Scintillator array, radiation detector, and radiation inspection apparatus

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 apparatus.

Background Art

[0002] In fields such as medical diagnosis and industrial non-destructive inspection, inspections are performed using radiation inspection apparatuses such as X-ray computed tomography apparatuses (hereinafter referred to as X-ray CT apparatuses). An X-ray CT apparatus includes an X-ray tube (X-ray source) that irradiates a fan-shaped fan beam X-ray and an X-ray detector including a large number of X-ray detection elements, which are arranged to face each other with a tomographic plane of a subject therebetween.

[0003] The X-ray CT apparatus irradiates a fan beam X-ray from the X-ray tube while rotating with respect to the subject, and collects X-ray absorption data that has passed through the subject using the X-ray detector. Thereafter, a tomographic image is reconstructed by analyzing the X-ray absorption data with a computer.

[0004] Radiation detectors of X-ray CT apparatuses widely use detection elements using solid scintillators. Since a radiation detector including detection elements using solid scintillators can easily miniaturize the detection elements and increase the number of channels, the resolution of X-ray CT apparatuses and the like can be further enhanced.

[0005] Radiation inspection apparatuses such as X-ray CT apparatuses are used in various fields such as medical and industrial fields. Examples of X-ray CT apparatuses include multi-slice type apparatuses in which detection elements such as photodiodes are arranged two-dimensionally in the vertical and horizontal directions, and a scintillator array is mounted thereon. The multi-slice type apparatus can stack computerized tomography (CT), and thereby can show a CT image three-dimensionally.

[0006] The radiation detector mounted on the radiation inspection apparatus includes a plurality of detection elements arranged in a plurality of vertical and horizontal rows, and each detection element has a scintillator segment. The radiation detector converts X-rays incident on the scintillator segment into visible light, converts the visible light into an electrical signal with the detection element, and forms an image. In recent years, in order to obtain high resolution, the detection elements are miniaturized, and further, the pitch between adjacent detection elements is narrowed. Along with these, the size of the scintillator segment has also become smaller.

[0007] Among various scintillator materials used for the scintillator segment as described above, rare earth oxysulfide-based phosphor ceramics have high luminous efficiency and suitable characteristics for use in the scintillator segment. For this reason, a radiation detector combining a scintillator segment processed by a processing method such as cutting or grooving from a sintered body (ingot) of rare earth oxysulfide-based phosphor ceramics as a scintillator material and a photodiode as a detection element is becoming popular.

[0008] Examples of scintillators using phosphor ceramics include scintillators made of sintered bodies of gadolinium oxysulfide phosphors. A scintillator array using the above scintillator is manufactured, for example, as follows. First, rare earth oxysulfide-based phosphor powder as a scintillator material is formed into an appropriate shape and sintered to form a sintered body (ingot). Cutting processes such as cutting or grooving are performed on this sintered body to form scintillator segments corresponding to a plurality of detection elements. Further, a reflective layer that reflects light is formed between these scintillator segments and integrated to manufacture a scintillator array.

