Quantitative heel ultrasound in 3180 women between 45 and 75 years of age: compliance, normal ranges and relationship to fracture history

Ultrasonic Through-Transmission Measurements of Human Musculoskeletal and Fat Properties

The study described here was aimed at investigating the feasibility of using the ultrasonic through-transmission technique to estimate human musculoskeletal and fat properties. Five hundred eighty-two volunteers were assessed by dual-energy X-ray absorptiometry (DXA) and ultrasonic transmission techniques. Bone mineral density (BMD), muscle and fat mass were measured for both legs and the whole body. Hip BMD and spine BMD were also measured. Ultrasonic transmission measurements were performed on the heel, and the measured parameters were broadband ultrasound attenuation (BUA), speed of sound (SOS), ultrasonic stiffness index (SI), T-score and Z-score, which were significantly correlated with all measured BMDs. The optimal correlation was observed between SI and left-leg BMD (p < 0.001) before and after adjustment for age, sex and body mass index (BMI). The linear and partial correlation analyses revealed that BUA and SOS were closely associated with muscle and fat mass, respectively. Multiple regressions revealed that muscle and fat mass significantly contributed to the prediction of transmission parameters, explaining up to 17.83% (p < 0.001) variance independently of BMD. The results suggest that the ultrasonic through-transmission technique could help in the clinical diagnosis of skeletal and muscular system diseases.

CORRELATIONS BETWEEN ISOMETRIC QUADRICEPS MUSCLE STRENGTH AND BONE MINERAL DENSITY

The purpose of this study was to evaluate the relationship between isometric quadriceps muscle strength and measurements of bone density (BMD), mass (BMC) and ultrasound properties. A total of 113 individuals were included, 53 men and 60 women aged 22-85 years. Isometric quadriceps muscle strength correlated significantly to BMD of the total body for both men (r=0.63, p=0.02) and women r=0.77, p=0.04) after adjustments for age, weight and height. In women, there was also an association between isometric quadriceps muscle strength and BMD of the lumbar spine (r=0.67, p=0.04). These correlations were evident in premenopausal women for BMD at the lumbar spine, femoral neck and total body whereas no significant relationships were seen in postmenopausal women or any age group of men. For isometric quadriceps muscle strength and the ultrasound measurements of the heel, a positive correlation was seen in men and women aged 41-60 years. The findings point to a role of endogenous sex steroids, primarily estrogens, in the correlation between BMD and isometric quadriceps muscle strength.

Quantitative ultrasound normative reference data for community-dwelling white and black females in the United States

Quantitative ultrasound (QUS) race-specific normative reference data are not available for accurate calculation of Z-scores. The primary aims of this study were (1) to develop a race-specific QUS reference database for white and black females and to compare estimated fracture risk between these 2 racial groups and (2) to compare stiffness index (SI) values of white females in this study to manufacturer-obtained values. Subjects included 1111 females (31% black), aged 20-85 yr (52 ± 19 yr), with a mean SI score of 93.7 ± 20.1. White females, aged 20-39 yr (n=213), were used to calculate T-scores, whereas Z-scores were age and race specific. Black females had significantly higher SI scores than white females (p<0.001). White females aged 50+ yr in this study had significantly higher SI scores compared with manufacturer-derived values. Results highlight the need for population- and race-specific normative data when using QUS as a screening tool for identifying high fracture risk.

Association of glycated albumin, but not glycated hemoglobin, with calcaneus quantitative ultrasound in male hemodialysis patients with type 2 diabetes mellitus

Sustained high glucose impairs bone metabolism in patients with type 2 diabetes mellitus (T2DM). In this study, the relationship between glycemic control and bone metabolism was examined in male hemodialysis (HD) patients with T2DM. To avoid the effect of menstruation and the menstrual cycle, obesity, and glycosuria-induced hypercalciuria on bone metabolism, male anuric nonobese HD patients with T2DM (n = 42) were enrolled. Calcaneus stiffness index (SI) was determined using ultrasound after HD session. Casual plasma glucose (PG), glycated hemoglobin (HbA(1c)), and glycated albumin (GA) were measured before the HD session. In simple regression analysis, log PG (r = -0.333, P < .05) and log GA (r = -0.350, P < .05), but not log HbA(1c) (r = -0.134, P = .3985), exhibited significant and negative correlations with calcaneus SI. In multiple regression analysis including log BMI, log cCa x Pi product, and log PG, log PG was associated significantly in a negative manner with calcaneus SI, in addition to log cCa x Pi product. When log PG was replaced with log GA or log HbA(1c), log GA, but not log HbA(1c), emerged as a significant factor associated. The mechanism as to why HbA(1c) failed to associate could be explained by its false reduction by erythropoietin injection. The present study supported the notion of GA as an appropriate indicator for glycemic control in HD patients with T2DM. Furthermore, it is suggested that poor glycemic control might be a significant factor toward decreasing calcaneus SI in T2DM HD patients.

Mineralization density and apparent density in mandibular condyle bone

OBJECTIVES

This study evaluated a method for determining the density and distribution of bone of mandibular condyles using proprietary computerized tomography (CT) software.

STUDY DESIGN

Thirty-eight condylar specimens were investigated with a high-resolution multislice CT. The density was determined by using bone density analysis algorithms available within the proprietary software. Apparent density was estimated over the total cross-sectional area, the total trabecular bone area apart from the cortical fraction, and on individually selected points. Color-coded pictures were created to demonstrate density differences.

RESULTS

The cortical bone presented significantly higher densities than the trabecular bone. The anterior cortical bone had significantly higher densities than the posterior. The central anterior cortical and the central trabecular areas showed significantly higher densities than the medial and lateral areas.

CONCLUSION

This technique proved to be a valuable method for determination of the differences in density in the mandibular condyle. It shows potential in providing clinicians with an imaging modality for specific clinical use.

Imaging of metabolic bone diseases

Osteoporosis is a serious public health problem. The incidence of osteoporotic fractures increases with age. As life expectancy increases, social costs associated with osteoporotic fractures will multiply exponentially. The early diagnosis of osteoporosis, thanks to evermore precise devices, becomes, therefore, fundamental to prevent complications of disease and unnecessary suffering.

Mechanisms for attenuation in cancellous-bone-mimicking phantoms

Broadband ultrasound attenuation (BUA) in cancellous bone is useful for prediction of osteoporotic fracture risk, but its causes are not well understood. To investigate attenuation mechanisms, 9 cancellous-bone-mimicking phantoms containing nylon filaments (simulating bone trabeculae) embedded within soft-tissue-mimicking fluid (simulating marrow) were interrogated. The measurements of frequency-dependent attenuation coefficient had 3 separable components: 1) a linear (with frequency) component attributable to absorption in the soft-tissue-mimicking fluid, 2) a quasilinear (with frequency) component, which may include absorption in and longitudinal-shear mode conversion by the nylon filaments, and 3) a nonlinear (with frequency) component, which may be attributable to longitudinal-longitudinal scattering by the nylon filaments. The slope of total linear (with frequency) attenuation coefficient (sum of components #1 and #2) versus frequency was found to increase linearly with volume fraction, consistent with reported measurements on cancellous bone. Backscatter coefficient measurements in the 9 phantoms supported the claim that the nonlinear (with frequency) component of attenuation coefficient (component #3) was closely associated with longitudinal-longitudinal scattering. This work represents the first experimental separation of these 3 components of attenuation in cancellous bone-mimicking phantoms.

Ultrasonic scattering from cancellous bone: a review

This paper reviews theory, measurements, and computer simulations of scattering from cancellous bone reported by many laboratories. Three theoretical models (binary mixture, Faran cylinder, and weak scattering) for scattering from cancellous bone have demonstrated some consistency with measurements of backscatter. Backscatter is moderately correlated with bone mineral density in human calcaneus in vitro (r(2) = 0.66 - 0.68). Backscatter varies approximately as frequency cubed and trabecular thickness cubed in human calcaneus and femur in vitro. Backscatter from human calcaneus and bovine tibia exhibits substantial anisotropy. So far, backscatter has demonstrated only modest clinical utility. Computer simulation models have helped to elucidate mechanisms underlying scattering from cancellous bones.

