Comments on the Inert Gas Elimination Method for the Determination of Cerebral Blood Flow

Abstract

In the compartmental analysis of inert gas elimination curves from the brain the curves are customarily resolved into two components, regarded as representing flow in grey and white matter, respectively. However, very often a careful analysis of the initial part of curves obtained after short intra-arterial injections reveals another component, which may be relatively large in quantity, but which, because of its high disappearance rate, is evident only for a very short time. This fast initial component, described earlier by us [1], has attracted little attention, although, apart from its obvious theoretical interest, it is of definite practical importance for the calculation of mean cerebral blood flow, either from the initial slope, where it will tend to make the slope steeper, or by the height-over-area-method, where its presence may give a considerable uncertainty to the determination of the initial amplitude of the curve.