Using a Monte Carlo simulation to analyze the ideal activity for a phosphorus-32 polymeric brachytherapy source for paraspinal tumors

Abstract

A promising radioactive source for use in intracavitary brachytherapy is phosphorus-32. This source has been prominent as a minimally invasive treatment for craniopharyngiomas and in the treatment of metastatic bone diseases in general and has been developed at Nuclear and Energy Research Institute (IPEN). In this work, a Monte Carlo simulation was used to evaluate the ideal activity this source must have to deliver a 1 Gy/min dose rate. TOPAS was used to model the simulation, and its geometry was simulated with the source centered in the origin point, inserted into an isotropic volume of water of 17.42 cm3. The source has the decay properties of phosphorus-32. The total dose was calculated using volumetric scorers. The results were promising, showing that the initial activity must be 86.14 mCi or 2871 MBq to obtain the 1 Gy/min dose rate. With the initial activity measured in this work, it is possible to minimize the patient's exposure to radiation, while ensuring the quality of the treatment.