Ultrasound Velocity Measurements Research Articles

Flow dynamics in a stenosed carotid bifurcation model—Part II: Derived indices

Basic velocity measurements from the previous study in this issue of modelled carotid artery bifurcation disease are post-processed to derive indices potentially useful for clinical diagnosis. Selected parameters are based upon ultrasound pulse Doppler velocity measurements made at sites ±0.625 radius at axial distances of 0, 1, 3, 5, and 10 diameters downstream of smooth, axially symmetric constrictions of 0, 20, 40, 60, and 80% diameter reduction. Indices based on single point velocity measurements include: (a) the center-line velocity index (CVI) at the throat of the constrictor which is sensitive to all degrees of constriction ( p < 0.05), and (b) various measures of velocity disturbance (VDII-VDI4) which show greatest sensitivity when measured at one-fourth diameter from the tube wall. Cross-sectional indices include: (a) the maximum slope index (MSI) which separates constrictions of ≤60% diameter reduction from those having ≥60% diameter reduction ( p < 0.05), and (b) the cross-sectional profile index (CPI) which separates constrictions of ≤20% diameter reduction from those having ≥20% diameter reduction ( p < 0.05). A field profile index (FPI) utilizes data from all available sites up to 5 diameters downstream and is able to separate all constrictor groups ( p < 0.05). Presence of constrictions produces characteristic flow patterns which can be quantified using indices based on the downstream velocity spectra. Specifically, locally increased velocity is very sensitive to degree of constriction and is best detected along the center line. Disturbance effects, while less pronounced, are complementary to changes in velocity magnitude and are first seen off-axis. Multiple point profile measures (cross sectional and full field) are also sensitive to degree of constriction and are best evaluated at 1 diameter and over 5 diameters, respectively, downstream of the constriction. All of the nondimensional indices offer the advantages of reduced probe and angle dependence and particular approaches may be implemented according to the data collection capability of the instrument used.

Combined 2.25 MHz ultrasound velocity and bone mineral density measurements in the equine metacarpus and their in vivo applications.

A simple noninvasive ultrasound method is described for estimating the transverse cortical bone ultrasound velocity and the cross-sectional area of the equine third metacarpal bone (MC3). The method relies on measuring the time of flight of the ultrasound for each of two pathways, via the cortical shaft and through the central medulla. Ten metacarpal bones of approximately the same dimensions were selected to evaluate the method and to determine the practiocal correction factors Factors were established for the ovality of the external cortical boundary and the medullary cavity as well as corrections for the presence of the splint bones (second and fourth metacarpal bones, MC2 and MC4) which influence, the total cortical cross-sectional area. Conventional single-photon absorptiometry was used to measure the bone mineral content which, together with the cross-sectional area determined ultrasonically, was then used to estimate the bone mineral density. The bone mineral density was also determined for some bone sections from ash weight and volume. The compact bone density (i.e. relative density) together with the ultrasound velocity were then used to estimate a modulus of elasticity in the transverse direction.

Adiabatic compressibility of alkyltrimethylammonium bromides in aqueous solutions

The adiabatic compressibility of aqueous solutions of octyl-, decyl-, dodecyl- and tetradecyltrimethylammonium bromides has been determined from measurements of ultrasound velocity and density at 25°C. A theoretical treatment giving the adiabatic compressibility as a function of concentration has been developed, and the apparent adiabatic compressibility of a surfactant in the monomeric and micellar forms is derived from the experimental results. The apparent adiabatic compressibility of surfactant in either form is constant, independent of concentration, so that it is identified with the apparent adiabatic compressibility in each form. The adiabatic compressibility in the monomeric form decreases from −0.25 × 10 −5 bar −1 for the octyl to −2.52 × 10 −5 bar −1 for the tetradecyl derivative, while that in the micellar form increases from 3.41 × 10 −5 bar −1 for the octyl to 4.17 × 10 −5 bar −1 for the tetradecyl derivative. The former includes the hydration of ionic head group of the surfactant, while the latter is related to the structure of micelle. If the same treatment is applied to the literature data, the apparent adiabatic compressibility of sodium alkyl sulfate in the monomeric form changes conversely with the alkyl chain length, while that in the micellar form is qualitatively similar.

Measurement of Ultrasound Velocity in Gases under High Pressures up to 3.5 GPa

Using the high-pressure apparatus described in a previous paper, the freezing points of nitrogen and krypton at room temperature were determined from the volume and ultrasound velocity changes. The ultrasound velocity of neon was also measured up to 3.5 GPa. Taking account of the results of the ultrasound velocity and the volume measurements, empirical formulae for the pressure dependence of ultrasound velocities of helium, neon, argon, krypton and xenon were proposed. The phase diagram of a krypton and helium gas mixture under high pressures up to 1.6 GPa at room temperature was also obtained from the velocity measurement.

