1. An imaging apparatus comprising: a processor configured to generate volume images of an object including a region of interest and extract a reference plane of the volume images, and configured to automatically set a distance from the reference plane to a plane which is preset or input by a user; a memory configured to store distances corresponding to one or more reference data; and an input configured to receive a reference data from the user, wherein the processor sets a distance corresponding to the reference data inputted through the input as the distance from the reference plane, and the processor generates a 3D data of the region of interest based on a cross sectional data of the reference plane and the volume image data existing in the distance.