[Insight-users] Image Registration

[Torsten Rohlfing]

Hi Vikash:

In general the transformation should not map the origin of M to the 
origin of F.

For starters, the direction of the mapping of coordinates is reversed 
with respect to the mapping of image data, so if anything applying the 
transformation to the origin of F should give you the origin of M (so 
that then you can take whatever image intensity you find there, bring it 
back to the space of R and thus build a reformatted moving image that 
matches the fixed image).

But even that won't be true if you used, for example, the image content 
for registration. Unless you have the same anatomical landmark at the 
image origin in both images, why would the registration map one image 
origin to the other? In most cases, there will be image background at 
the origin, because the origin is usually a corner pixel, but in affine 
registration the transformation is global, thus the transformation 
applied to the image background is determined by the transformation that 
aligns the image foreground information in M and F.

Hope this makes sense.

Torsten

> Hi everyone,
> I have a quick question about registration, So, if I do an affine registration of a Moving Image "M" to a Fixed Image "F", and it also results a transformation matrix. Is it so, that when applying the transformation matrix T (directed M->F), to the origin of the moving image, it should give me the origin of the fixed image.
>
>
> When I think about it, it should, but i am getting different results, probably I am missing something,
> Anyone can throw some light on it, it will be really great.
>
>
> Thanks in advance
> Vikash


-- 
Torsten Rohlfing, PhD          SRI International, Neuroscience Program
  Senior Research Scientist      333 Ravenswood Ave, Menlo Park, CA 94025
   Phone: ++1 (650) 859-3379      Fax: ++1 (650) 859-2743
    torsten at synapse.sri.com        http://www.stanford.edu/~rohlfing/

      "Though this be madness, yet there is a method in't"

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