The invention relates to a method and an apparatus for providing device sizing support, the method comprising obtaining an X-ray image of a vessel, introducing a guide wire having a radiopaque wire tip into the vessel, obtaining an X-ray image of the wire tip, segmenting the wire tip when it passes through the vessel, and providing sizing information relating to the size of the vessel based on the size of the wire tip. The imaging system according to the invention includes means providing functionality for performing the method according to the invention.