Cardiac C-arm CT: Efficient Motion Correction for 4D-FBP

Cardiac C-arm CT is a promising technique that enables 3D cardiac image acquisition and real-time fluoroscopy on the same system. The goal is to bring 3D imaging to the interventional suite for improved therapy planning, guidance, and monitoring. For the reconstruction of 3D cardiac image data, a complete set of projections from a specific heart phase is required. One approach to reduce motion blurring caused by the beating heart is to acquire multiple sweeps using the C-arm and retrospectively select the projections that are closest to the desired cardiac phase. In order to further improve the temporal resolution, novel image processing algorithms that utilize retrospective motion correction were investigated in this study. The main focus of this work is to extend the well established FDK algorithm to incorporate motion correction during the back-projection step using a subject specific computed motion field. In a simulation study we show that motion blurring can be decreased significantly using the subjects' individual estimated heart motion based on a time series of retrospectively gated FDK reconstructions. In our experiments using an animal model we investigated the following two scenarios: (I) Can the image quality from a single sweep be improved given a subjects' individual prior computed motion field? (II) Can improved image quality be achieved using the full temporal resolution of a multi-sweep scan for motion estimation in combination with motion correction? Our results show that increasing temporal resolution using an first order estimated 4D motion vector field of the subjects' individual heart motion in the FDK-4D algorithm can decrease motion blurring substantially for both investigated scenarios.