Qualitative and quantitative imaging of alpha-emitting radiopharmaceuticals

Targeted alpha (α) therapy (TAT) is an emerging therapeutic strategy for cancer treatment. To evaluate the safety and efficacy of targeted α-therapy, the biodistribution and internal radiation dose of α-emitting radionuclides should be determined. In vivo imaging of these radionuclides often involves the detection of gamma rays, X-rays, and positrons generated during their complex decay processes. This review aims to classify the α-emitting radionuclides (astatine-211, actinium-225, radium-223, bismuth-212, bismuth-213, thorium-227, and terbium-149) according to their imageable signals. Additionally, this study summarizes various imaging modalities, including gamma camera imaging, single-photon emission computed tomography, positron emission tomography, Compton imaging, bremsstrahlung imaging, and Cerenkov luminescence imaging, which hold potential for imaging α-emitting radionuclides, to explore their biomedical applications in qualitative nuclide tracing and diagnosis, quantifying pharmacokinetics, and assessing prognosis and response to therapy.