[1] Hallym Univ, Dept Pulm & Crit Care Med, Kangdong Sacred Heart Hosp, Seoul, South Korea
[2] Univ Ulsan, Asan Med Ctr, Dept Radiol, Seoul, South Korea
[3] Univ Ulsan, Asan Med Ctr, Res Inst Radiol, Seoul, South Korea
[4] Univ Ulsan, Coll Med, Asan Med Ctr, Dept Pulm & Crit Care Med, Seoul, South Korea
[5] Univ Ulsan, Coll Med, Asan Med Ctr, Clin Res Ctr Chron Obstruct Airway Dis, Seoul, South Korea