[Insight-users] Re: Resample Time

[Luis Ibanez]

Hi George,

There is something confusing in your message.

The resample filter doesn't need an optimizer nor a metric.

Resampling is the action that you take once the registration
has finished.


The ITK registration framework does not explicitly resample
the image. It just map the pixel coordinates one by one and
interpolates the values on the moving image.

Could you please let us know what Transform are you using ?

Could you please report the time of ONE iteration ?

Performance of the mapping should be evaluated on ONE iteration,
since poor parameter seetings of the optimizer maybe forcing
the registration to use too many iterations.

I would strongly encourage you to post a minimal in size
but fully working example of your code.  There are so many
parameters involved in registration that it is unlikely that
we could provide you with any useful support only from a
qualitative description of your registration.


Trivial questions:

1) Are you building for release ?
2) What kind of machine are you using ?
3) What is your operating system ?




Trivial answer to your question about performance:

             The way to improve performance
              is to use multi-resolultion.

You can register volumes of size 200x200x200 pixels in about 20
seconds when using 3 levels of a multi-resolution pyramid, by
subsampling by 2 at each level, in a typical Pentium 4 machine
at 2Ghz, and 512Mb of memory.

You can also reduce computation time by using NearestNeighborhod
interpolation instead of LinearInterpolation.




     Regards




         Luis


-----------------------------
Li, George (NIH/NCI) wrote:

> Hi, Luis and all:
> 
> The resampleFilter seems taking longer than expected time
> to update(), usually around 30 seconds, roughly about 500
> iteration time for OnePlusOneEvolutionary optimizer with
> Mattes metric on my computer.
> 
> Is there a way to improve the performance? Or I did miss
> something? I would think voxel coordinate transformation,
> linear interpolation and voxel reassignment should not
> take more than 3 seconds for a regular sized volume, such
> as 320x320x100 volume.
> 
> Thanks,
> 
> George
> 
>