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Sample records for precision radiotherapy techniques

  1. Imaging Instrumentation and Techniques for Precision Radiotherapy

    NASA Astrophysics Data System (ADS)

    Parodi, Katia; Parodi, Katia; Thieke, Christian; Thieke, Christian

    Over the last decade, several technological advances have considerably improved the achievable precision of dose delivery in radiation therapy. Clinical exploitation of the superior tumor-dose conformality offered by modern radiotherapy techniques like intensity-modulated radiotherapy and ion beam therapy requires morphological and functional assessment of the tumor during the entire therapy chain from treatment planning to beam application and treatment response evaluation. This chapter will address the main rationale and role of imaging in state-of-the-art external beam radiotherapy. Moreover, it will present the status of novel imaging instrumentation and techniques being nowadays introduced in clinical use or still under development for image guidance and, ultimately, dose guidance of precision radiotherapy.

  2. Precision radiotherapy for cancer of the pancreas: technique and results. [Photons and electrons

    SciTech Connect

    Dobelbower, R.R. Jr.; Borgelt, B.B.; Strubler, K.A.; Kutcher, G.J.; Suntharalingam, N.

    1980-09-01

    Forty patients with locally extensive, unresectable adenocarcinoma of the pancreas received precision high dose (PHD) radiation therapy with a 45 MeV betatron. PHD radiotherapy was generally well tolerated. During treatment, only 7 patients experienced significant nausea, vomiting, diarrhea or anorexia. Late gastrointestinal radiation reactions were observed in 7 patients. Twelve patients received adjuvant chemotherapy. The projected survival of patients with unresectable pancreatic cancer treated with PHD radiotherapy is comparable to that of patients with resectable disease operated on for cure. The projected one year survival rate is 49%.

  3. Cellular signalling effects in high precision radiotherapy

    NASA Astrophysics Data System (ADS)

    McMahon, Stephen J.; McGarry, Conor K.; Butterworth, Karl T.; Jain, Suneil; O'Sullivan, Joe M.; Hounsell, Alan R.; Prise, Kevin M.

    2015-06-01

    Radiotherapy is commonly planned on the basis of physical dose received by the tumour and surrounding normal tissue, with margins added to address the possibility of geometric miss. However, recent experimental evidence suggests that intercellular signalling results in a given cell’s survival also depending on the dose received by neighbouring cells. A model of radiation-induced cell killing and signalling was used to analyse how this effect depends on dose and margin choices. Effective Uniform Doses were calculated for model tumours in both idealised cases with no delivery uncertainty and more realistic cases incorporating geometric uncertainty. In highly conformal irradiation, a lack of signalling from outside the target leads to reduced target cell killing, equivalent to under-dosing by up to 10% compared to large uniform fields. This effect is significantly reduced when higher doses per fraction are considered, both increasing the level of cell killing and reducing margin sensitivity. These effects may limit the achievable biological precision of techniques such as stereotactic radiotherapy even in the absence of geometric uncertainties, although it is predicted that larger fraction sizes reduce the relative contribution of cell signalling driven effects. These observations may contribute to understanding the efficacy of hypo-fractionated radiotherapy.

  4. Precision radiotherapy for small animal research.

    PubMed

    Matinfar, Mohammad; Iordachita, Iulian; Ford, Eric; Wong, John; Kazanzides, Peter

    2008-01-01

    Preclinical research using well characterized small animal models has provided tremendous benefits to medical research, enabling low cost, large scale trials with high statistical significance of observed effects. The goal of the Small Animal Radiation Research Platform (SARRP) is to make those models available for the development and evaluation of novel radiation therapies. SARRP demonstrates the capabilities of delivering high resolution, sub-millimeter, optimally planned conformal of radiation with on-board cone-beam CT (CBCT) guidance. The system requires accurate calibration of the x-ray beam for both imaging and radiation treatment. In this paper, we present a novel technique using an x-ray camera for calibration of the treatment beam. This technique does not require precise positioning or calibration of the x-ray camera. PMID:18982656

  5. Segmentation precision of abdominal anatomy for MRI-based radiotherapy.

    PubMed

    Noel, Camille E; Zhu, Fan; Lee, Andrew Y; Yanle, Hu; Parikh, Parag J

    2014-01-01

    The limited soft tissue visualization provided by computed tomography, the standard imaging modality for radiotherapy treatment planning and daily localization, has motivated studies on the use of magnetic resonance imaging (MRI) for better characterization of treatment sites, such as the prostate and head and neck. However, no studies have been conducted on MRI-based segmentation for the abdomen, a site that could greatly benefit from enhanced soft tissue targeting. We investigated the interobserver and intraobserver precision in segmentation of abdominal organs on MR images for treatment planning and localization. Manual segmentation of 8 abdominal organs was performed by 3 independent observers on MR images acquired from 14 healthy subjects. Observers repeated segmentation 4 separate times for each image set. Interobserver and intraobserver contouring precision was assessed by computing 3-dimensional overlap (Dice coefficient [DC]) and distance to agreement (Hausdorff distance [HD]) of segmented organs. The mean and standard deviation of intraobserver and interobserver DC and HD values were DC(intraobserver) = 0.89 ± 0.12, HD(intraobserver) = 3.6mm ± 1.5, DC(interobserver) = 0.89 ± 0.15, and HD(interobserver) = 3.2mm ± 1.4. Overall, metrics indicated good interobserver/intraobserver precision (mean DC > 0.7, mean HD < 4mm). Results suggest that MRI offers good segmentation precision for abdominal sites. These findings support the utility of MRI for abdominal planning and localization, as emerging MRI technologies, techniques, and onboard imaging devices are beginning to enable MRI-based radiotherapy. PMID:24726701

  6. Segmentation precision of abdominal anatomy for MRI-based radiotherapy

    SciTech Connect

    Noel, Camille E.; Zhu, Fan; Lee, Andrew Y.; Yanle, Hu; Parikh, Parag J.

    2014-10-01

    The limited soft tissue visualization provided by computed tomography, the standard imaging modality for radiotherapy treatment planning and daily localization, has motivated studies on the use of magnetic resonance imaging (MRI) for better characterization of treatment sites, such as the prostate and head and neck. However, no studies have been conducted on MRI-based segmentation for the abdomen, a site that could greatly benefit from enhanced soft tissue targeting. We investigated the interobserver and intraobserver precision in segmentation of abdominal organs on MR images for treatment planning and localization. Manual segmentation of 8 abdominal organs was performed by 3 independent observers on MR images acquired from 14 healthy subjects. Observers repeated segmentation 4 separate times for each image set. Interobserver and intraobserver contouring precision was assessed by computing 3-dimensional overlap (Dice coefficient [DC]) and distance to agreement (Hausdorff distance [HD]) of segmented organs. The mean and standard deviation of intraobserver and interobserver DC and HD values were DC{sub intraobserver} = 0.89 ± 0.12, HD{sub intraobserver} = 3.6 mm ± 1.5, DC{sub interobserver} = 0.89 ± 0.15, and HD{sub interobserver} = 3.2 mm ± 1.4. Overall, metrics indicated good interobserver/intraobserver precision (mean DC > 0.7, mean HD < 4 mm). Results suggest that MRI offers good segmentation precision for abdominal sites. These findings support the utility of MRI for abdominal planning and localization, as emerging MRI technologies, techniques, and onboard imaging devices are beginning to enable MRI-based radiotherapy.

  7. Precision, high dose radiotherapy: helium ion treatment of uveal melanoma

    SciTech Connect

    Saunders, W.M.; Char, D.H.; Quivey, J.M.; Castro, J.R.; Chen, G.T.Y.; Collier, J.M.; Cartigny, A.; Blakely, E.A.; Lyman, J.T.; Zink, S.R.

    1985-02-01

    The authors report on 75 patients with uveal melanoma who were treated by placing the Bragg peak of a helium ion beam over the tumor volume. The technique localizes the high dose region very tightly around the tumor volume. This allows critical structures, such as the optic disc and the macula, to be excluded from the high dose region as long as they are 3 to 4 mm away from the edge of the tumor. Careful attention to tumor localization, treatment planning, patient immobilization and treatment verification is required. With a mean follow-up of 22 months (3 to 60 months) the authors have had only five patients with a local recurrence, all of whom were salvaged with another treatment. Pretreatment visual acuity has generally been preserved as long as the tumor edge is at least 4 mm away from the macula and optic disc. The only serious complication to date has been an 18% incidence of neovascular glaucoma in the patients treated at our highest dose level. Clinical results and details of the technique are presented to illustrate potential clinical precision in administering high dose radiotherapy with charged particles such as helium ions or protons.

  8. Principles and techniques for designing precision machines

    SciTech Connect

    Hale, L C

    1999-02-01

    This thesis is written to advance the reader's knowledge of precision-engineering principles and their application to designing machines that achieve both sufficient precision and minimum cost. It provides the concepts and tools necessary for the engineer to create new precision machine designs. Four case studies demonstrate the principles and showcase approaches and solutions to specific problems that generally have wider applications. These come from projects at the Lawrence Livermore National Laboratory in which the author participated: the Large Optics Diamond Turning Machine, Accuracy Enhancement of High- Productivity Machine Tools, the National Ignition Facility, and Extreme Ultraviolet Lithography. Although broad in scope, the topics go into sufficient depth to be useful to practicing precision engineers and often fulfill more academic ambitions. The thesis begins with a chapter that presents significant principles and fundamental knowledge from the Precision Engineering literature. Following this is a chapter that presents engineering design techniques that are general and not specific to precision machines. All subsequent chapters cover specific aspects of precision machine design. The first of these is Structural Design, guidelines and analysis techniques for achieving independently stiff machine structures. The next chapter addresses dynamic stiffness by presenting several techniques for Deterministic Damping, damping designs that can be analyzed and optimized with predictive results. Several chapters present a main thrust of the thesis, Exact-Constraint Design. A main contribution is a generalized modeling approach developed through the course of creating several unique designs. The final chapter is the primary case study of the thesis, the Conceptual Design of a Horizontal Machining Center.

  9. Abridged Technique for Precise Implant Angulation.

    PubMed

    Perumal, Praveen; Chander, Gopi Naveen; Viswanathan, Anitha Kuttae; Reddy, Ramesh; Muthukumar, B

    2015-12-01

    Enormous scientific knowledge with evidence and clinical dexterity impart definitive ground for success in implant dentistry. Nevertheless, the unfeasibility to access the inner bone tissue makes the situation altogether more demanding. Presently the advent of numerous imaging techniques and associated surgical guide templates are documented for evaluation of implant angulation. However, they are not cost effective and consume more time to plan and design the structure. This article describes a simple concise technique for precise implant angulation. PMID:26816997

  10. Abridged Technique for Precise Implant Angulation

    PubMed Central

    Perumal, Praveen; Chander, Gopi Naveen; Reddy, Ramesh; Muthukumar, B.

    2015-01-01

    Enormous scientific knowledge with evidence and clinical dexterity impart definitive ground for success in implant dentistry. Nevertheless, the unfeasibility to access the inner bone tissue makes the situation altogether more demanding. Presently the advent of numerous imaging techniques and associated surgical guide templates are documented for evaluation of implant angulation. However, they are not cost effective and consume more time to plan and design the structure. This article describes a simple concise technique for precise implant angulation. PMID:26816997

  11. A precise technique for manufacturing correction coil

    SciTech Connect

    Schieber, L.

    1992-11-01

    An automated method of manufacturing correction coils has been developed which provides a precise embodiment of the coil design. Numerically controlled machines have been developed to accurately position coil windings on the beam tube. Two types of machines have been built. One machine bonds the wire to a substrate which is wrapped around the beam tube after it is completed while the second machine bonds the wire directly to the beam tube. Both machines use the Multiwire{reg_sign} technique of bonding the wire to the substrate utilizing an ultrasonic stylus. These machines are being used to manufacture coils for both the SSC and RHIC.

  12. A precise technique for manufacturing correction coil

    SciTech Connect

    Schieber, L.

    1992-01-01

    An automated method of manufacturing correction coils has been developed which provides a precise embodiment of the coil design. Numerically controlled machines have been developed to accurately position coil windings on the beam tube. Two types of machines have been built. One machine bonds the wire to a substrate which is wrapped around the beam tube after it is completed while the second machine bonds the wire directly to the beam tube. Both machines use the Multiwire[reg sign] technique of bonding the wire to the substrate utilizing an ultrasonic stylus. These machines are being used to manufacture coils for both the SSC and RHIC.

  13. Development of three-dimensional radiotherapy techniques in breast cancer

    NASA Astrophysics Data System (ADS)

    Coles, Charlotte E.

    Radiotherapy following conservation surgery decreases local relapse and death from breast cancer. Currently, the challenge is to minimise the morbidity caused by this treatment without losing efficacy. Despite many advances in radiation techniques in other sites of the body, the majority of breast cancer patients are still planned and treated using 2-dimensional simple radiotherapy techniques. In addition, breast irradiation currently consumes 30% of the UK's radiotherapy workload. Therefore, any change to more complex treatment should be of proven benefit. The primary objective of this research is to develop and evaluate novel radiotherapy techniques to decrease irradiation of normal structures and improve localisation of the tumour bed. I have developed a forward-planned intensity modulated (IMRT) breast radiotherapy technique, which has shown improved dosimetry results compared to standard breast radiotherapy. Subsequently, I have developed and implemented a phase III randomised controlled breast IMRT trial. This National Cancer Research Network adopted trial will answer an important question regarding the clinical benefit of breast IMRT. It will provide DNA samples linked with high quality clinical outcome data, for a national translational radiogenomics study investigating variation in normal tissue toxicity. Thus, patients with significant late normal tissue side effects despite good dose homogeneity will provide the best model for finding differences due to underlying genetics. I evaluated a novel technique using high definition free-hand 3-dimensional (3D) ultrasound in a phantom study, and the results suggested that this is an accurate and reproducible method for tumour bed localisation. I then compared recognised methods of tumour bed localisation with the 3D ultrasound method in a clinical study. The 3D ultrasound technique appeared to accurately represent the shape and spatial position of the tumour cavity. This tumour bed localisation research

  14. Predicting radiotherapy outcomes using statistical learning techniques*

    PubMed Central

    El Naqa, Issam; Bradley, Jeffrey D; Lindsay, Patricia E; Hope, Andrew J; Deasy, Joseph O

    2013-01-01

    Radiotherapy outcomes are determined by complex interactions between treatment, anatomical and patient-related variables. A common obstacle to building maximally predictive outcome models for clinical practice is the failure to capture potential complexity of heterogeneous variable interactions and applicability beyond institutional data. We describe a statistical learning methodology that can automatically screen for nonlinear relations among prognostic variables and generalize to unseen data before. In this work, several types of linear and nonlinear kernels to generate interaction terms and approximate the treatment-response function are evaluated. Examples of institutional datasets of esophagitis, pneumonitis and xerostomia endpoints were used. Furthermore, an independent RTOG dataset was used for ‘generalizabilty’ validation. We formulated the discrimination between risk groups as a supervised learning problem. The distribution of patient groups was initially analyzed using principle components analysis (PCA) to uncover potential nonlinear behavior. The performance of the different methods was evaluated using bivariate correlations and actuarial analysis. Over-fitting was controlled via cross-validation resampling. Our results suggest that a modified support vector machine (SVM) kernel method provided superior performance on leave-one-out testing compared to logistic regression and neural networks in cases where the data exhibited nonlinear behavior on PCA. For instance, in prediction of esophagitis and pneumonitis endpoints, which exhibited nonlinear behavior on PCA, the method provided 21% and 60% improvements, respectively. Furthermore, evaluation on the independent pneumonitis RTOG dataset demonstrated good generalizabilty beyond institutional data in contrast with other models. This indicates that the prediction of treatment response can be improved by utilizing nonlinear kernel methods for discovering important nonlinear interactions among model

  15. Predicting radiotherapy outcomes using statistical learning techniques

    NASA Astrophysics Data System (ADS)

    El Naqa, Issam; Bradley, Jeffrey D.; Lindsay, Patricia E.; Hope, Andrew J.; Deasy, Joseph O.

    2009-09-01

    Radiotherapy outcomes are determined by complex interactions between treatment, anatomical and patient-related variables. A common obstacle to building maximally predictive outcome models for clinical practice is the failure to capture potential complexity of heterogeneous variable interactions and applicability beyond institutional data. We describe a statistical learning methodology that can automatically screen for nonlinear relations among prognostic variables and generalize to unseen data before. In this work, several types of linear and nonlinear kernels to generate interaction terms and approximate the treatment-response function are evaluated. Examples of institutional datasets of esophagitis, pneumonitis and xerostomia endpoints were used. Furthermore, an independent RTOG dataset was used for 'generalizabilty' validation. We formulated the discrimination between risk groups as a supervised learning problem. The distribution of patient groups was initially analyzed using principle components analysis (PCA) to uncover potential nonlinear behavior. The performance of the different methods was evaluated using bivariate correlations and actuarial analysis. Over-fitting was controlled via cross-validation resampling. Our results suggest that a modified support vector machine (SVM) kernel method provided superior performance on leave-one-out testing compared to logistic regression and neural networks in cases where the data exhibited nonlinear behavior on PCA. For instance, in prediction of esophagitis and pneumonitis endpoints, which exhibited nonlinear behavior on PCA, the method provided 21% and 60% improvements, respectively. Furthermore, evaluation on the independent pneumonitis RTOG dataset demonstrated good generalizabilty beyond institutional data in contrast with other models. This indicates that the prediction of treatment response can be improved by utilizing nonlinear kernel methods for discovering important nonlinear interactions among model

  16. Late sensorial alterations in different radiotherapy techniques for nasopharyngeal cancer.

    PubMed

    Riva, Giuseppe; Raimondo, Luca; Ravera, Mattia; Moretto, Francesco; Boita, Monica; Potenza, Ilenia; Rampino, Monica; Ricardi, Umberto; Garzaro, Massimiliano

    2015-05-01

    Intensity-modulated radiation therapy (IMRT) for nasopharyngeal cancer (NPC) allowed a better distribution of the dose to the tumor volume, sparing surrounding structures. Aim of the study is the objective evaluation of olfactory and gustatory impairments in patients who underwent chemo-radiotherapy for NPC. Correlation between smell and taste alterations, xerostomy, and radiation technique was investigated. Thirty healthy subjects and 30 patients treated with chemo-radiation therapy for NPC, with at least a 2-years follow-up period, were evaluated. All subjects underwent symptoms evaluation, endoscopic fiber optic nasal examination, taste strips, Sniffin' sticks tests, Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer late radiation morbidity scoring system. Patients were divided in 2 groups: 2-dimensional radiotherapy/conformal 3-dimensional radiotherapy and IMRT. A higher percentage of rhinorrhea, nasal obstruction, xerostomy, hyposmia, hypogeusia, mucosal hyperemia, and presence of nasopharyngeal secretions was found in irradiated subjects (P < 0.05). Concerning olfactory and gustatory scores, we demonstrated a statistically significant difference between healthy subjects and irradiated patients (P < 0.05), with lower gustatory total score in IMRT group (P < 0.01). In conclusion, chemo-radiotherapy for NPC induces long-term smell and taste impairments, which can compromise quality of life. Although based on small samples, it is also important to consider that IMRT can induce higher taste dysfunction compared with traditional techniques. PMID:25800268

  17. Analysis of precision in tumor tracking based on optical positioning system during radiotherapy.

    PubMed

    Zhou, Han; Shen, Junshu; Li, Bing; Chen, Junting; Zhu, Xixu; Ge, Yun; Wang, Yongjian

    2016-03-19

    Tumor tracking is performed during patient set-up and monitoring of respiratory motion in radiotherapy. In the clinical setting, there are several types of equipment for this set-up such as the Electronic Portal imaging Device (EPID) and Cone Beam CT (CBCT). Technically, an optical positioning system tracks the difference between the infra ball reflected from body and machine isocenter. Our objective is to compare the clinical positioning error of patient setup between Cone Beam CT (CBCT) with the Optical Positioning System (OPS), and to evaluate the traditional positioning systems and OPS based on our proposed approach of patient positioning. In our experiments, a phantom was used, and we measured its setup errors in three directions. Specifically, the deviations in the left-to-right (LR), anterior-to-posterior (AP) and inferior-to-superior (IS) directions were measured by vernier caliper on a graph paper using the Varian Linear accelerator. Then, we verified the accuracy of OPS based on this experimental study. In order to verify the accuracy of phantom experiment, 40 patients were selected in our radiotherapy experiment. To illustrate the precise of optical positioning system, we designed clinical trials using EPID. From our radiotherapy procedure, we can conclude that OPS has higher precise than conventional positioning methods, and is a comparatively fast and efficient positioning method with respect to the CBCT guidance system. PMID:27257880

  18. Precision Learning Assessment: An Alternative to Traditional Assessment Techniques.

    ERIC Educational Resources Information Center

    Caltagirone, Paul J.; Glover, Christopher E.

    1985-01-01

    A continuous and curriculum-based assessment method, Precision Learning Assessment (PLA), which integrates precision teaching and norm-referenced techniques, was applied to a math computation curriculum for 214 third graders. The resulting districtwide learning curves defining average annual progress through the computation curriculum provided…

  19. New technique of machining high precision mirror surface press roller

    NASA Astrophysics Data System (ADS)

    Hongsen, Deng

    1991-03-01

    High precision mirror surface press roller machining technique of corrosion and grinding proof is one of the key techniques that the production enterprises as well as the machining and manufacturing of the following industries sought to resolve for a long time: plastics, papermaking, rubber, film, and chip production. In Oct. 1984, a new comprehensive machining technique of metal brush coating, grinding with abrasive belt, as well as buffing was used to conduct nearly 20 experiments. In Jan. 1985, a pair of middle convex high precision mirror surface press rollers was successfully machined. The technical process is described.

  20. Prostate Radiotherapy in the Era of Advanced Imaging and Precision Medicine.

    PubMed

    Dulaney, Caleb R; Osula, Daniel O; Yang, Eddy S; Rais-Bahrami, Soroush

    2016-01-01

    Tremendous technological advancements in prostate radiotherapy have decreased treatment toxicity and improved clinical outcomes for men with prostate cancer. While these advances have allowed for significant treatment volume reduction and whole-organ dose escalation, further improvement in prostate radiotherapy has been limited by classic techniques for diagnosis and risk stratification. Developments in prostate imaging, image-guided targeted biopsy, next-generation gene expression profiling, and targeted molecular therapies now provide information to stratify patients and select treatments based on tumor biology. Image-guided targeted biopsy improves detection of clinically significant cases of prostate cancer and provides important information about the biological behavior of intraprostatic lesions which can further guide treatment decisions. We review the evolution of prostate magnetic resonance imaging (MRI) and MRI-ultrasound fusion-guided prostate biopsy. Recent advancements in radiation therapy including dose escalation, moderate and extreme hypofractionation, partial prostate radiation therapy, and finally dose escalation by simultaneous integrated boost are discussed. We also review next-generation sequencing and discuss developments in targeted molecular therapies. Last, we review ongoing clinical trials and future treatment paradigms that integrate targeted biopsy, molecular profiling and therapy, and prostate radiotherapy. PMID:27022486

  1. Prostate Radiotherapy in the Era of Advanced Imaging and Precision Medicine

    PubMed Central

    Dulaney, Caleb R.; Osula, Daniel O.; Yang, Eddy S.; Rais-Bahrami, Soroush

    2016-01-01

    Tremendous technological advancements in prostate radiotherapy have decreased treatment toxicity and improved clinical outcomes for men with prostate cancer. While these advances have allowed for significant treatment volume reduction and whole-organ dose escalation, further improvement in prostate radiotherapy has been limited by classic techniques for diagnosis and risk stratification. Developments in prostate imaging, image-guided targeted biopsy, next-generation gene expression profiling, and targeted molecular therapies now provide information to stratify patients and select treatments based on tumor biology. Image-guided targeted biopsy improves detection of clinically significant cases of prostate cancer and provides important information about the biological behavior of intraprostatic lesions which can further guide treatment decisions. We review the evolution of prostate magnetic resonance imaging (MRI) and MRI-ultrasound fusion-guided prostate biopsy. Recent advancements in radiation therapy including dose escalation, moderate and extreme hypofractionation, partial prostate radiation therapy, and finally dose escalation by simultaneous integrated boost are discussed. We also review next-generation sequencing and discuss developments in targeted molecular therapies. Last, we review ongoing clinical trials and future treatment paradigms that integrate targeted biopsy, molecular profiling and therapy, and prostate radiotherapy. PMID:27022486

  2. Integral dose: Comparison between four techniques for prostate radiotherapy

    PubMed Central

    Ślosarek, Krzysztof; Osewski, Wojciech; Grządziel, Aleksandra; Radwan, Michał; Dolla, Łukasz; Szlag, Marta; Stąpór-Fudzińska, Małgorzata

    2014-01-01

    Aim Comparisons of integral dose delivered to the treatment planning volume and to the whole patient body during stereotactic, helical and intensity modulated radiotherapy of prostate. Background Multifield techniques produce large volumes of low dose inside the patient body. Delivered dose could be the result of the cytotoxic injuries of the cells even away from the treatment field. We calculated the total dose absorbed in the patient body for four radiotherapy techniques to investigate whether some methods have a potential to reduce the exposure to the patient. Materials and methods We analyzed CyberKnife plans for 10 patients with localized prostate cancer. Five alternative plans for each patient were calculated with the VMAT, IMRT and TomoTherapy techniques. Alternative dose distributions were calculated to achieve the same coverage for PTV. Integral Dose formula was used to calculate the total dose delivered to the PTV and whole patient body. Results Analysis showed that the same amount of dose was deposited to the treated volume despite different methods of treatment delivery. The mean values of total dose delivered to the whole patient body differed significantly for each treatment technique. The highest integral dose in the patient's body was at the TomoTherapy and CyberKnife treatment session. VMAT was characterized by the lowest integral dose deposited in the patient body. Conclusions The highest total dose absorbed in normal tissue was observed with the use of a robotic radiosurgery system and TomoTherapy. These results demonstrate that the exposure of healthy tissue is a dosimetric factor which differentiates the dose delivery methods. PMID:25859398

  3. Radiotherapy.

    PubMed

    Adamietz, Irenaus A

    2010-01-01

    The intrathoracic growth of the tumor causes several severe symptoms as cough, dyspnea, chest pain, hemoptysis, hoarseness, anorexia/nausea, and dysphagia. In patients with manifest or threatening symptoms radiotherapy (RT) as an effective measure should be implemented into the management concept. Palliative RT radiotherapy prefers short hypofractionated schemas (e.g. 10 x 3 Gy, 4 x 5 Gy, 2 x 8 Gy, 1 x 10 Gy). Careful radiation planning supports the precision of palliative RT and reduces significantly the complication rate. A good response and prolonged palliation effects (6-12 months) can be achieved in many cases. However, the minimum biologically equivalent dose should not be less than 35 Gy. RT produces a good outcome in all types of metastases of lung carcinoma. In emergencies like VCSS or spinal cord compression RT should be initiated immediately. The selection of the optimal therapy for locally advanced lung carcinoma with malignant airway obstruction is difficult. Both brachytherapy and percutaneous irradiation are effective, however published results including local a sum of response, functionality and life quality demonstrates more benefit by percutaneous RT. Due to different physical properties of these two methods the combination of brachytherapy and external beam irradiation may be advantageous. PMID:19955803

  4. Precise measurement techniques of millimeter-wave power

    NASA Astrophysics Data System (ADS)

    Inoue, T.

    1981-06-01

    Precise power measurement techniques in the millimeter-wave region are described, with attention to a calorimetric method based on thermal balance control, on the basis of which a calorimeter for measuring effective bolometer mount efficiency has been developed. Automatic power measurement systems which incorporate digital techniques are also designed and developed, and two types of circular bolometer mount having high effective efficiency in the 100 GHz band are described. For the case of the 30 GHz band, a method which employs a coupler as a comparator and quarter-wavelength spacer is proposed which significantly reduces the influence of impedance mismatch.

  5. Precision technique for side-polished fiber fabrication

    NASA Astrophysics Data System (ADS)

    Mishakov, Gennadi V.; Sokolov, Victor I.

    2002-04-01

    The precision technique for side polishing of single-mode quartz fibers is developed. The technique comprises cutting curved groove in silica block, gluing a section of bare fiber into the groove, and subsequent grinding and polishing of the silica block/fiber assembly. We succeeded in fabricating up to six side-polished fibers in one block with effective interaction length 2-4 mm. The accuracy of polishing depth was achieved at 1 micrometers using in-situ monitoring of transmission of 1.3 micrometers laser light through the fiber. The developed technique combines high accuracy, reproducibility and low cost in commercial production. Side- polished single-mode fibers fabricated with this technique can find application as elements of Bragg grating transmission filters, narrowband reflectors, optical add/drop multiplexers, couplers, polarizers, sensors, etc.

  6. Nasopharyngeal carcinoma--a review of radiotherapy techniques.

    PubMed

    Tsao, S Y

    1993-07-01

    With modern megavoltage external X-ray treatment for nasopharyngeal carcinoma, results have improved but late sequelae, which are more often associated with the treatment of advanced tumours or multiple courses of external treatment, have also surfaced. Life-threatening complications include temporal lobe necrosis and hypothalamic-pituitary dysfunction. As CT scanning is superior to conventional radiography in tumour mapping, a new dedicated working staging system, catering for cross-sectional imaging parameters, is proposed for a prospective, multi-centre exercise to finalise on a badly needed common system. With it, case selection for more conservative (to minimise complications) or intensified treatments is facilitated. Intracavitary radiation has now been developed well enough for the nasopharynx. For earlier cases, based on the new staging system, this method has the potential to complement a "sub-radical" external treatment dose designed to minimise complications. A multi-centre trial is indicated. To reach cancericidal doses for the more advanced tumours coming very close to vital structures, extra machine time, though precious, is fully justified so that smaller treatment fractions delivered with facial shells for accurate reproduction of precise machine geometry and field geography can be implemented. Otherwise, subsequent management of possible serious treatment complications may cost more than the treatment itself. Various possible complications of radiotherapy and avoidance and management are outlined. PMID:8257075

  7. Alignment techniques required by precise measurement of effective focal length

    NASA Technical Reports Server (NTRS)

    Wise, T. D.

    1980-01-01

    The characteristics of false color imagery produced by instrumentation on earth resource mapping satellites are examined. The spatial fidelity of the imagery is dependent upon the geometric accuracy (GA) and the band-to-band registration (BBR) with which the telescope instrument is assembled. BBR and GA require knowledge of telescope effective focal length (EFL) to one part in 10,000 in order that the next generation of earth mappers be able to carry out their missions. The basis for this level of precision is briefly considered, and a description is given of the means by which such precise EFL measurements have been carried out. Attention is given to accuracy requirements, the technique used to measure effective focal length, possible sources of error in the EFL measurement, approaches for eliminating errors, and the results of the efforts to control measurement errors in EFL determinations.

  8. Role of Radiotherapy and Newer Techniques in the Treatment of GI Cancers.

    PubMed

    Hajj, Carla; Goodman, Karyn A

    2015-06-01

    The role of radiotherapy in multidisciplinary treatment of GI malignancies is well established. Recent advances in imaging as well as radiotherapy planning and delivery techniques have made it possible to target tumors more accurately while sparing normal tissues. Intensity-modulated radiotherapy is an advanced method of delivering radiation using cutting-edge technology to manipulate beams of radiation. The role of intensity-modulated radiotherapy is growing for many GI malignancies, such as cancers of the stomach, pancreas, esophagus, liver, and anus. Stereotactic body radiotherapy is an emerging treatment option for some GI tumors such as locally advanced pancreatic cancer and primary or metastatic tumors of the liver. Stereotactic body radiotherapy requires a high degree of confidence in tumor location and subcentimeter accuracy of the delivered dose. New image-guided techniques have been developed to overcome setup uncertainties at the time of treatment, including real-time imaging on the linear accelerator. Modern imaging techniques have also allowed for more accurate pretreatment staging and delineation of the primary tumor and involved sites. In particular, magnetic resonance imaging and positron emission tomography scans can be particularly useful in radiotherapy planning and assessing treatment response. Molecular biomarkers are being investigated as predictors of response to radiotherapy with the intent of ultimately moving toward using genomic and proteomic determinants of therapeutic strategies. The role of all of these new approaches in the radiotherapeutic management of GI cancers and the evolving role of radiotherapy in these tumor sites will be highlighted in this review. PMID:25918298

  9. Kernel Regression Techniques for Enhancing Spitzer Photometric Precision

    NASA Astrophysics Data System (ADS)

    Ingalls, James G.; Krick, Jessica; Carey, Sean; Grillmair, Carl J.; Lowrance, Patrick; Glaccum, William; Laine, Seppo; Surace, Jason Anthony

    2015-08-01

    The Infrared Array Camera (IRAC) on the Spitzer Space Telescope has been used to measure < 0.01% temporal variations in the fluxes of exoplanet systems. The IRAC PSF at both 3.6 and 4.5 μm is undersampled and thus the detector arrays show variations of as much as 8% in sensitivity as the center of the PSF moves across a pixel due to normal spacecraft motions. This is the largest source of correlated noise in IRAC photometry. We describe the latest progress towards an independent calibration of the intra-pixel gain that does not rely on the measurements to be calibrated. The technique begins with: (1) localizing the sub-pixel position of a point source using Spitzer’s Pointing Calibration and Reference Sensor (PCRS); and (2) harnessing a “training set” of many thousands of densely spaced photometric measurements of a non-variable star. Kernel regression, where the training data are nonlinearly combined based on a distance metric for each data point, leads to significant improvements in photometric precision over our previous gridded method. The distance metric we use was derived from a supervised learning algorithm to minimize regression error. We conclude that these results rival the precision obtained with self-calibration techniques, but do not risk the removal of astrophysical signals.

  10. Radiotherapy of abdomen with precise renal assessment with SPECT/CT imaging (RAPRASI): design and methodology of a prospective trial to improve the understanding of kidney radiation dose response

    PubMed Central

    2013-01-01

    Background The kidneys are a principal dose-limiting organ in radiotherapy for upper abdominal cancers. The current understanding of kidney radiation dose response is rudimentary. More precise dose-volume response models that allow direct correlation of delivered radiation dose with spatio-temporal changes in kidney function may improve radiotherapy treatment planning for upper-abdominal tumours. Our current understanding of kidney dose response and tolerance is limited and this is hindering efforts to introduce advanced radiotherapy techniques for upper-abdominal cancers, such as intensity-modulated radiotherapy (IMRT). The aim of this study is to utilise radiotherapy and combined anatomical/functional imaging data to allow direct correlation of radiation dose with spatio-temporal changes in kidney function. The data can then be used to develop a more precise dose-volume response model which has the potential to optimise and individualise upper abdominal radiotherapy plans. Methods/design The Radiotherapy of Abdomen with Precise Renal Assessment with SPECT/CT Imaging (RAPRASI) is an observational clinical research study with participating sites at Sir Charles Gairdner Hospital (SCGH) in Perth, Australia and the Peter MacCallum Cancer Centre (PMCC) in Melbourne, Australia. Eligible patients are those with upper gastrointestinal cancer, without metastatic disease, undergoing conformal radiotherapy that will involve incidental radiation to one or both kidneys. For each patient, total kidney function is being assessed before commencement of radiotherapy treatment and then at 4, 12, 26, 52 and 78 weeks after the first radiotherapy fraction, using two procedures: a Glomerular Filtration Rate (GFR) measurement using the 51Cr-ethylenediamine tetra-acetic acid (EDTA) clearance; and a regional kidney perfusion measurement assessing renal uptake of 99mTc-dimercaptosuccinic acid (DMSA), imaged with a Single Photon Emission Computed Tomography / Computed Tomography (SPECT

  11. Assessing the Accuracy of the Precise Point Positioning Technique

    NASA Astrophysics Data System (ADS)

    Bisnath, S. B.; Collins, P.; Seepersad, G.

    2012-12-01

    The Precise Point Positioning (PPP) GPS data processing technique has developed over the past 15 years to become a standard method for growing categories of positioning and navigation applications. The technique relies on single receiver point positioning combined with the use of precise satellite orbit and clock information and high-fidelity error modelling. The research presented here uniquely addresses the current accuracy of the technique, explains the limits of performance, and defines paths to improvements. For geodetic purposes, performance refers to daily static position accuracy. PPP processing of over 80 IGS stations over one week results in few millimetre positioning rms error in the north and east components and few centimetres in the vertical (all one sigma values). Larger error statistics for real-time and kinematic processing are also given. GPS PPP with ambiguity resolution processing is also carried out, producing slight improvements over the float solution results. These results are categorised into quality classes in order to analyse the root error causes of the resultant accuracies: "best", "worst", multipath, site displacement effects, satellite availability and geometry, etc. Also of interest in PPP performance is solution convergence period. Static, conventional solutions are slow to converge, with approximately 35 minutes required for 95% of solutions to reach the 20 cm or better horizontal accuracy. Ambiguity resolution can significantly reduce this period without biasing solutions. The definition of a PPP error budget is a complex task even with the resulting numerical assessment, as unlike the epoch-by-epoch processing in the Standard Position Service, PPP processing involving filtering. An attempt is made here to 1) define the magnitude of each error source in terms of range, 2) transform ranging error to position error via Dilution Of Precision (DOP), and 3) scale the DOP through the filtering process. The result is a deeper

  12. Retinoblastoma-comparative analysis of external radiotherapy techniques, including an IMRT technique

    SciTech Connect

    Reisner, Marcio Lemberg . E-mail: mreisner@uol.com.br; Viegas, Celia Maria Pais; Grazziotin, Rachele Zanchet; Santos Batista, Delano Valdivino; Carneiro, Tulio Meneses; Mendonca de Araujo, Carlos Manoel; Marchiori, Edson

    2007-03-01

    Purpose: To compare the numerous external radiotherapy (RT) techniques for the treatment of retinoblastoma, as well as an intensity-modulated RT (IMRT) technique. The latter was elaborated to evaluate the potential dose reduction in the surrounding tissue, as well as the potential avoidance of subdosage in the ora serrata retinae. Methods and Materials: A 2-year-old patient with unilateral retinoblastoma underwent CT. With the aid of an ophthalmologist, the ocular structures were delimited, and 13 techniques described in published reports were reproduced on three-dimensional planning software and identified according to their authors. A technique with four noncoplanar fields using IMRT was also elaborated. These techniques were compared according to the dose to the ora serrata retinae, lens, orbit (volume that received a dose of {>=}20 Gy), vitreous, optic nerve, lacrimal gland (volume that received a dose of {>=}34 Gy), and cornea and according to their ease of reproducibility. Results: The techniques that attained the therapeutic dose to the ora serrata retinae were the IMRT technique and the techniques of Haye, Cassady, Cormack, and al-Beteri. The Cormack technique had the lowest volume that received a dose of {>=}20 Gy in the orbit, followed by the IMRT technique. The IMRT technique also achieved the lowest volume that received a dose of {>=}34 Gy (14%) in the lacrimal gland. The Abramson/McCormick/Blach, Cassady, Reese, and Schipper techniques were the easiest to reproduce and the Chin the most complex. Conclusion: Retinoblastoma treatment with IMRT has an advantage over the other techniques, because it allows for the greatest reduction of dose to the orbit and lacrimal gland, while maintaining the therapeutic dose to the ora serrata retinae and vitreous.

  13. Broadband Lidar Technique for Precision CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Heaps, William S.

    2008-01-01

    Presented are preliminary experimental results, sensitivity measurements and discuss our new CO2 lidar system under development. The system is employing an erbium-doped fiber amplifier (EDFA), superluminescent light emitting diode (SLED) as a source and our previously developed Fabry-Perot interferometer subsystem as a detector part. Global measurement of carbon dioxide column with the aim of discovering and quantifying unknown sources and sinks has been a high priority for the last decade. The goal of Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission is to significantly enhance the understanding of the role of CO2 in the global carbon cycle. The National Academy of Sciences recommended in its decadal survey that NASA put in orbit a CO2 lidar to satisfy this long standing need. Existing passive sensors suffer from two shortcomings. Their measurement precision can be compromised by the path length uncertainties arising from scattering within the atmosphere. Also passive sensors using sunlight cannot observe the column at night. Both of these difficulties can be ameliorated by lidar techniques. Lidar systems present their own set of problems however. Temperature changes in the atmosphere alter the cross section for individual CO2 absorption features while the different atmospheric pressures encountered passing through the atmosphere broaden the absorption lines. Currently proposed lidars require multiple lasers operating at multiple wavelengths simultaneously in order to untangle these effects. The current goal is to develop an ultra precise, inexpensive new lidar system for precise column measurements of CO2 changes in the lower atmosphere that uses a Fabry-Perot interferometer based system as the detector portion of the instrument and replaces the narrow band laser commonly used in lidars with the newly available high power SLED as the source. This approach reduces the number of individual lasers used in the system from three or more

  14. Application of x-ray techniques in precision farming

    NASA Astrophysics Data System (ADS)

    Arslan, Selcuk; Inanc, Feyzi; Gray, Joseph N.; Colvin, Thomas S.

    2000-05-01

    The precision farming is a relatively new concept basing farming upon quantitative determination of various parameters in the farming practices. One of these parameters is accurate measurement of grain flow rates on real time basis. Although there are various techniques already available for this purpose, x-rays provide a very competitive alternative to the current state of art. In this work, the use of low energy bremsstrahlung x-ray, up to 30 keV, densitometry is demonstrated for grain flow rate measurements. Mass flow rates for corn are related to measured x-ray intensity in gray scale units with a 0.99 correlation coefficient for flow rates ranging from 2 kg/s to 6 kg/s. Higher flow rate values can be measured by using slightly more energetic x-rays or a higher tube current. Measurements were done in real time at a 30 Hz sampling rate. Flow rate measurements are independent of grain moisture due to a negligible change in the x-ray attenuation coefficients at typical moisture content values from 15% to 25%. Grain flow profile changes do not affect measurement accuracy. X-rays easily capture variations in the corn stream. Due to the low energy of the x-ray photons, biological shielding can easily be accomplished with 2 mm thick lead foil or 5 mm of steel.

  15. The Effect of Adjuvant Postmastectomy Radiotherapy Bolus Technique on Local Recurrence

    SciTech Connect

    Tieu, Minh Thi; Graham, Peter; Browne, Lois; Chin, Yaw Sinn

    2011-11-01

    Purpose: Postmastectomy radiotherapy bolus is heterogenous, with little evidence to guide clinical practise. This study explores the effect of chest wall bolus technique on chest wall recurrence. Methods and Materials: This was a retrospective cohort study of 254 patients treated with adjuvant postmastectomy radiotherapy between 1993 and 2003. Patient and treatment characteristics including bolus details were extracted. Outcomes considered were treatment toxicities, treatment delivery, and local recurrence. Results: In all, 143 patients received radiotherapy with whole chest wall bolus, 88 patients with parascar bolus, and 23 with no bolus. Twenty patients did not complete radiotherapy because of acute skin toxicity: 17 in the whole chest wall bolus group, 2 in the parascar bolus group, and 1 in the group not treated with bolus. On multivariate analysis, whole chest wall bolus and chemotherapy were found to be significant predictors for early cessation of radiotherapy resulting from acute skin toxicity. There were 19 chest wall failures: 13 in the whole chest wall bolus group, 4 in the parascar bolus group, and 2 in the no-bolus group. On multivariate analysis, lymphovascular invasion and failure to complete radiotherapy because of acute skin toxicity were associated with chest wall recurrence. Conclusions: From our results, parascar bolus and no bolus performed no worse than did whole chest wall bolus with regard to chest wall recurrence. However, bolus may have an impact on early cessation of radiotherapy caused by skin toxicity, which then may influence chest wall recurrence.

