1. A method for rendering of CT image data, comprising steps of: acquiring 2-Dimensional (2D) image data of a background and 2D image data of a target; rendering the 2D image data of the target into a 3-Dimensional (3D) image of the target to obtain a first hit position of a ray; rendering the 2D image data of the background into a 3D image of the background; adjusting the 3D image of the background based on the first hit position; and synthetically rendering the 3D image of the background and the 3D image of the target.