[MINC-users] mincresample and slice-based scaling

[Alex Zijdenbos]

Hi all,

I came across something somewhat unexpected (at least to me), and was
wondering if anybody would be able to clarify this:

I have a volume with a real range [0,255] (signed short, the valid
range=full range of data type, no slice scaling). When I mincresample that
using a linear xfm and some new starts and steps, I end up with a global
range (from mincstats) of [-0.0002770616653,255.0002071]. I am used to
seeing over- and undershoots with tricubic interpolation, but I was always
under the impression that trilinear by definition should maintain the
extrema. When I add the -keep_real_range flag to the mincresample call, the
resulting range is the expected [0,255] (again from mincstats); so this
essentially fixes the problem. But why would the voxel range change when
using trilinear interpolation? Precision issues? Slice scaling issues?
Extrapolation instead of interpolation perhaps?

-- A