An apparatus that can obtain a subtraction image efficiently is provided. An image processing apparatus obtains a target image constituted by a set of voxels arranged in a discretized manner； sets a search area in the target image； and obtains, in a partial area included in the search area, on the basis of at least one of a voxel value included in the partial area or an interpolated value obtained by interpolation of a voxel of the target image, at least one of a maximum and a minimum of a voxel value or an interpolated value within the search area.
