[Insight-users] Setting the spacing of images for rigid registration

[Sims Richard (RKB) Clinical Scientist]

Hi all

 

I have ammended one of the example codes provided with ITK to perform rigid
registration using a Centered Rigid 2D Transform with a Mattes Mutual
Information Metric. My fixed and moving images are both bitmaps which of
512x512 size but have different pixel spacing, 0.898mm/pixel for the fixed
image and 0.527mm/pixel for the moving image. I have successfully registered
these images using a Similarity 2D Rigid Transform (the moving image being
re-scaled to the fixed image), but would like to rigidly register them
without scaling by accouting for their different pixel spacing. I've tried
to explicitly define the spacing of the pixels using the following code:

 

FixedImageType::SpacingType spf;

MovingImageType::SpacingType spm;

FixedImageType::PointType orf;

MovingImageType::PointType orm;

 

spm[0]=0.527344;

spm[1]=0.527344;

//spf[2]=1.000000;

 

orf[0]=0.0;

orf[1]=0.0;

//orf[2]=0.0;

 

spf[0]=0.898438;

spf[1]=0.898438;

//spm[2]=1.000000;

 

orm[0]=0.0;

orm[1]=0.0;

//orm[2]=0.0;

 

fixedImage->SetSpacing(spf);

fixedImage->SetOrigin(orf);

movingImage->SetSpacing(spm);

movingImage->SetOrigin(orm);

 

But it doesn't seem to have an effect... I'm guessing it has something to do
with the resample image filter, but have reached a stumbling block... could
anyone give me a pointer in the right direction?

 

Many thanks,

Richard.

 

 

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