1. Department of Radiology, University of California, Los Angeles, Los Angeles, California;
2. Department of Radiology,
3. Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, and
4. Department of Biostatistics, National Jewish Health, Denver, Colorado;
5. Department of Radiology, University of Trieste, Trieste, Italy; and
6. Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Michigan, Ann Arbor, Michigan