Systems and methods for tissue ablation and related measurements thereof

Abstract

This invention provides an exemplary ablation system. The system is designed to safely and efficiently deliver energy to tissue by, for example, emitting energy in a controlled and repeatable manner, allowing for feedback and energy emission titration based on sensed parameters (e.g., tissue temperature) measured during ablation. The system may include a switching antenna for both target tissue heating and radiation measurement to monitor the temperature of the heated tissue. For example, the switching antenna may include a monopole formed by a proximal radiating element and a distal radiating element, such that the proximal radiating element includes a short-circuit element to eliminate the choke effect of the proximal radiating element. The system further includes a processor for calculating the temperature of the target tissue and estimating the volume of the ablation lesion based on the target tissue temperature.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 112,101, filed November 10, 2020, and U.S. Provisional Patent Application No. 62 / 968,726, filed January 31, 2020, the entire contents of each of which are incorporated herein by reference. Technical Field

[0003] This application generally relates to systems and methods for safely and effectively ablating target tissue, for example by measuring parameters such as the temperature of the target tissue during ablation and estimating the volume of ablation damage based on the measured parameters. Background Technology

[0004] Tissue ablation can be used to treat a variety of clinical diseases, and several ablation techniques have been developed, including cryoablation, microwave ablation, radiofrequency (RF) ablation, and ultrasound ablation. Many treatment options use RF power applied by a catheter that contacts the medial wall of an artery to affect the nerve.

[0005] These techniques are typically performed by a clinician who introduces a catheter with an ablation tip into the target tissue via a vein, positions the ablation tip near what the clinician considers an appropriate area based on tactile feedback, thereby mapping electrocardiogram (ECG) signals, anatomical and / or fluoroscopic imaging, actuating the flow of an irrigation fluid to cool the surface of the selected area, and then actuating the ablation tip for a period of time deemed sufficient to destroy the tissue in the selected area.

[0006] Although commercially available ablation tips may include thermocouples for providing temperature feedback via a digital display, these thermocouples typically do not provide meaningful temperature feedback during flushing ablation. For example, thermocouples only measure surface temperature, while the heating or cooling of tissue that causes ablation can occur at a depth below the tissue surface. Furthermore, in procedures where the tissue surface is cooled with a flushing fluid, the thermocouple will measure the temperature of the flushing fluid, thus further obscuring any useful information about the temperature of the tissue, especially deep within it. Consequently, clinicians lack useful feedback regarding the temperature of the tissue during ablation or whether the ablation time period was adequate.

[0007] Therefore, it may only be revealed after the procedure that the abnormal target pathway was not properly disrupted. In this situation, the clinician may not know whether the procedure failed because the incorrect tissue area was ablated, because the ablation tip was not actuated for a sufficient period of time to destroy the target tissue, because the ablation tip did not touch or insufficiently touch the tissue, because the ablation energy was insufficient, or some combination of the above. After repeating the ablation procedure to try ablating the target tissue again, the clinician may immediately have as little feedback as during the first procedure, and therefore may therefore potentially fail to disrupt the abnormal pathway again. Additionally, there is a risk that the clinician may re-treat the previously ablated area of ​​the target tissue, and not only ablate the target tissue but also damage adjacent tissue.

[0008] In some cases, to avoid having to repeat the ablation procedure, clinicians may ablate a series of areas within the target tissue where the target tissue is located, in order to improve the chances of successful ablation. However, there is still insufficient feedback to help clinicians determine whether any of those ablation areas have been adequately destroyed.

[0009] Sterzer's U.S. Patent No. 4,190,053 describes a hyperthermia treatment device in which a microwave source is used to deposit energy in living tissue to achieve hyperthermia. The device includes a radiometer for measuring temperature deep within the tissue and a controller that feeds back a control signal corresponding to the measured temperature from the radiometer to control the application of energy from the microwave source.

[0010] U.S. Patent No. 7,769,469 to Carr et al. describes an integrated heating and sensing catheter device for treating arrhythmias, tumors, and the like, having a duplexer that allows for near-simultaneous heating and temperature measurement. This patent also describes how the temperature measured by the radiometer can be used to control energy application, for example, to maintain a selected heating distribution profile.

[0011] Despite the promise of providing precise temperature measurement sensitivity and control through radiometry, this technique has seen few successful commercial medical applications. A drawback of previously known systems is the inability to obtain highly reproducible results due to slight variations in the construction of the microwave antenna used in the radiometer, which can lead to significant differences in measured temperatures between different catheters. Issues have also arisen regarding the orientation of the radiometer antenna onto the catheter to properly capture the radiant energy emitted by the tissue and regarding shielding the high-frequency microwave components in the surgical environment to prevent interference between the radiometer components and other devices in the surgical field.

[0012] The acceptance of microwave-based hyperthermia therapy and temperature measurement techniques is also hampered by the capital costs associated with implementing radiation measurement temperature control schemes. Radiofrequency ablation technology has received considerable attention in the medical community, even though such systems can have significant limitations, such as the inability to accurately measure (e.g.) the temperature of deep tissues through irrigation. However, the widespread acceptance of RF ablation systems, the extensive knowledge base within the medical community regarding these systems, and the substantial costs required to transition to and train for these new techniques have significantly hindered the widespread adoption of radiation measurement techniques.

[0013] U.S. Patent Nos. 8,926,605 and 8,932,284 to McCarthy et al. describe systems for measuring temperature in a radiometric manner during ablation, the entire contents of each of which are incorporated herein by reference.

[0014] In light of the foregoing, it is desirable to provide a system and method that allows for highly radiometric measurements of temperature deep within tissues to achieve accurate temperature measurements using microwave heating.

[0015] It is further desirable to provide systems and methods for calibrating such microwave heating and radiation measurement systems.

[0016] In addition, it is desirable to provide an ablation system with a feedback mechanism for detecting and / or preventing overheating of the target tissue during ablation procedures to improve the efficacy and safety of the ablation system.

[0017] While there are various energy-based devices available for treating a range of diseases that promise to improve outcomes, reduce risks, and shorten recovery times, there remains a great deal of opportunity to leverage the capabilities of different technologies to implement optimal therapies to drive outcomes and improve risk profiles. Summary of the Invention

[0018] This invention provides an ablation system and method for ablating target tissue and sensing parameters (e.g., temperature) during ablation. In a preferred embodiment, the ablation system utilizes microwave energy for ablation. For example, the system for ablating target tissue in a patient may include a catheter having a proximal region and a distal region, and a main antenna disposed at the distal region of the catheter. The main antenna can emit energy to ablate the target tissue and measure a radiometer temperature resulting from the energy emission. The system further includes a reference terminal disposed at the distal region of the catheter for measuring a reference temperature at the distal region. The system is designed to safely and efficiently deliver energy to tissue by emitting energy, for example, in a controlled and repeatable manner, which allows for feedback and energy emission titration based on sensed parameters (e.g., tissue temperature) measured during ablation. The system may include a cooling sleeve disposed over at least the distal region of the catheter. The cooling sleeve is coupled to a coolant source and allows coolant flow through the main antenna and the reference terminal, thereby cooling the main antenna and the reference terminal during pre-ablation calibration and during the ablation procedure. In this way, the in vitro calibration prior to the in vivo ablation procedure is closely aligned with the ablation procedure to ensure accurate sensing of parameters, such as those of the target tissue, during ablation.

[0019] Additionally, the system may further include a processor operatively coupled to the main antenna and the reference terminal. The processor may alternately cause the main conduit to emit energy and measure the radiometer temperature, and cause the reference terminal to measure a reference temperature. For example, the processor may cause the main conduit to emit energy during a first time period, and alternately cause the main conduit to measure the radiometer temperature and the reference terminal to measure the reference temperature during a second time period. The first time period may be at least 80% of the sum of the first and second time periods. Furthermore, the processor may be programmed to alternately cause the main conduit to measure the radiometer temperature and cause the reference terminal to measure the reference temperature via a switch electrically coupled to the main antenna and the reference terminal.

[0020] The processor can be programmed to calculate the target tissue temperature based on the measured radiometer temperature and the measured reference temperature. Furthermore, the processor can be programmed to estimate the volume of the ablation lesion formed by the energy emission during the ablation procedure based on the target tissue temperature. For example, the volume of the ablation lesion can be estimated based on at least one of the average target tissue temperature or the area under the plotted curve of the target tissue temperature. Additionally, the processor can further permit titration of the energy emission based on the volume of the ablation lesion. Furthermore, the processor can modulate the energy emission such that the calculated target tissue temperature is maintained within a predetermined threshold.

[0021] According to another aspect of the invention, the processor can be programmed to perform reference terminal calibration to take into account heating of the reference terminal during energy emission via the main antenna, and to perform radiometer calibration to take into account heating of the environment adjacent to the target tissue during energy emission via the main antenna. Additionally, the processor can be programmed to calculate the target tissue temperature based on the measured radiometer temperature and the measured reference temperature, while taking into account heating of the reference terminal and the environment adjacent to the target tissue during energy emission via the main antenna.

