PET/SPECT: functional imaging beyond flow

In this review, first principles of positron emission tomography (PET) and single photon emission tomography (SPECT) are discussed together with the r elative strengths and weaknesses of both techniques. With both modalities i t is possible to image and, especially with PET, to measure regional tissue function, the particular function being interrogated depending on the actu al tracer being used. In the second part, the use of PET for neuroactivatio n studies is presented, illustrated with some key examples from the literat ure using both perfusion and metabolism tracers. It is argued that the futu re of PET (and SPECT) neuroactivation studies lies in the use of ligands. P ossible approaches For performing ligand activation studies are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.