CN102973269B - 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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- CN102973269B CN102973269B CN201210566200.4A CN201210566200A CN102973269B CN 102973269 B CN102973269 B CN 102973269B CN 201210566200 A CN201210566200 A CN 201210566200A CN 102973269 B CN102973269 B CN 102973269B
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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 impedance bioelectrical measurement, particularly a kind of electrical impedance imaging measuring device and method to human organ tissue.
Background technology
Electrical impedance imaging is a kind of need be measured at body surface, and reconstructs the means that internal driving distributes.It sets up electric field by injection current to target area, and the voltage subsequently target periphery being produced is measured.In traditional electrical impedance tomography technology, the placement of electrode is confined to certain plane conventionally, yet electrical impedance imaging is a three-dimensional problem in essence, and its electric current is not limited in certain plane and flows, and therefore, two-dimension image rebuild can produce pseudomorphism conventionally.And the subject matter of the anti-imaging of three-dimensional resistance is: system cannot be born complicated algorithm, pathosis makes algorithm sometimes be difficult to realize, and especially edge region, finally causes target location in reconstruction image to be difficult to judgement or shape distortion.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 the scope of 2 ~ 3 centimetres.The crossing plane electrod-array system of exploitation, by staggered two dimensional surface measurement data, can more effectively build three-dimensional imaging model for this reason, and under the prerequisite that guarantees effective accuracy, has reduced the amount of calculation of Direct Three-dimensional reconstruct.
Summary of the invention
The object of the invention is the problems referred to above for prior art, technical problem to be solved by this invention is to provide a kind of, a kind of voltage causing by installing exciting current for obtaining body surface is provided, thereby derives 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 from horizontal section and vertical section, carries out respectively the imaging on tangent plane, and then is combined to form space three-dimensional figure; Also can obtain voltage between all the other optional positions, and then realize multiple combination metering system by any contact point is encouraged, realize Multiple algorithm and expand, improve the precision of images.
One of object of the present invention is to propose a kind of crossing plane electrical impedance imaging measuring device; Two of object of the present invention is to propose a kind of crossing plane electrical impedance imaging measuring method.
One of object 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 in framework, described measuring unit be scattering device in framework for obtaining the measurement electrode of the voltage signal that testee surface causes under exciting current effect, described measurement electrode is input to output unit by the voltage signal obtaining.
Further, described framework is hemisphere, and described measurement electrode is equidistantly distributed in 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 longitudinal tangent plane of framework, and described measurement electrode arranges 2-8 along hemispheroidal longitudinal tangent plane and organizes vertical electrode group.
Further, described measurement electrode is along the symmetrical formation horizontal electrode of the horizontal section layer of framework, 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, obtains the electrical impedance distribution of testee inside for receiving and process voltage signal by three-dimensionalreconstruction algorithm;
Described imaging system, 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 driving source control unit, for produce digital sine signal by phase accumulator;
Described numerical frequency synthesis unit, for the digital sine signal of different frequency is synthesized, can improve measurement efficiency by the signal of telecommunication injecting after synthesizing, and increases the electrical impedance information of obtaining;
Described multiplexed control unit, for controlling the injection phase of pumping signal and voltage acquisition point;
Described high speed phase sensitive detection unit, for carrying out the amplitude that collects voltage signal separated and measure with phase place;
Described fast fourier transform demodulation measuring-signal unit, for by voltage signal by sampling, block, 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 object 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, comprises the following 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, rotation exciting electrode group, the corresponding measurement electrode group of rotation, records all signals successively;
S5: when all excitations of corresponding metering system and after measuring and having combined, complete 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; Described pumping signal converts analogue stimulus signal to and is input in central control processor after signal pre-processing circuit is processed.
Further, described input signal and metering system adopt following three kinds of combinations to carry out:
Mode one: the common electrode at framework top of take is that exciting current flows out point, take other measurement electrode successively as flowing into point as exciting current, measure the magnitude of voltage flowing between point and corresponding measurement electrode, successively in turn, finally obtain all voltage datas, as restructuring matrix element;
Mode two: measure first respectively the measurement electrode in each horizontal electrode layer, using successively two measurement electrode during measurement as the two ends of encouraging, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode; Then measure respectively the measurement electrode in each vertical electrode group, during measurement, using successively two adjacent measurement electrode as the two ends of encouraging, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode;
Mode three: with across plane, any two electrodes of spaning electrode, as the two ends of excitation, are measured respectively the magnitude of voltage of all the other all measurement electrode.
