US 20070112342 A1
A method and apparatus for controlling the extent of tissue ablation are disclosed. The method utilizes delivering energy from an energy deliver device to a plurality of deployed electrodes and regulating energy delivered to the electrodes based on the temperature sensed by at least one remote elongate sensor element. A control device may be used to supply energy to the electrodes, to produce tissue ablation that advances from individual-electrode ablation regions to fill a combined-electrode ablation volume. Information from the sensor element(s) is used for determining the extent of ablation in the regions of the sensor elements. The supply of energy to the electrodes can thus be regulated to control the level and extent of tissue ablation throughout the combined-electrode volume.
1. A method of controlling the extent of tissue ablation, comprising:
deploying a plurality of electrodes from an elongate delivery device, the electrodes defining a tissue volume;
deploying at least one elongate sensor element in the tissue volume at a position remote from the plurality of electrodes;
delivering energy from an energy delivery device to ablate or necrose at least a portion of the tissue volume;
sensing a temperature of the tissue volume with the sensor element; and
regulating energy delivery based on the temperature sensed by the sensor element.
2. The method of
3. The method of
determining a treatment endpoint responsive to the temperature of the tissue volume.
4. The method of
5. The method of
6. The method of
7. The method of
8. The method of
injecting a liquid through said electrodes into the tissue volume.
9. The method of
controlling liquid flow through each electrode individually.
10. The method of
moving the sheath axially between deployment and infusion positions at which the infusion ports are covered and exposed, respectively.
11. The method of
applying power between the plurality of electrodes and a body-surface electrode adapted to be applied to the surface of a patient.
12. The method of
13. The method of
14. The method of
This application is a continuation of U.S. patent application Ser. No. 10/142,713 filed May 10, 2002, now allowed, which claims the benefit of U.S. Provisional Application No. 60/290,060 filed May 10, 2001, both of which are incorporated herein by reference in their entirety.
This invention relates generally to a method for treating tissue, tissue masses, tissue tumors and lesions. More particularly, the invention relates to an apparatus and method for minimally invasive therapeutic treatment of tumors and tissue mass. Still more particularly, the invention relates to a method and apparatus utilizing fluid to enhance the delivery of energy to tumor and tissue masses to produce larger, faster ablation volumes with improved clinical outcomes.
Current methods for treating tumors using RF energy have several key shortcomings including incomplete ablation volumes, small ablation volumes, tissue desiccation and charring or protracted ablation times. The present invention provides a method and apparatus to solve these and other related problems.
The invention includes, in one aspect, a tissue-ablation apparatus composed of an elongate delivery device having a lumen terminating at a distal end and a plurality of electrodes carried in the device for movement between retracted positions at which the electrodes are disposed within the device's lumen, and deployed positions at which the electrodes are deployed from the distal end at a plurality of arcuate, laterally extending, angularly spaced positions. Each deployed electrode defines an individual-electrode ablation volume which, in the early phases of ablation, is proximate to that electrode when an RF current is applied to that electrode, with such deployed in tissue, where contained application of RF current to the electrodes causes the individual-electrode ablation volumes to grow and merge with each other to form a combined-electrode ablation volume.
Also in the apparatus is a plurality of elongate sensor elements carried in the device for movement between retracted positions at which the sensor elements are disposed within the device's lumen, and deployed positions at which the sensor are deployed from the distal end at a plurality of angularly spaced positions within the volume corresponding to the combined-electrode ablation volume.
A control device or unit in the apparatus is operatively connected to the electrodes and to the sensor elements for (i) supplying an RF power to the electrodes, with such deployed in tissue, to produce tissue ablation that advances from the individual-electrode ablation volumes to fill the combined-electrode ablation volume, and (ii) determining the extent of ablation in the regions of the sensor elements. The supply of RF power to the electrodes can thus be regulated to control the level and extent of tissue ablation throughout the combined-electrode volume.
The electrodes and sensor elements may be operatively connected for movement as a unit from their retracted to their deployed positions. Alternatively, the electrodes may be movable from their retracted to their retracted and deployed positions independent of the movement of the sensor elements from their retracted and deployed positions.
The sensor elements are in their deployed positions may be disposed outside of the individual-electrode ablation volumes, preferably midway between pairs of adjacent electrodes in their deployed state.
In one embodiment, the sensor elements are conductive wires, and the control device is operable to determine the impedance of tissue in the regions of the wires, as a measure of extent of ablation in the region of the sensor elements.
In another embodiment, the sensor elements have thermal sensors, and the control device is operable to determine tissue temperature in the region of the thermal sensors, as a measure of the extent of ablation in the region of the sensor elements.
In still another embodiment, the sensor elements are optical fibers, and the control device is operable to determine optical properties in the region of the fibers, as a measure of the extent of ablation in the region of the sensor elements.
The electrodes may be hollow-needle electrodes, allowing liquid to be injected through said electrodes into tissue, with the electrodes deployed in tissue. An exemplary liquid is an electrolyte, such as a physiological salt solution. In a preferred embodiment, the electrodes are designed to allow controlled fluid flow through each electrode individually.
Each infusion electrode may have a plurality of infusion ports along its distal end regions, and may be covered by a sheath that is axially movable between deployment and infusion positions at which the infusion ports are covered and exposed, respectively.
The control unit may include a display function for displaying to a user the extent of ablation of in the regions of the sensor elements, and an adjustable function, such as an RF power function, or liquid-infusion function, by which the user can adjust or modulate the rate or extent of ablation by modulating power level or amount of liquid infused into the ablation volume. Preferably the power of infusion functions can be controlled at the level of the individual electrodes, allowing for control over the rate and extent of individual-electrode volumes during the ablation procedure.
Alternatively, or in addition, the control unit may automatically control the power level and/or rate of infusion of liquid to one or more electrodes, during an ablation procedure, to modulate the rate and/or extent of individual regions of the desired ablation volume, for example, to ensure a uniform rate and extent of ablation throughout the desired combined-electrode ablation volume.
In one general embodiment, the electrodes, when deployed, are positioned near the center of the faces of a platonic solid that defines a desired combined-electrode ablation volume. The number of faces of the platonic solid, and therefore the number of electrodes deployed will be determined, for example, by the size of the desired ablation volume. The sensor elements, when deployed, may be positioned near the vertices of the platonic solid. For example, for ablating a substantially spherical volume that circumscribes a pyramid, the apparatus may have four electrodes that are positioned near the center of the faces of the pyramid when deployed, and four sensors that are placed near the vertices of the pyramid when deployed.
