Reducing electrical induction when treating subject using alternating electric field by deactivating selected electrode elements

Abstract

When an array of electrode elements is used to apply an alternating electric field to a subject's body, the subject may experience electrical induction. The electrical induction may be improved by selectively deactivating the different electrode elements (or reducing current flowing through the different electrode elements) during respective different time periods, and accepting feedback indicating whether the electrical induction is occurring during each of the respective different time periods. If deactivation of a given one of the electrode elements (or reduction of current) may improve the electrical induction, the subject may be treated with an alternating electric field when the given electrode element is deactivated (or driven with a smaller current).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 411,939, filed on September 30, 2022, which is incorporated herein by reference in its entirety. Background Art

[0003] Tumor Treatment Field (TTField) therapy is an effective method for treating tumors using alternating electric fields with frequencies between 50kHz and 1MHz (e.g., 150kHz to 200kHz). In the system, TTField is delivered to the patient via four transducer arrays, which are placed on the patient's skin near the tumor (e.g., on the front, back, left and right sides of a person with glioblastoma). The transducer arrays are arranged in two pairs, and each transducer array is connected to an AC signal generator via a multi-wire cable. The AC signal generator: (a) sends AC current for 1 second through a pair of front / rear transducer arrays, which induces an electric field with a first direction through the tumor; then (b) sends AC current for 1 second through a pair of left / right arrays, which induces an electric field with a second direction through the tumor; then repeats steps (a) and (b) for the duration of the treatment. Each transducer array includes a plurality of (e.g., 9 to 20) electrode elements wired together in parallel.

[0004] Alternating electric fields can also be used to treat medical conditions other than tumors. For example, as described in U.S. Pat. No. 10,967,167 (incorporated herein by reference in its entirety), alternating electric fields can be used to increase the permeability of the blood-brain barrier (BBB), allowing, for example, chemotherapeutic drugs to reach the brain. Summary of the invention

[0005] One aspect of the present invention relates to a first method of improving electrical induction in a subject being treated with an alternating electric field. The first method includes: selectively deactivating one or more different electrode elements during corresponding different time periods when an alternating electric field is being applied; receiving feedback indicating whether electrical induction is occurring during each of the corresponding different time periods; and determining whether deactivating a given one or more of the electrode elements improves the electrical induction.

[0006] Some examples of the first method further include treating the subject with an alternating electric field when the given one or more electrode elements are deactivated.

[0007] In some instances of the first method, receiving feedback is achieved by receiving input from the subject. In some instances of the first method, receiving feedback is achieved by processing electrical signals from a set of ECAP electrodes representing the subject's neural activity. In some instances of the first method, receiving feedback is achieved by processing electrical signals representing the subject's neural activity measurements or muscle activity measurements. In some instances of the first method, receiving feedback is achieved by processing electrical signals representing electromyographic signal measurements used to measure muscle activity. In some instances of the first method, receiving feedback is achieved by processing electrical signals representing accelerometer measurements used to measure muscle activity.

[0008] Another aspect of the invention relates to a second method of improving electrical induction in a subject being treated with an alternating electric field. The second method includes: selectively reducing current flowing through one or more different electrode elements during corresponding different time periods when the alternating electric field is being applied; receiving feedback indicating whether electrical induction is occurring during each of the corresponding different time periods; and determining whether reducing the current flowing through a given one or more of the electrode elements improves the electrical induction.

[0009] Some examples of the second method also include treating the subject with an alternating electric field when the given one or more electrode elements are operated at a lower current than other electrode elements.

[0010] In some instances of the second method, receiving feedback is achieved by receiving input from the subject. In some instances of the second method, receiving feedback is achieved by processing electrical signals from a set of ECAP electrodes representing the subject's neural activity. In some instances of the second method, receiving feedback is achieved by processing electrical signals representing the subject's neural activity measurements or muscle activity measurements. In some instances of the second method, receiving feedback is achieved by processing electrical signals representing electromyographic signal measurements used to measure muscle activity. In some instances of the second method, receiving feedback is achieved by processing electrical signals representing accelerometer measurements used to measure muscle activity.

[0011] Another aspect of the present invention relates to a third method of applying an electrical signal to a first group of at least four first electrode elements and a second group of at least four second electrode elements positioned on opposite sides of a target area of ​​a subject's body. The third method includes: (a) applying an AC signal between the second group of at least four second electrode elements and a majority of the first electrode elements of the first electrode elements, wherein during respective different time periods, one or more different members of the first group of at least four first electrode elements are not used or are operated with a reduced current. The third method also includes: receiving first feedback indicating whether the subject is experiencing or is about to experience electrical induction during the respective different time periods; and determining, based at least in part on the received first feedback, whether electrical induction is improved when one or more given members of the first group of at least four first electrode elements are not used or are operated with the reduced current.

[0012] Some examples of the third method further include: applying an alternating electric field to the target area using the second group of at least four second electrode elements and all of the first electrode elements except the one or more given members of the first group of at least four first electrode elements. Some examples of the third method further include: applying an alternating electric field to the target area using the one or more given members of the first group operating at a lower current than other members of the first group of at least four first electrode elements.

[0013] In some instances of the third method, receiving the first feedback is achieved by receiving input from the subject. In some instances of the third method, receiving the first feedback is achieved by processing electrical signals from a set of ECAP electrodes representing neural activity of the subject.

[0014] Some examples of the third method also include controlling the amplitude of the AC signal. Optionally, these examples may also include increasing the amplitude of the AC signal until the determination indicates that the subject is experiencing or is about to experience electrical induction.

[0015] Some examples of the third method also include: before step (a), during a first time period, applying an AC signal between the second group of at least four second electrode elements and all of the first electrode elements in the first electrode elements; and during the first time period, receiving feedback indicating whether the subject is experiencing or is about to experience electrical induction.

[0016] Some examples of the third method also include: applying a second AC signal between the first group of at least four first electrode elements and a majority of the second electrode elements in the second electrode elements, wherein during corresponding different time periods, one or more different members of the second group of at least four second electrode elements are not used or are operated with a reduced current; receiving second feedback indicating whether the subject is experiencing or is about to experience electrical induction during the application of the second AC signal; and determining, based at least in part on the received second feedback, whether electrical induction is improved when one or more given members of the second group of at least four second electrode elements are not used or are operated with the reduced current. Optionally, these examples may also include: applying an alternating electric field to the target area using the first group of at least four first electrode elements and all of the second electrode elements except the given member of the second group of at least four second electrode elements.

[0017] In some instances of the third method, receiving the first feedback is accomplished by processing an electrical signal representing a measurement of neural activity or a measurement of muscle activity of the subject. In some instances of the third method, receiving the first feedback is accomplished by processing an electrical signal representing an electromyographic signal measurement for measuring muscle activity. In some instances of the third method, receiving the first feedback is accomplished by processing an electrical signal representing an accelerometer measurement for measuring muscle activity.

