HK1208329B - Electrosurgical resection instrument - Google Patents

Description

Electrosurgical resection instrument

Technical Field

The present invention relates to an electrosurgical device for delivering radiofrequency and/or microwave frequency energy into biological tissue. In particular, the present invention relates to an electrosurgical instrument capable of delivering Radiofrequency (RF) energy for cutting tissue and/or microwave frequency energy for hemostasis (i.e., sealing ruptured blood vessels by promoting coagulation). The present invention may be particularly suitable for Gastrointestinal (GI) procedures associated with the upper and lower GI tracts, e.g. for removing polyps on the intestine, i.e. for endoscopic submucosal resection. The present invention can also be applied to precision endoscopic surgery, i.e., precision endoscopic resection, and can be used for ear-nose-throat surgery as well as hepatectomy. The device may also be used to address procedures associated with the pancreas, for example, to resect or remove tumors or foreign bodies in close proximity to the portal vein or pancreatic duct.

Background

Surgical resection is a means of removing an organ portion from the human or animal body. Such organs may possess densely packed blood vessels. When tissue is cut (dissected or transected), small blood vessels called arterioles are damaged or ruptured. The initial bleeding is followed by a coagulation cascade, in which the blood becomes a clot, attempting to block the bleeding site. During the procedure, it is desirable that the patient lose as little blood as possible, and therefore various devices have been developed in an attempt to provide bloodless cutting. For endoscopic surgery, it is also undesirable for bleeding to occur and not to be treated as quickly or in an advantageous manner, as blood flow may obscure the operator's vision, which may result in the need to terminate the surgery and require another method to be used instead, for example, open surgery.

The use of Radio Frequency (RF) energy in place of sharp blades to cut biological tissue is well known. The method of cutting using radiofrequency energy operates using the principle that the impedance of the flow of electrons across the tissue generates heat as a current passes through the tissue matrix (aided by the ionic content of the cells). When a pure sine wave is applied to the tissue matrix, sufficient heat is generated within the cells to evaporate the water content of the tissue. Therefore, the internal pressure of the cell is greatly increased, and the cell membrane cannot control it, causing cell rupture. When this happens to a large extent, it can be seen that the tissue has been transected.

While the above principle works well in lean tissue, it is less efficient in adipose tissue because fewer ionic components assist the flow of electrons through. This means that the energy required to evaporate the cell contents is much greater when the latent heat of fat evaporation is much greater than that of water.

By applying a weak waveform to the tissue, radiofrequency coagulation is performed whereby the cell contents are not evaporated, but are heated to about 65 ℃. This dries out the tissue by dehydration and also denatures the proteins in the vessel wall and the collagen that makes up the cell wall. Denaturing the protein for stimulating the coagulation cascade, thereby enhancing coagulation. At the same time, the collagen in the wall is denatured and changed from rod-like molecules to coil-like, which promotes vasoconstriction and reduces size, providing a site for coagulation and a smaller area to be occluded.

However, radio frequency coagulation is less effective with adipose tissue due to reduced electrical effects. Thus, it can be very difficult to seal a fat bleeding spot. The tissue does not have clean white edges, but rather has a blackened burn appearance.

In practice, the RF device may operate using a waveform having a crest factor intermediate between the cut and coag outputs.

GB 2472972 describes an electrosurgical instrument in the form of a spatula comprising a planar transmission line formed from a sheet of a first dielectric material having first and second conductive layers on opposite surfaces thereof, the planar transmission line being connected to a coaxial cable arranged to deliver microwave or radio frequency energy to the planar transmission line, the coaxial cable comprising: an inner conductor; an outer conductor coaxial with the inner conductor; and a second dielectric material separating the inner and outer conductors, the inner and outer conductors extending through the second dielectric at the connection interface so as to overlap opposite surfaces of the transmission line and make electrical contact with the first and second conductive layers, respectively. The first conductive layer is spaced from the end of the transmission line that is adjacent to the coaxial cable so as to electrically isolate the outer conductor from the first conductive layer, and the distance of the gap is related to matching the impedance of the energy delivered from the microwave source to the impedance of the biological tissue, and the widths of the first and second conductive layers are also selected to help create an impedance match between the transmission line and the coaxial cable.

The spatula arrangement proposed in GB 2472972 provides a desirable insertion loss between the coaxial feed line and the end radiating portion, while also providing desirable return loss properties to the edge of the spatula when in contact with air and biological tissue respectively. In more detail, the insertion loss along the structure can be less than 0.2dB at the frequencies of interest, and the return loss is less than (more negative values) -1dB, preferably less than-10 dB. These properties may also indicate a well-matched joint between the coaxial cable and the transmission line blade structure, whereby the microwave power is efficiently taken into the blade. Also, when the edge of the spatula is exposed to air or non-tissue of interest, the return loss may be substantially 0 (i.e., the power radiated into free space or undesired tissue is very small), while when in contact with the desired tissue, the return loss may be less than (more negative) -3dB, preferably less than-10 dB (i.e., most of the power in the spatula is transmitted to the tissue).

The instrument discussed in GB 2472972 is intended to radiate microwave energy from the edge of a planar transmission line in order to cause local tissue resection or coagulation.

GB 2472972 also discloses that the above-mentioned doctor blade may have a radio frequency cutting portion integral therewith. The rf cutting portion may be formed using the first and second conductive layers as active and return electrodes for rf energy. This arrangement can take advantage of the fact that the active and return electrodes are in close proximity to each other, thereby establishing a preferential return path to enable local tissue cutting activity to occur without the need for a remote return pad or highly conductive liquid, i.e., saline, to be present between the two electrodes.

