Electrosurgical instrument

Abstract

Various embodiments provide an electrosurgical instrument comprising a coaxial feed cable having an inner conductor, an outer conductor, and a first dielectric material separating the inner and outer conductors, the coaxial feed cable for conveying a microwave signal. The instrument further comprises a radiating tip disposed at a distal end of the coaxial feed cable for receiving the microwave signal. The radiating tip comprises an elongated conductor electrically connected to the inner conductor and extending in a longitudinal direction, a dielectric body disposed on at least a first portion of the elongated conductor, the dielectric body comprising a second dielectric material having a higher dielectric constant than the first dielectric material, and a conductive body disposed on at least a second portion of the elongated conductor, the second portion being different from the first portion. Some other embodiments provide an electrosurgical apparatus comprising the instrument.

Description

Technical Field

[0001] This invention relates to an electrosurgical device for delivering microwave energy to biological tissue to ablate it. The device may include a probe that can be inserted through a channel via an endoscope or catheter, or may be used in laparoscopic or open surgery. The device may be used for pulmonary or gastrointestinal applications, but is not limited thereto. Background Technology

[0002] Electromagnetic (EM) energy, and especially microwave energy, has been found to be useful in electrosurgery due to its ability to ablate biological tissue. Typically, devices for delivering EM energy to body tissues include a generator containing an EM energy source and electrosurgical instruments connected to the generator for delivering energy to the tissue.

[0003] Conventional electrosurgical instruments are often designed for percutaneous insertion into the patient. However, percutaneous positioning of the instrument can be challenging, for example, if the target site is in a thin-walled segment of the moving lung or gastrointestinal (GI) tract. Other electrosurgical instruments can be delivered to the target site via surgical endoscopic devices (such as endoscopes) that can operate through channels within the body, such as the airway or the lumen of the esophagus or colon. This allows for minimally invasive treatment, which can reduce patient mortality and intraoperative and postoperative complication rates.

[0004] Tissue ablation using microwave (EM) energy is based on the fact that biological tissues are primarily composed of water. The water content of human soft tissues is typically between 70% and 80%. Water molecules possess permanent electric dipole moments, meaning there is a charge imbalance throughout the molecule. This charge imbalance causes molecules to rotate in response to forces generated by an applied time-varying electric field, aligning their electric dipole moments with the polarity of the applied field. At microwave frequencies, rapid molecular vibrations lead to frictional heating, and the resulting field energy is dissipated as heat. This is known as dielectric heating.

[0005] This principle is utilized in microwave ablation therapy, where water molecules in the target tissue are rapidly heated by a localized electromagnetic field applied at microwave frequencies, leading to tissue coagulation and cell death. Microwave-emitting probes are known to be used to treat various diseases of the lungs and other organs. For example, in the lungs, microwave radiation can be used to treat asthma and ablate tumors or lesions. Summary of the Invention

[0006] In its most general sense, the present invention provides an electrosurgical instrument for delivering microwave energy to biological tissue, wherein the radiating tip includes a dielectric material comprising a dielectric material having a dielectric constant higher than that of the dielectric material in the coaxial cable used to supply microwave signals to the radiating tip. The inventors have discovered that using such a dielectric material in the radiating tip allows for an increase in the effective electrical length of the radiating tip without increasing its physical length.

[0007] It is generally desirable to reduce the size of electrosurgical instruments, for example, by making them thinner and / or shorter. Compact arrangement offers several advantages. For example, a compact arrangement allows instruments to be used within narrower viewing devices and / or smaller biological structures, makes instruments easier to manipulate, and / or can help improve control and precision at the instrument tip.

[0008] However, reducing the size of the device while maintaining its functionality is difficult. Specifically, to efficiently transfer energy into tissue, the device tip can be configured with a physical length corresponding to a specific electrical length (i.e., a certain number of wavelengths) at the desired energy frequency. For example, to provide efficient energy transfer at 5.8 GHz microwave energy, the physical length of the device tip can be selected to correspond to half a wavelength at that frequency (considering the dielectric constant of the material), so that the device tip acts as a half-wavelength resonator. However, because the physical length of the device tip is selected to provide a specific electrical length (i.e., corresponding to a certain number of wavelengths at the desired frequency), the physical length of the device tip cannot be reduced while maintaining the desired electrical properties. Instead, when the physical length is reduced, the electrical length also decreases, resulting in destructive reflections at the interface with biological tissue at the desired frequency (e.g., 5.8 GHz), and leading to a decrease in the efficiency of energy delivery through the device tip.

[0009] According to a first aspect of the invention, an electrosurgical instrument is provided, comprising: a coaxial feed cable having an inner conductor, an outer conductor, and a first dielectric material separating the inner and outer conductors, the coaxial feed cable being used to transmit microwave signals; and a radiating end disposed at a distal end of the coaxial feed cable for receiving the microwave signals; wherein the radiating end comprises: an elongated conductor electrically connected (directly or indirectly) to the inner conductor and extending in a longitudinal direction; a dielectric material disposed on at least a first portion of the elongated conductor, the dielectric material comprising a second dielectric material having a dielectric constant higher than the first dielectric material; and a conductor (e.g., made of a metallic material) disposed on at least a second portion of the elongated conductor, the second portion being different from the first portion. In this way, the radiating end comprises a microwave radiator formed by the elongated conductor and the conductor, wherein the radiating end thereby can function as a microwave monopole antenna, wherein microwave energy delivered to the radiating end is radiated from the elongated conductor and the conductor into surrounding target tissue. A conductor can make electrical contact with a slender conductor along most or all of its length.

