You are given a small dose of radioactive material, usually intravenously but sometimes orally, that localizes in specific body organ systems. This compound, called a radiopharmaceutical or tracer, eventually collects in the organ and gives off energy as gamma rays. The gamma camera detects these rays and works with a computer to produce images and measurements of organs and tissues.
After the radiopharmaceutical is administered, depending on which type of scan is being performed, the imaging will be done either immediately, a few hours later, or even several days after it's administration. Imaging time varies, generally ranging from 20 to 45 minutes.
The radiopharmaceutical that is used is determined by what part of the body is under study since some compounds collect in specific organs better than others. Depending on the type of scan, it may take several seconds to several days for the substance to travel through the body and accumulate in the organ under study, thus the wide range in scanning times.
While the images are being obtained, you must remain as still as possible. This is especially true when a series of images are obtained to show how an organ functions over time.
After the procedure, a physician with specialized training in nuclear medicine checks the quality of the images to ensure that an optimal diagnostic study has been performed.