CN203841697U - Respiratory process three-dimensional electrical impedance tomography system based on PXI bus - Google Patents

Abstract

The utility model relates to a respiratory process three-dimensional electrical impedance tomography system based on the PXI bus. The three-dimensional electrical impedance tomography system with three layers of 48 electrodes is established by the aid of a hardware and software tool suite with PXI bus high integration; a pair of adjacent exciting electrodes is selected in order through a gating switch; safe alternating current is injected into the chest cavity; voltage signals of other electrodes are acquired synchronously; after filtering, amplifying, analog-digital conversion, demodulation and transmission, a distribution image of an electrical impedance sensitive area in the chest chamber in the respiration process is obtained from a computer by an image reconstruction algorithm finally. Compared with the existing electrical impedance tomography systems, the respiratory process three-dimensional electrical impedance tomography system based on the PXI bus has the advantages that measurement precision is high, speed is high, reliability is high, no injury is caused to the human body, and continuous real-time bedside monitoring can be achieved; the respiratory process three-dimensional electrical impedance tomography system based on the PXI bus is applicable to clinical continuous monitoring of changes in the human lung respiration process.

Description

A kind of anti-imaging system of respiratory three-dimensional resistance based on PXI bus

Technical field

This utility model belongs to medical field, relates to medical monitoring equipment and medical science functional imaging technology, especially a kind of anti-imaging system of respiratory three-dimensional resistance based on PXI bus and.

Background technology

Electrical impedance tomography (ElectricalImpedanceTomography, EIT) is after form, structure imaging, the not damaged medical imaging technology of new generation occurring in recent years.Medical research shows, human body respectively organizes (organ) to have different impedance operators, and some pathological phenomenons and physiological activity all can cause tissue impedance variation.In the time that disease occurs, the functional variation of linked groups and organ often will be prior to organic disease and other clinical symptoms, if before tissue and organ structure change appearance, detection in time and the tissue of confirmation and disease association, the functional variation of organ, for the generaI investigation of relevant disease, prevention and early diagnosis and treatment will be very favorable.EIT technology is exactly the electrical impedance characteristics according to biological tissue, apply small alternating current (or voltage) signal by exciting electrode to measurand, measure voltage (or electric current) signal of tissue surface, drawn the electrical impedance distribution image of measurand taking measured signal as information by computer according to corresponding electricity tomographic image reconstructing algorithm.It is by the distribution of the bio-impedance of tissue or organ and changes with the showing of the formal intuition of 2D/3D image, and with this function image, tissue or organ is diagnosed and evaluated.Because EIT technology has radiationless, not damaged, a series of advantage such as simple and direct, safe with respect to current CT technology, have broad application prospects in fields such as clinical medicine monitoring.

EIT system is made up of three parts: stimulating module, acquisition module and image-forming module.At present, the stimulating module of the EIT system of existing biomedical sector research is mainly to utilize FPGA and DSP to produce, acquisition module is mainly to utilize the multi-channel switch of analog or digital to adopt the mode of asynchronous timesharing, and the voltage (electric current) that image-forming module utilization records obtains electrical impedance distribution image according to image reconstruction algorithm.Be difficult to because existing EIT system incentive source exists various non-linear distortions, clutter etc. the defect of eliminating, and driving frequency is mostly limited in below 1M; And the inevitable existence of selecting of multi-channel switch is crosstalked, is revealed and the channel difference opposite sex such as noise, asynchronous time data drainage pattern also will cause data demodulates result inaccurate poor with system stability, therefore improve the driving source of EIT system and the frequency of acquisition module and precision, improving metering system is the key that improves EIT system imaging resolution.

Utility model content

The purpose of this utility model is to overcome the deficiencies in the prior art part, and a kind of anti-imaging system of respiratory three-dimensional resistance based on PXI bus is provided, and this system can realize the anti-distributed image of lung internal resistance in high-quality human body respiration process.

The technical scheme that this utility model is realized object is:

A kind of anti-imaging system of respiratory three-dimensional resistance based on PXI bus, comprise driving source module, capture card module, controller module, three modules all connect by PXI bus, driving source module connects torso model by sensor electrode, capture card module comprises signal conditioning circuit and capture card, Digital I/O board, and controller module connects human-computer interaction module.

