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PubMed Journal Database | IEEE transactions on ultrasonics, ferroelectrics, and frequency control RSS

15:47 EST 20th January 2020 | BioPortfolio

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Showing PubMed Articles 1–25 of 371 from IEEE transactions on ultrasonics, ferroelectrics, and frequency control

Visibility of Bioresorbable Vascular Scaffold in Intravascular Ultrasound Imaging.

Bioresorbable vascular scaffold (BVS) has recently been spotlighted for its unique characteristics of absorbing into blood vessels and eventually disappearing. Although intravascular ultrasound (IVUS) is the most common guiding tool for stent deployment, the echogenicity of BVS struts has changed as the center of stent lumen and scanning rotation are not concentric, which may cause a critical erroneous measurement in practice. This study investigated the physical conditions for dimming the stent brightness ...

A Deep Learning approach to Photoacoustic Wavefront Localization in Deep-Tissue Medium.

Optical photons undergo strong scattering when propagating beyond one mm deep inside biological tissue. Finding the origin of these diffused optical wavefronts is a challenging task. Breaking through the optical diffusion limit, photoacoustic imaging (PAI) provides high-resolution and label-free images of human vasculature with high-contrast due to optical absorption of hemoglobin. In real time PAI, an ultrasound transducer array detects photoacoustic (PA) signals, and B-mode images are formed via delay-and...

An Optimized Spatial Sampling Strategy for Wide-view Planar Array 3D Sonar Sensors.

Array-based imaging sonar sensors often have the advantage that the sampling directions in which sensor data is processed can be arbitrarily chosen. The associated computational cost of the imaging algorithm scales linearly with the number of sampled directions, though, which may limit the use of such sensors for real-time applications such as robotics. This is especially true in case of wide-field sensors, which generally require a larger number of sampled directions (e.g. to cover the full frontal hemisph...

Measurement of Quasi-static 3D Knee Joint Movement Based on the Registration from CT to US.

The measurement of quasi-static three-dimensional (3D) knee joint movement is an important basis for studying the mechanism of knee joint injury. Most of the existing measurement methods make use of computed tomography (CT) and nuclear magnetic resonance (MR) imaging technology, and hence have the disadvantages of invasiveness, ionizing radiation, low accuracy and high cost. To overcome those drawbacks, this paper innovatively proposes a 3D motion measurement system for the knee joint based on the registrat...

Deep learning for US image quality assessment based on femoral cartilage boundaries detection in autonomous knee arthroscopy.

Knee arthroscopy is a complex minimally invasive surgery that can cause unintended injuries to femoral cartilage and/or post-operative complications. Autonomous robotic systems using real time volumetric ultrasound (US) imaging guidance hold potential for reducing significantly these issues and for improving patient outcomes. To enable the robotic system to navigate autonomously in the knee joint, the imaging system should provide the robot with a real-time comprehensive map of the surgical site. To this en...

Theoretically Estimating the Acoustic Intensity of High-Intensity Focused Ultrasound (HIFU) Using Infrared Thermography.

High-intensity focused ultrasound (HIFU) has been used successfully in clinics for the treatment of a variety of cancerous and benign tumors. Characterization of the focused acoustic field is of importance in the planning of ablation procedure and further development of HIFU technology. Quantitative estimation of acoustic intensity is feasible using the infrared thermography on an absorber. However, the current approach is limited to low power output. In this study, a theoretical model was established to de...

Evaluation of structural anisotropy in a porous titanium medium mimicking trabecular bone structure using mode-converted ultrasonic scattering.

The mode-converted (Longitudinal to Transverse, L-T) ultrasonic scattering method was utilized to characterize the structural anisotropy of a phantom mimicking the structural properties of trabecular bone. The sample was fabricated using metal additive manufacturing from high resolution Computed Tomography (CT) images of a sample of trabecular horse bone with strong anisotropy. Two focused transducers were used to perform the L-T ultrasonic measurements. A normal incidence transducer was used to transmit lo...

Dual-Frequency Chirp Excitation for Passive Cavitation Imaging in the Brain.

One of the main challenges that impedes cavitation-mediated imaging in the brain is restricted opening of the blood-brain barrier (BBB) making it difficult to locate cavitating microbubbles (MBs). Passive cavitation imaging (PCI) has received attention due to the possibility of performing real-time monitoring by listening to acoustic cavitation. However, the long excitation pulses associated with PCI degrade its axial resolution. The present study combined a coded excitation technique with a dual-frequency ...

