Single-wire temperature measurement solution for field application systems and methods of making and using same

Abstract

The present invention discloses a transducer array, tumor treatment field system, and method. The transducer array includes a first electrode, a second electrode, a temperature sensing circuit, and leads. The temperature sensing circuit includes a first thermistor adjacent to the first electrode, the first thermistor being a first variable resistor whose resistance varies with temperature, and an RC circuit connected in series with the first thermistor, the RC circuit including a second thermistor adjacent to the second electrode, and a capacitor in parallel with the second thermistor, the second variable resistor whose resistance varies with temperature. The leads, configured to transmit electrical signals to the first and second electrodes, further include a first sensor wire electrically coupled to the first thermistor and a second sensor wire electrically coupled to the RC circuit on the opposite side of the first thermistor.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 377,820, filed September 30, 2022, entitled "SINGLE WIRE TEMPERATURE MEASUREMENT SOLUTION FOR A TTFIELD APPLICATION SYSTEM AND METHODS OF PRODUCTION AND USE THEREOF," the entire contents of which are expressly incorporated herein by reference. [Background technology]

[0002] A tumor treating field (TT field or TTF) is a low-intensity (e.g., 1-3 V / cm) alternating electric field in the mid-frequency range (e.g., 50-1 MHz, such as 50-500 kHz) that targets solid tumors by disrupting mitosis. This non-invasive treatment targets solid tumors and is described, for example, in U.S. Patent Nos. 7,016,725, 7,089,054, 7,333,852, 7,565,205, 8,244,345, 8,715,203, 8,764,675, 10,188,851, and 10,441,776. TT fields are typically delivered through two pairs of transducer arrays, each pair positioned on opposite sides of the body to generate perpendicular fields within the tumor being treated. More specifically, in the case of the OPTUNE® system, one pair of electrodes of the transducer array is placed on the left and right (LR) sides of the tumor, and another pair of electrodes of the transducer array is placed on the anterior-posterior (AP) sides of the tumor. TT fields have been approved for the treatment of multiforme neuroblastoma (GBM) and are delivered, for example, via the OPTUNE® system (Novocure Limited, St. Helier, Jersey), which includes a transducer array placed on the patient's shaved head. Recently, TT field therapy has been approved as a combination therapy with chemotherapy for malignant pleural mesothelioma (MPM), and may also be used to treat tumors in other parts of the body.

[0003] The device is intended for patients to wear continuously for 2-4 days, then remove for hygiene and reshaving (if necessary), after which a new set of arrays is reapplied. As patients use the device to perform daily activities, prolonged use of the device can cause the transducer array to become active and heat up. To ensure patient comfort while wearing the transducer array, a temperature sensor is placed within the array to monitor the temperature of the transducer array and skin interface.

[0004] The amplitude of the alternating current delivered through the transducer array is controlled so that the skin temperature (measured at the skin beneath the transducer array) does not exceed a comfort threshold. In existing Optune® systems, each array contains eight temperature sensors.

[0005] The temperature sensors of each transducer array are connected via wires to a controller, which measures the temperature from all the temperature sensors and converts each temperature sensor's analog value to a digital value. The controller uses the temperature measurements to control the current supplied through each pair of arrays to maintain the patient's skin temperature below a comfort threshold. The current itself is delivered to each array via additional wires (i.e., one wire for each array) that run from the electric field generator to the transducer arrays.

[0006] In the existing Optune® system, there are four long 10-wire cables (each running between a corresponding transducer array and the controller) running between the electric field generator and the controller. Each 10-wire cable has eight wires to carry signals from the eight temperature sensors, one wire common to all eight temperature sensors, plus one wire to provide the TT field signal to the transducer array.

[0007] Attaching temperature sensors and transducer arrays to a patient can be cumbersome due to the quality of the wires and the combined weight of the transducer array and wiring. Due to the increased number and weight of wires, patient movement can unintentionally loosen the transducer array, causing weight-related discomfort to the patient. Therefore, there is a need for a temperature measurement solution that uses fewer wires. The present disclosure is directed to such a system, as well as methods for making and using the same. Summary of the Invention

[0008] The problem of reducing the number of wires required for temperature measurement is solved by the systems and methods disclosed herein. The system can be a transducer array including a first electrode, a second electrode, a temperature sensing circuit, and leads. The temperature sensing circuit includes a first thermistor adjacent to the first electrode, the first thermistor being a first variable resistor whose resistance varies with temperature, and an RC circuit coupled in series with the first thermistor, the RC circuit including a second thermistor adjacent to the second electrode, and a capacitor in parallel with the second thermistor, the second variable resistor whose resistance varies with temperature. The leads, configured to transmit an electrical signal to the first and second electrodes, further include a first sensor wire electrically coupled to the first thermistor and a second sensor wire electrically coupled to the RC circuit on the opposite side of the first thermistor.

[0009] An exemplary method includes providing a TTF signal having a frequency in a range of 50 kHz to 1 MHz to a transducer array having a first electrode and a second electrode; providing a first sense signal having a first frequency to a temperature sensing circuit coupled in series with an RC circuit having a first thermistor adjacent to the first electrode, a second thermistor adjacent to the second electrode, and a capacitor in parallel with the second thermistor; measuring a first impedance of the temperature sensing circuit; providing a second sense signal having a second frequency greater than the first frequency to the temperature sensing circuit; measuring the second impedance of the temperature sensing circuit; measuring a first temperature of the first thermistor based on the second impedance; and measuring a second temperature of the second thermistor based on the first impedance and the second impedance.

[0010] The details of one or more implementations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages of the subject matter will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more implementations described herein and, together with the description, explain these implementations. The drawings are not intended to be drawn to scale, and certain features and certain views of the figures may be emphasized and shown to scale or in schematic form for the sake of clarity and conciseness. Not all components may be labeled in all figures. Like reference numbers in the figures may represent and refer to the same or similar elements or functions. In the drawings,

[0012] [Figure 1] 1 is an exemplary embodiment of a schematic diagram of electrodes applied to biological tissue. [Figure 2] 1 is an exemplary embodiment of an electronic device configured to generate a TT field constructed in accordance with the present disclosure. [Figure 3] FIG. 1 is a block diagram of an exemplary embodiment of a transducer array constructed in accordance with the present disclosure. [Figure 4] Capacitive reactance graph showing reactance against frequency, showing the reactance of two RC circuits when subjected to various frequencies. [Figure 5A] FIG. 1 is a schematic diagram of a temperature sensing circuit constructed in accordance with the present disclosure. [Figure 5B] FIG. 10 is a schematic diagram of another embodiment of a temperature sensing circuit constructed in accordance with the present disclosure. [Figure 6] FIG. 1 is a process flow diagram of a method for measuring the temperature of an electrode in a transducer array according to the present disclosure. [Figure 7] 1 is a parallel resistance-inductance-capacitance (i.e., RLC) circuit used to measure temperature in accordance with the present disclosure. [Figure 8] FIG. 8 is a schematic diagram illustrating the flow of an AC current tuned to the resonant frequency of the inductance and capacitance in the RLC circuit through the RLC circuit of FIG. 7. [Figure 9] 1 is a graph showing how the impedance of an RLC circuit changes when the frequency is changed. [Figure 10]FIG. 10 is a schematic diagram of another version of a temperature sensing circuit having three RLC circuits connected in series constructed in accordance with the present disclosure. [Figure 11] 11 is another impedance graph showing how the impedance of the temperature sensing circuit of FIG. 10 changes as the frequency is changed. [Figure 12] FIG. 10 is a process flow diagram of another method for measuring the temperature of electrodes in a transducer array in accordance with the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] Before describing at least one embodiment of the inventive concept(s) in detail by way of illustrative language and results, it should be understood that application of the inventive concept(s) is not limited to the details of construction and the arrangement of components set forth in the following description. The inventive concept(s) may be embodied in other embodiments or may be practiced or carried out in various ways. Therefore, the words used herein are intended to be accorded the broadest possible scope and meaning. Also, the embodiments are intended to be illustrative, not exhaustive. It should also be understood that the terminology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

[0014] Names are provided for convenience only and should not be construed as limiting the invention in any aspect. Embodiments shown under any heading or in any portion of this disclosure may be combined with embodiments shown under the same or any other heading or portion of this disclosure. Unless otherwise indicated herein or clearly contradicted by context, all possible combinations of the elements described herein in all possible variations are included in this disclosure.

[0015] Unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[0016] All compositions, assemblies, systems, kits, and / or methods disclosed herein can be made and performed without undue experimentation in light of this disclosure. Thus, unless a method claim specifically recites in the claim or description that the steps are limited to a particular order, no order is intended to be inferred in any respect. This applies to any implied basis of interpretation, including questions of logic regarding the arrangement of steps or operational flow, the simple meaning derived from grammatical construction or punctuation, and the number or type of embodiments described in the specification.

