This study was conducted as part of the Area-detector Computed Tomography for the Investigation of Thoracic Diseases (ACTIve) Study, an ongoing multicenter research project in Japan. The research committee of the study project outlined and approved our study protocols. This study was planned as a supplementary analysis after our previous research,13 which did not include any quantitative measurements of pulmonary emphysema.
The Institutional Review Board of each participating institution approved this study: Kobe University, Osaka University, Tenri Hospital, and University of the Ryukyus. Written informed consent was obtained from all enrolled patients.