Surgery – Instruments – Electrical application
Reexamination Certificate
2000-03-27
2002-04-30
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C606S049000, C606S050000, C607S099000, C607S113000, C607S116000
Reexamination Certificate
active
06379353
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the structure and use of radio frequency electrosurgical probes for the treatment of solid tissue. More particularly, the present invention relates to an electrosurgical probe having multiple tissue-penetrating electrodes which are deployed in an array to treat large volumes of tissue, particularly for tumor treatment.
The delivery of radio frequency energy to target regions within solid tissue is known for a variety of purposes of particular interest to the present invention, radio frequency energy may be delivered to diseased regions in target tissue for the purpose of 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 electrosurgical probe described in 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 precisely defined volumetric region of target tissue. In order to assure that the target tissue is adequately treated and 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 needle as it is advanced through the tissue.
Referring now to
FIGS. 1-5
, a shortcoming of electrosurgical probes of the type described in WO 96/29946 will be discussed. Such electrosurgical probes
10
typically comprise a cannula
12
having a plurality of resilient, pre-shaped electrodes
14
therein. The electrodes
14
may be mounted at the distal end of a reciprocatable shaft
16
, and the electrodes
14
will be shaped so that they assume an arcuate shape to produce an everting array when the electrodes are advanced from the cannula
12
into solid tissue, as illustrated in
FIGS. 4 and 5
. With prior electrode probes, such as the illustrated probe
12
, the electrodes
14
have been received within lumen
18
of the cannula
12
. The electrodes have had circular cross-sections, and no provisions have been made to maintain the individual electrodes
14
in any particular ordered fashion within the cannula. Usually, a random pattern of electrodes
14
exist within the cannula
12
, as shown in
FIGS. 1 and 2
. When electrodes
14
are initially present in such a random pattern (i.e. prior to distal deployment into tissue), the electrodes will adopt a similar random pattern or configuration when first entering into tissue T. When the electrode pattern is non-uniform at the time of first entering into tissue, the non-uniformity will be propagated as the electrodes are fully deployed, as illustrated in FIG.
4
. Such a random, irregular pattern is undesirable since it results in non-uniform heating and tissue necrosis.
It would be desirable to provide improved electrosurgical probes of the type described in WO 96/29946, where the individual electrodes
14
′ are maintained in a uniform pattern within the cannula
12
, as illustrated in FIG.
3
. In particular, the electrodes
14
′ should be equally circumferentially spaced-apart and preferably axially aligned with each other within the cannula so that they will follow uniform, equally spaced-apart lines of travel as they penetrate into tissue, as shown in FIG.
5
. It will be appreciated that the initial point at which the electrodes penetrate tissue is critical to maintain proper spacing of the electrodes as they penetrate further into the tissue. Should electrodes be misaligned when they first enter the target (i.e. emerge from the cannula) tissue, they will almost certainly remain misaligned as they penetrate further into the tissue. Moreover, the individual electrodes will generally not be steerable or capable of being redirected within the tissue, so there are few options for correcting the configuration after the needles have first penetrated into the tissue. In contrast, by properly aligning the electrodes prior to and at the time they first enter into tissue from the cannula, the proper electrode pattern can be assured as the electrodes deploy radially outwardly into the tissue. It would be still further desirable to provide electrosurgical probes and methods for their deployment which would provide for improved propagation through tissue having non-uniform characteristics. Even when the electrodes are disposed in a symmetrical pattern at the outset of deployment, the electrode paths can be deflected or deviated when the electrodes encounter relatively hard or dense regions within the tissue. It would be beneficial if the electrodes were capable of passing through such regions with minimum or no deflection.
For these reasons, it would be desirable to provide improved electrosurgical probes having multiple, tissue-penetrating electrodes. In particular, it would be desirable to provide improved electrosurgical probes and tissue ablation apparatus of the type described in WO 96/29946, where the electrodes are configured within the probes so that they deploy in a uniform, evenly spaced-apart manner as they penetrate into tissue to be treated, thus overcoming at least some of the shortcomings noted above.
SUMMARY OF THE INVENTION
The present invention provides both apparatus and methods for the electrical treatment of a specific region within solid tissue, referred to hereinafter as a “treatment region.” The apparatus and methods rely on introducing a plurality of electrodes, usually being at least three electrodes, to a target site within the treatment region and thereafter deploying the electrodes into a three-dimensional array and preferably in a configuration which conforms to or encompasses the entire volume of the treatment region, or as large a portion of the volume of the treatment region as possible. The present invention particularly provides for uniform deployment of the electrodes within the solid tissue. By “uniform deployment,” it is meant that adjacent electrodes are evenly spaced-apart from each other and that pairs of adjacent electrodes are spaced-apart in a repeating, uniform pattern so that the application of electrical current through the electrodes will result in generally uniform heating and necrosis of the entire tissue volume being treated. Usually, the treatment current is radio frequency (RF) current which may be applied to the tissue in a monopolar or bipolar fashion, as described in more detail below.
Apparatus according to the present invention comprises a probe system for penetrating a plurality of electrodes into tissue. The probe system includes a cannula having a proximal end, a distal end, and a lumen extending at least to the distal end, and usually from the proximal end to the distal end. The individual electrodes are resilient and pre-shaped to assume a desired configuration when advanced into tissue. Usually, the individual electrodes will have an arcuate shape (when unconstrained) so that the electrode arrays deploy radially outwardly as the electrodes are advanced distally from the probe. In a particularly preferred configuration, the electrode arrays are “everting” where the electrode tips first diverge radially outwardly and thereafter turn by more than 90°, often to 180°, or more, in the proximal direction. The deployed electrodes will usually define a generally cylindrical,
Cohen Lee
Radiotherapeutics Corporation
Townsend and Townsend / and Crew LLP
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