Power supply device and catheter system

Abstract

A power supply device (14) is connected to a catheter (12) that has a plurality of electrodes. The power supply device (14) comprises: a measurement unit (42) that supplies a measurement signal subjected to amplitude modulation so as to include an increase period in which the amplitude increases and a decrease period in which the amplitude decreases; a switching circuit (48) that is provided between the plurality of electrodes and the measurement unit (42) and that is capable of switching an electrode connected to the measurement unit (42); a switching control unit (58) that maintains the state of the switching circuit (48) from the start of the increase period to the end of the decrease period and changes the state of the switching circuit (48) from the end of the decrease period before the start of the increase period; and a calculation unit (60) that calculates impedance using an output value of the electrode connected to the measurement unit (42).

Description

Power supply device and catheter system

[0001] The present disclosure relates to a power supply device and a catheter system.

[0002] There is known an ablation therapy by electropermeabilization in which a catheter having a plurality of electrodes is inserted into a patient's body and a high-voltage pulse is applied. Before applying the high-voltage pulse, the impedance between the plurality of electrodes is measured.

[0003] Japanese Unexamined Patent Application Publication No. 2022-45316

[0004] When measuring the impedance of a plurality of electrodes of a catheter, it is necessary to switch the electrodes to be measured. If switching noise is generated by switching the electrodes to be measured, it will affect the electrocardiogram waveform measured by the electrocardiograph.

[0005] The present disclosure has been made in view of such a situation, and one of its purposes is to suppress switching noise during impedance measurement.

[0006] A power supply device according to an aspect of the present invention is a power supply device connected to a catheter having a plurality of electrodes, and includes a measurement unit that supplies a measurement signal amplitude-modulated to include an increasing period in which the amplitude increases and a decreasing period in which the amplitude decreases, a switching circuit provided between the plurality of electrodes and the measurement unit and capable of switching the electrodes connected to the measurement unit, a switching control unit that maintains the state of the switching circuit from the start of the increasing period to the end of the decreasing period and changes the state of the switching circuit from the end of the decreasing period to the start of the increasing period, and a calculation unit that calculates impedance using the output value of the electrode connected to the measurement unit.

[0007] Another aspect of the present invention is a catheter system. This catheter system comprises a catheter having a plurality of electrodes and a power supply connected to the plurality of electrodes. The power supply includes a measurement unit that supplies an amplitude-modulated measurement signal including an increasing period in which the amplitude increases and a decreasing period in which the amplitude decreases; a switching circuit provided between the plurality of electrodes and the measurement unit and capable of switching the electrodes connected to the measurement unit; a switching control unit that maintains the state of the switching circuit from the start of the increasing period to the end of the decreasing period and changes the state of the switching circuit from the end of the decreasing period to the start of the increasing period; and a calculation unit that calculates impedance using the output values ​​of the electrodes connected to the measurement unit.

[0008] Any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, etc., are also valid as aspects of this disclosure.

[0009] According to this disclosure, switching noise during impedance measurement can be suppressed.

[0010] This is a schematic diagram showing an ablation system according to an embodiment. This is a perspective view showing an example of the configuration of the electrode assembly of a catheter. This is a schematic diagram showing the circuit configuration of the measurement unit according to an embodiment. Figure 4(a) is a schematic diagram showing the waveform of the carrier wave, Figure 4(b) is a schematic diagram showing the waveform of the modulated wave, and Figure 4(c) is a schematic diagram showing the waveform of the measurement signal. This is a schematic diagram showing the output waveform of the measurement signal. This is a schematic diagram showing the circuit configuration of the measurement unit according to a modified example.

[0011] The present disclosure will be described below with reference to the drawings, based on preferred embodiments. The embodiments are illustrative and not limiting, and not all features or combinations thereof described in the embodiments are necessarily essential to the present disclosure. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant descriptions are omitted where appropriate. The scale and shape of each part shown in each drawing are set for convenience to facilitate explanation and are not to be interpreted restrictively unless otherwise specified. Furthermore, where terms such as "first," "second," etc. are used in this specification or claims, unless otherwise specified, these terms do not indicate any order or importance, but are used to distinguish one configuration from another. In addition, some components that are not important for explaining the embodiments are omitted in each drawing.

[0012] Figure 1 is a schematic diagram showing a catheter system 10 according to an embodiment. The catheter system 10 comprises a catheter 12, a power supply 14, and a counter electrode plate 16. The catheter system 10 is used to ablate the tissue of a patient 20 in a affected area 22. The catheter system 10 is also called an ablation system.

