Nagoya Institute of Technology, Department of Electrical and Mechanical Engineering, Nagoya, Aichi, 466-8555, Japan.
Aalto University, Department of Electrical Engineering and Automation, Espoo, FI-00076, Finland.
Neuroimage. 2018 May 15;172:85-93. doi: 10.1016/j.neuroimage.2018.01.039. Epub 2018 Jan 28.
Transcranial magnetic stimulation (TMS) is used for the mapping of brain motor functions. The complexity of the brain deters determining the exact localization of the stimulation site using simplified methods (e.g., the region below the center of the TMS coil) or conventional computational approaches.
This study aimed to present a high-precision localization method for a specific motor area by synthesizing computed non-uniform current distributions in the brain for multiple sessions of TMS.
Peritumoral mapping by TMS was conducted on patients who had intra-axial brain neoplasms located within or close to the motor speech area. The electric field induced by TMS was computed using realistic head models constructed from magnetic resonance images of patients. A post-processing method was implemented to determine a TMS hotspot by combining the computed electric fields for the coil orientations and positions that delivered high motor-evoked potentials during peritumoral mapping. The method was compared to the stimulation site localized via intraoperative direct brain stimulation and navigated TMS.
Four main results were obtained: 1) the dependence of the computed hotspot area on the number of peritumoral measurements was evaluated; 2) the estimated localization of the hand motor area in eight non-affected hemispheres was in good agreement with the position of a so-called "hand-knob"; 3) the estimated hotspot areas were not sensitive to variations in tissue conductivity; and 4) the hand motor areas estimated by this proposal and direct electric stimulation (DES) were in good agreement in the ipsilateral hemisphere of four glioma patients.
CONCLUSION(S): The TMS localization method was validated by well-known positions of the "hand-knob" in brains for the non-affected hemisphere, and by a hotspot localized via DES during awake craniotomy for the tumor-containing hemisphere.
经颅磁刺激（TMS）用于大脑运动功能的映射。由于大脑的复杂性，使用简化方法（例如，TMS 线圈中心下方的区域）或传统的计算方法很难确定刺激部位的精确位置。
本研究旨在通过综合多次 TMS 计算出的大脑中非均匀电流分布，提出一种特定运动区域的高精度定位方法。
对位于运动言语区内部或附近的脑内轴内肿瘤患者进行 TMS 肿瘤周围映射。使用基于患者磁共振图像构建的真实头部模型计算 TMS 诱导的电场。实施后处理方法，通过结合在肿瘤周围映射过程中产生高运动诱发电位的线圈方向和位置的计算电场，确定 TMS 热点。该方法与术中直接脑刺激和导航 TMS 定位的刺激部位进行了比较。
得出了四个主要结果：1）评估了计算热点区域与肿瘤周围测量次数的依赖性；2）在 8 个非受累半球中，对手运动区的估计定位与所谓的“手旋钮”位置吻合良好；3）估计的热点区域对组织电导率的变化不敏感；4）通过本研究提出的方法和直接电刺激（DES）估计的手运动区在 4 例脑肿瘤患者的同侧半球中吻合良好。
该 TMS 定位方法通过非受累半球中“手旋钮”的已知位置以及肿瘤半球中通过清醒开颅术定位的热点得到了验证。
