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Understanding of the propagation of ultrasound through a bubbly medium is a challenging task because of the nonlinear dynamics of the bubbles and their effect on the attenuation and sound speed of the medium. The majority of the studies on this subject apply linear models, which will generate inaccurate results, especially at higher-pressure excitations. These studies have also ignored the effect...
I.H.P. SAW (Incredible High-Performance SAW) has a novel multi-layered structure to confine SAW energy in substrate surface area, and it shows extremely high quality (Q) factor, low temperature coefficient of frequency (TCF) and improved electromechanical coupling coefficient (K2). This paper introduces its mechanism of the high acoustic Q factor, both theoretically and experimentally, and its applications...
The control of acoustic fields in 3-D is vital in many areas of physical acoustics. Recently, a new approach for the generation of complex diffraction limited acoustic fields in 3-D was introduced. This works by calculating a phase hologram designed to generate a desired acoustic field. The output of a simple planar transducer is then mapped onto this phase distribution using a 3-D printed kinoform...
In order to study relaxation characteristics of viscoelasticity of the liquid, a wide frequency sweep in the range of MHz to GHz is desired. We, therefore, report a new type HBAR (High-overtone Bulk Acoustic Resonator: shear mode ScAlN film on AT-cut quartz plate) sensor which makes it possible to operate in a wide frequency range as shown in Fig. 1. When a thickness shear acoustic mode (TSM) resonator...
A dual beam vector Doppler method was proposed (DOI: 10.1016/j.ultrasmedbio.2009.11.004), in which one beam is continuously tracked perpendicular to the flow direction, and the second one is used to perform velocity measurements with known Doppler angle. Since two consecutive transmission (TX) and reception (RX) events (one for each beam) are needed, the effective Doppler pulse repetition frequency...
Finite element method (FEM) has been extensively used for analyzing both static and dynamic behaviour of CMUTs. Typical parameters being evaluated include the pull-in voltage, pressure, sensitivity, bandwidth, and crosstalk. PZFlex is a commercial FEA software and has been optimized for the ultrasound industry and is commonly used to design piezo-electric ultrasound transducers. However, PZFlex is...
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...
Skin stiffening is an early biomarker of many systemic sclerosis or fibrosis diseases. The Modified Rodnan Skin Score (MRSS) is considered the gold standard measurement in the majority of clinical studies of scleroderma or systemic sclerosis (SSc). However, the MRSS is a subjective palpation method. We have developed a noninvasive ultrasound surface wave elastography (USWE) technique for measuring...
Shear wave (SW) propagation in viscoelastic materials is characterized by a complex, frequency-dependent shear modulus μ(f). Measurements of μ(f) typically require Fourier transform techniques to decompose an observed SW signal into discrete frequency components and two independent measurements such as the phase velocity c(f) and attenuation α(f) to determine the real and imaginary parts of μ(f).
CMUTs make very sensitive gravimetric chemical sensors in air. Selectivity can be improved by using arrays of these sensors with different functionalization coatings. However, operating multiple sensor on the same chip can be challenging because of sensor frequency locking and greater difficulty of functionalization. In prior work, or only two or three sensors have been used at once on the same chip...
The energy transduction of a Capacitive Micromachined Ultrasonic Transducer (CMUT) depends on the movement of a flexible plate, which has a low mechanical impedance compared to its bulky piezoelectric counterpart. Consequently, the output pressure of a CMUT is generally lower. This limits the penetration depth, and thus the visualization of deeper structures in the body, as well as non-linear imaging...
Acoustic backscatter systems offer a flexible technique to measure dispersion concentration and particle size, via inversion of the return echo voltage response of pulse-echo signals in the MHz range. While there have been recent developments in how backscatter models can be broadened in marine applications there is little data available for the Rayleigh regime (ka<1) as direct inversion is not...
In Magnetomotive Ultrasound (MMUS), tissue embedded magnetic nanoparticles (MNP) are mechanically excited by a magnetic field. Relatively small forces on the MNP result in small tissue displacements and a low SNR, when US-based displacement tracking is performed. From the application of elastography techniques it is known that the axial displacement of soft tissues shows a resonant behavior depending...
For ultrasonic molecular imaging, evaluation for molecular expression has been discussed for decades. However, there is no method to quantify the precious expression level of molecules using ultrasonography. To solve this problem, it is important to understand the chemical kinetics between targeted microbubbles (TMBs) and target molecules as a fundamental study. Therefore, we construct the system...
Short pulse transmission and reception is important for piezoelectric micromachined ultrasonic transducer (PMUT) arrays to achieve high resolution. However, coupling effects cause PMUT arrays to exhibit long decay times following the transmit pulse and poor axial resolution. Here, we model the mutual acoustic impedance that couples PMUTs in an array to show that the decay behavior can be accurately...
Further reduction of nonlinearity is demanded in RF SAW/BAW devices, but even their generation mechanisms have not been fully understood. Although phase possesses comparable information to amplitude, it has not been paid much attention in the nonlinear signal measurement. Nonlinear vector network analyzers (NVNAs) may be used for the purpose. However, NVNAs have limited linearity than spectrum analyzers...
Commercially available tissue-mimicking-materials (TMMs) and phantoms are designed to exhibit acoustic properties similar to those measured from soft tissue at ultrasound frequencies up to 15MHz. Many of these phantoms are manufacturing using the IEC agar-TMM. However, there are increasing applications of ultrasound at frequencies above 15MHz for both clinical (skin and vascular) and preclinical (small...
Porous piezoelectric ceramics are often integrated as constitutive elements in several devices such as ultrasound transducers. For high-frequency (HF) applications (i.e., >20 MHz), unpoled, porous lead zirconate titanate (PZT) can be used as a backing. The porosity content allows the acoustical impedance value to be adjusted but it also affects the acoustic attenuation according to the size and...
SAW sensors offer a mechanical motion in MHz to GHz range and can be immune to effects from boundary loss through the bulk and edges. SAW based gyroscopes have been implemented by added masses which impose an effect on wave prorogation fronts through the Coriolis force. A key challenge in implementing SAW based gyroscopes is to improve the sensitivity owing to small forces and SAW signals. significant...
Ultrasonography is not widely used in clinic for lung assessment because ultrasound cannot image deep lung tissue. We have developed a noninvasive technique termed lung ultrasound surface wave elastography (LUSWE) for measuring superficial lung tissue elastic properties. The purpose of this abstract is to demonstrate the clinical use of LUSWE for assessing patients with interstitial lung disease (ILD)...
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