Detector unit, radiation detection device, and radiation tomography device

Abstract

A detector unit 10 comprises a first detector group 11 and a second detector group 12. The first detector group 11 includes: rectangular parallelopiped-shaped scintillators 31-33 which have a longitudinal direction in a second direction and are disposed in parallel to each other in a first direction; and optical detection parts 41-43 which are optically coupled to surfaces in the longitudinal direction of the respective scintillators 31-33. The second detector group 12 includes: rectangular parallelopiped-shaped scintillators 34-36 which have a longitudinal direction in the first direction and are disposed in parallel to each other in the second direction; and optical detection parts 44-46 which are optically coupled to surfaces in the longitudinal direction of the respective scintillators 34-36. The first detector group 11 and the second detector group 12 are layered in a third direction orthogonal to both the first direction and the second direction. Accordingly, a detector unit capable of making both TOF resolution and DOI resolution satisfactory while suppressing deterioration in radiation detection sensitivity is realized.

Description

Detector unit, radiation detection device and radiation tomography device

[0001] The present disclosure relates to a detector unit, a radiation detection apparatus, and a radiation tomography apparatus.

[0002] Radiation tomography devices, such as positron emission tomography (PET) devices and single photon emission computed tomography (SPECT) devices, are devices that use a radiation detection device to detect radiation (gamma rays) emitted within a subject and collect data for reconstructing a tomographic image of the subject. Radiation detection devices are used not only in radiation tomography devices but also in various other devices that detect gamma rays and other radiation.

[0003] A radiation detection device generally includes a scintillator that generates scintillation light through interaction with incident radiation, a photodetector that receives the scintillation light and outputs a signal, and a processing unit that processes the signal output from the photodetector. Hereinafter, the component of the radiation detection device that includes the scintillator and the photodetector will be referred to as a detector unit.

[0004] For example, it is important for a radiation detection device used in a PET device to detect both the time and position of interaction between radiation and a scintillator with high resolution in order to reconstruct a highly accurate tomographic image.

[0005] The better the resolution for detecting the time of radiation interaction (Time of Flight (TOF) resolution), the better the S / N ratio of the tomographic image. Also, the better the resolution for detecting the position of radiation interaction (Depth of Interaction (DOI) resolution), the better the uniformity of the tomographic image. Therefore, it is desirable to improve both the TOF resolution and the DOI resolution in a radiation detection device.

[0006] To improve the TOF resolution, it is necessary to reduce the variation in the time it takes for scintillation light generated at the radiation interaction position in the scintillator to reach the photodetector, that is, to shorten the distance from the photodetector to the farthest end of the scintillator. However, in this case, the scintillator must be made smaller, which reduces the sensitivity of radiation detection.

[0007] To improve the DOI resolution, multiple photodetectors may be provided for one scintillator, and the scintillation light generated in the scintillator may be diffused and detected by the multiple photodetectors. However, this would result in a deterioration in the TOF resolution.

[0008] The radiation detection devices described in Non-Patent Documents 1 and 2 have characteristic configurations with respect to the shapes and arrangements of the scintillator and the light detection section.

[0009] The radiation detection device described in Non-Patent Document 1 includes a plurality of columnar scintillators arranged in parallel, a plurality of photodetectors provided on one side of the plurality of columnar scintillators, and a light guide provided on the other side of the plurality of columnar scintillators.The radiation detection device described in Non-Patent Document 2 includes a plurality of stacked plate-shaped scintillators and a plurality of photodetectors provided on each of the four side surfaces of the plurality of plate-shaped scintillators.

[0010] M. Pizzichemi et al., "On light sharing TOF-PET modules with depth of interaction and 157 ps FWHM coincidence time resolution", Phys. Med. Biol., 64, 155008, 2019P. Peng et al., "Compton PET: a layered structure PET detector with high performance", Phys. Med. Biol., 64, 10LT01, 2019

[0011] The radiation detection device described in Non-Patent Document 1 can achieve both good TOF resolution and DOI resolution, but if the scintillator is made thicker in an attempt to improve radiation detection sensitivity, the TOF resolution deteriorates.

