Acoustic clutter supporession with weighted phase-difference coherence factor

Various forms of coherence factor have been proposed to improve spatial resolution and suppress acoustic clutters. Regardless of the forms of definition, coherence factors evaluate focusing quality at given field points based on the degrees of coherence of the aperture data. These methods work effectively for coherent sources such as pin targets, whose correlation length is infinite. For incoherent sources with finite correlation lengths, however, the coherence factors suffer from the decorrelation effect from the source. As a consequence, most of the coherence factors tend to introduce large speckle variance. In this paper, we propose the weighted phase-difference coherence factor (WPD-CF) and its computation-efficient form vector coherence factor (VCF), in an attempt to suppress acoustic clutters while preserving tissue speckles. By evaluating the degrees of coherence of the phase differences, WPD-CF precisely segments pin target main lobes, pin target side lobes, grating lobes, soft tissue speckles, and random acoustic clutters. A computation-efficient form of WPD-CF, named vector coherence factor (VCF), were derived based on the fact that the cosine of the angle between two vectors is proportional to their dot product. The advantages of WPD-CF and VCF were demonstrated by phantom and in vivo imaging results.