[Mristudio-users] DiffeoMap Interpolation Accuracy

[susumu mori]

Hi Jeff,

Maybe I didn't quite understand your question, but if you are talking
about the LDDMM-based image segmentation, each ROI is 3D. So, I'm not
sure if you encounter a situation where you deal with a ROI in one
slice, although maybe this is not relevant to your question.

Suppose your original image is 3mm and you resample it to 1mm. Then if
you draw one 2D ROI, you have a choice of 3 slices within the native
3mm slice. The center slice could be identical to the original image
but the edge two slices may be interpolated if you used trilinear
interpolation option. If you use the nearest neighbor, you simply get
3 1mm copies of the original 3mm slice.

I believe your question can be generalized as "what is the effect of
interpolation". Interpolation is a difficult issue. If you have an FA
map and interpolate it, you get a different result from interpolating
a tensor map and re-calculate a FA map from the interpolated tensor
map. There are also multiple options for interpolation. I would
recommend you to stick with one method and I don't think that we can
conclude one is better than the other.

You can also bring the pre-segmented atlas map all the way to your
original image space. In this way, you can at least forget about the
interpolation issue.

Susumu

On Fri, Mar 25, 2011 at 1:47 PM, Jeff Sadino <jsadino.queens at gmail.com> wrote:
> Hello,
> I am wondering about how DiffeoMap upsamples the slice number when
> performing linear registration to the JHU template.  After doing the LDDMM
> process, I have some ROIs that look interesting.  However, these ROIs are
> smaller than my slice thickness.  I am wondering how valid it is to draw
> conclusions about an ROI that exists entirely at sub-native voxel
> resolution.
> Thank you,
> Jeff Sadino
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