CN104027112A - Electrical impedance imaging device - Google Patents
Electrical impedance imaging device Download PDFInfo
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- CN104027112A CN104027112A CN201410241019.5A CN201410241019A CN104027112A CN 104027112 A CN104027112 A CN 104027112A CN 201410241019 A CN201410241019 A CN 201410241019A CN 104027112 A CN104027112 A CN 104027112A
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Abstract
The invention discloses an electrical impedance imaging device. The electrical impedance imaging device is composed of a signal generator, an amplitude frequency adjustment circuit, a voltage control current source circuit, a multiway switch, an electrode plate set, a physical model, a signal amplification circuit, a band-pass filter, a phase-sensitive demodulator circuit, an A/D conversion circuit, a single-chip microcomputer and an upper computer. The electrical impedance imaging device has the advantages that first, the signal generator can generate a high-precision voltage signal without an extra filter; second, a stable and multi-frequency alternating-current source signal with the amplitude value adjustable can be generated by a voltage signal through the amplitude frequency adjustment circuit and the voltage control current source circuit; third, because electrode plates are made of stainless steel materials, the electrode plates are not prone to rusting corrosion and stable and reliable in performance, and because the electrode plates are connected with stainless steel alligator clips, disassembly and replacement are facilitated, and good electrical conductivity is achieved; fourth, in the phase-sensitive demodulator circuit, a sinusoidal signal is adopted for replacing a square signal to serve as a reference signal for on-off demodulation, and therefore the demodulation effect is better compared with square wave demodulation.
Description
Technical field
The invention discloses a kind of electrical impedance imaging device, belong to medical science detection field.
Background technology
Review of Electrical Impedance Tomography (Electrical Impedance Tomography, EIT) is the novel medical imaging technology of the one that is distributed as imageable target that utilizes the resistivity in organism.It has different impedance operators according to tissues different in organism, obtain the body surface voltage signal of organism by configuring corresponding electrode system, and adopt specific algorithm, finally reconstruct the figure of reaction organism internal electrical characteristic, thereby obtain physiology and the pathological information that organism comprises.EIT technology has broad prospect of application, has caused great concern in fields such as geophysics, environmental monitoring, nondestructive inspection and medical science detections.1987, the Brown of Sheffield university of Britain and professor Barber developed the complete electrical impedance data measuring system of First.All over the world, if more than 30 research groups such as the U.S., Britain, Germany, France, Sweden, India are all at the research work that carries out EIT technology.
At home, be engaged in EIT aspect research group and have University Of Chongqing, The Fourth Military Medical University, the Chinese Academy of Medical Sciences, BJ University of Aeronautics & Astronautics, Hebei University of Technology, University Of Tianjin, Shanghai University etc.Wherein comparatively outstanding with the research work of The Fourth Military Medical University, at present The Fourth Military Medical University and University Of Chongqing joint research and development go out the Review of Electrical Impedance Tomography test platform of degree of precision, also continuing deep research to clinical practice simultaneously.
The Major Difficulties of prior art is mainly manifested in: need to produce precisely and compared with the current source of high output impedance; Maximum attainable physiological impedance variation can only cause the variation of measuring voltage 10% at present, requires the certainty of measurement of electric impedance imaging system to be greater than 0.1% for this reason; The quantity of information that current EIT system can gather is few, although can increase measurement data amount by the method that increases number of poles, this will make hardware system become complicated, and the increase of electrode number is also limited; The picture quality that at present impedance imaging algorithm reconstructs can't be satisfactory, need to design image quality better, more accurate algorithm.
Than before I application " a kind of bio-electrical impedance imaging device " patent (201310545684.9), this device improves.Thereby can producing interference noise, original DDS signal source affects the quality of signal source, now adopt MAX038 signal generator to replace original DDS signal source, do not need additional wave filter just can produce the voltage signal of degree of precision, be conducive to improve the sampling precision of system rear class output signal; Adopt stainless steel electrode to replace original copper electrode, the corrosion that gets rusty easily of copper electrode, is unfavorable for carrying out measurement steady in a long-term, and stainless steel electrode sheet has the corrosion of being difficult for, stable and reliable for performance, and be connected with rustless steel alligator clamp, be convenient to dismounting and change, thering is good electric conductivity; In phase-sensitive demodulating circuits, adopt sinusoidal signal to replace square-wave signal as carrying out switch demodulation with reference to signal, better than square wave demodulation effect, overcome original employing square-wave signal carry out demodulation have unstable, have an impact of crosstalking.Therefore,, through above-mentioned improvement, this electrical impedance imaging device has higher precision, better stability.
