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Author: Keivan Jabbari Najafabadi Publisher: ISBN: Category : Languages : en Pages :
Book Description
A fast and accurate treatment planning system is essential for radiation therapy and Monte Carlo (MC) techniques produce the most accurate results for dose calculation in treatment planning. In this work, we developed a fast Monte Carlo code based on pre-calculated data (PMC, Pre-calculated Monte Carlo) for applications in radiation therapy treatment planning. The PMC code takes advantage of large available memory in current computer hardware for extensive generation of pre-calculated data. Primary tracks of electrons are generated in the middle of homogeneous materials (water, air, bone, lung) and with energies between 0.2 and 18 MeV using the EGSnrc code. Secondary electrons are not transported but their position, energy, charge and direction are saved and used as a primary particle. Based on medium type and incident electron energy, a track is selected from the pre-calculated set. The performance of the method is tested in various homogeneous and heterogeneous configurations and the results were generally within 2% compared to EGSnrc but with a 40-60 times speed improvement. Pre-calculated Monte Carlo codes are accurate, fast and physics-independent and therefore applicable to different radiation types including heavy-charged particles. In another project, we worked on Monte Carlo feasibility study to use orthogonal bremsstrahlung beams for imaging in radiation therapy. The basic characteristics of orthogonal bremsstrahlung beams are studied and the feasibility of improved contrast imaging in linear accelerator with such a beam is evaluated. In the context of this work orthogonal bremsstrahlung beams represent the component of the bremsstrahlung distribution perpend.
Author: Keivan Jabbari Najafabadi Publisher: ISBN: Category : Languages : en Pages :
Book Description
A fast and accurate treatment planning system is essential for radiation therapy and Monte Carlo (MC) techniques produce the most accurate results for dose calculation in treatment planning. In this work, we developed a fast Monte Carlo code based on pre-calculated data (PMC, Pre-calculated Monte Carlo) for applications in radiation therapy treatment planning. The PMC code takes advantage of large available memory in current computer hardware for extensive generation of pre-calculated data. Primary tracks of electrons are generated in the middle of homogeneous materials (water, air, bone, lung) and with energies between 0.2 and 18 MeV using the EGSnrc code. Secondary electrons are not transported but their position, energy, charge and direction are saved and used as a primary particle. Based on medium type and incident electron energy, a track is selected from the pre-calculated set. The performance of the method is tested in various homogeneous and heterogeneous configurations and the results were generally within 2% compared to EGSnrc but with a 40-60 times speed improvement. Pre-calculated Monte Carlo codes are accurate, fast and physics-independent and therefore applicable to different radiation types including heavy-charged particles. In another project, we worked on Monte Carlo feasibility study to use orthogonal bremsstrahlung beams for imaging in radiation therapy. The basic characteristics of orthogonal bremsstrahlung beams are studied and the feasibility of improved contrast imaging in linear accelerator with such a beam is evaluated. In the context of this work orthogonal bremsstrahlung beams represent the component of the bremsstrahlung distribution perpend.
Author: Alexander J. Egan Publisher: ISBN: Category : Monte Carlo method Languages : en Pages : 159
Book Description
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.
Author: H. Zaidi Publisher: CRC Press ISBN: 1000687686 Category : Medical Languages : en Pages : 441
Book Description
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
Author: Michael Ljungberg Publisher: CRC Press ISBN: 1439841098 Category : Medical Languages : en Pages : 361
Book Description
From first principles to current computer applications, Monte Carlo Calculations in Nuclear Medicine, Second Edition: Applications in Diagnostic Imaging covers the applications of Monte Carlo calculations in nuclear medicine and critically reviews them from a diagnostic perspective. Like the first edition, this book explains the Monte Carlo method and the principles behind SPECT and PET imaging, introduces the reader to some Monte Carlo software currently in use, and gives the reader a detailed idea of some possible applications of Monte Carlo in current research in SPECT and PET. New chapters in this edition cover codes and applications in pre-clinical PET and SPECT. The book explains how Monte Carlo methods and software packages can be applied to evaluate scatter in SPECT and PET imaging, collimation, and image deterioration. A guide for researchers and students developing methods to improve image resolution, it also demonstrates how Monte Carlo techniques can be used to simulate complex imaging systems.
