Spatially Resolved Automatic Cardiac Rest Phase Determination in Coronary Computed Tomography Angiography (CTA)

Abstract

We present a method to determine separately and automatically the individual cardiac rest phases of the right coronary artery (RCA), left anterior descending artery (LAD), and circumflex artery (LCX) for optimal image quality in retrospectively ECG-gated coronary CTA. We reconstruct a series of low resolution 3D images over the cardiac cycle to represent the different motion states of the heart. An average surface model of the heart is then automatically adapted to one of these images. The model contains labeled mesh regions corresponding to the typical locations of the three main coronary arteries. From the starting point, the model adaptation propagates over the image series for the entire cardiac cycle and follows the location of the arteries. Optimal phase points for diagnostic image reconstruction are determined as the points of minimal motion calculated from the 4D heart shape model on a per-artery basis. In an initial study of clinical cases, we determined cardiac rest phases individually for the RCA, LAD and LCX, and performed ECG-gated image reconstruction in the artery specific rest phase instead of a default rest phase of the whole heart. In cases where the rest phases differ between the three arteries, image quality is significantly improved using the presented approach. Motion artifacts are reduced and vessels appear less disrupted.