JP5870537B2 - Ferrite composition for noninvasive temperature measurement - Google Patents

Description

  The present invention relates to a ferrite composition for noninvasive temperature measurement that can be suitably used as a part of a temperature sensor for injecting into the body or the like and measuring the temperature from the outside.

  Based on the knowledge that there is a difference in heat sensitivity between normal cells and abnormal cells such as cancers and brain tumors in living tissues, the affected area where the abnormal cells are thought to exist is measured several times from the body temperature. Is known to have a thermotherapy that raises the temperature to about 43 ° C. and suppresses or reduces the proliferation of abnormal cells.

  For example, hyperthermia is known as a treatment method using the thermal sensitivity of cancer cells. In hyperthermia, there are an RF method in which a human body is sandwiched between electrodes and a high frequency electric field is applied to heat the affected part, a soft heating method in which the internal tumor part is locally heated by induction heating, and the like.

  However, for example, in the case of the RF method, it is difficult to confirm whether the heated part has reached the target temperature unless the deep part is heated over a wide area, or the temperature sensor is pierced invasively into the tumor part in the body. There is a problem.

  On the other hand, in the case of the soft heating method, as shown in Patent Document 1 below, when a temperature-sensitive magnetic material having a low Curie temperature is used as a heating target and the magnetic material reaches the Curie temperature, it is automatically performed. By utilizing the property of stopping heat generation, it is not necessary to use an invasive temperature sensor.

  However, although there are magnetic materials with high heat generation efficiency, in the conventional soft heating method, there is a limit to the Curie temperature of the ferrite used as a heat generating element, so at the expense of heat generation efficiency, several degrees higher than body temperature, specifically A magnetic material having a Curie temperature of about 43 ° C. was used as a heating element. That is, in the conventional soft heating method, it is desired to use a magnetic material with higher heat generation efficiency as a heating element, but in that case, it is necessary to use an invasive temperature sensor separately, Has the problem of increasing the burden of

  Therefore, a noninvasive temperature measurement system shown in Patent Document 2 below has been proposed. However, the development of a ferrite composition suitable for use in such a non-invasive temperature measurement system has just started.

Japanese Patent No. 4492370 WO2009 / 088062 Publication

  The present invention has been made in view of such a situation, and an object thereof is non-invasive temperature measurement ferrite that can be suitably used as a part of a temperature sensor for injecting into the body or the like and measuring temperature from the outside. It is to provide a composition.

In order to achieve the above object, the ferrite composition for noninvasive temperature measurement according to the present invention comprises:
Iron oxide is 48.0 to 49.7 mol% in terms of Fe ₂ O ₃ , zinc oxide is 29.7 to 30.25 mol% in terms of ZnO, and copper oxide is 5.5 to 6.8 mol% in terms of CuO. The balance has a main component composed of magnesium oxide, and 30 to 350 ppm of silicon oxide in terms of SiO ₂ is contained as an accessory component with respect to 100% by weight of the main component.

  According to the ferrite composition for noninvasive temperature measurement according to the present invention, although it has a high magnetic flux density at about body temperature, the magnetic flux density rapidly increases at an upper limit of temperature suitable for treatment, specifically at a temperature of 43 to 44 ° C. To change. That is, the change rate of the magnetic flux density becomes maximum in this temperature range. By measuring the change in the magnetic flux, it is possible to measure the temperature of the tumor part (for example, the upper limit of the temperature appropriate for treatment). Therefore, the non-invasive temperature measurement can be performed by injecting the ferrite composition for non-invasive temperature measurement according to the present invention into the body, for example, in the form of particles and measuring the change in magnetic flux from the outside.

  That is, it is an effective means for improving the QOL of patients with advanced cancer. QOL: Quality of Life (QOL) generally refers to the quality of each person's life and the quality of life in terms of society, that is, how human life is for a person. It is a concept that captures, as a measure, whether you have a personal life and find happiness in your life.

