol and their differences between the two groups at specific points from anaesthesia induction through to aortic cannulation were investigated. Following propofol induction, CCS and BIS but not CI showed a significant reduction. Following the first dose of fentanyl, CI, CCS and BIS decreased in both groups. Following the second dose of fentanyl, there was a significant reduction in CI in the FLD group but not the FMD group, with no significant change found for BIS or CCS in either group. The BAR monitor demonstrates the potential to monitor the level of hypnosis following anaesthesia induction with propofol via the CCS index and to facilitate the titration of fentanyl as a component of balanced anaesthesia via the CI index.

Reduction of patulin in apple cider by UV radiation.

PubMed

Dong, Qingfang; Manns, David C; Feng, Guoping; Yue, Tianli; Churey, John J; Worobo, Randy W

2010-01-01

The presence of the mycotoxin patulin in processed apple juice and cider presents a continual challenge to the food industry as both consumer health and product quality issues. Although several methods for control and/or elimination of patulin have been proposed, no unifying method has been commercially successful for reducing patulin burdens while maintaining product quality. In the present study, exposure to germicidal UV radiation was evaluated as a possible commercially viable alternative for the reduction and possible elimination of the patulin mycotoxin in fresh apple cider. UV exposure of 14.2 to 99.4 mJ/cm(2) resulted in a significant and nearly linear decrease in patulin levels while producing no quantifiable changes in the chemical composition (i.e., pH, Brix, and total acids) or organoleptic properties of the cider. For the range of UV doses tested, patulin levels decreased by 9.4 to 43.4%; the greatest reduction was achieved after less than 15 s of UV exposure. The method of UV radiation (the CiderSure 3500 system) is an easily implemented, high-throughput, and cost-effective method that offers simultaneous UV pasteurization of cider and juice products and reduction and/or elimination of patulin without unwanted alterations in the final product.

Simultaneously optimizing dose and schedule of a new cytotoxic agent.

PubMed

Braun, Thomas M; Thall, Peter F; Nguyen, Hoang; de Lima, Marcos

2007-01-01

Traditionally, phase I clinical trial designs are based upon one predefined course of treatment while varying among patients the dose given at each administration. In actual medical practice, patients receive a schedule comprised of several courses of treatment, and some patients may receive one or more dose reductions or delays during treatment. Consequently, the overall risk of toxicity for each patient is a function of both actual schedule of treatment and the differing doses used at each adminstration. Our goal is to provide a practical phase I clinical trial design that more accurately reflects actual medical practice by accounting for both dose per administration and schedule. We propose an outcome-adaptive Bayesian design that simultaneously optimizes both dose and schedule in terms of the overall risk of toxicity, based on time-to-toxicity outcomes. We use computer simulation as a tool to calibrate design parameters. We describe a phase I trial in allogeneic bone marrow transplantation that was designed and is currently being conducted using our new method. Our computer simulations demonstrate that our method outperforms any method that searches for an optimal dose but does not allow schedule to vary, both in terms of the probability of identifying optimal (dose, schedule) combinations, and the numbers of patients assigned to those combinations in the trial. Our design requires greater sample sizes than those seen in traditional phase I studies due to the larger number of treatment combinations examined. Our design also assumes that the effects of multiple administrations are independent of each other and that the hazard of toxicity is the same for all administrations. Our design is the first for phase I clinical trials that is sufficiently flexible and practical to truly reflect clinical practice by varying both dose and the timing and number of administrations given to each patient.

SU-E-J-243: Possibility of Exposure Dose Reduction of Cone-Beam Computed Tomography in An Image Guided Patient Positioning System by Using Various Noise Suppression Filters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamezawa, H; Fujimoto General Hospital, Miyakonojo, Miyazaki; Arimura, H

Purpose: To investigate the possibility of exposure dose reduction of the cone-beam computed tomography (CBCT) in an image guided patient positioning system by using 6 noise suppression filters. Methods: First, a reference dose (RD) and low-dose (LD)-CBCT (X-ray volume imaging system, Elekta Co.) images were acquired with a reference dose of 86.2 mGy (weighted CT dose index: CTDIw) and various low doses of 1.4 to 43.1 mGy, respectively. Second, an automated rigid registration for three axes was performed for estimating setup errors between a planning CT image and the LD-CBCT images, which were processed by 6 noise suppression filters, i.e.,more » averaging filter (AF), median filter (MF), Gaussian filter (GF), bilateral filter (BF), edge preserving smoothing filter (EPF) and adaptive partial median filter (AMF). Third, residual errors representing the patient positioning accuracy were calculated as an Euclidean distance between the setup error vectors estimated using the LD-CBCT image and RD-CBCT image. Finally, the relationships between the residual error and CTDIw were obtained for 6 noise suppression filters, and then the CTDIw for LD-CBCT images processed by the noise suppression filters were measured at the same residual error, which was obtained with the RD-CBCT. This approach was applied to an anthropomorphic pelvic phantom and two cancer patients. Results: For the phantom, the exposure dose could be reduced from 61% (GF) to 78% (AMF) by applying the noise suppression filters to the CBCT images. The exposure dose in a prostate cancer case could be reduced from 8% (AF) to 61% (AMF), and the exposure dose in a lung cancer case could be reduced from 9% (AF) to 37% (AMF). Conclusion: Using noise suppression filters, particularly an adaptive partial median filter, could be feasible to decrease the additional exposure dose to patients in image guided patient positioning systems.« less

TH-A-18C-03: Noise Correlation in CBCT Projection Data and Its Application for Noise Reduction in Low-Dose CBCT

DOE Office of Scientific and Technical Information (OSTI.GOV)

ZHANG, H; Huang, J; Ma, J

2014-06-15

Purpose: To study the noise correlation properties of cone-beam CT (CBCT) projection data and to incorporate the noise correlation information to a statistics-based projection restoration algorithm for noise reduction in low-dose CBCT. Methods: In this study, we systematically investigated the noise correlation properties among detector bins of CBCT projection data by analyzing repeated projection measurements. The measurements were performed on a TrueBeam on-board CBCT imaging system with a 4030CB flat panel detector. An anthropomorphic male pelvis phantom was used to acquire 500 repeated projection data at six different dose levels from 0.1 mAs to 1.6 mAs per projection at threemore » fixed angles. To minimize the influence of the lag effect, lag correction was performed on the consecutively acquired projection data. The noise correlation coefficient between detector bin pairs was calculated from the corrected projection data. The noise correlation among CBCT projection data was then incorporated into the covariance matrix of the penalized weighted least-squares (PWLS) criterion for noise reduction of low-dose CBCT. Results: The analyses of the repeated measurements show that noise correlation coefficients are non-zero between the nearest neighboring bins of CBCT projection data. The average noise correlation coefficients for the first- and second- order neighbors are about 0.20 and 0.06, respectively. The noise correlation coefficients are independent of the dose level. Reconstruction of the pelvis phantom shows that the PWLS criterion with consideration of noise correlation (PWLS-Cor) results in a lower noise level as compared to the PWLS criterion without considering the noise correlation (PWLS-Dia) at the matched resolution. Conclusion: Noise is correlated among nearest neighboring detector bins of CBCT projection data. An accurate noise model of CBCT projection data can improve the performance of the statistics-based projection restoration algorithm for low-dose CBCT.« less

Using a Reduced Spot Size for Intensity-Modulated Proton Therapy Potentially Improves Salivary Gland-Sparing in Oropharyngeal Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Water, Tara A. van de, E-mail: t.a.van.de.water@rt.umcg.nl; Lomax, Antony J.; Bijl, Hendrik P.

2012-02-01

Purpose: To investigate whether intensity-modulated proton therapy with a reduced spot size (rsIMPT) could further reduce the parotid and submandibular gland dose compared with previously calculated IMPT plans with a larger spot size. In addition, it was investigated whether the obtained dose reductions would theoretically translate into a reduction of normal tissue complication probabilities (NTCPs). Methods: Ten patients with N0 oropharyngeal cancer were included in a comparative treatment planning study. Both IMPT plans delivered simultaneously 70 Gy to the boost planning target volume (PTV) and 54 Gy to the elective nodal PTV. IMPT and rsIMPT used identical three-field beam arrangements.more » In the IMPT plans, the parotid and submandibular salivary glands were spared as much as possible. rsIMPT plans used identical dose-volume objectives for the parotid glands as those used by the IMPT plans, whereas the objectives for the submandibular glands were tightened further. NTCPs were calculated for salivary dysfunction and xerostomia. Results: Target coverage was similar for both IMPT techniques, whereas rsIMPT clearly improved target conformity. The mean doses in the parotid glands and submandibular glands were significantly lower for three-field rsIMPT (14.7 Gy and 46.9 Gy, respectively) than for three-field IMPT (16.8 Gy and 54.6 Gy, respectively). Hence, rsIMPT significantly reduced the NTCP of patient-rated xerostomia and parotid and contralateral submandibular salivary flow dysfunction (27%, 17%, and 43% respectively) compared with IMPT (39%, 20%, and 79%, respectively). In addition, mean dose values in the sublingual glands, the soft palate and oral cavity were also decreased. Obtained dose and NTCP reductions varied per patient. Conclusions: rsIMPT improved sparing of the salivary glands and reduced NTCP for xerostomia and parotid and submandibular salivary dysfunction, while maintaining similar target coverage results. It is expected that rsIMPT improves quality of life during and after radiotherapy treatment.« less

SU-F-J-16: Planar KV Imaging Dose Reduction Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gershkevitsh, E; Zolotuhhin, D

Purpose: IGRT has become an indispensable tool in modern radiotherapy with kV imaging used in many departments due to superior image quality and lower dose when compared to MV imaging. Many departments use manufacturer supplied protocols for imaging which are not always optimised between image quality and radiation dose (ALARA). Methods: Whole body phantom PBU-50 (Kyoto Kagaku ltd., Japan) for imaging in radiology has been imaged on Varian iX accelerator (Varian Medical Systems, USA) with OBI 1.5 system. Manufacturer’s default protocols were adapted by modifying kV and mAs values when imaging different anatomical regions of the phantom (head, thorax, abdomen,more » pelvis, extremities). Images with different settings were independently reviewed by two persons and their suitability for IGRT set-up correction protocols were evaluated. The suitable images with the lowest mAs were then selected. The entrance surface dose (ESD) for manufacturer’s default protocols and modified protocols were measured with RTI Black Piranha (RTI Group, Sweden) and compared. Image quality was also measured with kVQC phantom (Standard Imaging, USA) for different protocols. The modified protocols have been applied for clinical work. Results: For most cases optimized protocols reduced the ESD on average by a factor of 3(range 0.9–8.5). Further reduction in ESD has been observed by applying bow-tie filter designed for CBCT. The largest reduction in dose (12.2 times) was observed for Thorax lateral protocol. The dose was slightly increased (by 10%) for large pelvis AP protocol. Conclusion: Manufacturer’s default IGRT protocols could be optimised to reduce the ESD to the patient without losing the necessary image quality for patient set-up correction. For patient set-up with planar kV imaging the bony anatomy is mostly used and optimization should focus on this aspect. Therefore, the current approach with anthropomorphic phantom is more advantageous in optimization over standard kV quality control phantoms and SNR metrics.« less

Estimating radiation dose to organs of patients undergoing conventional and novel multidetector CT exams using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Angel, Erin

Advances in Computed Tomography (CT) technology have led to an increase in the modality's diagnostic capabilities and therefore its utilization, which has in turn led to an increase in radiation exposure to the patient population. As a result, CT imaging currently constitutes approximately half of the collective exposure to ionizing radiation from medical procedures. In order to understand the radiation risk, it is necessary to estimate the radiation doses absorbed by patients undergoing CT imaging. The most widely accepted risk models are based on radiosensitive organ dose as opposed to whole body dose. In this research, radiosensitive organ dose was estimated using Monte Carlo based simulations incorporating detailed multidetector CT (MDCT) scanner models, specific scan protocols, and using patient models based on accurate patient anatomy and representing a range of patient sizes. Organ dose estimates were estimated for clinical MDCT exam protocols which pose a specific concern for radiosensitive organs or regions. These dose estimates include estimation of fetal dose for pregnant patients undergoing abdomen pelvis CT exams or undergoing exams to diagnose pulmonary embolism and venous thromboembolism. Breast and lung dose were estimated for patients undergoing coronary CTA imaging, conventional fixed tube current chest CT, and conventional tube current modulated (TCM) chest CT exams. The correlation of organ dose with patient size was quantified for pregnant patients undergoing abdomen/pelvis exams and for all breast and lung dose estimates presented. Novel dose reduction techniques were developed that incorporate organ location and are specifically designed to reduce close to radiosensitive organs during CT acquisition. A generalizable model was created for simulating conventional and novel attenuation-based TCM algorithms which can be used in simulations estimating organ dose for any patient model. The generalizable model is a significant contribution of this work as it lays the foundation for the future of simulating TCM using Monte Carlo methods. As a result of this research organ dose can be estimated for individual patients undergoing specific conventional MDCT exams. This research also brings understanding to conventional and novel close reduction techniques in CT and their effect on organ dose.

Standard dose versus low dose non-vitamin K antagonist oral anticoagulants in Asian patients with atrial fibrillation: A meta-analysis of contemporary randomized controlled trials.

PubMed

Wang, Kang-Ling; Giugliano, Robert P; Goto, Shinya; Chiu, Chun-Chih; Lin, Chun-Yi; Lai, En-Yu; Chiang, Chern-En

2016-12-01

Although randomized controlled trials (RCTs) indicated that standard dose non-vitamin K antagonist oral anticoagulants (NOACs) were more compelling, low dose NOACs are commonly used in clinical practice in Asia. The purpose of this study was to assess the relative therapeutic benefit and risk of standard dose vs low dose NOACs in Asian patients enrolled in contemporary RCTs. We performed a prespecified meta-analysis of 3155 Asian patients with NOACs in the RE-LY (Randomized Evaluation of Long-Term Anticoagulation Therapy) and ENGAGE AF-TIMI 48 (Effective Anticoagulation with Factor Xa Next Generation in Atrial Fibrillation-Thrombolysis in Myocardial Infarction 48) trials. Efficacy and safety with standard dose vs low dose NOACs were compared by risk ratios (RRs) and 95% confidence intervals (CIs) in a random-effects model. An evidence network incorporating additional Asian patients from ROCKET AF, J- ROCKET AF, and ARISTOTLE was constructed with the Bayesian method. Risks of stroke or systemic embolism and ischemic stroke were significantly reduced with standard dose vs low dose NOACs (RR 0.62, 95% CI 0.45-0.85; and RR 0.55, 95% CI 0.38-0.79, respectively). Rates of major, intracranial, and life-threatening bleeding with 2 dosing regimens were broadly similar (RR 1.31, 95% CI 0.74-2.33; RR 1.54, 95% CI 0.72-3.30; and RR 1.49, 95% CI 0.87-2.55, respectively). Absolute rates of all-cause mortality and the net clinical outcome with standard dose NOACs were lower but not statistically significant (absolute reduction 0.4% per year and 1.1% per year, respectively). Network meta-analyses demonstrated that standard dose NOACs had the most favorable risk-benefit profile among oral anticoagulants. In Asian patients, standard dose NOACs represent a more appealing therapeutic option than low dose NOACs, with a significant reduction in ischemic stroke without an excess of major bleeding. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Reduced Radiation Dose with Model-based Iterative Reconstruction versus Standard Dose with Adaptive Statistical Iterative Reconstruction in Abdominal CT for Diagnosis of Acute Renal Colic.

PubMed

Fontarensky, Mikael; Alfidja, Agaïcha; Perignon, Renan; Schoenig, Arnaud; Perrier, Christophe; Mulliez, Aurélien; Guy, Laurent; Boyer, Louis

2015-07-01

To evaluate the accuracy of reduced-dose abdominal computed tomographic (CT) imaging by using a new generation model-based iterative reconstruction (MBIR) to diagnose acute renal colic compared with a standard-dose abdominal CT with 50% adaptive statistical iterative reconstruction (ASIR). This institutional review board-approved prospective study included 118 patients with symptoms of acute renal colic who underwent the following two successive CT examinations: standard-dose ASIR 50% and reduced-dose MBIR. Two radiologists independently reviewed both CT examinations for presence or absence of renal calculi, differential diagnoses, and associated abnormalities. The imaging findings, radiation dose estimates, and image quality of the two CT reconstruction methods were compared. Concordance was evaluated by κ coefficient, and descriptive statistics and t test were used for statistical analysis. Intraobserver correlation was 100% for the diagnosis of renal calculi (κ = 1). Renal calculus (τ = 98.7%; κ = 0.97) and obstructive upper urinary tract disease (τ = 98.16%; κ = 0.95) were detected, and differential or alternative diagnosis was performed (τ = 98.87% κ = 0.95). MBIR allowed a dose reduction of 84% versus standard-dose ASIR 50% (mean volume CT dose index, 1.7 mGy ± 0.8 [standard deviation] vs 10.9 mGy ± 4.6; mean size-specific dose estimate, 2.2 mGy ± 0.7 vs 13.7 mGy ± 3.9; P < .001) without a conspicuous deterioration in image quality (reduced-dose MBIR vs ASIR 50% mean scores, 3.83 ± 0.49 vs 3.92 ± 0.27, respectively; P = .32) or increase in noise (reduced-dose MBIR vs ASIR 50% mean, respectively, 18.36 HU ± 2.53 vs 17.40 HU ± 3.42). Its main drawback remains the long time required for reconstruction (mean, 40 minutes). A reduced-dose protocol with MBIR allowed a dose reduction of 84% without increasing noise and without an conspicuous deterioration in image quality in patients suspected of having renal colic.

Predictors of the nicotine reinforcement threshold, compensation, and elasticity of demand in a rodent model of nicotine reduction policy*

PubMed Central

Grebenstein, Patricia E.; Burroughs, Danielle; Roiko, Samuel A.; Pentel, Paul R.; LeSage, Mark G.

2015-01-01

Background The FDA is considering reducing the nicotine content in tobacco products as a population-based strategy to reduce tobacco addiction. Research is needed to determine the threshold level of nicotine needed to maintain smoking and the extent of compensatory smoking that could occur during nicotine reduction. Sources of variability in these measures across sub-populations also need to be identified so that policies can take into account the risks and benefits of nicotine reduction in vulnerable populations. Methods The present study examined these issues in a rodent nicotine self- administration model of nicotine reduction policy to characterize individual differences in nicotine reinforcement thresholds, degree of compensation, and elasticity of demand during progressive reduction of the unit nicotine dose. The ability of individual differences in baseline nicotine intake and nicotine pharmacokinetics to predict responses to dose reduction was also examined. Results Considerable variability in the reinforcement threshold, compensation, and elasticity of demand was evident. High baseline nicotine intake was not correlated with the reinforcement threshold, but predicted less compensation and less elastic demand. Higher nicotine clearance predicted low reinforcement thresholds, greater compensation, and less elastic demand. Less elastic demand also predicted lower reinforcement thresholds. Conclusions These findings suggest that baseline nicotine intake, nicotine clearance, and the essential value of nicotine (i.e. elasticity of demand) moderate the effects of progressive nicotine reduction in rats and warrant further study in humans. They also suggest that smokers with fast nicotine metabolism may be more vulnerable to the risks of nicotine reduction. PMID:25891231

Low-dose X-ray computed tomography image reconstruction with a combined low-mAs and sparse-view protocol.

PubMed

Gao, Yang; Bian, Zhaoying; Huang, Jing; Zhang, Yunwan; Niu, Shanzhou; Feng, Qianjin; Chen, Wufan; Liang, Zhengrong; Ma, Jianhua

2014-06-16

To realize low-dose imaging in X-ray computed tomography (CT) examination, lowering milliampere-seconds (low-mAs) or reducing the required number of projection views (sparse-view) per rotation around the body has been widely studied as an easy and effective approach. In this study, we are focusing on low-dose CT image reconstruction from the sinograms acquired with a combined low-mAs and sparse-view protocol and propose a two-step image reconstruction strategy. Specifically, to suppress significant statistical noise in the noisy and insufficient sinograms, an adaptive sinogram restoration (ASR) method is first proposed with consideration of the statistical property of sinogram data, and then to further acquire a high-quality image, a total variation based projection onto convex sets (TV-POCS) method is adopted with a slight modification. For simplicity, the present reconstruction strategy was termed as "ASR-TV-POCS." To evaluate the present ASR-TV-POCS method, both qualitative and quantitative studies were performed on a physical phantom. Experimental results have demonstrated that the present ASR-TV-POCS method can achieve promising gains over other existing methods in terms of the noise reduction, contrast-to-noise ratio, and edge detail preservation.

Development of virtual patient models for permanent implant brachytherapy Monte Carlo dose calculations: interdependence of CT image artifact mitigation and tissue assignment.

PubMed

Miksys, N; Xu, C; Beaulieu, L; Thomson, R M

2015-08-07

This work investigates and compares CT image metallic artifact reduction (MAR) methods and tissue assignment schemes (TAS) for the development of virtual patient models for permanent implant brachytherapy Monte Carlo (MC) dose calculations. Four MAR techniques are investigated to mitigate seed artifacts from post-implant CT images of a homogeneous phantom and eight prostate patients: a raw sinogram approach using the original CT scanner data and three methods (simple threshold replacement (STR), 3D median filter, and virtual sinogram) requiring only the reconstructed CT image. Virtual patient models are developed using six TAS ranging from the AAPM-ESTRO-ABG TG-186 basic approach of assigning uniform density tissues (resulting in a model not dependent on MAR) to more complex models assigning prostate, calcification, and mixtures of prostate and calcification using CT-derived densities. The EGSnrc user-code BrachyDose is employed to calculate dose distributions. All four MAR methods eliminate bright seed spot artifacts, and the image-based methods provide comparable mitigation of artifacts compared with the raw sinogram approach. However, each MAR technique has limitations: STR is unable to mitigate low CT number artifacts, the median filter blurs the image which challenges the preservation of tissue heterogeneities, and both sinogram approaches introduce new streaks. Large local dose differences are generally due to differences in voxel tissue-type rather than mass density. The largest differences in target dose metrics (D90, V100, V150), over 50% lower compared to the other models, are when uncorrected CT images are used with TAS that consider calcifications. Metrics found using models which include calcifications are generally a few percent lower than prostate-only models. Generally, metrics from any MAR method and any TAS which considers calcifications agree within 6%. Overall, the studied MAR methods and TAS show promise for further retrospective MC dose calculation studies for various permanent implant brachytherapy treatments.

Monte Carlo study on secondary neutrons in passive carbon-ion radiotherapy: Identification of the main source and reduction in the secondary neutron dose

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yonai, Shunsuke; Matsufuji, Naruhiro; Kanai, Tatsuaki

Purpose: Recent successful results in passive carbon-ion radiotherapy allow the patient to live for a longer time and allow younger patients to receive the radiotherapy. Undesired radiation exposure in normal tissues far from the target volume is considerably lower than that close to the treatment target, but it is considered to be non-negligible in the estimation of the secondary cancer risk. Therefore, it is very important to reduce the undesired secondary neutron exposure in passive carbon-ion radiotherapy without influencing the clinical beam. In this study, the source components in which the secondary neutrons are produced during passive carbon-ion radiotherapy weremore » identified and the method to reduce the secondary neutron dose effectively based on the identification of the main sources without influencing the clinical beam was investigated. Methods: A Monte Carlo study with the PHITS code was performed by assuming the beamline at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). At first, the authors investigated the main sources of secondary neutrons in passive carbon-ion radiotherapy. Next, they investigated the reduction in the neutron dose with various modifications of the beamline device that is the most dominant in the neutron production. Finally, they investigated the use of an additional shield for the patient. Results: It was shown that the main source is the secondary neutrons produced in the four-leaf collimator (FLC) used as a precollimator at HIAMC, of which contribution in the total neutron ambient dose equivalent is more than 70%. The investigations showed that the modification of the FLC can reduce the neutron dose at positions close to the beam axis by 70% and the FLC is very useful not only for the collimation of the primary beam but also the reduction in the secondary neutrons. Also, an additional shield for the patient is very effective to reduce the neutron dose at positions farther than 50 cm from the beam axis. Finally, they showed that the neutron dose can be reduced by approximately 70% at any position without influencing the primary beam used in treatment. Conclusions: This study was performed by assuming the HIMAC beamline; however, this study provides important information for reoptimizing the arrangement and the materials of beamline devices and designing a new facility for passive carbon-ion radiotherapy and probably passive proton radiotherapy.« less

TU-EF-204-09: A Preliminary Method of Risk-Informed Optimization of Tube Current Modulation for Dose Reduction in CT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Y; Liu, B; Kalra, M

Purpose: X-rays from CT scans can increase cancer risk to patients. Lifetime Attributable Risk of Cancer Incidence for adult patients has been investigated and shown to decrease as patient age. However, a new risk model shows an increasing risk trend for several radiosensitive organs for middle age patients. This study investigates the feasibility of a general method for optimizing tube current modulation (TCM) functions to minimize risk by reducing radiation dose to radiosensitive organs of patients. Methods: Organ-based TCM has been investigated in literature for eye lens dose and breast dose. Adopting the concept in organ-based TCM, this study seeksmore » to find an optimized tube current for minimal total risk to breasts and lungs by reducing dose to these organs. The contributions of each CT view to organ dose are determined through simulations of CT scan view-by-view using a GPU-based fast Monte Carlo code, ARCHER. A Linear Programming problem is established for tube current optimization, with Monte Carlo results as weighting factors at each view. A pre-determined dose is used as upper dose boundary, and tube current of each view is optimized to minimize the total risk. Results: An optimized tube current is found to minimize the total risk of lungs and breasts: compared to fixed current, the risk is reduced by 13%, with breast dose reduced by 38% and lung dose reduced by 7%. The average tube current is maintained during optimization to maintain image quality. In addition, dose to other organs in chest region is slightly affected, with relative change in dose smaller than 10%. Conclusion: Optimized tube current plans can be generated to minimize cancer risk to lungs and breasts while maintaining image quality. In the future, various risk models and greater number of projections per rotation will be simulated on phantoms of different gender and age. National Institutes of Health R01EB015478.« less

Effect of Dose of Behavioral Treatment for Obesity on Binge Eating Severity

PubMed Central

Ariel, Aviva H.; Perri, Michael G.

2016-01-01

Objectives We evaluated the effects of three doses of a behavioral intervention for obesity (High dose = 24 sessions, Moderate = 16 sessions, Low = 8 sessions) compared with a nutrition education control group (Control) on binge eating. We also examined whether participants with clinically significant improvements in binge eating had better treatment adherence and weight-loss outcomes than those who did not experience clinically significant improvements in binge eating. Finally, we examined the relation of pretreatment binge eating severity to changes at six months. Methods Participants included 572 adults (female = 78.7%; baseline mean ±SD: age = 52.7 ±11.2 years, BMI = 36.4 ±3.9 kg/m2) who provided binge eating data at baseline. We evaluated binge eating severity (assessed via the Binge Eating Scale) and weight status at baseline and six months, as well as treatment adherence over six months. Results At six months, participants in the Moderate and High treatment conditions reported greater reductions in binge eating severity than participants in the Low and Control conditions, ps < .02. Participants who demonstrated improvements in binge eating severity reported greater dietary self-monitoring adherence and attained larger weight losses than those who did not experience clinically significant reductions, ps < .001. Pretreatment binge eating severity predicted less improvement in binge eating severity over six months and fewer days with dietary self-monitoring records completed, ps ≤ .002. Conclusion A moderate or high dose of behavioral weight-loss treatment may be required to produce clinically significant reductions in binge eating severity in adults with obesity. PMID:27086049

Task-based measures of image quality and their relation to radiation dose and patient risk

PubMed Central

Barrett, Harrison H.; Myers, Kyle J.; Hoeschen, Christoph; Kupinski, Matthew A.; Little, Mark P.

2015-01-01

The theory of task-based assessment of image quality is reviewed in the context of imaging with ionizing radiation, and objective figures of merit (FOMs) for image quality are summarized. The variation of the FOMs with the task, the observer and especially with the mean number of photons recorded in the image is discussed. Then various standard methods for specifying radiation dose are reviewed and related to the mean number of photons in the image and hence to image quality. Current knowledge of the relation between local radiation dose and the risk of various adverse effects is summarized, and some graphical depictions of the tradeoffs between image quality and risk are introduced. Then various dose-reduction strategies are discussed in terms of their effect on task-based measures of image quality. PMID:25564960

Evaluation of forest decontamination using radiometric measurements.

PubMed

Cresswell, Alan J; Kato, Hiroaki; Onda, Yuichi; Nanba, Kenji

2016-11-01

An experiment has been conducted to evaluate the additional dose reduction by clear felling contaminated forestry in Fukushima Prefecture, Japan, and using the timber to cover the areas with wood chips. A portable gamma spectrometry system, comprising a backpack containing a 3 × 3″ NaI(Tl) detector with digital spectrometer and GPS receiver, has been used to map dose rate and radionuclide activity concentrations before, after and at stages during this experiment. The data show the effect of the different stages of the experiment on dose rate at different locations around the site. The spectrometric data have allowed the assessment of the contributions of natural and anthropogenic radionuclides to the dose rate at different parts of the site before and after the experiment. This has clearly demonstrated the value of radiometric methods in evaluating remediation, and the effect of other environmental processes. The value of spectrometric methods which directly measure radionuclide concentrations has also been shown, especially through the identification of the contribution of natural and anthropogenic activity to the measured dose rate. The experiment has shown that clearing trees and applying wood chips can reduce dose rates by 10-15% beyond that achieved by just clearing the forest litter and natural redistribution of radiocaesium. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of fucoidan from Fucus vesiculosus in reducing symptoms of osteoarthritis: a randomized placebo-controlled trial

PubMed Central

Myers, Stephen P; Mulder, Ann M; Baker, Don G; Robinson, Shelley R; Rolfe, Margaret I; Brooks, Lyndon; Fitton, J Helen

2016-01-01

Purpose Preliminary investigation of a fucoidan with demonstrated reduction in the symptoms of osteoarthritis (OA) of the hip and knee. Patients and methods A double-blind randomized controlled trial was carried out to determine the safety and efficacy of a 300 mg dose of a Fucus vesiculosus extract (85% fucoidan) over a 12-week period in a population (n=122) with mild-to-moderate OA of the hip and knee as measured by the validated instrument “Comprehensive Osteoarthritis Test.” Safety was measured by assessing cholesterol, liver function, renal function, and hematopoietic function, and closely monitoring adverse events. Result Ninety-six participants completed the study. The reduction in symptoms of OA was not significantly different from the placebo response. There were no changes in the blood measurements that were of any clinical significance during the course of the study. Conclusion The F. vesiculosus fucoidan extract was safe and well tolerated. At a dose of 300 mg, the extract showed no difference in reduction of OA symptoms from the placebo. PMID:27307702

High-Dose, Single-Fraction Irradiation Rapidly Reduces Tumor Vasculature and Perfusion in a Xenograft Model of Neuroblastoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jani, Ashish; Shaikh, Fauzia; Barton, Sunjay

Purpose: To characterize the effects of high-dose radiation therapy (HDRT) on neuroblastoma tumor vasculature, including the endothelial cell (EC)–pericyte interaction as a potential target for combined treatment with antiangiogenic agents. Methods and Materials: The vascular effects of radiation therapy were examined in a xenograft model of high-risk neuroblastoma. In vivo 3-dimensional contrast-enhanced ultrasonography (3D-CEUS) imaging and immunohistochemistry (IHC) were performed. Results: HDRT significantly reduced tumor blood volume 6 hours after irradiation compared with the lower doses used in conventionally fractionated radiation. There was a 63% decrease in tumor blood volume after 12-Gy radiation compared with a 24% decrease after 2 Gy. Analysis ofmore » tumor vasculature by lectin angiography showed a significant loss of small vessel ends at 6 hours. IHC revealed a significant loss of ECs at 6 and 72 hours after HDRT, with an accompanying loss of immature and mature pericytes at 72 hours. Conclusions: HDRT affects tumor vasculature in a manner not observed at lower doses. The main observation was an early reduction in tumor perfusion resulting from a reduction of small vessel ends with a corresponding loss of endothelial cells and pericytes.« less

A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device.

PubMed

Kavuma, Awusi; Glegg, Martin; Metwaly, Mohamed; Currie, Garry; Elliott, Alex

2010-01-21

In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. Electronic portal imaging device (EPID) images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model is used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected by relative measurements using an ionization chamber and an EPID. The 2D EPL is linked to the percentage exit dose table, for different thicknesses and field sizes, thereby converting the plane pixel values at each point into a 2D dose map. The off-axis ratio is corrected using envelope and boundary profiles generated from the treatment planning system (TPS). The method requires field size, monitor unit and source-to-surface distance (SSD) as clinical input parameters to predict the exit dose, which is then used to determine the entrance dose. The measured pixel dose maps were compared with calculated doses from TPS for both entrance and exit depth of phantom. The gamma index at 3% dose difference (DD) and 3 mm distance to agreement (DTA) resulted in an average of 97% passing for the square fields of 5, 10, 15 and 20 cm. The exit dose EPID dose distributions predicted by the algorithm were in better agreement with TPS-calculated doses than phantom entrance dose distributions.

A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device

NASA Astrophysics Data System (ADS)

Kavuma, Awusi; Glegg, Martin; Metwaly, Mohamed; Currie, Garry; Elliott, Alex

2010-01-01

In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. Electronic portal imaging device (EPID) images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model is used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected by relative measurements using an ionization chamber and an EPID. The 2D EPL is linked to the percentage exit dose table, for different thicknesses and field sizes, thereby converting the plane pixel values at each point into a 2D dose map. The off-axis ratio is corrected using envelope and boundary profiles generated from the treatment planning system (TPS). The method requires field size, monitor unit and source-to-surface distance (SSD) as clinical input parameters to predict the exit dose, which is then used to determine the entrance dose. The measured pixel dose maps were compared with calculated doses from TPS for both entrance and exit depth of phantom. The gamma index at 3% dose difference (DD) and 3 mm distance to agreement (DTA) resulted in an average of 97% passing for the square fields of 5, 10, 15 and 20 cm. The exit dose EPID dose distributions predicted by the algorithm were in better agreement with TPS-calculated doses than phantom entrance dose distributions.

Efficacy of Pregabalin in Childhood Refractory Partial Seizure

PubMed Central

Zamani, Gholamreza; Tavasoli, Alireza; Zare-Shahabadi, Ameneh; Rezaei, Nima; Ahmadvand, Alireza

2014-01-01

Objective: About one third of partial seizures are refractory to treatment. Several anticonvulsant drugs have entered the market in recent decades but concerns about intolerance, drug interactions, and the safety of the drug are notable. One of these new anticonvulsants is pregabalin, a safe drug with almost no interaction with other antiepileptic drugs. Methods: In this open label clinical trial study, pregabalin was used for evaluation of its efficacy on reducing seizure frequency in 29 children suffering from refractory partial seizures. Average daily and weekly seizure frequency of the patients was recorded during a 6-week period (baseline period). Then, during a period of 2 weeks (titration period), pregabalin was started with a dose of 25-75 mg/d, using method of flexible dose, and was brought to maximum dose of drug that was intended in this study (450 mg/d) based on clinical response of the patients and seizure frequency. Then the patients were given the drug for 12 weeks and the average frequency of daily and weekly seizures were recorded again (treatment period). Findings : Reduction in seizure frequency in this study was 36% and the responder rate or number of patients who gained more than 50% reduction in seizure frequency was 51.7%. Conclusion: This study showed that pregabalin can be used with safety and an acceptable efficacy in treatment of childhood refractory partial seizures. PMID:25793053

Reduction of antiproliferative capacities, cell-based antioxidant capacities and phytochemical contents of common beans and soybeans upon thermal processing.

PubMed

Xu, Baojun; Chang, Sam K C

2011-12-01

The effects of boiling and steaming processes on the antiproliferative and cellular antioxidant properties, as well as phytochemicals, of two types of common beans (pinto and black beans) and two types of soybeans (yellow and black) were investigated. All thermal-processing methods caused significant (p<0.05) decreases in total phenolic content (TPC), total saponin content (TSC) and phytic acid content (PAC) values in all bean types (except for TPC values in pressure-steamed yellow soybeans) as compared to those of the raw beans. All types of uncooked raw beans exhibited cellular antioxidant activities (CAA) in dose-dependent manners. Black soybeans exhibited the greatest CAA, followed by black beans, pinto beans and yellow soybeans. The CAA of cooked beans were generally diminished or eliminated by thermal processing. The hydrophilic extracts from raw pinto beans, black beans and black soybeans exhibited antiproliferation capacities against human gastric (AGS) and colorectal (SW480) cancer cells in dose-dependent manners. The raw yellow soybeans exhibited dose-dependent antiproliferation activities against the SW480 cells. Most of the cooked beans lost their antiproliferation capacities as observed in the raw beans. These results indicate that different processing methods may have various effects on phytochemical profiles and bioactivities. Overall, thermal processing caused a significant reduction of the health-promotion effects of beans. Copyright © 2011 Elsevier Ltd. All rights reserved.

