Multiplanar Reformations to Assess Tracheal Disorders

Medical Imaging has played a major role in the evaluation of airway disease. Although chest radiographies may detect features of airway disease, computed tomography (CT) has revolutionized the impact of Imaging on the diagnosis, characterization, extent assessment, and follow-up of most large and small airway diseases. Multidetector CT, by combining helical volumetric CT acquisition and thin collimation during a single breath hold both at full inspiration and full expiration provides an accurate assessment of proximal airways allowing multiplanar reformations and 3D rendering of very high quality. This is highly appreciated in the evaluation of various post-traumatic, infectious, inflammatory or tumoral disorders of the trachea and proximal bronchi. Multidetector CT has become the Imaging modality of reference for the diagnosis, and assessment of distribution and severity of bronchiectasis. Maximum intensity projection helps assess associated infectious bronchiolitis (tree-in bud sign), and minimum intensity projection on thick slabs and expiratory CT help assess the extent of hypoattenuated lung areas reflecting associated obliterative bronchiolitis. In COPD patients, both visual assessment and quantitative analysis of CT images of the lung parenchyma and airways allow identification of phenotypic abnormalities including emphysema lung destruction and airway remodelling. In asthma, the main clinical indication of CT remains restricted to the identfication of associated conditions such as allergic bronchopulmonary aspergillosis, and detection of conditions that mimic asthma. In severe asthmatics, CT may contribute to assess airway remodelling (extent of gas trapping after the inhalation of bronchodilator and bronchial wall thickening).