WO2019154523A1

WO2019154523A1 - Surgical cutting tool

Info

Publication number: WO2019154523A1
Application number: PCT/EP2018/053458
Authority: WO
Inventors: Lars Cato REKSTAD; Brynjulf YSTGAARD
Original assignee: Norwegian University Of Science And Technology (Ntnu)
Priority date: 2018-02-12
Filing date: 2018-02-12
Publication date: 2019-08-15

Abstract

A surgical cutting tool (24) comprises: a hollow cylindrical cutting head (25) with an open distal end, the cutting head (25) being for coupling to an ultrasound oscillator (34) at a proximal end of the cutting head (25); an anvil sheath (26) surrounding the cylindrical cutting head (25); a plurality of cutting tines (28) on the hollow cylindrical cutting head (25) and located around the open distal end thereof; and a plurality of anvil tines (30) at a distal end of the anvil sheath (26); wherein the cutting head (25) is arranged to transmit ultrasound vibration from the ultrasound oscillator (34) to the cutting tines (28) to vibrate the cutting tines (28) along their length; and wherein the anvil sheath (26) and cutting head (25) can rotate relative to one another in order that the cutting tines (28) move relative to the anvil tines (30). This tool (24) allows for a circular cut into body tissue with simultaneous ligation of blood vessels and the like.

Description

SURGICAL CUTTING TOOL

The invention relates to a surgical cutting tool, such as a tool for cutting into body tissue and for removing body tissue. In one example the surgical cutting tool may be used in relation to surgery to treat tumours in the liver.

It is necessary to remove body tissue for various reasons, including removing cancerous tissue from the body. Due to the nature of cancerous tissues it is important to effectively remove the entirety of a tumour. In many cases several tumours may be present, which can further complicate the situation. One example of this is in relation to colon cancer that metastasizes to the liver. The result of this is multiple tumours at different locations in the liver. Figures 1 a-1 c show examples of this situation. The liver 12 has tumours 14 at various locations as shown, with this being a typical outcome from colon cancer that metastasizes to the liver.

In the circumstances that are shown in Figures 1 a-1 c the surgeon may choose to remove a section 16 of the liver tissue either at one side of the liver 12 as shown in Figures 1 a and 1 c, or at the centre of the liver 12 as shown in Figure 1 b. The removed tissue 16 can be a significant proportion of the mass of the liver 12. It is possible to surgically remove up to 70% of the liver in order to remove tumours 14, so there is a relatively high degree of freedom for the surgeon, although if the patient needs multiple surgeries then this creates significant problems. After surgery the remaining liver tissue 18 can be in a single part or in two parts. In order that the remaining liver tissue 18 can function effectively then it must have a good blood supply. The distribution of blood vessels 20 within the liver 12 can be taken into account when deciding what part of the liver 12 should be removed. Where it is necessary to cut through blood vessels 20 then they are ligated. The liver 12 also has bile ducts, which are not shown in the Figures for simplicity. These should be cut and ligated in a similar way to the blood vessels 20.

Various cutting tools have been used for this type of surgery. Some tools such as sharp bladed scalpels are used to simply slice through body tissue, with ligation of the blood vessels then being carried out with separate techniques. Tools that can simultaneously cut and ligate have also been developed. Such tools use various techniques to seal blood vessels as they are cut such as by using heat, electrical ligation such as bipolar diathermy, or ligation via tools with ultrasonic vibration such as harmonic scalpels.

Viewed from a first aspect, the present invention provides a surgical cutting tool comprising: a hollow cylindrical cutting head with an open distal end, the cutting head being for coupling to an ultrasound oscillator at a proximal end of the cutting head; an anvil sheath surrounding the cylindrical cutting head; a plurality of cutting tines on the hollow cylindrical cutting head and located around the open distal end thereof; and a plurality of anvil tines at a distal end of the anvil sheath; wherein the cutting head is arranged to transmit ultrasound vibration from the ultrasound oscillator to the cutting tines to vibrate the cutting tines along their length; and wherein the anvil sheath and cutting head can rotate relative to one another in order that the cutting tines move relative to the anvil tines.

This cutting tool makes it possible to remove a relatively small and generally cylindrical volume of tissue from the body with simultaneous cutting and ligation. The surgeon can therefore target tumour tissue with the aim of retaining as much healthy tissue as possible. In the case of liver tumours then the individual tumours can be targeted with a cylindrical volume of tissue being removed that is centred on the tumour. Since a smaller amount of healthy tissue is removed then the patient can retain better liver function after surgery. In addition, if there is a need for additional surgery in future then the surgeon has a far greater ability to remove further tumours whilst still allowing for sufficient remaining liver tissue to keep the patient healthy. The tissue that is removed can include a greater volume of tumour tissue and a lesser volume of healthy tissue than if whole sections of the liver were removed as shown in Figures 1 a-1 c. The proposed tool therefore allows for increased efficiency during the surgical treatment as well as potentially greater flexibility in repeated surgical treatments to remove tumour tissue. This can reduce the need for more significant surgical interventions on the body, such as a liver transplant.

The proposed tool may be used to cut a circular path into body tissue to allow for a cylindrical mass of tissue to be removed from the body. The use of ultrasound allows for cutting and ligation of the body tissues. The tool may be advanced into the body with the cutting tines undergoing ultrasonic vibration to both cut and ligate body tissue. Then the tool may be held at a constant depth with relative rotation of the anvil sheath and the cutting head during ultrasonic vibration so that the anvil tines press body tissue against the cutting tines and body tissues between the tines is thereby cut and ligated. It can be beneficial to have some relative rotational movement without ultrasonic vibration in order to compress body tissue between the tines before it is then cut and ligated. Once the tissue between the tines has been cut and ligated then the tines are re-aligned. The tool can then be advanced further and the process repeated. Once the required depth is reached then the cylindrical volume of tissue held within the hollow cutting head can be cut across the base and removed. Alternatively, parts of the tool or the entire tool can be removed with other means being used to cut across the base of the circular path. This is described in more detail below.

