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This study aims to investigate the feasibility of quantitative ultrasonic backscatter in evaluating human cortical and trabecular bone densities in vivo based on a head-down-tilt bed rest study, with 36 participants tested through 90 d of bed rest and 180 d of recovery. Backscatter measurements were performed using an ultrasonic backscatter bone diagnostic instrument. Backscatter parameters were calculated with a dynamic signal-of-interest method, which was proposed to ensure the same ultrasonic interrogated volume in cortical and trabecular bones. The backscatter parameters exhibited significant correlations with site-matched bone densities provided by high-resolution peripheral quantitative computed tomography (0.33|R|0.72, p0.05). Some bone densities and backscatter parameters exhibited significant changes after the 90-d bed rest. The proposed method can be used to characterize bone densities, and the portable ultrasonic backscatter bone diagnostic device might be used to non-invasively reveal mean bone loss (across a group of people) after long-term bed rest and microgravity conditions of spaceflight missions.

Relationships of the backscatter coefficient (BC), the apparent integrated backscatter (AIB), and the integrated reflection coefficient (IRC) with the bone mineral density (BMD) and the microarchitectural parameters were investigated in 28 bovine femoral trabecular bone samples. The BC was highly correlated with the BMD and the microarchitectural parameters (R = -0.66 to 0.71). In contrast, the AIB and the IRC exhibited high correlations with the BMD and the bone volume fraction (R = -0.68 to 0.77) and relatively lower correlations with the remaining microarchitectural parameters (R = -0.62 to 0.60). The multiple regression models yielded the adjusted squared correlation coefficients of 0.54-0.76.

BACKGROUND/AIM: Radiotherapy (RT) related myocardial changes were analyzed by deformation imaging echocardiography in this study. PATIENTS AND METHODS: Ninety-nine breast cancer patients were studied at baseline, after chemotherapy, after RT, and three years after RT (3Y). Eighty patients received RT only, and twenty patients had right-sided breast cancer. Echocardiography included cyclic variation of the integrated backscatter in the septum (sCV) and posterior wall (pCV), global longitudinal strain (GLS), and left ventricular ejection fraction (LVEF). RESULTS: In patients with left-sided breast cancer, sCV declined from 11.3±3.3 dB at baseline to 10.3±2.9 dB after RT (p=0.001). No changes were observed after chemotherapy (p=0.211) or in patients with right-sided breast cancer after RT (p=0.977). No other parameters declined after RT. The decline in sCV was independently associated with the left anterior descending coronary artery radiation dose (β=-0.290, p=0.020). CONCLUSION: In contrast to other parameters, sCV correlated with heart radiation dose. publishedVersion

Most ultrasonic backscatter method excites a short single-pulse and then analyses the bone's response for diagnosing osteoporosis. However, the bone responses to the ultrasound excitation have not been fully understood, such as the response to amplitude modulation (AM) excitation, which may contain more information about bone characteristics for diagnosing. The objectives of this study were to observe the response that the cancellous bones to the AM excitation, and then to investigate extracting AM backscatter parameter for estimating bone mineral density (BMD) and structure. An innovative instrument was developed and realized both AM excitation and real-time calculation parameter AIB AM . The results showed that AIB AM has strong and stable correlations with BMD and structure model index (SMI) ( $\vert \mathrm{R}\vert =0.82-0.91, \mathrm{p} ). These results indicate that AM ultrasonic backscatter method combined with the portable device might have the potential for screening and diagnosing osteoporosis.

The ultrasonic backscatter coefficient and the exponent n (frequency dependence of the backscatter coefficient) were measured in 24 bovine femoral trabecular bone samples. The binary mixture model for ultrasonic scattering from trabecular bone was applied to predict the variations of the ultrasound parameters with the bone volume fraction (BV/TV) and the trabecular thickness (Tb.Th) in trabecular bone. The backscatter coefficient exhibited significant, positive correlations with the BV/TV (R = 0.82) and the Tb.Th (R = 0.79). In contrast, the exponent n was found to be significantly, negatively correlated with the BV/TV (R = -0.77) and the Tb.Th, (R = -0.71).

