1. A method of automatically detecting an aorta without requiring a user seed input, the method comprising: receiving image data corresponding to a series of axial image slices, wherein the series of image slices is used to reconstruct a three-dimensional (3D) image; searching axial image slices from a starting image slice and calculating a confidence score for a candidate cross-section image of the ascending aorta in an image slice; identifying one or more candidate clusters as a set of candidate image slices that meet an image slice similarity criterion; identifying a candidate cluster having a maximum number of candidate image slices as a seed cluster; identifying an image slice having a highest confidence score within the seed cluster as a seed image slice; and growing a segmentation of the ascending aorta by stacking ascending aorta image disks located in consecutive image slices to the ascending aorta seed disk.