What is SPECT? It is an acronym for Single Photon Emission Computerized Tomography. SPECT is a sophisticated nuclear medicine study that looks directly at cerebral blood flow and indirectly at brain activity (or metabolism).
A radioactive isotope is bound to a substance that is readily taken up by the cells in the brain. A small amount of this compound is injected into the patient’s vein where it runs throughout the blood stream and is taken up by certain receptor sites in the brain. The patient then lies on a table for 14-16 minutes while a SPECT “gamma” camera rotates slowly around his head. The camera has special crystals that detect where the compound has gone. A supercomputer then reconstructs 3-D images of brain activity levels. The elegant brain snapshots that result offer a sophisticated blood flow/ metabolism brain map. With these maps, physicians have been able to identify certain patterns of brain activity that correlate with psychiatric and neurological illnesses.
During the late 70s and 80s SPECT studies were being replaced in many cases by the sophisticated anatomical CAT and later MRI studies. The resolution of those studies was far superior to SPECT as far as seeing tumors, cysts and blood clots. In fact, they nearly eliminated the use of SPECT studies altogether. Yet despite their clarity, CAT scans and MRIs could offer only images of a static brain, and its anatomy; they gave little or no information on the activity in a working brain. It was analogous to looking at the parts of a car’s engine without being able to turn it on. In the last decade it has become increasingly recognized that many neurological and psychiatric disorders are not disorders of the brain’s anatomy, but problems in how it functions.
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