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H K Genant

Publications and source records attributed to H K Genant.

At least 289 records · Page 16Linked to original sources
PubMed1993

Broadband ultrasound attenuation signals depend on trabecular orientation: an in vitro study.

Quantitative ultrasound (QUS) techniques have recently been introduced as alternative methods free of ionizing radiation for non-invasive assessment of skeletal status in osteoporosis. We carried out an in vitro study on bone specimens to investigate whether broadband ultrasound attenuation (BUA) signals are associated with bone structure, specifically with the orientation of the trabeculae, and whether this association is independent of the association between orientation and bone mineral density (BMD) as measured by dual-energy X-ray absorptiometry (DXA). BUA and BMD of 10 cubical specimens of purely trabecular bovine bone were examined along the three principal axes. The relative orientation of the trabeculae with respect to the direction of the ultrasound beam was evaluated on high-resolution conventional radiographs employing a semiquantitative ALIGNMENT score ranging from -2 (for perpendicular) to +2 (parallel). BUA variability was 27.6 dB/MHz, reflecting both inter-specimen (18.2 dB/MHz) and intra-specimen (19.4 dB/MHz) variability at comparable levels and to a much lesser extent reproducibility errors (1 dB/MHz). BUA was 44%-54% larger along the axis of the compressive trabeculae as compared with the two perpendicular axes. BMD and ALIGNMENT showed independent significant associations with BUA. A change in ALIGNMENT from perpendicular to parallel corresponded to a difference in BUA of 36.1 dB/MHz. The substantial level of intra-specimen variability suggests that BUA reflects anisotropical characteristics of trabecular bone. The association of BUA and ALIGNMENT indicates that BUA signals depend of trabecular orientation. This association is independent of BMD, indicating that BUA has considerable potential for non-invasive assessment of bone structure and strength, free of ionizing radiation, and for complementing existing bone densitometry examinations.

Absorptiometry, Photon↗
PubMed1993

Quality assurance for bone densitometry research studies: concept and impact.

A concept for quality assurance (QA) in bone densitometry has been developed for clinical multicenter studies. Major elements provided by a coordinating center comprise (1) consulting services and certification of participating centers in the start-up phase of the study, (2) review of scan data acquired on QA standards for cross-calibration and longitudinal assessment of scanner stability, (3) review of selected patient data as well as of problem cases during the study, and (4) comprehensive review and correction of patient results based on QA data after conclusion of the study. Limitations of phantom-based QA data should be acknowledged. Typical problems encountered during research studies and guidelines for solutions are presented. Successful implementation of QA measures may yield substantial enhancement of statistical power. Depending on the study design and the variability of response within patient groups, improvement in precision due to QA measures may reduce the smallest detectable difference between subject groups or, alternatively, sample size by a few to more than 50%, and thus may contribute to a substantial reduction in study cost. Formulae for calculation of the magnitude of these effects are presented. To maximize the net benefit, QA efforts have to be limited to levels that assure reliability of the data at acceptable QA cost. While QA programs at individual clinical sites or for local practitioners may not need to be as extensive as for multicenter clinical trials, awareness of the potential problems and implementation of basic QA measures will help in obtaining high-quality bone densitometry results.

Bone Density↗
PubMed1993

Four-year study of intermittent cyclic etidronate treatment of postmenopausal osteoporosis: three years of blinded therapy followed by one year of open therapy.