[0012] The radiation detection device described in Non-Patent Document 2 can achieve good DOI resolution regardless of the number of stacked plate-shaped scintillators, but because scintillation light is received by a large number of photodetectors, the number of photons detected per photodetector decreases, resulting in a deterioration of TOF resolution.

[0013] The present invention aims to provide a detector unit, a radiation detection device, and a radiation tomography device that can improve both TOF resolution and DOI resolution while suppressing deterioration in radiation detection sensitivity.

[0014] An embodiment of the present invention is a detector unit including: (1) a first detector group and a second detector group stacked in a third direction orthogonal to both the first direction and the second direction, (2) the first detector group including a plurality of rectangular parallelepiped scintillators having a longitudinal direction in the second direction and arranged in parallel in the first direction, and a photodetector optically coupled to a side surface of each of the plurality of scintillators in the longitudinal direction, and (3) the second detector group including a plurality of rectangular parallelepiped scintillators having a longitudinal direction in the first direction and arranged in parallel in the second direction, and a photodetector optically coupled to a side surface of each of the plurality of scintillators in the longitudinal direction.

[0015] An embodiment of the present invention is a radiation detection device including a detector unit having the above-described configuration, and a processing unit that processes a signal output from the photodetector of the detector unit when radiation interacts with any scintillator in the detector unit to generate scintillation light, and determines the position of interaction of the radiation.

[0016] An embodiment of the present invention is a radiation tomography apparatus including a detector unit having the above-described configuration.

[0017] According to the embodiment of the present invention, it is possible to improve both the TOF resolution and the DOI resolution, and to suppress deterioration of radiation detection sensitivity.

[0018] Fig. 1 is a diagram showing the configuration of the radiation detection device 1. Fig. 2 is a diagram showing the first detector group 11 and the second detector group 12 of the detector unit 10 spaced apart from each other. Fig. 3 is a diagram showing the scintillator 31, the photodetector 41, and the reflector 51. Fig. 4 is a diagram explaining the propagation of scintillation light when radiation interacts with one of the scintillators of the detector unit 10 to generate scintillation light. Fig. 5 is a diagram explaining the reception of scintillation light by each photodetector when radiation interacts with one of the scintillators of the detector unit 10 to generate scintillation light, in which (a) is a diagram of the first detector group 11 viewed in the z direction, and (b) is a diagram of the second detector group 12 viewed in the z direction. 6A and 6B are diagrams showing waveforms of signals output from each photodetector when radiation interacts with a scintillator in the detector unit 10 to generate scintillation light, with (a) a diagram schematically showing waveforms of signals S1 to S3 output from the photodetectors 41 to 43 of the first detector group 11, and (b) a diagram schematically showing waveforms of signals S4 to S6 output from the photodetectors 44 to 46 of the second detector group 12. FIG. 7 is a diagram explaining a simplified representation of the detector unit 10. FIG. 8 is a diagram showing the configuration of the detector unit 10A. FIG. 9 is a diagram showing the configuration of the detector unit 10B. FIG. 10 is a diagram showing the configuration of the PET device 2. FIG. 11 is a diagram showing an experimental system including the detector unit 10. FIG. 12 is a histogram of gamma-ray interaction positions. FIG. 13 is a histogram of differences in gamma-ray interaction times.

[0019] Hereinafter, embodiments of a detector unit, a radiation detection apparatus, and a radiation tomography apparatus will be described in detail with reference to the accompanying drawings. In the description of the drawings, identical elements are designated by the same reference numerals, and duplicated explanations will be omitted. The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0020] Fig. 1 is a diagram showing the configuration of a radiation detection device 1. The radiation detection device 1 includes a detector unit 10 and a processing unit 20. The detector unit 10 includes a first detector group 11 and a second detector group 12. Fig. 2 is a diagram showing the first detector group 11 and the second detector group 12 of the detector unit 10 spaced apart from each other. For ease of explanation, these figures show an xyz Cartesian coordinate system. This also applies to the subsequent figures.

