Broadband ultrasound attenuation imaging: a new imaging method in osteoporosis

The Ability of Ultrasonic Backscatter Parametric Imaging to Characterize Bovine Trabecular Bone

The ultrasonic backscatter technique holds the promise of characterizing bone density and microstructure. This paper conducts ultrasonic backscatter parametric imaging based on measurements of apparent integrated backscatter (AIB), spectral centroid shift (SCS), frequency slope of apparent backscatter (FSAB), and frequency intercept of apparent backscatter (FIAB) for representing trabecular bone mass and microstructure. We scanned 33 bovine trabecular bone samples using a 7.5 MHz focused transducer in a 20 mm × 20 mm region of interest (ROI) with a step interval of 0.05 mm. Images based on the ultrasonic backscatter parameters (i.e., AIB, SCS, FSAB, and FIAB) were constructed to compare with photographic images of the specimens as well as two-dimensional (2D) μ-CT images from approximately the same depth and location of the specimen. Similar structures and trabecular alignments can be observed among these images. Statistical analyses demonstrated that the means and standard deviations of the ultrasonic backscatter parameters exhibited significant correlations with bone density (|R| = 0.45-0.78, p < 0.01) and bone microstructure (|R| = 0.44-0.87, p < 0.001). Some bovine trabecular bone microstructure parameters were independently associated with the ultrasonic backscatter parameters (ΔR² = 4.18%-44.45%, p < 0.05) after adjustment for bone apparent density (BAD). The results show that ultrasonic backscatter parametric imaging can provide a direct view of the trabecular microstructure and can reflect information about the density and microstructure of trabecular bone.

Quantitative imaging techniques for the assessment of osteoporosis and sarcopenia

Bone and muscle are two deeply interconnected organs and a strong relationship between them exists in their development and maintenance. The peak of both bone and muscle mass is achieved in early adulthood, followed by a progressive decline after the age of 40. The increase in life expectancy in developed countries resulted in an increase of degenerative diseases affecting the musculoskeletal system. Osteoporosis and sarcopenia represent a major cause of morbidity and mortality in the elderly population and are associated with a significant increase in healthcare costs. Several imaging techniques are currently available for the non-invasive investigation of bone and muscle mass and quality. Conventional radiology, dual energy X-ray absorptiometry (DXA), computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound often play a complementary role in the study of osteoporosis and sarcopenia, depicting different aspects of the same pathology. This paper presents the different imaging modalities currently used for the investigation of bone and muscle mass and quality in osteoporosis and sarcopenia with special emphasis on the clinical applications and limitations of each technique and with the intent to provide interesting insights into recent advances in the field of conventional imaging, novel high-resolution techniques and fracture risk.

Ultrasonic scanner for in vivo measurement of cancellous bone properties from backscattered data

A dedicated ultrasonic scanner for acquiring RF echoes backscattered from the trabecular bone was developed. The design of device is based on the goal of minimizing of custom electronics and computations executed solely on the main computer processor and the graphics card. The electronic encoder-digitizer module executing all of the transmission and reception functions is based on a single low-cost field programmable gate array (FPGA). The scanner is equipped with a mechanical sector-scan probe with a concave transducer with 50 mm focal length, center frequency of 1.5 MHz and 60% bandwidth at -6 dB. The example of femoral neck bone examination shows that the scanner can provide ultrasonic data from deeply located bones with the ultrasound penetrating the trabecular bone up to a depth of 20 mm. It is also shown that the RF echo data acquired with the scanner allow for the estimation of attenuation coefficient and frequency dependence of backscattering coefficient of trabecular bone. The values of the calculated parameters are in the range of corresponding in vitro data from the literature but their variation is relatively high.

Characterization of controlled bone defects using 2D and 3D ultrasound imaging techniques

Ultrasound is emerging as an attractive alternative modality to standard x-ray and CT methods for bone assessment applications. As of today, however, there is a lack of systematic studies that investigate the performance of diagnostic ultrasound techniques in bone imaging applications. This study aims at understanding the performance limitations of new ultrasound techniques for imaging bones in controlled experiments in vitro. Experiments are performed on samples of mammalian and non-mammalian bones with controlled defects with size ranging from 400 microm to 5 mm. Ultrasound findings are statistically compared with those obtained from the same samples using standard x-ray imaging modalities and optical microscopy. The results of this study demonstrate that it is feasible to use diagnostic ultrasound imaging techniques to assess sub-millimeter bone defects in real time and with high accuracy and precision. These results also demonstrate that ultrasound imaging techniques perform comparably better than x-ray imaging and optical imaging methods, in the assessment of a wide range of controlled defects both in mammalian and non-mammalian bones. In the future, ultrasound imaging techniques might provide a cost-effective, real-time, safe and portable diagnostic tool for bone imaging applications.

Trabecular and cortical bone separately assessed at radius with a new ultrasound device, in a young adult population with various physical activities

The aim was to evaluate a new ultrasound device in a young adult population and to assess its reproducibility via comparison to DXA measurements and geometrical measurements from high-resolution radiographs. Ninety-three subjects aged between 20 and 51 years were recruited and divided into four groups according to their gender and physical activity status: 22 male athletes, 19 male controls, 21 female athletes, and 31 female controls. Ultrasonic measurements were assessed by the prototype LD-100 (Oyo Electric Co., Kyoto, Japan) on the dominant distal radius. Attenuation in the radius (dB), cortical bone thickness (mm), radius thickness (mm), mass density of cancellous bone (mg/cm(3)), and elasticity (GPa) of cancellous bone were obtained. BMD was measured by DXA at the dominant distal radius. Radius images were obtained with a direct high-resolution digital X-ray device (BMA, D(3)A Medical Systems), and radius and cortical thicknesses were estimated using a specific software (ImageJ, Bethesda, USA), in an area site-matched with LD-100. There was a significant positive correlation between site-matched BMD measurement and LD-100 parameters (p<0.004), X-ray radius thickness, and LD-100 parameters except elasticity (p<0.05, r>0.32), X-ray cortical thickness and LD-100 attenuation and cortical thickness (p<0.01). A significantly higher attenuation, cortical and radius thicknesses were found in athletes compared to controls (p<0.05). The radius thickness measured on radiographs was significantly higher in athletes versus controls in both sexes, and cortical thickness was significantly higher in male athletes versus controls. These data suggest a positive influence of physical activity on bone cortical measurements. This study also confirmed the particular interest of bone assessment by ultrasound.

Quantitative ultrasound in the management of osteoporosis: the 2007 ISCD Official Positions

Dual-energy X-ray absorptiometry (DXA) is commonly used in the care of patients for diagnostic classification of osteoporosis, low bone mass (osteopenia), or normal bone density; assessment of fracture risk; and monitoring changes in bone density over time. The development of other technologies for the evaluation of skeletal health has been associated with uncertainties regarding their applications in clinical practice. Quantitative ultrasound (QUS), a technology for measuring properties of bone at peripheral skeletal sites, is more portable and less expensive than DXA, without the use of ionizing radiation. The proliferation of QUS devices that are technologically diverse, measuring and reporting variable bone parameters in different ways, examining different skeletal sites, and having differing levels of validating data for association with DXA-measured bone density and fracture risk, has created many challenges in applying QUS for use in clinical practice. The International Society for Clinical Densitometry (ISCD) 2007 Position Development Conference (PDC) addressed clinical applications of QUS for fracture risk assessment, diagnosis of osteoporosis, treatment initiation, monitoring of treatment, and quality assurance/quality control. The ISCD Official Positions on QUS resulting from this PDC, the rationale for their establishment, and recommendations for further study are presented here.

