CN102973269A - Device and method for measuring crossed plane electrical impedance tomography - Google Patents
Device and method for measuring crossed plane electrical impedance tomography Download PDFInfo
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- CN102973269A CN102973269A CN2012105662004A CN201210566200A CN102973269A CN 102973269 A CN102973269 A CN 102973269A CN 2012105662004 A CN2012105662004 A CN 2012105662004A CN 201210566200 A CN201210566200 A CN 201210566200A CN 102973269 A CN102973269 A CN 102973269A
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Abstract
The invention discloses a device and a method capable of preferably reconstructing three-dimensional electrical impedance distribution in an object and improving electric field space distribution nonuniformity through obtaining object surface voltage information in particular relating to human organ tissues such as heads and breasts. Through the adoption of the scheme, voltage information can be obtained from both a horizontal section and a vertical section and images on the sections are respectively combined to form a space three-dimensional graphic; and voltages between the rest positions can be also obtained through exciting any contact point on the surface and then a plurality of combined measuring methods are achieved to realize multi-algorithm extension and improve image accuracy. The design mainly comprises 65 special electrodes distributed on a hemispherical surface; with a high-performance FPAG (Field Programmable Gate Array) as core, functions such as exciting source control, digital frequency synthesis, multiplex control, high speed phase-sensitive detection, fast Fourier transformation and measuring signal demodulation are integrated in a single chip; and a circuit design capable of self-adaptively adjusting output impedance of a detected object is achieved.
Description
Technical field
The present invention relates to contact and measuring device in the impedance bioelectrical measurement, particularly a kind of electrical impedance imaging measuring device and method to the human organ tissue.
Background technology
Electrical impedance imaging is that a kind of need are measured at body surface, and reconstructs the means that internal driving distributes.It sets up electric field by injection current to a target area, and the voltage that subsequently the target periphery is produced is measured.In traditional electrical impedance tomography technology, the placement of electrode is confined to certain plane usually, yet electrical impedance imaging is a three-dimensional problem in essence, and its electric current is not limited on certain plane and flows, and therefore, two-dimension image rebuild can produce pseudomorphism usually.And the subject matter of the anti-imaging of three-dimensional resistance is: system can't bear complicated algorithm, and pathosis is so that algorithm is difficult to sometimes realize that edge region especially causes finally that the target location is difficult to judge or shape distortion in the reconstructed image.Open electric impedance imaging system can be realized the top layer impedance judgement of object well, but is limited by the factor of investigation depth, and precision can only guarantee in 2 ~ 3 centimetres scope.The crossing plane electrod-array system that for this reason develops, the two dimensional surface measurement data by staggered can more effectively make up the three-dimensional imaging model, and has reduced the amount of calculation of Direct Three-dimensional reconstruct under the prerequisite that guarantees effective accuracy.
Summary of the invention
The objective of the invention is the problems referred to above for prior art, technical problem to be solved by this invention provides a kind of, provide a kind of be used to obtain body surface by the device exciting current voltage that causes, thereby derive the device and method of the anti-information of three-dimensional resistance of interior of articles.This scheme all can be obtained information of voltage on horizontal section and vertical section, carry out respectively the imaging on the tangent plane, and then is combined to form the space three-dimensional figure; Also can obtain voltage between all the other optional positions by any contact point is encouraged, and then realize the multiple combination metering system, realize the Multiple algorithm expansion, improve the precision of images.
One of purpose of the present invention is to propose a kind of crossing plane electrical impedance imaging measuring device; Two of purpose of the present invention is to propose a kind of crossing plane electrical impedance imaging measuring method.
One of purpose of the present invention is achieved through the following technical solutions:
A kind of crossing plane electrical impedance imaging measuring device provided by the invention, comprise framework, be distributed in measuring unit and output unit on the framework, described measuring unit is scattering device in the measurement electrode that is used for obtaining the voltage signal that the testee surface causes on the framework under the exciting current effect, and described measurement electrode is input to output unit with the voltage signal that obtains.