In another aspect, the invention includes a method for ablating a selected volume of tissue in a patient. The method includes inserting into the tissue, a tissue-ablation apparatus having (a) an elongate delivery device with a lumen terminating at a distal end, and (b) a plurality of hollow-needle electrodes carried in the device for movement between retracted positions at which the electrodes are disposed within the device's lumen, and deployed positions at which the electrodes are deployed from the distal end at a plurality of arcuate, laterally extending, angularly spaced positions. The electrodes, in their deployed positions, define the selected tissue volume to be ablated. Liquid, such as an electrolyte is introduced into the tissue through the hollow-needle electrodes, by separately controlling the rate of liquid flow through each hollow-needle electrode. RF power is applied to the electrodes, to produce RF ablation of the tissue.
The liquid may be introduced at substantially equal flow rates through each electrode. An electrolyte having a desired electrolyte concentration may be selected. The liquid may be introduced prior to, during, or following the RF ablation step.
The method may further include monitoring the extent of ablation in the tissue volume during said applying step, and adjusting the rate at which liquid is introduced through individual hollow-needle electrodes in response to the monitoring, for example, to produce a uniform rate and extent of ablation throughout tissue volume being ablated.
These and other objects and features of the invention will become more fully apparent when the following detailed description of the invention is read in conjunction with the accompanying drawings.
Embodiments of the present invention provide the benefit of a method and apparatus to treat tumors and lesions such as hepatic tumors by utilizing conductivity enhancing solutions to deliver ablative electromagnetic energy to produce faster, larger and more consistent ablation volumes than by conventional means. However one of the potential problems in infusing fluids through a hollow tube or hollow electrode is plugging of the electrode fluid lumen as the electrode is inserted into tissue, or a resulting of tissue coagulation from heating of the electrode during energy delivery or a combination of both. Further embodiments of the present invention provide a number of solutions to problem of tissue plugging of electrodes and infusion lumens occurring during insertion of the electrode into tissue or during the delivery of ablative energy.
An embodiment of a tissue infusion ablation apparatus 10 to treat tumors and lesions is shown in
Referring now to
For ease of discussion, shaft 12 will now be referred to as an introducer or delivery device 12, but all other embodiments discussed herein are equally applicable. Referring now to
Further, ports 24′ can include opto-electronic connections which allow optical and electronic coupling of optical fibers and/or viewing scopes (such as an orthoscope) to illuminating sources, eye pieces, video monitors and the like. Actuators 24″ can include rocker switches, pivot bars, buttons, knobs, ratchets, cams, rack and pinion mechanisms, levers, slides and other mechanical actuators known in the art, all or portion of which can be indexed. These actuators can be configured to be mechanically, electro-mechanically, or optically coupled to pull wires, deflection mechanisms and the like allowing selective control and steering of introducer 12. Hand piece 24 can be coupled to tissue aspiration/collection devices 26, fluid delivery devices 28 (e.g. infusion pumps) fluid reservoirs (cooling, electrolytic, irrigation etc) 30 or power source 20 through the use of ports 24′. Tissue aspiration/collection devices 26 can include syringes, vacuum sources coupled to a filter or collection chamber/bag. Fluid delivery device 28 can include medical infusion pumps, Harvard pumps, peristaltic pumps, syringe pumps, syringes and the like.
Referring back to
In various embodiments, at least portions of tissue infusion ablation apparatus 10 including introducer 12 and distal end 16 may be sufficiently radiopaque to be visible under fluoroscopy and the like and/or sufficiently echogenic to be visible using ultrasonography. In specific embodiments, introducer 12 can include radiopaque, magnopaque or echogenic markers 11, at selected locations including along all or portions of introducer 12 including distal end 16′. Markers 11 can be disposed along introducer 12 to facilitate identification and location of tissue penetrating portion 16 including tissue collection portions, ports, sensors as well as other components and sections of tissue infusion ablation apparatus 10 described herein. In an embodiment, markers 11 can be ultrasound emitters known in the art. Also tissue infusion ablation apparatus 10 can include imaging capability including, but not limited to, fiber optics, viewing scopes such as a orthoscope, an expanded eyepiece, video imaging devices, ultrasound imaging devices and the like.
In various embodiments, apparatus 10 can be configured to be percutaneously introduced into tissue through a trocar, biopsy device, or orthoscope or other percutaneous or surgical access device known in the art. For any of these devices, apparatus 10 can be introduced with the aid of a guide wire 15 which introducer 12 is configured to track over. Guide wire 15 can be any of a variety of flexible and/or steerable guide wires or hypotubes known in the art. Introducer 12 can have sufficient length to position distal tip 16′ in any portion or lobe of the bone 5 using either a percutaneous or a bronchial/transoral approach. The length of introducer 12 can range from 5 to 180 cm with specific embodiments of 20, 40, 80, 100, 120 and 140 cm. A preferred range includes 25 to 60 cm. The length and other dimensional aspects of introducer 12 can also be configured for pediatric applications with a preferred range in these embodiments of 15 to 40 cm. The diameter of introducer 12 can range from 0.020 to 0.5 inches with specific embodiments of 0.05, 0.1 and 0.3 inches as well as 1, 3, 6, 8 and 10 french sizes as is known in the art. Again, the diameter can be configured for pediatric applications with pediatric sizes of 1, 3 and 6 french. In various embodiments, the diameter of distal end 16 can range from 0.010 to 0.1 inches, with specific embodiments of 0.020, 0.030 and 0.040 inches. The diameter of distal end 16′ can be configured to be positioned in various anatomical ducts, vasculature and bronchioles, such embodiment includes diameters of 0.40″ or smaller.
In various embodiments, introducer 12 can be a catheter, multi-lumen catheter, or a wire-reinforced or metal-braided polymer shaft, port device (such as those made by the Heartport® Corp., Redwood City, Calif.), subcutaneous port or other medical introducing device known to those skilled in the art. In a specific embodiment introducer 12 is a trocar or a safety trocar and the like. Introducer 12 can be constructed of a variety of metal grade metals known in the art including stainless steel such as 304 or 304V stainless steel as well shape memory metal such as Nitino. Introducer 12 can also be constructed from rigid polymers such as polycarbonate or ABS or resilient polymers including Pebax®, polyurethane, silicones HDPE, LDPE, polyesters and combinations thereof.
In various embodiments, introducer 12 can be rigid, semi-rigid, flexible, articulated and steerable and can contain fiber optics (including illumination and imaging fibers), fluid and gas paths, and sensor and electronic cabling. In an embodiment introducer 12 is sufficiently rigid (e.g. has sufficient column strength) to pierce tissue including bone tissue without significant deflection along it longitudinal axis so as to maintain a longitudinal or other position within a tissue site. In another embodiment, all or portions (e.g. the distal portion) of introducer 12 are sufficiently flexible to pierce tissue, and move in any desired direction through tissue to a desired tissue site 5′. In yet another embodiment, introducer 12 is sufficiently flexible to reverse its direction of travel and move in direction back upon itself.
