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.

翻译：直接从磁共振成像计算下颌髁突轨迹可提供全面的检查，从而同时获取解剖学和运动学细节。本研究旨在探讨从二维实时磁共振成像中提取三维髁突轨迹的可行性，并评估其精度。二十名健康受试者在进行开闭口运动时接受了实时磁共振成像扫描。采用基于U-Net的算法对一个轴位和两个矢状位切片进行分割。所得掩模的质心被投影到基于解剖标记的坐标系中，并通过公共投影进行时间配准。使用专门设计的指标评估计算轨迹的质量，这些指标用于估计运动重复性、头部运动以及切片放置对称性。轴位切片的分割质量良好至优秀；然而，矢状位切片的分割需要一定程度的精细调整。在多数情况下运动重复性可接受；尽管如此，头部运动平均使轨迹偏移1毫米。下颌闭合位时髁突上下坐标的平均差值为1.7毫米。尽管存在精度限制，实时磁共振成像能够以足够的准确度提取髁突轨迹，可用于评估临床相关参数，如髁突位移、轨迹形态及对称性。