The influence of Monte Carlo source parameters on detector design and dose perturbation in small field dosimetry

Charles, Paul, Crowe, Scott, Kairn, Tanya, Knight, Richard, Hill, Brendan, Kenny, John, Langton, Christian M., & Trapp, Jamie (2014) The influence of Monte Carlo source parameters on detector design and dose perturbation in small field dosimetry. Journal of Physics : Conference Series, 489 (012006).

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Abstract

To obtain accurate Monte Carlo simulations of small radiation fields, it is important model the initial source parameters (electron energy and spot size) accurately. However recent studies have shown that small field dosimetry correction factors are insensitive to these parameters. The aim of this work is to extend this concept to test if these parameters affect dose perturbations in general, which is important for detector design and calculating perturbation correction factors.

The EGSnrc C++ user code cavity was used for all simulations. Varying amounts of air between 0 and 2 mm were deliberately introduced upstream to a diode and the dose perturbation caused by the air was quantified. These simulations were then repeated using a range of initial electron energies (5.5 to 7.0 MeV) and electron spot sizes (0.7 to 2.2 FWHM).

The resultant dose perturbations were large. For example 2 mm of air caused a dose reduction of up to 31% when simulated with a 6 mm field size. However these values did not vary by more than 2 % when simulated across the full range of source parameters tested.

If a detector is modified by the introduction of air, one can be confident that the response of the detector will be the same across all similar linear accelerators and the Monte Carlo modelling of each machine is not required.

Impact and interest:

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ID Code: 69076
Item Type: Journal Article
Refereed: Yes
DOI: 10.1088/1742-6596/489/1/012006
ISSN: 1742-6588
Subjects: Australian and New Zealand Standard Research Classification > PHYSICAL SCIENCES (020000) > OTHER PHYSICAL SCIENCES (029900) > Medical Physics (029903)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Funding:
Copyright Owner: The authors
Deposited On: 24 Mar 2014 05:16
Last Modified: 06 Sep 2016 03:13

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