Hi. I am interested in doing a TBSS analysis of lambda parallel and perpendicular with MD
subtracted (to discern the magnitude of directional rather than general changes in water
movement). Has anyone done this before and is this a legitimate approach? Any comments
would be appreciated.
Also, I have found that when I subtract MD from L1 (fslmaths L1 -sub MD) I get a range of
around 0 to 0.001500 and a mean of around 0.00025. When I do tbss_1_preproc (TBSS v
1.1 and using a scale factor of 6,000,000 (gives a range of 0 to 9000)), this works for most
images, but there are a couple of subjects where subtracting MD from L1 gives large holes
in my images when I look at the slicesdir output. The data range and mean seems to be
similar for the images with and without holes. I am puzzled as to what this means. Do holes
mean negative values?
I have run dtifit again and can't see any obvious problems with the original images.
Any help would be greatly appreciated!!
|