PURPOSE: To determine the effect of long-term intermittent cyclic etidronate treatment on spinal bone density and vertebral fracture rates. PATIENTS AND METHODS: Postmenopausal osteoporotic women (n = 423) were randomized initially into a 2-year, double-blind, multicenter study; it was extended to a third year of blinded treatment followed by open-label treatment: 357 patients continued treatment in Year 3 (305 receiving blinded therapy and 52 receiving calcium supplementation) and 277 in Year 4. During Years 1 through 3, patients received double-blind treatment with phosphate (1.0 g) or placebo twice daily for 3 days, etidronate (400 mg) or placebo daily for 14 days, and calcium (500 mg) daily for the remainder of each 91-day treatment cycle. During Year 4, open-label intermittent cyclic etidronate therapy (without preceding phosphate) was administered to all patients. Spinal bone density and vertebral fracture rates were the main outcome measures. RESULTS: During Year 3, etidronate therapy maintained the significant increases in spinal bone mineral density of the first 2 years. Over the 3-year period, proximal femur bone density increased in etidronate-treated patients. Etidronate therapy for 3 years significantly decreased the vertebral fracture rate in patients at higher risk for fracture (low spinal bone density and three or more vertebral fractures at study entry), as compared with nonetidronate treatment (228 versus 412 fractures per 1,000 patient-years, respectively; p < 0.05). After 1 year of open-label treatment, patients previously treated with etidronate maintained bone mass, and vertebral fracture rates in all groups were lower than in any other study period. There were no apparent serious adverse effects. CONCLUSIONS: Three years of intermittent cyclic etidronate therapy produced significant increases in spinal and hip bone density, with a significant reduction in vertebral fracture rates in patients at higher fracture risk. Maintenance of bone mass and low fracture rate were observed when etidronate was continued for an additional year.

Analysis of Variance↗
PubMed1993

Precision and accuracy for rat whole body and femur bone mineral determination with dual X-ray absorptiometry.

Precision and accuracy for rat whole body and excised femur bone mineral density (BMD) measurements were evaluated with two dual X-ray absorptiometry (DXA) systems. The 'small subject' mode on the Norland XR-26 (XR), and the 'ultra high resolution mode' on the Hologic QDR-1000/W(QDR) were used for the analysis. The whole body mode was only available on the XR. The lowest precision error for the whole body was found using a scan resolution of 1.0 x 1.0 mm and a scan speed of 15 mm/s. The scan spatial resolution of the femur measurement was approximately eight times higher on the QDR than on the XR. However, the XR allowed analysis of an arbitrary region of interest within the femur, which was not easily done with the QDR. Precision for the total femur measurement on the QDR (0.5-0.9%) was approximately two to four times superior to that of the XR (1.5-4.3%). The difference may be due to the superior scan resolution of the QDR. Bone mineral content and BMD on the QDR significantly declined with an increase of water depth (P < 0.001). No significant change was observed on the XR. Both DXA systems demonstrated an excellent correlation (r > or = 0.98) with ash weight under the scan conditions examined. The optimal scan condition for the excised femur measurement on the XR was obtained with 1.5-2.5 cm of perspex or water and a scan speed of 10 mm/s. For the QDR, we recommend scanning the rat femur with approximately 2.5 cm of perspex or water in terms of precision and accuracy.

Absorptiometry, Photon↗
PubMed1993

Two segments of the supraspinous muscle: cause of high signal intensity at MR imaging?

A zone of increased signal intensity seen in asymptomatic subjects near the insertion of the supraspinous tendon onto the greater tuberosity ("pseudogap") leads to difficulty in the interpretation of magnetic resonance (MR) images of the shoulder. To better understand this pseudogap, the authors dissected and sectioned the shoulders of four cadavers and analyzed 20 MR images of patients' shoulders. They found that the supraspinous muscle consists of two distinct portions: an anterior fusiform portion that contains the dominant tendon and a straplike posterior portion. The orientation of the dominant tendon differs from that of the main muscle by approximately 10 degrees. In addition, oblique-coronal MR images were obtained parallel to the supraspinous main muscle and the central tendon in six volunteers; the appearance of the pseudogap was similar with both projections. Fat-saturated and gradient-echo images of the shoulder were obtained with increasing echo times in four additional volunteers. There was no evidence of fat within the pseudogap. Because the anatomic composition of the pseudogap could not be explained with partial volume averaging with adjacent muscle or fat, the authors conclude that it may represent a manifestation of unique focal tissue relaxation parameters or depend on the tendon orientation in the main magnetic field.

Adult↗
PubMed1993

Calcification demonstrated as high signal intensity on T1-weighted MR images of the disks of the lumbar spine.

