I don't know about effects on quantitative diffusion values, besides the
fact that they will have partial voluming in the z direction, which could
lead to lower values. Presumably if the acquisition were consistent across
individuals it would not lead you to detect a difference between study
groups, however you might not be able to directly compare values with
analyses done with isotropic data.
As far as tractography goes, there are two issues with this dataset: 1)
tractography will not be as accurate for pathways with a significant
superior/inferior component as your resolution in that direction is poor.
2) Interpolation by the scanner leading to sub 1mm resolution will result in
increased processing time and memory requirements (increase 4x for both over
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Jenifer Juranek
Sent: Wednesday, March 25, 2009 1:45 PM
To: [log in to unmask]
Subject: [FSL] anisotropic DTI data
I'm curious about the limitations of using anisotropic DTI data for either
FA/MD maps or tractography. The data were acquired in the axial plane on a
3T scanner using 21 directions and b=0,1000. The voxdims were
0.9735x0.9735x3.0. Total scan time is 7'00".
Are there limitations for using this dataset for
ROI-based MD/FA studies?
I hope to get the acquisition changed to 32dir 2x2x2 for new studies.
Many thanks for any comments.