Microwave ablation probe

Abstract

To provide an apparatus, system, and method that may include a microwave ablation probe. [Solution] The microwave ablation probe may include a feed line having an inner conductor, an outer conductor and a dielectric, and an antenna including a helical arm electrically connected to the outer conductor of the feed line at a junction, and a linear arm electrically connected to the inner conductor of the feed line.

Description

Technical Field

[0001] The present disclosure relates to a microwave ablation probe.

Background Art

[0002] In the treatment of diseases such as cancer, it has been found that certain tissues denature at high temperatures. These types of treatments, generally known as hyperthermia treatments, typically utilize electromagnetic radiation to heat cancerous tissue to temperatures above 60°C while maintaining healthy tissue at lower temperatures where irreversible cell destruction does not occur. Microwave ablation is one of these treatments that uses electromagnetic radiation to heat tissue.

[0003] Microwave tissue ablation is a less invasive procedure than surgical removal. Microwave tissue ablation is preferred in many situations where tumors are difficult to remove surgically. Such situations are, for example, when the tumor is relatively small, near a relatively small organ, or near a major blood vessel. This technique has been used in organs such as the prostate, heart, and liver where surgical removal of tumors may be difficult.

[0004] To effectively plan and optimize a treatment, it is desirable for an ablation device to cause an ablation of a volume of a predictable size and shape. For this reason, a predictable ablation volume of a regular shape is preferred, and it is particularly preferred to generate a spherical or substantially spherical ablation volume. An ablation device that provides an ablation volume of a predictable size and shape simplifies surgical procedures and reduces unwanted medical complications.

[0005] The embodiments disclosed herein aim to mitigate the effects of the aforementioned problems associated with microwave tissue ablation apparatus. More specifically, the embodiments disclosed herein provide a microwave antenna that can be used to generate predictable ablation volumes of a regular shape, as well as spherical or substantially spherical ablation volumes. [Overview of the Initiative]

[0006] Aspects of the present invention relate to a microwave ablation probe including a feed line and an antenna. The feed line may have an inner conductor, an outer conductor, and a dielectric disposed between them. The antenna may include a helical arm and a linear arm. The helical arm may be electrically connected to the outer conductor of the feed line at a junction, and the helical arm may further extend distally from the junction. The linear arm may be electrically connected to the inner conductor of the feed line and may further extend distally from the distal end of the feed line. The helical arm may be coaxially arranged around the linear arm. The linear arm may further include a first part and a second part, the first part being surrounded by a dielectric, and the second part being without a dielectric and distal to the first part.

[0007] The linear arm of the antenna can constitute an extension of the inner conductor of the feed line. The linear arm may be, for example, 4 to 14 mm in length. In some methods, the second part of the linear arm may be longer than the first part. If the second part is longer than the first part, the second part may have a larger diameter than the inner conductor of the feed line. Alternatively, the first part of the linear arm may be longer than the second part. The second part may be, for example, 0.1 to 2 mm in length. If the second part is longer than the first part, the first part may be 0.1 to 2 mm in length. The helical arm of the antenna may be 1 to 18 mm in length and / or may have 1 to 14 turns.

[0008] The helical arm typically does not enclose the feed line and / or outer conductor by more than two turns of the helical arm or less than one turn. Alternatively, the helical arm may not enclose the feed line and / or outer conductor by more than 2 mm, or more than 1 mm, or more than 0.5 mm.

[0009] Some aspects of the present invention relate to a microwave ablation probe further comprising a shaft, wherein an antenna and a feed line are disposed within the shaft. Furthermore, the shaft may include a metal portion and a ceramic portion. The ceramic portion may extend axially so as to occupy at least the same extent as the antenna.

[0010] Aspects of the present invention may additionally or alternatively include a cooling system configured to pass a coolant fluid across the antenna. In addition, the cooling system may include a coolant chamber configured to pass a coolant fluid across at least a portion of the feed line and across the antenna, and / or defined between the inner walls of the device shaft. In addition, the cooling system may include a cooling tube arranged around a linear arm. In an additional aspect, the cooling tube may divide the cooling chamber into a first cooling conduit and a second cooling conduit. The first cooling conduit may be located between the linear arm and the inner wall of the cooling tube. The second cooling conduit may be located between the outer wall of the cooling tube and the inner wall of the device shaft. In this arrangement, the linear arm of the antenna may be located within the first cooling conduit, and the helical arm of the antenna may be located within the second cooling conduit.

[0011] Additionally or alternatively, the cooling tube may extend distally to the distal portion of the feed line and around at least a portion of the antenna. Additionally or alternatively, the cooling tube is coaxial with the linear arm. Furthermore, the cooling tube may extend to and / or beyond the linear arm of the antenna. In some embodiments, the helical arm of the antenna may be wound around the cooling tube and / or the linear arm, and may extend distally from the junction in a series of windings around each of the cooling tube and / or linear arm.

[0012] In some embodiments, the microwave ablation probe may have a metal cap. Furthermore, the linear arm of the antenna may be electromagnetically coupled to the metal cap, but may not be connected to the cap. Additionally or alternatively, the distal tip of the antenna may be separated from the cap by a distance of 0.2 mm to 3 mm.

[0013] Additional aspects of the present disclosure relate to a microwave ablation needle having a feed line and a shaft. The feed line may be electrically connected to a microwave antenna, and the shaft may surround the microwave antenna and the feed line. The shaft may include a non-metallic portion and a metallic portion. The non-metallic portion may extend axially to occupy the same area as at least a portion of the microwave-emitting antenna.

[0014] In some embodiments, the non-metallic portion of the shaft may be ceramic. Additionally or alternatively, the microwave ablation needle may include an elastic element. The elastic element may be positioned between the non-metallic portion and the metallic portion and may be further configured to provide elasticity or strain relief at the joint between the non-metallic portion and the metallic portion of the probe shaft.

[0015] In some embodiments of the microwave ablation needle described above, the microwave antenna may comprise a helical arm and a linear arm. The helical arm may be electrically connected to the outer conductor of the feed line at a junction, and the helical arm may further extend distally from the junction. The linear arm may be electrically connected to the inner conductor of the feed line, and further extend distally from the distal end of the feed line. The helical arm may be arranged coaxially around the linear arm. The linear arm may further comprise a first portion and a second portion, the first portion being surrounded by a dielectric, and the second portion being without a dielectric and distal to the first portion.

[0016] Additional aspects of the present invention may relate to a microwave ablation system having one or more microwave ablation probes, each of which may include a feed line, an antenna, a power module, and one or more power cables. The feed line may have an inner conductor, an outer conductor, and a dielectric disposed between them. The antenna may include a helical arm and a linear arm. The helical arm may be electrically connected to the outer conductor of the feed line at a junction, and the helical arm may further extend distally from the junction. The linear arm may be electrically connected to the inner conductor of the feed line and may further extend distally from the distal end of the feed line. The helical arm may be arranged coaxially around the linear arm. The linear arm may further include a first part and a second part, the first part being surrounded by a dielectric, and the second part being without a dielectric and distal to the first part. The power module may be configured to supply microwave energy to the antenna. One or more power cables can be configured to connect power modules to each microwave antenna and to deliver microwave energy provided by the power modules to the antennas for tissue ablation.

[0017] An additional aspect of the present invention may relate to a microwave ablation system for tissue ablation, comprising one or more microwave ablation needles, a power module, and one or more power cables. One or more microwave needles may include a feed line and a shaft. The feed line may be electrically connected to a microwave antenna, and the shaft may surround the microwave antenna and the feed line. The shaft surrounds the microwave antenna and the feed line and may include a non-metallic portion and a metallic portion. The non-metallic portion may extend axially so as to occupy the same area as at least the radiating portion of the antenna. The power module may be configured to supply microwave energy to the antenna. One or more power cables may connect the power modules to each microwave antenna and may be configured to deliver the microwave energy provided by the power modules to the antenna for tissue ablation.

[0018] In some embodiments, a microwave ablation system may include a feed line and an antenna. The feed line may have an inner conductor, a dielectric coaxially arranged around the inner conductor, and an outer conductor coaxially arranged around the dielectric. The antenna may include a helical arm and a linear arm. The helical arm may be electrically connected to the outer conductor of the feed line at a junction and may extend distally from the junction. The linear arm may be electrically connected to the inner conductor of the feed line and may extend distally from the distal end of the feed line. The linear arm may further include a first part and a second part. The first part may be surrounded by a dielectric, and the second part may be without a dielectric and be distal to the first part.

[0019] Additionally or alternatively, one or more microwave ablation needles may each include a cooling system for cooling at least a portion of the antenna and / or feed line. The ablation system may further include a cooling system configured to deliver a coolant fluid to the cooling system of one or more microwave ablation probes in order to cool at least a portion of the antenna and feed line of each of the one or more microwave ablation probes.

[0020] In some aspects of the present disclosure, the power cables of one or more microwave ablation needles may be cooled power cables, and the cooling system may be configured to cool the power cables of one or more microwave ablation needles.

[0021] Additionally or alternatively, the majority of the helical arm may not enclose the feed line and / or the outer conductor. Furthermore, the outer conductor may not extend distally beyond the junction and / or may extend through only a small portion of the helical arm. In some embodiments of the invention, the helical arm does not form electrical contact with the inner or outer conductor except at the junction. In one variation of the linear arm, the second portion may be positioned distal to the distal end of the helical arm so as not to extend through the helical arm. Furthermore, the helical arm may have a larger diameter than the first portion.

[0022] Details of one or more examples are shown in the attached drawings and the following description. Other features, purposes, and advantages will become apparent from the description and drawings, and from the claims. Other embodiments of the present invention will be discussed throughout this specification. Any embodiment discussed in relation to one aspect of the present invention is applicable to other aspects of the present invention, and vice versa. Each embodiment described herein is understood to be an embodiment of the present invention applicable to all aspects of the present invention. Any embodiment discussed herein may be implemented in relation to any method or composition of the present invention, and vice versa. Furthermore, the compositions and kits of the present invention can be used to achieve the methods of the present invention. The following includes definitions of various terms and phrases used throughout this specification.

[0023] The term "spherical shape" refers to a three-dimensional shape that is generally spherical. The term "distal" refers to the location or part furthest from the user, while the term "proximal" refers to the location or part closest to the user.

[0024] The term "pitch" in helical antennas refers to the height of one turn of the spiral, measured parallel to the axis of the spiral. The terms "electrically connected," "electrically coupled," or "electrically in contact" are defined as the ability of an electric current to flow from one article to another. Typically, two articles are physically connected by a conductor, such as a metal wire, or through a conductor.

[0025] The term "electromagnetically coupled" is defined as the ability of electromagnetic energy to flow from one article to another without physical contact, such as influencing the shape of the energy field and the resulting ablation volume. The two articles do not need to be physically connected by or through a conductor, and electromagnetic energy can be transmitted from one article to another (e.g., electromagnetic induction).

[0026] The terms "insulating layer", "dielectric", and "insulator" mean a layer of non-conductive material that forms no electrical contact under the operable use of the device. In the embodiments disclosed herein, an insulating layer or a dielectric layer is used to prevent unwanted electrical contact.

[0027] The terms "about" and "approximately" are defined as being near to what would be understood by a person skilled in the art, and in non-limiting embodiments, these terms are defined as being within 20%. The use of the word "a", "an" in conjunction with the term "comprising" in the claims or specification may mean "one", but is also consistent with the meaning of "one or more", "at least one", and "one or two or more".

[0028] The terms "comprising" (and any form of "comprise" such as "comprise" and "comprises"), "having" (and any form of "have" such as "have" and "has"), or "containing" (and any form of "contain" such as "contains" and "contain") are inclusive or open-ended and do not exclude additional unrecited elements or method steps.

[0029] An assembly, device, or method disclosed herein can "comprise", "consist essentially of", or "consist of" certain method steps, components, elements, compositions, etc.