PURPOSE: To report that calcification of lumbar disks may not show the usual low signal intensity on T1-weighted magnetic resonance (MR) images. MATERIALS AND METHODS: The authors present five cases of high signal intensity on T1-weighted MR images of a lumbar disk that reflect the presence of calcium deposition. RESULTS: In four cases there was conventional radiographic confirmation and in one case there was computed tomographic confirmation of the disk calcification, which corresponded to the high signal intensity seen on the MR studies. One patient had undergone surgical removal of a partially calcified protruding disk. CONCLUSION: Lumbar disk calcification can vary in signal intensity from low to high on T1-weighted MR images.

Adult↗
PubMed1993

The effect of short term treatment with alendronate on vertebral density and biochemical markers of bone remodeling in early postmenopausal women.

The effects of oral alendronate treatment on spinal bone mineral density and biochemical markers of bone turnover were assessed in women in the early postmenopausal period. Sixty-five women were treated with placebo or 5, 20, or 40 mg alendronate daily for 6 weeks in a double blind study. Treatment with alendronate decreased both urinary markers of bone resorption (pyridinolines, hydroxyproline, and calcium) and serum markers of bone formation (osteocalcin and alkaline phosphatase) in a dose-dependent fashion. This short term treatment with alendronate also produced a dose-dependent increase in lumbar bone mineral density measured 7.5 months after the completion of therapy. Median percent changes in integral spinal bone mineral density, as assessed by dual x-ray absorptiometry, were -2.3, -1.2, +0.7, and +1.2 after treatment with placebo and 5, 20, and 40 mg alendronate, respectively. Treatment with alendronate was well tolerated and produced no fever; gastrointestinal intolerance was no more common than with placebo treatment. Short term alendronate treatment in early postmenopausal women decreased bone turnover and increased vertebral density.

Adult↗
PubMed1993

Reliability of new indices of radiographic osteoarthritis of the hand and hip and lumbar disc degeneration.

OBJECTIVE: To develop a method for assessing the presence and severity of radiographic features of osteoarthritis (OA) of the hip and hand, and thoracic and lumbar disc degeneration. METHODS: An atlas illustrating scoring of individual radiographic features and summary grades for individual joints was developed. Three readers evaluated 31 pelvic films, 27 hand films, and 25 lateral lumbar and thoracic spine films selected from a community based sample of healthy elderly women. Interrater agreement between the 3 readers, and test-retest agreement for one of the readers, were estimated by the intraclass correlation coefficient (ICC) and kappa statistic. RESULTS: Interrater agreement (ICC, unless otherwise noted) for individual radiographic features of the hip ranged from 0.66 for osteophytes to 0.80 for narrowing. For the 9 interphalangeal (IP) joints of the hand, agreement ranged from 0.42 (kappa) for sclerosis to 0.93 for narrowing, and for the lumbar spine from 0.55 (kappa) for sclerosis to 0.95 for narrowing. Interrater agreement for summary grades of radiographic findings was as follows: hip, 0.81; 5 distal interphalangeal joints (DIP), 0.89; 4 proximal interphalangeal joints (PIP), 0.82; and lumbar spine, 0.93. Intrarater agreement for summary grades was as follows: hips, 0.79; 5 DIP, 0.86; 4 PIP, 0.81; and lumbar spine, 0.90. CONCLUSION: We have developed reliable indices of the presence and severity of radiographic features of hip and hand OA and spinal disc degeneration for use in epidemiologic studies. The assessment includes grading of individual radiographic features, which allows for the independent variation in these features often found in OA and a summary grade of disease that is derived from the presence and severity of individual features.

Aged↗
PubMed1993

Radiologic diagnosis of osteoporosis. Current methods and perspectives.

Osteoporosis is defined as a decrease in bone mass accompanied by structural changes, leading to an increase in fracture propensity. Early diagnosis of osteoporosis, fracture risk prediction, and assessment of efficacy of therapy therefore are of great interest. A number of noninvasive techniques are available for measuring bone mass at multiple sites of the skeleton. This article reviews basic methodology and developments in radiology such as x-ray and photon absorptiometry and quantitative computed tomography, which are routinely used in clinical practice. Recent techniques for assessment of bone mineral density and structure, such as ultrasound measurements, and their possible clinical applications also are discussed.

