Biomedical Engineering Reference
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(a)
(b)
(c)
Figure 12.8
Three-dimensional rendering of: (a) electrodes, potential map, color scale, time axis, BEM head
model, and fitted dipole; (b) electrodes, potential map, MRI slice, and fitted dipole; and (c) electrodes, poten-
tial map, cortical sLORETA result with 15-mm source extension, and color scale.
12.1.5.1 Comparison of Grid, Cortical, and Extended Cortical Sources
To demonstrate the effect of various source space constellations and of extended
sources onto the results of CDR, a point source (dipole) was simulated and noise
was added to achieve an SNR of 15. The simulated data was analyzed using
sLORETA [34, 35] CDRs for the following source spaces: a 7-mm three-dimen-
sional grid, a 3-mm cortex without source orientation constraint, a 3-mm cortex
with cortical source orientation constraint, and extended sources of 20-mm patch
size based on the same 3-mm cortex and its source orientations. Simulated dipole
and reconstruction results are shown in Figure 12.9.
Moving from a grid to a cortical source space, using cortical orientations and
extended sources, adds a priori information to the source reconstruction and deliv-
ers results that are even closer to reality. However, the interpretation of results
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