Monte Carlo Algorithm-Based Dosimetric Comparison between Commissioning Beam Data across Two Elekta Linear Accelerators with Agility^TM MLC System

Abstract

The beam characteristics of both machines are similar because of the same Agility TM MLC Model. We compared measured beam data calculated using the Elekta treatment planning system, Monaco ® , for each institute.Methods: Beam of the commissioning Elekta linear accelerator were measured in two independent institutes. After installing the beam model based on the measured beam data into the Monaco ® , Monte Carlo (MC) simulation data were generated, mimicking the beam data in a virtual water phantom. Measured beam data were compared with the calculated data, and their similarity was quantitatively evaluated by the gamma analysis.Results: We compared the percent depth dose (PDD) and off-axis profiles of 6 MV photon and 6MeV electron beams with MC calculation. With a 3%/3 mm gamma criterion, the photon PDD and profiles showed 100% gamma passing rates except for one inplane profile at 10 cm depth from VMTH. Gamma analysis of the measured photon beam off-axis profiles between the two institutes showed 100% agreement. The electron beams also indicated 100% agreement in PDD distributions. However, the gamma passing rates of the off-axis profiles were 91%-100% with a 3%/3 mm gamma criterion. Conclusions:The beam and their comparison with MC calculation for each institute showed good performance. Although the measuring tools were orthogonal, no significant difference was found.