Theoretical and experimental determination of dosimetric characteristics for brachyseed ™ Pd-103, model Pd-1, source

Abstract

Dosimetric characteristics of the BrachySeed™ Pd-103, Model Pd-1 source have been determined using both theoretical and experimental methods. Dose rate constant, radial dose function, and anisotropy functions of the source have been obtained following the TG-43 recommendations. Derivation of the dose rate constant was based on recent NIST WAFAC calibration performed in accordance with their 1999 Standard. Measurements were performed in Solid Water™ using LiF TLD chips. Theoretical simulation calculations were performed in both Solid Water™ and water phantom materials using MCNP4C2 Monte Carlo code using DLC-200 interaction data. The results of the Monte Carlo simulation indicated a dose rate constant of 0.65 cGy h −1 U −1 and 0.61 cGy h −1 U −1 in water and Solid Water™, respectively. The measured dose rate constant in Solid Water™ was found to be 0.63±7% cGy h −1 U −1, which is within the experimental uncertainty of the Monte-Carlo simulated results. The anisotropy functions of the source were calculated in both water and in Solid Water™ at the radial distances of 1 to 7 cm. Measurements were made in Solid Water™ at distances of 2, 3, 5, and 7 cm. The Monte-Carlo calculated anisotropy constant of the new source was found to be 0.98 in water. The tabulated data and 5th order polynomial fit coefficients for the radial dose function along with the dose rate constant and anisotropy functions are provided to support clinical use of this source.