WO2013076439A1

WO2013076439A1 - Apparatus for destroying solid tumours in- situ

Info

Publication number: WO2013076439A1
Application number: PCT/GB2012/000844
Authority: WO
Inventors: Zhigang Wang; Alfred Cuschieri; Stuart Brown; Stuart Coleman
Original assignee: The University Of Dundee
Priority date: 2011-11-21
Filing date: 2012-11-20
Publication date: 2013-05-30
Also published as: GB2510534B; GB2510534A; GB201120009D0; GB201409103D0

Abstract

An apparatus for detaching a solid tumour from surrounding tissue. It has an elongate radio frequency (RF) probe having a distal portion with an elongate electrode and at least one tissue detaching electrode connected to the elongate electrode. The tissue detaching electrode is extensible from a retracted position to a position at a predetermined distance from the longitudinal electrode to define an enclosed boundary of an area within which a solid tumour may be located. An RF current source provides an RF ablating current with a current return path between the elongate electrode and the tissue detaching electrode such that the RF ablating current extends through the region between the tissue detaching electrode and the elongate electrode to cause tissue death in that region and wherein the RF current source provides an RF cutting current for separating the tissue from surrounding tissue.

Description

APPARATUS FOR DESTROYING SOLID TUMOURS IN- SITU

Introduction The present invention relates to an apparatus and method for ablating and

detaching/removing solid tumours and in particular to the application of

radiofrequency (RF) electromagnetic energy this purpose.

Background

Cancer in solid organs (e.g. liver, kidney, breast) can be destroyed by heat created by an alternating current or a direct current to weaken or kill cells. This technique is generally known as thermal therapy and there are three commonly used techniques for destroying cells in this way.

Cell hyperthermia exposes the cancer cells to slightly higher temperatures of around 39 to 50°C to damage and kill cancer cells or to make cancer cells more sensitive to the effects of radiation and certain anti-cancer drugs. Hyperthermia is known to be useful for treatment of a small number of cancer types, is not in widespread use and is most effective when used alongside conventional therapies.

Electrosurgery is the application of a high-frequency electric current to biological tissue as a means to cut, coagulate or desiccate tissue. Its benefits include the ability to make precise cuts with limited blood loss. Electrosurgical devices are frequently used during surgical operations helping to prevent blood loss in hospital operating rooms or in outpatient procedures.

In electrosurgical procedures, the tissue is heated by an electric current to around 100°C which causes rapid heating and destruction of cells at or near the "blade". Although electrical devices may be used for the cauterization of tissue in some applications, the term electrosurgery is usually used to refer to a quite different method than electrocautery. The latter uses heat conduction from a probe heated to a glowing temperature by a direct current (much in the manner of a soldering iron). Electrosurgery, by contrast, uses alternating current to directly heat the tissue itself.

Radio frequency ablation (RFA) is a technique in which dysfunctional tissue is ablated using the heat generated from a high frequency alternating current to treat a medical disorder. An important advantage of RF current (over previously used low frequency AC or pulses of DC) is that it does not directly stimulate nerves or heart muscle and can therefore often be used without the need for general anaesthetic. RFA is performed to treat tumours in lung, liver, kidney, bone and (rarely) in other body organs. Once a patient has been diagnosed as having a tumour, the medical procedure involves the insertion of a needle-like RFA probe inside the tumour. The radiofrequency waves passing through the probe increase the temperature within tumour to around 50°C which results in the destruction of the tumour. Generally RFA is used to treat patients with small tumours that originated within the organ (primary tumours) or those tumours which have spread to the organ (metastasis).

One advantage of this approach is that it may allow the patient to avoid major surgery for the removal of the tumour. An RF signal may be applied percutaneously with image guidance by CT, MRI or external ultrasound, or laparoscopically with visual guidance accompanied by contact ultrasound.

One of the challenges in thermal therapy is delivering the appropriate amount of heat to the correct part of the patient's body. For this technique to be effective, the temperatures must be high enough, and the temperatures must be sustained long enough, to damage or kill the cancer cells. However, if the temperatures are too high, or if they are kept elevated for too long, then serious side effects, including death can result. The smaller the area to which the heat is applied and the shorter the

treatment time the less are the side effects.

RF probes and instruments come in various designs and configurations. For example, the 17-gauge needle electrode (Cool-tip RFA, Valleylab-Covidien, USA approved by the United States Food and Drug Administration (FDA)), can be configured as a cluster (3-needles) and may be used in treating non-resectable liver tumours, This is a mono-polar RFA system which requires a skin pad-electrode to provide an electrode for the current return path to the RF generator. Monopolar RFA systems such as that described in Zerfas et al, US patent 7458971 B2, Dec. 2008 can use a probe with an array of electrodes or expandable hooks.