[0009] When using a scintillator array as described above in a radiation detector, the dimensional accuracy of the scintillator array affects the resolution of CT diagnostic images. Furthermore, a temperature of up to 50°C or more and 60°C or less is applied to the radiation detector mounted on the X-ray CT apparatus. In a scintillator array having a reflective layer containing resin, expansion of the reflective layer due to heating and contraction due to temperature drop occur, resulting in minute dimensional changes between adjacent scintillator segments, that is, pitch deviation of the scintillator segments, variations in the outer dimensions mainly due to warping of the scintillator array, and the like. With such warping and variations in the outer dimensions, when attached to the diode array which is the detector, the adhesive layer thickness therebetween becomes non-uniform, causing deterioration of the resolution of the diagnostic image of the radiation detector. As the high resolution of the diagnostic image of the radiation detector progresses, a scintillator array with less warping and less variation in the outer dimensions is required. Furthermore, with the miniaturization of the detection area of the radiation detector, the uniformity of the adhesive layer between the scintillator array and the diode array has become important.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0011] The scintillator array of the embodiment includes a plurality of scintillator segments, a first reflective layer that surrounds each of the plurality of scintillator segments and is provided between the scintillator segments arranged in the vertical direction and between the scintillator segments arranged in the horizontal direction among the plurality of scintillator segments and reflects light, and a structure in which each of the plurality of scintillator segments is made of a sintered body, and a second reflective layer that is provided on the structure and reflects light. The first reflective layer includes a resin and reflective particles that reflect light. The first reflective layer has a first portion that protrudes toward the second reflective layer rather than the scintillator segments between the scintillator segments arranged in the vertical direction and between the scintillator segments arranged in the horizontal direction. The ratio D / T of the length D of the first portion to the thickness T of the second reflective layer is 0.10 or more and 1.00 or less.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described with reference to the drawings. The relationship between the thickness and the planar dimensions of each component shown in the drawings, the ratio of the thicknesses of each component, etc. may be different from the actual object. Also, in the embodiments, substantially the same components are denoted by the same reference numerals and the description thereof will be omitted as appropriate.

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

[0015] (Scintillator Array) FIG. 1 is a plan view showing a structural example of the scintillator array according to the embodiment. FIG. 2 is a cross-sectional view showing a structural example of a conventional scintillator array. FIG. 3 is a cross-sectional view showing a structural example of the scintillator array according to the embodiment. FIGS. 4, 5, and 6 are cross-sectional views showing other structural examples of the scintillator array according to the embodiment. FIGS. 1 to 6 illustrate a scintillator array 1, a scintillator segment 2, a reflective layer 3, and a reflective layer (top plate reflective layer) 4. Note that the reflective layer 4 is omitted for convenience 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 segment 2 and the reflective layer 3 form a structure 20 having a surface 20a which is an X-ray incident surface and a surface 20b on the opposite side of the surface 20a. The number of scintillator segments 2 is appropriately set according to the structure and resolution of the radiation detector, etc.

[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 the scintillator array of the embodiment, as shown in FIG. 3, in the cross-section in the thickness direction of the scintillator array 1, the reflective layer 3 partially penetrates into the interior of the reflective layer 4. In other words, the reflective layer 3 has a portion that extends into the interior of the reflective layer 4.

[0018] In another example of the scintillator array of the embodiment, as shown in FIG. 4, the reflective layer 4 is bonded onto the surface 20a via the adhesive layer 5, and in the cross-section in the thickness direction of the scintillator array 1, the reflective layer 3 may 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 through the adhesive layer 5 into the interior of the reflective layer 4.

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

[0020] In yet another example of the scintillator array of the embodiment, as shown in FIG. 6, the reflective layer 4 is bonded onto the surface 20a via the adhesive layer 5, and in the cross-section in the thickness direction of the scintillator array 1, a part of the reflective layer 3 may penetrate through the reflective layer 4.

[0021] The scintillator segment 2 converts the incident radiation (X-ray) into light (visible light). The plurality of scintillator segments 2 are integrated by the reflective layer 3 adhered thereto to form the structure 20.

[0022] The reflective layer 3 reflects light (visible light). The reflective layer 3 can transmit 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 can transmit X-rays. The reflective layer 4 is provided on the surface 20a and covers the structure 20, for example, as shown in FIG. 3.

[0024] The scintillator array 1 may have either a structure in which a plurality of scintillator segments 2 are arranged in a row or a structure in which a plurality of scintillator segments 2 are two-dimensionally arranged in a predetermined number in the vertical and horizontal directions as shown in FIG. 1. When the plurality of scintillator segments 2 are two-dimensionally arranged, the 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 the rare earth oxysulfide include oxysulfides of rare earth elements such as yttrium (Y), gadolinium (Gd), lanthanum (La), and lutetium (Lu).

