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Bronchiolitis obliterans after lung transplantation: appearance on expiratory minimum intensity projection images
1Department of Medical Imaging, The Toronto Hospital, Ont. Conrad.Wittram@bmc.org
Objective:
Bronchiolitis obliterans can manifest as a mosaic pattern of lung attenuation on computed tomographic (CT) scans. This study was conducted to investigate image enhancement using expiratory minimum intensity projection images and to compare these with thin-section scans.
Methods:
Eleven patients (21 transplanted lungs) with biopsy-proven bronchiolitis obliterans were studied. Ten 1-mm thin-section scans were acquired helically at the level of the carina after full expiration. Expiratory minimum intensity projection images 10 mm thick were generated from a multiplanar reconstruction of data. Two thoracic radiologists analyzed the images.
Results:
In comparison 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 involved an average of 52% of the cross-sectional area of 1 lung.
Conclusions:
Air trapping due to bronchiolitis obliterans is accentuated by forced expiration; minimum intensity projection images improve the detection of differences in lung attenuation. Therefore, expiratory minimum intensity projection images are very useful in demonstrating the mosaic pattern of lung attenuation caused by bronchiolitis obliterans.