1. A computer-readable storage medium storing a computer program for causing a computer to perform a procedure, the procedure comprising: setting a first point on a first part represented in a plurality of tomographic images of an organ; determining a relative position of the first point with respect to a reference position of the first part represented in the plurality of tomographic images and a reference position of a second part represented in the plurality of tomographic images; setting a second point in association with the first point, on a first part in a 3D model representing a structure of the organ, such that a relative position of the second point with respect to a reference position of the first part in the 3D model and a reference position of a second part in the 3D model matches the relative position of the first point; and deforming the 3D model such that, when the plurality of tomographic images and the 3D model are placed in a same coordinate system, a position of the second point matches a position of the first point corresponding to the second point.