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Hi all, I’m running trac-all for a longitudinal study (2 sessions per subject) using BIDS-formatted DWI data. My sequence includes the following scans per session:

* pre_dwi_b0_AP * dwi_AP (first volume is also b0_AP) * b0_post_dwi_AP * b0_post_dwi_PA (reverse polarity)

I want to use reverse polarity distortion correction (dob0 = 2) and FSL's eddy (doeddy = 2). My dmrirc includes: set pedir = ( AP AP AP PA ). I’ve tried the following:

1. merging AP b0s with dwi and keeping PA separate, using dcmlist, boplist, and b0mlist, but trac-all doesn’t seem to recognize the reverse polarity b0. 2. I also tried merging all into one 4D file — still no luck.

Any advice on how to structure the files and configure dmrirc properly for topup to work? Thanks!

Best wishes,

Mohammed Mudarris, M.Sc.

PhD Candidate | Health, Medical, and Neuropsychology Unit | Leiden University |

Classified as Internal | Intern