[0030] Other purposes, features, and advantages disclosed herein will become apparent from the following figures, detailed description, and examples. However, it should be understood that while such figures, detailed description, and examples illustrate specific embodiments of the invention, they are given merely as examples and are not intended to be limiting. Furthermore, variations and modifications within the spirit and scope of the invention are expected to become apparent to those skilled in the art from this detailed description.

[0031] The advantages of the present invention may become apparent to those skilled in the art by benefiting from the following detailed description and by referring to the accompanying drawings. [Brief explanation of the drawing]

[0032] [Figure 1] Figure 1A is a block diagram according to one aspect of the present disclosure, where Figure 1A is a block diagram including components of a system that performs an ablation process, and Figure 1B is a block diagram illustrating the operation of an ablation device interface connected to an ablation device. [Figure 2] A simplified diagram of a cooling system according to one aspect of this disclosure. [Figure 3A] A perspective view of a microwave tissue ablation apparatus with a handle, according to one embodiment of the present disclosure. [Figure 3B] An enlarged cross-sectional view showing the joint between the metal and ceramic parts of the ablation device shaft. [Figure 4] A side view of the handle of a microwave tissue ablation apparatus according to one embodiment of the present disclosure. [Figure 5] A simplified cross-sectional view of a microwave tissue ablation apparatus according to one embodiment of the present disclosure. [Figure 5A] A simplified cross-sectional view of a microwave tissue ablation apparatus having a cooling system according to one embodiment of the present disclosure. [Figure 5B] A simplified cross-sectional view of a microwave tissue ablation apparatus having an alternative cooling system according to one embodiment of the present disclosure. [Figure 5C]A simplified cross-sectional view of a microwave tissue ablation apparatus having a further alternative cooling system according to one embodiment of the present disclosure. [Figure 5D] A simplified cross-sectional view of a microwave tissue ablation apparatus having an alternative antenna design according to one embodiment of the present disclosure. [Figure 6A] A schematic diagram of a microwave tissue ablation apparatus equipped with a metal cap according to one embodiment of the present invention. [Figure 6B] A schematic diagram of a microwave tissue ablation apparatus equipped with a metal cap according to one embodiment of the present invention. [Figure 6C] A schematic diagram of a microwave tissue ablation apparatus equipped with a metal cap according to one embodiment of the present invention. [Figure 6D] A schematic diagram of a microwave tissue ablation apparatus equipped with a metal cap according to one embodiment of the present invention. [Figure 7] Figure 7A shows a perspective view of the apparatus according to one embodiment of the present disclosure, and Figure 7B shows an XY cross-sectional view of Figure 7A. [Figure 8A] A photograph showing an ablation pattern generated using an ablation apparatus according to one embodiment of the present disclosure. [Figure 8B] Another photograph showing an ablation pattern generated using an ablation apparatus according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0033] While various modifications and alternative forms are possible for this invention, the drawings illustrate specific embodiments as examples. The drawings may not be to exact scale. The size and dimensions of the ablation area created by a microwave tissue ablation apparatus are determined, among other factors, primarily by the type of microwave antenna. A clinician can select a microwave antenna capable of generating an ablation area larger than the size and dimensions of the target tissue, and can insert the microwave antenna so that the ablation area created by the microwave antenna includes the target tissue. If the tissue to be ablated is larger than the size of the ablation volume generated by the apparatus, two or more apparatuses can be used, and the ablation volumes can be combined to cover the tissue to be ablated. Using the embodiments of microwave tissue ablation apparatus described herein, tailing can be reduced, and an ablation area with a predictable shape can be created, thereby facilitating ablation planning and preventing damage to tissue outside the volume to be treated.

[0034] In some embodiments, the ablation apparatus disclosed herein is a microwave ablation apparatus, i.e., one that causes ablation by emitting microwave energy that kills tissue by heating. Typically, the apparatus is a microwave ablation needle having a microwave antenna, such as that described herein. In additional embodiments, the present invention provides a system for microwave ablation of tissue, comprising one or more microwave ablation apparatuses, such as probes or needles, as described herein. The microwave ablation apparatus comprises a microwave antenna configured to transmit microwave energy to tissue, a microwave generator configured to supply microwave energy to the microwave antenna via a feed line, and one or more power cables connected to the microwave antenna of the ablation apparatus and configured to deliver the microwave energy provided by the microwave generator to the antenna for tissue ablation.

[0035] Ablation apparatuses such as those described herein can be configured to operate for a maximum of 20 minutes or longer at an output of up to 150 watts. The apparatus heats up during use due to resistive heating of the antenna and energy reflected from the tissue. Therefore, typically, at least the distal portion of the apparatus, including the feed line and the distal portion of the antenna, requires cooling. Conveniently, in various embodiments, the entire feed line and antenna are cooled. Cooling the antenna prevents damage to the apparatus itself and prevents tissue near the antenna from overheating or burning. This can alter the physical properties of the tissue, including its energy absorption and reflection properties, and therefore reduce the efficiency of the antenna and alter the ablation zone. In one embodiment, the tissue ablation apparatus may further include a cooling system to cool at least a portion of the antenna and / or feed line. Such a cooling system is typically further configured to pass a cooling fluid, such as a coolant (e.g., water), over at least a portion of the feed line and over the antenna. Typically, such systems include a coolant inlet and a coolant outlet, which work together to pass coolant over the antenna and optionally at least part of the feed line, thereby cooling the antenna and optionally at least part, perhaps all, of the feed line. The antenna and feed line are typically in contact with the coolant.

[0036] Figure 1A shows a block diagram including components of a system for performing an ablation process according to one embodiment of the present disclosure. The system includes a console 102 which includes a user interface 104, a controller 106, and an ablation apparatus interface 108. In one embodiment, the user interface 104 includes a display that presents information to the user and an input device that receives input from the user, such as via one or more buttons, dials, switches, or other operable elements. In one embodiment, the user interface 104 includes a touchscreen display that functions as both a display and an input device for the user interface 104.

[0037] According to one aspect of the present invention, the ablation device interface 108 of the console 102 is arranged to connect to one or more ablation devices. In the embodiment of Figure 1A, the ablation device interface 108 connects to three ablations 120a, 120b, and 120c via lines 110a, 110b, and 110c, respectively. In one embodiment, the console 102 can connect to one, two, or all three ablation devices (120a, 120b, and 120c) individually or simultaneously. Although three ablation devices are shown in the embodiment of Figure 1A, it will be understood that different aspects of the present invention may include a console having an ablation device interface that can connect to a different number of ablation devices.

[0038] In one embodiment, the console includes an ablation device interface that can connect to a single ablation device. In other embodiments, the console includes an ablation device interface that can connect to two, three, four, or five ablation devices. In some examples, the ablation device interface can be configured to connect to any number of ablation devices.

[0039] According to some aspects of the present invention, a console can be used to operate any number of ablation devices up to the number of ablation devices supported by the ablation device interface. For example, a console having an ablation device interface that can accept three ablation devices simultaneously can be configured to operate one, two, or three ablation devices.

[0040] In one embodiment, lines 110a, 110b, and 110c are configured to supply coolant (e.g., from a coolant source 140) and ablation output (e.g., a microwave signal) to ablation devices 120a, 120b, and 120c, respectively. Lines 110a, 110b, and 110c can be configured to provide pathways for supplying coolant to each ablation device and return pathways for receiving coolant after it has passed through the coolant flow path within each ablation device.

[0041] According to one aspect of the present invention, the controller 106 is configured to connect to a user interface 104 and an ablation device interface 108. In one embodiment, the controller 106 can be configured to receive one or more inputs via the user interface 104 and to output one or more items via the user interface 104.

[0042] The controller 106 can be configured to control the operation of one or more ablation devices (e.g., 120a, 120b, 120c) via the ablation device interface 108. In one embodiment, the controller 106 can be configured to provide a coolant to one or more ablation devices via the ablation device interface 108. The controller 106 can be configured to provide an ablation output to one or more ablation devices in order to cause them to perform the ablation process. In one embodiment, the ablation output provided to the ablation device causes the microwave ablation device to emit microwave radiation. The power supply 130 can provide the power used to generate the ablation output.

[0043] In one example, the controller includes one or more processors and memory containing instructions that cause one or more processors to execute via the controller. In various embodiments of the present invention, the controller can be implemented as one or more processors, either individually or in any preferred combination, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), programmable logic circuits, etc. The controller may also include memory that, when executed, stores program instructions and associated data that cause the controller to perform functions belonging to the controller in this disclosure. The memory may include any fixed or removable magnetic, optical, or electrical medium, such as RAM, ROM, CD-ROM, flash memory, EEPROM, etc. The memory may also include a removable memory portion that can be used to provide memory updates or increases in memory capacity. The removable memory may also be used to allow image data to be easily transferred to another computing device. The controller may be implemented as a system-on-a-chip that integrates some or all components of a computer or other electronic system onto a single chip.

[0044] Figure 1B shows a block diagram illustrating the operation of an ablation apparatus interface connected to an ablation apparatus that performs an ablation process according to one embodiment of the present disclosure. In one example, the ablation apparatus interface 108 includes one or more fluid pumps, each of which is configured to pump coolant to its respective ablation apparatus. For example, as shown, pump 148a may be in communication with a coolant source 140 and configured to supply coolant to an ablation apparatus (e.g., 120a) via a coolant line 114a. Such pumps can be controlled by a controller. The controller may be configured to control the flow rate of fluid supplied from the pumps (e.g., 148a) to the ablation apparatus (e.g., 120a), such as starting the pumps that supply coolant to the ablation apparatus and stopping the pumps that supply coolant to the ablation apparatus.

[0045] In the example shown in Figure 1B, the ablation apparatus interface 108 includes three pumps 148a, 148b, and 148c that supply coolant to each ablation apparatus via coolant lines 114a, 114b, and 114c, respectively. The coolant lines 114a, 114b, and 114c may be included in lines 110a, 110b, and 110c shown in Figure 1, respectively. In one embodiment, each pump is controlled by a controller, for example, independently of other pumps, so that any pump can operate independently of the operating status of other pumps.

[0046] In another embodiment, each of the pumps 148a, 148b, and 148c includes a peristaltic pump driven by a single motor controlled by a controller. In some such examples, each pump operates at the same speed defined by the motor, and the coolant flows through any connected ablation device via the coolant lines 114a, 114b, and 114c. The controller can adjust the flow rate of the coolant through the ablation device by controlling the motor speed.

[0047] In some examples, the coolant supplied to the ablation apparatus is supplied in a closed-loop recirculation system, and the coolant is received from the ablation apparatus and returned to the coolant source 140. In one embodiment, the coolant source 140 comprises a reservoir of coolant such as sterile water, and the coolant is drawn from the reservoir and directed to one or more ablation apparatuses via a coolant line, and returned from one or more ablation apparatuses to the reservoir via a coolant outlet line configured to carry the coolant out of the ablation apparatuses. In some alternative examples, the coolant outlet line transports the coolant from the ablation apparatuses toward waste (e.g., toward a drainpipe). The ablation apparatus interface in Figure 1B includes a microwave generator 138. The microwave generator 138 generates a microwave signal and provides it to a microwave antenna in a microwave ablation apparatus configured to transmit microwave energy to tissue. Providing a microwave signal to the ablation apparatus may include providing the ablation apparatus with an ablation output so that the apparatus emits microwave radiation. The microwave generator 138 can supply microwave signals to ablation devices via power cables. In the embodiment shown in Figure 1B, the microwave generator 138 can supply microwave signals to up to three ablation devices via power cables 112a, 112b, and 112c, respectively.

[0048] The power cables 112a, 112b, and 112c may be coaxial cables rated to at least 30 watts, possibly at least 100 watts, and possibly at least 150 watts of power. The cables may be cooled cables configured to be cooled by a coolant supply. The coolant supply may circulate coolant along the cable between a cable coolant inlet and a cable coolant outlet. In some examples, fluid lines 114a to 114c provide coolant along the power cables 112a to 112c, respectively. In one configuration example, the system includes a cooling system configured to cool both the cables and the microwave ablation apparatus.

