Articles de revues : « Ultrasound Pulse Wave »

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Nogueira, Rodrigo B., Lucas A. Pereira, Alice F. Basso, Ingrid S. da Fonseca et Lorena A. Alves. « Arterial pulse wave propagation velocity in healthy dogs by pulse wave Doppler ultrasound ». Veterinary Research Communications 41, n^o 1 (8 décembre 2016) : 33–40. http://dx.doi.org/10.1007/s11259-016-9669-2.

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Szabo, Thomas L. « Langevin’s contributions to pulse echo piezoelectric transducers ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A30. http://dx.doi.org/10.1121/10.0015433.

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Paul Langevin made fundamental discoveries which laid the foundations of modern pulse echo ultrasound over a hundred years ago. He was the first to employ piezoelectric crystals, X-cut quartz, with the propagation and electric axes aligned. In his design, the crystal thickness was a half-wavelength longitudinal wave resonator for both a transmitter and receiver which is the most popular configuration in use today. He invented the Langevin transducer which added two quarter wave layers on either side of the piezoelectric crystal to increase overall efficiency. A mosaic pattern embodied smaller pieces of scarce quartz. His original designs will be demonstrated through simulator models. By selecting ultrasound frequency of 40 KHz, he was able to make more directive beams and extend range for pulse echo detection. By adding triode amplifiers, the sensitivity of reception was increased greatly, and transmission powers of a kilowatt were achieved. With special circuits for making short pulses, long range, high resolution pulse echo ranging became a practical reality. Langevin’s innovations led to sonar and eventually to ultrasound imaging.

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Gurevich, S. Yu, et A. A. Shulginov. « TO THE THEORY OF LASER GENERATION OF ELASTIC WAVES IN FERROMAGNETIC METALS AT THE TEMPERATURE OF MAGNETIC PHASE TRANSITION ». Bulletin of the South Ural State University series "Mathematics. Mechanics. Physics" 13, n^o 3 (2021) : 69–78. http://dx.doi.org/10.14529/mmph210309.

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Laser generation of ultrasound has found wide application in modern technologies: to control the quality of composite materials, to detect layer separation in adhesive-bonded joints, subsurface and surface defects, as well as the quality of a product's surface in the process of manufacture. For excitation of waves in metals, pulse laser is normally used. In metallurgy, as well as in promising 3D technologies, it is necessary to control products at high temperatures (800°С and higher). To design ultrasound equipment with a pulsed laser radiation generator as the ultrasound source, it is required to conduct theoretical research of the process of laser generation of ultrasound in ferromagnetic metals at the temperature of magnetic phase transition, since the hot metal conversion for ferrum and ferrum-based alloys is, as a rule, performed namely at this temperature of 768 °С. The results of the experimental works allow to conclude that the temperature dependence of normalized amplitude of acoustic pulse in ferrum is of extreme character in the range of magnetic phase transition, i.e., in the range of Curie point. In this work a goal has been set to study the process of laser generation of ultrasound in ferromagnetic metal in the condition of non-linear dependence of the volume-expansion coefficient on the temperature. The task of thermoelastic excitation of longitudinal and transverse waves in ferromagnetic metal by a laser pulse at the temperature of magnetic phase transition has been solved. Diagrams of longitudinal and transverse wave patterns when ferromagnetic metal is exposed to laser pulses of various diameters have been obtained. Recommendations for effective use of laser generation of ultrasound in non-destructive testing and thickness measurement have been given.

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Jiang, Benyu, Baoming Liu, Karen L. McNeill et Philip J. Chowienczyk. « Measurement of Pulse Wave Velocity Using Pulse Wave Doppler Ultrasound : Comparison with Arterial Tonometry ». Ultrasound in Medicine & ; Biology 34, n^o 3 (mars 2008) : 509–12. http://dx.doi.org/10.1016/j.ultrasmedbio.2007.09.008.

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Shimizu, Kyosuke, Ayumu Osumi et Youichi Ito. « Lamb wave pulse compression in airborne ultrasound excitation ». Acoustical Science and Technology 44, n^o 2 (1 mars 2023) : 141–44. http://dx.doi.org/10.1250/ast.44.141.

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WESTERMARK, Sara, Hans WIKSELL, Håkan ELMQVIST, Kjell HULTENBY et Hans BERGLUND. « Effect of externally applied focused acoustic energy on clot disruption in vitro ». Clinical Science 97, n^o 1 (21 mai 1999) : 67–71. http://dx.doi.org/10.1042/cs0970067.

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Application of low-frequency ultrasound for clot disruption has been suggested as a potential therapy to enhance thrombus dissolution, but the optimal mode for delivery of ultrasound with clot-disruptive properties has not yet been extensively explored. Target-specific effects are desirable and may be accomplished by focusing the ultrasound. Adequate focusing, however, requires a short wavelength. The aim of this study was to compare the clot-disruptive effects of different modalities of focused acoustic energy. An in vitro model (10 blood clots for each modality) was used to test the clot-disruptive capacity of (i) shock waves generated in an electrohydraulic lithotriptor; (ii) focused continuous ultrasound of frequency 1.1 MHz, delivered from a specially constructed piezoelectric transducer; and (iii) focused pulse-modulated ultrasound of frequency 1.1 MHz delivered from the same transducer. Exposure to 30 s of focused pulse-modulated ultrasound caused a marked reduction (99±2%) in clot weight compared with 30 shock waves (11±5%) or 30 s exposure to focused continuous wave ultrasound (11±6%) (P< 0.0001). The observed marked and rapid disruptive effect on blood clots of focused high-frequency ultrasound indicates an alternative approach for external ultrasound-mediated thrombus destruction in vivo. The focused pulse-modulated technique has potential to exhibit the desired effect in a well-defined target volume and provides the means for control of the average power.

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Hisaka, Masaki, Tadao Sugiura et Satoshi Kawata. « Optical cross-sectional imaging with pulse ultrasound wave assistance ». Journal of the Optical Society of America A 18, n^o 7 (1 juillet 2001) : 1531. http://dx.doi.org/10.1364/josaa.18.001531.

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Song, Minho, Oleg A. Sapozhnikov, Yak-Nam Wang, Joo Ha Hwang et Tatiana D. Khokhlova. « Passive and Doppler-based assessment of cavitation activity induced by pulsed focused ultrasound ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A249—A250. http://dx.doi.org/10.1121/10.0016171.

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Pulsed focused ultrasound (pFUS) exposures utilizing short, nonlinearly distorted pulses at low duty cycle have been shown to enhance drug and gene delivery to targeted tissue through inertial cavitation activity. Passive cavitation detection (PCD) and mapping of broadband emissions are current conventional methods to monitor and quantify cavitation but provide limited spatial resolution. Here, plane-wave Doppler imaging was used with PCD to quantify pFUS-induced cavitation in ex vivo bovine tissues and in vivo surgically exposed porcine liver, kidney, and pancreas. A 1.5 MHz FUS transducer (aperture 75 mm, F-number 0.75) was used to deliver 60 pulses (duration 1 ms, 0.1% duty cycle, focal pressure p+ = 70i–110 MPa, p− = 13–20 MPa). A coaxially mounted ATL P7-4 ultrasound imaging probe was used for PCD during the FUS pulse, and Doppler and B-mode sequences. Disrupted tissue areas were collected for histology and compared to Doppler power images. Maximum Doppler power was found to correlate to broadband noise level for each FUS pulse. The Doppler power map integrated over the exposure was observed to correlate spatially with tissue disruption area from histology, which thus represents a promising real-time metric for quantifying cavitation activity induced by pFUS exposures. [Work supported by NIH R01CA154451, R01EB025187, and R01EB23910.]

