Electrode quality testing

Abstract

To provide a system for testing electrode quality.SOLUTION: A system includes a signal generator, configured to pass a generated signal, which has two different generated frequencies, through a circuit including an intra-body electrode. The system further includes a processor, configured to identify, while the generated signal is passed through the circuit, a derived frequency, which is derived from the generated frequencies, on the circuit, and to generate, in response to identifying the derived frequency, an output indicating a flaw in the electrode. Other embodiments are also described.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application is related to another application, entitled "DETECTING ASYMMERY IN A BIDIRECTIONAL SEMICONDUCOR DEVICE" (Attorney Docket No. 1002-2170|ID-1790|BIO6343USNP1), filed on even date herewith, the disclosure of which is incorporated herein by reference.

[0002] FIELD OF THEINVENTION The present invention relates to the field of electronic circuits, especially for medical applications. [Background technology]

[0003] In many applications, symmetric bidirectional semiconductor devices control the flow of electrical current through a circuit. Summary of the Invention [Means for solving the problem]

[0004] According to some embodiments of the present invention, there is provided a system including a signal generator configured to pass a generated signal having two different generated frequencies through a circuit including a bi-directional semiconductor device. The system further includes a processor configured to identify a derived frequency that is derived from the generated frequency on the circuit while the generated signal is passing through the circuit. The processor is further configured to generate an output indicative of an asymmetric characteristic of the bi-directional semiconductor device in response to identifying the derived frequency.

[0005] In some embodiments, the processor is configured to identify frequencies derived via electrophysiological channels that belong to the circuit.

[0006] In some embodiments, the derived frequency is within the bandwidth of the electrophysiological signal carried across the electrophysiological channel.

[0007] In some embodiments, each of the generated frequencies is outside the bandwidth.

[0008] In some embodiments, the characteristic includes impedance.

[0009] In some embodiments, the derived frequency is the difference between the generated frequencies.

[0010] In some embodiments, the processor is further configured to disable a power source coupled to the circuit in response to detecting the derived frequency.

[0011] In some embodiments, the power source is selected from the group of power sources consisting of a cardiac defibrillator, a cardiac pacer, and an ablation generator.

[0012] In some embodiments, the bi-directional semiconductor device belongs to a voltage suppression device.

[0013] In some embodiments, the bidirectional semiconductor device belongs to a semiconductor switch.

[0014] According to some embodiments of the present invention, there is further provided a method including passing a generated signal having two different generated frequencies through a circuit including a bi-directional semiconductor device. The method further includes identifying a derived frequency derived from the generated frequencies on the circuit while passing the two generated signals through the circuit. The method further includes generating an output in response to identifying the derived frequency, the output indicating that a characteristic of the bi-directional semiconductor device is asymmetric.

[0015] According to some embodiments of the invention, there is further provided a system including a signal generator configured to pass a generated signal having two different generated frequencies through a circuit including an intracorporeal electrode, the system further including a processor configured to identify a derived frequency derived from the generated frequency on the circuit while the generated signal is passing through the circuit, the processor further configured to generate an output indicative of a defect in the electrode in response to identifying the derived frequency.

[0016] In some embodiments, the derived frequency is the difference between the generated frequencies.

[0017] In some embodiments, each of the generated frequencies is less than 100 Hz.

[0018] In some embodiments, the amplitude of the generated signal is less than 50 μA.

[0019] In some embodiments, the signal generator is configured to pass a generated signal through the circuit while the electrodes are immersed in the electrolyte.

[0020] In some embodiments, the electrolyte comprises saline.

[0021] In some embodiments, the electrodes belong to an intracellular probe.

[0022] In some embodiments, the system further comprises a kit, the kit comprising: A signal generator, and and an electrical interface configured to connect the kit to the probe, thereby connecting the electrodes to a signal generator.

[0023] In some embodiments, the kit further includes a communications interface, and the processor is configured to identify the derived frequency by processing an output signal received from the kit via the communications interface.

[0024] In some embodiments, the electrode is one of a plurality of electrodes belonging to a probe, and the kit further comprises a multiplexer configured to selectively connect the electrode to the signal generator.

