CN106075730B - It is a kind of to join the electromagnetic excitation method for realizing time-scale extension with multiple activation source level - Google Patents

Abstract

The electromagnetic excitation method of the present invention realizes time expansion by cascading multiple excitation sources, uses a small current as the excitation current of the coil, and quickly cuts off the current to increase the rate of change of the current to reduce the amplitude of the excitation current to generate The transient electromagnetic field meets the requirements, and the excitation time is extended by adopting multiple coils cascaded and sequentially discharged to realize the expansion of the excitation time. The multiple coils are cascaded and sequentially discharged to complete the charging of multiple coils. Then discharge in sequence, or for multiple coils to switch between charging and discharging of the coils during the charging process to complete sequential cyclic discharge. The invention enables the electromagnetic field excitation system using small current as the coil excitation current to realize the effective expansion of single excitation time, and the realization method is simple and easy to control or adjust.

Description

An Electromagnetic Excitation Method Realizing Time Expansion by Cascading Multiple Excitation Sources

technical field

The invention relates to an electromagnetic excitation method, in particular to an electromagnetic excitation method for realizing time expansion by cascading multiple excitation sources, and the specific application in medical instruments is transcranial magnetic stimulation based on small current.

Background technique

A typical application of transient electromagnetic fields in the medical field is a technique called Transcranial Magnetic Stimulation (Transcranial Magnetic Stimulation, abbreviation: TMS). TMS is a form of electrodeless stimulation, which uses an excitation coil to generate a time-varying magnetic field to induce a current in the target tissue to stimulate excitable tissue. When the current flows through the TMS excitation coil, a time-varying magnetic field will be generated around it. This strong and rapidly changing magnetic field can penetrate human skin and skull and other tissues. The ability to stimulate nerves was first discovered by D'Arsonval in 1896 when he observed the phenomenon of magneto-induced flashes. For a long time thereafter, the research on magnetic stimulation was limited to magneto-induced flashes. Brickford et al. observed skeletal muscle twitches when they magnetically stimulated intact rabbits, frogs, and humans in 1965, but further work was not carried out because there was no clear application purpose. In 1985, Barker et al. used a small magnetic coil driven by a pulse current below 0.3 Hz to stimulate the normal human brain cortex almost painlessly and non-invasively, observed hand muscle twitching, and recorded movement in the little finger abductor muscle with surface electrodes Cortical evoked potentials (MEPs), and presented to delegates from around the world at the 11th EEG and Clinical Neurophysiology Congress in London, the encouraging results caused a great sensation, this method was later called transcranial Magnetic stimulation (Transcranial Magnetic Stimulation, TMS). In 1987, Amassian et al., and in 1990, Cohen et al. respectively proved by experiments that stimulation coils placed in different directions can cause different finger activities on the cerebral cortex.

The above-mentioned applied electromagnetic field excitation system is usually driven by a large current pulse to obtain the required transient electromagnetic field. In order to obtain sufficient electromagnetic field strength, the driving current of the excitation system is large, the pulse width is large, the hardware circuit of the excitation system consumes a lot of power, it is difficult to realize, and there are great safety hazards, especially the application safety in the medical field is a problem that cannot be ignored. important question.

Aiming at the problems of high power consumption and safety, the patent with the publication number of 102614592A proposes to use a small current to replace the traditional high current working method. Although this method overcomes the problems of power consumption and safety, the discharge time of the small current is short, and the resulting Transient electromagnetic fields often have insufficient stimulation time, which may not be enough to trigger the expected nerve excitation, so they have great limitations in medical efficacy.

Contents of the invention

The purpose of the present invention is to provide a safe, reliable, and long stimulation time electromagnetic excitation method that realizes time expansion by cascading multiple excitation sources. The transient electromagnetic field in the present invention can stimulate target media such as nerves. And effectively extend the incentive time.

The present invention is realized through the following technical solutions: an electromagnetic excitation method that realizes time expansion by cascading multiple excitation sources, uses a small current as the excitation current of the coil, and cuts off the current quickly to increase the current change rate to reduce the amplitude of the excitation current. A transient electromagnetic field that meets the requirements is generated around the coil, and the electromagnetic field excitation system prolongs the excitation time by cascading multiple coils and sequentially discharging to realize the extension of the excitation time.

