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PubMedDate not supplied

Evaluation of a new set of calibration standards for the measurement of fat content via DPA and DXA.

A simulation study was performed to evaluate a new set of calibration standards for estimating the fat content of the body via dual-photon absorptiometry (DPA) and dual-energy x-ray absorptiometry (DXA). The standards, proposed by Nord and Payne [presented at the 2nd meeting of The Bath Conference on Bone Mineral Measurement (1990)] consist of stearic acid (100% fat) and 0.6% NaCl in water (100% lean). They were compared with other standards consisting of average composition adipose/muscle tissues and fatty adipose/lean muscle tissues. Source and detector properties of a Gd-153 DPA system and three commercial DXA systems were modeled. For each system and calibration set, rms errors in the calculated fat contents of simulated tissues having fat mass percentages that ranged from about 4%-44% and thicknesses that ranged from 5-20 cm were determined. Beam hardening errors for the systems were evaluated as was a calibration technique employed by one of the manufacturers to correct for such errors. In general, the smallest rms errors (2% or less when the calibration standards and tissues were of equal thickness) were obtained with the average adipose/muscle standards. Equivalent results were obtained with standards consisting of stearic acid and 0.8% NaCl. The latter is a higher salt content than proposed by Nord and Payne and results from differences in the x-ray attenuation coefficients that were employed in calculating the fat equivalence of water. Other, more convenient standards, such as lucite and water may be employed by using appropriate fat equivalences (approximately 69% for lucite and approximately 10% for water). Beam hardening errors for the DXA systems are considerable, and the simulated correction technique was shown to be effective.

Absorptiometry, Photon↗

PubMed1997

The skeletal calcium/phosphorus ratio: a new in vivo method of determination.

We describe a new method for assessing the Ca/P ratio of bone in vivo using gamma-ray photon absorptiometry. The theoretical approach of the method and the estimation of the variance are presented. Two radiation sources, Gd-153 (100 keV), and I-125 (27.5 keV), and a germanium detector were used to determine this ratio. Measurements were made on bone phantoms with different Ca/P ratios; also, the ratio was measured on lamb and sheep tibias, rabbit tibias, and human fingers. Since the accuracy of the method is affected by the amount of fat and collagen in the measurement field, the effect of collagen and fat on the measurements also was investigated. In all cases, the precision of the method, expressed as the coefficient of variation (CV): 100x standard deviation/mean, was near to the theoretical one, ranging from 1.8% to 3.2%. For human fingers, the CV was 3.2%, a value near to the theoretical 2.9% with a dose to the skin ranging from 0.044 to 0.066 mGy, depending on the width of the finger.

Absorptiometry, Photon↗

PubMed1990

Spontaneous resolution of bone mineral depletion in preterm infants.

Fifteen preterm infants and 17 born at full term whose gestational ages ranged from 25 to 34 weeks and 38 to 42 weeks, respectively, were examined initially at postconceptional ages ranging from 38 to 44 weeks and subsequently at 46 to 71 weeks. Each examination included measurement of bone mineral content of the mid-forearm by single photon absorptiometry. For the preterm group, the mean (SD) value of bone mineral content at the first examination was 109.0 (27.6) mg/cm and was significantly lower than the corresponding value of 194.4 (19.6) mg/cm for the whole full term group. The mean subsequent rate of mineral accretion in the preterm group was 8.70 (4.60) mg/cm/week, the mean individual duration of observation being 9.7 weeks. Rate of mineral accretion for the full term group was independent of the duration of observation and averaged 1.60 (2.20) mg/cm/week. The difference between mean values of rate of mineral accretion in the preterm and full term groups was highly significant. Our results show that there is a phase of rapid mineral accretion starting at 40 weeks' postconception in preterm infants that substantially reduces the perinatal mineralisation deficit.

Absorptiometry, Photon↗

PubMed1993

Physical activity as a determinant of bone conservation in the radial diaphysis in rheumatoid arthritis.

