Technetium-99m is a radioactive isotope commonly used in medical imaging. It emits gamma rays, which can be detected by special cameras to create images of organs and tissues in the body. This helps doctors diagnose various conditions, including heart disease and cancer. The isotope has a short half-life of about six hours, meaning it decays quickly and minimizes radiation exposure to patients. Technetium-99m is often used in procedures like single-photon emission computed tomography (SPECT) scans, making it a valuable tool in modern medicine for non-invasive diagnostics.