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[en] A restricted angular scattering model for electron penetration in dense media is presented. In the model, the Fermi-Eyges transport equation is modified through the addition of an extra term which may be interpreted as representing an apparent force opposing the scattering of electrons into wider angles. The introduction of this extra term allows the modeling of the measured saturation in the mean square angular spread of electrons with depth. The restricted scattering model retains the Gaussian features of the Fermi-Eyges model and, therefore, may be readily incorporated into existing dose computation algorithms. Good agreement is obtained with measured angular electron distribution data for a point monodirectional beam over a wide range of incident electron energies (5-20 MeV) and scattering media (atomic numbers of 6 to 82). Also, a comparison of the restricted scattering model predictions with measurements of the lateral pencil beam spread shows an improvement over the predictions of Fermi-Eyges model close to the end of the electron range. Broad beam profiles were generated using both the Fermi-Eyges and restricted scattering models. A comparison of predicted and measured beam profiles shows that the restricted scattering model is a significant improvement over the Fermi-Eyges model for the prediction of beam penumbra shape in homogeneous media
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[en] The aim of this work is to analyse the equivalence of two classes of radiation therapy. One class of therapy is characteristic of Gamma Knife type irradiations and is defined by pencil beam concentric irradiation converging on multiple centres throughout the patient's body. The other class of treatment is characteristic of accelerator based, beam intensity modulated type irradiation defined by a rotation of wide beams around a single centre. We focus our attention on deriving formulae that relate treatments in these two classes and characterize conditions under which they are valid. (author)
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Physics in Medicine and Biology (Online); ISSN 1361-6560; ; v. 45(2); p. 399-409
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Sandison, G.; Huda, W.; Savoie, D.; Papiez, L.; McLellan, J.
Proceedings of the Canadian Nuclear Society ninth annual conference, 19881988
Proceedings of the Canadian Nuclear Society ninth annual conference, 19881988
AbstractAbstract
[en] Magnetically scanned therapeutic electron beams from the Sagittaire Therac 40 accelerator can be modelled using a collimated isotropic source in which the emitted electrons scatter according to Fermi-Eyges small angle multiple scattering theory. This theory predicts a Gaussian spatial and angular spread of an electron pencil beam with depth in tissue. A semi-empirical method based on this theory can be used to derive the standard deviation σ of this Gaussian with depth in a tissue-equivalent medium from broad electron beam penumbra. The results obtained with this semi-empirical method at 16 and 22 Mev beam energies are compared to Fermi-Eyges theory and a range straggling modification to this theory, for homogeneous tissue-equivalent media corresponding to muscle, lung and bone. The semi-empirically derived values of σ demonstrate that neither Fermi-Eyges theory nor the range straggling modification to this theory possesses universal validity and this may lead to significant dose computation errors in the treatment planning of radiotherapy patients. A 'friction' term is introduced into the Fermi-Eyges electron transport equation to account for the effects of range straggling. This friction component is successful in modelling the measured variation of mean square scattering angle with depth in homogeneous media
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Canadian Nuclear Society, Toronto, ON (Canada); 488 p; 1988; p. 459-465; Canadian Nuclear Society 9. annual conference; Winnipeg, MB (Canada); 13-15 Jun 1988
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Papiez, L.; Moskvin, V.; Tulovsky, V.
Advanced Monte Carlo for radiation physics, particle transport simulation and applications. Proceedings2001
Advanced Monte Carlo for radiation physics, particle transport simulation and applications. Proceedings2001
AbstractAbstract
[en] The process of angular-spatial evolution of multiple scattering of charged particles can be described by a special case of Boltzmann integro-differential equation called Lewis equation. The underlying stochastic process for this evolution is the compound Poisson process on the surface of the unit sphere. The significant portion of events that constitute compound Poisson process that describes multiple scattering have diffusional character. This property allows to analyze the process of angular-spatial evolution of multiple scattering of charged particles as combination of soft and hard collision processes and compute appropriately its transition densities. These computations provide a method of the approximate solution to the Lewis equation. (orig.)
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Kling, A. (Instituto Tecnologico e Nuclear, Sacavem (Portugal)); Barao, F.J.C. (Laboratorio de Instrumentacao e Particulas, Lisboa (Portugal)); Nakagawa, M. (Department of Nuclear Energy System (JAERI), Ibaraki (Japan)); Tavora, L. (Coimbra Univ. (Portugal). Dept. de Fisica); Vaz, P. (Departamento de Fisica (IST), Lisboa (Portugal)) (eds.); 1218 p; ISBN 3-540-41795-8; ; 2001; p. 1129-1138; MC Monte Carlo 2000: International conference on advanced Monte Carlo for radiation physics, particle transport simulation and applications; Lisbon (Portugal); 23-26 Oct 2000
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[en] The International Commission on Radiological Units and Measurements (ICRU) has defined fluence in terms of the number of the radiation particles crossing a small sampling sphere. A second definition has been proposed in which the length of track segments contained within any sampling volume are used to calculate the incident fluence. This approach is often used in Monte Carlo simulations of individual particle tracks, allowing the fluence to be scored in small volumes of any shape. In this paper we stress that the second definition generalizes the classical (ICRU) concept of fluence. We also identify the assumptions inherent in the two definitions of fluence and prove their equivalence for the case of straight-line particle trajectories. (author)
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Moskvin, V.; Papiez, L.; Das, I.J.
