Recent advances in film dosimetry for quality assurance in microbeam radiation therapy

Microbeam Radiation Therapy (MRT) is currently on the verge of entering the clinical phase, necessitating robust qualityassurance (QA) with appropriate dosimeters to ensure patient safety. However, MRT dosimetry presents significant challengesdue to its intrinsic characteristics, including steep dose gradients with alternating high and low dose regions—referred toas peaks and valleys (valley doses comprising only 5-7% of peak doses)—micrometric resolution requirements, the use oflow-to-medium energy X-rays and extremely high dose rates of up to 16 kGy/s. Currently, Gafchromic films are considered thegold standard for patient QA. Previous studies have reported discrepancies of 10% to 30% between measured and calculatedpeak and valley doses. This study aimed to evaluate four types of films (EBT-3, EBT-XD, MD-V3, and HD-V2) to determine themost suitable option for MRT QA. Discrepancies were observed between calculated and film-measured peak and valley doses,and several hypotheses were proposed to explain these differences. Possible causes include simplifications in dose calculationengines, intrinsic limitations of the films, uncertainties in experimental setups, and variations in readout methods. The studysuggests that MD-V3 may be the most suitable film for MRT dosimetry, offering a dynamic range that effectively covers bothpeak and valley doses