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Tumor growth requires formation of new angiogenic vessels, 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 following an intravenous injection of ultrasound contrast agent: assessment of perfusion...
In most studies on vascular shear wave imaging (SWI), longitudinal section is mainly concerned, and the radial motion and reflected waves are not considered in cross section. It is important to investigate the SWI in cross section when evaluating the anisotropy of the vessel wall or the complete plaque composition. In our previous study, a novel method based on coordinate transformation and directional...
Ultrasonic guided wave inspection has been in use for more than two decades. Its main advantage is that large sections of pipes can rapidly be screened. However, large area coverage comes at the cost of reduced resolution. Higher resolution can be achieved at higher frequencies-thickness products (> 300 kHz∗mm in steel), where more wave modes are excited; however, this makes the received signals...
Electromagnetic [1] and acoustic [2] metamaterials that exhibit linear dispersion at a nonzero frequency and a wave vector (k) of zero, leading to a conical dispersion surface or so-called Dirac cone dispersion, have been demonstrated recently. These materials display unusual behavior associated with the occurrence of a finite group velocity at k = 0, leading to a wave which propagates with a uniform...
Recently we demonstrated non-contact excitation of broadband mechanical waves in soft media for transient elastography. Using US from an air-coupled transducer focused on an air/medium interface, this method (called “acoustic micro-tapping”, or AμT) provides sufficient radiation force to launch a transient displacement. Combined with ultrafast phase sensitive OCT, AμT-OCT can track propagating mechanical...
Suppression of the SH-SAW response is mandatory to design TC SAW devices on θ degree rotated Y-cut LiNbO3. However, it is not easy because K2 for SH SAW changes rapidly with θ, and its optimal value in terms of the SH-SAW suppression is dependent on electrode and SiO2 thicknesses. The authors found that the optimal θ always locates close to θ where difference in velocities of two SAWs is minimum....
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...
Measuring a magnetic field by pulsing electrical current through a wire placed in the magnetic field, followed by measuring the displacement of the wire as a travelling wave passes a displacement sensor, is a technique typically referred to as a pulsed wire measurement. The goal of these measurements is to extract the magnetic field distribution of the magnet from the time dependent wire displacement...
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...
Type I Lamb wave modes exhibit a strong affinity toward multimode behavior, especially the high-transduction-efficiency modes: S0 and S1 mode. Apodization, the standard technique to suppress the transverse modes for IDT-excited resonators, suffers from drawbacks such as additional loss and reduction of the effective coupling coefficient (k2eff). Most Lamb wave modes in AlN show a positive slope in...
The concept of the band structure is central to the field of phononic crystals. Indeed, capturing the dispersion of Bloch waves — the eigenmodes of propagation in periodic media — gives invaluable information on allowed propagation modes, their phase and group velocities, local resonances, and band gaps. Band structures are usually obtained by solving an eigenvalue problem defined on a closed and...
The estimation of Ultrasound-Contrast-Agent (UCA) kinetics from Dynamic Contrast-Enhanced Ultrasound (DCE-US) recordings has shown promise to localize prostatic malignancy. In a two-dimensional (2D) approach, UCA dispersion and velocity provide a characterization of the prostate (micro)vasculature with diagnostic value [1]. To this end, the UCA transport kinetics are modelled with strong assumptions...
Quasi-collinear type of acousto-optic (AO) diffraction by bulk acoustic waves (BAW) is widely used for high-resolution tunable optical filters and dispersive delay lines for ultrashort laser pulse shaping. Most often, quasi-collinear paratellurite (TeO2) AO filters are used due to high AO figure of merit of this material (V. Molchanov et al. Quant. Electron. 39:353, 2009). Lithium niobate (LN, LiNbO...
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...
Accurate measurement of acoustic dispersion has important applications in theoretical acoustics, ultrasound tissue characterization, ultrasound measurement systems, etc. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this work is focused on the study of the variation in the propagation...
Ultrasound shear wave elastography is a well established tool for characterization of biologic tissues. While it has found applications in various medical disciplines such as oncology and urology its feasibility for pneumology still has to be shown. We provide experimental results of ultrasound shear wave elastography of soft porous materials in phantoms. Shear wave dispersion and evidence of the...
This article is focused on the characterization of the lack of homogeneity in the dispersive acoustic properties of polymeric materials used in industrial pipes. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this paper, studies the variation in the propagation velocity, as a...
A method for measurement of the bladder wall nonlinear elasticity is presented. The method is based on acoustoelasticity modeling of the bladder tissue modulus of elasticity changes at different volumetric loading levels. At each loading volume, tissue strain is obtained from the real-time images. Using acoustic radiation force, a transient Lamb wave is excited on the bladder wall and shear elasticity...
The propagation of the S0 Lamb mode in AlN membrane combined with continuous and structured SiO2 thin films is theoretically studied with respect of the materials geometrical parameters and electrical boundaries conditions. A comparison is made in terms of the phase velocity, electromechanical coupling coefficient and temperature coefficients of frequency (TCF) between the studied structures. The...
A mathematical model to predict the ultrasonic attenuation coefficient as a function of frequency in cortical bone is proposed, and the effects of micro-architectural changes on model parameters are studied in this work. Spectroscopy was performed in numerical finite differences time domain simulations to study the individual effects of pore diameter on ultrasonic attenuation. The attenuation coefficient...
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