Scintillator array, radiation detector, and radiation inspection device

Abstract

To solve such a problem that a scintillator array with less warpage and variations in the outer shape dimension is demanded while the resolution of a diagnostic image of a radiation detector has been increased.SOLUTION: A scintillator array includes: a structure having scintillator segments and a first reflective layer, the first reflective layer surrounding each of the scintillator segments and being provided between the scintillator segments arrayed in the vertical direction of the scintillator segments and between the scintillator segments arrayed in the lateral direction of the scintillator segments and being configured to reflect light; and a layer provided so as to be in contact with the surface of the structure and having a second reflective layer being configured to reflect light. The first reflective layer protrudes from the surface of the structure between the scintillator segments arrayed in the vertical direction and between the scintillator segments arrayed in the lateral direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present embodiment relates to a scintillator array, a radiation detector, and a radiation inspection device. [Background technology]

[0002] In the fields of medical diagnosis and industrial non-destructive testing, inspections are performed using radiological inspection equipment such as X-ray computed tomography (hereinafter referred to as X-ray CT equipment). X-ray CT equipment consists of an X-ray tube (X-ray source) that emits a fan-shaped X-ray beam, and an X-ray detector equipped with multiple X-ray detection elements, which are arranged opposite each other across the tomographic plane of the object being inspected.

[0003] X-ray CT equipment rotates while irradiating the object under inspection with a fan beam of X-rays from the X-ray tube, and the X-ray detector collects absorption data of the X-rays that pass through the object. The X-ray absorption data is then analyzed by a computer to reconstruct a tomographic image.

[0004] The radiation detectors of X-ray CT scanners widely use detection elements that use solid scintillators. Radiation detectors equipped with detection elements that use solid scintillators can easily reduce the size of the detection elements and increase the number of channels, which can further improve the resolution of X-ray CT scanners and other devices.

[0005] Radiation inspection devices such as X-ray CT scanners are used in a variety of fields, including medical and industrial applications. Examples of X-ray CT scanners include multi-slice devices in which detector elements such as photodiodes are arranged two-dimensionally, vertically and horizontally, with a scintillator array mounted on top. Multi-slice devices can overlay computed tomography (CT) images, allowing for three-dimensional display of the CT image.

[0006] A radiation detector installed in a radiological inspection device has multiple detector elements arranged in multiple rows and columns, each with a scintillator segment. The radiation detector converts X-rays incident on the scintillator segments into visible light, which is then converted into an electrical signal by the detector elements to form an image. In recent years, detector elements have been made smaller to achieve higher resolution, and the pitch between adjacent detector elements has also been narrowed. As a result, the size of the scintillator segments has also been reduced.

[0007] Among the various scintillator materials used for the scintillator segments described above, rare earth oxysulfide phosphor ceramics have high luminous efficiency and properties suitable for use in scintillator segments. For this reason, radiation detectors that combine scintillator segments processed by cutting or grooving a sintered body (ingot) of rare earth oxysulfide phosphor ceramics, which is the scintillator material, with a photodiode as a detection element are becoming increasingly popular.

[0008] An example of a scintillator using phosphor ceramics includes a scintillator made of a sintered body of a gadolinium oxysulfide phosphor. A scintillator array using the above scintillator is manufactured, for example, as follows. First, a rare earth oxysulfide phosphor powder, which is the scintillator material, is molded into an appropriate shape and sintered to form a sintered body (ingot). This sintered body is then cut, such as by cutting or grooving, to form scintillator segments corresponding to multiple detection elements. Furthermore, a reflective layer that reflects light is formed between these scintillator segments to integrate them, thereby manufacturing a scintillator array.

[0009] When using the scintillator array described above in a radiation detector, the dimensional accuracy of the scintillator array affects the resolution of CT diagnostic images. Furthermore, radiation detectors installed in X-ray CT systems are subjected to temperatures ranging from 50°C to 60°C. In scintillator arrays with a resin-containing reflective layer, the reflective layer expands when heated and contracts when cooled, resulting in minute dimensional changes between adjacent scintillator segments, i.e., pitch misalignment between the scintillator segments and dimensional variations primarily due to warping of the scintillator array. Such warping and dimensional variations can cause uneven adhesive layer thickness when attached to the detector diode array, degrading the resolution of the radiation detector's diagnostic images. As the resolution of diagnostic images from radiation detectors continues to increase, there is a demand for scintillator arrays with minimal warping and dimensional variations. Furthermore, as the detection area of ​​radiation detectors continues to shrink, uniformity of the adhesive layer between the scintillator array and the diode array is becoming increasingly important. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 5,866,908 [Patent Document 2] International Publication No. 2017 / 082337 [Patent Document 3] International Publication No. 2017 / 110850 Summary of the Invention

