JP2012052072A - Thermoluminescent plate, thermoluminescent laminate, and method for manufacturing thermoluminescent plate and thermoluminescent laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoluminescent plate in which the light emission intensity distribution of thermoluminescent light is present in a visible light region not overlapping a peak of the light emission intensity due to heating, and which has a higher light emission intensity of thermoluminescence than the case where lithium triborate containing copper is used as a material; and to provide a method for manufacturing the same.SOLUTION: The thermoluminescent plate includes a thermoluminescent phosphor and an epoxy resin. The thermoluminescent phosphor includes lithium heptaborate as a parent body, and copper as a luminescence center present in the parent body, wherein the light emission intensity distribution in wavelength of thermoluminescence is only one and unimodal, and is present in the visible light region of shorter wavelengths than 600 nm.

Description

  The present invention relates to a thermoluminescent plate, a thermoluminescent laminate, and methods for producing them, which are used for obtaining a three-dimensional dose distribution of radiation.

  As is well known, in recent radiotherapy, for example, a hard X-ray, electron beam, or accelerated particle beam is irradiated as a three-dimensional conformation irradiation (3D) that appropriately sets the shape of radiation to be irradiated and the size of the dose. -CRT) and highly stereotactic radiation such as intensity-modulated radiation therapy (IMRT) are attracting attention (see Non-Patent Document 1, for example). In these treatment methods, for example, radiation planning is performed by setting various parameters such as the radiation irradiation position and range or output using a treatment planning apparatus. As a result, efforts are made to realize precise treatment, for example, avoiding important organs close to the lesion and irradiating only the lesion with radiation at a high dose. Therefore, in such radiotherapy, it is important to determine various parameters described above to suitable values. And high precision is calculated | required in management of the mechanical precision of irradiation apparatus itself, various filters with which an apparatus is provided, a line | wire width expander, etc.

  Therefore, in such radiotherapy, it is necessary to determine the above-mentioned various parameter values and verify the accuracy by measuring the dose of radiation used for the therapy. In particular, it is necessary to obtain a lot of empirical data regarding a three-dimensional dose distribution of radiation in the vicinity of a lesion to be irradiated with radiation.

  Here, as a dosimeter for measuring a three-dimensional dose distribution of radiation, that is, a three-dimensional dose distribution, a thermoluminescent laminate including a plurality of three-dimensional thermoluminescent plate-like bodies is well known ( For example, see Patent Document 1).

  According to Patent Document 1, the thermoluminescent plate-like body constituting the thermoluminescent laminate is a flat plate-like body, and a thermoluminescent substance, that is, lithium tetraborate or the like is used as a base, and the base is used as a light emission center. The material is formed from a thermoluminescent material to which manganese is added. And if a thermoluminescent laminated body comprised by this thermoluminescent plate-like body is irradiated with radiation, a three-dimensional dose distribution of radiation can be obtained.

  More specifically, after irradiating the thermoluminescent layered product with radiation, each thermoluminescent plate is heated after the thermoluminescent plates are separated. And the light intensity distribution of the thermofluorescence generated by this heating is acquired from each thermoluminescent plate. As is well known, there is a fixed correspondence between the light intensity of thermofluorescence and the exposure dose. Therefore, based on the acquired light intensity distribution information, the planar exposure dose distribution (hereinafter referred to as the radiation dose distribution along the surface irradiated with radiation) , Simply referred to as a dose distribution), that is, information on a two-dimensional dose distribution can be obtained. Then, if the obtained dose distribution information is restored as the dose distribution information of the radiation irradiated on the original thermoluminescent laminate, a three-dimensional, that is, three-dimensional dose distribution can be acquired.

  According to Patent Document 1, the thermoluminescent plate-like body constituting the thermoluminescent laminate is tissue equivalent to a biological tissue (eg, muscle tissue) constituting the human body, that is, the effective atomic number is adjusted to the same level. .

  Therefore, in the thermoluminescent layered product according to Patent Literature 1, when radiation is irradiated, actions such as a photoelectric action, a Compton effect, and an electron pair generation action occur to the same extent as a human body. Therefore, when such a thermoluminescent layered product is used as a dosimeter, it is possible to acquire data on the radiation exposure dose to the human body using the obtained measurement values without performing various corrections. .

  Here, in addition to the manganese-containing lithium tetraborate disclosed in Patent Document 1 described above, for example, the following thermoluminescent materials are well known as thermoluminescent materials that can be used as a material for the dosimeter. (For example, refer nonpatent literature 2, nonpatent literature 3, and nonpatent literature 4.).

That is, according to Non-Patent Document 2 and Non-Patent Document 3, it is disclosed that lithium triborate (LiB ₃ O ₅ ) containing copper is a thermoluminescent material exhibiting thermofluorescence.

Non-Patent Document 4 discloses that a thermoluminescent material can be obtained as a thermal reaction product of lithium tetraborate (Li ₂ B ₄ O ₇ ), boron oxide, and copper (II) oxide. And in this nonpatent literature 4, the thermoluminescent material which has various characteristics according to this mixing ratio is formed by changing the mixing ratio of these lithium tetraborate, boron oxide, and copper (II) oxide. It is disclosed.

  In order to create a dosimeter for measuring a three-dimensional dose distribution using the thermoluminescent material according to Non-Patent Document 2, Non-Patent Document 3, or Non-Patent Document 4 as a material, first, for example, Patent Document 2 The thermoluminescent material is molded into a flat plate-like body using a resin as a binder. And it is thought that a thermoluminescent laminated body can be produced by laminating | stacking this plate-like body similarly to the thermoluminescent plate-like body currently disclosed by patent document 1 mentioned above.

JP 2010-127930 A JP 61-269100 A

Journal of Japanese Society of Radiological Technology Vol.58 No.6 Dose verification in IMRT (Intensity Modulated Radiation Therapy) June 2002 p. 761 to 772 Zeynep Ozdemir Jemir, Gulhan Ozbayoglu, and Aysen Yilmaz, J. et al. Mater Sci (2007) 42: 8501-8508 CDPS-ICCD Card No. 32-549 V. W. Holovey, V.M. I. Lyamayev, A.R. M.M. Solomon, N.M. N. Birov, P.M. P. Puga, and V.A. T.A. Maslyuk, Neoganichesky Material (Inorganic Materials), 2006, Vol. 42, no. 11, pp 1384-1392: Inorganic Materials, 2006, Vol. 42, no. 11, pp1265-1272

  The thermoluminescent plate and thermoluminescent laminate composed of manganese-containing lithium tetraborate disclosed in Patent Document 1 have a thermoluminescent emission intensity distribution in the wavelength region of 550 to 750 nm.

  In general, when an object having thermoluminescent properties is heated to a high temperature state, the object itself emits light due to the heating as is well known. When this object is made of manganese-containing lithium tetraborate, the intensity distribution of light emission of the manganese-containing lithium tetraborate itself due to heating exists in the wavelength region where the bottom on the short wavelength side is near 600 nm. Therefore, the wavelength region of the emission intensity distribution resulting from heating partially overlaps the wavelength region of the emission intensity distribution due to thermofluorescence.

  The thermoluminescent plate and the thermoluminescent laminate according to Patent Document 1 need to be heated to a temperature at which light emission due to the heating described above can occur in order to generate thermofluorescence.

  Therefore, in order to accurately measure the light emission intensity due to thermofluorescence, it is necessary to separate light emission due to thermofluorescence and light emission due to heating using, for example, a near infrared cut filter.

  Further, the copper-containing lithium triborate according to Non-Patent Document 2 and Non-Patent Document 3 has a problem that the emission intensity of thermofluorescence is low.

  Further, in the thermoluminescent material according to Non-Patent Document 4, the emission intensity distribution of thermofluorescence related to the wavelength exists in the ultraviolet region.

  As already explained, in order to create a dosimeter for measuring a three-dimensional dose distribution using a thermoluminescent material according to Non-Patent Document 4, a thermoluminescent material is made into a plate using a resin as a binder. It is necessary to mold. In particular, in order to create a dosimeter equivalent to the human body, it is preferable to form a plate-like body using a resin having an effective atomic number equivalent to that of the human body, for example, an epoxy resin as a binder. More specifically, for use as a binder, for example, GM-9005 (trade name) of Brennie Giken is well known as an epoxy resin having a suitable effective atomic number similar to that of the human body.

  However, the epoxy resin used as such a binder has a property of absorbing ultraviolet light. Therefore, in the thermoluminescent material according to Non-Patent Document 4, when used as a material for a dosimeter for the purpose of measuring a three-dimensional dose distribution, thermofluorescence is absorbed by the resin, and as a result, the emission intensity of thermofluorescence is low. There is a problem of becoming.

  In Non-Patent Document 4, in addition to the above-described thermoluminescent material having a thermoluminescent emission intensity distribution in the ultraviolet region, a thermoluminescent material having a thermoluminescent emission intensity distribution in the wavelength region near 410 nm (hereinafter, Non-Patent Document 4 also referred to as a second thermoluminescent material).

  In the second thermoluminescent material according to Non-Patent Document 4, the emission intensity distribution of thermofluorescence according to temperature is in a low temperature portion, that is, in a temperature range of about 94 to 124 ° C, and in a high temperature portion, that is, in a temperature range of about 172 to 186 ° C. Exists in each.

  Here, the presence of a plurality of emission intensity distributions of thermofluorescence related to temperature means that there are a plurality of metastable states in which the thermofluorescent substance accumulates energy at different temperatures when irradiated with radiation. . In such a thermoluminescent material, when heating for observing thermofluorescence is performed, energy transfer occurs between the metastable states. As a result, the energy accumulated in the thermoluminescent material in a certain metastable state is involved in the emission intensity distribution of different thermofluorescence in a plurality of temperature regions. This complicates the relationship between the exposure dose and the emission intensity of thermofluorescence, and as a result, various corrections must be made when calculating the exposure dose from the measured emission intensity of thermofluorescence.

  In addition, when a thermofluorescent substance having a plurality of thermoluminescent emission intensity distributions related to such temperature is repeatedly used as a dosimeter, in order to release the energy accumulated by radiation irradiation in the previous measurement, Before performing the measurement, it is necessary to heat the thermoluminescent material to a temperature higher than at least the temperature range in which the emission intensity distribution of the thermofluorescence exists in the high temperature portion.

  However, the above-described epoxy resin, for example, GM-9005, does not have optical heat resistance at a temperature of 180 ° C. or higher. That is, GM-9005 changes color when heated to 180 ° C. or higher. Therefore, GM-9005 absorbs light emitted by thermofluorescence at a temperature of 180 ° C. or higher. Therefore, when creating a dosimeter for the purpose of measuring a three-dimensional dose distribution using the second thermoluminescent material according to Non-Patent Document 4, the thermoluminescence emission intensity distribution in the high temperature part is measured with sufficient emission intensity. There is a problem that can not be.

