Temperature measurement in an array for delivering tumor treatment electric fields

Abstract

Temperature measurement in arrays for delivering tumor treating electric fields. Tumor treating electric field therapy is a proven method for treating tumors using electric fields. This application describes systems and methods for measuring temperature at the electrode elements of a transducer array used to administer tumor treating electric fields to a subject. A distal circuit is disposed proximate to each transducer array, and the distal circuit interfaces with temperature sensors in the transducer array to obtain temperature readings. Those temperature readings are transmitted to a central hub. In some embodiments, temperature measurements from all distal circuits occur simultaneously.

Description

[0001] Cross-reference of related applications

[0002] This application claims the benefit of U.S. Provisional Application 62 / 376,885, filed August 18, 2016, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Tumor therapeutic electric fields (TTFields) therapy is a proven method for treating tumors. Existing technologies for delivering therapeutic electric fields to tumors... In the system, a tumor-treating electric field is delivered to the patient via four transducer arrays placed on the patient's skin in close proximity to the tumor. The transducer arrays are arranged in two pairs, and each transducer array is connected to a field generator via a multi-cable. The field generator (a) transmits alternating current (AC) through one pair of arrays during a first time period; then (b) transmits AC current through the other pair of arrays during a second time period; steps (a) and (b) are then repeated for the duration of treatment.

[0004] Each transducer array is configured as a set of capacitively coupled electrode elements (approximately 2 cm in diameter) interconnected via flexible wires. Each electrode element includes a ceramic disc sandwiched between a layer of conductive medical gel and adhesive tape. When the array is placed on a patient, the medical gel adheres to the contours of the patient's skin and ensures good electrical contact between the device and the body. As the patient performs their daily activities, the adhesive tape holds the entire array in place on the patient.

[0005] The amplitude of the alternating current delivered via the transducer array is controlled so that skin temperature (as measured on the skin beneath the transducer array) does not exceed a safe threshold of 41°C. Temperature measurements on the patient's skin are obtained using thermistors placed beneath some of the disks within the transducer array. In existing... In the system, each array includes eight thermistors, with one thermistor positioned below a corresponding disk within the array. (Note that most arrays include more than eight disks; in this case, temperature measurement is performed only below a subset of the disks within the array.)

[0006] Thermistors in each of the four arrays are connected via long wires to electronics called a “cable box”, where the temperature from all 32 thermistors (4 arrays × 8 thermistors per array) is measured and converted from analog to digital into a digital value for each thermistor. These measurements are then transmitted from the cable box to the field generator via two additional wires that facilitate bidirectional digital serial communication between the cable box and the field generator. A controller in the field generator uses the temperature measurements to control the current delivered through each pair of arrays to maintain the temperature on the patient's skin below 41°C. The current itself is delivered to each array via the additional wires (i.e., one wire per array), which run from the field generator through the cable box to the array.

[0007] In the existing The system comprises four 10-wire cables (each of which operates between its respective array and cable box) and an 8-wire spiral strip operating between the field generator and the cable box. Each of the 10-wire cables has eight conductors for carrying signals from eight thermistors, one conductor shared by all eight thermistors, and one conductor for providing the tumor therapy electric field signal to the array. The 8-wire spiral strip has one conductor for power to the cable box (Vcc), one conductor for ground to the cable box, two conductors for data communication (for sending temperature readings to the field generator), and four conductors for the tumor therapy electric field signal (i.e., one conductor for each of the four arrays). Summary of the Invention

[0008] One aspect of the invention relates to a first device for use with an AC signal generator that applies an electric field through a target area in the body of a subject. The first device includes a plurality of capacitively coupled electrode elements configured to rest against the body of the subject. A substrate is configured to hold the plurality of electrode elements against the body of the subject. A plurality of temperature sensors are positioned to sense temperature at corresponding locations among the plurality of electrode elements. The first device also includes an analog multiplexer having an analog output and a plurality of selectable analog inputs, each of the plurality of analog inputs being operatively connected to a corresponding one of the plurality of temperature sensors. The first device also includes an analog-to-digital converter and a controller, wherein the analog-to-digital converter is configured to digitize signals arriving from the analog output. The controller is configured to (a) sequentially select each of the plurality of analog inputs, (b) sequentially obtain a plurality of temperature readings from the analog-to-digital converter, each of the plurality of temperature readings corresponding to a corresponding one of the plurality of temperature sensors, and (c) transmit digital data corresponding to the plurality of temperature readings. The first device also includes a cable having a proximal end and a distal end. The cable includes (i) a conductor that allows AC current to flow between a proximal end and a distal end of the cable, and (ii) a data path configured to carry transmitted digital data from the distal end to the proximal end of the cable. Multiple electrode elements are electrically connected to the conductor. An analog multiplexer, an analog-to-digital converter, and a controller are mounted to the substrate or to the distal end of the cable.

[0009] In some embodiments of the first device, the multiple temperature sensors include multiple thermistors.

[0010] In some embodiments of the first device, the cable has a length of 25 cm or less. In some embodiments of the first device, the cable has a length of 10 cm or less.