[0013] Figure 1 shows some of the components of the catheter system 10 as functional blocks. At least some of these functional blocks can be implemented as hardware components and circuits, such as a computer's CPU and memory, and as software components, such as computer programs. It will be understood by those skilled in the art that these functional blocks can be implemented in various ways through combinations of hardware and software.

[0014] The catheter system 10 performs ablation on the affected area 22 using irreversible electroporation (IRE). In IRE, pulsed electric field ablation (PFA) is performed. PFA is an ablation procedure that uses a pulsed electric field generated by applying a high voltage between the catheter 12 and the counter electrode plate 16 to kill cells in the affected area 22 and form a lesion in the affected area 22. Since IRE is non-thermal, damage to surrounding tissues and nerves can be minimized.

[0015] The affected area 22 to be ablated is, for example, the heart where arrhythmia is occurring. For example, when pulmonary vein isolation is performed to treat atrial fibrillation, damage to the esophagus and phrenic nerve around the affected area can be suppressed, thereby suppressing the occurrence of complications such as esophageal fistula and phrenic nerve paralysis. The catheter system 10 can also be used for ablation of other organs and tissues.

[0016] The catheter 12 comprises an electrode assembly 24, a shaft 26, and a handle 28. The electrode assembly 24 is located at the tip of the shaft 26 and has multiple electrodes. The electrode assembly 24 is inserted into the body when the catheter 12 is used.

[0017] The shaft 26 is composed of a flexible tubular body. The shaft 26 is made of a known flexible material, including resins such as polyolefin, polytetrafluoroethylene, polyether block amide, and polyamide. The shaft 26 has a multi-lumen structure, for example, having multiple lumens. Various thin wires (not shown), such as conductor wires and operating wires, and an inner tube 34 (see Figure 2), which will be described later, are inserted through the lumens.

[0018] The handle 28 is provided on the proximal end side of the shaft 26. The handle 28 is positioned outside the body when the catheter 12 is in use and is grasped and operated by the operator. The handle 28 comprises a main body that is grasped by the operator and an operating part for advancing and retracting the inner tube 34. When the inner tube 34 is displaced towards the proximal end relative to the shaft 26 by operating the operating part, the folded electrode assembly 24 unfolds away from the axis of the shaft 26. When the inner tube 34 is displaced towards the tip relative to the shaft 26 by operating the operating part, the unfolded electrode assembly 24 is folded.

[0019] Figure 2 is a perspective view showing an example of the configuration of the electrode assembly 24 of the catheter 12. The electrode assembly 24 comprises a plurality of splines 36a, 36b, 36c, 36d, 36e, 36f (collectively referred to as splines 36) and a plurality of electrodes 38a1, 38a2, 38a3, 38a4, 38b1, 38b2, 38b3, 38b4, 38c1, 38c2, 38c3, 38c4, 38d1, 38d2, 38d3, 38d4, 38e1, 38e2, 38e3, 38e4, 38f1, 38f2, 38f3, 38f4, 38g (collectively referred to as electrodes 38). Figure 2 shows the splines 36 in an unfolded state.

[0020] The multiple splines 36 are linear bodies extending in the axial direction of the shaft 26 and are made of the same flexible material as the shaft 26. The multiple splines 36 can, for example, consist of six splines: a first spline 36a, a second spline 36b, a third spline 36c, a fourth spline 36d, a fifth spline 36e, and a sixth spline 36f. The number of splines 36 is not limited to six; it may be five or fewer, or seven or more.

[0021] Multiple splines 36 are arranged around the axis of the shaft 26 at intervals from each other. The tips of the multiple splines 36 are fixed to the tip 32. The base ends of the multiple splines 36 are inserted into the shaft 26 from the tip and fixed to the shaft 26. The tip 32 is fixed to the tip of the inner tube 34. The inner tube 34 passes through the lumen of the shaft 26. The base end of the inner tube 34 is connected to the handle 28. The tip 32 and the inner tube 34 can be displaced toward the tip or base end relative to the shaft 26 by operating the handle 28.