Metabolic bone disease (MBD) impacts the prognosis of premature infants. There is an urgent need for a portable, noninvasive, and radiation-free method for assessing neonatal bone status. The objective of this study is to evaluate the feasibility of the ultrasonic backscatter technique for assessing and monitoring cancellous bone status in neonates. Ultrasonic backscatter measurements were performed on 766 infants at birth and followed up weekly during hospitalization, utilizing transducers with central frequencies of 3.5 MHz and 5.0 MHz. Backscatter parameters, including apparent integrated backscatter (AIB), frequency intercept of apparent backscatter (FIAB), and frequency slope of apparent backscatter (FSAB) were calculated. Correlations were analyzed with both anthropometric and biochemical indices. We found that AIB ( $\vert r\vert = 0.40-0.47$ , $p ), FIAB ( $\vert r\vert = 0.36-0.45$ , $p ), and FSAB ( $\vert r\vert = 0.10-0.25$ , $p ) were significantly correlated with gestational age, weight, length, and head circumference at birth at both the 3.5 MHz and 5.0 MHz frequencies. Backscatter parameters showed regular changes at different postnatal age and correlations with anthropometric indices persisted during the first month of life. Significant differences were also found in subgroup analyses based on gestational age, birth weight, gender, multiple births, and intrauterine growth. AIB and FIAB were shown to be more effective than FSAB. This study suggests the ultrasonic backscatter technique is feasible for neonatal cancellous bone status evaluation at birth and for dynamic monitoring.

Objective: the purpose of this paper was to investigate the effect of spectral computation methods on the estimation of the four ultrasonic backscatter parameters, namely, the apparent integrated backscatter (AIB), the zero frequency intercept of apparent backscatter (FIAB), the frequency slope of apparent backscatter (FSAB), and the backscatter spectral centroid shift (SCS) from the backscattered signal of interest (SOI), and their subsequent correlations with cancellous bone parameter [bone volume/total volume (BV/TV)]. Methods: ultrasonic backscatter measurements were performed on 26 bovine cancellous bone specimens using a 1.0-MHz focused transducer. Four spectral estimation algorithms, including the classical periodogram, the autoregressive (AR) Burg algorithm, the AR covariance algorithm, and the AR modified covariance algorithm, were used to calculate the ultrasonic parameters. Influence of the signal's delay time (T1) and its length (T2) on the strength of correlation between BV/TV and backscatter parameters was also studied. Results: the results have demonstrated that the AR-based estimators provide much more reliable and stronger correlations between the BV/TV and backscatter parameters than the classical periodogram. Recommendations for choosing SOI were also suggested. Conclusion: these results indicate that the AR-based method has a promising potential to enhance the performance of evaluation and diagnosis of the cancellous bone using the ultrasonic backscatter method. Significance: the enhancement of the correlation may provide a positive impact on the ultrasonic backscatter method to diagnose and monitor the bone quantity.

Ultrasonic backscatter techniques are being developed to detect changes in cancellous bone caused by osteoporosis. One technique, called the backscatter difference technique, measures the power difference between two portions of a backscatter signal. The goal of the present study is to investigate how bone mineral density (BMD) and the microstructure of human cancellous bone influence four backscatter difference parameters: the normalized mean of the backscatter difference (nMBD) spectrum, the normalized slope of the backscatter difference spectrum, the normalized intercept of the backscatter difference spectrum, and the normalized backscatter amplitude ratio (nBAR). Ultrasonic measurements were performed with a 3.5 MHz broadband transducer on 54 specimens of human cancellous bone from the proximal femur. Volumetric BMD and the microstructural characteristics of the specimens were measured using x-ray micro-computed tomography. Of the four ultrasonic parameters studied, nMBD and nBAR demonstrated the strongest univariate correlations with density and microstructure. Multivariate analyses indicated that nMBD and nBAR depended on trabecular separation and possibly other microstructural characteristics of the specimens independently of BMD. These findings suggest that nMBD and nBAR may be sensitive to changes in the density and microstructure of bone caused by osteoporosis.

Surface texture is an important parameter which affects functions and performance of industrial components. Although stylus and optical techniques are commonly used for evaluating the surface topology, they are applicable only to accessible surfaces. In practice, the geometrical features measurement of inaccessible surfaces from back side is sometimes demanded, for example, in inspection of safety-critical parts such as inner surfaces of pipes. For evaluating such internal surfaces, ultrasonic technique is one of the most effective among others. However, little attention has been paid to the evaluation of inaccessible periodic surfaces so far. In this paper, an ultrasonic pulse-echo technique, namely, master curve technique is developed for evaluating the pitch and the height of periodic triangular surfaces which is inaccessible or hidden on the back side. It is found that 60° of incident angle is appropriate for the development of the master curve equation to compromise between the resolution of measurement and the measurable range of the height-to-pitch ratio. By using P-wave at 60° of incidence angle, the pitch of the surface profile is evaluated from the classical diffraction grating equation, and then the height is evaluated by the master curve equation built from numerical simulation. The validity of the proposed method was verified by both numerical simulation and experiment. It was confirmed that the pitch is accurately measured in most cases. The height was also evaluated with good accuracy when it is smaller than a half of the pitch.

