Broadband 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.

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.

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.

Ethnic Variations in Serum 25(OH)D Levels and Bone Ultrasound Attenuation Measurements in Blacks and Whites.

Vitamin D deficiency is more common in Blacks, yet Blacks have lower prevalence of bone fragility fractures or osteoporosis than Whites. Broadband ultrasound attenuation (BUA) has been used to explore the association between serum 25(OH)D levels and bone quality in White and non-white populations. We investigated serum 25(OH)D status with corresponding BUA measurements assessed cross sectionally in a cohort of 232 Blacks and 260 Whites, aged 30-95years who were part of the calibration study of the large Adventist Health Study-2 (AHS-2). At the calibration clinics, calcaneal BUA was measured and blood drawn for serum 25(OH)D assessment. In multivariable analyses, BUA was negatively associated with age (β-coefficient=-0.38; p<0.0001) and positively associated with body mass index (BMI) (p (trend)<0.0001) and positively, but non-significantly, associated with serum 25(OH)D levels. Also, as expected, females had lower BUA (β-coefficient=-5.19; p<0.05) and Blacks had higher BUA (β-coefficient=4.26; p<0.05). Gender and race modified the relationship of serum 25(OH)D on BUA with a positive association in males (p (trend)≤0.05), but no significant association in females after also controlling for menopausal status and hormone therapy. After also controlling for serum 25(OH)D levels, Black males had higher BUA than White men, but such differences were not found among the females. When stratifying on race, a positive association between serum 25(OH)D levels and BUA (p (trend)≤0.05) was found in Blacks, but not among Whites. Further studies are needed to understand how racial/ethnic differences in serum 25(OH)D levels influence bone health.

Polymorphisms of the WNT16 gene are associated with the heel ultrasound parameter in young adults.

Bone mineral content is influenced by genetic factors. We investigated the role of WNT16 in bone properties determined using quantitative ultrasound (QUS) on young adults. Three WNT16 genetic markers (rs2908007, rs2908004, and rs2707466) were found to have a significant association with the broadband ultrasound attenuation (BUA) measurement, suggesting that WNT16 influences bone mass in young adults. The aim of this study was to investigate whether genetic markers on the WNT16 gene are associated with bone mass, as assessed using QUS in a population of healthy young Spanish adults. A cross-sectional study was conducted on 575 individuals (mean age 20.41 ± 2.69). Bone quality was assessed using BUA measurements (dB/MHz) on the right calcaneus. Six single nucleotide polymorphisms (SNPs) (rs2908007, rs2908004, rs3801387, rs3801385, rs2707466, and rs2536184) covering the WNT16 gene were selected as genetic markers and genotyped to test their association with BUA variations. The rs2908007, rs2908004, and rs2707466 SNPs were found to have a significant association with BUA (p = 0.004, p = 0.001, and p = 0.004, respectively). We demonstrate for the first time that WNT16 genetic polymorphisms influence QUS traits in a population of young adults. This finding suggests that WNT16 might be an important genetic factor in determining peak bone mass acquisition.

WE‐E‐134‐05: Noncontact Ultrasound Applied to Osteroporosis Diagnostics Updated to Include Broadband Ultrasonic Attenuation and Offline Data Analysis

Purpose: The purpose was to push forward our efforts on applying noncontact ultrasound to quantitative imaging of cortical bone as described in our recent paper on speed of sound and attenuation, and integrated response to ultrasound spectroscopy including Broadband ultrasound attenuation (BUA) and to replace our noisy piezoelectric transducers with much quieter velocity correcting capacitive transducers at frequencies of 500 kHz and 850kHz. Methods: An NCU imaging system, a pair of broadband capacitive .500 and .850 MHz, non‐contact transducers, and cortical bone phantoms were used to determine bone mineral density (BMD), speed of sound (SOS), integrated acoustical response (IR), and ultrasonic transmittance. Air gaps of greater than 3 cm, two transmission and reflection paths, and a digital signal processor were used to collect data from phantoms of nominal mass density and (BMD) from 1.17 g/cm3 to 2.25 g/cm3 and from 0 g/cm3 to 1.7 g/cm3. Spectra were analyzed offline using Matlab, including its signal processing and Simulink tool boxes as well as customized Matlab based files, therefore providing much more detailed methods then online approaches, as used in our initial paper. Results: Good correlations between known BMD and measured SOS, IR, and transmittance were obtained for all 14 phantoms obtained in the original studies were complimented with spectroscopic and BUA measurements obtained with capacitive transducers that had much better stability then the original measurements and provided strong correlations with the known BMD of phantoms. Conclusion: The results suggest that the usage of capacitive transducers, offline analysis with Matlab including customized simulations and data analysis algorithms yields much better results than those in our original paper. The new results give us all the more impetus to extend the NCU methods to bone phantoms that more closely mimic human cortical bone and to subsequently apply our methods in vivo.

