Journal of Ultrasound in Medicine, Vol 19, Issue 5 323-327, Copyright © 2000 by American Institute of Ultrasound in Medicine
Shear rate estimation using a clinical ultrasound scanner
F. Forsberg, Z. Morvay, N. M. Rawool, C. R. Deane and L. Needleman
Department of Radiology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
Wall shear stress is a factor in the development of atherogenesis, thrombus
formation, and embolization, but its existence is very difficult to
determine with ultrasonography. Instead, we estimated shear rates using a
clinical ultrasound scanner and compared results from vessels with and
without stenoses. Velocity profiles were obtained from color M-mode images
on a P700 scanner. Maximum shear rates were calculated off-line as the
maximum velocity gradients. In vitro, studies were performed on a flow
phantom with a vessel containing a 50% stenosis. Shear rates within the
stenosis were significantly higher than those obtained outside the stenosis
(P < 0.00001) and varied more than the peak velocities. In vivo, the
internal carotid artery of 10 volunteers and 13 patients (with stenoses)
was studied. The mean shear rate was 414 s(-1) +/- 154.5 s(-1) in normal
vessels and 687 s(-1) +/- 263.5 s(-1) in stenotic vessels (P = 0.00017). In
conclusion, shear rate estimates can be obtained with a clinical ultrasound
scanner from color M-mode images. Shear rates estimated in vessels with
stenoses are significantly higher than those obtained in normal vessels in
vitro as well as in vivo.
