A simplified in vivo autoradiographic strategy for the determination of regional cerebral blood flow by positron emission tomography: Theoretical considerations and validation studies in the rat

A simplified mathematical model is described for the measurement of regional cerebral blood-flow by positron-emission tomography in man, based on a modification of the autoradiographic strategy originally developed for experimental animal studies. A modified ramp intravenous infusion of radio-labeled tracer is used; this results in a monotonically-increasing curvilinear arterial activity-curve that may be accurately described by a polynomial of low degree. Integrated cranial activity is measured in regions of interest during the latter portion of the tracer-infusion period. An on-line computer solution for blood flow is presented. This in-vivo autoradiographic paradigm was validated in a series of rats by comparing it to the classical autoradiographic strategy developed by Kety and associates. Excellent agreement was demonstrated between blood-flow values obtained by the two methods.