According to the present invention, an electromagnetic excitation method that realizes time expansion by cascading multiple excitation sources, the manner in which multiple coils are cascaded and sequentially discharged refers to that multiple coils that are charged start to discharge sequentially and extend the discharge equivalently. The end time, that is, the discharge start time of the Nth coil among the multiple coils is t _{as and} the discharge end time is t _ae , the discharge start time of the N+1th coil is t _bs and the discharge end time is t _be , and N is positive integer; said t _bs lags t _as and t _be lags t _ae .

In the electromagnetic excitation method of the present invention, which realizes time expansion by cascading multiple excitation sources, the overlapping time between the discharge duration of the Nth coil and the discharge duration of the N+1th coil is t _ab , t _ab =t _bs -t _ae ; said t _ab >0, that is, t _bs is ahead of t _ae .

In the electromagnetic excitation method of the present invention, which realizes time expansion by cascading multiple excitation sources, the overlapping time between the discharge duration of the Nth coil and the discharge duration of the N+1th coil is t _ab , t _ab =t _bs -t _ae ; said t _ab =0, that is, t _bs coincides with t _ae .

In the electromagnetic excitation method of the present invention, which realizes time expansion by cascading multiple excitation sources, the overlapping time between the discharge duration of the Nth coil and the discharge duration of the N+1th coil is t _ab , t _ab =t _bs -t _ae ; the time length for the induced voltage generated by the discharge of the Nth coil to freely decay to zero in the target medium is t _r , t _r ﹥0; the t _ab ﹤0 and |t _ab |≦ t _r .

According to the electromagnetic excitation method of the present invention, which implements time expansion by cascading multiple excitation sources, the Nth coil is charging or has completed charging when it starts to discharge.

According to the present invention, an electromagnetic excitation method that realizes time extension by cascading multiple excitation sources, the initial current before the coil starts to discharge and the end current after the discharge ends during the process of cascading multiple coils and sequentially discharging are constant currents.

It is suitable for an electromagnetic field excitation system of an electromagnetic excitation method that realizes time expansion by cascading multiple excitation sources according to the present invention. The electromagnetic field excitation system includes coils connected to each other and a coil drive circuit. Connected charging circuit, discharging circuit. The charging circuit is connected in series with the coil, and the discharging circuit is connected in parallel with the coil.

Specifically, the charging circuit includes a charging diode, a charging resistor, and a charging switch connected in series with the coil in sequence, and the discharging circuit includes a series circuit of a discharging resistor and a discharging diode connected in parallel at both ends of the coil.

Preferably, the charging switch adopts a semiconductor switching device, the control electrode of the semiconductor switching device is connected to the control signal circuit, and the spike absorbing circuit is connected in parallel to both ends of the charging switch to suppress the influence of the spike on the circuit.

The electromagnetic field excitation method of the present invention can adjust the discharge time by adjusting the inductance value of the coil and the resistance value in the discharge circuit, and adjust the current change rate by adjusting the parameter of the discharge duration in the discharge circuit.

Further, the coil driving circuit further includes a spike absorbing circuit connected to the coil.

Further, the electromagnetic field excitation system also includes a control signal circuit, a system protection circuit, and a power supply system respectively connected to the coil drive circuit, and the coil drive circuit, the coil, the control signal circuit, the system protection circuit, and the power supply system are all provided with a Above, the control signal circuits connected one by one to the coils are also connected to the control chip, and the control chip sends control signals to the corresponding coils respectively through the control signal circuits, and the timing of the control signals is controlled by the delay program in the computer software. Multiple control signal circuits can share one control chip.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The present invention adopts small electric current to replace traditional high electric current, is guaranteed aspect safety performance;

(2) The present invention adopts the mode of coil cascading, which solves the problem of time extension, so that the stimulation time to the target medium is sufficient;

(3) Since the discharge duration of each coil in the present invention can be different, although the initial current of each coil is a constant current, the current value can be different, although the end current of each coil is a constant current, but the current value can be different, so The specific operation of the invention to realize the expansion of the incentive time is very flexible, has few limiting factors, and is easy to realize;

(4) The device structure of the electromagnetic field excitation system involved in the present invention is simple, lightweight and portable.

