Ultrasonic Backscattered Signals Research Articles

Backscatter measurement of cancellous bone using the ultrasound transit time spectroscopy.

Recently, ultrasound transit time spectroscopy (UTTS) was proposed as a promising method for bone quantitative ultrasound measurement. Studies have showed that UTTS could estimate the bone volume fraction and other trabecular bone structure in ultrasonic through-transmission measurements. The goal of this study was to explore the feasibility of UTTS to be adapted in ultrasonic backscatter measurement and further evaluate the performance of backscattered ultrasound transit time spectrum (BS-UTTS) in the measurement of cancellous bone density and structure. First, taking ultrasonic attenuation into account, the concept of BS-UTTS was verified on ultrasonic backscatter signals simulated from a set of scatterers with different positions and intensities. Then, in vitro backscatter measurements were performed on 26 bovine cancellous bone specimens. After a logarithmic compression of the BS-UTTS, a linear fitting of the log-compressed BS-UTTS versus ultrasonic propagated distance was performed and the slope and intercept of the fitted line for BS-UTTS were determined. The associations between BS-UTTS parameters and cancellous bone features were analyzed using simple linear regression. The results showed that the BS-UTTS could make an accurate deconvolution of the backscatter signal and predict the position and intensity of the simulated scatterers eliminating phase interference, even the simulated backscatter signal was with a relatively low signal-to-noise ratio. With varied positions and intensities of the scatterers, the slope of the fitted line for the log-compressed BS-UTTS versus ultrasonic propagated distance (i.e., slope of BS-UTTS for short) yield a high agreement (r2 = 99.84%-99.96%) with ultrasonic attenuation in simulated backscatter signal. Compared with the high-density cancellous bone, the low-density specimen showed more abundant backscatter impulse response in the BS-UTTS. The slope of BS-UTTS yield a significant correlation with bone mineral density (r = 0.87; p < 0.001), BV/TV (r = 0.87; p < 0.001), and cancellous bone microstructures (r up to 0.87; p < 0.05). The intercept of BS-UTTS was also significantly correlated with bone densities (r = -0.87; p < 0.001) and trabecular structures (|r|=0.43-0.80; p < 0.05). However, the slope of the BS-UTTS underestimated attenuation when measurements were performed experimentally. In addition, a significant non-linear relationship was observed between the measured attenuation and the attenuation estimated by the slope of the BS-UTTS. This study demonstrated that the UTTS method could be adapted to ultrasonic backscatter measurement of cancellous bone. The derived slope and intercept of BS-UTTS could be used in the measurement of bone density and microstructure. The backscattered ultrasound transit time spectroscopy might have potential in the diagnosis of osteoporosis in the clinic.

Ultrasonic scattering model and identification experiment of polycrystalline materials

Ultrasonic identification has an important application value for national defense, military affairs, aerospace, nuclear facilities and other high-tech fields. Ultrasonic waves can be used to identify any metal material. At present, the researches focus on algorithms for identifying the difference in ultrasonic signal among materials, but the study on the corresponding identification theory is lacking. In this work, 10 primary models of the microstructure of 2A12 aluminum alloy are established as analogies to the complex microstructures of polycrystalline metallic materials. The grains of these models are different from each other in size, separation distance, shape, arrangement directions and orders. The time-domain ultrasonic echo signals of different microstructures are calculated by making use of the finite element method. The grass-like signals between two echoes are ultrasonic backscattering signals, which are sensitive to any change of microstructure. The backscattering signals between the primary echo and the secondary echo in the ultrasonic echo time domain signals are extracted as ultrasonic fingerprints. The feature difference &lt;i&gt;Q&lt;/i&gt; is defined to quantify the difference in ultrasonic fingerprint of each sample. The results show that the slight variation in microstructure will lead to difference in ultrasonic signal, and the difference caused by the variation in grain size is more distinct. And then, an ultrasonic identification algorithm is proposed, and the identification experiments are conducted on four 2A12 aluminum alloy samples with the same shape. The identification results show that the target sample can be accurately identified by using ultrasonic fingerprints and the ultrasonic fingerprints of the target sample are distinctly different from those of the other samples. The microstructure morphologies of the samples are examined by using scanning electron microscopy (SEM). The SEM results show that there are significant differences in grain size, separation distance and densification between samples although they are the same material. The features of the microstructure in the proposed ultrasonic scattering model in this work are confirmed by the actual y micromorphologies observed in the SEM images. The identification experiments and SEM results demonstrate that the established ultrasonic scattering model is effective. This work can provide a reference for theoretically studying ultrasonic identification and present an idea for developing some new identification algorithms in future.

