Emerging Technologies for Nutrition Research Potential for Assessing Military Performance Capability (1997) / Chapter Skim
Currently Skimming:
Pages 151-168
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 151... ...
Emerging Technologies for Nutrition Research, 1997 Pp.
|
From page 152... ...
(TBBM, fat, and nonbone lean tissue)
|
From page 153... ...
TABLE 6-1 Coefficients of Variation of Measurement of Bone Mineral Density by Dual-Energy X-Ray Absorptiometry Reference Scanner Manufacturer Site/Object CV (%) Kohrt and Birge, Jr., 1995 QDR-1000W Hologic Total body 0.6 PA spine 1.1 Femoral neck 1.5 Trochanter 1.1 Ward's 3.2 Ultradistal wrist 0.6 Jergas et al., 1995 QDR-2000 Hologic PA spine 1.3 Lateral spine 2.0 Mazess et al., 1992 DPX-L Lunar PA spine Fast*
|
From page 154... ...
obtained on different DXA scanners. In vivo assessments of the lumbar spine, proximal femur, and whole body and in vitro assessments of a number of different phantoms indicate that BMD values obtained from Lunar instruments are 12 to 24 percent higher (Genant et al., 1994; Horber et al., 1992; Lai et al., 1992; Pocock et al., 1992)
|
From page 155... ...
TABLE 6-2 Comparisons of Bone Mineral Density and Body Composition Measures from Various Scanners and X-Ray Beam Configurations DXA Instrument and X-Ray Configuration QDR-1000W (single-beam) QDR-2000 (single-beam)
|
From page 156... ...
TABLE 6-3 Coefficients of Variation of Body Composition Measurements by DualEnergy X-Ray Absorptiometry Reference Scanner Manufacturer Total Mass (%)
|
From page 157... ...
Figure 6-1 Overview of the general principles upon which the estimation of body composition by DXA is based. In those pixels that contain bone mineral, the xray attenuation is compared with attenuation characteristics of the appropriate reference materials for bone and nonbone tissue (Panel A)
|
From page 158... ...
The effects of hydration status have been studied in hemodialysis patients and in volunteers who ingest large volumes of fluid (Formica et al., 1993; Going et al., 1993; Horber et al., 1992)
|
From page 159... ...
16.5 g/kg fat loss. The results of this study suggest that changes in tissue thickness have a minimal effect on the assessment of bone mineral and that large reductions in body weight may result in a significant loss of bone mass.
|
From page 160... ...
body fat content by DXA and by hydrodensitometry are summarized in Table 6-4. While estimates of body fat by DXA closely approximated those by hydrodensitometry in some study cohorts, wide discrepancies occurred in others.
|
From page 161... ...
Body Fat (%) Reference Subjects (N)
|
From page 162... ...
ASSESSMENT OF REGIONAL BODY COMPOSITION A distinct advantage of DXA over hydrodensitometry is that it can be used to assess the composition of specific regions of the body. However, until the validity of soft tissue assessment by DXA is established, this technique is not suitable for use in research.
|
From page 163... ...
Whether this will occur depends largely on the manufacturers and whether the demand for this application of DXA is sufficient to justify the costs of research and development. Most of the expense associated with the use of DXA is in the cost of the instrument itself, which is likely to be in excess of $100,000.
|
From page 164... ...
Haarbo, J., A Gotfredsen, C
|
From page 165... ...
Mazess, R., C.H. Chesnut, III, M
|
From page 166... ...
Wellens, R., W.C. Chumlea, S
|
From page 167... ...
WENDY KOHRT: I think there are people working in this area who are trying to make the manufacturers much more accountable. Whether that will be successful, I do not know.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.