[Freesurfer] DTI directions and slice angulation

Hello Freesurfer experts,

I analysed my DTI data using dt_recon and the resulting fa.nii file. I did ROI analyses using the fa values for each subject. The data were acquired by Siemens 3T Trio-Tim. When I reported the results, I was asked whether the directions were corrected for slice angulation. Reading dt_recon -help, I think there is no such correction applied during the unpacking process, and found that dcm2nii command offered by MRICron does the correction.

I am wondering whether such correction is necessary for FA-ROI analysis, and if there is any potential problems of not using the correction. I'd appreciate any comments/suggestions.

Thank you, Yuko Yotsumoto