A compound according to formula II and the pharmaceutically acceptable salts thereof and the method of treating cancer in a patient in need thereof by administration of said compound. A flat region detection part is for detecting an image region in which a difference in brightness between neighboring pixels is small as a flat region from the decoded image signals. When voltages are applied on transparent electrodes 21 and 22, liquid crystal molecules 23 have their longitudinal directions oriented vertically with respect to the electrodes, so that the refractive index of the polymer layers 18 is substantially equal to that of the liquid crystal layers 19, resulting in no development of hologram. The diameter of the distal segment is greater than the diameter of the proximal segment.