Dear Vittorio,

This is pretty weird… you could in principle fix this by running

fspython -m pip install opencv-python

but the error is probably sign of a wider problem so you’re probably better off installing the latest dev.

Best wishes,

/Eugenio

Juan Eugenio Iglesias

http://www.jeiglesias.com

From: Vittorio Rispoli <vit.rispoli@gmail.com>
Date: Tuesday, March 3, 2026 at 4:47 AM
To: freesurfer@nmr.mgh.harvard.edu <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] nextbrain segmentation tool issue

External Email - Use Caution

Dear all,

I successfully downloaded the atlas, but when I try to run the segmentation tool, I have the following error. Could you help me please?

Best regards

Vittorio

disordinimovimento2@Disordini-Movimento-2 ~ % mri_histo_atlas_segment_fireants --i/Users/disordinimovimento2/Documents/Vittorio/T1.nii.gz --o /Users/disordinimovimento2/Documents/Vittorio/prova_nextbrain --device cpu --side left --mode invivo

Running command:

fspython /Applications/freesurfer/dev/python/packages/ERC_bayesian_segmentation//scripts/segment_fireants.py --i/Users/disordinimovimento2/Documents/Vittorio/T1.nii.gz --o /Users/disordinimovimento2/Documents/Vittorio/prova_nextbrain --device cpu --side left --mode invivo --atlas_dir /Applications/freesurfer/dev/python/packages/ERC_bayesian_segmentation//atlas_simplified

Traceback (most recent call last):

File "/Applications/freesurfer/dev/python/packages/ERC_bayesian_segmentation//scripts/segment_fireants.py", line 9, in <module>

import ext.my_functions as my

File "/Applications/freesurfer/dev/python/packages/ERC_bayesian_segmentation/ext/my_functions.py", line 4, in <module>

import cv2

ModuleNotFoundError: No module named 'cv2'

disordinimovimento2@Disordini-Movimento-2 ~ %