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In the field of clinical ultrasound, the full digitalization of diagnostic equipment in the 2000s enabled the technological development of quantitative ultrasound (QUS), followed by multiple diagnostic technologies that have been put into practical use in recent years. In QUS, tissue characteristics are quantified and parameters are calculated by analyzing the radiofrequency (RF) echo signals returning to the transducer. However, the physical properties (and pathological level structure) of the biological tissues responsible for the imaging features and QUS parameters have not been sufficiently verified as there are various conditions for observing living tissue with ultrasound and inevitable discrepancies between theoretical and actual measurements. A major issue of QUS in clinical application is that the evaluation results depend on the acquisition conditions of the RF echo signal as the source of the image information, and also vary according to the model of the diagnostic device. In this paper, typical examples of QUS techniques for evaluating attenuation, speed of sound, amplitude envelope characteristics, and backscatter coefficient in living tissues are introduced. Exemplary basic research and clinical applications related to these technologies, and initiatives currently being undertaken to establish the QUS method as a true tissue characterization technology, are also discussed.

The phenomena that occur during internal heating (release of the control radio power) of an acousto-optic deflector based on paratellurite with heat removal from the piezoelectric transducer through a liquid contact were experimentally investigated. It was found that, in addition to the temperature drift of the velocity of sound and the refractive indices, the temperature inhomogeneity has a significant effect on the deflector characteristics. In this case, the volume of the crystal behaves like an optical wedge, which is optically denser near the transducer and less dense at a distance from it. The effect of internal compensation of the thermal deviation of the diffracted-beam position at a certain deflector orientation is detected.

Aim of the study: At present, there are few scatter particles used in preparing blood-mimicking fluids, such as nylon, sephadex, polystyrene microsphere, and poly(4-methystyrene). In this study, we present cholesterol as a new scatter particle for blood-mimicking fluid preparation. Materials and methods: The procedure for the preparation of the proposed blood-mimicking fluid involved the use of propylene glycol, D(+)-Glucose and distilled water to form a ternary mixture fluid, with cholesterol used as scatter particles. Polyethylene glycol was first used as part of the mixture fluid but the acoustic and physical properties were not suitable, leading to its replacement with D(+)-Glucose, which is soluble in water and has a higher density. A common carotid artery wall-less phantom was also produced to assess the flow properties. Results: The prepared blood-mimicking fluid with new scatter particles has a density of 1.067 g/cm3, viscosity of 4.1 mPa.s, speed of sound 1600 m/s, and attenuation of 0.192 dB/cm at 5 MHz frequency. Peak systolic velocity, end diastolic velocity and mean velocity measurements were gotten to be 40.2 ± 2.4 cm/s, 9.9 ± 1.4 cm/s, and 24.0 ± 1.8 cm/s, respectively. Conclusion: Based on the results obtained, the blood-mimicking fluid was found suitable for ultrasound applications in carotid artery wall-less phantoms because of its good acoustic and physical properties.

Diffuse reverberation is ultrasound image noise caused by multiple reflections of the transmitted pulse before returning to the transducer, which degrades image quality and impedes the estimation of displacement or flow in techniques such as elastography and Doppler imaging. Diffuse reverberation appears as spatially incoherent noise in the channel signals, where it also degrades the performance of adaptive beamforming methods, sound speed estimation, and methods that require measurements from channel signals. In this paper, we propose a custom 3D fully convolutional neural network (3DCNN) to reduce diffuse reverberation noise in the channel signals. The 3DCNN was trained with channel signals from simulations of random targets that include models of reverberation and thermal noise. It was then evaluated both on phantom and in-vivo experimental data. The 3DCNN showed improvements in image quality metrics such as generalized contrast to noise ratio (GCNR), lag one coherence (LOC) contrast-to-noise ratio (CNR) and contrast for anechoic regions in both phantom and in-vivo experiments. Visually, the contrast of anechoic regions was greatly improved. The CNR was improved in some cases, however the 3DCNN appears to strongly remove uncorrelated and low amplitude signal. In images of in-vivo carotid artery and thyroid, the 3DCNN was compared to short-lag spatial coherence (SLSC) imaging and spatial prediction filtering (FXPF) and demonstrated improved contrast, GCNR, and LOC, while FXPF only improved contrast and SLSC only improved CNR.

International audience; Black tattoo ink comprises hydrophobic carbon black nanoparticles. We hypothesized that black tattoo ink demonstrates transient dynamic activity in an ultrasound field. Brightness-mode sonography was performed on cylindrical receptacles of different bore diameters, filled with black tattoo ink, water, saline, or air, using pulsed ultrasound with center frequencies of 13 MHz and 5 MHz. The scattering from black ink itself lasted less than ten minutes. At 13-MHz sonication, a transient drop in sound speed was observed, as well as a transient lessening of scattering from distal phantom tissue. The linear acoustic attenuation coefficient of pure black ink was measured to be 0.15±0.01 dB cm^{−1} MHz^{−1}, equal to whole blood. Low-intensity ultrasonic tattoo removal would be of interest as an alternative to techniques that damage surrounding tissue.

This letter proposes the use of ultrasound computed tomography (USCT) for handwriting by imaging sound velocity changes in a medium caused by a rod. The rod was used as a writing object, and the tomographic instrument was able to process the data over time with a temporal frequency of 4 frames per second. Tests are carried out in writing various words and letters using USCT data and automatic imaging software. The work shows the functional imaging capability offered by the USCT system combining qualitative and temporal imaging features.

Computed ultrasound tomography in echo mode (CUTE) is a promising ultrasound (US) based multi-modal technique that allows to image the spatial distribution of speed of sound (SoS) inside tissue using hand-held pulse-echo US. It is based on measuring the phase shift of echoes when detected under varying steering angles. The SoS is then reconstructed using a regularized inversion of a forward model that describes the relation between the SoS and echo phase shift. Promising results were obtained in phantoms when using a Tikhonov-type regularization of the spatial gradient (SG) of SoS. In-vivo, however, clutter and aberration lead to an increased phase noise. In many subjects, this phase noise causes strong artifacts in the SoS image when using the SG regularization. To solve this shortcoming, we propose to use a Bayesian framework for the inverse calculation, which includes a priori statistical properties of the spatial distribution of the SoS to avoid noise-related artifacts in the SoS images. In this study, the a priori model is based on segmenting the B-Mode image. We show in a simulation and phantom study that this approach leads to SoS images that are much more stable against phase noise compared to the SG regularization. In a preliminary in-vivo study, a reproducibility in the range of 10 ms−1 was achieved when imaging the SoS of a volunteer’s liver from different scanning locations. These results demonstrate the diagnostic potential of CUTE for example for the staging of fatty liver disease.

