[MINC-users] Register and Display: internal representation?

[Robert VINCENT]

Christopher,

I'm not certain what's going on here, but it could be that the valid_range
attribute is not set properly.  Could you send me the output of
mincinfo or mincheader on the input & output files?  It might also be
interesting to compare the results when performing the equivalent
subtraction with minccalc.

	-bert

On Fri, 25 Jun 2004, Christopher Bailey wrote:

>
> Dear MINC-users,
>
> I want to subtract one 3D (frame) from another:
>
> newframe = frame1 - frame0
>
> I use mincmath as follows (correct?):
>
> mincmath -sub frame1 frame0 newframe
>
> Both frames are signed floats with slightly different ranges (0->2e5 and
> 0->2e6) and are coregistered. They both contain lots of zeros at the edges
> of the image. When I open "newframe" in either register or Display, those
> same voxels that should still be zero, now have a mysterious value of
> -185.253! Doing the subtraction the other way round yields +185.253.
>
> I opened "newframe" in AFNI, which DID show zeros in the edge voxels! I
> also did a mnc2ana on the file and looked at it in mricro---again zeros
> on the edges as it should be.
>
> So what is going on with register and Display? We have concluded it must
> be an internal representation issue, but I would still like comments on
> this. I'm of course concerned about doing further analysis on these
> files---I want zero to be zero!
>
> All the best,
>
> Chris Bailey
> Center for Functionally Integrative Neuroscience
> Aarhus General Hospital, Denmark
>
>
>
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