[0021] The first detector group 11 includes three rectangular parallelepiped scintillators 31 to 33 that have their longitudinal direction in the second direction and are arranged in parallel in the first direction, and photodetectors 41 to 43 that are optically coupled to the longitudinal side surfaces of the scintillators 31 to 33, respectively. The second detector group 12 includes three rectangular parallelepiped scintillators 34 to 36 that have their longitudinal direction in the first direction and are arranged in parallel in the second direction, and photodetectors 44 to 46 that are optically coupled to the longitudinal side surfaces of the scintillators 34 to 36, respectively.

[0022] The first detector group 11 and the second detector group 12 are stacked in a third direction orthogonal to both the first direction and the second direction. The processing unit 20 processes signals S1 to S6 output from the light detecting units 41 to 46 when radiation interacts with any of the scintillators 31 to 36 of the detector unit 10 to generate scintillation light, and determines the position of interaction of the radiation. In each of the first detector group 11 and the second detector group 12, the number of scintillators arranged in parallel is not limited to three, but may be any number equal to or greater than two.

[0023] The first direction and the second direction are preferably perpendicular to each other. Hereinafter, the first direction is referred to as the x-direction, the second direction is referred to as the y-direction, and the third direction (stacking direction) is referred to as the z-direction. In the first detector group 11, the photodetectors 41 to 43 optically coupled to the scintillators 31 to 33, respectively, are preferably provided on a common side in the longitudinal direction (y-direction) of each scintillator. In the second detector group 12, the photodetectors 44 to 46 optically coupled to the scintillators 34 to 36, respectively, are preferably provided on a common side in the longitudinal direction (x-direction) of each scintillator.

[0024] In each of the first detector group 11 and the second detector group 12, the scintillator and the photodetector section that are optically coupled to each other may be bonded to each other with an optical adhesive.

[0025] The scintillators 31 to 36 interact with incident radiation such as gamma rays to generate scintillation light. For example, LSO (Lu2SiO5:Ce) or LYSO (Lu 2-X Y X The light detecting units 41 to 46 are preferably made of a material capable of detecting scintillation light at high speed and with high sensitivity, such as a photomultiplier tube or a SiPM (Silicon Photomultiplier).

[0026] In each of the first detector group 11 and the second detector group 12, the surfaces of two stacked scintillators facing each other are preferably air-coupled. That is, the upper surface of each of the scintillators 31 to 33 in the first detector group 11 and the lower surface of each of the scintillators 34 to 36 in the second detector group 12 are preferably air-coupled to each other.

[0027] In Figure 2, for the sake of convenience of explanation, the first detector group 11 and the second detector group 12 are shown spaced apart from each other, but it is preferable that the distance between the first detector group 11 and the second detector group 12 be narrow enough that the surfaces of the two opposing scintillators can be air-bonded by stacking them.

[0028] In each scintillator of the first detector group 11 and the second detector group 12, it is preferable that a reflective material that reflects scintillation light generated by the scintillator is provided on all surfaces except for the surfaces that face other scintillators due to stacking (the upper surfaces of scintillators 31 to 33 and the lower surfaces of scintillators 34 to 36) and the surfaces to which the light detection units are optically connected.

[0029] 3 is a diagram showing scintillator 31, photodetector 41, and reflector 51. Of the six faces of rectangular parallelepiped scintillator 31, reflector 51 that reflects scintillation light is provided on four faces, excluding the top face that faces scintillators 34 to 36 due to lamination and the face to which photodetector 41 is optically coupled. The same applies to the other scintillators.

