JP2012050777A - Apparatus and method for creating distribution image of electric conductivity, and body fat measuring apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple, safe and highly accurate apparatus for creating distribution image of electric conductivity and a visceral fat measuring apparatus by achieving impedance CT method to measure biological impedance of a subject with high accuracy.SOLUTION: Two pairs of electrode groups (51a and 51b) are located in a circular pattern on the outer periphery of the subject to be measured. Electric current is applied between two electrodes (Aand A) which are sequentially selected from a first electrode group (51a), and potential differences between adjacent electrodes at the electrodes (Band B) corresponding to the two electrodes on which the electric current is applied among the remaining electrodes (A, ..., A, A, A, ..., A) of the first electrode group and a second electrode group (52b) are measured sequentially. Since the potentials at all electrode locations are measured, measurement error is compensated and highly accurate biological impedance measurement can be achieved.

Description

  The present invention relates to an apparatus for generating a conductivity distribution image for measuring body fat by imaging a body fat distribution in a cross section of a measurement site by impedance CT method, a method thereof, and a body fat measurement apparatus using the method.

  Fat accumulated in the human abdomen is roughly classified into subcutaneous fat and visceral fat from the accumulation site. Among these, accumulation of visceral fat is said to be an inducing factor for metabolic syndrome, which is a pathological condition such as diabetes, hypertension, dyslipidemia, and other pathological conditions, and maintains and promotes health. Because of the importance of visceral fat mass management.

  X-ray CT, MRI, and the like are known as apparatuses capable of imaging fat distribution in the cross section of the measurement site and measuring each of the subcutaneous fat mass and visceral fat mass. However, these devices are extremely expensive, and the maintenance and management of the devices are expensive and troublesome. Further, since these devices require an isolated room and a large installation floor area, they become large-scale devices. In addition, in the case of X-ray CT, radiation exposure may cause health damage, and is not suitable for daily use by ordinary people for health management.

  The impedance CT method is known as a method for imaging the conductivity distribution in the cross section of the measurement site with a relatively simple device, and the present inventors paid attention to the application of this impedance CT method to body fat measurement. As disclosed in Patent Document 1, the impedance CT method is a technique for causing a current to flow through a measurement site and estimating a conductivity distribution at a cross-section of the measurement site from a potential distribution induced on the outer peripheral surface thereof.

JP 2003-339658 A

  By the way, in Patent Document 1, the method of estimating the fat area from the obtained image is binarized depending on whether it exceeds or falls below a threshold value. The abdomen, which is the main measurement target, has a relatively large cross-sectional size and a complicated fat distribution in the human body. Therefore, sufficient resolution comparable to X-ray CT is required to measure the fat ratio by this method. Necessary.

  In bioimpedance measurement, the 4-electrode method is used to avoid the influence of contact resistance between the electrode and the dermis. Therefore, an electrode that surrounds the abdomen in a ring shape is disposed, and two predetermined electrodes are used as electrodes for flowing current (hereinafter referred to as current electrodes), and the potential difference between adjacent electrodes is measured using the remaining electrodes. However, the measurement accuracy is limited because the potential in the vicinity of the current electrode cannot be measured.

  The present invention has been made by paying attention to such problems of the prior art, and according to the present invention, bioimpedance is measured with higher accuracy, a good impedance image is obtained, and more accurately. Visceral fat mass can be estimated.

  According to the technical aspect of the present invention, the body fat measurement device includes a first electrode group in which a plurality of electrode positions are defined in a ring shape on the outer periphery of a measurement target, and each electrode is disposed at each electrode position; A second electrode group in which each electrode is arranged in the vicinity of the electrode of the first electrode group at an electrode position; and (i) an electrode at two electrode positions sequentially selected from the first electrode group is selected as a current electrode. (Ii) impedance measurement means for selecting electrodes other than the current electrode as potential measurement electrodes for all electrode positions and sequentially measuring a potential difference between the potential measurement electrodes at adjacent electrode positions; and measurement A conductivity distribution calculating means for calculating and imaging the conductivity distribution on the cross section of the measurement object based on the result, and a fat mass calculating means for calculating the fat mass based on the calculated conductivity distribution. Table the amount of fat Characterized by comprising a display means for.

  According to another technical aspect of the present invention, the measurement error of the impedance measuring means is further compensated so that the sum of potential differences between the potential measuring electrodes at the adjacent electrode positions becomes zero. To do.

