Apparatus for applying alternating current and method for detecting skin condition, electrode element integrity and transducer placement

Abstract

By determining the condition of the participating electrode elements and / or the individual's skin condition beneath the positioned electrode elements, tumor therapeutic fields (TTFields) can be delivered to an individual's body with improved safety and efficacy. This can be achieved by applying an AC signal to a pair or group of electrode elements and obtaining corresponding impedance measurements. In some embodiments, these impedance measurements indicate the condition of the electrode elements and / or the skin condition. These determined conditions can be used to adjust or pause TTField treatment, for example, to allow skin recovery or to ensure that the participating electrode elements function properly.

Description

[Technical Field]

[0001] This application relates to a system and method for delivering a tumor therapeutic field and measuring impedance. Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 216,763, filed on June 30, 2021, which is incorporated herein by reference in its entirety. [Previous Technology]

[0003] Tumor therapeutic field (TTFields) therapy is a proven and effective method for treating tumors. Figure 1 is a schematic diagram of the prior art Optune® system for delivering tumor therapeutic fields. Tumor therapeutic fields are delivered to a patient via four transducer arrays 21 to 24, which are placed on the patient's skin close to the tumor (e.g., as depicted in Figures 2A to 2D for individuals with glioblastoma). The transducer arrays 21 to 24 are arranged in two pairs, and each transducer array is connected to an AC signal generator 20 via a multi-wire cable. The AC signal generator (a) sends an AC current via one pair of arrays 21, 22 during a first time period, which induces an electric field with a first direction through the tumor; then (b) sends an AC current via another pair of arrays 23, 24 during a second time period, which induces an electric field with a second direction through the tumor; then steps (a) and (b) are repeated during treatment.

[0004] Each transducer array 21 to 24 is configured as a set of capacitively coupled electrode elements E (e.g., a set of nine electrode elements, each with a diameter of approximately 2 cm) interconnected via a flexural circuit. Each electrode element includes a conductive substrate on which a dielectric layer (e.g., a ceramic material layer with a high dielectric constant) is disposed. Each electrode element is sandwiched between a layer of conductive medical gel and an adhesive tape. When the array is placed on a patient, the medical gel conforms to the contours of the patient's skin and ensures good electrical contact between the device and the body. When the patient performs daily activities, the adhesive tape holds the entire array in place on the patient. The transducer array is used to deliver long-term tumor therapeutic field therapy (e.g., 15 hours per day for at least one month). [Summary of the Invention]

[0005] One aspect of the present invention relates to a first device for applying alternating current between at least four first electrode elements positioned on a first side of a body and at least four second electrode elements positioned on a second side of a body. The first device comprises: an AC signal generator that generates a first polarity and a second polarity of an AC output signal; at least four first switches, each configured to selectively apply the first polarity of the AC output signal to each of the first electrode elements according to the state of a respective control signal; at least four second switches, each configured to selectively apply the second polarity of the AC output signal to each of the second electrode elements according to the state of a respective control signal; and at least one third switch, each configured to selectively apply the second polarity of the AC output signal to each of the first electrode elements according to the state of a respective control signal.

[0006] The first device also includes: a controller configured to control a plurality of first switches, a plurality of second switches and at least one third switch, such that in a first mode, the controller issues control signals that cause a majority of the first switches to apply a first polarity of the AC output signal to a corresponding first electrode element and cause a majority of the second switches to apply a second polarity of the AC output signal to a corresponding second electrode element, and in a second mode, the controller issues control signals that (a) cause the first switches to sequentially apply the first polarity of the AC output signal to each individual first electrode element, while at least one third switch applies the second polarity of the AC output signal to at least one individual first electrode element, and (b) sequentially receive impedance measurements corresponding to each combination of the first electrode elements.

[0007] In some embodiments of the first device, in a second mode, the controller issues control signals that (a) cause a first switch to sequentially apply the first polarity of the AC output signal to each individual first electrode element, while at least one third switch applies the second polarity of the AC output signal to each individual first electrode element, and (b) sequentially receive impedance measurements corresponding to each combination of the first electrode elements.

[0008] In some embodiments, the first device further includes at least one fourth switch, each configured to selectively apply a first polarity of the AC output signal to each of the second electrode elements according to the state of each control signal. The controller is configured to control a plurality of first switches, a plurality of second switches, and at least one fourth switch such that, in a third mode, the controller issues control signals that (a) cause the second switches to sequentially apply a second polarity of the AC output signal to each of the second electrode elements, while at least one fourth switch applies a first polarity of the AC output signal to at least one of the second electrode elements, and (b) sequentially receive impedance measurements corresponding to each combination of the second electrode elements.

[0009] In some embodiments of the first device, in the third mode, the controller issues control signals that (a) cause the second switches to sequentially apply the second polarity of the AC output signal to each individual second electrode element, while at least one fourth switch applies the first polarity of the AC output signal to each individual second electrode element, and (b) sequentially receive impedance measurements corresponding to each combination of the second electrode elements.

[0010] In some embodiments of the first device, in a first mode and based on the received impedance measurement results, the controller is configured to issue a control signal to cause a decrease in the current at one or more of the first electrode elements.

[0011] Another aspect of the present invention relates to a second device for applying alternating current between at least four first electrode elements positioned on a first side of a body and at least four second electrode elements positioned on a second side of a body. The second device comprises: an AC signal generator that generates an AC output signal; at least four first switches, each configured to selectively apply the AC output signal to a respective first electrode element according to the state of a respective control signal; and at least four second switches, each configured to selectively apply the AC output signal to a respective second electrode element according to the state of a respective control signal.

[0012] The second device also includes: a controller configured to control a plurality of first switches and a plurality of second switches such that, in a first mode, the controller issues control signals that cause a majority of the first switches to apply an AC output signal to a corresponding first electrode element and a majority of the second switches to apply an AC output signal to a corresponding second electrode element, and in a second mode, the controller issues control signals that (a) cause the second switches to apply an AC output signal to a corresponding second electrode element, (b) sequentially cause different or subsets of the first switches to apply an AC output signal to a corresponding first electrode element, and (c) sequentially receive impedance measurements corresponding to respective combinations of the first and second electrode elements, wherein, in the first mode, the AC output signal has a frequency between 100 and 500 kHz, and in the second mode, the AC output signal has a frequency below 20 kHz.

[0013] In some embodiments of the second device, in the second mode, the controller issues control signals that (a) cause the second switch to apply an AC output signal to a corresponding second electrode element, (b) sequentially cause each of the first switches to apply an AC output signal to a corresponding individual first electrode element, and (c) sequentially receive impedance measurements corresponding to each combination of the individual first electrode element and the second electrode element.

[0014] In some embodiments of the second device, the controller is further configured to control a plurality of first switches and a plurality of second switches such that, in a third mode, the controller issues control signals that (a) cause the first switches to apply AC output signals to corresponding first electrode elements, (b) sequentially cause each of the second switches to sequentially apply AC output signals to corresponding individual second electrode elements, and (c) sequentially receive impedance measurements corresponding to individual combinations of the individual second electrode elements and the first electrode elements.

[0015] In some embodiments of the second device, in a first mode and based on the received impedance measurement results, the controller is configured to issue a control signal to cause a reduction in the current at one or more of the first electrode elements.

[0016] Another aspect of the present invention relates to a first method for detecting the condition of skin areas on an individual's body. The first method includes: positioning at least four electrode elements on an individual's body such that each of the electrode elements is coupled to a separate skin area on the body; sequentially applying AC signals to different subsets of the electrode elements; measuring the impedance of the applied AC signals while sequentially applying AC signals to different subsets of the electrode elements; comparing the measured impedance with a standard; and determining the condition of the skin area based on the comparison.

[0017] In some cases of the first method, the first polarity of the AC signal is sequentially applied to each individual electrode element, while the second polarity of the AC signal is applied to each different individual electrode element, and impedance measurements corresponding to each combination of electrode elements are sequentially received.

[0018] In some cases of the first method, the comparison includes comparing the measured impedance with a constant. In some cases of the first method, the comparison includes comparing the measured impedance with previously measured impedances of individual skin regions.

[0019] In some cases of the first method, when the measured impedance meets the standard, most of at least four electrode elements are used to induce an electric field through the individual body. In some cases of the first method, the AC signal has a frequency below 20 kHz.

[0020] Another aspect of the present invention relates to a second method for detecting the integrity of electrode elements. The second method includes: positioning at least four electrode elements on a body such that each of the electrode elements is coupled to a different area of ​​the body; sequentially applying AC signals to different subsets of the electrode elements; measuring the impedance of the applied AC signals while sequentially applying AC signals to different subsets of the electrode elements; comparing the measured impedance with a standard; and determining the condition of one or more of the electrode elements based on the comparison.

[0021] In some cases of the second method, the first polarity of the AC signal is sequentially applied to each individual electrode element, while the second polarity of the AC signal is applied to each different individual electrode element, and impedance measurements corresponding to each combination of electrode elements are sequentially received.

[0022] In some cases of the second method, when the measured impedance meets the standard, the electrode element is used to induce an electric field through the body.

[0023] Some cases of the second method further include generating a notification when the measured impedance does not meet the standard. In some cases of the second method, the AC signal has a frequency below 20 kHz.

[0024] Another aspect of the present invention relates to a third method for detecting the condition of skin areas on an individual's body. The third method includes: positioning at least four first electrode elements on skin areas on a first side of an individual's body, and positioning at least four second electrode elements on a second side of an individual's body; sequentially applying an AC signal to different subsets of the first and second electrode elements, each subset including one or more of the first electrode elements and one or more of the second electrode elements, wherein the AC signal has a frequency below 20 kHz; measuring the impedance of the applied AC signal while sequentially applying the AC signal to each subset; comparing the measured impedance with a standard; and determining the condition of skin areas on the individual's body based on the comparison.