[0022] For example, the reference terminal calibration may include: measuring the output voltage caused by energy emission from the reference terminal for varying levels of energy emitted by the main antenna while the main antenna and the reference terminal are in a thermostatic bath, the thermostatic bath providing a high fluid flow across the main antenna such that the temperature of the environment adjacent to the main antenna remains constant; and comparing the measured voltage with the varying levels of energy emission to take into account the effects of energy emission on the reference terminal during energy emission.

[0023] Furthermore, the radiometer calibration may include: measuring a first temperature and a second temperature in response to impacts to the main antenna at a first noise level and a second noise level, respectively, when the main antenna and the reference terminal are in a constant-temperature bath; and comparing the first temperature and the second temperature with the first noise level and the second noise level to take into account the effects of energy emission on the environment adjacent to the target tissue during energy emission. Alternatively, the radiometer calibration may include: measuring a first output voltage and a first temperature in response to a first radiometer signal when the main antenna and the reference terminal are in a first bath having a first temperature; measuring a second output voltage and a second temperature in response to a second radiometer signal when the main antenna and the reference terminal are in a second bath having a second temperature different from the first temperature; and comparing the first output voltage and the second output voltage with the first temperature and the second temperature to take into account the effects of energy emission on the environment adjacent to the target tissue during energy emission.

[0024] According to another aspect of the invention, the processor can be programmed to calculate the target tissue temperature based on the measured radiometer temperature and the measured reference temperature, and to monitor the target tissue temperature to predict and / or detect abrupt changes within the target tissue temperature, such as a rapid increase in target tissue temperature followed by a sudden decrease. Therefore, if such abrupt change is detected, the processor can generate an alert. Furthermore, the processor can be programmed to automatically modulate the energy emission via the main antenna to reduce at least one of the target tissue temperature or the rate of increase in the target tissue temperature if the abrupt change is predicted. Additionally, the system may further include a display operatively coupled to the processor, such that the processor causes the display to show the abrupt change within the target tissue temperature.

[0025] According to another aspect of the invention, an alternative system for ablating target tissue in a patient is provided. The system may include a catheter having a proximal region and a distal region, and a main antenna having a monopole. The main antenna may be disposed at the distal region of the catheter and may emit energy to ablate the target tissue and measure a radiometer temperature as a result of the energy emission. Additionally, the system may include a reference terminal disposed at the distal region of the catheter, such that the reference terminal may measure a reference temperature at the distal region. Furthermore, the system may include a processor operatively coupled to the main antenna and the reference terminal, the processor being configured to: alternately cause the main catheter to measure the radiometer temperature and cause the reference terminal to measure the reference temperature via a switch electrically coupled to the main antenna and the reference terminal; and calculate the target tissue temperature based on the measured radiometer temperature and the measured reference temperature.

[0026] The monopole may include a near-end radiating element and a far-end radiating element, such that the near end of the near-end radiating element has a short-circuit element designed to eliminate the choke effect of the near-end radiating element. Therefore, the switch may be positioned between the near-end radiating element and the far-end radiating element. Alternatively, the switch may be positioned in a near-end region of the near-end radiating element, wherein the near-end region is close to the junction between the near-end radiating element and the far-end radiating element.

[0027] The switch may include a first switching diode and a second switching diode. Furthermore, the switch may further include a third switching diode to improve the isolation between the reference terminal and the radiometer temperature during ablation of the target tissue. Additionally, the switch may include a fourth switching diode to improve the isolation between the reference terminal and the radiometer temperature during measurement of the reference temperature. The second and fourth switching diodes may be connected in series with the main antenna and separated by a microstrip transmission line. The system may further include a switch module sized and shaped to house the switch. The switch module may include a proximal coaxial connector and a distal coaxial connector structured for removable coupling to a coaxial cable of the conduit. Attached Figure Description

[0028] Figure 1 This is a simplified block diagram of a microwave radiometer with a Dicke switch.

[0029] Figure 2 This is a block diagram of a microwave heating and temperature sensing system in which the Dick switch and reference terminal are located at the end of the coaxial cable near the connection with the antenna.

[0030] Figure 3 This is a block diagram of an exemplary microwave ablation system constructed according to the principles of the present invention.

[0031] Figure 4A Diagram illustrating the cause Figure 3 Computer simulation of the temperature field and power loss density generated by microwave heating of the system, and Figure 4B The diagram illustrates the temperature distribution on the cutting plane.

[0032] Figure 5A The diagram illustrates an exemplary microwave ablation system in which the reference terminal is positioned between the dipoles of the radiometer antenna, and Figure 5B Diagram Explanation Figure 5A The switching network of the microwave ablation system, and Figure 5C Diagram Explanation Figure 5A Microwave ablation system.

[0033] Figure 6The diagram illustrates the basic dipole of the microwave radiating element of an exemplary microwave ablation system constructed according to the principles of the present invention.

[0034] Figure 7 The diagram illustrates the balanced and unbalanced transformers of the microwave radiation element in an exemplary microwave ablation system according to the principles of the present invention.

[0035] Figure 8 This is a cross-sectional view of the radiometer antenna of an exemplary microwave ablation system constructed according to the principles of the present invention.

[0036] Figure 9A The diagram illustrates the back-to-back balanced and unbalanced transformers of the microwave radiation element in an exemplary microwave ablation system constructed according to the principles of the present invention.

[0037] Figure 9B A diagram illustrating a switching diode according to the principle of the present invention. Figure 9A Back-to-back balanced and unbalanced transformers and reference terminating resistors.

[0038] Figure 10A The diagram illustrates power dissipation in tissue when the diodes of the exemplary microwave ablation system are biased to the on state. Figure 10B The diagram illustrates power dissipation in tissue when the diodes of the exemplary microwave ablation system are biased to the off position.

[0039] Figure 11 It is the cross-section of the three-conductor transmission line of a balanced or unbalanced transformer constructed according to the principle of the present invention.

[0040] Figure 12 The diagram illustrates an encapsulated unencapsulated diode in an exemplary microwave ablation system based on the principles of the present invention.

[0041] Figure 13 The illustration shows an exemplary microwave ablation system with a coolant jacket constructed according to the principles of the present invention.

[0042] Figure 14 This is a flowchart illustrating the steps of ablation of target tissue according to the principles of the present invention.

[0043] Figure 15 This is a flowchart illustrating the steps of calibrating an exemplary reference terminal according to the principles of the present invention.

[0044] Figure 16A This is a flowchart illustrating the steps of calibrating an exemplary radiometer according to the principles of the present invention.

[0045] Figure 16B This is a flowchart illustrating the steps of an alternative exemplary radiometer calibration according to the principles of the present invention.

[0046] Figure 17 This is a graph illustrating the temperature versus time during an ablation procedure performed according to the principles of this invention.

[0047] Figure 18A This is a graph illustrating the ablation damage volume versus average target tissue temperature during an ablation procedure performed according to the principles of this invention.

[0048] Figure 18B This is a graph illustrating the area under the radiometer curve of the ablation lesion volume versus the target tissue temperature during an ablation procedure performed according to the principles of this invention.

[0049] Figure 19 It is a chart that illustrates the abrupt changes within the target tissue temperature range.

[0050] Figure 20 The diagram illustrates data indicating induced thermal injury in homogeneous tissues.

[0051] Figures 21A to 21C The diagram illustrates the results of radiator testing using the ablation system based on the principles of the present invention.

[0052] Figure 22 The illustration shows the results of a radiator test on bovine liver using an ablation procedure performed according to the principles of this invention.

[0053] Figure 23 The illustration shows the results of a lung ablation test performed on bovine liver using an ablation procedure based on the principles of this invention.

[0054] Figure 24A The diagram illustrates the radiometer AUC data resulting from lung ablation testing, and Figure 24B The diagram illustrates data on the energy delivered as a result of a lung ablation test.

[0055] Figure 25A A diagram illustrating the basic dipole of the microwave radiating element in a demonstrative microwave ablation system.

[0056] Figure 25B The diagram illustrates the principle of the present invention. Figure 25A The basic dipole is transformed into a unipolar.

[0057] Figure 25C The diagram illustrates a fine monopole constructed according to the principles of the present invention.

[0058] Figure 26A The diagram illustrates an exemplary microwave ablation system according to the principles of the present invention, in which a switching network is arranged within a single pole.

[0059] Figure 26B Diagram Explanation Figure 26A The switching network of the microwave ablation system.

[0060] Figure 26C Diagram Explanation Figure 26A The alternative switching network for microwave ablation systems.

[0061] Figure 27A and 27B The diagram illustrates an exemplary microwave ablation system according to the principles of the present invention, in which the switching network is pushed back.

[0062] Figures 28A to 28C The diagram illustrates an exemplary switch module constructed according to the principles of the present invention.

