A method to check a tissue located in the vicinity of an object of examination when a treatment instrument such as a puncture needle is inserted into a subject, wherein a first planar image construction block included in an image construction unit reconstructs in real time two-dimensional planar images, which represent subject's slice planes, on the basis of projection data. A stereoscopic image construction block included in the image construction unit constructs three-dimensional stereoscopic images, which represent the subject's slice planes, on the basis of projection data. The planar images constructed by the first planar image construction block are displayed in real time on the screen of a display unit, and the stereoscopic images constructed by the stereoscopic image construction block are displayed on the screen of the display unit while being juxtaposed with the first planar images constructed by the first planar image construction block.