[0011] Some embodiments of the first device also include a connector disposed between the controller and the distal end of the cable. In some of these embodiments, an analog multiplexer, an analog-to-digital converter, and a controller are mounted to a substrate.

[0012] Some embodiments of the first device also include a connector disposed between multiple temperature sensors and multiple analog inputs. In some of these embodiments, an analog multiplexer, an analog-to-digital converter, and a controller are mounted to the distal end of the cable.

[0013] Some embodiments of the first device also include a precision resistor. In these embodiments, the analog multiplexer has an additional selectable analog input operatively connected to the precision resistor. In these embodiments, the controller is also configured to (d) select the additional analog input, (e) obtain an additional reading corresponding to the precision resistor from an analog-to-digital converter, and (f) transmit digital data corresponding to the additional reading.

[0014] Some embodiments of the first device also include a precision resistor. In these embodiments, the analog multiplexer has an additional selectable analog input operatively connected to the precision resistor. In these embodiments, the controller is also configured to (d) select the additional analog input, (e) obtain an additional reading corresponding to the precision resistor from an analog-to-digital converter, and (f) calibrate each of a plurality of temperature readings based on the additional readings before transmitting the corresponding digital data.

[0015] In some embodiments of the first device, the cable uses a single conductor to provide a data path that carries the transmitted digital data from the distal end of the cable to the proximal end of the cable.

[0016] In some embodiments of the first device, the cable uses a single conductor to provide a data path carrying the transmitted digital data from the distal end of the cable to the proximal end of the cable, a single conductor for supplying power to the controller, and a single conductor for grounding.

[0017] In some embodiments of the first device, energy arriving via a conductor in a cable is used to power the controller.

[0018] Another aspect of the invention relates to a second device for use with an AC signal generator that applies an electric field through a target area in the body of a subject. The second device includes a hub configured to receive digital data corresponding to a first plurality of temperature readings, a second plurality of temperature readings, a third plurality of temperature readings, and a fourth plurality of temperature readings, and to output digital data corresponding to the first plurality of temperature readings, the second plurality of temperature readings, the third plurality of temperature readings, and the fourth plurality of temperature readings to the AC signal generator. The hub includes first, second, third, and fourth conductors configured to route current from the AC signal generator to a location distally positioned beyond the hub.

[0019] The second device also includes a first plurality of capacitively coupled electrode elements, a second plurality of capacitively coupled electrode elements, a third plurality of capacitively coupled electrode elements, and a fourth plurality of capacitively coupled electrode elements, which are configured to be placed against the body of a subject at a first position, a second position, a third position, and a fourth position, respectively. The second device also includes a first substrate, a second substrate, a third substrate, and a fourth substrate, which are configured to hold corresponding plurality of electrode elements against the body of the subject at the first, second, third, and fourth positions. The second device also includes a first plurality of temperature sensors, a second plurality of temperature sensors, a third plurality of temperature sensors, and a fourth plurality of temperature sensors, which are positioned to sense the temperature at corresponding locations among the first plurality of electrode elements, the second plurality of electrode elements, the third plurality of electrode elements, and the fourth plurality of electrode elements. The second device also includes a first analog multiplexer, a second analog multiplexer, a third analog multiplexer, and a fourth analog multiplexer, each having a first analog output, a second analog output, a third analog output, and a fourth analog output, respectively. These multiplexers each have a first plurality of selectable analog inputs, a second plurality of selectable analog inputs, a third plurality of selectable analog inputs, and a fourth plurality of selectable analog inputs. Each analog input among the first plurality of analog inputs, the second plurality of analog inputs, the third plurality of analog inputs, and the fourth plurality of analog inputs is operatively connected to a corresponding temperature sensor among the first plurality of temperature sensors, the second plurality of temperature sensors, the third plurality of temperature sensors, and the fourth plurality of temperature sensors. The second device also includes a first analog-to-digital converter, a second analog-to-digital converter, a third analog-to-digital converter, and a fourth analog-to-digital converter, configured to digitize signals arriving from the first analog output, the second analog output, the third analog output, and the fourth analog output, respectively. The second device also includes a first controller, a second controller, a third controller, and a fourth controller.These controllers are configured to (a) sequentially select each of the first plurality of analog inputs, the second plurality of analog inputs, the third plurality of analog inputs, and the fourth plurality of analog inputs, respectively; (b) sequentially obtain the first plurality of temperature readings, the second plurality of temperature readings, the third plurality of temperature readings, and the fourth plurality of temperature readings from the first plurality of analog-to-digital converters, the second plurality of analog-to-digital converters, the third plurality of analog-to-digital converters, and the fourth plurality of analog-to-digital converters, respectively—each of the first plurality of temperature readings, the second plurality of temperature readings, the third plurality of temperature readings, and the fourth plurality of temperature readings corresponding to a corresponding temperature sensor among the first plurality of temperature sensors, the second plurality of temperature sensors, the third plurality of temperature sensors, and the fourth plurality of temperature sensors; and (c) transmit the first digital data, the second digital data, the third digital data, and the fourth digital data corresponding to the first plurality of temperature readings, the second plurality of temperature readings, the third plurality of temperature readings, and the fourth plurality of temperature readings to a hub. The second device also includes a first cable, a second cable, a third cable, and a fourth cable, which are arranged to route current arriving via the first conductor, the second conductor, the third conductor, and the fourth conductor in the hub to the first plurality of electrode elements, the second plurality of electrode elements, the third plurality of electrode elements, and the fourth plurality of electrode elements, respectively; and to route first digital data, second digital data, third digital data, and fourth digital data from the first controller, the second controller, the third controller, and the fourth controller to the hub, respectively.