[0025] In some cases of the third method, sequentially applying the AC signal further includes: sequentially applying the AC signal to a particular first electrode element while simultaneously applying the AC signal to a second electrode element, wherein impedance measurements corresponding to respective combinations of the particular first electrode element and the second electrode element are received sequentially.

[0026] In some cases of the third method, the first electrode element and the second electrode element are capacitively coupled and positioned to induce an alternating electric field through the individual body when AC signals are applied sequentially.

[0027] In some cases of the third method, the comparison includes comparing the measured impedances with a constant. In some cases of the first method, the comparison includes comparing the measured impedances with previously measured impedances of individual skin areas.

[0028] In some cases of the third method, when the measured impedance meets the standard, most of the four electrode elements are used to induce an electric field through the individual body.

[0029] Another aspect of the present invention relates to a fourth method for detecting the integrity of electrode elements. The fourth method includes: positioning at least four first electrode elements on a first side of the body and positioning at least four second electrode elements on a second side of the body; sequentially applying an AC signal to different subsets of the first and second electrode elements, each subset including one or more of the first electrode elements and one or more of the second electrode elements, wherein the AC signal has a frequency below 20 kHz; measuring the impedance of the applied AC signal while sequentially applying the AC signal to each subset; comparing the measured impedance with a standard; and determining the condition of one or more of the first electrode elements based on the comparison.

[0030] In some cases of the fourth method, sequentially applying the AC signal further includes: sequentially applying the AC signal to a particular first electrode element while simultaneously applying the AC signal to a second electrode element, wherein impedance measurements corresponding to respective combinations of the particular first electrode element and the second electrode element are received sequentially.

[0031] In some cases of the fourth method, the first electrode element and the second electrode element are capacitively coupled and positioned to induce an alternating electric field through the body when an AC signal is applied sequentially.

[0032] Some cases of the fourth method further include: when the measured impedance meets the standard, applying an AC signal to most of the first electrode elements and most of the second electrode elements to induce an electric field through the body.

[0033] Some of the fourth methods further include generating a notification when the measured impedance does not conform to the standard.

[0034] Another aspect of the present invention relates to a fifth method for detecting the integrity of electrode elements. The fifth method includes: positioning at least two electrode elements on a body such that each of the electrode elements is coupled to a separate area of ​​the body; applying an AC signal between the electrode elements; measuring at least one impedance while the AC signal is applied between the electrode elements; and determining the condition of the electrode elements based on the measured at least one impedance, wherein when the condition meets at least one criterion, the electrode elements are used to induce an electric field through the body.

[0035] Another aspect of the present invention relates to a sixth method for detecting the integrity of electrode elements. The sixth method includes: positioning at least two first electrode elements on a first side of a body and positioning at least two second electrode elements on a second side of a body; applying a first AC signal between (a) at least one of the first electrode elements and (b) at least one of the second electrode elements, wherein the first AC signal has a frequency of less than 20 kHz; measuring at least one impedance while applying the first AC signal; determining the condition of one or more of the first electrode elements based on the measured at least one impedance; and when the condition of the electrode elements meets at least one criterion, applying a second AC signal between (a) at least one of the first electrode elements and (b) at least one of the second electrode elements to induce an electric field through the body, wherein the second AC signal has a frequency of greater than 50 kHz.

[0036] Another aspect of the present invention relates to a seventh method for detecting the condition of a skin region on an individual's body. The seventh method includes: positioning at least two electrode elements on the skin region; applying an AC signal between the electrode elements; measuring at least one impedance while the AC signal is applied between the electrode elements; and determining the condition of the skin region based on the measured at least one impedance, wherein when the condition of the skin region meets at least one criterion, the electrode elements are used to induce an electric field through the individual's body.

[0037] Another aspect of the present invention relates to an eighth method for detecting the condition of a skin region on an individual's body. The eighth method includes: positioning at least two first electrode elements on a skin region on a first side of the individual's body, and positioning at least two second electrode elements on a second side of the individual's body; applying a first AC signal between (a) at least one of the first electrode elements and (b) at least one of the second electrode elements, wherein the first AC signal has a frequency of less than 20 kHz; measuring at least one impedance while applying the first AC signal; determining the condition of the skin region based on the measured at least one impedance; and when the condition of the skin region meets at least one criterion, applying a second AC signal between at least one of the first electrode elements and (b) at least one of the second electrode elements to induce an electric field through the individual's body, wherein the second AC signal has a frequency of greater than 50 kHz.

[0038] Another aspect of the present invention relates to a ninth method for detecting improper placement of a transducer array on an individual's body. The ninth method includes: positioning at least four electrode elements on the individual's body such that each of the electrode elements is coupled to a separate skin region on the body; sequentially applying AC signals to different subsets of the electrode elements; measuring the impedance of the applied AC signals while sequentially applying the AC signals to the different subsets of the electrode elements; comparing the measured impedance with a standard; and determining, based on the comparison, that the transducer array is improperly placed.

[0039] In some cases of the ninth method, the first polarity of the AC signal is sequentially applied to each individual electrode element, while the second polarity of the AC signal is applied to each different individual electrode element, and impedance measurements corresponding to each combination of electrode elements are sequentially received.

[0040] In some cases of the ninth method, the comparison includes comparing the measured impedance with a constant. In some cases of the ninth method, the comparison includes comparing the measured impedance with the previously measured impedance of a defect-free electrode on a separate healthy skin area.

[0041] In some cases of the ninth method, when the measured impedance conforms to a standard, most of at least four electrode elements are used to induce an electric field through the individual body. In some cases of the ninth method, the AC signal has a frequency below 20 kHz.

[0042] In some of the sixth and eighth methods, the second AC signal is applied for at least 72 hours.

Implementation Method

[0044] Although the method of Figure 1 described above is highly effective for delivering a tumor treatment field to the tumor, the effectiveness of the treatment will decrease if good electrical contact is not maintained between each of the electrode elements in the four transducer arrays 21 to 24 and the individual's body. This can occur, for example, if one or more of the electrode elements are defective (such as defects in the dielectric layer of the electrode element) or if the hydrogel beneath the electrode element dries out.

[0045] The embodiments described herein advantageously provide the ability to detect the condition of the transducer array electrode elements, thereby maintaining good electrical contact with the patient's body to improve tumor treatment field therapy.

[0046] Another source of treatment variability is the individual's body and their tolerance to long-term treatment. For example, a transducer array is positioned on an individual's body to target a tumor with a tumor treatment field; however, the individual's skin under the transducer array may undergo changes due to treatment (e.g., rash, irritation, etc.), or other factors may affect the individual's tolerance to treatment (e.g., underlying skin conditions).

[0047] The embodiments described herein advantageously provide the ability to detect the condition of the patient’s skin and to adjust the treatment characteristics as needed so that the patient can better tolerate the treatment.

[0048] Some embodiments detect the condition of the transducer array electrodes and / or the patient's skin condition by using the same electrodes for delivering the tumor treatment field to receive impedance measurements. Embodiments may sequentially apply an AC signal to pairs or groups of electrode elements to receive a plurality of impedance measurements. These impedance measurements may indicate the condition of the participating electrode elements and / or the condition of the patient's skin beneath the participating electrode elements.

[0049] Embodiments may include a single system having at least two operating modes, wherein a) in a first mode, the system delivers a tumor therapeutic field treatment to a patient's body, and b) in a second mode, the system measures impedance values ​​indicating the condition of participating electrode elements and / or the condition of the patient's skin. The same transducer array configuration may implement both operating modes based on control signals issued by a controller. In an example implementation, at least two transducer arrays are positioned on different sides of the patient's body. In the first mode (e.g., tumor therapeutic field treatment mode), an AC signal is applied to the positioned transducer array to deliver the target tumor therapeutic field treatment to the patient. However, the delivery of the tumor therapeutic field treatment can be improved by determining certain conditions, such as the condition of the skin beneath the positioned array and / or the condition of individual electrode elements of the array. In the second mode, at least one electrode of the positioned transducer array is used to measure impedance values ​​indicating the skin condition and / or electrode condition. The delivery of the tumor therapeutic field treatment (i.e., the first operating mode) can be adjusted based on the conditions detected in the second mode to optimize the results. For example, electrode integrity can be assessed before using a new transducer array to ensure the integrity of electrodes in previously used transducer arrays, and generally to ensure good electrical contact is maintained for tumor therapeutic field therapy. Alternatively, skin condition can be assessed to ensure the patient's tolerance to long-term use of tumor therapeutic field therapy, and / or treatment characteristics can be modified to ensure patient skin health. Based on the detected conditions, treatment characteristics such as transducer array positioning, participating electrodes, AC signal characteristics, and other properties can be adjusted to optimize treatment. In some cases, electrode condition and / or skin condition may necessitate suspending tumor therapeutic field therapy, for example, to protect the patient's health and safety.

[0050] Various techniques can be used to measure impedance values ​​in the embodiments. For example, in a first technique, at least one first electrode of a first polarity is positioned close to at least one second electrode of a second polarity, such that the first electrode and the second electrode are directly coupled (e.g., via an individual's body). An AC signal is then applied between the positioned first and second electrodes, and the impedance is measured. In a second technique, at least one first electrode of a first polarity is positioned on a first side of the individual's body, and at least one second electrode of a second polarity is positioned on a second side of the individual's body, such that the first electrode and the second electrode are capacitively coupled. An AC signal is then applied between the positioned first and second electrodes, and the impedance is measured.

[0051] Some embodiments of impedance measurement using the first or second technique have individual conductors for each of the plurality of electrode elements in each of the transducer arrays. Unlike prior art configurations where all electrode elements E in each of the transducer arrays 21 to 24 are wired in parallel, the individual conductor of each electrode element makes it possible to independently turn current on and off for any given individual electrode element in any of the arrays. For example, in the first or second technique, embodiments can sequentially apply AC signals between different pairs or groups of electrode elements, and this can be achieved by the ability to independently turn current on and off for individual electrode elements.