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Xu, Lirui, Peng Wang, Pan Xia, Pang Wu, Xianxiang Chen, Lidong Du, Jiexin Liu, Ning Xue et Zhen Fang. « A Flexible Ultrasound Array for Local Pulse Wave Velocity Monitoring ». Biosensors 12, n^o 7 (30 juin 2022) : 479. http://dx.doi.org/10.3390/bios12070479.

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Pulse wave velocity (PWV) measured at a specific artery location is called local PWV, which provides the elastic characteristics of arteries and indicates the degree of arterial stiffness. However, the large and cumbersome ultrasound probes require an appropriate sensor position and pressure maintenance, introducing usability constraints. In this paper, we developed a light (0.5 g) and thin (400 μm) flexible ultrasound array by encapsulating 1–3 composite piezoelectric transducers with a silicone elastomer. It can capture the distension waveforms of four arterial positions with a spacing of 10 mm and calculate the local PWV by multi-point fitting. This is illustrated by in vivo experiments, where the local PWV value of five normal subjects ranged from 3.07 to 4.82 m/s, in agreement with earlier studies. The beat-to-beat coefficient of variation (CV) is 12.0% ± 3.5%, showing high reliability. High reproducibility is shown by the results of two groups of independent measurements of three subjects (the error between the mean values is less than 0.3 m/s). These properties of the developed flexible ultrasound array enable the bandage-like application of local PWV monitoring to skin surfaces.

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Ricci, Stefano, et Valentino Meacci. « Data-Adaptive Coherent Demodulator for High Dynamics Pulse-Wave Ultrasound Applications ». Electronics 7, n^o 12 (14 décembre 2018) : 434. http://dx.doi.org/10.3390/electronics7120434.

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Pulse-Wave Doppler (PWD) ultrasound has been applied to the detection of blood flow for a long time; recently the same method was also proven effective in the monitoring of industrial fluids and suspensions flowing in pipes. In a PWD investigation, bursts of ultrasounds at 0.5–10 MHz are periodically transmitted in the medium under test. The received signal is amplified, sampled at tens of MHz, and digitally processed in a Field Programmable Gate Array (FPGA). First processing step is a coherent demodulation. Unfortunately, the weak echoes reflected from the fluid particles are received together with the echoes from the high-reflective pipe walls, whose amplitude can be 30–40 dB higher. This represents a challenge for the input dynamics of the system and the demodulator, which should clearly detect the weak fluid signal while not saturating at the pipe wall components. In this paper, a numerical demodulator architecture is presented capable of auto-tuning its internal dynamics to adapt to the feature of the actual input signal. The proposed demodulator is integrated into a system for the detection of the velocity profile of fluids flowing in pipes. Simulations and experiments with the system connected to a flow-rig show that the data-adaptive demodulator produces a noise reduction of at least of 20 dB with respect to different approaches, and recovers a correct velocity profile even when the input data are sampled at 8 bits only instead of the typical 12–16 bits.

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Maeda, Kazuo. « Diagnostic Ultrasound Safety ». Donald School Journal of Ultrasound in Obstetrics and Gynecology 8, n^o 2 (2014) : 178–83. http://dx.doi.org/10.5005/jp-journals-10009-1353.

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ABSTRACT Ultrasound bioeffect is discussed from its physical property, i.e. thermal effect by thermal index, mechanical effect by mechanical index, and by the output intensity of ultrasound. Generally, thermal and mechanical indices should be lower than 1 in obstetrical setting, and threshold output intensity of no bioeffect is lower than SPTA 240 mW/cm2 in pulse wave. Pulsed Doppler ultrasound thermal and mechanical indices should be also lower than 1, and should be carefully used it in 11 to 13+6 weeks of pregnancy. Real-time B-mode, transvaginal scan, pulsed Doppler, 3D and 4D ultrasound were separately discussed in the ultrasound safety. Generally diagnostic ultrasound is safe for the fetus and embryo, if thermal and mechanical indices are lower than 1, and ultrasound devices are safe, if it is used under official limitation, e.g. the output intensity is less than SPTA 10 mW/cm2 in Japan. The ultrasound user is responsible ultrasound safety, e.g. higher thermal and mechanical indices than 1 should be lowered to be lower than 1, controlling the device output intensity. The user should learn bioeffects of ultrasound and prudent use of ultrasound under the ALARA principle. How to cite this article Maeda K, Kurjak A. Diagnostic Ultrasound Safety. Donald School J Ultrasound Obstet Gynecol 2014;8(2):178-183.

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Vappou, J., J. Luo, K. Okajima, M. Di Tullio et E. E. Konofagou. « Non-invasive measurement of local pulse pressure by pulse wave-based ultrasound manometry (PWUM) ». Physiological Measurement 32, n^o 10 (9 septembre 2011) : 1653–62. http://dx.doi.org/10.1088/0967-3334/32/10/012.

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Rahman, Anum, Yu-Qing Zhou, Yohan Yee, Jun Dazai, Lindsay S. Cahill, John Kingdom, Christopher K. Macgowan et John G. Sled. « Ultrasound detection of altered placental vascular morphology based on hemodynamic pulse wave reflection ». American Journal of Physiology-Heart and Circulatory Physiology 312, n^o 5 (1 mai 2017) : H1021—H1029. http://dx.doi.org/10.1152/ajpheart.00791.2016.

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Abnormally pulsatile umbilical artery (UA) Doppler ultrasound velocity waveforms are a hallmark of severe or early onset placental-mediated intrauterine growth restriction (IUGR), whereas milder late onset IUGR pregnancies typically have normal UA pulsatility. The diagnostic utility of these waveforms to detect placental pathology is thus limited and hampered by factors outside of the placental circulation, including fetal cardiac output. In view of these limitations, we hypothesized that these Doppler waveforms could be more clearly understood as a reflection phenomenon and that a reflected pulse pressure wave is present in the UA that originates from the placenta and propagates backward along the UA. To investigate this, we developed a new ultrasound approach to isolate that portion of the UA Doppler waveform that arises from a pulse pressure wave propagating backward along the UA. Ultrasound measurements of UA lumen diameter and flow waveforms were used to decompose the observed flow waveform into its forward and reflected components. Evaluation of CD1 and C57BL/6 mice at embryonic day (E)15.5 and E17.5 demonstrated that the reflected waveforms diverged between the strains at E17.5, mirroring known changes in the fractal geometry of fetoplacental arteries at these ages. These experiments demonstrate the feasibility of noninvasively measuring wave reflections that originate from the fetoplacental circulation. The observed reflections were consistent with theoretical predictions based on the area ratio of parent to daughters at bifurcations in fetoplacental arteries suggesting that this approach could be used in the diagnosis of fetoplacental vascular pathology that is prevalent in human IUGR. Given that the proposed measurements represent a subset of those currently used in human fetal surveillance, the adaptation of this technology could extend the diagnostic utility of Doppler ultrasound in the detection of placental vascular pathologies that cause IUGR. NEW & NOTEWORTHY Here, we describe a novel approach to noninvasively detect microvascular changes in the fetoplacental circulation using ultrasound. The technique is based on detecting reflection pulse pressure waves that travel along the umbilical artery. Using a proof-of-principle study, we demonstrate the feasibility of the technique in two strains of experimental mice.

