CN107374628A - A kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode and measuring method - Google Patents
A kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode and measuring method Download PDFInfo
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- CN107374628A CN107374628A CN201710572524.1A CN201710572524A CN107374628A CN 107374628 A CN107374628 A CN 107374628A CN 201710572524 A CN201710572524 A CN 201710572524A CN 107374628 A CN107374628 A CN 107374628A
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/053—Measuring electrical impedance or conductance of a portion of the body
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
- A61B2562/02—Details of sensors specially adapted for in-vivo measurements
- A61B2562/0209—Special features of electrodes classified in A61B5/24, A61B5/25, A61B5/283, A61B5/291, A61B5/296, A61B5/053
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Abstract
A kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode and measuring method; electrode has the unprotected electrode and guard electrode on the inside of the parallel U-shaped electrode suppor of insertion; be provided with the ring of guard electrode wafer architecture by guard electrode; the distance of setting is mutually separated with by the inner rim of the neighboring of guard electrode and guard electrode; guard electrode connects the ground of outside with being corresponded to respectively by guard electrode by guard electrode line with by guard electrode line, and unprotected electrode passes through the excitation power supply outside the connection of unprotected electrode connecting line.Method is that measuring electrode is inserted into tested biological tissue, and ac-excited power supply known to unprotected electrode rate of connections will be grounded by guard electrode and guard electrode；The voltage between unprotected electrode and ground is measured, and measurement is flowed through by the electric current of guard electrode；So as to obtain electrical impedance, electric capacity, electrical conductivity and the relative dielectric constant of tested biological tissue.The present invention can measure the electrical impedance of the biological tissue of small volume, realize live body in bulk measurement.
Description
Technical field
The present invention relates to a kind of minimally invasive measuring biological tissue electrode.More particularly to a kind of minimally invasive biological tissue's electrical conductivity/
Dielectric constant measurement electrode and measuring method
Background technology
The electrical characteristics of biological tissue mainly include electrical conductivity and dielectric constant.
Mainly there are lumped-circuit method, Transmission line method resonant cavity method in biological dielectric electrical characteristics measuring method at present, transmit
Collimation method resonant cavity method measurement accuracy is high, but high for the shape and size precision prescribed of measured material, suitable for high-frequency electrical
Measurement when magnetic wave encourages.
Lumped-circuit method is the method for the dielectric constant that electrical parameter calculating material is obtained using measurement, typically uses four electrodes
The method of measurement, measurement apparatus generally is formed by four metal needles, four metal needles are arranged in a row in tissue interior edge straight line, from two
The electrode input stimulus voltage at end, electric current is measured from a pair of electrodes of inner side；Exciting electrode inputs constant voltage, measuring electrode
The electric current in current path is measured, the electrical impedance of tested tissue is calculated by Ohm's law, reuses the electrode of measuring electrode
Constant, the electrical conductivity and dielectric constant of tested biological tissue is calculated.This measuring method principle is simple, suitable for low-frequency electrical
Measurement during magnetic pumping；But because biological tissue is three-dimensional, the electric field that exciting electrode is formed in tissue is not parallel electric field,
The line of the path that the electric current that measuring electrode measures flows through not only exciting electrode, additionally flows through other paths, i.e., can not obtain electric current
The accurate geometry shape of the tissue flowed through, the anti-value error of tissue resistance being calculated are larger.
Influence, can be used in bulk measurement biological tissue electricity it is therefore desirable to which one kind can reduce or eliminate non-parallel electric field
The measuring electrode and measuring method of impedance operator.
The content of the invention
The minimally invasive of non-parallel electric field influence can be reduced or eliminate the technical problem to be solved by the invention is to provide a kind of
Biological tissue's electrical conductivity/dielectric constant measurement electrode and measuring method.
