Quantitative Ultrasound Variables Research Articles

Comparative analysis of bone outcomes between quantitative ultrasound and dual-energy x-ray absorptiometry from the UK Biobank cohort

SummaryThis large cohort study investigated reliability and validity of heel ultrasound to estimate bone mineral density in adults. Reliability calculated between left and right heels was relatively poor and so was criterion validity assessed relative to dual-energy X-ray absorptiometry. Heel ultrasound should be used cautiously when estimating bone mineral density.IntroductionCalcaneal quantitative ultrasound (QUS) may be used as a safe, low cost, and portable means to estimate bone mineral density (BMD) in large cohorts. The purpose of this study was to quantify the reliability and validity of QUS in comparison to dual-energy X-ray absorptiometry (DXA), which is the reference method for BMD measurement and diagnoses of osteopenia and osteoporosis.MethodsBone outcomes measured on the large UK Biobank cohort were used. The reliability of QUS estimated BMD was quantified by comparing values obtained from the left and right heel measured in the same session. Criterion validity was assessed through agreement between QUS and DXA, quantifying correlations, and sensitivity and specificity of osteopenia and osteoporosis diagnoses.ResultsReliability calculations were made using data from over 216,000 participants demonstrating similar QUS BMD values between left and right heels in the absolute scale (Sd of difference for men: 0.12 and 0.07 g·cm−2). However, when expressed in relative scales, including concordance of quartiles, reliability was poor. Agreement between QUS and DXA was quantified using data from 5042 participants. Low to modest correlations (r = 0.29 to 0.44) were obtained between multiple QUS variables and DXA BMD, with sensitivity identified as very poor (0.05 to 0.23) for osteoporosis, and poor (0.37 to 0.62) for osteopenia diagnoses.ConclusionsThe findings of this large comparative analysis identify that whilst calcaneal QUS has the potential to produce reliable absolute BMD measurements and demonstrate modest associations with DXA BMD measures, use of that information to make relative statements about participants in the context of the larger population or to appropriately diagnose osteopenia or osteoporosis may be severely limited.

The ability of calcaneal and multisite quantitative ultrasound variables in the identification of osteoporosis in women and men.

The aim of this study was to assess the ability of calcaneal and multisite quantitative ultrasound (QUS) parameters in the identification of osteoporosis in women and men. A total of 131 women (mean age 53.7±11.9 years; range, 21 to 79 years) and 109 men (mean age 57.8±13.7 years; range, 24 to 85 years) whose bone mineral density (BMD) at the spine and proximal femur was measured between January 2010 and January 2012, using dual-energy X-ray absorptiometry (DXA) were included. Acoustic bone properties were also examined using both a calcaneal and a multisite QUS. The receiver operating characteristic analysis with the calculation of areas under the curve (AUCs) to evaluate the ability of both QUS devices for the identification of osteoporosis. We also calculated a lower and an upper threshold at a specificity of 90% and at a sensitivity of 90%, respectively, for the identification of osteoporosis along with a threshold/cut-off value with the best compromise between sensitivity and specificity. All calcaneal QUS parameters showed significant AUCs within the range of 0.712 (for Broadband Ultrasound Attenuation [BUA]) and 0.764 (for Speed of Sound [SOS]) in women and ranging from 0.661 (for BUA) to 0.735 (for SOS) in men, while only radial SOS of the multisite QUS demonstrated a significant AUC value of 0.661 for identifying osteoporosis in women. A Quantitative Ultrasound Index T-score of -1.53 for women and -1.68 for men showed sensitivity and specificities around 70%. Based on the results of this study, all calcaneal QUS parameters in both women and men and possibly radial SOS measurements of the multisite QUS in women may be helpful for the identification of osteoporosis.

Are calcaneal quantitative ultrasound variables better than radial bone mineral density in identifying women with osteoporosis?

