Hi Sean - Are you using 5.1 or 5.2? What registration options are you
using? Does your patient population have pronounced anatomical changes
(e.g. atrophy) compared to controls? Which pathways did you expect to show
reduced anisotropy in your patient population?
Thanks,
a.y
On Wed, 3 Apr 2013, Sean Hatton wrote:
Hi Freesurfer gurus,
I have been using Tracula to investigate white matter abnormalities in a patient
cohort (n=20) compared to matched controls (n=40). In line with the literature,
we
expected to see reductions in FA in the patients' tracts but instead they have
significantly higher FA means. To double-check, we ran TBSS over the same
cohorts and
got the results as per the literature (I.e. reduced FA in the patient group).
The FA,
RD, AD, MD and volume outputs are normally distributed and there are no extreme
outliners. So wondering:
1. The patient group had significantly reduced tract volumes. If this volume
calculation is incorrect I expect it could influence the calculation of the
mean
FA, RD, AD etc. Is there a way of checking the volume and subsequent
calculations?
2. Yendiki et al 2011 had no corrections – do I need corrections?
3. Should I be thresholding tract stats?
Thank you in advance,
Sean Hatton
Brain and Mind Research Institute
University of Sydney
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