[0018] In some examples of the third method, during the applying, at least two different members of the first set of at least four first electrode elements are not used or are operated with a reduced current during the respective different time periods. In these examples, the determining includes determining whether electrical induction is improved when at least two given members of the first set of at least four first electrode elements are not used or are operated with the reduced current.

[0019] Another aspect of the present invention relates to a first device for applying an electrical signal to a first group of at least four first electrode elements and a second group of at least four second electrode elements positioned on opposite sides of a target area of ​​a subject's body. The first device includes an AC signal source, a first group of at least four first electrically controlled switches, and a controller. The AC signal source has at least one amplitude control input. Each of the first switches is configured to be: (i) closed, so that current can flow between the AC signal source and the corresponding first electrode element; or (ii) open, so that current does not flow between the AC signal source and the corresponding first electrode element, depending on the state of the corresponding first control input. The controller is configured to control the state of the first control input of each of the first switches, and is further configured to: (a) apply a first control signal to the first control input, the first control signal causing a selected one of the first switches to be disconnected during a corresponding time period; (b) when the selected one of the first switches is disconnected during the corresponding time period, receive a plurality of first feedback signals indicating whether the subject is experiencing or is about to experience electrical induction; and (c) determine, based at least in part on the received plurality of first feedback signals, whether electrical induction is improved when a given one of the first switches is disconnected.

[0020] In some embodiments of the first device, the controller is further configured to: control the application of the electrical signal to the first group of at least four first electrode elements and the second group of at least four second electrode elements, so that when the subject is being treated with an alternating electric field, a given one of the first switches is disconnected.

[0021] Some embodiments of the first device also include a user interface, wherein the user interface is configured to generate the plurality of first feedback signals based on input received from the subject. Some embodiments of the first device also include an ECAP measurement system, wherein the ECAP measurement system is configured to receive signals representing neural activity from a set of ECAP electrodes, wherein the ECAP measurement system generates the plurality of first feedback signals.

[0022] In some embodiments of the first device, the controller is further configured to control the amplitude control input. Optionally, in these embodiments, the controller is further configured to: before step (a), apply a first control signal to the first control input, the first control signal closing all the first switches; control the amplitude control input so that the amplitude increases; and receive a third signal indicating whether the subject is experiencing or is about to experience electrical induction.

[0023] Some embodiments of the first device further include: a second group of at least four second electrically controlled switches, wherein each of the second switches is configured to, depending on the state of the corresponding second control input: (i) close so that current can flow between the AC signal source and the corresponding second electrode element; or (ii) open so that current does not flow between the AC signal source and the corresponding second electrode element. In these embodiments, the controller is further configured to control the state of the second control input of each of the second switches, and the controller is further configured to: (x) apply a second control signal to the second control input, the second control signal causing a selected second switch of the second switches to be opened during a corresponding time period; (y) when the selected second switch of the second switches is opened during the corresponding time period, receive a plurality of second feedback signals indicating whether the subject is experiencing or is about to experience electrical induction; and (z) determine whether electrical induction is improved when a given second switch of the second switches is opened based at least in part on the received plurality of second feedback signals.

[0024] Optionally, in the embodiment of the first device described in the preceding paragraph, the controller is further configured to control the application of the electrical signal to the first group of at least four first electrode elements and the second group of at least four second electrode elements, so that when the subject is being treated with an alternating electric field, the given one of the second switches is disconnected. Optionally, the embodiment described in the preceding paragraph may also include a user interface, wherein the user interface is configured to generate the multiple first feedback signals and the multiple second feedback signals based on input received from the subject. Optionally, the embodiment described in the preceding paragraph may also include an ECAP measurement system, which is configured to receive signals representing neural activity from a group of ECAP electrodes, wherein the ECAP measurement system generates the multiple first feedback signals and the multiple second feedback signals.

[0025] Some embodiments of the first device further include: a second group of at least four second electrically controlled switches, wherein each of the second switches is configured to, depending on the state of the corresponding second control input: (i) close so that current can flow between the AC signal source and the corresponding second electrode element; or (ii) open so that current does not flow between the AC signal source and the corresponding second electrode element. In these embodiments, the controller is further configured to control the state of the second control input of each of the second switches, and the controller is further configured to: (x) apply a second control signal to the second control input, the second control signal causing a selected second switch of the second switches to be opened during a corresponding time period; (y) when the selected second switch of the second switches is opened during the corresponding time period, receive a plurality of second feedback signals indicating whether the subject is experiencing electrical induction or is about to experience electrical induction; and (z) determine whether electrical induction is improved when a given second switch of the second switches is opened based at least in part on the received plurality of second feedback signals. And the controller is further configured to control the amplitude control input.

[0026] Optionally, in an embodiment of the first device described in the preceding paragraph, the controller is further configured to: before step (a), apply a first control signal to the first control input terminal, the first control signal closing all the first switches; control the amplitude control input terminal so that the amplitude increases; and receive a third signal indicating whether the subject is experiencing or is about to experience electrical induction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Describes how a transducer array is positioned on a subject's head to treat glioblastoma using alternating electric fields.

[0028] Figure 2 is a block diagram of an embodiment of treating a subject using an alternating electric field with one or more electrode elements deactivated to improve electrical induction.

[0029] Figure 3 is a flow chart of a method for determining which transducer array contributes most to electrical induction.

[0030] Figure 4 is a flow chart of a method for determining which electrode elements within a given transducer array contribute most to electrical induction.

[0031] Figure 5 is a block diagram of another embodiment of treating a subject using an alternating electric field with one or more electrode elements deactivated to improve electrical induction.

[0032] Various embodiments are described in detail below with reference to the drawings, wherein like reference numerals refer to like elements. DETAILED DESCRIPTION

[0033] When using an alternating electric field to treat a subject, higher amplitudes are closely associated with higher therapeutic efficacy. However, as the amplitude of the alternating electric field increases, and / or as the frequency of the alternating electric field decreases (e.g., to around 100kHz), some subjects experience electro-induction effects when the alternating electric field switches direction. This electro-induction may be, for example, a sense of vibration, paresthesia, and / or a sense of twitching or contraction of muscle fibers, or light flashes (phosphenes) in the eyes. And these sensations may prevent some subjects from continuing to use alternating electric fields for treatment. Electro-induction is believed to originate from the interaction between the alternating electric field and nerve cells or fibers (i.e., neurons or axons) located near or adjacent to the transducer array. Disclosed herein are devices and methods for reducing electro-induction when using an alternating electric field to treat a subject by deactivating one or more electrode elements.

[0034] Figure 1 An example is shown in which four transducer arrays 21, 22, 23, and 24 are positioned at the front, back, left, and right sides of the subject's head, respectively. As the amplitude of the alternating electric field increases and / or the frequency of the alternating electric field decreases, the subject may begin to experience electrical induction under or near one or more of the transducer arrays 21 to 24.