Referring now to
The amount of deflection of introducer 12 is selectable and can be configured to allow the maneuvering of introducer 12 through very tortuous anatomy and negotiate both obtuse or oblique turns in around various and anatomical structures including vasculature, ducts and bone. In specific embodiments, the distal portions of introducer 12 can be configured to deflect 0-180° or more in up to three axes to allow the tip of introducer 12 to have retrograde positioning capability. The deflection can be continuous or indexed to pre-determined amounts selectable on handpiece 24 using an indexed actuator 25′.
Referring now to
In another embodiment introducer 12 can include side ports which allow electrodes 18 to be deployed at a selectable angle with respect to the longitudinal axis 12 al of introducer 12, including about 45 and 90°. The use of such side ports is described in U.S. Pat. No. 5,683,384, which is incorporated by reference herein.
A variety of energy delivery devices and power sources can be utilized by embodiments of the invention. Specific energy delivery devices 18 and power sources 20 that can be employed in one or more embodiments include, but are not limited to, the following: (i) a microwave power source coupled to a microwave antenna providing microwave energy in the frequency range from about 915 MHz to about 2.45 GHz (ii) a radio-frequency (RF) power source coupled to an RF electrode, (iii) a coherent light source coupled to an optical fiber or light pipe, (iv) an incoherent light source coupled to an optical fiber, (v) a heated fluid coupled to a catheter with a closed or at least partially open lumen configured to receive the heated fluid, (vi) a cooled fluid coupled to a catheter with a closed or at least partially open lumen configured to receive the cooled fluid (viii) a cryogenic fluid, (ix) a resistive heating source coupled to a conductive wire, (x) an ultrasound power source coupled to an ultrasound emitter, wherein the ultrasound power source produces ultrasound energy in the range of about 300 KHZ to about 3 GHz, (xi) and combinations thereof.
For ease of discussion for the remainder of this application, the energy delivery device includes a plurality of RF electrodes 18 and the power source utilized is an RF power supply. For these and related embodiments RF power supply delivers 5 to 200 watts, preferably 5 to 100, and still more preferably 5 to 50 watts of electromagnetic energy is to the electrodes of energy delivery device 18 without impeding out. The electrodes 18 are electrically coupled to energy source 20. The coupling can be direct from energy source 20 to each electrode 18 respectively, or indirect by using a collet, sleeve, connector, cable and the like which couples one or more electrodes to energy source 20. Delivered energies can be in the range of 1 to 100,000 joules, more preferably in the range 100 to 50000 joules, still more preferably in the range of 100 to 5000 and still yet more preferably in the range 100 to 1000 joules. Lower amounts of energy can be delivered for the ablation of smaller structures such as nerves and small tumors with higher amounts of energy for larger tumors. Also delivered energies can be modified (by virtue of the signal modulation and frequency) to ablate or coagulate blood vessels vascularizing the tumor. This provides the benefit of providing a higher degree of assurance of destroying other otherwise occluding the blood supply of the tumor.
Turning now to a discussion of the fabrication and configuration of the RF electrodes, in various embodiments electrode 18 can be made of a variety of conductive materials, both metallic and non-metallic. Suitable materials for electrode 18 include, steel such as 304 stainless steel of hypodermic quality, platinum, gold, silver and alloys and combinations thereof. Also, electrode 18 can be made of conductive solid or hollow straight wires of various shapes such as round, flat, triangular, rectangular, hexagonal, elliptical and the like. In a specific embodiment all or portions of electrodes 18 can be made of a shaped memory metal, such as NiTi, commercially available from Raychem Corporation, Menlo Park, Calif.
Referring back to
The electrodes are typically ganged together at their proximal ends for movement as a unit between the retracted and deployed positions (which can include partially deployed positions). A handle or other actuator is carried on or otherwise functions with the device to allow the user to move the electrodes from their retracted positions to various deployed (partially or fully deployed) positions. Such electrode construction is known.
Electrodes, such as electrode 18, can include one or more coupled sensors 22 to measure temperature and impedance (both of the electrode and surrounding tissue), voltage and current other physical properties of the electrode and adjacent tissue. Sensors 22 can be positioned on the exterior or interior surfaces of electrodes 18 at their distal ends or intermediate sections. A radiopaque marker 11 can be attached, soldered or coated on electrodes 18 for visualization purposes. Referring now to
Electrode 18 can have selectable lengths 38 that are advanced from distal end 16 of introducer 12. The lengths can be determined by the actual physical length of electrode(s) 18, the length of an energy delivery surface 38′ of electrode 18 and the length, 38″ of electrode 18 that is covered by an insulator. Suitable lengths 38 include but are not limited to a range from 1-30 cm with specific embodiments of 0.5, 1, 3, 5, 10, 15 and 25.0 cm. The actual lengths of electrode 18 depends on the location of tissue site 5′ to be ablated, its distance from the site, its accessibility as well as whether or not the physician chooses a endoscopic, percutaneous, surgical or other procedure.
Referring now to
Suitable fluids 27 that can infused or introduced via ports 23 include but are not limited to liquids, pastes, gels emulsions, conductivity enhancing fluids, electrolytic solutions, saline solutions, cooling fluids, cryogenic fluids, gases, chemotherapeutic agents, medicaments, gene therapy agents, photo-therapeutic agents, contrast agents, infusion media and combinations thereof. Examples of suitable conductive gels are carboxymethylcellulose gels made from aqueous electrolyte solutions such as physiological saline solutions, and the like.
In various embodiments the size and diameter of ports 23 can vary depending upon their position on the electrode as well as the size and shape of the electrode. Preferably at least a portion of apertures 23 are positioned and even more preferably concentrated near the distal ends 18 de of electrodes 18. In various embodiments 1 to 10 side apertures 23 are positioned near distal end 18 de, with specific embodiments of 2, 3 and five apertures. These and related configurations allow for the infusion of an conductivity enhancing solution 27 at a location where current density in around the electrode is greatest, allowing the electrode and tissue adjacent the electrode to carry increased current density without desiccation, charring and appreciable impedance rises causing impedance shut downs of power supply 20. This in turn permits larger and faster ablation volumes to be performed without appreciable risk of impedance shut down. Apertures 23 are also configured to wet the surface 18 s of electrode 18 (as is more fully described herein) to cool it, increase conductivity and prevent tissue adhesion and charring.
In an embodiment shown in
Referring now to
In these and related embodiments apertures 23 can be fabricated using laser drilling or micro-machining or drilling techniques known in the art. The position of force neutral axis 18 nfa can be determined from the geometric centerline of electrode 18, calculated using mechanical engineering methods known in the art or identified real time using analytical optical techniques including but not limited to photo-elastic optical methods known in the art including but not limited to moire interferometry, digital speckle pattern interferometry (DSPI) and computer analysis of the fine grid technique. In one embodiment, apertures 23 can be drilled while the optical measurement of lines of stress or strain is being made to obtain a more accurate placement of the apertures along the force neutral line of the electrode. In these and related embodiments drilling of apertures 23 can be facilitated by the use of one or more fixtures known in the art.
