Effects of nonmineral tissues on measurement of bone mineral content by dual-photon absorptiometry.

Computer simulations were performed to investigate the effects of nonmineral tissue (overlying soft tissue and nonmineral components of bone) on the measurement of bone mineral content by dual-photon absorptiometry (DPA). Selected experimental studies were performed to test the predictions of the simulations. The results indicate that variations in the composition of nonmineral tissue can significantly affect measurement precision and accuracy at the levels achievable with modern x-ray based absorptiometry systems (0.5%). Thus biological variables may limit further improvements in measurement precision and accuracy. Biological variables also can affect intercalibration of systems that use different radiation sources and/or calibration techniques.