Ultrasound Wave Propagation Research Articles

Effect of different sterilization processing methods on the mechanical properties of human cancellous bone allografts

Use of new sterilization methods applied to human bone is likely to affect both the mechanical and biological properties of human cancellous grafts. The mechanical properties of the transplanted bone inevitably determine the short- and mid-term results of the orthopedic procedure performed. The aim of this study was to compare, under similar conditions, the mechanical effects of gamma irradiation, lipid extraction, and treatment with 6 m urea on trabecular bone samples, through conventional mechanical tests and measurement of the ultrasound wave propagation rate. Deteriorations measured for gamma irradiation and lipid extraction were low: 2.4% and 2.5%, respectively, for ultrasound propagation wave measurements. They were clearly significant for protocol including 6 m urea, corresponding to a loss of 30% in values measured in the control sample for the stress to failure, inciting prudence when grafted bone is used for support in orthopedic assembly. High consistency in the results obtained between travel time of the ultrasound wave, easily done, and measurement of stress to failure through conventional tests, favor the use of ultrasound protocol, described as a quality test performed on bone grafts in the tissue bank before distribution and implantation.

A 3-D simulation of focused ultrasound propagation for extracorporeal shock wave osteotomy

We have previously proposed a method of cutting bones using high-intensity focused ultrasound. The goal of the method is to cut bones in a body without incising the skin, but the condition under which bones are cut properly is so sensitive that 1 mm of displacement makes cutting bones fail, resulting in necrosis around the focal point. In this paper, we have developed a focused ultrasound propagation simulator in full 3-D simulation. The Finite Difference Time Domain method has been implemented to simulate ultrasound wave propagation through multiclass tissues. We have employed Perfectly Matched Layer as an absorbing boundary condition to minimize reflections from the boundary of a simulation domain. A comparison of simulation and experimental results has shown that the simulation results are correlative with actual phenomenon and that the presenting method can be used to predict the conditions under which bones can be cut.

Irritation cutanée et vitesse de propagation d'ondes ultrasonores

Cutaneous irritation is a stereotyped response of the skin to any physical or chemical insult. Its main manifestations encompass inflammatory erythema and an alteration of the cutaneous microrelief showing increased roughness, dehydration and erratic desquamation. Several instrumental methods can indirectly assess the issues of cutaneous irritation on human stratum corneum. The aim of the present study was to measure the speed of propagation of ultrasound shear waves in the skin irritated by anionic surfactants. The study was performed in 25 healthy subjects of both sexes. Occlusive patches of a 10% solution of anionic surfactants were applied to a forearm of each volunteer. The other forearm served as an untreated control site. Patches remained in place for 24 h. Three hours later, another patch was placed again for 21 h. Resonance running time measurements (RRTM) of the ultrasound shear wave were performed using a Reviscometer RVM 600. Measurements were performed at entry in the study and 2 days after removing the second patch. Desquamative xerosis was obvious at the sites patched with the surfactant solution. RRTM values were significantly (P < 0.0001) lower than those at the control site. Hence, the speed of propagation of ultrasound shear waves was shown to be increased at an irritated site compared to an intact site. In conclusion, this study shows that the propagation speed of ultrasounds is influenced by the skin surface nature, being considerably increased in skin altered by surfactants.

Electrosensitive Fluids in Acoustic Devices

This article is aimed at elucidation of the specific features in propagation of ultrasound waves in an electrostructurized medium, of their dependence on an applied electric field and implementation of the effects obtained in practice.

Investigation in solid–liquid extraction: influence of ultrasound

The extraction of active principles or oils from vegetable products by means of an appropriate solvent is a classical unit operation in chemical engineering. The aim of the present work is to improve the yield or the selectivity of the extraction using ultrasound. Two solid–liquid extractions have been investigated: pyrethrines from pyrethrum flowers (Chrysanthemum cineraria) and oil from woad seeds (Isatis tinetoria). In the case of the first one, an acceleration of the kinetics and of the yield of the extraction has been obtained, probably linked to the increase of the intraparticular diffusion of the solute, which is the limiting step of mass transfer. On the other hand, ultrasound seems to have a weak effect in the case of woad seeds, probably because of the structure of the seeds. In order to distinguish the various effects acting on the ultrasound activation, a thermoelectric probe has been built for measuring the ultrasonic intensity profile. By this method, it is possible to investigate the influence of the presence of solid particles on the ultrasound wave propagation.

