|Publication number||US20060142757 A1|
|Application number||US 11/335,092|
|Publication date||29 Jun 2006|
|Filing date||18 Jan 2006|
|Priority date||21 Aug 2002|
|Also published as||US7008421, US20040039429, WO2004017851A1|
|Publication number||11335092, 335092, US 2006/0142757 A1, US 2006/142757 A1, US 20060142757 A1, US 20060142757A1, US 2006142757 A1, US 2006142757A1, US-A1-20060142757, US-A1-2006142757, US2006/0142757A1, US2006/142757A1, US20060142757 A1, US20060142757A1, US2006142757 A1, US2006142757A1|
|Inventors||Steven Daniel, David Morris|
|Original Assignee||Daniel Steven A, Morris David L|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (4), Classifications (12), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of U.S. Provisional Application No. 60/405,051, filed Aug. 21, 2002, which is currently pending.
This invention relates generally to an apparatus and method that aids in the resection of tissue, and more particularly to the bloodless or near bloodless resection of tissue.
Standard surgical procedures for trauma, cancer and transplants in the kidney, liver, and like organs have several key shortcomings affecting efficacy, morbidity and mortality. In an effort to fully remove or resect an organ, the surgeon may be forced to breach the tissue causing a large amount of bleeding. Careful hemostasis can minimize blood loss and complications but is laborious and time consuming using the systems and methods known in the art. Uncontrollable bleeding, for example, is one of the leading causes that prevent such treatments from being offered to patients with cirrhotic livers. In cancer patients, the surgeon must exercise care in an attempt not to allow any tumor cells to remain at a site of resection since any viable tumor cells may cause a recurrence of the cancer and negate the benefit of the procedure. Furthermore, surgeons can reduce the risk of complications by performing these procedures in an expedient manner to minimize anesthesia time and blood loss.
Typical methods for creating resections or controlling bleeding and blood loss include scalpels, electrocautery, ultrasonic scalpels, argon beam coagulators, and radio frequency (RF) surface dissectors. However, these therapies in their present form have several critical drawbacks including: (i) a complete lack or partial inability to create a hemostatic or near-hemostatic resection plane with any significant depth; (ii) a partial or complete lack of ability to make the tissue resection plane unable to support the growth of cancer cells left on the surface; (iii) a partial or complete lack of ability to kill cancerous cells remaining from an in adequate resection margin; (iv) an ability to reduce the operative time and likewise the complications resulting from the prolonged exposure to anesthesia; and (v) an ability to reduce the level of skill required to perform a safe and effective resection thereby allowing a greater availability of the treatment to the patient population.
In the drawings, the same reference numbers identify identical or substantially similar elements or acts. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 102 is first introduced and discussed with respect to
A tissue ablation system including numerous components and methods is described in detail herein. The tissue ablation system generates an avascular volume of coagulated tissue that aids in the bloodless or near-bloodless resection of various biological tissues from a variety of organs including, for example, the liver, spleen, kidney, and various other organs of the body. In the following description, numerous specific details are introduced to provide a thorough understanding of, and enabling description for, embodiments of the invention. One skilled in the relevant art, however, will recognize that the invention can be practiced without one or more of the specific details, or with other components, systems, etc. In other instances, well-known structures or operations are not shown, or are not described in detail, to avoid obscuring aspects of the invention.
The energy director guide 102 and the energy directors 104 are coupled among at least one generator 110, or power source, but are not so limited. The energy directors 104 of an embodiment couple to the generator 110 via the energy director guide 102. Alternatively, the energy directors 104 can couple directly to the generator 110 via a wire, cable, or other conduit.
Using the bipolar configuration of the energy directors 104, one electrode of an electrode pair serves as a source and the other electrode of the pair serves as a sink for the power received from the generator 110. Therefore, one electrode is disposed at the opposite voltage (pole) to the other so that power from the generator is drawn directly from one electrode to the other. The bipolar electrode arrangement insures more localized and smaller heat ablation volumes, but the embodiment is not so limited.
