Radiation environment on the Mir orbital station during solar minimum.

PubMed

Badhwar, G D; Atwell, W; Cash, B; Petrov, V M; Akatov YuA; Tchernykh, I V; Shurshakov, V A; Arkhangelsky, V A

1998-01-01

The Mir station has been in a 51.65 degrees inclination orbit since March 1986. In March 1995, the first US astronaut flew on the Mir-18 mission and returned on the Space Shuttle in July 1995. Since then three additional US astronauts have stayed on orbit for up to 6 months. Since the return of the first US astronaut, both the Spektr and Priroda modules have docked with Mir station, altering the mass shielding distribution. Radiation measurements, including the direct comparison of US and Russian absorbed dose rates in the Base Block of the Mir station, were made during the Mir-18 and -19 missions. There is a significant variation of dose rates across the core module; the six locations sampled showed a variation of a factor of nearly two. A tissue equivalent proportional counter (TEPC) measured a total absorbed dose rate of 300 microGy/day, roughly equally divided between the rate due to trapped protons from the South Atlantic Anomaly (SAA) and galactic cosmic radiation (GCR). This dose rate is about a factor of two lower than the rate measured by the thinly shielded (0.5 g cm-2 of Al) operational ion chamber (R-16), and about 3/2 of the rate of the more heavily shielded (3.5 g cm-2 of Al) ion chamber. This is due to the differences in the mass shielding properties at the location of these detectors. A comparison of integral linear energy transfer (LET) spectra measured by TEPC and plastic nuclear track detectors (PNTDs) deployed side by side are in remarkable agreement in the LET region of 15-1000 keV/micrometer, where the PNTDs are fully efficient. The average quality factor, using the ICRP-26 definition, was 2.6, which is higher than normally used. There is excellent agreement between the measured GCR dose rate and model calculations, but this is not true for trapped protons. The measured Mir-18 crew skin dose equivalent rate was 1133 microSv/day. Using the skin dose rate and anatomical models, we have estimated the blood-forming organ (BFO) dose rate and the maximum stay time in orbit for International Space Station crew members.

Variation among states in prescribing of opioid pain relievers and benzodiazepines--United States, 2012.

PubMed

Paulozzi, Leonard J; Mack, Karin A; Hockenberry, Jason M

2014-12-01

Overprescribing of opioid pain relievers (OPR) can result in multiple adverse health outcomes, including fatal overdoses. Interstate variation in rates of prescribing OPR and other prescription drugs prone to abuse, such as benzodiazepines, might indicate areas where prescribing patterns need further evaluation. CDC analyzed a commercial database (IMS Health) to assess the potential for improved prescribing of OPR and other drugs. CDC calculated state rates and measures of variation for OPR, long-acting/extended-release (LA/ER) OPR, high-dose OPR, and benzodiazepines. In 2012, prescribers wrote 82.5 OPR and 37.6 benzodiazepine prescriptions per 100 persons in the United States. State rates varied 2.7-fold for OPR and 3.7-fold for benzodiazepines. For both OPR and benzodiazepines, rates were higher in the South census region, and three Southern states were two or more standard deviations above the mean. Rates for LA/ER and high-dose OPR were highest in the Northeast. Rates varied 22-fold for one type of OPR, oxymorphone. Factors accounting for the regional variation are unknown. Such wide variations are unlikely to be attributable to underlying differences in the health status of the population. High rates indicate the need to identify prescribing practices that might not appropriately balance pain relief and patient safety. State policy makers might reduce the harms associated with the abuse of prescription drugs by implementing changes that will make the prescribing of these drugs more cautious and more consistent with clinical recommendations. Published by Elsevier Ltd.

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.

Evaluation of characteristics of high-energy electron beams using N-isopropyl-acrylamide gel dosimeter

NASA Astrophysics Data System (ADS)

Shih, Tian-Yu; Yen, Tsung-Hsien; Liu, Yan-Lin; Luzhbin, Dmytro; Wu, Jay

2017-11-01

The advantage of electron beam radiotherapy is that the absorbed dose rapidly decreases with the increasing depth, which can prevent damage to deeper organs and tissues. Accurately evaluating the absorbed dose in the superficial tumor is imperative. This study assessed the characteristics of electron beams by using the N-isopropyl-acrylamide (n-NIPAM) gel dosimeter. The n-NIPAM gel was composed of 6% gelatin, 5% monomer, and 2.5% cross-linker with 5 mM tetrakis (hydroxymethyl) phosphonium chloride for deoxygenation. The gel was irradiated with 6-, 9-, and 12-MeV electron beams with dose rates of 100-600 MU/min, respectively. The energy dependence and dose rate dependence were assessed. The beam profiles and percentage depth doses were measured and compared with the results of the Gafchromic film and ionization chamber. The linearity of the n-NIPAM gel under 6-, 9-, and 12-MeV electrons was larger than 0.990 with 2% variation in sensitivity. The sensitivity of the gel under 100-600 MU/min showed 5% variations. The energy and dose rate dependence can be negligible. The beam profiles and percentage depth doses measured by the n-NIPAM gel matched well with the results of the ionization chamber and film. This study reveals the possibility of using the n-NIPAM gel dosimeter for electron beam measurements in clinical radiotherapy.

The features of radiation dose variations onboard ISS and Mir space station: comparative study.

PubMed

Tverskaya, L V; Panasyuk, M I; Reizman, S Ya; Sosnovets, E N; Teltsov, M V; Tsetlin, V V

2004-01-01

The dynamics of the ISS-measured radiation dose variations since August 2000 is studied. Use is made of the data obtained with the R-16 instrument, which consists of two ionization chambers behind different shielding thicknesses. The doses recorded during solar energetic particle (SEP) events are compared with the data obtained also by R-16 on Mir space station. The SEP events in the solar maximum of the current cycle make a much smaller contribution to the radiation dose compared with the October 1989 event recorded on Mir space station. In the latter event, the proton intensity was peaking during a strong magnetic storm. The storm-time effect of solar proton geomagnetic cutoff decreases on dose variations is estimated. The dose variations on Mir space stations due to formation of a new radiation belt of high-energy protons and electrons during a sudden commencement of March 24, 1991 storm are also studied. It was for the first time throughout the ISS and Mir dose measurement period that the counting rates recorded by both R-16 channels on ISS in 2001-2002 were nearly the same during some time intervals. This effect may arise from the decreases of relativistic electron fluxes in the outer radiation belt. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Surface applicator calibration and commissioning of an electronic brachytherapy system for nonmelanoma skin cancer treatment.

PubMed

Rong, Yi; Welsh, James S

2010-10-01

The Xoft Axxent x-ray source has been used for treating nonmelanoma skin cancer since the surface applicators became clinically available in 2009. The authors report comprehensive calibration procedures for the electronic brachytherapy (eBx) system with the surface applicators. The Xoft miniature tube (model S700) generates 50 kVp low-energy x rays. The new surface applicators are available in four sizes of 10, 20, 35, and 50 mm in diameter. The authors' tests include measurements of dose rate, air-gap factor, output stability, depth dose verification, beam flatness and symmetry, and treatment planning with patient specific cutout factors. The TG-61 in-air method was used as a guideline for acquiring nominal dose-rate output at the skin surface. A soft x-ray parallel-plate chamber (PTW T34013) and electrometer was used for the output commissioning. GafChromic EBT films were used for testing the properties of the treatment fields with the skin applicators. Solid water slabs were used to verify the depth dose and cutout factors. Patients with basal cell or squamous cell carcinoma were treated with eBx using a calibrated Xoft system with the low-energy x-ray source and the skin applicators. The average nominal dose-rate output at the skin surface for the 35 mm applicator is 1.35 Gy/min with +/- 5% variation for 16 sources. The dose-rate output and stability (within +/- 5% variation) were also measured for the remaining three applicators. For the same source, the output variation is within 2%. The effective source-surface distance was calculated based on the air-gap measurements for four applicator sizes. The field flatness and symmetry are well within 5%. Percentage depth dose in water was provided by factory measurements and can be verified using solid water slabs. Treatment duration was calculated based on the nominal dose rate, the prescription fraction size, the depth dose percentage, and the cutout factor. The output factor needs to be measured for each case with varying shapes of cutouts. Together with TG-61, the authors' methodology provides comprehensive calibration procedures for medical physicists for using the Xoft eBx system and skin applicators for nonmelanoma skin cancer treatments.

SU-E-T-01: 2-D Characterization of DLG Among All MLC Leaf Pairs

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

Kumaraswamy, L; Xu, Z; Podgorsak, M

Purpose: The aim of this study is to evaluate the variation of dosimetric leaf-gap (DLG) along the travel path of each MLC leaf pair. This study evaluates whether the spatial variations in DLG could cause dose differences between TPS-calculated and measured dose. Methods: The 6MV DLG values were measured for all leaf pairs in the direction of leaf motion using a 2-D diode array and 0.6cc ion chamber. These measurements were performed on two Varian Linacs, employing the Millennium 120-leaf MLC and a 2-D-DLG variation map was created via in-house software. Several test plans were created with sweeping MLC fieldsmore » using constant gaps from 2mm to 10mm and corrected for 2-D variation utilizing in-house software. Measurements were performed utilizing the MapCHECK at 5.0cm depth for plans with and without the 2-D DLG correction and compared to the TPS calculated dose via gamma analysis (3%/3mm). Results: The measured DLGs for the middle 40 MLC leaf pairs (0.5cm width) were very similar along the central superior-inferior axis, with maximum variation of 0.2mm. The outer 20 MLC leaf pairs (1.0cm width) have DLG values from 0.32mm (mean) to 0.65mm (maximum) lower than the central leaf-pair, depending on off-axis distance. Gamma pass rates for the 2mm, 4mm, and 6mm sweep plans increased by 23.2%, 28.7%, and 26.0% respectively using the 2-D-DLG correction. The most improved dose points occur in areas modulated by the 1.0cm leaf-pairs. The gamma pass rate for the 10mm sweep plan increased by only 7.7%, indicating that the 2D variation becomes less significant for dynamic plans with larger MLC gaps. Conclusion: Fluences residing significantly off-axis with narrow sweeping gaps may exhibit significant variations from planned dose due to large differences between the true DLG exhibited by the 1.0cm leaf-pairs versus the constant DLG value utilized by the TPS for dose calculation.« less

Effect of intra-fraction motion on the accumulated dose for free-breathing MR-guided stereotactic body radiation therapy of renal-cell carcinoma

NASA Astrophysics Data System (ADS)

Stemkens, Bjorn; Glitzner, Markus; Kontaxis, Charis; de Senneville, Baudouin Denis; Prins, Fieke M.; Crijns, Sjoerd P. M.; Kerkmeijer, Linda G. W.; Lagendijk, Jan J. W.; van den Berg, Cornelis A. T.; Tijssen, Rob H. N.

2017-09-01

Stereotactic body radiation therapy (SBRT) has shown great promise in increasing local control rates for renal-cell carcinoma (RCC). Characterized by steep dose gradients and high fraction doses, these hypo-fractionated treatments are, however, prone to dosimetric errors as a result of variations in intra-fraction respiratory-induced motion, such as drifts and amplitude alterations. This may lead to significant variations in the deposited dose. This study aims to develop a method for calculating the accumulated dose for MRI-guided SBRT of RCC in the presence of intra-fraction respiratory variations and determine the effect of such variations on the deposited dose. For this, RCC SBRT treatments were simulated while the underlying anatomy was moving, based on motion information from three motion models with increasing complexity: (1) STATIC, in which static anatomy was assumed, (2) AVG-RESP, in which 4D-MRI phase-volumes were time-weighted, and (3) PCA, a method that generates 3D volumes with sufficient spatio-temporal resolution to capture respiration and intra-fraction variations. Five RCC patients and two volunteers were included and treatments delivery was simulated, using motion derived from subject-specific MR imaging. Motion was most accurately estimated using the PCA method with root-mean-squared errors of 2.7, 2.4, 1.0 mm for STATIC, AVG-RESP and PCA, respectively. The heterogeneous patient group demonstrated relatively large dosimetric differences between the STATIC and AVG-RESP, and the PCA reconstructed dose maps, with hotspots up to 40% of the D99 and an underdosed GTV in three out of the five patients. This shows the potential importance of including intra-fraction motion variations in dose calculations.

External exposure doses due to gamma emitting natural radionuclides in some Egyptian building materials.

PubMed

Moharram, B M; Suliman, M N; Zahran, N F; Shennawy, S E; El Sayed, A R

2012-01-01

Using of building materials containing naturally occurring radionuclides as (238)U, (232)Th and (40)K and their progeny results in an external exposures of the housing of such buildings. In the present study, indoor dose rates for typical Egyptian rooms are calculated using the analytical method and activity concentrations of natural radionuclides in some building materials. Uniform chemical composition of the walls, floor and ceiling as well as uniform mass concentrations of the radionuclides in walls, floor and ceiling assumed. Different room models are assumed to discuss variation of indoor dose rates according to variation in room construction. Activity concentrations of (238)U, (232)Th and (40)K content in eight samples representative Clay soil and different building materials used in most recent Egyptian building were measured using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The specific activity for (238)U, (232)Th and (40)K, from the selected samples, were in the range 14.15-60.64, 2.75-84.66 and 7.35-554.4Bqkg(-1), respectively. The average indoor absorbed dose rates in air ranged from 0.005μGyh(-1) to 0.071μGyh(-1) and the corresponding population-weighted annual effective dose due to external gamma radiation varies from 0.025 to 0.345mSv. An outdoor dose rate for typical building samples in addition to some radiological hazards has been introduced for comparison. Copyright © 2011 Elsevier Ltd. All rights reserved.

Artificial neural network based gynaecological image-guided adaptive brachytherapy treatment planning correction of intra-fractional organs at risk dose variation.

PubMed

Jaberi, Ramin; Siavashpour, Zahra; Aghamiri, Mahmoud Reza; Kirisits, Christian; Ghaderi, Reza

2017-12-01

Intra-fractional organs at risk (OARs) deformations can lead to dose variation during image-guided adaptive brachytherapy (IGABT). The aim of this study was to modify the final accepted brachytherapy treatment plan to dosimetrically compensate for these intra-fractional organs-applicators position variations and, at the same time, fulfilling the dosimetric criteria. Thirty patients with locally advanced cervical cancer, after external beam radiotherapy (EBRT) of 45-50 Gy over five to six weeks with concomitant weekly chemotherapy, and qualified for intracavitary high-dose-rate (HDR) brachytherapy with tandem-ovoid applicators were selected for this study. Second computed tomography scan was done for each patient after finishing brachytherapy treatment with applicators in situ. Artificial neural networks (ANNs) based models were used to predict intra-fractional OARs dose-volume histogram parameters variations and propose a new final plan. A model was developed to estimate the intra-fractional organs dose variations during gynaecological intracavitary brachytherapy. Also, ANNs were used to modify the final brachytherapy treatment plan to compensate dosimetrically for changes in 'organs-applicators', while maintaining target dose at the original level. There are semi-automatic and fast responding models that can be used in the routine clinical workflow to reduce individually IGABT uncertainties. These models can be more validated by more patients' plans to be able to serve as a clinical tool.

Poster — Thur Eve — 27: Flattening Filter Free VMAT Quality Assurance: Dose Rate Considerations for Detector Response

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

Viel, Francis; Duzenli, Cheryl; British Columbia Cancer Agency, Department of Medical Physics, Vancouver Centre

2014-08-15

Introduction: Radiation detector responses can be affected by dose rate. Due to higher dose per pulse and wider range of mu rates in FFF beams, detector responses should be characterized prior to implementation of QA protocols for FFF beams. During VMAT delivery, the MU rate may also vary dramatically within a treatment fraction. This study looks at the dose per pulse variation throughout a 3D volume for typical VMAT plans and the response characteristics for a variety of detectors, and makes recommendations on the design of QA protocols for FFF VMAT QA. Materials and Methods: Linac log file data andmore » a simplified dose calculation algorithm are used to calculate dose per pulse for a variety of clinical VMAT plans, on a voxel by voxel basis, as a function of time in a cylindrical phantom. Diode and ion chamber array responses are characterized over the relevant range of dose per pulse and dose rate. Results: Dose per pulse ranges from <0.1 mGy/pulse to 1.5 mGy/pulse in a typical VMAT treatment delivery using the 10XFFF beam. Diode detector arrays demonstrate increased sensitivity to dose (+./− 3%) with increasing dose per pulse over this range. Ion chamber arrays demonstrate decreased sensitivity to dose (+/− 1%) with increasing dose rate over this range. Conclusions: QA protocols should be designed taking into consideration inherent changes in detector sensitivity with dose rate. Neglecting to account for changes in detector response with dose per pulse can lead to skewed QA results.« less

Modeling intersubject variability of bronchial doses for inhaled radon progeny.

PubMed

Hofmann, Werner; Winkler-Heil, Renate; Hussain, Majid

2010-10-01

The main sources of intersubject variations considered in the present study were: (1) size and structure of nasal and oral passages, affecting extrathoracic deposition and, in further consequence, the fraction of the inhaled activity reaching the bronchial region; (2) size and asymmetric branching of the human bronchial airway system, leading to variations of diameters, lengths, branching angles, etc.; (3) respiratory parameters, such as tidal volume, and breathing frequency; (4) mucociliary clearance rates; and (5) thickness of the bronchial epithelium and depth of target cells, related to airway diameters. For the calculation of deposition fractions, retained surface activities, and bronchial doses, parameter values were randomly selected from their corresponding probability density functions, derived from experimental data, by applying Monte Carlo methods. Bronchial doses, expressed in mGy WLM-1, were computed for specific mining conditions, i.e., for defined size distributions, unattached fractions, and physical activities. Resulting bronchial dose distributions could be approximated by lognormal distributions. Geometric standard deviations illustrating intersubject variations ranged from about 2 in the trachea to about 7 in peripheral bronchiolar airways. The major sources of the intersubject variability of bronchial doses for inhaled radon progeny are the asymmetry and variability of the linear airway dimensions, the filtering efficiency of the nasal passages, and the thickness of the bronchial epithelium, while fluctuations of the respiratory parameters and mucociliary clearance rates seem to compensate each other.

Seasonal Variation in Solar Ultra Violet Radiation and Early Mortality in Extremely Preterm Infants.

PubMed

Salas, Ariel A; Smith, Kelly A; Rodgers, Mackenzie D; Phillips, Vivien; Ambalavanan, Namasivayam

2015-11-01

Vitamin D production during pregnancy promotes fetal lung development, a major determinant of infant survival after preterm birth. Because vitamin D synthesis in humans is regulated by solar ultraviolet B (UVB) radiation, we hypothesized that seasonal variation in solar UVB doses during fetal development would be associated with variation in neonatal mortality rates. This cohort study included infants born alive with gestational age (GA) between 23 and 28 weeks gestation admitted to a neonatal unit between 1996 and 2010. Three infant cohort groups were defined according to increasing intensities of solar UVB doses at 17 and 22 weeks gestation. The primary outcome was death during the first 28 days after birth. Outcome data of 2,319 infants were analyzed. Mean birth weight was 830 ± 230 g and median gestational age was 26 weeks. Mortality rates were significantly different across groups (p = 0.04). High-intensity solar UVB doses were associated with lower mortality when compared with normal intensity solar UVB doses (hazard ratio: 0.70; 95% confidence interval: 0.54-0.91; p = 0.01). High-intensity solar UVB doses during fetal development seem to be associated with risk reduction of early mortality in preterm infants. Prospective studies are needed to validate these preliminary findings. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Multicentre evaluation of a novel vaginal dose reporting method in 153 cervical cancer patients.

PubMed

Westerveld, Henrike; de Leeuw, Astrid; Kirchheiner, Kathrin; Dankulchai, Pittaya; Oosterveld, Bernard; Oinam, Arun; Hudej, Robert; Swamidas, Jamema; Lindegaard, Jacob; Tanderup, Kari; Pötter, Richard; Kirisits, Christian

2016-09-01

Recently, a vaginal dose reporting method for combined EBRT and BT in cervical cancer patients was proposed. The current study was to evaluate vaginal doses with this method in a multicentre setting, wherein different applicators, dose rates and protocols were used. In a subset of patients from the EMBRACE study, vaginal doses were evaluated. Doses at the applicator surface left/right and anterior/posterior and at 5mm depth were measured. In addition, the dose at the Posterior-Inferior Border of Symphysis (PIBS) vaginal dose point and PIBS±2cm, corresponding to the mid and lower vagina, was measured. 153 patients from seven institutions were included. Large dose variations expressed in EQD2 with α/β=3Gy were seen between patients, in particular at the top left and right vaginal wall (median 195 (range 61-947)Gy/178 (61-980)Gy, respectively). At 5mm depth, doses were 98 (55-212)Gy/91 (54-227)Gy left/right, and 71 (51-145)Gy/67 (49-189)Gy anterior/posterior, respectively. The dose at PIBS and PIBS±2cm was 41 (3-81)Gy, 54 (32-109)Gy and 5 (1-51)Gy, respectively. At PIBS+2cm (mid vagina) dose variation was coming from BT. The variation at PIBS-2cm (lower vagina) was mainly dependent on EBRT field border location. This novel method for reporting vaginal doses coming from EBRT and BT through well-defined dose points gives a robust representation of the dose along the vaginal axis. In addition, it allows comparison of vaginal dose between patients from different centres. The doses at the PIBS points represent the doses at the mid and lower parts of the vagina. Large variations in dose throughout the vagina were observed between patients and centres. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Dose-response characteristics of an amorphous silicon EPID.

PubMed

Winkler, Peter; Hefner, Alfred; Georg, Dietmar

2005-10-01

Electronic portal imaging devices (EPIDs) were originally developed for the purpose of patient setup verification. Nowadays, they are increasingly used as dosimeters (e.g., for IMRT verification and linac-specific QA). A prerequisite for any clinical dosimetric application is a detailed understanding of the detector's dose-response behavior. The aim of this study is to investigate the dosimetric properties of an amorphous silicon EPID (Elekta IVIEWGT) with respect to three photon beam qualities: 6, 10, and 25 MV. The EPID showed an excellent temporal stability on short term as well as on long term scales. The stability throughout the day was strongly influenced by warming up, which took several hours and affected EPID response by 2.5%. Ghosting effects increased the sensitivity of the EPID. They became more pronounced with decreasing time intervals between two exposures as well as with increasing dose. Due to ghosting, changes in pixel sensitivity amounted up to 16% (locally) for the 25 MV photon beam. It was observed that the response characteristics of our EPID depended on dose as well as on dose rate. Doubling the dose rate increased the EPID sensitivity by 1.5%. This behavior was successfully attributed to a dose per frame effect, i.e., a nonlinear relationship between the EPID signal and the dose which was delivered to the panel between two successive readouts. The sensitivity was found to vary up to 10% in the range of 1 to 1000 monitor units. This variation was governed by two independent effects. For low doses, the EPID signal was reduced due to the linac's changing dose rate during startup. Furthermore, the detector reading was influenced by intrabeam variations of EPID sensitivity, namely, an increase of detector response during uniform exposure. For the beam qualities which were used, the response characteristics of the EPID did not depend on energy. Differences in relative dose-response curves resulted from energy dependent temporal output characteristics of the accelerator. If ghosting is prevented from affecting the results and all dose-response effects are properly corrected for, the EPID signal becomes independent of dose rate, dose, and exposure time.

Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016.

PubMed

Andoh, Masaki; Yamamoto, Hideaki; Kanno, Takashi; Saito, Kimiaki

2018-05-17

Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 within an 80-km radius of the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months from June 2013 to the December 2016, which was beyond that attributable to the physical decay of radiocaesium. The ecological half-life of the slow decreasing component was evaluated to be 4.1 ± 0.2 y. The air dose rates decreased depending on the level of the evacuation areas, and the decrease in the dose rates was slightly larger in populated areas where humans are active. The dose rates as measured by walk surveys exhibited a good correlation with those by car-borne surveys, suggesting that car-borne survey data are reflecting the air dose rates in living environments surrounding roads. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area, and the variation is enhanced by human activities. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground, and they were found to be decreasing quickly compared with the air dose rate from the flat ground fixed-point measurements. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

SU-F-T-378: Evaluation of Dose-Volume Variability and Parameters Between Prostate IMRT and VMAT Plans

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

Chow, J; Jiang, R; Kiciak, A

2016-06-15

Purpose: This study compared the rectal dose-volume consistency, equivalent uniform dose (EUD) and normal tissue complication probability (NTCP) in prostate intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). Methods: For forty prostate IMRT and fifty VMAT patients treated using the same dose prescription (78 Gy/39 fraction) and dose-volume criteria in inverse planning optimization, the rectal EUD and NTCP were calculated for each patient. The rectal dose-volume consistency, showing the variability of dose-volume histogram (DVH) among patients, was defined and calculated based on the deviation between the mean and corresponding rectal DVH. Results: From both the prostate IMRT andmore » VMAT plans, the rectal EUD and NTCP were found decreasing with the rectal volume. The decrease rates for the IMRT plans (EUD = 0.47 × 10{sup −3} Gy cm{sup −3} and NTCP = 3.94 × 10{sup −2} % cm{sup −3}) were higher than those for the VMAT (EUD = 0.28 × 10{sup −3} Gy cm{sup −3} and NTCP = 2.61 × 10{sup −2} % cm{sup −3}). In addition, the dependences of the rectal EUD and NTCP on the dose-volume consistency were found very similar between the prostate IMRT and VMAT plans. This shows that both delivery techniques have similar variations of the rectal EUD and NTCP on the dose-volume consistency. Conclusion: Dependences of the dose-volume consistency on the rectal EUD and NTCP were compared between the prostate IMRT and VMAT plans. It is concluded that both rectal EUD and NTCP decreased with an increase of the rectal volume. The variation rates of the rectal EUD and NTCP on the rectal volume were higher for the IMRT plans than VMAT. However, variations of the rectal dose-volume consistency on the rectal EUD and NTCP were found not significant for both delivery techniques.« less

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

Hardin, M; Harrison, A; Lockamy, V

Purpose: Desire to improve efficiency and throughput inspired a review of our physics chart check procedures. Departmental policy mandates plan checks pre-treatment, after first treatment and weekly every 3–5 days. This study examined the effectiveness of the “after first” check with respect to improving patient safety and clinical efficiency. Type and frequency of variations discovered during this redundant secondary review was examined over seven months. Methods: A community spreadsheet was created to record variations in care discovered during chart review following the first fraction of treatment and before the second fraction (each plan reviewed prior to treatment). Entries were recordedmore » from August 2014 through February 2015, amounting to 43 recorded variations out of 906 reviewed charts. The variations were divided into categories and frequencies were assessed month-to-month. Results: Analysis of recorded variations indicates an overall variation rate of 4.7%. The initial rate was 13.5%; months 2–7 average 3.7%. The majority of variations related to discrepancies in documentation at 46.5%, followed by prescription, plan deficiency, and dose tracking related variations at 25.5%, 12.8%, and 12.8%, respectively. Minor variations (negligible consequence on patient treatment) outweighed major variations 3 to 1. Conclusion: This work indicates that this redundant secondary check is effective. The first month spike in rates could be due to the Hawthorne/observer effect, but the consistent 4% variation rate suggests the need for periodical re-training on variations noted as frequent to improve awareness and quality of the initial chart review process, which may lead to improved treatment quality, patient safety and increased clinical efficiency. Utilizing these results, a continuous quality improvement process following Deming’s Plan-Do-Study-Act (PDSA) methodology was generated. The first iteration of this PDSA was adding a specific dose tracking checklist item in the pre-treatment plan check assessment; the ramification of which will be assessed in future data.« less

SU-F-T-345: Quasi-Dead Beams: Clinical Relevance and Implications for Automatic Planning

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

Price, R; Veltchev, I; Lin, T

Purpose: Beam direction selection for fixed-beam IMRT planning is typically a manual process. Severe dose-volume limits on critical structures in the thorax often result in atypical selection of beam directions as compared to other body sites. This work demonstrates the potential consequences as well as clinical relevance. Methods: 21 thoracic cases treated with 5–7 beam directions, 6 cases including non-coplanar arrangements, with fractional doses of 150–411cGy were analyzed. Endpoints included per-beam modulation scaling factor (MSF), variation from equal weighting, and delivery QA passing rate. Results: During analysis of patient-specific delivery QA a sub-standard passing rate was found for a singlemore » 5-field plan (90.48% of pixels evaluated passing 3% dose, 3mm DTA). During investigation it was found that a single beam demonstrated a MSF of 34.7 and contributed only 2.7% to the mean dose of the target. In addition, the variation from equal weighting for this beam was 17.3% absolute resulting in another beam with a MSF of 4.6 contributing 41.9% to the mean dose to the target; a variation of 21.9% from equal weighting. The average MSF for the remaining 20 cases was 4.0 (SD 1.8) with an average absolute deviation of 2.8% from equal weighting (SD 3.1%). Conclusion: Optimization in commercial treatment planning systems typically results in relatively equally weighted beams. Extreme variation from this can result in excessively high MSFs (very small segments) and potential decreases in agreement between planned and delivered dose distributions. In addition, the resultant beam may contribute minimal dose to the target (quasi-dead beam); a byproduct being increased treatment time and associated localization uncertainties. Potential ramifications exist for automatic planning algorithms should they allow for user-defined beam directions. Additionally, these quasi-dead beams may be embedded in the libraries for model-based systems potentially resulting in inefficient and less accurate deliveries.« less

Calculating evidence-based renal replacement therapy - Introducing an excel-based calculator to improve prescribing and delivery in renal replacement therapy - A before and after study.

PubMed

Cottle, Daniel; Mousdale, Stephen; Waqar-Uddin, Haroon; Tully, Redmond; Taylor, Benjamin

2016-02-01

Transferring the theoretical aspect of continuous renal replacement therapy to the bedside and delivering a given "dose" can be difficult. In research, the "dose" of renal replacement therapy is given as effluent flow rate in ml kg -1  h -1 . Unfortunately, most machines require other information when they are initiating therapy, including blood flow rate, pre-blood pump flow rate, dialysate flow rate, etc. This can lead to confusion, resulting in patients receiving inappropriate doses of renal replacement therapy. Our aim was to design an excel calculator which would personalise patient's treatment, deliver an effective, evidence-based dose of renal replacement therapy without large variations in practice and prolong filter life. Our calculator prescribes a haemodialfiltration dose of 25 ml kg -1  h -1 whilst limiting the filtration fraction to 15%. We compared the episodes of renal replacement therapy received by a historical group of patients, by retrieving their data stored on the haemofiltration machines, to a group where the calculator was used. In the second group, the data were gathered prospectively. The median delivered dose reduced from 41.0 ml kg -1  h -1 to 26.8 ml kg -1  h -1 with reduced variability that was significantly closer to the aim of 25 ml kg -1 .h -1 ( p  < 0.0001). The median treatment time increased from 8.5 h to 22.2 h ( p  = 0.00001). Our calculator significantly reduces variation in prescriptions of continuous veno-venous haemodiafiltration and provides an evidence-based dose. It is easy to use and provides personal care for patients whilst optimizing continuous veno-venous haemodiafiltration delivery and treatment times.

Numerical simulation of the radiation environment on Martian surface

NASA Astrophysics Data System (ADS)

Zhao, L.

2015-12-01

The radiation environment on the Martian surface is significantly different from that on earth. Existing observation and studies reveal that the radiation environment on the Martian surface is highly variable regarding to both short- and long-term time scales. For example, its dose rate presents diurnal and seasonal variations associated with atmospheric pressure changes. Moreover, dose rate is also strongly influenced by the modulation from GCR flux. Numerical simulation and theoretical explanations are required to understand the mechanisms behind these features, and to predict the time variation of radiation environment on the Martian surface if aircraft is supposed to land on it in near future. The high energy galactic cosmic rays (GCRs) which are ubiquitous throughout the solar system are highly penetrating and extremely difficult to shield against beyond the Earth's protective atmosphere and magnetosphere. The goal of this article is to evaluate the long term radiation risk on the Martian surface. Therefore, we need to develop a realistic time-dependent GCR model, which will be integrated with Geant4 transport code subsequently to reproduce the observed variation of surface dose rate associated with the changing heliospheric conditions. In general, the propagation of cosmic rays in the interplanetary medium can be described by a Fokker-Planck equation (or Parker equation). In last decade,we witnessed a fast development of GCR transport models within the heliosphere based on accurate gas-dynamic and MHD backgrounds from global models of the heliosphere. The global MHD simulation produces a more realistic pattern of the 3-D heliospheric structure, as well as the interface between the solar system and the surrounding interstellar space. As a consequence, integrating plasma background obtained from global-dependent 3-D MHD simulation and stochastic Parker transport simulation, we expect to produce an accurate global physical-based GCR modulation model. Combined with the Geant4 transport code, this GCR model will provide valuable insight into the long-term dose rates variation on the Martian surface.

Artificial neural network based gynaecological image-guided adaptive brachytherapy treatment planning correction of intra-fractional organs at risk dose variation

PubMed Central

Jaberi, Ramin; Aghamiri, Mahmoud Reza; Kirisits, Christian; Ghaderi, Reza

2017-01-01

Purpose Intra-fractional organs at risk (OARs) deformations can lead to dose variation during image-guided adaptive brachytherapy (IGABT). The aim of this study was to modify the final accepted brachytherapy treatment plan to dosimetrically compensate for these intra-fractional organs-applicators position variations and, at the same time, fulfilling the dosimetric criteria. Material and methods Thirty patients with locally advanced cervical cancer, after external beam radiotherapy (EBRT) of 45-50 Gy over five to six weeks with concomitant weekly chemotherapy, and qualified for intracavitary high-dose-rate (HDR) brachytherapy with tandem-ovoid applicators were selected for this study. Second computed tomography scan was done for each patient after finishing brachytherapy treatment with applicators in situ. Artificial neural networks (ANNs) based models were used to predict intra-fractional OARs dose-volume histogram parameters variations and propose a new final plan. Results A model was developed to estimate the intra-fractional organs dose variations during gynaecological intracavitary brachytherapy. Also, ANNs were used to modify the final brachytherapy treatment plan to compensate dosimetrically for changes in ‘organs-applicators’, while maintaining target dose at the original level. Conclusions There are semi-automatic and fast responding models that can be used in the routine clinical workflow to reduce individually IGABT uncertainties. These models can be more validated by more patients’ plans to be able to serve as a clinical tool. PMID:29441094

Response to low-dose herbicide selection in self-pollinated Avena fatua.

PubMed

Busi, Roberto; Girotto, Marcelo; Powles, Stephen B

2016-03-01

When applied at the correct plant stage and dose, herbicides are highly toxic to plants. At reduced, low herbicide doses (below the recommended dose) plants can survive and display continuous and quantitative variation in dose-survival responses. Recurrent (directional) selection studies can reveal whether such a phenotypic variation in plant survival response to low herbicide dose is heritable and leads to herbicide resistance. In a common experimental garden study, we have subjected a susceptible population of self-pollinated hexaploid Avena fatua to low-dose recurrent selection with the ACCase-inhibiting herbicide diclofop-methyl for three consecutive generations. Significant differences in response to low-dose diclofop-methyl selection were observed between the selected progenies and parent plants, with a twofold diclofop-methyl resistance and cross-resistance to ALS-inhibiting herbicides. Thus, the capacity of self-pollinated A. fatua to respond to low-dose herbicide selection is marginal, and it is much lower than in cross-pollinated L. rigidum. Lolium rigidum in the same experiment evolved 40-fold diclofop-methyl resistance by progressive enrichment of quantitative resistance-endowing traits. Cross-pollination rate, genetic variation and ploidy levels are identified as possible drivers affecting the contrasting capacity of Avena versus Lolium plants to respond to herbicide selection and the subsequent likelihood of resistance evolution at low herbicide dose usage. © 2015 Society of Chemical Industry.

Application of the concept of biologically effective dose (BED) to patients with Vestibular Schwannomas treated by radiosurgery

PubMed Central

Millar, William T.; Lindquist, Christer; Nordström, Håkan; Lidberg, Pär; Gårding, Jonas

2013-01-01

In the application of stereotactic radiosurgery, using the Gamma Knife, there are large variations in the overall treatment time for the same prescription dose, given in a single treatment session, for different patients. This is due to not only changes in the activity of the Cobolt-60 sources, but also to variations in the number of iso-centers used, the collimator size for a particular iso-center, and the time gap between the different iso-centers. Although frequently viewed as a single dose treatment the concept of biologically effective dose (BED), incorporating concurrent fast and a slow components of repair of sublethal damage, would imply potential variations in BED because of the influence of these different variables associated with treatment. This was investigated in 26 patients, treated for Vestibular Schwannomas, using the Series B Gamma-Knife, between 1999 and 2005. The iso-center number varied between 2 and 13, and the overall treatment time from 25.4–129.58 min. The prescription doses varied from 10–14 Gy. To obtain physical dose and dose-rates from each iso-center, in a number of locations in the region of interest, a prototype version of the Leksell GammaPlan® was used. For an individual patient, BED values varied by up to 15% for a given physical iso-dose. This was due to variation in the dose prescription at different locations on that iso-dose. Between patients there was a decline in the range of BED values as the overall treatment time increased. This increased treatment time was partly a function of the slow decline in the activity of the sources with time but predominantly due to changes in the number of iso-centers used. Thus, variations in BED values did not correlate with prescription dose but was modified by the overall treatment time. PMID:29296371

A systematic evaluation of the dose-rate constant determined by photon spectrometry for 21 different models of low-energy photon-emitting brachytherapy sources.

PubMed

Chen, Zhe Jay; Nath, Ravinder

2010-10-21

The aim of this study was to perform a systematic comparison of the dose-rate constant (Λ) determined by the photon spectrometry technique (PST) with the consensus value ((CON)Λ) recommended by the American Association of Physicists in Medicine (AAPM) for 21 low-energy photon-emitting interstitial brachytherapy sources. A total of 63 interstitial brachytherapy sources (21 different models with 3 sources per model) containing either (125)I (14 models), (103)Pd (6 models) or (131)Cs (1 model) were included in this study. A PST described by Chen and Nath (2007 Med. Phys. 34 1412-30) was used to determine the dose-rate constant ((PST)Λ) for each source model. Source-dependent variations in (PST)Λ were analyzed systematically against the spectral characteristics of the emitted photons and the consensus values recommended by the AAPM brachytherapy subcommittee. The values of (PST)Λ for the encapsulated sources of (103)Pd, (125)I and (131)Cs varied from 0.661 to 0.678 cGyh(-1) U(-1), 0.959 to 1.024 cGyh(-1)U(-1) and 1.066 to 1.073 cGyh(-1)U(-1), respectively. The relative variation in (PST)Λ among the six (103)Pd source models, caused by variations in photon attenuation and in spatial distributions of radioactivity among the source models, was less than 3%. Greater variations in (PST)Λ were observed among the 14 (125)I source models; the maximum relative difference was over 6%. These variations were caused primarily by the presence of silver in some (125)I source models and, to a lesser degree, by the variations in photon attenuation and in spatial distribution of radioactivity among the source models. The presence of silver generates additional fluorescent x-rays with lower photon energies which caused the (PST)Λ value to vary from 0.959 to 1.019 cGyh(-1)U(-1) depending on the amount of silver used by a given source model. For those (125)I sources that contain no silver, their (PST)Λ was less variable and had values within 1% of 1.024 cGyh(-1)U(-1). For the 16 source models that currently have an AAPM recommended (CON)Λ value, the agreement between (PST)Λ and (CON)Λ was less than 2% for 15 models and was 2.6% for 1 (103)Pd source model. Excellent agreement between (PST)Λ and (CON)Λ was observed for all source models that currently have an AAPM recommended consensus dose-rate constant value. These results demonstrate that the PST is an accurate and robust technique for the determination of the dose-rate constant for low-energy brachytherapy sources.

Assessing dose rate distributions in VMAT plans

NASA Astrophysics Data System (ADS)

Mackeprang, P.-H.; Volken, W.; Terribilini, D.; Frauchiger, D.; Zaugg, K.; Aebersold, D. M.; Fix, M. K.; Manser, P.

2016-04-01

Dose rate is an essential factor in radiobiology. As modern radiotherapy delivery techniques such as volumetric modulated arc therapy (VMAT) introduce dynamic modulation of the dose rate, it is important to assess the changes in dose rate. Both the rate of monitor units per minute (MU rate) and collimation are varied over the course of a fraction, leading to different dose rates in every voxel of the calculation volume at any point in time during dose delivery. Given the radiotherapy plan and machine specific limitations, a VMAT treatment plan can be split into arc sectors between Digital Imaging and Communications in Medicine control points (CPs) of constant and known MU rate. By calculating dose distributions in each of these arc sectors independently and multiplying them with the MU rate, the dose rate in every single voxel at every time point during the fraction can be calculated. Independently calculated and then summed dose distributions per arc sector were compared to the whole arc dose calculation for validation. Dose measurements and video analysis were performed to validate the calculated datasets. A clinical head and neck, cranial and liver case were analyzed using the tool developed. Measurement validation of synthetic test cases showed linac agreement to precalculated arc sector times within  ±0.4 s and doses  ±0.1 MU (one standard deviation). Two methods for the visualization of dose rate datasets were developed: the first method plots a two-dimensional (2D) histogram of the number of voxels receiving a given dose rate over the course of the arc treatment delivery. In similarity to treatment planning system display of dose, the second method displays the dose rate as color wash on top of the corresponding computed tomography image, allowing the user to scroll through the variation over time. Examining clinical cases showed dose rates spread over a continuous spectrum, with mean dose rates hardly exceeding 100 cGy min-1 for conventional fractionation. A tool to analyze dose rate distributions in VMAT plans with sub-second accuracy was successfully developed and validated. Dose rates encountered in clinical VMAT test cases show a continuous spectrum with a mean less than or near 100 cGy min-1 for conventional fractionation.

SU-F-P-49: Comparison of Mapcheck 2 Commission for Photon and Electron Beams

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

Lu, J; Yang, C; Morris, B

2016-06-15

Purpose: We will investigate the performance variation of the MapCheck2 detector array with different array calibration and dose calibration pairs from different radiation therapy machine. Methods: A MapCheck2 detector array was calibrated on 3 Elekta accelerators with different energy of photon (6 MV, 10 MV, 15 MV and 18 MV) and electron (6 MeV, 9 MeV, 12 MeV, 15 MeV, 18 MeV and 20 MeV) beams. Dose calibration was conducted by referring a water phantom measurement following TG-51 protocol and commission data for each accelerator. A 10 cm × 10 cm beam was measured. This measured map was morphed bymore » applying different calibration pairs. Then the difference was quantified by comparing the doses and similarity using gamma analysis of criteria (0.5 %, 0 mm). Profile variation was evaluated on a same dataset with different calibration pairs. The passing rate of an IMRT QA planar dose was calculated by using 3 mm and 3% criteria and compared with respect to each calibration pairs. Results: In this study, a dose variation up to 0.67% for matched photons and 1.0% for electron beams is observed. Differences of flatness and symmetry can be as high as 1% and 0.7% respectively. Gamma analysis shows a passing rate ranging from 34% to 85% for the standard 10 × 10 cm field. Conclusion: Our work demonstrated that a customized array calibration and dose calibration for each machine is preferred to fulfill a high standard patient QA task.« less

Study of dosimetric variation due to interfraction organ movement in High Dose Rate Interstital (MUPIT) brachytherapy for gynecologic malignancies

NASA Astrophysics Data System (ADS)

Velmurugan, Thanigaimalai; Sukumar, Prabakar; Krishnappan, Chokkalingam; Boopathy, Raghavendiran

2010-01-01

Ten patients with cancer of uterine cervix who underwent interstitial brachytherapy using MUPIT templates were CT scanned (CT1) using which bladder, rectum and CTV were delineated. The treatment plan PCT1 was generated and optimized geometrically on the volume. CT scan (CT2) was repeated before the second fraction of the treatment CTV and critical organs were delineated. The plan (PCT2) was created by reproducing the Plan PCT1 in the CT2 images and compared with PCT1. Bladder, Rectum and CTV percentage volume variation ranges from +28.6% to -34.3%, 38.4% to -14.9% and 8.5% to -15.2% respectively. Maximum dose variation in bladder was +17.1%, in rectum was up to +410% and in CTV was -13.0%. The dose to these structures varies independently with no strong correlation with the volume variation. Hence it is suggested that repeat CT and re-planning is mandatory before second fraction execution.

Simulation and Comparison of Martian Surface Ionization Radiation

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Zeitlin, Cary; Hassler, Donald M.; Cucinotta, Francis A.

2013-01-01

The spectrum of energetic particle radiation and corresponding doses at the surface of Mars is being characterized by the Radiation Assessment Detector (RAD), one of ten science instruments on the Mars Science Laboratory (MSL) Curiosity Rover. The time series of dose rate for the first 300 Sols after landing on Mars on August 6, 2012 is presented here. For the comparison to RAD measurements of dose rate, Martian surface ionization radiation is simulated by utilizing observed space quantities. The GCR primary radiation spectrum is calculated by using the Badhwar-O'Neill 2011 (BO11) galactic cosmic ray (GCR) model, which has been developed by utilizing all balloon and satellite GCR measurements since 1955 and the newer 1997-2012 Advanced Composition Explorer (ACE) measurements. In the BO11 model, solar modulation of the GCR primary radiation spectrum is described in terms of the international smoothed sunspot number and a time delay function. For the transport of the impingent GCR primary radiation through Mars atmosphere, a vertical distribution of atmospheric thickness at each elevation is calculated using the vertical profiles of atmospheric temperature and pressure made by Mars Global Surveyor measurements. At Gale Crater in the southern hemisphere, the seasonal variation of atmospheric thickness is accounted for the daily atmospheric pressure measurements of the MSL Rover Environmental Monitoring Station (REMS) by using low- and high-density models for cool- and warm-season, respectively. The spherically distributed atmospheric distance is traced along the slant path, and the resultant directional shielding by Martian atmosphere is coupled with Curiosity vehicle for dose estimates. We present predictions of dose rate and comparison to the RAD measurements. The simulation agrees to within +/- 20% with the RAD measurements showing clearly the variation of dose rate by heliospheric conditions, and presenting the sensitivity of dose rate by atmospheric pressure, which has been found from the RAD experiments and driven by thermal tides on Martian surface.

Four-dimensional dose distributions of step-and-shoot IMRT delivered with real-time tumor tracking for patients with irregular breathing: Constant dose rate vs dose rate regulation

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

Yang Xiaocheng; Han-Oh, Sarah; Gui Minzhi

2012-09-15

Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase weremore » extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or slower than the planning day. In contrast, DRRT method showed less than 1% reduction in target dose and no noticeable change in OAR dose under the same breathing period irregularities. When {+-}20% variation of target motion amplitude was present as breathing irregularity, the two delivery methods show compatible plan quality if the dose distribution of CDRT delivery is renormalized. Conclusions: Delivery of 4D-IMRT treatment plans, stemmed from 3D step-and-shoot IMRT and preprogrammed using SAM algorithm, is simulated for two dynamic MLC-based real-time tumor tracking strategies: with and without dose-rate regulation. Comparison of cumulative dose distribution indicates that the preprogrammed 4D plan is more accurately and efficiently conformed using the DRRT strategy, as it compensates the interplay between patient breathing irregularity and tracking delivery without compromising the segment-weight modulation.« less

Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant

PubMed Central

Harada, Kouji H.; Niisoe, Tamon; Imanaka, Mie; Takahashi, Tomoyuki; Amako, Katsumi; Fujii, Yukiko; Kanameishi, Masatoshi; Ohse, Kenji; Nakai, Yasumichi; Nishikawa, Tamami; Saito, Yuuichi; Sakamoto, Hiroko; Ueyama, Keiko; Hisaki, Kumiko; Ohara, Eiji; Inoue, Tokiko; Yamamoto, Kanako; Matsuoka, Yukiyo; Ohata, Hitomi; Toshima, Kazue; Okada, Ayumi; Sato, Hitomi; Kuwamori, Toyomi; Tani, Hiroko; Suzuki, Reiko; Kashikura, Mai; Nezu, Michiko; Miyachi, Yoko; Arai, Fusako; Kuwamori, Masanori; Harada, Sumiko; Ohmori, Akira; Ishikawa, Hirohiko; Koizumi, Akio

2014-01-01

Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August–September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions. PMID:24567380

The impact of variation in scaling factors on the estimation of internal dose metrics: a case study using bromodichloromethane (BDCM)

EPA Science Inventory

Many physiologically based pharmacokinetic (PBPK) models include values for metabolic rate parameters extrapolated from in vitro metabolism studies using scaling factors such as mg of microsomal protein per gram of liver (MPPGL) and liver mass (FVL). Variation in scaling factor ...

SU-F-T-70: A High Dose Rate Total Skin Electron Irradiation Technique with A Specific Inter-Film Variation Correction Method for Very Large Electron Beam Fields

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

Yang, X; Rosenfield, J; Dong, X

2016-06-15

Purpose: Rotational total skin electron irradiation (RTSEI) is used in the treatment of cutaneous T-cell lymphoma. Due to inter-film uniformity variations the dosimetry measurement of a large electron beam of a very low energy is challenging. This work provides a method to improve the accuracy of flatness and symmetry for a very large treatment field of low electron energy used in dual beam RTSEI. Methods: RTSEI is delivered by dual angles field a gantry of ±20 degrees of 270 to cover the upper and the lower halves of the patient body with acceptable beam uniformity. The field size is inmore » the order of 230cm in vertical height and 120 cm in horizontal width and beam energy is a degraded 6 MeV (6 mm of PMMA spoiler). We utilized parallel plate chambers, Gafchromic films and OSLDs as a measuring devices for absolute dose, B-Factor, stationary and rotational percent depth dose and beam uniformity. To reduce inter-film dosimetric variation we introduced a new specific correction method to analyze beam uniformity. This correction method uses some image processing techniques combining film value before and after radiation dose to compensate the inter-variation dose response differences among films. Results: Stationary and rotational depth of dose demonstrated that the Rp is 2 cm for rotational and the maximum dose is shifted toward the surface (3mm). The dosimetry for the phantom showed that dose uniformity reduced to 3.01% for the vertical flatness and 2.35% for horizontal flatness after correction thus achieving better flatness and uniformity. The absolute dose readings of calibrated films after our correction matched with the readings from OSLD. Conclusion: The proposed correction method for Gafchromic films will be a useful tool to correct inter-film dosimetric variation for the future clinical film dosimetry verification in very large fields, allowing the optimizations of other parameters.« less

Remediation of incomplete nitrification and capacity increase of biofilters at different drinking water treatment plants through copper dosing.

PubMed

Wagner, Florian B; Nielsen, Peter Borch; Boe-Hansen, Rasmus; Albrechtsen, Hans-Jørgen

2018-04-01

Drinking water treatment plants based on groundwater may suffer from incomplete ammonium removal, which deteriorates drinking water quality and constrains water utilities in the operation of their plants. Ammonium is normally removed through nitrification in biological granular media filters, and recent studies have demonstrated that dosing of copper can stimulate the removal of ammonium. Here, we investigated if copper dosing could generically improve ammonium removal of biofilters, at treatment plants with different characteristics. Copper was dosed at ≤1.5 μg Cu/L to biofilters at 10 groundwater treatment plants, all of which had displayed several years of incomplete nitrification. Plants exceeded the Danish national water quality standard of 0.05 mg NH 4 + /L by a factor of 2-12. Within only 2-3 weeks of dosing, ammonium removal rates increased significantly (up to 150%). Nitrification was fully established, with ammonium effluent concentrations of <0.01 mg NH 4 + -N/L at most plants, regardless of the differences in raw water chemistry, ammonium loading rates, filter design and operation, or treatment plant configuration. However, for filters without primary filtration, it took longer time to reach complete ammonium removal than for filters receiving prefiltered water, likely due to sorption of copper to iron oxides, at plants without prefiltration. With complete ammonium removal, we subjected two plants to short-term loading rate upshifts, to examine the filters' ability to cope with loading rate variations. After 2 months of dosing and an average loading rate of 1.0 g NH 4 + -N/m 3 filter material/h, the loading rate was upshifted by 50%. Yet, a filter managed to completely remove all the influent ammonium, showing that with copper dosing the filter had extra capacity to remove ammonium even beyond its normal loading rates. Depth sampling revealed that the ammonium removal rate of the filter's upper 10 cm increased more than 7-fold from 0.67 to 4.90 g NH 4 + -N/m 3 /h, and that nitrite produced from increased ammonium oxidation was completely oxidized further to nitrate. Hence, no problems with nitrite accumulation or breakthrough occurred. Overall, copper dosing generically enhanced nitrification efficiency and allowed a range of quite different plants to meet water quality standards, even at increased loading rates. The capacity increase is highly relevant in practice, as it makes filters more robust towards sudden ammonium loading rate variations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multi-level effects of low dose rate ionizing radiation on southern toad, Anaxyrus [Bufo] terrestris

DOE PAGES

Stark, Karolina; Scott, David E.; Tsyusko, Olga; ...

2015-04-30

Despite their potential vulnerability to contaminants from exposure at multiple life stages, amphibians are one of the least studied groups of vertebrates in ecotoxicology, and research on radiation effects in amphibians is scarce. We used multiple endpoints to assess the radiosensitivity of the southern toad ( Anaxyrus [Bufo] terrestris) during its pre-terrestrial stages of development –embryonic, larval, and metamorphic. Toads were exposed, from several hours after oviposition through metamorphosis (up to 77 days later), to four low dose rates of ¹³⁷Cs at 0.13, 2.4, 21, and 222 mGy d⁻¹, resulting in total doses up to 15.8 Gy. Radiation treatments didmore » not affect hatching success of embryos, larval survival, or the length of the larval period. The individual family variation in hatching success of embryos was larger than the radiation response. In contrast, newly metamorphosed individuals from the higher dose-rate treatments had higher mass and mass/length body indices, a measure which may relate to higher post-metamorphic survival. The increased mass and index at higher dose rates may indicate that the chronic, low dose rate radiation exposures triggered secondary responses. Additionally, the increases in growth were linked to a decrease in DNA damage (as measured by the Comet Assay) in red blood cells at a dose rate of 21mGy d⁻¹ and a total dose of 1.1 Gy. In conclusion, the complex effects of low dose rates of ionizing radiation may trigger growth and cellular repair mechanisms in amphibian larvae.« less

'Real-life' study of imatinib therapy in chronic phase-chronic myeloid leukemia: A novel retrospective observational longitudinal analysis.

PubMed

Merante, Serena; Ferretti, Virginia; Elena, Chiara; Calvello, Celeste; Rocca, Barbara; Zappatore, Rita; Cavigliano, Paola; Orlandi, Ester

2017-01-01

Imatinib is a cornerstone of treatment of chronic myeloid leukemia. It remains unclear whether transient treatment discontinuation or dose changes affect outcome and this approach has not yet been approved for use outside clinical trials. We conducted a retrospective single-institution observational study to evaluate factors affecting response in 'real-life' clinical practice in 138 chronic myeloid leukemia patients in chronic phase treated with imatinib. We used a novel longitudinal data analytical model, with a generalized estimating equation model, to study BCR-ABL variation according to continuous standard dose, change in dose or discontinuation; BCR-ABL transcript levels were recorded. Treatment history was subdivided into time periods for which treatment was given at constant dosage (total 483 time periods). Molecular and cytogenetic complete response was observed after 154 (32%) and 358 (74%) time periods, respectively. After adjusting for length of time period, no association between dose and cytogenetic complete response rate was observed. There was a significantly lower molecular complete response rate after time periods at a high imatinib dosage. This statistical approach can identify individual patient variation in longitudinal data collected over time and suggests that changes in dose or discontinuation of therapy could be considered in patients with appropriate biological characteristics.

Characterization of a gated fiber-optic-coupled detector for application in clinical electron beam dosimetry

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

Tanyi, James A.; Nitzling, Kevin D.; Lodwick, Camille J.

2011-02-15

Purpose: Assessment of the fundamental dosimetric characteristics of a novel gated fiber-optic-coupled dosimetry system for clinical electron beam irradiation. Methods: The response of fiber-optic-coupled dosimetry system to clinical electron beam, with nominal energy range of 6-20 MeV, was evaluated for reproducibility, linearity, and output dependence on dose rate, dose per pulse, energy, and field size. The validity of the detector system's response was assessed in correspondence with a reference ionization chamber. Results: The fiber-optic-coupled dosimetry system showed little dependence to dose rate variations (coefficient of variation {+-}0.37%) and dose per pulse changes (with 0.54% of reference chamber measurements). The reproducibilitymore » of the system was {+-}0.55% for dose fractions of {approx}100 cGy. Energy dependence was within {+-}1.67% relative to the reference ionization chamber for the 6-20 MeV nominal electron beam energy range. The system exhibited excellent linear response (R{sup 2}=1.000) compared to reference ionization chamber in the dose range of 1-1000 cGy. The output factors were within {+-}0.54% of the corresponding reference ionization chamber measurements. Conclusions: The dosimetric properties of the gated fiber-optic-coupled dosimetry system compare favorably to the corresponding reference ionization chamber measurements and show considerable potential for applications in clinical electron beam radiotherapy.« less

Evaluation of indoor radon equilibrium factor using CFD modeling and resulting annual effective dose

NASA Astrophysics Data System (ADS)

Rabi, R.; Oufni, L.

2018-04-01

The equilibrium factor is an important parameter for reasonably estimating the population dose from radon. However, the equilibrium factor value depended mainly on the ventilation rate and the meteorological factors. Therefore, this study focuses on investigating numerically the influence of the ventilation rate, temperature and humidity on equilibrium factor between radon and its progeny. The numerical results showed that ventilation rate, temperature and humidity have significant impacts on indoor equilibrium factor. The variations of equilibrium factor with the ventilation, temperature and relative humidity are discussed. Moreover, the committed equivalent doses due to 218Po and 214Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of indoor air. The annual effective dose due to radon short lived progeny from the inhalation of indoor air by the members of the public was investigated.

Optimal mapping of terrestrial gamma dose rates using geological parent material and aerogeophysical survey data.

PubMed

Rawlins, B G; Scheib, C; Tyler, A N; Beamish, D

2012-12-01

Regulatory authorities need ways to estimate natural terrestrial gamma radiation dose rates (nGy h⁻¹) across the landscape accurately, to assess its potential deleterious health effects. The primary method for estimating outdoor dose rate is to use an in situ detector supported 1 m above the ground, but such measurements are costly and cannot capture the landscape-scale variation in dose rates which are associated with changes in soil and parent material mineralogy. We investigate the potential for improving estimates of terrestrial gamma dose rates across Northern Ireland (13,542 km²) using measurements from 168 sites and two sources of ancillary data: (i) a map based on a simplified classification of soil parent material, and (ii) dose estimates from a national-scale, airborne radiometric survey. We used the linear mixed modelling framework in which the two ancillary variables were included in separate models as fixed effects, plus a correlation structure which captures the spatially correlated variance component. We used a cross-validation procedure to determine the magnitude of the prediction errors for the different models. We removed a random subset of 10 terrestrial measurements and formed the model from the remainder (n = 158), and then used the model to predict values at the other 10 sites. We repeated this procedure 50 times. The measurements of terrestrial dose vary between 1 and 103 (nGy h⁻¹). The median absolute model prediction errors (nGy h⁻¹) for the three models declined in the following order: no ancillary data (10.8) > simple geological classification (8.3) > airborne radiometric dose (5.4) as a single fixed effect. Estimates of airborne radiometric gamma dose rate can significantly improve the spatial prediction of terrestrial dose rate.

The American brachytherapy society survey of brachytherapy practice for carcinoma of the cervix in the United States.

PubMed

Nag, S; Orton, C; Young, D; Erickson, B

1999-04-01

The purpose of this study was to survey the brachytherapy practice for cervical cancer in the United States. The Clinical Research Committee of the American Brachytherapy Society (ABS) performed a retrospective survey of individual physicians of the ABS and American Society of Therapeutic Radiologists and Oncologists regarding the details of the brachytherapy techniques they personally used in the treatment of cervical cancer patients for the year 1995. The replies (some of which may have been an estimate only) were tabulated. The scope of this survey did not allow us to verify the data by chart audits. A total of about 3500 questionnaires were mailed out; 521 responses were received. Of these responders, 206 (40%) did not perform any brachytherapy for carcinoma of the cervix in 1995. Of the other 315 responders reporting a total of 4892 patients treated in 1995, 88% used low dose rate (LDR) while 24% used high dose rate (HDR). There was a wide variation in the doses used. For LDR treatments, the median total external beam radiation therapy (EBRT) dose was 45 and 50 Gy and the LDR dose was 42 and 45 Gy for early and advanced cancers, respectively. For HDR treatments, the median EBRT dose was 48 and 50 Gy and the median HDR dose was 29 and 30 Gy for early and advanced cancers, respectively. The median dose per fraction was 6 Gy for a median of five fractions. Interstitial brachytherapy was used as a component of the treatment in 6% of the patients by 21% of responders. Very few responders treated with pulsed or medium dose rates. This retrospective survey showed the current brachytherapy practice pattern in the treatment of cervical cancer in the United States and can serve as a basis for future prospective national brachytherapy data registry. There was wide variation in the practice pattern, emphasizing the urgent need for consensus on these issues. Copyright 1999 Academic Press.

TU-D-201-07: Severity Indication in High Dose Rate Brachytherapy Emergency Response Procedure

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

Li, K; Rustad, F

Purpose: Understanding the corresponding dose to different staff during the High Dose Rate (HDR) Brachytherapy emergency response procedure could help to develop a strategy in efficiency and effective action. In this study, the variation and risk analysis methodology was developed to simulation the HDR emergency response procedure based on severity indicator. Methods: A GammaMedplus iX HDR unit from Varian Medical System was used for this simulation. The emergency response procedure was decomposed based on risk management methods. Severity indexes were used to identify the impact of a risk occurrence on the step including dose to patient and dose to operationmore » staff by varying the time, HDR source activity, distance from the source to patient and staff and the actions. These actions in 7 steps were to press the interrupt button, press emergency shutoff switch, press emergency button on the afterloader keypad, turn emergency hand-crank, remove applicator from the patient, disconnect transfer tube and move afterloader from the patient, and execute emergency surgical recovery. Results: Given the accumulated time in second at the assumed 7 steps were 15, 5, 30, 15, 180, 120, 1800, and the dose rate of HDR source is 10 Ci, the accumulated dose in cGy to patient at 1cm distance were 188, 250, 625, 813, 3063, 4563 and 27063, and the accumulated exposure in rem to operator at outside the vault, 1m and 10cm distance were 0.0, 0.0, 0.1, 0.1, 22.6, 37.6 and 262.6. The variation was determined by the operators in action at different time and distance from the HDR source. Conclusion: The time and dose were estimated for a HDR unit emergency response procedure. It provided information in making optimal decision during the emergency procedure. Further investigation would be to optimize and standardize the responses for other emergency procedure by time-spatial-dose severity function.« less

Calibration of Kodak EDR2 film for patient skin dose assessment in cardiac catheterization procedures.

PubMed

Morrell, Rachel E; Rogers, Andy

2004-12-21

Kodak EDR2 film has been calibrated across the range of exposure conditions encountered in our cardiac catheterization laboratory. Its dose-response function has been successfully modelled, up to the saturation point of 1 Gy. The most important factor affecting film sensitivity is the use of beam filtration. Spectral filtration and kVp together account for a variation in dose per optical density of -10% to +25%, at 160 mGy. The use of a dynamic wedge filter may cause doses to be underestimated by up to 6%. The film is relatively insensitive to variations in batch, field size, exposure rate, time to processing and day-to-day fluctuations in processor performance. Overall uncertainty in the calibration is estimated to be -20% to +40%, at 160 mGy. However, the uncertainty increases at higher doses, as the curve saturates. Artefacts were seen on a number of films, due to faults in the light-proofing of the film packets.

Neutron dosimetry of the Little Boy device

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

Pederson, R.A.; Plassmann, E.A.

1984-01-01

Neutron dose rates at several angular locations and at distances out to 0.5 mile have been measured during critical operation of the Little Boy replica. We used modified remmetes and thermoluminescent dosimetry techniques for the measurements. The present status of our analysis is presented including estimates of the neutron-dose-relaxation length in air and the variation of the neutron-to-gamma-ray dose ratio with distance from the replica. These results are preliminary and are subject to detector calibration measurements.

Characterization of responses and comparison of calibration factor for commercial MOSFET detectors.

PubMed

Bharanidharan, Ganesan; Manigandan, Durai; Devan, Krishnamurthy; Subramani, Vellaiyan; Gopishankar, Natanasabapathi; Ganesh, Tharmar; Joshi, Rakeshchander; Rath, Gourakishore; Velmurugan, Jagadeesan; Aruna, Prakasarao; Ganesan, Singaravelu

2005-01-01

A commercial metal oxide silicon field effect transistor (MOSFET) dosimeter of model TN502-RD has been characterized for its linearity, reproducibility, field size dependency, dose rate dependency, and angular dependency for Cobalt-60 (60Co), 6-MV, and 15-MV beam energies. The performance of the MOSFET clearly shows that it is highly reproducible, independent of field size and dose rate. Furthermore, MOSFET has a very high degree of linearity, with r-value>0.9 for all 3 energies. The calibration factor for 2 similar MOSFET detectors of model TN502-RD were also estimated and compared for all 3 energies. The calibration factor between the 2 similar MOSFET detectors shows a variation of about 1.8% for 60Co and 15 MV, and for 6 MV it shows variation of about 2.5%, indicating that calibration should be done whenever a new MOSFET is used. However, the detector shows considerable angular dependency of about 8.8% variation. This may be due to the variation in radiation sensitivity between flat and bubble sides of the MOSFET, and indicates that positional care must be taken while using MOSFET for stereotactic radiosurgery and stereotactic radiotherapy dosimetric applications.

Spiromax, a New Dry Powder Inhaler: Dose Consistency under Simulated Real-World Conditions.

PubMed

Canonica, Giorgio Walter; Arp, Jan; Keegstra, Johan René; Chrystyn, Henry

2015-10-01

Spiromax(®) is a novel dry powder inhaler for patients with asthma or chronic obstructive pulmonary disease (COPD). The studies presented here provide further data on attributes (in vitro dosing consistency with budesonide-formoterol (DuoResp) Spiromax; flow rates through empty versions of the Spiromax and Turbuhaler inhaler) of importance to patients with asthma or COPD. Dose-delivery studies were performed using low-, middle-, and high-strength DuoResp Spiromax. Dose consistency was assessed over inhaler life. Total emitted doses (TEDs) were measured at various flow rates, after exposure to high and low temperature or humidity, at different inhaler orientations, and after dropping the inhaler. The criterion for evaluating dose uniformity was whether mean TEDs were within the product specification limits. In separate studies, flow rates were measured after training, using the patient information leaflets, and again after enhanced training as part of a randomized, open-label, cross-over study. Mean values for both budesonide and formoterol were within 85%-115% of the label claim for each strength of DuoResp Spiromax for initial dose uniformity and for the other investigated conditions (temperature, humidity, orientation, dropping, knocking), with the exception of approximately an 80% increase in first dose after dropping the inhaler (subsequent doses not affected). In the flow rate patient study, two patients' inhalations with Spiromax and six with Turbuhaler were <30 L/min. The majority of asthma patients [91% (Spiromax) versus 82% (Turbuhaler)] achieved the preferred flow rate of >60 L/min. DuoResp Spiromax consistently meets dose uniformity criteria, under controlled laboratory conditions and with variations intended to mimic real-world use. Following enhanced training, all patients in the flow study were able to achieve the minimal inspiratory flow rate of >30 L/min, which is required for effective treatment.

Dose rate estimation around a 60Co gamma-ray irradiation source by means of 115mIn photoactivation.

PubMed

Murataka, Ayanori; Endo, Satoru; Kojima, Yasuaki; Shizuma, Kiyoshi

2010-01-01

Photoactivation of nuclear isomer (115m)In with a halflife of 4.48 h occurs by (60)Co gamma-ray irradiation. This is because the resonance gamma-ray absorption occurs at 1078 keV level for stable (115)In, and that energy gamma-rays are produced by Compton scattering of (60)Co primary gamma-rays. In this work, photoactivation of (115m)In was applied to estimate the dose rate distribution around a (60)Co irradiation source utilizing a standard dose rate taken by alanine dosimeter. The (115m)In photoactivation was measured at 10 to 160 cm from the (60)Co source. The derived dose rate distribution shows a good agreement with both alanine dosimeter data and Monte Carlo simulation. It is found that angular distribution of the dose rate along a circumference at radius 2.8 cm from the central axis shows +/- 10% periodical variation reflecting the radioactive strength of the source rods, but less periodic distribution at radius 10 and 20 cm. The (115m)In photoactivation along the vertical direction in the central irradiation port strongly depends on the height and radius as indicated by Monte Carlo simulation. It is demonstrated that (115m)In photoactivation is a convenient method to estimate the dose rate distribution around a (60)Co source.

Experimental assessment of the Advanced Collapsed-cone Engine for scalp brachytherapy treatments.

PubMed

Cawston-Grant, Brie; Morrison, Hali; Sloboda, Ron S; Menon, Geetha

To experimentally assess the performance of the Advanced Collapsed-cone Engine (ACE) for 192 Ir high-dose-rate brachytherapy treatment planning of nonmelanoma skin cancers of the scalp. A layered slab phantom was designed to model the head (skin, skull, and brain) and surface treatment mold using tissue equivalent materials. Six variations of the phantom were created by varying skin thickness, skull thickness, and size of air gap between the mold and skin. Treatment planning was initially performed using the Task Group 43 (TG-43) formalism with CT images of each phantom variation. Doses were recalculated using standard and high accuracy modes of ACE. The plans were delivered to Gafchromic EBT3 film placed between different layers of the phantom. Doses calculated by TG-43 and ACE and those measured by film agreed with each other at most locations within the phantoms. For a given phantom variation, average TG-43- and ACE-calculated doses were similar, with a maximum difference of (3 ± 12)% (k = 2). Compared to the film measurements, TG-43 and ACE overestimated the film-measured dose by (13 ± 12)% (k = 2) for one phantom variation below the skull layer. TG-43- and ACE-calculated and film-measured doses were found to agree above the skull layer of the phantom, which is where the tumor would be located in a clinical case. ACE appears to underestimate the attenuation through bone relative to that measured by film; however, the dose to bone is below tolerance levels for this treatment. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Mutagenic effects of carbon ion beam irradiations on dry Lotus japonicus seeds

NASA Astrophysics Data System (ADS)

Luo, Shanwei; Zhou, Libin; Li, Wenjian; Du, Yan; Yu, Lixia; Feng, Hui; Mu, Jinhu; Chen, Yuze

2016-09-01

Carbon ion beam irradiation is a powerful method for creating mutants and has been used in crop breeding more and more. To investigate the effects of carbon ion beams on Lotus japonicus, dry seeds were irradiated by 80 MeV/u carbon ion beam at dosages of 0, 100, 200, 300, 400, 500 and 600 Gy. The germination rate, survival rate and root length of M1 populations were explored and the dose of 400 Gy was selected as the median lethal dose (LD50) for a large-scale mutant screening. Among 2472 M2 plants, 127 morphological mutants including leaf, stem, flower and fruit phenotypic variation were found, and the mutation frequency was approximately 5.14%. Inter simple sequence repeat (ISSR) assays were utilized to investigate the DNA polymorphism between seven mutants and eight plants without phenotypic variation from M2 populations. No remarkable differences were detected between these two groups, and the total polymorphic rate was 0.567%.

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.

Model-derived dose rates per unit concentration of radon in air in a generic plant geometry.

PubMed

Vives i Batlle, J; Smith, A; Vives-Lynch, S; Copplestone, D; Pröhl, G; Strand, T

2011-11-01

A model for the derivation of dose rates per unit radon concentration in plants was developed in line with the activities of a Task Group of the International Commission on Radiological Protection (ICRP), aimed at developing more realistic dosimetry for non-human biota. The model considers interception of the unattached and attached fractions of the airborne radon daughters by plant stomata, diffusion of radon gas through stomata, permeation through the plant's epidermis and translocation of deposited activity to plant interior. The endpoint of the model is the derivation of dose conversion coefficients relative to radon gas concentration at ground level. The model predicts that the main contributor to dose is deposition of (214)Po α-activity on the plant surface and that diffusion of radon daughters through the stomata is of relatively minor importance; hence, daily variations have a small effect on total dose.

SU-F-T-18: The Importance of Immobilization Devices in Brachytherapy Treatments of Vaginal Cuff

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

Shojaei, M; Dumitru, N; Pella, S

2016-06-15

Purpose: High dose rate brachytherapy is a highly localized radiation therapy that has a very high dose gradient. Thus one of the most important parts of the treatment is the immobilization. The smallest movement of the patient or applicator can result in dose variation to the surrounding tissues as well as to the tumor to be treated. We will revise the ML Cylinder treatments and their localization challenges. Methods: A retrospective study of 25 patients with 5 treatments each looking into the applicator’s placement in regard to the organs at risk. Motion possibilities for each applicator intra and inter fractionationmore » with their dosimetric implications were covered and measured in regard with their dose variance. The localization immobilization devices used were assessed for the capability to prevent motion before and during the treatment delivery. Results: We focused on the 100% isodose on central axis and a 15 degree displacement due to possible rotation analyzing the dose variations to the bladder and rectum walls. The average dose variation for bladder was 15% of the accepted tolerance, with a minimum variance of 11.1% and a maximum one of 23.14% on the central axis. For the off axis measurements we found an average variation of 16.84% of the accepted tolerance, with a minimum variance of 11.47% and a maximum one of 27.69%. For the rectum we focused on the rectum wall closest to the 120% isodose line. The average dose variation was 19.4%, minimum 11.3% and a maximum of 34.02% from the accepted tolerance values Conclusion: Improved immobilization devices are recommended. For inter-fractionation, localization devices are recommended in place with consistent planning in regards with the initial fraction. Many of the present immobilization devices produced for external radiotherapy can be used to improve the localization of HDR applicators during transportation of the patient and during treatment.« less

Radiation protection for manned space activities

NASA Technical Reports Server (NTRS)

Jordan, T. M.

1983-01-01

The Earth's natural radiation environment poses a hazard to manned space activities directly through biological effects and indirectly through effects on materials and electronics. The following standard practices are indicated that address: (1) environment models for all radiation species including uncertainties and temporal variations; (2) upper bound and nominal quality factors for biological radiation effects that include dose, dose rate, critical organ, and linear energy transfer variations; (3) particle transport and shielding methodology including system and man modeling and uncertainty analysis; (4) mission planning that includes active dosimetry, minimizes exposure during extravehicular activities, subjects every mission to a radiation review, and specifies operational procedures for forecasting, recognizing, and dealing with large solar flaes.

Dactinomycin and Vincristine Toxicity in the Treatment of Childhood Cancer: A Retrospective Study from the Children’s Oncology Group

PubMed Central

Langholz, Bryan; Skolnik, Jeffrey M.; Barrett, Jeffrey S.; Renbarger, Jamie; Seibel, Nita L.; Zajicek, Anne; Arndt, Carola A.S.

2011-01-01

Background Dactinomycin (AMD) and vincristine (VCR) have been used for the treatment of childhood cancer over the past 40 years but evidence-based dosing guidance is lacking. Methods Patient AMD and VCR dose and drug-related adverse event (AE) information from four rhabdomyosarcoma (RMS) and two Wilms tumor (WT) studies were assembled. Statistical modeling was used to account for differences in AE data collection across studies, develop rate models for grade 3/4 CTCAE v3 hepatic- (AMD) and neuro- (AMD) toxicity, assess variation in toxicity rates over age and other factors, and predict toxicity risk under current dosing guidelines. Results For the same dose/body size, AMD toxicity rates were higher in patients <1 year than older patients and VCR toxicity rates increased with age. The statistical model provided estimates for AMD and VCR toxicity risk under current dosing schedules and indicated that patients of smaller body size were at lower risk of VCR toxicity than larger patients of the same age. The rate of AMD toxicity was highest early in treatment and was lower in patients who tolerated initial AMD without toxicity. Conclusion The observed decrease in AMD toxicity rate with cumulative dose may indicate sensitivity in a subgroup of patients while the observed increase in VCR toxicity risk with age may indicate changing sensitivity to VCR. Current dosing practices result in a fairly uniform toxicity profile within age group. However, PK/PD studies should be done to provide further provide further information on best dosing guidelines. PMID:21671362

Temporal variation of dose rate distribution around the Fukushima Daiichi nuclear power station using unmanned helicopter.

PubMed

Sanada, Yukihisa; Orita, Tadashi; Torii, Tatsuo

2016-12-01

Aerial radiological survey using an unmanned aerial vehicle (UAV) was applied to measurement surface contamination around the Fukushima Daiichi nuclear power station (FDNPS). An unmanned helicopter monitoring system (UHMS) was developed to survey the environmental effect of radioactive cesium scattered as a result of the FDNPS accident. The UHMS was used to monitor the area surrounding the FDNPS six times from 2012 to 2015. Quantitative changes in the radioactivity distribution trend were revealed from the results of these monitoring runs. With this information, we found that the actual reduction of dose rate was faster than the one calculated with radiocesium physical half-life. It is indicated that the attenuation effect of radiation by radiocesium penetration in soil is dominant as for reason of reduction of dose rate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Androgens and doping tests: genetic variation and pit-falls

PubMed Central

Rane, Anders; Ekström, Lena

2012-01-01

The large variation in disposition known for most drugs is also true for anabolic androgenic steroids. Genetic factors are probably the single most important cause of this variation. Further, there are reasons to believe that there is a corresponding variation in efficacy of doping agents. Doped individuals employ a large variety of doping strategies in respect of choice of substance, dose, dose interval, duration of treatment and use of other drugs for enforcement of effects or correction of side effects. Metabolic steps up-stream and down-stream of testosterone are genetically variable and contribute substantially to the variation in disposition of testosterone, the most common doping agent in sports and in society. Large inter- and intra-ethnic variation in testosterone glucuronidation and excretion is described as well as the pit-falls in evaluation of testosterone doping test results. The hydrolysis and bioactivation of testosterone enanthate is also genetically variable yielding a 2–3 fold variation in excretion rate and serum concentration, thereby implicating a substantial variation in ‘efficacy’ of testosterone. Given this situation it is logical to adopt the new findings in the doping control programme. The population based cut-off level for the testosterone : epitestosterone ratio should be replaced by a Bayesian interpretation of consecutive tests in the same individual. When combined with the above genetic information the sensitivity of the test is considerably improved. The combination of the three approaches should reduce the rate of falsely negative or positive results and the number of expensive follow-up tests, stipulated by the World Anti-Doping Agency. PMID:22506612

Absolute dose calibration of an X-ray system and dead time investigations of photon-counting techniques

NASA Astrophysics Data System (ADS)

Carpentieri, C.; Schwarz, C.; Ludwig, J.; Ashfaq, A.; Fiederle, M.

2002-07-01

High precision concerning the dose calibration of X-ray sources is required when counting and integrating methods are compared. The dose calibration for a dental X-ray tube was executed with special dose calibration equipment (dosimeter) as function of exposure time and rate. Results were compared with a benchmark spectrum and agree within ±1.5%. Dead time investigations with the Medipix1 photon-counting chip (PCC) have been performed by rate variations. Two different types of dead time, paralysable and non-paralysable will be discussed. The dead time depends on settings of the front-end electronics and is a function of signal height, which might lead to systematic defects of systems. Dead time losses in excess of 30% have been found for the PCC at 200 kHz absorbed photons per pixel.

Dedicated high dose rate 192Ir brachytherapy radiation fields for in vitro cell exposures at variable source-target cell distances: killing of mammalian cells depends on temporal dose rate fluctuation

NASA Astrophysics Data System (ADS)

Veigel, Cornelia; Hartmann, Günther H.; Fritz, Peter; Debus, Jürgen; Weber, Klaus-Josef

2017-02-01

Afterloading brachytherapy is conducted by the stepwise movement of a radioactive source through surgically implanted applicator tubes where at predefined dwell positions calculated dwell times optimize spatial dose delivery with respect to a planned dose level. The temporal exposure pattern exhibits drastic fluctuations in dose rate at a given coordinate and within a single treatment session because of the discontinuous and repeated source movement into the target volume. This could potentially affect biological response. Therefore, mammalian cells were exposed as monolayers to a high dose rate 192Ir source by utilizing a dedicated irradiation device where the distance between a planar array of radioactive source positions and the plane of the cell monolayer could be varied from 2.5 mm to 40 mm, thus varying dose rate pattern for any chosen total dose. The Gammamed IIi afterloading system equipped with a nominal 370 GBq (10 Ci) 192-Ir source was used to irradiate V79 Chinese hamster lung fibroblasts from both confluent and from exponential growth phase with dose up to 12 Gy (at room temperature, total exposure not exceeding 1 h). For comparison, V79 cells were also exposed to 6 MV x-rays from a clinical linear accelerator (dose rate of 2.5 Gy min-1). As biological endpoint, cell survival was determined by standard colony forming assay. Dose measurements were conducted with a diamond detector (sensitive area 7.3 mm2), calibrated by means of 60Co radiation. Additionally, dose delivery was simulated by Monte Carlo calculations using the EGSnrc code system. The calculated secondary electron fluence spectra at the cell location did not indicate a significant change of radiation quality (i.e. higher linear energy transfer) at the lower distances. Clonogenic cell survival curves obtained after brachytherapy exhibited an altered biological response compared to x-rays which was characterized by a significant reduction of the survival curve shoulder when dose rate fluctuations were high. Therefore, also for the time scale of the present investigation, cellular effects of radiation are not invariant to the temporal pattern in dose rate. We propose that with high dose rate variation the cells activate less efficiently their DNA damage response than after continuous irradiation.

Single Versus Customized Treatment Planning for Image-guided High-Dose-Rate Brachytherapy for Cervical Cancer: Dosimetric Comparison and Predicting Factor for Organs at Risk Overdose With Single Plan Approach

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

Chi, Alexander; Gao Mingcheng; Sinacore, James

2009-09-01

Purpose: To compare the dose distribution between customized planning (CP) and adopting a single plan (SP) in multifractionated high-dose-rate brachytherapy and to establish predictors for the necessity of CP in a given patient. Methods and Materials: A total of 50 computed tomography-based plans for 10 patients were evaluated. Each patient had received 6 Gy for five fractions. The clinical target volume and organs at risk (i.e., rectum, bladder, sigmoid, and small bowel) were delineated on each computed tomography scan. For the SP approach, the same dwell position and time was used for all fractions. For the CP approach, the dwellmore » position and time were reoptimized for each fraction. Applicator position variation was determined by measuring the distance between the posterior bladder wall and the tandem at the level of the vaginal fornices. Results: The organs at risk D{sub 2cc} (dose to 2 cc volume) was increased with the SP approach. The dose variation was statistically similar between the tandem and ring and tandem and ovoid groups. The bladder D{sub 2cc} dose was 81.95-105.42 Gy{sub 2} for CP and 82.11-122.49 Gy{sub 2} for SP. In 5 of the 10 patients, the bladder would have been significantly overdosed with the SP approach. The variation of the posterior bladder wall distance from that in the first fraction was correlated with the increase in the bladder D{sub 2cc} (SP/CP), with a correlation coefficient of -0.59. Conclusion: Our results support the use of CP instead of the SP approach to help avoid a significant overdose to the bladder. This is especially true for a decrease in the posterior wall distance of {>=}0.5 cm compared with that in the first fraction.« less

Integrating Genomic Based Information into Clinical Warfarin (Coumadin®) Management: An Illustrative Case Report

PubMed Central

LaSala, Anthony; Bower, Bruce; Windemuth, Andreas; White, C. Michael; Kocherla, Mohan; Seip, Richard; Duconge, Jorge; Ruaño, Gualberto

2013-01-01

Warfarin is a well established oral anticoagulant for the treatment of thromboembolic disorders. Warfarin therapy is complicated by a narrow therapeutic index and marked inter-individual dose variability with therapeutic doses ranging from 1 mg to 10 mg/day.1 Recently genetic variation and resultant drug metabolizing polymorphisms have been found to contribute to warfarin dose variability with resultant hemorrhagic or thromboembolic complications. Cytochrome P450 2C9 alters the rate of warfarin metabolism and clearance. A second enzyme, vitamin K epoxide reductase comple (VKOR) binds and reduces vitamin K which is necessary for activation of clotting Factors II, VII, IX and X. The VKORC1 gene encodes for vitamin K epoxide reductase complex subunit 1, a key component of VKOR. The combination of physiologic factors (30%), CYP2C9 variations (20%) and VKORC1 variants (25%) accounts for approximately 75% of warfarin dose variability. This illustrative case report demonstrates the clinical importance of this new information. Clinicians need to incorporate these new genomic findings into appropriate management of warfarin dose anticoagulation. PMID:18763667

Accelerating an Ordered-Subset Low-Dose X-Ray Cone Beam Computed Tomography Image Reconstruction with a Power Factor and Total Variation Minimization.

PubMed

Huang, Hsuan-Ming; Hsiao, Ing-Tsung

2016-01-01

In recent years, there has been increased interest in low-dose X-ray cone beam computed tomography (CBCT) in many fields, including dentistry, guided radiotherapy and small animal imaging. Despite reducing the radiation dose, low-dose CBCT has not gained widespread acceptance in routine clinical practice. In addition to performing more evaluation studies, developing a fast and high-quality reconstruction algorithm is required. In this work, we propose an iterative reconstruction method that accelerates ordered-subsets (OS) reconstruction using a power factor. Furthermore, we combine it with the total-variation (TV) minimization method. Both simulation and phantom studies were conducted to evaluate the performance of the proposed method. Results show that the proposed method can accelerate conventional OS methods, greatly increase the convergence speed in early iterations. Moreover, applying the TV minimization to the power acceleration scheme can further improve the image quality while preserving the fast convergence rate.

Accelerating an Ordered-Subset Low-Dose X-Ray Cone Beam Computed Tomography Image Reconstruction with a Power Factor and Total Variation Minimization

PubMed Central

Huang, Hsuan-Ming; Hsiao, Ing-Tsung

2016-01-01

In recent years, there has been increased interest in low-dose X-ray cone beam computed tomography (CBCT) in many fields, including dentistry, guided radiotherapy and small animal imaging. Despite reducing the radiation dose, low-dose CBCT has not gained widespread acceptance in routine clinical practice. In addition to performing more evaluation studies, developing a fast and high-quality reconstruction algorithm is required. In this work, we propose an iterative reconstruction method that accelerates ordered-subsets (OS) reconstruction using a power factor. Furthermore, we combine it with the total-variation (TV) minimization method. Both simulation and phantom studies were conducted to evaluate the performance of the proposed method. Results show that the proposed method can accelerate conventional OS methods, greatly increase the convergence speed in early iterations. Moreover, applying the TV minimization to the power acceleration scheme can further improve the image quality while preserving the fast convergence rate. PMID:27073853

Quantifying the performance of in vivo portal dosimetry in detecting four types of treatment parameter variations

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

Bojechko, C.; Ford, E. C., E-mail: eford@uw.edu

Purpose: To quantify the ability of electronic portal imaging device (EPID) dosimetry used during treatment (in vivo) in detecting variations that can occur in the course of patient treatment. Methods: Images of transmitted radiation from in vivo EPID measurements were converted to a 2D planar dose at isocenter and compared to the treatment planning dose using a prototype software system. Using the treatment planning system (TPS), four different types of variability were modeled: overall dose scaling, shifting the positions of the multileaf collimator (MLC) leaves, shifting of the patient position, and changes in the patient body contour. The gamma passmore » rate was calculated for the modified and unmodified plans and used to construct a receiver operator characteristic (ROC) curve to assess the detectability of the different parameter variations. The detectability is given by the area under the ROC curve (AUC). The TPS was also used to calculate the impact of the variations on the target dose–volume histogram. Results: Nine intensity modulation radiation therapy plans were measured for four different anatomical sites consisting of 70 separate fields. Results show that in vivo EPID dosimetry was most sensitive to variations in the machine output, AUC = 0.70 − 0.94, changes in patient body habitus, AUC = 0.67 − 0.88, and systematic shifts in the MLC bank positions, AUC = 0.59 − 0.82. These deviations are expected to have a relatively small clinical impact [planning target volume (PTV) D{sub 99} change <7%]. Larger variations have even higher detectability. Displacements in the patient’s position and random variations in MLC leaf positions were not readily detectable, AUC < 0.64. The D{sub 99} of the PTV changed by up to 57% for the patient position shifts considered here. Conclusions: In vivo EPID dosimetry is able to detect relatively small variations in overall dose, systematic shifts of the MLC’s, and changes in the patient habitus. Shifts in the patient’s position which can introduce large changes in the target dose coverage were not readily detected.« less

Development of a technique and conceptual design of a survey instrument for beta dosimetry in the nuclear power industry

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

Murphy, R.O.

1986-01-01

Before an employee of the nuclear power industry can be assigned to work in an area with radiation hazards, the total dose rate from all radiation present should be known to determine the risk. As the plants age, the level of maintenance has increased and certain tasks have required the workers to be exposed to intense beta radiation fields. Currently available survey instruments do not accurately assess the beta dose or dose rate in many circumstances due to several factors, including the fluctuation of the response of the detector due to the variation in the energy of the beta particlesmore » comprising the radiation field. This research involved developing a technique for calculating the beta dose rate, using the differential energy spectrum and the fluence rate for the beta particles, the fundamental features of the beta radiation. The energy spectrum was used to determine a spectrum weighted average mass stopping power (SWAMPS). The SWAMPS, when multiplied by the fluence rate, gives the energy deposited per unit mass per second, which is the absorbed dose rate for the beta radiation. Reference sources were developed and calibrated using an extrapolation chamber that had, itself, been calibrated using beta sources at the National Bureau of Standards. Different spectrometry systems were tested for applicability to the SWAMPS technique.« less

Novel delivery device for monolithical solid oral dosage forms for personalized medicine.

PubMed

Wening, Klaus; Breitkreutz, Jörg

2010-08-16

There is an evident need for solid oral dosage forms allowing patients' tailor-made dosing due to variations in metabolization or small therapeutic indexes of drug substances. The objective of this work is the development of a device equipped with a novel solid dosage form, containing carvedilol as model drug, for the delivery of monolithical drug carriers in individual doses. The device was developed and constructed enabling an exact feed rate and dose adjustment by a cutting mechanism. A twin-screw extruder was used for producing cylindrical solid dosage forms. Divided doses were characterized by mass variation, cutting behavior and drug dissolution in order to investigate their applicability for practical use. Different formulations could be extruded obtaining straight cylindrical rods, which are divisible in exact slices by using the novel device. Forces below 20 N were needed to divide doses which comply with pharmacopoeial specification "conformity of mass". The developed formulations exhibit a sustained release of carvedilol within a range from 7 up to 16 h. A novel system consisting of a device and a cylindrical dosage form was developed. Patients' individual doses can be applied as monolithical solid dosage forms for oral use.

Depth dependence of absorbed dose, dose equivalent and linear energy transfer spectra of galactic and trapped particles in polyethylene and comparison with calculations of models

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Cucinotta, F. A.; Wilson, J. W. (Principal Investigator)

1998-01-01

A matched set of five tissue-equivalent proportional counters (TEPCs), embedded at the centers of 0 (bare), 3, 5, 8 and 12-inch-diameter polyethylene spheres, were flown on the Shuttle flight STS-81 (inclination 51.65 degrees, altitude approximately 400 km). The data obtained were separated into contributions from trapped protons and galactic cosmic radiation (GCR). From the measured linear energy transfer (LET) spectra, the absorbed dose and dose-equivalent rates were calculated. The results were compared to calculations made with the radiation transport model HZETRN/NUCFRG2, using the GCR free-space spectra, orbit-averaged geomagnetic transmission function and Shuttle shielding distributions. The comparison shows that the model fits the dose rates to a root mean square (rms) error of 5%, and dose-equivalent rates to an rms error of 10%. Fairly good agreement between the LET spectra was found; however, differences are seen at both low and high LET. These differences can be understood as due to the combined effects of chord-length variation and detector response function. These results rule out a number of radiation transport/nuclear fragmentation models. Similar comparisons of trapped-proton dose rates were made between calculations made with the proton transport model BRYNTRN using the AP-8 MIN trapped-proton model and Shuttle shielding distributions. The predictions of absorbed dose and dose-equivalent rates are fairly good. However, the prediction of the LET spectra below approximately 30 keV/microm shows the need to improve the AP-8 model. These results have strong implications for shielding requirements for an interplanetary manned mission.

Intercomparison of radiation measurements on STS-63.

PubMed

Badhwar, G D; Atwell, W; Cash, B; Weyland, M; Petrov, V M; Tchernykh, I V; Akatov YuA; Shurshakov, V A; Arkhangelsky, V V; Kushin, V V; Klyachin, N A; Benton, E V; Frank, A L; Benton, E R; Frigo, L A; Dudkin, V E; Potapov YuV; Vana, N; Schoner, W; Fugger, M

1996-11-01

A joint NASA Russia study of the radiation environment inside the Space Shuttle was performed on STS-63. This was the second flight under the Shuttle-Mir Science Program (Phase 1). The Shuttle was launched on 2 February 1995, in a 51.65 degrees inclination orbit and landed at Kennedy Space Center on 11 February 1995, for a total flight duration of 8.27 days. The Shuttle carried a complement of both passive and active detectors distributed throughout the Shuttle volume. The crew exposure varied from 1962 to 2790 microGy with an average of 2265.8 microGy or 273.98 microGy/day. Crew exposures varied by a factor of 1.4, which is higher than usual for STS mission. The flight altitude varied from 314 to 395 km and provided a unique opportunity to obtain dose variation with altitude. Measurements of the average east-west dose variation were made using two active solid state detectors. The dose rate in the Spacehab locker, measured using a tissue equivalent proportional counter (TEPC), was 413.3 microGy/day, consistent with measurements made using thermoluminescent detectors (TLDs) in the same locker. The average quality factor was 2.33, and although it was higher than model calculations, it was consistent with values derived from high temperature peaks in TLDs. The dose rate due to galactic cosmic radiation was 110.6 microGy/day and agreed with model calculations. The dose rate from trapped particles was 302.7 microGy/day, nearly a factor of 2 lower than the prediction of the AP8 model. The neutrons in the intermediate energy range of 1-20 MeV contributed 13 microGy/day and 156 microSv/day, respectively. Analysis of data from the charged particle spectrometer has not yet been completed.