[0035] As the amplitude of the alternating electric field increases and / or the frequency decreases, electrical induction may begin to occur under or near all four of the transducer arrays 21 to 24 simultaneously. However, it is also possible that electrical induction begins to occur under only one, two, or three of these transducer arrays. For the purposes of discussion, assume that when the amplitude of the alternating electric field reaches a given value, a given subject begins to experience electrical induction only under the left transducer array 23. This electrical induction will limit the amplitude of the alternating electric field that can be comfortably applied to a given subject, which in turn limits the efficacy of the treatment.

[0036] In the illustrated example, each of the transducer arrays 21 to 24 (including the left transducer array 23) includes nine electrode elements. However, in alternative examples, each transducer array 21 to 24 may include a different number of electrode elements (e.g., between 4 electrode elements and 50 electrode elements). Each transducer array 21 to 24 is similar to the prior art in many aspects. The transducer array is similar. The transducer array is different. Figure 1The electrode elements in any given transducer array 21 to 24 are not all wired in parallel. Instead, each electrode element in any given transducer array 21 to 24 is provided with a separate conductor so that each electrode element in any given transducer array can be individually activated or deactivated. An example of a suitable approach for implementing a transducer array having electrode elements that can be individually activated or deactivated is disclosed in U.S. Patent 11,395,916 (Wasserman et al., hereinafter referred to as the "'916 patent"), which is incorporated herein by reference in its entirety.

[0037] Due to the layout of nerve fibers in the subject, the presence of sweat, or other factors, electrical induction may be caused by only a few (e.g., one or two) of the nine electrode elements within a given transducer array. In this case, electrical induction can be improved by the following actions: when an alternating electric field is being applied, by selectively deactivating one or more different electrode elements during corresponding different time periods; receiving feedback indicating whether electrical induction is occurring during each of the corresponding different time periods; and determining whether deactivating a given one (or more than one) of the electrode elements improves electrical induction. Then, when the given electrode element is deactivated, the subject is treated using an alternating electric field. This can increase the amplitude of the alternating electric field without causing discomfort to the subject.

[0038] Figures 2 to 4 A first approach is described for determining which electrode elements within a transducer array are responsible for electrical induction in a given subject, and then deactivating those electrode elements when the transducer array is used to treat the subject using alternating electric field therapy (e.g., TTField). More specifically, Figure 2 is a block diagram of one embodiment of treating a subject using an alternating electric field using one or more electrode elements that are deactivated to improve electrical induction; Figure 3 is a flow chart of a method for determining which transducer array contributes most to electrical induction; and Figure 4 is a flow chart of a method for determining which electrode elements within a given transducer array contribute most to electrical induction.

[0039] Figure 2 An apparatus for treating a target area of ​​a subject's body using an alternating electric field that avoids or improves electrical induction based on feedback received from a user via a user interface 80 is depicted. Figure 2Embodiments include an AC voltage generator 40 that generates an AC output having a frequency between 50 kHz and 1 MHz (e.g., 50 kHz to 500 kHz, 75 kHz to 300 kHz, or 150 kHz to 250 kHz). The AC voltage generator 40 has at least one control input that can be used, for example, to control the output amplitude of the AC voltage generator 40. The frequency of the AC voltage generator 40 will depend on the type of treatment. For example, to treat a tumor using TTField, the frequency may be between 150 and 200 kHz. Alternatively, to increase the permeability of the subject's blood-brain barrier, the frequency may be between 50 kHz and 200 kHz (e.g., 100 kHz).

[0040] exist Figure 2 In the depicted example, the transducer array 23 including a set of first electrode elements 45L is positioned on the subject's body (e.g., on shaved skin) to the left of the target area, and the transducer array 24 including a set of second electrode elements 45R is positioned on the subject's body to the right of the target area. In alternative embodiments, the first set of electrode elements 45L and the second set of electrode elements 45R may be implanted into the subject's body (e.g., just below the skin) to the left and right of the target area, respectively. When the AC voltage generator 40 applies a voltage between the electrode elements 45L and the electrode elements 45R, an alternating electric field having field lines extending generally from right to left is induced through the target area. The frequency of the alternating electric field will match the frequency of the AC voltage generator 40. The electrode elements 45L / 45R may be capacitively coupled electrode elements or conductive electrode elements.

[0041] It is noteworthy that the electrode elements within any given transducer array 23-24 are not all wired in parallel. Instead, each electrode element within any given transducer array 23-24 is provided with a separate conductor so that each electrode element within any given transducer array can be individually activated or deactivated. This can be accomplished using an electronic switch bank 60 that includes a dedicated switch for each electrode element 45R in the right transducer array 24 and also includes a dedicated switch for each electrode element 45L in the left transducer array 23 (e.g., as described in the '916 patent). Thus, in Figure 2 In the depicted example (wherein the left transducer array 23 and the right transducer array 24 each include nine electrode elements), the electronic switch bank 60 would have 9×2=18 switches.

[0042] The AC voltage generator 40 has one output pin for feeding the left electrode element 45L and another output pin for feeding the right electrode element 45R. Nine of the switches in the group 60: (a) allow the signal from the left output pin of the AC voltage generator 40 to reach a corresponding one of the electrode elements 45L in the transducer array 23; or (b) block the signal from the left output pin of the AC voltage generator 40 from reaching the corresponding electrode element, depending on the state of the control signal arriving from the controller 30. And, the other nine switches in the group 60: (a) allow the signal from the right output pin of the AC voltage generator 40 to reach a corresponding one of the electrode elements 45R in the transducer array 24; or (b) block the signal from the right output pin of the AC voltage generator 40 from reaching the corresponding electrode element, depending on the state of the control signal arriving from the controller 30. This allows the controller 30 to individually activate or deactivate each of the electrode elements 45L within the left transducer array 23 , and also allows the controller 30 to individually activate or deactivate each of the electrode elements 45R within the right transducer array 24 .

[0043] User interface 80 accepts input from the user indicating whether the subject is experiencing electrical induction. For example, it can be implemented using a touch screen, keyboard, dedicated buttons, voice recognition, or any of a variety of other methods that are obvious to those skilled in the relevant art.

[0044] Suppose we have a situation where a subject is experiencing electrical induction. Figure 3 and Figure 4 The flow chart in can be used to identify which electrode element within the transducer array contributes most to the electrical induction. Once this information is determined, the controller 30 can deactivate the identified electrode element. The patient can then be treated using an alternating electric field (e.g., TTField).

[0045] from Figure 3 Starting from S20 in the flowchart, the controller 30 sends a control signal to the switch group 60 so that the signal from the left terminal of the AC voltage generator 40 is applied to all electrode elements in the electrode element 45L in the left transducer array 23, and the signal from the right terminal of the AC voltage generator 40 is applied to all electrode elements in the electrode element 45R in the right transducer array 24. The controller 30 also sends a control signal to the AC voltage generator to control the amplitude of the AC voltage.

