A preliminary dual-energy X-ray absorptiometry-based finite element model for assessing osteoporotic hip fracture risk

To more accurately assess osteoporotic hip fracture risk in a specific patient, a dual-energy X-ray absorptiometry (DXA)-based finite element model was constructed from the patient's femur DXA image. The outermost contour of the femur bone segmented from the DXA image was used to generate a finite element mesh. Bone mechanical properties, such as Young's modulus, are correlated with areal bone mineral density (BMD) captured in the DXA image. A quasi-static loading condition representing a sideway fall was applied to the finite element model. Three fracture risk indices were introduced and expressed as ratios of internal forces caused by impact forces occurring in sideway fall to bone ultimate cross-section strength at the three critical locations, i.e. the femoral neck, the intertrochanteric region, and the subtrochanteric region. The proposed finite element modelling procedure was validated against six representative clinical cases extracted from the Manitoba BMD database, where initial and follow-up DXA images have been taken to monitor longitudinal variation of areal BMD in individual patients. It was found from the clinical validation that variations in the proposed fracture risk indices have the same trends as those indicated by the conventional areal BMD and T-score. In addition, by the three proposed fracture risk indices it is possible to further identify the specific fracture location. It was also found that for the same subject, the variations in the three fracture risk indices have quite different magnitudes, with intertrochanteric region the largest and subtrochanteric region the smallest, which is probably owing to the different content of trabecular and cortical bones in the three regions. With further development, it is promising that the proposed DXA-based finite element model will be a useful tool for accurate assessment of osteoporosis development and for treatment monitoring.     

A comparison of ultrasound and computed tomography in evaluating the mechanical properties of trabecular bone

This study compared ultrasound parameters and bone mineral density (BMD) in the assessment of the mechanical properties of trabecular bone. The BMD of bovine tibial trabecular bone specimens was measured by CT scanning each specimen in all three orthogonal directions. Similarly, ultrasound velocity and attenuation measurements were also made in these directions. Specimens were then divided into three groups for mechanical testing. the ultimate strength, Young's modulus and energy absorption were measured for each specimen. It was found that BMD was independent of trabecular orientation while ultrasound velocity and attenuation values were significantly higher in the superior/inferior (SI) direction corresponding to the load bearing axis at stance. All mechanical properties were also significantly higher in the SI direction. The linear correlation demonstrated that ultrasound parameters, particularly ultrasound velocity, were better than BMD as predictors of compressive mechanical properties     

Evaluation of bone strength: correlation between measurements of bone mineral density and drilling force

Bone drilling is a major part of modern orthopaedic surgery which involves the internal fixation of fractured bones. The investigation of bone drilling described in this paper demonstrates the contribution of automation technology towards the study of bone strength. The aim of this preliminary investigation is to establish a relationship between bone drilling forces and measurements of bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA). A linear relationship with a high coefficient of correlation has been found between average drilling forces and BMD measurements at both the greater trochanter and the femoral head of porcine femurs when drilling in the anterior-posterior (AP) direction (i.e. the direction of the DXA scan). It has also been found that in the normal drilling direction (i.e. in the cervical axis direction), which is orthogonal to the DXA scanning direction, there are similar trends between the drilling forces and BMD levels in regions where bone density is more consistent (e.g. the femoral head). The findings of this investigation indicate that analysis of bone drilling forces has the potential to provide useful information about the strength of bone.     

Investigation of the mechanical properties of bone using ultrasound

This paper examines the serial use of ultrasonic velocity measurement to monitor fracture healing. New Zealand White rabbit tibiae were fractured using a constant-energy technique and the ultrasonic velocity along the bone measured in animals sacrificed at 16 day intervals up to 96 days from fracture. In parallel with these measurements the mechanical performance of the healed tibiae were determined using a three-point bending test. Regression analysis failed to show a sufficiently good correlation between ultrasonic velocity measurements and the bending properties of healing fractures for the method to be of use clinically.     

