CN102688039A - Electrical impedance tomography imaging system and electrode shielding method thereof - Google Patents
Electrical impedance tomography imaging system and electrode shielding method thereof Download PDFInfo
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- CN102688039A CN102688039A CN2012101881303A CN201210188130A CN102688039A CN 102688039 A CN102688039 A CN 102688039A CN 2012101881303 A CN2012101881303 A CN 2012101881303A CN 201210188130 A CN201210188130 A CN 201210188130A CN 102688039 A CN102688039 A CN 102688039A
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Abstract
The invention discloses an electrical impedance tomography imaging system and an electrode shielding method, which mainly solve the problem that a too small capacitive reactance due to high working frequency, an increase in capacitance due to increase in wire length and the like affect the signal amplitude on a passageway of an electrode in the prior art. The electrical impedance tomography imaging system, comprises master control equipment, an image processing and displaying device, a signal processor and analogue and digital converter circuit, a switch system, a shield driving circuit and an excitation source generating circuit which are respectively connected with the master control equipment, and a shielded electrode which is connected with the switch system and the shielding driving circuit, wherein the switch system is respectively connected with the signal processor and analogue and digital converter circuit, the shield driving circuit and the excitation source generating circuit. Based on the electrical impedance tomography imaging system, the invention also provides a corresponding electrode shielding method, which is efficient and requires low cost for shielding the electrode.
Description
Technical field
The present invention relates to a kind of screen method, specifically, relate to a kind of screen method that is applied to the electrode in the electrical impedance tomography system.
Background technology
The electrical impedance tomography system is called for short the EIT system, is the medical imaging technology of new generation that grew up in nearly 20 years, and it has outstanding advantages such as not damaged, functional imaging and medical image monitoring.Weak current injects through external electrode in the EIT system, measures the voltage corresponding signal on other electrode simultaneously, rebuilds the distribution of conductivity of measurement target or the image of its variation through the inverse problem of finding the solution Laplace's equation.With nuclear medicine compared with techniques such as CT, MRI, EIT have harmless harmless, cost is low, volume is little, safe, simple to operate, to advantages such as early stage cancer sensitivities, doctor and patient are acceptant.
Because the quantity of the independent valid data that it obtained is lower than CT, MRI system 2 one magnitude, so the imaging precision of EIT is not high relatively.The EIT imaging is the inverse problem solution procedure of a serious morbid state, and on algorithm for reconstructing, what EIT adopted is soft field analysis, and hypothesis and boundary condition are many in its date processing and the image reconstruction algorithm, and algorithm requires high to the data convergence.Therefore no matter take which kind of data acquisition scheme, the picture quality of EIT imaging all depends on the data precision that is collected.Electrode is as the sensing element of EIT equipment; Comprise electrode wires and electrode slice; It is positioned at highly sensitive detection system foremost, on electrode through regular meeting disturb, noise, artifact, contact impedance, polarizing voltage, capacity effect etc., all can be amplified, handled by subsequent conditioning circuit as useful signal; Parameter signal is handled, thereby influences the effect of image reconstruction.In order to improve the capacity of resisting disturbance of electrode, way is to adopt the electrode of band screen layer, i.e. electrode tape screen layer usually at present.
In the prior art,, normally let the electrode wires shielding layer grounding in order to realize electrode screening.If but directly the electrode wires shielding layer grounding can be brought head effect again, be equivalent to the very little electric capacity of having connected between electrode wires and the ground.System comes input/output signal through electrode, and when operating frequency was low, capacitive reactance was very high; Can not influence system's input and output impedance, but when frequency was very high, capacitive reactance was very little; Will have a strong impact on system's input and output impedance; And then influence the signal amplitude on each electrode channel, and cause data precision to reduce, image reconstruction is unsuccessful.Along with the length increase of electrode wires, capacitance can increase, and the phenomenon of more than describing can be obvious more.
Summary of the invention
The object of the present invention is to provide a kind of electrical impedance tomography system and electrode screening method thereof; Solve the problem that meetings such as the capacitive reactance when operating frequency is very high that exists in the prior art is too small, electrode wires length increase capacitance can increase influence the signal amplitude on the electrode channel; Under the prerequisite that guarantees the signal transmission; Improve the efficient of electrode screening, reduce system development and use cost.
