Estimation of the magnitude of the error in bone mineral measurement due to fat: the effect of machine calibration.

An inhomogeneous fat distribution across the spine introduces an error into the measurement of bone mineral density by dual photon absorptiometry. Various published estimates of the mean error lie between 3 and 10%. This paper shows that while an estimate of the absolute error is sensitive to the attenuation coefficients entered for bone the relative or percentage error is independent of the bone calibration. This suggests that a re-evaluation is necessary of some of the published conclusions.