[0052] Figure 3 depicts a first embodiment of a transducer array 50 that provides individual conductors for individual electrode elements 52. As will be described below in conjunction with Figure 4, it is preferred to use four replicas of the transducer array 50 to deliver a tumor treatment field to an individual's head (or other body part).

[0053] Each transducer array 50 includes a plurality of electrode elements 52, which are labeled E1 to E9 in the embodiment of FIG. 3 for easy reference. Each of these electrode elements 52 has a conductive substrate (e.g., a circular metal substrate) on which a dielectric layer is disposed. In some embodiments, each of these electrode elements 52 is a disk-shaped capacitively coupled electrode element (e.g., with a diameter of 2 cm), similar to prior art electrode elements used in the Optune® system, and the dielectric layer comprises a thin ceramic material layer having a high dielectric constant. However, unlike the Optune® system and FIG. 1 (where all elements are wired in parallel), individual conductors in this embodiment of FIG. 3 extend from each of the electrode elements 52 to the connector 57. These conductors are numbered 1 to 9 directly above the “wire routing” block 55 (which brings the individual conductors together into a single cable 56). In some embodiments, the electrical connection of each of the electrode elements 52 comprises one or more traces and / or one or more conductive lines on a flexural circuit. In some embodiments, the dielectric layer comprises a polymer having a high dielectric constant (e.g., a dielectric constant greater than 10, preferably greater than 30).

[0054] In the embodiment depicted in FIG3, all capacitively coupled electrode elements 52 are held in place by a support structure 59. The support structure is configured to hold the electrode elements against an individual body such that the dielectric layer of the electrode element 52 faces the individual body and is positioned to contact the individual body. Where appropriate, this support structure may include a flexible backing 59 (e.g., a layer of foam material). Preferably, when the transducer array 50 is placed against an individual body, a layer of hydrogel or conductive adhesive is disposed between the dielectric layer of the electrode element 52 and the individual body. The support structure 59 can be constructed using any of a variety of known methods readily apparent to those skilled in the art, including but not limited to self-adhesive fabrics, foams, or rolls of plastic sheets.

[0055] In some embodiments, each transducer array 50 also includes a plurality of thermistors 54 to sense the temperature of each individual electrode element 52. This can be achieved, for example, by incorporating a hole or well at the center of each electrode element 52 and positioning the thermistor 54 in such hole or well. Examples of suitable hardware and procedures for thermistors are described in U.S. Application No. 17 / 129,088, filed December 21, 2020, which is incorporated herein by reference in its entirety, and examples of suitable hardware and procedures for obtaining temperature readings from thermistors are described in US 2018 / 0050200, which is incorporated herein by reference in its entirety.

[0056] Each transducer array 50 also has a connector 57 for sending and receiving electrical signals into and out of the transducer array 50. The connector 57 has a plurality of first pins and second pins. In the illustrated embodiment, the number of first pins is the same as the number of electrode elements 52, and each of the first pins corresponds to a specific electrode element 52. Furthermore, in the illustrated embodiment, only a single second pin, labeled C, is provided for temperature measurement. It should be noted that, as used herein, the term "pin" may refer to either a male or female pin of the connector 57.

[0057] Each transducer array 50 also has a plurality of first conductors, and the number of these first conductors will depend on the number of electrode elements 52. In the embodiment depicted in FIG3, there are nine electrode elements 52, and these conductors are labeled 1 to 9. Each of these first conductors provides a conductive path between (a) each of the first pins in the connector 57 and (b) the conductive substrate of each of the electrode elements 52 (E1 to E9). It should be noted that each of these first conductors may be implemented using a plurality of wire segments and / or a plurality of traces on a flexible circuit, as appropriate.

[0058] Because connector 57 has individual first pins corresponding to each of the individual electrode elements 52, and because there is a conductive path between each of the first pins and the individual electrode elements 52, a system cooperating with connector 57 can selectively energize or de-energize each of the electrode elements 52 individually by applying or not applying an AC signal to the individual first pins on connector 57. Embodiments use transducer arrays 50 positioned on different sides of the patient's body to induce an electric field through the patient's body. For example, in a first operating mode, the transducer array can deliver a tumor therapeutic field (e.g., using a target frequency between 100 kHz and 500 kHz). In a second operating mode, the transducer array can induce an electric field through the patient's body using a lower frequency (e.g., below 20 kHz), and impedance measurements can be acquired to detect a) the condition of the electrode elements of the transducer array and / or b) the condition of the patient's skin.

[0059] Figure 4A is a block diagram of a system using four replicas of transducer array 50 (described above in conjunction with Figure 3) to a) apply a tumor treatment field to an individual; and b) acquire impedance measurements. In Figure 4A, the four replicas are labeled 50A, 50P, 50L, and 50R, where A, P, L, and R represent front, back, left, and right, respectively. The lower portion of Figure 4A depicts the AC voltage generator 35 and the "CAD box" 30 as separate blocks, the latter including the controller 34 and switch groups 1L and 1R. In some embodiments, the components in these two blocks 35, 30 may be physically divided into two separate housings. However, in alternative embodiments, the components in these two blocks 35, 30 are combined into a single housing.

[0060] For clarity, the left and right channels are depicted in Figure 4A. However, the remaining channels (i.e., the front and rear channels) operate in the same manner as the left and right channels. Furthermore, for clarity, each of the transducer arrays 50 in Figure 4A is depicted with only four electrode elements 52. However, the actual system is expected to have a larger number of electrode elements (e.g., between 9 and 30), and also a larger number of certain other components (e.g., switches, conductors, etc.), depending on the actual number of electrode elements 52 used in each of the transducer arrays 50.

[0061] The system of Figure 4A can measure the impedance of an AC signal applied between or in a group of electrode elements 52. For example, the controller 34 can apply an AC signal to any one of the electrode elements 52 of the transducer array 50L by sequentially energizing one or more of the electrode elements using an electronically controlled switch in the control switch group 1L (which may be implemented using a bidirectional analog switch). Similarly, the controller 34 can apply an AC signal to any one of the electrode elements 52 of the transducer array 50R by sequentially energizing one or more of the electrode elements using an electronically controlled switch in the control switch group 1R. In some embodiments, the controller 34 can apply an AC signal to a pair or group of electrode elements 52 located on both sides of an individual's body, for example, by issuing control signals to the electronically controlled switch groups 1L and 1R. Corresponding switch groups (not shown) are also provided for other channels 50A, 50P, and a similar method is used in the channels.

[0062] An embodiment of the system in Figure 4A implements multiple operating modes: a) in a first operating mode, a first polarity of an AC signal is applied to most electrodes located on a first side (e.g., right or front) of the individual's body, and a second polarity of an AC signal is applied to most electrodes located on a second side (e.g., left or rear) of the individual's body; and b) in a second operating mode, a first polarity of an AC signal is applied to at least one electrode located on a first side (e.g., right or front) of the individual's body, and a second polarity of an AC signal is applied to at least one electrode located on a second side (e.g., left or rear) of the individual's body. In the first operating mode, the electrode elements can deliver a tumor therapeutic field (e.g., using a target frequency between 100 kHz and 500 kHz), while in the second operating mode, the electrode elements can use a lower frequency (e.g., below 20 kHz) to induce an electric field through the patient's body, allowing impedance measurements to be acquired. The impedance measurements are used to detect the condition of a) the electrode elements of the transducer array and / or b) the condition of the patient's skin. Given the detected conditions, the treatment delivery of the tumor treatment field can be adjusted (i.e., the first operating mode) to optimize the results.

[0063] In both the first operating mode (e.g., tumor treatment field mode) and the second operating mode (e.g., impedance measurement mode), an electric field can be induced between electrode elements positioned on a first and second side of an individual's body. However, in the first mode, the AC signal has a frequency range between 100 and 500 kHz (e.g., when projected onto a tumor treatment field), and in the second mode, the AC signal has a frequency below 20 kHz. The frequency range used in the first operating mode induces a tumor treatment field in the individual's body, while the frequency selected for the second operating mode allows for efficient impedance measurement. Using a lower frequency in the second operating mode improves the integrity of the electrode elements and / or the quality of skin condition measurements because it increases the impedance of the capacitive portion of the circuit without increasing the impedance of any resistive portion of the circuit. This thus pulls out background noise (i.e., the contribution from the capacitive element) from the desired signal (i.e., the contribution from the resistive element).

[0064] In some embodiments, during the second operating mode, the controller 34 may issue control signals that change the state of the switch groups 1L and 1R to sequentially apply AC signals between different pairs and / or different groups of the left and right electrode elements 52.

[0065] One method for obtaining impedance measurements corresponding to each of the electrode elements in transducer arrays 50L and 50R is as follows: (a) closing all switches in group 1L, closing only switch 1 in group 1R, and obtaining an impedance measurement; (b) closing all switches in group 1L, opening switch 1 in group 1R, closing switch 2 in group 1R, and then obtaining another impedance measurement; (c) continuing this process by individually stepping through each of the switches in group 1R until an impedance measurement is obtained. (d) Measure the impedance of each of the electrode elements in transducer array 50R; (e) Close all switches in group 1R, close only switch 1 in group 1L and obtain an impedance measurement; (f) Close all switches in group 1R, open switch 1 in group 1L, close switch 2 in group 1L, and then obtain another impedance measurement; and (c) Continue this process by individually stepping through each switch in group 1L until the impedance of each of the electrode elements in transducer array 50L is obtained. Individual impedance measurements (for any given set of switch settings) can be obtained, for example, by dividing the output voltage of AC voltage generator 35 (which may be known in advance or measured each time) by the current being delivered by AC voltage generator 35. For a particular set of switch settings, the measurement will be performed on an instantaneous basis (using any known method).

