Evaluation of a new body composition phantom for quality control and cross-calibration of DXA devices

This study evaluated a new body composition phantom and its use for quality control and cross-calibration of dual-energy X-ray absorptiometry (DXA) in struments for measurements of body composition. We imaged the variable comp osition phantom (Lunar, Madison, WI) on eight different DXA devices. Deviat ions of up to 7% fat were observed when we compared the percent fat values measured by the different devices with the nominal values provided by the m anufacturer. Absolute precision error of percent fat measurements for the p hantom ranged from 0.6 to 0.8%. The phantom's percent fat values were also compared with whole body composition measurements from 130 female and male volunteers. The phantom detected differences in percent fat values that wer e similar to those found by comparing in vivo measurements with values from different DXA scanner models from the same manufacturer. When comparing di fferent models of scanners from different manufacturers, such as the Hologi c QDR-4500 and the Lunar DPX-IQ, the phantom showed a different relationshi p than was seen for patients. Therefore, corrections or comparisons based o n the phantom data alone would be incorrect. In conclusion, the Lunar varia ble composition phantom is capable of accurately measuring the fat calibrat ion of DXA devices and may be suitable for cross-sectional cross-calibratio n between scanners from the same manufacturer; however, for comparison of D XA scanners from different manufacturers, in vivo cross-calibration is stil l the only accurate method. The phantom may be used in longitudinal quality control to verify an instrument's temporal stability.