Measurements and Monte Carlo calculation of radial dose and anisotropy functions of BEBIG 60Co high-dose-rate brachytherapy source in a bounded water phantom

Buchapudi Rekha Reddy; Marc J P Chamberland; Manickam Ravikumar; Chandraraj Varatharaj

doi:10.5114/jcb.2019.91224

Measurements and Monte Carlo calculation of radial dose and anisotropy functions of BEBIG ⁶⁰Co high-dose-rate brachytherapy source in a bounded water phantom

J Contemp Brachytherapy. 2019 Dec;11(6):563-572. doi: 10.5114/jcb.2019.91224. Epub 2019 Dec 25.

Authors

Buchapudi Rekha Reddy¹, Marc J P Chamberland^{2

3}, Manickam Ravikumar⁴, Chandraraj Varatharaj^{1

3}

Affiliations

¹ Department of Radiation Physics, Kidwai Memorial Institute of Oncology, Bangalore, India.
² Carleton Laboratory for Radiotherapy Physics, Department of Physics, Carleton University, Ottawa, Canada.
³ Division of Medical Physics, The University of Vermont Medical Center, Burlington VT, USA.
⁴ Department of Radiotherapy, Sri Shankara Cancer Hospital & Research Centre, Shankarapuram, Bangalore, India.

Abstract

Purpose: The study compared the experimentally measured radial dose function, g(r), and anisotropy function, F(r,θ), of a BEBIG ⁶⁰Co (Co0.A86) high-dose-rate (HDR) source in an in-house designed water phantom with egs_brachy Monte Carlo (MC) calculated values. MC results available in the literature were only for unbounded phantoms, and there are no currently published data in the literature for experimental data compared to MC calculations for a bounded phantom.

Material and methods: egs_brachy is a fast EGSnrc application designed for brachytherapy applications. For unbounded phantom calculation, we considered a cylindrical phantom with a length and diameter of 80 cm and used liquid water. These egs_brachy calculated TG43U1 parameters were compared with the consensus data. Upon its validation, we experimentally measured g(r) and F(r,θ) in a precisely machined 30 × 30 × 30 cm³ water phantom using TLD-100 and EBT2 Gafchromic Film and compared it with the egs_brachy results of the same geometry.

Results: The TG43U1 dosimetric dataset calculated using egs_brachy was compared with published data for an unbounded phantom, and found to be in good agreement within 2%. From our experimental results of g(r) and F(r,θ), the observed variation with the egs_brachy code calculation is found to be within the acceptable experimental uncertainties of 3%.

Conclusions: In this study, we validated the egs_brachy calculation of the TG43U1 dataset for the BEBIG ⁶⁰Co source for an unbounded geometry. Subsequently, we measured the g(r) and F(r,θ) for the same source using an in-house water phantom. In addition, we validated these experimental results with the values calculated using the egs_brachy MC code, with the same geometry and similar phantom material as used in the experimental methods.

Keywords: Monte Carlo code; anisotropy function; radial dose function.