In a related embodiment shown in
In an embodiment shown in
Referring now to
In various embodiments the use of conductivity enhancing solution 27 allows the delivery of up to 2000 watts of power into the tissue site impedance shut down, with specific embodiments of 50, 100, 150, 250, 500, 1000 and 1500 watts achieved by varying the flow, amount and concentration of infusion solution 27. The infusion of solution 27 can be continuous, pulsed or combinations thereof and can be controlled by a feedback control system described herein. In a specific embodiment a bolus of infusion solution 27 is delivered prior to energy delivery followed by a continuous delivery initiated before or during energy delivery with energy delivery device 18 or other means. In another embodiment feedback control is used to prevent impedance rises and failures by monitoring impedance at the electrode-tissue interface and increasing the flow rate of cooling and/or conductive fluid 27 in response to impedance increase using PID or other control algorithms known in the art. In related embodiment feedback control could also incorporate sensor input on the deployed length (e.g. deployment depth) of one or more electrodes and incorporate this into an algorithm to regulate fluid flow, energy delivery power level, duty cycle, duration and other ablation related parameters described herein.
In related embodiments, the conductivity of the tumor mass 5′ can be enhanced so as to preferentially increase the rate and total amount of energy delivery of energy to the tumor mass 5′ relative to healthy tissue. This can be achieved by infusing solution 27 directly into the tumor mass 5′ through the use of a needle electrode 18 placed within the tumor mass only. In related embodiments infusion solution 27 can be configured to remain or be preferentially absorbed or otherwise taken up by tumor mass 5″. This can be achieved by controlling by one or more of the osmolality, viscosity and concentration of solution 27.
Embodiments of the invention utilizing infusion of a conductivity enhancing solution 27 provide several important benefits including more consistent and homogeneous ablation volumes as well as faster ablation times. This is achieved by infusing conductivity enhancing solution 27 into the desired ablation volume or target tissue site to both increase and homogenize tissue conductivities throughout the desired ablation volume. This in turn significantly reduces the incidence of tissue desiccation, charring as well as the size zones of higher impedance any of which can slow or prevent the delivery of ablative RF or thermal energy.
Referring now to
In an embodiment shown in
Referring now to
Positioning of the slidable sheath 31 s can be controlled by configuring the sheath to be directly coupled to an actuator 24″ on handpiece 24. In alternative embodiments positioning of sheath 31 s can be controlled by the use of a positioning wire, cam, rocker switch, ratchet mechanism, micropositioner, or servomechanism and the like which is mechanically or electrically coupled to the sheath an actuable by an actuator 24″ on handpiece 24.
As discussed herein, sheath 31 s can be pulled back (e.g. proximally) once electrodes 18 are positioned at the desired tissue site or in an alternative embodiment sheath 31 s can have a sufficient inner diameter 31 sid to provide enough of an annular channel or thickness 31 at to allow fluid 27 to flow out in annular fashion from apertures 23 (either in a proximal or distal direction) to the desired tissue site. In an embodiment sheath 31 s can have diameter 1-5 mm greater than of electrode 18 providing an annular channel with a thickness between 0.5 to 2.5 mm Sheath 31 s can be actuated at handle 24 by the physician, and its position along electrode 18 is controlled. The sheath 31 s can be made from a variety of polymers including, but not limited to resilient polymers, elastomers, polyesters, polyimides, polyurethanes, silicicones, PARALENE, flouropolymers, TEFLON and the like. Also in various embodiments, slidable sheath 31 s can be configured to be electrically and/or thermally insulative or can be electrically and thermally conductive using conductive polymers known in the art. An example of a conductive polymer includes Durethane C manufactured by the Mearthane Products Corporation (Cranston, R.I.). Also, all or a portion of the sheath 31 s can have radio-opaque, magno-opaque, or echogenic markers to facilitate viewing and placement of the sheath using X-ray, CAT scans, nmr ultrasound and the like.
Referring now to
Referring now to
The packing or weave of braids or fibers 12 pds or 18 pds can be varied to control the fluid porosity of section 12 pds that is amount of fluid that diffuses or wicks through the fibers. In various embodiments the porosity of section 12 pds can be in the range of 1-2000 cc/min/cm2, preferably in the range of 10 to 1000 cc/min/cm2, with specific embodiments of 20, 50, 100, 250 and 500 cc/min/cm2.
In related embodiments all or portions of sections 12 pds or 18 pds can be fabricated from heat resistant materials and polymers such that the strength, stiffness or shape of section 12 pds or 18 pds is not appreciably degraded or altered during the delivery of RF or other thermal ablative energy. Such embodiments solve the problem of softening or deformation of a porous or fluid delivery section 12 pds or other section of elongate member 12 that can occur during delivery of thermally ablative energy to a tissue site. Suitable heat resistant polymers and materials include polyetherimide available from the General Electric Company under the trademark ULTEM® and polyetheretherketone available from the General Electric Company under the trademark UNITREX®). In other embodiments all or portions of section 12 pds can fabricated from electrically conductive or electrically dissipative polymers. Examples of electrically dissipative polymers include acetals such as UNITAL ESD available from the General Electric Company. In still other embodiments a braided porous section 12 pds is configured to increase the surface area for conductive heat transfer from section 12 pds and/or energy delivery device 18 to either fluid 27 or the surrounding tissue. These embodiments enhance the heat transfer from energy delivery device 18 and/or section 12 pds reducing the likelihood of tissue desiccation and charring on or near the energy delivery device in turn reducing impedance of the energy delivery device and impedance caused shut downs (i.e. called impeding out) of power supply 20.
In another embodiment porous section 12 pds including electrode 18 can comprise a porous, microporous or liquid permeable material 12 pm fluidically coupled to lumen 13 or 72 and configured to uniformly effuse or diffuse fluid through itself, onto its surface and into tissue. Suitable porous materials include polymer foam, polyester foam, OPCELL foam, ceramic, polyester, polyester membrane, Nylon membrane, glass fiber membranes DACRON, expanded PTFE membranes and porous ceramics known in the art. The pore sizes of porous material 12 pm can be in range from 5 to 1000 microns, preferably 40 to 500 microns and more preferably 50 to 150 microns. In these and related embodiments porous section 12 pds can be configured to wick, effuse, spray or jet fluid to wet, irrigate and cool the electrode by a combination of one or more of conductive, convective and evaporative cooling. Irrigating the electrodes provides the benefit of preventing and/or reducing an impedance rise at the electrode tissue interface. In embodiment the electrode can be coated with a hydrophilic coating or texture to facilitate wetting of the electrode surface. Examples of hydrophilic surfaces include metal, glass, and plasma treated polymers and metals, whereby the plasma treatment increases the surface tension of the substrate surface via chemical reaction and/or deposition with the surface. The plasma treatment can be a variety of plasma treatment known in the art such as argon plasma treatment.
