Background technique
Electrical impedance tomography technology (EIT) is not damaged, radiationless, low cost and image taking speed with functional imagingThe emerging medical imaging technology of the advantages such as fast.EIT can use the physiology that functional imaging embodies tissue, the letter such as pathologyBreath.The concept of bio-electrical impedance imaging was most proposed early in 1978 by John G.Webster.David C.Barber and BrianH.Brown is that earliest carry out applies EIT in the detection of human body distribution of conductivity.In decades hereafter, EIT is as a kind of toolThere is the medical imaging technology of tempting application prospect, it has also become one of the hot fields of contemporary scientific research.Currently, EIT technology isIn theory, hardware design, image reconstruction calculation is made great progress greatly, is had many researchs and is directed to specific clinical applicationPoint: the imaging of lung's monitoring of respiration, abdominal organs functional imaging, breast cancer detection imaging, brain detection imaging.
In the research process of the EIT technology at present towards human organ, current research work is concentrated mainly on imageReconstruction technique, the extraction and analytical technology of organ bioelectrical signals, however, core component one of of the electrode as whole system,The critical issue in its commercialization process and finally being needed to solve by one as clinical treatment Application of device, but previousIn scientific research there is no obtain Review of Electrical Impedance Tomography researcher enough attention, the still not deep enough of correlative study butIt is that the high performance electrode of R and D has become one of the critical issue of measuring accuracy for improving medical EIT technology.
It is most of all using Ag/AgCl electricity at present in electrical impedance tomography technology in the application study of medical domainPole is as excitation and measuring electrode.It is 2015, all big equal in " Science Bulletin " the 15th the 1352-1360 pages of the phase " biology deliveredElectrode for medical service manufacturing technology and application study progress " describe a kind of typical Ag/AgCl electrode use process.Firstly, it is necessary toOne personnel for having received professional training removes destratum corneum and cleaning skin according to the position that each electrode is placed, then by leadingCoagulation glue pastes electrode in skin surface.And Signa Gel is easy to happen dehydration and drying, so that electrode is easy to fall off, and leadsThe electrical impedance characteristics of coagulation glue can also change.Such electrode is not suitable for being used for a long time, electrode meeting and skin contactBad, current distribution is uneven is even, these can all cause collected resistance antinoise signal to be easy to appear abnormal fluctuation, influences finalImage result.
Key sensor part of the biomedical electrode as connection EIT data acquisition and processing (DAP) platform and human body, usually needsMultiple electrodes are wanted to motivate and measure bioelectrical signals.In addition, compared with the bio-imagings technology such as CT, nuclear magnetic resonance, EIT technologyIt is not damaged, radiationless, low-cost technologies advantage is but also it is to the long term monitoring of organism using upper more rich in valenceValue.Therefore, electrode used in EIT should also meet comfortable enough when wearing and wear for a long time, and in measurement processIn do not need the posture that patient remains stationary.EIT usually requires multiple electrodes to motivate and measure bioelectrical signals, multipleThe use of electrode can be involved in the problems, such as how electrode is distributed, and how overcome the interference problem that generation is moved in measurement process.This year, some researchs around this respect are also being unfolded, such as: Fiedler P in 2018 is in " IEEE transactions nervous systemWith rehabilitation project " (IEEE Transactions on Neural Systems&Rehabilitation Engineering)" contact pressure and flexibility of spininess dry type electroencephalographic electrode " (Contact pressure and that 99 phase 1-1 chapters are deliveredFlexibility of multipin dry eeg electrodes) a kind of dry electrode of spininess is proposed to be used for brain electricity prisonIt surveys, the quality of their result of study discovery measuring signal depends on contact stable between electrode and skin.They are by applyingPlus-pressure studies the relationship of pressure and contact impedance, using integrated pressure sensor on the electrode monitors electrode and skinContact impedance.The design of this electrode can monitor contact situation of the electrode with organism surface to a certain extent, stillIts structure is relative complex, and function is more single.
Summary of the invention
In order to solve the above technical problems, the present invention proposes a kind of test of EIT system based on flexible fiber pressure drag materialElectrode, and design a set of EIT for novel and multifunctional multiplexing electrode and improve test macro, shape occurs for monitoring flexible electrodeBecome the measurement with distortion, and it is merged with imaging data, to improve the image quality under organism motion conditions.
