Ultrasound Attenuation Measurements Research Articles

Electrical Impedance Spectroscopy as a Potential Tool for Detecting Bone Porosity

Electrical measurements of bovine trabecular bone samples revealed a perfect correlation between the electrical and mechanical properties. Electrical parameters have surpassed Broadband Ultrasound Attenuation measurements to predict the mechanical properties of bovine bones. There is a linear relationship between dielectric permittivity and bone mineral density. Studies utilizing electrical impedance spectroscopy to evaluate bone include the characterization and monitoring of titanium bone implants, the characterization of bone tissue, and the monitoring of bone fracture healing progress after osteosynthesis. These studies demonstrate that impedance spectroscopy has outstanding potential for assessing bone quality. This study proposes electrical impedance as a method for characterizing bone porosity. Using the DAQ Analog Discovery as an EIS, two electrodes were utilized to determine bone porosity. The procedures include the EIS scanning process and the analysis of its electrical components using the CPE(RC) circuit model. Five bovine samples were used to demonstrate that the EIS spectrum method can be used to determine bone porosity with a reasonable correlation between the parameters R (R2=0.987, F(1,3)=68.067, p<0.004). and C (R2=0.994, F(1,3)=94.041, p<0.002). While the parameter Q (R2=0.922, F(1,3)=22.568, p<0.018) of CPE can indicate the condition of the bovine cancellous bone scaffold surface.

High-resolution acoustic mapping of tunable gelatin-based phantoms for ultrasound tissue characterization.

Background: The choice of gelatin as the phantom material is underpinned by several key advantages it offers over other materials in the context of ultrasonic applications. Gelatin exhibits spatial and temporal uniformity, which is essential in creating reliable tissue-mimicking phantoms. Its stability ensures that the phantom's properties remain consistent over time, while its flexibility allows for customization to match the acoustic characteristics of specific tissues, in addition to its low levels of ultrasound scattering. These attributes collectively make gelatin a preferred choice for fabricating phantoms in ultrasound-related research. Methods: We developed gelatin-based phantoms with adjustable parameters and conducted high-resolution measurements of ultrasound wave attenuation when interacting with the gelatin phantoms. We utilized a motorized acoustic system designed for 3D acoustic mapping. Mechanical evaluation of phantom elasticity was performed using unconfined compression tests. We particularly examined how varying gelatin concentration influenced ultrasound maximal intensity and subsequent acoustic attenuation across the acoustic profile. To validate our findings, we conducted computational simulations to compare our data with predicted acoustic outcomes. Results: Our results demonstrated high-resolution mapping of ultrasound waves in both gelatin-based phantoms and plain fluid environments. Following an increase in the gelatin concentration, the maximum intensity dropped by 30% and 48% with the 5MHz and 1MHz frequencies respectively, while the attenuation coefficient increased, with 67% more attenuation at the 1MHz frequency recorded at the highest concentration. The size of the focal areas increased systematically as a function of increasing applied voltage and duty cycle yet decreased as a function of increased ultrasonic frequency. Simulation results verified the experimental results with less than 10% deviation. Conclusion: We developed gelatin-based ultrasound phantoms as a reliable and reproducible tool for examining the acoustic and mechanical attenuations taking place as a function of increased tissue elasticity and stiffness. Our experimental measurements and simulations gave insight into the potential use of such phantoms for mimicking soft tissue properties.

