Ultrasound Speed Measurements Research Articles

Measuring optimal ultrasound speed using endoscopic ultrasound in patients with chronic pancreatitis, including early stage.

Ultrasound speed (USS) correction improves image quality by estimating the optimal USS correcting the deviation from a predetermined USS. This study assessed USS differences between chronic pancreatitis (CP), early CP (ECP), and normal pancreas when using endoscopic ultrasound (EUS). The usefulness of measuring optimal USS was evaluated for patients with CP, including early stage patients. This study enrolled 116 consecutive patients for whom USS was measured using an EUS system. The USS correction principle is generation of a B-mode image by changing the USS in all ranges while correcting the delay in the received data. Final diagnoses were made according to the Japanese diagnostic criteria for CP in 2019. They were classified as CP, ECP, or normal. We compared USS applied for these three groups. The medians and ranges of USS values for patients in the normal, ECP, and CP groups were 1506.0 (1407-1600) m/s, 1580.0 (1520-1630) m/s, and 1574.0 (1537-1610) m/s, respectively. The USS values of the ECP and CP groups were significantly higher than those of the normal group (P < 0.001). Analyses of the receiver operating characteristic curve in the normal pancreas, ECP, and CP revealed the area as 0.957, with specificity and sensitivity of 95.9% and 87.5%, respectively, using the USS of 1535 m/s as a cut-off. Measurement of USS might be particularly useful for distinguishing between normal and ECP imaging.

Conventional ultrasound characteristics, TI-RADS category and shear wave speed measurement between follicular adenoma and follicular thyroid carcinoma.

The purpose of the study was to explore the differences of conventional ultrasound characteristics, thyroid imaging reporting and data system (TI-RADS) category and shear wave speed (SWS) measurement between follicular adenoma (FA) and follicular thyroid carcinoma (FTC). Twenty-eight FTCs and 67 FAs proven by surgery were retrospectively included for analysis. Conventional ultrasound and point-shear wave elastography (p-SWE) were performed in all of the included patients. The ultrasound features, American Thyroid Association (ATA) TI-RADS category and American College of Radiology (ACR) TI-RADS category, SWS measurement were compared between the two groups. Receiver operating characteristic (ROC) curve was performed and area under ROC curve (AUC) was obtained for significant features. There were no statistical differences in mean age (46.9±15.7years vs. 48.6±13.6years, P = 0.639), gender (9 males, 32.1% vs. 18 males, 29.0%, P = 0.766) and mean diameter (28.3±16.2 mm vs. 33.8±11.9 mm, P = 0.077) between FTCs and FAs. Hypoechogenicity, lobulated or irregular margin, macrocalcification were more common in FTCs than FAs (all P < 0.05). Mean SWS of FTCs (2.29±0.64 m/s) was slightly higher than that of FAs (1.94±0.68 m/s) (P = 0.023). The AUCs were 0.655, 0.744, and 0.744 with the cut-off SWS≥1.89 m/s, ACR TI-RADS category 4 and intermediate suspicion of ATA TI-RADS category. The sensitivity and AUC were 82.1% and 0.812 with combined ultrasound features of hypoechogenicity, lobulated or irregular margin and macrocalcification. In Conclusion, SWS measurement and TI-RADS categories were useful for the identification of FTCs from FAs.

Accurate ultrasound speed measurement using an MLS-modulated continuous wave

Abstract The continuous wave shows greater potential than the pulse signal to achieve high-accuracy ultrasound speed measurement thanks to its stronger noise resistance. However, the accuracy of ultrasound speed measurement would deteriorate if echoes exist in the received continuous wave. This paper presents an applicable method using the maximum length sequence-modulated continuous wave. The present method improves the accuracy of ultrasound speed measurement further by resisting echoes. The time delay between the received signal and the transmitted signal is estimated accurately by combining the cross-correlation, parabolic interpolation and phase shift technique. Moreover, both the inherent delays induced by physical system and the path length of ultrasound are expediently corrected through least square estimation. As a result, accurate time of flight and ultrasound speed measurement are achievable. For example, the standard deviation of ultrasound speed measurement in distilled water is less than 0.003 m/s, and the deviation between the ultrasound speed measurement and the reference is less than 0.04 m/s.