The alternating polarity series of energy directors includes various series combinations of alternating polarities. For example, in an embodiment using six (6) energy directors, the alternating polarity is: positive polarity (+), negative polarity (−), +, −+, −. An alternative polarity series is: +, +, −, −, +, +. Another alternative polarity series is: −, −, +, +, —, −. Yet another alternative polarity series is: +, +, +, −, −, −. Still other alternative polarity series can include: +, +, −, +, −, −. These examples are exemplary only, and the tissue ablation system 100 described herein is not limited to six (6) electrodes or to these alternating polarities.
The energy directors 104, while configured appropriately for insertion into particular tissue types, have a shape and a pattern that supports coupling to the target tissue and allows the energy directors 104 to deliver sufficient energy to cause the tissue to become hemostatic, such as by coagulation of the tissue, thereby facilitating resection of a selected tissue volume. The energy directors 104 of an embodiment include rigid shafts that are of sufficient stiffness to be easily urged into the target tissue 199 and coupled to the tissue 199 while retaining their shape.
The energy directors 104 terminate in non- or minimally-traumatic tissue-penetrating tips of various configurations known in the art as appropriate to the tissue type of the target tissue 199. The energy director tip configurations of an embodiment include fully rounded tips, flat tips, blunt tips, and rounded tips, but are not so limited. These configurations facilitate insertion of the energy directors into different types of target tissue while protecting the user from sharp points that, during normal handling, pose a puncture hazard to the user. This is particularly important since the energy directors could be contaminated with potentially deadly material including viruses such as Hepatitis-C and Human Immunodeficiency Virus (HIV) that could be transmitted to the user through a puncture wound.
The energy directors of an embodiment can have many different sizes depending upon the energy delivery parameters (current, impedance, etc.) of the corresponding system. For example, energy director diameters are approximately in the range of 0.015 inches to 0.125 inches, but are not so limited. Energy director lengths are approximately in the range of 4 cm to 10 cm, but are not so limited. Energy directors include materials selected from among conductive or plated plastics, super alloys including shape memory alloys, and stainless steel, to name a few.
The energy directors 104 of various alternative embodiments can include materials that support bending and/or shaping of the energy directors 104. Further, the energy directors 104 of alternative embodiments can include non-conducting materials, coatings, and/or coverings in various segments and/or proportions along the shaft of the energy director 104 as appropriate to the energy delivery requirements of the corresponding procedure and/or the type of target tissue.
The generator 110 of an embodiment delivers prespecified amounts of energy at selectable frequencies in order to coagulate and/or cut tissue, but is not so limited. The generator 110 of an embodiment is an RF generator that supports output power in the range of approximately zero to 200 Watts, output current in the range of approximately 0.1 amps to four (4) amps, and output impedances generally in the range of approximately two (2) to 150 Ohms, across a frequency range of approximately 1 kHz to 1 MHz, but is not so limited.
It is understood that variations in the choice of electrical output parameters from the generator to monitor or control the tissue ablation process may vary widely depending on operator experience, technique, and/or preference. For example, in one embodiment a common voltage is applied to all the energy directors of an array simultaneously. As an alternative embodiment, the operator may choose to control the current to the individual energy directors of the array or the total current of the array as a whole.
Further, voltage variations on each energy director can be applied to achieve constant current output from each energy director. Alternatively, constant power output from each energy director may be sought in some procedures. Additionally, voltage variations or phase differences between energy directors can be implemented to achieve prespecified temperature distributions in the tissue as monitored by temperature sensors in the tissue or by visualization of temperature distribution using techniques known in the art. Accordingly, the choice of electrical output type, sequence, and levels and the distribution to the energy directors of the array should be considered to have wide variations within the scope of this invention.
The tissue ablation system 100 can include any number of additional components like, for example, a controller 120 to semi-automatically or automatically control delivery of energy from the generator. The controller can, for example, increase the power output to the electrodes, control temperature when the energy directors include temperature sensors or when receiving temperature information from remote sensors, and/or monitor or control impedance, power, current, voltage, and/or other output parameters. The functions of the controller 120 can be integrated with those of the generator 110, can be integrated with other components of the tissue ablation system 100, or can be in the form of stand-alone units coupled among components of the tissue ablation system 100, but are not so limited.
