Array for delivering a tumor therapy field with selectively addressing subelements

Abstract

A tumor treatment field (TTField) can be delivered to the body of a subject at a higher field strength by disconnecting one or more overheated electrode elements without disconnecting other non-overheated electrode elements. This may be accomplished using a plurality of temperature sensors, each positioned to sense a temperature at a respective electrode element, and a plurality of electrically controlled switches, each wired to switch on or off current to a separate electrode element. A controller inputs a signal from the temperature sensor to determine the temperature at each electrode element and to control the state of the control input of each electrically controlled switch to selectively disconnect current or adjust the duty cycle at any overheated electrode element.

Description

[0001] This case is a divisional application. The invention name of the parent case is "Array for delivering tumor treatment fields (TTField) with selectively addressable subelements", the application date is November 18, 2019, and the application number is 201980076291.3. Background Art

[0002] TTField therapy is a proven method for treating tumors. Figure 1 is an existing technology for delivering TTField Schematic representation of the system. TTFields are delivered to the patient via four transducer arrays 21-24, which are placed on the patient's skin in close proximity to the tumor (e.g., Figure 2A-2D ). The transducer arrays 21-24 are arranged in two pairs, and each transducer array is connected to an AC signal generator 20 via a multi-conductor cable. The AC signal generator (a) sends an AC current through a pair of arrays 21, 22 during a first time period, which induces an electric field having a first direction through the tumor; then (b) sends an AC current through another pair of arrays 23, 24 during a second time period, which induces an electric field having a second direction through the tumor; and then repeats steps (a) and (b) for the duration of the treatment.

[0003] Each transducer array 21-24 is configured as a collection of capacitively coupled electrode elements E interconnected via flexible (flex) wires (e.g., a collection of 9 electrode elements, each electrode element having a diameter of approximately 2 cm). Each electrode element comprises a ceramic disc sandwiched between a layer of conductive medical gel and an adhesive tape. When the array is placed on a patient, the medical gel adheres to the contours of the patient's skin and ensures good electrical contact between the device and the body. The adhesive tape holds the entire array in place on the patient as the patient goes about his or her daily activities.

[0004] The amplitude of the alternating current delivered via the transducer array is controlled so that the skin temperature (as measured on the skin beneath the transducer array) does not exceed a safety threshold of 41°C. Temperature measurements on the patient's skin are obtained using a thermistor T placed beneath some of the discs of the transducer array. In the system, each array includes 8 thermistors, with one thermistor positioned beneath a corresponding disk in the array. (Note that most arrays include more than 8 disks, in which case temperature measurements are performed only beneath a subset of the disks in the array).

[0005] The AC signal generator 20 obtains temperature measurements from all 32 thermistors (4 arrays x 8 thermistors per array). A controller in the AC signal generator uses the temperature measurements to control the current delivered via each pair of arrays in order to maintain the temperature on the patient's skin below 41° C. The current itself is delivered to each array via additional wires extending from the AC signal generator 20 to each array (i.e., one wire 28 for each of the arrays 21-24). Summary of the invention

[0006] One aspect of the present invention is directed to a first device for applying an alternating electric field to a subject's body. The first device includes a plurality of capacitively coupled electrode elements, each electrode element having a dielectric layer; and a support configured to hold the plurality of electrode elements so that the dielectric layers of the electrode elements can be positioned in contact with the subject's body. The first device also includes a plurality of temperature sensors. Each temperature sensor is positioned to sense the temperature at a corresponding electrode element and generate a corresponding signal indicative of the sensed temperature. The first device also includes an electrical conductor; and a plurality of electrically controlled switches. Each switch is configured to, depending on the state of a corresponding control input, (a) allow current to flow between the electrical conductor and the corresponding electrode element, or (b) prevent current from flowing between the electrical conductor and the corresponding electrode element. The first device also includes a controller configured to control the state of a control input of each switch.

[0007] In some embodiments of the first device, the controller is further configured to receive a corresponding signal indicating the sensed temperature from each temperature sensor; determine a duty cycle at which a given electrode element should be driven based on the received signal; and periodically switch the state of a control input of a switch corresponding to the given electrode element at the determined duty cycle so as to periodically prevent current from flowing between the electrical conductor and the given electrode element.

[0008] In some embodiments of the first device, the controller is further configured to receive a respective signal from each temperature sensor indicating a sensed temperature; determine, based on the received signal, whether the temperature at each electrode element exceeds an upper threshold; and if it has been determined that the temperature at a given electrode element exceeds the upper threshold, control the state of the control input of the respective switch to prevent current from flowing between the electrical conductor and the given electrode element. Optionally, in these embodiments, the controller may be further configured to, after controlling the state of the control input of the given switch to prevent current from flowing between the electrical conductor and the respective electrode element, determine, based on the received signal from the respective temperature sensor, whether the temperature at the respective electrode element has dropped below a lower threshold, and then control the state of the control input of the given switch to allow current to flow between the electrical conductor and the respective electrode element.

[0009] In some embodiments of the first device, the controller is further configured to accept a signal from each temperature sensor; transmit data describing the temperature at each temperature sensor to a second controller; receive data from the second controller indicating which switch should be closed; and control the state of the control inputs of the plurality of switches based on the data received from the second controller.

