Apparatus for applying alternating electric field and method for reducing spread of operating temperatures between electrode elements

Abstract

Sensor arrays used to apply alternating electric fields (e.g., tumor therapeutic fields, also known as TTFields) to a subject's body typically comprise a plurality of capacitively coupled electrode elements. Some electrode elements on a given array often tend to operate at higher temperatures than others. For example, in many anatomical contexts, corner elements of the sensor array tend to operate at higher temperatures than non-corner elements. The temperature difference between the electrode elements that tend to operate at higher temperatures and other electrode elements can be reduced by wiring a capacitor in series with those electrode elements that tend to operate at higher temperatures (e.g., corner elements).

Description

[Technical Field]

[0001] This application relates to using a capacitor to adjust the current in a sensor array used to apply a tumor treatment field. Cross-reference to related applications.

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 216,678, filed June 30, 2021, which is incorporated herein by reference in its entirety. [Previous Technology]

[0003] Tumor therapeutic field therapy is a proven method for treating tumors. Figure 1 is a schematic diagram of the Optune® system, a conventional technology for delivering a tumor therapeutic field. The tumor therapeutic field is delivered to the patient via four sensor arrays 21 to 24, which are positioned on the patient's skin relatively close to the tumor (e.g., as illustrated in Figures 2A to 2D for a patient with glioblastoma multiforme). The sensor arrays 21 to 24 are configured in two pairs, and each sensor array is connected to an AC signal generator 20 via a multi-wire cable. The AC signal generator (a) delivers an AC current through one pair of arrays 21, 22 during a first time period, which senses an electric field having a first direction passing through the tumor; then (b) delivers an AC current through another pair of arrays 23, 24 during a second time period, which senses an electric field having a second direction passing through the tumor; then steps (a) and (b) are repeated during the duration of treatment.

[0004] Each sensor array 21 to 24 is configured as a set of capacitively coupled electrode elements E (e.g., a set of nine electrode elements, each electrode element being approximately 2 cm in diameter), interconnected via a flexible circuit. Each electrode element comprises a conductive substrate having a dielectric layer disposed thereon (more specifically, a layer of ceramic material having a high dielectric constant). Each electrode element is sandwiched between a layer of conductive medical gel and an adhesive tape or bandage. When the array is placed on a patient, the medical gel conforms to the contours of the patient's skin and ensures good electrical contact between the device and the body. As the patient performs their daily activities, the adhesive tape or bandage holds the entire array in place on the patient.

[0005] When a first sensor array is positioned against the skin on one side of a person's body, and a second sensor array is positioned against the skin on the opposite side of the person's body, and an AC voltage is applied between the leads of the first and second sensor arrays, a current is capacitively coupled into the person's body. For the tumor treatment field to be effective, a sufficient amount of current must be capacitively coupled into the person's body through the electrodes; and higher currents are strongly correlated with more effective treatment.

[0006] The conductive medical gel beneath the ceramic element and the skin will heat up during use; therefore, safety considerations require that the temperature of each measured component of the ceramic element be kept below a specific safety threshold (e.g., 41°C).

[0007] The amplitude of the alternating current transmitted via the sensor array is controlled such that the temperature (as measured in the ceramic element) will not exceed a safe threshold (e.g., 41°C). Temperature measurements are obtained using a thermistor T placed in the center of some of the ceramic disks within the sensor array. In existing Optune® systems, each array contains eight thermistors, each positioned within a separate disk within the array. (Note that most arrays contain more than eight disks; in this case, temperature measurements are performed only on a subset of the disks within the array.)

[0008] The AC signal generator 20 obtains temperature measurements from all 32 thermistors (4 arrays × 8 thermistors per array), and the controller in the AC signal generator uses the temperature measurements to control the current transmitted through each pair of arrays in order to maintain the temperature below a safe threshold. The current itself is transmitted to each array via an additional wire (i.e., a wire 28 for each of arrays 21 to 24), which runs from the AC signal generator 20 to each array. [Summary of the Invention]

[0009] One aspect of the present invention relates to a first device for applying an alternating electric field to a living subject. The first device includes a plurality of conductive regions, each conductive region having a front side and a further region. The plurality of conductive regions includes a plurality of first conductive regions and at least one second conductive region. The first device further includes a plurality of dielectric material regions, each dielectric material region having (i) a further front side and (ii) a further back side, disposed against the front side of a corresponding one of the plurality of conductive regions. The first device further includes a substrate configured to hold the front side of the plurality of dielectric material regions on or within the body of the subject, and to support the plurality of conductive regions at individual locations. The first device further includes a main conductor electrically connected to each of the second conductive regions. The first device further includes a plurality of capacitors, each capacitor having a further first terminal electrically connected to another first conductive region of the first conductive regions, and a further second terminal electrically connected to the main conductor.

[0010] In some embodiments of the first device, the individual locations are distributed around a centroid, and each of the first conductive regions is positioned further outward relative to the centroid than each of the second conductive regions. Alternatively, in these embodiments, the first device has at least four first conductive regions and at least five second conductive regions.

[0011] In some embodiments of the first device, it has at least three first conductive regions and at least six second conductive regions. The individual locations are distributed in a pattern such that each of the first conductive regions is positioned at a given single end of the pattern, and none of the second conductive regions are positioned at the given single end of the pattern.

[0012] Another aspect of the invention is a first method for reducing the temperature difference between (a) a plurality of first capacitively coupled electrode elements positioned on or in the body of a subject and (b) at least one second capacitively coupled electrode element positioned on or in the body of a subject. The first method includes driving an AC current through each of the plurality of first capacitively coupled electrode elements when a further first capacitor is wired in series with each of the plurality of first capacitively coupled electrode elements; and driving an AC current through the at least one second capacitively coupled electrode element.

[0013] In some instances of the first method, each of the plurality of first capacitively coupled electrode elements has a capacitance that is 2 to 5 times greater than that of the individual first capacitor.

[0014] Certain embodiments of the first method further include supporting the plurality of first capacitively coupled electrode elements and the at least one second capacitively coupled electrode element at individual locations distributed around a centroid. In these embodiments, each of the first capacitively coupled electrode elements is positioned more peripherally relative to the centroid than each of the second capacitively coupled electrode elements.

[0015] In some instances of the first method, there are at least three first capacitively coupled electrode elements and at least six second capacitively coupled electrode elements. In these instances, the first method further includes supporting the at least three first capacitively coupled electrode elements and the at least six second capacitively coupled electrode elements at individual locations. And the individual locations are distributed in a pattern such that each of the first capacitively coupled electrode elements is positioned at a given single end of the pattern, and none of the second capacitively coupled electrode elements are positioned at the given single end of the pattern.

