You might also consider using unsymmetrical tractography, e.g. use the
anterior optic radiation as your seed and V1 as your target (use
--waypoints=<V1> for your target mask. This should reduce the number of
pathways you find anteriorly, as samples will have to be moving posteriorly
from the seed to reach the target. As you are doing it currently, both
masks are alternately being used as the seed and target, and so tracts that
pass through both masks and continue on beyond the anterior mask will be
tracked when V1 is the seed and the anterior optic radiation is the target,
as Tim says.
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Tim Behrens
Sent: Tuesday, October 30, 2007 4:45 AM
To: [log in to unmask]
Subject: Re: [FSL] ProbTrack problem with symmetric masks (extraneous
fibres)
This is probably because the tracts pass through the two masks and
then go on to other parts of the brain - you can get rid of this
problem with stopping masks.
Cheers
T
On 29 Oct 2007, at 23:58, Clare Emily Bajraszewski wrote:
> Hi everyone,
>
> I have been using a dual-region-of-interest approach (2 masks-
> symmetric on
> FDT, with one mask in the primary visual cortex and another in the
> anterior optic radiation) to track the optic radiations on each
> side, but
> many tracts have been included that are not between the 2 masks.
>
> e.g. tracts crossing the midline, and tracts heading anteriorly to the
> frontal lobe- these are clearly not part of the optic radiations.
>
> Has anyone else had this problem and can anyone help?
>
> Many thanks!
>
> Clare Bajraszewski (Howard Florey Institute)
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