Spirometric assessment of emphysema presence and severity as measured by quantitative CT and CT-based radiomics in COPD

Mariaelena Occhipinti,Matteo Paoletti,Federico Lavorini,Vito Brusasco,Massimo Pistolesi,Riccardo Inchingolo,Ronald A Karwoski,Stefano Colagrande,Srinivasan Rajagopalan,Anna R Larici,Brian J Bartholmai,Cosimo Nardi,Gianna Camiciottoli

doi:10.1186/s12931-019-1049-3

Abstract

BackgroundThe mechanisms underlying airflow obstruction in COPD cannot be distinguished by standard spirometry. We ascertain whether mathematical modeling of airway biomechanical properties, as assessed from spirometry, could provide estimates of emphysema presence and severity, as quantified by computed tomography (CT) metrics and CT-based radiomics.MethodsWe quantified presence and severity of emphysema by standard CT metrics (VIDA) and co-registration analysis (ImbioLDA) of inspiratory-expiratory CT in 194 COPD patients who underwent pulmonary function testing. According to percentages of low attenuation area below − 950 Hounsfield Units (%LAA-950insp) patients were classified as having no emphysema (NE) with %LAA-950insp < 6, moderate emphysema (ME) with %LAA-950insp ≥ 6 and < 14, and severe emphysema (SE) with %LAA-950insp ≥ 14. We also obtained stratified clusters of emphysema CT features by an automated unsupervised radiomics approach (CALIPER). An emphysema severity index (ESI), derived from mathematical modeling of the maximum expiratory flow-volume curve descending limb, was compared with pulmonary function data and the three CT classifications of emphysema presence and severity as derived from CT metrics and radiomics.ResultsESI mean values and pulmonary function data differed significantly in the subgroups with different emphysema degree classified by VIDA, ImbioLDA and CALIPER (p < 0.001 by ANOVA). ESI differentiated NE from ME/SE CT-classified patients (sensitivity 0.80, specificity 0.85, AUC 0.86) and SE from ME CT-classified patients (sensitivity 0.82, specificity 0.87, AUC 0.88).ConclusionsPresence and severity of emphysema in patients with COPD, as quantified by CT metrics and radiomics can be estimated by mathematical modeling of airway function as derived from standard spirometry.

Highlights

The mechanisms underlying airflow obstruction in Chronic obstructive pulmonary disease (COPD) cannot be distinguished by standard spirometry
Airway narrowing and parenchymal destruction are recognized as the mechanisms responsible for airflow obstruction in COPD, but they cannot be distinguished by standard spirometry
The aim of the present study was to assess whether a mathematical model designed to fit the shape of the maximum expiratory flow-volume curve (MEFV) obtained by standard spirometry could provide estimates of the presence and the severity of emphysema comparable with parameters used to assess emphysema extent derived from quantitative computed tomography (CT) and CT-based radiomics

Summary

Introduction

The mechanisms underlying airflow obstruction in COPD cannot be distinguished by standard spirometry. Airway narrowing and parenchymal destruction are recognized as the mechanisms responsible for airflow obstruction in COPD, but they cannot be distinguished by standard spirometry. Chest computed tomography (CT) allows to depict and measure in vivo the lung pathologic changes of COPD by quantifying parenchymal destruction, the direct sign of emphysema, as well as bronchial wall thickening and gas trapping, which represent direct and indirect signs of conductive airway disease, respectively [1, 2]. A closer imaging definition of whether conductive airway disease or emphysema is the predominant mechanism of airflow obstruction has been lately obtained by using co-registration analysis of inspiratory and expiratory CT scans [3]. CALIPER (Computer Aided Lung Informatics for Pathology Evaluation and Rating) recently developed at Mayo Clinic (Rochester, MN), is a computational platform for the near real-time characterization and quantification of lung parenchymal patterns on CT scan [5, 6]

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