Cheyne Douglas, Bostan Andreea C, Gaetz William, Pang Elizabeth W
Program in Neurosciences and Mental Health, Hospital for Sick Children Research Institute, and Department of Medical Imaging, University of Toronto, Ontario, Canada.
Clin Neurophysiol. 2007 Aug;118(8):1691-704. doi: 10.1016/j.clinph.2007.05.064. Epub 2007 Jun 22.
We describe the application of a new spatial filtering technique--event-related beamforming (ERB)--for presurgical functional mapping of primary sensory areas using MEG. This method provides an alternative to equivalent current dipole (ECD) modeling that potentially eliminates problems of intracranial magnetic artifacts due to movement of ferromagnetic materials (e.g., orthodontic braces) or eye movements.
We compared localization results for ERB and ECD localization of primary somatosensory (M20) and auditory (M100) evoked responses in 12 healthy control subjects and four subjects with metallic dental implants. Data were recorded with a 151-channel CTF MEG system using standard presurgical mapping protocols.
We found a high level of agreement between the two methods in control subjects (overall localization difference was 5.9+/-2.2 mm for M20 and 10.4+/-5.6 mm for M100). Subjects with dental implants showed severely distorted evoked responses that could not be analyzed using ECD, whereas the ERB method localized sources to expected anatomical locations.
MEG functional mapping may be carried out without removal of orthodontic or other metallic implants using event-related beamformer analysis.
Spatial filtering methods can overcome some of the limitations associated with MEG expanding its applicability, particularly in pediatric clinical environments.
我们描述一种新的空间滤波技术——事件相关波束形成（ERB）在使用脑磁图（MEG）进行初级感觉区术前功能映射中的应用。该方法为等效电流偶极子（ECD）建模提供了一种替代方案，有可能消除由于铁磁材料（如正畸托槽）移动或眼球运动引起的颅内磁伪影问题。
我们比较了12名健康对照受试者和4名有金属牙种植体的受试者中，ERB和ECD对初级体感（M20）和听觉（M100）诱发反应的定位结果。使用标准术前映射协议，通过151通道CTF MEG系统记录数据。
我们发现两种方法在对照受试者中具有高度一致性（M20的总体定位差异为5.9±2.2毫米，M100为10.4±5.6毫米）。有牙种植体的受试者显示诱发反应严重扭曲，无法使用ECD进行分析，而ERB方法将源定位到预期的解剖位置。
使用事件相关波束形成器分析，在不摘除正畸或其他金属植入物的情况下即可进行MEG功能映射。
空间滤波方法可以克服与MEG相关的一些局限性，扩大其适用性，特别是在儿科临床环境中。
