  Computing the trajectories of mandibular condyles directly from MRI could
provide a comprehensive examination, allowing for the extraction of both
anatomical and kinematic details. This study aimed to investigate the
feasibility of extracting 3D condylar trajectories from 2D real-time MRI and to
assess their precision.Twenty healthy subjects underwent real-time MRI while
opening and closing their jaws. One axial and two sagittal slices were
segmented using a U-Net-based algorithm. The centers of mass of the resulting
masks were projected onto the coordinate system based on anatomical markers and
temporally adjusted using a common projection. The quality of the computed
trajectories was evaluated using metrics designed to estimate movement
reproducibility, head motion, and slice placement symmetry.The segmentation of
the axial slices demonstrated good-to-excellent quality; however, the
segmentation of the sagittal slices required some fine-tuning. The movement
reproducibility was acceptable for most cases; nevertheless, head motion
displaced the trajectories by 1 mm on average. The difference in the
superior-inferior coordinate of the condyles in the closed jaw position was 1.7
mm on average.Despite limitations in precision, real-time MRI enables the
extraction of condylar trajectories with sufficient accuracy for evaluating
clinically relevant parameters such as condyle displacement, trajectories
aspect, and symmetry.
