JP6330618B2 - Radiation detector - Google Patents

Description

  The present invention relates to a radiation detector used in a combined positron emission tomography-magnetic resonance tomography apparatus for simultaneously obtaining nuclear medicine images and magnetic resonance images.

  Conventionally, positron emission tomography (PET) is known as a medical imaging method. A positron emission tomography apparatus, that is, a PET apparatus, is an apparatus that generates a PET image showing a distribution of a radiopharmaceutical labeled with a positron emission nuclide in a subject.

  The PET apparatus includes a plurality of radiation detectors arranged so as to surround the subject M in a ring shape. The radiopharmaceutical administered to the subject is accumulated at the site of interest, and positrons are released from the accumulated drug. The emitted positron causes pair annihilation with the electron, and generates a pair of γ rays having diametrically opposite momentum. A pair of gamma rays are emitted in opposite directions, and each gamma ray is detected simultaneously by the radiation detector. The position of the radiopharmaceutical is calculated based on the detected γ-ray information, and an image showing the distribution of the radiopharmaceutical in the region of interest is provided by the PET apparatus.

  On the other hand, a magnetic resonance tomography apparatus (MR apparatus) is known as a medical imaging apparatus along with a PET apparatus, and an image acquired by the MR apparatus is suitable for anatomical diagnosis. In recent years, in order to acquire images suitable for both physiological and anatomical diagnosis, a magnetic resonance tomography apparatus (MR apparatus) is combined with a PET apparatus, and a positron emission tomography-magnetic resonance tomography combined apparatus. It may be used as (PET-MR).

  In this case, as a light receiving element (photoelectric conversion element) used for the radiation detector, an element such as SiPM (Silicon Photo Multiplier) or APD (Avalanche Photo Diode) can be used. Since the SiPM element and the APD element are not affected by the strong magnetic field generated from the MR apparatus, PET-MR using a SiPM element or the like as a light receiving element has been reported (for example, see Patent Documents 1 to 3).

  Here, the configuration of a conventional PET apparatus will be described. As shown in FIG. 9, the conventional PET apparatus 51 includes a gantry 53 provided with an introduction hole 52 for introducing a subject. Inside the gantry 53, a plurality of radiation detectors 55 arranged in a ring shape so as to surround the introduction hole 52, a housing 57 containing each of the radiation detectors 55, and each of the radiation detectors 55 are housed. And a connection base portion 59 that is connected to 57.

  Next, the configuration of the radiation detector 55 used in the conventional PET apparatus 51 is reported in Patent Document 4, Non-Patent Document 1, and the like. As shown in FIG. 10A, the conventional radiation detector 55 has a configuration in which a scintillator block 61, a light guide 63, and a photodetector 65 are laminated in order from the upper layer. In the radiation detector 55, the upper layer means a side close to the introduction hole 52 of the subject provided in the PET apparatus 51, and the lower layer means a side close to the casing 57 provided in the PET apparatus 51.

  The scintillator block 61 has a structure in which rectangular parallelepiped scintillator crystals 61a are two-dimensionally arranged, and absorbs γ rays emitted from the subject to emit light. Note that light emitted from the scintillator block 61 is scintillator light. The light guide 63 is optically coupled to the scintillator block 61 and the photodetector 65, and transmits the scintillator light to the photodetector 65.

  The photodetector 65 has a configuration in which a photoelectric conversion layer 67 is laminated on one surface of a printed circuit board 69, and the photoelectric conversion layer 67 and the light guide 63 are optically coupled. In the photoelectric conversion layer 67, photoelectric conversion elements that are not affected by a magnetic field, such as SiPM and APD, are two-dimensionally arranged. The photoelectric conversion element constituting the photoelectric conversion layer 67 detects the scintillator light transmitted by the light guide 63 and converts it into an electric signal.

  In general, the other surface of the printed circuit board 69 is provided with an integrated circuit 71 such as an ASIC and a plurality of screw receiving portions 73. That is, the photoelectric conversion layer 67, the printed circuit board 69, and the integrated circuit 71 are laminated in order from the upper layer to the lower layer. The integrated circuit 71 transmits the electrical signal converted by the photoelectric conversion layer 67 to a signal processing circuit described later.

  On the lower layer of the integrated circuit 71, a thermal sheet 75 and a cover plate 77 are sequentially laminated. Each of the thermal sheet 75 and the cover plate 77 is provided with drill holes 75a and 77a. The printed circuit board 69, the thermal sheet 75, and the cover plate 77 are fastened by screwing the screws 79 and the screw receiving portions 73. The thermal sheet 75 is made of a heat conductive material.

  The outer periphery of each of the scintillator block 61, the light guide 63, the photodetector 65, and the thermal sheet 75 is covered with a light shielding case 80. The light shielding case 80 is made of thick black plastic as an example, and prevents light from entering the radiation detector 55 from the outside of the PET apparatus 51. The light shielding case 80 protects the radiation detector 55 from an impact or the like.

  Under the cover plate 77, a cooling plate 81 and a signal processing board 83 are sequentially laminated. The signal processing board 83 is connected to the connection base portion 59. Further, the cover plate 77, the cooling plate 81, the signal processing board 83, and the connection base portion 59 are connected to each other by screwing with screws or fitting with an uneven structure.

