Bow-tie wobble artifact: Effect of source assembly motion on cone-beam CT
CBCT images of (a) a patient thorax, (b) a cylindrical water phantom centered in the FOV, and (c) an off-centered water phantom. (a) and (b) were reconstructed with our in-house software, and (c) was reconstructed with vendor software.
Full-fan BTF symmetry axis shifts along U axis (perpendicular to gantry axis) as a function of gantry angle.
The relative 2D trajectories of all three BBs on the detector superimposed with one another, with the 3 BB markers attached to the x-ray head cage window.
(a) Superimposed average BB motion trajectories of some representative x-ray head assembly components as illustrated in (b). (b) The three levels of the x-ray head assembly the BBs were set to: (1) at the x-ray tube exit window, (2) at the U blades, and (3) at the back surface of the BTF.
Images of the cylindrical water phantom before and after the BWA correction. (a) Simulated images incorporating the modeled BTF motion, (b) simulated images incorporating BTF motion but reconstructed following a translational correction to NP(U,V,θ0) projection for each angle Eq. (3), (c) experimental images before BWA correction, (d) experimental images with measurement-based correction [angle-dependent normalization scans Eq. (2)], (e) experimental images with the model-based correction [the NP translation strategy Eq. (3)], (f) central profiles on the images (c)–(e).
Along-ray filtration thickness plot of the full-fan BTF with its slope in relative units superimposed. The regions shaded in red show the portions of the filter corresponding to the BWA on reconstructed images.
System description of one OBI system in our clinic following Cho et al. geometric calibration.
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