CN116726396A - MRI compatible implantable electric stimulator system and working method thereof - Google Patents
MRI compatible implantable electric stimulator system and working method thereof Download PDFInfo
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- 230000001629 suppression Effects 0.000 claims abstract description 68
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- 238000001514 detection method Methods 0.000 claims description 37
- 238000004891 communication Methods 0.000 claims description 24
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- 238000000338 in vitro Methods 0.000 claims description 4
- 230000007613 environmental effect Effects 0.000 claims description 3
- 238000011282 treatment Methods 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 4
- 238000002595 magnetic resonance imaging Methods 0.000 description 148
- 210000001519 tissue Anatomy 0.000 description 24
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 208000018737 Parkinson disease Diseases 0.000 description 1
- 230000001746 atrial effect Effects 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/362—Heart stimulators
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/02—Details
- A61N1/04—Electrodes
- A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/02—Details
- A61N1/04—Electrodes
- A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
- A61N1/056—Transvascular endocardial electrode systems
- A61N1/0563—Transvascular endocardial electrode systems specially adapted for defibrillation or cardioversion
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- A—HUMAN NECESSITIES
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- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/02—Details
- A61N1/08—Arrangements or circuits for monitoring, protecting, controlling or indicating
- A61N1/086—Magnetic resonance imaging [MRI] compatible leads
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
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- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/3605—Implantable neurostimulators for stimulating central or peripheral nerve system
- A61N1/3606—Implantable neurostimulators for stimulating central or peripheral nerve system adapted for a particular treatment
- A61N1/36103—Neuro-rehabilitation; Repair or reorganisation of neural tissue, e.g. after stroke
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- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/3605—Implantable neurostimulators for stimulating central or peripheral nerve system
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- A—HUMAN NECESSITIES
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- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/362—Heart stimulators
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- A61N1/3718—Monitoring of or protection against external electromagnetic fields or currents
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- A—HUMAN NECESSITIES
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- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
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- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
- A61N1/39—Heart defibrillators
- A61N1/395—Heart defibrillators for treating atrial fibrillation
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/125—Discriminating pulses
- H03K5/1252—Suppression or limitation of noise or interference
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Abstract
The invention relates to the technical field of electric stimulators, and discloses an MRI compatible implantable electric stimulator system and a working method thereof, wherein the system comprises: a pulse generating circuit, an interference suppressing circuit and a control circuit; the pulse generating circuit is used for generating and outputting a stimulation pulse; the interference suppression circuit performs impedance adjustment on the stimulation loop based on a resistance variable mode, and comprises a resistance adjustment device or circuit module; the resistance-adjusting device comprises an adjustable resistor, a sliding rheostat, a digital potentiometer or a semiconductor device with impedance change characteristics; the circuit module for adjusting the resistance comprises a plurality of fixed resistors or resistor strings and a gating switch, and at least one fixed resistor or resistor string is connected into a stimulation loop for adjusting the impedance by controlling the gating switch; the control circuit is used for controlling the impedance adjustment of the interference suppression circuit and the output of the pulse generation circuit. The invention can effectively inhibit the interference stimulation in the MRI environment, reduce the scanning risk of patients and obtain corresponding treatment effects.
Description
Technical Field
The invention relates to the technical field of electric stimulators, in particular to an MRI compatible implantable electric stimulator system and a working method thereof.
Background
Implantable electrical stimulator systems are used in a wide variety of clinical settings, including implantable cardiac pacemakers, implantable atrial defibrillators, implantable neural stimulators, implantable muscle stimulators, and the like.
In the prior art, an implantable electric stimulator system and human tissues form a stimulation loop, and electric pulses with specific parameters are determined and output by communicating with an external device, so that the human tissues are stimulated by the electric pulses to achieve the treatment purpose.
However, in an environment like magnetic resonance imaging (Magnetic Resonance Imaging, MRI), the magnetic field changes so that the magnetic flux passing through the stimulation loop also changes, thereby generating induced electromotive force in the loop direction and inducing induced current, which deflects the electrical pulse acting on the human tissue from specific parameters, disturbing normal stimulation, and bringing a safety risk to the patient.
By post-operative programming, the implantable electrical stimulator system determines an appropriate parameter for treating the respective condition, and stimulation of the target tissue with the parameter tends to achieve optimal therapeutic results, and the parameter varies from person to person. Stimulation of tissues above this parameter tends to have side effects that threaten patient safety; although the stimulation is less than the optimal treatment effect, the stimulation can also play a certain role in treatment. For some scenes that may have security risks (e.g., MRI environments), smaller parametric stimuli than in normal scenes may be allowed.
The maximum output capability of implantable electrical stimulator systems is generally higher than the therapeutic pulse requirements. Taking deep brain stimulator for Parkinson's disease treatment as an example, in voltage stimulation mode, typical therapeutic pulse voltage amplitude ranges generally between 0.5-3.6V; in current stimulation mode, typical therapeutic current pulse amplitudes are generally in the range of 0.7-1.7 mA. However, the stimulation voltage pulse amplitude range of the existing deep brain electric stimulator product is generally between 0 and 10V, and the stimulation current pulse amplitude range of the existing deep brain electric stimulator product is generally between 0 and 20mA under 500 omega load. There is a margin between the technical parameters and typical treatment parameters of existing deep brain electrical stimulator products, existing related products lack full utilization of the typical treatment parameter margin, and the output range of the products is limited.
Disclosure of Invention
In view of the above, the present invention provides an MRI-compatible implantable electrical stimulator system and a working method thereof, which can effectively inhibit the interference stimulation in the MRI environment, output a suitable therapeutic stimulation pulse, reduce the therapeutic safety risk caused by the induced current, and simultaneously ensure the therapeutic effect in the MRI environment, so as to solve the technical problems set forth in the background above.
