MO‐FG‐303‐06: Evaluation of the Performance of Very High‐Energy Electron (VHEE) Beams in Radiotherapy: Five Clinical Cases

Abstract

Purpose:To evaluate the performance of 100–120 MeV very‐high energy electron (VHEE) scanning pencil beams to radiotherapy by means of Monte Carlo (MC) simulations.Methods:We selected five clinical cases with target sizes of 1.2 cm3 to 990.4 cm3. We calculated VHEE treatment plans using the MC EGSnrc code implemented in a MATLAB‐based graphical user interface developed by our group. We generated phase space data for beam energies: 100 and 120 MeV and pencil beam spot sizes of 1, 3, and 5 mm at FWHM. The number of equidistant beams considered in this work was 16 or 32. Dose was calculated and then imported into a research version of RayStation where treatment plan optimization was performed. We compared the VHEE plans with the clinically delivered volumetric modulated arc therapy (VMAT) plan to evaluate VHEE plans performance.Results:VHEE plans provided the same PTV coverage and dose homogeneity than VMAT plans for all the cases. In average, the mean dose to organs at risk (OARs) was 24% lower for the VHEE plans. The structures that benefited the most from using VHEE were: large bowel for the esophagus case, chest wall for the liver case, brainstem for the acoustic case, carina for the lung case, and genitalia for the anal case, with 23.7–34.6% lower dose. VHEE dose distributions were more conformal than VMAT solution as confirmed by conformity indices CI100 and CI50. Integral dose to the body was in average 19.6% (9.2%–36.5%) lower for the VHEE plans.Conclusion:We have shown that VHEE plans resulted in similar or superior dose distributions compared to clinical VMAT plans for five different cases and a wide range of target volumes, including a case with a small target (1.2 cm3), which represents a challenge for VMAT planning and might require the use of more complex non‐coplanar VMAT plans.B Palma: None. M Bazalova: None. B Hardemark: Employee, RaySearch Laboratories AB. E Hynning: Employee, RaySearch Laboratories AB. B Qu: None. B Loo Jr.: Research support, RaySearch, Varian. P Maxim: Research support, RaySearch, Varian