Further, described framework is hemisphere, and described measurement electrode equidistantly is distributed on the hemisphere framework annularly, and described framework center of top is provided with common electrode, and described common electrode is connected with output unit;
Further, described measurement electrode is along the vertical electrode group of the symmetrical formation of vertical tangent plane of framework, and described measurement electrode arranges 2-8 along hemispheroidal vertical tangent plane and organizes vertical electrode group.
Further, described measurement electrode is along the symmetrical formation horizontal electrode of the horizontal section of framework layer, and described measurement electrode is horizontally disposed with 2-10 layer horizontal electrode layer along framework.
Further, also comprise central control processor and imaging system,
Described central control processor is used for receiving and processing voltage signal obtains testee inside by the three-dimensionalreconstruction algorithm electrical impedance distribution;
Described imaging system is used for exporting the electrical impedance distribution information of testee inside.
Further, described central control processor comprises driving source control unit, numerical frequency synthesis unit, multiplexed control unit, high speed phase sensitive detection unit, fast fourier transform demodulation measuring-signal unit;
Described arithmetic processing system comprises the driving source control unit, is used for producing the digital sine signal by phase accumulator;
Described numerical frequency synthesis unit is used for the digital sine signal of different frequency is synthesized, and can improve measurement efficient by the signal of telecommunication that injects after synthesizing, and increases the electrical impedance information of obtaining;
Described multiplexed control unit is used for injection phase and the voltage acquisition point of pumping signal are controlled;
Described high speed phase sensitive detection unit separates and measurement with phase place for the amplitude that will collect voltage signal;
Described fast fourier transform demodulation measuring-signal unit, be used for will to voltage signal block by sampling, time signal is converted into discrete series, to obtain the frequency domain characteristic of signal;
Further, also comprise switch arrays, described driving source control unit is connected with measuring unit by switch arrays.
Two of purpose of the present invention is achieved through the following technical solutions:
A kind of electrical impedance imaging measuring method of utilizing crossing plane electrical impedance imaging measuring device to carry out provided by the invention may further comprise the steps:
S1: input signal;
S2: State selective measurements mode and exciting electrode group;
S3: obtain the voltage signal between corresponding measurement electrode and be input to arithmetic processor and process;
S4: according to the metering system of selecting, the exciting electrode group is rotated corresponding measurement electrode group by turns, records successively all signals;
S5: when all excitations of corresponding metering system and measure after combination finishes, finish the electrical impedance images reconstruct of testee on three dimensions according to all signals.
Further, described pumping signal produces to central control processor by sending instruction; Converting analogue stimulus signal to after described pumping signal is processed through signal pre-processing circuit is input in the central control processor again.
Further, described input signal and metering system adopt following three kinds of combinations to carry out:
Mode one: flow out point take the common electrode at framework top as exciting current, successively as flowing into point as exciting current, measure the magnitude of voltage between inflow point and corresponding measurement electrode, successively in turn take other measurement electrode, finally obtain all voltage datas, as the restructuring matrix element;
Mode two: measure at first respectively the measurement electrode in each horizontal electrode layer, successively with the two ends of two measurement electrode as excitation, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode during measurement; Then measure respectively the measurement electrode in each vertical electrode group, successively with the two ends of two adjacent measurement electrode as excitation, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode during measurement;
Mode three: to stride the plane, any two electrodes of spaning electrode are measured respectively the magnitude of voltage of all the other all measurement electrode as the two ends of excitation.
The invention has the advantages that:
1) by staggered voltage measurement and follow-up electrical impedance reconstruct, can reflect testee minor variations spatially, small variable quantity has then been given prominence in the increment signal amplification, so only just can detect the minor variations of measured signal with the analog-digital converter of low resolution, improve certainty of measurement.
2) contact impedance of this system and skin surface is little, and because the application of output impedance auto-compensation, so that the capacity of resisting disturbance of this system is strong, the measurement drift is little, good stability.
3) this system incentive sampling mixing frequency digital signal occurs, and can realize the multifrequency stack, can arrange according to measurand electrical impedance characteristics under different frequency, Effective Raise the motility of measuring, also further improved certainty of measurement simultaneously.