  According to still another technical aspect of the present invention, the body fat measurement method includes a first electrode in which each electrode is disposed at each electrode position with respect to a plurality of electrode positions defined in a ring shape on the outer periphery of the measurement target. Applying a current between two electrodes sequentially selected from the group; and a second electrode group in which each electrode is disposed in the vicinity of the electrode of the first electrode group at each electrode position; and the first electrode group; Measuring the potential difference by sequentially selecting the electrodes other than the electrode to which the current is applied for all adjacent electrode positions from the above, and the measurement error of each potential difference so that the sum of the potential differences between the electrodes at the adjacent electrode positions becomes zero Is compensated, the conductivity distribution on the cross section of the measurement object is calculated based on each compensated potential difference, and the fat amount is calculated based on the calculated conductivity distribution. It is characterized by including.

  According to the present invention, since the potential difference over the entire circumference of the abdomen to be measured can be measured uniformly by adopting a two-stage electrode, it becomes possible to apply Kirchhoff's second law, and in the measurement circuit A highly accurate impedance distribution can be measured by compensating for a measurement error caused by an incoming noise or the like that is difficult to offset or eliminate. In addition, error compensation can be automated.

The block diagram of the body fat measuring apparatus of embodiment of this invention. The block diagram of an impedance measurement means. The block diagram of an electrode unit and a circuit unit. FIG. 3 is a plan view of an electrode group. The perspective view which shows arrangement | positioning of a 1st electrode group and a 2nd electrode group. The conceptual diagram of the impedance measurement using the 1st electrode group and the 2nd electrode group. The block diagram of an integrated electrode part. Conceptual diagram of another embodiment of impedance measurement

  Embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 is a configuration diagram showing a body fat measuring device according to a first embodiment of the present invention. The body fat measurement device includes two sets of electrode groups 1a and 1b having a plurality of electrodes arranged on the outer peripheral surface of a measurement object (measurement target), and a current between two electrodes sequentially selected from the plurality of electrodes. Impedance measuring means 2 for measuring the potential of the remaining electrode or the potential difference between the electrodes, contour information measuring means 3 for measuring the contour information of the measured object from the position of the electrode, and the measured potential or potential difference and contour Conductivity distribution calculating means 4 for obtaining the conductivity distribution on the measurement site cross section of the body to be measured from the information, and the body fat mass, body fat percentage, visceral fat mass of the body to be measured based on the obtained conductivity distribution, It comprises fat mass calculation means 5 for calculating the subcutaneous fat mass and the like, and display means 6 for displaying the calculation result. The two sets of electrode groups 1a and 1b, the impedance measuring means 2, and the contour information measuring means 3 included in the body fat measuring device constitute a conductivity distribution image generating device.

<Configuration of electrode group>
FIG. 2 is a configuration diagram of the electrode group and the impedance measuring means. The electrode part 70 including the electrode groups 51a and 51b of the present embodiment can have a structure having a plan view as shown in FIG. On the ring-shaped support plate 53, a plurality of air cylinders 55a, 55b are fixed toward the center of the ring, and an electrode 51a (51b) is disposed at the tip of the rod 56a (56b) of the air cylinder 55a (55b). ing. The measured object 50 enters the central portion of the support plate 51 by opening the opening / closing portion 52 of the support plate 53, and is used for measurement after the opening / closing portion 52 is closed.

  The electrode 51a (51b) is brought into contact with the surface of the measurement object by applying air pressure to the air cylinder 55a (55b) to extend the rod 56a (56b) and pressing the electrode 51a (51b) against the surface of the measurement object. . For example, when the measurement site is the human abdomen, the subject is placed in a standing position at the center of the support plate 53, and the height of the support plate 53 is adjusted to the height of the subject's umbilicus to place electrodes on the outer periphery of the subject's abdomen. To do.

  As shown in FIGS. 5 and 6, the body fat measurement device of this embodiment has two sets of electrode groups 51 a and 51 b arranged in a two-stage upper and lower ring shape, and a constant current circuit 23 that uses any two electrodes as a current source. Is selected as an electrode (current electrode) to be connected to the electrode, and an electrode disposed in the vicinity thereof is selected as a voltage measurement electrode at the electrode position, whereby the potential difference can be measured over the entire circumference of the abdomen. In the present embodiment, it is assumed that a pair of electrodes of the first electrode group 51a is selected as a current electrode, and the voltage measurement electrode at the electrode position selects the second electrode group 51b corresponding to the current electrode. In FIG. 5, the structure for supporting the electrodes 51a and 51b is omitted.