In this example, the radio frequency cutting portion may include: a radio frequency voltage source coupled to the planar transmission line; a frequency diplexer/diplexer unit (or signal summer) that includes a low pass filter to prevent high frequency microwave energy from returning to a low frequency radio frequency energy source and a high pass filter to prevent low frequency radio frequency energy from returning to a higher frequency microwave energy source. In one example, a frequency diplexer/diplexer may be used to allow microwave and radio frequency energy sources to be combined at the generator and transmitted along a single slot (e.g., coaxial cable, waveguide assembly, or twisted pair) to the blade structure. The radiofrequency cutting energy may be delivered into the tissue alone or may be mixed with or added to the microwave energy and delivered simultaneously to establish a hybrid mode of operation.

US 2010/0249769 discloses microwave forceps for sealing tissue, wherein opposing jaws include one or more microwave antennas for transmitting microwave energy to biological tissue.

US 2003/0130658 discloses an electrosurgical cutting instrument in which an electrical insulator separates a first electrode from a different second electrode. The second electrode is shaped to cause it to operate as a return electrode. To provide the coagulation function, a third electrode may be mounted on an insulating layer formed on the second electrode.

Disclosure of Invention

In general, the present invention proposes an improvement to the shaver concept discussed in GB 2472972, in which the underside of the shaver comprises a protective shell comprising a shaped piece of dielectric material which overlaps the lower conductive layer and acts as a barrier to protect tissue which may be located under the shaver from damage during treatment. The protective shell may be particularly advantageous for procedures performed in the pancreas in the gastrointestinal tract involving bowel perforation or where damage to the portal vein or pancreatic duct may occur when a tumor or other foreign body is resected, cut or removed.

The protective shell can be applied to scrapers adapted to different functions. For example, aspects of the invention contemplated herein include: a shaver adapted to transmit Radio Frequency (RF) energy for cutting biological tissue; a scraper adapted to deliver radio frequency and microwave frequency energy separately or simultaneously; and a shaver adapted to deliver radiofrequency and/or microwave energy and having a retractable needle for delivering fluid (liquid or gas) to or removing fluid from the treatment site. For example, a needle may be used to introduce a gas (e.g., argon) to generate a hot or non-hot plasma for surface solidification (thermal) or sterilization (non-thermal). Radio frequency and/or microwave fields may be used to strike and sustain or generate the plasma. The protective shell may include a passageway (e.g., a groove) through which the telescoping needle passes, or through which fluid may be transferred without the use of a needle, e.g., for clinical or cleaning purposes.

In accordance with the present invention, there is provided an electrosurgical ablation instrument (EM) for applying Radiofrequency (RF) Electromagnetic (EM) energy to biological tissue, the instrument comprising: an instrument tip comprising a planar body made of a first dielectric material separating a first conductive element on a first surface thereof from a second conductive element on a second surface thereof, the second surface facing in an opposite direction to the first surface; a coaxial feeder cable, comprising: an inner conductor; an outer conductor coaxial with the inner conductor; and a second dielectric material separating the inner and outer conductors, the coaxial feed cable for carrying radio frequency signals; and a protective case including a third piece of dielectric material mounted to form a bottom side of the instrument tip, wherein the inner conductor is electrically connected with the first conductive element and the outer conductor is electrically connected with the second conductive element so as to enable the instrument tip to receive radio frequency signals, wherein the first and second conductive elements extend up to a distal edge of the planar body to form a radio frequency cutting portion, in which they are arranged to act as active and return electrodes (active and return electrodes) for emitting radiofrequency EM radiation corresponding to a radiofrequency signal from a distal edge of the planar body, and wherein the protective shell has a smoothly contoured convex bottom surface facing away from the planar body, the bottom surface includes a longitudinally extending groove formed in the bottom surface between a pair of ridges.

The first and second conductive elements may be arranged to provide a local return path for the radio frequency energy, i.e. a low impedance route for the radio frequency energy transferred between the first and second conductive elements. The first and second conductive elements may be metallization layers formed on opposite surfaces of the first dielectric material. The first and second conductive elements may be arranged to establish a local electric field in a contact region in which the instrument tip is in contact with biological tissue. The local electric field may be very high, which may cause formation of microplasmas (i.e. thermal plasmas) in a distal portion of the planar body, e.g. in contact with biological tissue. Microplasmas are desirable in achieving effective cutting. The first and second conductive elements may include portions made of a conductive material (e.g., titanium, tungsten, etc.) having a high melting point (e.g., 1500 ℃ or more), such as plated regions in and adjacent to the distal portion. With this material, the high temperature of the microplasma can be prevented from attacking the first and second conductive elements. The first and second conductive elements may also include connecting portions made of conductive materials having lower melting points (e.g., silver, gold, etc.) that are deposited or plated on the higher melting point conductors. The connecting portion may facilitate connection of the inner and outer conductors of the coaxial cable, for example, by soldering or the like. In one embodiment, a titanium Tungsten (TiW) seed layer may be used with a layer of silver (Ag) or gold (Au) deposited on top. The lower melting point material may be deposited on the higher melting point material only in the region where the inner and outer conductors of the coaxial cable are connected, i.e. only at the proximal portion of the instrument, and not along its side where the microplasma will be generated. This arrangement is adopted because: the electric field at the point where the coaxial transmission line is connected to the planar transmission line should be low and therefore the temperature at this point should be much higher than the melting point of the lower melting point material.

