In medical imaging, some commonly used isotopes include technetium-99m, fluorine-18, and iodine-123. These isotopes are often used in techniques like PET (Positron Emission Tomography) scans or SPECT (Single Photon Emission Computed Tomography). Each isotope emits radiation that can be detected by imaging equipment, allowing physicians to visualize and diagnose various medical conditions, including tumors and organ function. Their short half-lives make them ideal for diagnostic use, minimizing exposure to radiation.