Broadband spectrograms from surface ships are employed in convolutional neural networks (CNNs) to predict the seabed type, ship speed, and closest point of approach (CPA) range. Three CNN architectures of differing size and depth are trained on different representations of the spectrograms. Multitask learning is employed; the seabed type prediction comes from classification, and the ship speed and CPA range are estimated via regression. Due to the lack of labeled field data, the CNNs are trained on synthetic data generated using measured sound speed profiles, four seabed types, and a random distribution of source parameters. Additional synthetic datasets are used to evaluate the ability of the trained CNNs to interpolate and extrapolate source parameters. The trained models are then applied to a measured data sample from the 2017 Seabed Characterization Experiment (SBCEX 2017). While the largest network provides slightly more accurate predictions on tests with synthetic data, the smallest network generalized better to the measured data sample. With regard to the input data type, complex pressure spectral values gave the most accurate and consistent results for the ship speed and CPA predictions with the smallest network, whereas using absolute values of the pressure provided more accurate results compared to the expected seabed types.

In this research paper, various machine learning techniques are implemented to predict the velocity of sound at sea. An analysis of various potential predictors and their correlations are also underlined. The dataset used for this research is a synthetic dataset. Multi beam echo sounder, an instrument that calculates various parameters like temperature, salinity, depth, etc. is used for making the dataset. This equipment is generally used on research ships to study the seawater characteristics in ocean at various places. It was permitted for use from such an Indian Coastal Research Vessel (CRV) on request for academic purpose only. The methodology proposed in this paper learns the pattern of every observation using the following algorithms: Linear Regression, Random Forest and Stochastic Gradient Descent (SGD). Furthermore, an analysis of the features and their correlations with the target variable, with the help of various Data Mining methods is presented.

In Nondestructive Evaluation (NDE), ultrasound imaging is a useful tool for detecting flaws or measuring corrosion in metal pipes. Phased-array systems are becoming standard in NDE, as well as post-processing imaging techniques such as the Total Focusing Method. These techniques require knowledge of parameters such as distance between transducer elements, times of arrival and sound speed to produce sharp images. A deviation in sound speed, for instance, may compromise image accuracy. In this paper, we propose a sound speed estimator based on image quality metrics. The approach consists in generating several reconstructed images from the same acquisition signals, but using a set of candidate sound speeds. The speed value that yields the sharpest image is then chosen as the estimated sound speed. Estimates made on data obtained by simulation of a typical scenario presented relative combined uncertainties as low as 0.0166%. The results, obtained in both simulated and real scenarios, show good agreement with expected speeds. The proposed method can be considered a reference-free sound speed calibration method aimed at field applications.

An equation of state based on the perturbed-chain statistical associating fluid theory (PC-SAFT) for estimates of sound speed in natural-gas mixtures is successfully applied in this work. Prediction results of the speed of sound for five binary and six multicomponent systems (dataset includes 1000 data points taken from literature) containing hydrocarbons, nitrogen, and carbon dioxide in a wide range of temperatures (250–415 K) and pressures (0.1–60 MPa) are presented. The fitting parameters of the binary interaction were not used in the calculations. The results of modeling for the speed of sound are shown to be in good agreement with the literature data.

Methods for measuring the composition of a binary gas mixture using the dependence of the speed of sound in a gas on its molecular weight, in particular, using an acoustic resonator, are considered. The described atmospheric hydrogen sensor target station for the cyclotron of the S-70 accelerator, which allows the production of medical isotopes, as well as a sensor for the content of neon in helium during its liquefaction, was developed based on this principle at the Kurchatov Institute IHEP SIC. Optimization of the resonator characteristics allowed a resolution of 10–5.

This paper presents the observational report of the authors on measured density (ρ), speed of sound (u) of pure liquids of Ethyl propionate (EP), and various renewable oxygenated fossil fuels (1,2-...

The United States, Russia, and China are developing an array of hypersonic weapons—maneuverable vehicles that carry warheads through the atmosphere at more than five times the speed of sound. Propo...

The acoustic properties of ultrasound phantom materials have always been important, but with new applications interrogating tissue mechanical properties, viscoelasticity has also become an interesting feature to consider. Along with Young's modulus, the viscous component of tissue is affected by certain diseases and can therefore be used as a biomarker. Furthermore, viscoelasticity varies between tissue types and individuals, and therefore it would be useful with a phantom material that reflects this physiological range. Here we describe a gel for ultrasound imaging with a range of mechanical properties given by mixing different ratios of two oil-based gels, clear ballistic and styrene-ethylene/butylene-styrene (SEBS). The gels were mixed in five different proportions, ranging from 0-100% of either gel. For each of the gel compositions, we measured time of flight to determine speed of sound, narrowband ultrasound transmission for attenuation, stress-relaxation for viscoelasticity, mass and volume. Analysis of the stress-relaxation data using the generalized Maxwell model suggests that the material can be described by five parameters, E0, E1, E2, η1 and η2, and that each of these parameters decreases as more SEBS is incorporated into the mixed material. Instantaneous Young's modulus (the sum of E0, E1 and E2 in our model) ranges between 49 and 117 kPa for the different ratios, similar to values reported for cancerous tissue. Despite the large span of obtainable mechanical properties, speed of sound is relatively constant regardless of composition, with mean value estimates (± 95 % CI) between 1438 ± 9 and 1455 ± 3 m/s for pure and mixed gels. This was attributed to a variation in density and Poisson's ratio, following from the relation linking them to speed of sound and elasticity. Furthermore, both speed of sound and attenuation were within a suitable range for ultrasound phantoms. Combining this ballistic gel with SEBS copolymer in oil allows for control of mechanical properties, both elastic and viscous as evaluated by the material model. Furthermore, it does so without compromising ease of use, longevity and safety of the pre-made gel.