Biological Effects of Nuclear Explosions (BENE) Domain Guide

DTIC Science & Technology

2012-09-01

DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED (From – To) Technical Report October 2004-April 2005 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER...greatly increased in the nearby region because increasing amounts of contaminated earth and debris are sucked up into the radioactive cloud. In the case...or a denial scenario involving radioisotopes will be non-uniform exposure with various doses and dose rates producing very large variations in

Passive dosimetry aboard the Mir Orbital Station: internal measurements.

PubMed

Benton, E R; Benton, E V; Frank, A L

2002-10-01

Passive radiation dosimeters were exposed aboard the Mir Orbital Station over a substantial portion of the solar cycle in order to measure the change in dose and dose equivalent rates as a function of time. During solar minimum, simultaneous measurements of the radiation environment throughout the habitable volume of the Mir were made using passive dosimeters in order to investigate the effect of localized shielding on dose and dose equivalent. The passive dosimeters consisted of a combination of thermoluminescent detectors to measure absorbed dose and CR-39 PNTDs to measure the linear energy transfer (LET) spectrum from charged particles of LET infinity H2O > or = 5 keV/micrometers. Results from the two detector types were then combined to yield mean total dose rate, mean dose equivalent rate, and average quality factor. Contrary to expectations, both dose and dose equivalent rates measured during May-October 1991 near solar maximum were higher than similar measurements carried out in 1996-1997 during solar minimum. The elevated dose and dose equivalent rates measured in 1991 were probably due to a combination of intense solar activity, including a large solar particle event on 9 June 1991, and the temporary trapped radiation belt created in the slot region by the solar particle event and ensuing magnetic storm of 24 March 1991. During solar minimum, mean dose and dose equivalent rates were found to vary by factors of 1.55 and 1.37, respectively, between different locations through the interior of Mir. More heavily shielded locations tended to yield lower total dose and dose equivalent rates, but higher average quality factor than did more lightly shielding locations. However, other factors such as changes in the immediate shielding environment surrounding a given detector location, changes in the orientation of the Mir relative to its velocity vector, and changes in the altitude of the station also contributed to the variation. Proton and neutron-induced target fragment secondaries, not primary galactic cosmic rays, were found to dominate the LET spectrum above 100 keV/micrometers. This indicates that in low earth orbit, trapped protons in the South Atlantic Anomaly are responsible for the major fraction of the total dose equivalent. c2002 Elsevier Science Ltd. All rights reserved.

Are radiosensitivity data derived from natural field conditions consistent with data from controlled exposures? A case study of Chernobyl wildlife chronically exposed to low dose rates.

PubMed

Garnier-Laplace, J; Geras'kin, S; Della-Vedova, C; Beaugelin-Seiller, K; Hinton, T G; Real, A; Oudalova, A

2013-07-01

The discrepancy between laboratory or controlled conditions ecotoxicity tests and field data on wildlife chronically exposed to ionising radiation is presented for the first time. We reviewed the available chronic radiotoxicity data acquired in contaminated fields and used a statistical methodology to support the comparison with knowledge on inter-species variation of sensitivity to controlled external γ irradiation. We focus on the Chernobyl Exclusion Zone and effects data on terrestrial wildlife reported in the literature corresponding to chronic dose rate exposure situations (from background ~100 nGy/h up to ~10 mGy/h). When needed, we reconstructed the dose rate to organisms and obtained consistent unbiased data sets necessary to establish the dose rate-effect relationship for a number of different species and endpoints. Then, we compared the range of variation of radiosensitivity of species from the Chernobyl-Exclusion Zone with the statistical distribution established for terrestrial species chronically exposed to purely gamma external irradiation (or chronic Species radioSensitivity Distribution - SSD). We found that the best estimate of the median value (HDR50) of the distribution established for field conditions at Chernobyl (about 100 μGy/h) was eight times lower than the one from controlled experiments (about 850 μGy/h), suggesting that organisms in their natural environmental were more sensitive to radiation. This first comparison highlights the lack of mechanistic understanding and the potential confusion coming from sampling strategies in the field. To confirm the apparent higher sensitive of wildlife in the Chernobyl Exclusion Zone, we call for more a robust strategy in field, with adequate design to deal with confounding factors. Copyright © 2012 Elsevier Ltd. All rights reserved.

Dose of Biocoagulant-Mixing Rate Combinations for Optimum Reduction of COD in Wastewater

NASA Astrophysics Data System (ADS)

Patricia, Maria Faustina; Purwono; Budihardjo, Mochamad Arief

2018-02-01

Chemical oxygen demand (COD) in domestic wastewater can be treated using flocculation-coagulation process with addition of Oyster mushroom (Pleurotus ostreatus) in powder form as biocoagulant. The fungal cell wall of Oyster mushroom comprises of chitin that is high polyelectrolyte and can be function as an absorbent of heavy metals in wastewater. The effectiveness of flocculation-coagulation process in treating wastewater depends on dose of coagulant and mixing rate. Therefore, this study aims to determine the best combination of three variation of dose of biocoagulant which are 600 mg/l, 1000 mg/l, and 2000 mg/l and mixing rate which are 100 rpm, 125 rpm, and 150 rpm that give the most reduction of COD in the wastewater. The result indicates that the combination of 1000 mg/l of biocoagulant and 100 rpm of mixing rate were found to be the most optimum combination to treat COD in the wastewater with COD reduction of 47.7%.

Spiromax, a New Dry Powder Inhaler: Dose Consistency under Simulated Real-World Conditions

PubMed Central

Canonica, Giorgio Walter; Arp, Jan; Keegstra, Johan René

2015-01-01

Abstract Background: Spiromax® is a novel dry powder inhaler for patients with asthma or chronic obstructive pulmonary disease (COPD). The studies presented here provide further data on attributes (in vitro dosing consistency with budesonide–formoterol (DuoResp) Spiromax; flow rates through empty versions of the Spiromax and Turbuhaler inhaler) of importance to patients with asthma or COPD. Methods: Dose-delivery studies were performed using low-, middle-, and high-strength DuoResp Spiromax. Dose consistency was assessed over inhaler life. Total emitted doses (TEDs) were measured at various flow rates, after exposure to high and low temperature or humidity, at different inhaler orientations, and after dropping the inhaler. The criterion for evaluating dose uniformity was whether mean TEDs were within the product specification limits. In separate studies, flow rates were measured after training, using the patient information leaflets, and again after enhanced training as part of a randomized, open-label, cross-over study. Results: Mean values for both budesonide and formoterol were within 85%–115% of the label claim for each strength of DuoResp Spiromax for initial dose uniformity and for the other investigated conditions (temperature, humidity, orientation, dropping, knocking), with the exception of approximately an 80% increase in first dose after dropping the inhaler (subsequent doses not affected). In the flow rate patient study, two patients' inhalations with Spiromax and six with Turbuhaler were <30 L/min. The majority of asthma patients [91% (Spiromax) versus 82% (Turbuhaler)] achieved the preferred flow rate of >60 L/min. Conclusions: DuoResp Spiromax consistently meets dose uniformity criteria, under controlled laboratory conditions and with variations intended to mimic real-world use. Following enhanced training, all patients in the flow study were able to achieve the minimal inspiratory flow rate of >30 L/min, which is required for effective treatment. PMID:26352860

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

Saleh, H; Ferjani, S; Masssey, V

Purpose: Perform dosimetric comparison between planned and delivered dose in the junction area, measure daily dose variation in the arc junction area for pediatric patients treated for medulloblastoma using Craniospinal axis irradiation(CSI) Material and methods Dose comparison in the junction area, daily dose variation in the arc junction area for a Rando Phantom and 5 pediatric patients treated using CSI technique were analyzed. Plans were created using the Eclipse treatment planning system. Two arcs for cranium and 1 arc for spine region were used. Planar dose matrix was created by projecting phantom and patient plan into the ArcCheck phantom. EBT3more » film was placed in the middle of ArcCheck plug to measure dose distribution in the junction areaDuring patient treatment, strip of EBT3 film was placed daily at each junction area for verification. EBT3 films were scanned using a flatbed scanner, Epson Expression 10000 XL. Film QA pro software was used to analyze film. Scanning and analysis was performed according to vendor recommendations and AAPM TG-55 report. Films were scanned and analyzed daily after each treatment and at the end of treatment course. Planar dose distributions from films were compared with planar dose distribution from treatment planning system. Results: Comparison of planned vs. measured dose distributions for patients have passing rates of 90%–100% with 3% and 3 mm gamma analysis. In some of the treatment fractions, daily setup film showed variation in dose distribution in the junction area. Conclusion: It is critical to measure dose distribution in the arc junction area and use additional quality assurance measures to verify daily setup for CSI patient where one or more junctions are present. EBT3 film prove to be a good tool to achieve this task considering flexibility associated with the film such as symmetry, self-developing and ease of use.« less

Radiation dosimetry measurements with real time radiation monitoring device (RRMD)-II in Space Shuttle STS-79

NASA Technical Reports Server (NTRS)

Sakaguchi, T.; Doke, T.; Hayashi, T.; Kikuchi, J.; Hasebe, N.; Kashiwagi, T.; Takashima, T.; Takahashi, K.; Nakano, T.; Nagaoka, S.;

Effects of arbuscular mycorrhizal inoculation and fertilization on mycorrhizal Statute of Jacaranda mimosifolia D.Don cultivated in nurseries.

PubMed

Zaouchi, Yousr; Bahri, Nada Ben; Rezgui, S; Bettaieb, Taoufik

2013-10-01

The effects of fertilization and the nature of the inoculum as well as the variation of the dose intake of the latter on the level of Jacaranda mimosifolia D.Don mycorhization were tested. Young plants were treated with two inoculums presenting different origins, compositions and modes of application: one is a commercial product containing Glomus irregulare, and the other is a composite indigenous inoculum resulting from trapping five species of genus Glomus and also from multiplication on mycotrophic plants: leek (Allium porrum L.) and vetch (Vicia sativa L.). For each inoculum, two doses were tested and for each dose of inoculum, four levels of fertilization based on a complete commercial fertilizer (Osmocote) were tested: 0 g/plant, 2 g/plant, 4 g/plant, and 6g/plant. Three repetitions were performed for each combination treatment of inoculum/fertilizer. One-year-old young Jacaranda plants, being about 40 cm high, were cultured under greenhouse in 10/12 cm caliber pots. After six months, all the inoculated plants were mycorrhized. According to endomycorrhizal structures found on their roots, plants receiving doses of composite indigenous inoculum reached a more advanced stage of mycorrhization than those treated with the commercial inoculum. The existence of an interaction effect between the inoculum dose and the level of fertilization on Jacaranda mycorhization rate was excluded. These two parameters of variation were studied as simple effects. The increase in commercial inoculum dose had a significant positive influence on the level of Jacaranda plants mycorrhization (P=0.05). The rate of mycorrhization jumped from 12.69% to 21.92%. Nonetheless, for plants receiving increasing doses of composite indigenous inoculum, the level of mycorrhization has varied randomly. In both instances of inoculum treatments, increasing the dose of fertilizer significantly inhibited endomycorrhizal colonization of Jacaranda roots (P=0.01). Thus, the rate of root colonization decreased from 47.43% to 2.41% for plants receiving the composite indigenous inoculums. It decreased from 32.35% to 3.95% for those treated with the commercial inoculum. Mycorrhization had a positive effect on root dry biomass of Jacaranda, as in the case of unfertilize ave the highest rates of colonization. Copyright © 2013. Published by Elsevier SAS.

Measurement of soil contamination by radionuclides due to the Fukushima Dai-ichi Nuclear Power Plant accident and associated estimated cumulative external dose estimation.

PubMed

Endo, S; Kimura, S; Takatsuji, T; Nanasawa, K; Imanaka, T; Shizuma, K

2012-09-01

Soil sampling was carried out at an early stage of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Samples were taken from areas around FDNPP, at four locations northwest of FDNPP, at four schools and in four cities, including Fukushima City. Radioactive contaminants in soil samples were identified and measured by using a Ge detector and included (129 m)Te, (129)Te, (131)I, (132)Te, (132)I, (134)Cs, (136)Cs, (137)Cs, (140)Ba and (140)La. The highest soil depositions were measured to the northwest of FDNPP. From this soil deposition data, variations in dose rates over time and the cumulative external doses at the locations for 3 months and 1y after deposition were estimated. At locations northwest of FDNPP, the external dose rate at 3 months after deposition was 4.8-98 μSv/h and the cumulative dose for 1 y was 51 to 1.0 × 10(3)mSv; the highest values were at Futaba Yamada. At the four schools, which were used as evacuation shelters, and in the four urban cities, the external dose rate at 3 months after deposition ranged from 0.03 to 3.8μSv/h and the cumulative doses for 1 y ranged from 3 to 40 mSv. The cumulative dose at Fukushima Niihama Park was estimated as the highest in the four cities. The estimated external dose rates and cumulative doses show that careful countermeasures and remediation will be needed as a result of the accident, and detailed measurements of radionuclide deposition densities in soil will be important input data to conduct these activities. Copyright © 2011 Elsevier Ltd. All rights reserved.

Impact of head morphology on local brain specific absorption rate from exposure to mobile phone radiation.

PubMed

Adibzadeh, Fatemeh; Bakker, Jurriaan F; Paulides, Margarethus M; Verhaart, René F; van Rhoon, Gerard C

2015-01-01

Among various possible health effects of mobile phone radiation, the risk of inducing cancer has the strongest interest of laymen and health organizations. Recently, the Interphone epidemiological study investigated the association between the estimated Radio Frequency (RF) dose from mobile phones and the risk of developing a brain tumor. Their dosimetric analysis included over 100 phone models but only two homogeneous head phantoms. So, the potential impact of individual morphological features on global and local RF absorption in the brain was not investigated. In this study, we performed detailed dosimetric simulations for 20 head models and quantified the variation of RF dose in different brain regions as a function of head morphology. Head models were exposed to RF fields from generic mobile phones at 835 and 1900 MHz in the "tilted" and "cheek" positions. To evaluate the local RF dose variation, we used and compared two different post-processing methods, that is, averaging specific absorption rate (SAR) over Talairach regions and over sixteen predefined 1 cm(3) cube-shaped field-sensors. The results show that the variation in the averaged SAR among the heads can reach up to 16.4 dB at a 1 cm(3) cube inside the brain (field-sensor method) and alternatively up to 15.8 dB in the medulla region (Talairach method). In conclusion, we show head morphology as an important uncertainty source for dosimetric studies of mobile phones. Therefore, any dosimetric analysis dealing with RF dose at a specific region in the brain (e.g., tumor risk analysis) should be based upon real morphology. © 2014 Wiley Periodicals, Inc.

Cost-effectiveness of allopurinol and febuxostat for the management of gout.

PubMed

Jutkowitz, Eric; Choi, Hyon K; Pizzi, Laura T; Kuntz, Karen M

2014-11-04

Gout is the most common inflammatory arthritis in the United States. To evaluate the cost-effectiveness of urate-lowering treatment strategies for the management of gout. Markov model. Published literature and expert opinion. Patients for whom allopurinol or febuxostat is a suitable initial urate-lowering treatment. Lifetime. Health care payer. 5 urate-lowering treatment strategies were evaluated: no treatment; allopurinol- or febuxostat-only therapy; allopurinol-febuxostat sequential therapy; and febuxostat-allopurinol sequential therapy. Two dosing scenarios were investigated: fixed dose (80 mg of febuxostat daily, 0.80 success rate; 300 mg of allopurinol daily, 0.39 success rate) and dose escalation (≤120 mg of febuxostat daily, 0.82 success rate; ≤800 mg of allopurinol daily, 0.78 success rate). Discounted costs, discounted quality-adjusted life-years, and incremental cost-effectiveness ratios. In both dosing scenarios, allopurinol-only therapy was cost-saving. Dose-escalation allopurinol-febuxostat sequential therapy was more costly but more effective than dose-escalation allopurinol therapy, with an incremental cost-effectiveness ratio of $39 400 per quality-adjusted life-year. The relative rankings of treatments did not change. Our results were relatively sensitive to several potential variations of model assumptions; however, the cost-effectiveness ratios of dose escalation with allopurinol-febuxostat sequential therapy remained lower than the willingness-to-pay threshold of $109 000 per quality-adjusted life-year. Long-term outcome data for patients with gout, including medication adherence, are limited. Allopurinol single therapy is cost-saving compared with no treatment. Dose-escalation allopurinol-febuxostat sequential therapy is cost-effective compared with accepted willingness-to-pay thresholds. Agency for Healthcare Research and Quality.

Microstructural characterization and density change of 304 stainless steel reflector blocks after long-term irradiation in EBR-II

NASA Astrophysics Data System (ADS)

Huang, Y.; Wiezorek, J. M. K.; Garner, F. A.; Freyer, P. D.; Okita, T.; Sagisaka, M.; Isobe, Y.; Allen, T. R.

2015-10-01

While thin reactor structural components such as cladding and ducts do not experience significant gradients in dpa rate, gamma heating rate, temperature or stress, thick components can develop strong local variations in void swelling and irradiation creep in response to gradients in these variables. In this study we conducted microstructural investigations by transmission electron microscopy of two 52 mm thick 304-type stainless steel hex-blocks irradiated for 12 years in the EBR-II reactor with accumulated doses ranging from ∼0.4 to 33 dpa. Spatial variations in the populations of voids, precipitates, Frank loops and dislocation lines have been determined for 304 stainless steel sections exposed to different temperatures, different dpa levels and at different dpa rates, demonstrating the existence of spatial gradients in the resulting void swelling. The microstructural measurements compare very well with complementary density change measurements regarding void swelling gradients in the 304 stainless steel hex-block components. The TEM studies revealed that the original cold-worked-state microstructure of the unirradiated blocks was completely erased by irradiation, replaced by high densities of interstitial Frank loops, voids and carbide precipitates at both the lowest and highest doses. At large dose levels the amount of volumetric void swelling correlated directly with the gamma heating gradient-related temperature increase (e.g. for 28 dpa, ∼2% swelling at 418 °C and ∼2.9% swelling at 448 °C). Under approximately iso-thermal local conditions, volumetric void swelling was found to increase with dose level (e.g. ∼0.2% swelling at 0.4 dpa, ∼0.5% swelling at 4 dpa and ∼2% swelling at 28 dpa). Carbide precipitate formation levels were found to be relatively independent of both dpa level and temperature and induced a measurable densification. Void swelling was dominant at the higher dose levels and caused measurable decreases in density. Void swelling at the lowest doses was larger than might be expected based on the dpa level, an observation in agreement with earlier studies showing that the onset of void swelling is accelerated by decreasing dpa rates.

A Swiss cheese error detection method for real-time EPID-based quality assurance and error prevention.

PubMed

Passarge, Michelle; Fix, Michael K; Manser, Peter; Stampanoni, Marco F M; Siebers, Jeffrey V

2017-04-01

To develop a robust and efficient process that detects relevant dose errors (dose errors of ≥5%) in external beam radiation therapy and directly indicates the origin of the error. The process is illustrated in the context of electronic portal imaging device (EPID)-based angle-resolved volumetric-modulated arc therapy (VMAT) quality assurance (QA), particularly as would be implemented in a real-time monitoring program. A Swiss cheese error detection (SCED) method was created as a paradigm for a cine EPID-based during-treatment QA. For VMAT, the method compares a treatment plan-based reference set of EPID images with images acquired over each 2° gantry angle interval. The process utilizes a sequence of independent consecutively executed error detection tests: an aperture check that verifies in-field radiation delivery and ensures no out-of-field radiation; output normalization checks at two different stages; global image alignment check to examine if rotation, scaling, and translation are within tolerances; pixel intensity check containing the standard gamma evaluation (3%, 3 mm) and pixel intensity deviation checks including and excluding high dose gradient regions. Tolerances for each check were determined. To test the SCED method, 12 different types of errors were selected to modify the original plan. A series of angle-resolved predicted EPID images were artificially generated for each test case, resulting in a sequence of precalculated frames for each modified treatment plan. The SCED method was applied multiple times for each test case to assess the ability to detect introduced plan variations. To compare the performance of the SCED process with that of a standard gamma analysis, both error detection methods were applied to the generated test cases with realistic noise variations. Averaged over ten test runs, 95.1% of all plan variations that resulted in relevant patient dose errors were detected within 2° and 100% within 14° (<4% of patient dose delivery). Including cases that led to slightly modified but clinically equivalent plans, 89.1% were detected by the SCED method within 2°. Based on the type of check that detected the error, determination of error sources was achieved. With noise ranging from no random noise to four times the established noise value, the averaged relevant dose error detection rate of the SCED method was between 94.0% and 95.8% and that of gamma between 82.8% and 89.8%. An EPID-frame-based error detection process for VMAT deliveries was successfully designed and tested via simulations. The SCED method was inspected for robustness with realistic noise variations, demonstrating that it has the potential to detect a large majority of relevant dose errors. Compared to a typical (3%, 3 mm) gamma analysis, the SCED method produced a higher detection rate for all introduced dose errors, identified errors in an earlier stage, displayed a higher robustness to noise variations, and indicated the error source. © 2017 American Association of Physicists in Medicine.

Measles, mumps, and rubella antibody patterns of persistence and rate of decline following the second dose of the MMR vaccine.

PubMed

Seagle, Emma E; Bednarczyk, Robert A; Hill, Tenisha; Fiebelkorn, Amy Parker; Hickman, Carole J; Icenogle, Joseph P; Belongia, Edward A; McLean, Huong Q

2018-02-01

Antibodies to measles, mumps, and rubella decline 3% per year on average, and have a high degree of individual variation. Yet, individual variations and differences across antigens are not well understood. To better understand potential implications on individual and population susceptibility, we reanalyzed longitudinal data to identify patterns of seropositivity and persistence. Children vaccinated with the second dose of measles, mumps, rubella vaccine (MMR2) at 4-6 years of age were followed up to 12 years post-vaccination. The rates of antibody decline were assessed using regression models, accounting for differences between and within subjects. Most of the 302 participants were seropositive throughout follow-up (96% measles, 88% mumps, 79% rubella). The rate of antibody decline was associated with MMR2 response and baseline titer for measles and age at first dose of MMR (MMR1) for rubella. No demographic or clinical factors were associated with mumps rate of decline. One month post-MMR2, geometric mean titer (GMT) to measles was high (3892 mIU/mL), but declined on average 9.7% per year among those with the same baseline titer and <2-fold increase post-MMR2. Subjects with ≥2-fold experienced a slower decline (≤7.4%). GMT to rubella was 149 one month post-MMR2, declining 2.6% and 5.9% per year among those who received MMR1 at 12-15 months and >15 months, respectively. GMT to mumps one month post-MMR2 was 151, declining 9.2% per year. Only 14% of subjects had the same persistence trends for all antigens. The rate of antibody decay varied substantially among individuals and the 3 antigen groups. A fast rate of decline coupled with high variation was observed for mumps, yet no predictors were identified. Future research should focus on better understanding waning titers to mumps and its impacts on community protection and individual susceptibility, in light of recent outbreaks in vaccinated populations. Copyright © 2018 Elsevier Ltd. All rights reserved.

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.

Variation in treatment strategies of Swiss general practitioners for subclinical hypothyroidism in older adults.

PubMed

Baumgartner, Christine; den Elzen, Wendy P J; Blum, Manuel R; Coslovsky, Michael; Streit, Sven; Frey, Peter; Herzig, Lilli; Haller, Dagmar M; Mooijaart, Simon P; Bischoff, Thomas; Rosemann, Thomas; Gussekloo, Jacobijn; Rodondi, Nicolas

2015-01-01

As the best management of subclinical hypothyroidism is controversial, we aimed to assess variations in treatment strategies depending on different Swiss regions, physician and patient characteristics. We performed a case-based survey among general practitioners (GPs) in different Swiss regions, which consisted of eight hypothetical cases presenting a female patient with subclinical hypothyroidism and nonspecific complaints differing by age, vitality status and thyroid-stimulating hormone (TSH) concentration. A total of 262 GPs participated in the survey. There was considerable variation in the levothyroxine starting dose chosen by GPs, ranging from 25 µg to 100 µg. Across the Swiss regions, GPs in the Bern region were significantly more inclined to treat, with a higher probability of initiating treatment (60%, p = 0.01) and higher mean starting doses (45 µg, p <0.01) compared with the French-speaking region (44%, 36 µg); the Zurich region had intermediate values (52%, 39 µg). We found no association between treatment rate and other physician characteristics. GPs were more reluctant to initiate treatment in 85-year-old than in 70-year-old women (odds ratio [OR] 0.77, 95% confidence interval [CI] 0.63-0.94), and more likely to treat women with a TSH of 15 mU/l than those with a TSH of 6mU/l (OR 8.71, 95% CI 6.21-12.20). There are strong variations in treatment strategies for elderly patients with subclinical hypothyroidism across different Swiss regions, including use of higher starting doses than the recommended 25 µg in the Swiss guidelines, which recommend a starting dose of 25 µg. These variations likely reflect the current uncertainty about the benefits of treatment, which arise from the current lack of evidence from adequately powered clinical trials.

LET spectra measurements from the STS-35 CPDs

NASA Technical Reports Server (NTRS)

1995-01-01

Linear energy transfer (LET) spectra derived form automated track analysis system (ATAS) track parameter measurements for crew passive dosimeters (CPD's) flown with the astronauts on STS-35 are plotted. The spread between the seven individual spectra is typical of past manual measurements of sets of CPD's. This difference is probably due to the cumulative net shielding variations experienced by the CPD's as the astronauts carrying them went about their activities on the Space Shuttle. The STS-35 mission was launched on Dec. 2, 1990, at 28.5 degrees inclination and 352-km altitude. This is somewhat higher than the nominal 300-km flights and the orbit intersects more of the high intensity trapped proton region in the South Atlantic Anomaly (SAA). However, in comparison with APD spectra measured on earlier lower altitude missions (STS-26, -29, -30, -32), the flux spectra are all roughly comparable. This may be due to the fact that the STS-35 mission took place close to solar maximum (Feb. 1990), or perhaps to shielding differences. The corresponding dose and dose equivalent spectra for this mission are shown. The effect of statistical fluctuations at the higher LET values, where track densities are small, is very noticeable. This results in an increased spread within the dose rate and dose equivalent rate spectra, as compared to the flux spectra. The contribution to dose and dose equivalent per measured track is much greater in the high LET region and the differences, though numerically small, are heavily weighted in the integral spectra. The optimum measurement and characterization of the high LET tails of the spectra represent an important part of the research into plastic nuclear track detector (PNTD) response. The integral flux, dose rate, dose equivalent rate and mission dose equivalent for the seven astronauts are also given.

High dose gamma ray exposure effect on the properties of CdSe nanowires

NASA Astrophysics Data System (ADS)

Narula, Chetna; Chauhan, R. P.

2018-03-01

We report high dose gamma-ray (γ-ray) induced modifications incurred by polycrystalline cadmium selenide (CdSe) nanowires of 80 nm diameter. The nanowires have been synthesized using polycarbonate template assisted electro-deposition technique. The samples were irradiated with 60Co γ-radiation at a dose rate of 4.533 kGy/h for different time intervals with doses varying from 0 to 400 kGy. The effects of γ rays on the structural, morphological, optical and electrical properties of nanowires are discussed. XRD patterns of as-synthesized and gamma irradiated CdSe nanowires did not show any phase transformations but the variation in relative intensity was observed. The crystallite size evaluated using Scherrer's formula was found to vary. The optical parameters were obtained using UV-vis spectrometer measurements of absorption. Band gap was found to decrease with γ irradiation up to a dose of 300 kGy after which it was seen to increase. Refractive index and optical dielectric constants were also evaluated. Subjection of γ-radiation also brings about key changes in the electrical properties of CdSe nanowires. The attained data shows that the electrical conductivity varies with absorbed dose. The variations in the properties of CdSe nanowires can be considered as a consequence of ionization process, defect production and its annihilation.

Commissioning dosimetry and in situ dose mapping of a semi-industrial Cobalt-60 gamma-irradiation facility using Fricke and Ceric-cerous dosimetry system and comparison with Monte Carlo simulation data

NASA Astrophysics Data System (ADS)

Mortuza, Md Firoz; Lepore, Luigi; Khedkar, Kalpana; Thangam, Saravanan; Nahar, Arifatun; Jamil, Hossen Mohammad; Bandi, Laxminarayan; Alam, Md Khorshed

2018-03-01

Characterization of a 90 kCi (3330 TBq), semi-industrial, cobalt-60 gamma irradiator was performed by commissioning dosimetry and in-situ dose mapping experiments with Ceric-cerous and Fricke dosimetry systems. Commissioning dosimetry was carried out to determine dose distribution pattern of absorbed dose in the irradiation cell and products. To determine maximum and minimum absorbed dose, overdose ratio and dwell time of the tote boxes, homogeneous dummy product (rice husk) with a bulk density of 0.13 g/cm3 were used in the box positions of irradiation chamber. The regions of minimum absorbed dose of the tote boxes were observed in the lower zones of middle plane and maximum absorbed doses were found in the middle position of front plane. Moreover, as a part of dose mapping, dose rates in the wall positions and some selective strategic positions were also measured to carry out multiple irradiation program simultaneously, especially for low dose research irradiation program. In most of the cases, Monte Carlo simulation data, using Monte Carlo N-Particle eXtended code version MCNPX 2.7., were found to be in congruence with experimental values obtained from Ceric-cerous and Fricke dosimetry; however, in close proximity positions from the source, the dose rate variation between chemical dosimetry and MCNP was higher than distant positions.

Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators.

PubMed

Belley, Matthew D; Wang, Chu; Nguyen, Giao; Gunasingha, Rathnayaka; Chao, Nelson J; Chen, Benny J; Dewhirst, Mark W; Yoshizumi, Terry T

2014-03-01

Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. Average doses in soft-tissue organs were found to vary by as much as 23%-32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.

Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators

PubMed Central

Belley, Matthew D.; Wang, Chu; Nguyen, Giao; Gunasingha, Rathnayaka; Chao, Nelson J.; Chen, Benny J.; Dewhirst, Mark W.; Yoshizumi, Terry T.

2014-01-01

Purpose: Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. Methods: Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. Results: Average doses in soft-tissue organs were found to vary by as much as 23%–32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. Conclusions: This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigning a single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs. PMID:24593746

Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators

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

Belley, Matthew D.; Wang, Chu; Nguyen, Giao

2014-03-15

Purpose: Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. Methods: Organ doses were simulated in the Geant4 application formore » tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. Results: Average doses in soft-tissue organs were found to vary by as much as 23%–32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. Conclusions: This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.« less

SU-G-BRC-16: Theory and Clinical Implications of the Constant Dosimetric Leaf Gap (DLG) Approximation

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

Kumaraswamy, L; Xu, Z; Podgorsak, M

Purpose: Commercial dose calculation algorithms incorporate a single DLG value for a given beam energy that is applied across an entire treatment field. However, the physical processes associated with beam generation and dose delivery suggest that the DLG is not constant. The aim of this study is to evaluate the variation of DLG among all leaf pairs, to quantify how this variation impacts delivered dose, and to establish a novel method to correct dose distributions calculated using the approximation of constant DLG. Methods: A 2D diode array was used to measure the DLG for all 60 leaf pairs at severalmore » points along each leaf pair travel direction. This approach was validated by comparison to DLG values measured at select points using a 0.6 cc ion chamber with the standard formalism. In-house software was developed to enable incorporation of position dependent DLG values into dose distribution optimization and calculation. The accuracy of beam delivery of both the corrected and uncorrected treatment plans was studied through gamma pass rate evaluation. A comparison of DVH statistics in corrected and uncorrected treatment plans was made. Results: The outer 20 MLC leaf pairs (1.0 cm width) have DLG values that are 0.32 mm (mean) to 0.65 mm (maximum) lower than the central leaf-pair. VMAT plans using a large number of 1 cm wide leaves were more accurately delivered (gamma pass rate increased by 5%) and dose coverage was higher (D100 increased by 3%) when the 2D DLG was modeled. Conclusion: Using a constant DLG value for a given beam energy will result in dose optimization, dose calculation and treatment delivery inaccuracies that become significant for treatment plans with high modulation complexity scores delivered with 1 cm wide leaves.« less

Influence of infusion pump operation and flow rate on hemodynamic stability during epinephrine infusion.

PubMed

Klem, S A; Farrington, J M; Leff, R D

1993-08-01

To determine whether variations in the flow rate of epinephrine solutions administered via commonly available infusion pumps lead to significant variations in blood pressure (BP) in vivo. Prospective, randomized, crossover study with factorial design, using infusion pumps with four different operating mechanisms (pulsatile diaphragm, linear piston/syringe, cyclic piston-valve, and linear peristaltic) and three drug delivery rates (1, 5, and 10 mL/hr). Two healthy, mixed-breed dogs (12 to 16 kg). Dogs were made hypotensive with methohexital bolus and continuous infusion. BP was restored to normal with constant-dose epinephrine infusion via two pumps at each rate. Femoral mean arterial pressure (MAP) was recorded every 10 secs. Pump-flow continuity was quantitated in vitro using a digital gravimetric technique. Variations in MAP and flow continuity were expressed by the coefficient of variation; analysis of variance was used for comparisons. The mean coefficients of variations for MAP varied from 3.8 +/- 3.1% (linear piston/syringe) to 6.1 +/- 6.6% (linear peristaltic), and from 3.4 +/- 2.2% (10 mL/hr) to 7.9 +/- 6.6% (1 mL/hr). The coefficients of variation for in vitro flow continuity ranged from 9 +/- 8% (linear piston-syringe) to 250 +/- 162% (pulsatile diaphragm), and from 35 +/- 44% (10 mL/hr) to 138 +/- 196% (1 mL/hr). Both the type of pump and infusion rate significantly (p < .001) influenced variation in drug delivery rate. The 1 mL/hr infusion rate significantly (p < .01) influenced MAP variation. Cyclic fluctuations in MAP of < or = 30 mm Hg were observed using the pulsatile diaphragm pump at 1 mL/hr. Factors inherent in the operating mechanisms of infusion pumps may result in clinically important hemodynamic fluctuations when administering a concentrated short-acting vasoactive medication at slow infusion rates.

Gypchek®: past and future strategies for use

Treesearch

J. D. Podgwaite

1985-01-01

The development of the gypsy moth nucleopolyhedrosis virus product Gypchek, and strategies for its use, have been largely patterned after conventional pesticide technology. Prior to Gypchek registration with the Environmental Protection Agency in 1978, several field tests involving variations in virus product, application hardware, dose rates, timing and formulation...

Gamma Radiation Dose Rate in Air due to Terrestrial Radionuclides in Southern Brazil: Synthesis by Geological Units and Lithotypes Covered by the Serra do Mar Sul Aero-Geophysical Project

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

Bastos, Rodrigo O.; Appoloni, Carlos R.; Pinese, Jose P. P.

2008-08-07

The absorbed dose rates in air due to terrestrial radionuclides were estimated from aerial gamma spectrometric data for an area of 48,600 km{sup 2} in Southern Brazil. The source data was the Serra do Mar Sul Aero-Geophysical Project back-calibrated in a cooperative work among the Geological Survey of Brazil, the Geological Survey of Canada, and Paterson, Grant and Watson Ltd. The concentrations of eU (ppm), eTh (ppm) and K (%) were converted to dose rates in air (nGy{center_dot}h{sup -1}) by accounting for the contribution of each element's concentration. Regional variation was interpreted according to lithotypes and a synthesis was performedmore » according to the basic geological units present in the area. Higher values of total dose were estimated for felsic igneous and metamorphic rocks, with average values varying up to 119{+-}24 nGy{center_dot}h{sup -1}, obtained by Anitapolis syenite body. Sedimentary, metasedimentary and metamafic rocks presented the lower dose levels, and some beach deposits reached the lowest average total dose, 18.5{+-}8.2 nGy{center_dot}h{sup -1}. Thorium gives the main average contribution in all geological units, the highest value being reached by the nebulitic gneisses of Atuba Complex, 71{+-}23 nGy{center_dot}h{sup -1}. Potassium presents the lowest average contribution to dose rate in 53 of the 72 units analyzed, the highest contribution being obtained by intrusive alkaline bodies (28{+-}12 nGy{center_dot}h{sup -1}). The general pattern of geographic dose distribution respects well the hypotheses on geo-physicochemical behavior of radioactive elements.« less

Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures

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

Safari, M. J.; Wong, J. H. D.; Ng, K. H., E-mail: ngkh@um.edu.my

2015-05-15

Purpose: The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. Methods: The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualitiesmore » were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. Results: The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (±1%), field size (±1%), frame rate (±3%), or beam energy (±5%). The detector angular dependence was within ±5% over 360° and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ±3%. Conclusions: The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures.« less

Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures.

PubMed

Safari, M J; Wong, J H D; Ng, K H; Jong, W L; Cutajar, D L; Rosenfeld, A B

2015-05-01

The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualities were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (± 1%), field size (± 1%), frame rate (± 3%), or beam energy (± 5%). The detector angular dependence was within ± 5% over 360° and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ± 3%. The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures.

A national patient dose survey and setting of reference levels for interventional radiology in Bulgaria.

PubMed

Zotova, R; Vassileva, J; Hristova, J; Pirinen, M; Järvinen, H

2012-06-01

A national study on patient dose values in interventional radiology and cardiology was performed in order to assess current practice in Bulgaria, to estimate the typical patient doses and to propose reference levels for the most common procedures. Fifteen units and more than 1,000 cases were included. Average values of the measured parameters for three procedures-coronary angiography (CA), combined procedure (CA + PCI) and lower limb arteriography (LLA)--were compared with data published in the literature. Substantial variations were observed in equipment and procedure protocols used. This resulted in variations in patient dose: air-kerma area product ranges were 4-339, 6-1,003 and 0.2-288 Gy cm(2) for CA, CA + PCI and LLA respectively. Reference levels for air kerma-area product were proposed: 40 Gy cm(2) for CA, 140 Gy cm(2) for CA + PCI and 45 Gy cm(2) for LLA. Auxiliary reference intervals were proposed for other dose-related parameters: fluoroscopy time, number of images and entrance surface air kerma rate in fluoroscopy and cine mode. There is an apparent necessity for improvement in the classification of peripheral procedures and for standardisation of the protocols applied. It is important that patient doses are routinely recorded and compared with reference levels. • Patient doses in interventional radiology are high and vary greatly • Better standardisation of procedures and techniques is needed to improve practice • Dose reference levels for most common procedures are proposed.

Evaluation of dose variation during total skin electron irradiation using thermoluminescent dosimeters.

PubMed

Weaver, R D; Gerbi, B J; Dusenbery, K E

1995-09-30

To determine acceptable dose variation using thermoluminescent dosimeters (TLD) in the treatment of Mycosis Fungoides with total skin electron beam (TSEB) irradiation. From 1983 to 1993, 22 patients were treated with total skin electron beam therapy in the standing position. A six-field technique was used to deliver 2 Gy in two days, treating 4 days per week, to a total dose of 35 to 40 Gy using a degraded 9 MeV electron beam. Thermoluminescent dosimeters were placed on several locations of the body and the results recorded. The variations in these readings were analyzed to determine normal dose variation for various body locations during TSEB. The dose to flat surfaces of the body was essentially the same as the dose to the prescription point. The dose to tangential surfaces was within +/- 10% of the prescription dose, but the readings showed much more variation (up to 24%). Thin areas of the body showed large deviations from the prescription dose along with a large amount of variation in the readings (up to 22%). Special areas of the body, such as the perineum and eyelid, showed large deviations from the prescription dose with very large (up to 40%) variations in the readings. The TLD results of this study will be used as a quality assurance check for all new patients treated with TSEB. The results of the TLDs will be compared with this baseline study to determine if the delivered dose is within acceptable ranges. If the TLD results fall outside the acceptable limits established above, then the patient position can be modified or the technique itself evaluated.

Study of variations in structural, optical parameters and bulk etch rate of CR-39 polymer due to electron irradiation

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

Sahoo, G. S.; Joshi, D. S.; Tripathy, S. P., E-mail: sam.tripathy@gmail.com, E-mail: tripathy@barc.gov.in

2016-07-14

In this work, electron induced modifications on the bulk etch rate, structural and optical parameters of CR-39 polymer were studied using gravimetric, FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) techniques, respectively. CR-39 samples were irradiated with 10 MeV electron beam for different durations to have the absorbed doses of 1, 10, 550, 5500, 16 500, and 55 000 kGy. From the FTIR analysis, the peak intensities at different bands were found to be changing with electron dose. A few peaks were observed to shift at high electron doses. From the UV-vis analysis, the optical band gaps for both direct and indirect transitions weremore » found to be decreasing with the increase in electron dose whereas the opacity, number of carbon atoms in conjugation length, and the number of carbon atoms per cluster were found to be increasing. The bulk etch rate was observed to be increasing with the electron dose. The primary objective of this investigation was to study the response of CR-39 to high electron doses and to determine a suitable pre-irradiation condition. The results indicated that, the CR-39 pre-irradiated with electrons can have better sensitivity and thus can be potentially applied for neutron dosimetry.« less

The consistency of Fletcher-Suit applicator geometry and of the rectal probe’s position in high dose rate brachytherapy treatment fraction of cervix carcinoma

PubMed Central

2009-01-01

Purpose The dose values computed with the treatment planning system and the in vivo dose measurements with semiconductor detectors in rectum during the high dose rate brachytherapy treatment fraction of the cervix carcinoma are occasionally significantly different. We’ve investigated the consistency of the Fletcher-Suit applicator geometry and the in vivo rectal probe’s position stability during the high dose rate brachytherapy treatment fraction. Material and methods The patient lied in a lithotomic position during a biplane reconstruction images, throughout the treatment planning and dose administration. We obtained post-treatment reconstruction images and prepared a post-treatment plan. The amount of 14 treatment fractions of 10 patients were considered in the study. Two methods were applied: evaluation of the difference of reconstructed pre-treatment and post-treatment applicator points and rectal probe’s detectors being relevant to the co-ordinate system fixed to the applicator, and estimation of applicators and rectal probe’s reallocation with respect to the pelvic bones with registration of pre- and post-treatment reconstruction images. Results We’ve experienced good consistency in the Fletcher-Suit applicator geometry in all treatment fractions. 70% of them presented small variation in the rectal probe’s position, while the rest showed significant shift in the applicator or rectal probe’s position with regard to the pelvic bones. PMID:27807458

Spatial variability of the dose rate from (137)Cs fallout in settlements in Russia and Belarus more than two decades after the Chernobyl accident.

PubMed

Bernhardsson, C; Rääf, C L; Mattsson, S

2015-11-01

Radionuclides from the 1986 Chernobyl accident were released and dispersed during a limited period of time, but under widely varying weather conditions. As a result, there was a high geographical variation in the deposited radioactive fallout per unit area over Europe, depending on the released composition of fission products and the weather during the 10 days of releases. If the plume from Chernobyl coincided with rain, then the radionuclides were unevenly distributed on the ground. However, large variations in the initial fallout also occurred locally or even on a meter scale. Over the ensuing years the initial deposition may have been altered further by different weathering processes or human activities such as agriculture, gardening, and decontamination measures. Using measurements taken more than two decades after the accident, we report on the inhomogeneous distribution of the ground deposition of the fission product (137)Cs and its influence on the dose rate 1 m above ground, on both large and small scales (10ths of km(2) - 1 m(2)), in the Gomel-Bryansk area close to the border between Belarus and Russia. The dose rate from the deposition was observed to vary by one order of magnitude depending on the size of the area considered, whether human processes were applied to the surface or not, and on location specific properties (e.g. radionuclide migration in soil). Copyright © 2015 Elsevier Ltd. All rights reserved.

Dosimetric characterization of a microDiamond detector in clinical scanned carbon ion beams.

PubMed

Marinelli, Marco; Prestopino, G; Verona, C; Verona-Rinati, G; Ciocca, M; Mirandola, A; Mairani, A; Raffaele, L; Magro, G

2015-04-01

To investigate for the first time the dosimetric properties of a new commercial synthetic diamond detector (PTW microDiamond) in high-energy scanned clinical carbon ion beams generated by a synchrotron at the CNAO facility. The detector response was evaluated in a water phantom with actively scanned carbon ion beams ranging from 115 to 380 MeV/u (30-250 mm Bragg peak depth in water). Homogeneous square fields of 3 × 3 and 6 × 6 cm(2) were used. Short- and medium-term (2 months) detector response stability, dependence on beam energy as well as ion type (carbon ions and protons), linearity with dose, and directional and dose-rate dependence were investigated. The depth dose curve of a 280 MeV/u carbon ion beam, scanned over a 3 × 3 cm(2) area, was measured with the microDiamond detector and compared to that measured using a PTW Advanced Markus ionization chamber, and also simulated using fluka Monte Carlo code. The detector response in two spread-out-Bragg-peaks (SOBPs), respectively, centered at 9 and 21 cm depths in water and calculated using the treatment planning system (TPS) used at CNAO, was measured. A negligible drift of detector sensitivity within the experimental session was seen, indicating that no detector preirradiation was needed. Short-term response reproducibility around 1% (1 standard deviation) was found. Only 2% maximum variation of microDiamond sensitivity was observed among all the evaluated proton and carbon ion beam energies. The detector response showed a good linear behavior. Detector sensitivity was found to be dose-rate independent, with a variation below 1.3% in the evaluated dose-rate range. A very good agreement between measured and simulated Bragg curves with both microDiamond and Advanced Markus chamber was found, showing a negligible LET dependence of the tested detector. A depth dose curve was also measured by positioning the microDiamond with its main axis oriented orthogonally to the beam direction. A strong distortion in Bragg peak measurement was observed, confirming manufacturer recommendation on avoiding such configuration. Very good results were obtained for SOBP measurements, with a difference below 1% between measured and TPS-calculated doses. The stability of detector sensitivity in the observation period was within the experimental uncertainty. Dosimetric characterization of a PTW microDiamond detector in high-energy scanned carbon ion beams was performed. The results of the present study showed that this detector is suitable for dosimetry of clinical carbon ion beams, with a negligible LET and dose-rate dependence.

SU-F-T-236: Comparison of Two IMRT/VMAT QA Systems Using Gamma Index Analysis

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

Dogan, N; Denissova, S

2016-06-15

Purpose: The goal of this study is to assess differences in the Gamma index pass rates when using two commercial QA systems and provide optimum Gamma index parameters for pre-treatment patient specific QA. Methods: Twenty-two VMAT cases that consisted of prostate, lung, head and neck, spine, brain and pancreas, were included in this study. The verification plans have been calculated using AcurosXB(V11) algorithm for different dose grids (1.5mm, 2.5mm, 3mm). The measurements were performed on TrueBeam(Varian) accelerator using both EPID(S1000) portal imager and ArcCheck(SunNuclearCorp) devices. Gamma index criteria variation of 3%/3mm, 2%/3mm, 2%/2mm and threshold (TH) doses of 5% tomore » 50% were used in analysis. Results: The differences in Gamma pass rates between two devices are not statistically significant for 3%/3mm, yielding pass rate higher than 95%. Increase of lower dose TH showed reduced pass rates for both devices. ArcCheck’s more pronounced effect can be attributed to higher contribution of lower dose region spread. As expected, tightening criteria to 2%/2mm (TH: 10%) decreased Gamma pass rates below 95%. Higher EPID (92%) pass rates compared to ArcCheck (86%) probably due to better spatial resolution. Portal Dosimetry results showed lower Gamma pass rates for composite plans compared to individual field pass rates. This may be due to the expansion in the analyzed region which includes pixels not included in the separate field analysis. Decreasing dose grid size from 2.5mm to 1.5mm did not show statistically significant (p<0.05) differences in Gamma pass rates for both QA devices. Conclusion: Overall, both system measurements agree well with calculated dose when using gamma index criteria of 3%/3mm for a variety of VMAT cases. Variability between two systems increases using different dose GRID, TH and tighter gamma criteria and must be carefully assessed prior to clinical use.« less

Levels of naturally occurring gamma radiation measured in British homes and their prediction in particular residences.

PubMed

Kendall, G M; Wakeford, R; Athanson, M; Vincent, T J; Carter, E J; McColl, N P; Little, M P

2016-03-01

Gamma radiation from natural sources (including directly ionising cosmic rays) is an important component of background radiation. In the present paper, indoor measurements of naturally occurring gamma rays that were undertaken as part of the UK Childhood Cancer Study are summarised, and it is shown that these are broadly compatible with an earlier UK National Survey. The distribution of indoor gamma-ray dose rates in Great Britain is approximately normal with mean 96 nGy/h and standard deviation 23 nGy/h. Directly ionising cosmic rays contribute about one-third of the total. The expanded dataset allows a more detailed description than previously of indoor gamma-ray exposures and in particular their geographical variation. Various strategies for predicting indoor natural background gamma-ray dose rates were explored. In the first of these, a geostatistical model was fitted, which assumes an underlying geologically determined spatial variation, superimposed on which is a Gaussian stochastic process with Matérn correlation structure that models the observed tendency of dose rates in neighbouring houses to correlate. In the second approach, a number of dose-rate interpolation measures were first derived, based on averages over geologically or administratively defined areas or using distance-weighted averages of measurements at nearest-neighbour points. Linear regression was then used to derive an optimal linear combination of these interpolation measures. The predictive performances of the two models were compared via cross-validation, using a randomly selected 70 % of the data to fit the models and the remaining 30 % to test them. The mean square error (MSE) of the linear-regression model was lower than that of the Gaussian-Matérn model (MSE 378 and 411, respectively). The predictive performance of the two candidate models was also evaluated via simulation; the OLS model performs significantly better than the Gaussian-Matérn model.

Improved sulfide mitigation in sewers through on-line control of ferrous salt dosing.

PubMed

Ganigué, Ramon; Jiang, Guangming; Liu, Yiqi; Sharma, Keshab; Wang, Yue-Cong; Gonzalez, José; Nguyen, Tung; Yuan, Zhiguo

2018-05-15

Water utilities worldwide spend annually billions of dollars to control sulfide-induced corrosion in sewers. Iron salts chemically oxidize and/or precipitate dissolved sulfide in sewage and are especially used in medium- and large-size sewers. Iron salt dosing rates are defined ad hoc, ignoring variation in sewage flows and sulfide levels. This often results in iron overdosing or poor sulfide control. Online dosing control can adjust the chemical dosing rates to current (and future) state of the sewer system, allowing high-precision, stable and cost-effective sulfide control. In this paper, we report a novel and robust online control strategy for the dosing of ferrous salt in sewers. The control considers the fluctuation of sewage flow, pH, sulfide levels and also the perturbation from rainfall. Sulfide production in the pipe is predicted using auto-regressive models (AR) based on current flow measurements, which in turn can be used to determine the dose of ferrous salt required for cost-effective sulfide control. Following comprehensive model-based assesment, the control was successfully validated and its effectiveness demonstrated in a 3-week field trial. The online control algorithm controlled sulfide below the target level (0.5 mg S/L) while reducing chemical dosing up to 30%. Copyright © 2018 Elsevier Ltd. All rights reserved.

Minimizing dose variation from the interplay effect in stereotactic radiation therapy using volumetric modulated arc therapy for lung cancer.

PubMed

Kubo, Kazuki; Monzen, Hajime; Tamura, Mikoto; Hirata, Makoto; Ishii, Kentaro; Okada, Wataru; Nakahara, Ryuta; Kishimoto, Shun; Kawamorita, Ryu; Nishimura, Yasumasa

2018-03-01

It is important to improve the magnitude of dose variation that is caused by the interplay effect. The aim of this study was to investigate the impact of the number of breaths (NBs) to the dose variation for VMAT-SBRT to lung cancer. Data on respiratory motion and multileaf collimator (MLC) sequence were collected from the cases of 30 patients who underwent radiotherapy with VMAT-SBRT for lung cancer. The NBs in the total irradiation time with VMAT and the maximum craniocaudal amplitude of the target were calculated. The MLC sequence complexity was evaluated using the modulation complexity score for VMAT (MCSv). Static and dynamic measurements were performed using a cylindrical respiratory motion phantom and a micro ionization chamber. The 1 standard deviation which were obtained from 10 dynamic measurements for each patient were defined as dose variation caused by the interplay effect. The dose distributions were also verified with radiochromic film to detect undesired hot and cold dose spot. Dose measurements were also performed with different NBs in the same plan for 16 patients in 30 patients. The correlations between dose variations and parameters assessed for each treatment plan including NBs, MCSv, the MCSv/amplitude quotient (TMMCSv), and the MCSv/amplitude quotient × NBs product (IVS) were evaluated. Dose variation was decreased with increasing NBs, and NBs of >40 times maintained the dose variation within 3% in 15 cases. The correlation between dose variation and IVS which were considered NBs was shown stronger (R 2  = 0.43, P < 0.05) than TMMCSv (R 2  = 0.32, P < 0.05). The NBs is an important factor to reduce the dose variation. The patient who breathes >40 times during irradiation of two partial arcs VMAT (i.e., NBs = 16 breaths per minute) may be suitable for VMAT-SBRT for lung cancer. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

A diamond detector in the dosimetry of high-energy electron and photon beams.

PubMed

Laub, W U; Kaulich, T W; Nüsslin, F

1999-09-01

A diamond detector type 60003 (PTW Freiburg) was examined for the purpose of dosimetry with 4-20 MeV electron beams and 4-25 MV photon beams. Results were compared with those obtained by using a Markus chamber for electron beams and an ionization chamber for photon beams. Dose distributions were measured in a water phantom with the detector connected to a Unidos electrometer (PTW Freiburg). After a pre-irradiation of about 5 Gy the diamond detector shows a stability in response which is better than that of an ionization chamber. The current of the diamond detector was measured under variation of photon beam dose rate between 0.1 and 7 Gy min(-1). Different FSDs were chosen. Furthermore the pulse repetition frequency and the depth of the detector were changed. The electron beam dose rate was varied between 0.23 and 4.6 Gy min(-1) by changing the pulse-repetition frequency. The response shows no energy dependence within the covered photon-beam energy range. Between 4 MeV and 18 MeV electron beam energy it shows only a small energy dependence of about 2%, as expected from theory. For smaller electron energies the response increases significantly and an influence of the contact material used for the diamond detector can be surmised. A slight sublinearity of the current and dose rate was found. Detector current and dose rate are related by the expression i alpha Ddelta, where i is the detector current, D is the dose rate and delta is a correction factor of approximately 0.963. Depth-dose curves of photon beams, measured with the diamond detector, show a slight overestimation compared with measurements with the ionization chamber. This overestimation is compensated for by the above correction term. The superior spatial resolution of the diamond detector leads to minor deviations between depth-dose curves of electron beams measured with a Markus chamber and a diamond detector.

Multiple anatomy optimization of accumulated dose

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

Watkins, W. Tyler, E-mail: watkinswt@virginia.edu; Siebers, Jeffrey V.; Moore, Joseph A.

Purpose: To investigate the potential advantages of multiple anatomy optimization (MAO) for lung cancer radiation therapy compared to the internal target volume (ITV) approach. Methods: MAO aims to optimize a single fluence to be delivered under free-breathing conditions such that the accumulated dose meets the plan objectives, where accumulated dose is defined as the sum of deformably mapped doses computed on each phase of a single four dimensional computed tomography (4DCT) dataset. Phantom and patient simulation studies were carried out to investigate potential advantages of MAO compared to ITV planning. Through simulated delivery of the ITV- and MAO-plans, target dosemore » variations were also investigated. Results: By optimizing the accumulated dose, MAO shows the potential to ensure dose to the moving target meets plan objectives while simultaneously reducing dose to organs at risk (OARs) compared with ITV planning. While consistently superior to the ITV approach, MAO resulted in equivalent OAR dosimetry at planning objective dose levels to within 2% volume in 14/30 plans and to within 3% volume in 19/30 plans for each lung V20, esophagus V25, and heart V30. Despite large variations in per-fraction respiratory phase weights in simulated deliveries at high dose rates (e.g., treating 4/10 phases during single fraction beams) the cumulative clinical target volume (CTV) dose after 30 fractions and per-fraction dose were constant independent of planning technique. In one case considered, however, per-phase CTV dose varied from 74% to 117% of prescription implying the level of ITV-dose heterogeneity may not be appropriate with conventional, free-breathing delivery. Conclusions: MAO incorporates 4DCT information in an optimized dose distribution and can achieve a superior plan in terms of accumulated dose to the moving target and OAR sparing compared to ITV-plans. An appropriate level of dose heterogeneity in MAO plans must be further investigated.« less

Environmental radioactivity in the UK: the airborne geophysical view of dose rate estimates.

PubMed

Beamish, David

2014-12-01

This study considers UK airborne gamma-ray data obtained through a series of high spatial resolution, low altitude surveys over the past decade. The ground concentrations of the naturally occurring radionuclides Potassium, Thorium and Uranium are converted to air absorbed dose rates and these are used to assess terrestrial exposure levels from both natural and technologically enhanced sources. The high resolution airborne information is also assessed alongside existing knowledge from soil sampling and ground-based measurements of exposure levels. The surveys have sampled an extensive number of the UK lithological bedrock formations and the statistical information provides examples of low dose rate lithologies (the formations that characterise much of southern England) to the highest sustained values associated with granitic terrains. The maximum dose rates (e.g. >300 nGy h(-1)) encountered across the sampled granitic terrains are found to vary by a factor of 2. Excluding granitic terrains, the most spatially extensive dose rates (>50 nGy h(-1)) are found in association with the Mercia Mudstone Group (Triassic argillaceous mudstones) of eastern England. Geological associations between high dose rate and high radon values are also noted. Recent studies of the datasets have revealed the extent of source rock (i.e. bedrock) flux attenuation by soil moisture in conjunction with the density and porosity of the temperate latitude soils found in the UK. The presence or absence of soil cover (and associated presence or absence of attenuation) appears to account for a range of localised variations in the exposure levels encountered. The hypothesis is supported by a study of an extensive combined data set of dose rates obtained from soil sampling and by airborne geophysical survey. With no attenuation factors applied, except those intrinsic to the airborne estimates, a bias to high values of between 10 and 15 nGy h(-1) is observed in the soil data. A wide range of technologically enhanced, localised contributions to dose rate values are also apparent in the data sets. Two detailed examples are provided that reveal the detectability of site-scale environmental impacts due to former industrial activities and the high dose values (>500 nGy h(-1)) that are associated with former, small-scale Uranium mining operations. Copyright © 2014. Published by Elsevier Ltd.

[Determination of radioactivity by smartphones].

PubMed

Hartmann, H; Freudenberg, R; Andreeff, M; Kotzerke, J

2013-01-01

The interest in the detection of radioactive materials has strongly increased after the accident in the nuclear power plant Fukushima and has led to a bottleneck of suitable measuring instruments. Smartphones equipped with a commercially available software tool could be used for dose rate measurements following a calibration according to the specific camera module. We examined whether such measurements provide reliable data for typical activities and radionuclides in nuclear medicine. For the nuclides 99mTc (10 - 1000 MBq), 131I (3.7 - 1800 MBq, therapy capsule) and 68Ga (50 - 600 MBq) radioactivity with defined geometry in different distances was measured. The smartphones Milestone Droid 1 (Motorola) and HTC Desire (HTC Corporation) were compared with the standard instruments AD6 (automess) and DoseGUARD (AEA Technology). Measurements with the smartphones and the other devices show a good agreement: linear signal increase with rising activity and dose rate. The long time measurement (131I, 729 MBq, 0.5 m, 60 min) demonstrates a considerably higher variation (by 20%) of the measured smartphone data values compared with the AD6. For low dose rates (< 1 µGy/h), the sensitivity decreases so that measurements of e. g. the natural radiation exposure do not lead to valid results. The calibration of the camera responsivity for the smartphone has a big influence on the results caused by the small detector surface of the camera semiconductor. With commercial software the camera module of a smartphone can be used for the measurement of radioactivity. Dose rates resulting from typical nuclear medicine procedures can be measured reliably (e. g., dismissal dose after radioiodine therapy). The signal shows a high correlation to measured values of conventional dose measurement devices.

TU-CD-304-04: Scanning Field Total Body Irradiation Using Dynamic Arc with Variable Dose Rate and Gantry Speed

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

Yi, B; Xu, H; Mutaf, Y

2015-06-15

Purpose: Enable a scanning field total body irradiation (TBI) technique, using dynamic arcs, which is biologically equivalent to a moving couch TBI. Methods: Patient is treated slightly above the floor and the treatment field scans across the patient by a moving gantry. MLC positions change during gantry motion to keep same field opening at the level of the treatment plane (170 cm). This is done to mimic the same geometry as the moving couch TBI technique which has been used in our institution for over 10 years. The dose rate and the gantry speed are determined considering a constant speedmore » of the moving field, variations in SSD and slanted depths resulting from oblique gantry angles. An Eclipse (Varian) planning system is commissioned to accommodate the extended SSD. The dosimetric foundations of the technique have been thoroughly investigated using phantom measurements. Results: Dose uniformity better than 2% across 180 cm length at 10cm depth is achieved by moving the gantry from −55 to +55 deg. Treatment range can be extended by increasing gantry range. No device such as a gravity-oriented compensator is needed to achieve a uniform dose. It is feasible to modify the dose distribution by adjusting the dose rate at each gantry angle to compensate for body thickness differences. Total treatment time for 2 Gy AP/PA fields is 40–50 minutes excluding patient set up time, at the machine dose rate of 100 MU/min. Conclusion: This novel yet transportable moving field technique enables TBI treatment in a small treatment room with less program development preparation than other techniques. Treatment length can be extended per need, and. MLC-based thickness compensation and partial lung blocking are also possible.« less

Patient-Specific QA of Spot-Scanning Proton Beams using Radiochromic Film.

PubMed

Chan, Maria F; Chen, Chin-Cheng; Shi, Chengyu; Li, Jingdong; Tang, Xiaoli; Li, Xiang; Mah, Dennis

2017-05-01

Radiochromic film for spot-scanning QA provides high spatial resolution and efficiency gains from one-shot irradiation for multiple depths. However, calibration can be a tedious procedure which may limit widespread use. Moreover, since there may be an energy dependence, which manifests as a depth dependence, this may require additional measurements for each patient. We present a one-scan protocol to simplify the procedure. A calibration using an EBT3 film, exposed by a 6-level step-wedge plan on a Proteus ® PLUS proton system (IBA, Belgium), was performed at depths of 18, 20, 24cm using Plastic Water ® (CIRS, Norfolk, VA). The calibration doses ranged from 65-250 cGy(RBE) (relative biological effectiveness) for proton energies of 170-200 MeV. A clinical prostate+nodes plan was used for validation. The planar doses at selected depths were measured with EBT3 films and analyzed using One-scan protocol (one-scan digitization of QA film and at least one film exposed to a known dose). The gamma passing rates, dose-difference maps, and profiles of 2D planar doses measured with EBT3 film and IBA MatriXX-PT, versus the RayStation TPS calculations were analyzed and compared. The EBT3 film measurement results matched well with the TPS calculation data with an average passing rate of ~95% for 2%/2mm and slightly lower passing rates were obtained from an ion chamber array detector. We were able to demonstrate that the use of a proton step-wedge provided clinically acceptable results and minimized variations between film-scanner orientation, inter-scan, and scanning conditions. Furthermore, for relative dosimetry (calibration is not done at the time of experiment) it could be derived from no more than two films exposed to known doses (one could be zero) for rescaling the master calibration curve at each depth. The sensitivity of the calibration to depth variations has been explored. One-scan protocol results appear to be comparable to that of the ion chamber array detector. The use of a proton step-wedge for calibration of EBT3 film potentially increases efficiency in patient-specific QA of proton beams.

SU-F-T-173: One-Scan Protocol: Verifying the Delivery of Spot-Scanning Proton Beam

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

Chan, M; Li, J; Chen, C

Purpose: Radiochromic film for spot-scanning QA provides high spatial resolution and efficiency gains from one-shot irradiation for multiple depths. However, calibration can be a tedious procedure which may limit widespread use. Moreover, since there may be an energy dependence, which manifests as a depth dependence, this may require additional measurements for each patient. We present a one-scan protocol to simplify the procedure. Methods: We performed the calibration using an EBT3 film at depths of 18, 20, 24cm of Plastic Water exposed by a 6-level step-wedge plan on a Proteus Plus proton system (IBA, Belgium). The calibration doses ranged 65–250 cGy(RBE)more » for proton energies of 170–200MeV. A clinical prostate+nodes plan was used for validation. The planar doses at selected depths were measured with EBT3 films and analyzed using one-scan protocol (one-scan digitization of QA film and at least one film exposed to known dose). The Gamma passing rates, dose-difference maps, and profiles of 2D planar doses measured with EBT3 film, IBA MatriXX PT, versus TPS calculations were analyzed and compared. Results: The EBT3 film measurement results matched well with the TPS calculation data with an average passing rate of ∼95% for 2%/2mm and slightly lower passing rates were obtained from an ion chamber array detector. We were able to demonstrate that the use of a proton step-wedge provided clinically acceptable results and minimized variations between film-scanner orientation, inter-scan, and scanning conditions. Furthermore, it could be derived from no more than two films exposed to known doses (one could be zero) for rescaling the master calibration curve at each depth. Conclusion: The use of a proton step-wedge for calibration of EBT3 film increases efficiency. The sensitivity of the calibration to depth variations has been explored. One-scan protocol results appear to be comparable to that of the ion chamber array detector. One author has a research grant from Ashland Inc., the manufacturer of the GafChromic film.« less

Effect of low-dose scopolamine on autonomic control of the heart

NASA Technical Reports Server (NTRS)

Raeder, E. A.; Stys, A.; Cohen, R. J.

1997-01-01

Background: In low doses, scopolamine paradoxically enhances parasympathetic outflow to the heart. The mechanisms which mediate this action are not fully understood. Moreover, there are conflicting data regarding the potential role of sympathetic activity. This study in 17 healthy individuals was designed to characterize the influence of low dose transdermal scopolamine on the gain of the baroreflex and respiratory heart rate reflex and to determine the role of sympathetic activity. Methods: The effect of scopolamine was analyzed in the time and frequency domain by computing heart rate variability indices. The gains of the respiratory heart rate reflex and the baroreflex were estimated simultaneously by means of a cardiovascular system identification approach using an optimized autoregressive moving average algorithm. Measurements were repeated in the upright posture to assess the influence of enhanced sympathetic activity. In six subjects ambulatory ECGs were recorded to determine whether there are diurnal variations of the effect of scopolamine. Results: Scopolamine enhances vagal modulation of heart rate through both the respiratory-heart rate reflex and the baroreflex, as the gains of both were augmented by the drug in the supine and in the upright postures. Conclusions: Scopolamine increases parasympathetic cardiac control by augmenting the gain of the respiratory-heart rate and baroreflex. This action is not attenuated in the upright posture when sympathetic tone is increased.

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

SU-E-J-274: Responses of Medulloblastoma Cells to Radiation Dosimetric Parameters in Intensity-Modulated Radiation Therapy

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

Park, J; Molecular Imaging Program at Stanford, Stanford, CA; Bio-X Program, Stanford, CA

2015-06-15

Purpose: To evaluate radiation responses of the medulloblastoma cell line Daoy in intensity-modulated radiation therapy (IMRT), quantitative variations to variable radiation dosimetic parameters were tracked by bioluminescent images (BLIs). Methods: The luciferase and green fluorescent protein positive Daoy cells were cultured on dishes. The medulloblastoma cells irradiated to different dose rate, interval of fractionated doses, field margin and misalignment, and dose uniformity in IMRT were monitored using bioluminescent images. The cultured cells were placed into a dedicated acrylic phantom to deliver intensity-modulated fluences and calculate accurate predicted dose distribution. The radiation with dose rate from 0.5 Gy/min to 15 Gy/minmore » was irradiated by adjusting monitor unit per minute and source-to-surface distances. The intervals of fractionated dose delivery were changed considering the repair time of double strand breaks (DSB) revealed by straining of gamma-H2AX.The effect of non-uniform doses on the cells were visualized by registering dose distributions and BLIs. The viability according to dosimetric parameters was correlated with bioluminescent intensities for cross-check of radiation responses. Results: The DSB and cell responses due to the first fractionated dose delivery significantly affected final tumor control rather than other parameters. The missing tumor volumes due to the smaller field margin than the tumor periphery or field misalignment caused relapse of cell responses on BLIs. The dose rate and gradient had effect on initial responses but could not bring out the distinguishable killing effect on cancer cells. Conclusion: Visualized and quantified bioluminescent images were useful to correlate the dose distributions with spatial radiation effects on cells. This would derive the effective combination of dose delivery parameters and fractionation. Radiation responses in particular IMRT configuration could be reflected to image based-dose re-optimization.« less

Radiation measurements aboard the fourth Gemini flight.

PubMed

Janni, J F; Schneider, M F

1967-01-01

Two special tissue-equivalent ionization chambers and 5 highly sensitive passive dosimetry packages were flown aboard the recent Gemini 4 flight for the purpose of obtaining precise values of instantaneous dose rate, accumulated dose. and shielding effectiveness. This experiment marked the first time that well-defined tissue dose and radiation survey measurements have been carried out in manned spaceflight operations. Since all measurements were accomplished under normal spacecraft environmental conditions, the biological dose resulted primarily from trapped inner Van Allen Belt radiation encountered by the spacecraft in the South Atlantic Anomaly. The experiment determined the particle type, ionizing and penetrating power, and variation with time and position within the Gemini spacecraft. Measured dose rates ranged from 100 mrad/hr for passes penetrating deeply into the South Atlantic Anomaly to less than 0.1 mrad/hr from lower latitude cosmic radiation. The accumulated tissue dose measured by the active ionization chambers, shielded by 0.4 gm/cm2 for the 4-day mission, was 82 mrad. Since the 5 passive dosimetry packages were each located in different positions within the spacecraft, the total mission surface dose measured by these detectors varied from 73 to 27 mrad, depending upon location and shielding. The particles within the spacecraft were recorded in nuclear emulsion, which established that over 90% of the tissue dose was attributable to penetrating protons. This experiment indicates that the radiation environment under shielded conditions at Gemini altitudes was not hazardous.

4D radiobiological modelling of the interplay effect in conventionally and hypofractionated lung tumour IMRT.

PubMed

Selvaraj, J; Uzan, J; Baker, C; Nahum, A

2015-01-01

To study the impact of the interplay between respiration-induced tumour motion and multileaf collimator leaf movements in intensity-modulated radiotherapy (IMRT) as a function of number of fractions, dose rate on population mean tumour control probability ([Formula: see text]) using an in-house developed dose model. Delivered dose was accumulated in a voxel-by-voxel basis inclusive of tumour motion over the course of treatment. The effect of interplay on dose and [Formula: see text] was studied for conventionally and hypofractionated treatments using digital imaging and communications in medicine data sets. Moreover, the effect of dose rate on interplay was also studied for single-fraction treatments. Simulations were repeated several times to obtain [Formula: see text] for each plan. The average variation observed in mean dose to the target volumes were -0.76% ± 0.36% for the 20-fraction treatment and -0.26% ± 0.68% and -1.05% ± 0.98% for the three- and single-fraction treatments, respectively. For the 20-fraction treatment, the drop in [Formula: see text] was -1.05% ± 0.39%, whereas for the three- and single-fraction treatments, it was -2.80% ± 1.68% and -4.00% ± 2.84%, respectively. By reducing the dose rate from 600 to 300 MU min(-1) for the single-fraction treatments, the drop in [Formula: see text] was reduced by approximately 1.5%. The effect of interplay on [Formula: see text] is negligible for conventionally fractionated treatments, whereas considerable drop in [Formula: see text] is observed for the three- and single-fraction treatments. Reduced dose rate could be used in hypofractionated treatments to reduce the interplay effect. A novel in silico dose model is presented to determine the impact of interplay effect in IMRT treatments on [Formula: see text].

4D radiobiological modelling of the interplay effect in conventionally and hypofractionated lung tumour IMRT

PubMed Central

Uzan, J; Baker, C; Nahum, A

2015-01-01

Objective: To study the impact of the interplay between respiration-induced tumour motion and multileaf collimator leaf movements in intensity-modulated radiotherapy (IMRT) as a function of number of fractions, dose rate on population mean tumour control probability () using an in-house developed dose model. Methods: Delivered dose was accumulated in a voxel-by-voxel basis inclusive of tumour motion over the course of treatment. The effect of interplay on dose and was studied for conventionally and hypofractionated treatments using digital imaging and communications in medicine data sets. Moreover, the effect of dose rate on interplay was also studied for single-fraction treatments. Simulations were repeated several times to obtain for each plan. Results: The average variation observed in mean dose to the target volumes were −0.76% ± 0.36% for the 20-fraction treatment and −0.26% ± 0.68% and −1.05% ± 0.98% for the three- and single-fraction treatments, respectively. For the 20-fraction treatment, the drop in was −1.05% ± 0.39%, whereas for the three- and single-fraction treatments, it was −2.80% ± 1.68% and −4.00% ± 2.84%, respectively. By reducing the dose rate from 600 to 300 MU min−1 for the single-fraction treatments, the drop in was reduced by approximately 1.5%. Conclusion: The effect of interplay on is negligible for conventionally fractionated treatments, whereas considerable drop in is observed for the three- and single-fraction treatments. Reduced dose rate could be used in hypofractionated treatments to reduce the interplay effect. Advances in knowledge: A novel in silico dose model is presented to determine the impact of interplay effect in IMRT treatments on . PMID:25251400

Comparison of particulate matter dose and acute heart rate variability response in cyclists, pedestrians, bus and train passengers.

PubMed

Nyhan, Marguerite; McNabola, Aonghus; Misstear, Bruce

2014-01-15

Exposure to airborne particulate matter (PM) has been linked to cardiovascular morbidity and mortality. Heart rate variability (HRV) is a measure of the change in cardiac autonomic function, and consistent links between PM exposure and decreased HRV have been documented in studies. This study quantitatively assesses the acute relative variation of HRV with predicted PM dose in the lungs of commuters. Personal PM exposure, HR and HRV were monitored in 32 young healthy cyclists, pedestrians, bus and train passengers. Inhaled and lung deposited PM doses were determined using a numerical model of the human respiratory tract which accounted for varying ventilation rates between subjects and during commutes. Linear mixed models were used to examine air pollution dose and HRV response relationships in 122 commutes sampled. Elevated PM2.5 and PM10 inhaled and lung deposited doses were significantly (p<0.05) associated with decreased HRV indices. Percent declines in SDNN (standard deviation of normal RR intervals) relative to resting, due to an inter-quartile range increase in PM10 lung deposited dose were stronger in cyclists (-6.4%, 95% CI: -11.7, -1.3) and pedestrians (-5.8%, 95% CI: -11.3, -0.5), in comparison to bus (-3.2%, 95% CI: -6.4, -0.1) and train (-1.8%, -7.5, 3.8) passengers. A similar trend was observed in the case of PM2.5 lung deposited dose and results for rMSSD (the square root of the squared differences of successive normal RR intervals) followed similar trends to SDNN. Inhaled and lung deposited doses accounting for varying ventilation rates between modes, individuals and during commutes have been neglected in other studies relating PM to HRV. The findings here indicate that exercise whilst commuting has an influence on inhaled PM and PM lung deposited dose, and these were significantly associated with acute declines in HRV, especially in pedestrians and cyclists. © 2013.

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

Ma, R; Zhu, X; Li, S

Purpose: High Dose Rate (HDR) brachytherapy forward planning is principally an iterative process; hence, plan quality is affected by planners’ experiences and limited planning time. Thus, this may lead to sporadic errors and inconsistencies in planning. A statistical tool based on previous approved clinical treatment plans would help to maintain the consistency of planning quality and improve the efficiency of second checking. Methods: An independent dose calculation tool was developed from commercial software. Thirty-three previously approved cervical HDR plans with the same prescription dose (550cGy), applicator type, and treatment protocol were examined, and ICRU defined reference point doses (bladder, vaginalmore » mucosa, rectum, and points A/B) along with dwell times were collected. Dose calculation tool then calculated appropriate range with a 95% confidence interval for each parameter obtained, which would be used as the benchmark for evaluation of those parameters in future HDR treatment plans. Model quality was verified using five randomly selected approved plans from the same dataset. Results: Dose variations appears to be larger at the reference point of bladder and mucosa as compared with rectum. Most reference point doses from verification plans fell between the predicted range, except the doses of two points of rectum and two points of reference position A (owing to rectal anatomical variations & clinical adjustment in prescription points, respectively). Similar results were obtained for tandem and ring dwell times despite relatively larger uncertainties. Conclusion: This statistical tool provides an insight into clinically acceptable range of cervical HDR plans, which could be useful in plan checking and identifying potential planning errors, thus improving the consistency of plan quality.« less

Prediction of the solar modulation of galactic cosmic rays and radiation dose of aircrews up to the solar cycle 26

NASA Astrophysics Data System (ADS)

Miyake, S.; Kataoka, R.; Sato, T.

2016-12-01

The solar modulation of galactic cosmic rays (GCRs), which is the variation of the terrestrial GCR flux caused by the heliospheric environmental change, is basically anti-correlated with the solar activity with so-called 11-year periodicity. In the current weak solar cycle 24, we expect that the flux of GCRs is getting higher than that in the previous solar cycles, leading to the increase in the radiation exposure in the space and atmosphere. In order to quantitatively evaluate the possible solar modulation of GCRs and resultant radiation exposure at flight altitude during the solar cycles 24, 25, and 26, we have developed the time-dependent and three-dimensional model of the solar modulation of GCRs. Our model can give the flux of GCRs anywhere in the heliosphere by assuming the variation of the solar wind velocity, the strength of the interplanetary magnetic field, and its tilt angle. We solve the curvature and gradient drift motion of GCRs in the heliospheric magnetic field, and therefore reproduce the 22-year variation of the solar modulation of GCRs. It is quantitatively confirmed that our model reproduces the energy spectra observed by BESS and PAMELA. We then calculate the variation of the GCR energy spectra during the solar cycles 24, 25, and 26, by extrapolating the solar wind parameters and tilt angle. We also calculate the neutron monitor counting rate and the radiation dose of aircrews at flight altitude, by the air-shower simulation performed by PHITS (Particle and Heavy Ion Transport code System). In this presentation, we report the quantitative forecast values of the solar modulation of GCRs, neutron monitor counting rate, and the radiation dose at flight altitude up to the cycle 26, including the discussion of the charge sign dependence on those results.

Radon Release and Its Simulated Effect on Radiation Doses.

PubMed

Orabi, Momen

2017-03-01

One of the main factors that affect the uncertainty in calculating the gamma-radiation absorbed dose rate inside a room is the variation in the degree of secular equilibrium of the considered radioactive series. A component of this factor, considered in this paper, is the release of radon (Rn) from building materials to the living space of the room. This release takes place through different steps. These steps are represented and mathematically formulated. The diffusion of radon inside the material is described by Fick's second law. Some of the factors affecting the radon release rate (e.g. covering walls, moisture, structure of the building materials, etc.) are discussed. This scheme is used to study the impact of radon release on the gamma-radiation absorbed dose rate inside a room. The investigation is carried out by exploiting the MCNP simulation software. Different building materials are considered with different radon release rates. Special care is given to Rn due to its relatively higher half-life and higher indoor concentration than the other radon isotopes. The results of the presented model show that the radon release is of a significant impact in some building materials.

Daily and Long Term Variations of Out-Door Gamma Dose Rate in Khorasan Province, Iran

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

Toossi, M. T. Bahreyni; Bayani, SH.

2008-08-07

In Iran before 1996, only a few hot spots had been identified, no systematic study had been envisaged. Since then preparation of out-door environmental gamma radiation map of Iran was defined as a long term goal in our center, at the same time simultaneous monitoring of outdoor gamma level in Khorasan was also proposed. A Rados area monitoring system (AAM-90) including 10 intelligent RD-02 detector and all associated components were purchased. From 2003 gradually seven stations have been setup in Khorasan. For all seven stations monthly average and one hour daily average on four time intervals have been computed. Statisticallymore » no significant differences have been observed. This is also true for monthly averages. The overall average dose rate for present seven stations varies from 0.11 {mu}Sv{center_dot}h{sup -1} for Ferdows, to 0.04 {mu}Sv{center_dot}h{sup -1} for Dargaz. Based on our data, 50 minutes sample in any time interval is an accurate sample size to estimate out door Gamma dose rate.« less

Variations in corticosteroid/anesthetic injections for painful shoulder conditions: comparisons among orthopaedic surgeons, rheumatologists, and physical medicine and primary-care physicians.

PubMed

Skedros, John G; Hunt, Kenneth J; Pitts, Todd C

2007-07-06

Variations in corticosteroid/anesthetic doses for injecting shoulder conditions were examined among orthopaedic surgeons, rheumatologists, and primary-care sports medicine (PCSMs) and physical medicine and rehabilitation (PMRs) physicians to provide data needed for documenting inter-group differences for establishing uniform injection guidelines. 264 surveys, sent to these physicians in our tri-state area of the western United States, addressed corticosteroid/anesthetic doses and types used for subacromial impingement, degenerative glenohumeral and acromioclavicular arthritis, biceps tendinitis, and peri-scapular trigger points. They were asked about preferences regarding: 1) fluorinated vs. non-fluorinated corticosteroids, 2) acetate vs. phosphate types, 3) patient age, and 4) adjustments for special considerations including young athletes and diabetics. 169 (64% response rate, RR) surveys were returned: 105/163 orthopaedic surgeons (64%RR), 44/77 PCSMs/PMRs (57%RR), 20/24 rheumatologists (83%RR). Although corticosteroid doses do not differ significantly between specialties (p > 0.3), anesthetic volumes show broad variations, with surgeons using larger volumes. Although 29% of PCSMs/PMRs, 44% rheumatologists, and 41% surgeons exceed "recommended" doses for the acromioclavicular joint, >98% were within recommendations for the subacromial bursa and glenohumeral joint. Depo-Medrol(R) (methylprednisolone acetate) and Kenalog(R) (triamcinolone acetonide) are most commonly used. More rheumatologists (80%) were aware that there are acetate and phosphate types of corticosteroids as compared to PCSMs/PMRs (76%) and orthopaedists (60%). However, relatively fewer rheumatologists (25%) than PCSMs/PMRs (32%) or orthopaedists (32%) knew that phosphate types are more soluble. Fluorinated corticosteroids, which can be deleterious to soft tissues, were used with these frequencies for the biceps sheath: 17% rheumatologists, 8% PCSMs/PMRs, 37% orthopaedists. Nearly 85% use the same non-fluorinated corticosteroid for all injections; <10% make adjustments for diabetic patients. Variations between specialists in anesthetic doses suggest that surgeons (who use significantly larger volumes) emphasize determining the percentage of pain attributable to the injected region. Alternatively, this might reflect a more profound knowledge that non-surgeons specialists have of the potentially adverse cardiovascular effects of these agents. Variations between these specialists in corticosteroid/anesthetic doses and/or types, and their use in some special situations (e.g., diabetics), bespeak the need for additional investigations aimed at establishing uniform injection guidelines, and for identifying knowledge deficiencies that warrant advanced education.

Variations in corticosteroid/anesthetic injections for painful shoulder conditions: comparisons among orthopaedic surgeons, rheumatologists, and physical medicine and primary-care physicians

PubMed Central

Skedros, John G; Hunt, Kenneth J; Pitts, Todd C

2007-01-01

Background Variations in corticosteroid/anesthetic doses for injecting shoulder conditions were examined among orthopaedic surgeons, rheumatologists, and primary-care sports medicine (PCSMs) and physical medicine and rehabilitation (PMRs) physicians to provide data needed for documenting inter-group differences for establishing uniform injection guidelines. Methods 264 surveys, sent to these physicians in our tri-state area of the western United States, addressed corticosteroid/anesthetic doses and types used for subacromial impingement, degenerative glenohumeral and acromioclavicular arthritis, biceps tendinitis, and peri-scapular trigger points. They were asked about preferences regarding: 1) fluorinated vs. non-fluorinated corticosteroids, 2) acetate vs. phosphate types, 3) patient age, and 4) adjustments for special considerations including young athletes and diabetics. Results 169 (64% response rate, RR) surveys were returned: 105/163 orthopaedic surgeons (64%RR), 44/77 PCSMs/PMRs (57%RR), 20/24 rheumatologists (83%RR). Although corticosteroid doses do not differ significantly between specialties (p > 0.3), anesthetic volumes show broad variations, with surgeons using larger volumes. Although 29% of PCSMs/PMRs, 44% rheumatologists, and 41% surgeons exceed "recommended" doses for the acromioclavicular joint, >98% were within recommendations for the subacromial bursa and glenohumeral joint. Depo-Medrol® (methylprednisolone acetate) and Kenalog® (triamcinolone acetonide) are most commonly used. More rheumatologists (80%) were aware that there are acetate and phosphate types of corticosteroids as compared to PCSMs/PMRs (76%) and orthopaedists (60%). However, relatively fewer rheumatologists (25%) than PCSMs/PMRs (32%) or orthopaedists (32%) knew that phosphate types are more soluble. Fluorinated corticosteroids, which can be deleterious to soft tissues, were used with these frequencies for the biceps sheath: 17% rheumatologists, 8% PCSMs/PMRs, 37% orthopaedists. Nearly 85% use the same non-fluorinated corticosteroid for all injections; <10% make adjustments for diabetic patients. Conclusion Variations between specialists in anesthetic doses suggest that surgeons (who use significantly larger volumes) emphasize determining the percentage of pain attributable to the injected region. Alternatively, this might reflect a more profound knowledge that non-surgeons specialists have of the potentially adverse cardiovascular effects of these agents. Variations between these specialists in corticosteroid/anesthetic doses and/or types, and their use in some special situations (e.g., diabetics), bespeak the need for additional investigations aimed at establishing uniform injection guidelines, and for identifying knowledge deficiencies that warrant advanced education. PMID:17617900

SU-E-I-24: Method for CT Automatic Exposure Control Verification

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

Gracia, M; Olasolo, J; Martin, M

Purpose: Design of a phantom and a simple method for the automatic exposure control (AEC) verification in CT. This verification is included in the computed tomography (CT) Spanish Quality Assurance Protocol. Methods: The phantom design is made from the head and the body phantom used for the CTDI measurement and PMMA plates (35×35 cm2) of 10 cm thickness. Thereby, three different thicknesses along the longitudinal axis are obtained which permit to evaluate the longitudinal AEC performance. Otherwise, the existent asymmetry in the PMMA layers helps to assess angular and 3D AEC operation.Recent acquisition in our hospital (August 2014) of Nomexmore » electrometer (PTW), together with the 10 cm pencil ionization chamber, led to register dose rate as a function of time. Measurements with this chamber fixed at 0° and 90° on the gantry where made on five multidetector-CTs from principal manufacturers. Results: Individual analysis of measurements shows dose rate variation as a function of phantom thickness. The comparative analysis shows that dose rate is kept constant in the head and neck phantom while the PMMA phantom exhibits an abrupt variation between both results, being greater results at 90° as the thickness of the phantom is 3.5 times larger than in the perpendicular direction. Conclusion: Proposed method is simple, quick and reproducible. Results obtained let a qualitative evaluation of the AEC and they are consistent with the expected behavior. A line of future development is to quantitatively study the intensity modulation and parameters of image quality, and a possible comparative study between different manufacturers.« less

An Interlaboratory Comparison of Dosimetry for a Multi-institutional Radiobiological

PubMed Central

Seed, TM; Xiao, S; Manley, N; Nikolich-Zugich, J; Pugh, J; van den Brink, M; Hirabayashi, Y; Yasutomo, K; Iwama, A; Koyasu, S; Shterev, I; Sempowski, G; Macchiarini, F; Nakachi, K; Kunugi, KC; Hammer, CG; DeWerd, LA

2016-01-01

Purpose An interlaboratory comparison of radiation dosimetry was conducted to determine the accuracy of doses being used experimentally for animal exposures within a large multi-institutional research project. The background and approach to this effort are described and discussed in terms of basic findings, problems and solutions. Methods Dosimetry tests were carried out utilizing optically stimulated luminescence (OSL) dosimeters embedded midline into mouse carcasses and thermal luminescence dosimeters (TLD) embedded midline into acrylic phantoms. Results The effort demonstrated that the majority (4/7) of the laboratories was able to deliver sufficiently accurate exposures having maximum dosing errors of ≤ 5%. Comparable rates of ‘dosimetric compliance’ were noted between OSL- and TLD-based tests. Data analysis showed a highly linear relationship between ‘measured’ and ‘target’ doses, with errors falling largely between 0–20%. Outliers were most notable for OSL-based tests, while multiple tests by ‘non-compliant’ laboratories using orthovoltage x-rays contributed heavily to the wide variation in dosing errors. Conclusions For the dosimetrically non-compliant laboratories, the relatively high rates of dosing errors were problematic, potentially compromising the quality of ongoing radiobiological research. This dosimetry effort proved to be instructive in establishing rigorous reviews of basic dosimetry protocols ensuring that dosing errors were minimized. PMID:26857121

An interlaboratory comparison of dosimetry for a multi-institutional radiobiological research project: Observations, problems, solutions and lessons learned.

PubMed

Seed, Thomas M; Xiao, Shiyun; Manley, Nancy; Nikolich-Zugich, Janko; Pugh, Jason; Van den Brink, Marcel; Hirabayashi, Yoko; Yasutomo, Koji; Iwama, Atsushi; Koyasu, Shigeo; Shterev, Ivo; Sempowski, Gregory; Macchiarini, Francesca; Nakachi, Kei; Kunugi, Keith C; Hammer, Clifford G; Dewerd, Lawrence A

2016-01-01

An interlaboratory comparison of radiation dosimetry was conducted to determine the accuracy of doses being used experimentally for animal exposures within a large multi-institutional research project. The background and approach to this effort are described and discussed in terms of basic findings, problems and solutions. Dosimetry tests were carried out utilizing optically stimulated luminescence (OSL) dosimeters embedded midline into mouse carcasses and thermal luminescence dosimeters (TLD) embedded midline into acrylic phantoms. The effort demonstrated that the majority (4/7) of the laboratories was able to deliver sufficiently accurate exposures having maximum dosing errors of ≤5%. Comparable rates of 'dosimetric compliance' were noted between OSL- and TLD-based tests. Data analysis showed a highly linear relationship between 'measured' and 'target' doses, with errors falling largely between 0 and 20%. Outliers were most notable for OSL-based tests, while multiple tests by 'non-compliant' laboratories using orthovoltage X-rays contributed heavily to the wide variation in dosing errors. For the dosimetrically non-compliant laboratories, the relatively high rates of dosing errors were problematic, potentially compromising the quality of ongoing radiobiological research. This dosimetry effort proved to be instructive in establishing rigorous reviews of basic dosimetry protocols ensuring that dosing errors were minimized.

Seasonal and diurnal variations in Martian surface ultraviolet irradiation: biological and chemical implications for the Martian regolith

NASA Astrophysics Data System (ADS)

Patel, M. R.; Bérces, A.; Kolb, C.; Lammer, H.; Rettberg, P.; Zarnecki, J. C.; Selsis, F.

2003-01-01

The issue of the variation of the surface ultraviolet (UV) environment on Mars was investigated with particular emphasis being placed on the interpretation of data in a biological context. A UV model has been developed to yield the surface UV irradiance at any time and place over the Martian year. Seasonal and diurnal variations were calculated and dose rates evaluated. Biological interpretation of UV doses is performed through the calculation of DNA damage effects upon phage T7 and Uracil, used as examples for biological dosimeters. A solar UV "hotspot" was revealed towards perihelion in the southern hemisphere, with a significant damaging effect upon these species. Diurnal profiles of UV irradiance are also seen to vary markedly between aphelion and perihelion. The effect of UV dose is also discussed in terms of the chemical environment of the Martian regolith, since UV irradiance can reach high enough levels so as to have a significant effect upon the soil chemistry. We show, by assuming that H2O is the main source of hydrogen in the Martian atmosphere, that the stoichiometrically desirable ratio of 2:1 for atmospheric H and O loss rates to space are not maintained and at present the ratio is about 20:1. A large planetary oxygen surface sink is therefore necessary, in contrast with escape to space. This surface oxygen sink has important implications for the oxidation potential and the toxicology of the Martian soil. UV-induced adsorption of O_{2}^{-} super-radicals plays an important role in the oxidative environment of the Martian surface, and the biologically damaging areas found in this study are also shown to be regions of high subsurface oxidation. Furthermore, we briefly cover the astrobiological implications for landing sites that are planned for future Mars missions

Change in Practice over Four Decades in the Management of Graves' Disease in Scotland.

PubMed

Smith, D M; Dutta, S; Ahmed, F; Thaha, M A

2016-01-01

There is continuing debate on the optimal treatment for Grave's thyrotoxicosis with a resultant variation in clinical practice. The present study aimed to ascertain changes in practice in the treatment of Grave's thyrotoxicosis in Tayside, Scotland, over the past four decades. Methods. The "Scottish automated follow-up register" (SAFUR) was queried to identify all patients treated for Grave's thyrotoxicosis from 1968 to 2007 inclusive. Patients were divided into 4 groups (Groups A to D) according to the decades. Demographic profile, treatment modalities, radioactive iodine (RAI) dose, and recurrence rates were studied and outcomes were compared by χ (2) test and ANOVA using SPSS v15.0. A p value of < 0.05 was considered significant. Results. Altogether, 3737 patients were diagnosed with Grave's thyrotoxicosis over the 4 decades. Use of RAI has increased from 43.1% in Group A to 68% in Group D (p < 0.001). The dose of RAI has increased (p < 0.001) and there has been a reduction in recurrence rate with higher dose of RAI. Surgical intervention rates decreased from 55.3% to 12.3% (p < 0.001) over time. Conclusions. Analysis of a large dataset of patients with Grave's thyrotoxicosis suggests increasing use of RAI as the preferred first line of treatment. Furthermore, using a single higher dose of RAI and adoption of total thyroidectomy have decreased recurrence rates.

