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Arterial Stiffness Assessment by Shear Wave Elastography and Ultrafast Pulse Wave Imaging: Comparison with Reference Techniques in Normotensives and Hypertensives
摘要： Shear wave elastography and ultrafast imaging of the carotid artery pulse wave were performed in 27 normotensive participants and 29 age- and sex-matched patients with essential hypertension, and compared with reference techniques: carotid–femoral pulse wave velocity (cfPWV) determined via arterial tonometry and carotid stiffness (carPWV) determined via echotracking. Shear wave speed in the carotid anterior (a-SWS) and posterior (p-SWS) walls were assessed throughout the cardiac cycle. Ultrafast PWV was measured in early systole (ufPWV-FW) and in end-systole (dicrotic notch, ufPWV-DN). Shear wave speed in the carotid anterior appeared to be the best candidate to evaluate arterial stiffness from ultrafast imaging. In univariate analysis, a-SWS was associated with carPWV (r = 0.56, p = 0.003) and carotid-to-femoral PWV (r = 0.66, p < 0.001). In multivariate analysis, a-SWS was independently associated with age (R2 = 0.14, p = 0.02) and blood pressure (R2 = 0.21, p = 0.004). Moreover, a-SWS increased with blood pressure throughout the cardiac cycle and did not differ between normotensive participants and patients with essential hypertension when compared at similar blood pressures.
关键词： Hypertension,Vascular ultrasound,Arterial stiffness,Pulse wave velocity,Shear wave elastography,Ultrafast imaging,Echotracking
更新于2025-09-23 15:22:29
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Anisotropy of acoustic and thermal expansion properties of TlInSe <sub/>2</sub> crystals
摘要： Based on experimental studies of acoustic wave velocities in TlInSe2 crystals, all components of their elastic stiffness and compliance tensors are determined. TlInSe2 has three acoustic axes parallel to the principal crystallographic directions. The lowest velocities of acoustic eigenwaves are used to estimate the acousto-optic figure of merit. We analyse deviations from purely longitudinal and transverse polarization states, as well as the obliquity of acoustic energy flow. Temperature dependences of strains along the three principal crystallographic directions and of acoustic wave velocities v11, v22 and v33 are measured. Anomalous behaviour of these parameters occur at T1≈245 K and T2≈145 K. It is shown that the symmetry of TlInSe2 becomes lower than tetragonal below the temperature point T1.
关键词： TlInSe2 crystals,Ferroics,elastic properties,thermal expansion,anisotropy,acoustic wave velocity
更新于2025-09-23 15:21:21
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Pulse Wave Imaging in Carotid Artery Stenosis Human Patients in Vivo
摘要： Carotid stenosis involves narrowing of the lumen in the carotid artery potentially leading to a stroke, which is the third leading cause of death in the United States. Several recent investigations have found that plaque structure and composition may represent a more direct biomarker of plaque rupture risk compared with the degree of stenosis. In this study, pulse wave imaging was applied in 111 (n = 11, N = 13 plaques) patients diagnosed with moderate (>50%) to severe (>80%) carotid artery stenosis to investigate the feasibility of characterizing plaque properties based on the pulse wave-induced arterial wall dynamics captured by pulse wave imaging. Five (n = 5 patients, N = 20 measurements) healthy volunteers were also imaged as a control group. Both conventional and high-frame-rate plane wave radiofrequency imaging sequences were used to generate piecewise maps of the pulse wave velocity (PWV) at a single depth along stenotic carotid segments, as well as intra-plaque PWV mapping at multiple depths. Intra-plaque cumulative displacement and strain maps were also calculated for each plaque region. The Bramwell(cid:3)Hill equation was used to estimate the compliance of the plaque regions based on the PWV and diameter. Qualitatively, wave convergence, elevated PWV and decreased cumulative displacement around and/or within regions of atherosclerotic plaque were observed and may serve as biomarkers for plaque characterization. Intra-plaque mapping revealed the potential to capture wave re?ections between calci?ed inclusions and differentiate stable (i.e., calci?ed) from vulnerable (i.e., lipid) plaque components based on the intra-plaque PWV and cumulative strain. Quantitatively, one-way analysis of variance indicated that the pulse wave-induced cumulative strain was signi?cantly lower (p < 0.01) in the moderately and severely calci?ed plaques compared with the normal controls. As expected, compliance was also signi?cantly lower in the severely calci?ed plaques regions compared with the normal controls (p < 0.01). The results from this pilot study indicated the potential of pulse wave imaging coupled with strain imaging to differentiate plaques of varying stiffness, location and composition. Such ?ndings may serve as valuable information to compensate for the limitations of currently used methods for the assessment of stroke risk. (E-mail: ek2191@columbia.edu) ? 2018 World Federation for Ultrasound in Medicine & Biology. All rights reserved.