[0030] 4 is a diagram illustrating the propagation of scintillation light when radiation interacts with one of the scintillators in the detector unit 10 to generate scintillation light. Here, it is assumed that radiation interacts with one another at a position within the scintillator 35 directly above the scintillator 31 to generate scintillation light.

[0031] The top surfaces of scintillators 31 to 33 and the bottom surface of scintillator 35 are air-bonded to each other. When each scintillator is made of LSO or LYSO, the refractive index of each scintillator is 1.8. The refractive index of the air between the top surfaces of scintillators 31 to 33 and the bottom surface of scintillator 35 is 1.0. The critical angle at the interface between the scintillator and the air is 33 degrees. If the angle of incidence of light from the scintillator to the interface is equal to or greater than the critical angle, the light is totally reflected.

[0032] Therefore, of the scintillation light generated at the radiation interaction position in scintillator 35, the scintillation light heading toward scintillator 31 located directly below the radiation interaction position has a small angle of incidence at the interface and can therefore propagate to scintillator 31. In contrast, the scintillation light heading toward scintillators 32 and 33 has a large angle of incidence at the interface and is therefore more likely to be totally reflected and received by light detection unit 45. In this case, it is desirable that the surfaces of the scintillators in each of first detector group 11 and second detector group 12 that face the other scintillators due to stacking are mirror-polished.

[0033] In this way, a large difference occurs in the amount of scintillation light traveling to the scintillators 31 to 33, which increases the contrast in intensity of the signals S1 to S3 output from the photodetectors 41 to 43, making it possible to detect with high resolution the radiation interaction position in the x direction in the scintillator 35. Furthermore, most of the scintillation light generated in the scintillator 35 is received by the photodetector 45 optically coupled to this scintillator 35, making it possible to detect the radiation interaction time with high resolution.

[0034] 5A and 5B are diagrams illustrating reception of scintillation light by each photodetector when radiation interacts with one of the scintillators in the detector unit 10 to generate scintillation light. Fig. 5A is a diagram of the first detector group 11 viewed in the z direction. Fig. 5B is a diagram of the second detector group 12 viewed in the z direction. Here, it is assumed that radiation interacts with one another to generate scintillation light near the center of the scintillator 31 in the first detector group 11.

[0035] Most of the scintillation light generated at the radiation interaction position in the scintillator 31 is received by the photodetector 41 optically coupled to the scintillator 31. When the reflector 51 is provided, a high proportion of the scintillation light generated in the scintillator 31 is received by the photodetector 41.

[0036] A portion of the scintillation light generated at the radiation interaction position within the scintillator 31 propagates to the scintillator 35 that is located directly above the radiation interaction position and is air-bonded to the top surface of the scintillator 31, and is received by the photodetector 45 that is optically coupled to the scintillator 35.

[0037] Even if some of the scintillation light generated at the radiation interaction position in scintillator 31 propagates to the other scintillators 32, 33, 34, and 36, the amount of light is small. In particular, when each scintillator is provided with a reflector, the amount of scintillation light propagating to scintillators 32 and 33 is extremely small.

[0038] 6A and 6B are diagrams showing waveforms of signals output from each photodetector when scintillation light is generated due to interaction of radiation with one scintillator in the detector unit 10. Fig. 6A is a diagram schematically showing waveforms of signals S1 to S3 output from each of the photodetectors 41 to 43 of the first detector group 11. Fig. 6B is a diagram schematically showing waveforms of signals S4 to S6 output from each of the photodetectors 44 to 46 of the second detector group 12. Here, as in Fig. 5, it is assumed that scintillation light is generated due to interaction of radiation near the center of the scintillator 31 of the first detector group 11.

[0039] The processing unit 20 determines the position of interaction of radiation by processing the signals S1 to S6 output from the photodetection units 41 to 46. In the case of the signal waveform example shown in Fig. 6, the processing unit 20 can determine that an interaction of radiation has occurred within the scintillator 31 optically coupled to the photodetection unit 41 that output the signal S1, based on the fact that the intensity peak of the signal S1 is the highest among the signals S1 to S6.

