Periodic operation of ablation devices

Abstract

Various aspects of the present invention relate to devices, systems and methods, including a tissue ablation system including a plurality of ablation devices, each ablation device providing ablation energy, at least one ablation generator providing ablation power to at least one of the plurality of ablation devices, and a controller selectively causing each of the plurality of ablation devices to receive ablation power and cycling activation of a plurality of ablation states.

Description

[Technical Field]

[0001] The present invention relates to a tissue ablation device and method of use. [Background technology]

[0002] In the treatment of diseases such as cancer, it is known that certain types of tissue denature at high temperatures. This type of treatment is commonly known as hyperthermia, and typically uses electromagnetic radiation to heat cancerous tissue to temperatures above 60°C while maintaining healthy tissue at a lower temperature to avoid irreversible cell destruction. Microwave ablation is one such treatment that uses electromagnetic radiation to heat tissue.

[0003] Microwave tissue ablation is a less invasive procedure than surgical resection and is preferred in many situations where tumor removal by surgery is difficult, such as when the tumor is relatively small, located near a relatively small organ, or located near a large blood vessel. This approach is used in organs where surgical resection of tumors may be difficult, such as the prostate, heart, and liver.

[0004] To effectively plan and optimize the procedure, it is desirable that the ablation device produce an ablation volume of predictable size and shape. For this reason, a predictable ablation volume of regular shape is preferred, and it is particularly preferable to produce a spherical or nearly spherical ablation volume. Ablation devices that produce an ablation volume of predictable size and shape facilitate the surgical procedure and reduce undesirable medical complications.

[0005] In some cases, tissue can be ablated using multiple ablation devices. However, operating multiple ablation devices may require a large amount of power, which can increase costs and / or reduce the portability of the system. Additionally, the ablation energies emitted from multiple devices may have unfavorable interactions with each other. For example, microwave radiation emitted from one microwave ablation device may interfere with microwave radiation emitted from other microwave ablation devices, resulting in undesirable interference and potentially incomplete ablation. [Overview of the Initiative] [Means for solving the problem]

[0006] In Example 1, the tissue ablation system comprises a plurality of ablation devices for placement at or near a target site of a patient's internal structure, each ablation device configured to supply ablation energy to an ablation region adjacent to such ablation device when the ablation device is supplied with ablation power; a plurality of ablation generators, each ablation generator configured to supply ablation power to one of the plurality of ablation devices; and a controller communicating with the ablation generators, configured to selectively allow each of the plurality of ablation devices to receive ablation power and to periodically activate one of each of the plurality of ablation states, each ablation state corresponding to a unique subset of the plurality of ablation devices, and the activation of an ablation state includes receiving ablation power in the ablation device within the corresponding subset of the plurality of ablation devices.

[0007] In Example 2, in the tissue ablation system of Example 1, activation of the ablation state includes the absence of ablation devices that are not in the corresponding subset of multiple ablation devices from receiving ablation power.

[0008] In Example 3, in the tissue ablation system of Example 1 or 2, activation of the ablation state includes an ablation device that is not in the corresponding subset of the multiple ablation devices receiving less power than the ablation device that receives ablation power.

[0009] In Example 4, in the tissue ablation system of Example 1 or 2, activation of the ablation state includes the absence of power from ablation devices that are not in the corresponding subset of the multiple ablation devices.

[0010] In Example 5, in any of the tissue ablation systems of Examples 1 to 4, the controller sequentially activates each of the multiple ablation states. In Example 6, in any of the tissue ablation systems of Examples 1 to 5, the controller repeatedly and periodically activates each of the multiple ablation states.

[0011] In Example 7, in any of the tissue ablation systems of Examples 1 to 6, the periodic execution of the activation of each of the multiple ablation states is configured such that not all of the multiple ablation devices receive ablation power simultaneously.

[0012] In Example 8, in any of the tissue ablation systems of Examples 1 to 7, the periodic execution of the activation of each of the multiple ablation states includes activating each ablation state for the same length of time.

[0013] In Example 9, each ablation state is activated for 100 to 300 ms in any of the tissue ablation systems of Examples 1 to 8. In Example 10, in any of the tissue ablation systems of Examples 1 to 9, the periodic execution of activation of each of the multiple ablation states is achieved by each ablation device receiving ablation power according to its respective duty cycle.

[0014] In Example 11, the duty cycles of the multiple instruments are equal in the tissue ablation system of Example 10. In Example 12, the duty cycles of each of the multiple instruments in the tissue ablation system of Example 10 are staggered in time.

[0015] In Example 13, in the tissue ablation system of Example 10, the duty cycles of each device are staggered in time so that not all of the multiple ablation devices receive ablation power simultaneously.

[0016] In Example 14, in the tissue ablation system of Example 10, the duty cycles are time-staggered so that every other ablation device does not receive ablation power while the controller periodically activates each of the multiple ablation states.

[0017] In Example 15, in any of the tissue ablation systems of Examples 1 to 14, each of the multiple ablation devices includes a microwave ablation needle. In Example 16, the tissue ablation system comprises a plurality of ablation devices for placement at or near a target site of a patient's internal structure, each ablation device configured to deliver ablation energy to an ablation region adjacent to the ablation device when receiving ablation power; a plurality of ablation generators, each ablation generator configured to provide ablation power to one of the plurality of ablation devices; and a controller communicating with the ablation generators, configured to selectively allow each of the plurality of ablation devices to receive ablation power and to periodically activate each of the plurality of ablation states, each ablation state corresponding to a unique subset of the plurality of ablation devices, and activation of one ablation state includes receiving ablation power at an ablation device within the corresponding subset of the plurality of ablation devices, and activation of an ablation state includes not receiving ablation power at an ablation device not within the corresponding subset of the plurality of ablation devices.

[0018] In Example 17, in the tissue ablation system of Example 16, activation of the ablation state includes an ablation device that is not in the corresponding subset of the multiple ablation devices receiving less power than the ablation device that receives ablation power.

[0019] In Example 18, in the tissue ablation system of Example 16, activation of the ablation state includes the absence of power from ablation devices that are not in the corresponding subset of the multiple ablation devices.

[0020] In Example 19, in the tissue ablation system of Example 16, the controller repeatedly and periodically activates each of the multiple ablation states. In Example 20, in the tissue ablation system of Example 16, the controller continuously activates each of the plurality of ablation states.

[0021] In Example 21, in the tissue ablation system of Example 16, the periodic execution of the activation of each of the plurality of ablation states is achieved by applying a duty cycle to receiving ablation power at each of the plurality of ablation instruments.

[0022] In Example 22, in the tissue ablation system of Example 20, the duty cycles of the plurality of electrodes are equal. In Example 23, in the tissue ablation system of Example 20, the duty cycle of each of the plurality of electrodes is shifted in time.

[0023] In Example 24, in the tissue ablation system of Example 16, each of the plurality of ablation instruments includes a microwave ablation needle. Example 25 provides a tissue ablation method comprising: providing a plurality of ablation devices for placement at or near a target site of a patient's internal structure, each ablation device configured to deliver ablation energy to an ablation region adjacent to the device when receiving ablation power; positioning two or more ablation devices in close proximity to each other such that, when the two or more ablation devices receive ablation power, one ablation region of each of the two or more ablation devices at least partially overlaps with another ablation region of the two or more ablation devices; and periodically activating each of a plurality of ablation states by selectively allowing and not allowing a particular ablation device to receive ablation power, each ablation state corresponding to a unique subset of the plurality of ablation devices, and when one of the plurality of ablation states is activated, the corresponding subset of the plurality of ablation devices receives ablation power.

[0024] In Example 26, in the method of Example 25, the activation of the ablation state includes an ablation device that is not in the corresponding subset of the multiple ablation devices receiving less power than the ablation device that receives ablation power.

[0025] In Example 27, in the method of Example 25, the activation of the ablation state includes the absence of power from ablation devices that are not in the corresponding subset of multiple ablation devices.

[0026] In Example 28, the step of periodically activating each of the multiple ablation states in the method of Example 25 includes a step of repeatedly and periodically activating each of the multiple ablation states.

[0027] In Example 29, the method of Example 25 includes the step of periodically activating each of the multiple ablation states, which involves repeatedly switching each ablation device between an on state and an off state, wherein the ablation power is received in the on state and not received by other devices in the off state.

[0028] Example 30 further includes the step of measuring the ablation power reflected on each ablation device when it is in the off state, wherein the reflected ablation power represents the ablation power from the on state of the ablation device that is not absorbed within the target site.

[0029] In Example 31, in the method of Example 25, one or more of the ablation states correspond to their respective unique subsets, which include less than all of the ablation devices among the ablation devices.

[0030] In Example 32, in the method of Example 25, the periodic execution of activation of each of the multiple ablation states is achieved by applying a duty cycle to each of the multiple ablation devices to receive ablation power.

[0031] Example 33 provides a tissue ablation method comprising: providing a plurality of ablation devices for placement at or near a target site of a patient's internal structure, each ablation device configured to deliver ablation energy in an ablation region adjacent to such ablation device when receiving ablation power; positioning two or more ablation devices in close proximity to each other such that, when the two or more ablation devices are receiving ablation power, each ablation region of the two or more ablation devices at least partially overlaps with the other ablation region of the two or more ablation devices; and supplying ablation power to the plurality of ablation devices according to their respective duty cycles, wherein the duty cycles are equally time-staggered so that every other ablation device does not receive ablation power.

[0032] In Example 34, in the method of Example 33, the two or more ablation devices are replaced with three or more ablation devices, and the three or more ablation devices are positioned at equal distances from each other.

[0033] In Example 35, in the method of Example 34, the duty cycle for each of the multiple ablation devices is configured in time such that at any given time, two of the three or more ablation devices are in the ON state and one of the three or more ablation devices is in the OFF state.

[0034] While several embodiments are disclosed, those skilled in the art will be able to understand from the following detailed description, which illustrates and describes exemplary embodiments of the disclosed subject matter, that yet more embodiments of the subject matter disclosed herein can also be understood. Therefore, the drawings and detailed description should be considered exemplary rather than restrictive.