And, driving source module comprises driving source, driving source modulate circuit and change-over switch, driving source adopts NIPXI-5404 signal source board, can produce the sinusoidal signal of 10K-100MHz, produce corresponding frequencies according to the instruction of controller, the sinusoidal voltage of phase place and amplitude, by the spuious spectral line of low-pass filter circuit filtering high frequency of modulate circuit, by the voltage controlled current source circuit of modulate circuit, sinusoidal voltage is converted into sinusoidal current again and is sent to as driving source the common port that change-over switch is multiplexer board, be injected into torso model by sensor electrode, sinusoidal current is less than 5mA, driving frequency is between 10KHz-10MHz, to carry out frequency sweep, voltage controlled current source circuit adopts Howland current source, the Butterworth second-order low-pass filter that low-pass filter circuit adopts.

And, described change-over switch adopts two NIPXI-2501 multiplexer switch boards, a switch board common port is connected with driving source, another piece switch board common port is connected with ground, this switchboard jig has 24 passages, and with hardware trigger, be defaulted as adjacent excitation synchro measure, by selecting successively adjacent electrode to be set as driving source position and earthing position, excitation is applied on sensor electrode array, set up sensitivity field distributes in measurand inside, sensor electrode be by 48 independently electrocardioelectrode equidistantly stick on human chest periphery by three layers.

And, the sensor electrode of described driving source module utilizes the signal condition module of capture card module first tentatively to amplify the voltage signal collecting, being amplified to capture card through programmable gain amplifier is again that oscillograph gathers in the desired voltage range of adapter, signal condition module comprises pre-amplification and programmable gain amplifier, and programmable gain amplifier is controlled by Digital I/O board NI6509.

And, described oscillograph gathers adapter and adopts two NI5752, coordinate 48 tunnels identical and independently difference amplifier and programmable gain amplifier circuit, frequency acquisition with 50MS/s carries out synchronous data collection, the analog voltage signal collecting is through analog digital conversion, digital signal is sent to FlexRIOFPGA module and carries out demodulation, obtain real part and the imaginary part information of measurement voltage signal.

And described digital signal is sent to FlexRIOFPGA module and carries out demodulation employing orthogonal sequence demodulation method, its algorithm is as follows:

If r (n) is homophase reference signal, q (n) is orthogonal reference signal, and u (n) is measuring-signal, R is real component, and I is imaginary part component, and θ is the phase shift that medium causes, N is the hits of a signal period, and the span of n is 0≤n≤N-1

r(n)＝cos(2πn/N)

q(n)＝sin(2πn/N)

u(n)＝Acos(2πn/N+θ)

$R=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}r\left(n\right)u\left(n\right)=\frac{1}{2}\mathrm{NA}\cos \mathrm{\θ}$

$I=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}q\left(n\right)u\left(n\right)=\frac{1}{2}\mathrm{NA}\sin \mathrm{\θ}.$

Advantage of the present utility model and good effect are:

1, native system adopts system design and the virtual instrument modularized design of Labview pattern development environment, there is good human-computer interaction interface, can reduce to greatest extent development time and the maintenance cost of application program, guarantee that software product possesses optimal performance, maximize software resource, the efficient powerful system design of exploitation.

2, the integrated crate controller of the PXI of native system based on NI and supporting signal source board, multiplexer switch board, multi-path digital I/O mouth, oscillograph gather adapter Adapter and FlexRIOFPGA module, have that transmission speed is fast, anti-noise ability is strong, systematic error is little, accuracy of detection advantages of higher.

3, native system, by the inherence compatibility of Labview programmed environment and the characteristic of NI board hardware module support hot plug, will make native system also will become very simple according to specific clinical practice configuration-system and in system hardware upgrading in the future flexibly.

4, native system, based on PXI bus transfer agreement, has the ability of high transmission data, can have the transmission performance up to 528Mbyte/s, can realize the Real-time Collection of mass data and processing and then realize accurate realtime imaging.

5, native system adopts the safe exciting current of 1-5mA, and driving frequency is carried out frequency sweep every 10KHz between 10KHz-10MHz, and each frequency range gathers 100 groups of data and carries out computing.

6, native system excitation measurement pattern adopts two adjacent electrodes as one group of exciting electrode, and the pattern of remaining electrode synchronous acquisition is carried out the collection of data.

