[Feasibility study of cone-beam CT in displaying facial nerve canal]

Objective: To evaluate the image clarity of cone-beam computed tomography (CBCT) in displaying facial nerve canal and to investigate the feasibility of CBCT to display facial nerve canal and whether there are some advantages compared with MSCT. Methods: Eight cadaveric heads were scanned using CBCT and MSCT and images of 16 temporal bones of each scanner were obtained.The imaging clarity of facial nerve canal of the two scanners was scored.Wilcoxon test was used to assess the difference of the two methods.P<0.05 was considered statistically significant. The defects of the wall of facial nerve canal were also observed in the images of both scanners. Results: Sixteen structures of facial nerve canal were evaluated, including the wall of labyrinthine segment, the anterior, medial, lateral, superior, inferior wall of the first genu, the lateral, inferior wall of the anterior part of tympanic segment, the lateral, inferior wall of the posterior part of tympanic segment, the medial and superior wall of tympanic segment, the lateral, inferior, superior, medial wall of the second genu and the wall of mastoid segment.The clarity of thirteen structures showed no differences between the two scanners (P>0.05). The clarity of three structures showed significant differences between CBCT and MSCT (P<0.05), which included the superior wall of the first genu, the posterior part of the lateral wall and the anterior part of the inferior wall of tympanic segment, and the scores of CBCT were higher than MSCT.The most frequent region of defect was in the anterior part of inferior wall of tympanic segment (14/16), followed by the inferior wall of labyrinthine segment (9/16) and the superior wall of tympanic segment (6/16). Conclusion: Compared with MSCT, CBCT could also gain quite good imaging clarity for displaying facial nerve canal. The display effect of some fine structures, such as the lateral wall of tympanic segment, is better in the images of CBCT than in those of MSCT.