The Protocol of Ultrasonic Backscatter Measurements of Musculoskeletal Properties.

This study aims to introduce the protocol for ultrasonic backscatter measurements of musculoskeletal properties based on a novel ultrasonic backscatter bone diagnostic (UBBD) instrument. Dual-energy X-ray absorptiometry (DXA) can be adopted to measure bone mineral density(BMD) in the hip, spine, legs and the whole body. The muscle and fat mass in the legs and the whole body can be also calculated by DXA body composition analysis. Based on the proposed protocol for backscatter measurements by UBBD, ultrasonic backscatter signals can be measured in vivo, deriving three backscatter parameters [apparent integral backscatter (AIB), backscatter signal peak amplitude (BSPA) and the corresponding arrival time (BSPT)]. AIB may provide important diagnostic information about bone properties. BSPA and BSPT may be important indicators of muscle and fat properties. The standardized backscatter measurement protocol of the UBBD instrument may have the potential to evaluate musculoskeletal characteristics, providing help for promoting the application of the backscatter technique in the clinical diagnosis of musculoskeletal disorders (MSDs), such as osteoporosis and muscular atrophy.

Spatial imaging of stratified heterogeneous microstructures: determination of the hardness penetration depth in thermally treated steel parts by laser ultrasound

We introduce an improved non-destructive and non-contact measurement technique for the hardness penetration depth of thermally hardened steel parts based on all-optical laser ultrasound. The hardening of the near-surface region results in a stratified system with layers of different microstructural characteristics caused by changes in grain size. We employ spatially resolved ultrasonic backscattering signals to provide subsurface imaging of the axial and lateral hardness profile. Spatial scans over a range of 30 mm with a lateral step size of 100 μm were obtained within 30 s. We investigated three common steel grades with different microstructural characteristics and hardened layer thicknesses ranging from about 3 to 10 mm. The hardened surface layer and the unhardened core material can be identified. The data evaluation is assisted by a supervised machine learning approach that takes advantage of the spatio-temporal ultrasonic backscattering information. This method also provides an alternative route to define the hardness penetration depth using spatio-temporal scattering characteristics.

Ultrasound Homodyned-K Contrast-Weighted Summation Parametric Imaging Based on H-scan for Detecting Microwave Ablation Zones.

The homodyned-K (HK) distribution is a generalized model of envelope statistics whose parameters α (the clustering parameter) and k (the coherent-to-diffuse signal ratio) can be used to monitor the thermal lesions. In this study, we proposed an ultrasound HK contrast-weighted summation (CWS) parametric imaging algorithm based on the H-scan technique and investigated the optimal window side length (WSL) of the HK parameters estimated by the XU estimator (an estimation method based on the first moment of the intensity and two log-moments, which was used in the proposed algorithm) through phantom simulations. H-scan diversified ultrasonic backscattered signals into low- and high-frequency passbands. After envelope detection and HK parameter estimation for each frequency band, the α and k parametric maps were obtained, respectively. According to the contrast between the target region and background, the (α or k) parametric maps of the dual-frequency band were weighted and summed, and then the CWS images were yielded by pseudo-color imaging. The proposed HK CWS parametric imaging algorithm was used to detect the microwave ablation coagulation zones of porcine liver ex vivo under different powers and treatment durations. The performance of the proposed algorithm was compared with that of the conventional HK parametric imaging and frequency diversity and compounding Nakagami imaging algorithms. For two-dimensional HK parametric imaging, it was found that a WSL equal to 4 pulse lengths of the transducer was sufficient for estimating the α and k parameters in terms of both parameter estimation stability and parametric imaging resolution. The HK CWS parametric imaging provided an improved contrast-to-noise ratio over conventional HK parametric imaging, and the HK αcws parametric imaging achieved the best accuracy and Dice score of coagulation zone detection.

