Validation of conventional proton calibration for flash proton therapy with Alanine/ESR dosimetry

Abstract

This study evaluated the feasibility of alanine/ESR dosimetry as a practical alternative to ionization chambers for quality assurance (QA) in ultra-high dose rate (Flash) proton therapy. Ionization chambers, although the clinical gold standard, suffer from reduced accuracy under Flash conditions due to ion recombination and charge collection losses. Alanine dosimeters exhibit minimal dose-rate dependence and excellent stability at high doses, yet their performance in Flash proton beams has not been fully established. An ESR-dose calibration curve was generated under conventional proton beam conditions (10–100 Gy), demonstrating excellent linearity (R2 = 0.9998) with deviations from ion-chamber reference doses within 1.25%. Under Flash conditions, uncorrected ESR-based doses were up to 4.0% higher than ion-chamber readings, a bias attributed to geometry-specific factors. Monte Carlo simulations quantified a 3.0% higher dose to the alanine pellet relative to the ionization chamber, yielding a correction factor of 1.03. Applying this factor reduced residual deviations to within ± 1.68% without dose-dependent bias. These findings demonstrate that alanine/ESR dosimetry can accurately verify Flash proton doses using a conventional calibration curve, supporting its use as a reliable, condition-independent QA tool in both standard and ultra-high dose rate proton therapy.