Measurements of postmenopausal bone loss with a new contact ultrasound system

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.

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.

Simultaneous densitometry and quantitative bone sonography in the estimation of osteoporotic fracture risk

759 post-menopausal women (41-80 years old), 175 with and 584 without vertebral fracture, were studied by quantitative bone sonography and densitometry of the distal radius in order to evaluate the ability of ultrasound transmission velocity (UTV) to separate fractured from healthy women independently of bone mineral density (BMD) and to test the possibility of improving the discriminant ability of BMD by the simultaneous use of UTV. A second BMD measurement was made at the mid radial shaft. Both BMD and UTV were higher in healthy subjects than in fractured women; the latter being older, shorter and having a longer postmenopausal status. On logistic regression, standardized for 1 SD from the mean value of healthy women, UTV differentiated between healthy and fractured subjects after correction for BMD. UTV was also a significant predictor of fracture in a selected subgroup of healthy and fractured women paired for BMD (144 pairs). In this same subgroup, the difference in UTV between fractured and healthy women regression lines was related to elasticity (E) variation between pairs. Simultaneously evaluating BMD and UTV as fracture predictors, logistic regression showed an odds ratio that was twice that of each predictor alone and 1.2 times higher than that derived from the simultaneous evaluation of two different BMD predictors. These data confirmed that UTV differentiates between healthy and fractured women both as well as and independent of BMD. In addition, UTV separated fractured from healthy BMD matched women by measuring non mass related differences. The simultaneous use of BMD and UTV improved the discriminant ability of each of them alone and of two simultaneous measurements of BMD detected at different skeletal sites.

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.

Utility of ultrasound to assess risk of fracture

Traditional assessments of bone properties have utilized densitometry techniques such as Dual Energy X-ray Absorptiometry (DXA). Recently, quantitative ultrasound (QUS) has been introduced as an alternative method of assessing bone properties. Advantages of QUS over X-ray techniques include low costs, portability, and nonionizing radiation. Proponents of QUS have claimed that this technology can provide information not only about the density but also about the structure and mechanical properties of bone. There are two major questions that need to be answered for those who seek to diagnose bone disorders with ultrasound: (1) what does quantitative ultrasound actually measure, and, even more importantly, (2) what is its clinical utility? In this review we will briefly examine the first question and will focus on the utility of ultrasound in clinical trials to discriminate between fractures and non-fractures and to predict the risk of fractures.

Precision and discriminatory ability of calcaneal bone assessment technologies

To determine if measuring skeletal status at the calcaneus is a potentially valuable technique for diagnosing osteoporosis, we examined five calcaneal assessment techniques in 53 young normal women and 108 postmenopausal women with osteoporosis and compared these measurements to dual-energy X-ray absorptiometry (DEXA) at the calcaneus, hip, and spine. The five instruments, including single-energy X-ray absorptiometry (SEXA) and four quantitative ultrasound (QUS) instruments, were evaluated for precision, ability to discriminate osteoporotic from young normal subjects, and correlation to the other instruments. The coefficient of variation (%CV) for instrument, positioning, interobserver, and short-term precision of the five calcaneal instruments ranged from 1.34-7.76%, 1.63-7.00%, 1.84-9.44%, and 1.99-7.04%, respectively. The %CVs for positioning, interobserver, and short-term precision were similar for calcaneal DEXA, calcaneal SEXA, and stiffness (as measured by Achilles). The %CVs for instruments precision were similar between calcaneal DEXA and SEXA. The ability of the five calcaneal instruments to discriminate osteoporotic from young normal subjects was similar based on the analysis of area under the receiver operating characteristic curves (range 0.88-0.93) and equivalent to DEXA of the calcaneus and hip (0.88-0.93). The correlations between the measurements of five calcaneal instruments were strong (0.80 < or = r < or = 0.91, p < 0.001). These data suggest that although the precision is variable, the calcaneal QUS and SEXA instruments can discriminate between osteoporotic patients and young normal controls and appear to be a useful technique for assessment of osteoporosis.

Water bath and contact methods in ultrasonic evaluation of bone

Ultrasonic devices for the measurement of speed of sound (SOS) and broadband ultrasonic attenuation (BUA) generally use either a contact or water bath method. The aim of this study was to compare these two methods while determining the influence of soft tissue, pathlength (heel width and bone width), and a fixed heel dimension on SOS (m/second) and BUA (dB/MHz). Ultrasonic measurements were made using a CUBA Research system utilizing a pair of 1 MHz unfocused transducers with mean precision CV = 0.7% and 6.0% for all SOS and BUA measurements, respectively. SOS and BUA were determined in 24 human cadaveric heels under three conditions: contact method (heel intact), water bath method (heel intact), water bath method (no soft tissue). Although there were significant differences between measurements using contact and water bath techniques (heel intact), their correlations were high (r = 0.858 for SOS and r = 0. 937 for BUA; P < 0.001). After removal of soft tissue, SOS significantly increased (78 m/second; P < 0.001) whereas there was no change in BUA (P > 0.05). Heel width correlated with SOS measurements (-0.224 < r < -0.347; P < 0.001) and bone width correlated with BUA measurements (0.198 < r < 0.276; P < 0.001). The practice of using a fixed heel dimension (Lunar Achilles) was investigated by comparing SOS calculated with measured heel thickness and a value of 4 cm (Lunar Achilles). SOS increased by 42 m/second (2.7%) using the fixed heel dimension compared with measured heel widths. This study demonstrates the similarity between contact and water bath-based methods, while showing that the presence of soft tissue reduces SOS but has no effect on BUA. The use of a fixed heel dimension for calculation of SOS overestimates values obtained when using measured heel dimensions, though the values correlate highly (r = 0.98, P < 0.001). In addition, an increase in heel width tends to cause an underestimation of SOS whereas an increase in bone width tends to overestimate BUA, although the effects are relatively small.

