Regional cerebral blood flow in man determined by the initial slope of the clearance of intra-arterially injected 133Xe

Abstract

The regional cerebral blood flow can be calculated from the initial slope of the logarithmically displayed clearance curve following intra-arterial injection of 133Xe (rCBFinltial). The relationship between this parameter and the values resulting from stochastic (height over area) and compartmental analyses is extensively discussed. Experimental results demonstrate the theoretically (rCBFinltial 20% to 30% lower than Fg). It is shown how the cerebral clearance curve (normally biexponential) with low flow values becomes gradually monoexponential. Thus only flow of gray substance changes, whereas flow of white substance is independent of CBFx. CBF10 was shown to overestimate CBFx with about 15% independent of the flow level. Correlation between CBFinltial and CBF10 was linear (r = 0.98) at CBF10 values above 20 ml/100 gm/min. The CBFinltial normal value is found to be 64 ± 9 ml/100 gm/min, and the interchannel coefficient of variation is 8.2%. A correction for remaining significant difference was found between repeated resting state measurements. The CBFinltial-Paco2 relationship was found to be best described as exponential. In a group of patients with various intracranial diseases, 1 mm Hg change in Paco2 resulted in 4% change of CBFinltial quite independent of the CBFinltial level. © 1971 American Heart Association, Inc.