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Intrauterine growth restriction (IUGR) is an anomaly of fetal growth dynamics, which is mainly caused by alterations in the vascular remodeling of utero-placental arteries. With a prevalence of 10% of pregnancies, IUGR remains the leading cause of perinatal mortality. Doppler velocimetry is the common screening tool for IUGR but this imaging modality remains controversial. In this context, we evaluated...
We have recently demonstrated the feasibility of vascular guided wave imaging (VGWI) in non-invasive estimation of bi-plane (i.e., longitudinal and transverse) transmural arterial Young's modulus (ELV, ETV) in tubular phantoms using phase velocity (cph) (Guo et al., ITEC 2016). In this study, we further compare the ETV estimated from the circumferential Lamb type (CLT) wave by VGWI with ETP from the...
Air-coupled transducers are used to conduct fast non-contact inspections in NDT. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled NDT. This paper presents a methodology for improving the bandwidth of an air-coupled diaphragm transducer without sensitivity loss by connecting a number...
Histotripsy with ultrasound is an emerging noninvasive therapeutic modality that uses cavitation to precisely destroy diseased soft tissue. Accurate simulations of histotripsy are needed for treatment planning and device design. These simulations are performed in the time-domain, span hundreds of wavelengths, and must handle strong shocks and discontinuities between materials, such as the brain and...
Burst wave lithotripsy (BWL) is an experimental method to noninvasively fragment urinary calculi using low-frequency focused bursts of ultrasound. To optimize many of the acoustic parameters for this technology, it is necessary to understand the physical interactions between ultrasound bursts and stones. In this study, the interaction of elastic waves with model stones was simulated and experimentally...
Photoacoustic (PA) imaging aims for the reconstruction of acoustic sources that originate in pulsed light absorption. While the speed of sound (SOS) in biological tissue is heterogeneous, standard reconstruction algorithms usually assume a constant SOS. This results in deformations of the reconstructed sources, which are referred to as aberration and can have a severe impact on the spatial resolution...
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...
Resonator based S0 Lamb wave mode in AlN thin films plate has drawn great attentions thanks to its high phase velocity up to 10 km/s and large electromechanical coupling coefficient (K2). Moreover, this structure allows operation at high temperature conditions. Although several significant research efforts are ongoing to enable AlN-based piezoelectric devices for high temperature applications, an...
Pulse Wave Velocity (PWV), a surrogate marker of arterial stiffness, is associated with cardiovascular mortality and vascular atherosclerotic burden. The Bramwell-Hill equation links PWV with arterial compliance. Pulse wave imaging (PWI) is a noninvasive technique developed by our group for tracking the propagation of pulse waves along the arterial wall at high spatial and temporal resolution. It...
Blood-brain and blood-tumor barriers (BBB and BTB) constitute a major obstacle to the transport of therapeutics in brain tumors. While several studies have demonstrated the potential of focused ultrasound (FUS) to disrupt transiently the BBB/BTB and improve drug delivery, there is a lack of fundamental understanding of the impact of this method on the pharmacokinetics of anticancer agents in the brain...
Assessment of medium nonlinearity parameter in pulse-echo mode usually demands information on the second harmonic. However, the acquisition of quantitative data on backscattered amplitude at the fundamental and second harmonic components is difficult using the same probe due to its limited bandwidth. In this paper we propose how to assess medium nonlinearity using only the fundamental harmonic and...
Filters operated at high power levels and comprising BAW resonators produce 2nd harmonic emissions. To model the emissions of a BAW resonator, Feld and Shim constructed a nonlinear Mason model, which implements an “extended” pair of piezoelectric constitutive equations containing arbitrary 2nd order terms: T = cES − eE + [1/2δ3cES2 − δ1eSE + 1/2δ2εSE2] D = eS + εSE + [1/2δ1eS2 − δ2εSSE +1/2δ4εSeE2...
Short-Lag Spatial Coherence (SLSC) is a beamforming technique that was initially developed for ultrasound imaging, then applied to photoacoustic imaging with sizable improvements in contrast and signal-to-noise ratios, when compared to traditional delay-and-sum beamforming. Although the SLSC beamformer was applied to experimental photoacoustic images, the theory describing its performance in photoacoustic...
There have been great interests in the nonlinear behavior of SAW resonators but realistic models for their frequency response characteristics have been limited. We present a general purpose finite element model that yields directly the nonlinear frequency response of second harmonic generation in SAW IDT resonators. The nonlinear model enabled us to study the effects of nonlinear material constants,...
Contrast-enhanced ultrasound (CEUS) permits quantification and monitoring of tumor vascular changes in response to anti-angiogenic treatment with the goal of informing targeted therapy. Conventional mean-intensity-based CEUS analysis discounts additional information that may be available from the first-order speckle statistics in a CEUS image. In this presentation, we demonstrate that our compound...
Linearity of RF filters is in the focus of system-architects as carrier aggregation (CA) schemes in down- and uplink emerge as a requirement. The nonlinear electro-thermal-acoustic constitutive equations of the piezoelectricity and the number of different materials involved in the manufacturing of BAW resonators make it difficult to discern between different sources of nonlinearity. It is hard to...
The modeling of acoustic streaming problems is usually treated by using simulation schemes based on perturbation theory to reduce the computational effort, where a quiescent fluid is assumed in the unperturbed state. However, when considering situations and applications where a steady background flow is present, this zero-order field would directly influence the first- and second-order velocity fields...
Third overtone and higher overtone thickness shear quartz resonators are used as a frequency source in ultra-stable oscillators. The governing equations for the force-frequency effect and the related acceleration sensitivity of these resonators are well established. The force exerted on the resonator causes initial stress and strain that in turn changes the resonator frequency. However, we have found...
Ultrafast vector flow imaging can provide detailed measurements of 2D/3D blood velocity patterns, but suffers from an increased variance due to reduced SNR and inherent estimator properties. Further, clutter filtering causes measurement dropouts during parts of the cardiac cycle and imposes an angle-dependent measurement accuracy. This work aims to demonstrate how simulation of the incompressible...
It was shown experimentally in [1], [2] that a macroscopic cylindrical solid can be rotated due to the excitation of two counter-propagating surface acoustic waves (SAWs) with different amplitudes on its surface. Arising internal distributed rotation force has been calculated phenomenologically in the partial case of a piezoelectric tube with a ring unidirectional electrode transducer (RUDT) using...
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