Sex differences in nicotine self-administration in rats during progressive unit dose reduction: implications for nicotine regulation policy.

PubMed

Grebenstein, Patricia; Burroughs, Danielle; Zhang, Yan; LeSage, Mark G

2013-12-01

Reducing the nicotine content in tobacco products is being considered by the FDA as a policy to reduce the addictiveness of tobacco products. Understanding individual differences in response to nicotine reduction will be critical to developing safe and effective policy. Animal and human research demonstrating sex differences in the reinforcing effects of nicotine suggests that males and females may respond differently to nicotine-reduction policies. However, no studies have directly examined sex differences in the effects of nicotine unit-dose reduction on nicotine self-administration (NSA) in animals. The purpose of the present study was to examine this issue in a rodent self-administration model. Male and female rats were trained to self-administer nicotine (0.06mg/kg) under an FR 3 schedule during daily 23h sessions. Rats were then exposed to saline extinction and reacquisition of NSA, followed by weekly reductions in the unit dose (0.03 to 0.00025mg/kg) until extinction levels of responding were achieved. Males and females were compared with respect to baseline levels of intake, resistance to extinction, degree of compensatory increases in responding during dose reduction, and the threshold reinforcing unit dose of nicotine. Exponential demand-curve analysis was also conducted to compare the sensitivity of males and females to increases in the unit price (FR/unit dose) of nicotine (i.e., elasticity of demand or reinforcing efficacy). Females exhibited significantly higher baseline intake and less compensation than males. However, there were no sex differences in the reinforcement threshold or elasticity of demand. Dose-response relationships were very well described by the exponential demand function (r(2) values>0.96 for individual subjects). These findings suggest that females may exhibit less compensatory smoking in response to nicotine reduction policies, even though their nicotine reinforcement threshold and elasticity of demand may not differ from males. Copyright © 2013 Elsevier Inc. All rights reserved.

Dosimetric evaluation of three adaptive strategies for prostate cancer treatment including pelvic lymph nodes irradiation.

PubMed

Cantin, Audrey; Gingras, Luc; Lachance, Bernard; Foster, William; Goudreault, Julie; Archambault, Louis

2015-12-01

The movements of the prostate relative to the pelvic lymph nodes during intensity-modulated radiation therapy treatment can limit margin reduction and affect the protection of the organs at risk (OAR). In this study, the authors performed an analysis of three adaptive treatment strategies that combine information from both bony and gold marker registrations. The robustness of those treatments against the interfraction prostate movements was evaluated. A retrospective study was conducted on five prostate cancer patients with 7-13 daily cone-beam CTs (CBCTs). The clinical target volumes (CTVs) consisting of pelvic lymph nodes, prostate, and seminal vesicles as well as the OARs were delineated on each CBCT and the initial CT. Three adaptive strategies were analyzed. Two of these methods relied on a two-step patient positioning at each fraction. First step: a bony registration was used to deliver the nodal CTV prescription. Second step: a gold marker registration was then used either to (1) complete the dose delivered to the prostate (complement); (2) or give almost the entire prescription to the prostate with a weak dose gradient between the targets to compensate for possible motions (gradient). The third method (COR) used a pool of precalculated plans based on images acquired at previous treatment fractions. At each new fraction, a plan is selected from that pool based on the daily position of prostate center-of-mass. The dosimetric comparison was conducted and results are presented with and without the systematic shift in the prostate position on the CT planning. The adaptive strategies were compared to the current clinical standard where all fractions are treated with the initial nonadaptive plan. The minimum daily prostate D95% is improved by 2%, 9%, and 6% for the complement, the gradient, and the COR approaches, respectively, compared to the nonadaptive method. The average nodal CTV D95% remains constant across the strategies, except for the gradient approach where a reduction of 7% is observed. However, a correction of the systematic shift reduced the problem, and the adaptive strategies remain robust against the prostate movement across the fraction. The bladder V55Gy is reduced by 35% on average for the adaptive strategies. Because they offer increased CTV coverage and OAR sparing, adaptive methods may be suitable candidates for simple and efficient adaptive treatment strategies for prostate cancer. Margin reduction and systematic error correction in the prostate position improve the protection of the OAR and the dose coverage. A cumulative dose to simulate a complete treatment would show real effects and allow a better comparison between each method.

SU-F-P-56: On a New Approach to Reconstruct the Patient Dose From Phantom Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bangtsson, E; Vries, W de

Purpose: The development of complex radiation treatment schemes emphasizes the need for advanced QA analysis methods to ensure patient safety. One such tool is the Delta4 DVH Anatomy software, where the patient dose is reconstructed from phantom measurements. Deviations in the measured dose are transferred to the patient anatomy and their clinical impact is evaluated in situ. Results from the original algorithm revealed weaknesses that may introduce artefacts in the reconstructed dose. These can lead to false negatives or obscure the effects of minor dose deviations from delivery failures. Here, we will present results from a new patient dose reconstructionmore » algorithm. Methods: The main steps of the new algorithm are: (1) the dose delivered to a phantom is measured in a number of detector positions. (2) The measured dose is compared to an internally calculated dose distribution evaluated in said positions. The so-obtained dose difference is (3) used to calculate an energy fluence difference. This entity is (4) used as input to a patient dose correction calculation routine. Finally, the patient dose is reconstructed by adding said patient dose correction to the planned patient dose. The internal dose calculation in step (2) and (4) is based on the Pencil Beam algorithm. Results: The new patient dose reconstruction algorithm have been tested on a number of patients and the standard metrics dose deviation (DDev), distance-to-agreement (DTA) and Gamma index are improved when compared to the original algorithm. In a certain case the Gamma index (3%/3mm) increases from 72.9% to 96.6%. Conclusion: The patient dose reconstruction algorithm is improved. This leads to a reduction in non-physical artefacts in the reconstructed patient dose. As a consequence, the possibility to detect deviations in the dose that is delivered to the patient is improved. An increase in Gamma index for the PTV can be seen. The corresponding author is an employee of ScandiDos.« less

Effectiveness of irradiation treatments in inactivating Listeria monocytogenes on fresh vegetables at refrigeration temperature.

PubMed

Bari, M L; Nakauma, M; Todoriki, S; Juneja, Vijay K; Isshiki, K; Kawamoto, S

2005-02-01

Ionizing radiation can be effective in controlling the growth of food spoilage and foodborne pathogenic bacteria. This study reports on an investigation of the effectiveness of irradiation treatment to eliminate Listeria monocytogenes on laboratory-inoculated broccoli, cabbage, tomatoes, and mung bean sprouts. Irradiation of broccoli and mung bean sprouts at 1.0 kGy resulted in reductions of approximately 4.88 and 4.57 log CFU/g, respectively, of a five-strain cocktail of L. monocytogenes. Reductions of approximately 5.25 and 4.14 log CFU/g were found with cabbage and tomato, respectively, at a similar dose. The appearance, color, texture, taste, and overall acceptability did not undergo significant changes after 7 days of postirradiation storage at 4 degrees C, in comparison with control samples. Therefore, low-dose ionizing radiation treatment could be an effective method for eliminating L. monocytogenes on fresh and fresh-cut produce.

Safety assessment of Hibiscus sabdariffa after maternal exposure on male reproductive parameters in rats.

PubMed

de Arruda, Aline; Cardoso, Claudia Andrea L; Vieira, Maria do Carmo; Arena, Arielle Cristina

2016-01-01

Hibiscus sabdariffa L. (Malvaceae) is a species widely used in folk medicine for the treatment of some disorders. This study evaluated the effects of H. sabdariffa (HS) on the development of the male reproductive tract in rats following in utero exposure. Pregnant rats received 250 or 500 mg/kg of HS extract or vehicle from gestational day 12 until day 21 of lactation. Both doses of HS increased the body weight of male offspring at weaning, without compromising the puberty onset parameters. At puberty, there was a significant increase in the vas deferens absolute weight and a significant reduction in the relative weight of kidney at higher dose. These animals also presented a significant reduction in the sperm number in the caput/corpus of epididymis after exposure to both doses and a reduction in the sperm number in the cauda epididymis for the lower dose. At adulthood, the highest dose significantly reduced the sperm production in relation to controls and both doses provoked a reduction in the relative sperm number in the epididymis without affecting the sperm morphology. These findings demonstrated that maternal exposure to H. sabdariffa can adversely influence the male reproductive system in rats.

Accuracy of Reduced-Dose Computed Tomography for Ureteral Stones in Emergency Department Patients

PubMed Central

Moore, Christopher L.; Daniels, Brock; Ghita, Monica; Gunabushanam, Gowthaman; Luty, Seth; Molinaro, Annette M.; Singh, Dinesh; Gross, Cary P.

2016-01-01

Study objective Reduced-dose computed tomography (CT) scans have been recommended for diagnosis of kidney stone but are rarely used in the emergency department (ED) setting. Test characteristics are incompletely characterized, particularly in obese patients. Our primary outcome is to determine the sensitivity and specificity of a reduced-dose CT protocol for symptomatic ureteral stones, particularly those large enough to require intervention, using a protocol stratified by patient size. Methods This was a prospective, blinded observational study of 201 patients at an academic medical center. Consenting subjects underwent both regular- and reduced-dose CT, stratified into a high and low body mass index (BMI) protocol based on effective abdominal diameter. Reduced-dose CT scans were interpreted by radiologists blinded to regular-dose interpretations. Follow-up for outcome and intervention was performed at 90 days. Results CT scans with both regular and reduced doses were conducted for 201 patients, with 63% receiving the high BMI reduced-dose protocol. Ureteral stone was identified in 102 patients (50.7%) of those receiving regular-dose CT, with a ureteral stone greater than 5 mm identified in 26 subjects (12.9%). Sensitivity of the reduced-dose CT for any ureteral stone was 90.2% (95% confidence interval [CI] 82.3% to 95.0%), with a specificity of 99.0% (95% CI 93.7% to 100.0%). For stones greater than 5 mm, sensitivity was 100% (95% CI 85.0% to 100.0%). Reduced-dose CT identified 96% of patients who required intervention for ureteral stone within 90 days. Mean reduction in size-specific dose estimate was 18.6 milligray (mGy), from 21.7 mGy (SD 9.7) to 3.4 mGy (SD 0.9). Conclusion CT with substantial dose reduction was 90.2% (95% CI 82.3% to 95.0%) sensitive and 98.9% (95% CI 85.0% to 100.0%) specific for ureteral stones in ED patients with a wide range of BMIs. Reduced-dose CT was 96.0% (95% CI 80.5% to 99.3%) sensitive for ureteral stones requiring intervention within 90 days. PMID:25441242

[Radiation protection in interventional cardiology].

PubMed

Durán, Ariel

2015-01-01

INTERVENTIONAL: cardiology progress makes each year a greater number of procedures and increasing complexity with a very good success rate. The problem is that this progress brings greater dose of radiation not only for the patient but to occupationally exposed workers as well. Simple methods for reducing or minimizing occupational radiation dose include: minimizing fluoroscopy time and the number of acquired images; using available patient dose reduction technologies; using good imaging-chain geometry; collimating; avoiding high-scatter areas; using protective shielding; using imaging equipment whose performance is controlled through a quality assurance programme; and wearing personal dosimeters so that you know your dose. Effective use of these methods requires both appropriate education and training in radiation protection for all interventional cardiology personnel, and the availability and use of appropriate protective tools and equipment. Regular review and investigation of personnel monitoring results, accompanied as appropriate by changes in how procedures are performed and equipment used, will ensure continual improvement in the practice of radiation protection in the interventional suite. Copyright © 2014 Instituto Nacional de Cardiología Ignacio Chávez. Published by Masson Doyma México S.A. All rights reserved.

Surface dose measurements from air gaps under a bolus by using a MOSFET dosimeter in clinical oblique photon beams

NASA Astrophysics Data System (ADS)

Chung, Jin-Beom; Kim, Jae-Sung; Kim, In-Ah; Lee, Jeong-Woo

2012-10-01

This study is intended to investigate the effects of surface dose from air gaps under the bolus in clinically used oblique photon beams by using a Markus parallel-plate chamber and a metal-oxide semiconductor field-effect transistor (MOSFET) dosimeter. To evaluate the performances of the two detectors, the percentage surface doses of the MOSFET dosimeters in without an air gap under the bolus material were measured and compared with those of the Markus parallel-plate chamber. MOSFET dosimeters at the surface provided results mostly in good agreement with the parallelplate chamber. The MOSFET dosimeters seemed suitable for surface dose measurements having excellent accuracy for clinical used photon beams. The relative surface doses were measured with air gaps (2, 5, 10 mm) and without an air gap under 3 different bolus setups: (1) unbolused (no bolus), (2) 5-mm bolus, and (3) 10-mm bolus. The reductions in the surface dose substantially increased with small field size, thick bolus, and large air gap. The absolute difference in the reductions of the surface dose between the MOSFET dosimeter and the Markus parallel-plate chamber was less than 1.1%. Results at oblique angles of incidence showed larger reductions in surface dose with increasing angle of incidence. The largest reduction in surface dose was recorded for a 6 × 6 cm2 field at a 60° angle of incidence with an 10-mm air gap under a 10-mm bolus. When a 10-mm bolus was used, a reduction in the surface dose with an air gap of up to 10.5% could be achieved by varying the field size and the incident angle. Therefore, air gaps under the bolus should be avoided in radiotherapy treatment, especially for photon beam with highly oblique angles of incidence.

CT breast dose reduction with the use of breast positioning and organ-based tube current modulation.

PubMed

Fu, Wanyi; Tian, Xiaoyu; Sturgeon, Gregory M; Agasthya, Greeshma; Segars, William Paul; Goodsitt, Mitchell M; Kazerooni, Ella A; Samei, Ehsan

2017-02-01

This study aimed to investigate the breast dose reduction potential of a breast-positioning (BP) technique for thoracic CT examinations with organ-based tube current modulation (OTCM). This study included 13 female anthropomorphic computational phantoms (XCAT, age range: 27-65 y.o., weight range: 52-105.8 kg). Each phantom was modified to simulate three breast sizes in standard supine geometry. The modeled breasts were then morphed to emulate BP that constrained the majority of the breast tissue inside the 120° anterior tube current (mA) reduction zone. The OTCM mA value was modeled using a ray-tracing program, which reduced the mA to 20% in the anterior region with a corresponding increase to the posterior region. The organ doses were estimated by a validated Monte Carlo program for a typical clinical CT system (SOMATOM Definition Flash, Siemens Healthcare). The simulated organ doses and organ doses normalized by CTDI vol were used to compare three CT protocols: attenuation-based tube current modulation (ATCM), OTCM, and OTCM with BP (OTCM BP ). On average, compared to ATCM, OTCM reduced breast dose by 19.3 ± 4.5%, whereas OTCM BP reduced breast dose by 38.6 ± 8.1% (an additional 23.8 ± 9.4%). The dose saving of OTCM BP was more significant for larger breasts (on average 33, 38, and 44% reduction for 0.5, 1, and 2 kg breasts, respectively). Compared to ATCM, OTCM BP also reduced thymus and heart dose by 15.1 ± 7.4% and 15.9 ± 6.2% respectively. In thoracic CT examinations, OTCM with a breast-positioning technique can markedly reduce unnecessary exposure to radiosensitive organs in anterior chest wall, specifically breast tissue. The breast dose reduction is more notable for women with larger breasts. © 2016 American Association of Physicists in Medicine.

Dose reduction of risperidone and olanzapine can improve cognitive function and negative symptoms in stable schizophrenic patients: A single-blinded, 52-week, randomized controlled study.

PubMed

Zhou, Yanling; Li, Guannan; Li, Dan; Cui, Hongmei; Ning, Yuping

2018-05-01

The long-term effects of dose reduction of atypical antipsychotics on cognitive function and symptomatology in stable patients with schizophrenia remain unclear. We sought to determine the change in cognitive function and symptomatology after reducing risperidone or olanzapine dosage in stable schizophrenic patients. Seventy-five stabilized schizophrenic patients prescribed risperidone (≥4 mg/day) or olanzapine (≥10 mg/day) were randomly divided into a dose-reduction group ( n=37) and a maintenance group ( n=38). For the dose-reduction group, the dose of antipsychotics was reduced by 50%; for the maintenance group, the dose remained unchanged throughout the whole study. The Positive and Negative Syndrome Scale, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects, and Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery were measured at baseline, 12, 28, and 52 weeks. Linear mixed models were performed to compare the Positive and Negative Syndrome Scale, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects and MATRICS Consensus Cognitive Battery scores between groups. The linear mixed model showed significant time by group interactions on the Positive and Negative Syndrome Scale negative symptoms, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects, speed of processing, attention/vigilance, working memory and total score of MATRICS Consensus Cognitive Battery (all p<0.05). Post hoc analyses showed significant improvement in Positive and Negative Syndrome Scale negative subscale, Negative Symptom Assessment-16, Rating Scale for Extrapyramidal Side Effects, speed of processing, working memory and total score of MATRICS Consensus Cognitive Battery for the dose reduction group compared with those for the maintenance group (all p<0.05). This study indicated that a risperidone or olanzapine dose reduction of 50% may not lead to more severe symptomatology but can improve speed of processing, working memory and negative symptoms in patients with stabilized schizophrenia.

Comparative reduction of Norwalk virus, poliovirus type 1, F+ RNA coliphage MS2 and Escherichia coli in miniature soil columns.

PubMed

Meschke, J S; Sobsey, M D

2003-01-01

Norwalk-like viruses (NLVs) are important agents of waterborne illness and have been linked to several groundwater-related outbreaks. The presence of human enteric viruses, in particular the presence of NLVs, is difficult to detect in the environment. Consequently, surrogate organisms are typically used as indicators of viruses from faecal contamination. Whether traditional bacterial indicators are reliable indicators for viral pathogens remains uncertain. Few studies have directly compared mobility and reduction of bacterial indicators (e.g. coliforms, Escherichia coli) and other surrogate indicators (coliphages) with pathogenic human viruses in soil systems. In this study the mobility and comparative reduction of the prototype NLV, Norwalk Virus (NV), was compared to poliovirus 1 (PV1), a bacterial indicator (E coli, EC) and a viral indicator (coliphage MS2) through miniature soil columns. Replicate, 10 cm deep, miniature columns were prepared using three soils representing a range of soil textures (sand, organic muck, and clay). Columns were initially conditioned, then incubated at 10-14 degrees C, dosed twice weekly for 8 weeks with one column pore volume of virus-seeded groundwater per dose, followed by 8 weeks of dosing with one column pore volume per dose of unseeded, simulated rainwater. Columns were allowed to drain after each dosing until an effluent volume equivalent to an applied dose was collected. Column effluents and doses were assayed for all viruses and EC. Rapid mobility with minimal reduction was observed for all organisms in the sand. Similar reductions were observed in organic muck for most organisms but NV showed a greater reduction. No organisms were shown to pass through the clay columns. Elution of viruses, in particular PV1, from the columns was gradual. After cessation of microbe dosing, E. coli was less detectable than viruses in column effluents and, therefore, unreliable as a virus indicator.

Metallic artifact mitigation and organ-constrained tissue assignment for Monte Carlo calculations of permanent implant lung brachytherapy.

PubMed

Sutherland, J G H; Miksys, N; Furutani, K M; Thomson, R M

2014-01-01

To investigate methods of generating accurate patient-specific computational phantoms for the Monte Carlo calculation of lung brachytherapy patient dose distributions. Four metallic artifact mitigation methods are applied to six lung brachytherapy patient computed tomography (CT) images: simple threshold replacement (STR) identifies high CT values in the vicinity of the seeds and replaces them with estimated true values; fan beam virtual sinogram replaces artifact-affected values in a virtual sinogram and performs a filtered back-projection to generate a corrected image; 3D median filter replaces voxel values that differ from the median value in a region of interest surrounding the voxel and then applies a second filter to reduce noise; and a combination of fan beam virtual sinogram and STR. Computational phantoms are generated from artifact-corrected and uncorrected images using several tissue assignment schemes: both lung-contour constrained and unconstrained global schemes are considered. Voxel mass densities are assigned based on voxel CT number or using the nominal tissue mass densities. Dose distributions are calculated using the EGSnrc user-code BrachyDose for (125)I, (103)Pd, and (131)Cs seeds and are compared directly as well as through dose volume histograms and dose metrics for target volumes surrounding surgical sutures. Metallic artifact mitigation techniques vary in ability to reduce artifacts while preserving tissue detail. Notably, images corrected with the fan beam virtual sinogram have reduced artifacts but residual artifacts near sources remain requiring additional use of STR; the 3D median filter removes artifacts but simultaneously removes detail in lung and bone. Doses vary considerably between computational phantoms with the largest differences arising from artifact-affected voxels assigned to bone in the vicinity of the seeds. Consequently, when metallic artifact reduction and constrained tissue assignment within lung contours are employed in generated phantoms, this erroneous assignment is reduced, generally resulting in higher doses. Lung-constrained tissue assignment also results in increased doses in regions of interest due to a reduction in the erroneous assignment of adipose to voxels within lung contours. Differences in dose metrics calculated for different computational phantoms are sensitive to radionuclide photon spectra with the largest differences for (103)Pd seeds and smallest but still considerable differences for (131)Cs seeds. Despite producing differences in CT images, dose metrics calculated using the STR, fan beam + STR, and 3D median filter techniques produce similar dose metrics. Results suggest that the accuracy of dose distributions for permanent implant lung brachytherapy is improved by applying lung-constrained tissue assignment schemes to metallic artifact corrected images.

Physical aspects of total-body irradiation at the Middlesex Hospital (UCL group of hospitals), London 1988 - 1993: II. In vivo planning and dosimetry

NASA Astrophysics Data System (ADS)

Planskoy, B.; Tapper, P. D.; Bedford, A. M.; Davis, F. M.

1996-11-01

Part II of this paper gives the results of applying the TBI methods described in part I, to in vivo patient planning and dosimetry. Patients are planned on nine CT based body slices, five of which pass through the lungs. Planned doses are verified with ten silicon diodes applied bi-laterally to five body sites, at each treatment. LiF TLDs are applied to seven other body sites at the first treatment only. For 84 patients and at least 1016 measurements per body site with the diodes, the mean measured total doses agreed with planned doses within at most 2% except at lung levels, where the mean measured dose was 3% too low. Standard deviations of the measurements about the mean were between 2.4 and 3.1%. For the LiF TLDs, the mean measured doses for all seven body sites were within of planned doses. A separate assessment of measured entrance and transmitted doses showed that the former agreed well with planned doses, but that the latter tended to be low, especially over the lungs, and that they had a wider dispersion. Possible reasons for this are discussed. These results show measurement uncertainties similar to those for non-TBI treatments of Nilsson et al, Leunens et al and Essers et al. An analysis of the treatment plans showed a mean dose inhomogeneity in the body (75 patients, nine slices) of (1 s.d.) and in the lungs (40 patients, five slices) of (1 s.d.). The conclusions are that, overall, the methods are reasonably satisfactory but that, with an extra effort, even closer agreement between measured and planned doses and a further limited reduction in the body dose inhomogeneity could be obtained. However, if it were thought desirable to make a substantial reduction in the dose inhomogeneity in the body and lungs, this could only be achieved with the available equipment by changing from lateral to anterior - posterior irradiation and any potential advantages of this change would have to be balanced against a likely deterioration in patient comfort and an increase in treatment set-up times.

A dual tracer ratio method for comparative emission measurements in an experimental dairy housing

NASA Astrophysics Data System (ADS)

Mohn, Joachim; Zeyer, Kerstin; Keck, Margret; Keller, Markus; Zähner, Michael; Poteko, Jernej; Emmenegger, Lukas; Schrade, Sabine

2018-04-01

Agriculture, and in particular dairy farming, is an important source of ammonia (NH3) and non-carbon dioxide greenhouse gas (GHG) emissions. This calls for the development and quantification of effective mitigation strategies. Our study presents the implementation of a dual tracer ratio method in a novel experimental dairy housing with two identical, but spatially separated housing areas. Modular design and flexible floor elements allow the assessment of structural, process engineering and organisational abatement measures at practical scale. Thereby, the emission reduction potential of specific abatement measures can be quantified in relation to a reference system. Emissions in the naturally ventilated housing are determined by continuous dosing of two artificial tracers (sulphur hexafluoride SF6, trifluoromethylsulphur pentafluoride SF5CF3) and their real-time detection in the ppt range with an optimized GC-ECD method. The two tracers are dosed into different experimental sections, which enables the independent assessment of both housing areas. Mass flow emissions of NH3 and GHGs are quantified by areal dosing of tracer gases and multipoint sampling as well as real-time analysis of both tracer and target gases. Validation experiments demonstrate that the technique is suitable for both areal and point emission sources and achieves an uncertainty of less than 10% for the mass emissions of NH3, methane (CH4) and carbon dioxide (CO2), which is superior to other currently available methods. Comparative emission measurements in this experimental dairy housing will provide reliable, currently unavailable information on emissions for Swiss dairy farming and demonstrate the reduction potential of mitigation measures for NH3, GHGs and potentially other pollutants.

Dynamic intensity-weighted region of interest imaging for conebeam CT

PubMed Central

Pearson, Erik; Pan, Xiaochuan; Pelizzari, Charles

2017-01-01

BACKGROUND Patient dose from image guidance in radiotherapy is small compared to the treatment dose. However, the imaging beam is untargeted and deposits dose equally in tumor and healthy tissues. It is desirable to minimize imaging dose while maintaining efficacy. OBJECTIVE Image guidance typically does not require full image quality throughout the patient. Dynamic filtration of the kV beam allows local control of CT image noise for high quality around the target volume and lower quality elsewhere, with substantial dose sparing and reduced scatter fluence on the detector. METHODS The dynamic Intensity-Weighted Region of Interest (dIWROI) technique spatially varies beam intensity during acquisition with copper filter collimation. Fluence is reduced by 95% under the filters with the aperture conformed dynamically to the ROI during cone-beam CT scanning. Preprocessing to account for physical effects of the collimator before reconstruction is described. RESULTS Reconstructions show image quality comparable to a standard scan in the ROI, with higher noise and streak artifacts in the outer region but still adequate quality for patient localization. Monte Carlo modeling shows dose reduction by 10–15% in the ROI due to reduced scatter, and up to 75% outside. CONCLUSIONS The presented technique offers a method to reduce imaging dose by accepting increased image noise outside the ROI, while maintaining full image quality inside the ROI. PMID:27257875

TH-EF-BRB-03: Significant Cord and Esophagus Dose Reduction by 4π Non-Coplanar Spine Stereotactic Body Radiation Therapy and Stereotactic Radiosurgery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, V; Tran, A; Nguyen, D

Purpose: To demonstrate significant organ-at-risk (OAR) sparing achievable with 4π non-coplanar radiotherapy on spine SBRT and SRS patients. Methods: Twenty-five stereotactic spine cases previously treated with VMAT (n = 23) or IMRT (n = 2) were included in this study. A computer-aided-design model of a Linac with a 3D-scanned human surface was utilized to determine the feasible beam space throughout the 4π steradian and beam specific source-to-target-distances (STD) required for collision avoidance. 4π radiotherapy plans integrating beam orientation and fluence map optimization were then created using a column-generation algorithm. Twenty optimal beams were selected for each case. To evaluate themore » tradeoff between dosimetric benefit and treatment complexity, 4π plans including only isocentrically deliverable beams were also created. Beam angles of all standard and isocentric 4π plans were imported into Eclipse to recalculate the dose using the same calculation engine as the clinical plans for unbiased comparison. OAR and PTV dose statistics for the clinical, standard-4π, and isocentric-4π plans were compared. Results: Comparing standard-4π to clinical plans, particularly significant average percent reduction in the [mean, maximum] dose of the cord and esophagus of [41%, 21.7%], and [38.7%, 36.4%] was observed, along with global decrease in all other OAR dose statistics. The average cord volume receiving more than 50% prescription dose was substantially decreased by 76%. In addition, improved PTV coverage was demonstrated with a maximum dose reduction of 0.93% and 1.66% increase in homogeneity index (D95/D5). All isocentric-4π plans achieved dosimetric performance equivalent to that of the standard-4π plans with higher delivery complexity. Conclusion: 4π radiotherapy significantly improves stereotactic spine treatment dosimetry. With the substantial OAR dose sparing, PTV dose escalation is considerably safer. Isocentric-4π is sufficient to achieve the dosimetric gain. The successful implementation of 4π using an FDA approved planning system paves the way for a prospective clinical trial. Varian Medical Systems, NIH R43CA183390 and R01CA188300, NSF graduate research fellowship DGE-1144087.« less

In-Plane Shielding for CT: Effect of Off-Centering, Automatic Exposure Control and Shield-to-Surface Distance

PubMed Central

Dang, Pragya; Singh, Sarabjeet; Saini, Sanjay; Shepard, Jo-Anne O.

2009-01-01

Objective To assess effects of off-centering, automatic exposure control, and padding on attenuation values, noise, and radiation dose when using in-plane bismuth-based shields for CT scanning. Materials and Methods A 30 cm anthropomorphic chest phantom was scanned on a 64-multidetector CT, with the center of the phantom aligned to the gantry isocenter. Scanning was repeated after placing a bismuth breast shield on the anterior surface with no gap and with 1, 2, and 6 cm of padding between the shield and the phantom surface. The "shielded" phantom was also scanned with combined modulation and off-centering of the phantom at 2 cm, 4 cm and 6 cm below the gantry isocenter. CT numbers, noise, and surface radiation dose were measured. The data were analyzed using an analysis of variance. Results The in-plane shield was not associated with any significant increment for the surface dose or CT dose index volume, which was achieved by comparing the radiation dose measured by combined modulation technique to the fixed mAs (p > 0.05). Irrespective of the gap or the surface CT numbers, surface noise increased to a larger extent compared to Hounsfield unit (HU) (0-6 cm, 26-55%) and noise (0-6 cm, 30-40%) in the center. With off-centering, in-plane shielding devices are associated with less dose savings, although dose reduction was still higher than in the absence of shielding (0 cm off-center, 90% dose reduction; 2 cm, 61%) (p < 0.0001). Streak artifacts were noted at 0 cm and 1 cm gaps but not at 2 cm and 6 cm gaps of shielding to the surface distances. Conclusion In-plane shields are associated with greater image noise, artifactually increased attenuation values, and streak artifacts. However, shields reduce radiation dose regardless of the extent of off-centering. Automatic exposure control did not increase radiation dose when using a shield. PMID:19270862

SU-E-P-03: Implementing a Low Dose Lung Screening CT Program Meeting Regulatory Requirements

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaFrance, M; Marsh, S; O'Donnell, G

Purpose: To provide information pertaining to IROC Houston QA Center's (RPC) credentialing process for institutions participating in NCI-sponsored clinical trials. Purpose: Provide guidance to the Radiology Departments with the intent of implementing a Low Dose CT Screening Program using different CT Scanners with multiple techniques within the framework of the required state regulations. Method: State Requirements for the purpose of implementing a Low Dose CT Lung Protocol required working with the Radiology and Pulmonary Department in setting up a Low Dose Screening Protocol designed to reduce the radiation burden to the patients enrolled. Radiation dose measurements (CTDIvol) for various CTmore » manufacturers (Siemens16, Siemens 64, Philips 64, and Neusoft128) for three different weight based protocols. All scans were reviewed by the Radiologist. Prior to starting a low dose lung screening protocol, information had to be submitted to the state for approval. Performing a Healing Arts protocol requires extensive information. This not only includes name and address of the applicant but a detailed description of the disease, the x-ray examination and the population to be examined. The unit had to be tested by a qualified expert using the technique charts. The credentials of all the operators, the supervisors and the Radiologists had to be submitted to the state. Results: All the appropriate documentation was sent to the state for review. The measured results between the Low Dose Protocol versus the default Adult Chest Protocol showed that there was a dose reduction of 65% for small (100-150 lb.) patient, 75% for the Medium patient (151-250 lbs.), and a 55% reduction for the Large patient ( over 250 lbs.). Conclusion: Measured results indicated that the Low Dose Protocol indeed lowered the screening patient's radiation dose and the institution was able to submit the protocol to the State's regulators.« less

The Effect of Realtime Monitoring on Dose Exposure to Staff Within an Interventional Radiology Setting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baumann, Frederic, E-mail: fredericbaumann@hotmail.com; Katzen, Barry T.; Carelsen, Bart

PurposeThe purpose of this study is to evaluate a new device providing real-time monitoring on radiation exposure during fluoroscopy procedures intending to reduce radiation in an interventional radiology setting.Materials and MethodsIn one interventional suite, a new system providing a real-time radiation dose display and five individual wireless dosimeters were installed. The five dosimeters were worn by the attending, fellow, nurse, technician, and anesthesiologist for every procedure taking place in that suite. During the first 6-week interval the dose display was off (closed phase) and activated thereafter, for a 6-week learning phase (learning phase) and a 10-week open phase (open phase).more » During these phases, the staff dose and the individual dose for each procedure were recorded from the wireless dosimeter and correlated with the fluoroscopy time. Further subanalysis for dose exposure included diagnostic versus interventional as well as short (<10 min) versus long (>10 min) procedures.ResultsA total of 252 procedures were performed (n = 88 closed phase, n = 50 learning phase, n = 114 open phase). The overall mean staff dose per fluoroscopic minute was 42.79 versus 19.81 µSv/min (p < 0.05) comparing the closed and open phase. Thereby, anesthesiologists were the only individuals attaining a significant dose reduction during open phase 16.9 versus 8.86 µSv/min (p < 0.05). Furthermore, a significant reduction of total staff dose was observed for short 51 % and interventional procedures 45 % (p < 0.05, for both).ConclusionA real-time qualitative display of radiation exposure may reduce team radiation dose. The process may take a few weeks during the learning phase but appears sustained, thereafter.« less

External beam boost versus interstitial high-dose-rate brachytherapy boost in the adjuvant radiotherapy following breast-conserving therapy in early-stage breast cancer: a dosimetric comparison

PubMed Central

Melchert, Corinna; Kovács, György

2016-01-01

Purpose This study aims to compare the dosimetric data of local tumor's bed dose escalation (boost) with photon beams (external beam radiation therapy – EBRT) versus high-dose-rate interstitial brachytherapy (HDR-BT) after breast-conserving treatment in women with early-stage breast cancer. Material and methods We analyzed the treatment planning data of 136 irradiated patients, treated between 2006 and 2013, who underwent breast-conserving surgery and adjuvant whole breast irradiation (WBI; 50.4 Gy) and boost (HDR-BT: 10 Gy in one fraction [n = 36]; EBRT: 10 Gy in five fractions [n = 100]). Organs at risk (OAR; heart, ipsilateral lung, skin, most exposed rib segment) were delineated. Dosimetric parameters were calculated with the aid of dose-volume histograms (DVH). A non-parametric test was performed to compare the two different boost forms. Results There was no difference for left-sided cancers regarding the maximum dose to the heart (HDR-BT 29.8% vs. EBRT 29.95%, p = 0.34). The maximum doses to the other OAR were significantly lower for HDR-BT (Dmax lung 47.12% vs. 87.7%, p < 0.01; rib 61.17% vs. 98.5%, p < 0.01; skin 57.1% vs. 94.75%, p < 0.01; in the case of right-sided breast irradiation, dose of the heart 6.00% vs. 16.75%, p < 0.01). Conclusions Compared to EBRT, local dose escalation with HDR-BT presented a significant dose reduction to the investigated OAR. Only left-sided irradiation showed no difference regarding the maximum dose to the heart. Reducing irradiation exposure to OAR could result in a reduction of long-term side effects. Therefore, from a dosimetric point of view, an interstitial boost complementary to WBI via EBRT seems to be more advantageous in the adjuvant radiotherapy of breast cancer. PMID:27648082

Biological uptake of polychlorinated biphenyls by Macoma balthica from sediment amended with activated carbon

USGS Publications Warehouse

McLeod, Pamela B.; van den Heuvel-Greve, Martine J.; Luoma, S.N.; Luthy, R.G.