[0011] The scintillator array of the embodiment comprises a structure having a plurality of scintillator segments, a first reflective layer surrounding each of the plurality of scintillator segments and being provided between the vertically arranged scintillator segments of the plurality of scintillator segments and between the horizontally arranged scintillator segments of the plurality of scintillator segments, and reflecting light, wherein each of the plurality of scintillator segments is made of a sintered body, and a second reflective layer provided on the structure and reflecting light. The first reflective layer includes a resin and reflective particles that reflect light. The first reflective layer has first portions that protrude further toward the second reflective layer than the scintillator segments between the vertically arranged scintillator segments and between the horizontally arranged scintillator segments. The ratio D / T of the length D of the first portion to the thickness T of the second reflective layer is not less than 0.10 and not more than 1.00. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a plan view showing an example of the structure of a scintillator array according to an embodiment. [Figure 2] FIG. 1 is a cross-sectional view showing an example of the structure of a conventional scintillator array. [Figure 3] 1 is a cross-sectional view showing an example of the structure of a scintillator array according to an embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing another example of the structure of the scintillator array according to the embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing another example of the structure of the scintillator array according to the embodiment. [Figure 6] FIG. 10 is a cross-sectional view showing another example of the structure of the scintillator array according to the embodiment. [Figure 7] 10A to 10C are cross-sectional views illustrating an example of a method for manufacturing a scintillator array. [Figure 8] 10A to 10C are cross-sectional views illustrating an example of a method for manufacturing a scintillator array. [Figure 9] 10A to 10C are cross-sectional views illustrating an example of a method for manufacturing a scintillator array. [Figure 10] 10A to 10C are cross-sectional views illustrating an example of a method for manufacturing a scintillator array. [Figure 11] FIG. 1 is a diagram illustrating an example of the configuration of a radiation detector. [Figure 12] FIG. 1 is a diagram illustrating an example of the configuration of a radiological inspection apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments will be described with reference to the drawings. The relationship between the thickness and planar dimensions of each component, the thickness ratio of each component, etc. shown in the drawings may differ from the actual product. Furthermore, in the embodiments, substantially identical components are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0014] A scintillator array, a radiation detector, and a radiation inspection apparatus according to the embodiments will be described below.

[0015] (Scintillator Array) FIG. 1 is a plan view showing an example of the structure of a scintillator array according to an embodiment. FIG. 2 is a cross-sectional view showing an example of the structure of a conventional scintillator array. FIG. 3 is a cross-sectional view showing an example of the structure of a scintillator array according to an embodiment. FIGS. 4, 5, and 6 are cross-sectional views showing other examples of the structure of a scintillator array according to an embodiment. FIGS. 1 to 6 illustrate a scintillator array 1, scintillator segments 2, a reflective layer 3, and a reflective layer (top plate reflective layer) 4. For convenience, the reflective layer 4 is omitted in FIG. 1.

[0016] The scintillator array 1 includes a plurality of scintillator segments 2, a reflective layer 3, and a reflective layer 4. The scintillator segments 2 and the reflective layer 3 form a structure 20 having a surface 20a, which is the X-ray incident surface, and a surface 20b opposite to surface 20a. The number of scintillator segments 2 is set appropriately depending on the structure, resolution, etc. of the radiation detector.

[0017] In a conventional scintillator array, as shown in Fig. 2, the surface 20a extends flush from the scintillator segment 2 to the reflective layer 3. In contrast, in an example of a scintillator array according to an embodiment, the reflective layer 3 partially penetrates into the reflective layer 4 in a cross section in the thickness direction of the scintillator array 1, as shown in Fig. 3. In other words, the reflective layer 3 has a portion that extends into the reflective layer 4.

[0018] 4 , in another example of the scintillator array of the embodiment, the reflective layer 4 may be attached to the surface 20a via the adhesive layer 5, and in a cross section of the scintillator array 1 in the thickness direction, the reflective layer 3 may be configured to partially penetrate into the interior of the reflective layer 4 through the adhesive layer 5. In other words, the reflective layer 3 has a portion that extends into the interior of the reflective layer 4 via the adhesive layer 5.

[0019] 5 , in another example of the scintillator array of the embodiment, the reflective layer 4 is bonded onto the surface 20a via the adhesive layer 5, and in a cross section of the scintillator array 1 in the thickness direction, the reflective layer 3 may partially penetrate into the adhesive layer 5 but may not penetrate into the reflective layer 4. In other words, the reflective layer 3 extends into the adhesive layer 5 and has a portion that does not extend to the reflective layer 4.

[0020] In another example of the scintillator array of the embodiment, as shown in Figure 6, the reflective layer 4 may be attached to the surface 20a via an adhesive layer 5, and in a cross section of the thickness direction of the scintillator array 1, a portion of the reflective layer 3 may penetrate the reflective layer 4.

[0021] The scintillator segments 2 convert incident radiation (X-rays) into light (visible light). A plurality of scintillator segments 2 are integrated together by a reflective layer 3 that adheres to them to form a structure 20.

