Scintillator array, radiation detection device, and positron emission tomography device

Abstract

The present invention facilitates manufacturing of a scintillator array, a radiation detection device, and a positron emission tomography device. A scintillator array (11) is provided with at least one pair of scintillators (11Uia, 11Uib), a light reflection member (LA) disposed in a first location between the scintillators for preventing light from passing between the scintillators, and an air layer (LB) disposed in a second location between the scintillators for allowing light to pass between the scintillators.

Description

Scintillator array, radiation detection device, and positron emission tomography device

[0001] The present invention relates to a scintillator array, a radiation detection device, and a positron emission tomography device.

[0002] Positron emission tomography devices that generate tomographic images of a living body by detecting γ-rays emitted from inside the living body are widely used. In a positron emission tomography device, γ-rays are usually detected using a radiation detection device in which detection units each including a scintillator and a light receiving element are arranged in a matrix.

[0003] It is known that by referring to the depth of the point where an interaction with γ-rays occurs in a scintillator (hereinafter, also referred to as DOI: Depth of Interaction), it is possible to reduce the measurement error caused by the thickness of the scintillator in γ-ray detection. Non-Patent Documents 1 and 2 disclose an example of a radiation detection device capable of measuring DOI. In these documents, by bonding the upper part between a pair of scintillators with an optical adhesive, an optical path is formed in the pair of scintillators. DOI can be measured using the intensity ratio of signals at both ends of this path.

[0004] Miyaoka RS, et al, Design of adepth of interaction (DOI) PET detector module. IEEE TransNucl Sci. 1998;45:1069-73.Yoshida E, et al, 2024 Timing estimation of the exponentiated energy-weighted average for crosshair light sharing TOF-DOI PET detector Nucl. Instrum. Methods Phys. Res. Sect. A: Accel., Spectrometers, Detect. Assoc. Equip. 1059 168949

[0005] However, the technologies described above may reduce the manufacturing efficiency of positron emission tomography (PTMO) systems and increase manufacturing costs. Specifically, in order to form light paths for multiple scintillators, it is necessary to bond some of them with optical adhesive and block the light in areas other than the desired path using reflective materials. Thus, the process of optically connecting and blocking multiple scintillators with optical adhesive and reflective materials is not easy. The difficulty of this process (manufacturing) could be a factor that hinders the widespread adoption (e.g., commercialization) of positron emission tomography systems, as shown in Non-Patent Documents 1 and 2.

[0006] One aspect of the present invention aims to facilitate the manufacture of scintillator arrays, radiation detection devices, and positron emission tomography (PTMS) devices.

[0007] The scintillator array according to the present invention comprises at least one pair of scintillators, each having sides facing each other; a light-reflecting member disposed at a first location between the opposing sides to block the passage of light between the at least one pair of scintillators; and an air layer disposed at a second location between the opposing sides to allow light to pass between the at least one pair of scintillators.

[0008] According to one aspect of the present invention, the manufacturing of scintillator arrays, radiation detection devices, and positron emission tomography (PTMS) devices can be facilitated.

[0009] This is a perspective view showing an example of a radiation detection device according to Embodiment 1 of the present invention. This is a cross-sectional view showing an example of a radiation detection device according to Embodiment 1 of the present invention. This is a side view showing an example of a radiation detection device according to Embodiment 2 of the present invention. This is a diagram showing the results of Experimental Example 1. This is a diagram showing the results of Experimental Example 2. This is a diagram showing the results of Experimental Example 3. This is a diagram showing the results of a comparative example.

[0010] [Embodiment 1] An embodiment of the present invention will be described in detail below.

[0011] Figure 1 is a perspective view showing an example of a radiation detection device 1 according to Embodiment 1 of the present invention. The radiation detection device 1 is used, for example, to detect gamma rays in a positron emission tomography (PTMO) system. Embodiment 1 describes a crosshair light-sharing (CLS) detector as shown in Non-Patent Document 2 as an example. The radiation detection device 1 comprises a scintillator array 11 and a light-receiving element array 12. A positron emission tomography system can be constructed by combining the radiation detection device 1 with a signal processing device that processes the output signal from the radiation detection device 1.