Experimental and computer simulation validation of ultrasound phase interference created by lateral inhomogeneity of transit time in replica bone: marrow composite models

The measurement of broadband ultrasound attenuation in cancellous bone for the assessment of osteoporosis follows a parabolic-type dependence with bone volume fraction, having minima values corresponding to both entire bone and entire marrow. Langton has recently proposed that the primary attenuation mechanism is phase interference due to variations in propagation transit time through the test sample as detected over the phase-sensitive surface of the receive ultrasound transducer. This fundamentally simple concept assumes that the propagation may be considered as an array of parallel 'sonic rays'. The transit time of each ray is defined by the proportion of bone and marrow propagated, being a minimum (t(min)) solely through bone and a maximum (t(max)) solely through marrow, from which a transit time spectrum, may be defined describing the proportion of sonic rays having a particular transit time. The aim of this study was to test the hypothesis that there is a dependence of phase interference upon the lateral inhomogeneity of transit time by comparing experimental measurements and computer simulation predictions of ultrasound propagation through a range of relatively simplistic solid:liquid models. From qualitative and quantitative comparison of the experimental and computer simulation results, there is an extremely high degree of agreement of 94.2%-99.0% between the two approaches. This combined experimental and computer simulation study has successfully demonstrated that lateral inhomogeneity of transit time has significant potential for phase interference to occur if a phase-sensitive receive ultrasound transducer is implemented as in most commercial ultrasound bone analysis devices.

Normative Data for Quantitative Calcaneal Ultrasound in Asian Children

Dual energy X-ray absorptiometry (DEXA) is currently the gold standard for the assessment of bone mineral density. Quantitative ultrasound (QUS), on the other hand, is a radiation-free alternative for the assessment of bone strength in the paediatric population. Establishing normative data for bone strength specific to the population would allow identification of children at risk of osteoporosis as a consequence of disease and its treatment. This cross-sectional study aims to establish the normal reference range for calcaneal broadband ultrasound attenuation (BUA) measurements in normal Singaporean children aged 6 to 12 years. Healthy Singaporean children were randomly selected from 11 primary schools for the assessment of calcaneal BUA, using the paediatric Contact Ultrasonic Bone Analyzer (CUBA, McCue Plc, Compton, Winchester, England). The height, weight, body mass index and BUA measurements for each age group and gender were expressed as the mean ± SD. One-way ANOVA was used to compare the mean calcaneal BUA by age and gender of Singaporean children with that of children from the United Kingdom, Turkey and Taiwan. A total of 750 healthy Singaporean children (417 males and 333 females) aged 6 to 12 years from 11 primary schools were enrolled. The calcaneal BUA values of Turkish and white British children were not statistically different from this Singaporean cohort. However, the Singaporean calcaneal BUA measurements were significantly higher compared to the Taiwanese children. This study provides the first normal reference data to evaluate bone strength in Singaporean children using the paediatric Contact Ultrasonic Bone Analyzer.

Association with replication between estrogen-related receptor γ (ESRRγ) Polymorphisms and bone phenotypes in women of European ancestry

