Electrons Contamination Effect on the Photon dose Distribution in the Planning Treatment for Cancerous Patients

Distribution of dose depends on the treatment field and the presence of multiple collimators sheet at the direction of the photons. The aim of this study is evaluating and comparing the effects of the presence and absence of electrons contamination on the dose distribution with the use of computed tomography.
Subjects and Varian linear accelerator (2100 C / D) was simulated with Primo and BEAMnrc codes for photon with 5.9 MV nominal energy. This study was done for 15 patients with eyes tumor undergoing single field photon therapy.
The maximum depth dose treatment volume aggregation in the presence and the absence of electrons contamination was occurred at 1.3cm3 and 2cm3, respectively. Differential dose volume histogram concluded 80% of total dose in the presence and absence of electrons, 90%±0.5 and 80%±2 of the eye volume covered, respectively.
The main goal of radiation therapy is delivering the highest dose to the planning treatment volume and minimal radiation dose to organs at risk. In this case, the percent of the eye and treatment volume which taken 80% and 90% dose has 10% reduction and 5% increased by removing electrons contamination, respectively.