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KMID : 1007020090070020096
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Korean Soceity of Osteroporosis
2009 Volume.7 No. 2 p.96 ~ p.102
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Precision of Lumbar Bone Mineral Density Measurement with and without Leg Elevation
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Yang Seoung-Oh
Park Su-Yeon
Jang Eung-Kyung
Kim Heung-Yeol
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Abstract
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Objectives: There are some report that BMD measurement with the legs down shows no significantchange on spine BMD accuracy and precision. We also studied to see the impact of leg elevation from DXA in our country.
Methods and Materials: Forty volunteers were scanned four times at the lumbarspine using Hologic QDR 4500A. Two scans were done with the leg elevated (E scan) by the spine positioning device supplied by manufacture. The other two scans were done with the legs lying flat (F scan) neutrally without femur positioner. Subjects were repositioned between all four scans. The precision error and linear regression ere determined for the BMD obtained in each position.
Results: Mean age of the subjects was 52 (range; 40～71). BMD was higher in the F scan (mean: 0.922 g/cm2) compared with E scan (0.907 g/cm2) except in two volunteers. T-scores at L1-4 were 0.13 higher for F scan. Only two volunteers had different diagnosis using T-scores from normal to osteopenia and vice versa from the two methods. Precisions (%CV) of the Escan were 1.50, 1.52, 1.96, 1.50, and 0.97% for the L1, L2, L3, L4, and L1-4 respectively. Precisions of the F scan were 1.46, 1.88, 1.63, 1.83, and 1.09% for the L1, L2, L3, L4, and L1-4 respectively. Correlation between two scans was high (r=0.99).
Conclusion: Diagnostic differences from E and F scan are very small (0.13 T scores). There is no significant statistical difference in spine BMD between with the legs elevated and with the legs flat on the scan table. One step scan with the leg flat with the dual femur positioner can expedite the examination without jeopardizing diagnostic value.
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KEYWORD
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Precision, Bone mineral density, Spine, One step scan
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