Application of low-complexity generalized coherence factor to in vivo data

Beamforming using the generalized coherence factor (GCF) reduces sidelobe artifacts and provides an excellent contrast-to-noise ratio. We previously proposed GCF_real, a method to calculate GCF without generating analytic signals, and GCF_bin, a method to calculate GCF by binarizing the received signals. In this study, we applied these methods to in vivo data and showed the effect of the computational complexity reduction on contrast performance.

Channel RF data were acquired from the human liver and gallbladder. We set up several observation points in each data set and investigated the mechanism that causes the differences in contrast performance among the methods based on the signals and their power spectra in the channel direction.

For GCF and GCF_real, the obtained values were almost the same. However, there were large differences in GCF_bin from GCF when the signals from the focus point or from outside the focus point were received on different channels. This is because the amplitudes of the signals with high coherence and those with low coherence were changed by binarizing the signals.

While GCF_bin can significantly reduce the computational complexity, there are differences in the values of GCF_bin and GCF due to binarizing of the received signals. However, this difference resulted in GCF_bin being superior to GCF in terms of artifact reduction. This is owing to the elimination of amplitude information in GCF_bin, which makes it a new efficient coherence factor with different characteristics from GCF.