Biomedical Engineering Reference
In-Depth Information
Fig. 3.51.
The display of MEG sources (AEF) on the reconstructed 3D head and
brain
[65], modified according to [66] to resolve the ambiguities of the initial algo-
rithm. Since the marching cube algorithm usually creates a very large number
of triangles, the user can parameterize the precision of the boundary com-
putation by adjusting the size of the marching cubes. This provides an easy
way to obtain different level of detail, allowing the user to adjust the tradeoff
between realism and speed of rendering. The obtained triangulation is then
used to display a three-dimensional representation of the head and of the
brain, along with the neuronal source estimations (Fig. 3.51).
3.4
Biomagnetic Measurement
3.4.1
Magnetoencephalography
In this section, we describe a specific MEG system developed at Kanazawa
Institute of Technology, and also some examples of MEG measurements.
Magnetoencephalogram Systems Developed at KIT.
We have deve-
loped new systems for magnetoencephalography (MEG). The pickup coil is
a coaxial type first-order gradiometer with a 50 mm baseline. The magnetic
field resolution of the system is about 4 fT/rtHz or 0.8 (fT/cm)/rtHz in the
white noise region. The unique feature of the system is the gantry-free ho-
rizontal dewar, which is fabricated through what we call a “ship-in-a-bottle
approach”. Less than 10-liter/day liquid helium consumption for the 100-liter
capacity is realized. One of the merits of the horizontal dewar is that a small
room is sucient for installation because of the low height (0.89 m) of the
