On 8/18/17 10:20 AM, John Anderson wrote:
Hi Dr Greve,
I followed the steps in WIKI to do SUV-surface based analyses + PVC. I
have the following questions and I highly appreciate your input:
1. Why the dimension of the images (mgx.gm, mgx.ctx.gm and
mgx.ctx.subgm) is not like the original SUV image that has been fed
to the pipeline. i.e. I start with image-dimensions 128X128X128 :
2X2X2 and end up with 79X113X102 : 2X2X2
Also FOV is different as well between the original SUV image /256/
and the output mgx images /158/. How this happen? I am I doing
something wrong?
I set up mri_gtmpvc to reduce the field of view to a bounding box around
the head to reduce memory and computational loads. You can turn this off
with --no-reduce-fov
2. Some voxels in the mgx images has negative signal intensity. is
this normal?
Yes. MG works by estimating the contribution of non-GM to GM and
subtracting it out. If the estimate is too high, then it can cause
negative values.
Thank you for any clarification.
John
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