Metabolic bone disease (MBD) is one of the major complications of prematurity. Ultrasonic backscatter technique has the potential to be a portable and noninvasive method for early diagnosis of MBD. This study firstly applied CAS to neonates, which was defined as a linear combination of the apparent integrated backscatter coefficient (AIB) and spectral centroid shift (SCS). The objective was to evaluate the feasibility of ultrasonic backscatter technique for assessing neonatal bone health using AIB, SCS, and CAS. Ultrasonic backscatter measurements at 3.5 MHz, 5.0 MHz, and 7.5 MHz were performed on a total of 505 newborns within 48 hours after birth. The values of backscatter parameters were calculated and compared among gestational age groups. Correlations between backscatter parameters, gestational age, anthropometric indices, and biochemical markers were analyzed. The optimal predicting models for CAS were determined. The results showed term infants had lower SCS and higher AIB and CAS than preterm infants. Gestational age and anthropometric indices were negatively correlated with SCS (|r| = 0.45 – 0.57, P r| = 0.36 – 0.60, P r| = 0.56 – 0.69, P P P P = 0.002), and serum calcium (P = 0.037) explained up to 40.3% of CAS variation. This study suggested ultrasonic backscatter technique was feasible to evaluate neonatal bone status. CAS was a promising parameter to provide more information about bone health than AIB or SCS alone.

The ultrasonic backscatter technique holds the promise of characterizing bone density and microstructure. This paper conducts ultrasonic backscatter parametric imaging based on measurements of apparent integrated backscatter (AIB), spectral centroid shift (SCS), frequency slope of apparent backscatter (FSAB), and frequency intercept of apparent backscatter (FIAB) for representing trabecular bone mass and microstructure. We scanned 33 bovine trabecular bone samples using a 7.5 MHz focused transducer in a 20 mm × 20 mm region of interest (ROI) with a step interval of 0.05 mm. Images based on the ultrasonic backscatter parameters (i.e., AIB, SCS, FSAB, and FIAB) were constructed to compare with photographic images of the specimens as well as two-dimensional (2D) μ-CT images from approximately the same depth and location of the specimen. Similar structures and trabecular alignments can be observed among these images. Statistical analyses demonstrated that the means and standard deviations of the ultrasonic backscatter parameters exhibited significant correlations with bone density (|R| = 0.45-0.78, p < 0.01) and bone microstructure (|R| = 0.44-0.87, p < 0.001). Some bovine trabecular bone microstructure parameters were independently associated with the ultrasonic backscatter parameters (Δ R2 = 4.18%-44.45%, p < 0.05) after adjustment for bone apparent density (BAD). The results show that ultrasonic backscatter parametric imaging can provide a direct view of the trabecular microstructure and can reflect information about the density and microstructure of trabecular bone.

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.

Osteoporosis is a degenerative bone disease that affects millions of people worldwide. The goal of this study was to test a new ultrasonic technique developed for clinical bone assessment called the backscatter amplitude decay constant (BADC). Ultrasonic backscatter measurements were performed on 97 volunteers at the left and right femoral necks using an ultrasonic imaging system (Terason T3000) equipped with a 3.5 MHz convex array transducer. The backscatter signals were analyzed to determine the backscatter amplitude decay constant (BADC), a parameter that measures the exponential decay in the amplitude of the backscatter signal. For comparison, additional ultrasonic measurements were performed at the left and right heels using an ultrasonometer (GE Achilles EXPII) to measure the stiffness index of the calcaneus. BADC demonstrated weak but statistically significant correlations with stiffness index (R < 0.25, p < 0.05). With further refinement of the measurement technique, BADC may be a useful parameter for ultrasonic bone assessment.

