Experimental excitation functions of 89Zr production by deuteron irradiations for theragnostic applications

The 89Zr is one of the most promising radionuclide in Nuclear Medicine for labelling monoclonal antibodies, bio-distribution studies and immuno-positron emission tomography – PET – imaging. Its great potentiality is related to its favorable physics characteristics: it has a half-life T1/2 = 78.41 h, suitable to study the slow metabolic processes, decays to the stable isotope 89Y by electron capture (76.6%) and beta+ (22.3%) and has an associated gamma emission at 908.96 keV (abundace = 99.87%) which is the main contribution to the absorbed dose. This radionuclide is produced via the (p,n) nuclear reaction in small medical cyclotrons, bombarding monoisotopic yttrium targets. The experimental excitation functions in this case are measured many times and the data are relatively consistent. On the other hand, the data related to deuteron induced reactions are few and are rather scattered. For this reason we are studying the possibility to produce 89Zr by 89Y(d,2n) reactions starting from the experimental re-measurement of the cross sections for deuteron beam irradiation, which present indisputable advantage in respect to proton irradiation. A new set of excitation functions for 89Y(d,2n)89Zr was measured and compared with the only other few sets presented in the literature. The irradiations were carried out with the IBA C70 cyclotron of the ARRONAX Center, Saint-Herblain (FR), which can deliver deuterons at variable energies in 15 – 35 MeV interval. It was used the standard staked foil technique, bombarding stacks of 89Y foils (purity 99%, 25μm nominal thickness, GoodFellow Cambridge Ltd.) interleaved with titanium and aluminum used as degraders and monitors. The experimental data were compared with the prediction obtained from nuclear model calculation codes EMPIRE 3.2.2, ALICE-IPPE and TALYS. The thin-target yields have been plotted as a function of their average energy into the targets and were fitted with the best mathematical functions. By integration of these functions the calculated Thick-Target Yields were obtained, in order to find the optimized couple of irradiation energy and energy loss inside the thick target to maximize the production of the radionuclide of interest. Some consideration about the radionuclidic purity obtainable with this kind of production will be discussed.