[0012] The scintillator array 11 includes a plurality of scintillator units 11U1 to 11Un (where n is any natural number greater than or equal to 1). Each scintillator unit 11Ui (where i is a natural number greater than or equal to 1 or less than or equal to n) is composed of a pair of scintillators 11Uia and 11Uib (hereinafter, scintillators 11Uia and 11Uib may be generalized to scintillator 11Uij). In Figure 1, four scintillator units 11U1 to 11U4 are shown as an example.

[0013] The scintillators 11Uia and 11Uib are columnar (e.g., rectangular) crystals with a square base. Examples of scintillators 11Uia and 11Uib include Ca-doped LYSO (Lutetium Yttrium Orthosilicate) and Ce-doped LGSO (Ce:Lu ｘ Gd ２－ｘ SiO ５ ), Fast-LGSO, GAGG (Gd ３ (Ga, Al) ５ O １２ Examples include (Ce) and LFS (Lutetium Fine Silica).

[0014] The scintillators 11Uia and 11Uib each have opposing sides. The light-reflecting member LAi and the air layer LBi are arranged between the scintillators 11Uia and 11Uib (the opposing sides thereof).

[0015] The light-reflecting member LAi is positioned at a first location between the opposing sides (sides) of the scintillators 11Uia and 11Uib, and prevents light from passing between the scintillators 11Uia and 11Uib. As the light-reflecting member LAi, for example, a resin film can be used. For example, (1) BaSO ４ The light reflection characteristics can be improved by mixing in materials with light-reflecting properties, such as (2) making the film multilayered. Examples of such films include Lumirror (manufactured by Toray Industries, Inc.) and ESR (Enhanced Specular Reflector) film (manufactured by 3M Corporation).

[0016] The air layer LBi is positioned at a second location between the opposing sides of the scintillators 11Uia and 11Uib, allowing light to pass between them. The air layer LBi is, for example, a layer of air that has entered the area where the light-reflecting members LAi of the scintillators 11Uia and 11Uib are not positioned. However, the air layer LBi may be composed of, for example, nitrogen gas or an inert gas (for example, argon gas) instead of air.

[0017] The scintillators 11Uia and 11Uib have a first end on the side of the light-receiving element array 12 (in this case, the negative Z-axis direction side) and a second end on the opposite side of this first end (in this case, the positive Z-axis direction side). The light-reflecting member LAi is located at the first location, i.e., the first end side (negative Z-axis direction side), and the air layer LBi is located at the second location, i.e., the second end side (in this case, the positive Z-axis direction side).

[0018] At least one pair of scintillators 11Uia, 11Uib have a columnar shape, and the axial length DA of the columnar shape of the light-reflecting member LAi is longer than the axial length DB of the columnar shape of the air layer LB. For example, length DA may be twice or more the length DB. As a result, the thickness of the air layer LB is stabilized. That is, the thickness of the air layer LB is maintained by the light-reflecting member LA, and as shown below, the thickness of the air layer LB is approximately the same as the thickness of the light-reflecting member LA.

[0019] The light-reflecting member LAi and the air layer LBi are arranged between the opposing sides of the scintillators 11Uia and 11Uib, and have approximately the same thickness, for example, in the range of 50 to 200 μm (75 μm as an example). If the thickness of the light-reflecting member LAi is 50 μm or less, some of the light may be transmitted. The light-reflecting member LA is also arranged in the insensitive region of the light-receiving element array 12, but the width of this insensitive region is about 200 μm.

[0020] The sides (sides) of the scintillators 11Uia and 11Uib facing each other across the air layer LBi may be roughened or chemically etched. Alternatively, roughening and mirror finishing may be combined. For example, of the four sides of scintillator 11Uia, one or two sides may be roughened, and the remaining sides may be mirror-finished (or chemically etched).

[0021] The photodetector array 12 faces the scintillator array 11 and includes a plurality of photodetectors 12Ui. Here, the photodetector array 12 includes photodetectors 12U1 to 12U9 arranged in a matrix in the x and y directions. Each photodetector 12Ui is a plate-shaped element with a square light-receiving surface. Examples of photodetectors 12Ui include MPPCs (Multi Pixel photon counters), which are a type of SiPM (Silicon Photo Multiplier), and PSPMTs (Position Sensitive Photo Multiplier Tubes).