[0066] An embodiment of the system in Figure 4B can use the same electrode elements to implement both a tumor therapeutic field treatment mode and an impedance measurement mode. In the impedance measurement mode, a single transducer array 50 positioned on one side of the patient's body is used to acquire impedance measurements. The transducer array 50 is used to a) induce an electric field and deliver tumor therapeutic field treatment in a first operating mode (e.g., tumor therapeutic field treatment mode), and b) measure the current impedance between two or more local electrodes on the single transducer array in a second operating mode (e.g., impedance measurement mode). For example, in the second mode, an AC signal can be applied between two or more local electrodes on the single transducer array 50, and impedance measurements can be acquired. The impedance measurements can indicate a) the condition of the electrode elements of the transducer array and / or b) the condition of the patient's skin.

[0067] The system of Figure 4B can apply a tumor treatment field to an individual and measure impedance in a manner similar to that of the system of Figure 4A, measuring the AC signal applied to the pairs or groups of electrode elements 52. However, the system of Figure 4B further includes switches 2L and 2R. In some embodiments, switches 2L and / or 2R can be controlled by controller 34 such that the AC signal is applied between pairs or groups of electrode elements on one side of the individual's body. For example, generally speaking, the system of Figure 4A applies a first polarity of the AC signal to electrode elements located on a first side (e.g., right or front) of the individual's body and applies a second polarity of the AC signal to electrode elements located on a second side (e.g., left or rear) of the individual's body. This system configuration can induce an electric field through the individual's body.

[0068] The system of Figure 4B includes a switch group 1L and at least one switch 2L, wherein the switch group 1L can apply a first polarity of an AC signal to one or more left-side electrode elements 52, and the switch 2L can apply a second polarity of an AC signal to at least one left-side electrode element 52. Because the transducer 50L is positioned such that the left-side electrode element 52 is coupled to the individual body, when the states of the switch group 1L and the switch 2L cause both the first polarity and the second polarity of the AC signal to be applied to the left-side electrode element 52, a direct current flows between or in the group of left-side electrode elements 52.

[0069] The embodiment of the system in Figure 4B implements multiple operating modes: a) In a first operating mode (which is a tumor treatment field treatment mode), a first polarity of the AC signal is applied to most electrodes located on a first side (e.g., right or front) of the individual's body, and a second polarity of the AC signal is applied to most electrodes located on a second side (e.g., left or rear) of the individual's body. In a second operating mode (which is an impedance measurement mode), a first polarity of the AC signal is applied to at least one electrode element located on a first side of the individual's body, and a second polarity of the AC signal is applied to at least one electrode element located on a first side (i.e., the same side) of the individual's body.

[0070] In the embodiment illustrated in FIG4B, the left electrode element 52 E3 has a switchable polarity because this electrode element corresponds to two switches, one from switch group 1L (for applying the first polarity of the AC signal) and switch 2L (for applying the second polarity of the AC signal). For example, in a first operating mode, the first polarity of the applied AC signal (i.e., via the closed switch from switch group 1L) can be applied to E3, while in a second operating mode, the second polarity of the applied AC signal (i.e., via the closed switch 2L) can be applied to E3.

[0071] During the second operating mode, consider the left-side electrode elements 52 E1, E2, E3, and E4 depicted in FIG4B. When the second polarity of the AC signal is applied to E3 (i.e., switch 2L is closed), the first polarity of the AC signal can be applied to one of E1, E2, or E4, and current can flow between the electrode element pairs via the individual skin. Alternatively, when the second polarity of the AC signal is applied to E3, the first polarity of the AC signal can be applied to two or more of E1, E2, or E4, and current can flow within the group of electrode elements. In some embodiments, the controller 34 can issue control signals that change the state of switch group 1L and / or switch 2L to sequentially apply AC signals between different pairs and / or different groups of the left-side electrode elements 52.

[0072] For example, sequentially applying an AC signal to an electrode pair may include a first pair E3 and E1, a second pair E3 and E2, and a third pair E3 and E4. In another example, sequentially applying an AC signal to an electrode group may include a first group E1, E2 and E3, a second group E2, E3 and E4, and a third group E1, E3 and E4. In both of these examples, E3 is consistently present in these pairs or groups because E3 is illustrated as a switchable polarity electrode element in FIG. 4B. Other embodiments include multiple switchable polarity electrode elements and / or a higher number of electrode elements that can realize more possible electrode pairs or groups.

[0073] In some embodiments, impedance is measured each time an AC signal is sequentially applied to an electrode pair or group. For example, an AC signal may be applied to a first pair of electrode elements, and impedance may be measured during the application; after the measurement, the AC signal may be interrupted and a control signal from controller 34 may change the state of switch group 1L and switch 2L; and then, after the state change, an AC signal may be applied to a second pair of electrodes, and impedance may be measured, etc.

[0074] Although the illustrated embodiment depicts only one switch routing opposite polarity to a given electrode element 52, switch 2L may include two, three, or more switches, such that two, three, or more left electrode elements 52 have switchable polarities. Switch 2R and right electrode element 52 may operate in a similar manner to switch 2L and left electrode element 52. Corresponding switches and switch groups (not shown) are also provided for other channels 50A, 50P, and a similar approach is used in the channels.

[0075] A method for obtaining impedance measurements corresponding to each of the electrode elements in the transducer array 50L of the embodiment of FIG. 4B is as follows: (a) closing switch 2L (e.g., corresponding to switchable polarity electrode element E3), closing only switch 1 in group 1L, and obtaining an impedance measurement; (b) closing switch 2L, opening switch 1 in group 1L, closing switch 2 in group 1L, and then obtaining another impedance measurement; (c) continuing this process by individually stepping through each of the switches in group 1L (except switch 3) until impedance measurements of each of the electrode elements in the transducer array 50L (except electrode element E3) are obtained. A similar method can be used to obtain impedance measurements corresponding to each of the electrode elements in the transducer array 50R. Individual impedance measurements (for any given set of switch settings) can be obtained, for example, as described above with respect to the embodiment of FIG. 4A. After obtaining the impedance measurements of each individual element in arrays 50L and 50R, the impedance measurements can be used, for example, to modify the tumor treatment field applied using the same arrays 50L and 50R.

[0076] An embodiment of the system in Figure 4C can implement a treatment operation mode and an impedance measurement operation mode similar to the system in Figure 4B; however, reverse polarity electrode elements (rather than switchable polarity electrode elements) are used to obtain impedance measurements. The transducer array 50 is used to a) induce an electric field and deliver a tumor therapeutic field in a first operation mode, and b) measure the current impedance between two or more local electrodes on a single transducer array in a second operation mode, wherein at least one of the two electrodes is a reverse polarity electrode dedicated to the second operation mode. For example, the transducer array 50 may be wired such that an applied AC signal applies a first polarity to most of the electrode elements of the array and a second polarity to at least one of the electrode elements of the array (i.e., a reverse polarity electrode element dedicated to the second operation mode). In these embodiments, a second polarity is selectively applied to the electrode element dedicated to the second mode, such that a) the element is "disconnected" when delivering the tumor therapeutic field in the first mode, and b) the element is selectively "connected" when acquiring local impedance measurements in the second mode. For example, in the second mode, an AC signal can be applied between the dedicated electrode element and at least one other electrode element (both on a single transducer array 50), and impedance measurements can be acquired. The impedance measurements can indicate a) the condition of the electrode elements of the transducer array and / or b) the condition of the patient's skin.

[0077] The system of Figure 4C can apply a tumor treatment field to an individual and measure impedance in a manner similar to that of the system of Figure 4B, measuring the AC signal applied to the pair or group of electrode elements 52. However, the switch groups 1L and 1R in the system of Figure 4C have fewer connections to the electrode elements 52. In Figure 4B, at least one electrode element located on a given side of the individual's body has a switchable polarity because the electrode element corresponds to one of the switches in switch groups 1L and switch 2L. In Figure 4C, the transducer 50 includes a plurality of electrode elements of a first polarity to which an AC signal can be applied and at least one electrode element of the opposite polarity to which the AC signal can be connected, rather than including electrode elements with switchable polarity.

[0078] In the embodiment illustrated in FIG. 4C, the transducer 50L includes left electrode elements 52 E1, E2, E3, and E4, wherein E1, E2, and E4 are connected to the AC generator 35 via switch group 1L, and E3 is connected to the AC generator 35 via switch 2L. Based on a control signal issued by the controller 34, a first polarity of the AC signal can be applied to E1, E2, and / or E4 (via switch group 1L), and a second polarity of the AC signal can be applied to E3 (via switch 2L). In the embodiment illustrated in FIG. 4B, the left electrode element 52 E3 has a switchable polarity, while in the embodiment illustrated in FIG. 4C, the left electrode element 52 E3 has the opposite polarity to the other left electrode elements 52 (but does not have a switchable polarity). Unlike the system in Figure 4B, where the switchable polarity electrode element E3 can deliver a tumor therapeutic field by inducing an electric field in a manner similar to that of electrode elements E1, E2, and E4, in the system in Figure 4C, electrode element E3 does not have a switchable polarity and therefore cannot deliver a tumor therapeutic field by inducing an electric field in a manner similar to that of electrode elements E1, E2, and E4.

[0079] An embodiment of the system in Figure 4C implements multiple operating modes: a) In a first operating mode (e.g., a tumor treatment field treatment mode), a first polarity of an AC signal is applied to most electrodes located on a first side (e.g., right or front) of the individual's body, and a second polarity of an AC signal is applied to most electrodes located on a second side (e.g., left or rear) of the individual's body; b) In a second operating mode (e.g., an impedance measurement mode), a first polarity of an AC signal is applied to at least one electrode element located on the first side of the individual's body, and a second polarity of an AC signal is applied to at least one electrode element located on the first side of the individual's body. In the first operating mode, a tumor treatment field can be induced between electrode elements located on the first and second sides of the individual's body. In the second operating mode, current can flow between pairs or groups of electrode elements located on the same side of the individual's body.