In certain circumstances when axial bone mineral density (BMD) cannot be measured using dual-energy X-ray absorptiometry (DXA), DXA BMD of the one-third radius (33% radius) can be used for the diagnosis of osteoporosis. Calcaneal quantitative ultrasound (cQUS) variables may also be used for assessing osteoporosis. The aim of this study was to test the hypothesis that cQUS variables may be better than one-third radius (33% radius) BMD for the identification of axial osteoporosis in women. Two hundred and nine women aged between 21 and 85 years whose posteroanterior spine, hip, and 33%radius DXA BMD measurements as well as cQUS variables were measured were included in this study. WHO criteria were employed for defining osteoporosis in postmenopausal women and premenopausal women with Z-scores of ≤ −2.0 were considered as having osteoporosis in axial regions. We used receiver operating characteristic (ROC) analysis to evaluate lumbar spine or hip osteoporosis discriminative performance of radius DXA BMD and cQUS parameters. While 33% radius BMD and its T-score revealed greater areas under ROC curves (AUCs) (0.760 and 0.759) than those of the cQUS variables [0.707 for quantitative ultrasound index (QUI), 0.705 for QUI T-score, 0.682 for broadband ultrasound attenuation (BUA), 0.718 for speed of sound (SOS), and 0.706 for estimated heel BMD (eBMD)] for identifying lumbar spine osteoporosis, the AUC values for all cQUS variables (0.816 for QUI, 0.815 for QUI T-score, 0.829 for BUA, 0.791 for SOS, and 0. 813 for eBMD) in the discrimination of femoral neck osteoporosis were greater than those of 33% radius DXA BMD and its T-score (0.779 and 0.783). The results of this study confirmed our hypothesis for femoral neck osteoporosis, but not for lumbar spine osteoporosis. Our results have implications that cQUS can be used for the prediction of femoral neck osteoporosis in women whose hip DXA BMD cannot be measured.

Impact of Age, Gender, and Body Composition on Bone Quality in an Adult Population From the Middle Areas of China

Identifying modifiable factors that influence bone status during adulthood to maximize bone quality is a potential primary strategy in the prevention of osteoporosis in later life. We investigated the impact of body height, body weight, body mass index, and body composition on calcaneal bone characteristics as measured with quantitative ultrasound in 441 Chinese adults (238 women) aged 20–55 yr from the middle areas of China. Body composition, including fat-free mass (FFM), muscle mass, and fat mass were obtained by bioelectrical impedance analysis. Bivariate correlation analysis demonstrated a significant negative correlation between age and broadband ultrasound attenuation (BUA), speed of sound (SOS), and stiffness index (SI) both in men (r = −0.177, p < 0.05; r = −0.499, p < 0.001; r = −0.530, p < 0.001, respectively) and women (r = −0.344, p < 0.001; r = −0.336, p < 0.001; r = −0.369, p < 0.001, respectively). Body height, body weight, FFM, and muscle mass had positive correlations with BUA, SOS, and SI in both genders, with FFM having the strongest correlation with BUA, SOS, and SI in men (r = 0.351, p < 0.001; r = 0.391, p < 0.001; r = 0.406, p < 0.001, respectively) and women (r = 0.331, p < 0.001; r = 0.288, p < 0.001; r = 0.324, p < 0.001, respectively). Fat mass had a positive correlation with BUA (r = 0.331, p < 0.001), SOS (r = 0.288, p < 0.001), and SI (r = 0.324, p < 0.001) in women, which was not found in men. Multivariate regression analysis revealed that, in both genders, FFM was a positive predictor for all 3 quantitative ultrasound variables.

Discriminative ability of calcaneal quantitative ultrasound compared with dual-energy X-ray absorptiometry in men with hip or distal forearm fractures

ObjectivesThe aim of this case–control study was to compare the discriminatory ability of bone mineral density (BMD) measurements and calcaneal quantitative ultrasound (QUS) parameters for fractures and to determine fracture thresholds for each variable in men with hip or distal forearm fractures. Patients and methodsA total of 20 men with hip and 18 men with distal forearm fractures and 38 age-matched controls were included in this study. Dual-energy X-ray absorptiometry (DXA) BMD (spine and hip) and calcaneal QUS measurements were made. Area under the curves (AUCs) were calculated to assess fracture discriminatory power of DXA and QUS variables. ResultsQuantitative Ultrasound Index (QUI) T-score and Speed of Sound (SOS) were found to be the best parameters for the identification of hip and distal forearm fractures, respectively, with AUCs greater than those of DXA BMD and other QUS parameters. While a QUI T-score of ≤−1.18 could identify and rule out hip fracture cases with approximately 80% sensitivity and specificity, a SOS value of ≤1529.75 reached to almost 90% for ruling in and out distal forearm fractures. ConclusionThe discriminatory performance of calcaneal QUS variables between fractured and non-fractured men was as good as those of the DXA BMD and even better. Since men appear to sustain fractures at closer QUS variable levels than those of the DXA BMD regardless of the fracture type, it may be speculated that calcaneal QUS may be more helpful in predicting the risk of fractures when BMD alone does not demonstrate impaired bones.Level of Evidence: Level III, Study of Diagnostic Test

