> the details of coregistration between spm99 and spm2 appear v.different
> and i have read what is available on the spm2 notes available on the
> website. however i was wondering if there is a descriptin of what exactly
> the information on the top half of my spm2 coregistration output is i.e.
> the xyz co-ordinates (are these some sort of mean transormations?) and the
> 2 histograms? i take i the bottom half is an image from e.g. run1 and then
> and image from run2 to allow you to be able to check how well the
> registrartion has gone (similar to using checkreg?)
The matrix at the top is an affine transform, which is a way of parameterising
rigid-body transformations. See Section 2.2 of the following for more info:
http://www.fil.ion.ucl.ac.uk/~john/thesis/chapter2.pdf
The histogram on the left is the joint histogram of one image versus the other
before the registration. The one on the right is the joint histogram after
registration (actually, in order to make them easier to visualise, the images
are of log(H+1), where H is the joint histogram).
These joint histograms are an indication of how well the intensity of a voxel
in one image will predict the intensity of the corresponding voxel in the
other image. The following page may help to explain this:
http://www-ipg.umds.ac.uk/d.hill/research/voxSimMeas.html
The bottom part of the figure is basically similar to checkreg.
Best regards,
-John
|