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张春成

2021/12/03  阅读:37  主题:默认主题

将FSL映射到FreesSurfer上

将FSL统计结果映射到FreesSurfer皮层上

这是一个工作过程记录。 总的目的是将FSL的预处理及统计分析结果, 映射到FreeSurfer的皮层空间上。

工作流可见我的GITHUB工程[1], 可视化代码可见我的ObservableHQ工程[2]


FreeSurfer Analysis Trace

The project records the analysis trace for the FreeSurfer analysis.


Prepare Data

The T1 MRI Image is required to make the cortex surfer. The first step is fit the data into the format of FreeSurfer.

  1. To do that, it is required to make the private subject folder in the $FreeSurfer_HOME/Subjects dir;
  2. And generate the structure as {subject}/mri/orig;
  3. Put the T1 Image into it, and name it like 001.mgz, the script of ./shells/initFolderFreeSurferSubject.sh is generated to do the stuff;
  4. The .mgz file is converted from .nii format by the shell tools named as mri_convert;
    # Convert the T1 MRI image <src> into <dst> file
    # The <src> file can be .nii file
    # Make sure the <dst> ends with .mgz
    mri_convert <src> <dst>
  5. Finally, just operate the magic command recon-all -s {subject} -all and the jobs will be done;
  6. Beware that the operation costs times, like hours;
  7. After the operation, the {subject} folder will be filled with the files ready for everything.

If everything is alright, The {subject} folder will follow the structure as below

name path description
./scripts
./mri
./mri/transforms
./mri/transforms/bak
./mri/orig
./surf
./tmp
./label
./touch
./stats
./trash

I will fill the blank table in later, (maybe not).


Cortex visualization

The freeview tool provides amazing GUI to display the cortex surface.


FSL portable

If you prefer using the FSL to do the fMRI analysis, it provides the registration method to register the feat into cortex surface.

I use 2-steps operation to do the job

  1. Link the directory of feat of FSL, use the script of ./shells/linkFeatDirs.sh;

  2. Register the .nii.gz files in the feat directory to the subject of FreeSurfer, use the script of ./shells/registerFeatdir.sh.

Basically, the functional of reg-feat2anat is used to do the registration

reg-feat2anat --feat $featdir --subject $subject

And it generates the nifti files in the folder of $featdir/reg_surf-<lh | rh>-<$subject | fsaverage>. The nifti has a very strange format of 1974 x 1 x 83 = 163842 for the fsaverage version. The document reads below

In this case, the common space is the left hemisphere of fsaverage. Surface-based smoothing of 5mm FWHM is used. The output lh.cope1.mgh looks like a volume because it is in mgh format, but it is really a surface stored in a volume format (note it's dimensions are 1974 x 1 x 83 = 163842 = number of vertices in fsaverage's surface).

The nifti file can be read by the python package of babel, and the script of ./read_nii.py gives an example.

Todo: I do not quite sure how to align the 1974 x 1 x 84 matrix with the 163842 vertex in the fsaverage's surface. Will arr.flatten() do the job?

The answer is NO, actually, the following code will put the values into the RIGHT position

const raw = await FileAttachment("zstat1.nii.gz.csv").csv();
const arr = [];
// This explains how to align .nii.gz matrix into the vertex array
for (let j = 0; j < 83; j++) {
    for (let i = 0; i < 1974; i++) {
        arr.push(1.0 * raw[i][j]);
    }
}
return arr;

参考资料

[1]

GITHUB工程: https://github.com/listenzcc/freesurferAnalysisScripts

[2]

ObservableHQ工程: https://observablehq.com/@listenzcc/free-surfer-cortex-v2

张春成

2021/12/03  阅读:37  主题:默认主题

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张春成