Motion-Compensated Cone Beam CT Using a Conjugate Gradient Least Squares Algorithm and EIT Imaging Motion Data

Cone Beam Computed Tomography (CBCT) is an imaging modality that has been used in image-guided radiation therapy (IGRT). For applications such as lung radiation therapy, CBCT images are greatly affected by the motion artefacts. This is mainly due to low temporal resolution of CBCT. Recently, a dual modality of Electrical Impedance Tomography (EIT) and CBCT has been proposed, in which the high temporal resolution EIT imaging system provides motion data to a motion compensated algebraic reconstruction technique (ART) based CBCT reconstruction software. High computational time associated with ART and indeed other variations of ART make it less practical for real applications. This paper develops a motion-compensated conjugate gradient least squares (CGLS) algorithm for CBCT. A motion-compensated CGLS offers several advantages over ART based methods; including possibilities for: explicit regularisation, rapid convergence, and parallel computations. This paper for the first time demonstrates motion compensated CBCT reconstruction using CGLS and reconstruction results are shown in limited data CBCT considering only a quarter of full data set. The proposed algorithm is tested using simulated motion data in generic motion compensated CBCT as well as measured EIT data in dual EIT-CBCT imaging.