[0049] In some examples, the microwave generator can be configured to supply microwave energy to the antenna in one or more of the 915 MHz, 2.45 GHz, or 5.8 GHz ranges. The device typically operates in the 2.45 GHz range, such as 2.45 GHz or approximately 2.45 GHz. The microwave generator can be configured to supply microwave energy to the antennas of up to five microwave ablation probes, which may consist of one, two, or three probes.

[0050] The microwave generator 138 can be configured to provide a microwave signal instructed by the controller 106. For example, in one embodiment, the controller 106 can instruct the microwave generator 138 to provide a specific microwave signal to a particular ablation apparatus. The controller can be configured to specify the magnitude of a particular ablation (e.g., desired microwave power and / or energy radiated from the ablation apparatus), the duration of the ablation, or other parameters such as duty cycle, phase shift, or other parameters related to the microwave signal. In some examples, the microwave signal includes power delivered to the ablation apparatus (e.g., 90 W). The microwave signal may include an electrical signal containing characteristics (power, frequency, etc.) to cause the ablation apparatus to radiate microwave radiation with desired characteristics (e.g., microwave power radiated to the surrounding tissue). The electrical signal can provide the microwave ablation apparatus with a desired ablation output.

[0051] In one embodiment, the controller 106 can instruct the microwave generator 138 to apply a microwave signal to each of the multiple ablation devices. For example, with respect to Figure 1B, the controller can instruct the microwave generator 138 to provide a first microwave signal to the first ablation device via power cable 112a, a second microwave signal to the second ablation device via power cable 112b, and a third microwave signal to the third ablation device via power cable 112c. In some such examples, the microwave generator 138 can provide these first, second, and third microwave signals simultaneously. These signals may be the same or different. For example, in one embodiment, each of the first, second, and third microwave signals provides the same level of ablation output.

[0052] In some examples, the controller can be configured to control one or more of the following parameters: output wavelength, output power, the duration for which microwave energy is delivered to one or more antennas, and the duration for which energy is delivered as output power. If the ablation apparatus includes sensors such as temperature sensors, the controller can be configured to control any one or more of the parameters in response to signals from the sensors (e.g., temperature readings). For example, the controller can be configured to turn off power to one or more antennas in response to overheating.

[0053] Figure 1B shows the implementation as a single microwave generator 138 configured to provide microwave signals to multiple ablation devices, but in some examples the ablation device interface 108 may include multiple microwave generators, each corresponding to a different ablation device. In one embodiment, the controller 106 may communicate with the multiple microwave generators and be configured to apply microwave signals to their respective power cables (e.g., 112a, 112b, 112c) and provide these microwave signals to the respective ablation devices.

[0054] Figure 1B shows one embodiment in which three lines 110a, 110b, and 110c can simultaneously supply microwave signals and coolant to each of the three ablation devices. In some aspects of the present invention, for example, when fewer than three ablation devices are connected to the console 102, microwave signals and coolant can be supplied to a subset of lines 110a, 110b, and 110c. Furthermore, in some aspects, even when three ablation devices are connected to the console 102, microwave signals and coolant can be supplied to a subset of lines 110a, 110b, and 110c. For example, one or more such connected ablation devices can be left unused.

[0055] In one embodiment, the controller 106 controls which ablation apparatus (e.g., line 110a, 110b, or 110c) receives the microwave signal and coolant. In one aspect of the present invention, the controller 106 can control the characteristics of the microwave signal, such as its magnitude, frequency, duty cycle, and duration. In another aspect of the present invention, the controller 106 can control the manner in which coolant is supplied to the ablation apparatus, such as controlling the flow rate of coolant by controlling the operation of each pump. In one embodiment, for each ablation apparatus, the controller controls both the microwave signal applied to the ablation apparatus and the manner in which coolant is supplied to the ablation apparatus. During operation, each different ablation apparatus may receive a microwave signal and an amount of coolant unrelated to the microwave signal and fluid received by the other ablation apparatus, which may be the same as or different from the amount of microwave signal and fluid supplied to the other ablation apparatus.

[0056] Figure 1B shows an ablation device interface connecting to three ablation devices, but it will be understood that consoles according to different embodiments may include ablation device interfaces that can connect to a different number of ablation devices.

[0057] The block diagram in Figure 1B shows an ablation device interface 108 that includes several components connected to an ablation device. However, it should be understood that the components shown as part of the ablation device interface 108 are not necessarily contained within a single module or housing. These components are classified as an ablation device interface in that they facilitate control by the controller 106 of the connected ablation device.

[0058] Furthermore, Figure 1B shows an ablation device interface connected to a microwave ablation device, but it will be understood that a similar ablation device interface concept can be used to provide an interface between the controller and other ablation devices such as RF ablation and cryoablation.

[0059] In one embodiment, the ablation apparatus interface includes one or more ports configured to accept a part of the ablation apparatus, such as a cartridge having a fluid interface connected to a fluid line (e.g., 114a) and an electrical interface connected to a power cable (e.g., 112a).

[0060] Figure 2 is a simplified diagram of the cooling system according to the present disclosure. System 201 comprises an ablation device 202. In this case, the microwave ablation device comprises a microwave ablation needle configured to deliver microwave energy to the patient's tissue to cauterize the tissue.

[0061] The microwave ablation apparatus 202 may have a tip 203 configured to penetrate tissue and a long shaft having a proximal end 205 and a distal end 206. The shaft encloses a coolant space 214 and a feed line 207, which may be a coaxial cable having an inner conductor, an outer conductor, and a dielectric between them (not shown in Figure 2). The feed line in Figure 2 includes a radiating region 208 on the distal side, which includes a microwave antenna 204. The proximal end of the feed line 207 may be attached to a cable 209 (typically a coaxial cable), which connects the microwave ablation apparatus 202 to a microwave generator 210 to provide microwave energy to the apparatus. The cable may be appropriately connectable or, as in this case, permanently attached to the apparatus. In some embodiments, as shown with reference to Figure 1, the microwave generator 210 may be housed in a console such as a console 102.

[0062] The device is supplied with coolant via a device coolant supply line 211, which can be permanently attached to the device coolant inlet 212. In some embodiments, the device coolant supply line may alternatively be releasably connected to the coolant inlet 212, such as via a Luer® connector. The device coolant inlet 212 is in fluid communication with the device coolant outlet 213 via a series of coolant passages 214, 215, and 216 configured to circulate the coolant within the device. In this simplified representation, the coolant enters the device via the coolant inlet pipe 215, circulates through the coolant chamber 214 to cool the device, and exits via the coolant outlet pipe 216 and the device coolant return line 217.

[0063] System 201 includes a manifold 218 that receives coolant fluid from a coolant fluid source 219 via a coolant system supply line 220. The coolant system supply line 220 may be permanently connected to the manifold 218 at a manifold fluid supply inlet 250, or it may be releasably connected to the supply inlet 250 by, for example, a LuerLok® connector. The coolant fluid source may be, for example, an IV bag. The incoming coolant can be distributed to one or more manifold outlet ports 221 via a manifold inlet conduit 222. In advantageous embodiments, as shown in Figure 2, the flow of coolant exiting the port 221 can be controlled by a manifold outlet valve 223. This valve can normally be in the closed position. In some embodiments, as shown with reference to Figure 1, the manifold 218 can be housed in a console such as a console 102.

[0064] The manifold 218 also includes a manifold coolant outlet conduit 224 that provides fluid connections between one or more manifold fluid inlet ports 225 and a coolant system return line 226. The coolant system return line 226 may be permanently connected to the manifold 218 at a manifold fluid return inlet 251, or it may be releasably connected to a supply inlet 250, for example, by a LuerLok® connector. In one embodiment of the design, a manifold inlet valve 227 controls the flow through each inlet port, and the manifold inlet valve 227 may also be normally in a closed state.

[0065] A supply fitting 229 is configured to connect to a manifold outlet port 221. The system may also include a return fitting 233 configured to connect to a manifold inlet port. In one embodiment, the manifold outlet valve 223 may be configured to open when connected to the supply fitting 229. In one method, the supply fitting may include a projection 230 that causes the valve to open when the fitting 229 is connected to port 221, but other arrangements are possible, as will be discussed elsewhere in this specification.

[0066] The coolant inlet 231 of the coolant circuit in the supply fitting 229 is in fluid communication with the device coolant supply line 211, and by connecting the supply fitting 229 to the outlet port 221, the cooling circuit 232 is in fluid communication with the cooling fluid supply unit 219.

[0067] The return fitting 233 may have a coolant circuit outlet 234 that is in fluid communication with the device coolant return line 217. The supply fitting 229 and the return fitting 233 may be arranged to be simultaneously connected to the manifold outlet port 221 and the inlet port 225, respectively.

[0068] A pumping unit 235 can be located within the apparatus cooling circuit 232, for example, within the supply line 211, and is configured to circulate the coolant through the microwave ablation apparatus 202. In the system shown in Figure 2, the pump is a disposable pump head 236 having pump impellers 237, the pump head 236 is permanently connected within the apparatus coolant supply line and adapted to be connected to a pump head drive unit (not shown). Alternative pumping units can be used, which are described elsewhere in this specification. In some embodiments, as shown with reference to Figure 1A or Figure 1B, the pumping unit 235 can be housed within a console such as a console 102.

[0069] Figure 3A is a perspective view of a microwave tissue ablation apparatus 300 equipped with a handle 305 according to one embodiment of the present disclosure. The microwave tissue ablation apparatus 300 includes a handle 305. The handle 305 is configured to provide a firmer grip for the surgeon to handle the tissue ablation apparatus 300. The handle is further configured to house a liquid manifold for coolant circulation and a coaxial connector for supplying power to the power lines.

[0070] The microwave tissue ablation apparatus 300 includes a probe 307. The probe 307 is configured to be inserted into the patient's body to heat target tissue. In one embodiment, the probe 307 includes various ablation apparatus components described elsewhere in this specification, such as a feed line, an asymmetric dipole antenna, and a cooling system having an inlet and outlet tube. In one embodiment, the microwave antenna is configured to emit microwave radiation in a frequency band selected from the 915 MHz band (902–928 MHz), the 2.45 GHz band (2.402–2.483 GHz), and / or the 5.8 GHz band (5.725–5.875 GHz). The wavelength may be within the 2.45 GHz band, and in particular, the antenna may be configured to emit microwave energy at 2.45 GHz or about 2.45 GHz. The apparatus is configured to operate with a maximum power of 150 watts supplied to the antenna.

[0071] The probe 307 includes a surface 315. The surface 315 is configured to come into contact with human tissue and is made of a biocompatible material. The device shaft is at least partially metal, for example, stainless steel, and includes a marking 311, for example, laser marking. The marking 311 is configured to inform the surgeon of the depth to which the probe has been inserted into the body. The marking 311 may include a lubricating surface layer, such as PTFE, to aid in insertion and prevent tissue from sticking to it.

[0072] The shafts of the apparatus described herein are typically cylindrical and are typically made from biocompatible composite materials such as biocompatible polymers, glass fiber reinforced polymers, or carbon fiber reinforced polymers, ceramics, or metals (such as stainless steel). While the shafts can be made from ceramics or metals, in optional embodiments, the shafts include both a metal portion and a non-metallic portion. The non-metallic portion may be a biocompatible composite material such as glass fiber reinforced polymers, carbon fiber reinforced polymers, or ceramics, but may be ceramic to improve its performance and strength. The ceramics may be alumina or zirconia ceramics.

[0073] The device shaft optionally terminates distal to the device cap. The shaft may be cylindrical. The feed line and antenna are optionally located within the device shaft. Typically, the device shaft extends from the proximal manifold and terminates distally at the distal cap. The manifold includes electrical connections to the shaft's electrical components, such as the feed line, and may also include coolant inlet and outlet connections if necessary.