2007-01-01

This work characterizes the efficacy of activated carbon amendment in reducing polychlorinated biphenyl (PCB) bioavailability to clams (Macoma balthica) from field-contaminated sediment (Hunters Point Naval Shipyard, San Francisco Bay, CA, USA) Test methods were developed for the use of clams to investigate the effects of sediment amendment on biological uptake. Sediment was mixed with activated carbon for one month. Bioaccumulation tests (28 d) were employed to assess the relationships between carbon dose and carbon particle size on observed reductions in clam biological uptake of PCBs. Extraction and cleanup protocols were developed for the clam tissue. Efficacy of activated carbon treatment was found to increase with both increasing carbon dose and decreasing carbon particle size. Average reductions in bioaccumulation of 22, 64, and 84% relative to untreated Hunters Point sediment were observed for carbon amendments of 0.34, 1.7, and 3.4%, respectively. Average bioaccumulation reductions of 41, 73, and 89% were observed for amendments (dose = 1.7% dry wt) with carbon particles of 180 to 250, 75 to 180, and 25 to 75 ??m, respectively, in diameter, indicating kinetic phenomena in these tests. Additionally, a biodynamic model quantifying clam PCB uptake from water and sediment as well as loss through elimination provided a good fit of experimental data. Model predictions suggest that the sediment ingestion route contributed 80 to 95% of the PCB burdens in the clams. ?? 2007 SETAC.

Three-Dimensional Radiobiologic Dosimetry: Application of Radiobiologic Modeling to Patient-Specific 3-Dimensional Imaging–Based Internal Dosimetry

PubMed Central

Prideaux, Andrew R.; Song, Hong; Hobbs, Robert F.; He, Bin; Frey, Eric C.; Ladenson, Paul W.; Wahl, Richard L.; Sgouros, George

2010-01-01

Phantom-based and patient-specific imaging-based dosimetry methodologies have traditionally yielded mean organ-absorbed doses or spatial dose distributions over tumors and normal organs. In this work, radiobiologic modeling is introduced to convert the spatial distribution of absorbed dose into biologically effective dose and equivalent uniform dose parameters. The methodology is illustrated using data from a thyroid cancer patient treated with radioiodine. Methods Three registered SPECT/CT scans were used to generate 3-dimensional images of radionuclide kinetics (clearance rate) and cumulated activity. The cumulated activity image and corresponding CT scan were provided as input into an EGSnrc-based Monte Carlo calculation: The cumulated activity image was used to define the distribution of decays, and an attenuation image derived from CT was used to define the corresponding spatial tissue density and composition distribution. The rate images were used to convert the spatial absorbed dose distribution to a biologically effective dose distribution, which was then used to estimate a single equivalent uniform dose for segmented volumes of interest. Equivalent uniform dose was also calculated from the absorbed dose distribution directly. Results We validate the method using simple models; compare the dose-volume histogram with a previously analyzed clinical case; and give the mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for an illustrative case of a pediatric thyroid cancer patient with diffuse lung metastases. The mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for the tumor were 57.7, 58.5, and 25.0 Gy, respectively. Corresponding values for normal lung tissue were 9.5, 9.8, and 8.3 Gy, respectively. Conclusion The analysis demonstrates the impact of radiobiologic modeling on response prediction. The 57% reduction in the equivalent dose value for the tumor reflects a high level of dose nonuniformity in the tumor and a corresponding reduced likelihood of achieving a tumor response. Such analyses are expected to be useful in treatment planning for radionuclide therapy. PMID:17504874

Intussusception reduction: Effect of air vs. liquid enema on radiation dose.

PubMed

Kaplan, Summer L; Magill, Dennise; Felice, Marc A; Edgar, J Christopher; Anupindi, Sudha A; Zhu, Xiaowei

2017-10-01

Both air and radiopaque liquid contrast are used to reduce ileocolic intussusception under fluoroscopy. Some suggest air lowers radiation dose due to shorter procedure times. However, air enema likely lowers radiation dose regardless of fluoroscopy time due to less density over the automatic exposure control cells. We test the hypothesis that air enema reduction of ileocolic intussusception results in lower radiation dose than liquid contrast enema independent of fluoroscopy time. We describe a role for automatic exposure control in this dose difference. We retrospectively evaluated air and liquid intussusception reductions performed on a single digital fluoroscopic unit during a 26-month period. We compared patient age, weight, gender, exam time of day and year, performing radiologist(s), radiographic image acquisitions, grid and magnification use, fluoroscopy time and dose area product. We compared categorical and continuous variables statistically using chi-square and Mann-Whitney U tests, respectively. The mean dose area product was 2.7-fold lower for air enema, 1.3 ± 0.9 dGy·cm 2 , than for liquid, 3.5 ± 2.5 dGy·cm 2 (P<0.005). The mean fluoroscopy time was similar between techniques. The mean dose area product/min was 2.3-fold lower for air, 0.6 ± 0.2 dGy·cm 2 /min, than for liquid, 1.4 ± 0.5 dGy·cm 2 /min (P<0.001). No group differences were identified in other measured dose parameters. Fluoroscopic intussusception reduction using air enema uses less than half the radiation dose of liquid contrast enema. Dose savings are independent of fluoroscopy time and are likely due to automatic exposure control interaction.

Patients with Fabry Disease after Enzyme Replacement Therapy Dose Reduction and Switch-2-Year Follow-Up.

PubMed

Lenders, Malte; Canaan-Kühl, Sima; Krämer, Johannes; Duning, Thomas; Reiermann, Stefanie; Sommer, Claudia; Stypmann, Jörg; Blaschke, Daniela; Üçeyler, Nurcan; Hense, Hans-Werner; Brand, Stefan-Martin; Wanner, Christoph; Weidemann, Frank; Brand, Eva

2016-03-01

Because of the shortage of agalsidase-β supply between 2009 and 2012, patients with Fabry disease either were treated with reduced doses or were switched to agalsidase-α. In this observational study, we assessed end organ damage and clinical symptoms with special focus on renal outcome after 2 years of dose-reduction and/or switch to agalsidase-α. A total of 89 adult patients with Fabry disease who had received agalsidase-β (1.0 mg/kg body wt) for >1 year were nonrandomly assigned to continue this treatment regimen (regular-dose group, n=24), to receive a reduced dose of 0.3-0.5 mg/kg and a subsequent switch to 0.2 mg/kg agalsidase-α (dose-reduction-switch group, n=28), or to directly switch to 0.2 mg/kg agalsidase-α (switch group, n=37) and were followed-up for 2 years. We assessed clinical events (death, myocardial infarction, severe arrhythmia, stroke, progression to ESRD), changes in cardiac and renal function, Fabry-related symptoms (pain, hypohidrosis, diarrhea), and disease severity scores. Determination of renal function by creatinine and cystatin C-based eGFR revealed decreasing eGFRs in the dose-reduction-switch group and the switch group. The Mainz Severity Score Index increased significantly in these two groups (P=0.02 and P<0.001, respectively), and higher frequencies of gastrointestinal pain occurred during follow-up. In conclusion, after 2 years of observation, all groups showed a stable clinical disease course with respect to serious clinical events. However, patients under agalsidase-β dose-reduction and switch or a direct switch to agalsidase-α showed a decline of renal function independent of the eGFR formula used. Copyright © 2016 by the American Society of Nephrology.

Patients with Fabry Disease after Enzyme Replacement Therapy Dose Reduction and Switch–2-Year Follow-Up

PubMed Central

Lenders, Malte; Canaan-Kühl, Sima; Krämer, Johannes; Duning, Thomas; Reiermann, Stefanie; Sommer, Claudia; Stypmann, Jörg; Blaschke, Daniela; Üçeyler, Nurcan; Hense, Hans-Werner; Brand, Stefan-Martin; Wanner, Christoph; Weidemann, Frank

2016-01-01

Because of the shortage of agalsidase-β supply between 2009 and 2012, patients with Fabry disease either were treated with reduced doses or were switched to agalsidase-α. In this observational study, we assessed end organ damage and clinical symptoms with special focus on renal outcome after 2 years of dose-reduction and/or switch to agalsidase-α. A total of 89 adult patients with Fabry disease who had received agalsidase-β (1.0 mg/kg body wt) for >1 year were nonrandomly assigned to continue this treatment regimen (regular-dose group, n=24), to receive a reduced dose of 0.3–0.5 mg/kg and a subsequent switch to 0.2 mg/kg agalsidase-α (dose-reduction-switch group, n=28), or to directly switch to 0.2 mg/kg agalsidase-α (switch group, n=37) and were followed-up for 2 years. We assessed clinical events (death, myocardial infarction, severe arrhythmia, stroke, progression to ESRD), changes in cardiac and renal function, Fabry-related symptoms (pain, hypohidrosis, diarrhea), and disease severity scores. Determination of renal function by creatinine and cystatin C–based eGFR revealed decreasing eGFRs in the dose-reduction-switch group and the switch group. The Mainz Severity Score Index increased significantly in these two groups (P=0.02 and P<0.001, respectively), and higher frequencies of gastrointestinal pain occurred during follow-up. In conclusion, after 2 years of observation, all groups showed a stable clinical disease course with respect to serious clinical events. However, patients under agalsidase-β dose-reduction and switch or a direct switch to agalsidase-α showed a decline of renal function independent of the eGFR formula used. PMID:26185201

Radiation dose reduction: comparative assessment of publication volume between interventional and diagnostic radiology.

PubMed

Hansmann, Jan; Henzler, Thomas; Gaba, Ron C; Morelli, John N

2017-01-01

We aimed to quantify and compare awareness regarding radiation dose reduction within the interventional radiology and diagnostic radiology communities. Abstracts accepted to the annual meetings of the Society of Interventional Radiology (SIR), the Cardiovascular and Interventional Radiological Society of Europe (CIRSE), the Radiological Society of North America (RSNA), and the European Congress of Radiology (ECR) between 2005 and 2015 were analyzed using the search terms "interventional/computed tomography" and "radiation dose/radiation dose reduction." A PubMed query using the above-mentioned search terms for the years of 2005-2015 was performed. Between 2005 and 2015, a total of 14 520 abstracts (mean, 660±297 abstracts) and 80 614 abstracts (mean, 3664±1025 abstracts) were presented at interventional and diagnostic radiology meetings, respectively. Significantly fewer abstracts related to radiation dose were presented at the interventional radiology meetings compared with the diagnostic radiology meetings (162 abstracts [1% of total] vs. 2706 [3% of total]; P < 0.001). On average 15±7 interventional radiology abstracts (range, 6-27) and 246±105 diagnostic radiology abstracts (range, 112-389) pertaining to radiation dose were presented at each meeting. The PubMed query revealed an average of 124±39 publications (range, 79-187) and 1205±307 publications (range, 829-1672) related to interventional and diagnostic radiology dose reduction per year, respectively (P < 0.001). The observed increase in the number of abstracts regarding radiation dose reduction in the interventional radiology community over the past 10 years has not mirrored the increased volume seen within diagnostic radiology, suggesting that increased education and discussion about this topic may be warranted.

Effectiveness of Ivermectin and Albendazole against Haemonchus contortus in Sheep in West Java, Indonesia.

PubMed

Puspitasari, Silvia; Farajallah, Achmad; Sulistiawati, Erni; Muladno

2016-02-01

Administering a half dose of an anthelmintic is a simple method for detecting resistance in parasites infesting small ruminants. When a single anthelmintic fails in native sheep from Indonesia, a combination of anthelmintics from different chemical classes with different modes of action are administered as an alternative parasite-control strategy. This study compared the anthelmintic efficacy of ivermectin (IVM) and albendazole (ABZ) given either separately as a single dose or half dose or co-administered to sheep naturally infected with Haemonchus contortus. Twelve sheep from Bogor, West Java, Indonesia were divided into the following six treatment groups: half-dose IVM, full-dose IVM, half-dose ABZ, full-dose ABZ, combined IVM + ABZ, and control. The treatment efficacy was determined using the faecal egg count reduction test (FECRT) at day 0 (pre-treatment) and post-treatment at days 7, 14, 21, 28, 35, and 42. The efficacies of half-dose IVM, full-dose IVM, half-dose ABZ, full-dose ABZ, and the combination treatment ranged from -1900% to 100%, 99% to 100%, -167% to 100%, -467% to 89%, and -200% to 100%, respectively. The FECRT for the half-dose IVM, half-dose ABZ, full-dose ABZ showed that H. contortus is resistant to half-dose IVM and ABZ. Full-dose IVM was effective against H. contortus. The combined treatment was more effective against H. contortus than ABZ alone.

Effectiveness of Ivermectin and Albendazole against Haemonchus contortus in Sheep in West Java, Indonesia

PubMed Central

Puspitasari, Silvia; Farajallah, Achmad; Sulistiawati, Erni; Muladno

2016-01-01

Administering a half dose of an anthelmintic is a simple method for detecting resistance in parasites infesting small ruminants. When a single anthelmintic fails in native sheep from Indonesia, a combination of anthelmintics from different chemical classes with different modes of action are administered as an alternative parasite-control strategy. This study compared the anthelmintic efficacy of ivermectin (IVM) and albendazole (ABZ) given either separately as a single dose or half dose or co-administered to sheep naturally infected with Haemonchus contortus. Twelve sheep from Bogor, West Java, Indonesia were divided into the following six treatment groups: half-dose IVM, full-dose IVM, half-dose ABZ, full-dose ABZ, combined IVM + ABZ, and control. The treatment efficacy was determined using the faecal egg count reduction test (FECRT) at day 0 (pre-treatment) and post-treatment at days 7, 14, 21, 28, 35, and 42. The efficacies of half-dose IVM, full-dose IVM, half-dose ABZ, full-dose ABZ, and the combination treatment ranged from −1900% to 100%, 99% to 100%, −167% to 100%, −467% to 89%, and −200% to 100%, respectively. The FECRT for the half-dose IVM, half-dose ABZ, full-dose ABZ showed that H. contortus is resistant to half-dose IVM and ABZ. Full-dose IVM was effective against H. contortus. The combined treatment was more effective against H. contortus than ABZ alone. PMID:27019686

Assessment of the dose reduction potential of a model-based iterative reconstruction algorithm using a task-based performance metrology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samei, Ehsan, E-mail: samei@duke.edu; Richard, Samuel

2015-01-15

Purpose: Different computed tomography (CT) reconstruction techniques offer different image quality attributes of resolution and noise, challenging the ability to compare their dose reduction potential against each other. The purpose of this study was to evaluate and compare the task-based imaging performance of CT systems to enable the assessment of the dose performance of a model-based iterative reconstruction (MBIR) to that of an adaptive statistical iterative reconstruction (ASIR) and a filtered back projection (FBP) technique. Methods: The ACR CT phantom (model 464) was imaged across a wide range of mA setting on a 64-slice CT scanner (GE Discovery CT750 HD,more » Waukesha, WI). Based on previous work, the resolution was evaluated in terms of a task-based modulation transfer function (MTF) using a circular-edge technique and images from the contrast inserts located in the ACR phantom. Noise performance was assessed in terms of the noise-power spectrum (NPS) measured from the uniform section of the phantom. The task-based MTF and NPS were combined with a task function to yield a task-based estimate of imaging performance, the detectability index (d′). The detectability index was computed as a function of dose for two imaging tasks corresponding to the detection of a relatively small and a relatively large feature (1.5 and 25 mm, respectively). The performance of MBIR in terms of the d′ was compared with that of ASIR and FBP to assess its dose reduction potential. Results: Results indicated that MBIR exhibits a variability spatial resolution with respect to object contrast and noise while significantly reducing image noise. The NPS measurements for MBIR indicated a noise texture with a low-pass quality compared to the typical midpass noise found in FBP-based CT images. At comparable dose, the d′ for MBIR was higher than those of FBP and ASIR by at least 61% and 19% for the small feature and the large feature tasks, respectively. Compared to FBP and ASIR, MBIR indicated a 46%–84% dose reduction potential, depending on task, without compromising the modeled detection performance. Conclusions: The presented methodology based on ACR phantom measurements extends current possibilities for the assessment of CT image quality under the complex resolution and noise characteristics exhibited with statistical and iterative reconstruction algorithms. The findings further suggest that MBIR can potentially make better use of the projections data to reduce CT dose by approximately a factor of 2. Alternatively, if the dose held unchanged, it can improve image quality by different levels for different tasks.« less

Radiation dose reduction in thoracic and lumbar spine instrumentation using navigation based on an intraoperative cone beam CT imaging system: a prospective randomized clinical trial.

PubMed

Pireau, Nathalie; Cordemans, Virginie; Banse, Xavier; Irda, Nadia; Lichtherte, Sébastien; Kaminski, Ludovic

2017-11-01

Spine surgery still remains a challenge for every spine surgeon, aware of the potential serious outcomes of misplaced instrumentation. Though many studies have highlighted that using intraoperative cone beam CT imaging and navigation systems provides higher accuracy than conventional freehand methods for placement of pedicle screws in spine surgery, few studies are concerned about how to reduce radiation exposure for patients with the use of such technology. One of the main focuses of this study is based on the ALARA principle (as low as reasonably achievable). A prospective randomized trial was conducted in the hybrid operating room between December 2015 and December 2016, including 50 patients operated on for posterior instrumented thoracic and/or lumbar spinal fusion. Patients were randomized to intraoperative 3D acquisition high-dose (standard dose) or low-dose protocol, and a total of 216 pedicle screws were analyzed in terms of screw position. Two different methods were used to measure ionizing radiation: the total skin dose (derived from the dose-area product) and the radiation dose evaluated by thermoluminescent dosimeters on the surgical field. According to Gertzbein and Heary classifications, low-dose protocol provided a significant higher accuracy of pedicle screw placement than the high-dose protocol (96.1 versus 92%, respectively). Seven screws (3.2%), all implanted with the high-dose protocol, needed to be revised intraoperatively. The use of low-dose acquisition protocols reduced patient exposure by a factor of five. This study emphasizes the paramount importance of using low-dose protocols for intraoperative cone beam CT imaging coupled with the navigation system, as it at least does not affect the accuracy of pedicle screw placement and irradiates drastically less.

Evaluation of normalized metal artifact reduction (NMAR) in kVCT using MVCT prior images for radiotherapy treatment planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paudel, M. R.; Mackenzie, M.; Rathee, S.

2013-08-15

Purpose: To evaluate the metal artifacts in kilovoltage computed tomography (kVCT) images that are corrected using a normalized metal artifact reduction (NMAR) method with megavoltage CT (MVCT) prior images.Methods: Tissue characterization phantoms containing bilateral steel inserts are used in all experiments. Two MVCT images, one without any metal artifact corrections and the other corrected using a modified iterative maximum likelihood polychromatic algorithm for CT (IMPACT) are translated to pseudo-kVCT images. These are then used as prior images without tissue classification in an NMAR technique for correcting the experimental kVCT image. The IMPACT method in MVCT included an additional model formore » the pair/triplet production process and the energy dependent response of the MVCT detectors. An experimental kVCT image, without the metal inserts and reconstructed using the filtered back projection (FBP) method, is artificially patched with the known steel inserts to get a reference image. The regular NMAR image containing the steel inserts that uses tissue classified kVCT prior and the NMAR images reconstructed using MVCT priors are compared with the reference image for metal artifact reduction. The Eclipse treatment planning system is used to calculate radiotherapy dose distributions on the corrected images and on the reference image using the Anisotropic Analytical Algorithm with 6 MV parallel opposed 5 × 10 cm{sup 2} fields passing through the bilateral steel inserts, and the results are compared. Gafchromic film is used to measure the actual dose delivered in a plane perpendicular to the beams at the isocenter.Results: The streaking and shading in the NMAR image using tissue classifications are significantly reduced. However, the structures, including metal, are deformed. Some uniform regions appear to have eroded from one side. There is a large variation of attenuation values inside the metal inserts. Similar results are seen in commercially corrected image. Use of MVCT prior images without tissue classification in NMAR significantly reduces these problems. The radiation dose calculated on the reference image is close to the dose measured using the film. Compared to the reference image, the calculated dose difference in the conventional NMAR image, the corrected images using uncorrected MVCT image, and IMPACT corrected MVCT image as priors is ∼15.5%, ∼5%, and ∼2.7%, respectively, at the isocenter.Conclusions: The deformation and erosion of the structures present in regular NMAR corrected images can be largely reduced by using MVCT priors without tissue segmentation. The attenuation value of metal being incorrect, large dose differences relative to the true value can result when using the conventional NMAR image. This difference can be significantly reduced if MVCT images are used as priors. Reduced tissue deformation, better tissue visualization, and correct information about the electron density of the tissues and metals in the artifact corrected images could help delineate the structures better, as well as calculate radiation dose more correctly, thus enhancing the quality of the radiotherapy treatment planning.« less

Paediatric x-ray radiation dose reduction and image quality analysis.

PubMed

Martin, L; Ruddlesden, R; Makepeace, C; Robinson, L; Mistry, T; Starritt, H

2013-09-01

Collaboration of multiple staff groups has resulted in significant reduction in the risk of radiation-induced cancer from radiographic x-ray exposure during childhood. In this study at an acute NHS hospital trust, a preliminary audit identified initial exposure factors. These were compared with European and UK guidance, leading to the introduction of new factors that were in compliance with European guidance on x-ray tube potentials. Image quality was assessed using standard anatomical criteria scoring, and visual grading characteristics analysis assessed the impact on image quality of changes in exposure factors. This analysis determined the acceptability of gradual radiation dose reduction below the European and UK guidance levels. Chest and pelvis exposures were optimised, achieving dose reduction for each age group, with 7%-55% decrease in critical organ dose. Clinicians confirmed diagnostic image quality throughout the iterative process. Analysis of images acquired with preliminary and final exposure factors indicated an average visual grading analysis result of 0.5, demonstrating equivalent image quality. The optimisation process and final radiation doses are reported for Carestream computed radiography to aid other hospitals in minimising radiation risks to children.

Angular on-line tube current modulation in multidetector CT examinations of children and adults: The influence of different scanning parameters on dose reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papadakis, Antonios E.; Perisinakis, Kostas; Damilakis, John

2007-07-15

The purpose of this study was to assess the potential of angular on-line tube current modulation on dose reduction in pediatric and adult patients undergoing multidetector computed tomography (MDCT) examinations. Five physical anthropomorphic phantoms that simulate the average individual as neonate, 1-year-old, 5-year-old, 10-year-old, and adult were employed in the current study. Phantoms were scanned with the use of on-line tube current modulation (TCM). Percent dose reduction (%DR) factors achieved by applying TCM, were determined for standard protocols used for head and neck, shoulder, thorax, thorax and abdomen, abdomen, abdomen and pelvis, pelvis, and whole body examinations. A preliminary studymore » on the application of TCM in MDCT examinations of adult patients was performed to validate the results obtained in anthropomorphic phantoms. Dose reduction was estimated as the percentage difference of the modulated milliamperes for each scan and the preset milliamperes prescribed by the scan protocol. The dose reduction in children was found to be much lower than the corresponding reduction achieved for adults. For helical scans the %DR factors, ranged between 1.6% and 7.4% for the neonate, 2.9% and 8.7% for the 1-year old, 2% and 6% for the 5-year-old, 5% and 10.9% for the 10-year-old, and 10.4% and 20.7% for the adult individual. For sequential scans the corresponding %DR factors ranged between 1.3% and 6.7%, 4.5% and 11%, 4.2% and 6.6%, 6.4% and 12.3%, and 8.9% and 23.3%, respectively. Broader beam collimations are associated with decreased %DR factors, when other scanning parameters are held constant. TCM did not impair image noise. In adult patients, the %DR values were found to be in good agreement with the corresponding results obtained in the anthropomorphic adult phantom. In conclusion, on-line TCM may be considered as a valuable tool for reducing dose in routine CT examinations of pediatric and adult patients. However, the dose reduction achieved with TCM in neonates and young children was found to be lower than that obtained for adults. Therefore, on-line TCM should work as an additional means to reduce dose and should not replace other conventional means of reducing dose, especially in neonates and young children.« less

Longitudinal study of radiation exposure in computed tomography with an in-house developed dose monitoring system

NASA Astrophysics Data System (ADS)

Renger, Bernhard; Rummeny, Ernst J.; Noël, Peter B.

2013-03-01

During the last decades, the reduction of radiation exposure especially in diagnostic computed tomography is one of the most explored topics. In the same time, it seems challenging to quantify the long-term clinical dose reduction with regard to new hardware as well as software solutions. To overcome this challenge, we developed a Dose Monitoring System (DMS), which collects information from PACS, RIS, MPPS and structured reports. The integration of all sources overcomes the weaknesses of single systems. To gather all possible information, we integrated an optical character recognition system to extract, for example, information from the CT-dose-report. All collected data are transferred to a database for further evaluation, e.g., for calculations of effective as well as organ doses. The DMS provides a single database for tracking all essential study and patient specific information across different modality as well as different vendors. As an initial study, we longitudinally investigated the dose reduction in CT examination when employing a noise-suppressing reconstruction algorithm. For this examination type a significant long-term reduction in radiation exposure is reported, when comparing to a CT-system with standard reconstruction. In summary our DMS tool not only enables us to track radiation exposure on daily bases but further enables to analyses the long term effect of new dose saving strategies. In the future the statistical analyses of all retrospective data, which are available in a modern imaging department, will provide a unique overview of advances in reduction of radiation exposure.

Efficacy of apolipoprotein B synthesis inhibition in subjects with mild-to-moderate hyperlipidaemia.

PubMed

Akdim, Fatima; Tribble, Diane L; Flaim, JoAnn D; Yu, Rosie; Su, John; Geary, Richard S; Baker, Brenda F; Fuhr, Rainard; Wedel, Mark K; Kastelein, John J P

2011-11-01

Mipomersen, an apolipoprotein (apo) B synthesis inhibitor, has been shown to produce potent reductions in apoB and LDL-cholesterol levels in animal models as well as healthy human volunteers. A randomized, double-blind, placebo-controlled, dose-escalation study was designed to evaluate the efficacy and safety of mipomersen monotherapy with or without dose loading in subjects with mild-to-moderate hyperlipidaemia. Fifty subjects with LDL-cholesterol levels between 119 and 266 mg/dL were enrolled into five cohorts at a 4:1 randomization ratio of active to placebo. Two 13-week dose regimens were evaluated at doses ranging from 50 to 400 mg/week. Mipomersen produced dose-dependent reductions in all apoB containing lipoproteins. In the 200 and 300 mg/week dose cohorts, mean reductions from baseline in LDL cholesterol were -45 ± 10% (P= 0.000) and -61 ± 8% (P= 0.000), corresponding to a -46 ± 11% (P= 0.000) and -61 ± 7% (P= 0.000) decrease in apoB levels. Triglyceride levels were also lowered with median reductions up to 53% (P= 0.021). The most common adverse events were injection site reactions. Seven of 40 subjects (18%) showed consecutive transaminase elevations >3× upper limit of normal. Five of these subjects received 400 mg/week, four of whom had apoB levels below the limit of detection. As a consequence, the 400 mg/week cohort was discontinued. Mipomersen administered as monotherapy in subjects with mild-to-moderate hyperlipidaemia produced potent reductions in all apoB-containing lipoproteins. Higher doses were associated with hepatic transaminase increases.

Shielding design of the Mayo Clinic Scottsdale cyclotron vault

NASA Astrophysics Data System (ADS)

Riper, Kenneth A. Van; Metzger, Robert L.; Nelson, Kevin

2017-09-01

Mayo Clinic Scottsdale (Scottsdale, Arizona) is building a cyclotron vault containing a cyclotron with adjacent targets and a beam line leading to an external target. The targets are irradiated by high energy (15 to 16.5 MeV) protons for the production of radioisotopes. We performed Monte Carlo radiation transport simulations to calculate the radiation dose outside of the vault during irradiation of the cyclotron and external targets. We present the Monte Carlo model including the geometry, sources, and variance reduction methods. Mesh tallies surrounding the vault show the external dose rate is within acceptable limits.

The development of a 4D treatment planning methodology to simulate the tracking of central lung tumors in an MRI-linac.

PubMed

Al-Ward, Shahad M; Kim, Anthony; McCann, Claire; Ruschin, Mark; Cheung, Patrick; Sahgal, Arjun; Keller, Brian M

2018-01-01

Targeting and tracking of central lung tumors may be feasible on the Elekta MRI-linac (MRL) due to the soft-tissue visualization capabilities of MRI. The purpose of this work is to develop a novel treatment planning methodology to simulate tracking of central lung tumors with the MRL and to quantify the benefits in OAR sparing compared with the ITV approach. Full 4D-CT datasets for five central lung cancer patients were selected to simulate the condition of having 4D-pseudo-CTs derived from 4D-MRI data available on the MRL with real-time tracking capabilities. We used the MRL treatment planning system to generate two plans: (a) with a set of MLC-defined apertures around the target at each phase of the breathing ("4D-MRL" method); (b) with a fixed set of fields encompassing the maximum inhale and exhale of the breathing cycle ("ITV" method). For both plans, dose accumulation was performed onto a reference phase. To further study the potential benefits of a 4D-MRL method, the results were stratified by tumor motion amplitude, OAR-to-tumor proximity, and the relative OAR motion (ROM). With the 4D-MRL method, the reduction in mean doses was up to 3.0 Gy and 1.9 Gy for the heart and the lung. Moreover, the lung's V12.5 Gy was spared by a maximum of 300 cc. Maximum doses to serial organs were reduced by up to 6.1 Gy, 1.5 Gy, and 9.0 Gy for the esophagus, spinal cord, and the trachea, respectively. OAR dose reduction with our method depended on the tumor motion amplitude and the ROM. Some OARs with large ROMs and in close proximity to the tumor benefited from tracking despite small tumor amplitudes. We developed a novel 4D tracking methodology for the MRL for central lung tumors and quantified the potential dosimetric benefits compared with our current ITV approach. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arbique, G; Anderson, J; Guild, J

Purpose: The National Lung Screening Trial mandated manual low dose CT technique factors, where up to a doubling of radiation output could be used over a regular to large patient size range. Recent guidance from the AAPM and ACR for lung cancer CT screening recommends radiation output adjustment for patient size either through AEC or a manual technique chart. This study evaluated the use of AEC for output control and dose reduction. Methods: The study was performed on a multidetector helical CT scanner (Aquillion ONE, Toshiba Medical) equipped with iterative reconstruction (ADIR-3D), AEC was adjusted with a standard deviation (SD)more » image quality noise index. The protocol SD parameter was incrementally increased to reduce patient population dose while image quality was evaluated by radiologist readers scoring the clinical utility of images on a Likert scale. Results: Plots of effective dose vs. body size (water cylinder diameter reported by the scanner) demonstrate monotonic increase in patient dose with increasing patient size. At the initial SD setting of 19 the average CTDIvol for a standard size patient was ∼ 2.0 mGy (1.2 mSv effective dose). This was reduced to ∼1.0 mGy (0.5 mSv) at an SD of 25 with no noticeable reduction in clinical utility of images as demonstrated by Likert scoring. Plots of effective patient diameter and BMI vs body size indicate that these metrics could also be used for manual technique charts. Conclusion: AEC offered consistent and reliable control of radiation output in this study. Dose for a standard size patient was reduced to one-third of the 3 mGy CTDIvol limit required for ACR accreditation of lung cancer CT screening. Gary Arbique: Research Grant, Toshiba America Medical Systems; Cecelia Brewington: Research Grant, Toshiba America Medical Systems; Di Zhang: Employee, Toshiba America Medical Systems.« less

Pilot Study of Low-Dose Nonenhanced Computed Tomography With Iterative Reconstruction for Diagnosis of Urinary Stones

PubMed Central

Park, Sang Ho; Moon, Young Tae; Myung, Soon Chul; Kim, Tae Hyoung; Chang, In Ho; Kwon, Jong Kyou

2014-01-01

Purpose To evaluate the efficacy of low-dose computed tomography (LDCT) for detecting urinary stones with the use of an iterative reconstruction technique for reducing radiation dose and image noise. Materials and Methods A total of 101 stones from 69 patients who underwent both conventional nonenhanced computed tomography (CCT) and LDCT were analyzed. Interpretations were made of the two scans according to stone characteristics (size, volume, location, Hounsfield unit [HU], and skin-to-stone distance [SSD]) and radiation dose by dose-length product (DLP), effective dose (ED), and image noise. Diagnostic performance for detecting urinary stones was assessed by statistical evaluation. Results No statistical differences were found in stone characteristics between the two scans. The average DLP and ED were 384.60±132.15 mGy and 5.77±1.98 mSv in CCT and 90.08±31.80 mGy and 1.34±0.48 mSv in LDCT, respectively. The dose reduction rate of LDCT was nearly 77% for both DLP and ED (p<0.01). The mean objective noise (standard deviation) from three different areas was 23.0±2.5 in CCT and 29.2±3.1 in LDCT with a significant difference (p<0.05); the slight increase was 21.2%. For stones located throughout the kidney and ureter, the sensitivity and specificity of LDCT remained 96.0% and 100%, with positive and negative predictive values of 100% and 96.2%, respectively. Conclusions LDCT showed significant radiation reduction while maintaining high image quality. It is an attractive option in the diagnosis of urinary stones. PMID:25237459

Virtual Colonoscopy Screening With Ultra Low-Dose CT and Less-Stressful Bowel Preparation: A Computer Simulation Study

NASA Astrophysics Data System (ADS)

Wang, Jing; Wang, Su; Li, Lihong; Fan, Yi; Lu, Hongbing; Liang, Zhengrong

2008-10-01

Computed tomography colonography (CTC) or CT-based virtual colonoscopy (VC) is an emerging tool for detection of colonic polyps. Compared to the conventional fiber-optic colonoscopy, VC has demonstrated the potential to become a mass screening modality in terms of safety, cost, and patient compliance. However, current CTC delivers excessive X-ray radiation to the patient during data acquisition. The radiation is a major concern for screening application of CTC. In this work, we performed a simulation study to demonstrate a possible ultra low-dose CT technique for VC. The ultra low-dose abdominal CT images were simulated by adding noise to the sinograms of the patient CTC images acquired with normal dose scans at 100 mA s levels. The simulated noisy sinogram or projection data were first processed by a Karhunen-Loeve domain penalized weighted least-squares (KL-PWLS) restoration method and then reconstructed by a filtered backprojection algorithm for the ultra low-dose CT images. The patient-specific virtual colon lumen was constructed and navigated by a VC system after electronic colon cleansing of the orally-tagged residue stool and fluid. By the KL-PWLS noise reduction, the colon lumen can successfully be constructed and the colonic polyp can be detected in an ultra low-dose level below 50 mA s. Polyp detection can be found more easily by the KL-PWLS noise reduction compared to the results using the conventional noise filters, such as Hanning filter. These promising results indicate the feasibility of an ultra low-dose CTC pipeline for colon screening with less-stressful bowel preparation by fecal tagging with oral contrast.

Exposure to Hexavalent Chromium Resulted in Significantly Higher Tissue Chromium Burden Compared With Trivalent Chromium Following Similar Oral Doses to Male F344/N Rats and Female B6C3F1 Mice

PubMed Central

Collins, Bradley J.; Stout, Matthew D.; Levine, Keith E.; Kissling, Grace E.; Fennell, Timothy R.; Walden, Ramsey; Abdo, Kamal; Pritchard, John B.; Fernando, Reshan A.; Burka, Leo T.; Hooth, Michelle J.

2010-01-01

In National Toxicology Program 2-year studies, hexavalent chromium [Cr(VI)] administered in drinking water was clearly carcinogenic in male and female rats and mice, resulting in small intestine epithelial neoplasms in mice at a dose equivalent to or within an order of magnitude of human doses that could result from consumption of chromium-contaminated drinking water, assuming that dose scales by body weight3/4 (body weight raised to the 3/4 power). In contrast, exposure to trivalent chromium [Cr(III)] at much higher concentrations may have been carcinogenic in male rats but was not carcinogenic in mice or female rats. As part of these studies, total chromium was measured in tissues and excreta of additional groups of male rats and female mice. These data were used to infer the uptake and distribution of Cr(VI) because Cr(VI) is reduced to Cr(III) in vivo, and no methods are available to speciate tissue chromium. Comparable external doses resulted in much higher tissue chromium concentrations following exposure to Cr(VI) compared with Cr(III), indicating that a portion of the Cr(VI) escaped gastric reduction and was distributed systemically. Linear or supralinear dose responses of total chromium in tissues were observed following exposure to Cr(VI), indicating that these exposures did not saturate gastric reduction capacity. When Cr(VI) exposure was normalized to ingested dose, chromium concentrations in the liver and glandular stomach were higher in mice, whereas kidney concentrations were higher in rats. In vitro studies demonstrated that Cr(VI), but not Cr(III), is a substrate of the sodium/sulfate cotransporter, providing a partial explanation for the greater absorption of Cr(VI). PMID:20843897

Exposure to hexavalent chromium resulted in significantly higher tissue chromium burden compared with trivalent chromium following similar oral doses to male F344/N rats and female B6C3F1 mice.