Measurement of ultrasound velocity in the spin-glass C uMn

Ultrasound velocity measurements may be used to study the dynamics of the spin-glass phase. Near the transition temperature, the sound speed deviates slightly from that of the pure nonmagnetic host. We measured the velocity anomaly in a 1-at. % CuMn sample near the transition temperature (12 K) as a function of frequency from 5 to 100 MHz and found its size to be frequency independent. We also found changes in the anomaly when the sample was field cooled in transverse 4.7- and 14.2- kG fields. These results are discussed in light of previously published theoretical predictions.

A theoretical study of arterial disease by transfer function analysis.

A general method is proposed for a theoretical evaluation of the hemodynamic effects of stenosis on the arterial subsystem affected by it. In particular, it is applied to a lower limb stenosis, so as to compare the results of the theoretical analysis to those that other authors have obtained experimentally by processing Doppler ultrasound blood flow velocity measurements proximal and distal to a stenosis in the superficial femoral artery (SFA).

Systematic study of the lattice dynamics of the uranium rocksalt-structure compounds.

The phonon-dispersion relations of USe and UTe have been determined by the inelastic scattering of thermal neutrons. All existing phonon measurements for the UX series, viz., UC, UN, UAs, USb, US, USe, and UTe, have been fitted to the rigid-ion and shell models and dispersion relations have been predicted for UP. The U-X force constants dominate the lattice dynamics and are nearly constant for the series, whereas the U-U force constants vary systematically from being large and positive for the compounds with the smallest lattice parameter to being negative for the chalcogenide series. The negative U-U force constant is identified with destabilizing f-d interactions. Elastic constants, derived from the slopes of the dispersion relations and from ultrasound velocity measurements, have been determined. The bulk modulus decreases unusually rapidly as the lattice parameter increases and is in fair agreement with band-structure calculations.

Measurement of ultrasound velocity in tissues utilizing a microcomputer-based system.

The continued interest in diagnostic applications of ultrasound has led to a need for more detailed knowledge of the ultrasonic properties of biological tissues. This communication describes an experimental system based on a Z-80 microprocessor which communicates with other devices via an STD bus for measuring ultrasound velocity in biological tissues as a function of temperature. Data have been collected for bovine heart, kidney, liver, and blood over the temperature range of 10-45 °C.

84 INTRAOPERATIVE EVALUATION OF SURGICALLY CREATED A SYSTEMIC TO PULMONARY SHUNTS WITH PULSED DOPPLER ULTRASOUND

Pulsed Doppler ultrasound (PDU) blood velocity measurements in the carotid artery were compared with outcome of surgically created systemic-to-pulmonary shunts. In 9 shunt cases an 8 MHz PDU probe was placed over the ipsilateral carotid artery and flow velocity was recorded while the shunt was mechanically manipulated from open to closed. The following indices were derived from the velocity waveforms: integrated systolic velocity to integrated diastolic velocity ratio (DV/SV), end diastolic velocity to peak systolic ratio (EDV/PSV), and reverse velocity to'forward velocity ratio (R/F). The mean for each index for each patient was less during the shunt open state than the corresponding mean during the shunt closed state. A paired t test for each index showed significance levels of p<.01, p<.001, and p<025 for DV/SV, EDV/PSV, and R/F, respectively. The patient with the smallest difference between means of DV/SV and EDV/PSV for the open and closed states required shunt enlargement and the patient with the greatest difference between means required shunt reduction. The remaining 7 shunts were bracketed by these two end points and were deemed adequate at the two week follow-up exam. This preliminary data suggests that PDU velocity derived indices correlate well with shunt magnitude in the acute operative setting. Noninvasive PDU is potentially an inexpensive, convenient, repeatable, and safe alternative to aortography and cardiac catheterization in the assessment of shunt function.

Technique for Ultrasound Group Velocity Measurements in Dispersive Media with Multipath Interference

Technique for Ultrasound Group Velocity Measurements in Dispersive Media with Multipath Interference

Development of methods of precise ultrasonic measurements in small volumes of liquids

The application of ultrasonic methods to investigation of problems of molecular physics and molecular biology is greatly limited by the necessity of precise measurements of ultrasound velocity and absorption in small volumes of liquids. Fixed path interferometric methods are the most adequate for such measurements in the low MHz region. In this paper disadvantages of the present interferometric methods of ultrasonic measurements are considered and new resonator cells and a simple device for such measurements are described. Accuracies of 10 −4% for the velocity change and to better than 1% for the attenuation change, at frequencies of about 7 MHz, are obtained by the device described. The volumes of the resonator cells vary within 0.1 to 0.8 ml depending on the purpose of investigation.

A final year physics undergraduate experiment on ultrasound propagation in liquids

We describe an advanced undergraduate physics experiment which permits the measurement of ultrasound velocity and absorption in liquid systems at frequencies between 10 and 30 MHz and temperatures between 25° and 60 °C.

Ultrasound velocity measurement and determination of elasticity constants of liquids as a function of temperature and pressure

A method for determining the compressibility coefficient and relative bulk modulus, and also the density of liquid petroleum products as function of temperature and pressure in the range of −50 to 80°C and 10 to 2.5 × 10 8 Pa is presented; the accuracy of the method is respectively 0.74%, 0.43% and 0.43%. The above-mentioned constants were determined from density measurements as a function of temperature at atmospheric pressure, and velocity of ultrasound propagation within the frequency band 2.5 to 10 MHz as a function of temperature and pressure. The theoretical foundation of the method and a description of the apparatus are given. The results are presented using the example of hydraulic oil.

