Photon‐counting computed tomography for stopping power ratio prediction in proton therapy

The DirectSPR application for PCCT achieved promising accuracy in SPR prediction. Overall, the absolute deviations were small and comparable across all three imaging modalities. However, concerning the performance of SECT, it should be noted that the SECT-based HLUT was calibrated using the same CIRS phantom as used during the evaluation, whereby these results are the best-case scenario. Although the clinical cases showed minimal differences in dose distributions between SECT and PCCT plans, PCCT may offer improved reliability, as it provides patient-specific direct SPR predictions without relying on HLUT conversion.