[MINC-users] Registration using only translation and scale in minc

[Andrew Janke]

> minctracc -lsq9 -w_rotations 0 0 0 source.mnc.gz target.mnc.gzno_rotation.xfm
> COG of v1: 60.239826 68.026634 58.329350
> COG of v2: 61.871235 58.958786 59.136723
>    [trans] = 1.631409 -9.067848 0.807373
> Initial objective function val = 0.07533003
> Final objective function value = 0.05163525
>
> more no_rotation.xfm
> Transform_Type = Linear;
> Linear_Transform =
>  0.974233269691467 -0.106358632445335 0.116122744977474 4.05126190185547
>  0.0418491959571838 0.463993549346924 0.0738773718476295 22.1566772460938
>  -0.139944493770599 -0.152131617069244 1.03475058078766 7.68611145019531;
>
> xfm2param no_rotation.xfm
> after parameter extraction
> -center         0.00000    0.00000    0.00000
> -translation    4.05126   22.15668    7.68611
> -rotation      -8.36385    7.62126    5.13547
> -scale          0.98688    0.47170    1.05520
> -shear          0.00000    0.00000    0.00000

Ah! now it begins to make sense..

minctracc works by a two step process, if no initial transformation is
given (I had imagined you were starting with identity or something).
If no initial transformation is given (be that via -transformation or
-identity) then first a PAT transformation is estimated.  From there a
simplex optimisation of this initial guess/stab in the dark is
performed.

Thus you also will have to restrict the initial PAT transformation (or
start from -identity).  This should work:

   minctracc -est_center -est_scale -est_translations \
      -lsq9 -w_rotations 0 0 0 \
      source.mnc target.mnc out.xfm

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