Radiation detector and positron emission tomography apparatus

Abstract

An object of the present application is to provide a radiation detector or the like which can reduce man-hours and time compared to a case where a scintillator is divided into individual sections by a modified region formed by laser irradiation, and can identify a section where scintillating light is generated in the same manner as in a case where a modified region is formed by laser irradiation. A radiation detector includes a first light detector, a second light detector, and an elongated scintillator disposed between the first light detector and the second light detector, one end surface of the elongated scintillator being optically coupled to the first light detector and the other end surface being optically coupled to the second light detector.

Description

Technical Field

[0001] This disclosure relates to a radiation detector and a positron emission tomography (PET) scanning device. Background Technology

[0002] A radiation detector is known, comprising a scintillator having two scintillator sections arranged parallel to each other, the scintillator being configured to allow light (scintillation light) to flow between one end face of each of the two scintillator sections (U-shaped scintillator) (see, for example, Patent Document 1). The scintillator section of Patent Document 1 is divided into multiple segments by a modified region (a light scattering region with light transmittance varying according to the incident angle) formed by laser irradiation. By forming the modified region, the proportion of scintillation light reaching the two end faces of the scintillator varies for each segment generating scintillation light, thus enabling the identification of the segment generating scintillation light by performing a predetermined calculation based on the output of a light-receiving element optically coupled to the two end faces.

[0003] [Patent Document 1] Japanese Patent No. 6726969 Summary of the Invention

[0004] However, since a large number of scintillators are typically used in positron emission tomography (PET) devices that employ radiation detectors, there is a problem that forming a modified region in each scintillator by laser irradiation requires a lot of time and effort (e.g., laser processing of a system can take six months to a year).

[0005] This disclosure is made to solve these problems, and its purpose is to provide a radiation detector and a positron emission tomography (PET) apparatus that, compared with the case where a scintillator is divided into segments by a modified region formed by laser irradiation, can reduce labor and time, and can identify the segments that generate scintillating light in the same way as the case where a modified region is formed by laser irradiation.

[0006] The radiation detector of the first aspect of the embodiment includes: a first photodetector; a second photodetector; and an elongated scintillator disposed between the first photodetector and the second photodetector, one end face of the elongated scintillator being optically coupled to the first photodetector and the other end face of the elongated scintillator being optically coupled to the second photodetector, wherein at least one narrow light-absorbing material is disposed on the outer peripheral surface of the scintillator, the light-absorbing material absorbing part of the scintillator light generated therein.

[0007] Alternatively, the positron emission tomography apparatus of the second aspect of the embodiment includes: a subject support bed configured to hold a subject to which a radiopharmaceutical has been administered; radiation detectors arranged in a ring for detecting radiation emitted from the subject; means for identifying the location of a radiation emission site based on the output of the radiation detectors; means for generating an image indicating the location of the radiation emission site; and a display means for displaying the image, wherein the radiation detectors include: a first photodetector; a second photodetector; and an elongated scintillator disposed between the first photodetector and the second photodetector, one end face of the elongated scintillator being optically coupled to the first photodetector and the other end face of the elongated scintillator being optically coupled to the second photodetector, wherein at least one narrow light-absorbing material is disposed on the outer peripheral surface of the scintillator, the light-absorbing material absorbing a portion of the scintillator light generated therein.

[0008] As described above, according to the first or second aspect, compared to the case where the scintillator is divided into segments by a modified region formed by laser irradiation, it is possible to reduce labor time and time, and to identify the segments that generate scintillating light in the same manner as in the case where the modified region is formed by laser irradiation.

[0009] Furthermore, according to the first aspect or the second aspect above, the scintillator is a U-shaped scintillator.

[0010] Furthermore, according to the first aspect or the second aspect above, the scintillator includes a plurality of segments divided by the light-absorbing material, and the light-absorbing material is the light-absorbing material in which the valleys between adjacent segments appear in the DOI separation characteristic histogram.

[0011] Furthermore, in the first or second aspect described above, the light-absorbing material may be black tape, black coating, anodized material, visible light-absorbing material, or light-absorbing film.

