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Effects of collimator backscatter in an Elekta linac by Monte Carlo simulation

Kairn, Tanya, Crowe, Scott, Poole, Christopher, & Fielding, Andrew L. (2009) Effects of collimator backscatter in an Elekta linac by Monte Carlo simulation. Australasian Physical and Engineering Sciences in Medicine, 32(3), pp. 129-135.

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Abstract

The effects of radiation backscattered from the secondary collimators into the monitor chamber in an Elekta linac (producing 6 and 10 MV photon beams) are investigated using BEAMnrc Monte Carlo simulations. The degree and effects of this backscattered radiation are assessed by evaluating the changes to the calculated dose in the monitor chamber, and by determining a correction factor for those changes. Additionally, the fluency and energy characteristics of particles entering the monitor chamber from the downstream direction are evaluated by examining BEAMnrc phase-space data. It is shown that the proportion of particles backscattered into the monitor chamber is small (<0.35 %), for all field sizes studied. However, when the backscatter plate is removed from the model linac, these backscattered particles generate a noticeable increase in dose to the monitor chamber (up to approximate to 2.4 % for the 6 MV beam and up to 4.4 % for the 10 MV beam). With its backscatter plate in place, the Elekta linac (operating at 6 and 10 MV) is subject to negligible variation of monitor chamber dose with field size.

At these energies, output variations in photon beams produced by the clinical Elekta linear accelerator can be attributed to head scatter alone. Corrections for field-size-dependence of monitor chamber dose are not necessary when running Monte Carlo simulations of the Elekta linac operating at 6 and 10 MV.

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5 citations in Web of Science®

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ID Code: 29877
Item Type: Journal Article
Additional URLs:
Keywords: linear accelerator, Monte Carlo, radiation therapy, scatter
DOI: 10.1007/BF03178640
ISSN: 0158-9938
Subjects: Australian and New Zealand Standard Research Classification > PHYSICAL SCIENCES (020000) > OTHER PHYSICAL SCIENCES (029900) > Medical Physics (029903)
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Copyright Owner: Copyright 2009 ACPSEM/Springer
Copyright Statement: The original publication is available at SpringerLink http://www.springerlink.com
Deposited On: 22 Jan 2010 10:06
Last Modified: 01 Mar 2012 00:08

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