Three-dimensional helical CT of the tracheobronchial tree: evaluation of imaging protocols and assessment of suspected stenoses with bronchoscopic correlation.
To assess the accuracy of three-dimensional (3D) helical CT of normal airways, we evaluated different imaging protocols in test objects and patients. The clinical value of 3D helical CT was composed with bronchoscopy in patients with suspected stenoses, especially before and after endobronchial procedures. Solid test objects--one of central airways and one of peripheral airways--were scanned and assessed for volume defects and stairstep artifacts. Fifty helical studies were performed in 36 patients. We evaluated these images for visualization of segmental bronchi; frequency of artifacts; and presence, localization, and degree of stenoses. Bronchoscopic correlation was available for 40 CT examinations. Follow-up 3D helical CT after endobronchial procedures was performed in nine patients. In test objects, thin sections reduced volume artifacts. Overlapping sections mainly diminished stairstep artifacts. In vivo, overlapping sections were superior to contiguous sections for good visualization of the origin (96% versus 89%, p < .01) and of the course (75% versus 54%, p < .001) of segmental bronchi. Three-dimensional helical CT allowed us to assess accurately 36 of 36 central stenoses that were seen on bronchoscopy; however, on 3D helical CT, we missed two of three segmental stenoses. At bronchoscopy, 18 stenoses could not be passed, whereas 3D helical CT provided details for possible endobronchial procedures: length of stenosis, patency (12/18), and spatial orientation of distal bronchi. Follow-up 3D helical CT documented the efficacy of endobronchial treatment. Three-dimensional helical CT based on thin overlapping sections accurately visualized the normal airways down to the origin of the segmental bronchi and central stenoses. When it complements bronchoscopy, 3D helical CT allows visualization beyond stenoses, supports planning of endobronchial procedures, and may even substitute for bronchoscopy after endobronchial procedures.