Bone mineral and body fat measurements by two absorptiometry systems: comparisons with neutron activation analysis.

In 185 adults (68 white and 31 black males, 66 white and 20 black females), total body bone mineral density and content and body fat% were measured by two dual energy X-ray absorptiometry (DXA) systems--Norland XR-26, software version 2.4, and Lunar DPX, software versions 3.4 and 3.6. In a subgroup of 18 males (10 white, 8 black), body fat% and total body calcium were also measured by in vivo neutron activation analysis (IVNA). For total body calcium, the DPX 3.4 system gave the highest (1239 g), IVNA the lowest (1195 g), and the XR-26 (1226 g) was not significantly different from the DPX 3.6 results. For fat%, the XR-26 system gave the highest estimate (23.5%), whereas measurements by the DPX 3.4 and 3.6 systems (17.4 and 18.2%) were similar to the IVNA measurements (18.3%). BMD and BMC measurements by the two DXA systems were highly correlated but significantly different for the entire studied population except in the case of BMC in black males.