A kind of electrical impedance imaging electrode and system suitable under motion state, including test electrode module, signal gatingDevice, measuring signal generator, controller, test signal picker and message handler；Wherein test electrode module passes through surveyData line connection signal gate is tried, signal gating device passes through control bus by excitation bus connecting test signal generatorController is connected, is assigned to test electrode module by data acquisition bus connecting test signal picker, and by bus signals, is surveyedTrial signal collector passes through data/address bus link information processor.
The test electrode module includes electrode, and the electrode is flexible pressure drag material, and electrode is using closely arrangementMode.
It further include interelectrode elastic connection section, it is preferred that the length ratio between the length and elastic connecting strip of electrodeGreater than 3:1.
Electrode connection mode are as follows: including electric conductor and DATA REASONING line, 1 electrode of electric conductor, DATA REASONING line and electricityPole connection, DATA REASONING line, including pumping signal line Ya, Xa for testing pressure drag variable signal, for testing pressure drag variationData acquisition line Yb, Xb of signal is tested the test and excitation signal wire A of field domain resistance and the impedance information for EIT imaging, is surveyedThe test of examination hall domain resistance and the impedance information for EIT imaging acquires signal wire B.
DATA REASONING line on each electrode accesses signal gating device, and is controlled by programmable controller and tested signalSource, signal picker gating.Wherein signal gating device is divided into multi-channel gating device Xa, multi-channel gating device Xb, multi-channel gating device Ya, moreSix road gate Yb, multi-channel gating device A, multi-channel gating device B modules, above six modules manage 6 data of gating respectively and surveyThe signal for trying line is connected.Wherein multi-channel gating device Xa, Ya is controlled by CtrXa, CtrYa signal of programmable controller respectively,The Xa of each electrode, the pressure drag material test signal of Ya signal wire and testing source are gated in the different testing times of test periodOr ground connection (reference level).Wherein multi-channel gating device Xb, Yb is controlled by CtrXb, CtrYb signal of programmable controller respectively,The Xb of each electrode, the pressure drag material acquisition mould of Yb signal wire and signal picker are gated in the different testing times of test periodBlock or ground connection (reference level).Wherein multi-channel gating device A, B is controlled by programmable controller CtrA, CtrB signal respectively, will be eachThe a-signal line of electrode and the impedance imaging measuring signal of testing source gate.The impedance imaging of B signal line and signal pickerData acquisition module gating.
A method of the electric impedance imaging system based on piezoresistive electrodes carries out electrical impedance imaging, includes the following steps:
(1) input test number of electrodes, and determine test period, starting measurement；
(2) electrode test: system enters the 1st electrode monitoring cycle, and in the period, controller passes through Ctr Xa, CtrYa controls multi-channel gating device gating 1Xa, 1Ya and pressure drag signal testing source, controls multi-channel gating device choosing by Ctr Xb, Ctr YbLogical 1Xb, 1Yb and pressure drag signal picker, the I/O channel of other multi-channel gating devices are in vacant state；
(3) impedance information measures: system enters the 1st impedance information measurement period, and in this period, controller passes throughCtr Xa, Ctr Ya, Ctr Xb, (gating is with reference to electricity for Ctr Yb control multi-channel gating device gating 2Xa, 2Ya, 2Xb, 2Yb ground connectionPole), gate is controlled by Ctr A and gates 1A and impedance test signal source, gate is controlled by Ctr A and gates 3B-numBAny two electrode combination and impedance signal collector in channel are connected, and rest channels are hanging；
(4) electrode test: after system enters i-th of electrode monitoring cycle, obtaining i divided by the remainder of N is number, and N isThe product of measuring electrode number num and smooth periodicity k, in the period, controller controls multichannel choosing by Ctr Xa, Ctr YaThe pressure drag signal testing source of logical device gating numberXa, numberYa and testing source, are controlled more by Ctr Xb, Ctr YbRoad gate gate numberXb, numberYb and signal picker pressure drag signal picker, other multi-channel gating devices it is defeatedEnter output channel and is in vacant state；
(5) impedance information measures: entering i-th of impedance and EIT information measurement period in system, obtains i divided by the remainder of NFor number, in this period, controller controls multi-channel gating device gating by Ctr Xa, Ctr Ya, Ctr Xb, Ctr Yb(number+1) Xa, (number+1) Ya, (number+1) Xb, (number+1) Yb ground connection (gating reference electrode), pass through CtrA controls gate gating 1A and impedance test signal source, controls gate gating except (number) B and (number by Ctr A+ 1) any two electrode combination Yu impedance signal collector of channel B are connected, and rest channels are hanging.