[0010] The device is operable to ablate target tissue within the body. It is particularly well-suited for ablating tissue in the lungs, however, it can also be used to ablate tissue in other organs (e.g., the uterus or gastrointestinal tract). For efficient ablation of target tissue, the radiating tip should be positioned as close as possible to the target tissue (and in many cases, within it). Reaching the target tissue (e.g., in the lungs) may require guiding the device through pathways (e.g., airways) and around obstacles. This means the device should ideally be as flexible as possible and have a small cross-section. In particular, the device should be very flexible near its tip, where it may need to be manipulated along narrow pathways (such as potentially narrow and tortuous bronchioles).

[0011] By providing a dielectric material using a second dielectric material with a higher dielectric constant than the first dielectric material used in the coaxial cable, the effective electrical length of the radiating tip is increased compared to a radiating tip of the same physical length using the same dielectric material as in the coaxial cable. This means that a tip with this new configuration can operate at the same frequency as existing instruments, but with a shorter physical length—and therefore may be easier to guide to the target tissue (e.g., allowing for a smaller radius of curvature relative to known arrangements). The coaxial feed cable used in embodiments of the invention can be a conventional low-loss coaxial cable that can be connected at one end to an electrosurgical generator. It should be noted that the coaxial cable needs to be relatively long (e.g., 1 meter or more) to ensure access to the target tissue, and therefore a dielectric material with a relatively low dielectric constant (e.g., relative to the radiating tip) is desired to minimize energy loss through the coaxial cable. Furthermore, the choice of material for the coaxial cable is limited by flexibility requirements, and a high-dielectric material with appropriate flexibility may not be selectable. However, due to the relatively short length of the radiating tip (as described in more detail herein), this is not a significant concern for the radiating tip according to one embodiment.

[0012] The ablation volume of the device (i.e., the volume of tissue ablated by radiated microwave energy) may be approximately spherical. The shape of the ablation volume may be influenced by the shape, size, and position of the dielectric and conductor. For example, in some examples, increasing the length of the dielectric can increase the length of the ablation volume along the longitudinal axis of the device.

[0013] As used herein, the phrase "electrical length" can refer to the length of the instrument tip calculated using the wavelength λ of the operating signal; that is, the length can refer to the length of the instrument tip as "seen" by the operating signal. Electrical length can be calculated as a fraction or multiple of the wavelength. For example, to act as a half-wavelength resonator, the instrument tip may have approximately... The electrical length. This can be calculated as , where is the speed of light and ε eff This is the effective dielectric constant of the radiating end. The effective dielectric constant can depend on the size of the conductive element and the material surrounding it. The effective dielectric constant can vary along the length of the conductive element (i.e., along the length of the radiating end), and therefore in this formula, for ε... eff The value used can be an approximation.

[0014] The radiating tip can be generally cylindrical. The dielectric and conductor can be cylindrical, for example, with their central axes collinear with the longitudinal axis of the elongated conductor. The longitudinal axis of the elongated conductor is the axis along the length of the elongated conductor. This improves the axisymmetry of the radiating profile of the radiating tip.

[0015] Optionally, the diameter of the conductor may be smaller than the diameter of the coaxial cable, and optionally smaller than the diameter of the outer conductor of the coaxial cable. In one embodiment, the diameter of the conductor is substantially the same as the diameter of the dielectric material of the coaxial cable. The diameter of the conductor also changes the effective electrical length of the radiating tip (e.g., increasing the diameter of the conductor increases the effective electrical length of the radiating tip), and therefore, providing a conductor with a diameter similar to that of the coaxial cable can be useful for increasing the effective electrical length. However, if the conductor is wider than the coaxial cable, the radiating tip may be more difficult to maneuver to the target treatment site; for example, this may result in an increase in the maximum outer diameter of the radiating tip.

[0016] Optionally, the outer diameter of the radiating end can be less than 5 mm, for example less than 2 mm, such as 1.5 mm or smaller.

[0017] Optionally, the conductor may be 7 mm or less in the longitudinal direction; for example, the conductor may be between 2 mm and 4 mm in the longitudinal direction. It has been found that, since the conductor is typically made of metallic material and is therefore usually a rigid structure, setting the conductor length to 7 mm or less ensures that the radius of curvature of the radiating tip remains within a suitable range for reaching the desired tissue treatment site (e.g., the patient's lungs).

[0018] Optionally, the dielectric may be 14 mm or less in length in the longitudinal direction. It has been found that materials with higher dielectric constants are generally less flexible and more rigid than those with lower dielectric constants; therefore, providing a dielectric with a length of 14 mm or less ensures that the radius of curvature of the radiating tip remains within a suitable range for reaching the desired tissue treatment site (e.g., a patient's lung). For example, dielectrics with lengths in the range of 1 mm to 7 mm may be particularly suitable for delivering energy at frequencies of 5.8 GHz, while dielectrics with lengths in the range of 6 mm to 14 mm may be particularly suitable for delivering energy at frequencies of 2.45 GHz.