[0063] Figure 29 The illustration shows an exemplary switching substrate constructed according to the principles of the present invention. Detailed Implementation

[0064] In light of the foregoing, it is desirable to provide systems and methods for treating living tissues that employ a radiometric system (e.g., a microwave radiometric system) for temperature measurement and control. According to one aspect of the invention, a system and method are provided for measuring temperature radiometrically during microwave ablation (i.e., calculating the temperature based on signals from a radiometer). In a microwave ablation system, an antenna determines how the ablation signal power is distributed within the target tissue. This can be quantified as a power loss density. In a radiation sensing system, the antenna operates in the opposite manner, where the power loss density becomes the power source density. The total received power is the sum of all power sources in the measurement volume. For both transmission and ablation cases, the relative received power of the power sources is the same as the relative dissipated power of the power loss.

[0065] Unlike standard thermocouple technology used in existing commercial ablation systems, radiometers can provide useful information about the temperature of tissue deep within the tissue (where tissue ablation occurs) and thus provide clinicians with feedback on the extent of tissue damage when a selected area of ​​the target tissue is ablated. Specifically, this disclosure overcomes the shortcomings of previously known systems by providing an improved system and method for microwave ablation of target tissue and measuring the temperature of the target tissue during ablation. Furthermore, this disclosure provides an improved system and method for performing: calibrating the ablation system to take into account the environmental effects of energy emission on the reference terminal and adjacent antenna; estimating the volume of ablation damage; and detecting and / or predicting abrupt changes indicating undesirable heating and / or movement of the ablation system, thereby improving the safety and efficacy of the system. The novel invention described herein has broad applicability to catheter / probe-based therapies, including but not limited to targets in the vascular system and soft tissue targets in the liver, kidneys, prostate, and lungs. For example, the principles of the invention described herein can be incorporated into known ablation systems, such as NeuWave. TMMicrowave ablation systems (available from Ethicon, a part of Johnson & Johnson, Bridgewater, New Jersey, and Cincinnati, Ohio).

[0066] Microwave heating of target tissue and microwave radiometry as a means of monitoring the temperature of the heated tissue ensure the delivery of the desired temperature to adequately treat the target tissue and achieve therapeutic goals, as described in U.S. Patent Application Publication No. 2019 / 0365466 by Allison, the entire contents of which are incorporated herein by reference. Specifically, heating and temperature sensing are accomplished via a catheter using a single antenna shared by both functions. Microwave heating can be targeted at the target tissue. A radiometer, operating at the same frequency and time as the microwave generator and sharing the antenna, senses microwave emissions from a region surrounding the antenna and converts these emissions into tissue temperature. In this case, the volume of the monitored tissue includes, for example, tumorous lung tissue. An algorithm correlates the temperature at the target region with a volumetric temperature reading.

[0067] However, achieving accurate temperature measurements using radiometry and microwave heating presents challenges. These are due to dissipative losses in the relatively long coaxial cable between the radiometer and the antenna. A common approach uses a Dick radiometer, which compares the unknown temperature of the target tissue to be heated with an internal reference temperature known within the radiometer. The radiometer output voltage is:

[0068] V rad =(T tissue -T reference ) × Slope + Offset

[0069] Here, the slope is the number of volts per degree of sensitivity, and the offset is the sum of all fixed errors. These constants are determined by calibration using both hot and cold input terminals.

[0070]

[0071] Figure 1 The diagram illustrates a simplified block diagram of such a system with a Dick radiometer. (See diagram for example.) Figure 1 As shown, an input switch (e.g., Dick switch 32) is used to select either antenna input 28 or an internal reference input (e.g., reference temperature terminal 30). This method is popular because everything in the measurement path following Dick switch 32 is shared by both the target measurement from antenna input 28 and the reference measurement from reference temperature terminal 30, and most potential measurement errors are eliminated from the calculation.

[0072] The problem with antenna ducts is the dissipative loss in the coaxial cable extending the length of the duct. Emissions caused by cable loss are indistinguishable from those received by the antenna. The antenna temperature is measured by a radiometer in combination with the cable temperature. The problem is exacerbated by the desired high-loss, small-diameter ducts, small-diameter coaxial cables, and the heating of the coaxial cable due to power dissipation from some generators.

[0073] exist Figure 2 The solution is revealed in the block diagram. For example... Figure 2 As illustrated in the diagram, the Dick switch 34 and reference terminal 36 have been moved to the end of the coaxial cable (e.g., a short flexible cable 38 at the distal end of the main conduit cable) near the connection with the antenna 40. Now, the coaxial cable is part of both the target measurement from the antenna 40 and the reference measurement from the reference terminal 36, and the heat dissipated from the coaxial cable is excluded from temperature calculations. However, the scheme may introduce some errors due to heating of the reference (attributed to the reference's proximity to the heated cable).

[0074] To overcome the shortcomings of previously known radiation measurement systems, this invention integrates the Dick switch radiometer function into the antenna. For example, see now for reference... Figure 3 A block diagram illustrating a microwave heating and temperature sensing system 10 constructed according to the principles of the present invention is provided. Figure 3 As shown, generator 12 supplies ablation energy to switching antenna 22 via transmit / receive (T / R) switch 16 followed by antenna switch bias duplexer 18. Generator 12 can be any previously known commercially available ablation energy generator, such as a microwave energy generator, thereby enabling the use of radiation measurement techniques with reduced capital expenditure.

[0075] Furthermore, radiometer 24 receives temperature measurements from switching antenna 22 via cable 20 (e.g., coaxial cable). Switching antenna 22 includes: a main antenna having one or more microwave radiating elements for emitting microwave energy and for measuring the temperature of tissue adjacent to the main antenna; and a reference terminal for measuring a reference temperature. Additionally, switching antenna 22 includes a switching network, such as a Dick switch, integrated therein for detecting the volumetric temperature of the ablated tissue. The switching network selects between a signal from switching antenna 22 indicating the measured radiometer temperature of the main antenna (e.g., the temperature of tissue adjacent to the main antenna during the ablation procedure) and a signal from the reference terminal of switching antenna 22 indicating the measured reference temperature. Because the switching network is integrated within switching antenna 22 and is sufficiently far from the connection point of cable 20 and switching antenna 22, heating of the reference terminal by cable 20 is avoided.

[0076] Switch 16 and antenna switch bias duplexer 18 may be housed together within handle 14, along with radiometer 24 for receiving temperature measurements from switching antenna 22 depending on the state of switch 16. For example, switch 16 may be in an ablation state, allowing microwave power to be transmitted from generator 12 to switching antenna 22, or switch 16 may be in a measurement state, allowing radiometer 24 to receive temperature measurements from switching antenna 22 (e.g., from the main antenna and / or reference terminal). Therefore, switch bias duplexer 18 may be in the main antenna state, allowing radiometer 24 to receive temperature measurements from the main antenna, or switch bias duplexer 18 may be in the reference terminal state, allowing radiometer 24 to receive temperature measurements from the reference terminal. Handle 14 may be reusable, while cable 20 and switching antenna 22 may be disposable.

[0077] System 10 further includes a controller 26, which is coupled to generator 12 and switching antenna 22 via, for example, handle 14 and cable 20 to coordinate signals therebetween. Controller 26 thereby provides generator 12 with the information required for operation, transmits ablation energy to switching antenna 22 under the control of a clinician, and can display the temperature deep within the tissue as it is ablated via a temperature display for clinician use. The displayed temperature can be calculated based on signals measured using computer algorithms from switching antenna 22. Therefore, controller 26 includes a processor with memory for storing instructions to be executed by controller 26. The processor may include one or more commercially available microcontroller units, which may include a programmable microprocessor, volatile memory, non-volatile memory (e.g., EEPROM) for storing programming, and non-volatile memory (e.g., flash memory) for storing firmware. The processor's memory stores program instructions that, when executed by the processor, cause the processor and functional components of system 10 to provide the functionality attributed to them herein. The processor is configured to be programmable, such that programming data is stored in the processor's memory or accessible via a network. As will be readily understood by those skilled in the art, although... Figure 3 The illustration depicts a single controller, but processors can be contained within a single location / housing or multiple processors used in multiple locations / housings. Furthermore, Figure 3 Reusable devices can be housed in a common enclosure or a separate enclosure.

[0078] The processor can guide switch 16 to move between an ablation state and a measurement state as described above. For example, when switch 16 is in the ablation state, the processor can cause the main antenna of switching antenna 22 to emit microwave energy, and when switch 16 is in the measurement state, the processor can cause radiometer 24 to receive a signal indicating temperature measurement from switching antenna 22 (e.g., from the main antenna and / or reference terminal). Additionally, the processor can guide switch bias duplexer 18 to move between a main antenna state and a reference terminal state as described above. For example, when switch bias duplexer 18 is in the main antenna state, the processor can receive a signal indicating the measured radiometer temperature from the main antenna of switching antenna 22, such as the temperature of tissue adjacent to switching antenna 22 during ablation, and when switch bias duplexer 18 is in the reference terminal state, it receives a signal indicating the measured reference temperature from the reference terminal of switching antenna 22. Therefore, the processor can calculate the volumetric temperature of the ablated tissue based on the signals. Furthermore, as part of the feedback loop, the processor can modulate the energy level emitted via the main antenna 43 based on the calculated volumetric temperature of the ablated tissue to ensure that the temperature of the target tissue is maintained within a predetermined threshold.

