IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

Detection of inertial and stable cavitation is important for guiding high-intensity focused ultrasound (HIFU). Acoustic transducers can passively detect broadband noise from inertial cavitation and the scattering of HIFU harmonics from stable cavitation bubbles. Conventional approaches to cavitation noise diagnostics typically involve computing the Fourier transform of the time domain noise signal, applying a custom comb-filter to isolate the frequency components of interest, followed by an Inverse-Fourier transform...

While in vivo Acoustic Radiation Force Impulse (ARFI)-induced peak displacement (PD) has been demonstrated to have high sensitivity and specificity for differentiating soft from stiff plaque components in patients with carotid plaque, the parameter exhibits poorer performance for distinguishing between plaque features with similar stiffness. To improve discrimination of carotid plaque features relative to PD, we hypothesize that signal correlation and SNR can be combined, outright or via displacement variance...

A new model for piezoelectric textured ceramics was developed that considers the presence of porosity, which can appear during heat treatment (ceramic sintering). In the long wavelength approximation, a matrix method, which has already been applied to piezoelectric composites, was extended to textured ceramics for three phases porosity (air), piezoelectric single-crystal (related to the texturation degree), and ceramic to calculate the effective electroelastic modulus. This method was first compared and validated with finite element calculations...

This study proposes a catheter consisting of dual-frequency transducer for intravascular ultrasound. Both ultrasonic elements with different frequencies were connected to one coaxial cable to make the connection simple. The aperture size of the ultrasound elements were 0.4×0.6 mm2 and 0.3×0.4 mm2 for the low frequency element and high frequency element, respectively. The center frequency and bandwidth of the fabricated low frequency transducer were 33.8 MHz and 49.3%, respectively. Meanwhile, the center frequency and bandwidth of the high frequency transducer were 80...

Non-contrast perfusion ultrasound imaging remains challenging due to spectral broadening of the tissue clutter signal caused by patient and sonographer hand motion. To address this problem, we previously introduced an adaptive demodulation scheme to suppress the bandwidth of tissue prior to high-pass filtering. Our initial implementation used single plane wave power Doppler imaging and a conventional tissue filter. Recent advancements in beamforming and tissue filtering have been proposed for improved slow-flow imaging, including coherent flow power Doppler (CFPD) imaging and singular value decomposition (SVD) filtering...

High-performance frequency standards are affected by power-law noises, and characterized by structure functions (i.e. variances). These variances with specified averaging time quantify the frequency stability of the oscillator. To improve stability estimated from measured data and extend its maximum averaging time, a method called 'StONA' (oscillator noise analysis under stochastic restrictions) is proposed based on convex optimization techniques. StONA also measures the intensity coefficients of noise processes as a by-product of extending averaging time...

In response to the increased mobile data traffic, there is a growing need for more low-loss RF band filters with steep frequency characteristics, and high quality (Q)-factor and low-temperature coefficient of frequency (TCF) resonators are required to achieve this. We previously reported that for a surface acoustic wave (SAW) resonator on a three-layer structure, which is composed of a thin LiTaO3 (LT) plate whose orientation is 50° rotated Y-X propagation, SiO2 layer and AlN layer on a Si substrate, a Q-factor several times higher than that of a SAW resonator on a standard 42° rotated Y-X propagation LiTaO3 (42YX-LT) substrate could be obtained...

Digital ultrasound probes integrate the analog front-end in the housing of the probe handle and provide a digital interface instead of requiring an expensive coaxial cable harness to connect. Current digital probes target the portable market and perform the bulk of the processing (beamforming) on the probe, which enables the probe to be connected to commodity devices such as tablets or smartphones running an ultrasound app to display the image and control the probe. Thermal constraints limit the number of front-end channels as well as the complexity of the processing...

Temporal- and spatial-resolved observations of micro-bubble cavitation generated through high-intensity ultrasound irradiation are key in improving both efficiency and efficacy of ultrasound-assisted drug delivery systems. A method of measuring bubble cavitation applying an image-reconstruction technique of back-propagation of an acoustic cavitation emission (ACE) signal is proposed. A high-intensity focused ultrasound wave (pump wave) irradiates the bubble synchronously using ultrasound recording equipment to acquire the timing of the RF signal, which is produced when the bubble radiates a secondary wave during bubble cavitation...

Time-domain Plane Wave Imaging (PWI) has recently emerged in medical imaging and is now taking to Non- Destructive Testing (NDT) due to its ability to provide images of good resolution and contrast with only a few steered plane waves. Insonifying a medium with plane waves is a particularly interesting approach in 3D imaging with matrix arrays because it allows to tremendously reduce the volume of data to be stored and processed as well as the acquisition time. However, even if the data volume is reduced with plane wave emissions, the image reconstruction in the time domain with a delay-and-sum algorithm is not sufficient to achieve low computations time in 3D due to the number of voxels...

