Development and verification of an electron Monte Carlo engine for applications in intraoperative radiation therapy

Background: In preparation of future clinical trials employing the Mobetron electron linear accelerator to deliver FLASH Intraoperative Radiation Therapy (IORT), the development of a Monte Carlo (MC)-based framework for dose
calculation was required. Purpose: To extend and validate the in-house developed fast MC dose engine
MonteRay (MR) for future clinical applications in IORT. Methods: MR is a CPU MC dose calculation engine written in C++ that is
capable of simulating therapeutic proton, helium, and carbon ion beams. In this work, development steps are taken to include electrons and photons in MR are presented. To assess MRs accuracy, MR generated simulation results were
compared against FLUKA predictions in water,in presence of heterogeneities as well as in an anthropomorphic phantom. Additionally, dosimetric data has been acquired to evaluate MRs accuracy in predicting dose-distributions generated by the Mobetron accelerator. Runtimes of MR were evaluated against those of the general-purpose MC code FLUKA on standard benchmark problems. Results: MR generated dose distributions for electron beams incident on a water phantom match corresponding FLUKA calculated distributions within 2.3% with range values matching within 0.01 mm. ... mehrIn terms of dosimetric validation, differences between MR calculated and measured dose values were below
3% for almost all investigated positions within the water phantom. Gamma passing rate (1%/1 mm) for the scenarios with inhomogeneities and gamma passing rate (3%/2 mm) with the anthropomorphic phantom, were > 99.8% and 99.4%