Young & Zerfas, (US patent 7524318, Apr 2009) discloses a system with various configured electrodes exemplified by the Christmas tree-like RITA needle (RITA Medical System, Inc., USA) or LeVeen electrode (umbrella-shaped array) from

Boston Scientific (www.bostonscientific.com). Tissue impedance and/or in-situ temperature measurement are used as feedback to a control system which provides the appropriate level of RF energy output. Bipolar RF probes can be created by closely arranging 2 electrodes at the tip of an RFA needle such as in CelonProSurge (www.celon.com) applicator [Anticancer Res 29:1309-1314 (2009)]. Bipolar and multipolar RFA electrode systems are shown in Lee, Jr. et al, US patent 7520877 B2, Apr 2009.

Where tumour cells have not been completely destroyed residual viable cancer cells will be present in the patient and will result in cancer recurrence after treatment.

When using existing RFA devices, it is difficult to know where the RFA treatment margin is and it is difficult to deliver the RFA within the margin. It is also difficult to heat the tumour uniformly across the tumour to achieve RF ablation of the whole targeted tissues within the treatment margin.

Current RFA technology provides an RFA electrode (or multiple electrodes) which when inserted into the target tumour, heats the tumour tissue around the electrode(s). The heat then conducts to the outer regions achieving volumetric thermal ablation The use of point source heating creates a reduction in heat intensity at a distance from the electrode and a non-uniform heat distribution especially to the periphery of the tumour and an inability to accurately determine the physical extent to which treatment has been effective and therefore the treatment margin. This problem accounts for the inability of the current RFA technology to treat effectively tumours which are >3.5 cm. Tissue heterogeneity and local thermal losses (heating sink effect from blood vessels) also contribute to non-uniform heat distribution and to the potential for incomplete ablation which causes the presence of residual viable cancer cells and hence recurrence of the cancer after treatment.

WO99/44506 Senorx discloses a method and apparatus for isolating a small target lesion using a rotatable cutting element positioned on a shaft. It is noted that the apparatus disclosed in WO99/44506 is used to cut tissue in order to isolate living tissue within a detached volume so that the tissue in the volume is suitable for biopsy. Therefore, the apparatus in WO99/44506 is configured to maintain a high current density at the cutting element where cells are to be destroyed and a significantly lower current density within the volume so as to minimise cell death within the volume.

Summary of the Invention In accordance with a first aspect of the invention there is provided an apparatus for detaching a solid tumour from surrounding tissue, the apparatus comprising:

an elongate radio frequency (RF) probe having a distal portion for detaching a tumour and a proximal portion,

wherein the distal portion comprises an elongate electrode having a longitudinal axis and at least one tissue detaching electrode which is operatively connected to the elongate electrode and which is radially extendable from a retracted position on the longitudinal axis of the elongate electrode to an extended position at a

predetermined distance from the longitudinal electrode to define an enclosed boundary of an area within which a solid tumour may be located, wherein, the elongate electrode and the tissue detaching electrode form an electrical circuit where the return path for the electricity is located substantially between the elongate shaft and the tissue detaching element,

and an RF current source which provides an RF ablating current with a current return path between the elongate electrode and the tissue detaching electrode such that the RF ablating current extends through the region between the tissue detaching electrode and the elongate electrode to cause tissue death in that region and wherein the RF current source provides an RF cutting current for separating the tissue from surrounding tissue. Preferably, the apparatus comprises first and second tissue detaching electrodes.

Preferably, the the elongate electrode and the tissue detaching electrode have opposite polarities.

Preferably, the first and second tissue detaching electrodes are arranged on opposing sides of the elongate electrode.

Optionally, the first and second detaching electrodes are arranged adjacent to one another on the elongate electrode.

Preferably, the extended position of the first detaching electrode is a greater distance from the elongate electrode than the extended position of the second detaching electrode.

Optionally, the tissue detaching electrode comprises a continuous flexible wire.

Optionally, the tissue detaching electrode comprises a shape memory alloy. Preferably, the shape memory alloy can be changed in-situ to its previously heat- treated shape to optimally conform to any specific requirements of the volume where the tumour is to be destroyed.,

Preferably, the apparatus further comprises a sleeve from which the distal portion is extendable.

Preferably, the wire is resiliently housed in the sleeve such that as the distal portion is extended from the sleeve, the wire progressively extends to the extended position. Preferably, the detaching electrode comprises at least two rigid arms articulatably connected to move from the retracted position to the extended position.

