[MINC-users] minctracc error after initialization fromregister-based xfm: one last question

[Andrew Janke]

On 8/18/07, Audette, Michel <Michel.Audette at medizin.uni-leipzig.de> wrote:
>
> It has to do with which parameters to tweak on minctracc, if one is not working with 1mm resolution MR, but something significantly more high-res. In my case 0.08mm and 0.2-0.3mm for the two volumes, with one volume only covering a small part of the second.
>
> Also, starting from a pretty good estimation: a rigidly registered resampled source volume, based on a transformation obtained via register.
>
> Is it -step value that gets tweaked, or -w_translations, for smaller volumes?

Usually all three.  I was hoping that Mallar (a post-doc of louis) has
had a lot of experience here.

But yes, certainly the step should be modified.  The -w_translations
and so on are scaled by the step so these should be OK. But you will
usually have to modify the -w_rotations parameter. If you use
minctracc -help you will see that it is set to a number that seems to
have no bearing in reality.  in fact it does... :)  the number used
works along the premise that a rotation of x degrees about the COM of
a "head sized object" should amount to a shift of 1mm at the surface
of the "head sized object".  Thus the number does have a meaning, just
not an obvious one.


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