[0079] According to one aspect of the invention, the processor guides switch 16 to be in the ablation state for most of the ablation cycle (e.g., greater than 50%, greater than 75%, greater than 80%, or preferably greater than 90%) to maximize the power dissipated. Therefore, the processor can guide switch 16 to be in the measurement state for the remaining ablation cycle (e.g., less than 50%, less than 25%, less than 20%, or preferably less than 10%). Furthermore, during the ablation cycle, when switch 16 is in the measurement state, the processor can guide switch bias duplexer 18 to alternate between a primary antenna state and a reference terminal state.

[0080] For example, in a one-second cycle, the processor can guide switch 16 to be in an ablation state for 900 milliseconds, causing the primary antenna to emit microwave energy toward the target tissue within 900 milliseconds, and then guide switch 16 to be in a measurement state for 100 milliseconds. During the 100 milliseconds that switch 16 is in the measurement state, the processor-guided switch bias duplexer 18 alternates between the primary antenna state and the reference terminal state every, for example, 1, 2, 3, 4, or 5 milliseconds. As those skilled in the art will understand, the processor-guided switch 16 may be in the ablation state for more or less than 900 milliseconds, and the processor-guided switch bias duplexer 18 may alternate in each time period, including any time less than 1 millisecond or greater than 5 milliseconds. Furthermore, at least one of the switching components (e.g., switch 16 and switch bias duplexer 18) may be integrated into the switching antenna 22, as described in further detail below.

[0081] Microwave power propagates from generator 12 down along cable 20 in the catheter to switching antenna 22 at the catheter tip. Microwave power is radiated outward from the main antenna of switching antenna 22 into the target tissue (e.g., target lung tissue, such as a tumor). In other instances, such as in the case of an ablation system used for denervation, an introducer device may be used to deliver the catheter within the body cavity, and a spacer device may be used to ensure that switching antenna 22 is positioned approximately at the center of the body cavity. The flow of blood through the body cavity at body temperature cools the surfaces of the body cavity in direct contact with the blood. Alternatively, coolant introduced from outside the body through the coolant lumen of the catheter may be used to cool the surfaces of the body cavity. Tissue outside the lumen that has not undergone this cooling becomes heated. Sufficient microwave power is supplied to heat the target tissue (e.g., a nerve region) to a temperature that destroys the target tissue.

[0082] Figure 4 shows a computer simulation of the temperature field created by microwave heating. Figure 4 illustrates the cut through the switching antenna and surrounding tissue. The effect is symmetrical around the antenna, so only half of the cut plane is shown. The temperature along the radial conduit through the peak temperature represents the temperature within the target tissue. The temperature rises near the tissue surface inside the tissue and reaches its maximum at a depth near the target tissue. Figure 4 also illustrates the microwave power loss density pattern sensed by the switching antenna. Since the switching antenna and frequency are common to both the generator and the radiometer, the patterns produced for both functions are consistent, and the radiometer monitors the heated area in an optimal manner.

[0083] For reference Figures 5A to 5C A switching antenna 22 is provided for the microwave ablation system 10. The switching antenna 22 includes a main antenna 43 for both microwave heating and temperature sensing, and a reference terminal 48 for measuring a reference temperature (e.g., the temperature adjacent to the switching antenna 22). For example, the main antenna 43 of the switching antenna 22 includes one or more microwave radiating elements, such as a first microwave radiating element 44a and a second microwave radiating element 44b, which are designed to receive power from the generator 12 via cable 20 and to emit microwave energy into the surrounding target tissue at a level sufficient to ablate the target tissue.

[0084] The main antenna 43 of the switching antenna 22 further includes components for detecting microwave emissions from a region surrounding the antenna (e.g., one or more circuits formed by microwave radiating elements 44a, 44b) and converting these microwave emissions into a temperature of tissue adjacent to the switching antenna 22 (i.e., a radiometer temperature). The switching antenna 22 further includes a reference terminal 48 for measuring a reference temperature. Additionally, the switching antenna 22 integrates a switching network 42 (e.g., a Dick switch) disposed between the dipole halves of the microwave radiating elements 44a, 44b of the main antenna 43 of the switching antenna 22. As described in detail above, the processor can guide the switching network 42 to alternate between allowing microwave energy emission via the main antenna 43 and allowing temperature measurement via the main antenna 43 or the reference terminal 48.

[0085] The volumetric temperature output will be the difference between the radiometer temperature (e.g., the temperature of the heated tissue surrounding the main antenna 43) and the reference temperature measured by the reference terminal 48. The volumetric temperature output can be calculated using algorithms (e.g., those described in U.S. Patent Nos. 8,932,284 and 8,926,605, which are incorporated herein by reference) based on signals indicating the measured radiometer temperature from the microwave radiating elements 44a, 44b of the main antenna 43 and signals indicating the measured reference temperature from the reference terminal 48.

[0086] Specifically, all switching components (e.g., switching diodes 46a, 46b and reference terminal 48) are located at the junction of the two antenna dipole halves. The junction between the two antenna dipole halves may have a length of, for example, no more than 5 mm and preferably no more than 3 mm. Therefore, the integrated antenna / switch configuration of the microwave ablation system 10 is physically shorter and more flexible. Switching diodes 46a, 46b are switched by biasing them to be on or off, and switching diodes 46a, 46b are switched to the same state uniformly. Therefore, only a single bias source is required, and this single bias source can be operatively coupled to the switching diodes 46a, 46b via the conductor of cable 20. Switching diodes 46a, 46b may be, for example, microwave PIN diodes, and are biased with a small forward current in the on state or reverse biased with a negative voltage in the off state.

[0087] Additionally, a microwave choke arrangement 52 is provided to minimize the radiation pattern of microwave energy from the microwave radiating elements 44a, 44b to the foldback on the coaxial conduit shaft. The choke is formed by connecting the near-end dipole half (e.g., microwave radiating element 44a) to the cable 20 at the feed point of the main antenna 43. A coaxial structure is formed between the microwave radiating element 44a and the cable 20, which creates an open-circuit choke between the main antenna 43 and the cable 20.

[0088] The input from the main antenna 43 or the reference terminal 48 is selected by reversing the polarity of the bias current applied to the center conductor 39 of cable 20. Depending on the bias polarity, the series-connected switching diodes 46a, 46b are either small resistors that transmit microwave signals or small capacitors that block signals. A resistor (e.g., bias component 53) allows the bias current to return through the outer conductor 41 of cable 110. A bias current duplexer supplies bias to the proximal end of the conduit outside the body.

[0089] The chip-level switching components (diodes, resistors, and capacitors) are very small and reside on ceramic cards within a short space between the dipole halves of microwave radiating elements 44a and 44b. Cable 20 and the antenna structure are formed of a flexible material that can navigate through the enclosed channel. The only rigid section can be a switching network 42 with a length not exceeding approximately 3 mm.

[0090] System 10 is suitable for applications such as lung tissue ablation, where the reference terminal 48 must establish a reference temperature. For this reason, the reference terminal 48 is located on the near-end side of the antenna structure, so that the temperature sensor does not have to cross the feed point of the main antenna 43 (which would disrupt the antenna radiation pattern). A thermocouple circuit formed by the outer conductor 41 and a very fine, dissimilar metal wire terminated near the reference resistor of the reference terminal 48 can be used for this purpose.

[0091] like Figure 6 As illustrated in the diagram, microwave radiating elements 44a and 44b are fundamental dipoles that receive power from generator 12 via cable 20. Figure 6 As shown, microwave radiating elements 44a and 44b can have a cylindrical shape. As those skilled in the art will understand, microwave radiating elements 44a and 44b can have other shapes including helical windings. A balun transformer is located within each of the microwave radiating elements 44a and 44b. The balun transformer transforms a single-ended transmission line system into a balanced system, such as... Figure 7 As shown in the image, Figure 7 Illustrated explanation of balanced and unbalanced transformer 54a.

[0092] Now for reference Figure 8 This provides an alternative exemplary microwave ablation system 60. The microwave ablation system 60 is constructed as similar to... Figure 3 The microwave ablation system 10, wherein similar components are identified by similar apostrophe reference numbers. For example, cable 20' corresponds to cable 20, switching antenna 22' corresponds to switching antenna 22, main antenna 43' corresponds to main antenna 43, microwave radiating elements 44a' and 44b' correspond to microwave radiating elements 44a and 44b, switching diodes 46a' and 46b' correspond to switching diodes 46a and 46b, and reference terminal 48' corresponds to reference terminal 48. Figure 8As shown, the balanced and unbalanced transformers 54a and 54b are located in each of the microwave radiating elements 44a and 44b, respectively.

[0093] The microwave ablation system 60 differs from the microwave ablation system 10 in that the reference terminal 48' is positioned at the distal end of the second microwave radiating element 44b'. Specifically, the switching antenna 22' integrates a switching network (e.g., a Dick switch containing switching diodes 46a', 46b') into the main antenna 43', which allows the reference terminal 48' to protrude from the distal end of the main antenna 43'. Therefore, system 60 can be used in applications such as renal denervation, where the reference terminal 48' can be maintained at body temperature via blood flow.

