S1691
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
facilitating treatment planning margin reduction. Moreover, we investigate the potential of PG spectroscopy to enhance system performance and provide additional information on the elemental composition of tissue. In this study, we explore the energy characteristics of the emitted PGs and FNs in silico for different patient groups. Material/Methods: Treatment plans were generated using RayStation TPS (RaySearch Laboratories, Stockholm, Sweden) for patients with different tumor locations, including pediatric brain, head-and-neck, prostate, and lung. PG and FN production coordinates, energies, target- and residual nuclei, were recorded in different clinical scenarios using Monte Carlo simulations. Two patients from each diagnostic group were selected for simulation. For each treatment field (ranging from 2 to 4 per patient), two pencil beam spots (one distal and one proximal) were simulated, yielding 44 scenarios in total. Results: Generally, the most energetic PGs were emitted in proximity to the Bragg peak; however, the PG energy was clearly dependent on the tissue composition, with, for instance, bone and adipose yielding a lower mean energy than surrounding tissues (Figure 1, upper panel). PGs from inelastic scattering reactions, specifically 16O(p,p)16O* (6.13 MeV) and 12C(p,p)12C* (4.44 MeV), were observed to best correlate with the proton beam range (Figure 2). This contrasts with PGs from non-elastic nuclear reactions, for instance 16O(p,pα)12C* (4.44 MeV), which started to decrease earlier along the beam path. FN emitted energy decreased with depth and reached its minimum near the proton end-of-range (Figure 1, lower panel).
Conclusion: PG and FN energy characteristics across tissues and proton energies demonstrated that the energies of both particles convey proton range information, with PGs additionally reflecting tissue-specific differences
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