An X-ray CT apparatus according to an embodiment includes an image processing circuit. The image processing circuit generates image data of an inside of a patient. The image processing circuit specifies a position of a tumor and a position of a surrounding site positioned in a surrounding of the tumor, from the generated pieces of image data. The image processing circuit calculates movement information related to movements of the tumor and the surrounding site, based on the specified positions of the tumor and the surrounding site. The image processing circuit calculates a relative relationship between the calculated movement information of the tumor and the surrounding site. The imaging processing circuit calculates a degree of coupling by which the tumor and the surrounding site are coupled, based on a relative relationship between the movement information of the tumor and the surrounding site.
