Not sure about “signed surface to surface distance” as I expect the distance to always be positive. Also not sure about using a non symmetric computation.
If you look at the Segmentation Evaluation Jupyter notebook you’ll see that we used a symmetric computation (
all_surface_distances = seg2ref_distances + ref2seg_distances). Using a non symmetric approach can underestimate the true distances as multiple points from the segmented volume can be mapped to the same point in the reference segmentation and vice versa.
Terminology recommendation: “reference segmentation”, not “ground truth”. The ground truth is only known in simulation, in all other cases it is a “reference segmentation”. By reference segmentation we mean, closest to ground truth using currently available approaches, possibly gets better in the future. Think one expert segmented the structure and later on we have 20 expert segmentations that yield a different/improved reference.