[0020] In some embodiments of the second device, the first controller, the second controller, the third controller, and the fourth controller are synchronized so that a first plurality of temperature readings, a second plurality of temperature readings, a third plurality of temperature readings, and a fourth plurality of temperature readings are obtained simultaneously.

[0021] In some embodiments of the second device, the first controller, the second controller, the third controller, and the fourth controller are synchronized such that at least a portion of the first plurality of temperature readings, the second plurality of temperature readings, the third plurality of temperature readings, and the fourth plurality of temperature readings are obtained simultaneously.

[0022] Some embodiments of the second device further include a first precision resistor, a second precision resistor, a third precision resistor, and a fourth precision resistor. In these embodiments, each of the analog multiplexers has an additional selectable analog input operatively connected to the corresponding precision resistor. The first, second, third, and fourth controllers are also configured to (d) select the corresponding additional analog input, (e) obtain a first, second, third, and fourth additional reading corresponding to the corresponding precision resistor from the corresponding analog-to-digital converter, and (f) transmit digital data corresponding to the first, second, third, and fourth additional readings to the hub. In some embodiments of these embodiments, the hub is also configured to calibrate each of the first plurality of temperature readings, the second plurality of temperature readings, the third plurality of temperature readings, and the fourth plurality of temperature readings based on the first, second, third, and fourth additional readings.

[0023] Some embodiments of the second device further include a first precision resistor, a second precision resistor, a third precision resistor, and a fourth precision resistor. In these embodiments, each of the analog multiplexers has an additional selectable analog input operatively connected to the corresponding precision resistor. The first, second, third, and fourth controllers are also configured to (d) select the corresponding additional analog input, (e) obtain a first, second, third, and fourth additional reading corresponding to the corresponding precision resistor from the corresponding analog-to-digital converter, and (f) calibrate each of the first plurality of temperature readings, the second plurality of temperature readings, the third plurality of temperature readings, and the fourth plurality of temperature readings based on the first, second, third, and fourth additional readings, respectively, before transmitting the corresponding digital data to the hub.

[0024] Some embodiments of the second device also include a first connector, a second connector, a third connector, and a fourth connector, which are respectively disposed between the first controller, the second controller, the third controller, and the fourth controller and the hub.

[0025] Some embodiments of the second device also include a first connector, a second connector, a third connector, and a fourth connector, which are respectively disposed between a first plurality of temperature sensors, a second plurality of temperature sensors, a third plurality of temperature sensors, and a fourth plurality of temperature sensors and a first plurality of analog inputs, a second plurality of analog inputs, a third plurality of analog inputs, and a fourth plurality of analog inputs.

[0026] In some embodiments of the second device, each of the first, second, third, and fourth cables uses a single conductor for routing current arriving via the first, second, third, and fourth conductors in the hub to the first plurality of electrode elements, the second plurality of electrode elements, the third plurality of electrode elements, and the fourth plurality of electrode elements, respectively. In these embodiments, each of the first, second, third, and fourth cables also has a single conductor for transferring digital data between the first, second, third, and fourth controllers and the hub, respectively.

[0027] In some embodiments of the second device, each of the first, second, third, and fourth cables uses a single conductor for routing current arriving via the first, second, third, and fourth conductors in the hub to the first plurality of electrode elements, the second plurality of electrode elements, the third plurality of electrode elements, and the fourth plurality of electrode elements, respectively. In these embodiments, each of the first, second, third, and fourth cables also has a single conductor for transferring digital data between the first, second, third, and fourth controllers and the hub, respectively; a single conductor for supplying power to the respective controller; and a single conductor for grounding the respective controller.

[0028] In some embodiments of the second device, energy arriving via the first, second, third, and fourth conductors in the hub is used to power the first, second, third, and fourth controllers, respectively. Attached Figure Description

[0029] Figure 1 This is a block diagram of a system for measuring the temperature of a transducer array used to apply an electric field for tumor treatment to the body of a subject.

[0030] Figure 2 Is Figure 1 A schematic diagram of the hub in the embodiment.

[0031] Figure 3 Is Figure 1 A schematic diagram of one of the remote circuits in the embodiment.

[0032] Figure 4A Describing the use of Figure 1 The first option for connectorization is the implementation example.

[0033] Figure 4B Describing the use of Figure 1 The second option for connectorization of the embodiment.

[0034] Figure 5A Depicting Figure 4AA detailed view of the location of the connector in the embodiment.