Description of drawings

Figure 1 is a schematic diagram of simulated nerve stimulation.

FIG. 2 is a schematic diagram of the time sequence of current decay in two adjacent coils in state A.

FIG. 3 is a schematic diagram of the timing sequence of current decay in two adjacent coils in the B state.

FIG. 4 is a schematic diagram of the time sequence of current decay in two adjacent coils in the C state.

Fig. 5 is a schematic diagram of the overall structure of the system of the present invention.

Fig. 6 is a schematic diagram of the core circuit of the present invention.

Fig. 7 is a system program flow chart of the present invention.

Among them: 1—nerve, 2—Nth coil, 3—N+1 coil, 4—coil drive circuit, 5—coil, 6—control signal circuit, 7—system protection circuit, 8—power supply system, 9 -control signal.

Detailed ways

The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

In order to improve the safety of current transcranial magnetic stimulation, the present invention abandons the large-current wide-pulse excitation scheme usually adopted in the traditional technology, and instead uses a small current as the excitation current of the excitation coil. According to the basic principle of electromagnetic induction, changing current produces a changing magnetic field, and the current stimulus excited by the changing magnetic field in the target medium is positively correlated with the rate of change of the excitation coil current. The present invention utilizes this principle and replaces the pulse current with a small rate of change and large amplitude with a pulse current with a large rate of change and a small amplitude to achieve the same stimulating effect.

In practical applications, there is often a problem of insufficient stimulation time when small currents pass through the coils. The solution of the present invention is to extend the excitation time by adopting multiple coils cascaded and sequentially discharging to realize the extension of the excitation time.

Example 1

Take the cascade connection of two coils as an example: as shown in FIG. 1 , the nerve 1 is stimulated by the transient magnetic field generated by the current decay in the Nth coil 2 and the N+1th coil 3 in the cascade.

The schematic diagram of the overall structure of the system of the present invention is shown in Figure 5. The system can be subdivided into two sets of identical systems controlled simultaneously by a control chip 9, wherein one set of systems includes a coil drive circuit 4 and is connected to the coil drive circuit 4 respectively. Coil 5, control signal circuit 6, system protection circuit 7, power supply system 8. Wherein the coil driving circuit 4 includes a charging circuit connected in series with the coil 5, a discharging circuit connected in parallel with the coil 5, and a peak absorbing circuit. The charging circuit and the discharging circuit provide charging and discharging paths for the coil 5 respectively, so that there is a variable current in the coil 5, This in turn produces a changing magnetic field. The control chip 9 is DSP5509. During the working process of the system, the control chip 9 will generate two control signals at the same time, and control the two systems respectively. The control signal is a pulse signal. In practical applications, the control chip 9 can also use other types DSP chip or single-chip microcomputer, FPGA (programmable gate array). The control signal circuit 6 uses the control chip 9 to control the on and off of the coil drive circuit 4 . The system protection circuit 8 is mainly for overheating and overcurrent protection. When the temperature in the circuit system is too high or the current is too large, the circuit system will automatically shut down and stop working. The power supply system is a 12V regulated power supply, but mature technologies such as switches can also be used in practical applications to convert the mains AC into the DC required for system work.