Osteoporosis is a systemic skeletal disease, which is characterized by the deterioration of microstructures and the decrease of bone mineral density (BMD). Ultrasonic backscatter technique has a promising potential to evaluate microstructures and BMD of cancellous bone for the diagnosis of osteoporosis. The dynamic time warping (DTW)algorithm, measuring the similarity between two signals, has been widely used in speech and image recognition. The purpose of this study is to investigate the feasibility of the DTW algorithm in extracting features from ultrasonic backscatter signals and estimating the microstructure of cancellous bones. Ultrasonic backscatter measurements were performed on twenty-six bovine cancellous bone specimens using an ultrasonic backscatter bone diagnostic system with a focused broadband transducer, which has a center frequency of 1.04 MHz. The dynamic time warped distance (DTWD)feature was extracted from the cost matrix between the ultrasonic backscatter signals and the reference signal. The associations between ultrasonic backscatter features (including DTWD)and trabecular microstructures (i.e., the average trabecular number (Tb. N)and the average trabecular bone spacing (Tb. Sp)), and BMD were analyzed using the simple Pearson's correlations and Partial correlations. The results showed that the DTWD significantly correlated with the Tb.N (R = −0.86±0.09, p

Ultrasonic backscatter technique has shown promise as a noninvasive cancellous bone assessment tool. A novel ultrasonic backscatter bone diagnostic (UBBD) instrument and an in vivo application for neonatal bone evaluation are introduced in this study. The UBBD provides several advantages, including noninvasiveness, non-ionizing radiation, portability, and simplicity. In this study, the backscatter signal could be measured within 5 s using the UBBD. Ultrasonic backscatter measurements were performed on 467 neonates (268 males and 199 females) at the left calcaneus. The backscatter signal was measured at a central frequency of 3.5 MHz. The delay (T1) and duration (T2) of the backscatter signal of interest (SOI) were varied, and the apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB), zero frequency intercept of apparent backscatter (FIAB), and spectral centroid shift (SCS) were calculated. The results showed that the SOI selection had a direct influence on cancellous bone evaluation. The AIB and FIAB were positively correlated with the gestational age (|R| up to 0.45, P10 µs. Moderate positive correlations (|R| up to 0.45, P10 µs). The T2 mainly introduced fluctuations in the observed correlation coefficients. The moderate correlations observed with UBBD demonstrate the feasibility of using the backscatter signal to evaluate neonatal bone status. This study also proposes an explicit standard for in vivo SOI selection and neonatal cancellous bone assessment.

Tumor response to neoadjuvant chemotherapy in patients (n=30) with locally advanced breast cancer (LABC) was examined using quantitative ultrasound. Three ultrasound backscatter parameters, the integrated backscatter coefficient (IBC), average scatterer diameter (ASD), and average acoustic concentration (AAC), were estimated from tumors prior to treatment and at four times during neoadjuvant chemotherapy treatment (weeks 0, 1, 4, 8, and prior to surgery) and compared to ultimate clinical and pathological tumor responses. Results demonstrated that among all parameters, AAC was the best indicator of tumor response early after starting treatment. The AAC parameter increased substantially in treatment-responding patients as early as one week after treatment initiation, further increased at week 4, and attained a maximum at week 8. In contrast, the backscatter parameters from non-responders did not show any changes after treatment initiation. The two patient populations exhibited a statistically significant difference in changes of AAC (p

BACKGROUND The aim of this study was the establishment of a rapid atrial pacing (RAP)-induced atrial fibrillation (AF) model with electrophotoluminescence and the application of ultrasonic backscatter quantitative analysis of the degree of myocardial fibrosis in New Zealand white rabbits. MATERIAL AND METHODS Sixteen New Zealand white rabbits were randomly divided into 2 groups: 1) a sham operation group (n=8) with implanted electrodes and no rapid pacing and 2) a pacing group (n=8) with an AF model induced by short-term rapid right atrial pacing for 12 h. Establishment of an AF model, atrial myocardium of myocardial fibrosis was tested by Masson staining and expression of collagen I and collagen III protein was detected with pathologic immunohistochemistry integrated back-scatter (IBS). Back scattering integral cycle variation (CVIB) were detected in atrial septal and posterior wall of the right atrium. RESULTS Rapid atrial pacing successfully induced the atrial fibrillation model in rabbits. Masson staining showed myocardial fibrosis significantly increased in the pacing group. Expression of collagen I and collagen III protein was strongly positive in the pacing group, and expression of collagen I and collagen III protein were weakly positive in the sham operation group. Compared with the sham operation group, AII was increased (8.24±0.85 vs. 15.56±1.30, P