[0022] Here, one light-receiving element 12Ui corresponds to four scintillators 11Uij. Specifically, one of the first to fourth pairs of scintillators (11U1a to 11U4a) corresponds to the first light-receiving element (12U1) (for example, optically connected). That is, light from scintillators 11U1a to 11U4a is incident on the light-receiving element 12U1 and detected. On the other hand, the other of the first to fourth pairs of scintillators (11U1b to 11U4b) each corresponds to the second to fifth light-receiving elements (12U2 to 12U5) (for example, optically connected). That is, light from scintillators 11U1b to 11U4b is incident on the light-receiving elements 12U2 to 12U5 and detected.

[0023] In this way, parts of the pair of scintillators 11Uia and 11Uib are optically connected by the air layer LBi, and the scintillators 11Uia and 11Uib are optically connected to the photodetectors 12Ui and 12Uj, respectively. As a result, measurement of DOI becomes possible.

[0024] Figure 2 is a cross-sectional view showing an example of a radiation detection device 1 according to Embodiment 1 of the present invention. In Figure 2, the left side is a side view showing the configuration of the radiation detection device 1, and 1(A-A'), 1(B-B'), and 1(C-C') are cross-sectional views showing the AA', BB', and CC' sections of the radiation detection device 1, respectively. Similar to Figure 1, a light-reflecting member LAi and an air layer LBi are arranged between the scintillators 11Uia and 11Uib.

[0025] Figure 2 differs from Figure 1 in the following respects (1) and (2): (1) An air layer LB is placed on the first end side (negative Z-axis side) of the scintillators 11U1b to 11U4b corresponding to the light-receiving element 12Ui (see 1(Y) and 1(C-C')). This makes it possible to increase the amount of light detected by the light-receiving element 12Ui, which is optically connected to the scintillators 11U1b to 11U4b.

[0026] (2) The assembly comprises at least one pair of fifth scintillators 11Uka and 11Ukb, the third portion between their opposing sides being optically bonded by an optical adhesive layer LC (see 1(Y) and 1(C-C')). By connecting a portion of the scintillators 11Uia and 11Uib with an optical adhesive layer LC in this way, the stability of holding the light-reflecting member LA and the air layer LB between the scintillators 11U can be improved.

[0027] In Figure 2, the third location (the location bonded by the optical adhesive layer LC) is located on the first end side (negative Z-axis side), but the third location may also be located on the second end side (positive Z-axis side). If the third location is located on the first end side, the stability of holding the light-reflecting member LAi and the air layer LBi between the scintillators 11Uia and 11Uib can be further improved. Also, if the third location (the optically bonded location) is located on the second end side (opposite side of the light-receiving element array 12), the accuracy of the DOI can be improved.

[0028] Furthermore, at least one pair of fifth scintillators 11Uka and 11Ukb are located on the outermost periphery (the edge of the lower layer) of the scintillator array 11. This arrangement enhances the stability of the retention of the light-reflecting members LAi and air layers LBi, not only within the fifth scintillators 11Uka and 11Ukb themselves, but also between the other scintillators 11Uia and 11Uib.

[0029] In addition, a portion of the air layer LB in Figure 2 may be replaced with an optical adhesive layer LC as appropriate. For example, the air layer LB on the first end side (negative Z-axis side) may be replaced with an optical adhesive layer LC, or the air layer LB on the second end side (positive Z-axis side) may be replaced with an optical adhesive layer LC.

[0030] On the other hand, for example, as shown in Figure 2, if at least one pair of fifth scintillators 11Uka and 11Ukb are located at the outermost periphery (edge) of the scintillator array 11, the adhesive layer LC at the third location between their opposing sides may be replaced with a light-reflecting member LA. In this way, although the detection performance at the edge is slightly degraded, almost the same stability can be obtained in terms of holding the air layer LBi. As a result, it becomes possible to manufacture the scintillator array 11 without using the optical adhesive layer LC.

[0031] In the radiation detection device 1 according to Embodiment 1, the scintillators 11Uia, 11Uia are optically connected by an air layer LBi. Therefore, the light emitted due to gamma rays incident on either scintillator 11Uia or 11Uib is detected by the photodetector 12Ui corresponding to scintillator 11Uia and the photodetector 12Uj corresponding to scintillator 11Uib. As a result, gamma ray detection depth (DOI) information can be obtained from the output ratio of the light received by the photodetectors 12Ui and 12Uj.

