JP2018149056A - In-vivo signal intensity detection method and in-vivo signal intensity detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-vivo signal intensity detecting method capable of detecting a signal intensity of a signal source in a living body by using a small number of electrodes. SOLUTION: A step of arranging at least two electrodes on the circumference of a living body surface so as to surround a plurality of signal sources in the living body, and a step of obtaining position information of the signal source in a plane including the two electrodes. The step of calculating the distance r between the signal source and each electrode from the position information of each electrode in the plane including the two electrodes and the position information of the signal source, and between each electrode and the ground potential, or The step of measuring the voltage V generated between the electrodes is included, and the signal strength of the signal source in the living body is detected based on the distance r, the voltage V, and the attenuation formula of the signal source in the body. [Selection diagram] Fig. 2

Description

  The present invention relates to an in-vivo signal intensity detection method and an in-vivo signal intensity detection device that detect the signal intensity of an active site (signal source) of a tissue that is active in a living body.

  An activity state of a tissue that is active in a living body is measured by attaching an electrode to the surface of the living body and measuring a voltage generated at the electrode.

  For example, Patent Document 1 discloses a method of obtaining a potential distribution in a cross section of a living body passing through the plane by measuring a surface potential at each point on an intersection line (closed curve) between the living body and a predetermined plane. ing.

Japanese Patent Laid-Open No. 11-113867 International Publication No. 2016 / 075726A1

  However, in the method disclosed in Patent Document 1, it is necessary to place and measure a large number of electrodes on a living body without any gaps, so that the burden on the living body is large. If the number of electrodes is small, the burden on the living body is reduced, but only a potential distribution with low resolution can be obtained.

  The present invention provides an in-vivo signal intensity detecting method and in-vivo signal intensity detecting apparatus capable of detecting the signal intensity of an active site (signal source) of a tissue that is active in a living body using a small number of electrodes. The purpose is to do.

The in vivo signal strength detection method according to the present invention is a method for detecting the signal strength of a signal source in a living body based on a voltage generated at an electrode arranged on the surface of the living body, and the signal source in the living body includes a plurality of muscles A linear signal source composed of fibers, the step of arranging at least two electrodes on the circumference of the living body surface so as to surround a plurality of signal sources, and the position of the signal source in a plane including the two electrodes A step of obtaining information (x, y), position information (X _i , Y _i ) (i = 1, 2) of each electrode in a plane including two electrodes, and position information (x, y) of the signal source ) To calculate the distance r _i (i = 1, 2) between the signal source and each electrode, and the voltage V _i (i = 1, 1) generated between each electrode and the ground potential or between each electrode. and a step of measuring a 2), the distance _r i (i = 1,2), voltage _V i (i = 1,2 , And, on the basis of the attenuation equation of the signal source in the body, and detecting the signal strength of the signal source in vivo.

  According to the present invention, an in-vivo signal intensity detection method and in-vivo signal intensity detection capable of detecting the signal intensity of an active site (signal source) of a tissue active in a living body using a small number of electrodes. An apparatus can be provided.

It is the figure which showed the model of the signal source made into the detection object of this invention. It is a figure explaining the method to detect the signal strength of the in-vivo signal source in this 1st embodiment of this invention. It is a figure explaining the method to detect the signal strength of the in-vivo signal source in this 2nd embodiment of this invention. It is the figure which showed the electric network explaining the position detection method of a signal source. It is the table | surface which showed the step of switching of the connection state of each electrode and external resistance. It is a figure explaining the method to detect the position of a signal source. It is a figure explaining the method to detect the position of a signal source. It is the figure which showed the electric network explaining the position detection method of a signal source. It is the table | surface which showed the step of switching of the connection state of each electrode and external resistance. It is a figure explaining the method to detect the position of a signal source. It is the block diagram which showed the structure of the in-vivo signal strength detection apparatus in other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention. In the following description, unless otherwise specified, “electrode” refers to a member attached to the surface of a living body, “potential” refers to an electrical level, and “voltage” refers to a measured electrical level.

  The present applicant has proposed a method capable of accurately detecting the position of an active site (signal source) of a tissue that is active in a living body using a small number of electrodes (Patent Document 2).

