WO2024111385A1 - Scintillator array, radiation detection device, and positron emission tomographic device - Google Patents
Scintillator array, radiation detection device, and positron emission tomographic deviceDownload PDFInfo
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- WO2024111385A1 WO2024111385A1PCT/JP2023/039817JP2023039817WWO2024111385A1WO 2024111385 A1WO2024111385 A1WO 2024111385A1JP 2023039817 WJP2023039817 WJP 2023039817WWO 2024111385 A1WO2024111385 A1WO 2024111385A1
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- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/161—Applications in the field of nuclear medicine, e.g. in vivo counting
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
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- the present inventionrelates to a scintillator array including a plurality of scintillators, a radiation detection device including such a scintillator array, and a positron emission tomography device including such a radiation detection device.
- Positron emission tomography devicesare widely used to generate tomographic images of living organisms by detecting gamma rays emitted from within the organism.
- gamma raysare usually detected using a radiation detection device in which detection units made of scintillators and light receiving elements are arranged in a matrix.
- Patent Document 1discloses a radiation detection device capable of measuring DOI.
- the radiation detection device described in Patent Document 1increases the number of scintillators per unit area without increasing the number of light receiving elements per unit area, thereby successfully improving the spatial resolution of gamma ray detection while suppressing increases in costs.
- the radiation detection device described in Patent Document 1leaves room for improvement in that it is not easy to achieve both time resolution and DOI resolution.
- the time resolution for gamma ray detectiontends to be high but the DOI resolution tends to be low.
- the side surface of the scintillatoris roughened, the DOI resolution tends to be high but the time resolution tends to be low.
- One aspect of the present inventionwas made in consideration of the above problems, and its purpose is to achieve both time resolution and DOI resolution in a radiation detection device capable of measuring DOI.
- a scintillator arrayincluding a plurality of scintillator units, each of which is composed of a first scintillator whose bottom surface is optically connected to one of two adjacent light receiving surfaces of a light receiving element in a light receiving element array, and a second scintillator whose side surface is at least partially optically connected to at least partially the side surface of the first scintillator and whose bottom surface is optically connected to the other light receiving surface of the two light receiving elements, and the first scintillator and the second scintillator have one or two side surfaces roughened.
- FIG. 1is a perspective view showing a configuration of a radiation detection device according to an embodiment of the present invention
- 2is a perspective view showing an example of the configuration of a scintillator unit included in the radiation detection device shown in FIG. 1 .
- FIG. 4is a perspective view showing another example of the configuration of the scintillator unit included in the radiation detection device shown in FIG. 2 is a block diagram showing the configuration of a positron emission tomography apparatus including the radiation detection device shown in FIG. 1
- 4A to 4Dare diagrams for explaining an outline of a first identification process executed by the positron emission tomography apparatus shown in Fig. 3.
- Fig. 4A to 4Dare plan views of the radiation detection apparatus shown in Fig. 1.
- FIG. 4is a diagram for explaining an overview of a second identification process executed by the positron emission tomography apparatus shown in Fig. 3.
- Figs. 4(a) to 4(d)are side views of the scintillator unit shown in Fig. 2.
- Fig. 4(e)is a graph showing a ratio of fluorescence intensities detected by two light receiving elements optically connected to the scintillator unit.
- 1Ais a side view of a radiation detection device according to an embodiment of the present invention, and FIGS. 1B to 1D are cross-sectional views of the radiation detection device.
- 1A to 1Care cross-sectional views showing the configurations of radiation detection devices according to examples and comparative examples of the present invention;
- Fig. 1is a perspective view showing the configuration of the radiation detection device 1.
- the radiation detection device 1includes a scintillator array 11 and a light receiving element array 12.
- the radiation detection device 1is used, for example, to detect gamma rays in a positron emission tomography apparatus.
- the scintillator array 11includes a plurality of scintillator units 11U1 to 11Un (n is any natural number equal to or greater than 2).
- Each scintillator unit 11Ui(i is a natural number equal to or greater than 1 and equal to or less than n) is composed of a first scintillator 11Uia and a second scintillator 11Uib.
- the first scintillator 11Uia and the second scintillator 11Uibare columnar crystals with square bottoms, and a portion of one side surface and a portion of the other side surface are optically connected to each other.
- Ca-doped LYSOLitium Yttrium Orthosilicate
- LYSOLitium Yttrium Orthosilicate
- Other scintillatorsinclude, for example, GAGG ( Gd3 (Ga,Al )5O12 ( Ce)), LGSO (Ce:Lu x Gd2 - xSiO5 ), and LFS (Lutetium Fine Silicate).
- GAGGGd3 (Ga,Al )5O12 ( Ce)
- LGSOCe:Lu x Gd2 - xSiO5
- LFSLiutetium Fine Silicate
- the light receiving element array 12includes a plurality of light receiving elements 12U1 to 12Um (m is any natural number equal to or greater than 2) arranged in a matrix.
- Each light receiving element 12Uj(j is a natural number equal to or greater than 1 and equal to or less than m) is a plate-shaped element with a square light receiving surface.
- the area of the bottom surface of each light receiving element 12Ujis four times the area of the bottom surfaces of the first scintillator 11Uia and the second scintillator 11Uib.
- a SiPMSilicon Photo Multiplier
- Other examples of light receiving elementsinclude, for example, PSPMTs (Position Sensitive Photo Multiplier Tubes).
- One bottom surface of the first scintillator 11U1a of the first scintillator unit 11U1is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light receiving element array 12.
- one bottom surface of the second scintillator 11U1b of the first scintillator unit 11U1is optically connected to the light receiving surface of the second light receiving element 12U2 adjacent to the first light receiving element 12U1 in the light receiving element array 12.
- the first scintillator unit 11U1is arranged to straddle the first side of the first light receiving element 12U1, which is the boundary with the second light receiving element 12U2.
- One bottom surface of the first scintillator 11U2a of the second scintillator unit 11U2is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light receiving element array 12, similar to one bottom surface of the first scintillator 11U1a of the first scintillator unit 11U1. Also, one bottom surface of the second scintillator 11U2b of the second scintillator unit 11U2 is optically connected to the light receiving surface of the third light receiving element 12U3 adjacent to the first light receiving element 12U1 in the light receiving element array 12.
- the second scintillator unit 11U2is arranged so as to straddle the second side of the first light receiving element 12U1, which is the boundary with the third light receiving element 12U3.
- the third light receiving element 12U3is a different light receiving element from the second light receiving element 12U2.
- One bottom surface of the first scintillator 11U3a of the third scintillator unit 11U3is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light receiving element array 12, similar to one bottom surface of the first scintillator 11U1a of the first scintillator unit 11U1. Also, one bottom surface of the second scintillator 11U3b of the third scintillator unit 11U3 is optically connected to the light receiving surface of the fourth light receiving element 12U4 adjacent to the first light receiving element 12U1 in the light receiving element array 12.
- the third scintillator unit 11U3is arranged so as to straddle the boundary between the first light receiving element 12U1 and the fourth light receiving element 12U4. That is, the third scintillator unit 11U3 is arranged so as to straddle the third side of the first light receiving element 12U1, which is the boundary with the fourth light receiving element 12U4.
- the fourth light receiving element 12U4is a different light receiving element from the second light receiving element 12U2 and the third light receiving element 12U3.
- One bottom surface of the first scintillator 11U4a of the fourth scintillator unit 11U4is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light receiving element array 12, similar to one bottom surface of the first scintillator 11U1a of the first scintillator unit 11U1. Also, one bottom surface of the second scintillator 11U4b of the fourth scintillator unit 11U4 is optically connected to the light receiving surface of the fifth light receiving element 12U5 adjacent to the first light receiving element 12U1 in the light receiving element array 12.
- the fourth scintillator unit 11U4is arranged so as to straddle the fourth side of the first light receiving element 12U1, which is the boundary with the fifth light receiving element 12U5.
- the fifth light receiving element 12U5is a light receiving element different from the second light receiving element 12U2, the third light receiving element 12U3, and the fourth light receiving element 12U4.
- Conventional radiation detection devices capable of measuring DOIemploy a configuration in which the two bottom surfaces of the scintillator array are each optically connected to the light receiving surface of the light receiving element array.
- the radiation detection device 1 according to this embodimentemploys a configuration in which only one bottom surface of the scintillator array 11 is optically connected to the light receiving surface of the light receiving element array 12.
- the radiation detection device 1is composed of a smaller number of light receiving element arrays. This allows for cost reduction.
- the scintillator unit 11Uiis composed of a first scintillator 11Uia and a second scintillator 11Uib, and the first scintillator 11Uia and the second scintillator 11Uib have one or two sides roughened.
- Figure 2is a perspective view showing the configuration of the scintillator unit 11Ui when one side of each of the first scintillator 11Uia and the second scintillator 11Uib is roughened.
- the side surface 11Uia1 of the first scintillator 11Uiais roughened and is optically connected to the second scintillator 11Uib.
- the second scintillator 11Uibhas a roughened side surface 11Uib1 and is optically connected to the first scintillator 11Uia.
- a region of the side surface 11Uia1 of the first scintillator 11Uia that is not covered with reflecting material and a region of the side surface 11Uib1 of the second scintillator 11Uib that is not covered with reflecting materialare bonded with an optical adhesive. This allows the fluorescence generated when radiation is incident on the first scintillator 11Uia to enter the second scintillator 11Uib via the region of the side surface 11Uia1 of the first scintillator 11Uia that is not covered with reflecting material.
- the fluorescence generated when radiation is incident on the second scintillator 11Uibcan enter the first scintillator 11Uia via the region of the side surface 11Uib1 of the second scintillator 11Uib that is not covered with reflecting material.
- the bottom surface 11Uia5 of the first scintillator 11Uia and the bottom surface 11Uib5 of the second scintillator 11Uibare optically connected to the light receiving elements 12Uj and 12Uk, respectively.
- the fluorescence generated in the first scintillator 11Uia and the fluorescence generated in the second scintillator 11Uib and incident on the first scintillator 11Uiaare incident on the light receiving element 12Uj via the bottom surface 11Uia5 of the first scintillator 11Uia.
- the fluorescence generated in the second scintillator 11Uib and the fluorescence generated in the first scintillator 11Uia and incident on the second scintillator 11Uibare incident on the light receiving element 12Uk via the bottom surface 11Uib5 of the second scintillator 11Uib.
- Figure 3is a perspective view showing the configuration of the scintillator unit 11Ui when two side surfaces of the first scintillator 11Uia and the second scintillator 11Uib are roughened.
- the second scintillator 11Uibhas side surfaces 11Uib1 and 11Uib3 roughened. Of the two roughened sides, side surface 11Uia1 is optically connected to the second scintillator 11Uia.
- the area of the side surface 11Uia1 of the first scintillator 11Uia that is not covered with reflective material and the area of the side surface 11Uib1 of the second scintillator 11Uib that is not covered with reflective materialare bonded with an optical adhesive.