FIG. 1A and FIG. 1B are conceptual diagrams of a non-invasive temperature measurement system having a temperature-sensitive magnetic body composed of a ferrite composition for non-invasive temperature measurement according to one embodiment of the present invention. FIG. 2 is a graph showing the relationship between the temperature and the magnetic flux density in the ferrite composition for noninvasive temperature measurement according to Examples and Comparative Examples of the present invention. FIG. 3 is a graph showing the relationship between temperature and magnetic flux density in the ferrite composition for noninvasive temperature measurement according to Examples and Comparative Examples of the present invention. FIG. 4 is a graph showing the relationship between the temperature and the magnetic flux density in the ferrite composition for noninvasive temperature measurement according to Examples and Comparative Examples of the present invention. FIG. 5 is a graph showing the relationship between the temperature and the magnetic flux density in the ferrite composition for noninvasive temperature measurement according to Examples and Comparative Examples of the present invention.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
The ferrite composition according to this embodiment is an Mg—Zn-based ferrite composition, containing iron oxide, zinc oxide, copper oxide, and magnesium oxide as main components, and silicon oxide as a subcomponent.

Specifically, the ferrite composition according to the present embodiment is
48.0 to 49.7 mol% of iron oxide calculated as _Fe 2 _{O 3,} preferably 48.0 to 49.1 mol%,
Zinc oxide is 29.7-30.25 mol% in terms of ZnO, preferably 30.0-30.25 mol%,
Copper oxide is 5.5 to 6.8 mol%, preferably 5.5 to 6.5 mol% in terms of CuO,
The remainder has a main component composed of magnesium oxide,
Silicon oxide is contained in an amount of 30 to 350 ppm, preferably 30 to 200 ppm in terms of SiO ₂ as an accessory component with respect to 100% by weight of the main component.

  When the content of iron oxide is small, the magnetic flux density tends to be low, and the change value of the magnetic flux density at 43 to 44 ° C. tends to be low. If the content of iron oxide is large, the magnetic flux density tends to be high, but if it is too large, the change value of the magnetic flux density at 43 to 44 ° C. tends to decrease.

  When there is too little content of zinc oxide, it exists in the tendency for the change value of the magnetic flux density in 43-44 degreeC to become small. When the amount of zinc oxide is large, the magnetic flux density tends to decrease. When the amount is too large, both are about 0 mT at 43 ° C. and 44 ° C., and the change value from 43 to 44 ° C. is 0 mT.

  When there is too little copper oxide, it exists in the tendency for the change value of the magnetic flux density in 43-44 degreeC to reduce. When the amount of copper oxide is large, the magnetic flux density tends to decrease. When the amount is too large, both are about 0 mT at 43 ° C. and 44 ° C., and the change value from 43 to 44 ° C. is 0 mT.

The content of silicon oxide is 30 to 350 ppm, preferably 30 to 200 ppm in terms of SiO _{2 with} respect to 100% by weight of the main component. If the amount of silicon oxide is small, the saturation magnetization tends to increase. If the amount is too small, the change value of the magnetic flux density at 43 to 44 ° C. tends to be small. When the amount of silicon oxide is large, the saturation magnetization tends to decrease. When the amount is too small, the change value of the magnetic flux density at 43 to 44 ° C. tends to be small.

  In addition, the ferrite composition according to the present embodiment may include about several ppm to several hundred ppm of inevitable impurity element oxides in the raw material.

  Specifically, B, C, P, S, Cl, As, Se, Br, Te, I, Li, Na, Mg, Al, K, Ga, Ge, Sr, Cd, In, Sn, Sb, Typical metal elements such as Ba, Pb, and Bi, and transition metal elements such as Sc, Ti, V, Cr, Co, Ni, Cu, Y, Zr, Nb, Mo, Pd, Ag, Hf, and Ta can be given.

Next, an example of a method for producing a ferrite composition according to this embodiment will be described.
First, starting materials (raw materials of main components and raw materials of subcomponents) are weighed and mixed so as to have a predetermined composition ratio to obtain a raw material mixture. Examples of the mixing method include wet mixing using a ball mill and dry mixing using a dry mixer. It is preferable to use a starting material having an average particle size of 0.1 to 3 μm.