Change in Practice over Four Decades in the Management of Graves' Disease in Scotland

PubMed Central

Smith, D. M.; Dutta, S.; Ahmed, F.; Thaha, M. A.

2016-01-01

There is continuing debate on the optimal treatment for Grave's thyrotoxicosis with a resultant variation in clinical practice. The present study aimed to ascertain changes in practice in the treatment of Grave's thyrotoxicosis in Tayside, Scotland, over the past four decades. Methods. The “Scottish automated follow-up register” (SAFUR) was queried to identify all patients treated for Grave's thyrotoxicosis from 1968 to 2007 inclusive. Patients were divided into 4 groups (Groups A to D) according to the decades. Demographic profile, treatment modalities, radioactive iodine (RAI) dose, and recurrence rates were studied and outcomes were compared by χ 2 test and ANOVA using SPSS v15.0. A p value of < 0.05 was considered significant. Results. Altogether, 3737 patients were diagnosed with Grave's thyrotoxicosis over the 4 decades. Use of RAI has increased from 43.1% in Group A to 68% in Group D (p < 0.001). The dose of RAI has increased (p < 0.001) and there has been a reduction in recurrence rate with higher dose of RAI. Surgical intervention rates decreased from 55.3% to 12.3% (p < 0.001) over time. Conclusions. Analysis of a large dataset of patients with Grave's thyrotoxicosis suggests increasing use of RAI as the preferred first line of treatment. Furthermore, using a single higher dose of RAI and adoption of total thyroidectomy have decreased recurrence rates. PMID:27313946

Elevated stress hormone diminishes the strength of female preferences for acoustic signals in the green treefrog.

PubMed

Davis, A Gabriell; Leary, Christopher J

2015-03-01

Mate selection can be stressful; time spent searching for mates can increase predation risk and/or decrease food consumption, resulting in elevated stress hormone levels. Both high predation risk and low food availability are often associated with increased variation in mate choice by females, but it is not clear whether stress hormone levels contribute to such variation in female behavior. We examined how the stress hormone corticosterone (CORT) affects female preferences for acoustic signals in the green treefrog, Hyla cinerea. Specifically, we assessed whether CORT administration affects female preferences for call rate - an acoustic feature that is typically under directional selection via mate choice by females in most anurans and other species that communicate using acoustic signals. Using a dual speaker playback paradigm, we show that females that were administered higher doses of CORT were less likely to choose male advertisement calls broadcast at high rates. Neither CORT dose nor level was related to the latency of female phonotactic responses, suggesting that elevated CORT does not influence the motivation to mate. Results were also not related to circulating sex steroids (i.e., progesterone, androgens or estradiol) that have traditionally been the focus of studies examining the hormonal basis for variation in female mate choice. Our results thus indicate that elevated CORT levels decrease the strength of female preferences for acoustic signals. Copyright © 2015 Elsevier Inc. All rights reserved.

An evaluation of some pertinent parameters that influence the dosimetric performance of synthetic diamond detectors

NASA Astrophysics Data System (ADS)

Ade, N.; Nam, T. L.; Mhlanga, S. H.

2013-05-01

Although the near-tissue equivalence of diamond allows the direct measurement of dose for clinical applications without the need for energy-corrections, it is often cited that diamond detectors require pre-irradiation, a procedure necessary to stabilize the response or sensitivity of a diamond detector before dose measurements. In addition it has been pointed out that the relative dose measured with a diamond detector requires dose rate dependence correction and that the angular dependence of a detector could be due to its mechanical design or to the intrinsic angular sensitivity of the detection process. While the cause of instability of response has not been meticulously investigated, the issue of dose rate dependence correction is uncertain as some studies ignored it but reported good results. The aims of this study were therefore to investigate, in particular (1) the major cause of the unstable response of diamond detectors requiring pre-irradiation; (2) the influence of dose rate dependence correction in relative dose measurements; and (3) the angular dependence of the diamond detectors. The study was conducted with low-energy X-rays and electron therapy beams on HPHT and CVD synthesized diamonds. Ionization chambers were used for comparative measurements. Through systematic investigations, the major cause of the unstable response of diamond detectors requiring the recommended pre-irradiation step was isolated and attributed to the presence and effects of ambient light. The variation in detector's response between measurements in light and dark conditions could be as high as 63% for a CVD diamond. Dose rate dependence parameters (Δ values) of 0.950 and 1.035 were found for the HPHT and CVD diamond detectors, respectively. Without corrections based on dose rate dependence, the relative differences between depth-doses measured with the diamond detectors and a Markus chamber for exposures to 7 and 14 MeV electron beams were within 2.5%. A dose rate dependence correction using the Δ values obtained seemed to worsen the performance of the HPHT sample (up to about 3.3%) but it had a marginal effect on the performance of the CVD sample. In addition, the angular response of the CVD diamond detector was shown to be comparable with that of a cylindrical chamber. This study concludes that once the responses of the diamond detectors have been stabilised and they are properly shielded from ambient light, pre-irradiation prior to each measurement is not required. Also, the relative dose measured with the diamond detectors do not require dose rate dependence corrections as the required correction is only marginal and could have no dosimetric significance.

Image perception by expert readers as a function of patient skin entrance dose levels in digital radiography

NASA Astrophysics Data System (ADS)

Lehnert, T.; Korkusuz, H.; Khan, F.; Vogl, T. J.; Mack, M. G.

2008-03-01

In this study, image quality was based on required clinical criteria, in order to investigate to what degree entrance dose could be lowered and what kind of added filtration can be used without impinging on radiologist confidence levels in diagnosing. Images were taken of extremities from a cadaver using stepwise decreasing dose levels and variation of added filtration (no filtration, aluminum, aluminum/copper) under digital projection radiography (Kodak DirectView DR7500). The starting point dose level for all body parts imaged was the current x-ray technique. Two experienced and two resident radiologists were presented the images in a blinded fashion and rated each with an image quality score from 1 to 9 indicated very satisfied and 1 as very unsatisfied indicating loss of diagnostic value. The readers were not aware of which dose level and added filtration corresponded to which image. Dose levels considered were 100%, 75%, 50% and 25% of the normal and customary x-ray techniques used for the particular body part and projection. Images were reviewed on a clinical diagnostic workstation with no time limits imposed. Readers were also able to change the image presentation by adjusting the window width and level. Without added filtration image quality mean score was rated with 6.3 (dose level 100%), 6.2 (dose level 75%), 5.3 (dose level 50%) and with 4.4 (dose level 25%). An added aluminum filtration induced an image quality mean score of 6.3 (dose level 100%), 6.0 (dose level 75%), 5.1 (dose level 50%) and of 4.2 (dose level 25%). Using aluminum/copper filtration image quality mean score was rated with 6.0 (dose level 100%), 6.1 (dose level 75%), 5.0 (dose level 50%) and with 3.8 (dose level 25%). Regardless of the added filtration a differentiation between dose levels 100% and 75% was possible in 38.9%, between dose levels 75% and 50% in 66.7%, and between dose levels 50% and 25% in 70.0% of the cases. It is possible, in the case of extremities, to lower entrance doses up to 75 % of the normal value, a reduction of 25% in dose, under simultaneous use of added aluminum or aluminum/copper filtration, without comprising the diagnostic value required.

MCNP simulations of material exposure experiments (u)

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

Temple, Brian A

2010-12-08

Simulations of proposed material exposure experiments were performed using MCNP6. The experiments will expose ampules containing different materials of interest with radiation to observe the chemical breakdown of the materials. Simulations were performed to map out dose in materials as a function of distance from the source, dose variation between materials, dose variation due to ampule orientation, and dose variation due to different source energy. This write up is an overview of the simulations and will provide guidance on how to use the data in the spreadsheet.

Carbon Heavy-ion Radiation Induced Biological effects on Oryza sativa L.

NASA Astrophysics Data System (ADS)

Zhang, Meng; Sun, Yeqing; Li, Xishan; Gong, Ning; Meng, Qingmei; Liu, Jiawei; Wang, Ting

2016-07-01

Large number of researches on rice after spaceflights indicated that rice was a favorable model organism to study biological effects induced by space radiation. The stimulative effect could often be found on rice seedlings after irradiation by low-dose energetic heavy-ion radiation. Spaceflight also could induce stimulative effect on kinds of seeds. To further understand the mechanism of low-dose radiation biological effects and the dose range, the germinated rice seeds which were irradiated by different doses of carbon heavy-ion (0, 0.02, 0.1, 0.2, 1, 2, 5, 10, 15 and 20Gy, LET=27.3keV/µm) were used as materials to study. By investigating the variation of rice phenotype under different doses, we found that 2Gy radiation dose was a dividing point of the phenotypic variation. Transmission electron microscopy was used to observe the variation of mitochondria, chloroplast, endoplasmic reticulum, ribosome and nucleus in mesophyll cell of rice apical meristem at 24 hours after radiation with different doses. The cells were not apparently physiologically damaged when the dose of radiation was less than 2Gy. The number of chloroplast did not change significantly, but the number of mitochondria was significantly increased, and gathered around in the chloroplast and endoplasmic reticulum; the obvious lesion of chloroplast and mitochondria were found at the mesophyll cells when radiation dose was higher than 2Gy. The mitochondria were swelling and appearing blurred crest. The chloroplast and mitochondrial mutation rate increased significantly (p<0.01). These phenomena showed that cell biological changes may be the reasons of the stimulation and inhibition effects with the boundary of 2Gy. Since mitochondrial was an important organelle involved in the antioxidative systems, its dysfunction could result in the increase of reactive oxygen species and lipid peroxidation. We found that the growth stimulation induced by low-dose radiation mainly occurred at three-leaf stage along with the increasing activity of antioxidase system and damages of lipid peroxidation. We also found that the relative expression of genes sdhb and aox1a which encode the key proteins in mitochondria changed differently after exposed to different doses of radiation, and the lower dose of the radiation could cause longer effect. The chlorophyll was an important organ of photosynthesis, its dysfunction could result in the phenotypic variation. We found that the chlorophyll fluorescence parameter Fv/Fm, the content of chlorophyll (including chlorophyll a, chlorophyll b and total chlorophyll) and both the relative expression of CP24 and its encoding gene lhcb6 changed significantly in different doses. The changes of the relative expression of CP24 and its encoding gene lhcb6 were completely opposite at the lower dose and agreed at the higher dose. The possible mechanisms of growth stimulation and inhibition effects induced by low and high dose radiations were discussed on multiple levels. Moreover, our findings were important to understand the spaceflight induced growth stimulation and inhibition effects of plant. Keywords: Heavy-ion radiation; Low dose; Stimulation effect; Inhibition effect; Rice.

Monte Carlo simulations of radioactive waste encapsulated by bisphenol-A polycarbonate and effect of bismuth-III oxide filler material

NASA Astrophysics Data System (ADS)

Özdemir, Tonguç

2017-06-01

Radioactive waste generated from the nuclear industry and non-power applications should carefully be treated, conditioned and disposed according to the regulations set by the competent authority(ies). Bisphenol-a polycarbonate (BPA-PC), a very widely used polymer, might be considered as a potential candidate material for low level radioactive waste encapsulation. In this work, the dose rate distribution in the radioactive waste drum (containing radioactive waste and the BPA-PC polymer matrix) was determined using Monte Carlo simulations. Moreover, the change of mechanical properties of BPA-PC was estimated and their variation within the waste drum was determined for the periods of 15, 30 and 300 years after disposal to the final disposal site. The change of the dose rate within the waste drum with different contents of bismuth-III oxide were also simulated. It was concluded that addition of bismuth-III oxide filler decreases the dose delivered to the polymeric matrix due to photoelectric effect.

Indoor terrestrial gamma dose rate mapping in France: a case study using two different geostatistical models.

PubMed

Warnery, E; Ielsch, G; Lajaunie, C; Cale, E; Wackernagel, H; Debayle, C; Guillevic, J

2015-01-01

Terrestrial gamma dose rates show important spatial variations in France. Previous studies resulted in maps of arithmetic means of indoor terrestrial gamma dose rates by "departement" (French district). However, numerous areas could not be characterized due to the lack of data. The aim of our work was to obtain more precise estimates of the spatial variability of indoor terrestrial gamma dose rates in France by using a more recent and complete data base and geostatistics. The study was based on the exploitation of 97,595 measurements results distributed in 17,404 locations covering all of France. Measurements were done by the Institute for Radioprotection and Nuclear Safety (IRSN) using RPL (Radio Photo Luminescent) dosimeters, exposed during several months between years 2011 and 2012 in French dentist surgeries and veterinary clinics. The data used came from dosimeters which were not exposed to anthropic sources. After removing the cosmic rays contribution in order to study only the telluric gamma radiation, it was decided to work with the arithmetic means of the time-series measurements, weighted by the time-exposure of the dosimeters, for each location. The values varied between 13 and 349 nSv/h, with an arithmetic mean of 76 nSv/h. The observed statistical distribution of the gamma dose rates was skewed to the right. Firstly, ordinary kriging was performed in order to predict the gamma dose rate on cells of 1*1 km(2), all over the domain. The second step of the study was to use an auxiliary variable in estimates. The IRSN achieved in 2010 a classification of the French geological formations, characterizing their uranium potential on the bases of geology and local measurement results of rocks uranium content. This information is georeferenced in a map at the scale 1:1,000,000. The geological uranium potential (GUP) was classified in 5 qualitative categories. As telluric gamma rays mostly come from the progenies of the (238)Uranium series present in rocks, this information, which is exhaustive throughout France, could help in estimating the telluric gamma dose rates. Such an approach is possible using multivariate geostatistics and cokriging. Multi-collocated cokriging has been performed on 1*1 km(2) cells over the domain. This model used gamma dose rate measurement results and GUP classes. Our results provide useful information on the variability of the natural terrestrial gamma radiation in France ('natural background') and exposure data for epidemiological studies and risk assessment from low dose chronic exposures. Copyright © 2014 Elsevier Ltd. All rights reserved.

Global real-time dose measurements using the Automated Radiation Measurements for Aerospace Safety (ARMAS) system

NASA Astrophysics Data System (ADS)

Tobiska, W. Kent; Bouwer, D.; Smart, D.; Shea, M.; Bailey, J.; Didkovsky, L.; Judge, K.; Garrett, H.; Atwell, W.; Gersey, B.; Wilkins, R.; Rice, D.; Schunk, R.; Bell, D.; Mertens, C.; Xu, X.; Wiltberger, M.; Wiley, S.; Teets, E.; Jones, B.; Hong, S.; Yoon, K.

2016-11-01

The Automated Radiation Measurements for Aerospace Safety (ARMAS) program has successfully deployed a fleet of six instruments measuring the ambient radiation environment at commercial aircraft altitudes. ARMAS transmits real-time data to the ground and provides quality, tissue-relevant ambient dose equivalent rates with 5 min latency for dose rates on 213 flights up to 17.3 km (56,700 ft). We show five cases from different aircraft; the source particles are dominated by galactic cosmic rays but include particle fluxes for minor radiation periods and geomagnetically disturbed conditions. The measurements from 2013 to 2016 do not cover a period of time to quantify galactic cosmic rays' dependence on solar cycle variation and their effect on aviation radiation. However, we report on small radiation "clouds" in specific magnetic latitude regions and note that active geomagnetic, variable space weather conditions may sufficiently modify the magnetospheric magnetic field that can enhance the radiation environment, particularly at high altitudes and middle to high latitudes. When there is no significant space weather, high-latitude flights produce a dose rate analogous to a chest X-ray every 12.5 h, every 25 h for midlatitudes, and every 100 h for equatorial latitudes at typical commercial flight altitudes of 37,000 ft ( 11 km). The dose rate doubles every 2 km altitude increase, suggesting a radiation event management strategy for pilots or air traffic control; i.e., where event-driven radiation regions can be identified, they can be treated like volcanic ash clouds to achieve radiation safety goals with slightly lower flight altitudes or more equatorial flight paths.

Optically stimulated luminescence (OSL) of carbon-doped aluminum oxide (Al{sub 2}O{sub 3}:C) for film dosimetry in radiotherapy

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

Schembri, V.; Heijmen, B. J. M.

2007-06-15

Introduction and Purpose: Conventional x-ray films and radiochromic films have inherent challenges for high precision radiotherapy dosimetry. Here we have investigated basic characteristics of optically stimulated luminescence (OSL) of irradiated films containing carbon-doped aluminum oxide (Al{sub 2}O{sub 3}:C) for dosimetry in therapeutic photon and electron beams. Materials and Methods: The OSL films consist of a polystyrene sheet, with a top layer of a mixture of single crystals of Al{sub 2}O{sub 3}:C, ground into a powder, and a polyester base. The total thickness of the films is 0.3 mm. Measurements have been performed in a water equivalent phantom, using 4, 6,more » 10, and 18 MV photon beams, and 6-22 MeV electron beams. The studies include assessment of the film response (acquired OSL signal/delivered dose) on delivered dose (linearity), dose rate (1-6 Gy/min), beam quality, field size and depth (6 MV, ranges 4x4-30x30 cm{sup 2}, d{sub max}-35 cm). Doses have been derived from ionization chamber measurements. OSL films have also been compared with conventional x-ray and GafChromic films for dosimetry outside the high dose area, with a high proportion of low dose scattered photons. In total, 787 OSL films have been irradiated. Results: Overall, the OSL response for electron beams was 3.6% lower than for photon beams. Differences between the various electron beam energies were not significant. The 6 and 18 MV photon beams differed in response by 4%. No response dependencies on dose rate were observed. For the 6 MV beam, the field size and depth dependencies of the OSL response were within {+-}2.5%. The observed inter-film response variation for films irradiated with the same dose varied from 1% to 3.2% (1 SD), depending on the measurement day. At a depth of 20 cm, 5 cm outside the 20x20 cm{sup 2} 6 and 18 MV beams, an over response of 17% was observed. In contrast to GafChromic and conventional x-ray films, the response of the Al{sub 2}O{sub 3}:C films is linear in the clinically relevant dose range 0-200 cGy. Conclusions: Measurement of the OSL signal of irradiated films containing Al{sub 2}O{sub 3}:C is a promising technique for film dosimetry in radiotherapy with no or small response variations with dose rate, beam quality, field size and depth, and a linear response from 0 to 200 cGy.« less

Analysis of lomustine drug content in FDA-approved and compounded lomustine capsules.

PubMed

KuKanich, Butch; Warner, Matt; Hahn, Kevin

2017-02-01

OBJECTIVE To determine the lomustine content (potency) in compounded and FDA-approved lomustine capsules. DESIGN Evaluation study. SAMPLE 2 formulations of lomustine capsules (low dose [7 to 11 mg] and high dose [40 to 48 mg]; 5 capsules/dose/source) from 3 compounders and from 1 manufacturer of FDA-approved capsules. PROCEDURES Lomustine content was measured by use of a validated high-pressure liquid chromatography method. An a priori acceptable range of 90% to 110% of the stated lomustine content was selected on the basis of US Pharmacopeia guidelines. RESULTS The measured amount of lomustine in all compounded capsules was less than the stated content (range, 59% to 95%) and was frequently outside the acceptable range (failure rate, 2/5 to 5/5). Coefficients of variation for lomustine content ranged from 4.1% to 16.7% for compounded low-dose capsules and from 1.1% to 10.8% for compounded high-dose capsules. The measured amount of lomustine in all FDA-approved capsules was slightly above the stated content (range, 104% to 110%) and consistently within the acceptable range. Coefficients of variation for lomustine content were 0.5% for low-dose and 2.3% for high-dose FDA-approved capsules. CONCLUSIONS AND CLINICAL RELEVANCE Compounded lomustine frequently did not contain the stated content of active drug and had a wider range of lomustine content variability than did the FDA-approved product. The sample size was small, and larger studies are needed to confirm these findings; however, we recommend that compounded veterinary formulations of lomustine not be used when appropriate doses can be achieved with FDA-approved capsules or combinations of FDA-approved capsules.

Effects of dose scaling on delivery quality assurance in tomotherapy

PubMed Central

Nalichowski, Adrian; Burmeister, Jay

2012-01-01

Delivery quality assurance (DQA) of tomotherapy plans is routinely performed with silver halide film which has a limited range due to the effects of saturation. DQA plans with dose values exceeding this limit require the dose of the entire plan to be scaled downward if film is used, to evaluate the dose distribution in two dimensions. The potential loss of fidelity between scaled and unscaled DQA plans as a function of dose scaling is investigated. Three treatment plans for 12 Gy fractions designed for SBRT of the lung were used to create DQA procedures that were scaled between 100% and 10%. The dose was measured with an ionization chamber array and compared to values from the tomotherapy treatment planning system. Film and cylindrical ion chamber measurements were also made for one patient for scaling factors of 50% to 10% to compare with the ionization chamber array measurements. The array results show the average gamma pass rate is ≥99% from 100% to 30% scaling. The average gamma pass rate falls to 93.6% and 51.1% at 20% and 10% scaling, respectively. Film analysis yields similar pass rates. Cylindrical ion chambers did not exhibit significant variation with dose scaling, but only represent points in the low gradient region of the dose distribution. Scaling the dose changes the mechanics of the radiation delivery, as well as the signal‐to‐noise ratio. Treatment plans which exhibit parameters that differ significantly from those common to DQA plans studied in this paper may exhibit different behavior. Dose scaling should be limited to the smallest degree possible. Planar information, such as that from film or a detector array, is required. The results show that it is not necessary to perform both a scaled and unscaled DQA plan for the treatment plans considered here. PACS numbers: 87.55.km, 87.55.Qr PMID:22231213

Optimization of equivalent uniform dose using the L-curve criterion.

PubMed

Chvetsov, Alexei V; Dempsey, James F; Palta, Jatinder R

2007-10-07

Optimization of equivalent uniform dose (EUD) in inverse planning for intensity-modulated radiation therapy (IMRT) prevents variation in radiobiological effect between different radiotherapy treatment plans, which is due to variation in the pattern of dose nonuniformity. For instance, the survival fraction of clonogens would be consistent with the prescription when the optimized EUD is equal to the prescribed EUD. One of the problems in the practical implementation of this approach is that the spatial dose distribution in EUD-based inverse planning would be underdetermined because an unlimited number of nonuniform dose distributions can be computed for a prescribed value of EUD. Together with ill-posedness of the underlying integral equation, this may significantly increase the dose nonuniformity. To optimize EUD and keep dose nonuniformity within reasonable limits, we implemented into an EUD-based objective function an additional criterion which ensures the smoothness of beam intensity functions. This approach is similar to the variational regularization technique which was previously studied for the dose-based least-squares optimization. We show that the variational regularization together with the L-curve criterion for the regularization parameter can significantly reduce dose nonuniformity in EUD-based inverse planning.

Variation in radiographic protocols in paediatric interventional cardiology.

PubMed

McFadden, S L; Hughes, C M; Winder, R J

2013-06-01

The aim of this work is to determine current radiographic protocols in paediatric interventional cardiology (IC) in the UK and Ireland. To do this we investigated which imaging parameters/protocols are commonly used in IC in different hospitals, to identify if a standard technique is used and illustrate any variation in practice. A questionnaire was sent to all hospitals in the UK and Ireland which perform paediatric IC to obtain information on techniques used in each clinical department and on the range of clinical examinations performed. Ethical and research governance approval was sought from the Office for Research Ethics Committees Northern Ireland and the individual trusts. A response rate of 79% was achieved, and a wide variation in technique was found between hospitals. The main differences in technique involved variations in the use of an anti-scatter grid and the use of additional filtration to the radiation beam, frame rates for digital acquisition and pre-programmed projections/paediatric specific programming in the equipment. We conclude that there is no standard protocol for carrying out paediatric IC in the UK or Ireland. Each hospital carries out the IC procedure according to its own local protocols resulting in a wide variation in radiation dose.

Effect of increasing radiation dose on pathologic complete response in rectal cancer patients treated with neoadjuvant chemoradiation therapy.

PubMed

Hall, Matthew D; Schultheiss, Timothy E; Smith, David D; Fakih, Marwan G; Wong, Jeffrey Y C; Chen, Yi-Jen

2016-12-01

Neoadjuvant chemoradiation therapy (CRT) increases pathological complete response (pCR) rates compared to radiotherapy alone in patients with stage II-III rectal cancer. Limited evidence addresses whether radiotherapy dose escalation further improves pCR rates. Our purpose is to measure the effects of radiotherapy dose and other factors on post-therapy pathologic tumor (ypT) and nodal stage in rectal cancer patients treated with neoadjuvant CRT followed by mesorectal excision. A non-randomized comparative effectiveness analysis was performed of rectal cancer patients treated in 2000-2013 from the National Oncology Data Alliance™ (NODA), a pooled database of cancer registries from >150 US hospitals. The NODA contains the same data submitted to state cancer registries and SEER combined with validated radiotherapy and chemotherapy records. Eligible patients were treated with neoadjuvant CRT followed by proctectomy and had complete data on treatment start dates, radiotherapy dose, clinical tumor (cT) and ypT stage, and number of positive nodes at surgery (n = 3298 patients). Multivariable logistic regression was used to assess the predictive value of independent variables on achieving a pCR. On multivariable regression, radiotherapy dose, cT stage, and time interval between CRT and surgery were significant predictors of achieving a pCR. After adjusting for the effect of other variates, patients treated with higher radiotherapy doses were also more likely to have negative nodes at surgery and be downstaged from cT3-T4 and/or node positive disease to ypT0-T2N0 after neoadjuvant CRT. Our study suggests that increasing dose significantly improved pCR rates and downstaging in rectal cancer patients treated with neoadjuvant CRT followed by surgery.

Estimated dose rates to members of the public from external exposure to patients with 131I thyroid treatment

DOE PAGES

Dewji, S.; Bellamy, M.; Hertel, N.; ...

2015-03-25

The purpose of this study is to estimate dose rates that may result from exposure to patients who had been administered iodine-131 ( 131I) as part of medical therapy were calculated. These effective dose rate estimates were compared with simplified assumptions under United States Nuclear Regulatory Commission Regulatory Guide 8.39, which does not consider body tissue attenuation nor time-dependent redistribution and excretion of the administered 131I. Methods: Dose rates were estimated for members of the public potentially exposed to external irradiation from patients recently treated with 131I. Tissue attenuation and iodine biokinetics were considered in the patient in a largermore » comprehensive effort to improve external dose rate estimates. The external dose rate estimates are based on Monte Carlo simulations using the Phantom with Movable Arms and Legs (PIMAL), previously developed by Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission. PIMAL was employed to model the relative positions of the 131I patient and members of the public in three exposure scenarios: (1) traveling on a bus in a total of six seated or standing permutations, (2) two nursing home cases where a caregiver is seated at 30 cm from the patient’s bedside and a nursing home resident seated 250 cm away from the patient in an adjacent bed, and (3) two hotel cases where the patient and a guest are in adjacent rooms with beds on opposite sides of the common wall, with the patient and guest both in bed and either seated back-to-back or lying head to head. The biokinetic model predictions of the retention and distribution of 131I in the patient assumed a single voiding of urinary bladder contents that occurred during the trip at 2, 4, or 8 h after 131I administration for the public transportation cases, continuous first-order voiding for the nursing home cases, and regular periodic voiding at 4, 8, or 12 h after administration for the hotel room cases. Organ specific activities of 131I in the thyroid, bladder, and combined remaining tissues were calculated as a function of time after administration. Exposures to members of the public were considered for 131I patients with normal thyroid uptake (peak thyroid uptake of ~27% of administered 131I), differentiated thyroid cancer (DTC, 5% uptake), and hyperthyroidism (80% uptake). Results: The scenario with the patient seated behind the member of the public yielded the highest dose rate estimate of seated public transportation exposure cases. The dose rate to the adjacent room guest was highest for the exposure scenario in which the hotel guest and patient are seated by a factor of ~4 for the normal and differentiated thyroid cancer uptake cases and by a factor of ~3 for the hyperthyroid case. Conclusions: It was determined that for all modeled cases, the DTC case yielded the lowest external dose rates, whereas the hyperthyroid case yielded the highest dose rates. In estimating external dose to members of the public from patients with 131I therapy, consideration must be given to (patient- and case-specific) administered 131I activities and duration of exposure for a more complete estimate. The method implemented here included a detailed calculation model, which provides a means to determine dose rate estimates for a range of scenarios. Finally, the method was demonstrated for variations of three scenarios, showing how dose rates are expected to vary with uptake, voiding pattern, and patient location.« less

Estimated dose rates to members of the public from external exposure to patients with 131I thyroid treatment

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

Dewji, S.; Bellamy, M.; Hertel, N.

The purpose of this study is to estimate dose rates that may result from exposure to patients who had been administered iodine-131 ( 131I) as part of medical therapy were calculated. These effective dose rate estimates were compared with simplified assumptions under United States Nuclear Regulatory Commission Regulatory Guide 8.39, which does not consider body tissue attenuation nor time-dependent redistribution and excretion of the administered 131I. Methods: Dose rates were estimated for members of the public potentially exposed to external irradiation from patients recently treated with 131I. Tissue attenuation and iodine biokinetics were considered in the patient in a largermore » comprehensive effort to improve external dose rate estimates. The external dose rate estimates are based on Monte Carlo simulations using the Phantom with Movable Arms and Legs (PIMAL), previously developed by Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission. PIMAL was employed to model the relative positions of the 131I patient and members of the public in three exposure scenarios: (1) traveling on a bus in a total of six seated or standing permutations, (2) two nursing home cases where a caregiver is seated at 30 cm from the patient’s bedside and a nursing home resident seated 250 cm away from the patient in an adjacent bed, and (3) two hotel cases where the patient and a guest are in adjacent rooms with beds on opposite sides of the common wall, with the patient and guest both in bed and either seated back-to-back or lying head to head. The biokinetic model predictions of the retention and distribution of 131I in the patient assumed a single voiding of urinary bladder contents that occurred during the trip at 2, 4, or 8 h after 131I administration for the public transportation cases, continuous first-order voiding for the nursing home cases, and regular periodic voiding at 4, 8, or 12 h after administration for the hotel room cases. Organ specific activities of 131I in the thyroid, bladder, and combined remaining tissues were calculated as a function of time after administration. Exposures to members of the public were considered for 131I patients with normal thyroid uptake (peak thyroid uptake of ~27% of administered 131I), differentiated thyroid cancer (DTC, 5% uptake), and hyperthyroidism (80% uptake). Results: The scenario with the patient seated behind the member of the public yielded the highest dose rate estimate of seated public transportation exposure cases. The dose rate to the adjacent room guest was highest for the exposure scenario in which the hotel guest and patient are seated by a factor of ~4 for the normal and differentiated thyroid cancer uptake cases and by a factor of ~3 for the hyperthyroid case. Conclusions: It was determined that for all modeled cases, the DTC case yielded the lowest external dose rates, whereas the hyperthyroid case yielded the highest dose rates. In estimating external dose to members of the public from patients with 131I therapy, consideration must be given to (patient- and case-specific) administered 131I activities and duration of exposure for a more complete estimate. The method implemented here included a detailed calculation model, which provides a means to determine dose rate estimates for a range of scenarios. Finally, the method was demonstrated for variations of three scenarios, showing how dose rates are expected to vary with uptake, voiding pattern, and patient location.« less

Detailed source term estimation of atmospheric release during the Fukushima Dai-ichi nuclear power plant accident by coupling atmospheric and oceanic dispersion models

NASA Astrophysics Data System (ADS)

Katata, Genki; Chino, Masamichi; Terada, Hiroaki; Kobayashi, Takuya; Ota, Masakazu; Nagai, Haruyasu; Kajino, Mizuo

2014-05-01

Temporal variations of release amounts of radionuclides during the Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident and their dispersion process are essential to evaluate the environmental impacts and resultant radiological doses to the public. Here, we estimated a detailed time trend of atmospheric releases during the accident by combining environmental monitoring data and coupling atmospheric and oceanic dispersion simulations by WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN developed by the authors. New schemes for wet, dry, and fog depositions of radioactive iodine gas (I2 and CH3I) and other particles (I-131, Te-132, Cs-137, and Cs-134) were incorporated into WSPEEDI-II. The deposition calculated by WSPEEDI-II was used as input data of ocean dispersion calculations by SEA-GEARN. The reverse estimation method based on the simulation by both models assuming unit release rate (1 Bq h-1) was adopted to estimate the source term at the FNPP1 using air dose rate, and air sea surface concentrations. The results suggested that the major release of radionuclides from the FNPP1 occurred in the following periods during March 2011: afternoon on the 12th when the venting and hydrogen explosion occurred at Unit 1, morning on the 13th after the venting event at Unit 3, midnight on the 14th when several openings of SRV (steam relief valve) were conducted at Unit 2, morning and night on the 15th, and morning on the 16th. The modified WSPEEDI-II using the newly estimated source term well reproduced local and regional patterns of air dose rate and surface deposition of I-131 and Cs-137 obtained by airborne observations. Our dispersion simulations also revealed that the highest radioactive contamination areas around FNPP1 were created from 15th to 16th March by complicated interactions among rainfall (wet deposition), plume movements, and phase properties (gas or particle) of I-131 and release rates associated with reactor pressure variations in Units 2 and 3.

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

Yang, K; Yu, Z; Chen, H

Purpose: To implement VMAT in RayStation with the Elekta Synergy linac with the new Agility MLC, and to utilize the same vendor softwares to determine the optimum Elekta VMAT machine parameters in RayStation for accurate modeling and robust delivery. Methods: iCOMCat is utilized to create various beam patterns with user defined dose rate, gantry, MLC and jaw speed for each control point. The accuracy and stability of the output and beam profile are qualified for each isolated functional component of VMAT delivery using ion chamber and Profiler2 with isocentric mounting fixture. Service graphing on linac console is used to verifymore » the mechanical motion accuracy. The determined optimum Elekta VMAT machine parameters were configured in RayStation v4.5.1. To evaluate the system overall performance, TG-119 test cases and nine retrospective VMAT patients were planned on RayStation, and validated using both ArcCHECK (with plug and ion chamber) and MapCHECK2. Results: Machine output and profile varies <0.3% when only variable is dose rate (35MU/min-600MU/min). <0.9% output and <0.3% profile variation are observed with additional gantry motion (0.53deg/s–5.8deg/s both directions). The output and profile variation are still <1% with additional slow leaf motion (<1.5cm/s both direction). However, the profile becomes less symmetric, and >1.5% output and 7% profile deviation is seen with >2.5cm/s leaf motion. All clinical cases achieved comparable plan quality as treated IMRT plans. The gamma passing rate is 99.5±0.5% on ArcCheck (<3% iso center dose deviation) and 99.1±0.8% on MapCheck2 using 3%/3mm gamma (10% lower threshold). Mechanical motion accuracy in all VMAT deliveries is <1°/1mm. Conclusion: Accurate RayStation modeling and robust VMAT delivery is achievable on Elekta Agility for <2.5cm/s leaf motion and full range of dose rate and gantry speed determined by the same vendor softwares. Our TG-119 and patient results have provided us with the confidence to use VMAT clinically.« less

Diamond detector in absorbed dose measurements in high-energy linear accelerator photon and electron beams.

PubMed

Ravichandran, Ramamoorthy; Binukumar, John Pichy; Al Amri, Iqbal; Davis, Cheriyathmanjiyil Antony

2016-03-08

Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue-equivalent properties. We investigated a commercially available 'microdiamond' detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1mm, thickness 1 x10(-3) mm, the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be ± 0.17% (1 SD) (n = 11). The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stop-ping power ratios compared well with Nd, water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long-term stability and reproducibility. Based on micro-dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance.

Dosimetry investigation of MOSFET for clinical IMRT dose verification.

PubMed

Deshpande, Sudesh; Kumar, Rajesh; Ghadi, Yogesh; Neharu, R M; Kannan, V

2013-06-01

In IMRT, patient-specific dose verification is followed regularly at each centre. Simple and efficient dosimetry techniques play a very important role in routine clinical dosimetry QA. The MOSFET dosimeter offers several advantages over the conventional dosimeters such as its small detector size, immediate readout, immediate reuse, multiple point dose measurements. To use the MOSFET as routine clinical dosimetry system for pre-treatment dose verification in IMRT, a comprehensive set of experiments has been conducted, to investigate its linearity, reproducibility, dose rate effect and angular dependence for 6 MV x-ray beam. The MOSFETs shows a linear response with linearity coefficient of 0.992 for a dose range of 35 cGy to 427 cGy. The reproducibility of the MOSFET was measured by irradiating the MOSFET for ten consecutive irradiations in the dose range of 35 cGy to 427 cGy. The measured reproducibility of MOSFET was found to be within 4% up to 70 cGy and within 1.4% above 70 cGy. The dose rate effect on the MOSFET was investigated in the dose rate range 100 MU/min to 600 MU/min. The response of the MOSFET varies from -1.7% to 2.1%. The angular responses of the MOSFETs were measured at 10 degrees intervals from 90 to 270 degrees in an anticlockwise direction and normalized at gantry angle zero and it was found to be in the range of 0.98 ± 0.014 to 1.01 ± 0.014. The MOSFETs were calibrated in a phantom which was later used for IMRT verification. The measured calibration coefficients were found to be 1 mV/cGy and 2.995 mV/cGy in standard and high sensitivity mode respectively. The MOSFETs were used for pre-treatment dose verification in IMRT. Nine dosimeters were used for each patient to measure the dose in different plane. The average variation between calculated and measured dose at any location was within 3%. Dose verification using MOSFET and IMRT phantom was found to quick and efficient and well suited for a busy radiotherapy department.

SU-C-202-02: A Comprehensive Evaluation of Adaptive Daily Planning for Cervical Cancer HDR Brachytherapy

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

Meerschaert, R; Paul, A; Zhuang, L

Purpose: To evaluate adaptive daily planning for cervical cancer patients who underwent high-dose-rate intra-cavitary brachytherapy (HDR-ICBT). Methods: This study included 22 cervical cancer patients who underwent 5 fractions of HDR ICBT. Regions of interest (ROIs) including high-risk clinical tumor volume (HR-CTV) and organs-at-risk (OARs) were manually contoured on daily CT images. All patients were treated with adaptive daily plans, which involved ROI delineation and dose optimization at each treatment fraction. Single treatment plans were retrospectively generated by applying the first treatment fraction’s dwell times adjusted for decay and dwell positions of the applicator to subsequent treatment fractions. Various existing similaritymore » metrics were calculated for the ROIs to quantify interfractional organ variations. A novel similarity score (JRARM) was established, which combined both volumetric overlap metrics (DSC, JSC, and RVD) and distance metrics (ASD, MSD, and RMSD). Linear regression was performed to determine a relationship between inter-fractional organ variations of various similarity metrics and D2cc variations from both plans. Wilcoxon Signed Rank Tests were used to assess adaptive daily plans and single plans by comparing EQD2 D2cc (α/β=3) for OARs. Results: For inter-fractional organ variations, the sigmoid demonstrated the greatest variations based on the JRARM and DSC similarity metrics. Comparisons between paired ROIs showed differences in JRARM scores and DSCs at each treatment fraction. RVD, MSD, and RMSD were found to be significantly correlated to D2cc variations for bladder and sigmoid. The comparison between plans found that adaptive daily planning provided lower EQD2 D2cc of OARs than single planning, specifically for the sigmoid (p=0.015). Conclusion: Substantial inter-fractional organ motion can occur during HDR-BT, which may significantly affect D2cc of OARs. Adaptive daily planning provides improved dose sparing for OARs compared to single planning.« less

In-flight radiation measurements on STS-60

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Golightly, M. J.; Konradi, A.; Atwell, W.; Kern, J. W.; Cash, B.; Benton, E. V.; Frank, A. L.; Sanner, D.; Keegan, R. P.;

Paediatric nurses' adherence to the double-checking process during medication administration in a children's hospital: an observational study.

PubMed

Alsulami, Zayed; Choonara, Imti; Conroy, Sharon

2014-06-01

To evaluate how closely double-checking policies are followed by nurses in paediatric areas and also to identify the types, frequency and rates of medication administration errors that occur despite the double-checking process. Double-checking by two nurses is an intervention used in many UK hospitals to prevent or reduce medication administration errors. There is, however, insufficient evidence to either support or refute the practice of double-checking in terms of medication error risk reduction. Prospective observational study. This was a prospective observational study of paediatric nurses' adherence to the double-checking process for medication administration from April-July 2012. Drug dose administration events (n = 2000) were observed. Independent drug dose calculation, rate of administering intravenous bolus drugs and labelling of flush syringes were the steps with lowest adherence rates. Drug dose calculation was only double-checked independently in 591 (30%) drug administrations. There was a statistically significant difference in nurses' adherence rate to the double-checking steps between weekdays and weekends in nine of the 15 evaluated steps. Medication administration errors (n = 191) or deviations from policy were observed, at a rate of 9·6% of drug administrations. These included 64 drug doses, which were left for parents to administer without nurse observation. There was variation between paediatric nurses' adherence to double-checking steps during medication administration. The most frequent type of administration errors or deviation from policy involved the medicine being given to the parents to administer to the child when the nurse was not present. © 2013 John Wiley & Sons Ltd.

Radioactive contamination mapping of northeastern and eastern Japan by a car-borne survey system, Radi-Probe.

PubMed

Kobayashi, Shingo; Shinomiya, Takayuki; Kitamura, Hisashi; Ishikawa, Takahiro; Imaseki, Hitoshi; Oikawa, Masakazu; Kodaira, Satoshi; Miyaushiro, Norihiro; Takashima, Yoshio; Uchihori, Yukio

2015-01-01

We constructed a new car-borne survey system called Radi-Probe with a portable germanium gamma-ray spectrometer onboard a cargo truck, to identify radionuclides and quantify surface contamination from the accident at Fukushima Dai-ichi Nuclear Power Station. The system can quickly survey a large area and obtain ambient dose equivalent rates and gamma-ray energy spectra with good energy resolution. We also developed a new calibration method for the system to deal with an actual nuclear disaster, and quantitative surface deposition densities of radionuclides, such as (134)Cs and (137)Cs, and kerma rates of each radionuclide can be calculated. We carried out car-borne survey over northeastern and eastern Japan (Tohoku and Kanto regions of Honshu) from 25 September through 7 October 2012. We discuss results of the distribution of ambient dose equivalent rate H(∗)(10), (134)Cs and (137)Cs surface deposition densities, spatial variation of (134)Cs/(137)Cs ratio, and the relationship between surface deposition densities of (134)Cs/(137)Cs and H(∗)(10). The ratio of (134)Cs/(137)Cs was nearly constant within our measurement precision, with average 1.06 ± 0.04 in northeastern and eastern Japan (decay-corrected to 11 March, 2011), although small variations from the average were observed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Comparative dosimetry of diode and diamond detectors in electron beams for intraoperative radiation therapy.

PubMed

Björk, P; Knöös, T; Nilsson, P

2000-11-01

The aim of the present study is to examine the validity of using silicon semiconductor detectors in degraded electron beams with a broad energy spectrum and a wide angular distribution. A comparison is made with diamond detector measurements, which is the dosimeter considered to give the best results provided that dose rate effects are corrected for. Two-dimensional relative absorbed dose distributions in electron beams (6-20 MeV) for intraoperative radiation therapy (IORT) are measured in a water phantom. To quantify deviations between the detectors, a dose comparison tool that simultaneously examines the dose difference and distance to agreement (DTA) is used to evaluate the results in low- and high-dose gradient regions, respectively. Uncertainties of the experimental measurement setup (+/- 1% and +/- 0.5 mm) are taken into account by calculating a composite distribution that fails this dose-difference and DTA acceptance limit. Thus, the resulting area of disagreement should be related to differences in detector performance. The dose distributions obtained with the diode are generally in very good agreement with diamond detector measurements. The buildup region and the dose falloff region show good agreement with increasing electron energy, while the region outside the radiation field close to the water surface shows an increased difference with energy. The small discrepancies in the composite distributions are due to several factors: (a) variation of the silicon-to-water collision stopping-power ratio with electron energy, (b) a more pronounced directional dependence for diodes than for diamonds, and (c) variation of the electron fluence perturbation correction factor with depth. For all investigated treatment cones and energies, the deviation is within dose-difference and DTA acceptance criteria of +/- 3% and +/- 1 mm, respectively. Therefore, p-type silicon diodes are well suited, in the sense that they give results in close agreement with diamond detectors, for practical measurements of relative absorbed dose distributions in degraded electron beams used for IORT.

Influence of CYP3A5 genetic variation on everolimus maintenance dosing after cardiac transplantation.

PubMed

Lesche, Dorothea; Sigurdardottir, Vilborg; Setoud, Raschid; Englberger, Lars; Fiedler, Georg M; Largiadèr, Carlo R; Mohacsi, Paul; Sistonen, Johanna

2015-12-01

Everolimus (ERL) has become an alternative to calcineurin inhibitors (CNIs) due to its renal-sparing properties, especially in heart transplant (HTx) recipients with kidney dysfunction. However, ERL dosing is challenging due to its narrow therapeutic window combined with high interindividual pharmacokinetic variability. Our aim was to evaluate the effect of clinical and genetic factors on ERL dosing in a pilot cohort of 37 HTx recipients. Variants in CYP3A5, CYP3A4, CYP2C8, POR, NR1I2, and ABCB1 were genotyped, and clinical data were retrieved from patient charts. While ERL trough concentration (C0 ) was within the targeted range for most patients, over 30-fold variability in the dose-adjusted ERL C0 was observed. Regression analysis revealed a significant effect of the non-functional CYP3A5*3 variant on the dose-adjusted ERL C0 (p = 0.031). ERL dose requirement was 0.02 mg/kg/d higher in patients with CYP3A5*1/*3 genotype compared to patients with CYP3A5*3/*3 to reach the targeted C0 (p = 0.041). ERL therapy substantially improved estimated glomerular filtration rate (28.6 ± 6.6 mL/min/1.73 m(2)) in patients with baseline kidney dysfunction. Everolimus pharmacokinetics in HTx recipients is highly variable. Our preliminary data on patients on a CNI-free therapy regimen suggest that CYP3A5 genetic variation may contribute to this variability. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Solar cycle variations of MIR radiation environment as observed by the LIULIN dosimeter.

PubMed

Dachev TsP; Tomov, B T; Matviichuk YuN; Koleva, R T; Semkova, J V; Petrov, V M; Benghin, V V; Ivanov YuV; Shurshakov, V A; Lemaire, J F

1999-06-01

Measurements on board the MIR space station by the Bulgarian-Russian dosimeter LIULIN have been used to study the solar cycle variations of the radiation environment. The fixed locations of the instrument in the MIR manned compartment behind 6-15 g/cm2 of shielding have given homogeneous series of particle fluxes and doses measurements to be collected during the declining phase of 22nd solar cycle between September 1989 and April 1994. During the declining phase of 22nd solar cycle the GCR (Galactic Cosmic Rays) flux observed at L>4 (where L is the McIlwain parameter) has enhanced from 0.6-0.7 cm-2 s-1 up to 1.4-1.6 cm-2 s-1. The long-term observations of the trapped radiation can be summarized as follows: the main maximum of the flux and dose rate is located at the southeast side of the geomagnetic field minimum of South Atlantic Anomaly (SAA) at L=1.3-1.4. Protons depositing few (nGy cm2)/particle in the detector predominantly populate this region. At practically the same spatial location and for similar conditions the dose rate rises up from 480 to 1470 microGy/h dose in silicon in the 1990-1994 time interval, during the declining phase of the solar cycle. On the other hand the flux rises from 35 up to 115 cm-2 s-1 for the same period of time. A power law dependence was extracted which predicts that when the total neutral density at the altitude of the station decreases from 8x10(-15) to 6x10(-16) g/cm3 the dose increase from about 200 microGy/h up to 1200 microGy/h. At the same time the flux increase from about 30 cm-2 s-1 up to 120 cm-2 s-1. The AP8 model predictions give only 5.8% increase of the flux for the same conditions.

Comparison between DCA - SSO - VDR and VMAT dose delivery techniques for 15 SRS/SRT patients

NASA Astrophysics Data System (ADS)

Tas, B.; Durmus, I. F.

2018-02-01

To evaluate dose delivery between Dynamic Conformal Arc (DCA) - Segment Shape Optimization (SSO) - Variation Dose Rate (VDR) and Volumetric Modulated Arc Therapy (VMAT) techniques for fifteen SRS patients using Versa HD® lineer accelerator. Fifteen SRS / SRT patient's optimum treatment planning were performed using Monaco5.11® treatment planning system (TPS) with 1 coplanar and 3 non-coplanar fields for VMAT technique, then the plans were reoptimized with the same optimization parameters for DCA - SSO - VDR technique. The advantage of DCA - SSO - VDR technique were determined less MUs and beam on time, also larger segments decrease dosimetric uncertainities of small fields quality assurance. The advantage of VMAT technique were determined a little better GI, CI, PCI, brain V12Gy and brain mean dose. The results show that the clinical objectives and plans for both techniques satisfied all organs at risks (OARs) dose constraints. Depends on the shape and localization of target, we could choose one of these techniques for linear accelerator based SRS / SRT treatment.

High resolution digital autoradiographic and dosimetric analysis of heterogeneous radioactivity distribution in xenografted prostate tumors.

PubMed

Timmermand, Oskar V; Nilsson, Jenny; Strand, Sven-Erik; Elgqvist, Jörgen

2016-12-01

The first main aim of this study was to illustrate the absorbed dose rate distribution from 177 Lu in sections of xenografted prostate cancer (PCa) tumors using high resolution digital autoradiography (DAR) and compare it with hypothetical identical radioactivity distributions of 90 Y or 7 MeV alpha-particles. Three dosimetry models based on either dose point kernels or Monte Carlo simulations were used and evaluated. The second and overlapping aim, was to perform DAR imaging and dosimetric analysis of the distribution of radioactivity, and hence the absorbed dose rate, in tumor sections at an early time point after injection during radioimmunotherapy using 177 Lu-h11B6, directed against the human kallikrein 2 antigen. Male immunodeficient BALB/c nude mice, aged 6-8 w, were inoculated by subcutaneous injection of ∼10 7 LNCaP cells in a 200 μl suspension of a 1:1 mixture of medium and Matrigel. The antibody h11B6 was conjugated with the chelator CHX-A″-DTPA after which conjugated h11B6 was mixed with 177 LuCl 3 . The incubation was performed at room temperature for 2 h, after which the labeling was terminated and the solution was purified on a NAP-5 column. About 20 MBq 177 Lu-h11B6 was injected intravenously in the tail vein. At approximately 10 h postinjection (hpi), the mice were sacrificed and one tumor was collected from each of the five animals and cryosectioned into 10 μm thick slices. The tumor slices were measured and imaged using the DAR MicroImager system and the M3Vision software. Then the absorbed dose rate was calculated using a dose point kernel generated with the Monte Carlo code gate v7.0. The DAR system produced high resolution images of the radioactivity distribution, close to the resolution of single PCa cells. The DAR images revealed a pronounced heterogeneous radioactivity distribution, i.e., count rate per area, in the tumors, indicated by the normalized intensity variations along cross sections as mean ± SD: 0.15 ± 0.15, 0.20 ± 0.18, 0.12 ± 0.17, 0.15 ± 0.16, and 0.23 ± 0.22, for each tumor section, respectively. The absorbed dose rate distribution for 177 Lu at the time of dissection 10 hpi showed a maximum value of 2.9 ± 0.4 Gy/h (mean ± SD), compared to 6.0 ± 0.9 and 159 ± 25 Gy/h for the hypothetical 90 Y and 7 MeV alpha-particle cases assuming the same count rate densities. Mean absorbed dose rate values were 0.13, 0.53, and 6.43 Gy/h for 177 Lu, 90 Y, and alpha-particles, respectively. The initial uptake of 177 Lu-h11B6 produces a high absorbed dose rate, which is important for a successful therapeutic outcome. The hypothetical 90 Y case indicates a less heterogeneous absorbed dose rate distribution and a higher mean absorbed dose rate compared to 177 Lu, although with a potentially increased irradiation of surrounding healthy tissue. The hypothetical alpha-particle case indicates the possibility of a higher maximum absorbed dose rate, although with a more heterogeneous absorbed dose rate distribution.

TU-G-204-05: The Effects of CT Acquisition and Reconstruction Conditions On Computed Texture Feature Values of Lung Lesions

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

Lo, P; Young, S; Kim, G

2015-06-15

Purpose: Texture features have been investigated as a biomarker of response and malignancy. Because these features reflect local differences in density, they may be influenced by acquisition and reconstruction parameters. The purpose of this study was to investigate the effects of radiation dose level and reconstruction method on features derived from lung lesions. Methods: With IRB approval, 33 lung tumor cases were identified from clinically indicated thoracic CT scans in which the raw projection (sinogram) data were available. Based on a previously-published technique, noise was added to the raw data to simulate reduced-dose versions of each case at 25%, 10%more » and 3% of the original dose. Original and simulated reduced dose projection data were reconstructed with conventional and two iterative-reconstruction settings, yielding 12 combinations of dose/recon conditions. One lesion from each case was contoured. At the reference condition (full dose, conventional recon), 17 lesions were randomly selected for repeat contouring (repeatability). For each lesion at each dose/recon condition, 151 texture measures were calculated. A paired differences approach was employed to compare feature variation from repeat contours at the reference condition to the variation observed in other dose/recon conditions (reproducibility). The ratio of standard deviation of the reproducibility to repeatability was used as the variation measure for each feature. Results: The mean variation (standard deviation) across dose levels and kernel was significantly different with a ratio of 2.24 (±5.85) across texture features (p=0.01). The mean variation (standard deviation) across dose levels with conventional recon was also significantly different with 2.30 (7.11) (p=0.025). The mean variation across reconstruction settings of original dose has a trend in showing difference with 1.35 (2.60) among all features (p=0.09). Conclusion: Texture features varied considerably with variations in dose and reconstruction condition. Care should be taken to standardize these conditions when using texture as a quantitative feature. This effort supported in part by a grant from the National Cancer Institute’s Quantitative Imaging Network (QIN): U01 CA181156; The UCLA Department of Radiology has a Master Research Agreement with Siemens Healthcare; Dr. McNitt-Gray has previously received research support from Siemens Healthcare.« less

Impact of bowel gas and body outline variations on total accumulated dose with intensity-modulated proton therapy in locally advanced cervical cancer patients.

PubMed

Berger, Thomas; Petersen, Jørgen Breede Baltzer; Lindegaard, Jacob Christian; Fokdal, Lars Ulrik; Tanderup, Kari

2017-11-01

Density changes occurring during fractionated radiotherapy in the pelvic region may degrade proton dose distributions. The aim of the study was to quantify the dosimetric impact of gas cavities and body outline variations. Seven patients with locally advanced cervical cancer (LACC) were analyzed through a total of 175 daily cone beam computed tomography (CBCT) scans. Four-beams intensity-modulated proton therapy (IMPT) dose plans were generated targeting the internal target volume (ITV) composed of: primary tumor, elective and pathological nodes. The planned dose was 45 Gy [Relative-Biological-Effectiveness-weighted (RBE)] in 25 fractions and simultaneously integrated boosts of pathologic lymph nodes were 55-57.5 Gy (RBE). In total, 475 modified CTs were generated to evaluate the effect of: 1/gas cavities, 2/outline variations and 3/the two combined. The anatomy of each fraction was simulated by propagating gas cavities contours and body outlines from each daily CBCT to the pCT. Hounsfield units corresponding to gas and fat were assigned to the propagated contours. D98 (least dose received by the hottest 98% of the volume) and D99.9 for targets and V43Gy(RBE) (volume receiving ≥43 Gy(RBE)) for organs at risk (OARs) were recalculated on each modified CT, and total dose was evaluated through dose volume histogram (DVH) addition across all fractions. Weight changes during radiotherapy were between -3.1% and 1.2%. Gas cavities and outline variations induced a median [range] dose degradation for ITV45 of 1.0% [0.5-3.5%] for D98 and 2.1% [0.8-6.4%] for D99.9. Outline variations had larger dosimetric impact than gas cavities. Worst nodal dose degradation was 2.0% for D98 and 2.3% for D99.9. The impact on bladder, bowel and rectum was limited with V43Gy(RBE) variations ≤3.5 cm 3 . Bowel gas cavities and outline variations had minor impact on accumulated dose in targets and OAR of four-field IMPT in a LACC population of moderate weight changes.

Adverse events following immunisation with bacille Calmette-Guérin vaccination: baseline data to inform monitoring in Australia following introduction of new unregistered BCG vaccine.

PubMed

Hendry, Alexandra J; Dey, Aditi; Beard, Frank H; Khandaker, Gulam; Hill, Richard; Macartney, Kristine K

2016-12-24

In recent years there has been a global shortage of bacille Calmette-Guérin (BCG) vaccine and, from September 2012, unregistered vaccines have needed to be used in Australia (a Danish product initially until the end of 2015, and a Polish product used in some jurisdictions from early 2016). We examined rates and types of adverse events following immunisation (AEFI) with BCG vaccine reported to the Therapeutic Goods Administration between 2009 and 2014 in children aged less than 7 years. Reporting rates of AEFI with BCG vaccine increased from 87 per 100,000 doses (registered Sanofi Pasteur product) in 2009 to 201 per 100,000 doses (unregistered Danish Statens Serum Institute product) in 2014, with Victoria having the highest rate each year. Substantial variation between jurisdictions exists, suggesting differential reporting of BCG vaccine doses administered and/or BCG vaccine-related AEFI. The most commonly reported reactions were abscess (31%), injection site reaction (27%) and lymphadenopathy/lymphadenitis (17%). This study provides baseline data on BCG vaccine safety to inform surveillance. Given the current use of unregistered vaccines in the context of vaccine supply issues, improved recording of both administered BCG vaccine doses and the reporting of BCG vaccine-related AEFI are required to facilitate close monitoring of vaccine safety.

Solar Modulation of Atmospheric Cosmic Radiation:. Comparison Between In-Flight and Ground-Level Measurements

NASA Astrophysics Data System (ADS)

Iles, R. H. A.; Taylor, G. C.; Jones, J. B. L.

January 2000 saw the start of a collaborative study involving the Mullard Space Science Laboratory, Virgin Atlantic Airways, the Civil Aviation Authority and the National Physical Laboratory in a program to investigate the cosmic radiation exposure to aircrew. The study has been undertaken in view of EU Directive 96/291 (May 2000) which requires the assessment of the level of radiation exposure to aircrew. The project's aims include validation of radiation dose models and evaluation of space weather effects on atmospheric cosmic radiation levels, in particular those effects not accounted for by the models. Ground level measurements are often used as a proxy for variations in cosmic radiation dose levels at aircraft altitudes, especially during Forbush Decreases (FDs) and Solar Energetic Particle (SEP) events. Is this estimation realistic and does the ground level data accurately represent what is happening at altitude? We have investigated the effect of a FD during a flight from Hong Kong to London Heathrow on the 15th July 2000 and compared count rate and dose measurements with simultaneous variations measured at ground level. We have also compared the results with model outputs.

SU-E-T-330: Dosimetric Impact of Intrafraction Respiratory Motion On Lung SBRT Treatment Using Cyberknife 0-View Tracking Mode

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

Rao, M; Chen, F; Cotrutz, C

2015-06-15

Purpose: To investigate the influence of respiratory motion on the delivered dose in lung stereotactic body radiotherapy (SBRT) using Cyberknife (CK) 0-View tracking mode. Methods: CT scans at inspiration and expiration of an anthropomorphic motion phantom were fused base on the spine and an internal target volume (ITV) was created. A 5mm expansion around the ITV resulted in the planning target volume. Three CK plans were generated in Accuray MultiPlan using Lung Optimization Tracking 0-View technique with the minimum MU per beam set to (a) 5MU, (b) 15MU and (c) 30MU, respectively. Doses were calculated on the expiration CT usingmore » Monte-Carlo algorithm. Each plan was delivered 5 times with a range of different starting phases in the respiratory cycle to assess the dose variation due to interplay effect. The delivered dose was measured with EBT3 Gafchromic film which was inserted in the moving target of the phantom. The target motion range is 3 cm in superior-inferior (SI) direction with the breathing period of 5 seconds. Results: The gamma analysis (5%/2mm) of the dose with the films in the transverse plane resulted in average passing rate of 95.5±4.1%, 96.7±2.6%, and 96.2±2.5% for plan (a), (b), and (c), respectively. For the sagittal films, the average passing rate was 91.1±4.9%, 92.1±3.6%, and 92.3±2.9% for the three plans, respectively. The disagreement between measurement and dose calculations were mostly on the target edges in SI direction. The mean measured versus calculated dose differences at the edge of target in SI direction were (a) 3.9±4.8%, (b) 2.4±3.3%, and (c) 2.2±3.2% for the three plans, respectively. Conclusions: The plans with low-MU beams (below 10MU) tend to cause slightly larger dose variation. However in terms of target coverage, the overall clinical dosimetric impact of the intrafraction respiratory motion in lung SBRT is insignificant when averaged over 3∼5 fractions.« less

Background radiation: natural and man-made.

PubMed

Thorne, M C

2003-03-01

A brief overview and comparison is given of dose rates arising from natural background radiation and the fallout from atmospheric testing of nuclear weapons. Although there are considerable spatial variations in exposure to natural background radiation, it is useful to give estimates of worldwide average overall exposures from the various components of that background. Cosmic-ray secondaries of low linear energy transfer (LET), mainly muons and photons, deliver about 280 microSv a(-1). Cosmic-ray neutrons deliver about another 100 microSv a(-1). These low- and high-LET exposures are relatively uniform to the whole body. The effective dose rate from cosmogenic radionuclides is dominated by the contribution of 12 microSv a(-1) from 14C. This is due to relatively uniform irradiation of all organs and tissues from low-energy beta particles. Primordial radionuclides and their progeny (principally the 238U and 232Th series, and 40K) contribute about 480 microSv a(-1) of effective dose by external irradiation. This is relatively uniform photon irradiation of the whole body. Internally incorporated 40K contributes a further 165 microSv a(-1) of effective dose in adults, mainly from beta particles, but with a significant gamma component. Equivalent doses from 40K are somewhat higher in muscle than other soft tissues, but the distinction is less than a factor of three. Uranium and thorium series radionuclides give rise to an average effective dose rate of around 120 microSv a(-1). This includes a major alpha particle component, and exposures of radiosensitive tissues in lung, liver, kidney and the skeleton are recognised as important contributors to effective dose. Overall, these various sources give a worldwide average effective dose rate of about 1160 microSv a(-1). Exposure to 222Rn, 220Rn and their short-lived progeny has to be considered separately. This is very variable both within and between countries. For 222Rn and its progeny, a worldwide average effective dose rate is about 1105 microSv a(-1). For 220Rn and its progeny, the corresponding value is 91 microSv a(-1). In both cases, the effective dose is mainly due to a particle irradiation of the bronchial tissues of the lungs. Overall, the worldwide average effective dose rate from natural background is about 2400 microSv a(-1) or 2.4 mSv a(-1). For comparison, worldwide average effective dose rates from weapons fallout peaked at 113 microSv a(-1) (about 5% of natural background) in 1963 and have since fallen to about 5.5 microSv a(-1) (about 0.2% of natural background). These values perhaps serve to emphasise that even gross insults to the natural environment from anthropogenic releases of radioactive materials are likely to be of limited significance when set in the context of the ambient radioactive environment within which all organisms, including humans, have developed.

Dosimetric characteristics of a PIN diode for radiotherapy application.

PubMed

Kumar, R; Sharma, S D; Philomina, A; Topkar, A

2014-08-01

The PIN diode developed by Bhabha Atomic Research Centre (BARC) was modified for its use as a dosimeter in radiation therapy. For this purpose the diode was mounted on a printed circuit board (PCB) and provided with necessary connections so that its response against irradiation can be recorded by a standard radiotherapy electrometer. The dosimetric characteristics of the diode were studied in Co-60 gamma rays as well as high energy X-rays. The measured sensitivity of this PIN diode is 4 nC/cGy which is about ten times higher than some commercial diode dosimeters. The leakage current from the diode is 0.04 nA. The response of the PIN diode is linear in the range of 20-1000 cGy which covers the full range of radiation dose encountered in radiotherapy treatments. The non-linearity of the diode response is 3.5% at 20 cGy and it is less than 1.5% at higher dose values. Its repeatability is within 0.5%. The angular response variation is about 5.6% within 6608 with respect to normal beam incidence. The response of the PIN diode at 6 and 18 MV X-rays varies within 2% with respect to its response at Co-60 gamma rays. The source to surface distance (SSD) dependence of the PIN diode was studied for Co-60 beam. It was found that the response of the diode decreases almost linearly relative to given dose for beams with constant collimator setting but increasing SSD (decreasing dose-rate). Within this study the diode response varied by about 2.5% between the maximum and minimum SSD. The dose-rate dependence of the PIN diode for 6 and 15 MV-rays was studied. The variation in response of diode for both energies in the studied dose range is less than 1%. The field size dependence of the PIN diode response is within 1% with respect to the response of ionisation chamber. These studies indicate that the characteristics of the PIN diode are suitable for use in radiotherapy dosimetry.

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.

EXOMARS IRAS (DOSE) radiation measurements.

NASA Astrophysics Data System (ADS)

Federico, C.; Di Lellis, A. M.; Fonte, S.; Pauselli, C.; Reitz, G.; Beaujean, R.

The characterization and the study of the radiations on their interaction with organic matter is of great interest in view of the human exploration on Mars. The Ionizing RAdiation Sensor (IRAS) selected in the frame of the ExoMars/Pasteur ESA mission is a lightweight particle spectrometer combining various techniques of radiation detection in space. It characterizes the first time the radiation environment on the Mars surface, and provide dose and dose equivalent rates as precursor information absolutely necessary to develop ways to mitigate the radiation risks for future human exploration on Mars. The Martian radiation levels are much higher than those found on Earth and they are relatively low for space. Measurements on the surface will show if they are similar or not to those seen in orbit (modified by the presence of ``albedo'' neutrons produced in the regolith and by the thin Martian atmosphere). IRAS consists of a telescope based on segmented silicon detectors of about 40\\userk\\milli\\metre\\user;k diameter and 300\\user;k\\micro\\metre\\user;k thickness, a segmented organic scintillator, and of a thermoluminescence dosimeter. The telescope will continuously monitor temporal variation of the particle count rate, the dose rate, particle and LET (Linear Energy Transfer) spectra. Tissue equivalent BC430 scintillator material will be used to measure the neutron dose. Neutrons are selected by a criteria requiring no signal in the anti-coincidence. Last, the passive thermoluminescence dosimeter, based on LiF:Mg detectors, regardless the on board operation timing, will measure the total dose accumulated during the exposure period and due to beta and gamma radiation, with a responsivity very close to that of a human tissue.

Advantages of Reduced Prophylaxis after Tubularized Incised Plate Repair of Hypospadias.

PubMed

Zeiai, Said; Nordenskjöld, Agneta; Fossum, Magdalena

2016-10-01

Concerns about antibiotic resistance, adverse drug reactions and questionable medical benefits have led to changes in prophylactic antibiotic management in hypospadias repair at our clinic. In March 2010 our guidelines were changed from continuous prophylaxis for 14 days to 1 dose preoperatively and another at removal of the stent. We analyze the effects of this new regimen. We performed a prospective journal cohort study of all our hypospadias operations from June 2008 to December 2011. We collected data from consecutive patients undergoing primary tubularized incised plate repair and postoperative stent. Patients operated on before March 2010 were compared to those operated on later. End points were postoperative infection requiring antibiotics and any complication that required redo surgery. The study included 113 primary tubularized incised plate repairs with postoperative stents. Patient distribution was the same in both groups. Of 58 patients in the group receiving continuous antibiotic prophylaxis 17 had a complication and/or infection, compared to 9 of 55 patients receiving 2-dose prophylaxis. The infection rate was 5% in the continuous prophylaxis group and 4% in the 2-dose group. In contrast to our expectations, a lower complication rate was observed in the group with lower antibiotic dose without an increased risk of infection. There is little documented evidence concerning benefits of antibiotic prophylaxis for postoperative complications, which gives rise to large variations in clinical practice. In our study lower antibiotic dose did not increase the number of infections, but rather decreased complication rates. We advocate antibiotic prophylaxis with only a 2-dose regimen. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Adaptation and validation of a commercial head phantom for cranial radiosurgery dosimetry end-to-end audit.

PubMed

Dimitriadis, Alexis; Palmer, Antony L; Thomas, Russell A S; Nisbet, Andrew; Clark, Catharine H

2017-06-01

To adapt and validate an anthropomorphic head phantom for use in a cranial radiosurgery audit. Two bespoke inserts were produced for the phantom: one for providing the target and organ at risk for delineation and the other for performing dose measurements. The inserts were tested to assess their positional accuracy. A basic treatment plan dose verification with an ionization chamber was performed to establish a baseline accuracy for the phantom and beam model. The phantom and inserts were then used to perform dose verification measurements of a radiosurgery plan. The dose was measured with alanine pellets, EBT extended dose film and a plastic scintillation detector (PSD). Both inserts showed reproducible positioning (±0.5 mm) and good positional agreement between them (±0.6 mm). The basic treatment plan measurements showed agreement to the treatment planning system (TPS) within 0.5%. Repeated film measurements showed consistent gamma passing rates with good agreement to the TPS. For 2%-2 mm global gamma, the mean passing rate was 96.7% and the variation in passing rates did not exceed 2.1%. The alanine pellets and PSD showed good agreement with the TPS (-0.1% and 0.3% dose difference in the target) and good agreement with each other (within 1%). The adaptations to the phantom showed acceptable accuracies. The presence of alanine and PSD do not affect film measurements significantly, enabling simultaneous measurements by all three detectors. Advances in knowledge: A novel method for thorough end-to-end test of radiosurgery, with capability to incorporate all steps of the clinical pathway in a time-efficient and reproducible manner, suitable for a national audit.

Influence of monte carlo variance with fluence smoothing in VMAT treatment planning with Monaco TPS.

PubMed

Sarkar, B; Manikandan, A; Nandy, M; Munshi, A; Sayan, P; Sujatha, N

2016-01-01

The study aimed to investigate the interplay between Monte Carlo Variance (MCV) and fluence smoothing factor (FSF) in volumetric modulated arc therapy treatment planning by using a sample set of complex treatment planning cases and a X-ray Voxel Monte Carlo-based treatment planning system equipped with tools to tune fluence smoothness as well as MCV. The dosimetric (dose to tumor volume, and organ at risk) and physical characteristic (treatment time, number of segments, and so on) of a set 45 treatment plans for all combinations of 1%, 3%, 5% MCV and 1, 3, 5 FSF were evaluated for five carcinoma esophagus cases under the study. Increase in FSF reduce the treatment time. Variation of MCV and FSF gives a highest planning target volume (PTV), heart and lung dose variation of 3.6%, 12.8% and 4.3%, respectively. The heart dose variation was highest among all organs at risk. Highest variation of spinal cord dose was 0.6 Gy. Variation of MCV and FSF influences the organ at risk (OAR) doses significantly but not PTV coverage and dose homogeneity. Variation in FSF causes difference in dosimetric and physical parameters for the treatment plans but variation of MCV does not. MCV 3% or less do not improve the plan quality significantly (physical and clinical) compared with MCV greater than 3%. The use of MCV between 3% and 5% gives similar results as 1% with lesser calculation time. Minimally detected differences in plan quality suggest that the optimum FSF can be set between 3 and 5.

Diamond detector in absorbed dose measurements in high‐energy linear accelerator photon and electron beams

PubMed Central

Binukumar, John Pichy; Amri, Iqbal Al; Davis, Cheriyathmanjiyil Antony

2016-01-01

Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue‐equivalent properties. We investigated a commercially available ‘microdiamond’ detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1 mm, thickness 1×10−3mm, the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be ±0.17% (1 SD) (n=11). The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stopping power ratios compared well with Nd, water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long‐term stability and reproducibility. Based on micro‐dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance. PACS number(s): 87.56.Da PMID:27074452

A quality assurance device for measuring afterloader performance and transit dose for nasobiliary high-dose-rate brachytherapy.

PubMed

Deufel, Christopher L; Mullins, John P; Zakhary, Mark J

2018-05-17

Nasobiliary high-dose-rate (HDR) brachytherapy has emerged as an effective tool to boost the radiation dose for patients with unresectable perihilar cholangiocarcinoma. This work describes a quality assurance (QA) tool for measuring the HDR afterloader's performance, including the transit dose, when the source wire travels through a tortuous nasobiliary catheter path. The nasobiliary QA device was designed to mimic the anatomical path of a nasobiliary catheter, including the nasal, stomach, duodenum, and bile duct loops. Two of these loops, the duodenum and bile duct loops, have adjustable radii of curvature, resulting in the ability to maximize stress on the source wire in transit. The device was used to measure the performance over time for the HDR afterloader and the differences between intraluminal catheter lots. An upper limit on the transit dose was also measured using radiochromic film and compared with a simple theoretical model. The QA device was capable of detecting performance variations among nasobiliary catheter lots and following radioactive source replacement. The transit dose from a nasobiliary treatment increased by up to one order of magnitude when the source wire encountered higher than normal friction. Three distinct travel speeds of the source wire were observed: 5.2, 17.4, and 54.7 cm/s. The maximum transit dose was 0.3 Gy at a radial distance of 5 mm from a 40.3 kU 192 Ir source. The source wire encounters substantially greater friction when it navigates through the nasobiliary brachytherapy catheter. A QA tool that mimics the nasal, stomach, duodenum, and bile duct loops may be used to evaluate transit dose and the afterloader's performance over time. Copyright © 2018 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Radon daughters' concentration in air and exposure of joggers at the university campus of Bangalore, India.

PubMed

Ashok, G V; Nagaiah, N; Shiva Prasad, N G

2008-09-01

The concentration of radon daughters in outdoor air was measured continuously from January 2006 to December 2006 near the Department of Physics, Bangalore University campus, Bangalore. The concentration was measured by collecting air samples at a height of 1 m above the ground level on a glass micro fibre filter paper with a known air flow rate. The results show that the radon progeny concentration exhibits distinct seasonal and diurnal variations that are predominantly caused by changes in the temperature gradient at the soil-atmosphere interface. The concentration was found to be high from 20.00 to 8.00 hrs, when the turbulence mixing was minimum and low during the rest of the time. In terms of the monthly concentration, January was found to be the highest with September/August being the lowest. The diurnal variations in the concentrations of radon progeny were found to exhibit positive correlation with the relative humidity and anti-correlation with the atmospheric temperature. From the measured concentration, an attempt was made to establish the annual effective dose to the general public of the region and was found to be 0.085 mSv/a. In addition, an attempt was also made for the first time to study the variation of inhalation dose with respect to the physical activity levels. Results show that in the light of both the effect of chemical pollutants and radiation dose due to inhalation of radon daughters, evening jogging is advisable.

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.

Collaboration of local government and experts responding to increase in environmental radiation level due to the nuclear disaster: focusing on their activities and latest radiological discussion.

PubMed

Iimoto, T; Nunokawa, J; Fujii, H; Takashima, R; Hashimoto, M; Fukuhara, T; Yajima, T; Matsuzawa, H; Kurosawa, K; Yanagawa, Y; Someya, S

2015-11-01

Activities were introduced in Kashiwa city in the Tokyo metropolitan area to correspond to the elevated environmental radiation level after the disaster of the Fukushima Daiichi nuclear power plant. These were based on a strong cooperation between local governments and experts. Ambient dose rate and radioactivity of foodstuff produced inside of the city have been monitored. Representative ambient dose rates around living environments have almost already become their original levels of the pre-accident because of the decontamination activity, natural washout and effective half-lives of radioactivity. The internal annual dose due to radioactive cesium under the policy of 'Local Production for Local Consumption' is estimated as extremely low comparing the variation range due to natural radioactivity. Systematic survey around a retention basin has been started. All of these latest monitoring data would be one of the core information for the policy making as well as a cost-benefit discussion and risk communication. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Synchrotron generated X-ray Excited Optical Luminescence (XEOL) from Quartz

NASA Astrophysics Data System (ADS)

King, Georgina; Finch, Adrian; Robinson, Ruth

2010-05-01

Quartz is the preferred mineral for optically stimulated luminescence (OSL) dating, due to its well constrained behaviour as a radiation dosimeter. However, despite the plethora of successful quartz OSL applications, no solution has been found to the problem that some quartz luminesce more brightly than others, which has limited the application of OSL in certain settings. This has been addressed through examination of the luminescence emission using a variety of excitation techniques and emission spectroscopy. X-ray Excited Optical Luminescence (XEOL) is luminescence excited by x-rays produced by a synchrotron. XEOL analyses were conducted upon a suite of quartz samples at Diamond, Great Britain, which had previously been analysed with Ionoluminescence (IL), at Sussex University. The samples were selected to include quartz of both poor and excellent OSL sensitivities. Therefore, two Scottish glacial outwash samples prepared at St Andrews, and a calibration quartz sample, prepared at the Risø National Laboratory in Denmark were analysed for these properties respectively. The XEOL emission spectra comprised three major emissions at 3.32, 3.81 and 4.05 eV, and one weaker emission at 1.94 eV in all samples. The calibration quartz sample had the most intense emission by an order of magnitude. Throughout increased exposure to x-rays, the intensity of the UV emission reduced, and an increase in the red (1.94 eV) emission was recorded. The derived XEOL spectra complement the IL spectra obtained previously. The IL spectra were dominated by only two broad emissions at 3.2-3.1 eV and 1.8-1.7 eV. However, throughout the IL experiments a dose dependent effect was also observed, whereby the UV emission was depleted to the benefit of the red with increasing exposure. Furthermore the gradient of the power law relationship between the UV and red emission change with dose is similar for both the IL and XEOL data: at -1.15 and -1.05 respectively for calibration quartz, when plotted on a log-log scale. IL and XEOL are complimentary techniques, as although the radiation dose rate of XEOL is three orders of magnitude greater than that of IL, the total experimental administered dose is similar. This contrast in dose rate is caused by the significant variation is dose per carrier for each technique. Within IL each ion delivers 1E-01 J whereas each photon delivers 1E-15 J in XEOL. It is the much greater flux of photons relative to ions, which makes XEOL the more energetic mode of analysis. Thus these complimentary techniques enable investigation of radiation dose rate, as well as cumulative dose effects. The observed variations in the XEOL and IL derived emission spectra are therefore attributed to the differences in radiation dose rate. The radiation sensitivity of the quartz emission may provide an explanation for the varied luminescence response of different quartz. The quartz luminescence emission thus may not just record the most recent period of irradiation, but rather its entire radiation history.

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

Volotskova, O; Xu, A; Jozsef, G

Purpose: To investigate the response and dose rate dependence of a scintillation detector over a wide energy range. Methods: The energy dependence of W1 scintillation detector was tested with: 1) 50–225 keV beams generated by an animal irradiator, 2) a Leksell Gamma Knife Perfexion Co-60 source, 3) 6MV, 6FFF, 10FFF and 15MV photon beams, and 4) 6–20MeV electron beams from a linac. Calibrated linac beams were used to deliver 100 cGy to the detector at dmax in water under reference conditions. The gamma-knife measurement was performed in solid water (100 cGy with 16mm collimator). The low energy beams were calibratedmore » with an ion chamber in air (TG-61), and the scintillation detector was placed at the same location as the ionization chamber during calibration. For the linac photon and electron beams, dose rate dependence was tested for 100–2400 and 100–800 MU/min. Results: The scintillation detector demonstrated strong energy dependence in the range of 50–225keV. The measured values were lower than the delivered dose and increased as the energy increased. Therapeutic photon beams showed energy independence with variations less than 1%. Therapeutic electron beams displayed the same sensitivity of ∼2–3% at their corresponding dmax depths. The change in dose-rate of photon and electron beams within the therapeutic energy range did not affect detector output (<0.5%). Measurements acquired with the gamma knife showed that the output data agreed with the delivered dose up to 3%. Conclusion: W1 scintillation detector output has a strong energy dependence in the diagnostic and orthovoltage energy range. Therapeutic photon beams exhibited energy independence with no observable dose-rate dependence. This study may aid in the implementation of a scintillation detector in QA programs by providing energy calibration factors.« less

Usefulness of Guided Breathing for Dose Rate-Regulated Tracking

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

Han-Oh, Sarah; Department of Radiation Oncology, University of Maryland Medical System, Baltimore, MD; Yi, Byong Yong

2009-02-01

Purpose: To evaluate the usefulness of guided breathing for dose rate-regulated tracking (DRRT), a new technique to compensate for intrafraction tumor motion. Methods and Materials: DRRT uses a preprogrammed multileaf collimator sequence that tracks the tumor motion derived from four-dimensional computed tomography and the corresponding breathing signals measured before treatment. Because the multileaf collimator speed can be controlled by adjusting the dose rate, the multileaf collimator positions are adjusted in real time during treatment by dose rate regulation, thereby maintaining synchrony with the tumor motion. DRRT treatment was simulated with free, audio-guided, and audiovisual-guided breathing signals acquired from 23 lungmore » cancer patients. The tracking error and duty cycle for each patient were determined as a function of the system time delay (range, 0-1.0 s). Results: The tracking error and duty cycle averaged for all 23 patients was 1.9 {+-} 0.8 mm and 92% {+-} 5%, 1.9 {+-} 1.0 mm and 93% {+-} 6%, and 1.8 {+-} 0.7 mm and 92% {+-} 6% for the free, audio-guided, and audiovisual-guided breathing, respectively, for a time delay of 0.35 s. The small differences in both the tracking error and the duty cycle with guided breathing were not statistically significant. Conclusion: DRRT by its nature adapts well to variations in breathing frequency, which is also the motivation for guided-breathing techniques. Because of this redundancy, guided breathing does not result in significant improvements for either the tracking error or the duty cycle when DRRT is used for real-time tumor tracking.« less

Oncogenic transformation through the cell cycle and the LET dependent inverse dose rate effect

NASA Technical Reports Server (NTRS)

Geard, C. R.; Miller, R. C.; Brenner, D. J.; Hall, E. J.; Wachholz, B. W. (Principal Investigator)

1994-01-01

Synchronised populations of mouse C3H/10T-1/2 cells were obtained by a stringent mitotic dislodgment procedure. Mitotic cells rapidly attach and progress sequentially through the cell cycle. Irradiation (3 Gy of X rays) was carried out at intervals from 0 to 18 h after initiating cell cycle progression of the mitotic cells. Oncogenic transformation was enhanced 10-fold over cells irradiated soon after replating (G1 and S phases) for cells in a near 2 h period corresponding to cells in G2 phase but not in mitosis. The cell surviving fraction had a 2-1/2-fold variation with resistant peaks corresponding to the late G1 and late S phases. These findings provide experimental support for the hypothesis initiated by Rossi and Kellerer and developed by Brenner and Hall to explain the LET dependent inverse dose rate effect for oncogenic transformation.

Dose uniformity analysis among ten 16-slice same-model CT scanners.

PubMed

Erdi, Yusuf Emre

2012-01-01

With the introduction of multislice scanners, computed tomographic (CT) dose optimization has become important. The patient-absorbed dose may differ among the scanners although they are the same type and model. To investigate the dose output variation of the CT scanners, we designed the study to analyze dose outputs of 10 same-model CT scanners using 3 clinical protocols. Ten GE Lightspeed (GE Healthcare, Waukesha, Wis) 16-slice scanners located at main campus and various satellite locations of our institution have been included in this study. All dose measurements were performed using poly (methyl methacrylate) (PMMA) head (diameter, 16 cm) and body (diameter, 32 cm) phantoms manufactured by Radcal (RadCal Corp, Monrovia, Calif) using a 9095 multipurpose analyzer with 10 × 9-3CT ion chamber both from the same manufacturer. Ion chamber is inserted into the peripheral and central axis locations and volume CT dose index (CTDIvol) is calculated as weighted average of doses at those locations. Three clinical protocol settings for adult head, high-resolution chest, and adult abdomen are used for dose measurements. We have observed up to 9.4% CTDIvol variation for the adult head protocol in which the largest variation occurred among the protocols. However, head protocol uses higher milliampere second values than the other 2 protocols. Most of the measured values were less than the system-stored CTDIvol values. It is important to note that reduction in dose output from tubes as they age is expected in addition to the intrinsic radiation output fluctuations of the same scanner. Although the same model CT scanners were used in this study, it is possible to see CTDIvol variation in standard patient scanning protocols of head, chest, and abdomen. The compound effect of the dose variation may be larger with higher milliampere and multiphase and multilocation CT scans.

Using rainfall radar data to improve interpolated maps of dose rate in the Netherlands.

PubMed

Hiemstra, Paul H; Pebesma, Edzer J; Heuvelink, Gerard B M; Twenhöfel, Chris J W

2010-12-01

The radiation monitoring network in the Netherlands is designed to detect and track increased radiation levels, dose rate more specifically, in 10-minute intervals. The network consists of 153 monitoring stations. Washout of radon progeny by rainfall is the most important cause of natural variations in dose rate. The increase in dose rate at a given time is a function of the amount of progeny decaying, which in turn is a balance between deposition of progeny by rainfall and radioactive decay. The increase in progeny is closely related to average rainfall intensity over the last 2.5h. We included decay of progeny by using weighted averaged rainfall intensity, where the weight decreases back in time. The decrease in weight is related to the half-life of radon progeny. In this paper we show for a rainstorm on the 20th of July 2007 that weighted averaged rainfall intensity estimated from rainfall radar images, collected every 5min, performs much better as a predictor of increases in dose rate than using the non-averaged rainfall intensity. In addition, we show through cross-validation that including weighted averaged rainfall intensity in an interpolated map using universal kriging (UK) does not necessarily lead to a more accurate map. This might be attributed to the high density of monitoring stations in comparison to the spatial extent of a typical rain event. Reducing the network density improved the accuracy of the map when universal kriging was used instead of ordinary kriging (no trend). Consequently, in a less dense network the positive influence of including a trend is likely to increase. Furthermore, we suspect that UK better reproduces the sharp boundaries present in rainfall maps, but that the lack of short-distance monitoring station pairs prevents cross-validation from revealing this effect. Copyright © 2010 Elsevier B.V. All rights reserved.

Importance of dosimetry protocol for cell irradiation on a low X-rays facility and consequences for the biological response.

PubMed

Dos Santos, Morgane; Paget, Vincent; Ben Kacem, Mariam; Trompier, François; Benadjaoud, Mohamed Amine; François, Agnès; Guipaud, Olivier; Benderitter, Marc; Milliat, Fabien

2018-06-01

The main objective of radiobiology is to establish links between doses and radiation-induced biological effects. In this context, well-defined dosimetry protocols are crucial to the determination of experimental protocols. This work proposes a new dosimetry protocol for cell irradiation in a SARRP and shows the importance of the modification of some parameters defined in dosimetry protocol for physical dose and biological outcomes. Once all parameters of the configuration were defined, dosimetry measurements with ionization chambers and EBT3 films were performed to evaluate the dose rate and the attenuation due to the cell culture medium. To evaluate the influence of changes in cell culture volume and/or additional filtration, 6-well plates containing EBT3 films with water were used to determine the impact on the physical dose at 80 kV. Then, experiments with the same irradiation conditions were performed by replacing EBT3 films by HUVECs. The biological response was assessed using clonogenic assay. Using a 0.15 mm copper filter lead to a variation of +1% using medium thickness of 0.104 cm to -8% using a medium thickness of 0.936 cm on the physical dose compare to the reference condition (0.313 cm). For the 1 mm aluminum filter, a variation of +8 to -40% for the same medium thickness conditions has been observed. Cells irradiated in the same conditions showed significant differences in survival fraction, corroborating the effects of dosimetric changes on physical dose. This work shows the importance of dosimetry in radiobiology studies and the need of an accurate description of the dosimetry protocol used for irradiation.

SU-F-T-550: Radiochromic Plastic Thin Sheet Dosimeter: Initial Performance

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

Jordan, K; Adamovics, J

Purpose: Thin sheets, of a high sensitivity formulation of radiochromic dosimeter, Presage were prepared and evaluated for optical readout. Methods: Sheets of radiochromic polyurethane, 12 cm long, 10 cm wide and 0.2 cm thick were prepared with leuco crystal violet as the reporter molecule. Sample transmission was evaluated at a wavelength of 590 nm with in-house constructed instruments: optical cone beam laser CT scanner, fixed and scanning spot densitometers. Sample sequential irradiations to a total dose of 40 Gy were conducted with a modified, Theratron 60, cobalt radiotherapy machine at dose rates of 1 or 0.25 Gy per minute. Exposuremore » to ambient and readout light was minimized to limit background photochromic signals. Samples were stored at 4°C. Optical activity was assessed from linearly polarized transmission images. Comparison sensitivity measurements with EBT3 film were conducted. Results: Samples were transparent, smooth and pale purple before irradiation. Radiochromic reaction was completed in less than 5 minutes. A linear dose response with a sensitivity of 0.5 cm-1Gy-1 was observed. Micrometer measurements found sheet thickness variations up to 20%. Uniform dose, 2 Gy attenuation images, correlated with local sheet thicknesses. Comparable measurements with EBT3 film were 3 times more sensitive at 1 Gy but above 15 Gy, EBT3 film had lower sensitivity than 0.2 cm thick Presage sheet dosimeter due to its non-linear response. Conclusion: Dose sensitivity provided a 10% decrease in transmission for a 1 Gy dose. Improvements in mold design are expected to allow production of sheets with less than 5% variation in thickness. Above, 10 Gy, Presage sheet dosimeter performance expected to exceed EBT3 film based on linearity, sensitivity, transparency and smoothness of samples. J Adamovics is owner of Heuris Inc.« less

Fate of classical faecal bacterial markers and ampicillin-resistant bacteria in agricultural soils under Mediterranean climate after urban sludge amendment.

PubMed

Gondim-Porto, Clarissa; Platero, Leticia; Nadal, Ignacio; Navarro-García, Federico

2016-09-15

The use of sewage sludge or biosolids as agricultural amendments may pose environmental and human health risks related to pathogen or antibiotic-resistant microorganism transmission from soils to vegetables or to water through runoff. Since the survival of those microorganisms in amended soils has been poorly studied under Mediterranean climatic conditions, we followed the variation of soil fecal bacterial markers and ampicillin-resistant bacteria for two years with samplings every four months in a split block design with three replica in a crop soil where two different types of biosolids (aerobically or anaerobically digested) at three doses (low, 40; intermediate, 80; and high, 160Mg·ha(-1)) were applied. Low amounts of biosolids produced similar decay rates of coliform populations than in control soil (-0.19 and -0.27log10CFUs·g(-1)drysoilmonth(-1) versus -0.22) while in the case of intermediate and high doses were close to zero and their populations remained 24months later in the range of 4-5log10CFUs·g(-1)ds. Enterococci populations decayed at different rates when using aerobic than anaerobic biosolids although high doses had higher rates than control (-0.09 and -0.13log10CFUs·g(-1)dsmonth(-1) for aerobic and anaerobic, respectively, vs -0.07). At the end of the experiment, counts in high aerobic and low and intermediate anaerobic plots were 1 log10 higher than in control (4.21, 4.03, 4.2 and 3.11log10CFUs·g(-1) ds, respectively). Biosolid application increased the number of Clostridium spores in all plots at least 1 log10 with respect to control with a different dynamic of decay for low and intermediate doses of aerobic and anaerobic sludge. Ampicillin-resistant bacteria increased in amended soils 4months after amendment and remained at least 1 log10 higher 24months later, especially in aerobic and low and intermediate anaerobic plots due to small rates of decay (in the range of -0.001 to -0.008log10CFUs·g(-1)dsmonth(-1) vs -0.016 for control). Aerobic plots had relative populations of ampicillin-resistant bacteria higher than anaerobic plots with different positive trends. Dose (22%) and time (13%) explained most of the variation of the bacterial populations. Dynamics of fecal markers did not correlate with ampicillin-resistant bacteria thus making necessary to evaluate specifically this trait to avoid possible risks for human and environmental health. Copyright © 2016 Elsevier B.V. All rights reserved.

Dosimetric characterization of a synthetic single crystal diamond detector in a clinical 62 MeV ocular therapy proton beam

NASA Astrophysics Data System (ADS)

Marinelli, Marco; Pompili, F.; Prestopino, G.; Verona, C.; Verona-Rinati, G.; Cirrone, G. A. P.; Cuttone, G.; La Rosa, R. M.; Raffaele, L.; Romano, F.; Tuvè, C.

2014-12-01

A synthetic single crystal diamond based Schottky photodiode was tested at INFN-LNS on the proton beam line (62 MeV) dedicated to the radiation treatment of ocular disease. The diamond detector response was studied in terms of pre-irradiation dose, linearity with dose and dose rate, and angular dependence. Depth dose curves were measured for the 62 MeV pristine proton beam and for three unmodulated range-shifted proton beams; furthermore, the spread-out Bragg peak was measured for a modulated therapeutic proton beam. Beam parameters, recommended by the ICRU report 78, were evaluated to analyze depth-dose curves from diamond detector. Measured dose distributions were compared with the corresponding dose distributions acquired with reference plane-parallel ionization chambers. Field size dependence of the output factor (dose per monitor unit) in a therapeutic modulated proton beam was measured with the diamond detector over the range of ocular proton therapy collimator diameters (5-30 mm). Output factors measured with the diamond detector were compared to the ones by a Markus ionization chamber, a Scanditronix Hi-p Si stereotactic diode and a radiochromic EBT2 film. Signal stability within 0.5% was demonstrated for the diamond detector with no need of any pre-irradiation dose. Dose and dose rate dependence of the diamond response was measured: deviations from linearity resulted to be within ±0.5% over the investigated ranges of 0.5-40.0 Gy and 0.3-30.0 Gy/min respectively. Output factors from diamond detector measured with the smallest collimator (5 mm in diameter) showed a maximum deviation of about 3% with respect to the high resolution radiochromic EBT2 film. Depth-dose curves measured by diamond for unmodulated and modulated beams were in good agreement with those from the reference plane-parallel Markus chamber, with relative differences lower than ±1% in peak-to-plateau ratios, well within experimental uncertainties. A 2.5% variation in diamond detector response was observed in angular dependence measurements carried-out by varying the proton beam incidence angle in the polar direction. The dosimetric characterization of the tested synthetic single crystal diamond detector clearly indicates its suitability for relative dosimetry in ocular therapy proton beams, with no need of any correction factors accounting for dose rate and linear energy transfer dependence.

