Development and benchmarking of a dose rate engine for raster‐scanned FLASH helium ions

Background:Radiotherapy with charged particles at high dose and ultra-highdose rate (uHDR) is a promising technique to further increase the therapeuticindex of patient treatments. Dose rate is a key quantity to predict the so-calledFLASH effect at uHDR settings. However, recent works introduced varying cal-culation models to report dose rate,which is susceptible to the delivery method,scanning path (in active beam delivery) and beam intensity.Purpose:This work introduces an analytical dose rate calculation engine forraster scanned charged particle beams that is able to predict dose rate from theirradiation plan and recorded beam intensity. The importance of standardizeddose rate calculation methods is explored here.Methods:Dose is obtained with an analytical pencil beam algorithm, usingpre-calculated databases for integrated depth dose distributions and lateralpenumbra. Dose rate is then calculated by combining dose information withthe respective particle fluence (i.e., time information) using three dose-rate-calculation models (mean, instantaneous, and threshold-based). Dose ratepredictions for all three models are compared to uHDR helium ion beam (145.7MeV/u, range in water of approximatively 14.6 cm) measurements performed