The clinical use of quantitative ultrasound (QUS) in the detection and management of osteoporosis

For the detection and management of osteoporosis and osteoporosis-related fractures, quantitative ultrasound (QUS) is emerging as a relatively low-cost and readily accessible alternative to dual-energy X-ray absorptiometry (DXA) measurement of bone mineral density (BMD) in certain circumstances. The following is a brief, but thorough review of the existing literature with respect to the use of QUS in 6 settings: 1) assessing fragility fracture risk; 2) diagnosing osteoporosis; 3) initiating osteoporosis treatment; 4) monitoring osteoporosis treatment; 5) osteoporosis case finding; and 6) quality assurance and control. Many QUS devices exist that are quite different with respect to the parameters they measure and the strength of empirical evidence supporting their use. In general, heel QUS appears to be most tested and most effective. Overall, some, but not all, heel QUS devices are effective assessing fracture risk in some, but not all, populations, the evidence being strongest for Caucasian females over 55 years old. Otherwise, the evidence is fair with respect to certain devices allowing for the accurate diagnosis of likelihood of osteoporosis, and generally fair to poor in terms of QUS use when initiating or monitoring osteoporosis treatment. A reasonable protocol is proposed herein for case-finding purposes, which relies on a combined assessment of clinical risk factors (CR.F) and heel QUS. Finally, several recommendations are made for quality assurance and control.

Broadband ultrasound attenuation in the calcaneal region: a comparative study of single-position versus scanning systems

This work describes a system developed to measure the broadband ultrasound attenuation (BUA) in the calcaneal region. The patient's calcanei were inspected using a microcomputer-controlled X-Y axis displacement unit with two 500-kHz, central-frequency, ultrasound transducers. The transducers facing each other are submerged in a small water tank with a support for the patient's foot between them. The system allows data to be collected from a single position or by scanning the calcaneal region to obtain a BUA map. Tests were carried out on 201 patients (110 using the single-position method, and 91 using the scanning method). The results were compared with those of densitometry tests performed using the dual energy X-ray absorptiometry (DEXA) technique (single position: r=0.50; P<0.0001; scanner: r=0.75; P<0.0001). It was concluded that the single position method is more susceptible to errors due to the difficulty in positioning the transducers relative to the calcaneus. The scanning method provides better results and can be used to screen patients before referring them for DEXA.

Instrumentation for in vivo ultrasonic characterization of bone strength

Although it has been more than 20 years since the first recorded use of a quantitative ultrasound (QUS) technology to predict bone fragility, the field has not yet reached its maturity. QUS has the potential to predict fracture risk in several clinical circumstances and has the advantages of being nonionizing, inexpensive, portable, highly acceptable to patients, and repeatable. However, the wide dissemination of QUS in clinical practice is still limited and suffering from the absence of clinical consensus on how to integrate QUS technologies in bone densitometry armamentarium. Several critical issues need to be addressed to develop the role of QUS within rheumatology. These include issues of technologies adapted to measure the central skeleton, data acquisition, and signal processing procedures to reveal bone properties beyond bone mineral quantity and elucidation of the complex interaction between ultrasound and bone structure. This article reviews the state-of-the art in technological developments applied to assess bone strength in vivo. We describe generic measurement and signal processing methods implemented in clinical ultrasound devices, the devices and their practical use, and performance measures. The article also points out the present limitations, especially those related to the absence of standardization, and the lack of comprehensive theoretical models. We conclude with suggestions of future lines and trends in technology challenges and research areas such as new acquisition modes, advanced signal processing techniques, and modelization.

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.

What is the role of DXA, QUS and bone markers in fracture prediction, treatment allocation and monitoring?

There is evidence that treatment can decrease the risk of fractures in osteoporotic patients, and screening of these patients is therefore relevant. Diagnosis of osteoporosis is based on the T-score calculated from bone mineral density (BMD) measurements. BMD measurements have been widely used for the management of osteoporosis, and a low BMD is a strong risk factor for fractures. But BMD measurement has several limitations in both diagnosis, prediction of fracture risk, and treatment follow-up. Quantitative ultrasound (QUS) parameters, an alternative to BMD in the assessment of bone, are independent risk factors for osteoporotic fracture. However, the use of QUS cannot be recommended for both allocation and monitoring of treatment. Biochemical markers of bone remodelling can be useful for both prediction of fracture risk and monitoring of treatment if sources of variability are controlled.

Bone status in primary hyperparathyroidism assessed by regional bone mineral density from the whole body scan and QUS imaging at calcaneus

To assess the bone mineral density status in primary hyperparathyroidism (PHPT), we studied 64 females with PHPT and 17 healthy women. Regional BMD (arms, trunk, legs) from the whole body scan and conventional sites (lumbar spine, femur, radius) were assessed by DXA. Quantitative ultrasound (QUS) imaging measurements were performed at calcaneus. Sixteen women had history of renal lithiasis, 11 had low impact fracture and 37 women had neither renal lithiasis nor fracture. In the entire group, the mean Z-scores were significantly decreased at all sites (lumbar spine, femur, radius). In all clinical subgroups, the mean Z-scores were significantly decreased at radius. The mean Z-scores in premenopausal women were significantly decreased comparatively to postmenopausal women at lumbar spine and femur. In a group of PHPT females matched to controls for age and BMI, only BMD values at radius were lower in PHPT patients than in control (P < 0.03). However, from the whole body scan data, all sites but no trunk were significantly involved in PHPT patients (P < 0.04). Using QUS measurements at calcaneus, the BUA but not SOS in PHPT females was significantly lower (P = 0.03) than in controls. Our results suggest that low BMD at lumbar spine and femur is encountered preferentially in premenopausal women. The BMD decrease predominates at limbs in PHPT with presumably a gradient from proximal to distal part of the limbs. Indeed, the distal part of the limbs are the most affected areas in PHPT whatever the amount of cortical or trabecular bone.

[Assessment of a matrix-based quantitative ultrasound imaging device (Beam scanner): reproducibility]

PURPOSE

A new matrix-based quantitative ultrasound (QUS) device was developed for the assessment of two parameters: BUA (Broadband Ultrasound Attenuation) and SOS (Speed Of Sound). This device, called Beam scanner, is a contact imaging device designed to evaluate the calcaneus. The aim of this preliminary study was to evaluate the reproducibility of results in a sample of patient with heterogeneous age distribution.

MATERIALS AND METHODS

Seventy-six subjects were included: 18 healthy young males, 18 healthy young women and 40 women aged over 50 years old, including 19 osteoporotic patients according to WHO criteria. Five measurements were made for each patient after foot repositioning. Short-term precision was estimated using the coefficient of variation (CV), standardized CV (SCV) and intra-class correlation coefficient (ICC).

RESULTS

SCV varied with the group of subjects between 2.0 and 4.3% for BUA, and between 3.1 and 4.5% for SOS. Mean values of BUA and SOS were statistically lower for osteoporotic women compared with healthy young women or healthy young males (p<0.001). For BUA, only SCV and ICC were better for women aged over 50 years old but without statistical difference.

CONCLUSION

This study shows that the heterogeneity of the studied sample population is not a significant factor when assessing precision. This new device has a precision similar to others QUS devices.