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Venugopal, Prem, et Luca Marinelli. « Localization of Arterial Bleeds Using Pulse Wave Reflections ». Military Medicine 186, Supplement_1 (1 janvier 2021) : 346–50. http://dx.doi.org/10.1093/milmed/usaa371.

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ABSTRACT Introduction Localization of internal arterial bleeds is necessary for treatment in the battlefield. In this article, we describe a novel approach that utilizes pulse wave reflections generated by a bleed to locate it. Materials and Methods To demonstrate our approach, velocity and diameter waveforms in the presence of bleeds were simulated using the 1D wave propagation equations in a straight-vessel model of the human thoracic aorta. The simulated waveforms were then decomposed into forward and backward components using wave intensity analysis. Reflections arising from the bleed were identified from the decomposed waveforms. Results Reflection generated by the bleed introduced a new feature in the backward component, compared to the normal, no-bleed condition. The bleed location could be determined from the time delay between this reflection feature and the forward wave creating it, and the pulse wave velocity in the vessel. Conclusions The findings of this study could be utilized by ultrasound for hemorrhage localization.

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Wahyulaksana, Geraldi, Luxi Wei, Jason Voorneveld, Nico de Jong, Antonius F. van der Steen et Hendrik Vos. « High-order singular value decomposition of contrast pulsing sequences for improved clutter suppression ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A184. http://dx.doi.org/10.1121/10.0015970.

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Contrast-enhanced ultrasound is a diagnostic tool used to visualize blood flow in the cardiovascular system. The use of ultrasound contrast agent (microbubbles) in combination with contrast pulsing scheme (CPS) improves the sensitivity and specificity of ultrasound flow imaging by enhancing the signal in the blood compartment. The commonly used CPS are pulse inversion (PI), amplitude modulation (AM), and amplitude-modulated pulse inversion (AMPI). Using differences in phase or amplitude of multiple pulses, the linear tissue clutter signal can be suppressed. However, this process can be degraded by motion or non-linear propagation of the ultrasound wave. These effects cause the cancellation of linear clutter signal to be ineffective We propose using higher-order singular value decomposition (HOSVD) with spatial, temporal, and pulsing dimensions as the input to improve clutter suppression under the conditions of motion and non-linear propagation. We performed systematic in-vitro- experiment emulating these conditions, as well as in-vivo cardiac measurements. The results showed that HOSVD increases the clutter suppression of all the 3 CPS compared to the conventional linear processing. The improvement of clutter reduction could be beneficial to various cardiac evaluation like myocardial perfusion or intra ventricular flow assessment.

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Collette, M., C. Morizzo, M. Kozakova, C. Palombo et G. Leftheriotis. « P6.18 CAROTID-FEMORAL PULSE WAVE VELOCITY ESTIMATED BY AN ULTRASOUND SYSTEM ». Artery Research 7, n^o 3-4 (2013) : 159. http://dx.doi.org/10.1016/j.artres.2013.10.199.

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Reesink, Koen D., Evelien Hermeling, M. Christianne Hoeberigs, Robert S. Reneman et Arnold P. G. Hoeks. « Carotid artery pulse wave time characteristics to quantify ventriculoarterial responses to orthostatic challenge ». Journal of Applied Physiology 102, n^o 6 (juin 2007) : 2128–34. http://dx.doi.org/10.1152/japplphysiol.01206.2006.

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Central blood pressure waveforms contain specific features related to cardiac and arterial function. We investigated posture-related changes in ventriculoarterial hemodynamics by means of carotid artery (CA) pulse wave analysis. ECG, brachial cuff pressure, and common CA diameter waveforms (by M-mode ultrasound) were obtained in 21 healthy volunteers (19–30 yr of age, 10 men and 11 women) in supine and sitting positions. Pulse wave analysis was based on a timing extraction algorithm that automatically detects acceleration maxima in the second derivative of the CA pulse waveform. The algorithm enabled determination of isovolumic contraction period (ICP) and ejection period (EP): ICP = 43 ± 8 (SD) ms (4-ms precision), and EP = 302 ± 16 (SD) ms (5-ms precision). Compared with the supine position, in the sitting position diastolic blood pressure (DBP) increased by 7 ± 4 mmHg ( P < 0.001) and R-R interval decreased by 49 ± 82 ms ( P = 0.013), reflecting normal baroreflex response, whereas EP decreased to 267 ± 19 ms ( P < 0.001). Shortening of EP was significantly correlated to earlier arrival of the lower body peripheral reflection wave ( r2 = 0.46, P < 0.001). ICP increased by 7 ± 7 ms ( P < 0.001), the ICP-to-EP ratio increased from 14 ± 3% (supine) to 19 ± 3% ( P < 0.001) and the DBP-to-ICP ratio decreased by 7% ( P = 0.023). These results suggest that orthostasis decreases left ventricular output as a result of arterial wave reflections and, presumably, reduced cardiac preload. We conclude that CA ultrasound and pulse wave analysis enable noninvasive quantification of ventriculoarterial responses to changes in posture.

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Carvalho, Camila Franco de, Jéssica Ribeiro Magalhães, Andreia Moreira Martins, Kyrla Cartynalle das Dores Silva Guimarães, Reiner Silveira de Moraes, Daniel Bartoli de Sousa et Andréia Vitor Couto do Amaral. « Pulsed-wave doppler ultrasound in canine reproductive system – Part 1 : technical aspects ». Research, Society and Development 10, n^o 5 (15 mai 2021) : e52510515348. http://dx.doi.org/10.33448/rsd-v10i5.15348.

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The purpose of this article is to review the literature on the essential technical aspects of implementing the pulsed Doppler, as part of the teachings to their use in the diagnosis of changes in the canine reproductive system. A narrative review was carried out, using scientific articles, monographs, theses and dissertations published and available in online databases: Periodical Capes (Coordination for the Improvement of Higher Education Personnel), SciELO (Scientific Electronic Library Online) and Google Scholar, in addition to specific books on the topic. Two-dimensional ultrasound has been widely used in medicine since 1942, leading to advancements in disease identification and subsequent prognosis. In terms of vascular assessment, Doppler ultrasound is used to evaluate the blood flow inside the vessel, its direction, and hemodynamic pattern. Among all types of Doppler ultrasound, the Color Doppler (CD), Power Doppler (PD), and the Pulsed-wave Doppler (PW) are commonly used in the identification of abnormalities through ultrasound flow imaging and the analysis of hemodynamic indices: peak systolic velocity (PSV), end diastolic velocity (EDV), resistance index (RI), and pulsatility index (PI). To accurately estimate these hemodynamic indices, however, it is essential to know the technical adjustments and parameters such as the pulse repetition frequency (PRF), size of the sample volume (Gate), angle of insonation, gain, baseline, and wall filter, which need to be corrected to avoid technician derive artifacts such as aliasing, signal absence, and mirror imaging. In medicine, the use of Doppler Mode in reproductive functions is already well established, but its use in veterinary medicine is still a subject of recent studies.

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Lascio, N., R. Bruno, F. Stea, V. Gemignani, E. Bianchini, L. Ghiadoni et F. Faita. « P2.10 ASSESSMENT OF CAROTID PULSE WAVE VELOCITY BY ULTRASOUND : A WAVE INTENSITY ANALYSIS-BASED APPROACH ». Artery Research 8, n^o 4 (2014) : 135. http://dx.doi.org/10.1016/j.artres.2014.09.106.