The coating metal layer may be composed of a biocompatible material, for example, any of silver, titanium, and gold. The melting and boiling points of the materials considered for the device are given in table 1 below:

material	Melting Point (. degree.C.)	Boiling point (. degree.C.)
			Tungsten (W)	3422	5555
Titanium (Ti)	1668	3287
			Silver (Ag)	961.78	2162
Gold (Au)	1064.18	2856

Table 1: melting and boiling points of conductive materials suitable for use on instrument tips

In one embodiment, the first dielectric material separating the conductive elements may provide a preferential return path between the inner conductor (active) and the outer conductor (return). Radiofrequency tissue cutting may be produced at the distal portion of the instrument tip if the first dielectric material has a high dielectric constant (e.g., greater than that of air) and the thickness of the first dielectric material at the distal portion (i.e., the separation of the first and second conductive elements at the edges of the distal portion) is small (i.e., less than 1 mm). This arrangement may provide the necessary preferential return path for current flow.

The bottom surface of the protective shell may be smoothly tapered at its periphery to meet the sides of the planar body (meet). The thickness of the protective shell may also decrease toward the distal end of the instrument tip. Thus, the outer portion of the protective shell may have a convex profile. A longitudinally extending groove may be formed in the bottom surface. The tapered edge profile and groove may cause the bottom surface of the protective shell to include a pair of ridges. Such a shape may reduce the risk of the instrument extending into the intestinal wall and causing an intestinal perforation, or may protect the portal vein or pancreatic duct from injury. The particular dimensions of the housing (e.g., length, width, thickness, etc.) may be adapted to the intended use and intended area of the body to be operated upon.

The protective shell may be constructed of a biocompatible, non-conductive material that does not adhere to the intestinal wall (or other biological tissue), such as a ceramic or biocompatible plastic, or the like. Alternatively, the housing may also be constructed of a metallic material (e.g., titanium, steel), or may be a multi-layered structure. May be connected (e.g., adhered) to either the first or second conductive elements on the bottom surface of the first dielectric material. However, in one embodiment, the protective shell may be constructed from the same material as the first dielectric material. The protective shell and the first dielectric material may be formed as a unitary body. In such an arrangement, one or more planar slots may be formed (e.g., cut) in the monolithic body to allow insertion of the conductive material to form the first and/or second conductive materials.

The distal end of the instrument tip between the lateral edges of the planar body may be curved (curved). The arc may describe a parabola in the plane of the planar body. The distal end of the protective hull may be curved in a similar manner. This shape prevents the instrument tip from presenting sharp corners to the biological tissue. This shape enables cutting in a direction diagonal to the long axis of the device, in addition to cutting in the same direction or perpendicular to the long axis.

The instrument may include a fluid feed conduit for delivering a fluid (e.g., saline) to the instrument tip. The fluid feed conduit may include a passageway through the protective housing for delivering fluid to the treatment site. The passageway may include an outlet located in a recess of the protective shell. The fluid (liquid or gas) can be delivered to the instrument (containment vessel) through corresponding passages formed in the coaxial feed cable. The fluid feed conduit may also be used to deliver other materials to the treatment site, such as gases or solids (e.g., powders). In one embodiment, a fluid (saline, etc.) is injected for inflating the biological tissue at the treatment site. This may be particularly useful where the instrument is used to treat the intestinal wall or esophageal wall or to protect the portal vein or pancreatic duct when a tumor or other foreign object is in close proximity, in order to protect these structures and create a fluid cushion. Expanding the tissue in this manner may help reduce the risk of bowel perforation, leakage from damaging the esophageal or pancreatic walls, or damage to the portal vein. This aspect of the invention makes it possible to treat other diseases where foreign bodies (tumors, hyperplasia, lumps, etc.) approach sensitive biological structures.

It is advantageous to use the same instrument for delivering the fluid as the radiofrequency and/or microwave energy, as shrinkage (e.g. due to fluid seepage) may occur if a separate instrument is introduced within the region or during treatment. The ability to introduce fluid using the same treatment structure enables filling of the level as soon as contraction occurs. Moreover, the use of a single instrument to perform the dehydration or cutting and the introduction of fluid also reduces the time to perform the overall polyp removal procedure, reduces the risk of injury to the patient, and also reduces the risk of infection. More generally, the infusion fluid may be used to flush the treatment area, for example, to remove waste or remove tissue, to provide better visibility during treatment. This is particularly useful in endoscopic procedures, as described above.

The fluid feed conduit may include a needle (e.g., a hypodermic needle) mounted below the planar body within the recess of the protective housing. The protective casing may include a guide passage for receiving the fluid feed conduit. The needle may have an outer diameter of less than 0.6mm (e.g., 0.4 mm.). The needle may be longitudinally movable between a deployed position protruding beyond the distal end of the instrument tip and a retracted position withdrawn from the distal edge of the instrument tip, e.g. below or near the planar body. The needle may be open to fluid flow at the proximal end or side of the needle and may be moved using one or more control wires. For example, the proximal end of the needle may be open to a passage formed within the coaxial feed cable. The needle may be mounted in a through hole formed in the protective case. The needle may form a slidable interference fit with the through-hole, wherein the needle is inserted into the through-hole when in the deployed position to create a minimally resistive fluid path through the needle. This arrangement prevents leakage from other parts of the instrument tip. The through hole may be formed by a pipe or similar tight fitting support surface mounted or formed at the bottom side of the protective shell, e.g. in a groove.

The instrument may include a sleeve for delivering the coaxial cable, fluid feed conduit (if present), and control wire (if present) to the instrument tip body. The instrument tip body and the protective sheath can be secured (e.g., glued) within the distal end of the sleeve. The sleeve may include a longitudinal braid to assist in transmitting torque from its proximal end to the instrument tip. In one embodiment, the braid cable may be made ofThe material is made and may include a plastic jacket having a metal braid attached to or connected to its inner wall. Such a sleeve may provide useful torque stability whereby torque forces applied in a handle connected to a proximal portion of a sheath of the sleeve are accurately translated into rotational movement of the instrument at the distal end of the sleeve. Preferably, the translation between the proximal and distal ends is 1:1, i.e. a 20 ° twist at the proximal end should cause a 20 ° rotation of the instrument tip.

