I used the FBA pipeline to analyze a specific white matter tract, and I need help understanding what the results (FD/FC/FDC) really mean on a microstructural and/or morphological level.
So for the tract I’m analyzing, I got a significant difference between a control group and a patient group for some metrics but not others. The FD was lower in the patient group, which I take it means the fiber density of that specific tract is significantly lower in the patient group. The FC showed no significant difference between the 2 groups, which is also easily understandable, the tract cross section shows no difference in size between the 2 groups. Finally, the FDC (like the FD) was significantly lower in the patient group, which is the part I’m struggling to wrap my head around. To summarize: decrease of FD and FDC, no difference of FC.
I’m having trouble interpreting what the decrease in FDC (with the no decrease in FC) says about the tract of interest. As far as I understand, FDC is basically a combination of both FD and FC, so the only interpretation that comes to mind is that perhaps the FD was much lower in the patient group that it “dragged down” the FDC enough to compensate for the lack of difference in FC. Does that make any sense? I’m not quite sure how the FDC is calculated, to be honest, so maybe I’m way off. What do you think such a result means??
As always, thanks for the help!