JP5051508B2 - Fat equivalent phantom and method for producing the same, fat thickness estimation method using the phantom - Google Patents

Description

The present invention relates fat equivalent phantom and method create its simulating the physical characteristics of the human body fat, the fat thickness estimated how using a phantom.

  Currently, body fat percentage measurement is based on the fact that the bioelectrical impedance of adipose tissue and other tissues is greatly different, and the whole body is considered to be composed of a single bioelectrical impedance. Has been done.

  On the other hand, local body fat measurement for each body part is considered useful. For example, measurement of muscle-fat balance of the thigh is effective for grasping an individual's exercise ability, health level, and the like. For this reason, development of a method for simply measuring the local fat thickness is required.

  Therefore, studies on bioelectrical impedance measurement using a human body model have been made for the purpose of realizing simple measurement of local fat thickness. Since various measurement conditions and electrical characteristics of the measurement target can be easily set, the model experiment is considered to be effective in examining bioelectrical impedance measurement.

As a human body model, a gel phantom (a simulated living body mainly composed of agar that reproduces physical characteristics such as the shape of the human body and electrical constants) mainly composed of agar and a thickener, particularly relates to EMC (Electro Magnetic Compatibility). Widely used in research fields. The muscle equivalent phantom is disclosed in Non-Patent Document 1, for example.
Koichi Ito et al., Living Body and Electromagnetic Environment (1) “New Living Body Equivalent Phantom” 12 No1 pp, 51-62 (1999)

  The inventors of the present application form a living body simulation model having a two-layer structure composed of fat and muscle, and examine the relationship between bioelectric impedance and body fat thickness. In order to form such a two-layer biological simulation model composed of fat and muscle, a muscle equivalent phantom and a fat equivalent phantom are required.

  Here, as a muscle equivalent phantom, those described in Non-Patent Document 1 are known, but a fat equivalent phantom has not been sufficiently studied so far.

  In addition, if a two-layered biological simulation model consisting of fat and muscle is used, fat thickness can be estimated using this model. This is considered to enable local body fat measurement for each body part.

  Accordingly, an object of the present invention is to provide a fat equivalent phantom suitable for use in forming a two-layer biological simulation model composed of fat and muscle and a method for producing the same.

Another object of the present invention is to provide a fat thickness estimation method that enables local body fat measurement for each part of the body using a two-layered biological simulation model composed of a fat equivalent phantom and a muscle equivalent phantom. To provide a law .

The present invention proposes the following items in order to solve the above-described problems.
(1) The present invention includes a and detergent purified water and vegetable oil combined mixed, the electrical characteristics by adjusting the mixing ratio of the said purified water and vegetable oil and detergent, produced in a gel-like by the agar and a thickener A fat-equivalent phantom characterized by the above has been proposed.

(2) The present invention proposes a fat equivalent phantom, characterized by mixing fat for equivalent phantom, the purified water and vegetable oil, the ratio of approximately 1: 1 (1).

(3) In the present invention, purified water and vegetable oil are mixed, a detergent and agar are added and mixed, a mixed liquid is heated, and a thickener is added to the heated liquid. There has been proposed a method for producing a fat equivalent phantom characterized by comprising a step of mixing and placing in a mold, and a step of cooling a liquid placed in the mold to produce a gel-like fat equivalent phantom .

(4) The present invention proposes a method for producing a fat equivalent phantom according to (3), wherein purified water and vegetable oil are mixed in a ratio of about 1: 1. ing.

( 5 ) The present invention includes a step of creating a two-layered human body model composed of a plurality of fat equivalent phantoms and muscle equivalent phantoms having different fat thickness patterns, and a plurality of electrodes arranged on the surface of the fat equivalent phantom. Measure the apparent resistivity of multiple patterns with different fat thicknesses in the human body model while changing the interval, and save the apparent resistivity of the multiple patterns from the process of storing and the apparent resistivity observed for the subject. see, the step of estimating the fat thickness of該被examiner, have a, the fat thickness estimation method which comprises using a fat equivalent phantom as the fat equivalent phantom (1) or (2) is suggesting.

