JPS58219471A - Manufacture of radiation detector - Google Patents

Abstract

PURPOSE:To achieve a highly accurate manufacture with a simple assembly work by a method wherein a phosphor is cut as fastened on a support plate with an adhesive to be separated into a plurality of scintillators which are fastened solidly with a mixture of light reflecting agents and then, after the support plate is separated by heat, it is joined to a photoelectric conversion element. CONSTITUTION:A phosphor is fastened on a support plate 12 with an adhesive 11 having a low softening point and cut into scintillator elements 13 with a slicer. Gaps between the elements 13 are filled with a mixture 14 of a light reflecting agent and an epoxy adhesive to fasten the element 13 together. After separated from the support plate 12 by heat, the elements 13 are fitted with reinforcing plates 15 and 15 and put together with a photoelectric conversion element 16 formed on a rectangular-plate-shaped protective substrate 17 by bonding the bottom thereof with the elements 13 by a glass adhesive. Thus, incident X ray can be converted into light with the quantity corresponding to the dose thereof with each of the scintillator elements 13 and then, to an electrical signal with the photoelectric conversion element 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention belongs to the technical field of radiation tomography apparatuses, and relates to a method of manufacturing a radiation detector installed in a radiation tomography apparatus.

[Technical background of the invention and its problems]

A radiation tomography device, for example, an X-ray CT device consists of an X-ray tube that rotates around the subject around the subject's body axis, and an X-ray tube that is placed opposite the X-ray tube across a space in which the subject is placed. and a detector for detecting the X-rays emitted from the X-ray tube and transmitted through the subject, and the X-ray tube is rotated, for example, by 0.6° about the center of the body axis of the subject. Tsutsu
The image is reconstructed based on a large number of projection data at intervals of 0 and 6 degrees output from the detector that detects the X-rays that pass through the subject, and the image is reconstructed on the display device. 5 to be able to display a tomographic image. For example, doctors etc.
Based on the tomographic images obtained by the device, medical judgments are made regarding the health condition of the subject, such as the patient, and the presence of lesions. Therefore, in order to make accurate medical decisions possible,
The tomographic images obtained by the X@CT apparatus are required to have extremely high quality. One of the factors that influences the quality of tomographic images is the performance of the detector.

Conventionally, a detector in an XIwCT apparatus is configured as follows, for example. That is, as shown in FIG.
is 0.91. , a scintillator element 1 formed into a rectangular parallelepiped with a height t of 2 mj, and a scintillator element 1 made of, for example, titanium dioxide (
A light reflecting layer 2 having a Ti0z)n component and a photoelectric conversion element 4
and a rectangular plate-shaped support member 5, and a light reflecting layer 2 is formed by coating all the surfaces of each scintillator element 1, except for the bottom surface, with a light reflecting agent containing titanium dioxide, for example. , then above the support member 5,
A large number of photoelectric conversion elements 4 having substantially the same surface as the bottom surface of the scintillator element 1 along the longitudinal direction are arranged in parallel with a predetermined pitch as small as possible, and the photoelectric conversion elements are arranged and fixed on the upper surface of the support member 5. A large number of scintillator elements 1 are arranged on the support member 5 by fixing the scintillator elements 1 to the bottom surface using, for example, a glass adhesive. Then, as shown in FIG. 1, when an X-ray flux emitted from an X-ray tube (not shown) enters the upper surface of the scintillator element 1, the scintillator element 1 receives X1ti! i! is converted into light, and scintillator element 1
The light emitted by the X-ray is detected and photoelectrically converted by the photoelectric conversion element 4, and the photoelectric conversion element 4 is configured to output a current signal proportional to the amount of incident X-rays.

However, the factors that affect the image quality of tomographic images are the dimensional accuracy of the scintillator element 1 and the assembly accuracy when arranging the detection blocks. It is extremely difficult to form scintillator elements 1, and even if scintillator elements 1 are formed into rectangular parallelepipeds having exactly the above dimensions, it is difficult to precisely arrange a plurality of scintillator elements 1 at a constant pitch on the upper surface of support member 5. Therefore, errors in assembly accuracy (also referred to as arrangement accuracy) in the detector are inevitable. If the arrangement of the scintillator elements 1 is out of alignment, response fluctuations will occur, which will adversely affect the quality of the tomographic image. Moreover, the above assembly method is complicated.

