What is a SPECT Scan?

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  • Written By: D. Jeffress
  • Edited By: Jenn Walker
  • Last Modified Date: 05 October 2019
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A single photon emission computerized tomography (SPECT) scan is a clinical test that doctors use to trace blood flow through certain parts of the body. During the test, a small amount of a radioactive substance is injected into the bloodstream. A specialized scanning camera that can detect the substance is then used to take three-dimensional images of internal tissues. The scan is useful in discovering abnormalities in the brain, heart, liver, and other internal organs. A SPECT scan can also detect some types of cancerous tumors and deep, subtle bone fractures.

Doctors first realized the benefits of SPECT scans in the 1970's, and decades of research and development have resulted in a highly reliable, non-invasive, safe method of diagnosing patients with various ailments. SPECT scans are painless except for the prick of the needle injection, and the dose of radiation received during testing is minimal. Most of the time, scans are performed in an outpatient nuclear medicine clinic and can be completed in less than one hour.

The type of radiation given depends on a patient's specific problem. Different radioactive isotopes work better as tracers in some areas of the body than in others. For example, technetium-99 is commonly used for assumed brain and heart abnormalities, while iodine-123 is better at detecting cancerous tumors. Doctors choose tracers that will concentrate heavily in suspected problem areas while dispersing lightly throughout the rest of the body.


Before a SPECT scan begins, a patient receives a carefully measured amount of radioactive tracer through a vein in the arm. He or she is then instructed to lie down on a table and relax for about 15 minutes while the tracer circulates through the bloodstream. A large machine with a rotating camera lens is rolled into place so the actual SPECT scan can begin. The camera takes several pictures from different angles that can later be combined to create 3-D images. It is able to illuminate organs and tissues by picking up gamma ray radiation given off by the isotopes in the blood.

After the SPECT scan, the patient is usually allowed to go home while test results are interpreted by nuclear medicine specialists. Experts upload images to computer programs and study accurate, 360-degree renderings of body parts. Areas that are especially dense in color indicate high concentrations of tracer. If a tumor, bone fracture, heart defect, or neurological problem exists, it usually shows up well on a SPECT scan. Results are explained to the patient in detail during a follow-up visit so decisions can be made about further testing and treatment options.


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