Patent Description:
One aspect of the disclosed technology provides a system for bipolar irrigated radiofrequency ablation that includes an elongate inner electrode assembly and an elongate outer electrode assembly. In some examples, the elongate inner electrode assembly includes a distal end, a proximal end, and an outer surface. In some examples, the inner electrode assembly has a sheath, a first lead within the sheath, and an electrode array comprising three or more electrode tines positioned at the distal end of the inner electrode assembly and electrically connected to the first lead. In some examples, this electrode array is moveable between a first position contained within the sheath and a second position protruding from a distal end of the sheath. In some examples, the elongate outer electrode assembly has a distal end and a proximal end, and the outer electrode assembly has a cannula with a distal end and a proximal end. In some examples, the outer electrode assembly includes an inner surface defining a lumen, a shaft electrode near the distal end of the cannula on an outer surface of the outer electrode assembly, and a conductive path from the proximal end of the outer electrode assembly to the shaft electrode. Some examples further provide an irrigation path defined between the outer surface of the inner electrode assembly and an outer surface of the outer electrode assembly, and some examples further provide that the inner electrode assembly is configured to be positioned within the lumen of the outer electrode assembly, and the system is configured for attaching to a generator to provide radiofrequency current flow between the electrode array and the shaft electrode.

Further examples of the disclosed technology can have one or more alternative or additional features. Alternatively or in addition, one or more examples of the technology further includes an insulation layer between the inner electrode assembly and the outer electrode assembly, and the insulation layer can be an insulation sheath positioned on the outer surface of the inner electrode assembly, or an insulating coating on the inner surface of the outer electrode assembly.

Alternatively or in addition, one or more examples of the technology further include an insulation layer between the inner electrode assembly and the outer electrode assembly, and the insulation layer comprises an insulation sheath positioned on the outer surface of the inner electrode assembly, and a distal segment of the insulation layer protrudes from the distal end of the outer electrode assembly.

Alternatively or in addition, in one or more examples of the technology, the irrigation path is defined between an outer surface of the inner electrode assembly and the inner surface of the outer electrode assembly, and further defined by irrigation openings defined in the shaft electrode.

Alternatively or in addition, in one or more examples of the technology, the outer electrode assembly has a proximal insulating segment adjacent to an outer surface of the cannula, and the proximal insulating segment extends from near the proximal end of the cannula to the shaft electrode. In some examples, the irrigation path is defined between the outer surface of the cannula and an inner surface of the proximal insulating segment.

Alternatively or in addition, in one or more examples of the technology, the shaft electrode is attached to the outer surface of the cannula, and the cannula defines irrigation openings near the shaft electrode. In some examples, the irrigation path is defined between the inner surface of the cannula and the outer surface of the inner electrode assembly.

Alternatively or in addition, in one or more examples of the technology, the shaft electrode is attached to the outer surface of the cannula and the cannula defines irrigation openings near the shaft electrode. In some examples, the irrigation path is defined within a wall of the cannula and through the irrigation openings.

Alternatively or in addition, in one or more examples, the irrigation path is defined through irrigation openings defined in the shaft electrode or defined near the shaft electrode.

Alternatively or in addition, in one or more examples the cannula includes a cannula body made of a conductive material, and the shaft electrode is formed by an exposed segment of the conductive material. The cannula can further include a proximal insulating segment on an outer surface of the cannula body extending from near the proximal end of the cannula body to the shaft electrode, the proximal insulating segment comprising an insulating tubing layer on an outer surface of the cannula body.

Alternatively or in addition, in one or more examples, the cannula body comprises stainless steel and wherein at least a portion of the outer surface of the cannula body is rough, textured, or threaded.

Alternatively or in addition, in one or more examples, the insulating tubing layer of the proximal insulating segment can be polyimide tubing, polyimide tubing with braided fibers within a wall of the tubing, polyethylene terephthalate (PET), polyether ether ketone (PEEK), and polytetrafluoroethylene (PTFE).

Alternatively or in addition, in one or more examples further include a distal insulating segment at the distal end of the cannula body comprising an insulating layer on an outer surface of the cannula body. Alternatively or in addition, the insulating layer of the distal insulating segment can me a heat shrink material, polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), fluoropolymers, fluorinated ethylene propylene (FEP), polyethylene terephthalate (PET), and combinations of these materials.

Alternatively or in addition, in one or more examples, the cannula has a cannula body made of an insulating material, and the shaft electrode is attached to an outer surface of the cannula body. In one or more examples, a second lead provides a conductive path from the proximal end of the cannula to the shaft electrode within a wall of the cannula body.

Alternatively or in addition, in one or more examples, the inner electrode assembly defines a central passage and an opening at the distal end of the inner electrode assembly, the system further comprising a stylet configured to be received within the central passage of the inner electrode assembly, the stylet comprising a sharp tip.

Alternatively or in addition, the irrigation path defines an exit path for open irrigation.