A method for improved standardization of in vivo calcaneal time-domain speed-of-sound measurements

Although calcaneal speed of sound (SOS) is an effective predictor of osteoporotic fracture risk, clinical SOS measurements exhibit a high degree of inter-system variability. Calcaneal SOS is usually computed from time-of-flight measurements of broadband ultrasound pulses that propagate through the foot. In order to minimize the effects of multi-path interference, many investigators measure time-of-flight from markers near the leading edge of the pulse. The calcaneus is a highly attenuating, highly inhomogeneous bone that distorts propagating ultrasound pulses via frequency-dependent attenuation, reverberation, dispersion, multiple scattering, and refraction. This pulse distortion can produce errors in leading-edge transit-time marker-based SOS measurements. In this paper, an equation to predict dependence of time-domain SOS measurements on system parameters (center frequency and bandwidth), transit-time marker location, and bone properties (attenuation coefficient and thickness) is validated with through-transmission measurements in a bone-mimicking phantom and in 73 women in vivo, using a clinical bone sonometer. In order to test the utility of the formula for suppressing system dependence of SOS measurements, a wideband laboratory data acquisition system was used to make a second set of through-transmission measurements on the phantom. The compensation formula reduced system-dependent leading-edge transit-time marker-based SOS measurements in the phantom from 41 m/s to 5 m/s and reduced average transit-time marker-related SOS variability in 73 women from 40 m/s to 10 m/s. The compensation formula can be used to improve standardization in bone sonometry.

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).

Quantitative ultrasound calcaneous measurements: normative data for the Italian population. the ESOPO study

Quantitative ultrasound (QUS) is a reliable technique to evaluate skeletal status, to identify osteoporotic subjects, and to estimate the risk of fractures. The purpose of this study was to generate QUS normative data for Italian females and males aged 60-79 yr participating in the Epidemiologic Study on the Prevalence of Osteoporosis (ESOPO) study, using the Achilles Plus apparatus. ESOPO is a cross-sectional study conducted in 2000, aiming at assessing risk of osteoporosis in a random sample of 11,011 women and 4981 men, representative of the Italian population. All participants were administered a questionnaire on the most relevant risk factors for osteoporosis and fractures; 3 QUS parameters were also measured: broadband ultrasound attenuation (BUA); speed of sound (SOS); and Stiffness Index (SI). We studied the age-dependent changes in QUS values, and their correlation with body size. For both men and women, weight was the variable with the highest correlation with BUA and SI; for SOS, age among women and body mass index (BMI) among men presented the highest correlation coefficients. Average decreases of 3.0% in BUA, 0.8% in SOS, and 9.1% in SI from 60 to 79 yr were detected for females, whereas no significant changes with age in males were observed. Our data show lower QUS values for women, and a decline at a greater rate than in men.

The dependence of time-domain speed-of-sound measurements on center frequency, bandwidth, and transit-time marker in human calcaneus in vitro

Time-domain speed-of-sound (SOS) measurements in calcaneus are effective predictors of osteoporotic fracture risk. High attenuation and dispersion in bone, however, produce severe distortion of transmitted pulses that leads to ambiguity of time-domain SOS measurements. An equation to predict the effects of system parameters (center frequency and bandwidth), algorithm parameters (pulse arrival-time marker), and bone properties (attenuation coefficient and thickness) on time-domain SOS estimates is derived for media with attenuation that varies linearly with frequency. The equation is validated using data from a bone-mimicking phantom and from 30 human calcaneus samples in vitro. The data suggest that the effects of dispersion are small compared with the effects of frequency-dependent attenuation. The equation can be used to retroactively compensate data. System-related variations in SOS are shown to decrease as the pulse-arrival-time marker is moved toward the pulse center. Therefore, compared with other time-domain measures of SOS, group velocity exhibits the minimum system dependence.

The effect of phase cancellation on estimates of calcaneal broadband ultrasound attenuation in vivo

Broadband ultrasonic attenuation (BUA) is a clinically-accepted measurement for prediction of osteoporotic fracture risk. Typical clinical BUA measurements are performed with phase-sensitive receivers and, therefore, can be affected by phase cancellation. In order to separate the effects of conventional attenuation (absorption plus scattering) from phase cancellation, BUA was measured on phantoms with acrylic wedge phase aberrators and on 73 women using both phase sensitive (PS) and phase insensitive (PI) reception. A clinical bone sonometer with a two-dimensional (2-D) receiver array was used. PI BUA measurements on phantoms with acrylic wedge phase aberrators were found to be far more resistant to phase cancellation than PS BUA measurements. In data from 73 women, means and standard deviations for BUA measurements were 81.4 +/- 21.4 dB/MHz (PS) and 67.2 +/- 9.7 dB/MHz (PI). The magnitude of the discrepancy between PS BUA and PI BUA tended to increase with bone mineral density (BMD).

More acidic dietary acid-base load is associated with reduced calcaneal broadband ultrasound attenuation in women but not in men: results from the EPIC-Norfolk cohort study

BACKGROUND

Dietary patterns that promote mild metabolic acidosis may have a negative effect on bone density.

OBJECTIVE

We investigated the relation between a measure of dietary acid-base load, potential renal acid load (PRAL), and calcaneal broadband ultrasound attenuation (BUA) after adjustment for confounders and also compared the results with different estimates of acid-base load.

DESIGN

A cross-sectional study was conducted in 14 563 men and women aged 42-82 y living in Norfolk, United Kingdom, in which measures of calcaneal BUA and dietary PRAL were estimated by using the European Prospective Investigation into Cancer and Nutrition Norfolk (EPIC-Norfolk) food-frequency questionnaire.

RESULTS

A more acidic dietary intake (high PRAL) was significantly associated with lower calcaneal BUA in women but not in men; there was a difference of approximately 2% in BUA between the highest and lowest quintiles of PRAL, independent of age, body mass index, smoking habit, physical activity, diagnosed osteoporosis, and history of fracture, and (in women) hormone replacement therapy. No relation was observed between history of fracture or incident fracture and PRAL. Those with the greatest PRAL had higher intakes of meat, fish, eggs, and cereal and cereal products and lower intakes of fruit and vegetables, tea, and coffee.

CONCLUSION

PRAL was inversely associated with bone ultrasound measures in women, but the magnitude of the association was relatively small compared with other known risk factors. Further longitudinal studies are required to establish whether, in the long term, these small effects are important in overall fracture risk in populations.

Group velocity, phase velocity, and dispersion in human calcaneus in vivo

Commercial bone sonometers measure broadband ultrasonic attenuation and/or speed of sound (SOS) in order to assess bone status. Phase velocity, which is usually measured in frequency domain, is a fundamental material property of bone that is related to SOS, which is usually measured in time domain. Four previous in vitro studies indicate that phase velocity in human cancellous bone decreases with frequency (i.e., negative dispersion). In order to investigate frequency-dependent phase velocity in vivo, through-transmission measurements were performed in 73 women using a GE Lunar Achilles Insight commercial bone sonometer. Average phase velocity at 500 kHz was 1489 +/- 55 m/s (mean +/- standard deviation). Average dispersion rate was -59 +/- 52 m/sMHz. Group velocity was usually lower than phase velocity, as is expected for negatively dispersive media. Using a stratified model to represent cancellous bone, the reductions in phase velocity and dispersion rate in vivo as opposed to in vitro can be explained by (1) the presence of marrow instead of water as a fluid filler, and (2) the decreased porosity of bones of living (compared with deceased) subjects.