The relative rotation of the anvil sheath and the cutting head may involve a rotation of the cutting heat whilst the anvil sheath remains stationary, or vice versa. Preferably the anvil sheath is held stationary in order to have minimal impact on the body tissue that is outside of the cutting head, and the cutting head is hence rotated within the anvil sheath during ultrasonic vibration in order to move the tines relative to one another.

The anvil sheath ideally does not vibrate with the cutting head. This avoids damage to tissue after it has been cut and ligated. The anvil sheath may be held around the cutting head such that transmission of vibrations from the cutting head to the anvil sheath is reduced. This may be done by locating any contact between the anvil sheath and the cutting heat at contact points around node points of the vibrational movement of the cutting head.

By location of the contact point(s) either at, or close to, points of minimum vibration then transmission of vibration into the anvil sheath is reduced. Ideally the transmission of vibrations is minimised or avoided entirely.

The anvil tines may be integrated with the anvil sheath such that the tines and the body of the anvil sheath can be manufactured in a single part. In some examples the anvil tines and the anvil sheath are made of a material with a relatively high damping capacity, for example a plastic material such as polyvinyl chloride (PVC), polyethylene, polypropylene, polystyrene, polyurethanes or polycarbonate. These types of materials are rigid enough to be pushed into body tissue, whilst at the same time they will damp any stray vibrations from the cutting head, reducing the risk of transmitting damaging levels of ultrasound vibrations to the body via the anvil sheath.

The cutting tines may be integrated with the cutting head such that the tines and the body of the cutting head can be manufactured in a single part. Integrated cutting tines also allows for better transmission and amplification of ultrasound vibration along the cutting head. The cutting head may be made of a relatively stiff material with a relatively low damping capacity, such that the damping capacity of the anvil sheath is higher than that of the cutting head. The cutting head is advantageously made of a metal material, such as stainless steel, titanium alloy or aluminium alloy.

The cutting head is shaped in order to transmit ultrasonic vibrations from the proximal end to the cutting tines at the distal end and preferably to increase the amplitude of the vibrations toward the cutting tines. The cutting head may be arranged with a natural frequency that corresponds to the natural frequency of the ultrasound oscillator. The cutting head may include at least one cylindrical ultrasound booster part at the proximal end thereof and the cross-section of the booster part may vary in order to amplify the ultrasound vibrations. There may be a plurality of ultrasound booster elements in some cases. The cutting head has an open cylindrical part that joins to the cutting tines at the distal end and the thickness of the wall of the open cylindrical part may vary in order to amplify the ultrasound vibrations as they propagate toward the cutting tines.

The cutting head may include one or more slots through the wall of the open cylindrical part. The slots may be in the form of elongate openings through the wall. It can be beneficial to add such slots in order to reduce or prevent radial contraction/expansion and/or to reduce radial oscillations. For example, it may be an advantage to reduce or prevent radial contraction/expansion at areas with high strain. The presence of slots may also facilitate the transfer of kinetic energy to the cutting tines and increase the amplitude of movement of the cutting tines. The one or more slots may comprise multiple slots spaced apart around a circumference of the wall of the open cylindrical part, for example with even spacing. The slots may be spaced apart with a similar spacing to spacing of the tines and may for example be placed at points on the circumference aligned with gaps between adjacent tines. There may be multiple sets of slots about two or more circumferences spaced apart along the axial length of the open cylindrical part. The slots may be placed at the nodes of the ultrasonic standing wave in the open cylindrical part. The nodes are points where the axial strain is high and the axial displacement is low. In some examples the primary purpose of the slots is to reduce radial contraction/expansion due to axial strain, and hence unwanted radial oscillations. Without the slots, substantial radial oscillations may be transferred to the anvil sheath and liner at the nodes, even if the axial oscillations are close to zero. A secondary purpose of the slots may be to attach an inner liner to the cutter or to the outer anvil.

The thickness of the cutting tines, i.e. in their dimension in the radial direction of the cutting head, and/or the width of the cutting tines, i.e. their dimension in the circumferential direction of the cutting head, may vary in order to control the amplitude of the ultrasound vibrations, for example to amplify the ultrasound vibrations.

There may be an odd number of cutting tines in order to minimise the risk of damaging harmonics from off-axis vibrational modes of the cutting tines. A prime number of cutting tines may be used. As noted below the cutting tool may be provided with a system having different sizes of cutting heads and in that case there may be smaller or larger numbers of cutting tines dependent on the diameter of the cutting head. Examples may include 7 cutting tines or 1 1 cutting tines. It is preferred that there is the same number of anvil tines as cutting tines. This allows the two sets of tines to be aligned during advancing of the cutting tool into body tissue, as well as ensuring that during relative movement of the anvil tines and cutting tines then the forces applied between the anvil tines and cutting tines are generally balanced around the circumference of the cutting head. The cutting tines may extend further forward than the anvil tines, such that the tip of the cutting tines protrudes forward of the tip of the anvil tines.

The anvil tines may have rounded ends in order to avoid inadvertently slicing body tissue with the anvil tines. It can be an advantage if the anvil tines will push blood vessels and bile ducts aside so that as the tool is advanced then blood vessels and bile ducts are directed into the gaps between tines. The cutting tines may also have rounded ends to assist with this. Directing blood vessels and bile ducts into the gaps between tines can allow for more effective cutting and ligation to occur during relative rotation of the anvil tines and cutting tines. The cutting tines may have blunt edges. That is to say they may not be sharp enough to cut body tissue when there is no ultrasonic vibration. The anvil tines may have similarly blunt edges. This ensures that the body tissue is only cut when it will be

simultaneously ligated due to the effects of the ultrasonic vibration. There may be a small, radial clearance between the anvil times and cutting tines, so that the tissue is not forcibly torn apart by the operator, but gently compressed, sealed and cut by ultrasonic energy. The anvil times may also be elastic to further limit the force imposed on the tissue.

