Wide-band X-ray and gamma-ray imaging of living mouse to reveal pharmacokinetics of At-211

Nuclear medicine therapy is a treatment method in which a radionuclide-labeled agent is selectively taken up by the lesion, and a tumor is directly irradiated. In particular, At-211, which is an alpha-ray-emitting nuclide and is expected to be highly effective with few side effects, has attracted attention in recent years. In actual treatment, real-time monitoring is required to confirm the dynamics of drug accumulation at the correct location and to estimate the exposure of normal tissues; therefore, accurate imaging technology is required. We used a hybrid Compton camera (HCC), which is capable of broadband imaging, from characteristic X-rays to nuclear gamma rays, to image mice treated with At-211 NaAt. Four HCCs were used to image the At-211 NaAt-injected mouse under anesthesia. As a result, we were able to observe 3D pharmacokinetics in the living mouse by using 79 keV X-rays, and the accumulation of At-211 NaAt in the stomach and thyroid. By implementing the BGO active shield, we also succeeded in visualizing the drug distribution of At-211 NaAt in the mouse using nuclear gamma rays of 570 keV for the first time.