The needle is slidably movable relative to the protective housing by one or more control wires, which, at the proximal end of the instrument, may be driven by a suitable sliding actuator. Preferably, the needle slides back and forth relative to a fluid supply channel that delivers fluid to the needle for delivery. The fluid supply passage may be an integral part of the sleeve or may be a conduit statically mounted within the sleeve. The ability to move the needle back and forth while delivering fluid to the needle through a catheter that does not move relative to the sleeve enables the provision of a telescoping needle within a smaller sleeve than devices in which the fluid delivery tube must slide along the length of the sleeve.

The sleeve may comprise a multi-lumen tube. The chamber may be formed by inserting an extruded separator element inside the single chamber tube. The extruded separator element may include a U-shaped channel for guiding the coaxial cable and one or more through-holes for receiving the fluid feed conduit and control wires.

The outer diameter of the sleeve is preferably less than 2.8mm to allow the sleeve to fit down the instrument channel of the endoscope. A handle for applying torque to the sleeve may be located at the proximal end of the sleeve, near the endoscope control.

The instrument may include a cap element at the distal end of the sleeve that covers the electrical connection between the coaxial cable and the first and second conductive elements. The cap member can be shrunk by heatMaterial or potting adhesive. By protecting the joint in this way, arcing at the electrical joint can be prevented during use. In particular, the cap element is arranged to seal the distal electrical connection at the instrument tip to isolate the fluid. It is undesirable for the fluid to enter the junction where the coaxial cable connects to the parallel plate planar transmission line because the microwave energy may be absorbed (which causes heating and does not transport energy along the edge of the blade in an efficient manner) or a lower breakdown voltage causes the device to break down or flashover. The potting adhesive may include a combination of adhesives, for example, low tack and high tack uv curable medical approved adhesives may be used, for example,4304 or4305, a low viscosity adhesive may be used to fill the gap, and the low viscosity may be used to wick the adhesive into very fine potential fluid paths.

The instrument tip may also be configured to receive microwave frequency energy. The coaxial cable may be arranged to carry the microwave signal separately or simultaneously to the radio frequency signal. The first and second conductive elements may be disposed on the first dielectric element to act as a near field antenna to transmit microwave EM radiation corresponding to the received microwave signal.

This embodiment may take advantage of the ability of the instrument to be "seen" differently by radio frequency signals and microwave signals. For radio frequency signals, the instrument tip can be molded as a (be molded as) parallel plate capacitor. By locating the edges of the first and second conductive layers back from the side edges of the planar body, the planar body (first dielectric material) may substantially contain the electric field established by the radio frequency signal between the first and second conductive elements. For radio frequency cutting, it is desirable that the electric field extends outside the planar body. In the present invention, it is possible to do so by extending the edges of the first and second conductive layers up to the side edges of the planar body in the region designated as the radio frequency cut. By making contact with one or more edges of the blade, the radio frequency field established between the two plates of the parallel plate capacitor (or planar transmission line) and coupled into the biological tissue can generate a controlled microplasma, and the microplasma enables or enhances the tissue cutting process.

Also, for microwave signals, the instrument tip may be molded as a parallel plate transmission line with a planar body representing a dielectric material separating two conductive plates. In this case, the radiation pattern of the microwave frequency EM energy depends on the overall shape of the planar body and the microwave feed structure. In this particular example, the gap at the proximal end between the coaxial feed line (center conductor) and the upper conductive layer plays an important role in ensuring that the impedance of the source's microwave energy matches the load impedance presented by the tissue. The overall length of the planar transmission line arrangement is also important in matching the impedance (or energy delivery) of (or from) the coaxial transmission line to (or to) the biological tissue, i.e. the structure may form a quarter-wave impedance transformer or a half-wave resonator. This can be modelled to control from which edges the microwave frequency EM energy is radiated, using known modelling tools. For example, the instrument tip may be configured to inhibit irradiation of the microwave EM radiation from the distal edge of the planar body.

Herein, Radio Frequency (RF) may refer to a stable fixed frequency in the range of 10kHz to 300MHz, and microwave frequency may refer to a stable fixed frequency in the range of 300kHz to 100 GHz. The frequency of the radiofrequency energy should be high enough to prevent the energy from causing nerve stimulation, and low enough to prevent the energy from causing tissue blanching or unnecessary thermal margin or damage to tissue structures. The preferred nominal frequency (spot frequency) of the radio frequency energy comprises any one or more of: 100kHz, 250kHz, 400kHz, 500kHz, 1MHz and 5 MHz. Preferred nominal frequencies of microwave energy include any one or more of the following: 915MHz, 2.45GHz, 5.8GHz, 14.5GHz and 24 GHz.