[0017] In the claims and / or specification, the use of the terms "a" or "an," when used in conjunction with the term "comprising," can mean "one," but is consistent with the meanings of "one or more," "at least one," and "one or more." "Plurality" can refer to "two or more."

[0018] Furthermore, use of the term "at least one of X, Y, and Z" is understood to include X alone, Y alone, and Z alone, as well as any combination of X, Y, and Z. Use of sequential terminology (e.g., "first," "second," "third," "fourth," etc.) is for the purpose of distinguishing between two or more items only and does not imply, for example, any order or priority or importance of one item over another or any order of additional items.

[0019] Use of the term "or" in the claims is used to mean an inclusive "and / or" unless expressly indicated to refer to alternatives only or unless the alternatives are mutually exclusive.

[0020] As used herein, a circuit may be analog and / or digital components, or one or more appropriately programmed processors (e.g., microprocessors) and associated hardware and software, or hardwired logic. Also, a "component" may perform one or more functions. A "component" may include hardware, such as a processor (e.g., a microprocessor), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of hardware and software. As used herein, the term "processor" refers to a single processor or multiple processors operating independently or cooperatively to jointly perform a task. A processor may be in communication with a non-transitory computer-readable medium that stores computer-executable instructions that, when executed by the processor, cause the processor to perform a specified function. Exemplary non-transitory computer-readable media may include non-volatile memory, random access memory (RAM), read-only memory (ROM), CD-ROM, hard drive, solid-state drive, flash drive, memory card, DVD-ROM, Blu-ray disc, laser disc, magnetic disk, optical drive, combinations thereof, and / or others.

[0021] As used herein, TT field (TT field, or TTF(s)) refers to a medium-frequency (approximately 50 kHz to 1 MHz, more preferably approximately 50 kHz to 500 kHz), low-intensity (e.g., 1 to 4 V / cm) alternating electric field that, when applied via electrodes to a conductive medium such as the human body, can be used to treat tumors, as described, for example, in U.S. Pat. Nos. 7,016,725, 7,089,054, 7,333,852, 7,565,205, 7,805,201, and 8,244,345 by Palti (each of which is incorporated herein by reference). TT fields have been shown to be capable of specifically acting on cancer cells and are useful in the treatment of cancers, among other things. TT field therapy is an approved monotherapy for recurrent glioblastoma (GBM) and an approved combination therapy with chemotherapy for newly diagnosed GBM patients.

[0022] As used herein, the term TTS signal is an electrical signal that, when received by electrodes applied to a conductive medium such as the human body, causes the electrodes to generate the TT field described above. TT signals are often alternating current electrical signals.

[0023] As used herein, unless the context clearly dictates otherwise, all numerical values ​​or ranges include values ​​within such ranges and fractional integers within such ranges. Numerical ranges specified herein include endpoints, all values, subranges of values ​​within the ranges, and values ​​and fractional integers within said ranges. Thus, for example, any two values ​​within the range of 1 mm to 10 m can be used to establish the lower and upper limits of a range according to embodiments of the present disclosure.

[0024] Illustrated here is an exemplary embodiment of a dividing cell 10 under the influence of an external TTF field, generally depicted as line 14, generated by a negatively charged first electrode 18a and a positively charged second electrode 18b. Also shown are microtubules 22, known to have a very strong dipole moment. This strong polarization makes the microtubules 22, as well as other polar macromolecules, particularly those with a specific orientation within the cell 10 or its surroundings, susceptible to the effects of the electric field. The positive charges on the microtubules 22 are located at the two centrioles 26, and two sets of negative poles are located at the center 30 of the dividing cell 10 and at the attachment points 34 of the microtubules 22 to the cell membrane. The locations of the charges form a double dipole assembly, making them susceptible to the effects of electric fields of different directions. In one embodiment, the cells are electroporated, i.e., DNA or chromosomes are introduced into the cells using an electric pulse, temporarily opening pores in the cell membrane.

[0025] Returning to FIG. 2, the beneficial TT field for destroying tumor cells described above may be generated by electronic device 50. FIG. 2 is a simplified schematic diagram illustrating the major components of electronic device 50. Electronic device 50 includes an electric field generator 54 and a pair of conductive leads 58, including a first conductive lead 58a and a second conductive lead 58b. First conductive lead 58a has a first end 62a and a second end 62b. Second conductive lead 58b has a first end 66a and a second end 66b. First end 62a of first conductive lead 58a is conductively attached to electric field generator 54, and first end 66a of second conductive lead 58b is conductively attached to electric field generator 54.

[0026] The electric field generator 54 is configured to provide power and generate as an output a desired electrical signal (TTS signal) in the form of a waveform or pulse train. The second end 62b of the first conductive lead 58a is connected to the transducer array 70a, and the second end 66b of the second conductive lead 58b is connected to the transducer array 70b. Both the transducer array 70a and the transducer array 70b are supplied with an electrical signal (e.g., a TT signal, waveform). When supplied with the electrical signal, the transducer array 70a and the transducer array 70b pass a current between the transducer array 70a and the transducer array 70b. This current generates an electric field (TT field) of a certain frequency and amplitude that is generated between the transducer array 70a and the transducer array 70b.

[0027] Although the electronic device 50 shown in FIG. 2 includes only two transducer arrays 70 (i.e., transducer array 70a and transducer array 70b), in some embodiments, the electronic device 50 may include three or more transducer arrays 70.

[0028] The electric field generator 54 generates an AC voltage waveform (i.e., a TT signal) at a frequency ranging from about 50 kHz to about 1 MHz (preferably from about 100 kHz to about 500 kHz). The required voltage is such that the electric field strength in the tissue within the treatment region ranges from about 0.1 V / cm to about 10 V / cm. To achieve this electric field strength, the potential difference between the two conductors 18 (e.g., electrode elements 78 in FIG. 3) in each transducer array 70a or transducer array 70b depends on the relative impedances of the system components; for example, the fraction of the electric field on each component is determined by the impedance of that component divided by the impedance of the overall circuit.

[0029] In certain (but non-limiting) embodiments, transducer arrays 70a and 70b generate alternating currents and fields within a target region of a patient. The target region typically includes at least one tumor, and the generation of the alternating currents and fields selectively destroys and / or inhibits tumor growth. The alternating currents and fields may be generated at any frequency that selectively destroys or inhibits tumor growth, such as any frequency of a TT field.

[0030] In certain (but not limiting) embodiments, the alternating current and magnetic field may be applied at two or more different frequencies, where two or more frequencies are present, each frequency being selected from a range consisting of any of the values ​​listed above or a range combining two integers between any of the values ​​listed above.

[0031] To optimize the electric field (TT field) distribution, the transducer arrays 70a and 70b (the pair of transducer arrays 70) may be configured differently depending on the application for which the pair of transducer arrays 70 is used. As described herein, the pair of transducer arrays 70 are applied externally to a patient, i.e., generally to the patient's skin, to apply an electric current and an electric field (TT field), thereby generating a current in the patient's tissue. Typically, the pair of transducer arrays 70 are placed on the patient's skin by a user so that an electric field is generated across the patient's tissue in the treatment area. The externally applied TT field may be of a localized type or a widely distributed type (e.g., for treating skin tumors or lesions close to the skin surface).

[0032] In one embodiment, the user may be a medical professional, such as a doctor, nurse, therapist, or other person acting under the direction of a doctor, nurse, or therapist. In another embodiment, the user may be a patient, i.e., the patient (and / or a helper) may position transducer arrays 70a and 70b over the patient's treatment area.

[0033] According to another exemplary embodiment, electronic device 50 includes controller 74. In one embodiment, controller 74 includes circuitry configured to control the output of electric field generator 54, e.g., to set the output to a maximum value that does not cause excessive heating of the treatment region. Controller 74 may also issue an alert or the like if the temperature of the treatment region (sensed by a plurality of temperature sensors 104, described in more detail below) exceeds a preset limit. Temperature sensors 104 may be mechanically connected and / or associated with either or both of transducer array 70a and / or transducer array 70b to more precisely detect the temperature of the treatment region, as described below.

[0034] In one embodiment, controller 74 may turn off or reduce the power of the TTS signal generated by electric field generator 54 if the temperature sensed by the temperature sensor meets or exceeds a comfort threshold. In one embodiment, the comfort threshold is the temperature at which the patient feels uncomfortable while using transducer array 70a and transducer array 70b. For example, the comfort threshold may be a temperature of 40°C or approximately 40°C. In one embodiment, the comfort threshold is a temperature between approximately 39°C and 42°C, or a specific selected temperature between approximately 39°C and 42°C.

