EUROPEAN SEMI-ANTHROPOMORPHIC PHANTOM FOR THE CROSS-CALIBRATION OF PERIPHERAL BONE DENSITOMETERS - ASSESSMENT OF PRECISION ACCURACY AND STABILITY

A semi-anthropomorphic ''distal radius like'' phantom, developed by Ka lender and Ruegsegger for use in peripheral bone densitometry using si ngle photon (DPA) dual X-ray (DXA) and quantitative computed tomograph y (QCT) machines, has been studied with a view to cross-calibrating di fferent types and brands of densitometers in current use. In the conte xt of an EU ''Concerted Action'' (second Framework Programme) the phan tom was repeatedly measured on six SPA machines, three DXA machines an d nine QCT machines (545 measurements). Linear regression equations we re derived, individual to each machine, which allowed the derivation o f ''standardized densities''. In this way we converted measurements ma de by machines of the same modality to a common scale of measurements. Two machines (one DXA, one SPA) showed statistically significant inst ability over time emphasising the need for rigorous quality control in the application of densitometry. In other respects these results prov ide an encouraging basis for the derivation of standardized normative ranges and the more effective use of peripheral densitometry in future clinical and epidemiological studies.