[0035] Figure 5B Depicting Figure 4B A detailed view of the location of the connector in the embodiment.

[0036] Figure 6A Describing for Figure 4A Mechanical layout of the embodiment.

[0037] Figure 6B Describing for Figure 4B Mechanical layout of the embodiment.

[0038] Various embodiments are described in detail below with reference to the accompanying drawings, wherein similar reference numerals denote similar elements. Detailed Implementation

[0039] Figure 1 This is a block diagram of an embodiment relying on distal circuitry 40 positioned close to each of four transducer arrays 50 to obtain temperature readings from temperature sensors within the transducer arrays 50. Each of the transducer arrays 50 includes multiple capacitively coupled electrode elements 52 and multiple temperature sensors 54 (both in... Figure 3 , Figure 6A and Figure 6B (As shown in the diagram). Temperature sensor 54 is positioned to detect the temperature at the corresponding electrode element 52. In some preferred embodiments, temperature sensor 54 is a thermistor.

[0040] Back Figure 1 Each remote circuit 40 is interfaced with a temperature sensor incorporated into the corresponding transducer array 50 to obtain temperature readings from each temperature sensor. The remote circuit 40 then performs analog-to-digital conversion on those temperature readings and forwards the digitized temperature readings together to the central hub 30. The central hub 30 then forwards these digitized temperature readings to the field generator 20 via a serial communication link, allowing the field generator 20 to determine, based on the temperature readings, whether the current flowing into the transducer array 50 must be adjusted.

[0041] Ten short conductors extend distally from the distal circuitry 40 into the transducer array 50 itself within wiring 45. These ten conductors include one for each of the eight temperature sensors, one for a common ground for the temperature sensors, and one for the tumor treatment electric field signal (i.e., AC current for the electrode elements). In some preferred embodiments, the distal circuitry 40 is implemented using a single-chip microcontroller or a programmable system-on-chip (PSoC) with a built-in analog front-end and multiplexer. Suitable part numbers for this purpose include CY8C4124LQI-443. In this case, no other active components are required in the distal circuitry 40. In alternative embodiments, other microcontrollers may be used with built-in or discrete analog front-ends and multiplexers, as will be apparent to those skilled in the art. The analog front-end and multiplexer obtain temperature readings from the temperature sensors. Those temperature readings are then digitized and preferably transmitted to the central hub 30 via a serial data link. In addition, each distal circuit 40 also has an associated through conductor (51, ) for routing the tumor therapy electric field signal originating from the field generator 20 to the transducer array 50. Figure 3 and Figure 6A (As shown in the image).

[0042] exist Figure 1 In this embodiment, each of the four remote circuits 40 is connected to the central hub 30 via a corresponding cable 35. Notably, each of the cables 35 running between the remote circuits 40 and the hub 30 requires only four conductors (i.e., one for Vcc, one for ground, one for serial data communication, and one for the tumor treatment electric field signal). This significantly reduces the number of wires required to interface with each transducer array 50.

[0043] Figure 2 It is suitable for use as Figure 1 The diagram depicts the circuitry of hub 30. Generally speaking, hub 30 receives data from remote circuit 40 (…). Figure 1 The temperature readings of each of the shown are sent together to the field generator 20. Figure 1 (As shown in the illustration). Any of a variety of architectures can be used to receive and transmit temperature readings. For example, in the illustrated embodiment, controller 32 sends a signal to digital multiplexer 33, which commands digital multiplexer 33 to select one of four inputs, one of which sets hub 30 to receive temperature readings from remote circuit 40 (as shown in the illustration). Figure 1 One of the inputs (shown in the diagram) receives digital data. The controller 32 then accepts all eight temperature readings from the selected input and transmits them together via transceiver 34 to the field generator 20. Figure 1(As shown in the diagram). After all temperature readings from the selected input (i.e., the selected remote circuit) have been transmitted to the field generator, the controller 32 updates the control signal to the digital multiplexer 33 and commands the digital multiplexer to select another of the four inputs (i.e., the other remote circuit). The controller 32 then accepts all eight temperature readings from the newly selected input and transmits these temperature readings to the field generator. The corresponding sequence is then executed to obtain eight temperature readings from the third input and eight temperature readings from the fourth input.

[0044] In some preferred embodiments, the controller 32, digital multiplexer 33, and transceiver 34 may be integrated together into a single chip. In other embodiments, the controller 32 and digital multiplexer 33 are integrated together into a single chip, and a separate transceiver 34 is used. For example, the controller 32 and digital multiplexer 33 can be implemented using Cypress's CY8C4244LQI-443, and the transceiver 34 can be implemented using Linear Technology's LTC2856CMS8-2#PBF.