PubMed

Collins, Bradley J; Stout, Matthew D; Levine, Keith E; Kissling, Grace E; Melnick, Ronald L; Fennell, Timothy R; Walden, Ramsey; Abdo, Kamal; Pritchard, John B; Fernando, Reshan A; Burka, Leo T; Hooth, Michelle J

2010-12-01

In National Toxicology Program 2-year studies, hexavalent chromium [Cr(VI)] administered in drinking water was clearly carcinogenic in male and female rats and mice, resulting in small intestine epithelial neoplasms in mice at a dose equivalent to or within an order of magnitude of human doses that could result from consumption of chromium-contaminated drinking water, assuming that dose scales by body weight(3/4) (body weight raised to the 3/4 power). In contrast, exposure to trivalent chromium [Cr(III)] at much higher concentrations may have been carcinogenic in male rats but was not carcinogenic in mice or female rats. As part of these studies, total chromium was measured in tissues and excreta of additional groups of male rats and female mice. These data were used to infer the uptake and distribution of Cr(VI) because Cr(VI) is reduced to Cr(III) in vivo, and no methods are available to speciate tissue chromium. Comparable external doses resulted in much higher tissue chromium concentrations following exposure to Cr(VI) compared with Cr(III), indicating that a portion of the Cr(VI) escaped gastric reduction and was distributed systemically. Linear or supralinear dose responses of total chromium in tissues were observed following exposure to Cr(VI), indicating that these exposures did not saturate gastric reduction capacity. When Cr(VI) exposure was normalized to ingested dose, chromium concentrations in the liver and glandular stomach were higher in mice, whereas kidney concentrations were higher in rats. In vitro studies demonstrated that Cr(VI), but not Cr(III), is a substrate of the sodium/sulfate cotransporter, providing a partial explanation for the greater absorption of Cr(VI).

4D planning over the full course of fractionation: assessment of the benefit of tumor trailing

NASA Astrophysics Data System (ADS)

McQuaid, D.; Bortfeld, T.

2011-11-01

Tumor trailing techniques have been proposed as a method of reducing the problem of intrafraction motion in radiotherapy. However the dosimetric assessment of trailing strategies is complicated by the requirement to study dose deposition over a full fraction delivery. Common 4D planning strategies allowing assessment of dosimetric motion effects study a single cycle acquired with 4DCT. In this paper, a methodology to assess dose deposited over an entire treatment course is advanced and used to assess the potential benefit of tumor trailing strategies for lung cancer patients. Two digital phantoms mimicking patient anatomy were each programmed to follow the tumor respiratory trajectory observed from 33 lung cancer patients. The two phantoms were designed to represent the cases of a small (volume = 13.6 cm3) and large (volume = 181.7 cm3) lung lesion. Motion margins required to obtain CTV coverage by 95% of the prescription dose to 90% of the available cases were computed for a standard treatment strategy and a trailing treatment strategy. The trailing strategy facilitated a margin reduction of over 30% relative to the conventional delivery. When the dose was computed across the entire delivery for the 33 cases, the trailing strategy was found to significantly reduce the underdosage to the outlier cases and the reduced trailing margin facilitated a 15% (small lesion) and 4% (large lesion) reduction for the mean lung dose and 7% (small lesion) and 10% (large lesion) for the mean esophagus dose. Finally, for comparison an ideal continuous tracking strategy was assessed and found to further reduce the mean lung and esophagus dose. However, this improvement comes at the price of increased delivery complexity and increased reliance on tumor localization accuracy.

[Comparison of radiation dose reduction of prospective ECG-gated one beat scan using 320 area detector CT coronary angiography and prospective ECG-gated helical scan with high helical pitch (FlashScan) using 64 multidetector-row CT coronary angiography].

PubMed

Matsutani, Hideyuki; Sano, Tomonari; Kondo, Takeshi; Fujimoto, Shinichiro; Sekine, Takako; Arai, Takehiro; Morita, Hitomi; Takase, Shinichi

2010-12-20

A high radiation dose associated with 64 multidetector-row computed tomography (64-MDCT) is a major concern for physicians and patients alike. A new 320 row area detector computed tomography (ADCT) can obtain a view of the entire heart with one rotation (0.35 s) without requiring the helical method. As such, ADCT is expected to reduce the radiation dose. We studied image quality and radiation dose of ADCT compared to that of 64-MDCT in patients with a low heart rate (HR≤60). Three hundred eighty-five consecutive patients underwent 64-MDCT and 379 patients, ADCT. Patients with an arrhythmia were excluded. Prospective ECG-gated helical scan with high HP (FlashScan) in 64 was used for MDCT and prospective ECG-gated conventional one beat scan, for 320-ADCT. Image quality was visually evaluated by an image quality score. Radiation dose was estimated by DLP (mGy･cm) for 64-MDCT and DLP.e (mGy･cm) for 320-ADCT. Radiation dose of 320-ADCT (208±48 mGy･cm) was significantly (P<0.0001) lower than that of 64-MDCT (484±112 mGy･cm), and image quality score of 320-ADCT (3.0±0.2) was significantly (P=0.0011) higher than that of 64-MDCT (2.9±0.4). Scan time of 320-ADCT (1.4±0.1 s) was also significantly (P<0.0001) shorter than that of 64-MDCT (6.8±0.6 s). 320-ADCT can achieve not only a reduction in radiation dose but also a superior image quality and shortening of scan time compared to 64-MDCT.

Statins in hypercholesterolaemia: A dose-specific meta-analysis of lipid changes in randomised, double blind trials

PubMed Central

Edwards, Jayne E; Moore, R Andrew

2003-01-01

Background Statins alter lipid concentrations. This systematic review determined the efficacy of particular statins, in terms of their ability to alter cholesterol. Review methods PubMed, the Cochrane Library, references lists of reports, and reviews were searched (September 2001) for randomised, double blind trials of statins for cholesterol in trials of 12 weeks or longer. Mean change in total cholesterol, LDL-cholesterol, HDL-cholesterol, and triglycerides was calculated using pooled data for particular statins, and for particular doses of a statin. Pre-planned sensitivity analyses were used to determine the effects of initial concentration of total cholesterol, study duration, the effects of major trials, and effects in placebo versus active controlled trials. Information was not collected on adverse events. Results Different statins at a range of doses reduced total cholesterol by 17–35% and LDL-cholesterol by 24–49% from baseline. Lower doses of statins generally produced less cholesterol lowering, though for most statins in trials of 12 weeks or longer there was at best only a weak relationship between dose and cholesterol reduction. Duration of treatment and baseline total cholesterol concentration did not alter the amount of the benefit attained. Conclusions Statins are effective medicines and confer benefit to patients in terms of primary and secondary prevention of coronary heart disease. Reductions in total cholesterol of 25% or more and LDL cholesterol of more than 30% were recorded for fixed doses of simvastatin 40 mg, atorvastatin 10 mg, and rosuvastatin 5 mg and 10 mg. PMID:14969594

Impact on dose and image quality of a software-based scatter correction in mammography.

PubMed

Monserrat, Teresa; Prieto, Elena; Barbés, Benigno; Pina, Luis; Elizalde, Arlette; Fernández, Belén

2018-06-01

Background In 2014, Siemens developed a new software-based scatter correction (Progressive Reconstruction Intelligently Minimizing Exposure [PRIME]), enabling grid-less digital mammography. Purpose To compare doses and image quality between PRIME (grid-less) and standard (with anti-scatter grid) modes. Material and Methods Contrast-to-noise ratio (CNR) was measured for various polymethylmethacrylate (PMMA) thicknesses and dose values provided by the mammograph were recorded. CDMAM phantom images were acquired for various PMMA thicknesses and inverse Image Quality Figure (IQF inv ) was calculated. Values of incident entrance surface air kerma (ESAK) and average glandular dose (AGD) were obtained from the DICOM header for a total of 1088 pairs of clinical cases. Two experienced radiologists compared subjectively the image quality of a total of 149 pairs of clinical cases. Results CNR values were higher and doses were lower in PRIME mode for all thicknesses. IQF inv values in PRIME mode were lower for all thicknesses except for 40 mm of PMMA equivalent, in which IQF inv was slightly greater in PRIME mode. A mean reduction of 10% in ESAK and 12% in AGD in PRIME mode with respect to standard mode was obtained. The clinical image quality in PRIME and standard acquisitions resulted to be similar in most of the cases (84% for the first radiologist and 67% for the second one). Conclusion The use of PRIME software reduces, in average, the dose of radiation to the breast without affecting image quality. This reduction is greater for thinner and denser breasts.

Declines in Outpatient Antimicrobial Use in Canada (1995–2010)

PubMed Central

Finley, Rita; Glass-Kaastra, Shiona K.; Hutchinson, Jim; Patrick, David M.; Weiss, Karl; Conly, John

2013-01-01

Background With rising reports of antimicrobial resistance in outpatient communities, surveillance of antimicrobial use is imperative for supporting stewardship programs. The primary objective of this article is to assess the levels of antimicrobial use in Canada over time. Methods Canadian antimicrobial use data from 1995 to 2010 were acquired and assessed by four metrics: population-adjusted prescriptions, Defined Daily Doses, spending on antimicrobials (inflation-adjusted), and average Defined Daily Doses per prescription. Linear mixed models were built to assess significant differences among years and antimicrobial groups, and to account for repeated measurements over time. Measures were also compared to published reports from European countries. Results Temporal trends in antimicrobial use in Canada vary by metric and antimicrobial grouping. Overall reductions were seen for inflation-adjusted spending, population-adjusted prescription rates and Defined Daily Doses, and increases were observed for the average number of Defined Daily Doses per prescription. The population-adjusted prescription and Defined Daily Doses values for 2009 were comparable to those reported by many European countries, while the average Defined Daily Dose per prescription for Canada ranked high. A significant reduction in the use of broad spectrum penicillins occurred between 1995 and 2004, coupled with increases in macrolide and quinolone use, suggesting that replacement of antimicrobial drugs may occur as new products arrive on the market. Conclusions There have been modest decreases of antimicrobial use in Canada over the past 15 years. However, continued surveillance of antimicrobial use coupled with data detailing antimicrobial resistance within bacterial pathogens affecting human populations is critical for targeting interventions and maintaining the effectiveness of these products for future generations. PMID:24146863

Use of tomotherapy in treatment of synchronous bilateral breast cancer: dosimetric comparison study

PubMed Central

Wadasadawala, T; Sarin, R; Upreti, R R; Paul, S; Phurailatpam, R

2015-01-01

Objective: Synchronous malignancy in both breasts is a rare incidence. The present study aims at dosimetric comparison of conventional bitangential radiotherapy (RT) technique with conventional [field-in-field (FIF)] and rotational [Helical TomoTherapy® and TomoDirect™ (TD); Accuray Inc., Sunnyvale, CA] intensity-modulated RT for patients with synchronous bilateral breast cancer (SBBC). Methods: CT data sets of 10 patients with SBBC were selected for the present study. RT was planned for all patients on both sides to whole breast and/or chest wall using the above-mentioned techniques. Six females with breast conservation on at least one side also had a composite plan along with tumour bed (TB) boost using sequential electrons for bitangential and FIF techniques or sequential helical tomotherapy (HT) boost (for TD) or simultaneous integrated boost (SIB) for HT. Results: All techniques produced acceptable target coverage. The hotspot was significantly lower with FIF technique and HT but higher with TD. For the organs at risk doses, HT resulted in significant reduction of the higher dose volumes. Similarly, TD resulted in significant reduction of the mean dose to the heart and total lung by reducing the lower dose volumes. All techniques of delivering boost to the TB were comparable in terms of target coverage. HT-SIB markedly reduced mean doses to the total lung and heart by specifically lowering the higher dose volumes. Conclusion: This study demonstrates the cardiac and pulmonary sparing ability of tomotherapy in the setting of SBBC. Advances in knowledge: This is the first study demonstrating feasibility of treatment of SBBC using tomotherapy. PMID:25605345

SU-F-J-145: MRI-Guided Interventional Boost Radiotherapy for Rectal Cancer: Investigating the Feasibility of Adapting the Anatomy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleijnen, J J E; Couwenberg, A M; Asselen, B van

Purpose: The recent development of an MRI-linac allows adaptation of treatments to the anatomy of the moment. This anatomy, in turn, could be altered into a more favorable situation for radiotherapy purposes. The purpose of this study is to investigate the potential dosimetric benefits of manipulating rectal anatomy in MRI-guided interventional external-beam radiotherapy for rectal cancer. Methods: For this retrospective analysis, four patients (1M/3F) diagnosed with rectal cancer were included. These underwent MR-imaging using sonography transmission gel as endorectal contrast at time of diagnosis and standard, non-contrast, MR-imaging prior to radiotherapy planning. In the contrast scan, the rectum is inflatedmore » by the inserted contrast gel, thereby potentially increasing the distance between tumor and the organs-at-risk (OAR). Both anatomies were delineated and 7- beam IMRT-plans were calculated for both situations (RT-standard and RT-inflated), using in-house developed treatment planning software. Each plan was aimed to deliver 15Gy to the planning target volume (PTV; tumor+3mm margin) with a D99>95% and Dmax<120% of the planned dose. The D2cc dose to the OAR were then compared for both situations. Results: At equal (or better) target coverage, we found a mean reduction in D2cc of 4.1Gy/237% [range 2.6Gy–6.3Gy/70%–621%] for the bladder and of 2.0Gy/145% [range −0.7Gy–7.9Gy/−73%–442%] for the small-bowel, for the RT-inflated compared to the RT-standard plans. For the three female patients, a reduction in D2cc of 5.2Gy/191% [range 3.2Gy–9.2Gy/44%–475%] for the gynecological organs was found. We found all D2cc doses to be better for the RT-inflated plans, except for one patient for whom the bladder D2cc dose was slightly increased. Conclusion: Reduction of OAR dose by manipulation of anatomy is feasible. Inflation of the rectum results in more distance between OAR and PTV. This leads to a substantial reduction in dose to OAR at equal or better target coverage.« less

Validation of CT dose-reduction simulation

PubMed Central

Massoumzadeh, Parinaz; Don, Steven; Hildebolt, Charles F.; Bae, Kyongtae T.; Whiting, Bruce R.

2009-01-01

The objective of this research was to develop and validate a custom computed tomography dose-reduction simulation technique for producing images that have an appearance consistent with the same scan performed at a lower mAs (with fixed kVp, rotation time, and collimation). Synthetic noise is added to projection (sinogram) data, incorporating a stochastic noise model that includes energy-integrating detectors, tube-current modulation, bowtie beam filtering, and electronic system noise. Experimental methods were developed to determine the parameters required for each component of the noise model. As a validation, the outputs of the simulations were compared to measurements with cadavers in the image domain and with phantoms in both the sinogram and image domain, using an unbiased root-mean-square relative error metric to quantify agreement in noise processes. Four-alternative forced-choice (4AFC) observer studies were conducted to confirm the realistic appearance of simulated noise, and the effects of various system model components on visual noise were studied. The “just noticeable difference (JND)” in noise levels was analyzed to determine the sensitivity of observers to changes in noise level. Individual detector measurements were shown to be normally distributed (p>0.54), justifying the use of a Gaussian random noise generator for simulations. Phantom tests showed the ability to match original and simulated noise variance in the sinogram domain to within 5.6%±1.6% (standard deviation), which was then propagated into the image domain with errors less than 4.1%±1.6%. Cadaver measurements indicated that image noise was matched to within 2.6%±2.0%. More importantly, the 4AFC observer studies indicated that the simulated images were realistic, i.e., no detectable difference between simulated and original images (p=0.86) was observed. JND studies indicated that observers’ sensitivity to change in noise levels corresponded to a 25% difference in dose, which is far larger than the noise accuracy achieved by simulation. In summary, the dose-reduction simulation tool demonstrated excellent accuracy in providing realistic images. The methodology promises to be a useful tool for researchers and radiologists to explore dose reduction protocols in an effort to produce diagnostic images with radiation dose “as low as reasonably achievable.” PMID:19235386

SU-D-BRA-07: Applications of Combined KV/MV CBCT Imaging with a High-DQE MV Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazalova-Carter, M; Newson, M; Wang, A

Purpose: To investigate whether a high detection quantum efficiency (DQE) MV detector makes combined kV/MV CBCT clinically practical. Methods: Combined kV/MV CBCT was studied for scan time reduction (STR) and metal artifact reduction (MAR). 6MV CBCT data (dose rate = 0.017 MU/degree) were collected using 1) a novel focused pixelated cadmium tungstate (CWO) scintillator (15mm thickness, DQE(0) = 22%, 0.784mm pixel pitch) coupled to a flat panel imager, and 2) a commercial portal imager with a 133mg/cm{sup 2} gadolinium oxysulfide (GOS) screen (DQE(0) = 1.2%). The 100kVp data were acquired using a commercial imager employing a columnar cesium iodide scintillatormore » (DQE(0) = 70%) with a dose rate of 0.0016 cGy/degree. For STR, MV and kV projections spanning 105° were combined to constitute a complete CBCT scan. Total dose was ∼2cGy and acquisition time was 18s. For MAR, only the metalcorrupted pixels in the kV projections were replaced with MV data resulting in a total dose of less than 1cGy for a 360° scan. Image quality was assessed using an 18-cm diameter electron density phantom with nine tissue inserts, some of which were replaced with steel rods for MAR studies. Results: The CWO contrast-to-noise ratio (CNR) was ∼4.0x higher than the GOS CNR and was ∼4.8x lower than the kV CNR when normalized for dose. When CWO MV data were combined with kV data for STR, all contrast inserts were visible, but only two were detectable in the composite kV/GOS image. Metal artifacts were greatly reduced using the kV/MV MAR technique with all contrast inserts clearly visible in the composite kV/CWO image but only two inserts visible in the composite kV/GOS image. Conclusion: We have demonstrated that a high DQE MV detector significantly improves kV/MV CBCT image quality thus enabling scan time reduction and metal artifact reduction without a severe dose penalty. AW and JS-L are employees of Varian, RF is an employee of Siemens.« less

Evaluation of normalized metal artifact reduction (NMAR) in kVCT using MVCT prior images for radiotherapy treatment planning.

PubMed

Paudel, M R; Mackenzie, M; Fallone, B G; Rathee, S

2013-08-01

To evaluate the metal artifacts in kilovoltage computed tomography (kVCT) images that are corrected using a normalized metal artifact reduction (NMAR) method with megavoltage CT (MVCT) prior images. Tissue characterization phantoms containing bilateral steel inserts are used in all experiments. Two MVCT images, one without any metal artifact corrections and the other corrected using a modified iterative maximum likelihood polychromatic algorithm for CT (IMPACT) are translated to pseudo-kVCT images. These are then used as prior images without tissue classification in an NMAR technique for correcting the experimental kVCT image. The IMPACT method in MVCT included an additional model for the pair∕triplet production process and the energy dependent response of the MVCT detectors. An experimental kVCT image, without the metal inserts and reconstructed using the filtered back projection (FBP) method, is artificially patched with the known steel inserts to get a reference image. The regular NMAR image containing the steel inserts that uses tissue classified kVCT prior and the NMAR images reconstructed using MVCT priors are compared with the reference image for metal artifact reduction. The Eclipse treatment planning system is used to calculate radiotherapy dose distributions on the corrected images and on the reference image using the Anisotropic Analytical Algorithm with 6 MV parallel opposed 5×10 cm2 fields passing through the bilateral steel inserts, and the results are compared. Gafchromic film is used to measure the actual dose delivered in a plane perpendicular to the beams at the isocenter. The streaking and shading in the NMAR image using tissue classifications are significantly reduced. However, the structures, including metal, are deformed. Some uniform regions appear to have eroded from one side. There is a large variation of attenuation values inside the metal inserts. Similar results are seen in commercially corrected image. Use of MVCT prior images without tissue classification in NMAR significantly reduces these problems. The radiation dose calculated on the reference image is close to the dose measured using the film. Compared to the reference image, the calculated dose difference in the conventional NMAR image, the corrected images using uncorrected MVCT image, and IMPACT corrected MVCT image as priors is ∼15.5%, ∼5%, and ∼2.7%, respectively, at the isocenter. The deformation and erosion of the structures present in regular NMAR corrected images can be largely reduced by using MVCT priors without tissue segmentation. The attenuation value of metal being incorrect, large dose differences relative to the true value can result when using the conventional NMAR image. This difference can be significantly reduced if MVCT images are used as priors. Reduced tissue deformation, better tissue visualization, and correct information about the electron density of the tissues and metals in the artifact corrected images could help delineate the structures better, as well as calculate radiation dose more correctly, thus enhancing the quality of the radiotherapy treatment planning.

Impact of Genetic Ancestry on Outcomes in ECOG-ACRIN-E5103

PubMed Central

Schneider, Bryan P.; Shen, Fei; Jiang, Guanglong; O'Neill, Anne; Radovich, Milan; Li, Lang; Gardner, Laura; Lai, Dongbing; Foroud, Tatiana; Sparano, Joseph A.; Sledge, George W.; Miller, Kathy D.

2017-01-01

Purpose Racial disparity in breast cancer outcomes exists between African American and Caucasian women in the United States. We have evaluated the impact of genetically determined ancestry on disparity in efficacy and therapy-induced toxicity for breast cancer patients in the context of a randomized, phase III adjuvant trial. Patients and Methods This study compared outcomes between 386 patients of African ancestry (AA) and 2473 patients of European ancestry (EA) in a randomized, phase III breast cancer trial; ECOG-ACRIN-E5103. The primary efficacy endpoint, invasive disease free survival (DFS) and clinically significant toxicities were compared including: anthracycline-induced congestive heart failure (CHF), taxane-induced peripheral neuropathy (TIPN), and bevacizumab-induced hypertension. Results Overall, AAs had significantly inferior DFS (p=0.002; HR=1.5) compared with EAs. This was significant in the estrogen receptor-positive subgroup (p=0.03); with a similar, non-significant trend for those who had triple negative breast cancer (TNBC; p=0.12). AAs also had significantly more grade 3-4 TIPN (OR=2.9; p=2.4 ×10-11) and grade 3-4 bevacizumab-induced hypertension (OR=1.6; p=0.02), with a trend for more CHF (OR=1.8; p=0.08). AAs had significantly more dose reductions for paclitaxel (p=6.6 ×10-6). In AAs, dose reductions in paclitaxel had a significant negative impact on DFS (p=0.03); whereas in EAs, dose reductions did not impact outcome (p=0.35). Conclusion AAs had inferior DFS with more clinically important toxicities in ECOG-ACRIN-E5103. The altered risk to benefit ratio for adjuvant breast cancer chemotherapy should lead to additional research with the focus centered on the impact of genetic ancestry on both efficacy and toxicity. Strategies to minimize dose reductions for paclitaxel, especially due to TIPN, are warranted for this population. PMID:29333527

Theoretical Benefits of Dynamic Collimation in Pencil Beam Scanning Proton Therapy for Brain Tumors: Dosimetric and Radiobiological Metrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moignier, Alexandra, E-mail: alexandra-moignier@uiowa.edu; Gelover, Edgar; Wang, Dongxu

Purpose: To quantify the dosimetric benefit of using a dynamic collimation system (DCS) for penumbra reduction during the treatment of brain tumors by pencil beam scanning proton therapy (PBS PT). Methods and Materials: Collimated and uncollimated brain treatment plans were created for 5 patients previously treated with PBS PT and retrospectively enrolled in an institutional review board–approved study. The in-house treatment planning system, RDX, was used to generate the plans because it is capable of modeling both collimated and uncollimated beamlets. The clinically delivered plans were reproduced with uncollimated plans in terms of target coverage and organ at risk (OAR) sparingmore » to ensure a clinically relevant starting point, and collimated plans were generated to improve the OAR sparing while maintaining target coverage. Physical and biological comparison metrics, such as dose distribution conformity, mean and maximum doses, normal tissue complication probability, and risk of secondary brain cancer, were used to evaluate the plans. Results: The DCS systematically improved the dose distribution conformity while preserving the target coverage. The average reduction of the mean dose to the 10-mm ring surrounding the target and the healthy brain were 13.7% (95% confidence interval [CI] 11.6%-15.7%; P<.0001) and 25.1% (95% CI 16.8%-33.4%; P<.001), respectively. This yielded an average reduction of 24.8% (95% CI 0.8%-48.8%; P<.05) for the brain necrosis normal tissue complication probability using the Flickinger model, and 25.1% (95% CI 16.8%-33.4%; P<.001) for the risk of secondary brain cancer. A general improvement of the OAR sparing was also observed. Conclusion: The lateral penumbra reduction afforded by the DCS increases the normal tissue sparing capabilities of PBS PT for brain cancer treatment while preserving target coverage.« less

Differences in rates of decrease of environmental radiation dose rates by ground surface property in Fukushima City after the Fukushima Daiichi nuclear power plant accident.

PubMed

Kakamu, Takeyasu; Kanda, Hideyuki; Tsuji, Masayoshi; Kobayashi, Daisuke; Miyake, Masao; Hayakawa, Takehito; Katsuda, Shin-ichiro; Mori, Yayoi; Okouchi, Toshiyasu; Hazama, Akihiro; Fukushima, Tetsuhito

2013-01-01

After the Great East Japan Earthquake on 11 March 2011, the environmental radiation dose in Fukushima City increased. On 11 April, 1 mo after the earthquake, the environmental radiation dose rate at various surfaces in the same area differed greatly by surface property. Environmental radiation measurements continue in order to determine the estimated time to 50% reduction in environmental radiation dose rates by surface property in order to make suggestions for decontamination in Fukushima. The measurements were carried out from 11 April to 11 November 2011. Forty-eight (48) measurement points were selected, including four kinds of ground surface properties: grass (13), soil (5), artificial turf (7), and asphalt (23). Environmental radiation dose rate was measured at heights of 100 cm above the ground surface. Time to 50% reduction of environmental radiation dose rates was estimated for each ground surface property. Radiation dose rates on 11 November had decreased significantly compared with those on 11 April for all surface properties. Artificial turf showed the longest time to 50% reduction (544.32 d, standard error: 96.86), and soil showed the shortest (213.20 d, standard error: 35.88). The authors found the environmental radiation dose rate on artificial materials to have a longer 50% reduction time than that on natural materials. These results contribute to determining an order of priority for decontamination after nuclear disasters.

Experimental benchmarking of a Monte Carlo dose simulation code for pediatric CT

NASA Astrophysics Data System (ADS)

Li, Xiang; Samei, Ehsan; Yoshizumi, Terry; Colsher, James G.; Jones, Robert P.; Frush, Donald P.

2007-03-01

In recent years, there has been a desire to reduce CT radiation dose to children because of their susceptibility and prolonged risk for cancer induction. Concerns arise, however, as to the impact of dose reduction on image quality and thus potentially on diagnostic accuracy. To study the dose and image quality relationship, we are developing a simulation code to calculate organ dose in pediatric CT patients. To benchmark this code, a cylindrical phantom was built to represent a pediatric torso, which allows measurements of dose distributions from its center to its periphery. Dose distributions for axial CT scans were measured on a 64-slice multidetector CT (MDCT) scanner (GE Healthcare, Chalfont St. Giles, UK). The same measurements were simulated using a Monte Carlo code (PENELOPE, Universitat de Barcelona) with the applicable CT geometry including bowtie filter. The deviations between simulated and measured dose values were generally within 5%. To our knowledge, this work is one of the first attempts to compare measured radial dose distributions on a cylindrical phantom with Monte Carlo simulated results. It provides a simple and effective method for benchmarking organ dose simulation codes and demonstrates the potential of Monte Carlo simulation for investigating the relationship between dose and image quality for pediatric CT patients.

Comparison of Kato-Katz thick-smear and McMaster egg counting method for the assessment of drug efficacy against soil-transmitted helminthiasis in school children in Jimma Town, Ethiopia.

PubMed

Bekana, Teshome; Mekonnen, Zeleke; Zeynudin, Ahmed; Ayana, Mio; Getachew, Mestawet; Vercruysse, Jozef; Levecke, Bruno

2015-10-01

There is a paucity of studies that compare efficacy of drugs obtained by different diagnostic methods. We compared the efficacy of a single oral dose albendazole (400 mg), measured as egg reduction rate, against soil-transmitted helminth infections in 210 school children (Jimma Town, Ethiopia) using both Kato-Katz thick smear and McMaster egg counting method. Our results indicate that differences in sensitivity and faecal egg counts did not imply a significant difference in egg reduction rate estimates. The choice of a diagnostic method to assess drug efficacy should not be based on sensitivity and faecal egg counts only. © The Author 2015. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method.

PubMed

Khosravi, H; Hashemi, B; Mahdavi, S R; Hejazi, P

2015-03-01

Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions. The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-192 and external 18MV radiotherapy practices. A Plexiglas phantom was made representing human pelvis. The GNP shaving 15 nm in diameter and 0.1 mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs) and bladder locations of the phantom. The phantom was irradiated to an Ir-192 source and 18 MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After 24 hours, the irradiated gels were read using a Siemens 1.5 Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared. The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were 15% and 8 % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of 14 % and 7 % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively. There was a good agreement between the dose enhancement factors (DEFs) estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal and external radiotherapy practices.

Linear response of mutans streptococci to increasing frequency of xylitol chewing gum use: a randomized controlled trial [ISRCTN43479664

PubMed Central

Ly, Kiet A; Milgrom, Peter; Roberts, Marilyn C; Yamaguchi, David K; Rothen, Marilynn; Mueller, Greg

2006-01-01

Background Xylitol is a naturally occurring sugar substitute that has been shown to reduce the level of mutans streptococci in plaque and saliva and to reduce tooth decay. It has been suggested that the degree of reduction is dependent on both the amount and the frequency of xylitol consumption. For xylitol to be successfully and cost-effectively used in public health prevention strategies dosing and frequency guidelines should be established. This study determined the reduction in mutans streptococci levels in plaque and unstimulated saliva to increasing frequency of xylitol gum use at a fixed total daily dose of 10.32 g over five weeks. Methods Participants (n = 132) were randomized to either active groups (10.32 g xylitol/day) or a placebo control (9.828 g sorbitol and 0.7 g maltitol/day). All groups chewed 12 pieces of gum per day. The control group chewed 4 times/day and active groups chewed xylitol gum at a frequency of 2 times/day, 3 times/day, or 4 times/day. The 12 gum pieces were evenly divided into the frequency assigned to each group. Plaque and unstimulated saliva samples were taken at baseline and five-weeks and were cultured on modified Mitis Salivarius agar for mutans streptococci enumeration. Results There were no significant differences in mutans streptococci level among the groups at baseline. At five-weeks, mutans streptococci levels in plaque and unstimulated saliva showed a linear reduction with increasing frequency of xylitol chewing gum use at the constant daily dose. Although the difference observed for the group that chewed xylitol 2 times/day was consistent with the linear model, the difference was not significant. Conclusion There was a linear reduction in mutans streptococci levels in plaque and saliva with increasing frequency of xylitol gum use at a constant daily dose. Reduction at a consumption frequency of 2 times per day was small and consistent with the linear-response line but was not statistically significant. PMID:16556326

Model-based iterative reconstruction for reduction of radiation dose in abdominopelvic CT: comparison to adaptive statistical iterative reconstruction.

PubMed

Yasaka, Koichiro; Katsura, Masaki; Akahane, Masaaki; Sato, Jiro; Matsuda, Izuru; Ohtomo, Kuni

2013-12-01

To evaluate dose reduction and image quality of abdominopelvic computed tomography (CT) reconstructed with model-based iterative reconstruction (MBIR) compared to adaptive statistical iterative reconstruction (ASIR). In this prospective study, 85 patients underwent referential-, low-, and ultralow-dose unenhanced abdominopelvic CT. Images were reconstructed with ASIR for low-dose (L-ASIR) and ultralow-dose CT (UL-ASIR), and with MBIR for ultralow-dose CT (UL-MBIR). Image noise was measured in the abdominal aorta and iliopsoas muscle. Subjective image analyses and a lesion detection study (adrenal nodules) were conducted by two blinded radiologists. A reference standard was established by a consensus panel of two different radiologists using referential-dose CT reconstructed with filtered back projection. Compared to low-dose CT, there was a 63% decrease in dose-length product with ultralow-dose CT. UL-MBIR had significantly lower image noise than L-ASIR and UL-ASIR (all p<0.01). UL-MBIR was significantly better for subjective image noise and streak artifacts than L-ASIR and UL-ASIR (all p<0.01). There were no significant differences between UL-MBIR and L-ASIR in diagnostic acceptability (p>0.65), or diagnostic performance for adrenal nodules (p>0.87). MBIR significantly improves image noise and streak artifacts compared to ASIR, and can achieve radiation dose reduction without severely compromising image quality.

Effects of dose reduction on bone strength prediction using finite element analysis

NASA Astrophysics Data System (ADS)

Anitha, D.; Subburaj, Karupppasamy; Mei, Kai; Kopp, Felix K.; Foehr, Peter; Noel, Peter B.; Kirschke, Jan S.; Baum, Thomas

2016-12-01

This study aimed to evaluate the effect of dose reduction, by means of tube exposure reduction, on bone strength prediction from finite-element (FE) analysis. Fresh thoracic mid-vertebrae specimens (n = 11) were imaged, using multi-detector computed tomography (MDCT), at different intensities of X-ray tube exposures (80, 150, 220 and 500 mAs). Bone mineral density (BMD) was estimated from the mid-slice of each specimen from MDCT images. Differences in image quality and geometry of each specimen were measured. FE analysis was performed on all specimens to predict fracture load. Paired t-tests were used to compare the results obtained, using the highest CT dose (500 mAs) as reference. Dose reduction had no significant impact on FE-predicted fracture loads, with significant correlations obtained with reference to 500 mAs, for 80 mAs (R2  = 0.997, p < 0.001), 150 mAs (R2 = 0.998, p < 0.001) and 220 mAs (R2 = 0.987, p < 0.001). There were no significant differences in volume quantification between the different doses examined. CT imaging radiation dose could be reduced substantially to 64% with no impact on strength estimates obtained from FE analysis. Reduced CT dose will enable early diagnosis and advanced monitoring of osteoporosis and associated fracture risk.