- the roughened side surface 11Uia4 of the first scintillator 11Uia and the roughened side surface 11Uib3 of the second scintillator 11Uibare bonded so as to be adjacent to each other. This allows each of the first scintillator 11Uia and the second scintillator 11Uib to have the same function as when one side surface is roughened.
- the bottom surface 11Uia5 of the first scintillator 11Uia and the bottom surface 11Uib5 of the second scintillator 11Uibare optically connected to the light receiving elements 12Uj and 12Uk, respectively.
- the roughened side surface 11Uia4 of the first scintillator unit 11Uiis located on the outer edge of the light receiving element 12Uj, and the roughened side surface 11Uib3 of the second scintillator 11Uib is optically connected to the outer edge of the light receiving element 12Uk. This provides the same functionality as when one side surface of each of the first scintillator 11Uia and the second scintillator 11Uib is roughened.
- the radiation detection device 1has the following distinctive features: (1) Of the four side surfaces 11Uia1 to 11Uia4 of the first scintillator 11Uia, one or two are roughened, and the remaining three or two are mirror-finished or chemically etched. (2) Of the four side surfaces 11Uib1 to 11Uib4 of the second scintillator 11Uib, one or two are roughened, and the remaining three or two are mirror-finished or chemically etched.
- the time resolutiontends to be high while the DOI resolution tends to be low.
- the boundary surface of each scintillatorcontains an air layer, which prevents leakage of fluorescence from the light receiving element boundary surface and causes diffuse reflection of the fluorescence in the air layer, which tends to increase the DOI resolution while decreasing the time resolution.
- one or two side surfaces of the first scintillator 11Uia and the second scintillator 11Uibare roughened, so that both the time resolution and the DOI resolution can be increased.
- the roughened side 11Uia1 of the first scintillator 11Uia and the roughened side 11Uib1 of the second scintillator 11Uibare optically connected.
- the roughened connection surface between the first scintillator 11Uia and the second scintillator 11Uib that constitute the scintillator unit 11Uiis located on the boundary between the light receiving element 12Uj and the light receiving element 12Uk.
- the other roughened side surface 11Uia4 of the first scintillator 11Uia and the other roughened side surface 11Uib3 of the second scintillator 11Uibare adjacent to each other, and the side surface 11Uia4 of the first scintillator 11Uia is located on the outer edge of the light receiving element 12Uj, and the roughened side surface 11Uib3 of the second scintillator 11Uib is located on the outer edge of the light receiving element 12Uk.
- the roughened side surfacesare located on all boundaries of each light receiving element 12Uj that constitutes the light receiving element array. This prevents leakage of fluorescence from the boundaries between each light receiving element 12Uj and each scintillator, further increasing the light collection rate to the light receiving element.
- FIG. 4is a block diagram of a positron emission tomography apparatus 10.
- the positron emission tomography apparatus 10includes the radiation detection apparatus 1 described above and a signal processing apparatus 2 that processes an output signal from the radiation detection apparatus 1 described above.
- the signal processing apparatus 2executes a first identification process and a second identification process.
- the first identification processis a process of identifying the scintillator unit 11Ux (x is 1, 2, 3, or 4) on which the gamma ray is incident, among the scintillator units 11U1 to 11U4.
- the second identification processis a process of (1) identifying the scintillator 11Uxy (y is a or b) on which the gamma ray is incident, among the two scintillators 11Uxa and 11Uxb that make up the scintillator unit 11Ux, and identifying the position (height) at which an interaction with the gamma ray occurs in the scintillator 11Uxy.
- FIG. 5is a diagram for explaining an overview of the first identification process, and (a) to (d) in FIG. 5 are each a plan view of the radiation detection device 1.
- the signal processing device 2uses this property to execute the first identification process described above.
- the signal processing device 2identifies the scintillator unit 11Ux into which the gamma rays are incident, for example, as follows: That is, (1) if the combination of light receiving elements that detected the fluorescence is the combination of the first light receiving element 12U1 and the second light receiving element 12U2, the first scintillator unit 11U1 is identified as the scintillator unit Ux into which the gamma rays are incident. Also, (2) if the combination of light receiving elements that detected the fluorescence is the combination of the first light receiving element 12U1 and the third light receiving element 12U3, the second scintillator unit 11U2 is identified as the scintillator unit Ux into which the gamma rays are incident.
- the third scintillator unit 11U3is identified as the scintillator unit Ux into which the gamma rays are incident. Furthermore, (4) if the combination of light receiving elements that detected the fluorescence is the combination of the first light receiving element 12U1 and the fifth light receiving element 12U5, the fourth scintillator unit 11U4 is identified as the scintillator unit Ux into which the gamma rays were incident.
- FIG. 6is a diagram for explaining an outline of the second identification process, and (a) to (d) of FIG. 6 are side views of the scintillator unit 11Ux on which gamma rays are incident.
- (e) of FIG. 6is a graph showing the ratios Ia/(Ia+Ib) and Ia/(Ia+Ib) of the fluorescence intensities Ia and Ib.
- the second identification processis as follows: 6A, when an interaction with a gamma ray occurs near the bottom surface (lower surface) of the first scintillator 11Uxa, most of the generated fluorescence is incident on the light receiving element 12Uj optically connected to the first scintillator 11Uxa. Therefore, the relationship between the fluorescence intensities Ia and Ib is Ia>>Ib. As a result, the ratio Ia/(Ia+Ib) is approximately 1, and the ratio Ib/(Ia+Ib) is approximately 0.
- the fluorescence intensity Ia detected by the light receiving element 12Uj optically connected to the first scintillator 11Uxais weaker than when an interaction with gamma rays occurs near the bottom surface of the first scintillator 11Uxa.
- the fluorescence intensity Ib detected by the light receiving element 12Uk optically connected to the second scintillator 11Uxbis stronger than when an interaction with gamma rays occurs near the bottom surface of the first scintillator 11Uxa.
- the fluorescence intensity Ia detected by the light receiving element 12Uj optically connected to the first scintillator 11Uxais weaker than when an interaction with gamma rays occurs at a position away from the bottom surface of the first scintillator 11Uxb.
- the fluorescence intensity Ib detected by the light receiving element 12Uk optically connected to the second scintillator 11Uxbis stronger than when an interaction with gamma rays occurs at a position away from the bottom surface of the first scintillator 11Uxa.
- the magnitude of the fluorescence intensities Ia, Ibis determined depending on which of the scintillators 11Uxa, 11Uxb constituting the scintillator unit 11Ux on which the gamma rays are incident, the scintillator into which the gamma rays are incident. Also, the ratios Ia/(Ia+Ib), Ib/(Ia+Ib) are determined depending on the position (height) at which the gamma rays interact with the scintillator on which the gamma rays are incident. The signal processing device 2 uses these properties to execute the second identification process described above.
- the signal processing device 2identifies the scintillator 11Uxy on which the gamma rays are incident, for example, as follows: That is, (1) if the relationship Ia>Ib holds between the fluorescence intensities Ia and Ib detected by the light receiving elements 12Uj and 12Uk, the first scintillator 11Uxa is identified as the scintillator 11Uxy on which the gamma rays are incident.
- the second scintillator 11Uxbis identified as the scintillator 11Uxy on which the gamma rays are incident.
- the signal processing device 2also identifies the position in the scintillator 11Uxy where an interaction with a gamma ray occurs, for example, as follows. That is, a table showing the correspondence between the ratio Ia/(Ia+Ib) and the interaction position is created in advance. Then, each time a gamma ray is incident on the scintillator 11Uxy, (1) the ratio Ia/(Ia+Ib) is calculated from the fluorescence intensities Ia and Ib detected by the light receiving elements 12Uj and 12Uk, and (2) the interaction position corresponding to the calculated ratio Ia/(Ia+Ib) is identified by referring to this table.
- a function showing the correspondence between the ratio Ia/(Ia+Ib) and the interaction positionis created in advance. Then, each time a gamma ray is incident on the scintillator 11Uxy, (1) the ratio Ia/(Ia+Ib) is calculated from the fluorescence intensities Ia and Ib detected by the light receiving elements 12Uj and 12Uk, and (2) the interaction position corresponding to the calculated ratio Ia/(Ia+Ib) is identified by substituting the ratio Ia/(Ia+Ib) into this function. Note that although an example using the ratio Ia/(Ia+Ib) is shown here, the ratio Ib/(Ia+Ib) may also be used.
- FIG. 7(a) is a side view showing the configuration of the radiation detection device 1 according to the embodiment and the comparative example, (b) is a cross-sectional view showing the AA' section of the radiation detection device 1, (c) is a cross-sectional view showing the BB' section of the radiation detection device 1, and (d) is a cross-sectional view showing the CC' section of the radiation detection device 1.
- the thick linesindicate the boundary surface between two adjacent scintillators where no reflective material is provided and which is optically connected by optical bonding.
- the scintillatorwas a prismatic LYSO:Ca crystal having a height of 15 mm and a square base with sides of 1.45 mm.
- the scintillator array 11was made up of three layers of reflector material consisting of a lower layer, a middle layer, and an upper layer, each of which had a height of 5 mm.
- two adjacent scintillatorswere optically connected at the boundary surface indicated by the thick line by an optical adhesive, and optically separated at the other boundary surfaces by a reflector.
- the scintillators that make up the scintillator array 11 shown in Figure 1are hatched in the same way. It can be seen from Figures 6 and 1 that the upper and middle layers of the scintillator array 11 shown in Figure 7 are made by combining the scintillator arrays 11 shown in Figure 1.
- the lower layer of the scintillator array 11 shown in Figure 7combines the scintillator arrays 11 shown in Figure 1, and is optically connected at a position up to a height of 5 mm from the bottom surface where it is optically connected to each light receiving element 12Uj, as shown in Figure 7(d). Note that the reflective material has been removed from the optically connected locations.
- the function of the lower layer of the scintillator array 11 shown in FIG. 7, which is newly added in this embodiment and the comparative example,will be described.
- the radiation detection device 1 according to the present disclosurefour scintillators are optically connected to one light receiving element. Therefore, the fluorescence generated when radiation is incident on the scintillator is incident on 1/4 of the total area of the light receiving element to which the scintillator is optically connected. In other words, only 1/4 of the light receiving element is utilized (the light receiving element cannot be used for a certain period of time after one detection has been performed).
- the fluorescence that has passed through the upper and middle layerscan be spread within the light receiving element, and it becomes possible to detect the fluorescence over the entire surface of the light receiving element to which the scintillator is optically connected. This increases the fluorescence detection efficiency in the light receiving element.
- FIG. 8is a cross-sectional view of the radiation detection device 1 according to the first embodiment.
- the thick lineindicates the side of the scintillator that has been roughened.
- the radiation detection device 1 according to the first embodimentuses a scintillator that has one side roughened and three sides mirror-finished.
- FIG. 8is a cross-sectional view of the radiation detection device 1 according to the second embodiment.
- the thick lineindicates the side of the scintillator that has been roughened.
- the radiation detection device 1 according to the second embodimentuses a scintillator with two sides that are roughened and two sides that are mirror-finished.
