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Monte Carlo verification of gel dosimetry measurements for stereotactic radiotherapy

Kairn, T., Taylor, M.L., Crowe, S.B., Dunn, L., Franich, R.D., Kenny, J., Knight, R.T., & Trapp, J.V. (2012) Monte Carlo verification of gel dosimetry measurements for stereotactic radiotherapy. Physics in Medicine and Biology, 57(11), pp. 3359-3369.

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Abstract

The quality assurance of stereotactic radiotherapy and radiosurgery treatments requires the use of small-field dose measurements that can be experimentally challenging.

This study used Monte Carlo simulations to establish that PAGAT dosimetry gel can be used to provide accurate, high resolution, three-dimensional dose measurements of stereotactic radiotherapy fields. A small cylindrical container (4 cm height, 4.2 cm diameter) was filled with PAGAT gel, placed in the parietal region inside a CIRS head phantom, and irradiated with a 12 field stereotactic radiotherapy plan. The resulting three-dimensional dose measurement was read out using an optical CT scanner and compared with the treatment planning prediction of the dose delivered to the gel during the treatment. A BEAMnrc DOSXYZnrc simulation of this treatment was completed, to provide a standard against which the accuracy of the gel measurement could be gauged. The three dimensional dose distributions obtained from Monte Carlo and from the gel measurement were found to be in better agreement with each other than with the dose distribution provided by the treatment planning system's pencil beam calculation. Both sets of data showed close agreement with the treatment planning system's dose distribution through the centre of the irradiated volume and substantial disagreement with the treatment planning system at the penumbrae. The Monte Carlo calculations and gel measurements both indicated that the treated volume was up to 3 mm narrower, with steeper penumbrae and more variable out-of-field dose, than predicted by the treatment planning system. The Monte Carlo simulations allowed the accuracy of the PAGAT gel dosimeter to be verified in this case, allowing PAGAT gel to be utilised in the measurement of dose from stereotactic and other radiotherapy treatments, with greater confidence in the future.

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3 citations in Web of Science®

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ID Code: 48106
Item Type: Journal Article
Additional Information: The authors would also like to acknowledge funding from the Wesley Research Institute 2008
Keywords: monte carlo, gel dosimetry, stereotactic, radiotherapy
ISSN: 1361-6560
Subjects: Australian and New Zealand Standard Research Classification > PHYSICAL SCIENCES (020000) > OTHER PHYSICAL SCIENCES (029900)
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
Past > Schools > Physics
Funding:
Copyright Owner: Copyright 2012 Institute of Physics
Deposited On: 18 Jan 2012 08:36
Last Modified: 14 Apr 2014 13:46

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