[Insight-users] difference between 2D and 3D anisotropic filter?

[Luis Ibanez]

Hi Rodrigo,

The reason why it takes longer to compute the filtering in a
degenerate 3D image (a single slice image), is that you are
asking the filter to explore thousands of pixel neighborhoods
that do not exist.

If you have a 3D image and would like to filter the slices
independently, then you must use the ExtractImageFilter in
order to get one slice at a time, and represent this slice
as a 2D image.

Note that running 2D anisotropic diffusion in all the slices
of a 3D volume *is not* equivalent to run anisotropic diffusion
in the original full 3D image.

However, it is common in applications that involve user supervision
to present the user with previews of the effects of 3D filtering
by running the 2D versions of the same filters only in the slice
being presented to the user.  This should be taken with caution
since Slice extraction and Filtering rarely commute.



   Regards,


      Luis



-----------------------
Rodrigo Vivanco wrote:

> HI:
> 
> perhaps someone can answer this. Why does it take so much longer to process a 
> single slice image stored as 3D (x,y,z)=(256,256,1) using the 3D anisotropic 
> filter versus the same image stored as 2D? Also, it displays a warning about 
> using a time-step that may introduce instability in the solution...
> 
> what if I have a 3D image, but would like to filter the slices independently 
> of each other, what would be the best way to do this, that is calling the 2D 
> version of the filter for each slice. Should I make a new 2D Image for every 
> slice? Can I use shally copies using Regions to do this?
> 
> thanks,
> 
> rodrigo
> 
> -------------------------------------------------
> This mail sent through IMP: http://horde.org/imp/
> _______________________________________________
> Insight-users mailing list
> Insight-users at itk.org
> http://www.itk.org/mailman/listinfo/insight-users
>