关键词： Arterial wall elasticity maps,Arterial wall motion,Atherosclerosis,Pulse wave velocity,Pulse wave imaging,High-frame-rate ultrasound,Calci?ed plaque,Arterial compliance
更新于2025-09-23 15:21:01
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Analysis of velocity calculation methods of laser-induced surface acoustic wave
摘要： The key to measuring residual stress by surface acoustic wave method is the accurate measurement of velocity. In this paper, the velocity of laser-induced broadband surface acoustic wave is studied, and three velocity calculation methods of surface acoustic wave, time domain method, phase method and wavelet method are compared. The calculation error of the time domain method under the condition of dispersion is analyzed. A recursive method for calculating phase difference is proposed to improve the efficiency of phase method. The simulated surface acoustic waves are used to compare the phase method and wavelet method under the conditions of attenuation and dispersion. Compared with the wavelet method, the phase method cannot distinguish the time when the frequency band appears, and the velocity calculation of adjacent frequency points is related, while the wavelet method is independent of each other. The wavelet method can improve the calculation accuracy of the velocity curve by interpolating the original data. After interpolation, the trend of curve is more obvious, and the fitting error is greatly reduced.
关键词： Wavelet,Dispersion,Comparative analysis,Surface acoustic wave,Wave velocity
更新于2025-09-11 14:15:04
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Electrochemical Polymerization-Fabricated Several Triphenylamine–Carbazolyl-Based Polymers with Improved Short-Circuit Current and High Adsorption Stability in Dye-Sensitized Solar Cells
摘要： Elastic impedance (EI) inversion as a popular pre-stack seismic inversion method has been studied in the past years. However, the robustness of estimating elastic parameters of P-wave velocity, S-wave velocity, and density in conventional EI inversion is still controversial, especially the accuracy of the S-wave velocity. In this paper, we show that the obvious inversion error of the Vs is associated with the accuracy of the ratio of VS to VP (VS/VP) when the three parameters are inverted. The deviation of the VS/VP in the linearized Zoeppritz equation provided by Aki and Richards results in the mismatch between the forward and backward modeling. A new kind of inversion formula containing VS/VP as the inversion parameter is proposed, by which VS can be estimated in terms of the new inverted parameter. Due to the nonlinear relationship between the new inverted term and the VS, the Newton downhill method is used to solve the nonlinear problem. The synthetic data inversion examples demonstrate the performance of the new formula.
关键词： Elastic impedance inversion,synthetic data inversion,Newton downhill method,VS/VP ratio,S-wave velocity
更新于2025-09-11 14:15:04
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[IEEE 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Novosibirsk, Russia (2018.10.2-2018.10.6)] 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE) - Up-to-Date Thermal Imaging Systems in the Multichannel Automated Measurements
摘要： A highly informative methodology, the essence of which is to obtain the parameters of an object under study by means of the data synchronous acquisition from several measurement channels, predominantly based on different physical principles, infrared thermography (IRT) as a leading research tool included in such a multichannel (multimodal) measuring system is considered in some detail. The IRT-aided multichannel approach is demonstrated with studying the physiological characteristics in humans. The measurement synchronism of different technical means is realized by the computerization and automation of the experiment. The programmable microcontroller ESP32 served as main operating and readout unit. With a time resolution of 100-200 measurements per second, the experimental data were obtained. It made it possible to reveal the human physiological characteristics as follows: the extremities temperature change, pulse waves and their velocity in the radial artery, breathing dynamics, blood pressure evaluated in two different regimes of brachial cuff air filling – inflation and deflation. The brachial cuff inflation also served as external interventional impact on the organism. It is found that, after the brachial artery cross-clamping, the pulse wave velocity in the radial artery is capable of doubling in comparison with that measured before compression. It is shown that the multimodal technology is a promising means in modern experimental science.
关键词： SEIRT,blood pressure measurement,breathing dynamics,experiment automation,multichannel (multimodal) measurements,pulse wave velocity,Infrared thermography,thermal imaging,programmable microcontroller,pulse wave,computer-aided measurements
更新于2025-09-04 15:30:14