In the signal source position detection method in the living body according to the present proposal, at least three electrodes are arranged on the surface of the living body, and two external resistors having different resistance values are connected in parallel between each electrode and the ground potential. The voltage V _i (i = 1, 2, 3) generated at each electrode when connected in parallel to the first external resistor and the voltage V ′ _i (i generated at each electrode when connected in parallel to the second external resistor = 1, 2, 3). Here, the internal resistance R _i (i = 1, 2, 3) between each electrode and the signal source is proportional to the distance L _i (i = 1, 2, 3) between each electrode and the signal source. Then, the distance L _i (i = 1, 2, 3) can be expressed by three simultaneous equations with the voltage ratio (V _i / V ′ _i ) as a variable. Accordingly, the three-dimensional coordinates (x, y, z) of the signal source can be obtained by solving the three simultaneous equations using the three measured voltage ratios (V _i / V ′ _i ).

  However, with the proposed method, the position of the signal source can be detected, but the signal strength of the signal source cannot be detected. Therefore, the present invention proposes an in-vivo signal intensity detection method capable of detecting the signal intensity of an active site (signal source) of a tissue active in a living body using a small number of electrodes.

(First embodiment)
FIG. 1 is a diagram showing a model of a signal source to be detected in the embodiment of the present invention.

  The signal source model shown in FIG. 1 is a plurality of muscle fibers 40 constituting a skeletal muscle such as an arm, and each muscle fiber 40 exists in a line along the direction of the arrow in the figure. When the skeletal muscle is activated (contracted), the specific muscle fiber 40 becomes the signal source Vs and generates a high potential. Since the active site of the muscle fiber 40 serving as the signal source Vs exists linearly along the direction of the muscle fiber 40, the potential distribution of the signal source Vs is uniform. Therefore, as shown in FIG. 1, if the detection range of the signal source Vs is limited to the cross section along the line AA, the linear signal source Vs is defined as a point of two-dimensional coordinates (x, y). Can be caught.

  FIG. 2 is a diagram schematically illustrating a method for detecting the signal intensity of the in-vivo signal source in the present embodiment.

  As shown in FIG. 2, the two electrodes 21 and 22 are arranged on a circumference 10 </ b> A on the surface of the living body 10 so as to surround a plurality of muscle fibers (linear signal sources) 40. A ground electrode (not shown) is also disposed on the surface of the living body 10 at a position not affected by the voltage measured by the electrodes 21 and 22.

By the way, the signal intensity V ₀ of the in-vivo signal source Vs attenuates as the distance from the signal source Vs increases. Therefore, the signal intensity (voltage V _i ) measured by the electrodes 21 and 22 arranged on the surface 10A of the living body 10 is expressed by the following equation when the distance from the signal source Vs to the electrodes 21 and 22 is r _i. (1-1) It is expressed by (attenuation formula).

  Here, η is an attenuation coefficient.

That is, the voltages V ₁ and V ₂ measured by the two electrodes 21 and 22 shown in FIG. 2 are expressed by the following formula (1-2).

When V ₀ is eliminated from the equation (1-2), the following equation (1-3) is derived.

  Therefore, from the equation (1-3), the attenuation number η can be obtained from the following equation (1-4).

Further, from the equation (1-2), the signal intensity V ₀ of the signal source Vs can be obtained from the following equation (1-5).

As shown in Expression (1-4), the attenuation coefficient η is determined by the voltages V ₁ and V ₂ measured at the electrodes 21 and 22 and the distances r ₁ and r from the signal source Vs to the electrodes 21 and 22. ₂ can be used.

Here, the position information (x, y) of the signal source Vs can be detected by a method described later. Therefore, from the position information (X _i , Y _i ) (i = 1, 2) of each electrode in the plane including the two electrodes 21 and 22 and the position information (x, y) of the signal source Vs, the signal source Vs. And distances r _i (i = 1, 2) between the electrodes 21 and 22 can be calculated.

As a result, as shown in the equation (1-5), the signal intensity V ₀ of the signal source Vs is obtained from the η obtained by the equation (1-4) and the voltages V ₁ and V measured at the electrode 21 or the electrode 22. ₂ and the distances r ₁ and r ₂ between the signal source Vs and the electrode 21 or the electrode 22 can be obtained.

That is, in the in-vivo signal intensity detection method according to the present embodiment, the step of arranging the two electrodes 21 and 22 on the circumference of the surface of the living body so as to surround a plurality of signal sources, and the two electrodes 21 and 22 are performed. A step of obtaining the position information (x, y) of the signal source Vs in the plane including the position information (X _i , Y _i ) (i = 1, 2) of each electrode in the plane including the two electrodes 21 and 22. And calculating the distance r _i (i = 1, 2) between the signal source Vs and each of the electrodes 21 and 22 from the position information (x, y) of the signal source Vs, and each of the electrodes 21 and 22 and the ground Measuring a voltage V _i (i = 1, 2) generated between the potential and the distance R _i (i = 1, 2), voltage V _i (i = 1, 2), and in the body Based on the attenuation formula of the signal source, the signal strength of the signal source in the living body is detected.