[0019] Optionally, the length of the dielectric in the longitudinal direction can be less than the length of the conductor in the longitudinal direction. Surprisingly, this arrangement can have an electrical length suitable for delivering energy to tissue at frequencies of 2.45 GHz and 5.8 GHz, but it also provides a shorter physical length of radiating tip and produces a shorter ablation zone in the longitudinal direction, thus achieving a highly spherical ablation zone. Therefore, electrosurgical instruments configured in this way are a good arrangement to balance the energy delivery to tissue at these frequencies while still producing a spherical and therefore predictable ablation morphology. For example, clinicians may find it simpler to use a spherical ablation zone than a teardrop-shaped ablation zone because the length and width of a spherical ablation zone are essentially the same (while the length and width of a teardrop-shaped ablation zone are different, i.e., the length is longer than the width), and therefore, it is easier to predict when the spherical ablation zone moves in different orientations in three-dimensional space. For example, the length of the dielectric can be between 1 mm and 3 mm, and the length of the conductor can be between 2 mm and 4 mm. Therefore, the size of the radiating tip allows electrosurgical instruments to be used to treat target tissue in a patient's lungs.

[0020] Optionally, the conductor may be located at the distal end of the elongated conductor. In other embodiments, the elongated conductor may extend distally beyond the distal end of the conductor, which can provide a more spherical ablation zone in use. For example, the elongated conductor may extend distally 1 mm to 3 mm, such as 2 mm, beyond the distal end of the conductor.

[0021] Optionally, the conductor can be configured as multiple conductive rings fitted around an elongated conductor, wherein the multiple conductive rings are electrically connected to each other (e.g., adjacent conductive rings can be in physical and electrical contact with each other). By configuring the conductor as multiple rings (e.g., rather than a single block of material), the conductor configuration has a degree of flexibility because adjacent rings can move relative to each other. However, since adjacent conductive rings are electrically connected, they behave (or "are perceived") as a single entity when a microwave signal is delivered to the radiating tip. For example, the length of each conductive ring in the longitudinal direction can be 0.5 mm. Configuring the conductor as multiple conductive rings can facilitate tuning the tip to a predetermined operating frequency during manufacturing (e.g., by allowing easy addition or removal of conductive rings to adjust the matching at a predetermined frequency) and allows for adjustment of the shape of the ablation zone.

[0022] Optionally, the dielectric can be configured as multiple dielectric rings that are looped around an elongated conductor. By configuring the dielectric as multiple rings (e.g., rather than a single block of material), the dielectric configuration provides a degree of flexibility, as adjacent rings can move relative to each other. This may be particularly suitable when a rigid material (such as ceramic) is chosen as the second dielectric material. For example, each dielectric ring may be 0.5 mm in length in the longitudinal direction. Configuring the dielectric as multiple dielectric rings can facilitate tuning the end to a predetermined operating frequency during manufacturing (e.g., by allowing easy addition or removal of dielectric rings to adjust the matching at a predetermined frequency) and allows for adjustment of the shape of the ablation zone.

[0023] Optionally, the radiating tip may further include a dielectric sheath surrounding the outer surfaces of the dielectric and conductor, wherein the dielectric sheath forms a pointed tip at its distal end. The dielectric sheath provides an outer protective layer to protect the radiating tip from environmental influences. For example, the dielectric sheath may be made of or coated with a non-adhesive material (e.g., PTFE) to prevent tissue from adhering to the dielectric. The outer surface of the dielectric sheath may be flush with the outer surface of the coaxial feed cable at the interface between the coaxial feed cable and the radiating tip. The distal tip may be pointed to facilitate insertion of the radiating tip into biological tissue, for example, for tissue puncture. In other cases, the distal tip may be rounded. Because the dielectric sheath may penetrate biological tissue during use, it may be made of a biocompatible material.

[0024] Optionally, the electrosurgical instrument may further include a conductive field-shaping element disposed at the distal end of the coaxial feed cable, the field-shaping element being electrically connected to the outer conductor. The field-shaping element can be used to reduce the back propagation of microwave energy along the coaxial feed cable. This can shorten the tail of the radiation profile extending along a portion of the coaxial feed cable. Therefore, the radiation profile may be concentrated around the radiation tip, and the ablation zone may be more spherical (i.e., the length of the ablation zone is similar to or equal to the diameter of the ablation zone). The field-shaping element may be made of any suitable conductive material. The field-shaping element may be disposed on the surface of the outer conductor, for example, on the outer or inner surface of the outer conductor. The field-shaping element may be electrically connected to the outer conductor by any suitable means (e.g., by conductive epoxy resin, or by brazing or welding). In some cases, the field-shaping element may be integrally formed with the distal portion of the coaxial feed cable. In some embodiments, the field-shaping element may have a length corresponding to a quarter wavelength of the microwave energy in the longitudinal direction. The field-shaping element may include a balun or choke.

[0025] Optionally, the dielectric constant of the second dielectric material can be in the range of 2.5 to 4. For example, the second dielectric material can be polyethylene terephthalate (PET). PET may be suitable for this application because it is flexible, but its dielectric constant is higher than that of polytetrafluoroethylene (PTFE), which is typically used in coaxial cables. For example, the dielectric constant of PET is approximately 3.0 to 3.5, while that of PTFE is 2.0 to 2.1. Of course, other materials can also be considered, such as ceramic materials in some embodiments.

