Grading Airway Stenosis Down to the Segmental Level Using Virtual Bronchoscopy: Discussion
We evaluated the success rate of noninvasive, multirow detector CT virtual bronchoscopy in detecting and grading central and segmental airway stenosis. In our present study, virtual bronchoscopy enabled high-resolution endoluminal imaging of the airways including segmental bronchi. Virtual bronchoscopy of segmental airway stenosis provides important additional information on the tracheobronchial tree and was not evaluated in earlier reports, where it has been applied exclusively for the detection of central airway stenosis. A preliminary study concluded that virtual bronchoscopy can render stenosis in anatomic detail, but that further studies were needed to evaluate its diagnostic potential. Other studies, have found virtual bronchoscopy to have a high sensitivity (> 90%) and specificity (> 98%) in detecting central airway stenosis in patients with bronchial carcinoma. The results of these studies were confirmed by our investigations, showing a sensitivity of 90% for detection of central airway stenosis. Additionally, we found a sensitivity of 90% for the detection of segmental airway stenosis, although the number of false-positive findings here was higher. Segmental airway stenosis had not been evaluated in any of the previously conducted studies.
There are several reasons for the misinterpretation of virtual bronchoscopic findings on stenosis. The present study had three false-positive findings of stenosis located in the middle lobar bronchus. It has been reported that stenoses occurring in the middle lobar bronchi and lingula may lead to the inaccurate estimation of the bronchial cali-ber. This occurs because these airways lie parallel to the axial scan plane and their walls are less well-depicted than those of bronchi running perpendicular to the scanning plane, such as the intermediate bronchus. Similarly, one false-positive and one false-negative finding of stenosis in the right inferior lobar superior segmental bronchus (B VI) may have been misread because of the difficulty in assessing this segmental airway using virtual bronchoscopy. False-positive readings in these bronchi may lead to further diagnostic studies with potential morbidity.