Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-07-14
2002-01-08
Dvorak, Linda C. M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S098000, C607S113000, C607S116000, C606S041000
Reexamination Certificate
active
06337998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the structure and use of radiofrequency electrosurgical apparatus for the treatment of solid tissue. More particularly, the present invention relates to an electrosurgical system having pairs of electrodes and electrode arrays which are deployed to treat large volumes of tissue, particularly for the treatment of tumors which lie close to the surface of an organ.
The delivery of radiofrequency energy to target regions within solid tissue is known for a variety of purposes. Of particular interest to the present invention, radiofrequency energy may be delivered to diseased regions in target tissue for the purpose of causing tissue necrosis. For example, the liver is a common depository for metastases of many primary cancers, such as cancers of the stomach, bowel, pancreas, kidney, and lung. Electrosurgical probes for deploying multiple electrodes have been designed for the treatment and necrosis of tumors in the liver and other solid tissues. See, for example, the LeVeen™ Needle Electrode available from RadioTherapeutics Corporation which is constructed generally in accord with published PCT application WO 96/29946.
The probes described in WO 96/29946 comprise a number of independent wire electrodes which are extended into tissue from the distal end of a cannula. The wire electrodes may then be energized in a monopolar or bipolar fashion to heat and necrose tissue within a defined volumetric region of target tissue. In order to assure that the target tissue is adequately treated and to limit damage to adjacent healthy tissues, it is desirable that the array formed by the wire electrodes within the tissue be precisely and uniformly defined. In particular, it is desirable that the independent wire electrodes be evenly and symmetrically spaced-apart so that heat is generated uniformly within the desired target tissue volume. Such uniform placement of the wire electrodes is difficult to achieve when the target tissue volume has non-uniform characteristics, such as density, tissue type, structure, and other discontinuities which could deflect the path of a wire as it is advanced through the tissue.
Of particular interest to the present invention, as recognized by the inventor herein, difficulties have arisen in using the multiple electrode arrangements of WO 96/29946 in treating tumors which lay at or near the surface of an organ, such as the liver. As illustrated in
FIG. 1
, a LeVeen™ Needle Electrode used for treating a tumor T near the surface S of a liver L can result in at least some of the tips of electrodes
12
emerging from the surface. Such exposure of the needle tips outside of the liver is disadvantageous in a number of respects. First, the presence of active electrodes outside of the confinement of the organ being treated subjects other tissue structures of the patient as well as the treating personnel to risk of accidental contact with the electrodes. Moreover, the presence of all or portions of particular electrodes outside of the tissue being treated can interfere with proper heating of the tissue and control of the power supply driving the electrodes. While it would be possible to further penetrate the needle electrode
10
into the liver tissue, such placement can damage excessive amounts of healthy liver. Moreover, the heating characteristics of the liver tissue near the surface will be different from those of liver tissue away from the surface, rendering proper treatment of the tumor tissue near the surface difficult even if the electrodes are not exposed above the surface.
In addition to difficulties in treating lesions near the surface of an organ, electrosurgical probes for performing large volume tissue ablation can have difficulty in treating highly vascularized tissues and/or tissue near a large blood vessel. In both cases, heat being introduced by the electrode can be rapidly carried away by the blood, making the heating and control of temperature in the tissue difficult.
For all of these reasons, it would be desirable to provide improved electrosurgical methods and systems for treating tumors which lie at or near the surface of an organ or tissue mass. It would be further desirable to provide such improved methods and systems which would be capable of improving beat transfer into and/or temperature uniformity of vascularized tissues where the heat can be taken away by blood flow. It would be particularly desirable if such methods and systems could lessen the risk of accidental exposure of the treating electrodes above the tissue surface. It would be further desirable if the methods and systems would enhance uniform treatment of the entire tumor mass, including those portions which lie near the surface of the organ being treated. Still further, it would be desirable if the methods and systems could achieve treatment of irregularly shaped tumors and tumors which extend from an organ surface to relatively deep within the organ. At least some of these objectives will be met by the invention of the present application.
2. Description of the Background Art
WO 96/29946 describes an electrosurgical probe having deployable electrode elements of the type described above. The LeVeen™ Needle Electrode constructed in accordance with the teachings of WO 96/229946 is available from Radio Therapeutics Corporation, assignee of the present application, and is illustrated in brochure RTC 002 published in 1998. Other electrosurgical devices having deployable electrodes are described in German Patent 2124684 (Stadelmayr); U.S. Pat. Nos. 5,472,441 (Edwards et al.); 5,536,267 (Edwards et al.); and 5,728,143 (Gough et al.); and PCT Publications WO 97/06739; WO 97/06740; WO 97/06855; and WO 97/06857. Medical electrodes having pins and other structures are shown in U.S. Pat. Nos. 3,991,770; Re. 32,066; 4,016,886; 4,140,130; 4,186,729; 4,448,198; 4,651,734; and 4,969,468. A skin surface treatment electrode for the removal of blemishes having a circular array of tissue-penetrating pins is described in Rockwell,
The Medical and Surgical Uses of Electricity,
E. B. Trent & Co., New York, 1903, at page 558. A cluster electrode comprising a plurality of electrodes projecting from a plate for insertion in tissue is described in WO 99/0410.
SUMMARY OF THE INVENTION
The present invention provides improved methods, systems, and kits for performing electrosurgical treatment of tumors and other disease conditions within body organs and other tissue masses. The methods, systems, and kits are particularly useful for treating tumors which lie at or near the surface of an organ, such as the liver, kidney, pancreas, stomach, spleen, particularly the liver. In a first aspect, the present invention relies on applying electrical energy, such as radiofrequency or other high frequency energy, to or between an internal tissue site and an external tissue site on the surface of the organ. The energy may be applied in a monopolar fashion where the internal and external sites are maintained at the same polarity and a dispersive or passive electrode disposed on the patient's skin is maintained at the opposite polarity. The high frequency energy can be applied simultaneously to both the internal and external sites, but will more usually be applied sequentially to one site and then to the other. The energy may also be applied in a bipolar fashion where the internal treatment site is maintained at one polarity and the external treatment site maintained at the opposite polarity. Monopolar treatment is advantageous in permitting formation of two fully formed lesions (necrosed regions) that can be overlapped to treat a desired region, but is disadvantageous since it requires use of a dispersive electrode. Bipolar treatment eliminates the need for a dispersive electrode and, by proper spacing, permits formation of a single, continuous lesion. Such approaches reduce the risk of passing internally deployed electrode(s) out through the surface of the body organ and enhances the uniform electrosurgical treatment of ti
Behl Robert S.
Kermit Eben L.
Dvorak Linda C. M.
Kearney R.
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