Systems and methods are provided for applying a high frequency voltage in
the presence of an electrically conductive fluid to create a relatively
low-temperature plasma for ablation of tissue adjacent to, or in contact
with, the plasma. In one embodiment, an electrosurgical probe or catheter
is positioned adjacent the target site so that one or more active
electrode(s) are brought into contact with, or close proximity to, a
target tissue in the presence of electrically conductive fluid. High
frequency voltage is then applied between the electrode terminal(s) and
one or more return electrode(s) to generate a plasma adjacent to the
active electrode(s), and to volumetrically remove or ablate at least a
portion of the target tissue. The high frequency voltage generates
electric fields around the active electrode(s) with sufficient energy to
ionize the conductive fluid adjacent to the active electrode(s). Within
the ionized gas or plasma, free electrons are accelerated, and
electron-atoms collisions liberate more electrons, and the process
cascades until the plasma contains sufficient energy to break apart the
tissue molecules, causing molecular dissociation and ablation of the
target tissue.