How to change the trajectory of the ray source

[JinZhaoMu]

Hello, I am modifying the geometry parameters for a planar CT scan, and now the situation is that both the detector and the ray source are offset during the scan, I have set the detector offset but don't know how to set the ray source offset.

[AnderBiguri]

All is relative positioning. In TIGRE the source doesnt move, so you can't change its position. But of both the detector and source move to the left, that is the same as the scanned object moving to the right. Just change geo.offOrigin 👍

[JinZhaoMu]

Thank you, but my ray source and detector are moving in opposite directions, which makes me wonder.

[AnderBiguri]

@JinZhaoMu All is relative positions, as I said. If you have more complex movement, you will indeed need to calculate what is the appropriate parameters, but given its all relative, you can chose any point as "static". In your description, you are choosing the object as "static". In TIGRE, its the source that must be "static". Recalculate your movement values with this in mind and it will be reconstructed well.

[Woohan0601]

Hello, I have a question and would appreciate your help. When the X-ray source has an offset, do we need to take into account that both SOD and SDD will change accordingly due to the altered geometry? Additionally, if the detector has out-of-plane rotation angles such as pitch and yaw, this could also affect the SDD—should this be considered as well?

[AnderBiguri]

@Woohan0601 what you describe is not enough to help, apologies.

few notes:

• in tigre you can't offset the source. But you can offset the image and detector, which is the same thing as offseting the source (its all relative positions).
• Out of plane rotations don't change SDD, given that SDD is distance from the source to the center of the detector. In nay case, in TIGRE the in-plane rotation of the detector is considered last, so you don't need to change SDD