[0035] In one embodiment, controller 74 comprises circuitry including a processor 75 and memory 76. Memory 76 may be a non-transitory computer-readable medium (e.g., random access memory and / or read-only memory) that stores computer-executable instructions that, when executed by processor 75, cause processor 75 to perform one or more functions. Processor 75 may be in communication with one or more temperature sensors 104 and / or may be in communication with circuitry such as an analog-to-digital converter, a multimeter, an ohmmeter, a voltmeter, and / or an ammeter.

[0036] Conductive leads 58 are preferably insulated conductors with a flexible metal shield that is grounded, thereby preventing the spread of the electric field generated by conductive leads 58. Transducer arrays 70a and 70b may have a particular shape and arrangement to generate a TT field of a desired configuration, direction, and intensity at, and only at, the treatment region to focus the treatment.

[0037] The specifications of the electronic device 50 as a whole and its individual components are heavily influenced by the fact that at the frequencies of the TT field, biological systems behave according to their "ohmic" rather than dielectric properties.

[0038] In one embodiment, the controller 74 further comprises a measurement circuit 77. For example, measuring the resistance of the temperature sensor 104 may include the processor 75 communicating with the measurement circuit 77 to measure the resistance. The measurement circuit 77 may comprise, for example, an ohmmeter, an ammeter, a voltmeter, and a multimeter. In one embodiment, the measurement circuit 77 may further comprise an analog-to-digital converter to convert the resistance measurement into a digital signal that is provided to the processor 75.

[0039] Referring now to Figure 3, there is shown a diagram of an exemplary embodiment of a transducer array 70 constructed in accordance with the present disclosure. The transducer array 70 includes one or more electrode elements 78. As shown in Figure 3, each transducer array 70 is configured as a collection of one or more electrode elements 78. The transducer array 70 may utilize electrode elements 78 that are capacitively coupled with the patient.

[0040] In the example shown in FIG. 3, the transducer array 70 consists of multiple electrode elements 78 (e.g., approximately 2 cm in diameter) connected via flexible wires 90 (connected to the electric field generator 54 via conductive leads 58).

[0041] In one embodiment, the transducer array 70 further comprises a plurality of temperature sensors 104 associated with one or more of the electrode elements 78. As shown in Figure 3, the transducer array 70 comprises eight temperature sensors 104 associated with eight of the nine electrode elements 78, although temperature sensors 104 may be associated with more or fewer electrode elements 78 of the transducer array 70. Each of the temperature sensors 104 is connected to at least one other temperature sensor 104 via a sensor wire 108.

[0042] In one embodiment, the transducer array 70 includes one or more RC circuits 112. Each RC circuit 112 may be connected to at least one of a temperature sensor 104 or an RC circuit 112, as shown in FIG. 5A and described in more detail below.

[0043] 4, there is shown a diagram of an exemplary embodiment of a capacitive reactance graph 150 constructed in accordance with the present disclosure. The capacitive reactance graph 150 is shown with a first axis 154 representing frequency and a second axis 158 representing the resulting resistance on a logarithmic scale. Also shown is a first plot 162 showing the capacitive reactance for a first capacitor with a first capacitance as the frequency of the applied current increases, and a second plot 166 showing the capacitive reactance for a second capacitor with a second capacitance as the frequency of the applied current increases, the second capacitance being 10 times the first capacitance.

[0044] As shown in Figure 4, as frequency increases, the resulting impedance of a capacitor decreases. For example, at a first frequency, f, the first resulting reactance, R, of the second capacitor is greater than the second resulting reactance, R, of the second capacitor at a second frequency, f, and is very close to a 0 Ω reactance, e.g., nearly a short circuit. However, at the same second frequency, f, the first capacitor has a third resulting reactance, R, that is greater than the second resulting reactance, R. Thus, as shown in Figure 4, as the frequency of the applied current increases, the resulting reactance of the capacitor decreases and reaches zero (0) Ω.

[0045] Referring now to FIG. 5A, there is shown a diagram of an exemplary embodiment of a temperature sensing circuit 200 constructed in accordance with the present disclosure. The temperature sensing circuit 200 generally includes a third thermistor 204c, i.e., temperature sensor 104, electrically connected to a first sensor wire 108a and arranged in series with at least one RC circuit 112, which is further connected to a second sensor wire 108b, opposite the first sensor wire 108a. The third thermistor 204c and each of the RC circuits 112a and 112b are in thermal communication with (e.g., attached to) an electrode element 78 (not shown in FIG. 5A). It should be noted that the third thermistor 204c, the RC circuit 112a, and the second RC circuit 112b can be arranged in series in any order within the temperature sensing circuit 200, not necessarily in the order shown in FIG. 5A.

[0046] 5A, the temperature sensing circuit 200 includes a third thermistor 204c electrically connected to the first sensor wire 108a and disposed in electrical series with a first RC circuit 112a and a second RC circuit 112b, which is further connected to the second sensor wire 108b. The temperature sensing circuit 200 may include additional RC circuits 112 for measuring the temperatures of other electrode elements 78 in series with the other RC circuits 112a and 112b and the third thermistor 204c.

[0047] In one embodiment, each thermistor 204 is a 10 kΩ thermistor (e.g., the thermistor 204 has a resistance of 10 kΩ at 20° C. and a resistance of approximately 5 kΩ at 40° C.), and the resistance R of the thermistor 204 is strongly related to the temperature of the thermistor, i.e., each thermistor 204 is a variable resistor having a resistance R that changes with temperature, and the thermistor 204 has known properties of corresponding resistance and temperature. For example, the temperature of the thermistor 204 can be determined by passing a known current through the thermistor 204 and measuring the voltage across the thermistor 204. Knowing the current (I) and voltage (V), the resistance R of the thermistor 204 can be determined according to Ohm's Law:

[0048]

number

[0049] In one embodiment, each RC circuit 112 includes a thermistor 204 and a capacitor 208 in parallel with the thermistor. As previously mentioned, the thermistor 204 may be a 10 kΩ thermistor, although other values ​​may be used. The capacitor 208 of each RC circuit 112 may be selected to have a capacitance smaller than the capacitance of the next smallest capacitor in the temperature sensing circuit 200. Thus, as more RC circuits 112 are added to the temperature sensing circuit 200, the capacitance of each capacitor in the newly added RC circuit 112 will be smaller than the capacitance of any other RC circuit 112 in the temperature sensing circuit 200. In one embodiment, the capacitance of each capacitor is selected within a range of about 10 mf (i.e., 10 millifarads) to about 1 pf (i.e., 1 picofarad). In some embodiments, the difference in capacitance between the capacitors 208 of each RC circuit 112 is within a range of one to four orders of magnitude. In some embodiments, the difference in capacitance between the capacitors 208 of each RC circuit 112 is in the range of 100 to 10,000 times.

[0050] 5A, the temperature sensing circuit 200 includes a third thermistor 204c (with no parallel capacitor), a first RC circuit 112a, and a second RC circuit 112b, all wired in series. The temperature sensing circuit 200 further includes a first sensor wire 108a and a second sensor wire 108b, respectively, electrically coupled to the temperature sensing circuit 200.

[0051] In one embodiment, the first RC circuit 112a includes a first capacitor 208a electrically disposed in parallel with the first thermistor, and the second RC circuit 112b includes a second capacitor 208b electrically disposed in parallel with the second thermistor 204b. The first capacitor 208a is selected such that a first capacitance of the first capacitor 208a is greater than a second capacitance of the second capacitor 208b. In some embodiments, the second capacitance of the second capacitor 208b is selected to be within a range of at least 1 / 10 (one tenth) of the first capacitance of the first capacitor 208a to 1 / 100,000 (one hundred thousandth) of the first capacitance of the first capacitor 208a. In some embodiments, the second capacitance of the second capacitor 208b is selected to be less than 1 / 1,000,000 (one millionth) of the first capacitance of the first capacitor 208a.

