Position emission tomography at the turn of the century: a perspective.

Nuclear medicine translates advances in molecular biology into the care of patients. In the future, diseases will be characterized at the molecular rather than the cellular level, often before detectable structural changes have occurred. Position emission tomography (PET) will play a major role in the study of intercellular communication by making it possible to characterize the actions of "molecules with messages." Diseases will be characterized by defects in intercellular communication. Treatment will be planned based on molecular abnormalities, and the response to treatment will be monitored with molecular probes. PET studies of the brain, heart, and cancer will be extended to all organs of the body. Pharmacology will be strongly influenced by PET because most drugs act by stimulating or blocking "recognition sites" on the surface of cells. In the next century, will single photon emission computed tomography (SPECT) makes PET unnecessary? The answer is no, because both PET and SPECT will have achieved a permanent role in medical practice; both make it possible to examine regional in vivo chemistry in human beings. Carbon-11 and fluorine-18 will continue to lead the way, but many drugs, and some body constituents such as proteins, can be radiolabeled with iodine-123 and technetium-99m. Today, PET is limited by the need to make one's own radiotracers. This is likely to change when regional radiopharmacies become widespread.(ABSTRACT TRUNCATED AT 250 WORDS)