[0022] The reflective layer 3 reflects light (visible light). The reflective layer 3 is capable of transmitting X-rays. The reflective layer 3 is provided between adjacent scintillator segments 2 and adheres to each scintillator segment 2.

[0023] The reflective layer 4 reflects light (visible light). The reflective layer 4 is capable of transmitting X-rays. The reflective layer 4 is provided on the surface 20a and covers the structure 20, as shown in FIG.

[0024] The scintillator array 1 may have either a structure in which a plurality of scintillator segments 2 are arranged in a line, or a structure in which a predetermined number of a plurality of scintillator segments 2 are arranged two-dimensionally in the vertical and horizontal directions, as shown in Fig. 1. When a plurality of scintillator segments 2 are arranged two-dimensionally, a reflective layer 3 is provided between the scintillator segments 2 arranged in the vertical direction and on the scintillator segments 2 arranged in the horizontal direction. The reflective layer 3 may surround the scintillator segments 2 along the surface 20a.

[0025] The scintillator segment 2 has a sintered body containing a rare earth oxysulfide phosphor. Examples of the rare earth oxysulfide phosphor include rare earth oxysulfide phosphors containing praseodymium (Pr) as an activator. Examples of rare earth oxysulfides include oxysulfides of rare earth elements such as yttrium (Y), gadolinium (Gd), lanthanum (La), and lutetium (Lu).

[0026] Rare earth oxysulfide phosphors are General formula: RE2O2S:Pr…(1) (RE represents at least one element selected from the group consisting of Y, Gd, La, and Lu) It is preferable that the composition be represented by the following formula:

[0027] Among the rare earth elements mentioned above, Gd has a particularly large X-ray absorption coefficient and contributes to improving the light output of the scintillator array 1. Therefore, it is more preferable that the scintillator segments 2 have a Gd2O2S:Pr phosphor (GOS phosphor). Note that a portion of Gd may be substituted with another rare earth element. In this case, the amount of Gd substituted with the other rare earth element is preferably 10 mol % or less. That is, the rare earth oxysulfide phosphor is General formula: (Gd1-x ,RE x )2O2S:Pr …(2) (wherein RE represents at least one element selected from the group consisting of Y, La, and Lu, and x is a number (atomic ratio) satisfying 0≦x≦0.1) It is preferable that the composition is substantially represented by the following formula:

[0028] The scintillator segments 2 may contain praseodymium (Pr) as an activator to increase light output. Pr can reduce afterglow compared to other activators. Therefore, rare earth oxysulfide phosphor ceramics containing Pr as an activator are effective as fluorescent emitters in radiation detectors.

[0029] The Pr content in the rare earth oxysulfide phosphor is preferably 0.001 mol % or more and 10 mol % or less relative to the content of the phosphor host (e.g., RE2O2S such as Gd2O2S). If the Pr content exceeds 10 mol %, the light output will decrease. If the Pr content is less than 0.001 mol %, the effect as a main activator cannot be fully obtained. The Pr content is more preferably 0.01 mol % or more and 1 mol % or less.

[0030] The rare earth oxysulfide phosphor may contain, in addition to Pr as the main activator, a trace amount of at least one element selected from the group consisting of cerium (Ce), zirconium (Zr), and phosphorus (P) as a co-activator. These elements are effective in suppressing exposure degradation and afterglow. The total content of these co-activators is preferably in the range of 0.00001 mol % to 0.1 mol % of the phosphor matrix.

[0031] The sintered body that constitutes the scintillator segment 2 is preferably made of high-purity rare earth oxysulfide phosphor ceramics (scintillator material). Impurities can reduce the sensitivity of the scintillator, so it is preferable to keep the impurity content as low as possible. In particular, phosphate radicals (PO4) can cause a decrease in sensitivity, so their content is preferably 100 ppm or less. When fluorides or other sintering aids are used to increase the density of the sintered body, the sintering aids remain as impurities, resulting in a decrease in sensitivity.

[0032] The sintered body has a cubic or rectangular parallelepiped shape. The volume of the scintillator segment 2 is 1 mm 3 By miniaturizing the scintillator segment 2, the detected image can be made more precise. The length (L), width (S), and thickness (T) of the scintillator segment 2 are not necessarily limited, but each is preferably 1 mm or less. When the volume of the scintillator segment 2 is 1 mm 3 When the width (W) of the reflective layer 3 is less than 40 μm, the width (W) of the reflective layer 3 can be reduced to 100 μm or less, or even 50 μm or less. However, when the width (W) of the reflective layer 3 is less than 40 μm, the manufacturing process becomes complicated, and therefore the width (W) of the reflective layer 3 is preferably 40 μm or more.

