Speckle reduction in pulse echo imaging using phase insensitive and phase sensitive signal processing techniques.

In conventional B-scan imaging, speckle often distorts the true representation of small structures and lesions and hence reduces the diagnostic potential of the technique. Considerable speckle reduction has been achieved with an f/2.4, cone hybrid system by cutting the large aperture transducers into sectors, and using either phase insensitive sector addition (PISA), phase insensitive sector multiplication (PISM), or an rf multiplicative processing technique. We have compared two modes of operation with the hybrid system. In the first, the cone acts as transmitter, and each sector of the f/2.4 spherical aperture is a receiver. In the second mode, the f/2.4 sphere acts as transmitter, and each sector of the cone is a receiver. Quantitative assessment using the contrast to speckle ratio developed by Patterson et al, indicates that processing under both modes results in reduced speckle noise and improved image quality, with the cone sector receive (rx) geometry offering the greatest improvement.