  Preamplifiers 37a and 37b are arranged in the vicinity of the electrodes 51a and 51b. When the electrodes are selected as voltage measurement electrodes, the outputs of the preamplifiers 37a and 37b are output to the differential amplifier 26 via the selection switch group 36. The The electrode 51a selected as the current electrode is connected to the current sources 72a and 72b of the constant current circuit 23 via the switch group 24, and the selection switch group 36 uses the corresponding second electrode group 51b as the voltage measurement electrode. select. Note that one unit of the switch group 24 includes a pair of switches, and each switch is connected to one of the current sources 72a and 72b to select a predetermined current electrode.

  In the first electrode group 51a, a plurality (N) of electrodes are arranged one-dimensionally so as to surround the outer peripheral surface of the measurement object, and the second electrode group 51b corresponds to each electrode of the first electrode group 51a. A plurality (N) of electrodes are arranged adjacent to each other. The number N of the electrodes 51a and 51b can be appropriately selected according to the type and size of the measurement site. In the present embodiment, N = 32 will be described.

When the subject (measurement target) is regarded as a long object (virtual model body) whose conductivity is distributed three-dimensionally, the first electrode group 51a and the second electrode group 51b are at a predetermined height (abdomen) of the object. Arranged so as to be orthogonal to the longitudinal direction. In this case, the electrodes are arranged in a ring shape substantially equidistantly from the reference position (for example, the umbilical high position) in the azimuth direction, and the first electrode group 51a is {A ₁ , A _{2 as} shown in FIG. ,..., A _i−1 , A _i , A _{i + 1} ,..., A _N }, and the second electrode group 51b are {B ₁ , B ₂ ,..., B _i−1 , B _i , B _{i + 1} ,..., B _N }. For example, the electrode B _i is disposed in the vicinity of the electrode A _i , and in the present embodiment, is disposed in the vicinity of the direction (vertical direction) parallel to the longitudinal direction of the elongated object with respect to the electrode A _i . Therefore, the electrode (A _i ) of the first electrode group and the electrode (B _i ) of the second electrode group are arranged in the vicinity of each other at one electrode position (i = 1, 2,..., N).

The precision measurement of impedance must be based on the 4-electrode method. Therefore, when the electrode A _i and the electrode A _{i + 2 of} the first electrode group 51a are selected as current electrodes, conventionally, the electrodes A _{i + 1} , A _{i + 3} , A _{i + 4} , A _{i + 5} ... A _N , A ₁ , A ₂ ... A _i-1 N-2 electrodes were used to measure the potential difference between adjacent electrodes. However, since the electrode position A _{i + 1} is a current electrode on both sides, it is substantially difficult to use for potential difference measurement. On the other hand, in the present invention, a potential difference between adjacent electrodes of electrodes A _i−1 , A _i , A _{i + 1} , A _{i + 2} , A _{i + 3} , which could not be measured conventionally, is substantially equivalent to A _i−1 , B _i , A A complete measurement can be realized by substituting the potential difference between adjacent electrodes of _{i + 1} , B _{i + 2} and A _{i + 3} .

Here, the potential of the electrode (A _i or B _i ) at the i-th electrode position is V _i , the potential of the electrode (A _{i + 1} or B _{i + 1} ) at the i + 1-th electrode position is V _{i + 1} , and the potential difference thereof is ΔV _i = V _{i + 1} −V _i , the total sum of potential differences between adjacent electrodes is determined by Kirchhoff's second law,

Is established. The adjacent electrodes of the electrode A _N (B _N ) are A _N-1 (B _N-1 ) and A ₁ (B ₁ ), and i is interpreted as modulo N (= 32) (A _N = A ₀ ).