The core circuit of this embodiment is shown in Figure 6, wherein the power supply PWR is the power supply system 8, and the power supply PWR provides a 12V regulated power supply for the system (the specific circuit is not shown in Figure 6). Coil L1 corresponds to coil 5 in the schematic diagram of the overall system structure in FIG. 5 . Resistor R6, diode D5, variable resistor VR2, resistor R11, diode D10, NMOS transistor Q4, ground GND, diode D11, capacitor C4, diode D12, and resistor R12 form a coil drive circuit 4, wherein the charging circuit includes a circuit connected in series with the coil L1 The diode D5, the variable resistor VR2, the NMOS transistor Q4, and the ground GND, wherein the NMOS transistor Q4 is used as the charging switch of the coil drive circuit 4, and the discharge circuit includes a series connection composed of a resistor R6, a resistor R11, and a diode D10 connected in parallel at both ends of the coil L1. circuit, the peak absorbing circuit is composed of diode D11, capacitor C4, diode D12, and resistor R12, and its function is to suppress the influence of the peak pulse on the circuit. The control signal circuit 6 includes a signal input terminal, an optocoupler U4 connected to the signal input terminal, and a push-pull output circuit composed of transistor Q5, transistor Q6, transistor Q7, resistor R17 and resistor R18 connected to the optocoupler U4, wherein the signal input The terminal is connected to the pulse signal PAS _- PULS output by the DSP5509 chip, and the pulse signal PAS _- PULS is input to the push-pull output circuit through the optocoupler U4, and finally input to the gate of the NMOS transistor Q4 in the coil drive circuit 4 through the resistor R15, thereby controlling the NMOS The drain and source of the tube Q4 are turned on or off. The optocoupler U4 plays the role of signal input and output through the conversion of electricity-optical-electricity. In addition, the input and output of the optocoupler U4 are isolated from each other, and the electrical signal transmission is It has the characteristics of unidirectionality, so it has good electrical insulation ability and anti-interference ability, and because the input end of the optocoupler is a low-resistance element with current-type operation, it has strong common-mode rejection ability, and the push-pull output circuit Mainly used to enhance driving ability. The core circuit of this example is a system protection circuit 8 except for the above-mentioned parts. The system protection circuit 8 is the protection of overcurrent and overheating, and the protection of the entire system is realized by a relay. Since the protection circuit belongs to mature technology, and the improvement of the present invention The point has nothing to do with the protection circuit, so the structure of the protection circuit will not be repeated here.

The working principle of the circuit in this example is that when the pulse signal PAS _- PULS output by the DSP5509 chip is at low level, the optocoupler U4 is turned on, and the pulse signal PAS _- PULS is input to the push-pull output circuit through the optocoupler U4 to amplify and generate polarity reversal. Change to a high level, and then input the gate of the NMOS transistor Q4. Since the NMOS transistor is a high-conduction MOS transistor, when the gate input signal is high, its drain and source are turned on, so the charging circuit is completely turned on. , the coil L1 starts to charge, when the pulse signal PAS _- PULS output by the DSP5509 chip is high level, the optocoupler U4 is cut off, the coil L1 starts to discharge through the discharge circuit, and the transient electromagnetic field can be generated when the current in the coil L1 decays and changes. In addition, since the time constant of the RL circuit is T=L/R, the charging time can be adjusted by adjusting the inductance value of the coil L1 and the resistance value of the charging circuit, and the charging time can be adjusted by adjusting the inductance value of the coil L1 and the resistance value of the discharging circuit. Adjust the discharge time.

The following is a schematic diagram of the current decay in the Nth coil 2 and the N+1th coil 3 during the specific implementation process of an electromagnetic excitation method that implements time expansion by cascading multiple excitation sources according to the present invention.

As shown in Figure 2, Figure 3, and Figure 4, the symbols in the figure are explained as follows:

I _as : initial current of the Nth coil;

I _ae : the ending current of the Nth coil;

I _bs : initial current of coil N+1;

I _be : the end current of the N+1th coil;

t ₀ : start time;

t _as : start time of Nth coil discharge;

t _ae : discharge end time of the Nth coil;

t _ad : the discharge duration of the Nth coil;

t _bs : start time of coil N+1 discharge;

t _be : end time of discharge of coil N+1;

t _bd : the discharge duration of the N+1th coil;

t ₂ : termination time;

t _ab : the overlapping time of the respective discharges of the Nth coil and the N+1th coil, that is, t _ab =t _bs -t _ae ;

t _r : target recovery time.

The Nth coil and the N+1th coil are two adjacent discharge coils, and the Nth coil discharges first and the N+1th coil discharges after the same round of discharge. If the Nth coil and the N+1th coil are in the middle of multiple coils, there may be multiple coils that have completed the discharge before the Nth coil starts to discharge (that is, before t _as ); similarly, the Nth coil After +1 coil starts discharging (i.e. after t _bs ), there may be multiple coils that continue to start discharging.

