A method for visualizing the interior of a bodily passageway comprising providing a visualization system comprising a tube, visualization apparatus disposed within the tube, and a deformable helical thread disposed on the exterior surface of the tube, the deformable helical thread 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 increased rigidity; inserting the visualization system into the bodily passageway at a location remote from the site which is to be visualized, with the deformable helical thread being in its second configuration; rotating the tube so as to induce relative movement between the passageway and the tube, whereby to move the visualization apparatus and the site which is to be visualized closer together; and using the visualization apparatus to visualize the interior of the passageway.