A Monte Carlo evaluation of the dosimetric characteristics of the EchoSeed™ Model 6733 125I brachytherapy source

Purpose: 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 EchoSeed™Model 6733 125I 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 American Association of Physicists in Medicine (AAPM) TG-43 guidelines. Methods and Materials: As per AAPM recommendation, it is required to perform at least one experimental study and one Monte Carlo simulation, preferably done by two independent investigators. Other investigators have experimentally determined the dosimetric parameters of this new source. In this project, the Monte Carlo simulated dosimetric parameters of the EchoSeed™ Model 6733 source have been provided. Results: The results of this evaluation indicate the value of the dose rate constant of 0.97 ± 3% cGyh−1U−1 in liquid water, which is in good agreement with the measured value of 0.99 ± 8% cGyh−1U−1 reported by Meigooni et al. The anisotropy constant of the EchoSeed™ 125I brachytherapy source was found to be 0.960 in liquid water. Conclusions: The Monte Carlo Simulated TG-43 dosimetric parameters of the EchoSeed™ were determined and the results were compared with the published measured data.