[0012] The radiation detector of this embodiment is a radiation detector, which includes [1] "a first photodetector; a second photodetector; and an elongated scintillator disposed between the first photodetector and the second photodetector, one end face of the elongated scintillator being optically coupled to the first photodetector, and the other end face of the elongated scintillator being optically coupled to the second photodetector, wherein at least one narrow light-absorbing material for absorbing part of the scintillator generated is disposed on the outer peripheral surface of the scintillator."

[0013] The radiation detector in this embodiment can be [2] "a radiation detector, which is the radiation detector described in [1], wherein the scintillator is a U-shaped scintillator."

[0014] The radiation detector in this embodiment may be [3] "a radiation detector, which is the radiation detector described in [1] or [2], wherein the scintillator comprises a plurality of segments separated by the light-absorbing material, and the light-absorbing material is the light-absorbing material in which the valleys between adjacent segments appear in the DOI separation characteristic histogram."

[0015] The radiation detector in this embodiment can be [4] "a radiation detector, which is the radiation detector described in [3], wherein the light-absorbing material is black tape, black coating, anodized material, visible light absorbing material or light-absorbing film."

[0016] The positron emission tomography (PET) apparatus of this embodiment may be [5] "a positron emission tomography apparatus comprising: a subject support bed configured to hold a subject to which a radiopharmaceutical has been administered; a ring-shaped array of radiation detectors for detecting radiation emitted from the subject; a means for identifying the location of a radiation emission site based on the output of the radiation detectors; a means for generating an image indicating the location of the radiation emission site; and a display means for displaying the image, wherein the radiation detector comprises: a first photodetector; a second photodetector; and an elongated scintillator disposed between the first photodetector and the second photodetector, one end face of the elongated scintillator being optically coupled to the first photodetector, and the other end face of the elongated scintillator being optically coupled to the second photodetector, wherein at least one narrow light-absorbing material for absorbing a portion of the scintillator-generated scintillation light is disposed on the outer peripheral surface of the scintillator."

[0017] According to this disclosure, a radiation detector and a positron emission tomography (PET) apparatus can be provided that, compared to the case where a scintillator is divided into segments by a modified region formed by laser irradiation, can reduce labor time and time, and can identify the segments that generate scintillating light in the same way as the case where a modified region is formed by laser irradiation.

[0018] The above and other objects, features and advantages of this disclosure will be more fully understood through the detailed description and accompanying drawings given below. Attached Figure Description

[0019] Figure 1 This is a schematic structural diagram of the radiation detector 1 according to embodiment 1;

[0020] Figure 2 From Figure 1 A stereoscopic view of the extracted scintillator 10 and photodetector 20 (partial);

[0021] Figure 3 It is a histogram summarizing the calculation results of DOI information (DOI separation characteristic histogram);

[0022] Figure 4 This is an example of a positron emission tomography (PET) apparatus 60 that uses the radiation detector 1 of this disclosure;

[0023] Figure 5 This is an example of a positron emission tomography (PET) apparatus 60 that uses the radiation detector 1 of this disclosure;

[0024] Figure 6A This is an example of applying black tape BT only to a portion of the outer peripheral surface, namely the left and right sides of the scintillator 10;

[0025] Figure 6B This is an example of applying black tape BT only to a portion of the outer peripheral surface, i.e., the front side of the scintillator 10;

[0026] Figure 6C This is an example of applying black tape BT only to a portion of the outer peripheral surface, namely the left and right sides and the front of the scintillator 10;

[0027] Figure 6D This is an example of dividing the scintillator 10 into three layers by attaching black tape BT to a portion of the outer peripheral surface of the scintillator 10;

[0028] Figure 7 This is a schematic diagram of scintillator 10A as a modified example;

[0029] Figure 8 This is an example of sharing a light-absorbing member 12 and a reflective member 13 between adjacent scintillators 10. Detailed Implementation

[0030] <Implementation Method 1>

[0031] Hereinafter, the radiation detector 1 of the first embodiment of the present disclosure will be described with reference to the accompanying drawings. In the drawings, corresponding components are labeled with the same reference numerals, and repeated descriptions thereof are omitted.

[0032] Figure 1 This is a schematic structural diagram of the radiation detector 1 according to the first embodiment.