The ultrasonic attenuation coefficient (ACE) can be used to classify tissue state. Pulse-echo spectral-based attenuation estimation techniques, such as the spectral-log-difference method (SLD), account for beam diffraction effects using a reference phantom having a sound speed close to the sound speed of the sample. Methods like SLD assume linear propagation of ultrasound and do not account for potential acoustic nonlinear distortion of the backscattered power spectra in both sample and reference. In this study, the ACE of a sample was computed and compared using the SLD with two independent references (high attenuating and low attenuating phantoms but with similar B/A values) and over several pressure levels. Both numerical and physical tissue-mimicking phantoms were used in the study. The results indicated that the biases in ACE increased when using a reference having low attenuation, whereas the high attenuating reference produced more consistent ACE. Furthermore, increments in ACE vs input pressure were correlated to the log-ratio of Gol'dberg numbers between the sample and reference ([Formula: see text] in simulations and [Formula: see text] in experiments). Therefore, the results suggest that to reduce bias in ACE using spectral-based methods, both the sound speed and the Gol'dberg number of the reference phantom should be matched to the sample.

Ultrasound computed tomography (UCT) is considered to have great potential for the early diagnosis of knee joint injuries. Combining prior knowledge and sound speeds of tissues, UCT can diagnose a variety of symptoms and the extent of tissue lesion. However, no existing studies can reconstruct the sound speed distributions of knee joints in UCT. Therefore, in this study, sound speed distributions of knee joints are reconstructed to provide an imaging basis for the formulation of a treatment plan. In addition, Full waveform inversion (FWI) methods are utilized to estimate highresolution images. However, for media with large variations in sound speeds, traditional FWI methods may lead to a cycle-skipping phenomenon and incorrect convergence direction. Hence, this study proposes a multi-centerfrequency source based FWI method to overcome the above limitations. A penalized least-squares optimization problem is constructed to obtain a numerical solution of the sound speed distribution. Computer simulations are conducted to prove the effectiveness and robustness of the proposed method. Furthermore, the reasons for selecting the center frequencies of sources are analyzed. Two numerical knee joint phantoms are used to evaluate the performance. The results suggest that the biases of the reconstructed images are less than 1% under a 5% noise condition.

The propagation of sound vibrations in two-phase molten mixtures of alkali halides with each other and with silver halides is studied. The experimental setup and methods for the measurement of speed of sound at high temperatures are described. The experimental data are presented in the form of tables and graphs. The critical indicators of system mixing are given. The results are discussed in terms of a model of charged solid spheres of arbitrary diameter.

Conventional ultrasound imaging is based on the scattering of sound from inhomogeneities in the density and the speed of sound and is often used in medicine to resolve pathologic compared to normal tissue. Here we demonstrate a difference-frequency ultrasound (dfUS) imaging method that is based on the interaction of two sound pulses that propagate non-collinearly and intersect in space and time. The dfUS signal arises primarily from the second-order non-linear coefficient, a contrast mechanism that differs from linear and harmonic US imaging. The distinct contrast mechanism allows dfUS to image anatomic features that are not identifiable in conventional US images of salmon and pig kidney tissue. Further, dfUS produces enhanced contrast of glioblastoma tumor implanted in the mouse brain, revealing its potential for improving medical diagnosis. Progress towards a real-time system is discussed.

PURPOSE: Articular cartilage is known to be mechanically anisotropic. In this paper, the acoustic anisotropy of bovine articular cartilage and the effects of freeze-thaw cycling on acoustic anisotropy were investigated. METHODS: We developed apparatus and methods that use a magnetic L-shaped sample holder, which allowed minimal handling of a tissue, reduced the number of measurements compared to previous studies, and produced highly reproducible results. RESULTS: SOS was greater in the direction perpendicular to the articular surface compared to the direction parallel to the articular surface (N=17, P = 0.00001). Average SOS was 1,758 ± 107 m/s perpendicular to the surface, and 1,617 ± 55 m/s parallel to it. The average percentage difference in SOS between the perpendicular and parallel directions was 8.2% (95% CI: 5.4% to 11%). Freeze-thaw cycling did not have a significant effect on SOS (P>0.4). CONCLUSION: Acoustic measurement of tissue properties is particularly attractive for work in our laboratory since it has the potential for nondestructive characterization of the properties of developing engineered cartilage. Our approach allowed us to observe acoustic anisotropy of articular cartilage rapidly and reproducibly. This property was not significantly affected by freeze-thawing of the tissue samples, making cryopreservation practical for these assays.

Ultrasound is now a clinically accepted modality in the management of osteoporosis. The most common commercial clinical devices assess fracture risk from measurements of attenuation and sound speed in cancellous bone. This review discusses fundamental mechanisms underlying the interaction between ultrasound and cancellous bone. Because of its two-phase structure (mineralized trabecular network embedded in soft tissue—marrow), its anisotropy, and its inhomogeneity, cancellous bone is more difficult to characterize than most soft tissues. Experimental data for the dependencies of attenuation, sound speed, dispersion, and scattering on ultrasound frequency, bone mineral density, composition, microstructure, and mechanical properties are presented. The relative roles of absorption, scattering, and phase cancellation in determining attenuation measurements in vitro and in vivo are delineated. Common speed of sound metrics, which entail measurements of transit times of pulse leading edges (to avoid multipath interference), are greatly influenced by attenuation, dispersion, and system properties, including center frequency and bandwidth. However, a theoretical model has been shown to be effective for correction for these confounding factors in vitro and in vivo . Theoretical and phantom models are presented to elucidate why cancellous bone exhibits negative dispersion, unlike soft tissue, which exhibits positive dispersion. Signal processing methods are presented for separating “fast” and “slow” waves (predicted by poroelasticity theory and supported in cancellous bone) even when the two waves overlap in time and frequency domains. Models to explain dependencies of scattering on frequency and mean trabecular thickness are presented and compared with measurements. Anisotropy, the effect of the fluid filler medium (marrow in vivo or water in vitro ), phantoms, computational modeling of ultrasound propagation, acoustic microscopy, and nonlinear properties in cancellous bone are also discussed.

