Precision, accuracy and cross-calibration measurements on dual X-ray absorptiometry systems using standard calibration phantoms

Dual-energy X-ray Absorptiometry (DXA) is considered the gold standard technique for clinical bone densitometry, but a general lack of standardisation in bone mineral measurements obtained with different scanners has been reported. The accuracy of DXA measurements is also influenced by the software version used for analysis. In this study we report on the comparison of the calibration results of the three absorptiometers routinely employed at S. Maugeri Foundation, a QDR-4500W Hologic and two XR-26 Norland, recently software upgraded. Calibration was made using the standard calibration phantoms provided by each manufactory. Both phantoms do not take into account vertebral morphology but through the Hologic one, consisting of four vertebral body-like structures with similar densities in each segment, a cross-calibration between the different systems could be established. The main result we achieved is that the differences in BMD values obtained with different scanners are less then 1.5% when using the Hologic phantom, despite the performance variability introduced by software and hardware upgrade.