OBJECTIVES: To determine if increasing physical activity is protective of diaphysial (cortical) bone mass METHODS: Fifteen patients attending two rheumatology clinics who had developed seropositive or classical rheumatoid arthritis up to 26 months previously were studied prospectively for two to three years. Rates of loss (or gain) in bone mass in the radial diaphysis and the trabecular bone of the distal radius were measured by quantitative computed tomography, and in the spine by dual photon absorptiometry. Physical activity was assessed by the Framingham physical activity index. Disease activity was followed at three-monthly clinic visits at which the haemoglobin, erythrocyte sedimentation rate, and platelet count were measured. The urinary hydroxyproline to creatinine ratio and plasma osteocalcin were measured at the beginning and end of the observation period. RESULTS: Eleven patients required treatment with disease modifying drugs but none was given corticosteroids. Those whose physical activity did not improve lost radial diaphysial bone at about 4% annually. There was, however, a statistically significant inverse relation, accounting for 48.5% of the variance, between bone loss at this site and improvement in physical activity as assessed by the Framingham index. The other two sites showed much weaker associations. Adjusting for indices of disease activity hardly affected the first relation. Three biochemical indices related to bone turnover showed weak tendencies to decrease with increasing physical activity. CONCLUSIONS: Peripheral cortical bone, distant from inflamed joints, is conserved more successfully in patients who achieve higher levels of physical rehabilitation. This may have implications for avoiding long bone fractures later in the disease.

Absorptiometry, Photon↗

PubMed1995

Cut off values of bone mineral density defining postmenopausal women with bone fractures.

OBJECTIVES: To define cut off values of bone mineral density (BMD), measured at different forearm sites by single photon absorptiometry, that discriminated postmenopausal women who have had fractures from those who have not, in order to provide an index of fracture risk for screening purposes. METHODS: BMD values were measured at distal third radius (DTR) and ultradistal radius (UDR) sites in two groups of postmenopausal women. Group 1 (n = 398) had not suffered fractures, and group 2 (n = 354) had appendicular fractures. Results were evaluated using receiver operating characteristic (ROC) curves. RESULTS: BMD values were significantly greater (p < 0.001) at both sites in group 1. Weight was lower in group 2 than in group 1 (p < 0.001). The BMD cut off value was 0.596 g/cm2 at DTR (sensitivity 63%, specificity 72%), and 0.310 g/cm2 at UDR (sensitivity 80%, specificity 80%). Values of area under ROC curves estimated for UDR were greater than for those DTR (p < 0.001). CONCLUSION: For screening purposes the BMD cut off value of 0.310 g/cm2 at the UDR may be useful in identifying women at high risk of fracture in an unselected postmenopausal population. BMD measured at UDR appeared to have a better predictive value than that at DTR.

Absorptiometry, Photon↗

PubMed1996

Exercise therapy for osteoporosis: results of a randomised controlled trial.

OBJECTIVE: To define the effects of therapeutic exercise on bone density and back complaints. METHODS: A randomised controlled trial with parallel groups was conducted in an outpatient clinic, Medical School, University of Vienna. Ninety two sedentary post-menopausal women with back problems were randomly allocated to either exercise (groups 1 and 2) or control (group 3, no exercise, n = 31); the exercise group was retrospectively subdivided into compliant (group 1, n = 27) and not fully compliant patients (group 2, n = 34). Regular, initially supervised therapeutic exercise aimed at restoring biomechanical function was performed for four years. Bone density in the forearm was measured by single photon absorptiometry at entry and after four years; subjective back complaints were documented. RESULTS: A significant decrease in bone density was observed in groups 2 and 3; no change was noted in group 1; back complaints decreased in group 1 only. CONCLUSIONS: Sedentary postmenopausal women may benefit from regular long term therapeutic exercise in terms of subjective back complaints and slowed loss of bone mass.

Absorptiometry, Photon↗

PubMed1993

Osteoporosis and the Marfan syndrome.

Fourteen patients with Marfan syndrome, defined according to present criteria, had bone mineral content of the distal forearm measured by single photon absorptiometry. Patients were matched for age and sex with a large local group of healthy volunteers. While further work is needed with other methods of densitometry with measurements at other sites, our results provide no evidence that there is an increased incidence of osteoporosis in Marfan syndrome. Previous reports of an association were probably due to incorrect clinical diagnosis or confusion with clinically similar syndromes known to cause osteoporosis.

