[Mristudio-users] entire structure/track or partial structure/track

[susumu mori]

Hi Santosh,

I want to explain the way we define white matter structures.
First, let me use the analogy to geological maps. If you open a map of your
city, there are two types of information; city and county boundaries and
roads. The former is defined by locations and boundaries. The latter, say
Route 40, doesn't belong to any specific locations.

When we define white matter structures, one way is based on locations. Many
classical names of white matter structures are based on locations. For
example, the posterior limb of the internal capsule is the white matter
region between the thalamus and the putamen/GP. Our BPM is based on this
type of  classical "location" definitions of various WM and GM structures.
Of course, many structures with specific names, such as the corona radiata,
do not have clear definitions about their boundaries. So, we had to use our
best, but subjective judgment. Once, somehow, boarders are defined, you can
use the BPM as a criteria to reproducibly define the structures.

To answer your question, the BPM defines almost the entire brain WM into
one of the labels.

Another way to define WM structures is based on tractography. This is
similar to the road information in a map. For example, we can define the
corticospinal tract (CST) that connects the motor cortex and the brainstem.
The resultant streamline pass through the corona radiata, the internal
capsule, the cerebral peduncle, but it doesn't belong to any of these.

If we consider both BPM and tractography are the tools to define ROIs, we
have two different ways to group voxels inside the WM. Depending on the
brain abnormality, one way could be more sensitive than the other.

In our atlas, more than 50 "routes" are predefined based on tractography
results of 20 - 30 normal subjects. You can use them as ROIs, just like you
use the BMP as ROIs. This tractography-based "route" ROIs, however, do not
cover the entire brain.

Susumu




On Wed, Mar 27, 2013 at 8:02 PM, Santosh Yadav
<santoshyadav20076 at gmail.com>wrote:

> Hi MRIStudio experts,
>
> I have one question regarding JhuMniSSTypeIIROI map. Is this ROI map
> includes the entire structure/track or partial structure/track for
> quantification of DTI matrices, for corticospinal tract and fornix?
>
>
> With best Regards,
>
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