Diagnostic Performance Comparison Between Ultrasound Attenuation Measurements From Right and Left Hepatic Lobes for Steatosis Detection in Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is currently diagnosed by liver biopsy or MRI proton density fat fraction (MRI-PDFF) from left hepatic lobe (LTHL) and/or right hepatic lobe (RTHL). The objective of this study was to compare the diagnostic value of ultrasound attenuation coefficients (ACs) from RTHL and LTHL in detecting hepatic steatosis using biopsy or MRI-PDFF as a reference standard. Sixty-six patients with suspected NAFLD were imaged with an Aplio i800 ultrasound scanner (Canon Medical Systems, Tustin, CA). Five AC measurements from RTHL and LTHL were averaged separately and together to be compared with the reference standard. Forty-seven patients (71%) were diagnosed with NAFLD. Mean ACs were significantly higher in fatty livers than non-fatty livers (RTHL: 0.73 ± 0.10 vs. 0.63 ± 0.07 dB/cm/MHZ; p < 0.0001, LTHL: 0.78 ± 0.11 vs. 0.63 ± 0.06 dB/cm/MHz; p < 0.0001, RTHL & LTHL: 0.76 ± 0.09 vs. 0.63 ± 0.05 dB/cm/MHz; p < 0.0001). Biopsy steatosis grades (n =31) were better correlated with the mean ACs of RTHL & LTHL (r=0.72) compared to LTHL (r=0.67) or RTHL (r=0.61). Correlation between MRI-PDFF (n=35) and mean ACs was better for LTHL (r=0.69) compared to the RTHL & LTHL (r=0.66) or RTHL (r=0.45). Higher diagnostic accuracy was shown for the mean ACs of RTHL & LTHL (AUC 0.89, specificity 94%, sensitivity 78%) compared to LTHL (AUC 0.89, specificity 88%, sensitivity 82%) or RTHL (AUC 0.81, specificity 89%, sensitivity 68%). Ultrasound ACs from RTHL and LTHL showed comparable diagnostic values in detection of hepatic steatosis with the highest diagnostic accuracy when they were averaged together.

Effect of Bone Marrow Mesenchymal Stem Cells on Mechanical Dynamics and BALP/CTX-1 Expression in Rats with Osteoporotic Vertebral Fracture

To analyze the effects of bone marrow mesenchyml stem cells (BMSCs) on bone alkaline phosphatase (BALP)/C-terminal telopeptide of type-Ⅰ collagen (CTX-1) expression and mechanical dynamics in rats with osteoporotic (OP) vertebral fracture. A total of 60 female Sprague-Dawley rats were evenly divided into three groups, a control group that received sham operation (sham group), a group consisting of rats with OP vertebral fracture (OP group), and the last group consisting of OP vertebral fracture rats given BMSCs treatment (BMSCs group). Comparison of the three groups of animals was made in terms of bone dynamic change, bone quantitative broadband ultrasound attenuation (BUA) measurement, and bone mineral density (BMD). HE staining was done to examine the bone histological morphological parameters of the vertebral body. Serum CTX-1 and BALP levels were determined by ELISA. Mechanical comparison showed that there were significant differences in mechanical changes of L 5 vertebra body and right femur among the three experimental groups ( P<0.05). The elastic modulus and maximum load of the OP group significantly decreased compared with those of the sham group ( P<0.05). After the intervention, the maximum load and elastic modulus of the BMSCs group were significantly higher than those of the OP group ( P<0.05). Compared with the sham group, BUA and BMD values in the OP group were significantly downregulated ( P<0.05). After intervention, BUA and BMD of the BMSCs group were significantly higher than those of the OP group and were comparable to those of the sham group ( P<0.05). Compared with the sham group, the number of trabeculae in the OP group was significantly fewer, and the distribution of trabeculae was disorderly and lacked regularity. Compared with the OP group, there were more trabeculae in the BMSCs group, and their distribution was more regular. Compared with sham group, bone histological morphological parameters of the vertebral body of rats in the OP group were significantly changed--mean trabecular plate thickness (MTPT) and trabecular bone volume (TBV) parameters were significantly decreased, while mineral apposition rate (MAR) and trabecula bone surface (TRS) parameters were significantly upregulated (all P<0.05). After the experimental intervention, bone histological morphological parameters of the vertebral body in the BMSCs group showed significant improvement compared with those of the OP group ( P<0.05). Compared with the sham group, serum BALP content in the OP group was greatly decreased, while the CTX-1 level was upregulated ( P<0.05). After the intervention, the BMSCs group had higher serum BALP content than that of the OP group and substantially lower CTX-1 content than that of the OP group ( P<0.05). BMSCs can improve the mechanical changes in rats with OP vertebral fracture, and can increase the maximum load and elastic modulus of bone tissue. In addition, BMSCs can upregulate the expression of BALP in serum and downregulate the expression of CTX-1, thus helping rats with OP vertebral fracture heal early.

