Wei-Ning Lee

Wei-Ning Lee
The University of Hong Kong | HKU · Department of Electrical and Electronic Engineering

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67
Publications
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Introduction
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Publications

Publications (67)
Conference Paper
Electrical impedance tomography (EIT) is a bio-medical imaging modality that has several clinical applications namely for human lungs. Yet, its relationship with gold standard lung diagnostic tools including spirometry is not available. In this study, simultaneous EIT and spirometry measurements were collected for 14 healthy subjects who performed...
Article
Objective: This study develops a biomedical ultrasound imaging method to infer microstructural information (i.e., tissue level) from imaging mechanical behavior of skeletal muscle (i.e., organ level). Methods: We first reviewed the constitutive model of skeletal muscle by regarding it as a transversely isotropic (TI) hyperelastic composite mater...
Article
Another type of natural wave, traced from longitudinal wall motion and propagation along the artery, is unprecedentedly observed in our in vivo human carotid artery experiments. We coin it as extension wave (EW) and hypothesize that EW velocity (EWV) is associated with arterial longitudinal stiffness. The EW is thus assumed to complement the PW, wh...
Article
Objective: Arterial wall deformation, stiffness, and luminal pressure are well-recognized predictors of cardiovascular diseases but intertwined. Establishing a relationship among these three predictors is therefore important for comprehensive assessment of the circulatory system, but very few studies focused on this. Methods: In this study, we f...
Article
The geometry and stiffness of a vessel are pertinent to blood dynamics and vessel wall mechanical behavior and may alter in diseased conditions. Ultrasound-based ultrafast Doppler (uDoppler) imaging and shear wave imaging (SWI) techniques have been extensively exploited for the assessment of vascular hemodynamics and mechanics. Their performance is...
Article
Full-text available
The heart is an organ with highly dynamic complexity, including cyclic fast electrical activation, muscle kinematics, and blood dynamics. Although ultrafast cardiac imaging techniques based on pulsed-wave ultrasound (PUS) have rapidly emerged to permit mapping of heart dynamics, they suffer from limited sonographic signal-to-noise ratio (SNR) and p...
Article
Studies of non-destructive bidirectional ultrasound assessment of non-linear mechanical behavior of the artery are scarce in the literature. We hereby propose derivation of a strain–shear modulus relationship as a new graphical diagnostic index using an ultrasound elastographic imaging framework, which encompasses our in-house bidirectional vascula...
Article
Guided wave imaging for the artery remains in its infancy in clinical practice mainly because of complex arterial microstructure, hemodynamics and boundary conditions. Despite the theoretically known potential effect of the surrounding medium on guided wave propagation in thin media in non-destructive testing, experimental evidence pertaining to th...
Article
We previously found that vascular guided wave imaging (VGWI) could non-invasively quantify transmural wall stiffness in both the longitudinal (r-z plane, 0°) and circumferential (r-θ plane, 90°) directions of soft hollow cylinders. Arterial stiffness estimation in multiple directions warrants further comprehensive characterization of arterial healt...
Article
Ultrafast ultrasound imaging using plane or diverging waves, instead of focused beams, has advanced greatly the development of novel ultrasound imaging methods for evaluating tissue functions beyond anatomical information. However, the sonographic signal-to-noise ratio (SNR) of ultrafast imaging remains limited due to the lack of transmission focus...
Article
Ultrafast ultrasound imaging using plane or diverging waves, not focused beams, has enabled quantitative assessment of biological tissue elasticity, kinematics, and hemodynamics beyond anatomical information in the past decade. However, its sonographic signal-to-noise ratio (SNR) and penetration depth are limited by insufficient energy delivery und...
Article
Plane-wave-based ultrafast imaging has become the prevalent technique for non-conventional ultrasound imaging. The image quality, especially in terms of the suppression of artifacts, is generally compromised by reducing the number of transmissions for a higher frame rate. We hereby propose a new ultrafast imaging framework that reduces not only the...
Article
Shear waveimaging has emerged as a potential non-invasive technique for the quantitative assessment of the arterial shear modulus. Nonetheless, the arterial elasticity estimation in the transverse direction has been overlooked compared with the longitudinal direction, and the estimated transmural stiffness has rarely been evaluated. Accurate depict...
Article
To use histotripsy safely, it is required to visualize the cavitation clouds and the lesion formation in real-time. Conventional ultrasound imaging (USI) is a good candidate for the real-time monitoring of the procedures. However, bubble clouds are not always clearly visible in vivo using USI because of flows, motion or high echogenicity of the tar...