The role of physical activity in early adulthood and middle-age on bone health after menopause in epidemiological population from Silesia Osteo Active Study.

Osteoporosis is a growing problem in women after menopause. Among factors protecting from this disease is a physical activity (PA). The objective of the study was to evaluate the influence of PA in early adulthood and at middle-age on bone health after menopause. The study group consisted of 362 randomly recruited postmenopausal women after menopause. Mean age was 65.2±6.9years. Medical history was collected from all participants, and they completed questionnaires assessing PA in early adulthood and at middle-age. Physical capacity was estimated using the Duke scale. Bone status was measured with use of densitometry (DXA) for lumbar spine and hip and calcaneus quantitative ultrasound (QUS) measurements. Physical activity and healthy lifestyle activity in early adulthood did not correlate with bone health, but current PA did (for QUS parameters r=.11; P<.05). Physical capacity correlated with all QUS parameters (r=.2 to .22; P<.05) and femoral neck (FN) BMD and T-score (for both r=.16; P<.05). Current PA frequency at the level of several times a week has the highest positive impact on FN DXA results (P=.01). Bone mass in DXA and QUS variables is related to the type of exercises (P<.05). Physical activity, especially several times a week, at middle-age is a major factor influencing bone health in women after menopause. Further studies concerning the type of exercises are needed.

Peak Bone Mass and Quantitative Ultrasound Bone Properties in Young Adulthood: A Study in the PEAK-25 Cohort of Women

Peak bone mass is normally reached in the third decade of life. Previously, in the population-based PEAK-25 cohort (n = 1061, age 25.5 ± 0.2), we demonstrated that bone mineral density in the population-based PEAK-25 cohort is comparatively high; therefore, this study aimed to determine if the calcaneus microarchitecture mirrored this. In the process, we describe normative quantitative ultrasound (QUS) values for 25-yr-old women and the relationship between QUS values and extremes of body weight. QUS variables speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index were measured. Young adult values were based on the manufacturer-supplied QUS reference values. Analyses were performed in the cohort as a whole, and additionally, to understand the relationship between body weight and QUS values in young women, the variables were categorized into octiles for weight or body mass index (BMI) and the lowest and highest octiles were compared. In the cohort, SOS values, reflecting bone density, were higher (108 ± 18%), whereas BUA values, reflecting bone complexity, were lower (90 ± 14%) compared to the young adult reference population. SOS did not correlate with body weight or BMI. In the cohort, overall correlations between BUA weight, and BMI were small and positive (Pearson's r coefficients 0.261 and 0.197, respectively; p < 0.001), although in the low-weight group, r coefficients were higher (r = 0.313 and 0.268; p < 0.05). In contrast, in the high-weight group, correlation with BUA values tended to be small, negative, and nonsignificant. Correlation between QUS and dual-energy X-ray absorptiometry-measured bone mineral density was low to moderate and significant at all skeletal sites (r = 0.37–0.52). Whereas coefficients tended to be higher in the low-weight group, the reverse was apparent for the low-BMI group. In these 25-yr-old women, a comparatively high dual-energy X-ray absorptiometry-measured bone mass is offset by less complex bone structures assessed by QUS. This may have implications for later osteoporosis assessment and future fracture risk.