  16. Current role of modern radiotherapy techniques in the management of breast cancer

    PubMed Central

    Ozyigit, Gokhan; Gultekin, Melis

    2014-01-01

    Breast cancer is the most common type of malignancy in females. Advances in systemic therapies and radiotherapy (RT) provided long survival rates in breast cancer patients. RT has a major role in the management of breast cancer. During the past 15 years several developments took place in the field of imaging and irradiation techniques, intensity modulated RT, hypofractionation and partial-breast irradiation. Currently, improvements in the RT technology allow us a subsequent decrease in the treatment-related complications such as fibrosis and long-term cardiac toxicity while improving the loco-regional control rates and cosmetic results. Thus, it is crucial that modern radiotherapy techniques should be carried out with maximum care and efficiency. Several randomized trials provided evidence for the feasibility of modern radiotherapy techniques in the management of breast cancer. However, the role of modern radiotherapy techniques in the management of breast cancer will continue to be defined by the mature results of randomized trials. Current review will provide an up-to-date evidence based data on the role of modern radiotherapy techniques in the management of breast cancer. PMID:25114857

  17. Cranio Spinal Irradiation of Medulloblastoma Using High Precision Techniques - A Dosimetric Comparison.

    PubMed

    Pichandi, A; Ganesh, K M; Jerrin, A; Balaji, K; Sridhar, P S; Surega, A

    2015-08-01

    Radiotherapy planning, delivery and junction dose verification remain exigent for Cranio Spinal Irradiation (CSI) in medulloblastoma patients. This study aims to evaluate high precision techniques such as Intensity Modulated Radiation Therapy (IMRT), Rapid Arc Therapy (RA) with and without flattening filter (FF) on the basis of dosimetric analysis. Five patients treated with jagged junction Intensity Modulated RadioTherapy (IMRT) using dynamic Multi Leaf Collimators (MLC) were randomly selected for this retrospective study. IMRT, Rapid Arc (RA) plans were simulated in the same CT data set with and without flattening filter. Total dose prescribed was 28.80 Gy in 16 fractions. An evaluation criterion of 98% of PTV receiving 100% of the prescription dose was followed in all plans. Twenty treatment plans with 260 Dose Volume Histograms (DVHs) was created. Dosimetric parameters such as Dmax, Dmin, Dmean, V95%, V107%, CI for PTV and Dmax, Dmean, V80%, V50%, V30%, V10% for Organs At Risk (OAR) were extracted from DVHs. Treatment delivery efficiency was also evaluated for total Beam On Time (BOT). FFF Rapid Arc therapy : 6F_RA) resulted in conformal doses throughout the cranio spinal axis. FF and FFF dynamic IMRT had minimal V107%, 1.23% and 2.88% compared to 49.15 and 66.36 of rapid arc therapy (with and without FF). 6F_IMRT resulted in lesser mean doses to eyes, liver, lungs and kidneys. Heart mean dose was less (3.08 Gy) with 6X_IMRT. Thyroid and esophagus doses could be reduced to about 41.2% and 10% respectively with 6F_RA. The BOT for the treatment techniques were 3.43 min (6X_IMRT), 1.59 min (6F_IMRT), 5min (6X_RA), 4.5 min (6F_RA). Removal of flattening filter in IMRT could improve dose coverage along the caniospinal axis and normal tissue sparing. A reduction of 46.3% BOT could increase treatment efficiency of 6F_IMRT compared to 6X_IMRT. CSI could be simpler since junction doses can be evaded in IMRT and RA techniques. PMID:26269611

  18. Radiation-Induced Cancers From Modern Radiotherapy Techniques: Intensity-Modulated Radiotherapy Versus Proton Therapy

    SciTech Connect

    Yoon, Myonggeun; Ahn, Sung Hwan; Kim, Jinsung; Shin, Dong Ho; Park, Sung Yong; Lee, Se Byeong; Shin, Kyung Hwan; Cho, Kwan Ho

    2010-08-01

    Purpose: To assess and compare secondary cancer risk resulting from intensity-modulated radiotherapy (IMRT) and proton therapy in patients with prostate and head-and-neck cancer. Methods and Materials: Intensity-modulated radiotherapy and proton therapy in the scattering mode were planned for 5 prostate caner patients and 5 head-and-neck cancer patients. The secondary doses during irradiation were measured using ion chamber and CR-39 detectors for IMRT and proton therapy, respectively. Organ-specific radiation-induced cancer risk was estimated by applying organ equivalent dose to dose distributions. Results: The average secondary doses of proton therapy for prostate cancer patients, measured 20-60cm from the isocenter, ranged from 0.4 mSv/Gy to 0.1 mSv/Gy. The average secondary doses of IMRT for prostate patients, however, ranged between 3 mSv/Gy and 1 mSv/Gy, approximately one order of magnitude higher than for proton therapy. Although the average secondary doses of IMRT were higher than those of proton therapy for head-and-neck cancers, these differences were not significant. Organ equivalent dose calculations showed that, for prostate cancer patients, the risk of secondary cancers in out-of-field organs, such as the stomach, lungs, and thyroid, was at least 5 times higher for IMRT than for proton therapy, whereas the difference was lower for head-and-neck cancer patients. Conclusions: Comparisons of organ-specific organ equivalent dose showed that the estimated secondary cancer risk using scattering mode in proton therapy is either significantly lower than the cases in IMRT treatment or, at least, does not exceed the risk induced by conventional IMRT treatment.

  19. Voluntary Breath-hold Technique for Reducing Heart Dose in Left Breast Radiotherapy

    PubMed Central

    Bartlett, Frederick R.; Colgan, Ruth M.; Donovan, Ellen M.; Carr, Karen; Landeg, Steven; Clements, Nicola; McNair, Helen A.; Locke, Imogen; Evans, Philip M.; Haviland, Joanne S.; Yarnold, John R.; Kirby, Anna M.

    2014-01-01

    Breath-holding techniques reduce the amount of radiation received by cardiac structures during tangential-field left breast radiotherapy. With these techniques, patients hold their breath while radiotherapy is delivered, pushing the heart down and away from the radiotherapy field. Despite clear dosimetric benefits, these techniques are not yet in widespread use. One reason for this is that commercially available solutions require specialist equipment, necessitating not only significant capital investment, but often also incurring ongoing costs such as a need for daily disposable mouthpieces. The voluntary breath-hold technique described here does not require any additional specialist equipment. All breath-holding techniques require a surrogate to monitor breath-hold consistency and whether breath-hold is maintained. Voluntary breath-hold uses the distance moved by the anterior and lateral reference marks (tattoos) away from the treatment room lasers in breath-hold to monitor consistency at CT-planning and treatment setup. Light fields are then used to monitor breath-hold consistency prior to and during radiotherapy delivery. PMID:25046661

  20. Improved target volume definition for precision radiotherapy planning of meningiomas by correlation of CT and dynamic, Gd-DTPA-enhanced FLASH MR imaging.

    PubMed

    Schad, L R; Blüml, S; Debus, J; Scharf, J; Lorenz, W J

    1994-10-01

    In this methodological paper the authors report a fast, T1-weighted gradient-echo sequence (FLASH) for dynamic, Gd-DTPA-enhanced magnetic resonance (MR) imaging of meningiomas and its application in precision radiotherapy planning. Indications for radiotherapy included unresected tumors, tumor remaining after surgery, and recurrences. The patient's head was fixed in a stereotactic localization system which is usable at the CT, MR and the linear accelerator installations. By phantom measurements different materials (steel, aluminum, titanium, plastic, wood, ceramics) used for the stereotactic system were tested for mechanical stability and geometric MR image distortion. All metallic stereotactic rings (closed rings made of massive metal) led to a more or less dramatic geometric distortion and signal cancellation in the MR images. The best properties--nearly no distortion and high mechanic stability--are provided by a ceramic ring. If necessary, the remaining geometric MR image distortion can be 'corrected' (reducing displacements to the size of a pixel) by calculations based on modeling the distortion as a fourth order two-dimensional polynomial. The target volume was defined in dynamic, T1-weighted FLASH MR images, which were measured before, during, and after the controlled intravenous infusion of 0.1 mmol/kg body weight Gd-DTPA. The stereotactic localization technique allows the precise transfer of the target volume information from MR onto CT data to provide a map of the radiation attenuation coefficient for dose calculation. In genera, the superior soft tissue contrast of MR showed an excellent tumor delineation, especially in regions, such as the base of the skull, where the target often was obscured in CT images.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7878213

  1. Key techniques of ultra-precision aerostatic system

    NASA Astrophysics Data System (ADS)

    Li, Dongsheng; Li, Jiafu; Cui, Ting; Hu, Jiacheng; Cheng, Yang; Wang, Meibao

    2013-10-01

    In the process of ultra-precision machining and measuring, nanoscale rotary and linear motion can be realized by aerostatic system. Aerostatic restrictors are one of core components in aerostatic system. An aerostatic restrictor with multi-micro channels was designed and developed, combined with the orifice and torus throttling methods. Besides, the mentioned restrictor has two individual parts assembled together by interference fit, which can alleviating the contradiction between its stiffness and stability. Its maximum bearing capacity was 708.4N when the supply gas pressure was 0.5MPa. Numerical simulation and experimental investigation indicates the pressure in gas film of this restrictor gradually reduces to atmospheric pressure from the center to the surrounding. The temperature decreases from the outlet to the edge and the maximum temperature difference is more than 5°, which verifies Joule-Thomson effect in the throttling process. In order to reduce the influence of gas source fluctuation on the parameters such as gas film thickness, pressure and temperature, high accuracy stable pressure source was developed applying two-stage series closed-loops feedback control, which can make the outlet pressure error below 1%. Because of the influence of ambient noise on ultra-precision aerostatic system, high precision vibration-isolation platform was developed applying air spring vibration-isolation technology, whose natural frequency can be as low as 1.22Hz.

  2. Laser frequency comb techniques for precise astronomical spectroscopy

    NASA Astrophysics Data System (ADS)

    Murphy, Michael T.; Locke, Clayton R.; Light, Philip S.; Luiten, Andre N.; Lawrence, Jon S.

    2012-05-01

    Precise astronomical spectroscopic analyses routinely assume that individual pixels in charge-coupled devices (CCDs) have uniform sensitivity to photons. Intra-pixel sensitivity (IPS) variations may already cause small systematic errors in, for example, studies of extra-solar planets via stellar radial velocities and cosmological variability in fundamental constants via quasar spectroscopy, but future experiments requiring velocity precisions approaching ˜1 cm s-1 will be more strongly affected. Laser frequency combs have been shown to provide highly precise wavelength calibration for astronomical spectrographs, but here we show that they can also be used to measure IPS variations in astronomical CCDs in situ. We successfully tested a laser frequency comb system on the Ultra-High-Resolution Facility spectrograph at the Anglo-Australian Telescope. By modelling the two-dimensional comb signal recorded in a single CCD exposure, we find that the average IPS deviates by <8 per cent if it is assumed to vary symmetrically about the pixel centre. We also demonstrate that a series of comb exposures with absolutely known offsets between them can yield tighter constraints on symmetric IPS variations from ˜100 pixels. We discuss measurement of asymmetric IPS variations and absolute wavelength calibration of astronomical spectrographs and CCDs using frequency combs.

  3. Precision compliance techniques for slow crack growth measurements

    NASA Technical Reports Server (NTRS)

    Noronha, P. J.

    1975-01-01

    A method is presented for using simple electronic components to obtain the high sensitivity needed to measure very slow crack growth rates. The technique presented can reduce the experimental time considerably and also yield a greater amount of data more accurately than optical techniques for measuring crack growth rates.

  4. A Precise Calibration Technique for Measuring High Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Schultz, Donald F.

    1999-01-01

    A technique was developed for direct measurement of gas temperatures in the range of 2050 K - 2700 K with improved accuracy and reproducibility. The technique utilized the low-emittance of certain fibrous Materials, and the uncertainty of the technique was limited by the uncertainty in the melting points of the materials, i.e., +/- 15 K. The materials were pure, thin, metal-oxide fibers whose diameters varied from 60 mm to 400 mm in the experiments. The sharp increase in the emittance of the fibers upon melting was utilized as indication of reaching a known gas temperature. The accuracy of the technique was confirmed by both calculated low emittance values of transparent fibers, of order 0.01, up to a few degrees below their melting point and by the fiber-diameter independence of the results. This melting-point temperature was approached by increments not larger than 4 K, which was accomplished by controlled increases of reactant flow rates in hydrogen-air and/or hydrogen- oxygen flames. As examples of the applications of the technique, the gas-temperature measurements were used (a) for assessing the uncertainty in infering gas temperatures from thermocouple measurements, and (b) for calibrating an IR camera to measure gas temperatures. The technique offers an excellent calibration reference for other gas-temperature measurement methods to improve their accuracy and reliably extending their temperature range of applicability.

  5. A Precise Calibration Technique for Measuring High Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Schultz, Donald F.

    2000-01-01

    A technique was developed for direct measurement of gas temperatures in the range of 2050 K 2700 K with improved accuracy and reproducibility. The technique utilized the low-emittance of certain fibrous materials, and the uncertainty of the technique was United by the uncertainty in the melting points of the materials, i.e., +/-15 K. The materials were pure, thin, metal-oxide fibers whose diameters varied from 60 microns to 400 microns in the experiments. The sharp increase in the emittance of the fibers upon melting was utilized as indication of reaching a known gas temperature. The accuracy of the technique was confirmed by both calculated low emittance values of transparent fibers, of order 0.01, up to a few degrees below their melting point and by the fiber-diameter independence of the results. This melting-point temperature was approached by increments not larger than 4 K, which was accomplished by controlled increases of reactant flow rates in hydrogen-air and/or hydrogen-oxygen flames. As examples of the applications of the technique, the gas-temperature measurements were used: (a) for assessing the uncertainty in inferring gas temperatures from thermocouple measurements, and (b) for calibrating an IR camera to measure gas temperatures. The technique offers an excellent calibration reference for other gas-temperature measurement methods to improve their accuracy and reliably extending their temperature range of applicability.

  6. Body radiation exposure in breast cancer radiotherapy: Impact of breast IMRT and virtual wedge compensation techniques

    SciTech Connect

    Woo, Tony; Pignol, Jean-Philippe . E-mail: Jean-Philippe.Pignol@sw.ca; Rakovitch, Eileen; Vu, Toni; Hicks, Deanna; O'Brien, Peter; Pritchard, Kathleen

    2006-05-01

    Purpose: Recent reports demonstrate a dramatically increased rate of secondary leukemia for breast cancer patients receiving adjuvant high-dose anthracycline and radiotherapy, and that radiation is an independent factor for the development of leukemia. This study aimed to evaluate the radiation body exposure during breast radiotherapy and to characterize the factors associated with an increased exposure. Patients and Methods: In a prospective cohort of 120 women, radiation measurements were taken from four sites on the body at the time of adjuvant breast radiotherapy. Multiple regression analysis was performed to analyze patient and treatment factors associated with the amount of scattered radiation. Results: For standard 50 Gy breast radiotherapy, the minimal dose received by abdominal organs is on average 0.45 Gy, ranging from 0.06 to 1.55 Gy. The use of physical wedges as a compensation technique was the most significant factor associated with increased scattered dose (p < 0.001), resulting in approximately three times more exposure compared with breast intensity-modulated radiation therapy (IMRT) and dynamic wedge. Conclusions: The amount of radiation that is scattered to a patient's body is consistent with exposure reported to be associated with excess of leukemia. In accordance with the As Low As Reasonably Achievable (ALARA) principle, we recommend using breast IMRT or virtual wedging for the radiotherapy of breast cancer receiving high-dose anthracycline chemotherapy.

  7. Analog-to-digital conversion techniques for precision photometry

    NASA Technical Reports Server (NTRS)

    Opal, Chet B.

    1988-01-01

    Three types of analog-to-digital converters are described: parallel, successive-approximation, and integrating. The functioning of comparators and sample-and-hold amplifiers is explained. Differential and integral linearity are defined, and good and bad examples are illustrated. The applicability and relative advantages of the three types of converters for precision astronomical photometric measurements are discussed. For most measurements, integral linearity is more important than differential linearity. Successive-approximation converters should be used with multielement solid state detectors because of their high speed, but dual slope integrating converters may be superior for use with single element solid state detectors where speed of digitization is not a factor. In all cases, the input signal should be tailored so that they occupy the upper part of the converter's dynamic range; this can be achieved by providing adjustable gain, or better by varying the integration time of the observation if possible.

  8. “Wire-Target” Technique for Precise Vascular Access

    PubMed Central

    Hamzeh, Rabih K.; Danon, Saar; Shah, Sanjay; Levi, Daniel S.; Moore, John W.

    2009-01-01

    Herein, we describe a technique that facilitates percutaneous vascular access when the traditional method of achieving access is unsuccessful. For multiple reasons, gaining access to small vessels in pediatric patients is sometimes difficult. In instances of atrial, ventricular, or great arterial communications, a wire can be positioned from a vein or artery across the communications into an artery or vein to which access needs to be gained. This wire then serves as a target for vascular access. All pediatric patients who underwent cardiac catheterization at Mattel Children's Hospital from July 2003 through June 2006, and at Rady Children's Hospital from July through December 2006, were considered for the wire-target technique when access could not be achieved in vessels of interest via traditional methods. Fifteen wire-target procedures were undertaken in 14 patients (ages, 4 d–11 yr). By use of a directional catheter, a Wholey or 0.014-inch coronary wire was positioned in a vessel to which access was desired. Anterior–posterior and lateral fluoroscopic views were used to target the wire and attain vascular access. The patients' diagnoses, ages, vessels to which access was gained via traditional methods and via the wire-target technique, and wire routes were retrospectively recorded, and outcomes were noted. In all instances, the technique was performed successfully and without complications. In selected pediatric patients in whom percutaneous vascular access is difficult, the wire-target technique may be used safely and effectively to establish arterial, venous, or transhepatic access. PMID:19693307

  9. Modified radiotherapy technique in the treatment of medulloblastoma

    SciTech Connect

    Dewit, L.; Van Dam, J.; Rijnders, A.; Van De Velde, G.; Ang, K.K.; Van Der Schueren, E.

    1984-02-01

    Craniospinal irradiation is a standard treatment technique in patients who receive surgery for medulloblastoma. In most centers megavoltage photon irradiation is used, resulting in significant irradiation exposure to critical organs. In order to overcome this difficulty, the authors recently modified the technique applied in their center, by using high energy electrons (20 MeV) for irradiation of the spinal cord. The reliability of this technique was checked by performing dosimetry in a specially constructed wax phantom. Attention was focused upon dose variations at the junction of fields. Furthermore, the influence of vertebrae on the absorbed dose distribution of high energy electrons is presented. This technique seems to be safe and reliable in selected patients (children and teenagers).

  10. Studying the precision of ray tracing techniques with Szekeres models

    NASA Astrophysics Data System (ADS)

    Koksbang, S. M.; Hannestad, S.

    2015-07-01

    The simplest standard ray tracing scheme employing the Born and Limber approximations and neglecting lens-lens coupling is used for computing the convergence along individual rays in mock N-body data based on Szekeres swiss cheese and onion models. The results are compared with the exact convergence computed using the exact Szekeres metric combined with the Sachs formalism. A comparison is also made with an extension of the simple ray tracing scheme which includes the Doppler convergence. The exact convergence is reproduced very precisely as the sum of the gravitational and Doppler convergences along rays in Lemaitre-Tolman-Bondi swiss cheese and single void models. This is not the case when the swiss cheese models are based on nonsymmetric Szekeres models. For such models, there is a significant deviation between the exact and ray traced paths and hence also the corresponding convergences. There is also a clear deviation between the exact and ray tracing results obtained when studying both nonsymmetric and spherically symmetric Szekeres onion models.

  11. Volumetric-Modulated Arc Therapy for Stereotactic Body Radiotherapy of Lung Tumors: A Comparison With Intensity-Modulated Radiotherapy Techniques

    SciTech Connect

    Holt, Andrea; Vliet-Vroegindeweij, Corine van; Mans, Anton; Belderbos, Jose S.; Damen, Eugene M.F.

    2011-12-01

    Purpose: To demonstrate the potential of volumetric-modulated arc therapy (VMAT) compared with intensity-modulated radiotherapy (IMRT) techniques with a limited number of segments for stereotactic body radiotherapy (SBRT) for early-stage lung cancer. Methods and Materials: For a random selection of 27 patients eligible for SBRT, coplanar and noncoplanar IMRT and coplanar VMAT (using SmartArc) treatment plans were generated in Pinnacle{sup 3} and compared. In addition, film measurements were performed using an anthropomorphic phantom to evaluate the skin dose for the different treatment techniques. Results: Using VMAT, the delivery times could be reduced to an average of 6.6 min compared with 23.7 min with noncoplanar IMRT. The mean dose to the healthy lung was 4.1 Gy for VMAT and noncoplanar IMRT and 4.2 Gy for coplanar IMRT. The volume of healthy lung receiving >5 Gy and >20 Gy was 18.0% and 5.4% for VMAT, 18.5% and 5.0% for noncoplanar IMRT, and 19.4% and 5.7% for coplanar IMRT, respectively. The dose conformity at 100% and 50% of the prescribed dose of 54 Gy was 1.13 and 5.17 for VMAT, 1.11 and 4.80 for noncoplanar IMRT and 1.12 and 5.31 for coplanar IMRT, respectively. The measured skin doses were comparable for VMAT and noncoplanar IMRT and slightly greater for coplanar IMRT. Conclusions: Coplanar VMAT for SBRT for early-stage lung cancer achieved plan quality and skin dose levels comparable to those using noncoplanar IMRT and slightly better than those with coplanar IMRT. In addition, the delivery time could be reduced by {<=}70% with VMAT.

  12. A reduced-dynamic technique for precise orbit determination

    NASA Technical Reports Server (NTRS)

    Wu, S. C.; Yunck, T. P.; Thornton, C. L.

    1990-01-01

    Observations of the Global Positioning System (GPS) will enable a reduced-dynamic technique for achieving subdecimeter orbit determination of earth-orbiting satellites. With this technique, information on the transition between satellite states at different observing times is furnished by both a formal dynamic model and observed satellite positional change (which is inferred kinematically from continuous GPS carrier-phase data). The relative weighting of dynamic and kinematic information can be freely varied. Covariance studies show that in situations where observing geometry is poor and the dynamic model is good, the model dominates determination of the state transition; where the dynamic model is poor and the geometry strong, carrier phase governs the determination of the transition. When neither kinematic nor dynamic information is clearly superior, the reduced-dynamic combination of the two can substantially improve the orbit-determination solution. Guidelines are given here for selecting a near-optimal weighting for the reduced-dynamic solution, and sensitivity of solution accuracy to this weighting is examined.

  13. Dosimetric Comparison of Intensity-Modulated Stereotactic Radiotherapy With Other Stereotactic Techniques for Locally Recurrent Nasopharyngeal Carcinoma

    SciTech Connect

    Kung, Shiris Wai Sum; Wu, Vincent Wing Cheung; Kam, Michael Koon Ming; Leung, Sing Fai; Yu, Brian Kwok Hung; Ngai, Dennis Yuen Kan; Wong, Simon Chun Fai; Chan, Anthony Tak Cheung

    2011-01-01

    Purpose: Locally recurrent nasopharyngeal carcinoma (NPC) patients can be salvaged by reirradiation with a substantial degree of radiation-related complications. Stereotactic radiotherapy (SRT) is widely used in this regard because of its rapid dose falloff and high geometric precision. The aim of this study was to examine whether the newly developed intensity-modulated stereotactic radiotherapy (IMSRT) has any dosimetric advantages over three other stereotactic techniques, including circular arc (CARC), static conformal beam (SmMLC), and dynamic conformal arc (mARC), in treating locally recurrent NPC. Methods and Materials: Computed tomography images of 32 patients with locally recurrent NPC, previously treated with SRT, were retrieved from the stereotactic planning system for contouring and computing treatment plans. Treatment planning of each patient was performed for the four treatment techniques: CARC, SmMLC, mARC, and IMSRT. The conformity index (CI) and homogeneity index (HI) of the planning target volume (PTV) and doses to the organs at risk (OARs) and normal tissue were compared. Results: All four techniques delivered adequate doses to the PTV. IMSRT, SmMLC, and mARC delivered reasonably conformal and homogenous dose to the PTV (CI <1.47, HI <0.53), but not for CARC (p < 0.05). IMSRT presented with the smallest CI (1.37) and HI (0.40). Among the four techniques, IMSRT spared the greatest number of OARs, namely brainstem, temporal lobes, optic chiasm, and optic nerve, and had the smallest normal tissue volume in the low-dose region. Conclusion: Based on the dosimetric comparison, IMSRT was optimal for locally recurrent NPC by delivering a conformal and homogenous dose to the PTV while sparing OARs.

  14. Prediction of Potato Crop Yield Using Precision Agriculture Techniques.

    PubMed

    Al-Gaadi, Khalid A; Hassaballa, Abdalhaleem A; Tola, ElKamil; Kayad, Ahmed G; Madugundu, Rangaswamy; Alblewi, Bander; Assiri, Fahad

    2016-01-01

    Crop growth and yield monitoring over agricultural fields is an essential procedure for food security and agricultural economic return prediction. The advances in remote sensing have enhanced the process of monitoring the development of agricultural crops and estimating their yields. Therefore, remote sensing and GIS techniques were employed, in this study, to predict potato tuber crop yield on three 30 ha center pivot irrigated fields in an agricultural scheme located in the Eastern Region of Saudi Arabia. Landsat-8 and Sentinel-2 satellite images were acquired during the potato growth stages and two vegetation indices (the normalized difference vegetation index (NDVI) and the soil adjusted vegetation index (SAVI)) were generated from the images. Vegetation index maps were developed and classified into zones based on vegetation health statements, where the stratified random sampling points were accordingly initiated. Potato yield samples were collected 2-3 days prior to the harvest time and were correlated to the adjacent NDVI and SAVI, where yield prediction algorithms were developed and used to generate prediction yield maps. Results of the study revealed that the difference between predicted yield values and actual ones (prediction error) ranged between 7.9 and 13.5% for Landsat-8 images and between 3.8 and 10.2% for Sentinel-2 images. The relationship between actual and predicted yield values produced R2 values ranging between 0.39 and 0.65 for Landsat-8 images and between 0.47 and 0.65 for Sentinel-2 images. Results of this study revealed a considerable variation in field productivity across the three fields, where high-yield areas produced an average yield of above 40 t ha-1; while, the low-yield areas produced, on the average, less than 21 t ha-1. Identifying such great variation in field productivity will assist farmers and decision makers in managing their practices. PMID:27611577

  15. A Dosimetric Analysis of IMRT and Multistatic Fields Techniques for Left Breast Radiotherapy

    SciTech Connect

    Moon, Seong Kwon; Kim, Yeon Sil; Kim, Soo Young; Lee, Mi Jo; Keum, Hyun Sup; Kim, Seung Jin; Youn, Seon Min

    2011-10-01

    The purpose of this study was to analyze the dosimetric difference between intensity-modulated radiation therapy (IMRT) using 3 or 5 beams and multistatic field technique (MSF) in radiotherapy of the left breast. We made comparative analysis of two kinds of radiotherapy that can achieve improved dose homogeneity. First is a MSF that uses both major and small irradiation fields at the same time. The other is IMRT using 3 or 5 beams with an inverse planning system using multiple static multileaf collimators. We made treatment plans for 16 early left breast cancer patients who were randomly selected and had undergone breast conserving surgery and radiotherapy, and analyzed them in the dosimetric aspect. For the mean values of V{sub 95} and dose homogeneity index, no statistically significant difference was observed among the three therapies. Extreme hot spots receiving >110% of prescribed dose were not found in any of the three methods. Using Tukey's test, IMRT showed a significantly larger increase in exposure dose to the ipsilateral lung and the heart than MSF in the low-dose area, but in the high-dose area, MSF showed a slight increase. To improve dose homogeneity, the application of MSF, which can be easily planned and applied more widely, is considered optimal as an alternative to IMRT for radiotherapy of early left breast cancer.

  16. Radiation dose verification using real tissue phantom in modern radiotherapy techniques

    PubMed Central

    Gurjar, Om Prakash; Mishra, S. P.; Bhandari, Virendra; Pathak, Pankaj; Patel, Prapti; Shrivastav, Garima

    2014-01-01

    In vitro dosimetric verification prior to patient treatment has a key role in accurate and precision radiotherapy treatment delivery. Most of commercially available dosimetric phantoms have almost homogeneous density throughout their volume, while real interior of patient body has variable and varying densities inside. In this study an attempt has been made to verify the physical dosimetry in actual human body scenario by using goat head as “head phantom” and goat meat as “tissue phantom”. The mean percentage variation between planned and measured doses was found to be 2.48 (standard deviation (SD): 0.74), 2.36 (SD: 0.77), 3.62 (SD: 1.05), and 3.31 (SD: 0.78) for three-dimensional conformal radiotherapy (3DCRT) (head phantom), intensity modulated radiotherapy (IMRT; head phantom), 3DCRT (tissue phantom), and IMRT (tissue phantom), respectively. Although percentage variations in case of head phantom were within tolerance limit (< ± 3%), but still it is higher than the results obtained by using commercially available phantoms. And the percentage variations in most of cases of tissue phantom were out of tolerance limit. On the basis of these preliminary results it is logical and rational to develop radiation dosimetry methods based on real human body and also to develop an artificial phantom which should truly represent the interior of human body. PMID:24600172

  17. On the use of an analytic source model for dose calculations in precision image-guided small animal radiotherapy

    NASA Astrophysics Data System (ADS)

    Granton, Patrick V.; Verhaegen, Frank

    2013-05-01

    Precision image-guided small animal radiotherapy is rapidly advancing through the use of dedicated micro-irradiation devices. However, precise modeling of these devices in model-based dose-calculation algorithms such as Monte Carlo (MC) simulations continue to present challenges due to a combination of very small beams, low mechanical tolerances on beam collimation, positioning and long calculation times. The specific intent of this investigation is to introduce and demonstrate the viability of a fast analytical source model (AM) for use in either investigating improvements in collimator design or for use in faster dose calculations. MC models using BEAMnrc were developed for circular and square fields sizes from 1 to 25 mm in diameter (or side) that incorporated the intensity distribution of the focal spot modeled after an experimental pinhole image. These MC models were used to generate phase space files (PSFMC) at the exit of the collimators. An AM was developed that included the intensity distribution of the focal spot, a pre-calculated x-ray spectrum, and the collimator-specific entrance and exit apertures. The AM was used to generate photon fluence intensity distributions (ΦAM) and PSFAM containing photons radiating at angles according to the focal spot intensity distribution. MC dose calculations using DOSXYZnrc in a water and mouse phantom differing only by source used (PSFMC versus PSFAM) were found to agree within 7% and 4% for the smallest 1 and 2 mm collimator, respectively, and within 1% for all other field sizes based on depth dose profiles. PSF generation times were approximately 1200 times faster for the smallest beam and 19 times faster for the largest beam. The influence of the focal spot intensity distribution on output and on beam shape was quantified and found to play a significant role in calculated dose distributions. Beam profile differences due to collimator alignment were found in both small and large collimators sensitive to shifts of 1

  18. An Integer Precise Point Positioning technique for sea surface observations using a GPS buoy

    NASA Astrophysics Data System (ADS)

    Fund, F.; Perosanz, F.; Testut, L.; Loyer, S.

    2013-04-01

    GPS data dedicated to sea surface observation are usually processed using differential techniques. Unfortunately, the precision of resulting kinematic positions is baseline-length dependent. So, high precision sea surface observations using differential GPS techniques are limited to coasts, lakes, and rivers. Recent improvements in GPS satellite products (orbits, clocks, and phase biases) make phase ambiguity fixing at the zero difference level achievable and opens up the observation of the sea surface without geographical constraints. This paper recalls the concept of the Integer Precise Point Positioning technique and discusses the precision of GPS buoy positioning. A sequential version of the GINS software has been implemented to achieve single epoch GPS positioning. We used 1 Hz data from a two week GPS campaign conducted in the Kerguelen Islands. A GPS buoy has been moored close to a radar gauge and 90 m away from a permanent GPS station. This infrastructure offers the opportunity to compare both kinematic Integer Precise Point Positioning and classical differential GPS positioning techniques to in situ radar gauge data. We found that Precise Point Positioning results are not significantly biased with respect to radar gauge data and that horizontal time series are consistent with differential processing at the sub-centimetre precision level. Nevertheless, standard deviations of height time series with respect to radar gauge data are typically [4-5] cm. The dominant driver for noise at this level is attributed to errors in tropospheric estimates which propagate into position solutions.

  19. [Current situation and future prospects of radiotherapy for malignant gliomas].

    PubMed

    Terahara, Atsuro

    2013-10-01

    Prognosis of malignant gliomas remains poor, although adjuvant radiotherapy increases survival time. To improve treatment outcomes, high-precision radiotherapy techniques such as three-dimensional conformal radiotherapy, stereotactic irradiation, intensity modulated radiotherapy, and charged particle radiotherapy have been developed for dose distribution optimization and dose escalation. Improvements in clinical outcomes with these new treatment strategies have been reported; however, the efficacy of these treatment strategies has not yet been verified in randomized trials. Further development of radiation delivery techniques, including boron neutron capture therapy, and ways of achieving more adequate target volume delineation using modern multimodality imaging technology are currently being intensively investigated to further improve patient outcomes. PMID:24105051

  20. Expansion and dissemination of a standardized accuracy and precision assessment technique

    NASA Astrophysics Data System (ADS)

    Kwartowitz, David M.; Riti, Rachel E.; Holmes, David R., III

    2011-03-01

    The advent and development of new imaging techniques and image-guidance have had a major impact on surgical practice. These techniques attempt to allow the clinician to not only visualize what is currently visible, but also what is beneath the surface, or function. These systems are often based on tracking systems coupled with registration and visualization technologies. The accuracy and precision of the tracking systems, thus is critical in the overall accuracy and precision of the image-guidance system. In this work the accuracy and precision of an Aurora tracking system is assessed, using the technique specified in " novel technique for analysis of accuracy of magnetic tracking systems used in image guided surgery." This analysis yielded a demonstration that accuracy is dependent on distance from the tracker's field generator, and had an RMS value of 1.48 mm. The error has the similar characteristics and values as the previous work, thus validating this method for tracker analysis.

  1. Involved-Node Radiotherapy and Modern Radiation Treatment Techniques in Patients With Hodgkin Lymphoma

    SciTech Connect

    Paumier, Amaury; Ghalibafian, Mithra; Beaudre, Anne; Ferreira, Ivaldo; Pichenot, Charlotte; Messai, Taha; Lessard, Nathalie Athalie; Lefkopoulos, Dimitri; Girinsky, Theodore

    2011-05-01

    Purpose: To assess the clinical outcome of the involved-node radiotherapy (INRT) concept using modern radiation treatments (intensity-modulated radiotherapy [IMRT]or deep-inspiration breath-hold radiotherapy [DIBH) in patients with localized supradiaphragmatic Hodgkin lymphoma. Methods and Materials: All but 2 patients had early-stage Hodgkin lymphoma, and they were treated with chemotherapy prior to irradiation. Radiation treatments were delivered using the INRT concept according to European Organization for Research and Treatment of Cancer guidelines. IMRT was performed with the patient free-breathing. For the adapted breath-hold technique, a spirometer dedicated to DIBH radiotherapy was used. Three-dimensional conformal radiotherapy was performed with those patients. Results: Fifty patients with Hodgkin lymphoma (48 patients with primary Hodgkin lymphoma, 1 patient with recurrent disease, and 1 patient with refractory disease) entered the study from January 2003 to August 2008. Thirty-two patients were treated with IMRT, and 18 patients were treated with the DIBH technique. The median age was 28 years (range, 17-62 years). Thirty-four (68%) patients had stage I - (I-IIA) IIA disease, and 16 (32%) patients had stage I - (I-IIB) IIB disease. All but 3 patients received three to six cycles of adriamycin, bleomycin, vinblastine, and dacarbazine (ABVD). The median radiation doses to patients treated with IMRT and DIBH were, respectively, 40 Gy (range, 21.6-40 Gy) and 30.6 Gy (range, 19.8-40 Gy). Protection of various organs at risk was satisfactory. Median follow-up was 53.4 months (range, 19.1-93 months). The 5-year progression-free and overall survival rates for the whole population were 92% (95% confidence interval [CI], 80%-97%) and 94% (95% CI, 75%-98%), respectively. Recurrences occurred in 4 patients: 2 patients had in-field relapses, and 2 patients had visceral recurrences. Grade 3 acute lung toxicity (transient pneumonitis) occurred in 1 case. Conclusions

  2. Evaluation of the field-in-field technique with lung blocks for breast tangential radiotherapy

    PubMed Central

    Tanaka, Hidekazu; Hayashi, Shinya; Kajiura, Yuichi; Kitahara, Masashi; Matsuyama, Katsuya; Kanematsu, Masayuki; Hoshi, Hiroaki

    2015-01-01

    ABSTRACT Several studies have reported the advantages of the field-in-field (FIF) technique in breast radiotherapy, including dose reduction in the lungs by using lung field blocks. We evaluated the FIF technique with lung blocks for breast tangential radiotherapy. Sixteen patients underwent free breathing (FB) computed tomography (CT), followed by two CT procedures performed during breath hold after light inhalation (IN) and light exhalation (EX). Three radiotherapy plans were created using the FIF technique based on the FB-CT images: one without lung blocks (LB0) and two with lung blocks whose monitor units (MUs) were 5 (LB5) and 10 (LB10), respectively. These plans were copied to the IN-CT and EX-CT images. V20Gy, V30Gy, and V40Gy of the ipsilateral lung and V100%, V95%, and the mean dose (Dmean) to the planning target volume (PTV) were analyzed. The extent of changes in these parameters on the IN-plan and EX-plan compared with the FB-plan was evaluated. V20Gy, V30Gy, and V40Gy were significantly smaller for FB-LB5 and FB-LB10 than for FB-LB0; similar results were obtained for the IN-plan and EX-plan. V100%, V95%, and Dmean were also significant smaller for FB-LB5 and FB-LB10 than for FB-LB0. The extent of changes in V20Gy, V30Gy, and V40Gy on the IN-plan and EX-plan compared with the FB-plan was not statistically significant. Lung blocks were useful for dose reduction in the lung and a simultaneous PTV decrease. This technique should not be applied in the general population. PMID:26412879

  3. Evaluation of the field-in-field technique with lung blocks for breast tangential radiotherapy.

    PubMed

    Tanaka, Hidekazu; Hayashi, Shinya; Kajiura, Yuichi; Kitahara, Masashi; Matsuyama, Katsuya; Kanematsu, Masayuki; Hoshi, Hiroaki

    2015-08-01

    Several studies have reported the advantages of the field-in-field (FIF) technique in breast radiotherapy, including dose reduction in the lungs by using lung field blocks. We evaluated the FIF technique with lung blocks for breast tangential radiotherapy. Sixteen patients underwent free breathing (FB) computed tomography (CT), followed by two CT procedures performed during breath hold after light inhalation (IN) and light exhalation (EX). Three radiotherapy plans were created using the FIF technique based on the FB-CT images: one without lung blocks (LB0) and two with lung blocks whose monitor units (MUs) were 5 (LB5) and 10 (LB10), respectively. These plans were copied to the IN-CT and EX-CT images. V20Gy, V30Gy, and V40Gy of the ipsilateral lung and V100%, V95%, and the mean dose (Dmean) to the planning target volume (PTV) were analyzed. The extent of changes in these parameters on the IN-plan and EX-plan compared with the FB-plan was evaluated. V20Gy, V30Gy, and V40Gy were significantly smaller for FB-LB5 and FB-LB10 than for FB-LB0; similar results were obtained for the IN-plan and EX-plan. V100%, V95%, and Dmean were also significant smaller for FB-LB5 and FB-LB10 than for FB-LB0. The extent of changes in V20Gy, V30Gy, and V40Gy on the IN-plan and EX-plan compared with the FB-plan was not statistically significant. Lung blocks were useful for dose reduction in the lung and a simultaneous PTV decrease. This technique should not be applied in the general population. PMID:26412879

  4. Three-Dimensional Conformal Simultaneously Integrated Boost Technique for Breast-Conserving Radiotherapy

    SciTech Connect

    Laan, Hans Paul van der

    2007-07-15

    Purpose: To compare the target coverage and normal tissue dose with the simultaneously integrated boost (SIB) and the sequential boost technique in breast cancer, and to evaluate the incidence of acute skin toxicity in patients treated with the SIB technique. Methods and Materials: Thirty patients with early-stage left-sided breast cancer underwent breast-conserving radiotherapy using the SIB technique. The breast and boost planning target volumes (PTVs) were treated simultaneously (i.e., for each fraction, the breast and boost PTVs received 1.81 Gy and 2.3 Gy, respectively). Three-dimensional conformal beams with wedges were shaped and weighted using forward planning. Dose-volume histograms of the PTVs and organs at risk with the SIB technique, 28 x (1.81 + 0.49 Gy), were compared with those for the sequential boost technique, 25 x 2 Gy + 8 x 2 Gy. Acute skin toxicity was evaluated for 90 patients treated with the SIB technique according to Common Terminology Criteria for Adverse Events, version 3.0. Results: PTV coverage was adequate with both techniques. With SIB, more efficiently shaped boost beams resulted in smaller irradiated volumes. The mean volume receiving {>=}107% of the breast dose was reduced by 20%, the mean volume outside the boost PTV receiving {>=}95% of the boost dose was reduced by 54%, and the mean heart and lung dose were reduced by 10%. Of the evaluated patients, 32.2% had Grade 2 or worse toxicity. Conclusion: The SIB technique is proposed for standard use in breast-conserving radiotherapy because of its dose-limiting capabilities, easy implementation, reduced number of treatment fractions, and relatively low incidence of acute skin toxicity.

  5. Measurement of radiation dose with BeO dosimeters using optically stimulated luminescence technique in radiotherapy applications.

    PubMed

    Şahin, Serdar; Güneş Tanır, A; Meriç, Niyazi; Aydınkarahaliloğlu, Ercan

    2015-09-01

    The radiation dose delivered to the target by using different radiotherapy applications has been measured with the help of beryllium oxide (BeO) dosimeters to be placed inside the rando phantom. Three-Dimensional Conformal Radiotherapy (3DCRT), Intensity-Modulated Radiotherapy (IMRT) and Intensity-Modulated Arc Therapy (IMAT) have been used as radiotherapy application. Individual treatment plans have been made for the three radiotherapy applications of rando phantom. The section 4 on the phantom was selected as target and 200 cGy doses were delivered. After the dosimeters placed on section 4 (target) and the sections 2 and 6 (non-target) were irradiated, the result was read through the OSL technique on the Risø TL/OSL system. This procedure was repeated three times for each radiotherapy application. The doses delivered to the target and the non-target sections as a result of the 3DCRT, IMRT and IMAT plans were analyzed. The doses received by the target were measured as 204.71 cGy, 204.76 cGy and 205.65 cGy, respectively. The dose values obtained from treatment planning system (TPS) were compared to the dose values obtained using the OSL technique. It has been concluded that, the radiation dose can be measured with the OSL technique by using BeO dosimeters in medical practices. PMID:26046521

  6. On-Line Use of Three-Dimensional Marker Trajectory Estimation From Cone-Beam Computed Tomography Projections for Precise Setup in Radiotherapy for Targets With Respiratory Motion

    SciTech Connect

    Worm, Esben S.; Hoyer, Morten; Fledelius, Walther; Nielsen, Jens E.; Larsen, Lars P.; Poulsen, Per R.

