Emerging Technologies for Nutrition Research Potential for Assessing Military Performance Capability (1997) / Chapter Skim
Currently Skimming:
Pages 127-150
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 127... ...
Emerging Technologies for Nutrition Research, 1997 Pp.
|
From page 128... ...
status of imaging methods; a final section provides suggestions for future research. Historical Development Students of human biology have expressed interest in body composition since the nineteenth century (Forbes, 1987; Lawes and Gilbert, 1859; von Bezold, 1857)
|
From page 129... ...
comorbidities (Björntorp, 1986)
|
From page 130... ...
Figure 5-1 First four levels of body composition and their main components. SOURCE: Baumgartner et al.
|
From page 131... ...
Figure 5-2 Main components of the tissue-system level of body composition. GI, gastrointestinal.
|
From page 132... ...
1979c; Wang et al., 1993)
|
From page 133... ...
Computerized Axial Tomography The cross-sectional CT image can be used to quantify the area of body composition components of interest (Chowdhury et al., 1994; Heymsfield et al., 1979a, b, c; Kvist et al., 1986; Seidell et al., 1990; Sjöström et al., 1986)
|
From page 134... ...
These and other similar studies over the past 15 years have gradually perfected the methods of evaluating body composition by CT. Once the amount of tissue in a specific slice is known, the total volume of the component can be calculated by compiling data from multiple slices.
|
From page 135... ...
procedures improve, manual correction of MR component analyses is required. The reliability of these procedures is discussed later in this review.
|
From page 136... ...
indicated good agreement between CT-measured and cadaver AT areas and ratios (r values ranged from 0.77–0.94)
|
From page 137... ...
Magnetic Resonance Imaging Phantoms Few attempts have been made to validate MRI using phantoms.
|
From page 138... ...
Comparison with CT Attempts to validate MRI have been made by comparing MRI measurements of AT with those obtained by CT using both animal and human models (Table 5-1)
|
From page 139... ...
TA B LE 5 -1 M R I V al id at io n St ud ie s C or re la tio n (S EE , % )
|
From page 140... ...
TA B LE 5 -2 M R I R el ia bi lit y St ud ie s*
|
From page 141... ...
the authors reported that for lean tissue volume in the leg, derived using 15 images, the CV was 3.9 percent. Although the issue of measurement reliability requires further investigation, these preliminary results are encouraging.
|
From page 142... ...
Another disadvantage of MRI is that motion artifacts can affect tissue contrast in the abdominal region. Although improvements in MRI technology now permit the acquisition of multiple transverse images in a breath hold (i.e., ~20 seconds)
|
From page 143... ...
current reference measure of total body lipid. However, it is important to note that most clinical interest centers on total body fat, and thus this second source of error may not be of primary concern.
|
From page 144... ...
20 to 100 µs acquisition rates (10 to 50 images per second) (Jolesz, 1992)
|
From page 145... ...
Bloch, F., W.W. Hansen, and M.E.
|
From page 146... ...
Garn, S.M. 1957 Roentgenogrammetric determination of body composition.
|
From page 147... ...
Purcell, E.M., H.C. Torrey, and R.V.
|
From page 148... ...
Sohlström, A., and E Forsum 1995 Changes in adipose tissue volume and distribution during reproductionin Swedish women as assessed by magnetic resonance imaging .
|
From page 149... ...
tion programs that people have developed to make these measurements, but there is subjectivity involved. One first specifies, say, a certain range of relaxation times in subcutaneous adipose tissue.
|
From page 150... ...
STEVEN HEYMSFIELD: I just know the Columbia magnet is also relatively small bore. DOUGLAS WILMORE: They are getting up to 1 meter.
|
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.