[0010] In some embodiments of the first device, the plurality of capacitive coupling electrode elements comprises at least 9 capacitive coupling electrode elements. In some embodiments of the first device, each capacitive coupling electrode element comprises a conductive plate having a plane, and a dielectric layer is disposed on the plane of the conductive plate. In some embodiments of the first device, the support comprises a foam layer. In some embodiments of the first device, the electrical conductor comprises a trace on a flexible circuit.

[0011] In some embodiments of the first device, the support is configured to hold the plurality of electrode elements against an outer surface of the subject's body, wherein the dielectric layers of the electrode elements face the subject's body. In some embodiments of the first device, the plurality of electrically controlled switches and the controller are positioned on a module that is attached to the support via a multi-conductor connector.

[0012] Another aspect of the present invention is directed to a second device for applying an alternating electric field to a subject's body. The second device includes a set of at least two electrode elements that are capacitively coupled, each electrode element having a dielectric layer; and a support configured to hold the set of multiple electrode elements so that the dielectric layer of the electrode element can be positioned in contact with the subject's body. The second device also includes a plurality of temperature sensors. Each temperature sensor is positioned to sense the temperature at the set of corresponding electrode elements and generate a corresponding signal indicative of the sensed temperature. The second device also includes an electrical conductor; and a plurality of electrically controlled switches. Each switch is configured to, depending on the state of a corresponding control input, (a) allow current to flow between the electrical conductor and the corresponding electrode element, or (b) prevent current from flowing between the electrical conductor and the corresponding electrode element. The second device also includes a controller configured to control the state of a control input of each switch.

[0013] In some embodiments of the second apparatus, all electrode elements within any given set of electrode elements are concentrically arranged.

[0014] In some embodiments of the second device, the controller is further configured to receive a corresponding signal indicative of a sensed temperature from each temperature sensor; determine, based on the received signal, a duty cycle at which a given electrode element should be driven; and periodically switch the state of a control input of a switch corresponding to the given electrode element at the determined duty cycle so as to periodically prevent current from flowing between the electrical conductor and the given electrode element.

[0015] In some embodiments of the second device, the controller is further configured to receive a corresponding signal indicating the sensed temperature from each temperature sensor; determine whether the temperature at each set of electrode elements exceeds an upper threshold based on the received signal; and if it has been determined that the temperature at a given set of electrode elements exceeds the upper threshold, control the state of a control input of at least one corresponding switch to prevent current from flowing between the electrical conductor and at least one electrode element in the given set of electrode elements.

[0016] In some embodiments of the second device, the controller is further configured to accept a signal from each temperature sensor; transmit data describing the temperature at each temperature sensor to the second controller; receive data from the second controller indicating which switch should be closed; and control the state of the control inputs of the plurality of switches based on the data received from the second controller.

[0017] In some embodiments of the second device, the support is configured to hold the set of multiple electrode elements against an outer surface of the subject's body, wherein the dielectric layer of the electrode elements faces the subject's body. In some embodiments of the second device, the multiple electrically controlled switches and controller are positioned on a module that is attached to the support via a multi-conductor connector.

[0018] Another aspect of the present invention is directed to a third device for applying an alternating electric field to a subject's body. The third device includes a plurality of first electrode elements; and a flexible support configured to hold the plurality of first electrode elements against the subject's body. The third device also includes a plurality of temperature sensors. Each temperature sensor is positioned to sense a temperature at a corresponding first electrode element and to generate a corresponding signal indicative of the sensed temperature. The third device also includes an electrical conductor; and a plurality of electrically controlled first switches. Each first switch is wired in series with a corresponding first electrode element in a circuit that starts at the electrical conductor and ends at the corresponding first electrode element, and each first switch is configured to be turned on or off independently of the other first switches based on the state of a corresponding control input. The third device also includes a controller configured to generate an output that determines the state of a control input of each first switch.

[0019] In some embodiments of the third apparatus, each first electrode element comprises a capacitive coupling electrode element having a dielectric layer, and the flexible support is configured to hold the plurality of first electrode elements against the body of the subject, wherein the dielectric layers of the first electrode elements face the body of the subject.

[0020] Some embodiments of the third device further include a plurality of second electrode elements, wherein each second electrode element is positioned adjacent to a corresponding first electrode element; and a plurality of electrically controlled second switches. Each second switch is wired in series with a corresponding second electrode element in a circuit that starts at an electrical conductor and ends at a corresponding second electrode element, and each second switch is configured to be turned on or off independently of other second switches based on the state of a corresponding control input. The support is configured to hold the plurality of second electrode elements against the subject's body. And the controller is further configured to generate an output that determines the state of the control input of each second switch.

[0021] Optionally, in these embodiments, each first electrode element comprises a capacitive coupling electrode element having a dielectric layer; and each second electrode element comprises a capacitive coupling electrode element having a dielectric layer; and the support member is configured to (a) hold the plurality of first electrode elements against the subject's body, wherein the dielectric layers of the first electrode elements face the subject's body, and (b) hold the plurality of second electrode elements against the subject's body, wherein the dielectric layers of the second electrode elements face the subject's body.

[0022] Optionally, in these embodiments, each second electrode element is concentric with an adjacent corresponding first electrode element. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is an existing technology for delivering TTField Schematic representation of the system.