[0046] Next, in S30, the controller 30 determines whether electrical induction is occurring. This determination is based on input received from the user interface 80. If electrical induction is not occurring, the process continues to S40, where the controller determines whether a temperature limit (e.g., 41° C.) has been reached. If the temperature limit has not been reached, the process continues to S42, where the controller 30 issues a command to the AC voltage generator to increase the amplitude. The process then returns to S30, and the S30 / S40 / S42 loop will continue until electrical induction occurs or the temperature limit is reached.

[0047] If the temperature limit is reached (which may be determined based on input from a temperature sensor incorporated into the transducer array, for example), processing continues to S60 where the controller 30 outputs an indication that temperature is the limiting factor.

[0048] If electrical induction occurs (which is determined based on input from the user interface 80 that notifies the controller 30 indicating which transducer array 23 / 24 caused the electrical induction), processing continues to S50, where the controller 30 stores an indication of which transducer array (i.e., the left array 23 or the right array 24) is responsible for the electrical induction, and the amplitude setting A1 of the AC signal generator 40 when the electrical induction began.

[0049] Once the controller 30 has identified which transducer array (i.e., the left array 23 or the right array 24) is responsible for the electrical induction, the controller 30 coordinates the application of electrical signals to a first set of at least four first electrode elements and a second set of at least four second electrode elements positioned on opposite sides of the subject's body. (Note that in this paragraph and in the discussion below, Figure 4 , the electrode elements on the side responsible for the electrical induction are referred to as the first set of first electrode elements, and the electrode elements on the opposite side are referred to as the second set of second electrode elements.) The controller 30 achieves this by setting the switches in the set 60 so that an AC signal is applied between the second set of at least four second electrode elements and a majority of the first electrode elements in the first electrode elements, wherein different members of the first set of at least four first electrode elements are not used during the respective different time periods; receiving (via the user interface 80) first feedback indicating whether the subject is experiencing or is about to experience electrical induction during the respective different time periods; and determining, based at least in part on the received first feedback, whether electrical induction is improved when a given member of the first set of at least four first electrode elements is not used.

[0050] One example of how the controller 30 may accomplish the steps set forth in the preceding paragraph is to implement Figure 4, to determine whether a particular electrode element in the identified transducer array contributes more to electrical induction than other electrode elements in the transducer array. More specifically, in S120, a loop is initialized, and in S130 to S150, a loop is implemented to set switches in group 60 so that an AC signal at amplitude A1 is applied to all but one of the first electrode elements, and feedback from a user is received via user interface 80 to see whether electrical induction is occurring. In each execution of the loop, another of the first electrode elements is deactivated. If electrical induction does not occur in a given execution of the loop, processing will jump from S140 to S170, where a second group of second electrode elements and all but a given one of the first group of electrode elements are used to apply an alternating electric field ("AEF") to a target area of ​​the subject's body. In this way, the electrode element that contributes most to electrical induction is deactivated, and the amplitude of the AC signal generated by AC voltage generator 40 can be increased to a level above A1.

[0051] If no electrical induction occurs for all executions of the loop (as reported via user interface 80), processing jumps from S150 to S160, where all electrode elements of the first and second groups of electrode elements are used to apply an alternating electric field to the subject's body with an amplitude less than A1.

[0052] Please note that in addition to using Figure 3 The steps shown isolate the induction problem to a specific transducer array and then use Figure 4 In addition to the steps shown to isolate the induction problem to a given electrode element within a particular transducer array by deactivating one electrode element at a time until the induction disappears, an alternative approach can be used. In this alternative approach, the Figure 3 Instead, perform the following steps: Figure 4 The process begins with the steps shown for a given transducer in the transducer array by deactivating one electrode element at a time to determine whether the electrical induction disappears when one of the electrode elements is deactivated. If all deactivations performed on the given transducer array in the transducer array do not eliminate the electrical induction, the controller 30 will perform the deactivation on the next transducer array. Figure 4 The controller 30 then performs the steps shown in the figure and deactivates one electrode element at a time to determine whether the electrical induction disappears when one of the electrode elements in the second transducer array is deactivated. If deactivating the electrode elements on the second transducer array causes the electrical induction to disappear, the controller 30 has identified the electrode element that is causing the problem and can continue to treat the subject when the electrode element is deactivated.

[0053] Figure 2 The operation of the embodiment is not limited to the above combination Figure 3 and Figure 4 The specific case described above, in which a single electrode element on any given transducer array is responsible for the electrical induction. Conversely, two or more electrode elements on a given transducer array may be responsible for the electrical induction. In this case, more than one electrode element may be closed at corresponding different time periods, and feedback is received indicating whether the subject is experiencing or is about to experience electrical induction during the corresponding different time periods. Finally, the system determines, at least in part based on the received feedback, whether the electrical induction is improved when the two or more electrode elements are not used.

[0054] Back to Figure 2 Instead of using a switch group 60 to individually turn on and off the current through each of the electrode elements 45L, 45R, a circuit group that can individually block the current flowing through each of the electrode elements can be used. When any of the circuits in the group is activated, it reduces the current flowing through the corresponding one of the electrode elements 45, rather than completely shutting off the current. In other respects, these embodiments are similar to the above-mentioned embodiments in combination with Figures 2 to 4 The described embodiment.

[0055] Additional situations can be envisioned where two or more electrode elements on a given transducer array will cause electrical induction. One example is when the electrode elements are configured in groups, and the groups are arranged so that all of the elements within any given group are turned on or off together. For example, a 3×3 array of electrode elements can be arranged into three groups, each with three electrode elements. In this case, as described above in conjunction with Figure 4 As described above, rather than shutting down each electrode element individually to determine whether the subject is experiencing electrical induction (or is about to experience electrical induction), each group of electrode elements is shut down together to determine whether the subject is experiencing electrical induction when the group is shut down. If the results show that any one group is responsible for the electrical induction, the group can be deactivated or the current to the group can be reduced to improve the electrical induction.

[0056] In another case, the electrode elements may be arranged in groups of two or more closely spaced electrode elements, with individual elements within any group being turned on or off to deliver different levels of current to specific areas on the subject's body. For example, 18 electrode elements may be arranged in a 3×3 array of electrode element pairs. When both elements in any given pair are turned on, a given level of current is delivered to the site below the pair. However, when only one of the elements in any given pair is turned on, only 50% of the given level of current is delivered to the site. Here again, the current delivered to each pair of electrode elements may be reduced to determine whether the subject is experiencing electrical induction (or is about to experience electrical induction). If the results show that any one group is responsible for the electrical induction, the group may be operated at a reduced current to improve the electrical induction.