[0032] Furthermore, in the radiation detection device 1 according to Embodiment 1, the Time of Flight (TOF) can be measured, that is, the time difference from the generation of a pair of annihilation radiation (gamma rays) to the time from conversion to light by a scintillator to the incident light on the photodetectors 12Ui and 12Uj. This makes it possible to identify the point of origin of the annihilation radiation (for example, its location within a living organism) from the time of flight difference of the pair of annihilation radiation (gamma rays).

[0033] As described above, the scintillator array 11 according to Embodiment 1 comprises at least one pair of scintillators 11Uia, 11Uib, each having sides facing each other; a light-reflecting member LAi disposed at a first location between the opposing sides to block the passage of light between the at least one pair of scintillators 11Uia, 11Uib; and an air layer LBi disposed at a second location between the opposing sides to allow light to pass between the at least one pair of scintillators.

[0034] As a result, the air layer LBi makes it possible to pass light between the pair of scintillators 11Uia and 11Uib, reducing the effort and time required to bond a portion of the pair of scintillators 11Uia and 11Uib with optical adhesive.

[0035] Until now, it has been common technical practice to use optical adhesive for the optical connection between scintillators 11Uia and 11Uib. If optical adhesive is not used, the reflectivity of light at the interface between scintillators 11Uia and 11Uib increases. This reflection is thought to obstruct the passage of light between scintillators 11Uia and 11Uib, causing large errors in the measurement of DOI by the radiation detection device 1, and making it difficult to construct a practical positron emission tomography (POST) system.

[0036] However, as shown in Examples 1 and 2 described later, it was found that detection and measurement of DOI within a practical range is possible even without bonding the scintillators 11Uia and 11Uib with an optical adhesive. In other words, the inventors were able to find and demonstrate that the common technical understanding that an optical adhesive is necessary for the optical connection between the scintillators 11Uia and 11Uib is not necessarily correct.

[0037] [Embodiment 2] Another embodiment of the present invention will be described below. For the sake of convenience of explanation, components having the same function as those described in the above embodiment will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0038] Figure 3 is a side view showing an example of a radiation detection device according to Embodiment 2 of the present invention. Embodiment 2 will be described using a U-shaped detector as shown in Non-Patent Document 1 as an example.

[0039] Embodiment 2 shares many similarities with Embodiment 1. In Embodiment 2 as well, multiple pairs of scintillators 11Uia and 11Uib each have opposing sides, and a light-reflecting member LAi and an air layer LBi are arranged between them.

[0040] The light-reflecting member LAi is positioned at a first location (on the side of the light-receiving element array 12) between the opposing sides of the scintillators 11Uia and 11Uib, and prevents light from passing between the scintillators 11Uia and 11Uib. The air layer LBi is positioned at a second location (on the side opposite the light-receiving element array 12) between the opposing sides of the scintillators 11Uia and 11Uib, and allows light to pass between the scintillators 11Uia and 11Uib.

[0041] At least a pair of scintillators 11Uia and 11Uib have a columnar shape, and the axial length DA of the columnar shape of the light reflecting member LAi is longer than the axial length DB of the columnar shape of the air layer LB. The ratio of the length DA to the length DB may be the same as in Embodiment 1.

[0042] On the other hand, different from Embodiment 1, in Embodiment 2, the scintillators 11Uia and 11Uib and the light receiving elements 12Uia and 12Uib of the light receiving element array 12 are in a one-to-one relationship. At least a pair of scintillators includes a pair of scintillators 11Uia and 11Uib, and a plurality of light receiving elements 12Uij (generalizing the light receiving elements 12Uia and 12Uib as light receiving elements 12Uij) include the first and second light receiving elements 12Uia and 12Uib. One 11Uia of the pair of scintillators corresponds to (for example, is optically connected to) the first light receiving element 12Uia, and the other 11b of the pair of scintillators 11Uia and 11Uib corresponds to (for example, is optically connected to) the second light receiving element 12Uib.