[0094] The structure of the primary antenna 43' is unique because it integrates the radiometer Dick switch function into a flexible remote antenna and allows the radiometer reference terminal 48' to protrude from the primary antenna 43' into a stable temperature region (e.g., a blood flow path). The volumetric temperature output will be the difference between the radiometer temperature (e.g., the temperature of heated tissue surrounding the primary antenna 43') and a reference temperature (e.g., a known stable body temperature provided by blood flow via the reference terminal 48', for example, in a renal artery). The volumetric temperature output can be calculated using algorithms (e.g., those described in U.S. Patent Nos. 8,932,284 and 8,926,605, which are incorporated herein by reference) based on signals from the microwave radiating elements 44a', 44b' of the primary antenna 43' indicating the measured radiometer temperature and signals from the reference terminal 48' indicating the measured reference temperature.

[0095] like Figure 9A The diagram illustrates that microwave radiating elements 44a' and 44b' comprise two back-to-back balanced and unbalanced transformers 54a and 54b. (As shown in the diagram...) Figure 9B As shown, two switching diodes (e.g., switching diodes 46a' and 46b') are integrated within the microwave radiating elements 44a' and 44b' of the main antenna 43'. Switching diode 46a' is positioned between baluns 54a and 54b, and switching diode 46b' is positioned at the distal end of balun 54b, for example, between balun 54b and reference terminal 48' (not shown). When switching diodes 46a' and 46b' are closed, the single-ended input is converted to a balanced output connected to the microwave radiating elements 44a' and 44b'. Balun 54a is shorted at the distal end of the main antenna 43' and thus becomes an open circuit at the balanced output. When switching diodes 46a' and 46b' are open (e.g., ...), the single-ended input is converted to a balanced output connected to the microwave radiating elements 44a' and 44b'. Balun 54a is shorted at the distal end of the main antenna 43' and thus becomes an open circuit at the balanced output. Figure 9A When (as shown in the diagram), no changes are made and the structure is such that it reaches the far end of the main antenna 43' (where a reference terminal is located, for example, reference terminal 48', as shown in the diagram). Figure 9BThe straight-through transmission pipeline path is illustrated in the diagram.

[0096] Figure 9B The diagram illustrates the switching antenna 22', which includes: back-to-back balanced / unbalanced transformers 54a and 54b, with switching diodes 46a' and 46b' integrated therein; and a reference terminal 48', which has a bias blocking capacitor 56 and a reference terminal resistor 58. (See diagram for details.) Figure 9B The diagram further illustrates that connection 62a is connected to microwave radiating element 44a', and connection 62b is connected to microwave radiating element 44b'. Switching diodes 46a' and 46b' are actuated by biasing them to be on or off, and are uniformly switched to the same state. Therefore, only a single bias source is required, and this single bias source can be operatively coupled to switching diodes 46a' and 46b' via the conductor of cable 20.

[0097] The switching diodes 46a' and 46b' can be, for example, microwave PIN diodes, and are biased with a small forward current in the ON state or reverse biased with a negative voltage in the OFF state. A bias blocking capacitor 56 prevents bias current dissipation in the reference terminating resistor 58 of the reference terminal 48'. The reference terminating resistor 58 can be located at any distance from the balancing / unbalancing transformers 54a and 54b of the microwave radiating elements 44a' and 44b' to minimize heating of the reference terminal 48', provided that the connecting transmission line has the same characteristic impedance as the reference terminating resistor 58.

[0098] For reference Figure 10A and 10B This provides antenna power loss density patterns for two switching positions (e.g., on and off) of switching diodes 46a' and 46b'. For example, Figure 10A The diagram illustrates the power dissipation in the tissue during operation of the switching antenna 22' when switching diodes 46a' and 46b' are biased to be on. Figure 10A As shown in the figure, the tissue volume at a predetermined depth within the target tissue (e.g., where the target tissue to be ablated is located) is heated to a desired temperature sufficient for ablation. Figure 10B The diagram illustrates the power dissipation in the tissue when switching diodes 46a' and 46b' are biased to be off, and therefore the dissipation is not shown, indicating that the switching antenna 22' only detects the reference terminal 48'.

[0099] To overcome the challenges of constructing balanced-unbalanced structures and mounting switching diodes within flexible, small-diameter conduits, a three-conductor transmission line structure is used to form balanced-unbalanced transformers 54a and 54b, such as... Figure 11 As shown in the image. Figure 11As illustrated in the diagram, a thin, flexible dielectric substrate 64 includes a center conductor 66 printed on the top surface of the substrate 64 and two split ground conductors 68a, 68b printed on the bottom surface of the substrate 64. The substrate 64 may be (for example) at most 0.005” thick, and preferably up to 0.005 inches thick. Additionally, the substrate 64 has a relatively high dielectric constant, for example, at least approximately 10. The transmission line impedance is a function of the conductor width and the size of the gap between the split ground conductors 68a, 68b.

[0100] The switching antenna 22' may need to bend during delivery to the target tissue site, for example, from the femoral artery to the renal artery. To keep the geometry of the switching antenna 22' small, an unencapsulated diode is used and encapsulated to prevent damage when the main antenna 43' bends. For example, Figure 12 The diagram illustrates the diode chip 70 and ribbon connection 76 located on the top-side circuit trace 72, as well as the encapsulant 74. Additionally, Figure 12 The diagram illustrates connection 62a, which is connected to microwave radiating element 44a', and connection 62b, which is connected to microwave radiating element 44b'.

[0101] In embodiments where the main antenna 43' is rigid in one plane of the substrate, the main antenna 43' is flexible in at least one plane, allowing it to navigate, for example, bends in a patient's artery. For instance, the main antenna 43' may be relatively rigid in the plane of the substrate 64, but may be coiled in a plane perpendicular to the substrate 64. This is considered flexible enough that only twisting of the catheter is required to orient it in the direction of the desired bend. Therefore, the structure of the main antenna 43' allows it to be flexible in at least one plane, and preferably in two planes. Foam dielectric may be used to fill the areas above and below the substrate 64 beneath the microwave radiating elements 44a', 44b'. Braided metal shielding may also be used to cover the baluns 54a, 54b beneath the microwave radiating elements 44a', 44b'.

[0102] For reference Figure 13 Provides an exemplary ablation system with a coolant jacket mounted on it. For example... Figure 13 As shown, the coolant sheath 80 can be mounted on the cable 20 and the switching antenna 22. The coolant sheath 80 may include an inner tube 82 having a channel 84 sized and shaped to surround the cable 20 and the switching antenna 22 and allow coolant to flow through it. The inner tube 82 may be coaxial with the cable 20 and the switching antenna 22. Additionally, the coolant sheath 80 may include an outer tube 86 having a channel 88 in fluid communication with the channel 84 of the inner tube 82 via a junction cavity 89, allowing coolant to flow through the channel 84, the junction cavity 89, and... Figure 13The arrows in the diagram indicate that the water flows out through channel 88. (As shown in the image) Figure 13 As shown, the outer tube 86 can also be coaxial with the cable 20 and the switching antenna 22. Therefore, the proximal end of the coolant sleeve 86 can be fluidly connected to a coolant source. As the coolant flows past the switching antenna 22, it cools the surface of the switching antenna 22 and prevents heating of the switching antenna 22 from exceeding a predetermined amount. The coolant sleeve 80 allows for closed-loop cooling, ensuring that the coolant remains within the coolant sleeve 80 and does not leak into the patient's body. As described in further detail below, the coolant sleeve 86 can also be used to prevent heating of the reference terminal 42 from exceeding a predetermined amount during pre-ablation calibration. The coolant can also be used to cool the surface of the ablated tissue, thereby allowing energy to deposit deeper into the target tissue. Thus, peak temperatures are achieved deep within the tissue rather than at the surface, as... Figure 4B As shown.

[0103] For reference Figure 14 An exemplary method 100 for ablation of target tissue according to the principles of the present invention is provided. During pre-ablation, at step 101, the system processor may perform reference terminal calibration to take into account the effect of microwave energy emission on the reference terminal. For example, there is a temperature offset between the primary antenna 43 (e.g., a reference temperature sensor (thermocouple) outside the switching antenna 22) and the reference terminal 42 (e.g., a microwave reference terminal within the switching antenna 22). This offset is a function of the thermal resistance between the primary antenna 43 and the reference terminal 42. Heating of the reference terminal 42 is caused by the dissipation of a small amount of microwave ablation power applied in the primary antenna 43. Calibration of the reference terminal 42 involves using a radiometer 24 to measure the temperature rise of the reference terminal 42 while maintaining a constant temperature for measuring tissue adjacent to the switching antenna 22.