[0033] The reflective layer 3 contains a resin that transmits light (translucent resin) and reflective particles that are dispersed in the resin and reflect light. The resin contains at least one selected from the group consisting of epoxy resin, silicone resin, phenolic resin, urea resin, melamine resin, polyester resin, polyurethane resin, and acrylic resin. For example, the epoxy resin is preferably a hydrogenated epoxy resin or an epoxy silicone resin. The reflective particles contain at least one selected from the group consisting of titanium oxide, aluminum oxide (alumina), barium sulfate, zinc oxide, zirconium oxide, and silicon oxide. Note that air bubbles contained in the resin may also function as reflective particles.

[0034] The reflective layer 4 can be made of the same light-transmitting resin and reflective particles as the reflective layer 3.

[0035] The ratio of the light-transmitting resin to the reflective particles in the reflective layers 3 and 4 is preferably such that the mass ratio of the light-transmitting resin is 15% or more and 60% or less, and the mass ratio of the reflective particles is 40% or more and 85% or less. The sum of the mass ratio of the light-transmitting resin and the mass ratio of the reflective particles is 100%. If the mass ratio of the reflective particles is less than 40%, the reflection efficiency of the reflective layer decreases, and the reflection efficiency of the reflective layer for light with a wavelength of 512 nm is likely to fall below 90%. If the mass ratio of the reflective particles exceeds 85%, the reflection efficiency of the reflective layer remains unchanged, but the mass ratio of the light-transmitting resin decreases relatively, making it difficult to stably solidify the reflective layer.

[0036] When a pre-fabricated reflective layer 4 is bonded to the surface 20a of the structure 20, the adhesive layer 5 contains at least one resin selected from the group consisting of epoxy resin, silicone resin, phenolic resin, urea resin, melamine resin, polyester resin, polyurethane resin, polyolefin resin, and acrylic resin, which is cured by light, heat, or moisture. The adhesive layer 5 may be a light-transmitting resin, but in order to reduce the penetration of light from one scintillator segment 2 into another scintillator segment 2 through the adhesive layer 5, the adhesive layer 5 preferably contains at least one selected from the group consisting of titanium oxide, zirconium oxide, aluminum oxide, and silicon oxide.

[0037] As described above, the scintillator array of the embodiment has a configuration in which the reflective layer 3 partially bites into the reflective layer 4 or the adhesive layer 5.

[0038] Scintillators used in radiation detection devices such as X-ray CT scanners confine light generated by X-rays within pixels using a reflective layer, efficiently extracting it to the photodiode. Typically, the reflective layer is formed to fill the spaces between the scintillator segments, and in some cases, a top-plate reflective layer is formed on the X-ray incident side to cover the scintillator array. The light emitted by the scintillator in response to X-rays is efficiently guided to the photodiode either directly or via the reflective layer. The scintillator array incorporated in an X-ray detector is exposed to temperatures ranging from 50°C to 60°C and is kept at room temperature when not in operation. Furthermore, during operation, it rotates around the object being inspected at high speed, which applies forces to the array. A problem believed to be caused by these environmental temperature fluctuations and internal stresses associated with rotation is frequent peeling of the top-plate reflective layer from the scintillator array, and a solution is needed.

[0039] In response to this, a technology is known that suppresses variations in light output and distortion between scintillator segments by selecting the color of the reflective particles contained in the epoxy resin in the reflective layer between the scintillator segments and combining an epoxy resin with a glass transition point of 80°C or higher.

[0040] The glass transition point of the light-transmitting resin constituting the reflective layer is 50°C or higher, and the thermal expansion coefficient of the light-transmitting resin at temperatures higher than the glass transition point is 3.5 x 10 -5 / °C or less. Generally, the thermal expansion coefficient of a translucent resin changes significantly at the glass transition point, and warping that occurs with this change can be adjusted by adjusting the conditions.

[0041] Also, in order to reduce warping of the scintillator array, a scintillator array is known in which multiple scintillator segments are integrated by a reflective layer, the reflective layer has a translucent resin with a glass transition point of 50°C or higher, and the second reflective layer, which is arranged on the side of the multiple scintillator segments where X-rays are incident, has a translucent resin with a glass transition point of 30°C or lower.

[0042] These scintillator arrays can reduce warpage to some extent, but in scintillator arrays having a top plate reflective layer, they are not necessarily effective in preventing peeling of the top plate reflective layer, and further improvement is required.

[0043] The materials used for the top plate reflective layer and the scintillator segments have large differences in their linear expansion coefficients and elastic moduli. When the scintillator array is incorporated into a detector and exposed to fluctuations in the ambient temperature and centrifugal forces associated with rotation, these differences generate stress, causing the top plate reflective layer to peel off.

[0044] In contrast, in this embodiment, by making the reflective layer 3 sink into the reflective layer 4 or the adhesive layer 5, the contact area is increased by these unevenness, and a so-called anchor effect is obtained, thereby preventing the reflective layer 4 from peeling off.

