Monte Carlo calculations and experimental measurements of dosimetric parameters of the IRA-103Pd brachytherapy source

This article presents a brachytherapy source having Pd-103 adsorbed onto a cylindrical silver rod that has been developed by the Agricultural, Medical, and Industrial Research School for permanent implant applications. Dosimetric characteristics (radial dose function, anisotropy function, and anisotropy factor) of this source were experimentally and theoretically determined in terms of the updated AAPM Task group 43 (TG-43U1) recommendations. Monte Carlo simulations were used to calculate the dose rate constant. Measurements were performed using TLD-GR200A circular chip dosimeters using standard methods employing thermoluminescent dosimeters in a Perspex phantom. Precision machined bores in the phantom located the dosimeters and the source in a reproducible fixed geometry, providing for transverse-axis and angular dose profiles over a range of distances from 0.5 to 5 cm. The Monte Carlo N-particle (MCNP) code, version 4C simulation techniques have been used to evaluate the dose-rate distributions around this model Pd-103 source in water and Perspex phantoms. The Monte Carlo calculated dose rate constant of the IRA-Pd-103 source in water was found to be 0.678 cGy h(-1) U-1 with an approximate uncertainty of +/- 0.1%. The anisotropy function, F(r,theta), and the radial dose function, g(r), of the IRA-Pd-103 source were also measured in a Perspex phantom and calculated in both Perspex and liquid water phantoms. (C) 2008 American Association of Physicists in Medicine.