In an embodiment of a method of the invention, tissue plugging can be prevented or reduced by infusing fluid through one or more electrode lumens 72 when the electrode is inserted into tissue and/or during the delivery of RF or other thermally ablative energy. In various embodiments the infusion rate can be in the range between 0.1 to 2 ml with specific embodiments of 0.2, 0.5, 1.0 and 1.5 ml/min. Tissue infusion flow via a fluid delivery device 28 such as an infusion or syringe pump can be initiated before or during insertion of apparatus 10 into tissue, or before or during deployment of needles 18 into tissue. Also in a related embodiment flow to one or more electrodes 18 can be monitored using sensors 22 to detect developing plugs and using feedback control (described herein) can be increased or otherwise modified to push out the plug or otherwise prevent plug formation. In specific embodiments feedback control can used to initiate a pressure or flow pulse or a series of pulses or related waveforms by the fluid delivery device (e.g. square waves, sinusoidal, step function, etc.) to push out a developing or existing plug. The pressure pulse can be in the range of 0.05 to 5 atm, preferably 0.1 to 2 atm and still more preferably 0.3 to 1 atm.
Turning now to a discussion of the use of infusion with RF energy delivery. While such a combination present advantages during ablative treatment there are also technical challenges as well. Two such challenges are (i) inconstant flow and (ii) inability to achieve a homogenous level of infusion, and or inability to infuse the entire volume of a target tissue volume particularly with only one infusion port or channel of infusion. Referring now to
In various embodiments feedback control described herein can also be employed to improve the uniformity of infusion volumes as well as better control the infusion process. This can be achieved by utilizing feedback control to monitor and control flow rates through each electrode 18 or infusion channels 72 to compensate for flow variation in any one channel and ensure more uniform volume of infusion and subsequent ablation volumes. Embodiments of the invention configured to infuse through multiple electrodes provide the advantage of reducing collective back pressure that results from a single infusion channel from fluidic pressure at the target tissue site 5″ due to tissue resistance, obstruction or plugging of a single electrode. Consequently, by distributing infusion over multiple electrodes and multiple apertures at multiple site overall flow rates, infusion rates and infusion volumes can be increased and more uniform infusion can be achieved for a selected target tissue site than via use of a single point of infusion. In particular, by controlling infusion of liquid to the individual electrodes, liquid can be supplied through each electrode at a desired flow rate, independent of the resistance to flow of other individual electrodes, allowing, for example, equal flow rates to be applied to the electrodes.
Referring now to
In alternative embodiments the delivery of an infusing solution 27 can be enhanced by several means. In one embodiment, ultrasound energy can be delivered to the selected target tissue site 5″ during or post infusion to increase the diffusion and permeation of fluid 27 into tissue site 5″ including the interstitial space of tissue site 5′ via a combination of fluid sonication, agitation (fluid and tissue and/or brownian motion, this analogous to shaking up a bottle containing a dissolvable solid in a liquid to get the solid to dissolve. Further the energy can be configured to cause cell lysis, enabling fluid 27 to diffuse into cells. The ultrasound energy can be delivered by a piezoelectric transducer known in the art that is coupled to one or more electrodes or to a separate catheter/probe in turn coupled to an ultrasound energy source. In various embodiments ultrasound energy can be delivered in the frequency range from 0.5 to 30 MHz, more preferably from 1 to 10 MHz, with specific embodiments of 2, 3, 5 and 8 Mhz.
In another embodiment fluid delivery device 28 can be configured to produce pressure pulses in flow and/or pulsed flow to enhance diffusion. Still another embodiment employs the use of RF or DC voltage to create an electroporation effect known in the art. The DC voltage can be delivered by a separate probe coupled to a DC power source with a voltage known in the art to produce an electroporation affect. Such a voltage source can be in the range of 0.1 to 10 volts.
Referring now to
Depending on the size and shape of the of the desired combined-electrode ablation volume 5 av, different number of electrodes 18 can be used to create the meta ablation volume 5 avce whose shape a volume approximates that of the desired ablation volume. In various embodiments a range of 2-12, typically 3-10, electrodes are employed to create a corresponding number of individual-electrode ablation volumes. In a specific embodiments four electrodes used to create four ablation volumes 5 ave which can have an approximately a tetrahedral orientation.
In a related embodiment platonic solids 5 ps (described herein) can be used as a positioning geometric template for individual electrode ablation volumes 5 ave to create the desired collective or meta ablation volume size 5 avc using the fewest number of individual ablation volumes 5 ave. In a specific embodiment each individual electrode ablation volumes 5 ave is positioned such that it is bisected by a single face or surface 5 pf of the respective platonic solid, with one ablation volume 5 ave positioned as such on all faces of the chosen platonic solid. Examples of suitable platonic solids include, but are not limited to a cube, tetrahedron and dodecahedron, as discussed below.
In accordance with one aspect of the invention, the progression of the ablation volumes 5 av is monitored using one or more passive (non ablating) sensor elements. Referring now to
Typically, the sensor elements, when deployed, are arrayed in an arcuate, laterally extending, angularly spaced configuration, with the sensor elements being positioned within the volume corresponding to the combined-electrode ablation volume, and with the individual sensor elements being disposed between adjacent electrodes, as detailed below. Specifically, the sensor elements are typically arrayed outside of the individual-electrode ablation volume in the region of coalescence of ablation volumes of two adjacent electrodes. In this configuration, in the early phases of RF ablation, the sensor elements are located outside of the individual-electrode ablation volumes. As the individual volumes expand and begin to coalesce, the regions of ablation begin to overlap with the sensor elements positions. By placing the sensor elements outside of the initial ablation volumes, the spread of the ablation volume, and ultimately, the desired extent of ablation throughout the combined-electrode ablation volume can be monitored and controlled, as detailed herein.
As will be appreciated, the plural sensor elements may be ganged together for movement as a unit between retracted and deployed positions, as described above for the electrodes, or they may be individually movable to place the sensor elements at different extended positions in the combined-electrode ablation volume. When ganged together, the sensor elements and electrodes and be moved independently of one another or moved as a combined electrode/sensor unit between retracted and deployed positions.
The sensor elements are designed to sense tissue properties rather than deliver ablative energy and accordingly can include one or more sensors 22 or alternatively, all or portion of passive members can be sensing elements 22. Preferably members 18 pm are configured to be non conductive and/or to not delivery appreciable amounts of RF or other electromagnetic energy. In various embodiments this can be accomplished by coating all or portions of members 18 m with an electrically insulative coating or layer 18 ic that can also be thermally insulative as well. Suitable insulative coatings 18 ic include, but are not limited to insulative polymers, PARALENE, polyimide, polyamide, TEFLON, NYLON, flouropolymers and other high dielectric materials and insulators known in the art. The coating can be applied using spray coating, dip-coating methods known in the art to produce a uniform coating thickness and consistency. The use of higher dielectric strength materials provides the benefit of thinner coatings which reduces the diameter of passive elements 18 mp in turn providing the benefit of making members 18 mp more flexible or maneuverable as well as allowing for the positioning and deployment of a greater number of members 18 mp from introducer 12. In various embodiments the thickness 18 ict of coating 18 ic can be in the range of 0.001 to 0.006 inches with specific embodiments of 0.002 and 0.003 inches.