Article
Estimation of tissue motion in the lateral direction remains a major challenge in 2-D ultrasound strain imaging (USI). Although various methodologies have been proposed to improve the accuracy of estimation of in-plane displacements and strains, the fundamental limitations of 2-D USI and how to choose optimal algorithmic parameters in various tissu...
Article
Full-text available
Objectives: The aim of this study was to investigate the potential of shear wave imaging (SWI), a novel ultrasound-based technique, to noninvasively quantify passive diastolic myocardial stiffness in an ovine model of ischemic cardiomyopathy. Background: Evaluation of diastolic left ventricular function is critical for evaluation of heart failur...
Article
Ultrasound tissue characterization is crucial for the detection of tissue abnormalities. Since the statistics of the backscattered ultrasound signals strongly depend on density and spatial arrangement of local scatterers, appropriate modeling of the backscattered signals may be capable of providing unique physiological information on local tissue p...
Article
Full-text available
Purpose: To determine the feasibility of two-dimensional (2D) ultrasonographic (US) strain imaging for quantifying and mapping mechanical behaviors of the median nerve, flexor retinaculum, and flexor tendons within the carpal tunnel in normal and carpal tunnel syndrome (CTS) disease states during active finger motion. Materials and methods: This...
Conference Paper
Strain compounding has been previously developed as an approach to reducing speckle noise. The technique is based on speckle de-correlation induced by different strain levels applied on the medium and has been demonstrated feasible in the human superficial soft tissues under external quasi-static compression. In this study, the efficacy of strain c...
Conference Paper
Full-text available
Diffusion Tensor Imaging (DTI) is a well-known MRI technique for the mapping of cardiac or neuronal fibers. In neuroscience, the mapping of the neuronal fibers network has enabled to better study the brain structures connectivity, their functions and their injuries. DTI has the potential to bring valuable in vivo clinical information about the loca...
Conference Paper
Full-text available
Carpal tunnel syndrome (CTS) is a common entrapment neuropathy. Nerve conduction studies (NCS) have been used as a standard for CTS diagnosis. Complementing NCS, ultrasound imaging provides anatomic information on pathologic changes of the median nerve, such as the reduced median nerve mobility. Motion of median nerve is dependent on mechanical cha...
Article
Full-text available
Monitoring the lesion formation induced by histotripsy has mainly relied on the quantitative change in backscatter intensity using ultrasound B-mode imaging. However, how the mechanical properties of the histotripsy-treated tissue region alter during the procedure is yet to be fully investigated. We thus proposed here to monitor such a therapeutic...
Article
Full-text available
We have previously proven the feasibility of ultrasound-based shear wave imaging (SWI) to non-invasively characterize myocardial fiber orientation in both in vitro porcine and in vivo ovine hearts. The SWI-estimated results were in good correlation with histology. In this study, we proposed a new and robust fiber angle estimation method through a t...
Article
The assessment of disrupted myocardial fiber arrangement may help to understand and diagnose hypertrophic or ischemic cardiomyopathy. We hereby proposed and developed shear wave imaging (SWI), which is an echocardiography-based, noninvasive, real-time, and easy-to-use technique, to map myofiber orientation. Five in vitro porcine and three in vivo o...
Data
Video clip of thoracolumbar fascia motion in human subject with LBP. Ultrasound B-scan acquired during passive trunk flexion induced by a motorized articulated table. Ultrasound transducer is placed longitudinally 2 cm from the midline at the level of the L2-3 interspace.
Data
Video clip of cumulative lateral shear strain map during one flexion cycle of the table. Red indicates shear strain toward the right (rostral) and blue indicates shear strain toward the left (caudal) (see color scales in Figure 5).
Data
Video clip of thoracolumbar fascia motion in human subject with No-LBP. Ultrasound B-scan acquired during passive trunk flexion induced by a motorized articulated table. Ultrasound transducer is placed longitudinally 2 cm from the midline at the level of the L2-3 interspace.
Data
Video clip of cumulative lateral displacement map during one flexion cycle of the table. Red indicates tissue displacement toward the right (rostral) and blue indicates tissue displacement or shear strain toward the left (caudal) (see color scales in Figure 5).
Article
Full-text available
Background: The role played by the thoracolumbar fascia in chronic low back pain (LBP) is poorly understood. The thoracolumbar fascia is composed of dense connective tissue layers separated by layers of loose connective tissue that normally allow the dense layers to glide past one another during trunk motion. The goal of this study was to quantify...
