CN108714027A - A kind of device and measurement method for measuring multi-electrode/scalp contact impedance in real time - Google Patents
A kind of device and measurement method for measuring multi-electrode/scalp contact impedance in real time Download PDFInfo
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Abstract
The invention discloses a kind of devices and measurement method for measuring multi-electrode/scalp contact impedance in real time, belong to bio-electrical impedance imaging technology and application field.The device includes host computer, main control unit, exciting current signal generation unit, boundary voltage signal measurement unit, excitation channel, Measurement channel and contact impedance measurement module.The present invention is on the basis of original imaging electrode, introduce a distal reference electrode, when contact impedance measures, multiple imaging electrodes are switched into contact impedance measuring circuit successively by electrode channel control unit, real-time synchronization Measured Boundary voltage data and contact impedance data may be implemented by electrode channel control unit.This method can accurately measure to obtain contact impedance following two dimensions information：1, the Space Consistency of multichannel contact impedance；2, the time stability of single channel contact impedance.It is easy to operate compared to existing measurement method, it can measure in real time.
Description
Technical field
The invention belongs to bio-electrical impedance imaging fields, and in particular to one kind connects for measuring multi-electrode/scalp in real time
Touch the device and measurement method of impedance.
Background technology
Cranium brain Review of Electrical Impedance Tomography is a kind of novel cranium brain functional imaging technology, has noninvasive, radiationless, imaging soon
Speed, can the advantages such as long-time continuous imaging.Its basic principle is：It is injected successively to cranium brain using the electrode being placed in scalp surface
The ac current signal of quantitative safety, while the response voltage signal on each related electrode is measured, and pass through specific image weight
Algorithm is built, reconstruct obtains to react the image of inside the cranium electrical impedance distribution.
Cranium brain electric impedance imaging system includes multiple imaging electrodes, 16 electrodes of generally use or 32 electrodes, and institute
There is imaging electrode to be multiplexed between applying current excitation and extracting response two kinds of functions of voltage signal.Compared to other simple biologies
Electric signal extracts occasion (such as electroencephalograph, brain-computer interface), and cranium brain electrical impedance imaging is influenced by electrode/scalp contact impedance
Degree is increasingly complex.In previous experiments room is studied, it is intradermal or be fixed on skull that electrode is usually pierced into postanesthetic animal head
On, it can effectively inhibit the influence of scalp/contact impedance.But in clinical application, electrode is attached at scalp surface, electrode/head
Skin contact impedance is larger, and is much larger than cranium brain organizing transmission impedance；In long-time continuous imaging, with conductive paste performance degradation
And patient's body is dynamic, electrode/scalp contact impedance generates fluctuation at any time.Correlative study proves, when the contact of multiple imaging electrodes
There are when larger difference between impedance, the performance by influencing signal acquiring system causes measurement error；It is continuously adopted for a long time
During collection, when contact impedance is larger with the fluctuation of time, image error is introduced in Difference Imaging process.
Currently, resting on simulation study about the research that electrode in cranium brain electrical impedance imaging/scalp contact impedance influences more
Stage temporarily lacks the means that can obtain multichannel contact impedance Space Consistency and time stability in real time.
Invention content
The purpose of the present invention is to provide a kind of device and measurements for measuring multi-electrode/scalp contact impedance in real time
Method, the device acquire gap using electrical impedance imaging data, can obtain the corresponding contact of multiple imaging electrodes quickly, in real time
Impedance information lays the foundation to research and analyse influence and corresponding suppressing method of the electrode/scalp contact impedance to imaging.
