A medical image system, including: a target region extraction section which extracts a target region from a medical image obtained by X-ray imaging of a target site; a first extraction section which extracts an initial region from the target region, the initial region having a brightness value which is equal to or larger than a first reference value; a second extraction section which extracts a region having a brightness value that is equal to or smaller than a second reference value from a region including the initial region in the target region; an acquisition section which calculates areas of the target region, the region including the initial region and the region extracted by the second extraction section, and acquires an index regarding a lesion based on the calculated areas; and a display section which displays the acquired index regarding the lesion.