On System-Dependent Sources of Uncertainty and Bias in Ultrasonic Quantitative Shear-Wave Imaging.

Ultrasonic quantitative shear-wave imaging methods have been developed over the last decade to estimate tissue elasticity by measuring the speed of propagating shear waves following acoustic radiation force excitation. This work discusses eight sources of uncertainty and bias arising from ultrasound system-dependent parameters in ultrasound shear-wave speed (SWS) measurements. Each of the eight sources of error is discussed in the context of a linear, isotropic, elastic, homogeneous medium, combining previously reported analyses with Field II simulations, full-wave 2-D acoustic propagation simulations, and experimental studies. Errors arising from both spatial and temporal sources lead to errors in SWS measurements. Arrival time estimation noise, speckle bias, hardware fluctuations, and phase aberration cause uncertainties (variance) in SWS measurements, while pulse repetition frequency (PRF) and beamforming errors, as well as coupling medium sound speed mismatch, cause biases in SWS measurements (accuracy errors). Calibration of the sources of bias is an important step in the development of shear-wave imaging systems. In a well-calibrated system, where the sources of bias are minimized, and averaging over a region of interest (ROI) is employed to reduce the sources of uncertainty, an SWS error can be expected.

Validity of acoustic method for the assessment of whole-body hydration status

In almost any sport, athletes undergoing dehydration often suffer from numerous dehydration related injuries. The purpose of this study was to evaluate the validity of acoustic method to detect changes in the hydration status of athletes after undergoing acute dehydration and a 2-hour rehydration protocol. The acoustic method of assessing body hydration status is based on the experimental fact that ultrasound speed in muscle is a linear function of the tissue water content. The assessment of water imbalance was conducted by measuring speed of ultrasound in the calf muscles using through transmission method. Eighty-two male and female collegiate athletes were examined to detect changes in hydration status before and after undergoing 3% acute dehydration. Results demonstrated that the changes of ultrasound velocity are in average about 1.1 m/s per 1% of body dehydration and ultrasound velocity in muscle potentially may serve as a measure of body hydration status. However, ultrasound speed measurement using through transmission mode implemented in this study is highly dependent on the positioning of the probe: even slight variation in the acoustic path results in significant changes in the measured values, which may results in unacceptable error. A solution to this problem is proposed and discussed. [NIH2R44AG042990.]

Concentration dependence of ionic hydration numbers.

Isothermal compressibility data of 23 aqueous electrolyte solutions at 25 °C from the literature are used to calculate their hydration numbers, which diminish as the concentration increases. Their limit at very high concentration is near the "number of adsorption sites" of water molecules on the ions, obtained by the BET method. On the contrary, hydration numbers obtained from ultrasound speed measurements yielding isentropic compressibilities cannot be valid, being much too large at infinite dilution.

Densitometry and ultrasound velocimetry of hyaluronan solutions in water and in sodium chloride solution

The densities of hyaluronan solutions in water and 0.15M NaCl were measured in the temperature range from 25 to 50°C for the hyaluronan molecular weights from 10 to 1750kDa. The density increased linearly with concentration and decreased with temperature. The data were fitted by the equation describing the density as a linear function of concentration and a quadratic function of temperature. The effect of molecular weight was negligible and thus single equation was sufficient to describe all data. The apparent and partial specific volumes were calculated from the density data including their extrapolated values to infinite dilutions. The measurement of ultrasound speed in the same solutions under the same conditions enabled to calculate the compressibility and its dependence on concentration and temperature. The compressibility decreased with both the concentration and the temperature but the effect of the concentration was only slight mild. The compressibility was used to estimate the hydration numbers which slightly decreased with increasing temperature and concentration. The addition of NaCl changed only the numerical values of density and ultrasound velocity while not changing the character of their dependence on temperature and concentration. Measured and calculated data indicate that hyaluronan does not disturb the specific water structure in the studied concentration range and support the idea of the existence of water clusters or nanodroplets hydrating the hyaluronan chains in solution.