The invention has the advantages that:
1) by staggered voltage measurement and follow-up electrical impedance reconstruct, can reflect testee minor variations spatially, increment signal is amplified and given prominence to small variable quantity, so only with the analog-digital converter of low resolution, just can detect the minor variations of measured signal, improve certainty of measurement.
2) contact impedance of this system and skin surface is little, and due to the application of output impedance auto-compensation, makes the capacity of resisting disturbance of this system strong, measures drift little, good stability.
3) this system incentive sampling mixing frequency digital signal occurs, and can realize multifrequency stack, can arrange according to measurand electrical impedance characteristics under different frequency, has effectively improved the motility of measuring, and has 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, noise is had to stronger inhibiting feature.
Accompanying drawing explanation
In order to make the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, the present invention is described in further detail, wherein:
Fig. 1 is arrange schematic diagram side view and top view of crossing plane electrode of the present invention;
Fig. 2 is arrange schematic diagram side view and top view of crossing plane electrode of the present invention;
Fig. 3 is the schematic diagram of an application model of the present invention;
Fig. 4 is the measurement electrode schematic diagram 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 schematic diagram 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 forming 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 forming 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 forming excitation and detection mode two;
Figure 11 is for to arrange based on crossing plane electrode of the present invention, and the signal forming excitation and detection mode three;
Figure 12 is the driving source output impedance testing circuit figure in electrical impedance auto-compensation modular circuit of the present invention;
Figure 13 is the negative impedance compensating circuit circuit diagram in electrical impedance auto-compensation modular circuit of the present invention;
Figure 14 is the electrical impedance information scattergram in 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 is only for the present invention is described, rather than in order to limit the scope of the invention.
Embodiment 1
Fig. 1 is arrange schematic diagram side view and top view of crossing plane electrode of the present invention, Fig. 2 is arrange schematic diagram side view and top view of crossing plane electrode of the present invention, Fig. 3 is the schematic diagram of an application model of the present invention, Fig. 4 is the measurement electrode schematic diagram 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 in framework, described measuring unit be scattering device in framework for obtaining the measurement electrode of the voltage signal that testee surface causes under exciting current effect, described measurement electrode is input to output unit by the voltage signal obtaining.
Described framework is hemisphere.Described measurement electrode is equidistantly distributed in framework annularly, and described measurement electrode is along the vertical electrode group of the symmetrical formation of longitudinal tangent plane of framework, and described measurement electrode arranges 2-8 along hemispheroidal longitudinal tangent plane and organizes vertical electrode group.Described measurement electrode is along the symmetrical formation horizontal electrode of the horizontal section layer of framework, 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, obtains the electrical impedance distribution of testee inside for receiving and process voltage signal by three-dimensionalreconstruction algorithm; Described imaging system, 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 driving source control unit, for produce digital sine signal by phase accumulator; Described numerical frequency synthesis unit, for the digital sine signal of different frequency is synthesized, can improve measurement efficiency by the signal of telecommunication injecting after synthesizing, and increases the electrical impedance information of obtaining; Described multiplexed control unit, for controlling the injection phase of pumping signal and voltage acquisition point; Described high speed phase sensitive detection unit, for carrying out the amplitude that collects voltage signal separated and measure with phase place; Described fast fourier transform demodulation measuring-signal unit, for by voltage signal by sampling, block, 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, comprises the following 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, rotation exciting electrode group, the corresponding measurement electrode group of rotation, records all signals successively;
S5: when all excitations of corresponding metering system and after measuring and having combined, complete 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; Described pumping signal converts analogue stimulus signal to and is input in central control processor after signal pre-processing circuit is processed.
Described input signal and metering system adopt following three kinds of combinations to carry out:
Mode one: the common electrode at framework top of take is that exciting current flows out point, take other measurement electrode successively as flowing into point as exciting current, measure the magnitude of voltage flowing between point and corresponding measurement electrode, successively in turn, finally obtain all voltage datas, as restructuring matrix element;
Mode two: measure first respectively the measurement electrode in each horizontal electrode layer, using successively two measurement electrode during measurement as the two ends of encouraging, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode; Then measure respectively the measurement electrode in each vertical electrode group, during measurement, using successively two adjacent measurement electrode as the two ends of encouraging, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode;
Mode three: with across plane, any two electrodes of spaning electrode, as the two ends of excitation, are measured respectively the magnitude of voltage of all the other all measurement electrode.
