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single photon emission computed tomography

(Science: radiology) Tomographic imaging of metabolic and physiological functions in tissues, the image being formed by computer synthesis of photons of a single energy emitted by radionuclides administered in suitable form to the patient.

The method uses radionuclides which emit a single photon of a given energy. The camera is then rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer then reconstructs the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the target area scanned.

The advantages of sPECT are that it can be used to observe biochemical and physiological processes as well as the size and volume of the organ.

The disadvantage is that, unlike positron emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, sPECT requires physical collimation to line up the photons, which results in the loss of available photons and hence degrades the image.

Acronym: SPECT