Speaker
Summary
Introduction
Targeted Alpha Therapy (TAT) is a promising cancer treatment exploiting the short range and high linear energy transfer of alpha particles. 211At (T1/2 = 7.2 h) is especially attractive because it emits a single alpha particle per decay and has chemical properties similar to iodine, enabling theranostic strategies with halogens. However, its production through the 209Bi(α,2n)211At reaction is challenged by the competing 209Bi(α,3n)210At channel above 28.6 MeV. 210At decays to 210Po, a long-lived (with a half-life of 138 years) and highly radiotoxic isotope that cannot be chemically separated. Accurate cross-section data for 210At and 211At are therefore essential to define optimal irradiation conditions for medical-grade 211At.
Description of the Work
We report the precise measurements of 210At and 211At cross sections performed with the SPIRAL2 superconducting linear accelerator at the Grand Accélérateur National d’Ions Lourds (GANIL, Caen, France). Mono-energetic alpha beams in the 28–31 MeV range were delivered onto Bi targets at the Neutrons For Science (NFS) facility. The accelerator’s energy precision (<0.1%) combined with an instrumented Faraday cup for beam monitoring and a pneumatic transfer system allowed accurate and reproducible irradiations. Gamma-ray spectroscopy was conducted using the high-efficiency EXOGAM clover detector array.
Cross sections for 211At were obtained via its 687 keV γ-line, while 210At was quantified through the 245, 1181, 143 and 1483 keV γ-lines. The results show good agreement with IAEA-recommended data for 211At and provide new measurements of 210At between 28.6 and 31 MeV which align well with the findings of Lambrecht et al. (Lambrecht & Mirzadeh, 1985). The rise in 210At production was clearly observed near threshold, confirming that operating around 29 MeV yields optimal 211At production with limited 210At contamination.
Conclusions
This study demonstrates the unique capability of SPIRAL2 to provide high-precision nuclear data for radionuclide production. The dataset will contribute to the optimization of 211At production, supporting its development as a key radionuclide for Targeted Alpha Therapy. These results also highlight the potential of SPIRAL2 for systematic studies of other isotopes relevant to nuclear medicine and other fields.
References
Lambrecht, R., & Mirzadeh, S. (1985). Cyclotron isotopes and radiopharmaceuticals—XXXV astatine-211. The International Journal of Applied Radiation and Isotopes, 36, 443‑450. https://doi.org/10.1016/0020-708X(85)90207-8