[0035] The advantages of the present invention may become apparent to those skilled in the art from the following detailed description and by referring to the accompanying drawings. [Brief explanation of the drawing]

[0036] [Figure 1A] A block diagram including elements of a system for performing an ablation process according to one embodiment of the present invention. [Figure 1B] A block diagram illustrating the operation of an ablation device interface for connecting to an ablation device for performing an ablation process, according to one embodiment of the present invention. [Figure 2] A simplified diagram showing the cooling system according to the present invention. [Figure 3] A perspective view showing a microwave tissue ablation apparatus equipped with a handle, according to one embodiment of the present invention. [Figure 4A] A perspective view showing a microwave tissue ablation system 400 according to one embodiment of the present invention. [Figure 4B] A cross-sectional view along line XY showing one embodiment of the cooling mechanism. [Figure 5] A side view showing a microwave tissue ablation device according to one embodiment of the present invention. [Figure 6A] A plan view showing the configuration of multiple microwave ablation needles. [Figure 6B] A front view showing multiple ablation devices arranged at different depths. [Figure 7] A diagram showing the SAR field around two ablation devices. [Figure 8] A diagram illustrating exemplary embodiments of three ablation devices and their respective ablation regions. [Figure 9A] A diagram illustrating three exemplary embodiments of ablation devices in various on / off states. [Figure 9B] A diagram illustrating three exemplary embodiments of ablation devices in various on / off states. [Figure 9C]A diagram illustrating three exemplary embodiments of ablation devices in various on / off states. [Figure 9D] Figure 9A-C shows the overlapping fields. [Figure 10] A diagram illustrating an exemplary sequence of a duty-cycling ablation device. [Figure 11] A diagram showing exemplary data of the power signal received by the first ablation device. [Figure 12] A diagram showing exemplary data of the power signal received by the second ablation device. [Modes for carrying out the invention]

[0037] The size and dimensions of the ablation area created by a microwave tissue ablation device depend, among several factors, on the type of microwave antenna. A clinician may select a microwave antenna capable of generating an ablation area larger than the size and dimensions of the target tissue, and insert this 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 ablation volume generated by the device, multiple devices may be used to combine ablation volumes to cover the tissue to be ablated. The embodiments of microwave tissue ablation devices described herein are used to create ablation areas with a predictable shape and minimal tailing, which aids in ablation planning and prevents damage to tissue outside the treatment volume.

[0038] In some embodiments, the ablation instruments disclosed herein are microwave ablation instruments configured to perform ablation by emitting microwave energy that causes tissue necrosis through heating. Generally, the instrument is a microwave ablation needle having a microwave antenna, such as that described herein.

[0039] In another embodiment, the present invention provides a system for microwave ablation of tissue, comprising one or more microwave ablation instruments, such as probes or needles, as described herein. The microwave ablation instrument includes 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 configured to connect the microwave generator to the microwave antenna of the ablation instrument and to deliver the microwave energy supplied by the microwave generator to the antenna for tissue ablation.

[0040] Ablation devices, such as those described herein, can be configured to operate for a maximum of 20 minutes or more with a power of up to 150 watts. During use, the device becomes heated by the resistive heating of the antenna and the energy reflected from the tissue, and therefore, cooling is generally required for the tip of the feedline and at least the tip of the device, including the antenna. Preferably, in various embodiments, the feedline and antenna are cooled as a whole. Cooling the antenna prevents damage to the device itself and prevents overheating or burning of the tissue near the antenna. This can alter the physical properties of the tissue, such as energy absorption and reflection characteristics, and therefore reduce the efficiency of the antenna and alter the ablation area. Therefore, in some embodiments, the tissue ablation device may additionally include a cooling system for cooling at least a portion of the antenna and / or feedline. Such a cooling system is generally configured such that a cooling fluid, such as a coolant (e.g., water), passes through at least a portion of the feedline and the antenna. Generally, such a system includes a coolant inlet and a coolant outlet, which work together to cool the antenna and, optionally, at least a portion of the feedline, preferably all of the feedline, by passing the coolant through the antenna and, optionally, at least a portion of the feedline. The antenna and the feedline are generally in contact with the coolant.

[0041] One option is a cooling system that includes a coolant chamber, the coolant chamber having a coolant inlet conduit configured to surround at least the leading edge of the antenna and feedline and to supply coolant to the coolant chamber, and a coolant outlet conduit configured to discharge the coolant from the coolant chamber, the coolant inlet conduit and the coolant outlet conduit configured to allow the coolant to pass through at least a portion of the feedline and at least a portion of the antenna.

[0042] Figure 1A shows a block diagram of elements of a system for performing an ablation process in one embodiment of the present invention. The system includes a console 102, which includes a user interface 104, a controller 106, and an ablation instrument interface 108. In one embodiment, the user interface 104 includes a display for presenting information to the user and an input device for receiving input from the user, for example, 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 the display and the input device of the user interface 104.

[0043] According to one embodiment of the present invention, the ablation device interface 108 of the console 102 is configured to connect to one or more ablation devices. In the embodiment shown in Figure 1A, the ablation device interface 108 connects to three ablation devices 120a, 120b, and 120c via lines 110a, 110b, and 110c, respectively. In one embodiment, the console 102 can connect to one, two, or all of the three ablation devices (120a, 120b, and 120c) individually or simultaneously. Although three ablation devices are shown in the embodiment of Figure 1A, various embodiments of the present invention may include a console having an ablation device interface that can connect to any other number of ablation devices.

[0044] In one embodiment, the console includes an ablation device interface that can be connected to one ablation device. In other embodiments, the console includes an ablation device interface that can be connected to two ablation devices, three ablation devices, four ablation devices, or five ablation devices. In some examples, the ablation device interface can be configured to connect to any number of ablation devices.

[0045] According to certain aspects of the present invention, a single 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.

[0046] In one embodiment, lines 110a, 110b, and 110c are configured to supply coolant (e.g., from a coolant source 140) and ablation power (e.g., a microwave signal) to ablation devices 120a, 120b, and 120c, respectively. Lines 110a, 110b, and 110c can be configured to form a path for supplying coolant to each ablation device and a return path for receiving coolant from each ablation device after passing through the coolant flow path within the ablation device.

[0047] 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.

[0048] 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 supply a coolant to one or more ablation devices via the ablation device interface 108. The controller 106 supplies ablation power to one or more ablation devices to cause the ablation devices to perform the ablation process. In one embodiment, the ablation power supplied to the ablation devices causes the microwave ablation devices to emit microwave radiation. The power supply 130 can supply the power used to generate the ablation power.

[0049] In one example, the controller includes one or more processors and memory storing instructions for the one or more processors to be executed via the controller. In some embodiments of the present invention, the controller is implemented as one or more processors, one or any preferred combination, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or programmable logic circuits. The controller may also include memory storing program instructions and associated data that, when executed, cause the controller to perform the functions assigned to the controller in this disclosure. The memory may also include any fixed or removable magnetic, optical, or electrical medium, such as RAM, ROM, CD-ROM, flash memory, or EEPROM. The memory may also include a removable memory portion that can be used to update the memory or increase the capacity of the memory. Removable memory may also allow for easy transfer of image data to other computing devices. The controller may also be implemented as a system-on-a-chip that integrates some or all elements of a computer or other electronic system onto a single chip.

[0050] Figure 1B shows a block diagram illustrating the operation of an ablation instrument interface connected to an ablation instrument for performing an ablation process, according to one embodiment of the present invention. In one example, the ablation instrument interface 108 includes one or more fluid pumps, each of which is configured to deliver coolant to its respective ablation instrument. For example, as shown in the figure, pump 148a may be in communication with a coolant source 140 and configured to supply coolant to an ablation instrument (e.g., 120a) via a coolant line 114a. Such pumps are controllable by a controller. The controller may be configured to control the flow rate of fluid supplied from the pump (e.g., 148a) to the ablation instrument (e.g., 120a), which includes starting and stopping the supply of coolant by the pump to the ablation instrument.

[0051] In the example shown in Figure 1B, the ablation instrument interface 108 includes three pumps 148a, 148b, and 148c for supplying coolant to each ablation instrument via coolant lines 114a, 114b, and 114c, respectively. Coolant lines 114a, 114b, and 114c can be included within lines 110a, 110b, and 110c shown in Figure 1A, respectively. In one embodiment, each pump is controlled by a controller, for example, independently of the other pumps, so that any pump can operate regardless of the operating status of the other pumps.

[0052] In other embodiments, each of the pumps 148a, 148b, and 148c includes a peristaltic pump driven by a motor controlled by a controller. In some such examples, each pump operates at the same speed as determined by the motor, and the coolant flows through the coolant lines 114a, 114b, and 114c to any of the connected ablation devices. The controller can adjust the flow rate of the coolant within the ablation device by controlling the speed of the motors.

[0053] In some examples, the coolant supplied to the ablation apparatus is provided 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 includes a coolant storage unit, such as sterile water, from which the coolant is drawn and delivered to one or more ablation apparatuses via coolant lines, and from one or more ablation apparatuses, the coolant is returned to the storage unit via coolant outlet lines configured to remove the coolant from the ablation apparatuses. In some alternative examples, the coolant outlet lines carry the coolant from the ablation apparatuses to a waste system (e.g., a drain).

[0054] The ablation apparatus interface in Figure 1B includes a microwave generator 138 that supplies a microwave antenna within the microwave ablation apparatus, which is configured to generate a microwave signal and transmit microwave energy to the tissue. Supplying a microwave signal to the ablation apparatus may include supplying ablation power to the ablation apparatus, which then emits microwave radiation. The microwave generator 138 can supply a microwave signal to the ablation apparatus via a power cable. In the embodiment of Figure 1B, the microwave generator 138 can supply a microwave signal to up to three ablation apparatuses via power cables 112a, 112b, and 112c, respectively.

[0055] The power cables 112a, 112b, and 112c are preferably coaxial cables, and they are preferably set to a rated power of at least 30 watts, preferably at least 100 watts, and preferably at least 150 watts. The cables may be cooling cables configured to be cooled by a coolant supply, preferably by circulating coolant along the cable between a cable coolant inlet and a cable coolant outlet. In some examples, coolant lines 114a to 114c supply coolant along the power cables 112a to 112c, respectively. In one exemplary configuration, the system includes a cooling system configured to cool both the cables and the microwave ablation apparatus.

