[Mristudio-users] UNC and IFO

[susumu mori]

Hi Durai,

The term "merge" is vague.

As a nature of deterministic streamline method, it is not possible for two
lines to actually merge regardless of true tract configurations.
Lines come from right always remain right side and those come from left
remain left side.

On the other hand, if we have a white matter location with homogeneous
fiber orientation (e.g. the posterior limb of the internal capsule is
homogeneously blue) and streamlines from different places (e.g. from the
motor and sensory cortices) "merge" into such an area, we could say, the
trajectory from the motor and sensory cortices "merged" into the internal
capsule.

Even in such a case, if you closely look at the tractography results, the
one from the motor and the other from the sensory occupy different
locations inside the internal capsule. Again, as a nature of the streamline
method, these two trajectories are always separated. Then one may say, "no,
they are not merged inside the internal capsule".

Past anatomical studies suggest that the axonal tracts from the motor and
sensory cortices merge into the internal capsule but within the internal
capsule, they occupy different locations. So, we can say the tractography
results faithfully reflect that, but DTI data do not have enough
information to judge if these two axonal bundles are actually separated
inside the internal capsule or they are merged. It's just tractography
method always gives the former result.

I hope this helps to interpret your data.

Susumu


On Mon, Jul 29, 2013 at 8:17 AM, Durai Arasan <durai23 at gmail.com> wrote:

> Hi All,
>
> Is it true that the fronto occipital fasciculus and the uncinate *merge*in the anterior portion of their tracts? I am unable to obtain these tracts
> in a non-overlapping manner in all subject data I have.
>
> Please refer to the circled merging region in the images attached
> (courtesy: Katherine Narr, LONI).
>
> Thanks
> Durai
>
>
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