In an electrosurgical generator for generating radio frequency power, the generator includes a radio frequency output stage having two or more output connections, and a power supply coupled to the output stage for supplying power to the output stage. A controller is operable to cause the generator to supply a blended output signal alternating constantly between a first output signal across the output connections in which the radio frequency output voltage developed across the output connections is limited to at least a first predetermined threshold value for cutting or vaporisation of tissue, and a second output signal across the output connections in which the radio frequency output voltage developed across the output connections is limited to a second threshold value for coagulation. There is also provided adjustment means, operable by a user of the electrosurgical generator, for changing between various preset settings for the blended signal, the preset settings each having a predetermined duty cycle of the blended signal that is limited to the first threshold value for cutting or vaporisation, and a predetermined duty cycle of the blended signal that is limited to the second threshold value for coagulation.

Electrosurgical generator and system

An electrosurgical probe comprises a shaft having an electrode array (12) at its distal end and a connector at its proximal end. The array (12) includes a plurality of isolated electrode terminals, and an electrosurgical power supply (28) is provided with a multiplicity of independently limited or controlled current sources and a connector. The electrosurgical probe and the power supply may be connected through their respective connectors so that the independent current sources are connected to individual electrode terminals. By applying very high frequency electrical energy to the electrode array, target tissue may be cut or ablated while heat dissipation through low impedance paths, such as blood and normal saline, will be minimized.

Methods and apparatus for surgical cutting

An impedance feedback electro-surgical system (100) is useful with electro-surgical tools (102) to maintain a preselected control range of tissue impedance within the tissue in contact with the tool (102). The system comprises an active electrode (108) associated with an electro-surgical tool (102), a return electrode (112), in the form of a remote ground pad which is in contact with the patient, an impedance monitoring device (116) and a power control unit (120). Energy sufficient to affect tissue is delivered through the active electrode (108) to tissue and to the return electrode. The impedance measuring device (116) determines the impedance of the tissue based on the voltage differential between the active electrode (108) and ground pad (112). A signal representative of the measured impedance is communicated to the power control unit (120) which adjusts the energy applied to the tissue to maintain a preselected impedance range.

Impedance feedback electrosurgical system

An electrosurgical system including an electrode assembly having two electrodes for use immersed in an electrically conductive fluid has a generator with control circuitry for rapidly reducing the delivered radio frequency output power by at least 50% within at most a few cycles of the peak radio frequency output voltage reaching a predetermined threshold limit. In this way, tissue coagulation can be performed in, for example, saline without significant steam generation. The same peak voltage limitation technique is used in a tissue vaporization or cutting mode to limit the size of the steam pocket at the electrodes and to avoid electrode burning.

Electrosurgical generator method

An electrosurgical probe (10) comprises a shaft (13) having an electrode array (58) at its distal end and a connector (19) at its proximal end for coupling the electrode array to a high frequency power supply (28). The shaft includes a return electrode (56) recessed from its distal end and enclosed within an insulating jacket (18). The return electrode defines an inner passage (83) electrically connected to both the return electrode and the electrode array for passage of an electrically conducting liquid (50). By applying high frequency voltage to the electrode array and the return electrode, the electrically conducting liquid generates a current flow path between the return electrode and the electrode array so that target tissue may be cut or ablated. The probe is particularly useful in dry environments, such as the mouth or abdominal cavity, because the electrically conducting liquid provides the necessary return current path between the active and return electrodes.

System and method for electrosurgical cutting and ablation

A guide wire (15) for supporting monopolar arcing for cutting tissue and for ablating occlusions includes a flexible metal wire (302) including a distal end, an electrically insulating coating (306) extending along the wire, and an electrically and thermally insulating tip (310) having a distal end and attached to the wire, the wire extending through the electrically and thermally insulating tip and forming an electrode (312) at the distal ends of the wire and the tip. An electrosurgical apparatus for cutting tissue and for ablating occlusions includes a pulse generator (5, 6) having a variable output impedance for selectively generating a train of pulses of electrical energy for application to a guide wire (15) having an attached electrode. The pulse generator senses the load impedance and adjusts the output impedance to match the load impedance. The generator measures the relative electrical energy produced by an arc in response to a pulse, compares the relative electrical energy to a predetermined value to determine an energy difference, and adjusts the energy of a subsequent pulse to reduce the energy difference toward zero.

George C. Rosar

Papers

Electrosurgical apparatus and method.