The technical solution adopted in the present invention is：A kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode, including
Have：U-shaped electrode suppor, on the inside of the U-shaped electrode suppor of parallel insertion and formed with the unprotected electrode and guard electrode at setting interval,
The guard electrode is loop configuration, and the unprotected electrode is wafer architecture, and insertion is provided with the ring of the guard electrode
Wafer architecture in U-shaped electrode suppor by guard electrode, the neighboring by guard electrode and the guard electrode
Inner rim is mutually separated with the distance of setting, described guard electrode and is corresponded to respectively by being embedded in U-shaped electrode branch by guard electrode
Guard electrode line in frame connects the ground of outside with by guard electrode line, and described unprotected electrode is U-shaped by being embedded in
The excitation power supply outside the connection of unprotected electrode connecting line in electrode suppor, or, described guard electrode and by guard electrode
The excitation electricity for connecting outside with by guard electrode line by the guard electrode line being embedded in U-shaped electrode suppor is corresponded to respectively
Source, described unprotected electrode pass through the ground outside the connection of the unprotected electrode connecting line that is embedded in U-shaped electrode suppor.
Described U-shaped electrode suppor is by upper backup pad, lower supporting plate and is integrally attached to the upper backup pad and lower branch
The electrode base of side is formed between fagging, described to be embedded in the upper of the U-shaped electrode suppor by guard electrode and guard electrode
On the medial surface of supporting plate, the unprotected electrode is embedded on the medial surface of the lower supporting plate of the U-shaped electrode suppor, described
Unprotected electrode, guard electrode and it is located at by guard electrode on same axis.
The one end of upper backup pad and lower supporting plate away from electrode base of described U-shaped electrode suppor is for ease of insertion biology
The wedge structure of tissue, the electrode base is arc surface with the leading flank of contact biological tissue.
A kind of side that electrical impedance characteristics of biological tissues is obtained using minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode
Method, comprise the following steps：
1) measuring electrode is inserted into tested biological tissue set depth, swashed being exchanged known to unprotected electrode rate of connections
Power supply is encouraged, will be grounded by guard electrode and guard electrode；
2) the voltage U between unprotected electrode and ground is measured, and measurement is flowed through by the electric current I of guard electrode；
3) electrical impedance Z is calculated in the voltage U divided by electric current I obtained with measurement, so as to obtain the electricity of tested biological tissue
Impedance Z：
Wherein | Z | for the modulus value of tested biological tissue impedance, θ is the impedance angle of tested biological tissue, and the value of impedance angle is anti-
The dielectric property of tissue is reflected；
4) the electric capacity C of tested biological tissue is obtained by following formula：
Wherein f is the frequency of ac-excited power supply；
5) conductivityσ of tested biological tissue is obtained by following formula：
Wherein r=5 × 10-4M, it is by the radius of guard electrode；D=1 × 10-3M, it is by guard electrode and unprotected electricity
The distance between pole；
6) the relative dielectric constant ε of tested biological tissue is obtained by following formular：
Wherein ε0=8.85 × 10-12F/m, it is the dielectric constant of vacuum.
5. minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode described in a kind of usage right requirement 1 carries out biology
The method of the anti-feature measurement of tissue resistance, it is characterised in that comprise the following steps：
1) measuring electrode is inserted into tested biological tissue's set depth, will be by guard electrode and guard electrode rate of connections
The ac-excited power supply known, unprotected electrode is grounded；
2) measurement is flowed through by the electric current I of guard electrode by the voltage U between guard electrode and ground, and measurement；
3) electrical impedance Z is calculated in the voltage U divided by electric current I obtained with measurement, so as to obtain the electricity of tested biological tissue
Impedance Z：
Wherein | Z | for the modulus value of tested biological tissue impedance, θ is the impedance angle of tested biological tissue, and the value of impedance angle is anti-
The dielectric property of tissue is reflected；
4) the electric capacity C of tested biological tissue is obtained by following formula：
Wherein f is the frequency of ac-excited power supply；
5) conductivityσ of tested biological tissue is obtained by following formula：
Wherein r=5 × 10-4M, it is by the radius of guard electrode；D=1 × 10-3M, it is by guard electrode and unprotected electricity
The distance between pole；
6) the relative dielectric constant ε of tested biological tissue is obtained by following formular：
Wherein ε0=8.85 × 10-12F/m, it is the dielectric constant of vacuum.
A kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode and measuring method of the present invention, first, electrode
Size is small, and effective contacting volume with tissue is 0.78mm3, the electrical impedance of the biological tissue of small volume can be measured, is realized
Live body is in bulk measurement；Secondly, unprotected electrode is placed in parallel with by guard electrode is coaxial, and connects high low potential respectively, so that
Unprotected electrode and a relatively uniform parallel electric field is established between guard electrode；Again, guard electrode surround and protected
Electrode, and with being insulated between guard electrode, ensure that, the bottom of as, to be pressed from both sides by guard electrode between guard electrode and unprotected electrode
Hold, be parallel electric field highly for the electric field in 1mm tested tissue, only measurement flows through the electric current in parallel electric field region, parallel
Electric current outside electric field region is shielded by guard electrode, so as to according to measurement obtained magnitude of voltage and current value, accurately
The electrical impedance characteristicses of biological tissue in the parallel electric field region are calculated, can be used for the measurement in body bio-electrical impedance characteristic；Most
Afterwards, the size of the electrode is small, and measuring principle is simple, and the reserved battery lead plate with external circuit interface, is easy to integrated and outer
Enclose the design of circuit.
Brief description of the drawings
Fig. 1 is a kind of overall structure diagram of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode of the present invention；
Fig. 2 is a kind of overall structure perspective view of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode of the present invention；
Fig. 3 is guard electrode in the present invention, unprotected electrode and the structural representation by guard electrode；
Fig. 4 is the structural representation of U-shaped electrode suppor in the present invention；
Fig. 5 is the perspective view of U-shaped electrode suppor in the present invention；
Fig. 6 is the schematic diagram of measuring method of the present invention；
Fig. 7 is the simulated effect figure using measuring method of the present invention measurement electrical impedance；
Fig. 8 is the measured result figure using electrode measurement muscle electrical impedance of the present invention；
Fig. 9 is the simulated effect figure using measuring method of the present invention measurement impedance angle；
Figure 10 is the measured result figure using electrode measurement muscle impedance angle of the present invention.
In figure
1：U-shaped electrode suppor 11：Upper backup pad
12：Lower supporting plate 13：Electrode base
2：Unprotected electrode 3：Guard electrode
4：By guard electrode 5：Unprotected electrode connecting line
6：Guard electrode line 7：By guard electrode line
Embodiment
With reference to embodiment and accompanying drawing to a kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode of the invention
It is described in detail with measuring method.
As shown in Figure 1, Figure 2, Figure 3 shows, a kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode of the invention, bag
Include：U-shaped electrode suppor 1, the U-shaped inner side of electrode suppor 1 of parallel insertion and the unprotected electrode 2 formed with setting interval and protection
Electrode 3, the guard electrode 3 are loop configuration, and the unprotected electrode 2 is wafer architecture, is set in the ring of the guard electrode 3
Be equipped with the wafer architecture that is embedded in U-shaped electrode suppor 1 by guard electrode 4, the neighboring by guard electrode 4 with it is described
The inner rim of guard electrode 3 is mutually separated with the distance of setting, and unprotected electrode 2 is with being established a parallel electricity between guard electrode 4
Place, described guard electrode 3 and being corresponded to respectively by guard electrode 4 are connected by the guard electrode that is embedded in U-shaped electrode suppor 1
Line 6 and the ground that outside is connected by guard electrode line 7, described unprotected electrode 2 is by being embedded in U-shaped electrode suppor 1
Unprotected electrode connecting line 5 connects the excitation power supply of outside, and exciting current never guard electrode 2 flows out, by being surveyed by guard electrode 4
Amount flows through the electric current in parallel electric field area, and the driving voltage of unprotected electrode 2, and biological group is obtained so as to accurate measurement
The electrical conductivity and dielectric constant knitted.
