Image Noise, Resolution, and Lesion Detectability in Single Photon Emission CT

Single Photon Emission Computed Tomography (SPECT) based on rotational scintillation gamma cameras in combination with filtered back-projection allows full 3-D imaging of isotope uptake in an organ volume. (1, 2,3,4) This paper treats the physical dependence of lesion detectability in SPECT imaging on the lesion uptake, lesion size, object size, and the number of photons collected. The lesion contrast depends on both camera resolution and reconstruction filtering. The relative photon-limited image noise is proportional to the three halves power of the number of linear samples covering the object, inversely proportional to the square root of the number of photons collected, and is also affected by the reconstruction filter chosen. Based on signal-to-noise analysis, the total number of counts necessary for lesion detection is determined.