基于呼气相不同阈值分析对COPD严重程度与肺功能的相关性研究

目的 分析深呼气末CT扫描肺气肿阈值-856HU、-910HU及-950HU以下低密度衰减区占全肺体积百分比（LAA%-950、LAA%-910、LAA%-856）对慢性阻塞性肺疾病（chronic obstructive pulmonary disease,COPD）严重程度的影响,并探讨定量指标与肺功能相关性。方法 收集104例COPD患者深呼气CT扫描数据与临床肺功能数据,根据GOLD指南将数据分为4组。将4组扫描原始数据导入“数字肺”检测及分析平台,计算出呼气相全肺平均肺密度（MLDex）、深呼气末阈值低于-856HU、-910HU及-950HU以下低密度衰减区占全肺体积百分比（LAA%-950、LAA%-910、LAA%-856）。肺功能指标包括：用力肺活量实测值（FVC）、用力肺活量实测值占预计值百分比率（FVC%）、第一秒用力呼气容积实测值占预计值百分率（FEV1%）、FEV1与用力肺活量比值（FEV1/FVC）、肺一氧化碳弥散量实测值占预计值百分率（DLCO%）、单位肺体积一氧化碳弥散量（DLCO/VA）及残气量与肺总量比值（RV/TLC）。采用单因素方差分析或Kruskal-Wallis H检验比较4组间肺功能及CT定量参数的差异。应用Pearson相关分析或Spearman秩相关分析CT定量参数与肺功能相关性。进行多元逐步回归分析确定LAA%-950、LAA%-910、LAA%-856与MLDex关系。结果 4组间CT定量参数：LAA%-910、LAA%-950、MLDex差异具有统计学意义（P＜0.01）,LAA%-856差异无统计学意义（P=0.265）。LAA%-910与FVC、FEV1/FVC、FEV1%、FVC%、DLCO%及DLCO/VA均呈负相关,与RV/TLV正相关。MLDex与LAA%-856、LAA%-910、LAA%-950均呈负相关。多元逐步回归分析：LAA%-910、LAA%-950与MLDex回归方程R2值0.917,p ＜0.01。结论 呼气相CT扫描定量指标LAA%-910能够准确评估COPD严重程度并且与肺功能具有良好相关。

Correlation pulmonary function and COPD severity based on different threshold analysis of expiratory phase CT scan

Objective To analyze the influence of the percentage of low density attenuation area in total lung volume (LAA% - 950, LAA% - 910, LAA% - 856) with threshold were lower than -856HU, -910HU, and -950HU on the severity of chronic obstructive pulmonary disease (COPD) in deep end expiratory CT scan, and the correlation between quantitative indicators and pulmonary function was explored. Methods The CT images of 104 COPD patients in deep expiratory and clinical lung function were collected. Divide the data into 4 groups according to GOLD guidelines. All of the data were imported into the "digital lung" detection and analysis platform to calculate the mean lung density (MLDex) and the percentage of low density attenuation area in total lung volume (LAA% - 950, LAA% - 910, LAA% - 856) with threshold were lower than -856HU, -910HU, and -950HU. Pulmonary function indicators included forced vital capacity (FVC), forced vital capacity expressed as percent predicted (FVC%), forced expiratory volume in 1 second expressed as percent predicted (FEV1%), forced expiratory volume in one second to forced vital capacity ratio (FEV1/FVC), carbon monoxide diffusion capacity expressed as percent predicted (DLCO%), carbon monoxide diffusion capacity corrected for alveolar volume (DLCO/VA) and residual volume to total lung capacity ratio (RV /TLC). The one-way ANOVA analysis or Kruskal-Wallis H test was used to compare the differences in CT quantitative parameters and pulmonary function indexes between 4 groups. Pearson correlation analysis or Spearman rank correlation analysis was used to analyze the correlation between CT quantitative parameters and lung function. Multiple stepwise regression analysis was performed to determine the relationship between LAA%-950, LAA%-910, LAA%-856 and MLDex. Results CT quantitative parameters between the 4 groups of LAA% -910, LAA% -950, and MLDex were statistically significant (P <0.01), but the LAA% -856 was not statistically significant (P = 0.265). LAA% - 910 was negatively correlated with FVC, FEV1 / FVC, FEV1%, FVC%, DLCO% and DLCO / VA, and positively correlated with RV / TLV. MLDex was negatively correlated with LAA% -856, LAA% -910, and LAA% -950. The further multivariate step wise regression demonstrated that LAA% - 910, LAA% - 950 and MLDex could introduce a regression equation with R2 =0.917, respectively (P <0.01). Conclusion The expiratory CT scan quantitative index LAA% -910 can accurately assess the severity of COPD and has a good correlation with pulmonary function.