CN102688039B - 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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- CN102688039B CN102688039B CN201210188130.3A CN201210188130A CN102688039B CN 102688039 B CN102688039 B CN 102688039B CN 201210188130 A CN201210188130 A CN 201210188130A CN 102688039 B CN102688039 B CN 102688039B
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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 Electrical Impedance Tomography System.
Background technology
Electrical Impedance Tomography System is called for short EIT system, is the medical imaging technology of new generation growing up for nearly 20 years, and it has the outstanding advantages such as not damaged, functional imaging and medical image monitoring.EIT system is injected Weak current by external electrode, measures the voltage corresponding signal on other electrode simultaneously, by solving the inverse problem of Laplace's equation, rebuilds the distribution of conductivity of measurement target or the image of its variation.Compare with the nuclear medicine technology such as CT, MRI, that EIT has is 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 its independent valid data that obtain is lower than CT, 2 orders of magnitude of MRI system, therefore the imaging precision of EIT is relatively not high.EIT imaging is the inverse problem solution procedure of a Very Ill-conditioned, and on algorithm for reconstructing, what EIT adopted is soft field analysis, and in its date processing and image reconstruction algorithm, hypothesis and boundary condition are many, and algorithm requires high to data convergence.Therefore no matter take which kind of data acquisition scheme, the picture quality of EIT imaging all depends on collected data precision.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, often can disturb, noise, artifact, contact impedance, polarizing voltage, capacity effect etc.; capital is amplified, is processed by subsequent conditioning circuit as useful signal; parameter signal is processed, thereby affects the effect of image reconstruction.In order to improve the capacity of resisting disturbance of electrode, way is the electrode adopting with screen layer, i.e. electrode tape screen layer conventionally at present.
In prior art, in order to realize electrode screening, normally allow electrode wires shielding layer grounding.If but directly electrode wires shielding layer grounding can be brought to head effect again, a very little electric capacity is equivalent to connect between electrode wires and ground.System is carried out input/output signal by electrode, when operating frequency is low, capacitive reactance is very high, can not affect system input and output impedance, but when frequency is very high, capacitive reactance is very little, will have a strong impact on system input and output impedance, and then affect 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 phenomenon described above can be more obvious.
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 the meetings such as the capacitive reactance when operating frequency is very high existing in prior art is too small, electrode wires length increase capacitance can increase affect the signal amplitude on electrode channel, guaranteeing under the prerequisite of signal transmission, improve the efficiency of electrode screening, reduce system development and use cost.
To achieve these goals, the technical solution used in the present invention is as follows:
A kind of Electrical Impedance Tomography System, comprise main control device, the image processing being connected with this main control device respectively and display device, signal condition and A/D convertor circuit, switching system, shield guard circuit and excitation source generating circuit, and the bucking electrode being connected with shield guard circuit with this switching system respectively, and this switching system is also connected with A/D convertor circuit, shield guard circuit and excitation source generating circuit with signal condition respectively.
Further, described shield guard circuit comprises two combination switches, and the control winding displacement and the operational amplifier that are connected in the input of each combination switch, and is placed in respectively the in-phase input end of this operational amplifier and the resistance of outfan; Meanwhile, each combination switch at least disposes two outfans.Described combination switch is simulation integrated switch or mechanical switch, or adopts discrete audion or metal-oxide-semiconductor to combine.
Again further, described bucking electrode is at least one, and each bucking electrode includes core, and is wrapped in the screen layer of this core outer surface; Described core is connected with the holding wire of switching system, and screen layer is connected with shield guard circuit.
Take above-mentioned hardware system as basis, the invention provides a kind of electrode screening method of Electrical Impedance Tomography System, comprise the following steps:
(1) select the bucking electrode by core outer surface parcel screen layer, and according to the quantity of bucking electrode, determine the quantity of combination switch, then take combination switch as basis, set up shield guard circuit;
(2) use main control device, image processing to set up into Electrical Impedance Tomography System with A/D convertor circuit, switching system, shield guard 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 shield guard circuit;
(3) operation Electrical Impedance Tomography System, make shield guard circuit produce electrode screening layer signal, this electrode screening layer signal transfers to the screen layer of bucking electrode, resist the interfering signal that bucking electrode is subject to, make in core signal consistent with screen layer, thereby eliminate the coupling capacitance between screen layer and core.
