Document Detail

A virtual source model for Monte Carlo modeling of arbitrary intensity distributions.
MedLine Citation:
PMID:  10659754     Owner:  NLM     Status:  MEDLINE    
A photon virtual source model was developed for simulating arbitrary, external beam, intensity distributions using the Monte Carlo method. The source model consists of a photon fluence grid composed of a matrix of square elements, located 25-cm downstream from the linear accelerator target. Each particle originating from the fluence map is characterized by the seven phase space parameters, position (x, y, z), direction (u, v, w), and energy. The map was reconstructed from fluence and energy spectra acquired by modeling components of the linear accelerator treatment head using the Monte Carlo code MCNP4B. The effect of contaminant electrons is accounted for by the use of a sub-source derived from a phase-space simulation of a 25-MV linac treatment head using the code BEAM. The BEAM sub-source was incorporated into the MCNP4B phase-space model and is sampled using a field-size dependent sampling ratio. A Gaussian blurring kernel is convolved with the photon fluence map to account for the finite focal spot size and scattering effects from structures such as the flattening filter and MLC leaves. Depth dose and profile source calculations for 6-MV and 25-MV photon beams, for 5 x 5 cm2, 10 x 10 cm2, and 15 x 15 cm2 field sizes, are in good agreement with measurement and are well within acceptability criteria suggested by the AAPM Task Group Report No. 53. Irregular field calculations compared with film measurement and with a 3-D pencil beam algorithm show that the source model is capable of accurately simulating arbitrary MLC fields.
I Chetty; J J DeMarco; T D Solberg
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  27     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2000 Jan 
Date Detail:
Created Date:  2000-03-03     Completed Date:  2000-03-03     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  166-72     Citation Subset:  IM    
Jonsson Comprehensive Cancer Center, Department of Radiation Oncology, University of California Los Angeles, 90024-6951, USA.
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MeSH Terms
Biophysical Phenomena
Models, Statistical
Monte Carlo Method
Particle Accelerators
Phantoms, Imaging
Radiotherapy Planning, Computer-Assisted / statistics & numerical data*
Radiotherapy, High-Energy

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