Radiopharmaceuticals are drugs containing radioactive isotopes used primarily for diagnosis and therapy. These compounds localize in specific organs or cellular receptors and emit radiation detectable by specialized imaging equipment. For instance, Technetium-99m is widely used for bone, kidney, and heart imaging; Iodine-131 is used for treating thyroid cancer and hyperthyroidism. Fluorodeoxyglucose (FDG) is essential in PET scans to detect cancer. These agents are part of nuclear medicine and provide targeted diagnostic or therapeutic benefits with minimal side effects. Most radiopharmaceuticals are designed to decay quickly, reducing radiation exposure to the patient while still enabling accurate diagnosis or treatment.