In this case, when two specific electrodes A _i and A _{i + 2} in the first electrode group are selected as current electrodes, the other 30 electrodes A _{i + 3} , A _{i + 4} , A _{i + 5} ... A ₃₂ , A ₁ , A ₂ ... A _i−1 , A _{i + 1} and the electrodes B _i and B _{i + 2} among the second electrode group are selected as voltage measuring electrodes. That is, the electrodes at the two electrode positions (i, i + 2) sequentially selected from the first electrode group 51a are selected as the current electrodes (A _i , A _{i + 2} ), the current is applied, and all the electrode positions (i = 1) are selected. , 2,..., N), a predetermined pair of electrodes is selected as a potential measurement electrode from 62 electrodes other than the current electrode, and a potential difference (ΔV _{1 to} ΔV _N ) between the potential measurement electrodes at adjacent electrode positions. Are measured sequentially.

More specifically, the switch group 24 controlled by a controller included in the computer 21 selects an arbitrary pair of electrodes 51a as current electrodes. As illustrated in FIG. 6, the switch group 24 is a switch group that selectively connects the _two output lines of the constant current circuit 23 to specific electrodes A _i and A _{i + 2} , but is simplified in FIG. 2. expressing.

  FIG. 2 illustrates only four of the 32 pairs of the first electrode group 51a and the second electrode group 51b. The same applies to the multiplexer 27 and the like. That is, in the figure, two electrodes of the first electrode group 51a of the upper two pairs of electrode groups are selected as current electrodes by the switch group 24 and connected to the current sources 72a and 72b, respectively, and the corresponding second electrode group 51b. These two electrodes are selected as voltage measuring electrodes by the switch group 36.

  In the figure, the first electrode group 51a is selected as the measurement electrode by the switch group 36 from the lower two electrode groups, but the second electrode group 51b is not connected to the impedance measuring means. Voltage measurement is performed by sequentially switching the measurement electrodes by the multiplexer 27.

<Electrode unit>
In FIG. 2, the two electrodes 51 a to be connected to the constant current circuit 23 are schematically represented by selecting ON / OFF of the switch group (matrix switch) 24, but the sine wave current is calculated based on the sine wave oscillator 22. The generated constant current circuit 23 may be arranged in the vicinity of each electrode 51a, and the switch group 24 may be arranged to switch ON / OFF.

  FIG. 3 schematically represents only one set of an electrode unit 40 including a pair of electrode groups 51a and 51b and a circuit unit 41 connected thereto.

Preamplifier electrode unit 40 which is connected to be switched to one electrode (e.g., A _i) and one electrode (e.g., B _i) and the electrodes of the second electrode group 51b disposed in the vicinity of the first electrode group 51a 37a and 37b are included. Further, the switch group 25 includes the intermittent function of the switch group 24 of FIG. 2, and when the first electrode group 51a is selected as a current electrode, the current of the constant current circuit 23 of the circuit unit 41 is supplied to the first electrode group 51a. In other cases, the first electrode group 51a is alternatively connected to the input of the preamplifier 37a. In addition, the switch group 36 connects the output of the preamplifier 37b connected to the second electrode 51b to the differential amplifier 26 when the first electrode group 51a is selected as the current electrode, and otherwise the first group 51a. The output of the preamplifier 37a connected to one electrode 51a is selectively connected to the differential amplifier 26. The voltage signal selected by the switch group 36 is output to the differential amplifier 26 of the circuit unit 41 via the line c and is output to the differential amplifier (not shown) of the adjacent circuit unit via the line f. The

  The circuit unit 41 includes a differential amplifier 26 and a buffer amplifier 43 as a measurement system, and a phase inverter 46, a phase selection switch 47, and a current source 45 as a current stimulation system. The differential amplifier 26 amplifies the potential difference between the potential of the measurement electrode selected by the switch group 36 and the potential of the measurement electrode at the adjacent position input from the adjacent circuit unit via the line e, and passes through the buffer amplifier 43. To the multiplexer 27 from the line a. A sine wave signal is input from the sine wave oscillator 22 to the phase inverter 46 via the line b, and a non-inverted output and an inverted output are selected by the switch 47. The selected sine wave voltage signal is voltage-current converted by the voltage control type current source 45 to generate a sine wave current, which is output to the current electrode 51a via the line d.

  With the configuration of the electrode unit 40 and the circuit unit 41 as shown in FIG. 3, the frequency characteristics are improved because the constant current circuit 23 and the current electrode are arranged close to each other. Note that the 32 sets of electrode units 40 and the circuit unit 41 may be configured to be incorporated into the 32 sets of electrode portions 70.

