Introduction:Dual energy X-ray absorptiometry (DXA) is widely used for the assessment of lean mass (LM), fat mass (FM) and bone mineral content (BMC). When observing standardised protocols, DXA has a high level of precision for the assessment of total body composition, including the head region. However, including the head region may have limited relevance in athletes and can be problematic when positioning taller athletes who exceed scan boundaries. This study investigated the precision of a new total-body-less-head (TBLH) DXA scan for three-compartment body composition measurement in athletes, with outcomes compared to the standard total-body DXA scan. Methods: Precision errors were calculated from two consecutive scans with re-positioning (Lunar iDXA, GE Healthcare, Madison, WI), in male and female athletes from a range of sports. TBLH precision was determined from repeat scans in 95 athletes (male n = 55; female n = 40; age: 26.0 ± 8.5 y; body mass: 81.2 ± 20.5 kg; stature: 1.77 ± 0.11 m), and standard total-body scan precision was derived from a sub-sample of 58 athletes (male n = 19; female n = 39; age: 27.6 ± 9.9 y; body mass: 69.6 ± 14.8 kg; stature: 1.72 ± 0.94 m). Data from the sub-sample were also used to compare precision error and 3-compartment body composition outcomes between the standard total-body scan and the TBLH scan. Results:: TBLH precision errors [root mean squared-standard deviation, RMS-SD (coefficient of variation, %CV)] were bone mineral content (BMC): 15.6 g (0.5%), lean mass (LM): 254.3 g (0.4%) and fat mass (FM): 199.4 g (1.3%). These outcomes compared favourably to the precision errors derived from the standard total-body scan [BMC: 12.4 g (0.4%), LM: 202.2 g (0.4%), and FM: 160.8 g (1.1%)]. The TBLH scan resulted in lower BMC (-19.5%), LM (-6.6%), and FM (-4.5%) compared to the total-body scan (BMC: 2,308 vs. 2,865 g; LM: 46,954 vs. 50,276 g; FM: 15,183 vs. 15,888 g, all p<0.005). ConclusionThe TBLH scan demonstrates high in-vivo precision comparable to that of the standard total-body scan in a heterogeneous cohort of athletes. Given the impact of head exclusion on total body composition outcomes, TBLH scans should not be used interchangeably with the standard total-body scan.

简介：双能 X 射线吸收测定法 (DXA) 广泛用于评估瘦体重 (LM)、脂肪量 (FM) 和骨矿物质含量 (BMC)。在观察标准化协议时，DXA 对全身成分（包括头部区域）的评估具有高精度。然而，包括头部区域可能与运动员的相关性有限，并且在定位超过扫描边界的较高运动员时可能会出现问题。本研究调查了一种新的全身无头部 (TBLH) DXA 扫描对运动员三隔室身体成分测量的精度，并将结果与​​标准全身 DXA 扫描进行了比较。方法：精度误差是根据两次连续扫描并重新定位（Lunar iDXA，GE Healthcare，Madison，WI）计算的，来自一系列运动的男性和女性运动员。TBLH 精度是通过对 95 名运动员（男性 n = 55；女性 n = 40；年龄：26.0 ± 8.5 岁；体重：81.2 ± 20.5 kg；身高：1.77 ± 0.11 m）和标准全身扫描的重复扫描确定的精度来自 58 名运动员的子样本（男性 n = 19；女性 n = 39；年龄：27.6 ± 9.9 岁；体重：69.6 ± 14.8 kg；身高：1.72 ± 0.94 m）。来自子样本的数据还用于比较标准全身扫描和 TBLH 扫描之间的精度误差和 3 室身体成分结果。结果：：TBLH 精度误差 [均方根标准偏差，RMS-SD（变异系数，%CV）] 骨矿物质含量 (BMC)：15.6 g (0.5%)，瘦体重 (LM)：254.3 g (0.4%) ) 和脂肪量 (FM)：199.4 克 (1.3%)。这些结果与标准全身扫描得出的精度误差 [BMC：12.4 g (0.4%)、LM：202.2 g (0.4%) 和 FM：160.8 g (1.1%)] 相比有优势。与全身扫描相比，TBLH 扫描导致较低的 BMC (-19.5%)、LM (-6.6%) 和 FM (-4.5%)（BMC：2,308 对 2,865 g；LM：46,954 对 50,276 g ; FM：15,183 对 15,888 g，所有 p<0.005）。结论TBLH 扫描显示出与异质运动员队列中的标准全身扫描相当的高体内精度。鉴于头部排除对全身成分结果的影响，TBLH 扫描不应与标准全身扫描互换使用。