Influence of radiation dose and reconstruction algorithm in MDCT assessment of airway wall thickness: A phantom study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gomez-Cardona, Daniel; Nagle, Scott K.; Department of Radiology, University of Wisconsin-Madison School of Medicine and Public Health, 600 Highland Avenue, Madison, Wisconsin 53792

Purpose: Wall thickness (WT) is an airway feature of great interest for the assessment of morphological changes in the lung parenchyma. Multidetector computed tomography (MDCT) has recently been used to evaluate airway WT, but the potential risk of radiation-induced carcinogenesis—particularly in younger patients—might limit a wider use of this imaging method in clinical practice. The recent commercial implementation of the statistical model-based iterative reconstruction (MBIR) algorithm, instead of the conventional filtered back projection (FBP) algorithm, has enabled considerable radiation dose reduction in many other clinical applications of MDCT. The purpose of this work was to study the impact of radiationmore » dose and MBIR in the MDCT assessment of airway WT. Methods: An airway phantom was scanned using a clinical MDCT system (Discovery CT750 HD, GE Healthcare) at 4 kV levels and 5 mAs levels. Both FBP and a commercial implementation of MBIR (Veo{sup TM}, GE Healthcare) were used to reconstruct CT images of the airways. For each kV–mAs combination and each reconstruction algorithm, the contrast-to-noise ratio (CNR) of the airways was measured, and the WT of each airway was measured and compared with the nominal value; the relative bias and the angular standard deviation in the measured WT were calculated. For each airway and reconstruction algorithm, the overall performance of WT quantification across all of the 20 kV–mAs combinations was quantified by the sum of squares (SSQs) of the difference between the measured and nominal WT values. Finally, the particular kV–mAs combination and reconstruction algorithm that minimized radiation dose while still achieving a reference WT quantification accuracy level was chosen as the optimal acquisition and reconstruction settings. Results: The wall thicknesses of seven airways of different sizes were analyzed in the study. Compared with FBP, MBIR improved the CNR of the airways, particularly at low radiation dose levels. For FBP, the relative bias and the angular standard deviation of the measured WT increased steeply with decreasing radiation dose. Except for the smallest airway, MBIR enabled significant reduction in both the relative bias and angular standard deviation of the WT, particularly at low radiation dose levels; the SSQ was reduced by 50%–96% by using MBIR. The optimal reconstruction algorithm was found to be MBIR for the seven airways being assessed, and the combined use of MBIR and optimal kV–mAs selection resulted in a radiation dose reduction of 37%–83% compared with a reference scan protocol with a dose level of 1 mGy. Conclusions: The quantification accuracy of airway WT is strongly influenced by radiation dose and reconstruction algorithm. The MBIR algorithm potentially allows the desired WT quantification accuracy to be achieved with reduced radiation dose, which may enable a wider clinical use of MDCT for the assessment of airway WT, particularly for younger patients who may be more sensitive to exposures with ionizing radiation.« less

The Impact of Different Levels of Adaptive Iterative Dose Reduction 3D on Image Quality of 320-Row Coronary CT Angiography: A Clinical Trial

PubMed Central

Feger, Sarah; Rief, Matthias; Zimmermann, Elke; Martus, Peter; Schuijf, Joanne Désirée; Blobel, Jörg; Richter, Felicitas; Dewey, Marc

2015-01-01

Purpose The aim of this study was the systematic image quality evaluation of coronary CT angiography (CTA), reconstructed with the 3 different levels of adaptive iterative dose reduction (AIDR 3D) and compared to filtered back projection (FBP) with quantum denoising software (QDS). Methods Standard-dose CTA raw data of 30 patients with mean radiation dose of 3.2 ± 2.6 mSv were reconstructed using AIDR 3D mild, standard, strong and compared to FBP/QDS. Objective image quality comparison (signal, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), contour sharpness) was performed using 21 measurement points per patient, including measurements in each coronary artery from proximal to distal. Results Objective image quality parameters improved with increasing levels of AIDR 3D. Noise was lowest in AIDR 3D strong (p≤0.001 at 20/21 measurement points; compared with FBP/QDS). Signal and contour sharpness analysis showed no significant difference between the reconstruction algorithms for most measurement points. Best coronary SNR and CNR were achieved with AIDR 3D strong. No loss of SNR or CNR in distal segments was seen with AIDR 3D as compared to FBP. Conclusions On standard-dose coronary CTA images, AIDR 3D strong showed higher objective image quality than FBP/QDS without reducing contour sharpness. Trial Registration Clinicaltrials.gov NCT00967876 PMID:25945924

Dosimetric evaluation of three adaptive strategies for prostate cancer treatment including pelvic lymph nodes irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cantin, Audrey; Gingras, Luc; Archambault, Louis, E-mail: louis.archambault@phy.ulaval.ca

Purpose: The movements of the prostate relative to the pelvic lymph nodes during intensity-modulated radiation therapy treatment can limit margin reduction and affect the protection of the organs at risk (OAR). In this study, the authors performed an analysis of three adaptive treatment strategies that combine information from both bony and gold marker registrations. The robustness of those treatments against the interfraction prostate movements was evaluated. Methods: A retrospective study was conducted on five prostate cancer patients with 7–13 daily cone-beam CTs (CBCTs). The clinical target volumes (CTVs) consisting of pelvic lymph nodes, prostate, and seminal vesicles as well asmore » the OARs were delineated on each CBCT and the initial CT. Three adaptive strategies were analyzed. Two of these methods relied on a two-step patient positioning at each fraction. First step: a bony registration was used to deliver the nodal CTV prescription. Second step: a gold marker registration was then used either to (1) complete the dose delivered to the prostate (complement); (2) or give almost the entire prescription to the prostate with a weak dose gradient between the targets to compensate for possible motions (gradient). The third method (COR) used a pool of precalculated plans based on images acquired at previous treatment fractions. At each new fraction, a plan is selected from that pool based on the daily position of prostate center-of-mass. The dosimetric comparison was conducted and results are presented with and without the systematic shift in the prostate position on the CT planning. The adaptive strategies were compared to the current clinical standard where all fractions are treated with the initial nonadaptive plan. Results: The minimum daily prostate D{sub 95%} is improved by 2%, 9%, and 6% for the complement, the gradient, and the COR approaches, respectively, compared to the nonadaptive method. The average nodal CTV D{sub 95%} remains constant across the strategies, except for the gradient approach where a reduction of 7% is observed. However, a correction of the systematic shift reduced the problem, and the adaptive strategies remain robust against the prostate movement across the fraction. The bladder V{sub 55Gy} is reduced by 35% on average for the adaptive strategies. Conclusions: Because they offer increased CTV coverage and OAR sparing, adaptive methods may be suitable candidates for simple and efficient adaptive treatment strategies for prostate cancer. Margin reduction and systematic error correction in the prostate position improve the protection of the OAR and the dose coverage. A cumulative dose to simulate a complete treatment would show real effects and allow a better comparison between each method.« less

SU-E-T-396: Dosimetric Accuracy of Proton Therapy for Patients with Metal Implants in CT Scans Using Metal Deletion Technique (MDT) Artifacts Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X; Kantor, M; Zhu, X

2014-06-01

Purpose: To evaluate the dosimetric accuracy for proton therapy patients with metal implants in CT using metal deletion technique (MDT) artifacts reduction. Methods: Proton dose accuracies under CT metal artifacts were first evaluated using a water phantom with cylindrical inserts of different materials (titanium and steel). Ranges and dose profiles along different beam angles were calculated using treatment planning system (Eclipse version 8.9) on uncorrected CT, MDT CT, and manually-corrected CT, where true Hounsfield units (water) were assigned to the streak artifacts. In patient studies, the treatment plans were developed on manually-corrected CTs, then recalculated on MDT and uncorrected CTs.more » DVH indices were compared between the dose distributions on all the CTs. Results: For water phantom study with 1/2 inch titanium insert, the proton range differences estimated by MDT CT were with 1% for all beam angles, while the range error can be up to 2.6% for uncorrected CT. For the study with 1 inch stainless steel insert, the maximum range error calculated by MDT CT was 1.09% among all the beam angles compared with maximum range error with 4.7% for uncorrected CT. The dose profiles calculated on MDT CTs for both titanium and steel inserts showed very good agreements with the ones calculated on manually-corrected CTs, while large dose discrepancies calculated using uncorrected CTs were observed in the distal end region of the proton beam. The patient study showed similar dose distribution and DVHs for organs near the metal artifacts recalculated on MDT CT compared with the ones calculated on manually-corrected CT, while the differences between uncorrected and corrected CTs were much pronounced. Conclusion: In proton therapy, large dose error could occur due to metal artifact. The MDT CT can be used for proton dose calculation to achieve similar dose accuracy as the current clinical practice using manual correction.« less

Prediction of Warfarin Dose Reductions in Puerto Rican Patients, Based on Combinatorial CYP2C9 and VKORC1 Genotypes

PubMed Central

Valentin, Isa Ivette; Vazquez, Joan; Rivera-Miranda, Giselle; Seip, Richard L; Velez, Meredith; Kocherla, Mohan; Bogaard, Kali; Cruz-Gonzalez, Iadelisse; Cadilla, Carmen L; Renta, Jessica Y; Felliu, Juan F; Ramos, Alga S; Alejandro-Cowan, Yirelia; Gorowski, Krystyna; Ruaño, Gualberto; Duconge, Jorge

2012-01-01

BACKGROUND The influence of CYP2C9 and VKORC1 polymorphisms on warfarin dose has been investigated in white, Asian, and African American populations but not in Puerto Rican Hispanic patients. OBJECTIVE To test the associations between genotypes, international normalized ratio (INR) measurements, and warfarin dosing and gauge the impact of these polymorphisms on warfarin dose, using a published algorithm. METHODS A retrospective warfarin pharmacogenetic association study in 106 Puerto Rican patients was performed. DNA samples from patients were assayed for 12 variants in both CYP2C9 and VKORC1 loci by HILOmet PhyzioType assay. Demographic and clinical nongenetic data were retrospectively collected from medical records. Allele and genotype frequencies were determined and Hardy-Weinberg equilibrium (HWE) was tested. RESULTS Sixty-nine percent of patients were carriers of at least one polymorphism in either the CYP2C9 or the VKORC1 gene. Double, triple, and quadruple carriers accounted for 22%, 5%, and 1%, respectively. No significant departure from HWE was found. Among patients with a given CYP2C9 genotype, warfarin dose requirements declined from GG to AA haplotypes; whereas, within each VKORC1 haplotype, the dose decreased as the number of CYP2C9 variants increased. The presence of these loss-of-function alleles was associated with more out-of-range INR measurements (OR = 1.38) but not with significant INR >4 during the initiation phase. Analyses based on a published pharmacogenetic algorithm predicted dose reductions of up to 4.9 mg/day in carriers and provided better dose prediction in an extreme subgroup of highly sensitive patients, but also suggested the need to improve predictability by developing a customized model for use in Puerto Rican patients. CONCLUSIONS This study laid important groundwork for supporting a prospective pharmacogenetic trial in Puerto Ricans to detect the benefits of incorporating relevant genomic information into a customized DNA-guided warfarin dosing algorithm. PMID:22274142

An investigation of kV CBCT image quality and dose reduction for volume-of-interest imaging using dynamic collimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, David, E-mail: david.parsons@dal.ca, E-mail: james.robar@cdha.nshealth.ca; Robar, James L., E-mail: david.parsons@dal.ca, E-mail: james.robar@cdha.nshealth.ca

2015-09-15

Purpose: The focus of this work was to investigate the improvements in image quality and dose reduction for volume-of-interest (VOI) kilovoltage-cone beam CT (CBCT) using dynamic collimation. Methods: A prototype iris aperture was used to track a VOI during a CBCT acquisition. The current aperture design is capable of 1D translation as a function of gantry angle and dynamic adjustment of the iris radius. The aperture occupies the location of the bow-tie filter on a Varian On-Board Imager system. CBCT and planar image quality were investigated as a function of aperture radius, while maintaining the same dose to the VOI,more » for a 20 cm diameter cylindrical water phantom with a 9 mm diameter bone insert centered on isocenter. Corresponding scatter-to-primary ratios (SPR) were determined at the detector plane with Monte Carlo simulation using EGSnrc. Dose distributions for various sizes VOI were modeled using a dynamic BEAMnrc library and DOSXYZnrc. The resulting VOI dose distributions were compared to full-field distributions. Results: SPR was reduced by a factor of 8.4 when decreasing iris diameter from 21.2 to 2.4 cm (at isocenter). Depending upon VOI location and size, dose was reduced to 16%–90% of the full-field value along the central axis plane and down to 4% along the axis of rotation, while maintaining the same dose to the VOI compared to full-field techniques. When maintaining constant dose to the VOI, this change in iris diameter corresponds to a factor increase of approximately 1.6 in image contrast and a factor decrease in image noise of approximately 1.2. This results in a measured gain in contrast-to-noise ratio by a factor of approximately 2.0. Conclusions: The presented VOI technique offers improved image quality for image-guided radiotherapy while sparing the surrounding volume of unnecessary dose compared to full-field techniques.« less

Quantitative Image Quality and Histogram-Based Evaluations of an Iterative Reconstruction Algorithm at Low-to-Ultralow Radiation Dose Levels: A Phantom Study in Chest CT

PubMed Central

Lee, Ki Baek

2018-01-01

Objective To describe the quantitative image quality and histogram-based evaluation of an iterative reconstruction (IR) algorithm in chest computed tomography (CT) scans at low-to-ultralow CT radiation dose levels. Materials and Methods In an adult anthropomorphic phantom, chest CT scans were performed with 128-section dual-source CT at 70, 80, 100, 120, and 140 kVp, and the reference (3.4 mGy in volume CT Dose Index [CTDIvol]), 30%-, 60%-, and 90%-reduced radiation dose levels (2.4, 1.4, and 0.3 mGy). The CT images were reconstructed by using filtered back projection (FBP) algorithms and IR algorithm with strengths 1, 3, and 5. Image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were statistically compared between different dose levels, tube voltages, and reconstruction algorithms. Moreover, histograms of subtraction images before and after standardization in x- and y-axes were visually compared. Results Compared with FBP images, IR images with strengths 1, 3, and 5 demonstrated image noise reduction up to 49.1%, SNR increase up to 100.7%, and CNR increase up to 67.3%. Noteworthy image quality degradations on IR images including a 184.9% increase in image noise, 63.0% decrease in SNR, and 51.3% decrease in CNR, and were shown between 60% and 90% reduced levels of radiation dose (p < 0.0001). Subtraction histograms between FBP and IR images showed progressively increased dispersion with increased IR strength and increased dose reduction. After standardization, the histograms appeared deviated and ragged between FBP images and IR images with strength 3 or 5, but almost normally-distributed between FBP images and IR images with strength 1. Conclusion The IR algorithm may be used to save radiation doses without substantial image quality degradation in chest CT scanning of the adult anthropomorphic phantom, down to approximately 1.4 mGy in CTDIvol (60% reduced dose). PMID:29354008

TH-E-BRF-01: Exploiting Tumor Shrinkage in Split-Course Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unkelbach, J; Craft, D; Hong, T

2014-06-15

Purpose: In split-course radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated by radiobiological considerations. However, using modern image-guidance, it also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. In this work, we consider the optimal design of split-course treatments, motivated by the clinical management of large liver tumors for which normal liver dose constraints prohibit the administration of an ablative radiation dose in a single treatment. Methods: We introduce a dynamic tumor model that incorporates three factors: radiation induced cell kill, tumor shrinkage, and tumor cellmore » repopulation. The design of splitcourse radiotherapy is formulated as a mathematical optimization problem in which the total dose to the liver is minimized, subject to delivering the prescribed dose to the tumor. Based on the model, we gain insight into the optimal administration of radiation over time, i.e. the optimal treatment gaps and dose levels. Results: We analyze treatments consisting of two stages in detail. The analysis confirms the intuition that the second stage should be delivered just before the tumor size reaches a minimum and repopulation overcompensates shrinking. Furthermore, it was found that, for a large range of model parameters, approximately one third of the dose should be delivered in the first stage. The projected benefit of split-course treatments in terms of liver sparing depends on model assumptions. However, the model predicts large liver dose reductions by more than a factor of two for plausible model parameters. Conclusion: The analysis of the tumor model suggests that substantial reduction in normal tissue dose can be achieved by exploiting tumor shrinkage via an optimal design of multi-stage treatments. This suggests taking a fresh look at split-course radiotherapy for selected disease sites where substantial tumor regression translates into reduced target volumes.« less

Post-focus expansion of ion beams for low fluence and large area MeV ion irradiation: Application to human brain tissue and electronics devices

NASA Astrophysics Data System (ADS)

Whitlow, Harry J.; Guibert, Edouard; Jeanneret, Patrick; Homsy, Alexandra; Roth, Joy; Krause, Sven; Roux, Adrien; Eggermann, Emmanuel; Stoppini, Luc

2017-08-01

Irradiation with ∼3 MeV proton fluences of 106-109 protons cm-2 have been applied to study the effects on human brain tissue corresponding to single-cell irradiation doses and doses received by electronic components in low-Earth orbit. The low fluence irradiations were carried out using a proton microbeam with the post-focus expansion of the beam; a method developed by the group of Breese [1]. It was found from electrophysiological measurements that the mean neuronal frequency of human brain tissue decreased to zero as the dose increased to 0-1050 Gy. Enhancement-mode MOSFET transistors exhibited a 10% reduction in threshold voltage for 2.7 MeV proton doses of 10 Gy while a NPN bipolar transistor required ∼800 Gy to reduce the hfe by 10%, which is consistent the expected values.

In vivo anticancer activity of vanillin semicarbazone

PubMed Central

Ali, Shaikh M Mohsin; Azad, M Abul Kalam; Jesmin, Mele; Ahsan, Shamim; Rahman, M Mijanur; Khanam, Jahan Ara; Islam, M Nazrul; Shahriar, Sha M Shahan

2012-01-01

Objective To evaluate the anticancer activity of vanillin semicarbazone (VSC) against Ehrlich ascites carcinoma (EAC) cells in Swiss albino mice. Methods The compound VSC at three doses (5, 7.5 and 10 mg/kg i.p.) was administered into the intraperitoneal cavity of the EAC inoculated mice to observe its efficiency by studying the cell growth inhibition, reduction of tumour weight, enhancement of survival time as well as the changes in depleted hematological parameters. All such parameters were also studied with a known standard drug bleomycin at the dose of 0.3 mg/kg (i.p.). Results Among the doses studied, 10 mg/kg (i.p.) was found to be quite comparable in potency to that of bleomycin at the dose of 0.3 mg/kg (i.p.). The host toxic effects of VSC was found to be negligible. Conclusions It can be concluded that VSC can therefore be considered as potent anticancer agent. PMID:23569946

Effect of propranolol in head tremor: quantitative study following single-dose and sustained drug administration.

PubMed

Calzetti, S; Sasso, E; Negrotti, A; Baratti, M; Fava, R

1992-12-01

The effect of the beta-adrenoceptor antagonist propranolol has been investigated in nine patients suffering from isolated (six patients) or prominent (three patients) essential tremor of the head. In a double-blind, placebo-controlled study the tremorolytic efficacy of propranolol has been assessed by a quantitative accelerometric method after a single oral dose (120 mg) and following 2 weeks of sustained treatment with two different dosage regimens of the drug (120 and 240 mg daily). As compared with placebo, a significant reduction in tremor magnitude was found following a single oral dose but not on sustained administration of the beta-blocker at either dosage. The results suggest that the efficacy of sustained propranolol on isolated or prominent essential head tremor is less predictable and satisfactory than expected on the basis of the single-dose response, as compared with hand tremor.

Gold Nanoparticle Hyperthermia Reduces Radiotherapy Dose

PubMed Central

Lin, Lynn; Slatkin, Daniel N.; Dilmanian, F. Avraham; Vadas, Timothy M.; Smilowitz, Henry M.

2014-01-01

Gold nanoparticles can absorb near infrared light, resulting in heating and ablation of tumors. Gold nanoparticles have also been used for enhancing the dose of X-rays in tumors during radiotherapy. The combination of hyperthermia and radiotherapy is synergistic, importantly allowing a reduction in X-ray dose with improved therapeutic results. Here we intratumorally infused small 15 nm gold nanoparticles engineered to be transformed from infrared-transparent to infrared-absorptive by the tumor, which were then heated by infrared followed by X-ray treatment. Synergy was studied using a very radioresistant subcutaneous squamous cell carcinoma (SCCVII) in mice. It was found that the dose required to control 50% of the tumors, normally 55 Gy, could be reduced to <15 Gy (a factor of >3.7). Gold nanoparticles therefore provide a method to combine hyperthermia and radiotherapy to drastically reduce the X-ray radiation needed, thus sparing normal tissue, reducing the side effects, and making radiotherapy more effective. PMID:24990355

Asymmetric collimation: Dosimetric characteristics, treatment planning algorithm, and clinical applications

NASA Astrophysics Data System (ADS)

Kwa, William

1998-11-01

In this thesis the dosimetric characteristics of asymmetric fields are investigated and a new computation method for the dosimetry of asymmetric fields is described and implemented into an existing treatment planning algorithm. Based on this asymmetric field treatment planning algorithm, the clinical use of asymmetric fields in cancer treatment is investigated, and new treatment techniques for conformal therapy are developed. Dose calculation is verified with thermoluminescent dosimeters in a body phantom. In this thesis, an analytical approach is proposed to account for the dose reduction when a corresponding symmetric field is collimated asymmetrically to a smaller asymmetric field. This is represented by a correction factor that uses the ratio of the equivalent field dose contributions between the asymmetric and symmetric fields. The same equation used in the expression of the correction factor can be used for a wide range of asymmetric field sizes, photon energies and linear accelerators. This correction factor will account for the reduction in scatter contributions within an asymmetric field, resulting in the dose profile of an asymmetric field resembling that of a wedged field. The output factors of some linear accelerators are dependent on the collimator settings and whether the upper or lower collimators are used to set the narrower dimension of a radiation field. In addition to this collimator exchange effect for symmetric fields, asymmetric fields are also found to exhibit some asymmetric collimator backscatter effect. The proposed correction factor is extended to account for these effects. A set of correction factors determined semi-empirically to account for the dose reduction in the penumbral region and outside the radiated field is established. Since these correction factors rely only on the output factors and the tissue maximum ratios, they can easily be implemented into an existing treatment planning system. There is no need to store either additional sets of asymmetric field profiles or databases for the implementation of these correction factors into an existing in-house treatment planning system. With this asymmetric field algorithm, the computation time is found to be 20 times faster than a commercial system. This computation method can also be generalized to the dose representation of a two-fold asymmetric field whereby both the field width and length are set asymmetrically, and the calculations are not limited to points lying on one of the principal planes. The dosimetric consequences of asymmetric fields on the dose delivery in clinical situations are investigated. Examples of the clinical use of asymmetric fields are given and the potential use of asymmetric fields in conformal therapy is demonstrated. An alternative head and neck conformal therapy is described, and the treatment plan is compared to the conventional technique. The dose distributions calculated for the standard and alternative techniques are confirmed with thermoluminescent dosimeters in a body phantom at selected dose points. (Abstract shortened by UMI.)

Computational and human observer image quality evaluation of low dose, knowledge-based CT iterative reconstruction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eck, Brendan L.; Fahmi, Rachid; Miao, Jun

2015-10-15

Purpose: Aims in this study are to (1) develop a computational model observer which reliably tracks the detectability of human observers in low dose computed tomography (CT) images reconstructed with knowledge-based iterative reconstruction (IMR™, Philips Healthcare) and filtered back projection (FBP) across a range of independent variables, (2) use the model to evaluate detectability trends across reconstructions and make predictions of human observer detectability, and (3) perform human observer studies based on model predictions to demonstrate applications of the model in CT imaging. Methods: Detectability (d′) was evaluated in phantom studies across a range of conditions. Images were generated usingmore » a numerical CT simulator. Trained observers performed 4-alternative forced choice (4-AFC) experiments across dose (1.3, 2.7, 4.0 mGy), pin size (4, 6, 8 mm), contrast (0.3%, 0.5%, 1.0%), and reconstruction (FBP, IMR), at fixed display window. A five-channel Laguerre–Gauss channelized Hotelling observer (CHO) was developed with internal noise added to the decision variable and/or to channel outputs, creating six different internal noise models. Semianalytic internal noise computation was tested against Monte Carlo and used to accelerate internal noise parameter optimization. Model parameters were estimated from all experiments at once using maximum likelihood on the probability correct, P{sub C}. Akaike information criterion (AIC) was used to compare models of different orders. The best model was selected according to AIC and used to predict detectability in blended FBP-IMR images, analyze trends in IMR detectability improvements, and predict dose savings with IMR. Predicted dose savings were compared against 4-AFC study results using physical CT phantom images. Results: Detection in IMR was greater than FBP in all tested conditions. The CHO with internal noise proportional to channel output standard deviations, Model-k4, showed the best trade-off between fit and model complexity according to AIC{sub c}. With parameters fixed, the model reasonably predicted detectability of human observers in blended FBP-IMR images. Semianalytic internal noise computation gave results equivalent to Monte Carlo, greatly speeding parameter estimation. Using Model-k4, the authors found an average detectability improvement of 2.7 ± 0.4 times that of FBP. IMR showed greater improvements in detectability with larger signals and relatively consistent improvements across signal contrast and x-ray dose. In the phantom tested, Model-k4 predicted an 82% dose reduction compared to FBP, verified with physical CT scans at 80% reduced dose. Conclusions: IMR improves detectability over FBP and may enable significant dose reductions. A channelized Hotelling observer with internal noise proportional to channel output standard deviation agreed well with human observers across a wide range of variables, even across reconstructions with drastically different image characteristics. Utility of the model observer was demonstrated by predicting the effect of image processing (blending), analyzing detectability improvements with IMR across dose, size, and contrast, and in guiding real CT scan dose reduction experiments. Such a model observer can be applied in optimizing parameters in advanced iterative reconstruction algorithms as well as guiding dose reduction protocols in physical CT experiments.« less

SU-F-T-404: Dosimetric Advantages of Flattening Free Beams to Prone Accelerated Partial Breast Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galavis, P; Barbee, D; Jozsef, G

2016-06-15

Purpose: Prone accelerated partial breast irradiation (APBI) results in dose reduction to the heart and lung. Flattening filter free beams (FFF) reduce out of field dose due to the reduced scatter from the removal of the flattening filter and reduce the buildup region. The aim of this work is to evaluate the dosimetric advantages of FFF beams to prone APBI target coverage and reduction in dose to organs at risk. Methods: Fifteen clinical prone APBI cases using flattened photon beams were retrospectively re-planned in Eclipse-TPS using FFF beams. FFF plans were designed to provide equivalent target coverage with similar hotspotsmore » using the same field arrangements, resulting in comparable target DVHs. Both plans were transferred to a prone breast phantom and delivered on Varian-Edge-Linac. GafChromic-film was placed in the coronal plane of the phantom, partially overlapping the treatment field and extending into OARs to compare dose profiles from both plans. Results: FFF plans were comparable to the clinical plans with maximum doses of (108.3±2.3)% and (109.2±2.4)% and mean doses of (104.5±1.0)% and (104.6±1.2)%, respectively. Similar mean dose doses to the heart and contralateral lungs were observed from both plans, whereas the mean dose to the contra-lateral breast was (2.79±1.18) cGy and (2.86±1.40) cGy for FFF and clinical plans respectively. However for both plans the error between calculated and measured doses at 4 cm from the field edge was 10%. Conclusion: The results showed that FFF beams in prone APBI provide dosimetrically equivalent target coverage and improved coverage in superficial target due to softer energy spectra. Film analysis showed that the TPS underestimates dose outside field edges for both cases. The FFF measured plans showed less dose outside the beam that might reduce the probability of secondary cancers in the contralateral breast.« less

Feasibility study on the verification of actual beam delivery in a treatment room using EPID transit dosimetry.

PubMed

Baek, Tae Seong; Chung, Eun Ji; Son, Jaeman; Yoon, Myonggeun

2014-12-04

The aim of this study is to evaluate the ability of transit dosimetry using commercial treatment planning system (TPS) and an electronic portal imaging device (EPID) with simple calibration method to verify the beam delivery based on detection of large errors in treatment room. Twenty four fields of intensity modulated radiotherapy (IMRT) plans were selected from four lung cancer patients and used in the irradiation of an anthropomorphic phantom. The proposed method was evaluated by comparing the calculated dose map from TPS and EPID measurement on the same plane using a gamma index method with a 3% dose and 3 mm distance-to-dose agreement tolerance limit. In a simulation using a homogeneous plastic water phantom, performed to verify the effectiveness of the proposed method, the average passing rate of the transit dose based on gamma index was high enough, averaging 94.2% when there was no error during beam delivery. The passing rate of the transit dose for 24 IMRT fields was lower with the anthropomorphic phantom, averaging 86.8% ± 3.8%, a reduction partially due to the inaccuracy of TPS calculations for inhomogeneity. Compared with the TPS, the absolute value of the transit dose at the beam center differed by -0.38% ± 2.1%. The simulation study indicated that the passing rate of the gamma index was significantly reduced, to less than 40%, when a wrong field was erroneously irradiated to patient in the treatment room. This feasibility study suggested that transit dosimetry based on the calculation with commercial TPS and EPID measurement with simple calibration can provide information about large errors for treatment beam delivery.

Comparison of different treatment planning optimization methods for vaginal HDR brachytherapy with multichannel applicators: A reduction of the high doses to the vaginal mucosa is possible.

PubMed

Carrara, Mauro; Cusumano, Davide; Giandini, Tommaso; Tenconi, Chiara; Mazzarella, Ester; Grisotto, Simone; Massari, Eleonora; Mazzeo, Davide; Cerrotta, Annamaria; Pappalardi, Brigida; Fallai, Carlo; Pignoli, Emanuele

2017-12-01

A direct planning approach with multi-channel vaginal cylinders (MVCs) used for HDR brachytherapy of vaginal cancers is particularly challenging. Purpose of this study was to compare the dosimetric performances of different forward and inverse methods used for the optimization of MVC-based vaginal treatments for endometrial cancer, with a particular attention to the definition of strategies useful to limit the high doses to the vaginal mucosa. Twelve postoperative vaginal HDR brachytherapy treatments performed with MVCs were considered. Plans were retrospectively optimized with three different methods: Dose Point Optimization followed by Graphical Optimization (DPO + GrO), Inverse Planning Simulated Annealing with two different class solutions as starting conditions (surflPSA and homogIPSA) and Hybrid Inverse Planning Optimization (HIPO). Several dosimetric parameters related to target coverage, hot spot extensions and sparing of organs at risk were analyzed to evaluate the quality of the achieved treatment plans. Dose homogeneity index (DHI), conformal index (COIN) and a further parameter quantifying the proportion of the central catheter loading with respect to the overall loading (i.e., the central catheter loading index: CCLI) were also quantified. The achieved PTV coverage parameters were highly correlated with each other but uncorrelated with the hot spot quantifiers. HomogIPSA and HIPO achieved higher DHIs and CCLIs and lower volumes of high doses than DPO + GrO and surflPSA. Within the investigated optimization methods, HIPO and homoglPSA showed the highest dose homogeneity to the target. In particular, homogIPSA resulted also the most effective in reducing hot spots to the vaginal mucosa. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Beneficial effects of low dose Musa paradisiaca on the semen quality of male Wistar rats

PubMed Central

Alabi, A. S.; Omotoso, Gabriel O.; Enaibe, B. U.; Akinola, O. B.; Tagoe, C. N. B.

2013-01-01

Background: This study aimed at determining the effects of administration of mature green fruits of Musa paradisiaca on the semen quality of adult male Wistar rats. Materials and Methods: The animals used for the study were grouped into three: the control group, given 2 ml of double distilled water, a low dose group given 500 mg/kg/day and a high dose group given 1000 mg/kg/day of the plantain fruits, which was made into flour, and dissolved in 2 ml of double distilled water for easy oral administration. Results: Significant increment in the semen parameters was noticed in animals that received a lower dose of the plantain flour, but those animals who received the high dose had marked and very significant reduction in sperm cell concentration and percentage of morphologically normal spermatozoa. Conclusion: Musa paradisiaca should be consumed in moderate quantities in order to derive its beneficial effects of enhancing male reproductive functions. PMID:23798793

Dose reduction of up to 89% while maintaining image quality in cardiovascular CT achieved with prospective ECG gating

NASA Astrophysics Data System (ADS)

Londt, John H.; Shreter, Uri; Vass, Melissa; Hsieh, Jiang; Ge, Zhanyu; Adda, Olivier; Dowe, David A.; Sabllayrolles, Jean-Louis

2007-03-01

We present the results of dose and image quality performance evaluation of a novel, prospective ECG-gated Coronary CT Angiography acquisition mode (SnapShot Pulse, LightSpeed VCT-XT scanner, GE Healthcare, Waukesha, WI), and compare it to conventional retrospective ECG gated helical acquisition in clinical and phantom studies. Image quality phantoms were used to measure noise, slice sensitivity profile, in-plane resolution, low contrast detectability and dose, using the two acquisition modes. Clinical image quality and diagnostic confidence were evaluated in a study of 31 patients scanned with the two acquisition modes. Radiation dose reduction in clinical practice was evaluated by tracking 120 consecutive patients scanned with the prospectively gated scan mode. In the phantom measurements, the prospectively gated mode resulted in equivalent or better image quality measures at dose reductions of up to 89% compared to non-ECG modulated conventional helical scans. In the clinical study, image quality was rated excellent by expert radiologist reviewing the cases, with pathology being identical using the two acquisition modes. The average dose to patients in the clinical practice study was 5.6 mSv, representing 50% reduction compared to a similar patient population scanned with the conventional helical mode.

The quantification of wound healing as a method to assess late radiation damage in primate skin exposed to high-energy protons

NASA Astrophysics Data System (ADS)

Cox, A. B.; Lett, J. T.

In an experiment examining the effects of space radiations on primates, different groups of rhesus monkeys (Macaca mulatta) were exposed to single whole-body doses of 32- or 55-MeV protons. Survivors of those exposures, together with age-matched controls, have been monitored continuously since 1964 and 1965. Late effects of nominal proton doses ranging from 2-6 Gray have been measured in vitro using skin fibroblasts from the animals. A logical extension of that study is reported here, and it involves observations of wound healing after 3-mm diameter dermal punches were removed from the ears (pinnae) of control and irradiated monkeys. Tendencies in the reduction of competence to repair cutaneous wound have been revealed by the initial examinations of animals that received doses greater than 2 Gy more than 2 decades earlier. These trends indicate that this method of assessing radiation damage to skin exposed to high-energy radiations warrants further study.

Detection and characterization of lesions on low-radiation-dose abdominal CT images postprocessed with noise reduction filters.

PubMed

Kalra, Mannudeep K; Maher, Michael M; Blake, Michael A; Lucey, Brian C; Karau, Kelly; Toth, Thomas L; Avinash, Gopal; Halpern, Elkan F; Saini, Sanjay

2004-09-01

To assess the effect of noise reduction filters on detection and characterization of lesions on low-radiation-dose abdominal computed tomographic (CT) images. Low-dose CT images of abdominal lesions in 19 consecutive patients (11 women, eight men; age range, 32-78 years) were obtained at reduced tube currents (120-144 mAs). These baseline low-dose CT images were postprocessed with six noise reduction filters; the resulting postprocessed images were then randomly assorted with baseline images. Three radiologists performed independent evaluation of randomized images for presence, number, margins, attenuation, conspicuity, calcification, and enhancement of lesions, as well as image noise. Side-by-side comparison of baseline images with postprocessed images was performed by using a five-point scale for assessing lesion conspicuity and margins, image noise, beam hardening, and diagnostic acceptability. Quantitative noise and contrast-to-noise ratio were obtained for all liver lesions. Statistical analysis was performed by using the Wilcoxon signed rank test, Student t test, and kappa test of agreement. Significant reduction of noise was observed in images postprocessed with filter F compared with the noise in baseline nonfiltered images (P =.004). Although the number of lesions seen on baseline images and that seen on postprocessed images were identical, lesions were less conspicuous on postprocessed images than on baseline images. A decrease in quantitative image noise and contrast-to-noise ratio for liver lesions was noted with all noise reduction filters. There was good interobserver agreement (kappa = 0.7). Although the use of currently available noise reduction filters improves image noise and ameliorates beam-hardening artifacts at low-dose CT, such filters are limited by a compromise in lesion conspicuity and appearance in comparison with lesion conspicuity and appearance on baseline low-dose CT images. Copyright RSNA, 2004

Tumor control probability reduction in gated radiotherapy of non-small cell lung cancers: a feasibility study.

PubMed

Siochi, R Alfredo; Kim, Yusung; Bhatia, Sudershan

2014-10-16

We studied the feasibility of evaluating tumor control probability (TCP) reductions for tumor motion beyond planned gated radiotherapy margins. Tumor motion was determined from cone-beam CT projections acquired for patient setup, intrafraction respiratory traces, and 4D CTs for five non-small cell lung cancer (NSCLC) patients treated with gated radiotherapy. Tumors were subdivided into 1 mm sections whose positions and doses were determined for each beam-on time point. (The dose calculation model was verified with motion phantom measurements.) The calculated dose distributions were used to generate the treatment TCPs for each patient. The plan TCPs were calculated from the treatment planning dose distributions. The treatment TCPs were compared to the plan TCPs for various models and parameters. Calculated doses matched phantom measurements within 0.3% for up to 3 cm of motion. TCP reductions for excess motion greater than 5mm ranged from 1.7% to 11.9%, depending on model parameters, and were as high as 48.6% for model parameters that simulated an individual patient. Repeating the worst case motion for all fractions increased TCP reductions by a factor of 2 to 3, while hypofractionation decreased these reductions by as much as a factor of 3. Treatment motion exceeding gating margins by more than 5 mm can lead to considerable TCP reductions. Appropriate margins for excess motion are recommended, unless applying daily tumor motion verification and adjusting thegating window.

3D conditional generative adversarial networks for high-quality PET image estimation at low dose.

