Radiation protection in proton therapy: Insights from a multi-institutional survey and experimental measurements within the SINFONIA project

This study, part of the EU-funded SINFONIA project, investigates radiation protection practices in European proton therapy (PT) centers through a multi-institutional survey and experimental neutron dose measurements. The aim was to assess whether current safety protocols may under- or overprotect staff and to validate monitoring practices with quantitative data. Seventeen of 23 PT centers responded to the survey, revealing that staff exposures are consistently below 1 mSv/year. Thermoluminescent and track detectors were the most used devices, with neutron monitoring included in the majority of centers. Experimental measurements were conducted at the Skandion Clinic (Uppsala, Sweden) using various neutron detectors, including WENDI-II, Berthold LB6411, and DIAMON spectrometers, during clinical and mono-energetic proton irradiations.

Measured occupational doses ranged from 5–10 μSv per year, far below regulatory limits, even under accidental exposure scenarios. Neutron contributions dominated dose composition but remained minimal outside treatment rooms. The study confirmed that the placement of shielding materials, such as water canisters, effectively mitigates stray radiation. Passive and active dosimeters showed consistent readings within a 50% variation, with DIAMON showing promise for improved neutron characterization. Pregnant workers and public exposures were also analyzed, demonstrating negligible risks compared with natural background levels or common medical exposures.

In conclusion, radiation protection in modern PT facilities is robust, with staff and public doses well within safety thresholds. The findings suggest that current regulatory frameworks may be overly conservative and that optimized, group-based monitoring approaches could maintain safety while simplifying radiation protection protocols across European PT centers.

Physica Medica 137 (2025) 105049 – September 2025 – Received in revised form 30 June 2025; Accepted 7 July 2025 – Available online 13 August 2025 1120-1797/© 2025 https://doi.org/10.1016/j.ejmp.2025.105049