Full Volumetric 3-D Vector Flow Imaging Using a 62+62 Row-Column Array

Row Column (RC) Arrays can produce highresolution 3-D volumetric images with only 2N interconnections compared to N2 for matrix probes. A 62+62 RC probe has four times larger surface area and one-eighth of the channel count when compared to the same-pitch fully populated 32x32 matrix probe. This research investigates the performance of such a prototype array for volumetric Synthetic Aperture (SA) B-mode and vector flow imaging using defocused waves.

An interleaved SA sequence was implemented on the SARUS scanner using a 3 MHz, λ/2-pitch 62+62 RC piezoelectric probe. The sequence contains repeated emissions with rows and columns interleaved with B-mode emissions. The sequence contains 80 emissions in total and can provide a volume rate above 125 Hz yielding continuous data.

Velocities were estimated using the Directional Transverse Oscillation Cross-Correlation method. Measurements were made on a circulating flow rig with a parabolic profile with a peak velocity of 0.25 m/s and beam-to-flow angle of 90º, and two different rotation angles (0º, 45º). Results showed a maximum bias of -17.5% and a standard deviation of 3.9%.

A second setup used a tissue mimicking phantom with pulsating flow showing full volumetric flow estimated using the method. The flow was visualized in the entire rectilinear volume at once, with B-mode planes selectable in the entire region. This was attained using only 62 channels in receive making full volumetric imaging and velocity estimation implementable on current scanner hardware.