[0033] Radiation detector 1 is a DOI (Depth of Interaction) detector, used to identify the location (depth direction) of scintillation light produced by the interaction of high-energy gamma rays (annihilation radiation) incident on scintillator 10 within scintillator 10. For example... Figure 1 As shown, the radiation detector 1 includes a plurality of scintillators 10 and a light detection unit 20. The plurality of scintillators 10 are arranged in a matrix in the XY direction. To prevent scintillating light from propagating between adjacent scintillators 10, each scintillator 10 is covered by a reflective member 16.

[0034] Figure 2 From Figure 1 A three-dimensional view of the extracted scintillator 10 and photodetector unit 20 (partial). For ease of illustration, Figure 2 The reflective component 16 is omitted from the text. For ease of explanation, as shown... Figure 2 As shown, the X-axis, Y-axis, and Z-axis are defined. The X-axis is... Figure 2 It extends along the left-right direction. The Z-axis is... Figure 2 The middle axis extends vertically. The Y-axis extends in a direction orthogonal to the XZ plane.

[0035] like Figure 2 As shown, the scintillator 10 is an elongated scintillator (U-shaped scintillator) disposed between the light-receiving element 20A (an example of the first photodetector of this disclosure) and the light-receiving element 20B (an example of the second photodetector of this disclosure), with one end optically coupled to the light-receiving element 20A and the other end optically coupled to the light-receiving element 20B. Specifically, the scintillator 10 includes a first scintillator portion 11A and a second scintillator portion 11B disposed parallel to each other. The material of the scintillator 10 is, for example, Bi4Ge3O. 12 (BGO), Ce-doped Lu2SiO5 (LSO), Lu 2(1-x) Y 2x SiO5 (LYSO), Gd2SiO5 (GSO), Pr-doped LuAG (Lu3Al5O) 12 Ce-doped LaBr3 (LaBr3), Ce-doped LaCl3 (LaCl3), or Ce-doped Lu 0.7 Y 0.3 AlO3 (LuYAP), lutetium fine silicate (LFS) and other crystals (ingots).

[0036] The first scintillator portion 11A and the second scintillator portion 11B will now be described. Since the first scintillator portion 11A and the second scintillator portion 11B have the same structure, the first scintillator portion 11A will be used as an example in the following description.

[0037] The first scintillator portion 11A is a scintillator extending along the Z direction. Specifically, the first scintillator portion 11A is a cuboid-shaped scintillator having a pair of surfaces parallel to the XY plane, a pair of surfaces parallel to the XZ plane, and a pair of surfaces parallel to the YZ plane. It should be noted that the first scintillator portion 11A can also be a polygonal prism shape other than a quadrangular prism shape. All surfaces of the first scintillator portion 11A are smoothed and polished. This polishing can be mechanical polishing or chemical polishing.

[0038] The first scintillator portion 11A and the second scintillator portion 11B are arranged adjacent to each other in the X direction, with their respective side surfaces (surfaces parallel to the YZ plane) facing each other. At this time, the arrangement of the first scintillator portion 11A and the second scintillator portion 11B is such that when projected onto the YZ plane, their respective shapes coincide on the YZ plane.

[0039] like Figure 2 As shown, at least one narrow light-absorbing material 12 is provided on the outer peripheral surface of the scintillator 10, which is configured to absorb a portion of the scintillator light generated in the scintillator 10. An example of using black tape BT as the light-absorbing material 12 will be described below. The black tape BT is, for example, industrial tape CP743 manufactured by Shurtape. The width WBT of the black tape BT is approximately 1 mm. The attachment position p1 of the black tape BT is the center position of the scintillator 10 in the Z direction. The black tape BT is attached to the entire circumference of the outer peripheral surface at the attachment position p1.

[0040] By means of the black tape BT pasted as described above, the first scintillator portion 11A is divided into a first layer scintillator segment 11A1 (hereinafter also referred to as segment (1)) and a second layer scintillator segment 11A2 (hereinafter also referred to as segment (2)). Similarly, the second scintillator portion 11B is divided into a first layer scintillator segment 11B1 (hereinafter also referred to as segment (3)) and a second layer scintillator segment 11B2 (hereinafter also referred to as segment (4)).

[0041] The reflective element 13 is disposed between section (1) and section (4) and is mainly used to prevent scintillation light from propagating between them. The reflective element 13 is, for example, an ESR (Enhanced Specular Reflector) reflective material.

