# Synb0 output in dwifslpreproc
**URL:** https://community.mrtrix.org/t/synb0-output-in-dwifslpreproc/8374
**Category:** Uncategorized
**Created:** [May 26, 2025, 3:49pm UTC](https://community.mrtrix.org/t/synb0-output-in-dwifslpreproc/8374 "2025-05-26T15:49:09Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@LM10](https://community.mrtrix.org/u/LM10)
#### Post date: [May 26, 2025, 3:49pm UTC](https://community.mrtrix.org/t/synb0-output-in-dwifslpreproc/8374/1 "2025-05-26T15:49:09Z")
Hi everyone,
I’ve seen a few threads about using Synb0 output in dwifslpreproc but they were from a while ago and the solutions mentioned there are not working for me. If anyone knows how synb0 results are supposed to be passed to dwifslpreproc I’d appreciate any pointers!
I tried what is described here [Synb0 for dwifslpreproc: How?](https://community.mrtrix.org/t/synb0-for-dwifslpreproc-how/6386), i.e. `for_each sub* : dwifslpreproc IN/dwi/PRE_denoised_dwi.mif IN/dwi/PRE_denoised_preprocessed_dwi.mif -fslgrad ../../sourcedata/IN/dwi/*bvec ../../sourcedata/IN/dwi/*bval -rpe_none -pe_dir AP -readout_time 0.0365754 -eddy_options " /home/rds/hpc-work/synb0/OUTPUTS/topup"` , which returned the error message `/home/rds/hpc-work/synb0/OUTPUTS/topup: is an unrecognised token!`.
Also I think there has been a small change in the synb0 code since that discussion because it does not create OUTPUTS/topup when I run it, so for the purpose of this I created the OUTPUTS/topup directory and moved the 4 topup outputs (topup\_movpar.txt, b0\_all\_topup.nii.gz, b0\_all.topup\_log, topup\_fieldcoef.nii.gz) into it. I’m not sure if this is where the issue lies.
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### Author:  [@AmirHussein](https://community.mrtrix.org/u/AmirHussein)
#### Post date: [June 5, 2025, 7:27am UTC](https://community.mrtrix.org/t/synb0-output-in-dwifslpreproc/8374/2 "2025-06-05T07:27:45Z")
Hi,
In the `-eddy_options` you should provide the relevant eddy flag ([eddy/UsersGuide](https://web.mit.edu/fsl_v5.0.10/fsl/doc/wiki/eddy(2f)UsersGuide.html)). In your case, you should provide `-eddy_options " --topup=path/to/topup"` (Don’t forget the space!). Hope it works!
Best,
Amir