DXA BODY-COMPOSITION - THEORY AND PRACTICE

Dual energy X-ray absorptiometry (DXA) was used to measure human body composition on a high speed fan beam scanner. High and low energy atte nuation pairs, produced by the various combinations of fat mass and fa t-free mass in the human body, were compared to attenuation values pro duced by standard materials (aluminum and acrylic). These standards we re measured in various combinations to construct calibration curves fo r fat and fat-free mass. Primary calibration of the aluminum/acrylic c ombinations was achieved by direct comparison to the dual energy atten uation produced by stearic acid and pure water. Whole body examination s were accomplished using three 45 s longitudinal passes of the fan be am. These passes were acquired and assembled to create a giant, isocen tric fan beam with a single center of focus. In vivo precision was 0.0 09 g/cm(2) for BMD and 425 g for fat mass and fat-free mass(SD). (C) 1 998 Elsevier Science Ltd. All rights reserved.