Measuring melt density in polymer extrusion processes using shear ultrasound waves

Ultrasound shear waves propagating at a frequency of 2.25 MHz are used to measure the density of polymer melt in real time during extrusion process. The acoustic impedance of the polymer melt is calculated using the measured reflection coefficient off the polymer melt interface boundary. A normalisation procedure was developed to normalise for the effect of other process and material parameters not pertinent to the melt density. The ultrasound measurement is independent of the attenuation in the polymer melt and the thickness of the melt stream, which makes this technique highly desirable for heavily loaded polymers and large extrusion dies. The system was evaluated using polyvinyl chloride compounds containing various levels of foaming agent and process aid at fixed processing conditions. The system measurements of the melt density are compared to the weight of the extrudate measured by a laboratory scale. The correlation coefficient between the two measurements is approximately 96%.     

Monitoring mineral slurry flow using pulse-echo ultrasound

Ultrasound based flow measurement methods have a large potential for the mining industry and its processing plants. Ultrasound travel through dense suspensions and is not affected by the magnetic fields sometimes present in this type of equipment.A cross-correlation based method is used for localized particle velocity measurements in one and two dimensions. Simultaneously, using the same data, information about local particle concentration is extracted from the power spectral density of the backscattered signal. Experiments are carried out both in simplified geometry and in full scale equipment in an iron ore pilot benefication plant.In the simple geometry it is possible to assess the precision of the methods by comparing the measurements to theory and numerical simulations. The results from the pilot plant experiments show that these methods can be applied to real world processes.     

Microscale mechanisms of ultrasound velocity measurement in metal melts

Ultrasound Doppler velocimetry (UDV) is a powerful, widely used technique for measuring flow in metal melts. However, UDV in metal melts suffers from substandard reliability because its operation depends on phenomena that are poorly understood. In this study, we investigate the poorly characterized source of bulk echoes in metal melts and the corresponding mechanisms of ultrasound signal deterioration. We present evidence from electron microscopy and ultrasound measurements that oxide inclusions are the main source of bulk echoes in gallium. By measuring their terminal velocity, we estimate the mean size of echoing objects in gallium to be 58–64 μm, implying that Mie scattering is the dominant scattering mechanism. By comparing UDV measurements in which signals were transmitted directly into the fluid, to others in which signals were transmitted through a vessel wall, we show evidence that there are two distinct mechanisms for signal degradation: the loss of echoing objects from the bulk and the deterioration of acoustic coupling and wetting at the transducer surface. We suggest stirring vigorously and using indirect-contact UDV measurement strategy to mitigate the signal degradation in metal melts.     

Utilization of I–Q signals of ultrasound Doppler velocimeter to obtain 1-D turbulence quantities in pipe flow

A new method based on using inphase–quadrature (I–Q) ultrasound (US) signals was developed in order to overcome time resolution limitations encountered in turbulent flow measurements by ultrasound Doppler velocimetry (UDV). First, mathematical relations to be used in obtaining probability density function (PDF) and auto correlation function (ACF) of randomly fluctuating velocity (u) in the probe direction were derived in the form of the experimental I–Q signals. The results were evaluated with respect to those obtained by UDV or other conventional techniques whenever possible. In terms of general trend, velocity PDFs obtained from analytical relation along with the I–Q signals and from UDV compare well with each other for Reynolds numbers (N_Re) of 16730 and 26300 at the pipe center. Smaller standard deviation of velocity PDF from spectrum of I–Q US signals than that of UDV measurements was the only major difference that could be attributed to the enhanced time resolution of the former technique. Effect of increased time resolution was also observed in the measurement of velocity auto correlation coefficients (ACC). Time correlations of the velocity fluctuations could be captured by using I–Q signals as opposed to UDV that resulted in correlations going to zero in one or two time steps.ACC from I–Q signals was used to get turbulence spectrum at the pipe center. In addition Reynolds number and radial position dependency of integral and Taylor microlength scales, Kolmogorov length scale, rate of energy dissipation and eddy diffusion coefficient were also established.     

