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IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

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https://www.readbyqxmd.com/read/28092534/a-k-space-pseudospectral-method-for-elastic-wave-propagation-in-heterogeneous-anisotropic-media
#1
Kamyar Firouzi, Butrus Khuri-Yakub
This paper presents the theory of the k-space method generalized to model elastic wave propagation in heterogeneous anisotropic media. The k-space methods are promising time integration techniques giving, in conjunction with collocation spectral methods, accurate and efficient numerical schemes for problems in heterogeneous media. In this study, the k-space operator is derived in a spatially continuous form using the Fourier analysis of the displacement formalism of elastodynamics. An efficient numerical algorithm is then constructed by applying a Fourier collocation spectral method, leading to define the discrete k-space scheme...
January 16, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28092533/linear-system-models-for-ultrasonic-imaging-intensity-signal-statistics
#2
Craig Abbey, Yang Zhu, Sara Bahramian, Michael Insana
Despite a great deal of work characterizing the statistical properties of radio-frequency backscattered ultrasound signals, less is known about the statistical properties of demodulated intensity signals. Analysis of intensity is made more difficult by a strong nonlinearity that arises in the process of demodulation. This limits our ability to characterize the spatial resolution and noise properties of B-mode ultrasound images. In this work, we generalize earlier results on two-point intensity covariance using a multivariate systems approach...
January 16, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28092532/improved-shear-wave-group-velocity-estimation-method-based-on-spatiotemporal-peak-and-thresholding-motion-search
#3
Carolina Amador Carrascal, Shigao Chen, Armando Manduca, James F Greenleaf, Matthew Urban
Quantitative ultrasound elastography is increasingly being used in the assessment of chronic liver disease. Many studies have reported ranges of liver shear wave velocities values for healthy individuals and patients with different stages of liver fibrosis. Nonetheless, ongoing efforts exist to stabilize quantitative ultrasound elastography measurements by assessing factors that influence tissue shear wave velocity values, such as food intake, body mass index (BMI), ultrasound scanners, scanning protocols, ultrasound image quality, etc...
January 11, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28092531/a-200-1380-khz-quadrifrequency-focused-ultrasound-transducer-for-neurostimulation-in-rodents-and-primates-transcranial-in-vitro-calibration-and-numerical-study-of-the-influence-of-skull-cavity
#4
Charlotte Constans, Thomas Deffieux, Pierre Pouget, Mickael Tanter, Jean-Francois Aubry
Low intensity transcranial focused ultrasound has been demonstrated to produce neuromodulation in both animals and humans. Primarily for technical reasons, frequency is one of the most poorly investigated critical wave parameters. We propose the use of a quadri-band transducer capable of operating at 200, 320, 850 and 1380 kHz for further investigation of the frequency dependence of neuromodulation efficacy while keeping the position of the transducer fixed with respect to the subject's head. This paper presents the results of the transducer calibration in water, in vitro transmission measurements through a monkey skull flap, 3D simulations based on both a μCT-scan of a rat and on CT-scans of 2 macaques...
January 11, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28092530/feasibility-of-multi-plane-transmit-beamforming-for-real-time-volumetric-cardiac-imaging-a-simulation-study
#5
Yinran Chen, Ling Tong, Alejandra Ortega, Jianwen Luo, Jan D'hooge
Today's three-dimensional (3-D) cardiac ultrasound imaging systems suffer from relatively low spatial and temporal resolution, limiting their applicability in daily clinical practice. To address this problem, 3-D diverging wave imaging with spatial coherent compounding (DWC) as well as 3-D multi-line-transmit (MLT) imaging have recently been proposed. Currently, the former improves the temporal resolution significantly at the expense of image quality and the risk of introducing motion artifacts whereas the latter only provides a moderate gain in volume rate but mostly preserves quality...
January 10, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28060706/comparison-of-the-thermal-degradation-of-heavily-nb-doped-and-normal-pzt-thin-films
#6
Jeong-Suong Yang, Yunsung Kang, Inyoung Kang, Seungmo Lim, Seung-Joo Shin, Jungwon Lee, Kangheon Hur
The degradation of Niobium-doped lead zirconate titanate (PZT) and two types of PZT thin films were investigated. Undoped PZT, 2-step PZT and heavily Nb-doped PZT (PNZT) around the morphotropic phase boundary (MPB) were in-situ deposited under optimum condition by RF-magnetron sputtering. All 2 μm thick films had dense perovskite columnar grain structure and self-polarized (100) dominant orientation. PZT thin films were deposited on Pt/TiOx bottom electrode on Si wafer, and Nb doped PZT thin film was on Ir/TiW electrode with help of orientation control...