[0052] A user can measure the impedance across the temperature sensing circuit 200, for example, by attaching a first probe of an ohmmeter to the first sensor wire 108a and a second probe of the ohmmeter to the second sensor wire 108b. By applying a first sensing signal having a known current and a first frequency, the total impedance R T (For example, the resistance R of the third thermistor 204c x and the resistance R of the first thermistor 204a. y and the resistance R of the second thermistor 204b. z ) can be measured. The user can then apply a second sensing signal having a known current and a second frequency sufficient to cause the first reactance of the first capacitor 208a to reach zero but insufficient to cause the second reactance of the second capacitor 208b to reach zero, thereby effectively shorting out the temperature sensing circuit 200 across the first thermistor 204a and creating a second impedance R a (For example, the resistance R of the second thermistor 204b z and the resistance R of the third thermistor 204c. x) in some embodiments, the second sensing signal has a second frequency in the range of one to four orders of magnitude greater than the first frequency. Finally, the user can apply a third sensing signal having a known current and a third frequency sufficient to cause the first reactance of the first capacitor 208a to reach zero and also sufficient to cause the second reactance of the second capacitor 208b to reach zero, thereby effectively shorting out the temperature sensing circuit 200 across the first thermistor 204a and the second thermistor 204b and creating a third impedance R b (For example, the resistance R of the third thermistor 204c x ) is measured. Therefore, the resistance R of the third thermistor 204c is x is the third impedance R b and the resistance R of the first thermistor 204a y teeth,

[0053]

number

[0054]

number

[0055] Next, in some embodiments, the first capacitor 208a and the second capacitor 208b can be selected such that the second frequency supplied to the first capacitor 208a is sufficient to cause the first reactance of the first capacitor 208a to reach zero, while the second capacitor 208b is selected such that the second frequency supplied to the second capacitor 208b is insufficient to cause the second reactance of the second capacitor 208b to reach zero.

[0056] In some embodiments, the third thermistor 204c can further include a third capacitor electrically disposed in parallel with the third thermistor 204c, thereby forming a third RC circuit 112. As described in more detail below, the third capacitor need not be disposed in parallel with the third thermistor 204c, although in such an arrangement, each sensing signal must have a frequency sufficient to effectively “short out” at least one capacitor. If a third capacitor is not present, i.e., if the third thermistor 204c does not have a capacitor disposed in parallel, a single sensing signal applied to the temperature sensing circuit 200 does not need to be of a frequency sufficient to effectively “short out” any capacitor, e.g., not sufficient to have the reactance of all capacitors reach zero.

[0057] 5B, there is shown a circuit diagram of an exemplary embodiment of a composite temperature sensing circuit 250 constructed in accordance with the present disclosure. Generally, the composite temperature sensing circuit 250 is comprised of two or more temperature sensing circuits 200, shown in FIG. 5B as a first temperature sensing circuit 200a and a second temperature sensing circuit 200b. Each of the first temperature sensing circuit 200a and the second temperature sensing circuit 200b is constructed similarly to the temperature sensing circuit 200 shown in FIG. 5A, except that each of the first temperature sensing circuit 200a and the second temperature sensing circuit 200b includes a third RC circuit 112.

[0058] As shown in FIG. B5, the first sensor wire 108a is connected to the first temperature sensing circuit 200a and is operable to communicate a first sensing signal from the controller 74 to the first temperature sensing circuit 200a. The second sensor wire 108b is connected to the first temperature sensing circuit 200a and is operable to communicate the first sensing signal from the first temperature sensing circuit 200a to the controller 74. A third sensor wire 108c is further shown that is operable to communicate a second sensing signal from the controller 74 to the second temperature sensing circuit 200b. The second temperature sensing circuit 200b is connected to the second sensor wire 108b, which is further operable to communicate the second sensing signal from the second temperature sensing circuit 200b back to the controller 74. By sharing the second sensor wire 108b, the combined temperature sensing circuit 250 can further reduce the number of wires required within the conductive lead 58. In the illustrated embodiment, the composite temperature sensing circuit 250 includes three wires, but the controller 74 is operable to measure the temperature of eight electrode elements 78, with each electrode element 78 in thermal communication with one of the RC circuits 112a-c, 112e-g, and thermistors 204d and 204h. While the composite temperature sensing circuit 250 is shown with only two temperature sensing circuits 200, it should be understood that additional composite temperature sensing circuits 250 may be included.

[0059] During operation, the composite temperature sensing circuit 250 can receive a plurality of first sensing signals along the first and second sensor wires 108a, 108b, for example, from the controller 74, to measure the temperature of each thermistor 204 of the first temperature sensing circuit 200a, and can receive a plurality of second sensing signals along the third and second sensor wires 108c, 108b, for example, from the controller 74, to measure the temperature of each thermistor 204 of the second temperature sensing circuit 200b. Because the first and second temperature sensing circuits 200a, 200b are not DC with respect to each other, the first and second sensing signals do not need to be frequency offset from each other.

[0060] Alternatively, in another embodiment, the controller 74 can poll the composite temperature sensing circuit 250 by providing a first sensing signal along the first sensor wire 108a at a first time and providing a first sensing signal along the third sensor wire 108c at a second time to measure the resistance for each thermistor 204. For example, the controller 74 can provide a first sensing signal having a first frequency along the first sensor wire 108a at a first time and measure a first impedance between the first sensor wire 108a and the second sensor wire 108b, and provide a first sensing signal having a first frequency along the third sensor wire 108c at a second time and measure a second impedance between the third sensor wire 108c and the second sensor wire 108b. Next, the controller 74 may provide a first sense signal having a second frequency along the first sensor wire 108a at a third time and measure a third impedance between the first sensor wire 108a and the second sensor wire 108b, provide a first sense signal having a second frequency along the third sensor wire 108c at a fourth time and measure a fourth impedance between the third sensor wire 108c and the second sensor wire 108b, provide a first sense signal having a third frequency along the first sensor wire 108a at a fifth time and measure a fifth impedance between the first sensor wire 108a and the second sensor wire 108b, and provide a first sense signal having a third frequency along the third sensor wire 108c at a sixth time and measure a sixth impedance between the third sensor wire 108c and the second sensor wire 108b. Finally, the controller 74 may provide a first sensing signal having a fourth frequency along the first sensor wire 108a at a seventh time and measure a seventh impedance between the first sensor wire 108a and the second sensor wire 108b, and provide a first sensing signal having a fourth frequency along the third sensor wire 108c at an eighth time and measure an eighth impedance between the third sensor wire 108c and the second sensor wire 108b.

[0061] In this embodiment, the first impedance may be, for example, a combination of the resistance of thermistor 204d and the impedances of RC circuits 112a-112c, while the second impedance may be a combination of the resistance of thermistor 204h and the impedances of RC circuits 112e-112g, the third impedance may be a combination of the resistance of thermistor 204d and the impedances of two of RC circuits 112a-112c (for example, RC circuits 112a-112b), and the fourth impedance may be a combination of the resistance of thermistor 204h and the impedances of two of RC circuits 112e-112g (for example, RC circuits 112e-112f). the fifth impedance may be a combination of the resistance of thermistor 204d and the impedance of one of the RC circuits 112a-112c (e.g., RC circuit 112a); the sixth impedance may be a combination of the resistance of thermistor 204h and the impedance of one of the RC circuits 112e-112g (e.g., RC circuit 112e); the seventh impedance may be the resistance of thermistor 204d; and the eighth impedance may be the resistance of thermistor 204h.

[0062] In this embodiment, when the same frequency is used for both temperature sensing circuit 200a and temperature sensing circuit 200b of composite temperature sensing circuit 250, at least one RC circuit 112 from each temperature sensing circuit 200 may have capacitors 208 within 15% of each other. For example, RC circuit 112a and RC circuit 112e may have capacitors within about 15% of each other, as well as second RC circuit 112b and RC circuit 112f, as well as RC circuit 112c and RC circuit 112g. In this manner, a frequency applied to a particular one of the temperature sensing circuits 200 is equally effective when applied to the other temperature sensing circuits 200.

[0063] 6, there is shown a process flow diagram of an exemplary embodiment of a sensing process 300 constructed in accordance with the present disclosure. The sensing process 300 generally includes measuring a first impedance of a temperature sensing circuit (step 304), measuring a second impedance of the temperature sensing circuit (step 308), measuring a first temperature of a thermistor (step 312), and measuring a second temperature of an RC circuit (step 316). The sensing process 300 may be stored in memory 76 as a series of computer-executable instructions and executed by processor 75.

[0064] In one embodiment, the sensing process 300 is performed more than once and may be performed periodically. For example, in one embodiment, once the sensing process 300 is completed, the sensing process 300 may be restarted. In another embodiment, once the sensing process 300 is completed, the sensing process 300 may be performed again after a period of time. The period of time may be predetermined or may be triggered by the processor 75 as needed or otherwise desired.

[0065] In one embodiment, measuring the first impedance of the temperature sensing circuit (step 304) includes measuring the first impedance of the first thermistor and the RC circuit in series, for example, by an ohmmeter in communication with and commanded by processor 75. For example, measuring the first impedance may include measuring the impedance between a first sensing wire connected to the first thermistor and a second sensing wire connected to the RC circuit, for example, by an ohmmeter, such as measurement circuit 77. In one embodiment, measurement circuit 77 may include an analog-to-digital converter to convert the impedance measurement to a digital signal that is provided to processor 75.

[0066] In one embodiment, measuring the first impedance of the temperature sensing circuit (Step 304) includes providing a first sensing signal having a first frequency to the temperature sensing circuit and measuring the impedance of the temperature sensing circuit with the first sensing signal applied to the temperature sensing circuit. In some embodiments, the first frequency may be zero. That is, the first sensing signal may be a DC signal. When the first frequency is zero, the first impedance is the total impedance of the temperature sensing circuit.

