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Technical Note: Modeling a complex micro‐multileaf collimator using the standard BEAMnrc distribution
Author(s) -
Kairn T.,
Kenny J.,
Crowe S. B.,
Fielding A. L.,
Franich R. D.,
Johnston P. N.,
Knight R. T.,
Langton C. M.,
Schlect D.,
Trapp J. V.
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3355873
Subject(s) - multileaf collimator , monte carlo method , collimated light , linear particle accelerator , collimator , radiosurgery , dosimetry , homogeneous , optics , computer science , physics , nuclear medicine , medical physics , radiation therapy , beam (structure) , mathematics , medicine , statistical physics , radiology , laser , statistics
Purpose: The component modules in the standard BEAMnrc distribution may appear to be insufficient to model micro‐multileaf collimators that have trifaceted leaf ends and complex leaf profiles. This note indicates, however, that accurate Monte Carlo simulations of radiotherapy beams defined by a complex collimation device can be completed using BEAMnrc's standard VARMLC component module. Methods: That this simple collimator model can produce spatially and dosimetrically accurate microcollimated fields is illustrated using comparisons with ion chamber and film measurements of the dose deposited by square and irregular fields incident on planar, homogeneous water phantoms. Results: Monte Carlo dose calculations for on‐axis and off‐axis fields are shown to produce good agreement with experimental values, even on close examination of the penumbrae. Conclusions: The use of a VARMLC model of the micro‐multileaf collimator, along with a commissioned model of the associated linear accelerator, is therefore recommended as an alternative to the development or use of in‐house or third‐party component modules for simulating stereotactic radiotherapy and radiosurgery treatments. Simulation parameters for the VARMLC model are provided which should allow other researchers to adapt and use this model to study clinical stereotactic radiotherapy treatments.