According to the present embodiment, the position information (X _i , Y) of the two electrodes 21 and 22 arranged on the circumference of the living body surface so as to surround the position information (x, y) of the signal source Vs and the signal source Vs. _i ) (i = 1, 2) and the voltage V _i (i = 1, 2) measured at each of the electrodes 21 and 22, the attenuation of the signal source Vs in the body shown by the equation (1-1) Based on the equation, the signal intensity V ₀ of the in-vivo signal source Vs can be detected. Thereby, it is possible to detect the signal intensity of the active site (signal source) of the tissue that is active in the living body using a small number of electrodes.

(Second Embodiment)
FIG. 3 is a diagram for explaining a method for detecting the signal intensity of the in-vivo signal source in the second embodiment of the present invention.

  As shown in FIG. 3, the three electrodes 21, 22, and 23 are arranged on a circumference 10 </ b> A on the surface of the living body 10 so as to surround a plurality of muscle fibers (linear signal sources) 40. A ground electrode (not shown) is also disposed on the surface of the living body 10 at a position not affected by the voltage measured by the electrodes 21, 22, and 23.

The voltage V ₁ generated between the electrode 21 and the electrode 22 shown in FIG. 3 is expressed as the following formula (2-1) based on the attenuation formula shown in the formula (1-1).

Here, V ₀ is the signal intensity of the signal source Vs in the living body, r ₁ and r ₂ are the distances from the signal source Vs to the electrodes 21 and 22, and η is the attenuation equation shown by the equation (1-1). Is the attenuation coefficient.

From the equation (2-1), the signal intensity V ₀ of the in-vivo signal source Vs is represented by the following equation (2-2).

Similarly, the voltage _{V 2} generated between the electrode 22 and the electrode 23, on the basis of the attenuation equation shown in equation (1-1) is expressed by the following equation (2-3).

Here, r ₃ is the distance from the signal source Vs to the electrode 23.

From the equation (2-3), the signal intensity V ₀ of the in-vivo signal source Vs is expressed by the following equation (2-4).

When V ₀ is eliminated from the equations (2-2) and (2-4), the following equation (2-5) is derived.

  Furthermore, from the equation (2-5), the attenuation coefficient η is expressed by the following equation (2-6).

  Here, when the right side of the formula (2-6) is replaced with a constant A as in the following formula (2-7), the formula (2-6) is expressed as in the following formula (2-8). Is done.

  Therefore, from the equation (2-8), the attenuation coefficient η can be obtained from the following equation (2-9).

Further, from the equation (2-2), the signal intensity V ₀ of the signal source Vs can be obtained from the following equation (2-10).

From the equations (2-9) and (2-7), the attenuation coefficient η is determined by V ₁ , V ₂ generated between the electrodes and the distances r ₁ , r ₂ , r ₃ from the signal source Vs to each electrode. Can be obtained using

Here, the position information (x, y) of the signal source Vs can be detected by a method described later. Therefore, from the position information (X _i , Y _i ) (i = 1, 2, 3) of each electrode in the plane including the three electrodes 21, 22, 23, and the position information (x, y) of the signal source Vs. The distance r _i (i = 1, 2, 3) between the signal source Vs and each of the electrodes 21, 22, 23 can be calculated.

Thus, from the equation (2-10), the signal intensity V ₀ of the signal source Vs is obtained from the η obtained by the equation (2-9), the voltages V ₁ and V ₂ generated between the electrodes, and the signal source Vs. And the distances r ₁ , r ₂ , r ₃ to the respective electrodes.

As described above, according to the present embodiment, the position information (x, y) of the signal source Vs and the positions of the three electrodes 21, 22, 23 arranged on the circumference of the living body surface so as to surround the signal source Vs. By using the information (X _i , Y _i ) (i = 1, 2, 3) and the voltage V _i (i = 1, 2) generated between the electrodes, Based on the attenuation formula of the signal source Vs, the signal intensity V ₀ of the in-vivo signal source Vs can be detected. Thereby, it is possible to detect the signal intensity of the active site (signal source) of the tissue that is active in the living body using a small number of electrodes.

In the present embodiment, as shown in the formula (2-1) and the formula (2-3), the voltages V ₁ and V ₂ generated between the electrodes are obtained from the difference between the voltages measured at the electrodes. Therefore, noise from the outside can be canceled. Therefore, the voltage V _i generated between the electrodes, it is possible to measure and reduce noise, it is possible to more accurately detect the signal strength of the signal source Vs.

