Radiation detector and radiation detection apparatus

Abstract

A radiation detecting apparatus according to one embodiment of the present application includes a scintillator that generates first scintillating light having a first peak wavelength and second scintillating light having a second peak wavelength in response to incidence of radiation, a light detecting section that detects the scintillating light generated by the scintillator, and a filter layer that is disposed between the scintillator and the light detecting section and selectively blocks the first scintillating light. The filter layer has a meta-surface configuration.

Description

Technical Field

[0001] This invention relates to a radiation detector and a radiation detection device.

[0002] Refer to relevant applications

[0003] This application claims the benefit of priority to Japanese Patent Application No. 2021-091678, filed on May 31, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0004] A radiation detector is known, comprising a scintillator that converts X-rays and other radiation into light, and a photodetector that detects the light converted by the scintillator. Patent Document 1 (Chinese Patent Application Publication No. 111081728) discloses a structure in which a light selection layer is disposed between a CsI-based scintillator and a TFT substrate serving as the photodetector. In this structure, the light selection layer absorbs or reflects the residual light component of the scintillating light (fluorescence) generated by the scintillator, thereby reducing the residual light component detected in the TFT substrate. Summary of the Invention

[0005] In the structure disclosed in Patent Document 1 above, a resin film (one or a combination of two or more PVC film, PET film, and PE film) is used as the light selective layer. However, when using a resin film as the light selective layer, it is difficult to adjust the selective transmission (or absorption or reflection) of light in the ultraviolet region (especially the wavelength region below 300 nm). In addition, when there are two emission peaks, and the wavelength of one peak is longer than the wavelength of the other, it is difficult to selectively transmit that one peak wavelength in the above-mentioned resin film.

[0006] One aspect of the present invention is to provide a radiation detector and a radiation detection device that can better detect light of interest wavelengths regardless of the wavelength region of the scintillation light or the shape of the emission peak.

[0007] One aspect of the present invention relates to a radiation detector comprising: a scintillator that generates a first scintillation light having a first peak wavelength and a second scintillation light having a second peak wavelength in response to incident radiation; a light detection unit that detects the scintillation light generated by the scintillator; and a filter layer disposed between the scintillator and the light detection unit, which selectively blocks the first scintillation light, the filter layer having an ultra-high surface structure.

[0008] In the aforementioned radiation detector, a scintillator generates a first scintillation light and a second scintillation light with different peak wavelengths. The first scintillation light, having the first peak wavelength, is selectively blocked by a filter layer disposed between the scintillator and the photodetector. That is, the second scintillation light, having the second peak wavelength, is selectively transmitted to the photodetector. Here, the filter layer is not made of a resin film, but of a metasurface structure. By using a metasurface structure to construct the filter layer, compared to using a resin film, the following advantages can be obtained: By controlling the shape of the metasurface structure, regardless of the wavelength region of the scintillation light and the shape of the emission peak (resonant peak width, etc.), better filtering performance can be obtained than when the filter layer is made of a resin film. That is, light of the wavelength of interest (here, the second scintillation light with the second peak wavelength) can be transmitted more effectively, and light of wavelengths other than the wavelength of interest (here, the first scintillation light with the first peak wavelength) can be blocked more effectively. Therefore, based on the above-mentioned radiation detector, light of interest wavelength can be detected well regardless of the wavelength range of the scintillation light or the shape of the emission peak.

[0009] The filter layer can also be a plasma filter utilizing surface plasmon. Based on the above structure, by utilizing surface plasmon, a filter structure that selectively blocks the first scintillation light can be easily obtained.

[0010] The filter layer can also have multiple columnar metal structures arranged periodically. Based on the above structure, by adjusting the arrangement (period) of the multiple metal structures and the width and height of the metal structures, a filter structure that selectively blocks the first scintillation light can be easily manufactured.

[0011] The metal structure can also be made of cylindrical aluminum. Based on the above structure, by adjusting the diameter and height of the cylindrical aluminum, a filter design for selectively blocking the first scintillation light can be easily carried out.

[0012] The decay time of the first scintillation light can also be longer than that of the second scintillation light. Based on the above configuration, by selectively blocking the first scintillation light, which has the longer decay time, the second scintillation light, with the shorter decay time, can be detected only in the photodetector. This improves the temporal resolution of the radiation detector.

[0013] The filter layer can also selectively reflect the first scintillation light generated by the scintillator toward the scintillator side. According to the above structure, the amount of the first scintillation light leaking toward the light detection unit can be effectively reduced, and therefore, the second scintillation light can be more appropriately detected in the light detection unit.

[0014] The scintillator can have a first surface opposite to the light detection unit and a second surface not opposite to the light detection unit. Alternatively, a light-absorbing layer that absorbs the first scintillator light reflected by the filter layer can be provided on at least a portion of the second surface. According to this configuration, by absorbing the first scintillator light reflected by the filter layer using the light-absorbing layer, it is possible to suppress the first scintillator light from re-incidentally striking the filter layer. Therefore, it is more suitable to detect only the second scintillator light in the light detection unit.

[0015] The aforementioned radiation detector may further include a second light detection unit, which is disposed opposite to the side where the filter layer is located, relative to the scintillator. According to this configuration, the second light detection unit can detect the first scintillation light reflected from the filter layer. Therefore, for example, by detecting the second scintillation light using the light detection unit, the temporal resolution is improved, and by detecting the first scintillation light reflected from the filter layer using the second light detection unit, a sufficient overall amount of detection light can be ensured. This improves the detection accuracy of the radiation detector.