Dosimetric impact of daily setup variations during treatment of canine nasal tumors using intensity-modulated radiation therapy.

PubMed

Deveau, Michael A; Gutiérrez, Alonso N; Mackie, Thomas R; Tomé, Wolfgang A; Forrest, Lisa J

2010-01-01

Intensity-modulated radiation therapy (IMRT) can be employed to yield precise dose distributions that tightly conform to targets and reduce high doses to normal structures by generating steep dose gradients. Because of these sharp gradients, daily setup variations may have an adverse effect on clinical outcome such that an adjacent normal structure may be overdosed and/or the target may be underdosed. This study provides a detailed analysis of the impact of daily setup variations on optimized IMRT canine nasal tumor treatment plans when variations are not accounted for due to the lack of image guidance. Setup histories of ten patients with nasal tumors previously treated using helical tomotherapy were replanned retrospectively to study the impact of daily setup variations on IMRT dose distributions. Daily setup shifts were applied to IMRT plans on a fraction-by-fraction basis. Using mattress immobilization and laser alignment, mean setup error magnitude in any single dimension was at least 2.5 mm (0-10.0 mm). With inclusions of all three translational coordinates, mean composite offset vector was 5.9 +/- 3.3 mm. Due to variations, a loss of equivalent uniform dose for target volumes of up to 5.6% was noted which corresponded to a potential loss in tumor control probability of 39.5%. Overdosing of eyes and brain was noted by increases in mean normalized total dose and highest normalized dose given to 2% of the volume. Findings suggest that successful implementation of canine nasal IMRT requires daily image guidance to ensure accurate delivery of precise IMRT distributions when non-rigid immobilization techniques are utilized. Unrecognized geographical misses may result in tumor recurrence and/or radiation toxicities to the eyes and brain.

DOSIMETRIC IMPACT OF DAILY SETUP VARIATIONS DURING TREATMENT OF CANINE NASAL TUMORS USING INTENSITY-MODULATED RADIATION THERAPY

PubMed Central

Deveau, Michael A.; Gutiérrez, Alonso N.; Mackie, Thomas R.; Tomé, Wolfgang A.; Forrest, Lisa J.

2009-01-01

Intensity-modulated radiation therapy (IMRT) can be employed to yield precise dose distributions that tightly conform to targets and reduce high doses to normal structures by generating steep dose gradients. Because of these sharp gradients, daily setup variations may have an adverse effect on clinical outcome such that an adjacent normal structure may be overdosed and/or the target may be underdosed. This study provides a detailed analysis of the impact of daily setup variations on optimized IMRT canine nasal tumor treatment plans when variations are not accounted for due to the lack of image guidance. Setup histories of ten patients with nasal tumors previously treated using helical tomotherapy were replanned retrospectively to study the impact of daily setup variations on IMRT dose distributions. Daily setup shifts were applied to IMRT plans on a fraction-by-fraction basis. Using mattress immobilization and laser alignment, mean setup error magnitude in any single dimension was at least 2.5mm (0-10.0mm). With inclusions of all three translational coordinates, mean composite offset vector was 5.9±3.3mm. Due to variations, a loss of equivalent uniform dose (EUD) for target volumes of up to 5.6% was noted which corresponded to a potential loss in TCP of 39.5%. Overdosing of eyes and brain was noted by increases in mean normalized total dose (NTDmean) and highest normalized dose given to 2% of the volume (NTD2%). Findings suggest that successful implementation of canine nasal IMRT requires daily image guidance to ensure accurate delivery of precise IMRT distributions when non-rigid immobilization techniques are utilized. Unrecognized geographical misses may result in tumor recurrence and/or radiation toxicities to the eyes and brain. PMID:20166402

SU-F-T-609: Impact of Dosimetric Variation for Prescription Dose Using Analytical Anisotropic Algorithm (AAA) in Lung SBRT

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

Kawai, D; Takahashi, R; Kamima, T

Purpose: Actual irradiated prescription dose to patients cannot be verified. Thus, independent dose verification and second treatment planning system are used as the secondary check. AAA dose calculation engine has contributed to lung SBRT. We conducted a multi-institutional study to assess variation of prescription dose for lung SBRT when using AAA in reference to using Acuros XB and Clarkson algorithm. Methods: Six institutes in Japan participated in this study. All SBRT treatments were planed using AAA in Eclipse and Adaptive Convolve (AC) in Pinnacle3. All of the institutes used a same independent dose verification software program (Simple MU Analysis: SMU,more » Triangle Product, Ishikawa, Japan), which implemented a Clarkson-based dose calculation algorithm using CT image dataset. A retrospective analysis for lung SBRT plans (73 patients) was performed to compute the confidence limit (CL, Average±2SD) in dose between the AAA and the SMU. In one of the institutes, a additional analysis was conducted to evaluate the variations between the AAA and the Acuros XB (AXB). Results: The CL for SMU shows larger systematic and random errors of 8.7±9.9 % for AAA than the errors of 5.7±4.2 % for AC. The variations of AAA correlated with the mean CT values in the voxels of PTV (a correlation coefficient : −0.7) . The comparison of AXB vs. AAA shows smaller systematic and random errors of −0.7±1.7%. The correlation between dose variations for AXB and the mean CT values in PTV was weak (0.4). However, there were several plans with more than 2% deviation of AAPM TG114 (Maximum: −3.3 %). Conclusion: In comparison for AC, prescription dose calculated by AAA may be more variable in lung SBRT patient. Even AXB comparison shows unexpected variation. Care should be taken for the use of AAA in lung SBRT. This research is partially supported by Japan Agency for Medical Research and Development (AMED)« less

Readmission rates are associated with differences in the process of care in acute asthma.

PubMed Central

Slack, R; Bucknall, C E

1997-01-01

OBJECTIVE: To test the hypothesis that sustained differences in readmission rate for acute asthma were associated with variations in clinical practice. DESIGN: Data were collected by retrospective review of case notes, using the criteria recommended by the British Thoracic Society. SETTING: Two city National Health Service (NHS) hospitals that had recorded a sustained difference in readmission rate for acute asthma. SUBJECTS: A random sample of 50 from each hospital, selected from all 16-44 year old patients discharged in 1992 with acute asthma (ninth revision of the international classification of diseases (ICD-9) 493). RESULTS: Hospital A had a lower readmission rate than hospital B. The sample groups were similar for age, sex, deprivation of area of residence, and severity of episode. Systemic corticosteroids were given early more often (p = 0.02) and oral corticosteroids were prescribed at discharge more often (p = 0.04) in hospital A. When a short course of oral corticosteroids was prescribed the duration stated was longer (p = 0.02) and inhaled corticosteroids were started or the dose increased more often (p = 0.02) in hospital A. CONCLUSIONS: These results support the hypothesis that differences in readmission rates for acute asthma are associated with variations in clinical practice. Sustained variation in readmission rates is an outcome of health care, for acute asthma. The findings also support audit of the process of hospital asthma care as a proxy for outcome. PMID:10177034

Climate impact on suicide rates in Finland from 1971 to 2003

NASA Astrophysics Data System (ADS)

Ruuhela, Reija; Hiltunen, Laura; Venäläinen, Ari; Pirinen, Pentti; Partonen, Timo

2009-03-01

Seasonal patterns of death from suicide are well-documented and have been attributed to climatic factors such as solar radiation and ambient temperature. However, studies on the impact of weather and climate on suicide are not consistent, and conflicting data have been reported. In this study, we performed a correlation analysis between nationwide suicide rates and weather variables in Finland during the period 1971-2003. The weather parameters studied were global solar radiation, temperature and precipitation, and a range of time spans from 1 month to 1 year were used in order to elucidate the dose-response relationship, if any, between weather variables and suicide. Single and multiple linear regression models show weak associations using 1-month and 3-month time spans, but robust associations using a 12-month time span. Cumulative global solar radiation had the best explanatory power, while average temperature and cumulative precipitation had only a minor impact on suicide rates. Our results demonstrate that winters with low global radiation may increase the risk of suicide. The best correlation found was for the 5-month period from November to March; the inter-annual variability in the cumulative global radiation for that period explained 40 % of the variation in the male suicide rate and 14 % of the variation in the female suicide rate, both at a statistically significant level. Long-term variations in global radiation may also explain, in part, the observed increasing trend in the suicide rate until 1990 and the decreasing trend since then in Finland.

Investigating output and energy variations and their relationship to delivery QA results using Statistical Process Control for helical tomotherapy.

PubMed

Binny, Diana; Mezzenga, Emilio; Lancaster, Craig M; Trapp, Jamie V; Kairn, Tanya; Crowe, Scott B

2017-06-01

The aims of this study were to investigate machine beam parameters using the TomoTherapy quality assurance (TQA) tool, establish a correlation to patient delivery quality assurance results and to evaluate the relationship between energy variations detected using different TQA modules. TQA daily measurement results from two treatment machines for periods of up to 4years were acquired. Analyses of beam quality, helical and static output variations were made. Variations from planned dose were also analysed using Statistical Process Control (SPC) technique and their relationship to output trends were studied. Energy variations appeared to be one of the contributing factors to delivery output dose seen in the analysis. Ion chamber measurements were reliable indicators of energy and output variations and were linear with patient dose verifications. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Childhood leukemia incidence and exposure to indoor radon, terrestrial and cosmic gamma radiation.

PubMed

Evrard, Anne-Sophie; Hémon, Denis; Billon, Solenne; Laurier, Dominique; Jougla, Eric; Tirmarche, Margot; Clavel, Jacqueline

2006-06-01

This study was undertaken to evaluate the ecological association between terrestrial and cosmic gamma radiation, indoor radon, and acute leukemia incidence among children under 15 y of age. From 1990 to 2001, 5,330 cases of acute leukemia were registered by the French National Registry of Childhood Leukemia and Lymphoma. Exposure to terrestrial gamma radiation was based on measurements, using thermoluminescent dosimeters, at about 1,000 sites covering all the "Départements." In addition, 8,737 indoor terrestrial gamma dose rate measurements covering 62% of the "Départements" and 13,240 indoor radon concentration measurements covering all the "Départements" were made during a national campaign. Cosmic ray doses were estimated in each of the 36,363 "Communes" of France. There was no evidence of an ecological association between terrestrial gamma dose (range: 0.22-0.90 mSv y) or total gamma dose (range: 0.49-1.28 mSv y) and childhood acute leukemia incidence, for acute myeloid leukemia (AML) or for acute lymphoblastic leukemia (ALL), in univariate or multivariate regression analyses including indoor radon. A significant positive association between indoor radon (range: 22-262 Bq m) and AML incidence among children was observed and remained significant in multivariate regression analyses including either terrestrial gamma dose [SIR per 100 Bq m = 1.29 (1.09-1.53)] or total gamma dose [SIR per 100 Bq m = 1.29 (1.09-1.53)]. The study showed no ecological association between terrestrial gamma radiation and childhood leukemia for the range of variation in gamma dose rates observed in France. The moderate ecological association between childhood AML incidence and indoor radon does not appear to be confounded by terrestrial gamma dose.

Cardiovascular tolerance of intravenous bupivacaine in broiler chickens (Gallus gallus domesticus) anesthetized with isoflurane.

PubMed

DiGeronimo, Peter M; da Cunha, Anderson F; Pypendop, Bruno; Brandão, João; Stout, Rhett; Rinaldi, Max; Tully, Thomas N

2017-03-01

To determine the median effective dose (ED 50 ) of intravenous (IV) bupivacaine associated with a 50% probability of causing clinically relevant cardiovascular effects [defined as 30% change in heart rate (HR) or mean arterial pressure (MAP)] in chickens anesthetized with isoflurane. Randomized up-and-down study. A total of 14 Ross-708 broiler chickens (Gallus gallus domesticus) weighing 1.70-2.75 kg. Anesthesia was induced and maintained with isoflurane. Monitoring included the electrocardiogram and invasive arterial pressures. Chickens were administered bupivacaine IV over 2 minutes using a dose based on the response of the previous animal. Dose was decreased when HR and/or MAP in the previous animal increased or decreased ≥30% after bupivacaine administration, or increased when HR or MAP changed <30%. The ED 50 was defined as the dose resulting in ≥30% variation in HR or MAP in 50% of the population studied. The IV ED 50 of bupivacaine was 1.94 mg kg -1 using Dixon's up-and-down method and 1.96 mg kg -1 by logistic regression. These results suggest that 1.33 and 1.96 mg kg -1 of IV bupivacaine are associated with a respective 1 or 50% probability of a clinically significant change in MAP in isoflurane-anesthetized chickens. Identification of the cardiovascular changes associated with different doses of bupivacaine can be used as the basis for studies of therapeutic applications in the domestic chicken. Further studies are required to determine interspecies variation. Published by Elsevier Ltd.

Estimated dose rates to members of the public from external exposure to patients with {sup 131}I thyroid treatment

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

Dewji, S., E-mail: dewjisa@ornl.gov; Bellamy, M.; Leggett, R.

Purpose: Estimated dose rates that may result from exposure to patients who had been administered iodine-131 ({sup 131}I) as part of medical therapy were calculated. These effective dose rate estimates were compared with simplified assumptions under United States Nuclear Regulatory Commission Regulatory Guide 8.39, which does not consider body tissue attenuation nor time-dependent redistribution and excretion of the administered {sup 131}I. Methods: Dose rates were estimated for members of the public potentially exposed to external irradiation from patients recently treated with {sup 131}I. Tissue attenuation and iodine biokinetics were considered in the patient in a larger comprehensive effort to improvemore » external dose rate estimates. The external dose rate estimates are based on Monte Carlo simulations using the Phantom with Movable Arms and Legs (PIMAL), previously developed by Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission. PIMAL was employed to model the relative positions of the {sup 131}I patient and members of the public in three exposure scenarios: (1) traveling on a bus in a total of six seated or standing permutations, (2) two nursing home cases where a caregiver is seated at 30 cm from the patient’s bedside and a nursing home resident seated 250 cm away from the patient in an adjacent bed, and (3) two hotel cases where the patient and a guest are in adjacent rooms with beds on opposite sides of the common wall, with the patient and guest both in bed and either seated back-to-back or lying head to head. The biokinetic model predictions of the retention and distribution of {sup 131}I in the patient assumed a single voiding of urinary bladder contents that occurred during the trip at 2, 4, or 8 h after {sup 131}I administration for the public transportation cases, continuous first-order voiding for the nursing home cases, and regular periodic voiding at 4, 8, or 12 h after administration for the hotel room cases. Organ specific activities of {sup 131}I in the thyroid, bladder, and combined remaining tissues were calculated as a function of time after administration. Exposures to members of the public were considered for {sup 131}I patients with normal thyroid uptake (peak thyroid uptake of ∼27% of administered {sup 131}I), differentiated thyroid cancer (DTC, 5% uptake), and hyperthyroidism (80% uptake). Results: The scenario with the patient seated behind the member of the public yielded the highest dose rate estimate of seated public transportation exposure cases. The dose rate to the adjacent room guest was highest for the exposure scenario in which the hotel guest and patient are seated by a factor of ∼4 for the normal and differentiated thyroid cancer uptake cases and by a factor of ∼3 for the hyperthyroid case. Conclusions: It was determined that for all modeled cases, the DTC case yielded the lowest external dose rates, whereas the hyperthyroid case yielded the highest dose rates. In estimating external dose to members of the public from patients with {sup 131}I therapy, consideration must be given to (patient- and case-specific) administered {sup 131}I activities and duration of exposure for a more complete estimate. The method implemented here included a detailed calculation model, which provides a means to determine dose rate estimates for a range of scenarios. The method was demonstrated for variations of three scenarios, showing how dose rates are expected to vary with uptake, voiding pattern, and patient location.« less

Geographical diffusion of prazosin across Veterans Health Administration: Examination of regional variation in daily dosing and quality indicators among veterans with posttraumatic stress disorder.

PubMed

Abrams, Thad E; Lund, Brian C; Alexander, Bruce; Bernardy, Nancy C; Friedman, Matthew J

2015-01-01

Posttraumatic stress disorder (PTSD) is a high-priority treatment area for the Veterans Health Administration (VHA), and dissemination patterns of innovative, efficacious therapies can inform areas for potential improvement of diffusion efforts and quality prescribing. In this study, we replicated a prior examination of the period prevalence of prazosin use as a function of distance from Puget Sound, Washington, where prazosin was first tested as an effective treatment for PTSD and where prazosin use was previously shown to be much greater than in other parts of the United States. We tested the following three hypotheses related to prazosin geographic diffusion: (1) a positive geographical correlation exists between the distance from Puget Sound and the proportion of users treated according to a guideline recommended minimum therapeutic target dose (>/=6 mg/d), (2) an inverse geographic correlation exists between prazosin and benzodiazepine use, and (3) no geographical correlation exists between prazosin use and serotonin reuptake inhibitor/serotonin norepinephrine reuptake inhibitor (SSRI/SNRI) use. Among a national sample of veterans with PTSD, overall prazosin utilization increased from 5.5 to 14.8% from 2006 to 2012. During this time period, rates at the Puget Sound VHA location declined from 34.4 to 29.9%, whereas utilization rates at locations a minimum of 2,500 miles away increased from 3.0 to 12.8%. Rates of minimum target dosing fell from 42.6 to 34.6% at the Puget Sound location. In contrast, at distances of at least 2,500 miles from Puget Sound, minimum threshold dosing rates remained stable (range, 18.6 to 17.7%). No discernible association was demonstrated between SSRI/SNRI or benzodiazepine utilization and the geographic distance from Puget Sound. Minimal threshold dosing of prazosin correlated positively with increased diffusion of prazosin use, but there was still a distance diffusion gradient. Although prazosin adoption has improved, geographic differences persist in both prescribing rates and minimum target dosing. Importantly, these regional disparities appear to be limited to prazosin prescribing and are not meaningfully correlated with SSRI/SNRI and benzodiazepine use as indicators of PTSD prescribing quality.

Radiation Measurements in Cruise and on Mars by the MSL Radiation Assessment Detector

NASA Astrophysics Data System (ADS)

Zeitlin, C. J.; Hassler, D.; Wimmer-Schweingruber, R. F.; Appel, J. K.; Boehm, E.; Boettcher, S.; Brinza, D.; Burmeister, S.; Cucinotta, F.; Ehresmann, B.; Guo, J.; Kohler, J.; Lohf, H.; Martin, C.; Posner, A.; Rafkin, S. C.; Reitz, G.; Team, M.

2013-12-01

The Radiation Assessment Detector (RAD) is one of ten science instruments on the Curiosity rover. The RAD team's science objectives include the measurement of radiation dose (a purely physical quantity) and dose equivalent (a derived quantity that can be related to cancer risk) on the surface of Mars. In addition, RAD acquired data for most of the cruise to Mars, from Dec. 2011 through July 2012, providing a measurement of the radiation environment under conditions similar to those expected on a human trip to Mars or other deep space destinations. The dose and dose equivalent measurements made during cruise have been published, but are presented in more detail here. Rates measured in cruise are compared to similar measurements made during Curiosity's first 269 sols on the surface of Mars. In the simplest picture, one expects rates to be a factor of two lower on the surface of a large airless body compared to free space, owing to the two-pi shielding geometry. The situation on Mars is complicated by the non-negligible shielding effects of the atmosphere, particularly in Gale Crater where diurnal variations in atmospheric column depth are significant. The diurnal variations - caused by the well-known thermal tides on Mars - result in reduced shielding of the surface in the afternoon as compared to the night and early morning hours. A major challenge in analyzing the surface data is the treatment of the background radiation dose coming from Curiosity's Radioisotope Thermoelectric Generator (RTG). Prior to launch, RAD acquired data in the full cruise configuration so that this background could be measured with only sea-level cosmic ray muons present - that is, almost all of what was measured was due to the RTG. Those effects could therefore be subtracted from the cruise measurements in a straightforward way. However, the situation on the surface is somewhat different than in cruise, in that the mass that was present above RAD - and caused scattering of particles into the detector - is no longer there. The RTG-induced dose rate in the surface configuration must therefore be less than it was in the cruise configuration, but there is no way to get a direct measurement of the background. Quantifying the change in RTG background is difficult but essential, as the subtraction affects every aspect of the dosimetry. Two approaches have been developed and yield roughly similar results. The differences allow us to estimate the uncertainties arising from the RTG subtraction, and propagate those into the dosimetry results.

Clinical decision-making tools for exam selection, reporting and dose tracking.

PubMed

Brink, James A

2014-10-01

Although many efforts have been made to reduce the radiation dose associated with individual medical imaging examinations to "as low as reasonably achievable," efforts to ensure such examinations are performed only when medically indicated and appropriate are equally if not more important. Variations in the use of ionizing radiation for medical imaging are concerning, regardless of whether they occur on a local, regional or national basis. Such variations among practices can be reduced with the use of decision support tools at the time of order entry. These tools help reduce radiation exposure among practices through the appropriate use of medical imaging. Similarly, adoption of best practices among imaging facilities can be promoted through tracking the radiation exposure among imaging patients. Practices can benchmark their aggregate radiation exposures for medical imaging through the use of dose index registries. However several variables must be considered when contemplating individual patient dose tracking. The specific dose measures and the variation among them introduced by variations in body habitus must be understood. Moreover the uncertainties in risk estimation from dose metrics related to age, gender and life expectancy must also be taken into account.

SU-F-T-178: Optimized Design of a Diamond Detector Specifically Dedicated to the Dose Distribution Measurements in Clinical Proton Pencil Beams

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

Moignier, C; Pomorski, M; Agelou, M

2016-06-15

Purpose: In proton-therapy, pencil beam scanning (PBS) dosimetry presents a real challenge due to the small size of the beam (about 3 to 8 mm in FWHM), the pulsed high dose rate (up to 100 Gy/s) and the proton energy variation (about 30 MeV to 250 MeV). In the framework of French INSERM DEDIPRO project, a specifically dedicated single crystal diamond dosimeter (SCDDo) was developed with the objective of obtaining accurate measurements of the dose distribution in PBS modality. Methods: Monte Carlo simulations with MCNPX were performed. A small proton beam of 5 mm in FWHM was simulated as wellmore » as diamond devices with various size, thickness and holder composition. The calculated doses-to-diamond were compared with the doses-to-water in order to reduce the perturbation effects. Monte-Carlo simulations lead to an optimized SCDDo design for small proton beams dosimetry. Following the optimized design, SCDDos were mounted in water-equivalent holders with electrical connection adapted to standard electrometer. First, SCDDos performances (stability, repeatability, signal-to-background ratio…) were evaluated with conventional photon beams. Then, characterizations (dose linearity, dose rate dependence…) with wide proton beams were performed at proton-therapy center (IC-CPO) from Curie Institute (France) with the passive proton delivery technique, in order to confirm dosimetric requirements. Finally, depth-dose distributions were measured in a water tank, for native and modulated Bragg Peaks with the collimator of 12 cm, and compared to a commercial PPC05 parallel-plate ionization chamber reference detector. Lateral-dose profiles were also measured with the collimator of 5 mm, and compared to a commercial SFD diode. Results: The results show that SCDDo design does not disturb the dose distributions. Conclusion: The experimental dose distributions with the SCDDo are in good agreement with the commercial detectors and no energy dependence was observed with this device configuration.« less

High brachytherapy doses can counteract hypoxia in cervical cancer—a modelling study

NASA Astrophysics Data System (ADS)

Lindblom, Emely; Dasu, Alexandru; Beskow, Catharina; Toma-Dasu, Iuliana

2017-01-01

Tumour hypoxia is a well-known adverse factor for the outcome of radiotherapy. For cervical tumours in particular, several studies indicate large variability in tumour oxygenation. However, clinical evidence shows that the management of cervical cancer including brachytherapy leads to high rate of success. It was the purpose of this study to investigate whether the success of brachytherapy for cervical cancer, seemingly regardless of oxygenation status, could be explained by the characteristics of the brachytherapy dose distributions. To this end, a previously used in silico model of tumour oxygenation and radiation response was further developed to simulate the treatment of cervical cancer employing a combination of external beam radiotherapy and intracavitary brachytherapy. Using a clinically-derived brachytherapy dose distribution and assuming a homogeneous dose delivered by external radiotherapy, cell survival was assessed on voxel level by taking into account the variation of sensitivity with oxygenation as well as the effects of repair, repopulation and reoxygenation during treatment. Various scenarios were considered for the conformity of the brachytherapy dose distribution to the hypoxic region in the target. By using the clinically-prescribed brachytherapy dose distribution and varying the total dose delivered with external beam radiotherapy in 25 fractions, the resulting values of the dose for 50% tumour control, D 50, were in agreement with clinically-observed values for high cure rates if fast reoxygenation was assumed. The D 50 was furthermore similar for the different degrees of conformity of the brachytherapy dose distribution to the tumour, regardless of whether the hypoxic fraction was 10%, 25%, or 40%. To achieve 50% control with external RT only, a total dose of more than 70 Gy in 25 fractions would be required for all cases considered. It can thus be concluded that the high doses delivered in brachytherapy can counteract the increased radioresistance caused by hypoxia if fast reoxygenation is assumed.

Investigation of effective decision criteria for multiobjective optimization in IMRT.

PubMed

Holdsworth, Clay; Stewart, Robert D; Kim, Minsun; Liao, Jay; Phillips, Mark H

2011-06-01

To investigate how using different sets of decision criteria impacts the quality of intensity modulated radiation therapy (IMRT) plans obtained by multiobjective optimization. A multiobjective optimization evolutionary algorithm (MOEA) was used to produce sets of IMRT plans. The MOEA consisted of two interacting algorithms: (i) a deterministic inverse planning optimization of beamlet intensities that minimizes a weighted sum of quadratic penalty objectives to generate IMRT plans and (ii) an evolutionary algorithm that selects the superior IMRT plans using decision criteria and uses those plans to determine the new weights and penalty objectives of each new plan. Plans resulting from the deterministic algorithm were evaluated by the evolutionary algorithm using a set of decision criteria for both targets and organs at risk (OARs). Decision criteria used included variation in the target dose distribution, mean dose, maximum dose, generalized equivalent uniform dose (gEUD), an equivalent uniform dose (EUD(alpha,beta) formula derived from the linear-quadratic survival model, and points on dose volume histograms (DVHs). In order to quantatively compare results from trials using different decision criteria, a neutral set of comparison metrics was used. For each set of decision criteria investigated, IMRT plans were calculated for four different cases: two simple prostate cases, one complex prostate Case, and one complex head and neck Case. When smaller numbers of decision criteria, more descriptive decision criteria, or less anti-correlated decision criteria were used to characterize plan quality during multiobjective optimization, dose to OARs and target dose variation were reduced in the final population of plans. Mean OAR dose and gEUD (a = 4) decision criteria were comparable. Using maximum dose decision criteria for OARs near targets resulted in inferior populations that focused solely on low target variance at the expense of high OAR dose. Target dose range, (D(max) - D(min)), decision criteria were found to be most effective for keeping targets uniform. Using target gEUD decision criteria resulted in much lower OAR doses but much higher target dose variation. EUD(alpha,beta) based decision criteria focused on a region of plan space that was a compromise between target and OAR objectives. None of these target decision criteria dominated plans using other criteria, but only focused on approaching a different area of the Pareto front. The choice of decision criteria implemented in the MOEA had a significant impact on the region explored and the rate of convergence toward the Pareto front. When more decision criteria, anticorrelated decision criteria, or decision criteria with insufficient information were implemented, inferior populations are resulted. When more informative decision criteria were used, such as gEUD, EUD(alpha,beta), target dose range, and mean dose, MOEA optimizations focused on approaching different regions of the Pareto front, but did not dominate each other. Using simple OAR decision criteria and target EUD(alpha,beta) decision criteria demonstrated the potential to generate IMRT plans that significantly reduce dose to OARs while achieving the same or better tumor control when clinical requirements on target dose variance can be met or relaxed.

Measurement of LET distribution and dose equivalent on board the space shuttle STS-65

NASA Technical Reports Server (NTRS)

Hayashi, T.; Doke, T.; Kikuchi, J.; Takeuchi, R.; Hasebe, N.; Ogura, K.; Nagaoka, S.; Kato, M.; Badhwar, G. D.

1996-01-01

Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD)" utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 microSv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit for space radiation with a small inclination (28.5 degrees) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15-200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks.

Measurement of LET distribution and dose equivalent on board the space shuttle STS-65.

PubMed

Hayashi, T; Doke, T; Kikuchi, J; Takeuchi, R; Hasebe, N; Ogura, K; Nagaoka, S; Kato, M; Badhwar, G D

1996-11-01

Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD)" utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 microSv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit for space radiation with a small inclination (28.5 degrees) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15-200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks.

A method for depth-dose distribution measurements in tissue irradiated by a proton beam

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

Gambarini, G.; Birattari, C.; Bartolo, D. de

1994-12-31

The use of protons and heavy ions for the treatment of malignant and non-malignant disease has aroused a growing interest in the last decade. The notable advantage of heavy charged particles over photons in external beam radiotherapy lies in the possibility of irradiating a small localized region within the body, keeping a low value for the entrance dose. Owing to this high disuniformity of energy deposition, an essential requirement for treatment planning is a precise evaluation of the spatial distribution of absorbed dose. The proposed method for depth-dose distribution measurements utilizes a chemical dosimeter (ferrous sulphate solution plus sulfuric acidmore » and eventually xylenol orange) incorporated in a gelatine, whose role is the maintenance of spatial information. Ionizing radiation causes a variation in some parameters of the system such as the proton relaxation rates in the solution (measurable by NMR analysis) or the optical absorption of the gel in the visible spectrum (measurable by spectrophotometry).« less

A novel approach to neutron dosimetry.

PubMed

Balmer, Matthew J I; Gamage, Kelum A A; Taylor, Graeme C

2016-11-01

Having been overlooked for many years, research is now starting to take into account the directional distribution of neutron workplace fields. Existing neutron dosimetry instrumentation does not account for this directional distribution, resulting in conservative estimates of dose in neutron workplace fields (by around a factor of 2, although this is heavily dependent on the type of field). This conservatism could influence epidemiological studies on the health effects of radiation exposure. This paper reports on the development of an instrument which can estimate the effective dose of a neutron field, accounting for both the direction and the energy distribution. A 6 Li-loaded scintillator was used to perform neutron assays at a number of locations in a 20 × 20 × 17.5 cm 3 water phantom. The variation in thermal and fast neutron response to different energies and field directions was exploited. The modeled response of the instrument to various neutron fields was used to train an artificial neural network (ANN) to learn the effective dose and ambient dose equivalent of these fields. All experimental data published in this work were measured at the National Physical Laboratory (UK). Experimental results were obtained for a number of radionuclide source based neutron fields to test the performance of the system. The results of experimental neutron assays at 25 locations in a water phantom were fed into the trained ANN. A correlation between neutron counting rates in the phantom and neutron fluence rates was experimentally found to provide dose rate estimates. A radionuclide source behind shadow cone was used to create a more complex field in terms of energy and direction. For all fields, the resulting estimates of effective dose rate were within 45% or better of their calculated values, regardless of energy distribution or direction for measurement times greater than 25 min. This work presents a novel, real-time, approach to workplace neutron dosimetry. It is believed that in the research presented in this paper, for the first time, a single instrument has been able to estimate effective dose.

Ultraviolet-B radiation increases serum 25-hydroxyvitamin D levels: the effect of UVB dose and skin color.

PubMed

Armas, Laura A G; Dowell, Susan; Akhter, Mohammed; Duthuluru, Sowjanya; Huerter, Christopher; Hollis, Bruce W; Lund, Richard; Heaney, Robert P

2007-10-01

Ultraviolet (UV)-B light increases vitamin D levels, but the dose response and the effect of skin pigmentation have not been well characterized. We sought to define the relationship between UVB exposure and 25-hydroxyvitamin D (25-OH-D) concentrations as a function of skin pigmentation. Seventy two participants with various skin tones had 90% of their skin exposed to UVB light (20-80 mJ/cm2) 3 times a week for 4 weeks. Serum 25-OH-D was measured weekly. Eighty percent of the variation in treatment response was explained by UVB dose and skin tone. Therapeutically important changes in 25-OH-D were achieved with minimal tanning. Four weeks was not long enough to reach a steady state at the higher dose rates. The response of 25-OH-D levels to UVB light is dependent on skin pigmentation and the amount of UVB given, and useful increases in vitamin D status can be achieved by defined UVB doses small enough to produce only minimal tanning.

The difference of scoring dose to water or tissues in Monte Carlo dose calculations for low energy brachytherapy photon sources.

PubMed

Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank

2011-03-01

The goal of this work is to compare D(m,m) (radiation transported in medium; dose scored in medium) and D(w,m) (radiation transported in medium; dose scored in water) obtained from Monte Carlo (MC) simulations for a subset of human tissues of interest in low energy photon brachytherapy. Using low dose rate seeds and an electronic brachytherapy source (EBS), the authors quantify the large cavity theory conversion factors required. The authors also assess whether ap plying large cavity theory utilizing the sources' initial photon spectra and average photon energy induces errors related to spatial spectral variations. First, ideal spherical geometries were investigated, followed by clinical brachytherapy LDR seed implants for breast and prostate cancer patients. Two types of dose calculations are performed with the GEANT4 MC code. (1) For several human tissues, dose profiles are obtained in spherical geometries centered on four types of low energy brachytherapy sources: 125I, 103Pd, and 131Cs seeds, as well as an EBS operating at 50 kV. Ratios of D(w,m) over D(m,m) are evaluated in the 0-6 cm range. In addition to mean tissue composition, compositions corresponding to one standard deviation from the mean are also studied. (2) Four clinical breast (using 103Pd) and prostate (using 125I) brachytherapy seed implants are considered. MC dose calculations are performed based on postimplant CT scans using prostate and breast tissue compositions. PTV D90 values are compared for D(w,m) and D(m,m). (1) Differences (D(w,m)/D(m,m)-1) of -3% to 70% are observed for the investigated tissues. For a given tissue, D(w,m)/D(m,m) is similar for all sources within 4% and does not vary more than 2% with distance due to very moderate spectral shifts. Variations of tissue composition about the assumed mean composition influence the conversion factors up to 38%. (2) The ratio of D90(w,m) over D90(m,m) for clinical implants matches D(w,m)/D(m,m) at 1 cm from the single point sources, Given the small variation with distance, using conversion factors based on the emitted photon spectrum (or its mean energy) of a given source introduces minimal error. The large differences observed between scoring schemes underline the need for guidelines on choice of media for dose reporting. Providing such guidelines is beyond the scope of this work.

Preliminary study on the effect of x-ray irradiation on Capsicum annum

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

Subhash, K.; Nizam, J.

The present experiment on Capsicum annum was conducted to study various cytological and genetic effects induced by x-ray irradiation. Dry and soaked seeds were exposed to irradiation by deep x rays at the Radium and Cancer Research Institute, Hyderabad at a dose rate of 99 rads/min. The doses administered were as follows: 3000 rads, 4000 rads, 5000 rads, and 10,000 rads. The cytological preparations were made by following Belling's technique. The irradiated seeds along with the controlled were sown in the soil to observe the morphological variations. The root tip squashes from the irradiated seed material revealed various chromosomal aberrationsmore » such as deletions, parallel bridges, and single and paired fragments of acentric chromosomes, showing cytological irregularities. Bridges were quite common at anaphases. The irradiated seeds were germinated in order to record morphological variations. A period of 150 days seems to be necessary from germination to seed formation; this period is not identical for the irradiated and controlled seeds. In some of the irradiated material the duration was reduced to 120 to 130 days. With this observation it may be presumed that mild doses of radiation have accelerated the germination time and also hastened the growth processes. (auth)« less

Comparison of TID Effects in Space-Like Variable Dose Rates and Constant Dose Rates

NASA Technical Reports Server (NTRS)

Harris, Richard D.; McClure, Steven S.; Rax, Bernard G.; Evans, Robin W.; Jun, Insoo

2008-01-01

The degradation of the LM193 dual voltage comparator has been studied at different TID dose rate profiles, including several different constant dose rates and a variable dose rate that simulates the behavior of a solar flare. A comparison of results following constant dose rate vs. variable dose rates is made to explore how well the constant dose rates used for typical part testing predict the performance during a simulated space-like mission. Testing at a constant dose rate equal to the lowest dose rate seen during the simulated flare provides an extremely conservative estimate of the overall amount of degradation. A constant dose rate equal to the average dose rate is also more conservative than the variable rate. It appears that, for this part, weighting the dose rates by the amount of total dose received at each rate (rather than the amount of time at each dose rate) results in an average rate that produces an amount of degradation that is a reasonable approximation to that received by the variable rate.

Cosmic Ray Modulation and Radiation Dose of Aircrews During Possible Grand Minimum

NASA Astrophysics Data System (ADS)

Miyake, S.; Kataoka, R.; Sato, T.; Imada, S.; Miyahara, H.; Shiota, D.; Matsumoto, T.; Ueno, H.

2017-12-01

The Sun is exhibiting low solar activity levels since the descending phase of the last solar cycle, and it is likely to be continued as well as in the case of the past grand solar minima. The cosmic-ray modulation, which is the variation of the galactic cosmic ray (GCR) spectrum caused by the heliospheric environmental change, is basically anti-correlated with the solar activity. In the recent weak solar cycle, we thus expect that the flux of GCRs is getting higher than that in the previous solar cycles, leading to the increase in the radiation exposure in the space and atmosphere. In order to quantitatively evaluate the possible solar modulation of GCRs and resultant radiation exposure at flight altitude, we have developed the time-dependent and three-dimensional model of the cosmic-ray modulation. Our model can give the flux of GCRs anywhere in the heliosphere by assuming the variation of the solar wind speed, the strength of the heliospheric magnetic field (HMF), and its tilt angle. We solve the gradient-curvature drift motion of GCRs in the HMF, and therefore reproduce the 22-year variation of the cosmic-ray modulation. We also calculate the neutron monitor counting rate and the radiation dose of aircrews at flight altitude, by the air-shower simulation performed by PHITS (Particle and Heavy Ion Transport code System). In our previous study [1], we calculated the radiation dose at a flight altitude during the coming solar cycle by assuming the variation of the solar wind speed and the strength of the HMF expressed by sinusoidal curve, and obtained that an annual radiation dose of aircrews in 5 years around the next solar minimum will be up to 19% higher than that at the last cycle. In this study, we predict the new model of the heliospheric environmental change on the basis of a prediction model for the sunspot number. The quantitative predictions of the cosmic-ray modulation and the radiation dose at a flight altitude during possible Grand Minimum considering the new model for the heliospheric environmental change will be presented at the meeting. [1] S. Miyake, R. Kataoka, and T. Sato, Space Weather, 15, 589-605, 2017.

A new single crystal diamond dosimeter for small beam: comparison with different commercial active detectors.

PubMed

Marsolat, F; Tromson, D; Tranchant, N; Pomorski, M; Le Roy, M; Donois, M; Moignau, F; Ostrowsky, A; De Carlan, L; Bassinet, C; Huet, C; Derreumaux, S; Chea, M; Cristina, K; Boisserie, G; Bergonzo, P

2013-11-07

Recent developments of new therapy techniques using small photon beams, such as stereotactic radiotherapy, require suitable detectors to determine the delivered dose with a high accuracy. The dosimeter has to be as close as possible to tissue equivalence and to exhibit a small detection volume compared to the size of the irradiation field, because of the lack of lateral electronic equilibrium in small beam. Characteristics of single crystal diamond (tissue equivalent material Z = 6, high density) make it an ideal candidate to fulfil most of small beam dosimetry requirements. A commercially available Element Six electronic grade synthetic diamond was used to develop a single crystal diamond dosimeter (SCDDo) with a small detection volume (0.165 mm(3)). Long term stability was studied by irradiating the SCDDo in a (60)Co beam over 14 h. A good stability (deviation less than ± 0.1%) was observed. Repeatability, dose linearity, dose rate dependence and energy dependence were studied in a 10 × 10 cm(2) beam produced by a Varian Clinac 2100 C linear accelerator. SCDDo lateral dose profile, depth dose curve and output factor (OF) measurements were performed for small photon beams with a micro multileaf collimator m3 (BrainLab) attached to the linac. This study is focused on the comparison of SCDDo measurements to those obtained with different commercially available active detectors: an unshielded silicon diode (PTW 60017), a shielded silicon diode (Sun Nuclear EDGE), a PinPoint ionization chamber (PTW 31014) and two natural diamond detectors (PTW 60003). SCDDo presents an excellent spatial resolution for dose profile measurements, due to its small detection volume. Low energy dependence (variation of 1.2% between 6 and 18 MV photon beam) and low dose rate dependence of the SCDDo (variation of 1% between 0.53 and 2.64 Gy min(-1)) are obtained, explaining the good agreement between the SCDDo and the efficient unshielded diode (PTW 60017) in depth dose curve measurements. For field sizes ranging from 0.6 × 0.6 to 10 × 10 cm(2), OFs obtained with the SCDDo are between the OFs measured with the PinPoint ionization chamber and the Sun Nuclear EDGE diode that are known to respectively underestimate and overestimate OF values in small beam, due to the large detection volume of the chamber and the non-water equivalence of both detectors.

Evaluation of external and internal irradiation on uranium mining enterprise staff by tooth enamel EPR spectroscopy

NASA Astrophysics Data System (ADS)

Zhumadilov, Kassym; Ivannikov, Alexander; Khailov, Artem; Orlenko, Sergei; Skvortsov, Valeriy; Stepanenko, Valeriy; Kuterbekov, Kairat; Toyoda, Shin; Kazymbet, Polat; Hoshi, Masaharu

2017-11-01

In order to estimate radiation effects on uranium enterprise staff and population teeth samples were collected for EPR tooth enamel dosimetry from population of Stepnogorsk city and staff of uranium mining enterprise in Shantobe settlment (Akmola region, North of Kazakhstan). By measurements of tooth enamel EPR spectra, the total absorbed dose in the enamel samples and added doses after subtraction of the contribution of natural background radiation are determined. For the population of Stepnogorsk city average added dose value of 4 +/- 11 mGy with variation of 51 mGy was obtained. For the staff of uranium mining enterprise in Shantobe settlment average value of added dose 95 +/- 20 mGy, with 85 mGy variation was obtained. Higher doses and the average value and a large variation for the staff, probably is due to the contribution of occupational exposure.

Impact of normalization methods on high-throughput screening data with high hit rates and drug testing with dose-response data.

PubMed

Mpindi, John-Patrick; Swapnil, Potdar; Dmitrii, Bychkov; Jani, Saarela; Saeed, Khalid; Wennerberg, Krister; Aittokallio, Tero; Östling, Päivi; Kallioniemi, Olli

2015-12-01

Most data analysis tools for high-throughput screening (HTS) seek to uncover interesting hits for further analysis. They typically assume a low hit rate per plate. Hit rates can be dramatically higher in secondary screening, RNAi screening and in drug sensitivity testing using biologically active drugs. In particular, drug sensitivity testing on primary cells is often based on dose-response experiments, which pose a more stringent requirement for data quality and for intra- and inter-plate variation. Here, we compared common plate normalization and noise-reduction methods, including the B-score and the Loess a local polynomial fit method under high hit-rate scenarios of drug sensitivity testing. We generated simulated 384-well plate HTS datasets, each with 71 plates having a range of 20 (5%) to 160 (42%) hits per plate, with controls placed either at the edge of the plates or in a scattered configuration. We identified 20% (77/384) as the critical hit-rate after which the normalizations started to perform poorly. Results from real drug testing experiments supported this estimation. In particular, the B-score resulted in incorrect normalization of high hit-rate plates, leading to poor data quality, which could be attributed to its dependency on the median polish algorithm. We conclude that a combination of a scattered layout of controls per plate and normalization using a polynomial least squares fit method, such as Loess helps to reduce column, row and edge effects in HTS experiments with high hit-rates and is optimal for generating accurate dose-response curves. john.mpindi@helsinki.fi. Supplementary information: R code and Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press.

SU-F-19A-05: Experimental and Monte Carlo Characterization of the 1 Cm CivaString 103Pd Brachytherapy Source

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

Reed, J; Micka, J; Culberson, W

Purpose: To determine the in-air azimuthal anisotropy and in-water dose distribution for the 1 cm length of the CivaString {sup 103}Pd brachytherapy source through measurements and Monte Carlo (MC) simulations. American Association of Physicists in Medicine Task Group No. 43 (TG-43) dosimetry parameters were also determined for this source. Methods: The in-air azimuthal anisotropy of the source was measured with a NaI scintillation detector and simulated with the MCNP5 radiation transport code. Measured and simulated results were normalized to their respective mean values and compared. The TG-43 dose-rate constant, line-source radial dose function, and 2D anisotropy function for this sourcemore » were determined from LiF:Mg,Ti thermoluminescent dosimeter (TLD) measurements and MC simulations. The impact of {sup 103}Pd well-loading variability on the in-water dose distribution was investigated using MC simulations by comparing the dose distribution for a source model with four wells of equal strength to that for a source model with strengths increased by 1% for two of the four wells. Results: NaI scintillation detector measurements and MC simulations of the in-air azimuthal anisotropy showed that ≥95% of the normalized data were within 1.2% of the mean value. TLD measurements and MC simulations of the TG-43 dose-rate constant, line-source radial dose function, and 2D anisotropy function agreed to within the experimental TLD uncertainties (k=2). MC simulations showed that a 1% variability in {sup 103}Pd well-loading resulted in changes of <0.1%, <0.1%, and <0.3% in the TG-43 dose-rate constant, radial dose distribution, and polar dose distribution, respectively. Conclusion: The CivaString source has a high degree of azimuthal symmetry as indicated by the NaI scintillation detector measurements and MC simulations of the in-air azimuthal anisotropy. TG-43 dosimetry parameters for this source were determined from TLD measurements and MC simulations. {sup 103}Pd well-loading variability results in minimal variations in the in-water dose distribution according to MC simulations. This work was partially supported by CivaTech Oncology, Inc. through an educational grant for Joshua Reed, John Micka, Wesley Culberson, and Larry DeWerd and through research support for Mark Rivard.« less

Interfractional Dose Variations in Intensity-Modulated Radiotherapy With Breath-Hold for Pancreatic Cancer

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

Nakamura, Mitsuhiro; Shibuya, Keiko, E-mail: kei@kuhp.kyoto-u.ac.jp; Nakamura, Akira

2012-04-01

Purpose: To investigate the interfractional dose variations for intensity-modulated radiotherapy (RT) combined with breath-hold (BH) at end-exhalation (EE) for pancreatic cancer. Methods and Materials: A total of 10 consecutive patients with pancreatic cancer were enrolled. Each patient was fixed in the supine position on an individualized vacuum pillow with both arms raised. Computed tomography (CT) scans were performed before RT, and three additional scans were performed during the course of chemoradiotherapy using a conventional RT technique. The CT data were acquired under EE-BH conditions (BH-CT) using a visual feedback technique. The intensity-modulated RT plan, which used five 15-MV coplanar ports,more » was designed on the initial BH-CT set with a prescription dose of 39 Gy at 2.6 Gy/fraction. After rigid image registration between the initial and subsequent BH-CT scans, the dose distributions were recalculated on the subsequent BH-CT images under the same conditions as in planning. Changes in the dose-volume metrics of the gross tumor volume (GTV), clinical target volume (CTV = GTV + 5 mm), stomach, and duodenum were evaluated. Results: For the GTV and clinical target volume (CTV), the 95th percentile of the interfractional variations in the maximal dose, mean dose, dose covering 95% volume of the region of structure, and percentage of the volume covered by the 90% isodose line were within {+-}3%. Although the volume covered by the 39 Gy isodose line for the stomach and duodenum did not exceed 0.1 mL at planning, the volume covered by the 39 Gy isodose line for these structures was up to 11.4 cm{sup 3} and 1.8 cm{sup 3}, respectively. Conclusions: Despite variations in the gastrointestinal state and abdominal wall position at EE, the GTV and CTV were mostly ensured at the planned dose, with the exception of 1 patient. Compared with the duodenum, large variations in the stomach volume receiving high-dose radiation were observed, which might be beyond the negligible range in achieving dose escalation with intensity-modulated RT combined with BH at EE.« less

Pharmacokinetics and pharmacodynamics of carboplatin administered in a high-dose combination regimen with thiotepa, cyclophosphamide and peripheral stem cell support.

PubMed Central

van Warmerdam, L. J.; Rodenhuis, S.; van der Wall, E.; Maes, R. A.; Beijnen, J. H.

1996-01-01

The aim of this pharmacokinetic/pharmacodynamic study was to define the relationships of the carboplatin exposure with the toxicity in patients treated with high dose carboplatin (400 mg m-2 day-1), cyclophosphamide (1500 mg m-2 day-1) and thiotepa (120 mg m-2 day-1) for four consecutive days, followed by peripheral stem cell transplantation. Exposure to carboplatin was studied in 200 treatment days by measuring the area under the carboplatin plasma ultrafiltrate (pUF) concentration vs time curve (AUC). The AUC was obtained by using a previously validated limited sampling model. A total of 31 patients was studied who received one, two or three courses of this high-dose chemotherapy regimen. The unbound, plasma ultrafiltrate carboplatin was almost completely cleared from the body before each next treatment day in a course; the day-to-day AUC variation was 3.3%. The mean cumulative AUC over 4 days was 19.6 (range 14.1-27.2) mg ml-1 min-1. In 97 treatment days the carboplatin dose was calculated using the Calvert formula with the creatinine clearance as the measure for the glomerular filtration rate (GFR). For these courses, the inter-patient variability in pharmacokinetics was significantly reduced from 21% to 15% (P = 0.007) in comparison with the schemes where it was given as a fixed dose of 400 mg m-2. There were no relationships found between toxicity and the AUC of carboplatin, which may be due to the influence of overlapping toxicities of cyclophosphamide and thiotepa. However, the ototoxicity was strongly related to the cumulative carboplatin AUC. This toxicity was dose limiting for carboplatin in this schedule. It appeared that the carboplatin pharmacokinetics in these regimens were similar to those reported at conventional dosages. To reduce the inter-patient variation, the carboplatin dose can be calculated using the Calvert-formula with the creatinine clearance as the measure for the GFR. PMID:8611435

Dosimetric benefit of adaptive re-planning in pancreatic cancer stereotactic body radiotherapy

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

Li, Yongbao; Center for Advanced Radiotherapy Technologies University of California San Diego, La Jolla, CA; Department of Radiation Oncology, University of California San Diego, La Jolla, CA

Stereotactic body radiotherapy (SBRT) shows promise in unresectable pancreatic cancer, though this treatment modality has high rates of normal tissue toxicity. This study explores the dosimetric utility of daily adaptive re-planning with pancreas SBRT. We used a previously developed supercomputing online re-planning environment (SCORE) to re-plan 10 patients with pancreas SBRT. Tumor and normal tissue contours were deformed from treatment planning computed tomographies (CTs) and transferred to daily cone-beam CT (CBCT) scans before re-optimizing each daily treatment plan. We compared the intended radiation dose, the actual radiation dose, and the optimized radiation dose for the pancreas tumor planning target volumemore » (PTV) and the duodenum. Treatment re-optimization improved coverage of the PTV and reduced dose to the duodenum. Within the PTV, the actual hot spot (volume receiving 110% of the prescription dose) decreased from 4.5% to 0.5% after daily adaptive re-planning. Within the duodenum, the volume receiving the prescription dose decreased from 0.9% to 0.3% after re-planning. It is noteworthy that variation in the amount of air within a patient's stomach substantially changed dose to the PTV. Adaptive re-planning with pancreas SBRT has the ability to improve dose to the tumor and decrease dose to the nearby duodenum, thereby reducing the risk of toxicity.« less

Inhalational and dermal exposures during spray application of biocides.

PubMed

Berger-Preiss, Edith; Boehncke, Andrea; Könnecker, Gustav; Mangelsdorf, Inge; Holthenrich, Dagmar; Koch, Wolfgang

2005-01-01

Data on inhalational and potential dermal exposures during spray application of liquid biocidal products were generated. On the one hand, model experiments with different spraying devices using fluorescent tracers were carried out to investigate the influence of parameters relevant to the exposure (e.g. spraying equipment, nozzle size, direction of application). On the other hand, measurements were performed at selected workplaces (during disinfection operations in food and feed areas; pest control operations for private, public and veterinary hygiene; wood protection and antifouling applications) after application of biocidal products such as Empire 20, Responsar SC, Omexan-forte, Actellic, Perma-forte; Fendona SC, Pyrethrum mist; CBM 8, Aldekol Des 03, TAD CID, Basileum, Basilit. The measurements taken in the model rooms demonstrated dependence of the inhalation exposure on the type of spraying device used, in the following order: "spraying with low pressure" < "airless spraying" < "fogging" indicating that the particle diameter of the released spray droplets is the most important parameter. In addition inhalation exposure was lowest when the spraying direction was downward. Also for the potential dermal exposure, the spraying direction was of particular importance: overhead spraying caused the highest contamination of body surfaces. The data of inhalational and potential dermal exposures gained through workplace measurements showed considerable variation. During spraying procedures with low-pressure equipments, dose rates of active substances inhaled by the operators ranged from 7 to 230 microg active substance (a.s.)/h. An increase in inhaled dose rates (6-33 mg a.s./h) was observed after use of high application volumes/time unit during wood protection applications indoors. Spraying in the veterinary sector using medium-pressure sprayers led to inhaled dose rates between 2 and 24mga.s./h. The highest inhaled dose rates were measured during fogging (114 mg a.s./h) and after-high-pressure applications in the antifouling sector (110-300 mg a.s./h). The potential dermal exposure of spray operators was lowest (dose rates from 0.2 to 7 mg a.s./h) in the areas of food and feed disinfection and private and public hygiene during spraying with low-pressure devices. During fogging, wood protection and antifouling applications, high-potential dermal exposures of the operators were determined. Dermal dose rates varied between 100 and 34,000 mg a.s./h.

Automatic exposure control at single- and dual-heartbeat CTCA on a 320-MDCT volume scanner: effect of heart rate, exposure phase window setting, and reconstruction algorithm.

PubMed

Funama, Yoshinori; Utsunomiya, Daisuke; Taguchi, Katsuyuki; Oda, Seitaro; Shimonobo, Toshiaki; Yamashita, Yasuyuki

2014-05-01

To investigate whether electrocardiogram (ECG)-gated single- and dual-heartbeat computed tomography coronary angiography (CTCA) with automatic exposure control (AEC) yields images with uniform image noise at reduced radiation doses. Using an anthropomorphic chest CT phantom we performed prospectively ECG-gated single- and dual-heartbeat CTCA on a second-generation 320-multidetector CT volume scanner. The exposure phase window was set at 75%, 70-80%, 40-80%, and 0-100% and the heart rate at 60 or 80 or corr80 bpm; images were reconstructed with filtered back projection (FBP) or iterative reconstruction (IR, adaptive iterative dose reduction 3D). We applied AEC and set the image noise level to 20 or 25 HU. For each technique we determined the image noise and the radiation dose to the phantom center. With half-scan reconstruction at 60 bpm, a 70-80% phase window- and a 20-HU standard deviation (SD) setting, the imagenoise level and -variation along the z axis manifested similar curves with FBP and IR. With half-scan reconstruction, the radiation dose to the phantom center with 70-80% phase window was 18.89 and 12.34 mGy for FBP and 4.61 and 3.10 mGy for IR at an SD setting SD of 20 and 25 HU, respectively. At 80 bpm with two-segment reconstruction the dose was approximately twice that of 60 bpm at both SD settings. However, increasing radiation dose at corr80 bpm was suppressed to 1.39 times compared to 60 bpm. AEC at ECG-gated single- and dual-heartbeat CTCA controls the image noise at different radiation dose. Copyright © 2013 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Dosimetric characterization of a single crystal diamond detector in X-ray beams for preclinical research.

PubMed

Kampfer, Severin; Cho, Nathan; Combs, Stephanie E; Wilkens, Jan J

2018-05-29

The aim of this study was to investigate a single crystal diamond detector, the microDiamond detector from PTW (PTW-Freiburg, Freiburg, Germany), concerning the particular requirements in the set-up and energy range used in small animal radiotherapy (RT) research (around 220kV). We tested it to find out the minimal required pre-irradiation dose, the dose linearity, dose rate dependency and the angular response as well as usability in the small animal radiation research platform, SARRP (Xstrahl Ltd., Camberley, UK). For a stable signal in the range of energies used in the study, we found a required pre-irradiation dose of 10Gy. The dose linearity and dose rate dependence measurements showed a very good performance of the microDiamond detector. Regarding the effect of angular dependency, the variation of the response signal is less than 0.5% within the first 15° of the polar angle. In the azimuthal angle, however, there are differences in detector response up to 20%, depending on the range of energies used in the study. In addition, we compared the detector to a radiosensitive film for a profile measurement of a 5×5mm 2 irradiation field. Both methods showed a good accordance with the field size, however, the film has a steeper dose gradient in the penumbra region but also a higher noise than the microDiamond detector. We demonstrated that the microDiamond detector is a useful measurement tool for small animal RT research due to its small size. Nevertheless, it seems to be very important to verify the response of the detector in the given set-up and energy range. Copyright © 2018. Published by Elsevier GmbH.

Assessment of monitor unit limiting strategy using volumetric modulated arc therapy for cancer of hypopharynx.

PubMed

Ahamed, Shabbir; Singh, Navin; Gudipudi, Deleep; Mulinti, Suneetha; Talluri, Anil; Soubhagya, Bhudevi; Sresty, Madhusudhana

2017-03-01

To quantify relative merit of MU deprived plans against freely optimized plans in terms of plan quality and report changes induced by progressive resolution optimizer algorithm (PRO3) to the dynamic parameters of RapidArc. Ten cases of carcinoma hypopharynx were retrospectively planned in three phases without using MU tool. Replicas of these baseline plans were reoptimized using "Intermediate dose" feature and "MU tool" to reduce MUs by 20%, 35%, and 50%. Overall quality indices for target and OAR, integral dose, dose-volume spread were assessed. All plans were appraised for changes induced in RapidArc dynamic parameters and pre-treatment quality assurance (QA). With increasing MU reduction strength (MURS), MU/Gy values reduced, for all phases with an overall range of 8.6-34.7%; mean dose rate decreased among plans of each phase, phase3 plans recorded greater reductions. MURS20% showed good trade-off between MUs and plan quality. Dose-volume spread below 5Gy was higher for baseline plans while lower between 20 and 35Gy. Integral dose was lower for MURS0%, not exceeding 1.0%, compared against restrained plans. Mean leaf aperture and control point areas increased systematically, correlated negatively with increasing MURS. Absolute delta dose rate variations were least for MURS0%. MU deprived plans exhibited GAI (>93%), better than MURS0% plans. Baseline plans are superior to MU restrained plans. However, MURS20% offers equivalent and acceptable plan quality with mileage of MUs, improved GAI for complex cases. MU tool may be adopted to tailor treatment plans using PRO3. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Variability of surface and center position radiation dose in MDCT: Monte Carlo simulations using CTDI and anthropomorphic phantoms

PubMed Central

Zhang, Di; Savandi, Ali S.; Demarco, John J.; Cagnon, Chris H.; Angel, Erin; Turner, Adam C.; Cody, Dianna D.; Stevens, Donna M.; Primak, Andrew N.; McCollough, Cynthia H.; McNitt-Gray, Michael F.

2009-01-01

The larger coverage afforded by wider z-axis beams in multidetector CT (MDCT) creates larger cone angles and greater beam divergence, which results in substantial surface dose variation for helical and contiguous axial scans. This study evaluates the variation of absorbed radiation dose in both cylindrical and anthropomorphic phantoms when performing helical or contiguous axial scans. The approach used here was to perform Monte Carlo simulations of a 64 slice MDCT. Simulations were performed with different radiation profiles (simulated beam widths) for a given collimation setting (nominal beam width) and for different pitch values and tube start angles. The magnitude of variation at the surface was evaluated under four different conditions: (a) a homogeneous CTDI phantom with different combinations of pitch and simulated beam widths, (b) a heterogeneous anthropomorphic phantom with one measured beam collimation and various pitch values, (c) a homogeneous CTDI phantom with fixed beam collimation and pitch, but with different tube start angles, and (d) pitch values that should minimize variations of surface dose—evaluated for both homogeneous and heterogeneous phantoms. For the CTDI phantom simulations, peripheral dose patterns showed variation with percent ripple as high as 65% when pitch is 1.5 and simulated beam width is equal to the nominal collimation. For the anterior surface dose on an anthropomorphic phantom, the percent ripple was as high as 40% when the pitch is 1.5 and simulated beam width is equal to the measured beam width. Low pitch values were shown to cause beam overlaps which created new peaks. Different x-ray tube start angles create shifts of the peripheral dose profiles. The start angle simulations showed that for a given table position, the surface dose could vary dramatically with minimum values that were 40% of the peak when all conditions are held constant except for the start angle. The last group of simulations showed that an “ideal” pitch value can be determined which reduces surface dose variations, but this pitch value must take into account the measured beam width. These results reveal the complexity of estimating surface dose and demonstrate a range of dose variability at surface positions for both homogeneous cylindrical and heterogeneous anthropomorphic phantoms. These findings have potential implications for small-sized dosimeter measurements in phantoms, such as with TLDs or small Farmer chambers. PMID:19378763

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

Battum, LJ van; Heukelom, S

Purpose This study investigates the origin of lateral optical density (OD) variation for Gafchromic film (EBT and EBT2) scanned in transmission mode with Epson flatbed scanners (1680 Expression Pro and 10000XL). Effects investigated are: cross talk, optical path length and polarization. Methods Cross talk has been examined with triangular shaped light-transmission sheets with OD ranging from 0 to opaque. Optical path length has been studied with absorptive and reflective OD-filters (OD range 0.2 to 2.0). Dependency on light-polarization on the scanner read out has been investigated using linear polarizer sheets. All experiments have been performed at centre scanner position (normmore » point) and at several lateral scan positions, without and with (un)irradiated EBT-film. Dose values used ranged between 0.2 to 9 Gy, yielding an OD-range between 0.25 to 1.1. Results The lateral OD variation is dose dependent and increases up to 14% at most lateral position for dose up to 9 Gy. Cross talk effect contributes to 0.5% in clinical used OD ranges but equals 2% for extreme high dose gradients. Film induced optical path length will effect the lateral OD variation up to 3% at most lateral points. Light polarization is inherent present in these scanners due to multiple reflection on mirrors. In addition film induced polarization is the most important effect generating the observed lateral OD variation. Both Gafchromic film base and sensitive layer have polarizing capabilities; for the sensitive layer its influence is dose dependent. Conclusions Lateral OD variation origins from optical physics (i.e. polarization and reflection) related to scanner and film construction. Cross talk can be ignored in film dosimetry for clinical used dose values and gradients. Therefore it is recommended to determine the lateral OD variation per film type and scanner.« less

Cohort-specific imputation of gene expression improves prediction of warfarin dose for African Americans.

PubMed

Gottlieb, Assaf; Daneshjou, Roxana; DeGorter, Marianne; Bourgeois, Stephane; Svensson, Peter J; Wadelius, Mia; Deloukas, Panos; Montgomery, Stephen B; Altman, Russ B

2017-11-24

Genome-wide association studies are useful for discovering genotype-phenotype associations but are limited because they require large cohorts to identify a signal, which can be population-specific. Mapping genetic variation to genes improves power and allows the effects of both protein-coding variation as well as variation in expression to be combined into "gene level" effects. Previous work has shown that warfarin dose can be predicted using information from genetic variation that affects protein-coding regions. Here, we introduce a method that improves dose prediction by integrating tissue-specific gene expression. In particular, we use drug pathways and expression quantitative trait loci knowledge to impute gene expression-on the assumption that differential expression of key pathway genes may impact dose requirement. We focus on 116 genes from the pharmacokinetic and pharmacodynamic pathways of warfarin within training and validation sets comprising both European and African-descent individuals. We build gene-tissue signatures associated with warfarin dose in a cohort-specific manner and identify a signature of 11 gene-tissue pairs that significantly augments the International Warfarin Pharmacogenetics Consortium dosage-prediction algorithm in both populations. Our results demonstrate that imputed expression can improve dose prediction and bridge population-specific compositions. MATLAB code is available at https://github.com/assafgo/warfarin-cohort.

Comparison of 10 efficient protocols for photodynamic therapy of actinic keratosis: How relevant are effective light dose and local damage in predicting the complete response rate at 3 months?

PubMed

Vignion-Dewalle, Anne-Sophie; Baert, Gregory; Thecua, Elise; Lecomte, Fabienne; Vicentini, Claire; Abi-Rached, Henry; Mortier, Laurent; Mordon, Serge

2018-04-18

Topical photodynamic therapy is an established treatment modality for various dermatological conditions, including actinic keratosis. In Europe, the approved protocols for photodynamic therapy of actinic keratosis involve irradiation with either an Aktilite CL 128 lamp or daylight, whereas irradiation with the Blu-U illuminator is approved in the United States. Many other protocols using irradiation by a variety of light sources are also clinically efficient. This paper aims to compare 10 different protocols with clinically proven efficacy for photodynamic therapy of actinic keratosis and the available spectral irradiance of the light source. Effective irradiance, effective light dose, and local damage are compared. We also investigate whether there is an association between the complete response rate at 3 months and the effective light dose or local damage. The effective irradiance, also referred to as protoporphyrin IX-weighted irradiance, is obtained by integrating the spectral irradiance weighted by the normalized absorption spectrum of protoporphyrin IX over the wavelength. Integrating the effective irradiance over the irradiation time yields the effective light dose, which is also known as the protoporphyrin IX-weighted light dose. Local damage, defined as the total cumulative singlet oxygen molecules produced during treatment, is estimated using mathematical modeling of the photodynamic therapy process. This modeling is based on an iterative procedure taking into account the spatial and temporal variations in the protoporphyrin IX absorption spectrum during treatment. The protocol for daylight photodynamic therapy on a clear sunny day, the protocol for daylight photodynamic therapy on an overcast day, the photodynamic therapy protocol for a white LED lamp for operating rooms and the photodynamic therapy protocol for the Blu-U illuminator perform better than the six other protocols-all involving red light illumination-in terms of both effective light dose and local damage. However, no association between the complete response rate at 3 months and the effective light dose or local damage was found. Protocols that achieve high complete response rates at 3 months and low pain scores should be preferred regardless of the effective light dose and local damage. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Dietary guar gum effects on postprandial blood glucose, insulin and hydroxyproline in humans.

PubMed

Torsdottir, I; Alpsten, M; Andersson, H; Einarsson, S

1989-12-01

Meals (425 kcal) containing various doses of guar gum (0, 2.5, 7.5 or 12.5 g) were ingested by nine healthy male subjects after a 12-h fast. The rise in blood glucose was higher after the control meal without guar gum than after the guar gum-containing meals, which all gave a similar rise in glucose. In contrast, increased doses of guar gum led to a greater reduction in the postprandial rise in insulin. The postprandial increase in serum hydroxyproline, an amino acid added to all meals, was decreased in a similar manner by all of the guar gum doses. Gastric emptying was measured after the control meal without guar gum and the meal containing 12.5 g of guar gum by monitoring 51Cr, which was added to the meals. Guar gum was found to reduce the variation between individuals, as well as the initial rate of gastric emptying, which correlated with changes in both serum hydroxyproline (rs = 0.93, P less than 0.01) and blood glucose (rs = 0.83, P less than 0.01). The effectiveness of guar gum in reducing postprandial response was lost after heating and homogenization for canning. A threshold in the reduction in rise of glucose or hydroxyproline was reached with the lowest dose (2.5 g) of viscous guar gum; larger doses had no additional effects. The reduced absorption seems to be an effect of a slower gastric emptying rate.

Physiologic variability at the verge of systemic inflammation: multiscale entropy of heart rate variability is affected by very low doses of endotoxin.

PubMed

Herlitz, Georg N; Arlow, Renee L; Cheung, Nora H; Coyle, Susette M; Griffel, Benjamin; Macor, Marie A; Lowry, Stephen F; Calvano, Steve E; Gale, Stephen C

2015-02-01

Human injury or infection induces systemic inflammation with characteristic neuroendocrine responses. Fluctuations in autonomic function during inflammation are reflected by beat-to-beat variation in heart rate, termed heart rate variability (HRV). In the present study, we determine threshold doses of endotoxin needed to induce observable changes in markers of systemic inflammation, investigate whether metrics of HRV exhibit a differing threshold dose from other inflammatory markers, and investigate the size of data sets required for meaningful use of multiscale entropy (MSE) analysis of HRV. Healthy human volunteers (n = 25) were randomized to receive placebo (normal saline) or endotoxin/lipopolysaccharide (LPS): 0.1, 0.25, 0.5, 1.0, or 2.0 ng/kg administered intravenously. Vital signs were recorded every 30 min for 6 h and then at 9, 12, and 24 h after LPS. Blood samples were drawn at specific time points for cytokine measurements. Heart rate variability analysis was performed using electrocardiogram epochs of 5 min. Multiscale entropy for HRV was calculated for all dose groups to scale factor 40. The lowest significant threshold dose was noted in core temperature at 0.25 ng/kg. Endogenous tumor necrosis factor α and interleukin 6 were significantly responsive at the next dosage level (0.5 ng/kg) along with elevations in circulating leukocytes and heart rate. Responses were exaggerated at higher doses (1 and 2 ng/kg). Time domain and frequency domain HRV metrics similarly suggested a threshold dose, differing from placebo at 1.0 and 2.0 ng/kg, below which no clear pattern in response was evident. By applying repeated-measures analysis of variance across scale factors, a significant decrease in MSE was seen at 1.0 and 2.0 ng/kg by 2 h after exposure to LPS. Although not statistically significant below 1.0 ng/kg, MSE unexpectedly decreased across all groups in an orderly dose-response pattern not seen in the other outcomes. By using repeated-measures analysis of variance across scale factors, MSE can detect autonomic change after LPS challenge in a group of 25 subjects using electrocardiogram epochs of only 5 min and entropy analysis to scale factor of only 40, potentially facilitating MSE's wider use as a research tool or bedside monitor. Traditional markers of inflammation generally exhibit threshold dose behavior. In contrast, MSE's apparent continuous dose-response pattern, although not statistically verifiable in this study, suggests a potential subclinical harbinger of infectious or other insult. The possible derangement of autonomic complexity prior to or independent of the cytokine surge cannot be ruled out. Future investigation should focus on confirmation of overt inflammation following observed decreases in MSE in a clinical setting.

SU-E-T-352: Why Is the Survival Rate Low in Oropharyngeal Squamous Cell Carcinoma?

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

Huang, Z; Feng, Y; Rasmussen, K

2014-06-01

Purpose: Tumors are composed of a large number of clonogens that have the capability of indefinite reproduction. Even when there is complete clinical or radiographic regression of the gross tumor mass after treatment, tumor recurrence can occur if the clonogens are not completely eradicated by radiotherapy. This study was to investigate the colonogen number and its association with the tumor control probability (TCP) in oropharyngeal squamous cell carcinoma (OSCCA). Methods: A literature search was conducted to collect clinical information of patients with OSCCA, including the prescription dose, tumor volume and survival rate. The linear-quadratic (LQ) model was incorporated into TCPmore » model for clinical data analysis. The total dose ranged from 60 to 70 Gy and tumor volume ranged from 10 to 50 cc. The TCP was calculated for each group according to tumor size and dose. The least χ{sup 2} method was used to fit the TCP calculation to clinical data while other LQ model parameters (α, β) were adopted from the literature, due to the limited patient data. Results: A total of 190 patients with T2–T4 OSCCA were included. The association with HPV was not available for all the patients. The 3-year survival rate was about 82% for T2 squamous cell carcinoma and 40% for advanced tumors. Fitting the TCP model to the survival data, the average clonogen number was 1.56×10{sup 12}. For the prescription dose of 70 Gy, the calculated TCP ranged from 40% to 90% when the tumor volume varied from 10 to 50 cc. Conclusion: Our data suggests variation between the clonogen number and TCP in OSCCA. Tumors with larger colonogen number tend to have lower TCP and therefore dose escalation above 70 Gy may be indicated in order to improve the TCP and survival rate. Our result will require future confirmation with a large number of patients.« less

A Reanalysis of Curvature in the Dose Response for Cancer and Modifications by Age at Exposure Following Radiation Therapy for Benign Disease

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

Little, Mark P., E-mail: mark.little@nih.gov; Stovall, Marilyn; Smith, Susan A.

Purpose: To assess the shape of the dose response for various cancer endpoints and modifiers by age and time. Methods and Materials: Reanalysis of the US peptic ulcer data testing for heterogeneity of radiogenic risk by cancer endpoint (stomach, pancreas, lung, leukemia, all other). Results: There are statistically significant (P<.05) excess risks for all cancer and for lung cancer and borderline statistically significant risks for stomach cancer (P=.07), and leukemia (P=.06), with excess relative risks Gy{sup -1} of 0.024 (95% confidence interval [CI] 0.011, 0.039), 0.559 (95% CI 0.221, 1.021), 0.042 (95% CI -0.002, 0.119), and 1.087 (95% CI -0.018,more » 4.925), respectively. There is statistically significant (P=.007) excess risk of pancreatic cancer when adjusted for dose-response curvature. General downward curvature is apparent in the dose response, statistically significant (P<.05) for all cancers, pancreatic cancer, and all other cancers (ie, other than stomach, pancreas, lung, leukemia). There are indications of reduction in relative risk with increasing age at exposure (for all cancers, pancreatic cancer), but no evidence for quadratic variations in relative risk with age at exposure. If a linear-exponential dose response is used, there is no significant heterogeneity in the dose response among the 5 endpoints considered or in the speed of variation of relative risk with age at exposure. The risks are generally consistent with those observed in the Japanese atomic bomb survivors and in groups of nuclear workers. Conclusions: There are excess risks for various malignancies in this data set. Generally there is a marked downward curvature in the dose response and significant reduction in relative risk with increasing age at exposure. The consistency of risks with those observed in the Japanese atomic bomb survivors and in groups of nuclear workers implies that there may be little sparing effect of fractionation of dose or low-dose-rate exposure.« less

Fast-track surgery for uncomplicated appendicitis in children: a matched case-control study.

PubMed

Cundy, Thomas P; Sierakowski, Kyra; Manna, Alexandra; Cooper, Celia M; Burgoyne, Laura L; Khurana, Sanjeev

2017-04-01

Standardized post-operative protocols reduce variation and enhance efficiency in patient care. Patients may benefit from these initiatives by improved quality of care. This matched case-control study investigates the effect of a multidisciplinary criteria-led discharge protocol for uncomplicated appendicitis in children. Key protocol components included limiting post-operative antibiotics to two intravenous doses, avoidance of intravenous opioid analgesia, prompt resumption of diet, active encouragement of early ambulation and nursing staff autonomy to discharge patients that met assigned criteria. The study period was from August 2015 to February 2016. Outcomes were compared with a historical control group matched for operative approach. Outcomes for 83 patients enrolled to our protocol were compared with those of 83 controls. There was a 29.2% reduction in median post-operative length of stay in our protocol-based care group (19.6 versus 27.7 h; P < 0.001). The rate of discharges within 24 h improved from 12 to 42%. There was no significant difference in complication rate (4.8 versus 7.2%; P = 0.51). Mean oral morphine dose equivalent per kilogram requirement was less than half (46%) that of control group patients (P < 0.001). Mean number of ondansetron doses was also significantly lower. Projected annual direct cost savings following protocol implementation was AUD$77 057. Implementation of a criteria-led discharge protocol at our hospital decreased length of stay, reduced variation in care, preserved existing low morbidity, incurred substantial cost savings, and safely rationalized opioid and antiemetic medication. These protocols are inexpensive and offer tangible benefits that are accessible to all health care settings. © 2016 Royal Australasian College of Surgeons.

Doping test results dependent on genotype of uridine diphospho-glucuronosyl transferase 2B17, the major enzyme for testosterone glucuronidation.

PubMed

Schulze, Jenny Jakobsson; Lundmark, Jonas; Garle, Mats; Skilving, Ilona; Ekström, Lena; Rane, Anders

2008-07-01

Testosterone abuse is conventionally assessed by the urinary testosterone/epitestosterone (T/E) ratio, levels above 4.0 being considered suspicious. The large variation in testosterone glucuronide (TG) excretion and its strong association with a deletion polymorphism in the uridine diphospho-glucuronosyl transferase (UGT) 2B17 gene challenge the accuracy of the T/E ratio test. Our objective was to investigate whether genotype-based cutoff values will improve the sensitivity and specificity of the test. This was an open three-armed comparative study. A total of 55 healthy male volunteers with either two, one, or no allele [insertion/insertion, insertion/deletion, or deletion/deletion (del/del)] of the UGT2B17 gene was included in the study. A single im dose of 500 mg testosterone enanthate was administered. Urinary excretion of TG after dose and the T/E ratio during 15 d were calculated. The degree and rate of increase in the TG excretion rate were highly dependent on the UGT2B17 genotype with a 20-fold higher average maximum increase in the insertion/insertion group compared with the del/del group. Of the del/del subjects, 40% never reached the T/E ratio of 4.0 on any of the 15 d after the dose. When differentiated cutoff levels for the del/del (1.0) and the other genotypes (6.0) were applied, the sensitivity increased substantially for the del/del group, and false positives in the other genotypes were eliminated. Consideration of the genetic variation in disposition of androgens will improve the sensitivity and specificity of the testosterone doping test. This is of interest not only for combating androgen doping in sports, but also for detecting and preventing androgen abuse in society.

Degradation Behaviour of Gamma Irradiated Poly(Acrylic Acid)-graft-Chitosan Superabsorbent Hydrogel

NASA Astrophysics Data System (ADS)

Ria Barleany, Dhena; Ilhami, Alpin; Yusuf Yudanto, Dea; Erizal

2018-03-01

A series of superabsorbent hydrogels were prepared from chitosan and partially neutralized acrylic acid at room temperature by gamma irradiation technique. The effect of irradiation and chitosan addition to the degradation behaviour of polymer were investigated. The gel content, swelling capacity, Equillibrium Degree of Swelling (EDS), Fourier Transform Infra Red (FTIR), and Scanning Electron Microscopy (SEM) study were also performed. Natural degradation in soil and thermal degradation by using of TGA analysis were observed. The variation of chitosan compositions were 0.5, 1, 1.5, and 2 g and the total irradiation doses were 5, 10, 15, and 20 kGy. The highest water capacity of 583.3 g water/g dry hydrogel was resulted from 5 kGy total irradiation dose and 0,5 g addition of chitosan. From the thermal degradation evaluation by using of TGA analysis showed that irradiation dose did not give a significant influence to the degradation rate. The rate of thermal degradation was ranged between 2.42 to 2.55 mg/min. In the natural test of degradation behaviour by using of soil medium, the hydrogel product with chitosan addition was found to have better degradability compared with the poly(acrylic acid) polymer without chitosan.

The assumption of heterogeneous or homogeneous radioactive contamination in soil/sediment: does it matter in terms of the external exposure of fauna?

PubMed

Beaugelin-Seiller, K

2014-12-01

The classical approach to environmental radioprotection is based on the assumption of homogeneously contaminated media. However, in soils and sediments there may be a significant variation of radioactivity with depth. The effect of this heterogeneity was investigated by examining the external exposure of various sediment and soil organisms, and determining the resulting dose rates, assuming a realistic combination of locations and radionuclides. The results were dependent on the exposure situation, i.e., the organism, its location, and the quality and quantity of radionuclides. The dose rates ranged over three orders of magnitude. The assumption of homogeneous contamination was not consistently conservative (if associated with a level of radioactivity averaged over the full thickness of soil or sediment that was sampled). Dose assessment for screening purposes requires consideration of the highest activity concentration measured in a soil/sediment that is considered to be homogeneously contaminated. A more refined assessment (e.g., higher tier of a graded approach) should take into consideration a more realistic contamination profile, and apply different dosimetric approaches. Copyright © 2014 Elsevier Ltd. All rights reserved.

Pharmacokinetics of insulin following intravenous and subcutaneous administration in canines.

PubMed

Ravis, W R; Comerci, C; Ganjam, V K

1986-01-01

Studies were conducted to examine the absorption and disposition kinetics of insulin in dogs following intravenous (IV) and subcutaneous (SC) administration of commercial preparations. After IV and SC dosing, the plasma levels were described by models which considered basal insulin level contributions. Intersubject variation in the disposition kinetics was small with half-lives of 0.52 +/- 0.05 h and total body clearances of 16.21 +/- 2.08 ml min-1 kg-1. Calculated insulin plasma secretion rates in the canines were 14.4 +/- 3.3 mUh-1 kg-1. Following SC injection of regular insulin, the rate and extent of absorption were noted to be quite variable. The absorption process appeared first-order with half-life values of 2.3 +/- 1.3 h and extents of absorption of 78 +/- 15 per cent with a range of 55-101 per cent. Insulin absorption from SC NPH preparations was evaluated as being composed of two zero-order release phases, a rapid and a slow release phase. With a dose of 1.65 U kg-1, the rapid release phase had an average duration of 1.5 h and a rate of 580 +/- 269 mUh-1 (4.2 per cent of dose) while the slow phase had a zero-order rate of 237 +/- 92 mU h-1 which continued beyond 12 h. The extent of absorption from the NPH preparation was 23.6 +/- 5.1 per cent and was significantly lower than that for the regular injection.

SU-E-T-582: On-Line Dosimetric Verification of Respiratory Gated Volumetric Modulated Arc Therapy Using the Electronic Portal Imaging Device

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

Schaly, B; Gaede, S; Department of Medical Biophysics, Western University, London, ON

2015-06-15

Purpose: To investigate the clinical utility of on-line verification of respiratory gated VMAT dosimetry during treatment. Methods: Portal dose images were acquired during treatment in integrated mode on a Varian TrueBeam (v. 1.6) linear accelerator for gated lung and liver patients that used flattening filtered beams. The source to imager distance (SID) was set to 160 cm to ensure imager clearance in case the isocenter was off midline. Note that acquisition of integrated images resulted in no extra dose to the patient. Fraction 1 was taken as baseline and all portal dose images were compared to that of the baseline,more » where the gamma comparison and dose difference were used to measure day-to-day exit dose variation. All images were analyzed in the Portal Dosimetry module of Aria (v. 10). The portal imager on the TrueBeam was calibrated by following the instructions for dosimetry calibration in service mode, where we define 1 calibrated unit (CU) equal to 1 Gy for 10×10 cm field size at 100 cm SID. This reference condition was measured frequently to verify imager calibration. Results: The gamma value (3%, 3 mm, 5% threshold) ranged between 92% and 100% for the lung and liver cases studied. The exit dose can vary by as much as 10% of the maximum dose for an individual fraction. The integrated images combined with the information given by the corresponding on-line soft tissue matched cone-beam computed tomography (CBCT) images were useful in explaining dose variation. For gated lung treatment, dose variation was mainly due to the diaphragm position. For gated liver treatment, the dose variation was due to both diaphragm position and weight loss. Conclusion: Integrated images can be useful in verifying dose delivery consistency during respiratory gated VMAT, although the CBCT information is needed to explain dose differences due to anatomical changes.« less

Development of Lateral Prestress in High-Strength Concrete-Filled FRP Tubes

NASA Astrophysics Data System (ADS)

Vincent, T.; Ozbakkaloglu, T.

2018-02-01

This paper reports on an experimental investigation into the axial and lateral strain development of fiber reinforced polymer (FRP) confined high-strength concrete (HSC) with prestressed FRP shells. A total of 24 aramid FRP (AFRP)-confined concrete specimens were manufactured as concrete-filled FRP tubes (CFFTs) with instrumentation to measure the strain variations during application of prestress, removal of end constraints and progressive prestress losses. Prestressed CFFT specimens were prepared with three different dose rates of expansive mineral admixture to create a range of lateral prestress applied to AFRP tubes manufactured with sheet thicknesses of 0.2 or 0.3 mm/ply and referred to as lightly- or well-confined, respectively. In addition to these three levels of prestress, non-prestressed companion specimens were manufactured and tested to determine baseline performance. The experimental results from this study indicate that lateral prestressing of CFFTs manufactured with HSC can be achieved by varying the expansive mineral admixture dose rate with a lateral prestress of up to 7.3 MPa recorded in this study. Significant strain variations were measured during removal of the end constraints with up to 700 microstrain recorded in the axial direction. Finally, the measurement of prestress losses for the month following prestress application revealed minimal progressive losses, with only 250 and 100 με recorded for the axial and hoop strains, respectively.

INVESTIGATION OF THE INFLUENCE OF THE POSITION INSIDE A SMALL AIRCRAFT ON THE COSMIC-RADIATION-INDUCED DOSE.

PubMed

Prado, A C M; Pazianotto, M T; Gonçalez, O L; Dos Santos, L R; Caldeira, A D; Pereira, H H C; Hubert, G; Federico, C A

2017-11-01

This article report the measurements on-board a small aircraft at the same altitude and around the same geographic coordinates. The measurements of Ambient Dose Equivalent Rate (H*(10)) were performed in several positions inside the aircraft, close and far from the pilot location and the discrimination between neutron and non-neutron components. The results show that the neutrons are attenuated close to fuel depots and the non-neutron component appears to have the opposite behavior inside the aircraft. These experimental results are also confronted with results from Monte Carlo simulation, obtained with the MCNPX code, using a simplified model of the Learjet-type aircraft and a modeling of the standard atmosphere, which reproduces the real energy and angular distribution of the particles. The Monte Carlo simulation agreed with the experimental measurements and shows that the total H*(10) presents small variation (around 1%) between the positions inside aircraft, although the neutron spectra present significant variations. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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

Chen, Q; Read, P

Purpose: Multiple error pathways can lead to delivery errors during the treatment course that cannot be caught with pre-treatment QA. While in vivo solutions are being developed for linacs, no such solution exists for tomotherapy. The purpose of this study is to develop a near real-time system for tomotherapy that can monitor the delivery and dose accumulation process during the treatment-delivery, which enable the user to assess the impact of delivery variations and/or errors and to interrupt the treatment if necessary. Methods: A program running on a tomotherapy planning station fetches the raw DAS data during treatment. Exit detector datamore » is extracted as well as output, gantry angle, and other machine parameters. For each sample, the MLC open-close state is determined. The delivered plan is compared with the original plan via a Monte Carlo dose engine which transports fluence deviations from a pre-treatment Monte Carlo run. A report containing the difference in fluence, dose and DVH statistics is created in html format. This process is repeated until the treatment is completed. Results: Since we only need to compute the dose for the difference in fluence for a few projections each time, dose with 2% statistical uncertainty can be computed in less than 1 second on a 4-core cpu. However, the current bottleneck in this near real-time system is the repeated fetching and processing the growing DAS data file throughout the delivery. The frame rate drops from 10Hz at the beginning of treatment to 5Hz after 3 minutes and to 2Hz after 10 minutes. Conclusion: A during-treatment delivery monitor system has been built to monitor tomotherapy treatments. The system improves patient safety by allowing operators to assess the delivery variations and errors during treatment delivery and adopt appropriate actions.« less

Evaluation of clinical use of OneDose™ metal oxide semiconductor field-effect transistor detectors compared to thermoluminescent dosimeters to measure skin dose for adult patients with acute lymphoblastic leukemia

PubMed Central

Al-Mohammed, Huda Ibrahim

2011-01-01

Background: Total body irradiation is a protocol used to treat acute lymphoblastic leukemia in patients prior to their bone marrow transplant. It involves the treatment of the whole body using a large radiation field with extended source-skin distance. Therefore, it is important to measure and monitor the skin dose during the treatment. Thermoluminescent dosimeters (TLDs) and the OneDose™ metal oxide semiconductor field effect transistor (MOSFET) detectors are used during treatment delivery to measure the radiation dose and compare it with the target prescribed dose. Aims: The primary goal of this study was to measure the variation of skin dose using OneDose MOSFET detectors and TLD detectors, and compare the results with the target prescribed dose. The secondary aim was to evaluate the simplicity of use and determine if one system was superior to the other in clinical use. Material and Methods: The measurements involved twelve adult patients diagnosed with acute lymphoblastic leukemia. TLD and OneDose MOSFET dosimetry were performed at ten different anatomical sites of each patient. Results: The results showed that there was a variation between skin dose measured with OneDose MOSFET detectors and TLD in all patients. However, the variation was not significant. Furthermore, the results showed for every anatomical site there was no significant different between the prescribed dose and the dose measured by either TLD or OneDose MOSFET detectors. Conclusion: There were no significant differences between the OneDose MOSFET and TLDs in comparison to the target prescribed dose. However, OneDose MOSFET detectors give a direct read-out immediately after the treatment, and their simplicity of use to compare with TLD detectors may make them preferred for clinical use. PMID:22171243

A pharmacokinetic and pharmacodynamic comparison of immediate-release metoprolol and extended-release metoprolol CR/XL in patients with suspected acute myocardial infarction: a randomized, open-label study.

PubMed

Karlson, Björn W; Dellborg, Mikael; Gullestad, Lars; Aberg, Jan; Sugg, Jennifer; Herlitz, Johan

2014-01-01

Previous metoprolol studies in myocardial infarction patients were performed with immediate-release (IR) metoprolol. This study aims to evaluate if extended-release metoprolol CR/XL once daily gives a similar β-blockade over 24 h compared to multiple dosing of metoprolol IR. After 2 days of routine metoprolol treatment, 27 patients with suspected acute myocardial infarction were randomized to open-label treatment with metoprolol IR (50 mg four times daily or 100 mg twice daily) or metoprolol CR/XL 200 mg once daily for 3 days. Metoprolol CR/XL 200 mg once daily gave more pronounced suppression of peak heart rate, with lower peak and less variation in peak to trough plasma levels. There were no differences in AUC between the CR/XL and IR formulations, although the trough plasma metoprolol levels were comparable for metoprolol CR/XL 200 mg once daily and metoprolol IR 50 mg four times daily, but lower for metoprolol IR 100 mg twice daily. Both treatments were well tolerated. Metoprolol CR/XL 200 mg once daily showed lower peak and less variation in peak to trough plasma levels compared to multiple dosing of metoprolol IR with the same AUC. This was accompanied by a more uniform β-blockade over time, which was reflected by heart rate, and a more pronounced suppression of peak heart rate with similar tolerability. This suggests metoprolol CR/XL may be used as an alternative to metoprolol IR in patients with myocardial infarction. © 2013 S. Karger AG, Basel.

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

Yi, B; Chung, H; Mutaf, Y

Purpose: To test a novel total body irradiation (TBI) system using conformal partial arc with patient lying on the stationary couch which is biologically equivalent to a moving couch TBI. This improves the scanning field TBI, which is previously presented. Methods: The Uniform MU Modulated arc Segments TBI or UMMS-TBI scans the treatment plane with a constant machine dose rate and a constant gantry rotation speed. A dynamic MLC pattern which moves while gantry rotates has been designed so that the treatment field moves same distance at the treatment plane per each gantry angle, while maintaining same treatment field sizemore » (34cm) at the plane. Dose across the plane varies due to the geometric differences including the distance from the source to a point of interest and the different attenuation from the slanted depth which changes the effective depth. Beam intensity is modulated to correct the dose variation across the plane by assigning the number of gantry angles inversely proportional to the uncorrected dose. Results: Measured dose and calculated dose matched within 1 % for central axis and 3% for off axis for various patient scenarios. Dose from different distance does not follow the inverse square relation as it is predicted from calculation. Dose uniformity better than 5% across 180 cm at 10cm depth is achieved by moving the gantry from −55 to +55 deg. Total treatment time for 2 Gy AP/PA fields is 40–50 minutes excluding patient set up time, at the machine dose rate of 200 MU/min. Conclusion: This novel technique, yet accurate but easy to implement enables TBI treatment in a small treatment room with less program development preparation than other techniques. The VMAT function of treatment delivery is not required to modulate beams. One delivery pattern can be used for different patients by changing the monitor units.« less

A novel method for routine quality assurance of volumetric-modulated arc therapy.

PubMed

Wang, Qingxin; Dai, Jianrong; Zhang, Ke

2013-10-01

Volumetric-modulated arc therapy (VMAT) is delivered through synchronized variation of gantry angle, dose rate, and multileaf collimator (MLC) leaf positions. The delivery dynamic nature challenges the parameter setting accuracy of linac control system. The purpose of this study was to develop a novel method for routine quality assurance (QA) of VMAT linacs. ArcCheck is a detector array with diodes distributing in spiral pattern on cylindrical surface. Utilizing its features, a QA plan was designed to strictly test all varying parameters during VMAT delivery on an Elekta Synergy linac. In this plan, there are 24 control points. The gantry rotates clockwise from 181° to 179°. The dose rate, gantry speed, and MLC positions cover their ranges commonly used in clinic. The two borders of MLC-shaped field seat over two columns of diodes of ArcCheck when the gantry rotates to the angle specified by each control point. The ratio of dose rate between each of these diodes and the diode closest to the field center is a certain value and sensitive to the MLC positioning error of the leaf crossing the diode. Consequently, the positioning error can be determined by the ratio with the help of a relationship curve. The time when the gantry reaches the angle specified by each control point can be acquired from the virtual inclinometer that is a feature of ArcCheck. The gantry speed between two consecutive control points is then calculated. The aforementioned dose rate is calculated from an acm file that is generated during ArcCheck measurements. This file stores the data measured by each detector in 50 ms updates with each update in a separate row. A computer program was written in MATLAB language to process the data. The program output included MLC positioning errors and the dose rate at each control point as well as the gantry speed between control points. To evaluate this method, this plan was delivered for four consecutive weeks. The actual dose rate and gantry speed were compared with the QA plan specified. Additionally, leaf positioning errors were intentionally introduced to investigate the sensitivity of this method. The relationship curves were established for detecting MLC positioning errors during VMAT delivery. For four consecutive weeks measured, 98.4%, 94.9%, 89.2%, and 91.0% of the leaf positioning errors were within ± 0.5 mm, respectively. For the intentionally introduced leaf positioning systematic errors of -0.5 and +1 mm, the detected leaf positioning errors of 20 Y1 leaf were -0.48 ± 0.14 and 1.02 ± 0.26 mm, respectively. The actual gantry speed and dose rate closely followed the values specified in the VMAT QA plan. This method can assess the accuracy of MLC positions and the dose rate at each control point as well as the gantry speed between control points at the same time. It is efficient and suitable for routine quality assurance of VMAT.