The utility of dual-energy X-ray absorptiometry, calcaneal quantitative ultrasound, and fracture risk indices (FRAX® and Osteoporosis Risk Assessment Instrument) for the identification of women with distal forearm or hip fractures: A pilot study

ABSTRACTPurpose: Dual-energy X-ray absorptiometry (DXA) is considered the “gold standard” in predicting osteoporotic fractures. Calcaneal quantitative ultrasound (QUS) variables are also known to predict fractures. Fracture risk assessment tools may also guide us for the detection of individuals at high risk for fractures. The aim of this case–control study was to evaluate the utility of DXA bone mineral density (BMD), calcaneal QUS parameters, FRAX® (Fracture Risk Assessment Tool), and Osteoporosis Risk Assessment Instrument (ORAI) for the discrimination of women with distal forearm or hip fractures. Materials and methods: This case–control study included 20 women with a distal forearm fracture and 18 women with a hip fracture as cases and 76 age-matched women served as controls. BMD at the spine, proximal femur, and radius was measured using DXA and acoustic parameters of bone were obtained using a calcaneal QUS device. FRAX® 10-year probability of fracture and ORAI scores were also calculated in all participants. Receiver operating characteristic (ROC) analysis was used to assess fracture discriminatory power of all the tools. Results: While all DXA BMD, and QUS variables and FRAX® fracture probabilities demonstrated significant areas under the ROC curves for the discrimination of hip-fractured women and those without, only 33% radius BMD, broadband ultrasound attenuation (BUA), and FRAX® major osteoporotic fracture probability calculated without BMD showed significant discriminatory power for distal forearm fractures. Conclusions: It can be concluded that QUS variables, particularly BUA, and FRAX® major osteoporotic fracture probability without BMD are good candidates for the identification of both hip and distal forearm fractures.

Positive Association Between Adipose Tissue and Bone Stiffness.

Obesity is often considered to have a protective effect against osteoporosis. On the other hand, several recent studies suggest that adipose tissue may have detrimental effects on bone quality. We therefore aimed to investigate the associations between body mass index (BMI), waist circumference (WC), visceral adipose tissue (VAT) or abdominal subcutaneous adipose tissue (SAT), and bone stiffness. The study involved 2685 German adults aged 20-79 years, who participated in either the second follow-up of the population-based Study of Health in Pomerania (SHIP-2) or the baseline examination of the SHIP-Trend cohort. VAT and abdominal SAT were quantified by magnetic resonance imaging. Bone stiffness was assessed by quantitative ultrasound (QUS) at the heel (Achilles InSight, GE Healthcare). The individual risk for osteoporotic fractures was determined based on the QUS-derived stiffness index and classified in low, medium, and high risk. Linear regression models, adjusted for sex, age, physical activity, smoking status, risky alcohol consumption, diabetes, and height (in models with VAT or abdominal SAT as exposure), revealed positive associations between BMI, WC, VAT or abdominal SAT, and the QUS variables broadband-ultrasound attenuation or stiffness index. Moreover, BMI was positively associated with speed of sound. Our study shows that all anthropometric measures including BMI and, WC as well as abdominal fat volume are positively associated with bone stiffness in the general population. As potential predictors of bone stiffness, VAT and abdominal SAT are not superior to easily available measures like BMI or WC.

The ability of quantitative ultrasound variables to identify osteoporosis in various regions of interest in female corticosteroid users

Searchable abstracts of presentations at key conferences on calcified tissues ISSN 2052-1219 (online)

Measurement Properties of Radial and Tibial Speed of Sound for Screening Bone Fragility in 10- to 12-Year-Old Boys and Girls

The objective of this study was to analyze measurement properties of the radial and tibial speed of sound (SoS) evaluated by quantitative ultrasound (QUS) for screening bone fragility. Bone fragility was defined as low whole body less head bone mineral density (WBLH BMD) measured by DXA (first tertile, 95% CI −1.1 to −0.9) and as past fractures evaluated by questionnaire. The sample included 319 nonobese boys and girls, ages 10–12 yr. All bone variables were standardized. The results revealed concordance coefficient correlations between WBLH BMD and radial and tibial SoS of 0.129 and 0.038, respectively. The regression lines between DXA and QUS variables were different from the identity lines. Cross-classification analysis by Kappa statistic showed that only 34% and 36% of the 113 participants categorized in the first tertile of WBLH BMD were also categorized in the first tertile of tibial and radial SoS, correspondingly. Logistic regression with gender and maturity adjustments demonstrates that radial SoS was the single significant variable in predicting OR for identifying participants with past fractures. In conclusion, the radial QUS revealed itself to be a valuable tool for screening bone fragility in youth of 10–12 yr, despite the absence of agreement with DXA WBLH BMD.

