TY - JOUR
T1 - On the magnetic field distribution generated by a dipolar current source situated in a realistically shaped compartment model of the head
T2 - On the magnetic field distribution generated by a dipolar current source situated in a realistically shaped compartment model of the head
AU - Meijs, J.W.H.
AU - Bosch, F.G.C.
AU - Peters, M. J.
AU - Lopes da Silva, F.H.
PY - 1987/3
Y1 - 1987/3
N2 - The magnetic field distribution around the head is simulated using a realistically shaped compartment model of the head. The model is based on magnetic resonance images. The 3 compartments describe the brain, the skull and the scalp. The source is represented by a current dipole situated in the visual cortex. The magnetic field distribution due to the source and that due to the volume currents are calculated separately. The simulations are carried out in order to ascertain which matrix of grid points is suitable as a measuring grid. The possibilities studied are grid points situated in a plane, in a surface which follows the contours of the head and in a sphere. This sphere is taken concentric to the sphere which is the best possible fit for the head. Taking into account the relative contribution of the volume currents and the possible accuracy in the positioning of the magnetic field detector, it can be concluded that the best choice is to measure the normal component of the magnetic field at points which are situated in the spherical surface. The results of this study also show that the magnetic field distribution based on a realistically shaped compartment model differs from that based on a compartment model consisting of concentric spheres. In the spherical model of the head no contribution of the volume currents to the component of the field normal to the sphere can be expected. The difference between the results obtained with these two volume conductor models increases with source depth.
AB - The magnetic field distribution around the head is simulated using a realistically shaped compartment model of the head. The model is based on magnetic resonance images. The 3 compartments describe the brain, the skull and the scalp. The source is represented by a current dipole situated in the visual cortex. The magnetic field distribution due to the source and that due to the volume currents are calculated separately. The simulations are carried out in order to ascertain which matrix of grid points is suitable as a measuring grid. The possibilities studied are grid points situated in a plane, in a surface which follows the contours of the head and in a sphere. This sphere is taken concentric to the sphere which is the best possible fit for the head. Taking into account the relative contribution of the volume currents and the possible accuracy in the positioning of the magnetic field detector, it can be concluded that the best choice is to measure the normal component of the magnetic field at points which are situated in the spherical surface. The results of this study also show that the magnetic field distribution based on a realistically shaped compartment model differs from that based on a compartment model consisting of concentric spheres. In the spherical model of the head no contribution of the volume currents to the component of the field normal to the sphere can be expected. The difference between the results obtained with these two volume conductor models increases with source depth.
KW - Magnetoencephalography
KW - Recording surfaces
KW - Simulation
KW - Visual cortex
KW - Volume conductor shape
UR - http://www.scopus.com/inward/record.url?scp=0023105206&partnerID=8YFLogxK
U2 - 10.1016/0013-4694(87)90078-2
DO - 10.1016/0013-4694(87)90078-2
M3 - Article
C2 - 2434313
SN - 0013-4694
VL - 66
SP - 286
EP - 298
JO - Electroencephalography and clinical neurophysiology
JF - Electroencephalography and clinical neurophysiology
IS - 3
ER -