The present invention is to be achieved through the following technical solutions：
A kind of device for measuring multi-electrode/scalp contact impedance in real time disclosed by the invention, including host computer, master
Control unit, exciting current signal generation unit, boundary voltage signal measurement unit, excitation channel, Measurement channel and contact impedance
Measurement module；The contact impedance measurement module is by electrode unit, electrode channel control unit, contact impedance signal measurement unit
And exciting current signal measurement unit composition；Wherein：
Electrode unit, including one group of imaging electrode and a reference electrode, imaging electrode is for obtaining electrical impedance imaging number
According to reference electrode is used for the contact impedance of each imaging electrode of subsidiary；
Electrode channel control unit, the switching for encouraging channel and Measurement channel by control realize that boundary voltage is surveyed
Amount and contact impedance measure the blocked operation of both of which, and the time interval of both of which is within 1s；
Contact impedance signal measurement unit is used for the (response between imaging electrode and reference electrode of contact impedance signal
Voltage signal) processing after be transmitted to main control unit；The processing such as processing refers to being filtered, amplify, signal condition, then carry out
A/D is converted；
Exciting current signal measurement unit, for will exciting current signal (voltage signals at sample resistance both ends) processing after
It is transmitted to main control unit；The processing such as processing refers to being filtered, amplify, signal condition, then carry out A/D conversions；
Host computer is interacted by data-interface with main control unit, for sending control instruction, main control unit to main control unit
The data of acquisition are uploaded to host computer；Main control unit is generating exchange just by controlling exciting current signal generation unit first
Then excitation channel and Measurement channel is arranged by electrode channel control unit in string current signal, finally by control boundary electricity
Press signal measurement unit, exciting current signal measurement unit and contact impedance signal measurement unit data acquisition.
Preferably, the imaging electrode has both two kinds of functions of current excitation and voltage measurement, is placed in scalp table to be measured
Face is usually uniformly distributed in a certain specific section of cranium brain；
Preferably, the reference electrode, there are two types of alternatives altogether：One is Dispoable medical monopolar needle electrode, syringe needles
Using inclined-plane low-angle sharpening structure；Another kind is tack surface electrode, and structure is similar to disposable electrocardioelectrode, but Ag/
AgCl plate areas is much larger than common electrocardioelectrode, can be placed at the top of cranium brain；Both the above electrode is purchased in regular medical treatment
Instruments, Inc, safety are ensured.
Preferably, the electrode channel control unit, including the multi-channel analog of multiple control imaging electrode channels switching are opened
Close the single-pole single-throw switch (SPST) device of device and multiple control reference electrode channel ON/OFF.
It is further preferred that multiple imaging electrodes are controlled using four 1 analog switch devices of multiselect, with MUX1 and MUX2 points
Not Kong Zhi positive incentive channel and negative incentive channel, MUX3 and MUX4 control positive Measurement channel respectively and negative sense measure it is logical
Road；Reference electrode is controlled using two single-pole single-throw switch (SPST) devices SPST1 and SPST2；
Under boundary voltage signal measurement pattern, SPST1 and SPST2 are disconnected, and MUX1, MUX2, MUX3 and MUX4's is enabled
Pin sets high level, by controlling the gating of MUX1, MUX2, MUX3 and MUX4, setting excitation channel and Measurement channel；
Under contact impedance signal measurement pattern, SPST1 and SPST2 are connected, and the enable pin of MUX1 and MUX3 set high electricity
Flat, the enable pin of MUX2 and MUX4 set low level, and by controlling the gating of MUX1 and MUX3, setting encourages channel and measures logical
Road.
Preferably, the contact impedance signal measurement unit, by filter circuit, fixed gain signal amplification circuit, program-controlled
Gain signal amplifying circuit and A/D conversion circuits composition, for measuring " two electrode methods " corresponding voltage signal；The excitation electricity
Signal measurement unit is flowed, by sample resistance, filter circuit, fixed gain signal amplification circuit, programme-controlled gain signal amplification circuit
It is formed with A/D conversion circuits, for measuring " two electrode methods " corresponding current signal.
It is further preferred that sample resistance, has high-precision, Low Drift Temperature characteristic；Filter circuit, by second order active low pass filtered
Wave device and second order active high-pass filter composition；Fixed gain signal amplification circuit is first order amplifying circuit, by precision resistance
It is formed with operational amplifier；Programme-controlled gain signal amplification circuit is second level amplifying circuit, by programmable gain amplifier part group
At, can dynamically adjust its gain ranging, with meet amplitude compared in wide dynamic range signal amplify demand；A/D conversion electricity
Road is made of, the late-class circuit as signal measurement unit the analog-digital converter of high-speed, high precision and its peripheral circuitry.