Summary of the invention
The object of the invention is to overcome the deficiency of existing electric impedance imaging system, develop a kind of improved electrical impedance imaging device.By in body surface configured electrodes sheet group and inject external drive signal, then obtain the body surface voltage signal of organism, utilize phase demodulation technology to obtain resistive information and the capacitive information of interior of articles, and adopt specific algorithm, finally reconstruct the electrical impedance images of reflection organism interior tissue characteristic.Method of the present invention can not directly draw the diagnostic result of disease or take the foundation of the measure for the treatment of as doctor, therefore adopt method of the present invention can only obtain intermediate object program information.
The technical solution used in the present invention comprises by signal generator, amplitude-frequency regulating circuit, Voltage-controlled Current Source circuit, variable connector, electrode slice group and physical model, signal amplification circuit, band pass filter circuit, phase-sensitive demodulating circuits, A/D change-over circuit, single-chip microcomputer, host computer composition.
Signal generator produces voltage signal, through amplitude-frequency regulating circuit, puts on Voltage-controlled Current Source circuit, is converted to constant-current source;
Pair of electrodes in Single-chip Controlling variable connector gate sheet group puts on physical model electric current as pumping signal;
The voltage signal that physical model produces is processed through signal conditioning circuit, then carries out A/D conversion and data acquisition by single-chip microcomputer, then sends into host computer by serial communication.
Described electrode slice group can be 16 electrodes.
Described electrode slice group is evenly distributed on the inwall of physical model, is connected to variable connector by rustless steel alligator clamp, and two groups of variable connectors carry out time-sharing multiplex.
Advantage of the present invention:
1) signal generator does not need additional wave filter just can produce the voltage signal of degree of precision;
2) voltage signal just can produce alternating current source signal stable, multifrequency, that amplitude is adjustable by amplitude-frequency regulating circuit and Voltage-controlled Current Source circuit;
3) stainless steel material has as electrode slice the corrosion of being difficult for, stable and reliable for performance, and is connected with rustless steel alligator clamp, is convenient to dismounting and changes, and has good electric conductivity;
4) in phase-sensitive demodulating circuits, adopt sinusoidal signal to replace square-wave signal as carrying out switch demodulation with reference to signal, better than square wave demodulation effect.
Brief description of the drawings
Fig. 1 is system structure schematic diagram of the present invention.
Fig. 2 is signal generator schematic diagram of the present invention.
Fig. 3 is amplitude-frequency regulating circuit schematic diagram of the present invention.
Fig. 4 is variable connector measuring principle figure of the present invention.
Fig. 5 is phase demodulation schematic diagram of the present invention.
Detailed description of the invention
Below in conjunction with accompanying drawing and specific implementation method, the present invention is described in further detail.
The present invention is based on single-chip computer control system and designed a kind of electric impedance imaging system, this system structure principle as shown in Figure 1.
Signal generator (1) adopts the precision high-frequency functional generator special chip MAX038 of MAXIM company, and MAX038 is a kind of needs few peripheral circuit just can realize high frequency, high accuracy output triangular wave, sawtooth waveforms, sine wave, square wave and impulse wave.Its reference frequency output to 20MHz, by 2 suitable logic levels of TTL logical address pin are set, just can be set sine wave, the output of square wave or triangular wave at 0.1Hz.The output of all waveforms is all that peak-to-peak value is ± signal of 2VP-P, and frequency and dutycycle are independent adjustable, can reach ± 20mA of Low ESR fan-out capability.
The frequency of output signal is by the size of current of injecting pin IIN, and the voltage VFADJ on capacitor C F size and the pin FADJ of COSC pin termination determines.In the time that VFADJ pin voltage is 0V, basic output frequency FO is determined by following formula:
FO(MHz)＝IIN(μA)÷CF(pF) (1)
IIN(μA)＝VREF(V)÷RIN(KΩ) (2)
VREF(V)＝VIN(V)÷2 (3)
Wherein: IIN is the electric current (2 μ A～750 μ A) that flows into IIN pin, CF is the electric capacity (20pF～100 μ F) that is connecting COSC pin and ground, if the signal of design will obtain optimum performance, preferably select IIN between 10 μ A～400 μ A, the scope of CF electric capacity is between the μ F of 20pF～100.