Influence of Aquatic and Weight-Bearing Exercises on Quantitative Ultrasound Variables in Postmenopausal Women

OBJECTIVE

In this prospective, controlled study, the effects of weight bearing and aquatic exercises on the calcaneal ultrasonic scores of postmenopausal sedentary women was investigated.

DESIGN

A total of 62 postmenopausal sedentary women (mean age, 54.1 +/- 7 yrs) with broadband ultrasound attenuation (BUA) T-score variables less than -1 were admitted to Ataturk Balneotherapy and Rehabilitation Center and randomized into aquatic exercise (n = 21), weight-bearing exercise (n = 21), and control (n = 20) groups. The subjects were told to perform the aerobic exercises according to the Borg scale. Quantitative ultrasound variables, BUA, and speed of ultrasound were evaluated after the 6-mo training study.

RESULTS

Calcaneal BUA increased in aquatic exercise and weight-bearing exercise groups by 3.1% and 4.2% (P < 0.05, P < 0.05) respectively. There was a decrease in BUA by 1.3% in the control group (P > 0.05). Speed of ultrasound did not change in the aquatic exercise, weight-bearing exercise, or the control groups. There were no statistically significant differences between the exercise groups for BUA and speed of ultrasound. The percentage changes in the aquatic exercise and weight-bearing exercise groups were statistically significant when compared with the control group for BUA (P < 0.01, P < 0.01) and speed of ultrasound (P < 0.05, P < 0.05).

CONCLUSIONS

Although weight-bearing physical activity is known to be superior to non-weight-bearing activity to increase the bone mass, our present evidence shows that aquatic and weight-bearing exercises both can increase calcaneal BUA.

Changed bone status in human immunodeficiency virus type 1 (HIV-1) perinatally infected children is related to low serum free IGF-I

INTRODUCTION

Adults and children affected by human immunodeficiency virus type-1 (HIV-1) infection show bone demineralization. Little is known about skeletal status using a quantitative high-frequency ultrasound (QUS) technique in these patients.

OBJECTIVE

To evaluate the bone quality and assess the role of the IGF system in the bone metabolism and skeletal status of HIV-1 perinatally infected children.

PATIENTS AND METHODS

Serum free and total IGF-I, IGFBP-3, serum osteocalcin level, urinary deoxypyridinoline concentration, spontaneous interleukin-6 (IL-6) release and broadband ultrasound attenuation (BUA) were evaluated in 44 prepubertal children who had perinatal HIV-1 infection. The patients were divided into two groups depending on the severity of their clinical condition: group 1 (23 children with no or mild clinical symptoms, mean age 8.0 +/- 2.9 years) and group 2 (21 children with severe clinical symptoms, mean age 8.58 +/- 2.47 years). Fifty-five healthy age- and sex-matched controls were analysed for comparison.

RESULTS

Compared with group 1 and the controls, group 2 patients showed a significantly reduced BUA Z-score (P < 0.001), and significantly reduced concentrations of serum osteocalcin (P < 0.001) and urinary deoxypyridinoline (P < 0.001 and P < 0.05, respectively). Group 2 patients also showed significantly reduced serum free IGF-I (P < 0.001) and total IGF-I (P < 0.05) levels compared with the controls, but not with group 1. No statistically significant differences were found between the three groups with regard to IGFBP-3. Group 2 patients showed significantly higher spontaneous IL-6 release than group 1 patients and controls (P < 0.001). BUA Z-scores displayed a significant correlation with free IGF-I in group 2 (r = 0.96; P < 0.001), group 1 (r = 0.56; P = 0.005) and controls (r = 0.50; P < 0.001).

CONCLUSION

Our study shows that only patients affected by perinatal HIV-1 infection with severe clinical manifestations present significant changes in bone quality and bone metabolism. Our data also show that impairment of skeletal status is related to reduction in serum total and free IGF-I. Children with perinatal HIV-1 infection, because of a considerable improvement in life expectancy, seem at great risk of not obtaining an optimal bone mass. A possible therapeutic approach should be considered in these children.

Discrimination of osteoporotic patients with quantitative ultrasound using imaging or non-imaging device

OBJECTIVES

Quantitative ultrasound (QUS) has emerged as a new tool in the assessment of fracture risk. The aim of this study was to compare the clinical utility of QUS parameters measured using imaging and non-imaging devices in the discrimination of osteoporotic patients.

METHODS

QUS (Broadband Ultrasound Attenuation, BUA dB/MHz, and Speed of Sound, SOS m/s) were measured and then statistical analyses were performed.

RESULTS

The 106 women included were 65 +/- 8 years aged. Using DXA, T score was < or = -2.5 at either lumbar spine or hip in 59% of patients, and 25% had osteoporotic fractures. QUS results were different among devices, and these differences were highly dependent on the measured value. There was a similar effect of age and duration of menopause for all parameters. To obtain 90% of sensitivity for the diagnosis of osteoporosis, the thresholds were 50.80 and 71.70 dB/MHz for BUA and 1544.80 and 1551.50 m/s for SOS, using imaging and non-imaging devices, respectively. Belonging to the highest tertile of QUS had a negative predictive value for osteoporosis ranging from 59% to 65%. In the lowest tertile of QUS, the proportion of osteoporotic women was between 73% and 80%. All QUS parameters, except BUA measured with the non-imaging device, were able to discriminate post-menopausal women with fractures after adjustment for age and hip BMD.

CONCLUSIONS

Our data suggest that an imaging system improves the utility of BUA measurement, but not SOS, for post-menopausal osteoporosis assessment.

In vitro acoustic waves propagation in human and bovine cancellous bone

The acoustic behavior of cancellous bone with regard to its complex poroelastic nature has been investigated. The existence of two longitudinal modes of propagation is demonstrated in both bovine and human cancellous bone. Failure to take into account the presence of these two waves may result in inaccurate material characterization.

INTRODUCTION

Acoustic wave propagation is now a commonly used nondestructive method for cancellous bone characterization. However, wave propagation in this material may be affected by fluid-solid interactions inherent to its poroelastic nature, resulting in two different longitudinal waves. This phenomenon has been demonstrated in previous studies and is in agreement with Biot's theory. The purpose of this paper is to extend these findings to human trabecular bone and to thoroughly investigate these two waves.

MATERIALS AND METHODS

Sixty human and 14 bovine cancellous bone cubic specimens were tested in vitro in three different directions using an immersion acoustic transmission method. Original procedures were developed to quantify both velocity and attenuation characteristics of each wave. In term of attenuation, a modified broadband ultrasound attenuation (BUA), describing the rate of change of the frequency-dependent attenuation, was defined for each wave (FDUA).

RESULTS

Both waves were identified in most of the specimens. The fast wave velocities demonstrated a negative linear correlation with porosity (1500-2300 m/s, R2 = 0.44, p < 10(-3)), whereas the slow wave velocities exhibited two different behaviors: (1) a first set of data clearly dependent on porosity showing a positive linear correlation (1150-1450 m/s, R2 = 0.26, p < 10(-3)) and (2) a second group independent on porosity. The fast wave FDUA (20-140 dB/cmMHz) showed a parabolic behavior and reached a maximum for 75% porosity (second degree relationship R2 = 0.41,p < 10(-3)), whereas a positive linear behavior was observed for the slow wave FDUA (15-40 dB/cmMHz; R2 = 0.15, p < 10(-2)).

