TY - JOUR
T1 - Estimation of percentage body fat by dual-energy x-ray absorptiometry
T2 - Evaluation by in vivo human elemental composition
AU - Wang, Zimian
AU - Heymsfield, Steven B.
AU - Chen, Zhao
AU - Zhu, Shankuan
AU - Pierson, Richard N.
PY - 2010
Y1 - 2010
N2 - Dual-energy x-ray absorptiometry (DXA) is widely applied for estimating body fat. The percentage of body mass as fat (%fat) is predicted from a DXA-estimated RST value defined as the ratio of soft tissue attenuation at two photon energies (e.g., 40 keV and 70 keV). Theoretically, the RST concept depends on the mass of each major element in the human body. The DXA RST values, however, have never been fully evaluated by measured human elemental composition. The present investigation evaluated the DXA RST value by the total body mass of 11 major elements and the DXA %fat by the five-component (5C) model, respectively. Six elements (i.e. C, N, Na, P, Cl and Ca) were measured by in vivo neutron activation analysis, and potassium (i.e. K) by whole-body 40K counting in 27 healthy adults. Models were developed for predicting the total body mass of four additional elements (i.e. H, O, Mg and S). The elemental content of soft tissue, after correction for bone mineral elements, was used to predict the RST values. The DXA RST values were strongly associated with the R ST values predicted from elemental content (r = 0.976, P < 0.001), although there was a tendency for the elemental-predicted RST to systematically exceed the DXA-measured RST (mean SD, 1.389 0.024 versus 1.341 0.024). DXA-estimated %fat was strongly associated with 5C %fat (24.4 12.0% versus 24.9 11.1%, r = 0.983, P < 0.001). DXA RST is evaluated by in vivo elemental composition, and the present study supports the underlying physical concept and accuracy of the DXA method for estimating %fat.
AB - Dual-energy x-ray absorptiometry (DXA) is widely applied for estimating body fat. The percentage of body mass as fat (%fat) is predicted from a DXA-estimated RST value defined as the ratio of soft tissue attenuation at two photon energies (e.g., 40 keV and 70 keV). Theoretically, the RST concept depends on the mass of each major element in the human body. The DXA RST values, however, have never been fully evaluated by measured human elemental composition. The present investigation evaluated the DXA RST value by the total body mass of 11 major elements and the DXA %fat by the five-component (5C) model, respectively. Six elements (i.e. C, N, Na, P, Cl and Ca) were measured by in vivo neutron activation analysis, and potassium (i.e. K) by whole-body 40K counting in 27 healthy adults. Models were developed for predicting the total body mass of four additional elements (i.e. H, O, Mg and S). The elemental content of soft tissue, after correction for bone mineral elements, was used to predict the RST values. The DXA RST values were strongly associated with the R ST values predicted from elemental content (r = 0.976, P < 0.001), although there was a tendency for the elemental-predicted RST to systematically exceed the DXA-measured RST (mean SD, 1.389 0.024 versus 1.341 0.024). DXA-estimated %fat was strongly associated with 5C %fat (24.4 12.0% versus 24.9 11.1%, r = 0.983, P < 0.001). DXA RST is evaluated by in vivo elemental composition, and the present study supports the underlying physical concept and accuracy of the DXA method for estimating %fat.
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U2 - 10.1088/0031-9155/55/9/013
DO - 10.1088/0031-9155/55/9/013
M3 - Article
C2 - 20393230
AN - SCOPUS:77951192301
SN - 0031-9155
VL - 55
SP - 2619
EP - 2635
JO - Physics in medicine and biology
JF - Physics in medicine and biology
IS - 9
ER -