In a first aspect, the present invention provides an MRI compatible implantable electrostimulator system, the system comprising:
a pulse generating circuit, an interference suppressing circuit and a control circuit;
a pulse generating circuit for generating and outputting a stimulation pulse in the form of: voltage pulses and current pulses;
an interference suppression circuit for impedance adjustment of a stimulation loop based on a resistance variable manner, comprising: a resistance-adjusting device or circuit module;
the resistance-adjusting device includes: an adjustable resistor, a sliding rheostat, a digital potentiometer or a semiconductor device with impedance change characteristics;
the circuit module for resistance adjustment comprises: the device comprises a plurality of fixed resistors or resistor strings and a gating switch, wherein at least one fixed resistor or resistor string is connected into a stimulation loop for impedance adjustment by controlling the gating switch, and the gating switch is a preset multiplexer or a plurality of discrete switching devices or a combination of a plurality of circuit devices and circuit modules;
and the control circuit is used for controlling the impedance adjustment of the interference suppression circuit and the output of the pulse generation circuit.
According to the embodiment, the impedance is adjusted based on the resistance variable mode of the interference suppression circuit, so that the impedance can be improved, the voltage drop of interference at two ends of a tissue is reduced, and the electric stimulator system outputs therapeutic stimulation pulses with proper parameters by controlling the adjustment of the output stimulation pulses, so that the interference stimulation can be effectively suppressed in an MRI environment, and the therapeutic safety risk caused by induced current is reduced.
In an alternative embodiment, in an MRI environment, the control circuit controls the disturbance rejection circuit to increase the stimulation loop impedance according to a preset stimulation loop impedance increment, and the manner in which the disturbance rejection circuit increases the stimulation loop impedance includes: means or circuit modules for disconnecting the stimulation loop and adjusting the resistance adjustment in the disturbance rejection circuit;
according to the output adjustment amount of the preset pulse generating circuit, the control circuit controls the adjustment of the output of the pulse generating circuit, and the output adjustment amount of the preset pulse generating circuit comprises: the pulse generating circuit outputs the voltage amplitude of the pulse and the output power of the pulse generating circuit.
In an alternative embodiment, the system further comprises an impedance detection module, configured to perform impedance sampling on human tissue to obtain tissue impedance information R.
In an alternative embodiment, the control circuit is configured to control the disturbance rejection circuit to increase the impedance while controlling the pulse generation circuit to adjust the output based on the acquired tissue impedance information R in an MRI environment. Specifically, the mode of collecting tissue impedance information through the impedance detection module to adjust the stimulation pulse output is considered, and other impedance information in practical application is considered, so that the interference suppression effect of the electric stimulator system is improved.
In an alternative embodiment, the impedance R of the interference suppression circuit in an MRI environment v The adjusting range is as follows: [0, R v (max)]Wherein R is v (max) is the limiting impedance;
the output regulation range of the pulse generation circuit is as follows: when the stimulus pulse is a voltage pulse VThe voltage regulation range of the output pulse of the pulse generating circuit is +.>If->The voltage regulation range of the output pulse of the pulse generating circuit is [0, V max ]Wherein V is max Is the limit output voltage; when the stimulus pulse is a current pulse I, if P max >I 2 (R+R v ) The power adjustment range of the output pulse of the pulse generating circuit is [0,I ] 2 (R+R v )]If P max ≤I 2 (R+R v ) The power regulation range of the output pulse of the pulse generating circuit is [0, P max ]Wherein P is max Is the limit output power.
In an alternative embodiment, the interference suppression circuit impedance and the pulse generation circuit output are adjusted in such a way that the optimal suppression effect is used in an MRI environment:
when the stimulus pulse is a voltage pulse VThe interference suppression circuit impedance is adjusted to R v (max) the voltage of the output pulse of the pulse generating circuit is adjusted to +.>If->The interference suppression circuit impedance is adjusted to +>The voltage of the output pulse of the pulse generating circuit is regulated to V max ；
When the stimulating pulse is a current pulse At I, if P max >I 2 (R+R v (max)), the interference suppression circuit impedance adjusts to R v (max) the pulse generating circuit outputs a pulse of power regulated at I 2 (R+R v (max); if P max ≤I 2 (R+R v (max)), the interference suppression circuit impedance adjusts toThe power of the output pulse of the pulse generating circuit is regulated to P max 。
The output range formulas of the electric stimulator system for interference suppression provide theoretical reference for researching the interference suppression of the electric stimulator system in the MRI environment.
In an alternative embodiment, the system further includes a feedback circuit for sampling the stimulation pulse to obtain pulse amplitude information, and the control circuit compares the pulse amplitude information obtained by the feedback circuit with a preset pulse amplitude, and adjusts the output of the pulse generating circuit according to the comparison result to ensure that the pulse amplitude information is consistent with the preset pulse amplitude.
In an alternative embodiment, in the MRI environment, the control circuit is configured to control the interference suppression circuit to increase the impedance, and control the pulse generation circuit to adjust the output based on the obtained pulse amplitude information, so as to ensure that the pulse amplitude information is consistent with the preset pulse amplitude within the limit output range of the pulse generation circuit, and if the actual output of the pulse generation circuit exceeds the limit output, control the pulse generation circuit to output at the limit. In particular, in an MRI environment, the present embodiment provides a variety of ways to suppress the interferential stimulation, which is helpful to perfect the function of the electrostimulator system and improve the therapeutic effect.
In an alternative embodiment, the system further comprises an MRI environment detection module for detecting whether the MRI compatible implantable electrostimulator system is in an MRI environment; when it is detected that it is in the MRI environment, transmitting MRI environment state information to the control circuit; transmitting non-MRI environmental status information to the control circuit when it is detected that it is not in the MRI environment; the control circuit adjusts the impedance of the interference suppression circuit and the output of the pulse generation circuit according to the detection result of the MRI environment detection module.
