Measurement of evoked vascular response to cerebral activation with PET

Different regions of the brain use more oxygen and glucose when they work harder. These changes are quite small, but there is a significant change in blood flow in “activated” regions. Some of the increase in the blood flow signal is due to an increase in the quantity of blood in the region. Blood volume can be measured as a relatively “steady state” method by labelling the blood with CO. It seems likely that the blood volume in activated regions changes and may change quite quickly after the onset of the activation. The authors postulate that if a stimulus was applied in a repetitive way, and PET data acquired in separate bins then the evoked vascular response could be measured. The data acquisition hardware of the Scanditronix PC-2048 PET system was modified so that the data for each of 8 phases can be acquired and stored in the corresponding region in the memory. Programs have been written to rearrange each phase of the data into an individual file in such a way that the data can be reconstructed into a series of images. Aside the hardware and software, a stimulator and a activity monitoring and controlling system were built. The technique has been tested with simulation studies with shaft encoder and is being tested on normal subjects by applying vibrotactile stimulation to the fingers of the left and right hands alternately after the administration of ¹¹C labelled CO