Spread?out Bragg peak proton FLASH irradiation using a clinical synchrocyclotron: Proof of concept and ion chamber characterization

Purpose The purpose of this work is to (a) demonstrate the feasibility delivering a spread-out Bragg peak (SOBP) proton beam in ultra-high dose rate (FLASH) using therapy synchrocyclotron as major step toward realizing an experimental platform for preclinical studies, and (b) evaluate response four models ionization chambers such radiation field. Methods A clinical Mevion HYPERSCAN® was adjusted delivery. Protons with nominal energy 230 MeV were delivered pulses temporal width ranging from 12.5 ?s 24 spanning conventional FLASH rates. boron carbide absorber range modulator block placed path modulation creating SOBP profile. field defined by brass aperture 11 mm diameter. Two Faraday cups used determine number protons per pulse at various dosimetric two cylindrical (IBA CC04 CC13) plane-parallel PPC05 PTW Advanced Markus®) evaluated. measured chambers. integral depth (IDD) Peak® chamber. lateral profile EBT-XD radiochromic film. Monte Carlo simulation performed TOPAS secondary check measurements tool further optimization modulators’ design. Results measurement showed that maximum 39.9 pC width. good agreement between simulated IDD profiles observed. very high ion recombination deemed not suitable absolute dosimetry average chamber 163 Gy/s pristine 126 1 cm beam. 24.4 19 mm, respectively. had 25.6 range. Simulation results flatness can be improved cavity diameter scanned spots, Conclusions Feasibility pattern >100 demonstrated. heterogeneity through spots. Plane-parallel smaller gap electrodes are more compared other work.