Drawings

Embodiments of the invention are discussed in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a partially transparent perspective view of an electrosurgical instrument as one embodiment of the present invention;

FIG. 2 is a front view of the instrument of FIG. 1;

FIG. 3 is a top view of the instrument of FIG. 1;

FIG. 4 is a side view of the instrument of FIG. 1;

FIG. 5 is a cross-sectional side view of the instrument of FIG. 1;

FIG. 6 is a perspective view of the radiating portion and telescoping needle of the electrosurgical instrument showing the needle in a deployed configuration in accordance with the present invention;

FIG. 7 is a perspective view of the radiating portion and the telescoping needle of FIG. 6, showing the needle in a retracted configuration;

FIG. 7A is a cross-sectional view of a retractable needle installed in the instrument;

FIG. 8 is a perspective view of an end of an electrosurgical instrument according to one embodiment of the present invention;

FIG. 9 is a cross-sectional side view through the instrument shown in FIG. 8;

FIG. 10 is a cross-sectional view through a shaft of an electrosurgical instrument according to one embodiment of the present invention;

FIG. 11 is a cross-sectional view through a shaft of an electrosurgical instrument according to another embodiment of the present invention;

FIGS. 12A and 12B are perspective front and rear views, respectively, of a protective shell component suitable for use with the present invention;

figures 13 to 16 illustrate the manner in which the length of the blade may be adjusted when the end of the blade is curved;

figures 17 to 20 show diagrams of simulated configurations of the blades with different gaps between the top conductor of the blade and the coaxial feed; and

fig. 21 to 23 are graphs showing the return loss of the blade with different gaps between the top conductor of the blade and the coaxial feed.

Detailed Description

Referring now to fig. 1 to 9, an electrosurgical instrument 100 as one embodiment of the present invention is described. The instrument includes a sleeve 102 having an instrument tip 104 attached at its distal end. Sleeve 102 is made of a resilient polymer material (e.g.,) Made with an axially extending braid (e.g., metal braid) sealed therein. This arrangement results in a torque-stable system. The braid may not extend all the way to the distal end of the sleeve, thereby introducing a safe distance (e.g., no less than 1mm, measured along the longitudinal axis) between the end of the braid and the proximal edge of the instrument tip to avoid heating of the braid by capacitive conductance during use of microwave energy. A sleeve without a braid can extend over this safety distance gap. This arrangement also prevents the two plates of the planar transmission line or the two conductors in the coaxial transmission line from being shorted or connected together. The braid structure enables precise translation of torque applied to the proximal portion of the sleeve into rotational motion of the instrument tip 104. For convenience, the sleeve 102 is shown in the drawings as transparent to allow its internal elements to be shown. In a practical embodiment, the sleeve may be opaque.

The instrument tip 104 includes a dielectric block 106 having a coating metal layer 105, 107 on its upper and lower surfaces. The coating metal layer corresponds to the first and second conductive elements of the present invention. The coating metal layers are separated by the thickness of the dielectric block 106 to form a bipolar radiating blade structure similar to that disclosed in GB 2472972.

The coating metal layer may be composed of a high melting point conductor (e.g., W or Ti). In such an arrangement, a lower melting point conductor may be provided around the region where the coaxial cable connects to the parallel plate planar transmission line to facilitate soldering of the coaxial arrangement and the planar transmission line. The lower melting point conductor may be silver (Ag) or gold (Au).

As can be seen most clearly in fig. 2, the distal end portions of the dielectric blocks are formed in an arcuate (e.g., parabolic) shape. This shape is preferred in order not to present sharp corners on the outer edge of the instrument and to enable use in multiple directions of travel. Such sharp corners are undesirable when the instrument is used in an environment with delicate tissue structures, such as the gastrointestinal tract (whose bowel wall is very thin).

The sleeve 102 defines a cavity (lumen) that houses the flexible coaxial feed cable 108 and the fluid transport structure. In this embodiment, the fluid transport structure includes a passageway formed in the space of the lumen around the coaxial feed cable 108 and the telescoping needle 110. The sleeve 102 houses a control wire 112 for deploying and retracting the needle 110. The operation of the needle is described below.

The inner conductor 114 of the coaxial feed cable 108 protrudes from the distal end portion of the coaxial feed cable 108 and is electrically joined (e.g., using solder) to the metal-coated upper layer 105 (first conductive element). The outer conductor of the coaxial cable 116 is electrically coupled to the lower metal-coated layer 107 (second conductive element) through the braid termination 118. Braid termination 118 includes: a tubular member electrically joined to the outer conductor; and a distally extending plate portion 109 mounted below the dielectric block 106 and electrically connected to the lower metallization layer 107.

In this embodiment, the shaped piece of dielectric material 120 is attached to the lower surface of the dielectric block 106. The dielectric material 120 may be secured to the lower metallization layer 107. The bottom side of the shaped piece of dielectric material 120 has a configuration that is particularly suited for procedures performed in the gastrointestinal tract. In the longitudinal direction, the shaped piece of dielectric material 120 includes a distal end portion that tapers (e.g., in an arcuate fashion) toward the dielectric block 106. This portion of the instrument is in close proximity to the tissue being treated at the time of use, e.g., the intestinal wall, esophageal wall, portal vein or pancreatic duct. By presenting an arc-shaped surface in this way, unnecessary perforation of the intestinal or esophageal wall or damage to the portal or pancreatic duct can be avoided.

As best seen in fig. 2, the bottom surface of the shaped dielectric material 120 has longitudinally extending grooves 122. The groove defines an access path for the retractable needle 110. The concave nature of the slot means that there are longitudinally extending ridges 124 of shaped dielectric material on both sides of the access path.

The surface of the shaped piece of dielectric material 120 that engages the underside of the radiating blade structure is shown in more detail in fig. 12A and 12B. The distal end of the shaped dielectric material 120 has a flat upper surface 126 that contacts the lower layer 107 of coating metal. A proximal end portion toward the flat upper surface 126 is formed with a rectangular recess 129 for receiving the plate portion 109 of the braid termination 118.

