Validation of an Analytical Approach for in vivo PET Verification in Carbon Ion Therapy: Comparison with Monte Carlo Simulations and PET Monitoring Measurements

Four carbon ion therapy patients treated at the Heidelberg Ion Beam Therapy Center (HIT) were selected, and their treatment plans and CT images were used for MC simulations and analytical prediction of β +activity distributions. The analytically predicted activity distributions, derived from the simulated dose with our analytical approach, were then compared with both simulated results and measured offline PET data. M ain results. The analytical and MC activity distributions demonstrated a good match in range with mean deviations less than 0.5 mm, and in amplitude with mean normalized rootmean-square error (NRMSE) less than 2%. Range shifts between the measured PET signals and the analytical activity patterns were evaluated and found to be consistent with published results. Signif icance. The obtained results demonstrate the capability of our analytical approach to predict PET images for range verification in carbon ion therapy under real clinical scenarios, offering faster predictions than MC simulations while maintaining comparable accuracy. The solution proposed also offers the possibility of a straightforward integration into TPS by leveraging the commonly used pencil beam algorithms (PBAs) present in analytical carbon ion dose engines.