[0022] Multiple electrodes 38 are provided on multiple splines 36. The multiple electrodes 38 are arranged at predetermined intervals in the longitudinal direction of each spline 36. Each electrode 38 is ring-shaped and made of a metal with good electrical conductivity such as platinum, gold, silver, copper, aluminum, or stainless steel, or an alloy thereof. Each spline 36a to 36f is provided with the same number of electrodes 38, for example, four electrodes 38 are provided. Each spline 36i (i=a to f) is provided with a first electrode 38i1, a second electrode 38i2, a third electrode 38i3, and a fourth electrode 38i4. For example, the first spline 36a is provided with a first electrode 38a1, a second electrode 38a2, a third electrode 38a3, and a fourth electrode 38a4. The same applies to the second splines 36b to the sixth splines 36f. The number of electrodes 38 provided on each spline 36 is not limited to four; it may be three or fewer, or five or more.

[0023] Electrode 38g is provided at a different location from the other electrodes 38i1 to 38i4 (i=a to f). For example, electrode 38g is provided at the base end of the first spline 36a and is separated from the other electrodes 38a1 to 38a4. Electrode 38g may be provided at another location, such as the tip of the shaft 26, rather than on the splines 36a to 36f. Electrode 38g is used as a reference electrode or an indifferent electrode for impedance measurement. Note that the electrode assembly 24 does not necessarily have to include electrode 38g, and any of electrodes 38a1 to 38f4 may be used as the indifferent electrode.

[0024] The tip of a conductor (not shown) is connected to each electrode 38. The conductors connected to each electrode 38 are passed through the lumen of the shaft 26. The base end of the conductors connected to each electrode 38 is connected to a connector (not shown) on the handle 28. The conductors connected to each electrode 38 are electrically connected to the power supply unit 14 via a cable 30 connected to the connector on the handle 28.

[0025] Returning to Figure 1, the counter electrode 16 is placed on the patient's body surface during ablation. The counter electrode 16 is electrically connected to the power supply 14. The power supply 14 applies a pulse voltage between the electrodes 38 of the catheter 12 and the counter electrode 16. The application of the pulse voltage performs ablation on the affected area 22 of the patient 20. The power supply 14 may also apply a pulse voltage between multiple electrodes 38 of the catheter 12. In this case, the catheter system 10 may be configured without the counter electrode 16.

[0026] The power supply unit 14 measures the impedance between the multiple electrodes 38 of the catheter 12 before applying a pulse voltage. The power supply unit 14 sequentially measures the impedance between, for example, one of the electrodes 38a1 to 38f4 and the indifferent electrode 38g. By measuring the impedance, the power supply unit 14 determines whether each electrode 38a1 to 38f4 is in proper contact with the tissue of the affected area 22.

[0027] The power supply unit 14 comprises a power supply unit 40, a measurement unit 42, a catheter connection unit 44, an electrocardiograph connection unit 46, a switching circuit 48, and a control unit 50.

[0028] The power supply unit 40 generates pulse voltages supplied to the multiple electrodes 38. The power supply unit 40 generates pulse voltages by switching the DC voltage output from a DC power supply, for example. The DC power supply includes a DC-DC converter such as a switching regulator and an output capacitor. The output voltage of the DC power supply is not particularly limited, but is for example 1kV or 2kV or more, and for example 4kV or less or 3kV or less. The power supply unit 40 includes a bridge circuit using semiconductor switches such as field-effect transistors (FETs) and insulated-gate bipolar transistors (IGBTs). The power supply unit 40 includes, for example, a first bridge circuit connected to a switching circuit 48 and a second bridge circuit connected to a counter electrode plate 16.

[0029] The measurement unit 42 generates a measurement signal for impedance measurement. The measurement signal includes a measurement waveform obtained by amplitude modulating a carrier wave with a modulating wave. The measurement signal includes multiple measurement waveforms, and each of the multiple measurement waveforms is supplied to one of the multiple electrodes 38a1 to 38f4. By acquiring the voltage value of each of the multiple electrodes 38a1 to 38f4 to which the measurement waveform is supplied, the impedance of each of the multiple electrodes 38a1 to 38f4 can be measured.

[0030] The catheter connection section 44 is a connector to which the cable 30 of the catheter 12 is connected. The catheter connection section 44 includes multiple connection terminals corresponding to each of the multiple electrodes 38 of the catheter 12. Each connection terminal of the catheter connection section 44 is connected to the switching circuit 48.

[0031] The electrocardiograph connection unit 46 is a connector to which a cable extending from the electrocardiograph 18 is connected. The electrocardiograph connection unit 46 includes multiple connection terminals corresponding to each of the multiple electrodes 38 of the catheter 12, for example. The electrocardiograph connection unit 46 is connected to the catheter connection unit 44 via a switching circuit 48. The electrocardiograph connection unit 46 outputs the electrocardiogram waveform measured at each of the multiple electrodes 38 to the electrocardiograph 18.