  Inside the cooling plate 81, a tube (not shown) for circulating the refrigerant is provided. The signal processing board 83 is provided with a signal processing circuit (not shown). The signal processing circuit reads the electrical signal output from the photoelectric conversion layer 67 via the integrated circuit 71. A tomographic image showing the distribution of positron emitting nuclides in the site of interest is generated based on the read electrical signal. Thus, the PET apparatus 51 generates a radiographic image suitable for diagnosis of a biochemical action or the like for a specific organ or tumor.

  The material constituting the PET apparatus 51 including the radiation detector 55 is a nonmagnetic member, that is, a nonmagnetic metal such as copper or aluminum, or a nonmetal. In particular, the photoelectric conversion element constituting the photoelectric conversion layer 67 is an element that is not affected by a magnetic field. Therefore, the user can combine the PET apparatus 51 with the MR apparatus and use it as a PET-MR apparatus.

International Publication No. 2009/139039 International Publication No. 2010/010608 JP 2014-152232 A JP 2013-231719 A

“Time-of-Flight PET-MR Detector Development with Silicon Photomultiplier”, PSMR2012, GE Healthcare company publication, p21

However, the conventional example having such a configuration has the following problems.
First, the conventional radiation detector has a problem that the cooling efficiency for the photoelectric conversion element is low. When the conventional radiation detector 55 is used, it is necessary to cool the photoelectric conversion element for reasons such as suppressing the generation of noise. Therefore, the radiation detector 55 is provided with a cooling plate 81, and the cooling plate 81 cools the photoelectric conversion layer 67 via a thermal sheet 75 or the like.

  However, in the photodetector 65, an integrated circuit 71 is generally provided on the other surface of the printed circuit board 69. Therefore, in the conventional structure of the PET apparatus 51, the cooling plate 81 cannot cool the photoelectric conversion layer 67 unless the integrated circuit 71 that is a main heat source is cooled. Therefore, it is necessary to strongly cool the cooling plate 81 in order to cool not only the photoelectric conversion layer 67 but also the integrated circuit 71.

  The thermal sheet 75 and the cover plate 77 are provided with drill holes 75a and 77a. Since the thermal conductivity is very low at the hole portion, the cooling efficiency for the photoelectric conversion layer 67 is further reduced. When the cooling plate 81 is strongly cooled to compensate for the reduced cooling efficiency, there is a concern that condensation may occur around the cooling plate 81 due to overcooling of the cooling plate 81.

  Next, with the conventional radiation detector 55, there is a concern that it is difficult to ensure a sufficient fastening strength in terms of structure. Since the radiation detector 55 includes the heavy scintillator block 61, it is necessary to ensure a sufficient fastening strength in terms of structure.

  The conventional radiation detector 55 has a configuration in which the printed circuit board 69, the thermal sheet 75, and the cover plate 77 are fastened by screwing for the purpose of temporarily disassembling and inspecting and repairing. However, the integrated circuit 71 occupies most of the back surface of the printed circuit board 69 due to the actual structure. Therefore, the area where the screw receiving portion 73 can be attached on the printed circuit board 69 is limited to a very narrow range.

  In this case, the number and the thickness of the screws 79 are also limited in accordance with the limitation of the attachable range of the screw receiving portion 73. Further, since the printed circuit board 69 provided with the screw receiving portion 73 is thin, the printed circuit board 69 is distorted when each of the screws 79 is fastened with a strong force so as to compensate for the limitation of the number and thickness. Therefore, it is difficult to ensure a sufficient fastening force between the printed circuit board 69 and the cover plate 77. As a result, there arises a problem that the respective components are separated in the radiation detector 55 and a problem that the position of the scintillator block 61 is shifted and the information of γ rays cannot be accurately detected.

  Further, in the conventional radiation detector 55, the screw 79 and the screw receiving portion 73 are generally made of a nonmagnetic metal and attached near the integrated circuit 71. In this case, since the metal constituting the screw 79 and the screw receiving portion 73 affects the alternating magnetic field, when the radiation detector 55 is used in the PET-MR apparatus, there is a concern that noise is generated in the PET-MR apparatus. Is done.

  Finally, there is a concern that the conventional radiation detector 55 is difficult to arrange so that the distance between adjacent radiation detectors is appropriate. As shown in FIG. 10B, the arrangement pitch of the scintillator crystals 61a in the scintillator block 61 is Da.

  The separation distance Db of the scintillator blocks 61 in the radiation detectors 55 adjacent to each other is preferably an integral multiple of the arrangement pitch Da. Further, in order to further increase the detection sensitivity of γ rays, the distance Db is preferably shorter.

  An ideal value of the separation distance Db that satisfies the two conditions is 3 mm as an example. However, the conventional radiation detector 55 is covered with a light shielding case 80. Since the plastic constituting the light shielding case 80 is thick, the separation distance Db between the scintillator blocks 61 is longer than an ideal value. As a result, the γ-ray detection sensitivity is lowered in the conventional apparatus.

  The present invention has been made in view of such circumstances. That is, an object of the present invention is to provide a radiation detector that can be used in a PET-MR apparatus, has a sufficient fastening strength in terms of structure, and has high cooling efficiency for a photoelectric conversion element.