  Therefore, when a thermoluminescent plate or a thermoluminescent laminate is prepared using the thermoluminescent material according to Non-Patent Document 2, Non-Patent Document 3, or Non-Patent Document 4, in these thermoluminescent plates or thermoluminescent laminates, These are disadvantageous as dosimeters used for three-dimensional dose distribution measurement because of the above-mentioned problems relating to wavelength characteristics or temperature characteristics.

As a result of repeated research, the inventors of this application have found that a thermoluminescent material containing copper-containing lithium heptaborate (Li ₃ B ₇ O ₁₂ ) as a thermoluminescent material is in the visible region and shorter than 600 nm. It has been found that the emission intensity distribution of thermofluorescence is present in a wavelength region within the wavelength range, and that this emission intensity distribution exists in a temperature range of 130 ° C. or lower.

  In addition, by using lithium tetraborate, boron oxide, and copper (II) oxide as materials, adjusting the mixing ratio of these materials and the temperature at which the mixture formed by mixing these materials is heat-treated, It has been found that a thermophosphor containing lithium heptaborate can be formed.

  Then, it has been conceived that a thermoluminescent plate having a tissue equivalent to that of a human body can be produced by molding an epoxy resin as a binder in a thermoluminescent material containing this copper-containing lithium heptaborate as a thermoluminescent material.

  Furthermore, it was conceived that a thermoluminescent laminate capable of obtaining a three-dimensional dose distribution can be formed by laminating a plurality of the thermoluminescent plate-like bodies.

  The present invention has been made to solve the above-described conventional problems.

  Therefore, the first object of the present invention is that the emission intensity distribution of thermofluorescence is only present in the visible region that does not overlap with the emission intensity distribution resulting from the heating described above, is unimodal, and has the above-described copper-containing three. An object of the present invention is to provide a thermoluminescent plate and a method for producing the same, in which the emission intensity of thermofluorescence is higher than that of a lithium borate material.

  The second object of the present invention is to achieve the first object described above, and the emission intensity distribution of thermofluorescence does not collapse the shape of the thermoluminescent plate, and the optical heat resistance described above. It is to provide a thermoluminescent plate that is unique and exists in a single peak within a temperature range that does not change color, that is, no discoloration, and a method for producing the same.

  A third object of the present invention is to provide a thermoluminescent plate that achieves the first and second objects described above and is equivalent to a human body and a method for producing the same.

  The fourth object of the present invention is to provide a thermoluminescent laminate capable of measuring a three-dimensional dose distribution using the thermoluminescent plate according to the above first to third objects, and a method for manufacturing the same. It is to provide.

  Therefore, in order to achieve the above object, the thermoluminescent plate according to the present invention has the following characteristics.

  That is, the thermoluminescent plate according to the present invention includes a thermophosphor and an epoxy resin.

  The thermoluminescent material contains lithium heptaborate as the base material and copper as the emission center existing in the base material, and the emission intensity distribution with respect to the wavelength of the thermofluorescence is the only and single-peak type. And in the visible region with a wavelength shorter than 600 nm.

  Further, in the thermoluminescent plate according to the present invention, it is preferable that the emission intensity distribution with respect to the temperature of the thermoluminescent phosphor is unique and unimodal in the temperature range of 45 to 130 ° C.

  Moreover, the manufacturing method of the thermoluminescent plate according to the present invention includes the following first to fourth steps.

  That is, first, in the first step, a first mixture is formed by mixing lithium tetraborate, boron oxide, and copper (II) oxide.

  In this first step, lithium tetraborate and boron oxide are mixed at a molar ratio of lithium tetraborate: boron oxide = 3: 1.

  Next, in the second step, by heat-treating the first mixture, the first mixture is converted into a thermophosphor containing lithium heptaborate as a base and copper as a luminescent center present in the base. Change.

  Next, in the third step, a second mixture is formed by mixing thermophosphor, cellulose, silicon oxide, and epoxy resin.

  Next, in the fourth step, a thermoluminescent plate is formed by heat-treating the second mixture.

  Moreover, the manufacturing method of the thermoluminescent plate according to the present invention includes the following first to fourth steps.

  That is, first, in the first step, a first mixture is formed by mixing lithium tetraborate, boron oxide, and copper (II) oxide.

  In this first step, lithium tetraborate and boron oxide are mixed at a molar ratio of lithium tetraborate: boron oxide = 6: 1.

  Next, in the second step, by heat-treating the first mixture, the first mixture is converted into a thermophosphor containing lithium heptaborate as a base and copper as a luminescent center present in the base. Change.

  Next, in the third step, a second mixture is formed by mixing thermophosphor, cellulose, silicon oxide, and epoxy resin.

  Next, in the fourth step, a thermoluminescent plate is formed by heat-treating the second mixture.

  Moreover, the manufacturing method of the thermoluminescent plate according to the present invention includes the following first to fourth steps.

  That is, first, in the first step, a first mixture is formed by mixing lithium tetraborate, boron oxide, and copper (II) oxide.

  In this first step, lithium tetraborate and boron oxide are mixed at a molar ratio of lithium tetraborate: boron oxide = 2: 1.

  Next, in the second step, by heat-treating the first mixture, the first mixture is converted into a thermophosphor containing lithium heptaborate as a base and copper as a luminescent center present in the base. Change.

  Next, in the third step, a second mixture is formed by mixing thermophosphor, cellulose, silicon oxide, and epoxy resin.

  Next, in the fourth step, a thermoluminescent plate is formed by heat-treating the second mixture.

  In the method for producing a thermoluminescent plate according to the present invention, the effective atomic number and density of the thermoluminescent plate are adjusted by adjusting the weights of the thermophosphor, cellulose, silicon oxide, and epoxy resin. Is preferred.

  The thermoluminescent laminate according to the present invention has the following characteristics.

  That is, the thermoluminescent laminate according to the present invention is formed by laminating a plurality of the above-described thermoluminescent plate-like bodies.

  Moreover, the manufacturing method of the thermoluminescent laminated body by this invention includes the following 1st processes and 2nd processes.

  That is, first, in the first step, a plurality of thermoluminescent plate-like bodies manufactured by the above-described method for manufacturing a thermoluminescent plate-like body are prepared.

  Next, in the second step, a thermoluminescent laminate is formed by laminating the plurality of thermoluminescent plates.

  In the thermoluminescent plate and the thermoluminescent laminate according to the present invention, the emission intensity distribution with respect to the thermofluorescence wavelength of the thermophosphor is unique and unimodal, and exists in the visible region with a wavelength shorter than 600 nm. Therefore, it is not necessary to consider the light emission caused by the heating described above during the measurement of thermofluorescence, and therefore, for example, it is not necessary to use a near infrared cut filter.

  In addition, when the emission intensity distribution of the thermoluminescent material with respect to the temperature of the thermofluorescence is unique and unimodal in the temperature range of 45 to 130 ° C., the emission intensity distribution of the thermofluorescence is the thermoluminescent plate-like body and the thermoluminescent material. The epoxy resin contained in the laminate is in a temperature range that can be mechanically heat-resistant, i.e., the shape is not collapsed, and optically heat-resistant, i.e., is not discolored.

  Therefore, in the thermoluminescent plate and the thermoluminescent laminate according to the present invention, it is possible to measure thermofluorescence without collapsing the shape and measuring the thermofluorescence without being absorbed by the epoxy resin. it can.

  In addition, since the emission intensity distribution of thermofluorescence is unique and unimodal, the relationship between the exposure dose and the emission intensity of thermofluorescence is simple compared to thermophosphors that have multiple emission intensity distributions of thermofluorescence. Become. As a result, it is not necessary to perform complicated correction when calculating the exposure dose from the measured thermoluminescence emission intensity.

  Further, in the thermoluminescent material constituting the thermoluminescent plate and the thermoluminescent laminate according to the present invention, lithium tetraborate and lithium triborate are used as the base material by forming the thermoluminescent material using lithium heptaborate as the base material. As compared with the case where it does, thermoluminescence is shown with high luminescence intensity.

  In addition, in the method for manufacturing the thermoluminescent plate and the thermoluminescent laminate according to the present invention, in forming the thermophosphors constituting the thermoluminescent plate and the thermoluminescent laminate, as described above, Lithium borate and boron oxide are mixed in a molar ratio of either lithium tetraborate: boron oxide = 3: 1, 6: 1, or 2: 1.

  As a result, the formed thermophosphor can contain lithium heptaborate as a base material.

  Furthermore, in the manufacturing method of the thermoluminescent plate and the thermoluminescent laminate according to the present invention, by adjusting the weights of the thermoluminescent material, cellulose, silicon oxide, and epoxy resin, the tissue is equivalent to the human body, that is, effective. A thermoluminescent plate and a thermoluminescent laminate having the same atomic number can be produced (suitable weights of thermophosphor, cellulose, silicon oxide, and epoxy resin will be described later).

  Therefore, in the manufacturing method of the thermoluminescent plate and the thermoluminescent laminate according to the present invention, it is possible to measure the three-dimensional dose distribution using the thermoluminescent plate equivalent to the human body and the thermoluminescent plate. A thermoluminescent laminate can be manufactured as a simple dosimeter.