Embodiment 2
Describe crossing plane electrical impedance imaging measuring device and measuring method below in detail:
Fig. 6 is the principle schematic of hybrid frequency driving source generator of the present invention, Fig. 7 is the schematic diagram 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 forming 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 forming 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 forming excitation and detection mode two, Figure 11 is for to arrange based on crossing plane electrode of the present invention, and the signal forming excitation and detection mode three, Figure 12 is the driving source output impedance testing circuit figure in electrical impedance auto-compensation modular circuit of the present invention, Figure 13 is the negative impedance compensating circuit circuit diagram in electrical impedance auto-compensation modular circuit of the present invention, Figure 14 is the electrical impedance information scattergram in 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 present invention 2 provides adopts consists of field programmable gate array (FPGA) chip.FPGA can select the chip of ALTERA or XILINX company, such as the CYCLONEII of ALTERA.FPGA realizes inside direct digital synthesiser DDS, produces the digital waveform signal of characteristic frequency and phase place.
The D/A converting circuit module adopting in the embodiment of the present invention, in Fig. 5 shown in DAC & Filter.High-speed digital-analog conversion chip can be selected the product of ADIHuoTIDeng company, such as the DAC2902 of TI.The digital stimulus signal that DAC2902 produces DDS is converted to analogue stimulus signal.
The impedance detection adopting in the embodiment of the present invention and impedance auto-compensation module, as shown in Figure 5, mainly used the high frequency difference amplifier AD8130 of LiaoADI company.
The use of electrical impedance auto-compensation module: can be according to the electrical impedance of testee and parasitic capacitance size, its adverse effect of auto-compensation, improves 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 is normally worked, two switches are all opened; And when regulating impedance, analog switch has been switched to load Rcal and non-loaded, the output voltage recording 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 formula, V
cal hrepresent to be connected to the output voltage while proofreading and correct resistance; V
r hrepresent to be connected to the in-phase voltage component while proofreading and correct resistance; V
q hrepresent to be connected to the quadrature voltage component while proofreading and correct resistance; V
cal lrepresent not connect the output voltage while proofreading and correct resistance; V
r lrepresent not connect the in-phase voltage component while proofreading and correct resistance; V
q lrepresent not connect the quadrature voltage component while proofreading and correct resistance;
And calculated by circuit:
In formula, a-signal amplitude represents; R
oresistance R in presentation graphs
oresistance; R
fresistance R in presentation graphs
fresistance; R
calresistance R in presentation graphs
calresistance; C
ocapacitor C in presentation graphs
ocapacitance; I represents to record size of current;
Compare and can obtain for two in (2):
Utilize the principle that real part and imaginary part are equal, by (3), solved:
From above two formulas, if V
cal l=V
cal h, R
o→ ∞, C
o→ 0, by electrical impedance auto-compensation, can greatly improve the output impedance value of current source.As shown in Figure 13, 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, there is the digital signal to be demodulated that ADC collects can be expressed as the pumping signal Asin (2 π n/N+ φ) flowing through after testee, with the stack of N dimension noise signal Vn (n),
In formula, V
i(n) signal that expression collects; V
n(n) represent noise signal;
Based on matched filter (MatchedFilter, MF) principle, phase-sensitive detector and Fourier transformation module can be considered as to relevant quadrature demodulator, input signal and reference signal Vrr, Vrq multiplies each other and produces direct current and second harmonic component.
In formula, V
rr(n) represent input signal; V
rq(n) represent reference signal;
Cumulative sum operation after 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 device filtering; Noise signal and reference signal are uncorrelated, and accumulation result is also zero, so be only left flip-flop, are called in-phase component Vr and quadrature component Vq:
In formula, V
rrepresent the in-phase voltage component after demodulation; V
qrepresent the quadrature voltage component after demodulation;
The amplitude and the phase place that obtain input signal are respectively:
The signal injection switch arrays module adopting in the embodiment of the present invention, adopts 65 electrode multiplexer switch parts.By a plurality of 16, select 1 analog switching ic ADG1206 to form.The switching controls end A0～A3 of analog switch is connected to 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 adopting in the embodiment of the present invention, circuit is that core forms by programmable gain amplifier AD8330 and difference amplifier AD8130.The low pass filter filtering consisting of AD8130 again after amplifying with certain gain from the signal of D/A converting circuit is exported, and the gain of programmable gain amplifier is controlled by SPI interface by center-control treatment circuit.
The analog to digital conversion circuit module adopting in the embodiment of the present 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 by HPI, pass to computer, computer utilizes these data to carry out the electrical impedance distribution that three-dimensionalreconstruction algorithm obtains testee inside, realizes the harmless fast detecting to target.