[0016] Another aspect of the invention relates to a second device for applying an alternating electric field to a living subject. The second device includes a plurality of conductive regions, each of which has a front side and a further region. The plurality of conductive regions includes a plurality of first conductive regions and at least one second conductive region. The second device further includes a plurality of dielectric material regions, each dielectric material region having (i) a further front side and (ii) a further back side, disposed abutting against the front side of a corresponding one of the plurality of conductive regions. The second device further includes a substrate configured to hold the front side of the plurality of dielectric material regions on or within the body of the subject and to support the plurality of conductive regions at individual locations. The second device further includes a plurality of first capacitors, each first capacitor being electrically connected in series with a further first conductive region.

[0017] In some embodiments of the second device, the individual locations are distributed around a centroid, and each of the first conductive regions is positioned further outward relative to the centroid than each of the second conductive regions. Optionally, in these embodiments, there are at least four first conductive regions and at least five second conductive regions.

[0018] In some embodiments of the second device, there are at least three first conductive regions and at least six second conductive regions. The individual locations are distributed in a pattern such that each of the first conductive regions is positioned at a given single end of the pattern, and none of the second conductive regions are positioned at the given single end of the pattern.

[0019] Some embodiments of the second device further include a plurality of electronically controllable switches, each switch (a) being electrically connected in parallel to another first capacitor of the first capacitor, and (b) being controllable by another electrical signal.

[0020] In some embodiments of the second device, each of the plurality of first capacitors is a variable capacitor whose capacitance can be controlled by a separate electrical signal.

[0021] Some embodiments of the second device further include a connector having a plurality of pins. The series electrical connection between each of the plurality of first capacitors and the individual first conductive regions is via another pin of the connector.

[0022] In some embodiments of the second device, the second device has at least four first conductive regions, at least five second conductive regions, and at least four first capacitors.

[0023] In some embodiments of the second device, the second device has at least four first conductive regions, at least five second conductive regions, and at least four first capacitors, and the second device further includes at least four electronically controllable switches, each switch (a) being electrically connected in parallel to another first capacitor, and (b) being controllable by another electrical signal. In these embodiments, each of the at least four first capacitors is a variable capacitor whose capacitance is controllable by another electrical signal.

[0024] In some embodiments of the second device, the second device has at least four first conductive regions, at least five second conductive regions, and at least four first capacitors, and the second device further includes a connector with at least four pins. The series connection between each of the at least four first capacitors and the individual first conductive regions is via another pin of the connector.

[0025] In some embodiments of the second device, the second device has at least four first conductive regions, at least five second conductive regions, and at least four first capacitors, and the second device further includes at least five second capacitors, each of which is electrically connected in series with another second conductive region.

[0026] In some embodiments of the second device, the second device has at least four first conductive regions, at least five second conductive regions, and at least four first capacitors, and the second device further includes at least five second capacitors, each of which is electrically connected in series with another second conductive region. These embodiments further include at least four electronically controllable switches, each switch being (a) electrically connected in parallel with another first capacitor of the first capacitors and (b) controllable by another electrical signal; and at least five electronically controllable switches, each switch being (a) electrically connected in parallel with another second capacitor of the second capacitors and (b) controllable by another electrical signal.

[0027] In some embodiments of the second device, the second device has at least four first conductive regions, at least five second conductive regions, and at least four first capacitors, and the second device further includes at least five second capacitors, each of which is electrically connected in series with another second conductive region. In these embodiments, each of the at least four first capacitors is a variable capacitor whose capacitance is controllable by another electrical signal, and each of the at least four second capacitors is a variable capacitor whose capacitance is controllable by another electrical signal.

[0028] Some embodiments of the second device further include a plurality of thermistors, each thermistor being (a) positioned in thermal contact with a separate first conductive region and (b) configured to generate a separate first signal in response to a detected temperature. In these embodiments, each of the first capacitors is a variable capacitor having a separate capacitance control input that receives a separate first signal from the first signals.

[0029] Certain embodiments of the second device further include a plurality of thermistors, each thermistor being (a) positioned in thermal contact with a different first conductive region and (b) configured to generate a different first signal in response to a detected temperature. Each of the first capacitors is a variable capacitor having a different capacitance control input that receives a different first signal from the first signals. These embodiments have at least four first conductive regions, at least five second conductive regions, at least four first capacitors, and at least four thermistors.

[0030] Certain embodiments of the second device further include a plurality of thermistors, each thermistor being (a) positioned in thermal contact with a separate first conductive region and (b) configured to generate a separate first signal in response to a detected temperature. Each of the first capacitors is a variable capacitor having a separate capacitance control input that receives a separate first signal from the first signals. These embodiments further include a plurality of resistors. Each thermistor has a first terminal connected to ground and a second terminal. One of the resistors is connected in series between the second terminal and a fixed voltage source. The second terminal of the thermistor is connected to the capacitance control input of the individual first capacitor to provide the individual first signal having a voltage determined according to the detected temperature of the individual first conductive region.

[0031] Certain embodiments of the second device further include a plurality of thermistors, each thermistor being (a) positioned in thermal contact with a separate first conductive region and (b) configured to generate a separate first signal in response to a detected temperature. Each of the first capacitors is a variable capacitor having a separate capacitance control input that receives a separate first signal from the first signals. These embodiments further include a plurality of resistors, each resistor being connected in series with a separate thermistor, such that a separate current flows through the separate thermistor to generate a separate first signal from the first signals. Alternatively, in these embodiments, the second device has at least four first conductive regions, at least five second conductive regions, at least four first capacitors, at least four thermistors, and at least four resistors.

[0032] Another aspect of the invention relates to a third device for applying an alternating electric field to a living subject. The third device includes a plurality of conductive regions, each of which has a front side and a further region. The plurality of conductive regions includes a plurality of first conductive regions and at least one second conductive region. The third device further includes a plurality of dielectric material regions, each dielectric material region having (i) a further front side and (ii) a further back side, disposed abutting against the front side of a corresponding one of the plurality of conductive regions. The third device further includes a substrate configured to hold the front side of the plurality of dielectric material regions on or within the body of the subject and to support the plurality of conductive regions at individual locations. The third device further includes a connector having a plurality of first pins and at least one second pin. The third device further includes at least one conductor, each conductor providing a conductive path between a further second pin and a further second conductive region. The third device further includes a plurality of capacitors, each capacitor having a separate first terminal electrically connected to a separate first conductive region of the first conductive region, and a separate second terminal electrically connected to a separate first pin of the first pin.

[0033] In some embodiments of the third device, the individual locations are distributed around a centroid, and each of the first conductive regions is positioned further outward relative to the centroid than each of the second conductive regions. Alternatively, in these embodiments, there are at least four first conductive regions, at least five second conductive regions, and at least five conductors.

