1. An apparatus comprising: an interface configured to receive information about a first contour defining a first tissue in an image and a second contour defining a second tissue in the image; and a controller configured to perform a correction on at least one of the first contour and the second contour such that the first contour and the second contour do not cross each other, based on the received information, wherein the controller performs the correction such that the first contour and the second contour are in contact with one another based on anatomical characteristics of at least one of the first tissue and the second tissue.