Absorptiometry, Photon↗
PubMed1993

[Advances in the diagnosis of osteoporosis].

Bone densitometry allows for an assessment of osteoporotic fracture risk. Well-established methods include dual X-ray absorptiometry (DXA), quantitative computed tomography (QCT), and single X-ray absorptiometry (SXA). The advantages and disadvantages of these methods are discussed. Promising innovative techniques include three new X-ray-based approaches: lateral DXA and peripheral QCT for the determination of bone mineral density of the spine and radius, respectively, and morphometric X-ray absorptiometry (MXA) for computerized quantification of vertebral deformities. Quantitative ultrasound (QUS) and quantitative magnetic resonance (QMR), on the other hand, open up new ways of assessing bone microarchitecture in addition to bone mineral density--without the use of ionizing radiation. These new approaches promise to yield new information on skeletal status. Complementing existing bone densitometry approaches, this may improve fracture risk assessment.

Absorptiometry, Photon↗
PubMed1993

[Osteoporosis diagnosis by broad-band ultrasound attenuation (BUA): its correlation with established measurement procedures of bone densitometry].

Broadband ultrasound attenuation (BUA) measurements of the os calcis of 54 women were correlated to single-energy x-ray absorptiometry (SXA) of the os calcis, dual-energy x-ray absorptiometry (DXA) of the lumbar spine, age and weight. The reproducibility of the BUA measurements was 2.1%. BUA was significantly correlated with SXA (r = 0.7), DXA (r = 0.5) and age (r = 0.6). BUA values ranged from 42 to 117 dB/MHz. Our results confirm BUA's potential as a simple, inexpensive, radiation free, and precise alternative technique for osteoporosis diagnostics of the os calcis. However, the correlation observed with bone mineral density of the spine is too weak to use BUA for predicting the lumbar density status. The ability of BUA to predict the risk of osteoporotic fractures has to be determined directly by assessing the association of BUA and the prevalence or preferably the incidence of fractures.

Absorptiometry, Photon↗
PubMed1992

Contribution of vertebral deformities to chronic back pain and disability. The Study of Osteoporotic Fractures Research Group.

Among 2992 white women aged 65-70 years recruited from population-based listings, we measured radiographic vertebral dimensions of T5-L4 and calculated ratios of heights: anterior/posterior, mid/posterior, and posterior/posterior of either adjacent vertebra. The degree of deformity for each vertebra was analyzed in terms of the number of standard deviations (SD) that ratio differed from the mean ratio calculated for the same vertebral level in this population. We correlated the severity of each woman's worst vertebral deformity with back pain, back disability in six activities of daily living, and height loss since age 25. Only 39.4% of the cohort had no vertebral deformity; 10.2% had a deformity greater than or equal to 4 SD. Vertebral deformities less than 4 SD below the mean were not associated with increased back pain, disability, or loss of height. In contrast, women whose deformity was greater than or equal to 4 SD had a 1.9 (95% CI, 1.5-2.4) times higher risk of moderate to severe back pain and a 2.6 (95% CI, 1.7-3.9) times higher risk of disability involving the back; they were also 2.5 (95% CI, 2.0-3.2) times more likely to have lost greater than or equal to 4 cm in height. All three types of vertebral deformity (wedge, end plate, and crush) were equally associated with these outcomes. Multiple deformities less than 4 SD did not increase the likelihood of these three outcomes, but multiple deformities greater than or equal to 4 SD tended to be associated with increased back pain, disability, and height loss. This large cross-sectional study suggests that vertebral deformities cause substantial pain, disability, or loss of height only if vertebral height ratios fall 4 SD below the normal mean. Much back pain could not be attributed to vertebral deformities, suggesting other causes.

Aged↗
PubMed1992

Age-related decrements in bone mineral density in women over 65.