To achieve these goals, the technical scheme of the present invention's employing is following:
A kind of electrical impedance tomography system; Comprise main control device; The Flame Image Process that is connected with this main control device respectively and display device, signal condition and A/D convertor circuit, switching system, shielding drive circuit and excitation source generating circuit; And respectively with this switching system and the bucking electrode that is connected of shielding drive circuit, and this switching system also respectively with signal condition with A/D convertor circuit, shield drive circuit and encourage source generating circuit to be connected.
Further, said shielding drive circuit comprises two combination switches, and be connected in each combination switch input control winding displacement and operational amplifier and place the in-phase input end of this operational amplifier respectively and the resistance of outfan; Simultaneously, each combination switch disposes two outfans at least.Said combination switch is simulation integrated switch or mechanical switch, perhaps adopts discrete audion or metal-oxide-semiconductor to combine.
Again further, said bucking electrode is at least one, and each bucking electrode includes core and is wrapped in the screen layer of this core outer surface; Said core links to each other with the holding wire of switching system, and screen layer then links to each other with the shielding drive circuit.
Be the basis with above-mentioned hardware system, the invention provides the electrode screening method of a kind of electrical impedance tomography system, may further comprise the steps:
(1) selecting bucking electrode by core outer surface parcel screen layer for use, and according to the quantity of bucking electrode, confirm the quantity of combination switch, is the basis again with the combination switch, sets up the shielding drive circuit;
(2) use main control device, Flame Image Process to set up into the electrical impedance tomography system with A/D convertor circuit, switching system, shielding drive circuit, excitation source generating circuit with bucking electrode with display device, signal condition; Wherein, The core of bucking electrode is connected with switching system, and screen layer is connected with the shielding drive circuit;
(3) operation electrical impedance tomography system; Make the shielding drive circuit produce the electrode screening layer signal; This electrode screening layer signal transfers to the screen layer of bucking electrode; Resist the interfering signal that bucking electrode receives, make in the core signal consistent, thereby eliminate the coupling capacitance between screen layer and the core with screen layer.
Further, the concrete grammar of said step (1) comprising:
(1a) according to bucking electrode and combination switch one to one mode confirm the quantity of combination switch;
(1b) outfan of each combination switch all connects the screen layer of a bucking electrode through output port, then connects an operational amplifier at the input of combination switch, disposes the auxiliary circuit of operational amplifier simultaneously;
(1c) utilize the control winding displacement to connect combination switch and main control device, the final shielding drive circuit that forms.
Again further, in order to reduce cost, the quantity of operational amplifier is two in the said shielding drive circuit.
Compared with prior art, the present invention has following beneficial effect:
(1) the present invention adopts the shielding drive circuit to produce the electrode screening layer signal; Thereby avoided traditional grounded shield method the EIT system to be existed the problem of the side effect that influences systematic function; Solve the capacity effect that bonding brings, and then improved shield effectiveness;
(2) combination switch of the present invention can adopt simulation integrated switch, mechanical switch, and perhaps audion or the metal-oxide-semiconductor by separation combines, and be not only cheap, and have very high selection motility;
(3) the present invention makes the quantity of operational amplifier be reduced to minimum through the ingenious design to the shielding drive circuit, only comes the realization system to connect and work through the quantity that changes combination switch; And the price of combination switch is well below operational amplifier; Therefore, compare with the shielding drive circuit of classics, the present invention has reduced system development costs effectively; Also reduce simultaneously the use power consumption of shielding drive circuit, practiced thrift use cost;
(4) the present invention has changed traditional design philosophy through design cleverly and reasonably collocation, has reached efficiently, electrode screening effect cheaply, has very high practical value, is fit to very much large-scale promotion application.
Description of drawings
Fig. 1 is the system block diagram of electrical impedance tomography system among the present invention.
Fig. 2 is the schematic block circuit diagram of shielding drive circuit among the present invention.
Fig. 3 is the schematic equivalent circuit between core among the present invention and the screen layer.
Fig. 4 is the equivalent circuit of Fig. 3.
Fig. 5 is a screen method sketch map of the present invention.
The specific embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is described further, embodiment of the present invention includes but not limited to the following example.
Embodiment
Like Fig. 1,2,3,4, shown in 5; A kind of electrical impedance tomography system; Comprise main control device, the Flame Image Process that is connected with this main control device respectively and display device, signal condition and A/D convertor circuit, switching system, shielding drive circuit and excitation source generating circuit; And respectively with this switching system and the bucking electrode that is connected of shielding drive circuit, and this switching system also respectively with signal condition with A/D convertor circuit, shield drive circuit and encourage source generating circuit to be connected.
