I was hoping someone could quickly explain the following.
Say I have a Thalamic seed mask with 1156 voxels, and I run probtrackx with Number of samples = 100
1) If I use no Target, then I get waytotal = 115600, which makes sense (1156*100)
2) If I use a Waypoint mask of a frontal ROI, I got waytotal = 18025
3) If I use that same frontal ROI as an Exclusion mask (and no other target masks) I got waytotal = 115262
Why is it that the waytotal values for (2) and (3) don't sum to 115600?
Or stated differently, I interpret (2) as indicating that 18025 streamlines hit the frontal ROI at some point but (3) seems to indicate that only 115600 - 115262 = 338 streamlines got excluded for hitting the frontal ROI when I used it as an exclusion mask.
thanks,
-MH
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Conte Center for the Neuroscience of Mental Disorders
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