The effect of copper grain size on laser ultrasonic backscattered signal

Grain size has an essential influence on the serviceability of metallic materials. In this paper, a noncontact laser ultrasonic testing platform is built to study the effect of copper grain size on the laser ultrasonic backscattered signal. According to the correlation between grain size and ultrasonic wavelength, the ultrasonic scattering by copper grains in the experiment contains not only Rayleigh scattering but also the transition region from Rayleigh scattering to stochastic scattering. Using time–frequency analysis, the influence of copper grain size on the characteristic parameters of backscattering was explored, and a prediction model of grain size was established, which was compared with the prediction model based on the attenuation method to verify the accuracy of the backscattering model. The results show that the backscattered signal can adequately characterize the grain size information and laser ultrasonics is a method that can realize on-line detection of grain size.

Grain size evaluation with time-frequency ultrasonic backscatter

The ultrasonic backscatter signal can be used to evaluate the grain size of polycrystalline media nondestructively. In this article, the joint time-frequency analysis is introduced into the ultrasonic backscatter model, with the independent scattering approximation. The time-frequency domain model is applied to predict the spatial variance surface (SVS) and fit the experimental results to evaluate the grain size with the approach giving a relative error of 2.26% in comparison with metallography. Moreover, it shows that the present method suppresses electrical noise better than either the time domain or the frequency domain models alone. Based on the global sensitivity analysis of Sobol's method, the sensitivities of transducer parameters and material parameters in the ultrasonic backscatter model are estimated. The sensitivity analysis shows that not all the transducer parameters in the model must be calibrated carefully. In addition, it is found that the grain size sensitivity index of the time-frequency backscatter model is higher than the time domain or the frequency-domain backscatter models. Overall, the backscatter model in the time-frequency domain can evaluate the microstructure more accurately.

Higher-order spatial correlation coefficients of ultrasonic backscattering signals using partial cross-correlation analysis.

The spatial correlation properties of ultrasonic backscattering signals in random media have important implications. For example, they can be used for microstructural characterization and flaw detection in engineering materials. However, the traditional spatial correlation coefficient (SCC) is only a leading order quantity that does not capture the true spatial correlations of random media. This is caused by neglecting confounding variables such as non-zero means or other non-zero odd-order moments. Here, the SCC is generalized from zeroth- to general-order through partial cross-correlation analysis. A series of indicators are defined to quantify the SCC curve at zero time lag, and the maximum time shift curve, which are both functions of lateral separation between two sensor positions. A stainless-steel specimen and a focused ultrasonic transducer are used to verify the method. Scattering measurements show that the higher-order SCC can consistently capture spatial correlations whereas the zeroth-order SCC is inadequate. The zeroth-order SCC is shown to predict a step size that can be more than six times too large. Thus, the present method can provide better understanding of statistical correlations and conditions to measure uncorrelated backscattering signals.

Microwave-Induced Thermal Lesion Detection via Ultrasonic Scatterer Center Frequency Analysis with Autoregressive Cepstrum.

