Hi Simon,
thank you very much for your quick reply. Your analysis was correct, I
needed to redefine the center.
I wish you a very nice day,
best regards,
Vincent
On 2018-10-01 20:43, Simon Rit wrote:
Hi Vincent,
This generally occurs when your detector offset is not adequately
passed to the geometry. When you say that you have "5.2mm and -8mm"
offsets, I guess it is with respect to a centered geometry, where the
central ray hits the detector. For this to be the case in RTK, you
must check that the coordinate (0,0) mm corresponds to the center of
the detector. By default, I guess that tif puts it in the corner. So
you probably need to add to rtkprojections an option like --neworigin
xorig,yorig,0 where xorig and yorig is something like
-0.5*(npixels-1)*spacing.
If that doesn't help, you don't need to share the data, the mhd
headers are sufficient to test the geometry.
Good luck!
Simon
On Mon, Oct 1, 2018 at 5:13 PM vincent <[email protected]
<mailto:[email protected]>> wrote:
Hi everyone,
I am facing a problem when I try to reconstruct an object. I'll
try to
be as complete as possible in the description.
I acquired 18000 views from a custom-made ct scanner, of which I
extracted 360 for the sake of reconstruction speed for my tests. The
images are cropped to 1001*1761 pixels. An external calibration
program
estimated that the x and y detector offsets where 5.2mm and -8mm
respectively. The sdd and sid are 983mm and 483mm. I used those
value
to generate a simulated geometry.
I then created a projection volume with the command
rtkprojections -v -o rec1Proj.mha -p . -r cropped.*.tif --i0 7000
where
I estimated the i0 value on the images background (for the sake of
completeness, I also tested with the automatic value which
resulted in
the same problem)
Finally, I wanted to reconstruct the volume with the command
rtkfdk -g geoCT.xml -p . -r rec1Proj.mha --spacing 0.2 --dimension
1761,1761,1761 -v -o recFDK.mha --hardware cuda
The exact error message is:
Reconstructing and writing... ExceptionObject caught with
writer->Update() in file
~/IPTools/RTK/RTK/applications/rtkfdk/rtkfdk.cxx line 218
itk::ExceptionObject (0x1cf4b90)
Location: "unknown"
File: ~/IPTools/RTK/RTK/code/rtkDisplacedDetectorImageFilter.hxx
Line: 155
Description: itk::ERROR: Cannot account for detector displacement
larger
than 50% of panel size. Corner inf=2.55504 and corner sup=100.826
I had a look at the aforementionned line in the
rtkDisplacedDetectorImageFilter.hxx file but I didn't really
understand
how the corners are computed in the
inputPtr->TransformIndexToPhysicalPoint(inputPtr->GetLargestPossibleRegion().GetIndex(),
corner function.
I have no problem sharing the projections if needed, but they
weight 1.3
Go altogether.
I thank you very much in advance for any kind of help you can provide.
Best regards,
Vincent
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