One aspect of the disclosed technology provides a system for bipolar irrigated radiofrequency ablation that includes an elongate inner electrode assembly and an elongate outer electrode assembly. In some examples, the elongate inner electrode assembly has a distal end, a proximal end, and an outer surface. In some examples, the inner electrode assembly includes a sheath, a first lead within the sheath, an electrode array comprising three or more electrode tines positioned at the distal end of the inner electrode assembly and electrically connected to the first lead, wherein the electrode array has a first position contained within the sheath and a second position protruding from a distal end of the sheath, and an insulation sleeve positioned on the outer surface of the sheath. In some examples, the elongate outer electrode assembly has a distal end and a proximal end, and the elongate outer electrode assembly includes a cannula having a cannula body made of an electrically conductive material, an inner surface defining a lumen, a shaft electrode formed by an exposed segment of the conductive material of the cannula on an outer surface of the outer electrode assembly, and a proximal insulating segment on the outer surface of the cannula body extending from near the proximal end of the cannula body to the shaft electrode. In some examples, an irrigation path is defined between the outer surface of the inner electrode assembly and the inner surface of the cannula, and the irrigation path is further defined through irrigation openings defined in the shaft electrode. In some examples, the inner electrode assembly is configured to be positioned within the lumen of the outer electrode assembly and the system is configured for attaching to a generator to provide radiofrequency current flow between the electrode array and the shaft electrode.

In another aspect, the disclosed technology provides a radiofrequency ablation method that includes the steps of providing an elongate inner electrode assembly having a distal end, a proximal end, and an outer surface. In some examples, the inner electrode assembly has a sheath, an electrode array comprising three or more electrode tines positioned at the distal end of the inner electrode assembly and electrically connected to a first lead, and the electrode array is moveable between a first position contained within the sheath and a second position protruding from a distal end of the sheath. In some examples, the method further includes the step of providing an elongate outer electrode assembly having a distal end and a proximal end and comprising a cannula having a distal end and a proximal end. In some examples, the cannula has an inner surface defining a lumen, a shaft electrode near the distal end of the cannula on an outer surface of the outer electrode assembly, and a conductive path from the proximal end of the cannula to the shaft electrode. In some examples, the method further includes the steps of positioning the inner electrode assembly within the cannula of the outer electrode assembly, attaching an irrigation source to an irrigation path defined between the outer surface of the inner electrode assembly and the outer surface of the outer electrode assembly, providing fluid flow through the irrigation path, and attaching the inner electrode assembly and outer electrode assembly to a generator and providing radiofrequency current flow between the electrode array and the shaft electrode.

This summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which is not to be taken in a limiting sense. The invention is defined in appended independent claim <NUM>. Further embodiments are defined in appended dependent claims.

While embodiments herein are susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example and drawings, and will be described in detail. It should be understood, however, that the scope herein is not limited to the particular examples described. On the contrary, the intention is to cover modifications, equivalents, and alternatives falling within the scope of appended claims.

This disclosure describes a radiofrequency ablation system with open irrigation and bipolar electrodes to enhance lesion formation for soft tissue ablation. The system can significantly improve the ablation performance over existing radiofrequency ablation systems. The disclosed technology provides larger lesions in a shorter application time. The improved performance is competitive with other energy systems such as microwave ablation, creating a lesion similar in size in a similar amount of time as microwave ablation methods.

In the following, an inch equals <NUM>,<NUM>.

In various examples of the technology, open irrigation cools down the temperature of the electrode and the surrounding tissue, which allows higher power and long duration for radiofrequency energy delivery. A coolant takes heat away from the electrode and surrounding tissue to prevent or slow tissue charring during radiofrequency ablation. It also can create an area of high conductivity fluid surrounding the radiofrequency ablation probe electrodes. This results in less resistive heating near the electrodes. Another result is spreading current density over a larger portion of the tissue. The open irrigation system rehydrates tissue for better thermal and electrical conductivity during radiofrequency ablation. Higher power application creates a deeper energy penetration into tissue. This allows for a longer duration for heat to conduct further to form the lesion before charring occurs.

This disclosure describes a bipolar radiofrequency ablation system where the majority of the energy is delivered locally, bounded by two electrodes. The more local delivery of energy compared to monopolar radiofrequency ablation, which uses ground pads on the patient's skin, has the advantages of more efficient energy delivery and faster lesion formation. Also, lesion formation is more consistent because energy delivery does not involve the rest of the patient body. There is a reduced risk of therapeutic heat being carried away from the target area by blood flowing through a nearby blood vessel. Another advantage is the elimination of ground pads.

The lesion shape achieved with bipolar radiofrequency ablation can also be beneficial compared to monopolar radiofrequency ablation, such as by being centered at the shaft electrode with the tine ends marking the outer boundary of the lesion, and by having a short axis to long axis ratio closer to one. This makes the lesion shape more predictable and easier to overlap with the tumor shape during treatment. With monopolar radiofrequency ablation using an electrode array, the lesion is formed in the area surrounding the tines of the electrode array, with a greater difference between the short axis and long axis of the lesion.

As used herein, the words proximal and distal express a relationship between two different elements. An element that is designated as being proximal is positioned closer to the external portion of the system, i.e., a portion that does not enter a patient's body. An element that is designated as being distal is positioned closer to the insertion end of the system.

Turning to the drawings, <FIG> is a side view of an outer electrode assembly <NUM> having a shaft electrode <NUM> of a radiofrequency ablation probe system according to some examples. <FIG> is a side view of an inner electrode assembly <NUM> of a radiofrequency ablation probe system having an electrode array <NUM> for a bipolar radiofrequency ablation that is compatible with the system of <FIG>. The inner electrode assembly <NUM> is configured to be received within an inner lumen of the outer electrode assembly <NUM>. The system is configured for attaching to a generator to provide radiofrequency current flow between the electrode array and the shaft electrode. The system is provided with a connection <NUM> to an irrigation fluid, and defines an open irrigation path which will be further described with reference to other figures.

