Download or read book Development and Validation of a Virtual Monte Carlo Radiotherapy Source Model and Characterization of the Influence of Heterogeneities on Dose Calculation Accuracy written by Michael Paul Speiser and published by . This book was released on 2008 with total page 750 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Enhancing the Speed of Radiotherapy Monte Carlo Dose Calculation with Applications in Dose Verification written by Reid William Townson and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Monte Carlo (MC) methods for radiotherapy dose calculation are widely accepted as capable of achieving high accuracy. In particular, MC calculations have been demonstrated to successfully reproduce measured dose distributions in complex situations where alternative dose calculation algorithms failed (for example, regions of charged particle disequilibrium). For this reason, MC methods are likely to play a central role in radiotherapy dose calculations and dose verification in the future. However, clinical implementations of MC calculations have typically been limited due to the high computational demands. In order to improve the feasibility of using MC simulations clinically, the simulation techniques must be made more efficient. This dissertation presents a number of approaches to improve the efficiency of MC dose calculations. One of the most time consuming parts of source modeling is the simulation of the secondary collimators, which absorb particles to define the rectangular boundaries of radiation fields. The approximation of assuming negligible transmission through and scatter from the secondary collimators was evaluated for accuracy and efficiency using both graphics processing unit (GPU)-based and central processing unit (CPU)-based MC approaches. The new dose calculation engine, gDPM, that utilizes GPUs to perform MC simulations was developed to a state where accuracy comparable to conventional MC algorithms was attained. However, in GPU-based dose calculation, source modeling was found to be an efficiency bottleneck.
Download or read book Development of an Accurate Monte Carlo Treatment Plan Calculation Framework for the Purpose of Developing Dose Calculation Error Predictors for a Widely Implemented Clinical Algorithm written by Alexander J. Egan and published by . This book was released on 2014 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: Monte Carlo (MC) algorithms are widely accepted as the most accurate method to calculate dose in a patient geometry. For this work the EGSnrc MC code was used as a benchmark for the identification of dose calculation errors produced by the widely implemented analytical anisotropic algorithm (AAA). By correlating the location and magnitude of these errors with the physical conditions under which AAA is known to fail, a set of error prediction methods was developed which can help to identify clinical plans that are at high risk for AAA dose calculation errors. Once these plans are identified, they can be recalculated with a more accurate algorithm. First, in order to calculate clinical treatment plans with MC, a treatment plan calculation framework (MCTPCF) was developed and validated. The underlying beam model used in the MCTPCF was thoroughly benchmarked against a standard open field data set. Radiochromic film measurements were then used to validate the geometry of the employed MC multileaf collimator (MLC) model. Mechanical functionality of the MCTPCF was verified by calculating several highly modulated clinical treatment plans and comparing them with AAA calculations. Next, three novel error prediction algorithms were developed and validated to a limited extent. The first, designated the field size index (FSI), identifies regions in the treatment plan space where many small fields or blocks overlap, leading to a build-up of beam modeling and volume averaging errors. The second, designated the heterogeneous scatter index (HSI), identifies regions within the electron density distribution where the AAA rectilinear kernel scaling approximation is stressed. The third, designated the low-density index (LDI), identifies regions of very low electron density where AAA is known to overestimate dose. An open field beam model for the 6MV Varian Clinac has been fully parameterized and is able to calculate dose to within 1.3% and 1.0 mm DTA ([sigma][mean] = 0.3%). The MCTPCF has been shown to accurately calculate highly modulated, multiple field treatments. FSI calculations show excellent agreement with MC/AAA deviations in highly modulated MLC fields in water, and to a lesser extent in patient geometry RapidArc treatments. The LDI accurately predicts AAA overdosing for simple geometries, however for the lung case investigated other sources of error made identifying any correlation a challenge. The theoretical structure of the HSI has been developed, however its implementation is still underway. An accurate MC based treatment plan calculation tool has been developed and validated. Three novel error prediction algorithms have been developed, two of which have been validated for homogenous geometries. In particular, the FSI shows promise as both a direct predictor of AAA error, and also as a general treatment plan complexity index. With sufficient benchmarking, these methods may be developed into a clinical tool that can identify treatment plans that are at high risk for AAA dose calculation errors.