In order to achieve such an object, the present invention has the following configuration.
That is, the radiation detector according to the present invention is
A scintillator block that is configured by two-dimensionally arranged block scintillator crystals, detects incident radiation and emits light, and is optically coupled to the scintillator block to transmit light emitted from the scintillator block. A light guide; a light detector configured to convert light transmitted from the light guide into an electrical signal; and a light detector optically coupled to the light guide; the light detector; the light guide; A fitting part that is provided on each side peripheral part of the scintillator block, and that fits and holds at least a part of a side peripheral part of the scintillator block and a bottom part of the light detector ; And disposed at a position facing the scintillator block across the photodetector. A holding member provided with a base fastening portion to be fastened to the base portion, and an adhesive thin-film light-shielding member that covers an outer peripheral portion of the scintillator block and a side peripheral portion of the holding member. Is.

[Operation and Effect] The radiation detector according to the present invention includes a holding member and a light shielding member. The holding member is provided on each side peripheral portion of the photodetector, the light guide, and the scintillator block, and includes a fitting portion and a base fastening portion. Since the fitting portion fits and holds at least a part of the side periphery of the photodetector , the light guide, and the scintillator block and the bottom portion of the photodetector, the positional deviation of the photodetector is preferably avoided by the holding member. The Since the photodetector is optically coupled to the scintillator block and the light guide, the displacement of the position of the scintillator block is preferably avoided by the holding member.

  The holding member is fastened via a base fastening portion and a base portion disposed at a position facing the scintillator block across the photodetector. In this case, the design of the base fastening part that makes the fastening of the base part and the holding member stronger is facilitated. Since the base portion and the holding member can be firmly fastened, the holding member can hold the photodetector more stably. Therefore, the fastening strength of the radiation detector becomes stronger.

  The light shielding member has adhesiveness and covers the outer periphery of the scintillator block and the side periphery of the holding member. In this case, the light shielding member is firmly coupled to each of the holding member and the scintillator block. That is, the light shielding member fixes the holding member and the scintillator block while integrally joining them. Therefore, since the radiation detector can have a stronger fastening strength as a whole, it is possible to more suitably avoid the displacement of the scintillator block. As a result of the stable position of the scintillator block, the radiation detector can detect γ-ray information more accurately.

  Furthermore, since the light shielding member is thin, even when the scintillator blocks are covered with the light shielding member, the separation distance between adjacent scintillator blocks can be an ideal short distance. Since the separation distance between the scintillator blocks is shortened, the γ-ray non-detection region becomes narrower. Therefore, it is possible to protect both the radiation detector from external light and to maintain high γ-ray detection sensitivity in the radiation detector.

  Further, in the above-described invention, it is constituted by a cooling means for cooling the photoelectric conversion element, and is constituted by a cooling layer tightly coupled to the photodetector and an integrated circuit for transmitting an electric signal converted by the photoelectric conversion element. It is preferable that the integrated circuit board is connected to the photodetector through a connection portion and disposed at a position not in contact with the cooling layer.

  [Operation / Effect] The radiation detector according to the present invention includes an integrated circuit board and a cooling layer tightly coupled to the photodetector. A cooling layer is comprised by the cooling means which cools a photoelectric conversion element. Since the cooling layer is tightly coupled with the photodetector, the photoelectric conversion element constituting the photodetector is suitably cooled. Further, the integrated circuit board including the integrated circuit as a main heat source is disposed at a position where it does not come into contact with the cooling layer. In this case, since the electric power to the cooling means of the heat generated in the integrated circuit is preferably avoided, the cooling efficiency of the cooling means with respect to the photoelectric conversion element becomes higher. Therefore, it is possible to more suitably avoid the occurrence of condensation due to the supercooling of the cooling means in the radiation detector.

  In the above-described invention, the cooling layer includes the cooling means and a heat conductive sheet made of a heat conductive resin, and the cooling means is tightly coupled to the photodetector via the heat conductive sheet. It is preferable.

  [Operation / Effect] According to the radiation detector of the present invention, the cooling layer includes the cooling means and the heat conduction sheet, and the cooling means is tightly coupled to the photodetector via the heat conduction sheet. Since the heat conductive sheet is made of resin, the adhesion between the cooling means and the photodetector is further increased. And the heat | fever of a photodetector is conducted to a cooling means more suitably through the heat conductive sheet which has heat conductivity, and is dissipated. With such a configuration, it is possible to further increase the cooling efficiency for the photoelectric conversion element in the radiation detector.

  In the above-described invention, the photoelectric conversion element is preferably a SiPM element or an APD element.

  [Operation and Effect] According to the radiation detector of the present invention, a SiPM element or an APD element is used as a photoelectric conversion element. These elements are not affected by the magnetic field generated from the magnetic resonance tomography apparatus (MR apparatus). Therefore, the radiation detector according to the present invention can be used for a positron emission tomography-magnetic resonance tomography combined apparatus (PET-MR).

  In the above-described invention, the light shielding member includes a light shielding layer composed of black polyethylene terephthalate and an adhesive layer composed of an adhesive material, and the light shielding member is interposed between the scintillator and the adhesive layer. It is preferable to cover the outer periphery of the block and the side periphery of the holding member.

  [Operation / Effect] According to the radiation detector of the present invention, the light shielding member includes the light shielding layer and the adhesive layer, and the light shielding layer is made of black polyethylene terephthalate (PET). Since black PET is a material having high strength and light blocking properties even in the form of a thin film, the thickness of the light shielding layer can be further reduced. That is, even when the scintillator blocks are covered with a light shielding member, the separation distance between adjacent scintillator blocks can be an ideal short distance. Therefore, it is possible to both protect the radiation detector suitably from impacts and external light and maintain high γ-ray detection sensitivity in the radiation detector.