[0056] In some examples, the microwave generator is preferably configured to supply microwave energy to the antennas in one or more of the 915 MHz band (902-928 MHz), 2.45 GHz band (2.402-2.483 GHz), or 5.8 GHz band (5.725-5.875 GHz), preferably in the 2.45 GHz range and most preferably at 2.45 GHz or about 2.45 GHz. The microwave generator may be configured to supply microwave energy to the antennas of up to five microwave ablation probes, preferably one, two, or three probes.

[0057] The microwave generator 138 can be configured to provide a microwave signal defined by the controller 106. For example, in an exemplary embodiment, the controller 106 can instruct the microwave generator 138 to provide a specific microwave signal to a specific ablation apparatus. The controller can be configured to specify the magnitude of a specific ablation (e.g., desired microwave power and / or energy emitted from the ablation apparatus), the ablation duration, 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 (e.g., power, frequency, etc.) for causing the ablation apparatus to emit microwave radiation with desired characteristics (e.g., microwave power radiated to the surrounding tissue). The electrical signal can provide the desired ablation power to the microwave ablation apparatus.

[0058] In one embodiment, the controller 106 can instruct the microwave generator 138 to apply microwave signals 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 a first ablation device via power cable 112a, a second microwave signal to a second ablation device via power cable 112b, and a third microwave signal to a 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, similar ablation power is provided by each of the first, second, and third microwave signals.

[0059] In some examples, the controller may be configured to control one or more of the following parameters, where the parameters are the 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 may be configured to control one or more of the parameters in response to signals from the sensors (e.g., temperature measurements). For example, the controller may be configured to turn off the power to one or more antennas in response to excessive temperatures.

[0060] In Figure 1B, it is shown to be implemented as a single microwave generator 138 configured to supply 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 be connected to the multiple microwave generators and configured to cause the multiple microwave generators to apply microwave signals to their respective power cables (e.g., 112a, 112b, 112c) so that such microwave signals are supplied to each ablation device.

[0061] Figure 1B shows an exemplary embodiment in which three lines 110a, 110b, and 110c can simultaneously supply microwave signals and coolant to each of three ablation devices. In some aspects of the present invention, microwave signals and coolant can also be supplied to some of lines 110a, 110b, and 110c, for example, when fewer than three ablation devices are connected to the console 102. Furthermore, in some embodiments, microwave signals and coolant can be supplied to some of lines 110a, 110b, and 110c even when three ablation devices are connected to the console 102. For example, one or more ablation devices connected in this manner can be kept unused.

[0062] In one embodiment, the controller 106 controls which ablation apparatus (e.g., which line of 110a, 110b, and 110c) receives the microwave signal and coolant. In one embodiment of the present invention, the controller 106 can control the characteristics of the microwave signal, such as the magnitude, frequency, duty cycle, and duration of the microwave signal. In another embodiment of the present invention, the controller 106 can control the manner in which the coolant is supplied to the ablation apparatus, for example, by controlling the operation of each pump to control the coolant flow rate. In one embodiment, for each ablation apparatus, the controller controls the characteristics of the microwave signal applied to the ablation apparatus and the manner in which the coolant is supplied to the ablation apparatus. During operation, each different ablation apparatus can receive a microwave signal and such amount of coolant that is independent of the signal and fluid received by the other ablation apparatus, and this may be the same as or different from the microwave signal and fluid amount supplied to the other ablation apparatus.

[0063] Figure 1B shows an ablation device interface that connects to three ablation devices, but consoles according to different embodiments may include ablation device interfaces that can connect to any number of ablation devices.

[0064] The block diagram in Figure 1B shows an ablation device interface 108 that includes several elements that connect to an ablation device, but the elements shown as being part of the ablation device interface 108 do not necessarily have to be contained within a single module or housing. Such elements are grouped together in the ablation device interface in that these elements facilitate control by the controller 106 of the connected ablation device.

[0065] Additionally, while Figure 1B shows an ablation instrument interface connected to a microwave ablation apparatus, a similar concept of an ablation instrument interface can also be used to form a connection between a controller and other ablation instruments, such as RF ablation or cryoablation.

[0066] In one embodiment, the ablation device interface includes one or more ports configured to accept a cartridge having a fluid interface for connecting to a fluid line (e.g., 114a) and an electrical interface for connecting to a power cable (e.g., 112a), which are part of the ablation device.

[0067] Figure 2 is a simplified diagram showing a cooling system according to the present invention. System 201 includes an ablation device 202. In this case, the microwave ablation device includes a microwave ablation needle, which is configured to deliver microwave energy to the patient's tissue to ablate the tissue.

[0068] The microwave ablation apparatus 202 comprises a tip 203 configured to puncture tissue and a long shaft having a proximal end 205 and a distal end 206. The shaft surrounds a coolant chamber 214 and a feed line 207, which may be a coaxial cable having an inner conductor, an outer conductor, and a dielectric (not shown in Figure 2) between them. 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 is attached to a cable 209 (generally a coaxial cable) for supplying microwave energy to the apparatus by connecting the microwave ablation apparatus 202 to a microwave generator 210. The cable may be detachably connected or, as in this case, permanently attached to the apparatus. In some embodiments, as shown with reference to Figure 1A or 1B, the microwave generator 210 is housed in a console, for example, console 102.

[0069] The coolant is supplied to the instrument via an instrument coolant supply line 211, which can be permanently attached to the instrument coolant inlet 212. In some embodiments, the instrument coolant supply line may instead be detachably connected to the coolant inlet 212 via, for example, a Luer® connector. The instrument coolant inlet 212 communicates with an instrument coolant outlet 213 via a series of coolant passages 214, 215, and 216 configured to circulate the coolant within the instrument. In this simplified diagram, the coolant enters the instrument through the coolant inlet pipe 215, circulates through the coolant chamber 214 to cool the instrument, and exits through the coolant outlet pipe 216 and the instrument coolant return line 217.

[0070] 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 detachably 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 21 via a manifold inlet conduit 222. In a preferred embodiment, as shown in Figure 2, the flow of coolant exiting port 221 may be controlled by a manifold outlet valve 223. This valve is normally in a closed position. In some embodiments, as shown with reference to Figure 1A or 1B, the manifold 218 may be housed in a console, for example, console 102.

[0071] The manifold 218 also includes a manifold coolant outflow conduit 224, which forms a fluid connection 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 detachably 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, which may also be normally closed.

[0072] The supply coupling 229 is configured to connect to the manifold outlet port 221. The system may also include a return coupling 233, which is configured to connect to the manifold inlet port. In one embodiment, the manifold outlet valve 223 may be configured to open when the supply coupling 229 is connected. In one configuration, the supply coupling includes a projection 230 which opens the valve when the coupling 229 is connected to port 221, but other configurations are possible as described elsewhere in this specification.

[0073] Since the coolant inlet 231 of the coolant circuit on the supply coupling 229 is in communication with the instrument coolant supply line 211, when the supply coupling 229 is connected to the outlet port 221, the cooling circuit 232 is in communication with the cooling fluid source 219.

[0074] The return coupling 233 may have a coolant circuit outlet 234 that communicates with the instrument coolant return line 217. The supply coupling 229 and the return coupling 233 can be configured to be simultaneously connected to the manifold outlet port 221 and the inlet port 225, respectively.

[0075] The pumping section 235 is located, for example, within the instrument cooling circuit 232 and within the supply line 211, and is configured to circulate the coolant within the microwave ablation instrument 202. In the system shown in Figure 2, the pump is a disposable pump head 236 having pump vanes 237, which is permanently connected within the instrument coolant supply line 211 and connected to a pump head drive (not shown). Alternative pumping sections may be used and are described elsewhere in this specification. In some embodiments, as shown with reference to Figure 1A or 1B, the pumping section 235 may be housed in a console, for example, console 102.

[0076] Figure 3 is a perspective view showing a microwave tissue ablation apparatus 300 equipped with a handle 305 according to one embodiment of the present invention. The microwave tissue ablation instrument 300 includes a handle 305. The handle 305 is configured to allow the surgeon to grip the tissue ablation instrument 300 more securely. The handle 305 is further configured to house a liquid manifold for coolant circulation and a coaxial connector for supplying power to the feed line.

[0077] The microwave tissue ablation apparatus 300 includes a probe 307. The probe 307 is inserted into the patient's body and configured to heat target tissue. In one embodiment, the probe 307 includes various ablation apparatus elements described elsewhere in this specification, such as a feedline, an asymmetric dipole antenna, a cooling system having an inlet tube and an outlet tube, etc. In one embodiment, the microwave antenna is configured to emit microwave radiation in frequency bands 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). Preferred wavelengths are within the 2.45 GHz band, and in particular, the antenna is preferably configured to emit microwave energy of 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.

[0078] The probe 307 includes a surface 315. The surface 315 is configured to come into contact with human tissue and is formed of a biocompatible material. The shaft of the instrument is at least partially metal, for example, stainless steel, and includes a marking 311, for example, a laser marking. The marking 311 is configured to inform the surgeon of the depth the probe penetrates into the body. This may include a lubricating surface layer such as PTFE to assist insertion and prevent tissue from adhering to the needle shaft during needle insertion or removal.

[0079] The shaft is generally cylindrical and is typically made of a biocompatible polymer, biocompatible composite material, such as glass fiber reinforced polymer or carbon fiber reinforced polymer, ceramic, or metal (such as stainless steel). The shaft is preferably made of ceramic or metal, but in a preferred embodiment, the shaft includes a metal portion and a non-metallic portion. The non-metallic portion may be a biocompatible composite material, such as glass fiber reinforced polymer or carbon fiber reinforced polymer, or ceramic, but ceramic is preferred due to its superior performance and strength. The ceramic is preferably alumina or zirconia ceramic.