4) this system adopts digital phase-sensitive demodulation (DPSD) and the FFT processing mode based on FPGA, by obtain amplitude and the phase value of measured signal with reference to the stack of signal and measuring-signal, the minor variations that has reflected measured signal, and it is fast to have speed, and noise is had stronger inhibiting characteristics.
Description of drawings
In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in further detail below in conjunction with accompanying drawing, wherein:
Fig. 1 is arrange sketch map side view and top view of crossing plane electrode of the present invention;
Fig. 2 is arrange sketch map side view and top view of crossing plane electrode of the present invention;
Fig. 3 is the sketch map of an application model of the present invention;
Fig. 4 is the measurement electrode sketch map that the present invention uses;
Fig. 5 is system principle diagram of the present invention;
Fig. 6 is the principle schematic of hybrid frequency driving source generator of the present invention;
Fig. 7 is the sketch map of the upper digital phase sensitivity detection principle of FPGA of the present invention;
Fig. 8 is for to arrange based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode one;
Fig. 9 is the top view of arranging based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode two;
Figure 10 is the front view of arranging based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode two;
Figure 11 is for to arrange based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode three;
Figure 12 is the driving source output impedance testing circuit figure in the electrical impedance auto-compensation modular circuit of the present invention;
Figure 13 is the negative impedance compensating circuit circuit diagram in the electrical impedance auto-compensation modular circuit of the present invention;
Figure 14 is the electrical impedance information scattergram on the Different Plane of using the present invention and obtaining;
The object dimensional space electrical impedance information distribution that Figure 15 obtains for using the present invention;
The operational flowchart of Figure 16 for using the present invention to measure.
The specific embodiment
Below with reference to accompanying drawing, the preferred embodiments of the present invention are described in detail; Should be appreciated that preferred embodiment only for the present invention is described, rather than in order to limit protection scope of the present invention.
Fig. 1 is arrange sketch map side view and top view of crossing plane electrode of the present invention, Fig. 2 is arrange sketch map side view and top view of crossing plane electrode of the present invention, Fig. 3 is the sketch map of an application model of the present invention, Fig. 4 is the measurement electrode sketch map that the present invention uses, Fig. 5 is system principle diagram of the present invention, as shown in the figure: a kind of crossing plane electrical impedance imaging measuring device provided by the invention, comprise framework, be distributed in measuring unit and output unit on the framework, described measuring unit is scattering device in the measurement electrode that is used for obtaining the voltage signal that the testee surface causes on the framework under the exciting current effect, and described measurement electrode is input to output unit with the voltage signal that obtains.
Described framework is hemisphere.Described measurement electrode equidistantly is distributed on the framework annularly, and described measurement electrode is along the vertical electrode group of the symmetrical formation of vertical tangent plane of framework, and described measurement electrode arranges 2-8 along hemispheroidal vertical tangent plane and organizes vertical electrode group.Described measurement electrode is along the symmetrical formation horizontal electrode of the horizontal section of framework layer, and described measurement electrode is horizontally disposed with 2-10 layer horizontal electrode layer along framework.Described framework center of top is provided with common electrode, and described common electrode is connected with output unit.Also comprise central control processor and imaging system, described central control processor is used for receiving and processing voltage signal obtains testee inside by the three-dimensionalreconstruction algorithm electrical impedance distribution; Described imaging system is used for exporting the electrical impedance distribution information of testee inside.Described central control processor comprises driving source control unit, numerical frequency synthesis unit, multiplexed control unit, high speed phase sensitive detection unit, fast fourier transform demodulation measuring-signal unit; Described arithmetic processing system comprises the driving source control unit, is used for producing the digital sine signal by phase accumulator; Described numerical frequency synthesis unit is used for the digital sine signal of different frequency is synthesized, and can improve measurement efficient by the signal of telecommunication that injects after synthesizing, and increases the electrical impedance information of obtaining; Described multiplexed control unit is used for injection phase and the voltage acquisition point of pumping signal are controlled; Described high speed phase sensitive detection unit separates and measurement with phase place for the amplitude that will collect voltage signal; Described fast fourier transform demodulation measuring-signal unit, be used for will to voltage signal block by sampling, time signal is converted into discrete series, to obtain the frequency domain characteristic of signal; Also comprise switch arrays, described driving source control unit is connected with measuring unit by switch arrays.
