MAGNETIC LOCALIZATION OF A DIPOLAR CURRENT SOURCE IMPLANTED IN A SPHERE AND A HUMAN CRANIUM
MAGNETIC LOCALIZATION OF A DIPOLAR CURRENT SOURCE IMPLANTED IN A SPHERE AND A HUMAN CRANIUM
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DOI：
10.1016/0013-4694(86)90094-5
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发表时间：
1986-03-01
期刊：
影响因子：
--
通讯作者：
BEATTY, J
中科院分区：
文献类型：
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作者：
BARTH, DS;SUTHERLING, W;BEATTY, J
本文用脑磁图（MEG）测量了植入球形导体的偶极源和人体颅骨标本产生的磁场。源的位置被准确地计算在球形导体从所确定的磁场极值使用方程的电流偶极子在一个球体。同样的方法不足以定位人类颅骨中的源，其中磁场图显示为经典偶极模式的扭曲。使用更完整的计算机建模程序，调整颅骨上记录矩阵的非球形尺寸。通过将计算机模拟场的梯度与颅外测量场的梯度进行拟合，大大提高了源定位的准确性。颅外磁场的最大失真是两个极值的测量幅度的不平等，这是由MEG探头在下面部和耳朵上记录时增加的距离和角度产生的。然而，颅骨切除术和植入绝缘球囊导致的颅骨电阻的总体不均匀性对颅外磁场模式的影响可以忽略不计。
Magnetic fields produced by a dipolar source implanted in a spherical conductor and a human cranial specimen were measured in the magnetoencephalogram (MEG). The location of the source was accurately computed in the spherical conductor from the identified magnetic field extrema using equations for a current dipole in a sphere. This same method was insufficient for localizing the source in a human cranium, where magnetic field maps appeared as distortions from the classical dipolar pattern. A more complete computer modeling procedure was used, adjusting for the non-spherical dimensions of the recording matrix on the cranium. By fitting the gradient of computer simulated fields to those measured outside the cranium, the accuracy of source localization was substantially improved. The greatest distortion of the extracranial magnetic field was an inequality in the measured amplitude of the two extrema, produced by an increased distance and angle of the MEG probe when recording over the lower face and ear. However, gross heterogeneities in the resistance of the skull due to a craniectomy and an implanted insulating balloon had a negligible effect on the extracranial magnetic field pattern.