JPS5985979A - Manufacture of radiation detector - Google Patents

Abstract

PURPOSE:To improve performance such as spatial resolution with a better assembly accuracy by a method wherein scintillator elements are fastened together with a mixture having the second adhesive with the softening point or the decomposition point higher than the softening point of a light reflecting agent and the first adhesive and heated up to a specified temperature. CONSTITUTION:A fluorescent body 10 produced by molding an agglomerate scintillator material into a rectangular body is fastened on a support plate 12 with an adhesive 11 (the first adhesive) having a low softening point. Then, the fluorescent body fastened on the support plate 12 is grooved into a scintillator element 13 with a grooving machine (a multiwire saw). The fluorescent body can be divided into a number of strip-shaped scintillator elements 13 arranged at a specified pitch by grooving it in a specified direction. An aluminum sheet 19 coated with a light reflecting agent is coated with an adhesive (the second adhesive) and inserted mutually into grooves of the scintillator elements 13 to fasten the scintillator elements 13 together. The scintillator elements 13 thus integrated are separated from the support plate 12 by heating the support plate 12 having the scintillator elements 13 fastened mutually thereon with the first adhesive 11.

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 equipped with a radiation tomography apparatus aK.

[Technical background of the invention and its problems]

Radiation tomography equipment, for example, X-ray CT equipment, uses
A detector that is arranged opposite to the X-ray tube across a space in which the subject is placed, and that detects X-rays emitted from the X-ray tube and transmitted through the subject. Then, the X-ray tube is rotated, for example, by 0.6 degrees around the subject's body axis, and X-rays are irradiated to the subject, and the X-rays transmitted through the subject are output from the detector. The apparatus is configured to perform image reconstruction processing based on a large number of projection data at intervals of 0 and 6 degrees, and display the reconstructed tomographic image on a display device. For example, doctors etc. fiX
Based on the tomographic images obtained by the CT apparatus, medical judgments are made regarding the health status of a patient, for example, and the identification of lesions. Therefore, in order to enable accurate medical judgment, the tomographic images obtained by the xHcr apparatus are required to have extremely high quality. Detector performance is one of the factors that influences the quality of tomographic images.

Conventionally, a detector in an X-ray CT apparatus has been configured, for example, as follows. That is, as shown in FIG. 1, the detector includes a scintillator element 1 formed by molding a fluorescent material into a rectangular parallelepiped having a length l of 28 m, a width W of 0.9 m, and a height t of 2 W. , for example, titanium dioxide (TtO
z) as a main component; a photoelectric conversion element 4;
A p-light reflecting layer 2t is formed by coating all surfaces of each scintillator element 1 except the bottom surface with a light reflecting agent containing titanium dioxide, for example. Next, the bottom surface of the scintillator element 1 and l't are placed on the upper surface of the support side 5 along its longitudinal direction.
? ``! A large number of photoelectric conversion elements 4 having the same surface are arranged in parallel with a predetermined bit as small as possible, arranged on the upper surface of the support member 5, and the photoelectric conversion elements 4 and the bottom surface of the scintillator element 1 are arranged for use in a lens, for example. By fixing with a transparent adhesive, a large number of scintillator elements 1 are arranged on the supporting member 5-A.As shown in FIG. When the X-ray flux X enters the upper surface of the scintillator element 1, the scintillator element 1 converts the X-rays into light.

The light emitted by the scintillator element 1 is detected and photoelectrically converted by a 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 influence the image quality of tomographic images are
Due to the dimensional accuracy of the scintillator element 1 and the assembly accuracy when arranging the detection blocks, it is extremely difficult to cut out each scintillator element 1 and form it into a rectangular parallelepiped with the above dimensions. Even if the scintillator elements 1 are formed into a rectangular parallelepiped, it is difficult to precisely arrange the scintillator elements 1 at a pitch of one foot on the upper surface of the support member 5, and the assembly accuracy of the detector is difficult. [Also called array precision. ] is 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, since there is a limit to the width W of the scintillator element 1 obtained by cutting out, the width IF'' of the scintillator element 1 cannot be made as small as desired, and the spatial resolution is naturally limited.

