A calibration method for misaligned scanner geometry in cone-beam computed tomography

Computed tomography (CT) images often suffer from artifacts caused by misaligned scanner geometry of CT system. Calibration and correction must be done before image reconstruction. A method for calibration of misaligned scanner geometry in cone-beam CT with single-circle orbit is proposed. In this method, a four-point phantom is used to estimate a set of parameters that describe the geometry of a cone-beam CT system. It requires only one projection of the phantom, instead of several projections at multi-angles. An analytical formula is derived, which avoids falling into local minimum. In addition, there is no restriction on any one of the geometric parameters. The simulated results are illustrated. It is proved that this method is applicable and efficient for misaligned scanner.