Super harmonic ultrasound for motion-independent localization microscopy: applications to microvascular imaging from low to high flow rates.

Recent advances in high frame rate biomedical ultrasound have led to the development of ultrasound localization microscopy, a method of imaging microbubble contrast agents beyond the diffraction limit of conventional coherent imaging techniques. By localizing and tracking the positions of thousands of individual microbubbles, ultra-high resolution vascular maps are generated which can be further analyzed to study disease. Isolating bubble echoes from tissue signal is a key requirement for super-resolution i...

Synthetic Aperture Focusing for Multi-covariate Imaging of Sub-resolution Targets.

Coherence-based imaging methods suffer from reduced image quality outside the depth of field for focused ultrasound transmissions. Synthetic aperture methods can extend the depth of field by coherently compounding time-delayed echo data from multiple transmit events. Recently, our group presented Multi-covariate Imaging of Sub-resolution Targets (MIST), an estimation-based method to image the statistical properties of diffuse targets. MIST has demonstrated improved image quality over conventional delay-and-...

Mean Scatterer Spacing Estimation using Cepstrum-based Continuous Wavelet Transform.

The goal of this study was to develop an ultrasound scatterer spacing estimation method using an enhanced cepstral analysis based on continuous wavelet transforms. Simulations of backscattering media containing periodic and quasi-periodic scatterers were carried out to test the developed algorithm. Experimental data from HT-29 pellets and in-vivo PC3 tumors were then used to estimate the mean scatterer spacing. For simulated media containing quasi-periodic scatterers at 1 mm and 100 μm spacing with 5% posi...

Aspect ratio-dependent dynamics of piezoelectric transducers in wireless acoustic power transfer.

Acoustic power transfer (APT) for wireless electronic components has received growing attention as a viable approach to deliver power to remotely located small electronic devices. The design of an efficient APT system requires accurate models to describe its individual components as well as the interaction between them. Most of the analytical models available to represent the bulk piezoelectric transducers used in APT are limited to either thin rod or thin plate transducers. However, transducers with modera...

Viscoelastic Response (VisR) Ultrasound Derived Relative Elasticity and Relative Viscosity Reflect True Elasticity and Viscosity: In Silico and Experimental Demonstration.

Viscoelastic Response (VisR) ultrasound characterizes the viscoelastic properties of tissue by fitting acoustic radiation force (ARF)-induced displacements in the region of ARF excitation to a 1-D mass-spring-damper (MSD) model. Elasticity and viscosity are calculated separately from each other but relative to the applied ARF amplitude. We refer to these parameters as 'relative elasticity (RE)' and 'relative viscosity (RV).' We herein test the hypothesis that RE and RV linearly correlate to true elasticity ...

The important role of N(2)(CH3)4 ion in the phase transition mechanism of N(CH3)42ZnBr4.

The chemical shift of the N(2)(CH3)4 ion, which has been found to exhibit the similar anomalous behavior of the monoclinic angle Δβ, was related to the order parameter to evaluate the temperature dependence of the linewidth (damping constant) for 14N NMR spectrum of this crystal in terms of the dynamical Ising models, namely the pseudospin-phonon coupled (PS) and the energy fluctuation (EF) models. The results from both PS and EF models were successful to explain the abnormal behavior of the linewidth in ...

Raman Spectra of La3Ga5SiO14 Crystal Modulated by Bulk Acoustic Wave.

Influence of bulk acoustic wave excitation in langasite crystal on Raman spectra was studied. It was found that acoustic wave propagating in the crystal volume changes the intensity and position of the Raman scattering lines. Under bulk acoustic wave propagation conditions Raman peak intensity changes less than on 5% and peak position shifts on 0.5 cm-1. To detect such small changes principal component analysis of Raman spectra was used.

Broadband Ultrasonic Array Transducer from Multilayer Piezoelectric Ceramic with Lowered Co-firing Temperature.

Increasing array transducer bandwidth and signal-to-nose ratio (SNR) is a critical issue for producing high-quality medical ultrasound image. However, array elements with small size tend to have a poor sensitivity due to a much higher impedance compared to the electrical impedance of transmit and receive circuit. Implementation of multilayer ceramic (MLC) is an effective way for reducing impedance, thus with potential for improving SNR for ultrasonic probe. In this work, we fabricated multilayer piezoelectr...