We proposed a new method for microwave-induced thermal lesion detection using the autoregressive spectrum analysis of ultrasonic backscattered signals in this paper. Eighteen cases of microwave ablation experiments and twenty cases of water bath heating experiments were conducted. Ultrasonic radiofrequency data of normal and coagulated porcine liver tissues were collected through these two experiments. Then, autoregressive spectrum analysis was performed; the mean frequency of the dominant peak in the autoregressive spectrum was computed based on water bath experiments; and a method for recognizing normal and solidified tissues was obtained by comparing the difference of the dominant peak in the autoregressive spectrum. Two bandpass finite impulse response filters, whose passbands corresponded respectively to the dominant peak in the autoregressive spectrum of normal and coagulated tissues, were used to compute the power spectral integration for the microwave-induced experiments. Microwave-induced thermal lesions were detected based on the differences between the power spectral integrations from the two filters. Compared to the caliper-measured area, the power spectral integration detected area had an error of (10.25 ± 3.59). Experimental results indicated that the proposed method may be used in preliminary detection of microwave-induced thermal lesions.

Recurrence quantitative analysis for porosity characterization of CFRP with complex void morphology

The porosity characterization of Carbon Fibre Reinforced Plastics (CFRP) by ultrasonic attenuation measurement is restricted when the back-wall echoes are weak or absent at high porosity, and the estimation accuracy is decreased with increment of porosity due to complex void morphology. In this paper, Real Morphology Void Models (RMVMs) with different porosity were established to simulate the interaction between ultrasonic waves and voids with complex morphology. Subsequently, Recurrence Quantification Analysis (RQA) was introduced to process ultrasonic backscattered signals generated by voids so as to present Recurrence Plots (RPs) for porosity characterization. Recurrence Rate (RR) was selected as RQA variable to quantitatively analyze RPs, avoiding the determination of additional parameters. The correlation between porosity P and RR was revealed by simulation for the first time, and verified by experiments with CFRP laminates having porosity of 0.8%–4.2%. The complex and random void morphology induced the non-mapping relationship between P and RR, influencing estimation accuracy of porosity. The normalized results indicated that porosity characterization with RR was less affected by void morphology for P > 1.97% in comparison with ultrasonic attenuation measurement. It is concluded that RQA is valuable for porosity characterization of CFRP with high porosity and strong attenuation.

A method to locate spatial distribution of scattering centers from ultrasonic backscatter signal.

The purpose of this work is to find a method to locate the scattering centers in spatial domain; by using this information, the mean scatter spacing (MSS) can be estimated, and the spatial information is the one-dimensional imaging of scattering centers. This paper presents a method that can locate the scattering centers in spatial domain robustly and automatically. By incorporating it with fast Fourier transformation, the MSS can be estimated. The three foremost processes, matched filtering, envelope extraction, and peak reconstruction, are incorporated in the authors' algorithm. Monte Carlo simulations demonstrate that the proposed method is a robust one to locate scattering centers in spatial domain, and has a better performance than spectrum-based MSS estimation techniques. Especially exploited in estimating MSS which varies from 0.6 to 1.2 mm in the range of human mean trabecular bone spacing, the proposed method shows great potential in medical use. Simple but widely used phantom experiments demonstrate that the proposed algorithm has the capacity to locate scattering centers in spatial domain.

Identification of Localized Void Defects in Composite by Recurrence Quantification Analysis of Ultrasonic Backscattered Signal

Voids usually have a detrimental effect on the performance of carbon fiber reinforced polymer (CFRP). This paper presents a nonlinear dynamic method, known as recurrence quantification analysis (RQA), for the identification of localized void defects. First, five standard CFRP specimens with known porosity ranging from 0.2 to 5.94% are tested using ultrasonic pulse-echo technique, and the obtained backscattered signals are subsequently analyzed by RQA. The result shows that two RQA characteristic parameters, the recurrence rate and the Shannon entropy, both clearly increase with increasing porosity. Next, the RQA is performed on another CFRP specimen with unknown porosity. Two regions in this specimen containing localized void defects are detected based on the above finding. This result is finally verified by a destructive experiment. The research demonstrates that RQA is an effective new method for the identification of localized void defects in CFRP.

Flaw detection with ultrasonic backscatter signal envelopes.

