Preliminary dosimetric analysis of DOTA-folate radiopharmaceutical radiolabelled with47Sc produced throughnatV(p,x)47Sc cyclotron irradiation.

47Sc is one of the most promising theranostic radionuclides, thanks to its low energy γ-ray emission (159 keV), suitable for SPECT imaging and its intense β-emission, useful for tumor treatment. Despite promising preclinical results, the translation of47Sc-therapeutic agents to the clinic is hampered by its limited availability. Among different47Sc-production routes currently being investigated, the recently reportednatV(p,x)47Sc reaction has proved to be of particular interest, thanks to the low-cost and easy availability on the market ofnatV material and the diffusion of medium energy proton cyclotrons. However, the cross section of this specific nuclear reaction is quite low and small amounts of Sc-contaminants are co-produced at energies EP≤ 45 MeV, namely48Sc and46Sc. The main concern with these Sc-contaminants is their contribution to the patient absorbed dose. For such a reason, the absorbed dose contributions to healthy organs and the effective dose contributions by the three radioisotopes,48Sc,47Sc and46Sc, were evaluated using DOTA-folate conjugate (cm10) as an example of radiopharmaceutical product. Considering as acceptable the limits of 99% for the radionuclidic purity and 10% for the contribution of radioactive Sc-contaminants to the total effective dose after47Sc-cm10 injection, it was obtained that proton beam energies below 35 MeV must be used to produce47Sc through irradiation of anatV target.