Abstract:
A technique is described that provides information about relative
cerebral responses to differing neurobehavioral tasks in normal subjects
studied with positron computed tomography and oxygen-15- labeled water.
Simulation studies demonstrate that this technique is sensitive to
changes in true local CBF within a physiological range and tends to
underestimate relative flow changes at high flow values (greater than 30
ml min-1 100 g-1) and to overestimate these changes for flow values of
less than 25 ml min-1 100 g-1. Image acquisition times of 60 s following
the arrival of oxygen-15-labeled water in the brain were the most
accurate for identifying such relative changes between radioisotope
administrations and were not limited by statistical noise from total
image counts. Studies in normal volunteers indicate that the technique
is highly reproducible, demonstrating a coefficient of variation for
small (less than 2 cm2) regions of 2.98 between studies in the same
state. Visual stimulation studies in normal volunteers demonstrated
relative radioisotope concentration changes between control and
stimulated states that are in good agreement with similar results
obtained using the same stimulation paradigm but with the use of
fluorodeoxyglucose to determine cerebral glucose metabolism