Ultrasonic imaging of 3D displacement vectors using a simulated 2D array and beamsteering

Most quasi-static ultrasound elastography methods image only the axial strain, derived from displacements measured in the direction of ultrasound propagation. In other directions, the beam lacks high resolution phase information and displacement estimation is therefore less precise. However, these estimates can be improved by steering the ultrasound beam through multiple angles and combining displacements measured along the different beam directions. Previously, beamsteering has only considered the 2D case to improve the lateral displacement estimates. In this paper, we extend this to 3D using a simulated 2D array to steer both laterally and elevationally in order to estimate the full 3D displacement vector over a volume. The method is tested on simulated and phantom data using a simulated 6-10 MHz array, and the precision of displacement estimation is measured with and without beamsteering. In simulations, we found a statistically significant improvement in the precision of lateral and elevational displacement estimates: lateral precision 35.69 mu m unsteered, 3.70 mu m steered; elevational precision 38.67 mu m unsteered, 3.64 mu m steered. Similar results were found in the phantom data: lateral precision 26.51 mu m unsteered, 5.78 mu m steered; elevational precision 28.92 mu m unsteered, 11.87 mu m steered. We conclude that volumetric 3D beamsteering improves the precision of lateral and elevational displacement estimates. (C) 2012 Elsevier B.V. All rights reserved.