Optimizing ²¹¹At production cross section by studying the rise of ²¹⁰At cross section: First measurement using Linac...

Targeted Alpha Therapy (TAT) offers a promising approach to treat cancer, particularly micrometastases, by utilizing the short range and high linear energy transfer of alpha particles emitted by radionuclides. ²¹¹At (half-life 7.2h) is one of the promising alpha emitters (only one alpha emitted during decay) that has been identified for nuclear medicine applications. It belongs to the halogen family and shares chemical properties with iodine, an element used for imaging (¹²³I, ¹²⁴I and ¹³¹I) and also widely used to treat thyroid cancer (¹³¹I). This chemical similarity enables the use of Iodine as an analogue for biodistribution and dosimetry studies while using ²¹¹At for treatment in a theranostic approach. In this study, an alpha beam accelerated by SPIRAL2, was used to produce ²¹¹At via the reaction ²⁰⁹Bi(α, 2n)²¹¹At on the NFS beam line. The production cross section of ²¹¹At increases with increasing alpha energy up to 31 MeV. However, above 28.6 MeV, the production of ²¹⁰At occurs via the ²⁰⁹Bi(α, 3n)²¹⁰At reaction. ²¹⁰At decays to ²¹⁰Po, a highly toxic alpha-emitting radionuclide with a half-life of 138.3 days which cannot be separated chemically. Therefore, it is crucial to have a thorough understanding of the rise in ²¹⁰At production to optimize the generation of ²¹¹At while minimizing the production of ²¹⁰At To achieve this, ²⁰⁹Bi targets were irradiated at various alpha beam energies between 28 to 31 MeV with high precision thanks to the characteristics of SPIRAL2 accelerator and ^210,211At cross sections were measured by using γ-ray spectroscopy. The incident particle flux was monitored using an instrumented Faraday cup. This flux measurement combined with the number of detected γ-rays allowed to determine the production cross sections of ^210,211At as a function of energy. The results are in good agreement with experimental values recommended by the International Atomic Energy Agency (IAEA) for ²¹¹At and provide supplemental data for ²¹⁰At between 28.6 and 31 MeV. The data collected in this study will help optimize the energy range of interest for the production of ²¹¹At and give ²¹¹At its rightful place as a radionuclide for TAT.