Medical Technology and Physics, Sir Charles Gairdner Hospital, Perth, Australia.
Osteoporos Int. 2009 Sep;20(9):1539-45. doi: 10.1007/s00198-008-0820-y. Epub 2008 Dec 24.
Two-dimensional areal bone mineral density (aBMD) of the proximal femur measured by three-dimensional quantitative computed tomography (QCT) in 91 elderly women was compared to dual-energy X-ray absorptiometry (DXA) aBMD results measured in the same patients. The measurements were highly correlated, though QCT aBMD values were marginally lower in absolute units. Transformation of the QCT aBMD values to T score values using National Health and Nutrition Examination Survey (NHANES) DXA-derived reference data improved agreement and clinical utility.
World Health Organization guidelines promulgate aBMD (g cm(-2)) measurement of the proximal femur for the diagnosis of bone fragility. In recent years, there has been increasing interest in QCT to facilitate understanding of three-dimensional bone structure and strength.
To assist in comparison of QCT-derived data with DXA aBMD results, a technique for deriving aBMD from QCT measurements has been developed.
To test the validity of the QCT method, 91 elderly females were scanned on both DXA and CT scanners. QCT-derived DXA equivalent aBMD (QCT(DXA) aBMD) was calculated using CTXA Hip software (Mindways Software Inc., Austin, TX, USA) and compared to DXA-derived aBMD results.
Test retest analysis indicated lower root mean square (RMS) errors for CTXA; F test between CTXA and DXA was significantly different at femoral neck (FN) and trochanter (TR) (p < 0.05). QCT underestimates DXA values by 0.02 +/- 0.05 g cm(-2) (total hip, TH), 0.01 +/- 0.04 g cm(-2) (FN), 0.03 +/- 0.07 g cm(-2) (inter-trochanter, IT), and 0.02 +/- 0.05 g cm(-2) (TR). The RMS errors (standard error of estimate) between QCT and DXA T scores for TH, FN, IT, and TR were 0.36, 0.40, 0.39, and 0.49, respectively.
This study shows that results from QCT aBMD appropriately adjusted can be evaluated against NHANES reference data to diagnose osteoporosis.
为了协助将 QCT 衍生数据与 DXA aBMD 结果进行比较，已经开发出一种从 QCT 测量值中得出 aBMD 的技术。
为了测试 QCT 方法的有效性，对 91 名老年女性同时进行 DXA 和 CT 扫描。使用 CTXA Hip 软件（Mindways Software Inc.，Austin，TX，USA）计算 QCT 衍生的 DXA 等效 aBMD（QCT(DXA) aBMD），并将其与 DXA 衍生的 aBMD 结果进行比较。
测试重测分析表明 CTXA 的 RMS 误差较低；CTXA 和 DXA 之间的 F 检验在股骨颈（FN）和转子间（TR）有显著差异（p < 0.05）。QCT 低估 DXA 值 0.02 +/- 0.05 g cm(-2)（全髋，TH），0.01 +/- 0.04 g cm(-2)（FN），0.03 +/- 0.07 g cm(-2)（转子间，IT）和 0.02 +/- 0.05 g cm(-2)（TR）。QCT 与 DXA T 评分之间的 RMS 误差（估计标准误差）分别为 TH、FN、IT 和 TR 的 0.36、0.40、0.39 和 0.49。
这项研究表明，经过适当调整的 QCT aBMD 结果可以根据 NHANES 参考数据进行评估，以诊断骨质疏松症。
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