BACKGROUND Total body volume (TBV), with the exclusion of internal air voids, is necessary to quantify body composition in Lohman's 4-compartment (4C) model. OBJECTIVE This investigation sought to derive a novel, TBV measure with the use of only dual-energy X-ray absorptiometry (DXA) attenuation values for use in Lohman's 4C body composition model. DESIGN Pixel-specific masses and volumes were calculated from low- and high-energy attenuation values with the use of first principle conversions of mass attenuation coefficients. Pixel masses and volumes were summed to derive body mass and total body volume. As proof of concept, 11 participants were recruited to have 4C measures taken: DXA, air-displacement plethysmography (ADP), and total body water (TBW). TBV measures with the use of only DXA (DXA-volume) and ADP-volume measures were compared for each participant. To see how body composition estimates were affected by these 2 methods, we used Lohman's 4C model to quantify percentage fat measures for each participant and compared them with conventional DXA measures. RESULTS DXA-volume and ADP-volume measures were highly correlated (R(2) = 0.99) and showed no statistically significant bias. Percentage fat by DXA volume was highly correlated with ADP-volume percentage fat measures and DXA software-reported percentage fat measures (R(2) = 0.96 and R(2) = 0.98, respectively) but were slightly biased. CONCLUSIONS A novel method to calculate TBV with the use of a clinical DXA system was developed, compared against ADP as proof of principle, and used in Lohman's 4C body composition model. The DXA-volume approach eliminates many of the inherent inaccuracies associated with displacement measures for volume and, if validated in larger groups of participants, would simplify the acquisition of 4C body composition to a single DXA scan and TBW measure.

中文翻译：

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基于双能 X 射线吸收法的身体体积测量 4 室身体成分。

背景总体积 (TBV)，排除内部空气空隙，对于量化 Lohman 的 4 室 (4C) 模型中的身体成分是必要的。目的 本研究旨在推导出一种新颖的 TBV 测量方法，仅使用双能 X 射线吸收测定法 (DXA) 衰减值，用于 Lohman 的 4C 身体成分模型。设计像素特定的质量和体积是通过使用质量衰减系数的第一性原理转换从低能和高能衰减值计算的。像素质量和体积相加得到体重和总体体积。作为概念证明，招募了 11 名参与者以采取 4C 措施：DXA、空气置换体积描记法 (ADP) 和全身水分 (TBW)。每个参与者都比较了仅使用 DXA（DXA 体积）和 ADP 体积测量的 TBV 测量。为了了解这两种方法如何影响身体成分估计，我们使用 Lohman 的 4C 模型来量化每个参与者的脂肪百分比测量值，并将它们与传统的 DXA 测量值进行比较。结果 DXA 体积和 ADP 体积测量高度相关 (R(2) = 0.99) 并且没有显示出统计学上显着的偏差。DXA 体积的脂肪百分比与 ADP 体积脂肪百分比测量和 DXA 软件报告的脂肪百分比测量高度相关（分别为 R(2) = 0.96 和 R(2) = 0.98），但略有偏差。结论 开发了一种使用临床 DXA 系统计算 TBV 的新方法，与作为原理证明的 ADP 进行比较，并用于 Lohman 的 4C 身体成分模型。