[0042] On the other hand, an optical discontinuity (here, an air layer) is provided between segment (2) and segment (3). This optical discontinuity may also be, for example, an optical adhesive layer, rather than an air layer. It should be noted that no optical discontinuity is provided between segment (1) and segment (2). That is, the first scintillator segment 11A is a single crystal (crystal block), and segment (1) and segment (2) are optically continuous with each other. Similarly, no optical discontinuity is provided between segment (3) and segment (4). That is, the second scintillator segment 11B is a single crystal (crystal block), and segment (3) and segment (4) are optically continuous with each other.

[0043] In the scintillator 10 having the above structure, that is, in the scintillating light generated in any one of the segments (1) to (4), the scintillating light (see Figure 1A portion of La, as it passes between segment (1) and segment (2), is absorbed by the black tape BT separating segment (1) and segment (2), and then propagates to an end face 14 of the first scintillator 11A parallel to the XY plane, and is incident on the light-receiving element 20A optically coupled to the end face 14. Similarly, in the scintillating light generated in any of the segments (1) to (4), the scintillating light (see...) Figure 1 Another portion of Lb, as it passes between segment (3) and segment (4), is partially absorbed by the black tape BT separating segment (3) and segment (4), and then propagates to another end face 15 of the second scintillator 11B that is parallel to the XY plane, and is incident on the light-receiving element 20B that is optically coupled to the end face 15. The light-receiving elements 20A and 20B each output an electrical signal corresponding to the light (photons) incident on them.

[0044] Next, we will describe a method for identifying the segments that produce flickering light.

[0045] First, such as Figure 2 As shown, a radiation source 50 (e.g., a disk radiation source using the radioactive isotope sodium-22) that emits radiation in a 360-degree direction is set on one side of the scintillator 10 or at a position facing the scintillator 10, and the DOI information is calculated using the following formula (1) and stored in a storage device (not shown) each time a scintillator light is generated during a predetermined time period (about 3 minutes).

[0046] [Mathematical Expression 1]

[0047]

[0048] Wherein, DOI represents DOI information, A represents the output value of light receiving element 20A, and B represents the output value of light receiving element 20B.

[0049] Figure 3 This is a histogram summarizing the results of DOI information calculations (DOI separation characteristic histogram). Figure 3 In the diagram, the vertical axis represents the number of events that occurred, and the horizontal axis represents the DOI information.

[0050] Reference Figure 3 It can be seen that valleys V1, V2, and V3 exist between segment (1) and segment (2), between segment (2) and segment (3), and between segment (3) and segment (4), respectively. Figure 3 In the diagram, DOI1, DOI2, and DOI3 are labeled to represent the DOI information corresponding to valleys V1, V2, and V3, respectively.

[0051] Each time a flash of light is generated and the output of light-receiving elements 20A and 20B is obtained, the DOI information can be calculated using the above formula (1). By comparing the calculated DOI information with DOI information DOI1 to DOI3 (thresholds), the segment that generates the flash of light can be identified.

[0052] For example, when the calculated DOI information is less than DOI1, the segment that produces flickering light can be identified as segment (1). Similarly, when DOI1 is less than the calculated DOI information and the calculated DOI information is less than DOI2, the segment that produces flickering light can be identified as segment (2). Similarly, when DOI2 is less than the calculated DOI information and the calculated DOI information is less than DOI3, the segment that produces flickering light can be identified as segment (3). Similarly, when DOI3 is less than the calculated DOI information, the segment that produces flickering light can be identified as segment (4). According to the inventors' research, when the outer peripheral surface of the scintillator 10 is not covered with black tape BT, the valleys between segments (especially) Figure 3 The valleys (V1 and V3) shown are not clearly visible, so the sections that produce the flickering light cannot be identified.

[0053] As described above, by attaching black tape BT to the outer peripheral surface of the scintillator 10, the segments that generate scintillating light can be identified (i.e., DOI separation can be achieved). This is because by attaching black tape BT, which is a light-absorbing material, to the outer peripheral surface of the scintillator 10 to separate the segments, the ratio of the amount of scintillating light incident on the light-receiving elements 20A and 20B changes, which is the same as the prior art of separating the segments by modifying the area formed by laser irradiation.

