Diagnostic Nuclear Medicine Examinations
Diagnostic Nuclear Medicine Examinations: Radioisotope Scintillation Scanning (Scintiscan)
In nuclear medicine, radioactive substances known as radioisotopes are administered to the patient in order to diagnose disease. A radioactive isotope disintegrates spontaneously (ultimately losing its radioactivity) and emits gamma rays from within the body which enable the physician to visualize internal abnormalities. This differs from x-ray procedures where the x-rays are passed through the body from an external source.
Examples of radioactive isotopes, commonly used for isotope-imaging studies, are gallium, iodine, and technetium. Sometimes non-radioactive compounds are simply labeled or tagged with a radioactive isotope and sometimes radioactive tracers (radioactive pharmaceuticals) are given by mouth or by vein. Some of the isotopes are selectively absorbed by tumors or by specific organs in the body. The concentrated radioisotopes outline the tumor or organ making it visible on the photoscanner by the emission of the radioactive energy. Much research in nuclear medicine is concerned with attempts to find new radioisotopes and to develop radioisotope-labeled compounds that will be selectively absorbed in specific parts of the body.
A device called a photoscanner is used to measure the radioactivity from the nuclear substance absorbed by various parts of the body. A two dimensional representation or map can be made of the rays emitted from the radioisotope which shows where it is concentrated in the body tissue. Findings of such an examination are photographically recorded and are referred to as scans. The more common scans are illustrated in the diagram on the next page (Diagnostic Imaging—Nuclear Medicine)—bone, kidney, thyroid, brain, salivary glands, heart/lung, liver/spleen, and total body. Bone scanning with various bone-seeking isotopes is advocated for earlier diagnosis of bone metastasis. Other names for these types of scans are scintiscan, gallium scan, and lymphoscintography.