| 1. |
- Chintada, Bhaskara R., et al.
(författare)
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Phase-Aberration Correction in Shear-Wave Elastography Imaging Using Local Speed-of-Sound Adaptive Beamforming
- 2021
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Ingår i: Frontiers in Physics. - : Frontiers Media S.A.. - 2296-424X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Shear wave elasticity imaging (SWEI) is a non-invasive imaging modality that provides tissue elasticity information by measuring the travelling speed of an induced shear-wave. It is commercially available on clinical ultrasound scanners and popularly used in the diagnosis and staging of liver disease and breast cancer. In conventional SWEI methods, a sequence of acoustic radiation force (ARF) pushes are used for inducing a shear-wave, which is tracked using high frame-rate multi-angle plane wave imaging (MA-PWI) to estimate the shear-wave speed (SWS). Conventionally, these plane waves are beamformed using a constant speed-of-sound (SoS), assuming an a-priori known and homogeneous tissue medium. However, soft tissues are inhomogeneous, with intrinsic SoS variations. In this work, we study the SoS effects and inhomogeneities on SWS estimation, using simulation and phantoms experiments with porcine muscle as an abbarator, and show how these aberrations can be corrected using local speed-of-sound adaptive beamforming. For shear-wave tracking, we compare standard beamform with spatially constant SoS values to software beamforming with locally varying SoS maps. We show that, given SoS aberrations, traditional beamforming using a constant SoS, regardless of the utilized SoS value, introduces a substantial bias in the resulting SWS estimations. Average SWS estimation disparity for the same material was observed over 4.3 times worse when a constant SoS value is used compared to that when a known SoS map is used for beamforming. Such biases are shown to be corrected by using a local SoS map in beamforming, indicating the importance of and the need for local SoS reconstruction techniques.
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| 2. |
- Chintada, Bhaskara R, et al.
(författare)
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Time Of Arrival Delineation In Echo Traces For Reflection Ultrasound Tomography
- 2021
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Konferensbidrag (refereegranskat)abstract
- Ultrasound Computed Tomography (USCT) is an imaging method to map acoustic properties in soft tissues, e.g., for the diagnosis of breast cancer. A group of USCT methods rely on a passive reflector behind the imaged tissue, and they function by delineating such reflector in echo traces, e.g., to infer time-of-flight measurements for reconstructing local speed-of-sound maps. In this work, we study various echo features and delineation methods to robustly identify reflector profiles in echos. We compared and evaluated the methods on a multi-static data set of a realistic breast phantom. Based on our results, a RANSAC based outlier removal followed by an active contours based delineation using a new “edge” feature we propose that detects the first arrival times of echo performs robustly even in complex media; in particular 2.1 times superior to alternative approaches at locations where diffraction effects are prominent.
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