Combining EEG and MRI Techniques - Quantitative EEG Analysis Methods and Clinical Applications - page 317

CHAPTER 12
Combining EEG and MRI Techniques

Michael Wagner 1
Soumyadipta Acharya, Joseph S. Paul, and Nitish V. Thakor 2

Simultaneous use of EEG and MRI offer new methodologies for studying the struc-
ture and function of the brain. Section 12.1 outlines the techniques for utilizing ana-
tomical information from the MRI in solving the EEG inverse problem. Section 12.2
addresses the theoretical and practical considerations for recording and analyzing
simultaneous EEG-fMRI, as well as some current and emerging applications. We
begin by presenting the technical challenges associated with recording EEG within
the high-field-strength magnet of the MRI scanner, including artifacts in the EEG
unique to the MRI environment as well as distortions in the MRI due to the presence
of EEG hardware.
We present some recent approaches for using fMRI techniques to study EEG
phenomena such as evoked potentials and rhythms. Concurrently, we review meth-
ods that aim to generate more meaningful fMRI images by incorporating informa-
tion from the EEG into the mathematical models used for generating functional MR
images. Some potential clinical applications, such as in studying epilepsy, as well as
sleep studies are also presented. The ultimate goal of combining with fMRI is to
exploit the complementary information in these two separate datasets to better
understand the functional dynamics of the brain.

12.1 EEG and MRI

Although this chapter appears in the applications part of the topic, it is predomi-
nantly a methods chapter. The methods proposed here deal with bringing EEG and
MRI together, creating realistically shaped volume conductor models (head models)
and enhancing EEG source analysis, both by means of information from MRI. After
defining the (cortical) source space, cortical current density reconstructions (CDRs)
as well as cortical dipole or beamformer scans are possible. The sections on volume
conductor models and source analysis techniques build on the information pre-
sented in Chapter 5, and the same notation as in Chapter 5 will be used. Finally, sen-
sors, mappings, anatomical structures, and reconstructed sources can be displayed
in a common visualization framework.

1. This author contributed to Section 12.1.

2. These authors contributed to Section 12.2.

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