Ultrasound speeds and molar isentropic compressions of (3-ethoxypropane-1-amine + water) mixtures from T = (283.15 to 303.15) K

Alkoxyamines containing two hydrophilic groups with great affinity to water are multipurpose compounds with important applications, either on theoretical or practical grounds. The thermodynamic characterization of aqueous mixtures of these compounds is scant. Ultrasound speed measurements have been made in 53 mixtures of the aqueous ethoxypropane-1-amine binary system, across the entire composition range and temperatures between T=(283.15 and 303.15)K, at atmospheric pressure. By combining ultrasound speed and density data, values of the isentropic compressibility were derived. Excess molar isentropic compressions were estimated and analytically fitted to Redlich–Kister polynomial equations. Excess partial molar quantities were then calculated including their limiting values, which were obtained from the Redlich–Kister fitting coefficients. The temperature dependences of limiting partial molar isentropic compressions and isobaric expansions were also scrutinized. Compressibility changes associated with different patterns of aggregation and hydration over the whole composition range are identified.

Carotid atherosclerotic plaque characterisation by measurement of ultrasound sound speed in vitro at high frequency, 20 MHz

This study aimed to utilise a tissue mimicking material (TMM) in order to embed in vitro carotid plaque tissue so that its acoustic properties could be assessed. Here, an International Electrotechnical Commission (IEC) agar-based TMM was adapted to a clear gel by removal of the particulates. This clear TMM was measured with sound speed at 1540ms−1 and an attenuation coefficient of 0.15dBcm−1MHz−1. Composite sound speed was then measured through the embedded material using a scanning acoustic microscope (SAM). Both broadband reflection and transmission techniques were performed on each plaque specimen in order to ensure the consistency of the measurement of sound speed, both at 21°C and 37°C. The plaque was measured at two temperatures to investigate any effect on the lipid content of the plaque. The contour maps from its associated attenuation plots were used to match the speed data to the photographic mask of the plaque outline. This physical matching was then used to derive the sound speed from the percentage composition seen in the histological data by solution of simultaneous equations. Individual speed values for five plaque components were derived; TMM, elastin, fibrous/collagen, calcification and lipid. The results for derived sound speed in the TMM were consistently close to the expected value of soft tissue, 1540ms−1. The fibrous tissue showed a mean value of 1584ms−1 at 37°C. The derived sound speeds for elastic and lipid exhibited large inter-quartile ranges. The calcification had higher sound speed than the other plaque components at 1760–2000ms−1. The limitations here lay in the difficulties in the matching process caused by the inhomogeneity of the plaque material and shrinkage during the histological process. Future work may concentrate on more homogeneous material in order to derive sound speed data for separate components. Nevertheless, this study increases the known data ranges of the individual components within a plaque. This information may be used help to assess the mechanical properties and structural integrity and its associated vulnerability or risk of embolization in future diagnostic ultrasound techniques.

Studies on the interactions of diglycine and triglycine with polyethylene glycol 400 in aqueous solutions by density and ultrasound speed measurements

Density and ultrasound speed were measured accurately for diglycine+water, triglycine+water, diglycine+water-polyethylene glycol 400 (PEG400) and triglycine+water-PEG400 solutions at T=(293.15, 298.15, 303.15 and 308.15)K. The results were used in evaluating thermodynamic properties as apparent molar volumes (VØ) and apparent molar isentropic compressions (KSΦ) of diglycine and triglycine in water and in PEG400 solutions. Infinite dilution values of these parameters, VoØ, and KoSΦ, were obtained from their plots as a function of molality by extrapolation and have been utilized in obtaining transfer volumes and transfer compressions at infinite dilution. All transfer volumes and transfer compressions were found to increase with increasing molality of PEG400. Apparent molar isobaric expansions were derived from the temperature dependence of VØ values at infinite dilution and at finite concentrations. All the results were interpreted in terms of solute (diglycine or triglycine) and co-solute (PEG400) and solvent (H2O) interactions.