[0057] In many anatomical locations, it is preferred to use an electric field whose orientation alternates between different directions. In these locations, each includes a set of at least four electrode elements 45 ( Figure 2 Additional transducer arrays (not shown in the figure) may be positioned on other sides (e.g., front and back) of the target area. In these embodiments, the AC voltage generator 40 is preferably configured to repeatedly alternate between (a) applying a voltage between the left electrode element 45L and the right electrode element 45R and (b) applying a voltage between the front electrode element and the back electrode element. The AC voltage generator 40 may switch between these two states every 1 second or at different intervals (e.g., between 50 ms and 10 s). Therefore, the orientation of the electric field in these embodiments will repeatedly alternate back and forth between the left / right direction and the front / back direction.

[0058] In these bidirectional embodiments, the electronic switch group 60 includes a dedicated switch for each electrode element in each additional array. Thus, in the example case where each transducer array includes nine electrode elements, the electronic switch group 60 will have 9×4=36 switches. This allows the controller 30 to individually activate or deactivate each of the electrode elements in the additional transducer arrays. The additional transducer arrays (i.e., the front transducer array 21 and the rear transducer array 22) are processed in a manner similar to the left transducer array 23 and the right transducer array 24 described above.

[0059] Combined with the above Figures 2 to 4 In the described embodiment, controller 30 determines whether electrical induction is occurring (in S30 and S140) based on feedback received from the subject via user interface 80. However, in alternative embodiments, the system may use hardware that measures electrically evoked compound action potentials (ECAPs) to automatically detect whether the subject is experiencing (or is about to experience) electrical induction, rather than relying on a user interface to notify the system that electrical induction is occurring.

[0060] During certain types of electrical stimulation of biological tissue, an electrically evoked compound action potential (ECAP) represents the approximately synchronous discharge of a group of electrically stimulated nerve fibers. When an electrical signal of sufficient energy is applied to activate nerve fibers, fibers of different diameters and different locations are activated at approximately the same time (e.g., within a few milliseconds), and their action potentials (APs) propagate to the vicinity of the recording electrode at different speeds. In addition, different nerve fibers of different diameters have different activation thresholds and conduction velocities, conveying different signals, such as sensory types of signals (vibration, temperature, hair movement, muscle contraction, joint position, etc.).

[0061] It turns out that ECAPs, which are related to electrical induction, can be measured using a set of electrodes placed on a subject's skin. These electrodes detect the composite sum of individual APs that arrive at approximately the same time, which is displayed as a curve of a given amplitude and duration. The signals from these electrodes can be used to detect or predict whether a subject may be experiencing electrical induction or is about to experience electrical induction.

[0062] Figure 5 Embodiments that rely on ECAP signals are depicted, using such electrodes to receive ECAP signals to detect or predict whether a subject may be experiencing or about to experience electrical induction. In these embodiments, the ECAP signal provides feedback to the controller 30 (rather than Figure 2 User interface 80 used in the embodiment).

[0063] Figure 5 The AC voltage generator 40, the switch group 60 and the electrode elements 45L, 45R in the embodiment are similar to those described above. Figure 2 The corresponding elements in the embodiment are similar. And the operation of the controller 30 is also the same as Figure 2 The operation of the controller in the embodiment is similar, but with one important exception. More specifically, in the Figure 5 In an embodiment, controller 30 receives feedback from ECAP system 50 indicating whether the subject is experiencing or is about to experience electrical induction, rather than Figure 2 A method of receiving feedback from a user interface indicating whether a subject is experiencing electro-induction.

[0064] In this Figure 5In the embodiment of the present invention, in addition to the electrode elements 45L / 45R for inducing an alternating electric field in the target area, an independent group of electrodes 55L, 55R are provided to determine whether the subject may be experiencing or about to experience electrical induction. More specifically, the first group of ECAP electrodes 55L configured to pick up ECAP signals is positioned near the group of first electrodes 45L, and the second group of ECAP electrodes 55R configured to pick up ECAP signals is positioned near the group of second electrodes 45R. The first group of ECAP electrodes 55L and the second group of ECAP electrodes 55R, respectively positioned on the left and right sides, can both be electrode passive arrays.

[0065] The signals from these ECAP electrodes 55L, 55R (which may be, for example, of the order of 0.2 mV to 2 mV) are received by the ECAP measurement system 50, and the ECAP measurement system 50 measures the ECAP on the left and right sides of the subject's body based on the signals from the ECAP electrodes 55L, 55R positioned on the left and right sides, respectively. The ECAP measurement system 50 processes these signals (e.g., using an amplifier and an analog-to-digital converter) and forwards the resulting data to the controller 30. In this way, the ECAP generated on each side of the subject's body in response to the application of an alternating electric field is measured.

[0066] Because ECAP associated with electrical induction is measured using ECAP electrodes 55L, 55R and ECAP measurement system 50, and these measurements are reported to controller 30, controller 30 can determine whether the subject is likely experiencing electrical induction and / or is about to experience electrical induction. Figure 5 The controller 30 in the embodiment may implement a method similar to the above combined Figure 3 to Figure 4 The steps described above are as follows, except that instead of receiving feedback from the user interface that the induction is occurring (in S30 and S140), the Figure 5 Controller 30 in receives feedback from ECAP system 50 indicating whether the subject is experiencing electrical induction or is about to experience electrical induction.

[0067] As explained above, in some anatomical locations, it is preferred to use an electric field whose orientation alternates between different directions. In these locations, additional transducer arrays positioned on other sides (e.g., front and back) of the target area may be provided. In this case, each group of electrode elements 45 preferably has its own associated group of ECAP electrodes 55x, which is used to determine whether the subject may be experiencing electrical induction or is about to experience electrical induction. For signals from the left group of ECAP electrodes 55L and the right group of ECAP electrodes 55R (pre-processed by the ECAP device 50), the controller 30 responds to signals from these additional groups of ECAP electrodes 55x (also pre-processed by the ECAP system 50) as described above.

[0068] Figure 5 Embodiments rely on a passive array of ECAP electrodes to measure neural activity based on the theory that neural activity can be used to determine that electrical induction is occurring or is about to occur. However, a variety of alternative approaches can be used to automatically determine that electrical induction is occurring or is about to occur, rather than the ECAP-based techniques described above. An example of an alternative approach is to use electromyographic signals to measure muscle activity based on the theory that muscle activity (e.g., twitching) can indicate that electrical induction is occurring. In these embodiments, EMG signals are obtained using a set of electromyographic (EMG) electrodes, preprocessed by the EMG system, and then forwarded to a controller (similar to the controller 30 described above, but programmed to interpret EMG signals instead of ECAP signals). Another example of an alternative approach is to use a mechanical sensor (e.g., accelerometer) to measure muscle activity based on the theory that muscle activity (e.g., twitching) can be an indication of electrical induction occurring. In these embodiments, mechanical sensors are used to capture vibration or acceleration signals, preprocessed by an appropriate front end, and forwarded to a controller (which is similar to the controller 30 described above, but programmed to interpret mechanical events instead of ECAP signals). Other approaches based on measured neural activity or muscle activity may also be used.

