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Bronchiectasis: functional significance of areas of decreased attenuation at expiratory CT
D M Hansell1, A U Wells, M B Rubens
1Department of Radiology, Royal Brompton National Heart and Lung Hospital and Institute, London, England.
Purpose:
To characterize areas of decreased attenuation on expiratory computed tomographic (CT) scans in patients with bronchiectasis.
Materials And Methods:
CT scans were obtained at full inspiration and end expiration in 70 patients with chronic purulent sputum production. Inspiratory scans were scored at a lobar level for the extent of bronchiectasis, and inspiratory and expiratory scans were scored for the presence and extent of areas of decreased attenuation. Total lobar observations were analyzed (n = 840).
Results:
Bronchiectasis was identified in 434 of 840 lobar observations. The total decreased attenuation score was related to extent of bronchiectasis (r = .49; P < .001), independent of functional indexes. Negative correlations were found between forced expiratory volume in 1 second (FEV1) and total decreased attenuation score (P < .002) and FEV1 to forced vital capacity ratio (P < .004) but not with indexes of gas transfer.
Conclusion:
Areas of decreased attenuation on expiratory CT scans are common in severe bronchiectasis. Such areas in lobes without overt bronchiectasis suggest that small airways disease may precede the development of bronchiectasis.