[Insight-users] Problem with translation scale and optimizer

[Johnson, Hans J]

Ali

This sounds similar to your findings.

Hans

Sent from my iPhone

> On Feb 18, 2014, at 9:23 PM, "zoro" <k09tranhoan at gmail.com> wrote:
>
> Dear Luis and everyone,
>
> My colleagues found a problem when setting translation scale and optimizer
> in itk. We do understand translation scale's role (to balance dynamic range
> of translation and rotation) but when apply with optimizer, the situation is
> very different.
>
> The situation is very simple. We have two volumes differed only by
> translation about 100mm. When we used rigid registration with regular step
> gradient descent optimizer and setting maximum step length = 0.05, the
> registered result was not good. In fact, moving volume almost didn't move.
>
> So in our considers, setting maximum step length=0.05 means maximum rotation
> = 0.05 rad = 9 degree (normally) but maximum translation = 0.05 mm (very
> small). Moving volume will not move to fixed volume with the number of
> iterations < 1000.
>
> I wonders that how to set maximum step length of rotation and translation
> separately to avoid this situation. In fact, we shrank voxel spacing and set
> all translation scale = 1 to avoid this problem.
>
>
>
> --
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