[0032] The switching circuit 48 switches the electrode 38 to which the pulse voltage generated by the power supply unit 40 is supplied. The switching circuit 48 also switches the electrode 38 to which the measurement signal generated by the measurement unit 42 is supplied. The switching circuit 48 includes, for example, an output switching unit 52 connected between the power supply unit 40 and the catheter connection unit 44, a measurement switching unit 54 connected between the measurement unit 42 and the catheter connection unit 44, and a connection switching unit 56 connected between the output switching unit 52 and the measurement switching unit 54 and the catheter connection unit 44.

[0033] The output switching unit 52 connects the power supply unit 40 to at least one of the multiple electrodes 38 when the power supply unit 40 supplies a pulse voltage. The output switching unit 52 includes, for example, multiple switches connected in parallel between the power supply unit 40 and the multiple electrodes 38a1 to 38f4. The multiple switches are configured using mechanical switches having mechanical contacts, such as mechanical relays. The multiple switches may also be configured using semiconductor switches such as field-effect transistors (FETs) or insulated-gate bipolar transistors (IGBTs).

[0034] The measurement switching unit 54 connects the measurement unit 42 to at least one of the multiple electrodes 38 when the measurement unit 42 supplies a measurement signal. The measurement switching unit 54 includes, for example, multiple switches connected in parallel between the measurement unit 42 and the multiple electrodes 38a1 to 38f4. The multiple switches are configured using mechanical switches having mechanical contacts, such as mechanical relays. The multiple switches may also be configured using semiconductor switches such as field-effect transistors (FETs) or insulated-gate bipolar transistors (IGBTs).

[0035] The connection switching unit 56 connects the catheter connection unit 44 to the output switching unit 52 or the measurement switching unit 54. When the power supply unit 40 supplies a pulse voltage, the connection switching unit 56 connects the catheter connection unit 44 to the output switching unit 52 and disconnects it from the measurement switching unit 54. When the measurement unit 42 supplies a measurement signal, the connection switching unit 56 connects the catheter connection unit 44 to the measurement switching unit 54 and disconnects it from the output switching unit 52. The connection switching unit 56 includes multiple switches connected to multiple electrodes 38a1 to 38f4. The multiple switches are configured using mechanical switches having mechanical contacts, such as mechanical relays. The multiple switches may also be configured using semiconductor switches such as field-effect transistors (FETs) or insulated-gate bipolar transistors (IGBTs).

[0036] The electrocardiograph connection unit 46 is connected between the measurement switching unit 54 and the connection switching unit 56. When the electrocardiograph 18 measures electrocardiographic potential, the connection switching unit 56 connects the catheter connection unit 44 to the measurement switching unit 54 and disconnects it from the output switching unit 52. The electrocardiograph connection unit 46 is connected to the multiple electrodes 38a1 to 38f4 when the measurement unit 42 supplies a measurement signal. The electrocardiograph connection unit 46 is disconnected from the multiple electrodes 38a1 to 38f4 when the power supply unit 40 supplies a pulse voltage.

[0037] The control unit 50 controls the overall operation of the power supply unit 14. The control unit 50 is constructed using an integrated circuit such as an FPGA (Field Programmable Gate Array). The control unit 50 may be implemented in hardware (circuit), in software (program), or in a combination of the two. If implemented in software, the software consists of a group of programs that cause a computer to execute each function. Each program may, for example, be pre-installed in the computer, or it may be installed in the computer from a network or recording medium.

[0038] The control unit 50 comprises a switching control unit 58 and a calculation unit 60. The switching control unit 58 controls the operation of the switching circuit 48. When the measurement unit 42 supplies a measurement signal, the calculation unit 60 acquires the voltage value of the electrode 38 to which the measurement signal is supplied and calculates the impedance using the acquired voltage value.

[0039] Figure 3 is a schematic diagram showing the circuit configuration of the measurement unit 42 according to the embodiment. The measurement unit 42 includes a carrier wave generation circuit 62, a modulated wave generation circuit 64, a multiplication circuit 66, an input resistor 70, and an operational amplifier 72. The measurement unit 42 has a first measurement terminal 42a and a second measurement terminal 42b.

