ANALYSIS OF THE AXIAL-FLOW FIELD IN STENOSED CAROTID-ARTERY BIFURCATION MODELS - LDA EXPERIMENTS

Laser Doppler anemometer (LDA) experiments were performed to gain quan titative information on the differences between the large-scale dow ph enomena in a non-stenosed and a stenosed model of the carotid artery b ifurcation. The influence of the presence of the stenosis was compared to the effect of flow pulse variation to evaluate the feasibility of early detection of stenosis in clinical practice. Three-dimensional Pl exiglass models of a non-stenosed and a 25% stenosed carotid artery bi furcation were perfused with a Newtonian fluid. The dow conditions app roximated physiological dow. The results of the velocity measurements in the non-stenosed model agreed with the results from previous hydrog en-bubble visualization. A shear layer separated the low-velocity area near the non-divider wall from the high-velocity area near the divide r wall. In this shear layer, vortex formation occurred during the dece leration phase of the dow pulse. The instability of this shear layer d ictated the dow disturbances. The influences of the mild stenosis, loc ated at the non-divider wall, was mainly limited to the stability of t he shear layer. No disturbances were found downstream of the stenosis near the non-divider wall. Using a pulse wave with an increased systol ic deceleration time, the velocity distribution showed an extended reg ion with reversed flow, a more pronounced shear layer and increased vo rtex strength. From these measurements it is obvious that the influenc e of the presence of a mild stenosis, mainly limited to the stability of the shear layer, can hardly be distinguished from the effects of a variation of the dow pulse. From this it can be concluded that methods for detection of mild stenosis, using solely the large-scale flow phe nomena, as can be measured by ultrasound or MRI techniques, will hardl y have any clinical relevance. Copyright (C) 1996 Elsevier Science Ltd .