plastimatch LANDWARP: What interpolation type is used in resampling?

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plastimatch LANDWARP: What interpolation type is used in resampling?

Eric Larson
Hi,
  I had a question about the plastimatch LANDWARP landmark-based deformable image registration plugin.  I am somewhat confused as to why the output of this plugin is a volume; I would expect it to be a transform, which could then be applied to the "moving" image via resampling with a  selected type of interpolantion function.  I assume that the module automatically is set to resample the "moving" image using a pre-determined type of interpolation function after the transform is computed and applied, but then I am curious as to what that function type is.  Is the radial basis function type selected for computation of the transform then also used as the interpolation function when the moving image is resampled? 
   Thanks,
       -Eric    

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Re: plastimatch LANDWARP: What interpolation type is used in resampling?

Andras Lasso

Hi Eric,

 

As you observed, Plastimatch Landwarp module currently does not return the resulting transformation in a transform node (it could be nice, but it is not implemented that way). Instead, the module applies the transformation to the input moving volume internally and returns the warped image as the result.

 

The transformation function (tps, gauss, wendland) just determines the moving image voxel position for each warped image voxel position. The interpolation function that is used for computing a voxel value for a non-integer voxel position is entirely different, it’s most probably a simple linear interpolation (you can check the Plastimatch source code or ask Greg Sharp to double-check this).

 

Andras

 

From: [hidden email] [mailto:[hidden email]] On Behalf Of Eric Larson
Sent: January 6, 2013 6:48 PM
To: [hidden email]
Subject: [slicer-users] plastimatch LANDWARP: What interpolation type is used in resampling?

 

Hi,

  I had a question about the plastimatch LANDWARP landmark-based deformable image registration plugin.  I am somewhat confused as to why the output of this plugin is a volume; I would expect it to be a transform, which could then be applied to the "moving" image via resampling with a  selected type of interpolantion function.  I assume that the module automatically is set to resample the "moving" image using a pre-determined type of interpolation function after the transform is computed and applied, but then I am curious as to what that function type is.  Is the radial basis function type selected for computation of the transform then also used as the interpolation function when the moving image is resampled? 

   Thanks,

       -Eric    


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Re: plastimatch LANDWARP: What interpolation type is used in resampling?

Sharp, Gregory C.
Hi Eric,

Hmm, you are right.  Landwarp saves the xform to a vector field file.
We will add the capability to create the tranform node, and send followup
email when it is ready.

Landwarp can save to a file, but it seems Slicer cannot load
a vector field as a transform?  Can that really be true?

Greg
________________________________________
From: [hidden email] [[hidden email]] on behalf of Andras Lasso [[hidden email]]
Sent: Monday, January 07, 2013 12:37 PM
To: 'Eric Larson'
Cc: [hidden email]
Subject: Re: [slicer-users] plastimatch LANDWARP: What interpolation type       is      used in resampling?

Hi Eric,

As you observed, Plastimatch Landwarp module currently does not return the resulting transformation in a transform node (it could be nice, but it is not implemented that way). Instead, the module applies the transformation to the input moving volume internally and returns the warped image as the result.

The transformation function (tps, gauss, wendland) just determines the moving image voxel position for each warped image voxel position. The interpolation function that is used for computing a voxel value for a non-integer voxel position is entirely different, it’s most probably a simple linear interpolation (you can check the Plastimatch source code or ask Greg Sharp to double-check this).

Andras

From: [hidden email] [mailto:[hidden email]] On Behalf Of Eric Larson
Sent: January 6, 2013 6:48 PM
To: [hidden email]
Subject: [slicer-users] plastimatch LANDWARP: What interpolation type is used in resampling?

Hi,
  I had a question about the plastimatch LANDWARP landmark-based deformable image registration plugin.  I am somewhat confused as to why the output of this plugin is a volume; I would expect it to be a transform, which could then be applied to the "moving" image via resampling with a  selected type of interpolantion function.  I assume that the module automatically is set to resample the "moving" image using a pre-determined type of interpolation function after the transform is computed and applied, but then I am curious as to what that function type is.  Is the radial basis function type selected for computation of the transform then also used as the interpolation function when the moving image is resampled?
   Thanks,
       -Eric
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