CT projection simulation problem

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I want to use MC-GPU to simulate CT projections, but encounter a problem.
The attachment is the input file which is modified from the sample file. The 
main changes are "SECTION CT SCAN TRAJECTORY" part. With these modification, I 
expect the projections of the scanned object locating at the center of the 
detector. But the results are not as expected. 
I looked at the coordinates of the source and detector after rotation. The 
coordinates of the source and the center of the detector are the same as 
expected, but the values of "new detector low corner (at +Y)" are not the same 
as expected. I do not quite understand the meaning of these values. Is this the 
coordinates of the low corner of the detector?

Original issue reported on code.google.com by zhao.yun...@gmail.com on 9 Aug 2012 at 3:10

Attachments:

• MC-GPU_v1.2_6voxels.in

[GoogleCodeExporter]

I tested your input file and it works fine for me. 
The only problem I see is that the "SOURCE-TO-ROTATION AXIS DISTANCE" is set to 
40 cm but it would be more logical to set it to 50 cm to have the rotation axis 
at the center of the phantom. 

What is not expected in the results you got, other than the fact that the 
object rotates in a strange way due to the wrong rotation axis distance?

Original comment by andre...@gmail.com on 10 Aug 2012 at 12:04

• Added labels: Type-Question
• Removed labels: Type-Other

[GoogleCodeExporter]

Oh! I set a wrong SOD. Thank you very much! 

Original comment by zhao.yun...@gmail.com on 10 Aug 2012 at 4:55

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Actually your source-to-object distance was correct because you had input the 
exact distance from the focal spot to the surface of the object. 
The problem is that the code asks for the source-to-axis-of-rotation distance, 
which is usually the distance to the center of the object (or the center of 
your region of interest).

Original comment by andre...@gmail.com on 10 Aug 2012 at 2:06

• Changed state: Done

[GoogleCodeExporter]

Original comment by andre...@gmail.com on 10 Aug 2012 at 2:07

• Changed state: Answered