Determination of dosimetric characteristics of OptiSeedTM a plastic brachytherapy 103Pd source

A new 103Pd plastic brachytherapy source, OptiSeedTM Model 1032P, is being introduced by International Brachytherapy sa (IBt). Measurements of the dose distributions about the source were performed using LiF thermoluminescent dosimeters (TLD-100) in Virtual WaterTM. MCNP5 calculations were performed to determine the dose distributions in Virtual WaterTM and liquid water. The source dose rate constant, radial dose function, anisotropy function and anisotropy factor have been determined following the updated AAPM TG-43 recommendations. The measured dose rate constant in the Virtual WaterTM phantom was determined to be 0.727±6.9% cGy h−1 U−1, and the computed value is 0.716±2.1% cGy h−1 U−1. The Monte-Carlo simulation yielded a dose rate constant of 0.665±2.1% cGy h−1 U−1 in water. The measured dose rate constant in water is 0.675±7.5% cGy h−1 U−1. It is determined by multiplying the dose rate constant measured in the Virtual WaterTM phantom with the ratio of the value calculated in water to that in Virtual WaterTM. The average of the measured and calculated dose rate constant is 0.670±5.5% cGy h−1 U−1. The radial dose functions of the new source were measured for distances ranging from 1 to 7 cm in a Virtual WaterTM phantom. The anisotropy functions in Virtual WaterTM phantom were measured for distances of 2, 3, 5, and 7 cm. The Monte-Carlo computed radial dose functions, anisotropy functions, and anisotropy factors in both Virtual WaterTM phantom and water are reported.