The Experts below are selected from a list of 1233 Experts worldwide ranked by ideXlab platform
Jennifer J Anderson - One of the best experts on this subject based on the ideXlab platform.
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the effects of analytic software and scan analysis technique on the comparison of dual x ray Absorptiometry with dual Photon Absorptiometry of the hip in the elderly
Journal of Bone and Mineral Research, 2009Co-Authors: Douglas P Kiel, Marian T Hannan, Clorinda M Cali, Cherlyn A Mercier, Bess Dawsonhughes, Jennifer J AndersonAbstract:As part of a longitudinal comparison of bone mineral density (BMD) results originally obtained using a Lunar dual Photon Absorptiometry (DPA) scanner and later, using a Lunar dual X-ray Absorptiometry (DXA) scanner, we compared femur results between DPA and DXA according to DXA analytic software (versions 1.3y and 1.4), and according to the method of placement of the femoral neck box (software algorithm or operator placement according to the appearance of the pair of images) in 58 elderly men and women. The mean BMD at each of three femoral sites was higher using DXA version 1.3y than DPA, but the use of software version 1.4 brought the BMD value closer to that of DPA at all sites. Of 58 scans, 12 (21%) were changed by the operator, resulting in an overall reduction in mean percent BMD difference between scan pairs of 79% (from 1.24% to 0.29%). Although the differences between the DPA/DXA software-driven analysis and the DPA/DXA operator-driven analysis appeared small (high r2 values and intra-class correlation coefficients), the increase in sample size that would be required for the same power to detect 2-year changes in BMD if the software-driven analysis was used instead of taking the time to perform the operator-driven analysis was 18%. The findings of this study highlight the need to account for upgrades in analytic software. Furthermore, we present a rational approach for the analysis of serial scans that has face validity and that results in smaller differences between pairs of scans performed on the same individual. The decision to adapt these methods must be based on the relative costs of reducing unwanted scan variability.
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effects of weight and body mass index on bone mineral density in men and women the framingham study
Journal of Bone and Mineral Research, 2009Co-Authors: David T Felson, Marian T Hannan, Yuqing Zhang, Jennifer J AndersonAbstract:We evaluated the association of weight and bone mass in elderly male and female subjects of the Framingham osteoporosis study, a subset of the Framingham study cohort. By examining the differences in the correlations of weight with bone mass among men and women in weight-bearing and non-weight-bearing sites and weight change since early adulthood, we attempted to understand different ways in which weight or body mass index affects bone mass. During biennial examination 20 of the Framingham cohort (1988–1989), 693 women and 439 men (mean age 76 years) had proximal femur bone mineral density assessed by dual-Photon Absorptiometry (DPA) and radius bone mass assessed by single-Photon Absorptiometry. The majority of these subjects also had spine measurements by DPA. Subjects had been weighed repeatedly over 40 years. After adjusting for other factors affecting bone density, we found that both recent weight and body mass index explained a substantial proportion of the variance in bone mineral density for all sites in women (8.9–19.8% of total variance, all p < 0.01) and for only weight-bearing sites (femur and spine) in men (2.8–6.9% of total variance, all p < 0.01). For bone mineral density at the proximal radius, weight and body mass index accounted for < 1% of variance in men (p NS). Weight change since biennial examination 1 (1948–1951) was the strongest explanatory factor for bone mineral density among women at all sites, but weight change did not affect radius bone mineral density in men. The effect of weight and of weight change on bone mineral density was in general much less in men than in women. Our results suggest that the strong effect of weight on bone mineral density is due to load on weight-bearing bones in both sexes. The sex difference is unexplained but may be due to adipose tissue production of estrogen in women after menopause.
Steve Heymsfield - One of the best experts on this subject based on the ideXlab platform.