In an alternative embodiment, the system further comprises a communication module, which is used for performing information interaction with an external device, and sending the received external command to the control circuit to perform impedance adjustment of the interference suppression circuit and output adjustment of the pulse generation circuit. In particular, the communication control method of the electric stimulator system of the embodiment has the advantage of diversification.
In an alternative embodiment, the system further incorporates an external control device for information interaction with the communication module for control of the MRI compatible implantable electrical stimulator system by the external control device and for acquisition of system information and patient information. Specifically, the communication control mode of the electric stimulator system has the advantage of integration, and the in-vitro control device is communicated with the electric stimulator after functional integration, so that the working efficiency of the electric stimulator is effectively improved.
In a second aspect, the present invention provides a method of operating an MRI compatible implantable electrical stimulator system, based on the first aspect, an MRI compatible implantable electrical stimulator system, the operating mode of the MRI compatible implantable electrical stimulator system comprising: MRI mode and normal mode;
a normal mode, representing the mode of operation that an MRI compatible implantable electrical stimulator system would assume in a non-MRI environment, comprising: the control circuit adjusts the impedance of the interference suppression circuit to be minimum, and controls the pulse generation circuit to output corresponding stimulation pulses according to a preset parameter value;
an MRI mode, representing the operational mode assumed by an MRI compatible implantable electrical stimulator system in an MRI environment, comprising: the control circuit controls the interference suppression circuit to increase impedance, or controls the pulse generation circuit to adjust output.
In an alternative embodiment, the method for switching between the normal mode and the MRI mode includes the steps of:
step S11, judging whether the communication module receives an MRI mode switching instruction of the external device, if so, entering step S12, and if not, continuing to repeat the step S11;
step S12, switching to an MRI mode, and proceeding to step S13;
step S13, judging whether the communication module receives a common mode switching instruction of the external device, if so, entering step S14, and if not, returning to step S13;
Step S14, switch to the normal mode, and return to step S11.
In an alternative embodiment, the method for switching between the normal mode and the MRI mode includes the steps of:
step S21, an MRI environment detection module detects an external environment and proceeds to step S22;
step S22, judging whether an external magnetic field environment is detected, if so, proceeding to step S23, otherwise, returning to step S21;
step S23, switching to an MRI mode, and proceeding to step S24;
step S24, the MRI environment detection module detects the external environment and proceeds to step S25;
step S25, judging whether the external magnetic field environment disappears, if yes, entering step S26, and if no, returning to step S24;
step S26, switching to the normal mode, and returning to step S21.
In an alternative embodiment, the method for switching between the normal mode and the MRI mode includes the steps of:
step S31, judging whether the communication module receives an MRI environment detection instruction of an external device, if so, entering step S32, and if not, continuing to repeat the step S31;
step S32, an MRI environment detection module detects an external environment and proceeds to step S33;
step S33, judging whether an external magnetic field environment is detected, if so, proceeding to step S34, otherwise, returning to step S32;
Step S34, switching to an MRI mode, and proceeding to step S35;
step S35, the MRI environment detection module detects the external environment and proceeds to step S36;
step S36, judging whether the external magnetic field environment disappears, if yes, entering step S37, if no, returning to step S35;
step S37, switch to the normal mode, and return to step S31.
The implantable electrical stimulator system based on MRI compatibility works, and the switching method corresponding to the working mode has the advantage of diversification, so that the electrical stimulator system can work more flexibly.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of a MRI compatible implantable electrostimulator system in accordance with an embodiment of the present invention;
FIG. 2 is a schematic diagram of an interference suppression circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the control circuit controlling the disturbance rejection circuit impedance and the pulse generation circuit output in both the normal mode and the MRI mode of the implantable electrical stimulator system of the present invention;
FIG. 4 is a block diagram of an MRI compatible implantable electrical stimulator system including an impedance detection module according to the present invention;
FIG. 5 is a schematic diagram of the control circuit controlling the interference suppression circuit impedance and the pulse generation circuit output in both the normal mode and the MRI mode of the implantable electrical stimulator system including the impedance detection module of the present invention;
FIG. 6 is a block diagram of an MRI compatible implantable electrostimulator system incorporating a feedback circuit provided by the present invention;
FIG. 7 is a schematic diagram of the control circuit controlling the interference suppression circuit impedance and the pulse generation circuit output in both the normal mode and the MRI mode of the implantable electrical stimulator system including the feedback circuit of the present invention;
FIG. 8 is a block diagram of an MRI compatible implantable electrical stimulator system including an MRI environment detection module provided in accordance with the present invention;
FIG. 9 is a block diagram of an MRI compatible implantable electrical stimulator system including a communication module provided in accordance with the present invention;
FIG. 10 is a block diagram of a MRI compatible implantable electrical stimulator system incorporating an extracorporeal control apparatus provided in accordance with the present invention;
FIG. 11 is a schematic diagram of an output waveform according to an embodiment of the present invention;
FIG. 12 is a flow chart of switching modes of operation of a system including a communication module according to the present invention;
FIG. 13 is a flow chart of a system operating mode switching process including an MRI environment detection module provided by the present invention;
FIG. 14 is a flow chart of switching modes of operation of a system including a communication module and an MRI environment detection module in accordance with the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
It should be noted that, the implantable electrical stimulator system provided by the present invention includes: an implantable cardiac pacemaker, an implantable neurostimulator, an implantable muscle stimulator, or other implantable electrical stimulator system. The embodiment of the invention is described by taking a deep brain stimulator as an example. The technical index range of the output therapeutic pulse of the existing deep brain stimulator is generally as follows: the voltage amplitude range is 0-10V, the current amplitude range is 0-20mA, the power range is 0-200mW, the pulse width range is 60-450 mu s, and the frequency range is 3-250Hz; the impedance range of the target human tissue is between 0.5 and 2kΩ; if the system adopts a voltage stimulation mode, the voltage amplitude range of typical therapeutic pulses for deep brain electrical stimulation is generally 0.5-3.6V; if the system adopts a current stimulation mode, the current amplitude range of typical therapeutic pulses for deep brain electrical stimulation is generally 0.7-1.7mA.