Identifying osteoporosis in a primary care setting with quantitative ultrasound: relationship to anthropometric and lifestyle factors

Dual-energy X-ray absorptiometry (DXA), the "gold standard" for diagnosis of osteoporosis, is not recommended for population screening, and thus quantitative ultrasound (QUS) of the calcaneus is gaining popularity. The aim of the present study was to evaluate the relationship between QUS values and anthropometric and lifestyle factors, and to assess the diagnostic performance of QUS in predicting DXA-defined osteoporosis. Eight hundred and thirty-two women and 87 men aged 40-88 years were included in the study. Anthropometric measurements, the questionnaire, and QUS and DXA measurements were performed by trained physicians. Both QUS and DXA T-scores were lower for women than for men. Postmenopausal women had significantly lower QUS T-scores compared to premenopausal women (P < 0.001). Age over 50, female sex, sedentary lifestyle, fracture history, presence of chronic disease, and > or =5 years since menopause were associated with QUS T-scores lower than -1.00 by multivariate analysis. Low QUS T-scores were related to lack of direct sun exposure, high parity, fair skin color, and no education by univariate analysis (P < 0.005). A weak correlation was found between calcaneal QUS and DXA T-scores at lumbar spine (r = 0.310, P < 0.001) and femoral neck (r = 0.288, P < 0.001). The sensitivity and specificity of the QUS test were 73.7% and 57.4%, respectively, regarding the identification of osteoporotic patients. Lower QUS T-scores were associated with several osteoporotic risk factors, and the sensitivity and specificity of QUS for predicting DXA-defined osteoporosis were at optimum values at ages between 50 and 59 years. We conclude that, even though the accuracy of QUS for predicting DXA-defined osteoporosis is not remarkably high, it can be applied to identify subjects at risk in this age group in developing countries and rural districts who should be the focus of fracture prevention.

Plasma organochlorine concentrations and bone ultrasound measurements: a cross-sectional study in peri-and postmenopausal Inuit women from Greenland

BACKGROUND

Inuit women are highly exposed through their traditional seafood based diet to organochlorine compounds, some of them displaying endocrine disrupting properties. We hypothesized that this exposure might be related to bone characteristics that are altered in osteoporosis, because hormone deficiency is a known risk factor for the disease.

METHODS

We measured quantitative ultrasound parameters (QUS) at the right calcaneum of 153 peri- and postmenopausal Inuit women (49-64 year old) from Nuuk, Greenland, and investigated the relation between these parameters and plasma organochlorine concentrations. We used high-resolution gas chromatography with electron capture detection to analyze plasma samples for 14 polychlorinated biphenyls (PCB) congeners and 11 chlorinated pesticides and metabolites. We analysed morning urine samples for cadmium, a potential confounder, by atomic absorption spectrometry. We used a validated questionnaire to document dietary and lifestyle habits as well as reproductive and medical histories.

RESULTS

Concentrations of PCB 153, a surrogate of exposure to most organochlorines present in plasma samples, were inversely correlated to QUS parameters in univariate analyses (p < 0.001). However, PCB 153 concentrations were not associated with QUS values in multivariate analyses that comprised potential confounding factors such as age, body weight, former oral contraceptive use and current hormone replacement therapy (HRT) use, which were all significant predictors of bone stiffness (total R2 = 0.39; p < 0.001).

CONCLUSION

Overall we found little evidence that organochlorines exposure is related to osteoporosis in Greenlandic Inuit women, but the hypothesis that exposure to dioxin-like compounds might be linked to decreased bone quality and osteoporosis deserves further attention.

Relationship between risk factors and QUS in a European Population: The OPUS study

There are many risk factors associated with low bone mineral density. Quantitative ultrasound (QUS) is a generally accepted method for measurement of bone and has been shown to be strongly associated with future fracture risk. The Osteoporosis and Ultrasound Study (OPUS) is a multi-centre European wide study examining 5 different QUS scanners (4 calcaneal, 1 finger device). The aim of this paper was to examine the relationship between risk factors (as assessed by questionnaire) and QUS measurements. 449 younger women (aged 20 to 39 years) and 2283 older women (aged 55 to 79 years) were included in this analysis. As expected, those with a self-reported previous fracture had lower QUS measurements than those without (P < 0.001). However, no significant difference was seen between those reporting a maternal hip fracture and those who did not report such an event. Differences were found for smokers vs. non-smokers for SOS but not for BUA measurements. Weight was positively correlated with all BUA variables but only with some SOS variables. We determined which risk factors were most strongly associated with QUS measurements by using step-wise multiple regression. Models for each QUS measurement were calculated, and the R2 values ranged from 0.18 to 0.28 for SOS, 0.27 to 0.32 for BUA and 0.31 to 0.42 for the finger QUS device. The most common risk factors across all models were age, use of hormone replacement therapy, self-reported previous fracture, self-reported diagnosis of osteoporosis, current weight, pulse rate and self-reported estimated height at age 20 years. We analysed relationships across the 5 centres and detected some geographical differences in the prevalence of the risk factors. In conclusion, similar relationships are seen with QUS measurements as are found for bone mineral density. However, the strength of the association is dependent on the type of QUS device and variable measured.

Assessment of low quantitative ultrasound values of calcaneus in Chinese mainland women

Calcaneus quantitative ultrasound (QUS) assessment is a safe and reliable method for evaluating skeletal status. Until now, considerable data have been accumulated on the distribution of QUS in Caucasian populations, whereas such data are still insufficient in Asian populations, especially in Chinese mainland. The present study aimed to obtain the distribution characteristic of calcaneus QUS in healthy Chinese women, and to further investigate the distribution of low bone mass by QUS stiffness index (SI). This study included 2,498 healthy Chinese females aged 10-87 yr. The QUS exhibited a characteristic mild rise and then fall pattern with increasing age. Age, body height, and weight were significant influencing factors on SI, especially age and weight. The prevalence of osteoporosis detected using instrument-derived T-score or internal T-score was different from that calculated according to calcaneus bone mass density (BMD) previously reported. Furthermore, between instrument-derived T-scores and internal T-scores, there were also significant differences. We concluded that the World Health Organization criteria from BMD may not be appropriate for QUS, and the instrument-derived T-score may also not be appropriate for the studied population. The results will be useful for predicting fracture risk of Chinese women and determining diagnostic criteria of osteoporosis by QUS.

Long-term fracture prediction by DXA and QUS: a 10-year prospective study

This study investigated the ability of DXA and QUS to predict fractures long term when measured around the time of the menopause. We found both DXA and QUS are able to predict both any fracture and "osteoporotic" fractures and that QUS can predict independently of BMD.

INTRODUCTION

There are now many treatments available for prevention of osteoporotic fracture. To be cost-effective, we need to target those most at risk. This study examines the ability of DXA and QUS to predict fractures in an early postmenopausal population of women.

MATERIALS AND METHODS

We prospectively measured 3883 women who had been randomly selected from a community-based register. At baseline, they were measured using DXA of spine and hip (Norland XR-26) and QUS of the heel (Walker Sonix UBA 575). Follow-up had a mean of 9.7 +/- 1.1 (SD) years. All incident fractures were identified and validated by examination of X-ray reports, and these were compared with those without fracture in a Cox-regression model to calculate hazard ratios (HRs).

RESULTS

We found adjusted HRs for any fracture per 1 SD reduction in spine BMD to be 1.61 (1.42-1.83), whereas neck of femur BMD was 1.54 (1.34-1.75). Areas under the curve (AUC) for a receiver operator characteristic (ROC) analysis were 0.62 for spine BMD and 0.59 for neck BMD. In a subgroup where QUS was also measured, the HR for a 1 SD reduction in BMD was 1.69 (1.29-2.22) for spine BMD and 1.55 (1.17-2.06) for neck BMD. The HR for a 1 SD reduction in broadband ultrasound attenuation (BUA) was 1.53 (1.19-1.96), and 1.44 (1.12-1.86) when further adjusted for neck BMD. The AUCs were 0.63 for spine BMD, 0.59 for neck BMD, and 0.62 for BUA. When only osteoporotic fractures were examined, the HRs increased in all situations. BUA showed the highest HR of 2.25 (1.51-3.34), and when further adjusted for neck BMD was 2.12 (1.38-3.28).