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Mobadersany, Nima, Nirvedh H. Meshram et Elisa Konofagou. « Pulse wave propagation through a stenotic artery with plaque constituents of different stiffnesses : In vitro-experiment and fluid–structure interaction simulation ». Journal of the Acoustical Society of America 151, n^o 4 (avril 2022) : A213. http://dx.doi.org/10.1121/10.0011083.

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Vulnerable (typically, softer) carotid plaques may rupture leading to blockages downstream in the brain with high potential for ischemic stroke. Pulse Wave Imaging (PWI) developed by our group is an ultrasound-based technique for pulse wave visualization and pulse wave velocity (PWV) mapping. In this study, the accuracy of PWV estimation in stenotic vessels was assessed in simulation and phantom studies. Fluid–structure interaction simulations were performed in a stenotic (50%) vessel. Experimental stenotic (50%) polyvinyl alcohol (PVA) phantoms (2 mm thickness, 8 mm lumen diameter, and 165 mm length) with soft/medium/hard plaque constituents of different stiffness (E0 = 12 kPa, 30 kPa, 94 kPa) were constructed matching the simulation geometry and parameters. Pulse waves were generated by a computer-controlled pump using a physiologic flow waveform. The RF frames were acquired by a Verasonics Vantage 256 system using a 5 MHz (L7-4) linear array. The acquired RF frames were beamformed using a delay and sum algorithm, and a GPU-based, 1-D cross correlation method was used to estimate the wall velocities. The acceleration peak of the pulse wave was tracked to estimate PWV. PWVs of 2.6 ms−1, 3.4 ms−1, and 4.5 ms−1 were, respectively, measured for the soft, medium, and stiff plaque material in experimental phantoms. The PWV of 2.7 m/s was confirmed for the medium plaque in simulation. This fundamental study demonstrated, thus, a good accuracy by PWI in the estimation of plaque PWV and its underlying stiffness for future stroke risk assessment.

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Liang, Haidong-Dong, Chun Sing Louis Tsui, Michael Halliwell et Peter N. T. Wells. « Continuous wave ultrasonic Doppler tomography ». Interface Focus 1, n^o 4 (juin 2011) : 665–72. http://dx.doi.org/10.1098/rsfs.2011.0018.

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In continuous wave ultrasonic Doppler tomography (DT), the ultrasonic beam moves relative to the scanned object to acquire Doppler-shifted frequency spectra which correspond to cross-range projections of the scattering and reflecting structures within the object. The relative motion can be circular or linear. These data are then backprojected to reconstruct the two-dimensional image of the object cross section. By using coherent processing, the spatial resolution of ultrasonic DT is close to an order of magnitude better than that of traditional pulse-echo imaging at the same ultrasound frequency.

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Mijarez, Rito. « Flood Detection in Steel Tubes Using Guided Wave Energy Leakage ». Sensors 23, n^o 3 (25 janvier 2023) : 1334. http://dx.doi.org/10.3390/s23031334.

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A study that evaluated the use of ultrasonic-guided waves to detect water in hollow pipes is presented. In this work, a guided wave system employed a 40 kHz piezoelectric (PZT) transmitter and a PZT ultrasound transducer. The transmitter was based on a battery-operated microcontroller, and the receiver was composed of a digital signal processor (DSP) module connected to a PC via a USB for monitoring purposes. The transmitter and receiver were attached, non-intrusively without perfect alignment, to the external wall of a steel tube 1 m × 270 mm × 2 mm in size. Flood detection was performed based on guided wave attenuation due to energy leakage from the internal steel wall of the tube to water. Two approaches were carried out. The former was an off-line signal response based on the wavelet energy entropy analysis of a received pulse; the latter was a real-time hit-and-miss analysis centered on measuring the time–space in-between two transmitted pulses. Experiments performed in the laboratory successfully identified flooded tubes.

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Ronda Peñacoba, Silvia, Mar Fernández Gutiérrez, Julio San Román del Barrio et Francisco Montero de Espinosa. « Effects of Non-thermal Ultrasound on a Fibroblast Monolayer Culture : Influence of Pulse Number and Pulse Repetition Frequency ». Sensors 21, n^o 15 (25 juillet 2021) : 5040. http://dx.doi.org/10.3390/s21155040.

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Despite the use of therapeutic ultrasound in the treatment of soft tissue pathologies, there remains some controversy regarding its efficacy. In order to develop new treatment protocols, it is a common practice to carry out in vitro studies in cell cultures before conducting animal tests. The lack of reproducibility of the experimental results observed in the literature concerning in vitro experiments motivated us to establish a methodology for characterizing the acoustic field in culture plate wells. In this work, such acoustic fields are fully characterized in a real experimental configuration, with the transducer being placed in contact with the surface of a standard 12-well culture plate. To study the non-thermal effects of ultrasound on fibroblasts, two different treatment protocols are proposed: long pulse (200 cycles) signals, which give rise to a standing wave in the well with the presence of cavitation (ISPTP max = 19.25 W/cm2), and a short pulse (five cycles) of high acoustic pressure, which produces a number of echoes in the cavity (ISPTP = 33.1 W/cm2, with Pmax = 1.01 MPa). The influence of the acoustic intensity, the number of pulses, and the pulse repetition frequency was studied. We further analyzed the correlation of these acoustic parameters with cell viability, population, occupied surface, and cell morphology. Lytic effects when cavitation was present, as well as mechanotransduction reactions, were observed.

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Cormack, John M., Marc A. Simon et Kang Kim. « Time-domain formulation for coherent plane wave compounding in horizontally layered media ». Journal of the Acoustical Society of America 151, n^o 4 (avril 2022) : A213. http://dx.doi.org/10.1121/10.0011086.

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The locations of origin of ultrasonic echoes from soft tissue in conventional ultrasound beamforming are based on measured time of flight. For simplicity it is usually assumed that the region of interest is homogeneous with a constant sound speed, but in many in vivo and benchtop applications the imaging region is composed of horizontal layers, each with a distinct sound speed. In addition to time-of-flight complications, sound speed differences between the layers result in refraction through the interface of both the transmitted pulse and those reflected from the tissue, further influencing the fidelity of beamforming for target localization or other quantitative ultrasound metrics. A formulation is presented for delay-and-sum coherent Plane Wave Compounding (PWC) that accounts for variation in sound speed and refraction of ultrasound pulses in a region with two horizontal layers. The algorithm is formulated completely in the time domain, enabling simple implementation or extension of existing homogeneous PWC algorithms. Simulated and experimental images are investigated for a typical two-layer benchtop configuration, where the sound speeds in the upper and lower layers are relatively slow (water or gel) and fast (muscle), respectively. Extension of the formulation to a medium with N distinct layers is discussed.

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Feeney, Robin N. M. « An investigation of ultrasound methods for the assessment of sex and age from intact human teeth ». Dental Anthropology Journal 18, n^o 1 (3 septembre 2018) : 2–11. http://dx.doi.org/10.26575/daj.v18i1.128.

