Transcostal imaging with large coherent apertures: Ex vivo studies

Jakovljevic, Marko; Kumar, Shalki; Kuo, Lily; Trahey, Gregg E.

doi:10.1109/ultsym.2014.0421

Cited by 3 publications

(2 citation statements)

References 9 publications

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“…The Siemens ACUSON SC2000 ultrasound system (Siemens Medical Solutions USA, Inc., Mountain View, CA) and 4Z1c volumetric transducer (0.4 mm pitch, 1.92 cm × 1.44 cm aperture) were used with a custom imaging sequence to collect sub-aperture receive channel I/Q data for 3×3 element groups across the lateral and elevation extents of the array [29]. Acquired data were stored with corresponding transducer positions for offline processing.…”

Section: Methodsmentioning

confidence: 99%

Feasibility of Swept Synthetic Aperture Ultrasound Imaging

Bottenus

Long

Zhang

et al. 2016

IEEE Trans. Med. Imaging

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Ultrasound image quality is often inherently limited by the physical dimensions of the imaging transducer. We hypothesize that, by collecting synthetic aperture data sets over a range of aperture positions while precisely tracking the position and orientation of the transducer, we can synthesize large effective apertures to produce images with improved resolution and target detectability. We analyze the two largest limiting factors for coherent signal summation: aberration and mechanical uncertainty. Using an excised canine abdominal wall as a model phase screen, we experimentally observed an effective arrival time error ranging from 18.3 ns to 58 ns (root-mean-square error) across the swept positions. Through this clutter-generating tissue, we observed a 72.9% improvement in resolution with only a 3.75 dB increase in side lobe amplitude compared to the control case. We present a simulation model to study the effect of calibration and mechanical jitter errors on the synthesized point spread function. The relative effects of these errors in each imaging dimension are explored, showing the importance of orientation relative to the point spread function. We present a prototype device for performing swept synthetic aperture imaging using a conventional 1-D array transducer and ultrasound research scanner. Point target reconstruction error for a 44.2 degree sweep shows a reconstruction precision of 82.8 μm and 17.8 μm in the lateral and axial dimensions respectively, within the acceptable performance bounds of the simulation model. Improvements in resolution, contrast and contrast-to-noise ratio are demonstrated in vivo and in a fetal phantom.

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Section: Methodsmentioning

confidence: 99%

Feasibility of Swept Synthetic Aperture Ultrasound Imaging

Bottenus

Long

Zhang

et al. 2016

IEEE Trans. Med. Imaging

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“…We have recently developed a method to detect elements blocked by ribs, and we have measured the resulting image degradation in vivo and ex vivo. 4,5 In the following, we adaptively weight the non-blocked elements to recover the system response in k-space and compensate for the loss of focus quality while imaging with large apertures ex vivo.…”

Section: Introductionmentioning

confidence: 99%

Detection of and compensation for blocked elements using large coherent apertures: ex vivo studies

et al. 2016

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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.

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