Row Transmission for High Volume-Rate Ultrasound Imaging with a Matrix Array.

The widely used Vermon 1024-element matrix array for three-dimensional (3D) ultrasound imaging has three blank rows in the elevational direction, which breaks the elevation periodicity, thus degrading volumetric image quality. To bypass the blank rows in elevation while maintaining the steering capability in azimuth, we proposed a row transmission (RT) scheme to improve 3D spatial resolution. Specifically, we divided the full array into four apertures, each with multiple rows along the elevation. Each multi-row aperture (MRA) was further divided into subapertures to transmit diverging waves sequentially. Coherent diverging wave compounding (CDWC) was realized in azimuth, while the elevation was multi-element synthetic aperture (M-SA) imaging by regarding each row as an array of dashed line elements. An in-house spatiotemporal coding strategy, cascaded synthetic aperture (CaSA), was incorporated into the RT scheme as RT-CaSA to increase the signal-to-noise ratio (SNR). We compared the proposed RT with conventional bank-by-bank transmission-reception (Bank) and sparse-random-aperture compounding (SRAC) in a wire phantom and the in vivo human abdominal aorta to assess the performance of anatomical imaging and aortic wall motion estimation. Phantom results demonstrated superior lateral resolution achieved by our RT scheme (+19.52% and +16.88% versus Bank, +15.32% and +19.72% versus SRAC, in the azimuth-depth and elevation-depth planes, respectively). Our RT-CaSA showed excellent contrast ratios (+8.19dB and +8.08dB versus Bank, +6.81dB and +5.85dB versus SRAC, +0.99dB and +0.90dB versus RT) and the highest in vivo aortic wall motion estimation accuracy. The RT scheme was demonstrated to have potential for various matrix array-based 3D imaging research.