I am trying to dissect fibers passing through two ROIs.
In order to do so, I am using
tckedit WB_tractogram.tck -include ROI1 -include ROI2 OUTPUT.tck -force
where the WholeBrain (WB) tractogram is a 20-Million-fiber whole-brain tractogram.
• My first question is whether using the 20M-fiber WB tractogram is a good approach or I should decrease the number of fibers of the tractogram from 20M to 2M and then run tckedit. I opted for the 20M-fiber tractogram since I get more fibers between the two ROIs, but I am not sure whether this is right. Since the threshold to consider that a tract exists at an individual level is usually set at 10 fibers, I am concerned that my results (the existence/not existence of that tract) are biased by the number of fibers of my WB tractogram. In other words, it is easier to find 10 fibers that pass through my ROIs with a 20M WB tractogram than with a 2M tractogram.
• My second question is whether I should use tckedit (with the WB tractogram) or tckgen (just considering my ROIs).
I apologize if my questions are too basic and thank you very much for the help you provide everyday.