High-Resolution MgB₄O₇:Ce,Li OSL Foils for Bragg Curve Mapping in Proton Eye Therapy

By using a PMMA-made therapeutic wedge and a recently developed reusable silicone foil dosimeter based on the optically stimulated luminescence (OSL) of MgB₄O₇:Ce,Li (MBO) material, direct measurements of the complete proton Bragg curves for two independent clinically relevant proton beams were achieved. The PMMA wedge compensator created a controlled range gradient across the beam field, enabling comprehensive characterisation of Bragg curve features, including the entrance plateau, the maximum of the Bragg peak, and the dosimetrically critical distal fall-off region. Measurements were performed using a dedicated, self-built (3D-printed) optical detection setup equipped with a blue LED (440 nm) that illuminates the MBO foil dosimeter and a highly sensitive electron-multiplication (EMCCD) camera, which simultaneously acquires 2D OSL light from the foil. The prototype technology enables single-shot 2D mapping of the complete Bragg curve. Validation against Monte Carlo (MC) simulations and Gafchromic^TM EBT3 films demonstrates sub-millimetre accuracy in localising the clinically critical proton parameters: peak-to-plateau, FWHM and distal fall-off. Measurements were performed for two independent therapeutic proton beams with initial energies of 58.8 and 61.1 MeV, routinely used for proton eye-beam treatments at IFJ PAN Krakow. As a proof of concept, the results demonstrate the potential of MBO-based silicone foil technology to reproduce clinically relevant Bragg-curve parameters with accuracy approaching that of the current gold standard for passive 2D dosimetry, Gafchromic^TM EBT3 films, while systematic differences attributable to optical diffusion, residual LET-dependent quenching, and the dual-foil junction remain to be corrected.