Quantitative imaging methods in combined pulmonary fibrosis and emphysema

Topic importance 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 co-morbidities. CPFE mortality also appears to outpace 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 ATS/ERJ/JRS/ALAT 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. Review findings Broadly, CPFE has been defined using visual interpretation of chest computed tomography (CT) documenting the presence of both emphysema and fibrosis, with varying distributions.When quantitative approaches were employed, varying thresholds of emphysema and fibrosis on imaging have been used across different studies. Summary 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, and concludes by discussing current challenges and how to focus our efforts so quantitative imaging methods can effectively address the most pressing clinical dilemmas in CPFE.