Quantifying symmetry in mandibular condyle motion: a real-time MRI approach

The temporomandibular joints (TMJs) are essential for daily function and must operate in synergy to ensure optimal jaw movement. Real-time magnetic resonance imaging (RT-MRI) enables direct visualization of mandibular condyle motion; however, its application for symmetry assessment remains insufficiently studied. This exploratory study focuses on the consistency of condylar motion symmetry assessments, including visual evaluation of raw image series and 3D trajectories calculated from RT-MRI, as well as automatically extracted quantitative parameters. Given that well-correlated parameters are more likely to be reliable, this work aims to identify optimal methods for assessing symmetry of the condylar pathway using RT-MRI.

The study includes 18 volunteers. A 2D real-time fast low angle shot (FLASH) sequence was used to acquire two sagittal and one axial planes. For quantitative analysis, mandibular condyles were segmented using a neural network. The extracted symmetry parameters were maximum displacement difference and maximum difference of amplitudes for spatial assessments, and latency and velocity peak delay for temporal evaluations. 3D trajectories were automatically generated using a previously validated method. Qualitative scoring of raw image series was conducted by two experts, and the 3D trajectories were evaluated by a dental surgeon. The agreement between qualitative scores was assessed using Cohen's kappa test, while correlations among quantitative parameters were analyzed using Spearman's test.

Results showed higher agreement in the axial plane (intra-observer κ = 0.68; inter-observer κ = 0.44) than in the sagittal plane (κ = 0.51 and 0.20, respectively). Inter-planar correlations were weak to moderate (ρ = 0.21-0.48), with latency showing the strongest correlation.

For our dataset, latency emerged as the most robust temporal parameter. Additionally, motion analysis in the axial plane demonstrated greater consistency in both quantitative measurements and visual scoring. These findings suggest that the axial plane may be preferable for assessing motion symmetry in RT-MRI.

"METHODO" ClinicalTrials.gov Identifier: NCT02887053, approval: CPP EST-III, 08.10.01; "EDEN" ClinicalTrials.gov Identifier: NCT05218460, approval: CPP SUD-EST IV, 26.07.21.