[0067] In one embodiment, measuring the second impedance of the temperature sensing circuit (step 308) includes measuring the second impedance of the first thermistor and the RC circuit in series, for example, with an ohmmeter in communication with and directed by processor 75. For example, measuring the second impedance may include measuring the second impedance between the first sensing wire connected to the first thermistor and the second sensing wire connected to the RC circuit with an ohmmeter, for example, measurement circuit 77. In one embodiment, measurement circuit 77 may include an analog-to-digital converter to convert the second impedance measurement to a digital signal that is provided to processor 75.

[0068] In one embodiment, measuring the second impedance of the temperature sensing circuit (STEP 308) includes providing a second sensing signal having a second frequency to the temperature sensing circuit and measuring the impedance of the temperature sensing circuit with the second sensing signal applied to the temperature sensing circuit. The second frequency can be 10 to 100,000 times greater than the first frequency. If the first frequency is 1 kHz, the second frequency can be, for example, 10 kHz to 100 MHz, or 10 kHz to 1 GHz.

[0069] In one embodiment, measuring the second impedance of the temperature sensing circuit (STEP 308) includes selecting a second frequency of the second sensing signal such that the capacitor of the RC circuit has a capacitive reactance that approaches zero.

[0070] In one embodiment, measuring the first temperature of the thermistor (Step 312) includes measuring the first temperature of the first thermistor based on the second impedance. For example, when the second sense signal is applied to the temperature sensing circuit, the capacitor of the RC circuit has a capacitive reactance that reaches zero, causing the impedance of the temperature sensing circuit to reach the resistance of the first thermistor. Thus, when the impedance of the temperature sensing circuit reaches the resistance of the first thermistor and is measured, the measured impedance is equal to the first resistance of the first thermistor. The first resistance, along with known characteristics and properties of the first thermistor related to temperature and resistance, can then be used to calculate the first temperature of the first thermistor.

[0071] In one embodiment, measuring the second temperature of the RC circuit (step 316) includes measuring the second temperature of a second thermistor in the RC circuit based on the first impedance and the second impedance. For example, as described in more detail above with reference to FIG. 4 , the first impedance is the combined resistance of the first thermistor and the impedance of the RC circuit, and the second impedance is effectively the resistance of the first thermistor. Thus, to measure the resistance of the second thermistor, the second resistance (e.g., the resistance of the first thermistor) is subtracted from the first impedance (e.g., the combined resistance of the first thermistor and the impedance of the RC circuit), thereby obtaining the impedance of the RC circuit, where the impedance of the RC circuit is equal to the resistance of the second thermistor. The resistance of the second thermistor, along with known characteristics and properties of the second thermistor related to temperature and resistance, can then be used to calculate the second temperature of the second thermistor.

[0072] In one embodiment, the sensing process 300 can be used to measure the temperature of a particular thermistor in a temperature sensing circuit, such as the particular thermistor in the first temperature sensing circuit 200a of FIG. 5B. In this embodiment, the particular thermistor can be, for example, the thermistor in the RC circuit 112f with a particular capacitor in parallel with the RC circuit 112f.

[0073] Here, measuring the first impedance of the temperature sensing circuit (step 304) includes providing a first sensing signal having a first frequency to the temperature sensing circuit and measuring the impedance of the temperature sensing circuit with the first sensing signal applied to the temperature sensing circuit. The first frequency is selected so that the next largest capacitor after the particular capacitor has a capacitive reactance that approaches zero when the first sensing signal is applied to the temperature sensing circuit. In this way, the first impedance is the combined impedance of the RC circuit with the particular thermistor and the impedances of all RC circuits with capacitors having a capacitance below the particular capacitor, including the resistance of the thermistor 204, if present, that is not wired in parallel with any of the capacitors.

[0074] Next, measuring the second impedance of the temperature sensing circuit (step 308) includes providing a second sensing signal having a second frequency to the temperature sensing circuit and measuring the second impedance of the temperature sensing circuit with the second sensing signal applied to the temperature sensing circuit. The second frequency is selected so that the particular capacitor has a capacitive reactance that approaches zero when the second sensing signal is applied to the temperature sensing circuit. In this way, the second impedance is then the composite impedance of all RC circuits with capacitors having a capacitance less than the particular capacitor, including the resistance of the thermistor 204, if present, that is not wired in parallel with any capacitor.

[0075] The temperature of the specific thermistor can therefore be determined based on the first impedance and the second impedance (e.g., similar to step 316). The specific resistance of the specific thermistor can be calculated by subtracting the second impedance from the first impedance. The specific resistance can then be used, along with the known characteristics and properties of the specific thermistor relating temperature and resistance, to calculate the specific temperature of the specific thermistor.

[0076] Referring now to FIG. 7 , there is shown a circuit diagram of an exemplary embodiment of a temperature sensing circuit 350 constructed in accordance with the present disclosure. The temperature sensing circuit 350 generally includes a thermistor 354 (constructed similarly to the thermistor 204 described above) having a resistance R, a capacitor 358 (constructed similarly to the capacitor 208 described above) having a capacitance C, and an inductor 362 having an inductance L. The thermistor 354, capacitor 358, and inductor 362 are each electrically arranged in parallel with one another to form a parallel resonant circuit (collectively, an RLC circuit 366). The temperature sensing circuit 350 further includes an RLC circuit 366 electrically arranged in series with the first and second sensor wires 108 a and 108 b. The RLC circuit 366 may be a temperature sensor 104 disposed in thermal communication with (e.g., attached to or adjacent to) the electrode element 78 (not shown in FIG. 7 ).

[0077] In one embodiment, RLC circuit 366 is further coupled to power source 370 (e.g., electric field generator 54) and ammeter 374 (e.g., measurement circuit 77) operable to measure the impedance Z of RLC circuit 366. Generally, when power source 370 supplies an AC waveform to RLC circuit 366, RLC circuit 366 has a low or normal impedance, and thus the AC waveform spans inductor 362 and capacitor 358 (collectively, the “LC circuit”), effectively shorting it. However, when current flowing through the parallel combination of thermistor 354, capacitor 358, and inductor 362 is in phase with the source voltage supplied by power source 370, RLC circuit 366 creates a parallel resonant (e.g., anti-resonant) circuit. At resonance, the created current resonance may cause a circulating current to exist between inductor 362 and capacitor 358 (e.g., in the LC circuit), effectively creating an open circuit in the LC circuit, as shown in FIG. 8 and discussed below.

[0078] 8, there is shown a diagram of an exemplary embodiment of a temperature sensing circuit 350 constructed in accordance with the present disclosure and subjected to a waveform tuned to the resonant frequency of the inductance of inductor 362 and the capacitance of capacitor 358 in an RLC circuit (e.g., of an LC circuit). R 7, except that the temperature sensing circuit 350' provides a particular waveform having a frequency of 100 Hz, and more specifically, a frequency at the resonant frequency of the capacitor 358 in parallel with the inductor 362 (i.e., the LC circuit). In one embodiment, the capacitor 358 and the inductor 362 are connected at a resonant frequency of 100 Hz.

[0079]

number

[0080]

number

[0081]

number

[0082] 8, when a particular waveform is applied to RLC circuit 366, the LC circuit acts like an open circuit and the current flowing through temperature sensing circuit 350 is measured by thermistor 354. In this manner, the impedance Z of RLC circuit 366 becomes the resistance R of thermistor 354 when applied with a particular waveform having the resonant frequency of the LC circuit. However, as shown below in FIG. 9, the frequency response of RLC circuit 366 can be changed by varying the resistance R.

[0083] 9, there is illustrated an impedance graph 400 of an exemplary embodiment of the temperature sensing circuit 350 of FIG. 7 constructed in accordance with the present disclosure and run through waveforms having various frequencies. The impedance graph 400 has an abscissa 404 axis of the frequency f of the waveform applied to the RLC circuit 366 and an ordinate 408 axis of the impedance 412 of the RLC circuit 366 at frequency f. As shown, the resonant frequency f R At resonant frequency f, impedance 412 has a dynamic impedance 416, and at maximum impedance 420, impedance 412 becomes a resistance R. At the resonant frequency, inductor 362 and capacitor 358 do not contribute significantly to impedance 412. Thus, at resonant frequency f R , the impedance 412 of the RLC circuit 366 is the resistance R of the thermistor 354. Outside the resonant frequency, the impedance graph 400 shows the nominal impedance 424, i.e., the impedance of the RLC circuit 366 when the LC circuit is effectively shorted.

