Radius-Adjustable Ring Ultrasound Transducer Array for Real-Time 3D Imaging of Large Volume Targets.

Objective: Three-dimensional (3D) ultrasound imaging overcomes the limitations of 2D ultrasound images by providing comprehensive spatial information. However, challenges remain when imaging larger body parts like legs and arms using traditional linear transducer arrays. The main difficulties include limited scanning range and angle, bone interference that affects penetration depth, and registration difficulties caused by squeezing targets.

Methods: In this study, we propose a free-scanning 3D ultrasound imaging system capable of real-time (18 fps) reconstruction at the sub-millimeter resolution level. The system uses a radius-adjustable ring transducer array for better adaptation to the imaging target, with its pose determined in real-time by an optical positioning system.

Results: We conducted an in vivo experiment on volunteer's forearm and limb. The imaging results were compared with X-ray computed tomography (CT) images. For the 2D image slices from X-ray CT and ultrasound, the average area errors for the fibula and tibia were 1.33% and 2.63%, respectively. When compared in 3D, the length differences for the ulna and fibula were 0.96% and 0.40%, respectively.

Conclusion: The proposed system integrates a ring ultrasound array and an optical positioning system, enabling rapid and precise free-scanning for 3D reconstruction of large-volume targets (e.g., limbs) and allows for the assessment of bone morphology. The proposed system enables rapid and precise 3D reconstruction of limbs for bone morphology assessment, as validated by low error margins (<2.7% in area, <1.0% in length) against CT imaging, confirming the system's strong potential for clinical applications in fracture diagnosis and prognostic monitoring.