(Signal source position detection method)
A signal source position detection method used in the signal intensity detection method of the signal source Vs in the present embodiment will be described with reference to FIGS.

  FIG. 4 is a diagram showing an electric network for explaining a method of detecting the position of the signal source Vs in the living body.

  As shown in FIG. 4, three electrodes 21, 22, and 23 are arranged on the surface of the living body 10. In addition, a first external resistor and a second external resistor that can be switched with each other are connected in parallel between the electrodes 21, 22, and 23 and the ground potential. Here, the resistance value of the first external resistor is infinite, and the resistance value of the second external resistor is Rg. Thus, the switching between the electrodes 21, 22, 23 and the ground potential is switched by the switching means SW between the case where the external resistor Rg is not connected and the case where the external resistor Rg is connected. The ground electrode 20 is disposed on the surface of the living body 10 at a position not affected by the voltage measured by the electrodes 21, 22, and 23, and is set to the ground potential. It is not necessary to arrange the electrode 20.

A voltage from the signal source Vs in the living body 10 is generated at each of the electrodes 21, 22, and 23 disposed on the surface of the living body 10, and the voltage is amplified by the amplifier 30 to output an output voltage Vout. Switches S ₁ , S ₂ , and S ₃ are respectively disposed between the electrodes 21, 22, and 23 and the amplifier 30, and the respective switches S ₁ , S ₂ , and S ₃ are sequentially turned on so that each electrode is electrically connected. The voltages generated at 21, 22, and 23 are measured as the output voltage Vout of the amplifier 30.

As shown in FIG. 5, the switching means SW and the switches S ₁ , S ₂ , S ₃ are switched (step 1 to step 6). As a result, the first voltages V ₁ , V ₂ , V ₃ , and the like generated at the electrodes 21, 22, 23 when no external resistance is connected between the electrodes 21, 22, 23 and the ground potential, and The second voltages V ′ ₁ , V ′ ₂ , V ′ ₃ generated at the electrodes 21, 22, 23 when the external resistor Rg is connected between the electrodes 21, 22, 23 and the ground potential are Measured. In FIG. 5, the electrodes 21, 22, and 23 are indicated as channels ch ₁ , ch ₂ , and ch ₃ , respectively.

FIG. 6 is a diagram in which three electrodes 21, 22, 23 are arranged on the circumference 10 </ b> A of the surface of the living body 10 so as to surround a plurality of muscle fibers 40, and the signal source Vs and each electrode 21, 22, 23. The internal resistances between are denoted as R _b1 , R _b2 , and R _b3 , respectively.

At this time, in Step 1 shown in FIG. 5, the first voltage (when no external resistor is connected) V ₁ generated at the electrode 21 (channel ch ₁ ) is given by Expression (3-1).

On the other hand, in step 4, the second voltage (when the external resistor Rg is connected) V ′ ₁ generated at the electrode 21 (channel ch ₁ ) is expressed by an equation (when the input resistance R _in of the amplifier 30 is very large) Given in 3-2).

Here, R _b0 represents the internal resistance between the signal source Vs and the ground electrode 20.

From the equations (3-1) and (3-2), the first voltage V ₁ when the external resistor Rg is not connected and the external resistor Rg are connected to the electrode 21 (channel ch ₁ ). The ratio V ′ ₁ / V ₁ (attenuation ratio) with the second voltage V ′ ₁ in the case is given by Expression (3-3).

Similarly, in the electrode 22 (channel ch ₂ ), the ratio between the first voltage V ₂ when the external resistor Rg is not connected and the second voltage V ′ ₂ when the external resistor Rg is connected. In V ′ ₂ / V ₂ (attenuation ratio) and the electrode 23 (channel ch ₃ ), the first voltage V ₃ when the external resistance Rg is not connected and the case where the external resistance Rg is connected The ratio V ′ ₃ / V ₃ (attenuation ratio) with the second voltage V ′ ₃ is given by Expression (3-4) and Expression (3-5), respectively.

By the way, assuming that the conductivity in the living body 10 is uniform, the resistance values R _b1 , R _b2 , and R _b3 of the internal resistance are respectively the signal source Vs in the living body 10 and the electrodes 21, 22, 23. It is thought that it is proportional to the distance. Therefore, from the equations (3-3), (3-4), and (3-5), the distances L ₁ , L ₂ , L ₃ between the signal source Vs in the living body 10 and the electrodes 21, 22, 23 are Are represented by formulas (3-6), (3-7), and (3-8), respectively.