[0040] The carrier wave generation circuit 62 is, for example, an oscillation source and generates a carrier wave Vc having a predetermined carrier frequency fc. Figure 4(a) shows the carrier wave V Ｃ This diagram schematically shows the waveform. The carrier wave Vc is, for example, a sine wave. The carrier frequency fc is, for example, 1 kHz or higher or 10 kHz or higher, and 1000 kHz or lower or 100 kHz or lower. The carrier frequency fc is set outside the range of the transmission frequency of the bandpass filter provided at the input of the electrocardiograph 18. The transmission frequency of the bandpass filter is, for example, 30 Hz to 500 Hz.

[0041] The modulation wave generation circuit 64 generates a modulation wave Vm for amplitude modulation of the carrier wave Vc. Figure 4(b) is a schematic diagram showing the waveform of the modulation wave Vm. The modulation wave Vm alternates between output periods T1 and stop periods T2. The output period T1 includes an increasing period Ta in which the amplitude increases and a decreasing period Tb in which the amplitude decreases. The modulation wave Vm is configured such that the amplitude remains constant during the holding period Tc from the end of the increasing period Ta to the start of the decreasing period Tb. The modulation wave Vm is configured such that the amplitude becomes zero during the stop period T2 from the end of the decreasing period Tb to the start of the increasing period Ta. The modulation wave Vm can include multiple output periods T1, for example, the same number of output periods T1 as the number of electrodes 38a1 to 38f4 to be measured (e.g., 24 times).

[0042] The multiplication circuit 66 multiplies the carrier wave Vc and the modulation wave Vm to generate the amplitude-modulated measurement signal V1. FIG. 4(c) is a diagram schematically showing the waveform of the measurement signal V1. Similar to the modulation wave Vm, the measurement signal V1 alternately includes an output period T1 and a stop period T2, and the output period T1 includes an increasing period Ta in which the amplitude increases, a holding period Tc in which the amplitude is held constant, and a decreasing period Tb in which the amplitude decreases.

[0043] The measurement signal V1 output from the multiplication circuit 66 is supplied to the inverting input of the operational amplifier 72 via the input resistor 70. The non-inverting input of the operational amplifier 72 is connected to the ground (0V). The inverting input of the operational amplifier 72 is connected to the first measurement terminal 42a. The first measurement terminal 42a is connected to the non-related electrode 38g of the catheter 12. The output of the operational amplifier 72 is connected to the second measurement terminal 42b. The second measurement terminal 42b is connected to the measurement switching unit 54. The measurement signal V2 output from the operational amplifier 72 is supplied to the plurality of electrodes 38a1 to 38f4 via the measurement switching unit 54. Note that the connection destinations of the first measurement terminal 42a and the second measurement terminal 42b may be reversed, that is, the first measurement terminal 42a may be connected to the measurement switching unit 54 and the second measurement terminal 42b may be connected to the non-related electrode 38g.

[0044] The measurement unit 42 is sequentially connected to each of the plurality of electrodes 38a1 to 38f4 by the measurement switching unit 54. The operational amplifier 72 constitutes an inverting amplifier circuit by the load resistor 74 between any one of the plurality of electrodes 38a1 to 38f4 and the non-related electrode 38g. The amplification factor V2 / V1 of the inverting amplifier circuit is equal to the ratio of the resistance value R1 of the input resistor 70 to the impedance R2 of the load resistor 74 (that is, V2 / V1 = R2 / R1). Therefore, the impedance R2 of the load resistor 74 can be calculated by the formula R2 = R1 × V2 / V1 using the measurement signal V2 output from the operational amplifier 72.

[0045] The switching control unit 58 maintains the state of the measurement switching unit 54 during the output period T1 and changes the state of the measurement switching unit 54 during the stop period T2. The switching control unit 58 controls the switching timing of the measurement switching unit 54 in synchronization with, for example, the waveform of the modulation wave Vm supplied from the modulation wave generation circuit 64. During the stop period T2 when the measurement signal V2 is not being output, the switching control unit 58 turns on and off the switch of the measurement switching unit 54 to suppress the generation of switching noise due to the state change of the measurement switching unit 54.

[0046] The stop period T2 is set to be longer than the switching time of the switch included in the measurement switching unit 54. The switching time of the switch included in the measurement switching unit 54 is, for example, less than 1 millisecond. The stop period T2 is, for example, 1 millisecond or more, 2 milliseconds or more, or 3 milliseconds or more. From the viewpoint of preventing the measurement time from becoming too long, the stop period T2 is preferably 1 second or less, for example, 100 milliseconds or less, 50 milliseconds or less, or 10 milliseconds or less.