The Precise Mechanisms of a High-Speed Ultrasound Gas Sensor and Detecting Human-Specific Lung Gas Exchange

In this paper, we propose and develop a new real-time human respiration process analysis method using a high-time-sampling gas concentration sensor based on ultrasound. A unique point about our proposed gas concentration sensor is its 1 kHz gas concentration sampling speed. This figure could not have been attained by previously proposed gas concentration measurement methods such as InfraRed, semiconductor gas sensors, or GC-MS, because the gas analysis speeds were a maximum of a few hundred milliseconds. First, we describe the proposed new ultrasound sound speed measurement method and the signal processing, and present the measurement circuit diagram. Next, we analyse the human respiration gas variation patterns of five healthy subjects using a newly developed gas-mask-type respiration sensor. This reveals that the rapid gas exchange from H2O to CO2 contains air specific to the human being. In addition, we also measured medical symptoms in subjects suffering from asthma, hyperventilation and bronchial asthma. The millisecond level high-speed analysis of the human respiration process will be useful for the next generation of healthcare, rehabilitation and sports science technology.

Ultrasonic Determination of Water Concentration in Ethanol Fuel Using Artificial Neural Networks

Detection of water concentration in ethanol is important for several industries because of ethanol's widespread use in a number of products, including alcoholic beverages, solvents, and transportation fuels. The miscibility of ethanol with water and other polar liquids makes ethanol susceptible to adulteration beyond the specifications. In this study, adulteration of ethanol was simulated by mixing anhydrous ethanol with water at known concentrations. Ultrasound speed and temperature measurements were used to estimate the water concentration in ethanol using two mathematical models. The first model was based on statistical curve fitting to the experimental data, and the second model was based on a feed-forward, back-propagation neural network algorithm. A total of 651 data sets containing ultrasound speed and temperature as inputs and water concentration in ethanol as output were used to train the neural network algorithm. Both models were validated by preparing ethanol and water mixtures at known concentrations. Validation experiments showed that water concentration in ethanol-water mixtures can be determined by using ultrasound speed and mixture temperature with a standard error of prediction of 8.6% with neural network model and 12.4% with an empirical model. Improving the accuracy and increasing the number of data points for neural network training would reduce the prediction error. The measurements of ultrasound speed and temperature do not involve any moving parts, and the method is rapid and non-invasive, which makes the ultrasound measurement system suitable for online monitoring of water concentration in ethanol.

High frequency poroelastic waves in hydrogels

In this work a continuum model for high frequency poroelastic longitudinal waves in hydrogels is presented. A viscoelastic force describing the interaction between the polymer network and the bounded water present in such materials is introduced. The model is tested by means of ultrasound wave speed and attenuation measurements in polyvinylalcohol hydrogel samples. The theory and experiments show that ultrasound attenuation decreases linearly with the increase in the water volume fraction beta of the hydrogel. The introduction of the viscoelastic force between the bounded water and the polymer network leads to a bi-phasic theory, showing an ultrasonic fast wave attenuation that can vary as a function of the frequency with a non-integer exponent in agreement with the experimental data in literature. When beta tends to 1 (100% of interstitial water) due to the presence of bounded water in the hydrogel, the ultrasound phase velocity acquires higher value than that of pure water. The ultrasound speed gap at beta=1 is confirmed by the experimental results, showing that it increases in less cross-linked gel samples which own a higher concentration of bounded water.