Furthermore, the width W of the scintillator element 1 due to the cutting process
Since there is a limit to the width W of the scintillator element 1, the width W of the scintillator element 1 cannot be made as small as desired, and the spatial resolution is naturally limited.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a radiation detector with high spatial resolution and high contrast resolution through simple assembly operations and with high assembly accuracy.

[Summary of the Invention] The outline of the present invention for achieving the above object is to cut a substantially rectangular block of phosphor while it is fixed on a support plate with a first adhesive having a low softening point. The scintillator elements are separated into a plurality of scintillator elements, and then the adjacent scintillator elements are heated to a softening point higher than that of the light reflecting agent and the first adhesive.

or a mixture having at least a second adhesive having a decomposition point, and then heated to a temperature between the softening point of the first adhesive and the softening point or decomposition point of the second adhesive. This method is characterized in that the support plate is separated by heating, and each scintillator and photoelectric conversion element that are fixed together are joined.

[Embodiments of the invention]

2 to 5 are schematic perspective views showing the steps of a manufacturing method according to an embodiment of the present invention, and FIGS. 6 to 8 are
The drawings are schematic perspective views showing a radiation detector manufactured by the method according to the present invention.

In the manufacturing method according to the present invention, first, a phosphor 10 is prepared by molding a block of fluorescent material into a rectangular parallelepiped, and this phosphor 1 is bonded to an adhesive 11 (hereinafter referred to as a first adhesive) having a low softening point. ) is fixed on the support plate 12. The fluorescent substance is a substance that can convert radiation, such as X-rays, such as cesium iodide (thallium-doped cesium iodide).
Csl; I'l), bismuth germanate (B14G
0.2), Tank (7) Cadmium state (CdWO4), Zinc tungstate (WO4), Magnesium tungstate Ckf!
IF04) etc. can be suitably used. The dimensions of the rectangular parallelepiped to be molded can be appropriately determined depending on the dimensions of the scintillator element 1 constituting the radiation detector. For example, as shown in FIG. The length 7 is 28 mV, and the length W in the longitudinal direction is 30 mV.
C. The support plate 12 only needs to have a flat surface at least where the phosphor 10 is placed. Further, it is preferable that the support plate 12 is made of a material that has high dimensional stability against heat and has a small coefficient of thermal expansion. This is because, as described later, the support plate 12
In order to separate the obtained scintillator element 16 from
When the first adhesive 11 is heated to a softened or flowing state, if the support plate 12 bends or expands, the arrangement of the scintillator elements 13 will be distorted, and the resulting radiation
This is because the performance of the J-ray detector deteriorates. The first adhesive 11 firmly fixes the phosphor 10 or scintillator (8) element 16 and the support plate 12 under working conditions, but when heated to a predetermined temperature, the first adhesive 11 softens. Any adhesive may be used as long as it is in a fluid state and can easily separate the scintillator element 13 and the support plate 12. For example, a hot melt adhesive having a softening point of 80 to 90°C is preferably used. can. In particular, as the first adhesive 11 that can be obtained, Adfix [trade name; manufactured by Yakka Seiko (Ten) Co., Ltd.] is mentioned. The fixation of the phosphor 10 onto the support plate 12 is achieved by applying the first adhesive 11 heated to a temperature higher than the softening point of 80 to 90° C. to the support plate 12 in an appropriate manner.
This can be easily done by simply placing the phosphor 10 on the coated surface of the support plate 12 and cooling it while pressing until the first adhesive 11 has solidified.

Next, the phosphor fixed on the support plate 12 as described above is cut into the scintillator element 1 using a groove cutting machine (multi-wire saw).
Cut into 3 pieces (see Figure 6). As a multi-wire saw, for example, the wire 14 of about 100 to 200μ is cut into 1. It is preferable that a large number of them be arranged at On intervals.

