A comparison of surface doses for very small field size x-ray beams : Monte Carlo calculations and radiochromic film measurements

Morales, Johnny, Hill, Robin, Crowe, Scott, Kairn, Tanya, & Trapp, Jamie (2014) A comparison of surface doses for very small field size x-ray beams : Monte Carlo calculations and radiochromic film measurements. Australasian Physical and Engineering Sciences in Medicine, 37(2), pp. 303-309.

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Abstract

Stereotactic radiosurgery treatments involve the delivery of very high doses for a small number of fractions. To date, there is limited data in terms of the skin dose for the very small field sizes used in these treatments. In this work, we determine relative surface doses for small size circular collimators as used in stereotactic radiosurgery treatments. Monte Carlo calculations were performed using the BEAMnrc code with a model of the Novalis 15 Trilogy linear accelerator and the BrainLab circular collimators. The surface doses were calculated at the ICRU skin dose depth of 70 m all using the 6 MV SRS x-ray beam. The calculated surface doses varied between 15 – 12% with decreasing values as the field size increased from 4 to 30 mm. In comparison, surface doses were measured using Gafchromic EBT3 film positioned at the surface of a Virtual Water phantom. The absolute agreement between calculated and measured surface doses was better than 2.5% which is well within the 20 uncertainties of the Monte Carlo calculations and the film measurements. Based on these results, we have shown that the Gafchromic EBT3 film is suitable for surface dose estimates in very small size fields as used in SRS.

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ID Code: 69072
Item Type: Journal Article
Refereed: Yes
Additional URLs:
Keywords: stereotactic radiosurgery, SRS, surface dosimetry, Monte Carlo, radiochromic
DOI: 10.1007/s13246-014-0260-2
ISSN: 1879-5447
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: Copyright 2014 Australasian College of Physical Scientists and Engineers in Medicine
Deposited On: 24 Mar 2014 02:49
Last Modified: 18 Mar 2017 14:26

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