[0040] Furthermore, the processing unit 20 can determine that radiation has interacted at a position in the scintillator 31 directly below the scintillator 35, based on the fact that the intensity peak of the signal S5 is the highest among the signals S4 to S6 output from the light detection units 44 to 46 corresponding to the scintillators 34 to 36 that are air-bonded to the scintillator 31. In this way, the processing unit 20 can determine the radiation interaction position in the detector unit 10.

[0041] The detector unit 10 described so far has a configuration in which one first detector group 11 and one second detector group 12 are stacked in the z direction. However, in the detector unit, the first detector groups 11 and the second detector groups 12 may be stacked alternately in the z direction. Also, in the detector unit, the first detector groups 11 and the second detector groups 12 stacked in the z direction may be arranged in parallel in both or either of the x direction and the y direction.

[0042] In the following, taking into account that the overall general shape of each of the first detector group 11 and the second detector group 12 is a rectangular parallelepiped as shown in Figure 2, for the sake of simplicity in the illustration, each of the first detector group 11 and the second detector group 12 will be represented as a rectangular parallelepiped as shown in Figure 7.

[0043] 8 is a diagram showing the configuration of the detector unit 10A. In this detector unit 10A, a first detector group 11a, a second detector group 12a, a first detector group 11b, and a second detector group 12b are stacked in this order to form a single stack. The first detector groups 11a and 11b have the same configuration as the first detector group 11. The second detector groups 12a and 12b have the same configuration as the second detector group 12. That is, in the detector unit 10A, the first detector groups 11 and the second detector groups 12 are stacked alternately in the z direction.

[0044] In this detector unit 10A, a reflective material does not need to be provided between the second detector group 12a and the first detector group 11b, but it is preferable to provide a reflective material when processing the signals output from the light detection section.

[0045] In this way, by increasing the number of alternating stacks of the first detector group 11 and the second detector group 12, it is possible to suppress deterioration in radiation detection sensitivity while maintaining DOI resolution and TOF resolution, and to increase the size of the detector unit.

[0046] In addition, the number of alternating layers of the first detector group 11 and the second detector group 12 is not limited to two layers each as shown in Figure 8, but may be three or more layers each, or one of the first detector group 11 and the second detector group 12 may have n layers and the other may have n+1 layers.

[0047] 9 is a diagram showing the configuration of the detector unit 10B. In this detector unit 10B, a first detector group 11a, a second detector group 12a, a first detector group 11b, and a second detector group 12b are stacked in this order to form a first stack. A first detector group 11c, a second detector group 12c, a first detector group 11d, and a second detector group 12d are stacked in this order to form a second stack.

[0048] The first detector group 11e, the second detector group 12e, the first detector group 11f, and the second detector group 12f are stacked in this order to form a third stack, and the first detector group 11g, the second detector group 12g, the first detector group 11h, and the second detector group 12h are stacked in this order to form a fourth stack.

[0049] The first stack, second stack, third stack, and fourth stack are arranged in parallel in both the x and y directions. The first detector groups 11a to 11h have the same configuration as the first detector group 11. The second detector groups 12a to 12h have the same configuration as the second detector group 12. Note that in this drawing, the first detector group 11g, the second detector group 12g, and the first detector group 11h of the fourth stack are hidden behind the other stacks and cannot be seen.

[0050] In this detector unit 10B, the photodetector corresponding to each scintillator may be provided on either longitudinal surface of the scintillator, but is preferably provided on a surface that does not face other scintillators (a surface facing outward from detector unit 10B). This makes it possible to reduce the spacing between each stack and also makes it easy to provide signal lines between each photodetector and processing unit 20.

