Cobalt Therapy Dosimetric Calculations Over a Voxelized Heterogeneous Phantom: Validation of Different Monte Carlo Models and Methodologies Against Experimental Data

The main goal of the present paper is to quantify, in homogeneous and heterogeneous phantoms, the differences between experimentally measured dose distributions inside it, and those calculated by the simulation of different transport models using the Monte Carlo computer code MCNP. This objective has been achieved simulating the electron and photon transport in a water phantom irradiated by a Theratron 780 (MDS Nordion) ⁶⁰Co radiotherapy unit, which has been realistically modeled, considering field sizes from 5 cmtimes5 cm to 20 cmtimes20 cm. The source description and characteristics of the incident beam have been slightly modified in order to study the results variations of these models. Different methodologies have also been applied to speed up the calculations with the aim of applying MCNP efficiently in radiotherapy treatment planning