[0026] The rare earth oxysulfide phosphor General formula: RE2O2S:Pr …(1) (RE represents at least one element selected from the group consisting of Y, Gd, La, and Lu) Preferably has a composition represented by.

[0027] Among the above-mentioned rare earth elements, in particular, Gd has a large X-ray absorption coefficient and contributes to the improvement of the light output of the scintillator array 1. Therefore, it is more preferable that the scintillator segment 2 has a Gd2O2S:Pr phosphor (GOS phosphor). Note that a part of Gd may be substituted with other rare earth elements. At this time, the substitution amount of Gd with other rare earth elements is preferably 10 mol% or less. That is, the rare earth oxysulfide phosphor General formula: (Gd1-x , RE x )2O2S:Pr…(2) (In the formula, 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 preferably has a composition substantially represented by

[0028] The scintillator segment 2 may have praseodymium (Pr) as an activator for increasing the light output. Pr can reduce the afterglow compared to other activators. Therefore, the rare earth oxysulfide phosphor ceramics containing Pr as an activator are effective as a fluorescent generator of a radiation detector.

[0029] The content of Pr in the rare earth oxysulfide phosphor is preferably 0.001 mol% or more and 10 mol% or less with respect to the content of the phosphor matrix (RE2O2S such as Gd2O2S). When the content of Pr exceeds 10 mol%, it causes a decrease in the light output. When the content of Pr is less than 0.001 mol%, the effect as a main activator cannot be sufficiently obtained. The content of Pr is more preferably 0.01 mol% or more and 1 mol% or less.

[0030] In addition to Pr as the main activator, the rare earth oxysulfide phosphor may contain 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 for suppressing exposure deterioration, suppressing afterglow, etc. The content of these co-activators is preferably in the range of 0.00001 mol% or more and 0.1 mol% or less in total with respect to the phosphor matrix.

[0031] The sintered body constituting the scintillator segment 2 is preferably made of a high-purity rare-earth oxysulfide-based phosphor ceramic (scintillator material). Since impurities are a factor in reducing the sensitivity of the scintillator, it is preferable that the amount of impurities is as small as possible. In particular, phosphate (PO4) causes a decrease in sensitivity, so its content is preferably 100 ppm or less. When using a fluoride or the like as a sintering aid to increase the density of the sintered body, the sintering aid remains as an impurity, resulting in a decrease in sensitivity.

[0032] The sintered body has a cubic shape or a rectangular parallelepiped shape. The volume of the scintillator segment 2 is preferably 3 1 mm or less. By miniaturizing the scintillator segment 2, the detected image can be made high-definition. The respective sizes of the length (L), width (S), and thickness (T) of the scintillator segment 2 are not necessarily limited, but are preferably 1 mm or less each. When the volume of the scintillator segment 2 is 3 1 mm or less, the width (W) of the reflective layer 3 can be made thinner, preferably 100 μm or less, and further preferably 50 μm or less. However, when it is less than 40 μm, the manufacturing process becomes complicated, so 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 (light-transmissive resin) and reflective particles that are dispersed in the resin and reflect light. The resin includes at least one selected from the group consisting of epoxy resin, silicone resin, phenol resin, urea resin, melamine resin, polyester resin, polyurethane resin, and acrylic resin. For example, as the epoxy resin, a hydrogenated epoxy resin, an epoxy silicone resin, etc. are preferable. The reflective particles include 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 serve as reflective particles.

[0034] For the reflective layer 4, the same light-transmissive resin and reflective particles as those of the reflective layer 3 can be used.

[0035] In the reflective layers 3 and 4, the ratio of the translucent resin to the reflective particles is preferably such that the mass ratio of the translucent 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 translucent 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 be lower than 90%. When the mass ratio of the reflective particles exceeds 85%, although the reflection efficiency of the reflective layer does not change, the mass ratio of the translucent resin relatively decreases, making it difficult to stably solidify the reflective layer.

