[Insight-users] FEM Registration

[Mike Bristow]

Hi,

I am a new user of ITK and I have been trying to implement the FEM 
deformable registration examples on some MR data without much luck. The 
DeformableRegistration1 example seems to run OK on the sample 
RatLungSlice data but it is difficult to see the effect. I have tried 
running the same program with the same parameters on some 512x512 
proton density-weighted MR images (to try to register two different 
patients). It seems as though part of the image moves but another part 
doesn't. I tried increasing the number of iterations (25 to 100) with 
pretty much the same result. As well, I tried deforming the same data 
with the FEM/FEMImageRegLMEx example application that implements a 
multiresolution scheme using the default parameters given and the 
results were worse (one local area gets deformed badly with no effect 
anywhere else). Does anyone have some documentation/articles/tips that 
might help me out with selecting better parameters?

I'm also having trouble getting the SquaredDifference of the results of 
the RatLungSlice data. It seems as though I'm having problems because 
the FEM filter writes the output as 32-bit. Rescaling and casting to 
float/internal, diffing, rescaling and then casting to short or long 
for output doesn't seem to work. When I output the 32-bit image as 
short or long it appears corrupted and I get the following error when I 
try to write the diffed image. Any ideas?

itk::ExceptionObject (0x26dab0)
Location: "Unknown"
File: /usr/local/include/InsightToolkit/IO/itkImageFileWriter.txx
Line: 119
Description: itk::ERROR: ImageFileWriter(0x26c000): No ImageIO set, or 
none could be created.

Thanks,
Mike Bristow