Moreover, the tissue ablation system 100 can include a display 130 that provides a display of heating parameters such as temperature for one or more of the energy directors, impedance, power, current, timing information, and/or voltage of the generator output. The functions of the display 130 can be integrated with those of the generator 110, can be integrated with other components of the tissue ablation system 100, or can be in the form of stand-alone units coupled among components of the tissue ablation system 100, but are not so limited.
Various alternative embodiments of the tissue ablation system 200 can also include a biocompatible thermal shield 140. The thermal shield 140 serves to protect the organs and tissue that surround the target biological tissue 199 from the effects of the procedures described herein associated with treatment using the tissue ablation system 200.
Placement of the energy directors described herein controls the distribution of energy imparted to the target tissue. As such, the energy director configurations described herein support approximately uniform energy distribution and/or current density, and thus more uniform temperatures, through the target tissue volume. An example of this includes the use of RF energy where, for a number of energy directors, and as described below, generally uniform energy distribution is obtained using relatively smaller spacing between the energy directors toward the outside of a linear energy director array and relatively larger spacing between the energy directors toward the center of the energy director array. The spacing between the energy directors is established and maintained using the energy director guide, a description of which follows.
While six (6) channels are shown for illustrative purposes, alternative embodiments can include differing numbers of channels. The spacing among the channels 202-212 varies according to the total number of energy directors received in the energy director guide 102, as described further below. Generally, to account for electromagnetic coupling among the energy directors when the energy directors are coupled to the generator, the relative spacing among the center-most channels (206 and 208 in this embodiment) is largest while relative spacing among the end-most channels (202/204 and 210/212 in this embodiment) is smallest.
As described above, uniform energy distribution is important when generating an avascular volume of tissue suitable for bloodless or near-bloodless resection. The energy director guide 102 described herein provides uniform energy distribution via the energy directors using a channel spacing, and consequently an energy director configuration, that accounts for electromagnetic coupling effects among neighboring energy directors. The energy director guide 102 of an embodiment includes six (6) channels 202-212 that, in operation, receive three (3) pairs of bipolar energy directors. The spacing between channels 202 and 204 is approximately 0.2995 inches. The spacing between channels 204 and 206 is approximately 0.3285 inches. The spacing between channels 206 and 208 is approximately 0.3937 inches. The spacing between channels 208 and 210 is approximately 0.3285 inches. The spacing between channels 210 and 212 is approximately 0.2995 inches.
The guide channel spacing that provides relatively uniform energy distribution is generated using resistive network models, but is not so limited.
Generally, the resistor configurations of the model 400 simulate the relative power dissipation, including the coupling effects among the various combinations of alternating polarity nodes, in the tissue volumes (“zones”) between the energy directors (nodes), as further described below. Given that biological tissue has a resistivity (resistance per unit volume) that is proportional to the spacing between energy directors, the resistor values of the model are iteratively varied to represent different channel spacing.
With reference to
Using the final values for the total power dissipation per zone 482, spacing ratios per zone 484 and 486 are generated. In an embodiment, two different spacing ratios per zone 484 and 486 are generated, but the embodiment is not so limited. A first spacing ratio per zone 484 references the spacing of the zones to the proximal-most/distal-most zones (zones 1 and 5) of the array, and a second spacing ratio per zone 486 references the spacing of the zones to the center zone (zone 3) of the array. Note, however, that the spacing ratios per zone can be referenced to any zone of the array in alternative embodiments.
Using either of the spacing ratios per zone 484 and 486, the relative spacing among the channels is determined by assigning a reference spacing value to the reference zone (the zone for which the spacing ration is one (1)). The spacing values for all other zones of the array are then each determined using the spacing ratio for each associated zone as a multiplier against the reference spacing value. Reference spacing values are selected using techniques known in the art, wherein the largest spacing value between the energy directors of an array is approximately in the range of 0.75 cm to 2.00 cm, but the embodiment is not so limited.