Estimation of femoral neck bone mineral density by ultrasound scanning: Preliminary results and feasibility

Aim of this paper was to assess the diagnostic accuracy of a novel ultrasound (US) approach for femoral neck densitometry. A total of 173 female patients (56–75 years) were recruited and all of them underwent a dual X-ray absorptiometry (DXA) of the proximal femur and an US scan of the same anatomical district. Acquired US data were analysed through a novel algorithm that performed a series of spectral and statistical analyses in order to calculate bone mineral density employing an innovative method. Diagnostic accuracy of US investigations was quantitatively assessed through a direct comparison with DXA results. The average diagnostic agreement resulted pretty good (85.55%), with a maximum (88.00%) in correspondence of the youngest investigated patients (56–60 y). Overall, diagnostic accuracy showed only minimal variations with patient age, indicating that the proposed approach has the potential to be effectively employable for osteoporosis diagnosis in the whole considered age interval.     

Ultrasonic investigation of blood flow.

Ultrasound and the Doppler effect are used to measure blood velocity non-invasively in order to diagnose blood vessel disease. Intrusive lesions on arterial walls give rise to an alteration of the time-varying blood velocity waveform and local blood flow disturbance which are detected and measured using the envelope and width of the Doppler signal spectrogram respectively. Flow may also be imaged in colour superimposed on a grey-scale anatomical image allowing vessel narrowing and the accompanying flow disturbance to be visualized. Developments in three-dimensional imaging, angle tolerant velocity measurements and increased sensitivity using second harmonic backscatter from encapsulated-bubble contrast media ensure increasing use of this modality.     

Doppler ultrasound-based measurement of tendon velocity and displacement for application toward detecting user-intended motion

The motivation of this research is to non-invasively monitor the wrist tendon's displacement and velocity, for purposes of controlling a prosthetic device. This feasibility study aims to determine if the proposed technique using Doppler ultrasound is able to accurately estimate the tendon's instantaneous velocity and displacement. This study is conducted with a tendon mimicking experiment consisting of two different materials: a commercial ultrasound scanner, and a reference linear motion stage set-up. Audio-based output signals are acquired from the ultrasound scanner, and are processed with our proposed Fourier technique to obtain the tendon's velocity and displacement estimates. We then compare our estimates to an external reference system, and also to the ultrasound scanner's own estimates based on its proprietary software. The proposed tendon motion estimation method has been shown to be repeatable, effective and accurate in comparison to the external reference system, and is generally more accurate than the scanner's own estimates. After establishing this feasibility study, future testing will include cadaver-based studies to test the technique on the human arm tendon anatomy, and later on live human test subjects in order to further refine the proposed method for the novel purpose of detecting user-intended tendon motion for controlling wearable prosthetic devices.     

Flow resistance due to shrubs and woody vegetation

In this paper, a theoretical open channel flow resistance equation was verified using flow depth and discharge measurements carried out by Freeman et al. in a large channel, 2.44 m wide, for ten different types of uniform-sized plants (shrubs and woody vegetation). The plants, which are broadleaf deciduous vegetation commonly found in floodplains and riparian zones, were placed in staggered rows inside the channel whose bed was constructed to accept plants with their root systems. For each species, the available measurements were carried out by Freeman et al. with plants having different values of plant density, height, and bending stiffness. The available literature database (87 measurements) was divided into two groups which were separately used to calibrate and test the theoretical approach. In particular, 46 measurements were used to calibrate the relationship between the scale factor Γ of the velocity profile, the Froude number, and the channel slope. This relationship was calibrated using the entire available dataset or varying the scaling coefficient a with the investigated vegetation type. The measured values of the Darcy-Weisbach friction factor, obtained by the measured flow velocity, water depth and slope values, were compared with those calculated by the theoretical flow resistance law, coupled with the relationship for estimating the Γ function having a scaling coefficient different for each investigated vegetation type. This comparison allowed to demonstrate that an accurate estimate of the Darcy-Weisbach friction factor (errors less than or equal to ±10% for 87% of the investigated cases) can be obtained. However, for the investigated vegetation species, that are characterized by a large range of bending stiffness, also a mean value of the scaling coefficient a equal to 0.3283 allows an accurate estimate of the Darcy-Weisbach friction factor.     