Here, β is a proportional constant between the internal resistance R _bi and the distance L _i (i = 1, 2, 3), and is determined by the conductivity of the living body 10 and the like.

As shown in the equations (3-6), (3-7), and (3-8), the distances L ₁ , L ₂ , and L ₃ are the attenuation ratios (V ′ ₁ / V ₁ , V ′ ₂ / V ₂ , V ′ ₃ / V ₃ ). Then, as shown in FIG. 7, the signal source Vs is considered to exist at the intersection of circles Q ₁ , Q ₂ , and Q _{3 having} radii L ₁ , L ₂ , and L ₃ centered on the electrodes 21, 22, and 23. It is done. The position coordinates of the electrodes _{21,22,23, (a 1, b 1} ), (a 2, b 2), (a 3, b 3) when to circle _{Q 1,} Q 2, _{Q 3} are each And represented by the following formulas (3-9), (3-10), and (3-11).

Therefore, the formula (3-6), (3-7), with _{L 1,} L 2, _{L 3} obtained in (3-8), the equation (3-9), (3-10), (3-11) becomes three simultaneous equations represented by the following formula (3-12).

Here, there are four unknowns of the three simultaneous equations represented by the equation (3-12): the two-dimensional coordinates (x, y) of the signal source Vs and the constants β and R _b0 . Therefore, by giving R _b0 in advance, the three simultaneous equations can be solved to obtain the two-dimensional coordinates (x, y) of the signal source Vs and the constant β.

  In this way, an external resistor is connected in parallel between the three electrodes 21, 22, and 23 arranged on the surface of the living body 10 and the ground potential, and the connection state is switched to be generated in each electrode 21, 22, 23. By measuring the voltage ratio (attenuation ratio), the two-dimensional position (x, y) of the signal source Vs in the living body 10 can be easily detected. Thereby, the two-dimensional position of the signal source Vs in the living body can be accurately detected using a small number of electrodes.

Further, the proportionality constant β between the internal resistance R _bi and the distance L _i (i = 1, 2, 3) can be obtained by solving the simultaneous equations. Therefore, the two-dimensional position of the signal source Vs in the living body can be detected with higher accuracy even if the proportionality constant β fluctuates due to the influence of the composition in the body or the value changes during the detection. be able to.

  Note that the description has been made assuming that there is one signal source Vs in the living body 10, but actually, a plurality of signal sources may be generated simultaneously. Even in such a case, the most dominant one of the electrical signals of these signal sources can be obtained as the signal source.

Further, as shown in FIG. 5, the switching means SW and the switches S1, S2, and S3 are switched, and the first voltages V ₁ , V ₂ , V ₃ , and the second voltages at the electrodes 21, 22, and 23 are switched. The voltages V ′ ₁ , V ′ ₂ and V ′ ₃ are measured sequentially. Therefore, if the potential of the signal voltage Vs changes within these switching times, an error may occur in the position measurement of the signal source Vs. Therefore, it is preferable to switch each electrode and the external resistance as fast as possible. For example, it is preferable to switch at 1 μs or less, desirably 0.1 μs or less.

  In the above description, the resistance value of the first external resistor is infinite (non-conductive), and the resistance value of the second external resistor is Rg. However, the first external resistor is the second external resistor. The resistance value may be different from the resistance value.

In this case, the three electrodes 21, 22, 23 are arranged on the circumference of the surface of the living body 10, and a first external resistor that can be switched between each electrode 21, 22, 23 and the ground potential. And a second external resistor are connected in parallel. Then, when a first external resistor is connected in parallel between each electrode 21, 22, 23 and the ground potential, a first voltage V _i (i = 1, 2, 2) generated at each electrode 21, 22, 23. 3) and a second voltage V ′ _i (i = 1) generated at each electrode 21, 22, 23 when a second external resistor is connected in parallel between each electrode 21, 22, 23 and the ground potential. , 2, 3). Then, a ratio V ₁ / V ′ _i (i = 1, 2, 3) is calculated from the first voltage V _i and the second voltage V ′ _i , and these three ratios V _i / V ′ _i (i = Based on 1, 2, 3), the position of the signal source Vs in the living body may be detected.

  Next, another signal source position detection method used for the signal intensity detection method of the signal source Vs in the present embodiment will be described with reference to FIGS.

  FIG. 8 is a diagram showing an electric network for explaining a method of detecting the position of the signal source Vs in the living body.

