An apparatus (100) includes: a expandable structure (140) formable into three dimensional shapes including a range of diameters (D) and corresponding lengths (L) a movable component (106) moveable between a range of positions (124, 126) effecting the range of diameters and a mechanical linkage (110) disposed between the movable component and the expandable structure. The expandable structure is configured to fit inside a working channel (204) of an endoscope (202) when the expandable structure is collapsed. The mechanical linkage is configured to move the collapsed expandable structure through the working channel to a selected location (400) past a distal end (404) of the endoscope and to increase and decrease a diameter of the expandable structure in response to changes in the position of the movable component when the expandable structure is at the selected location.