In the embodiment of the invention, an MRI scanner room is taken as the working environment of the embodiment, and a static magnetic field in an MRI system is generated by a main coil. The static magnetic field strengths commonly used in clinic at present are 1.5T and 3.0T. The static magnetic field is a stable magnetic field, in which the movement of the human body causes a change in magnetic flux in the loop, and since the movement of the human body in the MRI scan room is gentle, the time rate of change of the magnetic flux in the loop is small, and the induced current often cannot cause a neural response.
The gradient field and the radio frequency field are two time-varying fields, and can cause the magnetic flux in the loop to change during MRI scanning, thereby generating external induced voltage.
The gradient field is generated by a gradient coil consisting of three coils, an X-coil, a Y-coil and a Z-coil, which generate spatially varying magnetic fields in each direction, respectively. The gradient field is a magnetic field with a main frequency component of 1-10kHz, so that according to faraday's law of electromagnetic induction, the frequency of the induced voltage caused by the MRI gradient field is also in the range of 1-10kHz, and the induced voltage in this frequency range may trigger a neural response.
The radio frequency field is generated by a radio frequency transmitting coil for generating a radio frequency signal at the same frequency as the precession frequency of the hydrogen nuclei. The radio frequency field also generates an induced electric field at the electrode contact position of the deep brain electric stimulator, the radio frequency field of the MRI is a high-frequency pulse magnetic field with low duty ratio, and for 3.0T MRI, the radio frequency is about 128MHz; for a 1.5TMRI, its RF frequency is approximately 64MHz. Thus, the radio frequency induced electric field is also a MHz pulsed electric field according to faraday's law of electromagnetic induction. However, the International non-ionizing radiation protection Commission (International Commission on Non-Inizing Radiation Protection, ICNIRP) believes that low levels of electrical stimulation above 100kHz do not elicit a neural response.
Therefore, in MRI scanning environments, it is often necessary for patients implanted with medical devices to consider the effect of gradient field induced voltages on therapeutic pulsed electrical stimulation from the point of view of stimulation safety.
Taking the Achieva 3.0T TX multisource magnetic resonance system of Philips company as an example, the static magnetic field of the system is 3.0T, the frequency of the radio frequency field is about 128MHz, and the gradient field is an alternating magnetic field with the frequency range of 1-10 kHz. The maximum amplitude of induced voltage in the deep brain electric stimulator loop caused by the gradient field of the MRI system is 150mV through experimental measurement.
Example 1
An embodiment of the present invention provides an MRI compatible implantable electrostimulator system, as shown in fig. 1, comprising: pulse generation circuit, interference suppression circuit and control circuit.
In this embodiment, the pulse generating circuit is configured to generate and output a stimulation pulse, where the stimulation pulse includes: voltage pulses and current pulses; and the control circuit is used for controlling the impedance adjustment of the interference suppression circuit and the output of the pulse generation circuit.
In this embodiment, the interference suppression circuit is configured to perform impedance adjustment on the stimulation loop based on a resistance variable manner, and includes: a resistance-adjusting device or circuit module. Specifically, the resistance-adjusting device includes: an adjustable resistor, a sliding rheostat, a digital potentiometer or a semiconductor device with impedance change characteristics; the circuit module for resistance adjustment comprises: the device comprises a plurality of fixed resistors or resistor strings and a gating switch, wherein at least one fixed resistor or resistor string is connected into a stimulation loop for impedance adjustment by controlling the gating switch, and the gating switch is a preset multiplexer or a plurality of discrete switching devices or a combination of various circuit devices and circuit modules. It should be noted that, the impedance adjustment mode of the interference suppression circuit is determined according to the actual application requirement.
In this embodiment, the operating modes of the MRI compatible implantable electrical stimulator system include: MRI mode and normal mode; a normal mode, representing the mode of operation that an MRI compatible implantable electrical stimulator system would assume in a non-MRI environment, comprising: the control circuit adjusts the impedance of the interference suppression circuit to be minimum, and controls the pulse generation circuit to output corresponding stimulation pulses according to a preset parameter value; an MRI mode, representing the operational mode assumed by an MRI compatible implantable electrical stimulator system in an MRI environment, comprising: the control circuit controls the interference suppression circuit to increase impedance, or controls the pulse generation circuit to adjust output.
As shown in fig. 2, the present embodiment provides an interference suppression circuit based on a plurality of fixed resistors and a gate switch. As can be seen from the figure, the interference suppression circuit selects a fixed resistor with eight resistance values of 0 Ω, 500 Ω, 1kΩ, 2kΩ, 3kΩ, 5kΩ, 10kΩ, and 20kΩ as the impedance adjustment options, and selects a multiplexer with 1 to 8 as the gating switch. Specifically, in the MRI compatible implantable electrical stimulator system in the normal mode, the control circuit inputs corresponding high-low level signals to ports A0, A1, A2 and EN, and controls the multiplexer channel S1 to be turned on, and at this time, the impedance of the interference suppression circuit is the on impedance of the multiplexing switch, which is negligible; at the same time, the control circuit controls the pulse generating circuit to output corresponding stimulation pulses according to the set parameter values. In the MRI mode, the control circuit inputs corresponding high-low level signals to the ports A0, A1, A2 and EN according to the set parameter values and tissue impedance information R, so that the channels corresponding to the multiplexer are conducted, and at the moment, the impedance of the interference suppression circuit is a fixed resistance value for conducting channel connection. It should be noted that, the specific form of the interference suppression circuit and the impedance value in the loop are all taken as examples, and the interference suppression circuit is not limited thereto, and is adaptively adjusted according to practical application requirements.