The predominant causes of stroke and transient ischemic attacks is growth of atherosclerotic plaque in the carotid artery. To aid in diagnosis of these vulnerable plaques, there exists a clinical need for a point-of-care tool for determining plaque composition in carotid arteries. Ultrasound backscatter RF data was collected from 20 human subjects scheduled for a carotid endarterectomy (CEA). The excised plaque was histologically prepared and serially sectioned to permit matching to the pre-surgery ultrasound data. Based on matched histology slides, a square region of interest (ROI) was drawn on the grayscale in vivo image corresponding to homogeneous regions. ROIs for three tissue types were chosen: 32 fibrous or fibro-fatty, 74 hemorrhagic and/or necrotic core with or without micro-calcifications, and 32 calcified. In addition to the CEA subjects, 4 normal volunteers underwent a research ultrasound exam in order to collect data on healthy adventitial sites. The RF data for each ROI was extracted and an average power spectrum was obtained. Effects of attenuation, diffraction, and system transfer functions were compensated and a linear fit was applied to the useable bandwidth. The intercept values show no overlap for the 95% CI between all four tissue types, in contrast to the mid-band fit values which were only separable on a subset of tissue types. Thus spectral analysis of ultrasonic backscatter provides additional ability to distinguish between carotid plaque tissue types as compared to intensity based measures (e.g. mid-band fit, integrated backscatter, and grayscale value).

Ultrasound contrast agents (UCAs) have been explored as a means to enhance therapeutic techniques. Because the effectiveness of these techniques relies on the UCA concentration at a target site, it would be beneficial to estimate UCA concentration noninvasively. In this study, a noninvasive method for estimating UCA concentration was developed in vitro. Backscatter coefficients (BSCs) estimated from measurements of Definity(®) UCAs were fitted to a theoretical scattering model in the 15-25 MHz range using a Levenberg-Marquardt regression technique. The model was defined by the UCA size distribution and concentration, and therefore concentration estimates were extracted directly from the fit. Calculation of the BSC was accomplished using planar reference measurements from the back wall of a Plexiglas(®) chamber and an average of 500 snapshots of ultrasonic backscatter from UCAs flowing through the chamber. In order to verify the ultrasonically derived UCA concentration estimates, a sample of the UCAs was extracted from the flow path and the concentration was estimated with a hemacytometer. UCA concentrations of 1, 2, and 5 times the dose recommended by the manufacturer were used in experiments. All BSC-based estimates were within one standard deviation of hemacytometer based estimates for peak rarefactional pressures of 100-400 kPa.

This study examines the frequency dependence of apparent ultrasonic backscatter from human cancellous bone as quantified by the apparent backscatter transfer function (ABTF). The term 'apparent' means that the backscatter signals are not compensated for the frequency-dependent effects of diffraction and attenuation. Backscatter measurements were performed in vitro on 22 specimens of bone using five transducers ranging in centre frequency from 1 to 10 MHz. The ABTF was measured at multiple sites and spatially averaged. The resulting spatially averaged ABTF (in dB) generally was a monotonically decreasing, quasi-linear function of frequency over the analysis bandwidth of the study (0.6-9.1 MHz). The apparent backscattered power tended to decrease with specimen density and become more strongly frequency dependent. Three parameters were determined from the spatially averaged ABTF. Apparent integrated backscatter (AIB) was determined by frequency averaging the spatially averaged ABTF. The frequency slope of apparent backscatter (FSAB) and the zero frequency intercept of apparent backscatter (FIAB) were determined from the slope and intercept of the spatially averaged ABTF, respectively. AIB and FSAB demonstrated moderate to good linear correlations with specimen density (|r| = 0.570-0.933). Correlations with density were weaker for the intercept-based parameter FIAB (|r| = 0.299-0.676).

The left and right ventricular function of the heart are influenced by the complex structure of the ventricular septum. The cyclic variation of ultrasonic backscatter over the cardiac cycle is known to be sensitive to both structural and functional characteristics of the myocardium. The objective of this study was to investigate differences in the measured magnitude and normalized delay of cyclic variation between the left and right sides of the ventricular septum in normal adult subjects (N = 31). The measured mean magnitudes of cyclic variation were found to be 4.9 ± 0.4 dB and 2.4 ± 0.3 dB (mean ± SE; p < 0.0001) and the corresponding normalized delay values were found to be 0.94 ± 0.05 and 1.59 ± 0.12 (mean ± SE; p < 0.0001) for the left and right sides, respectively. These results show significant differences in the measured magnitude and normalized delay of cyclic variation between the left and right sides of the ventricular septum in normal subjects that appear consistent with predictions based on previously described models of cyclic variation of backscatter and reported measurements of transmural differences in strain properties of the septum.