Kovner Israel, Taicher Gersh Z, Mitchell Alva D
Echo Medical Systems, Houston, TX, USA.
Int J Body Compos Res. 2010 Mar 1;8(1):17-29.
A study was conducted to appraise a new EchoMRI™ device for body composition analysis (BCA) of infants and to compare it with dual energy X-ray absorptiometry (DXA), using chemical analysis as a reference method.The calibration part of the study included cross-validation comparisons between EchoMRI™ measurements of awake, anesthetized and dead piglets of the calibration set. It also included comparison of two different approaches to refining the calibration of EchoMRI™, by low- or by high-dimensional linear regressions. Only the low-dimensional approach was applied to DXA.The validation part yielded EchoMRI™ accuracy of 27 g and 70 g for fat and total water, respectively, on piglets scanned while anesthetized, as compared with 24 g and 57 g, respectively, for DXA.EchoMRI™ precision was found to be 4 g and 7 g for fat and total water, respectively, for anesthetized piglets, as compared to 16 g and 14 g, respectively, for DXA. The differences between fat measurements of awake, anesthetized and dead piglets can be statistically significant, but are comparable in magnitude to random errors.To summarize: Characterization of random errors by CV, especially that of fat, is not suitable for BCA, whereas absolute errors or errors relative to total body weight can be applicable. Low- and high-dimensional regressions offer nearly the same accuracy improvements. Improved DXA and EchoMRI™ offer nearly the same accuracy, within 1% of weight in fat, while EchoMRI™ has better precision, within 0.2 % of weight in fat for anesthetized and dead piglets as compared to DXA's 0.5-0.6%.
开展了一项研究，以评估一种用于婴儿身体成分分析（BCA）的新型EchoMRI™设备，并将其与双能X线吸收法（DXA）进行比较，以化学分析作为参考方法。该研究的校准部分包括对校准组中清醒、麻醉和死亡仔猪的EchoMRI™测量值进行交叉验证比较。它还包括比较通过低维或高维线性回归来改进EchoMRI™校准的两种不同方法。只有低维方法应用于DXA。验证部分得出，麻醉状态下扫描的仔猪，EchoMRI™测量脂肪和总水分的准确度分别为27克和70克，而DXA分别为24克和57克。对于麻醉状态下的仔猪，发现EchoMRI™测量脂肪和总水分的精密度分别为4克和7克，而DXA分别为16克和14克。清醒、麻醉和死亡仔猪脂肪测量值之间的差异可能具有统计学意义，但在大小上与随机误差相当。总之：通过CV来表征随机误差，尤其是脂肪的随机误差，不适用于BCA，而绝对误差或相对于总体重的误差可能适用。低维和高维回归提供的准确度提高几乎相同。改进后的DXA和EchoMRI™准确度几乎相同，脂肪重量误差在1%以内，而EchoMRI™精密度更高，麻醉和死亡仔猪脂肪重量误差为0.2%，而DXA为0.5 - 0.6%。