  In the above-described invention, the holding member may have a tapered shape that increases in thickness from a side provided on a side peripheral portion of the scintillator block toward a side provided on a side peripheral portion of the photodetector. preferable.

  [Operation and Effect] According to the radiation detector of the present invention, the holding member becomes thicker from the side provided on the side peripheral portion of the scintillator block toward the side provided on the side peripheral portion of the photodetector. Tapered. In this case, since the part covering the side periphery of the scintillator block is thin, the area where the shielding member that covers the scintillator block and the holding member comes into contact with the holding member becomes wider. In this case, the shielding member, the holding member, and the scintillator block are more united and more firmly bonded. Therefore, the fastening strength of the radiation detector can be further increased.

  In the above-described invention, the holding member is preferably made of a resin having insulating properties and light blocking properties.

  [Operation / Effect] According to the radiation detector of the present invention, the holding member is made of a resin having insulating properties and light blocking properties. In this case, like the light blocking member, the holding member preferably blocks light from the outside of the radiation detector. The resin constituting the holding member protects the radiation detector from impacts and the like. Therefore, the influence which a radiation detector receives with an impact and the light from the outside can be reduced suitably.

  The radiation detector according to the present invention includes a holding member and a light shielding member. The holding member is provided on each side peripheral portion of the photodetector, the light guide, and the scintillator block, and includes a fitting portion and a base fastening portion. Since the fitting portion fits and holds the side peripheral portion and the bottom portion of the photodetector, deviation of the position of the photodetector is preferably avoided by the holding member. Since the photodetector is optically coupled to the scintillator block and the light guide, the displacement of the position of the scintillator block is preferably avoided by the holding member.

  The holding member is fastened via a base fastening portion and a base portion disposed at a position facing the scintillator block across the photodetector. In this case, the design of the base fastening part that makes the fastening of the base part and the holding member stronger is facilitated. Since the base portion and the holding member can be firmly fastened, the holding member can hold the photodetector more stably. Therefore, the fastening strength of the radiation detector becomes stronger.

  The light shielding member has adhesiveness and covers the outer periphery of the scintillator block and the side periphery of the holding member. In this case, the light shielding member is firmly coupled to each of the holding member and the scintillator block. That is, the light shielding member fixes the holding member and the scintillator block while integrally joining them. Therefore, since the radiation detector can have a stronger fastening strength as a whole, it is possible to more suitably avoid the displacement of the scintillator block. As a result of the stable position of the scintillator block, the radiation detector can detect γ-ray information more accurately.

  Furthermore, since the light shielding member is thin, even when the scintillator blocks are covered with the light shielding member, the separation distance between adjacent scintillator blocks can be an ideal short distance. Since the separation distance between the scintillator blocks is shortened, the γ-ray non-detection region becomes narrower. Therefore, it is possible to protect both the radiation detector from external light and to maintain high γ-ray detection sensitivity in the radiation detector.

It is a longitudinal cross-sectional view which shows the whole structure of the radiation detector which concerns on an Example. It is a perspective view which shows the structure of the holding member which concerns on an Example. It is a longitudinal cross-sectional view explaining the connection state of the holding member which concerns on an Example, a connection base, and a scintillator complex. It is a figure explaining the structure of the connection base which concerns on an Example. (A) is a front view when the connection base of the state connected with the radiation detector is seen from the z direction, and (b) is when the connection base of the state not connected with the radiation detector is seen from the z direction. FIG. It is a longitudinal cross-sectional view which shows the structure of the light shielding film which concerns on an Example. (A) is a longitudinal cross-sectional view in yz plane about the PET apparatus which concerns on an Example, (b) is the schematic explaining the separation distance of an adjacent radiation detector about the PET apparatus which concerns on an Example. It is a longitudinal cross-sectional view in xy plane about the PET apparatus which concerns on an Example. It is a longitudinal cross-sectional view which shows the whole structure of the radiation detector which concerns on a modification. It is a longitudinal cross-sectional view which shows the whole structure of the PET apparatus which concerns on a prior art example. It is the schematic which shows the structure of the radiation detector which concerns on a prior art example. (A) is a longitudinal cross-sectional view which shows the whole structure of a radiation detector, (b) is the schematic explaining the separation distance of an adjacent radiation detector.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a radiation detector 1 according to an embodiment. The schematic configuration of the PET apparatus including the radiation detector 1 according to the embodiment is the same as that of the conventional example shown in FIG. In the radiation detector 1, the direction in which the introduction hole for introducing the subject into the PET apparatus extends is the x direction. The direction toward the center Po of the introduction hole provided in the PET apparatus is taken as the y direction (FIGS. 6 and 9). A direction orthogonal to each of the x direction and the y direction is defined as a z direction.

<Description of overall configuration>
As shown in FIG. 1, the radiation detector 1 according to the embodiment has a configuration in which a scintillator block 3, a light guide 5, a photodetector 7, and a cooling layer 9 are sequentially laminated from the upper layer toward the lower layer. Have. In the radiation detector 1, the upper layer means the side close to the introduction hole of the subject provided in the PET apparatus, and the lower layer means the side close to the casing provided in the PET apparatus. In the radiation detector 1, the y direction coincides with the direction in which the components including the scintillator block 3 are stacked.