[0069] Illustrative Embodiments

[0070] Embodiment 1 is a method of improving electrical induction in a subject being treated with an alternating electric field, the method comprising: selectively deactivating one or more different electrode elements during corresponding different time periods when an alternating electric field is being applied; receiving feedback indicating whether electrical induction is occurring during each of the corresponding different time periods; and determining whether deactivating a given one or more of the electrode elements improves the electrical induction.

[0071] Embodiment 2 is a method according to embodiment 1, the method further comprising: treating the subject using an alternating electric field when the given one or more electrode elements are deactivated.

[0072] Embodiment 3 is a method according to embodiment 1, wherein receiving feedback is achieved by receiving input from the subject.

[0073] Embodiment 4 is a method according to embodiment 1, wherein receiving feedback is achieved by processing electrical signals from a set of ECAP electrodes representing neural activity of the subject.

[0074] Embodiment 5 is a method according to embodiment 1, wherein receiving feedback is achieved by processing electrical signals representing the measurement results of neural activity or muscle activity of the subject.

[0075] Embodiment 6 is a method according to embodiment 1, wherein receiving feedback is achieved by processing an electrical signal representing the measurement results of an electromyography signal used to measure muscle activity.

[0076] Embodiment 7 is a method according to embodiment 1, wherein receiving feedback is achieved by processing electrical signals representing accelerometer measurements used to measure muscle activity.

[0077] Embodiment 8 is a method of improving electrical induction in a subject being treated with an alternating electric field, the method comprising: selectively reducing current flowing through one or more different electrode elements during corresponding different time periods when an alternating electric field is being applied; receiving feedback indicating whether electrical induction is occurring during each of the corresponding different time periods; and determining whether reducing the current flowing through a given one or more of the electrode elements improves the electrical induction.

[0078] Embodiment 9 is a method according to embodiment 8, the method further comprising: treating the subject with an alternating electric field when the given one or more electrode elements operate at a lower current than other electrode elements.

[0079] Embodiment 10 is a method according to embodiment 8, wherein receiving feedback is achieved by receiving input from the subject.

[0080] Embodiment 11 is a method according to embodiment 8, wherein receiving feedback is achieved by processing electrical signals from a set of ECAP electrodes representing neural activity of the subject.

[0081] Embodiment 12 is a method according to embodiment 8, wherein receiving feedback is achieved by processing electrical signals representing the subject's neural activity measurement results or muscle activity measurement results.

[0082] Embodiment 13 is a method according to embodiment 8, wherein receiving feedback is achieved by processing electrical signals representing the measurement results of electromyographic signals used to measure muscle activity.

[0083] Embodiment 14 is a method according to embodiment 8, wherein receiving feedback is achieved by processing electrical signals representing accelerometer measurements used to measure muscle activity.

[0084] Embodiment 15 is a method of applying an electrical signal to a first group of at least four first electrode elements and a second group of at least four second electrode elements positioned on opposite sides of a target area of ​​a subject's body, the method comprising: (a) applying an AC signal between the second group of at least four second electrode elements and a majority of the first electrode elements in the first electrode elements, wherein during corresponding different time periods, one or more different members of the first group of at least four electrode elements are not used or are operated with a reduced current; receiving first feedback indicating whether the subject is experiencing or is about to experience electrical induction during the corresponding different time periods; and determining, based at least in part on the received first feedback, whether electrical induction is improved when one or more given members of the first group of at least four electrode elements are not used or are operated with the reduced current.

[0085] Embodiment 16 is a method according to embodiment 15, the method further comprising: applying an alternating electric field to the target area using the second group of at least four second electrode elements and all of the first electrode elements except the one or more given members of the first group of at least four electrode elements.

[0086] Embodiment 17 is a method according to embodiment 15, the method further comprising: applying an alternating electric field to the target area using one or more given members of the first group operating at a lower current than other members of the first group of at least four first electrode elements.

[0087] Embodiment 18 is a method according to embodiment 15, wherein receiving the first feedback is achieved by receiving input from the subject.

[0088] Embodiment 19 is a method according to embodiment 15, wherein receiving the first feedback is achieved by processing electrical signals from a set of ECAP electrodes representing neural activity of the subject.

[0089] Embodiment 20 is a method according to embodiment 15, the method further comprising: controlling the amplitude of the AC signal.

[0090] Embodiment 21 is a method according to embodiment 20, the method further comprising: increasing the amplitude of the AC signal until the determination indicates that the subject is experiencing or is about to experience electrical induction.

[0091] Embodiment 22 is a method according to embodiment 15, the method further comprising: before step (a), during a first time period, applying an AC signal between the second group of at least four second electrode elements and all first electrode elements in the first electrode elements; and during the first time period, receiving feedback indicating whether the subject is experiencing or is about to experience electrical induction.

[0092] Embodiment 23 is a method according to embodiment 15, the method further comprising: applying a second AC signal between the first group of at least four first electrode elements and a majority of the second electrode elements in the second electrode elements, wherein during corresponding different time periods, one or more different members of the second group of at least four electrode elements are not used or are operated using a reduced current; receiving second feedback, the second feedback indicating whether the subject is experiencing electrical induction or is about to experience electrical induction during the application of the second AC signal; and determining, based at least in part on the received second feedback, whether electrical induction is improved when one or more given members of the second group of at least four electrode elements are not used or are operated using the reduced current.

[0093] Embodiment 24 is a method according to embodiment 23, the method further comprising: applying an alternating electric field to the target area using the first group of at least four first electrode elements and all of the second electrode elements except the given member of the second group of at least four electrode elements.

[0094] Embodiment 25 is a method according to embodiment 15, wherein receiving the first feedback is achieved by processing an electrical signal representing a measurement of neural activity or a measurement of muscle activity of the subject.

[0095] Embodiment 26 is a method according to embodiment 15, wherein receiving the first feedback is achieved by processing an electrical signal representing an electromyography signal measurement result used to measure muscle activity.

[0096] Embodiment 27 is a method according to embodiment 15, wherein receiving the first feedback is achieved by processing an electrical signal representing an accelerometer measurement result used to measure muscle activity.

[0097] Embodiment 28 is a method according to embodiment 15, wherein during the applying, at least two different members of the first group of at least four first electrode elements are not used or are operated using a reduced current during the corresponding different time periods; and wherein the determining includes determining whether electrical induction is improved when at least two given members of the first group of at least four first electrode elements are not used or are operated using the reduced current.

