1. An image processor, comprising: a storage that stores the volume data of a medical image including a chest of an examined body; a unit configured to specify a range including the heart based upon an air region corresponding to lungs in a tomographic image acquired based upon the volume data as a cardiac search range; a unit configured to detect a ventricular region within the specified cardiac search range; a unit configured to detect the long axis of a ventricle in the detected ventricular region; a unit configured to generate plural sectional images perpendicular to the detected ventricular long axis based upon the volume data; a unit configured to detect the inner wall and the outer wall of the ventricle from each of the plural sectional images; and a unit configured to analyze the ventricle based upon the detected ventricular inner/outer walls.