CONCLUSIONS

Existence of two wave propagation modes were demonstrated in human cancellous bone. Our data suggest that, in some cases, the amplitude of the slow wave is much larger than the amplitude of the fast wave. For this reason, care should be taken when using measurement systems that incorporate simple threshold detection because the fast wave could remain undetected. Moreover, failure to consider the presence of these two waves could result in an inaccurate quantification of cancellous bone physical properties.

[Non-invasive method for measuring bone mineral density]

Measurement of bone mineral density (BMD) using dual energy X-ray absorptiometry is the basis of the definition of osteoporosis. Accuracy, precision and sensitivity of the method are good enough for clinical use. Prospective studies have shown that there is a gradient of risk between the decrease in BMD, related to age and hormonal insufficiency, and the increase in the incidence of fracture. Thus, therapeutic decision is based on both BMD and clinical risk factors that contribute to fracture risk.

Reproducibility and concordance in quantitative ultrasound measurements between densitometers: a comparative study

Although calcaneal quantitative ultrasound (QUS) is an independent predictor of osteoporotic fracture, its role in monitoring changes in bone status remains limited because of its relatively poor precision compared to the rate of bone loss. Recently, imaging QUS has been developed that can standardize the region of interest in the calcaneus with the potential of improving precision. We assessed the concordance and precision of an imaging QUS scanner (UBIS 5000) and a nonimaging scanner (LUNAR Achilles+) in 52 subjects aged between 27 and 79 yr. Each subject had duplicate measurements on each scanner on the same day. The measurements were broad-band ultrasound attenuation (BUA), speed of sound (SOS), and stiffness index, which was derived from BUA and SOS. Precision was evaluated by the standard error of measurement (SEM) and within-subject coefficient of variation (CV). There was significant correlation between the two scanners in all QUS measurements (r > 0.8; p < 0.001); however, BUA and SOS measurements by the UBIS were significantly lower than by the Achilles+. The SEM of BUA (0.6 dB/MHz) and SOS (2.7 m/s) in the UBIS were significantly lower (p < 0.001) than the Achilles+ (1.4 dB/MHz for BUA and 6.3 m/s for SOS). When the SEM was expressed as the percentage of the mean, there were no significant differences in CVs between UBIS (0.9% for BUA and 0.2% for SOS) and Achilles+ (1.2% for BUA and 0.4% for SOS) scanners. The SEM of stiffness index derived by UBIS was not significantly different from that derived by the Achilles+. These data suggest that although there are systematic differences between the UBIS and Achilles+ scanners in QUS measurements, the precision of the two instruments is equivalent.

Daily physical movement and bone mineral density among a mixed racial cohort of women

PURPOSE

The impact of lifestyle physical activity on bone mineral density (BMD) is unclear. We examined the influence of physical activities typical of everyday life on BMD among 151 women (52.0 +/- 0.9 yr). These women were of low socioeconomic status, and 57.6% were Hispanic, 17.2% black, and 24.5% white.

METHODS

BMD was measured at the calcaneus by ultrasound with a Hologic Sahara sonometer. We measured physical activity with two questions from the Yale Physical Activity Survey that assessed h x d(-1) spent in motion typical of the past month and number of flights of stairs climbed up daily. Multivariate ANCOVA adjusted for adiposity and nutrients and medications known to influence BMD determined whether BMD differed between categories of physical activity (<2 vs > or = 2 flights x d(-1) and <7 vs > or = 7 h x d(-1)), menopausal status (pre- vs post-), and ethnic group (white vs nonwhite).

RESULTS

Among the premenopausal women (N = 63, 43.2+/-0.9 yr), adjusted mean calcaneal BMD and BMD T-score were similar between categories of stair climbing and accumulated daily movement regardless of ethnic origin (P > 0.05). Among the postmenopausal women (N = 88, 58.1 +/- 1.0 yr), adjusted mean calcaneal BMD (0.561 +/- 0.019 g x cm(-2) vs 0.503 +/- 0.016) (P = 0.022) and BMD T-score (-0.172 +/- 0.166 vs -0.695 +/- 0.143) (P = 0.020) were higher with more flights of stairs climbed daily in the Hispanic and black women only. Similarly, calcaneal BMD (0.579 +/- 0.023 g x cm(-2) vs 0.505 +/- 0.014) (P = 0.010) and BMD T-score (-0.020 +/- 0.209 vs -0.678 +/- 0.129) (P = 0.010) were higher with greater amounts of daily movement in only the older Hispanic and black women.

CONCLUSION

Lifestyle physical activity positively impacted BMD indicators in a mixed racial cohort of postmenopausal women. Older Hispanic and black women should be encouraged to engage in physical activities typical of everyday life to attenuate age-related bone loss.

Decreased bone density, elevated serum osteoprotegerin, and beta-cross-laps in Wilson disease

Osteopathia has been reported in Wilson disease (WD), but bone density has not been measured; therefore, we performed bone mineral density (BMD), bone mineral content (BMC), and quantitative bone ultrasound (QUS) assessments, as well as measured the serum levels of osteocalcin (OCN), beta-cross-laps (beta-CTx's), and the recently discovered osteoprotegerin (OPG) and its ligand RANKL to investigate the underlying mechanism of osseous disorders. Serum OCN, beta-CTx, OPG, and RANKL levels were measured by ELISA in 21 WD patients and in 20 age- and gender-matched healthy subjects. BMD, BMC, and QUS parameters were also determined. Osteoporosis was present in 9/21 (43%) WD patients. Abnormal QUS parameters were found in 7 (33%) of the patients. Although serum OCN levels were similar in patients and controls (29.93 +/- 24.65 mg/ml vs. 29.84 +/- 6.89 mg/ml), beta-CTx and OPG levels were significantly increased in WD compared with the healthy controls (625.4 +/- 312.3 pg/ml vs. 423.6 +/- 144.3 pg/ml and p = 0.022 and 7.2 +/- 3.4 pM vs. 3.5 +/- 1.0 pM and p < 0.001, respectively). No difference was observed in the RANKL level. There was a positive correlation between OCN and beta-CTx (r = 0.55; p = 0.01). We proved high occurrence of osteoporosis in WD. Negative bone remodeling balance is a consequence of increased bone resorption, which is indicated by elevated beta-CTx. The novel finding of elevated serum OPG may reflect a compensatory reaction to enhanced osteoclast activity, despite the normal OCN level.

In vivo performance of a matrix-based quantitative ultrasound imaging device dedicated to calcaneus investigation

We developed a prototype of an ultrasound (US) bone matrix densitometer, the BEAM scanner, in the context of a European Space Agency research program. This device, which is a contact imaging device, was designed to overcome the limitations of immersion devices in space. Broadband US attenuation (BUA) and speed of sound (SOS) parameters were calculated from the radiofrequency (RF) signal. The principle aim of this study was to evaluate in vivo performance in direct comparison with a currently available device (UBIS 3000, DMS, France). The short-term precision of the BEAM scanner for BUA was estimated at 2.8%, whereas it was 2.3% with UBIS 3000. The short-term precision for SOS was 0.3%, and this was the same as the coefficient of variation (CV) of the UBIS 3000. CVs of 3.4% and 0.6% for midterm precision were found for BUA and SOS, respectively, and UBIS 3000 scores were 3% and 0.4%, respectively. This preliminary study demonstrates the high performance of the BEAM scanner and its new concept offers a wide range of improvements and new applications.

