The Lunar DPX and the Hologic QDR-1000 were compared in a study of 46 women by Pocock et al. (9). These women underwent lumbar spine and proximal femur studies on both machines on the same day. The correlations were extremely good with r values of 0.98, 0.94, 0.96, and 0.96 for the lumbar spine, femoral neck, Ward's area, and the trochanter, respectively. The absolute BMD values were 16% lower on the QDR-1000
Conversion Formulas for BMDs of the AP Spine Between DXA Devices
Hologic QDR-2000 Spinebmd Hologic QDR-2000 SpineBMD Lunar DPX-L SpineBMD Lunar DPX-L SpineBMD Norland XR-26 SpineBMD Norland XR-26 SpineBMD
(0.906 x Lunar DPX-L SpineBMD) - 0.025 (0.912 x Norland XR 26 SpineBMD) + 0.088 (1.074 x Hologic QDR 2000 SpineBMD) + 0.054 (0.995 x Norland XR 26 SpineBMD) + 0.135 (0.983 x Lunar DPX-L SpineBMD) - 0.112 (1.068 x Hologic QDR 2000 SpineBMD) - 0.070
Adapted from ref. 10 with permission from the American Society for Bone and Mineral Research.
in the spine when compared to the DPX and 17% lower in the femoral neck. The equation for predicting the QDR BMD in the femoral neck based on a measurement of BMD in the femoral neck on the Lunar DPX was:
QDR Femoral NeckBMD = 0.007 + (0.76 x DPX Femoral NeckBMD)
This is in keeping with the study from McClung and Roberts (6), in which the ratios of Hologic QDR values to Lunar DPX values at these sites as seen in Table 5-1 suggested similar findings.
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