[0080] During the second operating mode, consider the left electrode elements 52 E1, E2, E3, and E4 depicted in FIG4C. When the second polarity of the AC signal is applied to E3 (i.e., switch 2L is closed), the first polarity of the AC signal can be applied to one of E1, E2, or E4, and current can flow between the electrode element pairs. Alternatively, when the second polarity of the AC signal is applied to E3, the first polarity of the AC signal can be applied to two or more of E1, E2, or E4, and current can flow in the group of electrode elements. In some embodiments, the controller 34 may issue control signals that change the state of switch group 1L and / or switch 2L to sequentially apply AC signals between different pairs and / or different groups of the left electrode elements 52.

[0081] For example, sequentially applying an AC signal to an electrode pair may include a first pair E3 and E1, a second pair E3 and E2, and a third pair E3 and E4. In another example, sequentially applying an AC signal to an electrode group may include a first group E1, E2 and E3, a second group E2, E3 and E4, and a third group E1, E3 and E4. In both of these examples, E3 is consistently present in these pairs or groups because E3 is illustrated as an opposite polarity electrode element in FIG. 4C. Other embodiments include multiple opposite polarity electrode elements and / or a higher number of integral electrode elements, which generate more possible pairs or groups of electrode elements to which an AC signal can be sequentially applied.

[0082] In some embodiments, impedance is measured each time an AC signal is sequentially applied to an electrode pair or group. For example, an AC signal may be applied to a first pair of electrode elements, and impedance may be measured during application; after measurement, the AC signal may be interrupted and a control signal from controller 34 may change the state of switch group 1L and switch 2L; and then, after the state change, an AC signal may be applied to a second pair of electrodes, and impedance may be measured, etc.

[0083] A method for obtaining impedance measurements corresponding to each of the electrode elements in the transducer array 50L of the embodiment of FIG. 4C is as follows: (a) closing switch 2L, closing only switch 1 in group 1L, and obtaining an impedance measurement; (b) closing switch 2L, opening switch 1 in group 1L, closing switch 2 in group 1L, and then obtaining another impedance measurement; (c) continuing this process by individually stepping through each of the switches in group 1L until impedance measurements of each of the electrode elements in the transducer array 50L are obtained. A similar method can be used to obtain impedance measurements corresponding to each of the electrode elements in the transducer array 50R. Individual impedance measurements (for any given set of switch settings) can be obtained, for example, as described above with respect to the embodiment of FIG. 4A. After obtaining the impedance measurements of each individual element in arrays 50L and 50R, the impedance measurements can be used, for example, to modify the tumor treatment field applied using the same arrays 50L and 50R.

[0084] Although the embodiment illustrated in FIG4C depicts only one switch 2L, switch 2L may include two, three, or more switches, such that two, three, or more left-side electrode elements 52 have opposite polarities. Switch 2R and right-side electrode element 52 may operate in a similar manner to switch 2L and left-side electrode element 52. Corresponding switches and switch groups (not shown) are also provided for other channels 50A, 50P, and a similar method is used in the channels.

[0085] Figure 5 is a flowchart of an example of using electrode elements positioned on one side of an individual's body to detect the condition of a skin area on an individual's body. For example, the transducer of Figure 3 and the system of Figure 4B or Figure 4C can be used to implement the flowchart of Figure 5.

[0086] At step 502, the electrode elements are positioned on one side of the body. For example, at least four electrode elements may be positioned on an individual body such that each of the electrode elements is coupled to a separate skin area on the same side of the body. In some embodiments, the electrode elements are part of an array (e.g., transducer array 50 of FIG3).

[0087] At step 504, a control signal is issued to select the electrode element pair or group. For example, a controller (e.g., controller 34 of FIG4B and FIG4C) may issue a control signal to configure switches (e.g., switch group 1L and switch 2L of FIG4B and FIG4C) to form a conductive path from the AC signal generator to the selected electrode element pair or group.

[0088] At step 506, an AC signal is applied to the selected pair or group of electrode elements. The applied AC signal causes current to flow between the selected pair or group of electrode elements. At step 508, during the application of the AC signal to the selected pair or group, the impedance of the AC signal is measured and stored.

[0089] At step 510, it is determined whether further measurements are required. For example, it may be determined whether all pairs in a set of electrode element pairs have been impedance measured, whether all groups in a set of electrode element groups have been impedance measured, whether any additional electrode element pairs or groups meet the measurement conditions, whether a limit number of impedance measurements have been performed, or any other suitable criteria. When further measurements are required, the flowchart proceeds along the loop to step 512. When further measurements are not required, the flowchart leaves the loop and proceeds to step 514.

[0090] At step 512, a control signal is issued to select a new pair or group of electrode elements. For example, a group of electrode element pairs or groups can be traversed by the loop in Figure 5 until each group or pair in the group has been selected for impedance measurement. The flowchart loops back from step 512 to steps 506 and 508, where an AC signal is applied to the new pair or group of electrode elements, and during this application, impedance measurement values ​​are acquired and stored.

[0091] The flowchart in Figure 5 cycles through steps 506, 508, 510, and 512 until no further measurements are required at step 510. Once this loop-breaking condition is met, the flowchart proceeds to step 514, where the stored impedance is compared to an impedance standard. For example, the impedance standard may be a range or a threshold, and the stored impedance value may be compared to this threshold or range. In some embodiments, the impedance standard may include previously stored impedance values, such as historical values ​​for multiple individual measurements over time or historical values ​​for individual measurements over time. For example, a metric may be calculated based on these historical values. The measured and stored impedance values ​​may be compared to these historical values ​​or a metric calculated based on historical values. In some embodiments, the comparison includes comparing the measured impedance to a constant.

[0092] At step 516, the condition of the skin area is determined based on the comparison. For example, it can be determined that the skin area is in a first condition when the stored impedance value is within the acceptable range of the standard or meets the threshold value of the standard, and the skin area is in a second condition when the stored impedance value exceeds the acceptable range of the standard or does not meet (e.g., greater than or less than) the threshold value of the standard. In another embodiment, it can be determined that the skin area is in a first condition when the difference (∆) between the stored impedance value and the historical impedance value or a measure based on the historical impedance value is less than or equal to the threshold value difference, and the skin area is in a second condition when the difference between the stored impedance value and the historical impedance value or a measure based on the historical impedance value is greater than the threshold value difference. In these examples, the first condition may generally indicate healthy skin and the second condition may indicate damaged skin.

[0093] Depending on the circumstances, if the condition of the skin area meets the criteria, the method may continue at step 518, wherein the electrode element is used to induce an electric field through the individual's body. For example, when an impedance comparison indicates that the skin area is in a first condition, meeting the criteria, a second AC signal (e.g., with a frequency between 100 kHz and 500 kHz) is applied to the electrode element to induce an electric field through the individual's body (e.g., to deliver a tumor treatment field to the individual).

[0094] In some embodiments, the application of the tumor treatment field can be adjusted based on the determined condition of the skin area. For example, when applying the tumor treatment field, the current at any given electrode element located at the damaged skin site can be reduced, or the tumor treatment field therapy can be paused for a period of time to allow the damaged skin to heal. Other suitable characteristics of the tumor treatment field can be adjusted based on the determined condition of the skin area.

[0095] Figure 6 is a flowchart of an example of using an electrode element positioned on one side of the body to detect the integrity of an electrode element. For example, the transducer of Figure 3 and the system of Figure 4B or Figure 4C can be used to implement the flowchart of Figure 6.

[0096] At step 602, the electrode elements are positioned on one side of the body. For example, at least four electrode elements may be positioned on the body. In some embodiments, the electrode elements are part of an array (e.g., transducer array 50 of FIG3).

[0097] At step 604, a control signal is issued to select the electrode element pair or group. For example, the controller (e.g., controller 34 of FIG4B and FIG4C) issues a control signal to configure the switches (e.g., switch group 1L and switch 2L of FIG4B and FIG4C) to form a conductive path from the AC signal generator to the selected electrode element pair or group.

[0098] At step 606, an AC signal is applied to the selected pair or group of electrode elements. The applied AC signal causes current to flow between the selected pair or group of electrode elements. At step 608, during the application of the AC signal to the selected pair or group, the impedance of the AC signal is measured and stored.

[0099] At step 610, it is determined whether further measurements are required. For example, it may be determined whether all pairs in a set of electrode element pairs have been impedance measured, whether all groups in a set of electrode element groups have been impedance measured, whether any additional electrode element pairs or groups meet the measurement conditions, whether a limit number of impedance measurements have been performed, or any other suitable criteria. When further measurements are required, the flowchart proceeds along the loop to step 612. When further measurements are not required, the flowchart leaves the loop and proceeds to step 614.

[0100] At step 612, a control signal is issued to select a pair or group of electrode elements. For example, a group of electrode element pairs or groups can be traversed by the loop in Figure 6 until each group or pair in the group has been selected for impedance measurement. The flowchart loops back from step 612 to steps 606 and 608, where an AC signal is applied to a new pair or group of electrode elements, and during this application, impedance measurement values ​​are acquired and stored.

[0101] The flowchart in Figure 6 cycles through steps 606, 608, 610, and 612 until no further measurements are required at step 610. Once this loop-breaking condition is met, the flowchart proceeds to step 614, where the condition of one or more of the electrode elements is determined by comparing the stored impedance with an impedance standard. For example, the impedance standard may be a range or a threshold, and the stored impedance value may be compared with this threshold or range. The stored impedance value may be associated with an individual electrode element selected (e.g., switched on) during measurement. The condition of these individual electrode elements may be determined by comparing their associated impedance value with an impedance standard. In some embodiments, the impedance may be compared with a range or threshold, previously stored impedance values ​​(e.g., historical values ​​measured over time for multiple electrode elements or historical values ​​measured over time for individual electrode elements), or a metric calculated based on these historical values. In some embodiments, the comparison includes comparing the measured impedance with a constant.