[0016] The aforementioned radiation detector may further include a second filter layer disposed between the scintillator and the second light detection unit, which selectively blocks the second scintillation light. According to this configuration, the second light detection unit can appropriately detect only the first scintillation light.

[0017] The second filter layer can also have a metasurface structure. Based on the above structure, by employing the same metasurface structure as the filter layer, the second filter layer can be suitably designed and manufactured.

[0018] The filter layer can also be composed of a plurality of periodically arranged columnar bodies, and the second filter layer can also be composed of a plurality of holes corresponding to the plurality of columnar bodies of the filter layer. Based on the above structure and the Babinette principle, a second filter layer having properties opposite to those of the filter layer can be easily designed and manufactured. That is, the metasurface structure of the second filter layer is designed to be a shape corresponding to the metasurface structure of the filter layer (i.e., a shape with an inverse relationship to the metasurface structure of the filter layer for negative (concave) and positive (convex) portions), thereby enabling the easy and reliable formation of a second filter layer with the property of selectively blocking the second scintillation light.

[0019] The light detection unit can also be a solid-state imaging element or an electron tube. According to the above structure, in a configuration where the scintillator and filter layer are arranged as external components for the solid-state imaging element or electron tube, the aforementioned radiation detector effect can be achieved. That is, by providing a scintillator and filter layer to existing solid-state imaging elements or electron tubes, a radiation detector that performs the aforementioned effects can be obtained.

[0020] The radiation detector can also be a vacuum tube, the scintillator can be the light entrance window of the vacuum tube, and the light detection unit can be the photoelectric surface of the vacuum tube. According to the above structure, by embedding the scintillator and filter layer inside the vacuum tube, compared to making the scintillator and filter layer external components of the vacuum tube, the overall size of the radiation detector can be miniaturized. Furthermore, the detection light (the second scintillator light) can be efficiently guided towards the photoelectric surface.

[0021] The aforementioned radiation detector may also include a protective film disposed between the filter layer and the photodetector. According to this structure, the protective film can appropriately prevent chemical reactions between the scintillator and the photoelectric surface (photodetector).

[0022] Other aspects of the present invention relate to a radiation detection apparatus comprising a gantry in which multiple radiation detectors are arranged. By using radiation detectors having the above-described structure to construct a radiation detection apparatus, it is possible to obtain a radiation detection apparatus that can perform the effects of the radiation detectors.

[0023] According to one aspect of the present invention, a radiation detector and a radiation detection device can be provided that can better detect light of interest wavelengths regardless of the wavelength region of the scintillation light or the shape of the emission peak. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of the radiation detector according to the first embodiment.

[0025] Figure 2 This is a graph showing the emission spectrum of the scintillator (BaF2).

[0026] Figure 3 It is a diagram showing the basic structure (unit grid) of the filter layer.

[0027] Figure 4 It is a graph showing the transmittance of each wavelength in the filter layer.

[0028] Figure 5 It is a graph showing the reflectivity of each wavelength in the filter layer.

[0029] Figure 6 This is a diagram illustrating an example of the manufacturing process of a filter layer.

[0030] Figure 7 This is a cross-sectional view of the radiation detector according to the second embodiment.

[0031] Figure 8 This is a cross-sectional view of the radiation detector according to the third embodiment.

[0032] Figure 9This is a cross-sectional view of the radiation detector according to the fourth embodiment.

[0033] Figure 10 This is a cross-sectional view of the radiation detector according to the fifth embodiment.

[0034] Figure 11 This is a cross-sectional view of the radiation detector according to the sixth embodiment.

[0035] Figure 12 This is a diagram showing the basic structure (unit grid) of the second filter layer.

[0036] Figure 13 This is a schematic structural diagram of a radiation detection device according to one embodiment. Detailed Implementation

[0037] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in the following description, the same or equivalent parts will be referred to by the same reference numerals, and repeated descriptions will be omitted. The dimensional scale of the accompanying drawings may not necessarily match the actual dimensional scale.

[0038] (First Embodiment)

[0039] like Figure 1 As shown, the radiation detector 1A in the first embodiment is a detector for detecting radiation such as X-rays. The radiation detector 1A is used, for example, in positron emission tomography (PET) devices that use the time-of-flight information of annihilated radiation for image reconstruction (such as TOP-PET, or see [reference]). Figure 13 The radiation detector 1A includes a scintillator 2, a light detection unit 3A, and a filter layer 4. The radiation detector 1A has a cylindrical shape (in this embodiment, as an example, it is cylindrical). The filter layer 4 is disposed between the scintillator 2 and the light detection unit 3A. In this specification, for ease of explanation, the direction in which the scintillator 2 and the light detection unit 3A sandwich the filter layer 4 is opposite is represented as the Z-axis direction, and two mutually orthogonal directions along a plane orthogonal to the Z-axis direction are represented as the X-axis direction and the Y-axis direction.

[0040] The scintillator 2 generates multiple (two or more) scintillation lights with different peak wavelengths and decay times based on the incident radiation such as X-rays. Examples of scintillators 2 with this property include BaF2 and CdF3:Pr3+. In this embodiment, the scintillator 2 is formed of BaF2.

