US Patent 7371234 Low profile radiofrequency electrode array

An electrosurgical device for tissue ablation includes a delivery cannula having a lumen and an open distal end in communication with the lumen, wherein an electrode array comprising a plurality of tines is deployable from, and retractable into, the cannula lumen through the open distal end. The electrode array tines have proximal ends secured to a mandrel carried in the cannula lumen, the mandrel being movable axially relative to the cannula, wherein the tines, when the electrode array is retracted into the cannula lumen, are nested in offset, circumferential layers about the mandrel.