Robust automatic rotation axis alignment mean projection image method in cone-beam and parallel-beam CT

The rotation axis position is an important parameter of classical reconstruction algorithms in X-ray computed tomography (CT). The use of incorrect values of the axis position parameters during the reconstruction leads to the appearance of various artifacts distorting the reconstructed image. Therefore, to obtain a reconstruction of better quality, automatic rotation axis position determination and misalignment correction methods are of use. Most of the existing high-precision automatic rotation axis position determination methods are either fast, but suitable only within a parallel-beam geometric scheme, or indifferent to the geometric scheme, but computationally laborious. In this paper, we propose a method for auto-detection of two scalar parameters of rotation axis position — axis shift and tilt in the plane parallel to the detector window plane — using a pixel-wise arithmetically averaged projection image. The described method is highly accurate within both parallel-beam and cone-beam geometric schemes whereas it is characterized by robustness to noise in projection data. The method has performed an increase in reconstruction quality when compared with some well-known and still used in practice methods both on synthetic data and on real data obtained in real laboratory conditions.