[0024] Figure 2A-2D Depicted is the positioning of a transducer array on a human head for treating a brain tumor.

[0025] Figure 3 A first embodiment is depicted which can switch current to each individual electrode element on or off based on the state of a set of electrically controlled switches.

[0026] Figure 4 It can be used for Figure 3 Schematic representation of the mechanical layout of one of the transducer assemblies depicted in .

[0027] Figure 5 An alternative configuration is depicted in which the transducer elements are grouped into n sets, and a single temperature sensor is used to measure the temperature of each of the n sets.

[0028] Figure 6 is suitable for implementing Figure 3-Figure 5 Schematic diagram of a circuit of a switch in an embodiment.

[0029] Various embodiments are described in detail below with reference to the drawings, wherein like reference numerals represent like elements. DETAILED DESCRIPTION

[0030] Although the above combination Figure 1 The prior art methods described are very effective for delivering TTFields to tumors, but if good electrical contact is not maintained between each element of the four transducer arrays 21-24 and the person's body, the effectiveness of the treatment will decrease. This can occur, for example, if the hydrogel beneath one or more elements of the transducer array dries out over time, or due to hair growth beneath one or more elements.

[0031] For example, assume that in a prior art system having 9 electrode elements E in each transducer array 21-24, the hydrogel under a single electrode element E on the front transducer array 21 has dried; and sufficient hydrogel exists under (a) all other electrode elements E of the transducer array 21 and (b) all electrode elements E of the other transducer arrays 22-24. In this case, the resistance between the single electrode element E and the human body will be higher than the resistance between any of the other electrode elements and the human body. And this increase in resistance will cause the temperature of the single electrode element E to rise more than the other electrode elements.

[0032] In this case, the prior art AC signal generator 20 must limit the current applied to the front / rear transducer array 21, 22 pair in order to keep the temperature of a single electrode element E on the front array 21 below 41° C., even though the temperatures at all the remaining electrode elements E on the front and rear transducer arrays 21, 22 may be much lower than 41° C. And this reduction in current results in a corresponding reduction in the electric field strength at the tumor.

[0033] The embodiments described herein can be used to minimize or eliminate the reduction in current coupled into a person's body, and thereby minimize or eliminate the reduction in electric field strength at a tumor. This can be accomplished by alternately switching the current on and off for each individual electrode element that begins to approach 41°C, so as to reduce the average current of those electrode elements, without affecting the current through the remaining electrode elements (which are not approaching 41°C).

[0034] For example, assume a situation where a current of 500 mA is passing through a transducer array comprising 10 electrode elements and only a single one of those electrode elements begins to approach 41° C. Assume further that a 10% reduction in the current through a single electrode element would be necessary to keep the temperature at that single electrode element below 41° C. Instead of achieving this 10% current reduction by cutting the current through the entire transducer array from 500 mA to 450 mA (as in the prior art), the embodiments described herein can cut the average current through that single electrode element by 10% by switching the current through that single electrode element on and off at a 90% duty cycle, while leaving the current through all remaining electrode elements on full time. Note that given the thermal inertia of the electrode elements, the switching rate must be fast enough so that the instantaneous temperature at a single electrode element never exceeds 41° C. For example, a 90% duty cycle can be achieved by switching the current on for 90 ms and switching the current off for 10 ms. In some preferred embodiments, the period of switching the current on and off is less than 1 s.

[0035] When this approach is used, the current through the remaining 9 electrode elements can remain unchanged (i.e., 50 mA per electrode element), and the current through only a single electrode element is reduced to an average of 45 mA. The average net total current through the transducer array will then be 495 mA (i.e., 9×50+45), which means that significantly more current can be coupled into a person's body without exceeding 41°C at any of the electrode elements.

[0036] The system can even be configured to increase the current through the remaining nine electrode elements in order to compensate for the reduction in current through a single electrode element. For example, the current through the remaining nine electrode elements can be increased to 50.5 mA per electrode element (e.g., by sending a request to the AC voltage generator to increase the voltage by 1%). If this solution is implemented, the average net total current through the entire transducer array will be (9 electrodes×50.5 mA+1 electrode×50.5 mA×0.9 duty cycle)=499.95 mA, which is extremely close to the original current of 500 mA.

[0037] If at some subsequent time (or even at the same time) the temperature at the second electrode element begins to approach 41°C, a similar technique (i.e., reducing the duty cycle from 100% to substantially less than 100%) can be used to prevent the temperature at the second electrode element from exceeding 41°C.

[0038] In some embodiments, the technique can be used to individually tailor the duty cycle at each electrode element in order to maximize the current flowing through each of those electrode elements while maintaining the temperature at each of those elements below 41°C. Alternatively, instead of taking remedial action to reduce the duty cycle only when the temperature at a given electrode element begins to approach 41°C, the system can be configured to proactively and individually set the duty cycle at each electrode element in a given transducer array in order to equalize the temperature across all electrode elements in the array. For example, the system can be configured to individually set the duty cycle at each electrode element in order to maintain a temperature hovering around 40.5°C at each electrode element. Alternatively, the system can be configured to send a request to the AC voltage generator to increase or decrease the voltage as needed in order to achieve this result.

[0039] This approach can be used to ensure that each electrode element will carry the maximum average current possible (not exceeding 41°C), which will provide increased field strength in the tumor and corresponding improvement in treatment.