<FIG> is a side view of a stylet <NUM> that optionally can be provided in a system. In various examples of the technology, the stylet <NUM> has a sharp trocar tip <NUM> and can be used with the disclosed radiofrequency ablation system. For example, the stylet <NUM> can have a radiopaque or echogenic tip, and can be precisely positioned within tissue to be ablated using imaging technology. The stylet can be inserted into a lumen of the inner electrode assembly <NUM>, after which the sharp tip <NUM> can be used to pierce patient tissue to facilitate entry of the probe assembly <NUM> into the patient tissue. Alternatively or in addition, the outer electrode assembly <NUM> or the inner electrode assembly <NUM> can be provided with a tissue-penetrating sharp tip to facilitate insertion into the body.

Examples of structures for bipolar irrigated radiofrequency ablation featuring differences in the irrigation path or other structures will now be described with respect to the FIGS.

One example of the technology, shown in <FIG>, provides a system <NUM> for bipolar, open irrigated, radiofrequency ablation. In the example of <FIG>, the system includes an elongate inner electrode assembly <NUM> having an electrode array <NUM>, and an elongate outer electrode assembly <NUM> having a shaft electrode <NUM>. The electrode array <NUM> can also be referred to as the distal electrode. The shaft electrode <NUM> can also be referred to as the proximal electrode or cannula electrode. The inner electrode assembly <NUM> is configured to be positioned within the lumen <NUM> of the outer electrode assembly <NUM>, and the system is configured for radiofrequency energy delivery between the electrode array <NUM> and the shaft electrode <NUM>.

The inner electrode assembly <NUM> has a distal end <NUM> and a proximal end <NUM>. The inner electrode assembly <NUM> includes a sheath <NUM>. The sheath <NUM> has a proximal end <NUM> and distal end <NUM>. The sheath <NUM> has a lumen <NUM> running through the sheath <NUM>. The lumen <NUM> ends at lumen opening <NUM>. The lumen <NUM> holds an electrode array <NUM> and a first lead <NUM>. The electrode array <NUM> includes a plurality of electrode tines <NUM> electrically connected to the first lead <NUM>. In one example, the electrode tines <NUM> are made of electrically conductive material. The sheath <NUM> of the inner electrode assembly can be made of stainless steel or other electrically conductive metal with adequate conductivity and strength. One example of a sheath <NUM>, electrode array <NUM>, and first lead <NUM> that can be used with the systems described herein is the LEVEEN COACCESS™ Needle Electrode, commercially available from Boston Scientific Corporation, Inc. of Marlborough, Massachusetts.

In some examples, the electrode tines <NUM> are retractable and form a three-dimensional shape, such as the umbrella shape in the example shown in <FIG>. Alternatively or in addition, the electrode array <NUM> includes three or more tines, any number of tines up to and including ten tines, twelve tines, or more tines. Alternatively or in addition, the electrode array <NUM> is retractable, being movable between a first position contained within the sheath <NUM> and a second position protruding from the distal end <NUM> of the sheath <NUM>.

The system further includes an elongate outer electrode assembly <NUM> having a distal end <NUM> and a proximal end <NUM>. In some examples, the outer electrode assembly <NUM> comprises a cannula <NUM> having a distal end <NUM> and a proximal end <NUM>. The outer electrode assembly <NUM> has an inner surface <NUM> defining a lumen <NUM>. In the example of <FIG>, the inner surface <NUM> is the inner surface of the cannula <NUM>. The lumen <NUM> is configured to receive the inner electrode assembly <NUM>. In some examples, the distal end <NUM> of the inner electrode assembly <NUM> protrudes from the lumen <NUM> at the distal end <NUM> of the outer electrode assembly <NUM>.

The outer electrode assembly <NUM> includes a shaft electrode <NUM> near the distal end <NUM> of the cannula <NUM> on an outer surface <NUM> of the outer electrode assembly <NUM>. In one example, a distal edge of the shaft electrode <NUM> is spaced away from the distal end of the outer electrode assembly by about <NUM>. In some examples, the space is at least about <NUM>, at least about <NUM>, at most about <NUM>, at most about <NUM>, or at most about <NUM>. In some examples, the space is at least about <NUM> and at most about <NUM>, or at least about <NUM> and at most about <NUM>.

In the example of <FIG>, the cannula <NUM> has a cannula body <NUM> that can be made of a conducting material, such as a metal including stainless steel. In this example, the shaft electrode <NUM> is an exposed portion of the outer surface <NUM> of the cannula body <NUM>. The cannula body <NUM> can serve as a conductive path from the proximal end <NUM> of the outer electrode assembly <NUM> to the shaft electrode <NUM>. The shaft electrode <NUM> and the electrode array <NUM> create a first electrode and a second electrode, respectively, in a bipolar radiofrequency ablation system.

In some examples, the cannula body is a stainless steel cannula with an inner diameter of about <NUM> inch and a wall thickness of about <NUM> inch. Many other dimensions are possible for the cannula.