[0047] The increasing period Ta and the decreasing period Tb are periods in which the amplitude is gradually changed, and are provided to suppress noise input to the electrocardiograph 18. The waveform of the modulation wave V in the increasing period Ta and the decreasing period Tb may be a sine wave, a trapezoidal wave, or a stepped shape. The increasing period Ta and the decreasing period Tb are set so as to be outside the range of the transmission frequency of the band-pass filter provided at the input of the electrocardiograph 18. The transmission frequency of the band-pass filter is, for example, 30 Hz to 500 Hz. The modulation frequency of the increasing period Ta and the decreasing period Tb is preferably, for example, 25 Hz or less. Each of the increasing period Ta and the decreasing period Tb is preferably 10 milliseconds or more, preferably 15 milliseconds or more, or 20 milliseconds or more. Each of the increasing period Ta and the decreasing period Tb may be longer than the stop period T2. Ｍ

[0048] ​The start timing of the increase period Ta may be when the amplitude value of the retention period Tc rises to 1%, 5%, or 10%. The end timing of the increase period Ta may be when the amplitude value of the retention period Tc rises to 90%, 95%, or 99%. The start timing of the decrease period Tb may be when the amplitude value of the retention period Tc falls to 99%, 95%, or 90%. The end timing of the decrease period Tb may be when the amplitude value of the retention period Tc falls to 10%, 5%, or 1%. The start timing of the retention period Tc may coincide with the end timing of the increase period Ta. The end timing of the retention period Tc may coincide with the start timing of the decrease period Tb. The start timing of the stop period T2 may coincide with the end timing of the decrease period Tb. The end timing of the stop period T2 may coincide with the start timing of the increase period Ta. The lengths of periods such as the increase period Ta, decrease period Tb, retention period Tc, output period T1, and stop period T2 may be time values ​​or time lengths from the start timing to the end timing of that period.

[0049] The calculation unit 60 calculates the impedance R2 using the output value of the electrode connected to the measurement unit 42. The calculation unit 60 acquires the measurement signal V2 output from the second measurement terminal 42b and calculates the effective value V2r of the measurement signal V2 during the holding period Tc. The measurement signal V2 is the output value of the electrode connected to the measurement unit 42. The calculation unit 60 calculates the impedance R2 of the load resistance 74 using the calculated effective value V2r. The calculation unit 60 calculates the effective value V1r of the measurement signal V1 output from the multiplication circuit 66 during the holding period Tc, and using a preset resistance value R1, it can calculate the impedance R2 using the formula R2 = R1 × V2r / V1r.

[0050] The calculation unit 60 may calculate the impedance R2 using a preset effective value Vr1 instead of calculating the effective value Vr1 each time. In this case, the calculation unit 60 does not need to acquire the measurement signal V1 output from the multiplication circuit 66. The calculation unit 60 may also acquire the modulated wave Vm output from the modulated wave generation circuit 64 and calculate the impedance R2 using the effective value Vr1 based on the amplitude value of the holding period Tc of the modulated wave Vm.

[0051] The retention period Tc is preferably set to a longer length from the viewpoint of improving the accuracy of impedance measurement. The retention period Tc is preferably longer than the increase period Ta or the decrease period Tb. The retention period Tc is, for example, 1.1 times or more, 1.5 times or more, or 2 times or more than the increase period Ta or the decrease period Tb. The retention period Tc is, for example, 10 milliseconds or more, 20 milliseconds or more, or 50 milliseconds or more. The retention period Tc is preferably 1 second or less from the viewpoint of preventing the time required for measurement from becoming too long, for example, 500 milliseconds or less, 200 milliseconds or less, or 100 milliseconds or less.

[0052] Figure 5 schematically shows the output waveform of the measurement signal V2. As shown in Figure 5, the measurement signal V2 includes multiple measurement waveforms 76a1 to 76f4. Each of the multiple measurement waveforms 76a1 to 76f4 is output to each of the multiple electrodes 38a1 to 38f4 by operating the measurement switching unit 54. The state of the measurement switching unit 54 is maintained during the output period T1 and changed during the stop period T2. In other words, the output destination of the measurement signal V2 is fixed during the output period T1 and changed during the stop period T2. In Figure 5, the amplitude values ​​of the multiple measurement waveforms 76a1 to 76f4 are the same, but in reality, they may differ depending on the impedance of each of the multiple electrodes 38a1 to 38f4.

[0053] According to this embodiment, by changing the state of the switching circuit 48 during the stop period T2 when the measurement signal V2 is not output, switching noise that may occur when switching the switch while the measurement signal V2 is output can be suppressed. This prevents switching noise from being superimposed on the electrocardiogram waveform measured using the catheter 12, thus preventing the measurement of an inaccurate electrocardiogram waveform.