  As shown in FIG. 8, three electrodes 21, 22, and 23 are arranged on the surface of the living body 10. Specifically, as shown in FIG. 6, the three electrodes 21, 22, and 23 are arranged on the circumference 10 </ b> A on the surface of the living body 10 so as to surround the plurality of muscle fibers 40. Further, between the first electrode 21 and the second electrode 22, between the second electrode 22 and the third electrode 23, and between the third electrode 23 and the first electrode 21, respectively. The first external resistor and the second external resistor that can be switched to each other are connected in parallel. In the present embodiment, similarly to the first embodiment, the resistance value of the first external resistor is set to infinity, and the resistance value of the second external resistor is set to Rg. Further, the ground electrode 20 is arranged on the surface of the living body 10 at a position not affected by the voltage measured by the electrodes 21, 22, and 23, and this is set to the ground potential.

As shown in FIG. 8, switches S ₁ , S ₂ , S ₃ , and SS ₁ , SS ₂ , SS ₃ are arranged between the electrodes 21, 22, 23 and the differential amplifier 30. Then, the respective switches S ₁ , S ₂ , S ₃ , and SS ₁ , SS ₂ , SS ₃ are sequentially brought into conduction as shown in FIG. 9, whereby the first electrode 21 and the second electrode 22 are connected. , The voltage generated between the second electrode 22 and the third electrode 23 and between the third electrode 23 and the first electrode 21 is measured as the output voltage Vout of the differential amplifier 30. The Also, the electrodes are switched by the switching means SW between when the external resistor is not connected and when the external resistor Rg is connected. Accordingly, as shown in FIG. 9, each electrode is switched by switching the switching means SW and each of the switches S ₁ , S ₂ , S ₃ , SS ₁ , SS ₂ , SS ₃ (Step 1 to Step 6). The first voltage V ₁₂ , V ₂₃ , V ₃₁ generated between the electrodes when the external resistor Rg is not connected therebetween, and between the electrodes when the external resistor Rg is connected between the electrodes. Second voltages V ′ ₁₂ , V ′ ₂₃ , V ′ ₃₁ ) are measured. In FIG. 8, the electrodes 21, 22, and 23 are indicated as channels ch ₁ , ch ₂ , and ch ₃ , respectively.

In step 1 shown in FIG. 9, the first voltage (when no external resistor is connected) V ₁₂ generated between the electrode 21 and the electrode 22 (between the channels ch ₁ and ch ₂ ) is expressed by the equation ( 4-1).

On the other hand, in step 4, the second voltage (when the external resistor Rg is connected) V ′ ₁₂ generated between the electrode 21 and the electrode 22 (between the channels ch ₁ and ch ₂ ) When the input resistance R _in is very large, it is given by equation (4-2).

Here, R _b1 and R _b2 are the internal resistance between the signal source Vs and the electrode 21 (channel ch ₁ ) in the living body 10 and the internal resistance between the signal source Vs and the electrode 22 (channel ch ₂ ), respectively. Represents.

From the expressions (4-1) and (4-2), the first voltage V ₁₂ and the second voltage V ′ ₁₂ generated between the electrode 21 and the electrode 22 (between the channels ch ₁ and ch ₂ ). The ratio V ′ ₁₂ / V ₁₂ (attenuation ratio) is given by equation (4-3).

Similarly, the ratio V ′ ₂₃ / V ₂₃ (attenuation ratio) of the first voltage V ₂₃ and the second voltage V ′ ₂₃ generated between the electrode 22 and the electrode 23 (between the channels ch ₂ and ch ₃ ). , And the ratio V ′ ₃₁ / V ₃₁ (attenuation ratio) between the first voltage V ₃₁ and the second voltage V ′ ₃₁ generated between the electrode 23 and the electrode 21 (between the channels ch ₃ and ch ₁ ). Are given by equations (4-4) and (4-5), respectively.

Here, R _b3 represents the resistance value of the internal resistance between the signal source Vs in the living body 10 and the electrode 23 (ch ₃ ).

In the measurement of the voltage generated between the electrodes, the internal resistance in the living body 10 is represented by the sum of the internal resistances between the electrodes and the signal source. For example, in the measurement of the first voltage V ₁₂ and the second voltage V ′ ₁₂ generated between the electrode 21 and the electrode 22 (between the channels ch ₁ and ch ₂ ), the internal resistance in the living body 10 is R It is represented by _b1 + R _b2 .

Here, assuming that the electrical conductivity in the living body 10 is uniform, the sum of internal resistances (R _b1 + R _b2 ) is the distance D ₁ between the electrode 21 and the signal source Vs, and the electrode 22 and the signal source Vs. It is considered that it is proportional to the sum (D ₁ + D ₂ ) with the distance D _{2 of} . Therefore, the sums (D ₁ + D ₂ ), (D ₂ + D ₃ ), (D ₃ ) of the distances between the electrodes and the signal source Vs are obtained from the equations (2-3), (2-4), and (2-5). + D ₁ ) is represented by formulas (4-6), (4-7), and (4-8), respectively.

