Pulmonary sarcoidosis - Correlation of expiratory high-resolution CT findings with inspiratory patterns and pulmonary function tests

Purpose: To assess the presence and extent of air trapping (AT) on chest hi gh-resolution CT (HRCT) in sarcoidosis and to correlate such findings with patterns, lesion extent on inspiratory CT and pulmonary function tests (PFT ). Material and Methods: Thirty patients with sarcoidosis underwent inspirator y and expiratory HRCT and PFT. HRCT images were evaluated for presence, dis tribution and AT extent as well as the predominant HRCT pattern and the ext ent of lesions at inspiration. Attenuation difference in the AT regions at expiration and at inspiration were calculated. The presence and extent of A T were correlated with PFT, extent of involvement and predominant inspirato ry patterns. Results: AT was present in 25/30 patients with no lung zone predilection. A T was the only CT indication of pulmonary sarcoidosis in 3/30 patients who also had normal PFT. Attenuation difference between inspiration and expirat ion ranged from -40 HU to 106 HU. In 2 patients, a paradoxical decrease of lung attenuation was observed at expiration. A significant correlation was found between AT extent at expiration, with residual volume-total lung capa city ratio and residual volume. Conclusion: AT is an additional HRCT finding in sarcoidosis. AT may involve any lung zone, including costophrenic angles and may be the only CT featur e of pulmonary sarcoidosis. Strong correlation is only found with PFT value s that are specific for incomplete lung emptying at expiration.