Pitch-catch phase aberration correction of multiple isoplanatic patches for 3-D transcranial ultrasound imaging

Abstract

Having previously presented the ultrasound brain helmet, a system for simultaneous 3-D ultrasound imaging via both temporal bone acoustic windows, the scanning geometry of this system is utilized to allow each matrix array to serve as a correction source for the opposing array. 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 3-D scanning resumes. A first attempt is made at using multiple arrival time maps to correct multiple unique aberrators within a single transcranial imaging volume, i.e., several isoplanatic patches. This adaptive imaging technique, which uses steered unfocused waves transmitted by the opposing, or beacon, array, 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 also increased by an average of 92%, whereas color flow variance decreased by an average of 10%. This approach has been applied to both 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%, suggesting that such a technique may be beneficial in the future for performing noninvasive 3-D color flow imaging of cerebrovascular disease, including stroke.

Catheter Hydrophone Aberration Correction for Transcranial Histotripsy Treatment of Intracerebral Hemorrhage: Proof-of-Concept

“…However, in the no aberration correction case, the innate, uncorrected aberration can reduce the magnitude of the losses generated by the additional misalignment due to steering and result in higher pressure amplitudes than with aberration correction. A similar discussion regarding differing propagation paths is proposed by Lindsey and Smith, where steering a 2D imaging probe 15° through skull bone showed decreased correlation of the steered wavefront arrival between adjacent elements on the imaging array [75]. We are currently investigating 1) how much this effect contributes to the observed results, 2) the farthest limit of steering locations beyond which aberration correction reduces the pressure even with multi-location measurements, and 3) methods of correcting for potential losses due to it.…”

3-D Transcranial Ultrasound Imaging with Bilateral Phase Aberration Correction of Multiple Isoplanatic Patches: A Pilot Human Study with Microbubble Contrast Enhancement

“…While we have demonstrated the ability to image blood flow transcranially in 3D in some individuals (Lindsey et al 2011; Lindsey and Smith 2013), we require microbubble contrast agent to achieve sensitivity levels that are diagnostically useful in a general population.…”

Short-lag spatial coherence imaging on matrix arrays, Part II: Phantom and in vivo experiments

“…Noteworthy are several implementations of phase-aberration correction algorithms on clinical 3-D ultrasound scanners using single channel data of partially beamformed subapertures [9-12]. Ivancevich et al [10] implemented multi-lag least-squares cross-correlation and speckle brightness algorithms and compared their performance in correcting for physical aberrators using a single sparsely-sampled 2-D array.…”

“…For the speckle-brightness method, no off-line processing was used; the entire method was implemented using the scanner beamforming routines. Lindsey et al [12] implemented a least-squares cross-correlation method on a pitch-catch setup in order to correct for phase aberration in 3-D transcranial ultrasound in vivo . Here, each matrix array was used as a correction source for the opposing array thus allowing estimation of multiple arrival time maps and reducing the error in aberration correction.…”