Multiple isoplanatic patch phase aberration correction in real-time 3D transcranial ultrasound

We present an approach for correcting multiple distinct aberrators within a single transcranial imaging volume, i.e. several isoplanatic patches. Aberration is estimated using cross-correlation of RF channel signals followed by least mean squares solution of the resulting overdetermined system. Delay maps are updated and real-time 3D scanning resumes. This adaptive imaging technique, which uses steered unfocused waves transmitted by the “beacon” array on the opposite side of the head, updates the transmit and receive delays of 5 isoplanatic patches within a 64°×64° volume. In phantom experiments, color flow voxels above a common threshold have increased by an average of 92%, while color flow variance decreased by an average of 10%. This approach has been applied to bilateral temporal acoustic windows of two human subjects, yielding increases in echo brightness in 5 isoplanatic patches, with a mean value of 24.3 ± 9.1%.