7, native system gatherer process is that remaining electrode measurement data is complete under one group of excitation passage, and oscillograph collection adapter makes to encourage passage to be switched to next group excitation passage by shake hands with multiplexer switch board (being hardware trigger) and realizes accurately collection.

8, native system oscillograph collection adapter carries out digital demodulation by the data that collect through being sent in real time FlexRIOFPGA module after A/D conversion, and the real part that demodulation is obtained and imaginary part information are transferred in computer again.。

9, native system is by means of the integrated hardware and software suite of tools of PXI bus height, build three layers of anti-imaging system of three-dimensional resistance of totally 48 electrodes, pass through gating switch, select successively a pair of adjacent exciting electrode, in thoracic cavity, inject safe alternating current, voltage signal on synchronous acquisition remaining electrode, through filtering, amplify, analog digital conversion, demodulation, transmission, obtain on computers the distributed image of respiratory mesothorax intracavity portion's electrical impedance sensitizing range finally by image reconstruction algorithm, it is high that existing electric impedance imaging system has certainty of measurement, speed is fast, reliability is high, to human zero damage, can realize the advantages such as continuously real-time bedside monitoring, can change for clinical continuously monitoring human body pulmonary respiratory.

Brief description of the drawings

Fig. 1 is system construction drawing of the present utility model;

Fig. 2 is excitation source signal modulate circuit schematic diagram of the present utility model;

Fig. 3 is data acquisition processing circuit schematic diagram of the present utility model;

Fig. 4 digital demodulation module diagram of the present utility model

Fig. 5 is human-computer interaction interface homepage schematic diagram of the present utility model;

Fig. 6 is system flow block diagram of the present utility model.

Detailed description of the invention

Describe embodiment of the present utility model in detail below in conjunction with accompanying drawing, it should be noted that, the present embodiment is narrative, is not determinate, can not limit protection domain of the present utility model with this.

The anti-imaging system of respiratory three-dimensional resistance based on PXI bus, its structural representation as shown in Figure 1.This system comprises driving source module, capture card module, controller module, three modules all connect by PXI bus, driving source module connects torso model by sensor electrode, capture card module comprises signal conditioning circuit and capture card, Digital I/O board, and controller module connects human-computer interaction module.

Driving source module comprises driving source, driving source modulate circuit and change-over switch, referring to Fig. 2, driving source adopts NIPXI-5404 signal source board, can produce the sinusoidal signal of 10K-100MHz, produce corresponding frequencies according to the instruction of controller, the sinusoidal voltage of phase place and amplitude, by the spuious spectral line of low-pass filter circuit filtering high frequency of modulate circuit, voltage controlled current source circuit by modulate circuit is converted into sinusoidal current using sinusoidal voltage and is sent to the common port of change-over switch (multiplexer board) as driving source again, be injected into torso model by sensor electrode, sinusoidal current is less than 5mA, driving frequency is between 10KHz-10MHz, to carry out frequency sweep.Voltage controlled current source circuit adopts improved Howland current source, has the ability of stronger driving load, and higher output impedance can too large variation can not occur output current in the time that load changes, thereby can improve the degree of accuracy of driving source.The Butterworth second-order low-pass filter that low-pass filter circuit adopts, what voltage controlled current source circuit adopted is improved howland current source.

Change-over switch adopts two NIPXI-2501 multiplexer switch boards, and a switch board common port is connected with driving source, and another piece switch board common port is connected with ground.This switchboard jig has 24 passages, and with hardware trigger.Can select the adjacent measurement of adjacent excitation according to program setting (can arrange) in the human-computer interaction interface as shown in 5 " system setting " options menu, adjacent excitation synchro measure, the adjacent measurement of excitation relatively, excitation synchro measure isotype (comprising with layer and non-with layer) relatively, native system is defaulted as with the adjacent excitation synchro measure of layer, by selecting successively adjacent electrode to be set as driving source position and earthing position, excitation is applied on sensor electrode array, set up sensitivity field distributes in measurand inside, sensor electrode be by 48 independently electrocardioelectrode equidistantly stick on human chest periphery by three layers.

