Investigation of Leakage and Transmission Radiation through the MLC Version I2 Applied To the Elekta Synergy 6 MV Photon Beam Linac

Radiotherapy and nuclear medicine extensively use Monte Carlo simulation to study particle transport and interactions. The aim of this task is the investigation and simulation of leakage and transmission (L&T) particles using the Multi-Leaf Collimator version i2 applied to the Elekta Synergy linac. In this study, all linac segments are included in the simulation model. In order to reduce MC calculation time, the new HPC-Slurm cluster platform and the Python phase space approach are used. To study the transmission between MLCi2 leaves, a detailed analysis of the dose distribution was conducted. The simulation results obtained with Gate 9.0 MC are excellently correlated with the measured data with error estimates for the 6 MV photon beam parameters less than 1% and a validation level of 99% in terms of the gamma index's (2%/2mm) threshold formalism for the cross profiles and PDD's dose distributions. The results indicate that contamination particles (e-, e+) have an effect on the distribution of dose in the patient. These particles are present in the beam produced previously and which is assumed to contain only X-rays. In addition, a three-dimensional distribution of dose inside the tumor (CT-scan) confirms the L&T effect of the studied version of the multi leaf collimator (MLCi2), with a dose range of around 70% of the delivered dose to the tumor, resulting in secondary outcomes at the DNA. Consequently, the production of a new generation of MLC that can limit this L&T effect should be encouraged.