The measuring unit of this system is distributed on a hemispheroidal edge, from horizontal direction, electrode has been distributed on 4 different layers, 16 electrodes of every layer are equidistantly distributed in the edge (as shown in Figure 1) of hemisphere annularly, and the good symmetry of this distribution mode can provide accurately measurement result reliably.In accompanying drawing 2, be a model of this application, its ground floor is apart from bottom 15mm, and each interlayer is afterwards 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 are spatially 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 is during from axial injection model, the angle between electrode is not wait, but is axial symmetry.
The requirement of high frequency pumping accurately being measured for meeting electrical impedance medical imaging technology, the electrode material therefor that device is used is ormolu (CuZn), surface gold-plating (Au), 150 ℃ of the highest tolerable temperatures, by electric current, can reach 50A, resistance value approximately 0.3 Ω, electrode diameter 4mm(is shown in Fig. 4), electrode bottom design becomes six-sided nut shape, for probe, on device, is fixed.This electrode is highly sensitive, little with the contact impedance of skin surface, and has no side effect, and regular shape is easy to electric current uniform-flow mistake, has improved the inhomogeneity same sex of spatial distribution of field, has reduced the impact of contact impedance on 3-D effect.
For completing, the voltage of measurement point is adopted, the present invention also comprises a set of hardware detection device, this device be take high-performance FPAG as core, and driving source is controlled, and numerical frequency is synthetic, multiplexed control, high speed phase sensitive detection, the functions such as fast fourier transform demodulation measuring-signal are integrated in single chip, as shown in Figure 5, peripheral circuit also comprises that 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, after Control of Voltage gain amplifier and Voltage-controlled Current Source, has low noise, high output impedance, as shown in Figure 6.Certain position that this signal is switched in electrod-array by FPGA gauge tap array is again to be connected with the current output terminal of excitation, or be connected with 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, which is integrated in phase accumulation and table lookup function in FPGA, by digital form, output current is set, this design has guaranteed the motility that frequency is selected, stability, has simplified hardware designs, and has reduced overall power.
2) another important feature of this system is that output impedance ZOUT significantly improves, existence due to stray capacitance in circuit, along with the rising output impedance ZOUT of operating frequency sharply declines, 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 in electrode group is via difference amplifier AD8130(common mode rejection ratio 80dB2MHz), be converted to single-ended voltage signal, through voltage control Amplifier AD8331(bandwidth 120MHz, noise 0.74nV/ √ Hz), make gain 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 to digital phase sensitivity detection (DPSD), the response signal of mixing constant-current source is carried out to fast Fourier transform (FFT), thereby isolate amplitude, phase place in 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, and random noise is had to 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 present invention 2 provides is as follows:
The work implementing procedure of measuring phases:
PC operation, sends instruction to central control processor FPGA, produces pumping signal;
Pumping signal, through signal pre-processing circuit, converts analogue stimulus signal to;
Central control processor by PC and instruction obtain metering system, select exciting electrode group;
By selected metering system, control simulation switch, obtains the voltage signal between corresponding measurement electrode;
The signal obtaining by signal filtering and analog digital conversion after, send into FPGA and be further processed;
According to metering system, rotation exciting electrode group, the corresponding measurement electrode group of rotation, records all signals successively;
When all excitations of corresponding metering system and after measuring and combine, by processing voltage and phase signal send PC back to, complete the electrical impedance images reconstruct on object dimensional space.
Different excitations and metering system measurement in a closed series process:
Signal energisation mode divides single-frequency or multifrequency to mix, and due to the application of many plane electrodes array, excitation and measurement pattern combination are able to great expansion.To different measuring objects, have different electrical impedance grade and distribution, and different injection way makes the inner CURRENT DISTRIBUTION forming of imaging region different, measure sensitivity difference, the signal to noise ratio of acquired signal is not identical.Mainly comprise following 3 class excitation and metering systems:
1) as shown in Figure 8, take the summit (remembering No. 65 point) of half spherical model is that exciting current flows out point, take other 64 electrodes successively as flowing 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 restructuring matrix element.
2) as shown in Fig. 9,10, first with 4 groups in Fig. 9,10, every group of circular electrod-array of 16 levels measured, during measurement, using two comparative electrodes successively as the two ends of encouraging, 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 accompanying drawing 9,10, every group of 9 vertical electrod-arrays are measured, during measurement, using two adjacent electrodes successively as the two ends of encouraging, 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 of 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 central area, to improve the resolution of electrical impedance imaging.
