A beam model and Boltzmann solver for radiotherapy treatment planning of superficial brain metastases using a scanned electron beam at ultra-high (FLASH) dose rate.
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ICR Authors
Authors
Bedford, J
Gross, M
Riemer, F
Amirkhanyan, Z
Stephan, F
Oelfke, U
Gross, M
Riemer, F
Amirkhanyan, Z
Stephan, F
Oelfke, U
Document Type
Journal Article
Date
2026-05-06
Date Accepted
2026-04-20
Abstract
Objective.Contemporary particle accelerators allow for the generation of a narrow pencil beam of electrons which can be scanned to deliver a clinical dose distribution at an ultra-high (FLASH) dose rate. This study develops a radiotherapy beam model and discrete ordinates Boltzmann solver for such an accelerator and then applies the method to treatment planning for superficial brain metastases.Approach.Beam profiles for the quasi-monoenergetic 17.5 MeV electron beam from the Photo Injector Test facility at Deutsches Elektronen-Synchrotron laboratory in Zeuthen (PITZ) were measured at various depths in a water tank using radiochromic film. The incident radiation was modelled as a Gaussian source and the electron distribution in the patient was modelled using classical observations with continuous slowing down approximation (CSDA). This distribution then formed the fixed source component in a discrete ordinates Boltzmann solver. The dose calculation method was then applied to a retrospective study of six patients with superficial brain metastases. The dose due to scanned electrons was compared with that from a single passively scattered proton beam at ultra-high dose rate (UHDR), a proton arc, and a robotic photon treatment.Main results.The calculated dose distribution in a homogeneous water phantom agreed with the measured data to within the 3% experimental uncertainty at all depths. Scanned electron beams were able to provide dose distributions for superficial brain metastases that had a better conformity index than either passively scattered protons or robotic photon treatment (1.02 ± 0.13 versus 1.54 ± 0.13 and 1.35 ± 0.26 respectively; median ± hemi-range; p < 0.05). Brain V12Gyand skin dose were acceptable for all treatments.Significance.The dose calculation provides a fast and efficient method for inverse planning in the potential clinical application of a scanned electron beam at UHDR. The results show that such an approach could be useful in the treatment of superficial target volumes.
Citation
Physics in Medicine and Biology, 2026,
Source Title
Physics in Medicine and Biology
Publisher
IOP Publishing Ltd
ISSN
0031-9155
eISSN
1361-6560
Collections
Research Team
Radiother Phys Modelling