Malmivuo J, Suihko V, Eskola H
Ragnar Granit Institute, Tampere University of Technology, FIN.
IEEE Trans Biomed Eng. 1997 Mar;44(3):196-208. doi: 10.1109/10.554766.
It is generally believed that because the skull has low conductivity to electric current but is transparent to magnetic fields, the measurement sensitivity of the magnetoencephalography (MEG) in the brain region should be more concentrated than that of the electroencephalography (EEG). It is also believed that the information recorded by these techniques is very different. If this were indeed the case, it might be possible to justify the cost of MEG instrumentation which is at least 25 times higher than that of EEG instrumentation. The localization of measurement sensitivity using these techniques was evaluated quantitatively in an inhomogeneous spherical head model using a new concept called half-sensitivity volume (HSV). It is shown that the planar gradiometer has a far smaller HSV than the axial gradiometer. However, using the EEG it is possible to achieve even smaller HSV's than with whole-head planar gradiometer MEG devices. The micro-superconducting quantum interference device (SQUID) MEG device does have HSV's comparable to those of the EEG. The sensitivity distribution of planar gradiometers, however, closely resembles that of dipolar EEG leads and, therefore, the MEG and EEG record the electric activity of the brain in a very similar way.
一般认为，由于颅骨对电流的传导性较低，但对磁场透明，所以脑磁图（MEG）在脑区的测量灵敏度应比脑电图（EEG）更集中。人们还认为，这些技术记录的信息差异很大。如果确实如此，那么MEG仪器至少比EEG仪器贵25倍的成本或许就能说得通了。利用一个名为半灵敏度体积（HSV）的新概念，在非均匀球形头部模型中对使用这些技术的测量灵敏度定位进行了定量评估。结果表明，平面梯度仪的HSV比轴向梯度仪小得多。然而，使用EEG有可能实现比全头平面梯度仪MEG设备更小的HSV。微型超导量子干涉装置（SQUID）MEG设备的HSV确实与EEG相当。然而，平面梯度仪的灵敏度分布与偶极EEG导联非常相似，因此，MEG和EEG以非常相似的方式记录大脑的电活动。