[0041] like Figure 2As shown, the scintillator 2 formed from BaF2 generates scintillating light L1 (first scintillating light) with a peak wavelength λ1 (first peak wavelength) and scintillating light L2 (second scintillating light) with a peak wavelength λ2 (second peak wavelength) in response to incident radiation. The peak wavelength λ1 is 300 nm, and the peak wavelength λ2 is 220 nm. Furthermore, the decay time t1 of scintillating light L1 is shorter than the decay time t2 of scintillating light L2 (t1 < t2). More specifically, the decay time t1 is 550 ns, and the decay time t2 is 0.6 ns. Figure 2 As shown, in BaF2, the luminous intensity of the flashing light L1 is greater than that of the flashing light L2.

[0042] As an example, the scintillator 2 is formed in a cylindrical shape. That is, when viewed from the Z-axis direction, the scintillator 2 is formed in a circular shape. The scintillator 2 has an inner surface 2a that faces the light detection unit 3A across the filter layer 4, an outer surface 2b located on the opposite side of the inner surface 2a in the Z-axis direction, and a cylindrical side surface 2c that extends along the Z-axis direction in a manner that connects the edge portion of the inner surface 2a and the edge portion of the outer surface 2b. As an example, the outer surface 2b of the scintillator 2 functions as an incident surface for the radiation of the detected object to be incident, and the inner surface 2a functions as an exit surface for the scintillating light generated inside the scintillator 2.

[0043] The light detection unit 3A detects the scintillating light generated by the scintillator 2. In this embodiment, the light detection unit 3A is, for example, a solid-state imaging element such as a SPAD (Single-Photon Avalanche Diode) or a SiPM (Silicon Photomultiplier). Alternatively, the light detection unit 3A may also be composed of other solid-state imaging elements such as an APD (Avalanche Photo Diode). The light detection unit 3A has a light detection surface 3a for incident light on the object being detected. The light detection surface 3a faces the inner surface 2a of the scintillator 2 across the filter layer 4.

[0044] The filter layer 4 has an ultra-high surface structure. The filter layer 4 selectively blocks the scintillating light L1 from the scintillating light L1 and L2 generated by the scintillator 2. That is, the filter layer 4 allows most of the scintillating light L2 to pass through from the scintillator 2 side to the light detection unit 3A side, while preventing most of the scintillating light L1 from passing through from the scintillator 2 side to the light detection unit 3A side. For example, the filter layer 4 selectively reflects or absorbs the scintillating light L1. In this embodiment, the filter layer 4 is configured to selectively reflect the scintillating light L1 towards the scintillator 2 side.

[0045] The filter layer 4 can be configured as a plasma filter using surface plasma (e.g., a plasma color filter). That is, the filter layer 4 has a metasurface structure configured in a manner that generates surface plasma. Figure 1 As shown, the filter layer 4 has a plurality of columnar metal structures 41 arranged periodically along the XY plane. As an example, the metal structures 41 can be formed in a cylindrical shape. The plurality of metal structures 41 are arranged in a two-dimensional (grid-like) arrangement along the XY plane. The filter layer 4 (i.e., the plurality of metal structures 41) can be formed on the inner surface 2a of the scintillator 2 by means of vapor deposition, or on the light detection surface 3a of the light detection unit 3A by means of vapor deposition. In this embodiment, the filter layer 4 is formed on the inner surface 2a of the scintillator 2.

[0046] The metal structure 41 constituting the filter layer 4 can be formed of, for example, aluminum (Al), titanium oxide (TiO2), hafnium oxide (HfO2), gallium nitride (GaN), or aSi (amorphous silicon). In this embodiment, the metal structure 41 is made of aluminum (Al).

[0047] Figure 3 This represents the unit grid C1 that constitutes filter layer 4. Filter layer 4 is... Figure 3 The unit grid C1 shown is a nanostructure (finely textured) formed by periodically arranging the unit grids along the X and Y axes. As an example, the unit grid C1 is a square region viewed from the Z-axis direction. A cylindrical (plate-like) metal structure 41 is formed in each unit grid C1. The metal structure 41 is erected on the inner surface 2a of the scintillator 2 at the center of the unit grid C1.

[0048] The period 'a' of the metal structure 41 (i.e., the distance (spacing) between the centers of two adjacent metal structures 41, and the length of one side of a unit grid C1) is set to be shorter than the wavelengths of the scintillating light L1 and L2 of the filter object. In this embodiment, the wavelengths of the scintillating light L1 and L2 are 300 nm and 220 nm, respectively; therefore, the period 'a' of the metal structure 41 is set to a value shorter than these wavelengths. The period 'a' can be selected, for example, from the range of 150 nm to 200 nm. The width 'd' (diameter) of the metal structure 41 can be selected, for example, from the range of 80 nm to 140 nm. The height 'h' of the metal structure 41 can be selected, for example, from the range of 30 nm to 70 nm. The height of the metal structure 41 is the length from the inner surface 2a of the scintillator 2 to the top surface 41a of the metal structure 41.