Scattering by a fluid cylinder in a porous medium: application to trabecular bone

In a trabecular bone, considered as a nondissipative porous medium, the scattering of an incident wave by cylindrical pores larger than the wavelength is studied. The goal is to know if scattering alone may cause such a high attenuation as that observed in calcaneus. The porous medium is modelized via Biot's theory and the scattering by a single pore is characterized from the definition of a scattering matrix. An approximation of weakly disordered medium is then discussed to estimate the effective attenuation and dispersion as a function of frequency. These effective properties are shown to be different of those measured on calcaneus, due to the neglect of wave conversions during the scattering process.

Broadband ultrasound attenuation imaging: algorithm development and clinical assessment of a region growing technique

This paper presents a computerized method for the selection of an irregular region of interest (ROI) in broadband ultrasound attenuation (BUA) images. A region growing algorithm searches an initial region in the posterior part of the calcaneus until the pixel with the lowest attenuation value is found; this is the starting seed. Then, the algorithm evaluates the values of the eight pixels neighbouring the starting seed. Pixels that have the closest value to the starting seed are accepted. This procedure is the first processing level. The procedure is repeated for the group of pixels neighbouring those accepted from the previous processing level. The algorithm ceases when the number of accepted pixels reaches a user-specified number. The clinical part of this study compares measurements of BUA at an automatic ROI implemented on a quantitative ultrasound imaging device, defined as the circular region of lowest attenuation in the posterior part of the calcaneus, and at irregular ROIs of various sizes generated by the algorithm developed in this study. The algorithm was applied to BUA images obtained from 24 post-menopausal women with hip fractures and 26 age-matched healthy female subjects. The use of the irregular ROI with a size of 2400 pixels is proposed because that region yielded better clinical results compared to irregular ROIs with different size and the circular automatic ROI.

Influence of region of interest and bone size on calcaneal BMD: implications for the accuracy of quantitative ultrasound assessments at the calcaneus

There is considerable technological diversity among quantitative ultrasound (QUS) devices used to assess osteoporosis. Because the distance between the transducer and the footplate remains constant, the location of the calcaneus measured will vary with foot size. This study was designed to quantify the variation in bone mineral density (BMD) between a manufacturer's region of interest (ROI_M), which is fixed relative to the footplate, and an anatomical region of interest (ROI_A), which is defined as 20% of calcaneal length. The effect of foot length and width on QUS variables measured using two Food and Drug Administration cleared QUS devices, the Sahara (Hologic) and the Achilles+ (Lunar) was assessed. 26 healthy subjects (12 male and 14 female), aged 22-54 years (35.6+/-10 years) and with foot lengths of 21.5 cm to 29.7 cm (25.1+/-2.3 cm) were recruited. QUS assessments were performed at the right calcaneus. In addition, a Hologic 4500 densitometer was used to measure the BMD of the calcaneus in the ROI_M and ROI_A. The sizes of the ROIs were approximated to the sizes of the transducers of the Sahara and Achilles+ devices. The results showed a significant difference in BMD between the two ROI locations for the Sahara device (BMD 0.642+/-0.135 g cm(-2) vs 0.616+/-0.114 g cm(-2), p=0.014), but no significant difference was found in BMD between the two locations for the Achilles device (BMD 0.661+/-0.120 g cm(-2) vs 0.662+/-0.123 g cm(-2), p=0.818). At the ROI_A, there was a significant difference in BMD between the two QUS devices (p<0.001). The correlation between QUS variables and BMD was slightly higher for the ROI_M (r=0.68-0.79, since this is site-matched) than the ROI_A (r=0.59-0.70) for the Achilles device, while for the Sahara device the correlations were r=0.35-0.40 and r=0.51-0.54, respectively. The smaller ROI of the Sahara device resulted in more than 50% of the subjects having BMD differences of greater than 5% between the ROI_A and the ROI_M, compared with only 20% of the subjects on the Achilles device. ROIs containing cortical bone edge and other soft tissues were found in 58% of cases for the Achilles device and 46% of cases for the Sahara device. The greatest differences occurred in very small and very large feet. Calcaneal length correlated significantly with Sahara speed of sound (SOS), and heel width correlated significantly with Achilles SOS. Heel width also correlated significantly with Sahara broadband ultrasound attenuation (BUA) but not Achilles+ BUA. These results suggest that variation in ROI and bone size might affect the accuracy of QUS measurements, since the calcaneus is heterogeneous both in terms of its external geometry and its internal structure and density.

Ultrasonic backscatter and transmission parameters at the os calcis in postmenopausal osteoporosis

Ultrasound technology has emerged as a new tool in the assessment of osteoporosis. Ultrasound parameters usually are measured in transmission; there is a potential for the analysis of backscattered signals to provide information on bone microarchitecture. The aim of this study was to explore a new technological development of the method, adding backscatter coefficient to transmission parameters, and to examine the appropriate thresholds to identify postmenopausal osteoporotic women. We examined 210 postmenopausal women (including 60 with osteoporotic fractures) and 30 healthy premenopausal controls. They had lumbar spine and hip bone mineral density (BMD) measurement and quantitative ultrasound (QUS) evaluation at the os calcis, measured in transmission (broadband ultrasound attenuation [BUA], speed of sound [SOS], ratio of transit time [dt] to BUA [dt/BUA], and "strength" index [STI]) and reflexion (broadband ultrasound backscattering [BUB]). The standardized CVs (sCVs) were between 2.27 % and 3.40 % for QUS measured in transmission and 4.41% for BUB. The odds ratio (OR) for fracture discrimination adjusted for age was 2.77 for hip BMD and between 1.6 and 2.9 for QUS. After adjustment for hip BMD, ORs were still highly significant for SOS, STI, and dt/BUA. According to hip BMD T score, prevalence of osteoporosis in our population was 39%. To detect the same prevalence, T scores ranged between -0.95 and -1.42 for QUS. QUS parameters have adequate ability to discriminate osteoporotic patients from controls. The World Health Organization (WHO) threshold for diagnosis of osteoporosis does not apply to this technology. The clinical utility of BUB at the os calcis, in addition to usual ultrasound parameters, is not yet proven. However, BUB evaluation, which does not require two transducers and may be implemented in conventional reflection mode systems, warrants further studies.

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.

Comparison between quantitative calcaneal and tibial ultrasound in a Dutch Caucasian pediatric and adolescent population

In the field of bone densitometry, attention has recently been focused on the pediatric population. Quantitative ultrasound (QUS) as bone assessment technique has many advantages for children in comparison with bone assessment techniques that use ionizing radiation. In this pilot study, we investigated the use of calcaneal and tibial QUS systems in a healthy Caucasian pediatric population. We studied 120 healthy Caucasian Dutch children between ages 7 and 19 yr: 53 boys (mean age of 12.5 yr, range 4.5-18) and 67 girls (mean age of 13.5 yr; range 7.1-19). We recruited children from a large population who previously had participated in a bone assessment study performed at our hospital. Two operators performed calcaneal QUS of the right calcaneus and tibial QUS of the right tibia. The correlation between calcaneal and tibial ultrasound was modest but significant (r = 0.29; p < 0.01). Using the calcaneal device, we found in girls a weak positive correlation between skeletal age and speed of sound (SOS) (r = 0.38), broadband ultrasound attenuation (r = 0.57), and quantitative ultrasound index (r = 0.46), all with a value of p < 0.01. For boys all parameters failed to reach significance. Using the tibial device, we found a good correlation between skeletal age and SOS in girls (r = 0.76) and modest correlation in boys (r = 0.50), both with a value of p < 0.01. This is one of the first studies to present a comparison between two ultrasound techniques in children. At present we feel that, in light of the poor correlation with skeletal age, calcaneal ultrasound has yet to prove its efficacy in children. Tibial ultrasound seems to be a good bone assessment technique in children.

