Electrosurgical system

An RF electrode can have a straight shaft to generate an RF heat lesion that is asymmetric about the central axis of the cannula through which the RF electrode is introduced into bodily tissue. For example, system for tissue ablation including a cannula and an electrode, the cannula including an elongated shaft having a proximal end and a distal end, the cannula shaft including an electrically conductive active tip distal to an electrically insulated cannula shaft portion, the cannula shaft including a lumen extending from a proximal opening at the proximal end of the shaft to a distal portion of the shaft.