The target recovery time t _r refers to the length of time for a certain coil to discharge and generate an induced voltage in the target medium, and the induced voltage freely decays to zero in the target medium. The t _r varies with the target medium and its state.

First of all, under normal circumstances, the current after the coil is discharged is 0, but there is no absolute requirement, as long as it is kept constant. Secondly, the initial currents of the multiple coils are not required to be consistent, as long as they are kept constant. Moreover, the discharge duration t _ad of the Nth coil and the discharge duration _tbd of the N+1th coil are not required to be consistent, and may be adjusted according to design requirements.

As shown in Figure 2, t ₀ ﹤t _as ﹤t _bs ﹤t _ae ﹤t _be ﹤t ₂ , at this time t _ab >0, that is, when the current in the Nth coil 2 begins to decay, the N+1th coil 3 starts to decay, and the N+1th coil 3 continues to decay after the Nth coil 2 decays, so that the excitation time can be extended.

As shown in Figure 3, t ₀ ﹤t _as ﹤t _bs ＝t _ae ﹤t _be ﹤t ₂ , at this time t _ab =0, that is, the current in the Nth coil 2 starts to decay first, when the Nth coil 2 At the end of the attenuation, the N+1th coil 3 begins to attenuate, and the N+1th coil 3 continues to attenuate for a period of time before ending, so that the excitation time can be extended.

As shown in Figure 4, t ₀ ﹤t _as ﹤t _ae ﹤t _bs ﹤t _be ﹤t ₂ and, at this time, t _ab ﹤0, that is, the N+1th coil after the current decay in the Nth coil 2 ends The current in 3 begins to decay, so that the extension of the excitation time can be realized.

On the basis of the timing diagram of current decay in two adjacent coils in state C as shown in Figure 4, if "t ₀ ﹤t _as ﹤t _ae ﹤t _bs ﹤t _be ﹤t ₂ , t _ab ﹤0 And |t _ab |≦t _r ”, that is, the time when the current in the N+1th coil 3 begins to decay and the time when the decay of the Nth coil 2 ends is less than or equal to the induced voltage generated by the discharge of the Nth coil 2 within the target The time for free decay to zero in the medium can better achieve the effect of continuous excitation.

After the currents in the Nth coil 2 and the N+1th coil 3 are both attenuated, the system starts to charge them again, and repeats the above attenuation process again.

In the above embodiment, the timing of the two pulse signals PAS _- PULS is controlled by the pre-set program in the DSP5509 chip. By adjusting the timing of the pulse signal PAS _- PULS, the timing of charging and discharging of the coil 5 and the time between the coils 5 can be controlled. Charge and discharge gap.

By analogy, three, four or even more coils can be cascaded according to needs, and the principle is the same as above to achieve longer expansion.

Example 2

This embodiment is further optimized on the basis of Embodiment 1: the manner in which multiple coils are cascaded and sequentially discharged in the present invention can be that multiple coils are discharged one by one after charging is completed, or that multiple During the charging process, the cycle discharge is carried out through the charging and discharging switching of the coil.

Take two adjacent coils that are discharged sequentially after charging as an example: the specific system program flow chart is shown in Figure 7. First, the clock is initialized, that is, the two I/O ports connected to the control signal circuit on the DSP5509 chip are set as High level and delay t ₁ After the system is stable, set the two I/O ports to low level, that is, charge the two coils at the same time, and then set the first I/O port to high level after charging is completed , the coil 5 in the circuit connected to the first I/O port starts to decay the current and generate a transient magnetic field. After the current decay in the coil 5 in the circuit connected to the first I/O port is completed, the second The two I/O ports are set to high level, and the coil 5 in the circuit connected to the second I/O port starts to decay the current and generate a transient magnetic field. When the currents in the two coils 5 are all decayed, the program Return to the initialization state again to enter the next round of work, so that the continuous cycle can realize the expansion of the incentive time.

Take two adjacent coils that are cyclically discharged through the charging and discharging switching of the coil during the charging process as an example: through the software control of the two pulse signals sent by the control chip, when one of the signals is set to high level, the other signal Set it to a low level, so that when one coil is discharged, the other coil is charged, that is, the two coils are complementary to each other to realize the cyclic discharge of the coils one by one without gaps.