[0051] In this detector unit 10B, a reflective material may or may not be provided on the surface of each scintillator in the longitudinal direction that faces the other scintillators.

[0052] In this way, by arranging the first detector group 11 and the second detector group 12 stacked in the z direction in parallel in both or either the x and y directions, it is possible to suppress deterioration in radiation detection sensitivity while maintaining DOI resolution and TOF resolution, and to increase the size of the detector unit.

[0053] 10 is a diagram showing the configuration of the PET device 2. Here, the PET device will be described as an example of a radiation tomography device.

[0054] The PET device 2 includes a measurement unit 3 and an image processing unit 4. The measurement unit 3 includes a number of detector units (10, 10A, 10B) arranged around a space in which a subject is placed. The detector units shown in this figure are configured such that detector unit 10A has first detector groups 11 and second detector groups 12, each of which has four detectors, stacked alternately. The z direction of each detector unit corresponds to the radial direction in the measurement unit 3.

[0055] The measurement unit 3 counts a pair of gamma rays with an energy of 511 keV, which are generated by an RI radiation source administered to the subject and travel in opposite directions, using a pair of detector units 10A, and outputs signals from the pair of detector units 10A that have counted the rays simultaneously to the image processing unit 4.

[0056] The image processing unit 4 obtains information regarding the position of each detector unit 10A that counted the gamma ray pair coincidentally, and the gamma ray interaction position and gamma ray interaction time in each detector unit 10A, based on the signal output from the measurement unit 3. The image processing unit 4 accumulates this information for a large number of coincidence counting events. The image processing unit 4 then reconstructs a tomographic image of the subject based on the accumulated information.

[0057] In the PET device 2 configured in this manner, the depth resolution (DOI resolution) depends on the thickness of the scintillator (the radial thickness of the measurement unit 3). The time resolution (TOF resolution) depends on the length of the scintillator (the length between the surface of the scintillator to which the photodetector unit is bonded and the opposing surface). By limiting the length of the scintillator, high TOF performance is expected to be obtained.

[0058] For example, if three scintillators are arranged in parallel at a pitch of 4.2 mm in each of the first detector group 11 and the second detector group 12, the length of each scintillator may be 12.6 mm. Compared to the length of a scintillator used in a normal PET device, which is 20 mm, a PET device using a detector unit is expected to have higher time resolution.

[0059] The depth resolution (DOI resolution) is expected to be 4.2 mm, which is also a good value. Furthermore, since radiation detection sensitivity depends only on the number of layers, by increasing the number of layers to five, the length becomes equivalent to that of the scintillator used in ordinary PET devices, and high radiation detection sensitivity can be obtained without degrading the TOF resolution and DOI resolution.

[0060] When scintillators each 12.6 mm long are simply stacked in the z direction, as in detector units 10 and 10A, the size of the detector unit in the x and y directions is smaller than the size of a scintillator used in a typical PET device. However, when the scintillators are arranged in parallel in both the x and y directions, as in detector unit 10B, the size of the detector unit in the x and y directions becomes 1 inch, which is approximately the same as the size of a scintillator used in a typical PET device.

[0061] Next, we will explain the results of an experiment conducted to confirm the operational effects of the detector unit 10. Fig. 11 is a diagram showing an experimental system including the detector unit 10. This experimental system includes the detector unit 10, a reference detector 60, a processing unit 70, and a radiation source 80. The reference detector 60 includes a scintillator 61 and a light detection unit 62.

[0062] The scintillators 31 to 36 and the scintillator 61 of the detector unit 10 each have a size of 3×3×10 mm. ３ The detector unit 10 was made of a rectangular parallelepiped LYSO with a size of 1.5 mm. Each of the photodetectors 41 to 46 in the detector unit 10 was an MPPC array manufactured by Hamamatsu Photonics K.K., S13361-3075. The photodetector 62 was an MPPC manufactured by Hamamatsu Photonics K.K., S13360-3075. The MPPC (Multi-Pixel Photon Counter, registered trademark) is a photon counting device that converts a Geiger-mode APD (Avalanche Photodiode) into a multi-pixel configuration, and has excellent detection capabilities.

