4Din vivoultrafast ultrasound imaging using a row-column addressed matrix and coherently-compounded orthogonal plane waves

Abstract

4D ultrafast ultrasound imaging was recently shown using a 2D matrix (i.e. fully populated) connected to a 1024-channel ultrafast ultrasound scanner. In this study, we investigate the row-column addressing (RCA) matrix approach, which allows a reduction of independent channels from N × N to N + N, with a dedicated beamforming strategy for ultrafast ultrasound imaging based on the coherent compounding of orthogonal plane wave (OPW). OPW is based on coherent compounding of plane wave transmissions in one direction with receive beamforming along the orthogonal direction and its orthogonal companion sequence. Such coherent recombination of complementary orthogonal sequences leads to the virtual transmit focusing in both directions which results into a final isotropic point spread function (PSF). In this study, a 32 × 32 2D matrix array probe (1024 channels), centered at 5 MHz was considered. An RCA array, of same footprint with 32 + 32 elements (64 channels), was emulated by summing the elements either along a line or a column in software prior to beamforming. This approach allowed for the direct comparison of the 32 + 32 RCA scheme to the optimal fully sampled 32 × 32 2D matrix configuration, which served as the gold standard. This approach was first studied through PSF simulations and then validated experimentally on a phantom consisting of anechoic cysts and echogenic wires. The contrast-to-noise ratio and the lateral resolution of the RCA approach were found to be approximately equal to half (in decibel) and twice the values, respectively, obtained when using the 2D matrix approach. Results in a Doppler phantom and the human humeral artery in vivo confirmed that ultrafast Doppler imaging can be achieved with reduced performances when compared against the equivalent 2D matrix. Volumetric anatomic Doppler rendering and voxel-based pulsed Doppler quantification are presented as well. OPW compound imaging using emulated RCA matrix can achieve a power Doppler with sufficient contrast to recover the vein shape and provides an accurate Doppler spectrum.

Imaging Performance for Two Row–Column Arrays

“…Imaging with RCA 2-D arrays has been investigated based on simulations [4], [7], [10]- [12] as well as measurements with arrays fabricated in CMUT [13]- [17] and PZT [18]- [21] technologies separately. The purpose of this paper is to evaluate the imaging performance attainable for RCA 2-D arrays quantitatively and comparatively when employing synthetic aperture data acquisition and using two beamforming schemes developed specially for row-column imaging.…”

3-D Super-Resolution Ultrasound Imaging With a 2-D Sparse Array

“…Many researchers have developed methods to use a large number of active elements with fewer channels (usually between 128 and 256) to reduce the cost and complexity of the ultrasound systems and the probes. It has been demonstrated in several studies that row-column addressed matrix arrays [47], [51]- [53], microbeamformers [54]- [56] and channel multiplexing can be an alternative to fully addressed 2-D matrix arrays. However, these methods have less flexibility and limitations due to the elements not being continuously connected to the ultrasound system.…”

Volumetric 3-D vector flow measurements using a 62+62 row-column addressed array

“…The imaging and volumetric power Doppler performance of an emulated 2-D RCA array was also lately investigated and compared with a corresponding matrix array [6]. This paper presents 3-D vector flow estimation in a full volume and expands on previous work, where a transmit sequence was designed to acquire 3-D vector flow estimates in a plane using an RCA array [5].…”