[0049] Figure 4 This is a graph showing the transmittance (relationship between wavelength and transmittance) of each wavelength in filter layer 4. Figure 4This represents the simulation results for a unit grid C1 with a period a of 150 nm, a height h of 30 nm, and a width d of 70 nm, 80 nm, 90 nm, and 100 nm. Figure 4 In the diagram, the horizontal axis represents the wavelength (nm) of the light incident on filter layer 4, and the vertical axis represents the transmittance of the light incident on filter layer 4. Figure 4 The transmittance shown is based on a transmittance of 100% (=1). For example... Figure 4 As shown, by setting the period a, height h, and width d as described above, the transmittance of the scintillation light L1 with a peak wavelength λ1 (=300nm) can be controlled to a value that is essentially close to 0. On the other hand, for the scintillation light L2 with a peak wavelength λ2 (=220nm), a transmittance of a certain level or higher (around 0.6) can be ensured. That is, by setting the period a, height h, and width d as described above, the filter layer 4 can be configured in a manner that selectively blocks the scintillation light L1 (i.e., selectively allows the scintillation light L2 to pass through).

[0050] Figure 5 This is a graph showing the reflectance (relationship between wavelength and reflectance) of each wavelength in filter layer 4. Figure 5 This represents the simulation results for a unit grid C1 with a period a of 150 nm, a height h of 30 nm, and a width d of 70 nm, 80 nm, 90 nm, and 100 nm. Figure 5 In the diagram, the horizontal axis represents the wavelength (nm) of the light incident on filter layer 4, and the vertical axis represents the reflectivity of the light incident on filter layer 4. Figure 5 The reflectance shown is based on a reference value of 100% reflectance (=1). For example... Figure 5 As shown, by setting the period a, height h, and width d as described above, the reflectivity of the scintillation light L1 with a peak wavelength λ1 (=300nm) can be controlled to a certain value or higher (0.5 or higher). On the other hand, the reflectivity of the scintillation light L2 with a peak wavelength λ2 (=220nm) can be controlled to a low value of about 0.2. That is, by setting the period a, height h, and width d as described above, the filter layer 4 can be configured to selectively reflect the scintillation light L1.

[0051] Reference Figure 6An example of the manufacturing process for filter layer 4 will be described. First, an electron line (EB) resist R is coated (film-formed) on the inner surface 2a of the scintillator 2 (step S1). The film thickness of the EB resist R is, for example, about 300 nm. Next, a pre-designed pattern is drawn on the EB resist R by EB photolithography (step S2). Specifically, by removing a portion of the EB resist R, an opening Ra corresponding to the portion where the metal structure 41 is to be formed is formed. Next, an aluminum film 40 is formed on the EB resist R by vapor deposition (e.g., resistance heating vapor deposition) (step S3). The film thickness of the aluminum film 40 is, for example, about 30 nm. By allowing a portion of the aluminum film 40 to enter the opening Ra formed on the EB resist R, an aluminum film 40 is also formed on the inner surface 2a of the scintillator 2 within the opening Ra. Next, the EB resist R is removed from the scintillator 2 by a stripping process (step S4). At this time, the aluminum film 40 formed on the EB resist R is also removed. As a result, on the inner surface 2a of the scintillator 2, only a circular aluminum film 40 remains, formed at the position corresponding to the opening Ra of the EB resist R. This cylindrical aluminum film 40 corresponds to the aforementioned metal structure 41.

[0052] The filter layer 4 (the top surface 41a of the metal structure 41) can be disposed either in contact with the light detection surface 3a of the light detection unit 3A or separately from it. From the viewpoint of effectively capturing the scintillation light passing through the filter layer 4 into the light detection unit 3A, it is preferable that the filter layer 4 is in contact (closely attached) with the light detection surface 3a. However, in this case, it is preferable not to provide an adhesive (adhesive layer) between the filter layer 4 and the light detection surface 3a of the light detection unit 3A (interface). This is to prevent the adhesive from absorbing the scintillation light of the object being detected (scintillation light L2 in the wavelength region of 220nm).

[0053] Alternatively, the filter layer 4 may not be formed on the inner surface 2a of the scintillator 2, but rather on the light detection surface 3a of the light detection unit 3A. In this case, the filter layer 4 can also be formed following the same steps as described above. That is, by operating the... Figure 6 The step of replacing "inner surface 2a of scintillator 2" with "light detection surface 3a of light detection unit 3A" in the illustrated steps allows the filter layer 4 to be formed on the light detection surface 3a of light detection unit 3A. Furthermore, in this case, the filter layer 4 (top surface 41a of metal structure 41) can either abut against the inner surface 2a of scintillator 2 or be arranged separately from the inner surface 2a. From the viewpoint of effectively capturing the scintillating light passing through the filter layer 4 into light detection unit 3A, it is preferable that the filter layer 4 abuts (is in close contact) with the inner surface 2a. However, in this case, for the same reasons as above, it is also preferable not to provide an adhesive (adhesive layer) between the filter layer 4 and the inner surface 2a of scintillator 2 (interface).

