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 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We assessed bone mass quantification at different skeletal sites by single and dual photon absorptiometric (SPA and DPA) methods. Improved DPA measurement of spinal bone mineral density in young healthy subjects showed a short- and long-term precision of 1.2% and 1.6%. Compared to the conventional DPA method the imprecision was reduced by more than 50%. The appendicular measurements were more precise (0.5-1.2%). We present the intercorrelations and predictive errors between peripheral measurements and improved spinal and total body bone measurements in early postmenopausal women (n = 144) recruited in 1988. To compare the improved system with the conventional methods, we retrieved data on age-matched early postmenopausal women (n = 151) recruited in 1983. In the 1988 population all peripheral methods had similar predictive errors in estimation of spinal bone mineral density (SEE = 11-13%) and total body bone mineral density (SEE = 4-5%). Measurement of trabecular bone in the heel and distal forearm did not improve the validity of predicting spinal bone mass. In a cadaver study (n = 11) the predictive error in estimation of the spinal ash weight from forearm measurements was of the same magnitude (15%) as that in estimation of the spinal BMC from the forearm (16%). We conclude that the predictive error in estimation of spinal bone mass from peripheral bone measurements is more likely to be caused by intra-skeletal variation in bone mass than by precision errors. However, this does not reflect the inability of peripheral bone mass measurements to predict fracture risk.
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PMID:Bone mass measured by photon absorptiometry: comparison of forearm, heel, and spine. 223 64

We measured the lumbar bone mineral of 19 cadavers (10 women, 9 men) by dual photon absorptiometry (DPA) and quantitative computed tomography (QCT). In addition, we determined the ultimate load and stress of each vertebra, and finally ash content and volumetric ash density of the vertebral body. We found that single energy QCT was inferior to DPA and dual energy QCT in the prediction of the ultimate load or stress of vertebrae (P less than 0.001). The ultimate stress was best predicted by using the dual energy QCT results (r = 0.71; SEE = 36.3 N/cm2) whereas the ultimate vertebral load was best predicted by using the DPA (BMC) results (r = 0.80; SEE = 740 N). If the QCT finding was multiplied with the surface area of the vertebral body it could be used to predict the ultimate load with good accuracy (r = 0.74; SEE = 841 N). All the above correlations were higher in women than in men. The frequency of vertebral compression fractures in the material was well correlated with the bone mineral findings. A nonlinear (third degree) relationship between mineral content and mechanical characteristics is proposed but within the area of measurement used in clinical practice a linear (first degree) equation is preferred.
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PMID:Prediction of vertebral strength by dual photon absorptiometry and quantitative computed tomography. 250 Oct 6

The lumbar spine of 14 cadavers was studied both by 153Gd dual photon absorptiometry (DPA) and quantitative computed tomography (QCT) at 96 and 125 kVp. The intact spine and the individual vertebrae were analyzed. After these measurements the ash content of the vertebral body, the posterior elements, and the transverse processes was determined. The fat content of the vertebral body as well as its volume was also measured. With DPA, the bone mineral content (BMC) determined in situ as well as on excised spine specimens correlated highly with the amount of total vertebral ash (r greater than 0.92, SEE less than 3.2 g). The bone mineral density (BMD, area density) of 3 lumbar vertebrae correlated accurately with the mean ash density of the vertebral body (r greater than 0.81, SEE less than 0.015 g/cm3). The so-called corpus density and central density determinations were less accurate. No difference in accuracy was found between measurements when using 3 mm and 4.5 mm step intervals. Variations in the distribution of mineral between the vertebral body and the posterior elements contribute to the error in predicting vertebral body mineral with DPA. QCT gave a smaller error when a cylindric portion of the vertebral body with a 20 mm diameter was measured compared with one with a 9 mm diameter, when the dual energy technique was used (p less than 0.01). With dual energy QCT a correlation was found between a center segment of 3 vertebrae in the lumbar spine and the mean ash density of the vertebral body of r = 0.92 (SEE = 0.010 g/cm3).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Vertebral bone mineral measurement using dual photon absorptiometry and computed tomography. 296 52