Osteoporosis is a bone disease characterized by low bone mineral density (BMD), a highly heritable polygenic trait. Women are more prone than men to develop osteoporosis owing to a lower peak bone mass and accelerated bone loss at menopause. Lack of estrogen thus is a major risk factor for osteoporosis. In addition to having strong similarity to the estrogen receptor 1 (ESR1), the orphan nuclear estrogen-related receptor gamma (ESRRgamma) is widely expressed and shows overlap with ESR1 expression in tissues where estrogen has important physiologic functions. For these reasons, we have undertaken a study of ESRRgamma sequence variants in association with bone measurements [heel quantitative ultrasound (QUS) by measurements of broadband ultrasound attenuation (BUA), speed of sound (SOS), and stiffness index (SI) and dual-energy X-ray absorptiometry (DXA) at the femoral neck (FN) and lumbar spine (LS)]. A silent variant was found to be associated with multiple bone measurements (LS, BUA, SOS, and SI), the p values ranging from .006 to .04 in a sample of 5144 Quebec women. The region of this variant was analyzed using the HapMap database and the Gabriel method to define a block of 20 kb. Using the Tagger method, eight TagSNPs were identified and genotyped in a sample of 1335 women. Four of these SNPs capture the five major block haplotypes. One SNP (rs2818964) and one haplotype were significantly associated with multiple bone measures. All SNPs involved in the associations were analyzed in two other sample sets with significant results in the same direction. These results suggest involvement of ESRRgamma in the determination of bone density in women.

Broadband ultrasound attenuation measurement of long bone using peak frequency of the echoes

The traditional peak frequency formulation requires the knowledge of the signal wavelet. We improved and applied the method to estimate attenuation for homogeneous silicon rubber and bovine cortical bone without recourse to the wavelet assumption. The estimated values for rubber and bone samples are 6.59 +/- 0.28 dB/MHz/cm and 4.59 +/- 1.09 dB/MHz/cm, respectively, as compared with 6.33 +/- 0.19 dB/ MHz/cm and 5.00 +/- 1.10 dB/MHz/cm, respectively, by the spectral ratio method.

Improved standardization methods for clinical measurements of BUA and SOS

BACKGROUND: Although calcaneal broadband ultrasound attenuation (BUA) and speed of sound (SOS) are good predictors of osteoporotic fracture risk, BUA and SOS measurements exhibit substantial inter‐system variability. PURPOSE: 1) Compare phase insensitive (PI) detection, which suppresses phase cancellation, and conventional phase sensitive (PS) detection for measurement of BUA. 2) Test a new compensation formula for reducing variability in SOS measurements. METHODS: Data from 73 women were acquired using a GE Lunar Achilles Insight bone sonometer. Radio frequency data were processed off‐line using both PI and PS algorithms. RESULTS: BUA measurements (mean ± sd) were 81.4 ± 21.4 dB/MHz (PS) and 67.2 ± 9.7 dB/MHz (PI). Compensation of SOS measurements reduced 1) average transit‐time‐marker‐related SOS variability by 75% in 73 women and 2) bandwidth‐related SOS variability by 80% in a bone‐mimicking phantom. CONCLUSION: These new methods will enable a substantial improvement in consistency in bone sonometry. The mention of commercial products, their sources, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products by the Department of Health and Human Services.

The effect of phase cancellation on estimates of broadband ultrasound attenuation and backscatter coefficient in human calcaneus in vitro

Broadband ultrasound attenuation (BUA) is a clinically proven indicator of osteoporotic fracture risk. BUA measurements are typically performed in throughtransmission with single-element phase sensitive (PS) receivers and therefore can be compromised by phase cancellation artifact. Phase-insensitive (PI) receivers suppress phase cancellation artifact. To study the effect of phase cancellation on BUA measurements, through-transmission measurements were performed on 16 human calcaneus samples in vitro using a two-dimensional receiver array that enabled PS and PI BUA estimation. The means plus or minus standard deviations for BUA measurements were 22.1 +/- 15.8 dB/MHz (PS) and 17.6 +/- 7.2 dB/MHz (PI), suggesting that, on the average, approximately 20% of PS BUA values in vitro can be attributed to phase cancellation artifact. Therefore, although cortical plates are often regarded as the primary source of phase cancellation artifact, the heterogeneity of cancellous bone in the calcaneal interior may also be a significant source. Backscatter coefficient estimates in human calcaneus that are based on PS attenuation compensation overestimate 1) average magnitude of backscatter coefficient at 500 kHz by a factor of about 1.6 +/- 0.3 and 2) average exponent (n) of frequency dependence by about 0.34 +/- 0.12 (where backscatter coefficient is fit to a power law form proportional to frequency to the nth power).