[0074] The shaft diameter is not limited and is typically adapted to the intended purpose. For example, in the case of ablation needles, it is important to have a thin needle to limit the damage caused during insertion and to allow for fine adjustment of positioning. As a result, the needle shaft diameter is typically 1.4–3 mm, optionally 1.5–2.5 mm, and especially 2–2.5 mm.

[0075] The apparatus according to this specification, as shown by probe 307 in Figure 3A, may include an applicator cap 330. In one embodiment, the applicator cap 330 is made from a biocompatible metal or ceramic, for example optionally stainless steel or ceramic. The applicator cap 330 may include a circular base and a distal tip (e.g., a trocar tip). The tip of the applicator cap 330 may include a sharp end positioned at the distal end of the applicator cap 330 and configured to penetrate tissue. The circular base may be configured to seal with the sheath of the probe 307 so that the inside of the probe 307 is fluidly isolated from the outside of the probe 307.

[0076] The shaft of the apparatus according to this specification may further include an echogenic region on its outer surface configured to be visible under ultrasonic imaging. In one embodiment, this region includes a coating containing acoustically reflective microspheres. The echogenic region extends to cover at least a region of the shaft radially outward from the antenna. The probe 307 in Figure 3A includes one embodiment which includes an echogenic region 325 configured to be visible under ultrasonic imaging and a coating containing acoustically reflective microspheres.

[0077] If the shaft of the apparatus of the present invention includes a metal portion and a non-metal portion, the joint between the two portions where the metal portion and the non-metal portion abut, can be a potential weak point, especially if the non-metal portion is ceramic, because ceramic is usually less flexible and more brittle than metals such as stainless steel. Therefore, the shaft may further include an elastic portion between this portion and the metal portion, configured to provide elasticity to the joint between the non-metallic (e.g., ceramic) portion and the metal portion of the probe shaft during use.

[0078] The apparatus (with respect to probe 307) may include a region 320 configured to mitigate strain induced in the probe during use, such as that caused by shaft bending. This region may include an elastic element positioned between the metal and non-metallic portions of the shaft. This strain-relieving region is particularly useful when the distal portion of the probe sheath is ceramic. The strain-relieving region 320 is configured to provide the probe 307 with added elasticity at the joint.

[0079] An elastic element may exist between the non-metallic region and the cap, but it is not essential as the strain on the shaft at this location is relatively low. The strain relief region may include, for example, an elastic annular spacer, which can be made from an elastic thermoplastic elastomer such as polyether block amide (PEBA), trade name PEBAX® or Vestimid® E (Evonik Industries), or a polyaryl ether ketone (PAEK) such as polyether ether ketone (PEEK). The spacer may be shaped and configured such that the proximal end of the non-metallic portion is separated from the distal end of the metal portion. The elastic spacer may optionally abut the metal portion on its proximal surface and the non-metallic portion on its distal surface. The elastic annular spacer typically extends radially outward, forming a surface coplanar with the outer surface of the probe shaft. The radially inner portion of the annular spacer may provide an annular step configured to extend proximal and / or distally to support the inner surface of the proximal end of the non-metallic portion and / or the distal end of the metallic portion. In one optional embodiment, the annular spacer provides an annular step configured to extend proximal to support the inner surface of the distal end of the metallic portion, but not distally. The apparatus shaft may also include an adapter sleeve that supports the joint between the non-metallic and metallic portions of the shaft. The adapter may be configured to accommodate any difference in thickness between the non-metallic and metallic portions, for example, to provide a smooth surface transition between the metallic and non-metallic portions of the shaft. The adapter may be metal, or a non-metallic material such as a thermoplastic elastomer such as PEBA® or Vestimid® E, or PAEK such as PEEK. If the non-metallic portion is ceramic, the adapter is particularly important because thickness is required for the further strength of the ceramic, and there is a risk of cracking at this location due to bending of the shaft. Conveniently, the sleeve extends sufficiently on each side of the joint to provide support for the joint, and is typically positioned between the feed line and the inner wall of the shaft, and typically radially inward of the shaft.The adapter sleeve may be made of metal.

[0080] The elastic spacer and adapter sleeve (if present) together constitute a strain relief region. The elastic spacer and adapter sleeve may be a single component or separate components; if a single component, they may be made of a nonmetallic material, or optionally a thermoplastic elastomer, as described above.

[0081] In one optional embodiment, the strain relief region comprises an elastic spacer as described above. The elastic spacer is shaped and configured to separate the proximal end of the non-metallic portion from the distal end of the metal portion. The spacer is configured to abut the metal portion on its proximal surface and the non-metallic portion on its distal surface. The spacer extends radially outward to form a surface coplanar with the outer surface of the probe shaft. The radially innermost portion of the spacer extends proximal to provide an annular step. The annular step is configured to support the inner surface of the distal end of the metal portion of the shaft. The strain relief region further comprises an adapter sleeve. The adapter sleeve may be made of metal and extend radially inward from each side of the joint and from the annular spacer. Optionally, the sleeve is configured to extend proximal to the annular spacer and contact and support the inner surface of the distal end of the metal portion of the shaft, or optionally, to extend distal to the spacer and contact and support the inner surface of the proximal end of the ceramic portion of the shaft.

[0082] The illustrated microwave tissue ablation apparatus 300 includes a housing 310. The housing 310 accommodates coaxial cables, fluid lines, electric wires, etc. Figure 3B shows a cross-section of one embodiment of the shaft 350 of the apparatus, showing the strain relief region 366. The proximal end of the shaft is indicated by A, and the distal end by B. For clarity, other features such as the coaxial cable, antenna, and cooling system are omitted. The shaft has a proximal metallic portion 351 and a distal non-metallic portion which may be made of ceramic 352. The shaft includes a strain relief region 366. The strain relief region 366 includes an elastic element in the form of an elastic annular spacer 353 positioned between the metallic and non-metallic portions of the shaft, and optionally an adapter sleeve 364 radially inward of the elastic spacer 353.

[0083] The elastic annular spacer 353 can be shaped and configured such that the proximal end of the non-metallic portion 355 is separated from the distal end of the metal portion 356. The spacer is configured to abut the metal portion at its proximal surface 357 and the non-metallic portion at its distal surface 358. The spacer extends radially outward to form a surface 359 that is coplanar with the outer surface of the probe shaft 360. The radially innermost portion of the annular spacer 361 can extend proximal to provide an annular stepped portion 362 configured to support the inner surface of the distal end of the metal portion 363. The adapter sleeve 364 can be positioned on each side of the joint between the metal section and the non-metallic section and to extend radially inward of the annular spacer 353. Optionally, the sleeve is configured to extend proximal to the annular spacer 353 and to contact and support the inner surface of the distal end of the metal portion 363 of the shaft 360. The sleeve extends distal to the spacer 353 and is configured to contact and support the inner surface of the proximal end of the ceramic portion of the shaft 365. The elastic annular spacer and the optional sleeve form a strain relaxation region.

[0084] Figure 4 is a side view of a microwave tissue ablation apparatus 400 according to one embodiment of the above design. The ablation apparatus 400 includes a handle 401, which houses a manifold 405.

[0085] The manifold 405 electrically connects a power supply (not shown) and a tissue ablation probe 430 through a coaxial cable connector 415. The tissue ablation probe 430 includes markings 435 configured to inform the surgeon of the depth to which the probe has been inserted during surgery.

[0086] The manifold 405 also fluidly connects a coolant source (not shown) and a tissue ablation probe 430. The manifold 405 includes a coolant inlet 420 and a coolant outlet 425. The coolant inlet 420 is fluidly connected to a coolant inlet conduit, and the coolant outlet 425 is fluidly connected to a coolant outlet conduit.

[0087] The tissue ablation apparatus 400 further includes a tubular housing 440 for housing electric wires and fluid tubes. As discussed elsewhere in this specification, multiple ablation apparatuses can be used simultaneously to carry out the ablation process. These ablation apparatuses can be arranged in various ways. In one example, microwave ablation apparatuses can be positioned equidistant from each other. Positioning multiple ablation apparatuses equidistant from each other can advantageously provide an approximately symmetrical net ablation volume formed by the multiple ablation apparatuses. In addition, arranging the ablation apparatuses in a regular polygonal configuration can provide an approximately spherical net ablation volume formed by the multiple ablation apparatuses. Alternatively, in other arrangements, the apparatuses may be arranged in a straight line or in an irregular shape. The ablation apparatuses can be arranged in multiple configurations to provide a suitable and desired ablation volume for a particular operation. Furthermore, these apparatuses can be inserted to the same or different insertion depths. Similar to different planned arrangements, the ablation apparatuses can be arranged in multiple configurations to provide a suitable and desired ablation volume for a particular operation.

[0088] In one option, the cooling system comprises a coolant chamber. The coolant chamber encloses the antenna and at least the distal portion of the feed line. The coolant chamber further includes a coolant inlet conduit configured to supply coolant to the coolant chamber and a coolant outlet conduit configured to carry coolant out of the coolant chamber. The coolant inlet and outlet conduits are configured to allow coolant to pass over at least a portion of the feed line and at least a portion of the antenna.

[0089] Figure 5 is a schematic side view of the distal end of the microwave tissue ablation apparatus 500. The apparatus has been simplified for ease of illustration. Figure 5 generally illustrates the characteristics of an asymmetric antenna.

[0090] As shown in Figure 5, the ablation device 500 includes a coaxial feed line 510. The feed line 510 may include an inner conductor 502. The feed line 510 includes a first insulator 504 arranged concentrically and circumferentially around the inner conductor 502. The inner conductor 502 may be a power line. The feed line 510 includes an outer conductor 506 arranged concentrically around the first insulator 504. The outer conductor 506 may be a ground wire. The feed line 510 includes a second insulator 508 arranged concentrically around the outer conductor 506.

[0091] The ablation device 500 includes an asymmetric dipole antenna 520. The asymmetric dipole antenna 520 includes a helical arm 518. The proximal end 525 of the helical arm 518 forms an electrical connection with the outer conductor 506 of the feed line 510 at a junction 517. The junction can be located at or near the distal end of the feed line. The helical arm 518 extends distally from the junction 517 in a series of windings. The helical arm 518 does not form electrical contact with the inner conductor 502 or the outer conductor 506 except at the junction 517.

[0092] In the antenna disclosed herein, referring to Figure 5, the helical arm 518 of the antenna has a length Lha 524. The height measured axially for each turn of the helix is ​​the pitch P 522. The number of helical turns and the pitch (P) may affect the microwave energy output, the shape of the radiation field, and the energy absorption spectrum.

[0093] The asymmetric dipole antenna 520 further includes a linear arm 519. The linear arm 519 is electrically connected to the inner conductor 502 of the feed line 510 and can constitute, for example, an extension of the inner conductor. The linear arm 519 extends distal to distal along the inner conductor 502. The helical arm 518 extends distally from the junction 517 in a series of windings around the linear arm 519, such that the linear arm 519 extends through the helical arm 518. A portion of the linear arm can be positioned distal to the distal end of the helical arm. The helical arm 518 can be coaxial with the linear arm 519, and the linear arm 519 itself may be coaxial with the shaft 514 of the device. The linear arm 519 can extend distally from the junction 517 at the proximal end 525 of the helical arm 518, passing through most of the helical arm 518. Therefore, the majority of the helical arm 518 does not enclose the outer conductor 506 or the second insulator 508. The outer conductor 506 and any second insulator 508 present may not extend beyond or far beyond the joint 517 at the proximal end 525 of the helical arm 518. The outer conductor 506 and any second insulator 508 may extend through only a small portion of the helical arm 518. Typically, the distance between the joint and the distal end of the feed line does not exceed the distance necessary to position and support the connection between the outer conductor and the proximal end of the helical arm. Typically, this is two turns or less of the helical arm, and optionally less than one turn. Typically, the distance between the joint and the distal end of the feed line is 2 mm or less, particularly 1 mm or less, and optionally 0.5 mm or less.

