Everyone is familiar with X-ray images, where the radiation that exits the body is recorded on film showing the intensity. However, X-ray imaging is only one of the noninvasive imaging techniques that are now in use. The most widely used imaging techniques are those that give diagnostic information on health of various body parts, by analyzing the distribution outline of radioactively tagged substances.
A radiopharmaceutical agent that concentrates on a specific organ or body part will be injected into the body and its distribution pattern is monitored by an external radiation detector, such as a gamma camera. It depends on the medical condition, but a diseased body part might concentrate more of the radiopharmaceutical and show up on the film as a hot spot on a cold background. Alternatively, a diseased part could show up as a cold spot.
Technetium-99m is among one of the most widely used radioisotopes for diagnostic imaging. Technetium-99m has a short half-life of only 6 hours, which minimizes the patient’s exposure to radioactivity. Bones scans that use Technetium-99m are important in the diagnosis of cancer and other medical conditions.
Tomography is a technique in which computer processing allows production of images through “slices” of the body, is now used in medical diagnosis. X-ray tomography, known as CT or CAT scans, uses multiple detectors that move rapidly in a circle around the body of a patient and collects up to 90,000 readings. These CT scans can detect structural abnormalities like tumors, without using radioactive materials.
When tomography and radioisotope imaging are combined we can get cross-sectional views of regions where the radioactive substances are concentrated. One of these techniques is known as positron emission tomography, PET. PET uses radioisotopes that emit positrons and produce gamma rays. PET commonly uses Oxygen-15, Nitrogen-13, Carbon-11, and Fluorine-18 because they are incorporated into many physiologically...