The accuracy of blood velocity measurement using ultrasound

In this study we explore the use of colour flow imaging to quantify blood velocity and wall shear rate. A known velocity profile was obtained using a straight tube flow rig. Colour Doppler ultrasound images were obtained and velocity profiles extracted off-line. There was a small discrepancy (2.6%) in maximum velocity, which was not present after convolution with the colour flow point spread function, hence is likely to be due to velocity gradient broadening within the sample volume. There was disagreement at the edge of the vessel due to loss of velocities below the clutter filter. At a typical clinical colour flow scale (12.8 cms^-1) the error in wall shear measurement is 62 % and at a lower scale setting (4.4 cms^-1) the error is 11%. This improvement seems to be due to the lower level of clutter filter that is used as the velocity scale decreases.