[MINC-users] 6-parameter fitting with minctracc

[Andrew Janke]

On Sun, Feb 21, 2010 at 17:27, EJ Nikelski <nikelski at bic.mni.mcgill.ca> wrote:
>   Thanks Andrew, I shall try your magic and report back to the list
> for completeness ... although the reason for non-linear fitting still
> confuses and angers me ...

One of the main reasons for a lowres nonlinear fit is that heads are
difficult to get back into the magnet perfectly the same as the last
time meaning there _will_ be some geometric distortion. If you are
scanning a phantom/plotting gradients/something else to correct this
then good and well. If not there will be small non-linear differences.

That and as mentioned the "non-brain bits" tend to move so if you do a
whole head registration (no masking) you will expect a single linear
registration to do a poor job of optimising both the non-moving bits
and the mobile bits.


--
Andrew Janke
(a.janke at gmail.com || http://a.janke.googlepages.com/)
Canberra->Australia    +61 (402) 700 883