I suspect that you passed it the name of a dicom directory, instead of a dicom file.

Please see step 6 of tutorial: https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/Tracula
"If DICOM files are available, you just need to specify the first DICOM file in the series that contains the DWIs, assuming the remaining DICOM files from the same series are in the same directory."
From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of Batra, Vinita R. <vbatra@lsuhsc.edu>
Sent: Monday, May 4, 2020 9:24 AM
To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>; Yendiki, Anastasia <AYENDIKI@mgh.harvard.edu>
Subject: [Freesurfer] TRACULA prep roc error
 

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Hello team,

 

I have encountered the following error while running the tracula pre-processing command and was hoping you could help me understand how

to correct this.

 

 

#@# Image corrections Sat May  2 19:57:18 CDT 2020

mri_convert --bvec-voxel /Users/sunlab/Documents/FreeSurferDirs/subjects_109_data/ /Users/sunlab/Documents/FreeSurferDirs/subjects_109//dmri/dwi_orig.nii.gz

mri_convert.bin --bvec-voxel /Users/sunlab/Documents/FreeSurferDirs/subjects_109_data/ /Users/sunlab/Documents/FreeSurferDirs/subjects_109//dmri/dwi_orig.nii.gz 

corRead(): can't open file /Users/sunlab/Documents/FreeSurferDirs/subjects_109_data/COR-.info

$Id: mri_convert.c,v 1.226 2016/02/26 16:15:24 mreuter Exp $

reading from /Users/sunlab/Documents/FreeSurferDirs/subjects_109_data/...

Darwin Suns-iMac-Pro.local 17.7.0 Darwin Kernel Version 17.7.0: Wed Oct 10 23:06:14 PDT 2018; root:xnu-4570.71.13~1/RELEASE_X86_64 x86_64

 

trac-preproc exited with ERRORS at Sat May  2 19:57:18 CDT 2020

 

 

Thank you,

 

Vinita Batra