We arrange waveform selection mode A1A0=10 just can produce sine wave, because the frequency general range of electrical impedance imaging pumping signal is at 1KHz～1MHz, we select the frequency of four typical frequencies as pumping signal for this reason, are respectively 1KHz, 10KHz, 50KHz and 100KHz.Utilize the needed driving frequency of selection that dial-up gauge tap just can be easy simultaneously.RIN variable resistance is 200K, selects electric capacity 100nF, 10nF, 2.2nF, 1nF respectively as the ground capacity of the COSC pin of frequency 1KHz, 10KHz, 50KHz and 100KHz.The schematic diagram of signal generator is as Fig. 2.
Amplitude regulating circuit adopts OP27 precision operational-amplifier, OP27 have low maladjustment voltage, low drift, at a high speed, high bandwidth and low-noise characteristic, be the choosing of the ideal of precision instrumentation application.Just can realize the adjusting of signal amplitude by selecting two adjustable resistances.The schematic diagram of amplitude-frequency regulating circuit is as Fig. 3.
Voltage-controlled Current Source circuit (3) adopts improved Howland current source circuit, improved Howland current source circuit equally also adopts OP27 composition double operational circuit, output current Io is only relevant with resistance R 5 with input voltage VI, just can change the amplitude of output current by changing resistance R 5, can not destroy the equilibrium condition of circuit.Be RL be 1K Ω in the situation that in output loading, the stability of output current source can reach to 1MHz, has higher output impedance and stability preferably.
Variable connector (4) adopts the MAX306 chip of MAXIM company, MAX306 is accurate CMOS analog multichannel switch, the conducting resistance of each passage is less than 100 Ω, matching error is less than 5 Ω, be less than-the 92dB that crosstalks, when conducting, Leakage Current is less than 25nA over the ground, and equivalent capacity is less than 140pF over the ground, be less than 400ns switch time, meet the requirement of electric impedance imaging system.It is selected 1 function by A3A2A1A0 and EN co-controlling 16, therefore use 4 just can realize the control requirement of EIT system to 16 electrodes, and wherein 2 form exciting current passage gating circuit, and 2 form voltage measurement passage gating circuit.Under the control of single-chip microcomputer (11), the mode that adopts two variable connectors and connect just can realize 16 and select 2 electric current injection modes arbitrarily, and voltage measurement gating circuit is similar to electric current injection gating circuit, just the flow direction of signal is contrary, to another of physical model (6) to gathering voltage signal in measurement electrode.
This device adopts adjacent driven mode, often completes the current drives of an adjacent electrode, just need on all the other adjacent electrodes, complete 13 voltage measurements.For example: electric current is from 1,2 electrode injections, now the address code of first switch is A3A2A1A0=0000, the address code of second switch is A3A2A1A0=0001, since 3 (A3A2A1A0=0010), 4 (A3A2A1A0=0011) electrode measuring voltage, measure again the voltage of 4 (A3A2A1A0=0011), 5 (A3A2A1A0=0100), measure successively to the voltage of 15 (A3A2A1A0=1110), 16 (A3A2A1A0=1111) electrode.So just complete the measurement of one-period, then measured to 2,3 electrode injection electric currents again, by that analogy.Until complete whole measurements, obtain 208 voltage datas.Figure is as Fig. 4 for variable connector measuring principle.
Because the current signal of injecting electrode is very little, peak-to-peak value generally only has 1mA～5mA left and right, so the voltage signal recording from electrode is also very little, tens millivolts of left and right of general Voltage Peak peak value, therefore need to utilize signal amplifier that signal is amplified, signal amplifier adopts AD620 instrument amplifier.AD620 is high-precision meter amplifier, only need a non-essential resistance that gain is set, gain ranging is 1～10000, there is higher common mode rejection ratio (CMRR), enough bandwidth, higher input impedance and less input bias current, can reduce the impact of measurement module on interior of articles CURRENT DISTRIBUTION to be measured.
