2.1 Study Population
We performed a retrospective chart review of 109 pediatric patients under 18 years of age (range, 2-16yrs) who underwent 3D chest CT from March 2019 to March 2021 at the Department of Pediatrics, Seoul St. Mary’s Hospital, College of Medicine at the Catholic University of Korea. Inclusion criteria were (a) physician-diagnosed BO (n=51), patients who underwent 3D chest CT with (b) pre-transplant evaluation in the Department of Hemato-oncology without previous lung disease (n=16), or (c) other respiratory complaints without lung disease (calcification, 8; chest pain, 3; GERD, 2; and inhalation burn, 1; total n=14, Table 1). Both (b) and (c) were included in the control group. Patients with asthma, chronic lung disease of prematurity, or obstructive lung disease other than BO were excluded from the study (n=26). Patient data with poor cooperation of inhalation and exhalation were also excluded (n=2). All chest CT lung densitometry, spirometry, and body plethysmography was performed with written informed consent obtained from the parent or guardian of each participant.