PubMed

Wang, Yan; Yu, Biting; Wang, Lei; Zu, Chen; Lalush, David S; Lin, Weili; Wu, Xi; Zhou, Jiliu; Shen, Dinggang; Zhou, Luping

2018-07-01

Positron emission tomography (PET) is a widely used imaging modality, providing insight into both the biochemical and physiological processes of human body. Usually, a full dose radioactive tracer is required to obtain high-quality PET images for clinical needs. This inevitably raises concerns about potential health hazards. On the other hand, dose reduction may cause the increased noise in the reconstructed PET images, which impacts the image quality to a certain extent. In this paper, in order to reduce the radiation exposure while maintaining the high quality of PET images, we propose a novel method based on 3D conditional generative adversarial networks (3D c-GANs) to estimate the high-quality full-dose PET images from low-dose ones. Generative adversarial networks (GANs) include a generator network and a discriminator network which are trained simultaneously with the goal of one beating the other. Similar to GANs, in the proposed 3D c-GANs, we condition the model on an input low-dose PET image and generate a corresponding output full-dose PET image. Specifically, to render the same underlying information between the low-dose and full-dose PET images, a 3D U-net-like deep architecture which can combine hierarchical features by using skip connection is designed as the generator network to synthesize the full-dose image. In order to guarantee the synthesized PET image to be close to the real one, we take into account of the estimation error loss in addition to the discriminator feedback to train the generator network. Furthermore, a concatenated 3D c-GANs based progressive refinement scheme is also proposed to further improve the quality of estimated images. Validation was done on a real human brain dataset including both the normal subjects and the subjects diagnosed as mild cognitive impairment (MCI). Experimental results show that our proposed 3D c-GANs method outperforms the benchmark methods and achieves much better performance than the state-of-the-art methods in both qualitative and quantitative measures. Copyright © 2018 Elsevier Inc. All rights reserved.

Radiation dose reduction in computed tomography: techniques and future perspective

PubMed Central

Yu, Lifeng; Liu, Xin; Leng, Shuai; Kofler, James M; Ramirez-Giraldo, Juan C; Qu, Mingliang; Christner, Jodie; Fletcher, Joel G; McCollough, Cynthia H

2011-01-01

Despite universal consensus that computed tomography (CT) overwhelmingly benefits patients when used for appropriate indications, concerns have been raised regarding the potential risk of cancer induction from CT due to the exponentially increased use of CT in medicine. Keeping radiation dose as low as reasonably achievable, consistent with the diagnostic task, remains the most important strategy for decreasing this potential risk. This article summarizes the general technical strategies that are commonly used for radiation dose management in CT. Dose-management strategies for pediatric CT, cardiac CT, dual-energy CT, CT perfusion and interventional CT are specifically discussed, and future perspectives on CT dose reduction are presented. PMID:22308169

Liraglutide, leptin, and their combined effects on feeding: additive intake reduction through common intracellular signaling mechanisms

PubMed Central

Kanoski, Scott E.; Ong, Zhi Yi; Fortin, Samantha M.; Schlessinger, Elizabeth S.; Grill, Harvey J.

2014-01-01

Aims Glucagon like peptide-1 receptor (GLP-1R) agonists and leptin each exert anorexigenic effects. In combination, the intake inhibitory and weight loss effects are greater than either treatment alone, however the mechanisms unclear. Materials and methods Effects of liraglutide (a long-acting GLP-1 analogue) and leptin co-treatment, delivered in low or moderate doses subcutaneously (SC) or to the 3rd ventricle respectively, on cumulative intake, meal patterns, and hypothalamic expression of intracellular signaling proteins [phosphorylated signal transducer and activator of transcription-3 (pSTAT3) and protein tyrosine phosphatase-1B (PTP1B)] were examined in lean rats. Results A low-dose combination of liraglutide (25μg/kg) and leptin (0.75μg) additively reduced cumulative food intake and body weight, a result mediated predominantly through a significant reduction in meal frequency that was not present with either drug alone. Liraglutide treatment alone also reduced meal size; an effect not enhanced with leptin co-administration. Moderate doses of liraglutide (75μg/kg) and leptin (4μg) examined separately each reduced meal frequency, cumulative food intake, and body weight; only liraglutide reduced meal size. In combination these doses did not further enhance the anorexigenic effects of either treatment alone. Ex vivo immunoblot showed elevated pSTAT3 in hypothalamic tissue following liraglutide-leptin co-treatment, an effect greater than leptin treatment alone. In addition, SC liraglutide reduced expression of PTP1B (a negative regulator of leptin receptor signaling), revealing a potential mechanism for the enhanced pSTAT3 response following liraglutide-leptin co-administration. Conclusions Collectively, these results provide novel behavioral and molecular mechanisms underlying the additive reduction in food intake and body weight following liraglutide-leptin combination treatment. PMID:25475828

Low radiation dose in computed tomography: the role of iodine

PubMed Central

Aschoff, Andrik J; Catalano, Carlo; Krix, Martin; Albrecht, Thomas

2017-01-01

Recent approaches to reducing radiation exposure during CT examinations typically utilize automated dose modulation strategies on the basis of lower tube voltage combined with iterative reconstruction and other dose-saving techniques. Less clearly appreciated is the potentially substantial role that iodinated contrast media (CM) can play in low-radiation-dose CT examinations. Herein we discuss the role of iodinated CM in low-radiation-dose examinations and describe approaches for the optimization of CM administration protocols to further reduce radiation dose and/or CM dose while maintaining image quality for accurate diagnosis. Similar to the higher iodine attenuation obtained at low-tube-voltage settings, high-iodine-signal protocols may permit radiation dose reduction by permitting a lowering of mAs while maintaining the signal-to-noise ratio. This is particularly feasible in first pass examinations where high iodine signal can be achieved by injecting iodine more rapidly. The combination of low kV and IR can also be used to reduce the iodine dose. Here, in optimum contrast injection protocols, the volume of CM administered rather than the iodine concentration should be reduced, since with high-iodine-concentration CM further reductions of iodine dose are achievable for modern first pass examinations. Moreover, higher concentrations of CM more readily allow reductions of both flow rate and volume, thereby improving the tolerability of contrast administration. PMID:28471242

SU-E-T-373: Evaluation and Reduction of Contralateral Skin /subcutaneous Dose for Tangential Breast Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butson, M; Carroll, S; Whitaker, M

2015-06-15

Purpose: Tangential breast irradiation is a standard treatment technique for breast cancer therapy. One aspect of dose delivery includes dose delivered to the skin caused by electron contamination. This effect is especially important for highly oblique beams used on the medical tangent where the electron contamination deposits dose on the contralateral breast side. This work aims to investigate and predict as well as define a method to reduce this dose during tangential breast radiotherapy. Methods: Analysis and calculation of breast skin and subcutaneous dose is performed using a Varian Eclipse planning system, AAA algorithm for 6MV x-ray treatments. Measurements weremore » made using EBT3 Gafchromic film to verify the accuracy of planning data. Various materials were tested to assess their ability to remove electron contamination on the contralateral breast. Results: Results showed that the Varian Eclipse AAA algorithm could accurately estimate contralateral breast dose in the build-up region at depths of 2mm or deeper. Surface dose was underestimated by the AAA algorithm. Doses up to 12% of applied dose were seen on the contralateral breast surface and up to 9 % at 2mm depth. Due to the nature of this radiation, being mainly low energy electron contamination, a bolus material could be used to reduce this dose to less than 3%. This is accomplished by 10 mm of superflab bolus or by 1 mm of lead. Conclusion: Contralateral breast skin and subcutaneous dose is present for tangential breast treatment and has been measured to be up to 12% of applied dose from the medial tangent beam. This dose is deposited at shallow depths and is accurately calculated by the Eclipse AAA algorithm at depths of 2mm or greater. Bolus material placed over the contralateral can be used to effectively reduce this skin dose.« less

Low-dose naltrexone for the treatment of fibromyalgia: findings of a small, randomized, double-blind, placebo-controlled, counterbalanced, crossover trial assessing daily pain levels.

PubMed

Younger, Jarred; Noor, Noorulain; McCue, Rebecca; Mackey, Sean

2013-02-01

To determine whether low dosages (4.5 mg/day) of naltrexone reduce fibromyalgia severity as compared with the nonspecific effects of placebo. In this replication and extension study of a previous clinical trial, we tested the impact of low-dose naltrexone on daily self-reported pain. Secondary outcomes included general satisfaction with life, positive mood, sleep quality, and fatigue. Thirty-one women with fibromyalgia participated in the randomized, double-blind, placebo-controlled, counterbalanced, crossover study. During the active drug phase, participants received 4.5 mg of oral naltrexone daily. An intensive longitudinal design was used to measure daily levels of pain. When contrasting the condition end points, we observed a significantly greater reduction of baseline pain in those taking low-dose naltrexone than in those taking placebo (28.8% reduction versus 18.0% reduction; P = 0.016). Low-dose naltrexone was also associated with improved general satisfaction with life (P = 0.045) and with improved mood (P = 0.039), but not improved fatigue or sleep. Thirty-two percent of participants met the criteria for response (defined as a significant reduction in pain plus a significant reduction in either fatigue or sleep problems) during low-dose naltrexone therapy, as contrasted with an 11% response rate during placebo therapy (P = 0.05). Low-dose naltrexone was rated equally tolerable as placebo, and no serious side effects were reported. The preliminary evidence continues to show that low-dose naltrexone has a specific and clinically beneficial impact on fibromyalgia pain. The medication is widely available, inexpensive, safe, and well-tolerated. Parallel-group randomized controlled trials are needed to fully determine the efficacy of the medication. Copyright © 2013 by the American College of Rheumatology.

Anal wall sparing effect of an endorectal balloon in 3D conformal and intensity-modulated prostate radiotherapy.

PubMed

Smeenk, Robert Jan; van Lin, Emile N J Th; van Kollenburg, Peter; Kunze-Busch, Martina; Kaanders, Johannes H A M

2009-10-01

To investigate the anal wall (Awall) sparing effect of an endorectal balloon (ERB) in 3D conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) for prostate cancer. In 24 patients with localized prostate carcinoma, two planning CT-scans were performed: with and without ERB. A prostate planning target volume (PTV) was defined, and the Awall was delineated, using two different methods. Three-field and 4-field 3D-CRT plans, and IMRT plans were generated with a prescription dose of 78Gy. In 144 treatment plans, the minimum dose (D(min)), maximum dose (D(max)), and mean dose (D(mean)) to the Awall were calculated, as well as the Awall volumes exposed to doses ranging from >or=20Gy to >or=70Gy (V(20)-V(70), respectively). In the 3D-CRT plans, an ERB significantly reduced D(mean), D(max), and V(30)-V(70). For IMRT all investigated dose parameters were significantly reduced by the ERB. The absolute reduction of D(mean) was 12Gy in 3D-CRT and was 7.5Gy in IMRT for both methods of Awall delineation. Application of an ERB showed a significant Awall sparing effect in both 3D-CRT and IMRT. This may lead to reduced late anal toxicity in prostate radiotherapy.

The Study of External Dose Rate and Retained Body Activity of Patients Receiving 131I Therapy for Differentiated Thyroid Carcinoma

PubMed Central

Zhang, Haiying; Jiao, Ling; Cui, Songye; Wang, Liang; Tan, Jian; Zhang, Guizhi; He, Yajing; Ruan, Shuzhou; Fan, Saijun; Zhang, Wenyi

2014-01-01

Radiation safety is an integral part of targeted radionuclide therapy. The aim of this work was to study the external dose rate and retained body activity as functions of time in differentiated thyroid carcinoma patients receiving 131I therapy. Seventy patients were stratified into two groups: the ablation group (A) and the follow-up group (FU). The patients’ external dose rate was measured, and simultaneously, their retained body radiation activity was monitored at various time points. The equations of the external dose rate and the retained body activity, described as a function of hours post administration, were fitted. Additionally, the release time for patients was calculated. The reduction in activity in the group receiving a second or subsequent treatment was more rapid than the group receiving only the initial treatment. Most important, an expeditious method was established to indirectly evaluate the retained body activity of patients by measuring the external dose rate with a portable radiation survey meter. By this method, the calculated external dose rate limits are 19.2, 8.85, 5.08 and 2.32 μSv·h−1 at 1, 1.5, 2 and 3 m, respectively, according to a patient’s released threshold level of retained body activity <400 MBq. This study is beneficial for radiation safety decision-making. PMID:25337944

A study of the parameters affecting the effectiveness of Moringa oleifera in drinking water purification

NASA Astrophysics Data System (ADS)

Pritchard, M.; Craven, T.; Mkandawire, T.; Edmondson, A. S.; O'Neill, J. G.

The powder obtained from the seeds of the Moringa oleifera tree has been shown to be an effective primary coagulant for water treatment. When the seeds are dried, dehusked, crushed and added to water, the powder acts as a coagulant binding colloidal particles and bacteria to form agglomerated particles (flocs), which settle allowing the clarified supernatant to be poured off. Very little research has been undertaken on the parameters affecting the effectiveness of M. oleifera, especially in Malawi, for purification of drinking water and there is a great need for further testing in this area. Conclusive data needs to be compiled to demonstrate the effects of various water parameters have on the efficiency of the seeds. A parametric study was undertaken at Leeds Metropolitan University, UK, with the aim to establish the most appropriate dosing method; the optimum dosage for removal of turbidity; the influence of pH and temperature; together with the shelf life of the M. oleifera seeds. The study revealed that the most suitable dosing method was to mix the powder into a concentrated paste, hence forming a stock suspension. The optimum M. oleifera dose, for turbidity values between 40 and 200 NTU, ranged between 30 and 55 mg/l. With turbidity set at 130 NTU and a M. oleifera dose within the optimum range at 50 mg/l, pH levels were varied between 4 and 9. It was discovered that the coagulant performance was not too sensitive to pH fluctuations when conditions were within the optimum range. The most efficient coagulation, determined by the greatest reduction in turbidity, occurred at pH 6.5. Alkaline conditions were overall more favourable than acidic conditions; pH 9 had an efficiency of 65% of optimum, whilst at pH 5 the efficiency dropped to around 55%. The efficiency further dropped at pH 4, where the powder only produced results of around 10% of optimum conditions. A temperature range of 4-60 °C was studied in this research. Colder waters (<15 °C) were found to hinder the effectiveness of the coagulation process. The higher the temperature the more effective was the coagulation. It was also found that the age of the seeds, up to 18 months, did not have any noticeable effect on dose level and percentage reduction in turbidity, although at 18 months the seeds had a narrower dosing range to produce near-optimum reduction. Seeds aged 24 months showed a significant decline in coagulant efficiency.

Dose reduction for abdominal and pelvic MDCT after change to graduated weight-based protocol for selecting quality reference tube current, peak kilovoltage, and slice collimation.

PubMed

Herts, Brian R; Baker, Mark E; Obuchowski, Nancy; Primak, Andrew; Schneider, Erika; Rhana, Harpreet; Dong, Frank

2013-06-01

The purpose of this article is to determine the decrease in volume CT dose index (CTDI(vol)) and dose-length product (DLP) achieved by switching from fixed quality reference tube current protocols with automatic tube current modulation to protocols adjusting the quality reference tube current, slice collimation, and peak kilovoltage according to patient weight. All adult patients who underwent CT examinations of the abdomen or abdomen and pelvis during 2010 using weight-based protocols who also underwent a CT examination in 2008 or 2009 using fixed quality reference tube current protocols were identified from the radiology information system. Protocol pages were electronically retrieved, and the CT model, examination date, scan protocol, CTDI(vol), and DLP were extracted from the DICOM header or by optical character recognition. There were 15,779 scans with dose records for 2700 patients. Changes in CTDI(vol) and DLP were compared only between examinations of the same patient and same CT system model for examinations performed in 2008 or 2009 and those performed in 2010. The final analysis consisted of 1117 comparisons in 1057 patients, and 1209 comparisons in 988 patients for CTDI(vol) and DLP, respectively. The change to a weight-based protocol resulted in a statistically significant reduction in CTDI(vol) and DLP on three MDCT system models (p < 0.001). The largest average CTDI(vol) decrease was 13.9%, and the largest average DLP decrease was 16.1% on a 64-MDCT system. Both the CTDI(vol) and DLP decreased the most for patients who weighed less than 250 lb (112.5 kg). Adjusting the CT protocol by selecting parameters according to patient weight is a viable method for reducing CT radiation dose. The largest reductions occurred in the patients weighing less than 250 lb.

Radiation Dose Reduction in CT Fluoroscopy-Guided Cervical Transforaminal Epidural Steroid Injection by Modifying Scout and Planning Steps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paik, Nam Chull, E-mail: pncspine@gmail.com

Background and PurposeIn CT fluoroscopy (CTF)-guided cervical transforaminal epidural steroid injection (TFESI), the majority of radiation dose is contributed by the planning CT scan rather than the CTF procedure itself. We replaced the planning helical CT with a spot CTF and accordingly changed the patient posture during scout and planning scans. The aim of this study was to test whether radiation dose reduction would be achieved by this protocol modification while still maintaining technical performance.MethodsOverall, 338 consecutive procedures before (control group: n = 163) and after (study group: n = 175) instituting the above-mentioned protocol modification were analyzed retrospectively, comparing patient characteristics (age, sex,more » neck diameter, and level injected) and technical performance [technical success rate, dose-length product (DLP), inadvertent contrast flow incidence, number of CTF acquisitions, and procedural time] between the two groups.ResultsAll injections were technically successful at every level from C3–C4 to C7–T1 without serious complications in both groups. The median DLP of the study group (7.92 mGy·cm) was significantly reduced compared to that of the control group (39.05 mGy·cm, P < 0.001). There were no significant differences between the two groups regarding the incidence of inadvertent contrast flow (20.6 vs. 17.2 %, P = 0.426), number of CTF acquisitions (median 5 vs. 4, P = 0.123), and the procedural time (median 6.62 vs. 6.90 min, P = 0.100).ConclusionsWhen conducting CTF-guided cervical TFESIs, a significant radiation dose reduction (median 79.7 % in DLP) can be achieved by modifying scout and planning steps, without compromising the technical performance.« less

Sex differences in nicotine self-administration in rats during progressive unit dose reduction: Implications for nicotine regulation policy

PubMed Central

Grebenstein, Patricia; Burroughs, Danielle; Zhang, Yan; LeSage, Mark G.

2013-01-01

Reducing the nicotine content in tobacco products is being considered by the FDA as a policy to reduce the addictiveness of tobacco products. Understanding individual differences in response to nicotine reduction will be critical to developing safe and effective policy. Animal and human research demonstrating sex differences in the reinforcing effects of nicotine suggests that males and females may respond differently to nicotine-reduction policies. However, no studies have directly examined sex differences in the effects of nicotine unit-dose reduction on nicotine self-administration (NSA) in animals. The purpose of the present study was to examine this issue in a rodent self-administration model. Male and female rats were trained to self-administer nicotine (0.06 mg/kg) under an FR 3 schedule during daily 23 h sessions. Rats were then exposed to saline extinction and reacquisition of NSA, followed by weekly reductions in the unit dose (0.03 to 0.00025 mg/kg) until extinction levels of responding were achieved. Males and females were compared with respect to baseline levels of intake, resistance to extinction, degree of compensatory increases in responding during dose reduction, and the threshold reinforcing unit dose of nicotine. Exponential demand-curve analysis was also conducted to compare the sensitivity of males and females to increases in the unit price (FR/unit dose) of nicotine (i.e., elasticity of demand or reinforcing efficacy). Females exhibited significantly higher baseline intake and less compensation than males. However, there were no sex differences in the reinforcement threshold or elasticity of demand. Dose–response relationships were very well described by the exponential demand function (r2 values > 0.96 for individual subjects). These findings suggest that females may exhibit less compensatory smoking in response to nicotine reduction policies, even though their nicotine reinforcement threshold and elasticity of demand may not differ from males. PMID:24201048

Low-dose X-ray computed tomography image reconstruction with a combined low-mAs and sparse-view protocol

PubMed Central

Gao, Yang; Bian, Zhaoying; Huang, Jing; Zhang, Yunwan; Niu, Shanzhou; Feng, Qianjin; Chen, Wufan; Liang, Zhengrong; Ma, Jianhua

2014-01-01

To realize low-dose imaging in X-ray computed tomography (CT) examination, lowering milliampere-seconds (low-mAs) or reducing the required number of projection views (sparse-view) per rotation around the body has been widely studied as an easy and effective approach. In this study, we are focusing on low-dose CT image reconstruction from the sinograms acquired with a combined low-mAs and sparse-view protocol and propose a two-step image reconstruction strategy. Specifically, to suppress significant statistical noise in the noisy and insufficient sinograms, an adaptive sinogram restoration (ASR) method is first proposed with consideration of the statistical property of sinogram data, and then to further acquire a high-quality image, a total variation based projection onto convex sets (TV-POCS) method is adopted with a slight modification. For simplicity, the present reconstruction strategy was termed as “ASR-TV-POCS.” To evaluate the present ASR-TV-POCS method, both qualitative and quantitative studies were performed on a physical phantom. Experimental results have demonstrated that the present ASR-TV-POCS method can achieve promising gains over other existing methods in terms of the noise reduction, contrast-to-noise ratio, and edge detail preservation. PMID:24977611

Simulation of Tracer Dose Reduction in 18F-FDG PET/MRI: Effects on Oncologic Reading, Image Quality, and Artifacts.

PubMed

Seith, Ferdinand; Schmidt, Holger; Kunz, Julia; Küstner, Thomas; Gatidis, Sergios; Nikolaou, Konstantin; la Fougère, Christian; Schwenzer, Nina

2017-10-01

The aim of our study was to evaluate the effect of stepwise-reduced doses on objective and subjective image parameters and on oncologic readings in whole-body 18 F-FDG PET/MRI. Methods: We retrospectively simulated the stepwise reduction of 18 F-FDG doses of 19 patients (mean age ± SD, 50.9 ± 11.7 y; mean body mass index ± SD, 22.8 ± 3.2 kg/m 2 ) who received a whole-body PET/MRI examination from 3 to 0.5 MBq/kg of body weight (kgBW) in intervals of 0.25. Objective imaging parameters were assessed by measuring the SUV and coefficient of variation in different regions (aorta, liver, spleen, kidney, small bowel, lumbar vertebra, psoas muscle, urinary bladder) as well as the noise-equivalent counting rates in each bed position. Subjective image quality was evaluated with a masked reading of each simulated PET compared with the dose of 2 MBq/kgBW. Oncologic reading was performed first according to PERCIST in each dose and second by defining malignant lesions in doses of 2 MBq/kgBW and the maximum dose image (gold standard). The diagnostic confidence of each lesion was measured using a Likert scale. Results: With decreasing doses, regions in the mid abdomen showed a stronger decrease of SUV mean and noise-equivalent counting rates than regions in the upper abdomen (SUV mean , -45% and -15% on average in the small bowel and the liver, respectively). The coefficient of variation showed a nonlinear increase, pronounced below 1.5 MBq/kgBW. Subjective image quality was stable over a range between 1.25 and 2.75 MBq/kgBW compared with 2 MBq/kgBW. However, large photopenic areas in the mid abdomen were observed in 2 patients. In the PERCIST reading, target lesions were above the liver threshold with a stable SUV peak in all cases down to 2 MBq/kgBW. Eighty-six of 90 lesions were identified correctly with a dose of 2 MBq/kgBW; Likert scores did not differ significantly. Conclusion: A reduction of doses in 18 F-FDG PET/MRI might be possible down to 2 MBq/kgBW in oncologic whole-body examinations. The image quality in the mid abdomen seems to be more affected by lower doses than in the upper abdomen, and in single cases large photopenic areas can occur. Therefore, we do not recommend reducing doses below 3 MBq/kgBW in adults at this time. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Antidiarrhoeal activity of leaf methanolic extract of Rauwolfia serpentina

PubMed Central

Ezeigbo, II; Ezeja, MI; Madubuike, KG; Ifenkwe, DC; Ukweni, IA; Udeh, NE; Akomas, SC

2012-01-01

Objective To evaluate the antidiarrhoeal property of methanol extract of the leaves of Rauwolfia serpentina (R. serpentina) in experimental diarrhoea induced by castor oil in mice. Methods Doses of 100, 200 and 400 mg/kg R. serpentina leaf methanol extracts were administered to castor oil induced diarrhoea mice to determine its antidiarrhoeal activity. Results All doses of the extract and the reference drug atropine sulphate (3 mg/kg, i.p.) produced a dose-dependent reduction in intestinal weight and fluid volume. The extracts also significantly reduced the intestinal transit in charcoal meal test when compared to diphenoxylate Hcl (5 mg/kg, p.o.). Conclusions The results show that the extract of R. serpentina leaves has a significant antidiarrhoeal activity and supports its traditional uses in herbal medicine. PMID:23569944

Radiation dose reduction in computed tomography perfusion using spatial-temporal Bayesian methods

NASA Astrophysics Data System (ADS)

Fang, Ruogu; Raj, Ashish; Chen, Tsuhan; Sanelli, Pina C.

2012-03-01

In current computed tomography (CT) examinations, the associated X-ray radiation dose is of significant concern to patients and operators, especially CT perfusion (CTP) imaging that has higher radiation dose due to its cine scanning technique. A simple and cost-effective means to perform the examinations is to lower the milliampere-seconds (mAs) parameter as low as reasonably achievable in data acquisition. However, lowering the mAs parameter will unavoidably increase data noise and degrade CT perfusion maps greatly if no adequate noise control is applied during image reconstruction. To capture the essential dynamics of CT perfusion, a simple spatial-temporal Bayesian method that uses a piecewise parametric model of the residual function is used, and then the model parameters are estimated from a Bayesian formulation of prior smoothness constraints on perfusion parameters. From the fitted residual function, reliable CTP parameter maps are obtained from low dose CT data. The merit of this scheme exists in the combination of analytical piecewise residual function with Bayesian framework using a simpler prior spatial constrain for CT perfusion application. On a dataset of 22 patients, this dynamic spatial-temporal Bayesian model yielded an increase in signal-tonoise-ratio (SNR) of 78% and a decrease in mean-square-error (MSE) of 40% at low dose radiation of 43mA.

Technical Note: Phantom study to evaluate the dose and image quality effects of a computed tomography organ-based tube current modulation technique.

PubMed

Gandhi, Diksha; Crotty, Dominic J; Stevens, Grant M; Schmidt, Taly Gilat

2015-11-01

This technical note quantifies the dose and image quality performance of a clinically available organ-dose-based tube current modulation (ODM) technique, using experimental and simulation phantom studies. The investigated ODM implementation reduces the tube current for the anterior source positions, without increasing current for posterior positions, although such an approach was also evaluated for comparison. Axial CT scans at 120 kV were performed on head and chest phantoms on an ODM-equipped scanner (Optima CT660, GE Healthcare, Chalfont St. Giles, England). Dosimeters quantified dose to breast, lung, heart, spine, eye lens, and brain regions for ODM and 3D-modulation (SmartmA) settings. Monte Carlo simulations, validated with experimental data, were performed on 28 voxelized head phantoms and 10 chest phantoms to quantify organ dose and noise standard deviation. The dose and noise effects of increasing the posterior tube current were also investigated. ODM reduced the dose for all experimental dosimeters with respect to SmartmA, with average dose reductions across dosimeters of 31% (breast), 21% (lung), 24% (heart), 6% (spine), 19% (eye lens), and 11% (brain), with similar results for the simulation validation study. In the phantom library study, the average dose reduction across all phantoms was 34% (breast), 20% (lung), 8% (spine), 20% (eye lens), and 8% (brain). ODM increased the noise standard deviation in reconstructed images by 6%-20%, with generally greater noise increases in anterior regions. Increasing the posterior tube current provided similar dose reduction as ODM for breast and eye lens, increased dose to the spine, with noise effects ranging from 2% noise reduction to 16% noise increase. At noise equal to SmartmA, ODM increased the estimated effective dose by 4% and 8% for chest and head scans, respectively. Increasing the posterior tube current further increased the effective dose by 15% (chest) and 18% (head) relative to SmartmA. ODM reduced dose in all experimental and simulation studies over a range of phantoms, while increasing noise. The results suggest a net dose/noise benefit for breast and eye lens for all studied phantoms, negligible lung dose effects for two phantoms, increased lung dose and/or noise for eight phantoms, and increased dose and/or noise for brain and spine for all studied phantoms compared to the reference protocol.

Significant Radiation Dose Reduction in the Hybrid Operating Room Using a Novel X-ray Imaging Technology.

PubMed

van den Haak, R F F; Hamans, B C; Zuurmond, K; Verhoeven, B A N; Koning, O H J

2015-10-01

To prospectively quantify radiation dose change in aortoiliac endovascular procedures in the hybrid operating room (OR) for patients and medical staff with a novel X-ray imaging technology (ClarityIQ technology), and to assess whether procedure or fluoroscopy time or dose of iodinated contrast was affected. A prospective study including 138 patients was performed to compare radiation dose before and after installation of a novel X-ray imaging technology. Endovascular aneurysm repair (EVAR) was performed in 37 patients and an endovascular procedure for aortoiliac occlusive disease (AIOD) in 101. Patient radiation dose in air kerma (AK) and dose area product (DAP), patient demographics, and procedural data were recorded. Staff radiation dose was measured with real time personal dosimetry measurements. In both the EVAR and AIOD groups the reference system, ALX (AlluraXper FD20; Philips Healthcare, Best, the Netherlands), was compared with the upgraded X-ray system, CIQ (AlluraClarity FD20; Philips Healthcare). Procedure time, fluoroscopy time, and iodinated contrast dose were recorded. Patient radiation dose reduction in the EVAR group, in median AK, was 56% (ALX = 1,262.5 mGy; CIQ = 556.0 mGy [p < .01]); and in median DAP it was 57% (ALX = 224.4 Gycm(2) and CIQ = 95.8 Gycm(2) [p < .01]). Patient radiation dose reduction in the AIOD group, in median AK, was 76% (ALX = 1,011.0 mGy; CIQ = 248.0 mGy [p < .01]); and in median DAP it was 73% (ALX = 138.1 Gycm(2); CIQ = 38.0 Gycm(2) [p < .01]). Staff dose reduction in the EVAR group was 16% (ALX = 70.1 μSv; CIQ = 59.2 μSv [p = .43]) and in the AIOD group it was 69% (ALX = 96.2 μSv; CIQ = 30.1 μSv [p < .01]). There was no statistically significant difference between patient demographics, procedure time, fluoroscopy time, and iodinated contrast medium use in the two treatment groups before and after installation. A novel X-ray imaging technology in the hybrid OR suite resulted in a significant reduction of patient and staff radiation dose without affecting procedure length, fluoroscopy time, or use of contrast. Copyright © 2015 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

CT dose reduction using Automatic Exposure Control and iterative reconstruction: A chest paediatric phantoms study.

PubMed

Greffier, Joël; Pereira, Fabricio; Macri, Francesco; Beregi, Jean-Paul; Larbi, Ahmed

2016-04-01

To evaluate the impact of Automatic Exposure Control (AEC) on radiation dose and image quality in paediatric chest scans (MDCT), with or without iterative reconstruction (IR). Three anthropomorphic phantoms representing children aged one, five and 10-year-old were explored using AEC system (CARE Dose 4D) with five modulation strength options. For each phantom, six acquisitions were carried out: one with fixed mAs (without AEC) and five each with different modulation strength. Raw data were reconstructed with Filtered Back Projection (FBP) and with two distinct levels of IR using soft and strong kernels. Dose reduction and image quality indices (Noise, SNR, CNR) were measured in lung and soft tissues. Noise Power Spectrum (NPS) was evaluated with a Catphan 600 phantom. The use of AEC produced a significant dose reduction (p<0.01) for all anthropomorphic sizes employed. According to the modulation strength applied, dose delivered was reduced from 43% to 91%. This pattern led to significantly increased noise (p<0.01) and reduced SNR and CNR (p<0.01). However, IR was able to improve these indices. The use of AEC/IR preserved image quality indices with a lower dose delivered. Doses were reduced from 39% to 58% for the one-year-old phantom, from 46% to 63% for the five-year-old phantom, and from 58% to 74% for the 10-year-old phantom. In addition, AEC/IR changed the patterns of NPS curves in amplitude and in spatial frequency. In chest paediatric MDCT, the use of AEC with IR allows one to obtain a significant dose reduction while maintaining constant image quality indices. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Can use of adaptive statistical iterative reconstruction reduce radiation dose in unenhanced head CT? An analysis of qualitative and quantitative image quality.

PubMed

Østerås, Bjørn Helge; Heggen, Kristin Livelten; Pedersen, Hans Kristian; Andersen, Hilde Kjernlie; Martinsen, Anne Catrine T

2016-08-01

Iterative reconstruction can reduce image noise and thereby facilitate dose reduction. To evaluate qualitative and quantitative image quality for full dose and dose reduced head computed tomography (CT) protocols reconstructed using filtered back projection (FBP) and adaptive statistical iterative reconstruction (ASIR). Fourteen patients undergoing follow-up head CT were included. All patients underwent full dose (FD) exam and subsequent 15% dose reduced (DR) exam, reconstructed using FBP and 30% ASIR. Qualitative image quality was assessed using visual grading characteristics. Quantitative image quality was assessed using ROI measurements in cerebrospinal fluid (CSF), white matter, peripheral and central gray matter. Additionally, quantitative image quality was measured in Catphan and vendor's water phantom. There was no significant difference in qualitative image quality between FD FBP and DR ASIR. Comparing same scan FBP versus ASIR, a noise reduction of 28.6% in CSF and between -3.7 and 3.5% in brain parenchyma was observed. Comparing FD FBP versus DR ASIR, a noise reduction of 25.7% in CSF, and -7.5 and 6.3% in brain parenchyma was observed. Image contrast increased in ASIR reconstructions. Contrast-to-noise ratio was improved in DR ASIR compared to FD FBP. In phantoms, noise reduction was in the range of 3 to 28% with image content. There was no significant difference in qualitative image quality between full dose FBP and dose reduced ASIR. CNR improved in DR ASIR compared to FD FBP mostly due to increased contrast, not reduced noise. Therefore, we recommend using caution if reducing dose and applying ASIR to maintain image quality.

Generative Adversarial Networks for Noise Reduction in Low-Dose CT.

PubMed

Wolterink, Jelmer M; Leiner, Tim; Viergever, Max A; Isgum, Ivana

2017-12-01

Noise is inherent to low-dose CT acquisition. We propose to train a convolutional neural network (CNN) jointly with an adversarial CNN to estimate routine-dose CT images from low-dose CT images and hence reduce noise. A generator CNN was trained to transform low-dose CT images into routine-dose CT images using voxelwise loss minimization. An adversarial discriminator CNN was simultaneously trained to distinguish the output of the generator from routine-dose CT images. The performance of this discriminator was used as an adversarial loss for the generator. Experiments were performed using CT images of an anthropomorphic phantom containing calcium inserts, as well as patient non-contrast-enhanced cardiac CT images. The phantom and patients were scanned at 20% and 100% routine clinical dose. Three training strategies were compared: the first used only voxelwise loss, the second combined voxelwise loss and adversarial loss, and the third used only adversarial loss. The results showed that training with only voxelwise loss resulted in the highest peak signal-to-noise ratio with respect to reference routine-dose images. However, CNNs trained with adversarial loss captured image statistics of routine-dose images better. Noise reduction improved quantification of low-density calcified inserts in phantom CT images and allowed coronary calcium scoring in low-dose patient CT images with high noise levels. Testing took less than 10 s per CT volume. CNN-based low-dose CT noise reduction in the image domain is feasible. Training with an adversarial network improves the CNNs ability to generate images with an appearance similar to that of reference routine-dose CT images.

Statistical analysis of radioimmunoassay. In comparison with bioassay (in Japanese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakano, R.

1973-01-01

Using the data of RIA (radioimmunoassay), statistical procedures for dealing with two problems of the linearization of dose response curve and calculation of relative potency were described. There were three methods for linearization of dose response curve of RIA. In each method, the following parameters were shown on the horizontal and vertical axis: dose x, (B/T)/sup -1/; c/x + c, B/T (C: dose which makes B/T 50%); log x, logit B/T. Among them, the last method seems to be most practical. The statistical procedures for bioassay were employed for calculating the relative potency of unknown samples compared to the standardmore » samples from dose response curves of standand and unknown samples using regression coefficient. It is desirable that relative potency is calculated by plotting more than 5 points in the standard curve and plotting more than 2 points in unknow samples. For examining the statistical limit of precision of measuremert, LH activity of gonadotropin in urine was measured and relative potency, precision coefficient and the upper and lower limits of relative potency at 95% confidence limit were calculated. On the other hand, bioassay (by the ovarian ascorbic acid reduction method and anteriol lobe of prostate weighing method) was done in the same samples, and the precision was compared with that of RIA. In these examinations, the upper and lower limits of the relative potency at 95% confidence limit were near each other, while in bioassay, a considerable difference was observed between the upper and lower limits. The necessity of standardization and systematization of the statistical procedures for increasing the precision of RIA was pointed out. (JA)« less

Efficacy and Safety of Fixed-Dose Perindopril Arginine/Amlodipine in Hypertensive Patients Not Adequately Controlled with Amlodipine 5 mg or Perindopril tert-Butylamine 4 mg Monotherapy.

