A signal process apparatus (4) includes a contour extraction unit (441) that acquires a plurality of image data items generated by sequential imaging of a subject, and extracts contour components from the acquired plurality of image data items； a shift amount detector (443) that compares shift amounts of contour components extracted by the contour extraction unit between image data items included in each of a plurality of image sets, each of the image sets having a predetermined number of the image data items, and detects a shift amount between image data items included in each of the image sets； and an image selection unit (444) that selects at least one image set among the image sets based on a detection result of the shift amount detector.