Ultrasound is a prominent nondestructive testing modality for the detection, localization, and sizing of defects in engineering materials. Often, inspectors analyze ultrasonic waveforms to determine if echoes, which stem from the scattering of ultrasound from a defect, exceed a threshold value. In turn, the initial selection of the threshold value is critical. In this letter, a time-dependent threshold or upper bound for the signal envelope is developed based on the statistics governing the scattering of ultrasound from microstructure. The utility of the time-dependent threshold is demonstrated using experiments conducted on sub-wavelength artificial defects. The results are shown to enhance current nondestructive inspection practices.

Measurement and compensation of frequency-dependent attenuation in ultrasonic backscatter signal from cancellous bone

Ultrasonic backscatter has been gradually applied to the assessment and diagnosis of bone disease. The heavy frequency-dependent attenuation of ultrasound results in weak ultrasonic signals with poor signal-to-noise ratio and serious wave distortions during propagation in cancellous bone. Ultrasonic attenuation measured with the through-transmission method is an averaged result of ultrasonically interrogated tissues (including the soft tissue, cortical bone and cancellous bone). Therefore, the through-transmission measurements can not accurately provide ultrasonic attenuation of cancellous bone of interest. The purpose of this study is to estimate ultrasonic frequency-dependent attenuation with ultrasonic backscatter measurements and to compensate for the frequency-dependent attenuation in an ultrasonic backscatter signal from cancellous bone. &lt;i&gt;In-vitro&lt;/i&gt; ultrasonic backscatter and through-transmission measurements are performed on 16 cancellous bone specimens by using 1.0-MHz transducers. Spatial scans are performed in a 10 mm × 10 mm scanned region with a spatial interval of 0.5 mm for each bone specimen. The frequency slope of ultrasonic attenuation is measured with the ultrasonic through-transmission signals serving as a standard value. Four different algorithms (the spectral shift method, the spectral difference method, the spectral log difference method, and the hybrid method) are used to estimate the frequency slope of ultrasonic attenuation coefficient from ultrasonic backscatter signal. The results show that the frequency-dependent attenuation coefficient ranges from 2.3 dB/mm/MHz to 6.2 dB/mm/MHz for the bovine bone specimens. The through-transmission measured frequency slope of ultrasonic attenuation coefficient is (4.14 ± 1.14) dB/mm/MHz (mean ± standard deviation), and frequency slopes of ultrasonic attenuation coefficient are estimated by four backscattering methods to be (3.88 ± 1.15) dB/mm/MHz, (4.00 ± 0.98) dB/mm/MHz, (3.77 ± 0.84) dB/mm/MHz, and (4.05 ± 0.85) dB/mm/MHz, respectively. The estimated frequency-dependent attenuation is significantly correlated with the standard attenuation value (&lt;i&gt;R&lt;/i&gt; = 0.78－0.92, &lt;i&gt;p&lt;/i&gt; &lt; 0.01), in which the spectral difference method (&lt;i&gt;R&lt;/i&gt; = 0.91, &lt;i&gt;p&lt;/i&gt; &lt; 0.01) and the hybrid method (&lt;i&gt;R&lt;/i&gt; = 0.92, &lt;i&gt;p&lt;/i&gt; &lt; 0.01) are more accurate with an estimated error less than 20%. The results prove that it is feasible to measure the frequency-dependent attenuation from ultrasonic backscatter signal of cancellous bone. Based on Fourier transform-inverse Fourier transform, the frequency-dependent attenuation can be compensated.The compensated ultrasonic signals are with significantly improved signal intensity and improved signal-to-noise ratio. This study is conducive to the subsequent ultrasonic backscatter measurement and ultrasonic imaging of cancellous bone.

