Can MRI be a potential substitute for CT in cephalometric analysis for radiation-free diagnoses?

The primary objective of this study was to investigate the feasibility of magnetic resonance imaging (MRI) usage over computed tomography (CT) to perform three-dimensional (3D) cephalometric analyses. The secondary objective is to find intra- and interobserver reliability of manual cephalometric landmarks identification in both CT and MRI scan data.

Data from 40 patients were used in this study, with orthodontists manually identifying 37 landmarks on both CT and MRI scans. The interclass correlation coefficient (ICC) was calculated individually for both CT and MRI scan data to find intra- and interobserver reliability. In addition to ICC, paired t‑test and mean error were also calculated. Ground truth landmarks were calculated by considering the mean values of manually located 37 landmarks by observers for both CT and MRI. Thirty-seven cephalometric measurements (29 linear, 6 angular, and 2 ratios) were measured using 37 ground truth landmarks. Mean error (ME) between CT and MRI measurements was calculated and paired t‑test was performed to find the reliability of MRI usage over CT. Bland-Altman analysis was also performed on the measurements to check the agreement between CT and MRI.

The intra- and interobserver reliability was found to be reliable (ICC > 0.98, and P > 0.05) for all 37 landmarks in both CT and MRI. The ME for linear measurements was found to be 1.81 mm for hard tissue, 1.72 mm for soft tissue, and 1.53° for hard tissue angular measurements between CT and MRI. The paired t‑test performed on measurements between CT and MRI proved to be statistically insignificant (p > 0.05). The Bland-Altman analysis also showed strong agreement and low systemic bias between CT and MRI data.

The strong ICC and P values shows the high reliability and reproducibility of manual landmark identification on both CT and MRI. The ME for the linear and angular measurements between CT and MRI was found to be well within acceptable limits. The results of paired t‑test and Bland-Altman analyses for cephalometric measurements between CT and MRI has shown strong evidence supporting the use of MRI as a substitute for CT.