Monte Carlo study of the eye lens exposure of medical staff administering Sc-47 and Cu-67 labelled radiopharmaceuticals

Purpose: In the last decades, new technologies and new radiopharmaceuticals for diagnosis and therapy have continuously grown, and that growth was accompanied by an increasing use in clinical practice, but, as with any other application involving radiation, the extent to which they may contribute to increasing the radiation dose to the operator must be studied. For that reason, EURADOS (European Radiation Dosimetry Group) decided to evaluate the exposure of medical staff in nuclear medicine to new possible radiopharmaceuticals labelled with Sc-47 and Cu-67. Methodology: Modified ICRP voxel model were employed to determine the exposure of the eye lens and of the thyroid of operators administrating radiopharmaceuticals in a typical Peptide Receptor Radionuclide Therapy scenario. The simulations were validated comparing Monte Carlo results with TLD measurements performed in hospital with Lu-177 labelled compounds. Results: Doses to the eye lens and thyroid are derived from the photon emissions (the beta contribution is three order of magnitude lower). The agreement obtained for Lu-177 provides confidence that, notwithstanding the limits of the simulations, the robustness of the followed approach can be extended also to the evaluation performed for Sc-47 and Cu-67. Conclusions: The dose to the lens of the eye is of the order of 2 µSv/GBq per patient for Lu-177 compounds and, due to the different energies and yields, about 8 µSv/GBq for both Sc-47 and Cu-67. These evaluations can be useful to optimize the radiation protection of medical staff in the nuclear medicine environment and assess the correct personnel workload in these kinds of practices.