[Purpose of the invention]

This invention provides a radiation J11m detector with high spatial resolution and high contrast resolution by a simple assembly process.
The object of the present invention is to provide a method that enables assembly and manufacturing with high efficiency.

[Summary of the invention]

The outline of the present invention for achieving the above-mentioned object is to fix a phosphor in the form of a block having a substantially rectangular shape on a support plate with a first adhesive having a low softening point. The scintillator elements are divided into a plurality of scintillator elements by cutting grooves so that connecting parts are formed near the surface, and then between adjacent scintillator elements 1-,
After being fixed together with a mixture having at least a light reflecting agent and a second adhesive having a softening point or decomposition point higher than the softening point of the first adhesive, the softening point of the first adhesive and the The support plate is separated by heating to a temperature between the softening point or decomposition point of the second adhesive, and then the connecting portion is removed, and each scintillator and photoelectric conversion element that are fixed together are joined. This is a percentage mark.

[Embodiments of the invention]

2 to 7 are schematic perspective views showing steps of a manufacturing method that is an embodiment of Jin's invention.

In the manufacturing method according to the present invention, as shown in FIG. 11 (hereinafter referred to as the first adhesive) on the support plate 12. The fluorescent substance is a substance that can convert X-rays into radiation. For example, cesium iodide doped with thallium (G tl ; 7'J
) s Bismuth kermanate (BiaGg*O1
x ) s Cadmium tungstate (Cd1VO4
) s Single crystal scintillators such as zinc tungstate (Zn1F'04) and magnesium tungstate (MgO2), as well as polycrystalline scintillators, can also 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 l in the direction can be 28H1 and the length l' in the longitudinal direction can be 60 fins. The support plate 12 only needs to have a flat surface at least where the phosphor 10 is placed. Further, the support plate 1
Preferably, the material 2 is made of a material that has high dimensional stability against heat and a low coefficient of thermal expansion. As will be described later, when the first adhesive 11 is heated to a softened or fluid state in order to separate the support plate 12 and the obtained scintillator element 16, the support plate 12 becomes clean. This is because if the scintillator elements 13 are bent or expanded, the arrangement of the scintillator elements 13 will be disturbed, and the performance of the resulting radiation detector will be degraded. The first adhesive 11 firmly adheres the phosphor 10 or mineral scintillator element 13 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 1-3 and the support plate 12, for example, an adhesive with a softening point of 80 to 90°C.
A hot melt adhesive can be suitably used. In particular, Adfix (trade name; manufactured by Nikka Seiko (Kyu)) is an available first adhesive 11. Solid iFi of the phosphor 10 on the support plate 12, for example the first adhesive 1 heated to a temperature above the softening point of 80-90°C
1 onto the support plate 12 by an appropriate method, and before the first adhesive 11 solidifies, the phosphor 10 is placed on the coated surface of the support plate 12 and cooled while being pressed. It can be done easily.

Next, the phosphor adhered to the support plate 12 as described above is cut into the scintillator element 1 using a groove cutting machine (multi-wire saw).
3. Machining grooves (see Figure 3).

The multi-wire saw is preferably one in which a large number of wires 14 of about 100 to 200 μm are arranged at intervals of, for example, 1 off. The distance between the wire saws 14 and the required aesthetic density of the scintillator elements 13 can be appropriately determined. Note that the direction in which the grooves are processed is a direction perpendicular to, for example, the longitudinal direction of the phosphor 10. When grooves are formed in the above direction, it can be divided into a large number of strip-shaped scintillator elements 13 arranged at a predetermined pitch. However, the groove machining may completely cut off the phosphor 10, and the support plate 12 of the phosphor 10 may not be completely cut off.
In other words, after the groove processing, each scintillator element 13 formed is formed by the groove processing rather than being integrally connected at the connection portion. In this case, the arrangement accuracy is determined by the height t and longitudinal length l of each scintillator element 16.
are the same, the upper surfaces of each scintillator element 13 are all on the same plane, and, for example, the ridges (m) of each scintillator element 13 are all on the same straight line.If there is a deviation in accuracy, , that is each scintillator element 130
However, this width W depends on the mutual spacing of the wire saws 14, and since the mutual spacing of the wire saws 14 can be set to be sufficiently equal, the width W of each scintillator element 13 obtained is can be made almost the same.