[0045] The entire sequence of all temperature measurements obtained from each of the four inputs is periodically (e.g., every 1 second, 10 seconds, or 30 seconds) repeated to update the temperature readings provided to the field generator 20. The hub 30 communicates with the field generator 20 using any conventional communication technology (e.g., RS485). The hub 30 also includes a through conductor 31 that transmits the tumor therapy electric field signal directly from the field generator 20 to each of the transducer array 50. In one example, the hub 30 communicates with the field generator 20 via an 8-conductor helical cable 25 (which includes four wires for the tumor therapy electric field signal from each array, one wire for ground, one wire for Vcc to the distal circuit 40, and two wires for communication). It is worth noting that this embodiment is backward compatible with previous versions of tumor therapy electric field delivery systems.

[0046] In the embodiment described above, two wires are used to implement data communication (i.e., for temperature data) between hub 30 and field generator 20. This can be accomplished, for example, by using a single wire to implement communication in each direction. In an alternative embodiment, the wire count between hub 30 and field generator 20 can be reduced by replacing the two data communication wires in the embodiment described above with a single data wire that implements bidirectional communication (using a conventional single-wire communication protocol).

[0047] Figure 3 It is used to connect hubs ( Figure 1The diagram shows a circuit connected to any given transducer array 50. Each transducer array 50 includes a plurality of capacitively coupled electrode elements 52 and a plurality of temperature sensors 54 positioned to sense the temperature at respective locations among the plurality of electrode elements. In some preferred embodiments, these temperature sensors 54 are thermistors.

[0048] The analog multiplexer 81 has an analog output and multiple selectable analog inputs, each of which is connected to a corresponding one of a plurality of temperature sensors 54. A second terminal of each temperature sensor 54 is connected to a common ground. The output of the analog multiplexer 81 is connected to an amplifier 82, preferably with high input impedance (e.g., an operational amplifier configured as a voltage follower). The output of amplifier 82 is provided to the input of an analog-to-digital converter 83, and the output of the analog-to-digital converter is provided to a controller 85.

[0049] The controller 85 coordinates the operation of all components within the dashed line 80. The controller 85 sends commands to the analog multiplexer 81 to select one of the temperature sensors 54 in order to obtain a temperature reading from that temperature sensor.

[0050] In an embodiment where a thermistor is used as temperature sensor 54, a temperature reading can be obtained by routing a known current through the thermistor and measuring the voltage appearing across the thermistor. In an illustrated embodiment, this can be achieved using a programmable current source 88, which can be programmed to generate a known current (e.g., 150 μA). The analog multiplexer 81 is bidirectional, so the known current will be routed to either thermistor selected by the analog multiplexer.

[0051] Temperature readings from all eight temperature sensors 54 can be obtained using the following procedure: Controller 85 sends a command to analog multiplexer 81 to select a first thermistor and configures current source 88 to generate a known current. Because the first thermistor has been selected, the known current from current source 88 flows through analog multiplexer 81 to the first thermistor. This causes a voltage to appear across the thermistor. Because the first thermistor has been selected, this voltage will appear at the output of analog multiplexer 81. Amplifier 82 provides this voltage to the input of analog-to-digital converter 83. Controller 85 instructs analog-to-digital converter 83 to digitize this voltage. Controller 85 obtains this reading from analog-to-digital converter 83 and temporarily stores the digitized reading (corresponding to the first thermistor) in a buffer. This process is then repeated sequentially for each of the other thermistors until digitized readings from each of the eight thermistors are in the buffer.

[0052] In alternative embodiments not shown, alternative methods for interfacing with a thermistor (e.g., conventional voltage divider methods) can be used instead of the constant current method described above. In other alternative embodiments, different types of temperature sensors can be used instead of the thermistors described above. Examples include thermocouples, RTDs, and integrated circuit temperature sensors such as Analog Devices' AD590 and Texas Instruments' LM135. Of course, when using any of these alternative temperature sensors, appropriate modifications to the circuitry are required (which will be apparent to those skilled in the art).

[0053] In some embodiments, additional readings may be obtained and used for self-calibration to increase the accuracy of temperature readings obtained from the thermistor. For example, in the illustrated embodiment, the bottom input of analog multiplexer 81 is grounded, and the top input of analog multiplexer 81 is connected to precision resistor 89. In some embodiments, precision resistor 89 is a 10 kΩ, 0.1% tolerance resistor. Readings can be obtained from precision resistor 89 using the same procedure described above for obtaining readings from any of the thermistors. Obtaining readings from the ground input of analog multiplexer 81 is similar, except that current source 88 can be deactivated when the ground input is selected. In these embodiments, controller 85 temporarily stores the digitized readings from the precision resistor and the ground input in a buffer (meaning a total of 10 readings are stored in the buffer). These additional readings can ultimately be used to calibrate the readings obtained from the thermistor. In some embodiments, this calibration is performed within controller 85 itself before transmitting the digital data corresponding to the temperature readings. In other embodiments, this calibration is performed in a downstream processor (e.g., controller 32 in hub 30, both in...). Figure 2 The calibration is performed in (as shown in the figure), in which digital data corresponding to the precision resistor (and optionally the ground input) is transmitted to the downstream processor along with the uncalibrated temperature reading obtained from the thermistor.

