Monte Carlo calculation of dosimetry parameters for the IR08‐ brachytherapy source

Abstract

PurposeFor the treatment of some cancerous tumors using brachytherapy methods and low‐energy photon sources, such as and , the American Association of Physicists in Medicine Task Group No. 43U1 report recommends that the dosimetric parameters of a new brachytherapy source must be determined in two experimental and Monte Carlo theoretical methods before using each new source clinically. This study presents the results of Monte Carlo calculations of the dosimetric parameters for IR08‐ brachytherapy source design. IR08‐ seed has been manufactured at the Agricultural, Medical and Industrial Research School.MethodsVersion 5 of the (MCNP) Monte Carlo radiation transport code was used to calculate the dosimetry parameters around the source. Three geometric models of the seed, based on different locations of beads inside the titanium capsule, were simulated. The seed contains five resin beads of 0.6 mm diameter having uniformly absorbed in the bead volume, which were contained within a cylindrical titanium capsule having 0.8 mm outside diameter and 4.8 mm length.ResultsThe Monte Carlo calculated dose rate constant of the IR08‐ seed was found to be . Also in this study, the geometry function , line and point‐source radial dose functions and , and the anisotropy function , have been calculated at distances from 0.25 to 7 cm. The results of these calculations have been compared with measured values for an actual IR08‐ seed.ConclusionsThere are no statistical significant dosimetric differences among the three seed orientations in this study (i.e., ideal, vertical, and diagonal). However, the observed differences between the calculated and measured values could be explained by the measurement uncertainty and the configuration of the resin beads within the capsule and capsule orientation.