Alternatively, all or portions of passive members 18 pm can be fabricated from nonconductive materials such as resilient polymers tubing including not limited to polyethylene, PEBAX, polyimide and other polymers known in the catheter arts.
Passive members 18 pm can be made of similar materials and/or have similar properties to electrodes 18, e.g. tissue penetrating ends, bendability, resiliency, memory, spring memory, etc. which enable members 18 pm to be deployed from introducer 12 and positioned at selectable locations within a target tissue site 5″, with the exceptions that members 18 pm are configured either to not be conductive and or not deliver ablative amounts of RF or other electromagnetic energy. In an embodiment passive member can made from 304v steel or spring steel which has an insulative coating 18 ic and also includes a lumen 72 for the passage of both fluids 27 and also electrical wires 15 for coupling to sensors 22.
Referring now to
In embodiment sensors 22 and/or passive members 18 pm can be coupled to monitoring resources 20 mr directly or via a multiplexing device allowing selective polling and signaling of one or more selected passive elements 18 pm and or sensors 22. In various embodiments, monitoring resources 20 mr can comprise monitoring circuitry such as temperature or impedance monitoring circuitry or a monitoring unit 20 mu comprising monitoring circuitry, a microprocessor/controller, a visual display known in the art and alarm circuitry. In an embodiment, the monitoring unit 20 mu can be integral to or otherwise electronically or optically coupled to power source 20.
Referring now to
Referring now to
Use of passive arrays positioned in zones 5 vz provides the benefit of a higher confidence of a complete and uniform ablation in that zones 5 vz are typically the last to reach a temperature necessary to cause ablation and/or cell necrosis and as such are the most difficult or challenging areas to ablate using RF energy. Further, the use of passive elements 18 pm eliminates any signal artifacts and/or hysteresis that might occur as result of positioning sensors 22 on the electrodes 18 or other active elements 18. Accordingly, by using passive arrays to sample ablation volume 5 av, embodiments of the invention provide the benefit of a more representative and/or accurate sampling of tissue temperature (or other tissue property indicative of ablation) of the entire desired ablation volume and in turn a higher confidence (including a higher statistical confidence) of achieving a complete ablation. More specifically, such embodiments provide a higher statistical correlation of measured temperature to actual tissue temperature throughout a desired tissue volume and thus a higher confidence of achieving a desired treatment endpoint (as indicated by temperature or other measured tissue property).
In an embodiment of a method of the invention, passive arrays can be used to measure a temperature at the outermost portions of the ablation volume or other zones 5 vz such that a clinical endpoint is established and energy is stopped or decreased once a selectable temperature is reached at or near those zones. Such embodiments provide the benefits of faster ablation times as well a decreased risk of damage to healthy surrounding tissue and structures including critical anatomical structures such as organs, nerves, blood vessels etc. In various embodiments the endpoint temperature can be in the range of 38 to 75° C., preferably 40 to 70° C. and still more preferably 50 to 70° C., with specific embodiments of 40, 41, 45, 50, 55, 60 and 65° C. In a related embodiment, temperature can continued to be monitored for a period of time after energy delivery is stopped and endpoint assessed by the time decay in tissue temperatures with a relatively constant post ablation tissue temperature or slower decay being indicative of endpoint.
In an embodiment the apparatus can include three or more power arrays or electrodes and three or more passive arrays. However other embodiment can comprise any number or combination of active electrodes and passive elements including, but not limited to (i) two or more electrodes and two or more passive elements; (ii) three or more electrodes and two or more passive elements; (iii) two or more electrodes and three or more passive elements; (iv) two or more electrodes and one or more passive elements; (v) one or more electrode and two or more passive elements; (vi) more electrodes than passive elements; (vii) more passive elements than electrodes; and (viii) and an equal number of passive elements and active elements. Further in various embodiments the exact number of the electrodes and passive elements as well as their defined volume (e.g. spherical, oval,) can be selectable by the physician depending upon factors such as the size and shape of the tumor, consistency and type of tumor (e.g. fibrous, degree of vascularity, necrotic, etc.), location of the tumor (e.g. liver vs. bone) and proximity of adjacent anatomical structures (e.g. blood vessels, organs etc.). This can be achieved though the use of a multiplexing device described herein, coupled to one or more electrodes and passive elements (so as to be able to switch them on or off) or advancing or withdrawing additional electrodes and passive elements through elongated member 12 and/or through electrodes or passive elements in place at the tissue site. Also the respective ablation or sample volume defined by the plurality of electrodes and passive elements can be adjusted by the physician by advancing or retracting one or more electrodes or passive elements or rotating one or more electrodes or passive elements or a combination of both techniques.
For ease of discussion introducer 12 will now be referred to as trocar 12; however all other embodiments discussed herein are equally applicable. Turning now to a discussion of trocar 12 and it use with passive arrays 18 pmp, one of the potential problems in using a sharpened trocar 12 with insulative passive arrays is the scraping or braiding of the insulation 18 ic on passive elements 18 pm. Referring now to
In various embodiments all or a portion of leading edge 16 le can be smoothed so as reduce or eliminate its propensity to abrade or cut insulation layer 18 ic. In an embodiment shown in
In various embodiments, the inner leading edge 16 lei can have a radius of curvature in the range of 0.0001 to 0.2 inches with specific embodiments of 0.0005, 0.001, 0.005, 0.0.01, 0.05 and 0.1 inches. In another embodiment shown in FIG. 28 c, inner leading edge 16 lei can be smoothed or otherwise made non-scything by virtue of an applied coating 16 c which can be a lubricous polymer coating known in the art such as TEFLON and the like or a hard smooth coating such as polycarbonate, acrylic and the like. Coating 16 c can be applied to all or a portion of leading edge 16 le as well as distal tip area 16 but is preferably only substantially applied to inner leading edge 16 lei. In still another alternative embodiment, the problem of insulating scything can be solved using a hardened or high strength insulative coating known in the art such as polycarbonate, LUCITE, acrylic or high strength polyimide. In a related embodiment, all or a portion of trocar distal end 16 can fabricated from molded or machined plastic or elastomer that is configured to have sufficient rigidity, column strength and related material properties to penetrate and be advanced into tissue, but is also configured to have a radiused or smooth inner leading edge 16 lei that is substantially non-scything. Plastic distal end 16 pl can be attached to the body of introducer 12 using adhesive bonding, ultrasonic welding, butt joining, crimping or other tube joining method known in the medical device arts. Suitable materials for plastic distal end 16 pl include polycarbonate, high-density polyethylene, acrylic and other rigid medical plastics known in the arts.