[0036] When bonding the prefabricated reflective layer 4 onto the surface 20a of the structure 20, the adhesive layer 5 is 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, and contains at least one resin cured by any of light, heat, and moisture. The adhesive layer 5 may be a translucent resin, but in order to reduce the entry 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] The scintillator used in a radiation detection device such as an X-ray CT device confines the light generated by X-rays within a pixel using a reflective layer and efficiently extracts it to the photodiode side. As the reflective layer, a reflective layer formed so as to fill the space between scintillator segments, and in some cases, a top plate reflective layer formed so as to cover the scintillator array on the X-ray incident surface side is generally provided. The light of the scintillator emitted by X-rays is efficiently guided to the photodiode directly or through such a reflective layer. The scintillator array incorporated in the X-ray detector is subjected to a temperature of 50 °C or more and 60 °C or less, and is placed at room temperature when not operating. Also, during operation, since it rotates at high speed around the subject to be examined, a force associated therewith is applied. As a problem presumably caused by such fluctuations in the operating ambient temperature and the generation of internal stress associated with rotation, the phenomenon that the top plate reflective layer peels off from the scintillator array often occurs, and a countermeasure is required.

[0039] On the other hand, in the reflective layer between the scintillator segments, a technique is known in which the color of the reflective particles contained in the epoxy resin is selected and a resin having a glass transition point of 80 °C or higher is combined with the epoxy resin to suppress variations and distortion in the light output between the scintillator segments.

[0040] In addition, a scintillator array is known in which the glass transition point of the light-transmitting resin constituting the reflective layer is 50 °C or higher, and the coefficient of thermal expansion of the light-transmitting resin at a temperature higher than the glass transition point is 3.5×10 -5 / °C or less. Generally, the coefficient of thermal expansion of the light-transmitting resin changes greatly at the boundary of the glass transition point, and the warpage caused by this change is adjusted by setting the conditions.

[0041] In addition, in order to reduce the warpage of the scintillator array, a plurality of scintillator segments are integrated by a reflective layer, the glass transition point of the light-transmitting resin of the reflective layer is 50 °C or higher, and the glass transition point of the light-transmitting resin of the second reflective layer arranged on the X-ray incident surface side of the plurality of scintillator segments is 30 °C or lower. A scintillator array having such a configuration is known.

[0042] In these scintillator arrays, warpage is improved to some extent. However, in a scintillator array having a top plate reflective layer, it is not always effective against the peeling of the top plate reflective layer, and further improvement is required.

[0043] The material used for the top plate reflective layer and the material used for the scintillator segment have a large difference in the linear expansion coefficient and the elastic modulus. This difference generates stress when the scintillator array is incorporated into a detector and exposed to temperature fluctuations in the use environment and centrifugal force associated with rotation, which causes the peeling of the top plate reflective layer.

[0044] On the other hand, in this embodiment, by allowing the reflective layer 3 to bite into the reflective layer 4 or the adhesive layer 5, the contact area can be increased due to these irregularities, and a so-called anchor effect can be obtained, so that the peeling of the reflective layer 4 can be suppressed.

[0045] Table 1 shows examples of the peeling occurrence rates in the respective forced tests of a conventional scintillator array having the structure shown in FIG. 2 and a scintillator array having the structure shown in FIG. 3. The forced test is to heat the scintillator array from room temperature to 50° C. in 5 minutes, leave it for 10 minutes, and then rotate it at a rotation speed of 200 rpm at room temperature for 5 minutes. These operations are defined as one cycle of operation, and 100 cycles of operation are performed for each sample. In the forced test of 100 prototype samples, there was no peeling in the scintillator array having the structure shown in FIG. 3, from which it can be seen that the peeling resistance is greatly improved.