- FIG. 8is a cross-sectional view of the radiation detection device 1 according to the comparative example.
- the radiation detection device 1 according to the comparative exampleuses a scintillator with four mirror-finished sides.
- the results of evaluating the performance of the radiation detection devices 1 according to the comparative example, the first embodiment, and the second embodimentare shown in Table 1.
- the CRT resolutionwas evaluated as the time resolution. It can be seen from Table 1 that the radiation detection devices 1 according to the first and second embodiments can improve the DOI resolution while suppressing degradation of the CRT resolution. Note that the radiation detection device 1 according to the first embodiment has a superior CRT resolution compared to the radiation detection device 1 according to the second embodiment.
- the scintillator array of aspect 1 of this embodimentis a scintillator array including a plurality of scintillator units, each of which is composed of a first scintillator whose bottom surface is optically connected to one of the light receiving surfaces of two adjacent light receiving elements in the light receiving element array, and a second scintillator whose side surface at least a portion of which is optically connected to at least a portion of the side surface of the first scintillator and whose bottom surface is optically connected to the other light receiving surface of the two light receiving elements, and the first scintillator and the second scintillator have one or two side surfaces roughened.
- the scintillator array according to aspect 2 of this embodimentis the same as in aspect 1 above, in that the area of the bottom surface of the first scintillator is 1/4 or less of the area of the light receiving surface of the light receiving element that is optically connected to the bottom surface of the two light receiving elements, and the area of the bottom surface of the second scintillator is 1/4 or less of the area of the light receiving surface of the light receiving element that is optically connected to the bottom surface of the two light receiving elements.
- the above configurationmakes it possible to increase the number of scintillators per unit area of the light receiving element, thereby improving the spatial resolution of gamma ray detection.
- the scintillator array according to aspect 3 of this embodimentis the same as in aspect 1 or 2 above, and includes a first scintillator unit, a second scintillator unit, a third scintillator unit, and a fourth scintillator unit as the plurality of scintillator units, and the bottom surfaces of the first scintillators of the first scintillator unit, the second scintillator unit, the third scintillator unit, and the fourth scintillator unit are optically connected to the light receiving surface of the first light receiving element included in the light receiving element array, and the bottom surface of the second scintillator of the first scintillator unit is optically connected to the light receiving surface of the first light receiving element included in the light receiving element array.
- the bottom surface of the second scintillator of the second scintillator unitis optically connected to the light receiving surface of the second light receiving element adjacent to the first light receiving element in the light receiving element array
- the bottom surface of the second scintillator of the third scintillator unitis optically connected to the light receiving surface of the fourth light receiving element adjacent to the first light receiving element in the light receiving element array
- the bottom surface of the second scintillator of the fourth scintillator unitis optically connected to the light receiving surface of the fifth light receiving element adjacent to the first light receiving element in the light receiving element array.
- the above configurationallows the number of scintillators per unit area to be increased without increasing the number of light receiving elements per unit area, thereby improving the spatial resolution of gamma ray detection while suppressing increases in costs.
- the scintillator array according to aspect 4 of this embodimentis any one of aspects 1 to 3 above, in which a portion of the roughened side surface of the first scintillator and a portion of the roughened side surface of the second scintillator are optically connected.
- the above configurationprevents leakage of fluorescence outside the scintillator unit and improves the detection efficiency of the light receiving element.
- a scintillator array according to aspect 5 of the present embodimentis any one of aspects 1 to 4 above,
- the above-described configurationmakes it possible to prevent leakage of fluorescence outside the scintillator unit and improve the detection efficiency in the light receiving element.
- the scintillator array according to aspect 6 of this embodimentis any one of aspects 1 to 5 above, in which the non-roughened side surfaces of the first scintillator and the second scintillator are mirror-finished.
- the scintillator array according to aspect 7 of this embodimentis any one of aspects 1 to 6 above, in which the non-roughened sides of the first scintillator and the second scintillator are chemically etched.
- the radiation detection deviceincludes a scintillator array according to any one of aspects 1 to 7 above, and the light receiving element array.
- the above configurationallows the radiation detection device to achieve both time resolution and DOI resolution.
- the positron emission tomography apparatuscomprises the radiation detection apparatus according to aspect 8 above, and a signal processing device that processes the output signal from the light receiving element array, and the signal processing device executes a first identification process that identifies the scintillator unit on which the radiation is incident based on a combination of two light receiving elements that detect fluorescence in the light receiving element array, and a second identification process that identifies the scintillator on which the radiation is incident and the position of incidence of the radiation on the scintillator based on the ratio of the fluorescence intensities detected by each of the two light receiving elements.
- the above configurationmakes it possible to achieve both time resolution and DOI resolution in a positron emission tomography device.
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Abstract
Description
Translated fromJapanese本発明は、複数のシンチレータを含むシンチレータアレイ、そのようなシンチレータアレイを含む放射線検出装置、及び、そのような放射線検出装置を含む陽電子放出断層撮影装置に関する。The present invention relates to a scintillator array including a plurality of scintillators, a radiation detection device including such a scintillator array, and a positron emission tomography device including such a radiation detection device.
生体の内部から放出されたγ線を検出することによって、その生体の断層画像を生成する陽電子放出断層撮影装置が広く利用されている。陽電子放出断層撮影装置においては、通常、シンチレータと受光素子とからなる検出ユニットをマトリクス状に配置した放射線検出装置を用いて、γ線の検出を行う。Positron emission tomography devices are widely used to generate tomographic images of living organisms by detecting gamma rays emitted from within the organism. In positron emission tomography devices, gamma rays are usually detected using a radiation detection device in which detection units made of scintillators and light receiving elements are arranged in a matrix.
断層画像の画質を向上させるためには、単位面積あたりのシンチレータの個数を増やして、γ線検出の空間分解能を向上させることに加えて、時間分解能を向上させることが重要になる。時間分解能の向上が断層画像の画質の向上に繋がるのは、時間分解能が向上するとγ線発生位置の同時計数線上における位置推定精度が改善するためである。In order to improve the image quality of tomographic images, it is important to increase the number of scintillators per unit area and improve the spatial resolution of gamma ray detection, as well as to improve the temporal resolution. Improved temporal resolution leads to improved image quality of tomographic images, because improved temporal resolution improves the accuracy of estimating the position of gamma ray generation on the coincidence line.
また、シンチレータにおいてγ線との相互作用が生じた点の深さ（以下、ＤＯＩ：Depth of Interactionとも記載する）を参照することによって、視差誤差を低減し得ることも知られている。特許文献１には、ＤＯＩを測定可能な放射線検出装置が開示されている。特許文献１に記載の放射線検出装置においては、単位面積あたりの受光素子の個数を増やすことなく単位面積あたりのシンチレータの個数を増やすことによって、コストの上昇を抑えながらγ線検出の空間分解能を向上させることに成功している。It is also known that parallax error can be reduced by referring to the depth of the point where interaction occurs in the scintillator with gamma rays (hereinafter also referred to as DOI: Depth of Interaction).
しかしながら、特許文献１に記載の放射線検出装置には、時間分解能とＤＯＩ分解能との両立を図ることが容易ではないという点で改善の余地が残されていた。例えば、シンチレータの側面を鏡面加工した場合、γ線検出の時間分解能は高くなるものの、ＤＯＩ分解能は低くなる傾向がある。逆に、シンチレータの側面を粗面加工した場合、ＤＯＩ分解能は高くなるものの、時間分解能は低くなる傾向がある。However, the radiation detection device described in
本発明の一態様は、上記の問題に鑑みてなされたものであり、その目的は、ＤＯＩを測定可能な放射線検出装置において、時間分解能とＤＯＩ分解能との両立を図ることにある。One aspect of the present invention was made in consideration of the above problems, and its purpose is to achieve both time resolution and DOI resolution in a radiation detection device capable of measuring DOI.
複数のシンチレータユニットを含むシンチレータアレイであって、前記複数のシンチレータユニットの各々は、その底面が受光素子アレイにおいて互いに隣接する２つの受光素子の一方の受光面と光学接続される第１シンチレータと、その側面の少なくとも一部が前記第１シンチレータの側面の少なくとも一部と光学接続され、その底面が前記２つの受光素子の他方の受光面と光学接続される第２シンチレータと、により構成されており、前記第１シンチレータ及び前記第２シンチレータは、１側面又は２側面が粗面加工されている。A scintillator array including a plurality of scintillator units, each of which is composed of a first scintillator whose bottom surface is optically connected to one of two adjacent light receiving surfaces of a light receiving element in a light receiving element array, and a second scintillator whose side surface is at least partially optically connected to at least partially the side surface of the first scintillator and whose bottom surface is optically connected to the other light receiving surface of the two light receiving elements, and the first scintillator and the second scintillator have one or two side surfaces roughened.
本発明の一態様によれば、時間分解能とＤＯＩ分解能との両立を図ることができる。According to one aspect of the present invention, it is possible to achieve both time resolution and DOI resolution.
