Orateur
Description
Targeted Alpha Therapy (TAT) offers a promising approach to treat cancer, particularly micrometastases, by utilizing the short range of alpha particles and their high linear energy transfer. Astatine-211, which belongs to the halogen family also shares chemical properties with Iodine, a radioisotope commonly used for imaging and also widely used to treat thyroid cancer. This similarity enables the use of Iodine as an analogue for biodistribution and dosimetry studies while using $^{211}$At for treatment. For these reasons, the production of $^{211}$At and the characterization of the contaminants must be studied and optimized.
In this study, we used an alpha beam at SPIRAL2, NFS to produce $^{211}$At via the reaction $^{209}$Bi(α,2n)$^{211}$At. The production cross-section of $^{211}$At increases with increasing alpha energy up to 31 MeV. However, caution must be exercised as $^{210}$At production also occurs via the $^{209}$Bi(α,3n)$^{210}$At reaction above 28.6 MeV. $^{210}$At decays to $^{210}$Po, an alpha-emitting radionuclide with a half-life of 138.3 days and is highly toxic, if released in tissues.
We irradiated $^{209}$Bi target at various alpha beam energies between 28 to 31 MeV to measure $^{210,211}$At cross-sections and to determine the $^{210}$At/$^{211}$At ratio. We employed gamma-ray spectroscopy using germanium detectors to evaluate the respective contribution of $^{210,211}$At. 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 $^{210,211}$At as a function of energy and the results are in good agreement with the literature values. We have also used well-known cross-sections of alpha on Cu from literature to cross-check and improve the accuracy of our flux measurements.
Astatine-211 is a promising radionuclide for TAT and needs careful monitoring of unwanted radionuclides. This study represents the first step in evaluating the cross-section to optimize the alpha beam energy and maximize $^{211}$At production while maintaining an acceptable level of $^{210}$At contamination. The next step will be $^{211}$At production with a high power target for interdisciplinary studies.
This study was financially supported by the REPARE ANR project (Projet-ANR-19-CE31-0013).
