Parr David G, Sevenoaks Martin, Deng Chunqin, Stoel Berend C, Stockley Robert A
Department of Respiratory Medicine, University Hospitals of Coventry and Warwickshire, Clifford Bridge Road, Coventry, CV2 2DX, UK.
Respir Res. 2008 Feb 13;9(1):21. doi: 10.1186/1465-9921-9-21.
Computer tomography (CT) densitometry is a potential tool for detecting the progression of emphysema but the optimum methodology is uncertain. The level of inspiration affects reproducibility but the ability to adjust for this variable is facilitated by whole lung scanning methods. However, emphysema is frequently localised to sub-regions of the lung and targeted densitometric sampling may be more informative than whole lung assessment.
Emphysema progression over a 2-year interval was assessed in 71 patients (alpha 1-antitrypsin deficiency with PiZ phenotype) with CT densitometry, using the 15th percentile point (Perc15) and voxel index (VI) -950 Hounsfield Units (HU) and -910 HU (VI -950 and -910) on whole lung, limited single slices, and apical, central and basal thirds. The relationship between whole lung densitometric progression (DeltaCT) and change in CT-derived lung volume (DeltaCTVol) was characterised, and adjustment for lung volume using statistical modelling was evaluated.
CT densitometric progression was statistically significant for all methods. DeltaCT correlated with DeltaCTVol and linear regression indicated that nearly one half of lung density loss was secondary to apparent hyperinflation. The most accurate measure was obtained using a random coefficient model to adjust for lung volume and the greatest progression was detected by targeted sampling of the middle third of the lung.
Progressive hyperinflation may contribute significantly to loss of lung density, but volume effects and absolute tissue loss can be identified by statistical modelling. Targeted sampling of the middle lung region using Perc15 appears to be the most robust measure of emphysema progression.
计算机断层扫描（CT）密度测定法是检测肺气肿进展的一种潜在工具，但最佳方法尚不确定。吸气水平会影响可重复性，但全肺扫描方法有助于对该变量进行调整。然而，肺气肿常局限于肺的亚区域，靶向密度测定采样可能比全肺评估更具信息量。
对71例（PiZ表型的α1抗胰蛋白酶缺乏症）患者进行CT密度测定，评估其在2年期间肺气肿的进展情况，使用全肺、有限单层面以及肺尖、肺中和肺底三分之一区域的第15百分位数（Perc15）和体素指数（VI）-950亨氏单位（HU）及-910 HU（VI -950和-910）。对全肺密度测定进展（DeltaCT）与CT衍生肺容积变化（DeltaCTVol）之间的关系进行了表征，并评估了使用统计模型对肺容积进行调整的情况。
所有方法的CT密度测定进展均具有统计学意义。DeltaCT与DeltaCTVol相关，线性回归表明近一半的肺密度损失继发于明显的肺过度充气。使用随机系数模型调整肺容积可获得最准确的测量结果，通过对肺中三分之一区域进行靶向采样检测到的进展最大。
进行性肺过度充气可能对肺密度损失有显著影响，但通过统计模型可识别容积效应和绝对组织损失。使用Perc15对肺中部区域进行靶向采样似乎是评估肺气肿进展最可靠的方法。
