A Monte Carlo evaluation of the dosimetric characteristics of the Best Model 2301 125I brachytherapy source.

Recently a new design of a 125I brachytherapy source was introduced for interstitial seed implants, particularly for prostate seed implants. This new source is the Best Model 2301 brachytherapy source. Due to the differences in source design and manufacturing process from one new source to the next, their dosimetric parameters should be determined according to the AAPM TG-43 guidelines. As per AAPM recommendation (Med. Phys. 25 (12) (1998) 2269), it is required to perform the seed dosimetry using at least one experimental study and one Monte Carlo simulation, preferably done by two separate investigators. Other investigators have experimentally determined the dosimetric parameters of this new source. In this project, the Monte Carlo simulated dosimetric parameters of the Best Model 2301 125I source have been provided. The results of this evaluation indicate the value of dose rate constant of 1.01 +/- 3% cGyh-1U-1 in liquid water, which is in good agreement with 1.02 +/- 8% cGyh-1U-1 reported by Nath and Yue, 2002. The anisotropy constant was found to be 0.98 in liquid water.