Precision of total-body and regional bone mineral measurement by dual-energy X-ray absorptiometry.

The precision of total-body and regional bone mineral measurements from whole body scans obtained by dual-energy X-ray absorptiometry (DEXA) was determined in a phantom and two normal subjects. Whole body scans were performed once a week for three months at the speed of 80 mm/sec. Coefficients of variation for measurements of total-body bone mineral content (BMC) in the phantom and the subjects were 1.7% and 1.5% (average), respectively. Moreover, plots of total-body BMC values with time showed no significant slope, indicating the stability of the instrument. Regional BMC measurement from whole body scans, however, resulted in larger precision errors than total-body BMC measurement. This is attributed to the more rapid scan speed and coarser scan width used in whole body scanning as compared with regional scanning. Good precision of total-body BMC measurement by DEXA is of great clinical value in the assessment of metabolic bone disease.     

Effects of metal implants on whole-body dual-energy x-ray absorptiometry measurements of bone mineral content and body composition.

OBJECTIVE: The purpose of this study was to evaluate the influence of metal implants on measurements of bone mineral content and body composition by x-ray-based dual-photon absorptiometry. METHODS: Four whole-body dual-photon absorptiometry scans were performed on 13 participants with metal rods either present or absent during the scans. The influence of the amount of metal (50 g, 100 g and 150 g), the proximity of the metal rod to the x-ray source and the reproducibility of any metal-induced effects were evaluated by altering the position or the size of the metal rod used, or both. RESULTS: The presence of metal rods weighing 100 g or 150 g significantly increased reported total body mass and bone mineral content (p < 0.034). Soft-tissue mass was increased when the scan included the 100-g rod (p < 0.003). The proximity of the metal to the x-ray source did not have a significant influence on the body composition changes induced by the metal. The effects of the metal rods on body composition variables were reproducible. CONCLUSION: The presence of metal rods inflated body composition variables measured by dual-photon absorptiometry; however, the effects are reproducible during repeat scans of an individual patient. Metal had the largest impact on whole-body bone mineral content, causing errors of 1.5%-3%.     

Measurement of forearm bone mineral density in normal women by dual-energy X-ray absorptiometry.

We report the results of forearm measurements, without the use of a water bath, using dual-energy X-ray absorptiometry (DEXA) in 100 normal women aged 29-69 years (average age, 52 years). Studies were performed using the Hologic QDR-1000, with bone mineral density (BMD) measured at three sites in the non-dominant forearm: ultradistal, distal one-third and a region between these two. The precision of the technique was 0.74%, 0.55% and 0.58%, respectively. The normal range for forearm BMD and variation with age was established. BMD was also measured in the lumbar spine (L1-L4) and femoral neck. Linear regression analysis gave a range of correlation coefficients between forearm and axial sites of r = 0.49-0.67. Standard errors of the estimate (SEE) in predicting axial from peripheral measurements gave average values from the three forearm sites of 0.085 g/cm2 for the femoral neck and 0.118 g/cm2 for the spine. Forearm measurements using DEXA can now be reliably performed in air. DEXA produces a high-resolution image, is fast and simple to perform, and enables both cortical and trabecular sites to be examined in one measurement. Forearm and axial measurements can be performed using the same equipment, where centres possess a suitable DEXA system.     

Total and regional bone mineral content in healthy Spanish subjects by dual-energy X-ray absorptiometry

Design  This is an observational cross-sectional study. Objective  The aim of the present study was to describe and analyze patterns of change in total and regional bone mineral content in relation to age and gender in a sedentary Spanish sample population (from the Community of Madrid). The age range of the sample population was from birth to 80 years. Materials and methods  One thousand one hundred twenty healthy subjects were recruited and divided into 16 groups according to age. Each subject underwent whole-body densitometry using dual-energy X-ray absorptiometry. An analysis was made of the amount of bone mineral content (BMC) in the whole body and in different regions: the head, trunk, upper limbs, and lower limbs. Results  Gender differences in mean values for upper limbs and lower limbs are statistically significant between 16 and 70 years of age. For the head and trunk, the mean BMC values show the most significant gender differences between 16 and 25 years of age (p ≤ 0.001). Total bone mineral content (TBMC) and TBMC-to-height ratio show significant gender differences between 16 and 70 years of age. In females, TBMC values increase up to 20 years of age and in males up to 25 years of age. Conclusion  We have determined an evolutionary normal pattern of bone mineral content in urban Spanish people.     