    2012-05-01

    Purpose: To develop and evaluate accurate and objective on-line patient setup based on a novel semiautomatic technique in which three-dimensional marker trajectories were estimated from two-dimensional cone-beam computed tomography (CBCT) projections. Methods and Materials: Seven treatment courses of stereotactic body radiotherapy for liver tumors were delivered in 21 fractions in total to 6 patients by a linear accelerator. Each patient had two to three gold markers implanted close to the tumors. Before treatment, a CBCT scan with approximately 675 two-dimensional projections was acquired during a full gantry rotation. The marker positions were segmented in each projection. From this, the three-dimensional marker trajectories were estimated using a probability based method. The required couch shifts for patient setup were calculated from the mean marker positions along the trajectories. A motion phantom moving with known tumor trajectories was used to examine the accuracy of the method. Trajectory-based setup was retrospectively used off-line for the first five treatment courses (15 fractions) and on-line for the last two treatment courses (6 fractions). Automatic marker segmentation was compared with manual segmentation. The trajectory-based setup was compared with setup based on conventional CBCT guidance on the markers (first 15 fractions). Results: Phantom measurements showed that trajectory-based estimation of the mean marker position was accurate within 0.3 mm. The on-line trajectory-based patient setup was performed within approximately 5 minutes. The automatic marker segmentation agreed with manual segmentation within 0.36 {+-} 0.50 pixels (mean {+-} SD; pixel size, 0.26 mm in isocenter). The accuracy of conventional volumetric CBCT guidance was compromised by motion smearing ({<=}21 mm) that induced an absolute three-dimensional setup error of 1.6 {+-} 0.9 mm (maximum, 3.2) relative to trajectory-based setup. Conclusions: The first on-line clinical use of

  7. Optimization of stereotactic radiotherapy treatment delivery technique for base-of-skull meningiomas.

    PubMed

    Clark, Brenda G; Candish, Charles; Vollans, Emily; Gete, Ermias; Lee, Richard; Martin, Monty; Ma, Roy; McKenzie, Michael

    2008-01-01

    This study compares static conformal field (CF), intensity modulated radiotherapy (IMRT), and dynamic arcs (DA) for the stereotactic radiotherapy of base-of-skull meningiomas. Twenty-one cases of base-of-skull meningioma (median planning target volume [PTV] = 21.3 cm3) previously treated with stereotactic radiotherapy were replanned with each technique. The plans were compared for Radiation Therapy Oncology Group conformity index (CI) and homogeneity index (HI), and doses to normal structures at 6 dose values from 50.4 Gy to 5.6 Gy. The mean CI was 1.75 (CF), 1.75 (DA), and 1.66 (IMRT) (p < 0.05 when comparing IMRT to either CF or DA plans). The CI (IMRT) was inversely proportional to the size of the PTV (Spearman's rho = -0.53, p = 0.01) and at PTV sizes above 25 cm3, the CI (IMRT) was always superior to CI (DA) and CI (CF). At PTV sizes below 25 cm3, there was no significant difference in CI between each technique. There was no significant difference in HI between plans. The total volume of normal tissue receiving 50.4, 44.8, and 5.6 Gy was significantly lower when comparing IMRT to CF and DA plans (p < 0.05). There was significantly improved dose sparing for the brain stem and ipsilateral temporal lobe with IMRT but no significant difference for the optic chiasm or pituitary gland. These results demonstrate that stereotactic IMRT should be considered to treat base-of-skull meningiomas with a PTV larger than 25 cm3, due to improved conformity and normal tissue sparing, in particular for the brain stem and ipsilateral temporal lobe. PMID:18674690

  8. Optimization of Stereotactic Radiotherapy Treatment Delivery Technique for Base-Of-Skull Meningiomas

    SciTech Connect

    Clark, Brenda G. Candish, Charles; Vollans, Emily; Gete, Ermias; Lee, Richard; Martin, Monty; Ma, Roy; McKenzie, Michael

    2008-10-01

    This study compares static conformal field (CF), intensity modulated radiotherapy (IMRT), and dynamic arcs (DA) for the stereotactic radiotherapy of base-of-skull meningiomas. Twenty-one cases of base-of-skull meningioma (median planning target volume [PTV] = 21.3 cm{sup 3}) previously treated with stereotactic radiotherapy were replanned with each technique. The plans were compared for Radiation Therapy Oncology Group conformity index (CI) and homogeneity index (HI), and doses to normal structures at 6 dose values from 50.4 Gy to 5.6 Gy. The mean CI was 1.75 (CF), 1.75 (DA), and 1.66 (IMRT) (p < 0.05 when comparing IMRT to either CF or DA plans). The CI (IMRT) was inversely proportional to the size of the PTV (Spearman's rho = -0.53, p = 0.01) and at PTV sizes above 25 cm{sup 3}, the CI (IMRT) was always superior to CI (DA) and CI (CF). At PTV sizes below 25 cm{sup 3}, there was no significant difference in CI between each technique. There was no significant difference in HI between plans. The total volume of normal tissue receiving 50.4, 44.8, and 5.6 Gy was significantly lower when comparing IMRT to CF and DA plans (p < 0.05). There was significantly improved dose sparing for the brain stem and ipsilateral temporal lobe with IMRT but no significant difference for the optic chiasm or pituitary gland. These results demonstrate that stereotactic IMRT should be considered to treat base-of-skull meningiomas with a PTV larger than 25 cm{sup 3}, due to improved conformity and normal tissue sparing, in particular for the brain stem and ipsilateral temporal lobe.

  9. Markerless gating for lung cancer radiotherapy based on machine learning techniques

    NASA Astrophysics Data System (ADS)

    Lin, Tong; Li, Ruijiang; Tang, Xiaoli; Dy, Jennifer G.; Jiang, Steve B.

    2009-03-01

    In lung cancer radiotherapy, radiation to a mobile target can be delivered by respiratory gating, for which we need to know whether the target is inside or outside a predefined gating window at any time point during the treatment. This can be achieved by tracking one or more fiducial markers implanted inside or near the target, either fluoroscopically or electromagnetically. However, the clinical implementation of marker tracking is limited for lung cancer radiotherapy mainly due to the risk of pneumothorax. Therefore, gating without implanted fiducial markers is a promising clinical direction. We have developed several template-matching methods for fluoroscopic marker-less gating. Recently, we have modeled the gating problem as a binary pattern classification problem, in which principal component analysis (PCA) and support vector machine (SVM) are combined to perform the classification task. Following the same framework, we investigated different combinations of dimensionality reduction techniques (PCA and four nonlinear manifold learning methods) and two machine learning classification methods (artificial neural networks—ANN and SVM). Performance was evaluated on ten fluoroscopic image sequences of nine lung cancer patients. We found that among all combinations of dimensionality reduction techniques and classification methods, PCA combined with either ANN or SVM achieved a better performance than the other nonlinear manifold learning methods. ANN when combined with PCA achieves a better performance than SVM in terms of classification accuracy and recall rate, although the target coverage is similar for the two classification methods. Furthermore, the running time for both ANN and SVM with PCA is within tolerance for real-time applications. Overall, ANN combined with PCA is a better candidate than other combinations we investigated in this work for real-time gated radiotherapy.

  10. Polarisation control through an optical feedback technique and its application in precise measurements

    PubMed Central

    Chen, Wenxue; Zhang, Shulian; Long, Xingwu

    2013-01-01

    We present an anisotropic optical feedback technique for controlling light polarisation. The technique is based on the principle that the effective gain of a light mode is modulated by the magnitude of the anisotropic feedback. A new physical model that integrates Lamb's semi-classical theory and a model of the equivalent cavity of a Fabry-Perot interferometer is developed to reveal the physical nature of this technique. We use this technique to measure the phase retardation, optical axis, angle, thickness and refractive index with a high precision of λ/1380, 0.01°, 0.002°, 59 nm and 0.0006, respectively. PMID:23771164

  11. Dosimetric Evaluation of a Simple Planning Technique for Improving Intensity-Modulated Radiotherapy for Nasopharyngeal Cancer

    PubMed Central

    Xie, Wen-Jia; Xie, Liang-Xi

    2015-01-01

    Purpose To evaluate the dosimetric outcomes of a simple planning technique for improving intensity-modulated radiotherapy (IMRT) for nasopharyngeal cancer (NPC). Methods For 39 NPC cases, generally acceptable original plans were generated and were improved by the two planning techniques, respectively: (1) a basal-dose-compensation (BDC) technique, in which the treatment plans were re-optimized based on the original plans; (2) a local-dose-control (LDC) technique, in which the original plans were re-optimized with constraints for hot and cold spots. The BDC, original, and LDC plans were then compared regarding homogeneity index (HI) and conformity index (CI) of planning target volumes (PTVs), organ-at-risk (OAR) sparing and monitor units (MUs) per fraction. The whole planning times were also compared between the BDC and LDC plans. Results The BDC plans had superior HIs / CIs, by 13-24% / 3-243%, respectively, over the original plans. Compared to the LDC plans, the BDC plans provided better HIs only for PTVnx (the PTV of nasopharyngeal primary tumor) by 11% and better CIs for all PTVs by 2-134%. The BDC technique spared most OARs, by 1-9%. The average MUs of the BDC, original, and LDC plans were 2149, 2068 and 2179, respectively. The average whole planning times were 48 and 69 minutes for the BDC and LDC plans, respectively. Conclusions For the IMRT of nasopharyngeal cancer, the BDC planning technique can improve target dose homogeneity, conformity and OAR sparing, with better planning efficiency. PMID:26132167

  12. Radiotherapy T1 glottic carcinoma

    SciTech Connect

    Zablow, A.I.; Erba, P.S.; Sanfillippo, L.J.

    1989-11-01

    From 1970 to 1985, curative radiotherapy was administered to 63 patients with stage I carcinoma of the true vocal cords. Precision radiotherapeutic technique yields cure rates comparable to surgical results. Good voice quality was preserved in a high percentage of patients.

  13. Indirect orthodontic bonding - a modified technique for improved efficiency and precision

    PubMed Central

    Nojima, Lincoln Issamu; Araújo, Adriele Silveira; Alves, Matheus

    2015-01-01

    INTRODUCTION: The indirect bonding technique optimizes fixed appliance installation at the orthodontic office, ensuring precise bracket positioning, among other advantages. In this laboratory clinical phase, material and methods employed in creating the transfer tray are decisive to accuracy. OBJECTIVE: This article describes a simple, efficient and reproducible indirect bonding technique that allows the procedure to be carried out successfully. Variables influencing the orthodontic bonding are analyzed and discussed in order to aid professionals wishing to adopt the indirect bonding technique routinely in their clinical practice. PMID:26154464

  14. A Dosimetric Evaluation of Conventional Helmet Field Irradiation Versus Two-Field Intensity-Modulated Radiotherapy Technique

    SciTech Connect

    Yu, James B.; Shiao, Stephen L.; Knisely, Jonathan . E-mail: jonathan.knisely@yale.edu

    2007-06-01

    Purpose: To compare dosimetric differences between conventional two-beam helmet field irradiation (external beam radiotherapy, EBRT) of the brain and a two-field intensity-modulated radiotherapy (IMRT) technique. Methods and Materials: Ten patients who received helmet field irradiation at our institution were selected for study. External beam radiotherapy portals were planned per usual practice. Intensity-modulated radiotherapy fields were created using the identical field angles as the EBRT portals. Each brain was fully contoured along with the spinal cord to the bottom of the C2 vertebral body. This volume was then expanded symmetrically by 0.5 cm to construct the planning target volume. An IMRT plan was constructed using uniform optimization constraints. For both techniques, the nominal prescribed dose was 3,000 cGy in 10 fractions of 300 cGy using 6-MV photons. Comparative dose-volume histograms were generated for each patient and analyzed. Results: Intensity-modulated radiotherapy improved dose uniformity over EBRT for whole brain radiotherapy. The mean percentage of brain receiving >105% of dose was reduced from 29.3% with EBRT to 0.03% with IMRT. The mean maximum dose was reduced from 3,378 cGy (113%) for EBRT to 3,162 cGy (105%) with IMRT. The mean percent volume receiving at least 98% of the prescribed dose was 99.5% for the conventional technique and 100% for IMRT. Conclusions: Intensity-modulated radiotherapy reduces dose inhomogeneity, particularly for the midline frontal lobe structures where hot spots occur with conventional two-field EBRT. More study needs to be done addressing the clinical implications of optimizing dose uniformity and its effect on long-term cognitive function in selected long-lived patients.

  15. Development and Evaluation of Multiple Isocentric Volumetric Modulated Arc Therapy Technique for Craniospinal Axis Radiotherapy Planning

    SciTech Connect

    Lee, Young K.; Brooks, Corrinne J.; Bedford, James L.; Warrington, Alan P.; Saran, Frank H.

    2012-02-01

    Purpose: To develop and compare a volumetric modulated arc therapy (VMAT) technique with conventional radiotherapy for craniospinal irradiation with respect to improved dose conformity and homogeneity in the planning target volume (PTV) and to reduced dose to organs at risk (OAR). Methods and Materials: Conventional craniospinal axis radiotherapy plans of 5 patients were acquired. The median (range) length of the PTV was 58.9 (48.1-83.7) cm. The 6-MV VMAT plans were inversely planned with one isocenter near the base of the brain and the minimum number of isocenters required for the specified lengths of spine. The plans were optimized with high weighting for PTV coverage and low weighting for OAR sparing. Conformity and heterogeneity indices, dose-volume histograms, mean doses, and non-PTV integral doses from the two plans (prescription dose 23.4 Gy in 13 fractions) were compared. Results: The median (range) conformity index of VMAT was 1.22 (1.09-1.45), compared with 1.69 (1.44-2.67) for conventional plans (p = 0.04). The median (range) heterogeneity index was also lower for VMAT compared with conventional plans: 1.04 (1.03-1.07) vs. 1.12 (1.09-1.19), respectively (p = 0.04). A significant reduction of mean and maximum doses was observed in the heart, thyroid, esophagus, optic nerves, and eyes with VMAT when compared with conventional plans. A decrease in body V{sub 10Gy} was observed, but for 4 of 5 patients non-PTV integral dose was increased with VMAT when compared with the conventional plans. Conclusions: A VMAT technique to treat the craniospinal axis significantly reduces OAR dose, potentially leading to lower late organ toxicity. However, this is achieved at the expense of increased low-dose volumes, which is inherent to the technique, carrying a potentially increased risk of secondary malignancies.

  16. Dosimetric Evaluation of Different Intensity-Modulated Radiotherapy Techniques for Breast Cancer After Conservative Surgery.

    PubMed

    Zhang, Fuli; Wang, Yadi; Xu, Weidong; Jiang, Huayong; Liu, Qingzhi; Gao, Junmao; Yao, Bo; Hou, Jun; He, Heliang

    2015-10-01

    Intensity-modulated radiotherapy (IMRT) potentially leads to a more favorite dose distribution compared to 3-dimensional or conventional tangential radiotherapy (RT) for breast cancer after conservative surgery or mastectomy. The aim of this study was to compare dosimetric parameters of the planning target volume (PTV) and organs at risk (OARs) among helical tomotherapy (HT), inverse-planned IMRT (IP-IMRT), and forward-planned field in field (FP-FIF) IMRT techniques after breast-conserving surgery. Computed tomography scans from 20 patients (12 left sided and 8 right sided) previously treated with T1N0 carcinoma were selected for this dosimetric planning study. We designed HT, IP-IMRT, and FP-FIF plans for each patient. Plans were compared according to dose-volume histogram analysis in terms of PTV homogeneity and conformity indices (HI and CI) as well as OARs dose and volume parameters. Both HI and CI of the PTV showed statistically significant difference among IP-IMRT, FP-FIF, and HT with those of HT were best (P < .05). Compared to FP-FIF, IP-IMRT showed smaller exposed volumes of ipsilateral lung, heart, contralateral lung, and breast, while HT indicated smaller exposed volumes of ipsilateral lung but larger exposed volumes of contralateral lung and breast as well as heart. In addition, HT demonstrated an increase in exposed volume of ipsilateral lung (except for fraction of lung volume receiving >30 Gy and 20 Gy), heart, contralateral lung, and breast compared with IP-IMRT. For breast cancer radiotherapy (RT) after conservative surgery, HT provides better dose homogeneity and conformity of PTV compared to IP-IMRT and FP-FIF techniques, especially for patients with supraclavicular lymph nodes involved. Meanwhile, HT decreases the OAR volumes receiving higher doses with an increase in the volumes receiving low doses, which is known to lead to an increased rate of radiation-induced secondary malignancies. Hence, composite factors including dosimetric advantage

  17. Precise Point Positioning technique for short and long baselines time transfer

    NASA Astrophysics Data System (ADS)

    Lejba, Pawel; Nawrocki, Jerzy; Lemanski, Dariusz; Foks-Ryznar, Anna; Nogas, Pawel; Dunst, Piotr

    2013-04-01

    In this work the clock parameters determination of several timing receivers TTS-4 (AOS), ASHTECH Z-XII3T (OP, ORB, PTB, USNO) and SEPTENTRIO POLARX4TR (ORB, since February 11, 2012) by use of the Precise Point Positioning (PPP) technique were presented. The clock parameters were determined for several time links based on the data delivered by time and frequency laboratories mentioned above. The computations cover the period from January 1 to December 31, 2012 and were performed in two modes with 7-day and one-month solution for all links. All RINEX data files which include phase and code GPS data were recorded in 30-second intervals. All calculations were performed by means of Natural Resource Canada's GPS Precise Point Positioning (GPS-PPP) software based on high-quality precise satellite coordinates and satellite clock delivered by IGS as the final products. The used independent PPP technique is a very powerful and simple method which allows for better control of antenna positions in AOS and a verification of other time transfer techniques like GPS CV, GLONASS CV and TWSTFT. The PPP technique is also a very good alternative for calibration of a glass fiber link PL-AOS realized at present by AOS. Currently PPP technique is one of the main time transfer methods used at AOS what considerably improve and strengthen the quality of the Polish time scales UTC(AOS), UTC(PL), and TA(PL). KEY-WORDS: Precise Point Positioning, time transfer, IGS products, GNSS, time scales.

  18. [Stereotactic radiotherapy in brain metastases].

    PubMed

    Dhermain, F; Reyns, N; Colin, P; Métellus, P; Mornex, F; Noël, G

    2015-02-01

    Stereotactic radiotherapy of brain metastases is increasingly proposed after polydisciplinary debates among experts. Its definition and modalities of prescription, indications and clinical interest regarding the balance between efficacy versus toxicity need to be discussed. Stereotactic radiotherapy is a 'high precision' irradiation technique (within 1mm), using different machines (with invasive contention or frameless, photons X or gamma) delivering high doses (4 to 25Gy) in a limited number of fractions (usually 1 to 5, ten maximum) with a high dose gradient. Dose prescription will depend on materials, dose constraints to organs at risk varying with fractionation. Stereotactic radiotherapy may be proposed: (1) in combination with whole brain radiotherapy with the goal of increasing (modestly) overall survival of patients with a good performance status, 1 to 3 brain metastases and a controlled extracranial disease; (2) for recurrence of 1-3 brain metastases after whole brain radiotherapy; (3) after complete resection of a large and/or symptomatic brain metastases; (4) after diagnosis of 3-5 asymptomatic new or progressing brain metastases during systemic therapy, with the aim of delaying whole brain radiotherapy (avoiding its potential neurotoxicity) and maintaining a high focal control rate. Only a strict follow-up with clinical and MRI every 3 months will permit to deliver iterative stereotactic radiotherapies without jeopardizing survival. Simultaneous delivering of stereotactic radiotherapy with targeted medicines should be carefully discussed. PMID:25640215

  19. Accuracy required and achievable in radiotherapy dosimetry: have modern technology and techniques changed our views?

    NASA Astrophysics Data System (ADS)

    Thwaites, David

    2013-06-01

    In this review of the accuracy required and achievable in radiotherapy dosimetry, older approaches and evidence-based estimates for 3DCRT have been reprised, summarising and drawing together the author's earlier evaluations where still relevant. Available evidence for IMRT uncertainties has been reviewed, selecting information from tolerances, QA, verification measurements, in vivo dosimetry and dose delivery audits, to consider whether achievable uncertainties increase or decrease for current advanced treatments and practice. Overall there is some evidence that they tend to increase, but that similar levels should be achievable. Thus it is concluded that those earlier estimates of achievable dosimetric accuracy are still applicable, despite the changes and advances in technology and techniques. The one exception is where there is significant lung involvement, where it is likely that uncertainties have now improved due to widespread use of more accurate heterogeneity models. Geometric uncertainties have improved with the wide availability of IGRT.

  20. Craniospinal Irradiation Techniques: A Dosimetric Comparison of Proton Beams With Standard and Advanced Photon Radiotherapy

    SciTech Connect

    Yoon, Myonggeun; Shin, Dong Ho; Kim, Jinsung; Kim, Jong Won; Kim, Dae Woong; Park, Sung Yong; Lee, Se Byeong; Kim, Joo Young; Park, Hyeon-Jin; Park, Byung Kiu; Shin, Sang Hoon

    2011-11-01

    Purpose: To evaluate the dosimetric benefits of advanced radiotherapy techniques for craniospinal irradiation in cancer in children. Methods and Materials: Craniospinal irradiation (CSI) using three-dimensional conformal radiotherapy (3D-CRT), tomotherapy (TOMO), and proton beam treatment (PBT) in the scattering mode was planned for each of 10 patients at our institution. Dosimetric benefits and organ-specific radiation-induced cancer risks were based on comparisons of dose-volume histograms (DVHs) and on the application of organ equivalent doses (OEDs), respectively. Results: When we analyzed the organ-at-risk volumes that received 30%, 60%, and 90% of the prescribed dose (PD), we found that PBT was superior to TOMO and 3D-CRT. On average, the doses delivered by PBT to the esophagus, stomach, liver, lung, pancreas, and kidney were 19.4 Gy, 0.6 Gy, 0.3 Gy, 2.5 Gy, 0.2 Gy, and 2.2 Gy for the PD of 36 Gy, respectively, which were significantly lower than the doses delivered by TOMO (22.9 Gy, 4.5 Gy, 6.1 Gy, 4.0 Gy, 13.3 Gy, and 4.9 Gy, respectively) and 3D-CRT (34.6 Gy, 3.6 Gy, 8.0 Gy, 4.6 Gy, 22.9 Gy, and 4.3 Gy, respectively). Although the average doses delivered by PBT to the chest and abdomen were significantly lower than those of 3D-CRT or TOMO, these differences were reduced in the head-and-neck region. OED calculations showed that the risk of secondary cancers in organs such as the stomach, lungs, thyroid, and pancreas was much higher when 3D-CRT or TOMO was used than when PBT was used. Conclusions: Compared with photon techniques, PBT showed improvements in most dosimetric parameters for CSI patients, with lower OEDs to organs at risk.

  1. Evaluation of a Single-Isocenter Technique for Axillary Radiotherapy in Breast Cancer

    SciTech Connect

    Beek, Suzanne van Jaeger, Katrien de; Mijnheer, Ben |; Vliet-Vroegindeweij, Corine van

    2008-10-01

    The aim of this study was to develop a technique for axillary radiotherapy that minimizes the risk of radiation-induced damage to the surrounding normal tissue (i.e., arm, shoulder, lung, esophagus, and spinal cord) while keeping the risk of a nodal recurrence to a minimum. A planning study was performed in 20 breast cancer patients. The target volume of the axillary treatment encompassed the periclavicular and axillary lymph node areas. The 3-dimensional (3D) computed tomography (CT) information in this study was used to outline the lymph node areas and the organs at risk (i.e., the esophagus, spinal cord, brachial plexus, and lung). A conventional AP-PA technique (with a transmission plate placed in the AP beam) was evaluated. In addition, a new single-isocenter technique consisting of AP/PA fields using a gantry rotation of {+-}20 deg. and a medial AP segment was developed. Both techniques were compared by evaluation of the calculated dose distributions and the dose-volume histograms of the target volume and surrounding organs at risk. The field borders and humeral shielding were redefined based on the 3D anatomical references. Adapting the humeral shielding reduced the irradiated volume by 19% and might contribute to a reduction of the incidence of arm edema and impairment of shoulder function. The maximum radiation dose in the esophagus and spinal cord was reduced by more than 50% using the single-isocenter technique. The difference between both techniques with respect to the mean doses in the target volume and lung, and the maximum dose in brachial plexus, was not statistically significant. Moreover, the single-isocenter technique allowed a fast and easy treatment preparation and reduced the execution time considerably (with approximately 10 minutes per fraction)

  2. Precise Heat Control: What Every Scientist Needs to Know About Pyrolytic Techniques to Solve Real Problems

    NASA Technical Reports Server (NTRS)

    Devivar, Rodrigo

    2014-01-01

    The performance of a material is greatly influenced by its thermal and chemical properties. Analytical pyrolysis, when coupled to a GC-MS system, is a powerful technique that can unlock the thermal and chemical properties of almost any substance and provide vital information. At NASA, we depend on precise thermal analysis instrumentation for understanding aerospace travel. Our analytical techniques allow us to test materials in the laboratory prior to an actual field test; whether the field test is miles up in the sky or miles underground, the properties of any involved material must be fully studied and understood in the laboratory.

  3. Radiotherapy for Head and Neck Cancer

    PubMed Central

    Yeh, Shyh-An

    2010-01-01

    Treatment for patients with head and neck cancer requires a multidisciplinary approach. Radiotherapy is employed as a primary treatment or as an adjuvant to surgery. Each specific subsite dictates the appropriate radiotherapy techniques, fields, dose, and fractionation scheme. Quality of life is also an important issue in the management of head and neck cancer. The radiation-related complications have a tremendous impact on the quality of life. Modern radiotherapy techniques, such as intensity-modulated radiotherapy and image-guided radiotherapy, can offer precise radiation delivery and reduce the dose to the surrounding normal tissues without compromise of target coverage. In the future, efforts should be made in the exploration of novel strategies to improve treatment outcome in patients with head and neck cancer. PMID:22550433

  4. Dosimetry verification on VMAT and IMRT radiotherapy techniques: In the case of prostate cancer

    NASA Astrophysics Data System (ADS)

    Maulana, A.; Pawiro, S. A.

    2016-03-01

    Radiotherapy treatment depends on the accuracy of the dose delivery to patients, the purpose of the study is to verify the dose in IMRT and VMAT technique in prostate cancer cases correspond to TPS dose using phantom base on ICRU No.50. The dose verification of the target and OAR was performed by placing the TLD Rod LiF100 and EBT2 Gafchromic film at slab hole of pelvic part of the Alderson RANDO phantom for prostate cancer simulation. The Exposed TLDs was evaluated using the TLD Reader Harshaw while EBT2 film was scanned using Epson scanner. The point dose measurements were compared between planned dose and measured dose at target volume and OAR. The result is the dose difference at target volume, bladder and rectum for IMRT and VMAT are less than 5%. On the other hand, the dose difference at the Femoral head is more than 5% for both techniques because the location of OAR already in low gradient dose. Furthermore, the difference dose of the target volume for IMRT technique tends to be smaller than VMAT either for TLD and EBT2 film detectors. From the measurement showed that the delivered dose on the phantom simulation match with ICRU No.50 criteria.

  5. High precision calcium isotope analysis using 42Ca-48Ca double-spike TIMS technique

    NASA Astrophysics Data System (ADS)

    Feng, L.; Zhou, L.; Gao, S.; Tong, S. Y.; Zhou, M. L.

    2014-12-01

    Double spike techniques are widely used for determining calcium isotopic compositions of natural samples. The most important factor controlling precision of the double spike technique is the choice of appropriate spike isotope pair, the composition of double spikes and the ratio of spike to sample(CSp/CN). We propose an optimal 42Ca-48Ca double spike protocol which yields the best internal precision for calcium isotopic composition determinations among all kinds of spike pairs and various spike compositions and ratios of spike to sample, as predicted by linear error propagation method. It is suggested to use spike composition of 42Ca/(42Ca+48Ca) = 0.44 mol/mol and CSp/(CN+ CSp)= 0.12mol/mol because it takes both advantages of the largest mass dispersion between 42Ca and 48Ca (14%) and lowest spike cost. Spiked samples were purified by pass through homemade micro-column filled with Ca special resin. K, Ti and other interference elements were completely separated, while 100% calcium was recovered with negligible blank. Data collection includes integration time, idle time, focus and peakcenter frequency, which were all carefully designed for the highest internal precision and lowest analysis time. All beams were automatically measured in a sequence by Triton TIMS so as to eliminate difference of analytical conditions between samples and standards, and also to increase the analytical throughputs. The typical internal precision of 100 duty cycles for one beam is 0.012‒0.015 ‰ (2δSEM), which agrees well with the predicted internal precision of 0.0124 ‰ (2δSEM). Our methods improve internal precisions by a factor of 2‒10 compared to previous methods of determination of calcium isotopic compositions by double spike TIMS. We analyzed NIST SRM 915a, NIST SRM 915b and Pacific Seawater as well as interspersed geological samples during two months. The obtained average δ44/40Ca (all relative to NIST SRM 915a) is 0.02 ± 0.02 ‰ (n=28), 0.72±0.04 ‰ (n=10) and 1

  6. Precision Mass Measurements at the Canadian Penning Trap using a Phase-Imaging Technique

    NASA Astrophysics Data System (ADS)

    Nystrom, Andrew; Aprahamian, A.; Marley, S. T.; Mumpower, M.; Paul, N.; Siegl, K.; Strauss, S.; Surman, R.; Kuta, T.; Savard, G.; Clark, J. A.; Levand, A. F.; Perez Galvan, A.; Hirsh, T.; Rohrer, J.; Caldwell, S.; van Schelt, J.; Orford, R.; Buchinger, F.; Morgan, G.; Sharma, K.

    2015-10-01

    Precision mass measurements at Penning Trap facilities have traditionally used a time-of-flight (TOF) technique to measure the cyclotron frequency of ions and therefore determine their masses. At the Canadian Penning Trap (CPT), this technique is able to provide mass measurements to a precision of about δm/m = 10-8 with measurement times as low as 200ms. However, a new phase-imaging technique, which instead determines the cyclotron frequency by projecting the radial ion motion on a position-sensitive detector, is being implemented at the CPT. It provides at least a tenfold gain in resolving power while allowing for measurement times of less than 100 ms, allowing measurements of more exotic neutron-rich nuclei from CARIBU with respect to the TOF technique. Details of its commissioning at the CPT will be discussed alongside new neutron-rich mass measurements. This work is supported by the following: NSERC, Canada, appl. # 239591, the U.S. DOE, Office of Nuclear Physics, under Contract DE-AC02-06CH11357, and NSF Grants PHY-1419765 and PHY-1430152.

  7. An imaging evaluation of the simultaneously integrated boost breast radiotherapy technique

    SciTech Connect

    Turley, Jessica; Claridge Mackonis, Elizabeth

    2015-09-15

    To evaluate in-field megavoltage (MV) imaging of simultaneously integrated boost (SIB) breast fields to determine its feasibility in treatment verification for the SIB breast radiotherapy technique, and to assess whether the current-imaging protocol and treatment margins are sufficient. For nine patients undergoing SIB breast radiotherapy, in-field MV images of the SIB fields were acquired on days that regular treatment verification imaging was performed. The in-field images were matched offline according to the scar wire on digitally reconstructed radiographs. The offline image correction results were then applied to a margin recipe formula to calculate safe margins that account for random and systematic uncertainties in the position of the boost volume when an offline correction protocol has been applied. After offline assessment of the acquired images, 96% were within the tolerance set in the current department-imaging protocol. Retrospectively performing the maximum position deviations on the Eclipse™ treatment planning system demonstrated that the clinical target volume (CTV) boost received a minimum dose difference of 0.4% and a maximum dose difference of 1.4% less than planned. Furthermore, applying our results to the Van Herk margin formula to ensure that 90% of patients receive 95% of the prescribed dose, the calculated CTV margins were comparable to the current departmental procedure used. Based on the in-field boost images acquired and the feasible application of these results to the margin formula the current CTV-planning target volume margins used are appropriate for the accurate treatment of the SIB boost volume without additional imaging.

  8. Advanced 3D-Sonographic Imaging as a Precise Technique to Evaluate Tumor Volume

    PubMed Central

    Pflanzer, R.; Hofmann, M.; Shelke, A.; Habib, A.; Derwich, W.; Schmitz-Rixen, T.; Bernd, A.; Kaufmann, R.; Bereiter-Hahn, J.

    2014-01-01

    Determination of tumor volume in subcutaneously inoculated xenograft models is a standard procedure for clinical and preclinical evaluation of tumor response to treatment. Practitioners frequently use a hands-on caliper method in conjunction with a simplified formula to assess tumor volume. Non-invasive and more precise techniques as investigation by MR or (μ)CT exist but come with various adverse effects in terms of radiation, complex setup or elevated cost of investigations. Therefore, we propose an advanced three-dimensional sonographic imaging technique to determine small tumor volumes in xenografts with high precision and minimized observer variability. We present a study on xenograft carcinoma tumors from which volumes and shapes were calculated with the standard caliper method as well as with a clinically available three-dimensional ultrasound scanner and subsequent processing software. Statistical analysis reveals the suitability of this non-invasive approach for the purpose of a quick and precise calculation of tumor volume in small rodents. PMID:25500076

  9. Simple Carotid-Sparing Intensity-Modulated Radiotherapy Technique and Preliminary Experience for T1-2 Glottic Cancer

    SciTech Connect

    Rosenthal, David I.; Fuller, Clifton D.; Barker, Jerry L.; Mason, Bryan M.S.; Garcia, John A. C.; Lewin, Jan S.; Holsinger, F. Christopher; Stasney, C. Richard; Frank, Steven J.; Schwartz, David L.; Morrison, William H.; Garden, Adam S.; Ang, K. Kian

    2010-06-01

    Purpose: To investigate the dosimetry and feasibility of carotid-sparing intensity-modulated radiotherapy (IMRT) for early glottic cancer and to report preliminary clinical experience. Methods and Materials: Digital Imaging and Communications in Medicine radiotherapy (DICOM-RT) datasets from 6 T1-2 conventionally treated glottic cancer patients were used to create both conventional IMRT plans. We developed a simplified IMRT planning algorithm with three fields and limited segments. Conventional and IMRT plans were compared using generalized equivalent uniform dose and dose-volume parameters for in-field carotid arteries, target volumes, and organs at risk. We have treated 11 patients with this simplified IMRT technique. Results: Intensity-modulated radiotherapy consistently reduced radiation dose to the carotid arteries (p < 0.05) while maintaining the clinical target volume coverage. With conventional planning, median carotid V35, V50, and V63 were 100%, 100%, and 69.0%, respectively. With IMRT planning these decreased to 2%, 0%, and 0%, respectively (p < 0.01). Radiation planning and treatment times were similar for conventional radiotherapy and IMRT. Treatment results have been excellent thus far. Conclusions: Intensity-modulated radiotherapy significantly reduced unnecessary radiation dose to the carotid arteries compared with conventional lateral fields while maintaining clinical target volume coverage. Further experience and longer follow-up will be required to demonstrate outcomes for cancer control and carotid artery effects.

  10. A precision technique for mounting scintillating fiber ribbons for charged particle tracking

    SciTech Connect

    Carabello, S.; Gau, D.; Howell, B.; Koltick, D.; Pischalnikov, Y.; Michael, D.

    1996-06-01

    The authors have undertaken a research program to develop a Scintillating Fiber charged particle Tracking (SFT) detector for the D0 upgrade experiment at FNAL. They have developed a construction method utilizing scintillating fibers first accurately formed into ribbons, then precisely locating these ribbons on the inside and outside of a lightweight cylindrical base. A Coordinate Measuring Machine (CMM) is used to control each step of the ribbon mounting procedure. Ribbons 2m long, containing 255 fibers each have been placed on composite structures with accuracy {approximately}20 {micro}m. The technique for producing highly accurate fiber ribbons and the method of precision placement of ribbons are presented. The spatial calibration of a charged particle tracker using the CMM measurements are discussed.

  11. Precise near-earth navigation with GPS: A survey of techniques

    NASA Technical Reports Server (NTRS)

    Yunck, T. P.; Wu, S. C.; Wu, J.

    1987-01-01

    The tracking accuracy of the low earth orbiters (below about 3000 km altitude) can be brought below 10 cm with a variety of differential techniques that exploit the Global Positioning System (GPS). All of these techniques require a precisely known global network of GPS ground receivers and a receiver aboard the user satellite, and all simultaneously estimate the user and GPS satellite orbits. Three basic approaches are the geometric, dynamic, and nondynamic strategies. The last combines dynamic GPS solutions with a geometric user solution. Two powerful extensions of the nondynamic strategy show considerable promise. The first uses an optimized synthesis of dynamics and geometry in the user solution, while the second uses a novel gravity-adjustment method to exploit data from repeat ground tracks. These techniques will offer sub-decimeter accuracy for dynamically unpredictable satellites down to the lowesst possible altitudes.

  12. Optimization of the performance of segmented scintillators for radiotherapy imaging through novel binning techniques

    NASA Astrophysics Data System (ADS)

    El-Mohri, Youcef; Antonuk, Larry E.; Choroszucha, Richard B.; Zhao, Qihua; Jiang, Hao; Liu, Langechuan

    2014-02-01

    Thick, segmented crystalline scintillators have shown increasing promise as replacement x-ray converters for the phosphor screens currently used in active matrix flat-panel imagers (AMFPIs) in radiotherapy, by virtue of providing over an order of magnitude improvement in the detective quantum efficiency (DQE). However, element-to-element misalignment in current segmented scintillator prototypes creates a challenge for optimal registration with underlying AMFPI arrays, resulting in degradation of spatial resolution. To overcome this challenge, a methodology involving the use of a relatively high resolution AMFPI array in combination with novel binning techniques is presented. The array, which has a pixel pitch of 0.127 mm, was coupled to prototype segmented scintillators based on BGO, LYSO and CsI:Tl materials, each having a nominal element-to-element pitch of 1.016 mm and thickness of ∼1 cm. The AMFPI systems incorporating these prototypes were characterized at a radiotherapy energy of 6 MV in terms of modulation transfer function, noise power spectrum, DQE, and reconstructed images of a resolution phantom acquired using a cone-beam CT geometry. For each prototype, the application of 8 × 8 pixel binning to achieve a sampling pitch of 1.016 mm was optimized through use of an alignment metric which minimized misregistration and thereby improved spatial resolution. In addition, the application of alternative binning techniques that exclude the collection of signal near septal walls resulted in further significant improvement in spatial resolution for the BGO and LYSO prototypes, though not for the CsI:Tl prototype due to the large amount of optical cross-talk resulting from significant light spread between scintillator elements in that device. The efficacy of these techniques for improving spatial resolution appears to be enhanced for scintillator materials that exhibit mechanical hardness, high density and high refractive index, such as BGO. Moreover, materials

  13. Optimization of the Performance of Segmented Scintillators for Radiotherapy Imaging through Novel Binning Techniques

    PubMed Central

    El-Mohri, Youcef; Antonuk, Larry E.; Choroszucha, Richard B.; Zhao, Qihua; Jiang, Hao; Liu, Langechuan

    2014-01-01

    Thick, segmented crystalline scintillators have shown increasing promise as replacement x-ray converters for the phosphor screens currently used in active matrix flat-panel imagers (AMFPIs) in radiotherapy, by virtue of providing over an order of magnitude improvement in the DQE. However, element-to-element misalignment in current segmented scintillator prototypes creates a challenge for optimal registration with underlying AMFPI arrays, resulting in degradation of spatial resolution. To overcome this challenge, a methodology involving the use of a relatively high resolution AMFPI array in combination with novel binning techniques is presented. The array, which has a pixel pitch of 0.127 mm, was coupled to prototype segmented scintillators based on BGO, LYSO and CsI:Tl materials, each having a nominal element-to-element pitch of 1.016 mm and thickness of ~1 cm. The AMFPI systems incorporating these prototypes were characterized at a radiotherapy energy of 6 MV in terms of MTF, NPS, DQE, and reconstructed images of a resolution phantom acquired using a cone-beam CT geometry. For each prototype, the application of 8×8 pixel binning to achieve a sampling pitch of 1.016 mm was optimized through use of an alignment metric which minimized misregistration and thereby improved spatial resolution. In addition, the application of alternative binning techniques that exclude the collection of signal near septal walls resulted in further significant improvement in spatial resolution for the BGO and LYSO prototypes, though not for the CsI:Tl prototype due to the large amount of optical cross-talk resulting from significant light spread between scintillator elements in that device. The efficacy of these techniques for improving spatial resolution appears to be enhanced for scintillator materials that exhibit mechanical hardness, high density and high refractive index, such as BGO. Moreover, materials that exhibit these properties as well as offer significantly higher light

  14. A cosmetic evaluation of breast cancer treatment: A randomized study of radiotherapy boost technique

    SciTech Connect

    Vass, Sylvie . E-mail: sylvie.vass@ssss.gouv.qc.ca; Bairati, Isabelle

    2005-08-01

    Purpose: To compare cosmetic results of two different radiotherapy (RT) boost techniques used in the treatment of breast cancer after whole breast radiotherapy and to identify factors affecting cosmetic outcomes. Methods and Materials: Between 1996 and 1998, 142 patients with Stage I and II breast cancer were treated with breast conservative surgery and adjuvant RT. Patients were then randomly assigned to receive a boost dose of 15 Gy delivered to the tumor bed either by iridium 192, or a combination of photons and electrons. Cosmetic evaluations were done on a 6-month basis, with a final evaluation at 36 months after RT. The evaluations were done using a panel of global and specific subjective scores, a digitized scoring system using the breast retraction assessment (BRA) measurement, and a patient's self-assessment evaluation. As cosmetic results were graded according to severity, the comparison of boost techniques was done using the ordinal logistic regression model. Adjusted odds ratios (OR) and their 95% confidence intervals (CI) are presented. Results: At 36 months of follow-up, there was no significant difference between the two groups with respect to the global subjective cosmetic outcome (OR = 1.40; 95%CI = 0.69-2.85, p = 0.35). Good to excellent scores were observed in 65% of implant patients and 62% of photon/electron patients. At 24 months and beyond, telangiectasia was more severe in the implant group with an OR of 9.64 (95%CI = 4.05-22.92, p < 0.0001) at 36 months. The only variable associated with a worse global cosmetic outcome was the presence of concomitant chemotherapy (OR = 3.87; 95%CI = 1.74-8.62). The BRA value once adjusted for age, concomitant chemotherapy, and boost volume showed a positive association with the boost technique. The BRA value was significantly greater in the implant group (p 0.03). There was no difference in the patient's final self-assessment score between the two groups. Three variables were statistically associated with

  15. Optimization of the performance of segmented scintillators for radiotherapy imaging through novel binning techniques.

    PubMed

    El-Mohri, Youcef; Antonuk, Larry E; Choroszucha, Richard B; Zhao, Qihua; Jiang, Hao; Liu, Langechuan

    2014-02-21

    Thick, segmented crystalline scintillators have shown increasing promise as replacement x-ray converters for the phosphor screens currently used in active matrix flat-panel imagers (AMFPIs) in radiotherapy, by virtue of providing over an order of magnitude improvement in the detective quantum efficiency (DQE). However, element-to-element misalignment in current segmented scintillator prototypes creates a challenge for optimal registration with underlying AMFPI arrays, resulting in degradation of spatial resolution. To overcome this challenge, a methodology involving the use of a relatively high resolution AMFPI array in combination with novel binning techniques is presented. The array, which has a pixel pitch of 0.127 mm, was coupled to prototype segmented scintillators based on BGO, LYSO and CsI:Tl materials, each having a nominal element-to-element pitch of 1.016 mm and thickness of ∼ 1 cm. The AMFPI systems incorporating these prototypes were characterized at a radiotherapy energy of 6 MV in terms of modulation transfer function, noise power spectrum, DQE, and reconstructed images of a resolution phantom acquired using a cone-beam CT geometry. For each prototype, the application of 8 × 8 pixel binning to achieve a sampling pitch of 1.016 mm was optimized through use of an alignment metric which minimized misregistration and thereby improved spatial resolution. In addition, the application of alternative binning techniques that exclude the collection of signal near septal walls resulted in further significant improvement in spatial resolution for the BGO and LYSO prototypes, though not for the CsI:Tl prototype due to the large amount of optical cross-talk resulting from significant light spread between scintillator elements in that device. The efficacy of these techniques for improving spatial resolution appears to be enhanced for scintillator materials that exhibit mechanical hardness, high density and high refractive index, such as BGO. Moreover, materials

  16. Usefulness of image morphing techniques in cancer treatment by conformal radiotherapy

    NASA Astrophysics Data System (ADS)

    Atoui, Hussein; Sarrut, David; Miguet, Serge

    2004-05-01

    Conformal radiotherapy is a cancer treatment technique, that targets high-energy X-rays to tumors with minimal exposure to surrounding healthy tissues. Irradiation ballistics is calculated based on an initial 3D Computerized Tomography (CT) scan. At every treatment session, the random positioning of the patient, compared to the reference position defined by the initial 3D CT scan, can generate treatment inaccuracies. Positioning errors potentially predispose to dangerous exposure to healthy tissues as well as insufficient irradiation to the tumor. A proposed solution would be the use of portal images generated by Electronic Portal Imaging Devices (EPID). Portal images (PI) allow a comparison with reference images retained by physicians, namely Digitally Reconstructed Radiographs (DRRs). At present, physicians must estimate patient positional errors by visual inspection. However, this may be inaccurate and consumes time. The automation of this task has been the subject of many researches. Unfortunately, the intensive use of DRRs and the high computing time required have prevented real time implementation. We are currently investigating a new method for DRR generation that calculates intermediate DRRs by 2D deformation of previously computed DRRs. We approach this investigation with the use of a morphing-based technique named mesh warping.