Embodiment provided by the invention also provides a kind of measuring method of utilizing the electrical impedance imaging that crossing plane electrical impedance imaging measuring device carries out, may further comprise the steps:
S1: input signal;
S2: State selective measurements mode and exciting electrode group;
S3: obtain the voltage signal between corresponding measurement electrode and be input to arithmetic processor and process;
S4: according to the metering system of selecting, the exciting electrode group is rotated corresponding measurement electrode group by turns, records successively all signals;
S5: when all excitations of corresponding metering system and measure after combination finishes, finish the electrical impedance images reconstruct of testee on three dimensions according to all signals.
Described pumping signal produces to central control processor by sending instruction; Converting analogue stimulus signal to after described pumping signal is processed through signal pre-processing circuit is input in the central control processor again.
Described input signal and metering system adopt following three kinds of combinations to carry out:
Mode one: flow out point take the common electrode at framework top as exciting current, successively as flowing into point as exciting current, measure the magnitude of voltage between inflow point and corresponding measurement electrode, successively in turn take other measurement electrode, finally obtain all voltage datas, as the restructuring matrix element;
Mode two: measure at first respectively the measurement electrode in each horizontal electrode layer, successively with the two ends of two measurement electrode as excitation, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode during measurement; Then measure respectively the measurement electrode in each vertical electrode group, successively with the two ends of two adjacent measurement electrode as excitation, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode during measurement;
Mode three: to stride the plane, any two electrodes of spaning electrode are measured respectively the magnitude of voltage of all the other all measurement electrode as the two ends of excitation.
The below describes crossing plane electrical impedance imaging measuring device and measuring method in detail:
Fig. 6 is the principle schematic of hybrid frequency driving source generator of the present invention, Fig. 7 is the sketch map of the upper digital phase sensitivity detection principle of FPGA of the present invention, Fig. 8 is for to arrange based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode one, Fig. 9 is the top view of arranging based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode two, Figure 10 is the front view of arranging based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode two, Figure 11 is for to arrange based on crossing plane electrode of the present invention, and the signal that forms excitation and detection mode three, Figure 12 is the driving source output impedance testing circuit figure in the electrical impedance auto-compensation modular circuit of the present invention, Figure 13 is the negative impedance compensating circuit circuit diagram in the electrical impedance auto-compensation modular circuit of the present invention, Figure 14 is the electrical impedance information scattergram on the Different Plane of using the present invention and obtaining, the object dimensional space electrical impedance information distribution that Figure 15 obtains for using the present invention, as shown in the figure: the signal generating circuit that the crossing plane electrical impedance imaging measuring device that the embodiment of the invention 2 provides adopts is made of field programmable gate array (FPGA) chip.FPGA can select the chip of ALTERA or XILINX company, such as the CYCLONEII of ALTERA.The inner direct digital synthesiser DDS that realizes of FPGA, the digital waveform signal of generation characteristic frequency and phase place.
The D/A converting circuit module that adopts in the embodiment of the invention, i.e. DAC﹠amp among Fig. 5; Shown in the Filter.The high-speed digital-analog conversion chip can be selected the product of the companies such as ADI or TI, such as the DAC2902 of TI.DAC2902 is converted to analogue stimulus signal with the digital stimulus signal that DDS produces.
The impedance detection that adopts in the embodiment of the invention and impedance auto-compensation module as shown in Figure 5, have mainly been used the high frequency difference amplifier AD8130 of ADI company.
The use of electrical impedance auto-compensation module: can be according to electrical impedance and the parasitic capacitance size of testee, its adverse effect of auto-compensation improves the output impedance value, and principle is as described below.