The proximal end of the shaped dielectric material 120 is formed with a U-shaped slot 128 for receiving and supporting the distal end of the coaxial feed cable 108. Fig. 12B shows a similar groove 130 formed on the underside of the proximal portion of the shaped piece of dielectric material 120 to receive the catheter of a telescoping needle (see fig. 6 and 7). The outer surface of the proximal end of the shaped piece of dielectric material 120 is cylindrical, with a diameter selected to fit inside the sleeve.

On the side of the shaped dielectric material 120 between the proximal and distal ends, there are a pair of standing wings 132, the inner surfaces of which engage the respective side edges of the radiating blade structure and the outer surfaces of which engage the inner surface of sleeve 102 by an interference fit.

The shaped dielectric material piece 120 is preferably made of ceramic or other material having a low thermal conductivity.

In another embodiment, the dielectric body 106 and the sheet of formed dielectric 120 may be formed as a unitary body, i.e., as a monolithic body. There may be planar slots formed (e.g., cut) in the monolithic body for receiving conductive material to form the metal-coated underlayer (second conductive element). The thickness of the socket, and hence the underlying layer of coated metal, may be 0.1mm or greater, but preferably does not exceed 0.2 mm.

The overall size of the instrument may be the size of an instrument slot suitable for insertion through an endoscope. Thus, the outer diameter of the sleeve may be 2.8mm or less, for example 2.7 mm.

Fig. 6, 7 and 7A illustrate the operation of the control wire 138 for deploying and retracting the retractable needle 136. The sleeve 102 and the shaped dielectric material 120 are omitted from fig. 6 and 7 for clarity. A retractable needle 136 is slidably mounted within a needle sleeve 134 that is secured within a slot 130 formed in the bottom side of the shaped dielectric material 120. The retractable needle 136 is slidable between a deployed position (shown in fig. 6) in which the needle protrudes from the distal end of the instrument and a retracted position (shown in fig. 7) in which the distal end of the needle is retracted from the distal end of the instrument. Attached to the end of the needle base unit 140 is a telescopic needle 136, which itself slides within the sleeve by operating (i.e. pushing or pulling as appropriate) a suitable control wire 138, as is conventional. The control wire 138 is preferably welded in series with the needle 138, as shown in fig. 6 and 7, as this allows for a more compact arrangement. Alternatively, the control line may be contiguous with the side of the needle or needle base unit, as shown in fig. 1.

When the control wire 138 pushes the needle 136 to its forward-most (i.e., deployed) position, the needle base unit 140 abuts the needle sleeve to create a seal. The needle base unit 140 prevents the needle from being pushed out of the instrument too far. As shown in FIG. 7A, a passage is formed in space 139 of the lumen located outside of coaxial cable 108 and retractable needle 136 for receiving proximal end fluid from the sleeve, which may be injected by a user, for example. An aperture 143 (shown in fig. 7 a) formed in the sidewall of needle base unit 140 provides a fluid flow path between space 139 within the cavity and the proximal end of needle 136. This allows fluid traveling down the length of the fluid conduit within the sleeve 102 to enter the proximal end of the needle and be injected out through the needle tip.

As shown in FIG. 7A, the control wire slides within the catheter 141, and the catheter 141 can prevent the control wire from bending when compressed, thereby improving the accuracy of control over the needle position. The conduit 141 may be formed in a semi-rigid insert mounted within the sleeve, as discussed below with reference to fig. 10 and 11.

In the retracted position, the distal end (i.e., the needle tip) of the needle 136 may be closed by the needle sleeve 134 to prevent accidental puncture of patient tissue or internal structures of the endoscope. The needle 136 may be a hypodermic needle terminating in a sharp point for piercing biological tissue.

When the apparatus is used to treat the intestinal or esophageal wall, it may be particularly useful to inject fluids (saline, etc.) to inflate or elevate biological tissue. For example, the instrument may be particularly useful for removing sessile polyps lying flat on the intestinal wall. Expanding the tissue in this manner may help reduce the risk of bowel or esophageal perforation. Since contraction may occur during treatment (e.g., due to fluid leakage) if a separate instrument is introduced within the region, it is advantageous to be able to deliver fluid using the same instrument as that delivering the radiofrequency and/or microwave energy. The ability to introduce fluid using the same treatment structure enables it to be filled as soon as a leak occurs. Moreover, the use of a single instrument to perform the dehydration or cutting and to introduce fluid also reduces the time to perform the polyp removal procedure, reduces the risk of injury to the patient, and also reduces the risk of infection. More generally, the injected fluid may be used to irrigate the treatment area, for example, to remove waste or remove tissue, in order to provide better visibility while treating. This is particularly useful in endoscopic surgery.

Fig. 8 shows a view of the instrument tip in which the distal end of sleeve 102 is "potted" within a cap element 142 that covers the electrical connection between the radiating blade structure and the coaxial cable. The cap member 142 may be constructed of a suitable heat shrinkable material or potting adhesive, such as an ultraviolet curing adhesive,for example4304 and/or4305. By protecting the joint in this way, arcing at the electrical joint can be prevented during use. The adhesive used should not lose or absorb energy at the selected microwave frequency. The use of a small amount of adhesive will also minimize the amount of energy coupled thereto. If the microwave power is absorbed by the adhesive, it causes localized heating and loss of microwave power available at the edge of the blade.

Fig. 9 shows a schematic cross-sectional view of the distal end of the instrument. In this illustration, the needle 136 is deployed. Here, the distal end of the sleeve 102 includes a widened portion 144 having a larger diameter. The widened portion 144 provides more space at the distal end, which provides more space for the needle deployment mechanism and a stronger connection between the coaxial cable 108 of the radiating blade structure 105, 106, 107 and the shaped dielectric material 120.

