<prompt> What is not a CT finding in bronchiectasis?Tree in bud appearanceCrazy paving appearanceSignet ring appearanceTraction bronchiectasis with lung fibrosis  <response>: While chest radiographs lack sensitivity, the presence of tram tracks indicating dilated airways is seen with bronchiectasis. Chest CT is more specific for bronchiectasis and is the imaging modality of choice for confirming the diagnosis. CT findings include airway dilation detected as a parallel tram tracks or as the signet-ring sign--a cross-sectional area of the airway with a diameter at least 1.5 times that of the adjacent vessel. The crazy-paving pattern is seen in pulmonary alveolar proteinosis and also can be observed in exogenous lipoid pneumonia, sarcoidosis, mucinous broncho-alveolar cell carcinoma and acute respiratory distress syndrome. 