Calculating dosimetry parameters in brachytherapy using the continuous beta spectrum of Sm-153 in the Monte Carlo simulation approach

摘要

Calculation of dosimetry parameters by TG-60 approach for beta sources and TG-43 approach for gamma sources can help to design brachytherapy sources. In this work, TG-60 dosimetry parameters are calculated for the Sm-153 brachytherapy seed using the Monte Carlo simulation approach. The continuous beta spectrum of Sm-153 and probability density are applied to simulate the Sm-153 source. Sm-153 is produced by neutron capture during the Sm-152(n,gamma)Sm-153 reaction in reactors. The Sm-153 radionuclide decays by beta rays followed by gamma-ray emissions with half-life of 1.928 days. Sm-153 source is simulated in a spherical water phantom to calculate the deposited energy and geometry function in the intended points. The Sm-153 seed consists of 20% samarium, 30% calcium and 50% silicon, in cylindrical shape with density 1.76 gr/cm(3). The anisotropy function and radial dose function were calculated at 0-4 mm radial distances relative to the seed center and polar angles of 0-90 degrees. The results of this research are compared with the results of Taghdiri et al. (Iran. J. Radiat. Res. 9, 103 (2011)). The final beta spectrum of Sm-153 is not considered in their work. Results show significant relative differences even up to 5 times for anisotropy functions at 0.6, 1 and 2 mm distances and some angles. MCNP4C Monte Carlo code is applied in both in the present paper and in the above-mentioned one.