The more parameters and iterations then the better the results should be
(in SPM99b anyway). The defaults are 7x8x7 and 12 iterations, which seemed
reasonable. The registration does not change so much after this many
iterations, and 7x8x7 basis functions give you a 1180x1180 matrix to
invert. Many more basis functions than this, and the warping becomes rather
slow. If you find you are getting too much distortion in your normalised
images, then try changing the regularisation (via the defaults button).
Also, the PET template in SPM99b may not be ideal for FDG images, as the
image contrast may differ slightly between your images and the O15-H2O
template.
All the best,
-John
| I am playing around with the number of basisfunctions and number of
| iterations for FDG PET studies. Right now I am using 5 basisfunctions in
| x,y,z and 8 iterations in addition to the affine transformation. Can
| anybody tell me if these are the correct parameters? What are the propper
| parameters for relatively high-count PET studies?
| Many thanks
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