[Insight-users] Joint Histogram same "appearance" number of samples MI Bspline

[Emma Saunders]

Hi Matt,

Thanks for the help.  I am not plotting the histogram however in an image
registration setting, but simply using the images themselves, so can't find
a way to alter the number of samples.  Could you possibly point me in the
right direction.

Is there also ball park time requirements for me to estimate if my
registration process is performing well from a convergence / speed point of
view.  My images are MRI 200 x 30 x 200 voxels.  I haven't reached
convergence as of yet and am running for around 2 hours?

Thanks for your help


On Thu, Dec 5, 2013 at 9:09 PM, Matt McCormick
<matt.mccormick at kitware.com>wrote:

> Hi Emma,
>
> > Hi I'm performing some Bspline registration and have looked on the list
> to
> > find this information give regarding the number of samples.
> >
> >    The number of samples to take must be enough
> >          for producing the same "appearance" of the joint histogram
> >
> >
> > I have plotted the joint histogram but not sure what the same appearance
> > means, how do I estimate the number of samples to use from the joint
> > histogram?
> >
>
> Plotting the histogram is a good first step.  Instead of plotting a
> single histogram, it may be sufficient to plot multiple histograms
> corresponding to different number of samples and look for convergence.
>
> >
> > As an aside what drives the number of grid nodes to use, is it simply the
> > detail in the image, the amount of motion?
> >
>
> It is related to how often the motion is expected to vary, i.e. how
> "high frequency" the motion is expected to be.  However, avoid too
> many grid nodes, at least initially, to prevent the node parameter
> optimization from falling into a local minimum.
>
> Hope this helps,
> Matt
>
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