[0034] In some embodiments of the third device, there are at least three first conductive regions and at least six second conductive regions. In these embodiments, the individual locations are distributed in a pattern such that each of the first conductive regions is positioned at a given single end of the pattern, and none of the second conductive regions are positioned at the given single end of the pattern.

Implementation Method

[0046] After examining temperature data captured from a 3×3 conventional technology sensor array of nine elements in numerous anatomical contexts, the inventors identified an interesting pattern. More specifically, when 80 conventional technology sensor arrays were used to apply a tumor treatment field to 20 randomly selected human subjects, the inventors obtained temperature data from those arrays. Each sensor array has nine ceramic elements configured in a 3×3 array, and all ceramic elements in any given sensor array have the same structure. The data comprises temperature measurements from individual ceramic elements within each sensor array (obtained using thermistors incorporated within the sensor array). The temperature measurements were analyzed to determine which ceramic element within any given sensor array first reached 41.1°C (in which case a voltage reduction is required to prevent the element from overheating and exceeding a predetermined threshold). This analysis revealed that more than 90% of the time, the first ceramic element to reach 41.1°C was one of the four corner elements. It is also noteworthy that in these cases, the temperature difference between the hottest and coldest elements was typically between 3 and 5°C. Computer simulations also revealed that the current flowing through corner components is higher than that through non-corner components.

[0047] Temperature measurement data were also analyzed to determine the average temperature and standard deviation for each disk location. This analysis revealed that the average temperature for the four corner elements was 37.84°C (standard deviation = 1.32; N = 639,413 temperature readings), while the average temperature for all measured non-corner elements was 37.14°C (standard deviation = 1.15; N = 641,708 temperature readings). This indicates that the four corner elements, on average, operated at a temperature 0.7°C higher than the measured non-corner elements.

[0048] As mentioned above, in many anatomical contexts, corner elements tend to operate at higher temperatures than non-corner elements. However, in other anatomical contexts, a different set of electrode elements may tend to operate at higher temperatures than the rest of the electrode elements. For example, elements at one end of the array may tend to operate at higher temperatures than (a) electrode elements at the opposite end of the array and (b) electrode elements in the middle of the array.

[0049] Whenever a given electrode element is operating below a safe critical temperature, it is safe to increase the current flowing through that electrode element. If the current flowing through elements at lower temperatures is increased until the temperature of those elements reaches a safe critical value, the total therapeutic current will increase.

[0050] The embodiments described herein balance and increase the average expected temperature of the electrode elements in a given sensor array (compared to conventional sensor arrays) by preemptively reducing the current flowing through electrode elements that tend to operate at higher temperatures. In most anatomical contexts, this would be the peripheral electrode elements (e.g., corner / end elements) of each sensor array. This allows a larger number of electrode elements in any given sensor array to operate closer to a safe critical temperature and increases the total therapeutic current delivered through the overall sensor array.

[0051] More specifically, the reduction in current is achieved by adding an individual capacitor connected in series with each of the electrode elements on the sensor array that tend to operate at higher temperatures. These capacitors increase the impedance in series with the individual electrode elements that are expected to heat at a higher-than-average rate. Therefore, the current through those electrode elements is reduced, thereby reducing the temperature of those electrode elements (in order to balance the temperature of the electrode elements that tend to operate at higher temperatures with the temperatures of the remaining elements). This balance will make it possible to increase the total current processed by the overall sensor array, which can increase the efficacy of the treatment.

[0052] FIG. 3A depicts a first embodiment of a sensor array 50 comprising a plurality of capacitively coupled electrode elements 52, which are designated E1 to E9 for ease of reference. Although FIG. 3A depicts nine electrode elements, this number can vary (e.g., between 6 and 50). As shown in FIG. 3B, which is a side view detail of a single electrode element 52 applicable to FIG. 3A (and FIG. 4 to 10 discussed below), each of these electrode elements 52 has a conductive region 52C and a dielectric material region 52D disposed thereon. More specifically, each conductive region 52C has a front side and an additional region, and each dielectric material region 52D has (i) an additional front side and (ii) an additional back side disposed against the front side of a corresponding one of the plurality of conductive regions 52C. In some embodiments, each of these electrode elements 52 includes a disk of ceramic material (serving as a dielectric material region 52D) and a metallization layer disposed on the back side of the ceramic disk (serving as a conductive region 52C), similar to the structure of conventional electrode elements used in Optune® systems. In alternative embodiments, different types of conductive regions may be used (e.g., pads on a flexible circuit), and different types of dielectric layers may be used (e.g., a layer of polymer with a high dielectric constant, such as Poly(VDF-TrFE-CtFE) and Poly(VDF-TrFE-CFE)). In some embodiments, the sum of the areas of all conductive regions 52C is at least 25 cm², and in some embodiments, the sum of all those areas is at least 50 cm² or at least 100 cm².

[0053] A substrate 59 is configured to hold the front surfaces of a plurality of dielectric material regions 52D of each electrode element 52 on or within the body of a subject, and to support a plurality of conductive regions 52C at individual locations distributed around a centroid. Optionally, the substrate 59 may include a flexible backing (e.g., a layer of foam material). Preferably, when the sensor array 50 is positioned against the body of a subject, a layer of hydrogel or conductive adhesive is disposed between the dielectric layer of the electrode element 52 and the body of the subject. The structure of the substrate 59 may be implemented using any of a variety of known methods that will be apparent to those skilled in the art, including, but not limited to, self-adhesive fabric, foam, or plastic sheets.

[0054] In the embodiment of FIG3A, the centroid of the conductive regions of electrode elements E1 to E9 coincides with the center of electrode element E5. However, when different numbers of electrode elements are contained in a sensor array, the centroid may not coincide with any of the electrode elements.

[0055] In the embodiment of FIG. 3A, the conductive regions 52C are divided into two groups, referred herein to as the first conductive regions and the second conductive regions. The substrate 59 supports the electrode elements 52 such that each of the first conductive regions is positioned further outward relative to the centroid than each of the second conductive regions. In the embodiment depicted in FIG. 3A, the conductive regions of each of the four corner elements (i.e., E1, E3, E7, E9, which are positioned further outward) correspond to the first conductive regions, and the conductive regions of the other electrode elements 52 (i.e., E2, E4 to E6, and E8) correspond to the second conductive regions.

[0056] The sensor array 50 also includes a plurality of first capacitors 55, which are also supported by a substrate 59. Each capacitor 55 is electrically connected in series with another first conductive region (which corresponds to the more peripheral electrode element). In the embodiment of FIG. 3A, this is achieved by wiring one terminal of each capacitor to another first conductive region and wiring the other terminal of each capacitor to a main conductor. Furthermore, in the embodiment of FIG. 3A, each of the second conductive regions (i.e., those corresponding to the more central electrode element) is also wired to the main conductor. Optionally (as shown in FIG. 3A), the main conductor is also connected to a connector 57, which connects the sensor array 50 to the AC signal generator 20 that drives the sensor array 50. It should be noted that the wiring described herein can be implemented using one or more lines and / or one or more wires on a flexible circuit.