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Determining sex and age in humanremains is necessary to achieve positive identificationof individuals in forensic settings, and to provide datarequired for demographic analyses in archaeologicalsamples. Due to their denser mineralization, teeth maybe better preserved than other skeletal elements, whichare often fragmentary and poorly preserved. This workis the first to investigate the use of ultrasound methodsto accurately, objectively, and non-destructively assesssex and estimate age of human skeletal remains fromintact teeth. An ultrasound imaging system usingpulse-echo technique and nominal frequency (3.5 MHz)longitudinal waves was developed for applicationon teeth. Mechanical and acoustic properties of teethwere examined to explore their relationship withthe interaction of ultrasound wave propagation.Experiments were conducted to determine differencesin wave propagation in teeth from individualsof different ages and sex, both permanent anddeciduous. Consistent differences in integral acousticresponse patterns in the different teeth were found.It is concluded that pulse-echo ultrasound is a viablenon-destructive technique to yield integral acousticcharacteristic properties of teeth, potentially usefulfor assessing sex and estimating age, and resolvingminimum numbers of individuals from commingledand scattered remains. Information developed fromthis study will be significant to future research insofaras it introduces a new potential method that is nondestructive,fast, and easy to administer in situ.

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He, Changde, Binzhen Zhang, Chenyang Xue, Wendong Zhang et Shengdong Zhang. « Wafer-Bonding Fabricated CMUT Device with Parylene Coating ». Micromachines 12, n^o 5 (4 mai 2021) : 516. http://dx.doi.org/10.3390/mi12050516.

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The advantages of the capacitive micromachined ultrasound transducer (CMUT) technology have provided revolutionary advances in ultrasound imaging. Extensive research on CMUT devices for high-frequency medical imaging applications has been conducted because of strong demands and fabrication realization by using standard silicon IC fabrication technology. However, CMUT devices for low-frequency underwater imaging applications have been rarely researched because it is difficult to fabricate thick membrane structures through depositing processes using standard IC fabrication technology due to stress-related problems. To address this shortcoming, in this paper, a CMUT device with a 2.83-μm thick silicon membrane is proposed and fabricated. The CMUT device is fabricated using silicon fusion wafer-bonding technology. A 5-μm thick Parylene-C is conformally deposited on the device for immersion measurement. The results show that the fabricated CMUT can transmit an ultrasound wave, receive an ultrasound wave, and have pulse-echo measurement capability. The ability of the device to emit and receive ultrasonic waves increases with the bias voltage but does not depend on the voltage polarity. The results demonstrate the viability of the fabricated CMUT in low-frequency applications from the perspectives of the device structure, fabrication, and characterization. This study presents the potential of the CMUT for underwater ultrasound imaging applications.

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Boardman, Henry, Katherine Birse, Esther F. Davis, Polly Whitworth, Veena Aggarwal, Adam J. Lewandowski et Paul Leeson. « Comprehensive multi-modality assessment of regional and global arterial structure and function in adults born preterm ». Hypertension Research 39, n^o 1 (24 septembre 2015) : 39–45. http://dx.doi.org/10.1038/hr.2015.102.

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Abstract Preterm birth is associated with higher blood pressure, which could be because preterm birth alters early aortic elastin and collagen development to cause increased arterial stiffness. We measured central and conduit artery size and multiple indices of arterial stiffness to define the extent and severity of macrovascular changes in individuals born preterm. A total of 102 young adults born preterm and 102 controls who were born after an uncomplicated pregnancy underwent cardiovascular magnetic resonance on a Siemens 1.5 T scanner to measure the aortic cross-sectional area in multiple locations. Ultrasound imaging with a Philips CX50 and linear array probe was used to measure carotid and brachial artery diameters. Carotid-femoral pulse wave velocity and the augmentation index were measured by SphygmoCor, brachial-femoral pulse wave velocity by Vicorder and aortic pulse wave velocity by cardiovascular magnetic resonance. The cardio-ankle vascular index (CAVI) was used as a measurement of global stiffness, and ultrasound was used to assess peripheral vessel distensibility. Adults born preterm had 20% smaller thoracic and abdominal aortic lumens (2.19±0.44 vs. 2.69±0.60 cm2, P<0.001; 1.25±0.36 vs. 1.94±0.45 cm2, P<0.001, respectively) but similar carotid and brachial diameters to adults born at term. Pulse wave velocity was increased (5.82±0.80 vs. 5.47±0.59 m s−1, P<0.01, 9.06±1.25 vs. 8.33±1.28 m s−1, P=0.01, 5.23±1.19 vs. 4.75±0.91 m s−1, P<0.01) and carotid distensibility was decreased (4.75±1.31 vs. 5.60±1.48 mm Hg−1103, P<0.001) in this group compared with the group born at term. However, the global and peripheral arterial stiffness measured by CAVI and brachial ultrasound did not differ (5.95±0.72 vs. 5.98±0.60, P=0.80 and 1.07±0.48 vs. 1.19±0.54 mm Hg−1103, P=0.12, respectively). Adults who are born preterm have significant differences in their aortic structure from adults born at term, but they have relatively small differences in central arterial stiffness that may be partially explained by blood pressure variations.

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HASEGAWA, Hideyuki, Kazue HONGO et Hiroshi KANAI. « Measurement of regional pulse wave velocity using very high frame rate ultrasound ». Choonpa Igaku 42, n^o 6 (2015) : 701–9. http://dx.doi.org/10.3179/jjmu.jjmu.k.8.

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Zhou, Lixia, Kirk W. Beach, Hai-Dong Liang, Mike Halliwell et Peter N. T. Wells. « Noninvasive measurement of local arterial pulse wave velocity in humans by ultrasound ». Journal of Medical Engineering & ; Technology 35, n^o 6-7 (27 juillet 2011) : 362–69. http://dx.doi.org/10.3109/03091902.2011.595532.

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Hoctor, Ralph, Aaron Dentinger et Kai Thomenius. « Array signal processing for local arterial pulse wave velocity measurement using ultrasound ». IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 54, n^o 5 (mai 2007) : 1018–27. http://dx.doi.org/10.1109/tuffc.2007.347.

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Rabben, Stein Inge, Nikos Stergiopulos, Leif Rune Hellevik, Otto A. Smiseth, Stig Slørdahl, Stig Urheim et Bjørn Angelsen. « An ultrasound-based method for determining pulse wave velocity in superficial arteries ». Journal of Biomechanics 37, n^o 10 (octobre 2004) : 1615–22. http://dx.doi.org/10.1016/j.jbiomech.2003.12.031.

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Hasegawa, Hideyuki, Kazue Hongo et Hiroshi Kanai. « Measurement of regional pulse wave velocity using very high frame rate ultrasound ». Journal of Medical Ultrasonics 40, n^o 2 (10 octobre 2012) : 91–98. http://dx.doi.org/10.1007/s10396-012-0400-9.

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Tian, Zixuan, Yun Jing et Aiguo Han. « Transcranial ultrasound imaging using pulse-echo ultrasound and deep learning : A numerical study ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A113. http://dx.doi.org/10.1121/10.0015722.

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Phase aberration caused by skulls is a main challenge in transcranial ultrasound imaging for adults. Aberration could be corrected if the skull profile (i.e., thickness distribution) and speed of sound (SOS) are known. We previously designed a deep learning (DL) model to estimate the skull profile and SOS using pulse-echo ultrasound signals. This study’s objective is to develop strategies to improve the estimation and evaluate the effectiveness of aberration correction in transcranial ultrasound imaging. Acoustic simulations were performed using k-Wave in this numerical study. The following strategies were used to improve estimation: (1) A phased array was used instead of a single-element transducer; (2) Channel radiofrequency data were used instead of beamformed data as the DL model input; (3) A DL model was developed to incorporate physics into architecture design and model training. Compared with previously reported results, these strategies improved the correlation coefficient between the estimated and ground-truth values from 0.82 to 0.94 for SOS, and from 0.98 to 0.99 for thickness. Simulated transcranial images of point targets with phase correction using the estimated SOS and thickness values showed significantly reduced artifacts than those without correction. The results demonstrate feasibility of the proposed approach for transcranial ultrasound imaging.

