The AAPM/RSNA physics tutorial for residents. Clinical aspects of emission tomography

Characteristics of single-photon emission computed tomography (SPECT) and positron emission tomography (PET) that have an important impact on clinical interpretation include increased image contrast compared with that in planar imaging and enhanced three-dimensional perception of spatial relationships. Negative factors of tomographic imaging compared with planar imaging include generally inferior spatial resolution and noise and the increased complexity of performing high-quality studies. Areas in which tomography is of value include assessment of recurrent tumors and seizure foci in the brain, myocardial perfusion imaging, and bone scintigraphy, especially in the spine. SPECT studies performed with labeled red blood cells are useful in the diagnosis of cavernous hemangiomas of the liver. SPECT is a valuable adjunct to planar imaging in assessment of infections and tumors. PET studies performed with fluorine-18 fluorodeoxyglucose are currently generating great interest in oncology. Areas of research that have potential clinical impact include development of improved tomographic reconstruction algorithms, correction for nonuniform attenuation of gamma rays, and multimodality image registration.