[0080] The shaft preferably terminates distally within the instrument cap. The shaft is preferably cylindrical. The feed line and antenna are preferably located within the instrument shaft. The instrument shaft generally extends from the proximal hub and terminates distally within the distal cap. The hub includes electrical connections to the electrical elements of the shaft, such as the feed line, and may optionally include coolant inlet and coolant outlet connections.

[0081] The diameter of the shaft is not limited and is generally made to suit the intended purpose. For example, in the case of ablation needles, it is important to have a narrow needle that limits damage during insertion and allows for fine control of positioning. As a result, the diameter of the needle shaft is 1.4 to 3 mm, preferably 1.5 to 2.5 mm, and particularly 2 to 2.5 mm.

[0082] The probe 307 in Figure 3 includes an applicator cap 330. In one embodiment, the applicator cap 330 is formed of a biocompatible metal or ceramic, for example, preferably 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 be sealed by a sheath of the probe 307, thereby fluidically insulating the inside of the probe 307 from the outside of the probe 307.

[0083] The shaft may further include an echo-generating region on its outer surface, configured to be visible in ultrasound imaging. In one embodiment, this region includes a coating containing acoustically reflective microspheres. The echo-generating region extends to cover at least the radially outer portion of the shaft relative to the antenna. The probe 307 in Figure 3 includes an echo-generating region 325 configured to be visible in ultrasound imaging, which in one embodiment includes a coating containing acoustically reflective microspheres.

[0084] When a shaft contains both metal and non-metallic parts, the joints between the metal and non-metallic parts where they come into contact can be potentially fragile, especially if the non-metallic part is ceramic, as ceramics are generally less flexible and more brittle than metals such as stainless steel. Therefore, it is preferable that the shaft additionally include an elastic element between this part and the metal part, configured to impart elasticity to the joint between the non-metallic (e.g., ceramic) part and the metal part of the probe shaft during use.

[0085] The probe 307 further includes a region 320 configured to reduce strain on the probe that is induced during use, for example, by bending of the shaft. This strain-reducing region is particularly beneficial when the distal portion of the probe sheath is ceramic. The strain-reducing region 320 is configured to further increase the flexibility of the probe 307 to avoid breakage of the probe 307 during medical work.

[0086] Elastic elements may also be present between the non-metallic region and the cap, but these may be omitted because the shaft strain in this region is smaller. Elastic elements may include, for example, elastic annular spacers, which can be formed from elastic thermoplastic elastomers, such as polyether block amide (PEBA) - trade name PEBAX® or Vestimid® E (Evonik Industries), or polyacrylether ketone (PAEK), such as polyetherether ketone (PEEK). The spacers are preferably shaped and configured to separate the proximal end of the non-metallic portion from the distal end of the metal portion. The elastic elements preferably abut the metal portion at their proximal surface and the non-metallic portion at their distal surface. The elastic annular spacers generally extend radially outward, forming a surface flush with the outer surface of the probe shaft. The radially inward portion of the annular spacer may be provided with 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 preferred embodiment, the annular spacer extends proximal to form an annular step configured to support the inner surface of the distal end of the metallic portion, but does not extend distally. The instrument shaft may also include an adapter sleeve for supporting the joint between the non-metallic and metallic portions of the shaft. The adapter may be configured to take into account, for example, the difference in thickness between the non-metallic and metallic portions of the shaft, and to form a smooth surface transition between the metallic and non-metallic portions. This may be a metal or a non-metallic material such as a thermoplastic elastomer, e.g., PEBA PEBAX® or Vestimid® E, or PAEK such as PEEK. The adapter is particularly important when the non-metallic portion is ceramic, due to the thickness required to increase the strength of the ceramic and because bending of the shaft may cause cracking at this point. In a preferred embodiment, the sleeve extends sufficiently on both sides of the joint to form support for the joint, generally positioned radially inward along the shaft, generally between the feed line and the inner wall of the shaft. The adapter sleeve is preferably made of metal.

[0087] Both the elastic element and the adapter sleeve include a strain reduction region. The elastic element and the adapter sleeve may be separate components or individual parts. In one preferred embodiment, the strain reduction region includes the elastic element, which includes an elastic annular spacer formed in a shape and configuration such that it separates the proximal end of the non-metallic portion from the distal end of the metal portion, the spacer being configured to abut the metal portion at its proximal surface and the non-metallic portion at its distal surface, the spacer extending radially outward to form a surface flush with the outer surface of the probe shaft, the innermost radial portion of the spacer extending proximal to form an annular step configured to support the inner surface of the distal end face of the metal portion, and the strain reduction region further includes adapter sleeves on both sides of the joint that extend radially inward of the annular spacer. Preferably, the sleeves extend proximal to the annular spacer and are configured to contact and support the inner surface of the distal end of the metal portion of the shaft, and preferably extend distal to the spacer and are configured to contact and support the inner surface of the proximal end of the ceramic portion of the shaft.

[0088] The microwave tissue ablation apparatus 300 includes a housing 310. The housing 310 houses coaxial cables, fluid lines, electric wires, etc. Figure 4A is a perspective view showing a microwave tissue ablation apparatus 400 according to one embodiment of the present invention. Figure 4B is a cross-sectional view along line XY illustrating one embodiment of the cooling mechanism.

[0089] The tissue ablation instrument 400 in Figure 4A has a shaft 401 having a metal portion 445 and a ceramic portion 402. The ceramic portion 402 extends from the distal end 406 of the collar 405 to the base 441 of the cap 440. The ceramic portion 402 is shown separated from the shaft 401 to show the internal elements of the instrument.

[0090] The tissue ablation instrument 400 includes an elastic element (e.g., a collar 405) and an adapter 410 for connecting the metal portion 445 of the shaft to the ceramic portion 402. In the instrument of the present invention, the adapter accommodates the difference in shaft thickness between the two portions and, in addition, acts to reduce bending between the metal portion 445 and the ceramic portion 402. In the instrument of the present invention, the elastic annular spacer between the ceramic portion and the metal portion of the shaft shown herein imparts elasticity to this region and acts to reduce the occurrence of breakage at this point due to distortion of the shaft during use.

[0091] For example, as described with respect to Figure 1A or 1B, 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 432 of the antenna 452 within the apparatus 400. The microwave ablation apparatus also has a shaft that surrounds and is generally coaxial with the microwave antenna and feed line, at least the distal end portion. The shaft generally extends from the proximal hub to the distal cap.

[0092] The feed line preferably includes 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 instrument and acts as an outer insulator to the feed line, but this is not required in all embodiments. In some embodiments, the further dielectric may not be present in the distal portion of the feed line, at least up to the junction. The feed line may lack such further dielectric within the instrument shaft, for example, between the proximal feed line connector of the distal hub and the junction of the antenna. The feed line is generally a coaxial cable having a central conductor surrounded by a first dielectric or insulator, the first dielectric surrounded by a second conductor, which may be covered with a further dielectric or insulator as described above. The inner conductor is generally a power conductor.

[0093] In the example shown in Figure 4A, the tissue ablation device 400 has an antenna 452 including a helical arm 412 and a linear arm 420. The distal end 435 of the helical arm 412 forms an electrical connection with the outer conductor 430 of the feed line 432 at a junction 436. In some embodiments, the junction is preferably located toward or at the most distal end of the feed line. The feed line 432 may extend beyond the junction to provide appropriate mechanical support to the electrical junction, but preferably the extension beyond the junction is 5 mm or less, particularly 1 mm or less.

[0094] Generally, a helical arm is in the form of a single conductor. The helical arm of an antenna may be in the form of a wire or ribbon, but is generally a wire or ribbon with a circular cross-section. The helical arm is preferably in the form of a cylindrical conductor, and has a helical gap extending from the proximal end to the distal end, and is provided with a helical conductor having a flat conductor surface that curves around the outer circumference of the feed line. The helical arm does not come into contact with any other part of the inner or outer conductor except at the joint.

[0095] In the example shown in Figure 4A, the helical arm 412 extends proximal to the feed line 432 from the joint 436, winding around it and positioned coaxially around the feed line. Except for the joint 436, the helical arm 412 does not form any electrical contact with the inner conductor 427 or the outer conductor 430. The helical arm may be fixed to its base with adhesive to hold it in place and to facilitate assembly. The helical arm may be embedded in a base material such as a polymer layer or coating to protect it, to insulate it from other parts of the device, or to form a seal.

[0096] In some embodiments, the helical arm is not wound in direct contact with the feed line. It may be wound, for example, at a position radially offset from the feed line. Preferably, the helical arm is wound around a base that supports it. If the feed line includes an outer insulator, this outer insulator may serve as the base for the helical arm, and the helical arm may be wound around the outer insulator. Alternatively, the helical arm may be wound around, for example, a tubular base, such as a cooling tube positioned around the feed line.

[0097] In some embodiments, the total number of turns (N) is in the range of 1 to 12, but is not limited to an integer. In preferred embodiments, N is generally 4 to 8. With respect to one complete turn of the helix, the axial distance is the pitch (P), which can be in the range of 0.7 to 1.5 mm, preferably in the range of 1 to 1.5 mm, and in preferred embodiments, the pitch (P) of the helical arm is 1.2 to 1.25 mm. The number of helical loops (N) and the pitch (P) can affect the microwave energy output, the shape of the irradiation field, and the energy absorption spectrum. By appropriately selecting a combination of each variable, it is possible to provide an ablation device with advantageous properties for tissue ablation.

[0098] In the example shown in Figure 4A, the helical arm is wound around a tube 426, which extends from a hub (not shown) through a metal portion 445 of the shaft to the tip 428 of the antenna 452. The electrical connection between the antenna's helical arm 412 and the outer conductor of the feed line 432 passes through the tube at the joint 436. In the example shown, the helical arm 412 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, preferably in the range of 4 to 10 mm. In a preferred embodiment, the helical arm is in the range of 4 to 7 mm.

[0099] The linear arm 420 is an extension of the inner conductor 427 of the feed line 432 and is surrounded by a dielectric layer 425, except for a second portion 423 that does not have a dielectric. The linear arm of the antenna described herein is electrically connected to the inner conductor of the feedline and is preferably a helical arm and / or a conductor extending distally on an axis coaxial with the feedline. The conductor is preferably in the form of a straight wire. In a particularly preferred embodiment, the linear arm includes a first proximal insulating portion and a second distal non-insulating portion. Generally, 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 preferably extends from the distal end of the feedline. In its simplest form, the linear arm of the antenna may be an extension of the inner conductor of the feedline. The dielectric may then be an extension of a dielectric positioned between the central and outer conductors of the coaxial feedline.

