Background/Purpose: This study aimed to evaluate the clinical outcomes of stereotactic body proton beam therapy (SBPT) for pancreatic cancer. Methods: This retrospective study included 49 patients who underwent SBPT for pancreatic cancer between 2017 and 2020. Survival outcomes, bowel-related toxicities, and failure patterns were analysed. SBPT was performed after induction chemotherapy in 44 (89.8%) patients. The dose-fractionation scheme included 60 gray (Gy) relative biological effectiveness (RBE) in five fractions (n = 42, 85.7%) and 50 GyRBE in five fractions (n = 7, 14.3%). The median follow-up was 16.3 months (range, 1.8–45.0 months). Results: During follow-up, the best responses were complete response, partial response, and stable disease in four (8.2%), 13 (26.5%), and 31 (63.3%) patients, respectively. The 2-year overall survival, progression-free survival, and local control (LC) rates were 67.6%, 38.0%, and 73.0%, respectively. Grade ≥ 3 gastroduodenal (GD) toxicity occurred in three (6.1%) patients. Among them, one patient underwent endoscopic haemostasis. The other two patients received surgical management. They were followed up without disease progression for >30 months after SBPT. Overall, there was no significant dosimetric difference between the grade ≥ 2 and lower toxicity groups. Conclusions: SBPT provides relatively high LC rates with acceptable toxicities in pancreatic cancer.

Photoacoustic and protoacoustic imaging share the common principle of acoustic wave generation through different excitation sources: optical absorption vs. proton Bragg-peak. These acoustic signals exhibit heterogeneity within the tissue, which strongly influence wave propagation and detection accuracy. In this study, we investigate how material variation affects time-of-flight (TOF)-based acoustic signal analysis in the context of protoacoustic proton range verification, providing insights relevant to broader photoacoustic imaging methodologies. A ±15 °C temperature difference in water caused only a 0.04 μs delay and thus had a minimal effect. In heterogeneous phantoms, lung-containing cases produced range errors up to 3.72 mm. In clinical scenarios, detectors aligned with air or low-density tissues showed large overestimations, up to 192.4 mm. Only 2 of 25 detector positions met the <2 mm error criterion. These results highlight that tissue composition and acoustic heterogeneity significantly influence protoacoustic wave propagation and range accuracy. Accurate range verification using protoacoustics must account for material variations along the wave path, particularly in lung regions, to ensure clinical applicability.