Specular surface reconstruction from multi-angle interrogation (SRMI) using a piston-array-based transducer for enhanced bone delineation

Bone surface detectability with ultrasound is limited due to several factors including off-axis reflection artifacts and low sensitivity to bone surfaces that are not perpendicular to the central axis of the transducer. To address these limitations, a technique termed specular surface reconstruction from multi-angle interrogation (SRMI) was investigated. The SRMI approach uses an array of individual mechanically sector-scanned pistons with overlapping fields of view. Simulations were performed in FIELD II to characterize the angular sensitivity to specular surfaces with varying sector-scan angular span and with comparison to a representative linear array-based spatial compounding technique. The SRMI approach was tested experimentally in an ex vivo, fractured, porcine rib bone embedded in tissue-mimicking phantom material. The SRMI approach with piston-array-based transducer produced several advantages over standard B-mode imaging including generally higher SNR gains with compounding than is readily achieved using a linear array - e.g. √6 versus √3.2. At fixed imaging depth, angular sensitivity improved by approximately 10 degrees with increased sector-scan angular span of 100 degrees versus 40 degrees. The SRMI approach avoids grating lobes typical of linear arrays, and thus provides an inherent advantage for bone imaging. Experimentally, the SRMI approach yielded enhanced bone delineation compared with a single aperture sector scan (6.7 dB contrast-to-noise ratio (CNR) improvement).