[0100] Preferably, the linear arm and helical arm of the antenna are coaxial with the shaft of the ablation device, so that the linear arm is coaxial with the helical arm and extends distally from the helical arm. As shown in the figure, the linear arm 420 of the asymmetric dipole antenna in Figure 4A has a length L1a. The linear arm includes a first portion L1 421 covered with an insulator, which is an extension of the first dielectric layer of the feed line 432, located between the inner conductor 427 and the outer conductor 430 and not visible in this figure. The linear arm 420 further includes a second portion 423, which has a length L2 422 and is not covered with an insulator. In one embodiment, the second portion L2 422 is exposed to a circulating coolant.

[0101] In one embodiment, the non-dielectric portion of the linear arm is partially or completely inserted into a metal cap, but without contact with the cap. This is achieved by forming an open pocket at 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 region.

[0102] If the distance between the tip and the cap is greater than 3 mm, they are not considered to be sufficiently bonded, especially in terms of the formation of ablation at 2.45 GHz. The length (Lla) of the linear arm 420 is preferably 4 mm to 14 mm, and more preferably 8 mm to 10 mm. The length (L2) of the second exposed portion 423 is preferably 0.1 mm to 2 mm, and more preferably 0.3 mm to 0.5 mm.

[0103] Therefore, in a preferred embodiment, the helical arm 412 of the antenna is in the form of a ribbon, having a length (Lha) of 1 to 18 mm and containing 1 to 14 turns, and the linear arm 420 of the antenna is 4 to 14 mm in length and has a second non-dielectric distal portion 423 with a length of 0.1 to 3 mm, the non-dielectric portion being 0.2 to 3 mm away from the base of the cap.

[0104] In a more preferred embodiment, the spiral arm 412 of the antenna is in the form of a ribbon, having a length (Lha) of 4 to 10 mm and containing 4 to 8 turns, and the linear arm 420 of the antenna has a length of 7 to 10 mm and a second distal portion 423 lacking dielectric material, which is 0.3 to 0.5 mm long and is 1 to 2 mm away from the base of the cap.

[0105] In a more preferred embodiment, the helical arm 412 of the antenna is in the form of a ribbon, with a length (Lha) of 4 to 6 mm and containing 3 to 5 turns. The linear arm 420 is 7 to 10 mm in length and has a second non-dielectric distal portion 423 with a length of 0.3 to 0.5 mm, the non-dielectric portion being 1 to 2 mm, preferably 1.5 mm or about 1.5 mm, away from the base of the cap.

[0106] If the shaft has a non-metallic portion (e.g., a ceramic portion 402), the non-metallic portion preferably extends axially to cover the antenna and therefore has at least the same extent as the radiating portion of the antenna. In one embodiment, the non-metallic portion extends at least from the most proximal point of the helical arm to the distal end of the shaft (e.g., the mounting point of the instrument tip). The non-metallic portion extends axially and circumferentially, so that the shaft is preferably non-metallic between the proximal and distal ranges of the non-metallic portion.

[0107] The cap may be configured to seal the distal end of the instrument to prevent leakage of coolant or penetration of tissue fluid. The cap may be manufactured as a separate component and configured to be attached to the shaft. The cap may preferably be configured to assist insertion into tissue and puncture the patient's skin, for example, to a distal point, or may be configured as a trocar. Cap 440 shown in Figure 4A includes a trocar tip. The trocar tip of cap 440 may be made of stainless steel and / or ceramic.

[0108] In some examples, the cap may be formed 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) may be configured to be electromagnetically coupled. This can be done 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 on 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 region. However, the cap and antenna do not have to be coupled in this way; i.e., the antenna can be electromagnetically separated from the cap. It is preferable that the tip and the cap do not come into contact. In practice, the gap between the tip and the cap is 0.2 mm or more, particularly 0.2 mm to 3 mm, most preferably 1 to 2 mm. Most preferably, this is 1.5 mm or about 1.5 mm.

[0109] The shape of the energy field, and therefore the ablation volume, is also influenced by the provision of a metal sheath concentric with the feedline. The sheath is preferably cylindrical and extends over at least the proximal portion of the feedline to the antenna. The sheath may also extend to cover at least a portion of the antenna, but preferably terminates at a point proximal to the most distal end of the antenna's helical arm and does not extend over the antenna. Preferably, the gap between the sheath and the most distal portion of the helical arm is at least 0.1 mm. The gap may be, for example, 0.1 to 2 mm or 0.1 to 1 mm, preferably 0.5 mm or about 0.5 mm. The sheath is preferably not installed on the outer surface of the shaft, but preferably radially offset from the feedline and coaxial with it. Preferably, the sheath is installed between the feedline and the inner wall of the shaft. In one configuration, the metal sheath may be an adapter sleeve, as described elsewhere in this specification.

[0110] Preferably, the coolant chamber is defined between the inner walls of the instrument shaft. The chamber may be defined by a distal boundary defined by a cap and a proximal boundary defined by one or more proximal seals that close the coolant chamber proximal. The one or more seals are preferably formed at the hub, or at a point between the hub and the proximal portion of the helical arm of the antenna. The cooling system includes at least one coolant inlet conduit configured to deliver coolant to the coolant chamber and at least one coolant outlet conduit for removing coolant from the chamber. The coolant inlet and outlet conduits generally pass through the proximal seals. In one configuration, the coolant inlet conduit is a coolant inlet tube configured to deliver coolant to a location adjacent to the antenna and / or feedline, and radially outward therefrom. In this case, the coolant inlet tube is preferably located within the coolant chamber between the antenna and the inner wall of the shaft. Preferably, it is offset radially outward from the feedline.

[0111] In an alternative configuration, the cooling system includes a coolant inlet conduit and a coolant outlet conduit, each conduit positioned around at least a portion of the feedline and a portion of the antenna. Each conduit is arranged in a helical shape, and the coolant inlet and outlet conduits are combined to form a double helix. In one preferred configuration, the cooling system includes a pair of helical partitions positioned as a double helix around the feedline and at least a portion of the antenna, each partition extending radially outward toward the inner wall of the shaft and radially inward toward the antenna and / or feedline, thereby forming the coolant inlet and outlet conduits between the two partitions, which form a double helix. The partitions may be in the form of filaments or ribbons, or a combination of both. If the partitions include ribbons, the ribbons are preferably generally perpendicular to the inner wall of the shaft. The filaments may be made of metal or elastic polymer. The partitions preferably extend to seal against the inner wall and at least a portion of the antenna and / or feedline.

[0112] The cooling system further includes a coolant mixing chamber communicating with both the coolant inlet conduit and the coolant outlet conduit, thereby connecting the coolant inlet and coolant outlet through the coolant mixing chamber. The coolant mixing chamber is preferably configured to allow the coolant to pass through at least a portion of the antenna, particularly at least a portion of the antenna's linear arms. In particular, the coolant mixing chamber is configured to allow the coolant to pass through the distal portion of the antenna's linear arms and at least a portion of the cap.

[0113] Alternatively, preferably, the cooling system includes a coolant chamber defined between the inner walls of the instrument shaft. The chamber's distal boundary may be defined by a cap, and its proximal boundary by a seal between the hub and the shaft, or by a point distal to the hub and between the antenna and the hub, as described above. The coolant chamber surrounds the antenna and at least the distal portion of the feed line.

[0114] In one embodiment, the cooling system includes a cooling tube positioned around the feedline, which preferably extends distally around the feedline and preferably coaxially therewith. The cooling tube preferably divides the coolant chamber into a first cooling conduit 448 and a second cooling conduit 460, with the first cooling conduit positioned between the feedline 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 instrument shaft. The cooling tube preferably extends to the distal portion of the feedline and distally around at least a portion of the antenna, and preferably extends to at least the tip of the linear arm of the antenna. Various materials are suitable for the cooling tube, which are preferably nonmetallic. In a preferred embodiment, the cooling tube may be made of a thermosetting polymer, such as polyimide, or a thermoplastic polymer resin, such as polyethylene terephthalate (PET), or a fluoropolymer, such as polytetrafluoroethylene (PTFE), or PAEK, such as PEEK.

[0115] As described elsewhere in this specification, in the example of Figure 4A, the helical arm is wound around the tube 426. In one embodiment, the tube 426 defines a first cooling conduit 448 between the inner wall 454 of the tube 426 and the feed line 432, and a second cooling conduit 460 between the outer wall 455 of the tube 426 and the inner wall of the shaft 453. The coolant may be delivered through the space between the tube 426 and the feed line 432 to a mixing chamber 429 between the tube 426 and the cap 440, return through the space between the outside of the tube 426 and the ceramic portion 402 of the shaft, pass through the space 411 between the inside of the shaft and the adapter 410, and return from the metal portion 445 of the shaft to the hub.

[0116] The spiral arm of the antenna may be positioned within a first cooling conduit, and for example, the distal portion of the feed line may include a second insulator as described above, the spiral arm of the antenna is directly wrapped around the feed line, and the second insulator extends axially at least between the spiral arm and the second conduit of the feed line. In this case, the cooling tube extends to cover a portion of the spiral arm, preferably the spiral arm and at least a portion of the linear arm, but most preferably the cooling tube extends at least to the distal end of the antenna, so that the first cooling conduit extends at least to the tip of the antenna.

[0117] Instead, the cooling tube extends to cover the tip of the feed line and part of the linear arm, but most preferably the cooling tube extends at least to the distal end of the antenna, so that the first cooling conduit extends at least to the tip of the antenna.

[0118] The cooling system may additionally include a coolant mixing chamber communicating with both a first and a second cooling conduit, thereby connecting the first and second coolant conduits via the coolant mixing chamber. The coolant mixing chamber is preferably configured so that the coolant can come into contact with a portion of the cap.