Article
Cardiovascular disease remains the primary killer worldwide. The heart, essentially an electrically driven mechanical pump, alters its mechanical and electrical properties to compensate for loss of normal mechanical and electrical function. The same adjustment also is performed in the vessels, which constantly adapt their properties to accommodate...
Article
Full-text available
Cardiac conduction abnormalities remain a major cause of death and disability worldwide. However, as of today, there is no standard clinical imaging modality that can noninvasively provide maps of the electrical activation. In this paper, electromechanical wave imaging (EWI), a novel ultrasound-based imaging method, is shown to be capable of mappin...
Article
Full-text available
The capability of currently available echocardiography-based strain estimation techniques to fully map myocardial abnormality at early stages of myocardial ischemia is yet to be investigated. In this study, myocardial elastography (ME), a radio-frequency (RF)-based strain imaging technique that maps the full 2D transmural angle-independent strain t...
Article
We have previously proposed a novel method for measuring arterial stiffness using shear wave imaging (SWI). In this study, we evaluate the performance of this method on a healthy population (N=30) and we compare it to local measurement of the arterial pulse wave velocity (PWV) achieved at the same arterial site using ultrafast imaging. Ultrafast im...
Article
The knowledge of the myocardial fiber architecture is deemed essential and yet to be nondestructively investigated for myocardial mechanics and its association with the progression of myocardial diseases. In this study, Supersonic Shear Wave Imaging (SSI) was performed for its first time to noninvasively assess the fiber orientation (i.e., anisotro...
Conference Paper
In contrast to other ultrasound-based strain imaging techniques, Myocardial Elastography (ME), developed by our group, is an ultrasound radio-frequency (RF)-based speckle tracking technique that aims at estimating and mapping transmural displacements and angle-independent strains in full echocardiographic views at high precision and high spatial an...
Conference Paper
Electromechanical Wave Imaging (EWI) has recently been introduced as a non-invasive, ultrasound-based imaging modality, which could map the electrical activation of the heart in various echocardiographic planes in mice, dogs and humans in vivo. By acquiring radio-frequency (RF) frames at very high frame rates (390-520Hz), the onset of small, locali...
Article
Two-dimensional myocardial elastography, an RF-based, speckle-tracking technique, uses 1-D cross-correlation and recorrelation methods in a 2-D search, and can estimate and image the 2-D transmural motion and deformation of the myocardium so as to characterize the cardiac function. Based on a 3-D finite-element (FE) canine left-ventricular model, a...
Article
Electromechanical Wave Imaging (EWI) has recently been introduced as a non-invasive, ultrasound-based imaging modality, which could map the electrical activation of the heart in various echocardiographic planes in mice, dogs and humans in vivo. By acquiring radio-frequency (RF) frames at very high frame rates (390-520Hz), the onset of small, locali...
Article
Full-text available
Electromechanical wave imaging (EWI) has recently been introduced as a noninvasive, ultrasound-based imaging modality, which could map the electrical activation of the heart in various echocardiographic planes in mice, dogs, and humans in vivo. By acquiring radio-frequency (RF) frames at very high frame rates (390-520 Hz), the onset of small, local...
Conference Paper
Full-text available
The objective of this study is to validate two-dimensional (2D) myocardial elastography estimates in canine hearts in vivo against direct sonomicrometry measurements at variable levels of myocardial ischemia induced by the occlusion of the left anterior descending (LAD) coronary artery. Two-dimensional myocardial elastography comprised transmural:...
Conference Paper
Vascular diseases (e.g., abdominal aortic aneurysm or, AAA) lead to changes in the regional aortic wall mechanical properties. Pulse-Wave Imaging (PWI) was previously developed by our group to map the pulse-wave propagation along the abdominal aorta of mice in vivo. In this study, the feasibility of PWI with real-time scanning is shown in human abd...
Article
High frame-rate ultrasound RF data acquisition has been proved to be critical for novel cardiovascular imaging techniques, such as high-precision myocardial elastography, pulse wave imaging (PWI), and electromechanical wave imaging (EWI). To overcome the frame-rate limitations on standard clinical ultrasound systems, we developed an automated metho...
Article
Myocardial elastography (ME), a radio-frequency (RF) based speckle tracking technique, was employed in order to image the entire two-dimensional (2D) transmural deformation field in full echocardiographic views and was validated against tagged magnetic resonance imaging (tMRI) in normal as well as reperfused (i.e., treated myocardial infarction [MI...