[0057] Each addition of capacitor 55 is connected in series with another electrode element located on the periphery (i.e., E1, E3, E7, and E9 in the illustrated embodiment) with a different impedance. Thus, a reduced current will flow through those electrode elements (compared to corner elements in the prior art that do not contain series capacitors). Due to the reduced current, electrode elements E1, E3, E7, and E9 will not become as hot as corner elements in the prior art that do not contain series capacitors.

[0058] A series of experiments were conducted to measure how connecting a capacitor in series with peripheral electrode elements affected the difference in operating temperature of electrode elements within a given array of electrode elements. As a control, a pair of capacitively coupled electrode elements in a 3×3 array from a conventional Optune® system were placed on the opposite side of the thigh of a subject in a live human experiment, and a current of 1.6 A was passed through those arrays until the temperature on the arrays reached a steady state. The capacitance of each electrode element in these arrays was 50 pF. For subject #1, the results are as follows (all values ​​are in °C): Table 1 Average temperature of the four corner elements Average temperature of 5 non-corner components Maximum temperature of the four corner components Maximum temperature of 5 non-corner components Difference between the means The difference between the maximum values Array #1 40.2 38.95 40.4 39.4 1.25 1 Array #2 39.225 38.55 39.6 38.7 0.675 0.9

[0059] And for subject #2, the results are as follows (all values ​​are in °C): Table 2 Average temperature of the four corner elements Average temperature of 5 non-corner components Maximum temperature of the four corner components Maximum temperature of 5 non-corner components Difference between the means The difference between the maximum values Array #1 39.1 38.5 40 38.9 0.6 1.1 Array #2 37.875 37.575 38.7 38.1 0.3 0.6

[0060] The same experiment was then repeated under the same conditions, except that each of the capacitively coupled electrode elements of the 3×3 array from the known Optune® system was modified using four 17pF capacitors (i.e., by adding one of the 17pF capacitors in series with each of the four corner electrode elements). For subject #1, the results are as follows (all values ​​are in °C): Table 3 Average temperature of the four corner elements Average temperature of 5 non-corner components Maximum temperature of the four corner components Maximum temperature of 5 non-corner components Difference between the means The difference between the maximum values Array #1 39.85 39.825 40 40.2 0.025 -0.2 Array #2 38.4 38.95 39.4 39.3 -0.55 0.1

[0061] And for subject #2, the results are as follows (all values ​​are in °C): Table 4 Average temperature of the four corner elements Average temperature of 5 non-corner components Maximum temperature of the four corner components Maximum temperature of 5 non-corner components Difference between the means The difference between the maximum values Array #1 38.6 38.425 38.9 39.1 0.175 -0.2 Array #2 38.3 38.55 39.1 38.9 -0.25 0.2

[0062] When comparing the data in (a) Table 1 with the data in Table 3, and (b) the data in Table 2 with the data in Table 4, it is evident that adding a capacitor in series with the corner element reduces the temperature difference between the electrode elements located at the corners of the array and those not located at the corners of the array. This ultimately enables a larger number of electrode elements in any given sensor array to operate closer to the safe critical temperature, meaning that the total therapeutic current transmitted through a given overall sensor array can be increased, which advantageously enhances the therapeutic efficacy.

[0063] It should be noted that the experiments described above with respect to Tables 1 to 4 utilize capacitively coupled electrode elements with a capacitance of 50 pF per element and a 17 pF capacitor. This indicates that the capacitance of the electrode elements is greater than three times that of the capacitor. However, in alternative embodiments, the capacitance of the electrode elements can be between two and five times that of the capacitor.

[0064] Preferably, each sensor array 50 also includes a temperature sensor (e.g., a thermistor, not shown) in thermal contact with the electrode element 52. These sensors sense the temperature of the electrode element and transmit corresponding signals to the field generator driving the sensor array 50 via additional wires (not shown) in connector 57. This can be accomplished using the same method used in the Optune® conventional system, in which case the sensor array 50 of FIG3A would be backward compatible with the conventional Optune® AC signal generator 20 shown in FIG1. ​​Any of various alternative methods for sensing the temperature of the electrode element and reporting those temperatures to the system 20 driving the sensor array 50 may also be used. However, if an alternative temperature sensing / reporting method is used, the sensor array 50 may no longer be compatible with the conventional Optune® AC signal generator.

[0065] FIG4 depicts a second embodiment of a sensor array 150, comprising a plurality of capacitively coupled electrode elements 52, labeled E1 to E9. As in the embodiment of FIG3A, the number of electrode elements may vary. As described above with respect to FIG3A / FIG3B, each of these electrode elements 52 has a conductive region 52C and a dielectric material region 52D disposed thereon. More specifically, each conductive region 52C has a front side and an additional region, and each dielectric material region 52D has (i) an additional front side and (ii) an additional back side, which is disposed against the front side of the corresponding one of the plurality of conductive regions. As described above with respect to FIG3A / FIG3B, the total area of ​​all conductive regions may be at least 25 cm², at least 50 cm², or at least 100 cm².

[0066] The conductive region 52C is divided into the same two groups as described in the related Figures 3A / 3B above. And as described in the related Figure 3A above, a substrate 59 supports the electrode elements 52 at individual locations distributed around a centroid.

[0067] The sensor array 150 also includes a plurality of first capacitors 55, which are also supported by a substrate 59. Each capacitor 55 is electrically connected in series with another first conductive region of the first conductive region (corresponding to the peripheral electrode element 52). In the embodiment of FIG4, this is achieved using a connector 157 having a plurality of first pins and at least one second pin. Each capacitor 55 has a separate first terminal electrically connected to another first conductive region of the first conductive region and a separate second terminal electrically connected to another first pin of the first pins. At least one conductor is also provided, each conductor providing a conductive path between a separate second pin and a separate second conductive region. The wiring described herein can be implemented using one or more lines and / or one or more wires on a flexible circuit.

[0068] It is worth noting that, since each of the electrode elements 52 (E1 to E9) in the embodiment of FIG4 is driven by its own dedicated wire, an alternative method for reducing the temperature of any given electrode element (E1 to E9) can be used in conjunction with a series capacitor-based method for reducing the temperature of corner elements (E1, E3, E7, E9). For example, if a given electrode element operates at a higher temperature than the other electrode elements, the AC signal generator 120 can reduce the duty cycle of the signal applied to the given element to cool it down, regardless of whether the given element is a corner element or a non-corner element.

[0069] An AC signal generator 120 provides one polarity of an AC signal to each pin of a connector 157 and provides the other polarity of an AC signal to each pin of a corresponding connector that feeds another, which may be the same sensor array 150.