[0104] Figure 15The illustration depicts step 101 of an exemplary method for performing reference terminal calibration. At step 108, the switching antenna 22 is positioned in a thermostatic bath, which acts as a dissipative structure. In practice, the normal temperature measurement is performed in reverse, where the known reference is the water bath as seen by the main antenna 43, and the unknown reference is the reference terminal 42. At step 109, a high circulating fluid flow is provided in the bath so that the environment around the switching antenna 22 is not heated, as the high fluid flow carries away all the heat generated by the microwave energy emitted by the main antenna 43. At step 110, varying levels of microwave energy are emitted via the main antenna 22. Due to the microwave energy passing through the cable / circuit, the reference terminal 42 is slightly heated, and for each of the varying levels of energy emitted, the voltage caused by the energy emitted by the reference terminal 42 is measured. As explained above, due to the high flow bath across the main antenna 43, the environment around the switching antenna 22 is not heated when varying levels of microwave energy are emitted. At step 111, the measured voltage is compared with the energy emission at varying levels to account for the effect of energy emission on the reference terminal 42 during energy emission via the main antenna 43. Specifically, a comparison of the temperature of the reference terminal 42 with respect to an external temperature sensor reveals a linear relationship with the applied microwave power, the slope of which is the thermal resistance. This thermal resistance constant, multiplied by the applied power level, yields the temperature of the reference terminal 42 during ablation.

[0105] Refer again Figure 14 During pre-ablation, at step 102, the system processor can perform radiometer calibration to take into account the effects of microwave energy emission on the environment of adjacent target tissue during energy emission via the main antenna 43. Radiometer calibration provides the ability to determine the effect of microwave energy sensed by radiometer 42 on the ambient temperature of adjacent target tissue during energy emission.

[0106] For reference Figure 16AAn exemplary method 102 for performing reference terminal calibration is provided. At step 112, the switching antenna 22 is located in a thermostatic bath. At step 113, a known microwave noise source calibrated to a temperature is used to impinge the main antenna 43 at a first noise level to establish a first known temperature, and at step 114, the first temperature is measured. At step 115, a known microwave noise source calibrated to a temperature is used to impinge the main antenna 43 at a second noise level different from the first noise level to establish a second known temperature, and at step 116, the second temperature is measured. Therefore, the reference terminal 42 does not need to be cooled during this radiometer calibration. At step 117, the first and second measured temperatures are compared with the first and second noise levels to calibrate the effects of energy emission via the main antenna 43 on the environment adjacent to the switching antenna 22. Furthermore, when measuring the first and second temperatures, the first and second output voltages caused by the energy emission generated by the reference terminal 42 can be recorded, so that the temperature difference between the first and second temperatures divided by the voltage difference provides the sensitivity of the radiometer 24 per volt.

[0107] For reference Figure 16B An alternative exemplary method 102' for performing reference terminal calibration is provided. At step 118, the switching antenna 22 is located in a first bath having a first known temperature. At step 119, a radiometer signal is applied to the main antenna 43, and at step 120, a first output voltage caused by energy emission generated by the reference terminal 42 in response to the application of the radiometer signal is measured. At step 121, the switching antenna 22 is located in a second bath having a second known temperature different from the first temperature. At step 122, a radiometer signal is again applied to the main antenna 43, and at step 123, the first output voltage caused by energy emission generated by the reference terminal 42 in response to the application of the radiometer signal is measured. As described above, coolant flow is permitted across the switching antenna 22, thereby cooling the switching antenna 22. Therefore, when placed in two different baths with different temperatures, the temperature of the reference terminal 42 does not change; the only temperature increase is the temperature increase of the unknown environment adjacent to the switching antenna 22. At step 124, the first measured output voltage and the second measured output voltage are compared with the first known temperature and the second known temperature to calibrate the effect of energy emission via the main antenna 43 on the environment adjacent to the switching antenna 22. As those skilled in the art will understand, users can use radiometer calibration method 102 or 102', and can further perform reference terminal calibration step 101 and radiometer calibration methods 102, 102' in any preferred order.

[0108] Refer again Figure 14At step 103, the switching antenna 22 is located near the target tissue (e.g., lung tissue). At step 104, as described above, the process alternately switches between allowing the main antenna 43 to emit microwave energy and allowing the main antenna 43 to measure the radiometer temperature as a result of the energy emitted by the main antenna 43 via the switching network of the switching antenna 22. At step 105, the processor switches between allowing the main antenna 43 to measure the radiometer temperature and allowing the reference terminal 42 to measure the reference temperature. For example, as described above, in an ablation cycle (which can be repeated as needed), the main antenna 43 may emit microwave energy for more than 90% of the ablation cycles to maximize power dissipation, and the main antenna 43 and the reference terminal 42 may alternately measure the radiometer temperature and the reference temperature, respectively, for the remaining ablation cycles. At step 106, the processor may calculate the target tissue temperature based on the measured radiometer temperature and the measured reference temperature, using the calibrated values ​​described above, to take into account the effects of energy emission on the reference terminal 42 and the effects of microwave energy emission on the environment of the adjacent target tissue during energy emission via the main antenna 43. For example, Figure 17 It is a graph illustrating the temperature of the target tissue measured during microwave ablation.

[0109] Refer again Figure 14 At step 107, the processor can estimate the volume of ablation damage caused by microwave energy emission via the main antenna 43 during the ablation procedure based on the target tissue temperature. Specifically, the volume of ablation damage formed by energy emission during the ablation procedure can be estimated based on at least one of the average target tissue temperature or the area under the plotted curve of the target tissue temperature. For example, Figure 18A The diagram illustrates the plotting of the average target tissue temperature versus the estimated ablation damage volume, while Figure 18B The graph illustrates the area under the curve plotted by the radiometer for target tissue temperature versus the estimated ablation lesion volume. Furthermore, the estimated ablation lesion volume can be used to allow for titration of energy emission to achieve the desired therapeutic goal.

[0110] For reference Figure 19 Algorithms programmed into the processor described above can be used to detect and / or predict mutations, such as vapor mutations. Figure 19 As shown, mutation condition 90 indicates a rapid rise in target tissue temperature followed by a sudden drop in target tissue temperature. A sudden drop could indicate that the antenna has been moved out of position and therefore heating of the target tissue has ceased. Therefore, when the processor monitors the target tissue temperature in real time, it can detect when the target tissue temperature rises too quickly or exceeds a predetermined threshold and predict when a mutation condition will be observed. When mutation condition 90 is detected or predicted, the processor can automatically cut off heating and / or generate an alert to notify the user of a problem.

[0111] Alternatively, the processor can be programmed to automatically modulate the energy emission via the main antenna 22 in response to the detection or prediction of abrupt changes, thereby preventing overheating and / or other problems in the target tissue. For example, if abrupt changes are predicted, the energy emission via the main antenna can be modulated to reduce at least one of the target tissue temperature or the rate of increase in the target tissue temperature. The detection and prediction of abrupt changes improve the safety and efficacy of the ablation system described herein. Furthermore, the processor can be coupled to a display to show the monitoring of the target tissue temperature, allowing the user to visualize abrupt changes within the target tissue temperature. Additionally, the temperature can be controlled to a set temperature point by modulating the power to achieve a constant temperature.

[0112] The clinical test results discussed below confirm the efficacy of the microwave heating and measurement system described in this article. For example, Figure 20 The diagram illustrates data indicating microwave ablation-induced thermal damage in homogeneous tissues.

[0113] Figures 21A to 21C The diagram illustrates test results for a radiator using an ablation system based on the principles of the present invention. For example, a glass tube is positioned within the ablation field to remove heat from the heating zone. This simulates a blood vessel. Figures 21A to 21C As shown, a lower area under the radiometer curve (“Rad AUC”) is obtained when the flow in the tube (or radiator) is open compared to when the flow in the tube (or radiator) is closed. This is associated with a smaller damage size. Therefore, the volume of the damage can be determined even when a radiator (e.g., a blood vessel) is present to carry heat away from the ablation area. Known methods only allow the user to control the power and set the power level and time, which does not allow the user to determine whether the heat is effectively heated and destroys the tissue. For example, the user cannot know whether there are ten blood vessels carrying away the heat (and producing a smaller damage) or no blood vessels carrying away the heat. According to the principles of the invention, the user can more accurately predict the size of the damage when a radiator, such as a blood vessel, is present.

[0114] Figure 22 The illustration shows the results of a radiator test on bovine liver using ablation surgery performed according to the principles of the invention. Specifically, a more extreme example of a radiator is simulated. The antenna is positioned directly below the surface of the tissue, which is placed in a water bath. Thus, on one side, the antenna sees all the tissue, while on the other side, it sees less tissue and mostly water / saline. Furthermore, the flow of water is created to remove heat from the water, an extreme form of heat dissipation. Again, here, the radiometer can detect when there is a significant radiator, where the antenna is close to the surface and the water will carry away the heat (low AUC), and when there is no radiator (completely embedded in the tissue), thus resulting in higher heating and a higher AUC.