Improved contrast to tissue ratio at higher harmonics

The challenge in ultrasound contrast imaging is a better discrimination between the perfused tissue and the contrast bubbles, which is usually expressed by contrast to tissue ratio (CTR). Imaging based on the second harmonic frequency showed a higher CTR than imaging at the fundamental frequency. However, because of nonlinear propagation of ultrasound waves, harmonic frequencies are generated. These harmonic frequencies will be linearly reflected by the tissue and therefore limit the CTR at the second harmonic frequency. In order to reduce the scattering of tissue at harmonic frequencies and by that increase the CTR, nonlinear distortion has to be reduced. We demonstrate in this study that the CTR increases with the harmonic number. The increase is substantial when transmitting at lower frequencies. To take advantage of the higher harmonics (third, fourth, fifth and the ultraharmonics and termed here super harmonics), we have developed a new phased array transducer with a wide frequency band. In-vitro measurements using the new probe show an increase of 40 dB of the CTR for super harmonic components over the conventional second harmonic system. The increase in CTR is in agreement with the calculations using existing models for the response of encapsulated bubbles and known theory of nonlinear propagation.

Application of the ultrasonic waves in structural investigation of ferrofluid

It has been established that structural changes in a ferrofluid (formation of clusters) upon the effect of an external magnetic field can be effectively studied by ultrasound spectroscopy. In particular, the resonance absorption of ultrasonic waves enables detection and determination of the size of spherical clusters. This paper reports results of a study of changes of the size of clusters formed in a magnetic field as a function of the rate of the magnetic field intensity changes, the ferrofluid temperature, the frequency of the ultrasound wave and the angle between the magnetic field vector and the direction of ultrasound wave propagation.

Ultrasound Shear Wave Propagation in Caucasian Hair

Background: The aspect of hair depends on the spatial organization of the hair shafts and on their chemical, physical and structural integrity. Some genetic disorders and exogenous influences may affect it. Aims: In vivo objective assessments are welcome in order to compare the consequences of hair damage and to assess the kinetics of the changes occurring in time after damaging or attempting to repair the hair structure. Method: Ultrasound shear wave propagation measured on hair is introduced as an objective non-invasive method with in vitro and in vivo applications. Results: With multiple measurements made on the scalp of 72 Caucasians, hair felting following damage appeared to be associated with an increase in the coefficient of variation of the shear wave velocity measurements. Maximum hydration of hair locks increased the shear wave velocity in vitro and decreased the intra-individual range of data. The relevance of the method and reproducibility of data were influenced by the experimentalist’s skill. Conclusion: Ultrasound shear wave propagation on hair is influenced by the physical integrity of the hair shafts and their three-dimensional arrangement.

Continuum description of rarefied gas dynamics. II. The propagation of ultrasound

The equations of fluid dynamics developed in Paper I [X. Chen, H. Rao, and E. A. Spiegel, Phys. Rev. E 64, 46308 (2001)] are applied to the study of the propagation of ultrasound waves. There is good agreement between the predicted propagation speed and experimental results for a wide range of Knudsen numbers.

Analytical model for tool wear monitoring in turning operations using ultrasound waves

This paper presents an analytical model to monitor the gradual wear of cutting tools, on-line, during turning operations using ultrasound waves. Ultrasound waves at a frequency of 10 MHz were pulsed continuously inside several cutting tools, towards their cutting edge. The change in tool geometry, due to gradual wear, has been related, in a mathematical form, to the change in the acoustic behavior of ultrasound waves inside the body of the cutting tools. Physical laws governing the propagation and reflection of ultrasound waves along with geometrical analysis of the wear area were used in deriving the mathematical model. The experimental setup and model evaluation is based on a previously published research work by the author, which presented an empirical model showing a corresponding change in the ultrasound behavior with tool gradual wear. The current work emphasizes the previous findings and presents the relation between the acoustic behavior of ultrasound waves and the progressive tool gradual wear in a mathematical form that can be easily used in machine control operations.