[0025] According to some embodiments of the present invention, there is further provided a method including passing a generated signal having two different generated frequencies through a circuit including an intracorporeal electrode. The method further includes identifying a derived frequency derived from the generated frequency on the circuit while passing the generated signal through the circuit. The method further includes generating an output indicative of a defect in the electrode in response to detecting the derived frequency. [Brief description of the drawings]

[0026] The invention is more fully understood when considered in conjunction with the drawings in which: [Figure 1] 1 is a schematic, illustrative diagram of an electrophysiological system, according to some exemplary embodiments of the present invention. [Diagram 2] 1 is a schematic, illustrative diagram of a circuit according to some exemplary embodiments of the present invention; [Diagram 3] 1 is a schematic, illustrative diagram of a system for testing electrode quality, according to some exemplary embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Glossary In the context of this application, including the claims, the term "bidirectional semiconductor device" may refer to any semiconductor device configured to conduct both the positive and negative portions of an alternating current (AC) signal. If the characteristics (e.g., impedance) of a bidirectional semiconductor device are the same for both portions of the signal, then the characteristics (or the device itself) are said to be "symmetrical"; if not, then the characteristics (or the device itself) are said to be "asymmetrical."

[0028] Overview In many cases, it is desirable for bidirectional semiconductor devices in a circuit to have symmetrical characteristics so that alternating current (AC) passing through the device does not generate any direct current (DC) voltage. For circuits connected to intracorporeal probes, such as electrophysiological probes disposed within a subject's body, this symmetry is particularly important because any DC voltage generated from, for example, ablation radiofrequency (RF) current flowing through the bidirectional semiconductor device is likely to be dangerous to the subject. Thus, there is a need for rapid and efficient detection of any asymmetry in bidirectional semiconductor devices.

[0029] To address this need, an exemplary embodiment of the present invention provides a system for testing the symmetry of a bidirectional semiconductor device in a circuit. The system comprises a signal generator connected to the circuit and configured to generate signals having two different frequencies. If the bidirectional semiconductor device is symmetric, the bidirectional semiconductor device behaves as a linear device and thus does not generate any additional frequencies. However, if the bidirectional semiconductor device is asymmetric (e.g., by having an asymmetric impedance), the device behaves nonlinearly and thus causes other "derived" frequencies to be carried on the circuit that are derived from the frequency of the generated signal. Thus, by identifying one of these derived frequencies, such as the difference between the frequencies of the generated signals, the asymmetry can be detected.

[0030] Advantageously, in electrophysiological applications, the symmetry tests described herein may be detected via existing electrophysiological channels so that no additional hardware is required. To facilitate this, the frequency of the generated signal may be selected such that the difference between the frequencies falls within the bandwidth of the electrophysiological signal carried across the channel. Nevertheless, the frequency itself may be selected to be outside this bandwidth so that the generated signal does not interfere with the detection of the electrophysiological signal.

[0031] An exemplary embodiment of the present invention further provides a test kit for testing the electrode quality while the electrode is immersed in the electrolyte. The kit, which includes the aforementioned signal generator, is connected to the electrode so that the generated signal flows through the electrode. In case of defects in the surface of the electrode (e.g., if the surface is rough or dirty), the nonlinearity of the interface between the electrode and the electrolyte increases, and as a result, the amplitude at which the derived frequencies are generated also increases. Thus, by identifying one of the derived frequencies, the defect can be detected.

[0032] It is emphasized that although this specification relates primarily to electrophysiological applications, embodiments of the present invention may be used to test the symmetry of any bidirectional semiconductor device and to test any electrode quality.

[0033] System Description Reference is initially made to FIG. 1, which is a schematic, illustrative illustration of an electrophysiology system 20, in accordance with certain exemplary embodiments of the present invention.

[0034] The system 20 includes an intracellular probe 26 including one or more intracellular electrodes 28 disposed at a distal end of the intracellular probe 26. Using the probe 26 and the electrodes 28, a physician 30 can obtain electrophysiological signals from the subject 22, such as electrogram signals from the heart 24 of the subject 22. Alternatively or additionally, the physician 30 can use the probe 26 and the electrodes 28 to pace or defibrillate the heart 24 or to ablate tissue of the heart 24.