As shown in figure 12, constant-current source represents with the circuit model of a desirable current source output resistance in parallel and output capacitance, wherein proofreaies and correct resistance R cal=10k Ω.When system worked, then two switches were all opened; And when be used for regulating impedance, analog switch has switched to load Rcal and non-loaded, and the output voltage that records with phase-sensitive detector is respectively V
Cal HAnd V
Cal L
Through phase sensitive detection, the measured value in two kinds of different loads situations is:
V
cal H＝V
r H+jV
q H (1)
V
cal L＝V
r L+jV
q L
In the formula, V
Cal HExpression is connected to the output voltage when proofreading and correct resistance; V
r HExpression is connected to the in-phase voltage component when proofreading and correct resistance; V
q HExpression is connected to the quadrature voltage component when proofreading and correct resistance; V
Cal LExpression does not connect the output voltage when proofreading and correct resistance; V
r LExpression does not connect the in-phase voltage component when proofreading and correct resistance; V
q LExpression does not connect the quadrature voltage component when proofreading and correct resistance;
And calculated by circuit:
In the formula, the a-signal amplitude represents; R
oResistance R in the presentation graphs
oResistance; R
fResistance R in the presentation graphs
fResistance; R
CalResistance R in the presentation graphs
CalResistance; C
oCapacitor C in the presentation graphs
oThe appearance value; I represents to record size of current;
Compare and can get by two in (2):
The principle of utilizing real part and imaginary part to equate is solved by (3):
By above two formulas as seen, if V
Cal L=V
Cal H, R then
o→ ∞, C
o→ 0, by the electrical impedance auto-compensation, can greatly improve the output impedance value of current source.As shown in Figure 13, the complex impedance translation circuit is exactly to utilize tunable capacitor Ccomp(to be about output 1.5 times of parasitic capacitance) as positive feedback to offset effect of parasitic capacitance, make R
0, C
0Be tending towards ideal value, thereby improve output impedance.
The amplitude of voltage signal and the extraction of phase place:
As shown in Figure 6, the digital signal to be demodulated that has ADC to collect can be expressed as the pumping signal Asin (2 π n/N+ φ) behind the testee of flowing through, with the stack of N dimension noise signal Vn (n),
In the formula, V
i(n) signal that collects of expression; V
n(n) expression noise signal;
Based on matched filter (MatchedFilter, MF) principle, phase-sensitive detector and Fourier transformation module can be considered as relevant quadrature demodulator, input signal and reference signal Vrr, Vrq multiply each other and produce direct current and second harmonic component.
In the formula, V
Rr(n) expression input signal; V
Rq(n) expression reference signal;
Cumulative sum operation after the multiplier is an integrator, plays the function of low-pass filtering.Integration complete cycle of second harmonic component is zero, is equivalent to be low pass filtering the device filtering; Noise signal and reference signal are uncorrelated, and accumulation result also is zero, so only be left flip-flop, are called in-phase component Vr and quadrature component Vq:
In the formula, V
rIn-phase voltage component after the expression demodulation; V
qQuadrature voltage component after the expression demodulation;
The amplitude and the phase place that obtain input signal are respectively:
The signal injection switch arrays module that adopts in the embodiment of the invention namely adopts 65 electrode multiplexer switch parts.Select 1 analog switching ic ADG1206 to consist of by a plurality of 16.The switching controls end A0～A3 of analog switch is connected to the center-control treatment circuit.The various combination of A0～A3 selects different electrode access points as signal injection end and different electrode measurement ends.
The signal filter circuit module that adopts in the embodiment of the invention, circuit are that core consists of by programmable gain amplifier AD8330 and difference amplifier AD8130.The low pass filter filtering output that consists of by AD8130 again after amplifying with certain gain from the signal of D/A converting circuit, the gain of programmable gain amplifier by the center-control treatment circuit by the control of SPI interface.
The analog to digital conversion circuit module that adopts in the embodiment of the invention, as shown in Figure 5, core devices is high speed analog-to-digital conversion chip AD9222,12bit resolution, the highest conversion speed can reach 65Msps.
The digital signal that sampling obtains obtains amplitude and the phase place of signal after FPGA processes, then pass to computer by HPI, computer utilizes these data to carry out the electrical impedance distribution that the three-dimensionalreconstruction algorithm obtains testee inside, realizes the harmless fast detecting to target.