[0046]

Table 1

[0047] As shown in FIGS. 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, when the penetration length becomes short, the peeling suppression effect is reduced. In order to realize an effective peeling suppression effect, in the cross section in the thickness direction of the scintillator array 1, 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 the adhesive layer 5 (the layer including the reflective layer 4) is preferably in the range of 0.10 or more and 1.00 or less, more preferably in the range of 0.20 or more and 1.00 or less. The thickness T and the length D can be measured from the observation image by observing the cross section in the thickness direction of the scintillator array 1 with an electron microscope or an optical microscope. Since the reflective layer 3, the reflective layer 4, and the adhesive layer 5 each form a polymer network structure in their respective layers, the interfaces of these layers are clear. Further, when the pigment concentrations are different, they are even clearer, making it easier to determine the thickness T and the length D.

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

[0049] FIGS. 7 to 10 are cross-sectional views for explaining an example of a method for manufacturing the scintillator array of the embodiment. First, in the first step, a white sheet having a predetermined size is formed of 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 translucent resin or a lacquer-based paint. The mixture of reflective particles and a translucent resin preferably has the same configuration 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 or more and 250 μm or less. When the thickness is less than 50 μm, the effect of improving the light reflection efficiency cannot be sufficiently obtained. When the thickness exceeds 250 μm, the amount of X-rays transmitted decreases and the detection sensitivity decreases.

[0052] In the first step, a scintillator material such as a rare earth oxysulfide-based phosphor sintered body is cut out as a thin plate having a predetermined size (thickness of 0.5 mm or more and 2 mm or less). As shown in FIG. 7, a plate-shaped sintered body 2a and a white sheet forming a reflective layer 4 are bonded and laminated via an adhesive layer 5 such as an epoxy resin.

[0053] Next, in the second step, as shown in FIG. 8, the sintered body 2a is subjected to grooving by dicing to partially remove the sintered body 2a, thereby forming a scintillator segment 2 and a groove S. In the cross section in the thickness direction of the sintered body 2a, the width of the groove S is, for example, in the range of 40 μm or more and 200 μm or less. The groove S extends to the inside of the reflective layer 4 through the sintered body 2a and the adhesive layer 5.

[0054] Next, in the third step, as shown in FIG. 9, a reflective layer 3 is formed in the groove S formed in the second step. First, a resin composition in an uncured state (uncured product of a light-transmitting resin) constituting reflective particles and a light-transmitting resin is prepared, and a slurry, which is a mixture thereof, is injected into the groove S.

[0055] The resin composition in the uncured state 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). When the viscosity of the resin composition exceeds 1.0 Pa·s, the fluidity is poor and the workability of injecting into the groove S deteriorates. When the viscosity of the resin composition is less than 0.2 Pa·s, the fluidity becomes too high, reducing the coatability or filling property. Also, the total light transmittance of the light-transmitting resin is preferably 85% or more. When the total light transmittance of the light-transmitting resin is less than 85%, the reflection efficiency of the reflective layer 3 tends to decrease.

[0056] After injecting the slurry into the groove S, the slurry is cured to form the reflective layer 3, thereby joining and integrating between adjacent scintillator segments 2 to form the structure 20. The curing process of the slurry is appropriately set according to the type of the uncured resin composition, hardener, and the like. 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, as shown in FIG. 10, peripheral processing for removing unnecessary portions at the periphery of the structure 20 and further polishing treatment are performed. The scintillator array 1 can be manufactured by the above steps.

[0058] (Radiation detector) The radiation detector of the embodiment includes the above-described scintillator array 1 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 a configuration example of the radiation detector, showing 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 segment 2. Examples of the photoelectric conversion element 7 include a photodiode and the like. The photoelectric conversion element 7 is arranged so as to correspond to each of the plurality of scintillator segments 2. These components constitute the radiation detector.

[0060] (Radiation inspection apparatus) The radiation inspection apparatus of the embodiment includes a radiation source that irradiates radiation toward a subject and a radiation detector that detects the radiation transmitted through the subject. As the radiation detector, the radiation detector of the above-described embodiment can be used.