Preferably, the articulatable connection comprises a hinge. Preferably, the detaching electrode is fixedly connected to the elongate electrode at the distal end of the apparatus end remote and is slidably connected to the elongate electrode at the proximal end of the apparatus. Preferably, the end of the elongate electrode which is remote from the handle comprises a cutting tip for easy insertion into a tumour.

Preferably, the cutting tip is heated. Preferably, the cutting tip is heated electrically.

Preferably, the RF current provides a heating effect by raising the temperature experienced by the tissue to between 50°C and 95°C for ablation and over 100 °C for detaching a solid tumour.

Optionally, the RF current heats provides a heating effect by raising the temperature experienced by the tissue to between 40°C and 50°C.

Preferably, the proximal end of the apparatus comprises a handle.

The present invention provides for RF ablation of tumour tissue and physical separation of the ablated target tumour tissue from its periphery margin.

In short, the disclosed method and device is novel in both RFA electrode

structure/configuration (stiff and rigid electrode material can be used while conformable electrode deployment can also be achieved) and RF power delivery method or RFA treatment procedures.

In accordance with a second aspect of the invention there is provided a method for detaching a solid tumour from surrounding tissue, the method comprising the steps of:

introducing an RF probe into the tumour;

radially extending at least one tissue detaching electrode from a longitudinal axis of the elongate electrode to a predetermined distance from the longitudinal electrode to define an enclosed boundary of an area within which a solid tumour may be located and

rotating the elongate electrode and detaching electrode about the longitudinal axis to detach the tissue and to ablate the tissue between the elongate electrode and the tissue detaching electrode, wherein

an RF current is provided to the device which heats the tissue surrounding the tissue detaching electrode to a temperature at which RF ablation occurs or RF cutting occurs during rotational tissue detaching period. The present invention provides for RF ablation of target tumour and for physical/RFA separation of the tumour from its periphery margin.

Preferably, the elongate electrode and the tissue detaching electrode form an electrical circuit where the return path for the electricity is located substantially between the elongate shaft and the tissue detaching element.

Preferably, the elongate electrode and the tissue detaching electrode form an electrical circuit where the return path for the electricity is located substantially between the elongate shaft and the tissue detaching element. Preferably, the RF current is amplitude-changeable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback.

Optionally, the RF current is waveform-switchable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback.

Preferably, the RF current provides a heating effect by raising the temperature experienced by the tissue to between 50°C and 95°C for ablation and over 100 °C for detaching a solid tumour. Preferably, the elongate electrode and the tissue detaching electrode form an electrical circuit where the return path for the electricity is located substantially between the elongate shaft and the tissue detaching element. In accordance with a third aspect of the invention there is provided an apparatus for detaching a solid tumour from surrounding tissue, the apparatus comprising:

predetermined distance from the longitudinal electrode to define an enclosed boundary of an area within which a solid tumour may be located, wherein, the detaching electrode comprises at least two rigid arms articulatably connected to move from the retracted position to the extended position.

Preferably, the apparatus comprises first and second tissue detaching electrodes. Preferably, the first and second tissue detaching electrodes are arranged on opposing sides of the elongate electrode.

Preferably, the extended position of the first detaching electrode is a greater distance from the elongate electrode than the extended position of the second detaching electrode. Preferably, the detaching electrode comprises at least two rigid arms articulatably connected to move from the retracted position to the extended position.

Preferably, the articulatable connection comprises a hinge. Optionally, the articulatable connection comprises a flexible mechanical structure or joint.

Preferably, the detaching electrode is fixedly connected to the elongate electrode at the distal end of the apparatus end remote and is slidably connected to the elongate electrode at the proximal end of the apparatus.

Preferably, the RF current is amplitude-changeable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback.

Preferably, the RF current is waveform-switchable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback.

Preferably, the end of the elongate electrode which is remote from the handle comprises a cutting tip for easy insertion into a tumour.

Preferably, the cutting tip is heated.

Preferably, the cutting tip is,heated electrically.

Preferably, the proximal end of the apparatus comprises a handle.

Preferably, an RF current is provided to the device which heats the tissue surrounding the tissue detaching electrode to a temperature at which RF ablation occurs whilst the apparatus is being turned about its longitudinal axis to detach the tissue and the tissue between the elongate electrode and the tissue detaching electrode is also ablated.