The sensor electrode of driving source module utilizes the signal condition module of capture card module first tentatively to amplify the voltage signal collecting, be amplified in the desired voltage range of capture card (oscillograph collection adapter) through programmable gain amplifier again, signal condition module comprises pre-amplification and programmable gain amplifier, and programmable gain amplifier is controlled by Digital I/O board NI6509.Because the voltage signal that sensor electrode collects is more weak, need to amplify through preliminary, in order to ensure that small-signal is not submerged, after overtesting, native system pre-amplification multiple is 100 times; The voltage that now the nearer measurement electrode of range sensor electrode records has exceeded the desired scope of follow-up analog digital conversion after amplifying, and the voltage that range sensor electrode measurement electrode far away records is still less after amplifying, so need to large voltage signal be carried out to suitable dwindling through programmable-gain, small voltage signal carries out suitable amplification, amplification is 0.64,1.26,2.52,5.01 fourth gear, thereby has ensured that follow-up analog digital conversion can be converted into digital signal the analog quantity voltage signal collecting accurately.

Oscillograph gathers adapter and adopts two NI5752, coordinates 48 tunnels identical and independently difference amplifier and programmable gain amplifier circuit, carries out synchronous data collection with the frequency acquisition of 50MS/s.The analog voltage signal collecting, through analog digital conversion, is sent to FlexRIOFPGA module (NIPXI-7953R) digital signal and carries out demodulation, obtains real part and the imaginary part information of measurement voltage signal.Native system adopts digital demodulation, and its block diagram as shown in Figure 4, can reduce analog quantity chance and approach affected by noise in transmitting procedure with respect to analog demodulator digital demodulation.

This utility model makes full use of the IP kernel resource of FPGA, adopts orthogonal sequence demodulation method, and its algorithm is as follows:

If r (n) is homophase reference signal, q (n) is orthogonal reference signal, and u (n) is measuring-signal, R is real component, and I is imaginary part component, and θ is the phase shift that medium causes, N is the hits of a signal period, and the span of n is 0≤n≤N-1.

r(n)＝cos(2πn/N) (1)

q(n)＝sin(2πn/N) (2)

u(n)＝Acos(2πn/N+θ) (3)

$R=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}r\left(n\right)u\left(n\right)=\frac{1}{2}\mathrm{NA}\cos \mathrm{\θ}---\left(4\right)$

$I=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}q\left(n\right)u\left(n\right)=\frac{1}{2}\mathrm{NA}\sin \mathrm{\θ}---\left(5\right)$

Utilize the DDS(Direct Digital of FPGA inside to synthesize) the IP kernel generation sine and cosine reference digital signal identical with driving frequency, ensure that in orthogonal sequence demodulation, reference signal is consistent with measuring-signal; The MAC(multiply accumulating device of recycling FPGA inside) IP kernel carries out multiply accumulating, thus obtain real part and the imaginary part information of measuring voltage, first deposit FIFO(data buffer in) in, then upload to host computer by PXI bus.

Relate to formation method of the present utility model, step is as follows:

(1) set initial excitation frequency, phase place, the amplitude of exciting current by computer user interface to controller write order, or directly Use Defaults.

(2) signal source board produces the sinusoidal voltage of corresponding frequencies, phase place, amplitude according to the instruction of controller, is sent to the common port of multiplexer board by the sinusoidal current of filter circuit, voltage controlled current source circuit generation alternation as driving source.

(3) multiplexer board is selected neighboring sensors electrode successively according to program setting, and exciting current is injected to torso model inside, forms sensitivity field.

(4) sensor electrode array first tentatively amplifies the voltage signal collecting, being amplified to oscillograph through programmable gain amplifier again gathers in the desired voltage range of adapter, oscillograph gathers adapter the analog voltage signal collecting is carried out to analog digital conversion, digital signal is sent to FlexRIOFPGA module and carries out digital demodulation and obtain measured real part and imaginary part information, upload in computer by PXI bus.

(5) human-computer interaction interface will utilize data after treatment carry out curve plotting, image reconstruction, data analysis etc. and show in real time at corresponding options menu interface.

The human-computer interaction interface of host computer will carry out drafting (can see data and curves corresponding under each frequency under curve waveform menu), image reconstruction (can see the dynamic image of pulmonary's respiratory under image display menu) and the data analysis (can see the data of storage and the signal to noise ratio of every width figure etc. under data analysis menu) of curve according to the data of uploading.The image reconstruction of native system has the many algorithms such as backprojection algorithm, Gauss newton's dynamic imaging algorithm, Newton-Laphson algorithm, conjugate gradient algorithms to select for user, and acquiescence is to utilize electricity tomographic image reconstructing algorithm " Gauss-newton dynamic imaging algorithm " to carry out imaging.