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differences in skeletal muscle and bone mineral mass between black and white females and their relevance to estimates of body composition
The American Journal of Clinical Nutrition, 1992Co-Authors: O Ortiz, Jack Wang, Mary Russell, T L Daley, R N Aumgartne, Masako Waki, Steve W Lichtma, Richard N Pierso, Steve HeymsfieldAbstract:This study tested the hypothesis that black females have an increase in skeletal muscle and bone mineral mass compared with white females matched for age (+/- 5 y), weight (+/- 2 kg), height (+/- 3 cm), and menstrual status. Conventional [underwater weighing, whole body 40K counting (WBC), 3H2O dilution] and newly developed (dual-Photon Absorptiometry) techniques were used to provide ethnicity-independent estimates of body composition in 28 pairs of matched subjects. Black females had greater appendicular skeletal muscle (P less than 0.001), bone mineral (P less than 0.001), and total body potassium (TBK) (P = 0.05) compared with white females. Two classic coefficients used in body composition research [density of fat-free mass (FFM) for underwater weighing and TBK/FFM for WBC] differed significantly (P less than 0.05) between black and white females; currently applied coefficients underestimated fat in black females. This study confirms that black and white females differ in body composition and that errors in fat estimates occur when ethnicity is not accounted for in body composition models.
R. M. Murray - One of the best experts on this subject based on the ideXlab platform.
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Validation of single Photon Absorptiometry for on-farm measurement of density and mineral content of tail bone in cattle
Animal Production Science, 2016Co-Authors: D. B. Coates, Rob Dixon, R. J. Mayer, R. M. MurrayAbstract:A validation study examined the accuracy of a purpose-built single Photon Absorptiometry (SPA) instrument for making on-farm in vivo measurements of bone mineral density (BMD) in tail bones of cattle. In vivo measurements were made at the proximal end of the ninth coccygeal vertebra (Cy9) in steers of two age groups (each n = 10) in adequate or low phosphorus status. The tails of the steers were then resected and the BMD of the Cy9 bone was measured in the laboratory with SPA on the resected tails and then with established laboratory procedures on defleshed bone. Specific gravity and ash density were measured on the isolated Cy9 vertebrae and on 5-mm2 dorso-ventral cores of bone cut from each defleshed Cy9. Calculated BMD determined by SPA required a measure of tail bone thickness and this was estimated as a fraction of total tail thickness. Actual tail bone thickness was also measured on the isolated Cy9 vertebrae. The accuracy of measurement of BMD by SPA was evaluated by comparison with the ash density of the bone cores measured in the laboratory. In vivo SPA measurements of BMD were closely correlated with laboratory measurements of core ash density (r = 0.92). Ash density and specific gravity of cores, and all SPA measures of BMD, were affected by phosphorus status of the steers, but the effect of steer age was only significant (P < 0.05) for steers in adequate phosphorus status. The accuracy of SPA to determine BMD of tail bone may be improved by reducing error associated with in vivo estimation of tail bone thickness, and also by adjusting for displacement of soft tissue by bone mineral. In conclusion a purpose-built SPA instrument could be used to make on-farm sequential non-invasive in vivo measurements of the BMD of tailbone in cattle with accuracy acceptable for many animal studies.
Lawrence B Riggs - One of the best experts on this subject based on the ideXlab platform.
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colles fracture and bone density of the ultradistal radius
Journal of Bone and Mineral Research, 2009Co-Authors: Lawrence B Riggs, Michael W Ofallon, Heinz W Wahner, Joseph L Melton, Peter C AmadioAbstract:: To determine whether Colles' fracture, generally considered a manifestation of postmenopausal osteoporosis, is associated with a decrease in bone density at the site of fracture, we measured bone mineral density of the ultradistal radius (UDR-BMD) by single-Photon Absorptiometry with computer-assisted image processing. In 119 normal women (ages 22-92 years), UDR-BMD decreased by 17% between ages 30 and 75 years. From UDR-BMD measurements in these normal women and in 40 women (ages 53-80 years) with Colles' fracture alone, a population-based analysis was made to estimate fracture risk at different values of UDR-BMD. Colles' fracture was uncommon at UDR-BMD greater than 0.40 g/cm2 (the "fracture threshold"). As bone density decreased below this level, fractures became more frequent (a "gradient of risk").
