On Jul 11, 2007, at 10:57 AM, Alon Keren wrote:
Hi.
I have been using CARET a lot lately, and found it very powerful
and useful for a variety of applications. There is a feature that I
am interested in, and I think is not available at the moment. I am
interested in a sophisticated measure of distance between nodes:
The "real" distance, or functional or connection distance between
two nodes is neither euclidean nor geodesic. Two nodes on opposite
walls of a sulcus are further away in the connectivity sense then
two nodes on opposite walls of a gyrus, with white matter bridging
the gap. In the first case a geodesic measure is suitable, whereas
in the second an euclidean measure is more adequate. I imagine it
is much more complicated to implement, but a measure of distance
that goes around CSF but cuts through WM would be very useful and
more accurate for functional purposes. For instance I would like to
estimate the relationship between this functional distance and co-
activation of nodes.
I understand what you are asking for, but I do not see a way to
perform this on a surface. Perhaps the distance measurement you are
seeking could be performed by creating topology and coordinate files
from the white and gray matter voxels (a uniform grid) and performing
a geodesic search. This probably would provide the shortest path
through the gray and white matter opposed to the surface which is
gray matter only.
A question on the same topic:
Is there an automatic way to produce a matrix of node to node
geodesic distances (of size #ofNodes^2)?
At this time, the only way to perform geodesic distance operations is
one node at a time using the surface region of interest dialog.
Thanks,
Alon.
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-----------------------------------
John Harwell
[EMAIL PROTECTED]
Department of Anatomy and Neurobiology
Washington University School of Medicine
660 S. Euclid Ave Box 8108
Saint Louis, MO 63110
