Apparatus for visualizing tissue, the apparatus comprising: a tube sized to receive visualization apparatus disposed within the lumen of the tube； a deformable helical thread disposed on the exterior surface of the tube, the deformable helical thread (i) being transformable between a first configuration wherein the deformable helical thread comprises a reduced profile and/or a reduced rigidity and a second configuration wherein the deformable helical thread comprises an expanded profile and/or an increased rigidity, and (ii) when in its second configuration, when the tube is disposed in a bodily passageway so that the deformable helical thread engages the interior side wall of the passageway, the rotation of the tube will induce a relative movement between the tube and the side wall of the passageway； and a thread varying element dynamically varying at least one of the height of the deformable helical thread and the rigidity of the deformable helical thread.