Comparison of quantitative ultrasound and dual X-ray absorptiometry in estrogen-treated early postmenopausal women

Identifying individuals at risk of developing osteoporosis is important in order to initiate early treatment. Many new techniques have been proposed as alternatives for DXA-scanning. Some of these alternatives certainly have advantages, but none have so far been demonstrated to predict fractures better, or even to identify individuals at risk of osteoporosis as well as with the standard method. In this study, comprising a group of women from the Danish Osteoporosis Prevention Study, we wished to investigate whether a technique based on quantitative ultrasound (QUS) could identify individuals with low BMC/BMD as measured by dual X-ray absorptiometry (DXA). Furthermore, we wished to test whether the method could detect differences between untreated individuals and those treated with hormone replacement therapy. We found that QUS could detect differences between the treated and untreated groups, but it was unable to identify women with low BMD, although it might be able to identify persons not at risk of osteoporosis. Low QUS values should be followed by a regular DXA measurement to confirm the presence of osteoporosis.

Quantitative ultrasound in postmenopausal osteoporosis

Ultrasound has been proposed as a low-cost, radiation-free method for osteoporosis assessment in postmenopausal women. Large prospective studies have shown that ultrasound parameters can be used for fracture risk estimate in this population, providing that adequate quality control is performed. The places of both ultrasound and the current gold standard method for bone assessment, dual energy x-ray absorptiometry, are still to be determined. Further studies are needed on the diagnosis of osteoporosis using ultrasound, because current diagnostic thresholds, designed by the World Health Organization, do not apply to this-new technology. Monitoring of skeletal changes and treatment effects by ultrasound cannot be recommended.

Quantitative ultrasound of the calcaneus with parametric imaging: correlation with bone mineral density at different sites and with anthropometric data in menopausal women

OBJECTIVE

To prospectively study the relationship of quantitative ultrasound of the calcaneus with anthromopometric variables and with bone mineral density (BMD) assessed at the level of the calcaneus as well as at other sites.

METHOD

Osteosonography of the non-dominant calcaneus was performed in 135 menopausal women, using a DTU-one device with parametric imaging. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were assessed. BMD of the calcaneus (BMDcal) was measured using dual energy X-ray absorptiometry (DXA), in a subregion matched with the region of interest for osteosonography. BMD of the lumbar trabecular bone was measured using quantitative computed tomography (BMD QCT) while the non-dominant hip was studied using DXA, which provided the total bone mineral density (BMDhip) and that of the Ward triangle (BMDWard).

RESULTS

The Pearson correlation coefficients between BUA, SOS and the various measurements of BMD ranged from 0.305 (SOS versus BMDhip) to 0.717 (BUA versus BMDcal). BMD QCT and BMDWard were found to depend on age, but not on weight or height, while BUA, SOS, BMDcal, BMDhip were unrelated to age, but correlated with weight (SOS, BMDhip) or with weight and height (BUA, BMDcal). In a multiple stepwise regression analysis, age was a significant predictor for BMD QCT, BMD hip and BMDWard; BMD QCT, BMDWard and BMDhip admitted BUA as sole predictor, while BMDcal was significantly related to both BUA and SOS.

CONCLUSION

BUA and SOS of the calcaneus, assessed in 135 menopausal women using a parametric imaging device, reflected BMDcal, measured with DXA at a matched region of interest, and did not decline significantly with age.

Quantitative ultrasound of the calcaneus: an in vivo comparison with dual-energy X-ray absorptiometry and magnetic resonance imaging

The current study was performed in a clinical setting and aimed to evaluate the relationship between quantitative ultrasound (QUS) of the calcaneus with bone mineral density (BMD) assessed with dual-energy X-ray absorptiometry (DXA) and with variables derived from magnetic resonance imaging (MRI). Thirty-two postmenopausal women (mean age 61 years) were studied at the level of the nondominant calcaneus. QUS was performed using a DTU-one device including parametric imaging and yielded speed of sound (SOS) and broadband ultrasound attenuation (BUA) data. DXA was performed at a matched region of interest (ROI) in the calcaneus, using a Hologic QDR 4500 device. MRI, also performed at a matched ROI, yielded, using a Siemens Magnetom Vision device, the inverse of the transverse relaxation time (1/T(2)(*)) and the phase standard deviation (PSD). The strongest relationship between QUS and the other variables involved BUA and BMD (r &equals: 0.677, p < 0.001); 1/T(2)(*) showed a trend to correlation with SOS (r = 0.359, p = 0. 044) and with BMD (r = 0.364, p = 0.040), while the relationship between 1/T(2)(*) and BUA, PSD and BUA, PSD and SOS, PSD and BMD remained far from significance. Regression analysis of QUS, DXA, and MRI variables against age showed a trend to significant decline only for 1/T(2)(*) (r = -0.409, p = 0.020). In conclusion, this study shows that BUA of the calcaneus has the best correlation with BMD, and that, at least in a clinical setting, the ability of QUS to give information about bone structure is limited.

Hip fracture discrimination by imaging ultrasound measurements of the calcaneus

Quantitative ultrasound measurements of the os calcis have recently been upgraded with imaging facilities. This has made measurements of a specific region of interest possible and improved the reproducibility of the method, but the diagnostic ability of imaging ultrasound has not yet been investigated thoroughly. We measured broadband ultrasound attenuation (BUA) and speed of sound (SOS) using imaging ultrasound as well as forearm bone mineral density (BMDarm) using dual-energy X-ray absorptiometry in three age-matched groups of women: (1) 25 women who were admitted to hospital due to a hip fracture; (2) 23 women who were admitted to hospital due to a fall without any fracture; and (3) 26 normal women. Furthermore, BMD of the hip (BMDhip) was measured in a subgroup of the hip fracture patients and those who had fallen. All measurements were performed during the index hospitalization in order to avoid any influence from bone loss due to immobilization after the fracture. We found a -0.48 SD deviation from expected age-matched values in BUA among the hip fracture patients, whereas the patients who had fallen showed a +0.16 SD deviance. For SOS, the figures were -0.70 SD for the hip fracture group and -0.06 SD for the patients who had fallen. For BMD of the arm we found values of -0.65 SD and +0.08 SD, respectively, whereas the figures for BMD of the hip were -0.66 SD and +0.13 SD, respectively. All parameters were significantly lower in the hip fracture group compared with the patients who had fallen. None of the parameters in the patients who had fallen deviated significantly from expected normal age-matched values. Neither BMD of the arm or BMD of the hip separated hip fracture patients and patients who had fallen significantly better than ultrasound (BUA or SOS) did. We conclude that imaging ultrasound (BUA or SOS) separates age-matched groups of hip fracture and non-fracture patients as well as BMD measurements do.