Strong increase in ultrasound attenuation below Tc in Sr2RuO4 : Possible evidence for domains

Recent experiments suggest that the superconducting order parameter of Sr$_2$RuO$_4$ has two components. A two-component order parameter has multiple degrees of freedom in the superconducting state that can result in low-energy collective modes or the formation of domain walls -- a possibility that would explain a number of experimental observations including the smallness of the time reversal symmetry breaking signal at T$_\mathrm{c}$ and telegraph noise in critical current experiments. We perform ultrasound attenuation measurements across the superconducting transition of Sr$_2$RuO$_4$ using resonant ultrasound spectroscopy (RUS). We find that the attenuation for compressional sound increases by a factor of seven immediately below T$_\mathrm{c}$, in sharp contrast with what is found in both conventional ($s$-wave) and high-T$_\mathrm{c}$ ($d$-wave) superconductors. We find our observations to be most consistent with the presence of domain walls between different configurations of the superconducting state. The fact that we observe an increase in sound attenuation for compressional strains, and not for shear strains, suggests an inhomogeneous superconducting state formed of two distinct, accidentally-degenerate superconducting order parameters that are not related to each other by symmetry. Whatever the mechanism, a factor of seven increase in sound attenuation is a singular characteristic with which any potential theory of the superconductivity in Sr$_2$RuO$_4$ must be reconciled.

Multi-frequency ultrasound tomography based on modified matrix regularization method and wavelet fusion

Ultrasound tomography (UT) is a promising sensing technique for industrial processes owing to its advantages non-invasive, low cost, implement flexibility. Traditional UT may lack the distinguishability to resolve the flow with the complicated distribution. We propose a method that exploits the multi-frequency information to improve spatial resolution and resolve different inclusions. Firstly, multi-frequency ultrasound attenuation measurement information was collected and demodulated for tomographic reconstruction. Secondly, a hybrid reconstruction algorithm is proposed consisting of the modified matrix regularization and wavelet fusion methods. The proposed method can effectively reduce the artefact for the inclusion and sharpen the boundary, and detailed information can be reserved from the wavelet fusion. Thirdly, a multi-frequency experimental UT system is established to accomplish the 32 channels ultrasound signal excitation and reception. The performance of the proposed method is validated through numerical simulation and experimental study. The results show that the reconstruction metrics have been improved compared with the linear back projection and Tikhonov algorithms. We believe the proposed method can be used in the flow process prediction and diagnosis for industrial applications.

High-Order Pulse-Echo Ultrasound

Multiple reflections between transducer and imaged object can naturally occur in ultrasound imaging and other acoustic sensing applications such as sonar. The repeated interaction of the emitted wave front with the imaged object is traditionally regarded as an undesired reverberation artifact, often misinterpreted as fictitious acoustic boundaries. We introduce high-order reflection pulse-echo (HOPE) ultrasound, a method that leverages high-order reflections to improve on several aspects of conventional ultrasound imaging. HOPE is experimentally demonstrated to resolve submicrometer features by breaking through the sampling limit. The major contrast enhancement of the high reflection orders allowed defects within materials invisible to conventional scanning acoustic microscopy to be revealed. The technique is further shown to improve accuracy of frequency-dependent ultrasound attenuation measurements from biological tissues. HOPE ultrasound requires no additional hardware and is easy to implement, underscoring its potential to boost imaging performance in biomedical imaging, nondestructive testing, and other acoustic sensing applications.

Association between LEPR polymorphism and susceptibility of osteoporosis in Chinese Mulao people

To explore the association between the single nucleotide polymorphism (SNP) of leptin receptor (LEPR) gene and the susceptibility to osteoporosis (OP) among Chinese Mulao people. A total of 738 people were involved. Bone mineral density (BMD) was examined by calcaneus ultrasound attenuation measurement. Six SNPs of LEPR were detected. The genotypes, allele frequencies, linkage disequilibrium, and haplotype were analyzed. BMD decreased with age and males had higher BMD than women. The proportion of normal bone mass decreased with age, and morbidity of OP increased. Three out of six SNPs showed a difference between OP and normal group. Individuals with AA genotype of rs1137100 in OP group outnumber the normal group, AA increased the risk of OP. In rs2767485, CT increased the risk of OP, C allele may be susceptible to OP. TT genotype of rs465555 was susceptible genotype of OP, T locus may be associated with OP. Strong linkage disequilibrium was detected among rs1137100, rs1137101, and rs4655555. Four haplotypes were constructed, among which, AACGCT and GGTGTA increased the risk of OP by 3.9 and 4.2 times, respectively, whereas, GGCGTA reduced 74% of OP susceptibility. The rs1137100, rs2767485, and rs465555 of LEPR were associated with OP in Chinese Mulao people.