Download or read book The Effect of Photon Dose Calculation Algorithms on the Clinical Outcome of Radiotherapy as Assessed by Radiobiological Models written by Mekala Chandrasekaran and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The accuracy of dose calculation algorithms used for radiotherapy treatment planning play a significant role in the clinical outcome of various treatment regimens. Heterogeneities in human anatomy such as lung, air cavities, bone, soft tissue and fat present challenges to the dose calculation algorithms as they are prone to disrupt the charged-particle equilibrium. Monte Carlo (MC) based dose calculation algorithms are proven to be superior to all the current analytical algorithms owing to their ability to account for all the physical interactions that are involved in radiation transport. Numerous publications have examined the differences in physical doses calculated by analytical algorithms when compared to MC in dealing with heterogeneities. However, before this work the clinical significance of these differences in physical dose has never been investigated in detail. An EGSnrc, BEAMnrc and DOSXYZnrc based MC dose calculation engine was set up in a parallel computing environment to simulate three-dimensional conformal radiotherapy (3DCRT) and intensity modulated radiation therapy (IMRT). A Varian 2100 C/D accelerator head was modeled and validated to match measurements of open and dynamic wedged fields in a homogeneous water phantom which was found to be in good agreement with measurements within 2%/2mm and 3%/3mm respectively. In addition, MC calculated doses in a heterogeneous lung phantom were compared to radiochromic film measurements. Overall, there was good agreement between the two, although large differences of upto 16% were found in some cases. This dose calculation system was used to perform MC simulations on computed tomography (CT) images. The clinical impact of the differences in absolute doses calculated by various photon dose calculation algorithms for two clinical tumour sites was investigated. The tumour control probability (TCP) and normal tissue complication probability (NTCP) were estimated using well established bio-mathematical radiobiological models. This work includes the analysis of 7 convolution (i.e. pencil-beam) and convolution-superposition (CS) based photon dose algorithms available in commercial treatment planning systems (TPSs) as well as MC, in treatment plans of non-small cell lung carcinoma (NSCLC) and nasopharyngeal carcinoma (NPC). In both NSCLC and NPC, the convolution algorithms overestimate the dose to the tumour and hence overestimate the TCP to up to 45%. Some of the CS algorithms were comparable to MC though others exhibit significant differences. In NSCLC, the absolute differences in the NTCP values with radiation pneumonitis and rib fracture as end points were not as large as the differences found in the TCPs. On the other hand, in NPC, the overestimation of probability of occurrence of xerostomia by some TPS algorithms may be preventing dose escalation. Parameters for the TCP model were derived by fitting the TCP predictions to published outcome for four widely varying dose-fractionation regimens for a patient cohort undergoing radical radiotherapy treatment for NSCLC. The derived parameter sets strongly depend on the accuracy of the dose calculation algorithm involved. Parameters derived based on dose-distribution data sets obtained using one particular dose calculation algorithm may not hold good when evaluating treatment plans calculated with a different algorithm. In this sub-study, the influence of dose calculation algorithms on TCP model parameters was evaluated. Significant differences were found in TCPs when calculated with inconsistent parameters. Hence, the choice of dose calculation algorithm is crucial and although some algorithms generally perform close to MC in handling inhomogeneities, it is necessary to understand how the underlying differences affect the predicted clinical outcome.
