A needle electrode deployment shaft comprising a central member having a proximal end, a distal end, a longitudinal axis therebetween, an outer surface, and a plurality of needle electrode advancement channels. Each channel has an axially aligned proximal portion and an outwardly directed distal ramp portion wherein the proximal portion is straight and parallel to the longitudinal axis and wherein the ramp portion follows an arcuate path and each ramp when viewed axially has (1) a ramp entrance located at a first angular orientation relative to the longitudinal axis of the needle deployment shaft and at a preselected radial distance between the longitudinal axis of the central member and the ramp entrance and (2) a ramp exit located at a second angular orientation angularly offset from the first angular orientation and on an outer surface of the central member, wherein said arcuate path increases a transverse component of the path relative to that of a path not having an offset ramp entrance and exit； and a plurality of needle electrodes having tissue penetrating tips slidably received in said channels.