[0054] (Effects)

[0055] In the radiation detector 1A described above, two scintillating lights L1 and L2 with different peak wavelengths are generated by the scintillator 2. A filter layer 4 disposed between the scintillator 2 and the photodetector 3A selectively blocks the scintillating light L1, which has a peak wavelength λ1 (300 nm in this embodiment). That is, the scintillating light L2, which has a peak wavelength λ2 (220 nm in this embodiment), selectively transmits to the photodetector 3A. Here, the filter layer 4 is not made of a resin film, but rather a metasurface structure. By using a metasurface structure to construct the filter layer 4, compared to the case where the filter layer 4 is made of a resin film, the following advantages can be obtained: That is, by controlling the shape of the metasurface structure, regardless of the wavelength region of the scintillating light or the shape of the emission peak (resonant peak width, etc.), better filtering performance than when the filter layer is made of a resin film can be obtained. That is, it is possible to allow light of the wavelength of interest (here, scintillation light L2 with a peak wavelength λ2) to pass through appropriately, and to appropriately block light of wavelengths other than the wavelength of interest (here, scintillation light L1 with a peak wavelength λ1). Therefore, according to the radiation detector 1A, light of the wavelength of interest can be appropriately detected regardless of the wavelength region of the scintillation light and the shape of the emission peak.

[0056] Filter layer 4 is a plasma filter utilizing surface plasma. Based on the above structure, by utilizing surface plasma, a filter structure that selectively blocks one of the scintillation lights L1 and L2 (in this embodiment, scintillation light L1) can be easily obtained. That is, by designing the metasurface structure of filter layer 4 (in this embodiment, a micro-uneven structure composed of multiple metal structures 41) to utilize the surface plasma effect, a filter layer 4 that selectively blocks only scintillation light of a specific wavelength band can be obtained.

[0057] The filter layer 4 has a plurality of periodically arranged columnar metal structures 41. According to the above structure, by adjusting the arrangement (period a) of the plurality of metal structures 41 and the width d and height h of the metal structures 41, a filter structure that selectively blocks one of the scintillating lights L1 and L2 (scintillating light L1 in this embodiment) can be easily obtained.

[0058] The metal structure 41 is made of cylindrical aluminum. Based on the above structure, by adjusting the diameter (width d) and height h of the cylindrical aluminum, a filter for selectively blocking the scintillating light L1 can be easily designed.

[0059] The decay time t1 of scintillation light L1 is longer than the decay time t2 of scintillation light L2. That is, in the radiation detector 1, the filter layer 4 is configured to selectively block the scintillation light L1, which has the longer decay time among the two scintillation lights L1 and L2, resulting in the two scintillation lights L1 and L2 having different decay times t1 and t2. According to this configuration, the light detection unit 3A can detect only the scintillation light L2, which has a shorter decay time. This improves the temporal resolution of the radiation detector 1A. Specifically, in this embodiment, BaF2 is used as the scintillator 2, and there is a very large difference of approximately 1000 times between the decay times t1 and t2 of the two scintillation lights L1 and L2 (i.e., t1 / t2 ≈ 1000). Here, if scintillation light L2 and a certain amount of scintillation light L1 are detected in the light detection unit 3A, the temporal resolution deteriorates due to the influence of the longer decay time of scintillation light L1. On the other hand, as in this embodiment, by using the filter layer 4 to shield the scintillation light L1, the scintillation light L2 with a shorter decay time is selectively guided to the light detection unit 3A, thereby suppressing the aforementioned deterioration of the time resolution.

[0060] The filter layer 4 selectively reflects the scintillator light L1 generated by the scintillator 2 toward the scintillator 2 side. According to the above structure, since the amount of scintillator light L1 leaking toward the light detection unit 3A side can be effectively reduced, it is more appropriate to detect only the scintillator light L2 in the light detection unit 3A.

[0061] The light detection unit 3A is a solid-state imaging element. According to the above configuration, in a structure where the scintillator 2 and the filter layer 4 are arranged as external components relative to the light detection unit 3A, which is a solid-state imaging element, the effects of the aforementioned radiation detector 1A can be achieved. That is, by providing the scintillator 2 and the filter layer 4 to a conventional solid-state imaging element, a radiation detector 1A that performs the aforementioned effects can be obtained.

[0062] (Second Implementation)

[0063] like Figure 7 As shown, the radiation detector 1B of the second embodiment differs from the radiation detector 1A in that it includes a light detection unit 3B instead of a light detection unit 3A. The other structures of the radiation detector 1B are the same as those of the radiation detector 1A. The light detection unit 3B is composed of a photomultiplier tube 10 with a built-in microchannel plate (so-called MCP-PMT). The photomultiplier tube 10 is an electron tube with a vacuum internal space S. The photomultiplier tube 10 includes: a light entrance window 11, a photoelectric surface 12, a cylindrical component 13, and an MCP (microchannel plate) 14.

[0064] The light incident window 11 is a component that allows the scintillated light generated by the scintillator 2 to enter. The light incident window 11 is, for example, formed in a cylindrical shape. The light incident window 11 is provided such that one open end (the open end on the scintillator 2 side) of the hermetically sealed cylindrical component 13 is sealed. The light incident window 11 is formed, for example, from MgF2 (magnesium fluoride), synthetic quartz, etc. A filter layer 4 is disposed between the inner surface 2a of the scintillator 2 and the light incident surface 11a, which serves as the outer surface of the light incident window 11. The filter layer 4 (multiple metal structures 41) can be formed either on the inner surface 2a of the scintillator 2 or on the light incident surface 11a of the light incident window 11.