[0119] Either the first or second cooling conduit can function as a coolant intake conduit or a coolant discharge conduit. The first and second cooling conduits are open at their distal ends, thereby allowing the coolant to circulate through the coolant mixing chamber between the distal end of the cooling conduit and the base of the applicator cap.

[0120] The cooling pipes preferably extend proximal to the hub. The first and second cooling pipes communicate with the coolant inlet and coolant outlet connectors of the hub for supplying and discharging the coolant during use.

[0121] In a particularly preferred configuration, the spiral arm of the antenna is wound around the cooling tube, preferably in the form of a ribbon. In this case, the spiral arm makes electrical contact with the outer conductor of the feed line at the junction and extends distally as a series of windings around the cooling tube as described above. In this case, the cooling tube preferably extends at least to the junction of the antenna and the feed line, preferably extending to cover at least a portion of the linear arm, but most preferably the cooling tube extends to the tip of the linear arm, thereby the first cooling conduit extends at least to the tip of the antenna. Preferably, the electrical contact between the distal end of the spiral arm and the outer conduit of the feed line passes through the cooling tube.

[0122] In this method, it is preferable that the outer insulator does not extend to the distal portion of the feedline. Preferably, it does not extend to at least the portion of the feedline from a point immediately proximal to the spiral arm of the antenna to the junction. The outer insulator does not need to be anywhere on the feedline within the shaft of the ablation device.

[0123] In embodiments of the cooling system that include the cooling tube described above, the helical arm may be either a wire or a ribbon, but most preferably a ribbon. The helical arm is preferably in the form of a cylindrical conductor, with a helical gap extending from its proximal end to its distal end, resulting in a helical conductor having a flat conductor surface around the feed line, preferably coaxial with the feed line.

[0124] The cooling systems described herein allow a coolant (e.g., water) to pass through the feed line and at least a portion of the antenna, preferably the entire antenna. For normal operation, the antenna does not need to be isolated from the coolant. In some embodiments described herein, a portion of the feed line lacks an outer insulator surrounding it. The feed line may lack insulation between the hub and the joint, or along its entire length within the instrument shaft. The helical arm of the antenna may lack insulation, particularly if it is wound around a cooling tube.

[0125] The ablation apparatus described herein may additionally include one or more temperature sensors, such as thermocouples, for measuring the temperature at points along the shaft. Generally, thermocouples may be placed within a cooling system and configured to measure the temperature of the coolant or other parts of the apparatus, such as the feed line or the apparatus shaft, during the operation of the apparatus. The tissue ablation apparatus 400 in Figure 4A includes a temperature sensor 450 housed next to an internal adapter 410 and having an electrical connection 451 to a control unit via a hub.

[0126] As described elsewhere in this specification, ablation instruments such as those described herein generally include a proximal hub, as already briefly stated. The hub generally includes connectors for connecting the feed line to the energy supply line and for connecting the electrical equipment within the instrument shaft to a control system. Such connectors may be permanent or removable. The hub may also include a coolant manifold with input and output connectors for connecting the coolant intake to the coolant supply and for connecting the coolant discharge to a waste or recirculation system. The hub may also form part of a handle configured to allow the surgeon to grip the tissue ablation instrument more securely.

[0127] Figure 5 is a side view showing a microwave tissue ablation apparatus according to one embodiment of the present disclosure. The ablation apparatus 500 includes a handle 501. The handle 501 houses a manifold 505.

[0128] The manifold 505 electrically connects a power source (not shown) and a tissue ablation probe 530 via a coaxial cable connector 515. The tissue ablation probe 530 includes a marker 535 configured to inform the surgeon of the probe's penetration depth during surgery.

[0129] Manifold 505 also connects a coolant source (not shown) to a tissue ablation probe 530. Manifold 505 includes a coolant inlet 520 and a coolant outlet 525. The coolant inlet 520 is connected to a coolant inflow conduit, and the coolant outlet 525 is connected to a coolant outflow conduit.

[0130] The tissue ablation apparatus 500 further includes a tubular housing 540 for housing electrical wires and fluid tubes. As described elsewhere in this specification, the ablation process can be performed using multiple ablation instruments, for example, tissue ablation instrument 300, simultaneously. Such ablation instruments can be arranged in various ways. Figure 6A shows plan views of various configurations of microwave ablation needles. In one example, the microwave ablation instruments can be arranged equidistant from each other, as in arrangement 600. The needles can be arranged in a regular polygonal arrangement, as in arrangements 600, 610, and 620. By arranging the ablation instruments equidistant from each other, preferably a substantially symmetrical net ablation volume can be formed by the multiple ablation instruments. Additionally, by arranging the ablation instruments in a regular polygonal arrangement, a substantially spherical net ablation volume can be formed by the multiple ablation instruments. Alternatively, the multiple instruments may be arranged in other arrangements, for example linearly, as in arrangement 630, or in an irregular shape, as in arrangement 640. The ablation instruments can be arranged in various configurations to form a desired ablation volume suitable for a particular surgery.

[0131] In addition, such instruments can be inserted to the same or different penetration depths. Figure 6B shows front views of several ablation instruments in arrangements at different depths. Ablation instruments, such as the microwave tissue ablation instrument 300, can be inserted to a specific depth, for example, as measured by the label 311. In some configurations, the instruments are inserted to approximately the same depth, as in arrangement 605. In other examples, the instruments can be inserted to different depths, as in arrangements 615, 625, and 635. As with different planned arrangements, ablation instruments can be arranged in various configurations to form a desired ablation volume suitable for a particular surgery.

[0132] During surgery involving one or more ablation devices, a pump (e.g., 148a) can be operated at a console (e.g., 102) to cause coolant to flow from a coolant source (e.g., 140) to each of the one or more ablation devices (e.g., 400). For each ablation device, the coolant can flow through a coolant line (e.g., 114a), a coolant inlet (e.g., 520), a first cooling conduit (e.g., 448), a second cooling conduit (e.g., 460), and a coolant outlet (e.g., 525). In some examples, the coolant line (e.g., 114a) forms a return path that receives fluid from the coolant outlet (e.g., 525) in a recirculation system where the coolant is recirculated back to the coolant source, for example. In one embodiment, the coolant can flow through such a channel to cool the ablation device.

[0133] As described herein, for example, a controller (e.g., 106) in a console (e.g., 102) that receives the ablation device (e.g., 400) can be used to control the fluid flow through the ablation device as well as the microwave energy emitted from the ablation device.

[0134] The coolant can also act as a dielectric for coupling microwave radiation emitted from a microwave antenna (e.g., 452) to surrounding tissue when the microwave ablation device is inserted into the patient's body. In one embodiment, the coolant flows through the needle at a therapeutic ablation flow rate during the ablation process for treatment. The coolant flowing through the needle at a therapeutic ablation flow rate can coupling the microwave energy emitted from the needle to the surrounding tissue, potentially affecting the penetration depth of the microwave energy into the tissue. By reducing the coolant flow, the coupling of microwave energy to the surrounding tissue can be reduced, resulting in a smaller ablation area. Additionally or alternatively, reducing the coolant flow may reduce the needle's ability to remove heat from the tissue near the needle, resulting in more localized heating of the tissue near the needle compared to the case of a higher flow rate.

[0135] As described herein, multiple ablation devices, for example, two or three ablation devices, may be used during the ablation procedure. The use of multiple ablation devices can increase the size of the ablation area. This increase in the size of the ablation area allows the physician to effectively cauterize the target site without having to position the ablation devices with greater precision. Similarly, the use of multiple needles allows the physician to ensure that the ablation area more accurately covers the target site (e.g., infected tissue). For example, in embodiments where the target site is irregular or non-circular in shape, multiple ablation devices can be positioned accordingly to adequately cauterize the target site and minimize the portion of the ablation area that does not overlap with the target site (e.g., minimize the ablation of healthy tissue). Additionally or alternatively, the use of multiple needles may improve the efficiency of the generator used to power the ablation devices. In some examples, the generator used may be most efficient when supplying a specific power range, for example, 90W of power. Instead of having a single ablation device receive 90W of power from the generator, it may be advantageous to divide the supplied power among multiple ablation devices, for example, 45W to two devices and 30W to three devices. In some cases, the power supplied to each individual ablation device may be different (for example, the first ablation device receives 70W and the second receives 20W), and / or the power supplied to each ablation device may be adjusted during the procedure.

[0136] However, the use of multiple ablation devices can have undesirable side effects, such as the creation of low-energy spots between the ablation devices. When waves from two or more sources interact, these waves may be added together or partially or completely cancel each other out, depending on how the waves match (e.g., wave amplitude or crest-trough matching). When the crests or troughs of the waves interfere with each other, constructive interference can occur, resulting in a wave magnitude greater than either of the original waves. When the crests and troughs interfere with each other, destructive interference occurs, resulting in a wave magnitude smaller than either of the original waves. With respect to microwave radiation sources, the microwave energy present at the location of destructive interference will be lower because the energies from the two sources can cancel each other out.

[0137] This effect can be seen in Figure 7. Figure 7 shows the simulation results of the specific absorption rate (SAR) field, which represents the energy transfer into the tissue from the two ablation devices 720a and 720b. As can be seen from Figure 7, the ablation energy is generally strongest around the two ablation devices and loses strength as it moves away from the devices.

[0138] In the example shown in Figure 7, a low-energy spot 735 appears between the ablation devices due to destructive interference. As shown in the figure, at spot 735, there is little to no microwave energy due to the interference of microwaves emitted by devices 720a and 720b. The location and size of the low-energy spot 735 depend on various factors, such as the frequency, amplitude, and phase of microwave radiation emitted by the two ablation devices, and the distance between the ablation devices. Furthermore, the electromagnetic and / or dielectric properties of the medium between the devices, and whether the medium is homogeneous or not, can also affect the location and size of the low-energy spot 735.

[0139] The presence of low-energy spots (e.g., low-energy spot 735) may prolong the ablation process and / or require more ablation power to deliver the necessary amount of energy to these spots. Additionally or alternatively, the presence of low-energy spots (e.g., low-energy spot 735) may result in an improper or incomplete ablation. For example, when ablation devices 720a and 720b are inserted into tissue, the microwave energy received by the tissue within low-energy spot 735 may be lower than expected, even if the surrounding tissue receives the expected or prescribed amount of microwave energy. Therefore, if the target area includes infected tissue, the infected tissue within low-energy spot 735 may not be completely treated during the ablation process.