[0040] Figure 3 A first embodiment is depicted that periodically switches the current on and off for each individual electrode element beginning at approximately 41°C. The AC signal generator 30 has two outputs (OUT1 and OUT2), each having two terminals. The AC signal generator 30 generates an AC signal (e.g., a 200kHz sine wave) between the two terminals of each of those outputs in an alternating sequence (e.g., activating OUT1 for one second and then activating OUT2 for one second in an alternating sequence). A pair of conductors 51 are connected to the two terminals of OUT1, and each of those conductors 51 goes to a corresponding one of the left transducer assembly 31 and the right transducer assembly 32. A second pair of conductors 51 are connected to the two terminals of OUT2, and each of those conductors 51 goes to a corresponding one of the front transducer assembly and the rear transducer assembly (not shown). The construction and operation of the front transducer assembly and the rear transducer assembly are similar to those of the first and second transducer assemblies. Figure 3 The construction of the left transducer assembly 31 and the right transducer assembly 32 depicted in FIG.

[0041] Each transducer assembly 31, 32 includes a plurality of electrode elements 52. In some preferred embodiments, each of these electrode elements 52 is a capacitive coupling electrode element similar to Prior art electrode elements used in the system. Figure 3In the embodiment of , instead of wiring all electrode elements 52 in parallel, an electrically controlled switch (S) 56 is wired in series with each electrode element (E) 52, and all of these S+E combinations 56+52 are wired in parallel. Each switch 56 is configured to be turned on or off independently of the other switches based on the state of the corresponding control input arriving from the digital output of the corresponding controller 85. When a given one of the switches 56 (in response to the first state of the corresponding control input) is turned on, current can flow between the electrical conductor 51 and the corresponding electrode element 52. Conversely, when a given one of the switches 56 (in response to the second state of the corresponding control input) is turned off, current cannot flow between the electrical conductor 51 and the corresponding electrode element 52.

[0042] In some preferred embodiments, each capacitive coupling electrode element 52 is disc-shaped (e.g., with a 2 cm diameter) and has a dielectric layer on one side. The transducer assemblies 31, 32 hold the electrode elements 52 against the subject's body, with the dielectric layer of the electrode elements facing the subject's body. Preferably, when the transducer assemblies 31, 32 are placed against the subject's body, a hydrogel layer is provided between the dielectric layer of the electrode elements and the subject's body, so it can hold the electrode elements 52 against the subject's body.

[0043] In some preferred embodiments, each capacitive coupling electrode element 52 includes a conductive plate having a plane, and a dielectric layer is disposed on the plane of the conductive plate. In some preferred embodiments, a support structure holds all capacitive coupling electrode elements in place. Optionally, the support structure may include a foam layer. In some preferred embodiments, the electrical connection to each electrode element 52 includes a trace on a flexible circuit.

[0044] Each transducer assembly 31, 32 also includes a temperature sensor 54 (e.g., a thermistor) positioned at each electrode element 52 so that each temperature sensor 54 can sense the temperature of the corresponding electrode element 52. Each temperature sensor 54 generates a signal indicative of the temperature at (e.g., below) the corresponding electrode element 52. The signal from the temperature sensor 54 is provided to the analog front end of the corresponding controller 85.

[0045] In an embodiment where thermistors are used as temperature sensors 54, temperature readings can be obtained by routing a known current through each thermistor and measuring the voltage that appears across each thermistor. In some embodiments, a thermistor-based temperature measurement can be implemented by selecting each thermistor in turn using a bidirectional analog multiplexer, wherein a current source that generates a known current (e.g., 150 μA) is positioned behind the multiplexer so that the known current will be routed to whichever thermistor is selected by the analog multiplexer at any given moment. The known current will cause a voltage to appear across the selected thermistor, and the temperature of the selected thermistor can be determined by measuring the voltage. The controller 85 runs a program that selects each thermistor in turn and measures the voltage that appears across each thermistor in turn (which indicates the temperature at the selected thermistor). Examples of suitable hardware and programs that can be used to obtain temperature readings from each thermistor are described in US2018 / 0050200, which is incorporated herein by reference in its entirety.

[0046] In some preferred embodiments, the controller 85 can be implemented using a single-chip microcontroller or a programmable system on chip (PSoC) with a built-in analog front end and multiplexer. Part numbers suitable for this purpose include CY8C4124LQI-443. In alternative embodiments, other microcontrollers can be used with built-in or discrete analog front ends and multiplexers, as will be apparent to those skilled in the relevant art.

[0047] In alternative embodiments (not shown), alternative methods for interfacing with thermistors (e.g., the conventional voltage divider method) may be used in place of the constant current method described above. In other alternative embodiments, different types of temperature sensors may be used in place of the thermistors described above. Examples include thermocouples, RTDs, and integrated circuit temperature sensors such as the AD590 from Analog Devices and the LM135 from Texas Instruments. Of course, when any of these alternative temperature sensors are used, appropriate modifications to the circuit will be required (which will be apparent to those skilled in the relevant art).