[0070] As in the embodiment of FIG. 3A above, each of the capacitors 55 in this embodiment of FIG. 4 incorporates an additional impedance connected in series with one of the individual electrode elements located in the more peripheral electrode elements. Thus, a reduced current will flow through those electrode elements, and they will not become as hot as corner elements of the prior art that do not include series capacitors. Preferably, each sensor array 150 also includes a temperature sensor (e.g., a thermistor as described in the related FIG. 3A above, which is not shown).

[0071] FIG. 5 depicts a third embodiment of a sensor array 250, comprising a plurality of capacitively coupled electrode elements 52, labeled E1 to E9. As in the embodiment of FIG. 3A, the number of electrode elements may vary. As described in the related FIG. 3A / 3B above, each of these electrode elements 52 has a conductive region 52C and a dielectric material region 52D disposed thereon. More specifically, each conductive region 52C has a front side and an additional region, and each dielectric material region 52D has (i) an additional front side and (ii) an additional back side, which is disposed against the front side of the corresponding one of the plurality of conductive regions. As described in the related FIG. 3A / 3B above, the total area of ​​all conductive regions may be at least 25 cm², at least 50 cm², or at least 100 cm².

[0072] The conductive region 52C is divided into the same two groups as described in the related Figures 3A / 3B above. And as described in the related Figure 3A above, a substrate 59 supports the electrode elements 52 at individual locations distributed around a centroid.

[0073] This embodiment of FIG. 5 also includes a plurality of first capacitors 55. However, instead of placing the capacitors 55 on the sensor array (supported by the substrate 59) as described above for the embodiments of FIG. 3A and FIG. 4, the capacitors 55 in this embodiment of FIG. 5 are located within the AC signal generator 220 (i.e., on the opposite side of connectors 57 / 257). Each of the first conductive regions and each of the second conductive regions of the sensor array 250 are wired to an individual pin of the connector 257 itself. And each of the capacitors 55 is electrically connected in series with another pin of the pin, the individual pin feeding one of the first conductive regions (which corresponds to the more peripheral electrode element). For example, in the embodiment of FIG. 5, electrode elements E1, E3, E7, and E9 correspond to the first conductive regions, and capacitors C1, C3, C7, and C9 are wired in series with the pins of the connector 257 that feed those first conductive regions.

[0074] An AC signal generator 220 includes an AC voltage generator 225 that provides one polarity of an AC signal to the lower terminals of each of C1, C3, C7, and C9, and also directly provides the same polarity of the AC signal to the pins of each of the feed second conductive areas of connector 257 (i.e., corresponding to electrode elements E2, E4, E5, E6, and E8). The other polarity of the AC signal is provided to the corresponding pins of a corresponding connector feeding a second sensor array (not shown), the second sensor array being identical, wherein the corresponding capacitors are wired in series with the pins of each of the first conductive areas feeding the second (identical) sensor array (which correspond to corner elements).

[0075] As in the embodiment of FIG. 3A above, each of the capacitors 55 in this embodiment of FIG. 5 incorporates an additional impedance connected in series with another electrode element located on the periphery of the electrode element 52. Thus, a reduced current will flow through those electrode elements, and they will not become as hot as corner elements of the prior art that do not include series capacitors. Preferably, each sensor array 250 also includes a temperature sensor (e.g., a thermistor as described in the related FIG. 3A above, which is not shown).

[0076] FIG6 depicts a fourth embodiment of a sensor array 350 comprising a plurality of capacitively coupled electrode elements 52 (labeled E1 to E9). This embodiment of FIG6 is similar to the embodiment of FIG5 described above (i.e., where capacitors 55 are present within the AC signal generator 320, and each capacitor is connected and wired as described for the embodiment of FIG5), except that an electronically controlled switch 60 is wired in parallel with each of the capacitors 55 (C1, C3, C7, and C9), and a controller 330 controls the state of each of these switches 60 (labeled S1, S3, S7, and S9, corresponding to the four capacitors C1, C3, C7, and C9).

[0077] As in the embodiment of FIG. 5 above, each of the capacitors 55 in this embodiment of FIG. 6 is connected in series with another electrode element located on the periphery. Thus, a reduced current will flow through those electrode elements, and they will not become as hot as corner elements of the prior art that do not contain series capacitors.

[0078] Preferably, each sensor array 350 also includes a temperature sensor (e.g., a thermistor (not shown) as described in the related Figure 3A above, which is associated with the electrode element 52 and supported by the substrate 59). The controller 330 can control the state of each of the switches 60 based on data received from the temperature sensor. For example, the controller 330 can be preset to an initial state in which all switches 60 are open. Then, if the controller 330 detects that one of the corner electrode elements 52 is cold enough to handle a larger current, the controller 330 can close the corresponding one of the switches 60. This will create a low-impedance path for the individual capacitor 55 in parallel, which will increase the current to the individual electrode element 52.

[0079] The AC signal generator 320, the AC voltage generator 325, and the connector 357 operate as described above in the corresponding elements 220, 225, and 257 in the related Figure 5.

[0080] FIG7 depicts a fifth embodiment of a sensor array 450 comprising a plurality of capacitively coupled electrode elements 52 (labeled E1 to E9). This embodiment of FIG7 is similar to the embodiment of FIG5 described above (i.e., where variable capacitors 455 are present within the AC signal generator 420, and where each capacitor is connected and wired as described for the embodiment of FIG5), except that each of the capacitors 55 in FIG5 is replaced by a variable capacitor 455 (C1, C3, C7, and C9), and a controller 430 controls the capacitance of each of these variable capacitors 455.

[0081] As in the embodiment of FIG. 5 above, each of the variable capacitors 455 in this embodiment of FIG. 7 incorporates an additional impedance connected in series with another electrode element located on the periphery of the electrode element 52. Thus, a reduced current will flow through those electrode elements, and they will not become as hot as corner elements of the prior art that do not contain series capacitors.

[0082] Preferably, each sensor array 450 also includes a temperature sensor (e.g., a thermistor associated with the electrode element 52 and supported by the substrate 59, as shown in the related Figure 3A above, which is not shown). The controller 430 can control the state of each of the variable capacitors 455 based on data received from the temperature sensor. For example, the controller 430 can be preset to an initial state in which all the variable capacitors 455 are set to their minimum capacitance, which provides the highest series impedance. Then, if the controller 430 detects that one of the corner electrode elements 52 is cold enough to handle a larger current, the controller 430 can increase the capacitance of the corresponding variable capacitor 455. This will reduce the impedance of the variable capacitor 455, which will increase the current to the individual electrode element 52.

[0083] The AC signal generator 420, the AC voltage generator 425, and the connector 457 operate as described above in the corresponding elements 220, 225, and 257 in the related Figure 5.

