You are given a radiopharmaceutical, usually intravenously but sometimes orally, that localizes in specific body organ systems. This compound eventually collects in the organ and gives off energy as gamma rays. The gamma camera detects the rays and works with a computer to produce images and measurements of organs and tissues.

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 the injection. Imaging time varies, generally ranging from 20 to 45 minutes.

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.