As a raw material of the main component, iron oxide (α-Fe ₂ O ₃ ), zinc oxide (ZnO), copper oxide (CuO), magnesium hydroxide (Mg (OH) ₂ ), or the like can be used. In addition, various compounds that become oxides or composite oxides by firing can be used. Examples of the oxide that becomes the above-mentioned oxide upon firing include simple metals, carbonates, oxalates, nitrates, hydroxides, halides, organometallic compounds, and the like. The content of magnesium oxide in the main component is calculated in terms of MgO, but Mg (OH) ₂ is preferably used as the main component material.

  Next, the raw material mixture is calcined to obtain a calcined material. Calcining causes thermal decomposition of raw materials, homogenization of ingredients, formation of ferrite, disappearance of ultrafine powder due to sintering and grain growth to an appropriate particle size, and converts the raw material mixture into a form suitable for the subsequent process. Done for. Such calcination is preferably performed at a temperature of 800 to 1100 ° C. for about 1 to 3 hours. The calcination may be performed in the air (air), or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. The mixing of the main component raw material and the subcomponent raw material may be performed before calcining or after calcining.

  Next, the calcined material is pulverized to obtain a pulverized material. The pulverization is performed in order to break down the coagulation of the calcined material to obtain a powder having appropriate sinterability. When the calcined material forms a large lump, wet pulverization is performed using a ball mill or an attritor after coarse pulverization. The wet pulverization is performed until the average particle diameter of the calcined material is preferably about 1 to 2 μm.

  Next, the pulverized material is granulated (granular) to obtain a granulated product. The granulation is performed in order to convert the pulverized material into aggregated particles having an appropriate size and convert it into a form suitable for molding. Examples of such a granulation method include a pressure granulation method and a spray drying method. The spray drying method is a method in which a commonly used binder such as polyvinyl alcohol is added to the pulverized material, and then atomized in a spray dryer and dried at a low temperature.

  Next, the granulated product is molded into a predetermined shape to obtain a molded body. Examples of the molding of the granulated product include dry molding, wet molding, and extrusion molding. The dry molding method is a molding method in which a granulated product is filled in a mold and compressed and pressed (pressed). The shape of the molded body is not particularly limited, and may be appropriately determined according to the application.

  Next, the molded body is fired. Firing is performed in order to obtain a dense sintered body by causing sintering in which the powder adheres at a temperature lower than the melting point between the powder particles of the compact including many voids. Such firing is preferably performed at a temperature of 1000 to 1200 ° C., usually for about 1 to 5 hours. The temperature rising rate is preferably 150 to 250 ° C./hour, and the temperature decreasing rate is preferably 150 to 250 ° C./hour. Firing may be performed in the air (air) or in an atmosphere having a higher oxygen partial pressure than in the air.

  Next, the obtained sintered body is pulverized to obtain the ferrite powder of the present embodiment. For grinding, a vibrator mill or jaw crusher is used. The particle size of the ferrite powder is preferably 40 to 150 μm, more preferably 80 to 120 μm. By using a ferrite powder having such a particle size as a temperature-sensitive magnetic material as described below, it becomes easy to inject it into the body by injection or the like.

  By injecting into the body a temperature-sensitive magnetic material made of the ferrite composition according to the present embodiment, for example, the temperature of the tumor part (43 ° C., which is the upper limit of temperature suitable for treatment) is accurately measured non-invasively. Thus, non-invasive and safe local heating treatment of the affected area can be realized.

  Next, a method for measuring temperature using a temperature-sensitive magnetic body made of the ferrite composition according to the present embodiment will be described.

  As shown in FIG. 1A, a magnetic flux M1 is generated from the temperature measurement drive coil 4 toward the temperature-sensitive magnetic body 2 with respect to the temperature-sensitive magnetic body 2 made of the ferrite composition according to the present embodiment. At this time, when the temperature T of the temperature-sensitive magnetic body 2 is lower than the Curie temperature Tc of the temperature-sensitive magnetic body 2, the magnetic flux M <b> 1 is concentrated near the temperature-sensitive magnetic body 2. When the concentration of the magnetic flux M1 occurs, the magnetic flux M2 in the vertical direction of the magnetic flux M1 can be detected by the detection coil 6.