[0054] According to this embodiment, by setting the modulation frequencies during the increasing period Ta and decreasing period Tb, which change the amplitude of the measurement signal V2, outside the range of the transmission frequency of the bandpass filter provided at the input of the electrocardiograph 18, it is possible to prevent the measurement signal from superimposing on the electrocardiogram waveform input to the electrocardiograph 18, thereby preventing the measurement of an inaccurate electrocardiogram waveform. Furthermore, by providing a holding period Tc that keeps the amplitude of the measurement signal V2 constant, the accuracy of impedance measurement can be improved.

[0055] Figure 6 is a schematic diagram showing the circuit configuration of the measurement unit 82 in a modified example. In this modified example, a voltage follower circuit using operational amplifier 80 is used instead of the inverting amplifier circuit using operational amplifier 72.

[0056] The measurement unit 82 includes a carrier wave generation circuit 62, a modulated wave generation circuit 64, a multiplication circuit 66, and an operational amplifier 80. The measurement unit 82 has a first measurement terminal 82a and a second measurement terminal 82b. The carrier wave generation circuit 62, the modulated wave generation circuit 64, and the multiplication circuit 66 are configured in the same manner as in the embodiment described above.

[0057] The measurement signal V1 output from the multiplication circuit 66 is supplied to the non-inverting input of the operational amplifier 80. The inverting input of the operational amplifier 80 is connected to the output of the operational amplifier 80. The output of the operational amplifier 80 is connected to the first measurement terminal 82a. The first measurement terminal 82a is connected to the indifferent electrode 38g of the catheter 12. Since the operational amplifier 80 constitutes a voltage follower circuit, the measurement signal V2 output from the operational amplifier 80 is equal to the measurement signal V1 output from the multiplication circuit 66. The second measurement terminal 82b is connected to the measurement switching unit 54. The second measurement terminal 82b is connected to one of the multiple electrodes 38a1 to 38f4 via the measurement switching unit 54. Note that the connections of the first measurement terminal 82a and the second measurement terminal 82b may be reversed, with the first measurement terminal 82a being connected to the measurement switching unit 54 and the second measurement terminal 82b being connected to the indifferent electrode 38g.

[0058] The calculation unit 60 calculates the impedance R2 using the output value of the electrode connected to the measurement unit 82. The calculation unit 60 acquires the measurement signal V2 output from the first measurement terminal 82a and calculates the effective value V2r of the measurement signal V2 during the holding period Tc. The measurement signal V2 is the output value of the electrode connected to the measurement unit 82. The calculation unit 60 acquires the current value I2 output from the second measurement terminal 82b and calculates the effective value I2r of the current value I2 during the holding period Tc. The current value I2 is the output value of the electrode connected to the measurement unit 82. The calculation unit 60 can calculate the impedance R2 using the formula R2 = V2r / I2r.

[0059] The calculation unit 60 may acquire the measurement signal V1 output from the multiplication circuit 66 and calculate the effective value V1r of the measurement signal V1 during the holding period Tc. In this case, the calculation unit 60 can calculate the impedance R2 using the formula R2 = V1r / I2r. Instead of calculating the effective value Vr1 each time, the calculation unit 60 may calculate the impedance R2 using a preset effective value Vr1. In this case, the calculation unit 60 does not need to acquire the measurement signal V1 output from the multiplication circuit 66. The calculation unit 60 may acquire the modulated wave Vm output from the modulated wave generation circuit 64 and calculate the impedance R2 using the effective value Vr1 based on the amplitude value of the modulated wave Vm during the holding period Tc.

[0060] The present disclosure has been described above based on embodiments. Various modifications are possible for each component and each combination of processes in the exemplary embodiments, and it will be obvious to those skilled in the art that such modifications are included within the scope of the present disclosure.

[0061] Certain aspects of this disclosure are as follows:

[0062] The first embodiment is a power supply device connected to a catheter having a plurality of electrodes, comprising: a measuring unit that supplies an amplitude-modulated measuring signal including an increasing period in which the amplitude increases and a decreasing period in which the amplitude decreases; a switching circuit provided between the plurality of electrodes and the measuring unit, which can switch the electrode connected to the measuring unit; a switching control unit that maintains the state of the switching circuit from the start of the increasing period to the end of the decreasing period, and changes the state of the switching circuit from the end of the decreasing period to the start of the increasing period; and a calculation unit that calculates impedance using the output value of the electrode connected to the measuring unit. According to the first embodiment, switching noise can be suppressed by reducing the amplitude of the measuring signal before changing the state of the switching circuit.