（放射線検出装置の構成）
本発明の一実施形態に係る放射線検出装置１の構成について、図１を参照して説明する。図１は、放射線検出装置１の構成を示す斜視図である。(Configuration of Radiation Detection Device)
The configuration of a
放射線検出装置１は、シンチレータアレイ１１と、受光素子アレイ１２と、を備えている。放射線検出装置１は、例えば、陽電子放出断層撮影装置においてγ線を検出するために利用される。The
シンチレータアレイ１１は、複数のシンチレータユニット１１Ｕ１～１１Ｕｎ（ｎは２以上の任意の自然数）を含んでいる。各シンチレータユニット１１Ｕｉ（ｉは１以上ｎ以下の各自然数）は、第１シンチレータ１１Ｕｉａと、第２シンチレータ１１Ｕｉｂと、により構成されている。第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂは、底面が正方形である柱状の結晶であり、一方の側面の一部と他方の側面の一部とが互いに光学接続されている。本実施形態においては、各シンチレータユニット１１Ｕｉを構成する第１シンチレータＵｉａ及び第２シンチレータＵｉｂとして、ＣａをドープしたＬＹＳＯ（Lutetium Yttrium Orthosilicate)を用いているが、本発明は、これに限定されない。その他のシンチレータとしては、例えば、ＧＡＧＧ（Gd3(Ga,Al)５O12(Ce)）、ＬＧＳＯ（Ce:LuxGd2-xSiO5）及びＬＦＳ（Lutetium Fine Silicate）が挙げられる。図１においては、４個のシンチレータユニット１１Ｕ１～１１Ｕ４を図示している。The
受光素子アレイ１２は、マトリクス状に配置された複数の受光素子１２Ｕ１～１２Ｕｍ（ｍは２以上の任意の自然数）を含んでいる。各受光素子１２Ｕｊ（ｊは１以上ｍ以下の各自然数）は、受光面が正方形の板状の素子である。各受光素子１２Ｕｊの底面の面積は、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの底面の面積の４倍である。本実施形態においては、各受光素子１２Ｕｊとして、ＳｉＰＭ（Silicon Photo Multiplier）を用いているが、本発明は、これに限定されない。その他の受光素子の例としては、例えば、ＰＳＰＭＴ（Position Sensitive Photo Multiplier Tubes）が挙げられる。図１においては、９個の受光素子１２Ｕ１～１２Ｕ９を図示している。The light
第１シンチレータユニット１１Ｕ１の第１シンチレータ１１Ｕ１ａの一方の底面は、受光素子アレイ１２の中央に配置された第１受光素子１２Ｕ１の受光面に光学接続されている。また、第１シンチレータユニット１１Ｕ１の第２シンチレータ１１Ｕ１ｂの一方の底面は、受光素子アレイ１２において第１受光素子１２Ｕ１に隣接する第２受光素子１２Ｕ２の受光面と光学接続されている。すなわち、第１シンチレータユニット１１Ｕ１は、第２受光素子１２Ｕ２との境界となる第１受光素子１２Ｕ１の第１の辺を跨ぐように配置されている。One bottom surface of the first scintillator 11U1a of the first scintillator unit 11U1 is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light
第２シンチレータユニット１１Ｕ２の第１シンチレータ１１Ｕ２ａの一方の底面は、第１シンチレータユニット１１Ｕ１の第１シンチレータ１１Ｕ１ａの一方の底面と同様、受光素子アレイ１２の中央に配置された第１受光素子１２Ｕ１の受光面に光学接続されている。また、第２シンチレータユニット１１Ｕ２の第２シンチレータ１１Ｕ２ｂの一方の底面は、受光素子アレイ１２において第１受光素子１２Ｕ１に隣接する第３受光素子１２Ｕ３の受光面と光学接続されている。すなわち、第２シンチレータユニット１１Ｕ２は、第３受光素子１２Ｕ３との境界となる第１受光素子１２Ｕ１の第２の辺を跨ぐように配置されている。なお、第３受光素子１２Ｕ３は、第２受光素子１２Ｕ２とは異なる受光素子である。One bottom surface of the first scintillator 11U2a of the second scintillator unit 11U2 is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light
第３シンチレータユニット１１Ｕ３の第１シンチレータ１１Ｕ３ａの一方の底面は、第１シンチレータユニット１１Ｕ１の第１シンチレータ１１Ｕ１ａの一方の底面と同様、受光素子アレイ１２の中央に配置された第１受光素子１２Ｕ１の受光面に光学接続されている。また、第３シンチレータユニット１１Ｕ３の第２シンチレータ１１Ｕ３ｂの一方の底面は、受光素子アレイ１２において第１受光素子１２Ｕ１に隣接する第４受光素子１２Ｕ４の受光面と光学接続されている。すなわち、第３シンチレータユニット１１Ｕ３は、第１受光素子１２Ｕ１と第４受光素子１２Ｕ４との境界を跨ぐように配置されている。すなわち、第３シンチレータユニット１１Ｕ３は、第４受光素子１２Ｕ４との境界となる第１受光素子１２Ｕ１の第３の辺を跨ぐように配置されている。なお、第４受光素子１２Ｕ４は、第２受光素子１２Ｕ２とも、第３受光素子１２Ｕ３とも異なる受光素子である。One bottom surface of the first scintillator 11U3a of the third scintillator unit 11U3 is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light
第４シンチレータユニット１１Ｕ４の第１シンチレータ１１Ｕ４ａの一方の底面は、第１シンチレータユニット１１Ｕ１の第１シンチレータ１１Ｕ１ａの一方の底面と同様、受光素子アレイ１２の中央に配置された第１受光素子１２Ｕ１の受光面に光学接続されている。また、第４シンチレータユニット１１Ｕ４の第２シンチレータ１１Ｕ４ｂの一方の底面は、受光素子アレイ１２において第１受光素子１２Ｕ１に隣接する第５受光素子１２Ｕ５の受光面と光学接続されている。すなわち、第４シンチレータユニット１１Ｕ４は、第５受光素子１２Ｕ５との境界となる第１受光素子１２Ｕ１の第４の辺を跨ぐように配置されている。なお、第５受光素子１２Ｕ５は、第２受光素子１２Ｕ２とも、第３受光素子１２Ｕ３とも、第４受光素子１２Ｕ４とも異なる受光素子である。One bottom surface of the first scintillator 11U4a of the fourth scintillator unit 11U4 is optically connected to the light receiving surface of the first light receiving element 12U1 arranged in the center of the light
ＤＯＩを測定可能な従来の放射線検出装置は、シンチレータアレイの２底面がそれぞれ受光素子アレイの受光面と光学接続される構成を採用している。一方で、本実施形態に係る放射線検出装置１は、上述したように、シンチレータアレイ１１の一方の底面のみが受光素子アレイ１２の受光面と光学接続される構成を採用している。この構成を採用することにより、放射線検出装置１は、より少ない数の受光素子アレイで構成される。これにより、コスト削減を図ることができる。Conventional radiation detection devices capable of measuring DOI employ a configuration in which the two bottom surfaces of the scintillator array are each optically connected to the light receiving surface of the light receiving element array. On the other hand, as described above, the
（シンチレータユニットの構成）
シンチレータユニット１１Ｕｉの構成について、図２および図３を参照して説明する。(Configuration of scintillator unit)
The configuration of the scintillator unit 11Ui will be described with reference to FIGS.
シンチレータユニット１１Ｕｉは、第１シンチレータ１１Ｕｉａと、第２シンチレータ１１Ｕｉｂと、により構成されており、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂは、１側面又は２側面が粗面加工されている。The scintillator unit 11Ui is composed of a first scintillator 11Uia and a second scintillator 11Uib, and the first scintillator 11Uia and the second scintillator 11Uib have one or two sides roughened.
図２は、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの各々において、１側面が粗面加工されている場合のシンチレータユニット１１Ｕｉの構成を示す斜視図である。Figure 2 is a perspective view showing the configuration of the scintillator unit 11Ui when one side of each of the first scintillator 11Uia and the second scintillator 11Uib is roughened.
図２に示すように、第１シンチレータ１１Ｕｉａの側面１１Ｕｉａ１は、粗面加工されており、第２シンチレータ１１Ｕｉｂと光学接続される。また、第１シンチレータ１１Ｕｉａは、第２シンチレータ１１Ｕｉｂと光学接続される側面１１Ｕｉａ１以外の側面１１Ｕｉａ２～１１Ｕｉａ４及び受光素子１２Ｕｊ（図１の構成ではｊ＝１）と光学接続される底面１１Ｕｉａ５と反対側の底面１１Ｕｉａ６の全体が反射材で覆われており、第２シンチレータ１１Ｕｉｂと光学接続される側面１１Ｕｉａ１は、高さがｈ以下となる領域のみが反射材で覆われている。As shown in FIG. 2, the side surface 11Uia1 of the first scintillator 11Uia is roughened and is optically connected to the second scintillator 11Uib. In addition, the first scintillator 11Uia has all of its sides 11Uia2 to 11Uia4 other than the side surface 11Uia1 that is optically connected to the second scintillator 11Uib, and the bottom surface 11Uia5 that is optically connected to the light receiving element 12Uj (j=1 in the configuration of FIG. 1) and the bottom surface 11Uia6 opposite the bottom surface 11Uia5 are covered with a reflective material, and only the area of the side surface 11Uia1 that is optically connected to the second scintillator 11Uib that is equal to or less in height is covered with a reflective material.
同様に、第２シンチレータ１１Ｕｉｂは、側面１１Ｕｉｂ１が粗面加工されており、第１シンチレータ１１Ｕｉａと光学接続される。また、第２シンチレータ１１Ｕｉｂは、第１シンチレータ１１Ｕｉａと光学接続される側面１１Ｕｉｂ１以外の側面１１Ｕｉｂ２～１１Ｕｉｂ４及び受光素子１２Ｕｋ（図１の構成ではｋ＝ｊ＋１）と光学接続される底面１１Ｕｉｂ５と反対側の底面１１Ｕｉｂ６の全体が反射材で覆われており、第１シンチレータ１１Ｕｉａと光学接続される側面１１Ｕｉｂ１は、高さがｈ以下となる領域のみが反射材で覆われている。Similarly, the second scintillator 11Uib has a roughened side surface 11Uib1 and is optically connected to the first scintillator 11Uia. In addition, the second scintillator 11Uib has sides 11Uib2 to 11Uib4 other than the side surface 11Uib1 that is optically connected to the first scintillator 11Uia, and the bottom surface 11Uib5 that is optically connected to the light receiving element 12Uk (k=j+1 in the configuration of FIG. 1) and the bottom surface 11Uib6 opposite are entirely covered with a reflective material, and only the area of the side surface 11Uib1 that is optically connected to the first scintillator 11Uia that is equal to or less than h in height is covered with a reflective material.
第１シンチレータ１１Ｕｉａの側面１１Ｕｉａ１のうち、反射材で覆われていない領域と、第２シンチレータ１１Ｕｉｂの側面１１Ｕｉｂ１のうち、反射材で覆われていない領域とが光学接着剤によって接着される。これにより、第１シンチレータ１１Ｕｉａに放射線が入射したときに生じる蛍光は、第１シンチレータ１１Ｕｉａの側面１１Ｕｉａ１のうち、反射材で覆われていない領域を介して第２シンチレータ１１Ｕｉｂに入射することが可能になる。また、第２シンチレータ１１Ｕｉｂに放射線が入射したときに生じる蛍光は、第２シンチレータ１１Ｕｉｂの側面１１Ｕｉｂ１のうち、反射材で覆われていない領域を介して第１シンチレータ１１Ｕｉａに入射することが可能になる。A region of the side surface 11Uia1 of the first scintillator 11Uia that is not covered with reflecting material and a region of the side surface 11Uib1 of the second scintillator 11Uib that is not covered with reflecting material are bonded with an optical adhesive. This allows the fluorescence generated when radiation is incident on the first scintillator 11Uia to enter the second scintillator 11Uib via the region of the side surface 11Uia1 of the first scintillator 11Uia that is not covered with reflecting material. Also, the fluorescence generated when radiation is incident on the second scintillator 11Uib can enter the first scintillator 11Uia via the region of the side surface 11Uib1 of the second scintillator 11Uib that is not covered with reflecting material.
上述のように構成されたシンチレータユニット１１Ｕｉは、第１シンチレータ１１Ｕｉａの底面１１Ｕｉａ５及び第２シンチレータ１１Ｕｉｂの底面１１Ｕｉｂ５がそれぞれ受光素子１２Ｕｊ及び１２Ｕｋと光学接続される。これにより、第１シンチレータ１１Ｕｉａで発生した蛍光、及び、第２シンチレータ１１Ｕｉｂで発生し、第１シンチレータ１１Ｕｉａに入射した蛍光は、第１シンチレータ１１Ｕｉａの底面１１Ｕｉａ５を介して受光素子１２Ｕｊに入射する。また、第２シンチレータ１１Ｕｉｂで発生した蛍光、及び、第１シンチレータ１１Ｕｉａで発生し、第２シンチレータ１１Ｕｉｂに入射した蛍光は、第２シンチレータ１１Ｕｉｂの底面１１Ｕｉｂ５を介して受光素子１２Ｕｋに入射する。In the scintillator unit 11Ui configured as described above, the bottom surface 11Uia5 of the first scintillator 11Uia and the bottom surface 11Uib5 of the second scintillator 11Uib are optically connected to the light receiving elements 12Uj and 12Uk, respectively. As a result, the fluorescence generated in the first scintillator 11Uia and the fluorescence generated in the second scintillator 11Uib and incident on the first scintillator 11Uia are incident on the light receiving element 12Uj via the bottom surface 11Uia5 of the first scintillator 11Uia. In addition, the fluorescence generated in the second scintillator 11Uib and the fluorescence generated in the first scintillator 11Uia and incident on the second scintillator 11Uib are incident on the light receiving element 12Uk via the bottom surface 11Uib5 of the second scintillator 11Uib.
