For imaging, radiopharmaceuticals, also called radiotracers, are coupled with either gamma or positron emitters. Gamma cameras such as planar imaging or SPECT (single photon emission computed tomography) are used to detect gamma emitters, e.g., technetium-99m (99mTc) or iodine-123 (123I). However, positron emitters such as gallium-68 (68Ga) and fluorine-18 (18F), which are detected using PET (positron emission tomography), are used to achieve better resolution (Yordanova A et al. 2017).
Targeted molecular imaging is used not only for the initial diagnosis of tumors but also for staging, restaging, and monitoring therapy response. The procedure is minimally invasive and utilizes only trace amounts of radiopharmaceuticals. Nonetheless, the possible benefits of the procedure should be weighed against the increase in possible health risks due to ionizing radiation exposure before every procedure (Tsai CJ et al. 2022).
Some examples of radiotracers already in clinical use are 18F-FDG, 68Ga-somatostatin analogs, and radiolabeled prostate-specific membrane antigen (PSMA) ligands (Weber WA et al. 2020).
“We see what we treat, and we treat what we see”
References:
Yordanova, Anna et al. 2017. “Theranostics in Nuclear Medicine Practice.” OncoTargets and therapy 10: 4821–28. DOI: 10.2147/OTT.S140671
Tsai, Chi-Jung et al. 2022. “Very-Low-Dose Radiation and Clinical Molecular Nuclear Medicine.” Life 12(6): 912. DOI: 10.3390/life12060912
Weber, Wolfgang A. et al. 2020. “The Future of Nuclear Medicine, Molecular Imaging, and Theranostics.” Journal of Nuclear Medicine 61(Supplement 2): 263S-272S. DOI: 10.2967/jnumed.120.254532
Turner 2018. “Recent Advances in Theranostics and Challenges for the Future.” The British Journal of Radiology 91(1091): 20170893. DOI: 10.1259/bjr.20170893