1. A diagnosis assistance system for use with a lung field of a subject, the diagnosis assistance system comprising: an imaging unit structured to perform dynamic imaging of the lung field and generate a plurality of successive image frames; a first analysis unit structured to extract a lung field region from each of the plurality of generated image frames, divide the extracted lung field region into a plurality of regions, and analyze the divided regions correlated among the plurality of image frames, thereby calculating a feature quantity indicating motions of the divided regions; a second analysis unit structured to calculate a feature quantity indicating a motion of the entire lung field region based on at least one of movement of a rib, a diaphragm, a collarbone or a shoulder of the lung field region; and a display unit structured to simultaneously display the feature quantity, the feature quantity being calculated by the first analysis unit and the second analysis unit.