<Potential measurement>
When the potential difference ΔV _i between all adjacent electrodes is measured (N times), the potential difference ΔV _ij between any electrode positions i and j (i <j) is calculated using the potential difference ΔV _k obtained by the measurement,

It can be calculated from

  The potential generated on the surface of the measurement object is amplified by the differential amplifier 26 through the electrodes 51a and 51b, and the output signal is guided to the band pass filter (band pass filter) 28 through the multiplexer 27. The signal that has passed through the bandpass filter 28 is guided to the phase detection type amplifier 29, and is delayed by 90 degrees in phase and the same phase component (real part) as the sine wave oscillator 22 using the timing signal from the phase shifter 31. After being decomposed into components (imaginary part), it is converted into a DC voltage signal. Thereafter, the DC voltage signal is A / D converted by an A / D converter (DC voltmeter) 30 and taken into the computer 21.

  These operations are repeated by moving the contacts of the multiplexer 27, and output signals from all the differential amplifiers 26 are measured. Further, the switch group 24 (25) is sequentially switched to pass a current between the other electrodes, and the output signal from the differential amplifier 26 is measured in the same manner.

  The current electrode 51 a for applying a current to the measured object 50 can be selected as appropriate from the electrodes arranged on the outer periphery of the measured object 50. In addition, the electrode interval of the current electrodes 51a can be set as appropriate in consideration of the dynamic range of voltage measurement, etc., but in this embodiment, every two adjacent electrodes, that is, a distance corresponding to 2 units of the adjacent electrode interval is set, Two electrodes are selected for all positions (electrode positions i and i + 2) of the entire circumference of the measurement object 50. In this case, the combination of the selected electrode positions is {(i, i + 2)} = {(1, 3), (2, 4), (3, 5) (N-2, N), (N-1, 1), (N, 2)}.

<Measurement error compensation>
As already described, by using two sets of electrode groups 51a and 51b, the fact that the sum of potential differences between electrodes at adjacent positions over one round is always zero as shown in equation (1) is used. Can do. By the way, the potential difference actually measured via the measurement circuits such as the preamplifiers 37a and 37b, the differential amplifier 26, and the lock-in amplifier 29 is ΔV _i ′, the lock-in amplifier 29 that processes the DC signal, the A / D converter 30 and the like. the error voltage caused by (offset voltage, etc.) e, when the true value of the potential difference and [Delta] V _i, raw measurement data can be expressed as _{ΔV i '= ΔV i + e} . The error voltage e includes flying noise generated in the electronic circuit regardless of the potential difference caused by the bioelectrical impedance. That is, the input impedance of the preamplifiers 37a and 37b is very large in order to reduce the influence of the contact resistance as much as possible, so that it is easily affected by the same incoming noise as the measurement frequency propagating in the air.

  In order to reconstruct an image of impedance distribution from impedance measurement, an accuracy of 6 significant figures is generally required. Therefore, even if there is a slight measurement error, it becomes a serious problem for high-accuracy measurement. Therefore, there has been a demand for a method for easily and reliably removing measurement errors depending on the measurement circuit system.

According to the potential difference measuring method of the present invention that makes a round of the measurement object 50, the inventors have obtained the following equation (1):

So,

Thus, it was found that the measurement error e is compensated and the true value can be easily estimated. That is, based on the measured value [Delta] V i _'and the sum V _total of each potential difference can be obtained [Delta] V _i, further it is possible to calculate any potential difference [Delta] V _ij with high accuracy from the equation (2).

<Measurement of contour shape>
In order to image a complex fat distribution, it is not sufficient to approximate it with an ellipse or the like, and it is necessary to measure the contour shape of an actual measurement site section.

  The contour information measuring means 3 is composed of a position sensor 57a (57b) and a computer (controller) 21 arranged in the air cylinder 55a (55b) of the electrode unit 70. A position sensor 57a (57b) that outputs an electrical signal corresponding to the amount of ejection of the rod 55a (55b) is attached to the air cylinder 55a (55b). The computer 21 uses the position information of the electrode when the rod 56a (56b) is completely retracted and the ejection amount information of the rod 56a (56b) detected by the position sensor 57a (57b) to the measured object 50. The positions of the electrodes 51a and 51b in contact with each other are calculated. Therefore, by detecting the positions of the electrodes 51a (51b) in all the air cylinders 55a and 55b, the contour shape, cross-sectional area, etc. of the measured object 50 can be obtained.