[0035] Probe 26 is proximally connected to circuitry 34, which is typically housed within a console 32. System 20 typically further includes a processor 38 and a monitor 36. In response to output from circuitry 34, processor 38 may display associated output on monitor 36, as further described below with reference to FIG.

[0036] In general, the processor 38 may be embodied as a single processor or as a set of cooperatively networked or clustered processors. In some exemplary embodiments, the functions of the processor 38 described herein are implemented solely in hardware, for example, using one or more application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs). In other exemplary embodiments, the functions of the processor 38 are implemented at least partially in software. For example, in some exemplary embodiments, the processor 38 is embodied as a programmed digital computing device comprising at least a central processing unit (CPU) and a random-access memory (RAM). Program code, including a software program, and / or data are loaded into the RAM for execution and processing by the CPU. The program code and / or data can be downloaded to the processor in electronic form, for example, over a network. Alternatively or additionally, the program code and / or data may be provided and / or stored on a non-transitory tangible medium, such as a magnetic, optical, or electronic memory. Such program code and / or data, when provided to a processor, results in a machine or special purpose computer configured to perform the tasks described herein.

[0037] Reference is now made to FIG. 2, which is a schematic illustration of circuit 34 shown in FIG. 1, in accordance with some exemplary embodiments of the present invention.

[0038] Circuitry 34 includes at least one digitizer 40 configured to digitize electrophysiological signals from electrodes 28 and output digitized signals 66 to processor 38 (FIG. 1) via a wired or wireless connection. Digitizer 40 may include any suitable filter for filtering the signal prior to digitization.

[0039] Typically, the circuitry 34 further comprises at least one power source configured to supply power to the electrodes. For example, the circuitry 34 may comprise a cardiac pacer 42, a cardiac defibrillator, and / or an ablation generator. Typically, the circuitry further comprises at least one voltage suppression device 48 that suppresses the voltage supplied by the power source.

[0040] In an exemplary embodiment in which the probe includes multiple electrodes, the circuitry typically includes different respective electrophysiological channels for the electrodes. Each channel typically includes a separate digitizer 40 and voltage suppressor 48 connected in parallel to each other and to the electrode via a resistor 64. The circuitry 34 may further include a multiplexer 52 including a plurality of semiconductor switches 46, and a multiplexer controller 44. The multiplexer controller 44 is configured to control the switches 46 to selectively connect the channels to a power source.

[0041] In general, the circuitry may include any number of electrodes, and therefore any number of channels. By way of example, Figure 2 shows an exemplary embodiment in which the probe includes two electrodes, designated in the figure as "Electrode 1" and "Electrode 2," and the circuitry 34 correspondingly includes two channels, designated in the figure as "Channel 1" and "Channel 2."

[0042] The circuit 34 comprises at least one bidirectional semiconductor device.

[0043] For example, each switch 46 may comprise a bidirectional semiconductor device. As a particular example, each switch 46 may comprise a light-emitting diode (LED) 58 along with a pair of phototransistors 54 connected to each other and to a pair of parasitic diodes 56. In response to a control signal from the multiplexer controller 44, the LED 58 may emit light toward the phototransistor 54, causing the phototransistor to become conductive. Current (e.g., from the pacer 42) may then flow through the switch.

[0044] Alternatively or additionally, each voltage suppression device 48 may comprise a bidirectional semiconductor device. For example, each voltage suppression device 48 may comprise a pair of diodes 60 or thyristors connected in series or parallel with each other in opposing orientations. The diodes 60 may include, for example, avalanche diodes or Zener diodes.