[0048] In some embodiments, the controller 85 is programmed to use the intelligence built into each transducer assembly 31 to keep the temperature at all electrode elements below a safety threshold (e.g., below 41°C). This can be accomplished, for example, by programming the controller 85 to start by setting its digital output so that each switch 56 is continuously turned on (i.e., has a 100% duty cycle). Then, based on the signal arriving via the controller 85 analog front end, the controller 85 determines whether the temperature at each electrode element exceeds an upper threshold (e.g., 40°C) that is below the safety threshold. When the controller 85 detects this condition, the controller 85 reduces the duty cycle of the corresponding switch 56 by switching the corresponding digital output at the desired duty cycle. This will interrupt the current to the corresponding electrode element 52 at the same duty cycle, thereby reducing the average current at the specific electrode element 52 whose temperature exceeds the upper threshold. The level of current reduction is determined by the duty cycle. For example, using a 50% duty cycle will cut the current in half; and using a 75% duty cycle will cut the current by 25%.

[0049] Notably, this procedure interrupts the current flow to only specific ones of the electrode elements 52 on the transducer assembly 31, and does not interrupt the current flow to the remaining electrode elements 52 on the transducer assembly 31. This provides a very significant advantage over the prior art because it eliminates or reduces the need to cut back on the current flow routed through the electrode elements when only a few of those electrode elements are heating up.

[0050] A numerical example will help illustrate this. Figure 3 In the embodiment of FIG. 1 , it is assumed that the left transducer assembly 31 and the right transducer assembly 32 are positioned on the left and right sides of the subject's head, respectively; all switches 56 in the transducer assemblies 31 , 32 are in the ON state with a 100% duty cycle; and the AC signal generator 30 initially outputs a current of 500 mA to the conductor 51. An AC voltage will appear between the electrode elements 52 of the left transducer assembly 31 and the electrode elements 52 of the right transducer assembly 32, and the 500 mA AC current will be capacitively coupled through the electrode elements 52 through the subject's head. The controller 85 in each transducer assembly 31 , 32 monitors the temperature at each electrode element 52 in the transducer assembly by inputting a signal from each temperature sensor 54 via the analog front end of the controller 85. Now assume that the temperature at a given one of the electrode elements 52 in the transducer assembly 31 has risen to 40° C. This condition will be reported to the controller 85 in the transducer assembly 31 via a signal from the corresponding temperature sensor 54. When controller 85 recognizes that the temperature of a given electrode element 52 has risen to 40° C., controller 85 will switch the control signal to the corresponding switch 56 at a desired duty cycle to periodically interrupt the current to the given electrode element 52 and maintain a lower average current.

[0051] This is in stark contrast to prior art devices which had to reduce the current flowing through all electrode elements as soon as the temperature at even a single one of the electrode elements 52 approached 41°C.

[0052] Note that if the duty cycle at only one of the remaining electrode elements 52 is reduced, it may be possible to maintain the original 500mA current (and enjoy the advantages caused by using the full current). However, if the duty cycle at a sufficiently large number of electrode elements 52 is reduced, the original 500mA current may have to be reduced. To accomplish this, the controller 85 can send a request to the AC signal generator 30 via the UART in the controller 85. When the AC signal generator 30 receives the request, the AC signal generator 30 will reduce the output current at its corresponding output OUT1.

[0053] Alternatively, the duty cycle selected by the controller 85 may be controlled based on how quickly a given electrode element 52 heats after current is applied to the given electrode element 52 (as measured via the temperature sensor 54 and the analog front end of the controller 85). More specifically, if the controller 85 identifies that a given electrode element 52 is heating up twice as fast as expected, the controller 85 may select a 50% duty cycle for that electrode element. Similarly, if the controller 85 identifies that a given electrode element 52 is heating up 10% faster than expected, the controller 85 may select a 90% duty cycle for that electrode element.

[0054] In other embodiments, instead of deterministically cutting the average current by reducing the duty cycle, the controller 85 may reduce the average current at a given electrode element 52 based on real-time temperature measurements by shutting off the current to the given electrode element 52 and waiting until the temperature measured using the temperature sensor 54 drops below a second temperature threshold (e.g., below 38° C.). Once the temperature drops below the second temperature threshold, the controller 85 may restore the current to the given electrode element 52. This may be accomplished, for example, by controlling the state of a control input to a switch 56 that was previously closed so that the switch 56 reverts to an ON state, which will allow current to flow between the electrical conductor and the corresponding electrode element 52. In these embodiments, the current to a given electrode element 52 may be repeatedly turned off and on based on real-time temperature measurements in order to keep the temperature at the given electrode element 52 below a safe threshold.

[0055] exist Figure 3In the embodiment of the present invention, each transducer assembly 31, 32 is connected to the AC signal generator 30 via a corresponding cable. It is worth noting that only four conductors are required in each cable extending between the transducer assembly and the AC signal generator 30 (i.e., Vcc, data and ground for serial data communication, plus an additional conductor 51 for the AC current TTField signal).

[0056] Note that Figure 3 , each transducer assembly 31, 32 includes nine electrode elements 52, nine switches 56, and nine temperature sensors 54. However, in alternative embodiments, each transducer assembly 31, 32 may include a different number (e.g., between 8 and 25) of electrode elements 52 and a corresponding number of switches and temperature sensors.