Alternative embodiments of the tissue ablation system include differing numbers of energy directors and, therefore, differing numbers of channels in the energy director guide. For example, one alternative embodiment includes an energy director guide having a series of eight (8) channels that receive energy directors of alternating polarity. As described above, the channel spacing in this alternative embodiment is also determined using a resistive network model simulation, but is not so limited.
Continuing, the series combination of resistors R16, R17, and R18 couple between nodes 3 and 6 and model the power dissipation across zones 3, 4, and 5 as a result of the current flowing between nodes 3 and 6. The series combination of resistors R19, R20, R21, R22, and R23 couple between nodes 3 and 8 and model the power dissipation across zones 3, 4, 5, 6, and 7 as a result of the current flowing between nodes 3 and 8. The series combination of resistors R24, R25, and R26 couple between nodes 2 and 5 and model the power dissipation across zones 2, 3, and 4 as a result of the current flowing between nodes 2 and 5. The series combination of resistors R27, R28, and R29 couple between nodes 5 and 8 and model the power dissipation across zones 5, 6, and 7 as a result of the current flowing between nodes 5 and 8.
Further, the series combination of resistors R30, R31, and R32 couple between nodes 4 and 7 and model the power dissipation across zones 4, 5, and 6 as a result of the current flowing between nodes 4 and 7. The series combination of resistors R33, R34, R35, R36, and R37 couple between nodes 2 and 7 and model the power dissipation across zones 2, 3, 4, 5, and 6 as a result of the current flowing between nodes 2 and 7. Finally, the series combination of resistors R38, R39, R40, R41, R42, R43, and R44 couple between nodes 1 and 8 and model the power dissipation across zones 1, 2, 3, 4, 5, 6, and 7 as a result of the current flowing between nodes 1 and 8.
The embodiments described above with reference to
The guide channel spacing that provides relatively uniform current density is generated using resistive network models, but is not so limited.
Using the current density per zone 682, spacing ratios per zone 684 and 686 are generated. In an embodiment, two different spacing ratios per zone 684 and 686 are generated, but the embodiment is not so limited. A first spacing ratio per zone 684 references the spacing of the zones to the proximal-most/distal-most zones (zones 1 and 5) of the array, and a second spacing ratio per zone 686 references the spacing of the zones to the center zone (zone 3) of the array. Note, however, that the spacing ratios per zone can be referenced to any zone of the array in alternative embodiments.
Using either of the spacing ratios per zone 684 and 686, the relative spacing among the channels is determined by assigning a reference spacing value to the reference zone (the zone for which the spacing ration is one (1)). The spacing values for all other zones of the array are then each determined using the spacing ratio for each associated zone as a multiplier against the reference spacing value. Reference spacing values are selected using techniques known in the art.
Alternative embodiments of the tissue ablation system include differing numbers of energy directors and, therefore, differing numbers of channels in the energy director guide. As described above, the channel spacing in these alternative embodiments is also determined using a resistive network model simulation, but is not so limited.
The energy director guide of an alternative embodiment is reconfigurable to support a number of energy director configurations. For example, the energy director guide can include channels that are moveable between a number of prespecified locations in the energy director guide so that placement of the channels in a first set of prespecified locations along the guide supports the six energy guide configuration described above, and placement of the channels in a second set of prespecified locations along the guide supports the eight energy guide configuration described above. Using this embodiment, a user can support many different energy director configurations with a single energy director guide.
Referring again to
Regarding electrical coupling of the energy directors to the generator, the energy director guide of an embodiment uses direct electrical coupling, while alternative embodiments use indirect electrical coupling.
In an embodiment using indirect coupling, a coil of electrically conductive material that is insulated along its length is wound such that it forms a magnetic field around the electrically conductive energy director thereby inducing a current flow in the energy director.
As described above, the energy director guide of an embodiment supports independent control of the position of the corresponding energy directors.
Once inserted into the target tissue, components of the energy director guide exert enough force on the corresponding energy directors to secure them in the target tissue so that natural body movement will not push the energy directors out. The components of the energy director guide exert a force on the energy directors approximately in the range of 0.5 newton to 5 newton, but are not so limited.