January 4, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28060705/cross-spectrum-pm-noise-measurements-thermal-energy-and-metamaterial-filters
#7
Yannick Gruson, Vincent Giordano, Ulrich L Rohde, Ajay Kumar Poddar, Enrico Rubiola
Virtually all commercial instruments for the measurement of the oscillator PM noise make use of the Cross Spectrum method (arXiv:1004.5539 [physics.ins-det], 2010). High sensitivity is achieved by correlation and averaging on two equal channels which measure the same input, and reject the background of the instrument. We show that a systematic error is always present if the thermal energy of the input power splitter is not accounted for. Such error can result in noise under estimation up to a few dB in the lowest-noise quartz oscillators, and in an invalid measurement in the case of cryogenic oscillators...
January 4, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28055864/a-sub-nyquist-variable-sampling-high-frequency-phased-array-beamformer
#8
Christopher A Samson, Andre Bezanson, Jeremy A Brown
A digital receive beamformer implementing a 'one sample per pixel' variable sampling technique is described. The sampling method reduces the required sampling rates by a factor of 3, and reduces the data capture rate by a factor of 2, in comparison to previous systems based on variable sampling. The sampling method is capable of estimating broadband pulse envelopes accurate for bandwidths up to 83.0%. This beamforming method has been implemented on an FPGA with maximum transmit and receive delay errors measured to be less than ± 1...
December 30, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28029621/drifts-and-environmental-disturbances-in-atomic-clock-subsystems-quantifying-local-oscillator-control-loop-ion-resonance-interactions
#9
Daphna G Enzer, William A Diener, David W Murphy, Shanti R Rao, Robert L Tjoelker
Linear ion trap frequency standards are among the most stable continuously-operating frequency references and clocks. Depending on the application, they have been operated with a variety of Local Oscillators (LO) including quartz Ultra-Stable Oscillators (USO), Hydrogen-masers, and Cryogenic Sapphire Oscillators. The short, intermediate, and long term stability of the frequency output is a complicated function of the fundamental performances, the time dependence of environmental disturbances, the atomic interrogation algorithm, the implemented control loop, and the environmental sensitivity of the LO and atomic system components...
December 19, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27992335/ultrasonic-3-d-vector-flow-method-for-quantitative-in-vivo-peak-velocity-and-flow-rate-estimation
#10
Simon Holbek, Caroline Ewertsen, Hamed Bouzari, Michael Johannes Pihl, Kristoffer Lindskov Hansen, Matthias Bo Stuart, Carsten Thomsen, Michael Bachmann Nielsen, Jorgen Arendt Jensen
Current clinical ultrasound systems are limited to show blood flow movement in either 1-D or 2-D. In this paper, a method for estimating 3-D vector velocities in a plane using the Transverse Oscillation (TO) method, a 32 x 32 element matrix array, and the experimental ultrasound scanner SARUS is presented. The aim of this paper is to estimate precise flow rates and peak velocities derived from 3-D vector flow estimates. The emission sequence provides 3-D vector flow estimates at up to 1.145 frames per second in a plane, and was used to estimate 3-D vector flow in a cross sectional image plane...
December 13, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27992333/continuous-subresolution-displacements-in-finite-difference-simulations-of-ultrasound-propagation-and-imaging
#11
Gianmarco Pinton
Time domain finite difference simulations are used extensively to simulate wave propagation. They approximate the wave field on a discrete domain with a grid spacing that is typically on the order of a tenth of a wavelength. The smallest displacements that can be modeled by this type of simulation are thus limited to discrete values that are integer multiples of the grid spacing. This paper presents a method to represent continuous and subresolution displacements by varying the impedance of individual elements in a multi-element scatterer...
December 12, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27992332/left-ventricular-myocardial-segmentation-in-3d-ultrasound-recordings-effect-of-different-endoand-epicardial-coupling-strategies
#12
Joao Pedrosa, Daniel Barbosa, Brecht Heyde, Frederic Schnell, Assami Rosner, Piet Claus, Jan D Hooge
Cardiac volume/function assessment remains a critical step in daily cardiology and 3D ultrasound plays an increasingly important role. Though development of automatic endocardial segmentation methods has received much attention, the same cannot be said about epicardial segmentation, in spite of the importance of full myocardial segmentation. In this study, different ways of coupling the endo- and epicardial segmentation are contrasted and compared to uncoupled segmentation. For this purpose, the B-spline Explicit Active Surfaces framework was used...
December 12, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27959809/ultrasonic-imaging-in-solids-using-wave-mode-beamforming
#13
Francesco Lanza di Scalea, Simone Sternini, Thompson Nguyen
This paper discusses some improvements to ultrasonic synthetic imaging in solids with primary applications to non-destructive testing of materials and structures. Specifically, the study proposes new adaptive weights applied to the beamforming array that are based on the physics of the propagating waves, specifically the displacement structure of the propagating longitudinal (L) mode and shear (S) mode that are naturally co-existing in a solid. The wave mode structures can be combined with the wave geometrical spreading to better filter the array (in a matched filter approach) and improve its focusing ability compared to static array weights...