[0057] Figure 4 is a schematic representation of a mechanical layout that can be used Figure 3 Any given one of the left transducer assembly 31 / right transducer assembly 32 depicted in the figure, or connected to Figure 3 The front transducer assembly 33 / rear transducer assembly 34 of the second output OUT2 of the AC signal generator 30 depicted in FIG. Figure 3 ). In this embodiment, each transducer assembly 31-34 includes a plurality of capacitively coupled electrode elements 52 mounted on a support 59. The electrode elements 52 are configured to be placed against the body of the subject (preferably, having a hydrogel layer disposed on the surface of the electrode elements 52 facing the body of the subject), and the support 59 holds the plurality of electrode elements 52 against the body of the subject such that the dielectric layer of the electrode elements 52 faces the body of the subject. The support 59 is preferably flexible and may be made of a material such as cloth or dense medical foam. An adhesive layer may be used to secure the support 59 to the person's body. The temperature sensors 54 are positioned so that they can sense the temperature at each electrode element 52. For example, each temperature sensor 54 may be positioned adjacent to and / or below a corresponding one of the electrode elements 52. In some embodiments, each electrode element 52 has a small hole in its center, and the temperature sensor 54 is positioned in the small hole. Note that although in Figure 4 Only two electrode elements 52 and corresponding switches 56 and temperature sensors 54 are depicted, but it is preferred to use a large number (e.g., between 9 and 25) of each of those components. Figure 3 The terms E1...En, S1...Sn and T1...Tn are used to designate electrode elements, switches and temperature sensors respectively.

[0058] The module 60 is mounted to the support 59 (either directly or through an intermediate component). The module 60 includes a controller 85 and switches 56. Alternatively, the module 60 can be connected to the support 59 using an electrical connector 42, in which case one half of the connector 42 is provided on the module 60 and a mating half of the connector 42 is provided on the support 59. When the two halves of the connector 42 are mated, the signal from the thermistor 54 will propagate through the wiring (e.g., flex circuit wiring) on ​​the support 59, through the connector 42, and into the controller 85 on the module 60. In addition, the AC current signal from the output side of each switch 56 propagates through the connector 42 and through the wiring (e.g., flex circuit wiring) on ​​the support 59 to each electrode element 52.

[0059] The inclusion of the optional connector 42 provides advantages over embodiments that do not include the connector because the array of electrode elements 52 is preferably sterilized prior to use. Sterilization is typically performed using radiation or gas. Since radiation can interfere with electronics, assemblies in which electronics cannot be disconnected from the array of electrode elements 52 can only be sterilized with gas. On the other hand, if the electronic components 56, 85 can be disconnected from the array of electrode elements 52 via the connector 42 (as in Figure 4 ), the electronics can be inserted after sterilization. This allows the array of electrode elements 52 to be sterilized using gas or radiation without the risk of damaging sensitive electronic components 56, 85.

[0060] As described above, only four conductors are required in each cable extending between each transducer assembly 31-34 and the AC signal generator 30 (i.e., Vcc, data, and ground for serial data communications, plus an additional conductor 51 for the AC current TTField signal). In some preferred embodiments, the transducer assemblies 31-34 and the AC signal generator (e.g., Figure 3 The connection between the ) is made using, for example, an electrical connector 38.

[0061] In the embodiments described above, the decision to adjust the duty cycle or to close one or more switches 56 in a given transducer assembly 31, 32 in order to reduce the average current to one or more electrode elements 52 is made locally in each transducer assembly 31, 32 by the controller 85 within the transducer assembly 31, 32. However, in alternative embodiments, the decision to adjust the duty cycle or to close one or more switches 56 may be made by the AC signal generator 30 (or another remote device, such as a central hub disposed between the AC signal generator 30 and each transducer assembly 31, 32). In these embodiments, the controller 85 in each transducer assembly 31, 32 obtains temperature readings from each temperature sensor 54 in the corresponding transducer assembly and transmits these temperature readings to the AC signal generator 30 via the UART of the controller 85. The AC signal generator 30 decides which switch (if any) requires duty cycle adjustment or should be closed based on the temperature readings it receives, and transmits the corresponding command to the corresponding controller 85 in the corresponding transducer assembly 31, 32. When the controller 85 receives this command from the AC signal generator 30, the controller 85 responds by setting its digital output to a state that will open the corresponding switch 56 at the appropriate time to implement the command issued by the AC signal generator 30. In these embodiments, the AC signal generator 30 can also be programmed to reduce its output current if it is necessary to reduce the current to keep the temperature at each electrode element 52 below a safe threshold.

[0062] In these embodiments, the controller 85 can be programmed to operate as a slave controller of a master controller located in the AC signal generator 30. In these embodiments, the controller 85 starts in a quiescent state, where all it does is monitor incoming commands from the master controller arriving via the UART. Examples of commands that can arrive from the master controller include a "collect temperature data" command, a "send temperature data" command, and a "set switch" command. When the controller 85 recognizes that the "collect temperature data" command has arrived, the controller 85 will obtain temperature readings from each temperature sensor 54 and store the results in a buffer. When the controller 85 recognizes that the "send temperature data" command has arrived, the controller 85 will execute a program that transmits the temperature readings previously collected from the buffer to the AC signal generator 30 via the UART 86. And when the controller 85 recognizes that the "set switch" command has arrived, the controller 85 will execute a program to output an appropriate voltage on its digital output so that each switch 56 is set to a desired state (i.e., ON, OFF, or switched between on and off at a commanded duty cycle) based on the data arriving from the AC signal generator 30.