In other embodiments, insulative scything can be reduced or prevented via the geometric arrangement of the passive member and electrodes as they exit the trocar tip 16. Referring now to
Referring now to
Distal section 16 ds can be made of the same material as trocar 12 (e.g., stainless steel, 304 steel and the like) and fabricated using metal, machining, molding or forging methods known in the art. Section 16 ds can be integral with trocar section 12 i or alternatively can be joined to section 12 i using soldering, brazing, crimping or other metal joining methods known in the art. Configuring distal section 16 ds flush with trocar section 12 i reduces the force necessary to insert the trocar into tissue and also smoothes out the insertion process giving the physician a better tactile feel for properly positioning the trocar at the target tissue site. Further these and related embodiments of a stepped trocar distal end provide the benefit of facilitating insertion and positioning of trocar 12 and distal section 16 ds to the target tissue site, increasing the placement accuracy of distal section 16 ds, reducing procedure time and increasing procedure efficacy. In an embodiment, distal section 16 ds can have an outer diameter 16 dsod of 0.087 to 0.089 inches while the outer diameter 12 iod of the non-insulated trocar is 0.080 to 0.082 inches, and insulation layer 12 il thickness of between 0.0025 to 0.0045 inches. The length 16 dsl of distal section 16 ds can be in the range of 6.5 to 8.5 mm.
Referring now to
The radioactive material in section 18 r can include gamma, alfa- or beta- emitting materials. Suitable gamma emitters include, but are not limited to Cobalt-60, Iodine-131, Iodine-123, Indium-111, Gallium-67 and Technetium-99 m. Suitable beta emitting particles include tritium. The amount of radioactive material in portion 18 r can be configured to deliver 0.01 to 100 rads of radiation with specific embodiments of 0.1, 0.25, 0.5, 1, 10 and 50 rads. The amount of radiation delivered can measure using a radiation sensor 22 coupled to energy delivery device 18 or introducer 12. Radioactive absorbing sheath 18 s can include one or more radioactive absorbing materials known in the art that are impregnated or otherwise integral to a flexible metal or polymer layer. Such radioactive absorbing materials include but are not limited to lead, iron or graphite. In an embodiment, the radioactive absorbing material can be fabricated into a braided wire or sheath incorporated into the wall of sheath 18 s using catheter production methods known in the art.
In use, radioactive section 18 r provides the patient with the benefit of radiation therapy having a highly targeted delivery of radioactivity to the tumor mass while minimizing injury to surrounding tissue. The radiation can be delivered alone or as an adjunct to another ablative treatment describe herein (before during or after such treatment) to sensitize cancer cells to other forms of necrotic therapy or otherwise increase the probability of killing cancerous tissue. The dose of radiation can at such level for example below 1 rad that it has no affect on healthy or untreated tissue but when combined with another energetic therapy serves to surpass a lethal threshold for the selected tumorous tissue. Such therapy provides the benefit of an increased probability of killing all the cancer cells at the tumor site and thus an improved clinical outcome for the patient.
Other embodiments of the invention can employ photodynamic therapy described herein to treat tumors. Referring to
In various embodiments, photo-dynamic therapy can be conducted prior, concurrently or after with thermal ablative therapy such as RF ablative therapy. In a related embodiment, photo-agent 27 pa can also be configured to increase the hyperthermic affect of RF or other electromagnetic energy delivered to tumor mass 5″ or otherwise selectively sensitize tumor tissue to the necrotic affects of hyperthermic tumor treatment such as RF ablative treatment. In a specific embodiment photo-agent 27 pa is configured to be repelled by bone tissue including calcium-based tissue or collagen-based tissue and thus increase the agents specificity for tumorous tissue. In another embodiment the photosentisizing agent 27 pa can be configured to be activated by a wavelength of light that is reflected by bone tissue yet absorbed darker tumorous tissue. This and related embodiments provide the benefit of an agent 27 pa that is highly specific to tumor tissue yet has little or no affect on healthy bone. Further, the use of agent 27 pa allows the level of hypothermic treatment to be titrated to the size and type of tumor tissue. This can be accomplished by using a spectrum of agent's 27 pa that increases or decreases the level of tumor sensitization as needed.
Other embodiments of the invention can combine thermal or other ablative therapy described herein with chemotherapy or other medicinal based therapy. Apparatus 10 can be used to deliver various chemotherapeutic or medicinal agents along or in combination before, during or post ablation. One such family of agent includes antisense-based compounds configured to inhibit the metabolism by the liver (by inhibition of liver enzymes) of various chemotherapeutic agents and thus extend their biological half-life (e.g. effectiveness) while minimizing side-affects. An example of such a compound includes NEUGENE®) antisense compound manufacture by AVI BioPharma Inc (Portland Oreg.). Such compounds can be delivered directly to the liver using apparatus 10 or other drug delivery device described herein or known in the art.
Referring now to
The following discussion pertains particularly to the use of an RF energy source and lung treatment/ablation apparatus 10. For purposes of this discussion, energy delivery devices 314 and 316 will now be referred to as RF electrodes/antennas 314 and 316 and energy source 320 will now be an RF energy source. However it will be appreciated that all other energy delivery devices and sources discussed herein are equally applicable and devices similar to those associated with lung treatment/ablation apparatus 10 can be utilized with laser optical fibers, microwave devices and the like. The temperature of the tissue, or of RF electrodes 314 and 316 is monitored, and the output power of energy source 320 adjusted accordingly. The physician can, if desired, override the closed or open loop system.
The user of apparatus 10 can input an impedance value that corresponds to a setting position located at apparatus 10. Based on this value, along with measured impedance values, feedback control system 329 determines an optimal power and time needed in the delivery of RF energy. Temperature is also sensed for monitoring and feedback purposes. Temperature can be maintained to a certain level by having feedback control system 329 adjust the power output automatically to maintain that level.
In another embodiment, feedback control system 329 determines an optimal power and time for a baseline setting. Ablation volumes or lesions are formed at the baseline first. Larger lesions can be obtained by extending the time of ablation after a center core is formed at the baseline. The completion of lesion creation can be checked by advancing energy delivery device 316 from distal end 16′ of introducer 12 to a position corresponding to a desired lesion size and monitoring the temperature at the periphery of the lesion such that a temperature sufficient to produce a lesion is attained.
The dosed loop system 329 can also utilize a controller 338 to monitor the temperature, adjust the RF power, analyze the result, and then modulate the power. More specifically, controller 338 governs the power levels, cycles, and duration that the RF energy is distributed to electrodes 314 and 316 to achieve and maintain power levels appropriate to achieve the desired treatment objectives and clinical endpoints. Controller 338 can also in tandem govern the delivery of electrolytic, cooling fluid and, the removal of aspirated tissue. Controller 338 can also in tandem monitor for pressure leaks (via pressure flow sensors 324′) through introducer 312 tending to cause pneumothorax and actuate coupled control valves to block the fluid path causing the leak and/or initiate the delivery of sealant and/or energy at the target tissue site to seal the leak. Controller 338 can be integral to or otherwise coupled to power source 320. The controller 338 can be also be coupled to an input/output (I/O) device such as a keyboard, touchpad, PDA, microphone (coupled to speech recognition software resident in controller 338 or other computer) and the like.
