Achieving high-resolution spatial mapping of dose and linear energy transfer in ion-beam therapy

Objective.We present a novel detector system capable of simultaneously obtaining two-dimensional (2D) dose and linear energy transfer (LET) maps from Al₂O₃films of sizes up to(190×190) mm²using optically stimulated luminescence (OSL).Approach.The system is based on the OSL from doped Al₂O₃films measured using pulsed stimulation and time-resolved OSL detection. The system was calibrated in¹H-,⁴He-, and¹²C-ion beams. The minimal detectable dose (MDD), response homogeneity, pixel cross-stimulation, and precision were also investigated. To demonstrate the system's performance, 2D maps of dose and LET of a proton Bragg curve were measured.Main results.The system was demonstrated to be capable of obtaining absorbed dose and LET 2D maps with a spatial resolution set to(1.0×1.0) mm². The system was calibrated over a clinically relevant range of LET values and characterized through assessment of MDD (<25 mGy), readout protocols, response homogeneity, precision, and relative detector efficiency. Dose and LET were found to be measurable with precisions of 3.2% and 10%, respectively.Significance.To our knowledge, this is the first passive detector system capable of measuring LET and dose simultaneously in 2D with a 1.0 mm²spatial resolution requiring no prior information. Such properties are required to experimentally validate simulated dose and LET distributions in ion-beam therapy, paving the way for sub-mm mapping of radiation-induced relative biological effectiveness.