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Campos-Arias, Daime, Marc L. De Buyzere, Julio A. Chirinos, Ernst R. Rietzschel et Patrick Segers. « Longitudinal Changes of Input Impedance, Pulse Wave Velocity, and Wave Reflection in a Middle-Aged Population ». Hypertension 77, n^o 4 (avril 2021) : 1154–65. http://dx.doi.org/10.1161/hypertensionaha.120.16149.

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The changes experienced by the arterial system due to the aging process have been extensively studied but are incompletely understood. Within-subject patterns of changes in regards to input impedance and wave reflection parameters have not been assessed. The Asklepios study is a longitudinal population study including healthy (at onset) middle-aged subjects, with 974 males and 1052 females undergoing 2 rounds of measurements of applanation tonometry and ultrasound, 10.15±1.40 years apart. Carotid-femoral pulse wave velocity, aortic input impedance, and wave reflection parameters were assessed, and linear mixed-effects models were used to evaluate their longitudinal trajectories and determinants. Overall, the effective 10-year increase in pulse wave velocity was less than expected from first round cross-sectional data, and pulse wave velocity was found to accelerate more in women than in men. Interestingly, the increase in pulse wave velocity was not paralleled by a decrease in arterial volume compliance, particularly in younger males. Aortic root characteristic impedance decreased with age in younger subjects while it increased for the older subjects in the study. These changes suggest that aortic dilation and elongation may play an important role determining the longitudinal age-related changes in impedance parameters in middle-age. Wave reflection decreased with aging, whereas resistance increased in women and decreased in men. We conclude that the effective impact of aging on arterial system properties, in a middle-aged population, is not well reflected by cross-sectional studies. Future studies should assess the interaction between geometric remodeling and wall stiffening as determinants of pulsatile hemodynamics.

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Ran, Dan, Jinping Dong, He Li et Wei-Ning Lee. « Spontaneous extension wave for in vivo assessment of arterial wall anisotropy ». American Journal of Physiology-Heart and Circulatory Physiology 320, n^o 6 (1 juin 2021) : H2429—H2437. http://dx.doi.org/10.1152/ajpheart.00756.2020.

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An extension wave formed by longitudinal wall displacements was observed by high-frame-rate ultrasound in the human common carotid artery in vivo. A strong correlation between extension wave velocity and arterial longitudinal stiffness complements the well-established pulse wave, which is linked to circumferential stiffness, to noninvasively assess direction-dependent wall elasticity of the major artery. The proposed anisotropy index, which directly reflects arterial wall microstructure and function, might be a potential risk factor for screening (sub-) clinical cardiovascular diseases.

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Shen, Bin, Zhen Yun Zhang, Qiong Wei Li, Ming Xing Li et Bin Yang. « The Simulation Research on Ultrasound Signal Propagation Model for Oil and Gas Pipeline Corrosion ». Applied Mechanics and Materials 229-231 (novembre 2012) : 1702–5. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.1702.

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The elastic stress field theory is used to research the quantitative relation model between ultrasonic pulse-echo and layer structure when ultrasonic wave is vertical-incidence transmission, and numerical simulation has demonstrated the models are available.

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Munir, Shahzad, Benyu Jiang, Antoine Guilcher, Sally Brett, Simon Redwood, Michael Marber et Philip Chowienczyk. « Exercise reduces arterial pressure augmentation through vasodilation of muscular arteries in humans ». American Journal of Physiology-Heart and Circulatory Physiology 294, n^o 4 (avril 2008) : H1645—H1650. http://dx.doi.org/10.1152/ajpheart.01171.2007.

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Exercise markedly influences pulse wave morphology, but the mechanism is unknown. We investigated whether effects of exercise on the arterial pulse result from alterations in stroke volume or pulse wave velocity (PWV)/large artery stiffness or reduction of pressure wave reflection. Healthy subjects ( n = 25) performed bicycle ergometry. with workload increasing from 25 to 150 W for 12 min. Digital arterial pressure waveforms were recorded using a servo-controlled finger cuff. Radial arterial pressure waveforms and carotid-femoral PWV were determined by applanation tonometry. Stroke volume was measured by echocardiography, and brachial and femoral artery blood flows and diameters were measured by ultrasound. Digital waveforms were recorded continuously. Other measurements were made before and after exercise. Exercise markedly reduced late systolic and diastolic augmentation of the peripheral pressure pulse. At 15 min into recovery, stroke volume and PWV were similar to baseline values, but changes in pulse wave morphology persisted. Late systolic augmentation index (radial pulse) was reduced from 54 ± 3.9% at baseline to 42 ± 3.7% ( P < 0.01), and diastolic augmentation index (radial pulse) was reduced from 37 ± 1.8% to 25 ± 2.9% ( P < 0.001). These changes were accompanied by an increase in femoral blood flow (from 409 ± 44 to 773 ± 48 ml/min, P < 0.05) and an increase in femoral artery diameter (from 8.2 ± 0.4 to 8.6 ± 0.4 mm, P < 0.05). In conclusion, exercise dilates muscular arteries and reduces arterial pressure augmentation, an effect that will enhance ventricular-vascular coupling and reduce load on the left ventricle.

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Maxwell, Adam, Ga Won Kim, Elizabeth Lynch, Brian MacConaghy, Eva Furrow, Jody Lulich, Michael Borofsky et Michael R. Bailey. « A burst wave lithotripsy system for urinary stones in pet cats ». Journal of the Acoustical Society of America 150, n^o 4 (octobre 2021) : A353. http://dx.doi.org/10.1121/10.0008562.

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Upper urinary tract stones are becoming more prevalent in cats. Surgery to address obstructing stones has poor outcomes and such stones can rarely be treated with medical therapy. Burst wave lithotripsy (BWL) is a non-invasive, ultrasound-guided, handheld focused ultrasound technology to disintegrate urinary stones, which is now in human clinical trials. In this project, we created a scaled version of the system for use on pet cats, adjusting geometric parameters and frequency of the transducer to account for differences in anatomic scale and stone size. A 650-kHz prototype transducer was fabricated, calibrated, and tested on 25 natural feline stones 2–5 mm applying 20-cycle pulses at 10 Hz pulse repetition rate with three different focal pressure amplitudes ≤8.9 MPa in an in vitro tissue phantom. The fragments were sieved in 10-min intervals to assess breakage. The results demonstrated that between 73%–96% of the stone mass was reduced to fragments i<1 mm in a 30-min exposure, with only 2/25 stones showing no visible fragmentation. These data suggest BWL can fragment feline ureteral stones and that a high-frequency system can produce small fragments more likely to pass through the small ureter of a cat. [Work supported by NIDDK P01 DK043881.]

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Khokhlova, Tatiana D., Minho Song, Randall P. Williams, Joo Ha Hwang, Yak-Nam Wang et Oleg A. Sapozhnikov. « Passive and active Doppler methods and metrics to quantify inertial cavitation induced by pulsed focused ultrasound ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A215. http://dx.doi.org/10.1121/10.0016055.