Improved Ultrasound Attenuation Measurement Method for the Non-invasive Evaluation of Hepatic Steatosis Using FibroScan

Controlled attenuation parameter (CAP) is a measurement of ultrasound attenuation used to assess liver steatosis non-invasively. However, the standard method has some limitations. This study assessed the performance of a new CAP method by ex vivo and in vivo assessments. The major difference with the new method is that it uses ultrasound data continuously acquired during the imaging phase of the FibroScan examination. Seven reference tissue-mimicking phantoms were used to test the performance. In vivo performance was assessed in two cohorts (in total 195 patients) of patients using magnetic resonance imaging proton density fat fraction (MRI-PDFF) as a reference. The precision of CAP was improved by more than 50% on tissue-mimicking phantoms and 22%–41% in the in vivo cohort studies. The agreement between both methods was excellent, and the correlation between CAP and MRI-PDFF improved in both studies (0.71 to 0.74; 0.70 to 0.76). Using MRI-PDFF as a reference, the diagnostic performance of the new method was at least equal or superior (area under the receiver operating curve 0.889–0.900, 0.835–0.873). This study suggests that the new continuous CAP method can significantly improve the precision of CAP measurements ex vivo and in vivo.

Can ultrasound attenuation measurement be used to characterise grain statistics in castings?

Industrial inspection protocols are qualified using mock-ups manufactured according to the same procedure as the plant part. For coarse-grained castings, known for their low inspectability, relying on mock-ups becomes particularly challenging owing to the variability of grain properties among components. Consequently, there is a keen interest in the capability to verify whether the grain size of the component under test matches the qualification specification in-situ. This paper investigates the potential of an attenuation measurement for assessing the ultrasonic inspectability of coarse-grained components using qualified procedures in a practical setting. The experimental part of the study focuses on an industrial Inconel 600 mock-up with spatially varying attenuation, measured across the entire sample in an immersion tank. Three zones with distinctly different attenuations were examined using metallography, which allowed for calculating classical grain size histograms and two-point correlation functions. For one of the zones, we synthesised the microstructure with the same statistical properties numerically and simulated the propagation of ultrasound using a grain-scale finite element model. The results showed good agreement with the experiment, and lead to several suggestions for the reasons for the discrepancy, the varying grain size statistics being the most likely. A parametric study, which followed, depicted the effect of the mean and standard deviation-to-mean ratio of the log-normal grain size distribution on the attenuation of ultrasound and its frequency dependence. Most notably, we demonstrated the known non-uniqueness of the relationship between the log-normal grain size distribution parameters and the attenuation. We suggested that the correlation length calculated from a single exponential fit to the two-point correlation function is a more robust metric describing grain statistics for this context, which can be obtained from attenuation. The correlation lengths estimated from measured attenuation using the second-order approximation model for the three zones of the studied mock-up yielded results of acceptable accuracy. We concluded that this metric could replace the average grain size in practical settings, as it retains more statistical information than the mean grain size and allows for linking measurements to the established theoretical attenuation models which this paper demonstrates.

ESTIMATING THE QUALITY OF POWDER WIRE SURFACING RESTORATION OF SCOOP CHAIN FAST-WEARING PARTS WITH THE USE OF ULTRASONIC

On the example of the fingers of the scoop chain, a technique is proposed for the integral assessment of the quality of restoration of parts using elastic waves - ultrasound. The purpose of the work is to ensure the efficiency of measurements when assessing the quality of remanufactured parts in the conditions of a repair base. For this, data on the attenuation of elastic waves when they pass through the restored part were used. Unlike precision measurements of the velocity of elastic waves, the measurement of ultrasound attenuation does not require laboratory equipment, a conventional industrial flaw detector is sufficient. To assess the quality of the product, the transducer was alternately installed at points determined along the length of the finger, the probe beam was directed along the diameter and the first pulse of elastic vibrations reflected from the opposite side of the finger was recorded and the second, which passed two additional diameters of the finger. Found a quantitative indicator that allows you to assess the quality of restoration of the part. The proposed method to a certain extent solves the problem of integral assessment of the state of the restored finger of the scoop chain. To prevent premature failure of parts restored by welding with flux-cored wire, it is enough to introduce into practice an easy procedure for controlling sound attenuation.

Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis: new trends and role of ultrasonography.

Nonalcoholic fatty liver disease (NAFLD) is entering a new era in terms of diagnosis and conceptualization. The term NAFLD is considered to not reflect current knowledge. Metabolic dysfunction-associated fatty liver disease (MAFLD) has been suggested as a more appropriate overarching term by experts in this field. Regarding NAFLD progression, most patients die from non-liver-related diseases, even patients with advanced fibrosis. Liver biopsy is essential for the diagnosis of nonalcoholic steatohepatitis (NASH); it is the only procedure that reliably differentiates NAFLD from NASH. Recently, various noninvasive methods for diagnosing steatosis and fibrosis have been developed. Ultrasound attenuation measurements and proton density fat fraction with magnetic resonance imaging (MRI) have been developed as imaging tools for predicting steatosis. Fibrosis-4 index and NAFLD fibrosis score are complex scores for predicting fibrosis in patients with NAFLD. In addition, elastography based on ultrasound and MRI has been developed as an imaging tool for predicting fibrosis. There is a strong correlation between values from various real-time shear wave elastography devices and transient elastography, which is the gold standard for ultrasound-based measurements of liver stiffness. In conclusion, NAFLD is at a turning point in terms of its conceptualization, terminology, and diagnostics. It is now time to reconfirm the role of ultrasonography for the assessment of NAFLD.

Experimental Measurements of Ultrasound Attenuation in Human Chest Wall and Assessment of the Mechanical Index for Lung Ultrasound

Knowledge of the acoustic attenuation characteristics of the chest wall is necessary to estimate the acoustic exposure at the pleural surface during lung ultrasound and is useful in the prediction of bio-effects (e.g., pulmonary capillary hemorrhage) and the development of safe, effective lung imaging. Currently, this property is not well characterized in humans. The aim of this work was to characterize ultrasonic attenuation in human chest wall such that the ultrasound exposures of the lung can be estimated for clinically relevant conditions. In this study, we experimentally measured ultrasound transmitted through the intercostal tissue of 15 human cadaver chest wall samples relative to ultrasound transmitted through saline to determine attenuation coefficients for each sample. A GE Vivid 7 diagnostic ultrasound machine (GE Vingmed, Horten, Norway) and 3 S and 5 S phased array probes were used at center frequencies from 1.6 to 5 MHz. The chest wall samples varied in thickness from 2.3–5.5 cm with a median thickness of 3.8 cm. The frequency-normalized attenuation coefficient was approximately 1.44 dB/cm/MHz based on a linear best fit through all attenuation measurements. Attenuation characteristics varied appreciably between samples, and the sample-averaged linear attenuation coefficient was 1.43 ± 0.32 (mean ± standard deviation) dB/cm/MHz. This attenuation is higher than that previously measured in mammalian chest wall samples (1.1–1.3 dB/cm/MHz for mice and rats) and is much greater than that used by the mechanical index (0.3 dB/cm/MHz). Mechanical index values calculated using saline values de-rated by 0.3 dB/cm/MHz were up to 1.2 MPa/MHz1/2 greater than those calculated using the measured through-tissue ultrasound waves. We conclude that the mechanical index overestimates exposures for lung ultrasound and thus may not be an appropriate dosimetry metric for pulmonary ultrasound.

Influence of cancellous bone microstructure on ultrasonic attenuation: a theoretical prediction

BackgroundQuantitative ultrasound has been used for the assessment of cancellous bone status. The attenuation mechanisms of cancellous bone, however, have not been well understood, because the microstructure of cancellous bone is significantly inhomogeneous and the interaction between ultrasound and the microstructure of cancellous bone is complex. In this study, a theoretical approach was applied to investigate the influence of the microstructure of cancellous bone on ultrasonic attenuation.ResultsThe scattering from a trabecular cylinder was significantly angle dependent. The dependencies of the ultrasonic attenuation on frequency, scatterer size, and porosity were explored from the theoretical calculation. Prediction results showed that the ultrasonic attenuation increased with the increase of frequency and decreased linearly with the increase in porosity, and the broadband ultrasound attenuation decreased with the increase in porosity. All these predicted trends were consistent with published experimental data. In addition, our model successfully explained the principle of broadband ultrasound attenuation measurement (i.e., the attenuation over the frequency range 0.3–0.65 MHz was approximately linearly proportional to frequency) by considering the contributions of scattering and absorption to attenuation.ConclusionThe proposed theoretical model may be a potentially valuable tool for understanding the interaction of ultrasound with cancellous bone.

