[Insight-users] Question about MI

[Henning Meyer]

Even if Mattes MI just takes a random subset it should be a stable
result, which does not change to much when running it over an over
again with the same initial parameters.
Furthermore it should be quite continious, which I guess you asked for.
But if it is just translation and rotation in 2D then why not take an
optimizer - it could to it automatically quite fast.

Henning

2006/6/28, Jonathan Wong <jon.the.wong at gmail.com>:
> Thanks, Henning. Actually, I want to try to semi-automatically obtain the
> registration transform, since I know there is only rotation and translation
> along the z-axis. I don't have a problem with translation, but it seems that
> depending on how far I intialize from the true angle of rotation, it will
> converge to different angle values, which may or may not be correct.
>
> Therefore, I was going to try a series of values, in a specific region, and
> find the lowest metric and use that resulting angle as the actual transform.
> However, since Mattes MI Metric supposedly takes a random subset of samples
> the metric should be somewhat different each time it's run during a process
> (if it runs in a loop).I was wondering if the metric values from running
> registration overagain with different initial values would have metrics that
> would be relative to one another, so I can effectively use the lowest metric
> to essentiall find the global minimum.
>
> Hopefuly I was more clear than previously.
>
> Jon
>
>
> On 6/28/06, Henning Meyer <tutmann at gmail.com> wrote:
> > If I got you right you won't need an optimizer.
> > You just want to have the metric value of you transforms (given in
> angles).
> > You could just create an instance of your metric and you transform and
> > then retrieve the metrics value.
> >
> > Henning
> >
> > 2006/6/27, Jonathan Wong <jon.the.wong at gmail.com >:
> > > Since MI takes a random sub set of samples from the images. Each time i
> run
> > > MI, it could give me a different value.
> > >
> > > Currently I want to try to intialize different angles to the MI
> registration
> > > method and compare their metrics to see which is indeed the correct
> > > registration?
> > >
> > > Would I have to do something with the optimizer, so that the metrics
> will be
> > > a relative value to one another, or can i simply instantiate a new
> > > optimizer?
> > >
> > > Thanks
> > > Jon
> > >
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