Either, described guard electrode 3 and by guard electrode 4 respectively correspond to by being embedded in U-shaped electrode suppor 1
Guard electrode line 6 and the excitation power supply that outside is connected by guard electrode line 7, described unprotected electrode 2 is by being embedded in U
Unprotected electrode connecting line 5 in type electrode suppor 1 connects the ground of outside.Exciting current flows out from by guard electrode 4, by not protecting
Shield electrode 2 measures the electric current for flowing through parallel electric field area, and the driving voltage by guard electrode 4, so as to accurate measurement
Obtain the electrical conductivity and dielectric constant of biological tissue.
As shown in Fig. 3, Fig. 4, Fig. 5, described U-shaped electrode suppor 1 is by upper backup pad 11, lower supporting plate 12 and integrally connected
The electrode base 13 for being connected on side between the upper backup pad 11 and lower supporting plate 12 is formed, described U-shaped electrode suppor 1 it is upper
The one end of supporting plate 11 and lower supporting plate 12 away from electrode base 13 is for ease of the wedge structure of insertion biological tissue, the electrode
Pedestal 13 is arc surface with the leading flank of contact biological tissue.It is described that the U is embedded in by guard electrode 4 and guard electrode 3
On the medial surface of the upper backup pad 11 of type electrode suppor 1, the unprotected electrode 2 is embedded in the lower branch of the U-shaped electrode suppor 1
On the medial surface of fagging 12, the unprotected electrode 2, guard electrode 3 and it is located at by guard electrode 4 on same axis.
In a kind of embodiment of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode of the present invention, described U-shaped electricity
Pole support 1 is to use to make of silica or Teflon, the good insulation preformance of silica or Teflon, can preferably be protected
Card measures the accurate of electric current.It is gold by guard electrode, guard electrode and the material of unprotected electrode, there is preferable biological tissue
Compatibility and good electric conductivity.When the size of tested biological tissue and guard electrode exceeds by twice of guard electrode or both sides
Above and by the distance between guard electrode and guard electrode it is less when, by between guard electrode and unprotected electrode
Cylindrical region is a parallel electric field region.It it is 500 μm by the radius of guard electrode 4, thickness is 300 μm, unprotected electrode 2
Radius be 1000 μm, thickness 100um, the external diameter of guard electrode is 1000 μm, and internal diameter is 600 μm, and thickness is 50 μm, protection
Electrode internal diameter and it is separated by 100 μm between guard electrode external diameter, guard electrode and the contact surface by guard electrode and biological tissue
In approximately the same plane.By guard electrode with being that the distance between guard electrode is d=1mm.
During amount, tested tissue position is reached using ultrasonic imaging device leading electrode, the center section of electrode base is
One semicylinder, when electrode is pierced into biological tissue, it can ensure that tested tissue is located at by guard electrode and unprotected as far as possible
Measurement zone between electrode, and surrounding tissue can leave measurement zone along the face of cylinder, eliminate as much as the influence of surrounding tissue.Quilt
Tissue is surveyed to be clipped in measurement zone by unprotected electrode and by guard electrode.
The minimally invasive biological tissue's electrical conductivity of use of the present invention/dielectric constant measurement electrode obtains electrical impedance characteristics of biological tissues
Method, comprise the following steps：
1) measuring electrode as shown in Figure 2, is inserted into tested biological tissue set depth, by unprotected electrode rate of connections
Known ac-excited power supply, it will be grounded by guard electrode and guard electrode；
As shown in Figure 6, tested organization internal, electric field is unevenly distributed Electric Field Distribution between electrode,
The edge of electrode, electric-field intensity is big, and by the region between guard electrode and unprotected electrode, Electric Field Distribution is uniform
And it is parallel electric field.