Further, the concrete grammar of described step (1) comprising:
(1a) according to bucking electrode and combination switch one to one mode determine the quantity of combination switch;
(1b) outfan of each combination switch all connects the screen layer of a bucking electrode by output port, at the input of combination switch, connects an operational amplifier, configures the auxiliary circuit of operational amplifier simultaneously;
(1c) utilize and control winding displacement connection combination switch and main control device, finally form shield guard circuit.
Again further, in order to reduce costs, in described shield guard circuit, the quantity of operational amplifier is two.
Compared with prior art, the present invention has following beneficial effect:
(1) the present invention adopts shield guard circuit to produce electrode screening layer signal, thereby avoided traditional grounded shield method EIT system to be existed to the problem of the side effect that affects 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, or is combined by discrete audion or metal-oxide-semiconductor, not only cheap, and has very high selection motility;
(3) the present invention is by the ingehious design to shield guard circuit, make the quantity of operational amplifier be reduced to minimum, only by changing the quantity of combination switch, realize system connection and work, and the price of combination switch is well below operational amplifier, therefore, compare with classical shield guard circuit, the present invention has reduced system development costs effectively, also reduced the use power consumption of shield guard circuit, saved use cost simultaneously;
(4) the present invention, by design cleverly and reasonably collocation, has changed traditional design philosophy, has reached efficiently, electrode screening effect cheaply, has very high practical value, is applicable to very much large-scale promotion application.
Accompanying drawing explanation
Fig. 1 is the system block diagram of Electrical Impedance Tomography System in the present invention.
Fig. 2 is the schematic block circuit diagram of shield guard circuit in the present invention.
Fig. 3 is the schematic equivalent circuit between core and screen layer in the present invention.
Fig. 4 is the equivalent circuit of Fig. 3.
Fig. 5 is screen method schematic diagram of the present invention.
The specific embodiment
Below in conjunction with drawings and Examples, the invention will be further described, and embodiments of the present invention include but not limited to the following example.
Embodiment
As shown in Fig. 1,2,3,4,5, a kind of Electrical Impedance Tomography System, comprise main control device, the image processing being connected with this main control device respectively and display device, signal condition and A/D convertor circuit, switching system, shield guard circuit and excitation source generating circuit, and the bucking electrode being connected with shield guard circuit with this switching system respectively, and this switching system is also connected with A/D convertor circuit, shield guard circuit and excitation source generating circuit with signal condition respectively.
Wherein, described shield guard circuit comprises two combination switches, and the control winding displacement and the operational amplifier that are connected in the input of each combination switch, be placed in respectively the in-phase input end of this operational amplifier and the resistance of outfan, and each combination switch at least disposes two outfans.Described combination switch is simulation integrated switch or mechanical switch, or adopts discrete audion or metal-oxide-semiconductor to combine.
Described 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; Described core is connected with switching system, and screen layer is connected with shield guard circuit.
The above-mentioned Electrical Impedance Tomography System of take is that EIT system is basis, and electrode screening method provided by the invention is as follows:
If EIT system has N bucking electrode, its core is numbered 1 ... N, screen layer is numbered SH1 ... SHN.Electrode channel signal signal+, signal-by EIT system after switching gate is connected with input IN+, the IN-of shield guard circuit respectively, N output of shield guard circuit is numbered to SH1 ... SHN, respectively be numbered SH1 ... corresponding being connected of screen layer of SHN.Control winding displacement control1+ in the mode of the main control device of EIT system by winding displacement and shield guard circuit on combination switch ... .conrtol (log2 (N))+and conrol1-.... conrtol (log2 (N))-being connected.
The circuit connecting mode of shield guard inside circuit is: from main control device, draw two groups of log2 (N) root winding displacement, through controlling winding displacement control1+ ... .conrtol (log2 (N))+and conrol1-.... conrtol (log2 (N))-be connected with combination switch; Input signal IN+, IN-are connected with the positive input terminal of two operational amplifiers by resistance respectively, the outfan of two operational amplifiers is connected with two outer two resistance respectively, meanwhile, the outfan of these two operational amplifiers is also connected with they self inverting input respectively.Two resistance that are connected with the outfan of operational amplifier are connected with two combination switches respectively again, the outfan of establishing these two combination switches 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 shield guard circuit to produce screen layer signal, thereby realize electrode screening, be a kind of efficient EIT electrode screening method, can overcome the adverse effect that distribution of electrodes parameter causes EIT input impedance to reduce.
