6 June 2000 Determination and correction of the wobble of a C-arm gantry
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Abstract
Digital subtraction angiographic image sequences of a calibration phantom are acquired at 30 frames per second from a C-arm gantry covering an angular arc of more than 180 degrees rotating at 40 degrees/s. For each frame, after XRII distortion correction, the relation between the source and its image plane orientation in 3D space is estimated from fiducial markers in the calibration phantom. This gives a mapping between the three-dimensional calibration object and its two- dimensional projection at each gantry angle. We derive eleven mapping coefficients as a function of gantry angle. We use the coefficients to backproject the contribution to any physical voxel. Thus the wobble correction is incorporated directly into cone-beam backprojection. In the absence of gantry wobble, this method is equivalent to the short-scan Feldkamp algorithm, any deviation of the coefficients from those perfect values can be taken as a measure of the gantry wobble. The mapping method requires no special knowledge of the system geometry and any wobble, twisting of the C-arm or XRII during rotation is automatically included. A phantom with tungsten- carbide beads is reconstructed. Accuracy is obtained by comparing reprojections of the center of the tungsten beads with their known values.
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Michael D. Silver, Anindya Sen, Satoru Oishi, "Determination and correction of the wobble of a C-arm gantry", Proc. SPIE 3979, Medical Imaging 2000: Image Processing, (6 June 2000); doi: 10.1117/12.387658; https://doi.org/10.1117/12.387658
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