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PubMedDate not supplied

[A comparison between double-photon absorptiometry (DEXA), impedance and anthropometry in the study of the body composition of obese subjects].

Dual-energy X ray absorptiometry (DEXA) is primarily used in the assessment of bone mineral. However, the transmissions of the two different energy beams in nonbone areas can be processed to calculate the amount of fat and free-fat mass of the soft tissues. We have compared the estimation of body fat mass (FM) by DEXA with data derived from anthropometric (A) (During & Womersley formula) and impedance (BIA) measurements. We have studied 10 subjects, 8 female and 2 male, age 39 +/- 17, weight 97.4 +/- 17.2 kg. The results were: FM 44.4 +/- 8.5 kg (DEXA), 40.6 +/- 6.3 kg (A) and 38.4 +/- 9.8 kg (BIA); FFM 52.1 +/- 14.1 kg (DEXA), 56.8 +/- 13.9 kg (A) and 58.8 +/- 13.6 kg (BIA). The correlation was higher between DEXA and A (r = 0.88, for women r = 0.94). BIA results change depending on the equation used to derive Lean Body Mass (LBM) according to different authors. DEXA measurements are independent from the explorer, whereas A and BIA determinations can change in separate occasions with the same or different observer. Therefore, DEXA method seems more reliable than BIA for the assessment of FM. If DEXA technology is not available, our results support the use of anthropometric over impedance measurements.

Absorptiometry, Photon↗
PubMed1993

[Measurement of vertebral bone density. Quantitative tomodensitometry or dual-photon absorptiometry?].

We have compared vertebral bone density measurements (QCT and DXA) in women in the postmenopausal period who underwent both examinations. Our aim was to study the results and to define the respective indications of QCT and DXA in various clinical pictures of osteoporosis. The subjects of the study were distributed into various groups according to the presence or absence of vertebral collapse and/or peripheral fractures. The results of the measurements were expressed as Z-scores (deviation from age-normal average) to suppress the age effect and to make comparison between both methods possible. The values of both measurements are significantly lower in case of vertebral involvement. QCT is more sensitive than DXA to discriminate vertebral collapse. A vertebral fragility threshold was defined at a Z-score of -1 with DXA and -1.25 with QCT, corresponding to the best sensitivity for an acceptable specificity. The results of densitometry suggest that there is a peripheral osteoporosis, different from vertebral osteoporosis, as early as the postmenopausal period. Since DXA is easy to implement, it can be used to screen osteoporosis. When the vertebral measurement with DXA is normal although osteoporosis is obvious (previous collapse or fracture), QCT must be used as it is more sensitive.

Absorptiometry, Photon↗
PubMed1988

Bone mineral content measurement in small infants by single-photon absorptiometry: current methodologic issues.

Single-photon absorptiometry (SPA), developed in 1963 and adapted for infants by Steichen et al. in 1976, is an important tool to quantitate bone mineralization in infants. Studies of infants in which SPA was used include studies of fetal bone mineralization and postnatal bone mineralization in very low birth weight infants. The SPA technique has also been used as a research tool to investigate longitudinal bone mineralization and to study the effect of nutrition and disease processes such as rickets or osteopenia of prematurity. At present, it has little direct clinical application for diagnosing bone disease in single patients. The bones most often used to measure bone mineral content (BMC) are the radius, the ulna, and, less often, the humerus. The radius appears to be preferred as a suitable bone to measure BMC in infants. It is easily accessible; anatomic reference points are easily palpated and have a constant relationship to the radial mid-shaft site; soft tissue does not affect either palpation of anatomic reference points or BMC quantitation in vivo. The peripheral location of the radius minimizes body radiation exposure. Trabecular and cortical bone can be measured separately. Extensive background studies exist on radial BMC in small infants. Most important, the radius has a relatively long zone of constant BMC. Finally, SPA for BMC in the radius has a high degree of precision and accuracy.

Bone Development↗
PubMed1989

Quality assurance and precision of dual photon absorptiometry in bone mineral measurement.