Measurements of ultrasound attenuation in human chest wall

Knowledge of the bulk acoustic properties of human chest wall is useful in the development and study of cardiac and lung ultrasound exposimetry. However, few studies have been performed on human tissue, and there is a need for attenuation data relevant to clinical diagnostic ultrasound. In this study, we measured the bulk acoustic attenuation in unembalmed, never-frozen human chest wall samples, using a GE Vivid 7, clinical diagnostic ultrasound machine. B-mode ultrasound with frequencies from 1.6 to 5.0 MHz was transmitted through human chest wall tissue samples and compared to equivalent-source signals transmitted through normal saline. The recorded signals were analyzed to characterize the acoustic attenuation. Preliminary results based on 9 donors show that both chest wall morphology and bulk attenuation properties vary widely between individuals. Chest wall thicknesses ranged from 2 to 6 cm. The mean linear acoustic attenuation coefficients, across all samples, ranged from 1.1 dB/cm MHz at 1.6 MHz to 1.7 dB/cm MHz at 5.0 MHz, with a frequency-averaged standard deviation of 0.4 dB/cm MHz. Across all donors and frequency and power settings, linear acoustic attenuation coefficients ranged from 0.5 to 2.3 dB/cm MHz. Variation in thoracic exposure may result from variations in the chest wall composition and morphology between patients.Knowledge of the bulk acoustic properties of human chest wall is useful in the development and study of cardiac and lung ultrasound exposimetry. However, few studies have been performed on human tissue, and there is a need for attenuation data relevant to clinical diagnostic ultrasound. In this study, we measured the bulk acoustic attenuation in unembalmed, never-frozen human chest wall samples, using a GE Vivid 7, clinical diagnostic ultrasound machine. B-mode ultrasound with frequencies from 1.6 to 5.0 MHz was transmitted through human chest wall tissue samples and compared to equivalent-source signals transmitted through normal saline. The recorded signals were analyzed to characterize the acoustic attenuation. Preliminary results based on 9 donors show that both chest wall morphology and bulk attenuation properties vary widely between individuals. Chest wall thicknesses ranged from 2 to 6 cm. The mean linear acoustic attenuation coefficients, across all samples, ranged from 1.1 dB/cm MHz at 1.6 MHz to...

Simultaneous measurements of ultrasound attenuation, phase velocity, thickness, and density spectra of polymeric sheets

The size distribution and mechanical properties of microparticle dispersed in liquid can be characterized by ultrasonic spectroscopy with the aid of acoustic scattering theories. In order to carry out the accurate analysis of the particles, the basic properties, such as the density, viscosity, longitudinal and shear velocities and intrinsic attenuation coefficient of the particle must be known prior to the analysis. Particularly, for soft elastomers or rubbers which exhibit complex mechanical properties with comparable real and imaginary parts, such fundamental information should be provided prior to the particle analysis to minimize the uncertainty of estimation associated with the number of adjustable parameters. In this study, we examined the acoustical properties of poly(methyl methacrylate)(PMMA) and cross-linked poly(dimethyl siloxane) sheets having different cross-linker concentrations by Multiple-Echo Reflection Ultrasonic Spectroscopy which simultaneously enabled us to acquire 4 fundamental properties, the ultrasound attenuation coefficient, phase velocity, density, and thickness (MERUS4 for solid plate). In addition, it was confirmed that the acoustic spectra of PMMA particles dispersed in water were reproduced well with the physical properties determined by MERUS4 using the PMMA plates.

An Artificial Neural Network (ANN) approach to extract micro-architectural properties of cortical bone using ultrasound attenuation: A numerical study

The goal of this study is to estimate the porosity parameters including pore diameter, pore density, and porosity of cortical bone from ultrasound attenuation measurements using an artificial neural network (ANN). Two-dimensional (2D) finite-difference time-domain simulations are conducted to calculate the frequency-dependent attenuation in the range of 1–8 MHz in mono-disperse structures (constant pore size) with a pore diameter and density ranging from 20 to 120 µm and 3–16 pore/mm2, respectively. Furthermore, poly-disperse structures (non-uniform pore distribution) are obtained from high resolution CT scans of human cortical bone and 2D numerical simulations are carried out in the same frequency range as for the mono-disperse cases. Then, a regression problem is formulated with the ultrasonic attenuation at different frequencies acting as the feature vectors and the output being set as the porosity parameters. Our dataset consists of 330 structures for the mono-disperse model and 668 structures for the poly-disperse model. ANN-based (3 hidden layers with 806 trainable weights) parameter prediction method achieves accuracies as high as 96% for pore size, 97% for porosity, and 78% for pore density for the poly-disperse model. This work demonstrates the potential of combining ultrasound methods to deep neural networks to quantify cortical bone parameters with high accuracies.