[0098] Embodiment 29 is a device for applying electrical signals to a first group of at least four first electrode elements and a second group of at least four second electrode elements positioned on opposite sides of a target area of ​​a subject's body, the device comprising: an AC signal source having at least one amplitude control input terminal; a first group of at least four first electrically controlled switches, wherein each of the first switches is configured to, depending on the state of the corresponding first control input terminal: (i) close so that current can flow between the AC signal source and the corresponding first electrode element; or (ii) open so that current does not flow between the AC signal source and the corresponding first electrode element; and a controller configured to control the state of the first control input terminal of each of the first switches. The controller is further configured to: (a) apply a first control signal to the first control input, the first control signal causing a selected first switch of the first switches to be disconnected for a corresponding time period; (b) receive a plurality of first feedback signals when the selected first switch of the first switches is disconnected for the corresponding time period, the plurality of first feedback signals indicating whether the subject is experiencing or is about to experience electrical induction; and (c) determine, based at least in part on the received plurality of first feedback signals, whether electrical induction is improved when a given first switch of the first switches is disconnected.

[0099] Embodiment 30 is a device according to embodiment 29, wherein the controller is further configured to control the application of the electrical signal to the first group of at least four electrode elements and the second group of at least four electrode elements so that when the subject is being treated with an alternating electric field, the given one of the first switches is disconnected.

[0100] Embodiment 31 is a device according to embodiment 29, wherein the device also includes a user interface, wherein the user interface is configured to generate the plurality of first feedback signals based on input received from the subject.

[0101] Embodiment 32 is a device according to embodiment 29, wherein the device also includes an ECAP measurement system, the ECAP measurement system being configured to receive signals representing neural activity from a set of ECAP electrodes, wherein the ECAP measurement system generates the plurality of first feedback signals.

[0102] Embodiment 33 is the apparatus of embodiment 29, wherein the controller is further configured to control the amplitude control input.

[0103] Embodiment 34 is a device according to embodiment 33, wherein the controller is further configured to: before step (a), apply a first control signal to the first control input terminal, the first control signal causing all of the first switches to close; control the amplitude control input terminal so that the amplitude increases; and receive a third signal, the third signal indicating whether the subject is experiencing or is about to experience electrical induction.

[0104] Embodiment 35 is a device according to embodiment 29, the device further comprising: a second group of at least four second electrically controlled switches, wherein each of the second switches is configured to be: (i) closed so that current can flow between the AC signal source and the corresponding second electrode element; or (ii) opened so that current does not flow between the AC signal source and the corresponding second electrode element, depending on the state of the corresponding second control input terminal, wherein the controller is further configured to control the state of the second control input terminal of each of the second switches. The controller is further configured to: (x) apply a second control signal to the second control input terminal, the second control signal causing a selected second switch of the second switches to be opened during a corresponding time period; (y) when the selected second switch of the second switches is opened during the corresponding time period, receive a plurality of second feedback signals indicating whether the subject is experiencing or is about to experience electrical induction; and (z) determine whether electrical induction is improved when a given one of the second switches is opened based at least in part on the received plurality of second feedback signals.

[0105] Embodiment 36 is a device according to embodiment 35, wherein the controller is further configured to control the application of the electrical signal to the first group of at least four electrode elements and the second group of at least four electrode elements so that when the subject is being treated with an alternating electric field, the given one of the second switches is disconnected.

[0106] Embodiment 37 is a device according to embodiment 35, wherein the device also includes a user interface, wherein the user interface is configured to generate the plurality of first feedback signals and the plurality of second feedback signals based on input received from the subject.

[0107] Embodiment 38 is a device according to embodiment 35, wherein the device also includes an ECAP measurement system, wherein the ECAP measurement system is configured to receive signals representing neural activity from a set of ECAP electrodes, wherein the ECAP measurement system generates the multiple first feedback signals and the multiple second feedback signals.

[0108] Embodiment 39 is the apparatus of embodiment 35, wherein the controller is further configured to control the amplitude control input.

[0109] Embodiment 40 is a device according to embodiment 39, wherein the controller is further configured to: before step (a), apply a first control signal to the first control input terminal, the first control signal causing all of the first switches to close; control the amplitude control input terminal so that the amplitude increases; and receive a third signal, the third signal indicating whether the subject is experiencing or is about to experience electrical induction.

[0110] The titles are provided only for convenience and should not be construed as limiting the present invention in any way. The embodiments shown under any title or in any part of the present disclosure may be combined with the embodiments shown under the same or any other title or other part of the present disclosure. Unless otherwise indicated herein or clearly contradicted by the context, the present invention covers any combination of the elements described herein in all possible variations thereof.

[0111] Although the present invention has been disclosed with reference to certain embodiments, various modifications, changes and variations may be made to the described embodiments without departing from the field and scope of the invention as defined in the appended claims. Therefore, it is intended that the present invention not be limited to the described embodiments, but rather has the full scope defined by the language of the appended claims and their equivalents.

Claims

1. A method of improving electrical induction in a subject being treated with alternating electric fields, the method comprising: selectively deactivating one or more different electrode elements during corresponding different time periods while an alternating electric field is being applied; receiving feedback indicating whether electrical induction is occurring during each of the respective different time periods; as well as A determination is made as to whether deactivating a given one or more of the electrode elements improves the electrical induction.

2. The method according to claim 1, further comprising: When the given one or more electrode elements are deactivated, the subject is treated with an alternating electric field.

3. The method of claim 1, wherein receiving feedback is accomplished by receiving input from the subject.

4. The method of claim 1, wherein receiving feedback is accomplished by processing electrical signals from a set of ECAP electrodes representing neural activity of the subject.

5. The method of claim 1, wherein receiving feedback is accomplished by processing electrical signals representing a measure of neural activity or a measure of muscle activity of the subject.

6. The method of claim 1, wherein receiving feedback is accomplished by processing electrical signals representing electromyographic signal measurements used to measure muscle activity.

7. The method of claim 1, wherein receiving feedback is accomplished by processing electrical signals representing accelerometer measurements used to measure muscle activity.

8. A method of improving electrical induction in a subject being treated with alternating electric fields, the method comprising: selectively reducing current flowing through one or more different electrode elements during corresponding different time periods when an alternating electric field is being applied; receiving feedback indicating whether electrical induction is occurring during each of the respective different time periods; as well as A determination is made as to whether reducing the current flowing through a given one or more of the electrode elements improves the electrical inductance.

9. The method according to claim 8, further comprising: When the given one or more electrode elements are operated at a lower current than the other electrode elements, the subject is treated with an alternating electric field.

10. The method of claim 8, wherein receiving feedback is accomplished by receiving input from the subject.

11. The method of claim 8, wherein receiving feedback is accomplished by processing electrical signals from a set of ECAP electrodes representing neural activity of the subject.

12. The method of claim 8, wherein receiving feedback is accomplished by processing electrical signals representing a measure of neural activity or a measure of muscle activity of the subject.

13. The method of claim 8, wherein receiving feedback is accomplished by processing electrical signals representing electromyographic signal measurements used to measure muscle activity.

14. The method of claim 8, wherein receiving feedback is accomplished by processing electrical signals representing accelerometer measurements used to measure muscle activity.

