Monte carlo simulation of electron beams from varian truebeam linear accelerator used in radiotherapy: estimation of initial beam parameters

Abstract

In Radiotherapy (RT), electron beams are widely used to treat superficial tumours. The dose delivered to the patients was precisely estimated by Monte Carlo (MC) methods. MC codes need Initial Beam Parameter (IBP) [mean energy, energy spectrum, spot size] and structural details of the machines as input to predict the dose. This study determined the IBP of Varian TrueBeam (TB) Linear Accelerator using PRIMO and validated it using depth dose curves and profiles. The MC Code GEANT 4 (VirtuaLinac) and PENELOPE (PRIMO) were used. The energies used were 6,9,12 & 18 MeV, the applicator used was 10x10 cm2 and 25x25 cm2, and the source to surface distance value was set as 100cm. The MC model available in PRIMO for TB was validated. Initial mean energies were obtained of 6.81, 9.77, 13.15 and 19.79 MeV for 6, 9, 12 and 18 MeV nominal energies, respectively. Sigma of Gaussian distribution was estimated as 0.59, 0.62, 0.71 and 0.82, respectively. The average values of percentage dose difference between the measured and MC simulated PDD and profiles were within 5%. Found that PRIMO is a convenient and easy-to-operate software application with the potential to estimate dose distribution in water phantoms or CT Images precisely.