Fig. 1. Distribution of current density on the exposed-tip Tuohy needle. (  A ) Photomicrograph of the needle tip. (  B ) Geometry of finite element model of the needle tip. (  C ) Current density distribution perpendicular to the plane of the needle orifice. (  D ) Current density perpendicular to the needle orifice (log scale) along a line parallel to the long axis of the needle and bisecting the orifice. (  E ) Current density perpendicular to the needle orifice (log scale) along a line perpendicular to the long axis of the needle and bisecting the orifice.