In vivo differences among scan modes in bone mineral density measurement at dual-energy X-ray absorptiometry

Purpose

Our aim was to estimate the in vivo reproducibility of bone mineral density (BMD) at dual-energy X-ray absorptiometry (DXA) and to compare fast array, array, and high-definition scan modes.

Materials and methods

A total of 378 patients (38 males and 340 females; mean age 63 ± 9 years) underwent DXA using a QDR-Discovery A densitometer (Hologic). Considering the three scan modes on lumbar spine and right femur, six independent groups of 30 patients were examined twice (for a total of 180 patients). Least significant change (LSC) and smallest detectable difference (SDD) were calculated. The remaining 198 patients underwent three scans of the lumbar spine (n = 92) or of the right femur (n = 106), one for each scan mode. The student t test and Bland–Altman analysis used were. Scan times were recorded and radiation dose was estimated using the ICRP60 method.

Results

Intra-scan mode reproducibility was 98–99 %, corresponding to an LSC of 1.49–2.08 %. The SDD was 0.018–0.023 g/cm² (lumbar spine) and 0.017–0.019 g/cm² (right femur). All comparisons among scan modes were statistically significant (p < 0.001) but lower than SDDs, i.e. not clinically relevant. Considering lumbar spine and the right femur, scan times were 50 and 38 s for fast array, 98 and 74 s for array, and 195 and 148 s for high definition, respectively; radiation doses were 6.7 and 4.7 μSv for fast array, and 13.3 and 9.3 μSv for both array and high definition, respectively.

Conclusion

Since all BMD differences were lower than the SSDs, the three scan modes can be considered interchangeable. As a consequence, although the absolute reduction in time and radiation dose is relatively low, when BMD measurement is the aim of DXA, fast array can be generally preferred.     

Mandibular bone mineral density measured using dual-energy X-ray absorptiometry: relationship to hip bone mineral density and quantitative ultrasound at calcaneus and hand phalanges

The main aim of this cross-sectional study was the estimation of relationships between mandibular bone mineral density (m-BMD), hip bone mineral densities (BMDs) and quantitative ultrasound at calcaneus and hand phalanges. Correlations between m-BMD and age, years since menopause (YSM) and body size were also evaluated. 42 edentulous persons (36 females and 6 males aged 60.5 +/- 6.9 years) were evaluated. In the group studied no factors affecting bone metabolism (either medical conditions or medications) were noted. Bone status was assessed by dual-energy X-ray absorptiometry (mandible, hip--Lunar DPX-L), and quantitative ultrasound (calcaneus--Lunar Achilles which measures speed of sound (SOS, m s-1) and broadband ultrasound attenuation (BUA, dB MHz-1); and phalanges of the hand--DBM Sonic 1200 which measures amplitude-dependent speed of sound (AD-SOS, m s-1)). CV% for mandibular measurements was 2.06%. m-BMD correlated significantly with the following measurements: femoral neck r = 0.39, p < 0.01; Ward's r = 0.39, p < 0.01; calcaneal BUA r = 0.39, p < 0.01; and phalangeal AD-SOS r = 0.4, p < 0.01. Negative correlation consistent with a significant decrease with age was observed in m-BMD (r = -0.36, p < 0.05) and AD-SOS (r = -0.4, p < 0.01). BMD in the mandible also decreased with YSM (r = -0.47, p < 0.01). m-BMD was correlated with age, YSM, height and weight in stepwise, multiple, linear regression analysis. The following equation was obtained: m-BMD = -2.21 + 0.018 x height (cm) -0.02 x YSM (years) + 0.13 x age (years). It may be concluded that mandibular BMD may be an appropriate measurement site for the evaluation of skeletal status in osteoporosis.     

Dual energy x-ray absorptiometry assessment of the bone mineral content and body composition during growth

PURPOSE: To propose a simple method of analysis of whole body DXA scan results, for the bone mineral content of the entire skeleton (BMCt) and the arms and legs (BMCa and BMCl), as well as the analysis of the body composition in lean (Lt, La and Ll) and fat (Ft, Fa and Fl) in children and adolescents with normal growth. Materials and methods. A whole body DXA scan (Norland XR36(TM) DXA system) was performed in 90 control females and 76 control males aged from 2.3 y to 21.0 y, and from 2.3 y to 20.1 y, respectively. BMC values, as well as L and F values were correlated with the body weight (BW) of the measured subjects. BMCt, Lt and Ft values corrected for the body surface area (BS), and the ratio BMCl/BMCa, were also calculated. RESULTS: High linear correlations (r>0.9) were found between BMCt, Lt or Ft values and BW, as well as between BMC (a & l) and BMCt, L (a & l) and Lt, F (a & l) and Ft. The ratios BMCt/BS(1.5), Lt/BS(1.5), and Ft/BS(1.5) had constant values of 1.2+/-0.1, 17.5+/-1.9, and 8.7+/-2.0, respectively, in females, and 1.2+/-0.1, 18.9+/-1.3, and 7.3+/-1.4, in males. The ratio BMCl/BMCa had a constant value of 2.8+/-0.4 in both sexes. CONCLUSION: The reference values obtained by DXA for the bone mineral content, lean and fat masses of the entire body and limbs are of interest, in our experience, to follow-up the growth in patients with long-term treatments, and to quantify orthopedic disorders and treatments.     

