Nuclear medicine is a specialized field of medical imaging that utilizes small amounts of radiopharmaceuticals for both diagnostic and therapeutic purposes, providing detailed insights into organ function and structure that surpass conventional imaging methods. Unlike traditional imaging, which primarily shows anatomical details, nuclear medicine offers critical functional data, enabling early disease detection and more accurate diagnosis. Techniques such as Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT), often combined with CT/MRI, are particularly advanced. PET, using positron-emitting radionuclides, is highly effective in oncology, cardiology, and neurology, while SPECT, which employs gamma-emitting radioisotopes, is superior for evaluating myocardial perfusion, bone pathology, and other conditions. These modalities offer better sensitivity and specificity in identifying disease processes at a molecular level. Additionally, theranostics, an emerging paradigm, integrates diagnostics and targeted radionuclide therapy using the same ligand, allowing for personalized treatment plans that seamlessly transition from diagnosis to therapy and monitoring, exemplified in neuroendocrine tumor and prostate cancer management.