Referring now to
A control signal is generated by controller 338 that is proportional to the difference between an actual measured value, and a desired value. The control signal is used by power circuits 340 to adjust the power output in an appropriate amount in order to maintain the desired power delivered at the respective primary and/or secondary antennas 314 and 316. In a similar manner, temperatures detected at sensors 324 provide feedback for maintaining a selected power. The actual temperatures are measured at temperature measurement device 342, and the temperatures are displayed at user interface and display 336. A control signal is generated by controller 338 that is proportional to the difference between an actual measured temperature, and a desired temperature. The control signal is used by power circuits 340 to adjust the power output in an appropriate amount in order to maintain the desired temperature delivered at the respective sensor 324. A multiplexer 346 can be included to measure current, voltage and temperature, at the numerous sensors 324 as well as deliver and distribute energy between primary electrodes 314 and secondary electrodes 316.
Controller 338 can be a digital or analog controller, or a computer with embedded, resident or otherwise coupled software. In an embodiment controller 338 can be a Pentium®) family microprocessor manufacture by the Intel® Corporation (Santa Clara, Calif.). When controller 338 is a computer it can include a CPU coupled through a system bus. On this system can be a keyboard, a disk drive, or other non-volatile memory systems, a display, and other peripherals, as are known in the art. Also coupled to the bus are a program memory and a data memory. In various embodiments controller 338 can be coupled to imaging systems, including but not limited to ultrasound, CT scanners (including fast CT scanners such as those manufacture by the Imatron Corporation (South San Francisco, Calif.), X-ray, MRI, mammographic X-ray and the like. Further, direct visualization and tactile imaging can be utilized.
User interface and display 336 can include operator controls and a display. In an embodiment user interface 336 can be a PDA device known in the art such as a Palm® family computer manufactured by Palm® Computing (Santa Clara, Calif.). Interface 336 can be configured to allow the user to input control and processing variables, to enable the controller to generate appropriate command signals. Interface 336 can also receives real time processing feedback information from one or more sensors 324 for processing by controller 338, to govern the delivery and distribution of energy, fluid etc.
The output of current sensor 330 and voltage sensor 332 is used by controller 338 to maintain a selected power level at primary and secondary antennas 314 and 316. The amount of RF energy delivered controls the amount of power. A profile of power delivered can be incorporated in controller 338, and a preset amount of energy to be delivered can also be profiled.
Circuitry, software and feedback to controller 338 results in process control, and the maintenance of the selected power, and are used to change, (i) the selected power, including RF, microwave, laser and the like, (ii) the duty cycle (on-off and wattage), (iii) bipolar or monopolar energy delivery and (iv) infusion medium delivery, including flow rate and pressure. These process variables are controlled and varied, while maintaining the desired delivery of power independent of changes in voltage or current, based on temperatures monitored at sensors 324. A controller 338 can be incorporated into feedback control system 329 to switch power on and off, as well as modulate the power. Also, with the use of sensor 324 and feedback control system 329, tissue adjacent to RF electrodes 314 and 316 can be maintained at a desired temperature for a selected period of time without causing a shut down of the power circuit to electrode 314 due to the development of excessive electrical impedance at electrode 314 or adjacent tissue.
Referring now to
Microprocessor 350 sequentially receives and stores digital representations of impedance and temperature. Each digital value received by microprocessor 350 corresponds to different temperatures and impedances. Calculated power and impedance values can be indicated on user interface and display 336. Alternatively, or in addition to the numerical indication of power or impedance, calculated impedance and power values can be compared by microprocessor 350 with power and impedance limits. When the values exceed predetermined power or impedance values, a warning can be given on user interface and display 336, and additionally, the delivery of RF energy can be reduced, modified or interrupted. A control signal from microprocessor 350 can modify the power level supplied by energy source 320 to RF electrodes 314 and 316. In a similar manner, temperatures detected at sensors 324 provide feedback for determining the extent and rate of (i) tissue hyperthermia, (ii) cell necrosis, and (iii) when a boundary of desired cell necrosis has reached the physical location of sensors 324.
Platonic Solid Embodiments: An embodiment of a method of the invention provides a method to utilize platonic solid geometry to minimize the number of individual ablations required to produce a collective ablation volume larger than any single ablation volume. More specifically the embodiment provides a method to maximize the effect of overlapping ablations to treat tumors larger than the capabilities of current commercially available products. This and related embodiments are also applicable to the design of a multi-electrode device where each electrode will create a sub-lesion in order to create a meta-lesion that is the combination of the smaller lesions.
Specific embodiments provide method for using one or more of a series of optimal geometries used as a template for positioning overlapping ablations to create a meta-ablation volume. In order to find the most efficient geometry for the placement of the sub-lesions it is obvious that the more symmetric the pattern the larger the meta-lesion will be for a given number of sub-lesions at a given size.
Platonic solids are composed of regular convex polygons that have the same number of polygons meeting at each corner. In all Platonic solids the number of sides is equal to or less than the number of vertices. Because the goal is to reduce the number of sub-lesions required, the sub-lesions will be placed on each face of the platonic solid and not at the vertices.
Referring now to
For platonic solids with 8 or fewer faces the sub-lesions overlap in the center of the meta-lesion. For platonic solids with 12 or more sides an additional sub-lesion in the center of the meta-lesion is required for a complete volumetric coverage. Using this concept and geometry it is possible to construct a table outlining the minimum number of ablations required to create a meta-lesion.
The apparatus and method of this invention are particularly useful for o benign and cancerous tumors using of RF energy and infused fluids. It will be readily apparent to a person skilled in the art that various embodiments and combinations of embodiments of the device and method can be used to sample or ablate/destroy body tissues, tissue locations that are accessible by percutaneous or endoscopic catheters, and is not limited to the bone in the liver, lung, bone, brain and breast. Such tissue locations and organs include, but are not limited to, the heart and cardiovascular system, upper respiratory tract and gastrointestinal system as well as the bone in the liver, lung, bone, brain and breast. Application of the apparatus and method in all of these organs and tissues are intended to be included within the scope of this invention.
Also this specification discloses various catheter-based systems and methods for treating the bone and adjoining tissue regions in the body. The systems and methods that embody features of the invention are also adaptable for use with systems and surgical techniques both in the bone and other areas of the body that are not necessarily catheter-based. Furthermore, this specification is not intended to be exhaustive or to limit the invention to the precise forms disclosed. It will be apparent that various modifications, applications, and different combinations of embodiments can be made without departing from the invention as claimed.