A Deep Learning Approach to Resolve Aliasing Artifacts in Ultrasound Color Flow Imaging

Nahas, Hassan; Au, Jason S.; Ishii, Takuro; Yiu, Billy Y. S.; Chee, Adrian J. Y.; Yu, Alfred C. H.

doi:10.1109/tuffc.2020.3001523

Cited by 26 publications

(28 citation statements)

References 39 publications

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“…It depends on an input variable that sometimes had to be adjusted manually. To make the dealiasing fully automatic, we will also resort to deep learning (Nahas et al, 2020). We will then have a ready-to-use iVFM software package for clinical routine purposes.…”

Section: Improvements To the Latest Version Of The Ivfmmentioning

confidence: 99%

Physics-constrained intraventricular vector flow mapping by color Doppler

Vixège¹,

Bérod²,

Sun³

et al. 2021

Phys. Med. Biol.

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Color Doppler by transthoracic echocardiography creates two-dimensional fan-shaped maps of blood velocities in the cardiac cavities. It is a one-component velocimetric technique since it only returns the velocity components parallel to the ultrasound beams. Intraventricular vector flow mapping (iVFM) is a method to recover the blood velocity vectors from the Doppler scalar fields in an echocardiographic three-chamber view. We improved our iVFM numerical scheme by imposing physical constraints. The iVFM consisted in minimizing regularized Doppler residuals subject to the condition that two fluid-dynamics constraints were satisfied, namely planar mass conservation, and free-slip boundary conditions. The optimization problem was solved by using the Lagrange multiplier method. A finite-difference discretization of the optimization problem, written in the polar coordinate system centered on the cardiac ultrasound probe, led to a sparse linear system. The single regularization parameter was determined automatically for non-supervision considerations. The physics-constrained method was validated using realistic intracardiac flow data from a patient-specific CFD (computational fluid dynamics) model. The numerical evaluations showed that the iVFM-derived velocity vectors were in very good agreement with the CFD-based original velocities, with relative errors ranged between 0.3 and 12%. We calculated two macroscopic measures of flow in the cardiac region of interest, the mean vorticity and mean stream function, and observed an excellent concordance between physics-constrained iVFM and CFD. The capability of physics-constrained iVFM was finally tested with in vivo color Doppler data acquired in patients routinely examined in the echocardiographic laboratory. The vortex that forms during the rapid filling was deciphered. The physics-constrained iVFM algorithm is ready for pilot clinical studies and is expected to have a significant clinical impact on the assessment of diastolic function.

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Section: Improvements To the Latest Version Of The Ivfmmentioning

confidence: 99%

Physics-constrained intraventricular vector flow mapping by color Doppler

Vixège¹,

Bérod²,

Sun³

et al. 2021

Phys. Med. Biol.

View full text Add to dashboard Cite

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“…Furthermore, although the proposed method uses the repeated transmit sequence, it still suffers from aliasing. Investigations on increasing the detectable velocity [26][27][28][29] would be preferable to expand the applicability of the proposed method.…”

Section: Discussionmentioning

confidence: 99%

Measurement of flow velocity vectors in carotid artery using plane wave imaging with repeated transmit sequence

et al. 2021

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Purpose Doppler-based methods are widely used for blood flow imaging in clinical settings. However, they inherently estimate the velocity component only in the axial direction. Therefore, various studies of angle-independent methods have been conducted. The multi-angle Doppler method is one such angle-independent method, in which the velocity vector is estimated using axial velocities obtained from multiple directions by steering an ultrasonic beam. Recently, plane wave imaging, which realizes a very high frame rate of several thousand frames per second, was applied to the multi-angle Doppler method. However, the maximum detectable velocity, i.e., the aliasing limit, was reduced depending on the number of steering angles. In the present study, the feasibility of a specific transmit sequence, namely, the repeated transmit sequence, was examined using the plane-wave multi-angle Doppler method. Method In the repeated transmit sequence, plane waves were emitted to the same direction twice, after which the steering angle was changed. By repeating the same procedure, a pair of beamformed radio-frequency (RF) signals could be obtained under each beam steering angle. By applying the autocorrelation method to each pair of RF signals, the time interval between the RF signals could be kept as the pulse repetition interval (PRI). The feasibility of such a transmit sequence was examined by numerical simulation and in vivo measurement of a human carotid artery. ResultsThe simulation results showed that the maximum steering angles of over 10 degrees were not feasible with the linear array used in the present study. The feasible maximum steering angle would depend on the element pitch of the probe relative to the ultrasonic wavelength. By limiting the maximum steering angles to 5 and 10 degrees, bias errors were 9.2% and 11.3%, respectively, and root mean squared errors were 21.5% and 16.9%, respectively. Also, flow velocity vectors in a human carotid artery could be visualized with the proposed method. ConclusionThe multi-angle Doppler method was implemented in plane wave imaging with the repeated transmit sequence, and the proposed method was shown to be feasible through numerical simulation and in vivo measurement of a carotid artery.

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“…It depends on an input variable that sometimes had to be adjusted manually. To make dealiasing fully automatic, we will resort to deep learning (Nahas et al 2020). In our study, the endocardial segmentation was performed manually for the analysis of the clinical cases.…”

Section: What Still Needs To Be Donementioning

confidence: 99%

Full-volume three-component intraventricular vector flow mapping by triplane color Doppler

Vixège¹,

Bérod²,

Courand³

et al. 2022

Phys. Med. Biol.

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Objective. Intraventricular vector flow mapping (iVFM) is a velocimetric technique for retrieving two-dimensional velocity vector fields of blood flow in the left ventricular cavity. This method is based on conventional color Doppler imaging, which makes iVFM compatible with the clinical setting. We have generalized the iVFM for a three-dimensional reconstruction (3D-iVFM). Approach. 3D-iVFM is able to recover three-component velocity vector fields in a full intraventricular volume by using a clinical echocardiographic triplane mode. The 3D-iVFM problem was written in the spherical (radial, polar, azimuthal) coordinate system associated to the six half-planes produced by the triplane mode. As with the 2-D version, the method is based on the mass conservation, and free-slip boundary conditions on the endocardial wall. These mechanical constraints were imposed in a least-squares minimization problem that was solved through the method of Lagrange multipliers. We validated 3D-iVFM in silico in a patient-specific CFD (computational fluid dynamics) model of cardiac flow and tested its clinical feasibility in vivo in patients and in one volunteer. Main results. The radial and polar components of the velocity were recovered satisfactorily in the CFD setup (correlation coefficients, r = 0.99 and 0.78). The azimuthal components were estimated with larger errors (r = 0.57) as only six samples were available in this direction. In both in silico and in vivo investigations, the dynamics of the intraventricular vortex that forms during diastole was deciphered by 3D-iVFM. In particular, the CFD results showed that the mean vorticity can be estimated accurately by 3D-iVFM. Significance. Our results tend to indicate that 3D-iVFM could provide full-volume echocardiographic information on left intraventricular hemodynamics from the clinical modality of triplane color Doppler.

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A Deep Learning Approach to Resolve Aliasing Artifacts in Ultrasound Color Flow Imaging

Cited by 26 publications

References 39 publications

Physics-constrained intraventricular vector flow mapping by color Doppler

Physics-constrained intraventricular vector flow mapping by color Doppler

Measurement of flow velocity vectors in carotid artery using plane wave imaging with repeated transmit sequence

Full-volume three-component intraventricular vector flow mapping by triplane color Doppler

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