Pre and post operative radiation protection in Ru-106 brachytherapy ophthalmic plaque surgery and related material shielding properties

Pre and post-operative exposure levels of medical staff and people from public in intra-operative Ru-106 ophthalmic brachytherapy are reported, together with attenuation properties of selected shielding materials. In particular radiation exposure of workers during plaque transportation and during medical assistance of implanted plaque patient was measured. Taking into account dose rates and considering standard assistance procedure of hospitalized patients, the exposure of medical staff and people of the public were evaluated for a given workload. In order to provide tools to optimize radiation protection, considering social and economic aspects due to possible hospital discharge or hospital stay, the attenuation properties of common shielding materials (lead, concrete, red brick, PMMA and gypsum) were measured, considering both narrow and broad beam setups. The eye was simulated using a water equivalent phantom and plaque was fixed on it. All measurements were performed with calibrated survey meters. Results were compared with numerical simulation of bremsstrahlung X-ray radiation spectra emitted from patient eye. Exposure levels measured at 1 m distance in front of the implanted eye are 0.05 µSv/h/MBq, at 10 cm from patient head, 0.44 µSv/h/MBq (plaque side), 0.4 µSv/h/MBq (front), 0.25 µSv/h/MBq (lateral, opposed to plaque), 0.2 µSv/h/MBq (back). Average exposure levels, under conservative assumptions, for medical staff is 17 µSv/patient and less than 23 µSv/patient for careers and comforters. TVLs in lead and concrete are about 1.6 cm and 11.5 cm respectively.