図３は、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの各々において、２側面が粗面加工されている場合のシンチレータユニット１１Ｕｉの構成を示す斜視図である。Figure 3 is a perspective view showing the configuration of the scintillator unit 11Ui when two side surfaces of the first scintillator 11Uia and the second scintillator 11Uib are roughened.
図３に示すように、第１シンチレータ１１Ｕｉａは、側面１１Ｕｉａ１及び側面１１Ｕｉａ４が粗面加工されている。粗面加工されている２側面のうち、側面１１Ｕｉａ１は、第２シンチレータ１１Ｕｉｂと光学接続される。また、第１シンチレータ１１Ｕｉａは、第２シンチレータ１１Ｕｉｂと光学接続される側面１１Ｕｉａ１以外の側面１１Ｕｉａ２～１１Ｕｉａ４及び受光素子１２Ｕｊ（図１の構成ではｊ＝１）と光学接続される底面１１Ｕｉａ５と反対側の底面１１Ｕｉａ６の全体が反射材で覆われており、第２シンチレータ１１Ｕｉｂと光学接続される側面１１Ｕｉａ１は、高さがｈ以下となる領域のみが反射材で覆われている。As shown in FIG. 3, the first scintillator 11Uia has side surfaces 11Uia1 and 11Uia4 roughened. Of the two roughened side surfaces, side surface 11Uia1 is optically connected to the second scintillator 11Uib. In addition, the first scintillator 11Uia has side surfaces 11Uia2 to 11Uia4 other than side surface 11Uia1 that is optically connected to the second scintillator 11Uib, and the bottom surface 11Uia5 that is optically connected to the light receiving element 12Uj (j=1 in the configuration of FIG. 1) and the bottom surface 11Uia6 opposite are entirely covered with a reflective material, and only the area of side surface 11Uia1 that is optically connected to the second scintillator 11Uib that is equal to or less in height is covered with a reflective material.
同様に、第２シンチレータ１１Ｕｉｂは、側面１１Ｕｉｂ１及び側面１１Ｕｉｂ３が粗面加工されている。粗面加工されている２側面のうち、側面１１Ｕｉａ１は、第２シンチレータ１１Ｕｉaと光学接続される。また、第２シンチレータ１１Ｕｉｂは、第１シンチレータ１１Ｕｉａと光学接続される側面１１Ｕｉｂ１以外の側面１１Ｕｉｂ２～１１Ｕｉｂ４及び受光素子１２Ｕｋ（図１の構成ではｋ＝ｊ＋１）と光学接続される底面１１Ｕｉｂ５と反対側の底面１１Ｕｉｂ６の全体が反射材で覆われており、第１シンチレータ１１Ｕｉａと光学接続される側面１１Ｕｉｂ１は、高さがｈ以下となる領域のみが反射材で覆われている。Similarly, the second scintillator 11Uib has side surfaces 11Uib1 and 11Uib3 roughened. Of the two roughened sides, side surface 11Uia1 is optically connected to the second scintillator 11Uia. In addition, the second scintillator 11Uib has side surfaces 11Uib2 to 11Uib4 other than side surface 11Uib1 that is optically connected to the first scintillator 11Uia, and the bottom surface 11Uib5 that is optically connected to the light receiving element 12Uk (k=j+1 in the configuration of FIG. 1) and the bottom surface 11Uib6 opposite are entirely covered with a reflective material, and only the area of side surface 11Uib1 that is optically connected to the first scintillator 11Uia that is equal to or less than h in height is covered with a reflective material.
第１シンチレータ１１Ｕｉａの側面１１Ｕｉａ１のうち、反射材で覆われていない領域と、第２シンチレータ１１Ｕｉｂの側面１１Ｕｉｂ１のうち、反射材で覆われていない領域とが光学接着剤によって接着される。なお、この時、第１シンチレータ１１Ｕｉａの粗面加工されている側面１１Ｕｉａ４と第２シンチレータ１１Ｕｉｂの粗面加工されている側面１１Ｕｉｂ３とは、隣接するように接着される。これにより、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの各々において、１側面が粗面加工されている場合と同様の機能を有する。The area of the side surface 11Uia1 of the first scintillator 11Uia that is not covered with reflective material and the area of the side surface 11Uib1 of the second scintillator 11Uib that is not covered with reflective material are bonded with an optical adhesive. At this time, the roughened side surface 11Uia4 of the first scintillator 11Uia and the roughened side surface 11Uib3 of the second scintillator 11Uib are bonded so as to be adjacent to each other. This allows each of the first scintillator 11Uia and the second scintillator 11Uib to have the same function as when one side surface is roughened.
上述のように構成されたシンチレータユニット１１Ｕｉは、第１シンチレータ１１Ｕｉａの底面１１Ｕｉａ５及び第２シンチレータ１１Ｕｉｂの底面１１Ｕｉｂ５がそれぞれ受光素子１２Ｕｊ及び１２Ｕｋと光学接続される。この時、第１シンチレータユニット１１Ｕｉの粗面加工されている側面１１Ｕｉａ４が受光素子１２Ｕｊの外縁上に位置し、第２シンチレータ１１Ｕｉｂの粗面加工されている側面１１Ｕｉｂ３が、受光素子１２Ｕｋの外縁上に位置するように光学接続される。これにより、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの各々において、１側面が粗面加工されている場合と同様の機能を有する。In the scintillator unit 11Ui configured as described above, the bottom surface 11Uia5 of the first scintillator 11Uia and the bottom surface 11Uib5 of the second scintillator 11Uib are optically connected to the light receiving elements 12Uj and 12Uk, respectively. At this time, the roughened side surface 11Uia4 of the first scintillator unit 11Ui is located on the outer edge of the light receiving element 12Uj, and the roughened side surface 11Uib3 of the second scintillator 11Uib is optically connected to the outer edge of the light receiving element 12Uk. This provides the same functionality as when one side surface of each of the first scintillator 11Uia and the second scintillator 11Uib is roughened.
本実施形態に係る放射線検出装置１において特徴的な点は、以下の点である。（１）第１シンチレータ１１Ｕｉａの４つの側面１１Ｕｉａ１～１１Ｕｉａ４のうち、１つ又は２つの側面が粗面加工されており、残りの３つ又は２つの側面は鏡面加工又はケミカルエッチングされている。（２）第２シンチレータ１１Ｕｉｂの４つの側面１１Ｕｉｂ１～１１Ｕｉｂ４のうち、１つ又は２つの側面が粗面加工されており、残りの３つ又は２つの側面は鏡面加工又はケミカルエッチングされている。The
第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの４つの側面が全て鏡面加工又は化学エッチングされている場合、時間分解能が高くなる一方で、ＤＯＩ分解能が低下する傾向がある。一方、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの４つの側面が全て粗面加工されている場合、各シンチレータの境界面に空気層を含んでいるため、受光素子境界面からの蛍光の漏れを防ぐ、かつ、空気層での蛍光の乱反射により、ＤＯＩ分解能が高くなる一方で時間分解能が低下する傾向がある。これに対して、本実施形態に係る放射線検出装置１においては、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの１側面又は２側面が粗面加工されているので、時間分解能とＤＯＩ分解能とを共に高くすることができる。If all four side surfaces of the first scintillator 11Uia and the second scintillator 11Uib are mirror-finished or chemically etched, the time resolution tends to be high while the DOI resolution tends to be low. On the other hand, if all four side surfaces of the first scintillator 11Uia and the second scintillator 11Uib are roughened, the boundary surface of each scintillator contains an air layer, which prevents leakage of fluorescence from the light receiving element boundary surface and causes diffuse reflection of the fluorescence in the air layer, which tends to increase the DOI resolution while decreasing the time resolution. In contrast, in the
なお、本実施形態においては、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの各々の１側面が粗面加工されている場合、第１シンチレータ１１Ｕｉａの粗面加工されている側面１１Ｕｉａ１と第２シンチレータ１１Ｕｉｂの粗面加工されている側面１１Ｕｉｂ１とが光学接続されている。この構成により、シンチレータユニット１１Ｕｉを構成する第１シンチレータ１１Ｕｉａと第２シンチレータ１１Ｕｉｂとの接続面であって、粗面加工されている接続面は、受光素子１２Ｕｊと受光素子１２Ｕｋとの境界上に位置している。これにより、第１シンチレータ１１Ｕｉａと第２シンチレータ１１Ｕｉｂとの接続面及び受光素子１２Ｕｊと受光素子１２Ｕｋとの境界からの蛍光の漏れを防ぎ、受光素子への集光率を上昇させる。In this embodiment, when one side of each of the first scintillator 11Uia and the second scintillator 11Uib is roughened, the roughened side 11Uia1 of the first scintillator 11Uia and the roughened side 11Uib1 of the second scintillator 11Uib are optically connected. With this configuration, the roughened connection surface between the first scintillator 11Uia and the second scintillator 11Uib that constitute the scintillator unit 11Ui is located on the boundary between the light receiving element 12Uj and the light receiving element 12Uk. This prevents leakage of fluorescence from the connection surface between the first scintillator 11Uia and the second scintillator 11Uib and the boundary between the light receiving element 12Uj and the light receiving element 12Uk, and increases the light collection rate to the light receiving element.