[0061] FIG. 12 is a diagram showing a configuration example of a radiation 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 where an imaging region of the subject 11 is disposed. An X-ray tube 12 that emits X-rays is installed at substantially 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 while performing X-ray imaging around the subject 11. Image information of the subject 11 is collected three-dimensionally from different angles. A signal obtained by X-ray imaging (an electrical signal converted by a photoelectric conversion element) is processed by the computer 13 and displayed as a subject image 15 on the display 14. The subject image 15 is, for example, a tomographic image of the subject 11. As shown in FIG. 1, it is also possible to configure a multi-slice type X-ray CT apparatus 10 by using a scintillator array 1 in which scintillator segments 2 are two-dimensionally arranged. In this case, a plurality of tomographic images of the subject 11 are simultaneously taken, and for example, the imaging results can be depicted three-dimensionally.

[0063] The X-ray CT apparatus 10 shown in FIG. 12 includes an X-ray detector 6 having a scintillator array 1. As described above, the scintillator array 1 has excellent light output because of the high reflection efficiency of visible light emitted from the scintillator segments 2 based on configurations such as the reflection layer 3 and the reflection layer 4. By using the X-ray detector 6 having such a scintillator array 1, the imaging time by the X-ray CT apparatus 10 can be shortened. As a result, the exposure time of the subject 11 can be shortened, and it becomes possible to achieve low exposure. The radiation inspection apparatus (X-ray CT apparatus 10) is applicable not only to X-ray inspections for medical diagnosis of the human body but also to X-ray inspections of animals and X-ray inspections for industrial use. Further, it also contributes to improvement of inspection accuracy by X-ray non-destructive inspection apparatuses.

Example

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

[0065] In presenting the examples and comparative examples, a plate-shaped sintered body 2a was fabricated as follows. A phosphor powder having a composition of Gd2O2S:Pr (Pr concentration = 0.05 mol%) was preformed by a rubber press, and this preform was degassed and sealed in a tantalum (Ta) capsule. After that, it was set in a hot isostatic pressing (HIP) treatment apparatus. Argon gas was enclosed in the HIP treatment apparatus as a pressure medium, and treatment was performed for 3 hours under the conditions of a pressure of 147 MPa and a temperature of 1425 °C. In this way, a columnar sintered body having a diameter of about 80 mm and a height of about 120 mm was produced. From this sintered body, GOS ceramic plates of various sizes were cut out to obtain the sintered bodies 2a of the examples and comparative examples.

[0066] (Example 1) On the surface of a GOS ceramic plate having a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm, a white polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical, thickness 100 μm) having an area slightly larger than that of the sintered body 2a was bonded via an epoxy adhesive as the adhesive layer 5. When bonding, the GOS ceramic plate, the epoxy adhesive, and the white PET film were stacked, a load of 16 kg was applied, and heating was performed at a temperature of 100 °C for bonding. After cooling to room temperature, the load was removed to produce a laminate. Grooving by dicing was performed on the surface of the GOS ceramic plate of this laminate to form the scintillator segment 2 and the groove S. The depth of the groove S was 1.25 mm. The groove S extended to the inside of the white PET film. A slurry containing titanium oxide and an epoxy resin was injected into the groove S, the slurry was thermally cured, and the surface of the scintillator segment 2 was polished. Then, the peripheral portion was cut to produce a scintillator array 1 corresponding to FIG. 4. The ratio D / T of the length D of the portion extending inside the layer including the reflective layer 4 in the reflective layer 3 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 with a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm. After the slurry was thermally cured, it was polished to form a reflective layer 4 with a thickness T of 0.3 mm. Then, grooving by dicing was performed on the surface of the GOS ceramic plate to form a scintillator segment 2 and a groove S. The depth of the groove S is 1.25 mm. The groove S extends to the inside of the reflective layer 4. A slurry containing titanium oxide and epoxy resin was injected into the groove S, the slurry was thermally cured, and the surface of the scintillator segment 2 was polished by 0.1 mm. Then, the surface of the reflective layer 4 was polished by 0.1 mm, the peripheral portion was cut, and a scintillator array 1 corresponding to FIG. 3 was fabricated. The ratio D / T was 0.25.