It is a flowchart which shows the manufacturing method of the thermoluminescent plate-like body by 1st Embodiment. It is process drawing explaining the manufacturing method of the thermoluminescent plate-like body by this 1st Embodiment. (A) And (B) is a figure which compares the emitted light intensity of the thermofluorescence in the thermoluminescent material by 1st Embodiment. (A) And (B) is a figure for pinpointing the substance which comprises the thermoluminescent substance by 1st Embodiment. (A) And (B) is a figure for pinpointing the substance which comprises the thermoluminescent substance by 1st Embodiment. (A) And (B) is a figure for pinpointing the substance which comprises the thermoluminescent substance by 1st Embodiment. (A) And (B) is a figure for pinpointing the substance which comprises the thermoluminescent substance by 1st Embodiment. It is a figure for pinpointing the substance which comprises the thermoluminescent material by 1st Embodiment. It is a figure for pinpointing the substance which comprises the thermoluminescent material by 1st Embodiment. It is a figure for pinpointing the substance which comprises the thermoluminescent material by 1st Embodiment. It is a figure for pinpointing the substance which comprises the thermoluminescent material by 1st Embodiment. It is a figure for pinpointing the substance which comprises the thermoluminescent material by 1st Embodiment. (A) And (B) is a figure which compares the emitted light intensity of the thermofluorescence in the thermoluminescent material by 1st Embodiment. It is a figure which shows the temperature characteristic of the thermoluminescent material by 1st Embodiment. (A) And (B) is a figure which compares the wavelength characteristic and temperature characteristic of the thermoluminescent material by 1st Embodiment, and the thermoluminescent material by a prior art. It is a figure which shows the relationship between the emitted light intensity of a thermofluorescence, and the exposure dose in the thermoluminescent material by 1st Embodiment. (A) And (B) is process drawing explaining the manufacturing method of the thermoluminescent laminated body by 2nd Embodiment. (A) And (B) is a process figure explaining the measuring method of three-dimensional dose distribution using the thermoluminescent laminated body by 2nd Embodiment. (A) shows the distance from the irradiation center position in the plane orthogonal to the X-ray irradiation direction and the emission intensity at each distance in the dose measurement using the thermoluminescent layered product according to the second embodiment. It is a figure which shows the relationship. (B) is a figure which shows the relationship between the separation distance from the irradiation center position in the surface orthogonal to the X-ray irradiation direction and the ionization degree at each distance in the dose measurement using the ionization chamber. (A) is a figure which shows the relationship between the distance along the irradiation direction of X-ray | X_line, and the emitted light intensity in each distance in the dose measurement using the thermoluminescent laminated body by 2nd Embodiment. (B) is a diagram showing the relationship between the distance along the X-ray irradiation direction and the degree of ionization at each distance in dose measurement using an ionization chamber. The distance from the irradiated surface along the X-ray irradiation direction when X-rays are irradiated from the surface of the thermoluminescent laminate according to the second embodiment and when X-rays are irradiated from the side surfaces, It is a figure which shows the relationship with the emitted light intensity in each distance.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 2, 17, and 18 only schematically show the shape, size, and arrangement relationship of each component to the extent that the present invention can be understood. The embodiment described below is merely a preferred example, and therefore the configuration of the present invention is not limited to the illustrated configuration example described below, and departs from the scope of the present invention. Obviously, many variations and modifications may be made without doing so.

<First Embodiment>
In the first embodiment, a thermoluminescent plate configured to include a thermoluminescent material and an epoxy resin and a manufacturing method thereof will be described.

  The method for manufacturing a thermoluminescent plate according to the first embodiment includes the first to fourth steps. Hereinafter, with reference to FIG.1 and FIG.2, it demonstrates per process in order from a 1st process.

  FIG. 1 is a diagram for explaining a first embodiment of the present invention, and is a flowchart of a method for manufacturing a thermoluminescent plate according to the first embodiment.

  FIG. 2 is a process diagram for explaining the method for manufacturing a thermoluminescent plate according to the first embodiment, and is obtained in the fourth step of the method for manufacturing a thermoluminescent plate according to the first embodiment. The resulting structure is shown in schematic perspective view.

First, in the first step, a first mixture is formed by grinding and mixing lithium tetraborate (Li ₂ B ₄ O ₅ ), boron oxide (B ₂ O ₃ ), and copper (II) oxide (CuO). (See S1 shown in FIG. 1).

  In the first embodiment, lithium heptaborate, which is the base of the thermophosphor to be formed, is formed from lithium tetraborate and boron oxide among the materials of the first mixture described above.

  And, using lithium tetraborate and boron oxide as materials, lithium heptaborate is obtained in good yield, that is, the content of impurities other than lithium heptaborate formed from lithium tetraborate and boron oxide is suppressed. To form, these lithium tetraborate and boron oxide are preferably mixed in a molar ratio of, for example, lithium tetraborate: boron oxide = 3: 1, 6: 1, or 2: 1. More preferably, by mixing lithium tetraborate and boron oxide at a molar ratio of lithium tetraborate: boron oxide = 3: 1, a better yield than when mixed at other molar ratios. Can form lithium heptaborate.

  Table 1 shows the amount of lithium tetraborate and boron oxide added in each preferred example of the molar ratio of lithium tetraborate to boron oxide. In Table 1, suitable examples of the addition amount of copper oxide (II) in each molar ratio, which will be described later, the effective atomic number when the thermoluminescent material is manufactured at each molar ratio, and the thermoluminescent plate shape to be manufactured The effective atomic number of the body is also shown side by side.

  In order to mix at a molar ratio of lithium tetraborate: boron oxide = 3: 1, it is preferable to mix, for example, 507.3 g of lithium tetraborate and 69.6 g of boron oxide.

  In order to mix lithium tetraborate: boron oxide in a molar ratio of 6: 1, it is preferable to mix 1014.6 g of lithium tetraborate and 69.6 g of boron oxide, for example.

  Further, in order to mix in a molar ratio of lithium tetraborate: boron oxide = 2: 1, it is preferable to mix, for example, 338.2 g of lithium tetraborate and 69.6 g of boron oxide.

  Further, copper contained in the copper oxide (II) acts as a light emission center existing in the base material in the manufactured thermophosphor.

  Here, the thermoluminescent emission intensity of the thermophosphor to be formed in the subsequent second step changes depending on the amount of copper (II) oxide mixed in the first step.

  Therefore, in order to increase the emission intensity of thermofluorescence, the copper (II) oxide is added to the first mixture (that is, a mixture of this copper (II) oxide, lithium tetraborate, and boron oxide), for example, 0. It is preferable to mix so that it may become a ratio in the range of 10-0.35 wt%.

  Thus, to add 507.3 g lithium tetraborate and 69.6 g boron oxide as described above to form the first mixture, copper (II) oxide is added, for example, 0.58-2. It is preferable to mix with a mass in the range of 0.02 g.

  Moreover, when adding 1014.6 g of lithium tetraborate and 69.6 g of boron oxide, it is preferable to mix copper (II) with the mass within the range of 1.08 to 3.79 g, for example.

  Moreover, when adding 338.2 g of lithium tetraborate and 69.6 g of boron oxide, it is preferable to mix copper (II) oxide with the mass within the range of 0.41-1.42 g, for example.

  Next, in the second step, lithium heptaborate is formed from lithium tetraborate and boron oxide contained in the first mixture by heat-treating the first mixture obtained in the first step. To do. As a result, the first mixture is changed to a thermophosphor containing lithium heptaborate as the base and copper as the emission center present in the base (see S2 shown in FIG. 1).

  The temperature of this heat treatment may be a temperature at which lithium heptaborate is generated from this first mixture, for example, a temperature within the range of 800 to 850 ° C., more preferably at a temperature of 850 ° C. for about 6 hours. It is preferable to perform a heat treatment. The lithium heptaborate obtained here contains copper as the emission center.

  As a result, a powdery thermoluminescent material containing lithium heptaborate as a base formed from lithium tetraborate and boron oxide, and copper as a luminescent center present in the base, derived from copper (II) oxide That is, a thermophosphor can be obtained.

  In addition, the copper that is the emission center may be contained not only as a single copper, but also in the form of an oxide or a compound with other substances contained in the thermoluminescent material. .

In order to use the thus obtained thermophosphor as a material for a dosimeter for obtaining data on radiation dose to the human body, the effective atomic number Z _eff of the thermophosphor is the effective atomic number of the human body. It is preferable to be adjusted to an approximate value.

  In general, the effective atomic number of the muscular tissue of the human body is about 7.42 (see, for example, “Medical Sciences, Rev. Radiation Metrology, Japanese Society of Radiological Technology P.136 (File No. 1-2)”). Therefore, in consideration of the calculation method of the effective atomic number and the variation at the time of determination, the thermoluminescent plate according to the first embodiment has a value within the range of the effective atomic number of about 7.3 to 7.6. Or a value in the vicinity thereof is preferably adjusted.

  Hereinafter, this point will be described more specifically.

  That is, in the first embodiment, in the first step described above, 507.3 g of lithium tetraborate, 69.6 g of boron oxide, and 0.10 wt% copper oxide ( When II) is mixed to form the first mixture, a thermophosphor having an effective atomic number adjusted to about 7.32 is obtained.

  In the first step described above, 507.3 g of lithium tetraborate, 69.6 g of boron oxide, and 0.35 wt% of copper (II) oxide are mixed with the first mixture to perform the first mixing. When the body is formed, a thermophosphor having an effective atomic number adjusted to about 7.59 is obtained.

  Therefore, the thermophosphor formed in the second step is oxidized at a ratio of 0.10 wt% with respect to the first mixture formed in the molar ratio of lithium tetraborate: boron oxide = 3: 1 in the first step. When copper (II) is mixed and when copper (II) oxide is mixed at a ratio of 0.35 wt% with respect to the first mixture, the effective atomic number is desired as a value approximate to the human body 7.3 It falls within the range of ˜7.6.

  In addition, as shown in Table 1, in the first step described above, 1014.6 g of lithium tetraborate, 69.6 g of boron oxide, and 0.10 wt% of copper (II) oxide with respect to the first mixture. To form a first mixture, a thermoluminescent material having an effective atomic number adjusted to about 7.32 is obtained.

  In the first step described above, 1014.6 g of lithium tetraborate, 69.6 g of boron oxide, and 0.35 wt% of copper (II) oxide are mixed with the first mixture to perform the first mixing. When the body is formed, a thermophosphor having an effective atomic number adjusted to about 7.59 is obtained.

  Further, in the first step described above, 338.2 g of lithium tetraborate, 69.6 g of boron oxide, and 0.10 wt% of copper (II) oxide are mixed with the first mixture. When the body is formed, a thermophosphor having an effective atomic number adjusted to about 7.33 is obtained.

  In the first step described above, 338.2 g of lithium tetraborate, 69.6 g of boron oxide, and 0.35 wt% of copper (II) oxide are mixed with the first mixture for the first mixing. When the body is formed, a thermophosphor having an effective atomic number adjusted to about 7.60 is obtained.

The effective atomic number Z _eff of the thermoluminescent material is described in, for example, “Satoshi Fukuda, Masayuki Maekawa, Radiation Physics Exercise (2nd edition) P63-64, Toyo Shoten, 2005”, etc. It can be calculated from (1).

Z _eff = (a ₁ Z ₁ ^2.94 + a ₂ Z ₂ ^2.94 + a ₃ Z ₃ ^2.94 + ...) ^{1 / 2.94} = (ΣaiZi ^2.94 ) ^{1 / 2.94} (1 )
In the formula (1), a ₁ , a ₂ , a ₃ ,... Represent the ratio of the electrons belonging to the atomic numbers Z ₁ , Z ₂ , Z ₃ ,. Show.

  Next, in the third step, the second mixture is formed by mixing the powdered thermophosphor obtained in the second step, cellulose, silicon oxide, and epoxy resin (shown in FIG. 1). (See S3).

  The epoxy resin functions as a binder for maintaining the shape of the thermoluminescent plate as a flat plate in the thermoluminescent plate produced in this embodiment.

  In order to adjust the effective atomic number of the thermoluminescent plate to be manufactured to a value approximate to that of the human body, it is preferable to use, for example, Brennie Giken GM-9005 (trade name) as an epoxy resin.