[0026] The electrosurgical instruments discussed above can form part of a complete electrosurgical device for treating biological tissues. For example, the device may include: an electrosurgical generator arranged to supply microwave energy; and the electrosurgical instrument of the present invention may be connected to receive the microwave energy from the electrosurgical generator. The electrosurgical device may also include: a surgical endoscopic device (e.g., an endoscope or bronchoscope) having a flexible cord for insertion into a patient's body, wherein the flexible cord has an instrument channel extending along its length, and wherein the electrosurgical instrument is sized to fit within the instrument channel.

[0027] In this specification, "microwave" can be used broadly to indicate a frequency range of 400 MHz to 100 GHz, but is preferably a range of 1 GHz to 60 GHz. Preferred calibration frequencies for microwave EM energy include: 433 MHz, 915 MHz, 2.45 GHz, 3.3 GHz, 5.8 GHz, 10 GHz, 14.5 GHz, and 24 GHz. 5.8 GHz may be preferred.

[0028] In this article, the terms "proximal" and "distal" refer to the ends of an electrosurgical instrument that are further away from and closer to the treatment site, respectively. Therefore, in use, the proximal end of an electrosurgical instrument is closer to the generator used to provide RF and / or microwave energy, while the distal end is closer to the treatment site, i.e., the target tissue in the patient's body.

[0029] Unless the context otherwise indicates otherwise, the term “conductive” is used herein to mean conductive.

[0030] The term "longitudinal" as used below refers to the direction parallel to the coaxial transmission line along the length of the electrosurgical instrument. The term "inner" means radially closer to the center of the instrument (e.g., the axis). The term "outer" means radially further away from the center of the instrument (the axis).

[0031] The term “electrosurgery” is used in connection with instruments, devices, or tools that are used during surgical procedures and utilize microwave and / or radio frequency electromagnetic (EM) energy.

[0032] The present invention includes combinations of the described aspects and preferred features, except where such combinations are explicitly not permitted or should be explicitly avoided. Attached Figure Description

[0033] The implementation schemes and experiments of the principles of the present invention will now be discussed and explained with reference to the accompanying drawings.

[0034] Figure 1 This is a schematic diagram of an electrosurgical system for tissue ablation, as an embodiment of the present invention.

[0035] Figure 2a This is a schematic cross-section of an electrosurgical instrument as an embodiment of the present invention.

[0036] Figure 2b Is it like this? Figure 2a Photograph of the electrosurgical instruments shown.

[0037] Figure 3 The drawing is shown Figure 2a and Figure 2b The graph shows the relationship between the return loss of electrosurgical instruments and the frequency of microwave signals.

[0038] Figure 4 It shows Figure 2a and Figure 2b A simulated power loss density map of approximate energy deposition of electrosurgical instruments in tissue.

[0039] Figure 5a This is a schematic cross-section of an electrosurgical instrument as a second embodiment of the present invention.

[0040] Figure 5b Is it like this? Figure 5a Photograph of the electrosurgical instruments shown.

[0041] Figure 6 This is a schematic cross-section of an electrosurgical device according to a third embodiment of the present invention.

[0042] Figure 7 This is a schematic cross-section of an electrosurgical device according to a fourth embodiment of the present invention. Detailed Implementation

[0043] Various aspects and embodiments of the invention will now be discussed with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned herein are incorporated by reference.

[0044] Figure 1This is a schematic diagram of a complete electrosurgical system 100 capable of supplying microwave energy to the distal end of an invasive electrosurgical instrument. The system 100 includes a generator 102 for controllably supplying microwave energy. Suitable generators for this purpose are described in WO 2012 / 076844, which is incorporated herein by reference. The generator may be arranged to monitor reflected signals received from the instrument to determine a suitable power level for delivery. For example, the generator may be arranged to calculate the impedance observed at the distal end of the instrument to determine the optimal power level for delivery. The generator may be arranged to deliver power in a series of pulses modulated to match the patient's respiratory cycle. This will allow power delivery to occur during lung deflation.

[0045] Generator 102 is connected to interface junction 106 via interface cable 104. Interface junction 106 may accommodate an instrument control mechanism, operable via a slide trigger 110, for example, to control the longitudinal (back-and-forth) movement of one or more control lines or push rods (not shown). If multiple control lines are present, multiple slide triggers may be present on the interface junction to provide comprehensive control. The function of interface junction 106 is to combine inputs from generator 102 and instrument control mechanism into a single flexible shaft 112 extending from the distal end of interface junction 106. In other embodiments, other types of inputs may also be connected to interface junction 106. For example, in some embodiments, a fluid supply may be connected to interface junction 106 to deliver fluid to the instrument.

[0046] The flexible shaft 112 can be inserted along the entire length of the instrument (working) channel through the endoscope 114.

[0047] The flexible shaft 112 has a distal assembly 118 (in Figure 1 (Not drawn to scale), the distal assembly is shaped to pass through the instrument channel of endoscope 114 and protrudes at the distal end of the endoscope's tube (e.g., into the patient's body). The distal end assembly includes a radiating tip for delivering microwave energy into biological tissue. The tip configuration is discussed in more detail below.

