Abstract
Target lung tissue selection remains a challenging task to perform for treating severe emphysema with lung volume reduction (LVR). In order to target the treatment candidate, the percentage of low attenuation volume (LAV%) representing the proportion of emphysema volume to whole lung volume is measured using computed tomography (CT) images. Although LAV% have shown to have a correlation with lung function in patients with chronic obstructive pulmonary disease (COPD), similar measurements of LAV% in whole lung or lobes may have large variations in lung function due to emphysema heterogeneity. The functional information of regional emphysema destruction is required for supporting the choice of optimal target. The purpose of this study is to develop an emphysema heterogeneity descriptor for the three-dimensional emphysematous bullae according to the size variations of emphysematous density (ED) and their spatial distribution. The second purpose is to derive a predictive model of airflow limitation based on the regional emphysema heterogeneity. Deriving the bullous representation and grouping them into four scales in the upper and lower lobes, a predictive model is computed using the linear model fitting to estimate the severity of lung function. A total of 99 subjects, 87 patients with mild to very severe COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I~IV) and 12 control participants with normal lung functions (forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) > 0.7) were evaluated. The final model was trained with stratified cross-validation on randomly selected 75% of the dataset (n = 76) and tested on the remaining dataset (n = 23). The dispersed cases of LAV% inconsistent with their lung function outcome were evaluated, and the correlation study suggests that comparing to LAV of larger bullae, the widely spread smaller bullae with equivalent LAV has a larger impact on lung function. The testing dataset has the correlation of r = −0.76 (p < 0.01) between the whole lung LAV% and FEV1/FVC, whereas using two ED % of scales and location-dependent variables to predict the emphysema-associated FEV1/FVC, the results shows their correlation of 0.82 (p < 0.001) with clinical FEV1/FVC.
Highlights
The two main components of chronic obstructive pulmonary disease (COPD) are chronic bronchitis and emphysema[1,2]
In order to build a predictive model for lung function outcome based on emphysema heterogeneity, we developed a series of methods to extract the anatomical image features of chest computed tomography (CT) in the previous works[20]
Wang et al draws the conclusion of −950 HU being acceptable based on the correlational studies between LAA% and five-category classification (GOLD staging), the HU thresholds corresponding to the highest correlations with FEV1/forced vital capacity (FVC) vary for each lobe, ranging from −925 to −935 and only the right middle lobe has the best result with HU −945
Summary
The two main components of COPD are chronic bronchitis and emphysema[1,2]. The consequence of the disturbances of gas exchange at the alveolar level caused by bronchitis and emphysema diminishes patients’ life quality when they frequently experience shortness of breath[3,4,5,6]. While PFT is an effective gold standard for the diagnosis of COPD, this criterion cannot objectively reflect regional pulmonary destruction, but the overall clinical presentation of lung function. One of the new clinical demands of emphysema assessment is the initial evaluation of lung volume www.nature.com/scientificreports reduction (LVR), which requires accurate and objective characterization methods for the regional distribution of emphysema on quantitative CT. The selection criteria of the target lobe are based on the evaluation of lobar LAV%, interlobar fissure completeness and emphysema heterogeneity[10,11]. Developing an accurate and objective predictive model for the lung function outcome base on the regional distribution of intra-lobar emphysema on quantitative CT is needed. The overall aim of this study is to develop a new radiomic feature representing the emphysematous density (ED) changes and use their spatial information to characterize the emphysema heterogeneity. The illustrative examples of emphysema heterogeneity having different impacts on lung function were demonstrated
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