A liner may be included within the hollow cylindrical cutting head. Thus, the cylindrical cutting head may include a recess for receiving body tissue as the cutting tool is advanced into the body tissue, and there may be a liner around the recess. The liner may fit concentrically inside the cutting head. It is preferred for the liner to reduce or minimise the ultrasonic vibration that is transmitted to body tissue within the recess and hence any contact point(s) between the liner and the cutting head may be at node points of the vibrational movement of the cutting head and/or at the location of slots as discussed above, if they are present. The liner may be made of a material with a relatively high damping capacity, such as a plastic material as discussed above in relation to the anvil sheath. By location of the contact point(s) either at, or close to, points of minimum vibration then transmission of vibration into the liner is reduced. Ideally the transmission of vibrations is minimised or avoided entirely. This has benefits since it means that the tissue removed from the body can be maintained intact, allowing for later testing and analysis such as biopsy of tumour tissue. The liner may be arranged to be released from the cutting head such that it may be left in the body tissue when the cutting head is removed. This can be useful in relation to performing a further surgical procedure to cut and optionally ligate across the base of the circular tube- shaped cut made by the cylindrical cutting head. When it has been released and left in the body then the liner may be used to guide such a further surgical procedure as well as to contain the cylindrical mass of tissue that is to be removed from the body.

At the proximal end the cutting head may be arranged to connect with the ultrasound oscillator via one or more separate booster, or a booster may be integrated into the cutting head via a booster part of the cutting head as mentioned above. There may be multiple boosters either separate to the cutting head or integrated with the cutting head. The cutting head can be bolted to the ultrasound oscillator. The surgical tool may include a handle portion holding an ultrasound oscillator for providing ultrasonic vibration and thus this ultrasonic oscillator may be connected with the cutting head at the proximal end. The vibrations at the cutting tines may be similar to those used in harmonic scalpels. In a typical example the ultrasound oscillator produces ultrasound at frequencies between 30 kHz to 70 kHz, such as a frequency of about 40 kHz, about 55 kHz or about 60kHz. The amplitude of the longitudinal vibration at the cutting tines may be in the range 30-70 pm, more narrowly 40-60 pm, for example an amplitude of about 50 pm. The ultrasound oscillator may vibrate at a considerably lower amplitude than the cutting tines with the amplitude being increased via the cutting head and/or booster. The amplification may be at a factor of 5-15 times, for example an amplification of about 10 times to take an input amplitude of 5 pm from the ultrasonic oscillator and amplify it to an amplitude of about 50 pm at the cutting tines.

The length, width and/or thickness of the cutting tines may be set based on a required geometry for effective transmission of the ultrasonic vibrations and could hence vary depending on the ultrasonic oscillator, the diameter of the cutting head, and the materials used. In typical examples with a cutting head diameter in the range 1 cm to 10 cm then the cutting tines may have a width in the range 1 mm to 30 mm, for example 1 mm to 10 mm, and a length in the range 5 mm to 50 mm, for example 5 mm to 20 mm. The thickness of the tines (i.e. their radial dimension along a radius of the cylindrical cutting head) will generally be less than the width (i.e. the circumferential dimension along the circumference of the cutting head) and this can be determined based on the vibration pattern of the cutting head. The anvil tines may have a similar width and thickness to the cutting tines but a slightly lesser length in order that the tips of the cutting tines protrude forward of the tips of the anvil tines. The anvil sheath has a diameter for fitting concentrically around the outside the cutting head, and the liner, where present, has a diameter for fitting concentrically within the cutting head.

The cutting tool can be arranged to fit to a handle portion and the handle portion may include the ultrasound oscillator as well as a connection to a power supply. The cutting tool may be interchangeable with other cutting tools of the same or different sizes. This can allow for a single handle portion and a single ultrasound oscillator to be used with varying cutting tool sizes so that the amount of tissue that is removed can be adjusted, for example to change the amount of tissue that is removed depending on the size of the tumour. The cutting tool may include a cooling system for removing heat from the cutting head. The cooling system may use a flow of water or air to remove heat from the cutting head.

The invention may hence take the form of a surgical tool system wherein multiple surgical cutting tools are supplied with an interchangeable connection to an ultrasound oscillator housed in a handle portion. This can allow for easy replacement of the cutting tool when it has worn out. It can also allow for interchangeable cutting sizes in which case the surgical tool system includes multiple different cutting tools of different sizes and/or different shapes. The different tools may have differing diameters and/or different lengths along the cylinder. Alternatively or additionally the different tools may have differing shapes with variations in diameter along the cylindrical cutting head, such as a via a frustoconical shape at the distal end of the tool.

The cutting tool may be used with a suitable surgical guidance system. In some cases this may not involve any adaptation to the tool. However, there may be advantages in providing the cutting tool and/or the handle portion with components having a guidance function. For example, ultrasound imaging transducers may be provided for tracking a target point, such as a target point identified by an ultrasound marker, and this may hence allow for the cutting head to be centred on a required target area. The cutting tool may be used with a 3-D system for guided surgery, such as a system using CT and/or MRI scans along with a tracking system at the cutting tool. Alternatively, or additionally, the cutting tool may include a passage for receiving a guide needle, such as a passage along the longitudinal axis of the cutting tool. With this arrangement a guide needle may be inserted into the body tissue to a required depth, for example whilst using surgical imaging to target the end of the needle on a centre of a tumour, and the cutting tool can then be advanced into the body tissue with guidance from the guide needle to ensure that it has the correct alignment and depth in order to effectively remove the required body tissue. In one example the cutting tool and the handle portion, including the ultrasound oscillator, has a longitudinal passage for a guide needle along the central axis of the cutting tool.

As noted above, the base of the cylindrical cut should also be cut and any blood vessels dealt with prior to removal of the cylindrical plug of body tissue within the circular cut made by the cylindrical tool head. In some cases the surgeon may be able to select an alignment and depth for the cutting tool that avoids blood vessels at the base of the cut. If there are blood vessels present then they may be dealt with via a suitable mechanism included as a part of the cutting tool or it may be done by a separate tool or other surgical steps.