[0048] The distal assembly 118 can be configured to have a maximum outer diameter suitable for passing through the working channel. Typically, the diameter of the working channel in a surgical endoscopic device (such as an endoscope) is less than 4.0 mm, for example, any one of 2.0 mm, 2.8 mm, 3.2 mm, 3.7 mm, or 3.8 mm. The length of the flexible shaft 112 can be equal to or greater than 0.3 m, for example, 2 m or longer. In other examples, the distal assembly 118 can be mounted at the distal end of the flexible shaft after the flexible shaft 112 has been inserted through the working channel (and before the instrument cord is introduced into the patient). Alternatively, the flexible shaft 112 can be inserted into the working channel from the distal end before its proximal connection is made. In these arrangements, the distal end assembly 118 can be allowed to have a size larger than the working channel of the surgical endoscopic device 114.

[0049] The system described above is one way to introduce an instrument into a patient's body. Other techniques are possible. For example, catheters can also be used to insert instruments.

[0050] Figure 2a A cross-sectional side view of an electrosurgical instrument 200, which is an embodiment of the present invention, is shown. Figure 2b A photograph of an electrosurgical instrument 200 is shown. The distal end of the electrosurgical instrument 200 may correspond, for example, to the distal assembly 118 discussed above. The electrosurgical instrument includes a coaxial feed cable 202, which can be connected at its proximal end to a generator (such as generator 102) to transmit microwave energy. The coaxial feed cable 202 may be the interface cable 104 that passes through the flexible shaft 112 discussed above. The coaxial feed cable 202 includes an inner conductor 204 and an outer conductor 206 separated by a first dielectric material 208. The coaxial feed cable 202 is preferably low-loss for microwave energy. A choke (not shown) may be provided on the coaxial feed cable 202 to suppress the back propagation of microwave energy reflected from the distal end, and thus limit reverse heating along the device. The coaxial feed cable 202 also includes a flexible outer sheath 210, which is disposed around the outer conductor 206 to protect the coaxial feed cable 202. The outer sheath 210 is made of an insulating material to electrically isolate the outer conductor 206 from its surrounding environment. The outer sheath may be made of or coated with a non-stick material such as PTFE to prevent tissue from adhering to the device.

[0051] The coaxial cable 202 has an outer diameter that is selected to fit through the working channel of a surgical endoscope (e.g., as mentioned above). Figure 1 The surgical endoscopic device (as described). Specifically, it has an outer diameter of 1.4 mm to accommodate a working channel with a diameter of 2 mm.

[0052] A radiating tip 212 is formed at the distal end of the coaxial feed cable 202. Dashed line 21 shows the interface between the coaxial feed cable 202 and the radiating tip 212. The radiating tip 212 is arranged to receive microwave energy transmitted by the coaxial feed cable 202 and to deliver said energy into biological tissue. The outer conductor 206 of the coaxial feed cable 202 terminates at the distal end of the coaxial feed cable 202; that is, the outer conductor 206 does not extend into the radiating tip 212. The radiating tip 212 includes a distal portion 214 of an inner conductor 204 extending beyond the distal end of the coaxial feed cable 202. Specifically, the distal portion 214 of the inner conductor 204 extends beyond the distal end of the outer conductor 206 to form an elongated conductor of the radiating tip 212. In other embodiments, the elongated conductor may include additional conductive elements (e.g., wires) electrically connected (e.g., by solder or conductive adhesive) to the distal end of the inner conductor 204 (in such embodiments, the inner conductor does not extend into the radiating end).

[0053] The outer sheath 210 also extends to cover the outer side of the radiating tip 212, thereby providing an insulating film that forms the outer surface of the radiating tip 212 to prevent moisture and / or tissue ingress. Thus, the outer sheath 210 serves to insulate the radiating tip 212 and protect it from environmental influences. The distal end 216 of the outer sheath 214 forms a pointed tip to facilitate penetration of the radiating tip 212 into the tissue to be treated.

[0054] A dielectric body 218, made of a dielectric material with a dielectric constant greater than that of the first dielectric material 208, is disposed on a first portion of the inner conductor 204 in the radiating end 212. Specifically, in this embodiment, the dielectric body 218 is made of PET, while the first dielectric material 208 is PTFE. The dielectric body 218 has a cylindrical shape and includes a channel through which the distal portion 214 of the inner conductor 204 passes. The diameter of the channel is substantially the same as the outer diameter of the inner conductor 204 to provide a secure fit. However, the dielectric body 218 can be further secured to the inner conductor 204, for example, using an adhesive. The dielectric body 218 is centered on the inner conductor 204. In other words, the central axis of the dielectric body 218 is collinear with the longitudinal axis of the inner conductor 204. In this way, the dielectric body 218 is disposed symmetrically around the distal portion 214 of the inner conductor 204 about the longitudinal axis of the inner conductor 204.

[0055] The radiating end 212 also includes a conductor 220 located distal to the dielectric 218 on the inner conductor 204. The conductor 220 is made of a metallic material and is electrically connected to the inner conductor 204. The conductor 220 is disposed on a second portion of the inner conductor 204 in the radiating end 212, distinct from the first portion, and extends from the distal end of the dielectric 220 to the distal end of the inner conductor 204. The conductor 220 has a cylindrical shape and includes a channel through which the distal portion 214 of the inner conductor 204 passes. The diameter of the channel is substantially the same as the outer diameter of the inner conductor 204 to provide a secure fit and to provide electrical connection to the inner conductor 204 along the length of the conductor 220. However, the conductor 220 can be further secured to the inner conductor 204, for example, using conductive adhesive, brazing, or soldering. The conductor 220 is centered on the inner conductor 204. In other words, the central axis of the conductor 220 is collinear with the longitudinal axis of the inner conductor 204. In this manner, the conductor 220 is arranged symmetrically about the longitudinal axis of the inner conductor 204 around the distal portion 214 of the inner conductor 204.