[0102] At step 616, the condition of the electrode element is determined based on these comparisons. For example, it can be determined that the given electrode element is in a first state when the stored impedance value associated with the given electrode element is within the acceptable range of the impedance standard or meets the threshold value of the impedance standard, and the given electrode element is in a second state when the stored impedance value associated with the given electrode element exceeds the acceptable range of the impedance standard or does not meet (e.g., greater than or less than) the threshold value of the impedance standard. In another embodiment, it can be determined that the given electrode element is in a first state when the difference between the stored impedance value associated with the given electrode and a historical impedance value or a measure based on the historical impedance value is less than or equal to the threshold value difference, and the given electrode element is in a second state when the difference between the stored impedance value associated with the given electrode and a historical impedance value or a measure based on the historical impedance value is greater than the threshold value difference.

[0103] In these examples, a first condition may indicate the operability of a given electrode element, while a second condition may indicate a defective condition of a given electrode element. Depending on the circumstances, if the condition of one or more electrode elements meets a criterion, the method may continue at step 618, where the electrode elements are used to induce an electric field through the body. For example, when an impedance comparison indicates that one or more electrode elements are in the first condition, a criterion is met, and a second AC signal (e.g., with a frequency between 100 kHz and 500 kHz) is applied to the electrode elements to induce an electric field through the body (e.g., to deliver a tumor treatment field to the body). Based on the determined condition of the electrode elements, the application of the tumor treatment field may be adjusted. For example, one or more electrode elements may be disconnected so that these electrode elements do not participate in the application of the tumor treatment field. Other suitable characteristics of the tumor treatment field may be adjusted based on the determined condition of the electrode elements.

[0104] Figure 7 is a flowchart of an example of using electrode elements positioned on both sides of an individual's body to detect the condition of skin areas on an individual's body. For example, the transducer of Figure 3 and the system of Figure 4A can be used to implement the flowchart of Figure 7.

[0105] At step 702, electrode elements are positioned on both sides of the body. For example, at least four first electrode elements are positioned on a first side of the individual's body, and at least four second electrode elements are positioned on a second side of the individual's body. The first electrode elements are positioned such that each of the first electrode elements is coupled to a specific skin area on the body. In some embodiments, the first electrode elements are part of an array (e.g., transducer array 50 of FIG. 3). In some embodiments, the second electrode elements are also part of an array.

[0106] At step 704, a control signal is issued to select a subset of the first electrode element and the second electrode element. For example, a controller (e.g., controller 34 of FIG. 4A) issues a control signal to configure switches (e.g., switch groups 1L and 1R of FIG. 4A) such that a conductive path is formed from the AC signal generator to the selected electrode element pair or group. In an embodiment, the subset includes one or more of the first electrode elements and one or more of the second electrode elements.

[0107] At step 706, a low-frequency AC signal is applied to a selected subset of the electrode elements. For example, the AC signal may have a frequency below 20 kHz. The applied AC signal causes the first and second electrode elements, which comprise the selected subset of electrode elements, to induce an electric field through the individual's body. At step 708, during the application of the AC signal to the selected subset, impedance is measured and stored.

[0108] At step 710, it is determined whether further measurements are required. For example, it may be determined whether all subsets (e.g., pairs) of a set of electrode elements have been impedance measured, whether any additional subsets of the first and second electrode elements meet the measurement criteria, whether a limit number of impedance measurements have been performed, or any other suitable criteria. When further measurements are required, the flowchart proceeds along the loop to step 712. When further measurements are not required, the flowchart leaves the loop and proceeds to step 714.

[0109] At step 712, a control signal is issued to select a new subset of electrode elements. For example, a set of electrode element subsets can be traversed by the loop of FIG7 until each subset in the set has been selected for impedance measurement, each of these electrode element subsets comprising at least one first electrode element and at least one second electrode element. The flowchart loops back from step 712 to steps 706 and 708, wherein an AC signal is applied to the new subset of electrode elements, and during this application, impedance measurement values ​​are acquired and stored.

[0110] The flowchart in Figure 7 cycles through steps 706, 708, 710, and 712 until no further measurements are required at step 710. Once this loop-breaking condition is met, the flowchart proceeds to step 714, where the condition of the skin area is determined based on comparing the stored impedance with an impedance standard. For example, the impedance standard may be a range or a threshold, and the stored impedance value may be compared with this threshold or range. In some embodiments, the impedance standard may include previously stored impedance values, such as historical values ​​measured over time for multiple individuals or historical values ​​measured over time for an individual. For example, a metric may be calculated based on these historical values. The measured and stored impedance values ​​may be compared with these historical values ​​or a metric calculated based on historical values. In some embodiments, this comparison includes comparing the measured impedance with a constant.

[0111] At step 716, the condition of the skin area is determined based on the comparison. For example, it can be determined that the skin area is in a first condition when the stored impedance value is within the acceptable range of the standard or meets the threshold value of the standard, and the skin area is in a second condition when the stored impedance value exceeds the acceptable range of the standard or does not meet (e.g., greater than or less than) the threshold value of the standard. In another embodiment, it can be determined that the skin area is in a first condition when the difference between the stored impedance value and the historical impedance value or a measure based on the historical impedance value is less than or equal to the threshold value difference, and the skin area is in a second condition when the difference between the stored impedance value and the historical impedance value or a measure based on the historical impedance value is greater than the threshold value difference.

[0112] In these examples, the first condition may typically indicate healthy skin and the second condition may indicate damaged skin. Depending on the situation, if the condition of the skin area meets the criteria, the method may continue at step 718, where a majority of the first electrode elements are used to induce an electric field through the individual's body. For example, when an impedance comparison indicates that the skin area is in the first condition, meeting the criteria, a second AC signal is applied to a majority of both the first and second electrode elements to induce an electric field through the individual's body (e.g., to deliver a tumor treatment field to the individual). For example, the second AC signal may have a frequency between 100 and 500 kHz.

[0113] The application of the tumor treatment field can be adjusted based on the assessed condition of the skin area. For example, when applying the tumor treatment field, the current at any given electrode element located at the damaged skin can be reduced, or the tumor treatment field therapy can be paused for a period of time to allow the damaged skin to heal. Other suitable characteristics of the tumor treatment field can be adjusted based on the assessed condition of the skin area.

[0114] Figure 8 is a flowchart of an example of using electrode elements positioned on both sides of the body to detect the integrity of electrode elements. For example, two or four copies of the transducer of Figure 3 and the system of Figure 4A can be used to implement the flowchart of Figure 8.

[0115] At step 802, electrode elements are positioned on both sides of the body. For example, at least four first electrode elements may be positioned on a first side of the body, and at least four second electrode elements may be positioned on a second side of the body. The first electrode elements are positioned such that each of the first electrode elements is coupled to a respective skin area on the body. Similarly, the second electrode elements are positioned such that each of the second electrode elements is coupled to a respective skin area on the body. In some embodiments, the first electrode elements are part of an array (e.g., transducer array 50 of FIG. 3); and in some embodiments, the second electrode elements are also part of an array.

[0116] At step 804, a control signal is issued to select a subset of the first electrode element and the second electrode element. For example, a controller (e.g., controller 34 of FIG. 4A) issues a control signal to configure switches (e.g., switch groups 1L and 1R of FIG. 4A) such that a conductive path is formed from the AC signal generator to the selected electrode element pair or group. In an embodiment, the subset includes one or more of the first electrode elements and one or more of the second electrode elements.

[0117] At step 806, a low-frequency AC signal is applied to a selected subset (e.g., a pair) of the electrode elements. For example, the AC signal may have a frequency below 20 kHz. The applied AC signal causes the first and second electrode elements, which comprise the selected subset of electrode elements, to induce an electric field through the body. At step 808, during the application of the AC signal to the selected subset (pair), impedance is measured and stored.

[0118] At step 810, it is determined whether further measurements are needed. For example, it may be determined whether all subsets of a set of electrode elements have been impedance measured, whether any additional subsets of the first and second electrode elements meet the measurement conditions, whether a limit number of impedance measurements have been performed, or any other suitable criteria. When further measurements are needed, the flowchart proceeds along the loop to step 812. When further measurements are not needed, the flowchart leaves the loop and proceeds to step 814.

[0119] At step 812, a control signal is issued to select a new subset of electrode elements. For example, a set of electrode element subsets can be traversed by the loop of FIG8 until each subset in the set has been selected for impedance measurement, each of these electrode element subsets comprising at least one first electrode element and at least one second electrode element. The flowchart loops back from step 812 to steps 806 and 808, wherein an AC signal is applied to the new subset of electrode elements, and during this application, impedance measurement values ​​are acquired and stored.

[0120] The flowchart in Figure 8 cycles through steps 806, 808, 810, and 812 until no further measurements are required at step 810. Once this loop-breaking condition is met, the flowchart proceeds to step 814, where the condition of one or more of the electrode elements is determined by comparing the stored impedance with an impedance standard. For example, the impedance standard may be a range or a threshold, and the stored impedance value may be compared with this threshold or range. The stored impedance value may be associated with an individual electrode element selected (e.g., switched on) during measurement. The condition of these individual electrode elements may be determined by comparing their associated impedance value with an impedance standard. In some embodiments, the impedance may be compared with previously stored impedance values ​​(e.g., historical values ​​measured over time for multiple electrode elements or historical values ​​measured over time for individual electrode elements) or a metric calculated based on these historical values. In some embodiments, the comparison includes comparing the measured impedance with a constant.

