A device for detaching parietal thrombi from a blood vessel is disclosed, comprising a catheter including at least one catheter section, wherein an outer diameter of the at least one catheter section is changeable and at least one wall opening extends transversely through a wall of the at least one catheter section. The catheter wall along the at least one catheter section is a resilient and deformable material. The catheter is transformed from a smaller catheter outer diameter to a uniform larger catheter outer diameter by a resilient change in shape. A displacement body can be introduced into the at least one catheter section which is transformed in diameter to deform the catheter from the smaller catheter outer diameter to the larger outer diameter for capturing thrombus material.