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Creating ROI datasets from Activation Maps
¥The program 3dmerge can find contiguous supra (above) threshold voxel clusters in an activation
(functional) map and then convert each cluster into a ROI with a separate data
value
HThese ROIs can then
be used as starting points for some analysis
¥Example:
3dmerge
-1clust_order 1 200
-1thresh 300 -prefix clust_roi Ôfunc_fred+tlrc[2]ÕH-1clust_order 1 500: Here weÕve told
the program to include voxels as part of
a ÒclusterÓ if they are no more than 1mm apart. The 500 indicates the minimum
volume required to form a cluster.
In this example, a cluster is defined
by 500 or more voxels grouped together, and each voxel is no more than
1 mm apart from each other
of
a ÒclusterÓ if they are no more than 1mm apart. The 500 indicates the minimum
volume required to form a cluster.
In this example, a cluster is defined
by 500 or more voxels grouped together, and each voxel is no more than
1 mm apart from each otherH-1thresh 0.4: Ignore voxels that
donÕt survive your threshold (e.g., 0.4) -- the threshold
could be any stat you have set, a t-test, an F-value, a correlation coefficient,
a mean, etc..
threshold
could be any stat you have set, a t-test, an F-value, a correlation coefficient,
a mean, etc..