Tesfai Agazi Samuel, Vollmer Andreas, Özen Ali Caglar, Braig Moritz, Semper-Hogg Wiebke, Altenburger Markus Jörg, Ludwig Ute, Bock Michael
From the Department of Radiology, Medical Physics.
Department of Oral and Craniomaxillofacial Surgery, Center for Dental Medicine, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg.
Invest Radiol. 2022 Mar 1;57(3):163-170. doi: 10.1097/RLI.0000000000000826.
Accurate visualization of dental root canals is vital for the correct diagnosis and subsequent treatment. This work assesses the improvement of a dedicated new coil for dental magnetic resonance imaging (MRI) in comparison to conventional ones in terms of signal-to-noise ratio (SNR) and visibility.
A newly developed intraoral flexible coil was used to display dental roots with MRI, and it provides improved sensitivity with a loop design and size adjusted to a single tooth anatomy. Ex vivo and in vivo measurements were performed on a 3 T clinical MR system, and results were compared with conventional head and surface coil images. Additional comparison was performed with a modified fast spin echo sequence and a constructive interference in steady-state sequence.
Ex vivo, an SNR gain of 6.3 could be achieved with the intraoral flexible coil setup, and higher visibility down to 200 μm was possible, whereas the external loop coil is limited to 400 μm. In vivo measurements in a volunteer resulted in an SNR gain of up to 4.5 with an improved delineation of the root canals, especially for the branch tissue splitting of the mesial root canal into mesial-buccal and mesial-lingual.
In summary, we showed the feasibility of implementing a wireless coil approach with readily available dental practice materials for sealing and placement. Highly improved MRI scans can be acquired within clinically feasible scan times, and this might provide additional medical findings to supplement available x-ray images.
准确显示牙根管对于正确诊断及后续治疗至关重要。本研究评估了一种新型牙科磁共振成像（MRI）专用线圈相较于传统线圈在信噪比（SNR）和可视性方面的改进情况。
使用新开发的口腔内柔性线圈通过MRI显示牙根，其采用环形设计且尺寸根据单颗牙齿解剖结构进行了调整，从而提高了灵敏度。在3T临床MR系统上进行了离体和活体测量，并将结果与传统头部和表面线圈图像进行比较。还使用改良快速自旋回波序列和稳态构成性干扰序列进行了额外比较。
在离体情况下，口腔内柔性线圈设置可实现6.3的SNR增益，并且能够清晰显示低至200μm的结构，而外部环形线圈只能显示至400μm。在一名志愿者身上进行的活体测量显示，SNR增益高达4.5，根管的描绘得到改善，尤其是近中根管分支为近中颊侧和近中舌侧的情况。
总之，我们展示了采用易于获得的牙科实践材料进行密封和放置的无线线圈方法的可行性。在临床可行的扫描时间内可以获得高度改进的MRI扫描结果，这可能为补充现有的X线图像提供额外的医学发现。
