Affiliation: | 1. Section of Pulmonary and Critical Care Medicine, School of Medicine, West Virginia University, , Morgantown, West Virginia;2. Division of Respiratory Disease Studies, Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, National Institute for Occupational Safety and Health, , Morgantown, West Virginia;3. Department of Radiology, School of Medicine, West Virginia University, , Morgantown, West Virginia |