また、本実施形態においては、第１シンチレータ１１Ｕｉａ及び第２シンチレータ１１Ｕｉｂの各々の２側面が粗面加工されている場合、第１シンチレータ１１Ｕｉａの粗面加工されている側面１１Ｕｉａ１と第２シンチレータ１１Ｕｉｂの粗面加工されている側面１１Ｕｉｂ１とが光学接続されている。さらに、第１シンチレータ１１Ｕｉａの粗面加工されている他の側面１１Ｕｉａ４と第２シンチレータ１１Ｕｉｂの粗面加工されている他の側面１１Ｕｉｂ３とは隣接し、第１シンチレータ１１Ｕｉａの側面１１Ｕｉａ４は、受光素子１２Ｕｊの外縁上に位置し、第２シンチレータ１１Ｕｉｂの粗面加工されている側面１１Ｕｉｂ３は、受光素子１２Ｕｋの外縁上に位置している。この構成により、受光素子アレイを構成する各受光素子１２Ｕｊの全ての境界上に粗面加工されている側面が位置する。これにより、各受光素子１２Ｕｊの境界及び各シンチレータの境界からの蛍光の漏れを防ぎ、受光素子への集光率をさらに上昇させる。In addition, in this embodiment, when two side surfaces of each of the first scintillator 11Uia and the second scintillator 11Uib are roughened, the roughened side surface 11Uia1 of the first scintillator 11Uia and the roughened side surface 11Uib1 of the second scintillator 11Uib are optically connected. Furthermore, the other roughened side surface 11Uia4 of the first scintillator 11Uia and the other roughened side surface 11Uib3 of the second scintillator 11Uib are adjacent to each other, and the side surface 11Uia4 of the first scintillator 11Uia is located on the outer edge of the light receiving element 12Uj, and the roughened side surface 11Uib3 of the second scintillator 11Uib is located on the outer edge of the light receiving element 12Uk. With this configuration, the roughened side surfaces are located on all boundaries of each light receiving element 12Uj that constitutes the light receiving element array. This prevents leakage of fluorescence from the boundaries between each light receiving element 12Uj and each scintillator, further increasing the light collection rate to the light receiving element.
ただし、第１シンチレータ１１Ｕｉａの４つの側面１１Ｕｉａ１～１１Ｕｉａ４のうち、どの側面を粗面加工した場合であっても、また、第２シンチレータ１１Ｕｉｂの４つの側面１１Ｕｉｂ１～１１Ｕｉｂ４のうち、どの側面を粗面加工した場合であっても、程度の差はあれ上述した効果が得られる。However, regardless of which of the four side surfaces 11Uia1 to 11Uia4 of the first scintillator 11Uia is roughened, and regardless of which of the four side surfaces 11Uib1 to 11Uib4 of the second scintillator 11Uib is roughened, the above-mentioned effects can be obtained to varying degrees.
（陽電子放出断層撮影装置の構成及び動作）
上述した放射線検出装置１を備えた陽電子放出断層撮影装置１０の構成及び動作について、図４～図６を参照して説明する。(Configuration and operation of positron emission tomography apparatus)
The configuration and operation of a positron emission tomography apparatus 10 including the above-described
図４は、陽電子放出断層撮影装置１０のブロック図である。陽電子放出断層撮影装置１０は、上述した放射線検出装置１と、上述した放射線検出装置１からの出力信号を処理する信号処理装置２と、を備えている。シンチレータアレイ１１を構成するシンチレータの何れかにγ線が入射すると、信号処理装置２は、１特定処理及び第２特定処理を実行する。ここで、第１特定処理は、シンチレータユニット１１Ｕ１～１１Ｕ４のうち、γ線が入射したシンチレータユニット１１Ｕｘ（ｘは１，２，３，４の何れか）を特定する処理である。また、第２特定処理は、（１）シンチレータユニット１１Ｕｘを構成する２つのシンチレータ１１Ｕｘａ，１１Ｕｘｂのうち、γ線が入射したシンチレータ１１Ｕｘｙ（ｙはａ，ｂの何れか）を特定すると共に、シンチレータ１１Ｕｘｙにおいてγ線との相互作用が生じた位置（高さ）を特定する処理である。FIG. 4 is a block diagram of a positron emission tomography apparatus 10. The positron emission tomography apparatus 10 includes the
図５は、第１特定処理の概要を説明するための図であり、図５の（ａ）～（ｄ）は、それぞれ、放射線検出装置１の平面図である。FIG. 5 is a diagram for explaining an overview of the first identification process, and (a) to (d) in FIG. 5 are each a plan view of the
図５の（ａ）の示すように、第１シンチレータユニット１１Ｕ１を構成する２つのシンチレータ１１Ｕ１ａ，１１Ｕ１ｂの何れかにγ線が入射すると、γ線が入射した方のシンチレータにおいて発生した蛍光が第１受光素子１２Ｕ１及び第２受光素子１２Ｕ２により検出される。As shown in FIG. 5(a), when gamma rays are incident on one of the two scintillators 11U1a, 11U1b that make up the first scintillator unit 11U1, the fluorescence generated in the scintillator on which the gamma rays are incident is detected by the first light receiving element 12U1 and the second light receiving element 12U2.
また、図５の（ｂ）に示すように、第２シンチレータユニット１１Ｕ２を構成する２つのシンチレータ１１Ｕ２ａ，１１Ｕ２ｂの何れかにγ線が入射すると、γ線が入射した方のシンチレータにおいて発生した蛍光が第１受光素子１２Ｕ１及び第３受光素子１２Ｕ３により検出される。Also, as shown in FIG. 5(b), when gamma rays are incident on one of the two scintillators 11U2a, 11U2b that make up the second scintillator unit 11U2, the fluorescence generated in the scintillator on which the gamma rays are incident is detected by the first light receiving element 12U1 and the third light receiving element 12U3.
また、図５の（ｃ）に示すように、第３シンチレータユニット１１Ｕ３を構成する２つのシンチレータ１１Ｕ３ａ，１１Ｕ３ｂの何れかにγ線が入射すると、γ線が入射した方のシンチレータにおいて発生した蛍光が第１受光素子１２Ｕ１及び第４受光素子１２Ｕ４により検出される。Also, as shown in FIG. 5(c), when gamma rays are incident on either of the two scintillators 11U3a, 11U3b that make up the third scintillator unit 11U3, the fluorescence generated in the scintillator on which the gamma rays are incident is detected by the first light receiving element 12U1 and the fourth light receiving element 12U4.
また、図５の（ｄ）に示すように、第４シンチレータユニット１１Ｕ４を構成する２つのシンチレータ１１Ｕ４ａ，１１Ｕ４ｂの何れかにγ線が入射すると、γ線が入射した方のシンチレータにおいて発生した蛍光が第１受光素子１２Ｕ１及び第５受光素子１２Ｕ５により検出される。Also, as shown in FIG. 5(d), when gamma rays are incident on either of the two scintillators 11U4a, 11U4b that make up the fourth scintillator unit 11U4, the fluorescence generated in the scintillator on which the gamma rays are incident is detected by the first light receiving element 12U1 and the fifth light receiving element 12U5.
すなわち、シンチレータユニット１１Ｕ１～１１Ｕ４のうち、何れのシンチレータユニットにγ線が入射するかに応じて、受光素子１２Ｕ１～１２Ｕ５のうち、何れの受光素子にて蛍光を検出するかが決まる。信号処理装置２は、この性質を利用して、上述した第１特定処理を実行する。In other words, depending on which of the scintillator units 11U1 to 11U4 the gamma rays are incident on, which of the light receiving elements 12U1 to 12U5 will detect the fluorescence. The
より具体的に言うと、信号処理装置２は、例えば以下のようにして、γ線が入射したシンチレータユニット１１Ｕｘを特定する。すなわち、（１）蛍光を検出した受光素子の組み合わせが、第１受光素子１２Ｕ１と第２受光素子１２Ｕ２との組み合わせである場合、γ線が入射したシンチレータユニットＵｘとして第１シンチレータユニット１１Ｕ１を特定する。また、（２）蛍光を検出した受光素子の組み合わせが、第１受光素子１２Ｕ１と第３受光素子１２Ｕ３との組み合わせである場合、γ線が入射したシンチレータユニットＵｘとして第２シンチレータユニット１１Ｕ２を特定する。また、（３）蛍光を検出した受光素子の組み合わせが、第１受光素子１２Ｕ１と第４受光素子１２Ｕ４との組み合わせである場合、γ線が入射したシンチレータユニットＵｘとして第３シンチレータユニット１１Ｕ３を特定する。また、（４）蛍光を検出した受光素子の組み合わせが、第１受光素子１２Ｕ１と第５受光素子１２Ｕ５との組み合わせである場合、γ線が入射したシンチレータユニットＵｘとして第４シンチレータユニット１１Ｕ４を特定する。More specifically, the
図６は、第２特定処理の概要を説明するための図であり、図６の（ａ）～（ｄ）は、それぞれ、γ線が入射したシンチレータユニット１１Ｕｘの側面図である。図６の（ｅ）は、蛍光強度Ｉａ，Ｉｂの比Ｉａ／（Ｉａ＋Ｉｂ），Ｉａ／（Ｉａ＋Ｉｂ）を表すグラフである。ここで、蛍光強度Ｉａは、γ線が入射したシンチレータユニット１１Ｕｘの第１シンチレータ１１Ｕｘａに光学接続された受光素子１２Ｕｊ（図１の構成ではｊ＝１）が検出する蛍光強度である。また、蛍光強度Ｉｂは、γ線が入射したシンチレータユニット１１Ｕｘの第２シンチレータ１１Ｕｘｂに光学接続された受光素子１２Ｕｋ（図１の構成ではｋ＝ｘ＋１）が検出する蛍光強度である。第２特定処理は、
図６の（ａ）に示すように、第１シンチレータ１１Ｕｘａの底面（下面）近傍においてγ線との相互作用が生じた場合、発生する蛍光の大部分は、第１シンチレータ１１Ｕｘａと光学接続された受光素子１２Ｕｊに入射する。したがって、蛍光強度Ｉａ，Ｉｂの間には、Ｉａ≫Ｉｂという関係が成り立つ。その結果、比Ｉａ／（Ｉａ＋Ｉｂ）は略１になり、比Ｉｂ／（Ｉａ＋Ｉｂ）は略０になる。FIG. 6 is a diagram for explaining an outline of the second identification process, and (a) to (d) of FIG. 6 are side views of the scintillator unit 11Ux on which gamma rays are incident. (e) of FIG. 6 is a graph showing the ratios Ia/(Ia+Ib) and Ia/(Ia+Ib) of the fluorescence intensities Ia and Ib. Here, the fluorescence intensity Ia is the fluorescence intensity detected by the light receiving element 12Uj (j=1 in the configuration of FIG. 1) optically connected to the first scintillator 11Uxa of the scintillator unit 11Ux on which gamma rays are incident. Also, the fluorescence intensity Ib is the fluorescence intensity detected by the light receiving element 12Uk (k=x+1 in the configuration of FIG. 1) optically connected to the second scintillator 11Uxb of the scintillator unit 11Ux on which gamma rays are incident. The second identification process is as follows:
6A, when an interaction with a gamma ray occurs near the bottom surface (lower surface) of the first scintillator 11Uxa, most of the generated fluorescence is incident on the light receiving element 12Uj optically connected to the first scintillator 11Uxa. Therefore, the relationship between the fluorescence intensities Ia and Ib is Ia>>Ib. As a result, the ratio Ia/(Ia+Ib) is approximately 1, and the ratio Ib/(Ia+Ib) is approximately 0.