CONCLUSIONS

In conclusion, it may be possible to scan women around the time of the menopause to predict future fractures. It seems that, for "osteoporotic" fractures, BUA may be an improved predictor of fractures in comparison with DXA, because the relative risk is highest for BUA, and independent of BMD.

Characteristics of calcaneus quantitative ultrasound normative data in Chinese mainland men and women

INTRODUCTION

Quantitative ultrasound (QUS) assessment at the calcaneus, as a safe and reliable method for evaluating skeletal status, is rapidly gaining in popularity. Assessment by QUS provides three parameters of skeletal status: broadband ultrasound attenuation (BUA), speed of sound (SOS) and derived data-stiffness index (STI). The objective of the present study was firstly to determine the normative QUS data on healthy Chinese mainland men and women and secondly to investigate the effects of sex, age and body size on these three QUS parameters.

METHODS

A study cohort consisting of 725 healthy Chinese women and 568 men aged 10-83 years participated in this investigation. The three QUS parameters all exhibited a characteristic mild rise-then-fall pattern with increasing age in both sexes. Younger men and women had similar QUS values, while older women had lower values than older men. Age-related differences were more pronounced among females. Pearson's correlation and regression analysis showed that weight was a major determinant of QUS in both sexes, along with age.

RESULTS

There were some discrepancies between our data and results from other populations, even when the same type of QUS instrument was used, probably as a result of various factors, including ethnic, life-style environment and diet, among others.

CONCLUSIONS

These normative data will be useful for comparing the results of individual studies, predicting fracture risk of Chinese men and women and determining diagnostic criteria of osteoporosis by QUS.

The dependencies of phase velocity and dispersion on trabecular thickness and spacing in trabecular bone-mimicking phantoms

Frequency-dependent phase velocity was measured in trabecular-bone-mimicking phantoms consisting of two-dimensional arrays of parallel nylon wires (simulating trabeculae) with thicknesses ranging from 152 to 305 microm and spacings ranging from 700 to 1000 microm. Phase velocity varied approximately linearly with frequency over the range from 400 to 750 kHz. Dispersion was characterized by the slope of a linear least-squares regression fit to phase velocity versus frequency data. The increase in phase velocity (compared with that in water) at 500 kHz was approximately proportional to the (1) square of trabecular thickness, (2) inverse square of trabecular spacing, and (3) volume fraction occupied by nylon wires. The first derivative of phase velocity with respect to frequency was negative and exhibited nonlinear, monotonically decreasing dependencies on trabecular thickness and volume fraction. The dependencies of phase velocity and its first derivative on volume fraction in the phantoms were consistent with those reported in trabecular bone.

In vitro speed of sound measurement at intact human femur specimens

Quantitative ultrasound has been recognized as a useful tool for fracture risk prediction. Current measurement techniques are limited to peripheral skeletal sites. Our objective was to demonstrate the in vitro feasibility of ultrasonic velocity measurements on human proximal femur and to investigate the relationship between velocity and bone mineral density (BMD). Sound velocity images were computed from 2-D scans performed on 38 excised human femurs in transmission at 0.5 MHz. Different regions-of-interest were investigated. Dual x-ray absorptiometry scans have been achieved for BMD measurements in site-matched regions. Our study demonstrates the feasibility of ultrasonic velocity measurements at the hip with reasonable precision (coefficient of variation of 0.3%). The best prediction of BMD was reached in the intertrochanter region (r(2) = 0.91, p < 10(-4)), with a residual error of 0.06 g/cm(2) (10%). Because BMD measured at the femur is the best predictor of hip fracture risk, the highly significant correlation and small residual error found in this study suggest that speed of sound measurement at the femur might be a good candidate for hip fracture risk prediction.

Quantitative ultrasound calcaneus measurements: normative data for the Greek population

Quantitative ultrasound (QUS) is a peripheral bone densitometry technique that is rapidly gaining in popularity, and is widely used worldwide for the assessment of skeletal status. This, however, generally occurs in the absence of adequate clinical guidelines. As accurate interpretation of the results and correct classification in individual fracture risk assessment are of great value, the present study was carried out to establish a reference database for calcaneal QUS measurements across age group and gender in Greece. A total of 1205 subjects (821 females and 384 males) from three age groups (409 children, 341 adults and 455 elderly) were recruited. QUS measurements were performed at the heel with the Sahara device, which measures broadband ultrasound attenuation (BUA) and speed of sound (SOS), and then combines these variables into a single parameter, the quantitative ultrasound index (QUI). Overall, gender-related differences were more pronounced among the elderly, while age-related differences were more pronounced among females. Elderly men had higher QUS parameters than women of peer age, but no major gender differences were observed in children and adults. In males, only BUA showed a variation with age, being higher in adult and elderly men compared to boys. On the other hand, all QUS parameters varied significantly with age in females, the general trends being mildly positive from childhood to adulthood, when peak levels were observed, and negative thereafter. The results for the Greek population were in the range reported previously for other populations, but some discrepancies were evident, probably resulting from ethno-specific characteristics and different QUS instrumentation. Importantly, using the manufacturer's or the local database as the reference population for computing T-scores led to significantly different classification of subjects into conventional categories of risk. These data could be useful as a guide for comparing the results of individual studies, as well as for the assessment of Greek men and women at risk of fracture.

The risk of Colles' fracture is associated with the collagen I alpha1 Sp1 polymorphism and ultrasound transmission velocity in the calcaneus only in heavier postmenopausal women

To compare the ability of the bone mineral density (BMD) at the distal forearm, collagen I alpha 1 (COLIA1) polymorphism, and ultrasound stiffness to identify individuals with increased risk of wrist fracture, we studied 183 postmenopausal Czech women with a wrist fracture and 178 postmenopausal controls, ages 45-70 years. The genotypes "Ss" and "ss" were significantly overrepresented among fracture cases. The BMD measurements at the femoral neck, total femur, and distal forearm as well as ultrasound stiffness of the heel, broadband ultrasound attenuation (BUA), and speed of sound (SOS) were significantly lower in the fracture cohort. BMD of the distal forearm was the main determinant of susceptibility to the wrist fracture. Weight, the COLIA1 genotype, and ultrasound SOS further strengthened the predictive value of BMD. However, we found interaction between weight and both the COLIA1 Sp1 polymorphism and ultrasound parameters. Presence of the "s" allele as well as low SOS acted as significant predictors of wrist fracture only in heavier women, (> or =62 kg) but not in women with a body weight of less than 62 kg. In heavier women, both the COLIA1 Sp1 polymorphism and ultrasound parameters acted as independent markers that contributed to BMD to enhance fracture prediction. However, the COLIA1 enabled a higher specificity (specificity 72.4%, sensitivity 44.2%), whereas SOS enabled a higher sensitivity (sensitivity 73.9%, specificity, 45.7%). We conclude that BMD at total forearm, the COLIA1 polymorphism, and ultrasound SOS are independent predictors of wrist fracture in postmenopausal women. The effect of the COLIA1 Sp1 polymorphism and SOS on wrist fracture risk is more pronounced in patients with a higher body weight.