The measuring unit of this system is distributed on the hemispheroidal edge, from horizontal direction, electrode has been distributed on 4 different layers, 16 electrodes of every layer equidistantly are distributed in the edge (as shown in Figure 1) of hemisphere annularly, and the good symmetry of this distribution mode can provide accurately reliably measurement result.Be a model of this application in the accompanying drawing 2, its ground floor is apart from bottom 15mm, and each interlayer afterwards is divided into 20mm.The top view of this model (as shown in Figure 2), wherein the electrode at top is as common electrode, and 65 electrodes spatially are divided into again 8 groups perpendicular to 4 groups of above-mentioned horizontal electrode arrays.By such division, each arc tangent plane comprises 9 electrodes, and when electrode during from the axial injection model, the angle between the electrode is not wait, but is axial symmetry.
The requirement of high frequency pumping accurately being measured for satisfying the electrical impedance medical imaging technology, the electrode material therefor that device uses is ormolu (CuZn), surface gold-plating (Au), 150 ℃ of the highest tolerable temperatures, can reach 50A by electric current, about 0.3 Ω of resistance value, electrode diameter 4mm(sees Fig. 4), the electrode bottom design becomes the six-sided nut shape, is used for probe and is fixed at device.This electrode is highly sensitive, and is little with the contact impedance of skin surface, and has no side effect, and regular shape is easy to electric current uniform-flow mistake, improved the inhomogeneity same sex of spatial distribution of field, reduced the impact of contact impedance on 3-D effect.
For the voltage of finishing measurement point adopts, the present invention also comprises a cover hardware detection device, this device is take high-performance FPAG as core, so that driving source control, numerical frequency is synthetic, multiplexed control, the high speed phase sensitive detection, the functions such as fast fourier transform demodulation measuring-signal are integrated in the single chip, as shown in Figure 5, peripheral circuit comprises that also the signal front end amplifies, and pumping signal is injected switch arrays, signal detection switch arrays, analog to digital conversion circuit, impedance auto compensatng circuit etc.; It is characterized in that:
1) by FPGA hybrid frequency driving source generation pumping signal, this driving source can produce the digital stimulus signal of 1kHz ~ 1MHz single-frequency or double frequency mixing, and this signal has low noise after Control of Voltage gain amplifier and Voltage-controlled Current Source, high output impedance, as shown in Figure 6.This signal is to be connected with the current output terminal of excitation by certain position that FPGA gauge tap array switches in the electrod-array again, or be connected with the voltage filter amplifying circuit, thereby change successively the position of current excitation electrode and measurement electrode, can obtain the only voltage response of locus.Be different from traditional numerical frequency generation technique, this mode is integrated in phase accumulation and table lookup function among the FPGA, by digital form output current is set, this design has guaranteed the motility that frequency is selected, stability has been simplified hardware designs, and has reduced overall power.
2) another important feature of this system is that output impedance ZOUT significantly improves, because the existence of stray capacitance in the circuit, along with the rising output impedance ZOUT of operating frequency sharply descends, a method of head it off is to adopt complex impedance translation circuit (NIC) to offset stray capacitance to improve output impedance.
3) voltage signal on the electrode group is via difference amplifier AD8130(common mode rejection ratio 80dB@2MHz), be converted to single-ended voltage signal, through voltage control Amplifier AD8331(bandwidth 120MHz, noise 0.74nV/ √ Hz), so that gain is adjustable at 14.5dB ~ 74.5dB.This signal is through 14 modulus conversion chip AD9259(50MSPS, power consumption 98mW, Spurious-Free Dynamic Range 84dBc) conversion after enter FPGA.The response signal of frequency sweep constant-current source is carried out digital phase sensitivity detection (DPSD), the response signal of mixing constant-current source is carried out fast Fourier transform (FFT), thereby isolate amplitude, phase place in the digital signal, to extract the electrical impedance information of measured target.The advantages such as shown in Figure 7, phase-sensitive detection and fast Fourier transform can be extracted amplitude and the phase place of small-signal from background noise, random noise is had stronger inhibitory action, have motility, and precision is high, and the linearity is good.
