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Proceedings Paper

Detection of and compensation for blocked elements using large coherent apertures: ex vivo studies
Author(s): Marko Jakovljevic; Nick Bottenus; Lily Kuo; Shalki Kumar; Jeremy Dahl; Gregg Trahey
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Paper Abstract

When imaging with ultrasound through the chest wall, it is not uncommon for parts of the array to get blocked by ribs, which can limit the acoustic window and significantly impede visualization of the structures of interest. With the development of large-aperture, high-element-count, 2-D arrays and their potential use in transthoracic imaging, detecting and compensating for the blocked elements is becoming increasingly important.

We synthesized large coherent 2-D apertures and used them to image a point target through excised samples of canine chest wall. Blocked elements are detected based on low amplitude of their signals. As a part of compensation, blocked elements are turned off on transmit (Tx) and receive (Rx), and point-target images are created using: coherent summation of the remaining channels, compounding of intercostal apertures, and adaptive weighting of the available Tx/Rx channel-pairs to recover the desired k-space response. The adaptive compensation method also includes a phase aberration correction to ensure that the non-blocked Tx/Rx channel pairs are summed coherently.

To evaluate the methods, we compare the point-spread functions (PSFs) and near-field clutter levels for the transcostal and control acquisitions. Specifically, applying k-space compensation to the sparse aperture data created from the control acquisition reduces sidelobes from -6.6 dB to -12 dB. When applied to the transcostal data in combination with phase-aberration correction, the same method reduces sidelobes only by 3 dB, likely due to significant tissue induced acoustic noise. For the transcostal acquisition, turning off blocked elements and applying uniform weighting results in maximum clutter reduction of 5 dB on average, while the PSF stays intact. Compounding reduces clutter by about 3 dB while the k-space compensation increases clutter magnitude to the non-compensated levels.

Paper Details

Date Published: 1 April 2016
PDF: 6 pages
Proc. SPIE 9790, Medical Imaging 2016: Ultrasonic Imaging and Tomography, 97900W (1 April 2016); doi: 10.1117/12.2217385
Show Author Affiliations
Marko Jakovljevic, Stanford School of Medicine (United States)
Nick Bottenus, Duke Univ. (United States)
Lily Kuo, Duke Univ. (United States)
Shalki Kumar, Duke Univ. (United States)
Jeremy Dahl, Stanford School of Medicine (United States)
Gregg Trahey, Duke Univ. (United States)

Published in SPIE Proceedings Vol. 9790:
Medical Imaging 2016: Ultrasonic Imaging and Tomography
Neb Duric; Brecht Heyde, Editor(s)

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