Nuclear medicine is a diagnostic and therapeutic discipline. This type of radiology takes advantage of differences in metabolism and function of normal versus diseased tissue to identify and treat diseases. To target different parts of the body or different types of disease, nuclear medicine uses various types of ingested or injected materials. These materials go to various parts of the body and are taken up differently by normal and diseased tissues such as cardiac, thyroid, and parathyroid tissues or lymph nodes. Other organ specific diagnostic and therapeutic tests include ones searching for infection, cancer (PET Scanning), or bleeding, and tests to determine physiologic function (gastric emptying, renal scans, certain cardiac scans).