[0068] (Example 3) A slurry containing titanium oxide and epoxy resin was applied to the surface of a GOS ceramic plate with a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm. After the slurry was thermally cured, it was polished to form a reflective layer 4 with a thickness of 0.3 mm. Then, grooving by dicing was performed on the surface of the GOS ceramic plate to form a scintillator segment 2 and a groove S. The depth of the groove S is 1.4 mm. The groove S extends to the inside of the reflective layer 4. A slurry containing titanium oxide and epoxy resin was injected into the groove S, the slurry was thermally cured, and the surface of the scintillator segment 2 was polished by 0.1 mm. Then, the surface of the reflective layer 4 was polished by 0.15 mm. After exposing the reflective layer 3 through the reflective layer 4 on the surface of the reflective layer 4, the peripheral portion was cut, and a scintillator array 1 was fabricated. The ratio D / T was 1.00.

[0069] (Example 4) A slurry containing titanium oxide and epoxy resin was applied to the surface of a GOS ceramic plate with a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm. After heat-curing the slurry, it was polished to form a reflective layer 4 with a thickness of 0.3 mm. Then, grooving by dicing was performed on the surface of the GOS ceramic plate to form a scintillator segment 2 and a groove S. The depth of the groove S is 1.22 mm. The groove S extends to the inside of the reflective layer 4. A slurry containing titanium oxide and epoxy resin was injected into the groove S, the slurry was heat-cured, and the surface of the scintillator segment 2 was polished by 0.1 mm. Then, the surface of the reflective layer 4 was polished by 0.1 mm, the peripheral portion was cut, and a scintillator array 1 corresponding to FIG. 3 was fabricated. The ratio D / T was 0.10.

[0070] (Example 5) A slurry containing titanium oxide and epoxy resin was applied to the surface of a GOS ceramic plate with a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm. After heat-curing the slurry, it was polished to form a reflective layer 4 with a thickness of 0.3 mm. Then, grooving by dicing was performed on the surface of the GOS ceramic plate to form a scintillator segment 2 and a groove S. The depth of the groove S is 1.35 mm. The groove S extends to the inside of the reflective layer 4. A slurry containing titanium oxide and epoxy resin was injected into the groove S, the slurry was heat-cured, and the surface of the scintillator segment 2 was polished by 0.1 mm. Then, the surface of the reflective layer 4 was polished by 0.1 mm, the peripheral portion was cut, and a scintillator array 1 corresponding to FIG. 3 was fabricated. The ratio D / T was 0.75.

[0071] (Comparative Example 1) A GOS ceramic plate with a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm was grooved by dicing to form a scintillator segment 2 and a groove S. A slurry containing titanium oxide and an epoxy resin was injected into the groove S. After the slurry was thermally cured, it was polished to form a reflective layer 3. A slurry containing titanium oxide and an epoxy resin was applied to the X-ray incident surface of this structure 20, and the slurry was heated and cured at a temperature of 100 °C for 3 hours. In order to make the thickness 150 μm, it was polished after curing to form a reflective layer 4, and a scintillator array 1 was fabricated. The reflective layer 3 does not extend to the reflective layer 4.

[0072] (Comparative Example 2) A GOS ceramic plate with a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm was grooved by dicing to form a scintillator segment 2 and a groove S. A slurry containing titanium oxide and an epoxy resin was injected into the groove S. After the slurry was thermally cured, a reflective layer 3 was formed by polishing. Next, a white PET film (manufactured by Mitsubishi Chemical, thickness 100 μm) 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, a load of 16 kg was applied, and it was heated and bonded at a temperature of 100 °C. After cooling to room temperature, the load was removed, and a scintillator array 1 was fabricated. The reflective layer 3 does not extend to the reflective layer 4.

