Dear FSL Gurus,
We have had some trouble analysing rather small brains (70-80mm anterior to posterior) with probtrackx2. Using just one seed mask and one target mask, while all other parameters are default, we get astronomical measures of "connection probability". That is – the sum of seed to target values divided by the total number of streamlines is almost '1' (sum seed2target over all seed voxels / (# streamlines per seed voxel x # seed voxels) ).
There is some local laboratory lore that setting a target mask to be a waypoint mask as well will produce "reasonable" connection probabilities. Indeed this works, but I am not sure why ; it seems counter-intuitive to me.
In general, when do we want to give a target mask more than one function? That is, when should a target mask also be a waypoint mask, or a termination mask, or all three things?
Many thanks,
Jackson
|