The invention also discloses the measurement methods based on above-mentioned measuring device, include the following steps：
1) electrode is arranged
One group of imaging electrode and fixation are placed by the conventional method of cranium brain resistance imaging, is then chosen and each imaging electrode
Between the approximately uniform position of distance place a reference electrode；
2) boundary voltage data acquire
By electrode channel control unit, reference electrode access is disconnected, and switches several imaging electricity in one group successively
Frame boundaries voltage data acquisition is completed in pole, and boundary piezo data is used to be imaged, as imaging data；
3) contact impedance data are acquired with exciting current data
Contact impedance data acquire：By electrode channel control unit, reference electrode access is connected, gates successively in order
Imaging electrode channel；Using two electrode methods, exciting current signal is injected between reference electrode and gated imaging electrode, and survey
The voltage signal between two electrodes is measured, U is denoted asi, wherein i=1,2 ..., N are electrode number, and N is the number of imaging electrode；
Exciting current data acquire：By measuring the voltage signal on sample resistance, exciting current signal, note are measured indirectly
Make USampling；
4) step 2) and step 3) are repeated, into next frame data collection cycle, until host computer is sent " terminating acquisition "
Instruction.
Preferably, it is selected as needed when arrangement reference electrode in step 1), if taking Dispoable medical monopole needle electric
Pole, is pierced under scalp and fixed after disinfecting, according to disposable customization reference electrode, its note is placed on scalp surface and solid
It is fixed；
Preferably, in step 3), the practical exciting current when imaging electrode i is gated is：
Ii=USampling/RSampling；
Then use the impedance value measured by two electrode methods for：
Zi=Ui/Ii=Ui/(USampling/RSampling)=Ui*RSampling/USampling；
ZiEssence be tested imaging electrode contact impedance Zci, transfer impedance between imaging electrode and reference electrode
ZtiThe sum of with the contact impedance Zcf three of reference electrode, i.e.,：
Zi=Zci+Zti+Zcf；
Define Δ Zm,nIt is as follows：
Wherein, m, n=1,2 ..., N and m ≠ n；Zcm-ZcnFor the difference of the contact impedance of imaging electrode m and imaging electrode n,
It is denoted as Δ Zcm,n；Ztm-ZtnFor the difference of imaging electrode m and imaging electrode the n transfer impedance between reference electrode respectively, it is denoted as
ΔZtm,n；Zcfm-ZcfnThe fluctuating error of reference electrode contact impedance when to measure twice, is denoted as Δ Zcfm,n。
Preferably, the two kinds of reference electrodes chosen in the present invention, one of which can be pierced under scalp, and one kind has larger
Effective contact area, it can be ensured that Zcf < < ZciAnd Δ Zcfm,n≈ 0, with reference between electrode and each imaging electrode
Distance it is approximately the same, can ensure each ZtiBetween otherness it is small, that is, meet：ΔZtm,n< < Δs Zcm,n；
Then have：ΔZcm,n=Zcm-Zcn≈Zm-Zn；
Define Δ Zi(t1, t2) is：
Wherein, i=1,2 ..., N；T1, t2 are two moment；Zci(t1)-Zci(t2) it is t1, i-th between two moment of t2
The changing value of a imaging electrode contact impedance, is denoted as Δ Zci(t1,t2)；Zti(t1)-Zti(t2) it is t1, the between two moment of t2
The changing value of i imaging electrode contact impedance is denoted as Δ Zti(t1,t2)；ΔZcfi(t1, t2) is t1, and t2 joins between two moment
Examine the changing value of electrode contact impedance；
Transfer impedance is influenced by electrode position and encephalic impedance variations, compared to contact impedance, time stability compared with
Height, i.e. Δ Zti(t1,t2)≈0；Reference electrode contact impedance reaches time stability, i.e. Δ Zcf by manual interventioni(t1,
t2)≈0。
We can obtain the contact impedance information of two dimensions, i.e. multi-channel image electrode by this method measurement as a result,
Contact impedance Space Consistency index Δ Zcm,nWith the time stability index Δ per the contact impedance of imaging electrode all the way
Zci(t1,t2)。
Compared with prior art, the present invention has technique effect beneficial below：
Device disclosed by the invention for measuring multi-electrode/scalp contact impedance in real time is provided with a contact and hinders
Anti- measurement module, the module are believed by electrode unit, electrode channel control unit, contact impedance signal measurement unit and exciting current
Number measuring unit composition.Wherein, electrode unit includes one group of imaging electrode and a reference electrode.The present invention is in original imaging electricity
On the basis of pole, introducing a distal reference electrode successively will be multiple by electrode channel control unit when contact impedance measures
Imaging electrode switches into contact impedance measuring circuit, and real-time synchronization Measured Boundary may be implemented by electrode channel control unit
Voltage data and contact impedance data.Contact impedance signal measurement unit, exciting current signal measurement unit in the present invention and
Boundary voltage signal measurement unit three is independent mutually, to meet the high-acruracy survey of different amplitudes, signal with different type.
