[MINC-users] hires vs. lowres registration

[minc-users@bic.mni.mcgill.ca]

Hello,

I've encountered a curious situation with image registration and would 
like to know if anyone has any insight or comments:

I'm aligning two images that represent MRI scans of the same object (i.e. 
the human brain) but in two different modalities (i.e. T2 and T1).  The 
registration process is essentially mritoself which calculates the 
transform function needed to register one image to the other, followed by 
mincresample, which applies the transform and places one image in the same 
space as the other.

Initially we decided to use the hi-res T1 images and to align them to the 
lower resolution T2 images, with the rationale that providing more 
information about the image should lead to a better fit.  But we have 
since found that using the lo-res T1 images actually produces better 
registration (i.e. alignment) results.  Does this make sense and what 
could be happening here within the mritoself and mincresample algorithms 
to cause this?

The lo-res T1 image resolution matches the T2 image resolution, but 
theoretically the hi-res T1 image should be less prone to partial volume 
etc. errors.

Any comments or ideas would be appreciated!


Ernest Lo
NeuroRX Research
Montreal, Canada