Download or read book Tissue Inhomogeneity Corrections for Megalovoltage Photon Beams written by and published by . This book was released on 2004 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Application of Monte Carlo Methods in Molecular Targeted Radionuclide Therapy written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Targeted radionuclide therapy promises to expand the role of radiation beyond the treatment of localized tumors. This novel form of therapy targets metastatic cancers by combining radioactive isotopes with tumor-seeking molecules such as monoclonal antibodies and custom-designed synthetic agents. Ultimately, like conventional radiotherapy, the effectiveness of targeted radionuclide therapy is limited by the maximum dose that can be given to a critical, normal tissue, such as bone marrow, kidneys, and lungs. Because radionuclide therapy relies on biological delivery of radiation, its optimization and characterization are necessarily different than for conventional radiation therapy. We have initiated the development of a new, Monte Carlo transport-based treatment planning system for molecular targeted radiation therapy as part of the MINERVA treatment planning system. This system calculates patient-specific radiation dose estimates using a set of computed tomography scans to describe the 3D patient anatomy, combined with 2D (planar image) and 3D (SPECT, or single photon emission computed tomography) to describe the time-dependent radiation source. The accuracy of such a dose calculation is limited primarily by the accuracy of the initial radiation source distribution, overlaid on the patient's anatomy. This presentation provides an overview of MINERVA functionality for molecular targeted radiation therapy, and describes early validation and implementation results of Monte Carlo simulations.
Download or read book Entropic Model for Dose Calculation in External Beam Radiotherapy and Brachytherapy written by Gabriele Birindelli and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work is dedicated to development of a completely new Grid-Based Boltzmann Solver (GBBS) for the transport and energy deposition by energetic particles and x-rays in human tissues. The entropic closure and structured mathematical formulation provide an efficient framework enabling calculations of the delivered dose with an accuracy comparable to Monte Carlo (MC) codes in a strongly reduced computational time and without any special processing power requirement.In contrast to discrete ordinates angular discretization methods, such as Acuros®, the entropic model is based on a reduced number of moment equations for the electrons and photons closed with Boltzmann's H-theorem. Keeping a good accuracy of calculations, the algorithm can simulate different treatment techniques such as the external radiotherapy even in presence of magnetic field (e.g., MRI&-guided radiotherapy), brachytherapy or intra-operative radiation therapy. The model has been compared with the full MC simulations by using the code PENELOPE and showed a good accuracy and performance for different materials and geometric structures.The validation procedure consisted in simulating dose distributions in complex numerical phantoms including a large number of heterogeneity shapes and materials such as bone, lung and air. For both, brachytherapy and external beam radiotherapy, simulations based on CT scans and using the real phase-space of the source, have been performed.The code is capable of calculating three-dimensional dose distributions with 1 mm3 voxels without statistical uncertainties in a few seconds instead of several minutes like PENELOPE. In brachytherapy applications the calculated dose distributions significantly differ from the ones calculated with the TG-43 approximations, thanks to a more accurate account for the material inhomogeneities and strong density gradients. For both applications the entropic model shows an excellent agreement with PENELOPE calculations within the 1%/1mm gamma-index criterion.This Ph. D. thesis presents the mathematical background and different steps of optimization and validation of the entropic model for the radiotherapy applications. Comparisons with the MC simulations demonstrates an excellent accuracy and efficiency of the model. Thanks to the significantly reduced computational time and its accuracy, this model is a promising candidate to become a real-time dose calculation algorithm.
Download or read book Monte Carlo Techniques in Radiation Therapy written by Frank Verhaegen and published by CRC Press. This book was released on 2021-11-29 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: About ten years after the first edition comes this second edition of Monte Carlo Techniques in Radiation Therapy: Introduction, Source Modelling, and Patient Dose Calculations, thoroughly updated and extended with the latest topics, edited by Frank Verhaegen and Joao Seco. This book aims to provide a brief introduction to the history and basics of Monte Carlo simulation, but again has a strong focus on applications in radiotherapy. Since the first edition, Monte Carlo simulation has found many new applications, which are included in detail. The applications sections in this book cover the following: Modelling transport of photons, electrons, protons, and ions Modelling radiation sources for external beam radiotherapy Modelling radiation sources for brachytherapy Design of radiation sources Modelling dynamic beam delivery Patient dose calculations in external beam radiotherapy Patient dose calculations in brachytherapy Use of artificial intelligence in Monte Carlo simulations This book is intended for both students and professionals, both novice and experienced, in medical radiotherapy physics. It combines overviews of development, methods, and references to facilitate Monte Carlo studies.
