Surgery – Instruments – Electrical application
Reexamination Certificate
2002-09-03
2004-10-12
Gibson, Roy D. (Department: 3739)
Surgery
Instruments
Electrical application
C600S373000, C600S382000
Reexamination Certificate
active
06802839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods, apparatus and kits used for protecting a body tissue which is adjacent to a target tissue undergoing thermal treatment. Particularly, the present invention relates to the protection of the adjacent body tissue from penetration and/or thermal effects by a tissue penetrating thermal device. More particularly, the present invention relates to an interface shield used to protect body tissue adjacent to target tissue from the possible effects of using a radiofrequency electrosurgical apparatus to treat tumors in the target tissue.
The delivery of radiofrequency energy to target regions or target tissues 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 U.S. Pat. Nos. 5,858,740; 5,855,576; 5,827,276 and international patents WO 96/29946 and WO 98/52480. The probes described in these patents 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 general, the larger the volume treated, the more wire electrodes are necessary to ensure homogeneity of treatment.
Of particular interest to the present invention, as recognized by the inventor herein, use of the multiple electrode arrangements in treating tumors which lay near an adjacent tissue structure requires particular care. For example, as illustrated in
FIG. 1
, a tumor T deep in the liver LVR may be close to a back or side surface S of the organ, adjacent to the diaphragm D and/or surrounding lung LNG. It may be desirable to access such a tumor T through an entry site E which is opposite this surface S, or at a location which is a considerable distance away from this surface S. A needle electrode
10
may be inserted through the entry point E, traverse healthy liver LVR tissue and be placed within or near the tumor T to be treated. However, if the tumor T is mistargeted, the needle electrode
10
may be misplaced, allowing the electrode tips
12
to protrude and traverse the surface S. Thus, the tip of the needle electrode
10
or the subsequently deployed electrode tips
12
may punch into or through the diaphragm D and possibly into the lung LNG. Such exposure of the electrode
10
or needle tips
12
outside of the liver LVR is disadvantageous in a number of respects. Beyond simple puncture damage, 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. This may directly destroy healthy tissue in the surrounding organs and tissues or it may cause heat damage. Moreover, the presence of all or portions of particular electrodes outside of the tissue being treated can interfere with proper heating of the target tissue and fail to destroy all or part of the tumor.
As illustrated in
FIG. 2
, a tumor T in a similar location near a surface S may likewise be accessed through an entry point E which is opposite to this surface S. Even if the tumor T is not mistargeted and the needle electrodes are properly placed within the tumor T such that they do not protrude outside of the liver LVR, surrounding tissue may still be damaged. Heat emanating from the tissue surrounding the electrode tips
12
may raise the temperature of additional non target tissues within a given radius via conduction, as illustrated by a dashed outlined area A. Some tissue in area A may be more fragile or thermally sensitive than the target tissue being treated. Thus, such tissue may be raised to a damaging or lethal temperature during the treatment of a surface tumor in an adjacent organ.
Electrosurgical treatment of such tumors within body organs often involves applying radiofrequency energy in a monopolar fashion where the treatment current travels between the treatment electrode and a dispersive or counter electrode disposed on the patient's skin. Such an electrode deployment is designed to disperse the energy, as much as possible, as distance increases from the treatment electrode in order to avoid local heating in unwanted locations. This is typically accomplished by designing the dispersive electrode to have a much larger surface area relative to the treatment electrode so that the current density is rapidly dispersed over a correspondingly larger area of tissue. However, despite proper surface area ratios of the treatment electrode to the dispersive electrode, placement of such a dispersive electrode on the outside of the patient's body may not optimally direct the dispersed energy flow through the tissues surrounding those targeted for treatment. Current flow will follow the path of minimal resistance, partly determined by the shortest distance between the treatment and dispersive electrodes. Thus, sufficient energy delivery to the treatment site may also inadvertently damage healthy tissue located between the treatment site and the dispersive electrode on the outside of the body.
For all of these reasons, it would be desirable to provide improved methods and systems for treating tumors within an organ or tissue, particularly those located adjacent to other tissue structures which are at risk of injury. It would be further desirable to provide such improved methods and systems which would protect surrounding tissue from thermal damage. It would also be particularly desirable if such methods and systems could lessen the risk of accidental penetration of a treatment device into adjacent tissue structures. It would be further desirable if the methods and systems could enhance and make more predictable the uniform treatment of the entire tumor mass, including those portions which lie near the surface of the organ being treated. Finally, it would be desirable to avoid excessive heating and the passage of excessive current through non-target tissues by providing the shortest path between active and dispersive electrodes. At least some of these objectives will be met by the invention of the present application.
2. Description of the Background Art
U.S. Pat. Nos. 5,868,740; 5,855,576; 5,827,276 and international patents WO 96/29946 and WO 98/52480 describe an electrosurgical probe having deployable electrode elements of the type described above. The LeVeen™ Needle Electrode constructed in accordance with the teachings of the above named patents is available from RadioTherapeutics 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.); U.S. Pat. No. 5,536,267 (Edwards et al.); U.S. Pat. No. 5,728,143 (Gough et al.); and U.S. Pat. No. 6,050,992 (Nichols); 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 plu
Bingham & McCutchen LLP
Gibson Roy D.
Radiotherapeutics Corporation
LandOfFree
Apparatus and method for shielding tissue during tumor ablation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for shielding tissue during tumor ablation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for shielding tissue during tumor ablation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3282828