[0084] 10 and 11 , a schematic diagram of an exemplary embodiment of a temperature sensing circuit 450 constructed in accordance with the present disclosure and including three RLC circuits connected in series is shown in FIG. 10. The temperature sensing circuit 450 generally includes a plurality of RLC circuits 366 (shown as RLC circuits 366a-366n) electrically coupled in series. The temperature sensing circuit 450 further includes a plurality of RLC circuits 366a-366n disposed electrically in series with the first and second sensor wires 108a-108b. The thermistors 354a, 354b, and 354n of the RLC circuits 366 of the plurality of RLC circuits 366a-366n may be disposed in thermal communication with (e.g., attached to, adjacent to, or in direct contact with) at least one electrode element 78 (not shown in FIG. 10 ). An impedance graph 500 of an exemplary embodiment of the temperature sensing circuit 450 of FIG. 10 constructed in accordance with the present disclosure and similar to the impedance graph 400 described above is shown in FIG. 11. The impedance graph 500 has an abscissa 404 axis of the frequency f of the waveform applied to the RLC circuit 366a-366n (e.g., the temperature sensing circuit 450) and an ordinate 408 axis of the impedance 412 of the temperature sensing circuit 450 at frequency f.

[0085] In one embodiment, each RLC circuit 366 of the plurality of RLC circuits 366a-366n has a different resonant frequency (e.g., a resonant frequency of an LC circuit) from the others in the plurality of RLC circuits 366a-366n of the temperature sensing circuit 450. For example, as shown in FIG. 11 , the first RLC circuit 366a has a first resonant frequency f R-a and the second RLC circuit 366b can have a second resonant frequency f R-b and the nth RLC circuit 366n may have an nth resonant frequency f R-n In one embodiment, the second resonant frequency f R-b is the first resonant frequency f R-a The range is 5 to 15 times that of

[0086] As shown, the first resonant frequency f R-a, the impedance 412 of the temperature sensing circuit 450 has a first dynamic impedance 416a because the LC circuit of the first RLC circuit 366a is substantially open circuited, while the second RLC circuit 366b through the nth RLC circuit 366n are substantially short circuited. R-a At the maximum impedance 420 of the temperature sensing circuit 450, the impedance 412 of the temperature sensing circuit 450 (e.g.,

[0087]

number

[0088] In one embodiment, the second resonant frequency f R-b In this example, the impedance 412 of the temperature sensing circuit 450 has a second dynamic impedance 416b because the LC circuit of the second RLC circuit 366b is substantially open circuited, while the other RLC circuits 366a-366n are substantially short circuited. In this way, the second resonant frequency f R-b At the maximum impedance 420 of the temperature sensing circuit 450, the impedance 412 of the temperature sensing circuit 450 (e.g.,

[0089]

number

[0090] In one embodiment, the nth resonant frequency f R-n In this example, the impedance 412 of the temperature sensing circuit 450 has an n-th dynamic impedance 416n because the LC circuit of the n-th RLC circuit 366n is substantially open circuited while the other RLC circuits 366a-366n are substantially short circuited. R-n At the maximum impedance 420 of the temperature sensing circuit 450, the impedance 412 of the temperature sensing circuit 450 (e.g.,

[0091]

number

[0092] In this manner, the controller 74 can measure the temperature of a particular thermistor 354 in the temperature sensing circuit 450 by selecting the power supply 370 and causing the power supply 370 to provide an electrical signal having the resonant frequency of an LC circuit electrically connected in parallel with the particular thermistor 354. In operation, the power supply 370 of the temperature sensing circuit 450 receives a plurality of signals, for example, from the controller 74, and causes the power supply 370 to transmit an electrical signal along the first sensor wire 108a and the second sensor wire 108b at the resonant frequency f R-a ~f R-n The temperature of each thermistor 354 in the temperature sensing circuit 450 can be measured by continuously providing a plurality of sensing signals having a resonant frequency, e.g., f R-a ~f R-n The AC waveform has a frequency f selected from

[0093] In one embodiment, the controller 74 may calibrate the temperature sensing circuit 450 before measuring the temperature of each of the thermistors 354a-354n. For example, the controller 74 may first transmit a calibration signal to the power supply 370 of the temperature sensing circuit 450, causing the power supply 370 to generate a sensing signal of known voltage and frequency. The controller 74 then reads the current from the ammeter 374 and calculates the nominal impedance 424 of the sensing circuit 470. The calibration signal may cause the power supply 370 to calibrate the resonant frequency of each of the RLC circuits 366a-366n, e.g., f R-a ~f R-n In this manner, the controller 74 measures the nominal impedance 424, i.e., the impedance of the RLC circuits 366a-366n when the LC circuits are substantially shorted, and calculates the measured resistance R a-n to account for manufacturing tolerances and other variations in the components used to construct the temperature sensing circuit 450.

[0094] 12 , there is shown a process flow diagram of another exemplary embodiment of a sensing process 550 constructed in accordance with the present disclosure. The sensing process 550 generally includes measuring a first impedance of a first RLC circuit of the temperature sensing circuit (step 554), measuring a second impedance of a second RLC circuit of the temperature sensing circuit (step 558), measuring a first temperature of the first RLC circuit (step 562), and measuring a second temperature of the second RLC circuit (step 566). The sensing process 550 may be stored in memory 76 as a series of computer-executable instructions and executed by processor 75.

[0095] In one embodiment, measuring the first impedance of the first RLC circuit of the temperature sensing circuit (step 554) determines whether the first RLC circuit 366 is substantially open circuited, such that the impedance 412 of the temperature sensing circuit 450 has a first dynamic impedance 416a, thereby detecting the first resonant frequency f R-a to a first RLC circuit (e.g., first RLC circuit 366a), while the second RLC circuit 366b through the nth RLC circuit 366n are substantially short-circuited. In this way, the first resonant frequency f R-a At the maximum impedance 420 of the temperature sensing circuit 450, the impedance 412 of the temperature sensing circuit 450 (e.g.,

[0096]

number

[0097] In one embodiment, measuring the second impedance of the second RLC circuit of the temperature sensing circuit (step 558) includes measuring the impedance 412 of the temperature sensing circuit 450 at a second resonant frequency f such that the impedance 412 of the temperature sensing circuit 450 has a second dynamic impedance 416b, with the LC circuit of the second RLC circuit 366b being substantially open circuited. R-b to a second RLC circuit (e.g., RLC circuit 366b), while the other RLC circuits 366a-366n are substantially shorted. In this manner, a second resonant frequency f R-b At the maximum impedance 420 of the temperature sensing circuit 450, the impedance 412 of the temperature sensing circuit 450 (e.g.,

[0098]

number

[0099] In one embodiment, measuring the first temperature of the first RLC circuit (step 562) includes measuring the first temperature of the first RLC circuit using the thermistor 204 and the first resistor R as described above in connection with FIG. 5A. a The first temperature of the first thermistor 354a may therefore be the temperature of the electrode element 78 associated with the first RLC circuit 366a.

[0100] In one embodiment, measuring the second temperature of the second RLC circuit (step 566) includes measuring the second temperature of the second RLC circuit using the thermistor 204 and the second resistor R as described above in connection with FIG. 5A. bThe second temperature of the second thermistor 354b may therefore be the temperature of the electrode element 78 associated with the second RLC circuit 366b. Illustrative Embodiments

[0101] The following is a non-limiting list of exemplary embodiments of the inventive concepts disclosed herein.

[0102] [Example Embodiment 1] 1. A transducer array comprising: A first electrode; A second electrode; 1. A temperature sensing circuit, comprising: a first thermistor adjacent to the first electrode, the first thermistor being a first variable resistor whose resistance varies with temperature; the temperature sensing circuit including an RC circuit connected in series with the first thermistor, the RC circuit including a second thermistor adjacent the second electrode and a capacitor in parallel with the second thermistor, the second thermistor being a second variable resistor whose resistance varies with temperature; the transducer array comprising: a lead configured to transmit an electrical signal to a first electrode and a second electrode, the lead further comprising a first sensor wire electrically coupled to the first thermistor and a second sensor wire electrically coupled to an RC circuit on an opposite side of the first thermistor.

[0103] [Exemplary embodiment 2] 10. The transducer array of exemplary embodiment 1, wherein the RC circuit is a first RC circuit, the capacitor is a first capacitor, and the temperature sensing circuit further comprises a third electrode and a second RC circuit connected in series with the first thermistor and the third RC circuit, the second RC circuit comprising a third thermistor adjacent to the third electrode and a second capacitor in parallel with the third thermistor, the third thermistor being a third variable resistor whose resistance changes with temperature.

[0104] Exemplary Embodiment 3 3. The transducer array of any one of exemplary embodiments 1 to 2, wherein the temperature sensing circuit does not have a capacitor in parallel with the first thermistor.