  Cellulose and silicon oxide are added to adjust the effective atomic number of the thermoluminescent plate to be produced to a value approximate to that of the human body.

  And in order to adjust the effective atomic number of the thermoluminescent plate to be manufactured to a value approximate to that of the human body, the weights of the thermophosphor, cellulose, silicon oxide, and epoxy resin constituting the second mixture are, for example, as follows: It is preferable to adjust as follows.

  That is, it is preferable to adjust the thermophosphor to 13.2 g, cellulose to 1.3 g, silicon oxide to 0.6 g, and epoxy resin to 3.2 g to form the second mixture.

And as a thermoluminescent substance, in the 1st process mentioned above, lithium tetraborate and boron oxide are mixed by lithium tetraborate: boron oxide = 3: 1, and 0.10 wt% oxidation is carried out with respect to a mixture. When a thermophosphor formed from a mixture obtained by mixing copper (II) is used, the empirical formula constituting the second mixture and the thermoluminescent plate formed from the second mixture is C _3.10 H _3.46 O _6.08 Li _1.35 Si _0.10 B ^3.16 Cu _0.0015 , and the effective atomic number of the entire thermoluminescent plate is 7 as shown in the above formula (1). .25 (see Table 1).

  Therefore, the effective atomic number of the thermoluminescent plate produced at this time is a value in the vicinity of the range of 7.3 to 7.5 desired as a value approximate to the human body.

  Further, as shown in Table 1, as the thermoluminescent material, in the first step described above, lithium tetraborate and boron oxide were mixed at a ratio of lithium tetraborate: boron oxide = 3: 1, and the mixture was When using a thermophosphor formed from a mixture obtained by mixing 0.35 wt% copper oxide (II), the effective atomic number of the entire thermoluminescent plate to be manufactured is 7.40. Further, as the thermophosphor, in the first step described above, lithium tetraborate and boron oxide are mixed at a ratio of lithium tetraborate: boron oxide = 6: 1, and 0.01 wt% oxidation with respect to the mixture. When a thermophosphor formed from a mixture obtained by mixing copper (II) is used, the effective atomic number of the entire thermoluminescent plate to be manufactured is 7.24. Further, as the thermophosphor, in the first step described above, lithium tetraborate and boron oxide are mixed at a lithium tetraborate: boron oxide = 6: 1, and 0.35 wt% oxidation with respect to the mixture. When a thermophosphor formed from a mixture obtained by mixing copper (II) is used, the effective atomic number of the entire thermoluminescent plate to be manufactured is 7.38. Further, as the thermophosphor, in the first step described above, lithium tetraborate and boron oxide are mixed at a ratio of lithium tetraborate: boron oxide = 2: 1, and 0.01 wt% of the mixture is oxidized. When a thermophosphor formed from a mixture obtained by mixing copper (II) is used, the effective atomic number of the entire thermoluminescent plate to be manufactured is 7.25. Further, as the thermophosphor, in the first step described above, lithium tetraborate and boron oxide are mixed at a ratio of lithium tetraborate: boron oxide = 2: 1, and 0.35 wt% of oxidation is performed on the mixture. When a thermoluminescent material formed from a mixture obtained by mixing copper (II) is used, the effective atomic number of the entire thermoluminescent plate to be manufactured is 7.39.

  In the first embodiment, the thermoluminescent plate to be manufactured is manufactured by mixing the thermophosphor, cellulose, silicon oxide, and epoxy resin with the respective weights described above to form the second mixture. In addition to the effective atomic number, the density can be adjusted to a value approximate to that of the human body.

That is, for example, in the first step described above, lithium tetraborate and boron oxide are mixed at a ratio of lithium tetraborate: boron oxide = 3: 1, and 0.10 wt% copper oxide (II In the case of using a thermophosphor formed from a mixture obtained by mixing the thermophosphor, cellulose, silicon oxide, and epoxy resin, the weights described above (that is, thermophosphor: 13.2 g, cellulose: 1.3 g, silicon oxide: 0.6 g, and epoxy resin: 3.2 g), the density of the thermoluminescent plate to be manufactured can be adjusted to 1 g / cm ³ . As is well known, since the density of the muscle tissue of the human body is about 1 gcm ⁻³ , the thermoluminescent plate manufactured in this embodiment is adjusted not only to the effective atomic number but also to the density approximate to the human body. Can do.

  Next, in the fourth step, the thermoluminescent plate 105 is formed by heat-treating the second mixture (see S4 shown in FIGS. 2 and 1).

  This heat treatment is performed for the purpose of changing to the thermoluminescent plate 105 by solidifying the second mixture. Therefore, this heat treatment is preferably performed at a temperature of about 80 ° C. for about 24 hours.

  Further, after that, in order to dry and solidify the thermoluminescent plate 105 more reliably, it is preferable to additionally perform a heat treatment at a temperature of about 130 ° C. for about 30 minutes.

  Moreover, when performing heat processing, before performing this 4th process, it is preferable to press-mold the 2nd mixture beforehand in arbitrary shapes according to the specification use of the thermoluminescent plate-like body 105, for example, flat form. More specifically, as an example, it is preferable that the thickness is about 2.5 mm and the planar shape of the surface orthogonal to the thickness direction is formed into a substantially square shape with a side of about 85 mm.

  When such a thermoluminescent plate 105 is irradiated with radiation, the irradiated portion, that is, the exposed portion of the thermoluminescent phosphor generates fluorescence. The light intensity of the thermofluorescence has a certain relationship with the exposure dose at the exposure site, as already described in the background art section. Therefore, if the thermoluminescent plate 105 is irradiated with radiation and the light intensity distribution of the thermofluorescence along the exposed surface, that is, the irradiated surface is measured, the irradiated light corresponding to the two-dimensional light intensity distribution is measured. An in-plane two-dimensional dose distribution can be measured.

  In addition, it is assumed that the thermoluminescent plate 105 according to the first embodiment is used as a thermoluminescent laminate by laminating a plurality of sheets to obtain a three-dimensional dose distribution of radiation. Yes. Therefore, the thermoluminescent plate 105 according to the first embodiment is laminated in a plurality of layers and, when irradiated with radiation, in order to obtain a detailed three-dimensional dose distribution by the irradiation, the thermoluminescent plate It is preferable to appropriately set the laminated surface, that is, the planar shape and thickness of the front surface 105a and the back surface 105b of the thermoluminescent plate 105 according to, for example, the quality of radiation to be measured, linearity, or application.

  Here, the inventors, regarding the molar ratio of lithium tetraborate and boron oxide when forming the mixture in the first step described above, and the temperature when heat-treating the mixture in the second step described above, Experiments were conducted to confirm their preferred values.

  In this experiment, the mixture in the first step is a plurality of thermophosphors manufactured with different molar ratios of lithium tetraborate and boron oxide, or the heat treatment in the second step is performed at different temperatures. A plurality of formed thermophosphors were prepared as samples.

  Table 2 shows the preparation conditions for each sample.

  Samples a1, a2, a3, a4, a5, and a6 were prepared by performing heat treatment on the mixture at a temperature of 700 ° C. in the second step.

  Samples b1, b2, b3, b4, b5, and b6 were prepared by performing heat treatment on the mixture at a temperature of 750 ° C. in the second step.

  Samples c1, c2, c3, c4, c5, and c6 were prepared by performing heat treatment on the mixture at a temperature of 800 ° C. in the second step.

  Samples d1, d2, d3, and d4 were prepared by performing heat treatment on the mixture at a temperature of 850 ° C. in the second step.

  Samples e1 and e2 were prepared by performing heat treatment on the mixture at a temperature of 900 ° C. in the second step.

  Samples a1, b1, c1, d1, and e1 were prepared by adding only boron tetraborate and copper (II) oxide to form a mixture without adding boron oxide in the first step.

  Samples a2, b2, c2, d2, and e2 were prepared by mixing lithium tetraborate and boron oxide at a molar ratio of lithium tetraborate: boron oxide = 6: 1 in the first step.

  Samples a3, b3, c3, and d3 were prepared by mixing lithium tetraborate and boron oxide at a molar ratio of lithium tetraborate: boron oxide = 3: 1 in the first step.

  Samples a4, b4, c4, and d4 were prepared by mixing lithium tetraborate and boron oxide at a molar ratio of lithium tetraborate: boron oxide = 2: 1 in the first step.

  Samples a5, b5, and c5 were prepared by mixing lithium tetraborate and boron oxide at a molar ratio of lithium tetraborate: boron oxide = 1: 1 in the first step.

  Samples a6, b6, and c6 were prepared by mixing lithium tetraborate and boron oxide at a molar ratio of lithium tetraborate: boron oxide = 1: 2 in the first step.

  In the first step, lithium tetraborate and boron oxide are mixed at a molar ratio of lithium tetraborate: boron oxide = 3: 1, and the mixture is heat treated at 900 ° C. in the second step. The prepared sample, lithium tetraborate and boron oxide were mixed at a molar ratio of lithium tetraborate: boron oxide = 2: 1 in the first step, and heat treatment at 900 ° C. was performed on the mixture in the second step. A sample prepared by mixing lithium tetraborate and boron oxide in a molar ratio of lithium tetraborate: boron oxide = 1: 1 in the first step, and 850 ° C. with respect to the mixture in the second step Sample prepared by heat treatment, lithium tetraborate and boron oxide were mixed at a molar ratio of lithium tetraborate: boron oxide = 1: 1 in the first step, and 9% to the mixture in the second step. Sample prepared by heat treatment at 0 ° C., lithium tetraborate and boron oxide were mixed at a molar ratio of lithium tetraborate: boron oxide = 1: 2 in the first step, and the mixture was mixed in the second step A sample prepared by performing a heat treatment at 850 ° C., and lithium tetraborate and boron oxide in a first step were mixed at a molar ratio of lithium tetraborate: boron oxide = 1: 2, and in the second step Regarding samples prepared by performing heat treatment at 900 ° C. on the mixture, it was confirmed that these samples could not be obtained as thermophosphors because the product was melted in the heat treatment in the second step. The other samples did not melt.

  Then, each sample was irradiated with 1 Gy of X-rays using an irradiation apparatus having an X-ray tube voltage of 6 MV, and then stored in a dark box and exposure of the CCD camera was started. Each luminescence intensity was observed for 280 seconds while the temperature was maintained at 135 ° C. while being heated to 150 ° C. A SYNERGY linac manufactured by Electa was used as the X-ray irradiation apparatus.

  In this experiment, the prepared samples are placed side by side on a single metal plate (for example, made of aluminum), and the above-described X-ray irradiation, heating, and observation of thermofluorescence are performed under the same conditions for each sample. (At once). Each sample was prepared by mixing copper (II) oxide at a ratio of 0.35 wt% with respect to the mixture in the first step.