In this embodiment, in an MRI environment, according to a preset stimulation loop impedance increment, the control circuit controls the disturbance rejection circuit to increase the stimulation loop impedance, and the manner in which the disturbance rejection circuit increases the stimulation loop impedance includes: means or circuit modules for disconnecting the stimulation loop and adjusting the resistance adjustment in the disturbance rejection circuit; according to the output adjustment amount of the preset pulse generating circuit, the control circuit controls the adjustment of the output of the pulse generating circuit, and the output adjustment amount of the preset pulse generating circuit comprises: the pulse generating circuit outputs the voltage amplitude of the pulse and the output power of the pulse generating circuit. It should be noted that, specific values and modes of the preset stimulation loop impedance increment, the preset pulse generation circuit output adjustment amount and the mode of improving the stimulation loop impedance are determined according to actual application requirements.
In one embodiment, the different modes of operation of the implantable electrical stimulator system and the corresponding pulse output conditions are shown in FIG. 3. In the normal mode, the control circuit adjusts the impedance of the interference suppression circuit to the minimum, and controls the pulse generation circuit to output corresponding pulses according to the preset stimulation pulse parameters. If the stimulating pulse is a voltage pulse, the amplitude of the pulse output by the pulse generating circuit is V OUT The amplitude of the stimulation pulse is V at the moment; if the stimulating pulse is a current pulse, the amplitude of the pulse output by the pulse generating circuit is I OUT The power is P OUT At this time, the amplitude of the stimulation pulse is I. In the MRI mode, the control circuit increases the interference suppression circuit impedance to R according to a preset stimulation loop impedance increment v The output of the pulse generating circuit is increased or decreased according to a preset pulse generating circuit adjustment amount. If the stimulating pulse is a voltage pulse, the amplitude of the pulse output by the pulse generating circuit is regulated to V OUT_MRI At this time, the amplitude of the stimulation pulse is V MRI ，V MRI V may be greater than or equal to V; if the stimulating pulse is a current pulse, the power of the pulse output by the pulse generating circuit is regulated to P OUT_MRI At this time, the amplitude of the stimulation pulse is I MRI ，I MRI I may be greater than or equal to I.
In this embodiment, as shown in fig. 4, the system further includes an impedance detection module, configured to perform impedance sampling on human tissue to obtain tissue impedance information R.
In this embodiment, in the MRI environment, the control circuit is configured to control the disturbance rejection circuit to increase the impedance, and control the pulse generation circuit to adjust the output based on the obtained tissue impedance information R. Specifically, the mode that the impedance detection module collects tissue impedance information to regulate the output of the stimulation pulse considers other impedance information in practical application, and is beneficial to improving the interference suppression effect of the electric stimulator system.
In the present embodiment, the impedance R of the interference suppression circuit is in the MRI environment v The adjusting range is as follows: [0, R v (max)]Wherein R is v (max) is the limiting impedance;
the output regulation range of the pulse generation circuit is as follows: when the stimulus pulse is a voltage pulse VThe voltage regulation range of the output pulse of the pulse generating circuit is +.>If->The voltage regulation range of the output pulse of the pulse generating circuit is [0, V max ]Wherein V is max Is the limit output voltage; when the stimulus pulse is a current pulse I, if P max >I 2 (R+R v ) The power adjustment range of the output pulse of the pulse generating circuit is [0,I ] 2 (R+R v )]If P max ≤I 2 (R+R v ) The power regulation range of the output pulse of the pulse generating circuit is [0, P max ]Wherein P is max Is the limit output power.
In this embodiment, when the optimal suppression effect is used in the MRI environment, the adjustment modes of the interference suppression circuit impedance and the pulse generation circuit output are as follows:
when the stimulus pulse is a voltage pulse VThe interference suppression circuit impedance is adjusted to R v (max) the voltage of the pulse output by the pulse generating circuit is adjusted to be; if->The interference suppression circuit impedance is adjusted to +>The voltage of the output pulse of the pulse generating circuit is regulated to V max ；
When the stimulus pulse is a current pulse I, if P max >I 2 (R+R v (max)), the interference suppression circuit impedance adjusts to R v (max) the pulse generating circuit outputs a pulse of power regulated at I 2 (R+R v (max); if P max ≤I 2 (R+R v (max)), the interference suppression circuit impedance adjusts toThe power of the output pulse of the pulse generating circuit is regulated to P max . Specifically, the output range formulas of the electric stimulator system for interference suppression in the embodiment provide theoretical reference for researching the interference suppression of the electric stimulator system in the MRI environment.
In one embodiment, the different operation modes and corresponding pulse output conditions of the implantable electrical stimulator system including the impedance detection module are shown in fig. 5. In the normal mode, the control circuit adjusts the impedance of the interference suppression circuit to the minimum, and controls the pulse generation circuit to output corresponding pulses according to the preset stimulation pulse parameters. If the stimulating pulse is a voltage pulse, the amplitude of the pulse output by the pulse generating circuit is V OUT The amplitude of the stimulation pulse is V at the moment; if the stimulating pulse is a current pulse, the amplitude of the pulse output by the pulse generating circuit is I OUT The power is P OUT At this time, the amplitude of the stimulation pulse is I. In the MRI mode, the control circuit increases the interference suppression circuit impedance to R according to a preset stimulation loop impedance increment v And increases or decreases the output of the pulse generating circuit based on the tissue impedance information R acquired by the impedance detecting module. If the stimulating pulse is a voltage pulse, the amplitude of the pulse output by the pulse generating circuit is regulated to V OUT_MRI When (when)When (I)>When->V at the time of OUT_MRI ∈[0,V max ]At this time, the amplitude of the stimulation pulse is V MRI And V is MRI V is less than or equal to V; if the stimulating pulse is a current pulse, the power of the pulse output by the pulse generating circuit is regulated to P OUT_MRI When P max >I 2 (R+R v ) At the time P OUT_MRI ∈[0,I 2 (R+R v )]When P max ≤I 2 (R+R v ) At the time P OUT_MRI ∈[0,P max ]At this time, the amplitude of the stimulation pulse is I MRI And I MRI ≤I。
In this embodiment, as shown in fig. 6, the system further includes a feedback circuit, configured to sample the stimulus pulse to obtain pulse amplitude information, and the control circuit compares the pulse amplitude information obtained by the feedback circuit with a preset pulse amplitude, and adjusts the output of the pulse generating circuit according to the comparison result, so as to ensure that the pulse amplitude information is consistent with the preset pulse amplitude.