  The scintillator block 3 has a structure in which rectangular parallelepiped scintillator crystals 3a are two-dimensionally arranged in each of the x direction and the z direction, and absorbs γ rays emitted from the subject to emit scintillator light. . Each of the scintillator crystals 3a is optically coupled with a transparent thermosetting resin or the like. As a material constituting the scintillator crystal 3a, for example, a crystal such as LYSO, LSO, LGSO, GSO, or BGO is used.

  The light guide 5 is composed of an optical member having high transparency, and transmits the scintillator light emitted from the scintillator block 3 to the photodetector 7. Each of the scintillator block 3, the light guide 5, and the photodetector 7 is optically coupled with a transparent thermosetting resin or the like. Each of the upper surface portion and the side peripheral portion of the scintillator block 3 and the side peripheral portion of the light guide 5 is covered with a reflection film (not shown) that reflects the scintillator light.

  The photodetector 7 has a configuration in which the photoelectric conversion layer 11 is laminated on the upper layer of the printed board 13, and the photoelectric conversion layer 11 and the light guide 5 are optically coupled. In the photoelectric conversion layer 11, photoelectric conversion elements 11a are two-dimensionally arranged. Examples of the material used for the photoelectric conversion element 11a include a light receiving element that is not affected by the magnetic field generated by the MR apparatus, such as SiPM or APD.

  The photoelectric conversion element 11a is provided with a light receiving portion 11b. The photoelectric conversion element 11a detects the scintillator light transmitted by the light guide 5 at the light receiving unit 11b and converts it into an electric signal. As a material constituting the printed circuit board 13, a plate-like ceramic, a plate-like glass epoxy resin, or the like is used.

  The cooling layer 9 has a configuration in which a thermal sheet 15 and a cooling plate 17 for cooling the photoelectric conversion element 11a are sequentially stacked. An example of the configuration of the cooling plate 17 is a configuration in which a tube (not shown) for circulating the refrigerant is provided inside. The thermal sheet 15 is made of a material having high thermal conductivity and flexibility. The thermal sheet 15 allows the cooling plate 17 and the photodetector 7 to be in close contact with each other, and efficiently conducts heat from the photoelectric conversion element 11 a to the cooling plate 17. The thermal sheet 15 corresponds to the heat conductive sheet in the present invention. The cooling plate 17 corresponds to the cooling means in the present invention.

  The cooling plate 17 preferably dissipates the conducted heat. Therefore, the cooling plate 17 can cool the photoelectric conversion element 11a more efficiently by contacting the photodetector 7 via the thermal sheet 15. However, the thermal sheet 15 may be omitted and the cooling plate 17 may be in direct contact with the photodetector 7.

  One end of a connector 19 is connected to the back surface of the printed board 13 (the surface on which the photoelectric conversion layer 11 is not laminated). The connector 19 passes through the cooling layer 9 and the other end is connected to the integrated circuit board 21. That is, in the radiation detector 1, the integrated circuit substrate 21 is disposed below the cooling layer 9 in a state of being separated from the cooling layer. The connector 19 is made of a material having low thermal conductivity. The connector 19 corresponds to a connection portion in the present invention.

  The integrated circuit board 21 has a configuration in which a printed board 23 and an integrated circuit 25 are stacked in order from the upper layer. The other end of the connector 19 is connected to the printed board 23. A connection base 27 is provided below the integrated circuit 25. The connection base 27 connects the radiation detector 1 to the housing 29 provided in the PET apparatus and containing the radiation detector 1. The detailed configuration of the entire PET apparatus will be described later. The connection base 27 corresponds to the base portion in the present invention.

  The integrated circuit 25 transmits the electrical signal converted by the photoelectric conversion element 11a to the signal processing circuit for reading. As a material constituting the integrated circuit 25, an application specific integrated circuit (ASIC) or the like is used. The signal processing circuit generates a tomographic image indicating the distribution of positron emitting nuclides in the region of interest based on the read electrical signal.

<Characteristic configuration in the embodiment>
As a characteristic configuration of the radiation detector 1 according to the embodiment, a holding member 31 is provided on the outer periphery of each of the scintillator block 3, the light guide 5, the photodetector 7, and the connection base 27. The holding member 31 is made of a resin having insulating properties and light blocking properties, and black polycarbonate or black ABS resin is preferable as an example of the constituent material. These materials are resins that have low light transmittance and can ensure stable shape accuracy.

  A perspective view of the holding member 31 is shown in FIG. The holding member 31 is a substantially rectangular parallelepiped having an opening penetrating in the y direction. The holding member 31 is provided with a fitting portion 31a and a drill hole 31b. The fitting portion 29 a is configured to fit with the side surface and the bottom surface of the photodetector 7. Since the holding member 31 holds the photodetector 7 in a stable state via the fitting portion 31a, the position of the scintillator block 3 coupled to the photodetector 7 becomes more stable.

  The drill holes 31b are provided on the lower side surface of the holding member 31, and each of the drill holes 31b penetrates the holding member 31 in the z direction. The holding member 31 and the connection base 27 are fastened by screwing the screw 33 through the drill hole 31b. When the inside of the radiation detector 1 is inspected and repaired, the holding member 31 and the connection base 27 can be separated by removing the screw 33 from the drill hole 31b as shown in FIG. Further, by removing the screw 33, the holding member 31 and the photodetector 7 which are fitted through the fitting portion 29a can be separated. The drill hole 31b corresponds to the base fastening portion in the present invention.