[0065] The photoelectric surface 12 is disposed on the inner surface 11b (the surface on the S side of the internal space) of the light incident window 11. If a filter layer 4 is formed on the light incident surface 11a, it is sufficient to form the filter layer 4 on the light incident surface 11a and then form the photoelectric surface 12 on the inner surface 11b. The photoelectric surface 12 is a so-called transmissive photoelectric surface. That is, when light is incident from the light incident window 11 side, the photoelectric surface 12 emits photoelectrons from the S side of the internal space. The photoelectric surface 12 is formed, for example, from an alkali metal. Examples of materials for the photoelectric surface 12 include alkali-antimony. The photoelectric surface 12 constitutes a cathode.

[0066] The cylindrical component 13 forms at least a portion of the side tube of the photoelectron multiplier tube 10. The MCP 14 and the anode (not shown) are housed within the cylindrical component 13. The MCP 14 receives photoelectrons emitted from the photoelectric surface 12, multiplying them. The anode collects the multiplied photoelectrons in the MCP 14 and extracts them to the outside as an electrical signal.

[0067] According to the second embodiment, in a configuration where the scintillator 2 and the filter layer 4 are arranged as external components to the light detection unit 3B of an electron tube (here, for example, a photoelectron multiplier tube), the same effect as the radiation detector 1A described above can be achieved. That is, by providing the scintillator 2 and the filter layer 4 to a conventional electron tube, a radiation detector 1B that performs the aforementioned effect can be obtained.

[0068] (Third Implementation)

[0069] like Figure 8 As shown, the radiation detector 1C of the third embodiment is configured as a photoelectron multiplier tube 10C (electron tube). In the radiation detector 1C, the scintillator 2 is the light entrance window of the photoelectron multiplier tube 10C, and the light detection unit 3C is the photoelectric surface 12. That is, in the radiation detector 1B described above, the scintillator 2 and the filter layer 4 are configured as external components to the photodetector (light detection unit 3B) which is a photoelectron multiplier tube, but in the radiation detector 1C, the scintillator 2 and the filter layer 4 are built into the photodetector (photoelectron multiplier tube 10C) which is a photoelectron multiplier tube.

[0070] In radiation detector 1C, similar to radiation detectors 1A and 1B, a filter layer 4 (multiple metal structures 41) is formed on the inner surface 2a of the scintillator 2. Furthermore, in radiation detector 1C, a protective film 15 is disposed between the filter layer 4 and the photoelectric surface 12 (photodetector 3C). The protective film 15 is formed, for example, of aluminum oxide (Al2O3). The protective film 15 functions as a blocking layer to shield the material of the scintillator 2 from reaction with the photoelectric surface 12.

[0071] Protective film 15, for example, is in Figure 6 Following step S4 (stripping process), a protective film is formed on the inner surface 2a of the scintillator 2, where multiple metal structures 41 are formed, using atomic layer deposition (ALD) or similar methods. The protective film 15 is formed to cover the inner surface 2a of the scintillator 2 (the portion where no metal structures 41 are present) and also to cover the top surface 41a of the metal structures 41. That is, the thickness of the protective film 15 (its height from the inner surface 2a) is greater than the height h of the metal structures 41 (see reference). Figure 3 The thickness of the protective film 15 is, for example, approximately "height h of metal structure 41 + 1 nm" to "height h of metal structure 41 + 5 nm". For example, when the height h of metal structure 41 is 30 nm, the thickness of the protective film 15 is approximately 31 nm to 35 nm.

[0072] The photoelectric surface 12 is disposed in the central portion excluding the edge portion of the surface 15a of the protective film 15 (the surface opposite to the inner surface 2a side of the scintillator 2). In addition, one open end of the cylindrical component 13 (the open end on the scintillator 2 side) is hermetically joined to the edge portion of the surface 15a of the protective film 15.

[0073] According to the third embodiment, by embedding the scintillator 2 and the filter layer 4 inside the electron tube (in this embodiment, a photoelectron multiplier tube is an example), the overall size of the radiation detector 1C can be miniaturized compared to the case where the scintillator 2 and the filter layer 4 are configured as external components of the electron tube. Furthermore, the detection light (scintillator light L2) can be efficiently guided towards the photoelectric surface 12. In addition, in the above configuration, the protective film disposed between the filter layer 4 and the photoelectric surface 12 (photodetector 3C) can appropriately prevent chemical reactions between the scintillator 2 and the photoelectric surface 12.

[0074] (Fourth implementation)

[0075] like Figure 9As shown, the radiation detector 1D of the fourth embodiment differs from the radiation detector 1A of the first embodiment in that it also includes a light-absorbing layer 5. The other structures of the radiation detector 1D are the same as those of the radiation detector 1A. As described in the first embodiment, the scintillator 2 has an inner surface 2a (first surface) opposite to the light detection unit 3A, and an outer surface 2b (second surface) and a side surface 2c (second side) not opposite to the light detection unit 3A. The light-absorbing layer 5 is disposed on at least a portion of the second surface (in this embodiment, for example, the entire outer surface 2b and side surface 2c). The light-absorbing layer 5 absorbs the scintillating light L1 reflected by the filter layer 4. The light-absorbing layer 5 is, for example, black adhesive tape adhered to the outer surface 2b and the side surface 2c.

