Quantitative Imaging Methods in Combined Pulmonary Fibrosis and Emphysema.

Abstract

Combined pulmonary fibrosis and emphysema (CPFE) is an underdiagnosed syndrome in which individuals have variable degrees of pulmonary fibrosis and emphysema. Patients with CPFE have high morbidity, including poor exercise tolerance and increased development of comorbidities. CPFE mortality also seems to outpace that of lone emphysema and pulmonary fibrosis. A major limitation to rigorous, large-scale studies of CPFE has been the lack of a precise definition for this syndrome. A 2022 American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Latin American Thoracic Association research statement called attention to fundamental gaps in our understanding of CPFE and highlighted the potential use of quantitative imaging techniques to better define CPFE. Broadly, CPFE has been defined using visual interpretation of chest CT imaging documenting the presence of both emphysema and fibrosis, with varying distributions. When quantitative approaches were involved, varying thresholds of emphysema and fibrosis on imaging have been used across different studies. This review is structured into three primary themes, starting with early imaging studies, then evaluating the use of quantitative methods and imaging-based thresholds, both in large population studies and single-center cohorts to define CPFE and assess patient outcomes. It concludes by discussing current challenges and how to focus our efforts so that quantitative imaging methods can effectively address the most pressing clinical dilemmas in CPFE.