The aim of this study was to evaluate the precision and accuracy of dual-energy X-ray absorptiometry (DXA) for measuring bone mineral content at different sites of the skeleton in rats. In vitro the reproducibility error was very small (< 1%), but in vivo the intra-observer variability ranged from 0.9% to 6.0%. Several factors have been shown to affect in vivo reproducibility: the reproducibility was better when the results were expressed as bone mineral density (BMD) rather than bone mineral content (BMC), intra-observer variability was better than the inter-observer variability, and a higher error was observed for the tibia compared with that for vertebrae and femur. The accuracy of measurement at the femur and tibia was assessed by comparing the values with ash weight and with biochemically determined calcium content. The correlation coefficients (R) between the in vitro BMC and the dry weight or the calcium content were higher than 0.99 for both the femur and the tibia. SEE ranged between 0.0 g (ash weight) and 2.0 mg (Ca content). Using in vitro BMC, ash weight could be estimated with an accuracy error close to 0 and calcium content with an error ranging between 0.82% and 6.80%. The R values obtained between the in vivo and in vitro BMC were 0.98 and 0.97 respectively for femur and tibia, with SEE of 0.04 and 0.02 g respectively. In conclusion, the in vivo precision of the technique was found to be too low. To be of practical use it is important in the design of experimentation to try to reduce the measurement error.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Precision and accuracy of in vivo bone mineral measurement in rats using dual-energy X-ray absorptiometry. 770 24

The predictive accuracy of race-specific and fatness-specific bioelectrical impedance analysis (BIA) equations for estimating criterion fat-free mass (FFM) derived from two-component (2C) and multicomponent (MC) models was examined. Body density (Db) of Native American women (n = 151) aged 18-60 y was measured by hydrostatic weighing at residual volume. Total body bone ash was obtained by dual-energy, x-ray absorptiometry. Cross-validation of the Rising (5), Segal (3), and Gray (4) equations against FFM2C yielded high correlation coefficients (0.86-0.95) and acceptable SEEs (1.47-2.72 kg). Cross-validation of these equations against criterion FFMMC, with Db adjusted for total body mineral, yielded similar correlation coefficients (0.82-0.94) and SEEs (1.69-2.80 kg). However, each BIA equation significantly overestimated FFMMC. A new race-specific BIA equation based on an MC model was developed: FFMMC = 0.001254(HT2)-0.04904(R) + 0.1555(WT) + 0.1417(Xc) - 0.0833(AGE) + 20.05 (R = 0.864, and SEE = 2.63 kg).
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PMID:Predictive accuracy of bioelectrical impedance in estimating body composition of Native American women. 817 1

The accuracy of a radiographic absorptiometry (RA) technique called digital image processing (DIP), discriminative ability of RA for osteoporotic fracture, and the relationship between RA and dual X-ray absorptiometry (DXA) of the spine and forearm were evaluated. We measured 16 cadaver hands, 32 healthy non-black premenopausal women, 39 healthy non-black postmenopausal women, and 35 non-black osteoporotic postmenopausal females. The overall correlation between the ash weights of the entire metacarpal and the DIP values was excellent (r = 0.954, P < 0.001, SEE = 0.14, CV = 6.4%). Short-term precision error of DIP was 3.5%. Age-related bone loss determined by DIP is comparable to that of spinal and forearm DXA: annual BMD decreases were 0.46% for DIP, 0.45% for forearm, and 0.32% for the spine. DIP of the 2nd metacarpal shows a gradient of risk for spinal fracture only slightly below that of forearm DXA, but substantially below that of spinal DXA. Age-adjusted odds ratios were 1.81 for RA, 2.45 for spinal DXA, and 1.94 for forearm DXA.
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PMID:Accuracy and diagnostic sensitivity of radiographic absorptiometry of the second metacarpal. 943 40

We evaluated the use of dual-energy x-ray absorptiometry (DXA) for measuring the gross body composition of small subjects in 97 pigs that ranged from 5 to 27 kg live body weight. Scans were performed using a Lunar DPXL densitometer in the pediatric mode (Version 3.8e). The DXA scans of the live pigs provided measurements of total fat, lean, and bone mineral content. After scanning, the pigs were killed, the entire body was ground, and samples were analyzed chemically (CHEM) for fat, protein, ash, and water content. We found that DXA significantly underestimated the percentage of fat in the body (DXA, 6.9+/-.33% vs CHEM, 10.9+/-.31%, P < .001). The correlation (r) between DXA and chemical measures of percentage fat was .86 and for grams of fat it was .96. Lean tissue mass measured by DXA was highly correlated with CHEM measurements of total grams of body water (r = .99), total grams of body protein (r = .94), and lean body mass (r = .99). The average DXA bone mineral content was within 2% of the amount estimated from total body ash and the correlation between the two values was .94. The relationships between DXA and CHEM measurements for percentages of body composition of pigs that weighed between 5 and 27 kg are described by the following regression equations: %fatCHEM = 5.22 + [.817.fatDXA], (r = .86, standard error of the estimate, SEE = 1.56); %proteinCHEM = -7.8 + [.256%leanDXA], (r = .35, SEE = 2.3); %waterCHEM = -5.2 + [.808-%leanDXA], (r = .59, SEE = 3.67). These results are consistent with previously reported results and suggest that even though direct use of DXA readings may not be sufficiently accurate, the high degree of correlation indicates that with proper calibration the DXA values can be used to predict body composition.
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PMID:Body composition analysis of small pigs by dual-energy x-ray absorptiometry. 978 95

