Accurate registration of coronary arteries for volumetric CT digital subtraction angiography

In the diagnosis of coronary artery disease with coronary computed tomography angiography, accurate evaluation remains challenging in the presence of calcifications or stents. Volumetric CT Digital Subtraction Angiography is a novel method that may become a powerful tool to overcome these limitations. However, precise registration of structures is essential, as even small misalignments can produce striking and disruptive bright and dark artefacts. Moreover, for clinical acceptance, the tool should require minimal user interaction and fast turnaround, thereby raising several challenges. In this paper we address the problem with a registration method based on a global non- rigid step, followed by local rigid refinement. In our quantitative analysis based on 10 datasets, each consisting of a pair of pre- and post-contrast scans of the same patient, we achieve an average Target Registration Error of 0.45 mm. Runtimes are less than 90 seconds for the global step, while each local refinement takes less than 15 seconds to run. Initial clinical evaluation shows good results in cases of moderate calcification, and indicates that around 50% of severely calcified and previously non-interpretable cases have been made interpretable by application of our method.