TG-60 dosimetry parameters calculation for the β-emitter 153Sm brachytherapy source using MCNP

Background: The formalism recommended by Task Group 60 (TG-60) of the American Association of Physicists in Medicine (AAPM) is applicable for β sources. Radioactive biocompatible and biodegradable 153Sm glass seed without encapsulation is a β-emitter with a short half life and delivers a high dose rate to the tumor in the millimeter range. In this work the dosimetry parameters of the seed for brachytherapy were evaluated. Materials and Methods: Using MCNP4C code data, the Dosimetric parameters of AAPM TG-60 recommendations including the reference dose rate, the radial dose function and the anisotropy function were obtained. Two dimensional dose distributions were also calculated. Results: The dose rate at reference point was estimated to be 9.41 cGy.h-1.μCi-1 for 153Sm. 153Sm with its relatively low energy beta component falls off the most rapidly of the other beta emitters. The calculated data was compared with that of several beta and photon emitting seeds. Conclusion: The results showed the advantage of the beta emitting 153Sm source in comparison with the other beta emitting sources, Because of its rapid dose fall-off of beta-ray and high dose rate at the short distances of the seed. The results would be helpful in development of the radioactive implants using 153Sm seeds for the brachytherapy treatment.