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In this paper, we describe a 920 MHz band long range wireless SAW passive tag system (WSPTS) for vibration monitoring, which achieves more than 10m reading distance. For the purpose of structural health monitoring (SHM) of aging infrastructures (e.g. bridge, building, and so forth), passive wireless sensor systems are an attractive option because they are operated battery-less and almost maintenance...
The pulse-echo method based on transmission of an ultrasonic pulse and time-of-flight determination of a reflected echo is one of the typical methods of ultrasonic distance measurement. To improve the SNR of the reflected echo, pulse compression using an M-sequence is employed in the pulseecho method. In the case of a moving object, however, the echo is modulated owing to the Doppler effect The Doppler-shifted...
Carotid plaque rupture is a primary cause of ischemic strokes and transient ischemic attacks (TIAs). Probability of stroke and TIAs depend on the mechanical stability of plaque. Ultrasound strain can provide a non-invasive assessment of plaque stiffness to assess mechanical stability. We report on ultrasound strain indices from multiple regions of interest (ROI) in plaque as biomarkers for plaque...
The Delay-Multiply-And-Sum (DMAS) beamformer has recently been presented in the context of medical ultrasound image formation. Images obtained with the DMAS beamformer present improved contrast resolution and noise rejection when compared to images obtained with the standard Delay-And-Sum (DAS) beamformer. We study here the signal statistics for a homogeneous medium using both the DAS and DMAS beamformers...
Color Doppler and Vector Flow imaging are ultrasound imaging modalities that are primarily used for qualitative measurements or navigation. One main challenge before these modalities can be used quantitatively in clinical applications, is that clutter suppression filters or residual clutter signal lead to bias and variance in the blood velocity estimates which varies throughout the cardiac cycle....
Time delay estimation using cross correlation between successive RF lines is an established method to estimate tissue velocity. We have applied this method on our system using 10 MHz transducers sutured to the epicardium to measure the myocardial contraction pattern at high spatial and temporal resolution. In this setup, the myocardial tissue velocity will generally increase with the depth, as the...
Stroke is commonly caused by thromboembolic events originating from a ruptured carotid plaque. Histological studies have shown that plaque rupture potential is related to plaque composition rather than degree of stenosis. The use of Acoustic Radiation Force Impulse (ARFI) ultrasound imaging has enabled assessment of carotid plaque composition and structure. In particular, a previous study has shown...
In this paper, we describe a 920 MHz band long range wireless SAW passive tag system (WSPTS) for vibration monitoring, which achieves more than 15 m reading distance. For the purpose of structural health monitoring (SHM) of aging infrastructures (e.g. bridge, building, and so forth), passive wireless sensor systems are an attractive option because they are operated battery-less and almost maintenance...
Myocardial deformation imaging at a high frame rate (HFR) has the potential to gain new insights in cardiac mechanics by resolving short-lived mechanical events during the cardiac cycle. In order to achieve such high frame rate, our lab recently proposed to combine multi-line transmit with ‘anatomical imaging’ i.e. imaging only the anatomically relevant spatial domain (e.g. the myocardium). Although...
Abnormal biomechanical properties of the myocardium, such as increased passive stiffness, prevent the heart of patients with diastolic heart failure to completely relax during diastole. Therefore, non-invasively measuring the stiffness is of importance. In this study, we used shear wave propagation velocities as a measure of stiffness of a thin plate phantom. We tested the applicability of a spatio-temporal...
Tumor growth requires angiogenesis and neovascularization, resulting in the formation of microvessels which differ in their morphology from those of healthy tissue. These vascular abnormalities result in altered blood flow dynamics, which can be assessed by dynamic contrast-enhanced ultrasound (DCE-US). Two distinct approaches are typically employed in DCE-US: the assessment of either perfusion or...
Whereas the use of flow diverter stents (FDs) represents a powerful treatment alternative to surgical clipping of intracranial aneurysms (IAs) presenting at arterial bifurcations, endovascular deployment of FDs often involves the jailing of daughter vessels (DV), and can affect the patency of the jailed DV.
Strain imaging is gaining traction as a means to assess cardiac function by tracking the cyclic deformation of the myocardium. Compared to traditional measures such as ejection fraction, global myocardial strain has been shown to be an earlier and more sensitive measure of overall ventricular function. Similarly, regional myocardial strain has been shown to be useful for identifying ischemia and myocardial...
There are two generally used ultrasonic approaches to extract sets of quantitative parameters: the Lizzi-Feleppa (LF) and quantitative ultrasound (QUS) approaches. The LF approach estimates LF parameters from the linear fit of the backscatter coefficient (BSC), and yields slope, intercept and midband. The QUS approach relies on the attenuation coefficient (AC) and BSC versus frequency, and yields...
Ultrafast ultrasound imaging provides investigators with the possibility of imaging events using thousands of frames/sec. With the success of ultrafast ultrasound imaging across a wide variety of disciplines, we now explore the ability of ultrafast imaging to capture spinal vibrations for non-invasive spinal testing in living subjects. Previous work has shown that invasive accelerometer-based methods...
Quantitative ultrasound parameter estimates from the Lizzi-Feleppa (LF slope, intercept and midband) and quantitative ultrasound (mean BSC, mean AC, ESD and EAC) approaches were compared for in vivo and ex vivo mouse liver fat content monitoring. The quantitative ultrasound parameters having the higher correlations with fat content were EAC (R2=0.68), mean BSC (R2=0.60), mean AC (R2=0.60) and LF midband...
High-intensity focused ultrasound (HIFU) is increasingly getting in focus of interest for polymer layer joining (Liebler 2008). Previous studies investigated the heating effect in polymer materials induced by HIFU with liquid sound conductor (Bo Liu et al. 2013) and with solid sound conductor (Oehm et al. 2016). An improved understanding of the physical mechanisms of HIFU to heat thin polymer layers,...
Grain-boundary scattering of acoustic waves in polycrystalline materials is studied with analytical and numerical methods in the presented paper. In particular, the attenuation of Surface Acoustic Waves (SAWs) propagating through a polycrys-talline microstructure is investigated. A three dimensional timedomain finite-element method (FEM) is utilized for the numerical simulation, whereby the granular...
Subharmonic aided pressure estimation (SHAPE) uses ultrasound contrast agents (UCAs) to estimate hydrostatic pressure by transmitting at one frequency, receiving at its subharmonic frequency and then monitoring the subharmonic amplitude variations. The subharmonic response of the UCAs has an inverse linear relationship with the ambient pressure. In order to optimize SHAPE, we studied the impact of...
Carotid plaque rupture is a primary cause of ischemic strokes and transient ischemic attacks (TIAs). Probability of stroke and TIAs depend on the mechanical stability of plaque. Ultrasound based Lagrangian carotid strain imaging (LCSI) can provide a non-invasive assessment of plaque stiffness to assess mechanical stability. We report on ultrasound strain indices from multiple regions of interest (ROI)...
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