PubMed

Hu, Dayi; Sun, Yihong; Liao, Yuhua; Huang, Jing; Zhao, Ruiping; Yang, Kan

2016-01-01

To assess the blood pressure-lowering efficacy and tolerability of perindopril/amlodipine fixed-dose combinations in Chinese patients with mild-to-moderate essential hypertension not adequately controlled with monotherapy alone. In 2 separate double-blind studies, patients received a 4-week run-in monotherapy of amlodipine 5 mg or perindopril 4 mg, respectively. Those whose blood pressure was uncontrolled were then randomized to receive the fixed-dose combination of perindopril 5 mg/amlodipine 5 mg (Per/Amlo group) or remain on the monotherapy for 8 weeks. Patients who were uncontrolled at the week 8 (W8) visit were up-titrated for the Per/Amlo combination, or received additional treatment if on monotherapy, for a further 4 weeks. The main efficacy assessment was at 8 weeks. After 8 weeks, systolic blood pressure (SBP; primary criterion) was statistically significantly lower in the Per/Amlo group (vs. Amlo 5 mg, p = 0.0095; vs. Per 4 mg, p < 0.0001). Uncontrolled patients at W8 who received an up-titration of the Per/Amlo combination showed a further SBP reduction. These changes were mirrored by reassuring reductions in diastolic blood pressure. The fixed-dose combinations were well tolerated. Single-pill combinations of perindopril and amlodipine provide hypertensive patients with a convenient and effective method of reducing blood pressure. © 2016 S. Karger AG, Basel.

Breast surface radiation dose during coronary CT angiography: reduction by breast displacement and lead shielding.

PubMed

Foley, Shane J; McEntee, Mark F; Achenbach, Stephan; Brennan, Patrick C; Rainford, Louise S; Dodd, Jonathan D

2011-08-01

The purpose of this study was to prospectively evaluate the effect of cranial breast displacement and lead shielding on in vivo breast surface radiation dose in women undergoing coronary CT angiography. Fifty-four women (mean age, 59.2 ± 9.8 years) prospectively underwent coronary 64-MDCT angiography for evaluation of chest pain. The patients were randomly assigned to a control group (n = 16), breast displacement group (n = 22), or breast displacement plus lead shielding group (n = 16). Thermoluminescent dosimeters (TLDs) were placed superficially on each breast quadrant and the areolar region of both breasts. Breast surface radiation doses, the degree of breast displacement, and coronary image quality were compared between groups. A phantom dose study was conducted to compare breast doses with z-axis positioning on the chest wall. A total of 1620 TLD dose measurements were recorded. Compared with control values, the mean breast surface dose was reduced 23% in the breast displacement group (24.3 vs 18.6 mGy, p = 0.015) and 36% in the displacement plus lead shielding group (24.3 vs 15.6 mGy, p = 0.0001). Surface dose reductions were greatest in the upper outer (displacement alone, 66%; displacement plus shielding, 63%), upper inner (65%, 58%), and areolar quadrants (44%, 53%). The smallest surface dose reductions were recorded for A-cup breasts: 7% for the displacement group and 3% for the displacement plus lead group (p = 0.741). Larger reductions in surface dose were recorded for B-cup (25% and 56%, p = 0.273), C-cup (38% and 60%, p = 0.001), and D-cup (31% and 25%, p = 0.095) sizes. Most of the patients (79%) had either good (< 50% of breast above scan range) or excellent (< 75% of breast above the scan range) breast displacement. No significant difference in coronary image quality was detected between groups. The phantom dose study showed that surface TLD measurements were underestimates of absorbed tissue dose by a mean of 9% and that a strong negative correlation exists between the amount of cranial displacement and breast dose. Use of breast displacement during coronary CTA substantially reduces the radiation dose to the breast surface.

A novel two-step optimization method for tandem and ovoid high-dose-rate brachytherapy treatment for locally advanced cervical cancer.

PubMed

Sharma, Manju; Fields, Emma C; Todor, Dorin A

2015-01-01

To present a novel method allowing fast volumetric optimization of tandem and ovoid high-dose-rate treatments and to quantify its benefits. Twenty-seven CT-based treatment plans from 6 consecutive cervical cancer patients treated with four to five intracavitary tandem and ovoid insertions were used. Initial single-step optimized plans were manually optimized, approved, and delivered plans created with a goal to cover high-risk clinical target volume (HR-CTV) with D90 >90% and minimize rectum, bladder, and sigmoid D2cc. For the two-step optimized (TSO) plan, each single-step optimized plan was replanned adding a structure created from prescription isodose line to the existent physician delineated HR-CTV, rectum, bladder, and sigmoid. New, more rigorous dose-volume histogram constraints for the critical organs at risks (OARs) were used for the optimization. HR-CTV D90 and OAR D2ccs were evaluated in both plans. TSO plans had consistently smaller D2ccs for all three OARs while preserving HR-CTV D90. On plans with "excellent" CTV coverage, average D90 of 96% (91-102%), sigmoid, bladder, and rectum D2cc, respectively, reduced on average by 37% (16-73%), 28% (20-47%), and 27% (15-45%). Similar reductions were obtained on plans with "good" coverage, average D90 of 93% (90-99%). For plans with "inferior" coverage, average D90 of 81%, the coverage increased to 87% with concurrent D2cc reductions of 31%, 18%, and 11% for sigmoid, bladder, and rectum, respectively. The TSO can be added with minimal planning time increase but with the potential of dramatic and systematic reductions in OAR D2ccs and in some cases with concurrent increase in target dose coverage. These single-fraction modifications would be magnified over the course of four to five intracavitary insertions and may have real clinical implications in terms of decreasing both acute and late toxicities. Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Pro blood clotting activity of Scoparia dulcis in rats

PubMed Central

Ediriweera, E. R. H. S. S.; Jayakody, J. R. A. C.; Ratnasooriya, W. D.

2011-01-01

Scoparia dulcis Linn (Family: Scrophulariaceae, Sinhala: WalKoththamalli) is a perennial herb growing in many tropical countries including Sri Lanka. Traditional Physicians in rural down south areas apply crushed S. dulcis plant on cuts and bruises to stop bleeding. S. dulcis may also have Rakta Sthambhana property. The study on effect of decoction (water extract) of S. dulcis on blood clotting time in rats was carried out to investigate this. Two groups of rats, 12 males and 42 females were used in this experimental study. Forty-two female rats were assigned into seven equal groups (n = 6/gp). Different doses of DE (25, 50, 100, 1000, 1500 mg/kg) (group 1-5) or 2 ml of distilled water (DW) (group 6) were orally administered. 0.1 ml of vitamin K was injected intramuscularly (group 7) as reference drug to seventh the group. Twelve male rats were assigned into two equal groups (n = 6/gp), 2 ml of distilled water (DW) and doses of DE (1500 mg/kg) were orally administered. Clotting time was determined on the Days 1, 2, and 7 using Lee and White method. In the DE treated groups with all doses, there was no reduction in clotting time on the Day 1 but a significant reduction of clotting time (P < 0.05) was observed on the Days 2 and 7. In the group treated with vitamin K, there was no significant reduction in clotting time on Day 1 or 2, but there was a significant reduction in clotting time on Day 7. It is concluded that S. dulcis has proclotting activity (rakthasthambhana property) and this was faster than vitamin K. PMID:22408315

Pro blood clotting activity of Scoparia dulcis in rats.

PubMed

Ediriweera, E R H S S; Jayakody, J R A C; Ratnasooriya, W D

2011-04-01

Scoparia dulcis Linn (Family: Scrophulariaceae, Sinhala: WalKoththamalli) is a perennial herb growing in many tropical countries including Sri Lanka. Traditional Physicians in rural down south areas apply crushed S. dulcis plant on cuts and bruises to stop bleeding. S. dulcis may also have Rakta Sthambhana property. The study on effect of decoction (water extract) of S. dulcis on blood clotting time in rats was carried out to investigate this. Two groups of rats, 12 males and 42 females were used in this experimental study. Forty-two female rats were assigned into seven equal groups (n = 6/gp). Different doses of DE (25, 50, 100, 1000, 1500 mg/kg) (group 1-5) or 2 ml of distilled water (DW) (group 6) were orally administered. 0.1 ml of vitamin K was injected intramuscularly (group 7) as reference drug to seventh the group. Twelve male rats were assigned into two equal groups (n = 6/gp), 2 ml of distilled water (DW) and doses of DE (1500 mg/kg) were orally administered. Clotting time was determined on the Days 1, 2, and 7 using Lee and White method. In the DE treated groups with all doses, there was no reduction in clotting time on the Day 1 but a significant reduction of clotting time (P < 0.05) was observed on the Days 2 and 7. In the group treated with vitamin K, there was no significant reduction in clotting time on Day 1 or 2, but there was a significant reduction in clotting time on Day 7. It is concluded that S. dulcis has proclotting activity (rakthasthambhana property) and this was faster than vitamin K.

Effect of variations in the redox potential of Gleysol on barium mobility and absorption in rice plants.

PubMed

Magalhães, Marcio Osvaldo Lima; Sobrinho, Nelson Moura Brasil do Amaral; Zonta, Everaldo; de Carvalho, Michel Miranda; Tolón-Becerra, Alfredo

2012-09-01

Two assays were designed to obtain information about the influence of redox potential variations on barium mobility and bioavailability in soil. One assay was undertaken in leaching columns, and the other was conducted in pots cultivated with rice (Oryza sativa) using soil samples collected from the surface of Gleysol in both assays. Three doses of barium (100,300 mg kg(-1) and 3000 mg kg(-1)-soil dry weight) and two redox potential values (oxidizing and reducing) were evaluated. During the incubation period, the redox potential (Eh) was monitored in columns and pots until values of -250 mV were reached. After the incubation period, geochemical partitioning was conducted on the barium using the European Communities Bureau of Reference (BCR) method. Rainfall of 200 mm d(-1) was simulated in the columns and in the planting of rice seedlings in the pots. The results of the geochemical partitioning demonstrated that the condition of reduction favors increased barium concentrations in the more labile chemical forms and decreased levels in the chemical forms related to oxides. The highest barium concentrations in leached extracts (3.36 mg L(-1)) were observed at the highest dose and condition of reduction at approximately five times above the drinking water standard. The high concentrations of barium in the soil did not affect plant dry matter production. The highest levels and accumulation of barium in roots, leaves, and grains of rice were found at the highest dose and condition of reduction. These results demonstrate that reduction leads to solubilization of barium sulfate, thereby favoring greater mobility and bioavailability of this element. Copyright © 2012 Elsevier Ltd. All rights reserved.

In vitro evaluation of a new iterative reconstruction algorithm for dose reduction in coronary artery calcium scoring

PubMed Central

Allmendinger, Thomas; Kunz, Andreas S; Veyhl-Wichmann, Maike; Ergün, Süleyman; Bley, Thorsten A; Petritsch, Bernhard

2017-01-01

Background Coronary artery calcium (CAC) scoring is a widespread tool for cardiac risk assessment in asymptomatic patients and accompanying possible adverse effects, i.e. radiation exposure, should be as low as reasonably achievable. Purpose To evaluate a new iterative reconstruction (IR) algorithm for dose reduction of in vitro coronary artery calcium scoring at different tube currents. Material and Methods An anthropomorphic calcium scoring phantom was scanned in different configurations simulating slim, average-sized, and large patients. A standard calcium scoring protocol was performed on a third-generation dual-source CT at 120 kVp tube voltage. Reference tube current was 80 mAs as standard and stepwise reduced to 60, 40, 20, and 10 mAs. Images were reconstructed with weighted filtered back projection (wFBP) and a new version of an established IR kernel at different strength levels. Calcifications were quantified calculating Agatston and volume scores. Subjective image quality was visualized with scans of an ex vivo human heart. Results In general, Agatston and volume scores remained relatively stable between 80 and 40 mAs and increased at lower tube currents, particularly in the medium and large phantom. IR reduced this effect, as both Agatston and volume scores decreased with increasing levels of IR compared to wFBP (P < 0.001). Depending on selected parameters, radiation dose could be lowered by up to 86% in the large size phantom when selecting a reference tube current of 10 mAs with resulting Agatston levels close to the reference settings. Conclusion New iterative reconstruction kernels may allow for reduction in tube current for established Agatston scoring protocols and consequently for substantial reduction in radiation exposure. PMID:28607763

Reduction of cardiac and pulmonary complication probabilities after breathing adapted radiotherapy for breast cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korreman, Stine S.; Pedersen, Anders N.; Aarup, Lasse Rye

Purpose: Substantial reductions of cardio-pulmonary radiation doses can be achieved using voluntary deep inspiration breath-hold (DIBH) or free breathing inspiration gating (IG) in radiotherapy after conserving surgery for breast cancer. The purpose of this study is to evaluate the radiobiological implications of such dosimetric benefits. Methods and Materials: Patients from previously reported studies were pooled for a total of 33 patients. All patients underwent DIBH and free breathing (FB) scans, and 17 patients underwent an additional IG scan. Tangential conformal treatment plans covering the remaining breast, internal mammary, and periclavicular nodes were optimized for each scan, prescription dose 48 Gy.more » Normal tissue complication probabilities were calculated using the relative seriality model for the heart, and the model proposed by Burman et al. for the lung. Results: Previous computed tomography studies showed that both voluntary DIBH and IG provided reduction of the lung V{sub 5} (relative volume receiving more than 50% of prescription dose) on the order of 30-40%, and a 80-90% reduction of the heart V{sub 5} for left-sided cancers. Corresponding pneumonitis probability of 28.1% (range, 0.7-95.6%) for FB could be reduced to 2.6% (range, 0.1-40.1%) for IG, and 4.3% (range, 0.1-59%) for DIBH. The cardiac mortality probability could be reduced from 4.8% (range, 0.1-23.4%) in FB to 0.5% (range, 0.1-2.6%) for IG and 0.1% (range, 0-3.0%) for DIBH. Conclusions: Remarkable potential is shown for simple voluntary DIBH and free breathing IG to reduce the risk of both cardiac mortality and pneumonitis for the common technique of adjuvant tangential breast irradiation.« less

Australasian trends in intra-aortic balloon counterpulsation weaning: results of a postal survey.

PubMed

Lewis, Peter A; Mullany, Daniel V; Courtney, Mary; Coyer, Fiona

2006-12-01

To generate baseline data describing Australasian intra-aortic balloon counterpulsation (IABP) weaning practice. A five-part questionnaire was mailed in April 2005 to all 192 intensive care units in Australia and New Zealand. 116 ICUs responded (response rate, 60%), and 54 reported using IABP. Most of the 54 were in hospitals which were public government-funded (65%), had between 100 and 500 beds (69%), and treated a minimum of 11 patients annually with IABP (60%). The most common method of withdrawing IABP support was ratio reduction alone (61%). ICUs most likely to undertake ratio weaning were higherend users of IABP (> 20 cases per annum) (P = 0.04). Other weaning practices involved a combination of ratio followed by volume reduction (17%), volume then ratio (11%), and volume only (4%). Approaching statistical significance, ratio reduction weaning less frequently required IABP reinsertion or inotropic increase after balloon removal (P = 0.07). ICUs with documented weaning policies were less likely to require IABP reinsertion or inotropic increase after balloon removal (P = 0.06). Criteria considered important before IABP weaning or removal were: blood pressure (92%); heart rate (76%); pulmonary artery wedge pressure (59%); noradrenaline dose (78%); adrenaline dose (57%); and dobutamine dose (57%). Ninety per cent of ICUs reported increasing inotropes after balloon removal only rarely (1:50 patients) or occasionally (1:10 patients), while 87% of ICUs reported never needing to reinsert the balloon or only rarely. The Australasian approach to IABP weaning is eclectic. While ratio reduction weaning appears the most successful manner of support withdrawal, it may be a consequence of a volume-outcome relationship, with high- end users achieving better results through IABP familiarity.

SU-F-19A-03: Dosimetric Advantages in Critical Structure Dose Sparing by Using a Multichannel Cylinder in High Dose Rate Brachytherapy to Treat Vaginal Cuff Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Syh, J; Syh, J; Patel, B

2014-06-15

Purpose: The multichannel cylindrical vaginal applicator is a variation of traditional single channel cylindrical vaginal applicator. The multichannel applicator has additional peripheral channels that provide more flexibility in the planning process. The dosimetric advantage is to reduce dose to adjacent organ at risk (OAR) such as bladder and rectum while maintaining target coverage with the dose optimization from additional channels. Methods: Vaginal HDR brachytherapy plans are all CT based. CT images were acquired in 2 mm thickness to keep integrity of cylinder contouring. The CTV of 5mm Rind with prescribed treatment length was reconstructed from 5mm expansion of inserted cylinder.more » The goal was 95% of CTV covered by 95% of prescribed dose in both single channel planning (SCP)and multichannel planning (MCP) before proceeding any further optimization for dose reduction to critical structures with emphasis on D2cc and V2Gy . Results: This study demonstrated noticeable dose reduction to OAR was apparent in multichannel plans. The D2cc of the rectum and bladder were showing the reduced dose for multichannel versus single channel. The V2Gy of the rectum was 93.72% and 83.79% (p=0.007) for single channel and multichannel respectively (Figure 1 and Table 1). To assure adequate coverage to target while reducing the dose to the OAR without any compromise is the main goal in using multichannel vaginal applicator in HDR brachytherapy. Conclusion: Multichannel plans were optimized using anatomical based inverse optimization algorithm of inverse planning simulation annealing. The optimization solution of the algorithm was to improve the clinical target volume dose coverage while reducing the dose to critical organs such as bladder, rectum and bowels. The comparison between SCP and MCP demonstrated MCP is superior to SCP where the dwell positions were based on geometric array only. It concluded that MCP is preferable and is able to provide certain features superior to SCP.« less

MO-FG-BRA-04: A Novel Time Weighted Density Correction for Stereotactic Lung Radiotherapy: A Phantom Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohatt, D; Malhotra, H

Purpose: Conventional treatment plans for lung radiotherapy are created using either the free breathing (FB) scheme which represents the tumor at an arbitrary breathing phase of the patient’s respiratory cycle, or the average computed tomography (ACT) intensity projection over 10-binned phases. Neither method is entirely accurate because of the absence of time dependence of tumor movement. In the present “Hybrid” method, the HU of tumor in 3D space is determined by relative weighting of the HU of the tumor and lung in proportion to the time they spend at that location during the entire breathing cycle. Methods: A Quasar respiratorymore » motion phantom was employed to simulate lung tumor movement. Utilizing 4DCT image scans, volumetric modulated arc therapy (VMAT) plans were generated for three treatment planning scenarios which included conventional FB and ACT schemes, along with a third alternative Hybrid approach. Our internal target volume (ITV) hybrid structure was created using Boolean operation in Eclipse (ver. 11) treatment planning system, where independent sub-regions created by the gross tumor volume (GTV) overlap from the 10 motion phases were each assigned a time weighted CT value. The dose-volume-histograms (DVH) for each scheme were compared and analyzed. Results: Using our hybrid technique, we have demonstrated a reduction of 1.9% – 3.4% in total monitor units with respect to conventional treatment planning strategies, along with a 6 fold improvement in high dose spillage over the FB plan. The higher density ACT and Hybrid schemes also produced a slight enhancement in target conformity and reduction in low dose spillage. Conclusion: All treatment plans created in this study exceeded RTOG protocol criteria. Our results determine the free breathing approach yields an inaccurate account of the target treatment density. A significant decrease in unnecessary lung irradiation can be achieved by implementing Hybrid HU method with ACT method second best.« less

A real-time regional adaptive exposure method for saving dose-area product in x-ray fluoroscopy

PubMed Central

Burion, Steve; Speidel, Michael A.; Funk, Tobias

2013-01-01

Purpose: Reduction of radiation dose in x-ray imaging has been recognized as a high priority in the medical community. Here the authors show that a regional adaptive exposure method can reduce dose-area product (DAP) in x-ray fluoroscopy. The authors' method is particularly geared toward providing dose savings for the pediatric population. Methods: The scanning beam digital x-ray system uses a large-area x-ray source with 8000 focal spots in combination with a small photon-counting detector. An imaging frame is obtained by acquiring and reconstructing up to 8000 detector images, each viewing only a small portion of the patient. Regional adaptive exposure was implemented by varying the exposure of the detector images depending on the local opacity of the object. A family of phantoms ranging in size from infant to obese adult was imaged in anteroposterior view with and without adaptive exposure. The DAP delivered to each phantom was measured in each case, and noise performance was compared by generating noise arrays to represent regional noise in the images. These noise arrays were generated by dividing the image into regions of about 6 mm2, calculating the relative noise in each region, and placing the relative noise value of each region in a one-dimensional array (noise array) sorted from highest to lowest. Dose-area product savings were calculated as the difference between the ratio of DAP with adaptive exposure to DAP without adaptive exposure. The authors modified this value by a correction factor that matches the noise arrays where relative noise is the highest to report a final dose-area product savings. Results: The average dose-area product saving across the phantom family was (42 ± 8)% with the highest dose-area product saving in the child-sized phantom (50%) and the lowest in the phantom mimicking an obese adult (23%). Conclusions: Phantom measurements indicate that a regional adaptive exposure method can produce large DAP savings without compromising the noise performance in the image regions with highest noise. PMID:23635281

Cumulative organophosphate pesticide exposure and risk assessment among pregnant women living in an agricultural community: a case study from the CHAMACOS cohort.

PubMed Central

Castorina, Rosemary; Bradman, Asa; McKone, Thomas E; Barr, Dana B; Harnly, Martha E; Eskenazi, Brenda

2003-01-01

Approximately 230,000 kg of organophosphate (OP) pesticides are applied annually in California's Salinas Valley. These activities have raised concerns about exposures to area residents. We collected three spot urine samples from pregnant women (between 1999 and 2001) enrolled in CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas), a longitudinal birth cohort study, and analyzed them for six dialkyl phosphate metabolites. We used urine from 446 pregnant women to estimate OP pesticide doses with two deterministic steady-state modeling methods: method 1, which assumed the metabolites were attributable entirely to a single diethyl or dimethyl OP pesticide; and method 2, which adapted U.S. Environmental Protection Agency (U.S. EPA) draft guidelines for cumulative risk assessment to estimate dose from a mixture of OP pesticides that share a common mechanism of toxicity. We used pesticide use reporting data for the Salinas Valley to approximate the mixture to which the women were exposed. Based on average OP pesticide dose estimates that assumed exposure to a single OP pesticide (method 1), between 0% and 36.1% of study participants' doses failed to attain a margin of exposure (MOE) of 100 relative to the U.S. EPA oral benchmark dose(10) (BMD(10)), depending on the assumption made about the parent compound. These BMD(10) values are doses expected to produce a 10% reduction in brain cholinesterase activity compared with background response in rats. Given the participants' average cumulative OP pesticide dose estimates (method 2) and regardless of the index chemical selected, we found that 14.8% of the doses failed to attain an MOE of 100 relative to the BMD(10) of the selected index. An uncertainty analysis of the pesticide mixture parameter, which is extrapolated from pesticide application data for the study area and not directly quantified for each individual, suggests that this point estimate could range from 1 to 34%. In future analyses, we will use pesticide-specific urinary metabolites, when available, to evaluate cumulative OP pesticide exposures. PMID:14527844

Dose comparison between conventional and quasi-monochromatic systems for diagnostic radiology

NASA Astrophysics Data System (ADS)

Baldelli, P.; Taibi, A.; Tuffanelli, A.; Gambaccini, M.

2004-09-01

Several techniques have been introduced in the last year to reduce the dose to the patient by minimizing the risk of tumour induced by radiation. In this work the radiological potential of dose reduction in quasi-monochromatic spectra produced via mosaic crystal Bragg diffraction has been evaluated, and a comparison with conventional spectra has been performed for four standard examinations: head, chest, abdomen and lumbar sacral spine. We have simulated quasi-monochromatic x-rays with the Shadow code, and conventional spectra with the Spectrum Processor. By means of the PCXMC software, we have simulated four examinations according to parameters established by the European Guidelines, and calculated absorbed dose for principal organs and the effective dose. Simulations of quasi-monochromatic laminar beams have been performed without anti-scatter grid, because of their inherent scatter geometry, and compared with simulations with conventional beams with anti-scatter grids. Results have shown that the dose reduction due to the introduction of quasi-monochromatic x-rays depends on different parameters related to the quality of the beam, the organ composition and the anti-scatter grid. With parameters chosen in this study a significant dose reduction can be achieved for two out of four kinds of examination.

Evidence of dose saving in routine CT practice using iterative reconstruction derived from a national diagnostic reference level survey.

PubMed

Thomas, P; Hayton, A; Beveridge, T; Marks, P; Wallace, A

2015-09-01

To assess the influence and significance of the use of iterative reconstruction (IR) algorithms on patient dose in CT in Australia. We examined survey data submitted to the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) National Diagnostic Reference Level Service (NDRLS) during 2013 and 2014. We compared median survey dose metrics with categorization by scan region and use of IR. The use of IR results in a reduction in volume CT dose index of between 17% and 44% and a reduction in dose-length product of between 14% and 34% depending on the specific scan region. The reduction was highly significant (p < 0.001, Wilcoxon rank-sum test) for all six scan regions included in the NDRLS. Overall, 69% (806/1167) of surveys included in the analysis used IR. The use of IR in CT is achieving dose savings of 20-30% in routine practice in Australia. IR appears to be widely used by participants in the ARPANSA NDRLS with approximately 70% of surveys submitted employing this technique. This study examines the impact of the use of IR on patient dose in CT on a national scale.

The Impact of Azilsartan Medoxomil Treatment (Capsule Formulation) at Doses Ranging From 10 to 80 mg: Significant, Rapid Reductions in Clinic Diastolic and Systolic Blood Pressure.

PubMed

Perez, Alfonso; Cao, Charlie

2017-03-01

In this phase 2, multicenter, parallel-group, double-blind, dose-ranging study, hypertensive adults (n=449) were randomized to receive one of five doses of a capsule formulation of azilsartan medoxomil (AZL-M; 5, 10, 20, 40, 80 mg), olmesartan medoxomil (OLM) 20 mg, or placebo once daily. The primary endpoint was change in trough clinic diastolic blood pressure (DBP) at week 8. AZL-M provided rapid statistically and clinically significant reductions in DBP and systolic blood pressure (SBP) vs placebo at all doses except 5 mg. Placebo-subtracted changes were greatest with the 40 mg dose (DBP, -5.7 mm Hg; SBP, -12.3 mm Hg). Clinic changes with AZL-M (all doses) were statistically indistinguishable vs OLM, although there were greater reductions with AZL-M 40 mg using 24-hour ambulatory blood pressure. Adverse event frequency was similar in the AZL-M and placebo groups. Based on these and other findings, subsequent trials investigated the commercial AZL-M tablet in the dose range of 20 to 80 mg/d. ©2016 Wiley Periodicals, Inc.

Digital radiography: optimization of image quality and dose using multi-frequency software.

PubMed

Precht, H; Gerke, O; Rosendahl, K; Tingberg, A; Waaler, D

2012-09-01

New developments in processing of digital radiographs (DR), including multi-frequency processing (MFP), allow optimization of image quality and radiation dose. This is particularly promising in children as they are believed to be more sensitive to ionizing radiation than adults. To examine whether the use of MFP software reduces the radiation dose without compromising quality at DR of the femur in 5-year-old-equivalent anthropomorphic and technical phantoms. A total of 110 images of an anthropomorphic phantom were imaged on a DR system (Canon DR with CXDI-50 C detector and MLT[S] software) and analyzed by three pediatric radiologists using Visual Grading Analysis. In addition, 3,500 images taken of a technical contrast-detail phantom (CDRAD 2.0) provide an objective image-quality assessment. Optimal image-quality was maintained at a dose reduction of 61% with MLT(S) optimized images. Even for images of diagnostic quality, MLT(S) provided a dose reduction of 88% as compared to the reference image. Software impact on image quality was found significant for dose (mAs), dynamic range dark region and frequency band. By optimizing image processing parameters, a significant dose reduction is possible without significant loss of image quality.

Multi-Case Knowledge-Based IMRT Treatment Planning in Head and Neck Cancer

NASA Astrophysics Data System (ADS)

Grzetic, Shelby Mariah

Head and neck cancer (HNC) IMRT treatment planning is a challenging process that relies heavily on the planner's experience. Previously, we used the single, best match from a library of manually planned cases to semi-automatically generate IMRT plans for a new patient. The current multi-case Knowledge Based Radiation Therapy (MC-KBRT) study utilized different matching cases for each of six individual organs-at-risk (OARs), then combined those six cases to create the new treatment plan. From a database of 103 patient plans created by experienced planners, MC-KBRT plans were created for 40 (17 unilateral and 23 bilateral) HNC "query" patients. For each case, 2D beam's-eye-view images were used to find similar geometric "match" patients separately for each of 6 OARs. Dose distributions for each OAR from the 6 matching cases were combined and then warped to suit the query case's geometry. The dose-volume constraints were used to create the new query treatment plan without the need for human decision-making throughout the IMRT optimization. The optimized MC-KBRT plans were compared against the clinically approved plans and Version 1 (previous KBRT using only one matching case with dose warping) using the dose metrics: mean, median, and maximum (brainstem and cord+5mm) doses. Compared to Version 1, MC-KBRT had no significant reduction of the dose to any of the OARs in either unilateral or bilateral cases. Compared to the manually planned unilateral cases, there was significant reduction of the oral cavity mean/median dose (>2Gy) at the expense of the contralateral parotid. Compared to the manually planned bilateral cases, reduction of dose was significant in the ipsilateral parotid, larynx, and oral cavity (>3Gy mean/median) while maintaining PTV coverage. MC-KBRT planning in head and neck cancer generates IMRT plans with better dose sparing than manually created plans. MC-KBRT using multiple case matches does not show significant dose reduction compared to using a single match case with dose warping.

Proton therapy to the subdiaphragmatic region in the management of patients with Hodgkin lymphoma.

PubMed

Sachsman, Suzanne; Hoppe, Bradford S; Mendenhall, Nancy P; Holtzman, Adam; Li, Zuofeng; Slayton, William; Joyce, Mike; Sandler, Eric; Flampouri, Stella

2015-07-01

Twelve consecutive patients with classical Hodgkin lymphoma (HL) involving diaphragmatic or subdiaphragmatic regions were treated on an institutional review board-approved outcomes tracking protocol. All patients underwent treatment with proton therapy following chemotherapy and had comparative three-dimensional conformal photon radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) plans to evaluate differences in dose to organs at risk (OARs). Among the cohort, stomach doses with 3DCRT, IMRT and proton therapy were 21 Gy (median), 14 Gy and 6 Gy, respectively. Median dose reductions with proton therapy compared with 3DCRT and IMRT were 13 Gy (p = 0.0022) and 8 Gy (p = 0.0022) for the stomach. Additionally, there was significant dose reduction using proton therapy for the liver, pancreas, bowel, left kidney and right kidney. Proton therapy reduces the dose to the stomach, liver, pancreas, small bowel and kidneys compared with 3DCRT or IMRT in patients with HL requiring abdominal radiotherapy. These dose reductions are expected to translate into lower risks of secondary cancers and other late toxicities in survivors of HL.

In-situ chemical reduction produced graphene paper for flexible supercapacitors with impressive capacitive performance

NASA Astrophysics Data System (ADS)

Ye, Xingke; Zhu, Yucan; Tang, Zhonghua; Wan, Zhongquan; Jia, Chunyang

2017-08-01

For practical applications of graphene-based materials in flexible supercapacitors, a technological breakthrough is currently required to fabricate high-performance graphene paper by a facile method. Herein, highly conductive (∼6900 S m-1) graphene paper with loose multilayered structure is produced by a high-efficiency in-situ chemical reduction process, which assembles graphite oxide suspensions into film and simultaneously conducts chemical reduction. Graphene papers with different parameters (including different types and doses of reductants, different thicknesses and areas of films) are successfully fabricated through this in-situ chemical reduction method. Meanwhile, the influences of the graphene papers with different parameters upon the supercapacitor performance are systematically investigated. Flexible supercapacitor based on the graphene paper exhibits high areal capacitance (152.4 mF cm-2 at current density of 2.0 mA cm-2 in aqueous electrolyte), and excellent rate performance (88.7% retention at 8.0 mA cm-2). Furthermore, bracelet-shaped all-solid supercapacitor with fascinating cycling stability (96.6% retention after 10 000 cycles) and electrochemical stability (an almost negligible capacity loss under different bending states and 99.6% retention after 4000 bending cycles) is established by employing the graphene paper electrode material and polymer electrolyte.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, M; Lee, V; Leung, R

Purpose: Investigating the relative sensitivity of Monte Carlo (MC) and Pencil Beam (PB) dose calculation algorithms to low-Z (titanium) metallic artifacts is important for accurate and consistent dose reporting in post¬operative spinal RS. Methods: Sensitivity analysis of MC and PB dose calculation algorithms on the Monaco v.3.3 treatment planning system (Elekta CMS, Maryland Heights, MO, USA) was performed using CT images reconstructed without (plain) and with Orthopedic Metal Artifact Reduction (OMAR; Philips Healthcare system, Cleveland, OH, USA). 6MV and 10MV volumetric-modulated arc (VMAT) RS plans were obtained for MC and PB on the plain and OMAR images (MC-plain/OMAR and PB-plain/OMAR).more » Results: Maximum differences in dose to 0.2cc (D0.2cc) of spinal cord and cord +2mm for 6MV and 10MV VMAT plans were 0.1Gy between MC-OMAR and MC-plain, and between PB-OMAR and PB-plain. Planning target volume (PTV) dose coverage changed by 0.1±0.7% and 0.2±0.3% for 6MV and 10MV from MC-OMAR to MC-plain, and by 0.1±0.1% for both 6MV and 10 MV from PB-OMAR to PB-plain, respectively. In no case for both MC and PB the D0.2cc to spinal cord was found to exceed the planned tolerance changing from OMAR to plain CT in dose calculations. Conclusion: Dosimetric impacts of metallic artifacts caused by low-Z metallic spinal hardware (mainly titanium alloy) are not clinically important in VMAT-based spine RS, without significant dependence on dose calculation methods (MC and PB) and photon energy ≥ 6MV. There is no need to use one algorithm instead of the other to reduce uncertainty for dose reporting. The dose calculation method that should be used in spine RS shall be consistent with the usual clinical practice.« less

[131I therapy in hyperthyroidism. Results of treatment from 1960-1974].

PubMed

Heinze, H G; Schenk, F

1977-02-01

488 PATIENTS WITH Graves' disease were treated by 131Iodine between 1960 and 1974. 427 (87,5%) of these patients were reexamined several times (clinically, 131I-uptake, PB127I, T4 (CPB-A), T3-uptake, and since 1973 TRH-test). The 131I was given as an individually calculated single dose treatment, using 7 000 -- 10 000 rd before 1965 and 6 000 rd thereafter. Two thirds of the patients became euthyroid after a single 131I-dose. In 20% the treatment had to be repeated. These patients show evidently a different biological behaviour of their disease, since multiple treatments revealed a higher rate of failure (33--35%). There is no principal difference between the out-come after 131I-therapy and surgery concerning the rate of failure, respectively relapse (3--4%) and hypothyroidism. Early incidence of hypothyrodism is dose--dependent, as could be shown in patients treated with higher doses before 1965. The reduction of the irradiation dose to 6 000 rd was followed by a drop of hypothyroidism from 18% to 7%. The reasons of late incidence of hypothyroidism are discussed. The incidence of hypothroidism was calculated by three different methods (over-all incidence, incidence within the observed interval after therapy, life-table method). All three methods revealed different results. This has to be taken into account comparing results after radioiodine as well as after surgery. Radioiodine therapy for hyperthyroidism offers a true alternative to surgery.