  Hereinafter, the results of this experiment will be described.

  3A and 3B are diagrams showing the results of this experiment.

  FIG. 3A is an image obtained by photographing the state of light emission by thermofluorescence of each sample described above. A cooled CCD camera (ATK-314L manufactured by ATIK Instruments) was used to capture these images.

  In addition, each light emission which attached | subjected each code | symbol of a1-a6, b1-b6, c1-c6, d1-d4, e1, and e2 to FIG. 3 (A) is each sample a1-a6, b1 mentioned above. ˜b6, c1 to c6, d1 to d4, e1, and e2 respectively. That is, in performing this experiment, the arrangement relationship of the samples placed on the metal plate is as shown in Table 2 and corresponds to the arrangement of the symbols shown in FIG.

  FIG. 3B is a diagram for comparing the emission intensity of each sample by thermofluorescence. In FIG. 3B, the vertical axis indicates the relative value of the emission intensity, and the horizontal axis indicates FIG. This corresponds to the distance in the arrangement direction of each sample indicated by a reference numeral (A). That is, the intensity distribution line 11 shown in FIG. 3B is an intensity distribution related to the emission intensity of the samples a1 to a6, the intensity distribution line 13 is an intensity distribution related to the emission intensity of the samples b1 to b6, and the intensity distribution line 15 is The intensity distribution related to the emission intensity of the samples c1 to c6, the intensity distribution line 17 represents the intensity distribution related to the emission intensity of the samples d1 to d4, and the intensity distribution line 19 represents the intensity distribution related to the emission intensity of the samples e1 and e2. Show. Note that these emission intensities are obtained by analyzing the image of thermofluorescence captured using the above-described cooled CCD camera (ATK-314L manufactured by ATIK Instruments) using ImageJ (registered trademark), which is a well-known image software. Obtained.

  As is apparent from the results of FIG. 3A, it can be confirmed that the samples c2, c3, c4, d2, d3, and d4 emit light with significantly higher emission intensity than the other samples.

  Further, as is apparent from each intensity distribution line in FIG. 3B, the peak 10 indicating the emission intensity of the sample c2, the peak 12 indicating the emission intensity of the sample c3, the peak 14 indicating the emission intensity of the sample c4, and the sample d2 The peak 16 indicating the light emission intensity, the peak 18 indicating the light emission intensity of the sample d3, and the peak 20 indicating the light emission intensity of the sample d4 show higher light emission intensity than the other samples. From FIG. 3B, it can be confirmed that the peak of the emission intensity of the sample d3 in particular shows the highest emission intensity.

  From this result, in the first embodiment, in the first step, lithium tetraborate and boron oxide are converted into a tetraborate: boron oxide = 3: 1, 6: 1, or 2: 1 mole. It was confirmed that the emission intensity of thermofluorescence of the thermophosphor to be formed can be increased by mixing at a ratio and performing heat treatment at an arbitrary temperature within the range of 800 to 850 ° C. in the second step.

  In particular, in the first embodiment, lithium tetraborate and boron oxide are mixed in a molar ratio of lithium tetraborate: boron oxide = 3: 1 in the first step, and a temperature of 850 ° C. in the second step. It was confirmed that the heat intensity of the thermofluorescence of the formed thermophosphor becomes the highest by performing the heat treatment at.

  Next, the inventor made these thermophosphors for the samples a1, b5, c2, c3, c4, d2, d3, d4, and e2 prepared in the experiment shown in FIGS. 3 (A) and (B). An experiment was conducted to confirm what kind of substance is composed of.

  In this experiment, XRD (X-ray diffraction: X-ray diffraction) measurement was performed on these samples a1, b5, c2, c3, c4, d2, d3, d4, and e2, and each of these heats was obtained from the obtained spectrum. Substances contained in the phosphor were identified. The X-ray diffractometer used is a RINT2000 type manufactured by RIGAKU.

  FIGS. 4A and 4B are diagrams for specifying a substance constituting the thermophosphor of the sample d3 described above.

  FIG. 4A shows an XRD spectrum of the sample d3. 4B is disclosed in, for example, “J. Aidong, L. Shilong, H. Qingzhen, C. Tianbin, and Acta Crystallogr., Sec. C, .46, 1999 (1990)”. It is a figure which shows the XRD spectrum of lithium borate. In each figure, the vertical axis indicates the relative value of the diffraction intensity, and the horizontal axis indicates the diffraction angle in degrees.

  As is clear from FIGS. 4A and 4B, it can be seen that the diffraction angle at which the peak exists in each XRD spectrum and the relative diffraction intensity of each peak are experimentally consistent.

  From this result, it was confirmed that the sample d3 was a thermophosphor containing lithium heptaborate as a main constituent.

  FIGS. 5A and 5B are diagrams for specifying a substance constituting the thermophosphor of the sample a1 described above.

  FIG. 5A shows an XRD spectrum of sample a1. 5B is a diagram showing an XRD spectrum of lithium tetraborate disclosed in, for example, “JCPDS-ICDD Card No. 18-717”. In each of these figures, the vertical axis indicates the relative value of the diffraction intensity, and the horizontal axis indicates the diffraction angle in degrees.

  As is apparent from FIGS. 5A and 5B, it can be seen that the diffraction angle at which a peak exists in each XRD spectrum and the relative diffraction intensity of each peak are experimentally consistent.

  From this result, it was confirmed that the sample a1 was a thermophosphor containing lithium tetraborate as a main constituent.

  FIGS. 6A and 6B are diagrams for specifying a substance constituting the thermoluminescent material of the sample e2 described above.

  FIG. 6A is a diagram showing an XRD spectrum of the sample e2. FIG. 6B is an XRD spectrum of the same lithium tetraborate as FIG. 5B described above. In each figure, the vertical axis indicates the relative value of the diffraction intensity, and the horizontal axis indicates the diffraction angle in degrees.

  As is clear from FIGS. 6A and 6B, it can be seen that the diffraction angle at which a peak exists in each XRD spectrum and the relative diffraction intensity of each peak are experimentally consistent.

  From this result, it was confirmed that the sample e2 was a thermophosphor containing lithium tetraborate as a main constituent.

  FIGS. 7A and 7B are diagrams for specifying a substance constituting the thermoluminescent material of the sample b5 described above.

  FIG. 7A is a diagram showing an XRD spectrum of sample b5. FIG. 7B is a diagram showing an XRD spectrum of lithium triborate disclosed in, for example, “JCPDS-ICDD Card No. 32-549”. In each figure, the vertical axis indicates the relative value of the diffraction intensity, and the horizontal axis indicates the diffraction angle in degrees.

  As is clear from FIGS. 7A and 7B, it can be seen that the diffraction angle at which a peak exists in each XRD spectrum and the relative diffraction intensity of each peak are experimentally consistent.

  From this result, it was confirmed that the sample b5 was a thermophosphor containing lithium triborate as a main constituent.

  8 shows the XRD spectrum of sample c2, FIG. 9 shows the XRD spectrum of sample c3, FIG. 10 shows the XRD spectrum of sample c4, FIG. 11 shows the XRD spectrum of sample d2, and FIG. 12 shows the XRD spectrum of sample d4. It is a figure which shows an XRD spectrum, respectively. In these figures, the vertical axis indicates the relative value of the diffraction intensity, and the horizontal axis indicates the diffraction angle in degrees.

  8, 9, 10, 11, and 12, the XRD spectrum of the lithium heptaborate shown in FIG. 4B described above, and the lithium tetraborate shown in FIG. 5B. Based on the XRD spectrum and the XRD spectrum of lithium triborate shown in FIG. 7 (B), the lithium heptaborate peak is indicated by ◯, the lithium tetraborate peak is indicated by x, and the lithium triborate Each peak is marked with Δ.

  From FIG. 8, FIG. 9, FIG. 10, FIG. 11 and FIG. 12, in each of the XRD spectra of the samples c2, c3, c4, d2, and d4, the peaks of lithium heptaborate and lithium tetraborate The diffraction intensity is higher than the peak of lithium borate.

  Therefore, samples c2, c3, c4, d2, and d4 contain thermo-fluorescence containing lithium heptaborate as the main constituent with the highest content and containing one or both of lithium tetraborate and lithium triborate. It was confirmed to be a body.

  In the sample c3 according to FIG. 9, the sample d2 according to FIG. 11, and the sample d4 according to FIG. 12, in particular, the peak of lithium heptaborate has higher diffraction intensity than lithium tetraborate and lithium triborate. From this, it was found that the content of lithium heptaborate constituting the thermoluminescent material is large.

  4 (A) and (B), FIG. 5 (A) and (B), FIG. 6 (A) and (B), FIG. 7 (A) and (B), FIG. 8, FIG. 9, FIG. 11 and FIG. 12, in the first embodiment, the conditions relating to the samples c2, c3, c4, d2, d3, and d4, that is, lithium tetraborate and boron oxide in the first step are changed to tetraboric acid. By mixing at a molar ratio of either lithium: boron oxide = 3: 1, 6: 1, or 2: 1 and performing heat treatment at a temperature in the range of 800 to 850 ° C. in the second step, It was confirmed that a thermophosphor containing lithium acid as a constituent material can be formed.

  Furthermore, since the yield of lithium heptaborate in samples c3, d2, d3, and d4, particularly sample d3, is high, in the first embodiment, in the first step, lithium tetraborate and boron oxide are mixed in four. It was confirmed that the yield of lithium heptaborate can be improved by mixing at a molar ratio of lithium borate: boron oxide = 3: 1 and performing heat treatment at a temperature of 850 ° C. in the second step.

  In addition, as already described, the samples c2, c3, c4, d2, d3, and d4, particularly the thermoluminescence emission intensity related to the thermophosphor of the sample d3, show a high value (FIG. 3A and FIG. 3). (Refer to (B)), and by preparing a large content of lithium heptaborate as a constituent of the thermophosphor, emission of thermofluorescence compared to the case where the content of lithium tetraborate and lithium triborate is large It was confirmed that the strength could be improved.

  In particular, light emission of samples a1 and e2 having lithium tetraborate as a main constituent, or sample b5 having lithium triborate as a main constituent, and d3 having lithium heptaborate as a main constituent. When the intensities are compared, it is clear from the above-described FIGS. 3A and 3B that the sample d3 exhibits a high emission intensity.

  Therefore, it is advantageous to construct a thermophosphor using lithium heptaborate as a base compared with the case where lithium tetraborate and lithium triborate are used as a base.

  In addition, the inventors conducted an experiment for confirming a suitable addition amount of copper (II) oxide to be mixed as a material when forming the mixture in the first step described above.

  Hereinafter, this experiment will be described with reference to FIG.

  In this experiment, in the first step, a plurality of thermoluminescent materials formed by mixing copper (II) oxide so as to have different ratios to the mixture were prepared as samples.