SU-C-16A-04: Dosimetric Validation of a Partially-Shielded Gd-153 Brachytherapy Concept

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

Li, X; Adams, Q; Flynn, R

Purpose: To demonstrate by measurement that using partially shielded Gd-153 sources for rotating-shield brachytherapy (RSBT) is feasible. RSBT is a potentially superior alternative to conventional high-dose-rate brachytherapy and provides the opportunity to dramatically improve tumor dose conformity for the treatment of, for example, prostate cancer. Methods: A custom-built, stainless steel encapsulated 150 mCi Gd-153 capsule with an outer length of 12.8 mm, outer diameter of 2.10 mm, active length of 9.98 mm, and active diameter of 1.53 mm was used. A partially shielded catheter was constructed with a 500 μm platinum shield and a 500 μm aluminum emission window, bothmore » with 180° azimuthal coverage. An acrylic phantom was constructed to measure the dose distributions from the shielded catheter in the transverse plane using Gafchromic EBT3 films. Film calibration curves were generated from 50, 70, and 100 kVp x-ray beams with NIST-traceable air kerma values to account for energy variation. Results: The transmission ratios of platinum to aluminum shielding at 1 cm off-axis are 7.5% and 7.6% for Monte Carlo (MCNP5) predicted and experimental results, respectively. The predicted/measured relative dose rates at 1 cm, 2 cm and 3 cm off-axis through the Al window were 100%/92.9%, 28.6%/27.0% and 13.8%/12.7%, respectively. Through the Pt shield, the predicted/measured relative dose rates were 7.5%/7.1%, 3.8%/3.0% and 2.4%/1.7%, respectively. Conclusion: Using partially-shielded Gd-153 sources for RSBT is a promising approach to improving brachytherapy dose distributions. The next step in making Gd-153 based RSBT a reality is developing a Gd-153 source that is small enough such that the source, shield, and catheter all fit within a 16 gauge needle, which has a 1.65 mm diameter. University of Iowa Research Foundation.« less

Image-Guided High-Dose Rate Brachytherapy in Cervix Carcinoma Using Balloon Catheter and Belt Immobilization System.

PubMed

Fan, Qiyong; Yeung, Anamaria R; Amdur, Robert; Helmig, Richard; Park, Justin; Li, Jonathan; Kahler, Darren; Liu, Chihray; Lu, Bo

2017-06-01

The efficacy of image-guided high-dose rate brachytherapy for cervical cancer is limited by the ineffective rectal sparing devices available commercially and the potential applicator movement. We developed a novel device using a balloon catheter and a belt immobilization system, serving for rectal dose reduction and applicator immobilization purposes, respectively. The balloon catheter is constructed by gluing a short inflatable tube to a long regular open-end catheter. Contrast agent (10) cm 3 is injected into the inflatable end, which is affixed to the tandem and ring applicator, to displace the posterior vaginal wall. The belt immobilization system consists of a specially designed bracket that can hold and fix itself to the applicator, a diaper-like Velcro fastener package used for connecting the patient's pelvis to the bracket, and a buckle that holds the fasteners to stabilize the whole system. The treatment data for 21 patients with cervical cancer using both balloon catheter and belt immobilization system were retrospectively analyzed. Computed tomography and magnetic resonance images, acquired about 30 minutes apart, were registered to evaluate the effectiveness of the immobilization system. In comparison with a virtual rectal blade, the balloon decreased the rectal point dose by 34% ± 4.2% (from 276 ± 57 to 182 ± 38 cGy), corresponding to an extra sparing distance of 7.9 ± 1.1 mm. The maximum sparing distance variation per patient is 1.4 ± 0.6 mm, indicating the high interfractional reproducibility for rectum sparing. With the immobilization system, the mean translational and rotational displacements of the applicator set are <3 mm and <1.5°, respectively, in all directions. The rectal balloon provides significant dose reduction to the rectum and it may potentially minimize patient discomfort. The immobilization system permits almost no movement of the applicator during treatment. This work has the potential to be promoted as a standardized solution for high-dose rate treatment of cervical cancer.

Epid cine acquisition mode for in vivo dosimetry in dynamic arc radiation therapy

NASA Astrophysics Data System (ADS)

Fidanzio, Andrea; Mameli, Alessandra; Placidi, Elisa; Greco, Francesca; Stimato, Gerardina; Gaudino, Diego; Ramella, Sara; D'Angelillo, Rolando; Cellini, Francesco; Trodella, Lucio; Cilla, Savino; Grimaldi, Luca; D'Onofrio, Guido; Azario, Luigi; Piermattei, Angelo

2008-02-01

In this paper the cine acquisition mode of an electronic portal imaging device (EPID) has been calibrated and tested to determine the in vivo dose for dynamic conformal arc radiation therapy (DCAT). The EPID cine acquisition mode, that allows a frame acquisition rate of one image every 1.66 s, was studied with a monitor unit rate equal to 100 UM/min. In these conditions good signal stability, ±1% (2SD) evaluated during three months, signal reproducibility within ±0.8% (2SD) and linearity with dose and dose rate within ±1% (2SD) were obtained. The transit signal, St, (due to the transmitted beam below the phantom) measured by the EPID cine acquisition mode was used to determine, (i) a set of correlation functions, F(w,L), defined as the ratio between St and the dose at half thickness, Dm, measured in solid water phantoms of different thicknesses, w and with square fields of side L, (ii) a set of factors, f(d,L), that take into account the different X-ray scatter contribution from the phantom to the St signal as a function of the variation, d, of the air gap between the phantom and the EPID. The reconstruction of the isocenter dose, Diso, for DCAT was obtained convolving the transit signal values, obtained at different gantry angles, with the respective reconstruction factors determined by a house-made software. The method was tested with cylindrical and anthropomorphic phantoms and the results show that the reconstructed Diso values can be obtained with an accuracy within ±2.5% in cylindrical phantom and within ±3.4% for anthropomorphic phantom. In conclusion, the transit dosimetry by EPID was assessed to be adequate to perform DCAT in vivo dosimetry, that is not realizable with the other traditional techniques. Moreover, the method proposed here could be implemented to supply in vivo dose values in real time.

Characterization of a novel two dimensional diode array the "magic plate" as a radiation detector for radiation therapy treatment.

PubMed

Wong, J H D; Fuduli, I; Carolan, M; Petasecca, M; Lerch, M L F; Perevertaylo, V L; Metcalfe, P; Rosenfeld, A B

2012-05-01

Intensity modulated radiation therapy (IMRT) utilizes the technology of multileaf collimators to deliver highly modulated and complex radiation treatment. Dosimetric verification of the IMRT treatment requires the verification of the delivered dose distribution. Two dimensional ion chamber or diode arrays are gaining popularity as a dosimeter of choice due to their real time feedback compared to film dosimetry. This paper describes the characterization of a novel 2D diode array, which has been named the "magic plate" (MP). It was designed to function as a 2D transmission detector as well as a planar detector for dose distribution measurements in a solid water phantom for the dosimetric verification of IMRT treatment delivery. The prototype MP is an 11 × 11 detector array based on thin (50 μm) epitaxial diode technology mounted on a 0.6 mm thick Kapton substrate using a proprietary "drop-in" technology developed by the Centre for Medical Radiation Physics, University of Wollongong. A full characterization of the detector was performed, including radiation damage study, dose per pulse effect, percent depth dose comparison with CC13 ion chamber and build up characteristics with a parallel plane ion chamber measurements, dose linearity, energy response and angular response. Postirradiated magic plate diodes showed a reproducibility of 2.1%. The MP dose per pulse response decreased at higher dose rates while at lower dose rates the MP appears to be dose rate independent. The depth dose measurement of the MP agrees with ion chamber depth dose measurements to within 0.7% while dose linearity was excellent. MP showed angular response dependency due to the anisotropy of the silicon diode with the maximum variation in angular response of 10.8% at gantry angle 180°. Angular dependence was within 3.5% for the gantry angles ± 75°. The field size dependence of the MP at isocenter agrees with ion chamber measurement to within 1.1%. In the beam perturbation study, the surface dose increased by 12.1% for a 30 × 30 cm(2) field size at the source to detector distance (SDD) of 80 cm whilst the transmission for the MP was 99%. The radiation response of the magic plate was successfully characterized. The array of epitaxial silicon based detectors with "drop-in" packaging showed properties suitable to be used as a simplified multipurpose and nonperturbing 2D radiation detector for radiation therapy dosimetric verification.

Baseline glucocorticoids are drivers of body mass gain in a diving seabird

USGS Publications Warehouse

Hennin, Holly; Berlin, Alicia; Love, Oliver P.

2016-01-01

Life-history trade-offs are influenced by variation in individual state, with individuals in better condition often completing life-history stages with greater success. Although resource accrual significantly impacts key life-history decisions such as the timing of reproduction, little is known about the underlying mechanisms driving resource accumulation. Baseline corticosterone (CORT, the primary avian glucocorticoid) mediates daily and seasonal energetics, responds to changes in food availability, and has been linked to foraging behavior, making it a strong potential driver of individual variation in resource accrual and deposition. Working with a captive colony of white-winged scoters (Melanitta fusca deglandi), we aimed to causally determine whether variation in baseline CORT drives individual body mass gains mediated through fattening rate (plasma triglycerides corrected for body mass). We implanted individuals with each of three treatment pellets to elevate CORT within a baseline range in a randomized order: control, low dose of CORT, high dose of CORT, then blood sampled and recorded body mass over a two-week period to track changes in baseline CORT, body mass, and fattening rates. The high CORT treatment significantly elevated levels of plasma hormone for a short period of time within the biologically relevant, baseline range for this species, but importantly did not inhibit the function of the HPA (hypothalamic–pituitary–adrenal) axis. Furthermore, an elevation in baseline CORT resulted in a consistent increase in body mass throughout the trial period compared to controls. This is some of the first empirical evidence demonstrating that elevations of baseline CORT within a biologically relevant range have a causal, direct, and positive influence on changes in body mass.

Baseline glucocorticoids are drivers of body mass gain in a diving seabird.

PubMed

Hennin, Holly L; Wells-Berlin, Alicia M; Love, Oliver P

2016-03-01

Life-history trade-offs are influenced by variation in individual state, with individuals in better condition often completing life-history stages with greater success. Although resource accrual significantly impacts key life-history decisions such as the timing of reproduction, little is known about the underlying mechanisms driving resource accumulation. Baseline corticosterone (CORT, the primary avian glucocorticoid) mediates daily and seasonal energetics, responds to changes in food availability, and has been linked to foraging behavior, making it a strong potential driver of individual variation in resource accrual and deposition. Working with a captive colony of white-winged scoters (Melanitta fusca deglandi), we aimed to causally determine whether variation in baseline CORT drives individual body mass gains mediated through fattening rate (plasma triglycerides corrected for body mass). We implanted individuals with each of three treatment pellets to elevate CORT within a baseline range in a randomized order: control, low dose of CORT, high dose of CORT, then blood sampled and recorded body mass over a two-week period to track changes in baseline CORT, body mass, and fattening rates. The high CORT treatment significantly elevated levels of plasma hormone for a short period of time within the biologically relevant, baseline range for this species, but importantly did not inhibit the function of the HPA (hypothalamic-pituitary-adrenal) axis. Furthermore, an elevation in baseline CORT resulted in a consistent increase in body mass throughout the trial period compared to controls. This is some of the first empirical evidence demonstrating that elevations of baseline CORT within a biologically relevant range have a causal, direct, and positive influence on changes in body mass.

High-Risk Prescribing to Medicaid Enrollees Receiving Opioid Analgesics: Individual- and County-Level Factors.

PubMed

Heins, Sara E; Sorbero, Mark J; Jones, Christopher M; Dick, Andrew W; Stein, Bradley D

2018-01-05

Prescription opioid overdoses have increased dramatically in recent years, with the highest rates among Medicaid enrollees. High-risk prescribing includes practices associated with overdoses and a range of additional opioid-related problems. To identify individual- and county-level factors associated with high-risk prescribing among Medicaid enrollees receiving opioids. In a four-states, cross-sectional claims data study, Medicaid enrollees 18-64 years old with a new opioid analgesic treatment episode 2007-2009 were identified. Multivariate regression analyses were conducted to identify factors associated with high-risk prescribing, defined as high-dose opioid prescribing (morphine equivalent daily dose ≥100 mg for >6 days), opioid overlap, opioid-benzodiazepine overlap. High-risk prescribing occurred in 39.4% of episodes. Older age, rural county of residence, white race, and major depression diagnosis were associated with higher rates of all types of high-risk prescribing. Individuals with prior opioid, alcohol, and hypnotic/sedative use disorder diagnoses had lower odds of high-dose opioid prescribing but higher odds of opioid overlap and opioid-benzodiazepine overlap than individuals without such disorders. High-dose opioid prescribing in Massachusetts was less common than in California, Illinois, and New York, whereas the rate of benzodiazepine overlap in Massachusetts was more common than in other states. Conclusions/Importance: High-risk prescribing was common and associated with several important demographic, clinical, and community factors. Findings can be used to inform targeted interventions designed to reduce such prescribing, and given state variation observed, further research is needed to better understand the effects of state policies on high-risk prescribing.

SU-E-T-598: Parametric Equation for Quick and Reliable Estimate of Stray Neutron Doses in Proton Therapy and Application for Intracranial Tumor Treatments

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

Bonfrate, A; Farah, J; Sayah, R

2015-06-15

Purpose: Development of a parametric equation suitable for a daily use in routine clinic to provide estimates of stray neutron doses in proton therapy. Methods: Monte Carlo (MC) calculations using the UF-NCI 1-year-old phantom were exercised to determine the variation of stray neutron doses as a function of irradiation parameters while performing intracranial treatments. This was done by individually changing the proton beam energy, modulation width, collimator aperture and thickness, compensator thickness and the air gap size while their impact on neutron doses were put into a single equation. The variation of neutron doses with distance from the target volumemore » was also included in it. Then, a first step consisted in establishing the fitting coefficients by using 221 learning data which were neutron absorbed doses obtained with MC simulations while a second step consisted in validating the final equation. Results: The variation of stray neutron doses with irradiation parameters were fitted with linear, polynomial, etc. model while a power-law model was used to fit the variation of stray neutron doses with the distance from the target volume. The parametric equation fitted well MC simulations while establishing fitting coefficients as the discrepancies on the estimate of neutron absorbed doses were within 10%. The discrepancy can reach ∼25% for the bladder, the farthest organ from the target volume. Finally, the validation showed results in compliance with MC calculations since the discrepancies were also within 10% for head-and-neck and thoracic organs while they can reach ∼25%, again for pelvic organs. Conclusion: The parametric equation presents promising results and will be validated for other target sites as well as other facilities to go towards a universal method.« less

A feature alignment score for online cone-beam CT-based image-guided radiotherapy for prostate cancer.

PubMed

Hargrave, Catriona; Deegan, Timothy; Poulsen, Michael; Bednarz, Tomasz; Harden, Fiona; Mengersen, Kerrie

2018-05-17

To develop a method for scoring online cone-beam CT (CBCT)-to-planning CT image feature alignment to inform prostate image-guided radiotherapy (IGRT) decision-making. The feasibility of incorporating volume variation metric thresholds predictive of delivering planned dose into weighted functions, was investigated. Radiation therapists and radiation oncologists participated in workshops where they reviewed prostate CBCT-IGRT case examples and completed a paper-based survey of image feature matching practices. For 36 prostate cancer patients, one daily CBCT was retrospectively contoured then registered with their plan to simulate delivered dose if (a) no online setup corrections and (b) online image alignment and setup corrections, were performed. Survey results were used to select variables for inclusion in classification and regression tree (CART) and boosted regression trees (BRT) modeling of volume variation metric thresholds predictive of delivering planned dose to the prostate, proximal seminal vesicles (PSV), bladder, and rectum. Weighted functions incorporating the CART and BRT results were used to calculate a score of individual tumor and organ at risk image feature alignment (FAS TV _ OAR ). Scaled and weighted FAS TV _ OAR were then used to calculate a score of overall treatment compliance (FAS global ) for a given CBCT-planning CT registration. The FAS TV _ OAR were assessed for sensitivity, specificity, and predictive power. FAS global thresholds indicative of high, medium, or low overall treatment plan compliance were determined using coefficients from multiple linear regression analysis. Thirty-two participants completed the prostate CBCT-IGRT survey. While responses demonstrated consensus of practice for preferential ranking of planning CT and CBCT match features in the presence of deformation and rotation, variation existed in the specified thresholds for observed volume differences requiring patient repositioning or repeat bladder and bowel preparation. The CART and BRT modeling indicated that for a given registration, a Dice similarity coefficient >0.80 and >0.60 for the prostate and PSV, respectively, and a maximum Hausdorff distance <8.0 mm for both structures were predictive of delivered dose ± 5% of planned dose. A normalized volume difference <1.0 and a CBCT anterior rectum wall >1.0 mm anterior to the planning CT anterior rectum wall were predictive of delivered dose >5% of planned rectum dose. A normalized volume difference <0.88, and a CBCT bladder wall >13.5 mm inferior and >5.0 mm posterior to the planning CT bladder were predictive of delivered dose >5% of planned bladder dose. A FAS TV _ OAR >0 is indicative of delivery of planned dose. For calculated FAS TV _ OAR for the prostate, PSV, bladder, and rectum using test data, sensitivity was 0.56, 0.75, 0.89, and 1.00, respectively; specificity 0.90, 0.94, 0.59, and 1.00, respectively; positive predictive power 0.90, 0.86, 0.53, and 1.00, respectively; and negative predictive power 0.56, 0.89, 0.91, and 1.00, respectively. Thresholds for the calculated FAS global of were low <60, medium 60-80, and high >80, with a 27% misclassification rate for the test data. A FAS global incorporating nested FAS TV _ OAR and volume variation metric thresholds predictive of treatment plan compliance was developed, offering an alternative to pretreatment dose calculations to assess treatment delivery accuracy. © 2018 American Association of Physicists in Medicine.

Polybutadiene and Styrene-Butadiene rubbers for high-dose dosimetry

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

Oliveira, Lucas N.; Instituto de Pesquisas Energeticas e Nucleares -IPEN, Sao Paulo-SP; Vieira, Silvio L.

2015-07-01

Polybutadiene and Styrene-Butadiene are synthetical rubbers used widely for pneumatic tires manufacturing. In this research, the dosimeter characteristics of those rubbers were studied for application in high-dose dosimetry. The rubber samples were irradiated with doses of 10 Gy up to 10 kGy, using a {sup 60}Co Gamma Cell-220 system (dose rate of 1.089 kGy/h) and their readings were taken on a Fourier Transform Infrared Spectroscopy-FTIR system (model Frontier/Perkin Elmer). The ratios of two absorbance peaks were taken for each kind of rubber spectrum, Polybutadiene (1306/1130 cm{sup -1}) and Styrene-Butadiene (1449/1306 cm{sup -1}). The ratio calculated was used as the responsemore » to the irradiation, and is not uniform across the sample. From the results, it can be concluded for both rubbers: a) the dose-response curves may be useful for high-dose dosimetry (greater than 250 Gy); b) their response for reproducibility presented standard deviations lower than 2.5%; c) the relative sensitivity was higher for Styrene-Butadiene (1.86 kGy{sup -1}) than for Polybutadiene (1.81 kGy{sup -1}), d) for doses of 10 kGy to 200 kGy, there was no variation in the dosimetric response. Both types of rubber samples showed usefulness as high-dose dosimeters. (authors)« less

Magnetization transfer proportion: a simplified measure of dose response for polymer gel dosimetry.

PubMed

Whitney, Heather M; Gochberg, Daniel F; Gore, John C

2008-12-21

The response to radiation of polymer gel dosimeters has most often been described by measuring the nuclear magnetic resonance transverse relaxation rate as a function of dose. This approach is highly dependent upon the choice of experimental parameters, such as the echo spacing time for Carr-Purcell-Meiboom-Gill-type pulse sequences, and is difficult to optimize in imaging applications where a range of doses are applied to a single gel, as is typical for practical uses of polymer gel dosimetry. Moreover, errors in computing dose can arise when there are substantial variations in the radiofrequency (B1) field or resonant frequency, as may occur for large samples. Here we consider the advantages of using magnetization transfer imaging as an alternative approach and propose the use of a simplified quantity, the magnetization transfer proportion (MTP), to assess doses. This measure can be estimated through two simple acquisitions and is more robust in the presence of some sources of system imperfections. It also has a dependence upon experimental parameters that is independent of dose, allowing simultaneous optimization at all dose levels. The MTP is shown to be less susceptible to B1 errors than are CPMG measurements of R2. The dose response can be optimized through appropriate choices of the power and offset frequency of the pulses used in magnetization transfer imaging.

Skin dose mapping for non-uniform x-ray fields using a backscatter point spread function

NASA Astrophysics Data System (ADS)

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

2017-03-01

Beam shaping devices like ROI attenuators and compensation filters modulate the intensity distribution of the xray beam incident on the patient. This results in a spatial variation of skin dose due to the variation of primary radiation and also a variation in backscattered radiation from the patient. To determine the backscatter component, backscatter point spread functions (PSF) are generated using EGS Monte-Carlo software. For this study, PSF's were determined by simulating a 1 mm beam incident on the lateral surface of an anthropomorphic head phantom and a 20 cm thick PMMA block phantom. The backscatter PSF's for the head phantom and PMMA phantom are curve fit with a Lorentzian function after being normalized to the primary dose intensity (PSFn). PSFn is convolved with the primary dose distribution to generate the scatter dose distribution, which is added to the primary to obtain the total dose distribution. The backscatter convolution technique is incorporated in the dose tracking system (DTS), which tracks skin dose during fluoroscopic procedures and provides a color map of the dose distribution on a 3D patient graphic model. A convolution technique is developed for the backscatter dose determination for the nonuniformly spaced graphic-model surface vertices. A Gafchromic film validation was performed for shaped x-ray beams generated with an ROI attenuator and with two compensation filters inserted into the field. The total dose distribution calculated by the backscatter convolution technique closely agreed with that measured with the film.

COMPARISON OF ORGAN DOSES IN HUMAN PHANTOMS: VARIATIONS DUE TO BODY SIZE AND POSTURE.

PubMed

Feng, Xu; Xiang-Hong, Jia; Qian, Liu; Xue-Jun, Yu; Zhan-Chun, Pan; Chun-Xin, Yang

2017-04-20

Organ dose calculations performed using human phantoms can provide estimates of astronauts' health risks due to cosmic radiation. However, the characteristics of such phantoms strongly affect the estimation precision. To investigate organ dose variations with body size and posture in human phantoms, a non-uniform rational B-spline boundary surfaces model was constructed based on cryosection images. This model was used to establish four phantoms with different body size and posture parameters, whose organs parameters were changed simultaneously and which were voxelised with 4 × 4 × 4 mm3 resolution. Then, using Monte Carlo transport code, the organ doses caused by ≤500 MeV isotropic incident protons were calculated. The dose variations due to body size differences within a certain range were negligible, and the doses received in crouching and standing-up postures were similar. Therefore, a standard Chinese phantom could be established, and posture changes cannot effectively protect astronauts during solar particle events. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Dose-Response Calculator for ArcGIS

USGS Publications Warehouse

Hanser, Steven E.; Aldridge, Cameron L.; Leu, Matthias; Nielsen, Scott E.

2011-01-01

The Dose-Response Calculator for ArcGIS is a tool that extends the Environmental Systems Research Institute (ESRI) ArcGIS 10 Desktop application to aid with the visualization of relationships between two raster GIS datasets. A dose-response curve is a line graph commonly used in medical research to examine the effects of different dosage rates of a drug or chemical (for example, carcinogen) on an outcome of interest (for example, cell mutations) (Russell and others, 1982). Dose-response curves have recently been used in ecological studies to examine the influence of an explanatory dose variable (for example, percentage of habitat cover, distance to disturbance) on a predicted response (for example, survival, probability of occurrence, abundance) (Aldridge and others, 2008). These dose curves have been created by calculating the predicted response value from a statistical model at different levels of the explanatory dose variable while holding values of other explanatory variables constant. Curves (plots) developed using the Dose-Response Calculator overcome the need to hold variables constant by using values extracted from the predicted response surface of a spatially explicit statistical model fit in a GIS, which include the variation of all explanatory variables, to visualize the univariate response to the dose variable. Application of the Dose-Response Calculator can be extended beyond the assessment of statistical model predictions and may be used to visualize the relationship between any two raster GIS datasets (see example in tool instructions). This tool generates tabular data for use in further exploration of dose-response relationships and a graph of the dose-response curve.

Dose specification and quality assurance of RTOG protocol 95-17; a cooperative group study of 192Ir breast implants as sole therapy

PubMed Central

Ibbott, Geoffrey S.; Hanson, W.F.; Martin, Elizabeth; Kuske, Robert R.; Arthur, Douglas; Rabinovitch, Rachel; White, Julia; Wilenzick, Raymond M.; Harris, Irene; Tailor, Ramesh C.

2007-01-01

Purpose RTOG protocol 95-17 was a phase I/II trial to evaluate multi-catheter brachytherapy as the sole method of adjuvant breast radiotherapy for stage I/II breast carcinoma following breast conserving surgery. Low or high dose rate sources were allowed. Dose prescription and treatment evaluation were based on recommendations in ICRU Report 58, and included the parameters mean central dose (MCD), average peripheral dose, dose homogeneity index (DHI), and the dimensions of the low and high dose regions. Methods and Materials Three levels of quality assurance were implemented: (1) Credentialing of institutions was required prior to entering patients onto the study. (2) Rapid review of each treatment plan was conducted prior to treatment, and (3) Retrospective review was performed by the Radiological Physics Center in conjunction with the study chairman and RTOG dosimetry staff. Results Credentialing focused on the accuracy of dose calculation algorithm and compliance with protocol guidelines. Rapid review was designed to identify and correct deviations from the protocol prior to treatment. The retrospective review involved recalculation of dosimetry parameters and review of dose distributions to evaluate the treatment. Specifying both central and peripheral doses resulted in uniform dose distributions, with a mean dose homogeneity index of 0.83 ±0.06. Conclusions Vigorous quality assurance resulted in a high-quality study with few deviations; only 4 of 100 patients were judged as minor variations from protocol and no patient was judged a major deviation. This study should be considered a model for quality assurance of future trials. PMID:18035213

Dose-rate effects on the radiation-induced oxidation of electric cable used in nuclear power plants

NASA Astrophysics Data System (ADS)

Reynolds, A. B.; Bell, R. M.; Bryson, N. M. N.; Doyle, T. E.; Hall, M. B.; Mason, L. R.; Quintric, L.; Terwilliger, P. L.

1995-01-01

Dose-rate effects were measured for typical ethylene propylene rubber (EPR) and crosslinked polyethylene (XLPE) electric cable used in nuclear power plants. The radiation source was the 60Co Irradiation Facility at the University of Virginia. Dose rates were varied from 5 Gy/h to 2500 Gy/h. It was found that there is little or no dose-rate effect at low doses for four of the five EPR cable products tested from 2500 Gy/h down to dose rates of 5 Gy/h but perhaps a small dose-rate effect at high doses for dose rates above 340 Gy/h. A small dose-rate exists for the fifth EPR above 340 Gy/h at all doses. A dose-rate effect exists above 40 Gy/h for two of the three XLPE cable products tested, but there is no dose-rate for these XLPE's between 40 Gy/h and 5 Gy/h. These results indicate that the dose-rate effects observed are due to oxygen diffusion effects during heterogeneous aging and suggest that there is no dose-rate effect for either EPR or XLPE during homogeneous aging.

Omentin-1 levels are reduced by pharmacologic doses of leptin, but remain unaffected by energy deprivation and display no day-night variation.

PubMed

Hamnvik, Ole-Petter Riksfjord; Thakkar, Bindiya; Chamberland, John; Aronis, Konstantinos; Schneider, Benjamin; Mantzoros, Christos S

2015-02-01

To study the day-night variation of omentin-1 levels and assess whether leptin and/or short- and long-term energy deprivation alter circulating omentin-1 levels via cytokines. Omentin-1 levels were measured hourly in serum samples from six healthy men to evaluate for day-night variation. To study effects of acute energy deprivation and of leptin administration, eight healthy subjects were studied in the fasting state for 72 h with administration of either placebo or metreleptin (recombinant human leptin) in physiologic replacement doses. We evaluated the effect of leptin in pharmacologic doses on serum omentin-1 and cytokine levels, as well as on omentin-1 levels in ex vivo omental adipose tissue, in 15 healthy volunteers. To study the effect of chronic energy deprivation and weight loss on omentin-1 levels, we followed 18 obese subjects for 12 months who underwent bariatric surgery. There is no day-night variation in omentin-1 levels. Short-term and chronic energy deprivation, as well as ex vivo leptin administration and physiologic replacement doses of leptin, do not alter omentin-1 levels; pharmacologic doses of metreleptin reduce omentin-1 levels, whereas levels of tumor necrosis factor-α receptor II and interleukin-6 tend to increase. Omentin-1 levels are reduced by pharmacologic doses of metreleptin independent of effects on cytokine levels.

Typical doses and dose rates in studies pertinent to radiation risk inference at low doses and low dose rates

PubMed Central

Rühm, Werner; Azizova, Tamara; Bouffler, Simon; Cullings, Harry M; Grosche, Bernd; Little, Mark P; Shore, Roy S; Walsh, Linda; Woloschak, Gayle E

2018-01-01

Abstract In order to quantify radiation risks at exposure scenarios relevant for radiation protection, often extrapolation of data obtained at high doses and high dose rates down to low doses and low dose rates is needed. Task Group TG91 on ‘Radiation Risk Inference at Low-dose and Low-dose Rate Exposure for Radiological Protection Purposes’ of the International Commission on Radiological Protection is currently reviewing the relevant cellular, animal and human studies that could be used for that purpose. This paper provides an overview of dose rates and doses typically used or present in those studies, and compares them with doses and dose rates typical of those received by the A-bomb survivors in Japan. PMID:29432579

Radiation Dose Estimation for Pediatric Patients Undergoing Cardiac Catheterization

NASA Astrophysics Data System (ADS)

Wang, Chu

Patients undergoing cardiac catheterization are potentially at risk of radiation-induced health effects from the interventional fluoroscopic X-ray imaging used throughout the clinical procedure. The amount of radiation exposure is highly dependent on the complexity of the procedure and the level of optimization in imaging parameters applied by the clinician. For cardiac catheterization, patient radiation dosimetry, for key organs as well as whole-body effective, is challenging due to the lack of fixed imaging protocols, unlike other common X-ray based imaging modalities. Pediatric patients are at a greater risk compared to adults due to their greater cellular radio-sensitivities as well as longer remaining life-expectancy following the radiation exposure. In terms of radiation dosimetry, they are often more challenging due to greater variation in body size, which often triggers a wider range of imaging parameters in modern imaging systems with automatic dose rate modulation. The overall objective of this dissertation was to develop a comprehensive method of radiation dose estimation for pediatric patients undergoing cardiac catheterization. In this dissertation, the research is divided into two main parts: the Physics Component and the Clinical Component. A proof-of-principle study focused on two patient age groups (Newborn and Five-year-old), one popular biplane imaging system, and the clinical practice of two pediatric cardiologists at one large academic medical center. The Physics Component includes experiments relevant to the physical measurement of patient organ dose using high-sensitivity MOSFET dosimeters placed in anthropomorphic pediatric phantoms. First, the three-dimensional angular dependence of MOSFET detectors in scatter medium under fluoroscopic irradiation was characterized. A custom-made spherical scatter phantom was used to measure response variations in three-dimensional angular orientations. The results were to be used as angular dependence correction factors for the MOSFET organ dose measurements in the following studies. Minor angular dependence (< +/-20% at all angles tested, < +/-10% at clinically relevant angles in cardiac catheterization) was observed. Second, the cardiac dose for common fluoroscopic imaging techniques for pediatric patients in the two age groups was measured. Imaging technique settings with variations of individual key imaging parameters were tested to observe the quantitative effect of imaging optimization or lack thereof. Along with each measurement, the two standard system output indices, the Air Kerma (AK) and Dose-Area Product (DAP), were also recorded and compared to the measured cardiac and skin doses -- the lack of correlation between the indices and the organ doses shed light to the substantial limitation of the indices in representing patient radiation dose, at least within the scope of this dissertation. Third, the effective dose (ED) for Posterior-Anterior and Lateral fluoroscopic imaging techniques for pediatric patients in the two age groups was determined. In addition, the dosimetric effect of removing the anti-scatter grid was studied, for which a factor-of-two ED rate reduction was observed for the imaging techniques. The Clinical Component involved analytical research to develop a validated retrospective cardiac dose reconstruction formulation and to propose the new Optimization Index which evaluates the level of optimization of the clinician's imaging usage during a procedure; and small sample group of actual procedures were used to demonstrate applicability of these formulations. In its entirety, the research represents a first-of-its-kind comprehensive approach in radiation dosimetry for pediatric cardiac catheterization; and separately, it is also modular enough that each individual section can serve as study templates for small-scale dosimetric studies of similar purposes. The data collected and algorithmic formulations developed can be of use in areas of personalized patient dosimetry, clinician training, image quality studies and radiation-associated health effect research.

Inhaled corticosteroid metered-dose inhalers: how do variations in technique for solutions versus suspensions affect drug distribution?

PubMed

Robinson, Christie A; Tsourounis, Candy

2013-03-01

To assess the literature that evaluates how variations in metered-dose inhaler (MDI) technique affect lung distribution for inhaled corticosteroids (ICSs) formulated as MDI suspensions and solutions. PubMed (up to November 2012) and Cochrane Library (up to November 2012) were searched using the terms metered-dose inhalers, HFA 134a, Asthma/*drug therapy, and inhaled corticosteroids. In addition, reference citations from publications identified were reviewed. All articles in English from the data sources that assessed MDI technique comparing total lung distribution (TLD) of MDI solutions or suspensions formulated with ICSs were included in the review. Five relevant studies were identified. Five controlled studies compared how variations in MDI technique affect TLD for ICS MDI solutions with suspensions. MDI solutions resulted in greater TLD compared with larger particle MDI suspensions. Delayed or early inspiration upon device actuation of MDI solutions resulted in less TLD than coordinated actuation, but with a 3- to 4-times greater TLD than MDI suspensions inhaled using a standard technique. A sixth study evaluated inspiratory flow rates (IFR) for small, medium, and large particles. Rapid and slow IFRs resulted in similar TLD for small particles, while far fewer particles reached the airways with medium and large particles at rapid, rather than slow, IFRs. Based on the literature evaluated, standard MDI technique should be used for ICS suspensions. ICS MDI solutions can provide a higher average TLD than larger-particle ICS suspensions using standard technique, discoordinated inspiration and medication actuation timing, or rapid and slow IFRs. ICS MDI solutions allow for a more forgiving technique, which makes them uniquely suitable options for patients with asthma who have difficultly with MDI technique.

A Wireless Implantable Micropump for Chronic Drug Infusion Against Cancer

PubMed Central

Cobo, Angelica; Sheybani, Roya; Tu, Heidi; Meng, Ellis

2016-01-01

We present an implantable micropump with a miniature form factor and completely wireless operation that enables chronic drug administration intended for evaluation and development of cancer therapies in freely moving small research animals such as rodents. The low power electrolysis actuator avoids the need for heavy implantable batteries. The infusion system features a class E inductive powering system that provides on-demand activation of the pump as well as remote adjustment of the delivery regimen without animal handling. Micropump performance was demonstrated using a model anti-cancer application in which daily doses of 30 μL were supplied for several weeks with less than 6% variation in flow rate within a single pump and less than 8% variation across different pumps. Pumping under different back pressure, viscosity, and temperature conditions were investigated; parameters were chosen so as to mimic in vivo conditions. In benchtop tests under simulated in vivo conditions, micropumps provided consistent and reliable performance over a period of 30 days with less than 4% flow rate variation. The demonstrated prototype has potential to provide a practical solution for remote chronic administration of drugs to ambulatory small animals for research as well as drug discovery and development applications. PMID:26855476

Dose rate mapping of VMAT treatments

NASA Astrophysics Data System (ADS)

Podesta, Mark; Antoniu Popescu, I.; Verhaegen, Frank

2016-06-01

Human tissues exhibit a varying response to radiation dose depending on the dose rate and fractionation scheme used. Dose rate effects have been reported for different radiations, and tissue types. The literature indicates that there is not a significant difference in response for low-LET radiation when using dose rates between 1 Gy min-1 and 12 Gy min-1 but lower dose rates have an observable sparing effect on tissues and a differential effect between tissues. In intensity-modulated radiotherapy such as volumetric modulated arc therapy (VMAT) the dose can be delivered with a wide range of dose rates. In this work we developed a method based on time-resolved Monte Carlo simulations to quantify the dose rate frequency distribution for clinical VMAT treatments for three cancer sites, head and neck, lung, and pelvis within both planning target volumes (PTV) and normal tissues. The results show a wide range of dose rates are used to deliver dose in VMAT and up to 75% of the PTV can have its dose delivered with dose rates  <1 Gy min-1. Pelvic plans on average have a lower mean dose rate within the PTV than lung or head and neck plans but a comparable mean dose rate within the organs at risk. Two VMAT plans that fulfil the same dose objectives and constraints may be delivered with different dose rate distributions, particularly when comparing single arcs to multiple arc plans. It is concluded that for dynamic plans, the dose rate range used varies to a larger degree than previously assumed. The effect of the dose rate range in VMAT on clinical outcome is unknown.

"Extended" antipsychotic dosing in the maintenance treatment of schizophrenia: a double-blind, placebo-controlled trial.

PubMed

Remington, Gary; Seeman, Philip; Feingold, Alan; Mann, Steve; Shammi, Chekkera; Kapur, Shitij

2011-08-01

In the treatment of schizophrenia, all currently available oral antipsychotics are administered at least once daily, with strict adherence strongly encouraged to minimize risk of relapse. Based on a better understanding of the brain kinetics of antipsychotics, we have proposed a variation of this approach, "extended" dosing, which allows for intermittent but regular dosing. We carried out a randomized, double-blind, placebo-controlled trial evaluating 35 individuals with DSM-IV-defined schizophrenia who had been stabilized on antipsychotic therapy. Over a 6-month interval, 18 subjects received their medication as usual (daily), while 17 received their antipsychotic therapy every second day (extended). Outcome measures included clinical scales to assess symptoms (Brief Psychiatric Rating Scale [the primary outcome measure], Calgary Depression Scale), illness severity (Clinical Global Impressions-Severity of Illness scale), and relapse (ie, rehospitalization) rates. Side effects were also assessed, including movement disorders (Barnes Akathisia Scale, Simpson-Angus Scale, Abnormal Involuntary Movement Scale) and weight. The study was conducted from February 2003 to July 2007. Individuals in the extended dosing group were not at greater risk of symptom exacerbation, relapse, or rehospitalization; indeed, more rehospitalizations occurred in those receiving regular dosing. At the same time, though, there was no indication that side effects were significantly reduced in the extended dosing group. These results challenge the long-standing dogma that oral antipsychotics must be administered daily in stabilized patients with schizophrenia. Further studies with larger samples are needed to replicate these findings, as well as to elucidate whether postulated clinical advantages can be established and determined to outweigh potential risks. clinicaltrials.gov Identifier: NCT00431574. © Copyright 2011 Physicians Postgraduate Press, Inc.

Error detection capability of a novel transmission detector: a validation study for online VMAT monitoring.

PubMed

Pasler, Marlies; Michel, Kilian; Marrazzo, Livia; Obenland, Michael; Pallotta, Stefania; Björnsgard, Mari; Lutterbach, Johannes

2017-09-01

The purpose of this study was to characterize a new single large-area ionization chamber, the integral quality monitor system (iRT, Germany), for online and real-time beam monitoring. Signal stability, monitor unit (MU) linearity and dose rate dependence were investigated for static and arc deliveries and compared to independent ionization chamber measurements. The dose verification capability of the transmission detector system was evaluated by comparing calculated and measured detector signals for 15 volumetric modulated arc therapy plans. The error detection sensitivity was tested by introducing MLC position and linac output errors. Deviations in dose distributions between the original and error-induced plans were compared in terms of detector signal deviation, dose-volume histogram (DVH) metrics and 2D γ-evaluation (2%/2 mm and 3%/3 mm). The detector signal is linearly dependent on linac output and shows negligible (<0.4%) dose rate dependence up to 460 MU min -1 . Signal stability is within 1% for cumulative detector output; substantial variations were observed for the segment-by-segment signal. Calculated versus measured cumulative signal deviations ranged from  -0.16%-2.25%. DVH, mean 2D γ-value and detector signal evaluations showed increasing deviations with regard to the respective reference with growing MLC and dose output errors; good correlation between DVH metrics and detector signal deviation was found (e.g. PTV D mean : R 2   =  0.97). Positional MLC errors of 1 mm and errors in linac output of 2% were identified with the transmission detector system. The extensive tests performed in this investigation show that the new transmission detector provides a stable and sensitive cumulative signal output and is suitable for beam monitoring during patient treatment.

Improving the Accuracy of a Heliocentric Potential (HCP) Prediction Model for the Aviation Radiation Dose

NASA Astrophysics Data System (ADS)

Hwang, Junga; Yoon, Kyoung-Won; Jo, Gyeongbok; Noh, Sung-Jun

2016-12-01

The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs), flares, and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP) prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA). However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015). In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1) real-time daily sunspot assessments, (2) predictions of the daily HCP by our prediction algorithm, and (3) calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.

Phase II Dose Escalation Study of Caspofungin for Invasive Aspergillosis ▿ §

PubMed Central

Cornely, O. A.; Vehreschild, J. J.; Vehreschild, M. J. G. T.; Würthwein, G.; Arenz, D.; Schwartz, S.; Heussel, C. P.; Silling, G.; Mahne, M.; Franklin, J.; Harnischmacher, U.; Wilkens, A.; Farowski, F.; Karthaus, M.; Lehrnbecher, T.; Ullmann, A. J.; Hallek, M.; Groll, A. H.

2011-01-01

Our objective was to evaluate the maximum tolerated dose of caspofungin for invasive aspergillosis (IA). The safety and pharmacokinetics of escalating dosages of caspofungin were investigated in IA. Eight patients each received caspofungin 70, 100, 150, or 200 mg once a day (QD). Dose-limiting toxicity (DLT) was defined as the same non-hematological treatment-related adverse event of grade ≥4 in 2 of 8 patients or ≥3 in 4 of 8 patients in a cohort. A total of 46 patients (median age, 61 years; 21 female; 89% with hematological malignancies) received caspofungin (9, 8, 9, and 20 patients in the 70-, 100-, 150-, and 200-mg cohorts) for a median of 24.5 days. Plasma pharmacokinetics were linear across the investigated dosages and followed a two-compartment model, with weight as the covariate on clearance and sex as the covariate on central volume of distribution. Simulated peak plasma concentrations at steady state ranged from 14.2 to 40.6 mg/liter (28%), trough concentrations from 4.1 to 11.8 mg/liter (58%), and area under the concentration-time curve from 175 to 500 mg/liter/h (32%) (geometric mean, geometric coefficient of variation). Treatment was well tolerated without dose-limiting toxicity. The rate of complete or partial responses was 54.3%, and the overall mortality at 12-week follow-up was 28.3%. In first-line treatment of invasive aspergillosis, daily doses of up to 200 mg caspofungin were well tolerated and the maximum tolerated dose was not reached. Pharmacokinetics was linear. Response rates were similar to those previously reported for voriconazole and liposomal amphotericin. PMID:21911573

Error detection capability of a novel transmission detector: a validation study for online VMAT monitoring

NASA Astrophysics Data System (ADS)

Pasler, Marlies; Michel, Kilian; Marrazzo, Livia; Obenland, Michael; Pallotta, Stefania; Björnsgard, Mari; Lutterbach, Johannes

2017-09-01

The purpose of this study was to characterize a new single large-area ionization chamber, the integral quality monitor system (iRT, Germany), for online and real-time beam monitoring. Signal stability, monitor unit (MU) linearity and dose rate dependence were investigated for static and arc deliveries and compared to independent ionization chamber measurements. The dose verification capability of the transmission detector system was evaluated by comparing calculated and measured detector signals for 15 volumetric modulated arc therapy plans. The error detection sensitivity was tested by introducing MLC position and linac output errors. Deviations in dose distributions between the original and error-induced plans were compared in terms of detector signal deviation, dose-volume histogram (DVH) metrics and 2D γ-evaluation (2%/2 mm and 3%/3 mm). The detector signal is linearly dependent on linac output and shows negligible (<0.4%) dose rate dependence up to 460 MU min-1. Signal stability is within 1% for cumulative detector output; substantial variations were observed for the segment-by-segment signal. Calculated versus measured cumulative signal deviations ranged from  -0.16%-2.25%. DVH, mean 2D γ-value and detector signal evaluations showed increasing deviations with regard to the respective reference with growing MLC and dose output errors; good correlation between DVH metrics and detector signal deviation was found (e.g. PTV D mean: R 2  =  0.97). Positional MLC errors of 1 mm and errors in linac output of 2% were identified with the transmission detector system. The extensive tests performed in this investigation show that the new transmission detector provides a stable and sensitive cumulative signal output and is suitable for beam monitoring during patient treatment.

Shared Dosimetry Error in Epidemiological Dose-Response Analyses

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

Stram, Daniel O.; Preston, Dale L.; Sokolnikov, Mikhail

2015-03-23

Radiation dose reconstruction systems for large-scale epidemiological studies are sophisticated both in providing estimates of dose and in representing dosimetry uncertainty. For example, a computer program was used by the Hanford Thyroid Disease Study to provide 100 realizations of possible dose to study participants. The variation in realizations reflected the range of possible dose for each cohort member consistent with the data on dose determinates in the cohort. Another example is the Mayak Worker Dosimetry System 2013 which estimates both external and internal exposures and provides multiple realizations of "possible" dose history to workers given dose determinants. This paper takesmore » up the problem of dealing with complex dosimetry systems that provide multiple realizations of dose in an epidemiologic analysis. In this paper we derive expected scores and the information matrix for a model used widely in radiation epidemiology, namely the linear excess relative risk (ERR) model that allows for a linear dose response (risk in relation to radiation) and distinguishes between modifiers of background rates and of the excess risk due to exposure. We show that treating the mean dose for each individual (calculated by averaging over the realizations) as if it was true dose (ignoring both shared and unshared dosimetry errors) gives asymptotically unbiased estimates (i.e. the score has expectation zero) and valid tests of the null hypothesis that the ERR slope β is zero. Although the score is unbiased the information matrix (and hence the standard errors of the estimate of β) is biased for β≠0 when ignoring errors in dose estimates, and we show how to adjust the information matrix to remove this bias, using the multiple realizations of dose. Use of these methods for several studies, including the Mayak Worker Cohort and the U.S. Atomic Veterans Study, is discussed.« less

Low-dose ionizing radiation limitations to seed germination: Results from a model linking physiological characteristics and developmental-dynamics simulation strategy.

PubMed

Liu, Hui; Hu, Dawei; Dong, Chen; Fu, Yuming; Liu, Guanghui; Qin, Youcai; Sun, Yi; Liu, Dianlei; Li, Lei; Liu, Hong

2017-08-01

There is much uncertainty about the risks of seed germination after repeated or protracted environmental low-dose ionizing radiation exposure. The purpose of this study is to explore the influence mechanism of low-dose ionizing radiation on wheat seed germination using a model linking physiological characteristics and developmental-dynamics simulation. A low-dose ionizing radiation environment simulator was built to investigate wheat (Triticum aestivum L.) seeds germination process and then a kinetic model expressing the relationship between wheat seed germination dynamics and low-dose ionizing radiation intensity variations was developed by experimental data, plant physiology, relevant hypotheses and system dynamics, and sufficiently validated and accredited by computer simulation. Germination percentages were showing no differences in response to different dose rates. However, root and shoot lengths were reduced significantly. Plasma governing equations were set up and the finite element analysis demonstrated H 2 O, CO 2 , O 2 as well as the seed physiological responses to the low-dose ionizing radiation. The kinetic model was highly valid, and simultaneously the related influence mechanism of low-dose ionizing radiation on wheat seed germination proposed in the modeling process was also adequately verified. Collectively these data demonstrate that low-dose ionizing radiation has an important effect on absorbing water, consuming O 2 and releasing CO 2 , which means the risk for embryo and endosperm development was higher. Copyright © 2017 Elsevier Ltd. All rights reserved.

Probability Distribution of Dose and Dose-Rate Effectiveness Factor for use in Estimating Risks of Solid Cancers From Exposure to Low-Let Radiation.

PubMed

Kocher, David C; Apostoaei, A Iulian; Hoffman, F Owen; Trabalka, John R

2018-06-01

This paper presents an analysis to develop a subjective state-of-knowledge probability distribution of a dose and dose-rate effectiveness factor for use in estimating risks of solid cancers from exposure to low linear energy transfer radiation (photons or electrons) whenever linear dose responses from acute and chronic exposure are assumed. A dose and dose-rate effectiveness factor represents an assumption that the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation, RL, differs from the risk per Gy at higher acute doses, RH; RL is estimated as RH divided by a dose and dose-rate effectiveness factor, where RH is estimated from analyses of dose responses in Japanese atomic-bomb survivors. A probability distribution to represent uncertainty in a dose and dose-rate effectiveness factor for solid cancers was developed from analyses of epidemiologic data on risks of incidence or mortality from all solid cancers as a group or all cancers excluding leukemias, including (1) analyses of possible nonlinearities in dose responses in atomic-bomb survivors, which give estimates of a low-dose effectiveness factor, and (2) comparisons of risks in radiation workers or members of the public from chronic exposure to low linear energy transfer radiation at low dose rates with risks in atomic-bomb survivors, which give estimates of a dose-rate effectiveness factor. Probability distributions of uncertain low-dose effectiveness factors and dose-rate effectiveness factors for solid cancer incidence and mortality were combined using assumptions about the relative weight that should be assigned to each estimate to represent its relevance to estimation of a dose and dose-rate effectiveness factor. The probability distribution of a dose and dose-rate effectiveness factor for solid cancers developed in this study has a median (50th percentile) and 90% subjective confidence interval of 1.3 (0.47, 3.6). The harmonic mean is 1.1, which implies that the arithmetic mean of an uncertain estimate of the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation is only about 10% less than the mean risk per Gy at higher acute doses. Data were also evaluated to define a low acute dose or low dose rate of low linear energy transfer radiation, i.e., a dose or dose rate below which a dose and dose-rate effectiveness factor should be applied in estimating risks of solid cancers.

Variations in energy spectra and water-to-material stopping-power ratios in three-dimensional conformal and intensity-modulated photon fields

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

Jang, Si Young; Liu, H. Helen; Mohan, Radhe

Because of complex dose distributions and dose gradients that are created in three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiation therapy (IMRT), photon- and electron-energy spectra might change significantly with spatial locations and doses. This study examined variations in photon- and electron-energy spectra in 3D-CRT and IMRT photon fields. The effects of spectral variations on water-to-material stopping-power ratios used in Monte Carlo treatment planning systems and the responses of energy-dependent dosimeters, such as thermoluminescent dosimeters (TLDs) and radiographic films were further studied. The EGSnrc Monte Carlo code was used to simulate megavoltage 3D-CRT and IMRT photon fields. The photon- and electron-energymore » spectra were calculated in 3D water phantoms and anthropomorphic phantoms based on the fluence scored in voxel grids. We then obtained the water-to-material stopping-power ratios in the local voxels using the Spencer-Attix cavity theory. Changes in the responses of films and TLDs were estimated based on the calculated local energy spectra and published data on the dosimeter energy dependency. Results showed that the photon-energy spectra strongly depended on spatial positions and doses in both the 3D-CRT and IMRT fields. The relative fraction of low-energy photons (<100 keV) increased inversely with the photon dose in low-dose regions of the fields. A similar but smaller effect was observed for electrons in the phantoms. The maximum variation of the water-to-material stopping-power ratio over the range of calculated dose for both 3D-CRT and IMRT was negligible (<1.0%) for ICRU tissue, cortical bone, and soft bone and less than 3.6% for dry air and lung. Because of spectral softening at low doses, radiographic films in the phantoms could over-respond to dose by more than 30%, whereas the over-response of TLDs was less than 10%. Thus, spatial variations of the photon- and electron-energy spectra should be considered as important factors in 3D-CRT and IMRT dosimetry.« less

Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model

NASA Astrophysics Data System (ADS)

Katata, G.; Chino, M.; Kobayashi, T.; Terada, H.; Ota, M.; Nagai, H.; Kajino, M.; Draxler, R.; Hort, M. C.; Malo, A.; Torii, T.; Sanada, Y.

2015-01-01

Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate the detailed atmospheric releases during the accident using a reverse estimation method which calculates the release rates of radionuclides by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric and oceanic transport, dispersion and deposition models. The atmospheric and oceanic models used are WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN-FDM (Finite difference oceanic dispersion model), both developed by the authors. A sophisticated deposition scheme, which deals with dry and fog-water depositions, cloud condensation nuclei (CCN) activation, and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The results revealed that the major releases of radionuclides due to the FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, midnight of 14 March when the SRV (safety relief valve) was opened three times at Unit 2, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of release rates. The simulation by WSPEEDI-II using the new source term reproduced the local and regional patterns of cumulative surface deposition of total 131I and 137Cs and air dose rate obtained by airborne surveys. The new source term was also tested using three atmospheric dispersion models (Modèle Lagrangien de Dispersion de Particules d'ordre zéro: MLDP0, Hybrid Single Particle Lagrangian Integrated Trajectory Model: HYSPLIT, and Met Office's Numerical Atmospheric-dispersion Modelling Environment: NAME) for regional and global calculations, and the calculated results showed good agreement with observed air concentration and surface deposition of 137Cs in eastern Japan.

The impact of the oxygen scavenger on the dose-rate dependence and dose sensitivity of MAGIC type polymer gels

NASA Astrophysics Data System (ADS)

Khan, Muzafar; Heilemann, Gerd; Kuess, Peter; Georg, Dietmar; Berg, Andreas

2018-03-01

Recent developments in radiation therapy aimed at more precise dose delivery along with higher dose gradients (dose painting) and more efficient dose delivery with higher dose rates e.g. flattening filter free (FFF) irradiation. Magnetic-resonance-imaging based polymer gel dosimetry offers 3D information for precise dose delivery techniques. Many of the proposed polymer gels have been reported to exhibit a dose response, measured as relaxation rate ΔR2(D), which is dose rate dependent. A lack of or a reduced dose-rate sensitivity is very important for dosimetric accuracy, especially with regard to the increasing clinical use of FFF irradiation protocols with LINACs at high dose rates. Some commonly used polymer gels are based on Methacrylic-Acid-Gel-Initiated-by-Copper (MAGIC). Here, we report on the dose sensitivity (ΔR2/ΔD) of MAGIC-type gels with different oxygen scavenger concentration for their specific dependence on the applied dose rate in order to improve the dosimetric performance, especially for high dose rates. A preclinical x-ray machine (‘Yxlon’, E  =  200 kV) was used for irradiation to cover a range of dose rates from low \\dot{D} min  =  0.6 Gy min-1 to high \\dot{D} max  =  18 Gy min-1. The dose response was evaluated using R2-imaging of the gel on a human high-field (7T) MR-scanner. The results indicate that all of the investigated dose rates had an impact on the dose response in polymer gel dosimeters, being strongest in the high dose region and less effective for low dose levels. The absolute dose rate dependence \\frac{(Δ R2/Δ D)}{Δ \\dot{D}} of the dose response in MAGIC-type gel is significantly reduced using higher concentrations of oxygen scavenger at the expense of reduced dose sensitivity. For quantitative dose evaluations the relative dose rate dependence of a polymer gel, normalized to its sensitivity is important. Based on this normalized sensitivity the dose rate sensitivity was reduced distinctly using an increased oxygen scavenger concentration with reference to standard MAGIC-type gel formulation at high dose rate levels. The proposed gel composition with high oxygen scavenger concentration exhibits a larger linear active dose response and might be used especially in FFF-radiation applications and preclinical dosimetry at high dose rates. We propose in general to use high dose rates for calibration and evaluation as the change in relative dose sensitivity is reduced at higher dose rates in all of the investigated gel types.

Estimation of organ and effective doses from newborn radiography of the chest and abdomen.

PubMed

Ma, Hillgan; Elbakri, Idris A; Reed, Martin

2013-09-01

Neonatal intensive care patients undergo frequent chest and abdomen radiographic imaging. In this study, the organ doses and the effective dose resulting from combined chest-abdomen radiography of the newborn child are determined. These values are calculated using the Monte Carlo simulation software PCXCM 2.0 and compared with direct dose measurements obtained from thermoluminescent detectors (TLDs) in a physical phantom. The effective dose obtained from PCXMC is 21.2 ± 0.7 μSv and that obtained from TLD measurements is 22.0 ± 0.5 μSv. While the two methods are in close agreement with regard to the effective dose, there is a wide range of variation in organ doses, ranging from 85 % difference for the testes to 1.4 % for the lungs. Large organ dose variations are attributed to organs at the edge of the field of view, or organs with large experimental error or simulation uncertainty. This study suggests that PCXMC can be used to estimate organ and effective doses for newborn patients.

Routine immunization in Pakistan: comparison of multiple data sources and identification of factors associated with vaccination.

PubMed

Imran, Hafsa; Raja, Dania; Grassly, Nicholas C; Wadood, M Zubair; Safdar, Rana M; O'Reilly, Kathleen M

2018-03-01

Within Pakistan, estimates of vaccination coverage with the pentavalent vaccine, oral polio vaccine (OPV) and measles vaccine (MV) in 2011 were reported to be 74%, 75% and 53%, respectively. These national estimates may mask regional variation. The reasons for this variation have not been explored. Data from the Multiple Indicator Cluster Surveys (MICS) for Balochistan and Punjab (2010-2011) are analysed to examine factors associated with receiving three or more doses of the pentavalent vaccine and one or more MVs using regression modelling. Pentavalent and OPV estimates from the MICS were compared to vaccine dose histories from surveillance for acute flaccid paralysis (AFP; poliomyelitis) to ascertain agreement. Adjusted coverage of children 12-23 months of age were estimated to be 16.0%, 75.5% and 34.2% in Balochistan and 58.0%, 87.7% and 72.6% in Punjab for the pentavalent vaccine, OPV and MV, respectively. Maternal education, healthcare utilization and wealth were associated with receiving the pentavalent vaccine and the MV. There was a strong correlation of district estimates of vaccination coverage between AFP and MICS data, but AFP estimates of pentavalent coverage in Punjab were biased toward higher values. National estimates mask variation and estimates from individual surveys should be considered alongside other estimates. The development of strategies targeted towards poorly educated parents within low-wealth quintiles that may not typically access healthcare could improve vaccination rates.

Predicting ecological effects of pollutants: A role for marine mesocosms

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

Ward, T.J.

1994-12-31

The major uncertainty in predicting the ecological effects of a pollutant is the relationship between dose and the ecological response. Mesocosms may be used to simulate population-level biological processes and to estimate the nature and shape of dose-related responses to pollutants, for use in predictive evaluations of pollutant impacts. To ensure that responses observed in mesocosm tests are representative it is necessary to confirm that the simulated processes operate at rates similar to those found in the field. Pilot experiments were conducted in small marine mesocosms simulating major processes in two local habitat types: unvegetated sand and sand colonized bymore » the brown macroalga Sargassum. The results showed that for a range of variates (such as the % of egg-bearing harpacticoid copepods, or the chlorophyll a concentration in surface sediments) the mean values for measurements in the tanks over a 9 week period did not consistently converge or diverge from those in the field. Also, for a number of the variates, a modelled decrease of more than about 60% in the mean could be detected with greater than 80% statistical power. This indicates that the effects of a pollutant could be detected with acceptable power. Use of a combination of such variates based on different functional or taxonomic groups for pollutant effects testing could greatly decrease uncertainty about the predicted effects of pollutants discharged to these habitats.« less

Diode‐based transmission detector for IMRT delivery monitoring: a validation study

PubMed Central

Li, Taoran; Wu, Q. Jackie; Matzen, Thomas; Yin, Fang‐Fang

2016-01-01

The purpose of this work was to evaluate the potential of a new transmission detector for real‐time quality assurance of dynamic‐MLC‐based radiotherapy. The accuracy of detecting dose variation and static/dynamic MLC position deviations was measured, as well as the impact of the device on the radiation field (surface dose, transmission). Measured dose variations agreed with the known variations within 0.3%. The measurement of static and dynamic MLC position deviations matched the known deviations with high accuracy (0.7–1.2 mm). The absorption of the device was minimal (∼ 1%). The increased surface dose was small (1%–9%) but, when added to existing collimator scatter effects could become significant at large field sizes (≥30×30 cm2). Overall the accuracy and speed of the device show good potential for real‐time quality assurance. PACS number(s): 87.55.Qr PMID:27685115

The association of single-nucleotide polymorphisms in the oxytocin receptor and G protein-coupled receptor kinase 6 (GRK6) genes with oxytocin dosing requirements and labor outcomes.

PubMed

Grotegut, Chad A; Ngan, Emily; Garrett, Melanie E; Miranda, Marie Lynn; Ashley-Koch, Allison E; Swamy, Geeta K

2017-09-01

Oxytocin is a potent uterotonic agent that is widely used for induction and augmentation of labor. Oxytocin has a narrow therapeutic index and the optimal dosing for any individual woman varies widely. The objective of this study was to determine whether genetic variation in the oxytocin receptor (OXTR) or in the gene encoding G protein-coupled receptor kinase 6 (GRK6), which regulates desensitization of the oxytocin receptor, could explain variation in oxytocin dosing and labor outcomes among women being induced near term. Pregnant women with a singleton gestation residing in Durham County, NC, were prospectively enrolled as part of the Healthy Pregnancy, Healthy Baby cohort study. Those women undergoing an induction of labor at 36 weeks or greater were genotyped for 18 haplotype-tagging single-nucleotide polymorphisms in OXTR and 7 haplotype-tagging single-nucleotide polymorphisms in GRK6 using TaqMan assays. Linear regression was used to examine the relationship between maternal genotype and maximal oxytocin infusion rate, total oxytocin dose received, and duration of labor. Logistic regression was used to test for the association of maternal genotype with mode of delivery. For each outcome, backward selection techniques were utilized to control for important confounding variables and additive genetic models were used. Race/ethnicity was included in all models because of differences in allele frequencies across populations, and Bonferroni correction for multiple testing was used. DNA was available from 482 women undergoing induction of labor at 36 weeks or greater. Eighteen haplotype-tagging single-nucleotide polymorphisms within OXTR and 7 haplotype-tagging single-nucleotide polymorphisms within GRK6 were examined. Five single-nucleotide polymorphisms in OXTR showed nominal significance with maximal infusion rate of oxytocin, and two single-nucleotide polymorphisms in OXTR were associated with total oxytocin dose received. One single-nucleotide polymorphism in OXTR and two single-nucleotide polymorphisms in GRK6 were associated with duration of labor, one of which met the multiple testing threshold (P = .0014, rs2731664 [GRK6], mean duration of labor, 17.7 hours vs 20.2 hours vs 23.5 hours for AA, AC, and CC genotypes, respectively). Three single-nucleotide polymorphisms, two in OXTR and one in GRK6, showed nominal significance with mode of delivery. Genetic variation in OXTR and GRK6 is associated with the amount of oxytocin required as well as the duration of labor and risk for cesarean delivery among women undergoing induction of labor near term. With further research, pharmacogenomic approaches may potentially be utilized to develop personalized treatment to improve safety and efficacy outcomes among women undergoing induction of labor. Copyright © 2017 Elsevier Inc. All rights reserved.

Opioid Utilization and Opioid-Related Adverse Events in Non-Surgical Patients in U.S. Hospitals

PubMed Central

Herzig, Shoshana J.; Rothberg, Michael B.; Cheung, Michael; Ngo, Long H.; Marcantonio, Edward R.

2014-01-01

Background Recent studies in the outpatient setting have demonstrated high rates of opioid prescribing and overdose-related deaths. Prescribing practices in hospitalized patients are unexamined. Objective To investigate patterns and predictors of opioid utilization in non-surgical admissions to U.S. hospitals, variation in use, and the association between hospital-level use and rates of severe opioid-related adverse events. Design, Setting, and Patients Adult non-surgical admissions to 286 U.S. hospitals. Measurements Opioid exposure and severe opioid-related adverse events during hospitalization, defined using hospital charges and ICD-9-CM codes. Results Of 1.14 million admissions, opioids were used in 51%. The mean ± s.d. daily dose received in oral morphine equivalents (OME) was 68 ± 185 mg; 23% of exposed received a total daily dose of ≥ 100 mg OME. Opioid prescribing rates ranged from 5% in the lowest to 72% in the highest prescribing hospital (mean 51% ± 10%). After adjusting for patient characteristics, the adjusted opioid prescribing rates ranged from 33–64% (mean 50% ± s.d. 4%). Among exposed, 0.97% experienced severe opioid-related adverse events. Hospitals with higher opioid prescribing rates had higher adjusted relative risk of a severe opioid-related adverse event per patient exposed (RR 1.23 [1.14–1.33] for highest compared to lowest prescribing quartile). Conclusions The majority of hospitalized non-surgical patients were exposed to opioids, often at high doses. Hospitals that used opioids most frequently had increased adjusted risk of a severe opioid-related adverse event per patient exposed. Interventions to standardize and enhance the safety of opioid prescribing in hospitalized patients should be investigated. PMID:24227700

Hepatitis C treatment among racial and ethnic groups in the IDEAL trial.

PubMed

Muir, A J; Hu, K-Q; Gordon, S C; Koury, K; Boparai, N; Noviello, S; Albrecht, J K; Sulkowski, M S; McCone, J

2011-04-01

Previous studies of chronic hepatitis C virus (HCV) treatment have demonstrated variations in response among racial and ethnic groups including poorer efficacy rates among African American and Hispanic patients. The individualized dosing efficacy vs flat dosing to assess optimaL pegylated interferon therapy (IDEAL) trial enrolled 3070 patients from 118 United States centres to compare treatment with peginterferon (PEG-IFN) alfa-2a and ribavirin (RBV) and two doses of PEG-IFN alfa-2b and RBV. This analysis examines treatment response among the major racial and ethnic groups in the trial. Overall, sustained virologic response (SVR) rates were 44% for white, 22% for African American, 38% for Hispanic and 59% for Asian American patients. For patients with undetectable HCV RNA at treatment week 4, the positive predictive value of SVR was 86% for white, 92% for African American, 83% for Hispanic and 89% for Asian American patients. The positive predictive values of SVR in those with undetectable HCV RNA at treatment week 12 ranged from 72% to 81%. Multivariate regression analysis using baseline characteristics demonstrated that treatment regimen was not a predictor of SVR. Despite wide-ranging SVR rates among the different racial and ethnic groups, white and Hispanic patients had similar SVR rates. In all groups, treatment response was largely determined by antiviral activity in the first 12 weeks of treatment. Therefore, decisions regarding HCV treatment should consider the predictive value of the early on-treatment response, not just baseline characteristics, such as race and ethnicity. © 2010 Blackwell Publishing Ltd.

An investigation of the impact of variations of DVH calculation algorithms on DVH dependant radiation therapy plan evaluation metrics

NASA Astrophysics Data System (ADS)

Kennedy, A. M.; Lane, J.; Ebert, M. A.

2014-03-01

Plan review systems often allow dose volume histogram (DVH) recalculation as part of a quality assurance process for trials. A review of the algorithms provided by a number of systems indicated that they are often very similar. One notable point of variation between implementations is in the location and frequency of dose sampling. This study explored the impact such variations can have on DVH based plan evaluation metrics (Normal Tissue Complication Probability (NTCP), min, mean and max dose), for a plan with small structures placed over areas of high dose gradient. Dose grids considered were exported from the original planning system at a range of resolutions. We found that for the CT based resolutions used in all but one plan review systems (CT and CT with guaranteed minimum number of sampling voxels in the x and y direction) results were very similar and changed in a similar manner with changes in the dose grid resolution despite the extreme conditions. Differences became noticeable however when resolution was increased in the axial (z) direction. Evaluation metrics also varied differently with changing dose grid for CT based resolutions compared to dose grid based resolutions. This suggests that if DVHs are being compared between systems that use a different basis for selecting sampling resolution it may become important to confirm that a similar resolution was used during calculation.

Physiologic variability at the verge of systemic inflammation: multi-scale entropy of heart rate variability is affected by very low doses of endotoxin

PubMed Central

Herlitz, Georg N.; Sanders, Renee L.; Cheung, Nora H.; Coyle, Susette M.; Griffel, Benjamin; Macor, Marie A.; Lowry, Stephen F.; Calvano, Steve E.; Gale, Stephen C.

2014-01-01

Introduction Human injury or infection induces systemic inflammation with characteristic neuro-endocrine responses. Fluctuations in autonomic function during inflammation are reflected by beat-to-beat variation in heart rate, termed heart rate variability (HRV). In the present study, we determine threshold doses of endotoxin needed to induce observable changes in markers of systemic inflammation, we investigate whether metrics of HRV exhibit a differing threshold dose from other inflammatory markers, and we investigate the size of data sets required for meaningful use of multi-scale entropy (MSE) analysis of HRV. Methods Healthy human volunteers (n=25) were randomized to receive placebo (normal saline) or endotoxin/lipopolysaccharide (LPS): 0.1, 0.25, 0.5, 1.0, or 2.0 ng/kg administered intravenously. Vital signs were recorded every 30 minutes for 6 hours and then at 9, 12, and 24 hours after LPS. Blood samples were drawn at specific time points for cytokine measurements. HRV analysis was performed using EKG epochs of 5 minutes. MSE for HRV was calculated for all dose groups to scale factor 40. Results The lowest significant threshold dose was noted in core temperature at 0.25ng/kg. Endogenous TNF-α and IL-6 were significantly responsive at the next dosage level (0.5ng/kg) along with elevations in circulating leukocytes and heart rate. Responses were exaggerated at higher doses (1 and 2 ng/kg). Time domain and frequency domain HRV metrics similarly suggested a threshold dose, differing from placebo at 1.0 and 2.0 ng/kg, below which no clear pattern in response was evident. By applying repeated-measures ANOVA across scale factors, a significant decrease in MSE was seen at 1.0 and 2.0 ng/kg by 2 hours post exposure to LPS. While not statistically significant below 1.0 ng/kg, MSE unexpectedly decreased across all groups in an orderly dose-response pattern not seen in the other outcomes. Conclusions By usingrANOVA across scale factors, MSE can detect autonomic change after LPS challenge in a group of 25 subjects using EKG epochs of only 5 minutes and entropy analysis to scale factor of only 40, potentially facilitating MSE’s wider use as a research tool or bedside monitor. Traditional markers of inflammation generally exhibit threshold dose behavior. In contrast, MSE’s apparent continuous dose-response pattern, while not statistically verifiable in this study, suggests a potential subclinical harbinger of infectious or other insult. The possible derangement of autonomic complexity prior to or independent of the cytokine surge cannot be ruled out. Future investigation should focus on confirmation of overt inflammation following observed decreases in MSE in a clinical setting. PMID:25526373

Influence of source batch S{sub K} dispersion on dosimetry for prostate cancer treatment with permanent implants

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

Nuñez-Cumplido, E., E-mail: ejnc-mccg@hotmail.com; Hernandez-Armas, J.; Perez-Calatayud, J.

2015-08-15

Purpose: In clinical practice, specific air kerma strength (S{sub K}) value is used in treatment planning system (TPS) permanent brachytherapy implant calculations with {sup 125}I and {sup 103}Pd sources; in fact, commercial TPS provide only one S{sub K} input value for all implanted sources and the certified shipment average is typically used. However, the value for S{sub K} is dispersed: this dispersion is not only due to the manufacturing process and variation between different source batches but also due to the classification of sources into different classes according to their S{sub K} values. The purpose of this work is tomore » examine the impact of S{sub K} dispersion on typical implant parameters that are used to evaluate the dose volume histogram (DVH) for both planning target volume (PTV) and organs at risk (OARs). Methods: The authors have developed a new algorithm to compute dose distributions with different S{sub K} values for each source. Three different prostate volumes (20, 30, and 40 cm{sup 3}) were considered and two typical commercial sources of different radionuclides were used. Using a conventional TPS, clinically accepted calculations were made for {sup 125}I sources; for the palladium, typical implants were simulated. To assess the many different possible S{sub K} values for each source belonging to a class, the authors assigned an S{sub K} value to each source in a randomized process 1000 times for each source and volume. All the dose distributions generated for each set of simulations were assessed through the DVH distributions comparing with dose distributions obtained using a uniform S{sub K} value for all the implanted sources. The authors analyzed several dose coverage (V{sub 100} and D{sub 90}) and overdosage parameters for prostate and PTV and also the limiting and overdosage parameters for OARs, urethra and rectum. Results: The parameters analyzed followed a Gaussian distribution for the entire set of computed dosimetries. PTV and prostate V{sub 100} and D{sub 90} variations ranged between 0.2% and 1.78% for both sources. Variations for the overdosage parameters V{sub 150} and V{sub 200} compared to dose coverage parameters were observed and, in general, variations were larger for parameters related to {sup 125}I sources than {sup 103}Pd sources. For OAR dosimetry, variations with respect to the reference D{sub 0.1cm{sup 3}} were observed for rectum values, ranging from 2% to 3%, compared with urethra values, which ranged from 1% to 2%. Conclusions: Dose coverage for prostate and PTV was practically unaffected by S{sub K} dispersion, as was the maximum dose deposited in the urethra due to the implant technique geometry. However, the authors observed larger variations for the PTV V{sub 150}, rectum V{sub 100}, and rectum D{sub 0.1cm{sup 3}} values. The variations in rectum parameters were caused by the specific location of sources with S{sub K} value that differed from the average in the vicinity. Finally, on comparing the two sources, variations were larger for {sup 125}I than for {sup 103}Pd. This is because for {sup 103}Pd, a greater number of sources were used to obtain a valid dose distribution than for {sup 125}I, resulting in a lower variation for each S{sub K} value for each source (because the variations become averaged out statistically speaking)« less

Individualized versus standard FSH dosing in women starting IVF/ICSI: an RCT. Part 1: The predicted poor responder.

PubMed

van Tilborg, Theodora C; Torrance, Helen L; Oudshoorn, Simone C; Eijkemans, Marinus J C; Koks, Carolien A M; Verhoeve, Harold R; Nap, Annemiek W; Scheffer, Gabrielle J; Manger, A Petra; Schoot, Benedictus C; Sluijmer, Alexander V; Verhoeff, Arie; Groen, Henk; Laven, Joop S E; Mol, Ben Willem J; Broekmans, Frank J M

2017-12-01

Does an increased FSH dose result in higher cumulative live birth rates in women with a predicted poor ovarian response, apparent from a low antral follicle count (AFC), scheduled for IVF or ICSI? In women with a predicted poor ovarian response (AFC < 11) undergoing IVF/ICSI, an increased FSH dose (225/450 IU/day) does not improve cumulative live birth rates as compared to a standard dose (150 IU/day). In women scheduled for IVF/ICSI, an ovarian reserve test (ORT) can predict ovarian response to stimulation. The FSH starting dose is often adjusted based on the ORT from the belief that it will improve live birth rates. However, the existing RCTs on this topic, most of which show no benefit, are underpowered. Between May 2011 and May 2014, we performed an open-label multicentre RCT in women with an AFC < 11 (Dutch Trial Register NTR2657). The primary outcome was ongoing pregnancy achieved within 18 months after randomization and resulting in a live birth. We needed 300 women to assess whether an increased dose strategy would increase the cumulative live birth rate from 25 to 40% (two-sided alpha-error 0.05, power 80%). Women with an AFC ≤ 7 were randomized to an FSH dose of 450 IU/day or 150 IU/day, and women with an AFC 8-10 were randomized to 225 IU or 150 IU/day. In the standard group, dose adjustment was allowed in subsequent cycles based on pre-specified criteria. Both effectiveness and cost-effectiveness of the strategies were evaluated from an intention-to-treat perspective. In total, 511 women were randomized, 234 with an AFC ≤ 7 and 277 with an AFC 8-10. The cumulative live birth rate for increased versus standard dosing was 42.4% (106/250) versus 44.8% (117/261), respectively [relative risk (RR): 0.95 (95%CI, 0.78-1.15), P = 0.58]. As an increased dose strategy was more expensive [delta costs/woman: €1099 (95%CI, 562-1591)], standard FSH dosing was the dominant strategy in our economic analysis. Despite our training programme, the AFC might have suffered from inter-observer variation. As this open study permitted small dose adjustments between cycles, potential selective cancelling of cycles in women treated with 150 IU could have influenced the cumulative results. However, since first cycle live birth rates point in the same direction we consider it unlikely that the open design masked a potential benefit for the individualized strategy. Since an increased dose in women scheduled for IVF/ICSI with a predicted poor response (AFC < 11) does not improve live birth rates and is more expensive, we recommend using a standard dose of 150 IU/day in these women. This study was funded by The Netherlands Organisation for Health Research and Development (ZonMW number 171102020). T.C.T., H.L.T. and S.C.O. received an unrestricted personal grant from Merck BV. H.R.V. receives monetary compensation as a member on an external advisory board for Ferring pharmaceutical BV. B.W.J.M. is supported by a NHMRC Practitioner Fellowship (GNT1082548) and reports consultancy for OvsEva, Merck and Guerbet. F.J.M.B. receives monetary compensation as a member of the external advisory board for Ferring pharmaceutics BV (the Netherlands) and Merck Serono (the Netherlands) for consultancy work for Gedeon Richter (Belgium) and Roche Diagnostics on automated AMH assay development (Switzerland) and for a research cooperation with Ansh Labs (USA). All other authors have nothing to declare. Registered at the ICMJE-recognized Dutch Trial Registry (www.trialregister.nl). Registration number NTR2657. 20 December 2010. 12 May 2011. © The Author 2017. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Proton therapy of prostate cancer by anterior-oblique beams: implications of setup and anatomy variations

NASA Astrophysics Data System (ADS)

Moteabbed, M.; Trofimov, A.; Sharp, G. C.; Wang, Y.; Zietman, A. L.; Efstathiou, J. A.; Lu, H.-M.

2017-03-01

Proton therapy of prostate by anterior beams could offer an attractive option for treating patients with hip prosthesis and limiting the high-dose exposure to the rectum. We investigated the impact of setup and anatomy variations on the anterior-oblique (AO) proton plan dose, and strategies to manage these effects via range verification and adaptive delivery. Ten patients treated by bilateral (BL) passive-scattering proton therapy (79.2 Gy in 44 fractions) who underwent weekly verification CT scans were selected. Plans with AO beams were additionally created. To isolate the effect of daily variations, initial AO plans did not include range uncertainty margins. The use of fixed planning margins and adaptive range adjustments to manage these effects was investigated. For each case, the planned dose was recalculated on weekly CTs, and accumulated on the simulation CT using deformable registration to approximate the delivered dose. Planned and accumulated doses were compared for each scenario to quantify dose deviations induced by variations. The possibility of estimating the necessary range adjustments before each treatment was explored by simulating the procedure of a diode-based in vivo range verification technique, which would potentially be used clinically. The average planned rectum, penile bulb and femoral heads mean doses were smaller for initial AO compared to BL plans (by 8.3, 16.1 and 25.9 Gy, respectively). After considering interfractional variations in AO plans, the target coverage was substantially reduced. The maximum reduction of V 79.2/D 95/D mean/EUD for AO (without distal margins) (25.3%/10.7/1.6/4.9 Gy, respectively) was considerably larger than BL plans. The loss of coverage was mainly related to changes in water equivalent path length of the prostate after fiducial-based setup, caused by discrepancies in patient anterior surface and bony-anatomy alignment. Target coverage was recovered partially when using fixed planning margins, and fully when applying adaptive range adjustments. The accumulated organs-at-risk dose for AO beams after range adjustment demonstrated full sparing of femoral heads and superior sparing of penile bulb and rectum compared to the conventional BL cases. Our study indicates that using AO beams makes prostate treatment more susceptible to target underdose induced by interfractional variations. Adaptive range verification/adjustment may facilitate the use of anterior beam approaches, and ensure adequate target coverage in every fraction of the treatment.

SU-E-T-455: Impact of Different Independent Dose Verification Software Programs for Secondary Check

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

Itano, M; Yamazaki, T; Kosaka, M

2015-06-15

Purpose: There have been many reports for different dose calculation algorithms for treatment planning system (TPS). Independent dose verification program (IndpPro) is essential to verify clinical plans from the TPS. However, the accuracy of different independent dose verification programs was not evident. We conducted a multi-institutional study to reveal the impact of different IndpPros using different TPSs. Methods: Three institutes participated in this study. They used two different IndpPros (RADCALC and Simple MU Analysis (SMU), which implemented the Clarkson algorithm. RADCALC needed the input of radiological path length (RPL) computed by the TPSs (Eclipse or Pinnacle3). SMU used CT imagesmore » to compute the RPL independently from TPS). An ion-chamber measurement in water-equivalent phantom was performed to evaluate the accuracy of two IndpPros and the TPS in each institute. Next, the accuracy of dose calculation using the two IndpPros compared to TPS was assessed in clinical plan. Results: The accuracy of IndpPros and the TPSs in the homogenous phantom was +/−1% variation to the measurement. 1543 treatment fields were collected from the patients treated in the institutes. The RADCALC showed better accuracy (0.9 ± 2.2 %) than the SMU (1.7 ± 2.1 %). However, the accuracy was dependent on the TPS (Eclipse: 0.5%, Pinnacle3: 1.0%). The accuracy of RADCALC with Eclipse was similar to that of SMU in one of the institute. Conclusion: Depending on independent dose verification program, the accuracy shows systematic dose accuracy variation even though the measurement comparison showed a similar variation. The variation was affected by radiological path length calculation. IndpPro with Pinnacle3 has different variation because Pinnacle3 computed the RPL using physical density. Eclipse and SMU uses electron density, though.« less

TU-G-BRD-03: IMRT Dosimetry Differences in An Institution with Community and Academic Model

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

Srivastava, S; Indiana University School of Medicine, Indianapolis, IN; Andersen, A

Purpose: Radiation outcome among institutions can be interpreted meaningfully if the dose delivery and prescription to the target volume is documented accurately and consistently. ICRU-83 recommended specific guidelines in IMRT for target volume definitions and dose reporting. This retrospective study evaluates the pattern of IMRT dose prescription and recording in an academic institution (AI) and a community hospital (CH) models in a single institution with reference to ICRU-83 recommendation. Materials & Methods: Dosimetric information of 625 (500 from academic and 125 from community) patients treated with IMRT was collected retrospectively from the AI and a CH. The dose-volume histogram (DVH)more » for the target volume of each patient was extracted. Standard dose parameters such as D2, D50, D95, D98, D100, as well as the homogeneity index (HI) defined as (D2-D98)/D50 and monitor units (MUs) were collected. Results: Significant dosimetric variations were observed in disease sites and between AI and CH. The variation in the mean value of D95 for AI is 98.48±4.12 and for CH is 96.41±4.13. A similar pattern was noticed for D50 (104.18±6.04 for AI and 101.05±3.49 for CH). Thus, nearly 95% of patients received dosage higher than 100% to the site viewed by D50 and varied between AI and CH models. The average variation of HI is found to be 0.12±0.08 and 0.11±0.08 for AI and CH model, showing better IMRT treatment plans for academic model compared to community. Conclusion: Even with the implementation of ICRU-83 guidelines, there is a large variation in dose prescription and delivery in IMRT. The variation is institution and site specific. For any meaningful comparison of the IMRT outcome, strict guidelines for dose reporting should be maintained in every institution.« less

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

Zhang, Y; Giebeler, A; Mascia, A

Purpose: To quantitatively evaluate dosimetric consequence of spot size variations and validate beam-matching criteria for commissioning a pencil beam model for multiple treatment rooms. Methods: A planning study was first conducted by simulating spot size variations to systematically evaluate dosimetric impact of spot size variations in selected cases, which was used to establish the in-air spot size tolerance for beam matching specifications. A beam model in treatment planning system was created using in-air spot profiles acquired in one treatment room. These spot profiles were also acquired from another treatment room for assessing the actual spot size variations between the twomore » treatment rooms. We created twenty five test plans with targets of different sizes at different depths, and performed dose measurement along the entrance, proximal and distal target regions. The absolute doses at those locations were measured using ionization chambers at both treatment rooms, and were compared against the calculated doses by the beam model. Fifteen additional patient plans were also measured and included in our validation. Results: The beam model is relatively insensitive to spot size variations. With an average of less than 15% measured in-air spot size variations between two treatment rooms, the average dose difference was −0.15% with a standard deviation of 0.40% for 55 measurement points within target region; but the differences increased to 1.4%±1.1% in the entrance regions, which are more affected by in-air spot size variations. Overall, our single-room based beam model in the treatment planning system agreed with measurements in both rooms < 0.5% within the target region. For fifteen patient cases, the agreement was within 1%. Conclusion: We have demonstrated that dosimetrically equivalent machines can be established when in-air spot size variations are within 15% between the two treatment rooms.« less

A direct reading exposure monitor for radiation processing

NASA Astrophysics Data System (ADS)

Kantz, A. D.; Humpherys, K. C.

Various plastic films have been utilized to measure radiation fields. In general such films are rugged, easily handled, small enough to cause neligible perturbation on the radiation fields, and relatively inexpensive. The radiachromic materials have been shown to have advantages over other plastic fabrications in stability, reproducibility, equivalent response to electron and gamma ray processing fields, dose rate independence, and ready availability of calibration standards. Using a nylon matrix radiachromic detector, a system of direct read-out of absorbed dose has been developed to facilitate monitoring in the megarad region. When an exposed detector is inserted into the reader, the optical transmission signal is processed through an analog to digital converter. The digitized signal addresses a memory bank where the standard response curve is stored. The corresponding absorbed dose is displayed on a digital panel meter. The variation of relative sensitivity of detectors, the background of unirradiated detectors, environmental parameters, and the capacity of the memory bank are contributing factors to the total precision of the read-out system.

Ultrafast treatment plan optimization for volumetric modulated arc therapy (VMAT)

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

Men Chunhua; Romeijn, H. Edwin; Jia Xun

2010-11-15

Purpose: To develop a novel aperture-based algorithm for volumetric modulated arc therapy (VMAT) treatment plan optimization with high quality and high efficiency. Methods: The VMAT optimization problem is formulated as a large-scale convex programming problem solved by a column generation approach. The authors consider a cost function consisting two terms, the first enforcing a desired dose distribution and the second guaranteeing a smooth dose rate variation between successive gantry angles. A gantry rotation is discretized into 180 beam angles and for each beam angle, only one MLC aperture is allowed. The apertures are generated one by one in a sequentialmore » way. At each iteration of the column generation method, a deliverable MLC aperture is generated for one of the unoccupied beam angles by solving a subproblem with the consideration of MLC mechanic constraints. A subsequent master problem is then solved to determine the dose rate at all currently generated apertures by minimizing the cost function. When all 180 beam angles are occupied, the optimization completes, yielding a set of deliverable apertures and associated dose rates that produce a high quality plan. Results: The algorithm was preliminarily tested on five prostate and five head-and-neck clinical cases, each with one full gantry rotation without any couch/collimator rotations. High quality VMAT plans have been generated for all ten cases with extremely high efficiency. It takes only 5-8 min on CPU (MATLAB code on an Intel Xeon 2.27 GHz CPU) and 18-31 s on GPU (CUDA code on an NVIDIA Tesla C1060 GPU card) to generate such plans. Conclusions: The authors have developed an aperture-based VMAT optimization algorithm which can generate clinically deliverable high quality treatment plans at very high efficiency.« less

Ultrafast treatment plan optimization for volumetric modulated arc therapy (VMAT).

PubMed

Men, Chunhua; Romeijn, H Edwin; Jia, Xun; Jiang, Steve B

2010-11-01

To develop a novel aperture-based algorithm for volumetric modulated are therapy (VMAT) treatment plan optimization with high quality and high efficiency. The VMAT optimization problem is formulated as a large-scale convex programming problem solved by a column generation approach. The authors consider a cost function consisting two terms, the first enforcing a desired dose distribution and the second guaranteeing a smooth dose rate variation between successive gantry angles. A gantry rotation is discretized into 180 beam angles and for each beam angle, only one MLC aperture is allowed. The apertures are generated one by one in a sequential way. At each iteration of the column generation method, a deliverable MLC aperture is generated for one of the unoccupied beam angles by solving a subproblem with the consideration of MLC mechanic constraints. A subsequent master problem is then solved to determine the dose rate at all currently generated apertures by minimizing the cost function. When all 180 beam angles are occupied, the optimization completes, yielding a set of deliverable apertures and associated dose rates that produce a high quality plan. The algorithm was preliminarily tested on five prostate and five head-and-neck clinical cases, each with one full gantry rotation without any couch/collimator rotations. High quality VMAT plans have been generated for all ten cases with extremely high efficiency. It takes only 5-8 min on CPU (MATLAB code on an Intel Xeon 2.27 GHz CPU) and 18-31 s on GPU (CUDA code on an NVIDIA Tesla C1060 GPU card) to generate such plans. The authors have developed an aperture-based VMAT optimization algorithm which can generate clinically deliverable high quality treatment plans at very high efficiency.

Integration of an Axcelis Optima HD Single Wafer High Current Implanter for p- and n-S/D Implants in an Existing Batch Implanter Production Line

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

Schmeide, Matthias; Kontratenko, Serguei; Krimbacher, Bernhard

2008-11-03

This paper is focused on the integration and qualification of an Axcelis Optima HD single wafer high current spot beam implanter in an existing 200 mm production line with different types of Axcelis batch implanters for high current applications. Both the design of the beamline and the beam shape are comparable between single wafer and batch high current spot beam implanters. In contrast to the single wafer high current ribbon beam implanter, energy contamination is not a concern for the considered spot beam tool because the drift mode can be used down to energies in the 2 keV region. Themore » most important difference between single wafer and batch high current implanters is the significantly higher dose rate and, therefore, the higher damage rate for the single wafer tool due to the different scanning architecture. The results of the integration of high dose implantations, mainly for p- and n-S/D formation, for DRAM 110 nm without pre-amorphization implantation (PAI), CMOS Logic from around 250 nm down to 90 nm without and with PAI, are presented and discussed. Dopant concentration profile analysis using SIMS was performed for different technologies and implantation conditions. The impurity activation was measured using sheet resistance and in some cases spreading resistance technique was applied. The amorphous layer thickness was measured using TEM. Finally, device data are presented in combination with dose, energy and beam current variations. The results have shown that the integration of implantation processes into crystalline structure without PAI is more complex and time consuming than implantations into amorphous layer where the damage difference due to the different dose rates is negligible.« less

Assessment of natural radioactivity levels in soil samples from some areas in Assiut, Egypt.

PubMed

El-Gamal, Hany; Farid, M El-Azab; Abdel Mageed, A I; Hasabelnaby, M; Hassanien, Hassanien M

2013-12-01

The natural radioactivity of soil samples from Assiut city, Egypt, was studied. The activity concentrations of 28 samples were measured with a NaI(Tl) detector. The radioactivity concentrations of (226)Ra, (232)Th, and (40)K showed large variations, so the results were classified into two groups (A and B) to facilitate the interpretation of the results. Group A represents samples collected from different locations in Assiut and characterized by low activity concentrations with average values of 46.15 ± 9.69, 30.57 ± 4.90, and 553.14 ± 23.19 for (226)Ra, (232)Th, and (40)K, respectively. Group B represents samples mainly collected from the area around Assiut Thermal Power Plant and characterized by very high activity concentrations with average values of 3,803 ± 145, 1,782 ± 98, and 1,377 ± 78 for (226)Ra, (232)Th, and (40)K, respectively. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity (Raeq), the absorbed dose rate (D), the annual effective dose rate (E), the external hazard index (H ex), and the annual gonadal dose equivalent (AGDE) have been calculated and compared with the internationally approved values. For group A, the calculated averages of these parameters are in good agreement with the international recommended values except for the absorbed dose rate and the AGDE values which are slightly higher than the international recommended values. However, for group B, all obtained averages of these parameters are much higher by several orders of magnitude than the international recommended values. The present work provides a background of radioactivity concentrations in the soil of Assiut.

The acute physiological and mood effects of tea and coffee: the role of caffeine level.

PubMed

Quinlan, P T; Lane, J; Moore, K L; Aspen, J; Rycroft, J A; O'Brien, D C

2000-05-01

The objective of this study was to determine the effect of caffeine level in tea and coffee on acute physiological responses and mood. Randomised full crossover design in subjects after overnight caffeine abstention was studied. In study 1 (n = 17) the caffeine level was manipulated naturalistically by preparing tea and coffee at different strengths (1 or 2 cups equivalent). Caffeine levels were 37.5 and 75 mg in tea, 75 and 150 mg in coffee, with water and no-drink controls. In study 2 (n = 15) caffeine level alone was manipulated (water, decaffeinated tea, plus 0, 25, 50, 100, and 200 mg caffeine). Beverage volume and temperature (55 degrees C) were constant. SBP, DBP, heart rate, skin temperature, skin conductance, and mood were monitored over each 3-h study session. In study 1, tea and coffee produced mild autonomic stimulation and an elevation in mood. There were no effects of tea vs. coffee or caffeine dose, despite a fourfold variation in the latter. Increasing beverage strength was associated with greater increases in DBP and energetic arousal. In study 2, caffeinated beverages increased SBP, DBP, and skin conductance and lowered heart rate and skin temperature compared to water. Significant dose-response relationships to caffeine were seen only for SBP, heart rate, and skin temperature. There were significant effects of caffeine on energetic arousal but no consistent dose-response effects. Caffeinated beverages acutely stimulate the autonomic nervous system and increase alertness. Although caffeine can exert dose-dependent effects on a number of acute autonomic responses, caffeine level is not an important factor. Factors besides caffeine may contribute to these acute effects.

