Mimicking large spot-scanning radiation fields for proton FLASH preclinical studies with a robotic motion platform

TL;DR

This study demonstrates a robotic platform that can expand the effective field size for proton FLASH preclinical experiments, maintaining dose accuracy and high dose rates, enabling more versatile radiation studies.

Contribution

We developed a robotic motion system to mimic large proton FLASH fields, allowing precise, automated shifting of biological samples during irradiation.

Findings

Achieved dose rates over 113 Gy/s for cells and 191 Gy/s for mice.

Validated dose profiles with Monte Carlo simulations showing >95% gamma pass rate.

Successfully increased field size for preclinical proton FLASH studies.

Abstract

Previously, a synchrotron-based horizontal proton beamline (87.2 MeV) was successfully commissioned to deliver radiation doses in FLASH and conventional dose rate modes to small fields and volumes. In this study, we developed a strategy to increase the effective radiation field size using a custom robotic motion platform to automatically shift the positions of biological samples. The beam was first broadened with a thin tungsten scatterer and shaped by customized brass collimators for irradiating cell/organoid cultures in 96-well plates (a 7-mm-diameter circle) or for irradiating mice (1-cm2 square). Motion patterns of the robotic platform were written in G-code, with 9-mm spot spacing used for the 96-well plates and 10.6-mm spacing for the mice. The accuracy of target positioning was verified with a self-leveling laser system. The dose delivered in the experimental conditions was validated with EBT-XD film attached to the 96-well plate or the back of the mouse. Our film-measured dose profiles matched Monte Carlo calculations well (1D gamma pass rate >95%). The FLASH dose rates were 113.7 Gy/s for cell/organoid irradiation and 191.3 Gy/s for mouse irradiation. These promising results indicate that this robotic platform can be used to effectively increase the field size for preclinical experiments with proton FLASH.