Factors influencing an ultrasound-estimated bone mass in postmenopausal women

OBJECTIVE

There are various methods for determining bone-mineral density for diagnosing osteoporosis. The most accurate method among them is dual-energy X-ray absorptiometry (DEXA), and the simplest one utilizes an ultrasound bone densitometer. We investigated factors influencing the correlation between bone-density values determined by dual-energy X-ray absorptiometry and by the use of an ultrasound bone densitometer.

METHODS

Sixty-seven postmenopausal Japanese women aged from 31 to 68 years old were enrolled in the study. Bone-mineral densities (BMDs) of the lumbar spine (L2-4) measured by DEXA and broadband ultrasound attenuation (BUA) of the right os calcaneus measured by an ultrasound bone densitometer were subjected to statistical analysis.

RESULTS

Multivariate analysis indicated that the patient's exercise history was useful-following the number of years since menopause and body weight-for determining lumbar spine bone-mineral density. The influence of hormone replacement therapy (HRT) on bone mass in postmenopausal women is also considered to be marked, but the results of the present multivariate analysis showed almost no influence on BUA or the L2-4 BMD.

CONCLUSIONS

The patient's exercise history should be taken into consideration when lumbar spine bone-mineral density is estimated using an ultrasound bone densitometer instead of DEXA.

Quantitative ultrasound of the calcaneus reflects the mechanical properties of calcaneal trabecular bone

To provide new information about the potential role of quantitative ultrasound (QUS) in fracture risk prediction, we assessed whether QUS and densitometric variables derived from measurements of intact cadaveric feet were associated with the mechanical properties of calcaneal trabecular bone. We obtained 31 intact cadaveric feet from the local anatomic gifts program, including 13 men and 18 women, with a mean age of 77 years (range 50-91 years). Broadband ultrasound attenuation (BUA) and ultrasound transit velocity (SOS) were assessed in the intact cadaveric feet using a water-based ultrasound system. In addition, we measured the bone mineral density (BMD) of the posterior calcaneus using dual-energy X-ray absorptiometry. Cubes of trabecular bone were then removed from the calcaneus at approximately the same location as the QUS measurements were obtained, and the elastic modulus and ultimate strength of the trabecular bone specimens were measured by compressing them in the mediolateral direction. We found that QUS variables were moderately to strongly correlated with the mechanical properties of calcaneal trabecular bone (r2 = 0.48-0.63, p < 0.001 for all). However, the strongest associations with the mechanical properties trabecular bone were provided by calcaneus BMD and trabecular bone apparent density (r2 = 0.66-0.88). BUA and densitometric measurements were independently associated with elastic modulus, but not with ultimate strength. Our results indicate that QUS measurements of the intact heel are associated with the mechanical properties of calcaneal trabecular bone and, in some cases, provide information in addition to that provided by BMD or density measurements.

The effect of cortical endplates on ultrasound velocity through the calcaneus: an in vitro study

Ultrasound velocity has been reported as a good predictor of bone strength measured in vitro using standard mechanical testing techniques. Such mechanical investigation of bone strength cannot be carried out in vivo, because of the invasive nature of the testing. Therefore to be able to extrapolate the in vitro findings to the clinical situation, the effect of cortex on ultrasound transmission velocity through the calcaneus is required. This was investigated in vitro by measuring ultrasound velocity through samples of different modification using a CUBAResearch ultrasound machine. The different sample modifications were: "whole" (soft tissue removed), "core" (cylindrical sample), "can" (cancellous sample without the cortex) and "def" (defatted cancellous sample). Ultrasound transmission velocity for the various sample modification were highly correlated with each other (r = 0.80-0.97). Coring resulted in a 0.77% increase in the mean velocity. Substituting bone marrow (defatting) with water at room temperature had no measurable effect on the ultrasound velocity. The velocity in the whole samples and the cancellous samples were statistically different with the cortex introducing only a 2% increase in the ultrasound velocity. Therefore the in vivo ultrasound velocity measured at the calcaneus is determined mainly by the cancellous bone component which is more sensitive to osteoporotic changes. Hence the reported ability of ultrasound velocity in vitro to predict bone strength could be expected in vivo.

Ultrasound bone densitometry of os calcis in elderly Japanese women with hip fracture

We evaluated 138 elderly patients (mean age 79 years) within 2 weeks after hip fracture (67 cervical and 71 trochanteric) using an Achilles ultrasound bone densitometer (Lunar Corporation, Madison, WI). The ultrasound variables of speed of sound (SOS in m/second), broadband ultrasound attenuation (BUA in dB/MHz), and stiffness (%) index were measured on the os calcis. Ultrasound densitometry also was done on 563 normal postmenopausal women to assess normal age changes. An elderly subgroup (n = 138) served as age-matched controls for the hip fracture group. Further subgroups of 33 patients and 33 controls were compared for lumbar spine and femoral neck BMD. There were no statistically significant differences between the hip fracture group and age-matched controls in height and weight, but each ultrasound variable was significantly lower for the hip fracture group (P < 0.0001). For the hip fracture group, SOS was 1470 +/- 19 m/second, BUA was 84.3 +/- 8.4 dB/MHz, and the stiffness index was 47.8 +/- 9.2%, whereas for the age-matched controls, SOS was 1486 +/- 27 m/second, BUA was 94.0 +/- 11.4 dB/MHz, and the stiffness index was 59.1 +/- 12.5%. There were no significant differences between cervical and trochanteric hip fracture groups. Logistic regression analysis showed that a change of the ultrasound values by 1 standard deviation (SD) changed the odds ratio for SOS, BUA, and stiffness index by 2.51, 3.24, and 3.60, respectively. Ultrasound variables, particularly stiffness, were good indicators of hip fracture risk.

