Image display apparatus, image display method and storage medium storing image display program

An image display apparatus comprising a computer to execute a program to cause the image display apparatus to perform an image displaying process including:

• identifying a peripheral edge of a predetermined part in each of two CT images that are taken in different time periods;
• determining opposite two points on the peripheral edge in one of the CT images, the two points being positioned on a straight line passing through a designated point designated in the one of the CT images;
• identifying two points on the peripheral edge corresponding to the two points on the peripheral edge of the one of the CT images from among points on the peripheral edge in the other CT image based on feature amounts of each point on the peripheral edges in the CT images;
• identifying a distance from the designated point in the one of the CT images to each of the two points determined in the one of the CT images;
• and
• identifying in the other CT image a point satisfying a ratio of the identified distances.

An image display method of displaying a first CT image and a second CT image simultaneously, the first CT image and the second CT image representing the same object but taken in different time periods, the image display method comprising:

• displaying the first and second CT images simultaneously on a display device according to a first display mode;
• determining a target portion designated in the first CT image;
• and
• changing a display mode of a corresponding portion of the second CT image from the first display mode into a second display mode, the corresponding portion corresponding to the target portion designated in the first CT image.