Cc subsegment ordering

[ClePol]

This PR proposes a fix for an unnoticed regression prior to the FastSurfer 2.5.0 release, where the midline was not always oriented anterior->posteior. This caused inconsistent mapping of CC subsegments, where only two large segments would be written to the aseg. This is commit 9a255f0

The second, larger, commit hardens the sub-segmentation logic by not interrupting the control flow when subsegmentation fails for one slice. This can happen for bad CC segmentations, e.g. images with head motion.
We can however recover from this if at least one slice is intact. In that case the subsegmentation can still be propagated to adjacent slices and painted into the aseg. The code also includes a WARNING for this special case.

Testing was done on 5 previously failing cases with --seg_only

[Copilot]

Pull request overview

Fixes a regression where the CC midline was not consistently oriented anterior→posterior (causing CC subsegments to be mismapped), and hardens the per-slice subsegmentation pipeline so a single bad slice no longer aborts the whole run.

Changes:

• In thickness.py, after solving the Laplace level path, flip the equidistant midline if it does not start at the anterior endpoint.
• In postprocessing.py, switch from executor.map + _zip_failed to as_completed, store per-slice results/contours in fixed-position lists (with None for failures), and propagate num_failed_slices cleanly.
• In fastsurfer_cc.py, derive result_slice_indices, pick the nearest valid slice when the middle slice fails (with a warning), gate volume/area-change checks on num_failed_slices == 0, and record selected_morphometry_slice* metrics.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
CorpusCallosum/shape/thickness.py	Enforce anterior→posterior orientation of the midline level path.
CorpusCallosum/shape/postprocessing.py	Reorder slice processing via as_completed and tolerate per-slice failures via positional None placeholders.
CorpusCallosum/fastsurfer_cc.py	Fallback to nearest valid middle slice, expose new fallback metrics, guard volume/area checks when slices failed.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.