Surgery – Instruments – Electrical application
Reexamination Certificate
2001-12-18
2004-05-25
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C606S050000, C607S101000
Reexamination Certificate
active
06740084
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to RF (radio frequency) electrode devices for use in the performance of RF thermal treatment and, more particularly, to such devices adapted for the percutaneous or luminal insertion into an affected tissue area of a patient to be treated.
BACKGROUND OF THE INVENTION
RF ablation (electrosurgery) is the application of RF energy from a source or device placed in tissue. Its use is to thermally treat malignant and nonmalignant tissue pathology and avoid or minimize a surgical procedure. The device may be placed percutaneously to assure minimally invasive techniques.
An RF electrode device is bipolar if it has both an active and a return electrode member (a negative (−) and a positive (+) electrode member) and if a return patch is not needed on the skin (as in electrosurgery). The RF signal is an alternating current at frequencies typically between 100 kHz and 2 MHz, optimally around 500 kHz. It will be understood that the positive (+) and negative (−) labels used herein are for descriptive purposes only. The active and return electrodes in the bipolar device could be swapped at a generator source with no change in performance. Unfortunately, the physics of bipolar designs limits their performance to small heated volumes due to the shape and proximity of the electrodes and the shape of the electric field. Due to the rapid falloff of an electric field that is produced by these RF electrode devices when in use, the area of treatment within a patient is limited.
Problems associated with previous RF electrode devices include the penetration and shape of the electric field being limited for these current RF electrode devices, as the heated volume within a patient cannot be increased without having to increase the number of RF electrode devices or having to increase the size of the RF electrode devices. If an increase in the number of RF electrode devices or in the size of the RF electrode devices is required, the RF ablation would be impractical, difficult to apply, and lose its percutaneous application.
Other RF electrode devices have tried to solve the foregoing problems by deploying needles in a fan-like branch array to spread out the conductive surfaces. The deployment of these RF electrode devices having a predetermined size and shape may depend on the tissue type of a patient, and the fan-like branch array could easily bend during deployment within the tissue of a patient. Current deployable electrodes may converge or diverge, which is not desirable in RF heating and may overheat when the conductive sources are close together and fail to interact when they are far apart.
Bipolar RF electrodes of various configurations, designs, structures and materials of construction are well known in the prior art, as shown in U.S. Pat. No. 6,066,139. The RF electrode device disclosed in this patent, however, suffers from one or both of the following shortcomings: (1) it does not produce a uniform RF thermal treatment field for treating the diseased tissue; and (2) the RF thermal treatment field is limited in size because of the structural arrangement of the negative (−) and positive (+) electrode members on a bipolar electrode catheter.
FIG. 1A
depicts a prior art RF electrode device A used in the performance of RF ablation so as to treat an affected tissue area B of a patient. The RF electrode device A is powered by an RF energy source, such as an electrosurgical generator C. As shown in
FIG. 1A
, the RF electrode device A includes a catheter D having two spaced-apart, electrically conductive cylindrical bipolar electrode members, one being a negative electrode assembly E and the other being a positive electrode assembly F. The electrode assemblies E, F are made from a metal that has a high electrical conductivity (&sgr;) value.
A negative electrical lead line G is connected to the negative electrode assembly E, while a positive electrical lead line H is connected to the positive electrode assembly F. Both electrical lead lines G, H are connected to the electrosurgical generator C, which supplies voltage to the electrode assemblies E, F, via the lead lines G, H, respectively. When voltage is supplied to the electrode assemblies, E, F, RF energy is emitted from the electrode assemblies E, F, to the surrounding tissue areas. The emitted RF energy will encounter resistance from the surrounding tissue areas. This resistance generates heat in the surrounding tissue areas. The heat is then transferred to more remote tissue areas through thermal conductivity.
With reference to
FIG. 1B
, the amount of heat generated in the surrounding tissue areas is delineated by a plurality of isotherms, each representing a temperature zone. As depicted in
FIG. 1B
, the location of the hottest temperature zone is adjacent to the center of the RF electrode device A. It would be desirable to manipulate the temperature distribution, such that the hottest temperature zone is distributed from the center of the RF electrode device A to the outer ends of the electrode assemblies E, F.
In the foregoing circumstances, there remains a need for an RF electrode device used to perform RF ablation that minimizes the RF electrode size that has to be inserted into the affected tissue of a patient. Further, the RF electrode device will have the ability to treat a pathologic region with a single insertion thereof into the affected tissue. Additionally, the RF electrode device will provide a voltage gradient along an electrode, thereby reshaping the electric field within the pathologic region so as to custom configure the thermal treatment zone.
Accordingly, it is an object of the present invention to provide an RF electrode that minimizes the size and shape of an electrode housing that has to be inserted into the affected or diseased tissue of a patient.
Another object of the present invention is to provide an RF electrode that is comparable in performance to that of a larger electrode.
Another object of the present invention is to provide an RF electrode that has the ability to treat a pathologic region with a single insertion thereof into the affected tissue.
Another object of the present invention is to provide an RF electrode that will generate a voltage gradient along the electrode so as to reshape the electric field within the pathologic region and to custom configure the thermal treatment zone.
Another object of the present invention is to provide an RF electrode that allows for the reshaping of the thermal field during treatment if the present heating field configuration is not optimally heating the pathologic region of the affected tissue being treated.
Another object of the present invention is to provide an RF electrode that includes the ability to reshape the electric field for different tissue types that have different electrical and thermal properties.
Another object of the present invention is to provide an RF electrode that has multiple bipolar segments so as to achieve higher levels of safety and eliminate the incidence of skin burns under a return electrode.
A further object of the present invention is to provide an RF electrode that has enhanced performance characteristics which can be mass produced in an automated and economical manner and is readily affordable by the practitioner.
SUMMARY OF THE INVENTION
In accordance with the present invention, a bipolar electrode instrument is provided for use in the performance of RF ablation electrosurgery. The bipolar electrode instrument includes an elongated catheter for insertion into an affected tissue to be treated within a patient, and at least one pair of spaced-apart bipolar electrode members, each of the electrode members being connected to the catheter. Means for applying voltage to each of the electrode members is also included. The bipolar electrode instrument further includes regulating means for regulating the amount of heat generated by each of the electrode members when voltage is applied thereto.
Other features and aspects of the present invention will become more fu
Ethicon Inc.
Peffley Michael
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