Method for real-time measurement disclosed by the invention for multi-electrode/scalp contact impedance in cranium brain electrical impedance imaging,
Using " two electrode methods " measuring principle, it is utilized respectively exciting current signal measurement unit and contact impedance signal measurement unit measures
It is actually implanted into current signal and response voltage signal between each imaging electrode and reference electrode, and each is calculated
Impedance value between imaging electrode and reference electrode；Thus Space Consistency and the time stability letter of analyzing multiple contact impedance
Breath.This method can accurately measure to obtain contact impedance following two dimensions information：1, the space one of multichannel contact impedance
Cause property；2, the time stability of single channel contact impedance.It is easy to operate compared to existing measurement method, it can measure in real time, more than acquisition
The accuracy higher of two dimensional informations, influence and its suppressing method for research contact impedance to cranium brain electrical impedance imaging are established
Basis.
Description of the drawings
Fig. 1 is cranium brain electrical impedance imaging DATA REASONING pattern diagram；
Fig. 2 is contact impedance collecting method schematic diagram；
Fig. 3 is that imaging electrode is placed with schematic diagram with reference electrode；
Fig. 4 is cranium brain electrical impedance imaging hardware system structure block diagram；
Fig. 5 is the structural schematic diagram of electrode channel control unit；
Fig. 6 is 16 path electrodes/scalp contact impedance Space Consistency analysis result (16 road contact impedances are more uniform)；Its
In, (a) is 16 road contact impedance measured values (Ω)；(b) it is 16 road contact impedance relative differents (%)；
Fig. 7 is 16 path electrodes/scalp contact impedance Space Consistency analysis result (deposit by the contact impedance of No. 6 imaging electrodes
In exception)；Wherein, (a) is 16 road contact impedance measured values (Ω)；(b) it is 16 road contact impedance relative differents (%)；
Fig. 8 is 16 path electrodes/scalp contact impedance time stability analysis result (contact impedance wave of No. 8 imaging electrodes
Dynamic property is larger)；Wherein, (a) is measured value (Ω) of the 16 road contact impedances at t1 moment and t2 moment；(b) it is the contact resistance of 16 tunnels
Resist the opposite variation (%) between t1 moment and t2 moment.
Specific implementation mode
With reference to specific embodiment, the present invention is described in further detail, it is described be explanation of the invention and
It is not to limit.
The purpose of the present embodiment is that realizing the contact impedance for measuring 16 road imaging electrodes in real time.For 16 electrode cranium brain electricity
Impedance imaging system, using the data acquisition scheme of " offside encourages, neighbouring to measure ".The system encourages electrode pair for totally 16, often
One excitation electrode to corresponding to 16 measuring electrodes pair respectively, therefore a partial data acquisition includes 256 measurements, i.e. a frame number
According to including 256 measured values.It is shown referring to Fig. 1, Fig. 1：It encourages electrode opposite direction cranium brain to inject exciting current by 1-9, measures
3-4 measuring electrodes are to upper response voltage signal.Since there are contact impedances, i.e. Zc in figure between imaging electrode and scalp1、
Zc3、Zc4And Zc9.Therefore, pumping signal circuit and measuring signal circuit are influenced by contact impedance simultaneously.
1, measuring principle introduction
Provided by the present invention for the real-time measurement side of multi-electrode in cranium brain electric impedance imaging system/scalp contact impedance
Method, principle are：The impedance value between each imaging electrode and reference electrode is measured in real time using two electrode methods, and is analyzed according to this
The contact impedance information of multi-channel image electrode is obtained, as shown in Figure 2.