PURPOSE. Studies have shown that a decrease in mammographic density (MD) or lowering of background parenchymal enhancement (BPE) on MRI after initiation of tamoxifen therapy predicts a favorable response in the preventive or adjuvant settings. However, performing serial mammograms poses radiation concerns, while serial MRIs carry high cost as well as risk of multiple Gadolinium doses. Previous studies have shown that tissue sound speed, derived from whole breast ultrasound tomography measurements, is a surrogate biomarker of MD. Ultrasound is ideal for performing serial measurements because it is fast and poses almost no risks. The purpose of this study was to evaluate repeated measures of the sound speed biomarker at 3, 6 and 12-months following tamoxifen initiation. METHOD AND MATERIALS. We performed a case-control comparison involving 74 participants referred by a health professional to undergo tamoxifen therapy (cases) and 150 matched participants with no history of breast cancer (controls). The cases were scanned with ultrasound tomography at baseline (i.e. before start of tamoxifen therapy), and then at 3, 6 and 12 months after tamoxifen initiation. Controls were scanned at baseline and 12 months. In the case group, sound speed was measured pre-treatment in the contralateral breast to avoid potential influences of tumor-related changes on density. In the control group, a single randomized breast was scanned. A pairwise t-test was used to assess differences in sound speed over time and between cases and controls. RESULTS. There was a steady decline in sound speed over the 12-month period for women undergoing tamoxifen therapy (mean(SD): -3.0(8.2) m/s; P=0.001). Furthermore, significant sound speed reductions were observed as early as 4-6 months after tamoxifen initiation (mean(SD): -2.1(6.8) m/s; P=0.008). In contrast, the controls demonstrated no significant change in sound speed over a 12-month period, and the difference between case-control groups was statistically significant (P=0.0009). DISCUSSION. Breast sound speed decreases rapidly after tamoxifen initiation while it remains steady for the control group. These results suggest that sound speed may be a biomarker of response to tamoxifen. Further studies are needed to assess whether this observation can predict clinical response. CONCLUSION. Ultrasound tomography may have utility in monitoring breast sound speed change as a potential biomarker of clinical tamoxifen response. Citation Format: Neb Duric, Mark Sak, Mark Sherman, Ruth Pfeiffer, Sharon Fan, Michael Simon, David Gorski, Teri Albrecht, Haythem Ali, Peter Littrup, Rachel Brem, Gretchen Gierach. Tissue sound speed: A novel imaging biomarker for measuring tamoxifen response [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-11-11.

Objectives: The purpose of this cross-sectional study was to investigate the association between daily physical activity and sonographically measured bone status among women during the lactation period. Methods: Final participants were 152 women 4 months after childbirth. Bone status of the participants was measured using quantitative ultrasonometry of the calcaneus (speed of sound). Daily physical activity was assessed using the Japanese version of International Physical Activity Questionnaire short version. After getting the International Physical Activity Questionnaire results, we classified participants into three categories (low/moderate/high) according to a protocol. Participants categorized into the low group according to the International Physical Activity Questionnaire were considered to be in the low physical activity group and those categorized into the moderate and high groups were considered to be in the moderate to vigorous physical activity group. Results: Speed of sound was significantly higher in the moderate to vigorous physical activity group (moderate to vigorous physical activity versus low physical activity, 1533 m/s versus 1523 m/s, p = 0.03). Daily physical activity was significantly associated with speed of sound, even after adjustment for confounding factors and prognosticators ( β = 0.195, p = 0.02). Conclusion: Sonographically measured bone status was significantly higher in women who were physically active than in those who were physically inactive, suggesting that daily physical activity might help to maintain good bone status.

The objective of this paper is the numerical simulation of accident consequences of natural gas release. Failure of the pipeline can lead to various outcomes, some of which can pose a significant threat of irretrievable damage to people and properties in the immediate vicinity of the failure location. To make the solution and results more similar to actual scenario, Gas Leakage Rate from Pipeline Fracture is investigated in the steady state flow (hole and Pipeline models) and transient flow modes are examined. The numerical results show that if the pressure at the fracture point is equal to the atmospheric pressure, the Mach number is smaller than one. In the pipe model, if the length of the pipe is long and the pressure difference between the inside and outside of the pipe is high, then the Mach number tends to one and the gas leak rate to the sound speed. The fugitive emission from all instruments was measured using Hi-Flow Sampler and the emission from accidents was calculated using PHAST software.

Acoustoelectric effect (AE) in a non-degenerate fluorinated single walled carbon nanotube (FSWCNT) semiconductor was carried out using a tractable analytical approach in the hypersound regime , where q is the acoustic wavenumber and is the electron mean-free path. In the presence of an external electric field, a strong nonlinear dependence of the normalized AE current density , on ( is the electron drift velocity and is the speed of sound in the medium) was observed and depends on the acoustic wave frequency, , wavenumber q, temperature T and the electron-phonon interactions parameter, . When , decreases to a resonance minimum and increases again, where the FSWCNT is said to be amplifying the current. Conversely, when , rises to a maximum and starts to decrease, similar to the observed behaviour in negative differential conductivity which is a consequence of Bragg’s reflection at the band edges at T=300K. However, FSWCNT will offer the potential for room temperature application as an acoustic switch or transistor and also as a material for ultrasound current source density imaging (UCSDI) and AE hydrophone devices in biomedical engineering. Moreover, our results prove the feasibility of implementing chip-scale non-reciprocal acoustic devices in an FSWCNT platform through acoustoelectric amplification.

We report on the time-dependent optical diffraction from ultra-high frequency laser-induced acoustic waves in thin layers of ruthenium deposited on glass substrates. We show that the thermo-optic and strain-optic effects dominate the optical response of Ru layers to a traveling longitudinal strain wave. In addition, we show the generation and detection of acoustic waves with a central frequency ranging from 130 GHz to 750 GHz on ultra-thin layers with thicknesses in the range of 1.2 - 20 nm. For these ultra-thin layers we measure a strong dependency of the speed of sound on the layer thickness and, thus, the frequency. This frequency-dependent speed of sound results in a frequency-dependent acoustic impedance mismatch between the ruthenium and the glass substrate, leading to a faster decay of the measured signals for increasing frequency. Furthermore, for these extremely high-frequency oscillations, we find that the frequency and phase remain constant for times longer than about 2 ps after optical excitation. Back extrapolation of the acquired acoustic signals to t = 0 gives a starting phase of −π/2. As this seems unlikely, we interpret this as an indication of possible dynamic changes in the phase/frequency of the acoustic wave in the first 2 ps after excitation.