Ultrasound assessment of bone with ultrasound: Present and future

Bone is a composite, porous and anisotropic material whose complex hierarchical structure extends over several levels of organization from the nanoscale to the macroscopic scale. One of the striking features of this tissue is its ability to adapt to variable loading conditions. This results in spatially, temporally and directionally variable elastic properties leading to a perfect adaptation to locally varying functional demands. Elastic properties of bone are nowadays widely used in fundamental studies, in conjunction with numerical models, to investigate the structure-function relationships and in clinical applications to predict fracture risk or to monitor fracture healing. However, the problem of multiscale assessment of bone elastic properties, spanning the full range of applications from in vitro to in vivo applications, remains a challenge. Novel emerging quantitative ultrasound technologies, taking benefit of the scalability of ultrasound, have emerged to noninvasively investigate elastic properties at multiple organization level. These include scanning acoustic microscopy, ultrasonic resonant spectroscopy and guided waves propagation. These techniques will be presented to show how they can help in characterizing the anisotropic stiffness tensor in vitro or determine bone properties in vivo. Relationships of quantitative ultrasound variables with structural and elastic alterations will be illustrated through multiple examples.

A European multicenter comparison of quantitative ultrasound measurement variables: The OPUS study

Quantitative ultrasound (QUS) measurement variables vary between European countries in a different way to hip bone mineral density. Standardization of data can be achieved through statistical approaches to reduce any between-center differences in QUS measurement variables. However, further validation of this method is required before it can be widely applied. European between-center differences in hip bone mineral density (BMD) have been shown to exist; however, little is known about the geographical heterogeneity of QUS measurement variables. We aimed to examine the differences in QUS variables between three different European countries. Five calcaneal and phalangeal QUS devices in Sheffield, Aberdeen (UK), Kiel and Berlin (Germany), and three devices in Paris (France) were used to measure QUS variables in younger (n = 463, 20-39 years old) and older (n = 2,399, 55-79 years old) women participating in the European multicenter Osteoporosis and Ultrasound (OPUS) study. Broadband ultrasound attenuation, speed of sound, stiffness index, amplitude-dependent speed of sound, bone transmission time, and ultrasonic bone profiler index data were collected. Between-center differences were examined using ANOVA followed by post hoc Fisher's least significant difference tests, and ANCOVA with linear contrasts. p < 0.05 indicated statistical significance. Between-center differences in nonstandardized QUS measurement variables existed for younger (p = 0.0023 to p < 0.0001) and older women (p < 0.001). Anthropometric characteristics exerted a significant influence on nonstandardized data (p = 0.045 to p < 0.001). However, following statistical standardization, based on height and weight or based on measurements made in young people, geographical heterogeneity in QUS measurement variables was no longer apparent. QUS measurement variables vary between European countries in a different way to those for hip BMD. Standardization of data can be achieved through statistical approaches to reduce any between-center differences in QUS measurement variables. However, further validation of this method is required before it can be widely applied.

過体重および肥満男性を対象とした形態，体力，体組成および超音波骨指標を用いた骨密度推定式の開発の試み

過体重および肥満男性を対象とした形態，体力，体組成および超音波骨指標を用いた骨密度推定式の開発の試み

Analysis of quantitative ultrasound graphic trace and derived variables assessed at proximal phalanges of the hand in healthy subjects and in patients with cerebral palsy or juvenile idiopathic arthritis.: A pilot study

Amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT) are the quantitative ultrasound (QUS) variables usually assessed at proximal phalanges of the hand to estimate bone mineral status. The aim of the study was to provide a reference database for some additional QUS variables reflecting morphology of the ultrasound graphic trace according to gender, age, height, weight, and body mass index (BMI), and to assess their clinical usefulness. Fifty-two patients (age 3.1–20.9 years) affected by cerebral palsy with spastic tetraplegia (CPST, n = 38) or polyarticular active juvenile idiopathic arthritis (JIA, n = 14) were examined. In addition to AD-SoS and BTT, two QUS variables derived from the morphological analysis of ultrasound graphic trace, such as energy, extrapolated from the area under the ultrasound signal received, and weighted-slope (W-slope), derived from the angular coefficient of the regression line fitting the top point of the peaks of the ultrasound signal, were measured by phalangeal QUS (DBM Sonic, IGEA). The values of all the QUS variables measured in the patients were compared with our own sex- and age-reference values ( n = 1083, 587 males and 496 females, aged 3–21 years). The mean values of AD-SoS, BTT, energy, and W-slope were reduced ( P < 0.0001) in patients as a whole compared with normative data (− 2.4 ± 1.2, − 2.7 ± 1.5, − 2.5 ± 1.1, − 2.5 ± 1.1 Z-score, respectively). Fractured patients showed lower ( P < 0.001– P < 0.0001) values of the QUS variables than fracture-free patients (AD-SoS, − 3.3 ± 1.2 and − 1.8 ± 0.9; BTT, − 3.9 ± 1.7 and − 1.8 ± 1.1; energy, − 3.2 ± 1.2 and − 2.2 ± 0.7; W-slope, − 3.4 ± 1.4 and − 2.2 ± 0.9 Z-score, respectively). There was no difference ( P = NS) between patients with CPST and those with JIA. Age and height were positively correlated with all the QUS variables ( r = 0.55–0.79, P < 0.01– P < 0.0001). QUS variables were positively correlated among them ( r = 0.74–0.94, P < 0.0001). Age and number of fractures were independent predictors of the QUS variables (coefficients: AD-SoS, 11.466 and − 17.642; BTT, 0.049 and − 0.045; energy, 1.072 and − 1.303; W-slope, 0.046 and − 0.067; respectively). In conclusion, measurement of QUS variables derived from the morphological analysis of the ultrasound signal could give additional information in estimating bone mineral status in children and adolescents, probably reflecting some aspect related to bone structure.

Vitamin D status and common risk factors for bone fragility as determinants of quantitative ultrasound variables in a nationally representative population sample

Calcaneal quantitative ultrasound (QUS) can predict bone strength and fracture risk. Bone fragility has no single cause but results from a complex interplay of several etiologic or contributing factors. Vitamin D is essential for bone health even though it is still unclear how much of this vitamin is required to maintain bone strength and prevent fractures. Measurements of serum 25-hydroxyvitamin D [S-25(OH)D] have indicated a high prevalence of inadequate vitamin D status in a number of studies mostly based on selected study populations. The objective of this study was to examine the associations between S-25(OH)D, common risk factors for bone fragility, and QUS variables in a large unselected population sample.The study population consisted of 2736 men and 3299 women from a nationally representative population sample, aged 30 years or over. Information on lifestyle was elicited by means of interviews and questionnaires. Body fat mass was estimated using an impedance-meter. S-25(OH)D was measured by radioimmunoassay. Calcaneal QUS was performed on the Hologic Sahara apparatus recording broadband ultrasound attenuation (BUA) and speed of sound (SOS). The potential determinants of BUA and SOS were analysed using separate multiple linear regression models for men and women.S-25(OH)D proved to be an independent determinant of BUA (P<0.0001 for men, P<0.001 for women) and SOS (P<0.0001 for men, P<0.05 for women). BUA was also independently associated with age, height, weight, alcohol consumption, and postmenopausal status in women, and with weight, alcohol consumption, smoking and physical activity in men. All of the above variables, except for weight in women, were also found to be independent determinants of SOS in both men and women. A reverse association was found between S-25(OH)D and adiposity in spite of higher intakes of vitamin D in those with higher fat mass.In this unselected sample of men and women, vitamin D status, several lifestyle factors and physical characteristics proved to be significant determinants of BUA and SOS. Inadequate vitamin D status was common, and measures ensuring adequate intakes of vitamin D in the population thus deserve continued attention. Obesity should be taken into account in future assessments of vitamin D status in Finland as in other countries.