[0056] Both dielectric 218 and conductor 220 have the same outer diameter. The outer diameters of dielectric 218 and conductor 220 may be slightly smaller than the outer diameter of electrosurgical instrument 200, and in particular, slightly smaller than the outer diameter of coaxial cable 202. Specifically, the outer diameters of dielectric 218 and conductor 220 are the same as the outer diameter of the first dielectric material 208 of coaxial cable 202.

[0057] In this embodiment, the length of dielectric 218 in the longitudinal direction (i.e., the length of dielectric 218 between the distal end of coaxial cable 202 and the proximal end of conductor 220) is less than the length of conductor 220 (i.e., the length of conductor 220 between the distal end of dielectric 218 and the distal end of inner conductor 204). Specifically, the length of dielectric 218 is 2 mm, and the length of conductor 220 is 3 mm (the total length of the distal portion 216 as an elongated conductor is 5 mm). As described in more detail below, this arrangement provides an electrical length that allows the radiating tip 210 to have good impedance matching with tissue at frequencies of 2.45 GHz and 5.8 GHz, while maintaining a short physical length of the radiating tip 210. This allows the radius of curvature of the electrosurgical instrument 200 to be adapted to deliver the radiating tip 210 to areas difficult to treat, such as lung tissue. Furthermore, the physical length of the radiating tip 210 ensures that the ablation zone is approximately spherical, thereby facilitating the use of the electrosurgical instrument 200.

[0058] Figure 3 A graph 300 showing the relationship between return loss and frequency for an electrosurgical instrument according to an embodiment of the present invention is shown, specifically, as described above. Figure 2a and Figure 2bThe electrosurgical instrument 200 is described herein. As described above, the dimensions of the dielectric 218, the conductor 220, and the elongated conductor (i.e., the distal portion 214 of the inner conductor 204) are selected to exhibit return loss at frequencies of 2.45 GHz (indicated at 301) and 5.8 GHz (indicated at 302), thereby allowing the electrosurgical instrument 200 to be adapted to perform electrosurgical procedures (e.g., ablation) at these frequencies. It should be understood that alternative dimensions and geometries (e.g., as described herein) may be selected to provide suitable return loss at the desired microwave frequencies.

[0059] Figure 4 It shows Figure 2a and Figure 2b The simulated power loss density diagram 400 shows the approximate energy deposition (i.e., simulated microwave radiation profile) of the electrosurgical instrument 200 in the target tissue. The radiation profile was simulated using finite element analysis software for a microwave frequency of 5.8 GHz. The radiation profile indicates the shape of the tissue ablated by microwave energy. Figure 4 As can be seen, the radiating profile is concentrated around the radiating tip and defines an approximately spherical region. In this way, tissue can be ablated in an approximately spherical region around the radiating tip 210. The interface 211 between the radiating tip and the coaxial feed cable is shown to help visualize the position and shape of the field relative to the tip of the instrument.

[0060] Figure 5a This is a schematic cross-section of an electrosurgical instrument 500 as a second embodiment of the present invention. Figure 5b A photograph of the electrosurgical instrument 500 is shown. Many features of the electrosurgical instrument 500 are similar to... Figure 2a and Figure 2b The electrosurgical instrument 200 shown has the same features as described above, so the description of those features will not be repeated, and only the differences will be described in detail below. Figure 2a and Figure 2b The reference numerals used in the figures are in Figure 5a And in Figure 5n, the symbols used to indicate the correspondence with the above regarding... Figure 2a and Figure 2b The characteristics of the figures and symbols discussed.

[0061] In this embodiment, the dielectric 518 is configured as a plurality of dielectric rings 518a-518d, which are fitted onto the distal portion 214 of the inner conductor 204. Each of the dielectric rings 518a-518d is made of a dielectric material with a dielectric constant higher than that of the first dielectric material 208. For example, each of the dielectric rings 518a-518d may be made of PET. Each dielectric ring 518a-518d has a cylindrical shape and includes a channel through which the distal portion 214 of the inner conductor 204 passes. The diameter of the channel is substantially the same as the outer diameter of the inner conductor 204 to provide a secure fit. However, each dielectric ring 518a-518d may be further secured to the inner conductor 204, for example, using an adhesive. Each dielectric ring 518a-518d is centered on the inner conductor 204. In other words, the central axis of the dielectric 518 is collinear with the longitudinal axis of the inner conductor 204. In this manner, the dielectric 518 is arranged around the distal portion 214 of the inner conductor 204 in a manner symmetrical about the longitudinal axis of the inner conductor 204.