Ultrasound bone velocity on proximal phalanges in premenopausal, perimenopausal, and postmenopausal healthy women

RATIONALE AND OBJECTIVES

The authors studied premenopausal, perimenopausal, and postmenopausal women to determine if ultrasound bone velocity (UBV) on proximal phalanges of women reflect bone changes related to gonadal status and age.

METHODS

A total of 166 healthy women-64 postmenopausal women (mean age 58.7 +/- 9.4 years), 41 perimenopausal women (mean age 49.5 +/- 2.9 years), and 61 premenopausal women (mean age 36.8 +/- 7.1 years)-were studied. All the women underwent UBV study of the 2nd to 5th proximal phalanges on the nondominant hand and the mean value of all ultrasound measurements was calculated.

RESULTS

The postmenopausal women had a UBV that differed significantly, one-way analysis of variance, from that of the perimenopausal women and premenopausal women (both P < 0.001). The UBV measurements of the perimenopausal women differed significantly from those of the premenopausal women (P < 0.01). Simple linear regression analysis of the relation between UBV and age showed that this was significant and negative in the overall group of women (r = -0.69; P < 0.0001), significant in the perimenopausal (r = -0.66; P < 0.001) and postmenopausal women (r = -0.69; P < 0.001) and nonsignificant in the premenopausal women (r = 0.08; P not significant). In the postmenopausal women, the correlation between UBV and years since menopause was larger (r = -0.71; P < 0.0001) than the correlation between UBV and chronological age.

CONCLUSIONS

Ultrasound bone velocity of the phalanx, as a method for measuring changes in bone with age, has a precision that makes it possible to detect changes in bone mass in perimenopausal women and may perform similarly to other bone mass measurements.

The role of ultrasound in the assessment of osteoporosis: a review

Osteoporosis is now being recognized as a "silent epidemic" and there is an increasing need to improve its diagnosis and management. Quantitative ultrasound (QUS) measurement [broadband ultrasound attenuation (BUA) and velocity] is emerging as an alternative to photon absorptiometry techniques in the assessment of osteoporosis. The fundamental principles governing ultrasound measurements are discussed, and some of the commercially available clinical systems are reviewed, particularly in relation to data acquisition methods. A review of the published in vivo and in vitro data is presented. The general consensus is that ultrasound seems to provide structural information in addition to density. The diagnostic sensitivity of ultrasound measurement of the calcaneus in the prediction of hip fracture has been shown by recent large prospective studies to be similar to hip bone mineral density (BMD) measured with dual-energy X-ray absorptiometry (DXA) and superior to spine BMD. Ultrasound has also been shown to correlate better with the type of hip fracture (intertrochanteric or cervical) than BMD and to provide comparable diagnostic sensitivity to spine BMD in vertebral fractures. It has also been observed that combining the results of both ultrasound and DXA BMD significantly improved hip fracture prediction. Areas where further research is required are identified.

The epidemiology of quantitative ultrasound: a review of the relationships with bone mass, osteoporosis and fracture risk

Quantitative ultrasound (QUS) is a simple, inexpensive and non-invasive measure of bone which has been used in research settings for the prediction of osteoporosis. This review summarizes the current status of the epidemiology of QUS analysis, including its relationship with bone mineral density (BMD), risk of osteoporotic fracture and risk factors for osteoporosis. Although only moderately correlated with BMD, QUS appears to be as strong a predictor of osteoporotic fracture as BMD and may predict fracture independent of BMD. Risk factors for low QUS, including age, menopause, body composition and physical inactivity, seem to parallel those of low BMD. More longitudinal research is needed to confirm the clinical utility of QUS and more experimental and population-based studies are needed to determine whether the etiology of low QUS values is different from that of low bone mass.

Ultrasound bone densitometry and dual energy X-ray absorptiometry in patients with spinal cord injury: a cross-sectional study

Bone is lost following spinal cord injury (SCI) and in the long-term may become osteopenic and liable to fracture. Two non-invasive techniques, ultrasound bone densitometry (USBD) and dual energy X-ray absorptiometry (DXA), have been applied to monitor bone changes after spinal injury. 31 SCI patients were scanned using an ultrasound bone densitometer, to give measurements of speed of sound (SOS), broadband ultrasound attenuation (BUA) and "stiffness'. The time since injury of these patients ranged between 5 weeks to 36 years with a mean of 5.87 +/- 10.21 years. Ultrasonic properties at the calcaneus of these patients were significantly lower than the healthy reference population, and a rapid decline in ultrasound properties occurred in the first 3 months. The fall continued up to 54 months but at a slower rate. The normal linear relationship between SOS and BUA was not altered by SCI. Eighteen patients had DXA measurements at the lumbar spine and the right proximal femur. Bone mineral density (BMD) at the femoral neck was significantly lower than the normal reference population (P < 0.05). SOS and "stiffness' correlated significantly with BMD at the lumbar spine, Ward's triangle, the femoral neck, the greater trochanter and the intertrochanteric site (P < 0.05). BUA correlated significantly at all these sites with the exception of the trochanter. A negative correlation was found between the ultrasonic properties at the calcaneus and BMD at the lumbar spine which is in contrast to the positive relationship in normal subjects. There was a tendency for BMD to increase at the lumbar spine after the first 12 months after injury, although this trend was not significant overall. The "stiffness' at the calcaneus and BMD at the femoral neck were lower than the reference population following 12 months since injury. These results show that bone deficit at the calcaneus occurs rapidly and to a severe degree after SCI, and that ultrasound has an important role to play in the assessment of bone status in these patients.

