Single‐photon Emission Computed Tomography (SPECT)

Single-photon emission computed tomography (SPECT) cameras acquire multiple planar views of the radioactivity in an organ. SPECT utilizes the single photons emitted by gamma-emitting radionuclides such as 99m Tc, 111 In, and 123 I. The simplest camera design for SPECT imaging is similar to that of a planar camera but with two additional features. First, the SPECT camera is constructed so that the head can rotate about the patient to acquire multiple views. Second, it is equipped with a computer that integrates the multiple images to produce the cross-sectional views of the organ. Cardiac imaging is performed on a general purpose two-headed SPECT camera with the heads oriented at 90 degrees; the gantry rotates approximately 90 degrees to acquire the 180 degrees of cardiac SPECT data. An estimate of the amount of radionuclide activity in a lesion can be helpful in differentiating benign from malignant lesions and for tracking disease progression or response to treatment.