1. A method in a Computed Tomography (CT) system for security check, comprising steps of: reading inspection data of an inspected object; inserting at least one three-dimensional (3D) Fictional Threat Image (FTI) into a 3D inspection image of the inspected object, wherein the 3D inspection image is obtained from the inspection data; receiving a selection of at least one region in the 3D inspection image including the 3D FTI or at least one region in a two-dimensional (2D) inspection image including a 2D FTI corresponding to the 3D FTI, wherein the 2D inspection image is obtained from the 3D inspection image or is obtained from the inspection data; and providing a feedback of the 3D inspection image including at least one 3D FTI in response to the selection.