Broadband ultrasound attenuation imaging: a new imaging method in osteoporosis

The purpose of this study was to evaluate the usefulness in osteoporosis of a new ultrasound imaging device able to create a parametric image of broadband ultrasound attenuation (BUA) at the os calcis. Three regions of interest were located in the great tuberosity of the os calcis. Precision was evaluated in 37 patients. Calcaneal bone mineral density (BMD) and BUA were compared in 33 patients. In 236 patients (including 77 with osteoporotic fractures), BUA and lumbar and femoral BMD measurements were performed. The measurements were compared using correlation coefficients. Their clinical value was estimated by comparisons of the results between patients with fractures and age-matched controls, using comparisons of the means, areas under the ROC curves, and logistic regression. Precision was in a 1.4-3.3% range. Local BUA and BMD were highly correlated (r = 0.88). Significant correlations were found between BUA and lumbar (r = 0.56) and femur (r = 0.66) BMD. In multiple regression, years since menopause and weight were significant predictors of BUA. Patients with fractures had lower BUA and BMD than age-matched controls. BUA showed the largest difference between the two populations (13-16%). Areas under the ROC curves were similar for BUA and BMD. Logistic regression after adjustment for confounding factors showed that BUA discriminated between fracture and nonfracture subjects. Broadband ultrasound attenuation imaging improves the reproducibility of ultrasound measurements. It may be useful in osteoporosis, due to its good discriminating value.

Bone quality factor analysis: a new noninvasive technique for the measurement of bone density and bone strength

The sensitivity of bone mineral density (BMD) as a predictor of fracture risk is limited by the fact that this index does not take into account the geometrical and material characteristics of bone. In contrast, both BMD and bone architecture influence the quality factor (QF), the fraction of the inverse of the energy lost in one cycle of deformation. In this study we have compared the sensitivity of a QF analyzer and dual-energy X-ray absorptiometry (DXA) in detecting the changes induced by ovariectomy (OVX) on the QF, impact strength, and BMD of the femur of mature rats. QF and BMD were measured noninvasively before and 4 weeks after OVX or sham operation using a QF analyzer developed in our laboratory and a Hologic QDR 2000 bone densitometry, respectively. Impact strength was measured in excised femurs at the end of the study. The in vivo short-term precision (coefficient of variation) of the QF analyzer was 1.9%. BMD and QF measurements were highly correlated (r = 0.80,p <0.0001). At baseline, QF and BMD were similar in OVX and sham-operated rats. At 4 weeks, BMD was 14.7 + or - 0.9% lower than at baseline (p < 0.001) in OVX rats and 5.3 + or - 1.3% lower in sham-operated rats (p <0.05). QF decreased 36.0 + or - 2.8% (p <0.0001) in OVX and 10.6 + or - 3.6% in sham rats (p <0.01). As a result, at 4 weeks the difference between sham-operated and OVX rats was larger (p < 0.05) by QF than by BMD. Moreover, QF correlated better than BMD with impact strength and the difference in impact strength between sham and OVX mice was closer to that in QF than that in BMD. These data demonstrate that QF analysis is a precise technique that is more sensitive than DXA in detecting the changes in bone density and strength induced by OVX. QF analysis may represent a new, simple, and economic technique for predicting fracture risk.

Influence of marrow on ultrasonic velocity and attenuation in bovine trabecular bone

Measurements of ultrasonic velocity and specific differential attenuation (SDA) were obtained on 24 bovine trabecular bone specimens from the femoral condyles. The measurements were obtained using two pairs of ultrasonic transducers, one with a low nominal center frequency (500 kHz) and the other pair with a high nominal center frequency (1 MHz). The ultrasonic velocity and specific differential attenuation associated with the bone samples were determined both with and without marrow, i.e., replacing the marrow with water in the pores of the trabecular bone. Significant increases (2.1% and 2.9%) in the velocity of ultrasound were observed after removal of the marrow, for the low and high frequency transducer pairs, respectively. In contrast, significant decreases (-6.5% and -8.8%) in SDA were observed after removal of the marrow, for the low and high frequency transducer pairs, respectively. The bone densities (BD) of the samples were also determined using single photon absorptiometry (SPA). Correlations between ultrasonic parameters and bone densities for samples both with and without marrow were found to be similar. For example, for the 1 MHz transducer pair, the correlation between BD and velocity was r = 0. 86 with marrow, and r = 0.89 without marrow. This study also compared the results obtained using a contact (no water bath) technique and an insertion (with a water bath) technique of ultrasonic measurements. For the high frequency transducer pair, the correlation coefficients between the two methods were r = 0.99 and r = 0.93, for the velocity and specific differential attenuation, respectively. Similar results were found for the low frequency transducer pair as well. In addition, approximately equal correlations between BD and ultrasonic velocity and SDA were also found, indicating that contact and insertion measurements provide essentially equivalent information.

Ultrasonic assessment of human and bovine trabecular bone: a comparison study

A comparison study is reported on the ultrasonic assessment of human trabecular and bovine trabecular bone samples. Both ultrasonic velocity and ultrasonic attenuation were evaluated through a transmission insertion technique and correlated with bone mineral density as determined with single photon absorptiometry. For a 1-MHz ultrasonic transducer pair and the human cancellous bone samples the correlations were 0.91 and 0.89 between density and velocity and attenuation, respectively. For a 500-kHz ultrasonic transducer pair the correlations were 0.89 and 0.81 between density and velocity and attenuation, respectively. For the bovine bone samples, the correlations were 0.90 and -0.31 for the velocity and attenuation, respectively, for the 1 MHz transducer pair. For the 500-kHz transducers, the correlations were 0.85 and -0.17 for the velocity and attenuation, respectively. By combining both velocity and attenuation in a multivariate regression, an improvement was achieved in the estimation of bone density in the human samples for both the 500-kHz and 1-MHz transducer pairs. No significant improvement was achieved in the multivariate regressions for the bovine bone samples. In conclusion, the results indicate that ultrasonic measurements are in general highly correlated with bone mineral density in trabecular bone samples. This correlation is more consistent and strong in relatively low density human samples compared with the higher density bovine samples.