Preferably, the RF current provides a heating effect by raising the temperature experienced by the tissue to between between 50°C and 95°C for ablation and over 100°C for detaching a solid tumour. Brief Description of the Drawings

The present invention will now be described by way of example only, with reference to the accompanying drawings in which:

Figure 1a shows a schematic diagram of a first embodiment of the present invention in the retracted position, figure 1b shows a schematic diagram of the first

embodiment in its extended position and figure 1c depicts the device in use; Figure 2a shows a schematic diagram of a second embodiment of the present invention in the retracted position, figure 2b shows a schematic diagram of the second embodiment in its extended position and figure 2c depicts the device in use ;

Figure 3a shows a schematic diagram of a third embodiment of the present invention in the retracted position, figure 3b shows a schematic diagram of the third

embodiment in its extended position and figure 3c depicts the device in use;

Figure 4a shows a schematic diagram of a fourth embodiment of the present invention in the retracted position, figure 4b shows a schematic diagram of the fourth embodiment in its extended position;

Figure 5a shows a photograph of a fifth embodiment of the present invention in the retracted position, figure 5b shows a photograph of the fifth embodiment in its extended position, figure 5c shows the embodiment in its extended position with handle, figure 5d shows the embodiment separating and ablating the target volume using a potato model and a radio frequency ablation gel phantom and figure 5e shows the effect of RF ablation on a piece of chicken.

Detailed Description of the Drawings

Figures 1a, 1b and 1c show a first embodiment of the present invention. Figure 1a shows the apparatus 1 in its retracted position. The apparatus 1 has a distal portion 3 and a proximal portion 5 which contains a handle 7 at the proximal end. A slidable coupling or sleeve 9 is concentric with the proximal portion and can slide along the length of the apparatus 1. The elongate electrode 11 forms part of the distal portion 3 of the apparatus 1 and has a tip 13 shaped to a point to assist insertion of the device. In this and some other embodiments of the invention, the tip 13 may be heated using electricity or some other means to further assist with insertion (also minimising blood loose and avoiding tumour cell spreading by ablative killing). A fixed coupling 15 is located at the distal end of the apparatus 1 beside the tip 13.

Detaching electrode 17 comprises a proximal arm 19 which is connected to the slidable coupling 9 and a distal arm 23 which is connected to the fixed coupling 5. The proximal arm 19 and the distal arm 23 are connected by an articulating connector 21 which allows the angle between the arms to be varied. Both arms are made of a rigid electrically conducting material. Figure 1b shows the detaching electrode in its extended position which is caused by movement of the slid-able coupling towards the distal end 3 of the apparatus 1. The detaching electrode and the elongate electrode have opposite polarity which means that an electrical return path is created between the elongate electrode and the detaching electrode which concentrates the energy from the RF current in that area.

Figure 1c shows the apparatus 1 in situ 25 with tissue represented by shading 27 and a tumour 29 shown centrally within the bounded area formed between the detaching electrode and the elongate electrode.

Figures 2a, 2b and 2c show a second embodiment of the present invention. Figure 2a shows the apparatus 31 in its retracted position. The apparatus 31 has a distal portion 33 and a proximal portion 35 which contains a handle 37 at the proximal end. A slidable coupling or sleeve 39 is concentric with the proximal portion and can slide along the length of the apparatus 31. The elongate electrode 41 forms part of the distal portion 33 of the apparatus 31 and has a tip 43 shaped to a point to assist insertion of the device. In this and some other embodiments of the invention, the tip 43 may be heated using electricity or some other means to further assist with insertion. A fixed coupling 45 is located at the distal end of the apparatus 31 beside the tip 43. The detaching electrode comprises a first detaching electrode 47 having a proximal arm 49 which is connected to the slidable coupling 39 and a distal arm 53 which is connected to the fixed coupling 45. The proximal arm 57 and the distal arm 59 are connected by an articulating connector 51 which allows the angle between the arms to be varied. Both arms are made of a rigid electrically conducting material.

The detaching electrode further comprises a second detaching electrode 55 having a proximal arm 57 which is connected to the slidable coupling 39 and a distal arm 59 which is connected to the fixed coupling 45. The proximal arm 57 and the distal arm 59 are connected by an articulating connector 61 which allows the angle between the arms to be varied. Both arms are made of a rigid electrically conducting material.

The first and second detaching electrodes 47, 55 are substantially identical in size and because they are attached to the same slidable coupling 39 and fixed coupling 45 they will extend outwards approximately to the same distance from the elongate electrode 41 and their arms 49, 53 and 57, 59 will be at the same angle to one another.

Figure 2b shows the detaching electrodes in their extended position which is caused by movement of the slidable coupling towards the distal portion 33 of the apparatus 31. The detaching electrodes and the elongate electrode have opposite polarity which means that an electrical return path is created between the elongate electrode and the detaching electrodes which concentrates the energy from the RF current in that area.