Dual photon absorptiometry (DPA) has evolved as a powerful technique in measuring bone mineral density (BMD) to assess osteoporosis and metabolic bone diseases in recent years. We introduced the first installation of DPA instrument into this country in Aug. 1987. Since the comparison among longitudinal BMD values influences the diagnosis, monitoring and medical decision-making, high precision of the system performance and strict quality assurance program are prerequisite for judgment of the difference between two successive measurements. However, the automation and black-box software design of the instrument make users gain very little knowledge how the instruments acquire the long-term system reliability. The first part of this study was designed to establish a standardized procedure to evaluate the long-term quality of the DPA instrument. Our instrument was proved to have stable sensitivity, resolution, accuracy and reproducibility in the four months of study. Three subjects with different BMD levels were scanned to evaluate the intraobserver and interobserver errors in BMD analysis expected in our laboratory (2.2 and 1.6% at 95% confidence level, respectively). The results indicated that reanalyzing the same scan by either of the two observers would produce a BMD precision error within 2.2% at a 95% confidence level. Serial scans of 7 normal volunteers within five weeks were then conducted to evaluate the overall precision of the BMD measurements. Our findings indicated that two scans would be considered as having a real BMD change if they differ by more than 3.3% at a 95% confidence level. There are at least five sets of DPA instruments that have been installed in Taiwan presently.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Bone density in idiopathic hypercalciuria in men. Study by dual photon absorptiometry, X-ray computed tomography and histomorphometry].

Lumbar bone mineral density (BMD) of the L3 vertebra was evaluated by double photon absorptiometry or tomodensitometry (TDM) in 55 hypercalciuric individuals in two separate studies. In the first, in a department of nephrology, 29 lithiasis patients were studied by TDM of L3. By this technique, trabecular density was 75 +/- 23% of normal. It was lower in the 17 patients in whom hypercalciuria persisted after calcium restriction (66 +/- 15% of normal and below the "fracture threshold" in 9 cases) than in the 12 patients in whom it disappeared after the prescription of such a diet (88 +/- 26%, below the "fracture threshold" in 3 cases), this difference being significant (p less than 0.01). In another 26 patients, seen in a department of rheumatology, three of whom had osteoporosis with vertebral fracture, density was measured in 21 cases by double photon absorptiometry (mean Z score -1.9 +/- 1.0) and in 5 cases by TDM (mean BMD of L3 69 +/- 21% of normal). Mean iliac trabecular volume, measured in 8 cases only, was 70 +/- 25% of normal and was below the "fracture threshold" in 3 cases. Comparison of the two study groups was not possible because of differences in recruitment and methods of investigation. These two studies nevertheless show the existence of significant vertebral bone rarefaction during hypercalciuria in the young man. Confirmed and quantified in patients in whom the metabolic disturbance was discovered as a result of radiological abnormalities, this quantitative abnormality was also seen in patients in whom hypercalciurie was found because of renal lithiasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1990

Effect of calcitonin on total body bone mineral contents of experimental osteoporotic rats determined by dual photon absorptiometry.

Total body bone mineral (TBBM) content in rats was measured by dual photon absorptiometry (DPA). TBBM showed significant increases over 4 weeks in control groups with significant bone loss over the same time in prednisolone-injected rats on low calcium feed. Daily injections of calcitonin significantly reduced loss of bone mass. Both prednisolone- and prednisolone-calcitonin-injected groups showed significantly elevated serum alkaline phosphatase with the prednisolone-calcitonin group also exhibiting elevated serum calcium and phosphate levels, confirming the impact of the experimental protocol. TBBM measured by DPA in all groups correlated well (r = 0.928, P less than 0.001 n = 20) with the total ash weight suggesting that the method reflects total skeletal mineral content in the small animal. TBBM measurement by DPA proves well-suited to monitoring bone mineral in a small animal experimental setting.

Absorptiometry, Photon↗
PubMed1989

Dual photon absorptiometry of the proximal tibia.

