Background: Targeted alpha-particle therapy (TAT) has great promise as a cancer treatment. Arguably the most promising TAT radionuclide that has been proposed is 225 Ac. The development of 225 Ac-based radiopharmaceuticals has been hampered due to the lack of effective means to study the daughter redistribution of these agents in small animals at the preclinical stage.
Purpose: The ability to directly image the daughters, namely 221 Fr and 213 Bi, via their gamma-ray emissions would be a boon for preclinical studies. That said, conventional medical imaging modalities, including single photon emission computed tomography (SPECT) based on nonmultiplexed collimation, cannot be employed due to sensitivity limitations.
Methods: As an alternative, we propose the use of both coded aperture and Compton imaging with the former modality suited to the 218-keV gamma-ray emission of 221 Fr and the latter suited to the 440-keV gamma-ray emission of 213 Bi.
Results: This work includes coded aperture images of 221 Fr and Compton images of 213 Bi in tumor-bearing mice injected with 225 Ac-based radiopharmaceuticals.
Conclusions: These results are the first demonstration of visualizing and quantifying the 225 Ac daughters in small animals through the application of coded aperture and Compton imaging.
Keywords: Actinium-225; Compton imaging; coded aperture imaging; small-animal molecular imaging; targeted alpha-particle therapy.
© 2023 The Authors. Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.