December 7, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27959807/ultrasonic-needles-for-bone-biopsy
#14
Andrew Mathieson, Robert Wallace, Rebecca Cleary, Li Li, Hamish Simpson, Margaret Lucas
Bone biopsy is an invasive clinical procedure where a bone sample is recovered for analysis during the diagnosis of a medical condition. When the architecture of the bone tissue is required to be preserved, a core-needle biopsy is taken. Although this procedure is performed while the patient is under local anaesthesia, the patient can still experience significant discomfort. Additionally, large haematoma can be induced in the soft tissue surrounding the biopsy site due to the large axial and rotational forces which are applied through the needle to penetrate bone...
December 7, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913343/a-frequency-shift-method-to-measure-shear-wave-attenuation-in-soft-tissues
#15
Simon Bernard, Siavash Kazemirad, Guy Cloutier
In vivo quantification of shear wave attenuation in soft tissues may help to better understand human tissue rheology and lead to new diagnostic strategies. Attenuation is difficult to measure in acoustic radiation force elastography because the shear wave amplitude decreases due to a combination of diffraction and viscous attenuation. Diffraction correction requires assuming a cylindrical wavefront and an isotropic propagation medium, which may not be the case in some applications. In this study, the frequency shift method, used in ultrasound imaging and seismology, was adapted for shear wave attenuation measurement in elastography...
December 1, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913342/efficient-strategies-for-estimating-the-spatial-coherence-of-backscatter
#16
Dongwoon Hyun, Anna Lisa C Crowley, Jeremy J Dahl
The spatial coherence of ultrasound backscatter has been proposed to reduce clutter in medical imaging, to measure the anisotropy of the scattering source, and to improve the detection of blood flow. These techniques rely on correlation estimates that are obtained using computationally expensive strategies. In this study, we assess existing spatial coherence estimation methods and propose three computationally efficient modifications: a reduced kernel, a downsampled receive aperture, and the use of an ensemble correlation coefficient...
December 1, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913341/quantification-of-shear-wave-scattering-from-far-surface-defects-via-ultrasonic-wavefield-measurements
#17
Alexander J Dawson, Jennifer E Michaels, Joseph W Kummer, Thomas E Michaels
Nondestructive evaluation methods rely on prior knowledge of the expected interaction of ultrasonic waves with defects to inform detection and characterization decisions. Wavefield imaging, which refers to the measurement of signals originating from a spatially fixed source on a two-dimensional rectilinear grid, can be applied to visualize the effect of a subsurface scatterer on surface-measured wave motion. Here, obliquely-incident shear waves are directed at the far surface of a plate containing a through-hole using the well-known angle-beam ultrasonic inspection method...
December 1, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913340/efficient-3d-reconstruction-in-ultrasound-elastography-via-a-sparse-iteration-based-on-markov-random-fields
#18
Atul Ingle, Tomy Varghese, William Sethares
Percutaneous needle-based liver ablation procedures are becoming increasingly common for treatment of small isolated tumors in hepatocellular carcinoma patients who are not candidates for surgery. Rapid three dimensional visualization of liver ablations has potential clinical value because it can enable interventional radiologists to plan and execute needle-based ablation procedures with real time feedback. Ensuring the right volume of tissue is ablated is desirable to avoid recurrence of tumors from residual untreated cancerous cells...
November 29, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913339/a-parametric-study-for-the-design-of-an-optimized-ultrasonic-percussive-planetary-drill-tool
#19
Xuan Li, Patrick Harkness, Kevin Worrall, Ryan Timoney, Margaret Lucas
Traditional rotary drilling for planetary rock sampling, in-situ analysis and sample return, is challenging because the axial force and holding torque requirements are not necessarily compatible with lightweight spacecraft architectures in low-gravity environments. This article seeks to optimize an ultrasonic-percussive drill tool to achieve rock penetration with lower reacted force requirements, with a strategic view towards building an Ultrasonic Planetary Core Drill (UPCD) device. The UPCD is a descendant of the Ultrasonic/Sonic Driller/Corer (USDC) technique...
November 29, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913338/intracardiac-vortex-dynamics-by-high-frame-rate-doppler-vortography-i-in-vivo-i-comparison-with-vector-flow-mapping-and-4-d-flow-mri
#20
Julia Faurie, Mathilde Baudet, Kondo Claude Assi, Dominique Auger, Guillaume Gilbert, Francois Tournoux, Damien Garcia
Recent studies have suggested that intracardiac vortex flow imaging could be of clinical interest to early diagnose the diastolic heart function. Doppler vortography has been intro-duced as a simple color Doppler method to detect and quantify intraventricular vortices. This method is able to locate a vortex core based on the recognition of an antisymmetric pattern in the Doppler velocity field. Because the heart is a fast-moving organ, high frame rates are needed to decipher the whole blood vortex dynamics during diastole...
November 29, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
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