# Problems when working with both fMRI and dMRI data of HCP

**URL:** <https://community.mrtrix.org/t/problems-when-working-with-both-fmri-and-dmri-data-of-hcp/6500>\
**Category:** Uncategorized\
**Tags:** tractography, preprocessing\
**Created:** [March 14, 2023, 7:43am UTC](https://community.mrtrix.org/t/problems-when-working-with-both-fmri-and-dmri-data-of-hcp/6500 "2023-03-14T07:43:39Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![ZackGuo](https://community.mrtrix.org/letter_avatar_proxy/v4/letter/z/b77776/32.png) [@ZackGuo](https://community.mrtrix.org/u/ZackGuo)\
**Post date:** [March 23, 2023, 8:54am UTC](https://community.mrtrix.org/t/problems-when-working-with-both-fmri-and-dmri-data-of-hcp/6500/4 "2023-03-23T08:54:38Z")

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Hello Fiona

Thanks again for your reply~I still have some confusion When performing the transformation between diffusion space and MNI space according to the [files](https://community.mrtrix.org/t/hcp-deformation-files-for-registration-in-mni-template/6122) you provided.

In the `PreFreeSurfer` section of [HCP Pipelines](https://github.com/Washington-University/HCPpipelines), The [registration](https://github.com/Washington-University/HCPpipelines/blob/655e69b5da61464fbdb985c7e98b933dbf655388/PreFreeSurfer/scripts/AtlasRegistrationToMNI152_FLIRTandFNIRT.sh#L152) from T1w to MNI space generated two files, `acpc2MNILinear.mat` generated by `flirt` and `${OutputTransform} (i.e. acpc_dc2standard.nii.gz)` generated by `fnirt`.

A s far as I know, the file `acpc_dc2standard.nii.gz` only contains non linear transformation, and the linear transformation file is not included in folder `<subject>/MNINonLinear/xfms`. I am not familiar with `HCP Pipelines`, and some understanding may be incorrect…

And I donnot understand ““acpc\_dc”” , so could you please interpret the meaning of the term “acpc\_dc” in the context for me? Thank you again~~~

Finally, I have another [problem](https://community.mrtrix.org/t/extract-roi-time-series/6511), could you please help me resolve it if you have free time? Thanks a lot!!!

Zack

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