The influence of cortical end-plate on broadband ultrasound attenuation measurements at the human calcaneus using scanning confocal ultrasound

Quantitative ultrasound (QUS) assessment, including broadband ultrasound attenuation (BUA), is an efficient technique for assessing bone quality in various statuses, e.g., osteoporosis. While assessing trabecular bone loss is essential to bone quality, the existence of cortical bone can substantially reduce the accuracy of BUA measurement. In this study, we developed an approach to quantify the influence of the cortical end-plate in the QUS on 18 cadaver calcanei using both analytical and experimental analyses. A simplified cortical-trabecular-cortical sandwich model has been developed for simulation of wave propagations. Results show that the cortical end-plate has a significant effect on BUA (yielding 8.5 +/- 3.6 dB/MHz in cortical bone alone), approximately 15% of the BUA value over the whole bone BUA measurement (54.1 +/- 20.1 dB/MHz). The phenomenon has been predicted by the developed analytical model with a high correlation (r2 = 0.63, p < 0.0001). The data have suggested that the mechanism of the BUA attributed to the cortical end-plate is primarily due to the ultrasonic wave transmission and reflection within the cortical layers. Therefore, the influence of the cortical end-plate in BUA can be quantified and incorporated into the QUS assessment for bone quality, which may provide insight into BUA measurement for accurate diagnosis of bone diseases.

Effects of weight bearing and non-weight bearing exercises on bone properties using calcaneal quantitative ultrasound

Objective: This study was designed to investigate bone properties using heel quantitative ultrasound (QUS) in young adults participating in various sports. Methods: A cross sectional study was performed on Chinese...

Theoretical and experimental investigation of the behaviour of ultrasound contrast agent particles in whole blood

The majority of the existing models for the behaviour of ultrasound (US) contrast agents consider a single contrast agent particle (CAP) surrounded by an infinite, homogeneous and Newtonian fluid. In vivo, however, CAPs are suspended within the confines of blood vessels, in fluid containing both other CAPs and a high volume fraction of cells of comparable size. The aim of this work was to investigate the influence of blood cells upon CAP acoustic response to determine how existing models should be modified for the purposes of improving CAP design. A new model for a CAP surrounded by a cluster of cells was derived and solved numerically. Broadband US attenuation measurements were then made in suspensions of Optison® (Amersham PLC, Bucks, UK) in plasma and in whole blood. Both the theoretical and experimental results indicate that the presence of blood cells has a relatively small effect upon CAP dynamics and hence acoustic response. This implies that it is justifiable to model blood as homogeneous and Newtonian for the purposes of CAP design.(E-mail: e_stride@meng.ucl.ac.uk)

Normative data for ultrasound measurement of the calcaneus within different female ethnic groups.

The purpose of this study was to generate normative broadband ultrasound attenuation data for UK resident Indian-Asian, African-Caribbean and Chinese women, aged 20-80 years, using the McCue Cubaclinical II device. Additionally, comparisons were made against available Caucasian data previously collected by the authors. Exclusions were: use of hormone replacement therapy, corticosteroids or thyroxine for more than 6 months; menopause before the age of 45 years; oophrectomy; lactation within the preceding year; rheumatoid arthritis or a previous osteoporotic fracture. 977 women were recruited from various community centres, from a local GP surgery and from university colleges in the London area. Broadband ultrasound attenuation and velocity of sound were determined for the left and right os calces. Repeat measures on each side after re-positioning, to allow for anatomical variation, were averaged. Significance was set at a minimum level of 0.05. There were significant differences in non-dominant and dominant measures in all ethnic groups except African-Caribbean. For comparison purposes the means of the non-dominant measurements were plotted against age using a polynomial model to give the best data fit. No significant difference was found between non-dominant broadband ultrasound attenuation measurements for either Asian or Chinese when compared with the Caucasian sample populations. A significant difference in broadband ultrasound attenuation was found between African-Caribbean and Caucasian, with African-Caribbean between 10% (age group 20-30 years) and 29% (age group 70-80 years) higher. There was no significant difference in body mass index between Caucasian and Chinese groups, but significant differences were found between Caucasian and Asian, and between Caucasian and African-Caribbean groups.

Bone mass and bone metabolism in pediatric gastrointestinal disorders.

Bone mass and bone metabolism in pediatric gastrointestinal disorders.