[0105] Exemplary Embodiment 4 3. The transducer array of exemplary embodiment 2, wherein the second capacitor has a second capacitance, the first capacitor has a first capacitance, and the first capacitance is greater than the second capacitance.

[0106] Exemplary Embodiment 5 3. The transducer array of exemplary embodiment 2, wherein the first capacitor has a first capacitance of approximately 1,000 nf and the second capacitor has a second capacitance of approximately 1 nf.

[0107] Exemplary Embodiment 6 3. The transducer array of Exemplary Embodiment 2, wherein the first thermistor is in direct contact with the first electrode.

[0108] Exemplary Embodiment 7 3. The transducer array of exemplary embodiment 2, wherein the first thermistor is a negative temperature coefficient thermistor and the second thermistor is a negative temperature coefficient thermistor.

[0109] Exemplary Embodiment 8 1. An oncology treatment field system, comprising: an electric field generator configured to generate an electric signal having an AC waveform at a frequency of 50 kHz to 1 MHz; A first electrode; A second electrode; a lead electrically coupled to the electric field generator, the lead configured to transmit the electrical signal to the first electrode and the second electrode, the lead further comprising a first sensor wire and a second sensor wire; 1. A temperature sensing circuit, comprising: a first thermistor adjacent to the first electrode, the first thermistor being a first variable resistor whose resistance varies with temperature and electrically coupled to the first sensor wire; an RC circuit coupled in series with the first thermistor, the RC circuit including a second thermistor adjacent the second electrode and a capacitor in parallel with the second thermistor, the RC circuit electrically coupled to the second sensor wire, the second thermistor being a second variable resistor having a resistance that varies with temperature; a controller in communication with the electric field generator, the first sensor wire, and the second sensor wire, the controller having a processor and a controller that, when executed by the processor, providing a first sensing signal having a first frequency along the first sensor wire; measuring a first impedance between the first sensor wire and the second sensor wire; providing a second sense signal along the first sensor wire, the second sense signal having a second frequency greater than the first frequency; measuring a second impedance between the first sensor wire and the second sensor wire; measuring a first temperature of the first thermistor based on the second impedance; and the controller having a non-transitory computer-readable medium storing computer-executable instructions that cause the processor to: measure a second temperature of the second thermistor based on the first impedance and the second impedance.

[0110] Exemplary Embodiment 9 The tumor treatment field system of exemplary embodiment 8, wherein the second frequency is in a range of one to four orders of magnitude greater than the first frequency.

[0111] Exemplary Embodiment 10 9. The tumor treatment field system of Exemplary embodiment 8, wherein the first thermistor and the second thermistor are negative temperature coefficient variable resistors.

[0112] Exemplary Embodiment 11 9. The tumor treatment field system of exemplary embodiment 8, wherein each of the first thermistor and the second thermistor has a resistance of approximately 10 kΩ at 20°C.

[0113] Exemplary Embodiment 12 The tumor treatment field system of exemplary embodiment 8, wherein the RC circuit is a first RC circuit and the capacitor is a first capacitor, and the tumor treatment field system further comprises a third electrode and a second RC circuit coupled in series with the first RC circuit and the first thermistor, the second RC circuit comprising a third thermistor adjacent to the third electrode and a capacitor in parallel with the third thermistor, the second RC circuit being electrically coupled to the second sensor wire.

[0114] Exemplary Embodiment 13 13. The tumor treatment field system of exemplary embodiment 12, wherein the first capacitor has a first capacitance and the second capacitor has a second capacitance that is approximately 100 to 10,000 times greater than the first capacitance.

[0115] Exemplary Embodiment 14 9. The tumor treatment field system of exemplary embodiment 8, wherein the temperature sensing circuit does not have a capacitor in parallel with the first thermistor.

[0116] Exemplary Embodiment 15 The controller, when executed by the processor, further providing a third sensing signal along the first sensor wire, the third sensing signal having a third frequency greater than the second frequency; measuring a third impedance between the first sensor wire and the second sensor wire; 13. The tumor treatment field system of exemplary embodiment 12, further comprising the non-transitory computer-readable medium storing computer-executable instructions that cause the processor to: measure a third temperature of the third thermistor based on the first impedance, the second impedance, and the third impedance.

[0117] Exemplary Embodiment 16 13. The tumor treatment field system of exemplary embodiment 12, wherein the controller further comprises the non-transitory computer-readable medium storing computer-executable instructions that, when executed by the processor, cause the processor to: provide a third sensing signal having a third frequency that is in a range of one to four orders of magnitude greater than the second frequency and the first frequency.

[0118] Exemplary Embodiment 17 1. A method comprising: providing a TTF signal having a frequency in the range of 50 kHz to 1 MHz to a transducer array having a first electrode and a second electrode; providing a first sensing signal having a first frequency to a temperature sensing circuit having a first thermistor adjacent to the first electrode and coupled in series with an RC circuit having a second thermistor adjacent to the second electrode and a capacitor in parallel with the second thermistor; measuring a first impedance of the temperature sensing circuit; providing a second sensing signal to the temperature sensing circuit having a second frequency greater than the first frequency; measuring a second impedance of the temperature sensing circuit; measuring a first temperature of the first thermistor based on the second impedance; and determining a second temperature of the second thermistor based on the first impedance and the second impedance.

[0119] Exemplary Embodiment 18 the transducer array further comprises a third electrode, the RC circuit is a first RC circuit, the temperature sensing circuit comprises a second RC circuit in series with the first RC circuit, the second RC circuit comprising a third thermistor adjacent to the third electrode and a second capacitor in parallel with the third thermistor; providing a third sensing signal to the temperature sensing circuit having a third frequency greater than the second frequency; measuring a third impedance of the temperature sensing circuit; 18. The method of exemplary embodiment 17, further comprising: measuring a third temperature of the third thermistor based on the first impedance, the second impedance, and the third impedance.

[0120] Exemplary Embodiment 19 19. The method of Exemplary embodiment 18, wherein providing the third sensing signal includes providing the third sensing signal having a third frequency that is in a range of one to four orders of magnitude greater than the second frequency.

[0121] Exemplary Embodiment 20 18. The method of Exemplary embodiment 17, wherein providing the second sense signal includes providing the second sense signal having a second frequency that is in a range of one to four orders of magnitude greater than the first frequency.

[0122] Exemplary Embodiment 21 1. A transducer array comprising: A first electrode; A second electrode; 1. A temperature sensing circuit, comprising: a first circuit comprising a first thermistor in parallel with a first capacitor, the first thermistor being a first variable resistor whose resistance varies with temperature, a first reactance of the first circuit varying with frequency, the first thermistor adjacent to the first electrode; the temperature sensing circuit including a second circuit comprising a second thermistor in parallel with a second capacitor, the second thermistor being a second variable resistor whose resistance varies with temperature, a second reactance of the second circuit varying with frequency, the second thermistor adjacent to the second electrode, and the first circuit in series with the second circuit; a lead configured to transmit an electrical signal to the first electrode and the second electrode, the lead further comprising a first sensor wire electrically coupled to the first circuit and a second sensor wire electrically coupled to the second circuit.

[0123] Exemplary Embodiment 22 22. The transducer array of exemplary embodiment 21, further comprising a first inductor in parallel with the first capacitor and a second inductor in parallel with the second capacitor.

[0124] Exemplary Embodiment 23 23. The transducer array of exemplary embodiment 22, wherein the first capacitor and the first inductor have a first resonant frequency, and the second capacitor and the second inductor have a second resonant frequency different from the first resonant frequency.

[0125] Exemplary Embodiment 24 24. The transducer array according to any one of exemplary embodiments 21 to 23, wherein the second resonant frequency is in a range of 5 to 15 times the first resonant frequency.

[0126] Exemplary Embodiment 25 1. An oncology treatment field system, comprising: an electric field generator configured to generate an electric signal having an AC waveform at a frequency of 50 kHz to 1 MHz; A first electrode; A second electrode; a lead electrically coupled to the electric field generator, the lead configured to transmit the electrical signal to the first electrode and the second electrode, the lead further comprising a first sensor wire and a second sensor wire; 1. A temperature sensing circuit, comprising: a first circuit comprising a first thermistor in parallel with a first capacitor, the first thermistor being a first variable resistor whose resistance varies with temperature, a first reactance of the first circuit varying with frequency, the first thermistor adjacent to the first electrode; the temperature sensing circuit including a second circuit comprising a second thermistor in parallel with a second capacitor, the second thermistor being a second variable resistor whose resistance varies with temperature, a second reactance of the second circuit varying with frequency, the second thermistor adjacent to the second electrode, and the first circuit in series with the second circuit; a controller in communication with the electric field generator, the first sensor wire, and the second sensor wire, the controller having a processor and a controller that, when executed by the processor, providing a first sensing signal having a first frequency along the first sensor wire; measuring a first impedance between the first sensor wire and the second sensor wire; providing a second sense signal along the first sensor wire, the second sense signal having a second frequency greater than the first frequency; measuring a second impedance between the first sensor wire and the second sensor wire; and the controller having a non-transitory computer-readable medium storing computer-executable instructions that cause the processor to: determine a first temperature of the first thermistor and a second temperature of the second thermistor based on the first impedance and the second impedance.

