A New Coordinate System for Magnetic Resonance Imaging of the Vestibular System

Objectives: To develop and evaluate a new coordinate system for MRI of the vestibular system.Methods: In this study, 53 internal auditory canal MRI and 78 temporal bone CT datasets were analyzed. Mimics Medical software version 21.0 was used to visualize and three-dimensionally reconstruct the image data. We established a new coordinate system, named W-X, based on the center of the bilateral eyeballs and vertex of the bilateral superior semicircular canals. Using the W-X coordinate system and Reid's coordinate system, we measured the orientations of the planes of the anterior semicircular canal (ASCC), the lateral semicircular canal (LSCC), and the posterior semicircular canal (PSCC).Results: No significant differences between the angles measured using CT and MRI were found for any of the semicircular canal planes (p > 0.05). No statistical differences were found between the angles measured using Reid's coordinate system (CT) and the W-X coordinate system (MRI). The mean values of angle ASCC & LSCC, angle ASCC & PSCC, and angle LSCC & PSCC were 84.67 +/- 5.76, 94.21 +/- 3.81, and 91.79 +/- 5.22 degrees, respectively. The angle between the LSCC plane and the horizontal imaging plane was 15.64 +/- 3.92 degrees, and the angle between the PSCC plane and the sagittal imaging plane was 48.79 +/- 4.46 degrees.Conclusion: A new W-X coordinate system was developed for MRI studies of the vestibular system and can be used to measure the orientations of the semicircular canals.