According to the present invention, a fat equivalent phantom that simulates human body fat is generated by mixing purified water and vegetable oil , adjusting electrical characteristics with a detergent, and gelling with agar and thickener. There is an effect that can be.

Further, according to the present invention, using the above-described fat equivalent phantom, to create a human body model having a two-layer structure consisting of a plurality of fat equivalent phantom and muscle equivalent phantom with different patterns of fat thickness, the surface of the fat equivalent phantom The apparent resistivity of a plurality of patterns with different fat thicknesses of the human body model is measured and stored while changing the interval between the plurality of electrodes arranged on the body. By referring to the apparent specific resistance of the pattern and estimating the fat thickness of the subject, there is an effect that local body fat measurement for each part of the body becomes possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a method for creating a fat equivalent phantom to which the present invention is applied will be described.

<About fat equivalent phantom>
The fat-equivalent phantom to which the present invention is applied is a mixture of purified water and salad oil (vegetable oil made from soybeans, rapeseed, corn, olives, cottonseed, rice, etc.) at a predetermined ratio, and further contains a detergent (mainly The electrical properties (dielectric constant and conductivity) are adjusted with a fatty acid salt refined from oil and fat and sodium hydroxide, and a thickener (for example, TX-151) and agar (D-galactose, 3, 6-anhydrogalactose-containing polysaccharide gel), which is hardened into a gel shape so that its physical characteristics approach those of human fat.

FIG. 1 shows a procedure for creating a fat equivalent phantom to which the present invention is applied.
First, as shown in FIG. 2, each material consisting of 100 ml of purified water, 100 ml of salad oil, 20 ml of detergent, 10 g of agar, and 5 g of thickener (TX-151) is prepared. And based on the quantity mentioned above, in a container containing purified water, put salad oil, detergent, and agar, mix at room temperature (step S1), and heat them all at once with strong heat while stirring them well (step S1). Step S2).

  When signs of boiling appear (about 90 to 95 degrees), the fire is immediately turned off (step 3), and the thickener (TX-151) is mixed (step S4).

  The heated liquid is stirred so that air does not enter (step 5), placed in a mold (step S6), and cooled to room temperature (step S7).

  When cooled to room temperature, a gel-like substance solidifies in the mold, and this gel-like substance becomes a fat equivalent phantom. When a gel-like fat equivalent phantom is generated in the mold, the gel-like fat equivalent phantom is removed from the mold (step S8).

  3 and 4 compare the electrical characteristics of the fat equivalent phantom created as described above with the actual electrical characteristics of fat as a reference, and FIG. 3 shows the measured conductivity. FIG. 4 shows the measured dielectric constant.

  In FIG. 3, the horizontal axis indicates the frequency, and the vertical axis indicates the conductivity. A1 indicates the conductivity characteristic of the fat equivalent phantom created as described above, and A2 indicates the conductivity characteristic of the human fat as a reference value. In FIG. 4, the horizontal axis indicates the frequency, the vertical axis indicates the dielectric constant, and B1 indicates the conductivity characteristic of the fat equivalent phantom created as described above. B2 indicates the conductivity characteristic of human body fat as a reference value.

  As is clear from the characteristics shown in FIGS. 3 and 4, the fat equivalent phantom of the present invention prepared as described above has a human body fat as a reference value and its electrical characteristics (conductivity and dielectric constant). It can be seen that the values are very close.

  As shown in FIG. 5 (A), the measurement of electrical characteristics is carried out by preparing an acrylic case 11 (40 mm × 60 mm × 20 mm), and as shown in FIG. The fat equivalent phantom 13 generated as described above is encapsulated, and the impedance is measured by the bipolar method using the acrylic case 11 having the copper plates 12a and 12b attached to both sides as electrodes. Here, assuming that the electrode area is S, the electrode interval is d, and the length is l, the characteristics of conductivity and relative permittivity are calculated from the following relational expressions (1) and (2) of resistance and capacitance. Is done.