[0054] The light detection unit 20 includes a first light-receiving element 20A optically coupled to the end face 14 of the first scintillator portion 11A, and a second light-receiving element 20B optically coupled to the end face 15 of the second scintillator portion 11B. The light-receiving elements 20A and 20B are, for example, semiconductor photodetectors using an MPPC (multi-pixel photon counter). An MPPC is a photon counting device composed of multiple Geiger-patterned APD pixels. The light-receiving elements 20A and 20B output electrical signals corresponding to the light (photons) incident upon them. These electrical signals are input to the signal processing circuit 30 (see [link to circuit 30]). Figure 5 ).

[0055] Next, a brief description will be given of the positron emission tomography (PET) apparatus 60 that uses the radiation detector 1 disclosed herein.

[0056] Figure 4 and Figure 5An example of a positron emission tomography (PET) apparatus 60 employing the radiation detector 1 of this disclosure is shown. Figure 4 and Figure 5 As shown, the positron emission tomography (PET) apparatus 60 includes: a subject support bed 62 supporting a subject 61 to which a radiopharmaceutical has been administered; a plurality of radiation detectors 1 arranged in a ring to detect radiation (annihilated gamma rays) emitted from the subject 61; means (e.g., signal processing circuit 30) for identifying the location of radiation emission sites based on the output of the radiation detectors 1 (light detection unit 20); means (e.g., information processing device 63 such as a personal computer) for generating an image representing the location of the emission site; and a display device 64 configured to display the image representing the location of the emission site.

[0057] The signal processing circuit 30 compares the DOI information calculated as described above with the DOI information DOI1 to DOI3 (thresholds) stored in a storage device (not shown) to identify the location (segment) where the flickering light is generated, i.e., the location of the radiation emission site. The output of the signal processing circuit 30 is input to the information processing device 63.

[0058] The information processing device 63 generates an image representing the location of the radiation emission part based on the output of the signal processing circuit 30, i.e. the segment that generates the flashing light (the location of the radiation emission part), and displays the generated image on the display device 64.

[0059] As described above, according to this embodiment, by using black tape BT, which is a light-absorbing material, to divide the scintillator 10 into segments, compared with dividing the scintillator into segments by a modified region formed by laser irradiation, the number of processes and processing time can be reduced, and the segments that generate scintillating light can be identified in the same way as in the case where a modified region formed by laser irradiation is provided.

[0060] Next, we will explain the variations.

[0061] In the above embodiment, the sticking position p1 of the black tape BT is described (refer to...). Figure 2 Located at the center of scintillator 10 in the Z direction, with a width WBT (refer to...). Figure 2 The example shown is approximately 1mm, but this disclosure is not limited thereto. That is, the application position p1 and width WBT of the black tape BT can be appropriately adjusted so that the valley (especially) Figure 3 The valleys (V1 and V3) shown are clearly visible. The reflectivity of the black tape BT is also the same.

[0062] For example, the application position p1 of the black tape BT can be a position offset from the center position of the scintillator 10 in the Z direction. On the other hand, if the width WBT of the black tape BT is too large, the amount of scintillating light incident on the light-receiving elements 20A and 20B will be reduced, making it impossible to identify the segment that generates scintillating light. Therefore, considering the amount of scintillating light incident on the light-receiving elements 20A and 20B and the DOI separation characteristics, the width WBT of the black tape BT is preferably about 1 mm or less.

[0063] In the above embodiments, an example of black tape BT being pasted on the entire circumference of the outer peripheral surface has been described, but this disclosure is not limited thereto. That is to say, as long as the valley (especially Figure 3 Valleys V1 and V3 are clearly visible, and the black tape BT can be seen as... Figures 6A to 6C As shown, it is only pasted on a portion of the outer circumference, not the entire circumference. For example, as... Figure 6A As shown, the black tape BT can be applied only to the left and right sides of the scintillator 10, which is part of the outer peripheral surface. Alternatively, as... Figure 6B As shown, the black tape BT can be applied only to the front side of the scintillator 10, which is part of the outer peripheral surface. Furthermore, as... Figure 6C As shown, the black tape BT can be applied only to the left and right sides and the front of the scintillator 10, which is part of the outer peripheral surface. Although not shown, the black tape BT can also be applied only to the back of the scintillator 10, or only to its front and back, or to other parts of the outer peripheral surface.

