I would scan with 25 directions and no gap. For tractography, you would
ideally have isotropic voxels, as otherwise you would be biased against
tracts in the superior/inferior direction. For the TBSS, the FA values you
extract will have more partial volume artifact in the superior/inferior
direction and thus be lower, but if both your groups are similar in this
regard you shouldn't find spurious differences.
How many averages are you intending to acquire?
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Ed Roberts
Sent: Thursday, July 02, 2009 9:05 AM
To: [log in to unmask]
Subject: [FSL] FDT/TBSS inter-slice spacin
Hi,
I'm planning on acquiring some diffusion data for a controls vs patients
analysis.
The system is a GE 1.5T clinical scanner, and I'm hoping to do some TBSS and
tractography analyses.
Because the scanner buffer is limited, I can choose between 30 directions
with a 0.5 or 1mm inter-slice gap; Or 25 directions with no gap. [With voxel
sizes probably about 2x2x3.]
I'd like to know whether having a gap between slices will affect a
tractography analysis, and whether there's a trade-off I need to consider.
Many thanks,
Ed
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