Purpose We demonstrate a novel method for automatic direct lesion depth (LD) tracking during coagulation from time series of a single A-mode ultrasound (US) transducer custom fit at the tip of a RFA catheter. This method is named thermal expansion imaging (TEI). Methods A total of 35 porcine myocardium samples were ablated (LD 0.5–5 mm) while acquiring US, electrical impedance (EI) and contact force (CF) data. US images are generated in real time in terms of echo intensity (M-mode) and phase (TEI). For TEI, displacements between US time series are estimated with time-domain cross-correlation. A modified least squares strain estimation with temporal and depth smoothing reveals a thermal expansion boundary (TEB)—negative zero-crossing of temporal strain—which is associated to the coagulated tissue front. Results M-mode does not reliably delineate RFA lesions. TEI images reveal a traceable TEB with RMSE = 0.50 mm and 𝑅2=0.85 with respect to visual observations. The conventional technique, EI, shows lower 𝑅2=0.7 and >200 % variations with CF. The discontinuous time progression of the TEB is qualitatively associated to tissue heterogeneity and CF variations, which are directly traceable with TEI. The speed of sound, measured in function of tissue temperature, increases up to a plateau at 55 ∘C, which does not explain the observed strain bands in the TEB. Conclusions TEI successfully tracks LD in in vitro experiments based on a single US transducer and is robust to catheter/tissue contact, ablation time and even tissue heterogeneity. The presence of a TEB suggests thermal expansion as the main strain mechanism during coagulation, accompanied by compression of the adjacent non-ablated tissue. The isolation of thermally induced displacements from in vivo motion is a matter of future research. TEI is potentially applicable to other treatments such as percutaneous RFA of liver and high-intensity focused ultrasound., International Journal of Computer Assisted Radiology and Surgery, 10 (6), ISSN:1861-6410, ISSN:1861-6429

The methods and results presented here test the ability of the multi-band finite element method to simulate the frequency dependence of attenuation of ultrasound within soft tissue like materials, and the potential translation of the approach from its previous applications in non-destructive testing into medical ultrasound. Using a variety of materials, the approach was tested by comparing the theoretical attenuation (based on the input attenuation constants and path length through the materials) to the attenuation of the signal energy within the simulation. In two models, hypothetical materials were devised, with arbitrary attenuation properties and acoustic impedance matched to a background with the density and sound speed of water. In the third model, acoustic impedance mismatches were introduced to simulate the signal energy loss due to reflection and attenuation as an ultrasound beam passes from water into parallel layers of human skin, fat and muscle. In all cases, the calculated signal loss (from the reflection coefficients and attenuation constants) agreed with the signal loss measured within the simulation to a high degree, reproducing the input parameters to four significant figures in all cases.

Hyperthermia-enhanced chemo- and radiation therapies have been used in the treatment of various types of cancers such as breast, and soft-tissue sarcoma. Localized hyperthermia can increase the effectiveness of treatment and reduce the dosage requirements. Simultaneous temperature monitoring has generally required the use of additional modalities such as magnetic resonance imaging (MRI). Ultrasound (US) offers the potential for an all-in-one solution for heat induction and temperature monitoring through speed of sound (SOS) measurements. Such a system would ease the utility of hyperthermia-enhanced therapies and minimize the required hardware/costs, thereby presenting an attractive alternative. In this study, we present the results for 1) all-acoustic, in-silico, localized heating of a numerical breast phantom with embedded tumor, and 2) ex-vivo thermometry results, which look at monitoring the changes in water sound speed at 25, 35, and 45 °C in a heterogeneous lamb tissue phantom. The measurements from the thermometry experiment were then compared against the known values from the literature. The results from this study show successful all-acoustic induced localized heating and good agreement between the measured water sound speed values and their literature counterparts, which represent a significant step toward the development of a real-time US hyperthermia system.

The conventional delay-and-sum algorithm is based on the assumption that a target object is composed of substances with identical speed-of-sound (SoS)(i.e. 1540 m/s) and proper delay is applied to received RF signals to synthesize output images. However, such an assumption compromises the resolution of images due to the inhomogeneity of body tissues. In this paper, we propose an SoS adaptive Rx beamforming method that generates high-resolution ultrasonic images. A neural network (NN) approach has been adopted to reconstruct SoS distribution and determine the accurate time-of-flight (ToF) of each channel from the generated SoS map.

Speed of sound estimation in propagation medium of ultrasound is essential to improve an ultrasound imaging quality. In an estimation method based on received time differences among elements in a transducer array, it is generally assumed that the received ultrasound wave is scattered from the ideal point scatterer. However, there is a scatterer that has a size in a living body, such as small blood vessels. In our previous study, we confirmed that the positive estimation error occurs if the target scatterer has a size and the speed of sound is estimated without considering the target size. In the present study, we proposed the correction method of erroneously estimated speed of sound by considering the size of the target scatterer under the assumption that the target diameter is known as a preliminary study. The proposed method was confirmed in a water tank experiment using wires with several diameters. As the result, the speed of sound in water was estimated within 0.15% error regardless of target diameter.

Multi-modal imaging via thermoacoustic (TA) approaches provides contrast mechanisms differing from conventional ultrasound (US) imaging - opening up new applications like non-invasive, non-contact below-ground sensing. Due to the high correlation between soil moisture content and speed-of-sound (SoS), knowledge about the SoS in soil can be utilized to improve below-ground image reconstruction and soil moisture mapping at depth. In this work, we present multi-task deep learning networks to accurately predict arbitrarily varying SoS distributions in soil while concurrently reconstructing high-fidelity TA images of root structures. We deploy multi-task U-Net based fully convolutional neural networks trained using US data generated through TA simulations on a wheat root dataset. A multi-input, multi-output architecture performed best - achieving the highest root image contrast-to-noise ratio and lowest SoS mean absolute error.

Ultrasound computed tomography (USCT) systems based on capacitive micromachined ultrasonic transducer (CMUT) arrays have a wide range of application prospects. For this paper, a high-precision image reconstruction method based on the propagation path of ultrasound in breast tissue are designed for the CMUT ring array, that is, time-reversal algorithms and FBP algorithms are respectively used to reconstruct sound speed distribution and acoustic attenuation distribution. The feasibility of this reconstruction method is verified by numerical simulation and breast model experiments. According to reconstruction results, sound speed distribution reconstruction deviation can be reduced by 53.15% through a time-reversal algorithm based on wave propagation theory. The attenuation coefficient distribution reconstruction deviation can be reduced by 61.53% through FBP based on ray propagation theory. The research results in this paper will provide key technological support for a new generation of ultrasound computed tomography systems.