In addition, in an experiment, the standard deviation of W was several μm. In addition, since the phosphor 10 is firmly fixed on the support plate 12 with the first adhesive 11, the phosphor 10 does not get stuck on the support plate 12 during groove processing. Since the connecting portions formed by the above are firmly fixed on the support plate 12 with the first adhesive 11, the positions of the scintillator elements 16 will not shift or the scintillator elements 16 will not be in a chess position.

Next, as described above, the aluminum sheet 19 coated with a light reflecting agent is placed in the grooves between the scintillator elements 13 fixed on the support plate 12 and arranged at a predetermined pitch using an adhesive (hereinafter referred to as 2) is inserted, and each scintillator element 16f is fixed to each other (see FIG. 4). The light reflecting agent may be any material as long as it can reflect the light emitted by the scintillator element 13, and examples thereof include light reflecting agents containing titanium dioxide (TiO2), barium sulfate (BaSO4), and the like. The second adhesive preferably has a good percent light transmittance and is much higher in softening point than the first adhesive. The reason why the second adhesive needs to have a high softening point or high decomposition point is that regardless of the heating conditions when separating the support plate 12 or the stress when separating the support plate 12, the second adhesive has a high softening point or high decomposition point. This is because it is necessary to connect all of the scintillator elements 16 together while maintaining pitch accuracy. Further, the reason why the second adhesive needs to have good light transmittance is to prevent light absorption between the scintillator elements 16. A second adhesive with such requirements, for example, has a softening point or decomposition point of 200 to 600.
Examples include epoxy adhesives that are ℃. However, other additives may be mixed in to prevent the second adhesive from deteriorating due to heating.

Next, in the manner described above, the scintillator elements 16 were each inserted into the grooves through the aluminum sheet 19 with the repellent applied thereto and the second adhesive.

The scintillator element 13 and the support plate 12 which have been integrated with each other are separated by heating the support plate 12 which is fixed to each other and the scintillator element 13 is fixed with the first adhesive 11 (p1). (See Figure 4). In this case, the heating temperature may be any temperature at which the first adhesive 11 softens or flows to the extent that the scintillator element 16 and the support plate 12 can be separated with a slight force. The temperature may be slightly higher than the softening point of the adhesive 11 in No. 1. In addition, it is preferable that the heating operation is performed so that heat is applied only to the first adhesive 11. For example, the scintillator element 13 is placed on a hot grate heated to a predetermined temperature.
This can be done by placing a support plate 12 on which the parts are fixed.

The scintillator element 16 obtained by separating from the support plate 12 in this manner is shown in the 51st figure. Each scintillator element 13 shown in FIG.
It is integrated with 4. Next, the element 13 is attached overnight to the cinch from the surface to which it is fixed to the support plate 12 to a certain height and depth.
The connection 13.4 is removed, for example by sanding or lapping the part. As a result, as shown in FIG. 6, each scintillator element 13tj can be made completely independent and connected together with an adhesive. If t in FIG. 5 is, for example, 2.2N, then t' in FIG. 6 can be reduced to, for example, 2.2N by polishing or lapping. It can be turned off.

Note that the connecting portion 13. (In the removal process, it is preferable to attach a reinforcing plate 15 as shown in FIG. 7.

This is to prevent deviations in the arrangement accuracy of each scintillator element 13.

Next, the photoelectric conversion element 16 formed on the rectangular plate-shaped protective substrate 17 and the bottom surface of the scintillator element 13 integrated with each other as described above are glued together with a lens adhesive (see FIG. 7). ). 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 13 into an electrical signal according to the amount of light.
Examples include photodiodes and phototransistors, which can be formed on the protective substrate 17-1 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 16, and is formed with the same pitch as the arrangement pitch of the integrated scintillator elements 16 as described above. In addition, the protective board 17
At the top, a part of the exposed surface of the photoelectric conversion element 16 is extended to provide an output terminal 18 for extracting the current signal output from the photoelectric conversion element 16 and connecting it to a subsequent circuit, such as an amplifier. It is also preferable to form the same. The lens adhesive is an optically clear 4f#, N agent, and adhesives based on Canada balsam, epoxy resin, cyanoacrylate, etc. can be used, for example.

