In an imaging system, vascular tomographic images and vascular fluoroscopic images which each include a plurality of frames are collected. A position of an image of the probe included in each of the frames of the fluoroscopic images is acquired. The frame of the fluoroscopic image and the frame of the tomographic image which is taken at substantially the same time as the frame of the fluoroscopic image are displayed at the same time. A position of a blood vessel designated by a user is acquired from the displayed frame of the fluoroscopic image. The frame of the fluoroscopic image which includes the image of the probe at a position closer to the position of the blood vessel designated by the user is displayed at the same time as the frame of the tomographic image which is taken at substantially the same time as the frame of the fluoroscopic image.
