Functional brain studies with H2(15)O-PET: strategies and problems for approaching higher brain functions with H2(15)O-PET.

Activation study using H2(15)O and PET is promising as a noninvasive approach to higher brain functions in humans. However before reaching a more complex paradigm, many fundamental problems need to be solved. In this study, we investigated the following issues: (1) reproducibility of regional cerebral blood flow in the resting state as measured by this method, (2) effect of physiological stimulation on cerebral blood flow, and (3) identification of activated areas on anatomical structures. Our data suggest that relative CBF images and their paired subtraction are more suitable for tapping functional localization. Changes in rCBF in the association cortex for more complicated tasks are, in general, smaller than those in the primary cortex. Combined display of PET images with three-dimensional reconstructed brain surface MR images was the most reliable technique for anatomical identification of the activated site.