In some examples, the shaft electrode <NUM> has a length of about <NUM>. In some examples, the electrode length is at least about <NUM>, at least about <NUM>, or at least about <NUM>. In some examples, the electrode length is at most about <NUM>, at most about <NUM>, or at most about <NUM>. In some examples, the electrode length is at least about <NUM> and at most about <NUM>, or at least about <NUM> and at most about <NUM>.

In some examples, the outer surface <NUM> of the cannula <NUM> has a proximal insulating segment <NUM>. The proximal insulating segment <NUM> extends from near the proximal end <NUM> of the cannula <NUM> to the shaft electrode <NUM>. The proximal insulating segment <NUM> can be an insulating tubing layer on an outer surface <NUM> of the cannula body <NUM>. For example, the insulating tubing layer of the proximal insulating segment <NUM> can be polyimide tubing, and optionally can be polyimide tubing with braided fibers within a wall of the tubing, polyethylene terephthalate (PET), polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE) (or other fluoropolymers), fluorinated ethylene propylene (FEP), or other electrically insulating materials or combinations of these materials.

In some examples, the outer electrode assembly <NUM> includes a distal insulating segment <NUM> at the distal end <NUM> of the cannula body <NUM>. The distal insulating segment <NUM> can be an insulating layer on an outer surface <NUM> of the cannula body <NUM>. The distal insulating segment <NUM> can be made of polyethylene terephthalate (PET), polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), or combinations of these materials covering the distal end <NUM> of the cannula body <NUM>. The distal insulating segment <NUM> can be made using a heat shrink material. In alternative examples, the distal insulating segment <NUM> can be a tubing or a coating. Additional examples use an extrusion combined with a heat shrink and reflow techniques. In some examples, the portion of the outer surface <NUM> of the cannula body <NUM> that forms the distal insulating segment is rough, textured, or threaded. The rough, textured, or threaded surface can improve adhesion of the insulating materials, such as the heat shrink material. In some examples (not explicitly shown in <FIG>), the distal insulating segment <NUM> is configured to create a seal between the insulation sheath <NUM> and the distal end <NUM> of the cannula <NUM> to prevent fluid from exiting the distal end <NUM> of the cannula <NUM>. In this configuration, irrigation openings <NUM>, described in more detail below, provide the primary irrigation fluid exit path.

The inner electrode assembly <NUM> has an outer surface <NUM>. In some examples, the inner electrode assembly <NUM> includes an insulation layer <NUM> to insulate it from the inner surface of the conductive cannula body <NUM>. In the example of <FIG>, the insulation layer <NUM> is an insulation sheath <NUM> positioned on the outer surface <NUM> of the inner electrode assembly <NUM>. The insulation layer <NUM> can be an insulation sheath <NUM> positioned on the outer surface <NUM> of the inner electrode assembly <NUM>. The insulation sheath <NUM> can be a polyimide insulation sheath, which, in some examples, has an inner diameter of about <NUM> inch and a wall thickness of about <NUM> inch. Alternatively or in addition, the insulation sheath <NUM> can include insulators such as polyethylene terephthalate (PET), polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE) (or other fluoropolymers), fluorinated ethylene propylene (FEP), or combinations of these materials.

In some examples, including that of <FIG>, a distal segment <NUM> of the insulation sheath <NUM> protrudes from a distal end <NUM> of the outer electrode assembly <NUM>. This configuration isolates the two electrodes of the bipolar radiofrequency ablation system.

The system <NUM> includes an open irrigation system. A fluid, such as saline, is supplied to an irrigation path at the proximal end of the ablation probe and flows through the system into the body of the patient near the electrodes. The fluid cools both the electrodes and the tissue being ablated. The structure of the irrigation path for the example of <FIG> will now be described.

In the example of <FIG>, an irrigation path <NUM> is defined between the outer surface <NUM> of the inner electrode assembly <NUM> and the inner surface <NUM> of the outer electrode assembly <NUM>. The irrigation path <NUM> has an annular shape. In some examples, the thickness of the annular irrigation path <NUM> shown in <FIG> is about <NUM> inch, such as where the outer diameter of the inner electrode assembly <NUM> is about <NUM> inch and the inner diameter of the cannula <NUM> is about <NUM> inch.

Furthermore, the irrigation path <NUM> is defined through irrigation openings <NUM> in the shaft electrode <NUM>. At the proximal end of the system <NUM>, a fluid enters a gap <NUM> between the outer surface <NUM> of the inner electrode assembly <NUM> and the inner surface <NUM> of the outer electrode assembly <NUM>. The fluid travels along the outer circumference of the inner electrode assembly <NUM> toward the distal end <NUM> of the inner electrode assembly <NUM>. The fluid exits the gap <NUM> through irrigation openings <NUM> defined in the shaft electrode <NUM>. The irrigation openings <NUM> can be irrigation ports that are circular in shape, or a variety of other shapes, and distributed around the outer circumference of the cannula <NUM>.

