Preliminary dosimetric analysis of DOTA-folate radiopharmaceutical radiolabelled with Sc produced through V(p,x)Sc cyclotron irradiation.

Sc is one of the most promising theranostic radionuclides, thanks to its low energy γ-ray emission (159 keV), suitable for single photon emission computed tomography imaging and its intense β emission, useful for tumour treatment. Despite promising preclinical results, the translation of Sc-therapeutic agents to the clinic is hampered by its limited availability. Among different Sc-production routes currently being investigated, the V(p,x)Sc reaction has proved to be of particular interest, thanks to the low-cost and easy availability on the market of V 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 E ≤ 45 MeV, namely Sc and Sc. 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, Sc, Sc and Sc, 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 after Sc-cm10 injection, it was obtained that proton beam energies below 35 MeV must be used to produce Sc through irradiation of a V target.