[0043] Also in the radiation detection device 1 according to Embodiment 2, by connecting the second location side (Z-axis positive direction side) of the pair of scintillators 11Uia and 11Uib with the air layer LB, a light path is formed in the scintillators 11Uia and 11Uib. Therefore, the DOI can be measured using the signal intensity ratio at both ends of this path.

[0044] In addition, since the pair of scintillators 11Uia and 11Uib are connected by the air layer LB, it becomes possible to reduce the necessity of adhering the scintillators 11Uij, and efficient production of the scintillator array can be achieved.

[0045] As described above, the scintillator array according to Embodiment 2 is the same as the scintillator array according to Embodiment 1, and includes at least a pair of scintillators each having side portions facing each other, a light reflecting member disposed at a first location between the side portions facing each other and blocking the passage of light between the at least a pair of scintillators, and an air layer disposed at a second location between the side portions facing each other and allowing light to pass between the at least a pair of scintillators.

[0046] (Summary) The scintillator array according to embodiment 1 of the present invention comprises at least one pair of scintillators, each having sides facing each other; a light-reflecting member disposed at a first location between the opposing sides to block the passage of light between the at least one pair of scintillators; and an air layer disposed at a second location between the opposing sides to allow light to pass between the at least one pair of scintillators.

[0047] According to embodiment 1 of the present invention, since light is passed between a pair of scintillators by an air layer without using an optical adhesive, the manufacturing of a scintillator array becomes easier.

[0048] In the scintillator array according to embodiment 2 of the present invention, in embodiment 1 described above, the at least pair of scintillators may be columnar in shape, and the axial length of the columnar shape of the light reflecting member may be longer than the axial length of the columnar shape of the air layer.

[0049] According to aspect 2 of the present invention, the axial length of the columnar light-reflecting member, which is arranged between the opposing sides of at least one pair of columnar scintillators, is longer than the axial length of the columnar air layer. This makes it easier to maintain the thickness of the air layer with the light-reflecting member. That is, the thickness of the air layer can be made, for example, equivalent to the thickness of the light-reflecting member.

[0050] A scintillator array according to embodiment 3 of the present invention may be configured such that, in embodiment 1 or 2 above, at least one pair of scintillators has a first end on the side of the photodetector array having a plurality of photodetectors, and a second end on the opposite side of the first end, the first portion is located on the first end side, and the second portion is located on the second end side.

[0051] According to aspect 3 of the present invention, the side opposite to the photodetector array between the pair of scintillators is optically connected by an air layer. This forms a U-shaped light path between the pair of scintillators, enabling measurement of DOI.

[0052] A scintillator array according to aspect 4 of the present invention may be configured such that, in aspect 3 above, the at least pair of scintillators includes a pair of scintillators, the plurality of light-receiving elements includes first and second light-receiving elements, one of the pair of scintillators corresponds to the first light-receiving element, and the other of the pair of scintillators corresponds to the second light-receiving element.

[0053] According to aspect 4 of the present invention, a so-called U-shaped detector can be constructed by optically connecting a pair of scintillators with an air layer.

[0054] A scintillator array according to embodiment 5 of the present invention may be configured such that, in embodiment 3 above, the at least pair of scintillators includes first to fourth pairs of scintillators, the plurality of photodetectors includes first to fifth photodetectors, one of the first to fourth pairs of scintillators corresponds to the first to fourth photodetectors, and the other of the first to fourth pairs of scintillators corresponds to the fifth photodetector.

[0055] According to aspect 5 of the present invention, a so-called CLS detector can be constructed by optically connecting the first to fourth pairs of scintillators with an air layer.

[0056] The scintillator array according to embodiment 6 of the present invention may be configured to include at least one pair of fifth scintillators, in which a third location between their opposing sides is optically bonded, as in embodiment 5 described above.

[0057] According to aspect 6 of the present invention, a third location between the opposing sides of at least one pair of fifth scintillators is optically bonded. By optically bonding a portion of the scintillator, the stability of the scintillator within the scintillator array can be improved.

[0058] In the scintillator array according to embodiment 7 of the present invention, the third location may be located on the first end side or the second end side, as in embodiment 6 described above.