Acoustic waves in hydrogels: A bi-phasic model for ultrasound tissue-mimicking phantom

In the present paper a continuum poroelastic model for high frequency acoustic waves in hydrogels has been developed. The model has been used to obtain the acoustic longitudinal wave equation for ultrasound. In order to obtain a satisfactory model for hydrogels, a viscoelastic force describing the interaction between the polymer network of the matrix and the bounded water is introduced. The model is validated by means of ultrasound (US) wave speed and attenuation measurements in polyvinylalcohol (PVA) hydrogel samples as a function of their water volume fraction “β” and polymer matrix cross-linking. The model predicts that the law ∝ ν (1 + δ) for ultrasound attenuation can be applied as a function of the frequency ν, where δ is the frequency exponent of the polymer-bounded water viscosity. This outcome can well explain the attenuation of the US frequency in natural gels where δ is typically about 0.25÷0.50 while the value for pure water is 1. The theory and experiments show that US attenuation in hydrogels decreases steadily with the increase of its water volume fraction β in a linear. The new proposed dissipative mechanism leads to a US wave speed c that follows the law: c = c w( β − ϕ) − 3/2 , where c w is the US wave speed in water and ϕ is the volume fraction of the bounded water. Since 0 < β < 1 and ϕ > 0, the hydrogel US velocity is always higher than that of pure water. If β tends to 1 (100% water), then the US speed in hydrogels converges to a higher value than that of pure water. The US speed gap at β = 1, between hydrogels and water, is the direct consequence of the introduction of the polymer network-bounded water interaction. This is in line with the experimental results that show that the US speed gap at β = 1 decreases in the gel samples with a more cross-linked polymer matrix that has a lower bounded water volume fraction. On the contrary, if the water content is very low (i.e., β < 0.4), the measured US speed converges to that of the dry hydrogel matrix which increases in the samples with a higher degree of network cross-linking with greater elastic moduli.

Uncertainties of useful thermodynamic properties calculated from ultrasound speed measurements in liquids and solutions

Calibration of a modified sing-around ultrasound velocimeter, with ultra-pure water, has been done using sound speed data recommended in the literature for pure water. Empirical calibration parameters were evaluated by a least-squares fitting method and the impact of both the uncertainties in measured quantities and propagation of uncertainties in the calibration parameters and other influence quantities on uncertainties in the calculated sound speed in water have been estimated. Examples are given for calculating the uncertainties of some useful thermodynamic properties derived from ultrasound speed data that are used in important industrial applications such as estimating concentration of solutions and density of binary liquid mixtures.

Molar volumes and isentropic compressions of pluronics L64 and P123 in aqueous surfactant solutions, over the critical temperature range of aggregation

Interactions between triblock copolymers of poly(ethylene oxide) and poly(propylene oxide), EO x PO y EO x , and ionic surfactants, have been investigated using density and ultrasound speed measurements over the temperature range 288.15–318.15 K. Two copolymers, denoted L64 ( x = 13, y = 30) and P123 ( x = 20, y = 69) were selected because their critical micellar temperatures (CMT) could be conveniently covered. The ionic surfactants were the sodium dodecylsulfate, SDS, and the hexadecyltrimethylammonium bromide, CTAB. The transfer molar volumes and transfer molar isentropic compressions of each copolymer from water to aqueous micellar solution were calculated and analysed at a constant copolymer concentration ( w p = 1 % ) for varying surfactant concentrations up to 0.15 mol kg −1. The trends in the variations of the transfer properties of either L64 or P123 gradually decrease from positive to negative values over the range that encompasses the critical micellar temperature. By contrast, they are remaining mostly similar apart from CMT, i.e. the copolymer is present either in monomeric or micellar state, and are weakly dependent on the temperature. The transfer values are assumed to be the sum of two contributions of opposite sign. A positive one arises from the hydrophobic interactions between the monomers and SDS and gives rise to the formation of copolymer–surfactant complexes. A negative one arises from the rehydration of the copolymer molecules expelled from the pluronic micellar core during the disruption of the pluronic micelles with increasing concentration of SDS. This negative contribution has been shown to be rigorously equivalent to the value of the micellisation properties of the pluronics in water. Results obtained in the present work for CTAB solutions reveal seemingly similar mechanisms of binding between the surfactant and the pluronics.