Analysis of Exposure-Dose Variation of Inhaled Particles in Adult Subjects.

EPA Science Inventory

Although internal dose is a key factor for determining the health risk of inhaled pollutant particles, available dose information is largely limited to young healthy adults under a few typical exposure conditions. Extrapolation of the limited dose information to different populat...

Radiation dose response of N channel MOSFET submitted to filtered X-ray photon beam

NASA Astrophysics Data System (ADS)

Gonçalves Filho, Luiz C.; Monte, David S.; Barros, Fabio R.; Santos, Luiz A. P.

2018-01-01

MOSFET can operate as a radiation detector mainly in high-energy photon beams, which are normally used in cancer treatments. In general, such an electronic device can work as a dosimeter from threshold voltage shift measurements. The purpose of this article is to show a new way for measuring the dose-response of MOSFETs when they are under X-ray beams generated from 100kV potential range, which is normally used in diagnostic radiology. Basically, the method consists of measuring the MOSFET drain current as a function of the radiation dose. For this the type of device, it has to be biased with a high value resistor aiming to see a substantial change in the drain current after it has been irradiated with an amount of radiation dose. Two types of N channel device were used in the experiment: a signal transistor and a power transistor. The delivered dose to the device was varied and the electrical curves were plotted. Also, a sensitivity analysis of the power MOSFET response was made, by varying the tube potential of about 20%. The results show that both types of devices have responses very similar, the shift in the electrical curve is proportional to the radiation dose. Unlike the power MOSFET, the signal transistor does not provide a linear function between the dose rate and its drain current. We also have observed that the variation in the tube potential of the X-ray equipment produces a very similar dose-response.

Space Radiation Peculiarities in the Extra Vehicular Environment of the International Space Station (ISS)

NASA Astrophysics Data System (ADS)

Dachev, Tsvetan; Bankov, Nikolay; Tomov, Borislav; Matviichuk, Yury; Dimitrov, Plamen

2013-12-01

The space weather and the connected with it ionizing radiation were recognized as a one of the main health concern to the International Space Station (ISS) crew. Estimation the effects of radiation on humans in ISS requires at first order accurate knowledge of the accumulated by them absorbed dose rates, which depend of the global space radiation distribution and the local variations generated by the 3D surrounding shielding distribution. The R3DE (Radiation Risks Radiometer-Dosimeter (R3D) for the EXPOSE-E platform on the European Technological Exposure Facility (EuTEF) worked successfully outside of the European Columbus module between February 2008 and September 2009. Very similar instrument named R3DR for the EXPOSE-R platform worked outside Russian Zvezda module of ISS between March 2009 and August 2010. Both are Liulin type, Bulgarian build miniature spectrometers-dosimeters. They accumulated about 5 million measurements of the flux and absorbed dose rate with 10 seconds resolution behind less than 0.41 g cm-2 shielding, which is very similar to the Russian and American space suits [1-3] average shielding. That is why all obtained data can be interpreted as possible doses during Extra Vehicular Activities (EVA) of the cosmonauts and astronauts. The paper first analyses the obtained long-term results in the different radiation environments of: Galactic Cosmic Rays (GCR), inner radiation belt trapped protons in the region of the South Atlantic Anomaly (SAA) and outer radiation belt (ORB) relativistic electrons. The large data base was used for development of an empirical model for calculation of the absorbed dose rates in the extra vehicular environment of ISS at 359 km altitude. The model approximate the averaged in a grid empirical dose rate values to predict the values at required from the user geographical point, station orbit or area in geographic coordinate system. Further in the paper it is presented an intercomparison between predicted by the model dose rate values and data collected by the R3DE/R instruments and NASA Tissue Equivalent Proportional Counter (TEPC) during real cosmonauts and astronauts EVA in 79 the 2008-2010 time interval including large relativistic electrons doses during the magnetosphere enhancement in April 2010. The model was also used to be predicted the accumulated along the orbit of ISS galactic cosmic rays and inner radiation belt dose for 1 orbit (1.5 hours) and 4 consequences orbits (6 hours), which is the usual EVA continuation in dependence by the longitude of the ascending node of ISS. These predictions of the model could be used by space agencies medical and other not specialized in the radiobiology support staff for first approach in the ISS EVA time and space planning.

Dose rate effect of pulsed electron beam on micronucleus frequency in human peripheral blood lymphocytes.

PubMed

Acharya, Santhosh; Sanjeev, Ganesh; Bhat, Nagesh N; Narayana, Yerol

2010-03-01

The micronucleus assay in human peripheral blood lymphocytes is a sensitive indicator of radiation damage and could serve as a biological dosimeter in evaluating suspected overexposure to ionising radiation. Micronucleus (MN) frequency as a measure of chromosomal damage has also extensively been employed to quantify the effects of radiation dose rate on biological systems. Here we studied the effects of 8 MeV pulsed electron beam emitted by Microtron electron accelerator on MN induction at dose rates between 35 Gy min-1 and 352.5 Gy min-1. These dose rates were achieved by varying the pulse repetition rate (PRR). Fricke dosimeter was employed to measure the absorbed dose at different PRR and to ensure uniform dose distribution of the electron beam. To study the dose rate effect, blood samples were irradiated to an absorbed dose of (4.7+/-0.2) Gy at different rates and cytogenetic damage was quantified using the micronucleus assay. The obtained MN frequency showed no dose rate dependence within the studied dose rate range. Our earlier dose effect study using 8 MeV electrons revealed that the response of MN was linear-quadratic. Therefore, in the event of an accident, dose estimation can be made using linear-quadratic dose response parameters, without adding dose rate as a correction factor.

Dummy run of quality assurance program in a phase 3 randomized trial investigating the role of internal mammary lymph node irradiation in breast cancer patients: Korean Radiation Oncology Group 08-06 study.

PubMed

Chung, Yoonsun; Kim, Jun Won; Shin, Kyung Hwan; Kim, Su Ssan; Ahn, Sung-Ja; Park, Won; Lee, Hyung-Sik; Kim, Dong Won; Lee, Kyu Chan; Suh, Hyun Suk; Kim, Jin Hee; Shin, Hyun Soo; Kim, Yong Bae; Suh, Chang-Ok

2015-02-01

The Korean Radiation Oncology Group (KROG) 08-06 study protocol allowed radiation therapy (RT) technique to include or exclude breast cancer patients from receiving radiation therapy to the internal mammary lymph node (IMN). The purpose of this study was to assess dosimetric differences between the 2 groups and potential influence on clinical outcome by a dummy run procedure. All participating institutions were asked to produce RT plans without irradiation (Arm 1) and with irradiation to the IMN (Arm 2) for 1 breast-conservation treatment case (breast-conserving surgery [BCS]) and 1 mastectomy case (modified radical mastectomy [MRM]) whose computed tomography images were provided. We assessed interinstitutional variations in IMN delineation and evaluated the dose-volume histograms of the IMN and normal organs. A reference IMN was delineated by an expert panel group based on the study guidelines. Also, we analyzed the potential influence of actual dose variation observed in this study on patient survival. Although physicians intended to exclude the IMN within the RT field, the data showed almost 59.0% of the prescribed dose was delivered to the IMN in Arm 1. However, the mean doses covering the IMN in Arm 1 and Arm 2 were significantly different for both cases (P<.001). Due to the probability of overdose in Arm 1, the estimated gain in 7-year disease-free survival rate would be reduced from 10% to 7.9% for BCS cases and 7.1% for MRM cases. The radiation doses to the ipsilateral lung, heart, and coronary artery were lower in Arm 1 than in Arm 2. Although this dummy run study indicated that a substantial dose was delivered to the IMN, even in the nonirradiation group, the dose differences between the 2 groups were statistically significant. However, this dosimetric profile should be studied further with actual patient samples and be taken into consideration when analyzing clinical outcomes according to IMN irradiation. Copyright © 2015 Elsevier Inc. All rights reserved.

Dummy Run of Quality Assurance Program in a Phase 3 Randomized Trial Investigating the Role of Internal Mammary Lymph Node Irradiation in Breast Cancer Patients: Korean Radiation Oncology Group 08-06 Study

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

Chung, Yoonsun; Kim, Jun Won; Shin, Kyung Hwan

2015-02-01

Purpose: The Korean Radiation Oncology Group (KROG) 08-06 study protocol allowed radiation therapy (RT) technique to include or exclude breast cancer patients from receiving radiation therapy to the internal mammary lymph node (IMN). The purpose of this study was to assess dosimetric differences between the 2 groups and potential influence on clinical outcome by a dummy run procedure. Methods and Materials: All participating institutions were asked to produce RT plans without irradiation (Arm 1) and with irradiation to the IMN (Arm 2) for 1 breast-conservation treatment case (breast-conserving surgery [BCS]) and 1 mastectomy case (modified radical mastectomy [MRM]) whose computed tomographymore » images were provided. We assessed interinstitutional variations in IMN delineation and evaluated the dose-volume histograms of the IMN and normal organs. A reference IMN was delineated by an expert panel group based on the study guidelines. Also, we analyzed the potential influence of actual dose variation observed in this study on patient survival. Results: Although physicians intended to exclude the IMN within the RT field, the data showed almost 59.0% of the prescribed dose was delivered to the IMN in Arm 1. However, the mean doses covering the IMN in Arm 1 and Arm 2 were significantly different for both cases (P<.001). Due to the probability of overdose in Arm 1, the estimated gain in 7-year disease-free survival rate would be reduced from 10% to 7.9% for BCS cases and 7.1% for MRM cases. The radiation doses to the ipsilateral lung, heart, and coronary artery were lower in Arm 1 than in Arm 2. Conclusions: Although this dummy run study indicated that a substantial dose was delivered to the IMN, even in the nonirradiation group, the dose differences between the 2 groups were statistically significant. However, this dosimetric profile should be studied further with actual patient samples and be taken into consideration when analyzing clinical outcomes according to IMN irradiation.« less

Practice variation in the treatment of rheumatoid arthritis among German rheumatologists.

PubMed

Zink, A; Listing, J; Ziemer, S; Zeidler, H

2001-10-01

To describe practice variation in the treatment of rheumatoid arthritis (RA) among German rheumatologists with regard to drug and non-drug therapy. We used data of 7,326 patients with RA registered in a national German rheumatological database in 1998. In the database, every patient with an inflammatory rheumatic disease seen at one of the German Collaborative Arthritis Centres is registered once a year with a standard clinical data form and a patient questionnaire. We compared health care provided by 29 rheumatological outpatient units. For drug and non-drug treatment unit prescription rates, ranges and outliers were calculated. Logistic regression analysis was used for case mix adjustment and for the identification of practice patterns. We observed variation concerning the frequency of use of single disease modifying antirheumatic drugs (DMARD). The median of the prescription rates in the 29 units for methotrexate (MTX) was 55% in 1998 (1st quartile: 51%, 3rd quartile: 63%); sulfasalazine had a median of 15% (quartiles: 10%/19%), antimalarials a median of 8% (quartiles: 5%/21%). Combination DMARD therapy was used in 11% (quartiles: 6%/18%). Prescriptions of low dose steroids (< or = 7.5 mg) had a median of 45% (quartiles: 35%/55%), and nonsteroidal antiinflammatory drugs (NSAID) had a median prescription rate of 58% (quartiles: 50%/70%). High variation was also found concerning active physiotherapy (median: 41%; quartiles 34%/55%) and passive physical measures (median 14%, quartiles 9%/37%). Differences in case mix (age, sex, rheumatoid factor, disease duration, severity, disability) only explained a small proportion of the total variation. When the units were grouped according to the frequency of prescription of DMARD combination therapy, treatment patterns could be identified. Units with higher rates of DMARD combination therapy used more drugs for the prevention and treatment of osteoporosis, more active physiotherapy but fewer NSAID and fewer passive physical therapies. Variation in drug and non-drug treatment indicates significant differences in health care provision. Trends in the drug management of RA are adopted differentially by the members of the rheumatology community. The large variability in non-drug therapies may, apart from differences in availability, suggest a lack of agreement on therapeutic effectiveness.

SU-F-J-64: Comparison of Dosimetric Robustness Between Proton Therapy and IMRT Plans Following Tumor Regression for Locally Advanced Non-Small Cell Lung Cancer (NSCLC)

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

Teng, C; Ainsley, C; Teo, B

Purpose: In the light of tumor regression and normal tissue changes, dose distributions can deviate undesirably from what was planned. As a consequence, replanning is sometimes necessary during treatment to ensure continued tumor coverage or to avoid overdosing organs at risk (OARs). Proton plans are generally thought to be less robust than photon plans because of the proton beam’s higher sensitivity to changes in tissue composition, suggesting also a higher likely replanning rate due to tumor regression. The purpose of this study is to compare dosimetric deviations between forward-calculated double scattering (DS) proton plans with IMRT plans upon tumor regression,more » and assesses their impact on clinical replanning decisions. Methods: Ten consecutive locally advanced NSCLC patients whose tumors shrank > 50% in volume and who received four or more CT scans during radiotherapy were analyzed. All the patients received proton radiotherapy (6660 cGy, 180 cGy/fx). Dosimetric robustness during therapy was characterized by changes in the planning objective metrics as well as by point-by-point root-mean-squared differences for the entire PTV, ITV, and OARs (heart, cord, esophagus, brachial plexus and lungs) DVHs. Results: Sixty-four pairs of DVHs were reviewed by three clinicians, who requested a replanning rate of 16.7% and 18.6% for DS and IMRT plans, respectively, with a high agreement between providers. Robustness of clinical indicators was found to depend on the beam orientation and dose level on the DVH curve. Proton dose increased most in OARs distal to the PTV along the beam path, but these changes were primarily in the mid to low dose levels. In contrast, the variation in IMRT plans occurred primarily in the high dose region. Conclusion: Robustness of clinical indicators depends where on the DVH curves comparisons are made. Similar replanning rates were observed for DS and IMRT plans upon large tumor regression.« less

Enhanced Low Dose Rate Sensitivity at Ultra-Low Dose Rates

NASA Technical Reports Server (NTRS)

Chen, Dakai; Pease, Ronald; Forney, James; Carts, Martin; Phan, Anthony; Cox, Stephen; Kruckmeyer, Kriby; Burns, Sam; Albarian, Rafi; Holcombe, Bruce;

The Effects of ELDRS at Ultra-Low Dose Rates

NASA Technical Reports Server (NTRS)

Chen, Dakai; Forney, James; Carts, Martin; Phan, Anthony; Pease, Ronald; Kruckmeyer, Kirby; Cox, Stephen; LaBel, Kenneth; Burns, Samuel; Albarian, Rafi;

Population pharmacokinetics of transdermal fentanyl in patients with cancer-related pain.

PubMed

Kokubun, Hideya; Ebinuma, Keiichi; Matoba, Motohiro; Takayanagi, Risa; Yamada, Yasuhiko; Yago, Kazuo

2012-06-01

Determining the appropriate dose of transdermal fentanyl (TDF) for the alleviation of cancer pain requires determining the factors causing variations in serum fentanyl concentration after TDF treatment. The objective of this study was to identify these factors and incorporate them into a formula that can be used to predict serum fentanyl concentration after application of a TDF patch. Blood samples of cancer patients treated with a TDF patch for the alleviation of pain were collected at 24, 48, and 72 hours after application to evaluate population pharmacokinetics using the nonlinear mixed-effect model (NONMEM). Based upon this evaluation, Child-Pugh Score and use of a cytochrome P450 3A4 (CYP3A4) inducer were identified as the most significant factors in variations in serum fentanyl concentration and incorporated into the following Final Model formula: CL(fenta) (L/h) = 3.53 × (15 - Child-Pugh Score) × (1 + 1.38 × use or no use of CYP3A4 inducer). Bootstrap evaluation of the Final Model revealed a high convergence rate, suggesting that the model formula is a reliable and useful tool for determining TDF dose for the alleviation of cancer pain.

Patient-specific dose estimation for pediatric abdomen-pelvis CT

NASA Astrophysics Data System (ADS)

Li, Xiang; Samei, Ehsan; Segars, W. Paul; Sturgeon, Gregory M.; Colsher, James G.; Frush, Donald P.

2009-02-01

The purpose of this study is to develop a method for estimating patient-specific dose from abdomen-pelvis CT examinations and to investigate dose variation across patients in the same weight group. Our study consisted of seven pediatric patients in the same weight/protocol group, for whom full-body computer models were previously created based on the patients' CT data obtained for clinical indications. Organ and effective dose of these patients from an abdomen-pelvis scan protocol (LightSpeed VCT scanner, 120-kVp, 85-90 mA, 0.4-s gantry rotation period, 1.375-pitch, 40-mm beam collimation, and small body scan field-of-view) was calculated using a Monte Carlo program previously developed and validated for the same CT system. The seven patients had effective dose of 2.4-2.8 mSv, corresponding to normalized effective dose of 6.6-8.3 mSv/100mAs (coefficient of variation: 7.6%). Dose variations across the patients were small for large organs in the scan coverage (mean: 6.6%; range: 4.9%-9.2%), larger for small organs in the scan coverage (mean: 10.3%; range: 1.4%-15.6%), and the largest for organs partially or completely outside the scan coverage (mean: 14.8%; range: 5.7%-27.7%). Normalized effective dose correlated strongly with body weight (correlation coefficient: r = -0.94). Normalized dose to the kidney and the adrenal gland correlated strongly with mid-liver equivalent diameter (kidney: r = -0.97; adrenal glands: r = -0.98). Normalized dose to the small intestine correlated strongly with mid-intestine equivalent diameter (r = -0.97). These strong correlations suggest that patient-specific dose may be estimated for any other child in the same size group who undergoes the abdomen-pelvis scan.

Inducing rat brain CYP2D with nicotine increases the rate of codeine tolerance; predicting the rate of tolerance from acute analgesic response.

PubMed

McMillan, Douglas M; Tyndale, Rachel F

2017-12-01

Repeated opioid administration produces analgesic tolerance, which may lead to dose escalation. Brain CYP2D metabolizes codeine to morphine, a bioactivation step required for codeine analgesia. Higher brain, but not liver, CYP2D is found in smokers and nicotine induces rat brain, but not liver, CYP2D expression and activity. Nicotine induction of rat brain CYP2D increases acute codeine conversion to morphine, and analgesia, however the role of brain CYP2D on the effects of repeated codeine exposure and tolerance is unknown. Rats were pretreated with nicotine (brain CYP2D inducer; 1mg/kg subcutaneously) or vehicle (saline; 1ml/kg subcutaneously). Codeine (40-60mg/kg oral-gavage) or morphine (20-30mg/kg oral-gavage) was administered daily and analgesia was assessed daily using the tail-flick reflex assay. Nicotine (versus saline) pretreatment increased acute codeine analgesia (1.32-fold change in AUC 0-60 min ; p<0.05) and the rate of loss of peak analgesia (11.42%/day versus 4.20%; p<0.006) across the first four days of codeine administration (time to negligible analgesia). Inducing brain CYP2D with nicotine did not alter acute morphine analgesia (1.03-fold; p>0.8), or the rate of morphine tolerance (8.1%/day versus 7.6%; p>0.9). The rate of both codeine and morphine tolerance (loss in peak analgesia from day 1 to day 4) correlated with initial analgesic response on day 1 (R=0.97, p<001). Increasing brain CYP2D altered initial analgesia and subsequent rate of tolerance. Variation in an individual's initial response to analgesic (e.g. high initial dose, smoking) may affect the rate of tolerance, and thereby the risk for dose escalation and/or opioid dependence. Copyright © 2017 Elsevier Inc. All rights reserved.

Seasonal variation in the nature of DOM in a river and drinking water reservoir of a closed catchment.

PubMed

Awad, John; van Leeuwen, John; Chow, Christopher W K; Smernik, Ronald J; Anderson, Sharolyn J; Cox, Jim W

2017-01-01

Dissolved organic matter (DOM) in surface waters used for drinking purposes can vary markedly in character depending on its source within catchments and the timing and intensity of rainfall events. Here we report the findings of a study on the character and concentration of DOM in waters collected during different seasons from Myponga River and Reservoir, South Australia. The character of DOM was assessed in terms of its treatability by enhanced coagulation and potential for disinfection by-product i.e. trihalomethane (THM) formation. During the wet seasons (winter and spring), water samples from the river had higher DOC concentrations (X¯: 21 mg/L) and DOM of higher average molecular weight (AMW: 1526 Da) than waters collected during the dry seasons (summer and autumn: DOC: 13 mg/L; AMW: 1385 Da). Even though these features led to an increase in the percentage removal of organics by coagulation with alum (64% for wet compared with 53% for dry season samples) and a lower alum dose rate (10 versus 15 mg alum/mg DOC removal), there was a higher THM formation potential (THMFP) from wet season waters (treated waters: 217 μg/L vs 172 μg/L). For reservoir waters, samples collected during the wet seasons had an average DOC concentration (X¯: 15 mg/L), percentage removal of organics by alum (54%), alum dose rates (13 mg/mg DOC) and THMFP (treated waters: 207 μg/L) that were similar to samples collected during the dry seasons (mean DOC: 15 mg/L; removal of organics: 52%; alum dose rate: 13 mg/mg DOC; THMFP: 212 μg/L for treated waters). These results show that DOM present in river waters and treatability by alum are highly impacted by seasonal environmental variations. However these in reservoir waters exhibit less seasonal variability. Storage of large volumes of water in the reservoir enables mixing of influent waters and stabilization of water quality. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

The use of megavoltage CT (MVCT) images for dose recomputations

NASA Astrophysics Data System (ADS)

Langen, K. M.; Meeks, S. L.; Poole, D. O.; Wagner, T. H.; Willoughby, T. R.; Kupelian, P. A.; Ruchala, K. J.; Haimerl, J.; Olivera, G. H.

2005-09-01

Megavoltage CT (MVCT) images of patients are acquired daily on a helical tomotherapy unit (TomoTherapy, Inc., Madison, WI). While these images are used primarily for patient alignment, they can also be used to recalculate the treatment plan for the patient anatomy of the day. The use of MVCT images for dose computations requires a reliable CT number to electron density calibration curve. In this work, we tested the stability of the MVCT numbers by determining the variation of this calibration with spatial arrangement of the phantom, time and MVCT acquisition parameters. The two calibration curves that represent the largest variations were applied to six clinical MVCT images for recalculations to test for dosimetric uncertainties. Among the six cases tested, the largest difference in any of the dosimetric endpoints was 3.1% but more typically the dosimetric endpoints varied by less than 2%. Using an average CT to electron density calibration and a thorax phantom, a series of end-to-end tests were run. Using a rigid phantom, recalculated dose volume histograms (DVHs) were compared with plan DVHs. Using a deformed phantom, recalculated point dose variations were compared with measurements. The MVCT field of view is limited and the image space outside this field of view can be filled in with information from the planning kVCT. This merging technique was tested for a rigid phantom. Finally, the influence of the MVCT slice thickness on the dose recalculation was investigated. The dosimetric differences observed in all phantom tests were within the range of dosimetric uncertainties observed due to variations in the calibration curve. The use of MVCT images allows the assessment of daily dose distributions with an accuracy that is similar to that of the initial kVCT dose calculation.

SU-E-T-287: Dose Verification On the Variation of Target Volume and Organ at Risk in Preradiation Chemotherapy IMRT for Nasopharyngeal Cancer

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

Zhang, X; Kong, L; Wang, J

2015-06-15

Purpose: To quantify the target volume and organ at risk of nasopharyngeal carcinoma (NPC) patients with preradiation chemotherapy based on CT scanned during intensity-modulated radiotherapy (IMRT), and recalculate the dose distribution. Methods: Seven patients with NPC and preradiation chemotherapy, treated with IMRT (35 to 37 fractions) were reviewed. Repeat CT scanning was required to all of the patients during the radiotherapy, and the number of repeat CTs varies from 2 to 6. The plan CT and repeat CT were generated by different CT scanner. To ensure crespectively on the same IMPT plan. The real dose distribution was calculated by deformablemore » registration and weighted method in Raystation (v 4.5.1). The fraction of each dose is based on radiotherapy record. The volumetric and dose differences among these images were calculated for nascIpharyngeal tumor and retro-pharyngeal lymph nodes (GTV-NX), neck lymph nodes(GTV-ND), and parotid glands. Results: The volume variation in GTV-NX from CT1 to CT2 was 1.15±3.79%, and in GTV-LN −0.23±4.93%. The volume variation in left parotid from CT1 to CT2 was −6.79±11.91%, and in right parotid −3.92±8.80%. In patient 2, the left parotid volume were decreased remarkably, as a Result, the V30 and V40 of it were increased as well. Conclusion: The target volume of patients with NPC varied lightly during IMRT. It shows that preradiation chemotherapy can control the target volume variation and perform a good dose repeatability. Also, the decreasing volume of parotid in some patient might increase the dose of it, which might course potential complications.« less

SU-E-P-05: Is Routine Treatment Planning System Quality Assurance Necessary?

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

Alaei, P

Purpose: To evaluate the variation of dose calculations using a treatment planning system (TPS) over a two year period and assessment of the need for TPS QA on regular intervals. Methods: Two phantoms containing solid water and lung- and bone-equivalent heterogeneities were constructed in two different institutions for the same brand treatment planning system. Multiple plans, consisting of photons and electron beams, including IMRT and VMAT ones, were created and calculated on the phantoms. The accuracy of dose computation in the phantoms was evaluated at the onset by dose measurements within the phantoms. The dose values at up to 24more » points of interest (POI) within the solid water, lung, and bone slabs, as well as mean doses to several regions of interest (ROI), were re-calculated over a two-year period which included two software upgrades. The variations in POI and ROI dose values were analyzed and evaluated. Results: The computed doses vary slightly month-over-month. There are noticeable variations at the times of software upgrade, if the upgrade involves remodeling and/or re-commissioning of the beams. The variations are larger in certain points within the phantom, usually in the buildup region or near interfaces, and are almost non-existent for electron beams. Conclusion: Routine TPS QA is recommended by AAPM and other professional societies, and is often required by accreditation organizations. The frequency and type of QA, though, is subject to debate. The results presented here demonstrate that the frequency of these tests could be at longer intervals than monthly. However, it is essential to perform TPS QA at the time of commissioning and after each software upgrade.« less

Dose rate in brachytherapy using after-loading machine: pulsed or high-dose rate?

PubMed

Hannoun-Lévi, J-M; Peiffert, D

2014-10-01

Since February 2014, it is no longer possible to use low-dose rate 192 iridium wires due to the end of industrial production of IRF1 and IRF2 sources. The Brachytherapy Group of the French society of radiation oncology (GC-SFRO) has recommended switching from iridium wires to after-loading machines. Two types of after-loading machines are currently available, based on the dose rate used: pulsed-dose rate or high-dose rate. In this article, we propose a comparative analysis between pulsed-dose rate and high-dose rate brachytherapy, based on biological, technological, organizational and financial considerations. Copyright © 2014 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

Forbush Decrease events in Lunar Radiation Environment observed by the LRO/CRaTER

NASA Astrophysics Data System (ADS)

Sohn, J.; Oh, S.; Yi, Y.; Kim, E.; Lee, J.; Spence, H. E.

2012-12-01

The Lunar Reconnaissance Orbiter (LRO) launched on June 16, 2009 has six experiments including of the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) onboard. The CRaTER instrument characterizes the radiation environment to be experienced by humans during future lunar missions. The CRaTER instrument measures the effects of ionizing energy loss in matter specifically in silicon solid-state detectors due to penetrating solar energetic protons (SEP) and galactic cosmic rays (GCR) after interactions with tissue-equivalent plastic (TEP), a synthetic analog of human tissue. The CRaTER instrument houses a compact and highly precise microdosimeter. It measures dose rates below one micro-Rad/sec in lunar radiation environment. Forbush decrease (FD) event is the sudden decrease of galactic cosmic ray (GCR) flux. The FD event is considered to be caused by exclusion of GCR due to intense interplanetary magnetic field (IMF) structures of interplanetary shock (IP) sheath region and/or the interplanetary coronal mass ejection (CME) following the IP shocks as a shock driver. We use the data of cosmic ray flux and dose rates observed by the CRaTER instrument. We also use the CME list of STEREO SECCHI inner, outer coronagraph and the IMF (Interplanetary CME) data of the ACE/MAG instrument. We examine the origins and the characteristics of the FD-like events in lunar radiation environment. We also compare these events with the FD events on the Earth. We find that whenever the FD events are recorded at ground Neutron Monitor stations, the FD-like events also occur on the lunar environments. The flux variation amplitude of FD-like events on the Moon is approximately two times larger than that of FD events on the Earth. We compare time profiles of GCR flux with of the dose rate of FD-like events in the lunar environment. We figure out that the distinct FD-like events correspond to dose rate events in the CRaTER on lunar environment during the event period.

[The predictive value of dynamic arterial elastance in arterial pressure response after norepinephrine dosage reduction in patients with septic shock].

PubMed

Liang, F M; Yang, T; Dong, L; Hui, J J; Yan, J

2017-05-01

Objective: To assess whether dynamic arterial elastance(Ea(dyn))can be used to predict the reduction of arterial pressure after decreasing norepinephrine (NE) dosage in patients with septic shock. Methods: A prospective observational cohort study was conducted. Thirty-two patients with septic shock and mechanical ventilationwere enrolledfrom January 2014 to December 2015 in ICU of Wuxi People's Hospital of Nanjing Medical University. Hemodynamic parameters were recorded by pulse contour cardiac output(PiCCO)monitoring technology before and after decreasing norepinephrine dosage. Ea(dyn) was defined as the ratio of pulse pressure variation (PPV) to stroke volume variation (SVV). Mean arterial pressure(MAP) variation was calculated after decreasing the dose of NE. Response was defined as a ≥15% decrease of MAP. AUC was plotted to assess the value of Ea(dyn) in predicting MAP response. Results: A total of 32 patients were enrolled in our study, with 13 responding to NE dose decrease where as the other 19 did not. Ea(dyn) was lower in responders than in nonresponders (0.77±0.13 vs 1.09±0.31, P <0.05). Baseline Ea(dyn) was positively correlated with systolic blood pressure variation, diastolic blood pressure variation, systemic vascular resistance variation and MAP variation( r =0.621, P =0.000; r =0.735, P =0.000; r =0.756, P =0.000; r =0.568, P =0.000 respectively). However, stoke volume variation, baseline level of systemic vascular resistance and NE baseline dose were not correlated with Ea(dyn) baseline value( r =0.264, P =0.076; r =0.078, P =0.545; r =0.002, P =0.987 respectively). Ea(dyn)≤0.97 predicted a decrease of MAP when decreasing NE dose, with an area under the receiver-operating characteristic curve of 0.85.The sensitivity was 100.0% and specificity was 73.7%. Conclusions: In septic shock patients treated with NE, Ea(dyn) is an index to predict the decrease of arterial pressure in response to NE dose reduction.

Role of step size and max dwell time in anatomy based inverse optimization for prostate implants

PubMed Central

Manikandan, Arjunan; Sarkar, Biplab; Rajendran, Vivek Thirupathur; King, Paul R.; Sresty, N.V. Madhusudhana; Holla, Ragavendra; Kotur, Sachin; Nadendla, Sujatha

2013-01-01

In high dose rate (HDR) brachytherapy, the source dwell times and dwell positions are vital parameters in achieving a desirable implant dose distribution. Inverse treatment planning requires an optimal choice of these parameters to achieve the desired target coverage with the lowest achievable dose to the organs at risk (OAR). This study was designed to evaluate the optimum source step size and maximum source dwell time for prostate brachytherapy implants using an Ir-192 source. In total, one hundred inverse treatment plans were generated for the four patients included in this study. Twenty-five treatment plans were created for each patient by varying the step size and maximum source dwell time during anatomy-based, inverse-planned optimization. Other relevant treatment planning parameters were kept constant, including the dose constraints and source dwell positions. Each plan was evaluated for target coverage, urethral and rectal dose sparing, treatment time, relative target dose homogeneity, and nonuniformity ratio. The plans with 0.5 cm step size were seen to have clinically acceptable tumor coverage, minimal normal structure doses, and minimum treatment time as compared with the other step sizes. The target coverage for this step size is 87% of the prescription dose, while the urethral and maximum rectal doses were 107.3 and 68.7%, respectively. No appreciable difference in plan quality was observed with variation in maximum source dwell time. The step size plays a significant role in plan optimization for prostate implants. Our study supports use of a 0.5 cm step size for prostate implants. PMID:24049323

Low Dose PET Image Reconstruction with Total Variation Using Alternating Direction Method.

PubMed

Yu, Xingjian; Wang, Chenye; Hu, Hongjie; Liu, Huafeng

2016-01-01

In this paper, a total variation (TV) minimization strategy is proposed to overcome the problem of sparse spatial resolution and large amounts of noise in low dose positron emission tomography (PET) imaging reconstruction. Two types of objective function were established based on two statistical models of measured PET data, least-square (LS) TV for the Gaussian distribution and Poisson-TV for the Poisson distribution. To efficiently obtain high quality reconstructed images, the alternating direction method (ADM) is used to solve these objective functions. As compared with the iterative shrinkage/thresholding (IST) based algorithms, the proposed ADM can make full use of the TV constraint and its convergence rate is faster. The performance of the proposed approach is validated through comparisons with the expectation-maximization (EM) method using synthetic and experimental biological data. In the comparisons, the results of both LS-TV and Poisson-TV are taken into consideration to find which models are more suitable for PET imaging, in particular low-dose PET. To evaluate the results quantitatively, we computed bias, variance, and the contrast recovery coefficient (CRC) and drew profiles of the reconstructed images produced by the different methods. The results show that both Poisson-TV and LS-TV can provide a high visual quality at a low dose level. The bias and variance of the proposed LS-TV and Poisson-TV methods are 20% to 74% less at all counting levels than those of the EM method. Poisson-TV gives the best performance in terms of high-accuracy reconstruction with the lowest bias and variance as compared to the ground truth (14.3% less bias and 21.9% less variance). In contrast, LS-TV gives the best performance in terms of the high contrast of the reconstruction with the highest CRC.

Low Dose PET Image Reconstruction with Total Variation Using Alternating Direction Method

PubMed Central

Yu, Xingjian; Wang, Chenye; Hu, Hongjie; Liu, Huafeng

2016-01-01

In this paper, a total variation (TV) minimization strategy is proposed to overcome the problem of sparse spatial resolution and large amounts of noise in low dose positron emission tomography (PET) imaging reconstruction. Two types of objective function were established based on two statistical models of measured PET data, least-square (LS) TV for the Gaussian distribution and Poisson-TV for the Poisson distribution. To efficiently obtain high quality reconstructed images, the alternating direction method (ADM) is used to solve these objective functions. As compared with the iterative shrinkage/thresholding (IST) based algorithms, the proposed ADM can make full use of the TV constraint and its convergence rate is faster. The performance of the proposed approach is validated through comparisons with the expectation-maximization (EM) method using synthetic and experimental biological data. In the comparisons, the results of both LS-TV and Poisson-TV are taken into consideration to find which models are more suitable for PET imaging, in particular low-dose PET. To evaluate the results quantitatively, we computed bias, variance, and the contrast recovery coefficient (CRC) and drew profiles of the reconstructed images produced by the different methods. The results show that both Poisson-TV and LS-TV can provide a high visual quality at a low dose level. The bias and variance of the proposed LS-TV and Poisson-TV methods are 20% to 74% less at all counting levels than those of the EM method. Poisson-TV gives the best performance in terms of high-accuracy reconstruction with the lowest bias and variance as compared to the ground truth (14.3% less bias and 21.9% less variance). In contrast, LS-TV gives the best performance in terms of the high contrast of the reconstruction with the highest CRC. PMID:28005929

Dosimetric impact of cylinder size in high-dose rate vaginal cuff brachytherapy (VCBT) for primary endometrial cancer.

PubMed

Zhang, Hualin; Gopalakrishnan, Mahesh; Lee, Plato; Kang, Zhuang; Sathiaseelan, Vythialingam

2016-09-08

The purpose of this study was to evaluate the dosimetric impact of cylinder size in high-dose-rate (HDR) vaginal cuff brachytherapy (VCBT). Sample plans of HDR VCBT in a list of cylinders ranging from 2.5 to 4 cm in diameter at 0.5 cm incre-ment were created and analyzed. The doses were prescribed either at the 0.5cm depth with 5.5 Gy for 4 fractions or at the cylinder surface with 8.8 Gy for 4 frac-tions, in various treatment lengths. A 0.5 cm shell volume called PTV_Eval was contoured for each plan and served as the target volume for dosimetric evaluation. The cumulative and differential dose volume histograms (c-DVH and d-DVH), mean doses (D-mean) and the doses covering 90% (D90), 10% (D10), and 5% (D5) of PTV_Eval were calculated. In the 0.5 cm depth regimen, the DVH curves were found to have shifted toward the lower dose zone when a larger cylinder was used, but in the surface regimen the DVH curves shifted toward the higher dose zone as the cylinder size increased. The D-means of the both regimens were between 6.9 and 7.8 Gy and dependent on the cylinder size but independent of the treatment length. A 0.5 cm variation of diameter could result in a 4% change of D-mean. Average D90s were 5.7 (ranging from 5.6 to 5.8 Gy) and 6.1 Gy (from 5.7 to 6.4 Gy), respectively, for the 0.5 cm and surface regimens. Average D10 and D5 were 9.2 and 11 Gy, respectively, for the 0.5 cm depth regimen, and 8.9 and 9.7 Gy, respectively, for the surface regimen. D-mean, D90, D10, and D5 for other prescription doses could be calculated from the lookup tables of this study. Results indicated that the cylinder size has moderate dosimetric impact, and that both regimens are comparable in dosimetric quality. © 2016 The Authors.

Preparation and evaluation of unitary doses of propafenone used in children with supraventricular tachycardia: a pilot study.

PubMed

Flores Pérez, J; Ramírez Mendiola, B; Flores Pérez, C; García Álvarez, R; Juárez Olguín, H

2013-01-01

The aim was to prepare and evaluate unitary doses of propafenone (UDP) used in children with supraventricular tachycardia. UDP were prepared from four brands of tablets at doses of propafenone, 11, 25 and 90 mg, used in the Cardiology Service of this Institute. The stability of doses was determined at 20±5°C and 40°C for up to day 30. Besides, a weight variation test was performed. Plasma levels of propafenone were determined at steady state in 3 children diagnosed with supraventricular tachycardia under treatment with UDP. Concentrations of drug in blood were measured using a high pressure liquid chromatography method, previously validated. The stability of UDP, showed no significant statistical differences (p > 0.05) between doses or brands up to day 30, at both temperatures. The coefficient of variation from the weight variation was less than 6%. The plasma levels of propafenone at steady state were: patient 1, 31.57 ng/ml; patient 2, 226.46 ng/ml; and patient 3, 221.29 ng/ml. The actual administered dose for the patients could vary up to 6%, and doses prepared from different brands of tablets remain stables for up to day 30 at both temperatures. UDP is a temporal, safe and alternative option when pediatrics formulation of this drug is lacking.

Thermal Characteristics of ThermoBrachytherapy Surface Applicators (TBSA) for Treating Chestwall Recurrence

PubMed Central

Arunachalam, K.; Maccarini, P. F.; Craciunescu, O. I.; Schlorff, J. L.; Stauffer, P. R.

2010-01-01

Purpose To study temperature and thermal dose distributions of ThermoBrachytherapy Surface Applicators (TBSA) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial disease. Methods A steady state thermodynamics model coupled with the fluid dynamics of water bolus and electromagnetic radiation of hyperthermia applicator is used to characterize the temperature distributions achievable with TBSA applicators in an elliptical phantom model of the human torso. Power deposited by 915 MHz conformal microwave array (CMA) applicators is used to assess the specific absorption rate (SAR) distributions of rectangular (500 cm2) and L-shaped (875 cm2) TBSA. The SAR distribution in tissue and fluid flow distribution inside the Dual-Input Dual-Output (DIDO) water bolus are coupled to solve the steady state temperature and thermal dose distributions of rectangular TBSA (R-TBSA) for superficial tumor targets extending 10–15 mm beneath the skin surface. Thermal simulations are carried out for a range of bolus inlet temperature (Tb=38–43°C), water flow rate (Qb=2–4 L/min) and tumor blood perfusion (ωb=2–5 kg/m3/s) to characterize their influence on thermal dosimetry. Results Steady state SAR patterns of R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside tumor target sparing surrounding normal tissues and nearby critical organs. Acceptably low variation in tissue surface cooling and surface temperature homogeneity was observed for the new DIDO bolus at 2 L/min water flow rate. Temperature depth profiles and thermal dose volume histograms indicate bolus inlet temperature (Tb) to be the most influential factor on thermal dosimetry. A 42 °C water bolus was observed to be the optimal choice for superficial tumors extending 10–15 mm from the surface even under significant blood perfusion. Lower bolus temperature may be chosen to reduce thermal enhancement ratio (TER) in the most sensitive skin where maximum radiation dose is delivered and to extend thermal enhancement of radiation dose deeper. Conclusion This computational study indicates that well-localized elevation of tumor target temperature to 40–44 °C can be accomplished by large surface-conforming TBSA applicators using appropriate selection of coupling bolus temperature. PMID:20224154

Pharmacogenetic approach to losartan in Marfan patients: a starting point to improve dosing regimen?

PubMed

Falvella, Felicia Stefania; Marelli, Susan; Cheli, Stefania; Montanelli, Stefano; Viecca, Federico; Salvi, Lucia; Ferrara, Alfio; Clementi, Emilio; Trifirò, Giuliana; Pini, Alessandro

2016-09-01

Losartan is under evaluation for managing Marfan patients with aortic root dilatation. Cytochrome P450 (CYP) enzymes convert losartan to E3174 active metabolite. The aim of this study is to describe the distribution of CYP2C9*2, CYP2C9*3, CYP3A4*22 and CYP3A5*3 defective alleles, according to losartan tolerance in paediatric Marfan patients. We genotyped 53 paediatric Marfan patients treated with losartan. The rate of aortic root dilatation was evaluated using the delta z-score variation. Differences in tolerated losartan daily doses with respect to CYP metabolic classes were assessed through the Kruskal-Wallis test. The losartan daily dose spans from 0.16 to 2.50 mg/kg (median 1.10 mg/kg). As we expect from the pharmacokinetics pathway, we observe highest tolerated dose in CYP2C9 poor metabolisers (median 1.50 mg/kg, interquartile range 1.08-1.67 mg/kg); however, this difference is not statistically significant. The optimal dose of angiotensin receptor blocker is not known, and no data are available about losartan pharmacogenetic profile in Marfan syndrome; we have proposed a strategy to tackle this issue based on evaluating the major genetic polymorphisms involved in the losartan conversion into active carboxylic acid metabolite. Further studies are needed to support the use of genetic polymorphisms as predictors of the right dose of losartan.

An Economic Analysis of Bromocriptine Versus Trans-Sphenoidal Surgery for the Treatment of Prolactinoma.

PubMed

Duan, Lian; Yan, Hua; Huang, Minqiang; Zhang, Yuhui; Gu, Feng

2017-06-01

Prolactinomas account for ∼40% of all pituitary adenomas and are important causes of infertility and gonadal dysfunction. In general, most prolactinomas are treated medically with dopaminergic agonists, while surgery is reserved for patients intolerant or nonresponsive to these medications. The aim of this study was to carry out a comparative analysis of the cost-effectiveness of medical therapy with bromocriptine and surgical therapy with trans-sphenoidal surgery. A Markov model was developed based on retrospective data from 126 patients with prolactinoma treated in our hospital between October 2008 and May 2009, and from data published previously. For patients with microadenoma, the cost of medical treatment was estimated to be ¥20,555, while the cost of surgery was calculated to be ¥22,527. For patients with macroadenoma, the cost of therapy with bromocriptine was ¥31,461 in males and ¥27,178 in females, while the cost of surgery was ¥42,357 in males and ¥44,094 in females. Sensitivity analyses (carried our using variations in patient age, bromocriptine therapeutic dose, bromocriptine maintenance dose, and the success rate of bromocriptine withdrawal) indicated that our model showed good stability, although our results were most heavily influenced by variations in the bromocriptine maintenance dose. It is concluded that, from an economic viewpoint, medical therapy with bromocriptine should be the first-line treatment option for patients with prolactinoma, irrespective of whether this is a microadenoma or macroadenoma.

Low-dose cerebral perfusion computed tomography image restoration via low-rank and total variation regularizations

PubMed Central

Niu, Shanzhou; Zhang, Shanli; Huang, Jing; Bian, Zhaoying; Chen, Wufan; Yu, Gaohang; Liang, Zhengrong; Ma, Jianhua

2016-01-01

Cerebral perfusion x-ray computed tomography (PCT) is an important functional imaging modality for evaluating cerebrovascular diseases and has been widely used in clinics over the past decades. However, due to the protocol of PCT imaging with repeated dynamic sequential scans, the associative radiation dose unavoidably increases as compared with that used in conventional CT examinations. Minimizing the radiation exposure in PCT examination is a major task in the CT field. In this paper, considering the rich similarity redundancy information among enhanced sequential PCT images, we propose a low-dose PCT image restoration model by incorporating the low-rank and sparse matrix characteristic of sequential PCT images. Specifically, the sequential PCT images were first stacked into a matrix (i.e., low-rank matrix), and then a non-convex spectral norm/regularization and a spatio-temporal total variation norm/regularization were then built on the low-rank matrix to describe the low rank and sparsity of the sequential PCT images, respectively. Subsequently, an improved split Bregman method was adopted to minimize the associative objective function with a reasonable convergence rate. Both qualitative and quantitative studies were conducted using a digital phantom and clinical cerebral PCT datasets to evaluate the present method. Experimental results show that the presented method can achieve images with several noticeable advantages over the existing methods in terms of noise reduction and universal quality index. More importantly, the present method can produce more accurate kinetic enhanced details and diagnostic hemodynamic parameter maps. PMID:27440948

Characterization of optically stimulated luminescence dosemeters to measure organ doses in diagnostic radiology

PubMed Central

Endo, A; Katoh, T; Kobayashi, I; Joshi, R; Sur, J; Okano, T

2012-01-01

Objective The aim of this study was to assess the characteristics of an optically stimulated luminescence dosemeter (OSLD) for use in diagnostic radiology and to apply the OSLD in measuring the organ doses by panoramic radiography. Methods The dose linearity, energy dependency and angular dependency of aluminium oxide-based OSLDs were examined using an X-ray generator to simulate various exposure settings in diagnostic radiology. The organ doses were then measured by inserting the dosemeters into an anthropomorphic phantom while using three panoramic machines. Results The dosemeters demonstrated consistent dose linearity (coefficient of variation<1.5%) and no significant energy dependency (coefficient of variation<1.5%) under the applied exposure conditions. They also exhibited negligible angular dependency (≤10%). The organ doses of the X-ray as a result of panoramic imaging by three machines were calculated using the dosemeters. Conclusion OSLDs can be utilized to measure the organ doses in diagnostic radiology. The availability of these dosemeters in strip form proves to be reliably advantageous. PMID:22116136

Skin dose measurements using MOSFET and TLD for head and neck patients treated with tomotherapy.

PubMed

Kinhikar, Rajesh A; Murthy, Vedang; Goel, Vineeta; Tambe, Chandrashekar M; Dhote, Dipak S; Deshpande, Deepak D

2009-09-01

The purpose of this work was to estimate skin dose for the patients treated with tomotherapy using metal oxide semiconductor field-effect transistors (MOSFETs) and thermoluminescent dosimeters (TLDs). In vivo measurements were performed for two head and neck patients treated with tomotherapy and compared to TLD measurements. The measurements were subsequently carried out for five days to estimate the inter-fraction deviations in MOSFET measurements. The variation between skin dose measured with MOSFET and TLD for first patient was 2.2%. Similarly, the variation of 2.3% was observed between skin dose measured with MOSFET and TLD for second patient. The tomotherapy treatment planning system overestimated the skin dose as much as by 10-12% when compared to both MOSFET and TLD. However, the MOSFET measured patient skin doses also had good reproducibility, with inter-fraction deviations ranging from 1% to 1.4%. MOSFETs may be used as a viable dosimeter for measuring skin dose in areas where the treatment planning system may not be accurate.

Radiation resistance of elastomeric O-rings in mixed neutron and gamma fields: Testing methodology and experimental results

NASA Astrophysics Data System (ADS)

Zenoni, A.; Bignotti, F.; Donzella, A.; Donzella, G.; Ferrari, M.; Pandini, S.; Andrighetto, A.; Ballan, M.; Corradetti, S.; Manzolaro, M.; Monetti, A.; Rossignoli, M.; Scarpa, D.; Alloni, D.; Prata, M.; Salvini, A.; Zelaschi, F.

2017-11-01

Materials and components employed in the presence of intense neutron and gamma fields are expected to absorb high dose levels that may induce deep modifications of their physical and mechanical properties, possibly causing loss of their function. A protocol for irradiating elastomeric materials in reactor mixed neutron and gamma fields and for testing the evolution of their main mechanical and physical properties with absorbed dose has been developed. Four elastomeric compounds used for vacuum O-rings, one fluoroelastomer polymer (FPM) based and three ethylene propylene diene monomer rubber (EPDM) based, presently available on the market have been selected for the test. One EPDM is rated as radiation resistant in gamma fields, while the other elastomers are general purpose products. Particular care has been devoted to dosimetry calculations, since absorbed dose in neutron fields, unlike pure gamma fields, is strongly dependent on the material composition and, in particular, on the hydrogen content. The products have been tested up to about 2 MGy absorbed dose. The FPM based elastomer, in spite of its lower dose absorption in fast neutron fields, features the largest variations of properties, with a dramatic increase in stiffness and brittleness. Out of the three EPDM based compounds, one shows large and rapid changes in the main mechanical properties, whereas the other two feature more stable behaviors. The performance of the EPDM rated as radiation resistant in pure gamma fields does not appear significantly better than that of the standard product. The predictive capability of the accelerated irradiation tests performed as well as the applicable concepts of threshold of radiation damage is discussed in view of the use of the examined products in the selective production of exotic species facility, now under construction at the Legnaro National Laboratories of the Italian Istituto Nazionale di Fisica Nucleare. It results that a careful account of dose rate effects and oxygen penetration in the material, both during test irradiations and in operating conditions, is needed to obtain reliable predictions.

Radiation resistance of elastomeric O-rings in mixed neutron and gamma fields: Testing methodology and experimental results.

PubMed

Zenoni, A; Bignotti, F; Donzella, A; Donzella, G; Ferrari, M; Pandini, S; Andrighetto, A; Ballan, M; Corradetti, S; Manzolaro, M; Monetti, A; Rossignoli, M; Scarpa, D; Alloni, D; Prata, M; Salvini, A; Zelaschi, F

2017-11-01

Materials and components employed in the presence of intense neutron and gamma fields are expected to absorb high dose levels that may induce deep modifications of their physical and mechanical properties, possibly causing loss of their function. A protocol for irradiating elastomeric materials in reactor mixed neutron and gamma fields and for testing the evolution of their main mechanical and physical properties with absorbed dose has been developed. Four elastomeric compounds used for vacuum O-rings, one fluoroelastomer polymer (FPM) based and three ethylene propylene diene monomer rubber (EPDM) based, presently available on the market have been selected for the test. One EPDM is rated as radiation resistant in gamma fields, while the other elastomers are general purpose products. Particular care has been devoted to dosimetry calculations, since absorbed dose in neutron fields, unlike pure gamma fields, is strongly dependent on the material composition and, in particular, on the hydrogen content. The products have been tested up to about 2 MGy absorbed dose. The FPM based elastomer, in spite of its lower dose absorption in fast neutron fields, features the largest variations of properties, with a dramatic increase in stiffness and brittleness. Out of the three EPDM based compounds, one shows large and rapid changes in the main mechanical properties, whereas the other two feature more stable behaviors. The performance of the EPDM rated as radiation resistant in pure gamma fields does not appear significantly better than that of the standard product. The predictive capability of the accelerated irradiation tests performed as well as the applicable concepts of threshold of radiation damage is discussed in view of the use of the examined products in the selective production of exotic species facility, now under construction at the Legnaro National Laboratories of the Italian Istituto Nazionale di Fisica Nucleare. It results that a careful account of dose rate effects and oxygen penetration in the material, both during test irradiations and in operating conditions, is needed to obtain reliable predictions.

Can a Compact Pre-Filled Auto-Disable Injection System (cPAD) Save Costs for DTP-HepB-Hib Vaccine as Compared with Single-Dose (SDV) and Multi-Dose Vials (MDV)? Evidence from Cambodia, Ghana, and Peru.

PubMed

Nogier, Cyril; Hanlon, Patrick; Wiedenmayer, Karin; Maire, Nicolas

2015-03-01

A compact pre-filled auto-disable injection (cPAD) presentation is being developed for the fully liquid pentavalent DTP-HepB-Hib vaccine. A cost analysis (CA) to compare this presentation with the presently used single-dose vial (SDV) and multi-dose vial (MDV) was conducted in Cambodia, Ghana, and Peru. The CA included the development of an excel-based costing model and considered the costs of vaccine, safe injection equipment, procurement, storage, transport and distribution, vaccine administration by health staff, medical waste management, start-up activities, as well as coverage, birth cohort, vaccine, and safe injection equipment wastage rates. The outcome was the change in cost per pentavalent fully immunized child (PFIC) for a switch to cPAD. Field visits to health facilities, and interviews with key informants from immunization services and regulatory authorities, were conducted to collect data and to test the costing model in country context. Cost data were also obtained from manufacturers, published price lists, and author estimates. A sensitivity analysis (SA) was conducted to explore possible variations in values of data collected. Based on vaccine price trends estimated for 2016, cPAD is less costly in Ghana [incremental cost per PFIC: $US-0.59 (-6.46 %)] than the current presentation (ten-dose MDV) and in Peru (SDV): $US-0.89 (-7.14 %). In Cambodia, cPAD is more costly than SDV: $US+0.33 (+3.90 %). The most significant cost item per PFIC is the vaccine (reflecting wastage rates) in all presentations. The dominance of the vaccine price per dose and, to a lesser extent, the wastage rates in the incremental cost per PFIC show potential to simplify future analyses. Other relevant considerations at country level for a change of presentation include the potential for improved safety with cPAD, planned introduction of other vaccines, environmental and safety issues, and financial sustainability.

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

TU-G-BRB-03: Iterative Optimization of Normalized Transmission Maps for IMRT Using Arbitrary Beam Profiles.

PubMed

Choi, K; Suh, T; Xing, L

2012-06-01

Newly available flattening filter free (FFF) beam increases the dose rate by 3∼6 times at the central axis. In reality, even flattening filtered beam is not perfectly flat. In addition, the beam profiles across different fields may not have the same amplitude. The existing inverse planning formalism based on the total-variation of intensity (or fluence) map cannot consider these properties of beam profiles. The purpose of this work is to develop a novel dose optimization scheme with incorporation of the inherent beam profiles to maximally utilize the efficacy of arbitrary beam profiles while preserving the convexity of the optimization problem. To increase the accuracy of the problem formalism, we decompose the fluence map as an elementwise multiplication of the inherent beam profile and a normalized transmission map (NTM). Instead of attempting to optimize the fluence maps directly, we optimize the NTMs and beam profiles separately. A least-squares problem constrained by total-variation of NTMs is developed to derive the optimal fluence maps that balances the dose conformality and FFF beam delivery efficiency. With the resultant NTMs, we find beam profiles to renormalized NTMs. The proposed method iteratively optimizes and renormalizes NTMs in a closed loop manner. The advantage of the proposed method is demonstrated by using a head-neck case with flat beam profiles and a prostate case with non-flat beam profiles. The obtained NTMs achieve more conformal dose distribution while preserving piecewise constancy compared to the existing solution. The proposed formalism has two major advantages over the conventional inverse planning schemes: (1) it provides a unified framework for inverse planning with beams of arbitrary fluence profiles, including treatment with beams of mixed fluence profiles; (2) the use of total-variation constraints on NTMs allows us to optimally balance the dose confromality and deliverability for a given beam configuration. This project was supported in part by grants from the National Science Foundation (0854492), National Cancer Institute (1R01 CA104205), and Leading Foreign Research Institute Recruitment Program by the Korean Ministry of Education, Science and Technology (K20901000001-09E0100-00110). To the authors' best knowledgement, there is no conflict interest. © 2012 American Association of Physicists in Medicine.

The feasibility of a scanner-independent technique to estimate organ dose from MDCT scans: Using CTDI{sub vol} to account for differences between scanners

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

Turner, Adam C.; Zankl, Maria; DeMarco, John J.

2010-04-15

Purpose: Monte Carlo radiation transport techniques have made it possible to accurately estimate the radiation dose to radiosensitive organs in patient models from scans performed with modern multidetector row computed tomography (MDCT) scanners. However, there is considerable variation in organ doses across scanners, even when similar acquisition conditions are used. The purpose of this study was to investigate the feasibility of a technique to estimate organ doses that would be scanner independent. This was accomplished by assessing the ability of CTDI{sub vol} measurements to account for differences in MDCT scanners that lead to organ dose differences. Methods: Monte Carlo simulationsmore » of 64-slice MDCT scanners from each of the four major manufacturers were performed. An adult female patient model from the GSF family of voxelized phantoms was used in which all ICRP Publication 103 radiosensitive organs were identified. A 120 kVp, full-body helical scan with a pitch of 1 was simulated for each scanner using similar scan protocols across scanners. From each simulated scan, the radiation dose to each organ was obtained on a per mA s basis (mGy/mA s). In addition, CTDI{sub vol} values were obtained from each scanner for the selected scan parameters. Then, to demonstrate the feasibility of generating organ dose estimates from scanner-independent coefficients, the simulated organ dose values resulting from each scanner were normalized by the CTDI{sub vol} value for those acquisition conditions. Results: CTDI{sub vol} values across scanners showed considerable variation as the coefficient of variation (CoV) across scanners was 34.1%. The simulated patient scans also demonstrated considerable differences in organ dose values, which varied by up to a factor of approximately 2 between some of the scanners. The CoV across scanners for the simulated organ doses ranged from 26.7% (for the adrenals) to 37.7% (for the thyroid), with a mean CoV of 31.5% across all organs. However, when organ doses are normalized by CTDI{sub vol} values, the differences across scanners become very small. For the CTDI{sub vol}, normalized dose values the CoVs across scanners for different organs ranged from a minimum of 2.4% (for skin tissue) to a maximum of 8.5% (for the adrenals) with a mean of 5.2%. Conclusions: This work has revealed that there is considerable variation among modern MDCT scanners in both CTDI{sub vol} and organ dose values. Because these variations are similar, CTDI{sub vol} can be used as a normalization factor with excellent results. This demonstrates the feasibility of establishing scanner-independent organ dose estimates by using CTDI{sub vol} to account for the differences between scanners.« less

Repeatability of dose painting by numbers treatment planning in prostate cancer radiotherapy based on multiparametric magnetic resonance imaging

NASA Astrophysics Data System (ADS)

van Schie, Marcel A.; Steenbergen, Peter; Viet Dinh, Cuong; Ghobadi, Ghazaleh; van Houdt, Petra J.; Pos, Floris J.; Heijmink, Stijn W. T. J. P.; van der Poel, Henk G.; Renisch, Steffen; Vik, Torbjørn; van der Heide, Uulke A.

2017-07-01

Dose painting by numbers (DPBN) refers to a voxel-wise prescription of radiation dose modelled from functional image characteristics, in contrast to dose painting by contours which requires delineations to define the target for dose escalation. The direct relation between functional imaging characteristics and DPBN implies that random variations in images may propagate into the dose distribution. The stability of MR-only prostate cancer treatment planning based on DPBN with respect to these variations is as yet unknown. We conducted a test-retest study to investigate the stability of DPBN for prostate cancer in a semi-automated MR-only treatment planning workflow. Twelve patients received a multiparametric MRI on two separate days prior to prostatectomy. The tumor probability (TP) within the prostate was derived from image features with a logistic regression model. Dose mapping functions were applied to acquire a DPBN prescription map that served to generate an intensity modulated radiation therapy (IMRT) treatment plan. Dose calculations were done on a pseudo-CT derived from the MRI. The TP and DPBN map and the IMRT dose distribution were compared between both MRI sessions, using the intraclass correlation coefficient (ICC) to quantify repeatability of the planning pipeline. The quality of each treatment plan was measured with a quality factor (QF). Median ICC values for the TP and DPBN map and the IMRT dose distribution were 0.82, 0.82 and 0.88, respectively, for linear dose mapping and 0.82, 0.84 and 0.94 for square root dose mapping. A median QF of 3.4% was found among all treatment plans. We demonstrated the stability of DPBN radiotherapy treatment planning in prostate cancer, with excellent overall repeatability and acceptable treatment plan quality. Using validated tumor probability modelling and simple dose mapping techniques it was shown that despite day-to-day variations in imaging data still consistent treatment plans were obtained.

Metabolism and pathophysiology of sodium and chlorine in tissue after neutron irradiation.

PubMed

Koester, L; Knopf, K; Auberger, T

1994-01-01

The photon emission of tissue was measured after radiotherapy with various doses of fission neutrons. Spectral analyses of the decay rates resulted in data for the exchange of sodium and chlorine between the irradiated tissue and the whole body. In 12 cases we found that about three fifths of Na and Cl exchange rapidly between the extravascular and vascular liquids with a turnover half-life of 13 +/- 2 min. Slowly exchangeable or non-exchangeable fractions are deposited in the soft tissue. New defined mass exchange rates for Na and Cl amount to an average of 0.8 mval min-1 kg-1 of soft tissue. The turnover of the electrolytes in tissue with large tumours is about twice that in tissues with small metastasis. Depending on dose, radiotherapy led in all cases to distinct variations of the metabolism. A maximum of the exchange of Cl combined with a minimum of Na occurs at about 85 Gy of conventional or at 10 Gy of lead-filtered fission neutron radiation. These results show directly for the first time the local response of the electrolyte metabolism to therapy.

Assessment of the Survival of Dental Implants in Irradiated Jaws Following Treatment of Oral Cancer: A Retrospective Study

PubMed Central

Rana, Meenakshi Chauhan; Solanki, Swati; Pujari, Sudarshan C; Shaw, Eisha; Sharma, Swati; Anand, Abhishek; Singh, Harkanwal Preet

2016-01-01

Background: In patients undergoing head and neck surgery for various pathologic conditions, implants are one of the best restorative options and are increasing widely used. Therefore, we evaluated the success of dental implants in the irradiated jaws of patients following treatment of oral cancer oral cancer treated patients. Materials and Methods: Data of oral cancer treated patients was collected retrospectively from 2002 to 2008. We took 46 oral cancer treated patients in which implants were placed in irradiated jaws for rehabilitation. Results: It was found that out of 162 dental implants placed, 52 failed. Furthermore, there was no variation in the implant survival rate in between both the jaws. Radiation dose of <50 Gy units also showed significantly increased amount of implant survival rate. Conclusions: Implant survival is multifactorial and depends upon a number of factors like level of radiation exposure in that area, time gap between last radiation doses etc., Further research is required in this field to improve the esthetics and quality of life of cancer treated patients. PMID:27843270

Fine structure of the absorbed dose rate monitored in Zagreb, Croatia, in the period 1985-2011.

PubMed

Babić, D; Senčar, J; Petrinec, B; Marović, G; Bituh, T; Skoko, B

2013-04-01

We report on the fine structure of the absorbed dose rate D which was measured and recorded on a daily basis at the Institute for Medical Research and Occupational Health in Zagreb, Croatia, throughout the period 1985-2011. After the Chernobyl accident, D increased steeply by a factor of 3.5, but this is the only prominent feature in the D versus time (t) curve. In the absence of accidental conditions, the D(t) is flat and amounts to 30-35 pGy/s. Despite the apparent plainness of D(t), its Fourier transform reveals several periodic modulations hidden in the noise. Some of the corresponding periods (6 and 12 months) can be related to seasonal atmospheric changes but this is not the case with the other periods identified (9.3, 13.7, 15.7, 20, 31, and 39 months). These are found to agree well with literature data on periodicities in solar activity, which implies that they are most probably linked to variations in the atmospheric production of (7)Be by cosmic rays. Copyright © 2012 Elsevier Ltd. All rights reserved.

Radiation measurements on the Mir Orbital Station.

PubMed

Badhwar, G D; Atwell, W; Reitz, G; Beaujean, R; Heinrich, W

2002-10-01

Radiation measurements made onboard the MIR Orbital Station have spanned nearly a decade and covered two solar cycles, including one of the largest solar particle events, one of the largest magnetic storms, and a mean solar radio flux level reaching 250 x 10(4) Jansky that has been observed in the last 40 years. The cosmonaut absorbed dose rates varied from about 450 microGy day-1 during solar minimum to approximately half this value during the last solar maximum. There is a factor of about two in dose rate within a given module, and a similar variation from module to module. The average radiation quality factor during solar minimum, using the ICRP-26 definition, was about 2.4. The drift of the South Atlantic Anomaly was measured to be 6.0 +/- 0.5 degrees W, and 1.6 +/- 0.5 degrees N. These measurements are of direct applicability to the International Space Station. This paper represents a comprehensive review of Mir Space Station radiation data available from a variety of sources. c2002 Elsevier Science Ltd. All rights reserved.

Radiological impact of natural radioactivity in Egyptian phosphate rocks, phosphogypsum and phosphate fertilizers.

PubMed

El-Bahi, S M; Sroor, A; Mohamed, Gehan Y; El-Gendy, N S

2017-05-01

In this study, the activity concentrations of the natural radionuclides in phosphate rocks and its products were measured using a high- purity germanium detector (HPGe). The obtained activity results show remarkable wide variation in the radioactive contents for the different phosphate samples. The average activity concentration of 235 U, 238 U, 226 Ra, 232 Th and 40 K was found as (45, 1031, 786, 85 and 765Bq/kg) for phosphate rocks, (28, 1234, 457, 123 and 819Bq/kg) for phosphate fertilizers, (47, 663, 550, 79 and 870Bq/kg) for phosphogypsum and (25, 543, 409, 54 and 897Bq/kg) for single super phosphate respectively. Based on the measured activities, the radiological parameters (activity concentration index, absorbed gamma dose rate in outdoor and indoor and the corresponding annual effective dose rates and total excess lifetime cancer risk) were estimated to assess the radiological hazards. The total excess lifetime cancer risk (ELCR) has been calculated and found to be high in all samples, which related to high radioactivity, representing radiological risk for the health of the population. Copyright © 2017 Elsevier Ltd. All rights reserved.

ELDRS Characterization for a Very High Dose Mission

NASA Technical Reports Server (NTRS)

Harris, Richard D.; McClure, Steven S.; Rax, Bernard G.; Kenna, Aaron J.; Thorbourn, Dennis O.; Clark, Karla B.; Yan, Tsun-Yee

2010-01-01

Evaluation of bipolar linear parts which may have Enhanced Low Dose Rate Sensitivity (ELDRS) is problematic for missions that have very high dose radiation requirements. The accepted standards for evaluating parts that display ELDRS require testing at a very low dose rate which could be prohibitively long for very high dose missions. In this work, a methodology for ELDRS characterization of bipolar parts for mission doses up to 1 Mrad(Si) is evaluated. The procedure employs an initial dose rate of 0.01 rad(Si)/s to a total dose of 50 krad(Si) and then changes to 0.04 rad(Si)/s to a total dose of 1 Mrad(Si). This procedure appears to work well. No change in rate of degradation with dose has been observed when the dose rate is changed from 0.01 to 0.04 rad(Si)/s. This is taken as an indication that the degradation due to the higher dose rate is equivalent to that at the lower dose rate at the higher dose levels, at least for the parts studied to date. In several cases, significant parameter degradation or functional failure not observed at HDR was observed at fairly high total doses (50 to 250 krad(Si)) at LDR. This behavior calls into question the use of dose rate trend data and enhancement factors to predict LDR performance.

Characterisation of a plastic scintillation detector to be used in a multicentre stereotactic radiosurgery dosimetry audit

NASA Astrophysics Data System (ADS)

Dimitriadis, A.; Patallo, I. Silvestre; Billas, I.; Duane, S.; Nisbet, A.; Clark, C. H.

2017-11-01

Scintillation detectors are considered highly suitable for dosimetric measurement of small fields in radiotherapy due to their near-tissue equivalence and their small size. A commercially available scintillation detector, the Exradin W1 (Standard Imaging, Middleton, USA), has been previously characterised by two independent studies (Beierholm et al., 2014; Carrasco et al., 2015a, 2015b) but the results from these publications differed in some aspects (e.g. energy dependence, long term stability). The respective authors highlighted the need for more studies to be published (Beierholm et al., 2015; Carrasco et al., 2015a, 2015b). In this work, the Exradin W1 was characterised in terms of dose response, dependence on dose rate, energy, temperature and angle of irradiation, and long-term stability. The observed dose linearity, short-term repeatability and temperature dependence were in good agreement with previously published data. Appropriate corrections should therefore be applied, where possible, in order to achieve measurements with low-uncertainty. The angular dependence was characterised along both the symmetrical and polar axis of the detector for the first time in this work and a dose variation of up to 1% was observed. The response of the detector was observed to decrease at a rate of approximately 1.6% kGy-1 for the first 5 kGy delivered, and then stabilised to 0.2% kGy-1 in the subsequent 20 kGy. The main goal of this work was to assess the suitability of the Exradin W1 for use in dose verification measurements for stereotactic radiosurgery. The results obtained confirm that the detector is suitable for use in such situations. The detector is now utilised in a multi-centre stereotactic radiosurgery dosimetric audit, with the application of appropriate correction factors.

Quality Control of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control

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

Able, Charles M., E-mail: cable@wfubmc.edu; Bright, Megan; Frizzell, Bart

Purpose: Statistical process control (SPC) is a quality control method used to ensure that a process is well controlled and operates with little variation. This study determined whether SPC was a viable technique for evaluating the proper operation of a high-dose-rate (HDR) brachytherapy treatment delivery system. Methods and Materials: A surrogate prostate patient was developed using Vyse ordnance gelatin. A total of 10 metal oxide semiconductor field-effect transistors (MOSFETs) were placed from prostate base to apex. Computed tomography guidance was used to accurately position the first detector in each train at the base. The plan consisted of 12 needles withmore » 129 dwell positions delivering a prescribed peripheral dose of 200 cGy. Sixteen accurate treatment trials were delivered as planned. Subsequently, a number of treatments were delivered with errors introduced, including wrong patient, wrong source calibration, wrong connection sequence, single needle displaced inferiorly 5 mm, and entire implant displaced 2 mm and 4 mm inferiorly. Two process behavior charts (PBC), an individual and a moving range chart, were developed for each dosimeter location. Results: There were 4 false positives resulting from 160 measurements from 16 accurately delivered treatments. For the inaccurately delivered treatments, the PBC indicated that measurements made at the periphery and apex (regions of high-dose gradient) were much more sensitive to treatment delivery errors. All errors introduced were correctly identified by either the individual or the moving range PBC in the apex region. Measurements at the urethra and base were less sensitive to errors. Conclusions: SPC is a viable method for assessing the quality of HDR treatment delivery. Further development is necessary to determine the most effective dose sampling, to ensure reproducible evaluation of treatment delivery accuracy.« less

Characteristics of mobile MOSFET dosimetry system for megavoltage photon beams

PubMed Central

Kumar, A. Sathish; Sharma, S. D.; Ravindran, B. Paul

2014-01-01

The characteristics of a mobile metal oxide semiconductor field effect transistor (mobile MOSFET) detector for standard bias were investigated for megavoltage photon beams. This study was performed with a brass alloy build-up cap for three energies namely Co-60, 6 and 15 MV photon beams. The MOSFETs were calibrated and the performance characteristics were analyzed with respect to dose rate dependence, energy dependence, field size dependence, linearity, build-up factor, and angular dependence for all the three energies. A linear dose-response curve was noted for Co-60, 6 MV, and 15 MV photons. The calibration factors were found to be 1.03, 1, and 0.79 cGy/mV for Co-60, 6 MV, and 15 MV photon energies, respectively. The calibration graph has been obtained to the dose up to 600 cGy, and the dose-response curve was found to be linear. The MOSFETs were found to be energy independent both for measurements performed at depth as well as on the surface with build-up. However, field size dependence was also analyzed for variable field sizes and found to be field size independent. Angular dependence was analyzed by keeping the MOSFET dosimeter in parallel and perpendicular orientation to the angle of incidence of the radiation with and without build-up on the surface of the phantom. The maximum variation for the three energies was found to be within ± 2% for the gantry angles 90° and 270°, the deviations without the build-up for the same gantry angles were found to be 6%, 25%, and 60%, respectively. The MOSFET response was found to be independent of dose rate for all three energies. The dosimetric characteristics of the MOSFET detector make it a suitable in vivo dosimeter for megavoltage photon beams. PMID:25190992

WE-E-BRE-03: Biological Validation of a Novel High-Throughput Irradiator for Predictive Radiation Sensitivity Bioassays

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

Fowler, TL; Martin, JA; Shepard, AJ

2014-06-15

Purpose: The large dose-response variation in both tumor and normal cells between individual patients has led to the recent implementation of predictive bioassays of patient-specific radiation sensitivity in order to personalize radiation therapy. This exciting new clinical paradigm has led us to develop a novel high-throughput, variable dose-rate irradiator to accompany these efforts. Here we present the biological validation of this irradiator through the use of human cells as a relative dosimeter assessed by two metrics, DNA double-strand break repair pathway modulation and intercellular reactive oxygen species production. Methods: Immortalized human tonsilar epithelial cells were cultured in 96-well micro titermore » plates and irradiated in groups of eight wells to absorbed doses of 0, 0.5, 1, 2, 4, and 8 Gy. High-throughput immunofluorescent microscopy was used to detect γH2AX, a DNA double-strand break repair mechanism recruiter. The same analysis was performed with the cells stained with CM-H2DCFDA that produces a fluorescent adduct when exposed to reactive oxygen species during the irradiation cycle. Results: Irradiations of the immortalized human tonsilar epithelial cells at absorbed doses of 0, 0.5, 1, 2, 4, and 8 Gy produced excellent linearity in γH2AX and CM-H2DCFDA with R2 values of 0.9939 and 0.9595 respectively. Single cell gel electrophoresis experimentation for the detection of physical DNA double-strand breaks in ongoing. Conclusions: This work indicates significant potential for our high-throughput variable dose rate irradiator for patient-specific predictive radiation sensitivity bioassays. This irradiator provides a powerful tool by increasing the efficiency and number of assay techniques available to help personalize radiation therapy.« less

A protective role of HSP90 chaperone in gamma-irradiated Arabidopsis thaliana seeds

NASA Astrophysics Data System (ADS)

Kozeko, Liudmyla; Talalaiev, Oleksandr; Neimash, Volodymyr; Povarchuk, Vasyl

2015-07-01

The heat shock protein 90 (HSP90) is required for the maturation and conformational regulation of many regulatory proteins affecting morphogenetic pathways and stress tolerance. The purpose of this work is to disclose a role of HSP90 in radioresistance of seeds. Arabidopsis thaliana (Ler) seeds were exposed to γ-ray irradiation with doses of 0.1-1 kGy using 60Co source to obtain a viable but polymorphic material. A comet assay of the seeds showed a dose-dependent increase in DNA damage. Phenotypic consequences of irradiation included growth stimulation at doses of 0.1-0.25 kGy and negative growth effects at doses from 0.5 kGy and beyond, along with increasing heterogeneity of seedling growth rate and phenotype. The frequencies of abnormal phenotypes were highly correlated with the degree of DNA damage in seeds. Treatment of seeds with geldanamycin (GDA), an inhibitor of HSP90, stimulated the seedling growth at all radiation doses and, at the same time, enhanced the growth rate and morphological diversity. It was also found that HSP70 induction by γ-rays was increased following GDA treatment (shown at 1 kGy). We suppose that the GDA-induced HSP70 can be involved in elimination of detrimental radiation effects that ultimately results in growth stimulation. On the other hand, the increase in phenotypic variation, when HSP90 function was impaired, confirms the supposition that the chaperone may control the concealment of cryptic genetic alterations and the developmental stability. In general, these results demonstrate that HSP90 may interface the stress response and phenotypic expression of genetic alterations induced by irradiation.

Characteristics of mobile MOSFET dosimetry system for megavoltage photon beams.

PubMed

Kumar, A Sathish; Sharma, S D; Ravindran, B Paul

2014-07-01

The characteristics of a mobile metal oxide semiconductor field effect transistor (mobile MOSFET) detector for standard bias were investigated for megavoltage photon beams. This study was performed with a brass alloy build-up cap for three energies namely Co-60, 6 and 15 MV photon beams. The MOSFETs were calibrated and the performance characteristics were analyzed with respect to dose rate dependence, energy dependence, field size dependence, linearity, build-up factor, and angular dependence for all the three energies. A linear dose-response curve was noted for Co-60, 6 MV, and 15 MV photons. The calibration factors were found to be 1.03, 1, and 0.79 cGy/mV for Co-60, 6 MV, and 15 MV photon energies, respectively. The calibration graph has been obtained to the dose up to 600 cGy, and the dose-response curve was found to be linear. The MOSFETs were found to be energy independent both for measurements performed at depth as well as on the surface with build-up. However, field size dependence was also analyzed for variable field sizes and found to be field size independent. Angular dependence was analyzed by keeping the MOSFET dosimeter in parallel and perpendicular orientation to the angle of incidence of the radiation with and without build-up on the surface of the phantom. The maximum variation for the three energies was found to be within ± 2% for the gantry angles 90° and 270°, the deviations without the build-up for the same gantry angles were found to be 6%, 25%, and 60%, respectively. The MOSFET response was found to be independent of dose rate for all three energies. The dosimetric characteristics of the MOSFET detector make it a suitable in vivo dosimeter for megavoltage photon beams.

Dose rate effects in the radiation damage of the plastic scintillators of the CMS hadron endcap calorimeter

DOE PAGES

Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; ...

2016-10-07

We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. Here, we show that the scaling with dose rate is consistent with that expected from diffusion effects.

Real-Time Variable Rate Spraying in Orchards and Vineyards: A Review

NASA Astrophysics Data System (ADS)

Wandkar, Sachin Vilas; Bhatt, Yogesh Chandra; Jain, H. K.; Nalawade, Sachin M.; Pawar, Shashikant G.

2018-06-01

Effective and efficient use of pesticides in the orchards is of concern since many years. With the conventional constant rate sprayers, equal dose of pesticide is applied to each tree. Since, there is great variation in size and shape of each tree in the orchard, trees gets either oversprayed or undersprayed. Real-time variable rate spraying technology offers pesticide application in accordance with tree size. With the help of suitable sensors, tree characteristics such as canopy volume, foliage density, etc. can be acquired and with the micro-processing unit coupled with proper algorithm, flow of electronic proportional valves can be controlled thus, controlling the flow rate of nozzles according to tree characteristics. Also, sensors can help in the detection of spaces in-between trees which allows to control the spray in spaces. Variable rate spraying helps in achieving precision in spraying operation especially inside orchards. This paper reviews the real-time variable rate spraying technology and efforts made by the various researchers for real-time variable application in the orchards and vineyards.

Real-Time Variable Rate Spraying in Orchards and Vineyards: A Review

NASA Astrophysics Data System (ADS)

Wandkar, Sachin Vilas; Bhatt, Yogesh Chandra; Jain, H. K.; Nalawade, Sachin M.; Pawar, Shashikant G.

2018-02-01

Effective and efficient use of pesticides in the orchards is of concern since many years. With the conventional constant rate sprayers, equal dose of pesticide is applied to each tree. Since, there is great variation in size and shape of each tree in the orchard, trees gets either oversprayed or undersprayed. Real-time variable rate spraying technology offers pesticide application in accordance with tree size. With the help of suitable sensors, tree characteristics such as canopy volume, foliage density, etc. can be acquired and with the micro-processing unit coupled with proper algorithm, flow of electronic proportional valves can be controlled thus, controlling the flow rate of nozzles according to tree characteristics. Also, sensors can help in the detection of spaces in-between trees which allows to control the spray in spaces. Variable rate spraying helps in achieving precision in spraying operation especially inside orchards. This paper reviews the real-time variable rate spraying technology and efforts made by the various researchers for real-time variable application in the orchards and vineyards.

Wearable glass beads for in vivo dosimetry of total skin electron irradiation treatments

NASA Astrophysics Data System (ADS)

Nabankema, S. K.; Jafari, S. M.; Peet, S. C.; Binny, D.; Sylvander, S. R.; Crowe, S. B.

2017-11-01

Glass beads have recently been proposed for use as radiation therapy dosimeters. Glass beads have a number of characteristics that make them suitable for in vivo skin dose measurements, including an ability to be worn on a string, and therefore avoid possible patient discomfort that may result from the use of adhesives. In this study, their use for in vivo dose measurements in total skin electron irradiation treatments has been tested. First, the dosimetric properties of cylindrical beads with a 3 mm diameter were characterised using electron fields produced by a linear accelerator. The mean individual bead reproducibility was demonstrated to be within 3%; and a batch variation of 7% was observed. The beads were shown to have a linear dose response, and both dose rate and beam energy independence, within the measurement uncertainty. Phantom measurements were then performed for a total skin electron irradiation beam arrangement, and results compared against optically stimulated luminescent dosimeters at five anatomical sites. For a majority of measurement locations, agreement within 3% was observed between the two dosimetry techniques, demonstrating the feasibility of glass beads as in vivo dosimeters for total skin electron irradiation; though further investigation may be needed to minimise uncertainty in results.

Accurate low-dose iterative CT reconstruction from few projections by Generalized Anisotropic Total Variation minimization for industrial CT.

PubMed

Debatin, Maurice; Hesser, Jürgen

2015-01-01

Reducing the amount of time for data acquisition and reconstruction in industrial CT decreases the operation time of the X-ray machine and therefore increases the sales. This can be achieved by reducing both, the dose and the pulse length of the CT system and the number of projections for the reconstruction, respectively. In this paper, a novel generalized Anisotropic Total Variation regularization for under-sampled, low-dose iterative CT reconstruction is discussed and compared to the standard methods, Total Variation, Adaptive weighted Total Variation and Filtered Backprojection. The novel regularization function uses a priori information about the Gradient Magnitude Distribution of the scanned object for the reconstruction. We provide a general parameterization scheme and evaluate the efficiency of our new algorithm for different noise levels and different number of projection views. When noise is not present, error-free reconstructions are achievable for AwTV and GATV from 40 projections. In cases where noise is simulated, our strategy achieves a Relative Root Mean Square Error that is up to 11 times lower than Total Variation-based and up to 4 times lower than AwTV-based iterative statistical reconstruction (e.g. for a SNR of 223 and 40 projections). To obtain the same reconstruction quality as achieved by Total Variation, the projection number and the pulse length, and the acquisition time and the dose respectively can be reduced by a factor of approximately 3.5, when AwTV is used and a factor of approximately 6.7, when our proposed algorithm is used.

SU-D-207A-07: The Effects of Inter-Cycle Respiratory Motion Variation On Dose Accumulation in Single Fraction MR-Guided SBRT Treatment of Renal Cell Carcinoma

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

Stemkens, B; Glitzner, M; Kontaxis, C

Purpose: To assess the dose deposition in simulated single-fraction MR-Linac treatments of renal cell carcinoma, when inter-cycle respiratory motion variation is taken into account using online MRI. Methods: Three motion characterization methods, with increasing complexity, were compared to evaluate the effect of inter-cycle motion variation and drifts on the accumulated dose for an SBRT kidney MR-Linac treatment: 1) STATIC, in which static anatomy was assumed, 2) AVG-RESP, in which 4D-MRI phase-volumes were time-weighted, based on the respiratory phase and 3) PCA, in which 3D volumes were generated using a PCA-model, enabling the detection of inter-cycle variations and drifts. An experimentalmore » ITV-based kidney treatment was simulated in a 1.5T magnetic field on three volunteer datasets. For each volunteer a retrospectively sorted 4D-MRI (ten respiratory phases) and fast 2D cine-MR images (temporal resolution = 476ms) were acquired to simulate MR-imaging during radiation. For each method, the high spatio-temporal resolution 3D volumes were non-rigidly registered to obtain deformation vector fields (DVFs). Using the DVFs, pseudo-CTs (generated from the 4D-MRI) were deformed and the dose was accumulated for the entire treatment. The accuracies of all methods were independently determined using an additional, orthogonal 2D-MRI slice. Results: Motion was most accurately estimated using the PCA method, which correctly estimated drifts and inter-cycle variations (RMSE=3.2, 2.2, 1.1mm on average for STATIC, AVG-RESP and PCA, compared to the 2DMRI slice). Dose-volume parameters on the ITV showed moderate changes (D99=35.2, 32.5, 33.8Gy for STATIC, AVG-RESP and PCA). AVG-RESP showed distinct hot/cold spots outside the ITV margin, which were more distributed for the PCA scenario, since inter-cycle variations were not modeled by the AVG-RESP method. Conclusion: Dose differences were observed when inter-cycle variations were taken into account. The increased inter-cycle randomness in motion as captured by the PCA model mitigates the local (erroneous) hotspots estimated by the AVG-RESP method.« less

Singlet oxygen explicit dosimetry to predict long-term local tumor control for Photofrin-mediated photodynamic therapy

NASA Astrophysics Data System (ADS)

Penjweini, Rozhin; Kim, Michele M.; Ong, Yi Hong; Zhu, Timothy C.

2017-02-01

Although photodynamic therapy (PDT) is an established modality for the treatment of cancer, current dosimetric quantities do not account for the variations in PDT oxygen consumption for different fluence rates (φ). In this study we examine the efficacy of reacted singlet oxygen concentration ([1O2]rx) to predict long-term local control rate (LCR) for Photofrin-mediated PDT. Radiation-induced fibrosarcoma (RIF) tumors in the right shoulders of female C3H mice are treated with different in-air fluences of 225-540 J/cm2 and in-air fluence rate (φair) of 50 and 75 mW/cm2 at 5 mg/kg Photofrin and a drug-light interval of 24 hours using a 1 cm diameter collimated laser beam at 630 nm wavelength. [1O2]rx is calculated by using a macroscopic model based on explicit dosimetry of Photofrin concentration, tissue optical properties, tissue oxygenation and blood flow changes during PDT. The tumor volume of each mouse is tracked for 90 days after PDT and Kaplan-Meier analyses for LCR are performed based on a tumor volume <=100 mm3, for the four dose metrics light fluence, photosensitizer photobleaching rate, PDT dose and [1O2]rx. PDT dose is defined as a temporal integral of photosensitizer concentration and Φ at a 3 mm tumor depth. φ is calculated throughout the treatment volume based on Monte-Carlo simulation and measured tissue optical properties. Our preliminary studies show that [1O2]rx is the best dosimetric quantity that can predict tumor response and correlate with LCR. Moreover, [1O2]rx calculated using the blood flow changes was in agreement with [1O2]rx calculated based on the actual tissue oxygenation.

Routine immunization in Pakistan: comparison of multiple data sources and identification of factors associated with vaccination

PubMed Central

Imran, Hafsa; Raja, Dania; Grassly, Nicholas C; Wadood, M Zubair; Safdar, Rana M; O’Reilly, Kathleen M

2018-01-01

Abstract Background Within Pakistan, estimates of vaccination coverage with the pentavalent vaccine, oral polio vaccine (OPV) and measles vaccine (MV) in 2011 were reported to be 74%, 75% and 53%, respectively. These national estimates may mask regional variation. The reasons for this variation have not been explored. Methods Data from the Multiple Indicator Cluster Surveys (MICS) for Balochistan and Punjab (2010–2011) are analysed to examine factors associated with receiving three or more doses of the pentavalent vaccine and one or more MVs using regression modelling. Pentavalent and OPV estimates from the MICS were compared to vaccine dose histories from surveillance for acute flaccid paralysis (AFP; poliomyelitis) to ascertain agreement. Results Adjusted coverage of children 12–23 months of age were estimated to be 16.0%, 75.5% and 34.2% in Balochistan and 58.0%, 87.7% and 72.6% in Punjab for the pentavalent vaccine, OPV and MV, respectively. Maternal education, healthcare utilization and wealth were associated with receiving the pentavalent vaccine and the MV. There was a strong correlation of district estimates of vaccination coverage between AFP and MICS data, but AFP estimates of pentavalent coverage in Punjab were biased toward higher values. Conclusions National estimates mask variation and estimates from individual surveys should be considered alongside other estimates. The development of strategies targeted towards poorly educated parents within low-wealth quintiles that may not typically access healthcare could improve vaccination rates. PMID:29432552

The role of dose rate in radiation cancer risk: evaluating the effect of dose rate at the molecular, cellular and tissue levels using key events in critical pathways following exposure to low LET radiation

PubMed Central

Brooks, Antone L.; Hoel, David G.; Preston, R. Julian

2016-01-01

Abstract Purpose: This review evaluates the role of dose rate on cell and molecular responses. It focuses on the influence of dose rate on key events in critical pathways in the development of cancer. This approach is similar to that used by the U.S. EPA and others to evaluate risk from chemicals. It provides a mechanistic method to account for the influence of the dose rate from low-LET radiation, especially in the low-dose region on cancer risk assessment. Molecular, cellular, and tissues changes are observed in many key events and change as a function of dose rate. The magnitude and direction of change can be used to help establish an appropriate dose rate effectiveness factor (DREF). Conclusions: Extensive data on key events suggest that exposure to low dose-rates are less effective in producing changes than high dose rates. Most of these data at the molecular and cellular level support a large (2–30) DREF. In addition, some evidence suggests that doses delivered at a low dose rate decrease damage to levels below that observed in the controls. However, there are some data human and mechanistic data that support a dose-rate effectiveness factor of 1. In summary, a review of the available molecular, cellular and tissue data indicates that not only is dose rate an important variable in understanding radiation risk but it also supports the selection of a DREF greater than one as currently recommended by ICRP (2007) and BEIR VII (NRC/NAS 2006). PMID:27266588

Computation of mean and variance of the radiotherapy dose for PCA-modeled random shape and position variations of the target.

PubMed

Budiarto, E; Keijzer, M; Storchi, P R M; Heemink, A W; Breedveld, S; Heijmen, B J M

2014-01-20

Radiotherapy dose delivery in the tumor and surrounding healthy tissues is affected by movements and deformations of the corresponding organs between fractions. The random variations may be characterized by non-rigid, anisotropic principal component analysis (PCA) modes. In this article new dynamic dose deposition matrices, based on established PCA modes, are introduced as a tool to evaluate the mean and the variance of the dose at each target point resulting from any given set of fluence profiles. The method is tested for a simple cubic geometry and for a prostate case. The movements spread out the distributions of the mean dose and cause the variance of the dose to be highest near the edges of the beams. The non-rigidity and anisotropy of the movements are reflected in both quantities. The dynamic dose deposition matrices facilitate the inclusion of the mean and the variance of the dose in the existing fluence-profile optimizer for radiotherapy planning, to ensure robust plans with respect to the movements.

Individualized versus standard FSH dosing in women starting IVF/ICSI: an RCT. Part 2: The predicted hyper responder.