[0045] Advantageously, the circuit 34 is configured to test the symmetry of any of the bidirectional semiconductor devices belonging to the circuit. To facilitate this test, the circuit comprises at least one signal generator 50 configured to generate a signal having a first frequency f1 and a second frequency f2. Typically, the amplitude of the generated signal is relatively low, such as less than 10 μA, so as not to pose a danger to the subject. If the impedance or another characteristic (e.g., cut-off voltage) of one of the bidirectional semiconductor devices is asymmetric, the device will behave nonlinearly and thus generate other frequencies derived from f1 and f2, such as a frequency that is a linear combination of f1 and f2. The processor may detect the asymmetry by identifying one of these other frequencies, such as the beating frequency |f1-f2|, f1+f2, 2f1+f2, or |2f1-f2|, in the digitized signal 66.

[0046] In some exemplary embodiments, the signal generator 50 comprises a voltage source. In such embodiments, as shown in FIG. 2, the signal generator may be modeled as a first voltage source 50a configured to generate a first signal having a first frequency f1, and a second voltage source 50b configured to generate a second signal having a second frequency f2, each of the voltage sources connected in series with a respective resistor 62. In other exemplary embodiments, the signal generator 50 comprises a current source.

[0047] In some exemplary embodiments, circuitry 34 includes a different respective signal generator for each channel, while in other exemplary embodiments a single signal generator is connected to all of the channels via a multiplexer.

[0048] Typically, f1 and f2 are outside the bandwidth of the electrophysiological signal carried across the channel (i.e., outside the range of frequencies exhibited by it), so that the generated signals do not interfere with the processing of the electrophysiological signal. For example, in applications where an electrogram signal is carried across the channel, each of the generated frequencies may be greater than 500 Hz, such as greater than 1000 Hz. Nevertheless, at least one derived frequency, such as the difference between f1 and f2, will typically be within the above-mentioned bandwidth, such that the sampling rate of the digitizer, which generally corresponds to the highest frequency within the bandwidth, is sufficient to capture the derived frequency. For example, in electrogram applications, the derived frequency may be less than 500 Hz, such as 400-500 Hz. Thus, advantageously, the derived frequency may be identified in the signal 66, i.e., the regular digitized electrophysiological signal received from the digitizer 40.

[0049] In response to identifying the derived frequency (e.g., in response to identifying a component of signal 66 having a derived frequency and an amplitude above a predetermined threshold), the processor may generate an output indicating that the impedance of the bi-directional semiconductor device is asymmetric, for example, by displaying a suitable warning on monitor 36 (FIG. 1). Alternatively or additionally, in response to identifying the derived frequency, the processor may disable the power supply.

[0050] Electrode quality testing Reference is now made to FIG. 3, which is a schematic, illustrative diagram of a system 67 for testing the quality of electrodes 28 prior to use of probe 26, according to some exemplary embodiments of the present invention.

[0051] The system 67 includes a signal generator 50, as described above with respect to FIG. 2, which may be modeled as a first voltage source 50a configured to generate a first signal having a first frequency f1, and a second voltage source 50b configured to generate a second signal having a second frequency f2, each of the voltage sources connected in series with a respective resistor 62 and a digitizer 40 configured to communicate with a processor 82 via a wired or wireless connection. To test each electrode, a generated signal from the signal generator is passed through a circuit including the electrode. While the generated signal is passed through the circuit, the processor 82 monitors the circuit for a derived frequency, such as |f1-f2|, by processing the digitized signal 66 as described above with reference to FIG. 2. In response to identifying the derived frequency (e.g., in response to identifying a component of the signal 66 having the derived frequency and an amplitude exceeding a predetermined threshold), the processor 82 generates an output indicative of a defect in the electrode.

[0052] Typically, the signal generator and digitizer reside in a test kit 76 that is configured to connect to the probe 26, e.g., at its proximal end. Typically, the test kit 76 further comprises a multiplexer 52 (which may comprise any type of switch) and a multiplexer controller 44. Each switch in the multiplexer 52 is configured to connect via a different respective wire to a different respective electrode at the distal end of the probe. The wires may be contained in a cable 86 that may be connected to the probe 26 via a suitable interface in the handle 74 of the probe 26. In response to control signals 80 from the processor 82, the multiplexer controller 44 controls the multiplexer 52 such that the multiplexer selectively connects the electrodes for testing to the signal generator.