[0059] According to embodiment 7 of the present invention, the fifth scintillator is optically bonded to either the side facing the photodetector array or the side opposite to the photodetector array. This improves the stability of the scintillator within the scintillator array. Furthermore, optically bonding the side of the fifth scintillator opposite to the photodetector array improves the accuracy of the DOI.

[0060] In the scintillator array according to embodiment 8 of the present invention, in embodiment 6 or 7 described above, the at least pair of fifth scintillators may be located on the outermost periphery of the scintillator array.

[0061] According to aspect 8 of the present invention, by optically bonding at least one pair of fifth scintillators located on the outermost periphery of the scintillator array, the stability of the scintillators located on the inner periphery is improved compared to the at least one pair of fifth scintillators located on the outermost periphery.

[0062] A radiation detection device according to aspect 9 of the present invention comprises the scintillator array and the light-receiving element array according to any one of aspects 3 to 8.

[0063] According to aspect 9 of the present invention, the manufacture of a radiation detection device becomes easier.

[0064] The positron emission tomography apparatus according to embodiment 10 of the present invention is configured to include a radiation detection device according to embodiment 9.

[0065] According to embodiment 10 of the present invention, the manufacture of a positron emission tomography (POST) scanner becomes easier.

[0066] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0067] Example 1 of the present invention is described below. A radiation detection device 1 (CLS detector) shown in Figure 2 was manufactured. Fast-LGSO was used as the scintillator 11Uij and MPPC was used as the photodetector 12Ui. As Comparative Example 1, a radiation detection device 1 was manufactured in which the entire air layer LB in Figure 2 was replaced with an optical adhesive layer LC.

[0068] Comparative Example 1 required 266 optical bonding points, resulting in a lengthy manufacturing process. In contrast, Example 1 required only 24 optical bonding points, reducing the manufacturing time to less than one-tenth.

[0069] Figures 4 and 5 show the results of measuring a standard sample (gamma-ray source) using the radiation detection device 1 of Example 1 and Comparative Example 1, respectively. Exa, Exb, and Exc are figures representing the two-dimensional position histogram, DOI resolution, and timing histogram of Example 1, respectively. Cea, Ceb, and Cec are figures representing the two-dimensional position histogram, DOI resolution, and timing histogram of Comparative Example 1, respectively.

[0070] The two-dimensional position histogram represents the result of centroid calculation of the detection results of the photodetector element 12Ui. The DOI resolution was calculated based on the two-dimensional position histogram. A smaller DOI resolution indicates better performance of the radiation detector 1.

[0071] A timing histogram represents the distribution of the time difference between the detection of a pair of gamma rays from an intermediate standard sample (positron-emitting nuclide) by a pair of opposing radiation detectors 1. The full width at half maximum (FWHM) of the timing histogram is the Coincidence Resolving Time (CRT). A smaller CRT indicates better performance of the radiation detector 1.

[0072] As shown in EXa and CEa, all crystals (scintillators) could be easily identified in both Example 1 and Comparative Example 1. As shown in EXb and CEb, the DOI resolution was approximately 0.5 mm higher in Example 1 (3.6 mm) compared to 3.1 mm in Comparative Example 1. As shown in EXc and CEc, the CRT was approximately 10 ps faster in Example 1 (187.2 ps) compared to 197.3 ps in Comparative Example 1.

[0073] As shown above, the radiation detection device 1 of Example 1, although showing some performance changes compared to Comparative Example 1, can be said to have sufficient performance as a radiation detection device 1. The DOI resolution is slightly reduced, but the CRT is actually improved.

[0074] An embodiment 2 of the present invention is described below. A radiation detection device 1 (U-shaped detector) shown in Figure 3 was manufactured. Fast-LGSO was used as the scintillator 11Uij and MPPC was used as the photodetector 12Ui. As comparative examples, a radiation detection device 1 (U-shaped detector: Comparative Example 2) in which the entire air layer LB in Figure 3 was replaced with an optical adhesive layer LC, and a radiation detection device 1 (general detector: Comparative Example 3) in which the entire air layer LB was replaced with a light-reflecting member LA were manufactured.