Determination of a standard site for the measurement of bone mineral density of the human calcaneus

Ultrasound of the calcaneus may be used as a cheap, ionising radiation-free and easy to use indicator of skeletal status, and hence of osteoporotic fracture risk. At present ultrasound is not widely used as it suffers from high precision errors. As ultrasound parameters are determined in part by bone mineral density (BMD), an increase in the accuracy and precision of BMD measurements should reduce the precision error associated with ultrasound measurements. The aim of this study was to define an anatomical site on the calcaneus at which accurate and precise measurements of BMD can be made. Ten dry calcanei and 10 cadaveric feet were scanned using a DXA scanner; 9 anatomically defined regions (1 cm2) were selected in the posterior part of the calcaneus for analysis. The centre of region 1 was positioned halfway along the line joining the anterior border of the calcaneal tubercle and the peak of the posterior superior tubercle, and the remaining 8 regions were placed around this central area. The BMD in these 9 regions was compared with the whole bone BMD and the variability of BMD within each of the 9 regions was measured. The reproducibility of the technique was assessed by taking 10 repeated measurements of 2 bone and 2 cadaveric specimens, each specimen being removed and repositioned between measurements. Region 1 was found to be the most representative of total BMD in cadaveric feet. This region also showed the least variability of BMD and consistently gave the lowest coefficients of variation in the reproducibility study both in the bone and the cadaveric specimens. This region is hence the most suitable site on the calcaneus for measuring absolute values of and changes in BMD. The surface position of region 1 was found to be consistently 5/9 along the line at 45 degrees to the vertical, from the lateral malleolus to the heel. The identification of the surface location of region 1 relative to anatomical landmarks of the foot has enabled the same anatomical site to be measured in all subjects. This allows meaningful intersubject comparisons to be made. Preliminary data suggest that precision errors using ultrasound are also reduced when measurements are taken at this region of the calcaneus. The reduction in the precision error of ultrasound assessment of skeletal status may provide a cheap and safe way to identify individuals at risk from osteoporotic fracture.

Genetic and environmental contributions to the association between quantitative ultrasound and bone mineral density measurements: a twin study

This study was designed to assess the relative contributions of genetic and environmental factors to the variation and covariation of quantitative ultrasound (QUS) measurements and their relationships to bone mineral density (BMD). Forty-nine monozygotic (MZ) and 44 dizygotic (DZ) female twins between 20 and 83 years of age (53 +/- 13 years, mean +/- SD) were studied. Digital (phalangeal) QUS (speed of sound [SOS]) and calcaneal QUS (broadband ultrasound attenuation [BUA] and velocity of sound [VOS]) were measured using a DBM Sonic 1200 ultrasound densitometer and a CUBA ultrasound densitometer, respectively. Femoral neck (FN), lumbar spine (LS), and total body (TB) BMD were measured using dual-energy X-ray absorptiometry. Familial resemblance and hence heritability (proportion of variance of a trait attributable to genetic factors) were assessed by analysis of variance, univariate, and multivariate model-fitting genetic analyses. In both QUS and BMD parameters, MZ twins were more alike than DZ pairs. Estimates of heritability for age- and weight-adjusted BUA, VOS, and SOS were 0.74, 0.55, and 0.82, respectively. Corresponding indices of heritability for LS, FN, and TB BMD were 0.79, 0.77, and 0.82, respectively. In cross-sectional analysis, both BUA and SOS, but not VOS, were independently associated with BMD measurements. However, analysis based on intrapair differences suggested that only BUA was related to BMD. Bivariate genetic analysis indicated that the genetic correlations between BUA and BMD ranged between 0.43 and 0.51 (p < 0.001), whereas the environmental correlations ranged between 0.20 and 0.28 (p < 0.01). While the genetic correlations within QUS and BMD measurements were significant, factor analysis indicates that common genes affect BMD at different sites. Also, individual QUS measurements appear to be influenced by some common sets of genes rather than by environmental factors. Significant environmental correlations were only found for BMD measurements and ranged between 0.50 and 0.65 (p < 0.001). These data suggest that QUS and BMD measurements are highly heritable traits. While it appears that there is a common set of genes influencing both QUS and BMD measurements, specific genes yet to be identified appear to have greater effects than that of shared genes in each trait.

Automatic detection of the boundary of the calcaneus from ultrasound parametric images using an active contour model; clinical assessment

This paper presents a computerized method for automated detection of the boundary of the os calcis on in vivo ultrasound parametric images, using an active dynamic contour model. The initial contour, defined without user interaction, is an iso-contour extracted from the textural feature space. The contour is deformed through the action of internal and external forces, until stability is reached. The external forces, which characterize image features, are a combination of gray-level information and second-order textural features arising from local cooccurrence matrices. The broadband ultrasound attenuation (BUA) value is then averaged within the contour obtained. The method was applied to 381 clinical images. The contour was correctly detected in the great majority of the cases. For the short-term reproducibility study, the mean coefficient of variation was equal to 1.81% for BUA values and 4.95% for areas in the detected region. Women with osteoporosis had a lower BUA than age-matched controls (p = 0.0005). In healthy women, the age-related decline was -0.45 dB/MHz/yr. In the group of healthy post-menopausal women, years since menopause, weight and age were significant predictors of BUA. These results are comparable to those obtained when averaging BUA values in a small region of interest.

The role of quantitative ultrasound in the assessment of bone: a review

Quantitative ultrasound (QUS) bone measurement is a promising, relatively new technique for the diagnosis of osteoporosis. Unlike to the more established method of bone densitometry [measurement of bone mineral density (BMD) e.g. using dual X-ray absorptiometry (DEXA)], QUS does not use ionizing radiation. It is cheaper, takes up less space and is easier to use than densitometry techniques. The two QUS parameters currently measured are broadband ultrasound attenuation (BUA) and speed of sound (SOS). The reported age-related changes for healthy women range from -0.27% to -1.62% per year for BUA and from -0.06% to -0.19% per year for SOS. Precision ranges from 1.0 to 3.8% (CV) for BUA and from 0.19 to 0.30% (CV) for SOS. The new method of imaging ultrasound has improved the precision of QUS measurements. QUS is significantly correlated with BMD. Studies with the latest equipment have shown r-values between 0.6 and 0.9 in site-specific measurements, and QUS is thus believed to reflect mainly BMD. However, other studies indicate that QUS measures something other than the actual mineral content of bone, namely bone quality, e.g. in vitro studies have shown that QUS reflects trabecular orientation independently of BMD. In both cross-sectional and prospective studies, QUS seems to be as good a predictor of osteoporotic fractures as BMD. In two large prospective studies, QUS also predicted fracture risk independently of BMD. QUS has just begun to be used systematically for monitoring the response to anti-osteoporotic treatments in prospective trials. In the studies performed, QUS has been found to be useful in the follow-up of patients. QUS is thus a promising new technique for bone assessment.

Effect of bovine bone constituents on broadband ultrasound attenuation measurements

Broadband ultrasound attenuation (BUA) has been found to correlate positively with bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. However, because there is a significant amount of unexplained variation in this correlation, it has been suggested that BUA might also provide information about bone structure. The purpose of this study was to determine the contribution of bone mineral and organic matrix to BUA and BMD measurements. The influence of sample length on both BUA and BMD was also investigated by normalizing these measurements to length. BUA (Walker Souix, 575+) and BMD (Lunar DPX) values were obtained on bicortical cores removed from 12 bovine femoral necks. BMD and BUA measurements were repeated on the samples after: (1) mechanical removal of the cortices; (2) defatting using a 2:1 chloroform:methanol solution; and (3) decalcifying using formic acid. The data demonstrate that the cortical component of the bone contributes significantly to BMD. We found that 41.7% of the normalized BMD reflect cortical bone. Defatting the samples did not affect BUA. Decalcifying the trabecular bone while maintaining an intact collagenous structure significantly reduces BUA by 89% and BMD by 96% compared to the whole core samples. Normalizing BMD and BUA to sample length, in cases where large variation is present, does influence the correlation between the variables. We conclude that BUA is influenced mainly by the presence of bone mineral, whereas the presence of the organic matrix contributes very little to BUA.

