Improved delineation of CT virtual bronchoscopy by ultrahigh-resolution CT: comparison among different reconstruction parameters.

PURPOSE: We compared the maximal recognizable bronchial bifurcation order (MRBBO) in CT virtual bronchoscopy (CTVB) using ultrahigh-resolution CT (UHRCT) and different reconstruction parameters. MATERIALS AND METHODS: We enrolled 38 patients undergoing noncontrast chest CT by UHRCT and reconstructed CTVB utilizing 3 different combinations of reconstruction parameters, as classified into Group A (matrix size, 512; slice thickness, 1.0 mm), Group B (matrix size, 512; slice thickness, 0.5 mm), and Group C (matrix size, 1024; slice thickness, 0.25 mm). In right S1, left S1 + 2, and both S3 and S10, two reviewers counted the number of consecutively identified bronchial bifurcations to compare MRBBO among these groups using Kruskal-Wallis test. RESULTS: In these segments, MRBBO increased from Group A to C. MRBBO was significantly higher in Group C than in both Groups A and B in all the segments except left S10 (P < 0.05 for all). In left S10, it was significantly higher in Group C than in Group A (P < 0.05) but comparable between Groups B and C (P = 0.122). CONCLUSIONS: MRBBO is higher in CTVB by UHRCT utilizing 1024-matrix size and 0.25-mm thickness than parameters currently recommended for CTVB (matrix size, 512; slice thickness, 0.5-1.0 mm).