[0054] A suitable method for performing calibration using the precision resistor 89 is to compare the actual voltage measured across the resistor with the expected voltage based on Ohm's law, the known value of the precision resistor 89, and the expected value of the current generated by the current source 88. Any deviation between the actual measured voltage and the expected voltage can then be used as a multiplier for subsequent measurements from the thermistor 54.

[0055] The controller 85 in the remote circuit 40 is connected to the hub 30 via UART 86. Figure 1The controller 85 communicates with the temperature sensor 54 and transmits the temperature readings obtained from the temperature sensor 54 to the hub. In some embodiments, the controller 85 may be programmed to operate autonomously, in which case the controller 85 will automatically collect temperature readings from each of the temperature sensors 54 and store the results in a buffer as described above, and then transmit the contents of the buffer (i.e., the readings for each of the eight temperature sensors 54, and optionally the additional readings described above) to the hub.

[0056] In an alternative embodiment, controller 85 may be programmed to operate as a slave to a master controller located in a hub. In these embodiments, controller 85 begins in a static state, where all controller 85 does is monitor incoming commands arriving from the master controller via UART 86. Examples of commands that may arrive from the master controller include a "collect sample" command and a "send data" command. When controller 85 recognizes that a "collect sample" command has arrived, controller 85 initiates the process described above to obtain temperature readings from each of the eight temperature sensors 54 and stores the results in their buffers. When controller 85 recognizes that a "send data" command has arrived, controller 85 executes the process of transmitting the previously collected temperature readings from the buffers to the hub via UART 86.

[0057] In those embodiments where controller 85 operates as a slave to the master controller located in hub 30, it becomes possible to transmit signals from the four transducer arrays 50 ( Figure 1 Each acquired temperature measurement in (as shown in the diagram) is synchronized. One way to accomplish this is to have the master controller in hub 30 send a “collect sample” command simultaneously or rapidly in succession to all four controllers 85, so that temperature readings acquired from each of the transducer arrays will be obtained simultaneously or nearly simultaneously. Temperature readings can then be collected by hub 30 from each of the four controllers 85 in batches of eight.

[0058] Most systems that use tumor treatment electric fields to treat tumors periodically (e.g., every second) switch the direction of the field applied to the tumor. To minimize noise in temperature measurements, short time gaps can be introduced where no field is applied in either direction, and temperature measurements can be taken during these gaps. In some preferred embodiments, the master controller located in hub 30 synchronizes the timing of the “collect sample” command with all four controllers 85, such that each of the distal circuits 40 will acquire its temperature reading during the gap. In embodiments where temperature readings are acquired simultaneously from each of the four transducer arrays, this method can be used to minimize the duration of the gap. For example, if the system requires 100 μs to acquire a single measurement, performing all 32 measurements sequentially (i.e., 4 distal circuits × 8 thermistors per circuit) would take 3.2 ms. In contrast, if each of the four distal circuits operates in parallel, each distal circuit can complete its work in 800 μs, in which case all 32 samples can be acquired in 800 μs. Note that because the "Send Data" command is not sensitive to noise, it can be executed while the field remains open, and therefore it is not time-critical.

[0059] In some embodiments, a single integrated circuit implements some or all of the following components: an analog multiplexer 81, an amplifier 82, an analog-to-digital converter 83, a controller 85, a UART 86, and a current source 88. An example of a single integrated circuit that includes all these functional blocks is Cypress's CY8C4 124LQI-443T programmable system-on-chip (PSoC).

[0060] Optionally, connectors may be included in the path between hub 30 and each of transducer array 50, as for a single transducer array. Figure 4A and Figure 4B As shown. In Figure 4A In this embodiment, connector 42 is positioned distally beyond distal circuitry 40; and Figure 4B In this embodiment, connector 38 is positioned on the proximal side of the distal circuit 40.

[0061] Figure 5A A more detailed view is depicted to show precisely what is shown in Figure 4A Where is connector 42 positioned in this embodiment? In this embodiment, connector 42 is positioned distally, extending beyond distal circuitry 40. Figure 5A The operation of the embodiment is similar to that discussed above. Figure 3 The operation of this embodiment differs in that 10 signals pass through connector 42: one for AC current to the electrode element 52; one for each of the eight temperature sensors 54 (for a total of eight); and one for a common ground, which is used for all eight temperature sensors 54.

[0062] Figure 5B A more detailed view is depicted to show precisely what is shown in Figure 4B Where is connector 38 located in this embodiment? In this embodiment, connector 38 is located on the proximal side of the distal circuit 40. Figure 5B The operation of the embodiment is similar to that discussed above. Figure 3 The operation of this embodiment differs in that four signals pass through connector 38: one for AC current to the electrode element 52, one for data traveling between the UART 86 and the hub, one for power to the remote circuit 40, and one for grounding the remote circuit 40.

[0063] Figure 6A Describing for Figure 4A / Figure 5A Mechanical layout of the embodiment. In this embodiment, a substrate 59 supports a plurality of capacitively coupled electrode elements 52. The electrode elements 52 are configured to rest against the body of a subject, and the substrate 59 is configured to hold the plurality of electrode elements 52 against the body of the subject. A plurality of temperature sensors 54 are positioned adjacent to and / or below respective portions of the electrode elements 52, such that the temperature sensors 54 can sense the temperature of these electrode elements.

