# Preprocessing error when trying to concatenate all b-images

**URL:** https://community.mrtrix.org/t/preprocessing-error-when-trying-to-concatenate-all-b-images/6875
**Category:** Uncategorized
**Created:** [August 14, 2023, 6:47am UTC](https://community.mrtrix.org/t/preprocessing-error-when-trying-to-concatenate-all-b-images/6875 "2023-08-14T06:47:29Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![H.A.N.K](https://community.mrtrix.org/user_avatar/community.mrtrix.org/h.a.n.k/32/4793_2.png) [@H.A.N.K](https://community.mrtrix.org/u/H.A.N.K)
#### Post date: [August 14, 2023, 6:47am UTC](https://community.mrtrix.org/t/preprocessing-error-when-trying-to-concatenate-all-b-images/6875/1 "2023-08-14T06:47:29Z")

</div>

Hi MRtrix Community,

I am completely new to MRtrix, as such I have just started the BATMAN tutorial and am struggling with the preprocessing step. When attempting to concatenate the b-images I keep getting this error:

mrcat: [ERROR] unknown format for image “b1000\_AP/”  
mrcat: [ERROR] error opening image “b1000\_AP/”

Any help would be greatly appreciated!