[0075] Figure 6 shows the two-dimensional position histograms for Example 2 (EX), Comparative Example 2 (CE1), and Comparative Example 3 (CE2). The right side of Figure 6 shows the two-dimensional position histogram obtained by calculating the centroid of the detection results of the photodetector 12Ui, and the left side shows an enlarged portion of it. Figure 7 shows the timing histograms for Example 2 (EX), Comparative Example 2 (CE1), and Comparative Example 3 (CE2).

[0076] As can be seen by comparing Example 2 (EX) and Comparative Example 2 (CE1) in Figure 6 with Comparative Example 3 (CE2), by using a U-shaped detector instead of a normal detector, DOI information is projected onto the two-dimensional position histogram. The DOI resolution of Example 2 (EX) is slightly worse than that of Comparative Example 2 (CE1). However, the DOI resolution of Example 2 is significantly improved compared to Comparative Example 3 (CE2), which has virtually no DOI resolution.

[0077] As shown in EX and CE1 of Figure 7, the CRT of Example 2 was 234 ps, which is about 10 ps faster than the 242 ps of Comparative Example 2. The CRT of Comparative Example 3 was 229 ps, which is better than both Example 2 and Comparative Example 2.

[0078] This increase in CRT is thought to be due to the connection of pathways between pairs of scintillators in order to acquire DOI information. In other words, an increase in scintillator pathways tends to lead to an increase in CRT.

[0079] As described above, comparing Examples 1 and 2 (connection by air layer) with Comparative Examples 1 and 2 (connection by optical adhesive layer), the DOI resolution was slightly better in the Comparative Examples than in the Examples, but the difference was relatively small and it was found to be sufficiently practical. The reason for this is thought to be that the refractive index difference between the air layer LB and the scintillator 11Uij is larger in the air layer LB than in the optical adhesive layer LC, and the light transmittance is reduced due to reflection at the interface between the scintillators 11Uia and 11Uib and the air layer LB. On the other hand, the performance of the CRT was better in the air layer LB than in the optical adhesive layer LC.

[0080] 1 Radiation detection device 11 Scintillator array 11U1 to 11U9, 11Ui Scintillator unit 11Uia, 11Uib, 11Uij Scintillator 12 Light-receiving element array 12U1 to 12U9, 12Ui Light-receiving element (Embodiment 1) 12Uia, 12Uib, 12Uij Light-receiving element (Embodiment 2) LAi (LA) Light-reflecting member LBi (LB) Air layer LCi (LC) Optical adhesive layer

Claims

1. A scintillator array comprising: at least one pair of scintillators, each having opposite sides; a light-reflecting member disposed at a first location between the opposite sides to block the passage of light between the at least one pair of scintillators; and an air layer disposed at a second location between the opposite sides to allow light to pass between the at least one pair of scintillators.

2. The scintillator array according to claim 1, wherein the at least pair of scintillators are columnar, and the axial length of the columnar shape of the light-reflecting member is longer than the axial length of the columnar shape of the air layer.

3. The scintillator array according to claim 1 or 2, wherein the at least pair of scintillators have a first end on the side of the photodetector array having a plurality of photodetectors, and a second end on the opposite side of the first end, the first portion being located on the first end side, and the second portion being located on the second end side.

4. The scintillator array according to claim 3, wherein the at least pair of scintillators includes a pair of scintillators, the plurality of photodetectors includes first and second photodetectors, one of the pair of scintillators corresponds to the first photodetector, and the other of the pair of scintillators corresponds to the second photodetector.

5. The scintillator array according to claim 3, wherein the at least pair of scintillators includes first to fourth pairs of scintillators, the plurality of photodetectors includes first to fifth photodetectors, one of the first to fourth pairs of scintillators corresponds to the first photodetector, and the other of the first to fourth pairs of scintillators each corresponds to the second to fifth photodetectors.

6. The scintillator array according to claim 5, comprising at least one pair of fifth scintillators, the third portion between which opposing sides are optically bonded.

7. The scintillator array according to claim 6, wherein the third location is located on the first end side or the second end side.

8. The scintillator array according to claim 6 or 7, wherein the at least pair of fifth scintillators are located on the outermost periphery of the scintillator array.

9. A radiation detection device comprising a scintillator array and a photodetector array according to any one of claims 3 to 8.

10. A positron emission tomography apparatus comprising the radiation detection device described in claim 9.

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