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Catheterization remains the gold standard for bladder volume assessment, but it is invasive, uncomfortable to the patient, and introduces the risk of infections and trauma. To reduce the need for a urinary catheter, a new method has recently been introduced that non-invasively and instantaneously measures the bladder volume on the basis of nonlinear wave propagation and using a single diverging acoustic...
Low peak power frequency-modulated continuous wave (FMCW) radar is used in various fields, such as vehicle collision warning systems, airborne radio altimeters, and other applications. The authors proposed an ultrasound FMCW range measurement system based on the same principle as the FMCW radar. In the proposed system, the transmitter and receiver operate at very low voltage. This advantage suggests...
In this paper, TriQuint's BAW PCS duplexer chipset will be presented, showing it's performance in a PCS power-amplifier front end module (FEM). Besides having a low insertion loss and a high rejection and isolation, today's application requirements dictate that special attention has to be paid to non-linearity (harmonics). This applies to the behavior of the single TX/RX chips as well as the duplexer...
Higher frequency components, which are induced by a nonlinear response of tissue under high pressures, have long been known to enhance thermal ablation due to the increased absorption of the higher frequencies. It has been proposed that aspects of nonlinear propagation could be used to control power deposition. This study describes an approach designed to exploit the enhanced heating effect of nonlinear...
The acoustic response of individual targeted microbubbles, sized optically, to high-frequency ultrasound was examined to improve nonlinear imaging techniques and aid signal quantification. Single bound phospholipid shell microbubbles (diameters 1.0 to 5.0 mum) were insonated with 30 MHz Gaussian-shaped pulses for pressures from 20 kPa to 4 MPa with a fractional -6 dB one-way bandwidth of 20%. The...
Phase aberration is one of the major causes that deteriorates the quality of medical acoustic imaging. To suppress the influence of aberration, we employ a focused transmit beam with a low center frequency for the calculation of an aberration correction value set. The aberration correction value set is applied to a imaging process utilizing high transmit frequency. We propose the equivalent half power...
Pulse-inversion sequences are sensitive to the nonlinear echoes from microbubbles allowing an improvement in the blood-to-tissue contrast. However, at larger mechanical indexes, this contrast is reduced by harmonics produced during nonlinear propagation. A method for tissue harmonics cancellation exploiting time-reversal is experimentally implemented using a 128-channel 12-bit emitter-receiver. The...
Ultrasound contrast harmonic imaging is one of the most used contrast detection method in common system used for diagnostic. Its success comes from the higher non linearity properties of ultrasound contrast agents compared to tissue. A way to further enhance agent to tissue ratio would be to locally suppress second harmonic that is generated due to non linear propagation in tissue. Reducing higher...
The long term goal of this project is to monitor and quantify intra-cardiac pressures via contrast-enhanced subharmonic imaging (SHI). Our group has proposed the concept of subharmonic aided pressure estimation (SHAPE) utilizing microbubble-based contrast agent signals for the noninvasive estimation of hydrostatic blood pressures in heart cavities and major blood vessels. An experimental system for...
Clutter is a noise artifact in ultrasound images, arising from multiple sources. Experiments were conducted with urine-filled in vivo bladders to differentiate among various clutter sources. Successive-frame image acquisitions with varying transmit PRFs were used to determine the clutter contributions from echoes of previously sent pulses and random electronic and/or acoustic noise. Images acquired...
Advantages of capacitive micromachined ultrasonic transducers (CMUTs) such as wide frequency bandwidth could be used in nonlinear contrast imaging. However, the driving electrostatic force induces a nonlinear behavior of the CMUT generating thus undesirable harmonic components. Consequently, the use of CMUT for harmonic imaging, with or without contrast agents becomes challenging. To insure their...
Longitudinal motion artifacts in intravascular ultrasound (IVUS) sequences hinders a properly 3D reconstruction and vessel measurements. Most of current techniques base on the ECG signal to obtain a gated pullback without the longitudinal artifact by using a specific hardware or the ECG signal itself. The potential of IVUS images processing for phase retrieval still remains little explored. In this...
Ultrasound contrast agents (UCAs) are designed to be used below 10 MHz, but interest is growing in studying the response of agents to high-frequency ultrasound (HFU). In this study, we analyzed the sub-harmonic response of polymer-shelled UCAs with a mean diameter of 1.1 mum excited with 40-MHz tone bursts of 1 to 20 cycles. UCAs were diluted in water and streamed through a flow phantom that permitted...
Surface acoustic waves (SAW) scattering into asemi-infinite solidhave been studied since the early 60-ies. In the case of a substrate with finite plate-like dimensions the scattering into bulk waves (BAW) is transformed into scattering to bulk plate modes. There have been some attempts to model the phenomenon but the most interesting case of interaction of SAW with BAW resonator, i.e. scattering in...
We use finite element analysis (FEA) to model capacitive micromachined ultrasonic transducer (CMUT) cells where stress stiffening affects static deflection, pull-in voltage, resonance frequency, and small-signal sensitivity. Determining the small-signal sensitivity is challenging because it requires a prestressed harmonic response analysis in which the geometric nonlinearities are activated during...
In ultrasonic harmonic imaging, the contrast-to-tissue ratio (CTR) is generally limited by tissue background signal comprising both the leakage harmonic signal and the tissue harmonic signal. In this paper, suppression of tissue background signal in harmonic imaging is studied by selecting an optimal phase of the transmit signal to achieve destructive cancellation between the tissue harmonic signal...
For several years the standard in ultrasound imaging has been second harmonic imaging. Recently, a new imaging modality dubbed super harmonic imaging (SHI) was proposed. SHI uses the higher - third to fifth - harmonics produced by either nonlinear propagation or contrast agent response. This modality requires a transducer with a high bandwidth (>130%), which was achieved by choosing different frequencies...
In order to improve the temperature stability of RF SAW devices, it is worth adding a layer of SiO2 on the surface of the piezoelectric substrate. This paper presents an original method, which allows the computation of the Harmonic Admittance of an infinite periodic grating covered with an SiO2 overlay. The origins of this method can be found in a previous paper. By comparison with S. Ballandras and...
To provide faster, more repeatable and stronger MEMS packaging technology, the dynamic characteristics of ultrasonic transducers are studied using finite element method (FEM), and the ultrasonic generator for driving the transducer is also presented in this paper. The finite element model of the high frequency ultrasonic transducer was established by using ANSYS software, and the vibration characteristics...
A straightforward approach has been developed for the general solution of the cumulative second harmonic by Lamb wave propagation in a solid plate. The present analyses of second-harmonic generation by Lamb waves focus on the cases where the phase velocity of the fundamental Lamb wave is exactly or approximately equal to that of the dominant double frequency Lamb wave (DFLW). Based on the general...
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