[0094] The linear arm 519 further includes a first portion 531 surrounded by a dielectric 535. The dielectric 535 may be an extension of a first insulator 504 positioned between the inner conductor 502 and the outer conductor 506 of the feed line 510. The linear arm 519 further includes a second portion 533 without a dielectric. The second portion 533 is distal to the first portion 531.

[0095] In one method, the second portion of the linear arm may be shorter than the first portion, as shown herein. Alternatively, the second portion may be longer than the first portion, as shown in Figure 5D.

[0096] In one approach, the helical arm 518 can be positioned proximal to the second part such that it extends around the first part 531 but not around the second part. This is particularly true when the first part 531 is longer than the second part 533, as shown in Figure 5. An alternative approach is shown in Figure 5D.

[0097] The helical arm 518 may extend around the first portion 531, but may have a larger diameter than the first portion 531, thereby creating a separation distance between them so that the helical arm is positioned radially outward of the linear arm, but radially inward of the inner wall of the shaft. The helical arm 518 may be freestanding, or it may be supported on its inner or outer surface. In Figure 5, the helical arm is physically supported on its inner surface via the support base material 521, but it may be supported in other ways, for example, by a cooling tube as shown in Figures 5C and 5D.

[0098] The linear arm 519 has a length L1a. The first part 531 of the linear arm 519 has a length L1 527. The second part 533 of the linear arm 519 has a length L2 528.

[0099] In Figure 5, the linear arm is not in contact with the base 534 of the applicator cap 530. See Figure 6 for an alternative arrangement. The antenna and feed line can be housed within the shaft 514, which has a separate distal applicator cap 530 attached to and sealed to the shaft 514. The applicator cap 530 is made of a biocompatible metal or ceramic, for example, optionally stainless steel or ceramic. The distal portion of the applicator cap 530 of the circular base 534 is conical in shape. The applicator cap 530 includes a sharp end 532 positioned at the distal end of the applicator cap 530 and configured to penetrate tissue. The applicator cap 530 includes a circular base 534 configured to be sealed with the sheath 514.

[0100] The ablation apparatus 500 may include a cooling system configured to cool the antenna and / or feed lines. Figures 5A to 5D provide further exemplary embodiments of the apparatus incorporating the cooling system. The antenna features shown in Figures 5A to 5D can be combined with any of the cooling systems shown in those figures. To avoid misunderstanding, ribbon and wire-type helical arms may be used in each cooling system, and variations in the length and configuration of the linear arms may also be used in any of the illustrated cooling systems.

[0101] Figure 5A shows one embodiment of the apparatus of the present invention having a cooling system. Other features of the apparatus in Figure 5A are illustrative. As shown in Figure 5, the device 500 shown in Figure 5A includes a coaxial power supply line 510 comprising an inner conductor 502, a first insulator 504 arranged concentrically around the inner conductor 502, an outer conductor 506 arranged concentrically around the first insulator 504, and a second insulator 508 arranged concentrically around the outer conductor 506.

[0102] The ablation apparatus 500 also includes an antenna 520 having a helical arm 518, the proximal end 525 of which forms an electrical connection with the outer conductor 506 of the feed line 510 at a junction 517 near the farther end of the feed line. The helical arm 518 extends distally from the junction 517 in a series of windings. The antenna 520 also includes a linear arm 519. The linear arm 519 is electrically connected to the inner conductor 502 of the feed line 510. The linear arm 519 extends distally from the farther end of the inner conductor 502 and includes a first portion 531 surrounded by a dielectric 535 and a second portion 533 without a dielectric. As shown in Figure 5, the helical arm 518 extends distally from the junction 517 in a series of windings around the linear arm 519 so that the linear arm 519 extends through the helical arm 518. The helical arm 518 may be coaxial with the linear arm 519. The linear arm 519 may extend distal to the joint 517 at the proximal end 525 of the helical arm 518, passing through most of the helical arm 518. Therefore, most of the helical arm 518 does not surround the outer conductor 506 or the second insulator 508. The outer conductor 506 and the second insulator 508 may not extend beyond or far beyond the joint 517 at the proximal end 525 of the helical arm 518. The outer conductor 506 and the second insulator 508 may extend through only a small portion of the helical arm 518. The helical arm 518 is positioned proximal to the second portion of the linear arm so as to extend around the first portion 531 but not around the second portion of the linear arm. The helical arm 518 may extend around the first portion 531 but have a larger diameter than the first portion 531, thereby providing a separation distance between them as will be discussed elsewhere in this specification. The helical arm 518 may be freestanding or supported on its inner or outer surface. In Figure 5A, the helical arm is physically supported on its inner surface via the support base material 521. The helical arm 518 does not form electrical contact with the inner conductor 502 or the outer conductor 506 except at the junction 517. As shown in Figure 5, the linear arm does not contact the applicator cap 530.

[0103] The antenna and feed line are housed within a shaft (simplified in this figure) 514 which terminates distally in a separate metal applicator cap 530, and the applicator cap 530 has a sharp end 532 located at its distal end, similar to the apparatus in Figure 5.

[0104] Figure 5A illustrates the overall characteristics of one type of cooling arrangement applicable to the antenna arrangements described herein. A coolant chamber 563 can be defined between the inner walls 560 of the shaft 514. The distal boundary of the coolant chamber 563 is defined by the base 534 of the cap 530, and the proximal boundary can be defined by a seal 562 or other stopper positioned at the distal end of a manifold (not shown) and at the antenna 520, through which the feed line 510 passes. The coolant inlet conduit 564 and coolant outlet conduit 567 also pass through the seal or stopper 562. The coolant inlet conduit 564 may be in the form of a coolant inlet pipe 565 located within the coolant chamber 563 and displaced radially outward from the feed line 510. The coolant inlet pipe 565 passes between the antenna 520 and the inner wall 560 of the shaft and can be sized and configured to deliver coolant from the coolant outlet of the coolant pipe 565 to a position adjacent to a portion of the antenna 520.

[0105] The coolant inlet conduit 564 can terminate close to the seal 562, or it can extend to deliver the cooling fluid to any part of the chamber. Delivery close to the antenna 520 is advantageous because it ensures that fresh cooling fluid passes over the antenna. The coolant outlet pipe 567 or return pipe can receive the coolant flowing out of the coolant chamber 563. By passing the cooling fluid through the cooling chamber in this way, at least some of the heat generated in the antenna and / or feed line can be dissipated.

[0106] Figure 5B shows a further embodiment of the ablation apparatus according to the present invention. The apparatus 500 shown in Figure 5B includes a coaxial feed line 510 having the same components as described with respect to Figure 5A, including an inner conductor 502, a first insulator 504 arranged concentrically around the inner conductor 502, and an outer conductor 506 arranged concentrically around the first insulator 504. The illustrated feed line does not have an outer insulator and is in contact with the cooling fluid during use.

[0107] The device includes an asymmetric dipole antenna 520 having a helical arm 518 formed from a metal ribbon. The proximal end of the helical arm 518 forms an electrical connection with the outer conductor 506 of the feed line 510 at a junction 517. The helical arm 518 extends distally from the junction 517 in a series of helical windings.

[0108] Antenna 520 also includes a linear arm 519. The linear arm 519 is electrically connected (either integrally or otherwise) to the inner conductor 502 of the feed line 510. The linear arm 519 extends distally from the distal end of the inner conductor 502 and includes a first portion 531 surrounded by a dielectric 535 and a second portion 533 without a dielectric. The first portion 531 of the linear arm 519 has a length L1 526. The second portion 533 of the linear arm 519 has a length L2 528. The linear arm 519 has a length of L1 plus L2. In the design of the linear arm 519 shown in Figure 5B, L1 is much larger than L2. The helical arm 518 extends distally from the junction 517 in a series of windings around the linear arm 519 so that the linear arm 519 extends through the helical arm 518. The helical arm 518 may be coaxial with the linear arm 519. The linear arm 519 may extend distal to the joint 517 at the proximal end 525 of the helical arm 518 through most of the helical arm 518. Thus, most of the helical arm 518 does not surround the outer conductor 506 or the second insulator 508. The outer conductor 506 and the second insulator 508 may not extend beyond or far beyond the joint 517 at the proximal end 525 of the helical arm 518. The outer conductor 506 and the second insulator 508 may extend through only a small portion of the helical arm 518. The helical arm may not surround the feed line and / or outer conductor with more than two turns or less than one turn of the helical arm. Alternatively, the helical arm may not enclose the feed line and / or outer conductor by more than 2 mm, or 1 mm, or 0.5 mm. The helical arm 518 is positioned proximal to the second portion 533 so as to extend only around the first portion 531. The helical arm 518 may extend around the first portion 531 but have a larger diameter than the first portion 531, thereby providing a separation distance between them. The helical arm 518 may be freestanding or may be supported on its inner or outer surface. In Figure 5C, the helical arm 518 is physically supported on its inner surface via a support base material 521. The helical arm 518 does not form electrical contact with the inner conductor 502 or the outer conductor 506 except at the junction 517.The linear arm does not come into contact with the applicator cap 530.

[0109] Figure 5B illustrates the overall characteristics of further types of cooling arrangements applicable to the antenna arrangements described herein. A cooling chamber 563 can enclose the feed line 583 and the antenna 520. A cooling chamber, as in another instance herein, can be defined between the inner wall 560 of the shaft 514, the antenna 520 and feed line 583, and the base 534 of the applicator cap 530. The device may include a cooling tube 582, which is coaxial with the feed line 510 and the antenna 520 and extends distally to a point near the end 584 of the linear arm of the antenna. The cooling tube 582 can divide the cooling chamber 563 into a first cooling conduit 580, which is coaxial with the distal portion of the feed line 583, extending across the helical arm 518 and the linear arm 519 of the antenna 520, and a second cooling conduit coaxial with the first cooling conduit, extending between the outer wall of the cooling tube 582 and the inner wall 560 of the sheath 514. The cooling tube 582 and the first and second conduits are open at their distal ends, allowing the cooling fluid to circulate through the cooling fluid mixing chamber 585 between the base 534 of the applicator cap 530 and the distal end of the cooling tube 582. The first and second cooling conduits work together to provide coolant circulation across the antenna. The first cooling conduit can be the coolant inlet and the second cooling conduit can be the coolant outlet, or vice versa. This arrangement of cooling conduits allows the antenna to be cooled all the way to the tip.

[0110] Figure 5C shows a further embodiment of the ablation apparatus according to the above design. The apparatus 500 shown in Figure 5C includes a coaxial feed line 510 having the same components as described with respect to Figure 5A, including an inner conductor 502, a first insulator 504 concentrically arranged around the inner conductor 502, and an outer conductor 506 concentrically arranged around the first insulator 504. The feed line may not have an outer insulator and may come into contact with the cooling fluid during use.

[0111] The device includes an asymmetric dipole antenna 520 having a helical arm 518 formed from a metal wire, although other forms such as ribbons are also possible. The proximal end of the helical arm 518 forms an electrical connection with the outer conductor 506 of the feed line 510 at a junction 517, as described elsewhere in this specification. The helical arm 518 extends distally from the junction 517 in a series of helical windings.

[0112] The antenna 520 also includes a linear arm 519. The linear arm 519 is electrically connected to the inner conductor 502 of the feed line 510. The linear arm can be an extension of the inner conductor of the feed line 510, as shown here, and the dielectric can be an extension of the dielectric of the feed line. The linear arm 519 extends distally from the distal end of the inner conductor 502 and includes a first portion 531 surrounded by a dielectric 535 and a second portion 533 without a dielectric. The first portion 531 of the linear arm 519 has a length L1 526. The second portion 533 of the linear arm 519 has a length L2 528. The linear arm 519 has a length of L1 plus L2. In the design of the linear arm 519 shown in Figure 5C, L1 is much larger than L2. As is generally described for other antennas, the helical arm 518 extends distally from the junction 517 in a series of turns around the linear arm 519, such that the linear arm 519 extends through the helical arm 518. The helical arm 518 may be coaxial with the linear arm 519. The linear arm 519 may extend distally from the junction 517 at the proximal end 525 of the helical arm 518, passing through most of the helical arm 518. Therefore, most of the helical arm 518 does not surround the outer conductor 506 or the second insulator 508. The outer conductor 506 and the second insulator 508 may not extend beyond or far beyond the junction 517 at the proximal end 525 of the helical arm 518. The helical arm may not surround the feed line and / or outer conductor in more than two turns or less than one turn of the helical arm. Alternatively, the helical arm may not enclose the feed line and / or outer conductor by more than 2 mm, or 1 mm, or 0.5 mm. The outer conductor 506 and the second insulator 508 may extend through only a small portion of the helical arm 518. The helical arm 518 is positioned proximal to the second portion 533 so as to extend around the first portion 531. The helical arm 518 may extend around the first portion 531 but may have a larger diameter than the first portion 531, thereby providing a separation distance between them. The helical arm 518 does not form electrical contact with the inner conductor 502 or the outer conductor 506 except at the junction 517.The linear arm does not come into contact with the applicator cap 530.