As another example in operation, the tissue ablation system can be used to incrementally ablate a volume of target tissue as the energy directors 1104 are incrementally advanced into the target tissue.
This method is particularly useful to help control several critical parameters including energy density, thermal load from the surrounding tissue, and the electrical impedance of the tissue. When the energy density is too low the thermal effect cannot be achieved. Likewise, when the thermal load from the surrounding tissue is too large the thermal effect will also not be achieved. Low electrical tissue impedance makes it difficult to heat since the dissipated power is proportional to the tissue impedance. Very low or high impedance will also be difficult for some power supplies to deliver the required energy.
The positioning of the energy directors in an embodiment is preplanned, for example using a workstation, and the heat isotherms and ablation volume and time-course of the ablation are determined. Based on historical or empirical information, the user may determine the desired power to be delivered to the tissue, the temperature as measured by the electrode or measured elsewhere in the tissue by either integrated temperature sensors in the energy directors or satellite temperature-sensing electrodes, the desired time duration of heating, and the characteristics of impedance, to determine energy application timing parameters and control against charring and other undesired effects.
Further, the selection of an embodiment includes sizing of the electrodes based on the target organ. For example, the user can estimate a transverse dimension of the target organ. Using the estimated dimension, the user sizes the electrodes individually or as a group so that the electrodes do not extend beyond the target organ when fully inserted in the target organ.
Following the configuration and planning, the user positions the energy director guide, and inserts the electrodes into the target tissue, at block 1304. The energy directors can be placed individually or in unison within the body tissue, as described herein. Real-time imaging can be used, for example CT, MRI, and/or ultrasound, during placement of the electrodes to determine their proper position within a targeted volume of tissue. The user inserts the energy directors to a desired depth. Additionally, if the energy directors are used with coolant, the user applies the coolant as appropriate.
During some procedures involving the tissue ablation system the user separates the target organ from one or more adjacent organs, but the embodiment is not so limited. This is done to prevent the electrodes from piercing the adjacent organs upon or during insertion into the target organ. Alternatively, the user can place a shield between the target organ and any adjacent organs to protect the adjacent organs from penetration by the electrodes.
The user couples or applies power from the generator to the energy director guide and the energy directors, at block 1306. Alternatively, the power is coupled directly to the energy directors. While power is described in this example, various alternative embodiments can, instead of using power as the controlling parameter, use current, voltage, impedance, temperature, time, and/or any combination of these, to control the tissue ablation process. The power can be coupled to all of the energy directors in unison, or sequentially in a predetermined sequence, as appropriate to the treatment procedure and/or the target tissue type. Likewise, the insertion depth of the energy directors and the amount of power coupled to the energy directors is varied according to the treatment procedure and/or the target tissue type.
The application of power can be controlled either automatically or manually. When using automatic control, the process can be controlled according to a microprocessor control within the generator system itself or by at least one separate controller coupled among the components of the tissue ablation system. Further, the application of power to the energy directors can be controlled in response to measurements of temperature, impedance, and/or other feedback parameters associated with the ablation process.
When controlling ablation using temperature feedback, the temperature is increased at a rate approximately in the range of 25 degrees Celsius/minute to 100 degrees Celsius/minute to a temperature endpoint in the target tissue that is approximately in the range of 55 degrees Celsius to 110 degrees Celsius, but is not so limited. Using an appropriate rise in tissue temperature (25-100 degrees Celsius/minute) around an energy director, the highly conductive fluid inside the cells is released. This lowers the impedance around the energy director helping to prevent charring and allowing the continued (or increasing) flow of energy to the target tissue. This release is caused by the thermal damage to the cell wall. If the energy rise is too quick, the fluid will be quickly boiled or flashed off. This will result in no significant benefit and help to increase the tendency for tissue charring and a loss of ability to deliver energy to the target tissue.
In monitoring the application of power to the energy directors and the ablation process, a determination is made, either manually or automatically, as to whether the applied power has exceeded a desired value based on real-time temperature monitoring or other feedback parameters appropriate to the procedure. When it is determined that the power is exceeding the desired value, the power is reduced. If the power is within the prespecified parameters, other parameters can be monitored, such as impedance, time, and/or direct visualization of the coagulation plane. When these other parameters are found to be within acceptable limits, the power can be increased further.