2) the voltage U between unprotected electrode and ground is measured, and measurement is flowed through by the electric current I of guard electrode；
3) electrical impedance Z is calculated in the voltage U divided by electric current I obtained with measurement, so as to obtain the electricity of tested biological tissue
Impedance Z：
Wherein | Z | for the modulus value of tested biological tissue impedance, θ is the impedance angle of tested biological tissue, and the value of impedance angle is anti-
The dielectric property of tissue is reflected；
4) the electric capacity C of tested biological tissue is obtained by following formula：
Wherein f is the frequency of ac-excited power supply；
5) conductivityσ of tested biological tissue is obtained by following formula：
Wherein r=5 × 10-4M, it is by the radius of guard electrode；D=1 × 10-3M, it is by guard electrode and unprotected electricity
The distance between pole；
6) the relative dielectric constant ε of tested biological tissue is obtained by following formular：
Wherein ε0=8.85 × 10-12F/m, it is the dielectric constant of vacuum.
The minimally invasive biological tissue's electrical conductivity of use of the present invention/dielectric constant measurement electrode obtains electrical impedance characteristics of biological tissues
Method, can also be and comprise the following steps：
1) measuring electrode is inserted into tested biological tissue's set depth, will be by guard electrode and guard electrode rate of connections
The ac-excited power supply known, unprotected electrode is grounded；
2) measurement is flowed through by the electric current I of guard electrode by the voltage U between guard electrode and ground, and measurement；
3) electrical impedance Z is calculated in the voltage U divided by electric current I obtained with measurement, so as to obtain the electricity of tested biological tissue
Impedance Z：
Wherein | Z | for the modulus value of tested biological tissue impedance, θ is the impedance angle of tested biological tissue, and the value of impedance angle is anti-
The dielectric property of tissue is reflected；
4) the electric capacity C of tested biological tissue is obtained by following formula：
Wherein f is the frequency of ac-excited power supply；
5) conductivityσ of tested biological tissue is obtained by following formula：
Wherein r=5 × 10-4M, it is by the radius of guard electrode；D=1 × 10-3M, it is by guard electrode and unprotected electricity
The distance between pole；
6) the relative dielectric constant ε of tested biological tissue is obtained by following formular：
Wherein ε0=8.85 × 10-12F/m, it is the dielectric constant of vacuum.
Fig. 7 is that Fig. 8 is to use electrode measurement of the present invention using the simulated effect figure of measuring method of the present invention measurement electrical impedance
The measured result figure of muscle electrical impedance；Two figures compare can be derived that impedance angle that actual measurement obtains with the trend that frequency changes with should
The impedance angle variation tendency that measuring method emulates to obtain is consistent.
Fig. 9 is that Figure 10 is surveyed using electrode of the present invention using the simulated effect figure of measuring method of the present invention measurement impedance angle
Measure the measured result figure of muscle impedance angle.Two figures compare can be derived that impedance that actual measurement obtains with the trend that frequency changes with should
The variation tendency that measuring method emulates obtained impedance is consistent.
Claims (5)
1. a kind of minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode, it is characterised in that include：U-shaped electrode suppor
(1), on the inside of the U-shaped electrode suppor of parallel insertion (1) and formed with the unprotected electrode (2) and guard electrode (3) at setting interval, institute
It is loop configuration to state guard electrode (3), and the unprotected electrode (2) is wafer architecture, is set in the ring of the guard electrode (3)
Have the wafer architecture that is embedded in U-shaped electrode suppor (1) by guard electrode (4), the neighboring by guard electrode (4) with
The inner rim of the guard electrode (3) is mutually separated with the distance of setting, described guard electrode (3) and by guard electrode (4) respectively
Corresponding guard electrode line (6) by being embedded in U-shaped electrode suppor (1) and by outside guard electrode line (7) connection
Ground, described unprotected electrode (2) by the connection of the unprotected electrode connecting line (5) that is embedded in U-shaped electrode suppor (1) outside
Excitation power supply, or, described guard electrode (3) and by guard electrode (4) respectively correspond to by being embedded in U-shaped electrode suppor
(1) guard electrode line (6) in and by the excitation power supply outside guard electrode line (7) connection, described unprotected electrode
(2) ground outside the connection of the unprotected electrode connecting line (5) that is embedded in U-shaped electrode suppor (1) is passed through.