  FIG. 7 shows an electrode portion 70 in which a pair of electrodes 51a and 51b are integrally formed. The electrode unit 70 includes a contour information measuring unit 3, an electrode unit (not shown), and a circuit unit (not shown). The pair of electrodes 51a and 51b are fixed to an electrode support 77 fixed to the tip of the rod 76 of the low friction air cylinder 75. The rod 76 is extendable in a direction A in which the main axis is substantially perpendicular to the contour of the measured object 50. Further, the feed amounts of the electrodes 51a and 51b are detected by a slide resistor 78 as a position sensor (linear potentiometer). That is, since the movable portion 78a of the slide resistor 78 is fixed to the electrode support portion 77 and the resistor 78b is fixed to the low friction air cylinder 75, the feed amounts of the electrodes 51a and 51b are converted into corresponding resistance values. The position is detected. Thus, the structure of the electrode unit 70 can be simplified and the size can be reduced, and the frequency characteristics and S / S can be reduced by incorporating the circuit portion (electrode unit 40, circuit unit 41) in the vicinity of the electrode. N is improved.

<Calculation of conductivity distribution>
The conductivity distribution calculating means 4 includes a computer and software installed in the computer, and calculates the conductivity distribution or impedance distribution based on the acquired data. The impedance [Ωm] is the reciprocal of the conductivity [Ω ⁻¹ m ⁻¹ ] and these are equivalent.

  First, a virtual model surface having the same contour shape as the measured object 50 based on the contour shape of the cross section of the measurement site obtained by the contour information measuring means 3 and the positional information of the electrodes 51a and 51b arranged on the outer circumference of the measurement site. Is configured. Next, an appropriate conductivity distribution is given as an initial value on the virtual model surface, and a potential distribution generated on the outer periphery of the virtual model surface when a similar current is passed between electrodes similar to the measurement by the impedance measuring means 2 is obtained. Calculate by the finite element method.

The calculated potential distribution is compared with the potential difference ΔV _ij measured with respect to the actual measured object 50 by the impedance measuring means 2, and the conductivity on the virtual model surface is reduced so that the difference (residual) between the two becomes small. Correct the distribution. In the same manner, the potential distribution on the outer periphery is calculated for the virtual model surface whose conductivity distribution is corrected, and is compared again with the actual measurement value. These operations are repeated until the residual becomes equal to or smaller than a predetermined set value or until the residual converges to a constant value, and the same conductivity distribution as that of the cross section of the measurement site is reproduced on the virtual model plane. Instead of the two-dimensional virtual model surface, a three-dimensional virtual model body having the same cross-sectional shape in the longitudinal direction may be used.

<Fat mass calculation>
The fat amount calculating means 5 is included in the computer and calculates the fat amount based on the conductivity distribution image obtained by the conductivity distribution calculating means 4. In other words, since the conductivity of fat and non-fat portions such as muscles is different, the distribution of conductivity reflects the distribution of fat, muscle, etc. It is determined that the region is a fat region, and other regions are determined to be non-fat regions, and the fat mass can be calculated based on these results. Other fat mass calculation methods can also be applied to the present invention. Any fat mass calculation method can improve the estimation accuracy of fat mass according to the impedance measurement method of the present invention.

  The display means 6 can be a video display device such as a liquid crystal display device or an organic EL display device, or a printing device for printing media such as paper and film. The calculated conductivity distribution image and fat distribution image are displayed on the screen of the video display device or the printing medium of the printing device, the input data such as the subject's profile and the numerical value of the output data such as the calculated body fat amount and Character information can be displayed.

(Modified embodiment)
In the present invention, as described above, when a current electrode at a predetermined electrode position (i, i + 2) is selected, the potential difference between adjacent electrodes is determined for all electrode positions (i = 1, 2,..., N). ΔV _i is measured. Therefore, in the present embodiment, two electrodes at predetermined electrode positions are selected as current electrodes from the first electrode group, and voltage measurement electrodes are sequentially selected so that the potential measurement surface matches the current electrode position as much as possible. Since the voltage measuring electrode in the vicinity of the current electrode is selected in a zigzag manner, it will be referred to as a zigzag mode. In this case, as shown in FIG. 6, it is necessary to sequentially switch the voltage measurement electrodes from the electrode 51 a and the second electrode group 51 b of the first electrode group via the electrode unit 40 and the circuit unit 41.

