There is disclosed a system and method for providing a 2-dimensional CT image corresponding to a 2-dimensional ultrasound image by performing an image registration between a 3-dimensional ultrasound image and a 3-dimensional CT image. The system comprises: a CT image forming unit configured to form a plurality of 3-dimensional CT images for an object of interest inside a target object; an ultrasound image forming unit configured to form at least one 3-dimensional ultrasound image for the object of interest; a processor configured to perform image registration between the 3-dimensional CT images and the at least one 3-dimensional ultrasound image to obtain a first transform function; and a user input unit configured to receive input information from a user, wherein the ultrasound image forming unit is further configured to form a 2-dimensional ultrasound image from the at least one 3-dimensional ultrasound image based on the input information, and wherein the processor is further configured to obtain a plurality of 2-dimensional CT images from the 3-dimensional CT images based on the input information and the first transform function and to detect similarities between the 2-dimensional ultrasound image and the 2-dimensional CT images to select one of the 2-dimensional CT images corresponding to the 2-dimensional ultrasound image.