Figure 2c shows the apparatus 31 in situ 63 with tissue represented by shading 65 and a tumour 67 shown centrally within the bounded area formed between the detaching electrode and the elongate electrode. Figures 3a, 3b and 3c show a third embodiment of the present invention. Figure 3a shows the apparatus 71 in its retracted position. The apparatus 71 has a distal portion 73 and a proximal portion 75 which contains a handle 77 at the proximal end. A slidable coupling or sleeve 79 is concentric with the proximal portion and can slide along the length of the apparatus 71. The elongate electrode 81 forms part of the distal portion 73 of the apparatus 71 and has a tip 83 shaped to a point to assist insertion of the device. In this and some other embodiments of the invention, the tip 83 may be heated using electricity or some other means to further assist with insertion. A fixed coupling 85 is located at the distal end of the apparatus 71 beside the tip 83.

The detaching electrode comprises a first detaching electrode 87 having a proximal arm 89 which is connected to the slidable coupling 79 and a distal arm 93 which is connected to the fixed coupling 85. The proximal arm 89 and the distal arm 93 are connected by an articulating connector 91 which allows the angle between the arms to be varied. Both arms are made of a rigid electrically conducting material.

The detaching electrode further comprises a second detaching electrode 95 having a proximal arm 97 which is connected to a second slidable coupling 103 which is connected to slidable coupling79 and a distal arm 101 which is connected to the fixed coupling 85. The proximal arm 97 and the distal arm 101 are connected by an articulating connector 99 which allows the angle between the arms to be varied. Both arms are made of a rigid electrically conducting material. The first detaching electrode 87 has larger dimensions than the second detaching electrodes 95 and when in their extended positions are asymmetrical. This allows the respective electrodes to contact with different parts of the tumour as illustrated in figure 3c. Figure 3b shows the detaching electrodes in their extended position which is caused by movement of the slidable couplings 79, 103 towards the distal portion 95 of the apparatus 7 . The detaching electrodes and the elongate electrode have opposite polarity which means that an electrical return path is created between the elongate electrode and the detaching electrodes which concentrates the energy from the RF current in that area.

Figure 3c shows the apparatus 71 in situ 105 with tissue represented by shading 107 and a tumour 109 shown centrally within the bounded area formed between the detaching electrode and the elongate electrode. The arms of the detaching electrodes are made of an electrically conducting material which is of sufficient rigidity to remain retain its shape during the process of deployment and use in surgery. Advantageously, the use of such arms allows the margins around the tumour to be well defined and predictable. This allows a surgeon greater confidence that the margin surgery has removed the margin of tissue around a tumour that was intended.

Use of the embodiments of the present invention shown in figures 1 to 3 will now be described with respect to a novel method for tissue removal. Other methods such as electrosurgery and high temperature ablation may be use with the apparatus of the present invention as exemplified in but not limited to those shown in figures 1 to 3.

In use, an RF current return path is created through the tissue between the tissue detaching electrode and the elongate electrode, the electrical current heats the tissue surrounding the tissue detaching electrode and the tissue between the tissue detaching electrode and the elongate electrode to a temperature at which RF ablation occurs and cell eath ensues. The device further provides for cutting of tissue whilst the apparatus is being turned about its longitudinal axis to detach the tissue. In the case of this method as described in relation to the above embodiments of the present invention, they may each be deployed in-situ to the periphery of the target or may be deployed in the margin lines/areas of the target. Both of these deployments they will provide RFA treatment outside the margin in line with prior diagnostic images such as those obtainable from magnetic resonance imaging ( RI), computed tomography (CT) or ultrasound (US).

Once electrodes have been deployed in the treatment margin, the probe can be rotated thus enabling the deployed electrodes to perform RF cutting/ablating of target periphery for physical separation of the RF treated tumour tissue from surrounding healthy tissues. A complete physical separation of the target tumour, with a clear margin of RF ablated tissue layer in between the outside healthy tissues and the inside tumour, will stop any blood supply to the target tumour cells which will cause cell death. The above embodiments show with multiple rigid electrodes for rotational RF periphery cutting and uniform RF ablation. The design of the probe with deployment mechanism has one or two detachment electrodes but additional detachment electrodes may be used. The extent to which the detachment electrodes are extended may be adjusted in situ.

The rigid electrodes can be made of shape memory alloy (S A) materials such as Nickel Titanium (NiTi or Nitinol) with any suitable pre-treated shapes. For example, a straight rigid SMA wire or strip in Figs. 1-3 can be changed in-situ to its previously heat-treated shape such as a curved wire or strip when it is heated (by RF current) above its transformation temperature. The transformation temperature of Nitinol material can be adjusted and may be set to that from body temperature up to 100 degree C, for example at 50 degree C. The selection of pre-treated shapes for the rigid electrode is to optimally conform to any specific or irregular cancer geometry of individual patient, thus this will cause less damage to the surrounding healthy tissue beyond its margin clearance (e.g. 5mm).