Absorptiometry, Photon↗

PubMed1994

Osteoporosis and genetic influence: a three-generation study.

We have studied 27 triads of mother, daughter and grandmother for possible genetic influence on distal and proximal forearm bone density, measured by single photon absorptiometry. We found a significant correlation of bone density at the proximal forearm between the mothers and grandmothers (r = 0.499, P < 0.01). There was also a weak correlation between proximal forearm bone densities of mothers and daughters (r = 0.327, P < 0.1). Significant correlations were found between the three generations for grip strength, pedometry, height and triceps skinfold thickness. There was also significant correlation between mother and grandmother for alcohol intake. There was no correlation for contraceptive pill use, smoking, dietary calcium intake, body weight or body mass index. The study concludes that, although there are similarities in bone mineral content between the three generations, genetic factors cannot be conclusively proven to be the major determinant of bone density. Lifestyle and environmental factors may have a bearing on achieving the peak bone mass and subsequent development of osteoporosis.

Absorptiometry, Photon↗

PubMed1991

Osteopenic effects of forelimb immobilisation in horses.

Methods for the non-invasive assessment of bone quality were used to monitor the osteopenia induced by immobilising a forelimb in a cast. These techniques included the measurement of ultrasound velocity, single photon absorptiometry and radiographic photodensitometry. Serial measurements were made before, during and after an eight week period of immobilisation of the left forelimb of four adult standardbreds in a light fibreglass cast which included the foot and extended above the carpus. The measurements continued for 12 weeks after the removal of the cast. The results indicated a trend to decreasing bone strength and mineral content in both forelimbs, with the decreases being greater in the limb with the cast. The values tended to recover slowly after the removal of the cast, then more quickly after the horses returned to the paddock four weeks later. The differences between the limb with the cast and the opposite limb were significant at only a few points of comparison.

Absorptiometry, Photon↗

PubMed1988

Three-dimensional quantitative CT of the proximal femur: relationship to vertebral trabecular bone density in postmenopausal women.

Dual-photon absorptiometry (DPA) of the proximal femur cannot independently measure cortical and high-turnover cancellous bone. In this investigation, integrated cancellous, cortical, and total bone densities in the femoral neck and intertrochanteric region were measured bilaterally in 22 women aged 42-75 years. Contiguous section data were analyzed with two different protocols by means of three-dimensional histogram software. Single-section quantitative computed tomography (CT) was used to determine mean mineral equivalent values for vertebral cancellous bone from T-11 to L-3 in each woman. Significant correlation was found between cancellous bone density at the two sites, as well as between total femoral and vertebral measurements. Femoral cortical bone density was predicted less well by means of the vertebral cancellous data. Cortical, cancellous, and total proximal femoral density values tended to exhibit bilateral symmetry. Quantitative three-dimensional volumetric CT affords comprehensive evaluation of proximal femoral mineral status because of its capability for selective measurement of cortical, cancellous, and total bone density.

Absorptiometry, Photon↗

PubMed1992

Regional changes in muscle mass following 17 weeks of bed rest.

This work reports on the muscle loss and recovery after 17 wk of continuous bed rest and 8 wk of reambulation in eight normal male volunteers. Muscle changes were assessed by urinary levels of 3-methylhistidine (3-MeH), nitrogen balance, dual-photon absorptiometry (DPA), magnetic resonance imaging (MRI), and isokinetic muscle performance. The total body lean tissue loss during bed rest calculated from nitrogen balance was 3.9 +/- 2.1 (SD) kg (P < 0.05). Although the total loss is minimal, DPA scans showed that nearly all of the lean tissue loss occurred in the lower limbs. Similarly, MRI muscle volume measurements showed greater percent loss in the limbs relative to the back muscles. MRI, DPA, and nitrogen balance suggest that muscle atrophy continued throughout bed rest with rapid recovery after reambulation. Isokinetic muscle strength decreased significantly (P < 0.05) in the thigh and calf with no loss in the arms and with rapid recovery during reambulation. We conclude that there is great variability in the degree and location of muscle loss in bed rest and that the lower limb muscles are primarily affected.

Absorptiometry, Photon↗

PubMed1993

Comparison of three techniques for body composition analysis in cystic fibrosis.