Two-dimensional echo-encephalography. 1. Acoustic properties of some tissues and the characteristics of echo patterns obtained using equipment especially adapted for detection of these tissues.

In this paper the results of measurements of ultrasound velocity in, and density of, a number of normal and pathological tissues are given. From the results it can be concluded that intracranial pathological regions will often be detectable with ultrasound techniques, but is is not possible with any degree of certainty to localise precisely the morphological boundaries of these abnormal regions. Because, in the large majority of cases, the echoes from intracranial pathological structural changes are of weak intensity, a simple electronic device is described which, in conjunction with standard echo equipment, has been shown to be of use for better detection of these weak signals.

Physicomechanical properties of volume-strained sintered porous nickel

1. Measurement of the velocity of propagation of longitudinal USV in sintered solids offers a highly sensitive means of detecting contact imperfections and artificial defects and also of examining their healing during sintering. 2. An evaluation of macrodefect concentrations based on ultrasound-velocity measurements established that cold healing of defects is possible at high repressing pressures. 3. Ultrasound velocity measurements revealed an appreciable anisotropy of macrodefects forming during sintering and re-pressing in porous nickel sintered with a volatile pore-forming agent.

Ultrasound propagation in glasses in the metastable immiscibility region of the sodium borosilicate system

Measurements of ultrasound wave velocity and attenuation have been made between 1.3 K and 400 K in a series of both quenched and heat-treated Na 2OB 2O 3SiO 2 glasses. As in many other inorganic glasses, the ultrasound attenuation of both longitudinal and shear waves below room temperature is dominated by a broad and intense loss peak; the height and temperature of the peak maximum are frequency sensitive. The loss peak characteristics are consistent with a structural relaxation mechanism with a distribution of activation energies and this model is used to analyse the data. The features of the acoustic loss peak and also the absolute value and temperature coefficient of ultrasound velocity are strongly dependent on the total Na 2O network modifier content of the glasses. The ultrasound wave propagation is also affected by phase-separation inducing heat treatment: a steady rise in the height of the acoustic loss peak and an upward shift in the peak temperature takes place with increasing time of heat treatment at 550°C, a finding which suggests that structural rearrangements are still occurring in the individual glassy phases even after long periods of heat treatment. It is proposed that heat treatment causes migration of Na + ions away from BOB bonds in the B 2O 3 rich phase.

Propagation of ultrasonic waves in suspensions and emulsions: 2. Relation between ultrasonic properties and certain characteristics of the medium

The results obtained in the measurement of ultrasound velocity and absorption coefficient in pigment suspensions merit an attempt to interpret the functional dependence of these ultrasonic properties on suspension concentration and dispersion degree.

Measurement of ultrasound velocity in human tissue

This paper describes a method of measuring ultrasound velocity to high accuracy in small samples of reasonably homogenous substances. Results obtained with some body fluids and brain tumours are given.

Investigation of Peculiarities in the Hardening Process of Portland Cements with Active Additives out of Waste

This study deals with the impact of waste fluid cracking catalyst (FCC) and cupola dust (CD) on hardening process of various Portland cements (CEM I 42.5 R (PCR), CEM I 42.5 N (PCN), CEM II/A-S 42.5 N (PCSN)). The plain cement pastes and waste modified pastes (with cements replacement for 10 % of additives), also pastes with the well-known pozzolana additive, microsilica (MS), were investigated. The studies of development of hardening structure by ultrasound wave velocity (UWV) measurement method, of change of mineral composition and physical-mechanical properties were carried out. Impact of additives is subject to both the own properties (chemical, mineral composition and fineness) of additive and of cement. FCC accelerates noticeably the development of initial structure of finer cement (PCR) only. Beyond 24 h development of structure in all FCC modified pastes is going somewhat slower, nevertheless, after 28 days their structure is already more compact than that of plain pastes. The strength properties are changing accordingly. The development of initial structure of CD modified PCR, and especially PCSN, pastes is going faster, PCN - almost does not change. Beyond 24 h compacting of structure of all CD modified pastes was slower. For the early strength of cements, the impact of CD was negligible, after 28 and 90 days the strength of CD modified PCR and PCN pastes was lower than that of plain pastes. In the case of PCSN, the slag is activated by alkali and the strength increased. CD additive, like MS and FCC, decreases the OH" concentration in the liquid phase of hydrating cement suspensions at the initial period (till 3 h), however further in the course of 28 days it was growing and became higher than that of plain cement suspensions.http://dx.doi.org/10.5755/j01.ms.17.1.254

Ultrasonic examination of cold pressing with a counter press

Measurements of ultrasound velocity and attenuation during cold pressing have enabled the authors to locate small volumes of coarse-grained material and to detect incipient cracks by detecting the alignment of crystals and the presence of dislocations. They photograph the oscilloscope trace at high speed and are able to obtain a continuous record of changes during the pressing process