Resonant mechanical sensors are often considered as mass balance, which responds to an analyte adsorbed on or absorbed in a thin sensitive (and selective) layer deposited on the surface of the resonant device. In a more general sense, the sensor measures properties at the interface of the mechanical resonator to the medium under inspection. A phononic crystal (PnC) sensor employs mechanical resonance as well; however, the working principle is fundamentally different. The liquid medium under inspection becomes an integral part of the PnC sensor. The liquid-filled compartment acts as a mechanical resonator. Therefore, the sensor probes the entire liquid volume within this compartment. In both sensor concepts, the primary sensor value is a resonant frequency. To become an attractive new sensing concept, specifically as a bio and chemical sensor, the PnC sensor must reach an extraordinary sensitivity. We pay attention to the liquid viscosity, which is an important factor limiting sensitivity. The main part of our analysis has been performed on 1D PnC sensors, since they underlie the same material-related acoustic dissipation mechanisms as 2D and 3D PnC sensors. We show that an optimal relation of frequency shift to bandwidth and amplitude of resonance is the key to an enhanced sensitivity of the sensor-to-liquid analyte properties. We finally address additional challenges of 2D and 3D PnC sensor design concept. We conclude that the sensor should seek for a frequency resolution close to 10−6 the probing frequency, or a resolution with speed of sound approaching 1 mm s−1, taking water-based analytes as an example.

Underwater acoustic networks operate in an inhomogeneous and dynamic environment, which makes it difficult to model the propagation path of signals. In essence acoustic signals experience reflection and refraction due to sound speed variation, based on many parameters such as salinity, temperature, and depth. To enable modeling of signal propagation, the sound speed profile (SSP) has to be accurately estimated. The most famous SSP equation has been proposed by Mackenzie and has been widely used among others like the Coppens’ and UNESCO equations. The drawback of these equations is that they yield different accuracy levels for various setups. They are also valid only for certain limits of salinity, depth and temperature. Moreover, the SSP estimation method should suit both deep and shallow water environments. In this paper, we use machine learning algorithms to predict sound speed in both deep and shallow waters and compare our results with data collected from acoustic tomography measurements. For training we have considered sound speed measurements across various oceans like Pacific Ocean, Arctic Ocean, Indian Ocean, etc. Our results show that our model achieves 99.99% accuracy and outperforms Leroy and Mackenzie equations.

Processing the Si3N4 ceramic is a big challenge because of its high hardness and brittleness. Femtosecond (fs) laser is an excellent method to process the Si3N4 ceramic. However, the temporal evolution of the fs laser induced plasma from the initialization to the disappearance is still lacking for deeply understanding the laser-matter mechanisms. In this study, we employ the pump-probe shadowgraphy and the ultrafast plasma imaging to observe the whole shockwave evolution on Si3N4 ceramic. We find that the shockwave propagates in a spherical law and the velocity of shockwave decreases rapidly in the first 50 ns, and finally approaches to the speed of sound at the delay of 430 ns. The relationship between plasma melting, expansion and shockwave propagation was revealed to provide further insight into the fs laser ablation of Si3N4 ceramic.

Physiotherapy ultrasound is one of the most used electrophysical agents in the clinic for its widely therapeutic effects. To guarantee safe and effective treatment, physiotherapy devices must be capable of applying correct ultrasound radiation to the body (or part of the body) under the procedure. The effectiveness of the therapy depends on the ultrasound device's performance and calibration. For performance testing and calibration, tissue-mimicking phantoms are used. This study's objective is to characterize the acoustic parameters of muscle phantom used in the calibration of physiotherapy ultrasound, by following per under the metrology principles. Muscle phantom was prepared. Then, the phantom's sound speed, attenuation coefficient was measured with the pulse-echo method, density, and acoustic impedance calculations were performed. A detailed uncertainty study in measurements was also presented in the paper. The acoustic parameters of muscle phantom were measured as given; the speed of sound 1549.8 ± 3.89 m/s (expanded uncertainty, U=6.7), attenuation coefficient 1.14 ± 0.8 dB/cm MHz (expanded uncertainty, U=0.55). Its acoustic impedance was calculated as 1.632 MRayl; it's density as 1053.5 kg/ m³. Muscle phantom's acoustic properties were found similar to the muscle tissue. It can be used in testing the physiotherapy ultrasound device's performance and calibration as it is cheap, easy to make, and

Turbomachinery systems are often subject to variations in ambient conditions and applied loads in operation. Standard maps (perhaps the most common being pressure ratio verses mass flow for compressors) are usually presented in terms of fixed inflow conditions. To account for changes in performance due to varying inlet conditions, compressors maps are often presented in standardized form where the mass flow and rotational speeds are normalized as a function of the reference condition total pressure and temperature. These methods are very widely used, particularly in the turbo charger industry. With these normalized maps, the actual performance of a compressor in a given environment can be deduced simply and easily with very reasonable accuracy in most cases. The underlaying assumption of this conventional normalization process is that the fluid behaves as a perfect gas. While this is usually sufficient for air compressors, the method is not viable where the fluid properties are not near perfect gas conditions, which is certainly the case for supercritical applications. The highly variable fluid properties near the critical point, and the challenges they present in design, have been well documented in the literature. The two most critical properties to consider in the design process are the density and the speed of sound. The density determines the volumetric flow for a given mass flow and this in turn determines the incidence angle, a primary driver of performance. The speed of sound directly affects the range of the compressor via choking. Choking range can be further complicated by the fact that under certain conditions, the choked state can be reached at Mach numbers less than one. While rare, this situation can occur when the inflow conditions are found close to the liquid side of the saturation dome. To account for these effects, a new method is proposed to generate normalized maps of performance that can be used to determine actual performance of a wide range of inlet conditions for highly non-linear thermodynamic properties. Although not as simple as the conventional perfect gas method that can be applied in a “back-of-the-envelope” style, the new method can be applied very rapidly using a spreadsheet-based method directly calling high fidelity NIST thermodynamic models. The end result of this tool is that a compressor map that has been painstakingly generated with testing or CFD can be applied to any inlet condition and the range and performance predicted very rapidly with high accuracy.