図６の（ｂ）に示すように、第１シンチレータ１１Ｕｘａの底面から離れた位置においてγ線との相互作用が生じた場合、第１シンチレータ１１Ｕｘａと光学接続された受光素子１２Ｕｊにて検出される蛍光強度Ｉａは、第１シンチレータ１１Ｕｘａの底面近傍においてγ線との相互作用が生じた場合と比べて弱くなる。一方、第２シンチレータ１１Ｕｘｂと光学接続された受光素子１２Ｕｋにて検出される蛍光強度Ｉｂは、第１シンチレータ１１Ｕｘａの底面近傍においてγ線との相互作用が生じた場合と比べて強くなる。したがって、蛍光強度Ｉａ，Ｉｂの間には、Ｉａ≒Ｉｂ（ただし、Ｉａ＞Ｉｂ）という関係が成り立つ。その結果、比Ｉａ／（Ｉａ＋Ｉｂ），Ｉｂ／（Ｉａ＋Ｉｂ）は、略０．５（ただし、Ｉａ／（Ｉａ＋Ｉｂ）＞Ｉｂ／（Ｉａ＋Ｉｂ））になる。As shown in FIG. 6B, when an interaction with gamma rays occurs at a position away from the bottom surface of the first scintillator 11Uxa, the fluorescence intensity Ia detected by the light receiving element 12Uj optically connected to the first scintillator 11Uxa is weaker than when an interaction with gamma rays occurs near the bottom surface of the first scintillator 11Uxa. On the other hand, the fluorescence intensity Ib detected by the light receiving element 12Uk optically connected to the second scintillator 11Uxb is stronger than when an interaction with gamma rays occurs near the bottom surface of the first scintillator 11Uxa. Therefore, the relationship Ia ≒ Ib (where Ia > Ib) holds between the fluorescence intensities Ia and Ib. As a result, the ratios Ia/(Ia + Ib) and Ib/(Ia + Ib) are approximately 0.5 (where Ia/(Ia + Ib) > Ib/(Ia + Ib)).
図６の（ｃ）に示すように、第２シンチレータ１１Ｕｘｂの底面から離れた位置においてγ線との相互作用が生じた場合、第１シンチレータ１１Ｕｘａと光学接続された受光素子１２Ｕｊにて検出される蛍光強度Ｉａは、第１シンチレータ１１Ｕｘｂの底面から離れた位置においてγ線との相互作用が生じた場合と比べて更に弱くなる。一方、第２シンチレータ１１Ｕｘｂと光学接続された受光素子１２Ｕｋにて検出される蛍光強度Ｉｂは、第１シンチレータ１１Ｕｘａの底面から離れた位置においてγ線との相互作用が生じた場合と比べて更に強くなる。したがって、蛍光強度Ｉａ，Ｉｂの間には、Ｉａ≒Ｉｂ（ただし、Ｉａ＜Ｉｂ）という関係が成り立つ。その結果、比Ｉａ／（Ｉａ＋Ｉｂ），Ｉｂ／（Ｉａ＋Ｉｂ）は、略０．５（ただし、Ｉａ／（Ｉａ＋Ｉｂ）＜Ｉｂ／（Ｉａ＋Ｉｂ））になる。As shown in FIG. 6(c), when an interaction with gamma rays occurs at a position away from the bottom surface of the second scintillator 11Uxb, the fluorescence intensity Ia detected by the light receiving element 12Uj optically connected to the first scintillator 11Uxa is weaker than when an interaction with gamma rays occurs at a position away from the bottom surface of the first scintillator 11Uxb. On the other hand, the fluorescence intensity Ib detected by the light receiving element 12Uk optically connected to the second scintillator 11Uxb is stronger than when an interaction with gamma rays occurs at a position away from the bottom surface of the first scintillator 11Uxa. Therefore, the relationship Ia ≒ Ib (where Ia < Ib) holds between the fluorescence intensities Ia and Ib. As a result, the ratios Ia/(Ia + Ib) and Ib/(Ia + Ib) are approximately 0.5 (where Ia/(Ia + Ib) < Ib/(Ia + Ib)).
図６の（ｄ）に示すように、第２シンチレータ１１Ｕｘｂの底面近傍においてγ線との相互作用が生じた場合、発生する蛍光の大部分は、第２シンチレータ１１Ｕｘｂと光学接続された受光素子１２Ｕｋに入射する。したがって、蛍光強度Ｉａ，Ｉｂの間には、Ｉａ≪Ｉｂという関係が成り立つ。その結果、比Ｉａ／（Ｉａ＋Ｉｂ）は略０になり、比Ｉｂ／（Ｉａ＋Ｉｂ）は略１になる。As shown in FIG. 6(d), when interaction with gamma rays occurs near the bottom surface of the second scintillator 11Uxb, most of the generated fluorescence is incident on the light receiving element 12Uk optically connected to the second scintillator 11Uxb. Therefore, the relationship Ia<<Ib holds between the fluorescence intensities Ia and Ib. As a result, the ratio Ia/(Ia+Ib) is approximately 0, and the ratio Ib/(Ia+Ib) is approximately 1.
すなわち、γ線が入射するシンチレータユニット１１Ｕｘを構成するシンチレータ１１Ｕｘａ，１１Ｕｘｂのうち、何れのシンチレータにγ線が入射するかに応じて、蛍光強度Ｉａ，Ｉｂの大小が決まる。また、γ線が入射するシンチレータにおいてγ線との相互作用が生じる位置（高さ）に応じて、比Ｉａ／（Ｉａ＋Ｉｂ），Ｉｂ／（Ｉａ＋Ｉｂ）が決まる。信号処理装置２は、これらの性質を利用して、上述した第２特定処理を実行する。In other words, the magnitude of the fluorescence intensities Ia, Ib is determined depending on which of the scintillators 11Uxa, 11Uxb constituting the scintillator unit 11Ux on which the gamma rays are incident, the scintillator into which the gamma rays are incident. Also, the ratios Ia/(Ia+Ib), Ib/(Ia+Ib) are determined depending on the position (height) at which the gamma rays interact with the scintillator on which the gamma rays are incident. The
より具体的に言うと、信号処理装置２は、例えば以下のようにして、γ線が入射したシンチレータ１１Ｕｘｙを特定する。すなわち、（１）受光素子１２Ｕｊ，１２Ｕｋが検出した蛍光強度Ｉａ，Ｉｂの間に関係Ｉａ＞Ｉｂが成立する場合、γ線が入射したシンチレータ１１Ｕｘｙとして第１シンチレータ１１Ｕｘａを特定する。また、（２）受光素子１２Ｕｊ，１２Ｕｋが検出した蛍光強度Ｉａ，Ｉｂの間に関係Ｉａ＜Ｉｂが成立する場合、γ線が入射したシンチレータ１１Ｕｘｙとして第２シンチレータ１１Ｕｘｂを特定する。More specifically, the
また、信号処理装置２は、例えば以下のようにして、シンチレータ１１Ｕｘｙにおいてγ線との相互作用が生じた位置を特定する。すなわち、比Ｉａ／（Ｉａ＋Ｉｂ）と相互作用位置との対応関係を示すテーブルを予め作成しておく。そして、γ線がシンチレータ１１Ｕｘｙに入射する度に、（１）受光素子１２Ｕｊ，１２Ｕｋが検出した蛍光強度Ｉａ，Ｉｂから比Ｉａ／（Ｉａ＋Ｉｂ）を算出し、（２）算出した比Ｉａ／（Ｉａ＋Ｉｂ）に対応する相互作用位置を、このテーブルを参照することによって特定する。あるいは、比Ｉａ／（Ｉａ＋Ｉｂ）と相互作用位置との対応関係を示す関数を予め作成しておく。そして、γ線がシンチレータ１１Ｕｘｙに入射する度に、（１）受光素子１２Ｕｊ，１２Ｕｋが検出した蛍光強度Ｉａ，Ｉｂから比Ｉａ／（Ｉａ＋Ｉｂ）を算出し、（２）算出した比Ｉａ／（Ｉａ＋Ｉｂ）に対応する相互作用位置を、この関数に比Ｉａ／（Ｉａ＋Ｉｂ）を代入することによって特定する。なお、ここでは、比Ｉａ／（Ｉａ＋Ｉｂ）を用いる例を示したが、比Ｉｂ／（Ｉａ＋Ｉｂ）を用いてもよい。The
（放射線検出装置の実施例）
放射線検出装置１の実施例について、図６及び図７を参照して説明する。(Example of Radiation Detection Apparatus)
An embodiment of the
図７において、（ａ）は、実施例及び比較例に係る放射線検出装置１の構成を示す側面図であり、（ｂ）は、それらの放射線検出装置１のＡＡ’断面を示す断面図であり、（ｃ）は、それらの放射線検出装置１のＢＢ’断面を示す断面図であり、（ｄ）は、それらの放射線検出装置１のＣＣ’断面を示す断面図である。図７において、太線は、隣接する２つのシンチレータの境界面のうち、反射材が設けられておらず、光学接着によって光学接続された境界面を示す。In FIG. 7, (a) is a side view showing the configuration of the
実施例及び比較例に係る放射線検出装置１においては、シンチレータアレイ１１として、１４×１４＝１９６個のシンチレータにより構成されたシンチレータアレイを用いた。シンチレータとしては、１辺１．４５ｍｍの正方形の底面を有する高さ１５ｍｍの角柱状のＬＹＳＯ：Ｃａ結晶を用いた。シンチレータアレイ１１は、高さ５ｍｍの下層、中層、及び上層からなる３層の反射材の構成とした。上層においては、図７の（ｂ）に示すように、互いに隣接する２つのシンチレータを、太線で示す境界面において光学接着剤により光学接続し、その他の境界面において反射材により光学分離した。中層においては、図７の（ｃ）に示すように、互いに隣接する２つのシンチレータを、全ての境界面において反射材により光学分離した。下層においては、各受光素子１２Ｕｊ内で隣接するシンチレータを、太線で示す境界面において光学接着剤により光学接続し、その他の境界面において反射材により光学分離した。また、受光素子としては、１辺３ｍｍの正方形の受光面を有するＳｉＰＭを用いた。In the
なお、図７においては、図１に示すシンチレータアレイ１１を構成するシンチレータに同じハッチングを付している。図７に示すシンチレータアレイ１１の上層及び中層は、図１に示すシンチレータアレイ１１を組み合わせることにより構成されていることが、図６及び図１から見て取れる。図７に示すシンチレータアレイ１１の下層は、図１に示すシンチレータアレイ１１を組み合わせ、各受光素子１２Ｕｊと光学接続される底面から高さ５ｍｍまでの位置に図７（ｄ）に示すように光学接続した。なお、光学接続される箇所においては、反射材を取り除いた。In addition, in Figure 7, the scintillators that make up the
上述のように、本実施例及び比較例において新たに追加された図７に示すシンチレータアレイ１１の下層の機能について説明する。本開示に係る放射線検出装置１は、１つの受光素子に対し４つのシンチレータが光学接続されている。そのため、放射線がシンチレータに入射したときに生じる蛍光は、当該シンチレータが光学接続されている受光素子の全面積の１／４に入射する。すなわち、受光素子の１／４しか活用できていない（受光素子は１度検出を行うと一定時間利用できない）。図７に示すシンチレータアレイ１１の下層を新たに追加することで、上層及び中層を通過した蛍光を受光素子内で広げることができ、当該シンチレータが光学接続されている受光素子の全面において蛍光の検出が可能になる。これにより、受光素子における蛍光の検出効率が上昇する。As described above, the function of the lower layer of the
図８の（ａ）は、第１の実施例に係る放射線検出装置１の断面図である。図８の（ａ）において太線は、粗面加工されたシンチレータの側面を示す。図８の（ａ）から見て取れるように、第１の実施例に係る放射線検出装置１においては、シンチレータとして、一側面が粗面加工され、三側面が鏡面加工されたシンチレータを用いた。(a) in FIG. 8 is a cross-sectional view of the
図８の（ｂ）は、第２の実施例に係る放射線検出装置１の断面図である。図８の（ｂ）において太線は、粗面加工されたシンチレータの側面を示す。図８の（ｂ）から見て取れるように、第２の実施例に係る放射線検出装置１においては、シンチレータとして、二側面が粗面加工され、二側面が鏡面加工されたシンチレータを用いた。(b) of FIG. 8 is a cross-sectional view of the
図８の（ｃ）は、比較例に係る放射線検出装置１の断面図である。図８の（ｃ）から見て取れるように、比較例に係る放射線検出装置１においては、シンチレータとして、四側面が鏡面加工されたシンチレータを用いた。(c) of FIG. 8 is a cross-sectional view of the
比較例、第１の実施例、及び第２の実施例に係る放射線検出装置１の性能を評価した結果を表１に示す。本実施例及び比較例においては、時間分解能としてＣＲＴ分解能を評価した。
（まとめ）
本実施形態の態様１に係るシンチレータアレイは、複数のシンチレータユニットを含むシンチレータアレイであって、前記複数のシンチレータユニットの各々は、その底面が受光素子アレイにおいて互いに隣接する２つの受光素子の一方の受光面と光学接続される第１シンチレータと、その側面の少なくとも一部が前記第１シンチレータの側面の少なくとも一部と光学接続され、その底面が前記２つの受光素子の他方の受光面と光学接続される第２シンチレータと、により構成されており、前記第１シンチレータ及び前記第２シンチレータは、１側面又は２側面が粗面加工されている。(summary)
The scintillator array of
上記の構成により、時間分解能とＤＯＩ分解能との両立を図ることができる。The above configuration makes it possible to achieve both time resolution and DOI resolution.