  Further, the holding member 31 is tapered so as to increase in thickness from the upper end downward. That is, the holding member 31 is thicker from the side provided on the side peripheral part of the scintillator block 3 toward the side provided on the side peripheral part of the photodetector 7. In this case, since the adhesion area of the light shielding film 35 and the holding member 31 which will be described later becomes wider, the holding member 31 and the light shielding film 35 are bonded more firmly. As a result, the fastening strength of the radiation detector 1 is further increased.

  As shown in FIG. 4A, the connection base 27 extends in the x direction and is connected to each of the three radiation detectors 1 arranged in series in the x direction. As shown in FIG. 4B, the connection base 27 is provided with a recess 27 a, and the recess 27 a is fitted to the lower end portion of the holding member 31 provided in the radiation detector 1. A screw receiving portion 27 b that is screwed with the screw 33 is provided on the surface of the connection base 27 in the z direction. That is, when the screw 33 and the screw receiving portion 27 are screwed through the drill hole 31b, the holding member 31 and the connection base 27 are fastened.

  Furthermore, as shown in FIG. 1 as a characteristic configuration of the radiation detector 1, the upper surface portion and the side periphery of the scintillator block 3 and the side periphery of the holding member 31 are covered with a light shielding film 35. As shown in FIG. 5, the light shielding film 35 has a two-layer structure of a light shielding layer 35a and an adhesive layer 35b. As a material constituting the light shielding layer 35a, black polyethylene terephthalate (PET) or the like is preferable. Black PET is a material that can efficiently block light even in the form of a thin film. Moreover, since PET has high strength and high insulation even if it is a thin film, the light shielding film 35 can protect the radiation detector 1 from impact and external light. The light shielding film 35 corresponds to the light shielding member in the present invention.

  The adhesive layer 35b is made of an adhesive material, and a known adhesive or the like may be used. The light shielding layer 35a adhesively covers the scintillator block 3 or the holding member 31 through the adhesive layer 35b. The thickness of the light shielding layer 33a is 30 μm as an example, and the thickness of the adhesive layer 35b is 20 μm as an example. That is, since the thickness of the light shielding film 35 is about 50 μm, even when the scintillator block 3 is covered with the light shielding film 35, the distance between the adjacent scintillator blocks 3 can be set to a predetermined short distance. Thus, the radiation detector 1 is firmly fastened by the holding member 31 and the light shielding film 35. Therefore, the position of the scintillator block 3 can be prevented from shifting.

<Configuration of PET apparatus>
Next, the configuration of the PET apparatus 37 including the radiation detector 1 according to the embodiment will be described. 6A is a longitudinal sectional view of the PET apparatus 37 on the yz plane, and FIG. 7 is a longitudinal sectional view of the PET apparatus 37 on the xy plane.

  A longitudinal sectional view in the yz plane of the PET apparatus 37 according to the embodiment is common to the conventional PET apparatus shown in FIG. That is, the PET apparatus 37 includes a gantry 41 provided with an introduction hole 39 for introducing a subject. A housing 43 is provided inside the gantry 41. Inside the housing 43, the radiation detectors 1 are arranged in a ring shape so as to surround the introduction hole 39. Although the number of radiation detectors 1 arranged in a ring shape in FIG. 6A is eight, the number of radiation detectors 1 forming the ring structure may be changed as appropriate.

  The connection base 27 connects each of the radiation detectors 1 and the housing 43. As shown in FIG. 7, the connection base 27 is disposed such that the longitudinal direction thereof coincides with the x direction. Accordingly, the three radiation detectors 1 connected to one connection base 27 are arranged in series in the x direction. The number of connection bases arranged in the x direction is not limited to one, and a plurality of connection bases 27 may be arranged in series in the x direction.

  Here, in the radiation detector 1, the arrangement pitch of the scintillator crystals 3a in the scintillator block 3 is defined as Da. Further, in the scintillator blocks 3 adjacent to each other, the distance between the upper ends is set to Db (FIGS. 6B and 7). In the radiation detector 1, the separation distance Db is preferably an integer multiple of the arrangement pitch Da.

  In this case, the radiation detectors 1 are arranged so that the scintillator crystals 3a are arranged in a regular manner and surround the entire periphery of the introduction hole 39. Further, in order to further increase the detection sensitivity of γ rays, it is preferable that the separation distance Db is shorter. In the radiation detector 1, the arrangement pitch Da of the scintillator crystals 3a is about 1.5 mm as an example. In this case, an example of an ideal distance of the separation distance Db is 3 mm.

<Effects of Configuration of Example>
By having the structure mentioned above, the radiation detector 1 which concerns on an Example can raise the cooling efficiency with respect to a photoelectric conversion element, and the fastening intensity | strength of a detector. Hereinafter, the effect by the structure which concerns on an Example is demonstrated.

  The radiation detector 1 according to the embodiment includes a holding member 31 and a light shielding film 35. The holding member 31 is provided with a fitting portion 31 a, and the fitting portion 31 a is configured to fit with the side surface and the bottom surface of the photodetector 7. That is, the holding member 31 holds the side surface and the bottom surface of the photodetector 7 through the fitting portion 31a.