The detachment electrode connectors may be flexible mechanical structures or mechanical joints with sliding/locking mechanisms, such as pin/hinge (shoulder and elbow joints). Due to the rigidity of the structure, the deployed shape and size are well controlled and pre-determined by the user. This, along with the rigidity of the arms, assists in creating a clear and pre-defined treatment margin along the deployed electrode elements (and treatment area/volume within the margin). The electrode element can be a rounded rod or tube or sharp blade to suit physical cutting and RF ablation and cutting.

A forced probe rotation, with deployed electrodes (arms) heated by optimal RF current, will cut through the target tissue volume along its margin line and separate the target tissue from the surrounding healthy tissues, as illustrated in Figures 1c, 2c and 3c. After use the probe will be withdrawn from the surgical site with RF separated and ablated target tissue within the organ. The treated target tissue remains in-situ and will completely die and gradually shrink, as occurs when using clinical RFA or HIFU (high intensity focused uttrasound) for the treatment of tumours. If needed, the separated target tissue can be further RF ablated to destroy the whole separated tissue volume. One obvious advantage to treating the separated target using RFA is that there will be no blood supply into the separated tissue, thus no 'heat sink' effect due to blood flow. More uniform heat distribution and faster RFA treatment time would be achieved. Further removal of this separated target tissue is possible since the probe can further cut/slice the target into smaller pieces which would facilitate the removal.

Figure 4 shows an alternative embodiment of the present invention, the fourth embodiment. The apparatus 111 comprises a distal portion 1 3 and a proximal portion 115 which has a handle 17 at the distal end. The detaching electrode is a resilient wire electrode which is extendible from a sheath along with the elongate electrode. Insertion of the apparatus 111 allows the elongate electrode and the wire to extend outwards from the sheath 1 9 allowing the wire electrode to expand to an extended position (Figure 4b) at a suitable size for providing a clear margin around a tumour 27. As with the previous embodiment, this example of the present invention allows the rotational RF ablation and separation of the tumour.

In use, an RF current is provided to the device which heats the tissue surrounding the tissue detaching electrode to a temperature at which RF ablation occurs whilst the apparatus is being turned about its longitudinal axis to detach the tissue and the tissue between the elongate electrode and the tissue detaching electrode is also ablated.

When in the retracted-state, the apparatus is inserted by puncturing the patient's tissue and withdrawal after treatment completion. The apparatus is deployed into its expanded state at which point the RF current is applied to the circuit and the space between the detaching electrode (s) and the elongate electrode forms the return path for the RF current thereby ablating the tissue in its path. Figures 5a to 5e shows photographs of one prototype device in an alternative embodiment of the present invention, the fifth embodiment. The apparatus 131 comprises a distal portion 135 and a proximal portion 137 which has a handle 139 at the distal end. The detaching electrode 141 is made of a shape memory alloy (SMA) super-elastic wire which can be retracted into the probe shaft 142, which has an outside diameter of 3mm, in the retracted position (Fig.5a) and extended to a predetermined position in-situ (Fig.5b) for providing a clear margin around a target tumour. In this embodiment of the present invention, the detaching electrode and the central shaft have opposite polarities making the device bipolar. The device is capable of resecting and ablating a lesion with a range of sizes, up to a maximum lesion diameter of around 36mm. The device has two electrodes; the central electrode 43 is made from stainless steel and has dimensions of 3x22mm length. It is connected to a high-temperature resistant wire which runs inside the instrument to its proximal end, and to insulating polymer components.

The detaching (arc) electrode 141 is made of 0.5mm nickel-titanium alloy wire. The wire is formed into an approximately semi-circular shape by heat-treatment. When retracted this wire will lie alongside the central electrode 43 (Figure 5a), but when deployed it will return to its set shape due to the superelastic effect (Figure 5b). This effect allows the wire to undergo large strains during deployment without sustaining damage, thus a relatively large and stiff electrode can be deformed into a range of shapes. The alloy composition and heat treatment of the arc electrode have been selected to maximise the temperature range in which the superelastic effect will operate.

A number of materials are used in this embodiment of the inventin. 30% glass-fibre filled Polyetheretherketone (PEEK) was used to produce insulating components due to its high strength and rigidity and good high-temperature performance.