The operational flowchart of Figure 16 for using the present invention to measure, as shown in the figure, the crossing plane electrical impedance imaging measuring method that the embodiment of the invention 2 provides is as follows:
The work implementing procedure of measuring phases:
The PC operation sends instruction to central control processor FPGA, produces pumping signal;
Pumping signal converts analogue stimulus signal to through signal pre-processing circuit;
Central control processor obtains metering system by the instruction that PC reaches, and selects the exciting electrode group;
By selected metering system, the control simulation switch obtains the voltage signal between corresponding measurement electrode;
The signal that obtains by signal filtering and analog digital conversion after, send into FPGA and be further processed;
According to metering system, the exciting electrode group is rotated corresponding measurement electrode group by turns, records successively all signals;
When all excitations of corresponding metering system and measure after combination finishes, with process voltage and phase signal send PC back to, finish the electrical impedance images reconstruct on the object dimensional space.
Different excitations and metering system measurement in a closed series process:
The signal energisation mode divides single-frequency or multifrequency to mix, and because the application of many plane electrodes array, excitation and measurement pattern combination are able to great expansion.To different measuring objects, different electrical impedance grade and distribution are arranged, and different injection way is measured the sensitivity difference so that the inner CURRENT DISTRIBUTION that forms of imaging region is different, the signal to noise ratio of acquired signal is not identical.Mainly comprise following 3 classes excitation and metering system:
1) as shown in Figure 8, flow out point take the summit (remembering No. 65 point) of half spherical model as exciting current, take other 64 electrodes successively as flow into point as exciting current, measure all the other 63 points and No. 65 interelectrode magnitudes of voltage, successively in turn, finally obtain 64*63 voltage data, as the restructuring matrix element.
2) shown in Fig. 9,10, at first with 4 groups among Fig. 9,10, every group of circular electrod-array of 16 levels measured, during measurement successively with two comparative electrodes as the excitation two ends, measure respectively the magnitude of voltage between all adjacent electrodes, thus, each horizontal electrode group obtains 16*16 measurement data altogether, and 4 groups come to 4*16*16 data; Then with 8 groups in the accompanying drawing 9,10, every group of 9 vertical electrod-arrays are measured, during measurement successively with two adjacent electrodes as the excitation two ends, measure respectively the magnitude of voltage between all the other all adjacent electrodes, thus, each horizontal electrode group obtains 8*7 measurement data altogether, and 9 groups come to 9*8*7 data.By analyzing, this kind compound mode can provide more independently measurement data, reduces the inhomogeneous impact of excited current distribution, improves common mode noise rejection, and improves the sensitivity in the central area, to improve the resolution of electrical impedance imaging.
When 3) using, will stride the plane, any two electrodes of spaning electrode are as the two ends of excitation, and measurement electrode can be between adjacent electrode, also can be to stride plane, any two points of spaning electrode.This metering system is used in the very inhomogeneous testee of electrical impedance distribution, can analyze more exactly the electrical impedance distribution of regional area.
The electrical conductivity of can packing into during practical application is the agar material as a setting of 0.1S/m, and places a spherical Radix Dauci Sativae at the second layer and the 3rd layer of horizontal electrode array central authorities, 4 centimetres of diameters, electrical conductivity 0.2Sm-1(is activated at 100kHz).Because the conductivity characteristic of Radix Dauci Sativae differs under different frequency, therefore can reconstruct by the mode of frequency difference position and the volume of this Radix Dauci Sativae.
Figure 14 is the electrical impedance information scattergram on 4 horizontal planes obtaining by excitation and data acquisition modes in the aforesaid the 2nd and 8 vertical sections.
Figure 15 is by above-mentioned 12 profile combinations, the electrical impedance distribution on the three dimensions through forming behind the date processing, and σ values different among the figure represent different electrical impedance ranking score cloth covers.
The above is the preferred embodiments of the present invention only, is not limited to the present invention, and obviously, those skilled in the art can carry out various changes and modification and not break away from the spirit and scope of the present invention the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.
Claims (10)
1. crossing plane electrical impedance imaging measuring device, it is characterized in that: comprise framework, be distributed in measuring unit and output unit on the framework, described measuring unit is scattering device in the measurement electrode that is used for obtaining the voltage signal that the testee surface causes on the framework under the exciting current effect, and described measurement electrode is input to output unit with the voltage signal that obtains.
