Expansion of the isoplanatic patch for correction of ultrasonic aberration by assignment of corrections based on similarity of propagation paths

Abstract

Aberration correction for ultrasonic b-scan images can be effectively implemented with less computation by employing cross correction, i.e., using a single set of aberration corrections computed for a reference aperture position to correct the transmit and receive focus at other points within an image region defined as the isoplanatic patch. An uncomplicated implementation of this approach compensates the signal at each location in the aperture with the aberration correction from the corresponding location in the reference aperture regardless of the aperture position. Alternatively, the signal at each location in the aperture may be compensated using the correction for the reference aperture signal with a propagation path most similar to the propagation path of the signal being corrected. This latter approach requires a different map of the reference aberration corrections for each aperture position, but the map can be implemented by simple shift operations. Measurements using a novel 2-D array system demonstrate that the assignment of corrections based on similarity of propagation paths can significantly improve the effectiveness of cross correction and enlarges the effective size of the isoplanatic patch.