In this embodiment, in an MRI environment, the control circuit is configured to control the disturbance suppression circuit to increase impedance, and control the pulse generation circuit to adjust output based on the obtained pulse amplitude information, so as to ensure that the pulse amplitude information is consistent with the preset pulse amplitude within the limit output range of the pulse generation circuit, and if the actual output of the pulse generation circuit exceeds the limit output, control the pulse generation circuit to output with the limit.
In one embodiment, the different modes of operation and corresponding pulse output of the implantable electrical stimulator system including the feedback circuit are shown in fig. 7. In the normal mode, the control circuit adjusts the impedance of the interference suppression circuit to the minimum, and controls the pulse generation circuit to output corresponding pulses according to the preset stimulation pulse parameters. If the stimulating pulse is a voltage pulse, the amplitude of the pulse output by the pulse generating circuit is V OUT The amplitude of the stimulation pulse is V at the moment; if the stimulating pulse is a current pulse, the amplitude of the pulse output by the pulse generating circuit is I OUT The power is P OUT At this time, the amplitude of the stimulation pulse is I. In the MRI mode, the control circuit controls the stimulation circuit according to the preset stimulation circuitIncreasing the interference rejection circuit impedance by an increase in impedance to R v And increases the output of the pulse generating circuit based on the pulse amplitude information acquired by the feedback circuit. If the stimulating pulse is a voltage pulse, the amplitude of the pulse output by the pulse generating circuit is increased to V OUT_MRI When (when)When (I)>When->V at the time of OUT_MRI ＝V max At this time, the amplitude of the stimulation pulse is V MRI When->V at the time of MRI =v, when->V at the time of MRI <V, V; if the stimulating pulse is a current pulse, the power of the pulse output by the pulse generating circuit is increased to P OUT_MRI When P max >I 2 (R+R v ) At the time P OUT_MRI ＝I 2 (R+R v ) When P max ≤I 2 (R+R v ) At the time P OUT_MRI ＝P max At this time, the amplitude of the stimulation pulse is I MRI When P max ≥I 2 (R+R v ) When I MRI =i, when P max <I 2 (R+R v ) When I MRI <I。
In this embodiment, as shown in fig. 8, the system further comprises an MRI environment detection module for detecting whether the MRI compatible implantable electrostimulator system is in an MRI environment; when it is detected that it is in the MRI environment, transmitting MRI environment state information to the control circuit; transmitting non-MRI environmental status information to the control circuit when it is detected that it is not in the MRI environment; the control circuit adjusts the impedance of the interference suppression circuit and the output of the pulse generation circuit according to the detection result of the MRI environment detection module.
In this embodiment, as shown in fig. 9, the system further includes a communication module, configured to interact with an external device, and send a received external command to the control circuit to perform impedance adjustment of the interference suppression circuit and output adjustment of the pulse generation circuit.
In this embodiment, as shown in fig. 10, the system further combines the external control device to perform information interaction with the communication module, so as to control the MRI compatible implantable electro-stimulator system and acquire system information and patient information by the external control device. Specifically, the communication control mode of the electric stimulator system has the advantage of integration, and the in-vitro control device is communicated with the electric stimulator after functional integration, so that the working efficiency of the electric stimulator is effectively improved.
It should be noted that, each module or circuit of the MRI compatible implantable electrostimulator system of the present embodiment not only can be used alone according to its function, but also can be used in combination with each other, and the specific use condition of each module or circuit is determined according to the actual application requirement.
In one embodiment, the method is applied to a deep brain stimulator system, and fig. 11 is a schematic diagram of an output waveform corresponding to the structure of the stimulator system of fig. 10. From the graph, the technical index range of the therapeutic pulse includes: the voltage amplitude range V is 0-10V, the power range P is 0-200mW, the pulse width range W is 60-450 mu s, and the frequency range f is 3-250Hz; the technical index range of the pulse output by the pulse generating circuit comprises: voltage amplitude range V OUT Power range P of 0-15V OUT The pulse width range W is 60-450 mu s, and the frequency range f is 3-250Hz; interference suppression circuit impedance adjustment range R v 0-20kΩ.
Specifically, in the current stimulation mode, if stimulation is performed using a maximum current amplitude of 1.7mA, the tissue impedance R is a maximum value of 2kΩ. In the normal mode, the voltage value U at two ends of human tissue is 3.4V; in an MRI environment, the gradient field induced voltage is V ind If the MRI mode does not take conservative stimulus, the interference suppression circuit impedance R v Should be set asThe voltage applied across the tissue by the gradient field induced voltage becomes +.>In this limit case, the suppression ratio of the gradient field induced voltage is +.>Therefore, in the current stimulation mode, if no conservative stimulation is adopted, the voltage of the gradient field induced voltage loaded to the two ends of the tissue can be reduced by 77.3%, so that the interference of the gradient field induced voltage on the normal stimulation is greatly inhibited, and the safety risk of a patient is greatly reduced.
