Tothill P, Han T S, Avenell A, McNeill G, Reid D M
Department of Medical Physics and Medical Engineering, Western General Hospital, Edinburgh, UK.
Eur J Clin Nutr. 1996 Nov;50(11):747-52.
To compare the results of measurements of total and regional fat by dual-energy X-ray absorptiometry (DXA), underwater weighing (UWW) and magnetic resonance imaging (MRI) in women.
13 volunteer pre-menopausal women measured with a Norland XR26 HS DXA instrument, hydrodensitometry equipment and a 0.08 Tesla MRI scanner.
Aberdeen Royal Infirmary.
There were high correlations between measurements of total-body fat by the different techniques, but poor agreement. The mean values of fat as a percentage of the total body mass were UWW = 28.6%, DXA = 40.0%, MRI = 23.0%, although the MRI excluded the head, forearms and feet, estimated from the DXA measurements to contain 8% of the body fat. Although the correlations were apparently linear in the ranges examined, those including the Norland DXA had high intercepts. Bland and Altman plots showed no dependence of the differences on the degree of fatness. Evidence was obtained from in vivo comparisons and phantom measurements that the fat calibration of the Norland DXA had changed during a three year period, suggesting that fat calibration errors contributed to the MRI/DXA differences. Previous comparisons between the Norland DXA and other brands indicate that Hologic and Lunar instruments would show a closer agreement with MRI and UWW. Profiles of fat distribution along the body showed variations in the DXA/MRI ratio, particularly in the chest, with the DXA pattern thought to be the less accurate. The DXA measurements of bone mineral, fat and lean tissue were used to demonstrate the variable proportion of bone in fat-free tissue, leading to errors in UWW.
Each method has its assumptions, which are often not sufficiently appreciated. Each method may be useful for testing and improving the assumptions in the other methods. No method can yet be regarded as a satisfactory reference technique.
比较双能X线吸收法（DXA）、水下称重法（UWW）和磁共振成像（MRI）测量女性全身及局部脂肪的结果。
对13名绝经前志愿者女性使用Norland XR26 HS DXA仪器、人体密度计设备和0.08特斯拉MRI扫描仪进行测量。
阿伯丁皇家医院。
不同技术测量全身脂肪的结果之间存在高度相关性，但一致性较差。脂肪占总体重的百分比平均值分别为：水下称重法=28.6%，双能X线吸收法=40.0%，磁共振成像=23.0%，尽管磁共振成像排除了头部、前臂和足部，根据双能X线吸收法测量估计这些部位占体脂的8%。虽然在所检查的范围内相关性明显呈线性，但包括Norland双能X线吸收法的那些相关性有较高的截距。布兰德-奥特曼图显示差异与肥胖程度无关。通过体内比较和模型测量获得的证据表明，Norland双能X线吸收法的脂肪校准在三年期间发生了变化，这表明脂肪校准误差导致了磁共振成像/双能X线吸收法之间的差异。之前Norland双能X线吸收法与其他品牌之间的比较表明，Hologic和Lunar仪器与磁共振成像和水下称重法的一致性会更高。身体各部位的脂肪分布曲线显示双能X线吸收法/磁共振成像比值存在差异，尤其是在胸部，认为双能X线吸收法的模式准确性较低。双能X线吸收法测量的骨矿物质、脂肪和瘦组织用于证明无脂肪组织中骨的可变比例，从而导致水下称重法出现误差。
每种方法都有其假设，而这些假设往往没有得到充分认识。每种方法可能有助于检验和改进其他方法中的假设。尚无一种方法可被视为令人满意的参考技术。