One simple strategy is to use a wire to cut the tissue free, and then to deal with any blood vessels and the like after the tissue is removed, for example by a separate ligation device or by use of a sealing compound. A potentially more effective strategy would be to use a first wire loop at the base of the cut to throttle the tissue and hence throttle any blood vessels, and to then use a second wire loop to make a cut above the throttling wire. Any blood vessels that are at the base of the cut can then be dealt with before the throttling wire is released. Alternatively or additionally a heated wire or bipolar wire could be used to simultaneously cut and cauterise. The cutting tool described above might be adapted to allow for a suitable wire loop to be inserted and actuated whilst the cutting tool is in place after the cylindrical cut has been completed. Alternatively, the cutting tool could be removed with a separate specialised tool being used to cut the base of the cylinder. This may make use of a liner of the cutting tool as a guide, i.e. the cutting tool may have a releasable inner liner as mentioned above.

In one example the cutting tool is provided with a wire loop system that is mounted on a separate sheath mounted outside of the anvil sheath. This wire loop sheath may be arranged to be moved to the base of the cylindrical cut once cutting with the ultrasound system has been completed. Thus, the wire loop sheath may be arranged to slide along the length of the anvil sheath to the base of the cut. The wire loop sheath may include a noose of wire that can be tightened around the base of the cut after the wire loop sheath has been moved to the base of the cut. There may be a noose of wire extending from a tube that passes along one side of the cutting tool, with at least one free end of the wire passing along the tube to allow for it to be drawn along the tube to tighten the noose. Both free ends of the wire may pass along the tube so that the noose can be tightened by pulling two wires simultaneously, or one end of the wire may be fixed so that the noose is tightened by pulling one wire only. The wire may be a heated wire or a bipolar wire to allow for simultaneous cutting and ligation during tightening of the noose in order to separate the volume of tissue inside of the cylindrical cutting tool from the remainder of the body tissue.

With a wire loop type cutting system the cutting system (e.g. the wire loop sheath discussed above) can be removed from the body along with the anvil sheath and the cylindrical plug of tissue. The cutting head may be arranged to be removed from the anvil sheath prior to use of the wire loop cutting system.

In other alternatives the end cut may be made using a curved ultrasonic scissor, a bipolar scissor and/or a heated scissor.

The invention extends to the use of the cutting tool for surgical removal of tissue from the body. This may include use of a tool having any of the features set out above.

The method may include: advancing the tool into the body with the cutting tines undergoing ultrasonic vibration to both cut and ligate body tissue; holding the tool at a constant depth and rotating the anvil sheath and the cutting head relative to one another during ultrasonic vibration so that the anvil tines press body tissue against the cutting tines and body tissues between the tines is thereby cut and ligated; and optionally repeating these steps until a required depth is reached.

In some examples the method includes using imaging techniques in order to target the cutting tool, for example by focussing the centre of the circular cut on a location of a target area such as a tumour, and by cutting to a depth sufficient to fully enclose the target area with the cylindrical cutting head. The method may include using ultrasound guidance and an ultrasound marker placed at target area such as a tumour in order to direct the cutting tool to fully enclose the target area with the cylindrical cutting head. A 3-D surgical guidance system may be used. Alternatively, or additionally, the cutting tool may be arranged with a passage for receiving a guide needle, in which case the method may include inserting the guide needle into the body tissue along a required angle for the cutting tool, with the depth of the guide needle being known relative to the depth of the target area, which may be a depth of a tumour. With this feature then the cutting tool can be advanced into the body with the guide needle passing along the passage of the cutting tool so that both the angle and the depth of the cutting tool can be controlled to follow the guide needle and hence to fully enclose the tumour with the cylindrical cutting head. The method may include use of a wire loop sheath as described above in order to cut tissue across the base of the cylindrical cut.

Certain example embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figures 1a-1c show examples of surgical strategies to deal with liver tumours;

Figure 2 shows a proposed new strategy using a cylindrical cutting tool for removal of tumour tissue from the liver;

Figures 3a and 3b show an example of a cutting tool in more detail;

Figure 4 shows another cutting tool in perspective view;

Figure 5 is a close up of the tines of the cutting tool shown in Figure 4;

Figure 6 shows a cross-section through the cutting tool of Figure 4;

Figure 7 is a schematic diagram showing the ultrasound oscillator and amplification of the ultrasonic vibration of the cutting head;

Figures 8a-8e show an example of a base cut tool for cutting the base of the cylinder after a cylindrical cut has been made;

Figures 9a-9f show another example of a base cut tool;

Figure 10 shows another cutting tool with an alternative design used for the cutting head; and

Figure 11 is a cross-section showing further detail of the cutting head of Figure 10.

As discussed above Figures 1a through 1c show various possibilities for removal of sections of liver 12 in order to remove tumours 14 from the patient’s body. A different strategy is now proposed based on the use of a specialised circular cutting tool in order to allow for a more efficient removal of tumours from the liver 12. This is illustrated in Figure 2, which shows a patient’s liver 12 as shown in Figures 1a through 1c, with tumours 14 at various points in the liver 12 and with blood vessels 20 extending through the liver 12. With the use of a specialised circular cutting tool 24 such as that described below it is possible to remove a cylindrical section of the liver around each tumour 14 as shown in Figure 2 with reference to the removed sections 16.

Thus, even though the example of Figure 2 has a greater number of tumours 14 than the earlier examples shown in Figures 1a-1c it is possible to leave the patient with a larger amount of remaining liver tissue 18 than in the situations where it is required to remove a whole segment 16 of the liver 12 to remove the tumours 14 contained within that segment.

In addition to removing a smaller volume of the liver tissue the use of a cylindrical cutting strategy can also reduce the amount of ligation 22 that is required, as well as in some cases avoiding the need for larger vessels 20 to be ligated 22.