Sensitivity of QUS parameters to controlled variations of bone strength assessed with a cellular model

The physical principles underlying quantitative ultrasound (QUS) measurements are not fully understood yet. Therefore, the translation of QUS results into bone strength remains elusive. In the present study, we derive the sensitivity of broadband ultrasonic attenuation (BUA) and speed of sound (SOS) to variations of bone strength. For this purpose, a mechanical cellular model is combined to a multiple regression resulting from the analysis of finite-difference time domain (FDTD) simulations. Specifically, we investigate how QUS variables respond to a variation in strength of 10%, realized either by a change in material properties or a change in bone volume fraction (BV/TV). The results show that except when BV/TV is high, the variations of BUA in response to a variation in strength realized by a pure change of BV/TV exceeds the technique imprecision and thus can be detected. When the variation of strength is realized by changes of compressive or shear stiffness, the response in QUS properties is dominated by the variation in C(11), whereas changes in C(44), remaining below the precision error, cannot be detected. The interpretation of these data, however, is not straightforward due to sparse description of elastic properties at the tissue level. To overcome the limitation of the cellular model, more realistic computational models such as micro- finite element analysis have to be considered.

Model-based estimation of quantitative ultrasound variables at the proximal femur

To improve the prediction of the osteoporotic fracture risk at the proximal femur we are developing a scanner for quantitative ultrasound (QUS) measurements at this site. Due to multipath transmission in this complex shaped bone, conventional signal processing techniques developed for QUS measurements at peripheral sites frequently fail. Therefore, we propose a model-based estimation of the QUS variables and analyze the performance of the new algorithm. Applying the proposed method to QUS scans of excised proximal femurs increased the fraction of evaluable signals from approx. 60% (using conventional algorithms) to 97%. The correlation of the standard QUS variables broadband ultrasound attenuation (BUA) and speed of sound (SOS) with the established variable bone mineral density (BMD) reported in previous studies is maintained (BUA/BMD: r(2) = 0.69; SOS/BMD: r(2) = 0.71; SOS+BUA/BMD: r(2) = 0.88). Additionally, different wave types could be clearly detected and characterized in the trochanteric region. The ability to separate superimposed signals with this approach opens up further diagnostic potential for evaluating waves of different sound paths and wave types through bone tissue.

A device for in vivo measurements of quantitative ultrasound variables at the human proximal femur

Quantitative ultrasound (QUS) at the calcaneus has similar power as a bone mineral density (BMD)- measurement using DXA for the prediction of osteoporotic fracture risk. Ultrasound equipment is less expensive than DXA and free of ionizing radiation. As a mechanical wave, QUS has the potential of measuring different bone properties than dual X-ray absorptiometry (DXA,) which depends on X-ray attenuation and might be developed into a tool of comprehensive assessment of bone strength. However, site-specific DXA at the proximal femur shows best performance in the prediction of hip fractures. To combine the potential of QUS with measurements directly at the femur, we developed a device for in vivo QUS measurements at this site. Methods comprise ultrasound transmission through the bone, reflection from the bone surface, and backscatter from the inner trabecular structure. The complete area of the proximal femur can be scanned except at the femoral head, which interferes with the ilium. To avoid edge artifacts, a subregion of the proximal femur in the trochanteric region was selected as measurement region. First, in vivo measurements demonstrate a good signal to noise ratio and proper depiction of the proximal femur on an attenuation image. Our results demonstrate the feasibility of in vivo measurements. Further improvements can be expected by refinement of the scanning technique and data evaluation method to enhance the potential of the new method for the estimation of bone strength.

Relationship between QUS parameters and a cellular model‐ based estimation of bone strength

The final goal of quantitative ultrasound (QUS) techniques is to assess bone strength. However, the translation of QUS results into bone strength remains elusive because the physical principles of ultrasonic propagation in bone are not fully understood yet. Here, the sensitivity of Broadband Ultrasonic Attenuation and Speed of Sound to variations of bone strength is derived. Therefore, a cellular model is combined to a multiple regression analysis resulting from the analysis of finite‐difference time domain (FDTD) simulations coupled with imaging techniques. The variation of QUS variables induced by a variation of strength of 10%, realized either by a change in material properties or a change in bone volume fraction (BV/TV) is investigated. Except when BV/TV is high, the variations of BUA in response to a variation in strength realized by a pure change of BV/TV is higher than the technique imprecision and thus can be detected. When the variation of strength is realized by changes of elastic properties, th...