Precision and stability of dual-energy X-ray absorptiometry measurements

Abstract

This study was performed to determine the precision and stability of dual-energy X-ray absorptiometry (DEXA) measurements, to compare bone mineral density (BMD) of subjects measured by DEXA and radionuclide dual-photon absorptiometry (DPA), and to evaluate different absorber materials for use with an external standard. Short-term precision (% coefficient of variation, CV) was determined in 6 subjects scanned six times each with repositioning, initially and 9 months later. Mean CV was 1.04% for spine and 2.13% for femoral neck BMD; for whole-body measurements in 5 subjects, mean CV was 0.64% for BMD, 2.2% for fat, and 1.05% for lean body mass. Precision of aluminum phantom measurements made over a 9-month period was 0.89% with the phantom in 15.2 cm, 0.88% in 20.3 cm, and 1.42% in 27.9 cm of water. In 51 subjects, BMD by DEXA and DPA was correlated for the spine (r = 0.98, P = 0.000) and femoral neck (r = 0.91, P = 0.000). Spine BMD was 4.5% lower and femoral neck BMD 3.1% higher by DEXA than by DPA. An aluminum phantom was scanned repeatedly, in both water and in an oil/water (30:70) mixture at thickness ranging from 15.2 through 27.9 cm. Phantom BMD was lower at 15.2 cm than at higher thicknesses of both water and oil/water (P = 0.05, ANOVA). The phantom was scanned repeatedly in 15.2, 20.3, and 27.9 cm of water over a 9 month period. In 15.2 and 20.3 cm of water, phantom BMD did not vary significantly whereas in 27.9 cm of water (equivalent to a human over 30 cm thick), phantom BMD increased 2.3% (P = 0.01) over the 9 months.

A multi-center comparison of dual energy X-ray absorptiometers: In vivo and in vitro soft tissue measurement

“…An ample amount of work has been done to investigate the intra-and inter-site precision of DXA for bone (Mazess et al, 1990;Johnson et al, 1991;LeBlanc et al, 1990;Mazess et al, 1989;Nuti et al, 1987;Compston et al, 1992;Kelly et al, 1991;Economos et al, 1996;Seto et al, 1991). Within the last ®ve years, quite a few studies examining soft tissue intra-site precision have been published (see Table 1).…”

“…The precision of individual DXA instruments for the assessment of bone is excellent, with coef®cients of variation (CV)`1.0% (Johnson et al, 1991;LeBlanc et al, 1990;Mazess et al, 1989;Nuti et al, 1987;Compston et al, 1992). On the other hand, Cvs for soft tissue measurements of up to 3.1% for lean tissue, 8.6% for fat tissue, and 7.9% for percent body fat have been observed (Table 1) Mazess et al, 1990;Johnson et al, 1991;Compston et al, 1992;Kelly et al, 1991;Slosman et al, 1992;Haarbo et al, 1991;Pritchard et al, 1993;Rico et al, 1994). The difference in precision between bone and soft tissue is not surprising since DXA was essentially designed to assess bone and soft tissue is heterogeneous.…”

Efeitos da natação e do treinamento resistido na densidade mineral óssea de mulheres idosas

“…A estimativa de precisão do método (coeficiente de variação) foi descrita em ser 2,0% para o colo do fêmur e 1,0% para a coluna lombar, de acordo com Johnson & Dawson-Hughes (17) . A DMO foi expressa em gramas por centímetro ao quadrado (g/cm …”

Dietary supplements and physical exercise affecting bone and body composition in frail elderly persons

“…Chapuy et al 41 reported effects of supplementation on fracture rates even after 2 months, accompanied by a modest increase in bone density. Studies of the precision and stability of DXA measurements reported coefficients of variation of total body parameters between 0.6% and 1.0% 31,42 ; it is possible that we were able to detect statistically significant changes only because we recruited enough subjects to observe an effect and the standard deviation appeared to be smaller than expected. Nevertheless, the change in control and experimental groups is in the direction expected.…”