Fig. 10 shows a cross-sectional view through the sleeve 102 towards the distal end of the instrument. Mounted within the sleeve 102 is a semi-rigid insert 146 that is configured to maintain the position of the coaxial cable 108 and the push wire 112 along the length of the sleeve 102. The insert 146 may be a length of extruded plastic material or the like. In fig. 10, the insert 146 has a horseshoe-shaped cross-section with an outer surface for engaging the inner surface of the sleeve and a U-shaped slot for receiving the coaxial cable 108. Two longitudinally extending circular passageways are formed in the insert for receiving the push wire and for providing space for the fluid path, respectively. Maintaining the position of the pusher wire is particularly important because if the pusher wire is not restricted from movement within the lumen of the sleeve, control of the pusher wire may be lost, for example, by the pusher wire moving laterally within the sleeve.

Although shown as separate inserts in this embodiment, these passages may be incorporated into the sleeve itself, for example, as a single extrusion or by bonding or welding to the inner surface of the sleeve 102. The insert may exhibit lateral strength for providing crush resistance and durability to the device.

Fig. 11 shows a view similar to fig. 10 of another extruded rigid insert 148. The function of the semi-rigid inserts 146, 148 is to provide multiple cavities within the common sleeve 102.

When used to deliver microwave frequency energy, the radiating blade acts as a resonant microwave structure fed from a coaxial transmission line. Its function is to deliver microwave energy to biological tissue proximate to or in contact with the area near the tip of the shaver. As discussed above, the distal end of the radiating doctor blade is curved to avoid presenting a sharp edge or angle to the tissue during use. The effect of changing the shape of the end of the blade when delivering microwave energy is discussed below with reference to fig. 13 to 23.

The blade is a low impedance planar transmission line, i.e. the ratio of the voltage between the top and bottom metal plates to the (equal and opposite) current in the two plates is close to 30 Ω (calculated using microwave field modeling software). Typically, the transmission line feeding the blade has an impedance of 50 Ω. Thus, the transmission line and the biological tissue in contact with the end of the spatula appear to have a high impedance to the spatula.

The difference in impedance at each end typically presents a local obstruction to the power path into and out of the blade. However, as the spatula approaches the full number of half-wavelength lengths, the voltage at the end of the spatula increases and the current at that end decreases, all because of resonance effects, allowing power to be readily transferred from the coaxial line through the spatula into the tissue. For this reason, the length of the blade plays an important role in the effectiveness of the blade, from the end of the coaxial transmission line to the other end of the blade (or planar transmission line).

The length of the blade is carefully adjusted so that the blade approaches a half wavelength length at the operating frequency, taking into account the shape of the blade versus wavelength, the dielectric constant of the material between the plates, and the fringing fields at each end of the blade. In practice, the length can be found empirically by digital simulation and/or experimentation.

The effect of the shape change at the end of the doctor blade can be understood in terms of the change in capacitance at the end of the doctor blade.

Under resonant conditions, the center of the rectangular blade shown in fig. 13 works in a similar way to an inductor (coil) and each end works similarly to a capacitor, as schematically shown in fig. 14. The product of capacitance and inductance is proportional to the inverse square of the frequency at which the blade resonates. Standard electrical relationship for resonant frequency f of a resonant circuit having a capacitance C and an inductance LThis is described.

If the shape of the end of the blade changes, this causes a change in capacitance, so that the resonant frequency of the blade changes, or in other words, the blade is now not the correct length to resonate at the operating frequency.

However, the total length of the spatula may be adjusted so as to bring it back to resonance. A good approximation of the required length adjustment is to return the area of the blade to the value before the end rounding, which is equivalent to adjusting the capacitance back to its previous value.

The capacitance is proportional to the area of the capacitor. If the end of the blade is rounded to a semi-circular or elliptical shape, the length should be increased so that the additional rectangular portion has the same area as the portion cut out to make the semi-circular end, as shown in fig. 15.

The missing area in FIG. 15 is

Wherein r is₁Is half the width of the doctor blade, and r₂Is one of the length of the ellipse forming the curved endAnd half.

The area of the rectangle to be added shown in FIG. 16 is

2r₁x＝2r₁×0.2146r₂

Where x is the required extra length.

The required extra length is therefore approximately 0.215 times the length of the rounded part of the doctor blade. If the length of the rounded end is 3mm, the additional length required is about 0.64 mm. This increase in length was tested by simulations using the actual shape of the blade and found to be near optimal. The length of the model was adjusted empirically to find the optimum value of 0.6mm in practice.

Variations in the resonant frequency can also be corrected by changing the capacitance at the other end of the blade and changing the geometry of the connection to the 50 Ω coaxial cable. A simple way to do this is to change the spacing between the top plate of the spatula and the coaxial line.

The general shape of the blade is shown in fig. 17, and a side view of the blade with a 0.4mm gap is shown in fig. 18. A side view of the doctor blade with a 0.1mm gap is shown in fig. 19 and a close-up side view is shown in fig. 20.

In fig. 20, a capacitor that can be used to adjust the resonant frequency of the spatula is formed in the gap between the top plate of the spatula and the coaxial line. If the gap is reduced, the capacitance increases and the resonant frequency decreases.

Figure 21 shows the return loss of a 10.6mm long blade with a 0.4mm gap. The optimal return loss is close to 5.8 GHz.

Figures 22 and 23 compare the return loss of 10mm long blades with 0.3mm and 0.1mm gaps, respectively. It can be seen in fig. 22 that the optimum return loss is at 6GHz with a gap of 0.3mm, and in fig. 23 the optimum return loss is close to 5.8GHz with a gap of 0.1 mm.

