Nuclear medicine is a specialized area of radiology that uses minimal amounts of radioactive materials, or radiopharmaceuticals, to examine organ function and structure. Nuclear medicine imaging is a combination of many different disciplines. These include chemistry, physics, mathematics, computer technology, and medicine. This branch of radiology is often used to help diagnose and treat abnormalities early in the progression of a disease, such as thyroid cancer. Patients are given radioactive substances for diagnosis, and the radiation released is monitored. A gamma camera creates a picture for the bulk of this diagnostic examination. Although the use of radioactive isotopes to treat illnesses dates back to 1930, it did not flourish until the 1970s. Nuclear medicine mainly uses radioisotopes such as cobalt-60, iridium-192, gold-199, oxygen-15, nitrogen-13, gallium-68, and others. Cancer has been treated with cobalt-60, iridium-192, and gold-199, while thyroid diseases are treated with iodine-131. The functioning of the organs or tissues can be shown via nuclear medicine. A tracer containing the radioactive substance is often injected, eaten, or breathed during diagnostic procedures. In order to determine how much of the tracer is absorbed or how it responds in the organ or tissue, the healthcare practitioner or radiologist (a medical expert with specialized training to utilize radiation in healthcare) employs a radiation detector. Heart, lung, kidney, gallbladder, and thyroid scans are among the frequently used diagnostic procedures in nuclear medicine, as shown in Fig.1. Positron emission tomography (PET), a sort of nuclear medicine, uses a tracer to reveal the regular activity of cells. This allows for a more in-depth analysis of how organs function and whether there is cell damage. MRI or CT scans that produce three-dimensional pictures of the organ are frequently coupled with PET scans to produce these images, as shown in Fig.2. PET scans are frequently used to diagnose conditions including heart disease, Alzheimer's disease, and brain abnormality obtaining comprehensive information about malignant tumors to choose the most appropriate course of action.