Ultrasonic backscatter measurements at the calcaneus: An in vivo study

Osteoporosis is a systemic skeleton disease that has already been a major public health issue. As a traditional clinical method, dual-energy X-ray absorptiometry (DXA) measures the bone mineral density (BMD) to evaluate the bone status. However, the X-ray based method has the disadvantages of ionizing radiation and high cost. Quantitative ultrasound has played a role in the bone diagnostics with the advantages of non-ionizing radiation, portability, low cost and ease of use. This paper presents an in vivo approach of measuring the calcaneus using ultrasonic backscatter method, a total of 523 subjects were involved. The ultrasonic backscattered signals were acquired using a custom designed ultrasonic backscatter bone diagnostic (UBBD) instrument with a 5.0 MHz transducer. The time slope of apparent backscatter (TSAB) parameter was calculated and compared with the BMD measured from DXA. The TSAB and BMD showed a negative correlation (R = −0.65 ∼ −0.52, p < 0.05). Discrimination analysis was performed using receiver operating characteristic (ROC) curves to discriminate people who have been diagnosed with osteoporosis from people without osteoporosis using DXA. The area under the curve (AUC) for ultrasound backscatter parameter TSAB was 0.8 with p < 0.05. By means of the ROC analysis, the optimum thresholds of TSAB were determined to be −0.81 dB/µs. The sensitivity and specificity of TSAB for the optimum threshold were 77% and 74%, respectively. The Youden index and accuracy was 51% and 75% for the TSAB at 5.0 MHz, respectively. These results indicate that ultrasonic backscatter is promising in the in vivo bone characterization.

Correlation of ultrasonic backscatter difference parameters with bone density in clinical ultrasound images

The ultrasonic backscatter difference technique analyzes the power difference (in dB) between two gated regions of a backscatter signal and is being used to detect changes in bone caused by osteoporosis. The current study investigates correlations with bone density for these parameters determined from clinical ultrasound data. Ultrasonic backscatter images and signals were acquired from the hip and two vertebral bodies of human subjects using a 2.5 MHz phased-array transducer. Three backscatter parameters- normalized mean, slope, and intercept of the backscatter difference- were determined from the power difference between two gated regions of the signal. All three parameters were analyzed for 25 different gate choices. X-ray bone mineral density data for each subject were acquired for the three anatomical regions. Significant linear correlations (p<0.05) were found for all three ultrasonic parameters for at least one choice of gate parameters. R values ranged from to 0.38 to 0.63. For the first time, bac...

Time domain analysis of ultrasonic backscatter signals from cancellous bone

Ultrasonic backscatter techniques are being developed to detect changes in bone caused by osteoporosis. Most techniques analyze backscatter signals in the frequency domain by measuring quantities related to the power spectrum. Investigate the utility of two backscatter parameters determined from a time domain analysis of backscatter signals: the normalized backscatter amplitude ratio (nBAR) and the backscatter amplitude decay constant (BADC). A 3.5 MHz transducer was used to acquire backscatter signals from 54 specimens of bone prepared from 14 human femurs. nBAR was determined from the log of the ratio of the root mean square amplitude of two different portions of a backscatter signal. BADC was determined by measuring the exponential decay in the amplitude of a backscatter signal. nBAR and BADC both demonstrated highly significant (p < 0.001) linear correlations with bone density. However, the correlation coefficients were slightly stronger for nBAR (0.79 ≤ R ≤ 0.89) than for BADC (0.67 ≤ R ≤ 0.73). Parameters based on a time domain analysis of backscatter signals from bone may be sensitive to changes in bone caused by osteoporosis. Of the two parameters tested, nBAR demonstrated the strongest correlations with bone density. [Funding: NIH/NIAMS R15AR066900.]

