Department of Orthodontics and Orofacial Orthopedics, Friedrich-Alexander-University Erlangen-Nürnberg, Germany.
Magnetic Resonance and X-ray Imaging Department of the Development Centre X-ray Technology EZRT, Division of Fraunhofer Institute for Integrated Circuits IIS, Würzburg, Germany.
Eur J Orthod. 2021 Dec 1;43(6):614-621. doi: 10.1093/ejo/cjaa066.
Magnetic resonance imaging (MRI) enables a 3D-volume-imaging without ionizing radiation. Therefore, it was the aim of this study to present a post-processing-free method for cephalometric analysis of a MRI-dataset and to examine whether there is a significant difference between cephalometric analysis of conventional 2D cephalograms and MRI scans.
One MRI scan each was performed on three cadaver heads using a 3T-MR-scanner. Cephalometric analysis was conducted directly on the 3D dataset. All reference points were projected onto a virtual sagittal plane that was perpendicular to the Frankfort horizontal plane. Double-sided points were averaged. Cephalometric angles were measured from the projected points. Results were compared with cephalometric measurements on conventional lateral cephalometric radiographs (LCRs). The cephalometric analysis was performed by five raters.
390-angle measurements were obtained. The inter-rater reliability was high [intraclass correlation coefficients (ICCs) ≥ 0.74 for all angles]. Differences between the measurements on the cephalograms and MRI scans ranged between -0.91° (-1.88°, 0.07°) and 0.97° (-0.63°, 2.57°) on average and were equivalent with respect to a margin of [-2°, 2°] in all angles except L1-Me-Tgo (Bonferroni-Holm-corrected P < 0.05 in all angles except L1-Me-Tgo). The best match was found for the SNA angle.
The clinical comparability of the MRI- and LCR-based cephalometry could be stated. Using MRI in orthodontics would reduce radiation exposure and the risk of stochastic radiation damage, which is of importance especially in younger patients.
磁共振成像（MRI）可实现无需电离辐射的三维容积成像。因此，本研究旨在提出一种无需后处理的 MRI 数据集头影测量分析方法，并检验传统二维头颅侧位片和 MRI 扫描的头影测量分析是否存在显著差异。
使用 3T-MR 扫描仪对 3 个头颅骨各进行 1 次 MRI 扫描。直接对头影测量的 3D 数据集进行分析。所有参考点均投影到与法兰克福水平面垂直的虚拟矢状面上。双侧点取平均值。从投影点测量头影测量角度。将结果与传统侧位头颅 X 线片（LCR）的头影测量结果进行比较。头影测量由 5 名评估者进行。
共获得 390 个角度测量值。评估者间的可靠性较高[所有角度的组内相关系数（ICC）≥0.74]。LCR 和 MRI 扫描的测量值之间的差异平均在-0.91°（-1.88°，0.07°）和 0.97°（-0.63°，2.57°）之间，除 L1-Me-Tgo 外（除 L1-Me-Tgo 外，所有角度的 Bonferroni-Holm 校正 P<0.05），所有角度的差异均在[-2°，2°]的范围内等效。SNA 角度的匹配最佳。
可以说明 MRI 和 LCR 头影测量的临床可比性。在正畸中使用 MRI 可以减少辐射暴露和随机辐射损伤的风险，这在年轻患者中尤为重要。