[0121] At step 816, the condition of the electrode element is determined based on these comparisons. For example, it can be determined that the given electrode element is in a first state when the stored impedance value associated with the given electrode element is within the acceptable range of the impedance standard or meets the threshold value of the impedance standard, and the given electrode element is in a second state when the stored impedance value associated with the given electrode element exceeds the acceptable range of the impedance standard or does not meet (e.g., greater than or less than) the threshold value of the impedance standard. In another embodiment, it can be determined that the given electrode element is in a first state when the difference between the stored impedance value associated with the given electrode and a historical impedance value or a measure based on the historical impedance value is less than or equal to the threshold value difference, and the given electrode element is in a second state when the difference between the stored impedance value associated with the given electrode and a historical impedance value or a measure based on the historical impedance value is greater than the threshold value difference.

[0122] In these examples, the first condition may indicate the operability of a given electrode element, while the second condition may indicate a defective condition of a given electrode element. Depending on the circumstances, if the conditions of one or more electrode elements meet a criterion, the method may continue at step 818, where a majority of the electrode elements are used to induce an electric field through the body. For example, when an impedance comparison indicates that one or more electrode elements (e.g., a majority of the electrode elements) are in the first condition, a criterion is met, and a second AC signal is applied to a majority of the first electrode elements and a majority of the second electrode elements to induce an electric field through the body (e.g., to deliver a tumor treatment field to the body). For example, the second AC signal may have a frequency between 100 and 500 kHz.

[0123] The application of the tumor treatment field can be adjusted based on the determined status of the electrode elements. For example, one or more electrode elements can be disconnected so that these electrode elements do not participate in the application of the tumor treatment field. Other suitable characteristics of the tumor treatment field can be adjusted based on the determined status of the electrode elements.

[0124] In some embodiments, based on the determined electrode condition and / or the determined skin area condition, the controller 34 controls the switches in group 1L to turn the current (derived from the AC voltage generator 35) to each of the corresponding electrode elements 52 (E1 to E4) during treatment using the tumor treatment field. For example, in order to turn on the current to all four electrode elements 52, all four switches in group 1L should be closed. To interrupt the current reaching electrode element E1, switch 1 in group 1L should be turned off; and to interrupt the current reaching electrode element E2, switch 2 in group 1L should be turned off; and so on.

[0125] Controlling the routing of current through individual electrode elements based on electrode conditions can reduce or eliminate a decrease in the average current coupled to the individual's body. This, in turn, can advantageously reduce or eliminate a decrease in the electric field strength at the tumor site. For example, controller 34 can be programmed to alternately switch the current through individual electrode elements on and off during tumor treatment without affecting the current through the remaining electrode elements. In some embodiments, controller 34 can be configured to increase the current through the remaining electrode elements to compensate for the decrease in current through individual electrode elements during tumor treatment.

[0126] We can distinguish between improper setup of the transducer array due to defective electrodes (such as defects in the dielectric layer of the electrode elements, or if the hydrogel beneath the electrode elements dries out) and improper setup due to skin defects. This is because all impedance measurements, including those of defective electrodes, will be recorded as falling similarly outside the threshold of the impedance standard, and repositioning the array will not correct for unacceptable impedance measurements. On the other hand, improper setup of the transducer array due to skin defects may exhibit differences, specifically when the array is repositioned to different locations, because the skin will not be defective in all locations, or at least will have defects of varying degrees.

[0127] Figure 9 is a schematic diagram of a circuit suitable for implementing the switches in the embodiments of Figures 4A to 4C described above, and the corresponding switches or switch groups in the front and rear channels (not shown). The circuit includes two wired, series-connected field-effect transistors 66 and 67 configured to carry current in either direction. An example of a suitable FET for this circuit is the BSC320N20NSE. (Note that the diodes depicted in Figure 9 are inherently included within the FETs 66 and 67 themselves.) The series connection of the two FETs 66 and 67 will conduct or block current depending on the state of the control input arriving from one of the digital outputs of the controller 34 described above. When the series connection is conductive, current can flow between the common conductor and the individual electrode elements 52. On the other hand, when the series connection of the FETs 66 and 67 is not conductive, current will not flow between the common conductor and the individual electrode elements 52.

[0128] In the embodiments described above, the support structure 59 is configured to hold the electrode element 52 against the individual body, such that the dielectric layer of the electrode element 52 is against the individual body and can be positioned in contact with the individual body. However, in alternative embodiments, the dielectric layer of each electrode element is omitted. In this case, the support structure 59 holds the electrode element 52 against the individual body, such that the conductive surface of the electrode element 52 faces the individual body and can be positioned in contact with the individual body. Depending on the situation, in these embodiments, when the transducer array 50 is placed against the individual body, a layer of hydrogel or conductive adhesive may be disposed between the conductive surface of the electrode element 52 and the individual body.

[0129] Unless otherwise indicated herein or otherwise obviously contradicted by the context, the embodiments described under any heading or in any part of the invention (including the claims) may be combined with the embodiments described under the same or any other heading or other part of the invention.

[0130] Although the invention has been disclosed with reference to certain embodiments, numerous modifications, alterations, and changes to 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 invention be limited to the described embodiments but have the full scope defined by the language of the following claims and their equivalents. [Simplified Explanation of the Diagram]

[0043] [Figure 1] is a schematic diagram of a prior art Optune® system for delivering a tumor treatment field. [Figures 2A] through [Figure 2D] depict the positioning of a transducer array for treating brain tumors on an individual's head. [Figure 3] depicts a first embodiment of a transducer array providing individual conductors for individual electrode elements. [Figures 4A], [Figure 4B], and [Figure 4C] are block diagrams of three embodiments in which a tumor treatment field is applied to an individual using four replicas of the transducer array of Figure 3. [Figure 5] is a flowchart of an example of using electrode elements positioned on one side of an individual's body to detect the condition of a skin area on an individual's body. [Figure 6] is a flowchart of an example of using electrode elements positioned on one side of the body to detect the integrity of electrode elements. [Figure 7] is a flowchart of an example of using electrode elements positioned on both sides of an individual's body to detect the condition of a skin area on an individual's body. [Figure 8] is a flowchart of an example of using electrode elements positioned on both sides of the body to detect the integrity of electrode elements. [Figure 9] is a schematic diagram of a circuit suitable for implementing a single switch or a group of switches. Various embodiments are described in detail below with reference to the accompanying drawings, in which similar schematic element symbols denote similar elements.

Claims

1. An apparatus for applying alternating current between at least four first electrode elements positioned on a first side of a body and at least four second electrode elements positioned on a second side of the body, the apparatus comprising: an AC signal generator that generates an AC output signal having a first polarity and a second polarity; at least four first switches, each configured to selectively apply the first polarity of the AC output signal to one of the first electrode elements according to the state of the respective control signal; and at least four second switches, each configured to selectively apply the second polarity of the AC output signal to one of the second electrode elements according to the state of the respective control signal. At least one third switch, each configured to selectively apply the second polarity of the AC output signal to one of the first electrode elements according to the state of a respective control signal; and a controller configured to control the plurality of first switches, the plurality of second switches, and the at least one third switch, such that in a first mode, the controller issues control signals causing a majority of the first switches to apply the first polarity of the AC output signal to a corresponding first electrode element and causing a majority of the second switches to apply the second polarity of the AC output signal to a corresponding second electrode element; and in a second mode, the controller issues control signals that (a) cause the first switches to sequentially apply the first polarity of the AC output signal to each respective first electrode element, while the at least one third switch applies the second polarity of the AC output signal to at least one respective first electrode element, and (b) sequentially receive impedance measurements corresponding to each combination of the first electrode elements, wherein... Impedance measurement is not performed in this first mode.

2. The device of claim 1, wherein in the second mode, the controller issues control signals that (a) cause the first switches to sequentially apply the first polarity of the AC output signal to each individual first electrode element, while the at least one third switch applies the second polarity of the AC output signal to each individual first electrode element, and (b) sequentially receive impedance measurements corresponding to each combination of the first electrode elements.

3. The device of claim 1, further comprising: at least one fourth switch, each configured to selectively apply the first polarity of the AC output signal to one of the second electrode elements according to the state of a respective control signal, wherein the controller is configured to control the plurality of first switches, the plurality of second switches and the at least one fourth switch such that, in a third mode, the controller issues control signals that (a) cause the second switches to sequentially apply the second polarity of the AC output signal to each of the respective second electrode elements, while the at least one fourth switch applies the first polarity of the AC output signal to at least one of the respective second electrode elements, and (b) sequentially receive impedance measurements corresponding to each combination of the second electrode elements.

4. The device of claim 3, wherein in the third mode, the controller issues control signals that (a) cause the second switches to sequentially apply the second polarity of the AC output signal to each individual second electrode element, while the at least one fourth switch applies the first polarity of the AC output signal to each individual second electrode element, and (b) sequentially receive impedance measurements corresponding to each combination of the second electrode elements.

5. The device of claim 1, wherein in the first mode and based on the received impedance measurements, the controller is configured to issue a control signal to cause a decrease in current at one or more of the first electrode elements.

6. An apparatus for applying alternating current between at least four first electrode elements positioned on a first side of a body and at least four second electrode elements positioned on a second side of the body, the apparatus comprising: an AC signal generator that generates an AC output signal; and at least four first switches, each configured to selectively apply the AC output signal to one of the first electrode elements according to the state of the respective control signal. At least four second switches, each configured to selectively apply the AC output signal to one of the second electrode elements according to the state of a respective control signal; and a controller configured to control the plurality of first switches and the plurality of second switches such that, in a first mode, the controller issues control signals causing a majority of the first switches to apply the AC output signal to the corresponding first electrode element and a majority of the second switches to apply the AC output signal to the corresponding second electrode element; and in a second mode, the controller issues control signals that (a) cause the second switches to apply the AC output signal to the corresponding second electrode element, (b) sequentially cause different or subsets of the first switches to apply the AC output signal to the corresponding first electrode element, and (c) sequentially receive impedance measurements corresponding to each combination of the first and second electrode elements, wherein, in the first mode, the AC output signal has values ​​between 100 and 500. A frequency between kHz, and in this second mode, the AC output signal has a frequency below 20 kHz, wherein, Impedance measurement is not performed in this first mode.

