Dear everyone,
I am a fairly new user of FSL, and trying to run the command probtrackx from within Matlab. I use the following command:

system(sprintf('probtrackx --mode=seedmask -x %s -l -c 0.2 -S 2000 --steplength=0.5 -P %d --xfm=%s --stop=%s --forcedir --opd -s %s -m %s --dir=%s',src_mask,num_samples,standard2diff_out_mat,tar_mask,bedpostx_merged,nodif_brain_mask,out_dir));

and get the following message:

** ERROR (nifti_image_read): failed to find header file for '~/Documents/fMRI_data/17-R-subject4/e006443/DTI/fsl_dti/masks/target_mask_001'
** ERROR: nifti_image_open(~/Documents/fMRI_data/17-R-subject4/e006443/DTI/fsl_dti/masks/target_mask_001): bad header info
ERROR: failed to open file ~/Documents/fMRI_data/17-R-subject4/e006443/DTI/fsl_dti/masks/target_mask_001
ERROR: Could not open image ~/Documents/fMRI_data/17-R-subject4/e006443/DTI/fsl_dti/masks/target_mask_001
Image Exception : #22 :: Failed to read volume ~/Documents/fMRI_data/17-R-subject4/e006443/DTI/fsl_dti/masks/target_mask_001.nii
terminate called after throwing an instance of 'RBD_COMMON::BaseException'

Has anyone encountered a similar issue? Any help would be most appreciated.
--

Farras Abdelnour
http://sacklerinstitute.academia.edu/FarrasAbdelnour 
Imaging Data Evaluation and Analytics Laboratory (IDEAL)
Department of Radiology | Weill Cornell Medical College
515 E. 71st St., S-125 | New York, NY 10065
email: [log in to unmask]cornell.edu
http://ideal-cornell.com