A kind of 2. minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode according to claim 1, it is characterised in that
Described U-shaped electrode suppor (1) is by upper backup pad (11), lower supporting plate (12) and is integrally attached to the upper backup pad (11)
The electrode base (13) of side is formed between lower supporting plate (12), described to be embedded in by guard electrode (4) and guard electrode (3)
On the medial surface of the upper backup pad (11) of the U-shaped electrode suppor (1), the unprotected electrode (2) is embedded in the U-shaped electrode
On the medial surface of the lower supporting plate (12) of support (1), the unprotected electrode (2), guard electrode (3) and by guard electrode (4)
On same axis.
A kind of 3. minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode according to claim 2, it is characterised in that
The one end of the upper backup pad (11) and lower supporting plate (12) of described U-shaped electrode suppor (1) away from electrode base (13) for ease of
The wedge structure of biological tissue is inserted, the electrode base (13) is arc surface with the leading flank of contact biological tissue.
4. minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode described in a kind of usage right requirement 1 obtains biological tissue
The method of electrical impedance characteristicses, it is characterised in that comprise the following steps：
1) measuring electrode is inserted into tested biological tissue set depth, by ac-excited electricity known to unprotected electrode rate of connections
Source, it will be grounded by guard electrode and guard electrode；
2) the voltage U between unprotected electrode and ground is measured, and measurement is flowed through by the electric current I of guard electrode；
3) electrical impedance Z is calculated in the voltage U divided by electric current I obtained with measurement, so as to obtain the electrical impedance of tested biological tissue
Z：
<mrow>
<mi>Z</mi>
<mo>=</mo>
<mfrac>
<mi>U</mi>
<mi>I</mi>
</mfrac>
<mo>=</mo>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<msup>
<mi>e</mi>
<mrow>
<mi>j</mi>
<mi>&theta;</mi>
</mrow>
</msup>
</mrow>
Wherein | Z | for the modulus value of tested biological tissue impedance, θ is the impedance angle of tested biological tissue, and the value of impedance angle reflects
The dielectric property of tissue；
4) the electric capacity C of tested biological tissue is obtained by following formula：
<mrow>
<mi>C</mi>
<mo>=</mo>
<mo>-</mo>
<mfrac>
<mn>1</mn>
<mrow>
<mn>2</mn>
<mi>&pi;</mi>
<mi>f</mi>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<mi>s</mi>
<mi>i</mi>
<mi>n</mi>
<mi>&theta;</mi>
</mrow>
</mfrac>
</mrow>
Wherein f is the frequency of ac-excited power supply；
5) conductivityσ of tested biological tissue is obtained by following formula：
<mrow>
<mi>&sigma;</mi>
<mo>=</mo>
<mfrac>
<mi>d</mi>
<mrow>
<msup>
<mi>&pi;r</mi>
<mn>2</mn>
</msup>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<mi>c</mi>
<mi>o</mi>
<mi>s</mi>
<mi>&theta;</mi>
</mrow>
</mfrac>
</mrow>
Wherein r=5 × 10-4M, it is by the radius of guard electrode；D=1 × 10-3M, it is by between guard electrode and unprotected electrode
Distance；
6) the relative dielectric constant ε of tested biological tissue is obtained by following formular：
<mrow>
<msub>
<mi>&epsiv;</mi>
<mi>r</mi>
</msub>
<mo>=</mo>
<mo>-</mo>
<mfrac>
<mi>d</mi>
<mrow>
<mn>2</mn>
<msup>
<mi>&pi;</mi>
<mn>2</mn>
</msup>
<msub>
<mi>f&epsiv;</mi>
<mn>0</mn>
</msub>
<msup>
<mi>r</mi>
<mn>2</mn>
</msup>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<mi>s</mi>
<mi>i</mi>
<mi>n</mi>
<mi>&theta;</mi>
</mrow>
</mfrac>
</mrow>
Wherein ε0=8.85 × 10-12F/m, it is the dielectric constant of vacuum.