Numerical simulations of heating patterns and tissue temperature response due to high-intensity focused ultrasound

The results of this paper show-for an existing high intensity, focused ultrasound (HIFU) transducer-the importance of nonlinear effects on the space/time properties of wave propagation and heat generation in perfused liver models when a blood vessel also might be present. These simulations are based on the nonlinear parabolic equation for sound propagation and the bio-heat equation for temperature generation. The use of high initial pressure in HIFU transducers in combination with the physical characteristics of biological tissue induces shock formation during the propagation of a therapeutic ultrasound wave. The induced shock directly affects the rate at which heat is absorbed by tissue at the focus without significant influence on the magnitude and spatial distribution of the energy being delivered. When shocks form close to the focus, nonlinear enhancement of heating is confined in a small region around the focus and generates a higher localized thermal impact on the tissue than that predicted by linear theory. The presence of a blood vessel changes the spatial distribution of both the heating rate and temperature.

Ultrasound measurement method: Errors, noise, and sensitivity

At the National Center of Aerospace Research (ONERA), the burning rate of solid propellants has been determined by means of an ultrasound technique for many years. This paper presents the results obtained on composite propellants for different initial pressures and temperatures, which allow one to discuss the advantages and limitations of the method in terms of the measurement possibility and accuracy. The sensitivity of propagation of ultrasound waves to pertinent physical parameters or operating conditions is illustrated. The errors induced by inadequate corrective terms taken into account in the measurement theory, the effect of the electronic noise of the equipment, and the procedure of differentiating experimental data are shown. Selecting suitable operating conditions allows one to reduce the instrumental error down to 1% of the burning-rate value. Though the ultrasound method is not absolutely universal and perfect, the quality of the data obtained is good enough to be noted.

The velocity of ultrasound propagation through brain tissue at low ultrasound frequencies

The acoustic properties of the brain tissue have been in the focus of much scientific research. These properties determine the possibilities of the application and development of the ultrasound methods, as well as the development of the equipment used by the neurosurgeon during the resection of the brain tissue. The results of the measurements of these acoustic properties done at megahertz frequency range have been published. Although the velocity of ultrasound wave propagation does not directly influence the distribution of the ultrasound field within the cranium, it enables the determination of the specific resistance, which has an important role in the distribution of the ultrasound field within the cranium. Using the published results and the conditions of the measurements that have been done, the velocity of ultrasound propagation for the frequency range at which cavitation ultrasonic surgical aspirators work has been estimated. After that the measurement of the velocity of the propagation has been done at the frequency of 24 kHz. The values of both the estimated and the measured velocities of the ultrasound propagation prove the validity of the assumptions on which the estimation is based on.

Laser ultrasonic investigation of the elastic properties of unidirectional graphite-epoxy composites

An ultrasonic method is proposed for the determination of the elastic constants of orthotropic solids with a laser source of ultrasound and wide-band registration of acoustic pulses. The propagation of acoustic transients in unidirectional fiber-reinforced graphite-epoxy composites is investigated. The experimental data show that the model of orthotropic solids is valid for the description of the mechanical properties of these materials. The absence of frequenc dispersion of the phase velocity in the spectral range of 1–15 MHz for every direction of propagation of ultrasound waves in the composite was confirmed. A complete set of elastic constants of unidirectional fiber-reinforced graphite-epoxy composites is calculated.

Ultrasonic characterization of thermoplastic multiblock elastomers

The propagation of ultrasound waves in thermoplastic multiblock elastomers was investigated by measurements of the ultrasound velocity and attenuation. Three polymer series with amorphous-crystalline structure were studied. The soft-segment material was composed of three different oligomers for the three series: poly(1,4-oxypropylene)diol for series A, oligo(oxyethylene)diol for series B, and dimerized fatty acid for series C. The hard-segment material was composed of poly(butylene terephthalate) (PBT). The ultrasound velocity and attenuation of these elastomers with variable hard-segment concentration were investigated as a function of the temperature. The observed relaxation processes were ascribed to the glass transition of the soft phase. The possibility of a general description of these systems is discussed.