  Next, it will be described that a fat equivalent phantom that simulates the physical characteristics of human body fat can be generated by preparing each material in the amount described above and performing the work procedure according to the process shown in FIG.

  FIG. 6 shows the measured dielectric constants of purified water, salad oil, and tap water. In FIG. 6, C1 represents the dielectric constant of purified water, C2 represents the dielectric constant of salad oil, C3 represents the dielectric constant of tap water, and C4 represents the dielectric constant of human fat as a reference value.

  From the characteristics shown in FIG. 6, it can be seen that the dielectric constant of human body fat (characteristic C4) as a reference value is between the dielectric constant of purified water (characteristic C1) and the dielectric constant of salad oil (characteristic C2). From such a relationship, it is considered that if purified water and salad oil are mixed at a predetermined ratio, an equivalent of the dielectric constant of human body fat can be generated.

  Next, the ratio of purified water and salad oil will be examined. FIG. 7 shows the measured dielectric constant of a mixture of purified water and salad oil in various proportions. Samples were prepared by mixing purified water and salad oil in a ratio of (1: 3), mixed in a ratio of (3: 1), and mixed in a ratio of (1: 1).

  In FIG. 7, D1 shows the dielectric constant of a mixture of purified water and salad oil in a ratio of (1: 3), and D2 shows the dielectric constant of a mixture of purified water and salad oil in a ratio of (3: 1). D3 shows the dielectric constant of a mixture of purified water and salad oil in a ratio of (1: 1), and D4 shows the dielectric constant of the human body fat as a reference.

  From the characteristics shown in FIG. 7, it can be seen that when purified water and salad oil are mixed at a ratio of (1: 1) (characteristic D3), the human fat characteristic (characteristic D4) as the reference value is the closest. Therefore, in the fat equivalent phantom to which the present invention is applied, purified water and salad oil are mixed at a ratio of (1: 1).

  The fat equivalent phantom to which the present invention is applied is a gel-like phantom. Therefore, the gel is hardened by agar and thickener.

  Furthermore, in the present invention, the electrical characteristics (dielectric constant and conductivity) are adjusted with a detergent. As samples, 100 ml of purified water, 100 ml of salad oil, 10 g of agar, and 5 g of thickener were prepared in three different amounts of detergent: 10 ml, 20 ml, and 28 ml.

  FIG. 8 shows changes in the dielectric constant characteristics depending on the amount of detergent. In FIG. 8, E1 indicates the dielectric constant when the amount of the detergent is 10 ml, E2 indicates the dielectric constant when the amount of the detergent is 20 ml, and E3 indicates the dielectric constant when the amount of the detergent is 28 ml. , E4 represents the dielectric constant of human fat as a reference value. From the characteristics of FIG. 8, it can be seen that the dielectric constant can be lowered by increasing the amount of detergent. Further, in the characteristics of FIG. 8, it can be seen that the dielectric constant (characteristic E3) when the amount of the detergent is 28 ml is close to the dielectric constant of human fat (characteristic E4) as a reference value. In addition, it can be seen that the dielectric constant (characteristic E2) when the amount of detergent is 20 ml is quite close to the dielectric constant of human body fat (characteristic E4) as the reference value.

  FIG. 9 shows the change in conductivity characteristics depending on the amount of detergent. In FIG. 9, F1 indicates the dielectric constant when the amount of detergent is 10 ml, F2 indicates the dielectric constant when the amount of detergent is 20 ml, and F3 indicates the dielectric constant when the amount of detergent is 28 ml. F4 represents the electrical conductivity of human body fat as a reference value. From the characteristics of FIG. 9, it can be seen that the electrical conductivity can be increased by increasing the amount of detergent. From the characteristics in FIG. 9, it can be seen that the conductivity when the amount of detergent is 20 ml (characteristic F2) is closest to the human fat conductivity (characteristic F4) as the reference value.