Figures 3a and 3b show an example of a cutting tool 24 in more detail. The cutting tool 24 has a cylindrical cutting head 25 that is surrounded by an outer anvil sheath 26. The cylindrical cutting head 25 has an open distal end and is formed with a number of cutting tines 28 extending from the distal end and spaced apart around the circumference of the distal end. The anvil sheath 26 is also generally cylindrical and fits in concentric fashion around the cylindrical cutting head 25. At the end of the anvil sheath 26 a number of anvil tines 30 are formed with a broadly similar shape and size to the cutting tines 28. There is the same number of anvil tines 30 as cutting tines 28. Figure 3a shows a cylindrical cutting tool 24 by itself. Figure 3b shows the cylindrical cutting tool 24 attached to a handle portion 32. The handle portion 32 includes a power supply and an ultrasound oscillator 34 (not visible in Figure 3b). When the device as a whole is assembled then a proximal end of the cylindrical cutting head 25 is connected to the ultrasound oscillator 34 in order that ultrasound oscillations can be transmitted from the oscillator 30 through the body of the cylindrical cutting head 25 and to the cutting tines 28.

The cutting tool 24 can be advanced into body tissue whilst creating a circular tube- like cut. This allows body tissue to be removed in a cylindrical section 16 such as a cylinder 16 centred on a tumour 14 as shown in Figure 2. The use of ultrasonic vibration of the cutting tines 28 means that the tool has an effective cutting motion along with simultaneous ligation of blood vessels 20 and other body structures (e.g. bile ducts) that cross into the cylinder. The principle of operation of the tool is broadly similar to that of a harmonic scalpel using ultrasonic vibration for simultaneous cutting and ligation. The tool is operated by aligning the anvil tines 30 and cutting tines 28, activating the ultrasonic vibration, and advancing the tool forward into body tissue. This simultaneously cuts and ligates along the path of the cutting tines 28. As is shown in more detail in the example of Figure 5 the cutting tines 28 protrude forward of the anvil tines 30 in order for an effective cutting and ligation to be provided as the tool 24 advances forward. Once the tines 28, 30 are within the body tissue then the forward motion of the tool 24 is stopped and the anvil sheath 26 is held stationary whilst the cylindrical cutting head 25 and hence the cutting tines 28 are rotated in order to thereby create a fully circular cut. It has been found that an effective cut can be obtained by stopping the ultrasonic vibration of the cutting tines 28 whilst the cutting tines 28 are rotated in order to compress body tissues between the cutting tines 28 and the anvil tines 30, restarting the ultrasonic vibration after the tissue has been initially compressed, and then turning the cutting head 25 further until the cutting tines 28 pass across the entirety of the gaps between the anvil tines 30. The tissue in between the tines 28, 30 can then be cut and ligated to complete the circle. Subsequently, the tool 24 may be advanced further and the process repeated until the desired depth is reached. It will be appreciated that the tool could be targeted for removal of any desired mass of tissue that fits within the cylindrical cutting head 25. In the example of removal of tumours 14 from the liver 12 then the centre of the circular cut would be targeted at the centre of the tumour 14, and the diameter of the cutting head 25 would be selected such that the surgeon could be confident that all tumour tissue would be fully removed.

A perspective view of another example of a cutting tool 24 is shown in Figure 4. This cylindrical cutting tool 24 is similar to the cylindrical cutting tool 24 of Figures 3a and 3b and it uses the same general principles of operation, although the shape and form of the tool 24 is slightly different. It will be appreciated that the shape and form of the tool 24 can be varied depending on the specification of the tool such as the materials that are selected, the required diameter and depth of the cut, the frequency of vibration, the amplitude of vibration at the ultrasound oscillator, and the amount of amplification required. In Figure 4 the cutting tool 24 is shown in perspective view looking partially into a recess 42 within the cylindrical cutting head 25. Figure 5 is a close up of the tines 28, 30 of the cutting tool 24 shown in Figure 4. Figure 6 shows a cross-section through the cutting tool 24.

With reference to the view shown in Figure 5 it will be seen that at the distal end of the cylindrical cutting head 25 the cutting tines 28 protrude further forward than the anvil tines 30. Thus, when the cutting tool 24 is advanced into body tissue with ultrasonic vibration of the cylindrical cutting head 25 then the tips of the cutting tines 28 can easily cut and ligate body tissue since they are not obscured by the tips of the anvil tines 30. In addition, Figure 5 shows clearly the rounded ends of the anvil tines 30 and the cutting tines 28. The purpose of the rounded ends is to guide tougher tissues such as blood vessels 20 in between the tines 28, 30 during forward movement of the cutting head 25, so that they are pushed aside rather than being cut. They can then be cut during the rotating phase of the cutting motion rather than cutting them as the tines 28, 30 are advanced forward into the body tissue. This allows for a more effective cutting and ligation of these tougher body tissues. Figure 5 also shows a further feature of the cutting tool 24, which is a liner 40 that sits within the cylindrical cutting head 25 and surrounds the recess 42. It will be noted that this liner 40 is not shown in Figure 4. The liner 40 is used to contain the body tissue in the cylindrical part that is to be removed from the body. It is advantageous to protect this body tissue from the ultrasonic vibration of the cylindrical cutting head 25 by using the liner 40 since then the body tissue can be removed intact. This allows for later testing and analysis that might not be possible if the body tissue were broken up due to the ultrasonic vibration. Keeping the body tissue intact also allows for more straightforward removal of a solid mass of tissue, which can be particularly important when the cutting tool is removing a tumour 14 since any breakup of the tumour 14 could lead to cancerous tissue remaining within the body.