Below to adopt system default value to set forth concrete operations flow process:

After computer and hardware connect, start human-computer interaction interface, first click " barnyard demarcations ", wait for barnyard demarcate complete, then click " startup " button, system starts normal work.In " curve waveform " menu, can see the real-time data curve (as boundary survey voltage curve) under respective frequencies, in " image demonstration " menu, can see the dynamic image of pulmonary's respiratory.The data that transmit on can seeing under " data analysis " menu and signal to noise ratio corresponding to every width image.After collection, click " stopping " button, end data collection is clicked and is logged off under " logging off " menu, exits this human-computer interaction interface.

The host computer interface of human-computer interaction module as shown in Figure 5, the human-computer interaction interface that utilizes Labview to write, homepage has just entered the picture of system for " welcome interface " shows, has that three buttons are from left to right respectively that barnyard is fixed above, startup and stop button can operate at six menu interfaces; Second menu is " system setting ", and frequency, phase place, amplitude, excitation metering system of driving source etc. can be set; The 3rd menu is " curve waveform ", can show in real time the data and curves that different frequency is corresponding, and the 4th menu is " image demonstration ", can show in real time the respiratory of pulmonary in tested thoracic cavity; The 5th menu is " data analysis ", can check the data that gather to come up and store, and can show in real time the signal to noise ratio of each two field picture; The 6th menu, for " logging off " is when having gathered after data, can log off normally under this interface.As shown in Figure 6, concrete implementation step is as follows for working-flow figure:

First under human-computer interaction interface " system setting " menu, set driving frequency, phase place, the amplitude of driving source, wherein driving frequency scope is 10KHz-10MHz, initial excitation frequency default value is 10KHz, carry out frequency sweep every 100KHz, each frequency range gathers 100 groups of data, also can set with fixed frequency and encourage separately; Initial phase can regulate at 0-360 degree, and default value is 0; Amplitude range is 1mA-5mA, sets rear click and preserves.Also can not arrange, adopt system default value directly to move.

Claims (3)

1. the anti-imaging system of respiratory three-dimensional resistance based on PXI bus, it is characterized in that: comprise driving source module, capture card module, controller module, three modules all connect by PXI bus, driving source module connects torso model by sensor electrode, capture card module comprises signal conditioning circuit and capture card, Digital I/O board, and controller module connects human-computer interaction module;

Driving source module comprises driving source, driving source modulate circuit and change-over switch, driving source adopts NIPXI-5404 signal source board, can produce the sinusoidal signal of 10K-100MHz, produce corresponding frequencies according to the instruction of controller, the sinusoidal voltage of phase place and amplitude, by the spuious spectral line of low-pass filter circuit filtering high frequency of modulate circuit, by the voltage controlled current source circuit of modulate circuit, sinusoidal voltage is converted into sinusoidal current again and is sent to as driving source the common port that change-over switch is multiplexer board, be injected into torso model by sensor electrode, sinusoidal current is less than 5mA, driving frequency is between 10KHz-10MHz, to carry out frequency sweep, voltage controlled current source circuit adopts Howland current source, the Butterworth second-order low-pass filter that low-pass filter circuit adopts.

2. the anti-imaging system of respiratory three-dimensional resistance based on PXI bus according to claim 2, it is characterized in that: described change-over switch adopts two NIPXI-2501 multiplexer switch boards, a switch board common port is connected with driving source, another piece switch board common port is connected with ground, this switchboard jig has 24 passages, and with hardware trigger, be defaulted as adjacent excitation synchro measure, by selecting successively adjacent electrode to be set as driving source position and earthing position, excitation is applied on sensor electrode array, set up sensitivity field distributes in measurand inside, sensor electrode be by 48 independently electrocardioelectrode equidistantly stick on human chest periphery by three layers.

3. the anti-imaging system of respiratory three-dimensional resistance based on PXI bus according to claim 1, it is characterized in that: the sensor electrode of described driving source module utilizes the signal condition module of capture card module first tentatively to amplify the voltage signal collecting, being amplified to capture card through programmable gain amplifier is again that oscillograph gathers in the desired voltage range of adapter, signal condition module comprises pre-amplification and programmable gain amplifier, and programmable gain amplifier is controlled by Digital I/O board NI6509.