In vitro ultrasound measurement at the human femur

Measurements of broadband ultrasonic attenuation (BUA) represent an established means of skeletal status assessment in osteoporosis. Today, the skeletal site that is the most widely used clinically is the calcaneus (heel bone). However, we hypothesized that fracture risk predictions could be improved if ultrasound measurements were performed directly at the main site of fracture, e.g., the proximal femur. The goal of this paper is to demonstrate in vitro the feasibility of quantitative ultra sound (QUS) imaging at the upper part of fee femur, and to investigate the relationships of BUA to bone mineral density (BMD). Forty-four excise human femurs were measured in transmission with a pair of focused 0.5-MHz central frequency transducers. Two-dimensional scans were performed, and the radio frequency (rf) signals were recorded at each measurement point. A data acceptance criterion for region of interest (ROI) selection was established based on the linearity of the frequency-dependent attenuation. Five measurements with repositioning were performed on each sample to determine the reproducibility. Dual energy x-ray absorptiometry (DXA) scans have been performed on the samples for BMD measurements: Three ROIs were selected in the specimens: greater, trochanter intertrochanteric, and femoral neck regions. Coefficient of variations were in the range 1.6% to 2.5%. The determination coefficients (r(2)) between BUA and BMD in site-matched ROIs were 0.81, 0.78, and 0.73, respectively, for the greater trochanteric, intertrochanteric, and femoral neck regions. Our results are consistent with data previously shown at the calcaneus and demonstrate the feasibility of QUS measurements at the femur in vitro, with reasonable reproducibility.

Evaluation of an osteoporosis self-referral program to enhance management outcomes

Osteoporosis is a common but undertreated condition. While bone density is known to predict fracture risk, there is currently no economical way of measuring general population risk. This study examined whether an economical screening technique could improve diagnosis and lead to appropriate outcomes in the management of osteoporosis. A self-referral program was established to provide women with information about osteoporosis and an individualized risk assignment. A high-risk designation was provided for postmenopausal women below the lower tertile of a calcaneal broadband ultrasound attenuation (BUA) (< or = 58 db/MHz) or those with a SCORE value > or = 6. A telephone survey was conducted 6 mo after program registration to evaluate osteoporosis management outcomes. Of 271 women surveyed, 181 (67%) were postmenopausal and thus potential candidates for estrogen replacement, and 21% and 63% were assigned a high-risk profile by either calcaneal ultrasound or SCORE, respectively. Women at higher risk were significantly more likely to discuss osteoporosis with their family physician (p < 0.001), and to undergo further testing with dual X-ray absorptiometry measurement (p < 0.005). Utilization of estrogen replacement by postmenopausal women at time of survey was significantly increased compared to registration (p = 0.01). The self-referral program positively impacted decisions women made about preventing osteoporosis, particularly if they considered themselves at higher risk.

Do appendicular bone measurements reflect changes in the axial skeleton?: the use of dual-energy X-ray absorptiometry and ultrasound measurements during lactation

The ability of different bone measurement techniques to monitor changes in bone mineral was studied. Lactation was used as a model because large, rapid, but reversible decreases in bone mineral content (BMC) occur in breast-feeding women. Spine and forearm dual-energy X-ray absorptiometry (DXA) and calcaneal quantitative ultrasound (QUS) measurements were made during 30 lactations. During the first 3 mo of lactation, decreases in the BMC, adjusted for area, were significant at the spine (-2.8%; standard error [SE] = 0.6; p < 0.001) but not the wrist (p = 0.40). Nonsignificant increases in normalized broadband ultrasound attenuation (nBUA) and velocity of sound (VOS) were observed at the calcaneus using QUS. From peak lactation to postlactation, the BMC increases at the spine were significant (4.1%; SE = 0.6; p < 0.001) but not those at the wrist (p = 0.17). Nonsignificant decreases were observed using QUS. Eleven breast-feeding women had longitudinal calcaneal and spine DXA measurements from peak lactation to postlactation. Significant BMC increases were observed at both sites (calcaneus: 2.4%, SE = 0.7, p < 0.01; spine: 3.3%, SE = 1.3, p < 0.03). The similarity of DXA calcaneal changes to spine changes indicates that DXA calcaneal measurements could be a useful alternative tool when it is difficult to monitor BMC at axial sites.

The dependence of ultrasonic backscatter on trabecular thickness in human calcaneus: theoretical and experimental results

Trabecular thickness within cancellous bone is an important determinant of osteoporotic fracture risk. Noninvasive assessment of trabecular thickness potentially could yield useful diagnostic information. Faran's theory of elastic scattering from a cylindrical object immersed in a fluid has been used to predict the dependence of ultrasonic backscatter on trabecular thickness. The theory predicts that, in the range of morphological and material properties expected for trabecular bone, the backscatter coefficient at 500 kHz should be approximately proportional to trabecular thickness to the power of 2.9. Experimental measurements of backscatter coefficient were performed on 43 human calcaneus samples in vitro. Mean trabecular thicknesses on the 43 samples were assessed using micro computed tomography (CT). A power law fit to the data showed that the backscatter coefficient empirically varied as trabecular thickness to the 2.8 power. The 95% confidence interval for this exponent was 1.7 to 3.9. The square of the correlation coefficient for the linear regression to the log transformed data was 0.40. This suggests that 40% of variations in backscatter may be attributed to variations in trabecular thickness. These results reinforce previous studies that offered validation for the Faran cylinder model for prediction of scattering properties of cancellous bone, and provide added evidence for the potential diagnostic utility of the backscatter measurement.

Performance of quantitative ultrasound in the discrimination of prevalent osteoporotic fractures in a bone metabolic unit

There is a growing interest in ultrasound evaluation of bone status as an alternative to the measurement with dual X-ray absorptiometry (DXA), due to its low cost, portability, and nonionizing radiation. The aim of our study was to investigate the relation among DXA, QUS, clinical, anthropometric, and lifestyle factors, and to determine QUS cutoff values in order to discriminate fractures in patients referred to the Bone Metabolic Unit at an Endocrinology Service. We studied 300 patients (281 females and 19 males; age 58 +/- 11 years) referred for evaluation of osteoporosis. In all cases we determined basic anthropometric parameters, a clinical history including previous osteoporotic fractures and risk factors for osteoporosis, and QUS parameters in calcaneus (Hologic Sahara), and BMD in lumbar spine (LS) and femoral neck (FN), by DXA (Hologic QDR 1000). Using the WHO densitometric criteria, 37, 46.7, and 16.3% of our population were osteoporotic, osteopenic, and normal, respectively. A QUI T-score </=-1.5 SD provided a sensitivity of 68.9% and a specificity of 64.7% for osteoporotic fracture discrimination and a sensitivity of 64.9% and a specificity of 74.1% for osteoporosis defined by WHO criteria using DXA. In the logistic regression, the presence of family history of fragility fractures (OR: 3.03; CI 95%: 1.3-7.03), a DXA T-score </=-2.5 (OR: 3.58; CI 95%: 1.66-7.73), and a QUI T-score </=-1.5 (OR: 2.56; CI 95%: 1.15-5.69) were independently associated with prevalent osteoporotic fractures. In conclusion, calcaneus ultrasound appears as a useful technique for the routine clinical practice, as its performance is similar to DXA for the discrimination of subjects with osteoporotic fracture.