Figure 6 illustrates a number of features relating to the layout of the cutting tool 24 in relation to the transmission and containment of the ultrasonic vibrations from the ultrasound transducer 34. In this example the ultrasound transducer 34 is held within the handle portion 32 and it is connected to the cylindrical cutting head 25 by bolts and through an ultrasound booster 36. The proximal end of the cylindrical cutting part 25 also forms a further ultrasound booster part. The ultrasound booster 36 along with the geometry of the cylindrical cutting head 25 acts to amplify ultrasound vibrations supplied by the ultrasound oscillator 34 as they are propagated along the length of the cutting tool 24 and through the cylindrical cutting head

25 to the cutting tines 28. The liner 40 is fitted concentrically within the cylindrical cutting head 25 which in turn is surrounded concentrically by the anvil sheath 26. The anvil sheath

26 is free to rotate relative to the cylindrical cutting head 25 in order that the cutting head 25 can be manually turned within the anvil sheath 26 to move the cutting tines 28 and press tissue against the anvil tines 30 to cut and ligate the tissue.

In order that there is minimal damping of the ultrasonic vibration of the cutting head 25 then the liner 40 as well as the angle sheath 26 are connected to the cutting edge 25 so as to receive minimal vibration. It is also advantageous to minimise the vibration past from the anvil sheath 26 to body tissue outside of the cylindrical cutting head 25 and from the liner 40 to body tissue inside the recess 42 of the cylindrical cutting head 25. The liner 40 is connected to the cylindrical cutting head 25 but contacts with the cylindrical cutting head 25 at node points 44 of the vibration. The anvil sheath 26 is also in contact with the cylindrical cutting head 25 and again the cutting tool 24 is configured so that the contact points between the anvil sheath 26 and the cutting head 25 are at node points 38 on the outside of the cutting head 25. Thus, both the liner 40 and the anvil sheath 26 are connected at node points 38, 44 and hence are only in contact with the cutting head 25 at points of minimum vibration of the cutting head 25. The result of this is that vibration transmitted from the cylindrical cutting head 25 to the liner 40 and the anvil sheath 26 is minimised. Figure 6 shows how the geometry and wall thickness of the cylindrical cutting head 25 is very along its length. These variations enable the application to be controlled as well as allowing for node points 38, 44 to be created at required locations.

Figure 7 is a schematic diagram showing the ultrasound oscillator 34 and

amplification of the ultrasonic vibration as it passes along the cutting tool 24 to the cutting tines 30 at the distal end of the cutting head 25. In this example, ultrasound vibrations are produced at the ultrasound oscillator 34 with an amplitude of 5 pm and a frequency of 40 kHz. It will be appreciated that different frequencies can be used, for example ultrasound oscillators providing vibrations with a frequency of 55 kHz or 60 kHz are available and are known for use with harmonic scalpels. The vibrations from the ultrasound oscillator 34 are passed into the booster 36 which includes a node point (i.e. zero vibration) that allows for connection of the handle portion 32 and the booster 36 without transmission of vibration into the handle portion 32. The booster 36 increases the amplitude of the ultrasound vibrations to 10 pm and passes these vibrations to the cylindrical cutting head 25. As the vibrations propagate through the cylindrical cutting head 25 they pass through a first set of node points 38, 44; increase in amplitude to 20 pm; pass through a second set of node points 38, 44; and then further increase in amplitude to 50 pm at the cutting tines 30. The booster 36 together with the geometry of the cylindrical cutting head 25 hence increase the amplitude of the ultrasonic vibrations by a factor of ten from 5 pm at the ultrasound oscillator 34 to 50 pm at the cutting tines 30. The two sets of node points 38, 44 allow for the liner 40 to be held within the cutting head 25 and the anvil sheath 26 to be held outside of the cutting head 25 with minimal transmission of vibration.

In order to allow for efficient transmission of vibrations then the cylindrical cutting head 25 is formed in a single piece with the cutting tines 30 integrated into a main body of the cutting head 25. The material of the cylindrical cutting head 25 should have a low damping capacity as well as being suitable for ultrasonic cutting and ligation of body tissue. An example of a suitable material is titanium alloy. Stainless steel or aluminium alloys might alternatively be used. The liner 40 and the anvil sheath 26 should, on the other hand, avoid transmission of vibrations into body tissue and therefore a material with a higher damping capacity is beneficial. The liner 40 and the anvil sheath 26 may be a plastic material, such as polyvinyl chloride (PVC), polyethylene, polypropylene, polystyrene, polyurethanes or polycarbonate. There may be a layer of a softer material in between the cutting head 25 and the liner 40 in order to minimise the transmission of vibrations. The dimensions of the cutting tool 24 can vary depending on the size of the target area. For removal of tumours 14 from the liver 12, for example as shown in Figure 2, then the diameter of the cutting head 25 could be in the range 1 cm to 10 cm. The cutting tines 30 may have a width of 1 mm to 30 mm, for example 1 mm to 10 mm, and a length of 5 mm to 50 mm, for example 5 mm to 20 mm. In some examples the length of the tines 30 is between 0.2 to 0.4 times the diameter of the cutting head 25. One arrangement has a cutting head 25 with an external diameter of 31 mm that is provided with seven tines 30 equally spaced at the distal end of the cutting head 25. The tines 30 each have a length of 1 1 .5 mm and a width (in the circumferential direction) of 2.6 mm.

A cutting tool 24 as described above can be used for making a circular tube like that into body tissue, for example cutting a tube into the liver 12 to remove a section of tissue 16 around a tumour 14. The result of this is a cylindrical plug of tissue that is contained within the recess 42 of the cylindrical cutting head 25. In order to then remove the cylindrical plug tissue it is necessary to make a further cut across the base of the tubular cut. If this cut passes through body structures such as blood vessels 20 then it would also be necessary to feel the blood vessels 20 in some way by ligation or similar techniques.

In some cases the surgeon may be able to select an alignment and depth for the cutting tool 25 that avoids blood vessels 20 at the base of the cut. However, it will be appreciated from even the simplified diagram of Figures 1 and 2 that the blood vessels of the liver 12 are widely distributed and that it is likely for at least some tumours 14 to be located close to a blood vessel 20 that may need ligation at the base of the tubular cut. If there are blood vessels 20 present then they may be dealt with via a suitable mechanism included as a part of the cutting tool 24. Alternatively they may be cut and sealed by a separate tool and/or during other surgical steps.