Acoustic cavitation field prediction at low and high frequency ultrasounds

Sonochemistry, or chemistry under ultrasound, has increased in interest in the past few years. Electricité de France is involved in scaling up this new technology to industrial plants. The propagation of a power ultrasound wave (from 20 to 800 kHz) through a liquid initiates a little-known phenomenon called acoustic cavitation. Inceptions and germs grow into bubbles which collapse, possibly giving rise to extreme conditions of temperature and pressure (assessed to be up to 10 000 K and 500 atm). These conditions initiate and greatly enhance chemical reactions. Thus, it is important to know where bubbles are and how intense cavitation is, depending on geometric and acoustic factors. Then, mathematical modelling may help to predict acoustic cavitation fields. Two computations, the first one based on linear acoustic equations and the second one based on fluid dynamics equations, are presented. Calculated pressure fields are obtained in the case of a cylindrical sonoreactor at 28 and 500 kHz. The comparison with experimental observations and measurements shows good agreement with both theory and calculations.

Ultrasound velocity measurement in long bones: Measurement method and simulation of ultrasound wave propagation

A new method for the measurement of ultrasound velocity in long bones is presented. The method can be applied in vitro as well as in vivo. It automatically corrects for the influence of soft tissue, such that the real velocity in bone is obtained. In a series of simulation experiments, hypotheses on the followed wave path were verified. A very good agreement was found between the measurement obtained in the experimental set-up and the values calculated for the hypothesised wave path in the experimental structure. These simulations revealed the feasibility of the technique to determine the velocity in a local site of the structure. Clinical applications of this technique include the monitoring of callus consolidation after fracture and the detection of bone degenerative diseases such as osteoporosis.

Ultrasound wave propagation through rough interfaces: Iterative methods

Two iterative methods for the calculation of acoustic transmission through a rough interface between two media are compared. The methods employ a continuous version of the conjugate gradient technique. One method is based on plane-wave expansions and the other on boundary integral equations and Green’s functions. A preconditioner is presented which improves the convergence for spectra that include evanescent modes. The methods are compared with regard to computational efficiency, rate of convergence, and residual error. The sound field differences are determined for a focused ultrasound beam distorted by surfaces having a Gaussian roughness spectrum. The differences are evaluated from the root-mean-square differences on the rough surface and in the focal plane.

Quantitative ultrasound of the tibia: A novel approach for assessment of bone status

An ultrasound instrument has recently been developed for the diagnosis and monitoring of osteoporosis (SoundScan 2000, Myriad Ultrasound Systems Ltd., Israel). The instrument measures the speed of propagation of ultrasound waves (SOS, meters per second) along a fixed longitudinal distance of the cortical layer at the tibial shaft. Its in vivo precision is 0.25%. The performance of the SoundScan 2000 was studied in 307 Caucasian women (age range 24–87 years) who also had their bone mineral density (BMD) measured at the spine, femoral neck, and radial shaft by absorptiometric techniques. The SOS ranged from 3471–4226 m/sec (mean 3867). The standardized coefficient of variation (CV), an expression of the effective clinical precision corrected for the spread of measurements (CV/[range/mean]), was 1.6% for the tibial SOS, compared to 1.5%, 3.8%, and 4.4% for spinal, femoral, and radial BMD, respectively. Tibial SOS significantly correlated with age ( r = −0.52), time since menopause ( r = −0.43), height ( r = 0.29), and weight ( r = 0.16), as well as with BMD at the radius ( r = 0.63), spine ( r = 0.50), and femur ( r = 0.47). After classification of bone measurements into textiles, about 60% of the women with low tertile spinal BMD fell within the low textile of either tibial SOS, femoral BMD, or radial BMD. The results show that measurement of tibial SOS is a precise method of assessing bone status without exposing the patient to sources of radiation.

Ultrasonic compression wave propagation in adhesive polymers described as a signal filtering process

The ability to test adhesively bonded metal structures non-destructively requires an understanding of ultrasound wave propagation in adhesive materials. This paper presents the results of an experimental study of wave absorption and phase velocity dispersion in a number of structural adhesives in terms of the frequency response and the time domain impulse response of propagation in a thin layer of material. A simple single relaxation time model provides a phenomenological basis on which to consolidate the measured data into a form that can be used to model wave propagation in more complex structures containing an adhesive. It is shown that high rates of attenuation, increasing with frequency, will seriously limit the frequency bandwidth available for ultrasonic non-destructive testing of adhered structures. Extensions to the model are appended that will provide the basis for its implementation by means of linear electric network simulation packages.