The effect of age, weight, and lifestyle factors on calcaneal quantitative ultrasound: the ESOPO study

Quantitative ultrasound (QUS) techniques have been shown to be as good as bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry (DXA), in predicting fracture risk: QUS technique could increase substantially the accessibility to a reliable bone osteoporosis risk evaluation, but little is know regarding the relationship of QUS to risk factors that have been found to predict DXA-BMD values and this is even more true in men. We studied 6,811 postmenopausal women 40 to 80 years of age and 4,981 men 60-80 years of age representative of the general population of all regions of Italy. All participants were questioned on lifestyle habits and on their medical history. After a physical examination "bone stiffness" (called here for simplicity, stiffness), which is derived from the values of broadband ultrasound attenuation (BUA) and speed of sounds (SoS) was measured by a heel QUS device (Achilles apparatus, Lunar, Madison, USA). The most common recognized determinants of bone mass (either categorical or continuous variables) were modeled with stiffness by multiple regression analysis or ANOVA. Stiffness was strongly related to age and weight. After adjusting for these variables, the women who had taken hormone replacement therapy for more than a year had significantly higher stiffness values. The difference versus nonusers remained significant for up to 20 years-since-menopause (YSM). This effect was so strong that for further analysis these women were excluded. By multivariate analysis, stiffness was then found to be significantly related to recalled body weight at 25 years of age, actual and past cigarettes smoked per day, and dairy calcium intake. Stiffness was also associated with a number of categorial factors adjusted for age, weight, and YSM: prior ovariectomy, history of more than 2 months confined to bed, outdoor physical activity, smoking, chronic use of any drug, and past corticosteroid use. All these categorial and continuous variables predicted stiffness equally in men and women. In conclusion, QUS bone measurements discriminate postmenopausal women according to past use of hormone replacement therapy. Risk factors usually associated to BMD as measured by DXA are also associated to calcaneal bone stiffness as measured by QUS, and most risk factors for osteoporosis usually observed in women are equally applicable to men.

Characterization of trabecular bone using the backscattered spectral centroid shift

Ultrasonic attenuation in bone in vivo is generally measured using a through-transmission method at the calcaneus. Although attenuation in calcaneus has been demonstrated to be a useful predictor for osteoporotic fracture risk, measurements at other clinically important sites, such as hip and spine, could potentially contain additional useful diagnostic information. Through-transmission measurements may not be feasible at these sites due to complex bone shapes and the increased amount of intervening soft tissue. Centroid shift from the backscattered signal is an index of attenuation slope and has been used previously to characterize soft tissues. In this paper, centroid shift from signals backscattered from 30 trabecular bone samples in vitro were measured. Attenuation slope also was measured using a through-transmission method. The correlation coefficient between centroid shift and attenuation slope was -0.71. The 95% confidence interval was (-0.86, -0.47). These results suggest that the backscattered spectral centroid shift may contain useful diagnostic information potentially applicable to hip and spine.

A comparison of calcaneal dual-energy X-ray absorptiometry and calcaneal ultrasound for predicting the diagnosis of osteoporosis from hip and spine bone densitometry

Peripheral densitometry is increasingly being used in the management of osteoporosis, but the optimal diagnostic thresholds have not been defined. The aim of this study was to determine the optimal T-score for peripheral dual-energy X-ray absorptiometry (pDXA) of the heel using a GE Lunar PIXI and quantitative ultrasound (QUS) of the heel using a GE Lunar Achilles Plus when compared with dual-energy X-ray absorptiometry (DXA) of central sites (spine, femoral neck, or total hip). Ninety-nine women (mean age 69 +/- 8, range 33-86 yr) referred from the metabolic bone clinic were studied. The optimal T-score for pDXA from ROC analysis was -1.7 and for QUS was -2.5. The pDXA T-score that defined the same prevalence of osteoporosis at any central site was also -1.7 and for QUS was -2.4. These results are similar to the manufacturer's recommendations. There is no significant difference in performance between the PIXI and QUS.

Age-associated changes in bone ultrasonometry of the os calcis

This cross-sectional study updated age changes for ultrasonometry (QUS) of the os calcis in a large sample of healthy German women. The speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) of the os calcaneus were measured in 5148 women (mean age 55.2 +/- 10.6 yr) using the Achilles ultrasonometer (GE/Lunar). There was an overall decline of 16% for BUA, 4% for SOS, and 32% for SI between late adolescence and old age. In premenopausal women, BUA decreased only slightly (-2%), whereas postmenopausal women showed a significantly increased decline (-12%). In contrast, SOS continuously decreased from the age of 15; there was a decline of 2% from adolescence to menopause. The SI of premenopausal women decreased only by 9%, but the postmenopausal decline of almost 21% was significantly greater. In accordance to our previous report, the age regression for SI in the larger sample differed from the earlier sample, indicating an increased bone loss with aging after the menopause. The SI values in premenopausal German women were comparable to those for British and American women 20-50 yr of age. After age 50, the SI of German women was significantly 3-7% higher in comparison to the British and American reference population.

Fundamental precision limitations for measurements of frequency dependence of backscatter: applications in tissue-mimicking phantoms and trabecular bone

Various models for ultrasonic scattering from trabecular bone have been proposed. They may be evaluated to a certain extent by comparison with experimental measurements. In order to appreciate limitations of these comparisons, it is important to understand measurement precision. In this article, an approach proposed by Lizzi and co-workers is adapted to model precision of estimates of frequency-dependent backscatter for scattering targets (such as trabecular bone) that contain many scatterers per resolution cell. This approach predicts uncertainties in backscatter due to the random nature of the interference of echoes from individual scatterers as they are summed at the receiver. The model is validated in experiments on a soft-tissue-mimicking phantom and on 24 human calcaneus samples interrogated in vitro. It is found that while random interference effects only partially explain measured variations in the magnitude of backscatter, they are virtually entirely responsible for observed variations in the frequency dependence (exponent of a power law fit) of backscatter.

A stratified model to predict dispersion in trabecular bone

Frequency-dependent phase velocity (dispersion) has previously been measured in trabecular bone by several groups. In contrast to most biologic tissues, phase velocity in trabecular bone tends to decrease with frequency. A stratified model, consisting of alternating layers of bone and marrow (in vivo) or water (in vitro), has been employed in an attempt to explain this phenomenon. Frequency-dependent phase velocity was measured from 300 to 700 kHz in 1) phantoms consisting of regularly spaced thin parallel layers of polystyrene sheets in water and 2) 30 calcaneus samples in vitro. For the polystyrene phantoms, the agreement between theory and experiment was good. For the calcaneus samples, the model has some limited usefulness (uncertainty of about 5%) in predicting average phase velocity. More importantly, the model seems to perform consistently well for predicting the frequency dependence of phase velocity in calcaneus.

Relationships among calcaneal backscatter, attenuation, sound speed, hip bone mineral density, and age in normal adult women

The present study was undertaken in order to investigate the use of calcaneal ultrasonic backscatter for the application of diagnosis of osteoporosis. Broadband ultrasonic attenuation (BUA), speed of sound (SOS), the average backscatter coefficient (ABC), and the hip bone mineral density (BMD) were measured in calcanea in 47 women (average age: 58 years, standard deviation: 13 years). All three ultrasound variables had comparable correlations with hip BMD (around 0.5). As reported previously by others, BUA and SOS were rather highly correlated with each other. The logarithm of the ABC was only moderately correlated with the other two. The three ultrasound parameters exhibited similar moderate negative correlations with age. These results taken collectively suggest that the ABC may carry important diagnostic information independent of that contained in BUA and SOS and, therefore, may be useful as an adjunct measurement in the diagnosis of osteoporosis.

Diagnostic disagreement of imaging quantitative sonography of the calcaneus with dual X-ray absorptiometry of the spine and femur

OBJECTIVE

This study evaluates the diagnostic agreement between imaging quantitative sonography of the calcaneus and dual X-ray absorptiometry of the spine and femur for diagnosing osteoporosis.

MATERIALS AND METHODS

In 498 female patients (56 +/- 18 years old), bone mineral density measurements by dual X-ray absorptiometry of the lumbar spine (posteroanterior, L1--L4) and the proximal femur and imaging quantitative sonography of the calcaneus were performed. The percentage of patients having T-scores less than or equal to a threshold of -2.5 standard deviations below a young normal reference was used to compare quantitative sonography with dual X-ray absorptiometry. The diagnostic agreement was assessed using kappa scores.

