Targeted Alpha Therapy Symposium

Isolation of At-211 by dry-distillation under oxidative conditions for targeted alpha therapy in Osaka University

Not scheduled

15m

Fairmont Château Laurier Hotel

Speaker

Dr Atsushi Toyoshima (Institute for Radiation Sciences, Osaka University)

Description

Astatine (At)-211 is one of the most promising radionuclides for the targeted alpha therapy (TAT). In Osaka University, we have recently started the collaborative project for the TAT using ²¹¹At which can be produced in nuclear reactions using an accelerator. At present, cyclotron production, chemical separation, radiopharmaceuticals preparation, and pre-clinical trials of ²¹¹At are under study. In this contribution, our cyclotron production and chemical purification of ²¹¹At are presented. Astatine-211 was produced in the ²⁰⁹Bi($\alpha$, 2n)²¹¹At reaction at Research Center of Nuclear Physics (RCNP), Osaka University. A thin metallic Bi target was bombarded by 28.2-MeV ⁴He²⁺ beam with 0.5-1 particle $\mu$A for a few hours. The Bi target was set at 45^o to the beam axis in an irradiation chamber. Beam energy was adjusted to avoid simultaneous synthesis of ²¹⁰At decaying into highly toxic ²¹⁰Po. After the irradiation, dry distillation was carried out with a simplified distillation apparatus to isolate ²¹¹At from the target materials . We used mixed helium and oxygen gas and also added a moisture content in the distillation system to yield oxidized At species which are easily transported, trapped, and dissolved in a small volume of distilled water. The irradiated Bi target was heated at 840^oC. Vapored At species were transported to a Teflon tube cooled with ice water. During accumulation of ²¹¹At in the trap, a trapped amount of ²¹¹At was monitored with a CdTeZn detector. After a few tens of minutes, trapped ²¹¹At was stripped with 100 $\mu$L of distilled water at a flow rate of 250 $\mu$L/min. The radioactivity of ²¹¹At was determined by $\gamma$-ray spectrometry using a Ge detector. The ²¹¹At solution was supplied to pharmaceutical preparations, pre-clinical tests, and/or our chemical analysis. Recovery yield of ²¹¹At was 70-80% under optimum conditions. The separation time was typically within 30 min. In the symposium, results on our chemical analysis will be also presented.