Bone mineral content (BMC) and bone mineral density (BMD) of the proximal tibia were determined by dual photon absorptiometry on 44 women, aged 23-87 years. The area of the tibia measured was a 2.01 cm region immediately distal to the medial and lateral tuberosities. Values of BMC ranged between 5.09 and 14.57 g and BMD between 0.380 and 1.180 g/cm2. Both tibial BMC and BMD declined with age and tibial BMD was significantly correlated with lumbar spine (r = 0.70), femoral neck (r = 0.73), and femoral trochanter (r = 0.74). However, the large standard errors of estimate (SEE) (0.08-0.14 g/cm2) do not allow for reliable prediction in an individual of other skeletal sites by the tibia. Repeated measurements demonstrated that dual photon absorptiometry of the proximal tibia is a reliable measurement and may be a useful tool in the monitoring of therapeutic or intervention modalities in those individuals with skeletal diseases in whom measurement of the lumbar spine or proximal femur may not be possible.

Absorptiometry, Photon↗
PubMed1994

Measurement of the natural uranium content of fabricated, tissue substitute lung sets by dual photon absorptiometry.

The assessment of tissue substitute materials by dual photon absorptiometry has been extended to detect the presence of high atomic weight materials. Commercial dual photon systems dedicated to the measurement of bone mineral mass can be used to detect other elements in fabricated tissue phantoms. The technique is sufficiently sensitive to quantitate the mass of natural uranium that had been distributed throughout the lungs of a thorax phantom.

Absorptiometry, Photon↗
PubMed1989

Discriminative ability of total body bone-mineral measured by dual photon absorptiometry.

We investigated the discriminative ability of total body bone-mineral expressed as the total body bone-density (TBBD) measured by dual photon absorptiometry (DPA) in 79 healthy premenopausal women, 27 healthy postmenopausal women, and 120 female osteoporotic fracture patients presenting with either Colles' fracture, vertebral fracture or femoral neck-fracture. TBBD was compared to the bone-mineral density of the lumbar spine (BMDspine) also measured by DPA, and to the bone-mineral content of the forearms (BMCforearm) measured by single photon absorptiometry (SPA). TBBD, BMDspine and BMCforearm showed that all the fracture patient groups had significantly reduced bone-mass. Using receiver operating characteristic (ROC) analysis, we found that TBBD had a tendency towards better discriminative ability than BMDspine or BMCforearm with regard to the discrimination between healthy premenopausal women and the three types of osteoporotic fractures (not significant in spinal fracture patients). BMCforearm had an intermediate position, whereas BMDspine had the smallest discriminative ability. TBBD also discriminated better between healthy postmenopausal women and hip-fracture patients than BMDspine or BMCforearm, whereas there was no significant difference between the three methods regarding the discrimination between the healthy postmenopausal women and the Colles' and spinal fracture patients. We conclude that the TBBD measurement by DPA has a discriminative potential which is better than the local spine or forearm measurements.

Absorptiometry, Photon↗
PubMedDate not supplied

[Applications and results of photon absorptiometry].

Bone mineral content (CMO, mg/cm2) was measured at the distal radius by dual photon absorptiometry (DPA, I125, Am241) in 1.161 women (w), aged 20-87 years. Women were subdivided into different groups according to the presence and duration of menopause. For gross evaluation of spinal osteoporosis (OP), the results of spinal X-rays were graded as follows: score 0: no signs of OP; score 1: aspecific signs of OP; score 2: typical signs of OP; score 3: wedging or collapse of one or more vertebrae. Women in postmenopausal state showed significantly reduced CMO (p less than .0005) when compared to women in premenopausal state; a significant correlation was found between CMO and years since menopause (p less than .0001). Concerning the relationship between CMO and spinal score, a progressive decreases in CMO from score 0 to score 3 was present and the correlation was significant (p less than .0001). In addition, women with score 3 showed a mean CMO below the "fracture threshold", in spite of the large overlap in individual CMO values. Our data suggest that radial DPA should be maintained as a "screening" procedure for OP.

Absorptiometry, Photon↗
PubMed1991

Effect of aortic sclerosis on bone mineral measurements by dual-photon absorptiometry.

