title: Lack of a Doppler signal from a PTFE graft.
mesh_terms: D006083:Graft Occlusion, Vascular / Q000175:diagnosis*; D006801:Humans; D011138:Polytetrafluoroethylene / Q000627:therapeutic use*; D014463:Ultrasonography
chemical_list: D011138:Polytetrafluoroethylene