3) while using, will be across plane, any two electrodes of spaning electrode are as the two ends of excitation, and measurement electrode can be between adjacent electrode, can be also across 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 agar that can pack electrical conductivity during practical application into and be 0.1S/m is material as a setting, 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 under different frequency differs, therefore can reconstruct by the mode of frequency difference position and the volume of this Radix Dauci Sativae.
Figure 14 is 4 horizontal planes by excitation and data acquisition modes obtain in the as above the 2nd and the electrical impedance information scattergram on 8 vertical sections.
Figure 15 is by above-mentioned 12 profile combinations, the electrical impedance distribution on the three dimensions forming after date processing, and in figure, different σ values represents different electrical impedance ranking score cloth covers.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, obviously, those skilled in the art can carry out various changes and modification and not depart from the spirit and scope of the present invention the present invention.Like this, if within of the present invention these are revised and modification belongs to the scope of the claims in the present invention and equivalent technologies thereof, the present invention is also intended to comprise these changes and modification interior.
Claims (9)
1. a crossing plane electrical impedance imaging measuring device, it is characterized in that: comprise framework, be distributed in measuring unit and output unit in framework, described measuring unit be scattering device in framework for obtaining the measurement electrode of the voltage signal that testee surface causes under exciting current effect, described measurement electrode is input to output unit by the voltage signal obtaining;
Described framework is hemisphere, and described measurement electrode is equidistantly distributed in hemisphere framework annularly, and described framework center of top is provided with common electrode, and described common electrode is connected with output unit.
2. 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 longitudinal tangent plane of framework, and described measurement electrode arranges 2-8 along hemispheroidal longitudinal tangent plane and organizes vertical electrode group.
3. crossing plane electrical impedance imaging measuring device according to claim 1, is characterized in that: described measurement electrode is along the symmetrical formation horizontal electrode of the horizontal section layer of framework, and described measurement electrode is horizontally disposed with 2-10 layer horizontal electrode layer along framework.
4. 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, obtains the electrical impedance distribution of testee inside for receiving and process voltage signal by three-dimensionalreconstruction algorithm;
Described imaging system, for exporting the electrical impedance distribution information of testee inside.
5. crossing plane electrical impedance imaging measuring device according to claim 4, 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 driving source control unit, for producing digital sine signal by phase accumulator;
Described numerical frequency synthesis unit, for the digital sine signal of different frequency is synthesized, can improve measurement efficiency by the signal of telecommunication injecting after synthesizing, and increases the electrical impedance information of obtaining;
Described multiplexed control unit, for controlling the injection phase of pumping signal and voltage acquisition point;
Described high speed phase sensitive detection unit, for carrying out the amplitude that collects voltage signal separated and measure with phase place;
Described fast fourier transform demodulation measuring-signal unit, for by voltage signal by sampling, block, time signal is converted into discrete series, to obtain the frequency domain characteristic signal of signal.
6. crossing plane electrical impedance imaging measuring device according to claim 5, is characterized in that: also comprise switch arrays, described driving source control unit is connected with measuring unit by switch arrays.
7. according to the measuring method of a kind of crossing plane electrical impedance imaging measuring device described in claim 1-6 any one, it is characterized in that: comprise the following 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, rotation exciting electrode group, the corresponding measurement electrode group of rotation, records all signals successively;
S5: when all excitations of corresponding metering system and after measuring and having combined, complete the electrical impedance images reconstruct of testee on three dimensions according to all signals.
8. the measuring method of a kind of crossing plane electrical impedance imaging measuring device according to claim 7, is characterized in that: described pumping signal produces to central control processor by sending instruction; Described pumping signal converts analogue stimulus signal to and is input in central control processor after signal pre-processing circuit is processed.
9. the measuring method of a kind of crossing plane electrical impedance imaging measuring device according to claim 8, is characterized in that: described input signal and metering system adopt following three kinds of combinations to carry out:
Mode one: the common electrode at framework top of take is that exciting current flows out point, take other measurement electrode successively as flowing into point as exciting current, measure the magnitude of voltage flowing between point and corresponding measurement electrode, successively in turn, finally obtain all voltage datas, as restructuring matrix element;
Mode two: measure first respectively the measurement electrode in each horizontal electrode layer, using successively two measurement electrode during measurement as the two ends of encouraging, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode; Then measure respectively the measurement electrode in each vertical electrode group, during measurement, using successively two adjacent measurement electrode as the two ends of encouraging, measure respectively the magnitude of voltage between all the other all adjacent measurement electrode;
Mode three: with across plane, any two electrodes of spaning electrode, as the two ends of excitation, are measured respectively the magnitude of voltage of all the other all measurement electrode.
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