[0062] Furthermore, the conductor 520 is configured with a plurality of conductive rings 520a-520f, which are fitted onto the distal portion 214 of the inner conductor 204. Each of the conductive rings 520a-520f is made of a metallic material, which may be the same material as the inner conductor 204, and is electrically connected to the distal portion 214 of the inner conductor 204 as well as to the adjacent ring. In this way, the conductor 520 functions essentially as a monolithic unit when microwave energy is delivered via a coaxial cable. Each conductive ring 520a-520f has a cylindrical shape and includes a channel through which the distal portion 214 of the inner conductor 204 passes. The diameter of the channel is substantially the same as the outer diameter of the inner conductor 204 to provide a secure fit. However, each conductive ring 520a-520f can be further secured to the inner conductor 204, for example, using conductive adhesive or by brazing or soldering. Each conductive ring 520a-520f is centered on the inner conductor 204. In other words, the central axis of the conductor 520 is collinear with the longitudinal axis of the inner conductor 204. In this way, the conductor 520 is arranged symmetrically about the longitudinal axis of the inner conductor 204 around the distal portion 214 of the inner conductor 204.

[0063] Although in the electrosurgical instrument 500 both dielectric 518 and conductor 520 are configured as multiple rings of material, it should be understood that in other embodiments, only one of dielectric 518 or conductor 520 is configured as multiple such rings.

[0064] By arranging the dielectric 518 as multiple dielectric rings 518a-518d and the conductor 520 as multiple conductive rings 520a-520f, it is easier to adjust and tune the radiating tip 510 during the manufacture of the electrosurgical instrument 500 to suit the delivery of energy at a predetermined frequency, for example, by adding or removing individual rings as needed; such fine-tuning of length would not be possible if the dielectric 518 and / or conductor 520 were provided as a single block of material. Furthermore, this arrangement can help reduce the radius of curvature of the radiating tip 510, because arranging the dielectric 518 and / or conductor 520 as multiple individual material rings provides a degree of flexibility that would not exist if they were provided as a single block of material, as each ring could move slightly relative to its adjacent rings when the radiating tip 510 is bent. This can facilitate the delivery of the electrosurgical instrument 500 to certain areas of the body (e.g., delivery to the treatment site via the patient's airway).

[0065] Figure 6 This is a schematic cross-section of an electrosurgical instrument 600, as a third embodiment of the present invention. Many features of the electrosurgical instrument 600 are similar to... Figure 2a and Figure 2b The electrosurgical instrument 200 shown has the same features as described above, so the description of those features will not be repeated, and only the differences will be described in detail below. Figure 2a and Figure 2b The reference numerals used in the figures are in Figure 6 The middle is used to indicate the correspondence with the above text about Figure 2a and Figure 2b The characteristics of the figures and symbols discussed.

[0066] Electrosurgical instrument 600 is similar to electrosurgical instrument 200 discussed above, except that it includes a field-shaping element 902 and alters the lengths of the dielectric 618 and conductor 620. Specifically, in this embodiment, the dielectric 618 is longer than the conductor 620. The dielectric 618 has a length of 6 mm in the longitudinal direction, and the conductor 620 has a length of 3 mm in the longitudinal direction. This arrangement can provide tissue matching at both 2.45 GHz and 5.8 GHz. In another example, the length of the dielectric 618 can be 12 mm, and the length of the conductor can be 2 mm, which provides a radiating tip particularly suitable for delivering energy to tissue at a frequency of 2.45 GHz.

[0067] The field shaping element 622 is an annular sleeve of conductive material disposed around the outer surface of the outer conductor 206. The field shaping element 622 is located at the distal end of the coaxial feed cable 202 and extends along the length of the coaxial feed cable 202 from the interface 211 toward its proximal end (towards the generator to which the coaxial cable 202 is connected). The length of the field shaping element 622 corresponds to a quarter wavelength of the microwave energy to be transmitted through the coaxial feed cable 202. For example, in the case of a microwave energy of 5.8 GHz, the length of the field shaping element 622 may be approximately 9 mm. The inner surface of the field shaping element 622 contacts the outer surface of the outer conductor 206, such that the field shaping element 622 is electrically connected to the outer conductor 206 along its length. The electrical connection between the field shaping element 622 and the outer conductor 206 can be ensured, for example, by fixing the field shaping element 622 to the outer conductor 206 using conductive epoxy resin or by brazing or soldering them together. In some embodiments (not shown), the field shaping element 622 may be integrally formed with the outer conductor 206. The field shaping element 622 functions to increase the effective thickness of the outer conductor 206 in the distal region of the coaxial feed cable 202. The field shaping element 622 reduces the tail of the radiation profile (ablation zone) extending along the coaxial cable 202 and concentrates the emission of microwave energy around the radiating tip 610, thereby providing a more spherical ablation zone. This can be particularly useful in embodiments with a longer dielectric 618, as increasing the length of the dielectric 618 increases the length of the tail in the radiation profile, and therefore providing the field shaping element 622 helps to reduce this effect.

[0068] Figure 7 This is a schematic cross-section of an electrosurgical instrument 700 as a fourth embodiment of the present invention. Many features of the electrosurgical instrument 700 are similar to... Figure 2a and Figure 2b The electrosurgical instrument 200 shown has the same features as described above, so the description of those features will not be repeated, and only the differences will be described in detail below. Figure 2a and Figure 2b The reference numerals used in the figures are in Figure 7 The middle is used to indicate the correspondence with the above text about Figure 2a and Figure 2b The characteristics of the figures and symbols discussed.