  17. Novel technique for high-precision Bragg-angle determination in crystal x-ray spectroscopy

    SciTech Connect

    Braun, J.; Bruhns, H.; Trinczek, M.; Lopez-Urrutia, J. R. Crespo; Ullrich, J.

    2005-07-15

    A novel technique for a high-precision large acceptance determination of the Bragg angle in crystal x-ray spectroscopy is presented and demonstrated. The method exploits visible light beams as fiducials reflected on the x-ray crystal's surface to ensure exact knowledge of the position on the crystal at which the x rays are reflected, replacing entrance slits, thus making flat crystals suitable for low x-ray fluxes. It can be shown that many error sources arising from uncertainties in the determination of geometrical properties are eliminated in this way. A flat crystal x-ray spectrometer based on this technique has been designed, built, and tested using the most precisely known wavelengths emitted by highly charged ions, namely H- and He-like argon. The result for the 1s2p {sup 1}P{sub 1}{yields}1s{sup 2} {sup 1}S{sub 0} w-line of He-like argon exhibits a statistical uncertainty of 3.8 ppm and an estimated systematic error of about 3 ppm, thus becoming the most accurate measurement of the He-like resonance transition in highly charged ions. It is shown that achieving a systematic error of below 1 ppm is feasible with this method. Therefore, our technique should allow reaching total accuracies approaching 1 ppm on transitions of mid-Z highly charged ions, which would provide challenging tests for state-of-the-art theoretical predictions.

  18. Radiotherapy of malignant melanoma

    SciTech Connect

    Cooper, J.S.

    1985-04-01

    The role of radiotherapy in the treatment of malignant melanoma is limited, and surgery generally forms the mainstay of medical practice. However, there are some circumstances in which radiotherapy should be considered the treatment of choice. Symptomatic metastatic lesions in bone or brain can effectively be palliated in a substantial proportion of instances. At the current stage of our knowledge, conventionally fractionated treatment of such lesions forms the standard against which other treatments should be measured. In contrast, metastatic lesions to skin or lymph nodes that do not overlie critical normal structures probably are better treated by high-dose-per-fraction techniques. Radiotherapy may play a definitive role in the treatment of lentigo maligna. The precise optimal energy of the beam to be used remains to be defined. Slightly more penetrating radiation appears to be required for lentigo maligna melanomas. Here, too, the optimal energy remains to be defined. The treatment of nonlentigenous melanomas primarily by radiotherapy is unproved in my opinion. Certainly, the data from the Princess Margaret Hospital is exciting, but I believe it must be corroborated by a well-designed trial before it can be accepted without question. Future directions in treatment of malignant melanoma are likely to include further trials of unconventional fractionation and the use of radiosensitizing agents in conjunction with radiotherapy. The time for dermatologists and radiation therapists to cooperate in such studies is at hand.

  19. RapidArc radiotherapy planning for prostate cancer: Single-arc and double-arc techniques vs. intensity-modulated radiotherapy

    SciTech Connect

    Sze, Henry C.K.; Lee, Michael C.H.; Hung, Wai-Man; Yau, Tsz-Kok; Lee, Anne W.M.

    2012-04-01

    RapidArc is a novel technique using arc radiotherapy aiming to achieve intensity-modulated radiotherapy (IMRT)-quality radiotherapy plans with shorter treatment time. This study compared the dosimetric quality and treatment efficiency of single-arc (SA) vs. double-arc (DA) and IMRT in the treatment of prostate cancer. Fourteen patients were included in the analysis. The planning target volume (PTV), which contained the prostate gland and proximal seminal vesicles, received 76 Gy in 38 fractions. Seven-field IMRT, SA, and DA plans were generated for each patient. Dosimetric quality in terms of the minimum PTV dose, PTV hotspot, inhomogeneity, and conformity index; and sparing of rectum, bladder, and femoral heads as measured by V70, V-40, and V20 (% of volume receiving >70 Gy, 40 Gy, and 20 Gy, respectively), treatment efficiency as assessed by monitor units (MU) and treatment time were compared. All plan objectives were met satisfactorily by all techniques. DA achieved the best dosimetric quality with the highest minimum PTV dose, lowest hotspot, and the best homogeneity and conformity. It was also more efficient than IMRT. SA achieved the highest treatment efficiency with the lowest MU and shortest treatment time. The mean treatment time for a 2-Gy fraction was 4.80 min, 2.78 min, and 1.30 min for IMRT, DA, and SA, respectively. However, SA also resulted in the highest rectal dose. DA could improve target volume coverage and reduce treatment time and MU while maintaining equivalent normal tissue sparing when compared with IMRT. SA achieved the greatest treatment efficiency but with the highest rectal dose, which was nonetheless within tolerable limits. For busy units with high patient throughput, SA could be an acceptable option.

  20. Estimating Cardiac Substructures Exposure From Diverse Radiotherapy Techniques in Treating Left-Sided Breast Cancer

    PubMed Central

    Zhang, Li; Mei, Xin; Chen, Xingxing; Hu, Weigang; Hu, Silong; Zhang, Yingjian; Shao, Zhimin; Guo, Xiaomao; Tuan, Jeffrey; Yu, Xiaoli

    2015-01-01

    Abstract The study compares the physical and biologically effective doses (BED) received by the heart and cardiac substructures using three-dimensional conformal RT (3D-CRT), intensity-modulated radiotherapy (IMRT), and simple IMRT (s-IMRT) in postoperative radiotherapy for patients with left-sided breast cancer. From October 2008 to February 2009, 14 patients with histologically confirmed left-sided breast cancer were enrolled and underwent contrast-enhanced computed tomography (CT) simulation and 18F-FDG positron emission tomography-CT to outline the left cardiac ventricle (LV) and other substructures. The linear-quadratic model was used to convert the physical doses received by critical points of inner heart to BED. The maximal dose, minimum dose, dose received by 99% of volume (D99) and dose received by 95% of volume (D95) in target areas were significantly better using IMRT and s-IMRT when compared with 3D-CRT (P < 0.05). IMRT and s-IMRT significantly reduced the maximal cardiac dose (5038.98 vs 5346.47 cGy, P = 0.002; 5146.66 vs 5346.47 cGy, P = 0.03). IMRT reduced the maximal dose to LV by 4% (P = 0.05) in comparison with 3D-CRT. The average doses to heart and LV in 3D-CRT plan were significantly lower than those in IMRT plan (P < 0.05). The average cardiac volumes receiving ≥25 Gy (V25 Gy) in IMRT, s-IMRT, and 3D-CRT plans were 73.98, 76.75, and 60.34 cm3, respectively. The average LV volumes receiving ≥25 Gy (V25 Gy) in IMRT, s-IMRT and 3D-CRT plans were 23.37, 24.68, and 17.61 cm3, respectively. In the IMRT plan, the mean BED to the critical points of inner heart located within the high physical dose area were substantially lower than in 3D-CRT or s-IMRT. Compared with 3D-CRT technique, IMRT and s-IMRT had superior target dose coverage and dose uniformity. IMRT significantly reduced the maximal RT dose to heart and LV. IMRT and s-IMRT techniques did not reduce the volume of heart and LV receiving high doses. PMID

  1. Accuracy of a new paired imaging technique for position correction in whole breast radiotherapy.

    PubMed

    Petillion, Saskia; Verhoeven, Karolien; Weltens, Caroline; Van den Heuvel, Frank

    2015-01-01

    Image-guided position verification in breast radiotherapy is accurately performed with kilovoltage cone beam CT (kV-CBCT). The technique is, however, time-consuming and there is a risk for patient collision. Online position verification performed with orthogonal-angled mixed modality paired imaging is less time-consuming at the expense of inferior accuracy compared to kV-CBCT. We therefore investigated whether a new tangential-angled single modality paired imaging technique can reduce the residual error (RE) of orthogonal-angled mixed modality paired imaging. The latter was applied to 20 breast cancer patients. Tangential-angled single modality paired imaging was investigated in 20 breast and 20 breast cancer patients with locoregional lymph node irradiation. The central lung distance (CLD) residual error and the longitudinal residual error were determined during the first 5 treatment fractions. Off-line matching of the tangential breast field images, acquired after online position correction, was used. The mean, systematic, and random REs of each patient group were calculated. The systematic REs were checked for significant differences using the F-test. Tangential-angled single modality paired imaging significantly reduced the systematic CLD residual error of orthogonal-angled mixed modality paired imaging for the breast cancer patients, from 2.3 mm to 1.0 mm, and also significantly decreased the systematic longitudinal RE from 2.4 mm to 1.3 mm. PTV margins, which account for the residual error (PTVRE), were also calculated. The PTVRE margin needed to account for the RE of orthogonal-angled mixed modality paired imaging (i.e., 8 mm) was halved by tangential-angled single modality paired imaging. The differences between the systematic REs of tangential-angled single modality paired imaging of the breast cancer patients and the breast cancer patients with locoregional lymph node irradiation were not significant, yielding comparable PTVRE margins. In this study, we

  2. Does obesity hinder radiotherapy in endometrial cancer patients? The implementation of new techniques in adjuvant radiotherapy – focus on obese patients

    PubMed Central

    Moszyńska-Zielińska, Małgorzata; Chałubińska-Fendler, Justyna; Żytko, Leszek; Bigos, Ewelina; Fijuth, Jacek

    2014-01-01

    The increasing incidence of obesity in Poland and its relation to endometrioid endometrial cancer (EEC) is resulting in the increasing necessity of treating obese women. Treatment of an overweight patient with EEC may impede not only the surgical procedures but also radiotherapy, especially external beam radiotherapy (EBRT). The problems arise both during treatment planning and when delivering each fraction due to the difficulty of positioning such a patient – it implies the danger of underdosing targets and overdosing organs at risk. Willingness to use dynamic techniques in radiation oncology has increased for patients with EEC, even those who are obese. During EBRT careful daily verification is necessary for both safety and treatment accuracy. The most accurate method of verification is cone beam computed tomography (CBCT) with soft tissue assessment, although it is time consuming and often requires a radiation oncologist. In order to improve the quality of such treatment, the authors present the practical aspects of planning and treatment itself by means of dynamic techniques in EBRT. The authors indicate the advantages and disadvantages of different types of on-board imaging (OBI) verification images. Considering the scanty amount of literature in this field, it is necessary to conduct further research in order to highlight proper planning and treatment of obese endometrial cancer patients. The review of the literature shows that all centres that wish to use EBRT for gynaecological tumours should develop their own protocols on qualification, planning the treatment and methods of verifying the patients’ positioning. PMID:26327837

  3. Anatomic and Pathologic Variability During Radiotherapy for a Hybrid Active Breath-Hold Gating Technique

    SciTech Connect

    Glide-Hurst, Carri K.; Gopan, Ellen; Hugo, Geoffrey D.

    2010-07-01

    Purpose: To evaluate intra- and interfraction variability of tumor and lung volume and position using a hybrid active breath-hold gating technique. Methods and Materials: A total of 159 repeat normal inspiration active breath-hold CTs were acquired weekly during radiotherapy for 9 lung cancer patients (12-21 scans per patient). A physician delineated the gross tumor volume (GTV), lungs, and spinal cord on the first breath-hold CT, and contours were propagated semiautomatically. Intra- and interfraction variability of tumor and lung position and volume were evaluated. Tumor centroid and border variability were quantified. Results: On average, intrafraction variability of lung and GTV centroid position was <2.0 mm. Interfraction population variability was 3.6-6.7 mm (systematic) and 3.1-3.9 mm (random) for the GTV centroid and 1.0-3.3 mm (systematic) and 1.5-2.6 mm (random) for the lungs. Tumor volume regressed 44.6% {+-} 23.2%. Gross tumor volume border variability was patient specific and demonstrated anisotropic shape change in some subjects. Interfraction GTV positional variability was associated with tumor volume regression and contralateral lung volume (p < 0.05). Inter-breath-hold reproducibility was unaffected by time point in the treatment course (p > 0.1). Increases in free-breathing tidal volume were associated with increases in breath-hold ipsilateral lung volume (p < 0.05). Conclusions: The breath-hold technique was reproducible within 2 mm during each fraction. Interfraction variability of GTV position and shape was substantial because of tumor volume and breath-hold lung volume change during therapy. These results support the feasibility of a hybrid breath-hold gating technique and suggest that online image guidance would be beneficial.

  4. Tests of a Two-Photon Technique for Measuring Polarization Mode Dispersion With Subfemtosecond Precision

    PubMed Central

    Dauler, Eric; Jaeger, Gregg; Muller, Antoine; Migdall, A.; Sergienko, A.

    1999-01-01

    An investigation is made of a recently introduced quantum interferometric method capable of measuring polarization mode dispersion (PMD) on sub-femtosecond scales, without the usual interferometric stability problems associated with such small time scales. The technique makes use of the extreme temporal correlation of orthogonally polarized pairs of photons produced via type-II phase-matched spontaneous parametric down-conversion. When sent into a simple polarization interferometer these photon pairs produce a sharp interference feature seen in the coincidence rate. The PMD of a given sample is determined from the shift of that interference feature as the sample is inserted into the system. The stability and resolution of this technique is shown to be below 0.2 fs. We explore how this precision is improved by reducing the length of the down-conversion crystal and increasing the spectral band pass of the system.

  5. High precision EPR dosimetry as a reference tool for validation of other techniques.

    PubMed

    Chumak, V V; Sholom, S V; Bakhanova, E V; Pasalskaya, L F; Musijachenko, A V

    2005-02-01

    We present here a particular application area for EPR dosimetry with teeth--use as a source of reference dose values for validation/verification of other retrospective dosimetry techniques and existing dose records. The conditions of application of EPR dosimetry in this role as well as practical design of such studies are shown. Particular attention is given to the requirements to the techniques in terms of precision and throughput, as well as to the issue of availability of samples for analysis and practical solution of this problem. Practical application of this approach is illustrated by several examples of completed validation sub-studies, which were performed in the framework of large-scale post-Chernobyl epidemiological studies. PMID:15607440

  6. Comparison study on disturbance estimation techniques in precise slow motion control

    NASA Astrophysics Data System (ADS)

    Fan, S.; Nagamune, R.; Altintas, Y.; Fan, D.; Zhang, Z.

    2010-08-01

    Precise low speed motion control is important for the industrial applications of both micro-milling machine tool feed drives and electro-optical tracking servo systems. It calls for precise position and instantaneous velocity measurement and disturbance, which involves direct drive motor force ripple, guide way friction and cutting force etc., estimation. This paper presents a comparison study on dynamic response and noise rejection performance of three existing disturbance estimation techniques, including the time-delayed estimators, the state augmented Kalman Filters and the conventional disturbance observers. The design technique essentials of these three disturbance estimators are introduced. For designing time-delayed estimators, it is proposed to substitute Kalman Filter for Luenberger state observer to improve noise suppression performance. The results show that the noise rejection performances of the state augmented Kalman Filters and the time-delayed estimators are much better than the conventional disturbance observers. These two estimators can give not only the estimation of the disturbance but also the low noise level estimations of position and instantaneous velocity. The bandwidth of the state augmented Kalman Filters is wider than the time-delayed estimators. In addition, the state augmented Kalman Filters can give unbiased estimations of the slow varying disturbance and the instantaneous velocity, while the time-delayed estimators can not. The simulation and experiment conducted on X axis of a 2.5-axis prototype micro milling machine are provided.

  7. Effect of bite tray impression technique on relocation accuracy in frameless stereotactic radiotherapy

    SciTech Connect

    Herbert, Clare E.; Ebert, Martin A.; Barclay, D.; Whittall, David S.; Joseph, David J.; Harper, Chris S.; Spry, Nigel A

    2003-03-31

    A previously developed method for achieving patient relocation in fractionated stereotactic radiotherapy (attachment of an infrared fiducial system to a bite tray) relies on the integrity of a bite tray system that incorporates moulding to the patient's upper dentition. Reproducible and accurate patient positioning requires stability of the bite tray and mould during the full treatment process, both during the time the bite tray is inserted in the patient's mouth, and between separate bite tray insertions. The optimum construction method for a stable reproducible tray has not been sufficiently investigated. We undertook a study to identify factors which might influence the integrity of the hard palate bite tray system. Reprosil Fast Set Putty was used to construct 3 impression conditions; teeth only; teeth and alveolar sulcus; and teeth, alveolar sulcus, and the hard palate. Reproducibility was assessed by volunteers inserting the impressions multiple times and recording the locations of 8 standard reference points. Our results showed the optimal impression technique (i.e., the one that led to the smallest ranges in positional and rotational errors) was that which incorporated the teeth, alveolar sulcus, and hard palate.

  8. Hippocampal-Sparing Whole-Brain Radiotherapy: A 'How-To' Technique Using Helical Tomotherapy and Linear Accelerator-Based Intensity-Modulated Radiotherapy

    SciTech Connect

    Gondi, Vinai; Tolakanahalli, Ranjini; Mehta, Minesh P.; Tewatia, Dinesh; Rowley, Howard; Kuo, John S.; Khuntia, Deepak; Tome, Wolfgang A.

    2010-11-15

    Purpose: Sparing the hippocampus during cranial irradiation poses important technical challenges with respect to contouring and treatment planning. Herein we report our preliminary experience with whole-brain radiotherapy using hippocampal sparing for patients with brain metastases. Methods and Materials: Five anonymous patients previously treated with whole-brain radiotherapy with hippocampal sparing were reviewed. The hippocampus was contoured, and hippocampal avoidance regions were created using a 5-mm volumetric expansion around the hippocampus. Helical tomotherapy and linear accelerator (LINAC)-based intensity-modulated radiotherapy (IMRT) treatment plans were generated for a prescription dose of 30 Gy in 10 fractions. Results: On average, the hippocampal avoidance volume was 3.3 cm{sup 3}, occupying 2.1% of the whole-brain planned target volume. Helical tomotherapy spared the hippocampus, with a median dose of 5.5 Gy and maximum dose of 12.8 Gy. LINAC-based IMRT spared the hippocampus, with a median dose of 7.8 Gy and maximum dose of 15.3 Gy. On a per-fraction basis, mean dose to the hippocampus (normalized to 2-Gy fractions) was reduced by 87% to 0.49 Gy{sub 2} using helical tomotherapy and by 81% to 0.73 Gy{sub 2} using LINAC-based IMRT. Target coverage and homogeneity was acceptable with both IMRT modalities, with differences largely attributed to more rapid dose fall-off with helical tomotherapy. Conclusion: Modern IMRT techniques allow for sparing of the hippocampus with acceptable target coverage and homogeneity. Based on compelling preclinical evidence, a Phase II cooperative group trial has been developed to test the postulated neurocognitive benefit.

  9. Centimeter-level group-delay altimetric precision using the new PARIS interferometric technique

    NASA Astrophysics Data System (ADS)

    Cardellach, E.; Nogues-Correig, O.; Ribo, S.; Rius, A.; Camps, A.; van der Marel, H.; Martin-Neira, M.

    2010-12-01

    Since its suggestion in 1993, the altimetric and scatterometric capabilities of the PAssive Reflectometry and Interferometry System (PARIS) have been tested extensively from ground- air- and even space-based experiments. The concept is based in the use of the Global Navigation Satellite System (GNSS) signals reflected off the Earth (Ocean, Ice, Land), in a bi-static radar configuration. ESA has proposed to use the PARIS Interferometric Technique in the future PARIS In-Orbit Demonstrator Instrument (PARIS-IOD). This is a novel instrumental approach respect to previous PARIS instruments which obtained the observables through cross-correlating direct and reflected signals against a GPS signal model (or replica). The limit of such an altimetric approach was given by the availability of the open-access GNSS codes. The new interferometric technique aligns the direct and reflected signals and directly computes the cross-correlation between them. Therefore, also encrypted signals can be used, increasing the available signal bandwidth and power, and thus the expected precision of the altimetric measurement. This project contributes to the PARIS-IOD concept trying to demonstrate the suitability of the interferometric technique for altimetric purposes, as well as to study and demonstrate the proposed calibration techniques for the PARIS-IOD instrument. We aim to confirm whether the interferometric technique is capable of measuring GPS signal delay differences with an associated 1 sigma error of 3 cm with 1 second of observation time. The first step to accomplish the objective of the activity was to build the appropriate receiver, able to perform the direct correlation of the signals. This was achieved by modifying the existing dedicated full-custom GNSS-Reflection Receiver GPS Open Loop Differential Real-Time Receiver (GOLD-RTR). The proof-of-concept instrument has been tested in two campaigns, during June and July 2010. The first campaign used synthetic signals generated by

  10. Technical advances in external radiotherapy for hepatocellular carcinoma

    PubMed Central

    Park, Shin-Hyung; Kim, Jae-Chul; Kang, Min Kyu

    2016-01-01

    Radiotherapy techniques have substantially improved in the last two decades. After the introduction of 3-dimensional conformal radiotherapy, radiotherapy has been increasingly used for the treatment of hepatocellular carcinoma (HCC). Currently, more advanced techniques, including intensity-modulated radiotherapy (IMRT), stereotactic ablative body radiotherapy (SABR), and charged particle therapy, are used for the treatment of HCC. IMRT can escalate the tumor dose while sparing the normal tissue even though the tumor is large or located near critical organs. SABR can deliver a very high radiation dose to small HCCs in a few fractions, leading to high local control rates of 84%-100%. Various advanced imaging modalities are used for radiotherapy planning and delivery to improve the precision of radiotherapy. These advanced techniques enable the delivery of high dose radiotherapy for early to advanced HCCs without increasing the radiation-induced toxicities. However, as there have been no effective tools for the prediction of the response to radiotherapy or recurrences within or outside the radiation field, future studies should focus on selecting the patients who will benefit from radiotherapy. PMID:27621577

  11. Technical advances in external radiotherapy for hepatocellular carcinoma.

    PubMed

    Park, Shin-Hyung; Kim, Jae-Chul; Kang, Min Kyu

    2016-08-28

    Radiotherapy techniques have substantially improved in the last two decades. After the introduction of 3-dimensional conformal radiotherapy, radiotherapy has been increasingly used for the treatment of hepatocellular carcinoma (HCC). Currently, more advanced techniques, including intensity-modulated radiotherapy (IMRT), stereotactic ablative body radiotherapy (SABR), and charged particle therapy, are used for the treatment of HCC. IMRT can escalate the tumor dose while sparing the normal tissue even though the tumor is large or located near critical organs. SABR can deliver a very high radiation dose to small HCCs in a few fractions, leading to high local control rates of 84%-100%. Various advanced imaging modalities are used for radiotherapy planning and delivery to improve the precision of radiotherapy. These advanced techniques enable the delivery of high dose radiotherapy for early to advanced HCCs without increasing the radiation-induced toxicities. However, as there have been no effective tools for the prediction of the response to radiotherapy or recurrences within or outside the radiation field, future studies should focus on selecting the patients who will benefit from radiotherapy. PMID:27621577

  12. [Radiotherapy Techniques and Radiation Pneumonitis: A Lot To A Little Or A Little To A Lot?].

    PubMed

    Yu, Bingqi; Wang, Jin; Xu, Yujin; Su, Feng; Shan, Guoping; Chen, Ming

    2015-12-01

    Radiotherapy is one of the main treatment for patients with lung cancer. Three-dimensional conformal radiation therapy (3D-CRT) and intensity modulated radiation therapy (IMRT) are widely used to deliver radiation. Here, we focus on the correlations between dose distribution in lung and radiation pneumonitis according to the analysis about radiotherapy for lung cancer: A lot to a little or a little to a lot, which is the main cause of radiation pneumonitis? PMID:26706952

  13. Near-real-time regional troposphere models for the GNSS precise point positioning technique

    NASA Astrophysics Data System (ADS)

    Hadas, T.; Kaplon, J.; Bosy, J.; Sierny, J.; Wilgan, K.

    2013-05-01

    The GNSS precise point positioning (PPP) technique requires high quality product (orbits and clocks) application, since their error directly affects the quality of positioning. For real-time purposes it is possible to utilize ultra-rapid precise orbits and clocks which are disseminated through the Internet. In order to eliminate as many unknown parameters as possible, one may introduce external information on zenith troposphere delay (ZTD). It is desirable that the a priori model is accurate and reliable, especially for real-time application. One of the open problems in GNSS positioning is troposphere delay modelling on the basis of ground meteorological observations. Institute of Geodesy and Geoinformatics of Wroclaw University of Environmental and Life Sciences (IGG WUELS) has developed two independent regional troposphere models for the territory of Poland. The first one is estimated in near-real-time regime using GNSS data from a Polish ground-based augmentation system named ASG-EUPOS established by Polish Head Office of Geodesy and Cartography (GUGiK) in 2008. The second one is based on meteorological parameters (temperature, pressure and humidity) gathered from various meteorological networks operating over the area of Poland and surrounding countries. This paper describes the methodology of both model calculation and verification. It also presents results of applying various ZTD models into kinematic PPP in the post-processing mode using Bernese GPS Software. Positioning results were used to assess the quality of the developed models during changing weather conditions. Finally, the impact of model application to simulated real-time PPP on precision, accuracy and convergence time is discussed.

  14. Development of Techniques for a Precision Neutron EDM Measurement at RCNP

    NASA Astrophysics Data System (ADS)

    Matsumiya, Ryohei; Masuda, Yasuhiro; Kawasaki, Shinsuke; Jeong, Sun-Chan; Watanabe, Yutaka; Hatanaka, Kichiji; Pierre, Edgard; Shin, Yunchang; Matsuta, Kensaku; Mihara, Mototsugu

    2014-09-01

    A non-zero neutron electric dipole moment (nEDM) breaks the time-reversal symmetry. A precision measurement of the nEDM is expected to be a good probe to search for theories beyond the standard model. We have been developing techniques for a nEDM measurement, using a high intensity ultra-cold neutron (UCN) source developed by the collaboration between KEK and RCNP. We have succeeded to polarize UCNs by a super conducting polarizer, and stored them in a cell. This cell will be installed in static magnetic and electric fields for a nEDM observation by the Ramsey separated-oscillatory-field magnetic resonance method. The homogeneity of the magnetic field is being improved aiming to increase the transverse relaxation time T2. A multilayered magnetic shielding and a compensation coil system was developed to cancel the geomagnetic field. Some materials around the cell which were not completely non-magnetic were replaced. We are developing a 129Xe co-magnetometer for the high precision field monitoring, and a high voltage system including electrodes with minimum UCN losses. In this talk, the present status of these apparatuses will be discussed.

  15. LAMOST fiber unit positional precision passive detection exploiting the technique of template matching

    NASA Astrophysics Data System (ADS)

    Wang, Mengxin; Zhao, Yongheng; Luo, Ali

    2012-09-01

    The large sky area multi-object fiber spectroscopic telescope (LAMOST) is an innovative reflecting schmidt telescope, promising a very high spectrum acquiring rate of several ten-thousands of spectra per night. By using the parallel controllable fiber positioning technique, LAMOST makes reconfiguration of fibers accurately according to the positions of objects in minutes and fine adjusting the fibers. As a key problem, High precision positioning detection of LAMOST fiber positioning unit has always been highly regarded and some detection schemes have been proposed. Among these, active detection method, which determines the final accurate position of optical fiber end with the help of lighting the fiber, has been most widely researched, but this kind of method could not be applied in LAMOST real-time observation because it needs projecting light into fiber. A novel detection idea exploiting the technique of template matching is presented in this paper. As we know, final position of a specific fiber end can be easily inferred by its corresponding revolving angles of the central revolving axle and bias revolving axle in double revolving style, so the key point in this problem is converted to the accurate determination of these revolving angles. Template matching technique are explored to acquire the matching parameters for its real-time collected imagery, and thus determine the corresponding revolving angle of the central revolving axle and bias revolving axle respectively. Experiments results obtained with data acquired from LAMOST site are used to verify the feasibility and effectiveness of this novel method.

  16. Region-growing technique adapted to precise microcalcification characterization in mammography

    NASA Astrophysics Data System (ADS)

    Darboux, Michel; Dinten, Jean-Marc; Nicolas, Eric

    1996-11-01

    The early detection of breast cancer is essential for increasing the survival rate of the disease. Today, mammography is the only breast screening technique capable of detecting breast cancer at a very early stage. The presence of a breast tumor is indicated by some features on the mammogram. One sign of malignancy is the presence of clusters of fine, granular microcalcifications. We present here a three-step method for detecting and characterizing these microcalcifications. We begin with the detection of potential candidates. The aim of this first step is to detect all the pixels that could be a microcalcification. Then we focus on our specific region growing technique which provides an accurate extraction of the shape of the region corresponding to each detected growing technique which provides an accurate extraction of the shape of the region corresponding to each detected seed. This second step is essential because microcalcifications shape is a very important feature for the diagnosis. It is then possible to determine precise parameters to characterize these microcalcifications. This three-step method has been evaluated on a set of images form the mammographic image analysis society database.

  17. Precise plant breeding using new genome editing techniques: opportunities, safety and regulation in the EU.

    PubMed

    Hartung, Frank; Schiemann, Joachim

    2014-06-01

    Several new plant breeding techniques (NPBTs) have been developed during the last decade, and make it possible to precisely perform genome modifications in plants. The major problem, other than technical aspects, is the vagueness of regulation concerning these new techniques. Since the definition of eight NPBTs by a European expert group in 2007, there has been an ongoing debate on whether the resulting plants and their products are covered by GMO legislation. Obviously, cover by GMO legislation would severely hamper the use of NPBT, because genetically modified plants must pass a costly and time-consuming GMO approval procedure in the EU. In this review, we compare some of the NPBTs defined by the EU expert group with classical breeding techniques and conventional transgenic plants. The list of NPBTs may be shortened (or extended) during the international discussion process initiated by the Organization for Economic Co-operation and Development. From the scientific point of view, it may be argued that plants developed by NPBTs are often indistinguishable from classically bred plants and are not expected to possess higher risks for health and the environment. In light of the debate on the future regulation of NPBTs and the accumulated evidence on the biosafety of genetically modified plants that have been commercialized and risk-assessed worldwide, it may be suggested that plants modified by crop genetic improvement technologies, including genetic modification, NPBTs or other future techniques, should be evaluated according to the new trait and the resulting end product rather than the technique used to create the new plant variety. PMID:24330272

  18. EDITORIAL: International Workshop on Monte Carlo Techniques in Radiotherapy Delivery and Verification

    NASA Astrophysics Data System (ADS)

    Verhaegen, Frank; Seuntjens, Jan

    2008-03-01

    Monte Carlo particle transport techniques offer exciting tools for radiotherapy research, where they play an increasingly important role. Topics of research related to clinical applications range from treatment planning, motion and registration studies, brachytherapy, verification imaging and dosimetry. The International Workshop on Monte Carlo Techniques in Radiotherapy Delivery and Verification took place in a hotel in Montreal in French Canada, from 29 May-1 June 2007, and was the third workshop to be held on a related topic, which now seems to have become a tri-annual event. About one hundred workers from many different countries participated in the four-day meeting. Seventeen experts in the field were invited to review topics and present their latest work. About half of the audience was made up by young graduate students. In a very full program, 57 papers were presented and 10 posters were on display during most of the meeting. On the evening of the third day a boat trip around the island of Montreal allowed participants to enjoy the city views, and to sample the local cuisine. The topics covered at the workshop included the latest developments in the most popular Monte Carlo transport algorithms, fast Monte Carlo, statistical issues, source modeling, MC treatment planning, modeling of imaging devices for treatment verification, registration and deformation of images and a sizeable number of contributions on brachytherapy. In this volume you will find 27 short papers resulting from the workshop on a variety of topics, some of them on very new stuff such as graphics processing units for fast computing, PET modeling, dual-energy CT, calculations in dynamic phantoms, tomotherapy devices, . . . . We acknowledge the financial support of the National Cancer Institute of Canada, the Institute of Cancer Research of the Canadian Institutes of Health Research, the Association Québécoise des Physicien(ne)s Médicaux Clinique, the Institute of Physics, and Medical

  19. Investigation of pulsed low dose rate radiotherapy using dynamic arc delivery techniques

    NASA Astrophysics Data System (ADS)

    Ma, C.-M.; Lin, M. H.; Dai, X. F.; Koren, Sion; Klayton, T.; Wang, L.; Li, J. S.; Chen, L.; Price, R. A.

    2012-07-01

    There has been no consensus standard of care to treat recurrent cancer patients who have previously been irradiated. Pulsed low dose rate (PLDR) external beam radiotherapy has the potential to reduce normal tissue toxicities while still providing significant tumor control for recurrent cancers. This work investigates the dosimetry feasibility of PLDR treatment using dynamic arc delivery techniques. Five treatment sites were investigated in this study including breast, pancreas, prostate, head and neck, and lung. Dynamic arc plans were generated using the Varian Eclipse system and the RapidArc delivery technique with 6 and 10 MV photon beams. Each RapidArc plan consisted of two full arcs and the plan was delivered five times to achieve a daily dose of 200 cGy. The dosimetry requirement was to deliver approximately 20 cGy/arc with a 3 min interval to achieve an effective dose rate of 6.7 cGy min-1. Monte Carlo simulations were performed to calculate the actual dose delivered to the planning target volume (PTV) per arc taking into account beam attenuation/scattering and intensity modulation. The maximum, minimum and mean doses to the PTV were analyzed together with the dose volume histograms and isodose distributions. The dose delivery for the five plans was validated using solid water phantoms inserted with an ionization chamber and film, and a cylindrical detector array. Two intensity-modulated arcs were used to efficiently deliver the PLDR plans that provided conformal dose distributions for treating complex recurrent cancers. For the five treatment sites, the mean PTV dose ranged from 18.9 to 22.6 cGy/arc. For breast, the minimum and maximum PTV dose was 8.3 and 35.2 cGy/arc, respectively. The PTV dose varied between 12.9 and 27.5 cGy/arc for pancreas, 12.6 and 28.3 cGy/arc for prostate, 12.1 and 30.4 cGy/arc for H&N, and 16.2 and 27.6 cGy/arc for lung. Advanced radiation therapy can provide superior target coverage and normal tissue sparing for PLDR

  20. [Application of molecular diagnostic techniques in precision medicine of personalized treatment for colorectal cancer].

    PubMed

    Fu, Ji; Lin, Guole

    2016-01-01

    Precision medicine is to customize the treatment options for individual patient based on the personal genome information. Colorectal cancer (CRC) is one of the most common cancer worldwide. Molecular heterogeneity of CRC, which includes the MSI phenotype, hypermutation phenotype, and their relationship with clinical preferences, is believed to be one of the main factors responsible for the considerable variability in treatment response. The development of powerful next-generation sequencing (NGS) technologies allows us to further understand the biological behavior of colorectal cancer, and to analyze the prognosis and chemotherapeutic drug reactions by molecular diagnostic techniques, which can guide the clinical treatment. This paper will introduce the new findings in this field. Meanwhile we integrate the new progress of key pathways including EGFR, RAS, PI3K/AKT and VEGF, and the experience in selective patients through associated molecular diagnostic screening who gain better efficacy after target therapy. The technique for detecting circulating tumor DNA (ctDNA) is introduced here as well, which can identify patients with high risk for recurrence, and demonstrate the risk of chemotherapy resistance. Mechanism of tumor drug resistance may be revealed by dynamic observation of gene alteration during treatment. PMID:26797832

  1. Technique for needle-free drop deposition: Pathway for precise characterization of superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Waghmare, Prashant R.; Das, Siddhartha; Mitra, Sushanta K.

    2013-11-01

    The most important step for characterizing the wettability of a surface is to deposit a water drop on the surface and measure the contact angle made by the drop on the surface. This innocuously simple process relies on bringing a needle holding the water drop in close proximity to the surface, with a ``desire'' that the drop would spontaneously detach from the needle and get deposited on the surface. Problem occurs when the surface is superhydrophobic, expressing an ``unwillingness'' to ``see'' the water drop in preference to a much more ``water-loving'' needle surface. There exists no solution to this problem, and surfaces are invariably characterized where the drop-needle assembly contacts the superhydrophobic surface. Such a configuration will always lead to an incorrect estimation of the contact angle, as there is no certainty of the existence of the drop-surface contact. Here we shall discuss our recently invented technique, where we solve this long-standing problem-we indeed ensure a needle-free drop in contact with the superhydrophobic surface, thereby ascertaining precise determination of the contact angle. The successful application of the technique will address a major headache of the big research community interested in science and technology of superhydrophobic surfaces.

  2. Different Techniques For Producing Precision Holes (>20 mm) In Hardened Steel—Comparative Results

    NASA Astrophysics Data System (ADS)

    Coelho, R. T.; Tanikawa, S. T.

    2009-11-01

    High speed machining (HSM), or high performance machining, has been one of the most recent technological advances. When applied to milling operations, using adequate machines, CAM programs and tooling, it allows cutting hardened steels, which was not feasible just a couple of years ago. The use of very stiff and precision machines has created the possibilities of machining holes in hardened steels, such as AISI H13 with 48-50 HRC, using helical interpolations, for example. Such process is particularly useful for holes with diameter bigger than normal solid carbide drills commercially available, around 20 mm, or higher. Such holes may need narrow tolerances, fine surface finishing, which can be obtained just by end milling operations. The present work compares some of the strategies used to obtain such holes by end milling, and also some techniques employed to finish them, by milling, boring and also by fine grinding at the same machine. Results indicate that it is possible to obtain holes with less than 0.36 m in circularity, 7.41 m in cylindricity and 0.12 m in surface roughness Ra. Additionally, there is less possibilities of obtaining heat affected layers when using such technique.

  3. A technique for evaluating cast foam positioning and immobilization devices used in breast cancer radiotherapy.

    PubMed

    McCune, K; Parsons, L; Schoenfeld, L; Maddeford, A

    1991-09-01

    Patient setup reproducibility when Alpha Cradles* are used is not well documented. A simple technique is described that localizes longitudinal and transverse planes in breast setups utilizing 4 mm lead-sphere markers embedded in a modified HS-2 Alpha Cradle. The markers are positioned in the cradle coincident with the projected simulator central axis crosshair when the x-ray beam is directed vertically down through a setup point on the patient. A reference film recording patient position relative to the Alpha Cradle is taken through the setup point at the end of the simulation procedure. On the treatment machine, the images of the lead markers on the portal film, taken through the same setup point, indicate longitudinal and transverse planes. These planes are then used to correlate and quantitate the reproducibility of the original reference planes. This technique is easily initiated, and when used in conjunction with a careful analysis of conventional treatment portal films, is very useful in determining the accuracy of patient repositioning in the Alpha Cradle, and precise field placement. Results of a study utilizing a modified HS-2 Alpha Cradle will be presented. PMID:1910468

  4. Application of Geo-Spatial Techniques for Precise Demarcation of Village/Panchayat Boundaries

    NASA Astrophysics Data System (ADS)

    Rao, S. S.; Banu, V.; Tiwari, A.; Bahuguna, S.; Uniyal, S.; Chavan, S. B.; Murthy, M. V. R.; Arya, V. S.; Nagaraja, R.; Sharma, J. R.

    2014-11-01

    In order to achieve the overall progress of the country with active and effective participation of all sections of society, the 12th Five Year Plan (FYP) would bring Panchayats centre-stage and achieve the inclusive growth agenda through inclusive governance. The concept of 'democratic decentralization' in the form of a three-tier administration was introduced in the name of "Panchayat Raj". Horizontally, it is a network of village Panchayats. Vertically, it is an organic growth of Panchayats rising up to national level. The Ministry of Panchayati Raj has three broad agenda: Empowerment, Enablement and Accountability. Space based Information Support for Decentralized Planning (SIS-DP) is one of the initiatives taken by Govt. of India with ISRO/DOS for generation and dissemination of spatial information for planning at the grass root level. The boundary layer for villages across different states/district/block is available with line departments. Most of these data exist at a much generalized scale. These boundaries do not overlay exactly with that of ground realities and may not be suitable for accurate analysis in terms of area, shape, position, etc. To deal with this problem, a strategy is adopted, which makes use of High Resolution Satellite Imagery (HRSI) from Indian Remote sensing satellites and cadastral maps at 1:4000 scale integrated with GIS techniques to enhance the accuracy of geo-spatial depiction of Village/Panchayat boundaries. Cadastral maps are used to depict the boundaries of land parcels and other features at the village level. These maps are registered to ortho products of HRSI using Ground Control Points. The cadastral maps are precisely overlaid on ortho-rectified HRSI and each parcel vertex is tagged with the real-world geographical coordinates. Village boundaries are extracted from the geo-referenced village cadastral maps. These boundaries are fine-tuned by considering under lap and overlap of neighboring villages and a mosaic is generated at

  5. Hypofractionated Accelerated Radiotherapy Using Concomitant Intensity-Modulated Radiotherapy Boost Technique for Localized High-Risk Prostate Cancer: Acute Toxicity Results

    SciTech Connect

    Lim, Tee S.; Cheung, Patrick Loblaw, D. Andrew; Morton, Gerard; Sixel, Katharina E.; Pang, Geordi; Basran, Parminder; Zhang Liying; Tirona, Romeo; Szumacher, Ewa; Danjoux, Cyril; Choo, Richard; Thomas, Gillian

    2008-09-01

    Purpose: To evaluate the acute toxicities of hypofractionated accelerated radiotherapy (RT) using a concomitant intensity-modulated RT boost in conjunction with elective pelvic nodal irradiation for high-risk prostate cancer. Methods and Materials: This report focused on 66 patients entered into this prospective Phase I study. The eligible patients had clinically localized prostate cancer with at least one of the following high-risk features (Stage T3, Gleason score {>=}8, or prostate-specific antigen level >20 ng/mL). Patients were treated with 45 Gy in 25 fractions to the pelvic lymph nodes using a conventional four-field technique. A concomitant intensity-modulated radiotherapy boost of 22.5 Gy in 25 fractions was delivered to the prostate. Thus, the prostate received 67.5 Gy in 25 fractions within 5 weeks. Next, the patients underwent 3 years of adjuvant androgen ablative therapy. Acute toxicities were assessed using the Common Terminology Criteria for Adverse Events, version 3.0, weekly during treatment and at 3 months after RT. Results: The median patient age was 71 years. The median pretreatment prostate-specific antigen level and Gleason score was 18.7 ng/L and 8, respectively. Grade 1-2 genitourinary and gastrointestinal toxicities were common during RT but most had settled at 3 months after treatment. Only 5 patients had acute Grade 3 genitourinary toxicity, in the form of urinary incontinence (n = 1), urinary frequency/urgency (n = 3), and urinary retention (n = 1). None of the patients developed Grade 3 or greater gastrointestinal or Grade 4 or greater genitourinary toxicity. Conclusion: The results of the present study have indicated that hypofractionated accelerated RT with a concomitant intensity-modulated RT boost and pelvic nodal irradiation is feasible with acceptable acute toxicity.

  6. The precision of bacterial quantification techniques on different kinds of environmental samples and the effect of ultrasonic treatment.