[0113] Figure 5C illustrates the overall characteristics of yet another type of cooling arrangement applicable to the antenna arrangement described herein. As described elsewhere in this specification, the cooling chamber 563 can enclose the feed line 583 and the antenna 520. The cooling chamber can be defined between the inner wall 560 of the shaft 514, the antenna 520 and the feed line 583, and the base 534 of the applicator cap 530. The device may include a cooling tube 582, which is coaxial with the feed line 510 and the linear arm 519 of the antenna and extends distally to a point near the end 584 of the linear arm. The cooling tube 582 divides the cooling chamber 563 into a first cooling conduit 580, which is coaxial with the distal portion of the feed line and the linear arm 519 of the antenna 520, and a second cooling conduit 581, which is coaxial with the first cooling conduit and extends between the outer wall of the cooling tube 582 and the inner wall 560 of the sheath 514. The cooling tube 582 can provide a support for the antenna's helical arm 518, which can be wound around the outside of the cooling tube 582, as shown here. A connection 517 can be created between the proximal end 525 of the helical arm and the furthest end of the outer conductor of the feed line 583, passing through the cooling tube 582. Thus, the antenna's helical arm 518 can be placed in the second cooling conduit 581, while the linear arm can be placed in the first cooling conduit 580.

[0114] The cooling tube 582 and the first and second conduits are open at their distal ends, allowing the cooling fluid to circulate through the cooling fluid mixing chamber 585 between the base 534 of the applicator cap 530 and the distal end of the cooling tube 582. The first and second cooling conduits work together to provide coolant circulation across the antenna. The first cooling conduit can be the coolant inlet and the second cooling conduit can be the coolant outlet, and vice versa. This arrangement of cooling conduits also allows the antenna to be cooled all the way to the tip, and the helical arm can be positioned radially outward of the linear arm without additional support structures.

[0115] Figure 5D shows yet another embodiment of the ablation apparatus according to the present invention. The design of Figure 5D is similar to the design described herein with respect to Figure 5C, with only the difference relating to the linear arm 519 being described hereafter.

[0116] Accordingly, further arrangements of the linear arm of the antenna are considered here with reference to Figure 5D. As described elsewhere in this specification, the linear arm 519 may include a first portion 531 surrounded by a dielectric and a second portion 533 without a dielectric. The first portion 531 of the linear arm 519 has a length L1 526. The second portion 533 of the linear arm 519 has a length L2 528. Thus, the entire linear arm 519 has a length of L1 plus L2. In contrast to the previously considered embodiments of the linear arm where L1 is greater than L2, in the antenna embodiment shown in Figure 5D, L2 is much greater than L1. In addition, in contrast to the design shown in Figure 5C, the second portion 533 of the linear arm 519 in Figure 5D can have a larger diameter. For example, the diameter may be larger than the diameter of the inner conductor of the feed line, or larger than the diameter of the dielectric of the first portion, or it may be the same diameter as, approximately the same diameter as, or larger than, the feed line. In one aspect of the design, the diameter of the second section 533 extends to approximately the same extent as the diameter of the outer conductor 506 of the feed line 510. In one method, the second section 533 may comprise an outer conductive sleeve 588 that surrounds and encloses the extension of the central conductor of the feed line 583 and is electrically connected to it. Instead of enclosing the conductor of the feed line 583, the conductive sleeve 588 may be integral with the inner conductor of the feed line 583. The conductive sleeve 588 may be formed from the same conductive material as the inner conductor of the feed line 583.

[0117] In this configuration, the second portion 533 of the linear arm and the outer conductor 506 can be adjacent to each other but are not electrically connected. The second portion 533 of the linear arm and the outer conductor can be separated by a distance L1 526, i.e., the length of the first portion 531 of the linear arm. Furthermore, the dielectric 535 surrounding the conductor of the first portion 531 can electrically insulate the second portion from the outer conductor 506.

[0118] If the second part is larger than the first part, the first part may be, for example, 0.1 to 2 mm in length. If the second portion 533 is longer than the first portion 531, the helical arm typically extends distally across both the first portion 531 and at least the proximal portion of the second portion 533.

[0119] The overall dimensions for the various parts of the antenna are as follows: The spiral arm can have an overall length (Lha) of 1 to 18 mm, and in particular, the spiral arm is in the range of 4 to 10 mm. In certain embodiments, the spiral arm is in the range of 4 to 7 mm.

[0120] The linear arm of the antenna in this specification may have a length of 4 mm to 14 mm, optionally 8 mm to 10 mm (L1a). In embodiments where length L1 is much larger than length L2, the second portion of the linear arm may have a length L2 of only 0.1 mm to 2 mm, or optionally 0.3 mm to 0.5 mm, and the remaining portion of length L1a of the linear arm is the length L1 of the first portion. In other embodiments of the antenna, such as the design shown in Figure 5D, length L2 is much larger than length L1, in which case the dimensions of L1 and L2 can be reversed (for example, the unexposed portion in Figure 5D has a length L1 of only 0.1 mm to 2 mm, or optionally 0.3 mm to 0.5 mm). In another embodiment of this design, the exposed portion of the linear arm in Figure 5D has a length of 9 mm to 11 mm.

[0121] Figure 6 shows a schematic diagram of the distal portion of the microwave tissue ablation apparatus, illustrating four embodiments of the metal cap and the relationship between the distal end of the antenna and the cap 602. Figure 6A shows a schematic diagram of a microwave tissue ablation apparatus 600 equipped with a metal cap 602 according to one embodiment of the present invention. The metal cap 602 is conical and has a circular base 603. A solid cylindrical projection 604 has a base 614 with a subtend from the base 603, and the cap has a shoulder 605, thereby allowing the cap 602 to be inserted into the distal end of an apparatus shaft 606, which may be metal or ceramic. The cap can be fixed to the shaft by adhesive (not shown). The microwave tissue ablation apparatus 600 further includes an asymmetric dipole antenna 607, shown here in a simple form and discussed in detail elsewhere herein. The antenna comprises a helical arm 611 and a linear arm 608. The linear arm has a proximal portion 609 surrounded by a dielectric 612 and a free distal portion 610 without a dielectric. The distal portion of the linear arm 608 has a tip 613 separated from the cap by a distance Hg. By adjusting the distance between the tip 613 and the cap, the degree to which the metal cap is electromagnetically coupled to the antenna is changed, thereby altering the shape of the energy radiation field and, consequently, the shape of the ablation zone.

[0122] Figure 6B shows a further embodiment. The microwave tissue ablation apparatus 625 includes a metal cap that is conical and has a circular base 626. The metal cap 625 includes a base 627 from which a hollow cylindrical projection 628 extends downward. The cap has a shoulder 631, which allows the cap 626 to be inserted into the distal end of the apparatus shaft 632. The cap can be fixed to the shaft by an adhesive (not shown). The microwave tissue ablation apparatus 625 further includes an asymmetric dipole antenna 629 having the features shown in Figure 6A.

[0123] As shown in Figure 6B, the gap Hg629 is located between the proximal end of the hollow cylindrical projection 628 and the distal end of the asymmetric dipole antenna 630. Figure 6C is a schematic diagram of a microwave tissue ablation apparatus 635 equipped with a metal cap 636 according to one embodiment of the present invention. The metal cap 636 is a circular-based cone having a base 637. The microwave tissue ablation apparatus 625 further includes an asymmetric dipole antenna 639 having the features described in Figure 6A.

[0124] The metal cap 636 is directly attached to the distal end 640 of the device shaft 641. The distal end of the linear arm of the antenna 639 is at a distance Hg 638 from the base of the cap 636. The gap Hg 638 is axially positioned between the proximal end of the base 637 and the distal end of the asymmetric dipole antenna 639.

[0125] Figure 6D is a schematic diagram of a microwave tissue ablation apparatus 645 equipped with a metal cap 646 according to one embodiment of the present invention. The metal cap 677 is conical and has a circular base 648. A cylindrical projection 649 extends downward from the center of the circular base 647 away from the shoulder 648, thereby allowing the cylindrical projection to be inserted into the distal end of the apparatus shaft 655. A cylindrical gap or pocket 650, which does not have a through end, is formed at the center of the base of the cylindrical projection and is configured to receive the length Hp 659 of the distal portion 652 of the linear arm of an antenna, which is spaced axially and radially from the wall 658 of the gap 650.

[0126] Other features of the antenna are shown in Figure 6A. Figures 7A and 7B illustrate some features of the apparatus. Figure 7A is a perspective view of a microwave tissue ablation apparatus 700 according to one embodiment of the present disclosure. Figure 7B is a cross-sectional view across line XY showing one embodiment of the cooling function.

[0127] The tissue ablation apparatus 700 in Figure 7A has a shaft 701 that surrounds and is typically coaxial with both the microwave antenna and at least a portion of the feed line. The shaft typically extends from the proximal manifold to the distal cap. Both the antenna and the feed line are located within the shaft. The shaft may be a single, integrated structure, or it may have a metal portion 745 and a non-metallic portion such as a ceramic portion 702, as shown in the figure. If present, the non-metallic portion may extend axially to occupy at least the same extent as the antenna. In Figure 7A, the ceramic portion extends from the distal end 706 of the collar 705 to the base 741 of the cap 740. To illustrate the internal features of the apparatus, the non-metallic portion 702 is shown to be displaced independently of the shaft 701.

[0128] As illustrated, the tissue ablation apparatus 700 may include an elastic element 705 (as described in more detail elsewhere herein, for example) and an adapter 710 that joins a metal portion 745 to a ceramic portion 702 of a shaft. In the apparatus of the present invention, an adapter may be used to absorb any difference in shaft thickness between the two portions, and the adapter may further act to reduce bending between the metal shaft 745 and the ceramic portion 702. In the apparatus of the present invention, an elastic annular spacer such as 705 between the ceramic portion and the metal portion of the shaft, as shown herein, provides elasticity to this area and therefore acts to reduce the occurrence of cracks in the shaft at this location due to strain during use. The tissue ablation apparatus 700 may include, for example, a temperature sensor 750 housed adjacent to the internal adapter 710, having an electrical connection 751 to a control unit via a manifold.

[0129] For example, as shown in Figure 1, the microwave energy generated by the microwave generator can be supplied to the antenna by a power cable that electrically connects the microwave generator to the feed line 732 of the antenna 752 within the apparatus 700. The microwave ablation apparatus also has a shaft that surrounds and is typically coaxial with both the microwave antenna and at least a portion of the feed line. The shaft typically extends from the proximal manifold to the distal cap.

[0130] A feed line may comprise an inner conductor, an outer conductor, and a dielectric disposed between them. The feed line may include a further dielectric or insulator that insulates the outer conductor from other parts of the device and acts as an outer insulator for the feed line, but this is not required in all embodiments. In some embodiments, the further dielectric may be absent from the distal end of the feed line at least to the junction. The feed line may thus be absent within the device shaft, such as between the proximal feed line connector of the distal manifold and the junction of the antenna. The feed line is typically a coaxial cable having a central conductor surrounded by a first dielectric or insulator, the first dielectric being surrounded by a second dielectric which may be covered by the further dielectric or insulator as described above. The inner conductor is typically a power conductor.

