Optically Stimulated Luminescence Dosimetry in Permanent Breast Seed Implant Brachytherapy: a Monte Carlo Approach

Abstract

Permanent breast seed implant (PBSI) brachytherapy, typically performed with low energy radioactive Pd-103 x-ray sources, is a convenient treatment option for many low risk breast cancer patients. Skin is a primary organ at risk (OAR) in PBSI and is susceptible to painful toxicities when exposed to large doses of radiation. The TG-43 formalism used to calculate clinical dose distributions relies on simple assumptions that often lead to inaccurate assessments of skin dose. In this thesis, sophisticated Monte Carlo dose calculations were performed using egs_brachy to determine conversion factors relating skin doses to doses accumulated in optically stimulated luminescence dosimeters (OSLDs). These were supplemented by a procedure to calibrate OSLDs to a Pd-103 source and experimentally derived OSLD calibration factors. These results enable in-vivo dosimetry of a PBSI patient's skin dose following treatment via OSLDs placed on the surface of the skin providing valuable measurements of the actual dose delivered.