Measurements of the proton-induced reaction 155Gd(p,n)155Tb at energies between 7 and 26 MeV with highly-enriched 155Gd targets

Abstract

International audienceBackground The need for new medical radionuclides continues to grow as treatments become more personalised. Terbium-155, a gamma emitter, is an appealing isotope that could be used for Single Photon Emission Computed Tomography (SPECT). Since it belongs to the Terbium quadruplet, it could be coupled with other Tb isotopes to form a theranostic pair. However, it is currently not accessible in sufficient quantities with an acceptable radionuclidic purity. An investigation of the excitation function of the nuclear reaction 155Gd(p,n) over an energy range accessible to most medical cyclotrons is relevant for optimizing 155Tb production. For the first time, we report the measurements of this reaction with highly enriched (> 99.0%) 155Gd targets. Methods Pure 155Gd targets, with isotopic enrichment better than 99%, have been produced using the highperformance electromagnetic separator SIDONIE at IJClab, Orsay, France. Proton activation measurements have been performed using two different cyclotrons and a linear accelerator (linac). Results The full excitation function of 155Gd(p,n)155Tb has been obtained over the 7-26 MeV range. All 18 measured cross-sections are consistent with each other, without the need of any renormalization. All the obtained data were compared with already published results and clearly show a maximum production at 11 MeV, with a cross section of 500 mb. Conclusion Experimental data indicates excitation function maximum around 11 MeV for the studied energy range, and cross sections are greater when target purity in 155Gd is higher