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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...
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....
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...
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...
Dispersive materials are commonly used in the manufacture of transducer wedges and pipes. Focusing on Clamp-on ultrasonic flowmeters, the incident angle is not normal to the pipe surface and a coupling wedge is necessary. In dispersive materials, the propagation velocity depends on the frequency. Therefore, when the excitation signal contain several frequential components, according to Snell's law,...
In chronic hepatitis diagnosis, shear wave elastography is utilized for evaluating fibrosis progression. It is expected that the accuracy will be improved by measuring the viscosity in addition to the elasticity. However, the shear wave dispersion in analyzing liver viscosity is affected by both viscosity and fibrous structure. In order to quantitatively evaluate hepatic fibrosis, we evaluated the...
Pathological processes in soft tissues cause changes in mechanical properties. Elastography methods have emerged to make quantitative measurements of the shear modulus or shear wave speed (SWS) as a noninvasive way to provide diagnostic information. In an effort to standardize ultrasound-based measurements of SWS, the Radiological Society of North America Quantitative Imaging Biomarkers Alliance (RSNA...
The backward waves with opposite directions of energy transport and phase velocity are in the focus of current studies in physics. Besides they are of interest for possible technical applications. This type of wave motion was previously studied in acoustics mainly in the case of Lamb modes. Nevertheless, shear-horizontal (SH) plate modes, as known, can also be backward waves if the plates are piezoelectric...
The attenuation of ultrasound in soft tissue follows a frequency-dependent power law. As an alternative to the time-fractional partial differential equations that describe power law attenuation and dispersion, Treeby and Cox derived a space-fractional model that accounts for both power law attenuation and dispersion. The Treeby-Cox space-fractional wave equation is convenient for simulations with...
Elasticity values reported by shear wave elastography techniques for Breast tissue/mass are a combination of elasticity and viscosity at the frequency with peak shear wave energy; thus, resulting in overestimation of tissue elasticity. To better estimate shear elasticity and to understand the role of shear viscosity in suspicious breast masses at different frequencies, the frequency dispersion of...
Ultrasound shear wave imaging has been extensively studied in thin tissues, such as the artery and cornea. The dispersion analysis of the guided wave propagating in such layered structures based on a modified Lamb wave model for homogeneous and isotropic thin soft media in water has been shown to yield accurate elasticity estimates. Nonetheless, thin soft tissues are often bounded with other tissue...
The diastolic functioning of the left ventricle is correlated to the stiffness of the myocardium. Shear wave (SW) elastography can be used for non-invasive stiffness measurements. These waves can have external sources such as an acoustic push, natural sources such as valve closure, or diffuse sources like breathing and flow noise. SW propagation velocities in diffuse wave fields can be analyzed after...
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