[Mristudio-users] questions about Fiber tracking

[Susumu Mori]

Hi Ying,

Here is my view of "registration".

> Imaging is all about what is where.
> When you quantify images, you have to make sure that you are measuring
the same structures or locations across subjects. This act of identifying
the same thing is "registration".
> For example, you can manually define the hippocampus across subjects. By
doing so, you identify a group of voxels that belong to the hippo and you
"register" the hippo locations across subjects. You defined corresponding
voxels across subjects. In this sense, manual ROI delineation is one of the
registration methods.
> Because the manual delineation is time consuming, people don't want to do
it. Then what we do is to align all images and assume all voxels are
registered automatically. This means, if I pick up an arbitrary location
(like a single voxel), I can immediately locate the corresponding location
(voxel) in each subject by using the same x, y, z coordinates.
> Tractography can also be considered as a registration tool because, for
example, we can identify a group of voxels that belong to the corticospinal
tract across subjects. Therefore, there is nothing wrong with defining the
cst in each subject without image-alignment.
> However, there could be several reasons why you may want to do image
alignment (thus voxel-by-voxel registration) first and then additional
registration by tractography. First, tractography requires manually (or
automatically) defined  ROIs for seed and destination. This could be done
more reproducibly if all images are aligned. Second, after tracts are
defined, you can easily create population-averaged probabilistic maps by
simply adding the 3D masking files that define the tract locations. On the
other hand, if you are just interested in voxel count (size of the tract)
and FA values, image alignment may not be necessary.

Susumu


On Fri, Aug 16, 2013 at 2:25 AM, <wyzyf at mail.ustc.edu.cn> wrote:

>
>
>
>   Hello professor:
>
>     As I understood, fiber tracking analysis with DTI studio should be a
> group analysis and image registration is
>   necessary. Am I right?
>
>     I have finished the image registration with DiffeoMap through linear
> and nonlinear(b0+FA) registration but I don`t
>   know how to achieve group analysis and the registrated FA doesn`t match
> the origin vector.
>
>     Thank you very much~!
>
>                                                     Ying Wang
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