Single-photon emission computed tomography (SPECT) is a medical imaging technique that is based on the conventional nuclear medicine imaging technique and tomographic reconstruction methods.

FIGURE 13.6 The conventional nuclear medicine imaging process. Gamma-ray photons emitted from the internally distributed radioactivity may experience photoelectric (a) or scatter (b) interactions. Photons that are not traveling in the direction within the acceptance analog of the collimator (c) will be intercepted by the lead collimator. Photons that experience no interaction and travel within the acceptance angle of the collimator will be detected (d).