1. An image data registration system for registering three-dimensional (3D) CT image data with two-dimensional (2D) fluoroscopic image data using a plurality of markers, the system comprising: one or more processors; and at least one memory coupled to the one or more processors, the at least one memory having instructions stored thereon which, when executed by the one or more processors, cause the image data registration system to: search for a lateral angle and a cranial angle by sampling values in a 2D grid and finding minima based on the sample values; move a 3D mass center of a marker to a half segment between a source and a 2D mass center of the marker; compute a roll angle; compute 3D translation coordinates, wherein computing the 3D translation coordinates includes: obtaining a parallel translation, and obtaining a perpendicular translation; compute the roll angle and the 3D translation coordinates for a predetermined number of times successively; and overlay the 3D CT image data on the 2D fluoroscopic image data based on the lateral angle, the cranial angle, the roll angle, and the 3D translation coordinates.