Catheter for insertion into a vessel, comprising a reversibly inflatable balloon (10, 25) provided in the area of the catheter tip, on the outside of which a stent (11) to be implanted in the vessel is arranged, and at least one imaging device (14, 21, 22) arranged in the area of the catheter tip for optical coherence tomography, which is arranged or configured such that the area of the vessel, in which the balloon (10, 25) is positioned, can be captured.