[0064] Cable 35 has a proximal end and a distal end. Cable 35 includes (i) a conductor 51 that allows AC current to flow between the proximal end and the distal end of the cable, and (ii) a data path configured to carry digital data corresponding to multiple temperature readings (which originate from the distal circuit 40) from the distal end of the cable to the proximal end of the cable (i.e., in the direction of the hub).

[0065] Module 60 (directly or via an intermediate component) is mounted to the distal end of cable 35. A distal circuit 40 is mounted within module 60. In some embodiments, power and ground for the distal circuit 40 are provided via cable 35. A first half of connector 42 is provided at the distal end of module 60, and a second half of connector 42 is provided on substrate 59. The first half of connector 42 mates with the second half of connector 42, allowing electrical signals to pass through both halves of connector 42. When both halves of connector 42 are engaged, signals from the eight thermistors 54 travel through wiring on substrate 59, through connector 42, and into the distal circuit 40. The distal circuit 40 includes an analog multiplexer, an analog-to-digital converter, and a controller (combined above). Figure 3(as described above). Furthermore, a common ground signal for all thermistors 54 is provided via connector 42. A path for AC current to the electrode elements 52 is also provided via connector 42. This path continues through appropriate wiring on the substrate 59, such that the plurality of electrode elements 52 are electrically connected to the corresponding conductors of the cable 35.

[0066] Figure 6B Describing for Figure 4B / Figure 5B Mechanical layout of the embodiment. In this embodiment, a substrate 59 supports a plurality of capacitively coupled electrode elements 52. The electrode elements 52 are configured to rest against the body of a subject, and the substrate 59 is configured to hold the plurality of electrode elements 52 against the body of the subject. A plurality of temperature sensors 54 are positioned adjacent to and / or below respective portions of the electrode elements 52, such that the temperature sensors 54 can sense the temperature of these electrode elements.

[0067] Cable 35 has a proximal end and a distal end. Cable 35 includes (i) a conductor 51 that allows AC current to flow between the proximal end and the distal end of the cable, and (ii) a data path configured to carry digital data corresponding to multiple temperature readings (which originate from the distal circuit 40) from the distal end of the cable to the proximal end of the cable (i.e., in the direction of the hub).

[0068] Module 65 (directly or via an intermediate component) is mounted to substrate 59. Remote circuitry 40 is mounted within module 65. In some embodiments, power and ground for remote circuitry 40 are provided via cable 35. A first half of connector 38 is provided at the remote end of cable 35, and a second half of connector 38 is provided on substrate 59. The first half of connector 38 mates with the second half of connector 38, allowing electrical signals to pass through both halves of connector 38. When both halves of connector 38 are engaged, signals from cable 35 travel through connector 38 and into remote circuitry 40. Remote circuitry 40 includes an analog multiplexer, an analog-to-digital converter, and a controller (combined above). Figure 3 (as described above). Furthermore, a path for AC current to the electrode elements 52 is also provided via connector 38. This path continues through appropriate wiring on the substrate 59, such that the plurality of electrode elements 52 are electrically connected to the corresponding conductors of the cable 35.

[0069] Compared to non-connector-based embodiments, the connector-based design depicted in Figures 4 through 6 offers significant advantages because patients or caregivers can attach the transducer array 50 to their skin without being obstructed by the presence of cables. In these embodiments, the cable 35 is preferably disconnected from the substrate 59 when the transducer array 50 is initially placed on the patient's body. The cable 35 is only connected to the transducer array 50 via connector 38 or connector 42 when the transducer array 50 is attached to its desired location. The connectors are preferably waterproof to prevent moisture (e.g., sweat, shower, etc.) from interfering with the circuitry.

[0070] Note that this is different from non-connectorized... Figure 1 Examples and Figure 4B / Figure 5B / Figure 6B Compared to the previous examples, Figure 4A / Figure 5A / Figure 6A The embodiment has advantages because the transducer array 50 is preferably sterilized before use. Sterilization is typically performed using radiation or gas. Since radiation can interfere with electronics, components where the distal circuit 40 cannot be disconnected from the transducer array 50 can only be sterilized with gas. On the other hand, if the distal circuit 40 is located on the proximal side of the connector 42 (e.g., the distal circuit 40 is on...), Figure 4A / Figure 5A / Figure 6A As in the embodiment), the portion including the distal circuit 40 will not require sterilization. This allows for sterilization using gas or radiation. Figure 4A / Figure 5A / Figure 6A The transducer array 50 in the embodiment is sterilized without the risk of damaging the remote circuitry 40.