In the voltage stimulation mode, the stimulation is performed by using the maximum voltage amplitude of 3.6V, and the tissue impedance R is the maximum value of 2kΩ; in an MRI environment, the gradient field induced voltage is V ind If the MRI mode does not take conservative stimulus, the interference suppression circuit impedance R v Should be set asThe voltage applied across the tissue by the gradient field induced voltage becomes +.>In this limit case, the suppression ratio of the gradient field induced voltage is +.>Therefore, in the voltage stimulation mode, if no conservative stimulation is adopted, the voltage of the gradient field induced voltage loaded to the two ends of the tissue can be reduced by 76.0%, so that the interference of the gradient field induced voltage on the normal stimulation is greatly inhibited, and the safety risk of a patient is greatly reduced.
In summary, according to the analysis of the limit conditions of different stimulation modes, the MRI-compatible implantable electro-stimulator system of the present embodiment effectively and largely suppresses the interference of the gradient field induced voltage on the normal stimulation, and practically reduces the safety risk of the patient in the MRI environment.
Example 2
The embodiment of the invention provides a working method of an MRI compatible implantable electric stimulator system, which is based on the MRI compatible implantable electric stimulator system of the embodiment 1. The MRI compatible implantable electrical stimulator system of the present embodiment includes a method for switching between a normal mode and an MRI mode of a communication module, as shown in fig. 12, including the following steps:
step S11, judging whether the communication module receives an MRI mode switching instruction of the external device, if so, entering step S12, and if not, continuing to repeat the step S11;
Step S12, switching to an MRI mode, and proceeding to step S13;
step S13, judging whether the communication module receives a common mode switching instruction of the external device, if so, entering step S14, and if not, returning to step S13;
step S14, switch to the normal mode, and return to step S11.
In this embodiment, the MRI compatible implantable electrical stimulator system includes a method for switching between a normal mode and an MRI mode of an MRI environment detection module, as shown in fig. 13, and includes the following steps:
step S21, an MRI environment detection module detects an external environment and proceeds to step S22;
step S22, judging whether an external magnetic field environment is detected, if so, proceeding to step S23, otherwise, returning to step S21;
step S23, switching to an MRI mode, and proceeding to step S24;
step S24, the MRI environment detection module detects the external environment and proceeds to step S25;
step S25, judging whether the external magnetic field environment disappears, if yes, entering step S26, and if no, returning to step S24;
step S26, switching to the normal mode, and returning to step S21.
In this embodiment, the MRI compatible implantable electrical stimulator system includes a normal mode of the communication module and the MRI environment detection module and an operation mode switching method of the MRI mode, as shown in fig. 14, including the steps of:
Step S31, judging whether the communication module receives an MRI environment detection instruction of an external device, if so, entering step S32, and if not, continuing to repeat the step S31;
step S32, an MRI environment detection module detects an external environment and proceeds to step S33;
step S33, judging whether an external magnetic field environment is detected, if so, proceeding to step S34, otherwise, returning to step S32;
step S34, switching to an MRI mode, and proceeding to step S35;
step S35, the MRI environment detection module detects the external environment and proceeds to step S36;
step S36, judging whether the external magnetic field environment disappears, if yes, entering step S37, if no, returning to step S35;
step S37, switch to the normal mode, and return to step S31.
The operation mode of the electric stimulator system provided by the embodiment of the invention has various switching methods, so that the electric stimulator system works more flexibly and has the advantage of diversification.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (15)
1. An MRI-compatible implantable electrostimulator system, the system comprising:
a pulse generating circuit, an interference suppressing circuit and a control circuit;
the pulse generation circuit is used for generating and outputting a stimulation pulse, and the form of the stimulation pulse comprises: voltage pulses and current pulses;
the interference suppression circuit is used for performing impedance adjustment on the stimulation loop based on a resistance variable mode, and comprises the following components: a resistance-adjusting device or circuit module;
the resistance-adjusting device includes: an adjustable resistor, a sliding rheostat, a digital potentiometer or a semiconductor device with impedance change characteristics;
the circuit module for resistance adjustment comprises: the device comprises a plurality of fixed resistors or resistor strings and a gating switch, wherein at least one fixed resistor or resistor string is connected into a stimulation loop for impedance adjustment by controlling the gating switch, and the gating switch is a preset multiplexer or a plurality of discrete switching devices or a combination of various circuit devices and circuit modules;
the control circuit is used for controlling the impedance adjustment of the interference suppression circuit and the output of the pulse generation circuit.
2. The MRI compatible implantable electrical stimulator system according to claim 1, wherein the control circuit controls the disturbance rejection circuit to increase the stimulation loop impedance according to a preset stimulation loop impedance increment in an MRI environment, the manner in which the disturbance rejection circuit increases the stimulation loop impedance comprising: means or circuit modules for disconnecting the stimulation loop and adjusting the resistance adjustment in the disturbance rejection circuit;
According to the output adjustment quantity of the preset pulse generating circuit, the control circuit controls the adjustment of the output of the pulse generating circuit, and the output adjustment quantity of the preset pulse generating circuit comprises: the pulse generating circuit outputs the voltage amplitude of the pulse and the output power of the pulse generating circuit.
3. The MRI compatible implantable electrical stimulator system according to claim 1, further comprising an impedance detection module for impedance sampling of human tissue to obtain tissue impedance information R.
4. The MRI compatible implantable electrical stimulator system according to claim 3, wherein the control circuit is configured to control the pulse generation circuit to adjust the output based on the obtained tissue impedance information R while controlling the disturbance rejection circuit to increase the impedance in the MRI environment.
5. The MRI compatible implantable electrical stimulator system according to claim 4, wherein the impedance R of the disturbance rejection circuit is in an MRI environment v The adjusting range is as follows: [0, R v (max)]Wherein R is v (max) is the limiting impedance;
the output regulation range of the pulse generation circuit is as follows: when the stimulus pulse is a voltage pulse VThe voltage regulation range of the output pulse of the pulse generating circuit is +.>If- >The voltage regulation range of the output pulse of the pulse generating circuit is [0, V max ]Wherein V is max Is the limit output voltage; when the stimulus pulse is a current pulse I, if P max >I 2 (R+R v ) The power adjustment range of the output pulse of the pulse generating circuit is [0,I ] 2 (R+R v )]If P max ≤I 2 (R+R v ) The power regulation range of the output pulse of the pulse generating circuit is [0, P max ]Wherein P is max Is the limit output power.