Polytetrafluoroethylene (PTFE) was also used to insulate metal components for its excellent high temperature performance and insulating properties. The devices shaft and point are made of stainless steel, due to its high strength and stiffness. Two thermocouples are integrated into the prototype at key locations to allow temperature monitoring during use. The instrument shaft 142 is approximately 200mm long and is attached to a handle 139 (Figure 5c). This handle allows for controlled deployment of the arc electrode by rotating the proximal section 33 of the handle, and allows electrical connections to be plugged in.

As with the previous embodiment, an RF current return path is created through the tissue between the tissue detaching electrode and the elongate electrode, the electrical current heats the tissue surrounding the tissue detaching electrode and the tissue between the tissue detaching electrode and the elongate electrode to a temperature at which RF ablation occurs and cell eath ensues. The device further provides for cutting of tissue whilst the apparatus is being turned about its

longitudinal axis to detach the tissue. Figure 5d shows the use of a potato evaluation model 49 (left figure) and the use of a (RFA evaluation) gel phantom 151 (right photograph) which shows a detached and ablated (spherical-shaped) volume 52, and a section of the gel phantom removed 53 for the purpose of viewing 52 (exposed view). Figure 5e shows an ex-vivo fresh chicken model for RF ablation wherein the RFA temperature and temperature distribution was measured and plotted on the graph of temperature Vs time. The key shown beside the graph represents the curves for positions 1 to 5 in the order they are shown on the graph. It is notable that the flesh in the entire region between the detaching electrode and the elongate electrode has turned white insicating that it has been cooked and the cells are dead. A margin around both electrodes is also white, showing the extent beyond the electrofes at which cell death will occur.

Temperature at position 4, located at the outside of the ablation margin, was monitored around 40 deg C which will not cause significant damage to the

surrounding healthy tissue. The ablated chicken tissue, with whiten colour, were all heated between 50 to 90 deg C after applying RF power in over 10 min, and heat was concentrated on the intended (treatment) area between the detaching electrode and axial electrode. This clearly shows heating localised inside the region between the detaching electrode 141 and the central electrode 143.

The following are examples of the way in which the present invention may be used for the destroying large solid tumours (>3cm diameter) in situ. . Example 1

a. extending the cutting electrode

b. ablating in and around the current return path

c. retracting the cutting electrode

d. turning the probe to a new position

e. repeating i to iii n times

f . cutting around the dead tissue.

2. Example 2

a. extending the cutting electrode

b. ablating in and around the current return path

c. switch off RF

d. turning the probe to a new position

e. ablating in and around the current return path

f. repeat

3. Example 3

a. extending the cutting electrode

b. ablating in and around the current return path

c. Turn to first position

d. Turn to second position

e. Repeat as required

In some examples of the present invention, carbonisation of the tissue around the tumour provides an extra margin within which cells have been destroyed. It also provides a barrier which will prevent blood from reaching the cite from where the tumour has been removed. Improvements and modifications may be incorporated herein without deviating from the scope of the invention.

Claims

Claims . An apparatus for detaching a solid tumour from surrounding tissue, the apparatus comprising:

an RF current source which provides an RF ablating current with a current return path between the elongate electrode and the tissue detaching electrode such that the RF ablating current extends through the region between the tissue detaching electrode and the elongate electrode to cause tissue death in that region and wherein the RF current source provides an RF cutting current for separating the tissue from surrounding tissue.

2. An apparatus as claimed in claim 1 wherein, the elongate electrode and the tissue detaching electrode have opposite polarities.

3. An apparatus as claimed in claim 1 or claim 2, comprising first and second tissue detaching electrodes.

4. An apparatus as claimed in claim 3 wherein, the first and second tissue detaching electrodes are arranged on opposing sides of the elongate electrode.

5. An apparatus as claimed in claim 3 wherein, the first and second detaching electrodes are arranged adjacent to one another on the elongate electrode.

6. An apparatus as claimed in any preceding claim wherein, the extended position of the first detaching electrode is a greater distance from the elongate electrode than the extended position of the second detaching electrode. 7. An apparatus as claimed in any preceding claim wherein, the apparatus further comprises a sleeve from which the distal portion is extendable.

8. An apparatus as claimed in any preceding claim wherein, the detaching electrode comprises at least two rigid arms articulatably connected to move from the retracted position to the extended position.

9. An apparatus as claimed in claim 8 wherein, the articulatable connection comprises a hinge or a flexible mechanical structure 10. An apparatus as claimed in any preceding claim wherein, the detaching electrode is fixedly connected to the elongate electrode at the distal end of the apparatus and is slidably connected to the elongate electrode at the proximal end of the apparatus. 11. An apparatus as claimed in any preceding claim wherein, the end of the elongate electrode which is remote from the handle comprises a cutting tip for easy insertion into a tumour.