[0084] FIG8 depicts a sixth embodiment of a sensor array 550, which includes a plurality of capacitively coupled electrode elements 52 (labeled E1 to E9). This embodiment of FIG8 is similar to the embodiment of FIG6 described above (i.e., where capacitors 55 are present within the AC signal generator 520, and where each capacitor is connected and wired as described for the embodiment of FIG5). In addition to the plurality of first capacitors 55 electrically connected in series with individual first conductive regions (where a corresponding electronically controlled switch 60 is wired in parallel with each capacitor 55), this embodiment also includes a plurality of second capacitors 55 electrically connected in series with individual second conductive regions (where a corresponding electronically controlled switch 60 is wired in parallel with each capacitor 55). Thus, in the exemplary embodiment depicted in Figure 8, there are nine electrode elements (labeled E1 to E9), nine capacitors 55 (labeled C1 to C9), and nine electrically controlled switches 60 (labeled S1 to S9), each of which is wired in parallel with another capacitor of the capacitors 55. This gives the controller 530 control over the impedance guiding all the electrode elements 52 (as opposed to controlling only the impedance guiding the more peripheral electrode elements 52).

[0085] Preferably, each sensor array 550 also includes a temperature sensor (e.g., a thermistor (not shown) as described in the related Figure 3A above, which is associated with the electrode element 52 and supported by the substrate 59). The controller 530 can control the state of each of the switches 60 based on data received from the temperature sensor. For example, the controller 530 can be preset to an initial state in which all switches 60 are open. Then, if the controller 530 detects that any electrode element 52 is cold enough to handle a larger current, the controller 530 can close the corresponding one of the switches 60. This will create a low-impedance path for the individual capacitor 55 in parallel, which will increase the current to the individual electrode element 52.

[0086] In the embodiment of FIG8, each of the capacitors 55 is connected in series with another electrode element. The controller 530 can therefore selectively increase the impedance to those paths leading to the first conductive region (i.e., the more peripheral region) to reduce the current flowing through the corresponding electrode element 52, which will result in a corresponding decrease in temperature.

[0087] The AC signal generator 520, the AC voltage generator 525, and the connector 557 operate as described in the corresponding elements 220, 225, and 257 in the related Figure 5 above.

[0088] FIG9 depicts a seventh embodiment of a sensor array 650, which includes a plurality of capacitively coupled electrode elements 52 (labeled E1 to E9). This embodiment of FIG9 is similar to the embodiment of FIG7 described above (i.e., where variable capacitors 455 are present within the AC signal generator 620, and where each capacitor is connected and wired as described in the embodiment of FIG5). In addition to the plurality of first variable capacitors 455 electrically connected in series with individual first conductive regions, this embodiment also includes a plurality of second variable capacitors 455 electrically connected in series with individual second conductive regions. Thus, in the exemplary embodiment depicted in FIG9, there are nine electrode elements (labeled E1 to E9) and nine variable capacitors 455 (labeled C1 to C9). This gives the controller 630 control over the impedance of all the electrode elements 52 (as opposed to controlling only the impedance of the electrode elements 52 located on the periphery).

[0089] Preferably, each sensor array 650 also includes a temperature sensor (e.g., a thermistor (not shown) as described in the related Figure 3A above, which is associated with the electrode element 52 and supported by the substrate 59). The controller 630 can control the state of each of the variable capacitors 455 based on data received from the temperature sensor. For example, the controller 630 can be preset to an initial state in which all the variable capacitors 455 are set to their minimum capacitance, providing the highest series impedance. Then, if the controller 630 detects that one of the corner electrode elements 52 is cold enough to handle a larger current, the controller 630 can increase the capacitance of the corresponding variable capacitor 455. This will reduce the impedance of the variable capacitor 455, which will increase the current to the individual electrode element 52.

[0090] In the embodiment of FIG9, each of the variable capacitors 455 is connected in series with another electrode element 52, adding an additional impedance. The controller 630 can therefore selectively increase the impedance to those paths leading to the first conductive region (i.e., the more peripheral region) in order to reduce the current flowing through the corresponding electrode element 52, which will result in a corresponding decrease in temperature.

[0091] The AC signal generator 620, the AC voltage generator 625, and the connector 657 operate as described above in the corresponding elements 220, 225, and 257 in the related Figure 5.

[0092] FIG. 10 depicts an eighth embodiment of a sensor array 750 comprising a plurality of capacitively coupled electrode elements 52 (labeled E1 to E9). This embodiment of FIG. 10 is similar to the embodiment of FIG. 3A described above, except that the fixed capacitor 55 in the embodiment of FIG. 3A is replaced by a variable capacitor 755, and a thermistor-based circuit (shown as A1, A3, A7, and A9 respectively at electrode elements E1, E3, E7, and E9) is used to automatically adjust the capacitance of the variable capacitor 755 according to the temperature of the individual electrode elements. An example of a circuit suitable for implementing each of the thermistor-based circuits A1, A3, A7, and A9 is depicted in the illustration in the lower right corner of FIG. 10 and labeled A (representing). However, various alternative circuits can be used to replace circuit A (representing) to control the series capacitor.

[0093] In the illustrated embodiment, each thermistor-based circuit includes a thermistor 770 (e.g., a positive temperature coefficient thermistor, shown as T9 in the illustration of FIG. 10), which is positioned in thermal contact with another electrode element of electrode element 52. Each thermistor 770 is wired in series with a pull-up resistor 760, so that the voltage at the node between any given thermistor 770 and its corresponding resistor 760 will increase as the temperature of the thermistor 770 increases. The signal at this node is the capacitance of a control variable capacitor 755 (shown as C9 in the illustration of FIG. 10). For example, the variable capacitor 755 may be a Murata LXRW0YV201-059, which has a capacitance varying from 200pF (when the control signal is 0V) to 100pF (when the control signal is 3V).

[0094] Suppose a given electrode element is started at a low temperature. This will generate a relatively low voltage at the control node, which will result in a relatively high capacitance of the variable capacitor 755. This relatively high capacitance will generate a relatively low series impedance, which will initially allow a maximum measured current to reach the electrode element 52.

[0095] Now let us assume that the maximum measured current causes one of the electrode elements 52 to heat up. Since the corresponding thermistor 770 is in thermal contact with the electrode element 52, it will heat up, which will increase the voltage at the control node. This increase in voltage will reduce the capacitance of the variable capacitor 755, which means that the impedance of the variable capacitor 755 will increase. And this increase in the impedance of the variable capacitor 755 will reduce the amount of current flowing through the electrode element 52 until equilibrium is reached. The value of resistor 760 and the nominal value of the thermistor 770 can be selected such that the equilibrium point is below 41°C.