Advanced Monte Carlo for radiation physics, particle transport simulation and applications. Proceedings2001
Advanced Monte Carlo for radiation physics, particle transport simulation and applications. Proceedings2001
AbstractAbstract
[en] The method of trajectory rotation (Lazurik and Moskvin, Nucl. Instr. and Meth. B134, 1998, p. 1-12) has been modified for calculations of deep penetration of electron beams through thick targets. The new algorithm obtained is presented together with its efficiency evaluated for calculations of the average energy of electrons transmitted through thick targets. The appearance of artifacts in calculations of the above problem by conventional binary-encounter Monte Carlo techniques is discussed. (orig.)
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Kling, A. (Instituto Tecnologico e Nuclear, Sacavem (Portugal)); Barao, F.J.C. (Laboratorio de Instrumentacao e Particulas, Lisboa (Portugal)); Nakagawa, M. (Department of Nuclear Energy System (JAERI), Ibaraki (Japan)); Tavora, L. (Coimbra Univ. (Portugal). Dept. de Fisica); Vaz, P. (Departamento de Fisica (IST), Lisboa (Portugal)) (eds.); 1218 p; ISBN 3-540-41795-8; ; 2001; p. 199-204; MC Monte Carlo 2000: International conference on advanced Monte Carlo for radiation physics, particle transport simulation and applications; Lisbon (Portugal); 23-26 Oct 2000
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[en] The moving table technique for total body irradiation (MTT TBI) has some advantages in regard to dose homogeneity, patient positioning and comfort. However, divergence of the radiation field coupled with patient motion necessitates corresponding motion of the shielding blocks and verification film so that penumbra is minimized. MTT TBI system is presented, together with dose calculations, incorporating moving trays for shields and film to ensure dose delivery with minimal penumbra of the blocked field. (author.)
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[en] High-energy electron beams in the range 150-250 MeV are studied to evaluate the feasibility for radiotherapy. Monte Carlo simulation results from the PENELOPE code are presented and used to determine lateral spread and penetration of these beams. It is shown that the penumbra is comparable to photon beams at depths less than 10 cm and the practical range (Rp) of these beams is greater than 40 cm. The depth dose distribution of electron beams compares favourably with photon beams. Effects caused by nuclear reactions are evaluated, including increased dose due to neutron production and induced radioactivity resulting in an increased relative biological effectiveness (RBE) factor of <1.03. (author)
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Country of input: International Atomic Energy Agency (IAEA); 34 refs; This record replaces 31040250
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Physics in Medicine and Biology (Online); ISSN 1361-6560; ; v. 45(7); p. 1781-1805
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[en] A numerical algorithm for calculating the penetration of electrons in dense media for future application to radiotherapy dose calculations is presented. The method is generic in the sense that it may be used with different theoretical models describing the angular scattering of electrons with depth. It is also general enough to be applied to electron dose calculations in heterogeneous as well as homogeneous media. The assumptions used in the algorithm are examined and equations describing the evolution of the distribution of electrons with depth are presented. Calculations have been performed for 10 MeV broad beams and pencil beams incident on water. It is shown that the Fermi-Eyges analytical solutions are recovered if the angular scattering process is assumed to be a Gaussian Markov process and the cumulative angle of electron travel remains small. (Author)
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[en] Dose to the total body from induced radiation resulting from primary exposure to radiotherapeutic beams is not detailed in routine treatment planning though this information is potentially important for better estimates of health risks including secondary cancers. This information can also allow better management of patient treatment logistics, suggesting better timing, sequencing, and conduct of treatment. Monte Carlo simulations capable of taking into account all interactions contributing to the dose to the total body, including neutron scattering and induced radioactivity, provide the most versatile and accurate tool for investigating these effects. MCNPX code version 2.2.6 with full IAEA library of photoneutron cross sections is particularly suited to trace not only photoneutrons but also protons and heavy ion particles that result from photoneutron interactions. Specifically, the MCNPX code is applied here to the problem of dose calculations in traditional (non-IMRT) photon beam therapy. Points of calculation are located in the head, where the primary irradiation has been directed, but also in the superior portion of the torso of the ORNL Mathematical Human Phantom. We calculated dose contributions from neutrons, protons, deutrons, tritons and He-3 that are produced at the time of photoneutron interactions in the body and that would not have been accounted for by conventional radiation oncology dosimetry
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(c) 2003 American Association of Physicists in Medicine.; Country of input: International Atomic Energy Agency (IAEA)
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BARYONS, BEAMS, BIOLOGICAL EFFECTS, BODY, CALCULATION METHODS, CENTRAL NERVOUS SYSTEM, CHARGED PARTICLES, DISEASES, DOSES, DOSIMETRY, ELEMENTARY PARTICLES, EVEN-ODD NUCLEI, FERMIONS, HADRONS, HELIUM ISOTOPES, IONS, ISOTOPES, LIGHT NUCLEI, MEDICINE, MOCKUP, NATIONAL ORGANIZATIONS, NERVOUS SYSTEM, NEUTRONS, NUCLEAR MEDICINE, NUCLEI, NUCLEON BEAMS, NUCLEONS, ORGANS, PARTICLE BEAMS, PHOTONUCLEONS, RADIATION EFFECTS, RADIOLOGY, STABLE ISOTOPES, STRUCTURAL MODELS, THERAPY, US AEC, US DOE, US ERDA, US ORGANIZATIONS
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