Additionally, the energy director temperatures or temperatures from satellite probes within and/or within proximity of the target tissue can be monitored. When the monitored temperatures remain within acceptable levels, the power can be increased or the flow of coolant modified.
Coupling power to the energy director guide/energy directors, at block 1306, results in generation of a plane of coagulated tissue in the target tissue, at block 1308. In an embodiment, a prespecified period of time for the application of power to the energy directors determines when the plane of coagulated tissue has been generated. Therefore, when the prespecified period of time elapses, the user stops the procedure. As described above, feedback of additional information can be used to determine successful completion of the procedure. Various portions of the procedure can be repeated, as appropriate to the target tissue, until the plane of coagulated tissue having the appropriate size and shape is generated, at block 1310.
Various alternative embodiments can simultaneously use any number of energy director guides/energy directors in a procedure in order to form volumes of coagulated tissue having shapes and sizes appropriate to the treatment procedure. Numerous alternatives would be recognized by those skilled in the art in view of the tissue ablation system described herein.
The tissue ablation system and associated processes described above can include other components in a variety of combinations. In addition to the display and controller described above, for example, a stereotactic frame or frameless navigator system may be used to direct and place the energy director guide/energy directors. Various guide tubes, templates, holding apparatus, arc systems, and spatial digitizers can also be used to assist in placement of the energy directors in the target tissue. Imaging modalities such as CT, MRI, ultrasound and the like can be used before, during, or after placement of the energy directors and/or creation of the ablation volume.
In addition to including numerous types and combinations of components, there are many alternative embodiments of the tissue ablation system components described above. Some of these alternatives include alternative embodiments of the energy director guide and the energy directors, as described below.
The energy director guide of one alternative embodiment includes a soft conformal bottom element that forms a conformal surface between the target tissue and the energy director guide. The conformal element takes on the shape of the surface of the underlying target tissue. Conformal bottom elements can be constructed from a variety of materials including silicone, biocompatible foam rubbers, and urethanes. Conformal bottom elements can also be formed with the use of inflated members.
The energy director guide of various alternative embodiments may take on a variety of shapes including, but not limited to, semi-circular, arcs, and angles. Many other shapes will be recognized by those skilled in the art.
These guides can be flexible or semi-flexible in a single or multiple planes. In a single plane, the guide can be shaped to the tissue targeted below the guide. With a second plane of flexibility, the guide can be used to contour to the shape of the surface or as necessary for location of the operative site.
The energy directors of an embodiment can be used with a variety of housings that enclose the energy directors prior to deployment into target tissue. Use of the housing minimizes unintentional deployment of the energy directors and reduces the potential for injury of a user or patient by the energy directors.
Many different types of energy directors can be used with the tissue ablation system of an embodiment. Descriptions follow of some example energy directors, but the embodiment is not so limited.
Another type of energy director 1804 supports delivery of agents through a lumen in the energy director and at least one aperture 1814 in the distal end of the energy director 1804. Yet another type of energy director 1806 supports delivery of agents through a lumen in the energy director in communication with a porous material 1816 around the outer surface of the energy director 1806.
The energy directors 1802, 1804, and 1806 support deliver of agents including, but not limited to, contrast agents used to better visualizes the detailed anatomy, sclerotic agents to help decrease the overall circulation in the target region, and chemotherapy agents for use as an adjunctive therapy. Still another example agent is a hyper- or hypo-tonic solution used to create a wet electrode.
The tissue ablation system of an embodiment includes one or more energy directors that support temperature monitoring within and/or around the target tissue. The temperature monitoring supported by the energy directors supports the real-time evaluation of an ablation procedure both outside and within the effected tissue zone. An example of this could be one or more thermocouples arranged in a configuration suitable for placement within the tissue, for example on and/or within an associated energy director, wherein the thermocouples couple to temperature monitoring equipment known in the art.