[0045] Table 1 shows examples of the incidence of peeling in forced tests for a conventional scintillator array with the structure shown in Figure 2 and a scintillator array with the structure shown in Figure 3. The forced test involves heating the scintillator array from room temperature to 50°C in 5 minutes, leaving it for 10 minutes, and then rotating it at room temperature at a rotation speed of 200 rpm for 5 minutes. These operations constitute one cycle, and 100 cycles were performed on each sample. In a forced test of 100 prototype samples, there was no peeling in the scintillator array with the structure shown in Figure 3, which indicates that peeling resistance is significantly improved.

[0046] [Table 1]

[0047] As shown in Figures 3, 4, 5, and 6, the scintillator array of the embodiment has a structure in which the reflective layer 3 partially penetrates into the layer including the reflective layer 4. However, as the penetration length becomes shorter, the peeling prevention effect decreases. To achieve an effective peeling prevention effect, in a cross section of the scintillator array 1 in the thickness direction, the ratio D / T of the length D of the portion of the reflective layer 3 extending into the layer including the reflective layer 4 to the thickness T of the reflective layer 4 or the reflective layer 4 and adhesive layer 5 (the layer including the reflective layer 4) is preferably in the range of 0.10 to 1.00, more preferably in the range of 0.20 to 1.00. The thickness T and length D can be measured from the image obtained by observing the cross section of the scintillator array 1 in the thickness direction using an electron microscope or optical microscope. The reflective layer 3, reflective layer 4, and adhesive layer 5 each form a polymer network structure, so the interfaces between these layers are clearly defined. Furthermore, when the pigment concentrations are different, the interfaces are even clearer, making it easier to determine the thickness T and length D.

[0048] Next, a description will be given of an example of a method for manufacturing the scintillator array 1. The scintillator array 1 is manufactured as follows. Here, the scintillator array 1 having the structure shown in FIG. 4 will be described as an example.

[0049] 7 to 10 are cross-sectional views illustrating an example of a method for manufacturing a scintillator array according to an embodiment. First, in a first step, a white sheet of a predetermined size is formed from a resin such as an epoxy resin containing a white reflective material.

[0050] The white sheet can be formed using a material such as a mixture of reflective particles and a light-transmitting resin or a lacquer-based paint. The mixture of reflective particles and a light-transmitting resin preferably has the same structure as the reflective layer 3. A commercially available white sheet may be used as the white sheet.

[0051] The white sheet forms the reflective layer 4, and its thickness is in the range of 50 μm to 250 μm. If the thickness is less than 50 μm, the effect of improving the light reflection efficiency cannot be sufficiently obtained. If the thickness exceeds 250 μm, the amount of transmitted X-rays decreases, resulting in a decrease in detection sensitivity.

[0052] In the first step, a scintillator material such as a rare earth oxysulfide phosphor sintered body is cut into a thin plate of a predetermined size (thickness: 0.5 mm to 2 mm), and as shown in Figure 7, the plate-shaped sintered body 2a and a white sheet that forms the reflective layer 4 are bonded together via an adhesive layer 5 made of epoxy resin or the like.

[0053] Next, in the second step, as shown in Fig. 8, the sintered body 2a is grooved by dicing to partially remove the sintered body 2a, thereby forming the scintillator segments 2 and the grooves S. In the cross section of the sintered body 2a in the thickness direction, the width of the grooves S is, for example, in the range of 40 µm to 200 µm. The grooves S extend into the interior of the reflective layer 4 through the sintered body 2a and the adhesive layer 5.

[0054] Next, in the third step, a reflective layer 3 is formed in the grooves S formed in the second step, as shown in Fig. 9. First, reflective particles and an uncured resin composition (uncured translucent resin) constituting the translucent resin are prepared, and a slurry, which is a mixture of these, is poured into the grooves S.

[0055] The uncured resin composition preferably has a viscosity of 0.2 Pa·s or more and 1.0 Pa·s or less (200 cps or more and 1000 cps or less). If the viscosity of the resin composition exceeds 1.0 Pa·s, the fluidity is poor, reducing the workability of injecting the resin into the grooves S. If the viscosity of the resin composition is less than 0.2 Pa·s, the fluidity becomes too high, reducing the applicability or filling ability. In addition, the total light transmittance of the translucent resin is preferably 85% or more. If the total light transmittance of the translucent resin is less than 85%, the reflection efficiency of the reflective layer 3 is likely to decrease.

[0056] After the slurry is poured into the grooves S, it is cured to form a reflective layer 3, thereby bonding and integrating adjacent scintillator segments 2 to form a structure 20. The curing treatment of the slurry is appropriately set depending on the type of uncured resin composition and curing agent, etc. For example, in the case of a thermosetting resin composition, the curing reaction is advanced by heat treatment. In the case of a resin composition such as a two-component epoxy resin, the curing reaction may be advanced by leaving it at room temperature.

