Clinical Utility of CT Imaging Techniques for Tracheobronchial Diseases was graded on a five-point scale: score 0, no information; 1, poor; 2, fair; 3, good; and 4, excellent. For statistical analysis, Wilcoxon’s matched-pairs signed- ranks test was used. A p value of less than 0.05 was con- sidered statistically significant. (n =2), left main bronchus (n=8), bronchus intermedius (n=7), right main bronchus and bronchus intermedius (n=2), trachea and right main bronchus (n=2), trachea and left main bronchus (n=5), left upper lobar bronchus (n=5), and trachea and both main bronchi (n=2). All but three RESULTS Lesions involved the trachea (n=8), right main bronchus Fig. 2. SSD image from which unnecessary lung was removed shows the trachea and bilateral main bronchi. Fig. 3. SSD image preprocessed with slice by slice editing to re- move unwanted structures shows complete focal obstruction of the left upper lobar bronchus (arrow). Table 1. Mean Score of Chest Radiography (CXR), Routine CT (RCT), Thin-section Spiral CT (TCT), Multiplanar Reconstruc- tion (MPR) and Shaded Surface Display (SSD) Imaging Detection Localization Extent Relationship Characterization Overall Note. Data are mean SD CXR 1.24 0.97 1.10 0.89 0.93 0.79 0.78 0.47 1.07 0.82 1.07 0.79 RCT 2.98 0.65 2.85 0.61 2.27 0.63 3.29 0.27 3.05 0.86 2.73 0.55 TCT 3.46 0.50 3.37 0.49 3.00 0.45 3.56 0.50 3.51 0.60 3.20 0.46 MPR 3.80 0.51 3.78 0.42 3.56 0.55 3.12 0.40 3.29 0.56 3.56 0.55 SSD 3.95 0.31 3.95 0.22 3.85 0.42 2.12 0.60 3.20 0.60 3.83 0.44 Table 2. p-Values for Difference between Various Techniques (Wilcoxon’s Matched-Pairs Signed-Ranks Test) Detection Localization Extent Relationship Characterization Overall TCT MPR SSD TCT MPR SSD TCT MPR SSD TCT MPR SSD TCT MPR SSD TCT MPR SSD RCT < .01 < .01 < .01 < .01 < .01 < .01 < .01 < .01 < .01 < .05 NS < .01 < .01 NS NS < .01 < .01 < .01 TCT <.01 < .01 < .01 < .01 < .01 < .01 < .01 < .01 NS < .05 < .01 < .01 MPR < .05 < .05 < .01 < .01 NS < .05 Note. NS = not significant, RCT = routine CT, TCT = thin-section spiral CT, MPR = multiplanar reconstruction imaging, SSD = shaded surface display imaging Korean J Radiol 1(3), September 2000 137