A diagnostic coordinate system specified by a first axis through a third axis is a coordinate system based on a major axis and a minor axis of a follicle F and the starting point is at the position of the center of gravity of the follicle F. The display coordinate system is an XYZ coordinate system. The diagnostic coordinate system is moved in parallel to the display coordinate system from (A) until the starting points are aligned at (B). The diagnostic coordinate system is then rotated until the first axis of the diagnostic coordinate system corresponding to the major axis of the follicle F overlaps the x axis where the angle with the first axis is smallest at (C). Additionally the diagnostic coordinate system is rotated until the second axis of the diagnostic coordinate system corresponding to the minor axis of the follicle F overlaps the z axis where the angle with the second axis is smallest at (D). A tomographic image of the follicle F is formed by an image in a plane that includes the z axis and the x axis an image in a plane that includes the y axis and the z axis and an image in a plane that includes the x axis and the y axis.