[0053] In general, the processor 82 may be embodied as a single processor or as a set of cooperatively networked or clustered processors. In some exemplary embodiments, the functions of the processor 82 described herein are implemented solely in hardware, for example, using one or more application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs). In other exemplary embodiments, the functions of the processor 82 are implemented at least partially in software, as described above with respect to the processor 38 (FIG. 1). The processor 82 may reside in the test kit 76 or, as alluded to in FIG. 3, in an external computer. In response to identifying the derived frequency, the processor 82 may generate another output, such as by displaying a suitable warning on a computer monitor, outputting an audible alert, and / or activating a warning light that resides in the test kit.

[0054] Typically, electrodes 28 are tested while immersed in an electrolyte solution 70, such as saline, that simulates the body's environment. The nonlinearity of the impedance at the interface between each electrode and solution 70, and therefore the amplitude of any derived frequency components of signal 66, increases with the degree of imperfections, e.g., roughness or dirt, of the electrode's surface. Thus, defects may be detected in response to identifying derived frequencies in signal 66, as described above.

[0055] A return electrode 72, typically disposed at the bottom of a container 68 containing the solution 70, is connected to the test kit via a wire 84. (Wire 84 may be contained within a cable.) Thus, the test circuit through which the generated signal passes includes the solution 70, the return electrode 72, and wire 84.

[0056] Generally, the test kit may include a case made of any suitable material, such as plastic, configured to hold the various components of the kit described herein. The test kit may include any suitable electrical interface, such as a port or socket, for connecting the kit to a probe such that the electrode 28 is connected to a signal generator. Similarly, the test kit may include any suitable electrical interface for connecting the kit to a return electrode 72. Alternatively or additionally, the test kit may include any suitable wired or wireless communication interface (e.g., a universal serial bus (USB) port) for communicating with a processor 82, such that the processor can receive signals 66 from the kit and / or the kit may receive control signals 80 from the processor via the communication interface.

[0057] Typically, frequencies f1 and f2 are relatively small, such as less than 100 Hz, so as to amplify any nonlinear response of the electrodes, and typically the amplitude of each of the generated signals is relatively small, such as less than 50 μA, so as to minimize any undesirable effects on the electrode surface.

[0058] It will be understood by those skilled in the art that the present invention is not limited to what has been specifically shown and described herein. Rather, the scope of the embodiments of the present invention includes both combinations and subcombinations of the various features described herein, as well as variations and modifications of features not present in the prior art that would occur to one skilled in the art upon reading the above description. Documents incorporated by reference into this patent application are to be considered as part of this application, except that if any term is defined in these incorporated documents in a manner that is inconsistent with the definition expressly or impliedly given herein, then only the definition in this specification shall be considered.

[0059] [Embodiment] (1) A system for testing electrode quality, comprising: a signal generator configured to pass a generated signal having two different generated frequencies through a circuit including an internal electrode; 1. A processor comprising: identifying a derived frequency that is derived from the generated frequency on the circuit while the generated signal passes through the circuit; a processor configured to generate an output indicative of a defect in the electrode in response to identifying the derived frequency. (2) The system of embodiment 1, wherein the derived frequency is the difference between the generated frequencies. (3) The system of embodiment 1, wherein each of the generated frequencies is less than 100 Hz. (4) The system of embodiment 1, wherein the amplitude of the generated signal is less than 50 μA. (5) The system of embodiment 1, wherein the signal generator is configured to pass the generated signal through the circuit while the electrodes are immersed in an electrolyte.

[0060] (6) The system of embodiment 5, wherein the electrolyte comprises saline. (7) The system described in embodiment 1, wherein the electrode belongs to an intracorporeal probe. (8) A kit further comprising: The signal generator; 8. The system of embodiment 7, further comprising: an electrical interface configured to connect the kit to the probe, thereby connecting the electrodes to the signal generator. (9) The system of embodiment 8, wherein the kit further comprises a communications interface, and the processor is configured to identify the derived frequency by processing an output signal received from the kit via the communications interface. (10) The system described in embodiment 8, wherein the electrode is one of a plurality of electrodes belonging to the probe, and the kit further comprises a multiplexer configured to selectively connect the electrode to the signal generator.

