Patent ID: 8016825

Claim:
A radio knife comprising: an electrically insulative flexible sheath having a flow channel inside, a distal end portion and a proximal end portion, the distal end portion of the sheath having a distal opening and an axis; a support member which closes the distal opening of the sheath, the support member having a slide hole with a diameter smaller than that of the distal opening extending along the axis thereof; an operating wire axially movable in the sheath; an electrode portion which has a distal end portion and a proximal end portion and of which at least a part forms a rod-shaped portion, the proximal end portion of the electrode portion being coupled to the operating wire, the rod-shaped portion being passed through the slide hole for axial projection and retraction; a control section which is provided on the proximal end portion of the sheath and controls the operating wire to project and retract the electrode portion in the axial direction, the control section having a high-frequency current supply portion which supplies a high-frequency current to the electrode portion; a liquid feed portion which is provided on the proximal end side of the sheath and feeds a liquid through the flow channel inside the sheath towards the distal opening; and a plurality of rectangular openings extending outward from the slide hole, an inner end portion of each of the rectangular openings being in communication with the slide hole and another end of each of the rectangular openings comprising a wall formed entirely in the support member, wherein an entire width of each of the plurality of rectangular openings is set to a dimension such that it cannot be penetrated by the electrode portion.