One simple strategy is to use a wire to cut the tissue free, and then to deal with any blood vessels 20 and the like after the tissue is removed, for example by a separate ligation device targeting any bleeders or by use of a sealing compound. Another possibility would be to use a first wire loop at the base of the cut to throttle the tissue and hence throttle any blood vessels 20, and to then use a second wire loop to make a cut above the throttling wire. Any blood vessels 20 that are at the base of the cut can then be dealt with before the throttling wire is released. A heated wire or a bipolar wire could be used to simultaneously cut and cauterise and this might be done with or without a throttling wire. Another possibility is to use a curved ultrasonic scissor, a bipolar scissor and/or a heated scissor.

Figures 8a-8e show one example of a base cut tool for cutting the base of the tubular cut and releasing the cylindrical plug of body tissue 16 after the initial cut has been made by the cutting tool 24. With this example the liner 40 is adapted to include a wire guide 50 and a cutting wire 46 that forms a loop 48 at the base of the liner 40. After the tubular cut is made then the liner 40 can either be released from the cutting tool 24, or it may remain in place whilst the base cut is made. For the sake of clarity the liner 40 is shown without the cutting tool 24 in Figures 8a-8e. As shown in the Figure 8b the liner 40 can be removed from the wire guide 50, which could be done together with removal of the cutting tool 24, or in a separate step after the liner 40 is released from the cutting tool 24. The cutting wire 46 is heated or otherwise excited by electrical current in order to allow for cutting of the body tissue with diathermy to ligate any blood vessels 20 that extend into the base of the cylinder of tissue. Tension is applied to the cutting wire 46 to tighten the loop 48 to compress the tissue and then, with the application of current, to cut and ligate as the loop 48 is closed.

This is shown in Figures 8c to 8e. When the cut has been completed then the wire guide 50 can be removed along with the cutting wire 46, and the cylindrical plug of tissue can also be removed. In an alternative to the process shown in Figures 8a-8e the base cut could be made by tightening the loop 48 with the liner 40 still present. This could allow for easier removal of the cylindrical section of tissue since it would be contained within the liner 40. It will be appreciated that other variations are also possible. The cutting tool 24 might be adapted to allow for a suitable wire loop 48 to be inserted and actuated whilst the cutting tool 24 is in place after the cylindrical cut has been completed.

Figures 9a-9f show another example of a wire loop system, which in this case uses a wire loop sheath 60 to deploy a wire loop 48. The wire loop sheath 60 is placed outside of the anvil sheath 26 and can slide along the length of the anvil sheath 26. As shown in Figure 9a during cutting the cutting tool 24 cuts into the body tissue with the wire loop sheath 60 slide toward a proximal end of the cutting tool 24. This allows the anvil sheath 26 and the cutting head 25, which is within the anvil sheath 26 and hence not visible in the Figure, to cut and ligate the body tissue without any hindrance from the wire loop sheath 60. The wire 46, not visible aside from in Figure 9f, passes through a wire guide 50. The wire guide 50 takes the form of a tube 50 that is pivotally connected to the wire loop sheath 60. When the wire loop sheath 60 is slid upward away from the distal end of the cutting tool 24 then the wire guide 50 can be angled away from the handle portion 32 of the device in order to avoid any obstruction to movement of the tool or to movement of the cutting head 25 relative to the anvil sheath 26. Figure 9a shows this configuration.

When the cylindrical cut has been completed then the cutting head 25 is removed along with the handle portion 32, leaving the anvil sheath 26 and the wire loop sheath 60 in place. The, as shown in Figures 9b to 9d the wire guide 50 can be swung upward and then slid downward along with the wire loop sheath 60 in order to move the wire loop sheath 60 to the base of the cut and to attach a clip 62 to the anvil sheath 26. With the anvil sheath 26 and the wire loop sheath 60 in this position the wire 46 can be pulled along the wire guide 50 in order to tighten the wire loop (noose) 48 and to make a cut across the base of the cylindrical cut as shown in Figures 9e and 9f. The wire 46 is arranged as a bipolar wire in order to simultaneously cut and ligate. As a result it is possible to cut and ligate both along the sides of the cylindrical cut (using the ultrasonic action of the cutting head 25) and also across the base of the cut. Once the base cut is completed then the anvil sheath 26 together with the wire loop sheath 60 can be removed along with the tissue that has been cut.

Figures 10 and 1 1 show another cutting tool 24 with an added feature of the cutting head compared to the cutting head of Figures 3 to 7. The added feature is the use of slots 70, 72 in order to reduce or prevent radial contraction/expansion and/or to reduce radial oscillations. The slots 70, 72 may be located at node points where there is maximum strain but minimum displacement. The cutting tool 24 of Figures 10 and 1 1 is otherwise similar to that describe above, and thus includes a handle portion 32 with ultrasound oscillator 34, the cutting head 25, an anvil sheath 26 and cutting tines 28 that work along with anvil tines 30 to achieve the required cylindrical cutting action. It will be appreciated that the slots 70, 72 of Figure 1 1 could be added to the other example cutting head designs described above to achieve similar advantages. It can be beneficial to reduce or prevent radial

contraction/expansion, especially at areas with high strain during vibration of the cutting head 25 The slots 70, 72 can also prevent vacuum inside the cylinder, which can make it easier to move the cylinder in and out of the tissue. As well as this the slots can also reduce heating of the tissue inside the cylinder. The slots 70, 72 may be used to attach an inner sheath to protect the tissue inside the cylinder. There can be one or more sets of slots spaced apart along the axis 66 of the cutting head 25, such as a first set of slots 70 at a mid- point along the cutting head 25 and a second set of slots 72 toward the open end of the cylindrical cutting head as shown in Figure 1 1. The slots 70, 72 comprise multiple slots 70, 72 spaced apart around respective circumferences of the wall of the open cylindrical part, for example with even spacing and a similar spacing to spacing of the cutting tines 28 as in Figure 1 1 , where the slots are placed at points on the circumference aligned with gaps between adjacent cutting tines 28.