Other parts of this embodiment are the same as those of Embodiment 1, so details are not repeated here.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications and equivalent changes made to the above embodiments according to the technical essence of the present invention all fall within the scope of the present invention. within the scope of protection.

Claims (10)

1. An electromagnetic excitation method that realizes time expansion by cascading multiple excitation sources, using a small current as the excitation current of the coil, and increasing the current change rate by quickly cutting off the current to reduce the required excitation current amplitude, so that the excitation current around the coil Generating a transient electromagnetic field that meets requirements is characterized in that the electromagnetic field excitation system prolongs the excitation time by adopting a plurality of coils cascaded and sequentially discharged to realize the extension of the excitation time. 2. An electromagnetic excitation method for realizing time extension by cascading multiple excitation sources according to claim 1, characterized in that: the method of cascading and sequentially discharging the plurality of coils refers to: charging multiple coils sequentially Start the discharge and extend the discharge end time equivalently, that is, the discharge start time of the Nth coil among the multiple coils is t _as , the discharge end time is t _ae , the discharge start time of the N+1th coil is t _bs , and the discharge end time is t ae . The moment is t _be , and N is a positive integer; t _bs lags behind t _as and t _be lags behind t _ae . 3. A kind of electromagnetic excitation method realizing time extension by multi-excitation source cascading according to claim 2, characterized in that: the intersection of the Nth coil discharge duration and the N+1th coil discharge duration The stacking time is t _ab , t _ab =t _bs −t _ae ; said t _ab >0, that is, t _bs is ahead of t _ae . 4. A kind of electromagnetic excitation method realizing time extension by multi-excitation source cascading according to claim 2, characterized in that: the intersection of the discharge duration of the Nth coil and the discharge duration of the N+1th coil The stacking time is _tab , where _tab =t _bs -t _ae ; the _tab =0, that is, t _bs coincides with t _ae . 5. An electromagnetic excitation method for realizing time extension by cascading multiple excitation sources according to claim 2, characterized in that: the intersection of the discharge duration of the Nth coil and the discharge duration of the N+1th coil The stacking time is t _ab , t _ab =t _bs -t _ae ; the time length for the induced voltage generated by the discharge of the Nth coil to freely decay to zero in the target medium is t _r , t _r ﹥0; the t _ab < 0 and |t _ab |≦t _r . 6. An electromagnetic excitation method for realizing time expansion by cascading multiple excitation sources according to claim 1, characterized in that: the initial current before the coils start to discharge during the process of cascading and sequentially discharging the plurality of coils And the end current after the end of the discharge is a constant current. 7. A kind of electromagnetic excitation method realizing time expansion by cascading multiple excitation sources according to any one of claims 1-6, characterized in that: the electromagnetic field excitation system includes interconnected coils (5), coil drive The circuit (4), the coil driving circuit (4) includes a charging circuit and a discharging circuit respectively connected to the coil (5). 8. A kind of electromagnetic excitation method realizing time expansion by cascading multiple excitation sources according to claim 7, characterized in that: the discharge time can be adjusted by adjusting the inductance value of the coil (5) and the resistance value in the discharge circuit , the rate of change of current is adjusted by adjusting the parameters of the discharge duration in the discharge circuit. 9 . The electromagnetic excitation method for realizing time extension by cascading multiple excitation sources according to claim 7 , characterized in that: the coil drive circuit ( 4 ) further comprises a peak absorbing circuit connected to the coil ( 5 ). 10. A kind of electromagnetic excitation method that realizes time extension with multi-excitation source cascading according to claim 7, is characterized in that: described electromagnetic field excitation system also comprises the control signal circuit ( 6), system protection circuit (7), power supply system (8), described coil drive circuit (4), coil (5), control signal circuit (6), system protection circuit (7), power supply system (8) all More than one control signal circuit (6) connected to the coil (5) in one-to-one correspondence is also connected to the control chip (9), and the control chip (9) sends a signal to the corresponding coil (5) through the control signal circuit (6). The control signals are sent out respectively, and the timing of the control signals is controlled by the delay program in the computer software.