Experimental validation of the DPM Monte Carlo code using minimally scattered electron beams in heterogeneous media

A comprehensive set of measurements and calculations has been conducted to investigate the accuracy of the Dose Planning Method (DPM) Monte Carlo code for electron beam dose calculations in heterogeneous media. Measurements were made using 10 MeV and 50 MeV minimally scattered, uncollimated electron...

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Bibliographic Details
Published in:Physics in medicine & biology 2002-06, Vol.47 (11), p.1837-1851, Article 301
Main Authors: Chetty, Indrin J, Moran, Jean M, Nurushev, Teamor S, McShan, Daniel L, Fraass, Benedick A, Wilderman, Scott J, Bielajew, Alex F
Format: Article
Language:English
Subjects:
Biological and medical sciences
Electrons
Humans
Medical sciences
Monte Carlo Method
Phantoms, Imaging
Radiometry - methods
Radiotherapy Planning, Computer-Assisted - methods
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Summary:A comprehensive set of measurements and calculations has been conducted to investigate the accuracy of the Dose Planning Method (DPM) Monte Carlo code for electron beam dose calculations in heterogeneous media. Measurements were made using 10 MeV and 50 MeV minimally scattered, uncollimated electron beams from a racetrack microtron. Source distributions for the Monte Carlo calculations were reconstructed from in-air ion chamber scans and then benchmarked against measurements in a homogeneous water phantom. The in-air spatial distributions were found to have FWHM of 4.7 cm and 1.3 cm, at 100 cm from the source, for the 10 MeV and 50 MeV beams respectively. Energy spectra for the electron beams were determined by simulating the components of the microtron treatment head using the code MCNP4B. Profile measurements were made using an ion chamber in a water phantom with slabs of lung or bone-equivalent materials submerged at various depths. DPM calculations are, on average, within 2% agreement with measurement for all geometries except for the 50 MeV incident on a 6 cm lung-equivalent slab. Measurements using approximately monoenergetic, 50 MeV, 'pencil-beam'-type electrons in heterogeneous media provide conditions for maximum electronic disequilibrium and hence present a stringent test of the code's electron transport physics; the agreement noted between calculation and measurement illustrates that the DPM code is capable of accurate dose calculation even under such conditions.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/47/11/301