• Eunsol Lee, Joon Beom Seo, Hyun Joo Lee, Eun Jin Chae, Sang Min Lee, Sang Young Oh, and Namkug Kim.
• Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
• Korean J Radiol. 2015 May 1; 16 (3): 632-40.

ObjectiveThe purpose of this study was to compare air trapping in healthy volunteers with asthmatics using pulmonary function test and quantitative data, such as specific volume change from paired inspiratory CT and registered expiratory CT.Materials And MethodsSixteen healthy volunteers and 9 asthmatics underwent paired inspiratory/expiratory CT. ΔSV, which represents the ratio of air fraction released after exhalation, was measured with paired inspiratory and anatomically registered expiratory CT scans. Air trapping indexes, ΔSV0.4 and ΔSV0.5, were defined as volume fraction of lung below 0.4 and 0.5 ΔSV, respectively. To assess the gravity effect of air-trapping, ΔSV values of anterior and posterior lung at three different levels were measured and ΔSV ratio of anterior lung to posterior lung was calculated. Color-coded ΔSV map of the whole lung was generated and visually assessed. Mean ΔSV, ΔSV0.4, and ΔSV0.5 were compared between healthy volunteers and asthmatics. In asthmatics, correlation between air trapping indexes and clinical parameters were assessed.ResultsMean ΔSV, ΔSV0.4, and ΔSV0.5 in asthmatics were significantly higher than those in healthy volunteer group (all p < 0.05). ΔSV values in posterior lung in asthmatics were significantly higher than those in healthy volunteer group (p = 0.049). In asthmatics, air trapping indexes, such as ΔSV0.5 and ΔSV0.4, showed negative strong correlation with FEF25-75, FEV1, and FEV1/FVC. ΔSV map of asthmatics showed abnormal geographic pattern in 5 patients (55.6%) and disappearance of anterior-posterior gradient in 3 patients (33.3%).ConclusionQuantitative assessment of ΔSV (the ratio of air fraction released after exhalation) shows the difference in extent of air trapping between health volunteers and asthmatics.

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