Harmouche Rola, Ross James C, Diaz Alejandro A, Washko George R, Estepar Raul San Jose
Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115.
Applied Chest Imaging Laboratory, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115.
Acad Radiol. 2016 Apr;23(4):421-8. doi: 10.1016/j.acra.2015.12.021. Epub 2016 Mar 2.
We propose a novel single index for the quantification of emphysema severity based on an aggregation of multiple computed tomographic features evident in the lung parenchyma of smokers. Our goal was to demonstrate that this single index provides complementary information to the current standard measure of emphysema, percent emphysema (percent low attenuation areas [LAA%]), and may be superior in its association with clinically relevant outcomes.
The inputs to our algorithm were objective assessments of multiple emphysema subtypes (normal tissue; panlobular; paraseptal; and mild, moderate, and severe centrilobular emphysema). We applied dimensionality reduction techniques to the emphysema quantities to find a space that maximizes the variance of these subtypes. A single emphysema severity index was then derived from a parametrization of the reduced space, and the clinical utility of the measure was explored in a large cross-sectional cohort of 8914 subjects from the COPDGene Study.
There was a statistically significant association between the severity index and the LAA%. Subjects with more severe chronic obstructive pulmonary disease (higher Global initiative for Obstructive Lung Disease stage) tended to have a higher computed tomography severity index. Finally, the severity index was associated with clinical outcomes such as lung function and provided a stronger association to these measures than the LAA%.
The method provides a single clinically relevant index that can assess the severity of emphysema and that provides information that is complimentary to the more commonly used LAA%.
我们基于吸烟者肺实质中明显的多个计算机断层扫描特征的汇总，提出了一种用于量化肺气肿严重程度的新型单一指标。我们的目标是证明该单一指标为当前肺气肿的标准测量指标——肺气肿百分比（低衰减区域百分比[LAA%]）提供补充信息，并且在与临床相关结局的关联方面可能更具优势。
我们算法的输入是对多种肺气肿亚型（正常组织；全小叶型；间隔旁型；以及轻度、中度和重度小叶中心型肺气肿）的客观评估。我们对肺气肿数量应用降维技术，以找到一个使这些亚型的方差最大化的空间。然后从降维空间的参数化中得出一个单一的肺气肿严重程度指数，并在来自慢性阻塞性肺疾病基因研究（COPDGene Study）的8914名受试者的大型横断面队列中探讨了该测量指标的临床效用。
严重程度指数与LAA%之间存在统计学上的显著关联。患有更严重慢性阻塞性肺疾病（慢性阻塞性肺疾病全球倡议分级更高）的受试者往往具有更高的计算机断层扫描严重程度指数。最后，严重程度指数与诸如肺功能等临床结局相关，并且与这些指标的关联比LAA%更强。
该方法提供了一个单一的临床相关指标，可评估肺气肿的严重程度，并提供与更常用的LAA%互补的信息。