    PubMed

    Böllmann, Jörg; Rathsack, Kristina; Martienssen, Marion

    2016-07-01

    The precision of cell number quantification in environmental samples depends on the complexity of the sample and on the applied technique. We compared fluorescence microscopy after filtration, quantification of gene copies and the cultivation based most probable number technique for their precision. We further analyzed the effect of increasing complexity of the sample material on the precision of the different methods by using pure cultures of Pseudomonas aeruginosa, fresh water samples and sediment slurries with and without ultrasonic treatment for analyses. Microscopy reached the highest precision, which was similar between pure cultures and water samples, but lower for sediment samples due to a higher percentage of cells in clusters and flocks. The PCR based quantification was most precise for pure cultures. Water and sediment samples were similar but less precise, which might be caused by the applied DNA extraction techniques. MPN measurements were equally precise for pure cultures and water samples. For sediment slurries the precision was slightly lower. The applied ultrasonic treatment of the slurries dispersed the cell clusters and flocks, increased the precision of microscopical and MPN measurements and also increased the number of potential colony forming units. However, the culturable cell number decreased by half. For MPN quantification of viable cells in samples with a high proportion of clustered cells we therefore recommend an optimization of ultrasonic treatment and a confirmation by microscopy and cultivation to reach highest possible dispersion of the cells with a minimum of inactivation. As a result of these observations we suggest a correction factor for MPN measurements to consider the effect of sonication on complex samples. The results are most likely applicable to other complex samples such as soil or biofilms. PMID:27184085

  7. A novel two-step laser ranging technique for a precision test of the theory of gravity

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin; Chui, Talso

    2003-01-01

    All powered spacecraft experience residual systematic acceleration due to anisotropy of the thermal radiation pressure and fuel leakage. The residual acceleration limits the accuracy of any test of gravity that relies on the precise determination of the spacecraft trajectory. We describe a novel two-step laser ranging technique, which largely eliminates the effects of non-gravity acceleration sources and enables celestial mechanics checks with unprecedented precision.

  8. Experimental Technique for Producing and Recording Precise Particle Impacts on Transparent Window Materials

    NASA Technical Reports Server (NTRS)

    Gray, Perry; Guven, Ibrahim

    2016-01-01

    A new facility for making small particle impacts is being developed at NASA. Current sand/particle impact facilities are an erosion test and do not precisely measure and document the size and velocity of each of the impacting particles. In addition, evidence of individual impacts is often obscured by subsequent impacts. This facility will allow the number, size, and velocity of each particle to be measured and adjusted. It will also be possible to determine which particle produced damage at a given location on the target. The particle size and velocity will be measured by high speed imaging techniques. Information as to the extent of damage and debris from impacts will also be recorded. It will be possible to track these secondary particles, measuring size and velocity. It is anticipated that this additional degree of detail will provide input for erosion models and also help determine the impact physics of the erosion process. Particle impacts will be recorded at 90 degrees to the particle flight path and also from the top looking through the target window material.

  9. Precision lifetime measurements of exotic nuclei based on Doppler-shift techniques

    SciTech Connect

    Iwasaki, Hironori

    2013-04-19

    A recent progress in precision lifetime measurements of exotic nuclei at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University is presented. The Recoil Distance Doppler-shift (RDDS) technique has been applied to nuclear reactions involving intermediate-energy rare isotope (RI) beams, to determine absolute transition strengths between nuclear states model independently from level lifetimes of interest. As such an example, recent lifetime measurements of the first 2{sup +} states in the neutron-rich {sup 62,64,66}Fe isotopes at and around N=40 are introduced. The experiment was performed at the Coupled Cyclotron Facility at NSCL using a unique combination of several experimental instruments; the Segmented Germanium Array (SeGA), the plunger device, and the S800 spectrograph. The reduced E2 transition probabilities B(E2) are determined directly from the measured lifetimes. The observed trend of B(E2) clearly demonstrates that an enhanced collectivity persists in {sup 66}Fe despite the harmonic-oscillator magic number N=40. The present results are also discussed in comparison with the large-scale shell model calculations, pointing to a possible extension of the deformation region beyond N=40.

  10. Accuracy improvement techniques in Precise Point Positioning method using multiple GNSS constellations

    NASA Astrophysics Data System (ADS)

    Vasileios Psychas, Dimitrios; Delikaraoglou, Demitris

    2016-04-01

    The future Global Navigation Satellite Systems (GNSS), including modernized GPS, GLONASS, Galileo and BeiDou, offer three or more signal carriers for civilian use and much more redundant observables. The additional frequencies can significantly improve the capabilities of the traditional geodetic techniques based on GPS signals at two frequencies, especially with regard to the availability, accuracy, interoperability and integrity of high-precision GNSS applications. Furthermore, highly redundant measurements can allow for robust simultaneous estimation of static or mobile user states including more parameters such as real-time tropospheric biases and more reliable ambiguity resolution estimates. This paper presents an investigation and analysis of accuracy improvement techniques in the Precise Point Positioning (PPP) method using signals from the fully operational (GPS and GLONASS), as well as the emerging (Galileo and BeiDou) GNSS systems. The main aim was to determine the improvement in both the positioning accuracy achieved and the time convergence it takes to achieve geodetic-level (10 cm or less) accuracy. To this end, freely available observation data from the recent Multi-GNSS Experiment (MGEX) of the International GNSS Service, as well as the open source program RTKLIB were used. Following a brief background of the PPP technique and the scope of MGEX, the paper outlines the various observational scenarios that were used in order to test various data processing aspects of PPP solutions with multi-frequency, multi-constellation GNSS systems. Results from the processing of multi-GNSS observation data from selected permanent MGEX stations are presented and useful conclusions and recommendations for further research are drawn. As shown, data fusion from GPS, GLONASS, Galileo and BeiDou systems is becoming increasingly significant nowadays resulting in a position accuracy increase (mostly in the less favorable East direction) and a large reduction of convergence

  11. Lung cancer. Radiotherapy in lung cancer: Actual methods and future trends

    PubMed Central

    Maciejczyk, Adam; Skrzypczyńska, Iga; Janiszewska, Marzena

    2014-01-01

    This survey is performed to update knowledge about methods and trends in lung cancer radiotherapy. A significant development has been noticed in radiotherapeutic techniques, but also in the identification of clinical prognostic factors. The improvement in the therapeutic line includes: application of the four-dimensional computer tomography (4DCT), taking advantage of positron emission tomography (PET-CT), designing of new computational algorithms, allowing more precise irradiation planning, development of treatment precision verification systems and introducing IMRT techniques in chest radiotherapy. The treatment outcomes have improved with high dose radiotherapy, but other fractionation alternations have been investigated as well. PMID:25337407

  12. Precision, high dose radiotherapy. II. Helium ion treatment of tumors adjacent to critical central nervous system structures

    SciTech Connect

    Saunders, W.M.; Chen, G.T.Y.; Austin-Seymour, M.; Castro, J.R.; Collier, J.M.; Gauger, G.; Gutin, P.; Phillips, T.L.; Pitluck, S.; Walton, R.E.

    1985-07-01

    In this paper, the authors present a technique for treating relatively small, low grade tumors located very close to critical, radiation sensitive central nervous system structures such as the spinal cord and the brain stem. A beam of helium ions is used to irradiate the tumor. The nearby normal tissues are protected by exploiting the superb dose localization properties of this beam, particularly its well defined and controllable range in tissue, the increased dose deposited near the end of this range (i.e., the Bragg peak), the sharp decrease in dose beyond the Bragg peak, and the sharp penumbra of the beam. To illustrate the technique, the authors present a group of 19 patients treated for chordomas, meningiomas and low grade chondrosarcomas in the base of the skull or spinal column. They have been able to deliver high, uniform doses to the target volumes, while keeping the doses to the nearby critical tissues below the threshold for radiation damage. Follow-up on this group of patients is short, averaging 22 months (2 to 75 months). Currently, 15 patients have local control of their tumor. Two major complications, a spinal cord transsection and optic tract damage, are discussed in detail. Their treatment policies have been modified to minimize the risk of these complications in the future, and they are continuing to use this method to treat such patients.

  13. A dosimetry technique for measuring kilovoltage cone-beam CT dose on a linear accelerator using radiotherapy equipment.

    PubMed

    Scandurra, Daniel; Lawford, Catherine E

    2014-01-01

    This work develops a technique for kilovoltage cone-beam CT (CBCT) dosimetry that incorporates both point dose and integral dose in the form of dose length product, and uses readily available radiotherapy equipment. The dose from imaging protocols for a range of imaging parameters and treatment sites was evaluated. Conventional CT dosimetry using 100 mm long pencil chambers has been shown to be inadequate for the large fields in CBCT and has been replaced in this work by a combination of point dose and integral dose. Absolute dose measurements were made with a small volume ion chamber at the central slice of a radiotherapy phantom. Beam profiles were measured using a linear diode array large enough to capture the entire imaging field. These profiles were normalized to absolute dose to form dose line integrals, which were then weighted with radial depth to form the DLPCBCT. This metric is analogous to the standard dose length product (DLP), but derived differently to suit the unique properties of CBCT. Imaging protocols for head and neck, chest, and prostate sites delivered absolute doses of 0.9, 2.2, and 2.9 cGy to the center of the phantom, and DLPCBCT of 28.2, 665.1, and 565.3mGy.cm, respectively. Results are displayed as dose per 100 mAs and as a function of key imaging parameters such as kVp, mAs, and collimator selection in a summary table. DLPCBCT was found to correlate closely with the dimension of the imaging region and provided a good indication of integral dose. It is important to assess integral dose when determining radiation doses to patients using CBCT. By incorporating measured beam profiles and DLP, this technique provides a CBCT dosimetry in radiotherapy phantoms and allows the prediction of imaging dose for new CBCT protocols. PMID:25207398

  14. Modified complete-arch impression technique for facilitating esthetic and biomechanical precision in complete-arch rehabilitation.

    PubMed

    Mizrahi, Basil

    2011-08-01

    Treating complex cases is clinically and technically challenging, yet highly rewarding to both patient and clinician when successfully completed. Precision in the fit of the restorations, the definitive occlusal scheme, and the esthetic result are the key elements to long-term success. Clinicians should aim to achieve the same level of precision when treating these cases as they do when treating simple cases; however, with the numerous stages and increased complexity involved comes the potential for errors to compound and magnify as treatment progresses. Areas particularly prone to difficulties are the making of a complete-arch impression and the ability to maintain patient comfort and eliminate unwanted dental emergencies throughout the time-consuming treatment. This report illustrates the techniques and concepts used to achieve esthetic and biomechanical precision when treating complex cases. Specific emphasis is placed on the importance of an accurate complete-arch impression technique, the detail of which is described in the article. PMID:21843229

  15. Stereotactic Body Radiotherapy as Monotherapy or Post-External Beam Radiotherapy Boost for Prostate Cancer: Technique, Early Toxicity, and PSA Response

    SciTech Connect

    Jabbari, Siavash; Weinberg, Vivian K.; Kaprealian, Tania; Hsu, I-Chow; Ma Lijun; Chuang, Cynthia; Descovich, Martina; Shiao, Stephen; Shinohara, Katsuto; Roach, Mack; Gottschalk, Alexander R.

    2012-01-01

    Purpose: High dose rate (HDR) brachytherapy has been established as an excellent monotherapy or after external-beam radiotherapy (EBRT) boost treatment for prostate cancer (PCa). Recently, dosimetric studies have demonstrated the potential for achieving similar dosimetry with stereotactic body radiotherapy (SBRT) compared with HDR brachytherapy. Here, we report our technique, PSA nadir, and acute and late toxicity with SBRT as monotherapy and post-EBRT boost for PCa using HDR brachytherapy fractionation. Patients and Methods: To date, 38 patients have been treated with SBRT at University of California-San Francisco with a minimum follow-up of 12 months. Twenty of 38 patients were treated with SBRT monotherapy (9.5 Gy Multiplication-Sign 4 fractions), and 18 were treated with SBRT boost (9.5 Gy Multiplication-Sign 2 fractions) post-EBRT and androgen deprivation therapy. PSA nadir to date for 44 HDR brachytherapy boost patients with disease characteristics similar to the SBRT boost cohort was also analyzed as a descriptive comparison. Results: SBRT was well tolerated. With a median follow-up of 18.3 months (range, 12.6-43.5), 42% and 11% of patients had acute Grade 2 gastrourinary and gastrointestinal toxicity, respectively, with no Grade 3 or higher acute toxicity to date. Two patients experienced late Grade 3 GU toxicity. All patients are without evidence of biochemical or clinical progression to date, and favorably low PSA nadirs have been observed with a current median PSA nadir of 0.35 ng/mL (range, <0.01-2.1) for all patients (0.47 ng/mL, range, 0.2-2.1 for the monotherapy cohort; 0.10 ng/mL, range, 0.01-0.5 for the boost cohort). With a median follow-up of 48.6 months (range, 16.4-87.8), the comparable HDR brachytherapy boost cohort has achieved a median PSA nadir of 0.09 ng/mL (range, 0.0-3.3). Conclusions: Early results with SBRT monotherapy and post-EBRT boost for PCa demonstrate acceptable PSA response and minimal toxicity. PSA nadir with SBRT boost

  16. Comparison of a simple dose-guided intervention technique for prostate radiotherapy with existing anatomical image guidance methods

    PubMed Central

    Smyth, G; Mccallum, H M; Pearson, M J M; Lawrence, G P

    2012-01-01

    Objectives A simple dose-guided intervention technique for prostate radiotherapy using an isodose overlay method combined with soft-tissue-based corrective couch shifts has been proposed previously. This planning study assesses the potential clinical impact of such a correction strategy. Methods 10 patients, each with 8–11 on-treatment CT studies (n=97), were assessed using this technique and compared with no intervention, bony anatomy intervention and soft-tissue intervention methods. Each assessment technique used a 4-mm action level for intervention. Outcomes were evaluated using measures of sensitivity, specificity and dosimetric effect, and compared across intervention techniques. Dosimetric effect was defined as the change in dosimetric coverage by the 95% isodose from the no intervention case of an evaluation construct called the verification target volume. Results Bony anatomy, soft tissue and dosimetric overlay-based interventions demonstrated sensitivity of 0.56, 0.73 and 1.00 and specificity of 0.64, 0.20 and 0.66, respectively. A detrimental dosimetric effect was shown in 7% of interventions for each technique, with benefit in 30%, 35% and 55% for bony anatomy, soft tissue and dosimetric overlay techniques, respectively. Conclusion Used in conjunction with soft-tissue-based corrective couch shifts, the dosimetric overlay technique allows effective filtering out of dosimetrically unnecessary interventions, making it more likely that any intervention made will result in improved target volume coverage. PMID:21385920

  17. Development of a novel treatment planning test for credentialing rotational intensity-modulated radiotherapy techniques in the UK

    PubMed Central

    Ciurlionis, L; Clark, C; Venables, K

    2013-01-01

    Objective: The increasing use of tomotherapy and volumetric-modulated arc therapy in UK centres will result in more centres choosing to use this technology in a clinical trial setting. The Radiotherapy Trials Quality Assurance (RTTQA) group has developed a new procedure to integrate into the UK intensity-modulated radiotherapy (IMRT) credentialing programme to cover rotational IMRT delivery techniques. Methods: A planning test [three-dimensional treatment planning system (3DTPS)] was designed specifically for rotational IMRT techniques. The feasibility of using this test in the credentialing programme for rotational IMRT was validated by 10 experienced UK centres. The study included five centres using Varian RapidArc™ (RA) (Varian Medical Systems, Milpitas, CA), two using Elekta VMAT™ (VMAT) (Elekta Inc., Norcross, GA) and three using helical tomotherapy (HT) plans. Centres were asked to carry out their own in-house quality assurance (QA) for the plans submitted for this study. A survey was sent out to centres aiming to gather information on their experience in undertaking the exercise and their QA results. Results: All centres fulfilled the primary goal by achieving the dose constraints of the primary planning target volume and organ at risk. Seven centres (three RA, one VMAT and three HT plans) were able to fulfil the secondary goal. Among those seven centres, three centres (two RA and one VMAT plans) achieved the tertiary goal. The results of the survey indicated that the 3DTPS test is a clinically relevant and practical planning test to be used. Conclusion: A planning test for rotational therapy techniques was developed for the RTTQA IMRT credentialing programme. Advances in knowledge: This study validated the feasibility of a 3DTPS test to be used as part of a credentialing programme for rotational IMRT techniques in the UK. PMID:23385993

  18. A novel method of island blocking in whole abdominal radiotherapy using a modified electronic tissue compensation technique.

    PubMed

    Goyal, Sharad; Osusky, Kate; Gabel, Molly; Yue, Ning J; Narra, Venkat

    2010-01-01

    Traditionally, large fields requiring island blocking used external beam radiation therapy (EBRT) with Cerrobend blocks to limit dose to the critical structures. It is laborious to construct blocks and use them on a daily basis. We present a novel technique for island blocking using a modified electronic tissue compensation (MECOMP) technique. Five patients treated at our institution were selected for this study. The study compared two planning techniques: a novel MECOMP and a conventional EBRT technique. Conventional fields were defined using anterior-posterior and posterior-anterior (PA) fields. The kidneys were contoured and an aperture cut-out block was fitted to the OAR with a 1-cm margin (OAR(CTV)) and placed in the PA field. A dynamic multileaf collimation (DMLC) plan with ECOMP was developed using identical beam and blocking strategy; this tissue compensation-based fluence map was modified to deliver a "zero" dose to the CTV(OAR) from the PA field. There were no significant differences in the mean, maximum, and minimum doses to the right or left kidney between the two methods. The mean, maximum, and minimum doses to the peritoneal cavity were also not significantly different. The number of monitor units (MUs) required was increased using the MECOMP (273 vs. 1152, p < 0.01). The MECOMP is effectively able to deliver DMLC-based radiotherapy, even with island blocks present. This novel use of MECOMP for whole abdominal radiotherapy should substantially reduce the labor, daily treatment time, and treatment-related errors through the elimination of cerrobend blocks. PMID:19931034

  19. A Novel Method of Island Blocking in Whole Abdominal Radiotherapy Using a Modified Electronic Tissue Compensation Technique

    SciTech Connect

    Goyal, Sharad

    2010-10-01

    Traditionally, large fields requiring island blocking used external beam radiation therapy (EBRT) with Cerrobend blocks to limit dose to the critical structures. It is laborious to construct blocks and use them on a daily basis. We present a novel technique for island blocking using a modified electronic tissue compensation (MECOMP) technique. Five patients treated at our institution were selected for this study. The study compared two planning techniques: a novel MECOMP and a conventional EBRT technique. Conventional fields were defined using anterior-posterior and posterior-anterior (PA) fields. The kidneys were contoured and an aperture cut-out block was fitted to the OAR with a 1-cm margin (OAR{sub CTV}) and placed in the PA field. A dynamic multileaf collimation (DMLC) plan with ECOMP was developed using identical beam and blocking strategy; this tissue compensation-based fluence map was modified to deliver a 'zero' dose to the CTV{sub OAR} from the PA field. There were no significant differences in the mean, maximum, and minimum doses to the right or left kidney between the two methods. The mean, maximum, and minimum doses to the peritoneal cavity were also not significantly different. The number of monitor units (MUs) required was increased using the MECOMP (273 vs. 1152, p < 0.01). The MECOMP is effectively able to deliver DMLC-based radiotherapy, even with island blocks present. This novel use of MECOMP for whole abdominal radiotherapy should substantially reduce the labor, daily treatment time, and treatment-related errors through the elimination of cerrobend blocks.

  20. Precision agricultural techniques for identifying yield limiting factors in Louisiana sugarcane

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision Agriculture enables growers to efficiently manage inputs, identify yield limiting soil properties, mitigate detrimental environmental or crop conditions, and increase profits. Soil grid sampling and yield mapping were used to document the extent of yield loss resulting from two very differ...

  1. Brain dose-sparing radiotherapy techniques for localized intracranial germinoma: Case report and literature review of modern irradiation.

    PubMed

    Leung, H W C; Chan, A L F; Chang, M B

    2016-05-01

    We examined the effects of intensity-modulated radiation therapy with dose-sparing and avoidance technique on a pediatric patient with localized intracranial germinoma. We also reviewed the literature regarding modern irradiation techniques in relation to late neurocognitive sequelae. A patient with a localized intracranial germinoma in the third ventricle anterior to the pineal gland received a dose-sparing intensity-modulated radiation therapy. The planning was compared to the radiation oncologist's guide of organs at risk and dose constraints for dosimetric analyses. The patient received radiation therapy alone. The total dose was 54Gy delivered in 2.0Gy fractions to the primary tumour and 37Gy in 1.4Gy fractions to whole ventricles using a dose-sculpting plan. Dosimetry analyses showed that dose-sparing intensity-modulated radiation therapy delivered reduced doses to the whole brain, temporal lobes, hippocampi, cochleae, and optic nerves. With a follow-up of 22 months, failure-free survival was 100% for the patient and no adverse events during radiation treatment process. Intensity-modulated radiation therapy with dose sparing and avoidance technique can spare the limbic circuit, central nervous system, and hippocampus for pineal germ cell tumours. This technique reduces the integral dose delivered to the uninvolved normal brain tissues and may reduce late neurocognitive sequelae caused by cranial radiotherapy. PMID:27080575

  2. Radiosensitization effect of folate-conjugated gold nanoparticles on HeLa cancer cells under orthovoltage superficial radiotherapy techniques

    NASA Astrophysics Data System (ADS)

    Khoshgard, Karim; Hashemi, Bijan; Arbabi, Azim; Javad Rasaee, Mohammad; Soleimani, Masoud

    2014-05-01

    Due to the high atomic number of gold nanoparticles (GNPs), they are known as new radiosensitizer agents for enhancing the efficiency of superficial radiotherapy techniques by increasing the dose absorbed in tumor cells wherein they can be accumulated selectively. The aim of this study was to compare the effect of various common low energy levels of orthovoltage x-rays and megavoltage γ-rays (Co-60) on enhancing the therapeutic efficiency of HeLa cancer cells in the presence of conjugated folate and non-conjugated (pegylated) GNPs. To achieve this, GNPs with an average diameter of 52 nm were synthesized and conjugated to folic acid molecules. Pegylated GNPs with an average diameter of 47 nm were also synthesized and used as non-conjugated folate GNPs. Cytotoxicity assay of the synthesized folate-conjugated and pegylated GNPs was performed using different levels of nanoparticle concentration incubated with HeLa cells for 24 h. The radiosensitizing effect of both the conjugated and pegylated GNPs on the cells at a concentration of 50 µM was compared using MTT as well as clonogenic assays after exposing them to 2 Gy ionizing radiation produced by an orthovoltage x-ray machine at four different kVps and γ-rays of a Co-60 unit. Significant differences were noted among various irradiated groups with and without the folate conjugation, with an average dose enhancement factor (DEF) of 1.64 ± 0.05 and 1.35 ± 0.05 for the folate-conjugated and pegylated GNPs, respectively. The maximum DEF was obtained with the 180 kVp x-ray beam for both of the GNPs. Folate-conjugated GNPs can significantly enhance the cell killing potential of orthovoltage x-ray energies (especially at 180 kVp) in folate receptor-expressing cancer cells, such as HeLa, in superficial radiotherapy techniques.

  3. Radiosensitization effect of folate-conjugated gold nanoparticles on HeLa cancer cells under orthovoltage superficial radiotherapy techniques.

    PubMed

    Khoshgard, Karim; Hashemi, Bijan; Arbabi, Azim; Rasaee, Mohammad Javad; Soleimani, Masoud

    2014-05-01

    Due to the high atomic number of gold nanoparticles (GNPs), they are known as new radiosensitizer agents for enhancing the efficiency of superficial radiotherapy techniques by increasing the dose absorbed in tumor cells wherein they can be accumulated selectively. The aim of this study was to compare the effect of various common low energy levels of orthovoltage x-rays and megavoltage γ-rays (Co-60) on enhancing the therapeutic efficiency of HeLa cancer cells in the presence of conjugated folate and non-conjugated (pegylated) GNPs. To achieve this, GNPs with an average diameter of 52 nm were synthesized and conjugated to folic acid molecules. Pegylated GNPs with an average diameter of 47 nm were also synthesized and used as non-conjugated folate GNPs. Cytotoxicity assay of the synthesized folate-conjugated and pegylated GNPs was performed using different levels of nanoparticle concentration incubated with HeLa cells for 24 h. The radiosensitizing effect of both the conjugated and pegylated GNPs on the cells at a concentration of 50 µM was compared using MTT as well as clonogenic assays after exposing them to 2 Gy ionizing radiation produced by an orthovoltage x-ray machine at four different kVps and γ-rays of a Co-60 unit. Significant differences were noted among various irradiated groups with and without the folate conjugation, with an average dose enhancement factor (DEF) of 1.64 ± 0.05 and 1.35 ± 0.05 for the folate-conjugated and pegylated GNPs, respectively. The maximum DEF was obtained with the 180 kVp x-ray beam for both of the GNPs. Folate-conjugated GNPs can significantly enhance the cell killing potential of orthovoltage x-ray energies (especially at 180 kVp) in folate receptor-expressing cancer cells, such as HeLa, in superficial radiotherapy techniques. PMID:24733041

  4. Online image-guided intensity-modulated radiotherapy for prostate cancer: How much improvement can we expect? A theoretical assessment of clinical benefits and potential dose escalation by improving precision and accuracy of radiation delivery

    SciTech Connect

    Ghilezan, Michel; Yan Di . E-mail: dyan@beaumont.edu; Liang Jian; Jaffray, David; Wong, John; Martinez, Alvaro

    2004-12-01

    Purpose: To quantify the theoretical benefit, in terms of improvement in precision and accuracy of treatment delivery and in dose increase, of using online image-guided intensity-modulated radiotherapy (IG-IMRT) performed with onboard cone-beam computed tomography (CT), in an ideal setting of no intrafraction motion/deformation, in the treatment of prostate cancer. Methods and materials: Twenty-two prostate cancer patients treated with conventional radiotherapy underwent multiple serial CT scans (median 18 scans per patient) during their treatment. We assumed that these data sets were equivalent to image sets obtainable by an onboard cone-beam CT. Each patient treatment was simulated with conventional IMRT and online IG-IMRT separately. The conventional IMRT plan was generated on the basis of pretreatment CT, with a clinical target volume to planning target volume (CTV-to-PTV) margin of 1 cm, and the online IG-IMRT plan was created before each treatment fraction on the basis of the CT scan of the day, without CTV-to-PTV margin. The inverse planning process was similar for both conventional IMRT and online IG-IMRT. Treatment dose for each organ of interest was quantified, including patient daily setup error and internal organ motion/deformation. We used generalized equivalent uniform dose (EUD) to compare the two approaches. The generalized EUD (percentage) of each organ of interest was scaled relative to the prescription dose at treatment isocenter for evaluation and comparison. On the basis of bladder wall and rectal wall EUD, a dose-escalation coefficient was calculated, representing the potential increment of the treatment dose achievable with online IG-IMRT as compared with conventional IMRT. Results: With respect to radiosensitive tumor, the average EUD for the target (prostate plus seminal vesicles) was 96.8% for conventional IMRT and 98.9% for online IG-IMRT, with standard deviations (SDs) of 5.6% and 0.7%, respectively (p < 0.0001). The average EUDs of

  5. Postoperative Radiotherapy for Lung Cancer: Improvement in Locoregional Control Using Three-Dimensional Compared With Two-Dimensional Technique

    SciTech Connect

    Masson-Cote, Laurence; Couture, Christian; Fortin, Andre; Dagnault, Anne

    2011-07-01

    Purpose: To determine whether lung cancer patients treated with three-dimensional (3D) postoperative radiotherapy (PORT) have more favorable outcomes than those treated with two-dimensional (2D) PORT. Patients and Methods: We retrospectively analyzed the charts of 153 lung cancer patients who underwent PORT with curative intent at our center between 1995 and 2007. The patients were grouped according to the RT technique; 66 patients were in the 2D group and 87 in the 3D group. The outcomes included locoregional control, survival, and secondary effects. All patients were treated using a linear accelerator at a total dose of approximately 50 Gy and 2 Gy/fraction. A few patients (21%) also received chemotherapy. Most tumors were in the advanced stage, either Stage II (30%) or Stage III (65%). The main clinical indications for PORT were positive resection margins (23%) and Stage pN2 (52%) and pN1 (22%). The patient characteristics were comparable in both groups. Results: Kaplan-Meier analysis showed that the 3D technique significantly improved the locoregional control rate at 5 years compared with the 2D technique (81% vs. 56%, p = .007 [Cox]). The 2D technique was associated with a more than twofold increased risk of locoregional recurrence (hazard ratio, 2.7; 95% confidence interval, 1.3-5.5; p = .006). The overall survival rate did not differ at 5 years (38% vs. 20%, p = .3 [Cox]). The toxicities were also similar and acceptable in both groups. Conclusion: The 3D technique for conformal PORT for lung cancer improved the locoregional control rates of patients compared with the 2D technique.

  6. Dosimetric Comparison of Bone Marrow-Sparing Intensity-Modulated Radiotherapy Versus Conventional Techniques for Treatment of Cervical Cancer

    SciTech Connect

    Mell, Loren K.; Tiryaki, Hanifi; Ahn, Kang-Hyun; Mundt, Arno J.; Roeske, John C.; Aydogan, Bulent

    2008-08-01

    Purpose: To compare bone marrow-sparing intensity-modulated pelvic radiotherapy (BMS-IMRT) with conventional (four-field box and anteroposterior-posteroanterior [AP-PA]) techniques in the treatment of cervical cancer. Methods and Materials: The data from 7 cervical cancer patients treated with concurrent chemotherapy and IMRT without BMS were analyzed and compared with data using four-field box and AP-PA techniques. All plans were normalized to cover the planning target volume with the 99% isodose line. The clinical target volume consisted of the pelvic and presacral lymph nodes, uterus and cervix, upper vagina, and parametrial tissue. Normal tissues included bowel, bladder, and pelvic bone marrow (PBM), which comprised the lumbosacral spine and ilium and the ischium, pubis, and proximal femora (lower pelvis bone marrow). Dose-volume histograms for the planning target volume and normal tissues were compared for BMS-IMRT vs. four-field box and AP-PA plans. Results: BMS-IMRT was superior to the four-field box technique in reducing the dose to the PBM, small bowel, rectum, and bladder. Compared with AP-PA plans, BMS-IMRT reduced the PBM volume receiving a dose >16.4 Gy. BMS-IMRT reduced the volume of ilium, lower pelvis bone marrow, and bowel receiving a dose >27.7, >18.7, and >21.1 Gy, respectively, but increased dose below these thresholds compared with the AP-PA plans. BMS-IMRT reduced the volume of lumbosacral spine bone marrow, rectum, small bowel, and bladder at all dose levels in all 7 patients. Conclusion: BMS-IMRT reduced irradiation of PBM compared with the four-field box technique. Compared with the AP-PA technique, BMS-IMRT reduced lumbosacral spine bone marrow irradiation and reduced the volume of PBM irradiated to high doses. Therefore BMS-IMRT might reduce acute hematologic toxicity compared with conventional techniques.

  7. Datum maintenance of the main Egyptian geodetic control networks by utilizing Precise Point Positioning "PPP" technique

    NASA Astrophysics Data System (ADS)

    Rabah, Mostafa; Elmewafey, Mahmoud; Farahan, Magda H.

    2016-06-01

    A geodetic control network is the wire-frame or the skeleton on which continuous and consistent mapping, Geographic Information Systems (GIS), and surveys are based. Traditionally, geodetic control points are established as permanent physical monuments placed in the ground and precisely marked, located, and documented. With the development of satellite surveying methods and their availability and high degree of accuracy, a geodetic control network could be established by using GNSS and referred to an international terrestrial reference frame used as a three-dimensional geocentric reference system for a country. Based on this concept, in 1992, the Egypt Survey Authority (ESA) established two networks, namely High Accuracy Reference Network (HARN) and the National Agricultural Cadastral Network (NACN). To transfer the International Terrestrial Reference Frame to the HARN, the HARN was connected with four IGS stations. The processing results were 1:10,000,000 (Order A) for HARN and 1:1,000,000 (Order B) for NACN relative network accuracy standard between stations defined in ITRF1994 Epoch1996. Since 1996, ESA did not perform any updating or maintaining works for these networks. To see how non-performing maintenance degrading the values of the HARN and NACN, the available HARN and NACN stations in the Nile Delta were observed. The Processing of the tested part was done by CSRS-PPP Service based on utilizing Precise Point Positioning "PPP" and Trimble Business Center "TBC". The study shows the feasibility of Precise Point Positioning in updating the absolute positioning of the HARN network and its role in updating the reference frame (ITRF). The study also confirmed the necessity of the absent role of datum maintenance of Egypt networks.

  8. Impact of beam quality on megavoltage radiotherapy treatment techniques utilizing gold nanoparticles for dose enhancement

    NASA Astrophysics Data System (ADS)

    Tsiamas, Panagiotis; Liu, Bo; Cifter, Fulya; Ngwa, Wilfred F.; Berbeco, Ross I.; Kappas, Constantin; Theodorou, Kiriaki; Marcus, Karen; Makrigiorgos, Mike G.; Sajo, Erno; Zygmanski, Piotr

    2013-02-01

    This study determines the optimal clinical scenarios for gold nanoparticle dose enhancement as a function of irradiation conditions and potential biological targets using megavoltage x-ray beams. Four hundred and eighty clinical beams were studied for different potential cellular or sub-cellular targets. Beam quality was determined based on a 6 MV linac with and without a flattening filter for various delivery conditions. Dose enhancement ratios DER = DGNP/Dwater were calculated for all cases using the GEANT4 Monte Carlo code and the CEPXS/ONEDANT radiation transport deterministic code. Dose enhancement using GEANT4 agreed with CEPXS/ONEDANT. DER for unflattened beams is ∼2 times larger than for flattened beams. The maximum DER values were calculated for split-IMRT fields (∼6) and for out-of-field areas of an unflattened linac (∼17). In-field DER values, at the surface of gold nanoparticles, ranged from 2.2 to 4.2 (flattened beam) and from 3 to 4.7 (unflattened beams). For a GNP cluster with thicknesses of 10 and 100 nm, the DER ranges from 14% to 287%. DER is the greatest for split-IMRT, larger depths, out-of-field areas and/or unflattened linac. Mapping of a GNP location in tumor and normal tissue is essential for efficient and safe delivery of nanoparticle-enhanced radiotherapy.

  9. Precision bone and muscle loss measurements by advanced, multiple projection DEXA (AMPDXA) techniques for spaceflight applications

    NASA Technical Reports Server (NTRS)

    Charles, H. K. Jr; Beck, T. J.; Feldmesser, H. S.; Magee, T. C.; Spisz, T. S.; Pisacane, V. L.

    2001-01-01

    An advanced, multiple projection, dual energy x-ray absorptiometry (AMPDXA) scanner system is under development. The AMPDXA is designed to make precision bone and muscle loss measurements necessary to determine the deleterious effects of microgravity on astronauts as well as develop countermeasures to stem their bone and muscle loss. To date, a full size test system has been developed to verify principles and the results of computer simulations. Results indicate that accurate predictions of bone mechanical properties can be determined from as few as three projections, while more projections are needed for a complete, three-dimensional reconstruction. c 2001. Elsevier Science Ltd. All rights reserved.

  10. Study of highly precise outdoor characterization technique for photovoltaic modules in terms of reproducibility

    NASA Astrophysics Data System (ADS)

    Fukabori, Akihiro; Takenouchi, Takakazu; Matsuda, Youji; Tsuno, Yuki; Hishikawa, Yoshihiro

    2015-08-01

    In this study, novel outdoor measurements were conducted for highly precise characterization of photovoltaic (PV) modules by measuring current-voltage (I-V) curves with fast sweep speeds and module’s temperature, and with a PV sensor for reference. Fast sweep speeds suppressed the irradiance variation. As a result, smooth I-V curves were obtained and the PV parameter deviation was suppressed. The module’s temperature was measured by attaching resistive temperature detector sensors on the module’s backsheet. The PV sensor was measured synchronously with the PV module. The PV parameters including Isc, Pmax, Voc, and FF were estimated after correcting the I-V curves using the IEC standards. The reproducibility of Isc, Pmax, Voc, and FF relative to the outdoor fits was evaluated as 0.43, 0.58, 0.24, and 0.23%, respectively. The results demonstrate that highly precise measurements are possible using a PV measurement system with the three above-mentioned features.

  11. A new technique for precise uranium-series dating of travertine micro-samples

    NASA Astrophysics Data System (ADS)

    Mallick, Ronzon; Frank, Norbert

    2002-12-01

    Secondary carbonate formations, such as travertine and calcareous tufa deposits, are important archives for quaternary continental climate studies and archaeology. The extremely complex growth mechanisms result in some serious problems for precise mass spectrometric uranium-series dating. Often, detrital and organic particles contaminate the carbonate and large pore volumes yield a great potential for open system behavior. We utilized microscopic, mineralogical and geochemical methods prior to sample selection to determine the abundance of primary calcite, i.e. micrite and spar. Furthermore, the state of alteration was characterized by cathodoluminescence and trace-element analysis. We conclude that travertine and calcareous tufa are appropriate for precise U-series age determination if a) micrite and/or spar are the dominant phases; b) cathodoluminescence of both phases is weak or absent; c) Fe and Al levels are low; and d) Sr concentrations are close to the average of the studied site. We mapped and sampled solely areas of major micrite/spar abundance having minor alteration for accurate U-series dating. When this new method was applied, travertines located in eastern Germany (sites Bad Langensalza, Burgtonna and Weimar-Ehringsdorf) gave single 230Th/ 238U-ages consistent with the lithological growth sequence and greatly improved compared to previously published chronologies. In addition, we determined 230Th/U isochron ages on bulk samples that confirm our single ages. In contrast to primary calcite, pore cements are homogeneously distributed throughout the travertine fabric and reflect early diagenetic processes and/or weathering.

  12. Tedlar bag sampling technique for vertical profiling of carbon dioxide through the atmospheric boundary layer with high precision and accuracy.

    PubMed

    Schulz, Kristen; Jensen, Michael L; Balsley, Ben B; Davis, Kenneth; Birks, John W

    2004-07-01

    Carbon dioxide is the most important greenhouse gas other than water vapor, and its modulation by the biosphere is of fundamental importance to our understanding of global climate change. We have developed a new technique for vertical profiling of CO2 and meteorological parameters through the atmospheric boundary layer and well into the free troposphere. Vertical profiling of CO2 mixing ratios allows estimates of landscape-scale fluxes characteristic of approximately100 km2 of an ecosystem. The method makes use of a powered parachute as a platform and a new Tedlar bag air sampling technique. Air samples are returned to the ground where measurements of CO2 mixing ratios are made with high precision (< or =0.1%) and accuracy (< or =0.1%) using a conventional nondispersive infrared analyzer. Laboratory studies are described that characterize the accuracy and precision of the bag sampling technique and that measure the diffusion coefficient of CO2 through the Tedlar bag wall. The technique has been applied in field studies in the proximity of two AmeriFlux sites, and results are compared with tower measurements of CO2. PMID:15296321

  13. The Effect of Changing Technique, Dose, and PTV Margin on Therapeutic Ratio During Prostate Radiotherapy

    SciTech Connect

    Huang Shaohui; Catton, Charles; Jezioranski, John M.Math.; Bayley, Andrew; Rose, Stuart; Rosewall, Tara

    2008-07-15

    Purpose: To quantify the dosimetric and radiobiological changes seen when using intensity-modulated radiation therapy (IMRT) or planning target volume (PTV) margin reduction with consistent planning parameters in a representative sample of localized prostate cancer patients. Methods and Materials: Twenty patients were randomly selected from a cohort that received 79.8 Gy using six-field conformal radiotherapy. Using the clinical contours, PTV margin, planning system, and dose constraints, five-field IMRT plans were generated for 79.8, 83.8, and 88.0 Gy. The 88.0-Gy IMRT plan was then reoptimized with a PTV margin reduced to 3 mm. These plans were then compared using various dosimetric and radiobiological endpoints calculated for various {alpha}/{beta}. Results: Intensity-modulated RT resulted in greater conformity to the PTV (p < 0.001). No improvement in mean normal tissue complication probabilities in the rectal wall (NTCPrw) was seen, and the modified therapeutic ratio (TR{sub mod}) was largely unchanged between six-field conformal and IMRT for the majority of the patients. When IMRT was used to escalate dose, NTCPrw increased by 9% at each 5% prescription increase (p < 0.001). Reducing the posterior PTV margin from 7 mm to 3 mm for an IMRT plan reduced the mean NTCPrw by 12% (p < 0.001) and resulted in a trend toward increased TR{sub mod}(p = 0.005). Changes in TR{sub mod} between conformal and IMRT planning or PTV reduction showed large interpatient variability. Conclusions: Changing from conformal to IMRT, or from PTV{sub 10-7} to PTV{sub 3}, did not produce a uniform interpatient increase in TR{sub mod}when the CTV contained the prostate alone. Radiobiological benefits of these two methods seem to be dependent on the particular anatomy of individual patients, supporting the use of patient-specific margin, planning, and dose prescription strategies.

  14. High-precision optomechanical lens system for space applications assembled by a local soldering technique

    NASA Astrophysics Data System (ADS)

    Pleguezuelo, Pol Ribes; Koechlin, Charlie; Hornaff, Marcel; Kamm, Andreas; Beckert, Erik; Fiault, Guillaume; Eberhardt, Ramona; Tünnermann, Andreas

    2016-06-01

    Soldering using metallic solder alloys is an alternative to adhesive bonding. Laser-based soldering processes are especially well suited for the joining of optical components made of fragile and brittle materials such as glass, ceramics, and optical crystals. This is due to a localized and minimized input of thermal energy. Solderjet bumping technology has been used to assemble a lens mount breadboard using specifications and requirements found for the optical beam expander for the European Space Agency EarthCare Mission. The silica lens and a titanium barrel have been designed and assembled with this technology in order to withstand the stringent mission demands of handling high mechanical and thermal loads without losing the optical performance. Finally, a high-precision optomechanical lens mount has been assembled with minimal localized stress (<1 MPa) showing outstanding performance in terms of wave-front error and beam depolarization ratio before and after environmental tests.

  15. Composite-light-pulse technique for high-precision atom interferometry.

    PubMed

    Berg, P; Abend, S; Tackmann, G; Schubert, C; Giese, E; Schleich, W P; Narducci, F A; Ertmer, W; Rasel, E M

    2015-02-13

    We realize beam splitters and mirrors for atom waves by employing a sequence of light pulses rather than individual ones. In this way we can tailor atom interferometers with improved sensitivity and accuracy. We demonstrate our method of composite pulses by creating a symmetric matter-wave interferometer which combines the advantages of conventional Bragg- and Raman-type concepts. This feature leads to an interferometer with a high immunity to technical noise allowing us to devise a large-area Sagnac gyroscope yielding a phase shift of 6.5 rad due to the Earth's rotation. With this device we achieve a rotation rate precision of 120  nrad s(-1) Hz(-1/2) and determine the Earth's rotation rate with a relative uncertainty of 1.2%. PMID:25723216

  16. Precision and costs of techniques for self-monitoring of serum glucose levels.

    PubMed Central

    Chiasson, J. L.; Morrisset, R.; Hamet, P.