Correlation of ultrasound bone velocity with dual-energy X-ray bone absorptiometry in rat bone specimens

RATIONALE AND OBJECTIVES

To investigate bone mass measurements by ultrasound bond velocity (UBV) in bone specimens obtained from experimental animals.

METHODS

The authors made UBV measurements in 40 femurs and tibias dissected from Sprague-Dawley rats (14 weeks-old, mean weight 290 g) and compared them with bone densitometric measurements made on the same material using dual-energy x-ray absorptiometry (DXA).

RESULTS

The coefficient of variation for UBV measurements, based on values obtained in five femurs and five tibias at different times, was 0.2% and 0.3% respectively. Regression studies yielded a correlation between UBV and bone mineral density in femur of r = 0.87 (P < 0.0001) and with bone mineral content of r = 0.65 (P < 0.0001); in the tibia similar levels of significance were obtained. The correlation between femur weight and UBV was r = 0.51 (P < 0.0005) and with bone mineral content it was r = 0.79 (P < 0.0001). Partial correlation between UBV and femur bone mineral density, with respect to bone weight, was r = 0.68 (P < 0.001), and with femur bone mineral content was r = 0.71 (P < 0.0001). In the tibia measurements were similarly significant.

CONCLUSIONS

Measurements of bone mass made with ultrasound transmission velocity are precise correlate well with DXA measurements.

Quantitative ultrasound of bone in institutionalized elderly women: a cross-sectional and longitudinal study

Quantitative ultrasound of bone is a promising method for bone assessment: radiation-free, portable and predictive of hip fracture. Its portability allowed us to study the relationships between ultrasonic parameters of bone with age and with non-vertebral fractures in elderly women living in 19 nursing homes. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) of the calcaneus were measured (and the stiffness index calculated) in a sample of 270 institutionalized women, aged 85 +/- 7 years, using an Achilles bone densitometer (Lunar). The effects of age, history of non-vertebral and non-traumatic fractures, body mass index, triceps skinfold and arm circumference were assessed on BUA, SOS and stiffness index. Furthermore, to evaluate longitudinally the influence of aging on the ultrasound parameters of bone, 60 subjects from the same group had a second ultrasound measurement after 1 year. The cross-sectional analysis of the data on all 270 women showed a significant decrease (p < 0.001) with age in BUA, SOS and stiffness index (-0.47%, -0.06%, and -1.01% respectively per year). In the 94 women, (35%) with a history of previous non-vertebral fractures, ultrasound parameters were significantly lower (p < 0.0001) than in the 176 women with no history of fracture (-8.3% for BUA, -1.3% for SOS, -18.9% for stiffness index). In contrast, there was no significant difference in anthropometric measurements between the groups with and without previous non-vertebral fractures, although the measurements decreased significantly with age. In the longitudinal study, repeated quantitative ultrasound after 11.4 +/- 0.8 months showed no significant decrease in BUA (-1%) but a significant decrease in SOS (-0.3%, p < 0.0001) and in stiffness index (-3.6%, p < 0.0002). In conclusion, quantitative ultrasound of the calcaneus measures properties of bone which continue to decline in institutionalized elderly women, and is able to discriminate women with previous non-vertebral fractures.

Ultrasonic measurement: an evaluation of three heel bone scanners compared with a bench-top system

Three commercial ultrasound bone scanners designed for os calcis measurements (Lunar Achilles, C.U.B.A. "Research" and UBA 575) were compared using the Leeds Ultrasonic Bone Phantoms. The porosity of the phantoms ranged from 50% to 83% with velocities between 1490 and 1621 m s-1 and broadband ultrasound attenuation (BUA) values in the range 46-115 dB MHz-1. The three devices tested were able to discriminate porosity differences of at least 3%, although the values obtained for the propagation parameters varied widely. Velocity differences of up to 38 m s-1 and BUA variations of up to 33 dB MHz-1 were found, although a relationship was identified between the velocity and BUA measurements. In some cases, the variation can be attributed to differences in the measurement technique adopted, although there also seem to be detailed differences in the definition of the parameters themselves. The variation between different devices from the same manufacturer (Lunar) was also studied. Measurements taken from five devices showed variation in velocity values of up to 25 m s-1 (SD 10.8 m s-1) and in BUA values of up to 11 dB MHz-1 (SD 4.3 dB MHz-1). We conclude that the variation both between manufacturers and between nominally identical machines may be of clinical significance. Both users and manufacturers need to consider urgently the introduction of quality standards and consensus definition of terms and techniques. The fact that all machines studied have been superseded commercially does not invalidate these conclusions, since many of the devices tested remain in clinical use and there is no evidence of fundamental change in manufacturers' procedures.

Advances in the noninvasive assessment of bone density, quality, and structure

Recent advances in the development of methods to assess the skeleton noninvasively have contributed to screening for risk of osteoporosis, early detection of the disease, and effective monitoring of its progression and response to therapy. The capability now exists to evaluate the peripheral, central, or entire skeleton as well as the trabecular bone or cortical bone envelopes accurately and precisely, with the capacity to determine bone strength and predict fracture risk. In this article we examine the current and future capabilities of quantitative computed tomography (QCT), quantitative ultrasound (QUS), and magnetic resonance microscopy (muMR) to assess architectural and densitometric properties of the skeleton to enhance the prediction of fracture risk.

