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Intrauterine growth restriction (IUGR) is an anomaly of fetal growth dynamics, which is mainly caused by alterations in the vascular remodeling of utero-placental arteries. With a prevalence of 10% of pregnancies, IUGR remains the leading cause of perinatal mortality. Doppler velocimetry is the common screening tool for IUGR but this imaging modality remains controversial. In this context, we evaluated...
We have recently demonstrated the feasibility of vascular guided wave imaging (VGWI) in non-invasive estimation of bi-plane (i.e., longitudinal and transverse) transmural arterial Young's modulus (ELV, ETV) in tubular phantoms using phase velocity (cph) (Guo et al., ITEC 2016). In this study, we further compare the ETV estimated from the circumferential Lamb type (CLT) wave by VGWI with ETP from the...
Carotid plaque vulnerability is difficult to characterize from B-mode ultrasound imaging alone. However, elastographic characterization of plaque mechanical properties may aid in the assessment of vulnerability. As an initial step to understand the complex wave propagation that can occur in plaques, we have developed simulation models that incorporate different shear moduli (μ) of the arterial wall,...
Ultrasound imaging of blood flow in the coronary arteries is hampered by small vessel diameters and rapid myocardial motion. This combination makes clutter suppression challenging, resulting in flashing artefacts and signal dropouts. This work investigates whether high frame-rate 3D ultrasound imaging in conjunction with eigen-based clutter filtering can be used to mitigate these problems, making...
Spectroscopic photoacoustic (sPA) can estimate blood oxygen saturation (SO2), which has been shown to correlate with hypoxia, and therefore could improve cancer diagnosis and treatment monitoring. However, accurate quantification of SO2 is often not straightforward as local fluence varies significantly at depth due to wavelength-dependent optical scattering and absorption. Additionally, assessing...
Dysfunctions on the coronary circulation can lead to adverse and severe clinical outcomes, e.g., ischemic heart failure (IHF) or coronary artery disease (CAD). The evaluation of coronary vasculature is consequently of extreme importance to the diagnosis of these conditions. However, intramyocardial coronary vasculature cannot yet be imaged in-vivo in humans with current angiography techniques or transthoracic...
Angiogenic vasa vasorum (VV) is an important marker for atherosclerotic plaque progression and vulnerability. However, current in vivo imaging of tiny VV near a major vessel is limited. The super-resolution ultrasound imaging (SRI) can be a promising candidate. Microbubbles (MBs) localization technique for common SRI excludes signals from densely distributed MBs, requiring a large number of frames,...
Several challenges limit the use of Pulsed Wave (PW) Doppler to assess blood flow in the coronary arteries. The transit time effect causes spectral broadening in regions with high blood velocities such as coronary stenoses, leading to overestimation of maximum velocities. In this work we use a modified commercial 3D ultrasound imaging system to perform trans-thoracic, 3D high frame-rate imaging of...
In vivo measurement of the mechanical properties of thin-walled soft tissues (e.g., mitral valve, artery and bladder) and in situ mechanical characterization of thin-walled artificial soft biomaterials in service are of great challenge. Those thin-walled structures are usually pre-stressed to achieve and/or improve their functional performance, which further complicate the inverse analysis to identify...
Our group has previously demonstrated that lower shear rate in the pulsatile blood flow yields greater red blood cell (RBC) aggregation which in turn results in a higher oxygen saturation (sO2) level and a higher photoacoustic (PA) signal. Higher shear rates led to disaggregation thereby decreasing the PA signal amplitude and the sO2. These results suggest that the interrelationship between the sO...
Quantification of local arterial wall elasticity may assist in differentiating lipid rich rupture prone atherosclerotic plaques from stable fibrous plaques. Because lipid cores can be present anywhere along the circumference, we focus on developing a noninvasive shear wave elastography technique for transverse carotid cross-sections. Tracking the induced wave is not trivial because the circular geometry...
Changes in the biomechanical functions of artery serve as important indicators for prediction of cardiovascular disease. One of the challenges of the ultrasonic arterial measurement is the compression of the artery due to the weight of a conventional ultrasound probe employed and/or undesired probe motion, resulting in artifacts on the measurement results. An approach to address this issue with a...
Intravascular ultrasound (IVUS) has frequently been used by the cardiologist to diagnose atherosclerosis and guide the interventional procedures. IVUS has gained widely clinical acceptance over the past twenty years because of its superior capability to assess plaque burden and monitor artery remodeling, which also makes it as the irreplaceable image modality for most innovative multimodality intravascular...
In order to generate trackable shear waves in soft tissues, transmitted pulses in shear wave elastography (SWE) are longer than conventional clinical ultrasound pulses. Nevertheless, they typically obey mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as acoustic radiation (ARF)-induced stresses and strain rates could potentially affect the arterial...
Changes in the biomechanical functions of artery serve as important indicators for prediction of cardiovascular disease. Endothelial dysfunction is known to play a role to develop atherosclerosis and cardiovascular disease. Ultrasound measurement of flow-mediated dilation of the brachial artery is a method to quantify endothelial function based on changes in arterial diameter. One challenge of the...
Early detection and diagnosis of high-risk or vulnerable plaques can reduce the death rate attributable to atherosclerosis. Many attempts to identify atherosclerosis plaques have focused on in vivo imaging techniques. An animal model with foregone plaque sites will be valuable to evaluate the validity of imaging method. Based on the “response-to-injury” hypothesis, lesions in the artery's endothelium...
In shear wave elastography (SWE), acoustic radiation forces (ARF) are employed to generate shear waves within the tissue. Although the transmitted pulses are longer than those in conventional clinical ultrasound, they typically obey the mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as ARF-induced stresses and strain rates could potentially...
With its thickness decreasing down to 60 μm, the (K0.45Na0.55)0.96Li0.04NbO3 (KNLN) single crystals maintains superior piezoelectric constant (d33 = 675 pC N−1). In combination with a 200 μm core multimode fiber, the successful fabrication of a tiny intravascular photoacoustic probe with a 1 mm outside diameter is achieved. The intravascular photoacoustic imaging of the atherosclerotic lesion of a...
Doppler measurements in coronary arteries are difficult due to rapid motion of the myocardium and small vessel dimensions. High frame rate 3D Doppler imaging with retrospective spectral Doppler processing could potentially solve this. However, the combination of low blood flow velocities and excessive tissue motion in parts of the cardiac cycle makes clutter suppression challenging. In the present...
Clinically used Intravascular Ultrasound (IVUS) imaging majorly operates in the 20∼40MHz range, providing resolution on the order of 100μm. Recent reports showed the potential of higher frequency (60–80MHz) of IVUS improving resolution to the level of 30–60μm, but still inferior to the resolution of OCT (10μm). Whether increasing the working frequency a step further could make IVUS comparable to OCT?...
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