Single Photon Emission Computed Tomography (SPECT)

... A medical imaging technique that uses small amounts of radioactive material (radioisotopes) attached to radiopharmaceuticals to map brain function

Single Photon Emission Computed Tomography (SPECT) is a medical imaging technique used for mapping brain metabolism and function. SPECT is similar to positron emission tomography in that once the radio-pharmaceutical is trapped in the brain, radiation is given off as a result of gamma emission. Various radioactive pharmaceuticals are injected into the blood and attach to targets in the brain’s gray matter for several hours. This allows researchers to image up to several hours after injection, yet study activity at the time of injection. Special detectors produce pictures of the radioisotopes in the brain, permitting scientists to distinguish between normal and abnormal tissue. This scanning procedure is somewhat the reverse of a traditional x-ray; instead of the x-rays coming from outside the body, the radiation source is inside the body.

At The University of Texas Health Science Center at Houston, SPECT technology is used to study:

Differences in brain metabolism characteristic of conditions such as attention deficit/hyperactivity disorder and various organic mood disorders.
Drug-induced changes in brain metabolism, caused by intravenous cocaine use among drug addicts, and use of Diamox in patients who have had strokes or obstructed blood supply to the brain, or transient ischemic attacks. Functional significance in stenosis of the carotid vessels can also be assessed.

Changes in the brain as a result of receiving a physical or psychological stimulus or challenge (these changes can be correlated with MRI findings).
Localization of regions of decreased perfusion/function, which may represent a focus of seizure activity. Identification of such a focus can help in surgical therapy.

Across the country, brain SPECT has been used to study various receptors, or groups of cells that receive stimuli. Receptors for the brain chemicals dopamine and serotonin have been studied, as well as receptors for opiates. Brain SPECT also can be used in identifying the location of brain tumors and in conjunction with agents that help detect brain tumors. The Division of Nuclear Medicine at UT-Houston, for example, uses Thalium-201 to evaluate recurrences of brain tumors after therapy – a process that can be very difficult with technologies that provide only images of structures in the body, such as MRI.