Claims

1. A surgical cutting tool comprising:

a hollow cylindrical cutting head with an open distal end, the cutting head being for coupling to an ultrasound oscillator at a proximal end of the cutting head;

an anvil sheath surrounding the cylindrical cutting head;

a plurality of cutting tines on the hollow cylindrical cutting head and located around the open distal end thereof; and

a plurality of anvil tines at a distal end of the anvil sheath;

wherein the cutting head is arranged to transmit ultrasound vibration from the ultrasound oscillator to the cutting tines to vibrate the cutting tines along their length; and wherein the anvil sheath and cutting head can rotate relative to one another in order that the cutting tines move relative to the anvil tines.

2. A surgical cutting tool as defined in claim 1 , wherein the anvil sheath is held around the cutting head with contact points between the anvil sheath and the cutting heat at, or close to, node points of the vibrational movement of the cutting head so that transmission of vibration from the cutting head into the anvil sheath is reduced.

3. A surgical cutting tool as defined in claim 1 or 2, wherein anvil tines are integrated with the anvil sheath, and wherein the anvil tines and the body of the anvil sheath comprise a single part formed out of plastic.

4. A surgical cutting tool as defined in claim 1 , 2 or 3, wherein the cutting tines are integrated with the cutting head, and wherein the cutting tines and the body of the cutting head comprise a single part formed out of metal.

5. A surgical cutting tool as defined in any preceding claim, wherein the cutting head is shaped in order to transmit ultrasonic vibrations from the proximal end to the cutting tines at the distal end and to increase the amplitude of the vibrations toward the cutting tines.

6. A surgical cutting tool as defined in any preceding claim, wherein the cutting head includes one or more slots through a wall of an open cylindrical part of the cutting head.

7. A surgical cutting tool as defined in claim 6, wherein the one or more slots are in the form of elongate openings through the wall and they comprise multiple slots spaced apart around a circumference of the wall of the open cylindrical part.

8. A surgical cutting tool as defined in any preceding claim, comprising an odd number of cutting tines.

9. A surgical cutting tool as defined in any preceding claim, comprising the same number of anvil tines as cutting tines.

10. A surgical cutting tool as defined in any preceding claim, wherein the cutting tines extend further forward than the anvil tines, such that the tip of the cutting tines protrudes forward of the tip of the anvil tines at the distal end of the cutting head.

11. A surgical cutting tool as defined in any preceding claim, wherein the anvil tines and the cutting tines have rounded ends.

12. A surgical cutting tool as defined in any preceding claim, wherein the cylindrical cutting head includes a recess for receiving body tissue as the cutting tool is advanced into the body tissue, and there is a liner around the recess.

13. A surgical cutting tool as defined in claim 12, wherein the contact point(s) between the liner and the cutting head are located either at, or close to, node points in the vibration of the cutting head in order that transmission of vibration into the liner is reduced.

14. A surgical cutting tool as defined in claim 12 or 13, wherein the liner is arranged to be released from the cutting head such that it can be left in the body tissue when the cutting head is removed.

15. A surgical cutting tool as defined in any preceding claim, wherein the cutting head diameter is in the range 1 cm to 10 cm, the cutting tines have a width of 1 mm to 30 mm, and the cutting tines have a length of 5 mm to 50 mm.

16. A surgical cutting tool as defined in any preceding claim, wherein the cutting tool includes ultrasound imaging transducers provided for tracking a target point in the body to thereby guide the cutting head to a target area in the body.

17. A surgical cutting tool as defined in any preceding claim, wherein the cutting tool includes a passage for receiving a guide needle.

18. A surgical cutting tool as defined in any preceding claim, wherein the surgical tool includes a handle portion holding the ultrasound oscillator for providing ultrasonic vibration with the ultrasound oscillator being connected with the cutting head at the proximal end, and wherein the ultrasound oscillator produces ultrasound at frequencies between 30 kHz to 70 kHz, such as a frequency of about 40 kHz, about 55 kHz or about 60 kHz.

19. A surgical cutting tool as defined in claim 18, wherein the amplitude of the longitudinal vibration at the cutting tines is in the range 30-70 pm, and wherein the ultrasound oscillator vibrates at a considerably lower amplitude than the cutting tines with the amplitude being increased by a factor of 5 to 15 as the vibrations propagate toward the cutting tines.

20. A surgical cutting tool as defined in any preceding claim, wherein the cutting tool is interchangeable with other cutting tools such that a single handle portion and a single ultrasound oscillator can be used with varying cutting tool sizes.

21. A surgical tool system wherein multiple surgical cutting tools as claimed in any preceding claim are supplied with an interchangeable connection to an ultrasound oscillator housed in a handle portion.

22. A method of surgical removal of tissue from the body, the method comprising: using the surgical tool of any preceding claim, advancing the tool into the body with the cutting tines undergoing ultrasonic vibration to both cut and ligate body tissue; holding the tool at a constant depth and rotating the anvil sheath and the cutting head relative to one another during ultrasonic vibration so that the anvil tines press body tissue against the cutting tines and body tissues between the tines is thereby cut and ligated; and optionally repeating these steps until a required depth is reached.

23. A method as claimed in claim 22, including using imaging techniques such as 3-D surgical guidance techniques, in order to target the cutting tool by focussing the centre of the circular cut on a location of a target area such as a tumour, and by cutting to a depth sufficient to fully enclose the target area with the cylindrical cutting head.

24. A method as claimed in claim 22 or 23 comprising using ultrasound guidance and an ultrasound marker placed at a target area in order to direct the cutting tool to fully enclose the target area with the cylindrical cutting head.

25. A method as claimed in claim 22, 23 or 24, wherein, the cutting tool is arranged with a passage for receiving a guide needle, and the method includes: inserting the guide needle into the body tissue along a required angle for the cutting tool with the depth of the guide needle being known relative to the depth of the target area; and then passing the guide needle along the passage during insertion of the cutting tool into the body in order to guide the cutting tool along the guide needle.