[Insight-users] Can metrics handle nodata/void data values ?

[Carolyn Johnston]

> Hi Carolyn,
>
> I probably missunderstood what you meant by "void" points,
> or "void" pixels. I assumed that those were pixels where the
> data is not valid. For example is the image is the result of resampling
> another image, and some areas didn't got any pixel data. That's common
> with ultrasound images.
>
> Could you explain why the "void" pixels will keep changing ?
> Shouldn't they be the same during the entire registration process ?
>
> Thanks
>
>   Luis


No, you have the right idea, although my images tend to be shot through 
with little clumps of void data here and there.

I am not saying that the locations of the void pixels in *image* space 
will change, (they won't) but as different transforms from the parameter 
space are applied, the locations of the moving image's voids in the 
fixed image's frame of reference will change. As I understood it, in 
your previous post you were talking about using a spatial object -- 
referenced to coordinate space, not image space -- to define the void 
mask.  But both the fixed and moving images are likely to have voids.

Carolyn