1. An image processing apparatus, comprising: a first memory configured to store data of a first image including a contrast enhanced cardiac region; a first specification unit configured to specify a specific region included in the cardiac region on the basis of a distribution of pixel values of the data of the first image; a setting unit configured to contract the specified specific region, and set an ROI to the contracted specific region; and a calculation unit configured to calculate an index concerning the set ROI, the index being associated with a function of the specific region, wherein the first specification unit is configured to specify an outer contour and an inner contour of a myocardial region included in the cardiac region, and to specify, as the specific region, a region between the specified outer contour and the specified inner contour.