  As described above, the electric characteristics (dielectric constant and conductivity) can be adjusted by introducing the detergent. From the above results, when the amount of the detergent is 20 ml, the characteristics closest to the reference value can be obtained.

  In the above example, the amount of detergent is 20 ml, but is not limited thereto. The amount of the detergent may be appropriately changed according to the purpose of the human body model.

  In the above example, agar is used to form a gel, but the present invention is not limited to this. Moreover, in the above-mentioned example, although TX-151 is used as a thickener, it is not limited to this. Further, the amount of agar and the amount of thickener are examples, and may be appropriately changed according to the purpose of the human body model.

  In addition, what contains surfactant, such as a synthetic detergent for kitchens, is used for detergent, for example. When such a detergent is introduced into purified water and vegetable oil, the detergent acts as a surfactant, and the purified water and vegetable oil are mixed. In addition, the surfactant contained in the detergent has an ionic lipophilic group, and for example, sulfonic acid surfactants such as sodium linear alkylbenzene sulfonate and sodium lauryl sulfate are more preferable. The ionicity of this lipophilic group affects the electrical conductivity among the electrical characteristics of the fat equivalent phantom to be produced. Therefore, the electrical conductivity of the fat equivalent phantom is adjusted by adjusting the amount of detergent to be introduced. be able to.

  In addition, as described above, in the present embodiment, purified water, vegetable oil, and a detergent for adjusting the conductivity are exemplified as the material for the fat equivalent phantom, but the present invention is not limited to this, and the detergent Alternatively, a surfactant may be used directly. In addition, a surfactant in which the lipophilic group does not exhibit ionicity may be used. In this case, the conductivity can be adjusted by using sodium chloride or calcium chloride to adjust the conductivity. .

<Measurement of fat thickness using fat equivalent phantom>
Next, a fat thickness measurement method using the fat equivalent phantom created as described above will be described.

  As described above, in the present invention, it is possible to create a fat equivalent phantom that approximates the fat of the human body with the electrical characteristics as a reference value. Using the fat equivalent phantom created in this way, a human body model with a two-layer structure consisting of fat and muscle is created, and the apparent specific resistance of the human body model with this two-layer structure is measured. Estimation can be performed.

  Apparent resistivity is known as one of the geophysical exploration methods for estimating the underground structure, and is a concept used in the electric exploration method. The apparent specific resistance can be measured by a four-electrode method as shown in FIG.

  In FIG. 10, four electrodes P1, P2, P3, and P4 are arranged on the surface of the medium 21 at an equal interval a, current is passed through the pair of electrodes P1 and P2, and the potential difference between the pair of electrodes P3 and P4 is determined. Observe. As described above, when the four electrodes P1, P2, P3, and P4 are arranged at equal intervals a, the current I is passed through the pair of electrodes P1 and P2, and the potential difference V between the pair of electrodes P3 and P4 is observed, It is known that the resistance ρ is expressed by the following equation (3).

  Here, the above formula is based on the premise that the medium 21 in which the electrodes are arranged is homogeneous, but the actual living body is not homogeneous. The specific resistance calculated using the above equation in a non-homogeneous medium is called apparent specific resistance.

  The apparent specific resistance obtained by the above formula represents the average specific resistance in the region up to the depth a. Therefore, as the electrode interval a increases, the value of the apparent specific resistance is affected to a deeper portion.

  As shown in FIG. 11, a human body model having a two-layer structure composed of fat and muscle has a fat equivalent phantom 32 stacked on a muscle equivalent phantom 31. Fat has a higher specific resistance than muscle. From this, it is considered that when the thickness d of the fat equivalent phantom 32 is increased, the value of the apparent specific resistance is increased.