[0096] It is worth noting that the embodiment of FIG10 automatically adjusts the capacitance of the variable capacitor 755, which is wired in series with the corner elements E1, E3, E7, and E9, to reduce the temperature difference between the corner elements (which are expected to operate at higher temperatures than other elements) and the non-corner elements. However, in an alternative embodiment, a copy of the circuit depicted in the illustration of FIG10 is incorporated in series with all the electrode elements E1 to E9. In this case, heating of any given electrode element (as opposed to only the corner elements) will reduce the capacitance of the individual variable capacitor 755 wired in series with the given element (and thereby increase the impedance). This increase in impedance will reduce the amount of current flowing through the given electrode element until equilibrium is reached. Therefore, these alternative embodiments provide automatic current regulation for all electrode elements E1 to E9 (as opposed to regulating only the corner elements).

[0097] As explained above, in many anatomical scenarios, corner elements tend to operate at higher temperatures than non-corner elements. Furthermore, in these scenarios, connecting a wiring capacitor in series with the corner element as described above will reduce the temperature difference between the corner and non-corner elements. However, in certain specific anatomical scenarios, it is not that corner elements tend to operate at higher temperatures than other elements. Rather, in these scenarios, electrode elements at one end of the array tend to operate at higher temperatures than electrode elements at the opposite end of the array and electrode elements in the middle of the array.

[0098] An example of this anatomical context is when a tumor treatment field is applied between a nine-element electrode assembly positioned at the front / top of a subject's head (e.g., as in Figure 2A) and a second nine-element electrode assembly positioned at the back of a subject's head (e.g., as in Figure 2B). In this anatomical context, if the same signal is applied between all nine electrode elements in the array of Figure 2A and all nine electrode elements in the array of Figure 2B, the last three elements of the array of Figure 2A and the top three elements of the array of Figure 2B will typically operate significantly hotter than the remaining elements in those arrays. More specifically, thermal analysis of this situation reveals that the last three elements of the array of Figure 2A are operating at approximately 37.5°C, while the other six elements of that array are operating at approximately 36.25°C. In these anatomical contexts, not because the wiring capacitor is connected in series with the corner element (as described above), the difference in operating temperature between electrode elements in a given array can be reduced by connecting the wiring capacitor in series with the three electrode elements in the array that operate at higher temperatures.

[0099] In other anatomical contexts, a different subset of electrode elements may tend to operate at higher temperatures than the rest of the electrode elements. In these contexts, the difference in operating temperatures between electrode elements on a given array can be reduced by connecting hardwired capacitors in series with whichever electrode element is expected to operate at a higher temperature.

[0100] When it is unknown in advance which electrode elements will operate at higher temperatures than others, it can be advantageous to use the embodiment with a separate switchable capacitor for each electrode element (as in the embodiment of FIG. 8), or to use a separate variable capacitor for each electrode element (as in the embodiment of FIG. 9). This is because the controller 530 / 630 can determine in real time which electrode elements are operating at higher temperatures and increase the series impedance to those electrode elements. The increased impedance will reduce the current to those electrode elements, which will lower the temperature of those electrode elements, thus reducing the temperature difference between operating elements.

[0101] It should be noted that although the exemplary embodiments depicted in Figures 3 to 10 all depict nine electrode elements E1 to E9 configured in a rectangular pattern, the concept described herein is equivalent to that applicable to electrode assemblies with different numbers of electrode elements, and / or electrode assemblies in which the electrode elements are configured in other patterns (e.g., circular, rectangular, polygonal, or irregular patterns).

[0102] Unless otherwise indicated herein or otherwise clearly contradicted by the context, any embodiment described under any heading or in any part of this disclosure may be combined with any embodiment described under the same or any other heading or in any other part of this disclosure.

[0103] Although the present invention has been disclosed with reference to certain embodiments, many modifications, alterations and variations of the embodiments are possible without departing from the scope and range of the invention as defined in the appended claims. Thus, it is intended that the invention is not limited to the disclosed embodiments, but has the broadest scope defined by the language of the following claims and their equivalents. [Simplified Explanation of the Diagram]

[0035] [Figure 1] is a schematic diagram of the Optune® system, a conventional technology used to deliver a tumor treatment field.

[0036] [Figure 2A] to [Figure 2D] depict the positioning of a sensor array on a person's head for the treatment of a brain tumor.

[0037] [Figure 3A] is a schematic diagram of a first embodiment of a sensor array used to apply a tumor treatment field to the body of a subject.

[0038] [Figure 3B] is a side view of a single electrode element in a sensor array.

[0039] [Figure 4] is a schematic diagram of a second embodiment of a sensor array used to apply a tumor treatment field to the body of a subject.

[0040] [Figure 5] is a block diagram of a third embodiment of a system including a sensor array, which is used to apply a tumor treatment field to the body of a subject.

[0041] [Figure 6] is a block diagram of a fourth embodiment of a system including a sensor array, which is used to apply a tumor treatment field to the body of a subject.

[0042] [Figure 7] is a block diagram of a fifth embodiment of a system including a sensor array, which is used to apply a tumor treatment field to the body of a subject.

[0043] [Figure 8] is a block diagram of a sixth embodiment of a system including a sensor array, which is used to apply a tumor treatment field to the body of a subject.

[0044] [Figure 9] is a block diagram of a seventh embodiment of a system including a sensor array, which is used to apply a tumor treatment field to the body of a subject.

[0045] [Figure 10] is a schematic diagram of an eighth embodiment of a sensor array used to apply a tumor treatment field to the body of a subject.

Claims

1. A device for applying an alternating electric field to a living subject, the device comprising: A plurality of conductive regions, each conductive region having a front side and an individual region, wherein the plurality of conductive regions includes a plurality of first conductive regions and at least one second conductive region; a plurality of dielectric material regions, each dielectric material region having (i) an individual front side and (ii) an individual back side, which is disposed against the front side of a corresponding one of the plurality of conductive regions; a substrate configured to hold the front side of the plurality of dielectric material regions on or within the body of the subject, and to support the plurality of conductive regions at individual locations; a main conductor electrically connected to each second conductive region; And a plurality of capacitors, each capacitor having an individual first terminal electrically connected to another first conductive region among the plurality of first conductive regions, and having an individual second terminal electrically connected to the main conductor.

2. The device of claim 1, wherein the individual locations are distributed around the centroid, and wherein each first conductive region is positioned further outward relative to the centroid than each second conductive region.

3. The device of claim 2, wherein the device has at least four first conductive regions and at least five second conductive regions.

4. The device of claim 1, wherein the device has at least three first conductive regions and at least six second conductive regions, and wherein the individual positions are distributed in a pattern such that each first conductive region is positioned at a given single end of the pattern, and each second conductive region is not positioned at the given single end of the pattern.

