I am running TBSS-style analysis on MD maps for patients and controls. After
all MD maps were registered to standard space, I run the movie loop to see
how well the skeleton from the FA analysis fits each subject. I noticed that
some of the subject have much higher (often twice the value of other
subjects) MD values throughout the brain, compared to other subjects. These
differences are seen in both controls and patient groups. The subjects that
show high MD values to not seem to show any abnormalities in the FA values.
What would be a possible explanation for these increased MD values?