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Inertial cavitation induced by pulses of nonlinearly distorted focused ultrasound (FUS) at moderate intensity can result in mild mechanical disruption of tissue, short of its complete mechanical disintegration—histotripsy. This effect can be used to enhance diffusion of subsequently systemically administered drugs or biologics. Previously, single-element passive cavitation detection (PCD) of broadband noise emissions was successfully used to quantify tissue disruption and enhancement in drug concentration. This metric, however, has limitations: minimal spatial resolution and challenges with calibration when used at large depths in acoustically variable tissue. To address this, we developed a combination of passive and active Doppler-based methods that relied on relative, rather than absolute signal metrics. Specifically, destructive cavitation behaviors were previously linked to substantial motion of the bubbles during the FUS pulse due to acoustic radiation force and shock scattering. This was reflected in the backscattered FUS harmonics as Doppler shift and measurable from PCD. The bubbles were observed to dissolve within milliseconds following each FUS pulse, thus their distribution could be visualized as an area of rapid change via fast plane wave Doppler ensemble following the FUS pulse. The Doppler power distribution was spatially correlated with the area of tissue disruption in the in vivo experiments. [Work supported by NIH R01CA154451, R01EB025187, and R01EB23910.]

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SHINTAKU, YUKO, TOSHIFUMI TAKABAYASHI, HIROYUKI SASAKI, NOBUYOSHI OZAWA et AKIRA YAJIMA. « Sister Chromatid Exchanges in Mouse after Exposure to Pulse-Wave Ultrasound in Utero. » Tohoku Journal of Experimental Medicine 170, n^o 2 (1993) : 63–69. http://dx.doi.org/10.1620/tjem.170.63.

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Collette, Mathieu, Carlo Palombo, Carmela Morizzo, Sara Sbragi, Michaela Kozakova et Georges Leftheriotis. « Carotid–Femoral Pulse Wave Velocity Assessed by Ultrasound : A Study with Echotracking Technology ». Ultrasound in Medicine & ; Biology 43, n^o 6 (juin 2017) : 1187–94. http://dx.doi.org/10.1016/j.ultrasmedbio.2017.02.005.

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Li, Xiaopeng, Jue Jiang, Hong Zhang, Hua Wang, Donggang Han, Qi Zhou, Ya Gao, Shanshan Yu et Yanhua Qi. « Measurement of carotid pulse wave velocity using ultrafast ultrasound imaging in hypertensive patients ». Journal of Medical Ultrasonics 44, n^o 2 (8 décembre 2016) : 183–90. http://dx.doi.org/10.1007/s10396-016-0755-4.

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Nosova, M. N., Yu A. Bondarchuk, I. I. Shakhmatov, A. V. Matsyura, P. S. Marshalkina et D. A. Prokopets. « Distress symptoms development after a single episode of ultrasound exposure ». Kazan medical journal 100, n^o 1 (15 décembre 2019) : 140–46. http://dx.doi.org/10.17816/kmj2019-140.

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Aim. To study the influence of a single 24-hour episode of exposure to ultrasound waves propagating in air on microcirculation and parameters of hemostasis in rats. Methods. The study was performed on 28 Wistar male rats. The experimental group was exposed to ultrasound for 24 hours. Geometric mean frequency was 25 kHz, acoustic pressure was 84.3 dB. Parameters of microcirculation of experimental rats received by laser Doppler flowmetry were compared with those of intact animals. Also comparative analysis of platelet and coagulation hemostasis, anticoagulant and fibrinolytic plasma activity was performed in rats from both groups. Results. In experimental rats in response to 24-hour exposure to ultrasound, significant decrease of the studied active and passive factors of blood flow modulation occurred compared to those of intact animals: parameters of microcirculation, flax, endothelial and vasomotor wave amplitude, respiratory and pulse wave amplitude. When studying the parameters of hemostasis, significant hypercoagulation of extrinsic pathway and at the latest stages of coagulation which worsened with anticoagulant plasma activity inhibition along with decrease of fibrinolytic activity. The character of changes of hemostatic parameters confirmed the development of stress-reaction in rats registered during the study of microcirculation. Conclusion. 24-hour ultrasound exposure causes significant disorders of microcirculation and unfavorable shifts in hemostasis - the signs of distress.

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Li, Ronny X., Ada Ip, Elena Sanz-Miralles et Elisa E. Konofagou. « Noninvasive evaluation of varying pulse pressures in vivo using brachial sphymomanometry, applanation tonometry, and Pulse Wave Ultrasound Manometry ». Artery Research 18, n^o C (2017) : 22. http://dx.doi.org/10.1016/j.artres.2017.02.002.

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Reimann, Manja, Norbert Weiss, Walthard Vilser et Tjalf Ziemssen. « Local endothelial dysfunction does not affect global endothelial function ». Vasa 44, n^o 4 (juillet 2015) : 277–84. http://dx.doi.org/10.1024/0301-1526/a000442.

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Abstract. Background: The purpose of this study was to evaluate two alternative non-invasive techniques for assessment of endothelial function in adults with special focus on their ability to monitor acute changes. Patients and methods: Twenty-five clinically healthy men (mean age 24 ± 2 years) underwent endothelial function measurements twice in fasting state and twice after experimental induction of transient endothelial dysfunction by oral application of 0.1g/kg L-methionine and by ingestion of 500 ml whipped cream (30 % fat), respectively. Microvascular vasodilator responses to flickering-light by retinal vessel analysis and vascular responses to inhaled salbutamol by pulse wave analysis were assessed at each occasion. Ultrasound based flow-mediated dilation (FMD) was used as reference method. Results: Transient endothelial dysfunction in response to acute hyperlipidaemia and hyperhomocysteinaemia was verified by blunted brachial responses to hyperaemia. Retinal vessel analysis demonstrated significantly impaired flicker-responses of retinal vessels to both challenges depending on the vessel type. Pulse wave analysis did not show any significant changes in salbutamol responses. Reproducibility of retinal vessel analysis was comparable to FMD and slightly better than pulse wave analysis. Conclusions: Acute changes in endothelial function can be monitored by retinal vessel analysis with comparable reproducibility as FMD. Salbutamol based pulse wave analysis is currently unsuited to detect endothelial dysfunction in serial measurements.

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Kenny, Jon-Émile S., Andrew M. Eibl, Matthew Parrotta, Bradley F. Long et Joseph K. Eibl. « The Feasibility of a Novel Index From a Wireless Doppler Ultrasound Patch to Detect Decreasing Cardiac Output in Healthy Volunteers ». Military Medicine 186, Supplement_1 (1 janvier 2021) : 751–56. http://dx.doi.org/10.1093/milmed/usaa248.

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ABSTRACTIntroductionEarly hemorrhage is often missed by traditional vital signs because of physiological reserve, especially in the young and healthy. We have developed a novel, wearable, wireless Doppler ultrasound patch that tracks real-time blood velocity in the common carotid artery.Materials and MethodsWe studied eight healthy volunteers who decreased their cardiac output using a standardized Valsalva maneuver. In all eight, we simultaneously monitored the velocity time integral (VTI) of the common carotid artery (using the ultrasound patch) as well as the descending aorta (using a traditional pulsed wave duplex imaging system); the descending aortic VTI was used as a surrogate for left ventricular stroke volume (SV). Additionally, in a subset of four, we simultaneously measured SV using a noninvasive pulse contour analysis device.ResultsFrom baseline to peak effect of Valsalva, there was a statistically significant fall in descending aortic and common carotid VTI of 37% (P = 0.0005) and 23% (P < 0.0001), respectively. Both values returned to baseline on recovery. Additionally, a novel index from the carotid ultrasound patch (i.e., the heart rate divided by the carotid artery VTI) detected a 10% fall in aortic VTI with high sensitivity and specificity (100% and 100%, respectively); this novel index also accurately detected a 10% decrease in SV as measured by the noninvasive SV monitor. The mean arterial pressure, measured by the noninvasive pulse contour device, did not correctly detect the fall in SV.ConclusionIn summary, a novel index from a wireless Doppler ultrasound patch may be more sensitive and specific for detecting decreased cardiac output than standard vital signs in healthy volunteers.