RESULTS

Approximately 30% of the patients had a T-score less than or equal to -2.5 standard deviations as assessed by imaging quantitative sonography (broadband ultrasound attenuation), 26.5% as assessed by dual X-ray absorptiometry of the spine, and 16.7--56.4% as assessed by dual X-ray absorptiometry of the different regions of interest at the femur. Kappa analysis showed that severe diagnostic disagreement exists among broadband ultrasound attenuation and dual X-ray absorptiometry (kappa = 0.28-0.42).

CONCLUSION

Considerable diagnostic disagreement exists between imaging quantitative sonography and dual X-ray absorptiometry of the spine and femur. The disagreement is in the same range as that reported recently in comparisons of dual X-ray absorptiometry and nonimaging quantitative sonography. In general, no distinct advantage for imaging quantitative sonography could be found when compared with other techniques.

Ultrasonic attenuation in human calcaneus from 0.2 to 1.7 MHz

Ultrasonic attenuation has been demonstrated to be a useful measurement in the diagnosis of osteoporosis. Most studies have employed ultrasound in a range of frequencies from about 200 kHz-300 kHz to 600 kHz-1 MHz, and many have assumed a linear dependence of attenuation on frequency. In order to investigate the attenuation properties of human calcaneus at higher frequencies, 16 defatted human calcanea were interrogated in vitro using two matched pairs of transducers with center frequencies of 500 kHz and 2.25 MHz. The linear dependence of attenuation on frequency seems to extend up to at least 1.7 MHz. The correlation between attenuation coefficient and frequency from 400 kHz to 1.7 MHz was r = 0.999 (95% confidence interval, CI, = 0.998-1.00). The measurements suggest that some deviations from linear frequency dependence of attenuation may occur at lower frequencies (below 400 kHz), however.

Quantitative ultrasound and bone mineral density are equally strongly associated with risk factors for osteoporosis

Because resources do not allow all women to be screened for osteoporosis, clinical risk factors are often used to identify those individuals at increased risk of fracture who are then assessed by bone densitometry. The aim of this study was to compare calcaneal quantitative ultrasound (QUS) and axial bone mineral density (BMD) T and Z scores in a large group of women, some with no clinical risk factors and others with one or more risk factors for osteoporosis. The study population consisted of 1115 pre- and postmenopausal women. A subgroup of 530 women was used to construct reference data for calculating T and Z scores. A total of 786 women was found to have one or more of the following risk factors: (i) atraumatic fracture since the age of 25 years, (ii) report of X-ray osteopenia, (iii) predisposing medical condition or use of therapy known to affect bone metabolism, (iv) premature menopause before the age of 45 years or a history of amenorrhea of longer than 6 months duration, (v) family history of osteoporosis, (vi) body mass index (BMI) <20 kg/m2, and (vii) current smoking habit. Calcaneal broadband ultrasound attenuation (BUA) and speed of sound (SOS) measurements were performed on a Hologic Sahara and a DTUone and BMD was measured at the spine and hip using dual-energy X-ray absorptiometry (DXA). The Z score decrements associated with the seven risk factors calculated using multivariate regression analysis were similar for QUS and BMD measurements. Z score decrements (mean of BMD and QUS measurements combined) associated with a history of atraumatic fracture (-0.67), X-ray osteopenia (-0.36), a family history of osteoporosis (-0.23), and a low BMI (-0.53) were all statistically significant compared with women with no risk factors. Z score decrements associated with a medical condition or use of therapy known to affect bone metabolism, a premature menopause or prolonged amenorrhea, or those who were current smokers were not significantly different from zero. As the number of risk factors present in each individual increased, the mean Z score decrements became more negative, increasing from -0.28 for women with one risk factor to -1.19 for those with four or more risk factors. QUS and BMD measurements yielded similar mean Z scores for women with one, two, three, or more than four risk factors. Using the World Health Organization (WHO) criteria to diagnose osteoporosis for BMD measurements and revised diagnostic criteria for QUS, approximately one-third of postmenopausal women aged 50+ years with clinical risk factors were classified as osteoporotic compared with only 12% of women without clinical risk factors. Over two-thirds of postmenopausal women with risk factors were classified as osteopenic or osteoporotic and approximately 28% were classified as normal. The proportion of women classified into each diagnostic category was similar for BMD and QUS. In conclusion, clinical risk factors for osteoporosis affected calcaneal BUA and SOS Z score measurements to the same extent as axial BMD Z score measurements. Provided revised diagnostic criteria are adopted for QUS, similar proportions of postmenopausal women are identified as osteopenic or osteoporotic as with BMD.

Potential roles for quantitative ultrasound in the management of osteoporosis

OBJECTIVE

To assess the validity of four models for the role of quantitative ultrasound (QUS) in the management of osteoporosis.

DESIGN

Cross-sectional survey and review of literature.

SETTINGS

Nuclear medicine departments of three teaching hospitals in Sydney.

SUBJECTS

1000 women aged 22 to 88 years (mean, 59 years) referred for assessment of osteoporotic fracture risk.

MAIN OUTCOME MEASURES

BMD categories as defined by dual-energy x-ray absorptiometry (DEXA) of the lumbar spine and proximal femur, and QUS category as defined by calcaneal ultrasound stiffness; prevalence of DEXA-defined osteoporosis in the different QUS categories.

RESULTS

In women with QUS Achilles stiffness < or = 70 the prevalence of axial osteoporosis was 51%, whereas in the group with stiffness > 70 the prevalence of axial osteoporosis was 8%. In women 65 years and over the corresponding values were 59% and 17%.

CONCLUSIONS

Of the four possible models for QUS, the use of QUS for the estimation of BMD, or in a "standalone" model, can not be recommended at the current time. The model of QUS as a "prescreening" modality may be acceptable assuming adequate education of clinicians and patients of its limitations, particularly the risk of false negatives. The model of QUS as one factor in a composite risk factor assessment of patients is promising but more data are required.

Relationships of ultrasonic backscatter with ultrasonic attenuation, sound speed and bone mineral density in human calcaneus

Ultrasonic attenuation and sound speed have been investigated in trabecular bone by numerous authors. Ultrasonic backscatter has received much less attention. To investigate relationships among these three ultrasonic parameters and bone mineral density (BMD), 30 defatted human calcanei were investigated in vitro. Normalized broadband ultrasonic attenuation (nBUA), sound speed (SOS), and logarithm of ultrasonic backscatter coefficient (LBC) were measured. Bone mineral density was assessed using single-beam dual energy x-ray absorptiometry (DEXA). The correlation coefficients of least squares linear regressions of the three individual ultrasound (US) parameters with BMD were 0.84 (nBUA), 0.84 (SOS) and 0.79 (LBC). The 95% confidence intervals for the correlation coefficients were 0. 69-0.92 (nBUA), 0.68-0.92 (SOS) and 0.60-0.90 (LBC). The correlations among pairs of US variables ranged from 0.63-0.79. Variations in nBUA accounted for r(2) = 62% of the variations in LBC. Variations in SOS accounted for r(2) = 40% of the variations in LBC. These results suggest that ultrasonic backscattering properties may contain substantial information not already contained in nBUA and SOS. A multiple regression model including all three US variables was somewhat more predictive of BMD than a model including only nBUA and SOS.

Quantitative ultrasound and dual X-ray absorptiometry measurements of the calcaneus in patients on maintenance hemodialysis

It has been suggested that quantitative ultrasound measurements (QUS), which reflect mainly bone density, could be influenced by bone micro-architecture. The aim of the study was to assess whether the relationship of QUS to dual X-ray absorptiometry (DXA) would reflect abnormalities of bone structure observed in renal osteodystrophy. QUS and bone mineral density of the calcaneus (BMDc) were measured by DXA in 30 patients on maintenance hemodialysis and 34 age- and gender-matched controls. QUS parameters and BMDc were significantly lower in hemodialysis patients than in controls (speed of sound [SOS] and broadband ultrasound attenuation [BUA], p = 0. 030; stiffness, p = 0.003; BMDc, p = 0.006). Bone measurements were not correlated with serum parathyroid hormone (PTH). The regression lines of SOS, BUA, and stiffness to BMDc were not significantly different from that of the controls. When dividing the patients into two subgroups according to their median PTH (203 pg/mL), the slopes of the regression lines of BUA to BMDc were significantly different between these two subgroups (p = 0.052). The slope of the subgroup with PTH </= 203 pg/mL was significantly different from that of the controls (p = 0.030). In conclusion, QUS of the calcaneus can be used for bone assessment in patients on maintenance hemodialysis. The differences in the slopes of patients with a less pronounced degree of hyperparathyroidism compared with patients with a higher degree of hyperparathyroidism and to controls suggest that BUA of the calcaneus contains information on bone complementary to DXA measured at the same site. The clinical relevance of this finding is presently unclear.