[0069] In this embodiment, the distal portion 214 of the inner conductor 204 extends distally beyond the distal end of the conductor 720. Therefore, a dielectric is disposed in a first portion 718a and a second portion 718b, the first portion being disposed proximal to the conductor 720 on the distal portion 214 of the inner conductor 204, and the second portion being disposed distal to the conductor 720 on the distal portion 214 of the inner conductor 204. Specifically, the first portion 718a of the dielectric block has a longitudinal length of 2 mm, the conductor 720 has a longitudinal length of 7 mm, and the second portion 718b of the dielectric has a longitudinal length of 2 mm. This arrangement is particularly suitable for delivering energy to tissue at a frequency of 5.8 GHz. Furthermore, extending the distal portion 214 of the inner conductor 204 distally beyond the distal end of the conductor 720 helps to shape the ablation zone, thereby providing a more spherical overall morphology.

[0070] The features disclosed in the foregoing description, the appended claims, or the drawings, expressed in their particular form or by means of performing the disclosed functions or by methods or processes for obtaining the disclosed results, may, where appropriate, be used alone or in any combination of such features to implement the invention in its various forms.

[0071] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when this disclosure is given. Therefore, the exemplary embodiments set forth above are to be considered illustrative rather than restrictive. Various changes may be made to the described embodiments without departing from the spirit and scope of the invention.

[0072] To avoid any doubt, any theoretical explanations provided herein are intended to enhance the reader's understanding. The inventor does not wish to be bound by any of these theoretical explanations.

[0073] Any chapter headings used in this article are for organizational purposes only and should not be construed as limiting the subject matter described.

[0074] Throughout the specification, including the appended claims, unless the context otherwise requires, the words “comprising” and “including” and their variations shall be understood to implicitly include the indicated integer or step or group of steps, but not exclude any other integer or step or group of steps.

[0075] It must be noted that, unless the context clearly indicates otherwise, the singular forms “a” and “the” as used in this specification and the appended claims include a plural referent. A range may be expressed herein as “about” a particular value and / or “about” another particular value. When such a range is expressed, another embodiment includes a range from one particular value and / or to another particular value. Similarly, when a value is expressed as an approximation using the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” with respect to numerical values ​​is optional and means, for example, + / - 10%.

Claims

1. An electrosurgical device comprising: A coaxial feed cable having an inner conductor, an outer conductor, and a first dielectric material separating the inner and outer conductors, the coaxial feed cable being used to transmit microwave signals, and A radiating end, wherein the radiating end is disposed at the distal end of the coaxial feed cable for receiving the microwave signal; The radiating end includes: A long, thin conductor electrically connected to the inner conductor and extending in the longitudinal direction; A dielectric material disposed on at least a first portion of the elongated conductor, the dielectric material comprising a second dielectric material having a dielectric constant higher than that of the first dielectric material; and A conductor disposed on at least a second portion of the elongated conductor, the second portion being different from the first portion.

2. The electrosurgical instrument of claim 1, wherein the diameter of the conductor is smaller than the diameter of the coaxial cable, and optionally, smaller than the diameter of the outer conductor of the coaxial cable.

3. The electrosurgical instrument according to claim 1 or 2, wherein the conductor has a length of 7 mm or less in the longitudinal direction.

4. The electrosurgical device according to any of the preceding claims, wherein the dielectric has a length of 14 mm or less in the longitudinal direction.

5. The electrosurgical instrument according to any of the preceding claims, wherein the length of the dielectric in the longitudinal direction is less than the length of the conductor in the longitudinal direction.

6. The electrosurgical instrument of claim 5, wherein the length of the dielectric is between 1 mm and 3 mm, and the length of the conductor is between 2 mm and 4 mm.

7. The electrosurgical instrument according to any of the preceding claims, wherein the conductor is located at the distal end of the elongated conductor.

8. The electrosurgical instrument according to any one of claims 1 to 6, wherein the elongated conductor extends distally beyond the distal end of the conductor.

9. The electrosurgical instrument according to any of the preceding claims, wherein the conductor is configured as a plurality of conductive rings, the plurality of conductive rings being sleeved on the elongated conductor, wherein the plurality of conductive rings are electrically connected to each other.

10. The electrosurgical instrument according to any of the preceding claims, wherein the dielectric is configured as a plurality of dielectric rings, the plurality of dielectric rings being sleeved on the elongated conductor.

11. The electrosurgical instrument according to any of the preceding claims, wherein the radiating tip further comprises a dielectric sheath surrounding the outer surfaces of the dielectric and the conductor, wherein the dielectric sheath forms a pointed tip at its distal end.

12. The electrosurgical instrument according to any of the preceding claims, further comprising a conductive field-forming element disposed at the distal end of the coaxial feed cable, the field-forming element being electrically connected to the outer conductor.

13. The electrosurgical element according to any of the preceding claims, wherein the dielectric constant of the second dielectric material is in the range of 2.5 to 4.

14. The electrosurgical instrument according to claim 13, wherein the second dielectric material is polyethylene terephthalate (PET).

15. An electrosurgical device for treating biological tissues, said electrosurgical device comprising: An electrosurgical generator, the electrosurgical generator being configured to supply microwave signals; as well as The electrosurgical device according to any of the preceding claims is connected to receive the microwave signal from the electrosurgical generator.

16. The electrosurgical device according to claim 15, further comprising: A surgical endoscopic device comprising a flexible cord having an instrument channel, wherein the electrosurgical instruments are sized to fit within the instrument channel.

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