Here, α is a proportional constant between the internal resistance R _bi and the distance D _i (i = 1, 2, 3), and is determined by the conductivity of the living body 10 and the like.

As shown in equations (4-6), (4-7), and (4-8), the sum of the distances between the electrodes and the signal source Vs (D ₁ + D ₂ ), (D ₂ + D ₃ ), (D ₃ + D ₁ ) is expressed as a function of the reciprocal of the attenuation ratio (V ′ ₁₂ / V ₁₂ ), (V ′ ₂₃ / V ₂₃ ), and (V ′ ₃₁ / V ₃₁ ), respectively. As shown in FIG. 10, the signal source Vs is focused on the ellipse E ₁ focusing on the electrodes 21 and 22 (channels ch ₁ and ch ₂ ) and on the electrodes 22 and 23 (channels ch ₂ and ch ₃ ). ellipse _{E 2,} and is considered to electrodes 23 and 21 (channel _ch 3, _{ch 1)} is present at the intersection of the ellipse _{E 3} to focus.

If the position coordinates of the electrodes 21, 22, 23 are (a ₁ , b ₁ ), (a ₂ , b ₂ ), (a ₃ , b ₃ ), the ellipses E ₁ , E ₂ , E ₃ are respectively And represented by the following formulas (4-9), (4-10), and (42-11).

Therefore, using (D ₁ + D ₂ ), (D ₂ + D ₃ ), and (D ₃ + D ₁ ) determined by equations (4-6), (4-7), and (4-8), the following equations The two-dimensional coordinates (x, y) of the signal source Vs can be obtained by solving the three simultaneous equations expressed by (4-12).

In the equation (4-12), the internal resistance _Rb0 between the signal source Vs and the ground electrode 20 is not included in the equation. Further, the unknowns of the three simultaneous equations represented by the equation (4-12) are three, that is, the two-dimensional coordinates (x, y) of the signal source Vs and the constant α. Therefore, the two simultaneous coordinates (x, y) of the signal source Vs and the constant α can be obtained by solving the three simultaneous equations expressed by the equation (4-12).

According to the above method, when obtaining the two-dimensional coordinates (x, y) of the signal source Vs, the proportionality between two constants, that is, the internal resistance R _bi and the distance L _i (i = 1, 2, 3). The constant α and the internal resistance R _b0 between the signal source Vs and the ground electrode 20 do not need to be obtained in advance, and the two-dimensional coordinates of the in-vivo signal source Vs can be easily obtained.

(In vivo signal strength detection device)
FIG. 11 is a block diagram showing a configuration of an in-vivo signal intensity detection device according to another embodiment of the present invention, and an apparatus for detecting the signal intensity of an in-vivo signal source based on a voltage generated at an electrode arranged on the surface of the organism. It is. The in-vivo signal source targeted in the present embodiment is a linear signal source composed of a plurality of muscle fibers.

  As shown in FIG. 11, the in-vivo signal intensity detection device 100 according to the present embodiment includes an electrode unit 110 in which at least two electrodes are connected, and the electrode unit 110 includes a plurality of electrode units 110 as shown in FIG. 2. It is arranged on the circumference 10 </ b> A of the surface of the living body 10 so as to surround the muscle fibers (linear signal source) 40.

Vivo signal intensity detector 100 further includes a means 120 for detecting the position information of the signal source Vs (x, y), between each electrode and the ground potential, or voltage V _{i (i} generated between the electrodes = 1, 2), means 140 for calculating the distance r _i (i = 1, 2) between the signal source Vs and each electrode, and means 150 for detecting the signal intensity of the signal source Vs. I have.

In the signal strength detection unit 150, the voltage V _i (i = 1, 2) measured by the voltage measurement unit 130, the distance r _i (i = 1, 2) calculated by the distance calculation unit 140, and the formula (1- Based on the attenuation formula of the signal source in the living body shown in 1), the signal intensity of the signal source Vs is detected.

  Here, the signal intensity can be detected using the in-vivo signal intensity detection method described in the first embodiment or the second embodiment.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, in the above embodiment, the equation (1-1) is used as the attenuation equation of the signal source in the body, but is not necessarily limited thereto.