It may be difficult to accurately manufacture a device with a 0.1mm gap, and therefore it may be preferable to increase the blade length to adjust the solution for changing the overall shape. However, other methods of increasing the capacitance at the cable end of the spatula may be used, for example increasing the thickness of the top plate, which may occur anyway when solder is applied.

Since it may be difficult to accurately describe the geometry actually achieved around the connection between the cable and the blade, the best approach is for a geometry that is easy to establish and repeatable.

Claims (27)

1. An electrosurgical resection instrument for applying Radiofrequency (RF) Electromagnetic (EM) energy to biological tissue, the instrument comprising:

an instrument tip comprising a planar body made of a first dielectric material separating a first conductive element on a first surface thereof from a second conductive element on a second surface thereof, the second surface facing in an opposite direction to the first surface;

a coaxial feeder cable, comprising: an inner conductor; an outer conductor coaxial with the inner conductor; and a second dielectric material separating the inner conductor and the outer conductor, the coaxial feed cable for carrying radio frequency signals; and

a protective case comprising a third piece of dielectric material mounted to form a bottom side of the instrument tip,

wherein the inner conductor is electrically connected with the first conductive element and the outer conductor is electrically connected with the second conductive element such that the instrument tip can receive the radio frequency signal, and

the method is characterized in that:

the first and second conductive elements extend up to a distal edge of the planar body to form a radio frequency cutting portion in which they act as an active electrode and a return electrode to emit radio frequency electromagnetic radiation corresponding to the radio frequency signal from the distal edge of the planar body, and

the protective case has a smoothly contoured convex bottom surface facing away from the planar body, the bottom surface including a longitudinally extending groove formed in the bottom surface between a pair of ridges.

2. The instrument of claim 1, wherein the bottom surface of the protective shell is smoothly thinned at its perimeter to meet the sides of the planar body.

3. An instrument according to claim 1 or 2, wherein the thickness of the protective hull decreases towards the distal end of the instrument tip.

4. The instrument of claim 1 or 2, wherein the first and second conductive elements are separated by less than 1mm at the distal portion edge.

5. The instrument of claim 1 or 2, wherein the first and second conductive elements each comprise a layer of metallization formed on opposing surfaces of a first dielectric material.

6. An instrument according to claim 5, wherein each coating metal layer comprises a plated region composed of a metal having a melting point above 1500 ℃.

7. The instrument of claim 6, wherein the first conductive element comprises a first connection portion between its plating region and the inner conductor and the second conductive element comprises a second connection portion between its plating region and the outer conductor, wherein the first and second conductive elements are made of a conductive material having a melting point of less than 1200 ℃.

8. The instrument of any one of claims 1, 2, 6 and 7, wherein the protective shell is constructed of ceramic or biocompatible plastic.

9. The instrument of any of claims 1, 2, 6 and 7, wherein the protective shell and first dielectric material are formed as a unitary body.

10. The instrument of any one of claims 1, 2, 6 and 7, wherein the instrument tip has an arcuate distal edge.

11. The instrument of any one of claims 1, 2, 6 and 7, comprising a fluid feed conduit for delivering fluid to the instrument tip for delivery out of the instrument.

12. The instrument of claim 11, wherein the fluid feed catheter comprises a sleeve defining a lumen for delivering fluid to the instrument tip, the sleeve having the instrument tip body and a protective sheath secured to a distal end thereof and being configured to receive the coaxial cable within the lumen.

13. The instrument of claim 12, comprising a fluid delivery mechanism mounted on a distal end of the lumen of the sleeve, the fluid delivery mechanism operable to deliver fluid from the lumen through the protective shell.

14. The instrument of claim 13, wherein the fluid delivery mechanism comprises a telescoping needle mounted below the planar body within the recess of the protective shell.

15. The instrument of claim 14, wherein the retractable needle is longitudinally movable between a deployed position protruding beyond a distal end of the instrument tip and a retracted position set back from a distal edge of the instrument tip.

16. The instrument of any one of claims 12 to 15, wherein there is a longitudinal braid within the sleeve to aid in transmitting torque from its proximal end to the instrument tip.

17. An instrument according to any one of claims 12 to 15, wherein the sleeve comprises a multilumen tubing.

18. The instrument of claim 17, wherein the sleeve comprises an extruded separator element inserted inside the single lumen tube, the extruded separator element comprising a U-shaped slot for guiding a coaxial cable and one or more longitudinal passages for fluid flow along the sleeve.

19. The instrument of any one of claims 12 to 15, and 18, wherein the sleeve has an outer diameter of 2.8mm or less.

20. The instrument of any one of claims 12 to 15 and 18, comprising a cap element at a distal end of the sleeve, the cap element covering an electrical junction between the coaxial cable and the first and second conductive elements.

21. The instrument of claim 20, wherein the cap element is comprised of a water-tight, insulating potting material.

22. The apparatus of any one of claims 1, 2, 6, 7, 12 to 15, and 18, wherein the coaxial cable is configured to convey a microwave signal separately or simultaneously from the radio frequency signal, and wherein the first and second conductive elements are configured on the first dielectric element to act as an antenna to emit microwave electromagnetic radiation corresponding to the received microwave signal.

23. An apparatus according to any one of claims 1, 2, 6, 7, 12 to 15, and 18 for removing foreign matter from the lower and/or upper gastrointestinal tract.

24. The apparatus of any one of claims 1, 2, 6, 7, 12 to 15, and 18 for resecting or removing a tumor in close proximity to a portal vein or pancreatic duct.

25. The apparatus of claim 6, wherein the metal is titanium or tungsten.

26. The apparatus of claim 7, wherein the conductive material is silver or gold.

27. The instrument of claim 23, the foreign body being a sessile polyp.