  The radiation detector 1 includes a laminate (hereinafter referred to as “scintillator complex”) in which a scintillator block 3, a light guide 5, a photodetector 7, and a cooling layer 9 are laminated in order. Each layer constituting the scintillator complex is firmly bonded. Therefore, when the fitting portion 31a holds the photodetector 7, the holding member 31 can prevent the position of the scintillator complex from shifting. In particular, since the fitting portion 31a can support the bottom surface of the photodetector 7, the holding member 31 can preferably avoid the scintillator complex from shifting toward the lower layer in the y direction.

  The holding member 31 has a drill hole 31b on the lower side surface. When the drill hole 31 and the screw 33 are screwed together, the holding member 31 that holds the scintillator complex is fastened to the connection base 27. In the radiation detector 55 according to the conventional example, since the screw receiving portion 73 is attached to the surface of the printed circuit board 69 that occupies most of the integrated circuit 71, the attachable range of the screw receiving portion 73 is narrow. As a result, since the number and thickness of the screws 79 are limited, it is difficult to secure a sufficient fastening force with the conventional radiation detector 55 (FIG. 12).

  On the other hand, the drill hole 31 b is provided on the lower side surface of the holding member 31 in the embodiment. As shown in FIG. 6A, the radiation detector 1 is arranged in a ring shape on the yz plane. In the radiation detector 1 used in the PET apparatus, it is preferable that the distance between the adjacent scintillator blocks 3 is short in order to increase the detection sensitivity of γ rays. Therefore, each of the radiation detectors 1 is arranged so that the z-direction separation distance Db in the upper layer of the radiation detector 1 is a predetermined short distance (3 mm as an example).

  However, each of the radiation detectors 1 is arranged so as to expand radially from the upper layer to the lower layer in the y direction. Therefore, the separation distance Dc in the z direction in the lower layer of the radiation detector 1 is longer than the separation distance Db in the upper layer of the radiation detector 1. The drill hole 31b is attached to the lower layer of the radiation detector 1 so as to penetrate the holding member 31 in the z direction. Therefore, in the lower layer of the radiation detector 1, each of the thickness of the holding member 31 and the length of the screw 33 can be increased.

  Further, the lower side surface of the holding member 31 is wide and is not occupied by another configuration (an integrated circuit or the like) that restricts the attachment of the drill hole 31b, so that the range in which the drill hole 31b can be attached is wide. In this case, the number and thickness of the screws 33 can be increased. Therefore, the holding member 31 and the connection base 27 can be tightened more firmly through the drill hole 31 b and the screw 33. Further, since the position of the drill hole 31b is away from the photodetector 7 and the integrated circuit board 21, the influence of the magnetic field received by the radiation detector 1 by the screw 33 or the like becomes smaller.

  Further, the holding member 31 and the scintillator block 3 are covered with a light shielding film 35. Since the light shielding film 35 is made of an adhesive material, the light shielding film 35 is firmly bonded to each of the holding member 31 and the scintillator block 3. The light shielding film 35 is wound and fixed while integrally bonding the holding member 31 and the scintillator complex. Therefore, the radiation detector 1 as a whole can have a stronger fastening strength. Moreover, it can prevent that the position of a scintillator complex shifts | deviates because the light shielding film 35 carries out adhesive coating. In particular, the light-shielding film 35 can suitably avoid the scintillator complex from shifting toward the upper layer in the y direction.

  The light shielding film 35 is made of film-like black PET. Since black PET is a material having high strength and light blocking properties even in the form of a thin film, the thickness of the light shielding film 35 can be reduced to about 50 μm. That is, even when the upper surface of the scintillator block 3 is covered with the reflection film and the light shielding film 35, the separation distance Db between the adjacent scintillator blocks 3 can be set to an ideal short distance. Therefore, it is possible to maintain high γ-ray detection sensitivity while improving the impact resistance and light blocking performance of the radiation detector 1.

  Each of the holding member 31 and the light shielding film 35 is made of a material having low light transmittance. The holding member 31 covers and holds the side surface of the scintillator complex, and the light shielding film 35 winds and fixes the holding member 31 and the scintillator complex while integrally bonding. Therefore, light outside the radiation detector 1 is preferably blocked by the holding member 31 and the light shielding film 35. Therefore, the radiation detector 1 can further reduce the influence of external light. Moreover, since both the holding member 31 and the light shielding film 35 are comprised with resin, the radiation detector 1 can be protected suitably from an impact.

  The holding member 31 has a tapered shape that increases in thickness from the upper layer toward the lower layer. That is, the holding member 31 is thicker from the side provided on the side peripheral part of the scintillator block 3 toward the side provided on the side peripheral part of the photodetector 7. In this case, the gap generated between the light shielding film 35 and the holding member 31 is narrower than that in the case where the thickness of the holding member 31 is constant. Therefore, the holding member 31 and the light shielding film 35 are more closely attached and firmly bonded. As a result, the fastening strength of the radiation detector 1 is further increased.

  Thus, by providing the holding member 31 and the light shielding film 35, the fastening strength of the radiation detector 1 becomes high. Moreover, since the shift | offset | difference of the position of a scintillator complex is avoided suitably, the radiation detector 1 can detect the information of a gamma ray more correctly.

