This workflow can be divided into three steps: calibration, transfomation of geometric parameters, using RTK
1.calibration
method1 : DLT and optional optimization on reprojection errors. If you want to understand DLT, detailed process can be seen in paper[1].
method2: use a one-dimensional phantom. see paper[2,3,4]. wish you are good at mathematics.
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transformation of geometric parameters
RTK model[5] is different from a pinhole model( DLT). After obtaining geometric parameters of a pinhole model (the Z axis of the pinhole model here is the rotation axis of CBCT system), you should transform what you get into RTK model.
I cannot share the code for some reasons. Learning Chaper 1,2 in Robotics may help a beginner to understand transformation matrix. A link[6] for Chinese. -
RTK
CBCT system I use is a object-rotated CBCT. 2D X-ray image is 768×768 with 0.56mm/pixel. The rotation direction of turntable is clockwise around the Z axis. Gantry angle is not necessary.
.\rtksimulatedgeometry.exe -n -o ‘’‘////xml’ --sdd --sid --source_x --source_y --proj_iso_x --proj_iso_y --out_angle --in_angle
.\rtkfdk.exe -g -o -p -r “.*.dcm” -v “on” --neworigin “-214.76,214.76,0” --newdirection ‘‘1,0,0,0,-1,0,0,0,1’’ --newspacing “0.56,0.56,1” --hardware “cuda” --spacing --dimension
newdirection is ‘‘1,0,0,0,-1,0,0,0,1’’ because the v diretion of RTK model is opppsite to the v direction of a 2D image.
214.76=(768-1)/2*0.56
[1] New Calibrator with Points Distributed Conical Helically for Online Calibration of C-Arm
[2] Analytic method based on identification of ellipse parameters for
scanner calibration in cone-beam tomography.
[3] A graphical method for determining the in-
plane rotation angle in geometric calibration of circular cone-beam ct
systems
[4] An analytical geometric calibration method for
circular cone-beam geometry,
[5]RTK: RTK 3D circular projection geometry
[6]台大机器人学之运动学——林沛群（含课件+书籍）_哔哩哔哩_bilibili