[Insight-developers] Please help mewithBSplineDeformableTransformation

[Henning Meyer]

Even with extra outside control points set to zero a translation of
the border of the image could happen - the parameter just has to be
adjusted to be a bit higher then resulting translation. But the
optimizer will take care of this.

Henning

2006/3/21, Stefan Klein <stefan at isi.uu.nl>:
> Hi,
>
> The B-spline control points outside the image are added with a reason. They
> influence the deformation of pixels at the edge of the image. If you force
> them to be zero, you somehow constrain the deformation field at the edge of
> the image. This might not at all be what you want, unless you are sure that
> the deformation at the edge of the image approaches zero. In the case of a
> translation of a part of the image close to the edge this assumption would
> for example already be violated.
>
> Regards,
>
> Marius and Stefan.
>
>
>
> At 11:26 21/03/06, you wrote:
> There a number of ways to this.  The one off the top of my head requires
> writing a new BSplineDeformableTransform subclass.
>
> If the control points outside the grid are to be fixed in location,
> then those control points could be stored in the transform's
> "FixedParameters".
> The "Parameters" for optimization would be just the control points over the
> domain
> of the image.
>
> Transforming a point with the new transform is now much more complicated
> because some
> of the spline coeffiecients are in the fixed parameters and some are in the
> parameters to be optimized.  One could keep an extra set of "full control
> points"
> and copy the parameters that are optimized into the full set of control
> points as
> needed, then use the current code for evaluating the deformation.  This is
> relatively
> simple to do but would be very slow in practice. Or, the transform code
> could be written
> such that information was pulled from the fixed parameters or from the
> parameters to be
> optimized as needed to evaluate the current position in the B-Spline. This
> would probably
> be a tad bit slower than the original code for evaluating the transform, due
> to some
> extra conditionals, but would be faster than the first option.  However, it
> requires
> writing new code for evaluating a BSpline.
>
> Another option is write a whole new optimizer that will actually avoid using
> the
> fixed control points in the any of the calculations of the metric dervitive,
> etc.
>
> Jim
>
>
>
>
> -----Original Message-----
> From:
> insight-developers-bounces+millerjv=crd.ge.com at itk.org
> [mailto:insight-developers-bounces+millerjv=crd.ge.com at itk.org]On
> Behalf
> Of Henning Meyer
> Sent: Tuesday, March 21, 2006 10:53 AM
> To: insight-developers at itk.org
> Subject: Re: [Insight-developers] Please help
> mewithBSplineDeformableTransformation
>
>
> Please help, isn't there a way? It has to be useful for every kind of
> flexible registration using BSplineDeformableTransform.
>
>
>
> > To have a switch for optimization would be very useful. Does anybody
> > have an idea? How complicated would a wrapper for
> > BSplineDeformableTransform be?
> >
> > Henning
> >
> > 2006/3/20, Miller, James V (GE, Research) <millerjv at crd.ge.com>:
> > > I think for the LBFGSBOptimizer, you use the SetBoundSelection() method
> along with the SetLowerBound(), SetUpperBound() methods.
> > >
> > > Jim
> > >
> > > -----Original Message-----
> > > From: Henning Meyer [mailto:tutmann at gmail.com]
> > > Sent: Monday, March 20, 2006 9:25 AM
> > > To: Miller, James V (GE, Research)
> > > Subject: Re: [Insight-developers] Please help me
> > > withBSplineDeformableTransformation
> > >
> > >
> > > How would one mark parameters for the optimizer, to tell it not optimize
> those?
> > >
> > > Henning
> > >
> >
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