Body composition analysis is an important component of nutritional assessment in cystic fibrosis (CF). No gold standard of measurement exists, and techniques applicable to healthy populations may be unsuitable for CF patients. We assessed lean body mass (LBM) in 12 children with CF by skinfold (SK) measurements, bioelectrical impedance analysis (BIA), and dual-photon absorptiometry (DPA) and repeated these measures in 10 subjects 6 mo later. SK and DPA measures in eight older CF patients and eight healthy controls were compared to evaluate any effect of disease on estimates of LBM by use of DPA. Good agreement between the measures was seen at baseline and 6 mo by use of concordance plots. However, the limits of agreement between measures ranged up to 19% of SK-derived LBM measures (baseline: SK and DPA, 2.63 to -3.93 kg; SK and BIA, 2.36 to -1.24 kg; BIA and DPA, 1.88 to -4.28 kg; 6 mo: SK and DPA, 2.10 to -3.58 kg; SK and BIA, 6.28 to -5.49 kg; BIA and DPA, 5.53 to -7.79 kg). The change in LBM over 6 mo did not correlate among the three measures. Only BIA change in LBM correlated with weight change (r = 0.716, P < 0.02), probably due to the inclusion of weight in the regression equations for determining LBM from impedance. The relationship between SK and DPA measures did not differ between the CF and control groups, suggesting that there was no effect of disease on the DPA measure. The results suggest that none of these methods is precise enough to follow short-term changes in the nutritional status of CF patients longitudinally.

Absorptiometry, Photon↗

PubMedDate not supplied

Assessment of body composition in elderly: accuracy of bioelectrical impedance analysis.

BACKGROUND: In the literature there are several body impedance analysis (BIA) prediction equations generally determined in younger populations and their accuracy in the elderly has not been adequately confirmed. OBJECTIVE: We verified the reliability of the BIA method in a body composition study in the elderly. METHODS: To assess the accuracy of bioelectrical impedance analysis we compared this method with dual photon absorptiometry (DPA), assumed as a gold standard; body composition was predicted by seven BIA prediction equations in 24 healthy elderly individuals. RESULTS: The best equation in fat-free mass (FFM) estimation is the RJL System formula (published by Segal in 1988); nevertheless, the wide range of the error in FFM estimating may limit its clinical application. The FFM hydration variability seems to be the principal variable which explains the error in FFM estimation by BIA prediction equations. CONCLUSION: These findings indicate that the use of BIA equations is not interchangeable, when FFM is calculated in an elderly population, and more validation studies are necessary in this age group to evaluate the clinical application of this method.

Absorptiometry, Photon↗

PubMed1993

Bone mineral density in patients with end-stage renal failure.

Renal osteodystrophy is a well-recognized complication of chronic renal failure (CRF) and is associated with a marked morbidity. Bone mineral density (BMD) has been shown to be the best predictor of fracture risk in different circumstances. In this cross-sectional study, we measured BMD using dual photon absorptiometry at three skeletal sites of functional importance such as the lumbar spine (LS), the femoral shaft (FS) and the femoral neck (FN) in 106 patients with end-stage renal failure (11 predialysis patients and 95 patients on maintenance dialysis). These skeletal sites are characterized by various relative amounts of trabecular and cortical bone. The results indicate that decreased bone mass was detectable in all skeletal sites before the beginning of dialysis and that BMD was negatively related to dialysis duration in LS and FS. Nevertheless, the deleterious effects of renal osteodystrophy were more pronounced at the FS level, where cortical bone is predominant. A separate analysis of BMD in both sexes revealed that females presented a more important bone loss in both cortical and trabecular bone than males. We did not find any significant difference in BMD at the three measured sites between patients on continuous ambulatory peritoneal dialysis and on regular hemodialysis. This study emphasizes the need to pay more attention to the prevention of bone loss in patients on CRF before the start of dialysis therapy, and to the fact that the female population might display a more pronounced susceptibility to bone loss.

Absorptiometry, Photon↗

PubMed1995

Skin thickness in patients with osteoporosis and controls quantified by ultrasound A scan.