Ultrasonic backscatter difference measurements of cancellous bone: Relationships with microstructure and bone mineral density

Background: Backscatter difference techniques are being developed to detect changes in bone caused by osteoporosis. Backscatter difference techniques compare the power in one portion of an ultrasonic backscatter signal to the power in a different portion of the same signal. Goal: Investigate how backscatter difference measurements depend on the density and microstructural characteristics of cancellous bone. Procedure: Ultrasonic backscatter signals were acquired from 30 specimens of bone using a 1 and 5 MHz broadband transducer. The normalized mean backscatter difference (nMBD) was determined by computing the power difference (in dB) between two gated portions of the backscatter signal and dividing by the center to center time separation between gates. Microstructural characteristics of the specimens and bone mineral density (BMD) were determined using high resolution x-ray micro-computed tomography. Results: nMBD demonstrated moderate to strong linear correlations with microstructure and BMD (0.50 ≤ |R| ...

Feasibility analysis of low-intensity pulsed ultrasound treatment for osteoporosis

Osteoporosis is a musculoskeletal disease which is mainly characterized by bone loss and deterioration of bone microstructure, to which the middle-aged and elderly people are susceptible. It is often accompanied with bone pain, humpback, fractures and other symptoms, seriously affecting the quality of life of patients. As the population ages, osteoporosis incidence is increasing year by year, and currently these are approximately 200 million patients suffered from osteoporosis in the whole world. Furthermore, osteoporotic fracture has also caused great economic burden to families and society. On the other hand, in the weightless space environment, osteoporosis induced by unloading bones has become one of the important problems of astronauts’ health, leading to impair their space exploration ability enhancement. Hence it is of great significance to its early diagnosis and timely treatment. Ultrasound as a therapeutic method has the advantage of low cost, non-invasive, non-ionizing radiation, fast and can be carried, and the findings in recent years show that ultrasonic backscatter signals can effectively reflect the micro-structure information of cancellous bone, therefore the evaluation of cancellous bone and diagnosis of osteoporosis with ultrasonic backscatter signal has become a focus. And clinical evaluation of bone has made significant progress in adults and newborns. Currently, the main treatment of osteoporosis is drug therapy (common used drugs are bisphosphonates, calcium, vitamin D, calcitonin, estrogen). Drug therapy typically has systemic effects along with side effects, however. Physical therapy such as ultrasound, magnetic therapy and hyperthermia is able to avoid the adverse effect of drug therapy. Low-intensity pulsed ultrasound (LIPUS) has been proved to be an effective mechanical signal to bone tissue and it is used to the treatment of orthopedic diseases, which can play its mechanical effect and avoid the damage of thermal effect to the tissue cells. Study in recent years has demonstrated that LIPUS with certain parameters plays a positive role in the progress of fracture healing, it can promote cell proliferation and differentiation, accelerate calcium mineralization and regulate gene expression and cell growth factors associated with bone tissue cells release, so as to accelerate the progress of bone formation and effectively shorten the healing time. Osteoporosis is a kind of bone disease with main feature of bone mass loss and it is reasonable to consider that the treatment of osteoporosis has the similar physiological mechanism as fracture healing, thus it may be an important potential means of osteoporosis treatment. By referring to numerous documentations related to “LIPUS”, “fracture”, “osteoporosis”, this article begins from the bone structure and function, biological mechanisms of LIPUS treatment for orthopedic diseases and experimental methods of LIPUS treatment for osteoporosis to analyze and demonstrate the effective basis for LIPUS treatment of osteoporosis and review the current study situation of LIPUS treatment for osteoporosis, so as to provide theoretical evidences and new ideas for treatment of osteoporosis.

Dependence of diffuse ultrasonic backscatter on residual stress in 1080 steel

In this article, the effects of residual stress on the ultrasonic scattering in a quenched steel sample are investigated by calculating the change of spatial variance amplitudes of ultrasonic signals after removing residual stress via annealing. The experimental results show that the average spatial variance amplitude decreases by about 11.89% for a scan area on the quenched surface after removing residual stress. This quantity was used to estimate the residual stress based on the developed stress-dependent backscatter model. In addition, the residual stress on the whole scan area was mapped by calculating the change of the spatial variance amplitude for each subarea after annealing, respectively. Diffuse ultrasonic backscatter signals show a high sensitivity to residual stress such that this technique has potential as a non-destructive method for measuring residual stress.