22 March 2007 C-arm calibration: is it really necessary?
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C-arm fluoroscopy is modelled as a perspective projection, the parameters of which are estimated through a calibration procedure. It has been universally accepted that precise intra-procedural calibration is a prerequisite for accurate quantitative C-arm fluoroscopy guidance. Calibration, however, significantly adds to system complexity, which is a major impediment to clinical practice. We challenge the status quo by questioning the assumption that precise intra-procedural C-arm calibration is really necessary. Using our theoretical framework, we derive upper bounds on the effect of mis-calibration on various algorithms like C-arm tracking, 3D reconstruction and surgical guidance in virtual fluoroscopy - some of the most common techniques in intra-operative fluoroscopic guidance. To derive bounds as a function of mis-calibration, we model the error using an a.ne transform. This is fairly intuitive, since small amounts of mis-calibration result in predictably linear transformation of the reconstruction space. Experiments indicate the validity of this approximation even for 50 mm mis-calibrations.
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Ameet Kumar Jain, Ameet Kumar Jain, Michael An, Michael An, Nicha Chitphakdithai, Nicha Chitphakdithai, Gouthami Chintalapani, Gouthami Chintalapani, Gabor Fichtinger, Gabor Fichtinger, "C-arm calibration: is it really necessary?", Proc. SPIE 6509, Medical Imaging 2007: Visualization and Image-Guided Procedures, 65092U (22 March 2007); doi: 10.1117/12.712301; https://doi.org/10.1117/12.712301

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