Evaluation of Regional Differences of Tracer Appearance Time in Cerebral Tissues Using [15O]Water and Dynamic Positron Emission Tomography

The tracer appearance time relative to the radial artery–sampling site has been evaluated in six brain locations in five human subjects using dynamic positron emission tomography (PET) following the bolus injection of H215O. There was a maximum difference of ± 2 s from the average in each location. T o globally adjust the timing difference between the measured arterial curve and the PET scan, a correction method was developed based on a nonlinear least-squares fitting procedure. This new technique determined the global time delay with an accuracy of ± 0.5 s. On the other hand, the linear backward extrapolation method resulted in a systematic error of 4 s.