[0063] The processing unit 70 included a digitizer V1742 manufactured by CAEN, and when the detector unit 10 and the reference detector 60 counted a pair of gamma rays simultaneously, it digitized and stored the waveforms of the signals S1 to S6 output from the photodetectors 41 to 46 of the detector unit 10, and also digitized and stored the waveform of the signal output from the photodetector 62. The processing unit 70 output data for evaluating the effectiveness of the detector unit 10 based on the signal waveforms stored for a large number of coincidence events.

[0064] As the radiation source 80 22 Na was used. The radiation source 80 was placed between the detector unit 10 and the reference detector 60. The relative positions of the radiation source 80 and the reference detector 60 were fixed so that a line connecting the radiation source 80 and the reference detector 60 was parallel to the x direction. Therefore, when one gamma ray photon of a pair of gamma rays generated by the radiation source 80 is detected by the reference detector 60, the other gamma ray photon travels parallel to the x direction and can be detected by the detector unit 10.

[0065] In order to evaluate the spatial resolution of the detector unit 10, the distance between the detector unit 10 and the radiation source 80 was set to 4 cm, the distance between the reference detector 60 and the radiation source 80 was set to 11 cm, and while maintaining the relative positional relationship between the radiation source 80 and the reference detector 60, they were moved in the y direction relative to the detector unit 10. Gamma rays were incident on a scintillator having a length of 10 mm in the longitudinal direction of the detector unit 10 at a position 1 mm from one end face (position y = 1 mm) and a position 1 mm from the other end face (position y = 9 mm).

[0066] Then, the processing unit 20 determined the gamma ray interaction positions in the detector unit 10 based on the signals S4 to S6 output from the light detection units 44 to 46. The positions of the scintillators 34 to 36 were determined as P ４ ~P ６ The peak values ​​of the signals S4 to S6 are V ４ ~V ６ The peak value V is expressed by the following formula: ４ ~V ６ The gamma ray interaction position P was determined as the position of the center of gravity of P = (V ４ P ４ +V ５ P ５ +V ６ P ６ ) / (P ４ +P ５ +P ６ )

[0067] 12 is a histogram of gamma-ray interaction positions. As shown in this figure, the gamma-ray interaction positions (positions in the y direction) obtained based on signals S4 to S6 can be clearly distinguished between the cases where gamma rays are incident at a position of y = 1 mm and where gamma rays are incident at a position of y = 9 mm, demonstrating that the system has good interaction position resolution in the longitudinal direction of the scintillator.

[0068] In order to evaluate the time resolution of the detector unit 10, the distance between the detector unit 10 and the radiation source 80 was increased, and the distance between the reference detector 60 and the radiation source 80 was decreased, thereby fixing the relative positions of the detector unit 10, the reference detector 60, and the radiation source 80, so that gamma ray photons from the radiation source 80 were incident on the detector unit 10 approximately uniformly. Then, the processing unit 20 calculated the difference in the gamma ray interaction time between the detector unit 10 and the reference detector 60.

[0069] Figure 13 shows a histogram of the gamma-ray interaction time difference. A Gaussian fit is also shown. The histogram showed a full width at half maximum of 185 ps, indicating good TOF resolution.

[0070] The detector unit, the radiation detection apparatus, and the radiation tomography apparatus are not limited to the above-described embodiments and configuration examples, and various modifications are possible.

[0071] The detector unit of the first aspect according to the above embodiment (1) comprises a first detector group and a second detector group stacked in a third direction perpendicular to both the first direction and the second direction, (2) the first detector group includes a plurality of rectangular parallelepiped scintillators having their longitudinal direction in the second direction and arranged in parallel in the first direction, and a light detection unit optically coupled to the longitudinal side surface of each of the plurality of scintillators, and (3) the second detector group includes a plurality of rectangular parallelepiped scintillators having their longitudinal direction in the first direction and arranged in parallel in the second direction, and a light detection unit optically coupled to the longitudinal side surface of each of the plurality of scintillators.

