Patent ID: 8585696

Claim:
A tissue ablation probe comprising: a proximal electrode array comprising a first plurality of electrodes; a distal electrode array comprising a second plurality of electrodes; and a shaft carrying the proximal and distal electrode arrays, the shaft comprising a proximal cannula having a plurality of apertures dimensioned for passage of the proximal electrode array and a distal cannula having a plurality of apertures dimensioned for passage of the distal electrode array, the proximal cannula and the distal cannula being electrically isolated from one another by an insulating member, wherein the distal cannula has an uninsulated outer surface located between the apertures of the proximal cannula and the apertures of the distal cannula, the uninsulated outer surface being electrically connected to the distal electrode array, and the uninsulated outer surface and the distal electrode array are insulated from the proximal electrode array, wherein the uninsulated outer surface is exposed during ablation, such that electrical current initially flows between the uninsulated outer surface and the proximal electrode array during ablation to initially form a lesion adjacent to the uninsulated outer surface.