(6) judge test period number whether be N=num*k integral multiple, if it is by pressure drag signal and impedance measurementSignal inputs message handler, and the data of collector are carried out fusion of imaging, if otherwise entering next electrode monitoring weekPhase and impedance information measurement period.
Further include step (7): the state classifier in message handler classifies collected pressure drag signal, callsThe sensitivity matrix of corresponding position, and the sensitivity matrix for showing imaging results is formed with EIT test information matrix.
By state classifier monitor electrode delamination disablement signal, to corresponding electrode sequence number issue information warning, otherwise afterThe continuous circulation into measurement period.
Before the step (1), include the case where for field domain boundary to be measured, will test electrode be evenly arranged inIt surveys around field domain；The process of test is initially entered later.
The pressure drag signal that signal processor is inputted by test, after state classifier is classified, and according to sensitivityThe data set of matrix obtains sensitivity matrix, tests signal by the EIT of test input and obtains EIT test information matrix,The radian matrix that information matrix obtains display imaging results is tested by sensitivity matrix and EIT.
Wherein state classifier passes through the principal component of the pressure drag signal of Different electrodes position in the simulation calculation of host computerWeight analysis, and obtained according to the clustering of the multi-electrode pressure drag signal of weighting and Different electrodes placement position pressure drag signal；
The data set of sensitivity matrix is to pass through the limited emulation of the different location of electrode in the simulation calculation of host computerIt calculates and obtains.
The present invention compared with the existing technology the advantages of are as follows:
The electrode of general ET technology is using common good conductor material (Ag-AgCl of such as electrode for medical service), this hairIt is bright to prepare material as electrode using flexible fiber pressure drag material.Used flexible fiber pressure drag material not only has generallyThe conductive characteristic of good conductor, in addition to this, resistance value can also change with the pressure to it, degreeof tortuosity and be changed, and pass throughThe variation of its resistance value is monitored, the situation of change of the states such as the position of electrode prepared therefrom can be monitored, it is easily prepared, conductiveProperty preferably, adapt to pressure, the sensitivity for distorting variation is higher.Its change in resistance is monitored in testing, judges the torsion of electrode accordinglyQu Bianhua.The present invention devises a set of time-ordered measurement process simultaneously, for realizing required for EIT technology simultaneously in EIT systemField domain impedance information to be measured acquisition with supplement electrode twisted state information acquisition.By being led to flexible piezoresistive electrodesElectrical measurement, quantifies the twisted state information of flexible electrode, and added in imaging algorithm, improves image quality.
Specific embodiment
The present invention is further elaborated below in conjunction with example, but the invention is not limited to specific embodiments.
As shown in Figure 1, the electrical impedance imaging electrode and system being suitable under motion state of the invention, to be a kind of based on softProperty piezoresistive electrodes electrical impedance imaging test macro, including test electrode module, signal gating device, measuring signal generator, controlDevice, test signal picker and message handler processed.Wherein test electrode module is gated by test data line connection signalDevice.Signal gating device connects controller by excitation bus connecting test signal generator, by control bus, total by acquiringLine connecting test signal picker, and bus signals are assigned to test electrode module.Test signal picker passes through dataBus link information processor.
Modules are described in detail below.
In test electrode module, the present invention use the electrode of flexible pressure drag material preparation as shown in Fig. 2, 1 to be conductive in figureBody, 2 electrodes prepared for flexible pressure drag material, wherein for the sewing of electric conductor 1 on pressure drag material 2, its purpose is to betterIt is contacted with pressure drag material, the sensitive resistance signal changed with the variation of flexible electrode, 3 be a series of DATA REASONING line,Wherein, Ya, Xa are the pumping signal line for testing pressure drag variable signal, and Yb, Xb are the number for testing pressure drag variable signalAccording to gathering line, A is the test and excitation signal wire for testing field domain resistance and the impedance information for EIT imaging, and B is test field domain electricityHinder and be used for the test acquisition signal wire of the impedance information of EIT imaging.
