Sci-Thur AM: Planning - 02: Validation of XiO's eMC module using Gafchromic EBT3 films and triple channel dosimetry.

Abstract

The aim of this study is to validate the electron Monte Carlo module implemented in XiO, a treatment planning system commercialized by Elekta CMS inc. Two types of phantoms were investigated: homogeneous water phantoms with irregular surfaces and phantoms containing slab and 3D heterogeneities. The phantoms were CT scanned, and dose to water calculations were performed in the eMC module using 2 ×2 × 2 mm2 voxels and a mean relative statistical uncertainty of 0.5%. Concurrently, Gafchromic EBT3 film measurements were performed in the same phantoms. To obtain reliable absolute dose readings from the films, a new method using triple channel dosimetry in the Film QA Pro software was developed. The accuracy of the proposed method was determined empirically and an uncertainty of ±1.5% was found over the range [75, 800] cGy. Dose comparisons between film and simulations were done using an in-house MATLAB program. XiO's eMC module provides accurate dose distributions in the presence of surface irregularities and slab heterogeneities for 12 MeV beams. In the presence of 3D heterogeneities, the percent dose difference comparisons highlighted the need to perform 3D gamma comparisons. In conclusion, the electron Monte Carlo module offered in the XiO treatment planning system is promising and could greatly improve the accuracy of clinical dose calculations. The validation of the software is ongoing, notably concerning more complex phantom geometries. Small field calculations, oblique incidences and cutout factors will also be investigated.