[0076] According to the fourth embodiment, the scintillation light L1 reflected by the filter layer 4 is absorbed in the light absorption layer 5, thereby suppressing the scintillation light L1 from re-entering the filter layer 4. This allows for more suitable detection of the scintillation light L2 in the light detection section 3A. For example, the filter layer 4 is designed to appropriately block (reflect or absorb) the scintillation light L1 incident at a specific incident angle (a specific incident angle range). If the scintillation light L1, incident at the filter layer 4 at the aforementioned specific incident angle and reflected by the filter layer 4, returns to the filter layer 4 at an incident angle different from the aforementioned specific incident angle, the scintillation light L1 (return light) may pass through the filter layer 4. By providing the light absorption layer 5, the generation of the aforementioned return light can be suppressed.

[0077] (Fifth Embodiment)

[0078] like Figure 10 As shown, the radiation detector 1E of the fifth embodiment differs from the radiation detector 1D of the fourth embodiment in that it has a light detection section 6 (second light detection section) on the outer surface 2b of the scintillator 2 instead of the light absorption layer 5. The other structures of the radiation detector 1E are the same as those of the radiation detector 1D. The light detection section 6 is arranged such that its light detection surface 6a faces the outer surface 2b of the scintillator 2. The type of light detection section 6 is not particularly limited; for example, it can be made of SiPM.

[0079] According to the fifth embodiment, the photodetector 6 can detect the scintillation light L1 reflected by the filter layer 4. Thus, for example, by using the photodetector 3A to detect scintillation light L2, whose decay time is shorter than that of scintillation light L1, the temporal resolution can be improved. Furthermore, by using the photodetector 6 to detect scintillation light L1, whose decay time is longer than that of scintillation light L2 but whose emission intensity is greater than that of scintillation light L2, a sufficient amount of detection light can be ensured overall. This improves the detection accuracy of the radiation detector 1E. In other words, by detecting scintillation light L1 and L2 in the photodetectors 3A and 6 respectively, both temporal resolution and detection light intensity can be improved. More specifically, the photodetector 3A obtains time information, while the photodetector 6 obtains information other than time information (e.g., the energy and type of the emission line). In this way, the functions of each photodetector 3A and 6 can be clearly defined, thus simplifying subsequent signal processing.

[0080] (Sixth Embodiment)

[0081] like Figure 11 As shown, the radiation detector 1F of the sixth embodiment differs from the radiation detector 1E of the fifth embodiment in that it also includes a filter layer 7 (second filter layer) disposed between the scintillator 2 and the light detection unit 6. The other structures of the radiation detector 1F are the same as those of the radiation detector 1E. The filter layer 7 is configured to selectively allow the scintillator light L1 to pass through. That is, the filter layer 7 is configured to selectively block the scintillator light L2. In this embodiment, the filter layer 7 is composed of a plurality of holes 71a corresponding to a plurality of pillars (metal structures 41) of the filter layer 4. That is, the filter layer 7 has a structure in which the space between the metal structures 41 (protrusions) and the space (the space where no metal structures 41 are provided) (recesses) of the filter layer 4 are reversed. More specifically, the filter layer 7, like the plurality of metal structures 41 in the filter layer 4, is formed by a plurality of cylindrical holes 71a (recesses) arranged in a grid pattern.

[0082] Figure 12 This represents the unit grid C2 that constitutes filter layer 7. Filter layer 7 is composed of... Figure 12 The unit grid C2 shown is a nanostructure (micro-uneven structure) formed by a periodic grid arrangement along the X-axis and Y-axis. As an example, the unit grid C2 is a square region viewed from the Z-axis direction. A cylindrical (plate-like) hole 71a is formed in each unit grid C2. The hole 71a is located in the center of the metal structure 71 in the unit grid C2.

[0083] The period a2 of the aperture 71a (i.e., the distance between the centers of two adjacent apertures 71a, and the length of one side of a unit grid C2) is set to be shorter than the wavelengths of the scintillating light L1 and L2 of the filtered object, similar to the period a of the filter layer 4 described above. Specifically, the wavelengths of the scintillating light L1 and L2 are 300 nm and 220 nm, respectively; therefore, the period a2 of the aperture 71a is set to a value shorter than these wavelengths. The period a2 can be selected, for example, from the range of 150 nm to 200 nm. The width d2 (diameter) of the aperture 71a is the same as the width d of the metal structure 41 described above, and can be selected, for example, from the range of 80 nm to 140 nm. The height h2 (depth) of the aperture 71a is the same as the height h of the metal structure 41 described above, and can be selected, for example, from the range of 30 nm to 70 nm. The height h2 of the aperture 71a is the length from the outer surface 2b of the scintillator 2 to the top 71b of the metal structure 71.

[0084] According to the sixth embodiment, since the component of the scintillating light L2 toward the outer surface 2b of the scintillator 2 is shielded by the filter layer 7, only the scintillating light L1 can be appropriately detected in the light detection unit 6. Furthermore, the filter layer 7 has a metasurface structure. In this case, the same metasurface structure as the filter layer 4 is adopted, thereby allowing for suitable design and manufacturing of the filter layer 7. Additionally, the filter layer 7 is composed of a plurality of holes 71a corresponding to the plurality of metal structures 41 of the filter layer 4. Based on the above structure, and based on the Babinette principle, a filter layer 7 having properties opposite to those of the filter layer 4 can be easily designed and manufactured. That is, the metasurface structure of the filter layer 7 is designed to correspond to the metasurface structure of the filter layer 4 (i.e., the negative (concave) and positive (convex) portions are in the opposite relationship to the metasurface structure of the filter layer 4), thereby making it easy and reliable to form a filter layer 7 with the property of selectively blocking scintillating light L2.