    1984-01-01

    The poor correlation between serum and urine glucose measurements has led to the development of new techniques for monitoring the blood glucose level in diabetic patients. Either a nurse or the patient can perform these tests, which involve spreading a single drop of blood onto a reagent strip. A colour change that is proportional to the serum glucose level can be read visually or with a reflectance meter. Evaluated against simultaneous serum glucose levels determined by the hospital biochemistry laboratory, those of the new techniques employing reflectance meters all showed excellent correlation (r2 = 0.85 to 0.96). Reagent strips used without meters showed poorer correlation (r2 = 0.69 to 0.90). The instruction given to the patients and one nurse enabled them to obtain more accurate results with one of the meters than nurses not specially trained (r2 = 0.94 and 0.92 v. 0.85 respectively). The mean cost per glucose determination with the new techniques was 75, compared with +1.45 for the laboratory determinations done with automated equipment. It was concluded that the new techniques compared well with the reference method, particularly when reflectance meters were used, and that they were easily applied by the patient, as well as the medical staff, at a reasonable cost. PMID:6689988

  17. Segmentation of IMRT plans for radical lung radiotherapy delivery with the step-and-shoot technique.

    PubMed

    Nioutsikou, Elena; Bedford, James L; Christian, Judith A; Brada, Michael; Webb, Steve

    2004-04-01

    The purpose of this work was to determine a segmentation protocol for the treatment of localized non-small-cell lung cancer (NSCLC) with intensity-modulated radiotherapy (IMRT) that is as effective as possible while practically simple and hence robust to known practical inaccuracies. This study focused on the stratification of continuous profiles into a discrete number of intensity levels. The selection of the segmentation parameters for the delivery of the fluence profiles using multiple static fields has been considered. Five-field equispaced IMRT treatment plans of five patients with NSCLC were selected. The study comprised nine treatment plans for each patient, starting from a conformal plan, optimizing it for IMRT and then segmenting it utilizing different numbers of segments in each case and optimizing for segment weights separately. A conformal plan, optimized for beam directions, collimator and wedge angles, was also used for comparison with the IMRT plans, so as to consider the best coplanar conformal case. A dose objective for the PTV and the organs-at-risk plus a constraint for the spinal cord were set for all inverse plans. All stages were compared with the aid of dose-volume histograms, dose distributions at the plane of the isocenter, intensity maps for key beams and plots of PTV homogeneity and overall conformality versus complexity. The unsegmented IMRT plans gave the best results but cannot be realized in practice with an MLC. They were best approximated by plans that needed 106-167 segments to deliver, but did not deteriorate significantly when approximated by plans which required 26-40 segments in total. All segmented IMRT plans gave a better lung sparing than the conformal plans, indicating that the deterioration of IMRT plans following segmentation is not equivalent to that of unmodulated, conformal plans. However, optimized conformal plans have the potential to approach the lung sparing achieved by segmented IMRT plans. Among the IMRT

  18. Dosimetric difference amongst 3 techniques: TomoTherapy, sliding-window intensity-modulated radiotherapy (IMRT), and RapidArc radiotherapy in the treatment of late-stage nasopharyngeal carcinoma (NPC)

    SciTech Connect

    Lee, Francis Kar-ho Yip, Celia Wai-yi; Cheung, Frankie Chun-hung; Leung, Alex Kwok-cheung; Chau, Ricky Ming-chun; Ngan, Roger Kai-cheong

    2014-04-01

    To investigate the dosimetric difference amongst TomoTherapy, sliding-window intensity-modulated radiotherapy (IMRT), and RapidArc radiotherapy in the treatment of late-stage nasopharyngeal carcinoma (NPC). Ten patients with late-stage (Stage III or IV) NPC treated with TomoTherapy or IMRT were selected for the study. Treatment plans with these 3 techniques were devised according to departmental protocol. Dosimetric parameters for organ at risk and treatment targets were compared between TomoTherapy and IMRT, TomoTherapy and RapidArc, and IMRT and RapidArc. Comparison amongst the techniques was done by statistical tests on the dosimetric parameters, total monitor unit (MU), and expected delivery time. All 3 techniques achieved similar target dose coverage. TomoTherapy achieved significantly lower doses in lens and mandible amongst the techniques. It also achieved significantly better dose conformity to the treatment targets. RapidArc achieved significantly lower dose to the eye and normal tissue, lower total MU, and less delivery time. The dosimetric advantages of the 3 techniques were identified in the treatment of late-stage NPC. This may serve as a guideline for selection of the proper technique for different clinical cases.

  19. Implications of diamond-turned versus diamond-ground mold fabrication techniques on precision-molded optics

    NASA Astrophysics Data System (ADS)

    Mertus, Lou; Symmons, Alan

    2012-10-01

    In recent years, the trend within the molded optics community has been an overall advancement in the capability to diamond grind molds using a variety of grinding techniques. Improvements in grinding equipment, materials and tooling have enabled higher quality ceramic and carbide molds and thereby lenses. Diamond turned molds from ductile metals are still used prevalently throughout the molding industry. Each technology presents a unique set of advantages and disadvantages whether used for precision injection molding of plastic optics or precision glass molding. This paper reviews the manufacturing techniques for each approach and applicable molding process. The advantages and disadvantages of each are compared and analyzed. The subtle differences that exist in optics molded from each technique and the impact they have on the performance in various applications is reviewed. Differences stemming from tooling material properties, material-specific minor defects, as well as cutting and grinding process-induced artifacts are described in detail as well as their influence on the roughness, waviness, and form errors present on the molded surface. A comparison with results between similar surfaces for both diamond grinding and diamond turning is presented.

  20. Delineating the Rattlesnake Springs, New Mexico Watershed Using Precision Gravity Techniques

    NASA Astrophysics Data System (ADS)

    Doser, D. I.; Boykov, N. D.; Baker, M. R.; Kaip, G. M.; Langford, R. P.

    2009-12-01

    Rattlesnake Springs serves as the sole domestic water source for Carlsbad Caverns National Park. The recent development of oil and gas leases and agricultural lands surrounding the springs has led to concern about contamination of the fracture controlled aquifer system. We have conducted a series of precision gravity surveys (station spacing 200 to 300 m in a 4 x 4 km area), combined with other geophysical studies and geologic mapping, to delineate possible fracture systems in the gypsum and carbonate bedrock that feed the spring system. Our combined results suggest several pathways for water to enter the springs. A series of WNW-ESE striking features are apparent in our gravity data that appear to align with relict spring valleys we have mapped to the west of the springs. A self potential survey indicates that water is entering the springs at a shallow level from the northwest direction. However, gravity data also indicate a north-south trending fracture system could be providing a pathway for water to enter from the south. This is consistent with drawdown tests conducted in the 1950’s and 1960’s on irrigation wells located to the south of the springs. The north-south fracture system appears related to a basin bounding fault system observed in the regional gravity data.

  1. Speed and amplitude of lung tumor motion precisely detected in four-dimensional setup and in real-time tumor-tracking radiotherapy

    SciTech Connect

    Shirato, Hiroki . E-mail: hshirato@radi.med.hokudai.ac.jp; Suzuki, Keishiro; Sharp, Gregory C.; Fujita, Katsuhisa R.T.; Onimaru, Rikiya; Fujino, Masaharu; Kato, Norio; Osaka, Yasuhiro; Kinoshita, Rumiko; Taguchi, Hiroshi; Onodera, Shunsuke; Miyasaka, Kazuo

    2006-03-15

    Background: To reduce the uncertainty of registration for lung tumors, we have developed a four-dimensional (4D) setup system using a real-time tumor-tracking radiotherapy system. Methods and Materials: During treatment planning and daily setup in the treatment room, the trajectory of the internal fiducial marker was recorded for 1 to 2 min at the rate of 30 times per second by the real-time tumor-tracking radiotherapy system. To maximize gating efficiency, the patient's position on the treatment couch was adjusted using the 4D setup system with fine on-line remote control of the treatment couch. Results: The trajectory of the marker detected in the 4D setup system was well visualized and used for daily setup. Various degrees of interfractional and intrafractional changes in the absolute amplitude and speed of the internal marker were detected. Readjustments were necessary during each treatment session, prompted by baseline shifting of the tumor position. Conclusion: The 4D setup system was shown to be useful for reducing the uncertainty of tumor motion and for increasing the efficiency of gated irradiation. Considering the interfractional and intrafractional changes in speed and amplitude detected in this study, intercepting radiotherapy is the safe and cost-effective method for 4D radiotherapy using real-time tracking technology.

  2. Precise control of caval and hepatic vessels: Surgical technique to treat level III caval thrombus concomitant to renal cell carcinoma

    PubMed Central

    Chen, Ming; Xu, Bin; Liu, Ning; Jiang, Hua; Wang, Yiduo; Yang, Yu; Zhang, Xiaowen; Sun, Chao; Liu, Jing; Zhu, Weidong; Chen, Shuqiu

    2015-01-01

    Introduction: We investigated the surgical techniques, safety, and prevention of complications of nephrectomy and removal of tumour thrombus for treating level III inferior vena cava (IVC) concomitant to renal cell carcinoma (RCC). We did this by precise controlling IVC and hepatic vessels without a vascular bypass. Methods: In this series, we included 5 patients with level III IVC tumour thrombus below the hepatic vein concomitant to RCC. After precisely controlling the IVC and hepatic vessels, we then removed the thrombus en bloc with the renal vein. Blood loss volume, IVC clamping time, hypotension time, resuscitation, cardiocerebrovascular complications, and postoperative organ dysfunction were observed. Results: Surgery was successfully performed without perioperative death. Blood loss volume was 900 to 1500 mL, operation time was 165 to 250 minutes, vascular clamping time was 8 to 12 minutes, and intraoperative hypotension time was 9 to 12 minutes. Serious perioperative complications were not observed. Local recurrence was not observed during the 9 to 24 months of follow-up. One patient exhibited disease-free survival, 3 developed lung or liver metastasis, and 1 died 11 months after surgery. Conclusion: Precise control of IVC and hepatic pedicle vessels, without vascular bypass, is a safe and effective surgical treatment for level III tumor thrombus below the hepatic vein concomitant to RCC. The procedure was conducted without increased risks of intraoperative hypotensive shock, difficult resuscitation, pulmonary embolism, and multiple organ dysfunctions. PMID:26600890

  3. Robotic-assisted femoral osteochondroplasty is more precise than a freehand technique in a Sawbone model

    PubMed Central

    Ranawat, Anil S.

    2015-01-01

    Robotic-assistance has the potential to improve the accuracy of bony resections, when performing femoral osteochondroplasty in the treatment of cam-type femoroacetabular impingement (FAI). The purpose of this study was to determine the accuracy of robotic-assisted femoral osteochondroplasty and compare this to a conventional open, freehand technique. We hypothesized that robotic-assistance would increase the accuracy of femoral head-neck offset correction in cam FAI. Sixteen identical sawbones models with a cam-type impingement deformity were resected by a single surgeon, simulating an open femoral osteochondroplasty. Eight procedures were performed using an open freehand technique and eight were performed using robotic-assistance, through the creation of a three-dimensional haptic volume. A desired arc of resection of 117.7° was determined pre-operatively using an anatomic plan. Post-resection, all 16 sawbones were laser scanned to measure the arc of resection, volume of bone removed and depth of resection. For each sawbone, these measurements were compared with the pre-operatively planned desired resection, to determine the resection error. Freehand resection resulted in a mean arc of resection error of 42.0 ± 8.5° compared with robotic-assisted resection which had a mean arc of resection error of 1.2 ± 0.7° (P < 0.0001). Over-resection occurred with every freehand resection with a mean volume error of 758.3 ± 477.1 mm3 compared with a mean robotic-assisted resection volume error of 31.3 ± 220.7 mm3 (P < 0.01). This study has shown that robotic-assisted femoral osteochondroplasty in the treatment of cam-type FAI is more accurate than a conventional, freehand technique, which are currently in widespread use. PMID:27011830

  4. Beams, brightness, and background: Using active spectroscopy techniques for precision measurements in fusion plasma research

    SciTech Connect

    Thomas, Dan M.

    2012-05-15

    The use of an injected neutral beam-either a dedicated diagnostic beam or the main heating beams-to localize and enhance plasma spectroscopic measurements can be exploited for a number of key physics issues in magnetic confinement fusion research, yielding detailed profile information on thermal and fast ion parameters, the radial electric field, plasma current density, and turbulent transport. The ability to make these measurements has played a significant role in much of our recent progress in the scientific understanding of fusion plasmas. The measurements can utilize emission from excited state transitions either from plasma ions or from the beam atoms themselves. The primary requirement is that the beam 'probe' interacts with the plasma in a known fashion. Advantages of active spectroscopy include high spatial resolution due to the enhanced localization of the emission and the use of appropriate imaging optics, background rejection through the appropriate modulation and timing of the beam and emission collection/detection system, and the ability of the beam to populate emitter states that are either nonexistent or too dim to utilize effectively in the case of standard or passive spectroscopy. In addition, some active techniques offer the diagnostician unique information because of the specific quantum physics responsible for the emission. This paper will describe the general principles behind a successful active spectroscopic measurement, emphasize specific techniques that facilitate the measurements and include several successful examples of their implementation, briefly touching on some of the more important physics results. It concludes with a few remarks about the relevance and requirements of active spectroscopic techniques for future burning plasma experiments.

  5. Novel techniques for high precision refractive index measurements, and application to assessing neutron damage and dose in crystals

    NASA Astrophysics Data System (ADS)

    Masuda, K.; Vaughan, E. I.; Arissian, L.; Hendrie, J. P.; Cole, J.; Diels, J.-C.; Hecht, A. A.

    2015-06-01

    In this work we present novel techniques for high precision index of refraction measurements for transparent crystals, and demonstrate a change from neutron irradiation. Radiation damage affects the structure of material, which can be read out nondestructively in transparent crystals. There is some difference in gamma-ray and neutron interactions which may be useful in characterization. Ionization from gamma rays produces color centers in the material, producing distinct spectral absorption, and some small shift in the index of refraction. Neutrons produce atomic recoils and, while the recoils do some ionization, they have a much greater efficiency for lattice displacement than do gamma rays, and these displacements can have a greater effect on the index of refraction. Using CaF2 crystals exposed to neutron radiation, together with a new high precision technique of detecting changes of index of refraction, we establish proof that this type of measurement can be used to monitor neutron exposure. This can provide a basic study of material changes with radiation and, with calibration of material in known neutron fields, this may even find application to neutron dosimetry.

  6. DETERMINATION OF INTERSTITIAL CHLORIDE IN SHALES AND CONSOLIDATED ROCKS BY A PRECISION LEACHING TECHNIQUE.

    USGS Publications Warehouse

    Manheim, Frank T.; Peck, E.E.; Lane, Candice M.

    1985-01-01

    The authors have devised a technique for determining chloride in interstitial water of consolidated rocks. Samples of rocks ranging from 5 to 10 g are crushed and sieved under controlled conditions and then ground with distilled water to submicron size in a closed mechanical mill. The chloride concentrations and total pore-water concentrations, obtained earlier from the same samples by low-temperature vacuum desiccation, are used to arrive at the 'original' pore-water chloride concentrations by a simple iteration procedure. Interstitial chlorinity results obtained from Cretaceous and Jurassic strata in the Gulf of Mexico coastal areas ranged from 20 to 100 g/kg Cl with reproducibility approaching plus or minus 1%.

  7. Intensity-modulated radiotherapy, not 3D conformal, is the preferred technique for treating locally advanced lung cancer

    PubMed Central

    Chang, Joe Y.

    2015-01-01

    When used to treat lung cancer, intensity-modulated radiotherapy (IMRT) can deliver higher dose to the targets and spare more critical organs in lung cancer than can 3D conformal radiotherapy (3DCRT). However, tumor-motion management and optimized radiotherapy planning based on four-dimensional computed tomography (4D CT) scanning are crucial to maximize the benefit of IMRT and to eliminate or minimize potential uncertainties. This article summarizes these strategies and reviews published findings supporting the safety and efficacy of IMRT for lung cancer. PMID:25771415

  8. An attenuation integral digital imaging technique for the treatment portal verification of conventional and intensity-modulated radiotherapy

    SciTech Connect

    Guan Huaiqun

    2010-07-15

    Purpose: To propose an attenuation integral digital imaging (AIDI) technique for the treatment portal verification of conventional and intensity-modulated radiotherapy (IMRT). Methods: In AIDI technique, an open in air fluence image I{sub o} and a patient fluence image I were acquired under the same exposure. Then after doing the dark field correction for both the I{sub o} and I, the AIDI image was simply calculated as log(I{sub o}/I), which is the attenuation integral along the ray path from the x-ray source to a detector pixel element. Theoretical analysis for the low contrast detection and the contrast to noise ratio (CNR) of AIDI was presented and compared to those for the fluence imaging. With AIDI, the variation of x-ray fluence and the variation of individual detector pixel's response can be automatically compensated without using the flood field correction. Results: The AIDI image for a contrast detail phantom demonstrated that it can efficiently suppress the background structures such as the couch and generate better visibility for low contrast objects with megavoltage x rays. The AIDI image acquired for a Catphan 500 phantom using a 60 deg. electronic dynamic wedge field also revealed more contrast disks than the fluence imaging did. Finally, AIDI for an IMRT field of a head/neck patient successfully displayed the anatomical structures underneath the treatment portal but not shown in fluence imaging. Conclusions: For IMRT and high degree wedge beams, direct imaging using them is difficult because their photon fluence is highly nonuniform. But AIDI can be used for the treatment portal verification of these beams.

  9. Treatment of nasal cavity and paranasal sinus cancer with modern radiotherapy techniques in the postoperative setting-the MSKCC experience

    SciTech Connect

    Hoppe, Bradford S.; Stegman, Lauren D.; Zelefsky, Michael J.; Rosenzweig, Kenneth E.; Wolden, Suzanne L.; Patel, Snehal G.; Shah, Jatin P.; Kraus, Dennis H.; Lee, Nancy Y. . E-mail: leen2@mskcc.org

    2007-03-01

    Purpose: To perform a retrospective analysis of patients with paranasal sinus (PNS) cancer treated with postoperative radiotherapy (RT) at Memorial Sloan-Kettering Cancer Center. Methods and Materials: Between January 1987 and July 2005, 85 patients with PNS and nasal cavity cancer underwent postoperative RT. Most patients had squamous cell carcinoma (49%; n = 42), T4 tumors (52%; n = 36), and the maxillary sinus (53%; n = 45) as the primary disease site. The median radiation dose was 63 Gy. Of the 85 patients, 76 underwent CT simulation and 53 were treated with either three-dimensional conformal RT (27%; n = 23) or intensity-modulated RT (35%; n = 30). Acute and late toxicities were scored according to the Radiation Therapy Oncology Group radiation morbidity scoring criteria. Results: With a median follow-up for surviving patients of 60 months, the 5-year estimates of local progression-free, regional progression-free, distant metastasis-free, disease-free, and overall survival rates were 62%, 87%, 82%, 55%, and 67%, respectively. On multivariate analysis, squamous cell histology and cribriform plate involvement predicted for an increased likelihood of local recurrence, and squamous cell histologic features predicted for worse overall survival. None of the patients who underwent CT simulation and were treated with modern techniques developed a Grade 3-4 late complication of the eye. Conclusion: Complete surgical resection followed by adjuvant RT is an effective and safe approach in the treatment of PNS cancer. Emerging tools, such as three-dimensional conformal treatment and, in particular, intensity-modulated RT for PNS tumors, may minimize the occurrence of late complications associated with conventional RT techniques. Local recurrence remains a significant problem.

  10. [Radiotherapy for Thyroid Cancer].

    PubMed

    Jingu, Keiichi; Maruoka, Shin; Umezawa, Rei; Takahashi, Noriyoshi

    2015-06-01

    Radioactive 131I therapy for differentiated thyroid cancer has been used since the 1940s and is an established and effective treatment. In contrast, external beam radiotherapy (EBRT) was considered to be effective for achieving local control but not for prolonging survival. Although clinicians were hesitant to administer EBRT owing to the potential radiation-induced adverse effects of 2 dimensional (2D)-radiotherapy until 2000, it is expected that adverse effects will be reduced and treatment efficacy improved through the introduction of more advanced techniques for delivering radiation (eg, 3D-radiotherapy and intensity modulated radiotherapy [IMRT]). The prognosis of undifferentiated thyroid cancer is known to be extremely bad, although in very rare cases, multimodality therapy (total or subtotal resection, chemotherapy, and radiotherapy) has allowed long-term survival. Here, we report the preliminary results of using hypofractionated radiotherapy for undifferentiated thyroid cancer in our institution. PMID:26199238

  11. Radiotherapy of inoperable lung cancer

    SciTech Connect

    Namer, M.; Lalanne, C.M.; Boublil, J.L.; Hery, M.; Chauvel, P.; Verschoore, J.; Aubanel, J.M.; Bruneton, J.N.

    1980-08-01

    Evaluation of loco-regional results obtained by radiotherapy for 31 patients with inoperable epidermoid lung cancer revealed objective remission (over 50%) in only 25% of patients. These results emphasize the limited effectiveness of radiotherapy in such cases and point out the need for increased research in radiotherapy techniques if survival rates are to be improved.

  12. Application of dynamic Monte Carlo technique in proton beam radiotherapy using Geant4 simulation toolkit

    NASA Astrophysics Data System (ADS)

    Guan, Fada

    Monte Carlo method has been successfully applied in simulating the particles transport problems. Most of the Monte Carlo simulation tools are static and they can only be used to perform the static simulations for the problems with fixed physics and geometry settings. Proton therapy is a dynamic treatment technique in the clinical application. In this research, we developed a method to perform the dynamic Monte Carlo simulation of proton therapy using Geant4 simulation toolkit. A passive-scattering treatment nozzle equipped with a rotating range modulation wheel was modeled in this research. One important application of the Monte Carlo simulation is to predict the spatial dose distribution in the target geometry. For simplification, a mathematical model of a human body is usually used as the target, but only the average dose over the whole organ or tissue can be obtained rather than the accurate spatial dose distribution. In this research, we developed a method using MATLAB to convert the medical images of a patient from CT scanning into the patient voxel geometry. Hence, if the patient voxel geometry is used as the target in the Monte Carlo simulation, the accurate spatial dose distribution in the target can be obtained. A data analysis tool---root was used to score the simulation results during a Geant4 simulation and to analyze the data and plot results after simulation. Finally, we successfully obtained the accurate spatial dose distribution in part of a human body after treating a patient with prostate cancer using proton therapy.

  13. [Prostate cancer external beam radiotherapy].

    PubMed

    de Crevoisier, R; Pommier, P; Latorzeff, I; Chapet, O; Chauvet, B; Hennequin, C

    2016-09-01

    The prostate external beam radiotherapy techniques are described, when irradiating the prostate or after prostatectomy, with and without pelvic lymph nodes. The following parts are presented: indications of radiotherapy, total dose and fractionation, planning CT image acquisition, volume of interest delineation (target volumes and organs at risk) and margins, Intensity modulated radiotherapy planning and corresponding dose-volume constraints, and finally Image guided radiotherapy. PMID:27516051

  14. Set-up uncertainty during postmastectomy radiotherapy with Segmented Photon Beams Technique

    PubMed Central

    Semaniak, Anna; Kukołowicz, Paweł

    2015-01-01

    Aim To verify the reproducibility of patients irradiated after mastectomy on the immobilization system designed and manufactured for our hospital and to compare the Internal Protocol (IP) with the modified-No Action Level Protocol. Background Application of forward IMRT techniques requires a good reproducibility of patient positioning. To minimize the set-up error, an effective immobilization system is important. Materials and methods The study was performed for two groups of 65 each. In the first group, portal images for anterior field were taken in 1–3 fractions and, subsequently, three times a week. In this group, the mNAL protocol was used. In the second group, the IP was used. The portal images from the anterior field and from the gantry 0 were taken during the 1–3 and 10 fractions. In both groups, image registration was performed off-line. For each group the systematic and random errors and PTV margin were calculated. Results In the first group the value of the population systematic errors and random errors were 1.6 ± 1.6 mm for the left–right, and 1.5 ± 1.7 mm for the cranial–caudal directions, respectively, 1.7 ± 1.3 mm, and 1.9 ± 1.3 mm for the second group. The PTV margins for the left–right and cranial–caudal directions were 5.1 and 4.9 mm for the first group and 5.4 and 6.4 mm for the second group. Conclusions For patients immobilized with our support device treated according to the mNAL protocol or IP, a good set-up reproducibility was obtained. Implementation of IP limits the number of required images. PMID:25949221

  15. Metrology study of high precision mm parts made by the deep x-ray lithography (LIGA) technique

    NASA Astrophysics Data System (ADS)

    Mäder, Olaf; Meyer, Pascal; Saile, Volker; Schulz, Joachim

    2009-02-01

    Microcomponents are increasingly applied in industrial products, e.g. smallest gears, springs or the watch industry. Apart from their small dimensions, such components are characterized by a high contour accuracy. Industry requires the tolerances to be in the µm range. Measurement of lateral dimensions in the mm range with submicrometer accuracy and precision, however, results in high requirements on measurement technology. The relevance of this problem is illustrated by the fact that the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) has launched the Collaborative Research Center 1159 on 'New Strategies of Measurement and Inspection for the Production of Microsystems and Nanostructures'. The Institut für Mikrostrukturtechnik, Karlsruhe (Institute of Microstructure Technology, Karlsruhe), produces microstructures by means of the LIG(A) technique (German acronym for lithography, electrodeposition, molding). Presently, a coordinate measurement machine equipped with an optical fiber probe to measure these microstructures is being tested. This paper will particularly focus on the precision and accuracy of the machine. The rules of measurement system analysis will be applied for this purpose. Following the elimination of the systematic error, reproducibility of deep-etch x-ray lithography will be highlighted using the LIGA production of gold gears as an example.

  16. A simple DVH generation technique for various radiotherapy treatment planning systems for an independent information system

    NASA Astrophysics Data System (ADS)

    Min, Byung Jun; Nam, Heerim; Jeong, Il Sun; Lee, Hyebin

    2015-07-01

    In recent years, the use of a picture archiving and communication system (PACS) for radiation therapy has become the norm in hospital environments and has been suggested for collecting and managing data using Digital Imaging and Communication in Medicine (DICOM) objects from different treatment planning systems (TPSs). However, some TPSs do not provide the ability to export the dose-volume histogram (DVH) in text or other format. In addition, plan review systems for various TPSs often allow DVH recalculations with different algorithms. These algorithms result in inevitable discrepancies between the values obtained with the recalculation and those obtained with TPS itself. The purpose of this study was to develop a simple method for generating reproducible DVH values by using the TPSs. Treatment planning information, including structures and delivered dose, was exported in the DICOM format from the Eclipse v8.9 or the Pinnacle v9.6 planning systems. The supersampling and trilinear interpolation methods were employed to calculate the DVH data from 35 treatment plans. The discrepancies between the DVHs extracted from each TPS and those extracted by using the proposed calculation method were evaluated with respect to the supersampling ratio. The volume, minimum dose, maximum dose, and mean dose were compared. The variations in DVHs from multiple TPSs were compared by using the MIM software v6.1, which is a commercially available treatment planning comparison tool. The overall comparisons of the volume, minimum dose, maximum dose, and mean dose showed that the proposed method generated relatively smaller discrepancies compared with TPS than the MIM software did compare with the TPS. As the structure volume decreased, the overall percent difference increased. The largest difference was observed in small organs such as the eye ball, eye lens, and optic nerve which had volume below 10 cc. A simple and useful technique was developed to generate a DVH with an acceptable

  17. Dosimetric comparison of two arc-based stereotactic body radiotherapy techniques for early-stage lung cancer

    SciTech Connect

    Liu, Huan Ye, Jingjing; Kim, John J.; Deng, Jun; Kaur, Monica S.; Chen, Zhe

    2015-04-01

    To compare the dosimetric and delivery characteristics of two arc-based stereotactic body radiotherapy (SBRT) techniques for early-stage lung cancer treatment. SBRT treatment plans for lung tumors of different sizes and locations were designed using a single-isocenter multisegment dynamic conformal arc technique (SiMs-arc) and a volumetric modulated arc therapy technique (RapidArc) for 5 representative patients treated previously with lung SBRT. The SiMs-arc plans were generated with the isocenter located in the geometric center of patient's axial plane (which allows for collision-free gantry rotation around the patient) and 6 contiguous 60° arc segments spanning from 1° to 359°. 2 RapidArc plans, one using the same arc geometry as the SiMs-arc and the other using typical partial arcs (210°) with the isocenter inside planning target volume (PTV), were generated for each corresponding SiMs-arc plan. All plans were generated using the Varian Eclipse treatment planning system (V10.0) and were normalized with PTV V{sub 100} to 95%. PTV coverage, dose to organs at risk, and total monitor units (MUs) were then compared and analyzed. For PTV coverage, the RapidArc plans generally produced higher PTV D{sub 99} (by 1.0% to 3.3%) and higher minimum dose (by 2.7% to 12.7%), better PTV conformality index (by 1% to 8%), and less volume of 50% dose outside 2 cm from PTV (by 0 to 20.8 cm{sup 3}) than the corresponding SiMs-arc plans. For normal tissues, no significant dose differences were observed for the lungs, trachea, chest wall, and heart; RapidArc using partial arcs produced lowest maximum dose to spinal cord. For dose delivery, the RapidArc plans typically required 50% to 90% more MUs than SiMs-arc plans to deliver the same prescribed dose. The additional intensity modulation afforded by variable gantry speed and dose rate and by overlapping arcs enabled RapidArc plans to produce dosimetrically improved plans for lung SBRT, but required more MUs (by a factor > 1.5) to

  18. The Technique, Resources and Costs of Stereotactic Body Radiotherapy of Prostate Cancer: A Comparison of Dose Regimens and Delivery Systems.

    PubMed

    Sharieff, Waseem; Greenspoon, Jeffrey N; Dayes, Ian; Chow, Tom; Wright, James; Lukka, Himu

    2016-02-01

    Robotic system has been used for stereotactic body radiotherapy (SBRT) of prostate cancer. Arc-based and fixed-gantry systems are used for hypofractionated regimens (10-20 ractions) and the standard regimen (39 fractions); they may also be used to deliver SBRT. Studies are currently underway to compare efficacy and safety of these systems and regimens. Thus, we describe the technique and required resources for the provision of robotic SBRT in relation to the standard regimen and other systems to guide investment decisions. Using administrative data of resource volumes and unit prices, we computed the cost per patient, cost per cure and cost per quality adjusted life year (QALY) of four regimens (5, 12, 20 and 39 fractions) and three delivery systems (robotic, arc-based and fixed-gantry) from a payer's perspective. We performed sensitivity analyses to examine the effects of daily hours of operation and in-room treatment delivery times on cost per patient. In addition, we estimated the budget impact when a robotic system is preferred over an arc-based or fixed-gantry system. Costs of SBRT were $6333/patient (robotic), $4368/patient (arc-based) and $4443/patient (fixed-gantry). When daily hours of operation were varied, the cost of robotic SBRT varied from $9324/patient (2 hours daily) to $5250/patient (10 hours daily). This was comparable to the costs of 39 fraction standard regimen which were $5935/patient (arc-based) and $7992/ patient (fixed-gantry). In settings of moderate to high patient volume, robotic SBRT is cost effective compared to the standard regimen. If SBRT can be delivered with equivalent efficacy and safety, the arc-based system would be the most cost effective system. PMID:24750007

  19. Preliminary analysis of the sequential simultaneous integrated boost technique for intensity-modulated radiotherapy for head and neck cancers

    PubMed Central

    Miyazaki, Masayoshi; Nishiyama, Kinji; Ueda, Yoshihiro; Ohira, Shingo; Tsujii, Katsutomo; Isono, Masaru; Masaoka, Akira; Teshima, Teruki

    2016-01-01

    The aim of this study was to compare three strategies for intensity-modulated radiotherapy (IMRT) for 20 head-and-neck cancer patients. For simultaneous integrated boost (SIB), doses were 66 and 54 Gy in 30 fractions for PTVboost and PTVelective, respectively. Two-phase IMRT delivered 50 Gy in 25 fractions to PTVelective in the First Plan, and 20 Gy in 10 fractions to PTVboost in the Second Plan. Sequential SIB (SEQ-SIB) delivered 55 Gy and 50 Gy in 25 fractions, respectively, to PTVboost and PTVelective using SIB in the First Plan and 11 Gy in 5 fractions to PTVboost in the Second Plan. Conformity indexes (CIs) (mean ± SD) for PTVboost and PTVelective were 1.09 ± 0.05 and 1.34 ± 0.12 for SIB, 1.39 ± 0.14 and 1.80 ± 0.28 for two-phase IMRT, and 1.14 ± 0.07 and 1.60 ± 0.18 for SEQ-SIB, respectively. CI was significantly highest for two-phase IMRT. Maximum doses (Dmax) to the spinal cord were 42.1 ± 1.5 Gy for SIB, 43.9 ± 1.0 Gy for two-phase IMRT and 40.3 ± 1.8 Gy for SEQ-SIB. Brainstem Dmax were 50.1 ± 2.2 Gy for SIB, 50.5 ± 4.6 Gy for two-phase IMRT and 47.4 ± 3.6 Gy for SEQ-SIB. Spinal cord Dmax for the three techniques was significantly different, and brainstem Dmax was significantly lower for SEQ-SIB. The compromised conformity of two-phase IMRT can result in higher doses to organs at risk (OARs). Lower OAR doses in SEQ-SIB made SEQ-SIB an alternative to SIB, which applies unconventional doses per fraction. PMID:26983983

  20. A technique using {sup 99m}Tc-mebrofenin SPECT for radiotherapy treatment planning for liver cancers or metastases

    SciTech Connect

    Shen, Sui; Jacob, Rojymon; Bender, Luvenia W.; Duan, Jun; Spencer, Sharon A.

    2014-04-01

    Radiotherapy or stereotactic body radiosurgery (SBRT) requires a sufficient functional liver volume to tolerate the treatment. The current study extended the work of de Graaf et al. (2010) [3] on the use of {sup 99m}Tc-mebrofenin imaging for presurgery planning to radiotherapy planning for liver cancer or metastases. Patient was immobilized and imaged in an identical position on a single-photon emission computed tomography/computed tomography (SPECT-CT) system and a radiotherapy simulation CT system. {sup 99m}Tc-mebrofenin SPECT was registered to the planning CT through image registration of noncontrast CT from SPECT-CT system to the radiotherapy planning CT. The voxels with higher uptake of {sup 99m}Tc-mebrofenin were transferred to the planning CT as an avoidance structure in optimizing a 2-arc RapidArc plan for SBRT delivery. Excellent dose coverage to the target and sparing of the healthy remnant liver volume was achieved. This report illustrated a procedure for the use of {sup 99m}Tc-mebrofenin SPECT for optimizing radiotherapy for liver cancers and metastases.

  1. Simultaneously precise frequency transfer and time synchronization using feed-forward compensation technique via 120 km fiber link

    PubMed Central

    Chen, Xing; Lu, Jinlong; Cui, Yifan; Zhang, Jian; Lu, Xing; Tian, Xusheng; Ci, Cheng; Liu, Bo; Wu, Hong; Tang, Tingsong; Shi, Kebin; Zhang, Zhigang

    2015-01-01

    Precision time synchronization between two remote sites is desired in many applications such as global positioning satellite systems, long-baseline interferometry, coherent radar detection and fundamental physics constant measurements. The recently developed frequency dissemination technologies based on optical fiber link have improved the transfer instability to the level of 10−19/day at remote location. Therefore it is possible to keep clock oscillation at remote locations continuously corrected, or to reproduce a “virtual” clock on the remote location. However the initial alignment and the correction of 1 pps timing signal from time to time are still required, besides the highly stabilized clock frequency transfer between distant locations. Here we demonstrate a time synchronization based on an ultra-stable frequency transfer system via 120-km commercial fiber link by transferring an optical frequency comb. Both the phase noise compensation in frequency dissemination and temporal basis alignment in time synchronization were implemented by a feed-forward digital compensation (FFDC) technique. The fractional frequency instability was measured to be 6.18 × 10−20 at 2000 s. The timing deviation of time synchronization was measured to be 0.6 ps in 1500 s. This technique also can be applied in multi-node fiber network topology. PMID:26691731

  2. Simultaneously precise frequency transfer and time synchronization using feed-forward compensation technique via 120 km fiber link.

    PubMed

    Chen, Xing; Lu, Jinlong; Cui, Yifan; Zhang, Jian; Lu, Xing; Tian, Xusheng; Ci, Cheng; Liu, Bo; Wu, Hong; Tang, Tingsong; Shi, Kebin; Zhang, Zhigang

    2015-01-01

    Precision time synchronization between two remote sites is desired in many applications such as global positioning satellite systems, long-baseline interferometry, coherent radar detection and fundamental physics constant measurements. The recently developed frequency dissemination technologies based on optical fiber link have improved the transfer instability to the level of 10(-19)/day at remote location. Therefore it is possible to keep clock oscillation at remote locations continuously corrected, or to reproduce a "virtual" clock on the remote location. However the initial alignment and the correction of 1 pps timing signal from time to time are still required, besides the highly stabilized clock frequency transfer between distant locations. Here we demonstrate a time synchronization based on an ultra-stable frequency transfer system via 120-km commercial fiber link by transferring an optical frequency comb. Both the phase noise compensation in frequency dissemination and temporal basis alignment in time synchronization were implemented by a feed-forward digital compensation (FFDC) technique. The fractional frequency instability was measured to be 6.18 × 10(-20) at 2000 s. The timing deviation of time synchronization was measured to be 0.6 ps in 1500 s. This technique also can be applied in multi-node fiber network topology. PMID:26691731

  3. SU-D-213-03: Towards An Optimized 3D Scintillation Dosimetry Tool for Quality Assurance of Dynamic Radiotherapy Techniques

    SciTech Connect

    Rilling, M; Goulet, M; Thibault, S; Archambault, L

    2015-06-15

    Purpose: The purpose of this work is to simulate a multi-focus plenoptic camera used as the measuring device in a real-time three-dimensional scintillation dosimeter. Simulating and optimizing this realistic optical system will bridge the technological gap between concept validation and a clinically viable tool that can provide highly efficient, accurate and precise measurements for dynamic radiotherapy techniques. Methods: The experimental prototype, previously developed for proof of concept purposes, uses an off-the-shelf multi-focus plenoptic camera. With an array of interleaved microlenses of different focal lengths, this camera records spatial and angular information of light emitted by a plastic scintillator volume. The three distinct microlens focal lengths were determined experimentally for use as baseline parameters by measuring image-to-object magnification for different distances in object space. A simulated plenoptic system was implemented using the non-sequential ray tracing software Zemax: this tool allows complete simulation of multiple optical paths by modeling interactions at interfaces such as scatter, diffraction, reflection and refraction. The active sensor was modeled based on the camera manufacturer specifications by a 2048×2048, 5 µm-pixel pitch sensor. Planar light sources, simulating the plastic scintillator volume, were employed for ray tracing simulations. Results: The microlens focal lengths were determined to be 384, 327 and 290 µm. A realistic multi-focus plenoptic system, with independently defined and optimizable specifications, was fully simulated. A f/2.9 and 54 mm-focal length Double Gauss objective was modeled as the system’s main lens. A three-focal length hexagonal microlens array of 250-µm thickness was designed, acting as an image-relay system between the main lens and sensor. Conclusion: Simulation of a fully modeled multi-focus plenoptic camera enables the decoupled optimization of the main lens and microlens

  4. Plasma microcontact patterning (PμCP): a technique for the precise control of surface patterning at small-scale.

    PubMed

    Picone, Remigio; Baum, Buzz; McKendry, Rachel

    2014-01-01

    Plasma microcontact patterning (PμCP) is a simple, efficient, and cost-effective method for the precise patterning of molecules on surfaces. It combines the use of low-pressure plasma with an elastomeric 3D mask to spatially control the removal of molecules, such as proteins, from a surface. The entire PμCP process is subdivided into three main steps: surface precoating, plasma micropatterning, and a surface postcoating step. Surfaces are first precoated with a molecular species and then placed in close contact with the 3D mask. This allows the formation of two distinct regions: an un-masked open-region which is accessible to the plasma, from which the surface layer is removed, and, a contact region which is physically protected from exposure to the plasma. In the final step, a second molecule is added to back-fill the pattern generated through plasma-treatment. The PμCP technique allows the patterning of virtually any organic molecules on different surface materials and geometries (e.g., flat, curved surfaces, and 3D microstructures). Moreover, it is a simple and robust procedure. The main advantages of this approach over traditional microcontact printing are twofold: The stability of molecule binding to plasma-treated surfaces, and the separation of the surface functionalization step from the actual micropatterning step, which enables the precise control of concentration and uniformity of patterned molecules. In conclusion, PμCP is a simple way to generate surface patterns that are highly reproducible, stable and uniform, making it a useful method for many applications. PMID:24439280

  5. Dosimetric comparison of axilla and groin radiotherapy techniques for high-risk and locally advanced skin cancer

    PubMed Central

    Mattes, Malcolm D.; Zhou, Ying; Berry, Sean L.; Barker, Christopher A.

    2016-01-01

    Purpose: Radiation therapy targeting axilla and groin lymph nodes improves regional disease control in locally advanced and high-risk skin cancers. However, trials generally used conventional two-dimensional radiotherapy (2D-RT), contributing towards relatively high rates of side effects from treatment. The goal of this study is to determine if three-dimensional conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), or volumetric-modulated arc therapy (VMAT) may improve radiation delivery to the target while avoiding organs at risk in the clinical context of skin cancer regional nodal irradiation. Materials and Methods: Twenty patients with locally advanced/high-risk skin cancers underwent computed tomography simulation. The relevant axilla or groin planning target volumes and organs at risk were delineated using standard definitions. Paired t-tests were used to compare the mean values of several dose-volumetric parameters for each of the 4 techniques. Results: In the axilla, the largest improvement for 3D-CRT compared to 2D-RT was for homogeneity index (13.9 vs. 54.3), at the expense of higher lung V20 (28.0% vs. 12.6%). In the groin, the largest improvements for 3D-CRT compared to 2D-RT were for anorectum Dmax (13.6 vs. 38.9 Gy), bowel D200cc (7.3 vs. 23.1 Gy), femur D50 (34.6 vs. 57.2 Gy), and genitalia Dmax (37.6 vs. 51.1 Gy). IMRT had further improvements compared to 3D-CRT for humerus Dmean (16.9 vs. 22.4 Gy), brachial plexus D5 (57.4 vs. 61.3 Gy), bladder D5 (26.8 vs. 36.5 Gy), and femur D50 (18.7 vs. 34.6 Gy). Fewer differences were observed between IMRT and VMAT. Conclusion: Compared to 2D-RT and 3D-CRT, IMRT and VMAT had dosimetric advantages in the treatment of nodal regions of skin cancer patients. PMID:27306779

  6. Fractionated beam radiotherapy is a special case of continuous beam radiotherapy when irradiation time is small.

    PubMed

    Biswas, Jayanta; Rajguru, Tapan K; Choudhury, Krishnangshu B; Dutta, Sumita; Sharma, Shyam; Sarkar, Aniruddha

    2013-01-01

    Fractionated beam radiotherapy, in other terms, external beam radiotherapy (EBRT) and continuous beam radiotherapy or Brachytherapy are two modes of radiotherapy techniques. Although in many ways, they appear to be different, radiobiologically, with the help of mathematics, it can be proved that the biological effective dose (BED) of EBRT is similar to BED of Brachytherapy, when irradiation time is small. Here an attempt is made to correlate these two predominant modes of radiotherapy techniques. PMID:24125964

  7. Evaluations of an adaptive planning technique incorporating dose feedback in image-guided radiotherapy of prostate cancer

    SciTech Connect

    Liu Han; Wu Qiuwen

    2011-12-15

    treatment course, then 11 patients fail. If the same criteria is assessed at the end of each week (every five fractions), then 14 patients fail, with three patients failing the 1st or 2nd week but passing at the end. The average dose deficit from these 14 patients was 4.4%. They improved to 2% after the weekly compensation. Out of these 14 patients who needed dose compensation, ten passed the dose criterion after weekly dose compensation, three patients failed marginally, and one patient still failed the criterion significantly (10% deficit), representing 3.6% of the patient population. A more aggressive compensation frequency (every three fractions) could successfully reduce the dose deficit to the acceptable level for this patient. The average number of required dose compensation re-planning per patient was 0.82 (0.79) per patient for schedule A (B) delivery strategy. The doses to OARs were not significantly different from the online IG only plans without dose compensation. Conclusions: We have demonstrated the effectiveness of offline dose compensation technique in image-guided radiotherapy for prostate cancer. It can effectively account for residual uncertainties which cannot be corrected through online IG. Dose compensation allows further margin reduction and critical organs sparing.