Article
Images of the propagation of an electromechanical wave (in red, denoted by the white arrows) along the posterior wall of a normal human left ventricle in a long axis view during systole are shown. The total time span of the wave propagation was 31 ms from a heart-beat total duration of 857 ms. ECG traces are not shown here, but are provided in the...
Article
The angle-independent myocardial elastography, which shows good performance in our proposed theoretical framework using a three-dimensional, ultrasonic image formation model based on well-established, 3D finite-element, canine, left-ventricular models in both normal and left-circumflex ischemic cases, is employed as well as validated in vivo to ass...
Conference Paper
Echocardiography is the most prevalent imaging modalities in clinical cardiology. However, current diagnostic techniques rely on qualitative image analysis, ignoring the quantitative data inherent to this modality. We seek to develop a quantitative system for analyzing echocardiographic images. In this study, the performance of myocardial elastogra...
Conference Paper
In this paper, two-dimensional angle-independent myocardial elastography (2DME) was employed in order to assess and image myocardial deformation (or, strains) in an entire left-ventricular view and was further validated against tagged magnetic resonance imaging (tMRI) in normal as well as abnormal human subjects. Both RF ultrasound and tMRI frames...
Conference Paper
The frame-rate of ultrasound radio-frequency (RF) data acquisition is critical for imaging of the pulse wave and electromechanical wave propagation in cardiovascular tissues as well as improving the strain estimation. Therefore, an automated method had been developed to overcome the frame-rate limitations on standard systems by retrospective multi-...
Conference Paper
In this paper, the requirement and optimization of the frame rate for myocardial elastography was investigated in normal mice and humans in vivo. Using a retrospective electrocardiogram (ECG) gating technique, the highest frame rate was 8 kHz and 481 Hz, respectively. Axial displacement and strain of myocardium were estimated using an RF speckle tr...
Article
Full-text available
Myocardial elastography (ME), a radio frequency (RF)-based speckle tracking technique with one-dimensional (1-D) cross correlation and novel recorrelation methods in a 2-D search was proposed to estimate and fully image 2-1) transmural deformation field and to detect abnormal cardiac function. A theoretical framework was first developed in order to...
Article
Full-text available
Robust indices of regional and global cardiac function are a key factor in detection and treatment of heart disease as well as understanding of the fundamental mechanisms of a healthy heart. Myocardial elastography provides a noninvasive method for imaging and measuring displacement and strain of the myocardium for the early detection of cardiovasc...
Conference Paper
Full-text available
In this paper, myocardial elastography (ME), a radio-frequency (RF) based speckle tracking technique, was employed in order to assess the contractility of a myocardium, and validated against tagged magnetic resonance imaging (tMRI) in vivo in normal as well as abnormal cases. Both RF ultrasound and tMRI frames were acquired in 2D short-axis (SA) vi...
Article
Full-text available
Several methods have been introduced in the past few years to quantify left-ventricular strain in order to detect myocardial ischemia and infarction. Myocardial Elastography is one of these methods, which is based on ultrasound Radio-Frequency (RF) signal processing at high frame rates for the highest precision and resolution of strain estimation....
Conference Paper
Full-text available
Ultrasound Myocardial Elastography (UME) and Tagged Magnetic Resonance Imaging (tMRI) are two imaging modalities that were developed in the recent years to quantitatively estimate the myocardial deformations. Tagged MRI is currently considered as the gold standard for myocardial strain mapping in vivo. However, despite the low SNR nature of ultraso...
Conference Paper
In this paper, we investigate the elevational beamwidth and the extent of 3D decorrelation on 3D motion estimation of multiple short-axis slices under a previously established theoretical framework, which simulated two sequences, including passive filling and active contraction, in normal and ischemic canine finite-element (FE) left ventricular mod...
Article
The main purpose of this paper is to develop a theoretical tool in order to fundamentally characterize the performance of Myocardial Elastography and identify the optimal parameters to be used for the more reliable detection of ischemia or infarction. A complete representation of the left-ventricular function throughout an entire cardiac cycle was...
Article
Abstract—A current ,limitation of the ,implementation ,of myocardial elastography in a clinical setting is the difficulty of interpreting the one-dimensional strain maps ,due to varying strain values in the wall of the left ventricle (LV). In this paper, wedemonstrate,a robust ,angle-independent method ,for 2D myocardial elastography on simulated 2...
Article
An efficient speckle tracking algorithm is proposed for motion estimation in ultrasonic imaging. Speckle tracking involves a matching process and a searching process. The matching process of the proposed algorithm is based on a Block Sum Pyramid algorithm that significantly reduces the computational complexity while maintaining the same accuracy as...

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