[0140] One way to overcome the problem of low-energy spots 735 is to add further ablation devices, as shown in Figure 8. Figure 8 shows ablation regions corresponding to three ablation devices. As shown in the figure, ablation devices 820a, 820b, and 820c emit radiation, resulting in ablation regions 825a, 825b, and 825c, respectively. However, in some situations, even with the use of three or more ablation devices, low-energy spots may still exist, for example, between any two ablation devices and / or near the center of multiple ablation devices. The location of any resulting low-energy spots can be adjusted by adding yet another ablation device or by changing the arrangement of the ablation devices. For example, with respect to Figure 8, if ablation devices 820a, 820b, and 820c emit microwave energy simultaneously, low-energy spots may still occur, for example, near the center of the ablation devices. Similarly, even with the addition of further ablation devices, low-energy spots may still occur between the ablation devices, for example, low-energy spots 835a, 835b, and 835c.

[0141] To properly cauterize low-energy spots resulting from interference between two or more ablation devices, an ablation device may operate in multiple ablation states to adequately cauterize any resulting low-energy spots. To the extent used herein in reference to a system comprising multiple ablation devices, an ablation state corresponds to a combination of operating states (e.g., on / off states) for each individual ablation device. In some embodiments, an on-state ablation device may represent an ablation device emitting ablation energy, and an off-state ablation device may represent an ablation device that is not emitting ablation energy. Alternatively, an on-state may represent an ablation device emitting a first energy level of ablation energy, and an off-state may represent an ablation device emitting a second energy level lower than the first energy level. Additionally or alternatively, operating states may also include other states, such as states at energy levels between the on-state and the off-state, for example, a 50% state where the ablation device emits 50% of the ablation energy emitted in the on-state. Preferably, an ablation device that does not emit ablation energy may be used to identify reflected or coupled power (e.g., power received from one or more ablation devices but not delivered to the medium).

[0142] Different ablation states can also correspond to different combinations of ablation devices that receive ablation power, for example, a subset of the total number of ablation devices. For example, in a system with three ablation devices, a single ablation state may include supplying ablation power to the first and second ablation devices, but not to the third ablation device. Another ablation state may include supplying ablation power to the second and third ablation devices, but not to the first ablation device.

[0143] In addition to or alternative to switching the ablation state (e.g., on / off state), the phase difference between two or more ablation devices can be changed to eliminate, reduce, or adjust the location of low-energy spots (e.g., low-energy spots 835a-835c) present within the ablation region. The phase difference between two or more ablation devices is the phase difference of the ablation energy emitted from the ablation devices and / or the phase difference of the ablation power supplied to the ablation devices.

[0144] Figures 9A-9C show examples of various ablation states using the three ablation devices 820a, 820b, and 820c shown in Figure 8. Each of Figures 9A-9D shows the ablation regions 825a-825c resulting from the microwave energy emitted from the ablation devices 820a-820c and the corresponding ablation devices. In the schematic diagrams of Figures 9A-9C, shaded ablation regions (e.g., 825a and 825b in Figure 9A) represent ablation regions associated with the ON state of the ablation device, while unshaded ablation regions (e.g., 825c in Figure 9A) represent the outlines of ablation regions corresponding to the OFF state of the ablation device. Figures 9A-9D also show low-energy spots 835a-835c that can result from the interference of microwave energy emitted from different ablation devices. In the example figure, low-energy spots that may occur in a certain ablation state are not shaded (835c in Figure 9A), indicating that no microwave energy is received at that location. Possible low-energy spots that are shaded (e.g., 835a and 835b in Figure 9A) are shown for reference in each ablation state, while low-energy spots that may occur from other ablation states are shown without shading.

[0145] In the ablation state shown in Figure 9A, ablation devices 820a and 820b are in the ON state, indicated by the corresponding ablation regions 825a and 825b with shading. On the other hand, ablation device 820c is in the OFF state, indicated by the unshaded ablation region 825c. As described elsewhere in this specification, destructive interference between ablation devices 820a and 820b may result in one or more low-energy spots, such as the unshaded low-energy spot 835c.

[0146] In the ablation state shown in Figure 9B, ablation devices 820a and 820c are in the ON state and are indicated by corresponding shaded ablation regions 825a and 825c. On the other hand, ablation device 820b is in the OFF state, which is indicated by an unshaded ablation region 825b. With respect to Figure 9B, destructive interference between ablation devices 820a and 820c can result in the unshaded low-energy spot 835b in Figure 9B. As shown in the figure, the low-energy spot 835c is shown as not receiving ablation energy in the unshaded state in Figure 9A, but in the ablation state in Figure 9B, it is shaded and receives ablation energy from ablation device 820a with little to no interference from the operating ablation device 820c.

[0147] In the ablation state shown in Figure 9C, ablation devices 820b and 820c are in the ON state and are indicated by corresponding shaded ablation regions 825b and 825c. On the other hand, ablation device 820a is in the OFF state, which is indicated by the unshaded ablation region 825c. With respect to Figure 9C, destructive interference between ablation devices 820b and 820c may result in the unshaded low-energy spot 835a in Figure 9C. As shown in the figure, the low-energy spot 835c, which is shown in Figure 9A as being unshaded and not receiving ablation energy, and the low-energy spot 835b, which is shown in Figure 9B as being unshaded and not receiving ablation energy, are shaded in the ablation state of Figure 9C and are receiving ablation energy from ablation devices 820b and 820c, respectively, with little to no interference from other operating ablation devices.

[0148] As shown in Figures 9A-9C, different low-energy spots (e.g., low-energy spots 835a-835c) may exist depending on which ablation device (e.g., ablation devices 820a-820c) is in the ON state. By changing the combination of ON and OFF states of the ablation devices over time, the low-energy spots that may arise from interference between ON devices switch periodically between low-energy spots 835a, 835b, and 835c, as shown in the example in the figures. However, as shown in Figures 9A-9C, the low-energy spots that may arise from interference between two devices (e.g., low-energy spot 835c between devices 820a and 820b in Figure 9A) receive ablation energy in other ablation states (e.g., Figures 9B and 9C).

[0149] In embodiments in which ablation devices 820a-820c emit microwave energy and are inserted into tissue, the tissue within each low-energy spot 835a-835c may receive little to no microwave energy in each ablation state (e.g., low-energy spot 835c in the ablation state shown in Figure 9A, low-energy spot 835b in the ablation state shown in Figure 9B, and low-energy spot 835a in the ablation state shown in Figure 9C). Preferably, any low-energy spots that may arise associated with a certain ablation state may receive microwave energy when the system operates in a different ablation state. By periodically switching between the ablation states shown in Figures 9A-9C, each low-energy spot can be well cauterized, and as a result, each region (e.g., ablation regions 825a-c) can receive an appropriate amount of microwave energy.

[0150] Each ablation state shown in Figures 9A-9C can be periodized by periodically switching each ablation device between an on and an off operating state. This periodic switching may be configured such that each ablation device has a first length of time in the on state and a second length of time in the off state. The total time of one on state and one off state can be defined as the period. In some embodiments, the periodic switching between the on and off states is performed by defining a duty cycle for each ablation device. In alternative embodiments, ablation devices may be periodically switched between the on and off states using other methods, such as those described herein.

[0151] Figure 10 shows a plot of ablation power supplied to multiple ablation devices. Figure 10 shows an exemplary embodiment in which the ablation system of Figure 8 is periodically switched between the ablation states shown in Figures 9A-9C using a duty cycle. With respect to Figure 10, the ablation signals supplied to each ablation device 820a-820c have the same period (P), first length of time (T1), and second length of time (T2). As shown in the figure, in the example shown, T2 is approximately twice the duration of T1. More specifically, in the example shown, T1 is approximately 200 ms and T2 is approximately 400 ms. Furthermore, the first length of time for each ablation device is temporally staggered from one another. More specifically, the first length of time in which one ablation device operates is temporally staggered by 200 ms from the first length of time for the other ablation devices.

[0152] Regarding Figure 10, the initial 200ms represents the ablation state shown in Figure 9A, where ablation devices 820a and 820b are ON and ablation device 820c is OFF. The time from 200 to 400ms in Figure 10 represents the ablation state in Figure 9B, where ablation devices 820a and 820b are ON and ablation device 820b is OFF. The time from 400 to 600ms in Figure 10 represents the ablation state in Figure 9C, where ablation devices 820b and 820c are ON and ablation device 820a is OFF. As can be seen from the figure, the pattern returns to the ablation state of Figure 9A at 600 to 900ms in Figure 10, and the repetition continues. As shown in Figures 9A-9C and 10, performing the various ablation states shown in Figures 9A-9C periodically by applying a duty cycle to each ablation device (820a, 820b, 820c) helps to ensure that the ablation energy is evenly distributed throughout the ablation region (e.g., ablation region 825a-c) while addressing the possibility of low-energy spots arising from interference between multiple devices. Such a distribution is shown in Figure 9D, where, as shown in Figure 10, the regions covered by each of the ablation states shown in Figures 9A-9C are combined over time, ensuring that no potentially occurring low-energy spots (e.g., 835a-c) are left uncauterized.

[0153] Figure 10 shows that three ablation devices (e.g., ablation devices 820a-c) periodically switch states every 600 ms. In some embodiments, the time taken for periodic switching may be longer or shorter than 600 ms. For example, the ablation states may cycle more quickly (e.g., 200 ms to 600 ms) so that the time taken to periodically switch states is less than 600 ms. Alternatively, the periodic switching of ablation states may cycle more slowly (e.g., 600 ms to 5 seconds) so that the time taken to periodically switch states is longer than 600 ms. In addition, times faster than 200 ms and times slower than 5 seconds are also conceivable.

