Psychosis and positron tomography.

The new technology of positron emission tomography (PET) offers hope in developing objective biological indices and correlates of various psychotic states, including schizophrenia. PET is of the order of a million to a billion times more sensitive than MRI (magnetic resonance imaging) and is now successfully measuring the densities of various brain neurotransmitter receptors in health and disease. PET data in schizophrenia patients confirm that delusions and hallucinations are controlled by neuroleptics when the D2 dopamine receptors are specifically blocked. D1 receptors are not involved. The elevation of D2 receptors as a possible basis for psychotic symptoms needs additional investigation because of technical difficulties which need to be resolved. The rapid development of PET indicates its promise for differential diagnosis as well as its value in treating the psychoses.