Experimental evaluation of the correlation interpolation technique to measure regional tissue velocity

A newly developed correlation interpolation method to measure the regional velocity of moving tissue is evaluated in an experimental setup. Pulsed ultrasound echo signals (center frequency 3.5 MHz) are received from a rotating Agar disk containing scattering particles. When averaging over a depth range of 2.2 mm at a pulse repetition frequency (PRF) of 930 Hz, the standard deviation of the measured displacement between 2 successive pulses was found to be +/- 6 microns. In a second series of experiments, the angular velocity of the disk is estimated from the displacement, as measured simultaneously in two different regions located on separate echo lines (PRF = 465 Hz per line). The exact position of both regions in respect to the center of rotation was found to be irrelevant. The accuracy of the calculated angular velocity was found to be better for large angles between the two lines of observation than for small angles.