16 imaging electrodes of the present embodiment, are placed in scalp surface, are uniformly distributed in a certain specific section of cranium brain；Ginseng
It examines electrode and uses tack surface electrode, be placed at the top of cranium brain, it is approximately the same at a distance from 16 imaging electrodes, such as Fig. 3 institutes
Show.
The real-time measuring modules of multi-electrode provided by the invention/scalp contact impedance, the cranium brain electrical impedance constituted
The structure diagram of imaging hardware system is as shown in Figure 4.The system is by host computer, data-interface, main control unit, exciting current signal
Generation unit, boundary voltage signal measurement unit, contact impedance signal measurement unit, exciting current signal measurement unit, electrode
Channel control unit and electrode unit composition.Wherein, included each unit constitutes 16 path electrodes/scalp contact impedance in dotted line frame
Measurement module.
The operation principle of cranium brain electric impedance imaging system is：Host computer sends control instruction by data-interface and gives master control list
Member.After main control unit receives data acquisition instructions, set frequency is generated by controlling exciting current signal generation unit first
The AC sine current signal of rate, amplitude；Then pass through electrode channel control unit, setting excitation channel and Measurement channel；Most
It is completed afterwards by controlling boundary voltage signal measurement unit, contact impedance signal measurement unit and exciting current signal measurement unit
Data acquire.Institute's gathered data is uploaded to host computer by main control unit by data-interface.Wherein, boundary voltage signal measurement list
Member is used for Measured Boundary voltage signal；Contact impedance signal measurement unit and exciting current signal measurement unit are respectively used for measuring
" two electrode methods " corresponding voltage signal and current signal, are then obtained by calculation contact impedance value.
In the present embodiment, exciting current signal when contact impedance measures and exciting current when boundary voltage signal measurement
Signal is generated by the same exciting current signal generation unit.Its operation principle is：Digital frequency synthesis technology is used first, by
DAC devices generate needed for frequency, amplitude sinusoidal AC voltage signal, after filtered, enhanced processing, converted by voltage-controlled current source
At simple sinusoidal alternating current signal.The electric amplitude range of the current signal is 10~2500uA, and frequency range is 1k~200kHz.This
Embodiment uses current amplitude for 1250uA, frequency 50kHz.
In the present embodiment, the concrete scheme of electrode channel control unit control excitation channel and Measurement channel is as shown in Figure 5.
1 analog switch device is selected to control 16 imaging electrodes using four 16, it is logical that MUX1 and MUX2 control positively and negatively excitation respectively
Road, MUX3 and MUX4 control positively and negatively Measurement channel respectively.Using two single-pole single-throw switch (SPST) devices (SPST1 and
SPST2 reference electrode) is controlled.Under boundary voltage data acquisition scheme, SPST1 and SPST2 are disconnected, the enabled pipe of MUX1~MUX4
Foot sets high level, by controlling the gating of MUX1~MUX4, setting excitation channel and Measurement channel；Contact impedance measurement pattern
Under, SPST1 and SPST2 conductings, the enable pin of MUX1 and MUX3 set high level, and the enable pin of MUX2 and MUX4 set low electricity
It is flat, by controlling the gating of MUX1 and MUX3, setting excitation channel and Measurement channel.
2, contact impedance data analysis is surveyed
In the present embodiment, use the impedance value measured by two electrode methods for：
Zi=Zci+Zti+Zcf
Wherein, i=1,2 ..., 16, ZciFor the contact impedance of imaging electrode i, ZtiFor imaging electrode i and reference electrode it
Between transfer impedance, Zcf be reference electrode contact impedance.
The qualitative analysis of (1) 16 path electrodes/scalp contact impedance
The reference electrode used in the present embodiment can be pierced under scalp for monopolar needle electrode, therefore the contact of reference electrode
Impedance is much smaller than the contact impedance of imaging electrode；
In addition, studies have reported that, the transfer impedance of cranium brain tissue is much smaller than the contact impedance of imaging electrode；I.e.：
Zcf < < Zci,Zti< < Zci
Therefore, Z can be utilizedi≈ZciThe contact impedance of 16 road imaging electrode of qualitative evaluation.
