Critical review of PET, SPECT and neuroreceptor studies in schizophrenia.

Hypotheses having to do with the neurochemical basis for mental disease can be tested by noninvasive measurement of flow, metabolism and neuroreceptor concentrations in various parts of the brain. The capabilities of these technologies for accurate absolute quantitation are limited by the instrument resolution and the limited statistics associated with allowable radiation doses. Nevertheless, very important new information regarding the brain function in normal and diseased states can be gleaned from the techniques of positron emission tomography (PET) and single photon emission tomography (SPECT). This chapter presents the critical problems which face the clinical researcher who endeavors to test hypotheses regarding mental illnesses using PET or SPECT. First, the quantitative capabilities of emission tomography will be discussed; then the special requirements of SPECT for attenuation correction will be reviewed. Next, the physiological principles required for inter-institutional comparisons are presented.