A first acquisition unit acquires stent regions from each of three-dimensional images. A second acquisition unit acquires blood vessel regions from each of the three-dimensional images. A positioning unit acquires a first positioning result by positioning the blood vessel regions for each of the three-dimensional images. A deviation information acquisition unit acquires deviation information indicating a deviation of a stent from a blood vessel between the three-dimensional images based on the stent regions for the three-dimensional images and a deformation vector which is the first positioning result.