Determination of dosimetric parameters for ¹²⁵I seed source using MCNP5 and EGSnrc MC codes

Background: Seed source has become a popular treatment option in the management of various tumors, particularly in the prostate. Purpose: The aim is to develop accurate and reliable dosimetric parameters that could be used to measure the dose delivered to organs at risk. Methods: Dosimetric parameters (dose rate constant, radial dose function and anisotropy function) of model 6711 ¹²⁵I seed source were calculated with MCNP5 and EGSnrc MC codes following AAPM TG43U1 recommendations. Results: The two results were compared with the relative data recommend by AAPM TG43U1, and the data were as follows: dose rate constant with MCNP5 was in agreement with 0.62%, while that with EGSnrc was 2.07%; radial dose function with MCNP5 was within 0.15%-5.12%, while that with EGSnrc was within 0%-2.48%. Conclusion: The results of two MC codes are in accordance with the recommendations. But that with EGSnrc MC code is better. (authors)