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

[Matt McCormick]

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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