[0131] Referring to Figure 7A, the tissue ablation apparatus 700 has an antenna 752 including a helical arm 712 and a linear arm 720. The proximal end 735 of the helical arm 712 forms an electrical connection with the outer conductor 730 of the feed line 732 at a junction 736 and extends distally from the junction 736. The helical arm 712 does not form electrical contact with the inner conductor 727 or the outer conductor 730 except at the junction 736.

[0132] The connection point is, conveniently, near or at the furthest end of the feed line 732. The feed line 732 may extend beyond the connection point 736 to provide suitable mechanical support to the electrical connection, as described elsewhere in this specification. It shall not optionally extend beyond the connection point 736 by more than 2 mm, and in particular by more than 1 mm. Alternatively, it shall not extend beyond two turns of the helical arm, and optionally less than one turn.

[0133] The linear arm 720 is electrically connected to the inner conductor 727 of the power supply line 732 and extends distally from the distal end of the power supply line 732. The spiral arm 712 is coaxially positioned around the linear arm 720.

[0134] The device has a cooling system configured to pass a coolant fluid across the antenna. The cooling system is configured to pass a coolant fluid across at least a portion of the feed line and across the antenna, as will be described in more detail below.

[0135] As shown in Figure 7A, the helical arm 712 can be spirally wound around the tube 726, which can act as a support base or, as in this case, as a cooling tube, which can extend from a manifold (not shown) through the metal portion 745 of the shaft to the tip of the antenna 728. The electrical connection between the antenna's helical arm 712 and the outer conductor 730 of the feed line 732 passes through the tube 726 at the junction 736. The helical arm 712 has a length (Lha). In some examples, the total length (Lha) of the helical arm can be in the range of 1 to 18 mm, and optionally, the helical arm is in the range of 4 to 10 mm. In optional embodiments, the helical arm is in the range of 4 to 7 mm.

[0136] The cooling tube 726 is positioned around the linear arm 720 of the antenna. It defines a first cooling conduit 748 between the inner wall 754 of the tube 726 and the linear arm 720, and a second cooling conduit 760 between the outer wall 755 of the tube 726 and the inner wall of the shaft 753. The coolant can be pumped through the space between the tube 726 and the linear arm 720 to the mixing chamber 729 between the tube 726 and the cap 740, through the space between the outside of the tube 726 and the ceramic portion 702 of the shaft, through the space 711 between the inside of the shaft and the adapter 710, down the metal portion 745 of the shaft and back to the manifold.

[0137] The linear arm 720 is an extension of the inner conductor 727 of the power supply line 732 and is surrounded by a dielectric layer 725, except for a second portion 723 which does not contain a dielectric. The linear arm of the antenna described herein is electrically connected to the inner conductor of the feed line 732 and, in particular, is a conductor extending distally from the inner conductor on a helical arm and / or coaxial axis with the feed line 732. This conductor is optionally in the form of a straight wire. In certain embodiments, the linear arm includes a first, proximal, insulated portion and a second, distal, uninsulated portion. Typically, the first portion is surrounded by a dielectric, and the second portion distal to the first portion lacks a dielectric. The second portion extends to the tip of the arm. The dielectric surrounding the first portion of the linear arm may extend from the distal end of the feed line 732. In its simplest form, the linear arm of the antenna may be an extension of the inner conductor of the feed line, and the dielectric may be an extension of a dielectric positioned between the central and outer conductors of the coaxial feed line.

[0138] Optionally, the linear and helical arms of the antenna are coaxial with the shaft of the ablation device, and therefore the linear arm is coaxial with the helical arm and extends distally therefrom. As shown in the figure, the linear arm 720 of the asymmetric dipole antenna in Figure 7A has a length L1a. The linear arm includes a first portion L1 721 coated with an insulator, which may be an extension of the first dielectric layer of the feed line 732 and may be located between the inner conductor 727 and the outer conductor 730, but is not visible in this figure.

[0139] The linear arm 720 further includes a second portion 723 having a length L2 722 and not coated with an insulator. In one embodiment, the second portion L2 722 is exposed to the circulating coolant.

[0140] As shown in Figure 7A, the linear arm 720 extends through the helical arm 712. The helical arm 712 may be coaxial with the linear arm 720. The linear arm 720 can extend distal to the joint 736 at the proximal end 735 of the helical arm 712, passing through most of the helical arm 712. Therefore, most of the helical arm 712 does not enclose the outer conductor 730 or the insulator surrounding the outer conductor 730. It may optionally not extend beyond 2 mm, and especially beyond 1 mm, from the joint 736. Alternatively, it may not extend beyond two turns of the helical arm, and optionally less than one turn.

[0141] The outer conductor 730 and the insulator surrounding the outer conductor 730 may not extend beyond or far beyond the joint 736 at the proximal end 735 of the helical arm 712. The outer conductor 730 and the insulator surrounding the outer conductor 730 may extend through only a small portion of the helical arm 712.

[0142] In one embodiment, the helical arm 712 is positioned proximal to the second portion of the linear arm L2 723 so as to extend only around the first portion of the linear arm L1 721. In a second method, the helical arm can extend over the entire first portion, and optionally over at least the proximal portion of the second portion of the linear arm, as considered based on Figure 5D.

[0143] In one embodiment, L2, i.e., the portion of the linear arm without dielectric material, is partially or completely inserted into the metal cap but does not come into contact with the cap. This can be achieved by creating an open pocket in the base of the cap into which this portion or part of the antenna is inserted. The extent to which the exposed distal tip is inserted affects the shape of the distal portion of the energy field, and therefore the shape of the ablation zone.

[0144] If the distance between the tip and the cap is greater than 3 mm, they are not considered to be sufficiently bonded to be useful for forming ablation, especially at 2.45 GHz.

[0145] Generally, the linear arm 720 of the antenna here can have a length (L1a) of only 4mm to 14mm, and in some cases only 8mm to 10mm. In one embodiment of the antenna design, such as the design shown in Figure 7A, length L1 is much larger than length L2. In this design, the exposed portion 723 of the linear arm has a length L2 of only 0.1mm to 2mm, and in some cases only 0.3mm to 0.5mm, and the remainder of length L1a of the linear arm 720 is length L1 of the first portion 721. In another embodiment of the antenna design, such as the design shown in Figure 5D, length L2 is much larger than length L1. In this embodiment, the dimensions of L1 and L2 can be reversed (for example, the unexposed portion in Figure 5D has a length L1 of only 0.1mm to 2mm, and in some cases only 0.3mm to 0.5mm). In another embodiment of the design, the exposed portion of the linear arm in the method of Figure 5D has a length of 9mm to 11mm.

[0146] The spiral arm can have a length of 1 to 18 mm and 1 to 14 turns, alternatively including 4 to 10 mm and 4 to 8 turns or 4 to 6 mm and 3 to 5 turns.

[0147] Therefore, in an optional embodiment, the helical arm 712 of the antenna may be in the form of a ribbon, have a length of 1 to 18 mm (Lha), and include 1 to 14 turns, while the linear arm 720 of the antenna may be 4 to 14 mm in length and have a second dielectric-free distal portion 723 of 0.1 to 3 mm in length. The dielectric-free portion may be separated from the base of the cap by only 0.2 to 3 mm.

[0148] In a more specific embodiment of this design, the helical arm 712 of the antenna is in the form of a ribbon having a length of 4 to 10 mm (Lha) and includes 4 to 8 turns, and the linear arm 720 of the antenna is 7 to 10 m long and has a second dielectric-free distal portion 723 of 0.3 to 0.5 mm in length. The dielectric-free portion can be separated from the base of the cap by only 1 to 2 mm.

[0149] In a more specific embodiment of this design, the helical arm 712 of the antenna is in the form of a ribbon having a length of 4-6 mm (Lha) and includes 3-5 turns. The linear arm 720 has a second dielectric-free distal portion 723 that is 0.3-0.5 mm long and is 7-10 mm long. The dielectric-free portion can be separated from the base of the cap by only 1-2 mm, optionally 1.5 mm, or about 1.5 mm.

[0150] If the shaft has a non-metallic portion (e.g., a ceramic portion 702), the non-metallic portion may extend axially to cover the antenna and thus occupy at least the same area as the radiating portion of the antenna. In one embodiment, the non-metallic portion extends at least from the nearest point of the helical arm to the distal end of the shaft (e.g., the mounting point at the tip of the device). The non-metallic portion extends coaxially and circumferentially such that the shaft can be non-metallic between the proximal and distal ranges of the non-metallic portion.

[0151] The cap can be configured to seal the distal end of the device to prevent coolant leakage or tissue fluid penetration. The cap can be manufactured as a separate part and configured to be attached to the shaft. The cap can be configured to facilitate insertion into tissue and to penetrate the patient's skin, and therefore can be located at the distal point or configured as a trocar. The cap 740 shown in Figure 7 includes a trocar tip. The trocar tip of the cap 740 can be made of stainless steel and / or ceramic.

[0152] In some examples, the cap can be made from any suitable biocompatible material, such as a biocompatible polymer, composite material, ceramic, or metal such as stainless steel. If the cap is metal, the cap and the distal end of the antenna (i.e., the distal end of the linear arm of the antenna) can be configured to be electromagnetically coupled. This can be achieved by adjusting the distance between the distal tip of the antenna and the cap so that they are electromagnetically coupled at the frequency and power in which the antenna is intended to operate. This effect can be used to adjust the shape of the distal portion of the energy field generated by the antenna, and therefore the shape of the ablation zone. However, it is not essential that the cap and the antenna be coupled in this way; i.e., the antenna may be electromagnetically separated from the cap. In one embodiment, the tip and the cap do not contact. In practice, the gap between the tip and the cap is 0.2 mm or more, more specifically 0.2 mm to 3 mm, and most specifically 1 to 2 mm. Most specifically, it is 1.5 mm or about 1.5 mm.

[0153] The shape of the energy field, and therefore the ablation volume, can also be influenced by the provision of a metal sheath concentric with the feed line. The sheath can be cylindrical and extend over at least a portion of the feed line on the proximal side of the antenna. The sheath may extend over at least a portion of the antenna, but optionally terminate at a point proximal to the farthest point of the antenna's helical arm and not extend across the antenna. Optionally, the gap between the sheath and the farthest portion of the helical arm is at least 0.1 mm. This gap may be, for example, 0.1–2 mm, or 0.1–1 mm, or about 0.5 mm. The sheath may not be located on the outer surface of the shaft, but is radially displaced from the feed line and coaxial with the feed line. The sheath can be located between the feed line and the inner wall of the shaft. In one configuration, the metal sheath may be an adapter sheath, as described elsewhere in this specification.

[0154] Optionally, the coolant chamber is defined between the inner walls of the device shaft. The chamber's distal boundary can be defined by a cap, and its proximal boundary can be defined by one or more proximal seals or stoppers that close the coolant chamber proximal. They are optionally formed on the manifold or at a location between the manifold and the proximal portion of the antenna's helical arm. The cooling system comprises at least one coolant inlet conduit configured to deliver coolant to the coolant chamber, and at least one coolant outlet configured to remove coolant from the chamber. The coolant inlet and outlet conduits can pass through the proximal seals / stoppers. In one method, the coolant inlet conduit is a coolant inlet tube configured to deliver coolant to a location adjacent to and radially outward of the antenna and / or feed line. In this case, the coolant inlet tube can be located within the coolant chamber between the antenna and the inner wall of the shaft. Optionally, it is located radially outward of the feed line.

[0155] The cooling system may further include a coolant mixing chamber that is in fluid communication with both the coolant inlet conduit and the coolant outlet conduit, so that the coolant inlet and coolant outlet are in fluid communication through the coolant mixing chamber. The coolant mixing chamber may be configured to allow the coolant to pass over at least a portion of the antenna, particularly at least a portion of the linear arm of the antenna. In particular, the coolant mixing chamber may be configured to allow the coolant to pass over at least a portion of the distal portion of the linear arm of the antenna and the cap.