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Liu, Wei-Wen, Sy-Han Huang et Pai-Chi Li. « Synchronized Optical and Acoustic Droplet Vaporization for Effective Sonoporation ». Pharmaceutics 11, n^o 6 (14 juin 2019) : 279. http://dx.doi.org/10.3390/pharmaceutics11060279.

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Inertial cavitation-based sonoporation has been utilized to enhance treatment delivery efficacy. In our previous study, we demonstrated that tumor therapeutic efficacy can be enhanced through vaporization-assisted sonoporation with gold nanodroplets (AuNDs). Specifically, the AuNDs were vaporized both acoustically (i.e., acoustic droplet vaporization, ADV) and optically (i.e., optical droplet vaporization, ODV). A continuous wave (CW) laser was used for ODV in combination with an ultrasound pulse for ADV. Although effective for vaporization, the use of a CW laser is not energy efficient and may create unwanted heating and concomitant tissue damage. In this study, we propose the use of a pulsed wave (PW) laser to replace the CW laser. In addition, the PW laser was applied at the rarefaction phase of the ultrasound pulse so that the synergistic effects of ADV and ODV can be expected. Therefore, a significantly lower laser average power can be expected to achieve the vaporization threshold. Compared to the CW laser power at 2 W/cm2 from the previous approach, the PW laser power was reduced to only 0.2404 W/cm2. Furthermore, we also demonstrate in vitro that the sonoporation rate was increased when the PW laser was applied at the rarefaction phase. Specifically, the vaporization signal, the inertial cavitation signal, and the sonoporation rate all displayed a 1-µs period, which corresponded to the period of the 1-MHz acoustic wave used for ADV, as a function of the relative laser delay. The increased sonoporation rate indicates that this technique has the potential to enhance sonoporation-directed drug delivery and tumor therapy with a lower laser power while keeping the cell death rate at the minimum. Photoacoustic imaging can also be performed at the same time since a PW laser is used for the ODV.

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Cahill, Lindsay S., Yu-Qing Zhou, Johnathan Hoggarth, Lisa X. Yu, Anum Rahman, Greg Stortz, Clare L. Whitehead et al. « Placental vascular abnormalities in the mouse alter umbilical artery wave reflections ». American Journal of Physiology-Heart and Circulatory Physiology 316, n^o 3 (1 mars 2019) : H664—H672. http://dx.doi.org/10.1152/ajpheart.00733.2018.

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Current methods to detect placental vascular pathologies that monitor Doppler ultrasound changes in umbilical artery (UA) pulsatility have only moderate diagnostic utility, particularly in late gestation. In fetal mice, we recently demonstrated that reflected pressure waves propagate counter to the direction of flow in the UA and proposed the measurement of these reflections as a means to detect abnormalities in the placental circulation. In the present study, we used this approach in combination with microcomputed tomography to investigate the relationship between altered placental vascular architecture and changes in UA wave reflection metrics. Fetuses were assessed at embryonic day (E) 15.5 and E17.5 in control C57BL6/J mice and dams treated with combination antiretroviral therapy (cART), a known model of fetal growth restriction. Whereas the reflection coefficient was not different between groups at E15.5, it was 27% higher at E17.5 in cART-treated mice compared with control mice. This increase in reflection coefficient corresponded to a 36% increase in the total number of vessel segments, a measure of overall architectural complexity. Interestingly, there was no difference in UA pulsatility index between groups, suggesting that the wave reflections convey information about vascular architecture that is not captured by conventional ultrasound metrics. The wave reflection parameters were found to be associated with the morphology of the fetoplacental arterial tree, with the area ratio between the UA and first branch points correlating with the reflection coefficient. This study highlights the potential for wave reflection to aid in the noninvasive clinical assessment of placental vascular pathology. NEW & NOTEWORTHY We used a novel ultrasound methodology based on detecting pulse pressure waves that propagate along the umbilical artery to investigate the relationship between changes in wave reflection metrics and altered placental vascular architecture visualized by microcomputed tomography. Using pregnant mice treated with combination antiretroviral therapy, a model of fetal growth restriction, we demonstrated that reflections in the umbilical artery are sensitive to placental vascular abnormalities and associated with the geometry of the fetoplacental tree.

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Connors, Bret A., Tony Gardner, Ziyue Liu, James E. Lingeman et James C. Williams. « Preliminary report on the functional changes associated with burst wave lithotripsy treated pig kidneys ». Journal of the Acoustical Society of America 150, n^o 4 (octobre 2021) : A352. http://dx.doi.org/10.1121/10.0008559.

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Burst Wave Lithotripsy (BWL) is a new stone treatment that utilizes ultrasound to fracture renal calculi. However, it is not known if BWL alters renal function, so we tested if a clinical dose of BWL impacts glomerular filtration rate (GFR) or kidney blood flow. Treatment consisted of placing each pig (32–42 kg) on its side, locating the lower pole of the right kidney, and treating that kidney with a BWL dose of 18,000 ultrasound pulses at 10Hz, 20 cycles/pulse and a peak negative pressure of −7 MPa (n = 6). Six additional pigs were used as sham controls. Inulin and para-aminohippuric acid (PAH) were infused into the pigs with blood and urine samples being collected both before and 1-h after BWL treatment. The concentrations of inulin and PAH were determined in the samples and used to calculate GFR and effective renal plasma flow (eRPF). For the BWL treated group, GFR and eRPF did not change after BWL exposure (−6.7 ± 7.2% for GFR, −10.9 ± 5.5% for eRPF), and this response was like the sham control group ( P = 0.23 for GFR, P = 0.08 for eRPF). A typical clinical dose of BWL caused no change in renal function. [Work supported by NIH, Grant P01 DK43881.]

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WANG, YI, SIPING CHEN, TIANFU WANG, TING ZHOU, QIAOLIANG LI, YI ZHENG et XIN CHEN. « DEVELOPMENT OF A GENERIC ULTRASOUND VIBRO-ACOUSTIC IMAGING PLATFORM FOR TISSUE ELASTICITY AND VISCOSITY ». Journal of Innovative Optical Health Sciences 05, n^o 01 (janvier 2012) : 1250002. http://dx.doi.org/10.1142/s1793545812500022.

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Tissue elasticity and viscosity are always associated with pathological changes. As a new imaging method, ultrasound vibro-acoustic imaging is developed for quantitatively measuring tissue elasticity and viscosity which have important significance in early diagnosis of cancer. This paper developed an ultrasound vibro-acoustic imaging research platform mainly consisting of excitation part and detection part. The excitation transducer was focused at one location within the medium to generate harmonic vibration and shear wave propagation, and the detection transducer was applied to detect shear wave at other locations along shear wave propagation path using pulse-echo method. The received echoes were amplified, filtered, digitized and then processed by Kalman filter to estimate the vibration phase. According to the phase changes between different propagation locations, we estimated the shear wave speed, and then used it to calculate the tissue elasticity and viscosity. Preliminary phantom experiments based on this platform show results of phantom elasticity and viscosity close to literature values. Upcoming experiments are now in progress to obtain quantitative elasticity and viscosity in vitro tissue.

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