  Specifically, sample f1 formed a mixture without adding copper (II) oxide in the first step. Sample f2 is 0.01 wt% with respect to the mixture, sample f3 is 0.03 wt% with respect to the mixture, and sample f4 is 0.05 wt% with respect to the mixture. Sample f5 is 0.07 wt% with respect to the mixture, sample f6 is 0.10 wt% with respect to the mixture, and sample f7 is 0.10 wt% with respect to the mixture, similar to sample f6. In proportion, the sample f8 is 0.35 wt% with respect to the mixture, the sample f9 is 0.70 wt% with respect to the mixture, and the sample f10 is 1.00 wt% with respect to the mixture. Sample f11 was added at a ratio of 2.00 wt% with respect to the mixture, and sample f12 was added at a ratio of 5.00 wt% with respect to the mixture to form a mixture by adding copper (II) oxide, respectively.

  Each of these samples was prepared by mixing lithium tetraborate and boron oxide at a molar ratio of lithium tetraborate: boron oxide = 3: 1 in the first step, and 850 ° C. with respect to the mixture in the second step. Prepared by heat treatment.

  Each of these samples was irradiated with 1 Gy of X-rays using an irradiation apparatus having an X-ray tube voltage of 6 MV. Then, after storing in a dark box and starting exposure of the CCD camera, the sample was heated to 135 ° C. in 20 seconds, and the emission intensity was observed for 280 seconds while maintaining the temperature of 135 ° C.

  In this experiment, the samples f1 to f6 were placed side by side on one metal plate, and the above-described X-ray irradiation, heating, and observation of thermofluorescence were simultaneously performed on each sample. Similarly, samples f7 to f12 were placed side by side on one metal plate (for example, made of aluminum), and X-ray irradiation, heating, and observation of thermofluorescence were simultaneously performed on each sample.

  13A and 13B are diagrams showing the results of this experiment.

  FIG. 13A is an image obtained by photographing the state of light emission by thermofluorescence of each sample described above. A cooled CCD camera (ATK-314L manufactured by ATIK Instruments) was used to capture these images.

  In addition, each light emission shown by attaching | subjecting each code | symbol of f1-f12 in FIG. 13 (A) respond | corresponds to light emission of each sample f1-f12 mentioned above, respectively. That is, in performing this experiment, the arrangement relationship of each sample placed on the metal plate corresponds to the arrangement of each symbol shown in FIG.

  FIG. 13B is a diagram for comparing the emission intensity of each sample by thermofluorescence. In FIG. 13B, the vertical axis indicates the relative value of the emission intensity, and the horizontal axis indicates FIG. This corresponds to the distance in the arrangement direction of each sample indicated by a reference numeral (A). That is, the intensity distribution line 111 shown in the upper part of FIG. 13B shows the intensity distribution related to the emission intensity of the samples f1 to f6, and the intensity distribution line 113 shown in the lower part of FIG. 13B shows the samples f7 to f12. Intensity distributions related to the emission intensity are shown. These emission intensities are obtained by analyzing the image of thermofluorescence captured using the above-described cooled CCD camera (ATK-314L manufactured by ATIK Instruments) using ImageJ (registered trademark), which is a well-known image software. It was.

  As already described, the sample f6 and the sample f7 are created under the same conditions in both the first step and the second step. Therefore, the peak 115 indicating the emission intensity of the sample f6 and the peak 117 indicating the emission intensity of the sample f7 have substantially the same emission intensity.

  As is apparent from the result of FIG. 13A, it can be confirmed that the samples f6, f7, and f8 emit light with higher emission intensity than the other samples.

  As is clear from the intensity distribution lines in FIG. 13B, a peak 115 indicating the emission intensity of the sample f6, a peak 117 indicating the emission intensity of the sample f7, and a peak 119 indicating the emission intensity of the sample f8 are: The emission intensity is higher than that of other samples. From this result, in the first embodiment, in the first step, the heat to be formed by adding copper (II) oxide at a ratio in the range of 0.10 to 0.35 wt% with respect to the mixture. It was confirmed that the emission intensity of the thermofluorescence of the phosphor can be increased.

  Next, the inventors conducted an experiment to confirm the temperature characteristics and wavelength characteristics of the emission intensity distribution of the thermofluorescence of the thermophosphor formed in the second step of the first embodiment.

  Hereinafter, this experiment will be described with reference to FIGS.

  In this experiment, in the first step, lithium tetraborate and boron oxide are in a molar ratio of lithium tetraborate: boron oxide = 3: 1, and copper (II) oxide with respect to the mixture is in a ratio of 0.35 wt%. These were mixed, and a thermoluminescent material prepared by performing heat treatment at 850 ° C. on the mixture in the second step was used as a sample. In order to confirm the emission intensity of the thermofluorescence with respect to the temperature, the thermophosphor was irradiated with 20 Gy of X-rays using a RINT2000 X-ray analyzer manufactured by RIGaku, and then heated at 0.5 ° C./sec. The emission intensity of thermofluorescence was measured. Further, in order to confirm the wavelength of the fluorescence emission, the thermoluminescent material was irradiated with 20 Gy of X-rays by an SZX type X-ray analyzer manufactured by RIGAKU, and then heated at 1 ° C./sec. The wavelength of thermoluminescent emission was measured using a photonics PMA-11 type multichannel detector.

  FIG. 14 is a diagram for explaining the results of this experiment, and is a diagram showing the temperature characteristics of the emission intensity distribution of the thermoluminescent material manufactured in the first embodiment. In FIG. 14, the vertical axis indicates the relative value of the emission intensity, and the horizontal axis indicates the temperature of the thermophosphor in units of ° C.

  FIGS. 15A and 15B are diagrams for explaining the results of this experiment. The thermophosphor formed in the first embodiment and the thermophosphor according to the prior art, that is, the above-described ones. It is a figure which compares the wavelength characteristic and temperature characteristic of light emission intensity distribution about the thermoluminescent material comprised by the manganese containing lithium tetraborate currently disclosed by the patent document 1 which were made. 15A shows the wavelength characteristics and temperature characteristics of the emission intensity distribution of the thermoluminescent material according to the first embodiment, and FIG. 15B shows the emission intensity distribution of the thermoluminescent material according to Patent Document 1. Wavelength characteristics and temperature characteristics are shown. In FIGS. 15A and 15B, the x-axis shows the wavelength of thermofluorescence in nm units, and the y-axis shows the temperature of the thermoluminescent material in ° C units. The z axis represents the relative value of the emission intensity.

  Note that, as disclosed in Patent Document 1, aluminum (III) is added to the manganese-containing lithium tetraborate according to FIG. 15B for the purpose of improving the emission intensity.

  As is apparent from FIGS. 14 and 15A, the thermoluminescent emission intensity of the thermoluminescent material according to the first embodiment is the only single-peak emission intensity within a temperature range of 45 to 130 ° C. It was confirmed that there was only a distribution and there was a peak in the vicinity of 98 ° C. For these measurements, a PMA-11 type multi-channel detector manufactured by Hamamatsu Photonics was used.

  The temperature range of 45 to 130 ° C. where the emission intensity distribution relating to this temperature exists is an epoxy resin that functions as a binder in the thermoluminescent plate 105 according to the first embodiment (for example, GM-9005 of Brennie Giken). Is in a temperature range that can be mechanically heat-resistant, i.e., in a temperature range where the shape does not collapse, and optically heat-resistant, i.e., in a temperature range that does not change color.

  Therefore, in the thermoluminescent plate 105 according to the first embodiment, there is no possibility of the shape being collapsed during heating for causing the thermophosphor to emit light during the measurement of thermofluorescence, and the thermofluorescence of the thermoluminescent phosphor is caused by the epoxy resin. There is no risk of luminescence being absorbed.

  In addition, this thermophosphor has a single peak since the emission intensity distribution of thermofluorescence is unimodal.

  Therefore, the relationship between the exposure dose and the emission intensity of thermofluorescence is simple, and as a result, it is not necessary to perform complicated correction when calculating the exposure dose from the measured emission intensity of thermofluorescence. The details will be described later with reference to FIG.

  Further, from FIG. 15A, in the thermoluminescence emission intensity of the thermoluminescent material formed in the first embodiment, the emission intensity distribution with respect to the wavelength of thermofluorescence is the only single-peak distribution in the visible region. Moreover, it was confirmed that the distribution exists in a wavelength region shorter than 600 nm, more specifically, in a wavelength region in the range of 400 to 550 nm.

  On the other hand, from FIG. 15B, it was confirmed that in the thermoluminescent material according to Patent Document 1, the emission intensity distribution of thermofluorescence exists in the wavelength region within the range of 550 to 750 nm.

  As already explained, the emission intensity distribution of manganese-containing lithium tetraborate itself due to heating exists in the wavelength region where the bottom on the short wavelength side is around 600 nm. Therefore, in the thermoluminescent material according to Patent Document 1, when the temperature is increased to a temperature at which light emission due to heating occurs, for example, it is necessary to separate light emission due to thermofluorescence and light emission due to heating using a near infrared cut filter, for example. There is.

  On the other hand, in the thermoluminescent material according to the first embodiment, the emission intensity distribution of thermofluorescence exists in the visible wavelength region shorter than 600 nm. There is no need to use a near infrared cut filter, for example.

  In the thermoluminescent material according to the first embodiment, the emission intensity distribution of thermofluorescence exists in the wavelength region within the visible region. Therefore, even if an epoxy resin is used as the binder in the thermoluminescent plate 105, the thermofluorescence emitted from the thermophosphor is not absorbed by the epoxy resin, and therefore the emission intensity of thermofluorescence does not decrease.

  Next, the inventors conducted an experiment for confirming the relationship between the emission intensity of the thermofluorescence and the exposure dose in the thermophosphor formed in the second step of the first embodiment.

  In this experiment, different doses of X-rays (0.25 Gy, 0.25 Gy, etc.) were applied to the same thermophosphor as in FIGS. 14 and 15A described above using an irradiation apparatus having an X-ray tube voltage of 6 MV. 0.5 Gy, 1 Gy, and 2 Gy) were irradiated, and the emission intensity of thermofluorescence corresponding to each exposure dose was observed. In observing the emission intensity, the thermoluminescent material after X-ray irradiation was heated to 135 ° C. at 0.5 ° C./sec in a dark box.

  FIG. 16 is a diagram showing the results of this experiment, and is a diagram showing the relationship between the emission intensity of thermofluorescence and the exposure dose in the thermoluminescent material formed in the first embodiment. In FIG. 16, the vertical axis indicates the relative value of the emission intensity, and the horizontal axis indicates the dose of irradiated X-rays, that is, the exposure dose of the thermophosphor in Gy units. In this experiment, a SYNERGY type linac manufactured by Elekta was used as an X-ray irradiation apparatus, and a cooled CCD camera (ATK Instruments 314L manufactured by ATIK Instruments) was used for measuring the emission intensity.

