Determination of dosimetry parameters for low energy brachytherapy sources based on TG-43U1 protocol using different MCNP tallies

Application of low energy 125I and 103Pd sources in prostate cancer brachytherapy has been considerably increased, recently. Accordingly, the Nuclear Research Center for Agriculture and Medicine has selected the production of 103Pd source seeds and their characterization as one of its main objectives. In this investigation, we have calculated TG-43U1 dosimetry parameters for a source similar to the primary Nuclear Research Center for Agriculture and Medicine design, using MCNP Monte Carlo computer code with F4, F6 and *F8 tallies. The results have been compared with the corresponding values reported in the literature and for most of the cases, all the three tallies and the reported values are in good agreement. It has been found that the F6 tally is about 20 times faster than *F8 tally without any considerable loss of accuracy. Therefore, it is concluded that for design analysis purposes, the F6 tally is adequately efficient to perform cumbersome recursive brachytherapy seed design calculations