Styrene-ethylene/butylene-styrene (SEBS) copolymer-in-mineral oil gel is an appropriate tissue-mimicking material to manufacture stable phantoms for ultrasound and photoacoustic imaging. Glycerol dispersion has been proposed to further tune the acoustic properties and to incorporate hydrophilic additives into SEBS gel. However, this type of material has not been investigated to produce wall-less vascular flow phantom for these imaging modalities. In this paper, the development of a wall-less vascular phantom for ultrasound and photoacoustic imaging is reported. Mixtures of glycerol/TiO2-in-SEBS gel samples were manufactured at different proportions of glycerol (10%, 15%, and 20%) and TiO2 (0% to 0.5%) to characterize their optical and acoustic properties. Optical absorption in the 500 – 950 nm range was independent of the amount of glycerol and TiO2, while optical scattering increased linearly with the concentration of TiO2. Acoustic attenuation and speed of sound were not influenced by the presence of TiO2. The sample manufactured using weight percentages of 10% SEBS, 15% glycerol, and 0.2% TiO2 was selected to make the vascular phantom. The phantom proved to be stable during the pulsatile blood-mimicking fluid (BMF) flow, without any observed damage to its structure or leaks. Ultrasound color Doppler images showed a typical laminar flow, while the B-mode images showed a homogeneous speckled pattern due to the presence of the glycerol droplets in the gel. The photoacoustic images of the phantom showed a well-defined signal coming from the surface of the phantom and from the vessels where BMF was flowing. The Spearman's correlations between the photoacoustic and tabulated spectra calculated from the regions containing BMF, in this case a mixture of salt solutions (NiCl2 and CuSO4), were higher than 0.95. Our results demonstrated that glycerol-in-SEBS gel was an adequate material to make a stable vascular flow phantom for ultrasound photoacoustic imaging.

Solid phononic crystal (PnC) lenses were made active on infiltration with thermosensitive polymers to produce a thermoactuated hybrid solid lens with variable focusing. Acoustic lenses, both solid state and PnCbased, are passive elements with a fixed focal length. Their focal characteristics are functions of the lens structure or the arrangement of the PnC unit cell. Dispersion effects, liquid-filled membranes, and phase delay in a multi-element emitter have been used for variable focusing. The high thermal, electric, and electromagnetic sensitivity of the elastic properties of poly(vinyl alcohol) (PVA) poly(N-isopropylacrylamide) (PNIPAm)-based hydrogels enable them to operate as tunable solids. However, these solids do not have strong enough contrast with water or well-controlled shape parameters to function as standalone lenses. Here, a tunable hybrid solid ultrasonic lens is realized by combining a PnC lens with PVA-PNIPAm thermoacoustic hydrogel to modify the transmission and dispersion properties of transient acoustic waves. Variable focusing is demonstrated from 40 to 50 mm using the anomalous thermosensitivity of the elasticity and speed of sound of the hydrogel.

[EN] In this work, we present a configurable spherical lens for underwater focusing applications, which consists on a hollow ABS container filled with a liquid mixture. Two miscible liquids with different sound speeds are required to implement this novel configurable lens. We show that by adjusting the mixing ratio between the volumes of both liquids, the sound speed of the liquid mixture can be accurately selected. This results in a modification of the acoustic jet properties and a continuous tuning on the lens focal length. This procedure can be fully automatized providing a dynamic control mechanism that can shift the lens focal length to any desired value inside a continuous range in both directions. Depending on the acoustic properties of the selected liquids, subwavelength resolution or even beyond the diffraction limit resolution can be achieved. We provide experimental measurements for ethanol-water mixtures achieving subwavelength resolution for a certain focal length ranging between 34.6 and 42.8 mm., This work has been supported by Spanish MINECO TEC2015-70939-R and MICINN RTI2018-100792-B-I00 projects. S.P.-L. acknowledges financial support from Universitat Politecnica de Valencia grant program PAID01-18. I.V.M. and O.V.M. acknowledge support from the Tomsk Polytechnic University Enhancement Program.

To evaluate the quantitative accuracy of the measured speed of sound in ultrasound computed tomography for breast imaging, it is necessary to use a phantom with inclusions whose speed of sound is known. Accordingly, a phantom with known-speed-of-sound inclusions (e.g., containing water and saltwater solution) under the control of temperature was developed. In addition, an oil gel was used as the phantom material for mimicking wave refraction from fatty breast tissue to dense breast tissue. The oil gel was generated by adding SEBS (styrene-ethylene/butylene-styrene, 10% w/w) to paraffin oil. The oil gel-based phantom has a cylindrical shape and contains rod-shaped inclusions that can be filled with water or saltwater solution (3.5% w/w sodium chloride in water). When temperature increases, the speed of sound in the water increases, while that in the oil gel decreases; in particular, the speed of sound in the oil gel was higher than that in the water at temperatures 20.6°C. It has been reported that the speed of sound in dense breast tissue is higher than that in water, while that in fatty breast tissue is lower than that in water. Ultrasound is refracted owing to the difference between the speed of sound in the breast tissue and that in the background water. By controlling the temperatures of the oil gel and water, the oil gel-based phantom simulates the refraction of an ultrasound wave from fatty breast tissue to dense breast tissue. For 43 d, the variation ranges of the speed of sound and attenuation in the oil gel in the reconstructed images were 0.7 m/s and 0.03 dB/MHz/cm, respectively. The concentration of the saltwater solution in the polyacrylamide gel-based phantom decreased from 1% (w/w) to 0.48% (w/w) after 24 h, while that in the oil-gel-based phantom was constant. In addition, magnetic resonance imaging of the oil gel-based phantom revealed that NiSO4 solution was stably contained in the phantom for 42 d. It is therefore concluded that the liquid cannot penetrate the oil gel. This oil gel-based phantom with such high temporal stability is suitable for multicenter distribution and may be used for standardization of data acquisition and image reconstruction across centers.