Wherein, Said shielding drive circuit comprises two combination switches; And the control winding displacement and the operational amplifier that are connected in the input of each combination switch; Place the in-phase input end of this operational amplifier and the resistance of outfan respectively, and each combination switch disposes two outfans at least.Said combination switch is simulation integrated switch or mechanical switch, perhaps adopts discrete audion or metal-oxide-semiconductor to combine.
Said bucking electrode quantity is at least one, and each bucking electrode includes core and is wrapped in the screen layer of this core outer surface; Said core links to each other with switching system, and screen layer then links to each other with the shielding drive circuit.
With above-mentioned electrical impedance tomography system is that the EIT system is the basis, and electrode screening method provided by the invention is following:
If there be N bucking electrode in the EIT system, its core is numbered 1 ... N, screen layer is numbered SH1 ... SHN.The EIT system is linked to each other with input IN+, the IN-of shielding drive circuit respectively through the electrode channel signal signal+ behind the switching gate, signal-; To shield drive circuit N output and be numbered SH1 ... SHN, respectively be numbered SH1 ... The screen layer of SHN is corresponding to link to each other.The main control device of EIT system passes through the mode of winding displacement and shields the control winding displacement control1+ on the combination switch in the drive circuit ... .conrtol (log2 (N))+and conrol1-.... conrtol (log2 (N))-link to each other.
The inner circuit connecting mode of shielding drive circuit is: draw two groups of log2 (N) root winding displacement from main control device, through control winding displacement control1+ ... .conrtol (log2 (N))+and conrol1-.... conrtol (log2 (N))-link to each other with combination switch; Input signal IN+, IN-link to each other with the positive input terminal of two operational amplifiers through resistance respectively; The outfan of two operational amplifiers then links to each other with two outer two resistance respectively; Simultaneously, the outfan of these two operational amplifiers also links to each other with they self inverting input respectively.Two resistance that are connected with the outfan of operational amplifier link to each other with two combination switches respectively again, the outfan of establishing these two combination switches then accordingly with the screen layer SH1 of electrode ... SHN connects.
According to anti-interference theory and electronic circuit ultimate principle; And EIT requirement of system design; Adopt above-mentioned shielding drive circuit to produce the screen layer signal; Thereby the realization electrode screening is a kind of electrode screening of EIT efficiently method, can overcome the adverse effect that the distribution of electrodes parameter causes the EIT input impedance to reduce.
Regard said electrode as a R, C equivalent circuit; When shielding layer grounding; There are electric potential difference U in core and screen layer; Electric current
from the core of bucking electrode to screen layer; This electric current makes the core signal amplitude of bucking electrode reduce, and its input impedance reduces; When screen layer consistent with the core signal magnitude, electric potential difference U=0, the core of bucking electrode is to the I=0 of screen layer, equivalent capacity does not exist, this moment bucking electrode distributed constant just the signal of core is not impacted, the input impedance of bucking electrode is constant.
When bucking electrode runs into external disturbance; According to anti-interference theory; Because screen layer is an equipotential face; Interfering signal is regarded the space of screen layer and encirclement thereof as the equipotentiality body, and inside does not have electric potential difference, and interfering signal can penetrate bucking electrode and can the core signal that screen layer surrounds do not impacted.
During use, when signal a, the b of certain two electrode channel need gather in the electrical impedance tomography system, through the switch controlling signal that main control device sends, the gauge tap system was communicated with signal+ with a, and signal-is communicated with b.Signal+ is the signal on a electrode wires core, and signal-is the signal on the b electrode wires core.Signal+, signal-are except being inserted signal condition and A/D convertor circuit, simultaneously also as the input that shields drive circuit.At this moment; Electrical impedance tomography system channel control signal control shielding drive circuit produces the screen layer signal of electrode a, b; That is: the shielding drive circuit produces the signal consistent with signal+ and is transferred to the screen layer of a electrode after receiving the control signal that main control device sends, and produces the signal consistent with signal-and looks into the screen layer to the b electrode.And the like; The signal of the different passages of the every collection of electrical impedance tomography system; Shielding drives and all to press above work, thus the external interference signal that signal through being transferred to screen layer and electrode receive cancel out each other, reach the purpose that realizes electrode screening efficiently, at low cost.
According to the foregoing description, just can realize the present invention well.