Measurements of the bone mineral content (BMC) of lumbar spine by dual-photon absorptiometry (DPA) are performed mainly in the anteroposterior (AP) projection. Due to superimposition of the abdominal aorta, the BMC measured for patients with aortic calcification usually is too high. To determine the influence of aortic calcifications, DPA scans were performed in the AP-projection on 100 dissected abdominal aortae with different degrees of atherosclerosis placed on a human lumbar spine cast in lucite. The measured values were compared with those obtained in the same projection without the aortae. The average increase of the BMC values relative to the mean for the vertebrae L2 to L4 for aortae with severe complicated lesions, i.e., those containing larger amounts of calcium, was 0.03 g/cm2, with a maximum deviation of 0.09 g/cm2. Aortae with fatty streaks or fibrous plaques did not cause significant increases of the BMC. The mean deviation for aortae with mild complicated lesions, i.e., those containing smaller amounts of calcium, was within the range of instrument precision.

Absorptiometry, Photon↗
PubMed1987

Measurement of hand bone mineral content using single-photon absorptiometry.

A single photon absorption imaging technique has been developed to assess the bone mass of the hand, especially in patients with rheumatoid arthritis or bronchial asthma. A modified rectilinear scanner images the hand by transmission scanning in a water bath with a 7.4 GBq 125I source. A microcomputer is used to calculate the bone mineral distribution, and the total bone mineral content (BMC) of the hand is determined from that distribution. The precision (coefficient of variation) of the measurement is 1.9%. A control population of 20 men and 58 women has been studied to determine normal variations in hand bone mineral content with age, sex, body size, hand volume and years since menopause. The normal men are found to have an average hand BMC of 25.1 g with a coefficient of variation (CV) of 22%, which is reduced to 12% by normalising for body size using span. The normal women had an average hand BMC of 18.0 g +/- 15%. The CV is reduced to 13% by normalising for span and years post-menopause.

Adult↗
PubMed1993

Influence of patient's weight on dual-photon absorptiometry and dual-energy X-ray absorptiometry measurements of bone mineral density.

Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1000) and by 153Gd dual-photon absorptiometry (DPA) (Novo Lab 22a) in 120 postmenopausal women. Though a high correlation existed between the two techniques, the ratio between DXA and DPA values was not constant. Using DXA we observed a higher dependence of BMD on weight than in the DPA measurements. To investigate the different behaviour of DXA and DPA machines with weight, we analysed the effects of increasing thickness of soft tissue equivalents on the BMD of the Hologic spine phantom and on the BMD equivalent of an aluminium standard tube. Increasing tissue-equivalent thickness caused the phantom BMD measured by DPA to decrease significantly but had not effect on the DXA measurements. The different behaviour of DPA and DXA equipment with regard to the phantoms could account for the differences observed in the relations between BMD and weight in the patients. Using multiple regression we studied the influence of weight and body mass index on the relation between BMD measured by the two techniques. The introduction of either of these variables into the regression resulted in an improvement of the prediction of the DXA values from the DPA values. However, the residual standard error of the estimate was still higher than the combined precision errors of the two methods, so that no simple relation allows a conversion of BMDDPA into BMDDXA. Our results confirm that BMD is positively correlated with weight in postmenopausal women; the influence of weight on BMD is blunted when the Novo Lab 22a DPA machine is used for measuring bone mineral.

Absorptiometry, Photon↗
PubMedDate not supplied

Reference values for radial bone width and mineral content using single photon absorptiometry in healthy children aged 4 to 10 years.

Bone width and mineral content were measured in 420 healthy Cambridge children aged 4 to 10 years using single photon absorptiometry. The results are expressed first in the form of standard centile charts, with additional prediction charts which provide body-size-adjusted estimates for the measurements, and interpretation centiles for comparing these estimates with the actual measurements. The values obtained are similar to those reported for American children aged five to six years after adjusting for body-size differences. We suggest that appropriate application of these prediction charts will facilitate the use of single photon absorptiometry in monitoring and treating children who have disorders of bone growth and mineralization.

Absorptiometry, Photon↗