Opening Windows – Increasing Window Size in Motion-Compensated ECG-gated Cardiac Vasculature Reconstruction

In interventional angiographic C-arm CT imaging (rotational angiography), 3-D reconstruction of coronary vasculature is a topic of ongoing research. Due to the slow gantry rotation speed, motion artefacts corrupt image quality. Many approaches use retrospective ECG-gating to limit data inconsistencies during reconstruction. This poses a trade-off between gating window size and artefact level. A large gating window reduces undersampling artefacts, but increases motion artefacts and vice versa. In this paper, we investigate how motion compensation can be used to successively increase the gating window size in a bootstrapping process. We use a deformable 2-D–2-D registration between the acquired projection data and a forward projection of the previous reconstruction to estimate motion inside the current gating window. We evaluated the approach using the publicly available CAVAREV platform and on six human clinical datasets. We found that an increased gating window size leads to better homogeneity and resolution of fine detailed structures and a reduction of undersampling artefacts, while motion artefacts can be controlled well up to a gating window size of 80%, depending on speed and amplitude of the motion. In addition, the use of more projection data allows for a sharper ramp filter kernel, increasing the sharpness of the reconstructed structures. The CAVAREV results showed a 10% improvement over the best result published online at the time of this writing.