Extended Field of View Imaging Through Correlation With an Experimental Database

In this article, a correlation-based (CB) ultrasound imaging technique is implemented to extend the field of view (FOV) in the inspected medium and to enhance image homogeneity. This implementation involves the acquisition, the compression, and the adaptation of a database of experimental reference signals (CB-Exp), consisting of backpropagated reflections on point-like scatterers at different positions, as an improvement over preceding implementations involving a database of numerical reference signals (CB-Num). Starting from a large database acquired in water to a database with a 99% size reduction that can be applied to tissue-like media, CB-Exp has been validated in vitro on a CIRS 040GSE phantom. When compared with the synthetic aperture focusing technique (SAFT) and CB-Num, CB-Exp results show reduced sensitivity to the probe's directivity, allowing an FOV extension from 25° with SAFT to 75° with CB-Exp. In vivo testing on a piglet's heart with CB-Exp imaging showed a 3.5-dB contrast improvement on the pericardium wall. Overall benefits of this method include a reduction in the background gCNR standard deviation (std) of 0.2 and a reduction in the std of 10 dB in the point-like targets levels, which translates to more homogeneous sensitivity in the axial and lateral directions of the image.