[0064] In the above embodiments, an example of dividing the scintillator 10 into two layers by pasting black tape BT has been described, but this disclosure is not limited thereto. For example, by pasting black tape BT, the scintillator 10 can be divided into three layers (see...). Figure 6D (or a multi-layered structure with more layers.) Figure 6D An example of a scintillator 10 divided into three layers is shown by attaching black tape BT to a portion of the outer peripheral surface of the scintillator 10.

[0065] In the above embodiments, the application of black tape BT as a light-absorbing material has been described. Figure 2 The example shown is of a U-shaped scintillator 10; however, this disclosure is not limited thereto. That is, the black tape BT can be applied not only to the U-shaped scintillator 10, but also to any scintillator, as long as the scintillator is an elongated scintillator disposed between the first photodetector and the second photodetector, and one end of which is optically coupled to the first photodetector and the other end of which is optically coupled to the second photodetector.

[0066] For example, such as Figure 7As shown, this disclosure can also be applied to a two-end readout DOI structure using a linear scintillator 10A and light-receiving elements 20A and 20B disposed at both ends of the scintillator. Figure 7 This is a schematic diagram of the scintillator 10A according to a modified example.

[0067] In the above embodiments, an example of using black tape BT as the light-absorbing member 12 has been described; however, this disclosure is not limited thereto. For example, other light-absorbing materials (such as black paint, anodized coating, visible light absorbing materials, or light-absorbing films) may also be used as the light-absorbing member 12. The position, width, reflectivity, etc., of such other light-absorbing materials (e.g., black paint) may be the same as those of the black tape BT described above.

[0068] When using a light-absorbing component 12 with a certain thickness (such as black tape BT), such as Figure 8 As shown, the light-absorbing component 12 and the reflective component 13 can be disposed between adjacent scintillators 10. Figure 8 An example is shown where the light-absorbing member 12 and the reflective member 13 are shared between adjacent scintillators 10. In this case, the light-absorbing member 12 and the reflective member 13 are preferably in close contact with each adjacent scintillator 10.

[0069] All the values ​​presented in the above embodiments are merely examples, and it goes without saying that other appropriate values ​​may also be used.

[0070] The embodiments described above are merely examples in all respects. This disclosure should not be construed as being limited to the description of the embodiments described above. This disclosure may be embodied in various other forms without departing from its spirit or essential characteristics.

[0071] As can be seen from the description herein, the embodiments of this disclosure can be modified in various ways. Such modifications should not be considered a departure from the spirit and scope of this disclosure, and all modifications that are obvious to those skilled in the art are intended to be included within the scope of the following claims.

Claims

1. A radiation detector, comprising: First optical detector; Second optical detector; as well as An elongated scintillator is disposed between the first photodetector and the second photodetector, with one end face of the elongated scintillator optically coupled to the first photodetector and the other end face optically coupled to the second photodetector. At least one narrow light-absorbing material is provided on the outer peripheral surface of the scintillator, which absorbs part of the scintillator light generated in the scintillator.

2. The radiation detector as claimed in claim 1, wherein, The scintillator is a U-shaped scintillator.

3. The radiation detector as described in claim 1 or 2, wherein, The scintillator comprises multiple segments separated by the light-absorbing material, and, The light-absorbing material is the light-absorbing material whose valleys between adjacent segments appear in the DOI separation characteristic histogram.

4. The radiation detector as claimed in claim 3, wherein, The light-absorbing material is black tape, black coating, anodized material, visible light absorbing material, or light-absorbing film.

5. A positron emission tomography (PET) scanner, comprising: Subject support bed, configured to hold a subject who has been given a radiopharmaceutical; Radiation detectors, arranged in a ring, are used to detect radiation emitted from the subject. A device for identifying the location of a radiation emission site based on the output of the radiation detector; Apparatus for generating an image indicating the location of the radiation emission site; as well as Display device for displaying the image, The radiation detector includes: First optical detector; Second photodetector; and An elongated scintillator is disposed between the first photodetector and the second photodetector, with one end face of the elongated scintillator optically coupled to the first photodetector and the other end face optically coupled to the second photodetector. At least one narrow light-absorbing material is provided on the outer peripheral surface of the scintillator, which absorbs part of the scintillator light generated in the scintillator.

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