In a further aspect of the disclosed technology, the system <NUM> includes an elongate inner electrode assembly <NUM> having a distal end <NUM>, a proximal end <NUM>, and an outer surface <NUM>. The inner electrode assembly <NUM> comprises a sheath <NUM>, a first lead <NUM> within the sheath <NUM>, and an electrode array <NUM>. The electrode array <NUM> includes three or more electrode tines <NUM> positioned at the distal end <NUM> of the inner electrode assembly <NUM>. The electrode tines <NUM> are electrically connected to the first lead <NUM>, and the electrode array <NUM> has a first position contained within the sheath <NUM> and a second position protruding from a distal end <NUM> of the sheath <NUM>. The system <NUM> also includes an insulation sleeve <NUM> positioned on the outer surface <NUM> of the sheath <NUM>. An elongate outer electrode assembly <NUM> is provided. The outer electrode assembly <NUM> has a distal end <NUM> and a proximal end <NUM>. In some examples, the outer electrode assembly <NUM> includes a cannula <NUM> having a cannula body <NUM> made of an electrically conductive material. The outer electrode assembly <NUM> has an inner surface <NUM> defining a lumen <NUM>. A shaft electrode <NUM> is formed by an exposed segment of the conductive material of the cannula <NUM> on an outer surface <NUM> of the outer electrode assembly <NUM>. A proximal insulating segment <NUM> on the outer surface <NUM> of the cannula body <NUM> extends from near the proximal end <NUM> of the cannula body <NUM> to the shaft electrode <NUM>. An irrigation path <NUM> is defined between the outer surface <NUM> of the inner electrode assembly <NUM> and the inner surface <NUM> of the cannula <NUM>. The irrigation path <NUM> is partially defined through irrigation openings <NUM> defined in the shaft electrode <NUM>. The inner electrode assembly <NUM> is configured to be positioned within the lumen <NUM> of the outer electrode assembly <NUM>, and the system is configured for radiofrequency current flow between the electrode array <NUM> and the shaft electrode <NUM>.

<FIG> provide an alternative example of a system for bipolar, irrigated, radiofrequency ablation. Like the example of <FIG>, the system <NUM> includes an inner electrode assembly, an outer electrode assembly, and an irrigation path that allows a fluid to flow through the body of the system and out of the system into patient tissue, where the fluid cools the radiofrequency ablation electrodes and the patient tissue.

In the example of <FIG>, the system <NUM> for bipolar, open irrigated radiofrequency ablation includes an elongate inner electrode assembly <NUM> having a distal end <NUM> and a proximal end <NUM>. The inner electrode assembly <NUM> is configured to be positioned within the lumen <NUM> of the outer electrode assembly <NUM>, and the system is configured for attaching to a generator to provide radiofrequency current flow between the electrode array <NUM> and the shaft electrode <NUM>.

The inner electrode assembly <NUM> has an outer surface <NUM>. The inner electrode assembly <NUM> includes a sheath <NUM>. The sheath <NUM>, electrode array <NUM> and other components within the sheath <NUM> are substantially similar to those described herein with respect to <FIG>, so that description will not be repeated here. A difference between the inner electrode assembly <NUM> of <FIG> compared to the inner electrode assembly <NUM> of <FIG> is that the inner electrode assembly <NUM> does not have an insulation layer forming its outer surface.

The system <NUM> further includes an elongate outer electrode assembly <NUM> having a distal end <NUM> and a proximal end <NUM>. In some examples, the outer electrode assembly <NUM> includes a cannula <NUM> having a distal end <NUM> and a proximal end <NUM>. The outer electrode assembly <NUM> has an inner surface <NUM> that defines a lumen <NUM>. The lumen <NUM> is configured to receive the inner electrode assembly <NUM>.

In some examples, the system <NUM> includes an insulation layer between the inner electrode assembly <NUM> and the outer electrode assembly <NUM>. In the example of <FIG>, the insulation layer <NUM> is an insulating coating <NUM> on the inner surface <NUM> of the outer electrode assembly <NUM>. Other than the presence of the insulating coating <NUM>, the outer electrode assembly <NUM> is substantially similar to the outer electrode assembly <NUM> of <FIG>, such as by having a conductive cannula body <NUM>, and an exposed portion of the cannula body <NUM> forming the shaft electrode <NUM>. As a result, the description of the components and structure of the outer electrode assembly <NUM> that are shared in common with the outer electrode assembly <NUM> will not be repeated here.

The system <NUM> includes an open irrigation system. A fluid, such as saline, is inserted into the proximal end of the ablation probe and flows through the system into the body of the patient. The fluid cools both the electrodes and the tissue being ablated. In the example of <FIG>, the irrigation path <NUM> is defined between the outer surface <NUM> of the inner electrode assembly <NUM> and the inner surface <NUM> of the outer electrode assembly <NUM>. Furthermore, like in the examples of <FIG>, the irrigation path <NUM> is defined through irrigation openings <NUM> in the shaft electrode <NUM>. The irrigation path <NUM> of <FIG> is similar to the irrigation path <NUM> of <FIG>, so that full description will not be repeated here.

<FIG>provide an alternative example of a system <NUM> for bipolar, irrigated, radiofrequency ablation. Like the examples of <FIG> and <FIG>, the system <NUM> includes an inner electrode assembly <NUM>, an outer electrode assembly <NUM>, and an irrigation path that allows a fluid to flow through the body of the system and out of the system into patient tissue, where the fluid cools the radiofrequency ablation electrodes and the patient tissue. Also like the examples of <FIG> and <FIG>, the outer electrode assembly <NUM> includes a cannula <NUM> having a cannula body <NUM> made of a conductive material and a shaft electrode <NUM> is an exposed portion of the cannula body. The cannula <NUM> can be substantially similar to the cannula <NUM> of <FIG> and <FIG>, so that description will not be repeated here.