[0057] Next, in the fourth step, unnecessary portions of the periphery of the structure 20 are removed, and then polished, as shown in Fig. 10. Through the steps above, the scintillator array 1 can be manufactured.

[0058] (Radiation detector) The radiation detector of this embodiment includes the scintillator array 1 described above as a fluorescence generator that emits light in response to incident radiation, and further includes a photoelectric converter that receives light from the fluorescence generator and converts the optical output into an electrical output. Fig. 11 is a diagram showing an example of the configuration of a radiation detector, and illustrates an X-ray detector. The X-ray detector 6 shown in Fig. 11 includes the scintillator array 1 as a fluorescence generator and a photoelectric conversion element 7 as a photoelectric converter.

[0059] The X-ray detector 6 includes a photoelectric conversion element 7 integrally provided on the surface 20b of the structure 20. The photoelectric conversion element 7 detects light (visible light) formed by converting X-rays in the scintillator segments 2. Examples of the photoelectric conversion element 7 include a photodiode, etc. The photoelectric conversion element 7 is arranged to correspond to each of the multiple scintillator segments 2. These components make up the radiation detector.

[0060] (Radiation inspection equipment) The radiation inspection apparatus of the embodiment includes a radiation source that irradiates radiation toward an object under inspection, and a radiation detector that detects radiation that has passed through the object under inspection. The radiation detector may be any of the radiation detectors of the above-described embodiments.

[0061] Fig. 12 is a diagram showing an example of the configuration of a radiological inspection apparatus. Fig. 12 illustrates an X-ray CT apparatus 10, a subject 11, an X-ray tube 12, a computer 13, a display 14, and a subject image 15. The X-ray CT apparatus 10 includes an X-ray detector 6. The X-ray detector 6 is attached, for example, to the inner wall surface of a cylinder on which an imaging region of the subject 11 is disposed. An X-ray tube 12 that emits X-rays is installed approximately at the center of the arc of the cylinder to which the X-ray detector 6 is attached. The subject 11 is disposed between the X-ray detector 6 and the X-ray tube 12. A collimator (not shown) is provided on the X-ray incident surface side of the X-ray detector 6.

[0062] The X-ray detector 6 and the X-ray tube 12 are configured to rotate around the subject 11 while taking X-ray images. Image information of the subject 11 is collected three-dimensionally from different angles. Signals obtained by X-ray imaging (electrical signals converted by photoelectric conversion elements) are processed by a computer 13 and displayed as a subject image 15 on a display 14. The subject image 15 is, for example, a tomographic image of the subject 11. As shown in FIG. 1, a multi-tomographic image type X-ray CT device 10 can be configured by using a scintillator array 1 in which scintillator segments 2 are arranged two-dimensionally. In this case, multiple tomographic images of the subject 11 are taken simultaneously, and the imaging results can be depicted three-dimensionally, for example.

[0063] The X-ray CT device 10 shown in FIG. 12 includes an X-ray detector 6 having a scintillator array 1. As described above, the scintillator array 1 has a high reflection efficiency of visible light emitted from the scintillator segments 2 based on the configuration of the reflective layers 3 and 4, and therefore has excellent optical output. By using an X-ray detector 6 having such a scintillator array 1, the imaging time using the X-ray CT device 10 can be shortened. As a result, the exposure time of the subject 11 can be shortened, making it possible to achieve low exposure. The radiation inspection device (X-ray CT device 10) is not limited to X-ray inspection for medical diagnosis of the human body, but can also be applied to X-ray inspection of animals and X-ray inspection for industrial purposes. Furthermore, it also contributes to improving the inspection accuracy of X-ray nondestructive inspection devices. [Example]

[0064] A specific example of the scintillator array 1 and the evaluation results thereof will be described.

[0065] To demonstrate the examples and comparative examples, a plate-shaped sintered body 2a was fabricated as follows. Phosphor powder having a composition of Gd2O2S:Pr (Pr concentration = 0.05 mol%) was preformed using a rubber press. This preform was then degassed and sealed in a tantalum (Ta) capsule and placed in a hot isostatic pressing (HIP) treatment device. Argon gas was sealed into the HIP treatment device as a pressurizing medium, and the HIP treatment was performed at a pressure of 147 MPa and a temperature of 1425°C for 3 hours. In this way, a cylindrical sintered body approximately 80 mm in diameter and 120 mm in height was fabricated. GOS ceramic plates of various sizes were cut out from this sintered body to form the sintered body 2a for the examples and comparative examples.