Total body calcium (TBCa) in 270 black and white women age 21-79 years was measured concurrently by delayed gamma neutron activation analysis (DGNA) and dual-energy X-ray absorptiometry (DXA). The mean value for TBCa calculated from DXA was 933 g compared with 730 g for DGNA. By regression, TBCa(DXA(g)) = 1.35 x TBCa(DGNA(g)) -54 (r = 0. 90, r(2) = 81.4%, SEE = 66.9 g). This remarkable difference of 203 g suggests that one or both these methods is not accurate. Adjustment of the regression of DXA versus DGNA for body mass index or trunk thickness explained 8.5-10% of the variability between methods. The unadjusted slope for the DXA values regressed against the DGNA values was 1.35, indicating significant discordance between the methods. There is greater agreement between the two DGNA facilities (Brookhaven National Laboratory and Baylor College of Medicine) and between the various DXA instruments. Either DGNA underestimates TBCa or DXA overestimates total-body bone mineral content. Resolution of these disparate results may possibly be achieved by concurrent measurement of whole human cadavers of different sizes with chemical determination of the calcium content of the ash. In the interim, cross-calibration equations between DGNA and standardized values for DXA for total-body bone mineral content may be used, which will permit reporting of consistent values for TBCa from the two technologies.
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PMID:Total-body calcium estimated by delayed gamma neutron activation analysis and dual-energy X-ray absorptiometry. 1098 73

This study tested the hypothesis that the mitral valve E point-to-septal separation (EPSS) can be used to quantify the left ventricular (LV) ejection fraction (EF) on a continuous scale rather than simply as "normal" or "reduced." After excluding 5 patients with mitral valve prostheses, asymmetric septal hypertrophy, or significant aortic insufficiency, EPSS was measured in 42 patients by 3 independent observers on a cardiac magnetic resonance image identical to the echocardiographic parasternal long-axis view. In each patient, the reference standard LVEF was calculated from the magnetic resonance short-axis cross-sectional stack images by Simpson's rule and ranged from 11% to 72%. For all 42 patients, linear regression revealed the relation magnetic resonance imaging (MRI) LVEF = 75.5 - 2.5. EPSS (millimeters). Correlation between EPSS and the MRI LVEF for the 3 observers agreed closely, ranging from r = 0.78 to r = 0.82 (SEE 9 to 10), with similar regression coefficients. After blinded segmental wall motion scoring of the gated magnetic resonance cine images of the left ventricle in each patient, correlations, SEEs, and regression coefficients were found to be very similar in the 21 patients with the most homogenous wall motion, compared with the 21 patients with the most heterogenous wall motion. In conclusion, clinically useful quantitative prediction of the LVEF as a continuous variable can be obtained from the EPSS with a simple linear regression equation in a substantial portion of patients and may be a useful adjunct for assessment of LV function.
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PMID:Quantitative estimation of left ventricular ejection fraction from mitral valve E-point to septal separation and comparison to magnetic resonance imaging. 1689 21

The floristic composition, the abundance, and the cover of pioneer plant species of spontaneously formed plant communities and the content of total phenolics and phenolic acids, as humus constituents, of an ash deposit after 7 years of recultivation were studied. The restoration of both the soil and the vegetation on the ash deposits of the "Nikola Tesla-A" thermoelectric power plant in Obrenovac (Serbia) is an extremely slow process. Unfavorable physical and chemical characteristics, the toxicity of fly ash, and extreme microclimatic conditions prevented the development of compact plant cover. The abundance and cover of plants increased from the central part of the deposit towards its edges (ranging from 1-80%). Festuca rubra L., Crepis setosa Hall., Erigeron canadensis L., Cirsium arvense (L.) Scop., Calamagrostis epigeios (L.) Roth., and Tamarix gallica L. were the most abundant species, thus giving the highest cover. Humus generated during the decomposition process of plant remains represents a completely new product absent in the ash as the starting material. The amount of total phenolics and phenolic acids (38.07-185.16 microg/g of total phenolics and 4.12-27.28 microg/g of phenolic acids) in fly ash increased from the center of the deposit towards its edges in correlation with the increase in plant abundance and cover. Ash samples contained high amounts of ferulic, vanillic, and p-coumaric acid, while the content of both p-hydroxybenzoic and syringic acid was relatively low. The presence of phenolic acids indicates the ongoing process of humus formation in the ash, in which the most abundant pioneer plants of spontaneously formed plant communities play the main role. Phenolic compounds can serve as reliable bioindicators in an assessment of the success of the recultivation process of thermoelectric power plants' ash deposits.
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PMID:Phenolic acids as bioindicators of fly ash deposit revegetation. 1641 90


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