Emphysema Quantification Using Low Dose Chest CT: Changes in Follow-Up Examinations of Asymptomatic Smokers

Abstract

Copyrights © 2012 The Korean Society of Radiology Purpose: To evaluate the changes of emphysema quantification in a follow-up low dose CT compared with pulmonary function test (PFT) results in asymptomatic smokers. Materials and Methods: We selected 66 asymptomatic smokers (> 40 years old) who underwent a follow-up low dose CT at least one year after the first CT as well as PFT within the same time period. Emphysema quantification was performed using an automated measurement software and an emphysema index (EI) was calculated using multiple threshold values (-970--900 HU). The interval change of EI (ΔEI) was compared with the change in the PFT values. Results: Mean follow-up %forced expiratory volume in 1 second (88.1), %forced vital capacity (FVC) (89.5) and forced expiratory flow between 25 and 75% of vital capacity (3.21) were significantly lower compared with the values of initial tests (93.3, 93.1, 3.48). The mean EIs (2.4-25.6%) increased on follow-up CTs compared with initial EIs (2.1-24.5%), though the increase was not statistically significant. In a group with a follow-up period of 2 years or more (n = 32), EI significantly increased when using -900 HU as the threshold. The ΔEIs were poorly correlated with the ΔPFT values, but significantly correlated with ΔFVC (r = -0.32--0.27). Conclusion: Emphysema quantification using low dose CT was not effective for the evaluation of short-term changes in less than a 2-year period, but may be used for long term follow-up series in asymptomatic smokers. Emphysema Quantification Using Low Dose Chest CT: Changes in Follow-Up Examinations of Asymptomatic Smokers 흉부저선량 CT를 이용한 폐기종 정량화: 무증상 흡연자에서 추적검사의 변화