Quantitative ultrasound bone measurements: normal values and comparison with bone mineral density by dual X-ray absorptiometry

Normative data for qualitative ultrasound (QUS) measurements: speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness were established in 118 healthy women aged 20-86 years and in 42 healthy men aged 22-76 years. The relations between age, weight, height, and QUS were studied. QUS measurements were negatively correlated with age in both sexes. In women, age was accepted as first factor (R2 = 0.39 for SOS, 0.35 for BUA, and 0.45 for stiffness, P < 0.001); weight was accepted as second factor for BUA (R2 = 0.44, P < 0.001). In men, age was the only significant parameter (R2 = 0.41 for SOS, 0.39 for BUA, 0.43 for stiffness, P < 0.001). QUS measurements of the right and left feet were highly correlated unless unilateral foot pathology such as algodystrophy was present. Significant correlations were found between QUS of the calcaneus and dual X-ray absorptiometry (DXA) of the lumbar spine (R = 0.67, P < 0.01 for SOS; R = 0.57, P < 0.02 for BUA; R = 0.65, P < 0.01 for stiffness).

Ultrasound and dual X-ray absorptiometry measurement of the calcaneus: influence of region of interest location

Ultrasound measurements of the calcaneus are related to incidence of osteoporotic fracture. Such measurements are generally made at fixed coordinates relative to a footplate. This study compares measurements at an anatomically located region of interest (ROIanat) and at fixed coordinates (ROIfixed), with bone mineral density measurements, in 84 postmenopausal women. Bone mineral density (BMD) was assessed using dual energy X-ray absorptiometry at both ROIs as well as at lumbar spine and femoral neck. Broadband ultrasound attenuation and velocity of sound were measured using a CUBA system at ROIanat and ROIfixed. Additionally, broadband ultrasound attenuation at ROIfixed was measured using a Walker Sonix instrument. Mean bone mineral density, broadband ultrasound attenuation and velocity of sound did not differ significantly between ROIfixed and ROIanat, although broadband ultrasound attenuation by Walker Sonix (81.4 +/- 14.6 dBMHz-1) was significantly (P < 0.001) greater than that by CUBA (63.7 +/- 14.2 dBMHz-1). The relationship between broadband ultrasound attenuation and BMD differed significantly between the 2 ROIs and the correlation of this relationship was significantly greater at ROIfixed than at ROIanat(r = 0.74 versus 0.46, P < 0.01). The differing relationship may reflect structural variation at different regions. ROI selection may thus be a possible confounding factor in ultrasound measurement.

Ultrasound in the evaluation of osteoporosis: a comparison with bone mineral density at distal radius

It is proven that, from a technical point of view, ultrasound transmission velocity (UTV) measurement can easily be taken at the distal end of the radius. The reproducibility of UTV is good (coefficient of variation 0.3% intraoperator and 0.5% interoperator). 248 normal and 65 osteoporotic women were then studied to establish the range of UTV values and to compare the ability of UTV and bone mineral density (BMD) measurement, taken at the same skeletal sites, to detect osteoporotic fragility. Osteoporosis was defined by the presence of atraumatic vertebral fractures on an X-ray of the spine. Ultrasound velocity averaged 1570.5 +/- 43.3 m s-1 in normal and 1519.2 +/- 15.2 m s-1 in osteoporotic women; the difference is also statistically significant (p < 0.01) for BMD. Both BMD and UTV decline after menopause and are significantly correlated with age. A weak correlation (r = 0.68) was found between UTV and BMD; this supports the thesis that ultrasound velocity measures bone mass as well as other fragility components of bone distinct from the decrease of mass. Receiver operating characteristic (ROC) curve analysis showed that UTV discriminates between normal and osteoporotic patients at least as well as radial BMD, indicating that UTV is a new available diagnostic modality which can be used to screen osteoporotic subjects.

Ultrasound bone measurement in pediatric subjects

Ultrasound bone measurement in healthy (n = 71) and osteopenic (n = 18) children aged 6 through 13 years of both sexes has been evaluated using the Achilles densitometer (Lunar Corporation). Measurements on the os calcis included speed of sound (SOS), broadband ultrasound attenuation (BUA), and a calculated "stiffness" index. The Achilles was adapted for children by a special positioning procedure that included the use of foot shims, and beam collimation on the receiving transducer. The precision of ultrasound results was comparable to that in adults (0.2% for SOS, 1.5% for BUA, and 1.8% for stiffness). SOS, BUA, and stiffness values increased with age in both sexes. Ultrasound measurements were correlated with bone mineral density (BMD in g/cm2) of the heel, AP spine (L2-L4), and total body by dual X-ray absorptiometry (DXA) densitometry (Lunar DPX-L). SOS, BUA, and stiffness measurements were significantly lower in osteopenic children (Z approximately -1.9 to -2.5) (P < 0.0001) than in normal age-matched controls. Total body BMD showed a higher Z-score than stiffness (-3.3 versus -2.5), but stiffness showed a greater percentage decrease (-30% versus -18%). In conclusion, ultrasound measurements of bone in children provide both good precision and discrimination of normals from osteopenic patients.

Ultrasound velocity, through bone predicts incident vertebral deformity

We followed 130 postmenopausal women without evidence of vertebral deformity by lateral spine radiographs on entry into study for 2 years, and repeat spine radiographs were taken at the end of that time. Incident deformities occurring within this 2 year period were detected by two methods, a level-specific radiogrammetric approach and visual inspection by skilled clinicians. Fourteen incident deformities were detected by the radiogrammetric method, and 19 by the clinicians. Ultrasound transmission velocity was measured at the patella in each subject on entry. Values for ultrasound velocity were significantly correlated with incident fracture occurrence, with individuals having velocity values more than one standard deviation below the mean for the group exhibiting from 3.3 to 4.6 times the probability of incident fracture as individuals with velocity values more than one standard deviation above the mean. Thus, low values for ultrasound transmission velocity at the patella detect yet-unexpressed bony fragility at the spine and predict future fracture.