  Further, in the above embodiment, the signal intensity of the signal source is detected by arranging at least two electrodes so as to surround the plurality of signal sources. However, by further arranging one or more electrodes, The position of the signal source may be detected.

Moreover, in the said embodiment, the detection of the positional information (x, y) of the signal source Vs is performed using the method described with reference to FIG. 4 to FIG. 7 or FIG. 8 to FIG. When at least three or more electrodes are arranged so as to surround, and two external resistors having different resistance values are connected in parallel between each electrode and the ground potential, each of the external resistors is connected in parallel. The voltage V _k (k = 1, 2, 3) and the voltage V ′ _k (k = 1, 2, 3) generated at the electrodes are measured, and the voltage ratio V _k / V ′ _k (k = 1, 2, 3) is measured. However, the method is not necessarily limited to this. For example, it was obtained by arranging a large number of electrodes on the surface of a living body in a lattice pattern, surface potential measured by each electrode, MRI (Magnetic Resonance Imaging), CT (Computed Tomography), etc. A method of obtaining the position information of the signal source in the living body by analyzing the potential distribution in the body based on the image data of the living body may be used.

10 Living body
10A circumference
20 Ground electrode
21 First electrode (channel ch ₁ )
22 Second electrode (channel ch ₂ )
23 3rd electrode (channel ch ₃ )
30 differential amplifier
40 muscle fibers
100 In vivo signal intensity detection device
110 Electrode unit
120 Position information detection means
130 Voltage measurement means
140 Distance calculation means
150 Signal strength detection means

Claims (5)

An in-vivo signal strength detection method for detecting a signal strength of a signal source in a living body based on a voltage generated in an electrode arranged on a living body surface,
The in-vivo signal source is a linear signal source composed of a plurality of muscle fibers,
Disposing at least two electrodes on the circumference of the biological surface so as to surround the plurality of signal sources;
Obtaining position information (x, y) of the signal source in a plane including the two electrodes;
From the position information (X _i , Y _i ) (i = 1, 2) of each electrode in the plane including the two electrodes and the position information (x, y) of the signal source, the signal source and the respective Calculating a distance r _i (i = 1, 2) from the electrode;
Measuring a voltage V _i (i = 1, 2) generated between each electrode and the ground potential or between each electrode,
Detecting the signal strength of the signal source in the living body based on the distance r _i (i = 1, 2), the voltage V _i (i = 1, 2), and the attenuation formula of the signal source in the body; In vivo signal strength detection method. The in vivo signal intensity detection method according to claim 1, wherein the attenuation formula is represented by the following formula (1-1).
(Where V ₀ is the signal strength of the signal source and η is the attenuation coefficient) The step of obtaining the position information (x, y) of the signal source includes:
Arranging one or more electrodes on the circumference where the two electrodes are arranged; and
A first external resistor and a second external resistor are connected in parallel so as to be switchable between the electrodes and the ground potential, or between the electrodes, and between the electrodes and the ground potential, or , A first voltage V _k (k = 1, 2, 3) generated when the first external resistor is connected between the electrodes, and between the electrodes and the ground potential, or Measuring a second voltage V ′ _k (k = 1, 2, 3) generated when the second external resistor is connected between the electrodes;
A ratio V _k / V ′ _k (k = 1, 2, 3) is calculated from the first voltage V _k and the second voltage V ′ _k , and these three ratios V _k / V ′ _k (k = 1, 2, 3), and detecting the position (x, y) of the signal source. The in-vivo signal intensity detection method according to claim 1 or 2.   The in-vivo signal intensity detection method according to claim 3, wherein one of the first external resistance and the second external resistance has an infinite resistance value. An in-vivo signal strength detection device that detects a signal strength of a signal source in a living body based on a voltage generated in an electrode disposed on the surface of the living body,
The in-vivo signal source is a linear signal source composed of a plurality of muscle fibers,
An electrode unit connected to at least two electrodes, arranged on the circumference of the biological surface so as to surround the plurality of signal sources;
Means for detecting position information (x, y) of the signal source in a plane including the two electrodes arranged on the circumference of the biological surface;
Means for measuring a voltage V _i (i = 1, 2) generated between each electrode and a ground potential or between each electrode;
From the position information (X _i , Y _i ) (i = 1, 2) of each electrode in the plane including the two electrodes and the position information (x, y) of the signal source, the signal source and the respective Means for calculating a distance r _i (i = 1, 2) from the electrode;
Based on the distance r _i (i = 1, 2), the voltage V _i (i = 1, 2), and the attenuation formula of the signal source in the living body, the signal intensity of the signal source in the living body is detected. An in-vivo signal intensity detection device comprising: means.