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Abstract

A tissue sampling instrument for aspirating sample tissue into a needle structure includes a suction chamber having first and second moveable chamber walls arranged to enlarge the volume of the chamber and reduce the pressure therein by movement of at least one of the first and second chamber walls. The needle structure has a lumen arranged in flow communication with the suction chamber to enable communication of the reduced pressure to the lumen in order to promote aspiration of sample tissue into a separate tissue entry aperture formed into the lumen. In one embodiment, the two moveable chamber walls are defined by a displaceable cylinder structure and piston structure moveable within the cylinder structure. The moveable cylinder and piston are formed within a separate housing. The suction action within the chamber is generated by a triggered advancement of the cylinder and cannula secured thereon relative to the piston and stylet so that the suction action is communicated to aspirate sample tissue into the cannula severed by the cutting advancement of the cannula carried on the cylinder. A variable stroke length of the cannula advancement is provided by a multiply-dimensioned stop structure.

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First Claim