Ultrasound Phase Array Tomography for Biphasic Medium Distribution Imaging Using Synthetic Aperture Beam Scanning

Abstract

Industrial ultrasonic tomography (UT) possesses unique advantages in visualizing multiphase medium and has received broad attention in the past decades. Facing small bubble distribution imaging, the current independent-transducer-based UT faces bottleneck problems of limited projection number and large projection diameter. To image the cross-sectional bubble distribution, an original concept of ultrasonic phase array tomography (UPAT) is proposed by introducing the ultrasound phase array (UPA) transducers and novel designed sensing strategy into UT. The UPAT emits a wide and directional acoustic beam toward the receivers, on which each element forms a narrow projection to detect small bubbles on its path. Hence, the UPAT forms a novel sensing strategy with shifting and multiangled acoustic beam scanning of the whole cross section, as well as the precise measurement on a high amount of narrow projections. To mathematically model the UPAT, the acoustic field distribution and beam steering algorithm are designed for beam scanning with shifted apertures, while the forward/inverse solutions are proposed for tomographic imaging. In numerical simulations, the eight-transducer UPAT is with much lower imaging error than the state-of-art 32-transducer transmissive/reflective UT with relative error reduced by 65.66% on average. In lab-scale experiments, the reconstructed bubble size, shape, and distribution are with good accuracy, boundary preservation, and image purity.