  From FIG. 16, in the thermoluminescent material according to the first embodiment, the relative value is 7 when the exposure dose is 0.25 Gy, the relative value 15 when the exposure dose is 0.50 Gy, and the relative value when the exposure dose is 1.0 Gy. 30 and a relative value of 60 when the exposure dose is 2.0 Gy, it can be confirmed that the emission intensity of thermofluorescence increases linearly as the exposure dose increases.

  Therefore, from this result, it was confirmed that in the thermoluminescent plate 105 according to the first embodiment, the exposure dose can be calculated without performing complicated correction using the measured emission intensity of thermofluorescence.

<Second Embodiment>
In the second embodiment, as a dosimeter using a thermoluminescent plate and capable of acquiring a three-dimensional dose distribution of radiation, the thermoluminescent plate according to the above-described first embodiment is used. A thermoluminescent laminate in which a plurality of bodies are laminated and a method for manufacturing the same will be described.

  The manufacturing method of the thermoluminescent layered product by a 2nd embodiment includes the 1st process and the 2nd process. Hereinafter, with reference to FIG. 17 (A) and (B), it demonstrates per process in order from a 1st process.

  FIGS. 17A and 17B are process diagrams illustrating a method of manufacturing a thermoluminescent layered product according to the second embodiment. Each of these drawings is a schematic perspective view showing the structure obtained in each manufacturing stage.

  First, in the first step, as shown in FIG. 17A, a plurality of thermoluminescent plates 105 according to the first embodiment described above are prepared.

  As described above, the effective atomic number and density of each thermoluminescent plate 105 are adjusted to values approximate to the human body.

  In addition, the number of thermoluminescent plates 105 prepared in the first step and the planar shape along the stacking direction, that is, the planar shapes of the front surface 105a and the back surface 105b of the thermoluminescent plate 105 are measured, for example, by radiation lines. Set appropriately according to quality, alignment, or application. Since the thermoluminescent plate 105 can be cut with, for example, a slicer or the like, each planar shape is appropriately formed in advance according to the radiation to be measured. In FIG. 17A, as an example, a configuration example in the case where ten thermoluminescent plate-like bodies 105 are prepared, and a configuration example in which the planar shape of each thermoluminescent plate-like body 105 is a substantially square shape. Show.

  Next, in the second step, a plurality of thermoluminescent plates 105 prepared in the first step are stacked to form a structure as shown in FIG.

  At this time, the plurality of thermoluminescent plates 105 are laminated by sequentially superposing the front surfaces 105a and the back surfaces 105b of the thermoluminescent plates 105 without using an adhesive. As a result, a thermoluminescent laminate 107 formed by laminating a plurality of thermoluminescent plates 105 is obtained.

  In FIG. 17B, as an example, a configuration example in the case where the thermoluminescent laminate 107 is formed by laminating ten thermoluminescent plates 105 is shown.

  As described above, each thermoluminescent plate 105 constituting the thermoluminescent laminate 107 according to the second embodiment has an effective atomic number and density set to values approximate to the human body. Therefore, when the thermoluminescent layered product 107 according to the second embodiment is used as a dosimeter, the data regarding the radiation exposure dose to the human body with the obtained measurement values without performing various corrections. Can be obtained. In addition, if the data acquired using the thermoluminescent layered product 107 according to the second embodiment is a substance having an effective atomic number approximate to that of the thermoluminescent plate 105 constituting this, the data for substances other than the human body is used. It can also be used as data on exposure dose.

  In addition, as described above, each thermoluminescent plate 105 constituting the thermoluminescent laminate 107 according to the second embodiment is irradiated with radiation so that the plane of the radiation along the irradiated surface is flat. Simple dose distribution, that is, a two-dimensional dose distribution can be measured. Therefore, the two-dimensional dose distribution of the radiation is measured from each thermoluminescent plate 105 by irradiating the thermoluminescent laminate 107 formed by superimposing such thermoluminescent plates 105 with each other. be able to. At this time, the two-dimensional dose is obtained from each thermoluminescent plate 105 by the exposure position of each thermoluminescent plate 105 and the light intensity distribution of thermofluorescence corresponding to the radiation intensity and linearity at these exposure positions. Each distribution is measured. Therefore, by superimposing the respective two-dimensional dose distributions obtained from the respective thermoluminescent plate-like bodies 105, the three-dimensional, that is, the three-dimensional dose distribution of the radiation applied to the thermoluminescent laminate 107 can be measured.

  Hereinafter, a method for measuring a three-dimensional dose distribution using the thermoluminescent laminate 107 according to the second embodiment will be described with reference to FIGS. 18 (A) and 18 (B).

  FIGS. 18A and 18B are process diagrams for explaining the method of measuring the three-dimensional dose distribution. Each of these figures is a schematic perspective view showing the thermoluminescent laminate 107 in each process. It is.

  When measuring the three-dimensional dose distribution of radiation using the thermoluminescent laminate 107, first, the thermoluminescent laminate 107 is exposed by irradiating the thermoluminescent laminate 107 with the radiation 110 to be measured. (See FIG. 18A). In FIG. 18A, as an example, a configuration in which the radiation 110 is applied to the surface 107a of the thermoluminescent laminate 107, that is, the surface 107a orthogonal to the stacking direction 109 in which the thermoluminescent plate 105 is laminated. An example is shown.

  Next, the thermoluminescent layered product 107 is separated into each thermoluminescent plate 105 constituting the thermoluminescent layered product 107 (see FIG. 18B).

  A plane along the surface 105 a of the thermoluminescent plate 105 is obtained by photographing the thermofluorescence generated by heating from each of the thermoluminescent plates 105 from the direction facing the surface 105 a of the thermoluminescent plate 105. Light intensity distribution information, that is, two-dimensional light intensity distribution information is acquired.

  Here, when photographing the thermofluorescence, the thermofluorescent plate-like body 105 separated from the thermofluorescent laminate 107 is housed in a dark box and heated, and the emitted thermofluorescence is photographed using, for example, a CCD camera. .

  As already explained, in the thermoluminescent material constituting the thermoluminescent plate 105, the peak top of the thermoluminescent light is present at around 98 ° C. Therefore, in photographing thermofluorescence from the thermoluminescent plate 105, the thermoluminescent plate 105 accommodated in the dark box is heated. Then, exposure of the CCD camera is started from the start of the heating, and the thermoluminescent plate 105 is heated to 135 ° C. in 20 seconds, for example, and the thermofluorescence is photographed for 280 seconds in a state where the temperature of 135 ° C. is maintained. .

  In addition, in order to obtain the light intensity distribution information obtained by photographing as information on the visualized light intensity distribution, for example, imageJ (trade name), OpenDX (trade name), and Photoshop (which are well-known software) It is preferable that the image is processed by a computer using a trademark name). As a result, the dose distribution of the exposed portion along the surface 105a of the thermoluminescent plate 105 is imaged as thermofluorescence having light intensity corresponding to the dose.

  Next, the dose distribution information as the imaged light intensity distribution information is sequentially overlapped in the stacking direction 109 (see FIG. 18A) in the stacking order when the thermoluminescent stack 107 is exposed. Acquire an image relating to a three-dimensional dose distribution.

  For this purpose, for example, VisualFortran (trade name) and OpenDX (trade name) are preferably used to perform image processing by a computer.

  Then, by superimposing the images obtained from each thermoluminescent plate 105, the image of the two-dimensional light intensity distribution information corresponding to each exposed location along each surface 105a of each thermoluminescent plate 105 is three-dimensional. Is laminated. As a result, each of the stacked images can be regarded as a three-dimensional exposure location of the thermoluminescent layered product 107, substantially a three-dimensional dose distribution of the irradiated radiation.

  Here, with reference to FIG. 18 (A), as an example, the measurement method of the three-dimensional dose distribution when the radiation 110 is applied to the surface 107a of the thermoluminescent laminate 107 has been described. Even when the radiation 110 is applied to each side surface 107b along the stacking direction 109 of the thermoluminescent layered body 107, the three-dimensional dose distribution of the radiation can be acquired by the same method as described above.

  Here, the inventors conducted an experiment to confirm the measurement accuracy in the thermoluminescent layered product 107 according to the second embodiment.

  Hereinafter, this experiment will be described with reference to FIGS. 19 and 20.

  In this experiment, the thermoluminescent layered product 107 according to the second embodiment and an ionization chamber (CC19 manufactured by Scandronix Wellhofer), which is a well-known dosimeter, are irradiated with the same dose from an irradiation device under the same conditions. The X-ray measurement results were compared. In this experiment, a CLINAC-21EX linear accelerator linac manufactured by Varian was used as the irradiation device.

  In the measurement using the thermoluminescent laminate 107, the surface 107a of the thermoluminescent laminate 107 was irradiated with X-rays along the lamination direction 109 (see FIG. 18A). Then, using a cooled CCD camera (ATK-314L manufactured by ATIK Instruments), the thermoluminescence of the thermoluminescent laminate 107 was photographed and the emission intensity was measured. In this experiment, the thermoluminescent layered body 107 was constituted by stacking 64 thermoluminescent plate-like bodies 105 having a thickness of 2.5 mm and a planar shape of approximately square with a side of 86 mm.

  Moreover, in the measurement using an ionization chamber, the ionization chamber was accommodated in the water tank filled with the water which functions as a phantom, and X-rays were irradiated from the outside of this water tank. And the ionization degree of the ionization chamber in each position in a water tank was measured by moving an ionization chamber to arbitrary positions in a water tank in the state which fixed the irradiation position of X-ray | X_line.

  In this experiment, the X-ray tube voltage of the irradiation apparatus was set to 4 MV, the irradiation field was set to 40 × 40 mm, and 2 Gy X-rays were emitted in each measurement using the thermoluminescent laminate 107 and the ionization chamber. Irradiated.

  FIGS. 19A and 19B are diagrams showing the results of this experiment. In the plane perpendicular to the X-ray irradiation direction, the distance from the irradiation center position, and the emission intensity or ionization at each distance. It is a figure which shows the relationship with a degree.

  FIG. 19A shows the distance from the irradiation center position along the straight line in the plane perpendicular to the X-ray irradiation direction in the thermoluminescent layered product 107, and the emission intensity of thermofluorescence at each distance. It is a figure which shows the relationship. In FIG. 19A, the vertical axis represents the relative value of the emission intensity of thermofluorescence, and the horizontal axis represents the distance from the irradiation center position in mm. And the point of 0 mm on this horizontal axis means the irradiation center position. FIG. 19A shows a measurement result at a depth of 80 mm from the surface 107a of the thermoluminescent layered product 107, that is, the irradiated surface.

