Figure 12 Bronchoscopic (a)  and virtual 3D reconstructed CT images (b) of the trachea showing complete tracheal rings and long segment tracheal stenosis. Bronchoscopy is more accurate and can determine the exact number of complete rings. Image 12c shows optical coherence tomography (OCT) with a pseudo-complete ring that does not join in the midline. The cartilage is visible as a black acoustic shadow (C). Each grading dot on the OCT image is 1 mm.