In order to study a possible association between skin thickness and osteoporosis, we measured skin thickness by A mode ultrasound scanning in 20 females with osteoporosis and 20 age- and sex-matched controls. Bone mineral content (BMC) of the lumbar spine and the forearm was measured by dual-photon absorptiometry. BMC of the lumbar spine was significantly reduced in the osteoporotic group as compared to controls (p < 0.002). No difference in skin thickness was found between osteoporotic patients and controls. A statistically significant correlation between skin thickness on the forearm and BMC of the forearm was found (p < 0.02), but was opposed by a lack of correlation between skin thickness and BMC of the lumbar spine. We found a correlation between skin thickness and body weight (p < 0.002), which to our knowledge had not been reported earlier.

Absorptiometry, Photon↗

PubMed1993

Bone loss in young women with primary hypogonadism and its prevention with calcitonin.

A total of 63 healthy young women with primary amenorrhea, 37 control women at the same age with normal ovarian function and 118 postmenopausal women underwent bone mineral density (BMD) measurements at the lumbar spine (L2-L4) by dual photon absorptiometry. Mean +/- SE BMD value in the primary amenorrheic patients (0.878 +/- 0.015 g/cm2) was significantly lower than in both the control ovulatory women (1.069 +/- 0.026 g/cm2) and the postmenopausal patients (0.967 +/- 0.013 g/cm2) (p < 0.05). When hormonal parameters were compared between primary amenorrheic and ovulatory control cases, only the prolactin mean levels were found to be significantly lower in the first group (8.74 +/- 0.86 vs. 16.31 +/- 1.05 ng/ml; p < 0.001). Serum total alkaline phosphatase activity and LDL-cholesterol were negatively correlated with bone mineral density. Total cholesterol and lipid levels were significantly higher in women with primary amenorrhea when compared with the eumenorrheic control group (p < 0.001).

Absorptiometry, Photon↗

PubMed1996

Effect on cortical and trabecular bone mass of different anti-inflammatory treatments in preadolescent children with chronic asthma.

Bone metabolism and density have been shown to be abnormal in adult asthmatic patients treated with inhaled corticosteroids. Because the largest increases in bone growth and mineral deposition occur during childhood and adolescence, we performed a cross-sectional evaluation of cortical and trabecular bone mass by dual-photon absorptiometry at the proximal one third of the radius (cortical bone) and by dual-energy X-ray absorptiometry at the L2-L4 lumbar spine (trabecular bone) in 64 prepubertal asthmatic children receiving beclomethasone dipropionate (BDP) or cromolyn sodium (CS). Dual-energy X-ray absorptiometry was performed by anteroposterior scan and also by lateral vertebral scan in order to exclude the posterior elements of the vertebrae, which are composed mainly of cortical bone and which are less sensitive to the negative effect of steroids. Furthermore, we calculated "volumetric" bone density, dividing lateral mineral content by the vertebral volume. Bone mineral areal density and volume bone density did not differ in children receiving BDP for 6.7 +/- 1.3 mo at a mean dose of 319.3 +/- 130 micrograms/d compared with those in children treated with CS. Furthermore, anteroposterior bone density in our study population was in agreement with published normative data and with that of normal age-related healthy nonasthmatic children living in the same area and with the same dietary intake of calcium. No normal values are available for lateral and calculated-volume bone density. In conclusion, treatment with BDP does not appear to have an adverse effect on bone mass in prepubertal children with mild moderate asthma. Longitudinal studies should be performed in order to evaluate the effect of early introduction of inhaled corticosteroids in children with mild asthma.

Absorptiometry, Photon↗

PubMed1995

Bone mineral content in nephrotic children on long-term, alternate-day prednisone therapy.

Bone mineral content (BMC) was measured by single-photon absorptiometry in 24 children with steroid-dependent, minimal-lesion nephrotic syndrome after 1 to 6.3 years of alternate-day prednisone therapy and in a sex- and age-matched control group. Bone mineral content was -0.002 +/- 1.2 standard deviation scores in patients and 0.3 +/- 1.4 in controls (t = 1.17; P = 0.25). No significant relation was found between BMC in patients and the amount of prednisone taken or the duration of therapy. Alternate-day prednisone therapy at doses usually needed to keep children with steroid-dependent nephrotic syndrome under control does not significantly affect BMC.

Absorptiometry, Photon↗