Bronchial Asthma: Correlation of Quantitative CT and the Pulmonary Function Test

Abstract

Purpose: The purpose of this study was to assess the availability of quantitative computed tomography (QCT) in the evaluation of asthma patients and to correlate its use with the pulmonary function test (PFT). Materials and Methods: Thirty asthmatic patients and thirty normal volunteers were prospectively evaluated by the use of HRCT and the PFT. By using 16 slice MDCT, HRCT was performed from the apex to the base of both lungs at the end inspiration and end expiration periods in all patients and images were reconstructed to a thickness of 1 mm (window level: - 750 HU, window width: 1,500 HU). We analyzed each image for the whole lung using the Pulmo CT program. PFTs including FVC and FEV1 were performed one week prior and one week after the completion of a HRCT. The Difference of QCT (the mean lung density and subrange ratio) between volunteers and asthmatic patients was analyzed by using the Student's t-test. Spearman's correlation test was used to determine the association between PFT and QCT. Results: The mean lung density (MLD) and subrange ratio were lower in asthmatic patients than in volunteers for end expiration and no difference was seen between asthmatic patients and volunteers for end inspiration. FVC and FEV1 were lower in asthmatic patients than in volunteers. A decrease in FVC and FEV1 correlated with changes in the MLD and subrange ratio for end expiration. Conclusion: QCT such as MLD and the subrange ratio using HRCT can be used to indirectly assess the pul- monary function of the asthma patient. The PFT seems to correlate better with the MLD and subrange ratio for expiratory QCT of the asthma patient than with inspiratory QCT.