[Mristudio-users] Fiber branching

[susumu mori]

FACT algorithm never branches. From one seed, only one unbranched line
propagates. However, there is a very important thing you need to know.

If you draw an ROI with 10 pixels and start FACT from these 10 pixels, you
get 10 unbranched lines passing through the ROI.

Alternatively, you can do a brute-force approach, in which you start FACT
from every single pixels inside the brain (above FA threshold). Maybe you
can find 10s of thousands of seed pixels and the equal number of propagated
lines in this way. Then you can retain all tracking results that go through
the 10-pixel ROI.

In this case, you likely to find more than 100 lines going into the ROI.
This is because many FACT reconstructed lines merge. So, even if FACT can
not branch, it can merge if you are using a brute-force method. The' speed
and simplicity of FACT algorithm allows us to use this "reverse" approach
within a short time (and this is what DtiStudio is using).

This aspect of FACT is often overlooked when it is compared to other more
sophisticated (but complex) methods.

On Wed, Sep 23, 2009 at 12:06 AM, [Seongjin] <choisj70 at gmail.com> wrote:

> Dear all,
>
> This might be a very naive question. But I need to know. Do the fibers
> tracked by FACT algorithm in DTIStudio contain branched fibers?
>
> As an example, let's consider some fibers passing through an ROI drawn in
> the mid-sagittal plane.
> In this case, the number of fiber passing through the ROI and the number of
> all fibers tracked are the same?
> If they are the same, it would be simply fiber panning. If the number of
> fibers tracked is more than the fibers passing through the ROI, then, it
> might be the case of branched fibers.
>
> Is there any opinion on this?
>
> Thanks.
>
> -SC
>
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