Monte Carlo Modelling of the Small Animal Radiation Research Platform (SARRP)

Abstract

At the Christie, differences in dose were observed between the dose calculated by the SARRP’s treatment planning system (TPS) and the dose measured in a mouse phantom. The SARRP’s TPS employs the superposition-convolution method for dose calculation. The Monte Carlo method is considered to be the gold standard for dose calculation, and it is currently the most accurate method in calculating dose in heterogeneous media. A Monte Carlo model of SARRP is built using Gate. Hopefully, the model defined here well be the basis of a more complete model allowing for the investigation of that dose difference. Currently, there is no commercially available treatment planning system that is able to provide accurate dose calculations in small animals. Therefore, the MC-model presented can be a valuable complementary tool for dose calculations and verification of SARRP.

The model was validated against film measurements of percentage depth dose curves (PDDs) for 5×5 mm2 and 3×3 mm2 field sizes at a source to surface distance (SSD) of 30.15 mm, 34.15 mm, and 38.15 mm. The MC calculations agreed well with measurements with an absolute mean percentage error of 3% for both of the examined fields. The maximum percentage error was 7% and 11% for 3×3 mm2 and 5×5 mm2 field sizes, respectively. The results are encouraging, and further validation that includes other field sizes and other dosimetric characteristics of the beam (e.g., lateral beam profiles) may be needed before the model is used in future studies.