PubMed

Oudshoorn, Simone C; van Tilborg, Theodora C; Eijkemans, Marinus J C; Oosterhuis, G Jur E; Friederich, Jaap; van Hooff, Marcel H A; van Santbrink, Evert J P; Brinkhuis, Egbert A; Smeenk, Jesper M J; Kwee, Janet; de Koning, Corry H; Groen, Henk; Lambalk, Cornelis B; Mol, Ben Willem J; Broekmans, Frank J M; Torrance, Helen L

2017-12-01

Does a reduced FSH dose in women with a predicted hyper response, apparent from a high antral follicle count (AFC), who are scheduled for IVF/ICSI lead to a different outcome with respect to cumulative live birth rate and safety? Although in women with a predicted hyper response (AFC > 15) undergoing IVF/ICSI a reduced FSH dose (100 IU per day) results in similar cumulative live birth rates and a lower occurrence of any grade of ovarian hyperstimulation syndrome (OHSS) as compared to a standard dose (150 IU/day), a higher first cycle cancellation rate and similar severe OHSS rate were observed. Excessive ovarian response to controlled ovarian stimulation (COS) for IVF/ICSI may result in increased rates of cycle cancellation, the occurrence of OHSS and suboptimal live birth rates. In women scheduled for IVF/ICSI, an ovarian reserve test (ORT) can be used to predict response to COS. No consensus has been reached on whether ORT-based FSH dosing improves effectiveness and safety in women with a predicted hyper response. Between May 2011 and May 2014, we performed an open-label, multicentre RCT in women with regular menstrual cycles and an AFC > 15. Women with polycystic ovary syndrome (Rotterdam criteria) were excluded. The primary outcome was ongoing pregnancy achieved within 18 months after randomization and resulting in a live birth. Secondary outcomes included the occurrence of OHSS and cost-effectiveness. Since this RCT was embedded in a cohort study assessing over 1500 women, we expected to randomize 300 predicted hyper responders. Women with an AFC > 15 were randomized to an FSH dose of 100 IU or 150 IU/day. In both groups, dose adjustment was allowed in subsequent cycles (maximum 25 IU in the reduced and 50 IU in the standard group) based on pre-specified criteria. Both effectiveness and cost-effectiveness were evaluated from an intention-to-treat perspective. We randomized 255 women to a daily FSH dose of 100 IU and 266 women to a daily FSH dose of 150 IU. The cumulative live birth rate was 66.3% (169/255) in the reduced versus 69.5% (185/266) in the standard group (relative risk (RR) 0.95 [95%CI, 0.85-1.07], P = 0.423). The occurrence of any grade of OHSS was lower after a lower FSH dose (5.2% versus 11.8%, RR 0.44 [95%CI, 0.28-0.71], P = 0.001), but the occurrence of severe OHSS did not differ (1.3% versus 1.1%, RR 1.25 [95%CI, 0.38-4.07], P = 0.728). As dose reduction was not less expensive (€4.622 versus €4.714, delta costs/woman €92 [95%CI, -479-325]), there was no dominant strategy in the economic analysis. Despite our training programme, the AFC might have suffered from inter-observer variation. Although strict cancellation criteria were provided, selective cancelling in the reduced dose group (for poor response in particular) cannot be excluded as observers were not blinded for the FSH dose and small dose adjustments were allowed in subsequent cycles. However, as first cycle live birth rates did not differ from the cumulative results, the open design probably did not mask a potential benefit for the reduced dosing group. As this RCT was embedded in a larger cohort study, the power in this study was unavoidably lower than it should be. Participants had a relatively low BMI from an international perspective, which may limit generalization of the findings. In women with a predicted hyper response scheduled for IVF/ICSI, a reduced FSH dose does not affect live birth rates. A lower FSH dose did reduce the incidence of mild and moderate OHSS, but had no impact on severe OHSS. Future research into ORT-based dosing in women with a predicted hyper response should compare various safety management strategies and should be powered on a clinically relevant safety outcome while assessing non-inferiority towards live birth rates. This trial was funded by The Netherlands Organization for Health Research and Development (ZonMW, Project Number 171102020). SCO, TCvT and HLT received an unrestricted research grant from Merck Serono (the Netherlands). CBL receives grants from Merck, Ferring and Guerbet. BWJM is supported by a NHMRC Practitioner Fellowship (GNT1082548) and reports consultancy for OvsEva, Merck and Guerbet. FJMB receives monetary compensation as a member of the external advisory board for Ferring pharmaceutics BV and Merck Serono for consultancy work for Gedeon Richter (Belgium) and Roche Diagnostics (Switzerland) and for a research cooperation with Ansh Labs (USA). All other authors have nothing to declare. Registered at the ICMJE-recognized Dutch Trial Registry (www.trialregister.nl). Registration number: NTR2657. 20 December 2010. 12 May 2011. © The Author 2017. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Fabrication and characterization of bolus material using polydimethyl-siloxane

NASA Astrophysics Data System (ADS)

Wiratma Jaya, Gede; Sutanto, Heri

2018-01-01

Bolus has been used in radiotherapy to reduce tissue harm and to increase the superficial dose for skin cancer treatment. Commonly, a bolus is made of melamine in several hospitals. In this research, polydimethyl-siloxane (PDMS) material was used for bolus fabrication. The aims of the study are to investigate bolus density, percentage surface dose and its structural strength for each various composition. In bolus preparation, bolus material used composition variation between PDMS volume and catalyst volume. Composition variation were 20:1, 22:1, 24:1, 26:1, 28:1, 30:1 and 32:1. PDMS and catalyst were mixed by chemical solution deposition method. Bolus was molded by using glass cast with the size of 10 × 10 × 0.5 cm3. Bolus density was analyzed by mass per volume equation, for bolus radiation was examined by the linear accelerator using two electron energy (5 and 7 MeV) and bolus strain and tensile strength were examined by Brookfield CT 3 machine. The results of bolus density were similar with soft tissue density, while the lowest and highest density each variation are 22:1 and 28:1. In general, the use of bolus has increased the surface dose. Percentage of surface dose at 5 MeV energy is higher than 7 MeV energy. The highest percentage of surface dose at 5 MeV energy with 0.5 and 1.0 cm bolus thickness was achieved at composition of 32:1. For strain and tensile strength result, the lowest and highest strain each variation are 22:1 and 28:1, then the lowest and highest tensile strength each variation are 32:1 and 28:1. These results is important to select composition material for bolus fabrication in radiotherapy treatment.

SU-F-T-474: Evaluation of Dose Perturbation, Temperature and Sensitivity Variation With Accumulated Dose of MOSFET Detector

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

Ganesan, B; Prakasarao, A; Singaravelu, G

Purpose: The use of mega voltage gamma and x-ray sources with their skin sparring qualities in radiation therapy has been a boon in relieving patient discomfort and allowing high tumor doses to be given with fewer restrictions due to radiation effects in the skin. However, high doses given to deep tumors may require careful consideration of dose distribution in the buildup region in order to avoid irreparable damage to the skin. Methods: To measure the perturbation of MOSFET detector in Co60,6MV and 15MV the detector was placed on the surface of the phantom covered with the brass build up cap.more » To measure the effect of temperature the MOSFET detector was kept on the surface of hot water polythene container and the radiation was delivere. In order to measure the sensitivity variation with accumulated dose Measurements were taken by delivering the dose of 200 cGy to MOSFET until the MOSFET absorbed dose comes to 20,000 cGy Results: the Measurement was performed by positioning the bare MOSFET and MOSFET with brass build up cap on the top surface of the solid water phantom for various field sizes in order to find whether there is any attenuation caused in the dose distribution. The response of MOSFET was monitored for temperature ranging from 42 degree C to 22 degree C. The integrated dose dependence of MOSFET dosimeter sensitivity over different energy is not well characterized. This work investigates the dual-bias MOSFET dosimeter sensitivity response to 6 MV and 15 MV beams. Conclusion: From this study it is observed that unlike diode, bare MOSFET does not perturb the radiation field.. It is observed that the build-up influences the temperature dependency of MOSFET and causes some uncertainty in the readings. In the case of sensitivity variation with accumulated dose MOSFET showed higher sensitivity with dose accumulation for both the energies.« less

Radiation dose-rate meter using an energy-sensitive counter

DOEpatents

Kopp, Manfred K.

1988-01-01

A radiation dose-rate meter is provided which uses an energy-sensitive detector and combines charge quantization and pulse-rate measurement to monitor radiation dose rates. The charge from each detected photon is quantized by level-sensitive comparators so that the resulting total output pulse rate is proportional to the dose-rate.

Shared dosimetry error in epidemiological dose-response analyses

DOE PAGES

Stram, Daniel O.; Preston, Dale L.; Sokolnikov, Mikhail; ...

2015-03-23

Radiation dose reconstruction systems for large-scale epidemiological studies are sophisticated both in providing estimates of dose and in representing dosimetry uncertainty. For example, a computer program was used by the Hanford Thyroid Disease Study to provide 100 realizations of possible dose to study participants. The variation in realizations reflected the range of possible dose for each cohort member consistent with the data on dose determinates in the cohort. Another example is the Mayak Worker Dosimetry System 2013 which estimates both external and internal exposures and provides multiple realizations of "possible" dose history to workers given dose determinants. This paper takesmore » up the problem of dealing with complex dosimetry systems that provide multiple realizations of dose in an epidemiologic analysis. In this paper we derive expected scores and the information matrix for a model used widely in radiation epidemiology, namely the linear excess relative risk (ERR) model that allows for a linear dose response (risk in relation to radiation) and distinguishes between modifiers of background rates and of the excess risk due to exposure. We show that treating the mean dose for each individual (calculated by averaging over the realizations) as if it was true dose (ignoring both shared and unshared dosimetry errors) gives asymptotically unbiased estimates (i.e. the score has expectation zero) and valid tests of the null hypothesis that the ERR slope β is zero. Although the score is unbiased the information matrix (and hence the standard errors of the estimate of β) is biased for β≠0 when ignoring errors in dose estimates, and we show how to adjust the information matrix to remove this bias, using the multiple realizations of dose. The use of these methods in the context of several studies including, the Mayak Worker Cohort, and the U.S. Atomic Veterans Study, is discussed.« less

The susceptibility of TaO x-based memristors to high dose rate ionizing radiation and total ionizing dose

DOE PAGES

McLain, Michael Lee; Sheridan, Timothy J.; Hjalmarson, Harold Paul; ...

2014-11-11

This paper investigates the effects of high dose rate ionizing radiation and total ionizing dose (TID) on tantalum oxide (TaO x) memristors. Transient data were obtained during the pulsed exposures for dose rates ranging from approximately 5.0 ×10 7 rad(Si)/s to 4.7 ×10 8 rad(Si)/s and for pulse widths ranging from 50 ns to 50 μs. The cumulative dose in these tests did not appear to impact the observed dose rate response. Static dose rate upset tests were also performed at a dose rate of ~3.0 ×10 8 rad(Si)/s. This is the first dose rate study on any type ofmore » memristive memory technology. In addition to assessing the tolerance of TaO x memristors to high dose rate ionizing radiation, we also evaluated their susceptibility to TID. The data indicate that it is possible for the devices to switch from a high resistance off-state to a low resistance on-state in both dose rate and TID environments. The observed radiation-induced switching is dependent on the irradiation conditions and bias configuration. Furthermore, the dose rate or ionizing dose level at which a device switches resistance states varies from device to device; the enhanced susceptibility observed in some devices is still under investigation. As a result, numerical simulations are used to qualitatively capture the observed transient radiation response and provide insight into the physics of the induced current/voltages.« less

TU-F-CAMPUS-T-04: Variations in Nominally Identical Small Fields From Photon Jaw Reproducibility and Associated Effects On Small Field Dosimetric Parameters

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

Muir, B R; McEwen, M R

2015-06-15

Purpose: To investigate uncertainties in small field output factors and detector specific correction factors from variations in field size for nominally identical fields using measurements and Monte Carlo simulations. Methods: Repeated measurements of small field output factors are made with the Exradin W1 (plastic scintillation detector) and the PTW microDiamond (synthetic diamond detector) in beams from the Elekta Precise linear accelerator. We investigate corrections for a 0.6x0.6 cm{sup 2} nominal field size shaped with secondary photon jaws at 100 cm source to surface distance (SSD). Measurements of small field profiles are made in a water phantom at 10 cm depthmore » using both detectors and are subsequently used for accurate detector positioning. Supplementary Monte Carlo simulations with EGSnrc are used to calculate the absorbed dose to the detector and absorbed dose to water under the same conditions when varying field size. The jaws in the BEAMnrc model of the accelerator are varied by a reasonable amount to investigate the same situation without the influence of measurements uncertainties (such as detector positioning or variation in beam output). Results: For both detectors, small field output factor measurements differ by up to 11 % when repeated measurements are made in nominally identical 0.6x0.6 cm{sup 2} fields. Variations in the FWHM of measured profiles are consistent with field size variations reported by the accelerator. Monte Carlo simulations of the dose to detector vary by up to 16 % under worst case variations in field size. These variations are also present in calculations of absorbed dose to water. However, calculated detector specific correction factors are within 1 % when varying field size because of cancellation of effects. Conclusion: Clinical physicists should be aware of potentially significant uncertainties in measured output factors required for dosimetry of small fields due to field size variations for nominally identical fields.« less

SU-F-T-516: Effects of Inter-Fraction Organ Displacement/deformation On the Delivered Doses to the Heart, Esophagus, and Lungs in Patients Receiving Thoracic Radiotherapy

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

Hammers, J; Matney, J; Kaidar-Person, O

Purpose: To quantitatively assess the effects of inter-fraction changes in organ shape and location on the delivered dose distribution to the organs at risk (OAR) in lung cancer patients. Methods: This study analyzes treatment data of 10 patients, who were treated to 60Gy in 30 fractions. In each fraction a cone beam CT (CBCT) was acquired. Each CBCT was registered with the planning CT using deformable registration tools within MIM Software. The daily setup shifts were used to translate the planned dose distribution on the deformed planning CT. The structures of lungs, esophagus and heart were re-delineated by a physicianmore » on each CBCT. The doses delivered to each OAR, reflecting changes in the position and shape variations, were recomputed. Resultant daily dose volume histograms (DVHs) for OARs were computed and compared to those from the planning CT. Results: Based on the findings of two patients and 24 CBCTs analyzed so far, higher doses are delivered to the lungs and esophagus compared to the treatment plan. The dose differences per fraction between the delivered doses and those in the treatment plan are: for patient 1, lung mean dose = 5.3±1.3cGy and esophagus mean dose = 3.4±3.5cGy. For patient 2, lung mean dose = 12.0±3.9cGy and esophagus mean dose = 34.2±7.5cGy. Regarding the maximum dose to heart, the results varied (−18.9±22.0cGy for patient1 and 53.0±62.2cGy for patient2). Conclusion: The dosimetric effects of inter-fractional anatomical variations could be estimated using deformable image registration and manual organ segmentation for each CBCT. A considerable dose distribution variation between fractions was observed for the OARs. These changes are currently not taken into account while treating the patients and these may explain cases with severe side effects even when the treatment plan looks satisfactory. These results suggest the need for automated daily dose tracking and accumulation.« less

The extreme solar cosmic ray particle event on 20 January 2005 and its influence on the radiation dose rate at aircraft altitude.

PubMed

Bütikofer, R; Flückiger, E O; Desorgher, L; Moser, M R

2008-03-01

In January 2005 toward the end of solar activity cycle 23 the Sun was very active. Between 15 and 20 January 2005, the solar active region NOAA AR 10720 produced five powerful solar flares. In association with this major solar activity several pronounced variations in the ground-level cosmic ray intensity were observed. The fifth of these flares (X7.1) produced energetic solar cosmic rays that caused a giant increase in the count rates of the ground-based cosmic ray detectors (neutron monitors). At southern polar neutron monitor stations the increase of the count rate reached several thousand percent. From the recordings of the worldwide network of neutron monitors, we determined the characteristics of the solar particle flux near Earth. In the initial phase of the event, the solar cosmic ray flux near Earth was extremely anisotropic. The energy spectrum of the solar cosmic rays was fairly soft during the main and the decay phase. We investigated also the flux of different secondary particle species in the atmosphere and the radiation dosage at flight altitude. Our analysis shows a maximum increment of the effective dose rate due to solar cosmic rays in the south polar region around 70 degrees S and 130 degrees E at flight altitude of almost three orders of magnitude.

SU-E-T-541: Measurement of CT Density Model Variations and the Impact On the Accuracy of Monte Carlo (MC) Dose Calculation in Stereotactic Body Radiation Therapy for Lung Cancer

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

Xiang, H; Li, B; Behrman, R

2015-06-15

Purpose: To measure the CT density model variations between different CT scanners used for treatment planning and impact on the accuracy of MC dose calculation in lung SBRT. Methods: A Gammex electron density phantom (RMI 465) was scanned on two 64-slice CT scanners (GE LightSpeed VCT64) and a 16-slice CT (Philips Brilliance Big Bore CT). All three scanners had been used to acquire CT for CyberKnife lung SBRT treatment planning. To minimize the influences of beam hardening and scatter for improving reproducibility, three scans were acquired with the phantom rotated 120° between scans. The mean CT HU of each densitymore » insert, averaged over the three scans, was used to build the CT density models. For 14 patient plans, repeat MC dose calculations were performed by using the scanner-specific CT density models and compared to a baseline CT density model in the base plans. All dose re-calculations were done using the same plan beam configurations and MUs. Comparisons of dosimetric parameters included PTV volume covered by prescription dose, mean PTV dose, V5 and V20 for lungs, and the maximum dose to the closest critical organ. Results: Up to 50.7 HU variations in CT density models were observed over the baseline CT density model. For 14 patient plans examined, maximum differences in MC dose re-calculations were less than 2% in 71.4% of the cases, less than 5% in 85.7% of the cases, and 5–10% for 14.3% of the cases. As all the base plans well exceeded the clinical objectives of target coverage and OAR sparing, none of the observed differences led to clinically significant concerns. Conclusion: Marked variations of CT density models were observed for three different CT scanners. Though the differences can cause up to 5–10% differences in MC dose calculations, it was found that they caused no clinically significant concerns.« less

Dynamic simulation of motion effects in IMAT lung SBRT.

PubMed

Zou, Wei; Yin, Lingshu; Shen, Jiajian; Corradetti, Michael N; Kirk, Maura; Munbodh, Reshma; Fang, Penny; Jabbour, Salma K; Simone, Charles B; Yue, Ning J; Rengan, Ramesh; Teo, Boon-Keng Kevin

2014-11-01

Intensity modulated arc therapy (IMAT) has been widely adopted for Stereotactic Body Radiotherapy (SBRT) for lung cancer. While treatment dose is optimized and calculated on a static Computed Tomography (CT) image, the effect of the interplay between the target and linac multi-leaf collimator (MLC) motion is not well described and may result in deviations between delivered and planned dose. In this study, we investigated the dosimetric consequences of the inter-play effect on target and organs at risk (OAR) by simulating dynamic dose delivery using dynamic CT datasets. Fifteen stage I non-small cell lung cancer (NSCLC) patients with greater than 10 mm tumor motion treated with SBRT in 4 fractions to a dose of 50 Gy were retrospectively analyzed for this study. Each IMAT plan was initially optimized using two arcs. Simulated dynamic delivery was performed by associating the MLC leaf position, gantry angle and delivered beam monitor units (MUs) for each control point with different respiratory phases of the 4D-CT using machine delivery log files containing time stamps of the control points. Dose maps associated with each phase of the 4D-CT dose were calculated in the treatment planning system and accumulated using deformable image registration onto the exhale phase of the 4D-CT. The original IMAT plans were recalculated on the exhale phase of the CT for comparison with the dynamic simulation. The dose coverage of the PTV showed negligible variation between the static and dynamic simulation. There was less than 1.5% difference in PTV V95% and V90%. The average inter-fraction and cumulative dosimetric effects among all the patients were less than 0.5% for PTV V95% and V90% coverage and 0.8 Gy for the OARs. However, in patients where target is close to the organs, large variations were observed on great vessels and bronchus for as much as 4.9 Gy and 7.8 Gy. Limited variation in target dose coverage and OAR constraints were seen for each SBRT fraction as well as over all four fractions. Large dose variations were observed on critical organs in patients where these organs were closer to the target.

Comparison of Vocal Vibration-Dose Measures for Potential-Damage Risk Criteria

PubMed Central

Hunter, Eric J.

2015-01-01

Purpose Schoolteachers have become a benchmark population for the study of occupational voice use. A decade of vibration-dose studies on the teacher population allows a comparison to be made between specific dose measures for eventual assessment of damage risk. Method Vibration dosimetry is reformulated with the inclusion of collision stress. Two methods of estimating amplitude of vocal-fold vibration are compared to capture variations in vocal intensity. Energy loss from collision is added to the energy-dissipation dose. An equal-energy-dissipation criterion is defined and used on the teacher corpus as a potential-damage risk criterion. Results Comparison of time-, cycle-, distance-, and energy-dose calculations for 57 teachers reveals a progression in information content in the ability to capture variations in duration, speaking pitch, and vocal intensity. The energy-dissipation dose carries the greatest promise in capturing excessive tissue stress and collision but also the greatest liability, due to uncertainty in parameters. Cycle dose is least correlated with the other doses. Conclusion As a first guide to damage risk in excessive voice use, the equal-energy-dissipation dose criterion can be used to structure trade-off relations between loudness, adduction, and duration of speech. PMID:26172434

[Brachytherapy for head and neck cancers].

PubMed

Peiffert, D; Coche-Dequéant, B; Lapeyre, M; Renard, S

2018-05-29

The main indications of the brachytherapy of head and neck cancers are the limited tumours of the lip, the nose, the oral cavity and the oropharynx. Nasopharynx tumours are nowadays treated by intensity-modulated radiotherapy. This technique can be exclusive, associated with external radiotherapy or postoperative. It can also be a salvage treatment for the second primaries in previously irradiated areas. If the low dose rate brachytherapy rules remain the reference, the pulse dose rate technique allows the prescription of the dose rate and the optimisation of the dose distribution. Results of high dose rate brachytherapy are now published. This paper reports the recommendations of the Gec-ESTRO, published in 2017, and takes into account the data of the historical low dose rate series, and is upgraded with the pulsed-dose rate and high dose rate series. Copyright © 2018. Published by Elsevier SAS.

Dosimetric properties of radiophotoluminescent glass detector in low-energy photon beams.

PubMed

Kadoya, Noriyuki; Shimomura, Kouhei; Kitou, Satoshi; Shiota, Yasuo; Fujita, Yukio; Dobashi, Suguru; Takeda, Ken; Jingu, Keiichi; Matsushita, Haruo; Namito, Yoshihito; Ban, Syuichi; Koyama, Syuji; Tabushi, Katsuyoshi

2012-10-01

A radiophotoluminescent glass rod dosimeter (RGD) has recently become commercially available. It is being increasingly used for dosimetry in radiotherapy to measure the absorbed dose including scattered low-energy photons on the body surface of a patient and for postal dosimetry audit. In this article, the dosimetric properties of the RGD, including energy dependence of the dose response, reproducibly, variation in data obtained by the RGD for each energy, and angular dependence in low-energy photons, are discussed. An RGD (GD-301, Asahi Techno Glass Corporation, Shizuoka, Japan) was irradiated with monochromatic low-energy photon beams generated by synchrotron radiation at Photon Factory, High Energy Accelerator Research Organization (KEK). The size of GD-301 was 1.5 mm in diameter and 8.5 mm in length and the active dose readout volume being 1 mm diameter and 0.6 mm depth located 0.7 mm from the end of the detector. The energy dependence of the dose response and reproducibility and variation were investigated for RGDs irradiated with a plastic holder and those irradiated without the plastic holder. Response of the RGD was obtained by not only conventional single field irradiation but also bilateral irradiation. Angular dependence of the RGD was measured in the range of 0°-90° for 13, 17, 40, and 80 keV photon beams by conventional single field irradiation. The dose responses had a peak at around 40 keV. For the energy range of less than 25 keV, all dose response curves steeply decreased in comparison with the ratio of mass energy absorption coefficient of the RGD to that of air. As for the reproducibility and variation in data obtained by the RGD, the coefficient of variance increased with decrease in photon energy. Furthermore, the variation for bilateral irradiation was less than that for single field irradiation. Regarding angular dependence of the RGD, for energies of 13 and 17 keV, the response decreased with increase in the irradiation angle, and the minimum values were 93.5% and 86%, respectively. Our results showed the dosimetric properties of the RGD, including the energy dependence of the dose response, reproducibly, variation, and angular dependence in low-energy photons and suggest that the accuracy of the absorbed dose in low-energy photons is affected by the readout method and the distribution of radiophotoluminescence centers in the RGD.

Multidimensional dosimetry of {sup 106}Ru eye plaques using EBT3 films and its impact on treatment planning

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

Heilemann, G., E-mail: gerd.heilemann@meduniwien.ac.at; Kostiukhina, N.; Nesvacil, N.

2015-10-15

Purpose: The purpose of this study was to establish a method to perform multidimensional radiochromic film measurements of {sup 106}Ru plaques and to benchmark the resulting dose distributions against Monte Carlo simulations (MC), microdiamond, and diode measurements. Methods: Absolute dose rates and relative dose distributions in multiple planes were determined for three different plaque models (CCB, CCA, and COB), and three different plaques per model, using EBT3 films in an in-house developed polystyrene phantom and the MCNP6 MC code. Dose difference maps were generated to analyze interplaque variations for a specific type, and for comparing measurements against MC simulations. Furthermore,more » dose distributions were validated against values specified by the manufacturer (BEBIG) and microdiamond and diode measurements in a water scanning phantom. Radial profiles were assessed and used to estimate dosimetric margins for a given combination of representative tumor geometry and plaque size. Results: Absolute dose rates at a reference depth of 2 mm on the central axis of the plaque show an agreement better than 5% (10%) when comparing film measurements (MCNP6) to the manufacturer’s data. The reproducibility of depth-dose profile measurements was <7% (2 SD) for all investigated detectors and plaque types. Dose difference maps revealed minor interplaque deviations for a specific plaque type due to inhomogeneities of the active layer. The evaluation of dosimetric margins showed that for a majority of the investigated cases, the tumor was not completely covered by the 100% isodose prescribed to the tumor apex if the difference between geometrical plaque size and tumor base ≤4 mm. Conclusions: EBT3 film dosimetry in an in-house developed phantom was successfully used to characterize the dosimetric properties of different {sup 106}Ru plaque models. The film measurements were validated against MC calculations and other experimental methods and showed a good agreement with data from BEBIG well within published tolerances. The dosimetric information as well as interplaque comparison can be used for comprehensive quality assurance and for considerations in the treatment planning of ophthalmic brachytherapy.« less

Influence of Herbicide Triasulfuron on Soil Microbial Community in an Unamended Soil and a Soil Amended with Organic Residues

PubMed Central

Pose-Juan, Eva; Igual, José M.; Sánchez-Martín, María J.; Rodríguez-Cruz, M. S.

2017-01-01

The effect of organic amendments and pesticides on a soil microbial community has garnered considerable interest due to the involvement of microorganisms in numerous soil conservation and maintenance reactions. The aim of this work was to assess the influence on a soil microbial community of the simultaneous application of the herbicide triasulfuron at three doses (2, 10, and 50 mg kg-1), with an organic amendment [sewage sludge (SS) or green compost (GC)]. Dissipation kinetics, soil microbial biomass, dehydrogenase activity (DHA) and respiration, and the profile of phospholipid fatty acids (PLFAs) extracted from the soil, were determined in unamended (S) soil and amended (S+SS and S+GC) ones. Triasulfuron dissipation followed the single first-order kinetics model. Half-life (DT50) values were higher in the amended soils than in the unamended one for the 10 and 50 mg kg-1 doses. The dissipation rates were lower in the S+GC soil for the three herbicide doses applied. In general, soil biomass, DHA and respiration values increased in SS- and GC-amended soils compared to the unamended one. DHA values decreased (S and S+SS) or increased (S+GC) with the incubation time of soil with herbicide at the different doses applied. Respiration values increased with the herbicide doses applied and decreased with the incubation time, although maximum values were obtained for soils treated with the highest dose after 70 days of incubation. PLFA analysis indicated different effects of triasulfuron on the soil microbial community structure depending on the organic amendments. While the increasing triasulfuron doses resulted in deeper alterations in the S soil, the time after triasulfuron application was the most important variation in the S+SS and S+GC soils. The overall results indicate that the soil amendment has an effect on herbicide dissipation rate and the soil microbial community. Initially, a high dose of triasulfuron had detrimental effects on the soil microbial community, which is important in the case of the long-term use of this compound. PMID:28337188

Experimental verification of Advanced Collapsed-cone Engine for use with a multichannel vaginal cylinder applicator.

PubMed

Cawston-Grant, Brie; Morrison, Hali; Menon, Geetha; Sloboda, Ron S

2017-05-01

Model-based dose calculation algorithms have recently been incorporated into brachytherapy treatment planning systems, and their introduction requires critical evaluation before clinical implementation. Here, we present an experimental evaluation of Oncentra ® Brachy Advanced Collapsed-cone Engine (ACE) for a multichannel vaginal cylinder (MCVC) applicator using radiochromic film. A uniform dose of 500 cGy was specified to the surface of the MCVC using the TG-43 dose formalism under two conditions: (a) with only the central channel loaded or (b) only the peripheral channels loaded. Film measurements were made at the applicator surface and compared to the doses calculated using TG-43, standard accuracy ACE (sACE), and high accuracy ACE (hACE). When the central channel of the applicator was used, the film measurements showed a dose increase of (11 ± 8)% (k = 2) above the two outer grooves on the applicator surface. This increase in dose was confirmed with the hACE calculations, but was not confirmed with the sACE calculations at the applicator surface. When the peripheral channels were used, a periodic azimuthal variation in measured dose was observed around the applicator. The sACE and hACE calculations confirmed this variation and agreed within 1% of each other at the applicator surface. Additionally for the film measurements with the central channel used, a baseline dose variation of (10 ± 4)% (k = 2) of the mean dose was observed azimuthally around the applicator surface, which can be explained by offset source positioning in the central channel. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Dosimetry Formalism and Implementation of a Homogenous Irradiation Protocol to Improve the Accuracy of Small Animal Whole-Body Irradiation Using a Cesium-137 Irradiator

PubMed Central

Brodin, N. Patrik; Chen, Yong; Yaparpalvi, Ravindra; Guha, Chandan; Tomé, Wolfgang A.

2015-01-01

Shielded 137Cs irradiators are routinely used in pre-clinical radiation research to perform in vitro or in vivo investigations. Without appropriate dosimetry and irradiation protocols in place, there can be large uncertainty in the delivered dose of radiation between irradiated subjects that could lead to inaccurate and possibly misleading results. Here, a dosimetric evaluation of the JL Shepard Mark I-68A 137Cs irradiator and an irradiation technique for whole-body irradiation of small animals that allows one to limit the between subject variation in delivered dose to ±3% are provided. Mathematical simulation techniques and Gafchromic EBT film were used to describe the region within the irradiation cavity with homogeneous dose distribution (100% ±5%), the dosimetric impact of varying source-to-subject distance, and the variation in attenuation thickness due to turntable rotation. Furthermore, an irradiation protocol and dosimetry formalism that allows calculation of irradiation time for whole-body irradiation of small animals is proposed, that is designed to ensure a more consistent dose delivery between irradiated subjects. To compare this protocol with the conventional irradiation protocol suggested by the vendor, high-resolution film dosimetry measurements evaluating the dose difference between irradiation subjects and the dose distribution throughout subjects was performed, using phantoms resembling small animals. Based on these results, there can be considerable variation in the delivered dose of > ±5% using the conventional irradiation protocol for whole-body irradiation doses below 5 Gy. Using the proposed irradiation protocol this variability can be reduced to within ±3% and the dosimetry formalism allows for more accurate calculation of the irradiation time in relation to the intended prescription dose. PMID:26710162

Radiation and chemical mutagen induced somaclonal variations through in vitro organogenesis of cotton (Gossypium hirsutum L.).

PubMed

Muthusamy, Annamalai; Jayabalan, Narayanasamy

2014-12-01

The purpose of the investigation was to induce somaclonal variations by gamma rays (GR), ethylmethane sulphonate (EMS) and sodium azide (SA) during in vitro organogenesis of cotton. The shoot tip explants were irradiated with 5-50 Gray (Gy) GR (Cobalt 60), 0.5-5.0 mM EMS and SA separately, and inoculated on Murashige and Skoog (MS) medium fortified with plant growth regulator (PGR) for organogenesis. The plantlets with well-developed root systems were acclimatized and transferred into the experimental field to screen the somaclonal variations during growth and development. The number of somaclonal variations was observed in growth of irradiated/treated shoot tips, multiplication, plantlet regeneration and growth in vitro and ex vitro. The lower doses/concentrations of mutagenic treatments showed significant enhancement in selected agronomical characters and they showed decreased trends with increasing doses/concentrations of mutagenic agents. The results of the present study revealed the influence of lower doses/concentrations of mutagenic treatments on in vitro and ex vitro growth of cotton plantlets and their significant improvement in agronomical characters which needs further imperative stability analysis. The present observations showed the platform to use lower doses/concentrations of mutagenic agents to induce variability for enhanced agronomical characters, resistant and tolerant cotton varieties.

Diurnal variation in the biliary excretion of flomoxef in patients with percutaneous transhepatic biliary drainage

PubMed Central

Hishikawa, Shuji; Kobayashi, Eiji; Sugimoto, Koh-ichi; Miyata, Michio; Fujimura, Akio

2001-01-01

Aims To examine diurnal variation in biliary excretion of flomoxef. Methods Flomoxef (1 g) was injected intravenously in eight patients with percutaneous transhepatic cholangiography with drainage at 09.00 h and 21.00 h by a cross-over design with a 36 h washout period. Drained biliary fluid was collected for 6 h after each dosing. These patients still had mild to moderate hepatic dysfunction. Results Bile flow and bile acid excretion for 6 h after dosing did not differ significantly between the 09.00 h and 21.00 h treatments. The maximum concentration of biliary flomoxef was significantly greater and its total excretion for 6 h tended to be greater after the 21.00 h dose [maximum concentration (µg ml−1): 34.2 ± 29.9 (09.00 h dose) vs 43.5 ± 28.3 (21.00 h dose) (95% confidence interval for difference: 2.6∼15.9, P = 0.013); total excretion (mg 6 h−1): 1.4 ± 1.3 (09.00 h dose) vs 1.6 ± 1.2 (21.00 h dose) (95% confidence interval for difference: −26.8, 313.7, P = 0.087)]. The period that biliary flomoxef remained above the minimal inhibitory concentration did not differ significantly between the two treatment times. Conclusions These results suggest that biliary excretion of flomoxef shows diurnal variation. However, as the difference was relatively small, flomoxef could be given at any time of day without any dosage adjustments. PMID:11453891

Diurnal variation in the biliary excretion of flomoxef in patients with percutaneous transhepatic biliary drainage.

PubMed

Hishikawa, S; Kobayashi, E; Sugimoto , K; Miyata, M; Fujimura, A

2001-07-01

To examine diurnal variation in biliary excretion of flomoxef. Flomoxef (1 g) was injected intravenously in eight patients with percutaneous transhepatic cholangiography with drainage at 09.00 h and 21.00 h by a cross-over design with a 36 h washout period. Drained biliary fluid was collected for 6 h after each dosing. These patients still had mild to moderate hepatic dysfunction. Bile flow and bile acid excretion for 6 h after dosing did not differ significantly between the 09.00 h and 21.00 h treatments. The maximum concentration of biliary flomoxef was significantly greater and its total excretion for 6 h tended to be greater after the 21.00 h dose [maximum concentration (microg ml(-1)): 34.2 +/- 29.9 (09.00 h dose) vs 43.5 +/- 28.3 (21.00 h dose) (95% confidence interval for difference: 2.6 approximately 15.9, P = 0.013); total excretion (mg 6 h(-1)): 1.4 +/- 1.3 (09.00 h dose) vs 1.6 +/- 1.2 (21.00 h dose) (95% confidence interval for difference: -26.8, 313.7, P = 0.087)]. The period that biliary flomoxef remained above the minimal inhibitory concentration did not differ significantly between the two treatment times. These results suggest that biliary excretion of flomoxef shows diurnal variation. However, as the difference was relatively small, flomoxef could be given at any time of day without any dosage adjustments.

An accurate derivation of the air dose-rate and the deposition concentration distribution by aerial monitoring in a low level contaminated area

NASA Astrophysics Data System (ADS)

Nishizawa, Yukiyasu; Sugita, Takeshi; Sanada, Yukihisa; Torii, Tatsuo

2015-04-01

Since 2011, MEXT (Ministry of Education, Culture, Sports, Science and Technology, Japan) have been conducting aerial monitoring to investigate the distribution of radioactive cesium dispersed into the atmosphere after the accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), Tokyo Electric Power Company. Distribution maps of the air dose-rate at 1 m above the ground and the radioactive cesium deposition concentration on the ground are prepared using spectrum obtained by aerial monitoring. The radioactive cesium deposition is derived from its dose rate, which is calculated by excluding the dose rate of the background radiation due to natural radionuclides from the air dose-rate at 1 m above the ground. The first step of the current method of calculating the dose rate due to natural radionuclides is calculate the ratio of the total count rate of areas where no radioactive cesium is detected and the count rate of regions with energy levels of 1,400 keV or higher (BG-Index). Next, calculate the air dose rate of radioactive cesium by multiplying the BG-Index and the integrated count rate of 1,400 keV or higher for the area where the radioactive cesium is distributed. In high dose-rate areas, however, the count rate of the 1,365-keV peak of Cs-134, though small, is included in the integrated count rate of 1,400 keV or higher, which could cause an overestimation of the air dose rate of natural radionuclides. We developed a method for accurately evaluating the distribution maps of natural air dose-rate by excluding the effect of radioactive cesium, even in contaminated areas, and obtained the accurate air dose-rate map attributed the radioactive cesium deposition on the ground. Furthermore, the natural dose-rate distribution throughout Japan has been obtained by this method.

Leuco-crystal-violet micelle gel dosimeters: Component effects on dose-rate dependence

NASA Astrophysics Data System (ADS)

Xie, J. C.; Katz, E. A. B.; Alexander, K. M.; Schreiner, L. J.; McAuley, K. B.

2017-05-01

Designed experiments were performed to produce empirical models for the dose sensitivity, initial absorbance, and dose-rate dependence respectively for leucocrystal violet (LCV) micelle gel dosimeters containing cetyltrimethylammonium bromide (CTAB) and 2,2,2-trichloroethanol (TCE). Previous gels of this type showed dose-rate dependent behaviour, producing an ˜18% increase in dose sensitivity between dose rates of 100 and 600 cGy min-1. Our models predict that the dose rate dependence can be reduced by increasing the concentration of TCE, CTAB and LCV. Increasing concentrations of LCV and CTAB produces a significant increase in dose sensitivity with a corresponding increase in initial absorbance. An optimization procedure was used to determine a nearly dose-rate independent gel which maintained high sensitivity and low initial absorbance. This gel which contains 33 mM CTAB, 1.25 mM LCV, and 96 mM TCE in 25 mM trichloroacetic acid and 4 wt% gelatin showed an increase in dose sensitivity of only 4% between dose rates of 100 and 600 cGy min-1, and provides an 80% greater dose sensitivity compared to Jordan’s standard gels with similar initial absorbance.

Dose and dose rate effects of whole-body gamma-irradiation: I. Lymphocytes and lymphoid organs

NASA Technical Reports Server (NTRS)

Pecaut, M. J.; Nelson, G. A.; Gridley, D. S.

2001-01-01

The major goal of part I of this study was to compare varying doses and dose rates of whole-body gamma-radiation on lymphoid cells and organs. C57BL/6 mice (n = 75) were exposed to 0, 0.5, 1.5, and 3.0 Gy gamma-rays (60Co) at 1 cGy/min (low-dose rate, LDR) and 80 cGy/min (high-dose rate, HDR) and euthanized 4 days later. A significant dose-dependent loss of spleen mass was observed with both LDR and HDR irradiation; for the thymus this was true only with HDR. Decreasing leukocyte and lymphocyte numbers occurred with increasing dose in blood and spleen at both dose rates. The numbers (not percentages) of CD3+ T lymphocytes decreased in the blood in a dose-dependent manner at both HDR and LDR. Splenic T cell counts decreased with dose only in HDR groups; percentages increased with dose at both dose rates. Dose-dependent decreases occurred in CD4+ T helper and CD8+ T cytotoxic cell counts at HDR and LDR. In the blood the percentages of CD4+ cells increased with increasing dose at both dose rates, whereas in the spleen the counts decreased only in the HDR groups. The percentages of the CD8+ population remained stable in both blood and spleen. CD19+ B cell counts and percentages in both compartments declined markedly with increasing HDR and LDR radiation. NK1.1+ natural killer cell numbers and proportions remained relatively stable. Overall, these data indicate that the observed changes were highly dependent on the dose, but not dose rate, and that cells in the spleen are more affected by dose rate than those in blood. The results also suggest that the response of lymphocytes in different body compartments may be variable.

Estimation of the Dose and Dose Rate Effectiveness Factor

NASA Technical Reports Server (NTRS)

Chappell, L.; Cucinotta, F. A.

2013-01-01

Current models to estimate radiation risk use the Life Span Study (LSS) cohort that received high doses and high dose rates of radiation. Transferring risks from these high dose rates to the low doses and dose rates received by astronauts in space is a source of uncertainty in our risk calculations. The solid cancer models recommended by BEIR VII [1], UNSCEAR [2], and Preston et al [3] is fitted adequately by a linear dose response model, which implies that low doses and dose rates would be estimated the same as high doses and dose rates. However animal and cell experiments imply there should be curvature in the dose response curve for tumor induction. Furthermore animal experiments that directly compare acute to chronic exposures show lower increases in tumor induction than acute exposures. A dose and dose rate effectiveness factor (DDREF) has been estimated and applied to transfer risks from the high doses and dose rates of the LSS cohort to low doses and dose rates such as from missions in space. The BEIR VII committee [1] combined DDREF estimates using the LSS cohort and animal experiments using Bayesian methods for their recommendation for a DDREF value of 1.5 with uncertainty. We reexamined the animal data considered by BEIR VII and included more animal data and human chromosome aberration data to improve the estimate for DDREF. Several experiments chosen by BEIR VII were deemed inappropriate for application to human risk models of solid cancer risk. Animal tumor experiments performed by Ullrich et al [4], Alpen et al [5], and Grahn et al [6] were analyzed to estimate the DDREF. Human chromosome aberration experiments performed on a sample of astronauts within NASA were also available to estimate the DDREF. The LSS cohort results reported by BEIR VII were combined with the new radiobiology results using Bayesian methods.

Margin estimation and disturbances of irradiation field in layer-stacking carbon-ion beams for respiratory moving targets.

PubMed

Tajiri, Shinya; Tashiro, Mutsumi; Mizukami, Tomohiro; Tsukishima, Chihiro; Torikoshi, Masami; Kanai, Tatsuaki

2017-11-01

Carbon-ion therapy by layer-stacking irradiation for static targets has been practised in clinical treatments. In order to apply this technique to a moving target, disturbances of carbon-ion dose distributions due to respiratory motion have been studied based on the measurement using a respiratory motion phantom, and the margin estimation given by the square root of the summation Internal margin2+Setup margin2 has been assessed. We assessed the volume in which the variation in the ratio of the dose for a target moving due to respiration relative to the dose for a static target was within 5%. The margins were insufficient for use with layer-stacking irradiation of a moving target, and an additional margin was required. The lateral movement of a target converts to the range variation, as the thickness of the range compensator changes with the movement of the target. Although the additional margin changes according to the shape of the ridge filter, dose uniformity of 5% can be achieved for a spherical target 93 mm in diameter when the upward range variation is limited to 5 mm and the additional margin of 2.5 mm is applied in case of our ridge filter. Dose uniformity in a clinical target largely depends on the shape of the mini-peak as well as on the bolus shape. We have shown the relationship between range variation and dose uniformity. In actual therapy, the upper limit of target movement should be considered by assessing the bolus shape. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

CBCT-based volumetric and dosimetric variation evaluation of volumetric modulated arc radiotherapy in the treatment of nasopharyngeal cancer patients

PubMed Central

2013-01-01

Objective To investigate the anatomic and dosimetric variations of volumetric modulated arc therapy (VMAT) in the treatment of nasopharyngeal cancer (NPC) patients based on weekly cone beam CT (CBCT). Materials and methods Ten NPC patients treated by VMAT with weekly CBCT for setup corrections were reviewed retrospectively. Deformed volumes of targets and organs at risk (OARs) in the CBCT were compared with those in the planning CT. Delivered doses were recalculated based on weekly CBCT and compared with the planned doses. Results No significant volumetric changes on targets, brainstem, and spinal cord were observed. The average volumes of right and left parotid measured from the fifth CBCT were about 4.4 and 4.5 cm3 less than those from the first CBCT, respectively. There were no significant dose differences between average planned and delivered doses for targets, brainstem and spinal cord. For right parotid, the delivered mean dose was 10.5 cGy higher (p = 0.004) than the planned value per fraction, and the V26 and V32 increased by 7.5% (p = 0.002) and 7.4% (p = 0.01), respectively. For the left parotid, the D50 (dose to the 50% volume) was 8.8 cGy higher (p = 0.03) than the planned values per fraction, and the V26 increased by 8.8% (p = 0.002). Conclusion Weekly CBCTs were applied directly to study the continuous volume changes and resulting dosimetric variations of targets and OARs for NPC patients undergoing VMAT. Significant volumetric and dosimetric variations were observed for parotids. Replanning after 30 Gy will benefit the protection on parotids. PMID:24289312

Using RADFET for the real-time measurement of gamma radiation dose rate

NASA Astrophysics Data System (ADS)

Andjelković, Marko S.; Ristić, Goran S.; Jakšić, Aleksandar B.

2015-02-01

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20  and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65  to 32.1 Gy h-1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose.

Polonium-210 in marine mussels (bivalve molluscs) inhabiting the southern coast of India.

PubMed

Khan, M Feroz; Wesley, S Godwin; Rajan, M P

2014-12-01

The present study focused on the determination of the alpha-emitter, (210)Po, in two species of marine mussels (bivalve molluscs) commonly available in the southern coastal region of India. The brown mussel, Perna indica was collected from the west coast and the green mussel, Perna viridis from the east coast. The concentration of (210)Po was related to the allometry (length of shell, wet/dry weight of shell/soft tissue) of the mussels and significant results were found. The study period focused on three seasons namely, pre-monsoon, monsoon and post-monsoon for a 1-year period (2010-2011). The results revealed higher activity levels in smaller-sized mussels compared to larger ones. Marked variation in (210)Po activity concentration was noted in the whole-body soft tissues between seasons and sampling site (p < 0.05). The dose rate assessment for mussels was performed using the ERICA Assessment tool. The chronic exposure to mussels due to (210)Po was found to be lesser than the global benchmark dose rate of 10 μGy h(-1). The effective ingestion dose to adults who intake mussels was estimated to be in the range 5.1-34.9 μSv y(-1). The measurement contributes to the furthering of knowledge of (210)Po, since no data exist in this region. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dose Rate Effects in Linear Bipolar Transistors

NASA Technical Reports Server (NTRS)

Johnston, Allan; Swimm, Randall; Harris, R. D.; Thorbourn, Dennis

2011-01-01

Dose rate effects are examined in linear bipolar transistors at high and low dose rates. At high dose rates, approximately 50% of the damage anneals at room temperature, even though these devices exhibit enhanced damage at low dose rate. The unexpected recovery of a significant fraction of the damage after tests at high dose rate requires changes in existing test standards. Tests at low temperature with a one-second radiation pulse width show that damage continues to increase for more than 3000 seconds afterward, consistent with predictions of the CTRW model for oxides with a thickness of 700 nm.

Outdoor 220Rn, 222Rn and terrestrial gamma radiation levels: investigation study in the thorium rich Fen Complex, Norway.

PubMed

Mrdakovic Popic, Jelena; Bhatt, Chhavi Raj; Salbu, Brit; Skipperud, Lindis

2012-01-01

The present study was done in the Fen Complex, a Norwegian area rich in naturally occurring radionuclides, especially in thorium ((232)Th). Measurement of radioactivity levels was conducted at the decommissioned iron (Fe) and niobium (Nb) mining sites (TENORM) as well as at the undisturbed wooded sites (NORM), all open for free public access. The soil activity concentrations of (232)Th (3280-8395 Bq kg(-1)) were significantly higher than the world and the Norwegian average values and exceeded the Norwegian screening level (1000 Bq kg(-1)) for radioactive waste, while radium ((226)Ra) was present at slightly elevated levels (89-171 Bq kg(-1)). Terrestrial gamma dose rates were also elevated, ranging 2.6-4.4 μGy h(-1). Based on long-term surveys, the air concentrations of thoron ((220)Rn) and radon ((222)Rn) reached 1786 and 82 Bq m(-3), respectively. Seasonal variation in the outdoor gamma dose rates and Rn concentrations was confirmed. Correlation analyses showed a linear relationship between air radiation levels and the abundance of (232)Th in soil. The annual outdoor effective radiation doses for humans (occupancy 5 h day(-1)) were estimated to be in the range of 3.0-7.7 mSv, comparable or higher than the total average (summarized indoor and outdoor) exposure dose for the Norwegian population (2.9 mSv year(-1)). On the basis of all obtained results, this Norwegian area should be considered as enhanced natural radiation area (ENRA).

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

Langner, U; Langen, K

Purpose: To investigate the effect of spot size variation as function of gantry angle on the quality of treatment plans for pencil beam scanning proton plans. Method: Three homogeneous 26×26×7cm dose volumes with different ranges and SOBPs were delivered on the matrixxPT 2D array at gantry angles of 0 and 270 degrees. The spot size sigma varies by 1.8, 7.8, and 1.4%, for nominal energies of 215, 183, and 103 MeV (Range 29, 22, and 8cm, respectively). The resulting dose planes are compared and evaluated with the gamma index for 2%/2mm and 1%/1mm criteria. Results: Patient specific QA is performedmore » at a gantry angle of 0 degrees. However, beam sigmas vary as function of gantry angle because of the beam optics for each gantry. This will cause differences between the delivered and planned treatment plans. Delivered plans were compared and a gamma pass rate of 96.5% for criteria of 2%/2mm and 91.4% for 1%/1mm were seen for plans with a nominal energy of 183 MeV. For plans with a nominal energy of 103 MeV, gamma pass rates of 97.3% for 2%/2mm and 91.5% for 1%/1mm were seen. For plans with a nominal energy of 215 MeV the pass rate was 99.8% for 1%/1mm between the two gantry angles. Conclusion: Differences in beam sigma of up to 7.8% do not cause significant differences in the dose distribution of different spot size gammas.« less

Mumps resurgences in the United States: A historical perspective on unexpected elements.

PubMed

Barskey, Albert E; Glasser, John W; LeBaron, Charles W

2009-10-19

In 2006 the United States experienced the largest nationwide mumps epidemic in 20 years, primarily affecting college dormitory residents. Unexpected elements of the outbreak included very abrupt time course (75% of cases occurred within 90 days), geographic focality (85% of cases occurred in eight rural Midwestern states), rapid upward and downward shift in peak age-specific attack rate (5-9-year olds to 18-24-year olds, then back), and two-dose vaccine failure (63% of case-patients had received two doses). To construct a historical context in which to understand the recent outbreak, we reviewed US mumps surveillance data, vaccination coverage estimates, and relevant peer-reviewed literature for the period 1917-2008. Many of the unexpected features of the 2006 mumps outbreak had been reported several times previously in the US, e.g., the 1986-1987 mumps resurgence had extremely abrupt onset, rural geographic focality, and an upward-then-downward age shift. Evidence suggested recurrent mumps outbreak patterns were attributable to accumulation of susceptibles in dispersed situations where the risk of endemic disease exposure was low and were triggered when this susceptible population was brought together in crowded living conditions. The 2006 epidemic followed this pattern, with two unique variations: it was preceded by a period of very high vaccination rates and very low disease incidence and was characterized by two-dose failure rates among adults vaccinated in childhood. Data from the past 80 years suggest that preventing future mumps epidemics will depend on innovative measures to detect and eliminate build-up of susceptibles among highly vaccinated populations.

Dosimetric characterization of optically stimulated luminescence dosimeter with therapeutic photon beams for use in clinical radiotherapy measurements.

PubMed

Ponmalar, Retna; Manickam, Ravikumar; Ganesh, K M; Saminathan, Sathiyan; Raman, Arun; Godson, Henry Finlay

2017-01-01

The modern radiotherapy techniques impose new challenges for dosimetry systems with high precision and accuracy in in vivo and in phantom dosimetric measurements. The knowledge of the basic characterization of a dosimetric system before patient dose verification is crucial. This incites the investigation of the potential use of nanoDot optically stimulated luminescence dosimeter (OSLD) for application in radiotherapy with therapeutic photon beams. Measurements were carried out with nanoDot OSLDs to evaluate the dosimetric characteristics such as dose linearity, dependency on field size, dose rate, energy and source-to-surface distance (SSD), reproducibility, fading effect, reader stability, and signal depletion per read out with cobalt-60 (60 Co) beam, 6 and 18 MV therapeutic photon beams. The data acquired with OSLDs were validated with ionization chamber data where applicable. Good dose linearity was observed for doses up to 300 cGy and above which supralinear behavior. The standard uncertainty with field size observed was 1.10% ± 0.4%, 1.09% ± 0.34%, and 1.2% ± 0.26% for 6 MV, 18 MV, and 60 Co beam, respectively. The maximum difference with dose rate was 1.3% ± 0.4% for 6 MV and 1.4% ± 0.4% for 18 MV photon beams. The largest variation in SSD was 1.5% ± 1.2% for 60 Co, 1.5% ± 0.9% for 6 MV, and 1.5% ± 1.3% for 18 MV photon beams. The energy dependence of OSL response at 18 MV and 60 Co with 6 MV beam was 1.5% ± 0.7% and 1.7% ± 0.6%, respectively. In addition, good reproducibility, stability after the decay of transient signal, and predictable fading were observed. The results obtained in this study indicate the efficacy and suitability of nanoDot OSLD for dosimetric measurements in clinical radiotherapy.

Radiation dose delivery verification in the treatment of carcinoma-cervix

NASA Astrophysics Data System (ADS)

Shrotriya, D.; Kumar, S.; Srivastava, R. N. L.

2015-06-01

The accurate dose delivery to the clinical target volume in radiotherapy can be affected by various pelvic tissues heterogeneities. An in-house heterogeneous woman pelvic phantom was designed and used to verify the consistency and computational capability of treatment planning system of radiation dose delivery in the treatment of cancer cervix. Oncentra 3D-TPS with collapsed cone convolution (CCC) dose calculation algorithm was used to generate AP/PA and box field technique plan. the radiation dose was delivered by Primus Linac (Siemens make) employing high energy 15 MV photon beam by isocenter technique. A PTW make, 0.125cc ionization chamber was used for direct measurements at various reference points in cervix, bladder and rectum. The study revealed that maximum variation between computed and measured dose at cervix reference point was 1% in both the techniques and 3% and 4% variation in AP/PA field and 5% and 4.5% in box technique at bladder and rectum points respectively.

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

Shrotriya, D., E-mail: shrotriya2007@gmail.com; Srivastava, R. N. L.; Kumar, S.

The accurate dose delivery to the clinical target volume in radiotherapy can be affected by various pelvic tissues heterogeneities. An in-house heterogeneous woman pelvic phantom was designed and used to verify the consistency and computational capability of treatment planning system of radiation dose delivery in the treatment of cancer cervix. Oncentra 3D-TPS with collapsed cone convolution (CCC) dose calculation algorithm was used to generate AP/PA and box field technique plan. the radiation dose was delivered by Primus Linac (Siemens make) employing high energy 15 MV photon beam by isocenter technique. A PTW make, 0.125cc ionization chamber was used for directmore » measurements at various reference points in cervix, bladder and rectum. The study revealed that maximum variation between computed and measured dose at cervix reference point was 1% in both the techniques and 3% and 4% variation in AP/PA field and 5% and 4.5% in box technique at bladder and rectum points respectively.« less

SU-E-T-92: Achieving Desirable Lung Doses in Total Body Irradiation Based On in Vivo Dosimetry and Custom Tissue Compensation

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

Cui, G; Shiu, A; Zhou, S

Purpose: To achieve desirable lung doses in total body irradiation (TBI) based on in vivo dosimetry and custom tissue compensation. Methods: The 15 MV photon beam of a Varian TrueBeam STx linac was used for TBI. Patients were positioned in the lateral decubitus position for AP/PA treatment delivery. Dose was calculated using the midpoint of the separation distance across the patient’s umbilicus. Patients received 200 cGy twice daily for 3 days. The dose rate at the patient’s midplane was approximately 10 cGy/min. Cerrobend blocks with a 5-HVL thickness were used for the primary lung shielding. A custom styrofoam holder formore » rice-flour filled bags was created based on the lung block cutouts. This was used to provide further lung shielding based on in vivo dose measurements. Lucite plates and rice-flour bags were placed in the head, neck, chest, and lower extremity regions during the treatment to compensate for the beam off-axis output variations. Two patients were included in the study. Patients 1 and 2 received a craniospinal treatment (1080 cGy) and a mediastinum treatment (2520 cGy), respectively, before the TBI. During the TBI nanoDot dosimeters were placed on the patient skin in the forehead, neck, umbilicus, and lung regions for dose monitoring. The doses were readout immediately after the treatment. Based on the readings, fine tuning of the thickness of the rice-flour filled bags was exploited to achieve the desirable lung doses. Results: For both patients the mean lung doses, which took into consideration all treatments, were controlled within 900 +/−10% cGy, as desired. Doses to the forehead, neck, and umbilicus were achieved within +/−10% of the prescribed dose (1200 cGy). Conclusion: A reliable and robust method was developed to achieve desirable lung doses and uniform body dose in TBI based on in vivo dosimetry and custom tissue compensator.« less

Usefulness of a new online patient-specific quality assurance system for respiratory-gated radiotherapy.

PubMed

Kurosawa, Tomoyuki; Tachibana, Hidenobu; Moriya, Shunsuke; Miyakawa, Shin; Nishio, Teiji; Sato, Masanori

2017-11-01

The accuracy of gated irradiation may decrease when treatment is performed with short "beam-on" times. Also, the dose is subject to variation between treatment sessions if the respiratory rate is irregular. We therefore evaluated the impact of the differences between gated and non-gated treatment on doses using a new online quality assurance (QA) system for respiratory-gated radiotherapy. We generated dose estimation models to associate dose and pulse information using a 0.6 cc Farmer chamber and our QA system. During gated irradiation with each of seven regular and irregular respiratory patterns, with the Farmer chamber readings as references, we evaluated our QA system's accuracy. We then used the QA system to assess the impact of respiratory patterns on dose distribution for three lung and three liver radiotherapy plans. Gated and non-gated plans were generated and compared. There was agreement within 1.7% between the ionization chamber and our system for several regular and irregular motion patterns. For dose distributions with measured errors, there were larger differences between gated and non-gated treatment for high-dose regions within the planned treatment volume (PTV). Compared with a non-gated plan, PTV D 95% for a gated plan decreased by -1.5% to -2.6%. Doses to organs at risk were similar with both plans. Our simple system estimated the radiation dose to the patient using only pulse information from the linac, even during irregular respiration. The quality of gated irradiation for each patient can be verified fraction by fraction. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Simulation-Based Sodium Thiosulfate Dosing Strategies for the Treatment of Calciphylaxis

PubMed Central

Singh, Rajendra Pratap; Derendorf, Hartmut

2011-01-01

Summary Background and objectives Calciphylaxis remains a poorly understood life-threatening disorder with limited therapeutic options. Sodium thiosulfate (STS) has reported efficacy, thought to be because solubilizing calcium deposits promote clearance by hemodialysis (HD). Lack of rigorous pharmacokinetic studies makes it problematic for determining proper STS dosing given the expanding range of dialysis prescriptions and intensities. Design, setting, participants, & measurements The purpose of this study was to determine the dosing strategies for STS during different dialysis regimens. Given reported successes using an empiric 25 g, intravenous, 3 times per week after HD, simulations were performed to predict dosing guidelines for alternative, more or less intense dialysis to produce equivalent area under the curve drug exposure. The modeled prescriptions varied HD time from 12 to 40 h/wk over three to six sessions (Qb 200 to 400 ml/min, Qd 500 to 800 ml/min), and continuous venovenous hemodialysis at low flow rates (Qb 100 to 200 ml/min, Qd 35 to 50 ml/min), using high-flux polysulfone hemofilters. Results Simulations showed a marked variation in STS doses depending on HD frequency and duration. Blood and dialysate flows have a less prominent effect. Assuming no residual renal function, HD prescription permutations caused the dose to vary from 72 to 245 g/wk (70-kg adult), and the simulations provide specific guidelines for clinicians. Conclusions Based on the success reported for one STS dosing regimen and assuming area under the curve exposure of STS is proportional to its effect, pharmacokinetic simulations can be used to calculate the dose for alternative, higher or lower intensity dialysis regimens. These strategies are imperative to assure adequate treatment for this mortal disease, as well as to avoid toxicity from excess dosing. PMID:21441129

LDR brachytherapy: can low dose rate hypersensitivity from the "inverse" dose rate effect cause excessive cell killing to peripherial connective tissues and organs?

PubMed

Leonard, B E; Lucas, A C

2009-02-01

Examined here are the possible effects of the "inverse" dose rate effect (IDRE) on low dose rate (LDR) brachytherapy. The hyper-radiosensitivity and induced radioresistance (HRS/IRR) effect benefits cell killing in radiotherapy, and IDRE and HRS/IRR seem to be generated from the same radioprotective mechanisms. We have computed the IDRE excess cell killing experienced in LDR brachytherapy using permanent seed implants. We conclude, firstly, that IDRE is a dose rate-dependent manifestation of HRS/IRR. Secondly, the presence of HRS/IRR or IDRE in a cell species or tissue must be determined by direct dose-response measurements. Thirdly, a reasonable estimate is that 50-80% of human adjoining connective and organ tissues experience IDRE from permanent implanted LDR brachytherapy. If IDRE occurs for tissues at point A for cervical cancer, the excess cell killing will be about a factor of 3.5-4.0 if the initial dose rate is 50-70 cGy h(-1). It is greater for adjacent tissues at lower dose rates and higher for lower initial dose rates at point A. Finally, higher post-treatment complications are observed in LDR brachytherapy, often for unknown reasons. Some of these are probably a result of IDRE excess cell killing. Measurements of IDRE need be performed for connective and adjacent organ tissues, i.e. bladder, rectum, urinary tract and small bowels. The measured dose rate-dependent dose responses should extended to <10 cGy h(-1) and involve multiple patients to detect patient variability. Results may suggest a preference for high dose rate brachytherapy or LDR brachytherapy without permanent retention of the implant seeds (hence the dose rates in peripheral tissues and organs remain above IDRE thresholds).

Rapid Acute Dose Assessment Using MCNP6

NASA Astrophysics Data System (ADS)

Owens, Andrew Steven

Acute radiation doses due to physical contact with a high-activity radioactive source have proven to be an occupational hazard. Multiple radiation injuries have been reported due to manipulating a radioactive source with bare hands or by placing a radioactive source inside a shirt or pants pocket. An effort to reconstruct the radiation dose must be performed to properly assess and medically manage the potential biological effects from such doses. Using the reference computational phantoms defined by the International Commission on Radiological Protection (ICRP) and the Monte Carlo N-Particle transport code (MCNP6), dose rate coefficients are calculated to assess doses for common acute doses due to beta and photon radiation sources. The research investigates doses due to having a radioactive source in either a breast pocket or pants back pocket. The dose rate coefficients are calculated for discrete energies and can be used to interpolate for any given energy of photon or beta emission. The dose rate coefficients allow for quick calculation of whole-body dose, organ dose, and/or skin dose if the source, activity, and time of exposure are known. Doses are calculated with the dose rate coefficients and compared to results from the International Atomic Energy Agency (IAEA) reports from accidents that occurred in Gilan, Iran and Yanango, Peru. Skin and organ doses calculated with the dose rate coefficients appear to agree, but there is a large discrepancy when comparing whole-body doses assessed using biodosimetry and whole-body doses assessed using the dose rate coefficients.

AREA RADIATION MONITOR

DOEpatents

Manning, F.W.; Groothuis, S.E.; Lykins, J.H.; Papke, D.M.

1962-06-12

S>An improved area radiation dose monitor is designed which is adapted to compensate continuously for background radiation below a threshold dose rate and to give warning when the dose integral of the dose rate of an above-threshold radiation excursion exceeds a selected value. This is accomplished by providing means for continuously charging an ionization chamber. The chamber provides a first current proportional to the incident radiation dose rate. Means are provided for generating a second current including means for nulling out the first current with the second current at all values of the first current corresponding to dose rates below a selected threshold dose rate value. The second current has a maximum value corresponding to that of the first current at the threshold dose rate. The excess of the first current over the second current, which occurs above the threshold, is integrated and an alarm is given at a selected integrated value of the excess corresponding to a selected radiation dose. (AEC)

Method to determine the position-dependant metal correction factor for dose-rate equivalent laser testing of semiconductor devices

DOEpatents

Horn, Kevin M.

2013-07-09

A method reconstructs the charge collection from regions beneath opaque metallization of a semiconductor device, as determined from focused laser charge collection response images, and thereby derives a dose-rate dependent correction factor for subsequent broad-area, dose-rate equivalent, laser measurements. The position- and dose-rate dependencies of the charge-collection magnitude of the device are determined empirically and can be combined with a digital reconstruction methodology to derive an accurate metal-correction factor that permits subsequent absolute dose-rate response measurements to be derived from laser measurements alone. Broad-area laser dose-rate testing can thereby be used to accurately determine the peak transient current, dose-rate response of semiconductor devices to penetrating electron, gamma- and x-ray irradiation.

Methylation of inorganic arsenic in different mammalian species and population groups.

PubMed

Vahter, M

1999-01-01

Thousands of people in different parts of the world are exposed to arsenic via drinking water or contaminated soil or food. The high general toxic of arsenic has been known for centuries, and research during the last decades has shown that arsenic is a potent human carcinogen. However, most experimental cancer studies have failed to demonstrate carcinogenicity in experimental animals, indicating marked variation in sensitivity towards arsenic toxicity between species. It has also been suggested that there is a variation in susceptibility among human individuals. One reason for such variability in toxic response may be variation in metabolism. Inorganic arsenic is methylated in humans as well as animals and micro-organisms, but there are considerable differences between species and individuals. In many, but not all, mammalian species, inorganic arsenic is methylated to methylarsonic acid (MMA) and dimethylarsinic acid (DMA), which are more rapidly excreted in urine than is the inorganic arsenic, especially the trivalent form (AsIII, arsenite) which is highly reactive with tissue components. Absorbed arsenate (AsV) is reduced to trivalent arsenic (AsIII) before the methyl groups are attached. It has been estimated that as much as 50-70% of absorbed AsV is rapidly reduced to AsIII, a reaction which seems to be common for most species. In most experimental animal species, DMA is the main metabolite excreted in urine. Compared to human subjects, very little MMA is produced. However, the rate of methylation varies considerably between species, and several species, e.g. the marmoset monkey and the chimpanzee have been shown not to methylate inorganic arsenic at all. In addition, the marmoset monkey accumulates arsenic in the liver. The rat, on the other hand, has an efficient methylation of arsenic but the formed DMA is to a large extent accumulated in the red blood cells. As a result, the rat shows a low rate of excretion of arsenic. In both human subjects and rodents exposed to DMA, about 5% of the dose is excreted in the urine as trimethylarsine oxide. It is obvious from studies on human volunteers exposed to specified doses of inorganic arsenic that the rate of excretion increases with the methylation efficiency, and there are large inter-individual variations in the methylation of arsenic. Recent studies on people exposed to arsenic via drinking water in northern Argentina have shown unusually low urinary excretion of MMA. Furthermore, children had a lower degree of methylation of arsenic than adults. Some studies indicate a lower degree of arsenic methylation in men than in women, especially during pregnancy. Whether the observed differences in methylation of arsenic are associated with variations in the susceptibility of arsenic remains to be investigated.

Methylphenidate side effect profile is influenced by genetic variation in the attention-deficit/hyperactivity disorder-associated CES1 gene.

PubMed

Johnson, Katherine A; Barry, Edwina; Lambert, David; Fitzgerald, Michael; McNicholas, Fiona; Kirley, Aiveen; Gill, Michael; Bellgrove, Mark A; Hawi, Ziarih

2013-12-01

A naturalistic, prospective study of the influence of genetic variation on dose prescribed, clinical response, and side effects related to stimulant medication in 77 children with attention-deficit/hyperactivity disorder (ADHD) was undertaken. The influence of genetic variation of the CES1 gene coding for carboxylesterase 1A1 (CES1A1), the major enzyme responsible for the first-pass, stereoselective metabolism of methylphenidate, was investigated. Parent- and teacher-rated behavioral questionnaires were collected at baseline when the children were medication naïve, and again at 6 weeks while they were on medication. Medication dose, prescribed at the discretion of the treating clinician, and side effects, were recorded at week 6. Blood and saliva samples were collected for genotyping. Single nucleotide polymorphisms (SNPs) were selected in the coding, non-coding and the 3' flanking region of the CES1 gene. Genetic association between CES1 variants and ADHD was investigated in an expanded sample of 265 Irish ADHD families. Analyses were conducted using analysis of covariance (ANCOVA) and logistic regression models. None of the CES1 gene variants were associated with the dose of methylphenidate provided or the clinical response recorded at the 6 week time point. An association between two CES1 SNP markers and the occurrence of sadness as a side effect of short-acting methylphenidate was found. The two associated CES1 markers were in linkage disequilibrium and were significantly associated with ADHD in a larger sample of ADHD trios. The associated CES1 markers were also in linkage disequilibrium with two SNP markers of the noradrenaline transporter gene (SLC6A2). This study found an association between two CES1 SNP markers and the occurrence of sadness as a side effect of short-acting methylphenidate. These markers were in linkage disequilibrium together and with two SNP markers of the noradrenaline transporter gene.

Within- and between- subject variability in methadone pharmacokinetics and pharmacodynamics in methadone maintenance subjects

PubMed Central

Hanna, Julia; Foster, David JR; Salter, Amy; Somogyi, Andrew A; White, Jason M; Bochner, Felix

2005-01-01

Aims To investigate within- and between-subject variability of the pharmacodynamics and pharmacokinetics of (R)- and (S)-methadone in methadone maintenance subjects at steady-state. Methods Six non-holder subjects were studied on three occasions at 7–16 day intervals; doses (20–170 mg/day) remained unchanged. Blood samples and pharmacodynamic data were collected 10–12 times over a 24-h inter-dosing interval. All pharmacodynamic data were expressed as the area under the end-point versus time curve. Using analyses of variance with mixed effects, best estimates were made of the ratio of between- to within-subject variation, with corresponding 95% confidence intervals (CI) for within-subject variation at the average value. Results Subjects were relatively consistent between occasions, whereas there was much greater between-subject variability (P < 0.02) for all measures. Estimates of the ratio of between- to within-subject variation ranged from 2.2–12.8 for pharmacodynamic measures, and 1.3–7.9 for pharmacokinetic parameters. For pain, total mood disturbance, withdrawal, pupil size and respiration rate, 95% CI for within-subject measures ranged ≤2-fold, while this was greater for subjective direct opioid effects (4.2-fold). For CL/F of the active (R)-methadone, the variance ratio was 4.9 (P < 0.0003), with 95% CI for within-subject measures ranging ≤2-fold. (S)-methadone CL/F demonstrated greater within-subject variability (3.4-fold), possibly contributing to a smaller (2.7; P < 0.0003) ratio of between- to within-subject variance. Conclusions Non-holder methadone maintenance treatment participants appear to respond consistently with respect to pharmacokinetics and pharmacodynamics over a 1–2 month period. Such knowledge may help prescribers to determine whether alternative dosing regimens or treatments might be more appropriate in this population. PMID:16187972

Impact of the Amount of Liquid Intake on the Dose Rate of Patients Treated with Radioiodine.

PubMed

Haghighatafshar, Mahdi; Banani, Aida; Zeinali-Rafsanjani, Banafsheh; Etemadi, Zahra; Ghaedian, Tahereh

2018-01-01

Despite therapeutic effects of radioiodine in patients with differentiated thyroid cancer, there are some disadvantages due to harmful radiation to other tissues. According to the current guidelines, patients are recommended to drink lots of water and frequent voiding to reduce the amount of 131 I in the body. This study was designed to assess the impact of the amount of liquid intake on reduction of the measured dose rate of radioiodine-treated patients. A total of 42 patients with differentiated thyroid cancer without metastasis who had undergone total thyroidectomy and had been treated with radioiodine were selected. The patients were divided into two groups according to the amount of their fluid intake which was measured during the first 48 h after 131 I administration. In all patients, the dose rate was measured immediately and 48 h after iodine administration. Each group included 21 patients. Dose rate ratio (the ratio of the second dose rate to the first dose rate) and dose rate difference ratio (the ratio of the difference between the two measured dose rates to the first dose rate) were calculated for each patient. Despite the significant difference in the amount of the liquid drunk, no statistically significant difference was seen between the different groups in parameters of dose-rate ratio and dose-rate difference ratio. Higher fluid intake (>60 ml/h in our study) alone would not effectively reduce the patient's radiation dose rate at least not more than a well-hydrated state. It seems that other interfering factors in the thyroidectomized patients may also have some impacts on this physiologic process.

Upgrades of DARWIN, a dose and spectrum monitoring system applicable to various types of radiation over wide energy ranges

NASA Astrophysics Data System (ADS)

Sato, Tatsuhiko; Satoh, Daiki; Endo, Akira; Shigyo, Nobuhiro; Watanabe, Fusao; Sakurai, Hiroki; Arai, Yoichi

2011-05-01

A dose and spectrum monitoring system applicable to neutrons, photons and muons over wide ranges of energy, designated as DARWIN, has been developed for radiological protection in high-energy accelerator facilities. DARWIN consists of a phoswitch-type scintillation detector, a data-acquisition (DAQ) module for digital waveform analysis, and a personal computer equipped with a graphical-user-interface (GUI) program for controlling the system. The system was recently upgraded by introducing an original DAQ module based on a field programmable gate array, FPGA, and also by adding a function for estimating neutron and photon spectra based on an unfolding technique without requiring any specific scientific background of the user. The performance of the upgraded DARWIN was examined in various radiation fields, including an operational field in J-PARC. The experiments revealed that the dose rates and spectra measured by the upgraded DARWIN are quite reasonable, even in radiation fields with peak structures in terms of both spectrum and time variation. These results clearly demonstrate the usefulness of DARWIN for improving radiation safety in high-energy accelerator facilities.

Radionuclides in resident and migratory fishes of a wedge bank region: Estimation of dose to human beings, South India.

PubMed

Khan, M Feroz; Wesley, S Godwin

2012-10-01

Baseline activity concentration of (137)Cs, (210)Po and (210)Pb was determined for 25 resident and 22 migratory fish species collected in a so-called wedge bank region in the extreme south of India. A nuclear power station is now under construction at Kudankulam near the target region and the data provide background information on the radionuclide activity concentration in the region. Three-way ANOVA revealed no significant variation in the concentrations of (137)Cs, (210)Po and (210)Pb between species based on feeding habit, habitat and migratory pattern except the effect of feeding habit on (210)Po concentration (p<0.05). The annual dose due to radionuclide ingestion through the fishes was calculated based on the survey results of fish consumption rates for the local population. The dose due to (137)Cs was negligibly small while those due to (210)Po and (210)Pb varied from 1.2 to 36.9 and 0.2 to 2.9μSv yr(-1), respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Intra-cavitary dosimetry for IMRT head and neck treatment using thermoluminescent dosimeters in a naso-oesophageal tube.

PubMed

Gagliardi, F M; Roxby, K J; Engström, P E; Crosbie, J C

2009-06-21

Complex intensity-modulated radiation therapy (IMRT) treatment plans require rigorous quality assurance tests. The aim of this study was to independently verify the delivered dose inside the patient in the region of the treatment site. A flexible naso-gastric tube containing thermoluminescent dosimeters (TLDs) was inserted into the oesophagus via the sinus cavity before the patient's first treatment. Lead markers were also inserted into the tube in order that the TLD positions could be accurately determined from the lateral and anterior-posterior electronic portal images taken prior to treatment. The measured dose was corrected for both daily linac output variations and the estimated dose received from the portal images. The predicted dose for each TLD was determined from the treatment planning system and compared to the measured TLD doses. The results comprise 431 TLD measurements on 43 patients. The mean measured-to-predicted dose ratio was 0.988 +/- 0.011 (95% confidence interval) for measured doses above 0.2 Gy. There was a variation in this ratio when the measurements were separated into low dose (0.2-1.0 Gy), medium dose (1.0-1.8 Gy) and high dose (>1.8 Gy) measurements. The TLD-loaded, naso-oesophageal tube for in vivo dose verification is straightforward to implement, and well tolerated by patients. It provides independent reassurance of the delivered dose for head and neck IMRT.

Intra-cavitary dosimetry for IMRT head and neck treatment using thermoluminescent dosimeters in a naso-oesophageal tube

NASA Astrophysics Data System (ADS)

Gagliardi, F. M.; Roxby, K. J.; Engström, P. E.; Crosbie, J. C.

2009-06-01

Complex intensity-modulated radiation therapy (IMRT) treatment plans require rigorous quality assurance tests. The aim of this study was to independently verify the delivered dose inside the patient in the region of the treatment site. A flexible naso-gastric tube containing thermoluminescent dosimeters (TLDs) was inserted into the oesophagus via the sinus cavity before the patient's first treatment. Lead markers were also inserted into the tube in order that the TLD positions could be accurately determined from the lateral and anterior-posterior electronic portal images taken prior to treatment. The measured dose was corrected for both daily linac output variations and the estimated dose received from the portal images. The predicted dose for each TLD was determined from the treatment planning system and compared to the measured TLD doses. The results comprise 431 TLD measurements on 43 patients. The mean measured-to-predicted dose ratio was 0.988 ± 0.011 (95% confidence interval) for measured doses above 0.2 Gy. There was a variation in this ratio when the measurements were separated into low dose (0.2-1.0 Gy), medium dose (1.0-1.8 Gy) and high dose (>1.8 Gy) measurements. The TLD-loaded, naso-oesophageal tube for in vivo dose verification is straightforward to implement, and well tolerated by patients. It provides independent reassurance of the delivered dose for head and neck IMRT.

Recommended de minimis radiation dose rates for Canada. Report No. INFO-0355

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

Not Available

1990-01-01

A de minimis dose or dose rate as used in this report represents a level of risk which is generally accepted as being of no significance to an individual, or in the case of a population, of no significance to society. The report describes the risk of biological effects from radiation; radiation from natural and man-made sources; normal incidences of cancer and genetic defects; initiatives by other agencies in the U.S., the U.K. and internationally; the importance of collective dose and dose rate; assigning values to the de minimis dose rates; and application of the de minimis dose rates.

Occurrence of 210Po in marine macroalgae inhabiting a coastal nuclear zone, southeast coast of India.

PubMed

Praveen Pole, R P; Feroz Khan, M; Godwin Wesley, S

2017-04-01

The activity concentration of 210 Po in 26 species of marine macroalgae found along coast near to a nuclear installation in southeast coast of India was studied. Phaeophytes were found to accumulate the maximum 210 Po concentration and chlorophytes the minimum. The average 210 Po activity concentration values in the three groups were 6.2 ± 2.5 Bq kg -1 (Chlorophyta), 14.4 ± 5.2 Bq kg -1 (Phaeophyta) and 11.3 ± 3.9 Bq kg -1 (Rhodophyta). A statistically significant variation in accumulation was found between groups (p < 0.05). The un-weighted dose rate to these algae due to 210 Po was calculated to be well below the benchmark dose limit of 10 μGy h -1 . Copyright © 2017 Elsevier Ltd. All rights reserved.

Reload of an industrial cylindrical cobalt source rack

NASA Astrophysics Data System (ADS)

Gharbi, F.; Kadri, O.; Trabelsi, A.

2006-10-01

This work presents a Monte Carlo study of the cylindrical cobalt source rack geometry of the Tunisian gamma irradiation facility, using the GEANT code developed at CERN. The study investigates the question of the reload of the source rack. The studied configurations consist in housing four new cobalt pencils, two in the upper and two in the lower cylinder of the source rack. Global dose rate uniformity inside a "dummy" product for the case of routine and nonroutine irradiation, and as function of the product bulk density, was calculated for eight hypothetical configurations. The same calculation was also performed for both of the original and the ideal (but not practical) configurations. It was shown that hypothetical cases produced dose uniformity variations, according to product density, that were statistically no different than the original and the ideal configurations and that the reload procedure cannot improve the irradiation quality inside the facilities using cylindrical cobalt source racks.

Study of the dose rate effect of 180 nm nMOSFETs

NASA Astrophysics Data System (ADS)

He, Bao-Ping; Yao, Zhi-Bin; Sheng, Jiang-Kun; Wang, Zu-Jun; Huang, Shao-Yan; Liu, Min-Bo; Xiao, Zhi-Gang

2015-01-01

Radiation induced offstate leakage in the shallow trench isolation regions of SIMC 0.18 μm nMOSFETs is studied as a function of dose rate. A “true” dose rate effect (TDRE) is observed. Increased damage is observed at low dose rate (LDR) than at high dose rate (HDR) when annealing is taken into account. A new method of simulating radiation induced degradation in shallow trench isolation (STI) is presented. A comparison of radiation induced offstate leakage current in test nMOSFETs between total dose irradiation experiments and simulation results exhibits excellent agreement. The investigation results imply that the enhancement of the leakage current may be worse for the dose rate encountered in the environment of space.

Organ Doses Associated with Partial-Body Irradiation with 2.5% Bone Marrow Sparing of the Non-Human Primate: A Retrospective Study.

PubMed

Prado, C; MacVittie, T J; Bennett, A W; Kazi, A; Farese, A M; Prado, K

2017-12-01

A partial-body irradiation model with approximately 2.5% bone marrow sparing (PBI/BM2.5) was established to determine the radiation dose-response relationships for the prolonged and delayed multi-organ effects of acute radiation exposure. Historically, doses reported to the entire body were assumed to be equal to the prescribed dose at some defined calculation point, and the dose-response relationship for multi-organ injury has been defined relative to the prescribed dose being delivered at this point, e.g., to a point at mid-depth at the level of the xiphoid of the non-human primate (NHP). In this retrospective-dose study, the true distribution of dose within the major organs of the NHP was evaluated, and these doses were related to that at the traditional dose-prescription point. Male rhesus macaques were exposed using the PBI/BM2.5 protocol to a prescribed dose of 10 Gy using 6-MV linear accelerator photons at a rate of 0.80 Gy/min. Point and organ doses were calculated for each NHP from computed tomography (CT) scans using heterogeneous density data. The prescribed dose of 10.0 Gy to a point at midline tissue assuming homogeneous media resulted in 10.28 Gy delivered to the prescription point when calculated using the heterogeneous CT volume of the NHP. Respective mean organ doses to the volumes of nine organs, including the heart, lung, bowel and kidney, were computed. With modern treatment planning systems, utilizing a three-dimensional reconstruction of the NHP's CT images to account for the variations in body shape and size, and using density corrections for each of the tissue types, bone, water, muscle and air, accurate determination of the differences in dose to the NHP can be achieved. Dose and volume statistics can be ascertained for any body structure or organ that has been defined using contouring tools in the planning system. Analysis of the dose delivered to critical organs relative to the total-body target dose will permit a more definitive analysis of organ-specific effects and their respective influence in multiple organ injury.

A new tissue segmentation method to calculate 3D dose in small animal radiation therapy.

PubMed

Noblet, C; Delpon, G; Supiot, S; Potiron, V; Paris, F; Chiavassa, S

2018-02-26

In pre-clinical animal experiments, radiation delivery is usually delivered with kV photon beams, in contrast to the MV beams used in clinical irradiation, because of the small size of the animals. At this medium energy range, however, the contribution of the photoelectric effect to absorbed dose is significant. Accurate dose calculation therefore requires a more detailed tissue definition because both density (ρ) and elemental composition (Z eff ) affect the dose distribution. Moreover, when applied to cone beam CT (CBCT) acquisitions, the stoichiometric calibration of HU becomes inefficient as it is designed for highly collimated fan beam CT acquisitions. In this study, we propose an automatic tissue segmentation method of CBCT imaging that assigns both density (ρ) and elemental composition (Z eff ) in small animal dose calculation. The method is based on the relationship found between CBCT number and ρ*Z eff product computed from known materials. Monte Carlo calculations were performed to evaluate the impact of ρZ eff variation on the absorbed dose in tissues. These results led to the creation of a tissue database composed of artificial tissues interpolated from tissue values published by the ICRU. The ρZ eff method was validated by measuring transmitted doses through tissue substitute cylinders and a mouse with EBT3 film. Measurements were compared to the results of the Monte Carlo calculations. The study of the impact of ρZ eff variation over the range of materials, from ρZ eff  = 2 g.cm - 3 (lung) to 27 g.cm - 3 (cortical bone) led to the creation of 125 artificial tissues. For tissue substitute cylinders, the use of ρZ eff method led to maximal and average relative differences between the Monte Carlo results and the EBT3 measurements of 3.6% and 1.6%. Equivalent comparison for the mouse gave maximal and average relative differences of 4.4% and 1.2%, inside the 80% isodose area. Gamma analysis led to a 94.9% success rate in the 10% isodose area with 4% and 0.3 mm criteria in dose and distance. Our new tissue segmentation method was developed for 40kVp CBCT images. Both density and elemental composition are assigned to each voxel by using a relationship between HU and the product ρZ eff . The method, validated by comparing measurements and calculations, enables more accurate small animal dose distribution calculated on low energy CBCT images.

Quality improvement in neonatal digital radiography: implementing the basic quality improvement tools.

PubMed

Eslamy, Hedieh K; Newman, Beverley; Weinberger, Ed

2014-12-01

A quality improvement (QI) program may be implemented using the plan-do-study-act cycle (as a model for making improvements) and the basic QI tools (used to visually display and analyze variation in data). Managing radiation dose has come to the forefront as a safety goal for radiology departments. This is especially true in the pediatric population, which is more radiosensitive than the adult population. In this article, we use neonatal digital radiography to discuss developing a QI program with the principle goals of decreasing the radiation dose, decreasing variation in radiation dose, and optimizing image quality. Copyright © 2014 Elsevier Inc. All rights reserved.

The threshold vs LNT showdown: Dose rate findings exposed flaws in the LNT model part 1. The Russell-Muller debate

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

Calabrese, Edward J., E-mail: edwardc@schoolph.uma

This paper assesses the discovery of the dose-rate effect in radiation genetics and how it challenged fundamental tenets of the linear non-threshold (LNT) dose response model, including the assumptions that all mutational damage is cumulative and irreversible and that the dose-response is linear at low doses. Newly uncovered historical information also describes how a key 1964 report by the International Commission for Radiological Protection (ICRP) addressed the effects of dose rate in the assessment of genetic risk. This unique story involves assessments by two leading radiation geneticists, Hermann J. Muller and William L. Russell, who independently argued that the report'smore » Genetic Summary Section on dose rate was incorrect while simultaneously offering vastly different views as to what the report's summary should have contained. This paper reveals occurrences of scientific disagreements, how conflicts were resolved, which view(s) prevailed and why. During this process the Nobel Laureate, Muller, provided incorrect information to the ICRP in what appears to have been an attempt to manipulate the decision-making process and to prevent the dose-rate concept from being adopted into risk assessment practices. - Highlights: • The discovery of radiation dose rate challenged the scientific basis of LNT. • Radiation dose rate occurred in males and females. • The dose rate concept supported a threshold dose-response for radiation.« less

Quantitative assessment of hit detection and confirmation in single and duplicate high-throughput screenings.

PubMed

Wu, Zhijin; Liu, Dongmei; Sui, Yunxia

2008-02-01

The process of identifying active targets (hits) in high-throughput screening (HTS) usually involves 2 steps: first, removing or adjusting for systematic variation in the measurement process so that extreme values represent strong biological activity instead of systematic biases such as plate effect or edge effect and, second, choosing a meaningful cutoff on the calculated statistic to declare positive compounds. Both false-positive and false-negative errors are inevitable in this process. Common control or estimation of error rates is often based on an assumption of normal distribution of the noise. The error rates in hit detection, especially false-negative rates, are hard to verify because in most assays, only compounds selected in primary screening are followed up in confirmation experiments. In this article, the authors take advantage of a quantitative HTS experiment in which all compounds are tested 42 times over a wide range of 14 concentrations so true positives can be found through a dose-response curve. Using the activity status defined by dose curve, the authors analyzed the effect of various data-processing procedures on the sensitivity and specificity of hit detection, the control of error rate, and hit confirmation. A new summary score is proposed and demonstrated to perform well in hit detection and useful in confirmation rate estimation. In general, adjusting for positional effects is beneficial, but a robust test can prevent overadjustment. Error rates estimated based on normal assumption do not agree with actual error rates, for the tails of noise distribution deviate from normal distribution. However, false discovery rate based on empirically estimated null distribution is very close to observed false discovery proportion.

SU-E-T-800: Verification of Acurose XB Dose Calculation Algorithm at Air Cavity-Tissue Interface Using Film Measurement for Small Fields of 6-MV Flattening Filter-Free Beams

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

Kang, S; Suh, T; Chung, J

2015-06-15

Purpose: To verify the dose accuracy of Acuros XB (AXB) dose calculation algorithm at air-tissue interface using inhomogeneous phantom for 6-MV flattening filter-free (FFF) beams. Methods: An inhomogeneous phantom included air cavity was manufactured for verifying dose accuracy at the air-tissue interface. The phantom was composed with 1 and 3 cm thickness of air cavity. To evaluate the central axis doses (CAD) and dose profiles of the interface, the dose calculations were performed for 3 × 3 and 4 × 4 cm{sup 2} fields of 6 MV FFF beams with AAA and AXB in Eclipse treatment plainning system. Measurements inmore » this region were performed with Gafchromic film. The root mean square errors (RMSE) were analyzed with calculated and measured dose profile. Dose profiles were divided into inner-dose profile (>80%) and penumbra (20% to 80%) region for evaluating RMSE. To quantify the distribution difference, gamma evaluation was used and determined the agreement with 3%/3mm criteria. Results: The percentage differences (%Diffs) between measured and calculated CAD in the interface, AXB shows more agreement than AAA. The %Diffs were increased with increasing the thickness of air cavity size and it is similar for both algorithms. In RMSEs of inner-profile, AXB was more accurate than AAA. The difference was up to 6 times due to overestimation by AAA. RMSEs of penumbra appeared to high difference for increasing the measurement depth. Gamma agreement also presented that the passing rates decreased in penumbra. Conclusion: This study demonstrated that the dose calculation with AXB shows more accurate than with AAA for the air-tissue interface. The 2D dose distributions with AXB for both inner-profile and penumbra showed better agreement than with AAA relative to variation of the measurement depths and air cavity sizes.« less

Quality assurance of dynamic parameters in volumetric modulated arc therapy.

PubMed

Manikandan, A; Sarkar, B; Holla, R; Vivek, T R; Sujatha, N

2012-07-01

The purpose of this study was to demonstrate quality assurance checks for accuracy of gantry speed and position, dose rate and multileaf collimator (MLC) speed and position for a volumetric modulated arc treatment (VMAT) modality (Synergy S; Elekta, Stockholm, Sweden), and to check that all the necessary variables and parameters were synchronous. Three tests (for gantry position-dose delivery synchronisation, gantry speed-dose delivery synchronisation and MLC leaf speed and positions) were performed. The average error in gantry position was 0.5° and the average difference was 3 MU for a linear and a parabolic relationship between gantry position and delivered dose. In the third part of this test (sawtooth variation), the maximum difference was 9.3 MU, with a gantry position difference of 1.2°. In the sweeping field method test, a linear relationship was observed between recorded doses and distance from the central axis, as expected. In the open field method, errors were encountered at the beginning and at the end of the delivery arc, termed the "beginning" and "end" errors. For MLC position verification, the maximum error was -2.46 mm and the mean error was 0.0153 ±0.4668 mm, and 3.4% of leaves analysed showed errors of >±1 mm. This experiment demonstrates that the variables and parameters of the Synergy S are synchronous and that the system is suitable for delivering VMAT using a dynamic MLC.

TU-EF-304-12: Proton Radiation Therapy for Left-Sided Breast Cancer: LET and RBE Considerations for Cardiac Toxicity

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

Giantsoudi, D; Jee, K; MacDonald, S

Purpose: Increased risk of coronary artery disease has been documented for patients treated with radiation for left-sided breast cancer. Proton therapy (PRT) has been shown to significantly decrease cardiac irradiation, however variations in relative biological effectiveness (RBE) have been ignored so far. In this study we evaluate the impact of accounting for RBE variations on sensitive structures located within high linear energy transfer (LET) areas (distal end) of the proton treatment fields, for this treatment site. Methods: Three patients treated in our institution with PRT for left-sided breast cancer were selected. All patients underwent reconstructive surgery after mastectomy and treatedmore » to a total dose of 50.4Gy with beam(s) vertical to the chest wall. Dose and LET distributions were calculated using Monte Carlo (MC-TOPAS - TOol for PArticle Simulation). The LET-based, variable-RBE-weighted dose was compared to the analytical calculation algorithm (ACA) and MC dose distributions for a constant RBE of 1.1, based on volume histograms and mean values for the target, heart and left anterior descending coronary artery (LAD). Results: Assuming a constant RBE and compared to the ACA dose, MC predicted lower mean target and heart doses by 0.5% to 2.7% of the prescription dose. For variable RBE, plan evaluation showed increased mean target dose by up to 5%. Mean variable-RBE-weighted doses for the LAD ranged from 2.7 to 5.9Gy(RBE) among patients increased by 41%–64.2% compared to constant RBE ACA calculation (absolute dose: 1.7–3.9Gy(RBE)). Smaller increase in mean heart doses was noticed. Conclusion: ACA overestimates the target mean dose by up to 2.7%. However, disregarding variations in RBE may lead to significant underestimation of the dose to sensitive structures at the distal end of the proton treatment field and could thus impact outcome modeling for cardiac toxicities after proton therapy. These results are subject to RBE model and parameter uncertainties.« less

Characteristics of flattening filter free beams at low monitor unit settings.

PubMed

Akino, Yuichi; Ota, Seiichi; Inoue, Shinichi; Mizuno, Hirokazu; Sumida, Iori; Yoshioka, Yasuo; Isohashi, Fumiaki; Ogawa, Kazuhiko

2013-11-01

Newer linear accelerators (linacs) have been equipped to deliver flattening filter free (FFF) beams. When FFF beams are used for step-and-shoot intensity-modulated radiotherapy (IMRT), the stability of delivery of small numbers of monitor units (MU) is important. The authors developed automatic measurement techniques to evaluate the stability of the dose profile, dose linearity, and consistency. Here, the authors report the performance of the Artiste™ accelerator (Siemens, Erlangen, Germany) in delivering low-MU FFF beams. A 6 MV flattened beam (6X) with 300 MU/min dose rate and FFF beams of 7 (7XU) and 11 MV (11XU), each with a 500 MU/min dose rate, were measured at 1, 2, 3, 5, 8, 10, and 20 MU settings. For the 2000 MU/min dose rate, the 7 (7XUH) and 11 MV (11XUH) beams were set at 10, 15, 20, 25, and 30 MU because of the limits of the minimum MU settings. Beams with 20 × 20 and 10 × 10 cm(2) field sizes were alternately measured ten times in intensity modulated (IM) mode, with which Siemens linacs regulate beam delivery for step-and-shoot IMRT. The in- and crossplane beam profiles were measured using a Profiler™ Model 1170 (Sun Nuclear Corporation, Melbourne, FL) in multiframe mode. The frames of 20 × 20 cm(2) beams were identified at the off-axis profile. The 6X beam profile was normalized at the central axis. The 7 and 11 MV FFF beam profiles were rescaled to set the dose at the central axis at 145% and 170%, respectively. Point doses were also measured using a Farmer-type ionization chamber and water-equivalent solid phantom to evaluate the linearity and consistency of low-MU beam delivery. The values displayed on the electrometer were recognized with a USB-type camera and read with open-source optical character recognition software. The symmetry measurements of the 6X, 7XU, and 11XU beam profiles were better than 2% for beams ≥ 2 MU and improved with increasing MU. The variations in flatness of FFF beams ≥ 2 MU were ± 5%. The standard deviation of the symmetry and flatness also decreased with increasing MU. The linearity of the 6X beam was ± 1% and ± 2% for the beams of ≥ 5 and ≥ 3 MU, respectively. The 7XU and 11XU beams of ≥ 2 MU showed linearity with ± 2% except the 7XU beam of 8 MU (+2.9%). The profiles of the FFF beams with 2000 and 500 MU/min dose rate were similar. The characteristics of low-MU beams delivered in IM mode were evaluated using an automatic measurement system developed in this study. The authors demonstrated that the profiles of FFF beams of the Artiste™ linac were highly stable, even at low MU. The linearity of dose output was also stable for beams ≥ 2 MU.