The distance between the wire saws 14 can be appropriately determined depending on the required mounting density of the scintillator elements 16. Note that the cutting direction is a direction perpendicular to the longitudinal direction of the phosphor 10, for example. By cutting in this direction, it can be separated into a large number of strip-shaped no scintillator elements 16 arranged at a predetermined pitch. In this case, as for the precision of the arrangement, the height t1 and length l in the longitudinal direction of each scintillator element 13 are the same, the upper surfaces of each scintillator element 16 are all on the same plane, and, for example, the ridge of each scintillator element 16 is the same. @AB are all on the same straight line. If there is a discrepancy in accuracy, it is the width W of each scintillator element 13, but this width W is different from the wire saw 14.
Since the mutual spacing of the wire saws 14 can be set to be sufficiently equal depending on the mutual spacing of the scintillator elements 13, the widths W of the obtained scintillator elements 13 can also be made almost the same.

Further, the phosphor 10 is firmly attached to the support plate 1 with the first adhesive 11.
2, the phosphor 10 does not shift on the support plate 12 during cutting, and even after cutting, each scintillator element 13 is attached to the support plate 12 with the first adhesive 11.
Each scintillator element 16
The position of the player will not shift or the player will not be able to play shogi.

Next, as described above, a light reflecting agent and an adhesive (hereinafter referred to as a second adhesive) are applied between the scintillator elements 13 fixed on the support plate 12 and arranged at a predetermined pitch. ) and fill each scintillator element 1 with a mixture 14 of
6 to each other (see Figure 4). The light reflecting agent may be any material as long as it can reflect the source emitted by the scintillator element 13, such as titanium dioxide (
Examples include light reflecting agents containing T, 1ot), barium sulfate (Ba504), and the like. When the second adhesive is mixed with the light reflecting agent, it can be uniformly dispersed, and the softening point or decomposition point of the second adhesive is higher than the softening point of the first adhesive. Much higher is preferred. The reason why the second adhesive has a high softening point or high decomposition point is that it is necessary to keep each scintillator element 16 integrally bonded even under the heating conditions when separating the support plate 12. It is from. Further, the reason why the second adhesive needs to be able to contain the light reflecting agent in a uniformly dispersed manner is to prevent crosstalk between the scintillator elements 16. As a second adhesive with such requirements, for example, a material with a softening point or decomposition point of 200~
An example is an epoxy adhesive having a temperature of 600°C. The light-reflecting agent and the second adhesive can be mixed by a known method, and the resulting mixture 14 has good dispersion of the light-reflecting agent, and the mixing of the second adhesive by heating and pressure. It may be mixed with other additives to prevent deterioration. The filling of the mixture 14 into each gap of each scintillator element 13 is as follows:
This can be done by any known method such as a caulking gun.

Next, as described above, the scintillator elements 13 are bonded together, and the support plate 12 that fixes the scintillator elements 16 with the first adhesive 11 is heated, so that the scintillator elements 13 are bonded together. scintillator element 1
6 and the support plate 12 (see FIG. 4). In this case, the heating temperature is set to such a level that the scintillator element 16 and the support plate 12 can be separated with a slight force. The temperature at which the first adhesive 11 softens or flows may be used, for example, the temperature may be slightly higher than the softening point of the first adhesive 11. Further, it is preferable that the heating operation is performed so that heat is applied only to the first adhesive 11. For example, the support plate 12 for fixing the scintillator element 13 is placed on a heat plate heated to a predetermined temperature. It can be done by In addition, during the heating operation, some heat is applied to the mixture between the scintillator elements 13 and its viscosity decreases, which may reduce the alignment accuracy of the scintillator elements 13, which may occur when separating the support plate 12. In order to prevent misalignment, it is preferable to attach reinforcing plates 15 and 15 along the arrangement direction of the scintillator elements 16 (
(See Figure 5).

Next, the photoelectric conversion element 16 formed on the rectangular plate-shaped protective substrate 17 and the bottom surface of the scintillator element 16, which has been heated for 5K and turned into m = bodies as described above, are bonded with a glass adhesive (see (See Figure 5). The protective substrate 17 can be made of ceramic or the like.

The photoelectric conversion element 16 is an element that converts the light emitted by the scintillator element 16 into an electric signal according to the amount of light, and includes, for example, a photodiode and a phototransistor.
It can be formed on the protective substrate 17 by a known method such as vapor deposition. The exposed surface of the photoelectric conversion element 16 has the same shape as the bottom surface of the scintillator element 13, and is formed with the same pitch as the array pitch of the scintillator elements 13 integrated as described above. Note that on the protective substrate 17, a part of the exposed surface of the photoelectric conversion element 16 is extended to provide an output terminal for extracting the current signal output from the photoelectric conversion element 16 and connecting it to a subsequent circuit, such as an amplifier. 18
It is preferable to also form Glass adhesives are optically clear adhesives, such as Canada Balsam,
Adhesives based on epoxy resins, cyanoacrylates, etc. can be used.