[0156] In an alternative embodiment, the cooling system comprises a coolant chamber defined between the inner walls of the apparatus shaft. The chamber may have a distal boundary defined by a cap, and a proximal boundary defined by a seal between the manifold and the shaft, or at any point distal to the manifold and between the antenna and the manifold as described above. The coolant chamber may enclose the antenna and at least the distal portion of the feed line.

[0157] In one embodiment (see, for example, Figure 7A), the cooling system further comprises a cooling tube arranged around a feed line, the cooling tube extending distally around the feed line and optionally coaxially with the feed line. The cooling tube optionally divides the cooling chamber into a first cooling conduit 748 and a second cooling conduit 760, the first cooling conduit positioned between the feed line and the inner wall of the cooling tube, and the second cooling conduit positioned between the outer wall of the cooling tube and the inner wall of the device shaft. The cooling tube optionally extends over the distal portion of the feed line and distally around at least a portion of the antenna, and optionally extends to at least the tip of the linear arm of the antenna. Various materials are suitable for the cooling tube, but the cooling tube may be nonmetallic. Conveniently, the cooling tubes can be made from thermosetting polymers such as polyimide, thermoplastic polymer resins such as polyethylene terephthalate (PET), fluoropolymers such as polytetrafluoroethylene (PTFE), or PAEK such as PEEK.

[0158] As described elsewhere in this specification, in the example of Figure 7A, the helical arm can be spirally wound around the tube 726. In one embodiment, the tube may be a cooling tube 726 defining a first cooling conduit 748 between the inner wall 754 of the tube 726 and the feed line 732, and a second cooling conduit 760 between the outer wall 755 of the tube 726 and the inner wall of the shaft 753. Coolant can be pumped through the space between the tube 726 and the feed line 732, and through the mixing chamber 729 between the tube 726 and the cap 740, and the coolant returns to the manifold down the metal portion 745 of the shaft through the space 711 between the inside of the shaft and the adapter 710, in the space between the outside of the tube 726 and the ceramic portion of the shaft.

[0159] The spiral arm of the antenna can be located within a first or second cooling conduit. For example, in one embodiment, the device may include an antenna support coaxially arranged around a linear arm (as shown in Figure 5B). The spiral arm of the antenna can be supported by the antenna support, for example, on the inner surface or outer surface of the support. The antenna support can be located radially outward of the linear arm, but radially inward of the cooling conduit. Thus, the spiral arm is located within the first cooling conduit. In this case, the cooling conduit may optionally extend to cover a portion of the spiral arm and a portion of the linear arm, but most specifically, the cooling conduit extends at least to the distal end of the antenna, such that the first cooling conduit extends at least to the tip of the antenna.

[0160] Otherwise, the cooling tube extends to the distal portion of the feed line and at least the proximal portion of the linear arm, but more specifically, the cooling tube extends to at least the distal end of the linear arm such that the first cooling conduit extends at least to the tip of the antenna. The helical arm can then be wound around the cooling tube so as to be positioned within the second cooling conduit.

[0161] The cooling system may further include a coolant mixing chamber that is in fluid communication with both the first and second cooling conduits, so that the first and second cooling conduits are in fluid communication through the cooling mixing chamber. The coolant mixing chamber may be configured so that the coolant can come into contact with a portion of the cap.

[0162] Either the first or second cooling conduit can act as a coolant input conduit or a coolant output conduit. The first and second cooling conduits open at their distal ends to allow the coolant to circulate through a coolant mixing chamber between the distal end of the cooling conduit and the base of the applicator cap.

[0163] The cooling pipes optionally extend proximal to the manifold. The first and second cooling pipes are in fluid communication with the manifold's coolant input and output connectors to supply and discharge coolant during use.

[0164] In certain methods, the helical arm of the antenna, optionally in the form of a ribbon, is wound around a cooling tube. In this case, the helical arm is electrically in contact with the outer conductor of the feed line at the junction and extends distally in a series of windings around the cooling tube, as described above. In this case, the cooling tube optionally extends distally at least to the junction of the antenna and the feed line, optionally extends further to cover at least a portion of the linear arm, but most specifically, the cooling tube extends to the tip of the linear arm such that the first cooling conduit extends at least to the tip of the antenna. Optionally, the electrical contact between the distal end of the helical arm and the outer conductor of the feed line passes through the cooling tube.

[0165] In this method, it is optional that the outer insulator does not extend over the distal portion of the feed line. Optionally, the outer insulator does not extend over the portion of the feed line from the immediate proximal side of the antenna's spiral arm to the junction. The outer insulator does not need to be present over the entire feed line within the shaft of the ablation device.

[0166] In embodiments of the cooling system comprising a cooling tube as described above, the helical arm may be either a wire or a ribbon, but most specifically a ribbon. The helical arm may be in the form of a cylindrical conductor having a helical gap extending from its proximal end to its distal end, so as to provide a helical conductor around the feed line having a planar conductor surface optionally arranged coaxially with the feed line.

[0167] The cooling systems described herein pass a coolant (e.g., water) through the feed line and at least a portion of the antenna, or optionally, through the entire antenna. For normal operation, it is not necessary to insulate the antenna from the coolant. In some embodiments described herein, portions of the feed line lack an outer insulator surrounding it. The feed line may not have insulation along its entire length between the manifold and the connection point, or within the device shaft. The helical arm of the antenna may lack any insulation, especially when wound around a cooling tube.

[0168] The ablation apparatus described herein may further include one or more temperature sensors, such as thermocouples, for measuring temperature at locations along the shaft. Typically, the thermocouple may be placed in a cooling system and configured to measure the temperature of the coolant or other parts of the apparatus, such as power lines or the apparatus shaft, during the operation of the apparatus. The tissue ablation apparatus 700 in Figure 7A may include a temperature sensor 750 housed adjacent to the internal adapter 710 and having an electrical connection 751 to a control unit via a manifold.

[0169] As described elsewhere in this specification, ablation devices such as those described herein typically include a proximal manifold, as briefly described above. The manifold typically includes connectors for connecting power lines to an energy supply line and connectors for connecting electrical devices in the device shaft to a control system. These connectors may be permanent or removable. The manifold may also include a coolant manifold having an input connector for connecting a coolant input to a coolant supply and an output connector for connecting a coolant output to a discharge or recirculation system. The manifold may also form part of a handle configured to provide a firmer grip for the surgeon to handle the tissue ablation device.

[0170] The apparatus 700 includes a trocar tip 740. In one embodiment, the trocar tip 740 may consist of an applicator cap 130 shown in Figure 5, a metal cap shown in Figures 6A to 6D, and a trocar tip 330 shown in Figure 3A. The trocar tip 740 may be made from stainless steel and / or ceramic.

[0171] Figure 8A is a photograph showing the ablation effect of a tissue ablation apparatus according to one embodiment of the present disclosure. The tissue was heated at 25-30W for 5 minutes. As shown in Figure 8A, the ablation volume is approximately spherical.

[0172] Figure 8B is a photograph showing the ablation effect of a tissue ablation apparatus according to one embodiment of the present disclosure. Physiological saline was heated at 90W for 4 minutes. As shown in Figure 8B, the ablation volume is approximately spherical.

[0173] (Note) As a preferred embodiment, the technical concept that can be understood from the above embodiment is described below.

[0174] [Item 1] A microwave ablation probe, The microwave ablation probe comprises a feed line connected to an antenna, the feed line having an inner conductor, an outer conductor, and a dielectric disposed between the inner conductor and the outer conductor, The microwave ablation probe is equipped with a cap made of a metal material. The microwave ablation probe comprises a shaft surrounding the antenna and the feed line, the shaft being connected to the cap, the shaft comprising a non-metallic portion and a metallic portion, the non-metallic portion extending axially to occupy the same area as at least a portion of the antenna that radiates microwaves, The antenna includes a helical arm, which is electrically connected to the outer conductor of the feed line at a joint, and the helical arm extends distally from the joint. The antenna includes a linear arm, which is electrically connected to the inner conductor of the feed line, and which extends distally from the distal end of the feed line; the spiral arm is coaxially arranged around the linear arm, and the linear arm further includes a first portion surrounded by a dielectric and a second portion without a dielectric, which is distal to the first portion. A microwave ablation probe that changes the shape of the energy radiation field of the microwave ablation probe by adjusting the distance between the antenna and the cap.

[0175] [Item 2] The microwave ablation probe described in item 1, wherein the non-metallic portion is made of a ceramic material.

[0176] [Item 3] The microwave ablation probe according to item 1 or 2, wherein the helical arm of the antenna is a ribbon.

[0177] [Item 4] A microwave ablation probe according to any one of items 1 to 3, wherein the linear arm of the antenna is electromagnetically coupled to the cap, but is not connected to the cap.

[0178] [Item 5] A microwave ablation probe according to any one of items 1 to 4, further comprising a cooling system configured to pass a coolant fluid across the antenna.

[0179] [Item 6] The microwave ablation probe according to item 5, wherein the cooling system comprises a cooling tube and a coolant chamber defined between the inner wall of the shaft.

[0180] [Item 7] The microwave ablation probe according to item 6, wherein the cooling tube divides the coolant chamber into a first cooling conduit and a second cooling conduit, the first cooling conduit is positioned between the linear arm and the inner wall of the cooling tube, and the second cooling conduit is positioned between the outer wall and the inner wall of the cooling tube.

[0181] [Item 8] The microwave ablation probe according to any one of items 1 to 7, further comprising an elastic element disposed between the non-metallic portion and the metallic portion and configured to provide elasticity to the joint between the non-metallic portion and the metallic portion.

[0182] [Item 9] A microwave ablation system comprising one or more microwave ablation probes, Each microwave ablation probe is equipped with a feed line connected to an antenna, the feed line having an inner conductor, a dielectric coaxially arranged around the inner conductor, and an outer conductor coaxially arranged around the dielectric. Each microwave ablation probe is equipped with a cap made of metal material. Each microwave ablation probe comprises a shaft surrounding the antenna and the feed line, the shaft being connected to the cap, the shaft comprising a non-metallic portion and a metallic portion, the non-metallic portion extending axially to occupy the same area as at least a portion of the antenna that radiates microwaves, The antenna includes a helical arm, which is electrically connected to the outer conductor of the feed line at a joint, and the helical arm extends distally from the joint. The antenna includes a linear arm, which is electrically connected to the inner conductor of the feed line, and the linear arm extends distally from the distal end of the feed line, and the linear arm is The first part is surrounded by a dielectric, A second portion without a dielectric, which is the distal side of the first portion, It further includes, By adjusting the distance between the antenna and the cap, the shape of the energy radiation field of the microwave ablation probe is changed. Each microwave ablation probe is equipped with a power module, which is configured to supply microwave energy to the antenna. A microwave ablation system comprising one or more power cables, each of which is configured to connect the power modules to each antenna and to deliver microwave energy provided by the power modules to the antennas for tissue ablation.

[0183] [Item 10] The above or each microwave ablation probe is equipped with a cooling system for cooling at least a portion of the antenna or the feed line, or at least a portion of the antenna and the feed line. The microwave ablation system according to item 9, further comprising a cooling system configured to deliver a coolant fluid to the cooling system of the microwave ablation probe in order to cool at least a portion of the antenna and the feed line.

Claims

[Claim 1] A microwave ablation probe, The microwave ablation probe comprises a feed line, the feed line having an inner conductor, an outer conductor, and a dielectric disposed between the inner conductor and the outer conductor. The microwave ablation probe is equipped with an antenna, The antenna includes a helical arm, which is electrically connected to the outer conductor of the feed line at a joint, and the helical arm extends distally from the joint. A microwave ablation probe comprising a linear arm, which is electrically connected to the inner conductor of the feed line, the linear arm extending distally from the distal end of the feed line, and a helical arm coaxially arranged around the linear arm.

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