Monte Carlo simulation and experimental evaluation of dose distributions produced by a 6 MV medical linear accelerator.

Abstract

The purpose of this work was to quantify the differences in dose distributions computed by Monte Carlo simulations against experimental measurements from an Elekta Synergy™ linear accelerator. The study was done using PRIMO, a PENELOPE-based Monte Carlo code. The dose calculation algorithm was compared under static field irradiations at 6 MV in a virtual water phantom for field sizes 10 × 10, 5 × 5 and 3 × 3 cm2. Experimental depth doses and profiles were obtained using a pair of CC13 iba® ionization chambers at a SSD = 100 cm in an iba Blue phantom™. Simulations and experimental data were compared in terms of point by point differences. Gamma analysis was also used in order to evaluate dose- differences and distance to agreement (2%, 2mm respectively) of calculated and experimental dose distributions. The evaluation of depth dose distributions indicated that differences increased by decreasing the field size. In all cases the mean dose difference was below 1%. Lateral profiles differences were also below 1% for all field sizes. Gamma analysis results were in an agreement of 99% for almost all the dose distributions for the chosen criteria. The performed Monte Carlo simulation using PRIMO showed good agreement compared to experimental measurements for both, depth dose and dose profiles for the evaluated fields sizes, largely used in commonly radiotherapy treatments.