| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2005: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
1.We have developed an 'equivalent multipole moment method with polar translations (EMMM-PT)'. This method enables us to numerically calculate exact solution described by Laplace's equation in multi spheres model. We also have developed a 'fast-multipole surface-charge-simulation method for voxel models (FMM-SCM-V)'. This method adopts the FMM that is well known as an efficient 0(N) solver, and it enables us to treat high-resolution human model composed of several to hundred million voxels based on MR images.
2.Numerical calculation procedures for magnitude of MEG coil signal are classified. One way traces 'Equivalent current dipole→Potential on boundary→Magnetic flux by Geselowitz formula', the other traces 'AC coil current→Induced electric field-Magnetic flux by Eaton's reciprocity theorem'. Analyses by EMMM-PT numerically proved the identification of these two ways in multi-media tissue models.
3.The accuracy of FMM-SCM-V is estimated by comparing the numerical results by FMM-SCM-V and EMMM-PT in the grey matter region of a seven spheres head model. The standard deviation of error vector of the electric field is about 0.81% (normalized by the maximum field in the grey matter region) in the case of 0.34mm voxel size. In this case, the number of voxels, the number of surface elements, and calculation time are 106,575,801 voxels, 4,936,874 elements, 59 min. 39 sec., respectively.
4.fMRI-MEG Integrative method is performed by utilizing 'an anomalously applied least squares' and 'linearly-constrained adaptive beamformer' based on the lead field matrix calculated by the Sarvas equation. It has been found that a non-adaptive version of the latter is equivalent to the former, and the both methods have advantages and disadvantages in the spatial and temporal resolution properties.
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