Radioactive Tracers

The detector most commonly used with radioactive tracers is the Anger scintillation camera, invented by Hal Anger in the late 1950s. Gamma radiation causes crystals of sodium iodide to emit photons of light. This is called scintillation. This light is converted into electrical signals by photomultiplier tubes. The more photomultiplier tubes in the camera, the sharper the image. The electrical signals are electronically processed to give the final image, which is recorded permanently on a photographic plate. The Anger camera and the patient must remain stationary during imaging, which can take many minutes. To get high-quality images, the camera must be placed close to the body, which may be uncomfortable for the patient. The resulting image is planar, or two-dimensional. This is adequate for many applications, but tomography has broadened the scope of scintigraphy.