Claims (7)
1. electrical impedance tomography system; It is characterized in that; Comprise main control device, the Flame Image Process that is connected with this main control device respectively and display device, signal condition and A/D convertor circuit, switching system, shielding drive circuit and excitation source generating circuit; And respectively with this switching system and the bucking electrode that is connected of shielding drive circuit, and this switching system also respectively with signal condition with A/D convertor circuit, shield drive circuit and encourage source generating circuit to be connected.
2. a kind of electrical impedance tomography according to claim 1 system; It is characterized in that; Said shielding drive circuit comprises two combination switches; Be connected in the control winding displacement and the operational amplifier of the input of each combination switch, and place the in-phase input end of this operational amplifier and the resistance of outfan respectively; Simultaneously, each combination switch disposes two outfans at least.
3. a kind of electrical impedance tomography according to claim 2 system is characterized in that said combination switch is simulation integrated switch or mechanical switch.
4. according to claim 1 or 2 or 3 described a kind of electrical impedance tomography systems, it is characterized in that said bucking electrode is at least one, and each bucking electrode includes core and is wrapped in the screen layer of this core outer surface; Said core links to each other with the holding wire of switching system, and screen layer then links to each other with the shielding drive circuit.
5. the electrode screening method of an electrical impedance tomography system is characterized in that, may further comprise the steps:
(1) selecting bucking electrode by core outer surface parcel screen layer for use, and according to the quantity of bucking electrode, confirm the quantity of combination switch, is the basis again with the combination switch, sets up the shielding drive circuit;
(2) use main control device, Flame Image Process to set up into the electrical impedance tomography system with A/D convertor circuit, switching system, shielding drive circuit, excitation source generating circuit with bucking electrode with display device, signal condition; Wherein, The core of bucking electrode is connected with switching system, and screen layer is connected with the shielding drive circuit;
(3) operation electrical impedance tomography system; Make the shielding drive circuit produce the electrode screening layer signal; This electrode screening layer signal transfers to the screen layer of bucking electrode; Resist the interfering signal that bucking electrode receives, make in the core signal consistent, thereby eliminate the coupling capacitance between screen layer and the core with screen layer.
6. the electrode screening method of a kind of electrical impedance tomography according to claim 5 system is characterized in that the concrete grammar of said step (1) comprising:
(1a) according to bucking electrode and combination switch one to one mode confirm the quantity of combination switch;
(1b) outfan of each combination switch all connects the screen layer of a bucking electrode through output port, then connects an operational amplifier at the input of combination switch, disposes the auxiliary circuit of operational amplifier simultaneously;
(1c) utilize the control winding displacement to connect combination switch and main control device, the final shielding drive circuit that forms.
7. according to the electrode screening method of claim 5 or 6 described a kind of electrical impedance tomography systems, it is characterized in that the quantity of operational amplifier is two in the said shielding drive circuit.
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| CN105976411A (en) * | 2016-05-18 | 2016-09-28 | 中国人民解放军第四军医大学 | Prepositioned measuring module for electrical impedance tomography imaging data acquisition system and alignment and calibration method |
| CN110361069A (en) * | 2019-08-15 | 2019-10-22 | 上海交通大学 | A kind of measurement method and device of wave section |
| CN110798963A (en) * | 2019-09-24 | 2020-02-14 | 惠州市金百泽电路科技有限公司 | Control method for amplitude consistency of 5G antenna PCB |
| CN114052701A (en) * | 2021-11-01 | 2022-02-18 | 河南师范大学 | Capacitive coupling resistance tomography image reconstruction method |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105976411A (en) * | 2016-05-18 | 2016-09-28 | 中国人民解放军第四军医大学 | Prepositioned measuring module for electrical impedance tomography imaging data acquisition system and alignment and calibration method |
| CN105976411B (en) * | 2016-05-18 | 2017-06-20 | 中国人民解放军第四军医大学 | A kind of preposition measurement module and Calibration Method for electrical impedance tomography data collecting system |
| CN110361069A (en) * | 2019-08-15 | 2019-10-22 | 上海交通大学 | A kind of measurement method and device of wave section |
| CN110798963A (en) * | 2019-09-24 | 2020-02-14 | 惠州市金百泽电路科技有限公司 | Control method for amplitude consistency of 5G antenna PCB |
| CN114052701A (en) * | 2021-11-01 | 2022-02-18 | 河南师范大学 | Capacitive coupling resistance tomography image reconstruction method |
| CN114052701B (en) * | 2021-11-01 | 2024-08-20 | 河南师范大学 | Method for reconstructing capacitive coupling resistance tomography image |
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