Quantitative ultrasound techniques for the assessment of osteoporosis: expert agreement on current status. The International Quantitative Ultrasound Consensus Group

Quantitative ultrasound (QUS) methods have been introduced in recent years for the assessment of skeletal status in osteoporosis. The performance of QUS techniques has been evaluated in a large number of studies. Reviewing existing knowledge, an international expert panel formulated the following consensus regarding the current status of this technology. To date, evidence supports the use of QUS techniques for the assessment of fracture risk in elderly women. This has been best established for water-based calcaneal QUS systems. Future studies should include the predictive validity of other QUS systems. Additional clinical applications of QUS, specifically the assessment of rates of change for monitoring disease progression or response to treatment, require further investigation. Its low cost and portability make QUS an attractive technology for assessing risk of fractures in larger populations than may be suitable or feasible for bone densitometry. Additional investigations that assess innovative QUS techniques in well defined research settings are important to determine and utilize the full potential of this technology for the benefit of early detection and monitoring of osteoporosis.

Peripheral measurement techniques for the assessment of osteoporosis

Peripheral measurement techniques have been the first to be developed for the assessment of osteoporosis, and they remain useful. Besides traditional approaches such as radiographic absorptiometry (RA), radiogrammetry, and single-photon absorptiometry (SPA), new peripheral approaches have been developed that offer powerful ways to assess skeletal status in osteoporosis. These include single x-ray absorptiometry (SXA), peripheral dual x-ray absorptiometry (pDXA), peripheral quantitative computed tomography (pQCT), quantitative ultrasound (QUS) techniques, and magnetic resonance imaging (MRI) approaches. This review describes the current role of peripheral imaging techniques vis-à-vis their central imaging counterparts. Peripheral measurement techniques are attractive because equipment cost is substantially lower, radiation exposure is small, and the devices require less space and sometimes are even portable. Additionally, QUS and MRI offer the potential to measure aspects of bone status beyond the limits of bone densitometry. Peripheral techniques represent important diagnostic methods for the assessment of osteoporosis.

In vitro assessment of the relationship between acoustic properties and bone mass density of the calcaneus by comparison of ultrasound parametric imaging and quantitative computed tomography

This in vitro study aimed to add new experimental evidence to clarify the relation between acoustic properties of bone and bone mineral density (BMD) of the human calcaneus. Parametric images of normalized broadband ultrasonic attenuation (nBUA) and ultrasound bone velocity (UBV) were compared with quantitative computed tomography (QCT) images of the calcaneus. The experimental protocol was designed to control the different potential sources of error in acoustic measurements, including the shape and thickness of the samples, intervening soft tissues and cortical bone, boundary effects, and variation in location of the regions of interest (ROIs) analyzed by ultrasound and X-ray. The present study was based on bone specimens from calcaneus removed from 15 cadavers (six male and nine female donors ranging from 69 to 89 years of age). Immersion ultrasonic measurements were performed in the through-thickness direction at normal incidence using a pair of focused broad-band 0.5-MHz transducers. QCT of the specimens was performed using standard 10-mm-thick slices with the Cann-Genant calibration standard. Identical, site-matched ROIs were selected for quantitative analysis on the three images. The pattern of acoustic parameters was similar to that of BMD with QCT. The relationships between nBUA and BMD (r2 = 0.75), between UBV and BMD (r2 = 0.88) and between nBUA and UBV (r2 = 0.84) were highly significant (p < 10(-4). From this study, it appears that ultrasound parameters as measured with current transmission techniques reflect mainly bone quantity and only reflect microarchitecture to a small extent and that BUA and UBV reflect the same bone property.

Assessment of the relationship between broadband ultrasound attenuation and bone mineral density at the calcaneus using BUA imaging and DXA

The purposes of this study was to determine the relationship between broadband ultrasound attenuation (BUA) and bone mineral density (BMD) measured at different regions of the calcaneus with identical site-matched regions of interest (ROIs). Dual-energy X-ray absorptiometry (DXA) measurements of the calcaneus and BUA imaging were performed in 30 women (15 premenopausal and 15 postmenopausal). Four square ROIs were located in the great tuberosity and one square ROI in the foramen calcaneus. A ROI adapted to the shape and size of the whole calcaneus was also considered. All ROIs were analyzed three times with both techniques to minimize intra-observer variability. The correlation coefficient between attenuation and frequency was used as an index of BUA measurement error. Before accepting a measurement of BUA in inhomogeneous material, it could be useful to map the spatial variations of the measurement error. In all ROIs we found the BUA and BMD were strongly related (r = 0.78-0.91, p < 0.001). The correlation between BUA and BMD was slightly higher in the inferior part of the posterior tuberosity than in the superior part and in the foramen calcaneus. The very high correlation between attenuation and frequency found in all ROIs (r = 0.99) suggests that measurement errors of propagation were probably not significant. Ultrasound imaging yields the opportunity for studying the spatial acoustic properties in the calcaneus and their relation to bone mass or structural parameters provided by independent imaging techniques. BUA measured with current transmission techniques reflects mainly bone mass, and microarchitecture to a smaller extent.

Quantitative ultrasound imaging at the calcaneus using an automatic region of interest

A new approach to measuring bone properties at the calcaneus using ultrasound parametric imaging has recently emerged. However, an additional source of observer-related error is the substantial regional variations in the pattern of ultrasound parameters. The contribution of intra-observer and inter-observer variability to the coefficient of variation can be eliminated using an algorithm which selects the region of interest (ROI) completely automatically. The objective of the present study was the clinical assessment of an automatic ROI for both broadband ultrasonic attenuation (BUA) and speed of sound (SOS) measurement using ultrasound parametric imaging. The automatic ROI was defined as the circular region of lowest attenuation in the posterior tuberosity of the calcaneus. We have tested this algorithm using clinical images of the calcaneus from 265 women. Mean coefficients of variation were 1.6% (95% confidence interval 1.4%-1.9%) and 0.26% (95% confidence interval 0.23%-0.32%) for BUA and SOS respectively (standardized CV was 2.1% for BUA and 2.6% for SOS). Z-scores in an osteoporotic group were -0.61 and -0.52 for BUA and SOS respectively. In healthy women, the age-related decline was -0.50 dB/ MHz per year (0.7%/year) for BUA and -1.2 m/s per year (0.08%/year) for SOS. In the subgroup of healthy postmenopausal women, using stepwise multiple regression, we found that BUA was predicted best by years since menopause (YSM) and weight, with overall model r2 = 0.28; SOS was predicted best by YSM only (r2 = 0.21). Neither the range of biological variation of ultrasound parameters nor the clinical value were affected by the choice of the region of lowest attenuation for measurement. The automatic procedure was totally independent of operator interaction, therefore excluding loss of precision due to intra- or inter-observer variability. The results showed the high precision and robustness of the procedure. These factors make this approach viable for routine clinical use.