1. From the Departments of Radiology (A.S.O., D.A.L., S.M.H.) and Biostatistics (D.B.) and Division of Pulmonary and Critical Care Medicine, Department of Medicine (J.D.C.), National Jewish Health, 1400 Jackson St, Denver, CO 80206; and Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women’s Hospital, Boston, Mass (S.Y.A.).