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° coverage for each phase. The motion was estimated from images reconstructed by combining projections from two phases (for a full 180° coverage). To reconstruct the image at phase k, the motion fields were used to warp images at phase k to phase j (j = 1∼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.