Referring to Fig. 6 (a) and Fig. 7 (a), the measured value of 16 road contact impedances is showed using radar chart method.16 in Fig. 6 (a)
A contact impedance value is close, indicates that the contact situation of 16 electrodes is close.And in Fig. 7 (a), it is observed that the 6th measured value
Significantly greater than other values indicate that the contact impedance of No. 6 imaging electrodes is extremely big, can tentatively infer：No. 6 imaging electrodes contact shape
Condition is bad.
The Space Consistency of (2) 16 path electrodes/scalp contact impedance is analyzed
Space Consistency refers to a certain moment, the otherness between 16 road contact impedances.
First, 16 measured values are compared, find out minimum value, counter electrode number is a, defines Δ Zi,aIt is as follows：
ΔZi,a=Zi-Za
=(Zci+Zti+Zcfi)-(Zca+Zta+Zcfa)
=(Zci-Zca)+(Zti-Zta)+(Zcfi-Zcfa)
Wherein, i=1,2 ..., 16.Zci-ZcaFor the difference of the contact impedance of imaging electrode i and imaging electrode a, it is denoted as Δ
Zci,a；Zti-ZtaFor the difference of imaging electrode i and imaging electrode a transfer impedance between reference electrode respectively, it is denoted as Δ Zti,a；
Zcfi-ZcfaThe fluctuating error of reference electrode contact impedance when to measure twice, is denoted as Δ Zcfi,a。
Due to Δ Zcfi,a≈ 0 and Δ Zti,a< < Δs Zci,a, then,
ΔZci,a=Zci-Zca≈Zi-Za
Then the Space Consistency coefficient of 16 road contact impedances can be expressed as：
It is corresponding with Fig. 6 (a) and Fig. 7 (a) respectively referring to Fig. 6 (b) and Fig. 7 (b), present the space of 16 road contact impedances
Consistency, i.e. relative different.16 numerical value are close in Fig. 6 (b), indicate that the contact situation of 16 electrodes is close；And in Fig. 7 (a),
It is observed that the 6th numerical value is significantly greater than other numerical value, indicate that the contact impedance of No. 6 imaging electrodes is extremely big, it can also be first
Step is inferred：No. 6 imaging electrode contact conditions are bad.
The time stability of (3) 16 path electrodes/scalp contact impedance is analyzed
Time stability refers to certain two moment, 16 road contact impedances with the time relative change rate.First by two
When inscribe, 16 road contact impedance measured values are illustrated in same radar chart, as shown in Fig. 8 (a).It is observed that the 8th number
The variable quantity being worth between two moment is maximum, may infer that：The time stability of No. 8 imaging electrodes is significantly worse than other imaging electricity
Pole.
In order to which 16 road contact impedance of quantitative analysis is with the opposite variation of time, Δ Z is definedi(t1, t2) is：
ΔZi(t1, t2)=Zi(t1)-Zi(t2)
=[Zci(t1)-Zci(t2)]+[Zti(t1)-Zti(t2)]+ΔZcfi(t1,t2)
Wherein, i=1,2 ..., 16.Zci(t1)-Zci(t2) it is t1, the contact impedance of imaging electrode i between two moment of t2
Variable quantity, be denoted as Δ Zci(t1,t2)；Zti(t1)-Zti(t2) it is t1, the contact impedance of imaging electrode i between two moment of t2
Variable quantity, be denoted as Δ Zti(t1,t2)；ΔZcfi(t1, t2) is t1, the variation of reference electrode contact impedance between two moment of t2
Amount.
Due to Δ Zti(t1, t2) ≈ 0 and Δ Zcfi(t1, t2) ≈ 0, then,
ΔZci(t1, t2)=Zci(t1)-Zci(t2)≈Zi(t1)-Zi(t2)。
Then the time stability coefficient of 16 road contact impedances can be expressed as：
It is corresponding with Fig. 8 (b) referring to Fig. 8 (b), present the time stability of 16 road contact impedances, i.e. when t1, t2 two
Opposite variation between quarter.It is observed that the 8th numerical value maximum, may infer that：The time stability of No. 8 imaging electrodes is obviously poor
In other imaging electrodes.
We can obtain the contact impedance information of two dimensions, the i.e. sky of 16 contact impedances by analyzing data as a result,
Between the coincident indicator α and time stability index β per the contact impedance of imaging electrode all the way.