15. A method of applying an electrical signal to a first set of at least four first electrode elements and a second set of at least four second electrode elements positioned on opposite sides of a target area of ​​a subject's body, the method comprising: (a) applying an AC signal between the second group of at least four second electrode elements and a majority of the first electrode elements, wherein one or more different members of the first group of at least four first electrode elements are not used or are operated with a reduced current during corresponding different time periods; receiving first feedback indicating whether the subject is experiencing or is about to experience electrical induction during the respective different time periods; as well as Based at least in part on the received first feedback, it is determined whether electrical induction is improved when one or more given members of the first set of at least four first electrode elements are not used or are operated using the reduced current.

16. The method according to claim 15, further comprising: An alternating electric field is applied to the target area using the second set of at least four second electrode elements and all of the first electrode elements except the one or more given members of the first set of at least four first electrode elements.

17. The method according to claim 15, further comprising: An alternating electric field is applied to the target area with the one or more given members of the first set operating at a lower current than other members of the first set of at least four first electrode elements.

18. The method of claim 15, wherein receiving the first feedback is accomplished by receiving input from the subject.

19. The method of claim 15, wherein receiving the first feedback is accomplished by processing electrical signals from a set of ECAP electrodes representing neural activity of the subject.

20. The method according to claim 15, further comprising: The amplitude of the AC signal is controlled.

21. The method according to claim 20, further comprising: The amplitude of the AC signal is increased until the determination indicates that the subject is experiencing or is about to experience electrical induction.

22. The method according to claim 15, further comprising: Prior to step (a), applying an AC signal between the second group of at least four second electrode elements and all first electrode elements of the first electrode element during a first time period; as well as During the first time period, feedback is received indicating whether the subject is experiencing or is about to experience electrical induction.

23. The method according to claim 15, further comprising: applying a second AC signal between the first set of at least four first electrode elements and a majority of the second electrode elements of the second electrode elements, wherein one or more different members of the second set of at least four second electrode elements are not used or are operated with a reduced current during respective different time periods; receiving second feedback indicating whether the subject is experiencing or is about to experience electrical induction during application of the second AC signal; as well as Based at least in part on the received second feedback, it is determined whether electrical inductance is improved when one or more given members of the second set of at least four second electrode elements are not used or are operated using the reduced current.

24. The method according to claim 23, further comprising: An alternating electric field is applied to the target area using the first set of at least four first electrode elements and all but the given member of the second set of at least four second electrode elements.

25. The method of claim 15, wherein receiving the first feedback is accomplished by processing an electrical signal representing a measure of neural activity or a measure of muscle activity of the subject.

26. The method of claim 15, wherein receiving the first feedback is accomplished by processing an electrical signal representing an electromyographic signal measurement for measuring muscle activity.

27. The method of claim 15, wherein receiving the first feedback is accomplished by processing an electrical signal representing an accelerometer measurement used to measure muscle activity.

28. The method of claim 15, wherein during said applying, at least two different members of said first set of at least four first electrode elements are not used or are operated with a reduced current during said respective different time periods; and Wherein said determining comprises determining whether electrical inductance is improved when at least two given members of said first set of at least four first electrode elements are not used or are operated using said reduced current.

29. An apparatus for applying an electrical signal to a first set of at least four first electrode elements and a second set of at least four second electrode elements positioned on opposite sides of a target area of ​​a subject's body, the apparatus comprising: An AC signal source having at least one amplitude control input terminal; A first set of at least four first electrically controlled switches, wherein each of the first switches is configured to, depending on the state of a corresponding first control input: (i) close to enable current to flow between the AC signal source and a corresponding first electrode element; or (ii) disconnected so that current does not flow between the AC signal source and the corresponding first electrode element; and a controller configured to control the state of the first control input terminal of each of the first switches, The controller is further configured to: (a) applying a first control signal to the first control input terminal, the first control signal causing a selected first switch among the first switches to be turned off during a corresponding time period; (b) receiving a plurality of first feedback signals when a selected one of the first switches is off during the corresponding time period, the plurality of first feedback signals indicating whether the subject is experiencing electrical induction or is about to experience electrical induction; as well as (c) determining, based at least in part on the received plurality of first feedback signals, whether inductance is improved when a given one of the first switches is opened.

30. The apparatus of claim 29, wherein the controller is further configured to control application of the electrical signal to the first group of at least four first electrode elements and the second group of at least four second electrode elements such that when the subject is being treated with an alternating electric field, the given one of the first switches is disconnected.

31. The device of claim 29, further comprising a user interface, wherein the user interface is configured to generate the plurality of first feedback signals based on input received from the subject.

32. The device of claim 29, further comprising an ECAP measurement system configured to receive signals representative of neural activity from a set of ECAP electrodes, wherein the ECAP measurement system generates the plurality of first feedback signals.

33. The apparatus of claim 29, wherein the controller is further configured to control the amplitude control input.

34. The apparatus of claim 33, wherein the controller is further configured to, before step (a), Applying a first control signal to the first control input terminal, the first control signal closing all of the first switches; controlling the amplitude control input terminal so that the amplitude increases; and A third signal is received, the third signal indicating whether the subject is experiencing or is about to experience electrical induction.

35. The apparatus of claim 29, further comprising: a second group of at least four second electrically controlled switches, wherein each of the second switches is configured to, depending on the state of the corresponding second control input terminal: (i) be closed so that current can flow between the AC signal source and the corresponding second electrode element; or (ii) be opened so that current does not flow between the AC signal source and the corresponding second electrode element; and wherein the controller is further configured to control the state of the second control input terminal of each of the second switches, and The controller is further configured to: (x) applying a second control signal to the second control input terminal, the second control signal causing selected ones of the second switches to be turned off during a corresponding time period; (y) receiving a plurality of second feedback signals when selected ones of the second switches are off during the corresponding time periods, the plurality of second feedback signals indicating whether the subject is experiencing electrical induction or is about to experience electrical induction; as well as (z) determining, based at least in part on the received plurality of second feedback signals, whether inductance is improved when a given one of the second switches is opened.

36. The apparatus of claim 35, wherein the controller is further configured to control application of the electrical signal to the first group of at least four first electrode elements and the second group of at least four second electrode elements such that when the subject is being treated with an alternating electric field, the given one of the second switches is disconnected.

37. The device of claim 35, further comprising a user interface, wherein the user interface is configured to generate the plurality of first feedback signals and the plurality of second feedback signals based on input received from the subject.

38. The device of claim 35, further comprising an ECAP measurement system configured to receive signals representing neural activity from a set of ECAP electrodes, wherein the ECAP measurement system generates the plurality of first feedback signals and the plurality of second feedback signals.

39. The apparatus of claim 35, wherein the controller is further configured to control the amplitude control input.

40. The apparatus of claim 39, wherein the controller is further configured to, before step (a), Applying a first control signal to the first control input terminal, the first control signal closing all of the first switches; controlling the amplitude control input terminal so that the amplitude increases; and A third signal is received, the third signal indicating whether the subject is experiencing or is about to experience electrical induction.

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