  Furthermore, in the radiation detector 1 according to the embodiment, the photodetector 7 and the cooling layer 9 are stacked in close contact. Therefore, each of the photoelectric conversion elements 11 a provided in the photodetector 7 is suitably cooled by the cooling plate 17. The integrated circuit board 21 which is a main heat source is disposed in a state of being separated from the cooling layer 9. Therefore, conduction of heat generated in the integrated circuit board 21 to the cooling layer 9 can be suitably avoided. Therefore, the cooling efficiency of the cooling plate 17 with respect to the photoelectric conversion element 11a can be increased. In this case, since it is not necessary to cool the cooling plate 17 more strongly than necessary, the radiation detector 1 can prevent the occurrence of condensation due to the overcooling of the cooling plate 17.

  The present invention is not limited to the above embodiment, and can be modified as follows.

  (1) In the embodiment described above, the connector 19 is configured to penetrate the cooling layer 9, but is not limited thereto. That is, as shown in FIG. 8, the connector 19 may be configured to extend so as to bypass the side circumference of the cooling layer 9. In this case, it is not necessary to provide a through hole in the thermal sheet 15 and the cooling plate 17. Therefore, the cooling efficiency of the cooling plate 17 with respect to the photoelectric conversion element 11a can be further increased.

  (2) In the embodiment described above, the holding member 31 is tapered, but is not limited to this, and may have a uniform thickness structure from the upper end to the lower end. Further, the upper end of the holding member 31 has a structure in contact with the side peripheral portion of the scintillator block 3, but the upper end of the holding member 31 may have a structure in contact with the side peripheral portion of the photodetector 7, or the light guide 5 side. The structure which touches a peripheral part may be sufficient.

  (3) In the above-described embodiments, the configuration using the radiation detector 1 has been described with reference to a PET apparatus that can be used as a PET-MR apparatus, but is not limited thereto. That is, the radiation detector 1 according to the embodiment can be applied to a TOF-PET (TOF: Time of Flight) apparatus in addition to the PET apparatus.

  In the TOF-PET apparatus, the generation position of the γ-ray is specified by measuring the time-of-flight difference from the radiation position to the detection position by both radiation detectors for two γ-rays. When the radiation detector 1 is used in the TOF-PET apparatus, the scintillator block 3 is composed of block-like scintillator crystals arranged three-dimensionally. In this case, the scintillator block 3 can discriminate the light source position of the scintillator light in the depth direction.

DESCRIPTION OF SYMBOLS 1 ... Radiation detector 3 ... Scintillator block 5 ... Light guide 7 ... Photo detector 9 ... Cooling layer 11 ... Photoelectric conversion layer 11a ... Photoelectric conversion element 15 ... Thermal sheet (thermal conduction sheet)
17 ... Cooling plate (cooling means)
19 ... Connector (connection part)
21 ... Integrated circuit board 25 ... Integrated circuit 27 ... Connection base (base part)
29 ... Housing
31 ... Holding member 31a ... Fitting part 31b ... Drilling hole (base fastening part)
33 ... Screw 35 ... Light shielding film (light shielding member)

Claims (7)

A scintillator block configured by two-dimensionally arranged block scintillator crystals, which detects incident radiation and emits light;
A light guide optically coupled to the scintillator block and transmitting light emitted from the scintillator block ;
A photo-detector configured by a photoelectric conversion element that converts light transmitted from the light guide into an electrical signal, and optically coupled to the light guide;
The light detector, the light guide, and the scintillator block are provided on each side peripheral portion of the light detector, the light guide, and at least a part of the scintillator block side periphery and the light detector. A holding member provided with a fitting portion that fits and holds the bottom portion, and a base fastening portion that is fastened to a base portion that is disposed at a position facing the scintillator block across the photodetector;
A radiation detector, comprising: an adhesive thin film-shaped light shielding member that covers an outer peripheral portion of the scintillator block and a side peripheral portion of the holding member. The radiation detector according to claim 1.
A cooling layer constituted by a cooling means for cooling the photoelectric conversion element and tightly coupled to the photodetector;
An integrated circuit board configured by an integrated circuit that transmits an electrical signal converted by the photoelectric conversion element,
The integrated circuit board is connected to the photodetector through a connection portion, and is a radiation detector disposed at a position not in contact with the cooling layer. The radiation detector according to claim 2, wherein
The cooling layer includes the cooling means and a heat conductive sheet formed of a heat conductive resin,
The cooling means is a radiation detector that is tightly coupled to the photodetector through the heat conductive sheet. The radiation detector according to any one of claims 1 to 3,
The said photoelectric conversion element is a radiation detector which is a SiPM element or an APD element. The radiation detector according to any one of claims 1 to 4,
The light shielding member includes a light shielding layer composed of black polyethylene terephthalate, and an adhesive layer composed of an adhesive material,
The said light shielding member is a radiation detector which coat | covers the outer peripheral part of the said scintillator block and the side peripheral part of the said holding member through the said adhesion layer. The radiation detector according to any one of claims 1 to 5,
The said holding member is a radiation detector which is a taper shape which becomes thick toward the side provided in the side peripheral part of the said photodetector from the side provided in the side peripheral part of the said scintillator block. The radiation detector according to any one of claims 1 to 6,
The holding member is a radiation detector composed of a resin having insulating properties and light blocking properties.

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