[0063] A second embodiment is a power supply device according to the first embodiment, wherein the measuring unit stops supplying the measuring signal during a stop period from the end of the decrease period to the start of the increase period, and the switching control unit changes the state of the switching circuit during the stop period. According to the second embodiment, switching noise can be suppressed by changing the state of the switching circuit during the stop period when the supply of the measuring signal is stopped.

[0064] A third embodiment is the power supply device according to the second embodiment, wherein each of the increase period and the decrease period is longer than the stop period. According to the third embodiment, switching noise can be suppressed by lengthening the increase period and the decrease period.

[0065] A fourth embodiment is a power supply device according to any one of the first to third embodiments, wherein the measuring unit maintains the amplitude of the measurement signal constant during a holding period from the end of the increasing period to the start of the decreasing period, and the calculation unit calculates the impedance using the output value acquired during the holding period. According to the fourth embodiment, the accuracy of impedance measurement can be improved by providing a holding period during which the amplitude of the measurement signal is maintained constant.

[0066] A fifth embodiment is the power supply device according to the fourth embodiment, wherein the holding period is longer than the increase period or the decrease period. According to the fifth embodiment, the accuracy of impedance measurement can be improved by lengthening the holding period for which the amplitude of the measurement signal is kept constant.

[0067] A sixth embodiment is a catheter system comprising a catheter having a plurality of electrodes and a power supply connected to the plurality of electrodes, wherein the power supply includes a measurement unit that supplies an amplitude-modulated measurement signal including an increasing period in which the amplitude increases and a decreasing period in which the amplitude decreases, a switching circuit provided between the plurality of electrodes and the measurement unit and capable of switching the electrode connected to the measurement unit, a switching control unit that maintains the state of the switching circuit from the start of the increasing period to the end of the decreasing period and changes the state of the switching circuit from the end of the decreasing period to the start of the increasing period, and a calculation unit that calculates impedance using the output value of the electrode connected to the measurement unit. According to the sixth embodiment, switching noise can be suppressed by reducing the amplitude of the measurement signal before changing the state of the switching circuit.

[0068] According to this disclosure, switching noise during impedance measurement can be suppressed.

[0069] 10...Catheter system, 12...Catheter, 14...Power supply unit, 38...Electrode, 40...Power supply unit, 42...Measurement unit, 48...Switching circuit, 50...Control unit, 58...Switching control unit, 60...Calculation unit.

Claims

1. A power supply device connected to a catheter having multiple electrodes, comprising: a measuring unit that supplies an amplitude-modulated measuring signal including an increasing period in which the amplitude increases and a decreasing period in which the amplitude decreases; a switching circuit provided between the multiple electrodes and the measuring unit and capable of switching the electrode connected to the measuring unit; a switching control unit that maintains the state of the switching circuit from the start of the increasing period to the end of the decreasing period and changes the state of the switching circuit from the end of the decreasing period to the start of the increasing period; and a calculation unit that calculates impedance using the output value of the electrode connected to the measuring unit.

2. The power supply device according to claim 1, wherein the measuring unit stops supplying the measuring signal during the stop period from the end of the decrease period to the start of the increase period, and the switching control unit changes the state of the switching circuit during the stop period.

3. The power supply device according to claim 2, wherein each of the aforementioned increase period and the aforementioned decrease period is longer than the aforementioned stop period.

4. The power supply device according to any one of claims 1 to 3, wherein the measuring unit maintains the amplitude of the measuring signal constant during a holding period from the end of the increasing period to the start of the decreasing period, and the calculation unit calculates the impedance using the output value acquired during the holding period.

5. The power supply device according to claim 4, wherein the holding period is longer than the increasing period or the decreasing period.

6. A catheter system comprising: a catheter having a plurality of electrodes; a power supply connected to the plurality of electrodes, wherein the power supply includes: a measuring unit that supplies an amplitude-modulated measuring signal including an increasing period in which the amplitude increases and a decreasing period in which the amplitude decreases; a switching circuit provided between the plurality of electrodes and the measuring unit and capable of switching the electrode connected to the measuring unit; a switching control unit that maintains the state of the switching circuit from the start of the increasing period to the end of the decreasing period and changes the state of the switching circuit from the end of the decreasing period to the start of the increasing period; and a calculation unit that calculates impedance using the output value of the electrode connected to the measuring unit.

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