Thermodynamic evidence of magnetic-field-induced complete valley polarization in bismuth

We investigated the fundamental physical properties in the ultra-quantum limit state of bismuth through measurements of magnetoresistance, magnetization, magnetostriction, and ultrasound attenuation in magnetic fields up to 60T. For magnetic fields applied along the bisectrix direction of a single crystal, a drastic sign reversal in magnetostriction was observed at approximately 39T, which could be ascribed to the complete valley polarization in the electron Fermi pockets. The application of magnetic fields along the binary direction presented an anomalous feature at approximately 50T only in the magnetoresistance. The emergence of a field-induced splitting of a valley was proposed as a possible origin of this anomaly.

Predicting Structural Properties of Cortical Bone by Combining Ultrasonic Attenuation and an Artificial Neural Network (ANN): 2-D FDTD Study.

The goal of this paper is to predict the micro-architectural parameters of cortical bone such as pore diameter and porosity from ultrasound attenuation measurements using an artificial neural network (ANN). Slices from a 3-D CT scan of human femur are obtained. The micro-architectural parameters of porosity such as average pore size and porosity are calculated using image processing. When ultrasound waves propagate in porous structures, attenuation is observed due to scattering. Two-dimensional finite-difference time-domain simulations are carried out to obtain frequency dependent attenuation in those 2D structures. An artificial neural network (ANN) is then trained with the input feature vector as the frequency dependent attenuation and output as pore diameter and porosity . The ANN is composed of one input layer, 3 hidden layers and one output layer, all of which are fully connected. 340 attenuation data sets were acquired and trained over 2000 epochs with a batch size of 32. Data was split into train, validation and test. It was observed that the ANN predicted the micro-architectural parameters of the cortical bone with high accuracies and low losses with a minimum R2 (goodness of fit) value of 0.95. ANN approaches could potentially help inform the solution of inverse-problems to retrieve bone porosity from ultrasound measurements. Ultimately, those inverse-problems could be used for the non-invasive diagnosis and monitoring of osteoporosis.

Improving broadband ultrasound attenuation assessment in cancellous bone by mitigating the influence of cortical bone: Phantom and in-vitro study

The purpose of this work was to present a new approach that allows the influence of cortical bone on noninvasive measurement of broadband ultrasound attenuation (BUA) to be corrected. The method, implemented here at 1 MHz makes use of backscattered signal and once refined and clinically confirmed, it would offer an alternative to ionizing radiation based methods, such as DEXA (Dual-energy X-ray absorptiometry), quantitative computed tomography (QCT), radiographic absorptiometry (RA) or single X-ray absorptiometry (SXA), which are clinically approved for assessment of progress of osteoporosis. In addition, as the method employs reflected waves, it might substantially enhance the applicability of BUA - from being suitable to peripheral bones only it would extend this applicability to include such embedded bones as hip and femoral neck. The proposed approach allows the cortical layer parameters used for correction and the corrected value and parameter of the cancellous bone (BUA) to be determined simultaneously from the single (pulse-echo) bone backscattered wave; to the best of the authors’ knowledge such approach was not previously reported. The validity of the method was tested using acoustic data obtained from a custom-designed bone-mimicking phantom and a calf femur. The relative error of the attenuation coefficient assessment was determined to be 3.9% and 4.7% for the bone phantom and calf bone specimens, respectively. When the cortical shell influence was not taken into account the corresponding errors were considerably higher 8.3% (artificial bone) and 9.2% (calf femur). As indicated above, once clinically proven, the use of this BUA measurement technique in reflection mode would augment diagnostic power of the attending physician by permitting to include bones, which are not accessible for transmission mode evaluation, e.g. hip, spine, humerus and femoral neck.