MEASUREMENT OF THE EVOKED VASCULAR-RESPONSE (EVR) TO CEREBRAL ACTIVATION DUE TO VIBRO-TACTILE STIMULATION USING GATED C-11 CO PET ACQUISITION

Conventional positron emission tomography (PET) activation studies are performed using multiple injections of O-15 water and subtraction of base-line from activation studies. These studies are acquired over 30 to 60 seconds and can be repeated every ten to 15 minutes, so their te mporal resolution is poor. We report on a much more rapid technique to measure cerebral activation with PET. In our first successful studies the subject inhaled a tracer quantity (750 MBq) of C-11 carbon monoxi de mixed in medical air. A pulsed vibrator taped to the fingers of the right hand provided a stimulus in 8 five-second phases (four on, four off) over a period of 20 minutes. PET images were acquired with a Sca nditronix PC2048-15B whose data acquisition system had been modified t o allow cyclic acquisitions similar to gated cardiac studies. In a ser ies of four subjects the evoked vascular response (EVR) was clearly id entified When the subjects data is pooled a clear pattern of activatio n is easily seen, and the phase of the on-set is measurable. When anal yzing the data from individual subjects we found the studies with high er count-rates give the most conspicuous activation. It is anticipated that single-subject activation studies would yield improved image qua lity on a scanner capable of 3D acquisitions.