Comparison of speed of sound ultrasound with single photon absorptiometry for determining fracture odds ratios

The purpose of this study was to compare the ability of ultrasound velocity measurement with that of single photon absorptiometry to determine the odds of history of fracture since age 40, for a population-based study. To do this we computed odds ratios and 95% confidence intervals for 809 women and 502 men, aged 50 years and older, who are participants in the prospective phase of the Saunders County Bone Quality Study. These participants received both the ultrasound and single photon absorptiometry bone measurements at the initiation of the study. In addition, a history of all fractures that had occurred to participants since age 40 was obtained. The two bone assessment methods were compared by examining the magnitude of the odds ratios, to determine which produces the highest estimate of the probability of odds of fracture, and by examining widths of the respective confidence intervals to show which estimate of odds ratio is the most precise. Ultrasound velocity estimates a higher probability of odds of both low-trauma fractures and all fractures than distal radius and ulna bone mineral content, but lower than bone mineral density at the same sites for both women and men. However, the ultrasound measure is more precise than bone mineral density, but less precise than bone mineral content. We conclude that ultrasound velocity is as good as single photon absorptiometry in estimating odds of fracture.

Quantitative ultrasound: a technique to target women with low bone mass for preventive therapy

Assessment of bone mass is the best predictor of fracture. The current challenge is to develop a strategy to determine which women should be targeted for preventive therapy. The cost of dual-energy x-ray absorptiometry equipment precludes its widespread availability in physicians' offices and clinics. Quantitative ultrasound appears to offer a low-cost alternative method to assess bone mass and fracture risk. In addition, ultrasound is radiation free. Quantitative ultrasound values decrease with age, are lower in osteoporotic women, and are influenced by estrogen treatment. The associations observed between quantitative ultrasound and fracture indicate that it is comparable to densitometry in predicting fracture risk. This association remains significant after correction for bone mineral density, suggesting that ultrasound measures additional properties of bone that are determinants of strength. Quantitative ultrasound may prove to be a technique that will allow bone mass testing to become more readily available to the population. The ability of quantitative ultrasound to discriminate those women at greatest risk for fracture will allow physicians to target those women for preventive therapy.

Ultrasound discriminates patients with hip fracture equally well as dual energy X-ray absorptiometry and independently of bone mineral density

We measured the heels of 43 women who had recently sustained a hip fracture and 86 age matched controls, using an Achilles ultrasound device. Average BUA, SOS, and Stiffness were significantly lower in fractured patients (p < 0.0001). We also estimated ultrasound parameters for patients as a function of controls and found the mean BUA to be -1.09 SD compared with controls, the mean SOS -0.89 SD, and the mean Stiffness -0.98 SD. Femoral BMD measured at the neck, Ward's triangle, and the trochanter with a DPX Plus was also significantly lower in fractured patients (p < 0.0001). The increased risk of hip fracture associated with low ultrasound values was estimated with logistic regression analysis for each bone parameter, adjusted for height and weight. The adjusted regression coefficients associated with BUA, SOS, Stiffness, and BMD were all significant (p < 0.0001) demonstrating the influence of all ultrasound and DXA parameters on the risk of hip fracture. After adjusting the logistic regressions for BMD neck, BUA, SOS, and Stiffness were still significant independent predictors of hip fracture. Sensitivity and specificity of all measures were analyzed with the area under the ROC curve which were for BUA, 0.77 +/- 0.04; for SOS, 0.75 +/- 0.04; for Stiffness, 0.78 +/- 0.04; and for BMD, 0.74 +/- 0.04. We determined the range for the best compromise between sensitivity and specificity of BUA, 97-98 dB/MHz; SOS, 1482-1487 m/s; Stiffness 59-62% Young Adult; and of BMD, 0.64-0.69 g/cm2. The area under the ROC curves of BUA, SOS, Stiffness, and DXA were compared and no statistically significant difference was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting the in vivo precision of broad-band ultrasonic attenuation

The in vivo precision of broad-band ultrasonic attenuation (BUA) was measured in one normal male volunteer over periods of one day and six weeks and in a group of 10 volunteers over a period of two weeks using a Walker Sonix UBA 1001 bone mineral analyser in which the foot is immersed in a water tank. Coefficients of variation ranged from 1-3% and, in general, there was no difference in BUA variance between right and left feet. However, right foot BUA values were consistently greater than those of the left, but there was no difference between mediolateral and lateromedial transmission. The use of preboiled water improved precision and reduced measurement time. In addition, factors affecting BUA precision were investigated in the individual volunteer. Equipment stability and conditions of immersion (immersion time, water depth, water temperature and concentration of a detergent wetting agent) had comparatively little effect on BUA values. On the other hand, the effects of foot positioning were more pronounced: rotation about the long axis of the foot, translation across the water tank and foot movement in the dorsal-plantar direction each contributed a maximum of 1.5-2.0% variation in BUA. However, both rotation about the long axis of the leg and foot movement in the heel-toe direction could change BUA by as much as 9%. It is likely that foot positioning will limit the precision achievable with this technique.

