We had the exact same experience – and I also don’t think there was any evidence in the original paper of the method introducing artefacts that weren’t already there. So I asked Elias Kellner about this a while back, and he also thinks it’s perfectly fine to use. Here are selected parts of his thoughts on the issue (I hope he doesn’t mind me sharing them here…):
The unringer does not introduce or amplify additional artifacts. If there is “true” ringing, it removes it; to the rest, only a slight smoothing is introduced (but it does never “oversmooth”)
So in general, we fully support the statement that it is safe to apply it to any MR image as a black box.
But again, I think that additional smoothing in PF direction is not too strong (as you also observed), and for now, I would suggest to write in the help something like:
Note that this method is designed to work on images acquired with full k-space coverage. Running this method on partial Fourier (‘half-scan’) data will not fully remove the artifact, and you will observe residuals of the original artifact in the partial-fourier direction, but it is safe and worthwhile to apply it also in this case.
I guess it’s about time we updated the help text as suggested… 