International Journal of Science and Technology

International Journal of Science and Technology>> Volume 7, Number 7, July 2017

International Journal of Science and Technology


Functional Fitting of Monte Carlo Output Parameters for the Nucletron Pulsed Dose Rate Brachytherapy Source

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Author M. Pokoo Aikins, A. Kyere, F. Hasford, M. Boadu, G.F. Acquah and E. K. Sosu
On Pages 167-176
Volume No. 3
Issue No. 3
Issue Date March, 2013
Publishing Date March, 2013
Keywords Brachytherapy, Monte Carlo, functional fitting, TG 43 formalism.


Abstract

The current brachytherapy treatment planning system employs the TG 43 formalism proposed by the American Association of Medical Physicists in Medicine (AAPM). The TG 43 uses dose rate tables which assume cylindrical symmetry of the sources, and the medium in which the calculation is made is water equivalent, with no modification for different heterogeneities and no account for applicator attenuation. The dose rate tables sometimes require interpolation and extrapolation, which may lead to uncertainties in dose calculations. This work aims to fit functions for the Monte Carlo output parameters generated by Lliso et al. (2001) [10], in the quest to develop a functional form which will reduce the number of independent variables, reduce the uncertainties in dose calculation distribution around the Nucletron pulsed dose rate (PDR) 192Ir brachytherapy source, and hence to facilitate implementation of the TG 43 formalism. The fitting and verifications were done using different software of the computer, e.g., Matlab, MS word, MS excel. We used Matlab fitting tool to fit the functions for the Nucletron PDR MC output parameters generated by Lliso et al. The accuracy of the fit functional form obtained was verified by comparing the dose rate distribution per unit air kerma strength obtained from the fit, to the dose rate distribution per unit air kerma strength obtained directly for the work of Lliso. For the absolute dose rate error calculations, deviation and mean were used. The average discrepancies in the dose rate per unit air kerma strength (in cGyh-1U-1) obtained from the fit were all found to be less than 1 %, within the TG 43 recommended statistical uncertainty limit . The results from this study, it is hoped can be used as input data in TPS, and to verify calculations of TPS for precise brachytherapy treatment planning.

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