The example of <FIG> provides a system <NUM> for bipolar, irrigated, radiofrequency ablation. The inner electrode assembly <NUM> as shown in <FIG> can be substantially the same as described with respect to <FIG>, and thus the details will not be repeated here.

The system <NUM> further includes an elongate outer electrode assembly <NUM> having a distal end <NUM> and a proximal end <NUM>. The outer electrode assembly <NUM> includes a cannula <NUM> having a distal end <NUM> and a proximal end <NUM>. The outer electrode assembly <NUM> has an inner surface <NUM> defining a lumen <NUM>. In the example of <FIG>, the inner surface <NUM> is the inner surface of the cannula <NUM>. The lumen <NUM> is configured to receive the inner electrode assembly <NUM>. In some examples, the distal end <NUM> of the inner electrode assembly <NUM> protrudes from the lumen <NUM> at the distal end <NUM> of the outer electrode assembly <NUM>.

The outer electrode assembly <NUM> includes a shaft electrode <NUM> near the distal end <NUM> of the cannula <NUM> on an outer surface <NUM> of the outer electrode assembly <NUM>.

The system <NUM> includes an open irrigation system. A fluid, such as saline, is inserted into the proximal end of the ablation probe and flows through the system into the body of the patient. The fluid cools both the electrodes and the tissue being ablated. An irrigation path <NUM> is defined between the outer surface <NUM> of the inner electrode assembly <NUM> and an outer surface <NUM> of the outer electrode assembly <NUM>.

In the example of <FIG>, the outer electrode assembly <NUM> includes a proximal insulating segment <NUM> adjacent to an outer surface <NUM> of the cannula. A gap <NUM> exists between the cannula <NUM> and the insulating segment <NUM>. The proximal insulating segment <NUM> extends from near the proximal end <NUM> of the cannula <NUM> to the shaft electrode <NUM>. The irrigation path <NUM> is defined in the gap <NUM> between the outer surface <NUM> of the cannula and the inner surface <NUM> of the proximal insulating segment <NUM>.

The proximal insulating segment <NUM> can be an insulating tubing positioned around the circumference of the cannula body <NUM>. For example, the insulating tubing of the proximal insulating segment <NUM> can be polyimide tubing, and optionally can be polyimide tubing with braided fibers within a wall of the tubing.

In some examples, the outer electrode assembly <NUM> includes a distal insulating segment <NUM> at the distal end <NUM> of the cannula body <NUM>, which is substantially similar to the distal insulating segment described with respect to <FIG> and <FIG>.

<FIG> provide an alternative example of a system for bipolar, irrigated radiofrequency ablation. Like the example of <FIG>, <FIG>, and <FIG>, the system <NUM> includes an inner electrode assembly, an outer electrode assembly, and an irrigation path that allows a fluid to flow through the body of the system and out of the system into patient tissue, where the fluid cools the radiofrequency ablation electrodes and the patient tissue.

In the example of <FIG>, the system <NUM> for bipolar, irrigated radiofrequency ablation includes an elongate inner electrode assembly <NUM> having a distal end <NUM> and a proximal end <NUM>. The inner electrode assembly <NUM> as shown in <FIG> can be substantially the same as described with respect to <FIG>, and thus the details will not be repeated here. The system <NUM> further includes an elongate outer electrode assembly <NUM> having a distal end <NUM> and a proximal end <NUM>. The outer electrode assembly <NUM> includes a cannula <NUM> having a distal end <NUM> and a proximal end <NUM>. The outer electrode assembly <NUM> has an inner surface <NUM> defining a lumen <NUM>. In the example of <FIG>, the inner surface <NUM> is the inner surface of the cannula <NUM>.

The system <NUM> includes an open irrigation system. A fluid, such as saline, is inserted into the proximal end of the ablation probe and flows through the system into the body of the patient. The fluid cools both the electrodes and the tissue being ablated. An irrigation path <NUM> is defined between the outer surface <NUM> of the inner electrode assembly <NUM> and an outer surface <NUM> of the outer electrode assembly <NUM>. In some examples, the irrigation path <NUM> is defined between the outer surface of the sheath <NUM> and the inner surface <NUM> of the outer electrode assembly <NUM>.

In the examples of <FIG>, the cannula <NUM> has a cannula body <NUM> made of an insulating material. For example, the cannula body <NUM> can be polyimide tubing, and optionally can be polyimide tubing with braided fibers within a wall of the tubing. Alternatively or in addition, the cannula body <NUM> can comprise insulators such as polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE) (or other fluoropolymers), of combinations of these materials. The outer electrode assembly <NUM> has a shaft electrode <NUM> near the distal end <NUM> of the cannula <NUM> on an outer surface <NUM> of the outer electrode assembly <NUM>.

In the examples of <FIG>, the shaft electrode <NUM> is an electrically conductive structure attached to an outer surface <NUM> of the cannula body <NUM>. Options for the material of the shaft electrode <NUM> include metal, platinum, stainless steel, or the like. The shaft electrode <NUM> can have a ring shape. In addition or alternatively, the electrode is a stainless steel or platinum ring with a wall thickness of about <NUM> inch and a length of about <NUM>.

