Hi Paul,
AFNI lectures were very helpful for me to understand the concept of DTI.
But I have still some questions which I couldn’t solve from lecture notes.
My main question is for FA connectivity matrix and NT connectivity matrix.
1. Whole brain FA map can be obtained before tracking process. In order to calculate FA connectivity matrix (ROIs by ROIs), I ran 3dTrackID for probabilistic tracking. Now I can find FA connectivity matrix. For example, if I have a mean FA value between ROI_A and ROI_B from this matrix, this FA value is average value from voxels along the tract? If so, deterministic tracking(one or more streamlines) and probabilistic tracking (volume) provide different mean FA value for the same pair of ROIs?
2. Is NT calculated the same even in deterministic tracking or probabilistic tracking?
3. NT connectivity matrix gives straightforwardly the number of streamlines which shows how strong the pair of ROIs are connected each other through white matter. FA connectivity matrix shows how much directionality between ROIs. Do I understand them right way?
4. For FA connectivity matrix and NT connectivity matrix, why do we consider both differently? For me, both seem to show the strength of connection between ROIs. Is there any proper rationale that we try to see these two differently?
If you can give me answers about these, it will be very helpful.
Thanks,
Jung
