PROBLEM TO BE SOLVED: To provide an information processor whose operability, when measuring a distribution angle of a predetermined region within a vascular tomographic image is improved, and to provide its processing method and a program.SOLUTION: When an inner wall region of a blood vessel in the vascular tomographic image is detected upon instructions to start angle measurement, the information processor detects a center of the detected inner wall region as a first point, and when the inner wall region of the blood vessel is not detected, it detects a center of a catheter within the vascular tomographic image as the first point. Then the information processor detects coordinates of a group of second points designated based on operators instruction, and measures the angle between the first points and the group of the second points.