Example given above is to realize the present invention preferably example, and the present invention is not limited to the above embodiments.This field
Technical staff made according to the technical characteristic of technical solution of the present invention any nonessential addition, replace or simple
Setting and adjustment to decision threshold, all belong to the scope of protection of the present invention.
Claims (10)
1. a kind of device for measuring multi-electrode/scalp contact impedance in real time, which is characterized in that including host computer, master control
Unit, exciting current signal generation unit, boundary voltage signal measurement unit, excitation channel, Measurement channel and contact impedance are surveyed
Measure module；
The contact impedance measurement module is by electrode unit, electrode channel control unit, contact impedance signal measurement unit and swashs
Encourage current signal measuring unit composition；Wherein：
Electrode unit, including one group of imaging electrode and a reference electrode, imaging electrode is joined for obtaining electrical impedance imaging data
Examine contact impedance of the electrode for each imaging electrode of subsidiary；
Electrode channel control unit, for by control encourage channel and Measurement channel switching, realize boundary voltage measure and
Contact impedance measures the blocked operation of both of which；
Contact impedance signal measurement unit, for will be transmitted after the response voltage signal processing between imaging electrode and reference electrode
To main control unit；
Exciting current signal measurement unit, for being transmitted to main control unit after handling the voltage signal at sample resistance both ends；
Host computer is interacted by data-interface with main control unit, and for sending control instruction to main control unit, main control unit will be adopted
The data of collection are uploaded to host computer；Main control unit generates AC sine electricity by controlling exciting current signal generation unit first
Signal is flowed, excitation channel and Measurement channel are then arranged by electrode channel control unit, finally by control boundary voltage letter
Number measuring unit, exciting current signal measurement unit and contact impedance signal measurement unit data acquisition.
2. the device according to claim 1 for measuring multi-electrode/scalp contact impedance in real time, which is characterized in that
Imaging electrode has both current excitation and voltage measurement function, and one group of imaging electrode is placed in person under test's scalp surface.
3. the device according to claim 1 for measuring multi-electrode/scalp contact impedance in real time, which is characterized in that
Reference electrode selects Dispoable medical monopolar needle electrode or tack surface electrode.
4. the device according to claim 1 for measuring multi-electrode/scalp contact impedance in real time, which is characterized in that
The electrode channel control unit, including the multiway analog switch device of multiple control imaging electrode channels switching and multiple controls
The single-pole single-throw switch (SPST) device of reference electrode channel ON/OFF.
5. the device according to claim 4 for measuring multi-electrode/scalp contact impedance in real time, which is characterized in that
Control multiple imaging electrodes using four 1 analog switch devices of multiselect, with MUX1 and MUX2 control respectively positive incentive channel and
Negative incentive channel, MUX3 and MUX4 control positive Measurement channel and negative sense Measurement channel respectively；It is opened using two single-pole single-throw(SPSTs
It closes device SPST1 and SPST2 and controls reference electrode；
Under boundary voltage signal measurement pattern, SPST1 and SPST2 are disconnected, the enable pin of MUX1, MUX2, MUX3 and MUX4
High level is set, by controlling the gating of MUX1, MUX2, MUX3 and MUX4, setting excitation channel and Measurement channel；
Under contact impedance signal measurement pattern, SPST1 and SPST2 are connected, and the enable pin of MUX1 and MUX3 set high level,
The enable pin of MUX2 and MUX4 sets low level, by controlling the gating of MUX1 and MUX3, setting excitation channel and Measurement channel.
6. the device according to claim 1 for measuring multi-electrode/scalp contact impedance in real time, which is characterized in that
Contact impedance signal measurement unit, by filter circuit, fixed gain signal amplification circuit, programme-controlled gain signal amplification circuit and A/
D conversion circuits form, for measuring the corresponding voltage signal of two electrode methods；
Exciting current signal measurement unit is believed by sample resistance, filter circuit, fixed gain signal amplification circuit, programme-controlled gain
Number amplifying circuit and A/D conversion circuits composition, for measuring the corresponding voltage signal of two electrode methods.
