How to set the fan_beam

Hi, I would like to ask how to set the fan-beam. In the CT-example, the cone beam is used including the source setting. If I want to use the fan beam, what should I modify? Do I just need to modify the beam_aperture?

By default in GGEMS, only the cone-beam source is programmed. The command “beam_aperture” influences the generation of particles according to the angles theta and phi. For now, you cannot directly make a cone-beam. If you want to do so, you need to change the code in the file /src/kernel/ at the level of the calculation of phi and theta angle. I think that in a future version of GGEMS, I will add the fan-beam.

Hi, what do you mean is that if I want to change the angle size of the core-beam, that is, “beam_aperture”, I must modify If I keep the angle at 12.5 degrees, I can achieve core-beam? For core-beams with an angle greater than 5 degrees, I remember there is a significant artifact impact. Can the current algorithm with a angle of 12.5 degrees meet the requirements?
In addition, I have another question, which is that I use Python programs to modify and run. If I want to modify the “beam_aperture” you mentioned above, I also need to modify the underlying program GetPrimariesGGEMSXRaySource. cl, right?

The fan-beam in not implemented yet. When I wrote you can modify the is for you if you want implement yourself the fan beam and don’t wait my next release of GGEMS in few months. You can’t just modify the beam-aperture parameter in python to get a fan-beam from a cone-beam in GGEMS.
With Python you can just modify the beam-aperture in entry. I advice you to change is you want to create a real fan-beam source.

Hi,I’m very sorry. I have a few other questions I would like to ask. If I keep the core-beam unchanged and change the detector to one-dimensional (1,512,1), can I also obtain results similar to a fan beam?
What other files need to be modified if I want to delete phi?
Lastly, if I modify this cl file, do I need to recompile cmake?

Yes you right, you can do a one-dimensional detector, I think it’s similar to a fan-beam simulation in this case, but it’s very inefficient because you simulate lot of photons “for nothing”. If you do a one-dimensional detector beware to the photons diffracted inside you object from the cone-beam, I’m not sure it has a big impact on your final result.
If you modify a kernel file (*.cl) it’s not necessary to recompile GGEMS, it could work directly.


Hello, I set the detector to be one-dimensional (1512, 1) to establish a fan-shaped beam, using a particle count of 1e10. However, I found that there are large artifacts around the reconstructed image, and there is usually a large circle around it. What exactly is this large circle? Can the influence of this large circle be eliminated during reconstruction