Abstracts for the 2021 International Symposium on Ultrasonic Imaging and Tissue Characterization

S FROM THE 2021 INTERNATIONAL SYMPOSIUM ON ULTRASONIC IMAGING AND TISSUE CHARACTERIZATION Virtual Conference 02 to 04 June 2021 https://doi.org/10.1177/01617346211031090 Ultrasonic Imaging 2021, Vol. 43(4) 187 –233 © The Author(s) 2021 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/01617346211031090 journals.sagepub.com/home/uix Abstracts In vivo Lag-one Coherence Measurements Using Matrix Arrays Rifat Ahmed1, Nick Bottenus2, James Long1, David Bradway1, and Gregg Trahey1 1Dept. of Biomed. Eng., Duke University, NC, USA and 2Dept. of Mech. Eng., University of Colorado Boulder, CO, USA, rifat.ahmed@duke.edu Objectives: Diffuse reverberation is a significant source of image degradation in abdominal ultrasound. Clutter induced by reverberation is often considered to be spatially incoherent. The nearest element correlation of backscatter signals provides a robust measure of such incoherent clutter [1]. We recently presented Lag-one Spatial Coherence Adaptive Normalization (LoSCAN) [2], an image formation technique that adaptively compensates for the SNR loss due to incoherent clutter. Here, we present in vivo LoSCAN images obtained with a 1024-element matrix array and explore the benefits of 2D clutter reduction. Methods: We developed a 2D LoSCAN framework applicable to matrix arrays. We validated this framework using Field II-simulated cyst phantoms of varying native contrasts and channel SNR, with a modeled 64x64 symmetric 2D array. Using these simulated data, we studied the impact of partially correlated noise (PCN) with controlled spatial correlation lengths (1λ to 3λ). Sub-aperture beamforming and a short-lag version of LoSCAN were explored as strategies to circumvent the PCN-induced contrast loss. We also acquired experimental data using a custom 64x16 2D array connected to a 1024-channel Verasonics system. We acquired fundamental and harmonic channel data from the liver of two healthy volunteers and performed 2D spatial coherencebased clutter analysis. Results: Compared to B-mode imaging, matrix LoSCAN preserved the native contrast and improved the lesion detectability, measured with the generalized contrast-to-noise ratio (gCNR), over a wider range of channel SNR. In vivo observations demonstrated the anisotropy of reverberation-noise correlation length. Matrix LoSCAN also improved the gCNR of abdominal anechoic targets from 0.92 to 0.97 in fundamental images and from 0.91 to 0.97 in harmonic images. Conclusions: Matrix LoSCAN effectively suppressed the incoherent clutter in abdominal ultrasound images. In vivo examples demonstrated the advantages of multi-dimensional clutter analysis. [1] Long et al., IEEE-TUFFC, 2018 [2] Long et al., IEEE-TUFFC, 202