[0073] (Comparative Example 3) A GOS ceramic plate with a length of 76 mm, a width of 25 mm, and a thickness of 1.2 mm was grooved by dicing to form a scintillator segment 2 and a groove S. A slurry containing titanium oxide and an epoxy resin was injected into the groove S. After the slurry was thermally cured, a reflective layer 3 was formed by polishing. A slurry containing titanium oxide and an epoxy resin was applied to the X-ray incident surface of this structure 20, and it was heated and cured at a temperature of 100 °C for 4 hours. In order to make the thickness 100 μm, it was polished after curing to form a reflective layer 4, and a scintillator array 1 was fabricated. 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, left at a temperature of -20°C for 30 minutes, then heated to a temperature of 60°C at a heating rate of 5°C / min, left at a temperature of 60°C for 30 minutes, and then cooled to a temperature of -20°C at a cooling rate of 5°C / min. After repeating this cycle 1000 times, the periphery of the scintillator array 1 was observed to evaluate the presence or absence of peeling. The humidity in the test was 40%RH (Relative Humidity). The results are shown in Table 2.

[0075]

Table 2

[0076] From Table 2, in the scintillator array 1 of the example, by extending and biting the reflective layer 3 between the scintillator segments 2 to the inside of the layer including the reflective layer 4 and integrating them, a significant difference was observed in the peelability of the reflective layer 4 compared with the comparative example. Even when the degree of biting was small, the peeling was less than that in the comparative example.

[0077] According to the scintillator array of the embodiment, it is possible to substantially eliminate the peeling of the reflective layer 4 that has conventionally occurred at a certain rate, so it can be said to be industrially useful.

Claims

1. A structure comprising: a plurality of scintillator segments; a first reflective layer that surrounds each of the plurality of scintillator segments and is provided between the scintillator segments arranged in the vertical direction and between the scintillator segments arranged in the horizontal direction among the plurality of scintillator segments and reflects light, and each of the plurality of scintillator segments is made of a sintered body. A second reflective layer provided on the structure and reflecting light. Comprising. The first reflective layer Contains resin Reflective particles that reflect light Including The first reflective layer has a first portion that protrudes toward the second reflective layer from the scintillator segments between the scintillator segments arranged in the vertical direction and between the scintillator segments arranged in the horizontal direction. A scintillator array in which the ratio D / T of the length D of the first portion to the thickness T of the second reflective layer is 0.10 or more and 1.00 or less.

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

3. Further comprising an adhesive layer provided between the structure and the second reflective layer. The scintillator array according to claim 1, wherein the first portion is in contact with the adhesive layer.

4. Further comprising an adhesive layer provided between the structure and the second reflective layer. The scintillator array according to claim 1, wherein the first portion penetrates the adhesive layer and is in contact with the second reflective layer.

5. Further comprising an adhesive layer provided between the structure and the second reflective layer. The scintillator array according to 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 according to claim 2, wherein the second portion is in contact with the adhesive layer.

7. Further comprising an adhesive layer provided between the structure and the second reflective layer. The scintillator array according to claim 2, wherein the second portion penetrates the adhesive layer and is in contact with the second reflective layer.

8. Further comprising an adhesive layer provided between the structure and the second reflective layer. The scintillator array according to claim 2, wherein the second portion penetrates the adhesive layer and the second reflective layer.

9. The scintillator array according to claim 2, wherein the ratio D / T of the length D of the second portion to the thickness T of the second reflective layer is 0.10 or more and 1.00 or less.

10. The scintillator array according to 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 0.25 or more and 0.75 or less.

11. At least one reflective layer selected from the group consisting of the first and second reflective layers, A resin containing 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; Reflective particles containing at least one selected from the group consisting of titanium oxide, aluminum oxide, silicon oxide, barium sulfate, zinc oxide, zirconium oxide, and silicon oxide, and reflecting light; The scintillator array according to any one of claims 1 to 10, comprising:

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

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

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