  8. Precise oxygen and hydrogen isotope determination in nanoliter quantities of speleothem inclusion water by cavity ring-down spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Uemura, Ryu; Nakamoto, Masashi; Asami, Ryuji; Mishima, Satoru; Gibo, Masakazu; Masaka, Kosuke; Jin-Ping, Chen; Wu, Chung-Che; Chang, Yu-Wei; Shen, Chuan-Chou

    2016-01-01

    Speleothem inclusion-water isotope compositions are a promising new climatic proxy, but their applicability is limited by their low content in water and by analytical challenges. We have developed a precise and accurate isotopic technique that is based on cavity ring-down spectroscopy (CRDS). This method features a newly developed crushing apparatus, a refined sample extraction line, careful evaluation of the water/carbonate adsorption effect. After crushing chipped speleothem in a newly-developed crushing device, released inclusion water is purified and mixed with a limited amount of nitrogen gas in the extraction line for CRDS measurement. We have measured 50-260 nL of inclusion water from 77 to 286 mg of stalagmite deposits sampled from Gyokusen Cave, Okinawa Island, Japan. The small sample size requirement demonstrates that our analytical technique can offer high-resolution inclusion water-based paleoclimate reconstructions. The 1σ reproducibility for different stalagmites ranges from ±0.05 to 0.61‰ for δ18O and ±0.0 to 2.9‰ for δD. The δD vs. δ18O plot for inclusion water from modern stalagmites is consistent with the local meteoric water line. The 1000 ln α values based on calcite and fluid inclusion measurements from decades-old stalagmites are in agreement with the data from present-day farmed calcite experiment. Combination of coeval carbonate and fluid inclusion data suggests that past temperatures at 9-10 thousand years ago (ka) and 26 ka were 3.4 ± 0.7 °C and 8.2 ± 2.4 °C colder than at present, respectively.

  9. Peripheral dose measurements in cervical cancer radiotherapy: a comparison of volumetric modulated arc therapy and step-and-shoot IMRT techniques

    PubMed Central

    2014-01-01

    Purpose The aim of this study was to investigate the peripheral doses resulting from volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) techniques in cervical cancer radiotherapy. Methods Nine patients with cervical cancer had treatment planned with both VMAT and IMRT. A specially designed phantom was used for this study, with ion chambers placed at interest points approximating the position of the breast, thyroid, and lens. The peripheral doses at the phantom interest points were measured and compared between the VMAT and IMRT techniques. Results VMAT provides a potential dosimetric advantage compared with IMRT. The mean (± standard deviation) peripheral dose to the breast point for 1 fraction (2 Gy) during VMAT measured 5.13 ± 0.96 mGy, compared with 9.04 ± 1.50 mGy for IMRT. At the thyroid and lens interest points, the mean (± standard deviation) peripheral dose during VMAT was 2.19 ± 0.33 and 2.16 ± 0.28 mGy, compared with 7.07 ± 0.76 and 6.97 ± 0.91 mGy for IMRT, respectively. VMAT reduced the monitor units used by 28% and shortened the treatment delivery time by 54% compared with IMRT. Conclusion While the dosimetric results are similar for both techniques, VMAT results in a lower peripheral dose to the patient and reduces the monitor-unit usage and treatment delivery time compared with IMRT. PMID:24555547

  10. Reliable and integrated technique for determining resonant frequency in radio frequency resonators. Application to a high-precision resonant cavity-based displacement sensor

    NASA Astrophysics Data System (ADS)

    Jauregui, Rigoberto; Asua, Estibaliz; Portilla, Joaquin; Etxebarria, Victor

    2015-03-01

    This paper presents a reliable and integrated technique for determining the resonant frequency of radio frequency resonators, which can be of interest for different purposes. The approach uses a heterodyne scheme as phase detector coupled to a voltage-controlled oscillator. The system seeks the oscillator frequency that produces a phase null in the resonator, which corresponds to the resonant frequency. A complete explanation of the technique to determine the resonant frequency is presented and experimentally tested. The method has been applied to a high-precision displacement sensor based on resonant cavity, obtaining a theoretical nanometric precision.

  11. Filling the gap in central shielding: three-dimensional analysis of the EQD2 dose in radiotherapy for cervical cancer with the central shielding technique.

    PubMed

    Tamaki, Tomoaki; Ohno, Tatsuya; Noda, Shin-ei; Kato, Shingo; Nakano, Takashi

    2015-09-01

    This study aimed to provide accurate dose distribution profiles of radiotherapy for cervical cancer when treated with the central shielding technique by analysing the composite 3D EQD2 dose distribution of external beam radiotherapy (EBRT) plus intracavitary brachytherapy (ICBT). On a phantom, four patterns of the combinations of whole pelvis irradiation (WP) (4 fields), pelvis irradiation with central shielding technique (CS) [anterior-posterior/posterior-anterior (AP-PA fields), shielding width of 3 or 4 cm] and ICBT using Point-A prescription were created: 30 Gy/15 fractions + 20 Gy/10 fractions + 24 Gy/4 fractions [Plan (30 + 20 + 24)], 40 Gy/20 fractions + 10 Gy/5 fractions + 18 Gy/3 fractions [Plan (40 + 10 + 18)], 40 Gy/20 fractions + 10 Gy/5 fractions + 24 Gy/4 fractions [Plan (40 + 10 + 24)] and 45 Gy/25 fractions + 0 Gy + 28 Gy/4 fractions [Plan (45 + 0 + 28)]. The composite EQD2 dose distributions of the complete treatment were analysed. The Point-A dose of Plan (30 + 20 + 24), Plan (40 + 10 + 18), Plan (40 + 10 + 24) and Plan (45 + 0 + 28) were 78.0 Gy (CS 3 cm)/71.8 Gy (CS 4 cm), 72.1 Gy (CS 3 cm)/69.0 Gy (CS 4 cm), 80.1 Gy (CS 3 cm)/77.0 Gy (CS 4 cm) and 84.1 Gy, whereas it has been previously reported to be 62 Gy, 64 Gy, 72 Gy and 84 Gy, respectively. For all the treatment plans with CS, equivalent or wider coverage of 60 Gy (EQD2) was achieved in the right-left direction, while coverage in the anterior-posterior direction decreased in plans with CS. There were no irregularly 'cold' regions around the central target. The use of CS in radiotherapy for cervical cancer resulted in tumor coverage in the lateral direction with doses higher than the previously reported Point-A doses. PMID:26062811

  12. WE-G-18A-07: Clinical Evaluation of Normalized Metal Artifact Reduction in KVCT Using MVCT Prior Images (MVCT-NMAR) Technique in Radiotherapy

    SciTech Connect

    Paudel, M; MacKenzie, M; Fallone, B; Rathee, S

    2014-06-15

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

  13. SU-C-17A-07: The Development of An MR Accelerator-Enabled Planning-To-Delivery Technique for Stereotactic Palliative Radiotherapy Treatment of Spinal Metastases

    SciTech Connect

    Hoogcarspel, S J; Kontaxis, C; Velden, J M van der; Bol, G H; Vulpen, M van; Lagendijk, J J W; Raaymakers, B W

    2014-06-01

    Purpose: To develop an MR accelerator-enabled online planning-todelivery technique for stereotactic palliative radiotherapy treatment of spinal metastases. The technical challenges include; automated stereotactic treatment planning, online MR-based dose calculation and MR guidance during treatment. Methods: Using the CT data of 20 patients previously treated at our institution, a class solution for automated treatment planning for spinal bone metastases was created. For accurate dose simulation right before treatment, we fused geometrically correct online MR data with pretreatment CT data of the target volume (TV). For target tracking during treatment, a dynamic T2-weighted TSE MR sequence was developed. An in house developed GPU based IMRT optimization and dose calculation algorithm was used for fast treatment planning and simulation. An automatically generated treatment plan developed with this treatment planning system was irradiated on a clinical 6 MV linear accelerator and evaluated using a Delta4 dosimeter. Results: The automated treatment planning method yielded clinically viable plans for all patients. The MR-CT fusion based dose calculation accuracy was within 2% as compared to calculations performed with original CT data. The dynamic T2-weighted TSE MR Sequence was able to provide an update of the anatomical location of the TV every 10 seconds. Dose calculation and optimization of the automatically generated treatment plans using only one GPU took on average 8 minutes. The Delta4 measurement of the irradiated plan agreed with the dose calculation with a 3%/3mm gamma pass rate of 86.4%. Conclusions: The development of an MR accelerator-enabled planning-todelivery technique for stereotactic palliative radiotherapy treatment of spinal metastases was presented. Future work will involve developing an intrafraction motion adaptation strategy, MR-only dose calculation, radiotherapy quality-assurance in a magnetic field, and streamlining the entire treatment

  14. SU-E-J-47: Development of a High-Precision, Image-Guided Radiotherapy, Multi- Purpose Radiation Isocenter Quality-Assurance Calibration and Checking System

    SciTech Connect

    Liu, C; Yan, G; Helmig, R; Lebron, S; Kahler, D

    2014-06-01

    Purpose: To develop a system that can define the radiation isocenter and correlate this information with couch coordinates, laser alignment, optical distance indicator (ODI) settings, optical tracking system (OTS) calibrations, and mechanical isocenter walkout. Methods: Our team developed a multi-adapter, multi-purpose quality assurance (QA) and calibration device that uses an electronic portal imaging device (EPID) and in-house image-processing software to define the radiation isocenter, thereby allowing linear accelerator (Linac) components to be verified and calibrated. Motivated by the concept that each Linac component related to patient setup for image-guided radiotherapy based on cone-beam CT should be calibrated with respect to the radiation isocenter, we designed multiple concentric adapters of various materials and shapes to meet the needs of MV and KV radiation isocenter definition, laser alignment, and OTS calibration. The phantom's ability to accurately define the radiation isocenter was validated on 4 Elekta Linacs using a commercial ball bearing (BB) phantom as a reference. Radiation isocenter walkout and the accuracy of couch coordinates, ODI, and OTS were then quantified with the device. Results: The device was able to define the radiation isocenter within 0.3 mm. Radiation isocenter walkout was within ±1 mm at 4 cardinal angles. By switching adapters, we identified that the accuracy of the couch position digital readout, ODI, OTS, and mechanical isocenter walkout was within sub-mm. Conclusion: This multi-adapter, multi-purpose isocenter phantom can be used to accurately define the radiation isocenter and represents a potential paradigm shift in Linac QA. Moreover, multiple concentric adapters allowed for sub-mm accuracy for the other relevant components. This intuitive and user-friendly design is currently patent pending.

  15. Application of Phase Smoothing Pseudo Range PPP/INS Tightly Coupled Technique in Improving the Results of Low Precision MEMS

    NASA Astrophysics Data System (ADS)

    Luo, X.

    2015-12-01

    In land surveying and engineering surveying, we need to obtain high precision navigation results. However, due to the inertial device costs less than a introduction, commonly used low precision inertial navigation equipment with tightly coupled GPS / INS integrated to get high precision navigation results. Many studies have improved the accuracy of error by using the UKF and CKF filtering algorithm, but it is still using the traditional pseudo code directly, the improvement effect is not obvious, and the disturbance is large. In this study, the PPP /INSmodel is improved by using the carrier phase smoothing pseudo range algorithm. Experimental results show that based on phase smoothing pseudo range PPP/INS tight coupled method, the position precision and the velocity precision for of the measured data of higher accuracy of MEMS and GPS receiver can get to a decimeter level and centimeter level. This coupling method has higher accuracy, stronger anti disturbance and Have a better convergence than the traditional C/A code. Based on different phase smoothing epoch number combination the accuracy and smoothing effect is also different, the larger smooth epoch number is, the better treatment effect it has and The higher precision it has. For high precision measurement, the equipment cost is saved. It has a practical significance meaning in the measurement of outdoor ground.

  16. Image Guidance in Radiation Therapy: Techniques and Applications

    PubMed Central

    Kataria, Tejinder

    2014-01-01

    In modern day radiotherapy, the emphasis on reduction on volume exposed to high radiotherapy doses, improving treatment precision as well as reducing radiation-related normal tissue toxicity has increased, and thus there is greater importance given to accurate position verification and correction before delivering radiotherapy. At present, several techniques that accomplish these goals impeccably have been developed, though all of them have their limitations. There is no single method available that eliminates treatment-related uncertainties without considerably adding to the cost. However, delivering “high precision radiotherapy” without periodic image guidance would do more harm than treating large volumes to compensate for setup errors. In the present review, we discuss the concept of image guidance in radiotherapy, the current techniques available, and their expected benefits and pitfalls. PMID:25587445

  17. Clinical Applications of 3-D Conformal Radiotherapy

    NASA Astrophysics Data System (ADS)

    Miralbell, Raymond

    Although a significant improvement in cancer cure (i.e. 20% increment) has been obtained in the last 2-3 decades, 30-40% of patients still fail locally after curative radiotherapy. In order to improve local tumor control rates with radiotherapy high doses to the tumor volume are frequently necessary. Three-dimensional conformal radiation therapy (3-D CRT) is used to denote a spectrum of radiation planning and delivery techniques that rely on three-dimensional imaging to define the target (tumor) and to distinguish it from normal tissues. Modern, high-precision radiotherapy (RT) techniques are needed in order to implement the goal of optimal tumor destruction delivering minimal dose to the non-target normal tissues. A better target definition is nowadays possible with contemporary imaging (computerized tomography, magnetic resonance imaging, and positron emission tomography) and image registration technology. A highly precise dose distributions can be obtained with optimal 3-D CRT treatment delivery techniques such as stereotactic RT, intensity modulated RT (IMRT), or protontherapy (the latter allowing for in-depth conformation). Patient daily set-up repositioning and internal organ immobilization systems are necessary before considering to undertake any of the above mentioned high-precision treatment approaches. Prostate cancer, brain tumors, and base of skull malignancies are among the sites most benefitting of dose escalation approaches. Nevertheless, a significant dose reduction to the normal tissues in the vicinity of the irradiated tumor also achievable with optimal 3-D CRT may also be a major issue in the treatment of pediatric tumors in order to preserve growth, normal development, and to reduce the risk of developing radiation induced diseases such as cancer or endocrinologic disorders.

  18. In situ precision electrospinning as an effective delivery technique for cyanoacrylate medical glue with high efficiency and low toxicity.

    PubMed

    Dong, R H; Qin, C C; Qiu, X; Yan, X; Yu, M; Cui, L; Zhou, Y; Zhang, H D; Jiang, X Y; Long, Y Z

    2015-12-14

    The side effects or toxicity of cyanoacrylate used in vivo have been argued since its first application in wound closure. We propose an airflow-assisted in situ precision electrospinning apparatus as an applicator and make a detailed comparison with traditional spraying via in vitro and in vivo experiments. This novel method can not only improve operational performance and safety by precisely depositing cyanoacrylate fibers onto a wound, but significantly reduce the dosage of cyanoacrylate by almost 80%. A white blood cell count, liver function test and histological analysis prove that the in situ precision electrospinning applicator produces a better postoperative outcome, e.g., minor hepatocyte injury, moderate inflammation and the significant ability for liver regeneration. This in situ precision electrospinning method may thus dramatically broaden both civilian and military applications of cyanoacrylates. PMID:26531687

  19. In situ precision electrospinning as an effective delivery technique for cyanoacrylate medical glue with high efficiency and low toxicity

    NASA Astrophysics Data System (ADS)

    Dong, R. H.; Qin, C. C.; Qiu, X.; Yan, X.; Yu, M.; Cui, L.; Zhou, Y.; Zhang, H. D.; Jiang, X. Y.; Long, Y. Z.

    2015-11-01

    The side effects or toxicity of cyanoacrylate used in vivo have been argued since its first application in wound closure. We propose an airflow-assisted in situ precision electrospinning apparatus as an applicator and make a detailed comparison with traditional spraying via in vitro and in vivo experiments. This novel method can not only improve operational performance and safety by precisely depositing cyanoacrylate fibers onto a wound, but significantly reduce the dosage of cyanoacrylate by almost 80%. A white blood cell count, liver function test and histological analysis prove that the in situ precision electrospinning applicator produces a better postoperative outcome, e.g., minor hepatocyte injury, moderate inflammation and the significant ability for liver regeneration. This in situ precision electrospinning method may thus dramatically broaden both civilian and military applications of cyanoacrylates.

  20. Evaluation of Four-Dimensional Computed Tomography-Based Intensity-Modulated and Respiratory-Gated Radiotherapy Techniques for Pancreatic Carcinoma

    SciTech Connect

    Geld, Ylanga G. van der; Triest, Baukelien van; Verbakel, Wilko; Soernsen de Koste, John R. van; Senan, Suresh; Slotman, Ben J.; Lagerwaard, Frank J.

    2008-11-15

    Purpose: To compare conformal radiotherapy (CRT), intensity-modulated radiotherapy (IMRT), and respiration-gated radiotherapy (RGRT) planning techniques for pancreatic cancer. All target volumes were determined using four-dimensional computed tomography scans (4D CT). Methods and Materials: The pancreatic tumor and enlarged regional lymph nodes were contoured on all 10 phases of a planning 4D CT scan for 10 patients, and the planning target volumes (PTV{sub allphases}) were generated. Three consecutive respiratory phases for RGRT delivery in both inspiration and expiration were identified, and the corresponding PTVs (PTV{sub inspiration} and PTV{sub expiration}) and organ at risk volumes created. Treatment plans using CRT and IMRT, with and without RGRT, were created for each PTV. Results: Compared with the CRT plans, IMRT significantly reduced the mean volume of right kidney exposed to 20 Gy from 27.7% {+-} 17.7% to 16.0% {+-} 18.2% (standard deviation) (p < 0.01), but this was not achieved for the left kidney (11.1% {+-} 14.2% to 5.7% {+-} 6.5%; p = 0.1). The IMRT plans also reduced the mean gastric, hepatic, and small bowel doses (p < 0.01). No additional reductions in the dose to the kidneys or other organs at risk were seen when RGRT plans were combined with either CRT or IMRT, and the findings for RGRT in end-expiration and end-inspiration were similar. Conclusion: 4D CT-based IMRT plans for pancreatic tumors significantly reduced the radiation doses to the right kidney, liver, stomach, and small bowel compared with CRT plans. The additional dosimetric benefits from RGRT appear limited in this setting.

  1. From technological advances to biological understanding: The main steps toward high-precision RT in breast cancer.

    PubMed

    Leonardi, Maria Cristina; Ricotti, Rosalinda; Dicuonzo, Samantha; Cattani, Federica; Morra, Anna; Dell'Acqua, Veronica; Orecchia, Roberto; Jereczek-Fossa, Barbara Alicja

    2016-10-01

    Radiotherapy improves local control in breast cancer (BC) patients which increases overall survival in the long term. Improvements in treatment planning and delivery and a greater understanding of BC behaviour have laid the groundwork for high-precision radiotherapy, which is bound to further improve the therapeutic index. Precise identification of target volumes, better coverage and dose homogeneity have had a positive impact on toxicity and local control. The conformity of treatment dose due to three-dimensional radiotherapy and new techniques such as intensity modulated radiotherapy makes it possible to spare surrounding normal tissue. The widespread use of dose-volume constraints and histograms have increased awareness of toxicity. Real time image guidance has improved geometric precision and accuracy, together with the implementation of quality assurance programs. Advances in the precision of radiotherapy is also based on the choice of the appropriate fractionation and approach. Adaptive radiotherapy is not only a technical concept, but is also a biological concept based on the knowledge that different types of BC have distinctive patterns of locoregional spread. A greater understanding of cancer biology helps in choosing the treatment best suited to a particular situation. Biomarkers predictive of response play a crucial role. The combination of radiotherapy with molecular targeted therapies may enhance radiosensitivity, thus increasing the cytotoxic effects and improving treatment response. The appropriateness of an alternative fractionation, partial breast irradiation, dose escalating/de-escalating approaches, the extent of nodal irradiation have been examined for all the BC subtypes. The broadened concept of adaptive radiotherapy is vital to high-precision treatments. PMID:27542556

  2. Wide-capture-range, high-precision wavelength stabilization within ±50 MHz for flexible-grid wavelength division multiplexing by photomixing technique

    NASA Astrophysics Data System (ADS)

    Tsuboi, Jun; Kuboki, Takeshi; Kato, Kazutoshi

    2016-08-01

    The lasers for the flexible-grid wavelength division multiplexing (WDM) system are required to have high precision of wavelength stability. Previously, we proposed the wavelength-controlling system of the distributed feedback laser diode (DFB-LD) with the photomixing technique and a microwave filter to precisely measure the optical frequency error from the target value. To enlarge the wavelength-capture range, we improve the system to detect the wavelength error with two different microwave filters in parallel. Experimental results show that the wavelength-capture range is extended up to 4 GHz while the wavelength error is still kept within ±50 MHz.

  3. [Radiotherapy of benign intracranial tumors].

    PubMed

    Delannes, M; Latorzeff, I; Chand, M E; Huchet, A; Dupin, C; Colin, P

    2016-09-01

    Most of the benign intracranial tumors are meningiomas, vestibular schwannomas, pituitary adenomas, craniopharyngiomas, and glomus tumors. Some of them grow very slowly, and can be observed without specific treatment, especially if they are asymptomatic. Symptomatic or growing tumors are treated by surgery, which is the reference treatment. When surgery is not possible, due to the location of the lesion, or general conditions, radiotherapy can be applied, as it is if there is a postoperative growing residual tumor, or a local relapse. Indications have to be discussed in polydisciplinary meetings, with precise evaluation of the benefit and risks of the treatments. The techniques to be used are the most modern ones, as multimodal imaging and image-guided radiation therapy. Stereotactic treatments, using fractionated or single doses depending on the size or the location of the tumors, are commonly realized, to avoid as much a possible the occurrence of late side effects. PMID:27523417

  4. SU-E-P-56: Dosimetric Comparison of Three Post Modified Radical Mastectomy Radiotherapy Techniques for Locally Advanced Left-Sided Breast Cancer and Beyond

    SciTech Connect

    Ma, C; Zhang, W; Lu, J; Wu, L; Wu, F; Huang, B; Li, D

    2015-06-15

    Purpose: To compare the dosimetry of post modified radical mastectomy radiotherapy (PMRMRT) for left-sided breast cancer using 3-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). Methods: We created ten sets of PMRMRT plans for ten consecutive patients and utilized two tangential and one or two supraclavicular beams in 3DCRT, a total of 5 beams in IMRT and two optimized partial arcs in VMAT. The difference in results between any two of the three new plans, between new and previous 3DCRT plans were compared and analyzed by ANOVA (α =0.05) and paired-sample t-test respectively. P values less than 0.05 were considered statistically significant. Results: Both IMRT and VMAT plans had similar PTV coverage, hotspot area and conformity (all p>0.05), and significantly higher PTV coverage compared with new 3DCRT (both p<0.001). IMRT plans had significantly less heart and left lung radiation exposure compared with VMAT (all p<0.05). The 3DCRT plans with larger estimated CTV displacement had better target coverage but worse OARs sparing compared to those with smaller one. Conclusion: IMRT has dosimetrical advantages over the other two techniques in PMRMRT for left-sided breast cancer. Individually quantifying and minimizing CTV displacement can significantly improve dosage distribution. This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)

  5. Improving target dose coverage and organ-at-risk sparing in intensity-modulated radiotherapy of advanced laryngeal cancer by a simple optimization technique

    PubMed Central

    Lu, J-Y; Wu, L-L; Zhang, J-Y; Zheng, J; Cheung, M L-M; Ma, C-C; Xie, L-X

    2015-01-01

    Objective: To evaluate a simple optimization technique intended to improve planning target volume (PTV) dose coverage and organ-at-risk (OAR) sparing in intensity-modulated radiotherapy (IMRT) of advanced laryngeal cancer. Methods: Generally acceptable initial IMRT plans were generated for 12 patients and were improved individually by the following two techniques: (1) base dose function-based (BDF) technique, in which the treatment plans were reoptimized based on the initial IMRT plans; (2) dose-controlling structure-based (DCS) technique, in which the initial IMRT plans were reoptimized by adding constraints for hot and cold spots. The initial, BDF and DCS IMRT plans and additionally generated volumetric modulated arc therapy (VMAT) plans were compared concerning homogeneity index (HI) and conformity index (CI) of PTVs prescribed at 70 Gy/60 Gy (PTV70/PTV60), OAR sparing, monitor units (MUs) per fraction and total planning time. Results: Compared with the initial IMRT and DCS IMRT plans, the BDF technique provided superior HI/CI, by approximately 19–37%/4–11%, and lower doses to most OARs, by approximately 1–7%, except for the comparable HI of PTV60 to DCS IMRT plans. Compared with VMAT plans, the BDF technique provided comparable HI, CI and most-OAR sparing, except for the superior HI of PTV70, by approximately 13%. The BDF technique produced more MUs and reduced the planning time. Conclusion: The BDF optimization technique for IMRT of advanced laryngeal cancer can improve target dose homogeneity and conformity, spare most OARs and is efficient. Advances in knowledge: A novel optimization technique for improving IMRT was assessed and found to be effective and efficient. PMID:25494885

  6. Dosimetric study of the protection level of the bone marrow in patients with cervical or endometrial cancer for three radiotherapy techniques - 3D CRT, IMRT and VMAT. Study protocol.

    NASA Astrophysics Data System (ADS)

    Jodda, Agata; Urbański, Bartosz; Piotrowski, Tomasz; Malicki, Julian

    2016-03-01

    Background: The paper shows the methodology of an in-phantom study of the protection level of the bone marrow in patients with cervical or endometrial cancer for three radiotherapy techniques: three-dimensional conformal radiotherapy, intensity modulated radiotherapy, and volumetric modulated arc therapy, preceded by the procedures of image guidance. Methods/Design: The dosimetric evaluation of the doses will be performed in an in-house multi-element anthropomorphic phantom of the female pelvic area created by three-dimensional printing technology. The volume and position of the structures will be regulated according to the guidelines from the Bayesian network. The input data for the learning procedure of the model will be obtained from the retrospective analysis of imaging data obtained for 96 patients with endometrial cancer or cervical cancer treated with radiotherapy in our centre in 2008-2013. Three anatomical representations of the phantom simulating three independent clinical cases will be chosen. Five alternative treatment plans (1 × three-dimensional conformal radiotherapy, 2 × intensity modulated radiotherapy and 2 × volumetric modulated arc therapy) will be created for each representation. To simulate image-guided radiotherapy, ten specific recombinations will be designated, for each anatomical representation separately, reflecting possible changes in the volume and position of the phantom components. Discussion: The comparative analysis of planned measurements will identify discrepancies between calculated doses and doses that were measured in the phantom. Finally, differences between the doses cumulated in the hip plates performed by different techniques simulating the gynaecological patients' irradiation of dose delivery will be established. The results of this study will form the basis of the prospective clinical trial that will be designed for the assessment of hematologic toxicity and its correlation with the doses cumulated in the hip plates

  7. Dosimetric Comparison and Evaluation of Three Radiotherapy Techniques for Use after Modified Radical Mastectomy for Locally Advanced Left-sided Breast Cancer.

    PubMed

    Ma, Changchun; Zhang, Wuzhe; Lu, Jiayang; Wu, Lili; Wu, Fangcai; Huang, Baotian; Lin, Yan; Li, Dongsheng

    2015-01-01

    This study aimed to compare the post-modified radical mastectomy radiotherapy (PMRMRT) for left-sided breast cancer utilizing 3-dimensional conformal radiotherapy with field-in-field technique (3DCRT-FinF), 5-field intensity-modulated radiation therapy (5F-IMRT) and 2- partial arc volumetric modulated arc therapy (2P-VMAT). We created the 3 different PMRMRT plans for each of the ten consecutive patients. We performed Kruskal-Wallis analysis of variance (ANOVA) followed by the Dunn's-type multiple comparisons to establish a hierarchy in terms of plan quality and dosimetric benefits. P < 0.05 was considered statistically significant. Both 5F-IMRT and 2P-VMAT plans exhibited similar PTV coverage (V95%), hotspot areas (V110%) and conformity (all p > 0.05), and significantly higher PTV coverage compared with 3DCRT-FinF (both p < 0.001). In addition, 5F-IMRT plans provided significantly less heart and left lung radiation exposure than 2P-VMAT (all p < 0.05). The 3DCRT-FinF plans with accurately estimated CTV displacement exhibited enhanced target coverage but worse organs at risk (OARs) sparing compared with those plans with underestimated displacements. Our results indicate that 5F-IMRT has dosimetrical advantages compared with the other two techniques in PMRMRT for left-sided breast cancer given its optimal balance between PTV coverage and OAR sparing (especially heart sparing). Individually quantifying and minimizing CTV displacement can significantly improve dosage distribution. PMID:26194593

  8. Dosimetric Comparison and Evaluation of Three Radiotherapy Techniques for Use after Modified Radical Mastectomy for Locally Advanced Left-sided Breast Cancer

    PubMed Central

    Ma, Changchun; Zhang, Wuzhe; Lu, Jiayang; Wu, Lili; Wu, Fangcai; Huang, Baotian; Lin, Yan; Li, Dongsheng

    2015-01-01

    This study aimed to compare the post-modified radical mastectomy radiotherapy (PMRMRT) for left-sided breast cancer utilizing 3-dimensional conformal radiotherapy with field-in-field technique (3DCRT-FinF), 5-field intensity-modulated radiation therapy (5F-IMRT) and 2- partial arc volumetric modulated arc therapy (2P-VMAT). We created the 3 different PMRMRT plans for each of the ten consecutive patients. We performed Kruskal-Wallis analysis of variance (ANOVA) followed by the Dunn’s-type multiple comparisons to establish a hierarchy in terms of plan quality and dosimetric benefits. P < 0.05 was considered statistically significant. Both 5F-IMRT and 2P-VMAT plans exhibited similar PTV coverage (V95%), hotspot areas (V110%) and conformity (all p > 0.05), and significantly higher PTV coverage compared with 3DCRT-FinF (both p < 0.001). In addition, 5F-IMRT plans provided significantly less heart and left lung radiation exposure than 2P-VMAT (all p < 0.05). The 3DCRT-FinF plans with accurately estimated CTV displacement exhibited enhanced target coverage but worse organs at risk (OARs) sparing compared with those plans with underestimated displacements. Our results indicate that 5F-IMRT has dosimetrical advantages compared with the other two techniques in PMRMRT for left-sided breast cancer given its optimal balance between PTV coverage and OAR sparing (especially heart sparing). Individually quantifying and minimizing CTV displacement can significantly improve dosage distribution. PMID:26194593

  9. Precise determination of full matrix of piezo-optic coefficients with a four-point bending technique: the example of lithium niobate crystals.

    PubMed

    Krupych, Oleg; Savaryn, Viktoriya; Vlokh, Rostyslav

    2014-04-01

    A recently proposed technique representing a combination of digital imaging laser interferometry with a classical four-point bending method is applied to a canonical nonlinear optical crystal, LiNbO₃, to precisely determine a full matrix of its piezo-optic coefficients (POCs). The contribution of a secondary piezo-optic effect to the POCs is investigated experimentally and analyzed theoretically. Based on the POCs thus obtained, a full matrix of strain-optic coefficients (SOCs) is calculated and the appropriate errors are estimated. A comparison of our experimental errors for the POCs and SOCs with the known reference data allows us to claim the present technique as the most precise. PMID:24787189

  10. A precise radiographic method to determine the location of the inferior alveolar canal in the posterior edentulous mandible: implications for dental implants. Part 1: Technique.

    PubMed

    Stella, J P; Tharanon, W

    1990-01-01

    In severely atrophic or osteoporotic mandibles, the location of the inferior alveolar nerve may vary considerably, both superoinferiorly and mediolaterally. A clinician's ability to reliably locate this nerve within the mandible would permit the surgical planning of implant placement in the posterior edentulous mandible. Eight edentulous cadaver mandibles were studied. A technique that precisely locates the inferior alveolar nerve within the mandible is described. The technique will aid the surgeon in planning a surgical approach to the posterior mandible with reduced risk of injury to the inferior alveolar nerve. PMID:2391135

  11. [Which rules apply to hypofractionated radiotherapy?].

    PubMed

    Supiot, S; Clément-Colmou, K; Paris, F; Corre, I; Chiavassa, S; Delpon, G

    2015-10-01

    Hypofractionated radiotherapy is now more widely prescribed due to improved targeting techniques (intensity modulated radiotherapy, image-guided radiotherapy and stereotactic radiotherapy). Low dose hypofractionated radiotherapy is routinely administered mostly for palliative purposes. High or very high dose hypofractionated irradiation must be delivered according to very strict procedures since every minor deviation can lead to major changes in dose delivery to the tumor volume and organs at risk. Thus, each stage of the processing must be carefully monitored starting from the limitations and the choice of the hypofractionation technique, tumour contouring and dose constraints prescription, planning and finally dose calculation and patient positioning verification. PMID:26321647

  12. Craniospinal irradiation techniques

    NASA Astrophysics Data System (ADS)

    Scarlatescu, Ioana; Virag, Vasile; Avram, Calin N.

    2015-12-01

    In this paper we present one treatment plan for irradiation cases which involve a complex technique with multiple beams, using the 3D conformational technique. As the main purpose of radiotherapy is to administrate a precise dose into the tumor volume and protect as much as possible all the healthy tissues around it, for a case diagnosed with a primitive neuro ectoderm tumor, we have developed a new treatment plan, by controlling one of the two adjacent fields used at spinal field, in a way that avoids the fields superposition. Therefore, the risk of overdose is reduced by eliminating the field divergence.

  13. Craniospinal irradiation techniques

    SciTech Connect

    Scarlatescu, Ioana Avram, Calin N.; Virag, Vasile

    2015-12-07

    In this paper we present one treatment plan for irradiation cases which involve a complex technique with multiple beams, using the 3D conformational technique. As the main purpose of radiotherapy is to administrate a precise dose into the tumor volume and protect as much as possible all the healthy tissues around it, for a case diagnosed with a primitive neuro ectoderm tumor, we have developed a new treatment plan, by controlling one of the two adjacent fields used at spinal field, in a way that avoids the fields superposition. Therefore, the risk of overdose is reduced by eliminating the field divergence.

  14. An Investigation on the Reliability of Deformation Analysis at Simulated Network Depending on the Precise Point Position Technique

    NASA Astrophysics Data System (ADS)

    Durdag, U. M.; Erdogan, B.; Hekimoglu, S.

    2014-12-01

    Deformation analysis plays an important role for human life safety; hence investigating the reliability of the obtained results from deformation analysis is crucial. The deformation monitoring network is established and the observations are analyzed periodically. The main problem in the deformation analysis is that if there is more than one displaced point in the monitoring network, the analysis methods smear the disturbing effects of the displaced points over all other points which are not displaced. Therefore, only one displaced point can be detected successfully. The Precise Point Positioning (PPP) gives opportunity to prevent smearing effect of the displaced points. In this study, we have simulated a monitoring network that consisting four object points and generated six different scenarios. The displacements were added to the points by using a device that the GPS antenna was easily moved horizontally and the seven hours static GPS measurements were carried out. The measurements were analyzed by using online Automatic Precise Positioning Service (APPS) to obtain the coordinates and covariance matrices. The results of the APPS were used in the deformation analysis. The detected points and true displaced points were compared with each other to obtain reliability of the method. According to the results, the analysis still detect stable points as displaced points. For the next step, we are going to search the reason of the wrong results and deal with acquiring more reliable results.

  15. High precision micro-impulse measurements for micro-thrusters based on torsional pendulum and sympathetic resonance techniques.

    PubMed

    Zhang, Daixian; Wu, Jianjun; Zhang, Rui; Zhang, Hua; He, Zhen

    2013-12-01

    A sympathetic resonance theory is analyzed and applied in a newly developed torsional pendulum to measure the micro-impulse produced by a μN s-class ablative pulsed plasma thruster. According to theoretical analysis on the dynamical behaviors of a torsional pendulum, the resonance amplification effect of micro-signals is presented. In addition, a new micro-impulse measurement method based on sympathetic resonance theory is proposed as an improvement of the original single pulse measurement method. In contrast with the single pulse measurement method, the advantages of sympathetic resonance method are significant. First, because of the magnification of vibration signals due to resonance processes, measurement precision for the sympathetic resonance method becomes higher especially in reducing reading error. With an increase in peak number, the relative errors induced by readout of voltage signals decrease to approximately ±1.9% for the sympathetic resonance mode, whereas the relative error in single pulse mode is estimated as ±13.4%. Besides, by using the resonance amplification effect the sympathetic resonance method makes it possible to measure an extremely low-impulse beyond the resolution of a thrust stand without redesigning or purchasing a new one. Moreover, because of the simple operational principle and structure the sympathetic resonance method is much more convenient and inexpensive to be implemented than other high-precision methods. Finally, the sympathetic resonance measurement method can also be applied in other thrust stands to improve further the ability to measure the low-impulse bits. PMID:24387474

  16. High precision micro-impulse measurements for micro-thrusters based on torsional pendulum and sympathetic resonance techniques

    NASA Astrophysics Data System (ADS)

    Zhang, Daixian; Wu, Jianjun; Zhang, Rui; Zhang, Hua; He, Zhen

    2013-12-01

    A sympathetic resonance theory is analyzed and applied in a newly developed torsional pendulum to measure the micro-impulse produced by a μN s-class ablative pulsed plasma thruster. According to theoretical analysis on the dynamical behaviors of a torsional pendulum, the resonance amplification effect of micro-signals is presented. In addition, a new micro-impulse measurement method based on sympathetic resonance theory is proposed as an improvement of the original single pulse measurement method. In contrast with the single pulse measurement method, the advantages of sympathetic resonance method are significant. First, because of the magnification of vibration signals due to resonance processes, measurement precision for the sympathetic resonance method becomes higher especially in reducing reading error. With an increase in peak number, the relative errors induced by readout of voltage signals decrease to approximately ±1.9% for the sympathetic resonance mode, whereas the relative error in single pulse mode is estimated as ±13.4%. Besides, by using the resonance amplification effect the sympathetic resonance method makes it possible to measure an extremely low-impulse beyond the resolution of a thrust stand without redesigning or purchasing a new one. Moreover, because of the simple operational principle and structure the sympathetic resonance method is much more convenient and inexpensive to be implemented than other high-precision methods. Finally, the sympathetic resonance measurement method can also be applied in other thrust stands to improve further the ability to measure the low-impulse bits.

  17. An FBG sensor interrogation technique based on a precise optical recirculating frequency shifter driven by RF signals

    NASA Astrophysics Data System (ADS)

    Wang, Zifei; Yang, Tianxin; Jia, Dongfang; Wang, Zhaoying; Sang, Mei

    2013-03-01

    Fiber Bragg grating (FBG) sensors have numerous advantages to sense multi-physical quantities such as the temperature and strain simultaneously by monitoring the shift of the returned "Bragg" wavelength resulting from changes in these quantities. Several FBG interrogation systems have been set up using photo detectors instead of an optical spectrum analyzer (OSA) to convert wavelength to time measurements. However, in those systems, it is necessary to use mechanical tuning components to generate fast-speed wavelength-swept light sources for high-precision FBG interrogation. In this paper, a low-cost and delicate wavelength-shift detection system, without any mechanical scanning parts, is proposed and demonstrated. The wavelength scanning system is a recirculating frequency shifter (RFS) which consists of an optical amplifier, an under test FBG sensor and an optical single-sideband (SSB) modulator driven by RF signals at 10 GHz. The measurement accuracy of this system is 0.08nm.

  18. Radiotherapy in benign orbital disease. II: Ophthalmic Graves' disease and orbital histiocytosis X.

    PubMed Central

    Harnett, A. N.; Doughty, D.; Hirst, A.; Plowman, P. N.

    1988-01-01

    Ophthalmic Graves' disease and histiocytosis X involving the orbit are occasionally refractory to treatment, so that vision may be threatened. In these situations megavoltage external beam radiotherapy should be employed, and the indications for this treatment are discussed. A highly accurate technique is described, using precise planning with information obtained from high definition CT scans, a complete patient head shell for immobilisation, and modern megavoltage radiotherapy treatment machines. As a result the dose to the lens is minimised (to a maximum of 10% of the prescribed dose), and late morbidity will be small. Two cases are described to illustrate this procedure and the response to treatment. Images PMID:3259894

  19. Dosimetric Benefits of Intensity-Modulated Radiotherapy Combined With the Deep-Inspiration Breath-Hold Technique in Patients With Mediastinal Hodgkin's Lymphoma

    SciTech Connect

    Paumier, Amaury; Ghalibafian, Mithra; Gilmore, Jennifer; Beaudre, Anne; Blanchard, Pierre; El Nemr, Mohammed; Azoury, Farez; Al Hamokles, Hweej; Lefkopoulos, Dimitri; Girinsky, Theodore

    2012-03-15

    Purpose: To assess the additional benefits of using the deep-inspiration breath-hold (DIBH) technique with intensity-modulated radiotherapy (IMRT) in terms of the protection of organs at risk for patients with mediastinal Hodgkin's disease. Methods and Materials: Patients with early-stage Hodgkin's lymphoma with mediastinal involvement were entered into the study. Two simulation computed tomography scans were performed for each patient: one using the free-breathing (FB) technique and the other using the DIBH technique with a dedicated spirometer. The clinical target volume, planning target volume (PTV), and organs at risk were determined on both computed tomography scans according to the guidelines of the European Organization for Research and Treatment of Cancer. In both cases, 30 Gy in 15 fractions was prescribed. The dosimetric parameters retrieved for the statistical analysis were PTV coverage, mean heart dose, mean coronary artery dose, mean lung dose, and lung V20. Results: There were no significant differences in PTV coverage between the two techniques (FB vs. DIBH). The mean doses delivered to the coronary arteries, heart, and lungs were significantly reduced by 15% to 20% using DIBH compared with FB, and the lung V20 was reduced by almost one third. The dose reduction to organs at risk was greater for masses in the upper part of the mediastinum. IMRT with DIBH was partially implemented in 1 patient. This combination will be extended to other patients in the near future. Conclusions: Radiation exposure of the coronary arteries, heart, and lungs in patients with mediastinal Hodgkin's lymphoma was greatly reduced using DIBH with IMRT. The greatest benefit was obtained for tumors in the upper part of the mediastinum. The possibility of a wider use in clinical practice is currently under investigation in our department.

  20. Five-year prospective patient evaluation of bladder and bowel symptoms after dose-escalated radiotherapy for prostate cancer with the BeamCath (registered) technique

    SciTech Connect

    Fransson, Per . E-mail: Per.Fransson@onkologi.umu.se; Bergstroem, Per; Loefroth, Per-Olov; Widmark, Anders

    2006-10-01

    Purpose: Late side effects were prospectively evaluated up to 5 years after dose-escalated external beam radiotherapy (EBRT) and were compared with a previously treated series with conventional conformal technique. Methods and Materials: Bladder and bowel symptoms were prospectively evaluated with the Prostate Cancer Symptom Scale (PCSS) questionnaire up to 5 years posttreatment. In all, 257 patients completed the questionnaire 5 years posttreatment. A total of 168 patients were treated with the conformal technique at doses <71 Gy, and 195 were treated with the dose-escalated stereotactic BeamCath (registered) technique comprising three dose levels: 74 Gy (n = 68), 76 Gy (n = 74), and 78 Gy (n = 53). Results: For all dose groups analyzed together, 5 years after treatment, urinary starting problems decreased and urinary incontinence increased in comparison to baseline values. No increase in other bladder symptoms or frequency was detected. When comparing dose groups after 5 years, both the 74-Gy and 78-Gy groups reported increased urinary starting problems compared with patients given the conventional dose (<71 Gy). No increased incontinence was seen in the 76-Gy or the 78-Gy groups. Bowel symptoms were slightly increased during the follow-up period in comparison to baseline. Dose escalation with stereotactic EBRT (74-78 Gy) did not increase gastrointestinal late side effects after 5 years in comparison to doses <71 Gy. Conclusion: Dose-escalated EBRT with the BeamCath (registered) technique with doses up to 78 Gy is tolerable, and the toxicity profile is similar to that observed with conventional doses <71 Gy.