12. An apparatus as claimed in any preceding claim wherein, the cutting tip is heated.

13. An apparatus as claimed in claims 1 to 7 , 11 and 12 wherein, the tissue detaching electrode comprises a continuous flexible wire. 14. An apparatus as claimed in claim 13 wherein, the wire is resiliency housed in the sleeve such that as the distal portion is extended from the sleeve, the wire progressively extends to the extended position.

15. An apparatus as claimed in any preceding claim wherein, the tissue detaching electrode comprises a shape memory alloy.

16. An apparatus as claimed in claim 15 wherein, the shape memory alloy can be changed in-situ to its previously heat-treated shape to optimally conform to any specific requirements of the volume where the tumour is to be destroyed.,

17. An apparatus as claimed in any preceding claim wherein, the RF current provides a heating effect by raising the temperature experienced by the tissue to between between 50°C and 95°C for ablation and over 100 °C for detaching a solid tumour. 8. An apparatus as claimed in any preceding claim wherein, the RF current heats provides a heating effect by raising the temperature experienced by the tissue to between 40°C and 50°C.

19. A method for detaching a solid tumour from surrounding tissue, the method comprising the steps of:

introducing an RF probe into the tumour;

an RF current is provided to the device which heats the tissue surrounding the tissue detaching electrode to a temperature at which RF ablation occurs or RF cutting occurs during rotational tissue detaching period.

20. The method as claimed in claim 9 wherein, the elongate electrode and the tissue detaching electrode form an electrical circuit where the return path for the electricity is located substantially between the elongate shaft and the tissue detaching element.

21. The method as claimed in claim 19 or claim 20 wherein, the RF current is amplitude-changeable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback.

22. The method as claimed in any of claims 19 to 21 wherein, the RF current is waveform-switchable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback. 23. The method of any of claims 19 to 22 wherein, the RF current provides a heating effect by raising the temperature experienced by the tissue to between between 50°C and 95°C for ablation and over 100 °C for detaching a solid tumour.

24 The method of any of claims 9 to 23 wherein, the elongate electrode and the tissue detaching electrode form an electrical circuit where the return path for the electricity is located substantially between the elongate shaft and the tissue detaching element.

25. An apparatus for detaching a solid tumour from surrounding tissue, the apparatus comprising:

26. An apparatus as claimed in claim 25 wherein, the elongate electrode and the tissue detaching electrode form an electrical circuit where the return path for the electricity is located substantially between the elongate shaft and the tissue detaching element.

27. An apparatus as claimed in claim 25 or claim 26 wherein, the apparatus comprises first and second tissue detaching electrodes.

28. An apparatus as claimed in claim 27 wherein, the first and second tissue detaching electrodes are arranged on opposing sides of the elongate electrode. 29. An apparatus as claimed in claim 27 wherein, the first and second detaching electrodes are arranged adjacent to one another on the elongate electrode.

30. An apparatus as claimed in claims 27 to 29 wherein, the extended position of the first detaching electrode is a greater distance from the elongate electrode than the extended position of the second detaching electrode.

31. An apparatus as claimed in any of claims 25 to 30 wherein, the detaching electrode comprises at least two rigid arms articulatably connected to move from the retracted position to the extended position.

32. An apparatus as claimed in any of claims 25 to 31 wherein, the articulatable connection comprises a hinge or a flexible mechanical structure

33. An apparatus as claimed in any of claims 25 to 32 wherein the detaching electrode is fixedly connected to the elongate electrode at the distal end of the apparatus end remote and is slidably connected to the elongate electrode at the proximal end of the apparatus.

34. An apparatus as claimed in any of claims 25 to 33 wherein, the RF current is amplitude-changeable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback.

35. An apparatus as claimed in any of claims 25 to 34 wherein, the RF current is waveform-switchable for the purpose of ablation or cutting/detaching of tissue and controlled by temperature feedback. 36. An apparatus as claimed in any of claims 25 to 35 wherein, the end of the elongate electrode which is remote from the handle comprises a cutting tip for easy insertion into a tumour.

37. An apparatus as claimed in claim 36 wherein, the cutting tip is heated.

38. An apparatus as claimed in any of claims 25 to 30 wherein, an RF current is provided to the device which heats the tissue surrounding the tissue detaching electrode to a temperature at which RF ablation occurs whilst the apparatus is being turned about its longitudinal axis to detach the tissue and the tissue between the elongate electrode and the tissue detaching electrode is also ablated.

39. An apparatus as claimed in claim 38 wherein, the RF current provides a heating effect by raising the temperature experienced by the tissue to between between 50°C and 95°C for ablation and over 100°C for detaching a solid tumour.