[0085] (Radiation detection device)

[0086] like Figure 13 As shown, one embodiment of the radiation detection apparatus 50 includes a gantry 51 on which a plurality of radiation detectors 1A of the first embodiment are arranged. The radiation detection apparatus 50 is, for example, a positron emission tomography (TOP-PPET) apparatus. The gantry 51 is annular (donut-shaped). In this example, the plurality of radiation detectors 1A are arranged in a circular configuration around the entire circumference of the gantry 51. Each radiation detector 1A is arranged such that the scintillator 2 is located on the central side of the gantry 51, and the light detection unit 3A is located on the outer side of the gantry 51.

[0087] The rack 51 has an opening for allowing part or all of the body of a subject 100 (patient) lying on a bed (not shown) to enter. The subject 100 has pre-administered a radiopharmaceutical containing a positron-emitting nuclide. A radiation detector 1A detects annihilated gamma rays emitted from the subject 100.

[0088] By using the radiation detector 1A having the above-described structure to construct a radiation detection device 50, a radiation detection device 50 that can perform the effects of the radiation detector 1A described above can be obtained.

[0089] (Modified Example)

[0090] The present invention has been described above with reference to several embodiments, but the present invention is not limited to the embodiments described above. The materials and shapes of each component are not limited to those described above, and various materials and shapes can be used.

[0091] For example, in the second embodiment, the light detection unit 3B is shown to be composed of an MCP-PMT, but the light detection unit may also be composed of electron tubes other than those described above. That is, the light detection unit may be composed of a photoelectron multiplier tube other than an MCP-PMT, or it may be composed of a phototube (photoelectric conversion tube) that does not have electron multiplication function.

[0092] In the above embodiments (e.g., the first embodiment), the filter layer 4 is configured to selectively block the scintillation light L1 with the larger peak wavelength of the two scintillation lights L1 and L2. However, it can also be configured to selectively block the scintillation light L2 with the smaller peak wavelength. In this case, the light detection unit 3A can appropriately detect only the scintillation light L1 with the larger peak wavelength. Furthermore, in the above embodiments, the filter layer 4 is configured to selectively block the scintillation light L1 with the longer decay time of the two scintillation lights L1 and L2. However, it can also be configured to selectively block the scintillation light L2 with the shorter decay time. In this case, the light detection unit 3A can appropriately detect only the scintillation light L1 with the longer decay time.

[0093] Furthermore, the construction of a portion of one embodiment or modification described above can be arbitrarily applied to the construction of other embodiments or modifications. For example, in the radiation detector 1D of the fourth embodiment, the light detection unit of another embodiment (e.g., the light detection unit 3B of the radiation detector 1B of the second embodiment) can be used instead of the light detection unit 3A.

Claims

1. A radiation detector, characterized in that, have: A scintillator that generates a first scintillation light with a first peak wavelength and a second scintillation light with a second peak wavelength in response to incident radiation; The light detection unit detects the scintillating light generated by the scintillator; A filter layer is disposed between the scintillator and the light detection unit, and selectively blocks the first scintillating light; The second light detection unit is disposed on the side opposite to the side where the filter layer is provided, relative to the scintillator; A second filter layer is disposed between the scintillator and the second photodetector, and selectively blocks the second scintillator light. The filter layer has a super-advanced surface structure. The filter layer is composed of a plurality of periodically arranged columnar bodies. The second filter layer is composed of a plurality of holes corresponding to the plurality of columnar bodies of the filter layer.

2. The radiation detector as described in claim 1, characterized in that, The filter layer is a plasma filter that utilizes surface plasma.

3. The radiation detector as described in claim 1 or 2, characterized in that, The filter layer has a plurality of periodically arranged columnar metal structures.

4. The radiation detector as described in claim 3, characterized in that, The metal structure is made of cylindrical aluminum.

5. The radiation detector according to any one of claims 1 to 4, characterized in that, The decay time of the first flash light is longer than that of the second flash light.

6. The radiation detector according to any one of claims 1 to 5, characterized in that, The filter layer selectively reflects the first scintillation light generated by the scintillator toward the scintillator side.

7. The radiation detector as described in claim 6, characterized in that, The scintillator has a first surface opposite to the light detection unit and a second surface not opposite to the light detection unit. A light-absorbing layer is provided on at least a portion of the second surface to absorb the first scintillation light reflected by the filter layer.

8. The radiation detector as claimed in claim 1, characterized in that, The second filter layer has a super-smooth surface structure.

9. The radiation detector according to any one of claims 1 to 8, characterized in that, The light detection unit is a solid-state imaging element or an electron tube.

10. The radiation detector according to any one of claims 1 to 8, characterized in that, The radiation detector is a vacuum tube. The scintillator is the light entrance window of the electron tube. The photodetector is the photoelectric surface of the electron tube.

11. The radiation detector as claimed in claim 10, characterized in that, It also has a protective film disposed between the filter layer and the photodetector.

12. A radiation detection device, characterized in that, A rack is provided in which multiple radiation detectors according to any one of claims 1 to 11 are arranged.

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