The system <NUM> includes a conductive path from the proximal end <NUM> of the outer electrode assembly <NUM> to the shaft electrode <NUM>. In some examples, as shown in <FIG>. a second lead <NUM> provides a conductive path from the proximal end <NUM> of the cannula <NUM> to the shaft electrode <NUM> within a wall <NUM> of the cannula body <NUM>.

The cannula <NUM> defines irrigation openings <NUM> near the shaft electrode <NUM>. An irrigation path <NUM> is defined between the inner surface <NUM> of the cannula <NUM> and the outer surface <NUM> of the inner electrode assembly <NUM>. In some examples, thickness of the annular irrigation path <NUM> shown in <FIG> is about <NUM> inch, such as where the outer diameter of the inner electrode assembly <NUM> is about <NUM> inch and the inner diameter of the cannula <NUM> is about <NUM> inch.

The irrigation path <NUM> is further defined through the irrigation openings <NUM>. In some examples, irrigation openings <NUM> are located along the length of the cannula <NUM> on a proximal side of the shaft electrode <NUM>. Alternatively or in addition, irrigation openings <NUM> can be located along the length of the cannula <NUM> on a distal side of the shaft electrode <NUM>. In various example, a distance between the irrigation openings <NUM> and a nearest edge of the shaft electrode <NUM> is between about <NUM> and <NUM>, inclusive. In some examples, the distance is at most about <NUM> or at most about <NUM>. In some examples, the distance is at least about <NUM>.

Alternatively or in addition, irrigation openings are defined through the shaft electrode <NUM> and through the cannula body <NUM> underlying the shaft electrode <NUM>. This is not shown in the drawings.

In addition or alternatively, an irrigation path can be defined within a wall <NUM> of the cannula <NUM> to supply irrigation fluid to the irrigation openings <NUM> of <FIG>. <FIG> shows a radial cross section along line E-E in <FIG>, where an irrigation channel <NUM> is illustrated in the wall <NUM>, as an alternative to the irrigation path <NUM> structure shown in <FIG>. The irrigation path <NUM> is defined within a wall <NUM> of the cannula <NUM> and through the irrigation openings <NUM>. In this case, the irrigation path <NUM> is in fluid communication with one or more irrigation openings <NUM> shown in <FIG>. <FIG>are consistent with the example of <FIG>.

Irrigation openings are provided in different configurations in the FIGS. , including irrigation openings <NUM> of <FIG> and <FIG>, and irrigation openings <NUM> of <FIG>. In various examples, the irrigation openings are located along the length of the outer electrode assembly. Some examples provide irrigation openings along the length of the shaft electrode. Alternative examples provide irrigation openings proximal and/or distal to the shaft electrode. The irrigation openings provide a path for coolant to exit. In various examples, the irrigation openings are circular. In alternative examples, the irrigation openings can be oval or a variety of other shapes. The irrigation openings can have a diameter of about <NUM> inch, at least about <NUM> inch, at least about <NUM> inch, at least about <NUM> inch, at most about <NUM> inch, at most about <NUM> inch, at least about <NUM> inch and at most about <NUM> inch, or at least about <NUM> inch and at most about <NUM> inch.

The irrigation openings <NUM> of <FIG> and <FIG> are defined through the shaft electrode <NUM>. In the example arrangements of <FIG> and <FIG>, the irrigation openings <NUM> are arranged in two rows extending radially around the electrode with three holes in each row. Within each row, the irrigation openings are <NUM> degrees apart. In various examples, one, two, three or four rows of irrigation openings could extend radially around the shaft electrode, and one, two, three, four or five irrigation openings could be present in each row.

The two rows of irrigation openings <NUM> of <FIG> and <FIG> are <NUM> and <NUM> from the distal edge of the shaft electrode. Other spacing is possible in different examples.

The outer electrode assembly <NUM> of <FIG> and <FIG> includes the distal insulating portion <NUM> at the distal end of the outer electrode assembly, which plays a role in directing flow of the irrigation fluid out through the irrigation openings <NUM>. The distal insulating portion <NUM> extends off of the distal end of the outer electrode assembly and tapers toward its distal end to seal against the inner electrode assembly and prevent irrigation fluid from flowing out of the distal end of the outer electrode assembly.

The various examples of radiofrequency ablation system as described herein can be used to perform a method of radiofrequency ablation. <FIG> is a schematic view of a system for performing radiofrequency ablation according to some examples. The method includes providing an elongate inner electrode assembly having a distal end, a proximal end, and an outer surface. The inner electrode assembly can be that of any of the examples of <FIG>. The inner electrode assembly includes a sheath and an electrode array comprising three or more electrode tines positioned at the distal end of the inner electrode assembly and connected to the first lead. The electrode array is movable between a first position contained within the sheath and a second position protruding from a distal end of the sheath.

The method further includes providing an outer electrode assembly having a distal end and a proximal end and comprising a cannula having a distal end and a proximal end. The cannula has an inner surface defining a lumen. A shaft electrode is provided near the distal end of the cannula on an outer surface of the outer electrode assembly. A conductive path runs from the proximal end of the outer electrode assembly to the shaft electrode.

The method includes positioning the inner electrode assembly within the cannula of the outer electrode assembly, attaching an irrigation source to an irrigation path defined between the outer surface of the inner electrode assembly and the outer surface of the outer electrode assembly. The method further includes providing fluid flow through the irrigation path and attaching the system to a generator and providing radiofrequency current flow between the electrode array and the shaft electrode.