[0066] Example 1 A white polyethylene terephthalate (PET) film (Mitsubishi Chemical, 100 μm thick) with a surface area slightly larger than that of the sintered body 2a was bonded to the surface of a GOS ceramic plate measuring 76 mm in length, 25 mm in width, and 1.2 mm in thickness using an epoxy adhesive as an adhesive layer 5. The GOS ceramic plate, epoxy adhesive, and white PET film were stacked and heated to 100°C under a 16 kg load. After cooling to room temperature, the load was removed to form a laminate. The surface of the GOS ceramic plate in this laminate was diced to form grooves, forming scintillator segments 2 and grooves S. The grooves S were 1.25 mm deep and extended into the white PET film. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, which was then thermally cured. The surface of the scintillator segments 2 was then polished. The edges were then cut to produce a scintillator array 1 shown in Figure 4. The ratio D / T of the length D of the portion of the reflective layer 3 extending into the layer including the reflective layer 4 to the thickness T of the layer including the reflective layer 4 was 0.40.

[0067] Example 2 A slurry containing titanium oxide and epoxy resin was applied to the surface of a GOS ceramic plate measuring 76 mm in length, 25 mm in width, and 1.2 mm in thickness. The slurry was then thermally cured and polished to form a reflective layer 4 with a thickness T of 0.3 mm. The surface of the GOS ceramic plate was then diced to form grooves, forming scintillator segments 2 and grooves S. The grooves S were 1.25 mm deep and extended into the reflective layer 4. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, the slurry was thermally cured, and the surface of the scintillator segments 2 was polished by 0.1 mm. The surface of the reflective layer 4 was then polished by 0.1 mm, and the peripheral edges were cut to produce a scintillator array 1 similar to that shown in Figure 3. The D / T ratio was 0.25.

[0068] Example 3 A slurry containing titanium oxide and epoxy resin was applied to the surface of a 76 mm long, 25 mm wide, and 1.2 mm thick GOS ceramic plate. The slurry was then heat-cured and polished to form a 0.3 mm thick reflective layer 4. The surface of the GOS ceramic plate was then diced to form grooves, forming scintillator segments 2 and grooves S. The grooves S were 1.4 mm deep and extended into the reflective layer 4. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, heat-cured, and the surface of the scintillator segments 2 was polished 0.1 mm. The surface of the reflective layer 4 was then polished 0.15 mm, penetrating the reflective layer 4 to expose the reflective layer 3 on the surface of the reflective layer 4. The peripheral portion was then cut to produce a scintillator array 1. The D / T ratio was 1.00.

[0069] Example 4 A slurry containing titanium oxide and epoxy resin was applied to the surface of a GOS ceramic plate measuring 76 mm in length, 25 mm in width, and 1.2 mm in thickness. The slurry was then thermally cured and polished to form a reflective layer 4 with a thickness of 0.3 mm. The surface of the GOS ceramic plate was then diced to form grooves, forming scintillator segments 2 and grooves S. The grooves S were 1.22 mm deep and extended into the reflective layer 4. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, the slurry was thermally cured, and the surface of the scintillator segments 2 was polished by 0.1 mm. The surface of the reflective layer 4 was then polished by 0.1 mm, and the peripheral edges were cut to produce a scintillator array 1 similar to that shown in Figure 3. The D / T ratio was 0.10.

[0070] Example 5 A slurry containing titanium oxide and epoxy resin was applied to the surface of a GOS ceramic plate measuring 76 mm in length, 25 mm in width, and 1.2 mm in thickness. The slurry was then thermally cured and polished to form a reflective layer 4 with a thickness of 0.3 mm. The surface of the GOS ceramic plate was then diced to form grooves, forming scintillator segments 2 and grooves S. The grooves S were 1.35 mm deep and extended into the reflective layer 4. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, the slurry was thermally cured, and the surface of the scintillator segments 2 was polished by 0.1 mm. The surface of the reflective layer 4 was then polished by 0.1 mm, and the peripheral edges were cut to produce a scintillator array 1 similar to that shown in Figure 3. The D / T ratio was 0.75.

[0071] (Comparative Example 1) A GOS ceramic plate measuring 76 mm in length, 25 mm in width, and 1.2 mm in thickness was grooved by dicing to form scintillator segments 2 and grooves S. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, the slurry was thermally cured, and then polished to form a reflective layer 3. A slurry containing titanium oxide and epoxy resin was applied to the X-ray incidence surface of this structure 20, and the slurry was heated at 100°C for 3 hours to cure. To achieve a thickness of 150 μm, the plate was polished after curing to form a reflective layer 4, and the scintillator array 1 was produced. The reflective layer 3 does not extend to the reflective layer 4.

[0072] (Comparative Example 2) A GOS ceramic plate measuring 76 mm in length, 25 mm in width, and 1.2 mm in thickness was diced to form grooves to form scintillator segments 2 and grooves S. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, the slurry was thermally cured, and then polished to form a reflective layer 3. Next, a white PET film (manufactured by Mitsubishi Chemical, 100 μm thick) was bonded to the structure 20 via an epoxy adhesive as the reflective layer 4. When bonding, the structure 20, the epoxy adhesive, and the white PET film were stacked and heated to a temperature of 100°C under a load of 16 kg. After cooling to room temperature, the load was removed, and the scintillator array 1 was produced. The reflective layer 3 did not extend to the reflective layer 4.