Through the above steps, as shown in FIG. 8, each scintillator element 16 converts the X-rays incident from above into a light amount corresponding to the amount of X-rays, and the optical conversion element 16 converts the light into a light amount corresponding to the amount of X-rays. It is possible to manufacture radiation detectors that can be converted into electrical signals. The above process basically consists of forming grooves in the phosphor and bonding various parts, so that the radiation detector can be manufactured with simple operations. Furthermore, since the mutual spacing between the wire saws 14 can be freely set when machining the grooves, by reducing the mutual spacing, it is possible to reduce the arrangement pitch of each scintillator element 1'5 in the radiation detector. I can do it,
A radiation detector with high spatial resolution can be manufactured. Moreover, since the support plate 12JC is firmly fixed 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 embodiment described above, and can be modified and implemented as appropriate without changing the gist of the invention.

The shape of the reinforcing plate 15 used as necessary in the above embodiment was a rectangular plate that covered a part of the side surface of the rectangular parallelepiped formed by combining each scintillator element 16 (see FIG. 7). The shape of the scintillator element 15 is not limited to this, but may be a rectangular plate-like shape that covers all of the side surfaces of the rectangular parallelepiped, or a cross-sectional shape that covers a part of the upper surface of the scintillator element 13. Good too. The larger the area of the reinforcing plate 150 is, the more the accuracy of the arrangement of the scintillator elements 13 can be prevented. Note that a reflective agent may be applied to the inner surface of the reinforcing plate 15.

In the embodiment described above, the reflector plate 19 is inserted into the mutual gap between the scintillator elements 16, but the entire surface of each scintillator element 16 except for the X-ray incident surface and the bottom surface opposite thereto is coated with vapor deposition, sputtering, etc. The evening reflection M may also be formed. Forming a reflective film on the entire surface prevents leakage.

The emitted light can be efficiently converted into an electrical signal by the photoelectric conversion element 16.

〔Effect of the invention〕

According to the manufacturing method according to the present invention, the assembly process is simple, the assembly accuracy is high, and performance such as spatial resolution is excellent.
It is possible to manufacture radiation detectors with

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing a conventional radiation detector, FIGS. 2 to 7 are schematic perspective views showing steps of a manufacturing method according to an embodiment of the present invention, and FIG. It is a schematic perspective view showing the radiation detector obtained by manufacturing by the method concerning. 10... Fluorescent substance, 11... First adhesive, 12
...Support plate, 16...Scintillator element,
14...Wire saw, 15...Reinforcement plate,
18...Output terminal, 19...Reflector. Agent Patent Attorney Noriyuki Chika (and 1 other person) Figure 3 11 Figure 4 Figure 8

Claims (7)

[Claims] (1) A block-like phosphor having a substantially rectangular parallelepiped shape is fixed on a support plate with a first adhesive having a low softening point.''!, 11
The scintillator elements are divided into a plurality of scintillator elements by cutting grooves so that connecting parts are formed in the vicinity of the solid swamp, and then the space between adjacent scintillator elements is heated below the softening point of the light reflecting agent and the first adhesive. After bonding together with a mixture having at least a second adhesive having a high softening point or decomposition point, the softening point of the first adhesive and the softening point or decomposition point of the second adhesive are bonded together. Manufacturing a radiation detector characterized in that the supporting plate is separated by heating to a temperature between 1 and 2, and then the connecting portion is removed, and each scintillator and photoelectric conversion element that are fixed together are joined. Method. (2) Manufacturing a radiation detector according to claim 1, characterized in that the phosphor is selected from the group of cadmium tungstate, magnesium tungstate, zinc tungstate, and bismuth germanate. Method. (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 radiation according to any one of claims 1 to 3, wherein the first adhesive is a hot melt adhesive. Method for manufacturing R detector. (5) Claims 1 to 4, wherein the second adhesive is a transparent epoxy adhesive.
A method for manufacturing a radiation detector according to any one of paragraphs. (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.