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

Authors


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

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