Quantitative measurements of cerebral blood flow in volume imaging PET scanners

Quantitative measurements of cerebral blood flow (CBF) are performed in a volume imaging PET scanner by means of moderate activity infusions. In equilibrium infusions, activations are measured by scanning over 10 minutes with 16 minute activations. Typical measured whole brain CBF values are 37±8 ml/min/dl, close to the value of 42 ml/min/dl reported by other groups using this method. For ramped infusions, scanning over 4 minutes with 5 minute activations results in whole brain CBFs of 49±9 ml/min/dl, close to the Kety and Schmidt value of 50 ml/min/dl. Both equilibrium and ramped infusion methods have been used to study face and word memory in human subjects. Both methods were able to detect significant activations in regions implicated in human memory (amygdala and hippocampus). It is concluded that both accurate and precise quantitation of regional CBF (rCBF) is achieved using the methods described. In addition a simplified protocol for ramped infusion studies has been investigated. In this method the whole brain tissue time activity curve generated from dynamic scanning is replaced by an appropriately scaled camera coincidence countrate curve. The resulting whole brain CBF values are only 7% different from the dynamic scan results. Methods for obtaining the rCBF from the summed image and the resulting whole brain CBF are under investigation