[0061] (11) A method for testing electrode quality, comprising the steps of: passing a generated signal having two different generated frequencies through a circuit including an internal electrode; identifying a derived frequency derived from the generated frequency on the circuit while passing the generated signal through the circuit; and generating an output indicative of a defect in the electrode in response to detecting the derived frequency. (12) The method of claim 11, wherein the derived frequency is the difference between the generated frequencies. (13) The method of claim 11, wherein each of the generated frequencies is less than 100 Hz. (14) The method of embodiment 11, wherein the amplitude of the generated signal is less than 50 μA. 15. The method of claim 11, wherein passing the generated signal through the circuit comprises passing the generated signal through the circuit while the electrodes are immersed in an electrolyte.

[0062] 16. The method of claim 15, wherein the electrolyte solution comprises saline. (17) The method of embodiment 15, wherein the electrode belongs to an intracellular probe. (18) The method of embodiment 17, wherein the signal generator resides in a kit, and passing the generated signal through the circuit includes passing the generated signal through the circuit while the kit is connected to the probe. (19) The method of embodiment 18, wherein identifying the derived frequency includes identifying the derived frequency by processing an output signal received from the kit. (20) The method of embodiment 18, wherein the electrode is one of a plurality of electrodes belonging to the probe, and the kit further comprises a multiplexer configured to selectively connect the electrode to the signal generator.

Claims

1. 1. A system for testing electrode quality, comprising: a signal generator configured to pass a generated signal having two different generated frequencies to a circuit including an internal electrode; 1. A processor comprising: identifying a derived frequency that is derived from the generated frequency on the circuit while the generated signal passes through the circuit; a processor configured to generate an output indicative of a defect in the electrode in response to identifying the derived frequency. The system wherein the derived frequency is the difference between the generated frequencies.

2. The system of claim 1 , wherein each of the generated frequencies is less than 100 Hz.

3. 10. The system of claim 1, wherein the generated signal has an amplitude of less than 50 μA.

4. The system of claim 1 , wherein the signal generator is configured to pass the generated signal through the circuit while the electrodes are immersed in an electrolyte solution.

5. The system of claim 4 , wherein the electrolyte comprises a saline solution.

6. The system of claim 1 , wherein the electrodes belong to an intrabody probe.

7. The kit further comprises: The signal generator; 7. The system of claim 6, further comprising: an electrical interface configured to connect the kit to the probe, thereby connecting the electrodes to the signal generator.

8. 8. The system of claim 7, wherein the kit further comprises a communications interface, and the processor is configured to identify the derived frequency by processing an output signal received from the kit via the communications interface.

9. 8. The system of claim 7, wherein the electrode is one of a plurality of electrodes belonging to the probe, and the kit further comprises a multiplexer configured to selectively connect the electrode to the signal generator.

10. 1. A method for testing electrode quality, comprising: passing a generated signal having two different generated frequencies through a circuit including an internal electrode; identifying a derived frequency derived from the generated frequency on the circuit while passing the generated signal through the circuit; and generating an output indicative of a defect in the electrode in response to detecting the derived frequency. The method of claim 1, wherein the derived frequency is the difference between the generated frequencies.

11. The method of claim 10 , wherein each of the generated frequencies is less than 100 Hz.

12. The method of claim 10, wherein the generated signal has an amplitude of less than 50 μA.

13. The method of claim 10 , wherein passing the generated signal through the circuit comprises passing the generated signal through the circuit while the electrodes are immersed in an electrolyte.

14. The method of claim 13 , wherein the electrolyte comprises saline.

15. The method of claim 13 , wherein the electrode belongs to an intracellular probe.

16. The method of claim 15, wherein a signal generator belongs to a kit, and passing the generated signal through the circuit includes passing the generated signal through the circuit while the kit is connected to the probe.

17. 17. The method of claim 16, wherein identifying the derived frequency comprises identifying the derived frequency by processing an output signal received from the kit.

18. 17. The method of claim 16, wherein the electrode is one of a plurality of electrodes belonging to the probe, and the kit further comprises a multiplexer configured to selectively connect the electrode to the signal generator.

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