Hi,
I have a few questions about the optimal expansion origin for SSS.
1) According to the maxfilter manual, "the optimal device origin is at
0,13,-6mm." Why is this the optimal origin? Is it because it minimises
the volume between the inner and outer spheres?
2) With -trans default, the origin is set to 0,0,0 in the device
coordinate frame. Why is this different from the above coordinates? Is
it also optimal in another sense? Is there any geometric significance
to the device origin? Is it the centre of the best fitting sphere to
the sensors?
3) Is the following statement correct? "As the expansion origin moves
further from the sensors, the inner sphere will become larger and so
contain more non-neural sources. On the other hand, as the origin
moves closer to the sensors, the volume between the inner and outer
spheres will become larger, leaving a larger number of sources
unmodelled by the inner and outer expansions."
Many thanks,
Danny
(PS - I am assuming in all cases that I have used -trans to align the
centre of the subject's head to the SSS origin.)
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