[0115] Figure 23 The illustration shows the results of a lung ablation test on bovine liver using an ablation procedure performed according to the principles of this invention. Compared to the highly homogeneous liver tissue discussed above, liver tissue is heterogeneous, containing elements such as cavitation and connective tissue. For example... Figure 23 As demonstrated, the microwave ablation system constructed according to the principles of this invention can be further used for heterogeneous tissues to predict ablation lesion volumes that have a strong AUC correlation with lesion volume. Furthermore, Figure 24A The diagram illustrates the radiometer AUC data resulting from lung ablation testing, and Figure 24B The diagram illustrates data on the energy delivered as a result of a lung ablation test. Specifically, Figure 24A The diagram illustrates the regression of the radiometer's AUC on diameter, length, and volume (from left to right). Figure 24B The diagram illustrates the regression of delivered microwave energy on diameter, length, and volume (from left to right).

[0116] For reference Figure 25A This provides the basic dipole of the microwave radiating element for the switching antenna of an exemplary microwave ablation system. Specifically, Figure 25A Diagrammatic Explanation and Figure 5A The switching antenna 22 is constructed similarly to the switching antenna, wherein the switching network is omitted for clarity. For example... Figure 25A As shown, the switching antenna includes microwave radiating elements 44a and 44b, forming two dipole halves of the switching antenna. As described above, a microwave choke device 52 at the near end of microwave radiating element 44a minimizes the foldback of the microwave energy radiation field pattern from microwave radiating elements 44a and 44b onto the coaxial conduit shaft. This choke is formed by connecting the near-end dipole half (e.g., microwave radiating element 44a) to cable 20 at the feed point of the switching antenna. The coaxial structure formed between microwave radiating element 44a and cable 20 results in an open-circuit choke between the switching antenna and cable 20.

[0117] like Figure 25B As shown in the figure, by short-circuiting the near end of the microwave radiating element 44a” to eliminate the choke effect of the microwave radiating element 44a”, the microwave radiating element 44a” can be... Figure 25A The basic dipole of the switching antenna is converted into a monopole. Therefore, microwave radiating elements 44a” and 44b” can form a monopole. Figure 25C As shown, a monopole can have a diameter similar to that of a 20” cable, thus providing a switching antenna with a smaller overall diameter. The radiating foldback mode of the monopole is tolerable because the applications described herein may require a smaller diameter device.

[0118] For reference Figure 26A Diagrammatic Explanation Figure 25B and25C The switching antenna is depicted, with switching network 42" shown. (e.g.) Figure 26A As shown, the switching network 42” can be located at the junction between microwave radiating elements 44a” and 44b”. Figure 26B As shown, in addition to the first switching diode 46a and the second switching diode 46b, the switching network 42” may further include a third switching diode 46c and an additional bias element 53”. The switching network 42” can be configured similar to Figure 5B The switching network 42. The third switching diode 46c can improve the isolation between the reference terminal 48” and the radiometer temperature, for example, during the ablation of the target tissue due to tissue heating caused by ablation.

[0119] For reference Figure 26C An alternative switching network is provided. Switching network 42”' further includes a fourth switching diode 46d in addition to the first switching diode 46a”, the second switching diode 46b”, and the third switching diode 46c’. The fourth switching diode 46d improves the isolation between the reference terminal 48”' and the radiometer temperature during reference temperature measurement. Figure 26C As shown, the fourth switching diode 46d and the second switching diode 46b can be connected in series with the main antenna (e.g., microwave radiating element 44b) and separated by a microstrip transmission line 92 on the switching network substrate. The microstrip transmission line 92 improves the isolation achieved by the two switching diodes 46b and 46d, which may be particularly useful for applications using higher ablation frequencies. As those skilled in the art will understand, the switching network 42" can be replaced Figure 26A The switching network 42 in the switching antenna.

[0120] For reference Figure 27A and 27B Diagrammatic Explanation Figure 26A A switching antenna, wherein the switching network 42” is pushed back from the monopole tip to accommodate a smaller diameter coaxial cable (e.g., cable 20”) at or near the main antenna (e.g., microwave radiating element 44b”). Figure 27A As shown, switching network 42” can be pushed back to the distal region of cable 20”, close to the proximal end of microwave radiating element 44b”. Another option is, as... Figure 27BAs shown, the switching network 42” can be further pushed back to the distal region of the cable 20”, for example, at a point along the cable 20” where the cable 20” transitions from a smaller diameter coaxial cable portion 20a” to a larger diameter coaxial cable portion 20b”. Specifically, since the switching network 42” can be located within the larger diameter coaxial cable portion 20b” of the cable 20”, further away from the microwave radiating element 44b”, the cable 20” can be contained within the smaller diameter coaxial cable portion 20a extending between the microwave radiating element 44b” and the switching network 42”.

[0121] The switching network 42” can be housed in the switching module 130, which can be configured to be removably coupled to a coaxial cable of the target device. For example... Figure 27B As shown, the switch module 130 can be removably connected via a proximal connector 96 to the distal end of the larger diameter coaxial cable portion 20b” of the cable 20”, and via a distal connector 94 to the proximal end of the smaller diameter coaxial cable portion 20a” of the cable 20”, thereby providing an electrical connection between the generator and the microwave radiating element 44b”. As those skilled in the art will understand, although Figure 27B A cable portion 20b” with a diameter greater than that of cable portion 20a” is depicted, but cable portions 20a” and 20b” may have the same diameter, so that cable 20” may have a uniform diameter throughout.

[0122] For reference Figures 28A to 28C Provides exemplary switch modules. For example... Figure 28A As shown, the switch module 130 may include a near-end connector 132a electrically coupled to a near-end connector 96, and a far-end connector 132b electrically coupled to a far-end connector 94. For example, the near-end connector 132a may have a cavity sized and shaped to receive a portion of the near-end connector 96, such that the near-end connector 132a and the near-end connector 96 can be releasably engaged, and the far-end connector 132b may have a cavity sized and shaped to receive a portion of the far-end connector 94, such that the far-end connector 132b and the far-end connector 94 can be releasably engaged. Therefore, the switch module 130 can be easily integrated with existing target devices.

[0123] like Figure 28A As shown, the switching network 42” can be mounted on the substrate 64”, which can be housed within the switching module 130. For example, as Figure 28B As shown, the switch module 130 may include a conductor 134, such as the center conductor of the coaxial cable 20", to provide an electrical connection between the cable 20" and the substrate 64" within the switch module 130. Furthermore, as... Figure 28CAs shown, the switch module 130 may further include a bracket 136 to provide support for the substrate 64” within the switch module 130.

[0124] For reference Figure 29 Diagrammatic Explanation Figure 26B Switching network 42" on substrate 64". For example Figure 29 As shown, the first switching diode 46a” and the second switching diode 46b” can be disposed on the first side of the substrate 64” (left figure), and the third switching diode 46c can be disposed on the opposite side of the substrate 64” (right figure).

[0125] While various illustrative embodiments of the invention have been described above, those skilled in the art will appreciate that various changes and modifications can be made herein without departing from the invention. It will be further understood that the systems and methods described herein can be used for ablation and temperature measurement of tissues other than the renal artery. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.

Claims

1. A system for ablating target tissue in a patient, the system comprising: The catheter has a proximal region and a distal region; A main antenna, comprising a monopole, is positioned at the distal region of the conduit and configured to emit energy to ablate the target tissue and measure the radiometer temperature resulting from the emission of the energy. A reference terminal is disposed at the distal region of the catheter, the reference terminal being configured to measure a reference temperature at the distal region; and A processor operatively coupled to the main antenna and the reference terminal, the processor being configured to: A switch electrically coupled to the main antenna and the reference terminal alternately causes the main antenna to measure the radiometer temperature and the reference terminal to measure the reference temperature; and The target tissue temperature is calculated based on the measured radiometer temperature and the measured reference temperature. The monopole includes a near-end radiating element and a far-end radiating element, wherein the nearest end of the near-end radiating element includes a short-circuit element configured to eliminate the choke effect at the nearest end of the near-end radiating element.

2. The system of claim 1, wherein the switch is configured to be disposed between the near-end radiating element and the far-end radiating element.

3. The system of claim 1, wherein the switch is configured to be disposed in a proximal region of the proximal radiating element, the proximal region being close to the junction between the proximal radiating element and the distal radiating element.

4. The system according to claim 1, wherein the switch comprises a first switching diode and a second switching diode.

5. The system of claim 4, wherein the switch includes a third switching diode configured to improve the isolation between the reference terminal and the radiometer temperature during ablation of the target tissue.

6. The system of claim 5, wherein the switch includes a fourth switching diode configured to improve isolation between the reference terminal and the radiometer temperature during measurement of the reference temperature.

7. The system of claim 6, wherein the second switching diode and the fourth switching diode are connected in series with the main antenna and separated by a microstrip transmission line.

8. The system of claim 1, further comprising a switch module configured to house the switch, the switch module including a proximal coaxial connector and a distal coaxial connector configured to be removably coupled to a coaxial cable of the conduit.

9. The system of claim 1, wherein the processor is further configured to estimate the volume of ablation damage formed during the ablation procedure due to the emission of energy based on the target tissue temperature.

