Variant 3: Chronic dyspnea. Suspected central airways disease. Initial imaging. Radiography Chest Chest radiographs have the potential to identify conditions of the trachea, with accuracy dependent on the condition to be identified. Compared to CT, radiographs have an accuracy of 89% [34]. It should be noted that radiographic findings may be normal or nonspecific. In a single-institution retrospective study of tracheal neoplasms, <50% were directly detectable by a chest radiograph [35]. CT Chest Examples of airway conditions that may result in chronic dyspnea and can be accurately diagnosed by CT include stenoses, tumors, and end-expiratory airway collapse/tracheobronchomalacia, with strong correlations when compared with bronchoscopy [36,37]. For the last condition, expiratory images are required for diagnosis. Both dynamic airway imaging and static forced expiratory imaging are able to accurately characterize airway collapse when compared with bronchoscopy [38,39]. It has been shown that the degree of expiratory collapse is greater on dynamic studies compared to static forced expiratory images, although the clinical importance of this observation remains unclear [39,40]. Forced expiratory measurements show good reproducibility in healthy volunteers [41]. Volume acquisition of the airways allows for the production of 2-D and 3-D reformations that can better delineate the extent of abnormalities, while perspective volume rendering (virtual bronchoscopy) may be helpful in preprocedural planning. MRI Chest There are limited data supporting the use of MRI for the central airways in adult populations [42,43]. Some data supporting the use of MRI in pediatric populations [44,45] may be applicable in adults. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT has a supplemental role in the staging of tracheal neoplasms; however, there are no data to support its use in other tracheal conditions.
Chronic Dyspnea Noncardiovascular Origin. Variant 3: Chronic dyspnea. Suspected central airways disease. Initial imaging. Radiography Chest Chest radiographs have the potential to identify conditions of the trachea, with accuracy dependent on the condition to be identified. Compared to CT, radiographs have an accuracy of 89% [34]. It should be noted that radiographic findings may be normal or nonspecific. In a single-institution retrospective study of tracheal neoplasms, <50% were directly detectable by a chest radiograph [35]. CT Chest Examples of airway conditions that may result in chronic dyspnea and can be accurately diagnosed by CT include stenoses, tumors, and end-expiratory airway collapse/tracheobronchomalacia, with strong correlations when compared with bronchoscopy [36,37]. For the last condition, expiratory images are required for diagnosis. Both dynamic airway imaging and static forced expiratory imaging are able to accurately characterize airway collapse when compared with bronchoscopy [38,39]. It has been shown that the degree of expiratory collapse is greater on dynamic studies compared to static forced expiratory images, although the clinical importance of this observation remains unclear [39,40]. Forced expiratory measurements show good reproducibility in healthy volunteers [41]. Volume acquisition of the airways allows for the production of 2-D and 3-D reformations that can better delineate the extent of abnormalities, while perspective volume rendering (virtual bronchoscopy) may be helpful in preprocedural planning. MRI Chest There are limited data supporting the use of MRI for the central airways in adult populations [42,43]. Some data supporting the use of MRI in pediatric populations [44,45] may be applicable in adults. FDG-PET/CT Skull Base to Mid-Thigh FDG-PET/CT has a supplemental role in the staging of tracheal neoplasms; however, there are no data to support its use in other tracheal conditions.