Motion-compensated reconstruction for limited-angle multiphase cardiac CT

ECG-gated multiphase cardiac CT (MP-CCT) is free of motion artifacts and can provide the extra information of cardiac functions for the diagnosis of coronary artery disease. Used majority as a screening tool, the excessive radiation dose becomes a concern of MP-CCT. In this work, we propose a motion-compensated reconstruction method for MP-CCT with the limited angle acquisition for each phase in order to substantially reduce the radiation dose. MP-CCT of the XCAT phantom with eight cardiac phases was simulated with 90 degrees coverage for each phase. The motion was estimated from images reconstructed by combining projections from two phases (for a full 180 degrees coverage). To reconstruct the image at phase k, the motion fields were used to warp images at phase k to phase j (j = 1 similar to 8 and j.k) so that all projection data could be used for a total variation (TV) constrained reconstruction. The results show that TV reconstruction for each cardiac phase independently (TV-Single Phase) suffered severe limited-angle artifacts. TV reconstruction with two-phase projections (TV-Two Phases) improved the image quality and was suitable for good motion estimation. Motion-compensated TV reconstruction (TV-MC) achieved almost artifact-free images, although some motion errors could be seen. The root mean square error values are 254 HU, 64 HU and 47 HU for TV-Single Phase, TV-Two Phases, and TV-MC, respectively.