The dependence of acoustic emission performance on the crystal structures, dielectric, ferroelectric, and piezoelectric properties of the P(VDF-TrFE) sensors.

To clarify the influences of molar contents of vinylidene fluoride (VDF) on the piezoelectric and acoustic emission reception performances of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) sensors, we systematically investigate the crystal structures, dielectric and ferroelectric properties of P(VDF-TrFE) films with different compositions of VDF and TrFE monomers, and find that low proportion (

Linear phase design of piezoelectric transducers for acousto-optic dispersion delay lines using differential evolution for matching circuit optimization.

A numerical method for providing linear phase response of bulk acoustic wave (BAW) piezoelectric transducers of acousto-optic devices is developed. Our approach is based on analytic approximation of the phase response of the piezoelectric transducer with the matching electrical circuit and optimization with a differential evolution genetic algorithm. Simulations and experiments were performed for two typical BAW excitation schemes: direct and reflective. Variance of the group delay in the specified frequenc...

A Guided Wave Inspection Technique for Wedge Features.

Numerous engineering components feature prismatic wedge-like structures that require Non-destructive Evaluation (NDE) in order to ensure functionality or safety. This paper focuses on the inspection of the wedge-like seal fins of a jet engine drum, though the capabilities presented will be generic. It is proposed that anti-symmetric flexural edge modes, feature guided waves localised to the wedge tips, may be used for defect detection. Although analytical solutions exist that characterise the ultrasonic beh...

High-frequency multi-pulse, plane-wave acoustic contrast imaging.

Multi-pulse (MP) ultrasound contrast agent (UCA) imaging is a method to increase the contrast-to-background (CBR) ratio in regions of blood flow. Plane-wave imaging allows high frame rates, and with high-frequency ultrasound, fine-spatial and temporal resolution. MP and plane-wave imaging have not been applied to high-frequency ultrasound. Here, an 18-MHz linear array was employed to implement the MP methods of pulse inversion (PI) and amplitude modulation (AM) using high-speed, multi-angle, compound plane-...

High frame rate color Doppler echocardiography: a quantitative comparison of different approaches.

Ultrasound color Doppler imaging (CDI) provides a map of the axial blood flow velocities in a 2D/3D region of interest. While CDI is clinically effective for a qualitative analysis of abnormal blood flows, e.g. for valvular disease in cardiology, it is in limited use for quantitative measures, mainly hampered by low frame rate and measurement bias. These limitations can be reduced by different approaches towards high frame rate (HFR) imaging at the expense of reduced image quality and penetration depth. The...

Ex-vivo assessment of cortical bone properties using low-frequency ultrasonic guided waves.

The early diagnosis of osteoporosis through bone quality assessment is a major public health challenge. Research in axial transmission using ultrasonic guided waves has shown the method to be sensitive to the geometrical and mechanical properties of the cortical layer in long bones. However, because of the asymmetric nature of cortical bone, the introduction of a more elaborate numerical model than the analytical plate and cylinder models, as well as its inversion, continue to be challenging. The aim of thi...

Intensity detection noise in pulsed vapor cell frequency standards.

Laser intensity noise is currently recognized as one of the main factors limiting the short-term stability of vapor-cell clocks. In this paper, we propose a signal theory approach to estimate the contribution of the laser intensity fluctuations to the short-term stability of vapor-cell clocks working in pulsed regime. Specifically, given a laser intensity noise spectrum, an analytical expression is derived to evaluate its impact onto the clock Allan deviation. The theory has been tested for two intensity no...

A Practical Approach to Optimal Control Problem for Atomic Clocks.

Linear quadratic Gaussian (LQG) control is one of known techniques used for steering atomic clocks to external references. Complexity of the use of LQG method is caused by uncertainty in selection of the weight coefficients of the cost function. Therefore, modeling of the steering algorithm for particular noises of reference and controlled clock (oscillator) is required. In this paper we propose the algorithm, which allows to calculate weight coefficients, and consequently gain coefficients of the control l...

The effects of phase modulated excitation on the focused acoustic field.

Various modulation approaches, such as amplitude and frequency modulation, have been applied widely to modify the acoustic field and improve the performance of ultrasound imaging and therapy. However, phase modulation has not been investigated extensively in the ultrasound applications, especially at long pulse duration. In this study, the effects of phase modulation on the acoustic field were investigated. The radiated acoustic pressure waveforms produced using different phase modulation strategies (i.e., ...


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