[0072] In the detector unit of the second aspect, in the configuration of the first aspect, in each of the first detector group and the second detector group, the surfaces of the two scintillators facing each other due to stacking may be air-bonded.

[0073] In the detector unit of the third aspect, in the configuration of the first or second aspect, the scintillators of each of the first and second detector groups may be configured to have a reflective material that reflects scintillation light generated by the scintillator on surfaces other than the surface facing the other scintillator due to stacking and the surface to which the light detection unit is optically connected.

[0074] In the detector unit of the fourth aspect, in the configuration of any one of the first to third aspects, the first detector groups and the second detector groups may be alternately stacked in the third direction.

[0075] In the detector unit of the fifth aspect, in the configuration of any of the first to fourth aspects, the first detector group and the second detector group stacked in the third direction may be configured in parallel in both or either the first direction and the second direction.

[0076] The radiation detection device according to the above embodiment includes a detector unit having the configuration of any one of the first to fifth aspects above, and a processing unit that processes a signal output from the photodetector of the detector unit when radiation interacts with any scintillator in the detector unit to generate scintillation light, and determines the position of interaction of the radiation.

[0077] The radiation tomography apparatus according to the above embodiment includes a detector unit having the configuration of any one of the above first to fifth aspects.

[0078] The present invention can be used as a detector unit, a radiation detection apparatus, and a radiation tomography apparatus that can improve both the TOF resolution and the DOI resolution and suppress deterioration of radiation detection sensitivity.

[0079] 1...radiation detection device, 2...PET device, 3...measurement section, 4...image processing section, 10, 10A, 10B...detector unit, 11, 11a to 11h...first detector group, 12, 12a to 12h...second detector group, 20...processing section, 31 to 36...scintillators, 41 to 46...light detection section, 51...reflector, 60...reference detector, 61...scintillator, 62...light detection section, 70...processing section, 80...radiation source.

Claims

1. A detector unit comprising a first detector group and a second detector group stacked in a third direction perpendicular to both the first and second directions, wherein the first detector group includes a plurality of rectangular parallelepiped scintillators whose longitudinal direction is in the second direction and which are arranged in parallel in the first direction, and a light detecting unit optically coupled to a side surface of each of the plurality of scintillators in the longitudinal direction, and the second detector group includes a plurality of rectangular parallelepiped scintillators whose longitudinal direction is in the first direction and which are arranged in parallel in the second direction, and a light detecting unit optically coupled to a side surface of each of the plurality of scintillators in the longitudinal direction.

2. A detector unit according to claim 1, wherein in each of said first detector group and said second detector group, two opposing scintillator surfaces are air-bonded by stacking.

3. A detector unit as described in claim 1 or 2, wherein the scintillators of each of the first and second detector groups are provided with a reflective material that reflects scintillation light generated by the scintillator on all surfaces except for the surface facing the other scintillator due to stacking and the surface to which the light detection unit is optically connected.

4. A detector unit according to any one of claims 1 to 3, wherein the first detector groups and the second detector groups are stacked alternately in the third direction.

5. A detector unit described in any one of claims 1 to 4, wherein the first detector group and the second detector group stacked in the third direction are arranged in parallel in both or either of the first direction and the second direction.

6. A radiation detection device comprising: a detector unit according to any one of claims 1 to 5; and a processing unit that processes a signal output from a light detection unit of said detector unit when radiation interacts with any scintillator of said detector unit to generate scintillation light, thereby determining the position of interaction of the radiation.

7. A radiation tomography apparatus comprising a detector unit according to any one of claims 1 to 5.

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