Clinical evaluation of combined spatial compounding and adaptive imaging in breast tissue

When spatial compounding is applied to targets with significant acoustic velocity inhomogeneities, the correlation between speckle patterns of the images to be averaged decreases, thereby increasing the speckle reduction nominally obtained. Phase correction applied to these targets improves the coherence of the wavefield and restores image spatial frequencies. Combining these two modes can be used to effectively increase the contrast-to-noise ratio (CNR) of imaging targets and improve the general image quality of these targets over spatial compounding alone. This paper presents a clinical evaluation of combined spatial compounding and adaptive imaging in breast tissue and compares this combined technique to conventional imaging and to adaptive imaging and spatial compounding operating independently. Experiments were performed on a 1.75-D, 8 x 96 array attached to a commercially-available scanner. Cysts, microcalcifications and other breast structures were targeted in order to assess the impact of the combined mode on CNR, target width, target brightness and target peak-to-background ratio (PBR). In general, phase correction improved cyst CNR by 7.7%, decreased target width by 18.7%, increased target brightness by 30.1% and increased PBR by 17.9%. Compounding alone, using three overlapping 9.71 mm subapertures, increased cyst CNR by 24.6%, but increased target width by 25.4% and decreased PBR by 13.2%. Combining both modes, however, increased cyst CNR by 32.6%, inappreciably increased target width by 1.1% and marginally decreased PBR by 2.8%. The increase in target brightness with this combined mode was 20.0%