Tissue motion estimation is an essential step for ultrasound elastography. Our previous study has shown that the affine-model based optical flow (OF) method outperforms the normalized cross-correlation based block matching (BM) method in motion estimation. However, the quality of lateral estimation using OF is still low due to inherent limitation of ultrasound imaging. BM based spatial angular compounding (SAC) has been developed to obtain better motion estimation. In this paper, OF based SAC (OF-SAC) is proposed to further improve the performance of lateral (and axial) estimation, and it is compared with BM based SAC (BM-SAC)...

Phase-change perfluorohexane nanodroplets (PFHnDs) are a new class of recondensable sub-micrometer-sized contrast agents that have potential for contrast-enhanced and super-resolution ultrasound imaging with an ability to reach extravascular targets. The PFHnDs can be optically triggered to undergo vaporization, resulting in spatially stationary, temporally transient microbubbles. The vaporized PFHnDs are hyperechoic in ultrasound imaging for several to hundreds of milliseconds before recondensing to their native, hypoechoic, liquid nanodroplet state...

Ultrasound super-resolution techniques use the response of microbubble contrast agents (MBs) to visualize the microvasculature. Techniques that localize isolated bubble signals first require detection algorithms to separate the MB and tissue responses. This work explores the three main MB detection techniques for super-resolution of microvasculature. Pulse inversion (PI), differential imaging (DI) and singular value decomposition (SVD) filtering were compared in terms of the localization accuracy, precision and contrast to tissue ratio (CTR)...

A non-contact single-beam acoustic trapping technique has proven to be a promising tool for cell manipulation and characterization that provide essential knowledge for a variety of biomedical applications. Here, we investigated cell characteristics as to whether the calcium responses of suspended breast cancer cells to different acoustic trapping force are related to their invasiveness. For this, we combined a single-beam acoustic trapping system with a 30 MHz press-focused lithium niobate ultrasound transducer and an epi-fluorescence microscope...

In this paper, anisotropy of single crystalline silicon (SCS) is exploited to enable side-supported radial-mode thin-film piezoelectric-on-substrate (TPoS) disc resonators. In contrast to the case for isotropic material, it is demonstrated that the displacement of the disc periphery is not uniform for the radialmode resonance in SCS discs. Specifically, for high order harmonics, nodal points are formed on the edges, creating an opportunity for placing suspension tethers and enabling sidesupported silicon disc resonators at very-high-frequency (VHF) band with negligible anchor loss...

Polymer-piezoceramic composites show mutual properties of piezoceramics and polymers that can be efficiently utilized in energy harvesting applications. Here we fabricated 0-3 composite films using high performance low-lead piezo-ceramic (x)Bi(Ni1/2Zr1/2)O3-(1-x)PbTiO3 (BNZ-PT) as ceramic filler and polyvinylidene fluoride (PVDF) as polymer matrix. Unlike the conventional morphotropic phase boundary piezoelectrics such as the PZT, the large piezoelectric response of the BNZ-PT can be obtained by poling induced cubic-like to tetragonal phase transformation...

A mixed-domain method dubbed frequency-specific mixed domain method is introduced for the simulation of the second harmonic ultrasound field in weakly heterogeneous media. The governing equation for the second harmonics is derived based on the quasilinear theory. The speed of sound, nonlinear coefficient, and attenuation coefficient are all spatially varying functions in the equation. The fundamental frequency pressure field is first solved by the frequency-specific mixed domain method, and it is subsequently used as the source term for the second harmonics equation...

Complex flow patterns are prevalent in the vasculature, but they are difficult to image non-invasively in real-time. This paper presents the first real-time scanning platform for a high frame rate ultrasound technique called color encoded speckle imaging (CESI) and its use in visualizing arterial flow dynamics in-vivo. CESI works by simultaneously rendering flow speckles and color-coded flow velocity estimates on a time-resolved basis. Its live implementation was achieved by integrating a 192-channel programmable ultrasound front-end module, a 4...

This work presents a Lamé mode resonator featuring a novel gap closing mechanism which employs electrostatic force to reduce the capacitive transduction gaps to sub-micron values in order to overcome fabrication technology critical spacing limitations. This leads to significant resonator loss and motional resistance reduction while maintaining high Q-factor even in air. Prototypes were fabricated in two commercial siliconon- insulator processes. Upon the application of a DC voltage of 55 V between the resonator structure and the electrodes, the gaps sizes are reduced to as low as 200 nm...

Complete sets of elastic, dielectric and piezoelectric properties of flux grown rhombohedral Pb(Zn1/3Nb2/3)O3-xPbTiO3 (x = 0.0475, 0.055 and 0.065) single crystals poled along [001] crystal direction have been determined in the present work. Their phase transformation temperatures, coercive fields and mechanical quality factors are also provided. The results show that [001]-poled rhombohedral PZN-PT single crystals exhibit superior longitudinal piezoelectric properties (k33 ≥ 0.90, d33 ≈ 1580-2500 pC/N)...