[0073] (Comparative Example 3) A GOS ceramic plate measuring 76 mm in length, 25 mm in width, and 1.2 mm in thickness was grooved by dicing to form scintillator segments 2 and grooves S. A slurry containing titanium oxide and epoxy resin was poured into the grooves S, the slurry was thermally cured, and then polished to form a reflective layer 3. A slurry containing titanium oxide and epoxy resin was applied to the X-ray incidence surface of this structure 20 and cured by heating at a temperature of 100°C for 4 hours. To achieve a thickness of 100 μm, the structure was polished after curing to form a reflective layer 4, and the scintillator array 1 was produced. The reflective layer 3 does not extend to the reflective layer 4.

[0074] The peelability of the reflective layer 4 in the examples and comparative examples was evaluated by the following forced test. The obtained scintillator array 1 was placed in a thermo-hygrostat and left at -20°C for 30 minutes, then heated to 60°C at a heating rate of 5°C / min, left at 60°C for 30 minutes, and then cooled to -20°C at a heating rate of 5°C / min. This cycle was repeated 1000 times, and the periphery of the scintillator array 1 was observed to evaluate whether peeling had occurred. The humidity during the test was 40% RH (relative humidity). The results are shown in Table 2.

[0075] [Table 2]

[0076] As can be seen from Table 2, in the scintillator array 1 of the example, the reflective layer 3 between the scintillator segments 2 was extended and embedded into the layer including the reflective layer 4, thereby integrating the scintillator segments 2, and a significant difference was observed between the example and the comparative example in the peelability of the reflective layer 4. Even when the degree of embedding was small, peeling was less than in the comparative example.

[0077] The scintillator array of the embodiment can be said to be industrially useful because it can substantially eliminate peeling of the reflective layer 4, which has occurred at a certain rate in the past.

Claims

1. a structure comprising: a plurality of scintillator segments; and a first reflective layer surrounding each of the plurality of scintillator segments, the first reflective layer being provided between vertically arranged scintillator segments among the plurality of scintillator segments and between horizontally arranged scintillator segments among the plurality of scintillator segments, the first reflective layer reflecting light, wherein each of the plurality of scintillator segments is made of a sintered body; a second reflective layer provided on the structure and reflecting light; Equipped with The first reflective layer comprises: Resin and Reflective particles that reflect light; Including, the first reflective layer has first portions that protrude further toward the second reflective layer than the scintillator segments between the vertically arranged scintillator segments and between the horizontally arranged scintillator segments, A scintillator array, wherein a ratio D / T of a length D of the first portion to a thickness T of the second reflective layer is 0.10 or more and 1.00 or less.

2. 2. The scintillator array of claim 1, wherein the first reflective layer is provided on a side of the structure and has a second portion that protrudes from the side toward the second reflective layer beyond the scintillator segments.

3. further comprising an adhesive layer provided between the structure and the second reflective layer; The scintillator array of claim 1 , wherein the first portion contacts the adhesive layer.

4. further comprising an adhesive layer provided between the structure and the second reflective layer; The scintillator array of claim 1 , wherein the first portion passes through the adhesive layer and contacts the second reflective layer.

5. further comprising an adhesive layer provided between the structure and the second reflective layer; The scintillator array of claim 1 , wherein the first portion penetrates the adhesive layer and the second reflective layer.

6. further comprising an adhesive layer provided between the structure and the second reflective layer; The scintillator array of claim 2 , wherein the second portion contacts the adhesive layer.

7. further comprising an adhesive layer provided between the structure and the second reflective layer; The scintillator array of claim 2 , wherein the second portion passes through the adhesive layer and contacts the second reflective layer.

8. further comprising an adhesive layer provided between the structure and the second reflective layer; The scintillator array of claim 2 , wherein the second portion penetrates the adhesive layer and the second reflective layer.

9. 3. The scintillator array according to claim 2, wherein a ratio D / T of a length D of the second portion to a thickness T of the second reflective layer is equal to or greater than 0.10 and equal to or less than 1.

00.

10. A scintillator array as described in claim 1, wherein the ratio D / T of the length D of the first portion to the thickness T of the second reflective layer is greater than or equal to 0.25 and less than or equal to 0.

75.

11. At least one reflective layer selected from the group consisting of the first and second reflective layers is a resin including at least one selected from the group consisting of an epoxy resin, a silicone resin, a phenolic resin, a urea resin, a melamine resin, a polyester resin, a polyurethane resin, and an acrylic resin; reflective particles that reflect light and contain at least one selected from the group consisting of titanium oxide, aluminum oxide, silicon oxide, barium sulfate, zinc oxide, zirconium oxide, and silicon oxide; 11. The scintillator array of claim 1, comprising:

12. A radiation detector comprising a scintillator array according to any one of claims 1 to 11.

13. A radiation inspection device comprising the radiation detector according to claim 12.

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