Through the above steps, as shown in FIG. 6, each scintillator element 13 converts the Xi incident from above into light with an amount of light corresponding to the amount of X-rays, and the optical conversion element 16 converts the light into electricity according to the amount of light. Radiation detectors can be manufactured that can be converted into signals. Since the process basically consists of cutting the phosphor and gluing each part, the radiation detector can be manufactured with simple operations. Furthermore, when cutting, the mutual spacing between the wire saws 14 can be set freely, so by reducing the mutual spacing, the arrangement pitch of each scintillator element 16 in the radiation detector can be reduced, and the space A radiation detector with high resolution can be manufactured. Furthermore, since the scintillator elements 16 are firmly fixed to the support plate 12 with the first adhesive 11, the arrangement accuracy of each scintillator element 16 can be made extremely high.

Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment (and can be implemented with appropriate modifications within the scope of the gist of the invention.

The shape of the reinforcing plate 15 used in the above embodiment was a rectangular plate that covered part of the side surface of the rectangular parallelepiped formed by combining the scintillator elements 13, but the shape of the reinforcing plate 15 is not limited to this. As shown in FIG.
As shown in the figure, the cross-section may be curved so as to cover part of the upper surface of the scintillator element 13. As shown in FIGS. 7 and 8, the larger the area of the reinforcing plate 15 is.

It is possible to prevent variations in the arrangement accuracy of the scintillator elements 16.

Furthermore, in the embodiment described above, the mixture 14 is filled in the gaps between the scintillator elements 16, except for the X-ray incident surface of each scintillator element 13 and the bottom surface facing thereto (the mixture 14 is applied to the entire surface of the scintillator element 13). By applying the mixture 14 to the entire surface, leakage of light can be prevented, and the source of light emission can be efficiently converted into an electric signal by the photoelectric conversion element 16.

〔Effect of the invention〕

According to the manufacturing method of the present invention, it is possible to manufacture a radiation detector with high assembly accuracy and excellent performance such as spatial resolution through simple assembly operations.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing a conventional radiation detector, and FIGS. 2 to 5 are schematic perspective views showing steps of a manufacturing method according to an embodiment of the present invention, and FIGS. 6 to 8 The foregoing are schematic perspective views showing a radiation detector manufactured by the method according to the present invention. DESCRIPTION OF SYMBOLS 10... Phosphor, 11... Adhesive of thread 1, 12
...Support plate, 16...Scintillator element,
14...Wire saw, 15...Reinforcement plate,
16... Photoelectric conversion element, 17... Protection board,
18...Output terminal. Figure 1 Figure 2 Figure 1

Claims (7)

[Claims] (1) Cut the bulk phosphor in the shape of a rectangular parallelepiped while it is fixed on the support plate with a first adhesive having a low softening point to separate it into a plurality of scintillator elements, and then separate the adjacent scintillator elements. a second adhesive having a softening point or decomposition point higher than that of the light reflecting agent and the first adhesive;
and then separating the support plates by heating to a temperature between the softening point of the first adhesive and the softening point or decomposition point of the second adhesive. A method for manufacturing a radiation detector, comprising: joining each scintillator and a photoelectric conversion element that are fixed together. (2) The method for manufacturing a radiation detector according to claim 1, wherein the phosphor is selected from the group of cadmium tungstate, magnesium tungstate, zinc tungstate, and bismuth germanate. . (3) The first adhesive has a softening point of 80 to 90°C.
Claim 1 or 2 characterized in that
The method for manufacturing the radiation detector described in Section 1. (4) The method for manufacturing a radiation detector according to any one of claims 1 to 6, wherein the first adhesive is a hot melt adhesive. (5) The method for manufacturing a radiation detector according to any one of claims 1 to 4, wherein the second adhesive is an epoxy adhesive. (6) The method for manufacturing a radiation detector according to any one of claims 1 to 5, wherein the light receiving element is a photodiode. (7) The method for manufacturing a radiation detector according to any one of claims 1 to 5, wherein the light receiving element is a phototransistor.