[A study of quantitative measurement of singular nerve canal with cone-beam computed tomography]

Objective: To explore the feasibility of cone beam computed tomography (CBCT) in quantitatively assessing singular nerve canal and to propose a method to locate singular nerve canal in CBCT imaging. Methods: Eight cadaveric heads were scanned using CBCT and images of 16 temporal bones were obtained.The diameters of three points of singular nerve canal were measured which included the internal auditory canal aperture, the central turning area, and the aperture of ampulla of the posterior semicircular canal.The length of singular canal was measured.The distances from the three points to the inner edge of round window were measured.The best oblique axial plane to display the whole course of singular canal was adjusted and the angle between this plane and the lateral semicircular canal was measured.Two independent sample t-test was used to compare the left and right measurements. Results: The mean diameters of the three points were(0.98±0.51), (0.36±0.05) and(0.38±0.06) mm respectively.The mean length of singular nerve canal was(4.16±0.87) mm.The mean angle was 19.1°±10.2°.2D and 3D location graphs of singular nerve canal were made with the distance between the three points on singular nerve canal and the medial end of the round window.There was no significant statistical difference between left and right side in all the measurement (all P>0.05). Conclusion: CBCT can clearly display the whole course of singular nerve canal.Measurement can be done on CBCT images, and the specific location of singular nerve canal can be determined, which are important for surgery.