2. crossing plane electrical impedance imaging measuring device according to claim 1, it is characterized in that: described framework is hemisphere, described measurement electrode equidistantly is distributed on the hemisphere framework annularly, and described framework center of top is provided with common electrode, and described common electrode is connected with output unit.
3. crossing plane electrical impedance imaging measuring device according to claim 1, it is characterized in that: described measurement electrode is along the vertical electrode group of the symmetrical formation of vertical tangent plane of framework, and described measurement electrode arranges 2-8 along hemispheroidal vertical tangent plane and organizes vertical electrode group.
4. crossing plane electrical impedance imaging measuring device according to claim 1, it is characterized in that: described measurement electrode is along the symmetrical formation horizontal electrode of the horizontal section of framework layer, and described measurement electrode is horizontally disposed with 2-10 layer horizontal electrode layer along framework.
5. crossing plane electrical impedance imaging measuring device according to claim 1 is characterized in that: also comprise central control processor and imaging system,
Described central control processor is used for receiving and processing voltage signal obtains testee inside by the three-dimensionalreconstruction algorithm electrical impedance distribution;
Described imaging system is used for exporting the electrical impedance distribution information of testee inside.
6. crossing plane electrical impedance imaging measuring device according to claim 5, it is characterized in that: described central control processor comprises driving source control unit, numerical frequency synthesis unit, multiplexed control unit, high speed phase sensitive detection unit, fast fourier transform demodulation measuring-signal unit;
Described arithmetic processing system comprises the driving source control unit, is used for producing the digital sine signal by phase accumulator;
Described numerical frequency synthesis unit is used for the digital sine signal of different frequency is synthesized, and can improve measurement efficient by the signal of telecommunication that injects after synthesizing, and increases the electrical impedance information of obtaining;
Described multiplexed control unit is used for injection phase and the voltage acquisition point of pumping signal are controlled;
Described high speed phase sensitive detection unit separates and measurement with phase place for the amplitude that will collect voltage signal;
Described fast fourier transform demodulation measuring-signal unit, be used for will to voltage signal block by sampling, time signal is converted into discrete series, to obtain the frequency domain characteristic signal of signal.
7. crossing plane electrical impedance imaging measuring device according to claim 1, it is characterized in that: also comprise switch arrays, described driving source control unit is connected with measuring unit by switch arrays.
8. the measuring method of each described a kind of crossing plane electrical impedance imaging measuring device according to claim 1-7 is characterized in that: may further comprise the steps:
S1: input signal;
S2: State selective measurements mode and exciting electrode group;
S3: obtain the voltage signal between corresponding measurement electrode and be input to arithmetic processor and process;
S4: according to the metering system of selecting, the exciting electrode group is rotated corresponding measurement electrode group by turns, records successively all signals;
S5: when all excitations of corresponding metering system and measure after combination finishes, finish the electrical impedance images reconstruct of testee on three dimensions according to all signals.
9. crossing plane electrical impedance imaging measuring method according to claim 8 is characterized in that: described pumping signal produces to central control processor by sending instruction; Converting analogue stimulus signal to after described pumping signal is processed through signal pre-processing circuit is input in the central control processor again.
10. crossing plane electrical impedance imaging measuring method according to claim 8, it is characterized in that: described input signal and metering system adopt following three kinds of combinations to carry out:
Mode one: flow out point take the common electrode at framework top as exciting current, successively as flowing into point as exciting current, measure the magnitude of voltage between inflow point and corresponding measurement electrode, successively in turn take other measurement electrode, finally obtain all voltage datas, as the restructuring matrix element;
Mode two: measure at first respectively the measurement electrode in each horizontal electrode layer, successively with the two ends of two measurement electrode as excitation, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode during measurement; Then measure respectively the measurement electrode in each vertical electrode group, successively with the two ends of two adjacent measurement electrode as excitation, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode during measurement;
Mode three: to stride the plane, any two electrodes of spaning electrode are measured respectively the magnitude of voltage of all the other all measurement electrode as the two ends of excitation.
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