Functional imaging techniques provide complimentary information to that pro
vided by structural studies such as MRI and CT. Functional imaging is based
upon known parameters such as physiology, metabolism, biochemistry, pharma
cology, and any other biological process. As such, this methodology-plays a
major role in understanding the basic mechanisms of a multitude of disorde
rs, accurate diagnosis of certain diseases, and developing effective treatm
ent for serious illnesses such as cancer and central nervous system maladie
s. Although this type of imaging can be performed with various modalities,
nuclear procedures have played the leading role in this discipline. Advance
s made in labeling various radionuclides to biologically important compound
s, and development of sophisticated instruments have substantially contribu
ted to the growth of the field of functional imaging. The introduction of p
ositron emission topography (PET), which is based on growth imaging of comp
ounds labeled with elements such as carbon, nitrogen, and fluorine, has add
ed a major dimension to the evolution of the discipline. This review deals
with a brief introduction to the methodologies utilized with radiolabeled t
racers and then deals with specific applications of this technology. These
applications include assessment of blood flow and metabolism, receptor imag
ing, elucidating the pathophysiologic process, evaluating role of labeled t
herapeutic agents, and the potential of these techniques in the development
of novel biologic therapies. Functional imaging with radiolabeled tracers
will play an increasingly important role in modem medicine, and its impact
will be substantial in the management of patients with various disorders. (
C) 2000 Published by Elsevier Science B.V; All rights reserved.