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19 March 2014Effective one step-iterative fiducial marker-based compensation for involuntary motion in weight-bearing C-arm cone-beam CT scanning of knees
We previously introduced three different fiducial marker-based correction methods (2D projection shifting, 2D
projection warping, and 3D image warping) for patients’ involuntary motion in the lower body during weight-bearing Carm
CT scanning. The 3D warping method performed better than 2D methods since it could more accurately take into
account the lower body motion in 3D.
However, as the 3D warping method applies different rotational and translational movement to the
reconstructed image for each projection frame, distance-related weightings were slightly twisted and thus result in
overlaying background noise over the entire image. In order to suppress background noise and artifacts (e.g. metallic
marker-caused streaks), the 3D warping method has been improved by incorporating bilateral filtering and a Landwebertype
iteration in one step.
A series of projection images of five healthy volunteers standing at various flexion angles were acquired using a
C-arm cone-beam CT system with a flat panel. A horizontal scanning trajectory of the C-arm was calibrated to generate
projection matrices. Using the projection matrices, the static reference marker coordinates in 3D were estimated and
used for the improved 3D warping method.
The improved 3D warping method effectively reduced background noise down below the noise level of 2D
methods and also eliminated metal-generated streaks. Thus, improved visibility of soft tissue structures (e.g. fat and
muscle) was achieved while maintaining sharp edges at bone-tissue interfaces. Any high resolution weight-bearing
cone-beam CT system can apply this method for motion compensation.
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Jang-Hwan Choi, Andreas Maier, Martin Berger, Rebecca Fahrig, "Effective one step-iterative fiducial marker-based compensation for involuntary motion in weight-bearing C-arm cone-beam CT scanning of knees," Proc. SPIE 9033, Medical Imaging 2014: Physics of Medical Imaging, 903312 (19 March 2014); https://doi.org/10.1117/12.2043771