Age-related changes in bone density contribute to the risk of fractures. To describe the relationship between age and bone mass in elderly women, we studied a large cohort of women over age 65 years who were recruited from population-based lists in four cities in the United States. Bone density in g/cm2 was measured by single-photon absorptiometry (SPA) and dual x-ray absorptiometry (DXA) at the distal and proximal radius, the calcaneus, the lumbar spine, and the proximal femur. Centralized data collection was used to control data quality and consistency. We found a strong inverse relationship between bone density and age for most sites. Decrements in bone density between women aged 65-69 years and women 85 years and older exceeded 16% in all regions except the spine, where the difference between the two age groups was 6%. Ward's triangle and the calcaneus exhibited the largest decrements, with 26 and 21%, respectively. The estimates of annual changes in bone mineral density by linear regression at sites other than the spine ranged from -0.82% at the femoral neck and trochanter to -1.30% at Ward's triangle. Correlations between the different regions ranged from r = 0.51 between the proximal radius and Ward's triangle to r = 0.66 between the distal radius and calcaneus. We conclude that the inverse relationship between age and bone mass measured by absorptiometry techniques in white women continues into the ninth decade of life. The relationship is strongest for bone density of Ward's triangle and the calcaneus and weakest for the spine.

Absorptiometry, Photon↗
PubMed1992

Axial and appendicular bone density predict fractures in older women.

To determine whether measurement of hip and spine bone mass by dual-energy x-ray absorptiometry (DEXA) predicts fractures in women and to compare the predictive value of DEXA with that of single-photon absorptiometry (SPA) of appendicular sites, we prospectively studied 8134 nonblack women age 65 years and older who had both DEXA and SPA measurements of bone mass. A total of 208 nonspine fractures, including 37 wrist fractures, occurred during the follow-up period, which averaged 0.7 years. The risk of fracture was inversely related to bone density at all measurement sites. After adjusting for age, the relative risks per decrease of 1 standard deviation in bone density for the occurrence of any fracture was 1.40 for measurement at the proximal femur (95% confidence interval 1.20-1.63) and 1.35 (1.15-1.58) for measurement at the spine. Results were similar for all regions of the proximal femur as well as SPA measurements at the calcaneus, distal radius, and proximal radius. None of these measurements was a significantly better predictor of fractures than the others. Furthermore, measurement of the distal radius was not a better predictor of wrist fracture (relative risk 1.64: 95% CI 1.13-2.37) than other sites, such as the lumbar spine (RR 1.56; CI 1.07-2.26), the femoral neck (RR 1.65; CI 1.12-2.41), or the calcaneus (RR 1.83; CI 1.26-2.64). We conclude that the inverse relationship between bone mass and risk of fracture in older women is similar for absorptiometric measurements made at the hip, spine, and appendicular sites.

Absorptiometry, Photon↗
PubMed1992

Site-matched calcaneal measurements of broad-band ultrasound attenuation and single X-ray absorptiometry: do they measure different skeletal properties?

Because of the differences in the interactions of ultrasound and x-ray waves with bone, quantitative ultrasound (QUS) techniques may yield information about skeletal status not accessible by regular bone densitometry (BD) techniques. However, relatively strong correlations have been reported between broad-band ultrasound attenuation (BUA) and several x-ray-based BD methods. We assessed the precision and association of single x-ray absorptiometry (SXA) and BUA of the calcaneus. We examined both BUA and SXA at the calcaneus using special software for matching the regions of interest. An algorithm was derived and applied to correct the observed correlation coefficients for the attenuation effect caused by the precision errors for BUA and SXA. In a group of 33 volunteers covering a wide range of age and calcaneal bone mineral densities, the site-matched and precision-adjusted correlation coefficient between BUA and SXA was r = 0.58, with a standard error of the estimate (SEE) of 14.41 dB/MHz, or 17.08%. For the subgroup of 25 women the correlation was stronger, with r = 0.72 and SEE = 11.53 dB/MHz, or 14.33%. SXA precision was 0.79% for the regular region of interest (ROI) and 1.22% for the site-matched ROI. BUA precision was 2.76% for the entire subject group and 1.63% for women of age 40 or older. The observed correlation coefficient between ultrasound and x-ray based techniques of the order of 0.7 is significant, but it leaves about 50% of the variability unexplained.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