As shown in <FIG>, a radiofrequency ablation system <NUM> includes a probe <NUM>. The probe <NUM> is inserted into patient tissue <NUM> and into a volume of tissue <NUM> that is desired to be ablated. The system <NUM> includes tine electrodes <NUM> that protrude from a distal end of the probe <NUM>. A second electrode <NUM> along the body of the probe <NUM>, along with the electrodes <NUM>, are configured to provide bipolar radiofrequency ablation. A source of radiofrequency energy <NUM> is provided. The radiofrequency energy source <NUM> can be, for example an RF <NUM>™ Generator, manufactured by Boston Scientific, Inc. of Marlborough, Massachusetts.

An irrigation source, such as a saline source <NUM>, is used to inject saline through the probe <NUM> into the patient tissue <NUM>. In some examples, the saline is a <NUM>% saline solution. Other concentrations of saline solution can be used. An irrigation path <NUM> allows a fluid to irrigate the tissue to be ablated <NUM>, as indicated by arrows <NUM>. When radiofrequency energy is transferred into patient tissue, the tissue <NUM> becomes heated. The irrigation fluid regulates the temperature, reducing overheating, and allowing a larger area to be ablated in a shorter period of time.

In some examples, the flow rate of the fluid through the irrigation path <NUM> can be about <NUM> per minute. In some examples, the flow rate of the fluid through the irrigation path <NUM> can be about at least about <NUM> per minute and at most about <NUM> per minute, at least about <NUM> per minute and at most about <NUM> per minute, or at least about <NUM> per minute and at most about <NUM> per minute.

One example method of irrigated, bipolar radiofrequency ablation will now be described, where the system <NUM> is positioned within the patient tissue <NUM> to be ablated and the electrodes are electrically connected to the radiofrequency generator <NUM>. Before beginning ablation, saline irrigation is started at a rate of about <NUM>/min for about one minute. Different amounts of saline and different rates of saline irrigation could be used before starting radiofrequency ablation, such as irrigating with <NUM> of saline. After the initial saline infusion, radiofrequency ablation is started at <NUM> Watts while saline irrigation continues. The power of the radiofrequency ablation is increased by <NUM> Watts every <NUM> seconds, as long as the tissue impedance decreases over the previous <NUM> seconds. An example of a minimum decrease required by this protocol is <NUM> Ohms. When the impedance decrease plateaus, which is likely to occur at about <NUM>-<NUM> Watts, then the power is increased by <NUM> Watts every <NUM> seconds. When impedance starts to increase, the power is no longer adjusted. The generator is allowed to adjust itself down in response to the increasing impedance according to its programming. After <NUM> minutes, the radiofrequency ablation generator is stopped, although it may have shut itself down by that time according to its programming. For a larger lesion, the clinician can wait for <NUM> seconds and then restart this protocol at <NUM>% of highest power used so far.

In the second round of the protocol for larger lesions, the power of the radiofrequency ablation is increased by <NUM> Watts every <NUM> seconds, as long as the tissue impedance decreases over the previous <NUM> seconds. When the impedance decrease plateaus, such as by decreasing by about <NUM>-<NUM> Watts every <NUM> seconds, then the power is increased by <NUM> Watts every <NUM> seconds. When impedance starts to increase, the power is no longer adjusted. The generator is allowed to adjust itself down in response to the increasing impedance according to its programming. After <NUM> minutes, the radiofrequency ablation generator is stopped, although it may have shut itself down by that time according to its programming.

The present disclosure enables the creation of a larger lesion, such as a minimum of <NUM> on one axis, and often <NUM> by <NUM>, in a short application period such as about <NUM> minutes, using a single probe with lower power on the order of about <NUM> Watts or less, with no grounding pads, no risk of skin burns, and less heat transferred to the non-target portions of the body.

Some of the FIGS. are schematic in nature and are not drawn to scale. Certain features are shown larger than their scale and certain features are omitted from some views for ease of illustration.

It should be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

Claim 1:
A system for bipolar, irrigated, radiofrequency ablation comprising:
an elongate inner electrode assembly (<NUM>) having a distal end, a proximal end, and an outer surface, the inner electrode assembly comprising:
a sheath (<NUM>),
a first lead (<NUM>) within the sheath, and
an electrode array comprising three or more electrode tines (<NUM>) positioned at the distal end of the inner electrode assembly and electrically connected to the first lead, wherein the electrode array is moveable between a first position contained within the sheath and a second position protruding from a distal end of the sheath;
an elongate outer electrode assembly (<NUM>) having a distal end and a proximal end and comprising a cannula (<NUM>) having a distal end and a proximal end, the outer electrode assembly comprising:
an inner surface defining a lumen,
a shaft electrode near the distal end of the cannula on an outer surface of the outer electrode assembly, and
a conductive path (<NUM>) from the proximal end of the outer electrode assembly to the shaft electrode; and
an irrigation path (<NUM>) defined between the outer surface of the inner electrode assembly (<NUM>) and
an outer surface of the outer electrode assembly;
wherein the inner electrode assembly (<NUM>) is configured to be positioned within the lumen (<NUM>) of the outer electrode assembly, and wherein the system is configured for attaching to a generator to provide radiofrequency current flow between the electrode array and the shaft electrode.