  The degree of concentration of the magnetic flux M1 (corresponding to the magnetic flux density) varies depending on the temperature T of the temperature-sensitive magnetic body 2. That is, the concentration degree of the magnetic flux M1 decreases as the temperature T of the temperature-sensitive magnetic body 2 approaches the Curie temperature Tc, and the temperature T of the temperature-sensitive magnetic body 2 becomes lower than that of the magnetic body 2 as shown in FIG. When the temperature is equal to or higher than the Curie temperature Tc, the degree of concentration of the magnetic flux M1 becomes substantially zero, and the magnetic flux M2 in the vertical direction of the magnetic flux M1 becomes substantially zero.

  Therefore, it is possible to detect the temperature of the temperature-sensitive magnetic body 2 by detecting the change of the magnetic flux M2 detected by the detection coil 6, particularly the inflection point of the magnetic flux change. In the present embodiment, the composition range of the ferrite composing the thermosensitive magnetic body 2 is determined so that use at around a temperature appropriate for treatment, specifically 42 to 43 ° C., is possible, and particularly 43 ° C. can be detected. ing.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, the non-invasive temperature measurement ferrite composition according to the present invention includes other components such as typical non-metallic elements such as B, C, S, Cl, As, Se, Br, Te, and I, Li, Na Al, K, Ca, Ga, Ge, Sr, Cd, In, Sn, Sb, Ba, Pb, Bi and other typical metals, Sc, Ti, V, Cr, Co, Y, Nb, Mo, Pd, Transition metal elements such as Ag, Hf, and Ta may be included.

  In addition, the temperature-sensitive magnetic body composed of the ferrite composition for noninvasive temperature measurement according to the present invention is desirably used in a powder form, but is not necessarily in a powder form, and is used in other forms. Also good. The temperature measurement using the thermosensitive magnetic material composed of the ferrite composition of the present invention is not limited to medical use, but can be applied to any field where the temperature of a separated substance is desired to be measured in a non-contact manner. Can do.

Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.
Examples 1-11

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

First, Fe ₂ O ₃ , ZnO, CuO, and Mg (OH) ₂ were prepared as main component materials. SiO ₂ was prepared as a raw material for the accessory component.

  Next, the raw material powder of the main component prepared was weighed, and further, the powder of the subcomponent raw material was weighed to the amount shown in Table 1, and then wet mixed with a ball mill for 5 hours to obtain a raw material mixture. .

  Next, the obtained raw material mixture was calcined in air at 950 ° C. for 2 hours to obtain a calcined material, and then wet pulverized with a ball mill for 20 hours to obtain a pulverized material having an average particle diameter of 1.5 μm. Obtained.

Next, this pulverized material was dried, and then granulated by adding 1.0% by weight of polyvinyl alcohol as a binder to 100% by weight of the pulverized material, and granulated with a 20 mesh sieve to obtain granules. This granule was pressure-molded at a pressure of 196 MPa ( ² ton / cm ² ) to obtain a molded body having a toroidal shape (size = outer diameter 22 mm × inner diameter 12 mm × height 6 mm).

  Next, each of these molded bodies was fired in air at 1000 to 1200 ° C. for 2.5 hours to obtain a toroidal core sample as a sintered body. The obtained sample was subjected to fluorescent X-ray analysis to measure the composition of the ferrite core. The results are shown in Table 1. Furthermore, the following characteristics evaluation was performed with respect to the sample.

<Magnetic flux density (B)>
The obtained toroidal core sample was wound with the primary winding and the secondary winding 5 times each, and the magnetic flux density (B) was measured at 100 A / m, 100 kHz, 40 ° C., 42 ° C., 43 ° C. and 44 ° C. . The measurement was performed using a BH analyzer (SY-8232 manufactured by Iwasaki Tsushinki Co., Ltd.). Further, in order to examine whether each sample has an inflection point of magnetic flux density with respect to temperature change at 43 ° C., α = (B at _{43 ° C.−} B at _{44 ° C.} ) / ((B at _{40 ° C.−} B at _{43 ° C.} ) / 3). The results are shown in Table 1 and FIGS. _{Incidentally, B at40 ℃, B at43 ℃} , B at44 ℃, is, 40 ° C., respectively, a magnetic flux density at 43 ° C. and 44 ° C..

