Technical Note: Modeling a complex micro-multileaf collimator using the standard BEAMnrc distribution

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 comp...

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Bibliographic Details
Published in:Medical physics (Lancaster) 2010-04, Vol.37 (4), p.1761-1767
Main Authors: 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.
Format: Article
Language:English
Subjects:
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Collimation
COLLIMATORS
COMPUTERIZED SIMULATION
DISTRIBUTION
Distribution theory and Monte Carlo studies
DOSEMETERS
Dose‐volume analysis
dosimeters
DOSIMETRY
IONIZATION CHAMBERS
LINEAR ACCELERATORS
Medical imaging
MLC
Monte Carlo
MONTE CARLO METHOD
Monte Carlo methods
Multileaf collimators
PHANTOMS
Photons
RADIATION DOSES
radiation therapy
radiochromic film
RADIOLOGY AND NUCLEAR MEDICINE
Radiosurgery
RADIOTHERAPY
small field dosimetry
Stereotactic radiosurgery
SURGERY
WATER
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Summary: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.
ISSN:0094-2405
2473-4209
DOI:10.1118/1.3355873