[0127] Exemplary Embodiment 26 26. The tumor treatment field system of exemplary embodiment 25, further comprising a first inductor in parallel with the first capacitor and a second inductor in parallel with the second capacitor.

[0128] Exemplary Embodiment 27 27. The tumor treatment field system of exemplary embodiment 26, wherein the first capacitor and the first inductor have a first resonant frequency, and the second capacitor and the second inductor have a second resonant frequency different from the first resonant frequency.

[0129] Exemplary Embodiment 28 28. The tumor treatment field system according to any one of Exemplary Embodiments 25 to 27, wherein the second resonant frequency is in the range of 5 to 15 times the first resonant frequency.

[0130] Exemplary Embodiment 29 1. A method comprising: providing a TTF signal having a frequency in the range of 50 kHz to 1 MHz to a transducer array having a first electrode and a second electrode; providing a first sensing signal having a first frequency to a temperature sensing circuit having a first thermistor adjacent to the first electrode and coupled in series with a second thermistor adjacent to the second electrode and an RLC circuit having a capacitor and an inductor in parallel with the second thermistor; measuring a first impedance of the temperature sensing circuit; providing a second sensing signal to the temperature sensing circuit having a second frequency greater than the first frequency; measuring a second impedance of the temperature sensing circuit; measuring a first temperature of the first thermistor based on the first impedance; and determining a second temperature of the second thermistor based on the second impedance.

[0131] From the foregoing, it will be apparent that the inventive concepts described herein are adapted to achieve the features described in the present invention as well as those described in the present invention. While exemplary embodiments of the inventive concepts have been described for purposes of this disclosure, it will be understood that numerous modifications are possible which will readily occur to those skilled in the art.

[0132] The foregoing description provides illustration and description, but is not intended to be exhaustive or to limit the inventive concepts to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the methodologies described in the present disclosure.

[0133] Although particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure. Indeed, many of these features and steps can be combined in ways not specifically recited in the claims and / or disclosed in the specification. Although each dependent claim listed below may directly depend on only one other claim, the present disclosure includes each dependent claim in combination with every other claim in the claim set.

[0134] Similarly, while each exemplary embodiment listed above may depend directly on only one other exemplary embodiment, the present disclosure includes each exemplary embodiment in combination with all other exemplary embodiments within the set of exemplary embodiments for each mode of the inventive concepts disclosed herein.

[0135] No element, act, or instruction used herein should be construed as critical or essential to the present disclosure unless explicitly described outside of the preferred embodiments. Further, the phrase "based on" is intended to mean "based at least in part on," unless explicitly stated otherwise. [Explanation of symbols]

[0136] 18a 1st electrode 18b 2nd electrode 70 Transducer Array 108a First sensor wire 108b Second sensor wire 200 Temperature sensing circuit 204a First thermistor 204b Second thermistor

Claims

1. 1. A transducer array comprising: A first electrode; A second electrode; 1. A temperature sensing circuit, comprising: a first thermistor adjacent to the first electrode, the first thermistor being a first variable resistor whose resistance varies with temperature; the temperature sensing circuit comprising an RC circuit connected in series with the first thermistor, the RC circuit including a second thermistor adjacent the second electrode and a capacitor in parallel with the second thermistor, the second thermistor being a second variable resistor whose resistance varies with temperature; a lead configured to transmit an electrical signal to a first electrode and a second electrode, the lead further comprising a first sensor wire electrically coupled to the first thermistor and a second sensor wire electrically coupled to an RC circuit on an opposite side of the first thermistor.

2. the RC circuit is a first RC circuit, the capacitor is a first capacitor, and the temperature sensing circuit is A third electrode; 10. The transducer array of claim 1, further comprising: a second RC circuit coupled in series with the first thermistor and a third RC circuit, the second RC circuit comprising a third thermistor adjacent the third electrode and a second capacitor in parallel with the third thermistor, the third thermistor being a third variable resistor whose resistance changes with temperature.

3. The transducer array of claim 1 or 2, wherein the temperature sensing circuit does not have a capacitor in parallel with the first thermistor.

4. The transducer array of claim 2 , wherein the first thermistor is in direct contact with the first electrode.

5. 1. An oncology treatment field system, comprising: an electric field generator configured to generate an electric signal having an alternating current waveform at a frequency between 50 kHz and 1 MHz; A first electrode; A second electrode; a lead electrically coupled to the electric field generator, the lead configured to transmit the electrical signal to the first electrode and the second electrode, the lead further comprising a first sensor wire and a second sensor wire; 1. A temperature sensing circuit, comprising: a first thermistor adjacent to the first electrode, the first thermistor being a first variable resistor whose resistance varies with temperature and electrically coupled to the first sensor wire; an RC circuit coupled in series with the first thermistor, the RC circuit including a second thermistor adjacent to the second electrode and a capacitor in parallel with the second thermistor, the RC circuit being electrically coupled to the second sensor wire, the second thermistor being a second variable resistor having a resistance that varies with temperature; a controller in communication with the electric field generator, the first sensor wire, and the second sensor wire, the controller having a processor and a controller that, when executed by the processor, providing a first sensing signal having a first frequency along the first sensor wire; measuring a first impedance between the first sensor wire and the second sensor wire; providing a second sense signal along the first sensor wire having a second frequency greater than the first frequency; measuring a second impedance between the first sensor wire and the second sensor wire; measuring a first temperature of the first thermistor based on the second impedance; and the controller having a non-transitory computer-readable medium storing computer-executable instructions that cause the processor to: measure a second temperature of the second thermistor based on the first impedance and the second impedance.

6. 6. The tumor treatment field system of claim 5, wherein the second frequency is in the range of one to four orders of magnitude greater than the first frequency.

7. the RC circuit is a first RC circuit, the capacitor is a first capacitor, A third electrode; 6. The tumor treatment field system of claim 5, further comprising a second RC circuit coupled in series with the first RC circuit and the first thermistor, the second RC circuit comprising a third thermistor adjacent the third electrode and a capacitor in parallel with the third thermistor, the second RC circuit electrically coupled to the second sensor wire.

8. 8. The tumor treatment field system of claim 7, wherein the first capacitor has a first capacitance and the second capacitor has a second capacitance that is approximately 100 to 10,000 times greater than the first capacitance.

9. 6. The tumor treatment field system of claim 5, wherein the temperature sensing circuit does not have a capacitor in parallel with the first thermistor.

10. The controller, when executed by the processor, further providing a third sense signal along the first sensor wire, the third sense signal having a third frequency greater than the second frequency; measuring a third impedance between the first sensor wire and the second sensor wire; 10. The tumor treatment field system of claim 7, further comprising the non-transitory computer-readable medium storing computer-executable instructions that cause the processor to: measure a third temperature of the third thermistor based on the first impedance, the second impedance, and the third impedance.

11. The controller, when executed by the processor, further 10. The tumor treatment field system of claim 7, further comprising the non-transitory computer-readable medium storing computer-executable instructions that cause the processor to: provide a third sensing signal having a third frequency that is in the range of one to four orders of magnitude greater than the second frequency and the first frequency.

12. 1. A transducer array comprising: A first electrode; A second electrode; 1. A temperature sensing circuit, comprising: a first circuit comprising a first thermistor in parallel with a first capacitor, the first thermistor being a first variable resistor whose resistance varies with temperature, a first reactance of the first circuit varying with frequency, the first thermistor adjacent to the first electrode; the temperature sensing circuit including: a second circuit including a second thermistor in parallel with a second capacitor, the second thermistor being a second variable resistor whose resistance varies with temperature, a second reactance of the second circuit varying with frequency, the second thermistor adjacent the second electrode, and the first circuit in series with the second circuit; a lead configured to transmit an electrical signal to the first electrode and the second electrode, the lead further comprising a first sensor wire electrically coupled to the first circuit and a second sensor wire electrically coupled to the second circuit.

13. The transducer array of claim 12 further comprising a first inductor in parallel with the first capacitor and a second inductor in parallel with the second capacitor.

14. 14. The transducer array of claim 13, wherein the first capacitor and the first inductor have a first resonant frequency, and the second capacitor and the second inductor have a second resonant frequency different from the first resonant frequency.

15. 15. The transducer array of claim 14, wherein the second resonant frequency is in the range of 5 to 15 times the first resonant frequency.

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