Scientific Letter Radiation Safety for Pregnant Workers at a Proton Facility Genevieve Maquilan, MD, Marc R. Bussie `re, MSc, Joseph McCormack, AS, Tara Medich, MS, Andrzej Niemierko, PhD, and Helen A. Shih, MD Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts Received Sep 2, 2017, and in revised form Nov 1, 2017. Accepted for publication Nov 8, 2017. Summary Occupational radiation exposure was assessed for radiation therapy technolo- gists (RTTs) working in passively scattered proton therapy or photon therapy to inform safety practices for pregnant radiation workers. Over 14 weeks, the mean background-corrected dose was similar for proton and photon RTTs (39.9  5.4 mrem and 39.9  9.0 mrem, respectively; P Z .6). Our results support use of an equivalent radiation safety policy for pregnant radiation workers employed in either proton or photon facilities. Purpose: To quantify radiation exposure of radiation therapy technologists (RTTs) in a proton treatment facility in comparison with a photon therapy facility, to inform and establish these specialized occupational safety guidelines. Methods and Materials: Two groups of RTTs, consisting of 12 full-time passive scat- tering proton RTTs and 18 full-time conventional photon RTTs, wore an additional dosimetry badge at the waist for a period of 14 weeks. The 2 groups of RTTs were given identical instructions on the proper use of the badges. To compare exposures be- tween passive scatter and scanning beam systems, exposure rates from activated equip- ment in both systems were measured. Results: Over the 14-week period, the mean and standard deviation background- corrected dose for the passively scattered proton RTTs was 39.9  5.4 mrem. The mean and standard deviation background-corrected dose for the conventional photon RTTs was similar at 39.9  9.0 mrem (P Z .6). Exposure rates were lower in equip- ment activated in a scanning beam system in comparison with those from a passive scatter system. Conclusions: Radiation dose to passively scattered proton and photon radiation ther- apy technologists was similar when measured with a dosimeter worn at the waist over a period of 14 weeks. On the basis of these data, the departmental policy per- mits pregnant radiation workers to work in proton treatment areas, and the policy for pregnant workers does not differ between proton and photon radiation workers or between passive scatter and scanning beam systems. All employees are encouraged to limit time near and proximity to activated equipment. Ó 2017 Elsevier Inc. All rights reserved. Reprint requests to: Helen A. Shih, MD, Department of Radiation Oncology, Massachusetts General Hospital, Francis H. Burr Proton Therapy Center, 30 Fruit St, Boston, MA 02114-2696. Tel: (617) 724- 9627; E-mail: HSHIH@partners.org Conflict of interest: none. Int J Radiation Oncol Biol Phys, Vol. -, No. -, pp. 1e5, 2017 0360-3016/$ - see front matter Ó 2017 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.ijrobp.2017.11.016 Radiation Oncology International Journal of biology physics www.redjournal.org