Laser-Induced Grating Spectroscopy (LIGS) is applied to premixed CH4/air laminar flat flames under operating pressures of 1 to 6 bar. For the first time, temperature and water concentration have been acquired simultaneously in a reacting flow environment using LIGS. A 1064 nm pulsed laser is used as pump to generate a temporary stationary intensity grating in the probe volume. Water molecules in the flame products absorb the laser energy and generate a thermal grating if sufficiently high energies are delivered by the laser pulses, here more than 100 mJ per pulse. Such energies allow the electric field to polarize the dielectric medium, resulting in a detectable electrostrictive grating as well. This creates LIGS signals containing both the electrostrictive and the thermal contributions. The local speed of sound is derived from the oscillation frequency of LIGS signals, which can be accurately measured from the single shot power spectrum. Data show that the ratio between the electrostrictive and the thermal peak intensities is an indicator of the local water concentration. The measured values of speed of sound, temperature, and water concentration in the flames examined compare favorably with flame simulations with Chemkin, showing an estimated accuracy of 0.5 to 2.5% and a precision of 1.4–2%. These results confirm the potential for 1064 nm LIGS-based thermometry for high-precision temperature measurements of combustion processes.

Urethane-based test objects are routinely used for ultrasound quality assurance because of their durability and robustness. The acoustic properties of these phantoms including speed of sound and attenuation, however, have a strong dependence on temperature. Reliable measurement of low-contrast penetration, which is widely used for ultrasound system quality assurance testing, with these phantoms is therefore problematic. To alleviate this, a correction method was proposed using speed of sound estimated by measuring filament target separation. The method was developed using a range of 17 transducer geometry and frequency combinations across 5 ultrasound systems and validated using a further 5 systems. This was found to reduce the uncertainty of low-contrast penetration measurement from an average 17.6 mm to 4.9 mm over the temperature range 8°C to 32°C. This represents a greater than threefold improvement in precision of low-contrast penetration measurement.

A new generation of speed of sound (SOS) test object is presented that is fully constructed using additive manufacturing processes with a 3D-printer. The object contains 2 compartments with thin filaments and tubes that can be filled with fluid substances. The filaments are located at equal distances to each other; the tubes have fixed diameters. Depending on the chosen fluids (e.g. water, glycerol-water, corn oil, salt water) and room temperature, the mismatch in distance or diameter depending on the SOS error has been measured using ultrasound imaging equipment. The velocity of the fluid could be calculated deductively with high accuracy (range of total error: 0.1–3.4%). The results show that 3D-printed objects or additive manufacturing techniques can be suitable to use as teaching test objects within skills labs.

Compressive strength is the most important parameter in rock since all loads will be transferred and rest on the rock which is based on the load bearing capacity of rock in compression. However, obtaining the compressive strength or mostly measured, the uniaxial compressive strength (UCS) from the laboratory test requires certain standard and also cost constrain. This paper presents the application of Support Vector Machine (SVM) algorithm to predict the UCS. An algorithm has been tested on a series of rock data using dry density and velocity parameters. The relationship between the dry density, sonic velocity, and UCS was analyzed using RapidMiner Studio software. From the result, it was found that SVM is capable of predicting the missing values with a prediction trend accuracy of 75%. The results obtained and observation made in this study suggests that SVM could be a reliable tool to predict the UCS of a given rock. More robust prediction can be established with bigger sample number. It is worth mentioning, that the program module that has been set up could be used repeatedly for other correlation problems.

Pressure–density relationships derived from the experimentally obtained shock and particle velocities are critical to define a material’s equation of state (EOS). Typically, impact experiments coupled with velocimetry are used to map a material’s Hugoniot. Limitations such as sample geometry and varying indices of refraction may prevent proper characterization using traditional techniques such as photon doppler velocimetry (PDV) or velocity interferometer system for any reflector (VISAR). Here, traditional Hugoniot measurements using PDV are compared to dynamic x-ray imaging encompassing two different sample geometries on the gas gun platform. Through each of these methods an experimentally derived Hugoniot is determined for a previously uncharacterized polymeric material, Somos Watershed XC11122, that is used 3D printed stereolithography parts. A Us–up relationship was determined to be Us = 2.93 us + 1.73 mm/μs through traditional PDV. Slope and sound speed values determined from x-ray imaging methods varied 11% from PDV measurements. Each method yielded a Hugoniot with densities similar to poly(methyl methacrylate) (PMMA). The similarity shows the viability of such analyses for dynamic properties and Hugoniot data. The performance and analysis of both PDV and dynamic x-ray measurements are laid out in this work. Comparing PDV and x-ray imaging highlights distinct advantages and disadvantages among each method. PDV provides less uncertainty for velocity measurements, however x-ray imaging is more spatially resolved allowing for shock steadiness observations of value when studying heterogeneous materials. Additionally, x-ray imaging provides greater insight into the shape and heterogeneity of the shock front as well as uniaxial strain state (1D zone) assumptions.

Opportunities given by applying the PC-SAFT (Perturbed Chain-Statistical Association Fluid Theory) for estimating and calculating the speed of sound in natural gas were considered. Examples are presented of prognosticating the density and the speed of sound for five multicomponent gas mixtures containing alkanes, isoalkanes, nitrogen, and carbon dioxide in a wide range of temperatures and pressures (250–450 K and 0.5–60 MPa). The results of calculations are compared with published experimental data. It is shown that the model reproduces with high precision the experimental values of the density and the speed of sound.

This paper describes investigation of the possibilities of low-frequency ultrasonic tomography in medicine. The main application is the development of tomographic methods for differential diagnosis of breast cancer. To solve the inverse problem, a mathematical model is used that describes both the phenomena of diffraction and refraction and the absorption of ultrasound in an inhomogeneous medium. The algorithms developed for reconstructing the velocity structure were evaluated using the test bench for experimental studies. Broadband ultrasonic sources in the 50–600 kHz range were used for sounding. A Teledyne Reson TC4038 hydrophone with a sensitivity of approximately 4 µV/Pa and a frequency range of 10–800 kHz was used as a receiver. A Teledyne Reson VP1000 preamplifier was used to amplify the signals. The studies were carried out on phantoms with acoustic parameters close to the properties of human soft tissues. A layerwise model was used to reconstruct the three-dimensional velocity structure. The sound speed cross-sections reconstructed from the experimental data have a resolution of approximately 2 mm, while the central wavelength is approximately 4 mm. An important result of the work is an experimental confirmation of the correspondence of the model to physical processes.