radiotraceres

Radiotracers are radioactive compounds used to visualize and measure biological processes in living organisms. They are typically small molecules or biologically active ligands labeled with a radionuclide. The choice of radionuclide depends on the imaging modality and the biological process of interest. Commonly used radionuclides include technetium-99m, fluorine-18, gallium-68, iodine-123, iodine-131, carbon-11, and nitrogen-13. The radiotracer’s distribution reflects the underlying chemistry and physiology it is designed to probe, such as metabolism, receptor expression, perfusion, or enzyme activity.

Radiotracers are produced in specialized facilities. Some radionuclides are generated in nuclear reactors or cyclotrons, or provided by radionuclide generators (for example, Mo-99/Tc-99m). The radioactive isotope is attached to a biologically active molecule through chelation, covalent bonds, or other labeling chemistries under stringent quality controls to form a radiopharmaceutical suitable for human or veterinary use.

In clinical practice, positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are the main imaging modalities used with radiotracers. PET detects positron-emitting isotopes such as F-18, C-11, N-13, and Ga-68, often in combination with a tracer like fluorodeoxyglucose (FDG) to assess metabolic activity. SPECT uses gamma-emitting tracers such as Tc-99m for bone scans, myocardial perfusion imaging, and brain studies. Other radiotracers target specific receptors, proteins, or pathophysiological processes (for example, Ga-68 DOTATATE for neuroendocrine tumors; amyloid tracers in neurology).

Radiotracer use requires careful consideration of radiation dose, pharmacokinetics, and safety. Doses are minimized and justified, and production follows regulatory standards and good manufacturing practices. Limitations include short half-lives requiring on-site production, partial-volume effects, and the need for specialized imaging infrastructure.