A thermodynamic study of two anionic amphiphilic penicillins in aqueous solution by ultrasound speed measurements

Abstract The critical concentrations of sodium cloxacillin and sodium dicloxacillin penicillins in aqueous solution were determined over the temperature range 288.15–313.15 K by a method based on deconvolution into Gaussians of the second derivative of the measured ultrasound velocity. The mass action model was used to calculate the thermodynamic standard quantities: free Gibbs energy, enthalpy and entropy of aggregate formation. The results are discussed in terms of the structure of the drug aggregates.

Dorsal metacarpal cortex ultrasound speed and bone size and shape.

In Thoroughbred racehorses, the dorsal cortex (DC) of the third metacarpal bone (MC3) enlarges when horses are first exposed to fast exercise speeds. It is now possible to measure ultrasound speed through 3 to 5 mm depths of bone around the bone shaft using Sunlight Medical's 'Omnisense' machine. The aim of this experiment was to determine whether the ultrasound speed measured in the surface 3-5 mm of the midshaft dorsal cortex of MC3 could be related directly to the midshaft shape and size of the MC3s of young Thoroughbred racehorses at the same stage of training. Sixteen 2-year-old and sixteen 3 to 6-year-old racehorses, exercising at racing speed at the same training stable, had their ultrasound speed measured and were radiographed to measure their MC3 midshaft size (width of DC) and shape ([DC/palmar cortex] x [[DC+palmar cortex]/medulla widths]). There were significant linear relationships between ultrasound speed and radiographic bone size and shape measurements. The faster ultrasound speeds were associated with bones that were both absolutely and proportionately thinner in the dorsal cortex in both groups of racehorses. The measurement of ultrasound speed with the Sunlight Omnisense machine should allow more detailed and accurate predictions to be made for responses of the bone to exercise in the midshaft of MC3 than is possible using radiographic size and shape measurements alone. This should make it possible to predict, for example, how soon after a change in bone shape a specific horse can race with minimal risk of damage to the newly-forming bone surface.

Aggregative processes in aqueous solutions of isomeric 2-butoxyethanols at 298.15 K

Ultrasound speed measurements across the entire composition range of aqueous mixtures of both isobutoxyethanol (iC4E1) and tert-butoxyethanol (tC4E1) have been made at 298.15 K with a sonic solution monitor that employs a “pulse–echo–overlap” technique. In addition, densities of aqueous mixtures of tC4E1 were determined using a vibrating tube densimeter. These new data were complemented with literature values for densities of aqueous mixtures of tC4E1 and for densities and sound speeds of aqueous mixtures of n-butoxyethanol (nC4E1). In all cases, density values were converted to molar volumes, Vm, and excess molar volumes, VmE. Estimates of the isentropic molar compression, KS,m [= −(∂Vm/∂p)S], and of its excess counterpart, KS,mE, were obtained from the combination of the ultrasound speeds and density values. Data reduction procedures were used to generate consistent sets of values for thermodynamic properties of isomeric amphiphiles with increasing degree of alkyl branching. The graphs for the composition dependence of excess partial molar volumes and isentropic compressions of water show enhanced visual impact. These graphs are used for presenting evidence for identifying the prevailing patterns of molecular aggregation. Segmented-composition models, including a version onto which a mass action component has been grafted, are employed, together with a simplified pseudo-phase model, to analyse the various excess molar quantities. The experimental evidence thus obtained is used to relate the effect of chain branching with the degree of self-aggregation of amphiphiles in aqueous solution. An unexpectedly low self-aggregation among iC4E1 molecules is found and discussed in terms of vicinity to the lower critical solution temperature.

Phase correction on ultrasound speed measurement.

Phase correction on ultrasound speed measurement.