Two-Dimensional Random Arrays for Real Time Volumetric Imaging

Abstract

Two-dimensional arrays are necessary for a variety of ultrasonic imaging techniques, including elevation focusing, 2-D phase aberration correction, and real time volumetric imaging. In order to reduce system cost and complexity, sparse 2-D arrays have been considered with element geometries selected ad hoc, by algorithm, or by random process. Two random sparse array geometries and a sparse array with a Mills cross receive pattern were simulated and compared to a fully sampled aperture with the same overall dimensions. The sparse arrays were designed to the constraints of the Duke University real time volumetric imaging system, which employs a wide transmit beam and receive mode parallel processing to increase image frame rate. Depth-of-field comparisons were made from simulated on-axis and off-axis beamplots at ranges from 30 to 160 mm for both coaxial and offset transmit and receive beams. A random array with Gaussian distribution of transmitters and uniform distribution of receivers was found to have better resolution and depth-of-field than both a Mills cross array and a random array with uniform distribution of both transmit and receive elements. The Gaussian random array was constructed and experimental system response measurements were made at several ranges. Comparisons of B-scan images of a tissue mimicking phantom show improvement in resolution and depth-of-field consistent with simulation results.

Reducing the number of receiving channels using transmit-receive symmetry in synthetic transmit aperture imaging

“…When the number of receiving channels is large, the cost of the hardware system will be prohibitively high due to the electronics associated with the receiving channels for each element [5]. Therefore, many innovations in designing the effective sparse array have been investigated in [6][7][8][9][10][11][12]. However, the quality of images cannot be preserved due to the reduction of the number of elements.…”

Volumetric ultrasound system for left ventricle motion imaging

“…First, these transducers are based on a matrix composed of a large number of elements (up to 64 * 64) that are difficult to drive. One way to reduce the complexity of such arrays and the supporting electronics is to select a sparse array composed only of a subset of all the available elements, resulting in the same resolution [27], [29]. Choosing a random array, with uniform element density, also means that the main lobe width is decreased, and sidelobes are reduced compared to a fully sampled array with the same overall dimensions.…”

Two dimensional arrays for 3-D ultrasound imaging

“…Here the pitch of the receive elements is twice that of the transmit elements so that the grating lobes in transmit and receive do not overlap and are significantly reduced by the multiplicative pulse-echo process. Finally, we have used sparse random arrays for 3-D ultrasound imaging although with less success than the periodic vernier design [22].…”