What band filter adopted MAXIM company is integrated with source filter chip MAX275, and MAX275, without clock circuit, has lower noise, the better advantage of dynamic property than switching capacity, is widely used in various precision measurement equipment and data collecting system.Mid frequency, up to 300KHZ, only needs four resistance of simple configuration just can realize good filter effect.By garbage signal and interference noise in MAX275 filtering acquired signal, make waveform purer.
In biological tissue's organ, resistive part has all comprised abundant physiologic information with capacitive part, need to utilize phase demodulation technology to obtain the resistive part and capacitive part of biological tissue inside.In EIT system, what apply is actuated to current source, so what collect in measurement electrode is alternating voltage signal, it comprises real part information and imaginary part information, therefore needs to use phase demodulation technology to obtain recording real part information and the imaginary part information of voltage signal.Phase-sensitive demodulating circuits (9) adopts the high accuracy balance modulator chip AD630 of AD company, and by providing outstanding precision and temperature stability through the film resistor of laser wafer adjustment.
This device adopts switch demodulation techniques, switch demodulation be by with reference signal frequency and phase place all identical signal carry out halfwave rectifier, then by a low pass filter filtering unwanted signal component.Utilized switch demodulation techniques all to adopt square-wave signal as carrying out demodulation with reference to signal in the past, square-wave signal has unstable, jagged in actual applications, can produce pulse and spike, utilize square-wave signal to carry out demodulation meeting and worsen primary signal, be unfavorable for the Obtaining Accurate of experimental data.For this reason, under the basis of emulation, also reality proves, adopts sine wave signal to replace square-wave signal as carrying out phase demodulation with reference to signal, and the waveform demodulating, than square wave better effects if, has noise still less, meets the requirement of electric impedance imaging system.The schematic diagram of phase demodulation is as Fig. 5.
A/D change-over circuit (10) is to convert the signal of simulation to digital signal to export single-chip microcomputer (11) to.Data measured sends to host computer (12) by serial ports, and then host computer (12) obtains the electrical impedance distribution image of object under test by related algorithm.
Physical model (6) uses a columniform tank to be used as the physical model of tissue, the high 10cm of this tank, diameter 25cm, equidistantly lays 16 stainless steel electrode sheets at the inwall sustained height of tank along circumference, stainless steel electrode length of a film 4cm, wide 2cm.Stainless steel electrode sheet is connected to variable connector (4) by rustless steel alligator clamp, is convenient to dismounting and changes, and has good electric conductivity, is conducive to obtain experimental data accurately.In tank, holding solubility is 0.9%NaCI solution (being saline), as the physical model (6) of electrical impedance imaging.
After the present invention powers on by following works:
1, open power supply, by single-chip microcomputer (11) electrification reset, carry out control signal generator (1) by FREQUENCY CONTROL switch, amplitude regulating circuit and produce sine voltage signal, voltage signal converts the alternating current source signal of constant amplitude to by Voltage-controlled Current Source circuit (3);
2, single-chip microcomputer (11) is by IO mouth control variable connector (4), make its programme-control variable connector (4) carry out gating to injecting electrode and measurement electrode, constant-current source signal injection electrode then obtains corresponding voltage signal from electrode;
3, the voltage signal of measuring from electrode is amplified by signal amplification circuit (7), carries out filtering by band pass filter circuit (8), then demodulates the real part information of signal by phase-sensitive demodulating circuits (9).
4, the real part information demodulating is converted to digital signal by A/D change-over circuit (10) after low-pass filter circuit filtering noise.
5, A/D change-over circuit (10) exports the digital signal recording to single-chip microcomputer (11), and single-chip microcomputer (11) is sent data into host computer (12) by serial communication.
6, host computer (12) is drawn the electrical impedance imaging figure of object under test by corresponding algorithm.
Claims (1)
1. an electrical impedance imaging device, comprise by signal generator (1), amplitude-frequency regulating circuit (2), Voltage-controlled Current Source circuit (3), variable connector (4), electrode slice group (5) and physical model (6), signal amplification circuit (7), band pass filter circuit (8), phase-sensitive demodulating circuits (9), A/D change-over circuit (10), single-chip microcomputer (11), host computer (12) composition;
It is characterized in that:
Signal generator (1), by amplitude-frequency regulating circuit (2) and Voltage-controlled Current Source circuit (3), just can produce alternating current source signal stable, multifrequency, that amplitude is adjustable; Phase-sensitive demodulating circuits (9) adopts sinusoidal signal to replace square-wave signal as carrying out switch demodulation with reference to signal; Electrode slice group (5) is 16 stainless steel electrode sheets, and it is evenly distributed on the inwall of physical model (6), is connected to variable connector (4) by rustless steel alligator clamp, and two groups of variable connectors carry out time-sharing multiplex.