6. The MRI compatible implantable electrical stimulator system according to claim 5, wherein the interference suppression circuit impedance and the pulse generation circuit output are adjusted in a manner that:
when the stimulus pulse is a voltage pulse VThe interference suppression circuit impedance is adjusted to R v (max) the voltage of the output pulse of the pulse generating circuit is adjusted to +.>If->The interference suppression circuit impedance is adjusted to +>The voltage of the output pulse of the pulse generating circuit is regulated to V max ；
When the stimulus pulse is a current pulse I, if P max >I 2 (R+R v (max)), the interference suppression circuit impedance adjusts to R v (max) the pulse generating circuit outputs a pulse of power regulated at I 2 (R+R v (max); if P max ≤I 2 (R+R v (max)), the interference suppression circuit impedance adjusts toThe power of the pulse output by the pulse generating circuit is regulated to be P max 。
7. The MRI compatible implantable electrical stimulator system according to claim 1, further comprising a feedback circuit for sampling the stimulation pulses to obtain pulse amplitude information, wherein the control circuit compares the pulse amplitude information obtained by the feedback circuit with a preset pulse amplitude, and adjusts the output of the pulse generating circuit according to the comparison result to ensure that the pulse amplitude information is consistent with the preset pulse amplitude.
8. The MRI compatible implantable electrical stimulator system according to claim 7, wherein the control circuit is configured to control the disturbance rejection circuit to increase the impedance while controlling the pulse generation circuit to adjust the output based on the obtained pulse amplitude information, wherein the pulse amplitude information is ensured to be consistent with the preset pulse amplitude within a limit output range of the pulse generation circuit, and wherein the pulse generation circuit is controlled to output at a limit if an actual output of the pulse generation circuit exceeds the limit output.
9. The MRI-compatible implantable electrical stimulator system according to claim 1, further comprising an MRI environment detection module for detecting whether the MRI-compatible implantable electrical stimulator system is in an MRI environment; when it is detected that it is in the MRI environment, transmitting MRI environment state information to the control circuit; transmitting non-MRI environmental status information to the control circuit when it is detected that it is not in the MRI environment; the control circuit adjusts the impedance of the interference suppression circuit and the output of the pulse generation circuit according to the detection result of the MRI environment detection module.
10. The MRI compatible implantable electrical stimulator system according to claim 1, further comprising a communication module for interacting with an external device and transmitting received external commands to the control circuit for impedance adjustment of the disturbance rejection circuit and output adjustment of the pulse generation circuit.
11. The MRI compatible implantable electrical stimulator system according to claim 10, further comprising an in vitro control device in communication with the communication module for control of the MRI compatible implantable electrical stimulator system by the in vitro control device and for acquisition of system information and patient information.
12. A method of operating an MRI compatible implantable electrostimulator system, based on the MRI compatible implantable electrostimulator system according to any one of the claims 1 to 11, characterized in that,
an operational mode of an MRI compatible implantable electrical stimulator system, comprising: MRI mode and normal mode;
the normal mode, representing the operational mode assumed by the MRI compatible implantable electrical stimulator system in a non-MRI environment, comprises: the control circuit adjusts the impedance of the interference suppression circuit to be minimum, and controls the pulse generation circuit to output corresponding stimulation pulses according to a preset parameter value;
The MRI mode, representing an operational mode assumed by the MRI-compatible implantable electrostimulator system in an MRI environment, comprises: the control circuit controls the interference suppression circuit to increase impedance, or controls the pulse generation circuit to adjust output.
13. The method of operating an MRI-compatible implantable electrical stimulator system according to claim 12, wherein the method of switching between the normal mode and the MRI mode comprises the steps of:
step S11, judging whether the communication module receives an MRI mode switching instruction of the external device, if so, entering step S12, and if not, continuing to repeat the step S11;
step S12, switching to an MRI mode, and proceeding to step S13;
step S13, judging whether the communication module receives a common mode switching instruction of an external device, if so, entering step S14, and if not, returning to step S13;
step S14, switch to the normal mode, and return to step S11.
14. The method of operating an MRI-compatible implantable electrical stimulator system according to claim 12, wherein the method of switching between the normal mode and the MRI mode comprises the steps of:
step S21, an MRI environment detection module detects an external environment and proceeds to step S22;
Step S22, judging whether an external magnetic field environment is detected, if so, proceeding to step S23, otherwise, returning to step S21;
step S23, switching to an MRI mode, and proceeding to step S24;
step S24, the MRI environment detection module detects the external environment and proceeds to step S25;
step S25, judging whether the external magnetic field environment disappears, if yes, entering step S26, and if no, returning to step S24;
step S26, switching to the normal mode, and returning to step S21.
15. The method of operating an MRI-compatible implantable electrical stimulator system according to claim 12, wherein the method of switching between the normal mode and the MRI mode comprises the steps of:
step S31, judging whether the communication module receives an MRI environment detection instruction of an external device, if so, entering step S32, and if not, continuing to repeat the step S31;
step S32, an MRI environment detection module detects an external environment and proceeds to step S33;
step S33, judging whether an external magnetic field environment is detected, if so, proceeding to step S34, otherwise, returning to step S32;
step S34, switching to an MRI mode, and proceeding to step S35;
step S35, the MRI environment detection module detects the external environment and proceeds to step S36;
Step S36, judging whether the external magnetic field environment disappears, if yes, entering step S37, if no, returning to step S35;
step S37, switch to the normal mode, and return to step S31.
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