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Amorphous thin films are used as components of acoustic resonators because they could control temperature coefficient of resonator. Because elastic constants of thin films are often different from those of bulk materials, the direct measurement of sound velocity and temperature coefficient of velocity (TCV) for individual thin films becomes important in designing resonators. Because The TCV of amorphous...
To elicit bio-effects, ultrasound (US) stimulated microbubbles (MBs) must be in proximity to their target and this is not always the case (e.g. sonothrombolysis). Radiation forces can direct MBs to clots and our previous work suggested clot degradation patterns (Fig A) could be influenced by ‘transport pulses’. However, this is a complex process involving a population of MBs, with size-dependent radiation...
Cardiovascular diseases are the leading cause of death globally. Such diseases may affect the left ventricular function, which in turn is closely related to the left ventricular stiffness. Estimation of cardiac deformation can give information on the myocardial stiffness, and may therefore be important in assessment of cardiovascular diseases. A 3D motion estimation scheme is necessary to measure...
The Keller-Miksis equation (KME) is commonly used for numerical studies of inertial and stable-inertial cavitation. However, experimental validation of KME under clinically relevant exposure settings is scarce, particularly in terms of the acoustic emission signal generated by the cavitation. In this paper, the KME is validated against a cavitation cloud collapsing f0/2 and f0/3 sub-harmonically with...
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...
Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), enhancement of efficiency has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. One key experimental observation is that multi-frequency ultrasound can help lower the inertial cavitation threshold, thereby improving the power efficiency...
Strain and strain rate imaging can serve as noninvasive tools for quantitative assessment of regional myocardial contractility. Because of the 3D nature of cardiac motion, a 3D motion estimation scheme must be applied in order to be able to measure the full myocardial. Several method has been proposed to estimated the 3D velocity vectors field, such as 3D speckle tracking and 3D Transverse Oscillation...
Pulse wave velocity and blood flow velocity are two different physiological parameters which are generally assessed using two different ultrasound sequences and processing techniques. This can be explained by the difference in term of signal intensity between the tissue and blood (approx. 40 dB). On one side, blood velocity can be estimated using Doppler, speckle tracking or transverse oscillation...
In this paper a global estimation method based on transverse oscillation to simultaneously extract wall and flow velocities at high-framerate is presented. Several carotid phantoms with various parameters were made to validate the method. All acquisitions were performed at high-framerate (7 500 images per second) using horizontal plane wave with a 3 cycles sinusoidal transmit pulse. Transverse oscillation...
Pancreatic ductal adenocarcinoma (PDA) has one of the lowest prognosis due to non-specific symptoms leading to late diagnosis. The tumor is characterized by an unusually dense stroma limiting chemotherapeutic perfusion. Harmonic Motion Imaging (HMI) assesses tissue mechanical properties by inducing localized oscillation resulting from a periodic acoustic radiation force. The amplitude of the displacement...
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...
During deposition of metallic material on substrate, the morphological change from isolated islands to a continuous film occurs. The nano-structures obtained by stopping deposition around the discontinuous-continuous transition show characteristic electrical properties, and film-growth monitoring techniques are required to obtain the structures. Conductivity measurement and surface acoustic wave method...
The attenuation of ultrasound propagation in soft tissue follows a frequency-dependent power law. To model the power law attenuation while also accounting for the dispersion in soft tissue, Treeby and Cox proposed a space-fractional wave equation. Calculating the time-domain Green's function of the Treeby-Cox wave equation requires numerical evaluations of an inverse Fourier transform in the spatial...
The oscillation of microbubbles has long been hypothesized to provide the opportunity to enhance gene delivery as a result of changes in membrane permeability; however, translationally-relevant therapeutic protocols have not yet been realized. We sought to develop and validate a protocol to transfect endogenous mesenchymal stem cells (MSCs) via the local injection of plasmids and microbubbles and...
A high-speed observation system for sonoporation study was improved for observation of bubble and cell dynamics under ultrasound exposure from a lateral direction. The effect of the presence of a scaffold mimicking an in vivo situation on the dynamics was investigated to study the mechanisms by which bubbles cause cell membrane damage. Observations showed that the stiffness of the scaffold has a significant...
In ultrasonic tissue motion estimation, the accuracy in the lateral motion estimate is worse than the axial estimate. For improvement of the accuracy in the lateral motion estimate, the transverse oscillation (TO) was introduced to increase the lateral spatial frequency of the ultrasonic field. In the present study, adaptive beamforming was introduced to the TO method to further improve the accuracy...
We show here that temperature influences single microbubble dynamics by changing lipid shell viscoelastic properties. A newly developed photoacoustic measurement technique drove individual microbubbles into small-amplitude oscillations through ultrasound waves generated by the absorption of an amplitude-modulated laser. Forward light scattering was used to detect bubble oscillations as the modulation...
To suppress the hysteresis effect of the magnetostrictive film coated surface acoustic wave (SAW) current sensor, a patterned design on magnetostrictive FeCo coating was performed in this contribution. The developed sensor was composed of a configuration of dual-delay-line oscillators, and a strip-patterned magnetostrictive FeCo coated onto the SAW propagation path of the sensing SAW device. The patterned...
The first fully integrated oven-controlled temperature compensation system with the transformer coupled Colpitts oscillator is developed by 65nm CMOS tech. This work achieves ±1.55ppm frequency stability over the 85°C temperature range which can be used for the GPS application (<2ppm). An integrated heater in the FBAR chip consumes 14mW power at maximum. The temperature resolution of TDC is 150uK,...
Low power and low noise RF frequency reference is essential for radio system. Radio standards require reference frequency to be stable over a wide range of temperatures (−40 to 110°C for industrial). The state of the art radio architecture used temperature compensated resonator (ZDR), but the stability is not enough to meet the most stringent spec. for GPS application (<2ppm). The solution is here...
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