A needle electrode deployment shaft includes a central member and a plurality of needle electrodes. The central member has a plurality of needle advancement channels formed therein. The needle electrodes are disposed within the advancement channels and each advancement channel terminates in a ramp portion which deflects the needles radially outwardly as they are axially advanced. The ramps may be spirally or acutely configured in order to increase the distance through which the needles may be bent as they are axially advanced. Additionally, the central member may have a radially reduced distal tip in order to decrease tissue insertion forces.