Systemically alendronate was incorporated into dental tissues but did not cause morphological or mechanical changes in rats teeth

This study evaluated the effect of the systemic use of sodium alendronate in rats in vivo. Forty‐five Wistar rats aged 36 to 42 days and weighing 200 to 230 g were randomly assigned to a control group (n = 20), which received distilled water, and an experimental group (n = 25), which received 2 weekly doses of 1 mg/kg of chemically pure sodium alendronate. The animals were killed after 60 days of treatment. The tibias were removed for analysis of bone mineral density by dual‐energy X‐ray absorptiometry (DXA). Then, the maxillary incisors were extracted for analysis of the mineralized dental tissues using fluorescence spectroscopy (FS), scanning electron microscopy (SEM), bright field microscopy (BFM), and cross‐sectional microhardness (CSMH) testing. DXA and CSMH data were subjected to statistical analysis by Kruskal‐Wallis test (5% significance level). The experimental group presented higher bone mineral density than the control group by DXA. FS analysis revealed presence of alendronate in the mineralized dental tissues of the specimens of the experimental group. Significant morphological differences were not found by SEM and BFM. Enamel and dentin (100 and 300 μm from the dentinoenamel junction) CSMH data did not show significant difference between the control and experimental groups. Based on the obtained results, we conclude that while alendronate increased the bone mineral density and was incorporated into the mineralized dental tissues it did not cause significant alterations in the morphology and microhardness of rat incisor enamel and dentin. Microsc. Res. Tech. 75:1265–1271, 2012. © 2012 Wiley Periodicals, Inc.     

A Facility for Investigating Ultrasound Velocity and Absorption in Light and Heavy Water at High Temperatures and High Pressures

An experimental facility was designed to study the velocity and absorption factor of ultrasound in light and heavy water at high temperatures (up to 550°C) and high pressures (as great as 550 atm.) using the continuous variable-baseline interferometer method. The facility is composed of an autoclave, a liquid nitric thermostat, systems for temperature and pressure measurements and control, mechanical and electrical systems of the acoustical interferometer, and a deaeration and filling unit. Due to the design features of the facility and the measuring technique, which ensure a low temperature gradient and a small ballast volume, the velocity and absorption factor of ultrasound can be simultaneously measured with a high degree of accuracy (0.05–0.09% and 7–10%, respectively), and their frequency dependences can be obtained in the range 0.5–10.0 MHz even in the critical region.__________Translated from Pribory i Tekhnika Eksperimenta, No. 4, 2005, pp. 127–133.Original Russian Text Copyright © 2005 by Erokhin, Kompaniets.     

A review of the measurement of blood velocity and related quantities using Doppler ultrasound

Ultrasound systems can be used to investigate blood flow by use of the Doppler effect. The flow information may be displayed as either a real-time sonogram or a two-dimensional colour image. Estimates of maximum velocity using commercial systems are in error by typically 10-100 per cent; this is associated with the inability of the single-beam Doppler method to measure the true direction of flow, and with geometric spectral broadening. Vector Doppler systems acquire Doppler information along two beam directions and are able to measure accurately the velocity and direction of motion within the scan plane. The small beam width of modern Doppler systems means that the condition of uniform insonation, required for estimation of mean velocity from mean frequency shift, is not valid except for the very smallest vessels. Other quantities related to the velocity may also be estimated, such as the volumetric flow and wall shear stress. Flow visualization using colour flow imaging suffers from dependence of the displayed colour on the direction of blood motion. The vector Doppler technique may be extended to colour flow to give improved visualization of flow, in which there is no angle dependence within the scan plane.     

Effects of sample size and concentration of seeding in LDA measurements on the velocity bias in open channel flow

A Laser Doppler Anemometer was used to measure the mean flow and turbulence in fluid experiments despite it having a problem with the mean velocity bias when a LDA is used to measure turbulent flows. It is generally considered that given a sufficiently large sample size, LDA will produce measurements free of bias, even with high turbulence intensity, but there is no relative experimental validation to demonstrate how the sample size affects the mean velocity bias. This paper first tries to find the reasonable sample size that ensures a mean velocity calculation free of bias. Furthermore, the effects of particle seeding concentration on the measurements of velocity were also considered. Throughout the experimental process the particle velocities were measured using a Dantec 2-D LDA system. To describe the effects of sample size and particle seeding concentration, this paper will also address the reasonable sample size and range of concentration in the design of water flow prior to any experimental application.     