7. the device according to claim 6 for measuring multi-electrode/scalp contact impedance in real time, which is characterized in that
The filter circuit is made of second order active low-pass filter and second order active high-pass filter；The fixed gain signal is put
Big circuit is first order amplifying circuit, is made of precision resistance and operational amplifier；The programme-controlled gain signal amplification circuit,
For second level amplifying circuit, be made of programmable gain amplifier part, can dynamic adjust gain range with meet amplitude compared with
Signal in wide dynamic range amplifies demand；The A/D conversion circuits are made of analog-digital converter and its peripheral circuitry, as
The late-class circuit of signal measurement unit.
8. it is a kind of based on described in any one of claim 1~7 for measuring multi-electrode/scalp contact impedance in real time
The measurement method of device, which is characterized in that include the following steps：
1) electrode is arranged
One group of imaging electrode and fixation are placed by the conventional method of cranium brain resistance imaging, is then chosen between each imaging electrode
A reference electrode is placed apart from approximately uniform position；
2) boundary voltage data acquire
By electrode channel control unit, reference electrode access is disconnected, and switch several imaging electrodes in one group successively, it is complete
It is acquired at a frame boundaries voltage data, boundary piezo data is used to be imaged, as imaging data；
3) contact impedance data are acquired with exciting current data
Contact impedance data acquire：By electrode channel control unit, reference electrode access is connected, in order gated imaging successively
Electrode channel；Using two electrode methods, exciting current signal is injected between reference electrode and gated imaging electrode, and measure two
Voltage signal between electrode, is denoted as Ui, wherein i=1,2 ..., N are electrode number, and N is the number of imaging electrode；
Exciting current data acquire：By measuring the voltage signal on sample resistance, exciting current signal is measured indirectly, is denoted as
USampling；
4) step 2) and step 3) are repeated, into next frame data collection cycle, until host computer sends out termination acquisition instructions.
9. measurement method according to claim 8, which is characterized in that in step 3), the reality when imaging electrode i is gated
Exciting current is：
Ii=USampling/RSampling；
Then use the impedance value measured by two electrode methods for：
Zi=Ui/Ii=Ui/(USampling/RSampling)=Ui*RSampling/USampling；
ZiEssence be tested imaging electrode contact impedance Zci, transfer impedance Zt between imaging electrode and reference electrodeiWith
The sum of contact impedance Zcf three of reference electrode, i.e.,：
Zi=Zci+Zti+Zcf；
Define Δ Zm,nIt is as follows：
Wherein, m, n=1,2 ..., N and m ≠ n；Zcm-ZcnFor the difference of the contact impedance of imaging electrode m and imaging electrode n, it is denoted as
ΔZcm,n；Ztm-ZtnFor the difference of imaging electrode m and imaging electrode the n transfer impedance between reference electrode respectively, it is denoted as Δ
Ztm,n；Zcfm-ZcfnThe fluctuating error of reference electrode contact impedance when to measure twice, is denoted as Δ Zcfm,n。
10. measurement method according to claim 9, which is characterized in that effective contact area of reference electrode can ensure
Zcf < < ZciAnd Δ Zcfm,n≈ 0, it is approximately the same with reference to the distance between electrode and each imaging electrode, it can ensure
Each ZtiBetween otherness it is small, that is, meet：ΔZtm,n< < Δs Zcm,n；
Then have：ΔZcm,n=Zcm-Zcn≈Zm-Zn；
Define Δ Zi(t1, t2) is：
Wherein, i=1,2 ..., N；T1, t2 are two moment；Zci(t1)-Zci(t2) it is t1, i-th one-tenth between two moment of t2
As the changing value of electrode contact impedance, it is denoted as Δ Zci(t1,t2)；Zti(t1)-Zti(t2) it is t1, i-th between two moment of t2
The changing value of imaging electrode contact impedance is denoted as Δ Zti(t1,t2)；ΔZcfi(t1, t2) is t1, with reference to electricity between two moment of t2
The changing value of pole contact impedance；
Transfer impedance is influenced by electrode position and encephalic impedance variations, compared to contact impedance, time high stability, i.e.,
ΔZti(t1,t2)≈0；Reference electrode contact impedance reaches time stability, i.e. Δ Zcf by manual interventioni(t1,t2)≈0。
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