In generating coagulative ablation, the tissue ablation system and associated procedures of an embodiment deliver energy that results in tissue core temperatures approximately in the range between 65 degrees Celsius and 80 degrees Celsius in the coldest portions of the target tissue volume. The coldest portions of the target tissue volume are typically those areas that are the most distant from the energy directors or are thermally shielded from the effect of the energy directors by other anatomical structures.
Likewise, the tissue ablation system and associated procedures deliver energy that results in tissue core temperatures approximately in the range between 85 degrees Celsius and 105 degrees Celsius in the warmest portions of the target tissue volume. At temperatures below this, procedural times may be unnecessarily extended. At temperatures above this, instability may result due to the superficial charring caused by the excessive tissue heating. As noted herein, these conditions can be further mitigated with the use of other factors such has hypertonic agents. In particular, a continuous infusion of a 0.9% to 8% saline solution at an approximate rate of between 0.01 cc/min to 0.5 cc/min will aid in preventing tissue charring.
The temperature monitoring energy director provides the ability to control the energy delivered to the target tissue by controlling the energy with the use of a closed- or open-loop temperature feedback system. As such, optimum energy delivery can be achieved, thereby avoiding over delivery or under delivery of energy. Over delivery of energy can create superficially charred tissue resulting in a reduction or inability to deliver energy and an incomplete ablation. Under delivery of energy could significantly increase the procedural duration or even prevent the ability to complete the procedure. By controlling the transfer of energy to the target tissue in this manner, and by using non-stick surfaces such as fluoropolymers like polypropelene and parylene on the energy directors, charring can be minimized to produce optimal energy delivery and tissue ablation. In addition, the use of temperature monitoring also provides evidence and feedback as to the completion of the procedure, as described above.
As described above, the energy director guide of an embodiment configures the energy directors to provide approximately uniform power or energy distribution through the target tissue volume. Alternative embodiments of the tissue ablation system support the application of non-uniform energy distribution via either linear or non-linearly spaced arrays. This configuration monitors a parameter such as temperature, power, or impedance and, in response, controls the delivered energy to maintain the parameter(s) within a desired target range. By using individual energy channels for each bipolar pair, the energy can easily be altered as needed. For example, with a temperature goal of 80 degrees Celsius after initial ramps of 1.5 minutes to full power, or a predetermined maximum power, the time-temperature slopes are evaluated for each zone based on a predetermined ramp (approximately in the range of 50-80 degrees Celsius/minute). Based on the temperature ramp the power is altered to better match the desired rate.
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of “including, but not limited to.” Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words “herein,” “hereunder,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application.
The above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The teachings of the invention provided herein can be applied to other ablation systems, resection systems, and medical devices, not only for the tissue ablation system described above.
The elements and acts of the various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the invention in light of the above detailed description.
All of the above references and United States patent applications are incorporated herein by reference. Aspects of the invention can be modified, if necessary, to employ the systems, functions and concepts of the various patents and applications described above to provide yet further embodiments of the invention.
In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to include all processing systems that operate under the claims to provide a method for compressing and decompressing data files or streams. Accordingly, the invention is not limited by the disclosure, but instead the scope of the invention is to be determined entirely by the claims.
While certain aspects of the invention are presented below in certain claim forms, the inventors contemplate the various aspects of the invention in any number of claim forms. Accordingly, the inventors reserve the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the invention.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7744596 *||13 Oct 2005||29 Jun 2010||Boston Scientific Scimed, Inc.||Magnetically augmented radio frequency ablation|
|US8945144||8 Sep 2010||3 Feb 2015||Covidien Lp||Microwave spacers and method of use|
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|International Classification||A61B19/00, A61M31/00, A61B18/14|
|Cooperative Classification||A61B2018/1425, A61B2018/0016, A61B2018/1475, A61B2018/00577, A61B19/201, A61B2018/143, A61B18/1477|
|4 Oct 2012||AS||Assignment|
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:RESECT MEDICAL, INC.;REEL/FRAME:029077/0996
Effective date: 20090101
Owner name: S.D.M.H. PTY. LTD., AUSTRALIA