[0071] Each of the configurations described above offers significant advantages over existing technologies because only four conductors are required in each of the cables 35 that interface with each transducer array 50. Furthermore, because only four conductors are required, the cables 35 extending distally beyond the hub 30 can be made thinner and smaller than existing cables. This makes it easier to mount the hub 30 on a body part adjacent to the transducer array 50 and to achieve a small and lightweight interconnect between the hub 30 and the transducer array 50. For example, when the transducer array 50 is attached to a patient's scalp, the hub 30 can be mounted on the patient's head near the transducer array 50 without causing discomfort. In these embodiments, shorter cables 35 (e.g., less than 25 cm or even less than 10 cm) are preferably used to interconnect the hub 30 with both the transducer array 50 and the distal circuitry 40.

[0072] The configuration described herein can advantageously reduce cable tangling connected to the transducer array 50, reduce the number of times cables will interfere with the patient's daily activities, reduce the overall complexity of the system, improve patient comfort, and improve the maneuverability of the electrodes when they are attached to the patient's body.

[0073] Return to Figure 1 A display unit (not shown) may be added to the system. This display unit can be used to display information provided to the patient by the device, including but not limited to device status (e.g., power on / standby), error indications, battery charging status, compliance metrics, etc. The display unit may be installed anywhere along the cable 25 between the hub 30 and the field generator 20. In an alternative embodiment, the display unit 22 may be installed on the hub 30 itself.

[0074] In some alternative embodiments, the wires supplying power and ground to the distal circuit 40 can also be eliminated by using a coil to transfer a portion of the energy from the tumor therapy electric field signal (delivered via a through conductor), storing this energy in a capacitor adjacent to the distal circuit 40, and using the stored energy to power the distal circuit 40. A one-wire communication protocol for transmitting temperature data via the tumor therapy electric field signal wire can even be implemented. In such a configuration, both the data communication signal and the power supply (Vcc) for the distal circuit can be eliminated from the cables running to the transducer array 50. If all these wire reduction techniques are implemented, only two wires are needed between the hub 30 and each transducer array 50 (i.e., one for the tumor therapy electric field signal and one for ground). And the total number of wires running back from the four transducer arrays 50 to the field generator 20 will be reduced to five (i.e., one for common ground and a total of four for the tumor therapy electric field signal).

[0075] While the invention has been disclosed with reference to certain embodiments, various modifications, alterations, and variations can be made to the described embodiments without departing from the scope and intent of the invention as defined in the appended claims. Therefore, the invention is intended to be limited to the described embodiments, but rather to have the full scope defined by the language of the following claims and their equivalents.

Claims

1. An apparatus for use with an AC signal generator for applying an electric field through a target area in the body of a subject, the apparatus comprising: Multiple electrode elements configured to be placed against the body of the subject; A substrate configured to hold the plurality of electrode elements against the body of the subject; Multiple temperature sensors are positioned to sense the temperature at respective locations among the multiple electrode elements, wherein the temperature sensors are configured to perform temperature sensing during short time intervals in which no electric field is applied in either direction. An analog multiplexer having an analog output and a plurality of selectable analog inputs, wherein each of the plurality of analog inputs is operatively connected to a corresponding one of the plurality of temperature sensors; and A cable having a proximal end and a distal end, wherein the cable includes a conductor that allows AC current to flow between the proximal end and the distal end of the cable, and a data path configured to carry temperature data from the distal end of the cable to the proximal end of the cable. The plurality of electrode elements are driven by current flowing through a conductor, and The analog multiplexer is located at the transducer array or the field generator, or between the transducer array and the field generator.

2. The apparatus of claim 1, wherein the plurality of temperature sensors comprises a plurality of thermistors.

3. The device according to claim 1, wherein the cable has a length of 25 cm or less.

4. The device according to claim 1, wherein the cable has a length of 10 cm or less.

5. The apparatus of claim 1, further comprising a connector disposed between the analog multiplexer and the distal end of the cable.

6. The apparatus of claim 5, wherein the analog multiplexer is mounted to the substrate.

7. The apparatus of claim 1 further includes a connector disposed between the plurality of temperature sensors and the plurality of analog inputs.

8. The apparatus of claim 7, wherein the analog multiplexer is mounted to the distal end of the cable.

9. The apparatus of claim 1 further includes a precision resistor. The analog multiplexer described therein has an additional selectable analog input that is operatively connected to the precision resistor.

10. The apparatus according to claim 1, further comprising: An analog-to-digital converter, configured to digitize a signal from the analog output; as well as A controller configured to: (a) sequentially select each of a plurality of analog inputs, (b) sequentially obtain a plurality of temperature readings from the analog-to-digital converter, each of the plurality of temperature readings corresponding to a corresponding one of the plurality of temperature sensors, and (c) transmit temperature data, wherein the temperature data corresponds to the plurality of temperature readings.

11. The apparatus of claim 1, wherein the cable uses a single conductor to provide the data path carrying temperature data from the distal end of the cable to the proximal end of the cable.

12. The apparatus of claim 10, wherein the energy arriving via the conductor in the cable is used to power the controller.

13. The apparatus of claim 10, further comprising: A coil, which is positioned to transfer some of the energy passing through a conductor; And capacitors, which are arranged to store transferred energy; and The controller is powered by energy stored in a capacitor.

14. The apparatus of claim 1, wherein each of the electrode elements is a capacitively coupled electrode element.

Images