[0063] In the embodiments described above, a single controller 85 is used in each transducer assembly 31, 32 to control the switches 56 in that assembly and also to obtain temperature measurements from each temperature sensor 54 in that assembly. In alternative embodiments, instead of using a single controller 85 to control the switches 56 and obtain temperature measurements, those two tasks may be divided between two controllers, one of which is used only to control the switches 56, and the other of which is used to obtain temperature measurements (e.g., using any of the methods described above) from each temperature sensor 54. In these embodiments, the two controllers may communicate directly with each other, and / or with the AC signal generator 30.

[0064] In other alternative embodiments (not shown), temperature measurement does not rely on a local controller positioned near the electrode elements 52. Instead, wires extend from each temperature sensor 54 back to the AC signal generator 30 (or to a central hub disposed between the AC signal generator 30 and each transducer assembly 31, 32), and the AC signal generator uses the signals arriving via these wires to determine the temperature at each temperature sensor 54. Note, however, that in these embodiments, the cables extending to the transducer array will require a large number of conductors, which may reduce the flexibility of the cables and increase the bulkiness of the cables.

[0065] In the above described Figure 3 and Figure 4 In the embodiment of FIG. 5 , the number of temperature sensors 54 matches the number of electrode elements 52 , and each temperature sensor 54 is dedicated to sensing the temperature at a single one of the electrode elements 52 . Figure 5 An alternative configuration is depicted in which the electrode elements are grouped into n sets and a single temperature sensor is used to measure the temperature of each of the n sets. In some preferred embodiments, n is between 9 and 25.

[0066] For this to work, the electrode elements within any given set must be adjacent to each other. Figure 5 In the embodiment illustrated in FIG. 1 , each set includes a combination similar to the above Figure 4The electrode elements described are an inner disk-shaped electrode element 52, plus an additional outer ring-shaped electrode element 52', which surrounds the inner disk-shaped electrode element 52 and is concentric with it. A temperature sensor 54 is positioned in the center of the inner disk-shaped electrode element 52. Each electrode element 52, 52' has its own individual switch 56, 56', which enables the controller 85 to turn the current on or off. In alternative embodiments (not shown), additional concentric ring-shaped electrode elements can be added to each set. In other alternative embodiments (not shown), instead of arranging all electrode elements in any given set in concentric rings, the electrode elements in each set can be arranged adjacent to each other (for example, using electrode elements arranged like slices of a pie coil, and positioning the temperature sensor in the center of the pie coil). In these alternative embodiments, each electrode element will have its own individual switch, which enables the controller 85 to individually turn the current on or off.

[0067] Figure 5 The embodiment can be operated by programming the controller 85 to achieve the above combination Figure 3 and Figure 4 The same result described above is achieved by always turning the current on or off together to all electrode elements 52, 52' in any given set. However, this embodiment also provides additional flexibility. More specifically, if the controller 85 determines that there is a hot area in a given transducer assembly based on a signal from one of the temperature sensors 54, the controller in this embodiment has the option of reducing the current at the hot area by deactivating some but not all electrode elements corresponding to the hot area. For example, assume that the signal from the first temperature sensor 54 (T1) below the set of first electrodes 52, 52' (E1 / E1') indicates that the temperature below the set of electrodes has risen to above 40°C. The Figure 5 The controller 85 in the embodiment of has the option of reducing the current in the area by issuing a command to close only some of the corresponding switches. For example, this can be done by closing the switch S1 feeding the internal element E1 and keeping the switch S1' feeding the external element E1' on. Alternatively, the same result can also be achieved by closing the switch S1' feeding the external element E1' and keeping the switch S1 feeding the internal element E1 on.

[0068] Optionally, Figure 5 The duty cycle of each individual electrode element within any given set of electrode elements of the embodiments can be individually adjusted to obtain additional control over the average current coupled through any region, as described above in conjunction with Figure 3 and Figure 4 As described.

[0069] Note that although Figure 5 Only a set of two electrode elements 52, 52' and corresponding switches 56, 56' and temperature sensors 54, 54' are depicted in FIG, but a set of a large number (eg, between 9 and 25) of those components is preferably used. Figure 5 The electrode elements, switches and temperature sensors are indicated by the terms E1 ... En, E1' ... En', S1 ... Sn, S1' ... Sn', T1 ... Tn and T1' ... Tn' respectively.

[0070] Figure 6 is suitable for implementing the above described Figure 3-Figure 5 Schematic diagram of the circuit of the switches 56, 56' in the embodiment. The circuit includes two field effect transistors 66, 67 wired in series, which is a configuration that can pass current in either direction. An example of a FET suitable for this circuit is the BSC320N20NSE. (Note that Figure 6 The diodes depicted in are inherently included within the FETs 66, 67 themselves.) Depending on the state of the control input arriving from one of the digital outputs of the controller 85 described above, the series combination of the two FETs 66, 67 will conduct or block current. When the series combination is conducting, current can flow between the shared conductor 51 and the corresponding electrode element 52, 52'. On the other hand, when the series combination of the FETs 66, 67 is not conducting, current will not flow between the shared conductor 51 and the corresponding electrode element 52, 52'.

