1. An image processing apparatus comprising a processor coupled to a memory and programmed to provide: an acquisition unit configured to acquire a three-dimensional medical image including multiple frames of cross-sectional image from a database and to acquire a text description of an image finding selected by a user from candidates of text description findings after interpretation of the acquired three-dimensional medical image by the user; an identification unit configured to identify the type of an image feature to be calculated based on the acquired text description finding; a calculation unit configured to calculate the identified image feature from pixel values of the multiple frames of cross-sectional image; and a determination unit configured to determine a representative cross-sectional image from the multiple frames of cross-sectional image based on the calculated image feature.