All imaging modalities to be evaluated in this study are currently used in clinical practice. They are not experimental methods. The goal is to compare two modalities that have never been directly compared before. The CT angiography utilizes a standard CT scanner and intravenously injected contrast agent to visualize the left atrium. While the 3DATG is a method that achieves similar results to a CT scanner, the difference is that the 3DATG images are acquired by rotating the X-ray source around the patient on a C-arm instead of a dedicated CT scanner.