5. A method for reducing the temperature difference between (a) a plurality of first capacitively coupled electrode elements positioned on or in the body of a subject and (b) at least one second capacitively coupled electrode element positioned on or in the body of the subject, the method comprising: When another first capacitor is wired in series with each of the plurality of first capacitively coupled electrode elements, AC current is driven through each of the plurality of first capacitively coupled electrode elements; and the AC current is driven through the at least one second capacitively coupled electrode element.

6. The method of claim 5, wherein each of the plurality of first capacitively coupled electrode elements has a capacitance greater than 2 to 5 times that of the individual first capacitor.

7. The method of claim 5, further comprising supporting the plurality of first capacitively coupled electrode elements and the at least one second capacitively coupled electrode element at individual locations distributed around the centroid, wherein each first capacitively coupled electrode element is positioned more peripherally relative to the centroid than each second capacitively coupled electrode element.

8. The method of claim 5, wherein there are at least three first capacitively coupled electrode elements and at least six second capacitively coupled electrode elements, wherein the method further comprises supporting the at least three first capacitively coupled electrode elements and the at least six second capacitively coupled electrode elements at individual locations, wherein the individual locations are distributed in a pattern such that each first capacitively coupled electrode element is positioned at a given single end of the pattern, and each second capacitively coupled electrode element is not positioned at the given single end of the pattern.

9. A device for applying an alternating electric field to a living subject, the device comprising: A plurality of conductive regions, each conductive region having a front side and an individual region, wherein the plurality of conductive regions includes a plurality of first conductive regions and at least one second conductive region; a plurality of dielectric material regions, each dielectric material region having (i) an individual front side and (ii) an individual back side, which is disposed against the front side of a corresponding one of the plurality of conductive regions; a substrate configured to hold the front side of the plurality of dielectric material regions on or within the body of the subject, and to support the plurality of conductive regions at individual locations; And a plurality of first capacitors, each of which is connected in series with another first conductive region.

10. The device of claim 9, wherein the individual locations are distributed around the centroid, and wherein each first conductive region is positioned further outward relative to the centroid than each second conductive region.

11. The device of claim 10, wherein the device has at least four first conductive regions and at least five second conductive regions.

12. The device of claim 9, wherein the device has at least three first conductive regions and at least six second conductive regions, and wherein the individual positions are distributed in a pattern such that each first conductive region is positioned at a given single end of the pattern, and each second conductive region is not positioned at the given single end of the pattern.

13. The device of claim 9 further includes a plurality of electronically controllable switches, each electronically controllable switch being (a) electrically connected in parallel to another first capacitor of the plurality of first capacitors and (b) controllable by an individual electrical signal.

14. The apparatus of claim 9, wherein each of the plurality of first capacitors is a variable capacitor whose capacitance can be controlled by an individual electrical signal.

15. The device of claim 9, further comprising a connector having a plurality of pins, wherein the series electrical connection between each of the plurality of first capacitors and the individual first conductive regions is via the individual pins of the connector.

16. The device of claim 9, wherein the device has at least four first conductive regions, at least five second conductive regions, and at least four first capacitors.

17. The device of claim 16, further comprising at least four electronically controllable switches, each electronically controllable switch being (a) electrically connected in parallel to one of the at least four first capacitors and (b) controllable by an individual electrical signal.

18. The device of claim 16, further comprising a connector having at least four pins, wherein the series electrical connection between each of the at least four first capacitors and the individual first conductive regions is via the individual pins of the connector.

19. The device of claim 16, further comprising at least five second capacitors, each second capacitor being electrically connected in series with a separate second conductive region.

20. The device as claimed in claim 19, further comprising: At least four electronically controllable switches, each electronically controllable switch (a) being electrically connected in parallel to one of the at least four first capacitors and (b) being controllable by an individual electrical signal; and at least five electronically controllable switches, each electronically controllable switch (a) being electrically connected in parallel to one of the at least five second capacitors and (b) being controllable by an individual electrical signal.

21. The apparatus of claim 19, wherein each of the at least four first capacitors is a variable capacitor whose capacitance can be controlled by an individual electrical signal, and wherein each of the at least five second capacitors is a variable capacitor whose capacitance can be controlled by an individual electrical signal.

22. The apparatus of claim 16, wherein each of the at least four first capacitors is a variable capacitor whose capacitance can be controlled by an individual electrical signal.

23. The equipment as claimed in claim 9, further comprising: A plurality of thermistors, each thermistor (a) being positioned in thermal contact with a different first conductive region and (b) being configured to generate an individual first signal in response to a detected temperature, wherein each of the plurality of first capacitors is a variable capacitor having an individual capacitance control input that receives the individual first signal.

24. The device of claim 23, wherein the device has at least four first conductive regions, at least five second conductive regions, at least four first capacitors, and at least four thermistors.

25. The device of claim 23, further comprising a plurality of resistors, each thermistor having a first terminal and a second terminal, the first terminal being connected to ground, wherein one of the plurality of resistors is connected in series between the second terminal and a fixed voltage source, and wherein the second terminal of the thermistor is connected to the capacitance control input of a particular first capacitor to provide the particular first signal having a voltage determined according to a detected temperature of the particular first conductive region.

26. The device of claim 23 further includes a plurality of resistors, each resistor being connected in series with another thermistor of the plurality of thermistors, such that an individual current flows through the individual thermistor of the plurality of thermistors to generate the individual first signal.

27. The device of claim 26, wherein the device has at least four first conductive regions, at least five second conductive regions, at least four first capacitors, at least four thermistors, and at least four resistors.

28. A device for applying an alternating electric field to a living subject, the device comprising: A plurality of conductive regions, each conductive region having a front side and an individual region, wherein the plurality of conductive regions includes a plurality of first conductive regions and at least one second conductive region; a plurality of dielectric material regions, each dielectric material region having (i) an individual front side and (ii) an individual back side, which is disposed against the front side of a corresponding one of the plurality of conductive regions; a substrate configured to hold the front side of the plurality of dielectric material regions on or within the body of the subject, and to support the plurality of conductive regions at individual locations; A connector having a plurality of first pins and at least one second pin; At least one conductor, each conductor providing a conductive path between a particular second pin and a particular second conductive region; And a plurality of capacitors, each capacitor having an individual first terminal electrically connected to another first conductive region of the first conductive region, and having an individual second terminal electrically connected to another first pin of the plurality of first pins.

29. The device of claim 28, wherein the individual locations are distributed around the centroid, and wherein each first conductive region is positioned further outward relative to the centroid than each second conductive region.

30. The device of claim 29, wherein the device has at least four first conductive regions, at least five second conductive regions, and at least five conductors.

31. The device of claim 28, wherein the device has at least three first conductive regions and at least six second conductive regions, and wherein the individual positions are distributed in a pattern such that each first conductive region is positioned at a given single end of the pattern, and each second conductive region is not positioned at the given single end of the pattern.

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