Improved reliability analysis method based on the failure assessment diagram

With the uncertainties related to operating conditions,in-service non-destructive testing(NDT) measurements and material properties considered in the structural integrity assessment,probabilistic analysis based on the failure assessment diagram(FAD) approach has recently become an important concern.However,the point density revealing the probabilistic distribution characteristics of the assessment points is usually ignored.To obtain more detailed and direct knowledge from the reliability analysis,an improved probabilistic fracture mechanics(PFM) assessment method is proposed.By integrating 2D kernel density estimation(KDE) technology into the traditional probabilistic assessment,the probabilistic density of the randomly distributed assessment points is visualized in the assessment diagram.Moreover,a modified interval sensitivity analysis is implemented and compared with probabilistic sensitivity analysis.The improved reliability analysis method is applied to the assessment of a high pressure pipe containing an axial internal semi-elliptical surface crack.The results indicate that these two methods can give consistent sensitivities of input parameters,but the interval sensitivity analysis is computationally more efficient.Meanwhile,the point density distribution and its contour are plotted in the FAD,thereby better revealing the characteristics of PFM assessment.This study provides a powerful tool for the reliability analysis of critical structures.     

Viscoelastic responses of flow driven by a permeable disk investigated by ultrasound velocity profiling

Ultrasound velocity profiling was applied to viscoelastic flow induced around a moving permeable disk. There were two objectives to this measurement. The first was to find technical advantages and restrictions when applying ultrasonic Doppler velocimetry to a viscoelastic liquid. This issue has not been clarified even though ultrasonic pulses may interact with an elastic medium in the monitoring of the Doppler shift frequency. The second objective was to determine the fluid physics of a viscoelastic liquid around a permeable object, which will help in designing mixing process for materials subject to strong rheological resistance. In this paper, we report a representative response of a viscoelastic liquid in terms of its spatiotemporal velocity distribution. The response highlighted is cyclic lateral waves that form behind the disk, which were hardly detectable by particle image velocimetry. We discuss multiple reasons for this phenomenon considering not only fluid properties but also the measurement principle of ultrasound velocity profiling as applied to viscoelastic liquid.     

Comparison of Particle Image Velocimetry and Laser Doppler Anemometry measurement methods applied to the oil–water flow in horizontal pipe

In this work, a comparison of Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) measurement methods was made applied to oil–water two-phase flow in a horizontal pipe. The experiments were conducted in a 15 m long, 56 mm diameter stainless steel pipe using Exxsol D60 oil (density 790 kg/m³ and viscosity 1.64 mPa s) and water (density 996 kg/m³ and viscosity 1.0 mPa s) as test fluids. The experiments were performed at different mixture velocities and water cuts. Mixture velocity and water cut vary up to 1.06 m/s and 0.75, respectively. The instantaneous local velocities were measured using PIV and LDA, and based on the instantaneous local velocities mean velocities and turbulence profiles are estimated. The measurements are performed in the vertical plane through the pipe center. A double-pulsed Nd:yttrium aluminium garnet (YAG) laser and a high-speed camera with 1260×1024 px resolution (1.3 Mpx) were used for the PIV measurements. The LDA set-up is a two-colour backscatter system with 3 W Argon-Ion Laser. The time averaged cross-sectional distributions of oil and water phases were measured with a traversable gamma densitometer. The measured mean axial velocity and turbulence profiles using PIV were observed to compare favourably well with LDA measurements. Nevertheless, the PIV measurements are more sensitive for optical disturbances in the dispersed region close to the oil–water interface. Hence, this region cannot be confidently analyzed using PIV, whereas LDA offers full-field measurements even at higher mixture velocities.     

Microdistortions in the crystal lattice of steel IIIX15 as estimated via the optoacoustic method and velocimetry

Crystal-lattice microdistortions in thermally treated steel IIIX15 are estimated via measurement of Rayleigh waves’ propagation velocity by means of the technique based on speckle dynamic interferometry. A special feature of this technique is noncontact determination of the elastic-wave velocity and the possibility of performing short-distance measurements. The dependence of Rayleigh waves’ velocity on the crystal-lattice microdistortions is established relative to changes in heat treatment regimes.