Author: Katrin Henkner Publisher: ISBN: Category : Languages : en Pages : 93
Book Description
To benefit from high dose conformity in proton and heavy ion radiotherapy, dosimetry and treatment planning have to be improved. Clinically, dose distributions are calculated with analytical algorithms in water. In contrast, Monte Carlo (MC) hadron transport codes calculate ranges and dose distributions according to the real composition of the media taking into account nuclear and electromagnetic interactions in inhomogeneous media. In this work SHIELD-HIT is used to study the accuracy of analytical model in a comparison to MC absorbed dose and range calculations and to determine scaling methods. The I-value of water is revised from newly experimental Bragg peak and its influence on the water-to-air stopping power ratio is studied. Considerable improvements in depth-dose curve and differential cross section calculations are achieved by adjusting SHIELD-HIT results to measured data. An estimation on MC program specific model implementations is determined in a comparison to two other codes used in heavy ion therapy. Furthermore, preliminary data of the dose from secondary neutrons in human phantom geometries in the brain region is shown.
Book Description
"Modern treatment planning techniques such as inverse planning have increased the demand for rapid dose calculation methods to accommodate the large number of dose distributions required to generate a treatment plan. General-purpose Monte Carlo approaches for dose calculation are known to offer the highest accuracy in dose calculation at the expense of significant computing time. This work adapts a Macro Monte Carlo approach to dose calculation for electrons andprotons for use with a GPU card, using pre-generated tracks from general-purpose Monte Carlo codes. The algorithm was implemented on the CUDA framework for parallel programming on graphics cards. Comparisons of the algorithm inhomogeneous and inhomogeneous geometry with benchmark Monte Carlo codes yielded agreements within 1% in dose regions of at least 50% of Dmax and up to 3% in low dose regions. A Bragg peak positioning error of less than 1 mm was also observed. Additionally, the limited memory available in commercial graphics cards was overcome by subdividing a mother track bank residing on CPU memory into smaller samples of unique tracks. A method to quantify the latent uncertainty in dose values due to the limited size of a pre-generated track bank was developed. It was shown that the latent uncertainty follows a Poisson distribution as a function of the total number of unique tracks in the track bank. The implementation of the algorithm was found to transport particles in sub-second times per million history for every situation simulated, with speed-ups of 500-2600x for electrons over DOSXYZnrc and 2600-11500x for protons over GEANT4 depending on the particle energies and simulation media." --
Author: Oleg N. Vassiliev Publisher: Springer ISBN: 3319441418 Category : Science Languages : en Pages : 292
Book Description
This book is a guide to the use of Monte Carlo techniques in radiation transport. This topic is of great interest for medical physicists. Praised as a "gold standard" for accurate radiotherapy dose calculations, Monte Carlo has stimulated a high level of research activity that has produced thousands of papers within the past few years. The book is designed primarily to address the needs of an academically inclined medical physicist who wishes to learn the technique, as well as experienced users of standard Monte Carlo codes who wish to gain insight into the underlying mathematics of Monte Carlo algorithms. The book focuses on the fundamentals—giving full attention to and explaining the very basic concepts. It also includes advanced topics and covers recent advances such as transport of charged particles in magnetic fields and the grid-based solvers of the Boltzmann equation.
Author: Keivan Jabbari Najafabadi
Author: Keivan Jabbari Najafabadi
Author: Keivan Jabbari
Author: Keivan Jabbari
Author: Alexander J. Egan
Author: H. Zaidi
Author: Michael Ljungberg
Author: Katrin Henkner
Author: Frederik Carl Philippus Du Plessis
Author: Marc-André Renaud
Author: Oleg N. Vassiliev