  FIG. 19B shows the separation distance from the irradiation center position along the straight line in the plane orthogonal to the X-ray irradiation direction in the water tank containing the ionization chamber, and the ionization chamber measured at each distance. It is a figure which shows the relationship with the ionization degree of. In FIG. 19B, the vertical axis represents the relative value of the degree of ionization, and the horizontal axis represents the distance from the irradiation center position in mm. And the point of 0 mm on this horizontal axis means the irradiation center position. FIG. 19B shows a measurement result at a distance of 80 mm from the wall surface irradiated with X-rays of the water tank containing the ionization chamber, that is, the irradiated surface.

  From the result of FIG. 19A, in the measurement using the thermoluminescent layered product 107, the relative value of the emission intensity is about 100 and maximum (that is, the exposure dose is maximum) within a range 25 mm away from the irradiation center position on both sides. Thus, it can be seen that the emission intensity is extremely low at positions outside this range.

  Further, from the result of FIG. 19B, in the measurement using the ionization chamber, as in the measurement using the thermoluminescent laminate 107, the relative value of the ionization degree is within a range 25 mm away from the irradiation center position on both sides. Is about 100 (ie, the exposure dose is maximum), and the ionization degree becomes extremely low at a position outside this range.

  From these results, the measurement using the thermoluminescent layered product 107 and the measurement using the ionization chamber are measured at a distance from the irradiation center position and each distance in a plane orthogonal to the X-ray irradiation direction. It is clear that the relationship with the applied dose is experimentally consistent.

  20A and 20B are diagrams showing the results of this experiment, showing the relationship between the distance along the X-ray irradiation direction and the emission intensity or ionization degree at each distance. is there.

  20A shows the distance from the irradiated surface (that is, the surface 107a of the thermoluminescent layered body 107) along the X-ray irradiation direction at the irradiation center position of the thermoluminescent layered body 107, and It is a figure which shows the relationship with the emitted light intensity of the thermofluorescence in distance. In FIG. 20A, the vertical axis represents the relative value of the emission intensity of thermofluorescence, and the horizontal axis represents the distance from the irradiated surface in mm.

  FIG. 20B shows an irradiated surface along the X-ray irradiation direction at the irradiation center position in the water tank containing the ionization chamber (that is, the wall surface irradiated with X-rays from the water tank containing the ionization chamber). It is a figure which shows the relationship between the separation distance from and the ionization degree of the ionization chamber measured in each distance. In FIG. 20B, the vertical axis represents the relative value of the degree of ionization, and the horizontal axis represents the distance from the irradiated surface in mm.

  From the result of FIG. 20A, in the measurement using the thermoluminescent layered product 107, the relative value of the emission intensity is about 100 and maximum (that is, the exposure dose is maximum) at a position separated by about 10 mm from the irradiated surface. It can be seen that the emission intensity gradually decreases as the distance from the surface to be irradiated increases at a position separated by more than 10 mm.

  Further, from the result of FIG. 20B, in the measurement using the ionization chamber, the relative value of the degree of ionization is 100 at a position about 10 mm away from the irradiated surface, similarly to the measurement using the thermoluminescent laminate 107. It can be seen that the degree of ionization becomes maximum (that is, the exposure dose is maximum), and the ionization degree gradually decreases as the distance from the surface to be irradiated increases at a position separated by more than 10 mm.

  From these results, in the measurement using the thermoluminescent laminate 107 and the measurement using the ionization chamber, the relationship between the distance along the X-ray irradiation direction and the dose measured at each distance is experimental. It is clear that

  20A and 20B, the relative value of the ionization degree of the ionization chamber at the position 0 mm away from the irradiated surface, that is, the surface of the irradiated surface is It is larger than the relative value of the emission intensity. This is because in the measurement using an ionization chamber, the degree of ionization at a position exactly 0 mm away from the irradiated surface is measured by the thickness of the wall of the water tank containing the ionization chamber and the thickness of the outer wall of the ionization chamber itself in this experiment. It is thought that this is an error due to what cannot be done.

  As described above, as is clear from the results of FIGS. 19A and 19B and FIGS. 20A and 20B, the second X-ray dose is measured in the same condition. It was confirmed that the thermoluminescent laminate 107 according to the embodiment can be used with the same accuracy as an ionization chamber which is a well-known dosimeter.

  In addition, the inventors measured the radiation applied to the surface 107a (see FIG. 18A) and the side surface 107b (FIG. 18 (FIG. 18 (A)) of the thermoluminescent layered product 107 according to the second embodiment. An experiment for confirming measurement accuracy with respect to the case of measuring radiation with respect to A) was conducted.

  Hereinafter, this experiment will be described with reference to FIG.

  In this experiment, using the thermoluminescent layered product 107 according to the second embodiment, the surface 107a of the thermoluminescent layered product 107 is irradiated with the same dose of X-rays irradiated from the irradiation device under the same conditions. The measurement results were compared with the measurement results obtained by irradiating the side surface 107b. In this experiment, a CLINAC-21EX linear accelerator linac manufactured by Varian was used as the irradiation device.

  In this experiment, the fluorescence of the thermoluminescent laminate 107 was photographed using a cooled CCD camera (ATK-314L manufactured by ATIK Instruments), and the emission intensity was measured. In addition, in the case of irradiating the surface 107a and the side surface 107b, 64 thermoluminescent plate-like bodies 105 having a thickness of 2.5 mm and a planar shape of 86 mm on a side are laminated. The thermoluminescent layered product 107 configured as described above was used.

  FIG. 21 is a diagram showing the results of this experiment, and is a diagram showing the relationship between the distance from the irradiated surface along the X-ray irradiation direction and the emission intensity at each distance.

  In FIG. 21, the vertical axis represents the relative value of the emission intensity of thermofluorescence, and the horizontal axis represents the distance from the irradiated surface in mm.

  And the black triangular dot shown in FIG. 21 has shown the result at the time of irradiating with respect to the surface 107a (refer FIG. 18 (A)) of the thermoluminescent laminated body 107. FIG. Therefore, for a black triangular dot, the horizontal axis means the distance from the surface 107a that is the irradiated surface.

  Moreover, the black rhombus dots shown in FIG. 21 indicate the results when the side surface 107b of the thermoluminescent laminate 107 is irradiated. Therefore, for the black rhombus dots, the horizontal axis means the distance from the side surface 107b that is the irradiated surface.

  From the results shown in FIG. 21, in the case where the measurement is performed by irradiating the surface 107a of the thermoluminescent laminate 107 and the case where the measurement is performed by irradiating the side surface 107b, the in-plane orthogonal to the X-ray irradiation direction is obtained. It is clear that the relationship between the distance from the irradiation center position and the dose measured at each distance is experimentally consistent.

  Therefore, in the thermoluminescent layered product 107 according to the second embodiment, the radiation is irradiated with the same accuracy both when the surface 107a is irradiated with radiation and when the side surface 107b is irradiated. It was confirmed that the dose can be measured.

105: Thermoluminescent plate 107: Thermoluminescent laminate

Claims (13)

It is composed of thermophosphor and epoxy resin,
The thermoluminescent material contains lithium heptaborate as a base material and copper as an emission center existing in the base material, and the emission intensity distribution with respect to the wavelength of the thermofluorescence is the only and single peak type. And a thermoluminescent plate characterized by being in a visible region having a wavelength shorter than 600 nm. The thermoluminescent plate according to claim 1, wherein
The thermoluminescent plate, wherein the emission intensity distribution with respect to the wavelength exists in a wavelength region within a range of 400 to 550 nm. The thermoluminescent plate according to claim 1 or 2,
The thermoluminescent plate, wherein the emission intensity distribution of the thermoluminescent material with respect to the temperature of the thermoluminescent material is unique and unimodal within a temperature range of 45 to 130 ° C. The thermoluminescent plate according to any one of claims 1 to 3,
A thermoluminescent plate characterized by additionally containing cellulose and silicon oxide.   A thermoluminescent laminate, wherein a plurality of thermoluminescent plates according to any one of claims 1 to 4 are laminated. A first step of forming a first mixture by mixing lithium tetraborate, boron oxide, and copper (II) oxide;
A second step of heat-treating the first mixture into a thermophosphor containing lithium heptaborate as a base and copper as a luminescent center present in the base; ,
A third step of forming a second mixture by mixing the thermophosphor, cellulose, silicon oxide, and epoxy resin;
A fourth step of forming a thermoluminescent plate by heat-treating the second mixture,
In the first step, the lithium tetraborate and the boron oxide are mixed at a molar ratio of lithium tetraborate: boron oxide = 3: 1. A first step of forming a first mixture by mixing lithium tetraborate, boron oxide, and copper (II) oxide;
A second step of heat-treating the first mixture into a thermophosphor containing lithium heptaborate as a base and copper as a luminescent center present in the base; ,
A third step of forming a second mixture by mixing the thermophosphor, cellulose, silicon oxide, and epoxy resin;
A fourth step of forming a thermoluminescent plate by heat-treating the second mixture,
In the first step, the lithium tetraborate and the boron oxide are mixed at a molar ratio of lithium tetraborate: boron oxide = 6: 1. A first step of forming a first mixture by mixing lithium tetraborate, boron oxide, and copper (II) oxide;
A second step of heat-treating the first mixture into a thermophosphor containing lithium heptaborate as a base and copper as a luminescent center present in the base; ,
A third step of forming a second mixture by mixing the thermophosphor, cellulose, silicon oxide, and epoxy resin;
A fourth step of forming a thermoluminescent plate by heat-treating the second mixture,
In the first step, the lithium tetraborate and the boron oxide are mixed at a molar ratio of lithium tetraborate: boron oxide = 2: 1. It is a manufacturing method of the thermoluminescent plate-like object according to any one of claims 6-8,
In the second step, the heat treatment is performed at a temperature in the range of 800 to 850 ° C. It is a manufacturing method of the thermoluminescent plate-like object according to claim 9,
In the second step, the heat treatment is performed at a temperature of 850 ° C. A method for producing a thermoluminescent plate according to any one of claims 6 to 10,
In the first step, the copper oxide (II) is mixed at a ratio in the range of 0.1 to 0.35 wt% with respect to the mixture. It is a manufacturing method of the thermoluminescent plate-like object according to any one of claims 6-11,
The production of a thermoluminescent plate, wherein the effective atomic number and density of the thermoluminescent plate are adjusted by adjusting the weights of the thermophosphor, the cellulose, the silicon oxide, and the epoxy resin. Method. A first step of preparing a plurality of thermoluminescent plates obtained by the method for producing a thermoluminescent plate according to any one of claims 6 to 12,
And a second step of forming the thermoluminescent laminate by laminating the plurality of thermoluminescent plate-like bodies.