Assessing arterial stenoses by tracking turbulence with Doppler ultrasound

Abstract

When a stenosis, or narrowing, causes a significant area reduction of a blood vessel, turbulence in the post-stenotic jet can be detected with Doppler ultrasound distal to the stenosis. A technique is investigated for assessing the severity of a stenosis, defined as the pressure drop across the lesion, by extracting the streamwise turbulence intensity (or the normalized square root of the velocity variance) from the Doppler ultrasound in an arterial flow model. The model consists of an optically and acoustically transparent polyurethane tube that mimics femoral artery compliance, a pump capable of continuous and pulsatile flow, 10-μm glass spheres as an ultrasound and laser scatterer, and both blunt and rounded inlet stenoses. The flow field through three axisymmetric, Plexiglas stenoses with diameter reductions from 60% to 95% mH were investigated with an ATL HDI 3000 using the L7-4 linear array in Doppler mode (1.0-mm spatial pulse length) and a Dantec two-color 55X laser Doppler anemometer (0.7-mm major axis). To validate the ultrasound technique, correlation of Doppler ultrasound and laser Doppler anemometry flow measurements was examined. The correlation of the peak velocity, the maximum turbulence intensity, and the pressure drop across each stenosis was also investigated. This Doppler ultrasound technique could be sensitive to more subtle alterations in hemodynamics and therefore could aid early detection of atherosclerosis.