FIG. 8 shows a modified embodiment in which current electrodes are sequentially selected from the first electrode group 51a and voltage measurement electrodes are sequentially selected from the second electrode group 51b. Since the voltage measurement electrode is arranged on a plane slightly deviated from the current electrode position, it will be referred to as a parallel mode. In this case, Kirchhoff's second law can be used because the potential difference ΔV _i between adjacent electrodes is measured for all electrode positions. Furthermore, since it is not necessary to switch the electrical connection by the switch groups 25 and 36 in the electrode unit 40, the circuit can be simplified and miniaturized compared to the zigzag mode.

  According to the present invention, it is possible to accurately measure the impedance of a measurement target using two sets of electrodes, and therefore, it is possible to calculate a conductivity distribution image and a fat distribution image with higher spatial resolution.

1a, 1b Electrode group 21 Computer (controller)
22 Sine Wave Oscillator 23 Constant Current Circuit 24, 25, 36 Switch Group 26 Differential Amplifier 27 Multiplexer 28 Band Pass Filter 29 Lock-in Amplifier 30 A / D Converter 31 Phase Shifter 37a, 37b Preamplifier 40 Electrode Unit, 41 Circuit Unit 51a First electrode group, 51b Second electrode group 52 Opening / closing part 53 Support plate 55a, 55b, 75 Air cylinder 56a, 56b, 76 Rod 57a, 57b, 78 Position sensor 70 Electrode part 72a, 72b AC current source 77 Electrode support part 78 Slide resistor

Claims (7)

A first electrode group in which a plurality of electrode positions are defined annularly on the outer circumference of the measurement target, and each electrode is disposed at each electrode position;
A second electrode group in which each electrode is disposed in the vicinity of the electrode of the first electrode group at each electrode position;
(I) applying an electric current by selecting electrodes at two electrode positions sequentially selected from the first electrode group as current electrodes;
(Ii) impedance measurement means for selecting potential measurement electrodes from electrodes other than the current electrode for all electrode positions and sequentially measuring a potential difference between the potential measurement electrodes at adjacent electrode positions;
A conductivity distribution image generating apparatus, comprising: a conductivity distribution calculating unit that calculates a conductivity distribution on a cross section of the measurement object based on a measurement result, and forms an image.   2. The conductivity distribution image generating apparatus according to claim 1, wherein a measurement error of the impedance measuring unit is compensated so that a total sum of potential differences between the potential measuring electrodes at the adjacent electrode positions becomes zero.   The potential measuring electrode selected by the impedance measuring means is selected from an electrode not selected as the current electrode in the first electrode group and an electrode at the electrode position of the current electrode in the second electrode group. The conductivity distribution image generating device according to claim 1 or 2.   3. The conductivity distribution image generating apparatus according to claim 1, wherein the potential measuring electrode selected by the impedance measuring unit is selected from the second electrode group. Each electrode of the first electrode group and the corresponding electrode of the second electrode group are fixed to the electrode support part, and the electrode support part is movable in a direction toward the outer periphery of the measurement target,
5. The apparatus according to claim 1, further comprising a contour shape measuring unit that acquires a contour shape of an outer periphery of the measurement target based on a movement amount of the electrode support portion and outputs the contour shape to the conductivity distribution calculating unit. The conductivity distribution image generating device according to claim 1. The conductivity distribution image generating device according to any one of claims 1 to 5,
A fat amount calculating means for calculating a fat amount based on the calculated conductivity distribution;
A body fat measuring device comprising display means for displaying the calculated fat mass. Applying a current between two electrodes sequentially selected from the first electrode group in which each electrode is arranged at each electrode position with respect to a plurality of electrode positions defined in a ring shape on the outer circumference of the measurement object;
The electrodes other than the electrode to which the current is applied are sequentially applied to all adjacent electrode positions from the second electrode group and the first electrode group in which each electrode is disposed in the vicinity of the electrode of the first electrode group at each electrode position. Select and measure the potential difference;
Compensating the measurement error of each potential difference so that the sum of the potential differences between the electrodes at the adjacent electrode positions becomes zero;
A method of generating a conductivity distribution image, comprising: calculating and imaging a conductivity distribution on a cross section of the measurement object based on each compensated potential difference.

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