[0154] As shown in Figure 10, ablation power can be supplied to multiple ablation devices having duty cycles that are time-staggered from each other. As used herein, time staggering between duty cycles refers to the time difference between the on and off states of the duty cycles. For example, as shown in Figure 10, the duty cycle corresponding to ablation device 820a is time-staggered by about 200 ms from the duty cycle corresponding to ablation device 820b. In some embodiments, the time staggering between duty cycles is about 50 ms to about 500 ms. In some embodiments, the time staggering between duty cycles is about 100 ms to about 300 ms. In other examples, time staggerings of less than 50 ms and longer than 500 ms may also be used.

[0155] In the embodiment, the duty cycle associated with each ablation device has a similar duration. In some such examples, the time difference between consecutive duty cycles can be approximately equal to the duration divided by the number of ablation devices. For example, with respect to Figure 10, the duty cycle duration associated with each of the three ablation devices (820a to 820c) is approximately 600 ms, and the duty cycles are time-staggered by approximately 200 ms.

[0156] In some cases, the duty cycle itself can be implemented based on various factors, such as the number of ablation devices used and the maximum number of ablation devices that can be powered simultaneously. For example, in a case where three ablation devices are used and two of them can be powered simultaneously, a 2 / 3 duty cycle (two on and one off) may be implemented. Each ablation device may be supplied with ablation power to which a duty cycle is applied, and the duty cycles for each ablation device are time-staggered from one another.

[0157] Figure 10 generally illustrates each ablation device having equivalent but time-shifted duty cycles; however, in other embodiments, the various duty cycles do not need to be the same across ablation devices. In some embodiments, one or more ablation devices may operate with different duty cycles, for example, varying the duration of the on-state (T1) or off-state (T2) operation. Ablation devices may also have the same or similar duty cycles, but the period (P) associated with those duty cycles may differ.

[0158] Additionally or alternatively, Figure 10 generally illustrates the periodic switching between various ablation states, although the pattern of change between ablation states does not need to be periodic. For example, in some embodiments, manual switching of different ablation states in any order can be performed manually by a physician, for example, via a user interface. In general, with respect to a system using one or more ablation devices, any ablation state or any order in which such ablation states are applied is possible.

[0159] In some examples, ablation states can be achieved by periodically switching between different ablation devices between on and off operating states, for example, by a duty cycle. In some embodiments, different ablation states can be achieved by modulating the ablation power supplied to different ablation devices with a non-square waveform, such as a triangular wave, sawtooth wave, sinusoidal wave, or others. In some such examples, the relative power supplied to different ablation devices varies over time to eliminate or mitigate the possibility of low-energy spots being created by interference between the total power drawn from multiple ablation devices and / or the ablation energy emitted from the ablation devices.

[0160] In some embodiments, not all ablation devices are necessarily configured to supply the same ablation energy and / or average ablation energy to the ablation area. For example, if one ablation device (e.g., ablation device 820a) is close to an important component (e.g., an important blood vessel, organ, etc.), it may be advantageous for ablation device 820a to emit a lower ablation energy level and / or a lower average ablation energy level. A lower ablation energy level can be achieved by having the ablation generator supply less ablation power through ablation device 820a. A lower average ablation energy level can be achieved by operating ablation device 820a on a different duty cycle, for example, a duty cycle that includes a longer off-state than ablation devices 820b and / or 820c. Other methods known to those skilled in the art for supplying various ablation energy levels and / or average ablation energy levels are also conceivable.

[0161] The ablation power level can be controlled in at least two ways: by controlling the amplitude or by utilizing duty cycling. For example, if it is desirable to supply an average power level of 40W, this can be achieved by either setting the power level to 40W, or by setting the power level to a higher value of 80W and using a 50% duty cycle. Both methods of controlling the power level are considered.

[0162] In embodiments such as those shown in Figures 8-10, where multiple ablation devices are used, the distance between the ablation devices can affect the effectiveness of the ablation. If the ablation devices are too far apart, there may be areas in the medium that are not sufficiently cauterized, for example, areas that are not reached by any of the ablation regions for each ablation device (e.g., 824a-c). Alternatively, if the ablation devices are too close to each other or too close to the retaining device, the effectiveness of the ablation and / or the reliability of any data collected during the ablation may be reduced.

[0163] In some embodiments, the ablation system may provide data to the user to ensure that the placement of ablation devices is neither too far nor too close. In such embodiments, at least one of the ablation devices may include a directional coupler. The directional coupler may be used to measure the power delivered and the power received on the ablation device. Additionally or alternatively, other devices may also be used to identify the supplied and / or received power, such as another directional coupler on another ablation device or an antenna configured to receive power.

[0164] When using a directional coupler or similar device, reflected power is reflected power (e.g., S of the directional coupler). 11 This can be identified by monitoring the S of the first ablation device using a directional coupler. Figure 11 shows the S 11Provide some exemplary data of the signal. In FIG. 11, the second ablation device is brought close to the first ablation device. Initially, the second ablation device is far enough from the first ablation device so that the interference with the S 11 signal is minimized. Next, at time 1110 (around 55 seconds), the second ablation device is brought close to the first ablation device. As shown in the figure, S 11 The signal contains a greater amount of noise when the second ablation device is brought close to the first ablation device than when the second ablation device is far away.

[0165] In some embodiments, S 11 The signal can be measured when the first ablation needle is on and the second ablation needle is off. Alternatively, S 11 The signal can be measured when both the first ablation needle and the second ablation needle are on. Further, S 11 The noise in the signal may indicate that the first ablation device is close to a plurality of devices, such as two or more ablation devices or an ablation device and an auxiliary measurement device.

[0166] As described herein, a second directional coupler or a similar device on the second device can also be used to identify whether the first ablation device is too close to the second ablation device. FIG. 12 provides some exemplary data of the S 21 signal. S 21 The signal can be the magnitude of the signal from the first ablation device received on the second ablation device. Regarding FIG. 12, a high S 21 value may suggest that the second ablation device is close to the first ablation device, and a low S 21 value may suggest that the devices are far enough apart. As shown in the figure, at time region 1210, S 21The data shows high power, while time domain 1220 shows low power. As mentioned above, time domain 1210 represents the time when the ablation devices are in close proximity to each other, and time domain 1220 represents the time when the ablation devices are sufficiently far apart.

[0167] In some embodiments, S 21 The signal can be measured when the first ablation needle is ON and the second ablation needle is OFF. In another embodiment, S 21 The signal may represent multiple ablation devices that are in the ON state. For example, with respect to Figures 8-10, an ablation device that is ON at a given time may be used to determine whether it is getting too close to one or more other ablation devices that are ON.

[0168] In some embodiments, the user may use the data in Figures 11 and 12 to precisely position the ablation needle so that it is sufficiently far away. In certain embodiments, the user may receive data from one or more directional couplers in real time, for example, data similar to that shown in Figures 11 and 12, to precisely manipulate the ablation instrument during the ablation procedure.

[0169] Additionally or alternatively, the ablation system may, before initiating the ablation procedure, supply ablation power to the signal through one ablation device to determine whether it is too close to any ablation device or auxiliary device used during the ablation procedure.

[0170] Various non-limiting examples have been described. These and others are included in the following claims. In addition, the present invention is capable of various modifications and alternative forms, some specific embodiments of which are shown as examples in the drawings. The drawings may not be to scale.

Claims

1. It is a tissue ablation system, Three or more ablation devices for placement on or near a target site of a patient's internal structure, each ablation device having a microwave antenna configured to transmit microwave energy to the target site, and each ablation device, when ablation power is supplied to it, applies ablation energy to the ablation area adjacent to each ablation device, Multiple ablation generators, each ablation generator supplying ablation power to one of the three or more ablation devices, A controller that communicates with the ablation generator, comprising a controller that causes each of the three or more ablation devices to selectively receive ablation power, The controller repeatedly and periodically activates each of the multiple ablation states, and each ablation state corresponds to a combination of the on and off states of the three or more ablation devices. Each ablation state corresponds to a unique subset of the three or more ablation devices in the ON state, Activation of one of the multiple ablation states includes the state in which an ablation device within the corresponding subset is in the ON state and the state in which an ablation device not within the corresponding subset is in the OFF state. A tissue ablation system comprising: at least two of the three or more ablation devices being turned on at any given time; at least two of the three or more ablation devices being adjacent to each other; and enabling the ablation of low-energy spots caused by interference between the three or more ablation devices by repeatedly and periodically activating each of the multiple ablation states.

2. The tissue ablation system according to claim 1, wherein the activation of the ablation state includes the absence of the off-state ablation device among the three or more ablation devices from receiving ablation power.

3. The tissue ablation system according to claim 1, wherein the activation of the ablation state includes the off-state ablation device receiving less power than the ablation device receiving ablation power among the three or more ablation devices.

4. The tissue ablation system according to any one of claims 1 to 3, wherein the controller continuously activates each of the plurality of ablation states.

5. The tissue ablation system according to any one of claims 1 to 4, wherein repeatedly and periodically activating each of the multiple ablation states does not result in all three or more ablation devices receiving ablation power simultaneously.

6. The tissue ablation system according to any one of claims 1 to 5, wherein repeatedly and periodically activating each of the multiple ablation states includes activating each ablation state for the same length of time.

7. A tissue ablation system according to any one of claims 1 to 6, wherein each ablation state is activated over a period of 100 to 300 ms.

8. The tissue ablation system according to any one of claims 1 to 7, wherein the repeated and periodic activation of each of the multiple ablation states is achieved by each of the three or more ablation devices receiving ablation power according to its respective duty cycle.

9. The tissue ablation system according to claim 8, wherein the duty cycles of the three or more ablation devices are equal.

10. The tissue ablation system according to claim 8, wherein the duty cycles of each of the three or more ablation devices are staggered in time.

11. The tissue ablation system according to claim 8, wherein each of the duty cycles is time-staggered so that none of the three or more ablation devices receive ablation power simultaneously.

12. The tissue ablation system according to claim 8, wherein each of the duty cycles is time-staggered so that the three or more ablation devices do not receive ablation power at any one-in-a-half moment while the controller repeatedly and periodically activates each of the multiple ablation states.

13. The tissue ablation system according to any one of claims 1 to 12, wherein each of the three or more ablation devices includes a microwave ablation needle.

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