10. The system of claim 9, wherein the processor is further configured to allow titration of the energy emission based on the estimated volume of the ablation damage.

11. The system of claim 1, wherein the processor is further configured to estimate the volume of ablation damage formed during the ablation procedure based on at least one of the average target tissue temperature or the area under the plotted curve of the target tissue temperature.

12. The system of claim 1, wherein the processor is further configured to allow titration of the energy emission based on the target tissue temperature.

13. The system of claim 1, wherein the processor is further configured to cause the primary antenna to emit energy and measure the temperature of the radiometer in an interleaved manner, and to cause the reference terminal to measure the reference temperature.

14. The system of claim 13, wherein the processor is configured to cause the primary antenna to emit energy during a first time period and to alternately cause the primary antenna to measure the radiometer temperature and the reference terminal to measure the reference temperature during a second time period.

15. The system of claim 14, wherein the first time period is at least 80% of the sum of the first time period and the second time period.

16. The system of claim 1, wherein the processor is further configured to modulate the emission of the energy such that the calculated target tissue temperature is maintained within a predetermined threshold.

17. The system of claim 1, wherein the processor is further configured to perform reference terminal calibration to take into account heating of the reference terminal during energy emission via the main antenna, and to perform radiometer calibration to take into account heating of the environment adjacent to the target tissue during energy emission via the main antenna.

18. The system of claim 17, wherein the processor is further configured to calculate the target tissue temperature based on the measured radiometer temperature and the measured reference temperature, while taking into account the heating of the reference terminal and the environment adjacent to the target tissue during energy transmission via the primary antenna.

19. The system of claim 1, further comprising a cooling sleeve disposed over at least the distal region of the catheter, the cooling sleeve being coupled to a coolant source and configured to allow coolant flow through the primary antenna and the reference terminal, thereby cooling the primary antenna and the reference terminal during pre-ablation calibration and during ablation procedure.

20. A system for ablating target tissue in a patient, the system comprising: The catheter has a proximal region and a distal region; A main antenna, comprising a monopole and disposed at the distal region of the duct, is configured to emit energy to ablate the target tissue and measure the radiometer temperature resulting from the emission of the energy. A reference terminal is disposed at the distal region of the catheter, the reference terminal being configured to measure a reference temperature at the distal region; and Processor, configured to: Reference terminal calibration is performed to account for heating of the reference terminal during energy emission via the main antenna, and radiometer calibration is performed to account for heating of the environment adjacent to the target tissue during energy emission via the main antenna; and The target tissue temperature is calculated based on the measured radiometer temperature and the measured reference temperature, while taking into account the heating of the reference terminal and the environment adjacent to the target tissue during energy transmission via the main antenna. The monopole includes a near-end radiating element and a far-end radiating element, wherein the nearest end of the near-end radiating element includes a short-circuit element configured to eliminate the choke effect at the nearest end of the near-end radiating element.

21. The system of claim 20, wherein the processor is configured to perform the reference terminal calibration by: measuring, for varying levels of energy emitted by the reference terminal, an output voltage caused by energy emission from the reference terminal, with respect to the main antenna and the reference terminal in a thermostatic bath, the thermostatic bath providing a high fluid flow across the main antenna such that the temperature of the environment adjacent to the main antenna remains constant; and comparing the measured output voltage with the varying levels of energy emission to take into account the effects of energy emission on the reference terminal during energy emission.

22. The system of claim 20 or 21, wherein the processor is configured to perform the radiometer calibration by: measuring a first temperature and a second temperature, respectively, in response to impacts to the main antenna at a first noise level and a second noise level, while the main antenna and the reference terminal are in a thermostatic bath; and comparing the first temperature and the second temperature with the first noise level and the second noise level to take into account the effects of energy emission on the environment adjacent to the target tissue during energy emission.

23. The system of claim 20 or 21, wherein the processor is configured to perform the radiometer calibration by: measuring a first output voltage and a first temperature in response to a first radiometer signal when the main antenna and reference terminal are in a first bath having a first temperature; measuring a second output voltage and a second temperature in response to a second radiometer signal when the main antenna and reference terminal are in a second bath having a second temperature different from the first temperature; and comparing the first output voltage and the second output voltage with the first temperature and the second temperature to take into account the effects of energy emission on the environment adjacent to the target tissue during energy emission.

24. The system of claim 20 or 21, further comprising a cooling sleeve disposed over at least the distal region of the conduit, the cooling sleeve being coupled to a coolant source and configured to allow coolant flow through the primary antenna and the reference terminal, thereby cooling the primary antenna and the reference terminal during radiometer calibration and during ablation procedures.

25. A system for ablating target tissue in a patient, the system comprising: The catheter has a proximal region and a distal region; A main antenna, comprising a monopole and disposed at the distal region of the duct, is configured to emit energy to ablate the target tissue and measure the radiometer temperature resulting from the emission of the energy. A reference terminal is disposed at the distal region of the catheter, the reference terminal being configured to measure a reference temperature at the distal region; and A cooling sleeve, disposed over at least the distal region of the conduit, is coupled to a coolant source and configured to allow coolant flow through the primary antenna and the reference terminal, thereby cooling the primary antenna and the reference terminal during pre-ablation calibration and during the ablation procedure. The monopole includes a near-end radiating element and a far-end radiating element, wherein the nearest end of the near-end radiating element includes a short-circuit element configured to eliminate the choke effect at the nearest end of the near-end radiating element.

26. The system of claim 25, further comprising a processor operatively coupled to the main antenna and the reference terminal, the processor being configured to calculate the target tissue temperature based on the measured radiometer temperature and the measured reference temperature.

27. The system of claim 26, wherein the processor is further configured to estimate the volume of ablation damage formed during the ablation procedure due to the emission of energy based on the target tissue temperature.

28. The system of claim 27, wherein the processor is further configured to allow titration of the energy emission based on the volume of the ablation damage.

29. A system for ablating target tissue in a patient, the system comprising: The catheter has a proximal region and a distal region; A main antenna, comprising a monopole and disposed at the distal region of the duct, is configured to emit energy to ablate the target tissue and measure the radiometer temperature resulting from the emission of the energy. A reference terminal is disposed at the distal region of the catheter, the reference terminal being configured to measure a reference temperature at the distal region; and Processor, configured to: The target tissue temperature is calculated based on the measured radiometer temperature and the measured reference temperature; and The volume of ablation damage caused by energy emission during the ablation procedure is estimated based on at least one of the average target tissue temperature or the area under the plotted curve of the target tissue temperature. The monopole includes a near-end radiating element and a far-end radiating element, wherein the nearest end of the near-end radiating element includes a short-circuit element configured to eliminate the choke effect at the nearest end of the near-end radiating element.

30. The system of claim 29, wherein the processor is further configured to allow titration of the energy emission based on the target tissue temperature.

31. The system of claim 29 or 30, wherein the processor is further configured to cause the primary antenna to emit energy and measure the radiometer temperature in an interleaved manner, and to cause the reference terminal to measure a reference temperature.

32. The system of claim 31, wherein the processor is configured to cause the primary antenna to transmit energy during a first time period and to alternately cause the primary antenna to measure the radiometer temperature and the reference terminal to measure the reference temperature during a second time period.

33. The system of claim 32, wherein the first time period is at least 80% of the sum of the first time period and the second time period.

34. The system of claim 32 or 33, wherein the processor is configured to alternately cause the main antenna to measure the radiometer temperature and the reference terminal to measure the reference temperature via a switch electrically coupled to the main antenna and the reference terminal.

35. The system of claim 32 or 33, wherein the processor is further configured to modulate the emission of the energy such that the calculated target tissue temperature is maintained within a predetermined threshold.

36. A system for ablating target tissue in a patient, the system comprising: The catheter has a proximal region and a distal region; A main antenna, comprising a monopole and disposed at the distal region of the duct, is configured to emit energy to ablate the target tissue and measure the radiometer temperature resulting from the emission of the energy. A reference terminal is disposed at the distal region of the catheter, the reference terminal being configured to measure a reference temperature at the distal region; and Processor, configured to: The target tissue temperature is calculated based on the measured radiometer temperature and the measured reference temperature; and Monitor the target tissue temperature to predict and / or detect abrupt changes within the target tissue temperature. The monopole includes a near-end radiating element and a far-end radiating element, wherein the nearest end of the near-end radiating element includes a short-circuit element configured to eliminate the choke effect at the nearest end of the near-end radiating element.

37. The system of claim 36, wherein the mutation indicates a rapid rise in target tissue temperature followed by a sudden drop in target tissue temperature.

38. The system of claim 36 or 37, wherein the processor is further configured to generate an alert if the mutation is detected.

39. The system of claim 36 or 37, wherein the processor is further configured to automatically modulate the transmission of the energy via the main antenna to reduce at least one of the target tissue temperature or the rate of increase of the target tissue temperature if the abrupt change is predicted.

40. The system of claim 36 or 37, further comprising a display operatively coupled to the processor, wherein the processor is further configured such that the display shows the abrupt change within the target tissue temperature.

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