1. A diagnosis assisting apparatus, comprising: image storage means, for storing three dimensional functional images, in which evaluation index data regarding cardiac functions are arranged along the shape of a heart, and for storing three dimensional anatomical images that represent the structures of hearts and coronary arteries; cardiac function bulls eye image generating means, for extracting a cardiac cavity region from a three dimensional functional image and generating a cardiac function bulls eye image by arranging the evaluation index data, which are included in a plurality of cross sections perpendicular to a long axis set within the extracted cardiac cavity region, along the circumferences of concentric circles of which the radius differs for each cross section; coronary artery closed surface calculating means, for extracting coronary artery image data from three dimensional anatomical images and calculating coronary artery closed surfaces that include the extracted coronary artery image data; coronary artery bulls eye image generating means, for extracting a cardiac cavity region from the three dimensional anatomical images and generating a coronary artery bulls eye image by arranging the coronary artery image data, which are included in a plurality of cross sections perpendicular to the long axis set within the extracted cardiac cavity region, along the circumferences of concentric circles of which the radius differs for each cross section; distance calculating means, for defining a plurality of line segments within each of the cross sections of the three dimensional anatomical image that extend radially from the points at which the long axis and the cross sections intersect, and calculating the distance along each line segment from the boundary surface of the cardiac cavity region to the coronary artery closed surfaces; and display control means, for controlling display output such that the cardiac function bulls eye image, the coronary artery bulls eye image, and data representing the distances are displayed simultaneously on the screen of a display device.