Subjective and Cardiovascular Effects of Intravenous Methamphetamine during Perindopril Maintenance: A Randomized, Double-Blind, Placebo-Controlled Human Laboratory Study.

PubMed

Verrico, Christopher D; Haile, Colin N; De La Garza, Richard; Grasing, Kenneth; Kosten, Thomas R; Newton, Thomas F

2016-07-01

Our pilot study suggested that the angiotensin-converting enzyme inhibitor perindopril might reduce some subjective effects produced by i.v. methamphetamine. We characterized the impact of a wider range of perindopril doses on methamphetamine-induced effects in a larger group of non-treatment-seeking, methamphetamine-using volunteers. Before treatment, participants received 30mg methamphetamine. After 5 to 7 days of perindopril treatment (0, 4, 8, or 16mg/d), participants received 15 and 30mg of methamphetamine on alternate days. Before and after treatment, participants rated subjective effects and cardiovascular measures were collected. Prior to treatment with perindopril, there were no significant differences between treatment groups on maximum or peak subjective ratings or on peak cardiovascular effects. Following perindopril treatment, there were significant main effects of treatment on peak subjective ratings of "anxious" and "stimulated"; compared to placebo treatment, treatment with 8mg perindopril significantly reduced peak ratings of both anxious (P=.0009) and stimulated (P=.0070). There were no significant posttreatment differences between groups on peak cardiovascular effects. Moderate doses of perindopril (8mg) significantly reduced peak subjective ratings of anxious and stimulated as well as attenuated many other subjective effects produced by methamphetamine, likely by inhibiting angiotensin II synthesis. Angiotensin II is known to facilitate the effects of norepinephrine, which contributes to methamphetamine's subjective effects. The lack of a classic dose-response function likely results from either nonspecific effects of perindopril or from between-group differences that were not accounted for in the current study (i.e., genetic variations and/or caffeine use). The current findings suggest that while angiotensin-converting enzyme inhibitors can reduce some effects produced by methamphetamine, more consistent treatment effects might be achieved by targeting components of the renin-angiotensin system that are downstream of angiotensin-converting enzyme. © The Author 2016. Published by Oxford University Press on behalf of CINP.

Circadian variation in serum cortisol during hydrocortisone replacement is not attributable to changes in cortisol-binding globulin concentrations.

PubMed

Chung, T T; Gunganah, K; Monson, J P; Drake, W M

2016-04-01

Patients taking hydrocortisone (HC) replacement for primary or secondary adrenal failure require individual adjustment of their dose. In addition to modifying the administered doses of HC for each patient, physicians are increasingly interested in variations in the bioavailability of glucocorticoid replacement. One potential determinant of the bioavailability of replaced HC is a variation in serum cortisol-binding globulin (CBG) concentration, which may, in turn, affect interpretation of cortisol profiles and individual dose selection for patients on hydrocortisone replacement therapy. To investigate the hypothesis that there is a circadian variation in CBG levels. A total of 34 male patients divided into 3 groups (10 patients with non-somatotroph structural pituitary disease on HC replacement, 11 patients with treated acromegaly on HC replacement and 13 patients with treated acromegaly not on HC replacement) and 10 healthy volunteers were included. Cortisol and CBG levels were measured at 6 time points (0800, 1100, 1300, 1500, 1700 and 1900). No significant circadian variation in CBG concentration was found in any of the 4 groups. Circadian variation in serum cortisol during hydrocortisone replacement is not attributable to changes in cortisol-binding globulin concentration. Changes in serum cortisol levels may thus be explained by other factors including 11 β-hydroxysteroid dehydrogenase type 1 activity or circadian changes in the binding properties of CBG. © 2015 John Wiley & Sons Ltd.

128-slice Dual-source Computed Tomography Coronary Angiography in Patients with Atrial Fibrillation: Image Quality and Radiation Dose of Prospectively Electrocardiogram-triggered Sequential Scan Compared with Retrospectively Electrocardiogram-gated Spiral Scan.

PubMed

Lin, Lu; Wang, Yi-Ning; Kong, Ling-Yan; Jin, Zheng-Yu; Lu, Guang-Ming; Zhang, Zhao-Qi; Cao, Jian; Li, Shuo; Song, Lan; Wang, Zhi-Wei; Zhou, Kang; Wang, Ming

2013-01-01

Objective To evaluate the image quality (IQ) and radiation dose of 128-slice dual-source computed tomography (DSCT) coronary angiography using prospectively electrocardiogram (ECG)-triggered sequential scan mode compared with ECG-gated spiral scan mode in a population with atrial fibrillation. Methods Thirty-two patients with suspected coronary artery disease and permanent atrial fibrillation referred for a second-generation 128-slice DSCT coronary angiography were included in the prospective study. Of them, 17 patients (sequential group) were randomly selected to use a prospectively ECG-triggered sequential scan, while the other 15 patients (spiral group) used a retrospectively ECG-gated spiral scan. The IQ was assessed by two readers independently, using a four-point grading scale from excel-lent (grade 1) to non-assessable (grade 4), based on the American Heart Association 15-segment model. IQ of each segment and effective dose of each patient were compared between the two groups. Results The mean heart rate (HR) of the sequential group was 96±27 beats per minute (bpm) with a variation range of 73±25 bpm, while the mean HR of the spiral group was 86±22 bpm with a variationrange of 65±24 bpm. Both of the mean HR (t=1.91, P=0.243) and HR variation range (t=0.950, P=0.350) had no significant difference between the two groups. In per-segment analysis, IQ of the sequential group vs. spiral group was rated as excellent (grade 1) in 190/244 (78%) vs. 177/217 (82%) by reader1 and 197/245 (80%) vs. 174/214 (81%) by reader2, as non-assessable (grade 4) in 4/244 (2%) vs. 2/217 (1%) by reader1 and 6/245 (2%) vs. 4/214 (2%) by reader2. Overall averaged IQ per-patient in the sequential and spiral group showed equally good (1.27±0.19 vs. 1.25±0.22, Z=-0.834, P=0.404). The effective radiation dose of the sequential group reduced significantly compared with the spiral group (4.88±1.77 mSv vs. 10.20±3.64 mSv; t=-5.372, P=0.000). Conclusion Compared with retrospectively ECG-gated spiral scan, prospectively ECG-triggered sequential DSCT coronary angiography provides similarly diagnostically valuable images in patients with atrial fibrillation and significantly reduces radiation dose.

Risk-adjusted antibiotic consumption in 34 public acute hospitals in Ireland, 2006 to 2014

PubMed Central

Oza, Ajay; Donohue, Fionnuala; Johnson, Howard; Cunney, Robert

2016-01-01

As antibiotic consumption rates between hospitals can vary depending on the characteristics of the patients treated, risk-adjustment that compensates for the patient-based variation is required to assess the impact of any stewardship measures. The aim of this study was to investigate the usefulness of patient-based administrative data variables for adjusting aggregate hospital antibiotic consumption rates. Data on total inpatient antibiotics and six broad subclasses were sourced from 34 acute hospitals from 2006 to 2014. Aggregate annual patient administration data were divided into explanatory variables, including major diagnostic categories, for each hospital. Multivariable regression models were used to identify factors affecting antibiotic consumption. Coefficient of variation of the root mean squared errors (CV-RMSE) for the total antibiotic usage model was very good (11%), however, the value for two of the models was poor (> 30%). The overall inpatient antibiotic consumption increased from 82.5 defined daily doses (DDD)/100 bed-days used in 2006 to 89.2 DDD/100 bed-days used in 2014; the increase was not significant after risk-adjustment. During the same period, consumption of carbapenems increased significantly, while usage of fluoroquinolones decreased. In conclusion, patient-based administrative data variables are useful for adjusting hospital antibiotic consumption rates, although additional variables should also be employed. PMID:27541730

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

Buckley, L; Lambert, C; Nyiri, B

Purpose: To standardize the tube calibration for Elekta XVI cone beam CT (CBCT) systems in order to provide a meaningful estimate of the daily imaging dose and reduce the variation between units in a large centre with multiple treatment units. Methods: Initial measurements of the output from the CBCT systems were made using a Farmer chamber and standard CTDI phantom. The correlation between the measured CTDI and the tube current was confirmed using an Unfors Xi detector which was then used to perform a tube current calibration on each unit. Results: Initial measurements showed measured tube current variations of upmore » to 25% between units for scans with the same image settings. In order to reasonably estimate the imaging dose, a systematic approach to x-ray generator calibration was adopted to ensure that the imaging dose was consistent across all units at the centre and was adopted as part of the routine quality assurance program. Subsequent measurements show that the variation in measured dose across nine units is on the order of 5%. Conclusion: Increasingly, patients receiving radiation therapy have extended life expectancies and therefore the cumulative dose from daily imaging should not be ignored. In theory, an estimate of imaging dose can be made from the imaging parameters. However, measurements have shown that there are large differences in the x-ray generator calibration as installed at the clinic. Current protocols recommend routine checks of dose to ensure constancy. The present study suggests that in addition to constancy checks on a single machine, a tube current calibration should be performed on every unit to ensure agreement across multiple machines. This is crucial at a large centre with multiple units in order to provide physicians with a meaningful estimate of the daily imaging dose.« less

The impact of inter-fraction dose variations on biological equivalent dose (BED): the concept of equivalent constant dose.

PubMed

Zavgorodni, S

2004-12-07

Inter-fraction dose fluctuations, which appear as a result of setup errors, organ motion and treatment machine output variations, may influence the radiobiological effect of the treatment even when the total delivered physical dose remains constant. The effect of these inter-fraction dose fluctuations on the biological effective dose (BED) has been investigated. Analytical expressions for the BED accounting for the dose fluctuations have been derived. The concept of biological effective constant dose (BECD) has been introduced. The equivalent constant dose (ECD), representing the constant physical dose that provides the same cell survival fraction as the fluctuating dose, has also been introduced. The dose fluctuations with Gaussian as well as exponential probability density functions were investigated. The values of BECD and ECD calculated analytically were compared with those derived from Monte Carlo modelling. The agreement between Monte Carlo modelled and analytical values was excellent (within 1%) for a range of dose standard deviations (0-100% of the dose) and the number of fractions (2 to 37) used in the comparison. The ECDs have also been calculated for conventional radiotherapy fields. The analytical expression for the BECD shows that BECD increases linearly with the variance of the dose. The effect is relatively small, and in the flat regions of the field it results in less than 1% increase of ECD. In the penumbra region of the 6 MV single radiotherapy beam the ECD exceeded the physical dose by up to 35%, when the standard deviation of combined patient setup/organ motion uncertainty was 5 mm. Equivalently, the ECD field was approximately 2 mm wider than the physical dose field. The difference between ECD and the physical dose is greater for normal tissues than for tumours.

Impact of the Revised 10 CFR 835 on the Neutron Dose Rates at LLNL

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

Radev, R

2009-01-13

In June 2007, 10 CFR 835 [1] was revised to include new radiation weighting factors for neutrons, updated dosimetric models, and dose terms consistent with the newer ICRP recommendations. A significant aspect of the revised 10 CFR 835 is the adoption of the recommendations outlined in ICRP-60 [2]. The recommended new quantities demand a review of much of the basic data used in protection against exposure to sources of ionizing radiation. The International Commission on Radiation Units and Measurements has defined a number of quantities for use in personnel and area monitoring [3,4,5] including the ambient dose equivalent H*(d) tomore » be used for area monitoring and instrument calibrations. These quantities are used in ICRP-60 and ICRP-74. This report deals only with the changes in the ambient dose equivalent and ambient dose rate equivalent for neutrons as a result of the implementation of the revised 10 CFR 835. In the report, the terms neutron dose and neutron dose rate will be used for convenience for ambient neutron dose and ambient neutron dose rate unless otherwise stated. This report provides a qualitative and quantitative estimate of how much the neutron dose rates at LLNL will change with the implementation of the revised 10 CFR 835. Neutron spectra and dose rates from selected locations at the LLNL were measured with a high resolution spectroscopic neutron dose rate system (ROSPEC) as well as with a standard neutron rem meter (a.k.a., a remball). The spectra obtained at these locations compare well with the spectra from the Radiation Calibration Laboratory's (RCL) bare californium source that is currently used to calibrate neutron dose rate instruments. The measurements obtained from the high resolution neutron spectrometer and dose meter ROSPEC and the NRD dose meter compare within the range of {+-}25%. When the new radiation weighting factors are adopted with the implementation of the revised 10 CFR 835, the measured dose rates will increase by up to 22%. The health physicists should consider this increase for any areas that have dose rates near a posting limit, such as near the 100 mrem/hr for a high radiation area, as this increase in measured dose rate may result in some changes to postings and consequent radiological controls.« less

Comparison in vivo Study of Genotoxic Action of High- Versus Very Low Dose-Rate γ-Irradiation

PubMed Central

Osipov, A. N.; Klokov, D. Y.; Elakov, A. L.; Rozanova, O. M.; Zaichkina, S. I.; Aptikaeva, G. F.; Akhmadieva, A. Kh.

2004-01-01

The aim of the present study was to compare genotoxicity induced by high- versus very low dose-rate exposure of mice to γ-radiation within a dose range of 5 to 61 cGy using the single-cell gel electrophoresis (comet) assay and the micronucleus test. CBA/lac male mice were irradiated at a dose rate of 28.2 Gy/h (high dose rate) or 0.07 mGy/h (very low dose rate). The comet assay study on spleen lymphocytes showed that very low dose-rate irradiation resulted in a statistically significant increase in nucleoid relaxation (DNA breaks), starting from a dose of 20 cGy. Further prolongation of exposure time and, hence, increase of a total dose did not, however, lead to further increase in the extent of nucleoid relaxation. Doses of 20 and 61 cGy were equal in inducing DNA breaks in mouse spleen lymphocytes as assayed by the comet assay. Of note, the level of DNA damage by 20–61 cGy doses of chronic irradiation (0.07 mGy/h) was similar to that an induced by an acute (28.2 Gy/h) dose of 14 cGy. The bone marrow micronucleus test revealed that an increase in polychromatic erythrocytes with micronuclei over a background level was induced by very low-level γ-irradiation with a dose of 61 cGy only, with the extent of the cytogenetic effect being similar to that of 10 cGy high-dose-rate exposure. In summary, presented results support the hypothesis of the nonlinear threshold nature of mutagenic action of chronic low dose-rate irradiation. PMID:19330145

The estimation of galactic cosmic ray penetration and dose rates

NASA Technical Reports Server (NTRS)

Burrell, M. O.; Wright, J. J.

1972-01-01

This study is concerned with approximation methods that can be readily applied to estimate the absorbed dose rate from cosmic rays in rads - tissue or rems inside simple geometries of aluminum. The present work is limited to finding the dose rate at the center of spherical shells or behind plane slabs. The dose rate is calculated at tissue-point detectors or for thin layers of tissue. This study considers cosmic-rays dose rates for both free-space and earth-orbiting missions.

Estimation of ambient dose equivalent distribution in the 18F-FDG administration room using Monte Carlo simulation.

PubMed

Nagamine, Shuji; Fujibuchi, Toshioh; Umezu, Yoshiyuki; Himuro, Kazuhiko; Awamoto, Shinichi; Tsutsui, Yuji; Nakamura, Yasuhiko

2017-03-01

In this study, we estimated the ambient dose equivalent rate (hereafter "dose rate") in the fluoro-2-deoxy-D-glucose (FDG) administration room in our hospital using Monte Carlo simulations, and examined the appropriate medical-personnel locations and a shielding method to reduce the dose rate during FDG injection using a lead glass shield. The line source was assumed to be the FDG feed tube and the patient a cube source. The dose rate distribution was calculated with a composite source that combines the line and cube sources. The dose rate distribution was also calculated when a lead glass shield was placed in the rear section of the lead-acrylic shield. The dose rate behind the automatic administration device decreased by 87 % with respect to that behind the lead-acrylic shield. Upon positioning a 2.8-cm-thick lead glass shield, the dose rate behind the lead-acrylic shield decreased by 67 %.

Comparison of Monoenergetic Photon Organ Dose Rate Coefficients for the Female Stylized and Voxel Phantoms Submerged in Air

DOE PAGES

Hiller, Mauritius; Dewji, Shaheen Azim

2017-02-16

Dose rate coefficients computed using the International Commission on Radiological Protection (ICRP) reference adult female voxel phantom were compared with values computed using the Oak Ridge National Laboratory (ORNL) adult female stylized phantom in an air submersion exposure geometry. This is a continuation of previous work comparing monoenergetic organ dose rate coefficients for the male adult phantoms. With both the male and female data computed, effective dose rate as defined by ICRP Publication 103 was compared for both phantoms. Organ dose rate coefficients for the female phantom and ratios of organ dose rates for the voxel and stylized phantoms aremore » provided in the energy range from 30 to 5 MeV. Analysis of the contribution of the organs to effective dose is also provided. Lastly, comparison of effective dose rates between the voxel and stylized phantoms was within 8% at 100 keV and is <5% between 200 and 5000 keV.« less

Comparison of Monoenergetic Photon Organ Dose Rate Coefficients for the Female Stylized and Voxel Phantoms Submerged in Air

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

Hiller, Mauritius; Dewji, Shaheen Azim

Dose rate coefficients computed using the International Commission on Radiological Protection (ICRP) reference adult female voxel phantom were compared with values computed using the Oak Ridge National Laboratory (ORNL) adult female stylized phantom in an air submersion exposure geometry. This is a continuation of previous work comparing monoenergetic organ dose rate coefficients for the male adult phantoms. With both the male and female data computed, effective dose rate as defined by ICRP Publication 103 was compared for both phantoms. Organ dose rate coefficients for the female phantom and ratios of organ dose rates for the voxel and stylized phantoms aremore » provided in the energy range from 30 to 5 MeV. Analysis of the contribution of the organs to effective dose is also provided. Lastly, comparison of effective dose rates between the voxel and stylized phantoms was within 8% at 100 keV and is <5% between 200 and 5000 keV.« less

Poster — Thur Eve — 66: Robustness Assessment of a Novel IMRT Planning Method for Lung Radiotherapy

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

Ahanj, M.; Bissonnette, J.-P.; Heath, E.

2014-08-15

Conventional radiotherapy treatment planning for lung cancer accounts for tumour motion by increasing the beam apertures. We recently developed an IMRT planning strategy which uses reduced beam apertures in combination with an edge enhancing boost of 110% of the prescription dose to the volume that corresponds to the portion of the CTV that moves outside of the reduced beam. Previous results showed that this approach ensures target coverage while reducing lung dose. In the current study, we evaluate the robustness of this boost volume approach to changes in respiratory motion, including amplitude and phase weight variations. ITV and boost volumemore » plans were generated for 5 NSCLC patients with respiratory motion amplitudes ranging from 1 to 2 cm. A standard 5mm PTV margin was used for all plans. The ORBIT treatment planning tool was used to plan and accumulate dose over 10 respiratory phases defined by the 4DCT datasets. For the phase weight variation study, dose was accumulated for three scenarios: equally-weighted-phases, higher weight assigned to exhale phases and higher weight assigned to inhale phases. For the amplitude variation study, a numerical phantom was used to generate 4DCT datasets corresponding to 7 mm, 10 mm and 14 mm motion amplitudes. Preliminary results found that delivered plans for all phase weight scenarios were clinically acceptable. When normalized to mean lung dose, the boost volume plan delivered 5% more dose to the CTV which indicates the potential for dose escalation using this approach.« less

Discharge aspirin dose and clinical outcomes in patients with acute coronary syndromes treated with prasugrel versus clopidogrel: an analysis from the TRITON-TIMI 38 study (trial to assess improvement in therapeutic outcomes by optimizing platelet inhibition with prasugrel-thrombolysis in myocardial infarction 38).

PubMed

Kohli, Payal; Udell, Jacob A; Murphy, Sabina A; Cannon, Christopher P; Antman, Elliott M; Braunwald, Eugene; Wiviott, Stephen D

2014-01-28

The goal of this study was to determine whether there is a relationship between aspirin dose and the potent antiplatelet agent prasugrel in the TRITON-TIMI 38 (Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition With Prasugrel-Thrombolysis In Myocardial Infarction 38) study. Optimal aspirin dosing after acute coronary syndromes remains uncertain. Previous studies have raised questions regarding an interaction between high-dose aspirin and the potent antiplatelet agent ticagrelor. In TRITON-TIMI 38, we classified 12,674 patients into low-dose (<150 mg) or high-dose (≥150 mg) aspirin groups based on discharge dose. We identified independent correlates of dose selection and studied the impact of aspirin dose on the clinical effects of prasugrel. There was significant geographical variation in aspirin dosing, with North American patients receiving high-dose aspirin more frequently than other countries (66% vs. 28%; p < 0.001). Clinical factors correlating with high-dose aspirin included previous percutaneous coronary intervention and use of aspirin before randomization. Characteristics associated with the use of low-dose aspirin included age ≥75 years, white race, and use of bivalirudin or a glycoprotein IIb/IIIa inhibitor during coronary intervention. Regardless of low- or high-dose aspirin use, prasugrel had lower rates of the primary efficacy endpoint (cardiovascular death, myocardial infarction, or stroke [CVD/MI/stroke]) (hazard ratio [HR]CVD/MI/stroke = 0.78 [95% confidence interval (CI) 0.64 to 0.95] and HRCVD/MI/stroke = 0.87 [95% CI 0.69 to 1.10], respectively; p value for interaction = 0.48) and higher rates of the primary safety endpoint (HR TIMI major bleeding = 1.40 [95% CI 0.81 to 2.42] and TIMImajor bleeding = 1.30 [95% CI 0.63 to 2.68], respectively; p value for interaction = 0.84) compared with clopidogrel. In TRITON-TIMI 38, the safety and efficacy outcomes of prasugrel compared with those of clopidogrel were directionally consistent regardless of aspirin dose, although only the primary efficacy endpoint achieved statistical significance. There was no clinically meaningful interaction of aspirin with prasugrel, suggesting that previous observations with potent antiplatelet agents indicating differential results are not universal. (A Comparison of Prasugrel [CS-747] and Clopidogrel in Acute Coronary Syndrome Subjects Who Are to Undergo Percutaneous Coronary Intervention; NCT00097591). Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

SU-E-T-374: Evaluation and Verification of Dose Calculation Accuracy with Different Dose Grid Sizes for Intracranial Stereotactic Radiosurgery

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

Han, C; Schultheiss, T

Purpose: In this study, we aim to evaluate the effect of dose grid size on the accuracy of calculated dose for small lesions in intracranial stereotactic radiosurgery (SRS), and to verify dose calculation accuracy with radiochromic film dosimetry. Methods: 15 intracranial lesions from previous SRS patients were retrospectively selected for this study. The planning target volume (PTV) ranged from 0.17 to 2.3 cm{sup 3}. A commercial treatment planning system was used to generate SRS plans using the volumetric modulated arc therapy (VMAT) technique using two arc fields. Two convolution-superposition-based dose calculation algorithms (Anisotropic Analytical Algorithm and Acuros XB algorithm) weremore » used to calculate volume dose distribution with dose grid size ranging from 1 mm to 3 mm with 0.5 mm step size. First, while the plan monitor units (MU) were kept constant, PTV dose variations were analyzed. Second, with 95% of the PTV covered by the prescription dose, variations of the plan MUs as a function of dose grid size were analyzed. Radiochomic films were used to compare the delivered dose and profile with the calculated dose distribution with different dose grid sizes. Results: The dose to the PTV, in terms of the mean dose, maximum, and minimum dose, showed steady decrease with increasing dose grid size using both algorithms. With 95% of the PTV covered by the prescription dose, the total MU increased with increasing dose grid size in most of the plans. Radiochromic film measurements showed better agreement with dose distributions calculated with 1-mm dose grid size. Conclusion: Dose grid size has significant impact on calculated dose distribution in intracranial SRS treatment planning with small target volumes. Using the default dose grid size could lead to under-estimation of delivered dose. A small dose grid size should be used to ensure calculation accuracy and agreement with QA measurements.« less

Body Potassium Content and Radiation Dose from 40K for the Urals Population (Russia)

PubMed Central

Tolstykh, Evgenia I.; Degteva, Marina O.; Bougrov, Nikolay G.; Napier, Bruce A.

2016-01-01

Long-term whole-body monitoring of radionuclides in residents of the Urals Region has been performed at the Urals Research Center for Radiation Medicine (URCRM, Chelyabinsk). Quantification of 40K was achieved by measuring the 40K photopeak with four phoswich detectors in whole body counter SICH-9.1M. The current study presents the results of 40K measurements in 3,651 women and 1,961 t-test; U-test men aged 11–90; measurements were performed in 2006–2014. The residents belonged to two ethnic groups, Turkic (Tatar, Bashkir) and Slavs (mainly Russian). The levels of 40K-body contents depend upon gender, age, and body mass. Significant ethnic-differences were not found in 40K-body contents and 40K concentrations in terms of Bq per kg of body weight (in groups homogenous by age and gender). Both 40K-body contents and concentrations were significantly higher in men than in women in all age-groups; the difference was about 25%. The measured 40K-body content in men of 20–50 years was about 4200 Bq (134 g of K) and about 3000 Bq (95 g of K) in women. By the age of 80 these values decreased to 3200 Bq (102 g of K) in men and 2500 Bq (80 g of K) in women. Annual dose rates were maximal in the age group of 20–30 years– 0.16 mGy/y for men and 0.13 mGy/y for women. Further, the dose-rates decreased with age and in the groups of 60–80 years were 0.13 mGy/y for men and 0.10 mGy/y for women. Within groups homogeneous by age and gender, individual dose rates are described by a normal statistical distribution. The coefficient of variation ranges from 9 to 14%, and on the average is 12.5%. Doses from naturally occurring 40K accumulated over 70 years were found to be 9.9 mGy for men and 8.3 mGy for women; over 90 years - 12.5 and 10.4 mGy. PMID:27111330

Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides

NASA Technical Reports Server (NTRS)

Long, Edward R., Jr.; Long, Sheila Ann T.; Gray, Stephanie L.; Collins, William D.

1989-01-01

The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures.

WE-FG-BRA-05: Potential Clinical Benefit of LINAC Flattening-Filter-Free (FFF) Mode - Improvement of Treatment Therapeutic Ratio

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

Chang, S; Department of Biomedical Engineering, University of North Carolina- Chapel Hill/ North Carolina State University, Chapel Hill, North Carolina; Lineberger Clinical Cancer Center, University of North Carolina, Chapel Hill, NC

Purpose: Ultrahigh dose-rate radiation at >40Gy/s has demonstrated astonishing normal-tissue sparing and tumor control in recent preclinical naive and tumor-bearing rodent studies when compared to the same radiation dose at a conventional dose-rate. The working mechanism of this fascinating dose-rate effect is currently under investigation. The aims of this work include investigating 1) whether LINAC FFF mode radiation at approximately 1Gy/s also has an improved therapeutic ratio compared to the same radiation dose at the conventional dose-rate of 0.05Gy/s, and 2) the dose-rate effect’s potential working mechanism by studying the expression of the P53 gene, linked to tumor suppression andmore » cell regulation after radiation damage. Methods: We used mouse model C57BL/6J, the same as that used in the ultrahigh dose-rate studies, and exposed them to total body irradiation (TBI) using the Elekta Versa accelerator 10MV photons. Mice (N=20) were given a total dose of 12Gy in both the high dose-rate group (n=10) using the FFF-mode and the conventional dose-rate group (n=10) using the conventional does rate mode. The FFF-mode treatment setup consisted of a 15cm×15cm field size setting at 53.2cm SSD while the conventional-mode set-up consisted of a 10cm×10cm field size at 100SSD. Post-radiation, animals were monitored daily for survival analysis and signs of moribundity requiring euthanasia. In addition, mouse spleens were harvested for P53 analysis at different time points. Results: For 12Gy TBI, the 1.3Gy/s FFF-mode high dose-rate produced a statistically significant (p=0.02) improvement in mouse survival compared to the 0.05Gy/s conventional dose-rate. An initial P53 study at the time of death time-point indicates that high dose-rate radiation induced a stronger expression of P53 than conventional dose-rate radiation. Conclusion: Our pilot study indicates that the FFF-mode high dose-rate radiation, which has been used largely to improve clinical throughput, may provide the added clinical benefit of improving treatment therapeutic ratio. Animal Studies were performed within the LCCC Animal Studies Core Facility at the University of North Carolina at Chapel Hill. The LCCC Animal Studies Core is supported in part by an NCI Center Core Support Grant (CA16086) to the UNC Lineberger Comprehensive Cancer Center.« less

SU-E-T-790: Validation of 4D Measurement-Guided Dose Reconstruction (MGDR) with OCTAVIUS 4D System

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

Lee, V; Leung, R; Wong, M

2015-06-15

Purpose: To validate the MGDR of OCTAVIUS 4D system (PTW, Freiburg, Germany) for quality assurance (QA) of volumetric-modulated arc radiotherapy (VMAT). Methods: 4D-MGDR measurements were divided into two parts: 1) square fields from 2×2 to 25×25 cm{sup 2} at 0°, 10° and 45° gantry, and 2) 8 VMAT plans (5 nasopharyngeal and 3 prostate) collapsed to gantry 40° in QA mode in Monaco v5.0 (Elekta, CMS, Maryland Heights, MO) were delivered on the OCTAVIUS 4D phantom with the OCTAVIUS 1500 detector plane perpendicular to either the incident beam to obtain the reconstructed dose (OCTA4D) or the 0° gantry axis tomore » obtain the raw doses (OCTA3D) in Verisoft 6.1 (PTW, Freiburg, Germany). Raw measurements of OCTA3D were limited to < 45° gantry to avoid >0.5% variation of detector angular response with respect to 0° gantry as determined previously. Reconstructed OCTA4D and raw OCTA3D doses for all plans were compared at the same detector plane using γ criteria of 2% (local dose)/2mm and 3%/3mm criteria. Results: At gantry 0° and 10°, the γ results for all OCTA4D on detector plane coinciding with OCTA3D were over 90% at 2%/2mm except for the largest field (25×25 cm{sup 2} ) showing >88%. For square field at 45° gantry, γ passing rate is > 90% for fields smaller than 15x 15cm2 but < 80% for field size of 20 x20 cm{sup 2} upward. For VMAT, γ results showed 94% and 99% passing rate at 2%/2mm and 3%/3mm, respectively. Conclusion: OCTAVIUS 4D system has compromised accuracy in reconstructing dose away from the central beam axis, possibly due to the off-axis softening correction and errors of the percent depth dose data necessary as input for MGDR. Good results in VMAT delivery suggested that the system is relatively reliable for VMAT with small segments.« less

[Myocardial electrogenesis in laboratory rats under conditions of acute nitrite intoxication].

PubMed

Shumilova, T E; Shereshkov, V I; Ianvareva, I N; Nozdrachev, A D

2010-01-01

In anesthetized male rats the arterial blood pressure in femoral artery and electrocardiogram in standard leads were recorded uninterruptedly for 1-1.5 h under conditions of acute nitrite intoxication produced by a subcutaneous injection of water solution of sodium nitrite (donor of nitric oxide) at concentrations of 10, 30, and 50 mg/kg body mass. Results of the study have shown dose-dependent changes of arterial pressure as well as of time and amplitude characteristics of electrocardiogram under effect of NaNO2. At the threshold hypoxic dose, an increase of amplitude of R and S waves was observed by the 30-45th min, while at the maximal NaNO2 dose, amplitude of all waves rose by the 15th min of intoxication. High nitric doses often caused an increase of the ST segment above the isoelectric line and a rise of the amplitude of the T wave, on which a notch appeared in some cases. The change of the ECG time parameters was expressed in the dose-dependent development of bradycardia for the first 4-7 min; its level correlated with the progressively decreasing arterial pressure in the beginning (the 2-4th min) of nitrite intoxication. Variation analysis of heart rate spectral characteristics by Baevskii has revealed a rise of the total spectral power of pulse oscillations. Under effect of nitrite, in the spectrum of cardiointervals, quent recovery of the normal ECG spectrum in the end of the experimental period. The maximal nitrite dose produced more pronounced shifts of the heart rate spectrum towards the LF and VLF diapasons that were not restored for 1 h of experiment. Transitory processes of readjustment of the cardiac rhythm had discrete character. The nitrite dose of 50 mg/kg body mass increased the RR-interval after 4-7 min with amplitude steps of 3-5 imp/s and the time constant of 20-40 s. The revealed ECG changes had the reflex (enhancement of parasympathetic tonus) and metabolic (the hypoxic and histotoxic damage of myocardium) nature.

Dose rate effect on micronuclei induction in human blood lymphocytes exposed to single pulse and multiple pulses of electrons.

PubMed

Acharya, Santhosh; Bhat, N N; Joseph, Praveen; Sanjeev, Ganesh; Sreedevi, B; Narayana, Y

2011-05-01

The effects of single pulses and multiple pulses of 7 MV electrons on micronuclei (MN) induction in cytokinesis-blocked human peripheral blood lymphocytes (PBLs) were investigated over a wide range of dose rates per pulse (instantaneous dose rate). PBLs were exposed to graded doses of 2, 3, 4, 6, and 8 Gy of single electron pulses of varying pulse widths at different dose rates per pulse, ranging from 1 × 10(6) Gy s(-1) to 3.2 × 10(8) Gy s(-1). Different dose rates per pulse were achieved by changing the dose per electron pulse by adjusting the beam current and pulse width. MN yields per unit absorbed dose after irradiation with single electron pulses were compared with those of multiple pulses of electrons. A significant decrease in the MN yield with increasing dose rates per pulse was observed, when dose was delivered by a single electron pulse. However, no reduction in the MN yield was observed when dose was delivered by multiple pulses of electrons. The decrease in the yield at high dose rates per pulse suggests possible radical recombination, which leads to decreased biological damage. Cellular response to the presence of very large numbers of chromosomal breaks may also alter the damage.

The feasibility study and characterization of a two-dimensional diode array in "magic phantom" for high dose rate brachytherapy quality assurance.

PubMed

Espinoza, A; Beeksma, B; Petasecca, M; Fuduli, I; Porumb, C; Cutajar, D; Corde, S; Jackson, M; Lerch, M L F; Rosenfeld, A B

2013-11-01

High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly (192)Ir with an air KERMA strength range between 20,000 and 40,000 U, where 1 U = 1 μGy m(2)/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 × 11 epitaxial diode array, named "magic phantom." The HDR brachytherapy treatment plan is translated to the phantom with two rows of 10 (20 in total) HDR source flexible catheters, arranged above and below the diode array "magic plate" (MP). Four-dimensional source tracking in each catheter is based upon a developed fast iterative algorithm, utilizing the response of the diodes in close proximity to the (192)Ir source, sampled at 100 ms intervals by a fast data acquisition (DAQ) system. Using a (192)Ir source in a solid water phantom, the angular response of the developed epitaxial diodes utilized in the MP and also the variation of the MP response as a function of the source-to-detector distance (SDD) were investigated. These response data are then used by an iterative algorithm for source dwelling position determination. A measurement of the average transit speed between dwell positions was performed using the diodes and a fast DAQ. The angular response of the epitaxial diode showed a variation of 15% within 360°, with two flat regions above and below the detector face with less than 5% variation. For SDD distances of between 5 and 30 mm the relative response of the epitaxial diodes used in the MP is in good agreement (within 8%) with radial dose function measurements found within the TG-43 protocol, with SDD of up to 70 mm showing a 40% over response. A method for four-dimensional localization of the HDR source was developed, allowing the source dwell position to be derived within 0.50 mm of the expected position. An estimation of the average transit speed for varying step sizes was determined and was found to increase from (12.8 ± 0.3) up to (38.6 ± 0.4) cm/s for a step size of 2.5 and 50 mm, respectively. Our characterization of the designed QA "magic phantom" with MP in realistic HDR photon fields demonstrates the promising performance for real-time source position tracking in four dimensions and measurements of transit times. Further development of this system will allow a full suite for QA in HDR brachytherapy and analysis, and for future in vivo tracking.

Comparative performance analysis for computer aided lung nodule detection and segmentation on ultra-low-dose vs. standard-dose CT

NASA Astrophysics Data System (ADS)

Wiemker, Rafael; Rogalla, Patrik; Opfer, Roland; Ekin, Ahmet; Romano, Valentina; Bülow, Thomas

2006-03-01

The performance of computer aided lung nodule detection (CAD) and computer aided nodule volumetry is compared between standard-dose (70-100 mAs) and ultra-low-dose CT images (5-10 mAs). A direct quantitative performance comparison was possible, since for each patient both an ultra-low-dose and a standard-dose CT scan were acquired within the same examination session. The data sets were recorded with a multi-slice CT scanner at the Charite university hospital Berlin with 1 mm slice thickness. Our computer aided nodule detection and segmentation algorithms were deployed on both ultra-low-dose and standard-dose CT data without any dose-specific fine-tuning or preprocessing. As a reference standard 292 nodules from 20 patients were visually identified, each nodule both in ultra-low-dose and standard-dose data sets. The CAD performance was analyzed by virtue of multiple FROC curves for different lower thresholds of the nodule diameter. For nodules with a volume-equivalent diameter equal or larger than 4 mm (149 nodules pairs), we observed a detection rate of 88% at a median false positive rate of 2 per patient in standard-dose images, and 86% detection rate in ultra-low-dose images, also at 2 FPs per patient. Including even smaller nodules equal or larger than 2 mm (272 nodules pairs), we observed a detection rate of 86% in standard-dose images, and 84% detection rate in ultra-low-dose images, both at a rate of 5 FPs per patient. Moreover, we observed a correlation of 94% between the volume-equivalent nodule diameter as automatically measured on ultra-low-dose versus on standard-dose images, indicating that ultra-low-dose CT is also feasible for growth-rate assessment in follow-up examinations. The comparable performance of lung nodule CAD in ultra-low-dose and standard-dose images is of particular interest with respect to lung cancer screening of asymptomatic patients.

[Prevention and control of air pollution needs to strengthen further study on health damage caused by air pollution].

PubMed

Wu, T C

2016-08-06

Heath issues caused by air pollution such as particulate matter (PM) are much concerned and focused among air, water and soil pollutions because human breathe air for whole life span. Present comments will review physical and chemical characteristics of PM2.5 and PM10; Dose-response associations of PM10, PM2.5 and their components with mortality and risk of cardiopulmonary diseases, early health damages such as the decrease of lung functions and heart rate variability, DNA damage; And the roles of genetic variations and epigenetic changes in lung functions and heart rate variability, DNA damage related to PMs and their components. This comments list some limitations and perspectives about the associations of air pollution with health.

The impact of robustness of deformable image registration on contour propagation and dose accumulation for head and neck adaptive radiotherapy.

PubMed

Zhang, Lian; Wang, Zhi; Shi, Chengyu; Long, Tengfei; Xu, X George

2018-05-30

Deformable image registration (DIR) is the key process for contour propagation and dose accumulation in adaptive radiation therapy (ART). However, currently, ART suffers from a lack of understanding of "robustness" of the process involving the image contour based on DIR and subsequent dose variations caused by algorithm itself and the presetting parameters. The purpose of this research is to evaluate the DIR caused variations for contour propagation and dose accumulation during ART using the RayStation treatment planning system. Ten head and neck cancer patients were selected for retrospective studies. Contours were performed by a single radiation oncologist and new treatment plans were generated on the weekly CT scans for all patients. For each DIR process, four deformation vector fields (DVFs) were generated to propagate contours and accumulate weekly dose by the following algorithms: (a) ANACONDA with simple presetting parameters, (b) ANACONDA with detailed presetting parameters, (c) MORFEUS with simple presetting parameters, and (d) MORFEUS with detailed presetting parameters. The geometric evaluation considered DICE coefficient and Hausdorff distance. The dosimetric evaluation included D 95 , D max , D mean , D min , and Homogeneity Index. For geometric evaluation, the DICE coefficient variations of the GTV were found to be 0.78 ± 0.11, 0.96 ± 0.02, 0.64 ± 0.15, and 0.91 ± 0.03 for simple ANACONDA, detailed ANACONDA, simple MORFEUS, and detailed MORFEUS, respectively. For dosimetric evaluation, the corresponding Homogeneity Index variations were found to be 0.137 ± 0.115, 0.006 ± 0.032, 0.197 ± 0.096, and 0.006 ± 0.033, respectively. The coherent geometric and dosimetric variations also consisted in large organs and small organs. Overall, the results demonstrated that the contour propagation and dose accumulation in clinical ART were influenced by the DIR algorithm, and to a greater extent by the presetting parameters. A quality assurance procedure should be established for the proper use of a commercial DIR for adaptive radiation therapy. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

SU-E-T-16: A Comparison of Expected Dwell Times and Dose Variations for NAMD Patients Treated with An Episcleral Brachytherapy Device

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

Hamilton, R; Patel, P; Balaggan, K

2015-06-15

Purpose: To evaluate the variations in dwell times and doses expected when using an episcleral brachytherapy device for treatment of neovascular agerelated macular degeneration (n-AMD) based on accurate imaging modalities Methods: Data from 40 eyes from 40 subjects with known n- AMD acquired through the Distance of Choroid Study (DOCS) conducted at Moorfields Eye Hospital was used to determine the target depth; the distance from the outer scleral surface of the eye, through the choroid, to the apex of the choroidal neovascularization (CNV). Each subject underwent, in triplicate, enhanced-depth Spectral Domain Optical Coherence Tomography (SD-OCT), Swept Source Optical Coherence Tomography,more » (SS-OCT) and Ocular Ultrasound (O-US). These data are the most comprehensive and accurate measurements of the dimensions of the CNV and adjacent layers of the eye for this cohort of patients. During treatment of n-AMD, patients receive a dose of 24Gy to the apex at the target depth. Using the percentage depth dose for a Sr-90 episcleral brachytherapy device, dwell times and doses to the apex were computed to determine the expected variations. Results: The mean target depth and the 95% confidence interval (CI) determined by combining O-US with SD-OCT were 1326 (956,1696)µm and with SS-OCT were 1332 (970,1693)µm. The calculated corresponding mean dwell times and 95% (CI) were 334 (223,445)s and 335 (226,445)s for SD-OCT and SS-OCT determined depths, respectively. The corresponding mean apex dose and 95% (CI) were 24 (35.9,18.0)Gy (SD-OCT) and 24 (35.6,18.1)Gy (SS-OCT). Conclusion: For episcleral brachytherapy treatment of n-AMD, using a patient population average target depth for treatment planning is inadequate, resulting in dose variations of a factor of approximately two over the 95% CI and larger variations for a nontrivial segment of the population. Each patient should have individualized imaging studies to determine the target depth for use in the dwell time calculation. Study was sponsored by Salutaris Medical Devices, Ltd., a subsidiary of Salutaris Medical Devices, Inc. Hamilton and Marsteller are founders of Salutaris Medical Devices, Inc. Drew, McGovern and Vitali are minor equity holders in Salutaris Medical Devices, Inc.« less

SU-E-J-127: Real-Time Dosimetric Assessment for Adaptive Head-And-Neck Treatment Via A GPU-Based Deformable Image Registration Framework

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

Qi, S; Neylon, J; Chen, A

2014-06-01

Purposes: To systematically monitor anatomic variations and their dosimetric consequences during head-and-neck (H'N) radiation therapy using a GPU-based deformable image registration (DIR) framework. Methods: Eleven H'N IMRT patients comprised the subject population. The daily megavoltage CT and weekly kVCT scans were acquired for each patient. The pre-treatment CTs were automatically registered with their corresponding planning CT through an in-house GPU-based DIR framework. The deformation of each contoured structure was computed to account for non-rigid change in the patient setup. The Jacobian determinant for the PTVs and critical structures was used to quantify anatomical volume changes. Dose accumulation was performed tomore » determine the actual delivered dose and dose accumulation. A landmark tool was developed to determine the uncertainty in the dose distribution due to registration error. Results: Dramatic interfraction anatomic changes leading to dosimetric variations were observed. During the treatment courses of 6–7 weeks, the parotid gland volumes changed up to 34.7%, the center-of-mass displacement of the two parotids varied in the range of 0.9–8.8mm. Mean doses were within 5% and 3% of the planned mean doses for all PTVs and CTVs, respectively. The cumulative minimum/mean/EUD doses were lower than the planned doses by 18%, 2%, and 7%, respectively for the PTV1. The ratio of the averaged cumulative cord maximum doses to the plan was 1.06±0.15. The cumulative mean doses assessed by the weekly kVCTs were significantly higher than the planned dose for the left-parotid (p=0.03) and right-parotid gland (p=0.006). The computation time was nearly real-time (∼ 45 seconds) for registering each pre-treatment CT to the planning CT and dose accumulation with registration accuracy (for kVCT) at sub-voxel level (<1.5mm). Conclusions: Real-time assessment of anatomic and dosimetric variations is feasible using the GPU-based DIR framework. Clinical implementation of this technology may enable timely plan adaption and potentially lead to improved outcome.« less

Measurement of dose distribution in the spherical phantom onboard the ISS-KIBO module -MATROSHKA-R in KIBO-

NASA Astrophysics Data System (ADS)

Kodaira, Satoshi; Kawashima, Hajime; Kurano, Mieko; Uchihori, Yukio; Nikolaev, Igor; Ambrozova, Iva; Kitamura, Hisashi; Kartsev, Ivan; Tolochek, Raisa; Shurshakov, Vyacheslav

The measurement of dose equivalent and effective dose during manned space missions on the International Space Station (ISS) is important for evaluating the risk to astronaut health and safety when exposed to space radiation. The dosimetric quantities are constantly changing and strongly depend on the level of solar activity and the various spacecraft- and orbit-dependent parameters such as the shielding distribution in the ISS module, location of the spacecraft within its orbit relative to the Earth, the attitude (orientation) and altitude. Consequently, the continuous monitoring of dosimetric quantities is required to record and evaluate the personal radiation dose for crew members during spaceflight. The dose distributions in the phantom body and on its surface give crucial information to estimate the dose equivalent in the human body and effective dose in manned space mission. We have measured the absorbed dose and dose equivalent rates using passive dosimeters installed in the spherical phantom in Japanese Experiment Module (“KIBO”) of the ISS in the framework of Matroshka-R space experiment. The exposure duration was 114 days from May 21 to September 12, 2012. The phantom consists of tissue-equivalent material covered with a poncho jacket with 32 pockets on its surface and 20 container rods inside of the phantom. The phantom diameter is 35 cm and the mass is 32 kg. The passive dosimeters consisted of a combination of luminescent detectors of Al _{2}O _{3};C OSL and CaSO _{4}:Dy TLD and CR-39 plastic nuclear track detectors. As one of preliminary results, the dose distribution on the phantom surface measured with OSL detectors installed in the jacket pockets is found to be ranging from 340 muGy/day to 260 muGy/day. In this talk, we will present the detail dose distributions, and variations of LET spectra and quality factor obtained outside and inside of the spherical phantom installed in the ISS-KIBO.

A standard dose of radiation for microscopic disease is not appropriate

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

Marks, L.B.

1990-12-15

Elective irradiation of sites of potential occult tumor spread is often part of a patient's radiation therapy program. The required radiation dose (D) depends on the probability that occult disease exists (P(occ)), the number of sites at risk (A), the number of tumor clonogens present (Ni), their radiation sensitivity, and the desired control rate. An exponential model of cell survival is used to quantify the importance of these factors. Control Probability = (1 - Pocc x (1 - e-Ni x (SF2)D/2))A; SF2 = surviving fraction after 2 Gy. Implications for clinical radiation therapy include: 1. Since the number of clonogensmore » in an occult site may vary from 10 degrees to 10(8), Ni is the major determinant of the required dose. The intrinsic radiation sensitivity of the clonogens (SF2) is also extremely important in determining the dose. Other factors are less influential since they vary less. 2. The variability of Ni (8 logs) is larger than the variation in cell number seen with gross disease (1 cm3 versus 1000 cm3, 3 logs). When Ni approximately 10(8), the required dose approaches that needed for small volume gross disease (10(9) cells, 1 cm3). 3. The dose prescribed to elective sites should reflect the risk of occult disease based on the primary tumor site, stage, and grade. 4. Regions where clinicoradiologic evaluation is difficult (e.g., pelvis and obese neck) require higher doses because macroscopic tumor deposits may exist. 5. Relatively low doses (10 to 30 Gy) are often thought to be inadequate for microscopic tumor. However, similar doses have been reported to sterilize microscopic tumor in ovarian, rectal, bladder, breast, and head and neck carcinomas. Relatively low doses should not be discounted since they may be useful in select cases when normal tissue tolerances and/or previous irradiation treatment limit the radiation dose.« less

ESTIMATION OF ADULT PATIENT DOSES FOR CHEST X-RAY EXAMINATIONS AND COMPARISON WITH DIAGNOSTIC REFERENCE LEVELS (DRLs).

PubMed

Bas Mor, H; Altinsoy, N; Söyler, I

2018-05-08

The aim of this study was to evaluate the radiation doses to patient during chest (posterior anterior/and lateral) examinations. The study was performed in three public hospitals of İstanbul province with a total of 300 adult patients. Entrance surface dose (ESD) measurements were conducted on computed radiography, digital radiography and screen film system. ESD was estimated by using International Atomic Energy Agency (IAEA) model and Davies model which are the common indirect models. Results were compared with diagnostic reference levels from the European Commission, IAEA and National Radiological Protection Board. Although the results are compatible with the international diagnostic reference levels, they present variations between the hospitals. Dose variations for the same type of X-ray examination support the idea that further optimization is possible.

Species- and dose-specific pancreatic responses and progression in single- and repeat-dose studies with GI181771X: a novel cholecystokinin 1 receptor agonist in mice, rats, and monkeys.

PubMed

Myer, James R; Romach, Elizabeth H; Elangbam, Chandikumar S

2014-01-01

Compound-induced pancreatic injury is a serious liability in preclinical toxicity studies. However, its relevance to humans should be cautiously evaluated because of interspecies variations. To highlight such variations, we evaluated the species- and dose-specific pancreatic responses and progression caused by GI181771X, a novel cholecystokinin 1 receptor agonist investigated by GlaxoSmithKline for the treatment of obesity. Acute (up to 2,000 mg/kg GI181771X, as single dose) and repeat-dose studies in mice and/or rats (0.25-250 mg/kg/day for 7 days to 26 weeks) showed wide-ranging morphological changes in the pancreas that were dose and duration dependent, including necrotizing pancreatitis, acinar cell hypertrophy/atrophy, zymogen degranulation, focal acinar cell hyperplasia, and interstitial inflammation. In contrast to rodents, pancreatic changes were not observed in cynomolgus monkeys given GI181771X (1-500 mg/kg/day with higher systemic exposure than rats) for up to 52 weeks. Similarly, no GI181771X treatment-associated abnormalities in pancreatic structure were noted in a 24-week clinical trial with obese patients (body mass index >30 or >27 kg/m(2)) as assessed by abdominal ultrasound or by magnetic resonance imaging. Mechanisms for interspecies variations in the pancreatic response to CCK among rodents, monkeys, and humans and their relevance to human risk are discussed.

Dosimetric and Clinical Analysis of Spatial Distribution of the Radiation Dose in Gamma Knife Radiosurgery for Vestibular Schwannoma

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

Massager, Nicolas, E-mail: nmassage@ulb.ac.be; Neurosurgery-Department, Hospital Erasme, Brussels; Lonneville, Sarah

2011-11-15

Objectives: We investigated variations in the distribution of radiation dose inside (dose inhomogeneity) and outside (dose falloff) the target volume during Gamma Knife (GK) irradiation of vestibular schwannoma (VS). We analyzed the relationship between some parameters of dose distribution and the clinical and radiological outcome of patients. Methods and Materials: Data from dose plans of 203 patients treated for a vestibular schwannoma by GK C using same prescription dose (12 Gy at the 50% isodose) were collected. Four different dosimetric indexes were defined and calculated retrospectively in all plannings on the basis of dose-volume histograms: Paddick conformity index (PI), gradientmore » index (GI), homogeneity index (HI), and unit isocenter (UI). The different measures related to distribution of the radiation dose were compared with hearing and tumor outcome of 203 patients with clinical and radiological follow-up of minimum 2 years. Results: Mean, median, SD, and ranges of the four indexes of dose distribution analyzed were calculated; large variations were found between dose plans. We found a high correlation between the target volume and PI, GI, and UI. No significant association was found between the indexes of dose distribution calculated in this study and tumor control, tumor volume shrinkage, hearing worsening, loss of functional hearing, or complete hearing loss at last follow-up. Conclusions: Parameters of distribution of the radiation dose during GK radiosurgery for VS can be highly variable between dose plans. The tumor and hearing outcome of patients treated is not significantly related to these global indexes of dose distribution inside and around target volume. In GK radiosurgery for VS, the outcome seems more to be influenced by local radiation dose delivered to specific structures or volumes than by global dose gradients.« less

Measurement and comparison of skin dose using OneDose MOSFET and Mobile MOSFET for patients with acute lymphoblastic leukemia

PubMed Central

Mattar, Essam H.; Hammad, Lina F.; Al-Mohammed, Huda I.

2011-01-01

Summary Background Total body irradiation is a protocol used to treat acute lymphoblastic leukemia in patients prior to bone marrow transplant. It is involved in the treatment of the whole body using a large radiation field with extended source-skin distance. Therefore measuring and monitoring the skin dose during the treatment is important. Two kinds of metal oxide semiconductor field effect transistor (OneDose MOSFET and mobile MOSEFT) dosimeter are used during the treatment delivery to measure the skin dose to specific points and compare it with the target prescribed dose. The objective of this study was to compare the variation of skin dose in patients with acute lymphatic leukemia (ALL) treated with total body irradiation (TBI) using OneDose MOSFET detectors and Mobile MOSFET, and then compare both results with the target prescribed dose. Material/Methods The measurements involved 32 patient’s (16 males, 16 females), aged between 14–30 years, with an average age of 22.41 years. One-Dose MOSFET and Mobile MOSFET dosimetry were performed at 10 different anatomical sites on every patient. Results The results showed there was no variation between skin dose measured with OneDose MOSFET and Mobile MOSFET in all patients. Furthermore, the results showed for every anatomical site selected there was no significant difference in the dose delivered using either OneDose MOSFET detector or Mobile MOSFET as compared to the prescribed dose. Conclusions The study concludes that One-Dose MOSFET detectors and Mobile MOSFET both give a direct read-out immediately after the treatment; therefore both detectors are suitable options when measuring skin dose for total body irradiation treatment. PMID:21709641

Measurement and comparison of skin dose using OneDose MOSFET and Mobile MOSFET for patients with acute lymphoblastic leukemia.

PubMed

Mattar, Essam H; Hammad, Lina F; Al-Mohammed, Huda I

2011-07-01

Total body irradiation is a protocol used to treat acute lymphoblastic leukemia in patients prior to bone marrow transplant. It is involved in the treatment of the whole body using a large radiation field with extended source-skin distance. Therefore measuring and monitoring the skin dose during the treatment is important. Two kinds of metal oxide semiconductor field effect transistor (OneDose MOSFET and mobile MOSEFT) dosimeter are used during the treatment delivery to measure the skin dose to specific points and compare it with the target prescribed dose. The objective of this study was to compare the variation of skin dose in patients with acute lymphatic leukemia (ALL) treated with total body irradiation (TBI) using OneDose MOSFET detectors and Mobile MOSFET, and then compare both results with the target prescribed dose. The measurements involved 32 patient's (16 males, 16 females), aged between 14-30 years, with an average age of 22.41 years. One-Dose MOSFET and Mobile MOSFET dosimetry were performed at 10 different anatomical sites on every patient. The results showed there was no variation between skin dose measured with OneDose MOSFET and Mobile MOSFET in all patients. Furthermore, the results showed for every anatomical site selected there was no significant difference in the dose delivered using either OneDose MOSFET detector or Mobile MOSFET as compared to the prescribed dose. The study concludes that One-Dose MOSFET detectors and Mobile MOSFET both give a direct read-out immediately after the treatment; therefore both detectors are suitable options when measuring skin dose for total body irradiation treatment.

Recovery of brain and plasma cholinesterase activities in ducklings exposed to organophosphorus pesticides

USGS Publications Warehouse

Fleming, W.J.

1981-01-01

Brain and plasma cholinesterase (ChE) activities were determined for mallard ducklings (Anas platyrhynchos) exposed to dicrotophos and fenthion. Recovery rates of brain ChE did not differ between ducklings administered a single oral dose vs. a 2-week dietary dose of these organophosphates. Exposure to the organophosphates, followed by recovery of brain ChE, did not significantly affect the degree of brain ChE inhibition or the recovery of ChE activity at a subsequent exposure. Recovery of brain ChE activity followed the general model Y = a + b(logX) with rapid recovery to about 50% of normal, followed by a slower rate of recovery until normal ChE activity levels were attained. Fenthion and dicrotophos-inhibited brain ChE were only slightly reactivated in vitro by pyridine-2-aldoxime methiodide, which suggested that spontaneous reactivation was not a primary method of recovery of ChE activity. Recovery of brain ChE activity can be modeled for interpretation of sublethal inhibition of brain ChE activities in wild birds following environmental applications of organophosphates. Plasma ChE activity is inferior to brain ChE activity for environmental monitoring, because of its rapid recovery and large degree of variation among individuals.

Energy compensation after sprint- and high-intensity interval training.

PubMed

Schubert, Matthew M; Palumbo, Elyse; Seay, Rebekah F; Spain, Katie K; Clarke, Holly E

2017-01-01

Many individuals lose less weight than expected in response to exercise interventions when considering the increased energy expenditure of exercise (ExEE). This is due to energy compensation in response to ExEE, which may include increases in energy intake (EI) and decreases in non-exercise physical activity (NEPA). We examined the degree of energy compensation in healthy young men and women in response to interval training. Data were examined from a prior study in which 24 participants (mean age, BMI, & VO2max = 28 yrs, 27.7 kg•m-2, and 32 mL∙kg-1∙min-1) completed either 4 weeks of sprint-interval training or high-intensity interval training. Energy compensation was calculated from changes in body composition (air displacement plethysmography) and exercise energy expenditure was calculated from mean heart rate based on the heart rate-VO2 relationship. Differences between high (≥ 100%) and low (< 100%) levels of energy compensation were assessed. Linear regressions were utilized to determine associations between energy compensation and ΔVO2max, ΔEI, ΔNEPA, and Δresting metabolic rate. Very large individual differences in energy compensation were noted. In comparison to individuals with low levels of compensation, individuals with high levels of energy compensation gained fat mass, lost fat-free mass, and had lower change scores for VO2max and NEPA. Linear regression results indicated that lower levels of energy compensation were associated with increases in ΔVO2max (p < 0.001) and ΔNEPA (p < 0.001). Considerable variation exists in response to short-term, low dose interval training. In agreement with prior work, increases in ΔVO2max and ΔNEPA were associated with lower energy compensation. Future studies should focus on identifying if a dose-response relationship for energy compensation exists in response to interval training, and what underlying mechanisms and participant traits contribute to the large variation between individuals.

Total dose bias dependency and ELDRS effects in bipolar linear devices

NASA Technical Reports Server (NTRS)

Yui, C. C.; McClure, S. S.; Rex, B. G.; Lehman, J. M.; Minto, T. D.; Wiedeman, M.

2002-01-01

Total dose tests of several bipolar linear devices show sensitivity to both dose rate and bias during exposure. All devices exhibited Enhanced Low Dose Rate Sensitivity (ELDRS). An accelerated ELDRS test method for three different devices demonstrate results similar to tests at low dose rate. Behavior and critical parameters from these tests are compared and discussed.

The Impact of Dose Rate on the Accuracy of Step-and-Shoot Intensity-modulated Radiation Therapy Quality Assurance Using Varian 2300CD.

PubMed

Njeh, Christopher F; Salmon, Howard W; Schiller, Claire

2017-01-01

Intensity-modulated radiation therapy (IMRT) delivery using "step-and-shoot" technique on Varian C-Series linear accelerator (linac) is influenced by the communication frequency between the multileaf collimator and linac controllers. Hence, the dose delivery accuracy is affected by the dose rate. Our aim was to quantify the impact of using two dose rates on plan quality assurance (QA). Twenty IMRT patients were selected for this study. The plan QA was measured at two different dose rates. A gamma analysis was performed, and the degree of plan modulation on the QA pass rate was also evaluated in terms of average monitor unit per segment (MU/segment) and the total number of segments. The mean percentage gamma pass rate of 94.9% and 93.5% for 300 MU/min and 600 MU/min dose rate, respectively, was observed. There was a significant ( P = 0.001) decrease in percentage gamma pass rate when the dose rate was increased from 300 MU/min to 600 MU/min. There was a weak, but significant association between the percentage pass rate at both dose rate and total number of segments. The total number of MU was significantly correlated to the total number of segments ( r = 0.59). We found a positive correlation between the percentage pass rate and mean MU/segment, r = 0.52 and r = 0.57 for 300 MU/min and 600 MU/min, respectively. IMRT delivery using step-and-shoot technique on Varian 2300CD is impacted by the dose rate and the total amount of segments.

Enhanced Low Dose Rate Effects in Bipolar Circuits: A New Hardness Assurance Problem for NASA

NASA Technical Reports Server (NTRS)

Johnston, A.; Barnes, C.

1995-01-01

Many bipolar integrated circuits are much more susceptible to ionizing radiation at low dose rates than they are at high dose rates typically used for radiation parts testing. Since the low dose rate is equivalent to that seen in space, the standard lab test no longer can be considered conservative and has caused the Air Force to issue an alert. Although a reliable radiation hardness assurance test has not yet been designed, possible mechanisms for low dose rate enhancement and hardness assurance tests are discussed.

Spatial variation of dosimetric leaf gap and its impact on dose delivery

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

Kumaraswamy, Lalith K., E-mail: Lalith.Kumaraswamy@roswellpark.org; Schmitt, Jonathan D.; Bailey, Daniel W.

Purpose: During dose calculation, the Eclipse treatment planning system (TPS) retracts the multileaf collimator (MLC) leaf positions by half of the dosimetric leaf gap (DLG) value (measured at central axis) for all leaf positions in a dynamic MLC plan to accurately model the rounded leaf ends. The aim of this study is to map the variation of DLG along the travel path of each MLC leaf pair and quantify how this variation impacts delivered dose. Methods: 6 MV DLG values were measured for all MLC leaf pairs in increments of 1.0 cm (from the line intersecting the CAX and perpendicularmore » to MLC motion) to 13.0 cm off axis distance at dmax. The measurements were performed on two Varian linear accelerators, both employing the Millennium 120-leaf MLCs. The measurements were performed at several locations in the beam with both a Sun Nuclear MapCHECK device and a PTW pinpoint ion chamber. Results: The measured DLGs for the middle 40 MLC leaf pairs (each 0.5 cm width) at positions along a line through the CAX and perpendicular to MLC leaf travel direction were very similar, varying maximally by only 0.2 mm. The outer 20 MLC leaf pairs (each 1.0 cm width) have much lower DLG values, about 0.3–0.5 mm lower than the central MLC leaf pair, at their respective central line position. Overall, the mean and the maximum variation between the 0.5 cm width leaves and the 1.0 cm width leaf pairs are 0.32 and 0.65 mm, respectively. Conclusions: The spatial variation in DLG is caused by the variation of intraleaf transmission through MLC leaves. Fluences centered on the CAX would not be affected since DLG does not vary; but any fluences residing significantly off axis with narrow sweeping leaves may exhibit significant dose differences. This is due to the fact that there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value utilized by the TPS for dose calculation. Since there are large differences in DLG between the 0.5 cm width leaf pairs and 1.0 cm width leaf pairs, there is a need to correct the TPS plans, especially those with high modulation (narrow dynamic MLC gap), with 2D variation of DLG.« less

Dose fractionated gamma knife radiosurgery for large arteriovenous malformations on daily or alternate day schedule outside the linear quadratic model: Proof of concept and early results. A substitute to volume fractionation.

PubMed

Mukherjee, Kanchan Kumar; Kumar, Narendra; Tripathi, Manjul; Oinam, Arun S; Ahuja, Chirag K; Dhandapani, Sivashanmugam; Kapoor, Rakesh; Ghoshal, Sushmita; Kaur, Rupinder; Bhatt, Sandeep

2017-01-01

To evaluate the feasibility, safety and efficacy of dose fractionated gamma knife radiosurgery (DFGKRS) on a daily schedule beyond the linear quadratic (LQ) model, for large volume arteriovenous malformations (AVMs). Between 2012-16, 14 patients of large AVMs (median volume 26.5 cc) unsuitable for surgery or embolization were treated in 2-3 of DFGKRS sessions. The Leksell G frame was kept in situ during the whole procedure. 86% (n = 12) patients had radiologic evidence of bleed, and 43% (n = 6) had presented with a history of seizures. 57% (n = 8) patients received a daily treatment for 3 days and 43% (n = 6) were on an alternate day (2 fractions) regimen. The marginal dose was split into 2 or 3 fractions of the ideal prescription dose of a single fraction of 23-25 Gy. The median follow up period was 35.6 months (8-57 months). In the three-fraction scheme, the marginal dose ranged from 8.9-11.5 Gy, while in the two-fraction scheme, the marginal dose ranged from 11.3-15 Gy at 50% per fraction. Headache (43%, n = 6) was the most common early postoperative complication, which was controlled with short course steroids. Follow up evaluation of at least three years was achieved in seven patients, who have shown complete nidus obliteration in 43% patients while the obliteration has been in the range of 50-99% in rest of the patients. Overall, there was a 67.8% reduction in the AVM volume at 3 years. Nidus obliteration at 3 years showed a significant rank order correlation with the cumulative prescription dose (p 0.95, P value 0.01), with attainment of near-total (more than 95%) obliteration rates beyond 29 Gy of the cumulative prescription dose. No patient receiving a cumulative prescription dose of less than 31 Gy had any severe adverse reaction. In co-variate adjusted ordinal regression, only the cumulative prescription dose had a significant correlation with common terminology criteria for adverse events (CTCAE) severity (P value 0.04), independent of age, AVM volume, number of fractions and volume of brain receiving atleast 8 Gy of radiation. DFGKRS is feasible for large AVMs with a fair nidus obliteration rate and acceptable toxicity. Cumulative prescription dose seems to be the most significant independent predictor for outcome following DFGKRS with 29-30 Gy resulting in a fair nidus obliteration with least adverse events.

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators.

PubMed

Eichmann, Marion; Flühs, Dirk; Spaan, Bernhard

2009-10-01

The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning. In order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision. The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is <7%), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account. The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate distribution, which then can be used as input for a refined clinical treatment planning system. The improved dose rate measurements will facilitate a clinical study, which could correlate the therapeutic outcome of a brachytherapy treatment with an applicator and its individual dose rate distribution.

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators

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

Eichmann, Marion; Fluehs, Dirk; Spaan, Bernhard

2009-10-15

Purpose: The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning. Methods: Inmore » order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision. Results: The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is <7%), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account. Conclusions: The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate distribution, which then can be used as input for a refined clinical treatment planning system. The improved dose rate measurements will facilitate a clinical study, which could correlate the therapeutic outcome of a brachytherapy treatment with an applicator and its individual dose rate distribution.« less

In vitro biotransformation rates in fish liver S9: effect of dosing techniques.

PubMed

Lee, Yung-Shan; Lee, Danny H Y; Delafoulhouze, Maximilien; Otton, S Victoria; Moore, Margo M; Kennedy, Chris J; Gobas, Frank A P C

2014-08-01

In vitro biotransformation assays are currently being explored to improve estimates of bioconcentration factors of potentially bioaccumulative organic chemicals in fish. The present study compares thin-film and solvent-delivery dosing techniques as well as single versus multiple chemical dosing for measuring biotransformation rates of selected polycyclic aromatic hydrocarbons in rainbow trout (Oncorhynchus mykiss) liver S9. The findings show that biotransformation rates of very hydrophobic substances can be accurately measured in thin-film sorbent-dosing assays from concentration-time profiles in the incubation medium but not from those in the sorbent phase because of low chemical film-to-incubation-medium mass-transfer rates at the incubation temperature of 13.5 °C required for trout liver assays. Biotransformation rates determined by thin-film dosing were greater than those determined by solvent-delivery dosing for chrysene (octanol-water partition coefficient [KOW ] =10(5.60) ) and benzo[a]pyrene (KOW  =10(6.04) ), whereas there were no statistical differences in pyrene (KOW  =10(5.18) ) biotransformation rates between the 2 methods. In sorbent delivery-based assays, simultaneous multiple-chemical dosing produced biotransformation rates that were not statistically different from those measured in single-chemical dosing experiments for pyrene and benzo[a]pyrene but not for chrysene. In solvent-delivery experiments, multiple-chemical dosing produced biotransformation rates that were much smaller than those in single-chemical dosing experiments for all test chemicals. While thin-film sorbent-phase and solvent delivery-based dosing methods are both suitable methods for measuring biotransformation rates of substances of intermediate hydrophobicity, thin-film sorbent-phase dosing may be more suitable for superhydrophobic chemicals. © 2014 SETAC.

Integrated molecular analysis indicates undetectable change in DNA damage in mice after continuous irradiation at ~ 400-fold natural background radiation.

PubMed

Olipitz, Werner; Wiktor-Brown, Dominika; Shuga, Joe; Pang, Bo; McFaline, Jose; Lonkar, Pallavi; Thomas, Aline; Mutamba, James T; Greenberger, Joel S; Samson, Leona D; Dedon, Peter C; Yanch, Jacquelyn C; Engelward, Bevin P

2012-08-01

In the event of a nuclear accident, people are exposed to elevated levels of continuous low dose-rate radiation. Nevertheless, most of the literature describes the biological effects of acute radiation. DNA damage and mutations are well established for their carcinogenic effects. We assessed several key markers of DNA damage and DNA damage responses in mice exposed to low dose-rate radiation to reveal potential genotoxic effects associated with low dose-rate radiation. We studied low dose-rate radiation using a variable low dose-rate irradiator consisting of flood phantoms filled with 125Iodine-containing buffer. Mice were exposed to 0.0002 cGy/min (~ 400-fold background radiation) continuously over 5 weeks. We assessed base lesions, micronuclei, homologous recombination (HR; using fluorescent yellow direct repeat mice), and transcript levels for several radiation-sensitive genes. We did not observe any changes in the levels of the DNA nucleobase damage products hypoxanthine, 8-oxo-7,8-dihydroguanine, 1,N6-ethenoadenine, or 3,N4-ethenocytosine above background levels under low dose-rate conditions. The micronucleus assay revealed no evidence that low dose-rate radiation induced DNA fragmentation, and there was no evidence of double strand break-induced HR. Furthermore, low dose-rate radiation did not induce Cdkn1a, Gadd45a, Mdm2, Atm, or Dbd2. Importantly, the same total dose, when delivered acutely, induced micronuclei and transcriptional responses. These results demonstrate in an in vivo animal model that lowering the dose-rate suppresses the potentially deleterious impact of radiation and calls attention to the need for a deeper understanding of the biological impact of low dose-rate radiation.

Architecture of a minimal signaling pathway explains the T-cell response to a 1 million-fold variation in antigen affinity and dose.

PubMed

Lever, Melissa; Lim, Hong-Sheng; Kruger, Philipp; Nguyen, John; Trendel, Nicola; Abu-Shah, Enas; Maini, Philip Kumar; van der Merwe, Philip Anton; Dushek, Omer

2016-10-25

T cells must respond differently to antigens of varying affinity presented at different doses. Previous attempts to map peptide MHC (pMHC) affinity onto T-cell responses have produced inconsistent patterns of responses, preventing formulations of canonical models of T-cell signaling. Here, a systematic analysis of T-cell responses to 1 million-fold variations in both pMHC affinity and dose produced bell-shaped dose-response curves and different optimal pMHC affinities at different pMHC doses. Using sequential model rejection/identification algorithms, we identified a unique, minimal model of cellular signaling incorporating kinetic proofreading with limited signaling coupled to an incoherent feed-forward loop (KPL-IFF) that reproduces these observations. We show that the KPL-IFF model correctly predicts the T-cell response to antigen copresentation. Our work offers a general approach for studying cellular signaling that does not require full details of biochemical pathways.

Daily radionuclide ingestion and internal radiation doses in Aomori prefecture, Japan.

PubMed

Ohtsuka, Yoshihito; Kakiuchi, Hideki; Akata, Naofumi; Takaku, Yuichi; Hisamatsu, Shun'ichi

2013-10-01

To assess internal annual dose in the general public in Aomori Prefecture, Japan, 80 duplicate cooked diet samples, equivalent to the food consumed over a 400-d period by one person, were collected from 100 volunteers in Aomori City and the village of Rokkasho during 2006–2010 and were analyzed for 11 radionuclides. To obtain average rates of ingestion of radionuclides, the volunteers were selected from among office, fisheries, agricultural, and livestock farm workers. Committed effective doses from ingestion of the diet over a 1-y period were calculated from the analytical results and from International Commission on Radiological Protection dose coefficients; for 40K, an internal effective dose rate from the literature was used. Fisheries workers had significantly higher combined internal annual dose than the other workers, possibly because of high rates of ingestion of marine products known to have high 210Po concentrations. The average internal dose rate, weighted by the numbers of households in each worker group in Aomori Prefecture, was estimated at 0.47 mSv y-1. Polonium-210 contributed 49% of this value. The sum of committed effective dose rates for 210Po, 210Pb, 228Ra, and 14C and the effective dose rate of 40K accounted for approximately 99% of the average internal dose rate.

[Dose rate-dependent cellular and molecular effects of ionizing radiation].

PubMed

Przybyszewski, Waldemar M; Wideł, Maria; Szurko, Agnieszka; Maniakowski, Zbigniew

2008-09-11

The aim of radiation therapy is to kill tumor cells while minimizing damage to normal cells. The ultimate effect of radiation can be apoptotic or necrotic cell death as well as cytogenetic damage resulting in genetic instability and/or cell death. The destructive effects of radiation arise from direct and indirect ionization events leading to peroxidation of macromolecules, especially those present in lipid-rich membrane structures as well as chromatin lipids. Lipid peroxidative end-products may damage DNA and proteins. A characteristic feature of radiation-induced peroxidation is an inverse dose-rate effect (IDRE), defined as an increase in the degree of oxidation(at constant absorbed dose) accompanying a lower dose rate. On the other hand, a low dose rate can lead to the accumulation of cells in G2, the radiosensitive phase of the cell cycle since cell cycle control points are not sensitive to low dose rates. Radiation dose rate may potentially be the main factor improving radiotherapy efficacy as well as affecting the intensity of normal tissue and whole-body side effects. A better understanding of dose rate-dependent biological effects may lead to improved therapeutic intervention and limit normal tissue reaction. The study reviews basic biological effects that depend on the dose rate of ionizing radiation.

Dose rate effects on array CCDs exposed by Co-60 γ rays induce saturation output degradation and annealing tests

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

Wang, Zujun, E-mail: wangzujun@nint.ac.cn; Chen, Wei; He, Baoping

The experimental tests of dose rate and annealing effects on array charge-coupled devices (CCDs) are presented. The saturation output voltage (V{sub S}) versus the total dose at the dose rates of 0.01, 0.1, 1.0, 10.0 and 50 rad(Si)/s are compared. Annealing tests are performed to eliminate the time-dependent effects. The V{sub S} degradation levels depend on the dose rates. The V{sub S} degradation mechanism induced by dose rate and annealing effects is analyzed. The V{sub S} at 20 krad(Si) with the dose rate of 0.03 rad(Si)/s are supplemented to assure the degradation curves between the dose rates of 0.1 andmore » 0.01 rad(Si)/s. The CCDs are divided into two groups, with one group biased and the other unbiased during {sup 60}Co γ radiation. The V{sub S} degradation levels of the biased CCDs during radiation are more severe than that of the unbiased CCDs.« less

Statistical control process to compare and rank treatment plans in radiation oncology: impact of heterogeneity correction on treatment planning in lung cancer.

PubMed

Chaikh, Abdulhamid; Balosso, Jacques

2016-12-01

This study proposes a statistical process to compare different treatment plans issued from different irradiation techniques or different treatment phases. This approach aims to provide arguments for discussion about the impact on clinical results of any condition able to significantly alter dosimetric or ballistic related data. The principles of the statistical investigation are presented in the framework of a clinical example based on 40 fields of radiotherapy for lung cancers. Two treatment plans were generated for each patient making a change of dose distribution due to variation of lung density correction. The data from 2D gamma index (γ) including the pixels having γ≤1 were used to determine the capability index (Cp) and the acceptability index (Cpk) of the process. To measure the strength of the relationship between the γ passing rates and the Cp and Cpk indices, the Spearman's rank non-parametric test was used to calculate P values. The comparison between reference and tested plans showed that 95% of pixels have γ≤1 with criteria (6%, 6 mm). The values of the Cp and Cpk indices were lower than one showing a significant dose difference. The data showed a strong correlation between γ passing rates and the indices with P>0.8. The statistical analysis using Cp and Cpk, show the significance of dose differences resulting from two plans in radiotherapy. These indices can be used for adaptive radiotherapy to measure the difference between initial plan and daily delivered plan. The significant changes of dose distribution could raise the question about the continuity to treat the patient with the initial plan or the need for adjustments.

SU-E-T-285: Dose Variation at Bone in Small-Animal Irradiation: A Monte Carlo Study Using Monoenergetic Photon Beams

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

Vuong, A; Chow, J

Purpose: The aim of this study is to investigate the variation of bone dose on photon beam energy (keV – MeV) in small-animal irradiation. Dosimetry of homogeneous and inhomogeneous phantoms as per the same mouse computed tomography image set were calculated using the DOSCTP and DOSXYZnrc based on the EGSnrc Monte Carlo code. Methods: Monte Carlo simulations for the homogeneous and inhomogeneous mouse phantom irradiated by a 360 degree photon arc were carried out. Mean doses of the bone tissue in the irradiated volumes were calculated at various photon beam energies, ranging from 50 keV to 1.25 MeV. The effectmore » of bone inhomogeneity was examined through the Inhomogeneous Correction Factor (ICF), a dose ratio of the inhomogeneous to the homogeneous medium. Results: From our Monte Carlo results, higher mean bone dose and ICF were found when using kilovoltage photon beams compared to megavoltage. In beam energies ranging from 50 keV to 200 keV, the bone dose was found maximum at 50 keV, and decreased significantly from 2.6 Gy to 0.55 Gy, when 2 Gy was delivered at the center of the phantom (isocenter). Similarly, the ICF were found decreasing from 4.5 to 1 when the photon beam energy was increased from 50 keV to 200 keV. Both mean bone dose and ICF remained at about 0.5 Gy and 1 from 200 keV to 1.25 MeV with insignificant variation, respectively. Conclusion: It is concluded that to avoid high bone dose in the small-animal irradiation, photon beam energy higher than 200 keV should be used with the ICF close to one, and bone dose comparable to the megavoltage beam where photoelectric effect is not dominant.« less

Characteristics and verification of a car-borne survey system for dose rates in air: KURAMA-II.

PubMed

Tsuda, S; Yoshida, T; Tsutsumi, M; Saito, K

2015-01-01

The car-borne survey system KURAMA-II, developed by the Kyoto University Research Reactor Institute, has been used for air dose rate mapping after the Fukushima Dai-ichi Nuclear Power Plant accident. KURAMA-II consists of a CsI(Tl) scintillation detector, a GPS device, and a control device for data processing. The dose rates monitored by KURAMA-II are based on the G(E) function (spectrum-dose conversion operator), which can precisely calculate dose rates from measured pulse-height distribution even if the energy spectrum changes significantly. The characteristics of KURAMA-II have been investigated with particular consideration to the reliability of the calculated G(E) function, dose rate dependence, statistical fluctuation, angular dependence, and energy dependence. The results indicate that 100 units of KURAMA-II systems have acceptable quality for mass monitoring of dose rates in the environment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Immediate effects of 33 to 180 rad/min (60)Co exposure on performance and blood pressure in monkeys. Topical report

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

Bruner, A.

1976-09-01

Four groups of monkeys received 1000 rads (60)Co at 33, 50, 75, or 180 rad/min wholebody irradiation while performing a delayed matching-to-sample task. Systematic dose rate effects were observed on performance and blood pressure within the initial 20 min postirradiation. The incidence and severity of performance decrement (PD) increased with higher dose rate. The appearance of postirradiation hypotension was systematically delayed and its rate of fall prolonged as dose rate was lower. The hypotension likewise appeared less deep with lower dose rate exposure. Based on the calculated cumulative dose absorbed at the time of symptom appearance two coactive thresholds weremore » proposed to exist: a total dose threshold of approximately 300 rads (midbody measurement), and a dose rate threshold of about 25 rad/min.« less

Cosmic rays and terrestrial life: A brief review

NASA Astrophysics Data System (ADS)

Atri, Dimitra; Melott, Adrian L.

2014-01-01

“The investigation into the possible effects of cosmic rays on living organisms will also offer great interest.” - Victor F. Hess, Nobel Lecture, December 12, 1936 High-energy radiation bursts are commonplace in our Universe. From nearby solar flares to distant gamma ray bursts, a variety of physical processes accelerate charged particles to a wide range of energies, which subsequently reach the Earth. Such particles contribute to a number of physical processes occurring in the Earth system. A large fraction of the energy of charged particles gets deposited in the atmosphere, ionizing it, causing changes in its chemistry and affecting the global electric circuit. Remaining secondary particles contribute to the background dose of cosmic rays on the surface and parts of the subsurface region. Life has evolved over the past ∼3 billion years in presence of this background radiation, which itself has varied considerably during the period [1-3]. As demonstrated by the Miller-Urey experiment, lightning plays a very important role in the formation of complex organic molecules, which are the building blocks of more complex structures forming life. There is growing evidence of increase in the lightning rate with increasing flux of charged particles. Is there a connection between enhanced rate of cosmic rays and the origin of life? Cosmic ray secondaries are also known to damage DNA and cause mutations, leading to cancer and other diseases. It is now possible to compute radiation doses from secondary particles, in particular muons and neutrons. Have the variations in cosmic ray flux affected the evolution of life on earth? We describe the mechanisms of cosmic rays affecting terrestrial life and review the potential implications of the variation of high-energy astrophysical radiation on the history of life on earth.

SU-F-T-65: AutomaticTreatment Planning for High-Dose Rate (HDR) Brachytherapy with a VaginalCylinder Applicator

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

Zhou, Y; Tan, J; Jiang, S

Purpose: High dose rate (HDR) brachytherapy treatment planning is conventionally performed in a manual fashion. Yet it is highly desirable to perform computerized automated planning to improve treatment planning efficiency, eliminate human errors, and reduce plan quality variation. The goal of this research is to develop an automatic treatment planning tool for HDR brachytherapy with a cylinder applicator for vaginal cancer. Methods: After inserting the cylinder applicator into the patient, a CT scan was acquired and was loaded to an in-house developed treatment planning software. The cylinder applicator was automatically segmented using image-processing techniques. CTV was generated based on user-specifiedmore » treatment depth and length. Locations of relevant points (apex point, prescription point, and vaginal surface point), central applicator channel coordinates, and dwell positions were determined according to their geometric relations with the applicator. Dwell time was computed through an inverse optimization process. The planning information was written into DICOM-RT plan and structure files to transfer the automatically generated plan to a commercial treatment planning system for plan verification and delivery. Results: We have tested the system retrospectively in nine patients treated with vaginal cylinder applicator. These cases were selected with different treatment prescriptions, lengths, depths, and cylinder diameters to represent a large patient population. Our system was able to generate treatment plans for these cases with clinically acceptable quality. Computation time varied from 3–6 min. Conclusion: We have developed a system to perform automated treatment planning for HDR brachytherapy with a cylinder applicator. Such a novel system has greatly improved treatment planning efficiency and reduced plan quality variation. It also served as a testbed to demonstrate the feasibility of automatic HDR treatment planning for more complicated cases.« less

Characterization and prediction of monomer-based dose rate effects in electron-beam polymerization

NASA Astrophysics Data System (ADS)

Schissel, Sage M.; Lapin, Stephen C.; Jessop, Julie L. P.

2017-12-01

Properties of some materials produced by electron-beam (EB) induced polymerization appear dependent upon the rate at which the initiating dose was delivered. However, the magnitude of these dose rate effects (DREs) can vary greatly with different monomer formulations, suggesting DREs are dependent on chemical structure. The relationship among dose, dose rate, conversion, and the glass transition temperature (Tg) of the cured material was explored for an acrylate monomer series. A strong correlation was determined between the DRE magnitude and monomer size, and this correlation may be attributed to chain transfer. Using the Tg shift caused by changes in dose, a preliminary predictive relationship was developed to estimate the magnitude of the Tg DRE, enabling scale-up of process variables for polymers prone to dose rate effects.

A method to determine the planar dose distributions in patient undergone radiotherapy

NASA Astrophysics Data System (ADS)

Cilla, S.; Viola, P.; Augelli, B. G.; D'Onofrio, G.; Grimaldi, L.; Craus, M.; Digesù, C.; Deodato, F.; Macchia, G.; Morganti, A. G.; Fidanzio, A.; Azario, L.; Piermattei, A.

2008-06-01

A 2D-array equipped with 729 vented plane parallel ion-chambers has been calibrated as a portal dose detector for radiotherapy in vivo measurements. The array has been positioned by a radiographic film stand at 120 cm from the source orthogonal to the radiotherapy beam delivered with the gantry angle at 180°. The collision between the 2D-array and the patient's couch have been avoided. In this work, using the measurements of the portal detector, we present a method to reconstruct the dose variations in the patient treated with step and shoot intensity-modulated beams (IMRT) for head-neck tumours. For this treatment morphological changes often occur during the fractionated therapy. In a first step an in-house software supplied the comparison between the measured portal dose and the one computed by a commercial treatment planning system within the field of view of the computed tomography (CT) scanner. For each patient, the percentage Pγ of chambers, where the comparison is in agreement within a selected acceptance criteria, was determined 8 times. At the first radiotherapy fraction the γ-index analysis supplied Pγ values of about 95%, within acceptance criteria in terms of dose-difference, ΔD, and distance-agreement, Δd, that was equal to 5% and 4 mm, respectively. These acceptance criteria were taken into account for small errors in the patient's set-up reproducibility and for the accuracy of the portal dose calculated by the treatment planning system (TPS) in particular when the beam was attenuated by inhomogeneous tissues and the shape of the head-neck body contours were irregular. During the treatment, some patients showed a reduction of the Pγ below 90% because due to radiotherapy treatment there was a change of the patient's morphology. In a second step a method, based on dosimetric measurements that used standard phantoms, supplied the percentage dose variations in a coronal plane of the patient using the percentage dose variations measured by the 2D-array portal detector. The results showed that the dose variations due to the change of the patient's morphology reached 15% and such discrepancies were displayed on the digitally reconstructed radiography of the patient. The dose discrepancies were confirmed by the hybrid plan obtained by the treatment planning system. The good results here reported show that once it is possible to have the portal dose distributions even for other gantry angles, these tests could be introduced in the clinical protocol to have major support to decide when to repeat the patient's CT scan and to re-plan the new IMRT dose calculation.

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

Venencia, C; Pino, M; Caussa, L

Purpose: The purpose of this work was to quantify the dosimetric impact of Monte Carlo (MC) dose calculation algorithm compared to Pencil Beam (PB) on Spine SBRT with HybridARC (HA) and sliding windows IMRT (dMLC) treatment modality. Methods: A 6MV beam (1000MU/min) produced by a Novalis TX (BrainLAB-Varian) equipped with HDMLC was used. HA uses 1 arc plus 8 IMRT beams (arc weight between 60–40%) and dIMRT 15 beams. Plans were calculated using iPlan v.4.5.3 (BrainLAB) and the treatment dose prescription was 27Gy in 3 fractions. Dose calculation was done by PB (4mm spatial resolution) with heterogeneity correction and MCmore » dose to water (4mm spatial resolution and 4% mean variance). PTV and spinal cord dose comparison were done. Study was done on 12 patients. IROC Spine Phantom was used to validate HA and quantify dose variation using PB and MC algorithm. Results: The difference between PB and MC for PTV D98%, D95%, Dmean, D2% were 2.6% [−5.1, 6.8], 0.1% [−4.2, 5.4], 0.9% [−1.5, 3.8] and 2.4% [−0.5, 8.3]. The difference between PB and MC for spinal cord Dmax, D1.2cc and D0.35cc were 5.3% [−6.4, 18.4], 9% [−7.0, 17.0] and 7.6% [−0.6, 14.8] respectively. IROC spine phantom shows PTV TLD dose variation of 0.98% for PB and 1.01% for MC. Axial and sagittal film plane gamma index (5%-3mm) was 95% and 97% for PB and 95% and 99% for MC. Conclusion: PB slightly underestimates the dose for the PTV. For the spinal cord PB underestimates the dose and dose differences could be as high as 18% which could have unexpected clinical impact. CI shows no variation between PB and MC for both treatment modalities Treatment modalities have no impact with the dose calculation algorithms used. Following the IROC pass-fail criteria, treatment acceptance requirement was fulfilled for PB and MC.« less

TU-AB-303-11: Predict Parotids Deformation Applying SIS Epidemiological Model in H&N Adaptive RT

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

Maffei, N; Guidi, G; University of Bologna, Bologna, Bologna

2015-06-15

Purpose: The aim is to investigate the use of epidemiological models to predict morphological variations in patients undergoing radiation therapy (RT). The susceptible-infected-susceptible (SIS) deterministic model was applied to simulate warping within a focused region of interest (ROI). Hypothesis is to consider each voxel like a single subject of the whole sample and to treat displacement vector fields like an infection. Methods: Using Raystation hybrid deformation algorithms and automatic re-contouring based on mesh grid, we post-processed 360 MVCT images of 12 H&N patients treated with Tomotherapy. Study focused on parotid glands, identified by literature and previous analysis, as ROI moremore » susceptible to warping in H&N region. Susceptible (S) and infectious (I) cases were identified in voxels with inter-fraction movement respectively under and over a set threshold. IronPython scripting allowed to export positions and displacement data of surface voxels for every fraction. A MATLAB homemade toolbox was developed to model the SIS. Results: SIS model was validated simulating organ motion on QUASAR phantom. Applying model in patients, within a [0–1cm] range, a single voxel movement of 0.4cm was selected as displacement threshold. SIS indexes were evaluated by MATLAB simulations. Dynamic time warping algorithm was used to assess matching between model and parotids behavior days of treatments. The best fit of the model was obtained with contact rate of 7.89±0.94 and recovery rate of 2.36±0.21. Conclusion: SIS model can follow daily structures evolutions, making possible to compare warping conditions and highlighting challenges due to abnormal variation and set-up errors. By epidemiology approach, organ motion could be assessed and predicted not in terms of average of the whole ROI, but in a voxel-by-voxel deterministic trend. Identifying anatomical region subjected to variations, would be possible to focus clinic controls within a cohort of pre-selected patients eligible for adaptive RT. The research is partially co-funded by the Italian Research Grant: Dose warping methods for IGRT and Adaptive RT: dose accumulation based on organ motion and anatomical variations of the patients during radiation therapy treatments,MoH (GR-2010-2318757) and Tecnologie Avanzate S.r.l.(Italy)« less

Developing new extension of GafChromic RTQA2 film to patient quality assurance field using a plan-based calibration method

NASA Astrophysics Data System (ADS)

Peng, Jiayuan; Zhang, Zhen; Wang, Jiazhou; Xie, Jiang; Chen, Junchao; Hu, Weigang

2015-10-01

GafChromic RTQA2 film is a type of radiochromic film designed for light field and radiation field alignment. The aim of this study is to extend the application of RTQA2 film to the measurement of patient specific quality assurance (QA) fields as a 2D relative dosimeter. Pre-irradiated and post-irradiated RTQA2 films were scanned in reflection mode using a flatbed scanner. A plan-based calibration (PBC) method utilized the mapping information of the calculated dose image and film grayscale image to create a dose versus pixel value calibration model. This model was used to calibrate the film grayscale image to the film relative dose image. The dose agreement between calculated and film dose images were analyzed by gamma analysis. To evaluate the feasibility of this method, eight clinically approved RapidArc cases (one abdomen cancer and seven head-and-neck cancer patients) were tested using this method. Moreover, three MLC gap errors and two MLC transmission errors were introduced to eight Rapidarc cases respectively to test the robustness of this method. The PBC method could overcome the film lot and post-exposure time variations of RTQA2 film to get a good 2D relative dose calibration result. The mean gamma passing rate of eight patients was 97.90%  ±  1.7%, which showed good dose consistency between calculated and film dose images. In the error test, the PBC method could over-calibrate the film, which means some dose error in the film would be falsely corrected to keep the dose in film consistent with the dose in the calculated dose image. This would then lead to a false negative result in the gamma analysis. In these cases, the derivative curve of the dose calibration curve would be non-monotonic which would expose the dose abnormality. By using the PBC method, we extended the application of more economical RTQA2 film to patient specific QA. The robustness of the PBC method has been improved by analyzing the monotonicity of the derivative of the calibration curve.