  Further, as the electrode interval “a” increases, the value of the apparent specific resistance is affected to a deeper portion. Therefore, when the electrode interval a is small, the apparent specific resistance value is almost affected by the fat equivalent phantom 32, and when the electrode interval a is increased, the apparent equivalent ratio 31 is affected by the muscle equivalent phantom 31. The resistance value is considered to be small. At this time, it is considered that the apparent specific resistance is different depending on the thickness of the fat equivalent phantom 32.

  Accordingly, the inventors of the present application created a model of a two-layer structure of a fat equivalent phantom and a muscle equivalent phantom, measured an apparent specific resistance, and verified its characteristics.

  FIG. 12 is an example of a model used in the experiment. In this example, as shown in FIG. 12A, a fat equivalent phantom 42 is laminated on a muscle equivalent phantom 41 provided with a partial step 43 in the center of the acrylic box 40 to create a two-layer model. . The acrylic box 40 has a size of 300 mm × 200 mm × 100 mm and is provided with a step 43 of 25 mm in the center. The apparent specific resistance was measured by changing the electrode interval a by 10 mm between 10 mm and 50 mm using a four-electrode method using an LCR meter.

  FIG. 13 is a cross-sectional view in the Y-axis direction, and the arrangement of the electrodes was moved from 40 mm to 160 mm in increments of 30 mm on the Y-axis.

  A measurement line was set as shown in FIG. 14 in order to confirm the change in the measured value accompanying the change in the thickness of the fat, and to confirm the symmetry of the model with Y = 100 mm as an axis from the measured value.

FIG. 15 shows the measurement of the relationship between the electrode spacing and the apparent resistivity using the two-layered human model of the fat equivalent phantom and the muscle equivalent phantom as described above.
In FIG. 15, the horizontal axis indicates the electrode interval, and the vertical axis indicates the measured value of the apparent specific resistance. In FIG. 15, G1 indicates the characteristics when Y = 40 mm, G2 indicates the characteristics when Y = 70 mm, G3 indicates the characteristics when Y = 100 mm, and G4 indicates the characteristics when Y = 130 mm. G5 indicates characteristics when Y = 160 mm. From the characteristics shown in FIG. 15, the value of the apparent specific resistance increases as the survey line is moved to 40 mm, 70 mm, and 100 mm with the thickest fat in order. In addition, as it moves from 100 mm to 130 mm and 160 mm, the value of the apparent specific resistance decreases. This is thought to be because the specific resistance is higher in fat than in muscle and is reflected in the value of apparent specific resistance.

  In addition, when the electrode interval is changed, there is a portion where the apparent specific resistance greatly decreases at a certain electrode interval. This is due to the influence of the low specific resistance of the muscle portion, and it is considered that the value of the electrode interval a when the apparent specific resistance in the curve decreases is a clue to estimate the fat thickness.

  As described above, in the human body model having a two-layer structure including the fat equivalent phantom and the muscle equivalent phantom, the apparent specific resistance when the electrode interval a is moved shows a specific change depending on the layer thickness of the fat layer. Therefore, the fat thickness can be estimated by observing the apparent specific resistance of a human body model having a two-layer structure composed of fat and muscle.

  FIG. 16 shows a fat thickness estimation method using apparent resistivity of a two-layered human body model composed of fat and muscle.

  As shown in FIG. 16, a two-layered human body model composed of a number of fat equivalent phantoms and muscle equivalent phantoms having different fat thickness patterns is created (step S101), and these two layer structures are changed while changing the electrode spacing. The apparent specific resistance of the human body model is measured (step S102). In this way, apparent resistivity data measured by a human body model having a large number of patterns in a double structure is stored (step S103).

The apparent resistivity of the subject while changing the electrode spacing is measured (step S104). From the data of the observed apparent resistivity from the subject, with reference to a number of pattern data of apparent resistivity measured by the human body model of the double structure that had been previously stored at step S103, the subject's The fat thickness is estimated (step S105).

