  Three-dimensional (3D) ultrasound (US) imaging addresses the limitation in
field-of-view (FOV) in conventional two-dimensional (2D) US imaging by
providing 3D viewing of the anatomy. 3D US imaging has been extensively adapted
for diagnosis and image-guided surgical intervention. However, conventional
approaches to implement 3D US imaging require either expensive and
sophisticated 2D array transducers, or external actuation mechanisms to move a
one-dimensional array mechanically. Here, we propose a 3D US imaging mechanism
using actuated acoustic reflector instead of the sensor elements for volume
acquisition with significantly extended 3D FOV, which can be implemented with
simple hardware and compact size. To improve image quality on the elevation
plane, we introduce an adaptive-delay synthetic aperture focusing (AD-SAF)
method for elevation beamforming. We first evaluated the proposed imaging
mechanism and AD-SAF with simulated point targets and cysts targets. Results of
point targets suggested improved image quality on the elevation plane, and
results of cysts targets demonstrated a potential to improve 3D visualization
of human anatomy. We built a prototype imaging system that has a 3D FOV of 38
mm (lateral) by 38 mm (elevation) by 50 mm (axial) and collected data in
imaging experiments with phantoms. Experimental data showed consistency with
simulation results. The AD-SAF method enhanced quantifying the cyst volume size
in the breast mimicking phantom compared to without elevation beamforming.
These results suggested that the proposed 3D US imaging mechanism could
potentially be applied in clinical scenarios.
