DVF volume ratio (Jacobian) correction commented out in MotionTransform

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
python
Domain
data

Research direction

Read transforms/shared/motion.py:22-25, including _get_vol_ratio and _apply_dvf, to determine whether the commented-out volume-ratio correction is intentional. Check how gated OSEM/BSREM workflows use MotionTransform and define a reproducible conservation check for forward and backward passes; done means the intended behavior is documented and covered by an appropriate test.

Written by the indexing model from the issue text.

Description

Hi, I noticed that in transforms/shared/motion.py:22-25 the volume
ratio computed by _get_vol_ratio is commented out and hardcoded to

  1. _apply_dvf multiplies by this ratio, so for non-volume-preserving
    DVFs the total counts are not conserved between the forward and
    backward passes, which would affect quantitative reconstruction. I'm
    not sure if this was intentional - just wanted to flag it in case the
    missing Jacobian term matters for the gated OSEM/BSREM workflows.
Dominant language
Python
Stars
173
Forks
38
Avg merge
1h 17m
Merged PRs (30d)
5

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