In this paper we present Flow Rate Profiler (FRP), an instrument for measur
ing the blood velocity by means of ultrasound-based techniques. The velocit
y is directly related to the shear rate, which is in turn proportional to t
he shear stress, a parameter expressing the pressure exerted by the blood o
n the vessel walls. The knowledge of this value is important in medicine to
establish the state of the vessels, directly related to vascular diseases.
FRP provides a non-invasive measure of the blood velocity by exploiting th
e red corpuscles property of diffusing ultrasound waves: in practice blood
velocity is determined by a cross-correlation technique, which analyses the
time shift between correlated subsequent echo waves, instead of frequency
shift characteristic of the Doppler technique. The acquired data are then p
rocessed on a personal computer by means of mathematical techniques based o
n the evaluation of the correlation function, giving a reconstructed veloci
ty profile and showing a good adherence with experimental data, since the a
verage error is nearly the 10%. The reconstructed profile is displayed to t
he operator, who can follow the vessel status in real time. A few compariso
ns between the reconstructed and the experimental profiles are also present
ed, together with a study on a small set of patients suffering from artery
hypertension. (C) 2001 Elsevier Science B.V. All rights reserved.