What is a Radionuclide Scan?

A radionuclide scan is a diagnostic procedure where a combination of radionuclides and radioactive substances are introduced into the body to produce images of specific organs or tissues. The radionuclide chemical, known as a tracer, is used to generate gamma rays which are read in the same manner as an x-ray. Considered a safe procedure, the radionuclide scan does carry some risks and these should be discussed with a healthcare provider prior to testing.

Radionuclide scans are commonly used to evaluate areas such as the gallbladder, kidneys, lungs, and the bones. The type of tracer administered is dependent on the type of testing to be conducted since different tracers tend to accumulate in specific parts of the body. Tracers that are utilized include cobalt, thallium, and technetium. Since only a small amount of radioactive material is used, and it is quickly eliminated through urination, its introduction into the body is considered safe.

Tracer material is usually injected directly into a vein, but depending on test type it can also be inhaled or ingested. Once the chemical is administered, it causes the targeted area to emit gamma rays, which are visible with the use of a special camera known as a scintillation or gamma camera. The most active cells absorb greater amounts of the material and emit high intensity gamma rays making the targeted area more visible.

During a radionuclide scan, the patient is able to remain fully clothed and lies motionless on a table as the camera takes a series of images. The images registered by the camera are converted into signals that are interpreted by a computer to formulate a digital picture of the targeted area. The varying intensities of gamma rays emanating from the scanned area are coded by color, with the most intense areas characterized by red tones and the least intense denoted by lighter, or blue tones. The duration of the testing process and number of images taken depends on the area that is being scanned. When multiple images are needed, the testing process can take several hours.

Single-Photon Emission Computed Tomography (SPECT) is a variation of the radionuclide scan that utilizes electrically charged particles rather than x-rays to generate 3-D images. During the testing process, a number of pictures are taken of the body from multiple angles, each representing a different portion. The accumulation of images is used to create multi-dimensional pictures of the body, allowing for a more accurate analysis. The SPECT testing process generally takes less than two hours to complete.

The patient may be instructed to not consume food or beverages for several hours prior to a radionuclide scan. Tracer material may be administered up to four hours prior to testing to allow the material time to reach the specified area. Complications associated with radionuclide scans are rare but can occur. Women who are or think they may be pregnant should inform their physician prior to testing. Allergic reactions to tracer material are possible, and depending on the amount administered, overdose can occur.