1. A thoracic diagnosis assistance system comprising: a capturing unit which captures a dynamic state of a thoracic portion to generate a plurality of frame images; a deforming unit which sets a reference point in a position corresponding to each other among the plurality of generated frame images, extracts a lung field region from each of the plurality of frame images, and deforms a shape of the lung field region in each of the plurality of frame images so that a distance from the set reference point to an outline of an outer side of the lung field region becomes equal; and a generating unit which analyzes a dynamic state in the lung field region based on the plurality of frame images in which a shape of the lung field region is deformed by the deforming unit, and generates an analysis result image showing a result of the analysis in a corresponding position in the deformed lung field region.