Focal-point scanning for dose delivery and optimization with focused laser-accelerated very-high-energy electron beams

Zhiyuan Guo; Yifei Pi; Junwei Zhou; Guoqing Liu; Wenbo Zhang; Haiyang Wang; Yaping Qi; Xiaoming Guo; Yuhan Zhang; Bo Peng; Jianfei Hua; Yang Wan; Wei Lu

arXiv · 2608.13919

Focal-point scanning for dose delivery and optimization with focused laser-accelerated very-high-energy electron beams

Zhiyuan Guo·Yifei Pi·Junwei Zhou·Guoqing Liu·Wenbo Zhang·Haiyang Wang·Yaping Qi·Xiaoming Guo·Yuhan Zhang·Bo Peng·Jianfei Hua·Yang Wan·Wei Lu

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Abstract

Focused very-high-energy electron (VHEE) beams can produce localized dose enhancement at selected depths, but irradiation of a finite target requires coordinated control of multiple focal positions, incidence directions, and beam weights while limiting exposure of nearby organs at risk (OARs). We present Focal-Point Scanning (FPS), a dose delivery and optimization method developed for laser wakefield accelerator (LWFA)-driven VHEE beams. The method is based on a two-dipole focusing system that produces single-plane beam convergence and allows the focal position to be varied by changing the magnetic field strength. FPS distributes focal points throughout the planning target volume and determines focal-point-specific incidence sectors according to the geometry of nearby critical OARs. The method was evaluated using the AAPM TG119 C-shape benchmark and one previously treated lung radiotherapy case. At matched target coverage, FPS reduced the TG119 Core mean dose by approximately one half relative to parallel VHEE and intensity-modulated x-ray plans, approaching the single-field proton pencil-beam-scanning reference. In the lung case, FPS maintained target coverage comparable to the clinical volumetric modulated arc therapy reference while reducing the mean dose to every evaluated OAR; spinal-cord mean and maximum doses decreased by 93.2% and 87.2%, respectively. The evaluated OAR mean doses varied little across rms energy spreads of 0 to 10% and for a flat-top electron spectrum spanning 150 to 250 MeV. These results demonstrate that focal-point-specific angular selection can translate focused-beam physics into effective OAR sparing and support FPS as a planning strategy for broadband LWFA-VHEE radiotherapy.

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Zhiyuan Guo, Yifei Pi, Junwei Zhou, Guoqing Liu, Wenbo Zhang, Haiyang Wang, Yaping Qi, Xiaoming Guo, Yuhan Zhang, Bo Peng, Jianfei Hua, Yang Wan, Wei Lu. 2026-08-14. Focal-point scanning for dose delivery and optimization with focused laser-accelerated very-high-energy electron beams. https://arxiv.org/abs/2608.13919

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