Assessment of whole-body composition with dual-energy x-ray absorptiometry.

Dual-energy x-ray absorptiometry (DXA) allows noninvasive direct measurement of the three major components of body composition: lean body mass (LBM), fat body mass (FBM), and bone mineral body mass (BBM). To study the accuracy and short-term and long-term precision of body composition measurements, the authors measured body composition with DXA in 60 healthy young adults. Independent measurement of LBM (LBMK-40), obtained from the determination of the whole-body content of potassium-40 with a whole-body scintillation detector, was highly correlated with LBM determined with DXA (LBMDXA) (LBMK-40 = 1.069.LBMDXA,R2 = .996). Assessment of body composition in 10 patients with acquired immunodeficiency syndrome (AIDS) and 10 patients with cystic fibrosis was performed with DXA. The AIDS patients showed a marked decrease in LBM, while in patients with cystic fibrosis, LBM and BBM were decreased. DXA measurements of body composition appeared accurate and precise enough to be of clinical relevance in detecting specific alterations of body composition.     

An evaluation of forearm bone mineral measurement with dual-energy X-ray absorptiometry

Dual-energy x-ray absorptiometry (DEXA) has been reported to be a valuable means of bone mineral measurement of the lumbar spine and hip. In order to determine whether DEXA could be as useful for bone mineral analysis of the forearm, we compared its accuracy, precision and measurement performance to single-photon absorptiometry (SPA). There was high correlation between these techniques for integral bone mineral density in standard aluminum tubes (r = 0.99) and 30 adult volunteers or patients with osteoporosis (r = 0.95). The mean short-term precision of DEXA was 0.9% in vitro and about 1.5% in vivo. DEXA produced excellent bone images which enhance long-term in vivo precision. The measurement performance of both instruments was largely unaffected by localized fat deposits or increases in forearm thickness or proportion of fat subcutaneously. We conclude that DEXA is a clinically useful alternative to SPA for forearm bone mineral assessment.     

Pitfalls of bone mineral density evaluation by dual-photon absorptiometry.

Material absorbing photons aligned with the lumbar vertebrae can create falsely elevated measurements of bone mineral density during dual-photon absorptiometry. Three cases illustrating this phenomenon are presented. Although bone mineral density was overestimated in each case, calculated fracture risk was normal in two cases and greatly increased in the third. Photon-absorbing material can create overestimates of bone mineral density during dual-photon absorptiometry, even when a greatly increased fracture risk is computed.     

Dual-energy x-ray absorptiometry: a precise method of measuring bone mineral density in the lumbar spine

We compared two methods of measuring spinal bone mineral content and density (BMC/BMD): conventional dual-photon absorptiometry (DPA) and a more recent method, dual-energy x-ray absorptiometry (DEXA). The clinical usefulness of both methods was compared in the measurement of BMC in the forearm. DEXA had a long-term in vivo precision of 1% which was significantly better than that of DPA. Changes in the distribution of fatty tissue influenced the accuracy of the two spinal methods in different ways. Forearm BMC discriminated between the bone mass of early and late postmenopausal women to the same degree as DPA and DEXA. The variability in the response to estrogen treatment and placebo was much lower with DEXA and forearm BMC than with DPA. We conclude that DEXA provides a fast and precise measurement of spinal BMC/BMD. The accuracy remains to be evaluated for in vivo studies.     

Photon absorptiometry for non-invasive measurement of bone mineral content

Bone mineral content of the distal radius was determined in 106 patients by single photon absorptiometry using iodine-125 monochromatic source. The technique provided a reliable means to assess the degree of mineral loss in conditions such as osteoporosis, renal osteodystrophy in patients on chronic maintenance dialysis, subjects on long-term steroid therapy, and those with diabetes mellitus. It is more sensitive than conventional radiography and completely noninvasive compared to bone biopsy. It is suggested that photon absorptiometry is a simple, sensitive, and reliable technique for assessment and follow-up of the bone mineral content in a host of disorders associated with bone demineralization.