Anisotropy of ultrasonic backscatter and attenuation from human calcaneus: implications for relative roles of absorption and scattering in determining attenuation

Although bone sonometry has been demonstrated to be useful in the diagnosis of osteoporosis, much remains to be learned about the processes governing the interactions between ultrasound and bone. In order to investigate these processes, ultrasonic attenuation and backscatter in two orientations were measured in 43 human calcaneal specimens in vitro at 500 kHz. In the mediolateral (ML) orientation, the ultrasound propagation direction is approximately perpendicular to the trabecular axes. In the anteroposterior (AP) orientation, a wide range of angles between the ultrasound propagation direction and trabecular axes is encountered. Average attenuation slope was 18% greater while average backscatter coefficient was 50% lower in the AP orientation compared with the ML orientation. Backscatter coefficient in both orientations approximately conformed to a cubic dependence on frequency, consistent with a previously reported model. These results support the idea that absorption is a greater component of attenuation than scattering in human calcaneal trabecular bone.

Measurements of phase velocity and group velocity in human calcaneus

Ultrasonic velocity in calcaneus correlates highly with bone mineral density, which is a good predictor of osteoporotic fracture risk. Several commercial bone sonometers perform a velocity measurement based on the transit time of a broadband pulse to assess skeletal status. This approach is somewhat problematic, however, because several authors have reported ambiguities in measurements in calcaneus. Phase velocity is an alternative that may be less dependent on device spectral characteristics. In addition, dispersion (the frequency-dependence of phase velocity) is a fundamental property worth investigating to increase understanding of interaction between ultrasound and bone. To compare two group-velocity measurement methods and one phase-velocity measurement method, a polycarbonate sample (for method validation) and 24 human calcanei were investigated in vitro. Phase velocity in calcaneus at 500 kHz was 1511 m/s +/- 30 m/s (mean +/- standard deviation). Average phase velocity decreased approximately linearly with frequency (-18 m/s MHz). The two group velocity measurements were comparable and tended to be slightly lower than phase velocity. The magnitude of dispersion showed little correlation with bone mineral density.

Calcaneal ultrasound measurements are determined by age and physical activity. Studies in two Swedish random population samples

AIM

To present reference values and correlations with body composition, blood variables and lifestyle factors.

SUBJECTS

Two random population samples from Göteborg, Sweden, one comprising 184 men and 455 women aged 25-64 years (MONICA) and the other 860 women aged 55-82 years (BEDA) were studied.

METHODS

Calcaneal ultrasound measurement (LUNAR Achilles) and bioimpedance were measured. Smoking habits, coffee consumption, physical activity, psychological stress, education and marital status, as well as blood lipids, blood pressure, and fractures were studied.

RESULTS

Broadband ultrasound attenuation and stiffness were higher in men than in women (P < 0. 001), but speed of sound did not differ between sexes. Speed of sound, broadband ultrasound attenuation and stiffness decreased with age (P < 0.001). In both sexes speed of sound, broadband ultrasound attenuation and stiffness correlated positively to body size variables, and negatively with smoking in women after adjustment for age. Speed of sound, broadband ultrasound attenuation and stiffness were positively related to physical activity in both sexes, and these relationships were the only ones that remained in multivariate analyses in addition to age (negative). Osteoporotic fractures increased with age. Speed of sound, broadband ultrasound attenuation and stiffness were lower amongst women with osteoporotic fractures.

CONCLUSION

Speed of sound, broadband ultrasound attenuation and stiffness decreased with age and increased with physical activity, but body weight and height were not correlated in multivariate analyses. Osteoporotic fractures increased with age and were associated with lower calcaneal ultrasound values.

Quantitative ultrasound of the os calcis in postmenopausal women with spine and hip fracture

Quantitative ultrasonometry (QUS) of the os calcis has been shown to predict hip fracture in late postmenopausal women, and vertebral and forearm fracture in early postmenopausal women. Speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) of the os calcis were measured using the Achilles ultrasonometer (Lunar, Madison, WI). Osteoporosis risk factors were assessed by a detailed questionnaire. We examined 1314 normal women from age 48 to 79 yr, with a mean age 60 +/- 7.5 yr. In addition, we examined women of similar age, of whom 80 had suffered a hip fracture and 40 a spine fracture. The short-term precision in vivo expressed as the coefficient of variation was 1.2% for BUA, 0.2% for SOS, and 1.3% for SI. A total of 813 women were measured at both the right and left heel. There was high correlation between the two sides (r = 0.80-0.93) (p < 0.001), with no systematic offset. The ultrasound variables decreased significantly (p < 0.001) with age in healthy women; the annual decrease was -0.4% for BUA, -0.07% for SOS, and -0.7% for SI. BUA, SOS and SI discriminated (p < 0.001) between fracture and non-fracture subjects, but the fracture groups were 2 to 4 yr older. The T-score in the controls averaged -2.1 while that in the fracture patients averaged about -3.0. After control for age, years since menopause, and body size, BUA, SOS as well as the SI remained significantly lower (11 to 12% for SI) in women with fracture. The Z-score was -0.8 (p < 0.01) in spine fracture cases, and -0.9 (p < 0.001) in hip fracture patients. QUS provides a gradient of fracture risk comparable to X-ray densitometry of the axial skeleton, and gives comparable Z- and T-scores in younger postmenopausal women. It provides a precise, radiation-free, low-cost, and rapid method for fracture risk assessment in clinical practice.

The relationship between ultrasonic backscatter and bone mineral density in human calcaneus

Backscatter and attenuation coefficients were measured from 24 human calcanei in vitro. The logarithm of the backscatter coefficient at 500 kHz showed moderate correlations with bone mineral density (r=0.81, 95% confidence interval: 0.59-0.91) and attenuation (r=0.79, 95% CI: 0.56-0.91). These results suggest that backscatter measurements may be useful in the diagnosis of osteoporosis.

The effects of frequency-dependent attenuation and dispersion on sound speed measurements: applications in human trabecular bone

Sound speed may be measured by comparing the transit time of a broadband ultrasonic pulse transmitted through an object with that transmitted through a reference water path. If the speed of sound in water and the thickness of the sample are known, the speed of sound in the object may be computed. To measure the transit time differential, a marker such as a zero-crossing, may be used. A sound speed difference between the object and water shifts all markers backward or forward. Frequency-dependent attenuation and dispersion may alter the spectral characteristics of the waveform, thereby distorting the locations of markers and introducing variations in sound-speed estimates. Theory is derived to correct for this distortion for Gaussian pulses propagating through linearly attenuating, weakly dispersive media. The theory is validated using numerical analysis, measurements on a tissue mimicking phantom, and on 24 human calcaneus samples in vitro. Variations in soft tissue-like media are generally not exceptionally large for most applications but can be substantial, particularly for high bandwidth pulses propagating through media with high attenuation coefficients. At 500 kHz, variations in velocity estimates in bone can be very substantial, on the order of 40 to 50 m/s because of the high attenuation coefficient of bone. In trabecular bone, the effects of frequency-dependent attenuation are considerable, and the effects of dispersion are negligible.