4D cone-beam computed tomography (CBCT) using a moving blocker for simultaneous radiation dose reduction and scatter correction

NASA Astrophysics Data System (ADS)

Zhao, Cong; Zhong, Yuncheng; Duan, Xinhui; Zhang, You; Huang, Xiaokun; Wang, Jing; Jin, Mingwu

2018-06-01

Four-dimensional (4D) x-ray cone-beam computed tomography (CBCT) is important for a precise radiation therapy for lung cancer. Due to the repeated use and 4D acquisition over a course of radiotherapy, the radiation dose becomes a concern. Meanwhile, the scatter contamination in CBCT deteriorates image quality for treatment tasks. In this work, we propose the use of a moving blocker (MB) during the 4D CBCT acquisition (‘4D MB’) and to combine motion-compensated reconstruction to address these two issues simultaneously. In 4D MB CBCT, the moving blocker reduces the x-ray flux passing through the patient and collects the scatter information in the blocked region at the same time. The scatter signal is estimated from the blocked region for correction. Even though the number of projection views and projection data in each view are not complete for conventional reconstruction, 4D reconstruction with a total-variation (TV) constraint and a motion-compensated temporal constraint can utilize both spatial gradient sparsity and temporal correlations among different phases to overcome the missing data problem. The feasibility simulation studies using the 4D NCAT phantom showed that 4D MB with motion-compensated reconstruction with 1/3 imaging dose reduction could produce satisfactory images and achieve 37% improvement on structural similarity (SSIM) index and 55% improvement on root mean square error (RMSE), compared to 4D reconstruction at the regular imaging dose without scatter correction. For the same 4D MB data, 4D reconstruction outperformed 3D TV reconstruction by 28% on SSIM and 34% on RMSE. A study of synthetic patient data also demonstrated the potential of 4D MB to reduce the radiation dose by 1/3 without compromising the image quality. This work paves the way for more comprehensive studies to investigate the dose reduction limit offered by this novel 4D MB method using physical phantom experiments and real patient data based on clinical relevant metrics.

Noise correlation in CBCT projection data and its application for noise reduction in low-dose CBCT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hua; Ouyang, Luo; Wang, Jing, E-mail: jhma@smu.edu.cn, E-mail: jing.wang@utsouthwestern.edu

2014-03-15

Purpose: To study the noise correlation properties of cone-beam CT (CBCT) projection data and to incorporate the noise correlation information to a statistics-based projection restoration algorithm for noise reduction in low-dose CBCT. Methods: In this study, the authors systematically investigated the noise correlation properties among detector bins of CBCT projection data by analyzing repeated projection measurements. The measurements were performed on a TrueBeam onboard CBCT imaging system with a 4030CB flat panel detector. An anthropomorphic male pelvis phantom was used to acquire 500 repeated projection data at six different dose levels from 0.1 to 1.6 mAs per projection at threemore » fixed angles. To minimize the influence of the lag effect, lag correction was performed on the consecutively acquired projection data. The noise correlation coefficient between detector bin pairs was calculated from the corrected projection data. The noise correlation among CBCT projection data was then incorporated into the covariance matrix of the penalized weighted least-squares (PWLS) criterion for noise reduction of low-dose CBCT. Results: The analyses of the repeated measurements show that noise correlation coefficients are nonzero between the nearest neighboring bins of CBCT projection data. The average noise correlation coefficients for the first- and second-order neighbors are 0.20 and 0.06, respectively. The noise correlation coefficients are independent of the dose level. Reconstruction of the pelvis phantom shows that the PWLS criterion with consideration of noise correlation (PWLS-Cor) results in a lower noise level as compared to the PWLS criterion without considering the noise correlation (PWLS-Dia) at the matched resolution. At the 2.0 mm resolution level in the axial-plane noise resolution tradeoff analysis, the noise level of the PWLS-Cor reconstruction is 6.3% lower than that of the PWLS-Dia reconstruction. Conclusions: Noise is correlated among nearest neighboring detector bins of CBCT projection data. An accurate noise model of CBCT projection data can improve the performance of the statistics-based projection restoration algorithm for low-dose CBCT.« less

4D cone-beam computed tomography (CBCT) using a moving blocker for simultaneous radiation dose reduction and scatter correction.

PubMed

Zhao, Cong; Zhong, Yuncheng; Duan, Xinhui; Zhang, You; Huang, Xiaokun; Wang, Jing; Jin, Mingwu

2018-05-03

Four-dimensional (4D) X-ray cone-beam computed tomography (CBCT) is important for a precise radiation therapy for lung cancer. Due to the repeated use and 4D acquisition over a course of radiotherapy, the radiation dose becomes a concern. Meanwhile, the scatter contamination in CBCT deteriorates image quality for treatment tasks. In this work, we propose to use a moving blocker (MB) during the 4D CBCT acquisition ("4D MB") and to combine motion-compensated reconstruction to address these two issues simultaneously. In 4D MB CBCT, the moving blocker reduces the X-ray flux passing through the patient and collects the scatter information in the blocked region at the same time. The scatter signal is estimated from the blocked region for correction. Even though the number of projection views and projection data in each view are not complete for conventional reconstruction, 4D reconstruction with a total-variation (TV) constraint and a motion-compensated temporal constraint can utilize both spatial gradient sparsity and temporal correlations among different phases to overcome the missing data problem. The feasibility simulation studies using the 4D NCAT phantom showed that 4D MB with motion-compensated reconstruction with 1/3 imaging dose reduction could produce satisfactory images and achieve 37% improvement on structural similarity (SSIM) index and 55% improvement on root mean square error (RMSE), compared to 4D reconstruction at the regular imaging dose without scatter correction. For the same 4D MB data, 4D reconstruction outperformed 3D TV reconstruction by 28% on SSIM and 34% on RMSE. A study of synthetic patient data also demonstrated the potential of 4D MB to reduce the radiation dose by 1/3 without compromising the image quality. This work paves the way for more comprehensive studies to investigate the dose reduction limit offered by this novel 4D MB method using physical phantom experiments and real patient data based on clinical relevant metrics. © 2018 Institute of Physics and Engineering in Medicine.

Traditional and MLC based dose compensator design for patients with hip prostheses undergoing pelvic radiation therapy.

PubMed

Alecu, R; Alecu, M; Loomis, T; Ochran, T; He, T

1999-01-01

Perturbations in the dose distribution caused by a hip prosthesis when treating pelvic malignancies can result in unacceptable dose inhomogeneities within the target volume. Our results, obtained by in vivo exit dose measurements with diodes, showed a 55% reduction in the dose at the exit dmax of a lateral 15 MV photon beam after passing through a bilateral cobalt-chrome alloy hip prosthesis. Such an inhomogeneous dose distribution may decrease the curability. Solutions such as treatment techniques to avoid the prosthesis are often not the best choice as the dose to the rectum may be unacceptably high. In this work an alternative method of dose compensator is presented. Two types of dose compensators were designed based on a 3-D treatment planning system and CT images of a pelvic phantom containing a hip prosthesis: one was fabricated from a polyethylene-lead slab in the representation of step fringes and placed on a tray in the path of the beam while the other was produced by the use of several fields shaped with a multileaf collimator. The calculation procedures developed by the authors for generating the compensators are described. Results of film measurements performed in a phantom with and without the compensators in place are discussed.

Novel low-kVp beamlet system for choroidal melanoma

PubMed Central

Esquivel, Carlos; Fuller, Clifton D; Waggener, Robert G; Wong, Adrian; Meltz, Martin; Blough, Melissa; Eng, Tony Y; Thomas, Charles R

2006-01-01

Background Treatment of choroidal melanoma with radiation often involves placement of customized brachytherapy eye-plaques. However, the dosimetric properties inherent in source-based radiotherapy preclude facile dose optimization to critical ocular structures. Consequently, we have constructed a novel system for utilizing small beam low-energy radiation delivery, the Beamlet Low-kVp X-ray, or "BLOKX" system. This technique relies on an isocentric rotational approach to deliver dose to target volumes within the eye, while potentially sparing normal structures. Methods Monte Carlo N-Particle (MCNP) transport code version 5.0(14) was used to simulate photon interaction with normal and tumor tissues within modeled right eye phantoms. Five modeled dome-shaped tumors with a diameter and apical height of 8 mm and 6 mm, respectively, were simulated distinct positions with respect to the macula iteratively. A single fixed 9 × 9 mm2 beamlet, and a comparison COMS protocol plaque containing eight I-125 seeds (apparent activity of 8 mCi) placed on the scleral surface of the eye adjacent to the tumor, were utilized to determine dosimetric parameters at tumor and adjacent tissues. After MCNP simulation, comparison of dose distribution at each of the 5 tumor positions for each modality (BLOKX vs. eye-plaque) was performed. Results Tumor-base doses ranged from 87.1–102.8 Gy for the BLOKX procedure, and from 335.3–338.6 Gy for the eye-plaque procedure. A reduction of dose of at least 69% to tumor base was noted when using the BLOKX. The BLOKX technique showed a significant reduction of dose, 89.8%, to the macula compared to the episcleral plaque. A minimum 71.0 % decrease in dose to the optic nerve occurred when the BLOKX was used. Conclusion The BLOKX technique allows more favorable dose distribution in comparison to standard COMS brachytherapy, as simulated using a Monte Carlo iterative mathematical modeling. Future series to determine clinical utility of such an approach are warranted. PMID:16965624

SU-E-T-385: 4D Radiobiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fourkal, E; Hossain, M; Veltchev, I

2014-06-01

Purpose: The linear-quadratic model is the most prevalent model for planning dose fractionation in radiation therapy in the low dose per fraction regimens. However for high-dose fractions, used in SRS/SBRT/HDR treatments the LQ model does not yield accurate predictions, due to neglecting the reduction in the number of sublethal lesions as a result of their conversion to lethal lesions with subsequent irradiation. Proper accounting for this reduction in the number of sublethally damaged lesions leads to the dependence of the survival fraction on the temporal structure of the dose. The main objective of this work is to show that themore » functional dependence of the dose rate on time in each voxel is an important additional factor that can significantly influence the TCP. Methods: Two SBRT lung plans have been used to calculate the TCPs for the same patient. One plan is a 3D conformal plan and the other is an IMRT plan. Both plans are normalized so that 99.5% of PTV volume receives the same prescription dose of 50 Gy in 5 fractions. The dose rate in each individual voxel is calculated as a function of treatment time and subsequently used in the calculation of TCP. Results: The calculated TCPs show that shorter delivery times lead to greater TCP, despite all delivery times being short compared to the repair half-time for sublethal lesions. Furthermore, calculated TCP(IMRT) =0.308 for the IMRT plan is smaller than TCP(3D) =0.425 for 3D conformal, even though it shows greater tumor hot spots and equal PTV coverage. The calculated TCPs are considerably lower compared to those based on the LQ model for which TCP=1 for both plans. Conclusion: The functional dependence of the voxel-by-voxel dose rate on time may be an important factor in predicting the treatment outcome and cannot be neglected in radiobiological modeling.« less

SU-F-P-61: Does It Matter Not to Use Optimization Points at the Apex for Vaginal Cylinder HDR Brachytherapy Planning?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Y

2016-06-15

Purpose: To test the impact of the use of apex optimization points for new vaginal cylinder (VC) applicators. Methods: New “ClickFit” single channel VC applicators (Varian) that have a different top thicknesses but the same diameters as the old VC applicators (2.3 cm diameter, 2.6 cm, 3.0 cm, and 3.5 cm) were compared using phantom studies. Old VC applicator plans without apex optimization points were also compared to the plans with the optimization points. The apex doses were monitored at 5 mm depth doses (8 points) where a prescription dose (Rx) of 6Gy was prescribed. VC surface doses (8 points)more » were also analyzed. Results: The new VC applicator plans without apex optimization points presented significantly lower 5mm depth doses than Rx (on average −31 ± 7%, p <0.00001) due to their thicker VC tops (3.4 ± 1.1 mm thicker with the range of 1.2 to 4.4 mm) than the old VC applicators. Old VC applicator plans also showed a statistically significant reduction (p <0.00001) due to Ir-192 source anisotropic effect at the apex region but the % reduction over Rx was only −7 ± 9%. However, by adding apex optimization points to the new VC applicator plans, the plans improved 5 mm depth doses (−7 ± 9% over Rx) that were not statistically different from old VC plans (p = 0.923), along with apex VC surface doses (−22 ± 10% over old VC versus −46 ± 7% without using apex optimization points). Conclusion: The use of apex optimization points are important in order to avoid significant additional cold doses (−24 ± 2%) at the prescription depth (5 mm) of apex, especially for the new VC applicators that have thicker tops.« less

Implementation of an ergonomics intervention in a Swedish flight baggage handling company—A process evaluation

PubMed Central

Mathiassen, Svend Erik; Larsson, Johan; Kwak, Lydia

2018-01-01

Objective To conduct a process evaluation of the implementation of an ergonomics training program aimed at increasing the use of loading assist devices in flight baggage handling. Methods Feasibility related to the process items recruitment, reach, context, dose delivered (training time and content); dose received (participants’ engagement); satisfaction with training; intermediate outcomes (skills, confidence and behaviors); and barriers and facilitators of the training intervention were assessed by qualitative and quantitative methods. Results Implementation proved successful regarding dose delivered, dose received and satisfaction. Confidence among participants in the training program in using and talking about devices, observed use of devices among colleagues, and internal feedback on work behavior increased significantly (p<0.01). Main facilitators were self-efficacy, motivation, and perceived utility of training among the trainees. Barriers included lack of peer support, opportunities to observe and practice behaviors, and follow-up activities; as well as staff reduction and job insecurity. Conclusions In identifying important barriers and facilitators for a successful outcome, this study can help supporting the effectiveness of future interventions. Our results suggest that barriers caused by organizational changes may likely be alleviated by recruiting motivated trainees and securing strong organizational support for the implementation. PMID:29513671

Population pharmacokinetic and pharmacogenetic analysis of 6-mercaptopurine in paediatric patients with acute lymphoblastic leukaemia

PubMed Central

Hawwa, Ahmed F; Collier, Paul S; Millership, Jeff S; McCarthy, Anthony; Dempsey, Sid; Cairns, Carole; McElnay, James C

2008-01-01

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECTThe cytotoxic effects of 6-mercaptopurine (6-MP) were found to be due to drug-derived intracellular metabolites (mainly 6-thioguanine nucleotides and to some extent 6-methylmercaptopurine nucleotides) rather than the drug itself.Current empirical dosing methods for oral 6-MP result in highly variable drug and metabolite concentrations and hence variability in treatment outcome. WHAT THIS STUDY ADDSThe first population pharmacokinetic model has been developed for 6-MP active metabolites in paediatric patients with acute lymphoblastic leukaemia and the potential demographic and genetically controlled factors that could lead to interpatient pharmacokinetic variability among this population have been assessed.The model shows a large reduction in interindividual variability of pharmacokinetic parameters when body surface area and thiopurine methyltransferase polymorphism are incorporated into the model as covariates.The developed model offers a more rational dosing approach for 6-MP than the traditional empirical method (based on body surface area) through combining it with pharmacogenetically guided dosing based on thiopurine methyltransferase genotype. AIMS To investigate the population pharmacokinetics of 6-mercaptopurine (6-MP) active metabolites in paediatric patients with acute lymphoblastic leukaemia (ALL) and examine the effects of various genetic polymorphisms on the disposition of these metabolites. METHODS Data were collected prospectively from 19 paediatric patients with ALL (n = 75 samples, 150 concentrations) who received 6-MP maintenance chemotherapy (titrated to a target dose of 75 mg m−2 day−1). All patients were genotyped for polymorphisms in three enzymes involved in 6-MP metabolism. Population pharmacokinetic analysis was performed with the nonlinear mixed effects modelling program (nonmem) to determine the population mean parameter estimate of clearance for the active metabolites. RESULTS The developed model revealed considerable interindividual variability (IIV) in the clearance of 6-MP active metabolites [6-thioguanine nucleotides (6-TGNs) and 6-methylmercaptopurine nucleotides (6-mMPNs)]. Body surface area explained a significant part of 6-TGNs clearance IIV when incorporated in the model (IIV reduced from 69.9 to 29.3%). The most influential covariate examined, however, was thiopurine methyltransferase (TPMT) genotype, which resulted in the greatest reduction in the model's objective function (P < 0.005) when incorporated as a covariate affecting the fractional metabolic transformation of 6-MP into 6-TGNs. The other genetic covariates tested were not statistically significant and therefore were not included in the final model. CONCLUSIONS The developed pharmacokinetic model (if successful at external validation) would offer a more rational dosing approach for 6-MP than the traditional empirical method since it combines the current practice of using body surface area in 6-MP dosing with a pharmacogenetically guided dosing based on TPMT genotype. PMID:18823306

Delivery time comparison for intensity-modulated radiation therapy with/without flattening filter: a planning study

NASA Astrophysics Data System (ADS)

Fu, Weihua; Dai, Jianrong; Hu, Yimin; Han, Dongsheng; Song, Yixin

2004-04-01

The treatment delivery time of intensity-modulated radiation therapy (IMRT) with a multileaf collimator (MLC) is generally longer than that of conventional radiotherapy. In theory, removing the flattening filter from the treatment head may reduce the beam-on time by enhancing the output dose rate, and then reduce the treatment delivery time. And in practice, there is a possibility of delivering the required fluence distribution by modulating the unflattened non-uniform fluence distribution. However, the reduction of beam-on time may be discounted by the increase of leaf-travel time and (or) verification-and-recording (V&R) time. Here we investigate the overall effect of flattening filter on the treatment delivery time of IMRT with MLCs implemented in the step and shoot method, as well as with compensators on six hybrid machines. We compared the treatment delivery time with/without flattening filter for ten nasopharynx cases and ten prostate cases by observing the variations of the ratio of the beam-on time, segment number, leaf-travel time and the treatment delivery time with dose rate, leaf speed and V&R time. The results show that, without the flattening filter, the beam-on time reduces for both static MLC and compensator-based techniques; the number of segments and the leaf-travel time increase slightly for the static MLC technique; the relative IMRT treatment delivery time decreases more with lower dose rate, higher leaf speed and shorter V&R overhead time. The absolute treatment delivery time reduction depends on the fraction dose. It is not clinically significant at a fraction dose of 2 Gy for the technique of removing the flattening filter, but becomes significant when the fraction dose is as high as that for radiosurgery.

Changes in entrance surface dose in relation to the location of shielding material in chest computed tomography

NASA Astrophysics Data System (ADS)

Kang, Y. M.; Cho, J. H.; Kim, S. C.

2015-07-01

This study examined the effects of entrance surface dose (ESD) on the abdomen and pelvis of the patient when undergoing chest computed tomography (CT) procedure, and evaluated the effects of ESD reduction depending on the location of radiation shield. For CT scanner, the 64-slice multi-detector computed tomography was used. The alderson radiation therapy phantom and optically stimulated luminescence dosimeter (OSLD), which enabled measurement from low to high dose, were also used. For measurement of radiation dose, the slice number from 9 to 21 of the phantom was set as the test range, which included apex up to both costophrenic angles. A total of 10 OSLD nanoDots were attached for measurement of the front and rear ESD. Cyclic tests were performed using the low-dose chest CT and high-resolution CT (HRCT) protocol on the following set-ups: without shielding; shielding only on the front side; shielding only on the rear side; and shielding for both front and rear sides. According to the test results, ESD for both front and rear sides was higher in HRCT than low-dose CT when radiation shielding was not used. It was also determined that, compared to the set-up that did not use the radiation shield, locating the radiation shield on the front side was effective in reducing front ESD, while locating the radiation shield on the rear side reduced rear ESD level. Shielding both the front and rear sides resulted in ESD reduction. In conclusion, it was confirmed that shielding the front and rear sides was the most effective method to reduce the ESD effect caused by scatter ray during radiography.

Human Collagen Injections to Reduce Rectal Dose During Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noyes, William R., E-mail: noyes@cancercenternd.com; Hosford, Charles C.; Schultz, Steven E.

Objectives: The continuing search for interventions, which address the incidence and grade of rectal toxicities associated with radiation treatment of prostate cancer, is a major concern. We are reporting an investigational trial using human collagen to increase the distance between the prostate and anterior rectal wall, thereby decreasing the radiation dose to the rectum. Methods: This is a pilot study evaluating the use of human collagen as a displacing agent for the rectal wall injected before starting a course of intensity-modulated radiotherapy (IMRT) for prostate cancer. Using a transperineal approach, 20 mL of human collagen was injected into the perirectalmore » space in an outpatient setting. Computerized IMRT plans were performed pre- and postcollagen injection, and after a patient completed their radiotherapy, to determine radiation dose reduction to the rectum associated with the collagen injection. Computed tomography scans were performed 6 months and 12 months after completing their radiotherapy to evaluate absorption rate of the collagen. All patients were treated with IMRT to a dose of 75.6 Gy to the prostate. Results: Eleven patients were enrolled into the study. The injection of human collagen in the outpatient setting was well tolerated. The mean separation between the prostate and anterior rectum was 12.7 mm. The mean reduction in dose to the anterior rectal wall was 50%. All men denied any rectal symptoms during the study. Conclusions: The transperineal injection of human collagen for the purpose of tissue displacement is well tolerated in the outpatient setting. The increased separation between the prostate and rectum resulted in a significant decrease in radiation dose to the rectum while receiving IMRT and was associated with no rectal toxicities.« less

Conebeam CT of the head and neck, part 1: physical principles.

PubMed

Miracle, A C; Mukherji, S K

2009-06-01

Conebeam x-ray CT (CBCT) is a developing imaging technique designed to provide relatively low-dose high-spatial-resolution visualization of high-contrast structures in the head and neck and other anatomic areas. This first installment in a 2-part review will address the physical principles underlying CBCT imaging as it is used in dedicated head and neck scanners. Concepts related to CBCT acquisition geometry, flat panel detection, and image quality will be explored in detail. Particular emphasis will be placed on technical limitations to low-contrast detectability and radiation dose. Proposed methods of x-ray scatter reduction will also be discussed.

Measurements of air dose rates in and around houses in the Fukushima Prefecture in Japan after the Fukushima accident.

PubMed

Matsuda, Norihiro; Mikami, Satoshi; Sato, Tetsuro; Saito, Kimiaki

2017-01-01

Measurements of air dose rates for 192 houses in a less contaminated area (<0.5 μSv h -1 ) of the Fukushima Prefecture in Japan were conducted in both living rooms and/or bedrooms using optically stimulated luminescence (OSL) dosimeters and around the houses via a man-borne survey at intervals of several meters. The relation of the two air dose rates (inside and outside) for each house, including the background from natural radionuclides, was divided into several categories, determined by construction materials (light and heavy) and floor number, with the dose reduction factors being expressed as the ratio of the dose inside to that outside the house. For wooden and lightweight steel houses (classed as light), the dose rates inside and outside the houses showed a positive correlation and linear regression with a slope-intercept form due to the natural background, although the degree of correlation was not very high. The regression coefficient, i.e., the average dose reduction factor, was 0.38 on the first floor and 0.49 on the second floor. It was found that the contribution of natural radiation cannot be neglected when we consider dose reduction factors in less contaminated areas. The reductions in indoor dose rates are observed because a patch of ground under each house is not contaminated (this is the so-called uncontaminated effect) since the shielding capability of light construction materials is typically low. For reinforced steel-framed concrete houses (classed as heavy), the dose rates inside the houses did not show a correlation with those outside the houses due to the substantial shielding capability of these materials. The average indoor dose rates were slightly higher than the arithmetic mean value of the outdoor dose rates from the natural background because concrete acts as a source of natural radionuclides. The characteristics of the uncontaminated effect were clarified through Monte Carlo simulations. It was found that there is a great variation in air dose rates even within one house, depending on the height of the area and its closeness to the outside boundary. Measurements of outdoor dose rates required consideration of local variations depending on the environment surrounding each house. The representative value was obtained from detailed distributions of air dose rates around the house, as measured by a man-borne survey. Therefore, it is imperative to recognize that dose reduction factors fluctuate in response to various factors such as the size and shape of a house, construction materials acting as a shield and as sources, position (including height) within a room, floor number, total number of floors, and surrounding environment. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Ureteral Stones: Implementation of a Reduced-Dose CT Protocol in Patients in the Emergency Department with Moderate to High Likelihood of Calculi on the Basis of STONE Score1

PubMed Central

Moore, Christopher L.; Daniels, Brock; Singh, Dinesh; Luty, Seth; Gunabushanam, Gowthaman; Ghita, Monica; Molinaro, Annette; Gross, Cary P.

2016-01-01

Purpose To determine if a reduced-dose computed tomography (CT) protocol could effectively help to identify patients in the emergency department (ED) with moderate to high likelihood of calculi who would require urologic intervention within 90 days. Materials and Methods The study was approved by the institutional review board and written informed consent with HIPAA authorization was obtained. This was a prospective, single-center study of patients in the ED with moderate to high likelihood of ureteral stone undergoing CT imaging. Objective likelihood of ureteral stone was determined by using the previously derived and validated STONE clinical prediction rule, which includes five elements: sex, timing, origin, nausea, and erythrocytes. All patients with high STONE score (STONE score, 10–13) underwent reduced-dose CT, while those with moderate likelihood of ureteral stone (moderate STONE score, 6–9) underwent reduced-dose CT or standard CT based on clinician discretion. Patients were followed to 90 days after initial imaging for clinical course and for the primary outcome of any intervention. Statistics are primarily descriptive and are reported as percentages, sensitivities, and specificities with 95% confidence intervals. Results There were 264 participants enrolled and 165 reduced-dose CTs performed; of these participants, 108 underwent reduced-dose CT alone with complete follow-up. Overall, 46 of 264 (17.4%) of patients underwent urologic intervention, and 25 of 108 (23.1%) patients who underwent reduced-dose CT underwent a urologic intervention; all were correctly diagnosed on the clinical report of the reduced-dose CT (sensitivity, 100%; 95% confidence interval: 86.7%, 100%). The average dose-length product for all standard-dose CTs was 857 mGy · cm ± 395 compared with 101 mGy · cm ± 39 for all reduced-dose CTs (average dose reduction, 88.2%). There were five interventions for nonurologic causes, three of which were urgent and none of which were missed when reduced-dose CT was performed. Conclusion A CT protocol with over 85% dose reduction can be used in patients with moderate to high likelihood of ureteral stone to safely and effectively identify patients in the ED who will require urologic intervention. PMID:26943230

SU-G-IeP4-07: Feasibility of Low Dose 18FDG PET in Pediatric Oncology Patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, J; Binzel, K; Hall, NC

Purpose: To evaluate and demonstrate the feasibility of low dose FDG PET in pediatric oncology patients using virtual dose reduction as well as true patients PET/CT scans. Methods: Wholebody 18F-FDG PET/CT of 39 clinical pediatric patients (0.16±0.06MBq/kg) were scanned on a Gemini TF 64 system at 75±5 min post FDG injection using 3min/bed. Based on the 180s/bed listmode PET data, subsets of total counts in 120s, 90s, 60s, 30s and 15s per bed position were extracted for PET reconstruction to simulate lower dose PET at 2/3th, 1/2th, 1/3th, 1/6th and 1/12th dose levels. PET/CT scans of Jaszczak PET phantom withmore » 6 hot hollow spheres varying with sizes and contrast ratios were performed (real PET versus simulated PET) to validate the methodology of virtual dose PET simulation. Region of interests (ROIs) were placed on lesions and normal anatomical tissues with quantitative and qualitative assessment performed. Significant lower FDG dose PET/CT of 5 research adolescents were scanned to validate the proposal and low dose PET feasibility. Results: Although all lesions are visible on the 1/12th dose PET, overall PET image quality appears to be influenced in a multi-factorial way. 30%–60% dose reduction from current standard of care FDG PET is recommended to maintain equivalent quality and PET quantification. An optimized BMI-based FDG administration is recommended (from 1.1±0.5 mCi for BMI < 18.5 to 4.8±1.5 mCi for BMI > 30). A linear lowest “Dose-BMI” relationship is given. SUVs from 1/12th to full dose PETs were identified as consistent (R2 = 1.08, 0.99, 1.01, 1.00 and 0.98). No significant variances of count density, SUV and SNR were found across certain dose ranges (p<0.01). Conclusion: Pediatric PET/CT can be performed using current time-of-flight systems at substantially lower PET doses (30–60%) than the standard of care PET/CT without compromising qualitative and quantitative image quality in clinical.« less

Radiation dose reduction in CT with adaptive statistical iterative reconstruction (ASIR) for patients with bronchial carcinoma and intrapulmonary metastases.

PubMed

Schäfer, M-L; Lüdemann, L; Böning, G; Kahn, J; Fuchs, S; Hamm, B; Streitparth, F

2016-05-01

To compare the radiation dose and image quality of 64-row chest computed tomography (CT) in patients with bronchial carcinoma or intrapulmonary metastases using full-dose CT reconstructed with filtered back projection (FBP) at baseline and reduced dose with 40% adaptive statistical iterative reconstruction (ASIR) at follow-up. The chest CT images of patients who underwent FBP and ASIR studies were reviewed. Dose-length products (DLP), effective dose, and size-specific dose estimates (SSDEs) were obtained. Image quality was analysed quantitatively by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurement. In addition, image quality was assessed by two blinded radiologists evaluating images for noise, contrast, artefacts, visibility of small structures, and diagnostic acceptability using a five-point scale. The ASIR studies showed 36% reduction in effective dose compared with the FBP studies. The qualitative and quantitative image quality was good to excellent in both protocols, without significant differences. There were also no significant differences for SNR except for the SNR of lung surrounding the tumour (FBP: 35±17, ASIR: 39±22). A protocol with 40% ASIR can provide approximately 36% dose reduction in chest CT of patients with bronchial carcinoma or intrapulmonary metastases while maintaining excellent image quality. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Ultralow-dose computed tomography imaging for surgery of midfacial and orbital fractures using ASIR and MBIR.

PubMed

Widmann, G; Dalla Torre, D; Hoermann, R; Schullian, P; Gassner, E M; Bale, R; Puelacher, W

2015-04-01

The influence of dose reductions on diagnostic quality using a series of high-resolution ultralow-dose computed tomography (CT) scans for computer-assisted planning and surgery including the most recent iterative reconstruction algorithms was evaluated and compared with the fracture detectability of a standard cranial emergency protocol. A human cadaver head including the mandible was artificially prepared with midfacial and orbital fractures and scanned using a 64-multislice CT scanner. The CT dose index volume (CTDIvol) and effective doses were calculated using application software. Noise was evaluated as the standard deviation in Hounsfield units within an identical region of interest in the posterior fossa. Diagnostic quality was assessed by consensus reading of a craniomaxillofacial surgeon and radiologist. Compared with the emergency protocol at CTDIvol 35.3 mGy and effective dose 3.6 mSv, low-dose protocols down to CTDIvol 1.0 mGy and 0.1 mSv (97% dose reduction) may be sufficient for the diagnosis of dislocated craniofacial fractures. Non-dislocated fractures may be detected at CTDIvol 2.6 mGy and 0.3 mSv (93% dose reduction). Adaptive statistical iterative reconstruction (ASIR) 50 and 100 reduced average noise by 30% and 56%, and model-based iterative reconstruction (MBIR) by 93%. However, the detection rate of fractures could not be improved due to smoothing effects. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Heng, E-mail: hengli@mdanderson.org; Zhu, X. Ronald; Zhang, Xiaodong

Purpose: To develop and validate a novel delivery strategy for reducing the respiratory motion–induced dose uncertainty of spot-scanning proton therapy. Methods and Materials: The spot delivery sequence was optimized to reduce dose uncertainty. The effectiveness of the delivery sequence optimization was evaluated using measurements and patient simulation. One hundred ninety-one 2-dimensional measurements using different delivery sequences of a single-layer uniform pattern were obtained with a detector array on a 1-dimensional moving platform. Intensity modulated proton therapy plans were generated for 10 lung cancer patients, and dose uncertainties for different delivery sequences were evaluated by simulation. Results: Without delivery sequence optimization,more » the maximum absolute dose error can be up to 97.2% in a single measurement, whereas the optimized delivery sequence results in a maximum absolute dose error of ≤11.8%. In patient simulation, the optimized delivery sequence reduces the mean of fractional maximum absolute dose error compared with the regular delivery sequence by 3.3% to 10.6% (32.5-68.0% relative reduction) for different patients. Conclusions: Optimizing the delivery sequence can reduce dose uncertainty due to respiratory motion in spot-scanning proton therapy, assuming the 4-dimensional CT is a true representation of the patients' breathing patterns.« less

Radiotherapy of Painful Vertebral Hemangiomas: The Single Center Retrospective Analysis of 137 Cases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miszczyk, Leszek, E-mail: leszek@io.gliwice.pl; Tukiendorf, Andrzej

2012-02-01

Purpose: An evaluation of dose-response relationship and an attempt to define predictive factors. Methods and Materials: A total of 137 cases of painful vertebral hemangioma irradiations (101 patients). Fraction dose (fd) varied from 2 to 15 Gy (123 fractionated and 14 radiosurgical treatments), and total dose (TD) from 8 to 30 Gy (111 cases irradiated with fd of 2 GY to TD of 24 Gy). We evaluated pain relief, changes in analgesic requirements, and reossification. Results: Means of pain relief 1, 6, 12, and 18 months after radiotherapy (defined as a decrease of primary pain level expressed in percent) weremore » 60.5%, 65.4%, 68.3%, and 78.4%, respectively. Proportion of patients with no need for analgesics and patients using tramadol were 39%, 40%, 44%, 57%, and 20%, 17%, 22%, and 11% in these times. The proportion of patients experiencing complete/partial pain relief changed from 36/48% 1 month, to 64/22% 1.5 years after radiotherapy. No impact of radiotherapy on reossification was found. The positive impact of fd and TD increase for analgesics uptake reduction and pain relief was found. An increase of the fd by 1 Gy results in 27% chance of analgesics uptake reduction and 3.8% reduction of pain, whereas 14% analgesics uptake reduction and 2.2% of pain reduction in case of the TD. The predictive factors improving results were found: female gender, older age, better performance states (the chance of the lower analgesic treatment decreases over 2.5 times in comparison to the higher Zubrod degree), bigger Hb concentration, shorter symptoms duration and lower analgesics uptake before radiotherapy. Conclusions: The obtained data support the efficacy of radiotherapy in improving pain secondary to vertebral hemangioma, with the degree of pain amelioration being related to increasing fd and TD. The positive predictive factors were defined: female gender, older age, better performance status, increased Hb concentration, shorter symptoms duration, and lower analgesics uptake before radiotherapy.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eley, J; Mehta, M; Molitoris, J

Purpose: The purpose of this study was to propose a method to implement arc therapy that is compatible with existing particle therapy systems having gantries and pencil-beam scanning capacities. Furthermore, we sought to demonstrate expected benefits of this method for selected clival chordoma patients. Methods: We propose that a desired particle arc treatment plan can be discretized into a finite number of fixed beams and that only one (or a subset) of these beams be delivered in any single treatment fraction; the target should receive uniform dose during each fraction. For 3 clival-chordoma patients, robust-optimized, scanned proton beams were simulatedmore » to deliver 78 Gy (RBE) to clinical target volumes (CTVs), using either a single-field plan with a posterior-anterior (PA) beam or a discrete-arc plan with 16 beams that were equally spaced throughout a 360-degree axial arc. Dose-volume metrics were compared with emphasis on the brainstem, since risk of radiation necrosis there can often restrict application of tumoricidal doses for chordomas. Results: The mean volume of brainstem receiving a dose of 60 Gy (RBE) or higher (V60Gy) was 10.3±0.9 cm{sup 3} for the single-field plan and 4.7±1.8 cm{sup 3} for the discrete-arc plan, a reduction of 55% in favor of arcs. The mean dose to the brainstem was also reduced using arcs, by 18%, while the maximum dose was nearly identical for both methods. For the whole brain, V60Gy was reduced by 23%, in favor of arcs. Mean dose to the CTVs were nearly identical for both strategies, within 0.3%. Conclusion: Discrete arc treatments can be implemented using existing scanned particle-beam facilities. Aside from the physical advantages, the biological uncertainties of particle therapy, particularly high in the distal edge, can be reduced by arc therapy via rotational smearing, which may be of benefit for tumors near the brainstem.« less

The Characterization and Treatment of Aggressive Breast Cancer

DTIC Science & Technology

2005-05-01

of a cycle for over 7 days, the carboplatin dose will be decreased by 25% for subsequent cycles. For a second episode of febrile neutropenia , G-CSF...should be given with the next cycle. For an episode of febrile neutropenia despite dose reduction and G-CSF, protocol treatment should be discontinued... neutropenia despite a dose reduction in the previous course. G-CSF may also be used as clinically indicated for neutropenic infection. 4.2.4 The use of