Regard described electrode as a R, C equivalent circuit, when shielding layer grounding, there is electric potential difference U in core and screen layer, the electric current from the core of bucking electrode to screen layer
, this electric current reduces the core signal amplitude of bucking electrode, and its input impedance reduces; When screen layer consistent with 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, now the distributed constant of bucking electrode does not just impact the signal of core, 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 equipotentiality body, inside does not have electric potential difference, and interfering signal can penetrate bucking electrode and can not impact the core signal of screen layer encirclement.
During use, when Electrical Impedance Tomography System need to gather signal a, the b of certain two electrode channel, the switch controlling signal sending by main control device, gauge tap system is 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 b electrode wires core.Signal+, signal-be except being access in signal condition and A/D convertor circuit, simultaneously also as the input of shield guard circuit.Now, Electrical Impedance Tomography System channel control signals is controlled the screen layer signal that shielding drive circuit produces electrode a, b, that is: shield guard 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 b electrode.The like, the signal of the different passages of the every collection of Electrical Impedance Tomography System, shield guard is all pressed above work, thereby cancels out each other by being transferred to the signal of screen layer and external interference signal that electrode is subject to, reaches the object that realizes efficiently, at low cost electrode screening.
According to above-described embodiment, just can realize well the present invention.
Claims (5)
1. an Electrical Impedance Tomography System, it is characterized in that, comprise main control device, the image processing being connected with this main control device respectively and display device, signal condition and A/D convertor circuit, switching system, shield guard circuit and excitation source generating circuit, and the bucking electrode being connected with shield guard circuit with this switching system respectively, and this switching system is also connected with A/D convertor circuit, shield guard circuit and excitation source generating circuit with signal condition respectively; Described shield guard circuit comprises two combination switches, is connected in control winding displacement and the operational amplifier of the input of each combination switch, and is placed in respectively the in-phase input end of this operational amplifier and the resistance of outfan; Meanwhile, each combination switch at least disposes two outfans.
2. a kind of Electrical Impedance Tomography System according to claim 1, is characterized in that, described combination switch is simulation integrated switch or mechanical switch.
3. a kind of Electrical Impedance Tomography System according to claim 1 and 2, is characterized in that, described bucking electrode is at least one, and each bucking electrode includes core, and is wrapped in the screen layer of this core outer surface; Described core is connected with the holding wire of switching system, and screen layer is connected with shield guard circuit.
4. an electrode screening method for Electrical Impedance Tomography System, is characterized in that, comprises the following steps:
(1) select the bucking electrode by core outer surface parcel screen layer, and according to the quantity of bucking electrode, determine the quantity of combination switch, then take combination switch as basis, set up shield guard circuit;
(2) use main control device, image processing to set up into Electrical Impedance Tomography System with A/D convertor circuit, switching system, shield guard 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 shield guard circuit;
(3) operation Electrical Impedance Tomography System, make shield guard circuit produce electrode screening layer signal, this electrode screening layer signal transfers to the screen layer of bucking electrode, resist the interfering signal that bucking electrode is subject to, make in core signal consistent with screen layer, thereby eliminate the coupling capacitance between screen layer and core;
The concrete grammar of described step (1) comprising:
(1a) according to bucking electrode and combination switch one to one mode determine the quantity of combination switch;
(1b) outfan of each combination switch all connects the screen layer of a bucking electrode by output port, at the input of combination switch, connects an operational amplifier, configures the auxiliary circuit of operational amplifier simultaneously;
(1c) utilize and control winding displacement connection combination switch and main control device, finally form shield guard circuit.
5. the electrode screening method of a kind of Electrical Impedance Tomography System according to claim 4, is characterized in that, in described shield guard circuit, the quantity of operational amplifier is two.
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| 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 |
| CN110798963B (en) * | 2019-09-24 | 2022-11-15 | 惠州市金百泽电路科技有限公司 | Control method for amplitude consistency of 5G antenna PCB |
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| CN102370480A (en) * | 2011-09-30 | 2012-03-14 | 中国人民解放军第四军医大学 | Impedance detection device and detection method for craniocerebral radiation therapy treatment |
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| CN101524272A (en) * | 2008-03-04 | 2009-09-09 | 李平 | Digital pick-up device for body surface cardiac electric signals |
| CN202161408U (en) * | 2011-08-03 | 2012-03-14 | 武汉思创电子有限公司 | High-frequency electrotome interference suppression circuit |
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