[ITK Community] [Insight-users] Upsampling and Interpolators

[Bradley Lowekamp]

There is a separate filter which is optimized to just upscale an image by an integer factor, called "ExpandImageFilter". I have a little SimpleITK notebook on it here:
http://simpleitk.github.io/SimpleITK-Notebooks/20_Expand_With_Interpolators.html


On Feb 21, 2014, at 2:36 PM, Dženan Zukić <dzenanz at gmail.com> wrote:

> You can upscale by a non-integer multiplier. In fact, you can change extent, orientation of axes etc at the same time with a single resampling step. I don't think that integer multiplier upscaling is optimized, so there should be no performance penalty by not using that case.
> 
> 
> On Fri, Feb 21, 2014 at 3:33 PM, Jose Ignacio Prieto <joseignacio.prieto at gmail.com> wrote:
> Thanks a lot Luis, 
> And does anybody know if you can upsample to a non integer multiplier of the previous resolution. If so, does it have a performance penalty over an integer multiplier?
> 
> Thanks
> 
> 
> On Wed, Feb 19, 2014 at 2:37 AM, Luis Ibanez <luis.ibanez at kitware.com> wrote:
> Hi Jose,
> 
> Yes, your intuition is correct in this case.
> 
> If you keep the images as a 4D image, the interpolator will
> indeed blend values across time points. Since after all, they
> are just seen as another spatial dimension.
> 
> 
> You may want to do the 3D resampling within the original
> 3D images, before you compose them into a 4D image.
> 
> 
> Note that since ITK 4.0 there is a set of classes in ITK
> for managing ND+Time.
> 
> 
> You will find them under
> 
>                 /ITK/Modules/Video/Core/include
> 
> 
> In particular,
> you may find interesting the class
> 
>                          itkVideoStream.h
> 
> 
> where you could put 3D images into a time sequence.
> 
> 
>     Thanks
> 
>          Luis
> 
> 
> 
> 
> On Tue, Feb 18, 2014 at 4:40 PM, Jose Ignacio Prieto <joseignacio.prieto at gmail.com> wrote:
> Hi all, I am trying to upsample an image using this example as base http://www.itk.org/Doxygen/html/Filtering_2ResampleVolumesToBeIsotropic_8cxx-example.html#_a5
> I have MRI cine data with spacing like 1:1:8. I mounted all time frames into a 4D image and I would like to upsample on Z axis to get 1:1:1. I was wondering if I should better divide the 4D image  into a vector of 3D images so the interpolator wouldn't mix different times frames or it doesn't matter. ( also because I am interested in performance). Is it ok to use the linear interpolator for MRI? Or I should use BSPline? If so, is it faster to work on 3D  for the splines?? 
> 
> Thank you very much
> 
> Ignacio Prieto
> 
> Software Developer
> Biomedical Imaging Center
> Pontificia Universidad Católica de Chile
> 
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> 
> -- 
> José Ignacio Prieto
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> Kitware offers ITK Training Courses, for more information visit:
> http://www.kitware.com/products/protraining.php
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