  1. Bowel sparing in pediatric cranio-spinal radiotherapy: a comparison of combined electron and photon and helical TomoTherapy techniques to a standard photon method

    SciTech Connect

    Harron, Elizabeth; Lewis, Joanne

    2012-07-01

    The aim of this study was to compare the dose to organs at risk (OARs) from different craniospinal radiotherapy treatment approaches available at the Northern Centre for Cancer Care (NCCC), with a particular emphasis on sparing the bowel. Method: Treatment plans were produced for a pediatric medulloblastoma patient with inflammatory bowel disease using 3D conformal 6-MV photons (3DCP), combined 3D 6-MV photons and 18-MeV electrons (3DPE), and helical photon TomoTherapy (HT). The 3DPE plan was a modification of the standard 3DCP technique, using electrons to treat the spine inferior to the level of the diaphragm. The plans were compared in terms of the dose-volume data to OARs and the nontumor integral dose. Results: The 3DPE plan was found to give the lowest dose to the bowel and the lowest nontumor integral dose of the 3 techniques. However, the coverage of the spine planning target volume (PTV) was least homogeneous using this technique, with only 74.6% of the PTV covered by 95% of the prescribed dose. HT was able to achieve the best coverage of the PTVs (99.0% of the whole-brain PTV and 93.1% of the spine PTV received 95% of the prescribed dose), but delivered a significantly higher integral dose. HT was able to spare the heart, thyroid, and eyes better than the linac-based techniques, but other OARs received a higher dose. Conclusions: Use of electrons was the best method for reducing the dose to the bowel and the integral dose, at the expense of compromised spine PTV coverage. For some patients, HT may be a viable method of improving dose homogeneity and reducing selected OAR doses.

  2. Radiation-induced second malignancies after involved-node radiotherapy with deep-inspiration breath-hold technique for early stage Hodgkin Lymphoma: a dosimetric study

    PubMed Central

    2014-01-01

    Background To estimate the risk of radiation induced second cancers after radiotherapy using deep-inspiration breath-hold (DI) technique with three-dimensional conformal (3DCRT) and volumetric arc therapy (VMAT) for patients with Hodgkin’s lymphoma (HL). Methods Early-stage HL with mediastinal and supraclavicular involvement was studied using an Alderson phantom. A whole body CT was performed and all tissues were delineated. The clinical target volumes and planning target volumes (PTV) were determined according to the German Hodgkin study group guidelines. Free-breathing (FB) technique and DI technique were simulated by different safety margins for the PTV definition. In both cases, 30 Gy in 15 fractions was prescribed. Second cancer risk was estimated for various tissues with a second cancer model including fractionation. Results When compared with FB-3DCRT, estimated relative life time attributable risk (LAR) of cancer induction after DI-3DCRT was 0.86, 0.76, 0.94 and 0.92 for breast, lung, esophagus and stomach, respectively. With DI-VMAT, the corresponding values were 2.05, 1.29, 1.01, 0.93, respectively. For breast cancer, the LAR observed with DI-VMAT was not substantially distinguishable from the LAR computed for mantle RT with an administered dose of 40 Gy. Conclusions This study suggests that DI may reduce the LAR of secondary cancers of all OARs and may be a valuable technique when using 3DCRT. Conversely, VMAT may increase substantially the LAR and should be cautiously implemented in clinical practice. PMID:24548307

  3. A Dosimetric Comparison of Accelerated Partial Breast Irradiation Techniques: Multicatheter Interstitial Brachytherapy, Three-Dimensional Conformal Radiotherapy, and Supine Versus Prone Helical Tomotherapy

    SciTech Connect

    Patel, Rakesh R. . E-mail: patel@humonc.wisc.edu; Becker, Stewart J.; Das, Rupak K.; Mackie, Thomas R.

    2007-07-01

    Purpose: To compare dosimetrically four different techniques of accelerated partial breast irradiation (APBI) in the same patient. Methods and Materials: Thirteen post-lumpectomy interstitial brachytherapy (IB) patients underwent imaging with preimplant computed tomography (CT) in the prone and supine position. These CT scans were then used to generate three-dimensional conformal radiotherapy (3D-CRT) and prone and supine helical tomotherapy (PT and ST, respectively) APBI plans and compared with the treated IB plans. Dose-volume histogram analysis and the mean dose (NTD{sub mean}) values were compared. Results: Planning target volume coverage was excellent for all methods. Statistical significance was considered to be a p value <0.05. The mean V100 was significantly lower for IB (12% vs. 15% for PT, 18% for ST, and 26% for 3D-CRT). A greater significant differential was seen when comparing V50 with mean values of 24%, 43%, 47%, and 52% for IB, PT, ST, and 3D-CRT, respectively. The IB and PT were similar and delivered an average lung NTD{sub mean} dose of 1.3 Gy{sub 3} and 1.2 Gy{sub 3}, respectively. Both of these methods were statistically significantly lower than the supine external beam techniques. Overall, all four methods yielded similar low doses to the heart. Conclusions: The use of IB and PT resulted in greater normal tissue sparing (especially ipsilateral breast and lung) than the use of supine external beam techniques of 3D-CRT or ST. However, the choice of APBI technique must be tailored to the patient's anatomy, lumpectomy cavity location, and overall treatment goals.

  4. Evaluation of the relative precision of space-geodetic techniques at ITRF co-located sites with the Three Corner Hat approach

    NASA Astrophysics Data System (ADS)

    Abbondanza, C.; Chin, T. M.; Gross, R. S.; Heflin, M. B.; Wu, X.

    2012-04-01

    The International Terrestrial Reference Frame (ITRF) is a linear reference frame consisting of regularized positions and velocities for a set of global stations. It relies on the combination of station positions, velocities and Earth orientation parameters (EOPs) acquired by GPS, VLBI, SLR and DORIS at co-located sites. To properly combine the individual reference frames and suitably scale the variance-covariance information from the 4 space-geodetic solutions, an a-priori knowledge of the relative precisions of the four techniques is mandatory. In this study, focusing on the station position time series derived from GNSS, VLBI, SLR and DORIS at ITRF co-locations, we aim at assessing the relative uncertainty of the co-located space geodetic instruments contributing to ITRF. The investigation relies on the idea of pair-wise differencing station position time series of at least three co-located instruments in order to remove common geophysical signals. By computing the variances of the differenced time series, the relative precision of each time series can be recovered with the Three Corner Hat technique, under the assumption of absence of correlation between the noise processes of the different techniques. Results of the Three Corner Hat analysis of co-located station position time series will be presented.

  5. The evolution of rectal and urinary toxicity and immune response in prostate cancer patients treated with two three-dimensional conformal radiotherapy techniques

    PubMed Central

    2011-01-01

    Background Our research compared whole pelvic (WP) and prostate-only (PO) 3-dimensional conformal radiotherapy (3DCRT) techniques in terms of the incidence and evolution of acute and late toxicity of the rectum and urinary bladder, and identified the PTV-parameters influencing these damages and changes in antitumor immune response. Methods We analyzed 197 prostate cancer patients undergoing 3DCRT for gastrointestinal (GI) and genitourinary (GU) toxicities, and conducted a pilot immunological study including flow cytometry and an NK cell cytotoxicity assay. Acute and late toxicities were recorded according to the RTOG and the LENT-SOMA scales, respectively. Univariate and multivariate analyses were conducted for factors associated with toxicity. Results In the WP group, an increase of acute rectal toxicity was observed. A higher incidence of late GI/GU toxicity appeared in the PO group. Only 18 patients (WP-7.76% and PO-11.11%) suffered severe late GI toxicity, and 26 patients (WP-11.21% and PO-16.05%) severe late GU toxicity. In the majority of acute toxicity suffering patients, the diminution of late GI/GU toxicity to grade 1 or to no toxicity after radiotherapy was observed. The 3DCRT technique itself, patient age, T stage of TNM classification, surgical intervention, and some dose-volume parameters emerged as important factors in the probability of developing acute and late GI/GU toxicity. The proportion and differentiation of NK cells positively correlated during 3DCRT and negatively so after its completion with dose-volumes of the rectum and urinary bladder. T and NKT cells were down-regulated throughout the whole period. We found a negative correlation between leukocyte numbers and bone marrow irradiated by 44-54 Gy and a positive one for NK cell proportion and doses of 5-25 Gy. The acute GU, late GU, and GI toxicities up-regulated the T cell (CTL) numbers and NK cytotoxicity. Conclusion Our study demonstrates the association of acute and late damage of the

  6. [Radiotherapy for brain metastases].

    PubMed

    Latorzeff, I; Antoni, D; Gaudaire-Josset, S; Feuvret, L; Tallet-Richard, A; Truc, G; Noël, G

    2016-09-01

    Radiotherapy for brain metastases has become more multifaceted. Indeed, with the improvement of the patient's life expectancy, side effects must be undeniably avoided and the retreatments or multiple treatments are common. The cognitive side effects should be warned and the most modern techniques of radiation therapy are used regularly to reach this goal. The new classifications of patients with brain metastases help guiding treatment more appropriately. Stereotactic radiotherapy has supplanted whole brain radiation therapy both for patients with metastases in place and for those who underwent surgery. Hippocampus protection is possible with intensity-modulated radiotherapy. Its relevance in terms of cognitive functioning should be more clearly demonstrated but the requirement, for using it, is increasingly strong. While addressing patients in palliative phase, the treatment of brain metastases is one of the localisations where technical thinking is the most challenging. PMID:27523410

  7. A study on ultra-precision machining technique for Al6061-T6 to fabricate space infrared optics

    NASA Astrophysics Data System (ADS)

    Ryu, Geun-man; Lee, Gil-jae; Hyun, Sang-won; Sung, Ha-yeong; Chung, Euisik; Kim, Geon-hee

    2014-08-01

    In this paper, analysis of variance on designed experiments with full factorial design was applied to determine the optimized machining parameters for ultra-precision fabrication of the secondary aspheric mirror, which is one of the key elements of the space cryogenic infrared optics. A single point diamond turning machine (SPDTM, Nanotech 4μpL Moore) was adopted to fabricate the material, AL6061-T6, and the three machining parameters of cutting speed, feed rate and depth of cut were selected. With several randomly assigned experimental conditions, surface roughness of each condition was measured by a non-contact optical profiler (NT2000; Vecco). As a result of analysis using Minitab, the optimum cutting condition was determined as following; cutting speed: 122 m/min, feed rate: 3 mm/min and depth of cut: 1 μm. Finally, a 120 mm diameter aspheric secondary mirror was attached to a particularly designed jig by using mixture of paraffin and wax and successfully fabricated under the optimum machining parameters. The profile of machined surface was measured by a high-accuracy 3-D profilometer(UA3P; Panasonic) and we obtained the geometrical errors of 30.6 nm(RMS) and 262.4 nm(PV), which satisfy the requirements of the space cryogenic infrared optics.

  8. Liver-Directed Radiotherapy for Hepatocellular Carcinoma

    PubMed Central

    Keane, Florence K.; Wo, Jennifer Y.; Zhu, Andrew X.; Hong, Theodore S.

    2016-01-01

    Background The incidence of hepatocellular carcinoma (HCC) continues to increase world-wide. Many patients present with advanced disease with extensive local tumor or vascular invasion and are not candidates for traditionally curative therapies such as orthotopic liver transplantation (OLT) or resection. Radiotherapy (RT) was historically limited by its inability to deliver a tumoricidal dose; however, modern RT techniques have prompted renewed interest in the use of liver-directed RT to treat patients with primary hepatic malignancies. Summary The aim of this review was to discuss the use of external beam RT in the treatment of HCC, with particular focus on the use of stereotactic body radiotherapy (SBRT). We review the intricacies of SBRT treatment planning and delivery. Liver-directed RT involves accurate target identification, precise and reproducible patient immobilization, and assessment of target and organ motion. We also summarize the published data on liver-directed RT, and demonstrate that it is associated with excellent local control and survival rates, particularly in patients who are not candidates for OLT or resection. Key Messages Modern liver-directed RT is safe and effective for the treatment of HCC, particularly in patients who are not candidates for OLT or resection. Liver-directed RT, including SBRT, depends on accurate target identification, precise and reproducible patient immobilization, and assessment of target and organ motion. Further prospective studies are needed to fully delineate the role of liver-directed RT in the treatment of HCC. PMID:27493895

  9. Precision measurements of the total and partial widths of the psi(2S) charmonium meson with a new complementary-scan technique in anti-p p annihilations

    SciTech Connect

    Andreotti, M.; Bagnasco, S.; Baldini, W.; Bettoni, D.; Borreani, G.; Buzzo, A.; Calabrese, R.; Cester, R.; Cibinetto, G.; Dalpiaz, P.; Garzoglio, G.

    2007-03-01

    We present new precision measurements of the {Psi}(2S) total and partial widths from excitation curves obtained in antiproton-proton annihilations by Fermilab experiment E835 at the Antiproton Accumulator in the year 2000. A new technique of complementary scans was developed to study narrow resonances with stochastically cooled antiproton beams. It relies on precise revolution-frequency and orbit-length measurements, while making the analysis of the excitation curve almost independent of machine lattice parameters. For the {Psi}(2S) meson, by studying the processes {bar p}p {yields} e{sup +}e{sup -} and {bar p}p {yields} J/{Psi} + X {yields} e{sup +}e{sup -} + X, we measure the width {Gamma} = 290 {+-} 25(sta) {+-} 4(sys) keV and the combination of partial widths {Gamma}{sub e{sup +}e{sup -}}{Gamma}{sub {bar p}p}/{Gamma} = 579 {+-} 38(sta) {+-} 36(sys) meV, which represent the most precise measurements to date.

  10. IsoBED: a tool for automatic calculation of biologically equivalent fractionation schedules in radiotherapy using IMRT with a simultaneous integrated boost (SIB) technique

    PubMed Central

    2011-01-01

    Background An advantage of the Intensity Modulated Radiotherapy (IMRT) technique is the feasibility to deliver different therapeutic dose levels to PTVs in a single treatment session using the Simultaneous Integrated Boost (SIB) technique. The paper aims to describe an automated tool to calculate the dose to be delivered with the SIB-IMRT technique in different anatomical regions that have the same Biological Equivalent Dose (BED), i.e. IsoBED, compared to the standard fractionation. Methods Based on the Linear Quadratic Model (LQM), we developed software that allows treatment schedules, biologically equivalent to standard fractionations, to be calculated. The main radiobiological parameters from literature are included in a database inside the software, which can be updated according to the clinical experience of each Institute. In particular, the BED to each target volume will be computed based on the alpha/beta ratio, total dose and the dose per fraction (generally 2 Gy for a standard fractionation). Then, after selecting the reference target, i.e. the PTV that controls the fractionation, a new total dose and dose per fraction providing the same isoBED will be calculated for each target volume. Results The IsoBED Software developed allows: 1) the calculation of new IsoBED treatment schedules derived from standard prescriptions and based on LQM, 2) the conversion of the dose-volume histograms (DVHs) for each Target and OAR to a nominal standard dose at 2Gy per fraction in order to be shown together with the DV-constraints from literature, based on the LQM and radiobiological parameters, and 3) the calculation of Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) curve versus the prescribed dose to the reference target. PMID:21554675

  11. Optimizing the accuracy and precision of the single-pulse Laue technique for synchrotron photo-crystallography

    SciTech Connect

    Kaminski, Radoslaw; Graber, Timothy; Benedict, Jason B.; Henning, Robert; Chen, Yu-Sheng; Scheins, Stephan; Messerschmidt, Marc; Coppens, Philip

    2010-06-24

    The accuracy that can be achieved in single-pulse pump-probe Laue experiments is discussed. It is shown that with careful tuning of the experimental conditions a reproducibility of the intensity ratios of equivalent intensities obtained in different measurements of 3-4% can be achieved. The single-pulse experiments maximize the time resolution that can be achieved and, unlike stroboscopic techniques in which the pump-probe cycle is rapidly repeated, minimize the temperature increase due to the laser exposure of the sample.

  12. Optimizing the accuracy and precision of the single-pulse Laue technique for synchrotron photo-crystallography

    PubMed Central

    Kamiński, Radosław; Graber, Timothy; Benedict, Jason B.; Henning, Robert; Chen, Yu-Sheng; Scheins, Stephan; Messerschmidt, Marc; Coppens, Philip

    2010-01-01

    The accuracy that can be achieved in single-pulse pump-probe Laue experiments is discussed. It is shown that with careful tuning of the experimental conditions a reproducibility of the intensity ratios of equivalent intensities obtained in different measurements of 3–4% can be achieved. The single-pulse experiments maximize the time resolution that can be achieved and, unlike stroboscopic techniques in which the pump-probe cycle is rapidly repeated, minimize the temperature increase due to the laser exposure of the sample. PMID:20567080

  13. A novel numerical technique for the high-precision simulation of flow processes related to artificial recharge

    NASA Astrophysics Data System (ADS)

    Stevens, David; Orsini, Paolo; Power, Henry; Morvan, Herve; Bensabat, Jacob

    2010-05-01

    This paper presents a novel numerical technique for large-scale groundwater flow simulations, in the frame of artificial recharge planning. The implementation is demonstrated using two test-sites from the EU funded GABARDINE project (FP6): The Sindos test site, near Thessaloniki, Greece, examines the infiltration of water towards the water table, through several unsaturated soil layers. The test site at Campina de Faro, Portugal, investigates phreatic surface movement around a large-diameter well. For both test cases a numerical simulation is constructed, and the local subsurface flow regime is investigated. Numerical methods for solving PDEs using interpolation with radial basis functions (RBFs) will typically provide high accuracy solutions, achieve excellent convergence rates, and offer great flexibility with regards to the enforcement of arbitrary boundary conditions. However, RBF methods have traditionally been limited to the solution of small academic problems, due to issues of computational cost and numerical conditioning. Recent developments in locally supported RBF methods have led to techniques which can be scaled to the largest problem sizes, while maintaining many of the flexibilities of traditional RBF methods. As a contribution to the GABARDINE project, two such numerical techniques have been developed; the meshless LHI method and the control-volume based CV-RBF method. These numerical techniques are capable of modelling flow and transport in heterogeneous porous media, and are of order-N computational complexity, allowing problems to be solved on large and irregular datasets. For both numerical techniques, the RBF Hermitian collocation method is utilised to perform interpolation at the local level, allowing the simultaneous imposition of pressure and mass-flux matching conditions at soil-layer interfaces. The non-overlapping stencil configuration then allows the accurate capture of non-smooth solution profiles across layer interfaces, to a high

  14. X-ray extended-range technique for precision measurement of the X-ray mass attenuation coefficient and Im( f) for copper using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Chantler, C. T.; Tran, C. Q.; Paterson, D.; Cookson, D.; Barnea, Z.

    2001-08-01

    We reconsider the long-standing problem of accurate measurement of atomic form factors for fundamental and applied problems. We discuss the X-ray extended-range technique for accurate measurement of the mass attenuation coefficient and the imaginary component of the atomic form factor. Novelties of this approach include the use of a synchrotron with detector normalisation, the direct calibration of dominant systematics using multiple thicknesses, and measurement over wide energy ranges with a resulting improvement of accuracies by an order of magnitude. This new technique achieves accuracies of 0.27-0.5% and reproducibility of 0.02% for attenuation of copper from 8.84 to 20 keV, compared to accuracies of 10% using atomic vapours. This precision challenges available theoretical calculations. Discrepancies of 10% between current theory and experiments can now be addressed.

  15. Accuracy and precision of polyurethane dental arch models fabricated using a three-dimensional subtractive rapid prototyping method with an intraoral scanning technique

    PubMed Central

    Kim, Jae-Hong; Kim, Ki-Baek; Kim, Woong-Chul; Kim, Ji-Hwan

    2014-01-01

    Objective This study aimed to evaluate the accuracy and precision of polyurethane (PUT) dental arch models fabricated using a three-dimensional (3D) subtractive rapid prototyping (RP) method with an intraoral scanning technique by comparing linear measurements obtained from PUT models and conventional plaster models. Methods Ten plaster models were duplicated using a selected standard master model and conventional impression, and 10 PUT models were duplicated using the 3D subtractive RP technique with an oral scanner. Six linear measurements were evaluated in terms of x, y, and z-axes using a non-contact white light scanner. Accuracy was assessed using mean differences between two measurements, and precision was examined using four quantitative methods and the Bland-Altman graphical method. Repeatability was evaluated in terms of intra-examiner variability, and reproducibility was assessed in terms of inter-examiner and inter-method variability. Results The mean difference between plaster models and PUT models ranged from 0.07 mm to 0.33 mm. Relative measurement errors ranged from 2.2% to 7.6% and intraclass correlation coefficients ranged from 0.93 to 0.96, when comparing plaster models and PUT models. The Bland-Altman plot showed good agreement. Conclusions The accuracy and precision of PUT dental models for evaluating the performance of oral scanner and subtractive RP technology was acceptable. Because of the recent improvements in block material and computerized numeric control milling machines, the subtractive RP method may be a good choice for dental arch models. PMID:24696823

  16. Innovative radiotherapy of sarcoma: Proton beam radiation.

    PubMed

    DeLaney, Thomas F; Haas, Rick L M

    2016-07-01

    This review on proton beam radiotherapy (PBT) focusses on an historical overview, cost-effectiveness, techniques, acute and late toxicities and clinical results of PBT for sarcoma patients. PBT has gained its place among the armamentarium of modern radiotherapy techniques. For selected patients, it can be cost-effective. PMID:27258968

  17. A simulation study investigating a radiation detector utilizing the prompt gamma range verification technique for proton radiotherapy

    NASA Astrophysics Data System (ADS)

    Lau, Andrew David

    Proton therapy has shown to be a viable therapy for radiation oncology applications. The advantages of using protons as compared to photons in the treatments of diseases with radiation are numerous including the ability to deliver overall lower amounts of lethal radiation doses to the patient. This advantage is due to the fundamental interaction mechanism of the incident therapeutic protons with the patient, which produces a characteristic dose-distribution unique only to protons. Unlike photons, the entire proton beam is absorbed within the patent and the dose-distribution's maximum occurs near the end of the proton's path. Protons deliver less dose on the skin and intervening tissues, tighter dose conformality to the disease site, as well as no dose past the target volume, sparring healthy tissue distally in the patient. Current research in proton therapy is geared towards minimizing proton range uncertainty and monitoring in-vivo the location of the proton's path. Monitoring the beam's path serves also to verify which healthy structures/tissues were irradiated and whether the target volume has met the prescription dose. Among the many techniques used for in-vivo proton monitoring, the technique based on the emitted secondary particles, specifically the Prompt Gamma (PG) method, can be used for clinical implementation. This work focuses on developing a radiation detector system for using the PG method by investigating the characterizing the secondary particle field emitted from plastic and water phantoms as well as a radiation detector based on glass materials that exploits the Cherenkov phenomenon.

  18. Lateral high abdominal ovariopexy: an original surgical technique for protection of the ovaries during curative radiotherapy for Hodgkin's disease

    SciTech Connect

    Gaetini, A.; De Simone, M.; Urgesi, A.; Levis, A.; Resegotti, A.; Ragona, R.; Anglesio, S.

    1988-09-01

    An original surgical method for gonadal protection in young women given pelvic radiation for Hodgkin's disease is presented. Lateral high ovarian transposition (LHAO) consists of the transposition of the ovaries into the paracolic gutter during staging laparotomy, after disconnecting the gonads from the fallopian tubes by dividing the tubo-ovarian vessels. The technique's effectiveness was assessed by a study using clinical investigation, radioimmunoassay (RIA) determination of sex hormones, and dosimetry; of 18 patients treated, 10 participated in the study. All but one have normal menses and hormone values, and one pregnancy occurred. We also calculated the doses absorbed by the ovaries and proved that, during inverted Y irradiation following LHAO, the ovaries are exposed to nearly one-half the dose they receive after traditional medial transposition. During subtotal nodal irradiation after LHAO, the irradiation dose is higher than after medialisation, but absolute values are minimal and castration is not induced.

  19. Improving the Precision of Our Ecosystem Calipers: A Modified Morphometric Technique for Estimating Marine Mammal Mass and Body Composition

    PubMed Central

    Shero, Michelle R.; Pearson, Linnea E.; Costa, Daniel P.; Burns, Jennifer M.

    2014-01-01

    Mass and body composition are indices of overall animal health and energetic balance and are often used as indicators of resource availability in the environment. This study used morphometric models and isotopic dilution techniques, two commonly used methods in the marine mammal field, to assess body composition of Weddell seals (Leptonychotes weddellii, N = 111). Findings indicated that traditional morphometric models that use a series of circular, truncated cones to calculate marine mammal blubber volume and mass overestimated the animal’s measured body mass by 26.9±1.5% SE. However, we developed a new morphometric model that uses elliptical truncated cones, and estimates mass with only −2.8±1.7% error (N = 10). Because this elliptical truncated cone model can estimate body mass without the need for additional correction factors, it has the potential to be a broadly applicable method in marine mammal species. While using elliptical truncated cones yielded significantly smaller blubber mass estimates than circular cones (10.2±0.8% difference; or 3.5±0.3% total body mass), both truncated cone models significantly underestimated total body lipid content as compared to isotopic dilution results, suggesting that animals have substantial internal lipid stores (N = 76). Multiple linear regressions were used to determine the minimum number of morphometric measurements needed to reliably estimate animal mass and body composition so that future animal handling times could be reduced. Reduced models estimated body mass and lipid mass with reasonable accuracy using fewer than five morphometric measurements (root-mean-square-error: 4.91% for body mass, 10.90% for lipid mass, and 10.43% for % lipid). This indicates that when test datasets are available to create calibration coefficients, regression models also offer a way to improve body mass and condition estimates in situations where animal handling times must be short and efficient. PMID:24614685

  20. Improving the precision of our ecosystem calipers: a modified morphometric technique for estimating marine mammal mass and body composition.

    PubMed

    Shero, Michelle R; Pearson, Linnea E; Costa, Daniel P; Burns, Jennifer M

    2014-01-01

    Mass and body composition are indices of overall animal health and energetic balance and are often used as indicators of resource availability in the environment. This study used morphometric models and isotopic dilution techniques, two commonly used methods in the marine mammal field, to assess body composition of Weddell seals (Leptonychotes weddellii, N = 111). Findings indicated that traditional morphometric models that use a series of circular, truncated cones to calculate marine mammal blubber volume and mass overestimated the animal's measured body mass by 26.9±1.5% SE. However, we developed a new morphometric model that uses elliptical truncated cones, and estimates mass with only -2.8±1.7% error (N = 10). Because this elliptical truncated cone model can estimate body mass without the need for additional correction factors, it has the potential to be a broadly applicable method in marine mammal species. While using elliptical truncated cones yielded significantly smaller blubber mass estimates than circular cones (10.2±0.8% difference; or 3.5±0.3% total body mass), both truncated cone models significantly underestimated total body lipid content as compared to isotopic dilution results, suggesting that animals have substantial internal lipid stores (N = 76). Multiple linear regressions were used to determine the minimum number of morphometric measurements needed to reliably estimate animal mass and body composition so that future animal handling times could be reduced. Reduced models estimated body mass and lipid mass with reasonable accuracy using fewer than five morphometric measurements (root-mean-square-error: 4.91% for body mass, 10.90% for lipid mass, and 10.43% for % lipid). This indicates that when test datasets are available to create calibration coefficients, regression models also offer a way to improve body mass and condition estimates in situations where animal handling times must be short and efficient. PMID:24614685

  1. Small animal radiotherapy research platforms

    NASA Astrophysics Data System (ADS)

    Verhaegen, Frank; Granton, Patrick; Tryggestad, Erik

    2011-06-01

    Advances in conformal radiation therapy and advancements in pre-clinical radiotherapy research have recently stimulated the development of precise micro-irradiators for small animals such as mice and rats. These devices are often kilovolt x-ray radiation sources combined with high-resolution CT imaging equipment for image guidance, as the latter allows precise and accurate beam positioning. This is similar to modern human radiotherapy practice. These devices are considered a major step forward compared to the current standard of animal experimentation in cancer radiobiology research. The availability of this novel equipment enables a wide variety of pre-clinical experiments on the synergy of radiation with other therapies, complex radiation schemes, sub-target boost studies, hypofractionated radiotherapy, contrast-enhanced radiotherapy and studies of relative biological effectiveness, to name just a few examples. In this review we discuss the required irradiation and imaging capabilities of small animal radiation research platforms. We describe the need for improved small animal radiotherapy research and highlight pioneering efforts, some of which led recently to commercially available prototypes. From this, it will be clear that much further development is still needed, on both the irradiation side and imaging side. We discuss at length the need for improved treatment planning tools for small animal platforms, and the current lack of a standard therein. Finally, we mention some recent experimental work using the early animal radiation research platforms, and the potential they offer for advancing radiobiology research.

  2. SU-C-BRD-05: Implementation of Incident Learning in the Safety and Quality Management of Radiotherapy: The Primary Experience in a New Established Program with Advanced Techniques

    SciTech Connect

    Yang, R; Wang, J

    2014-06-15

    Purpose: To explore the implementation and effectiveness of incident learning for the safety and quality of radiotherapy in a new established radiotherapy program with advanced technology. Methods: Reference to the consensus recommendations by American Association of Physicist in Medicine, an incident learning system was specifically designed for reporting, investigating, and learning of individual radiotherapy incidents in a new established radiotherapy program, with 4D CBCT, Ultrasound guided radiotherapy, VMAT, gated treatment delivered on two new installed linacs. The incidents occurring in external beam radiotherapy from February, 2012 to January, 2014 were reported. Results: A total of 33 reports were analyzed, including 28 near misses and 5 incidents. Among them, 5 originated in imaging for planning, 25 in planning, 1 in plan transfer, 1 in commissioning and 1 in treatment delivery. Among them, three near misses originated in the safety barrier of the radiotherapy process. In terms of error type, 1 incident was classified as wrong patient, 7 near misses/incidents as wrong site, 6 as wrong laterality, 5 as wrong dose, 7 as wrong prescription, and 7 as suboptimal plan quality. 5 incidents were all classified as grade 1/2 of dosimetric severity, 1 as grade 0, and the other 4 as grade 1 of medical severity. For the causes/contributory factors, negligence, policy not followed, inadequate training, failure to develop an effective plan, and communication contributed to 19, 15, 12, 5 and 3 near misses/incidents, respectively. The average incident rate per 100 patients treated was 0.4; this rate fell to 0.28% in the second year from 0.56% in the first year. The rate of near miss fell to 1.24% from 2.22%. Conclusion: Effective incident learning can reduce the occurrence of near miss/incidents, enhance the culture of safety. Incident learning is an effective proactive method for improving the quality and safety of radiotherapy.

  3. Advanced Fabrication Techniques for Precisely Controlled Micro and Nano Scale Environments for Complex Tissue Regeneration and Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Holmes, Benjamin

    As modern medicine advances, it is still very challenging to cure joint defects due to their poor inherent regenerative capacity, complex stratified architecture, and disparate biomechanical properties. The current clinical standard for catastrophic or late stage joint degradation is a total joint implant, where the damaged joint is completely excised and replaced with a metallic or artificial joint. However, these procedures still only lasts for 10-15 years, and there are hosts of recovery complications which can occur. Thus, these studies have sought to employ advanced biomaterials and scaffold fabricated techniques to effectively regrow joint tissue, instead of merely replacing it with artificial materials. We can hypothesize here that the inclusion of biomimetic and bioactive nanomaterials with highly functional electrospun and 3D printed scaffold can improve physical characteristics (mechanical strength, surface interactions and nanotexture) enhance cellular growth and direct stem cell differentiation for bone, cartilage and vascular growth as well as cancer metastasis modeling. Nanomaterial inclusion and controlled 3D printed features effectively increased nano surface roughness, Young's Modulus and provided effective flow paths for simulated arterial blood. All of the approaches explored proved highly effective for increasing cell growth, as a result of increasing micro-complexity and nanomaterial incorporation. Additionally, chondrogenic and osteogenic differentiation, cell migration, cell to cell interaction and vascular formation were enhanced. Finally, growth-factor(gf)-loaded polymer nanospheres greatly improved vascular cell behavior, and provided a highly bioactive scaffold for mesenchymal stem cell (MSC) and human umbilical vein endothelial cell (HUVEC) co-culture and bone formation. In conclusion, electrospinning and 3D printing when combined effectively with biomimetic and bioactive nanomaterials (i.e. carbon nanomaterials, collagen, nHA, polymer

  4. Vision-based precision inspection system for profile and performance of small and micro gears using the intelligent image processing techniques and virtual master gears

    NASA Astrophysics Data System (ADS)

    Pahk, Heui Jae; Hwang, Young Min; Lee, Il Hwan; Ahn, Woo Jung

    2000-10-01

    As the product size become smaller, much smaller sized parts are increasingly required in many products fabrication such as cameras, camcorders, and electric appliances, etc. Small or micro gears whose sizes are about few hundred micrometers to few millimeters have been greatly required for the above products, as they become most efficient parts for power transmission. The small of micro gears are prone to geometrical and functioning inaccuracy during the micro fabrication processes, and thus the measurement system has been desired for the geometry and performance checking of gears. In this paper, a precision inspection system is developed for the gear checking, consisting of the optical vision microscope, vision image processing modules with subpixel accuracy, and the profile inspection software using the virtual master jigs/gears mathematically generated. For accurate analysis of the gear geometry from the captured gear image through the optical vision system, a highly accurate vision image processing algorithm has been implemented, where two dimensional subpixelling technique is developed having about one tenth subpixel accuracy. A mathematically generated mater gears/jigs are implemented: several core parameters of the gear profile are calculated from the comparison between the virtual master and the measured gears. Virtual precision ball jigs are simulated between gear teeth profile, and thus the runout parameter can be successfully evaluated from the virtual jig movement on the gear teeth image. The eccentricity parameters can also be calculated from the sinusoidal fitting of the virtual ball movement. The development precision inspection system for small or micro gears has been applied to practical gears of various range, and the essential gear parameters are successfully measured with sub micrometer accuracy.

  5. Adaption of a fragment analysis technique to an automated high-throughput multicapillary electrophoresis device for the precise qualitative and quantitative characterization of microbial communities.

    PubMed

    Trotha, René; Reichl, Udo; Thies, Frank L; Sperling, Danuta; König, Wolfgang; König, Brigitte

    2002-04-01

    The analysis of microbial communities is of increasing importance in life sciences and bioengineering. Traditional techniques of investigations like culture or cloning methods suffer from many disadvantages. They are unable to give a complete qualitative and quantitative view of the total amount of microorganisms themselves, their interactions among each other and with their environment. Obviously, the determination of static or dynamic balances among microorganisms is of fast growing interest. The generation of species specific and fluorescently labeled 16S ribosomal DNA (rDNA) fragments by the terminal restriction fragment length polymorphism (T-RFLP) technique is a suitable tool to overcome the problems other methods have. For the separation of these fragments polyacrylamide gel sequencers are preferred as compared to capillary sequencers using linear polymers until now because of their higher electrophoretic resolution and therefore sizing accuracy. But modern capillary sequencers, especially multicapillary sequencers, offer an advanced grade of automation and an increased throughput necessary for the investigation of complex communities in long-time studies. Therefore, we adapted a T-RFLP technique to an automated high-throughput multicapillary electrophoresis device (ABI 3100 Genetic Analysis) with regard to a precise qualitative and quantitative characterization of microbial communities. PMID:11981854

  6. Accuracy and Precision of an IGRT Solution

    SciTech Connect

    Webster, Gareth J. Rowbottom, Carl G.; Mackay, Ranald I.

    2009-07-01

    Image-guided radiotherapy (IGRT) can potentially improve the accuracy of delivery of radiotherapy treatments by providing high-quality images of patient anatomy in the treatment position that can be incorporated into the treatment setup. The achievable accuracy and precision of delivery of highly complex head-and-neck intensity modulated radiotherapy (IMRT) plans with an IGRT technique using an Elekta Synergy linear accelerator and the Pinnacle Treatment Planning System (TPS) was investigated. Four head-and-neck IMRT plans were delivered to a semi-anthropomorphic head-and-neck phantom and the dose distribution was measured simultaneously by up to 20 microMOSFET (metal oxide semiconductor field-effect transmitter) detectors. A volumetric kilovoltage (kV) x-ray image was then acquired in the treatment position, fused with the phantom scan within the TPS using Syntegra software, and used to recalculate the dose with the precise delivery isocenter at the actual position of each detector within the phantom. Three repeat measurements were made over a period of 2 months to reduce the effect of random errors in measurement or delivery. To ensure that the noise remained below 1.5% (1 SD), minimum doses of 85 cGy were delivered to each detector. The average measured dose was systematically 1.4% lower than predicted and was consistent between repeats. Over the 4 delivered plans, 10/76 measurements showed a systematic error > 3% (3/76 > 5%), for which several potential sources of error were investigated. The error was ultimately attributable to measurements made in beam penumbrae, where submillimeter positional errors result in large discrepancies in dose. The implementation of an image-guided technique improves the accuracy of dose verification, particularly within high-dose gradients. The achievable accuracy of complex IMRT dose delivery incorporating image-guidance is within {+-} 3% in dose over the range of sample points. For some points in high-dose gradients

  7. Accuracy and precision of an IGRT solution.

    PubMed

    Webster, Gareth J; Rowbottom, Carl G; Mackay, Ranald I

    2009-01-01

    Image-guided radiotherapy (IGRT) can potentially improve the accuracy of delivery of radiotherapy treatments by providing high-quality images of patient anatomy in the treatment position that can be incorporated into the treatment setup. The achievable accuracy and precision of delivery of highly complex head-and-neck intensity modulated radiotherapy (IMRT) plans with an IGRT technique using an Elekta Synergy linear accelerator and the Pinnacle Treatment Planning System (TPS) was investigated. Four head-and-neck IMRT plans were delivered to a semi-anthropomorphic head-and-neck phantom and the dose distribution was measured simultaneously by up to 20 microMOSFET (metal oxide semiconductor field-effect transmitter) detectors. A volumetric kilovoltage (kV) x-ray image was then acquired in the treatment position, fused with the phantom scan within the TPS using Syntegra software, and used to recalculate the dose with the precise delivery isocenter at the actual position of each detector within the phantom. Three repeat measurements were made over a period of 2 months to reduce the effect of random errors in measurement or delivery. To ensure that the noise remained below 1.5% (1 SD), minimum doses of 85 cGy were delivered to each detector. The average measured dose was systematically 1.4% lower than predicted and was consistent between repeats. Over the 4 delivered plans, 10/76 measurements showed a systematic error > 3% (3/76 > 5%), for which several potential sources of error were investigated. The error was ultimately attributable to measurements made in beam penumbrae, where submillimeter positional errors result in large discrepancies in dose. The implementation of an image-guided technique improves the accuracy of dose verification, particularly within high-dose gradients. The achievable accuracy of complex IMRT dose delivery incorporating image-guidance is within +/- 3% in dose over the range of sample points. For some points in high-dose gradients

  8. Precise identification of <1 0 0> directions on Si{0 0 1} wafer using a novel self-aligning pre-etched technique

    NASA Astrophysics Data System (ADS)

    Singh, S. S.; Veerla, S.; Sharma, V.; Pandey, A. K.; Pal, P.

    2016-02-01

    Micromirrors with a tilt angle of 45° are widely used in optical switching and interconnect applications which require 90° out of plane reflection. Silicon wet bulk micromachining based on surfactant added TMAH is usually employed to fabricate 45° slanted walls at the < 1 0 0> direction on Si≤ft\\{0 0 1\\right\\} wafers. These slanted walls are used as 45° micromirrors. However, the appearance of a precise 45° ≤ft\\{0 1 1\\right\\} wall is subject to the accurate identification of the < 1 0 0> direction. In this paper, we present a simple technique based on pre-etched patterns for the identification of < 1 0 0> directions on the Si≤ft\\{0 0 1\\right\\} surface. The proposed pre-etched pattern self-aligns itself at the < 1 0 0> direction while becoming misaligned at other directions. The < 1 0 0> direction is determined by a simple visual inspection of pre-etched patterns and does not need any kind of measurement. To test the accuracy of the proposed method, we fabricated a 32 mm long rectangular opening with its sides aligned along the < 1 0 0> direction, which is determined using the proposed technique. Due to the finite etch rate of the ≤ft\\{1 1 0\\right\\} plane, undercutting occurred, which was measured at 12 different locations along the longer edge of the rectangular strip. The mean of these undercutting lengths, measured perpendicular to the mask edge, is found to be 13.41 μm with a sub-micron standard deviation of 0.38 μm. This level of uniform undercutting indicates that our method of identifying the < 1 0 0> direction is precise and accurate. The developed method will be extremely useful in fabricating arrays of 45° micromirrors.

  9. Accuracy and precision of end-expiratory lung-volume measurements by automated nitrogen washout/washin technique in patients with acute respiratory distress syndrome

    PubMed Central

    2011-01-01

    Introduction End-expiratory lung volume (EELV) is decreased in acute respiratory distress syndrome (ARDS), and bedside EELV measurement may help to set positive end-expiratory pressure (PEEP). Nitrogen washout/washin for EELV measurement is available at the bedside, but assessments of accuracy and precision in real-life conditions are scant. Our purpose was to (a) assess EELV measurement precision in ARDS patients at two PEEP levels (three pairs of measurements), and (b) compare the changes (Δ) induced by PEEP for total EELV with the PEEP-induced changes in lung volume above functional residual capacity measured with passive spirometry (ΔPEEP-volume). The minimal predicted increase in lung volume was calculated from compliance at low PEEP and ΔPEEP to ensure the validity of lung-volume changes. Methods Thirty-four patients with ARDS were prospectively included in five university-hospital intensive care units. ΔEELV and ΔPEEP volumes were compared between 6 and 15 cm H2O of PEEP. Results After exclusion of three patients, variability of the nitrogen technique was less than 4%, and the largest difference between measurements was 81 ± 64 ml. ΔEELV and ΔPEEP-volume were only weakly correlated (r2 = 0.47); 95% confidence interval limits, -414 to 608 ml). In four patients with the highest PEEP (≥ 16 cm H2O), ΔEELV was lower than the minimal predicted increase in lung volume, suggesting flawed measurements, possibly due to leaks. Excluding those from the analysis markedly strengthened the correlation between ΔEELV and ΔPEEP volume (r2 = 0.80). Conclusions In most patients, the EELV technique has good reproducibility and accuracy, even at high PEEP. At high pressures, its accuracy may be limited in case of leaks. The minimal predicted increase in lung volume may help to check for accuracy. PMID:22166727

  10. A Three Corner Hat-based analysis of station position time series for the assessment of inter-technique precision at ITRF co-located sites

    NASA Astrophysics Data System (ADS)

    Abbondanza, C.; Chin, T. M.; Gross, R. S.; Heflin, M. B.; Hurst, K. J.; Parker, J. W.; Wu, X.; Altamimi, Z.

    2012-12-01

    Assessing the uncertainty in geodetic positioning is a crucial factor when combining independent space-geodetic solutions for the computation of the International Terrestrial Reference Frame (ITRF). ITRF is a combined product based on the stacking of VLBI, GPS, SLR and DORIS solutions and merging the single technique reference frames with terrestrial local tie measurements at co-located sites. In current ITRF realizations, the uncertainty evaluation of the four techniques relies on the analysis of the post-fit residuals, which are a by-product of the combination process. An alternative approach to the assessment of the inter-technique precision can be offered by a Three Corner Hat (TCH) analysis of the non-linear residual time series obtained at ITRF co-location sites as a by-product of the stacking procedure. Non-linear residuals of station position time series stemming from global networks of the four techniques can be modeled as a composition of periodic signals (commonly annual and semi-annual) and stochastic noise, typically characterized as a combination of flicker and white noise. Pair-wise differences of station position time series of at least three co-located instruments can be formed with the aim of removing the common geophysical signal and characterizing the inter-technique precision. The application of TCH relies on the hypothesis of absence of correlation between the error processes of the four techniques and assumes the stochastic noise to be Gaussian. If the hypothesis of statistical independence between the space-geodetic technique errors is amply verified, the assumption of pure white noise of the stochastic error processes appears to be more questionable. In fact, previous studies focused on geodetic positioning consistently showed that flicker noise generally prevails over white noise in the analysis of global network GPS time series, whereas in VLBI, SLR and DORIS time series Gaussian noise is predominant. In this investigation, TCH is applied