Framework for determination of geometric parameters of a cone beam CT scanner for measuring the system response function and improved object reconstruction

We present a mathematical framework for image-based geometric calibration of flat-panel, cone-beam, circular-trajectory based computed-tomography (CT) scanners. The geometric parameters are used to determine the system response function corrected for misalignment. The system response function includes the shift-variant detector point response, and the location dependent response of the focal-spot. We propose a technique to automatically determine the relative geometric parameters of the scanner by including calibration marks on the object container. These parameters include the relative location and orientation of the detector and location of the focal-spot with respect to the object at each scanner rotation angle. The estimated parameters are used to determine the system response function and perform object reconstruction. Results of the system response function and object reconstruction with misalignment correction are provided, showing relevance of our mathematical framework and proposed technique