5. minimally invasive biological tissue's electrical conductivity/dielectric constant measurement electrode described in a kind of usage right requirement 1 carries out biological tissue
The method of electrical impedance characteristicses measurement, it is characterised in that comprise the following steps：
1) measuring electrode is inserted into tested biological tissue set depth, will be known to guard electrode and guard electrode rate of connections
Ac-excited power supply, unprotected electrode is grounded；
2) measurement is flowed through by the electric current I of guard electrode by the voltage U between guard electrode and ground, and measurement；
3) electrical impedance Z is calculated in the voltage U divided by electric current I obtained with measurement, so as to obtain the electrical impedance of tested biological tissue
Z：
<mrow>
<mi>Z</mi>
<mo>=</mo>
<mfrac>
<mi>U</mi>
<mi>I</mi>
</mfrac>
<mo>=</mo>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<msup>
<mi>e</mi>
<mrow>
<mi>j</mi>
<mi>&theta;</mi>
</mrow>
</msup>
</mrow>
Wherein | Z | for the modulus value of tested biological tissue impedance, θ is the impedance angle of tested biological tissue, and the value of impedance angle reflects
The dielectric property of tissue；
4) the electric capacity C of tested biological tissue is obtained by following formula：
<mrow>
<mi>C</mi>
<mo>=</mo>
<mo>-</mo>
<mfrac>
<mn>1</mn>
<mrow>
<mn>2</mn>
<mi>&pi;</mi>
<mi>f</mi>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<mi>s</mi>
<mi>i</mi>
<mi>n</mi>
<mi>&theta;</mi>
</mrow>
</mfrac>
</mrow>
Wherein f is the frequency of ac-excited power supply；
5) conductivityσ of tested biological tissue is obtained by following formula：
<mrow>
<mi>&sigma;</mi>
<mo>=</mo>
<mfrac>
<mi>d</mi>
<mrow>
<msup>
<mi>&pi;r</mi>
<mn>2</mn>
</msup>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<mi>c</mi>
<mi>o</mi>
<mi>s</mi>
<mi>&theta;</mi>
</mrow>
</mfrac>
</mrow>
Wherein r=5 × 10-4M, it is by the radius of guard electrode；D=1 × 10-3M, it is by between guard electrode and unprotected electrode
Distance；
6) the relative dielectric constant ε of tested biological tissue is obtained by following formular：
<mrow>
<msub>
<mi>&epsiv;</mi>
<mi>r</mi>
</msub>
<mo>=</mo>
<mo>-</mo>
<mfrac>
<mi>d</mi>
<mrow>
<mn>2</mn>
<msup>
<mi>&pi;</mi>
<mn>2</mn>
</msup>
<msub>
<mi>f&epsiv;</mi>
<mn>0</mn>
</msub>
<msup>
<mi>r</mi>
<mn>2</mn>
</msup>
<mrow>
<mo>|</mo>
<mi>Z</mi>
<mo>|</mo>
</mrow>
<mi>s</mi>
<mi>i</mi>
<mi>n</mi>
<mi>&theta;</mi>
</mrow>
</mfrac>
</mrow>
Wherein ε0=8.85 × 10-12F/m, it is the dielectric constant of vacuum.
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| CN108888269A (en) * | 2018-04-19 | 2018-11-27 | 南京邮电大学 | A kind of electrical impedance imaging electrode physical model device |
| CN113273989A (en) * | 2021-04-07 | 2021-08-20 | 广东工业大学 | Bioelectrical impedance measuring device and method |
| CN113884549A (en) * | 2020-07-02 | 2022-01-04 | 浙江大学 | Biological tissue dielectric spectrum measuring electrode clamp |
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| CN102445574B (en) * | 2011-10-12 | 2013-10-09 | 中国人民解放军第四军医大学 | Annular arrangement type multi-needle biological tissue dielectric spectrum characteristic measuring probe and method |
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| CN113884549A (en) * | 2020-07-02 | 2022-01-04 | 浙江大学 | Biological tissue dielectric spectrum measuring electrode clamp |
| CN113273989A (en) * | 2021-04-07 | 2021-08-20 | 广东工业大学 | Bioelectrical impedance measuring device and method |
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