Contents

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• Introduction  
  • The origin of the signals
  • Measuring the MEG  
    • The SQUID
    • Flux transformers
    • Electronics
    • Shielded room
  • The Twente biomagnetic facility
  • Scope of this thesis
    • Measurements
    • Modelling the head
    • Visualization and evaluation of results
    • Errors
• Data acquisition and noise reduction  
  • The data-acquisition system
  • Data-processing
  • Environmental noise reduction  
    • Electronic balancing
    • Active shielding
• From electric and magnetic signals to their sources  
  • The inhomogeneous volume conductor
  • The source model
  • The Sphere Model
  • The inverse procedure
• Processing MRI-data for electromagnetic source Imaging  
  • The MRI-data
  • Histogram analysis
  • The segmentation of a slice  
    • The head
    • The brain
    • CSF
    • The skull
  • Generation of models of the head
  • Visualization of head and brain in three dimensions
• Integration of the MEG and EEG with the MRI  
  • Coordinate systems
  • Localization of the dipole  
    • Sphere fitting
    • The measurement positions
    • Displaying the dipole in the MRI
  • Influence of the head model
  • Estimation of the active patch of neurons  
    • Determination of the strength of a dipole
    • Determination of the active area of cortex
  • Conclusion
• Matching MRI with PET data  
  • The PET data
  • Method of matching PET scans to the MRI
  • Discussion
  • An example of combining MEG, EEG, MRI and PET
• Errors In source localization  
  • Measurement errors
  • Errors in the position and orientation of the recording device
  • Volume conductor model errors  
    • The electric case
    • The magnetic case
    • Discussion and conclusions
  • Errors in the position of the MRI-markers
  • Errors in the sphere location
  • Errors in the MRI
  • Overall error-estimate for the MEG
• Evaluation and Conclusions  
  • Data acquisition
  • Noise reduction
  • Display of dipoles in MRI images
  • Segmentation of the MRI
  • The volume conductor
  • Accuracy
  • Verification
  • Clinical use
• Overview of the software  
  • The Data-acquisition software
  • Segmentation of MRI-datasets
  • The Biomagnatic Imaging System
  • Non-interactive generation of 3D-images
  • Triangulation
• References
• Summary

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(c) MEG, EEG and the integration with Magnetic Resonance Images, H.J. Wieringa, 1993

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