[0071] Optionally, the current sensing circuit 60 may be positioned in series with the switches 56, 56'. The current sensing circuit 60 may be implemented using any of a variety of conventional methods that will be apparent to those skilled in the relevant art. When the current sensing circuit 60 is included, it generates an output representative of the current, and the output is reported back to the controller 85 (e.g., Figure 3-Figure 5 ). The controller 85 can then use this information to determine whether the measured current is as expected and take appropriate action if necessary. For example, if an overcurrent condition is detected, the controller 85 can close the corresponding switch. Of course, in those embodiments in which the current sensing circuit 60 is omitted, the current sensing circuit 60 should be replaced with a wire (or other conductor) so that current can flow between the shared conductor 51 and the top pin of the upper FET 60.

[0072] In the illustrated embodiment, the current sensing circuit 60 is positioned between the shared conductor 51 and the top pin of the upper FET 60. However, in alternative embodiments, the current sensing circuit may be positioned between the bottom pin of the lower FET 67 and the respective electrode element 52, 52'. And in other alternative embodiments (not shown), the current sensing circuit may be integrated within the circuitry of the switch itself.

[0073] Although the present invention has been disclosed with reference to certain embodiments, many modifications, changes and variations of the described embodiments are possible without departing from the field and scope of the invention as defined in the appended claims. Therefore, it is intended that the present invention is not limited to the described embodiments, but that it has the full scope defined by the language of the following claims and their equivalents.

Claims

1. A device for applying an alternating electric field to a subject's body, the device comprising: a plurality of capacitively coupled electrode elements, each electrode element having a dielectric layer; a support configured to hold the plurality of electrode elements against a body of a subject, wherein the dielectric layers of the electrode elements face the body of the subject; a plurality of temperature sensors, wherein each temperature sensor is positioned to sense a temperature at a respective electrode element and to generate a respective signal indicative of the sensed temperature; Electrical conductors; a plurality of electrically controlled switches, wherein each switch is configured to, depending on a state of a corresponding control input, (a) allow current to flow between the electrical conductor and the corresponding electrode element, or (b) prevent current from flowing between the electrical conductor and the corresponding electrode element; as well as a controller configured to control a state of a control input of each switch, The controller is further configured to receiving from each temperature sensor a respective signal indicative of the sensed temperature, Based on the received signal, determining whether the temperature at each electrode element exceeds an upper threshold, and If it has been determined that the temperature at a given electrode element exceeds an upper threshold, the state of the control input of the corresponding switch is controlled to prevent current from flowing between the electrical conductor and the given electrode element.

2. An apparatus according to claim 1, wherein the controller is further configured to, after controlling the state of the control input of a given switch to prevent current from flowing between the electrical conductor and the corresponding electrode element, determine whether the temperature at the corresponding electrode element has dropped below a lower threshold based on the received signal from the corresponding temperature sensor, and then control the state of the control input of the given switch to allow current to flow between the electrical conductor and the corresponding electrode element.

3. The apparatus of claim 1, wherein the controller is further configured to receive a signal from each temperature sensor, transmitting data describing the temperature at each temperature sensor to another controller, receiving data from the other controller indicating which switch should be closed, and States of control inputs to the plurality of switches are controlled based on data received from the other controller.

4. The device of claim 1, wherein the plurality of capacitively coupled electrode elements comprises at least 9 capacitively coupled electrode elements.

5. The apparatus of claim 1, wherein each capacitive coupling electrode element comprises a conductive plate having a plane, and wherein the dielectric layer is disposed on the plane of the conductive plate. The device of claim 1 , wherein the support member comprises a foam layer.

7. The device of claim 1, wherein the electrical conductors comprise traces on a flexible circuit.

8. The apparatus of claim 1, wherein the support is configured to hold the plurality of electrode elements against an outer surface of the subject's body, wherein the dielectric layers of the electrode elements face the subject's body.

9. The apparatus of claim 1, wherein the plurality of electrically controlled switches and the controller are positioned on a module, the module being attached to a support via a multi-conductor connector.

10. A device for applying an alternating electric field to a subject's body, the device comprising: a plurality of capacitively coupled sets of at least two electrode elements, each electrode element having a dielectric layer; a support configured to hold the set of a plurality of electrode elements against a body of a subject, wherein the dielectric layers of the electrode elements face the body of the subject; a plurality of temperature sensors, wherein each temperature sensor is positioned to sense a temperature at a corresponding set of electrode elements and to generate a corresponding signal indicative of the sensed temperature; Electrical conductors; a plurality of electrically controlled switches, wherein each switch is configured to, depending on a state of a corresponding control input, (a) allow current to flow between the electrical conductor and the corresponding electrode element, or (b) prevent current from flowing between the electrical conductor and the corresponding electrode element; as well as a controller configured to control a state of a control input of each switch, The controller is further configured to receiving from each temperature sensor a respective signal indicative of the sensed temperature, Based on the received signal, determining whether the temperature at the set of each electrode element exceeds an upper threshold, and If it has been determined that the temperature at a given set of electrode elements exceeds an upper threshold, the state of a control input of at least one corresponding switch is controlled to prevent current from flowing between the electrical conductor and at least one electrode element in the given set of electrode elements.

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