[Insight-users] Problems with Digitally Reconstructed Radiographs

[Christina Lacalli]

Hello,

I have problems with generating DRRs as it is described in the ITK 
example code 'DigitallyReconstructedRadiograph1.cxx'.
Especially I do not understand how to set the parameters correctly.

I use a real data set with size [256, 256, 17], pixel spacing [1.48, 1.48, 5]mm 
and origin [0,0,0]. According to the instructions from a previous thread I have 
changed the translation parameters to [-190, -190, -42,5] to center the DRR. 
Indeed, the resulting DRR is centered in x and y but it appears too close to the
camera so that I can only see a small region.
However, setting the z-part of the translation to -242,5 - that is the z-position
of the DRR - the resulting DRR seems to be correct?! How do I
calculate the right z-parameter?

Furthermore, when I change the rotation parameters, for example the x-part to
45 and leaving the translation unchanged (z = -242,5), I do not obtain the expected result.
The resulting DRR is identical to the one without rotation, except that it is not centered anymore.
But when I set the z-part again to -42,5 the rotation seems to work, but the
resulting DRR again does not show the whole image.

Can anyone give me some advice how to figure out this problem?!

Thank you

Christina