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long term fracture prediction by bone mineral assessed at different skeletal sites
Journal of Bone and Mineral Research, 2009Co-Authors: Joseph L Melton, Michael W Ofallon, Heinz W Wahner, Elizabeth J Atkinson, Lawrence B RiggsAbstract:Bone mineral density (BMD) was measured at the lumbar spine and cervical and intertrochanteric regions of the proximal femur by dual-Photon Absorptiometry and bone mineral content was assessed at the distal and midradius by single-Photon Absorptiometry in an age-stratified random sample of 304 Rochester, Minnesota women aged 30-94 years. Over follow-up extending to 10 years (median 8.3 years), 93 women experienced 163 new fractures. After adjusting for age, these bone mineral measurements predicted the likelihood of any incident fracture due to moderate trauma, with relative hazards varying from 1.4 to 1.6 per SD decrease in baseline bone mineral. A 1 SD decrease in lumbar spine BMD increased the risk of a new vertebral fracture comparably to a 17 year increase in age; a 1 SD decrease in femoral BMD was comparable to a 13-14 year increase in age on the risk of a hip fracture. We conclude that bone mineral measurements made at a variety of skeletal sites can predict the occurrence for at least 8-10 years of moderate trauma fractures of the sort that might be related to osteoporosis.
Richard B Mazess - One of the best experts on this subject based on the ideXlab platform.
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bone density of the radius spine and proximal femur in osteoporosis
Journal of Bone and Mineral Research, 2009Co-Authors: Richard B Mazess, Howard S Barden, M Ettinger, Eloy SchultzAbstract:Bone mineral density (BMD) was measured in 140 normal young women (aged 20 to 39 years) and in 423 consecutive women over age 40 referred for evaluation of osteoporosis. Lumbar spine and proximal femur BMD was measured using dual-Photon Absorptiometry (153Gd), whereas the radius shaft measurement used single-Photon Absorptiometry (125I). There were 324 older women with no fractures, of which 278 aged 60 to 80 years served as age-matched controls. There were 99 women with fractures including 32 with vertebral and 22 with hip fractures. Subsequently, another 25 women with hip fractures had BMD measured in another laboratory; their mean BMD was within 2% of that of the original series. The mean age in both the nonfracture and fracture groups was 70 +/- 5 years. The BMD in the age-matched controls was 20% to 25% below that of normal young women for the radius, spine, and femur, but the Ward's triangle region of the femur showed even greater loss (35%). The mean BMD at all sites in the crush fracture cases was about 10% to 15% below that of age-matched controls. Spinal abnormality was best discriminated by spine and femoral measurements (Z score about 0.9). In women with hip fractures, the BMD was 10% below that of age-matched controls for the radius and the spine, and the BMD for the femoral sites was about 25% to 30% below that of age-matched control (Z score about 1.6). Femoral densities gave the best discrimination of hip fracture cases and even reflected spinal osteopenia. In contrast, neither the spine nor the radius reflected the full extent of femoral osteopenia in hip fracture.
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effects of tamoxifen on bone mineral density in postmenopausal women with breast cancer
The New England Journal of Medicine, 1992Co-Authors: Richard R Love, Richard B Mazess, H S Barden, S Epstein, Polly A Newcomb, V C Jordan, P P Carbone, David L DemetsAbstract:Abstract Background and Methods. Tamoxifen, a synthetic antiestrogen, increases disease-free and overall survival when used as adjuvant therapy for primary breast cancer. Because it is given for long periods, it is important to know whether tamoxifen affects the skeleton, particularly since it is used extensively in postmenopausal women who are at risk for osteoporosis. Using Photon Absorptiometry, we studied the effects of tamoxifen on the bone mineral density of the lumbar spine and radius and on biochemical measures of bone metabolism in 140 postmenopausal women with axillary-node—negative breast cancer, in a two-year randomized, double-blind, placebo-controlled trial. Results. In the women given tamoxifen, the mean bone mineral density of the lumbar spine increased by 0.61 percent per year, whereas in those given placebo it decreased by 1.00 percent per year (P<0.001). Radial bone mineral density decreased to the same extent in both groups. In a subgroup randomly selected from each group, serum osteoc...