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Cited By (11)
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| CN104983422A (en) * | 2015-07-17 | 2015-10-21 | 南京邮电大学 | Electrical impedance tomography device of electrodes 32 |
| CN105030237A (en) * | 2015-07-17 | 2015-11-11 | 中国科学院电工研究所 | Spinal cord injury localization device |
| CN105089651A (en) * | 2014-05-07 | 2015-11-25 | 中国石油化工股份有限公司 | Logging-while-drilling resistivity measuring device and logging-while-drilling resistivity measuring method |
| CN105496409A (en) * | 2016-01-19 | 2016-04-20 | 北京四海华辰科技有限公司 | Human body composition analyzer |
| CN107753019A (en) * | 2017-10-20 | 2018-03-06 | 北京润脉科技有限公司 | Bio-electrical impedance measuring apparatus and measuring method |
| CN108387264A (en) * | 2018-01-30 | 2018-08-10 | 华南理工大学 | A kind of sensor device for face parameter detection |
| CN109431503A (en) * | 2018-10-11 | 2019-03-08 | 南京邮电大学 | A kind of miniature EIT device of wireless transmission |
| WO2020199367A1 (en) * | 2019-04-02 | 2020-10-08 | 北京华睿博视医学影像技术有限公司 | Electrical impedance tomography apparatus and method |
| CN112754455A (en) * | 2020-12-31 | 2021-05-07 | 点奇生物医疗科技(北京)有限公司 | Current excitation device for portable electrical impedance imaging system |
| CN113413148A (en) * | 2021-08-24 | 2021-09-21 | 常州先趋医疗科技有限公司 | Signal processing method and device for improving effect of impedance biosensor |
| CN113760025A (en) * | 2020-06-04 | 2021-12-07 | 中国科学院苏州生物医学工程技术研究所 | Adjustable constant current source, electrical impedance imaging system and image reconstruction method thereof |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105089651A (en) * | 2014-05-07 | 2015-11-25 | 中国石油化工股份有限公司 | Logging-while-drilling resistivity measuring device and logging-while-drilling resistivity measuring method |
| CN105089651B (en) * | 2014-05-07 | 2019-01-01 | 中国石油化工股份有限公司 | LWD resistivity log device and measurement method |
| CN104983422A (en) * | 2015-07-17 | 2015-10-21 | 南京邮电大学 | Electrical impedance tomography device of electrodes 32 |
| CN105030237A (en) * | 2015-07-17 | 2015-11-11 | 中国科学院电工研究所 | Spinal cord injury localization device |
| CN105496409A (en) * | 2016-01-19 | 2016-04-20 | 北京四海华辰科技有限公司 | Human body composition analyzer |
| CN107753019A (en) * | 2017-10-20 | 2018-03-06 | 北京润脉科技有限公司 | Bio-electrical impedance measuring apparatus and measuring method |
| CN108387264A (en) * | 2018-01-30 | 2018-08-10 | 华南理工大学 | A kind of sensor device for face parameter detection |
| CN109431503A (en) * | 2018-10-11 | 2019-03-08 | 南京邮电大学 | A kind of miniature EIT device of wireless transmission |
| WO2020199367A1 (en) * | 2019-04-02 | 2020-10-08 | 北京华睿博视医学影像技术有限公司 | Electrical impedance tomography apparatus and method |
| CN113760025A (en) * | 2020-06-04 | 2021-12-07 | 中国科学院苏州生物医学工程技术研究所 | Adjustable constant current source, electrical impedance imaging system and image reconstruction method thereof |
| CN112754455A (en) * | 2020-12-31 | 2021-05-07 | 点奇生物医疗科技(北京)有限公司 | Current excitation device for portable electrical impedance imaging system |
| CN113413148A (en) * | 2021-08-24 | 2021-09-21 | 常州先趋医疗科技有限公司 | Signal processing method and device for improving effect of impedance biosensor |
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Application publication date: 20140910 |