Is ultrasound of bone relevant for corticosteroid-treated patients? A comparative study with bone densitometry measured by DEXA

Corticosteroid treatment diminishes bone mass and alters bone quality. The objective was to evaluate bone in corticosteroid-treated patients and controls and in fractured and non-fractured patients treated with corticosteroids using both X-ray densitometry (DEXA) and ultrasound. We evaluated 34 women aged 58 ± 14 years (X ± SD), who had been on long-term low dose prednisone therapy for at least 6 months, and who had never received specific treatment for osteoporosis. Bone mineral density of total skeleton (TS), lumbar spine (LS), femoral neck (FN), and vertebral morphometry (MXA) were measured by DEXA. Speed of sound (SOS), broadband ultrasound attenuation (BUA) and stiffness were measured using an Achilles Plus system. Forty-two healthy women served as controls. Both densitometric and ultrasound parameters in the patients were significantly diminished compared with controls: TS: P < 0.002, LS: P < 0.025, FS: P < 0.005, Stiffness: P < 0.001, BUA: P < 0.002 and SOS: P < 0.002. The percentage of patients with a Z score below –2 was higher in Stiffness and BUA: 38% and 47%, respectively, compared with a range of 16–24% in the other parameters ( P < 0.05 BUA vs. DEXA measurements). Eleven patients with previous bone fracture had values lower than the non-fractured patients, both according to DEXA and ultrasound measurements, but the difference was only significant for BUA ( P < 0.02). BUA of the calcaneus was more effective in detecting the specific skeletal alterations and fracture risk of the group of patients receiving chronic corticosteroid treatment.

La mesure par ultrasons est-elle utile chez les patients traités par corticoïdes ? Étude comparative avec la densité minérale osseuse mesurée par absorptiométrie biphotonique

Corticosteroid treatment diminishes bone mass and alters bone quality. The objective was to evaluate bone in corticosteroid-treated patients and controls and in fractured and non-fractured patients treated with corticosteroids using both X-ray densitometry (DEXA) and ultrasound. We evaluated 34 women aged 58 ± 14 years (X ± SD), who had been on long-term low dose prednisone therapy for at least 6 months, and who had never received specific treatment for osteoporosis. Bone mineral density of total skeleton (TS), lumbar spine (LS), femoral neck (FN), and vertebral morphometry (MXA) were measured by DEXA. Speed of sound (SOS), broadband ultrasound attenuation (BUA) and stiffness were measured using an Achilles Plus system. Forty-two healthy women served as controls. Both densitometric and ultrasound parameters in the patients were significantly diminished compared with controls: TS: P < 0.002, LS: P < 0.025, FS: P < 0.005, Stiffness: P < 0.001, BUA: P < 0.002 and SOS: P < 0.002. The percentage of patients with a Z score below –2 was higher in Stiffness and BUA: 38% and 47%, respectively, compared with a range of 16–24% in the other parameters ( P < 0.05 BUA vs. DEXA measurements). Eleven patients with previous bone fracture had values lower than the non-fractured patients, both according to DEXA and ultrasound measurements, but the difference was only significant for BUA ( P < 0.02). BUA of the calcaneus was more effective in detecting the specific skeletal alterations and fracture risk of the group of patients receiving chronic corticosteroid treatment.

Development and validation of a multiecho computer simulation of ultrasound propagation through cancellous bone

Cancellous bone consists of a porous open-celled framework of trabeculae interspersed with marrow. Although the measurement of broadband ultrasound attenuation (BUA) has been shown to be sensitive to osteoporotic changes, the exact dependence on material and structural parameters has not been elucidated. A 3-D computer simulation of ultrasound propagation through cancellous bone has been developed, based upon simple reflective behavior at the multitude of trabecular/marrow interfaces. A cancellous bone framework is initially described by an array of bone and marrow elements. An ultrasound pulse is launched along each row of the model with partial reflection occurring at each bone/marrow interface. If a reverse direction wave hits an interface, a further forward (echo) wave is created, with phase inversion implemented if appropriate. This process is monitored for each wave within each row. The effective received signal is created by summing the time domain data, thus simulating detection by a phase-sensitive ultrasound transducer, as incorporated in clinical systems. The simulation has been validated on a hexagonal honeycomb design of variable mesh size, first against a commercial computer simulation solution (Wave 2000 Pro), and second, via experimental measurement of physical replicas produced by stereolithography.