Age-related changes in Os calcis ultrasonic indices: a 2-year prospective study

We performed repeated ultrasound measurements approximately 2 years apart (average 23 months +/- 3 months) on the os calcis of 113 healthy postmenopausal women recruited from two large prospective cohort studies named OFELY and EPIDOS. Group A (from OFELY) consisted of 88 women aged 52-72 (63 +/- 5) years, randomly selected from a large insurance company, and group B (from EPIDOS) consisted of 25 women aged 75-88 (80 +/- 4) years, randomly selected from the voting lists. We obtained broadband ultrasonic attenuation (BUA) and speed of sound (SOS) measurements, as well as the Stiffness index, with a Lunar Achilles ultrasound machine. We performed dual energy X-ray absorptiometry (DXA) measurements of femoral neck bone mineral density (neck BMD) with a Hologic QDR 2000 for group A and with a Lunar DPX Plus for group B. The decrease that we observed over 2 years was on average +/- 1 SD: -1.01 +/- 4.6 dB/MHz (p = 0.02) for BUA (which is approximately equal to the long-term precision error in vitro), -11.3 +/- 9.2 m/s (p = 0.0001) for SOS (approximately 5 times the precision error), -3.8 +/- 4.2% YA (p = 0.0001) for Stiffness (2.5 times the precision error) and -0.01 +/- 0.03 g/cm2 (p = 0.0001) for neck BMD (approximately equal to the precision error). In terms of percentage change this represents: -1.0% +/- 4.3% for BUA, -0.8% +/- 0.6% for SOS and -1.85% +/- 4.4% for neck BMD. At the individual level, most SOS and Stiffness values were consistent with a decrease, whereas BUA and neck BMD values were spread out above and below the zero line of no change. The decreases in SOS and Stiffness were significantly larger in the early postmenopause (< or = 20 years since menopause [YSM]) than in the late postmenopause (> 20 YSM). We observed a similar trend for BUA and BMD but this did not reach statistical significance. We found a weak but significant correlation between changes in ultrasound variables and changes in neck BMD. However, the 2-year changes observed in SOS were not significantly correlated with changes in BUA. This study suggests that the heel ultrasound measurements of SOS and Stiffness are valuable indices of postmenopausal bone loss, and could be used for follow-up in therapeutic trials.

Should broadband ultrasonic attenuation be normalized for the width of the calcaneus?

Broadband ultrasonic attenuation (BUA) is a measure of ultrasound transmission through the calcaneus that is dependent on bone thickness as well as the density of scattering centres. This report examines whether the normalization of BUA (units dB MHz-1) for calcaneal width (nBUA: units dB MHz-1mm-1) improves the discrimination of clinical studies. BUA and calcaneal width were measured in 200 women using a contact ultrasound (CUBA-Research) system and nBUA evaluated by dividing BUA by bone width. 150 subjects were early post-menopausal and the remaining 50 were osteoporotic women with confirmed vertebral crush fracture. The ability of BUA and nBUA to differentiate between the two groups of subjects was compared using receiver operating characteristic (ROC) analysis. The areas (and standard errors) under the ROC curves were 0.878 (0.033) for BUA and 0.910 (0.028) for nBUA. The difference (and standard error) between the areas under the ROC curves was 0.033 (0.026) and was not statistically significant.

Ultrasound measurements on the os calcis in a prospective multicenter study

Ultrasonic assessment is a new approach to assess both quality and density. Two ultrasonic parameters are measured on the os calcis: the attenuation or broadband ultrasound attenuation (BUA) and the velocity or speed of sound (SOS). The interunit variations in vitro and in vivo of an ultrasound instrument, the Lunar Achilles system, used in a French multicenter study named EPIDOS, were calculated and the stability of these instruments over a 12-month period was evaluated. A third parameter called "stiffness index," calculated from the SOS and BUA, was also used in this study. The average CV in vitro for the BUA and SOS was 0.92% and 0.12%, respectively, and the average CV in vivo for the BUA, the SOS, and the stiffness index was 1.83%, 0.23%, and 1.9%, respectively. The interunit (or inter-machines) variations were calculated by a one-way analysis of variance. We detected small but significant measurement differences among centers on a phantom for both SOS (maximum significant difference 0.4%) and stiffness (maximum significant difference 3.5%) but not for BUA. Similar differences were found in vivo. The precision over 12 months of the interunit variations in vitro was evaluated by measuring a single phantom traveling from one center to another several times. The range of the CV for the BUA (1.54-0.51%), for the SOS (0.25-0.14%), and for the stiffness index (2.26-1.10%) are explained in part by technical failures. The variation among the five Achilles was estimated by the combined CV which was 1.42% for the BUA, 0.32% for the SOS, and 2.33% for the stiffness index. In conclusion, our findings indicate that equipment from one manufacturer appears to be consistent between machines for the BUA, but not completely for the SOS. The results for this stiffness index are necessarily influenced by both SOS and BUA. The short-term and long-term interunit precision is good, both in vitro and in vivo. Such results provide increased confidence in multicenter clinical trials where ultrasonic data are pooled.

The ultrasonic assessment of osteopenia as defined by dual X-ray absorptiometry

Dual X-ray absorptiometry (DXA) studies of bone mineral density (BMD) of the lumbar spine and femoral neck were compared with measurements of broadband ultrasonic attenuation (BUA) and velocity of ultrasound (VOS) in the calcaneus in 300 pre- and postmenopausal women (mean age 53 years). The women were referred for evaluation of possible osteopenia as defined by DXA. The ability of ultrasound measurements to predict osteopenia in women was compared with the ability of lumbar spine and femoral neck DXA scans to predict osteopenia in the hip and spine. A new ultrasound parameter obtained by combining BUA and VOS (combined attenuation and velocity (CAV)) was also evaluated. Linear regression analysis of the three ultrasound parameters and lumbar spine and femoral neck BMD gave weak but statistically significant correlations (r = 0.45-0.54). The correlation between spine and femoral neck BMD was statistically significantly better (r = 0.72). Receiver-operating characteristic (ROC) analysis was used to investigate the sensitivity and specificity of ultrasound measurements in predicting patients with osteopenia. The areas under the ROC curves ranged from 0.64 to 0.75 and ultrasound parameters were shown to be poor at predicting osteopenia as defined by DXA. The ability of lumbar spine and femoral neck DXA measurement to predict osteopenia in the hip and spine, respectively, was statistically significantly better than any of the ultrasound parameters. Ultrasound measurements in the calcaneus did not appear to identify accurately patients with osteopenia defined by DXA measurements of bone density in the axial and appendicular skeleton.