As shown in figure 3, the arrangement of electrode of the present invention includes between electrode and electrode by taking the EIT test macro of eight electrodes as an exampleElastic connection section, wherein electrode use close arrangement mode, the length ratio between the length and elastic connecting strip of electrodeIn 3:1 or more, electrode can sufficiently be experienced under tight beam state electrode both direction because position changes a lot when byThe power arrived.
As shown in figure 4, the present invention is by taking a kind of EIT system of 8 electrodes as an example, 6 data lines on each electrode are accessedSignal gating device, and gated by programmable controller control and testing source, signal picker.Wherein signal gating device pointFor multi-channel gating device Xa, multi-channel gating device Xb, multi-channel gating device Ya, multi-channel gating device Yb, multi-channel gating device A, multi-channel gating device BSix modules, the signal that above six modules manage 6 data p-wires of gating respectively are connected.Wherein multi-channel gating device Xa, YaIt is controlled respectively by CtrXa, CtrYa command signal of programmable controller, 8 is gated in the different testing times of test periodThe pressure drag material of the Xa of electrode, Ya signal wire and testing source tests signal or ground connection (reference level).Wherein multi channel selectingDevice Xb, Yb are controlled by CtrXb, CtrYb command signal of programmable controller respectively, in the different testing times of test periodGate the Xb of 8 electrodes, the pressure drag material acquisition module or ground connection (reference level) of Yb signal wire and signal picker.It is wherein moreRoad gate A, B are controlled by programmable controller CtrA, CtrB signal respectively, by the a-signal line and testing source of 8 electrodesImpedance imaging measuring signal gating.The impedance imaging data acquisition module of B signal line and signal picker gating.
As shown in the test flow chart of Fig. 5 and Fig. 6, the specific imaging mode of this system is as follows:
Firstly, the case where being directed to field domain boundary to be measured, test electrode is evenly arranged in around field domain to be measured.Start laterInto the process of test.
The first step, input test number of electrodes, and determine test period, starting measurement；
Second step, system enters the 1st electrode monitoring cycle, and in this period, controller passes through Ctr Xa, Ctr YaMulti-channel gating device gating 1Xa, 1Ya and pressure drag signal testing source are controlled, multi-channel gating device gating is controlled by Ctr Xb, Ctr YbThe I/O channel of 1Xb, 1Yb and pressure drag signal picker, other multi-channel gating devices is in vacant state.And system enters theAfter i electrode monitoring cycle, if number is remainder of the i divided by N, in this period, controller passes through Ctr Xa, Ctr YaControl multi-channel gating device gating numberXa, numberYa and testing source pressure drag signal testing source, by Ctr Xb,Ctr Yb controls the pressure drag signal picker of multi-channel gating device gating numberXb, numberYb and signal picker, other are moreThe I/O channel of road gate is in vacant state.
Third step, system enter the 1st impedance information measurement period, in this period, controller by Ctr Xa,Ctr Ya, Ctr Xb, Ctr Yb control multi-channel gating device gating 2Xa, 2Ya, 2Xb, 2Yb ground connection (gating reference electrode), pass throughCtr A controls gate gating 1A and impedance test signal source, controls gate by Ctr A and gates any of the channel 3B-8BTwo electrode combinations and impedance signal collector are connected, and rest channels are hanging.And enter i-th of impedance information measurement week in systemPhase, if number is remainder of the i divided by N, in this period, controller passes through Ctr Xa, Ctr Ya, Ctr Xb, Ctr YbControl multi-channel gating device gating (number+1) Xa, (number+1) Ya, (number+1) Xb, (number+1) Yb ground connection (choosingLogical reference electrode), gate is controlled by Ctr A and gates 1A and impedance test signal source, gate gating is controlled by Ctr AExcept any two electrode combination and impedance signal collector of (number) B and (number+1) channel B are connected, rest channels are outstandingIt is empty.
4th step, judges whether test period number is the integral multiple of number of electrodes, if so, the data of collector are meltedSynthesized image, if not, into next electrode monitoring cycle and impedance information measurement period.
5th step, judges whether pendulous frequency reaches default smoothness period value k, is by pressure drag signal and impedance measurement signalInput message handler.
6th step, the state classifier in message handler classify collected pressure drag signal, call corresponding positionThe sensitivity matrix set participates in the imaging process of currently available impedance information matrix.And electricity is monitored by state classifierPole falls off disablement signal, issues information warning to corresponding electrode sequence number, otherwise goes successively to the circulation of measurement period.