Download or read book Accuracy Requirements and Uncertainties in Radiotherapy written by International Atomic Energy Agency and published by . This book was released on 2017-04-12 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accuracy requirements in radiation oncology have been defined in multiple publications; however, these have been based on differing radiation technologies. In the meantime, the uncertainties in radiation dosimetry reference standards have been reduced and more detailed patient outcome data are available. No comprehensive literature on accuracy and uncertainties in radiotherapy has been published so far. The IAEA has therefore developed a new international consensus document on accuracy requirements and uncertainties in radiation therapy, to promote safer and more effective patient treatments. This publication addresses accuracy and uncertainty issues related to the vast majority of radiotherapy departments including both external beam radiotherapy and brachytherapy. It covers clinical, radiobiological, dosimetric, technical and physical aspects.
Download or read book Proton Therapy Physics written by Harald Paganetti and published by CRC Press. This book was released on 2016-04-19 with total page 691 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton Therapy Physics goes beyond current books on proton therapy to provide an in-depth overview of the physics aspects of this radiation therapy modality, eliminating the need to dig through information scattered in the medical physics literature. After tracing the history of proton therapy, the book summarizes the atomic and nuclear physics background necessary for understanding proton interactions with tissue. It describes the physics of proton accelerators, the parameters of clinical proton beams, and the mechanisms to generate a conformal dose distribution in a patient. The text then covers detector systems and measuring techniques for reference dosimetry, outlines basic quality assurance and commissioning guidelines, and gives examples of Monte Carlo simulations in proton therapy. The book moves on to discussions of treatment planning for single- and multiple-field uniform doses, dose calculation concepts and algorithms, and precision and uncertainties for nonmoving and moving targets. It also examines computerized treatment plan optimization, methods for in vivo dose or beam range verification, the safety of patients and operating personnel, and the biological implications of using protons from a physics perspective. The final chapter illustrates the use of risk models for common tissue complications in treatment optimization. Along with exploring quality assurance issues and biological considerations, this practical guide collects the latest clinical studies on the use of protons in treatment planning and radiation monitoring. Suitable for both newcomers in medical physics and more seasoned specialists in radiation oncology, the book helps readers understand the uncertainties and limitations of precisely shaped dose distribution.
Download or read book The Modern Technology of Radiation Oncology written by Jake Van Dyk and published by Medical Physics Publishing Corporation. This book was released on 1999 with total page 1106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Details technology associated with radiation oncology, emphasizing design of all equipment allied with radiation treatment. Describes procedures required to implement equipment in clinical service, covering needs assessment, purchase, acceptance, and commissioning, and explains quality assurance issues. Also addresses less common and evolving technologies. For medical physicists and radiation oncologists, as well as radiation therapists, dosimetrists, and engineering technologists. Includes bandw medical images and photos of equipment. Paper edition (unseen), $145.95. Annotation copyrighted by Book News, Inc., Portland, OR
Download or read book Absorbed dose assessment in the presence of tissue heterogeneities in external radiotherapy written by Marta Bueno Vizcarra and published by . This book was released on 2014 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: The absorbed dose assessment in the presence of tissue heterogeneities in external radiotherapy is an issue that has concerned the medical physics community for almost three decades and it is still a matter of concern. Aiming to obtain dose distributions in clinically-acceptable computation times, analytical dose calculation algorithms integrated in treatment planning systems based their calculations on water-equivalent properties and elemental compositions of each material are disregarded despite the fact that radiation interaction processes strongly depend on them. This approximation provides reasonable accuracy in water-like tissues but the reliability of predicted dose distributions in the patient might be questioned when the radiation beam is traversing complex density heterogeneities, such as air, lung or bone. Experimental verification of dose calculation algorithms is essential and ionization chambers (IC) are the reference detectors for this purpose. However, correction factors to determine the absorbed dose in materials other than water are unknown for most IC types and therefore, they cannot procure reliable measurements