  In this way, if a two-layered biological simulation model consisting of fat and muscle is used, the fat thickness can be estimated by measuring the apparent specific resistance of this model.

  Further, by creating a human body model for each part of the body, local body fat measurement for each part can be performed.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to embodiment mentioned above, A various deformation | transformation and application are possible within the range which does not deviate from the summary of this invention.

  The present invention is suitable for experiments and discussions using various human body models including body fat, measurement of the health condition of the human body, etc. Can be widely used.

It is a flowchart which shows an example of the production | generation process of the fat equivalent phantom to which this invention was applied. It is explanatory drawing of the material for producing | generating the fat equivalent phantom to which this invention was applied, and its quantity. It is a graph which shows the measured value of the characteristic of the electrical conductivity of a fat equivalent phantom. It is a graph which shows the measured value of the dielectric constant characteristic of a fat equivalent phantom. It is the perspective view and sectional drawing used for description of the electrical property method of a fat equivalent phantom. It is a graph which shows the measured value of the dielectric constant of each substance. It is a graph which shows the measured value of the dielectric constant by the ratio of refined water and salad oil. It is a graph which shows the measured value of the dielectric constant of the phantom by the quantity of detergent. It is a graph which shows the measured value of the electrical conductivity of the phantom by the quantity of detergent. It is explanatory drawing of a measurement of an apparent specific resistance. It is explanatory drawing of the model of the two-layer structure of a fat equivalent phantom and a muscle equivalent phantom. It is explanatory drawing of an example of the two-layer structure model of a fat equivalent phantom and a muscle equivalent phantom. It is explanatory drawing of an example of the two-layer structure model of a fat equivalent phantom and a muscle equivalent phantom. It is explanatory drawing of an example of the two-layer structure model of a fat equivalent phantom and a muscle equivalent phantom. It is a graph which shows the change of apparent specific resistance by the two-layer structure model of a fat equivalent phantom and a muscle equivalent phantom. It is a flowchart used for description of the estimation method of fat thickness by the two-layer structure model of a fat equivalent phantom and a muscle equivalent phantom.

Explanation of symbols

11: Acrylic case 12a, 12b: Copper plate as electrode 13: Fat equivalent phantom 21: Medium 31: Muscle equivalent phantom 32: Fat equivalent phantom 40: Acrylic box 41: Muscle equivalent phantom 42: Fat equivalent phantom

Claims (5)

  Fat equivalent, characterized by mixing purified water, vegetable oil and detergent, adjusting the electrical characteristics by the mixing ratio of the purified water, vegetable oil and detergent, and gelled with agar and thickener phantom.   2. The fat equivalent phantom according to claim 1, wherein the purified water and the vegetable oil are mixed in a ratio of about 1: 1. Mixing purified water and vegetable oil, mixing detergent and agar, and mixing;
Heating the mixed liquid;
Mixing the thickener with the heated liquid and placing it in a mold;
Cooling the liquid in the mold to produce a gel-like fat equivalent phantom;
A method for producing a fat equivalent phantom characterized by comprising:   4. The method for producing a fat equivalent phantom according to claim 3, wherein the purified water and the vegetable oil are mixed in a ratio of approximately 1: 1. Creating a two-layered human model composed of a plurality of fat equivalent phantoms and muscle equivalent phantoms having different fat thickness patterns;
Measuring and storing apparent specific resistance of a plurality of patterns with different fat thicknesses of the human body model while changing the interval between a plurality of electrodes arranged on the surface of the fat equivalent phantom;
A step of estimating the fat thickness of the subject by referring to the apparent resistivity of the plurality of patterns stored from the apparent resistivity observed for the subject, as the fat equivalent phantom A fat thickness estimation method using the fat equivalent phantom according to claim 1.

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