Bronchiolitis obliterans after lung transplantation: appearance on expiratory minimum intensity projection images

Objective: Bronchiolitis obliterans can manifest as a mosaic pattern of lun g attenuation on computed tomographic (CT) scans. This study was conducted to investigate image enhancement using expiratory minimum intensity project ion images and to compare these with thin-section scans. Methods: Eleven pa tients (21 transplanted lungs) with biopsy-proven bronchiolitis obliterans were studied. Ten 1-mm thin-section scans were acquired helically at the le vel of the carina after full expiration. Expiratory minimum intensity proje ction images 10 mm thick were generated from a multiplanar reconstruction o f data. Two thoracic radiologists analyzed the images. Results: In comparis on with thin-section scans, expiratory minimum intensity projection images demonstrated a greater (in 17 lungs) or equal (in 4 lungs) percentage area of air trapping, with greater conspicuity (in all 21 lungs). Air trapping i nvolved an average of 52% of the cross-sectional area of 1 lung. Conclusion s: Air trapping due to bronchiolitis obliterans is accentuated by forced ex piration; minimum intensity projection images improve the detection of diff erences in lung attenuation. Therefore, expiratory minimum intensity projec tion images are very useful in demonstrating the mosaic pattern of lung att enuation caused by bronchiolitis obliterans.