in heterogeneous media. Monte Carlo (MC) simulations offer a high precision in dose calculation by tracking all particles individually taking into account the specific properties of each material. Unfortunately, accuracy and computation speed are inversely proportional and MC-based approaches generally entail long calculation times, unaffordable in the clinical routine. Nevertheless, for the cases where the expected errors in the predicted dose distributions during treatment planning are significant, i.e. when the radiation beam path is highly inhomogeneous, the benefit of resorting to MC dose calculations to achieve higher accuracy would be undoubtedly worth a presumably long computation time. In this thesis the suitability of several detectors to accurately determine the absorbed dose in the presence of high-density heterogeneities was evaluated. Ultra-thin thermoluminescent detectors (TLDs) and radiochromic films were considered as potential candidates for entailing low perturbation effects. MC dose calculations enabled to validate and understand the experimental results. Further, both dosimetric techniques were employed to thoroughly examine the behavior of a recently-released non-analytical dose calculation algorithm (AXB)¿which copes with the elemental composition of materials and thus, is claimed to yield promising results¿in heterogeneous phantoms. Finally, a fast algorithm named the heterogeneity index (HI) was developed to quantify the level of patient tissue heterogeneities traversed by the radiotherapy beam. The validity of this HI to easily predict the accuracy of dose distributions based on analytical dose calculations was analyzed by evaluating the correlation between the HI and the dose uncertainties estimated by using MC as the reference. The results show that a detector of 50μm thickness can provide reliable absorbed dose measurements in high-density heterogeneities since perturbation correction factors are unneeded. AXB was found to provide comparable accuracy to MC dose calculations in the presence of heterogeneities but uncertainties in the material assignment procedure might lead to significant changes in the dose distributions, which deserves a word of caution when carrying out experimental verifications. Finally, HI was found to be a fast and good indicator for the accuracy of dose delivery in terms of tumor dose coverage. Accordingly, HI can be implemented in the clinical routine to decide whether or not a MC dose recalculation of the plan should be considered to ensure that dose uncertainties are kept within tolerance levels. In conclusion, this thesis work tackled the main concerns on the absorbed dose calculation and measurement in the presence of tissue heterogeneities.
Download or read book Proton and Carbon Ion Therapy written by C-M Charlie Ma and published by CRC Press. This book was released on 2012-10-09 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton and Carbon Ion Therapy is an up-to-date guide to using proton and carbon ion therapy in modern cancer treatment. The book covers the physics and radiobiology basics of proton and ion beams, dosimetry methods and radiation measurements, and treatment delivery systems. It gives practical guidance on patient setup, target localization, and treatment planning for clinical proton and carbon ion therapy. The text also offers detailed reports on the treatment of pediatric cancers, lymphomas, and various other cancers. After an overview, the book focuses on the fundamental aspects of proton and carbon ion therapy equipment, including accelerators, gantries, and delivery systems. It then discusses dosimetry, biology, imaging, and treatment planning basics and provides clinical guidelines on the use of proton and carbon ion therapy for the treatment of specific cancers. Suitable for anyone involved with medical physics and radiation therapy, this book offers a balanced and critical assessment of state-of-the-art technologies, major challenges, and the future outlook of proton and carbon ion therapy. It presents a thorough introduction for those new to the field while providing a helpful, up-to-date reference for readers already using the therapy in clinical settings.
Download or read book Development of Procedures for in Vivo Dosimetry in Radiotherapy written by International Atomic Energy Agency and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive overview of the development of procedures for in vivo dosimetry in radiotherapy. It elaborates on the technology behind in vivo dosimetry and describes an initial set of measurements.
Download or read book Cumulated Index Medicus written by and published by . This book was released on 1998 with total page 1872 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Therapeutic Applications of Monte Carlo Calculations in Nuclear Medicine written by H. Zaidi and published by CRC Press. This book was released on 2002-09-01 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Therapeutic Applications of Monte Carlo Calculations in Nuclear Medicine examines the applications of Monte Carlo (MC) calculations in therapeutic nuclear medicine, from basic principles to computer implementations of software packages and their applications in radiation dosimetry and treatment planning. With chapters written by recognized authorit
