[Mristudio-users] Questions regarding Transformation in Landmark

[susumu]

Hi Rajesh,

Currently, our program can not register a tensor to another tensor file.

For linear transformation, most of the information to judge the good
registration comes from brain boundary. Therefore, as long as the brain
boundary is well defined, you can use any images and the results won't be
that much different. In our templates, you can find T1 / B0 / DWI images and
you can choose any of them.

Suppose you chose DWI from our atlas, then you want to use DWI of your data
to perform the linear transformation. Once DWI-to-DWI transformation is
done, the resultant transformation is applied to all loaded images. If FA
and ADC maps are loaded, they are transformed too. In this case, you are not
using FA and ADC to drive the registration. The registration was done
between the two DWI and only the resultant transformation information is
applied to loaded FA and ADC. 

If you save the transformation matrix, you can later apply it to any
co-registered images.

When you transform the tensor field, care must be taken because you have to
instruct Landmarker that it is a tensor file, not an ordinary scalar image,
because tensor requires re-orientations based on the transformation. That is
because there is an dedicated "open *.d" button in Landmarker. Once a tensor
file is loaded through this button, you can find 6 scalar maps for Dxx, Dyy,
Dzz, Dxy, Dxz, and Dyz.

If these images are loaded when the DWI-to-DWI transformation is performed,
these 6 tensor element images are automatically transformed. After the
transformation, you can save all 6 images into one file to recreate a
"registered tensor file". 

You can also apply the transformation to a tensor file if you already
finished the transformation and save the transformation matrix. 

The basic flow of the procedure is very similar for the LDDMM-based
non-linear transformation, although for the LDDMM, you get only a
transformation matrix. So, you have to load FA, ADC, tensor (via "open
*.d"), and other co-registered images and apply the transformation matrix.

-----Original Message-----
From: mristudio-users-bounces at mristudio.org
[mailto:mristudio-users-bounces at mristudio.org] On Behalf Of Rajesh Kumar
Sent: Friday, May 01, 2009 7:41 PM
To: DTI Studio, ROI Editor, Landmarker Questions/Support
Subject: Re: [Mristudio-users] Questions regarding Transformation in
Landmark

Hi List:

I want to normalize tensor map to common space (MNI template) in DTI
studio. Is there anybody who can suggest me how to proceed? I am not
sure that i should use b0 or trace template (in MNI space) for the same.

With regards

Rajesh


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