Regional Cerebral low in Man Determined by Intral-artrial Injection of Radioactive Inert Gas

Abstract

The intra-arterial injection of a radioactive inert gas is described for measurement of regional cerebral blood flow in man from externally recorded clearance curves. The stochastic analysis for calculating the average cerebral blood flow in ml/100 g/min is compared to an analysis of the curve into two compartments with fast and slow clearance rates representing flow in grey and white cerebral matter respectively. An estimate of the relative weight of the grey matter in the cerebral region counted from brain is also obtained. A detailed description is given of the experimental procedure using krypton 85 or xenon 133 as the tracer gas. A brief injection time and short time constant in the recording ratemeter are important for obtaining a correct estimate of the maximal height of the curve. Mono-exponential extrapolation beyond the time of observation (usually 15 minutes) is employed. The practical procedure for calculating the results according to the stochastic and compartmental models are described with particular emphasis on the simple "10 minutes-average-flow-value, " CBF (10) which corresponds directly to the results of the classical Kety-Schmidt inert gas inhalation method for measurement of the average blood flow of the whole brain.