7. The device of claim 6, wherein in the second mode, the controller issues control signals that (a) cause the second switches to apply the AC output signal to a corresponding second electrode element, (b) sequentially cause each of the first switches to apply the AC output signal to a corresponding individual first electrode element, and (c) sequentially receive impedance measurements corresponding to individual first electrode elements and respective combinations of the second electrode elements.

8. The device of claim 7, wherein the controller is further configured to control the plurality of first switches and the plurality of second switches such that, in a third mode, the controller issues control signals that (a) cause the first switches to apply the AC output signal to a corresponding first electrode element, (b) sequentially cause each of the second switches to apply the AC output signal to a corresponding individual second electrode element, and (c) sequentially receive impedance measurements corresponding to individual second electrode elements and respective combinations of the first electrode elements.

9. The device of claim 6, wherein in the first mode and based on the received impedance measurements, the controller is configured to issue a control signal to cause a decrease in current at one or more of the first electrode elements.

10. A method for detecting the condition of a skin region on an individual's body, the method comprising: positioning at least four electrode elements on the individual's body such that each of the electrode elements is coupled to a separate skin region on the body; sequentially applying an AC signal to different subsets of the electrode elements; measuring the impedance of the applied AC signal while sequentially applying the AC signal to the different subsets of the electrode elements; comparing the measured impedance to a standard; and determining the condition of the skin region based on the comparison.

11. The method of claim 10, wherein a first polarity of the AC signal is sequentially applied to each individual electrode element, a second polarity of the AC signal is applied to each different individual electrode element, and impedance measurements corresponding to each combination of the electrode elements are sequentially received.

12. The method of claim 10, wherein the comparison comprises comparing the measured impedances with a constant.

13. The method of claim 10, wherein the comparison comprises comparing the measured impedances with previously measured impedances of individual skin areas.

14. As in request item 10, wherein, When the measured impedances meet the standard, most of the at least four electrode elements are used to induce an electric field through the individual's body.

15. The method of claim 10, wherein the AC signal has a frequency below 20 kHz.

16. A method for detecting the integrity of electrode elements, the method comprising: positioning at least four electrode elements on a body such that each of the electrode elements is coupled to a separate region of the body; sequentially applying an AC signal to different subsets of the electrode elements; measuring the impedance of the applied AC signal while sequentially applying the AC signal to the different subsets of the electrode elements; comparing the measured impedances with a standard; and determining the condition of one or more of the electrode elements based on the comparison.

17. The method of claim 16, wherein a first polarity of the AC signal is sequentially applied to each individual electrode element, a second polarity of the AC signal is applied to each different individual electrode element, and impedance measurements corresponding to each combination of the electrode elements are sequentially received.

18. As in request item 16, wherein, When the measured impedances meet the standard, the electrode elements are used to induce an electric field through the body.

19. The method of claim 16 further comprises: generating a notification when the measured impedances do not conform to the standard.

20. The method of claim 16, wherein the AC signal has a frequency below 20 kHz.

21. A method for detecting the condition of a skin region on an individual's body, the method comprising: positioning at least four first electrode elements on the skin region on a first side of the individual's body, and positioning at least four second electrode elements on the skin region on a second side of the individual's body; sequentially applying AC signals to different subsets of the first electrode elements and the second electrode elements, each subset comprising one or more of the first electrode elements and one or more of the second electrode elements, wherein the AC signals have a frequency of less than 20 kHz; measuring the impedance of the applied AC signals as they are sequentially applied to each subset; comparing the measured impedances with a standard; and determining the condition of the skin region on the individual's body based on the comparison.

22. The method of claim 21, wherein the AC signal is sequentially applied to individual first electrode elements, and the AC signal is applied to the second electrode elements simultaneously with the sequential application of the AC signal to the individual first electrode elements, and the impedance measurements corresponding to the individual first electrode elements and the second electrode elements are received sequentially.

23. The method of claim 21, wherein sequentially applying the AC signal further comprises: sequentially applying the AC signal to individual first electrode elements while simultaneously applying the AC signal to the second electrode elements, wherein the impedance measurements corresponding to the respective combinations of the individual first electrode elements and the second electrode elements are received sequentially.

24. The method of claim 21, wherein the first electrode elements and the second electrode elements are capacitively coupled and positioned to induce an alternating electric field through the individual's body when the AC signal is applied sequentially.

25. The method of claim 21, wherein the comparison comprises comparing the measured impedances with a constant.

26. The method of claim 21, wherein the comparison comprises comparing the measured impedances with previously measured impedances of individual skin areas.

27. As in request item 21, wherein, When the measured impedances meet the standard, most of the at least four electrode elements are used to induce an electric field through the individual's body.

28. A method for detecting the integrity of electrode elements, the method comprising: positioning at least four first electrode elements on a first side of a body and positioning at least four second electrode elements on a second side of the body; sequentially applying an AC signal to different subsets of the first electrode elements and the second electrode elements, each subset comprising one or more of the first electrode elements and one or more of the second electrode elements, wherein the AC signal has a frequency of less than 20 kHz; measuring the impedance of the applied AC signal as it is sequentially applied to each subset; comparing the measured impedance with a standard; and determining a condition of one or more of the first electrode elements based on the comparison.

29. The method of claim 28, wherein the AC signal is sequentially applied to individual first electrode elements, and the AC signal is applied to the second electrode elements simultaneously with the sequential application of the AC signal to the individual first electrode elements, and the impedance measurements corresponding to the individual first electrode elements and the second electrode elements are received sequentially.

30. The method of claim 28, wherein sequentially applying the AC signal further comprises: sequentially applying the AC signal to individual first electrode elements while simultaneously applying the AC signal to the second electrode elements, wherein the impedance measurements corresponding to the individual first electrode elements and the second electrode elements are received sequentially.

31. The method of claim 28, wherein the first electrode elements and the second electrode elements are capacitively coupled and positioned to induce an alternating electric field through the body when the AC signal is applied sequentially.

32. The method of claim 28, further comprising: when the measured impedances conform to the criterion, applying the AC signal to most of the first electrode elements and most of the second electrode elements such that an electric field is induced through the body.

33. The method of claim 28 further comprises: generating a notification when the measured impedances do not conform to the standard.

34. A method for detecting the integrity of electrode elements, the method comprising: positioning at least two electrode elements on a body such that each of the electrode elements is coupled to a separate region of the body; applying an AC signal between the electrode elements; measuring at least one impedance while the AC signal is applied between the electrode elements; and determining the condition of the electrode elements based on the measured at least one impedance, wherein the electrode elements are used to induce an electric field through the body when the condition meets at least one criterion.

35. A method for detecting the integrity of electrode elements, the method comprising: positioning at least two first electrode elements on a first side of a body and positioning at least two second electrode elements on a second side of the body; applying a first AC signal between (a) at least one of the first electrode elements and (b) at least one of the second electrode elements, wherein the first AC signal has a frequency of less than 20 kHz; measuring at least one impedance while applying the first AC signal; determining the condition of one or more of the first electrode elements based on the measured at least one impedance; and when the condition of the electrode elements meets at least one criterion, applying a second AC signal between (a) at least one of the first electrode elements and (b) at least one of the second electrode elements to induce an electric field through the body, wherein the second AC signal has a frequency of greater than 50 kHz.

36. The method of claim 35, wherein the second AC signal is applied for at least 72 hours.

37. A method for detecting the condition of a skin region on an individual's body, the method comprising: positioning at least two electrode elements on the skin region; applying an AC signal between the electrode elements; measuring at least one impedance while the AC signal is applied between the electrode elements; and determining the condition of the skin region based on the measured at least one impedance, wherein the electrode elements are used to induce an electric field through the individual's body when the condition of the skin region meets at least one criterion.

38. A method for detecting the condition of a skin region on an individual's body, the method comprising: positioning at least two first electrode elements on the skin region on a first side of the individual's body, and positioning at least two second electrode elements on the skin region on a second side of the individual's body; applying a first AC signal between (a) at least one of the first electrode elements and (b) at least one of the second electrode elements, wherein the first AC signal has a frequency of less than 20 kHz; measuring at least one impedance while applying the first AC signal; determining the condition of the skin region based on the measured at least one impedance; and when the condition of the skin region meets at least one criterion, applying a second AC signal between at least one of the first electrode elements and (b) at least one of the second electrode elements to induce an electric field through the individual's body, wherein the second AC signal has a frequency of greater than 50 kHz.

39. The method of claim 38, wherein the second AC signal is applied for at least 72 hours.

40. A method for detecting improper placement of a transducer array on a body, the method comprising: positioning at least four electrode elements on the body such that each of the electrode elements is coupled to a separate region of the body; sequentially applying an AC signal to different subsets of the electrode elements; measuring the impedance of the applied AC signal while sequentially applying the AC signal to the different subsets of the electrode elements; comparing the measured impedances with a standard; and determining, based on the comparison, that the transducer array is improperly placed.

41. The method of claim 40, wherein a first polarity of the AC signal is sequentially applied to each individual electrode element, a second polarity of the AC signal is applied to each different individual electrode element, and impedance measurements corresponding to each combination of the electrode elements are sequentially received.

42. The method of claim 40, wherein the comparison comprises comparing the measured impedances with a constant.

43. The method of claim 40, wherein the comparison comprises comparing the measured impedances with previously measured impedances of defect-free electrodes on individual healthy skin areas.

44. The method of claim 40, further comprising, when the measured impedances meet the criterion, using a majority of the at least four electrode elements to induce an electric field through the individual's body.

45. The method of claim 40, wherein the AC signal has a frequency below 20 kHz.

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