  If α is 1.2 or more, preferably 1.5 or more, for example, as shown in Examples 1 to 3 shown in FIG. 2, it is determined that the magnetic flux density has an inflection point with respect to temperature change at 43 ° C. be able to. For this reason, a temperature-sensitive magnetic body composed of such a ferrite composition is injected into the body, and the change in the magnetic flux M2 is measured from outside the body, for example, by the detection coil 6 shown in FIG. It can be accurately detected that the temperature has reached 43 ° C.

From Table 1 and FIG. 2, when the content of Fe ₂ O ₃ is outside the scope of the present invention (Comparative Examples 1 and 2), the change value of the magnetic flux density at 43 to 44 ° C. is small, and α is 1 or less. It was confirmed that the inflection point of the magnetic flux density is substantially not present at 43 ° C. On the other hand, when the content of Fe ₂ O ₃ is within the range of the present invention (Examples 1 to 3), the magnetic flux density change value α at 43 to 44 ° C. is 1.6 or more, and 43 ° C. It was confirmed that it has an inflection point of magnetic flux density.

  From Table 1 and FIG. 3, when the content of ZnO is outside the scope of the present invention (Comparative Examples 3 and 4), the change value α of the magnetic flux density at 43 to 44 ° C. is small and 1 or less. Was confirmed to have substantially no inflection point of the magnetic flux density. On the other hand, when the content of ZnO is within the range of the present invention (Examples 2 and 4 to 7), the magnetic flux density change value α at 43 to 44 ° C. is 1.2 or more, and at 43 ° C. It was confirmed to have an inflection point of magnetic flux density.

  From Table 1 and FIG. 4, when the content of CuO is outside the range of the present invention (Comparative Examples 5 and 6), the change value α of the magnetic flux density at 43 to 44 ° C. is small and 1 or less, and is 43 ° C. Was confirmed to have substantially no inflection point of the magnetic flux density. On the other hand, when the content of CuO is within the range of the present invention (Examples 2, 8 and 9), the change value α of the magnetic flux density at 43 to 44 ° C. is 1.2 or more, and at 43 ° C. It was confirmed to have an inflection point of magnetic flux density.

From Table 1 and FIG. 5, when the content of SiO ₂ is outside the scope of the present invention (Comparative Examples 7 and 8), the change value of the magnetic flux density at 43 to 44 ° C. is small and 1 or less. Was confirmed to have substantially no inflection point of the magnetic flux density. On the other hand, when the content of SiO ₂ is within the range of the present invention (Examples 2, 10 and 11), the change value α of the magnetic flux density at 43 to 44 ° C. is 1.7 or more and 43 ° C. It was confirmed that it has an inflection point of magnetic flux density.

2 ... Temperature-sensitive magnetic body 4 ... Driving coil 6 ... Detection coil

Claims (1)

Iron oxide is 48.0 to 49.7 mol% in terms of Fe ₂ O ₃ , zinc oxide is 29.7 to 30.25 mol% in terms of ZnO, and copper oxide is 5.5 to 6.8 mol% in terms of CuO. , the balance has a main component composed of magnesium oxide, relative to the main component 100 wt%, as an auxiliary component, 30～350Ppm seen containing silicon oxide in terms of SiO _2,
At 100 A / m, 100 kHz,
The magnetic flux density measured at 40 ° _C. is _Bat 40 ° C.
The magnetic flux density measured at 43 ° _C is _Bat 43 ° C.
When the magnetic flux density measured at 44 ° _C. is _Bat 44 ° C. ,
A non-invasive temperature measurement ferrite characterized in that α _calculated by the equation: α = ( _{Bat43 ° C.} − _{Bat44 ° C.} ) / (( _{Bat40 ° C.} − _{Bat43 ° C.} ) / 3) is 1.2 or more Composition.

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