[Insight-users] Image Registration Metric Derivative Calculation

[Aviv Hurvitz]

Hi,

Sometimes it's hard or impossible to compute the derivative of a metric.

In these cases, you could use a derivative-free optimizer such as
AmoebaOptimizer or SPSAOptimizer. These optimizers don't call
GetDerivative() so you can just implement it with an empty function.

Their disadvantage is that they usually require more samples of the metric
(more calls to GetValue()).

- Aviv


2008/7/24 Luis Ibanez <luis.ibanez at kitware.com>:

> Hi 田光建
>
> Yes, if you are creating a new metric, you must
> derive it from itk::ImageToImageMetric, you should
> implement the method
>
>             GetValue( parameters )
>
> and you need to implement the methods:
>
>
>            GetDerivative( parameters )
>
> and
>
>            GetValueAndDerivative(...)
>
> Please take a look at other metrics, for example,
> the MeanSquaresImageToImageMetric would be an
> easy example to follow.
>
>
>   Regards,
>
>
>      Luis
>
>
> -------------
> 田光建 wrote:
> > Thank you for your answer, Luis. If I want to develope my own special
> > image metric, I need to calculate the derivative. What should I do?
> > Should I derive my own class from itk class and override the
> > GetDerivative() and GetValueAndDerivative()?
> >
> >  > Date: Wed, 23 Jul 2008 10:29:29 -0400
> >  > From: luis.ibanez at kitware.com
> >  > To: gjtian at hotmail.com
> >  > CC: insight-users at itk.org
> >  > Subject: Re: [Insight-users] Image Registration Metric Derivative
> > Calculation
> >  >
> >  >
> >  > Hi 田光建,
> >  >
> >  >
> >  > Simply call the method
> >  >
> >  >
> >  > GetDerivative()
> >  >
> >  > or
> >  >
> >  > GetValueAndDerivative()
> >  >
> >  > on the metric that you are using.
> >  >
> >  > It will return an array with the values of the derivative
> >  > of the Metric with respect to the transform parameters.
> >  >
> >  > Regards,
> >  >
> >  >
> >  > Luis
> >  >
> >  >
> >  > ------------------
> >  > 田光建 wrote:
> >  > > Hi,All
> >  > >
> >  > > I want to know how to calculate the metric derivative in ITK for
> >  > > registration. We assume that the first order derivative of the image
> >  > > metric with respect to the transformation parameters, I want to
> > know how
> >  > > to calculate it?
> >  > >
> >  > > Thank you all.
> >  > >
> >  > >
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> >
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