Signal is tested invention also provides the EIT of a kind of pressure drag signal by test input and test input to carry outThe method of imaging, as shown in figure 5, wherein g is the Grey imaging matrix of (N=a*b) that size is N, λ indicates the survey of EIT systemTry information M rank one-dimensional vector (sum that M is the electrode combination tested a test period), the vector according to every timeThe measurement result of the test signal of EIT is constantly updated.S is the normalization sensitivity matrix of preset standard field domain, and size is(M*N), that reflects on each pixel Their unit conductance rate variation can caused by potential variation, the calculation formula of SAre as follows:
In formula, i, j indicate measuring electrode serial number, and x, y indicate the position of the pixel of the picture of imaging, Si,j(x, y) is indicatedI, j measuring electrode information are to imaging point x, the mapping of y, p indicate imaged shape about pixel position x, y function, E indicates to existThe voltage that electrode measures, I indicate the exciting current in electrode.
Then the incidence relation of g, S and λ are as follows:
λ=Sg
In the present invention, the generation method of sensitivity matrix S is obtained using finite element simulation method, obtained sensitivityThere is direct relationship in the position of matrix and electrode.Simultaneously by the corresponding pressure drag signal matrix in Different electrodes position and specific movementThe pressure drag signal that movement generates carries out clustering, judges the concrete form of the pressure drag signal of each position signal, establishes associationSet, input state classifier.During the test, collected pressure drag signal is carried out electrode position point by state classifierClass, and the data set of corresponding sensitivity matrix is called to participate in imaging.
In order to improve the quality of clustering, prevent the noise information in test process from having an impact to classification.To signalPrincipal component analysis dimensionality reduction, to the principal component analysis dimensionality reduction of signal the step of is as follows:
1. testing the pressure drag information of the electrode output for being attached to organism surface under several typical electrode for medical service environmentSignal measures n sample altogether, and each sample is tieed up the voltage test signal of (number of electrodes that num is test) by p=num*2, togetherForm the matrix X of following form:
Data processing is standardized to above-mentioned formula, standardization formula is as follows:
WhereinIt is XjArithmetic mean of instantaneous value,It is XjStandard deviation.And remember Z=(zij)n*pFor the data after standardizationMatrix.
2. the covariance matrix of normalized data
Variable X=[X1X2…Xp] in, the related coefficient calculation formula of two variables are as follows:
Since the variable in Z has been standardized variable, the covariance matrix of the column variable of Z is exactly related coefficient at this timeMatrix.
3. calculating the characteristic root and feature vector of R
The characteristic equation of correlation matrix R is | R- λ I |=0, and the characteristic root λ of matrix R can be found out using characteristic equationi(j=1,2 ... p), and characteristic root is arranged from small to large, then finds out corresponding feature vector Υi=(Υi1,Υi2,…Υip) ', is weighted standardized index to obtain factor weighted method using the component value of feature vector as flexible strategy.
4. calculating the variance contribution ratio of weight and principal component
The size of the characteristic root of correlation matrix R reflects the specific gravity that i-th of principal component includes information, contribution rate are as follows:
5. setting contribution rate of accumulative totalIt indicates to akArrangement from big to small has been carried out, A is chosenkReachThe component of 90% principal component analysis determines corresponding electrode target m.
The step of wherein carrying out clustering to signal is as follows:
1, the data of test set
According to the principal component analysis of front, the position for the electrode sets for entering principal component is carried out enumerating design accordingly,Each combination is denoted as Yi,Yi=[y1,y2,…ym], thus constitute cluster Y={ Y1,Y2…Yt), such as in principal component analysis intoCapable analysis set takes the pressure drag signal set X of several typical actions as set to be sorted.
2, the classification similarity measure criterion of signal similitude
X (n) is the signal component of the specific dimension of actual signal, and y (n) is the pressure drag signal of the electrode position of setting.According to ρijJudge YiWith the similarity of X, ρ is setijThreshold value, statistics similarity be higher than ρijX-component quantity q, as Yi'sAvailability criterion
3, availability criterion Q is set, takes the electrode position of q > Q as sensitivity matrix simulation object.
The above description is only a preferred embodiment of the present invention, is not intended to limit the scope of the invention, all utilizationsEquivalent structure or equivalent flow shift made by present specification is applied directly or indirectly in other relevant technologiesField is included within the scope of the present invention.