UCSF

Targeted alpha therapy has demonstrated a great efficacy in the treatment of a number of malignancies, but the study of emerging radiopharmaceutical is hindered by the inability of current gamma cameras to image such radiopharmaceuticals in vivo. We use a collimator-less gamma camera consisting of BGO scintillators, multi-channel photomultipliers and an Anger logic circuit to achieve a high sensitivity and obtain planar images of the 225Ac daughters 221Fr and 213Bi for the first time in mice. 0.5 μCi of 225Ac-DOTA-YS5 was injected to a mouse bearing prostate cancer xenografts and imaged 13 days post-injection (0.2 μCi approximated activity). The images reveal the tumor position and the location of other organs with higher uptake. This provides a proof of principle of the power of proximity imaging for 225Ac, and potentially other targeted alpha therapy imaging radionuclides.