本実施形態の態様２に係るシンチレータアレイは、上記態様１において、前記第１シンチレータの前記底面の面積は、前記２つの受光素子のうち当該底面と光学接続される受光素子の受光面の面積の１／４以下であり、前記第２シンチレータの前記底面の面積は、前記２つの受光素子のうち当該底面と光学接続される受光素子の受光面の面積の１／４以下である。The scintillator array according to
上記の構成により、受光素子の単位面積あたりのシンチレータの個数を増やすことができる。これにより、γ線検出の空間分解能を向上させることができる。The above configuration makes it possible to increase the number of scintillators per unit area of the light receiving element, thereby improving the spatial resolution of gamma ray detection.
本実施形態の態様３に係るシンチレータアレイは、上記態様１又は２において、前記複数のシンチレータユニットとして、第１シンチレータユニット、第２シンチレータユニット、第３シンチレータユニット、及び第４シンチレータユニットを含み第１シンチレータユニット、第２シンチレータユニット、第３シンチレータユニット、及び第４シンチレータユニットの第１シンチレータの底面は、前記受光素子アレイに含まれる第１受光素子の受光面と光学接続され、第１シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第２受光素子の受光面と光学接続され、第２シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第３受光素子の受光面と光学接続され、第３シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第４受光素子の受光面と光学接続され、第４シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第５受光素子の受光面と光学接続される。The scintillator array according to aspect 3 of this embodiment is the same as in
上記の構成により、単位面積あたりの受光素子の個数を増やすことなく、単位面積あたりのシンチレータの個数を増やすことによって、コストの上昇を抑えながらγ線検出の空間分解能を向上させることができる。The above configuration allows the number of scintillators per unit area to be increased without increasing the number of light receiving elements per unit area, thereby improving the spatial resolution of gamma ray detection while suppressing increases in costs.
本実施形態の態様４に係るシンチレータアレイは、上記態様１～３の何れか１つにおいて、前記第１シンチレータの粗面加工された側面の一部と前記第２シンチレータの粗面加工された側面の一部とが光学接続されている。The scintillator array according to aspect 4 of this embodiment is any one of
上記の構成により、シンチレータユニット外への蛍光の漏れを防ぎ、受光素子における検出効率を向上させることができる。The above configuration prevents leakage of fluorescence outside the scintillator unit and improves the detection efficiency of the light receiving element.
本実施形態の態様５に係るシンチレータアレイは、上記態様１～４の何れか１つにおいて、
上記の構成により、シンチレータユニット外への蛍光の漏れを防ぎ、受光素子における検出効率を向上させることができる。A scintillator array according to aspect 5 of the present embodiment is any one of
The above-described configuration makes it possible to prevent leakage of fluorescence outside the scintillator unit and improve the detection efficiency in the light receiving element.
本実施形態の態様６に係るシンチレータアレイは、上記態様１～５の何れか１つにおいて、前記第１シンチレータ及び前記第２シンチレータにおいて、粗面加工されていない側面が鏡面加工されている。The scintillator array according to aspect 6 of this embodiment is any one of
上記の構成により、時間分解能とＤＯＩ分解能との両立を図ることができる。The above configuration makes it possible to achieve both time resolution and DOI resolution.
本実施形態の態様７に係るシンチレータアレイは、上記態様１～６の何れか１つにおいて、前記第１シンチレータ及び前記第２シンチレータにおいて、粗面加工されていない側面が化学エッチングされている。The scintillator array according to aspect 7 of this embodiment is any one of
上記の構成により、時間分解能とＤＯＩ分解能との両立を図ることができる。The above configuration makes it possible to achieve both time resolution and DOI resolution.
本実施形態の態様８に係る放射線検出装置は、上記態様１～７の何れか１つに記載のシンチレータアレイと、前記受光素子アレイと、を備えている。The radiation detection device according to aspect 8 of this embodiment includes a scintillator array according to any one of
上記の構成により、放射線検出装置において、時間分解能とＤＯＩ分解能との両立を図ることができる。The above configuration allows the radiation detection device to achieve both time resolution and DOI resolution.
本実施形態の態様９に係る陽電子放出断層撮影装置は、上記態様８に記載の放射線検出装置と、前記受光素子アレイからの出力信号を処理する信号処理装置と、を備え、前記信号処理装置は、前記受光素子アレイにおいて蛍光を検出した２つの受光素子の組合せに基づいて、放射線が入射したシンチレータユニットを特定する第１特定処理と、前記２つの受光素子の各々が検出した蛍光強度の比に基づいて、前記放射線が入射したシンチレータ、及び、該シンチレータにおける該放射線の入射位置を特定する第２特定処理と、を実行する。The positron emission tomography apparatus according to aspect 9 of this embodiment comprises the radiation detection apparatus according to aspect 8 above, and a signal processing device that processes the output signal from the light receiving element array, and the signal processing device executes a first identification process that identifies the scintillator unit on which the radiation is incident based on a combination of two light receiving elements that detect fluorescence in the light receiving element array, and a second identification process that identifies the scintillator on which the radiation is incident and the position of incidence of the radiation on the scintillator based on the ratio of the fluorescence intensities detected by each of the two light receiving elements.
上記の構成により、陽電子放出断層撮影装置において、時間分解能とＤＯＩ分解能との両立を図ることができる。The above configuration makes it possible to achieve both time resolution and DOI resolution in a positron emission tomography device.
（付記事項）
本発明は上述した各実施形態に限定されるものではなく、請求項に示した範囲で種々の変更が可能であり、異なる実施形態にそれぞれ開示された技術的手段を適宜組み合わせて得られる実施形態についても本発明の技術的範囲に含まれる。(Additional Notes)
The present invention is not limited to the above-described embodiments, 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.
１ 放射線検出装置
２ 信号処理装置
１０ 陽電子放出断層撮影装置
１１ シンチレータアレイ
１２ 受光素子アレイ
Claims (9)
Translated fromJapanese前記複数のシンチレータユニットの各々は、
その底面が受光素子アレイにおいて互いに隣接する２つの受光素子の一方の受光面と光学接続される第１シンチレータと、その側面の少なくとも一部が前記第１シンチレータの側面の少なくとも一部と光学接続され、その底面が前記２つの受光素子の他方の受光面と光学接続される第２シンチレータと、により構成されており、
前記第１シンチレータ及び前記第２シンチレータは、１側面又は２側面が粗面加工されている、
ことを特徴とするシンチレータアレイ。A scintillator array including a plurality of scintillator units,
Each of the plurality of scintillator units is
a first scintillator whose bottom surface is optically connected to one light receiving surface of two adjacent light receiving elements in the light receiving element array, and a second scintillator whose side surface at least partially is optically connected to at least a part of the side surface of the first scintillator and whose bottom surface is optically connected to the other light receiving surface of the two light receiving elements,
The first scintillator and the second scintillator have one or two side surfaces roughened.
1. A scintillator array comprising:
前記第２シンチレータの前記底面の面積は、前記２つの受光素子のうち当該底面と光学接続される受光素子の受光面の面積の１／４以下である、
ことを特徴とする請求項１に記載のシンチレータアレイ。an area of the bottom surface of the first scintillator is ¼ or less of an area of a light receiving surface of one of the two light receiving elements that is optically connected to the bottom surface of the first scintillator;
The area of the bottom surface of the second scintillator is ¼ or less of the area of the light receiving surface of the light receiving element that is optically connected to the bottom surface of the two light receiving elements.
2. The scintillator array of claim 1.
第１シンチレータユニット、第２シンチレータユニット、第３シンチレータユニット、及び第４シンチレータユニットの第１シンチレータの底面は、前記受光素子アレイに含まれる第１受光素子の受光面と光学接続され、
第１シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第２受光素子の受光面と光学接続され、
第２シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第３受光素子の受光面と光学接続され、
第３シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第４受光素子の受光面と光学接続され、
第４シンチレータユニットの第２シンチレータの底面は、前記受光素子アレイにおいて前記第１受光素子と隣接する第５受光素子の受光面と光学接続される、
ことを特徴とする請求項１に記載のシンチレータアレイ。the plurality of scintillator units include a first scintillator unit, a second scintillator unit, a third scintillator unit, and a fourth scintillator unit;
a bottom surface of the first scintillator of each of the first scintillator unit, the second scintillator unit, the third scintillator unit, and the fourth scintillator unit is optically connected to a light receiving surface of a first light receiving element included in the light receiving element array;
a bottom surface of the second scintillator of the first scintillator unit is optically connected to a light receiving surface of a second light receiving element adjacent to the first light receiving element in the light receiving element array;
a bottom surface of the second scintillator of the second scintillator unit is optically connected to a light receiving surface of a third light receiving element adjacent to the first light receiving element in the light receiving element array;
a bottom surface of the second scintillator of the third scintillator unit is optically connected to a light receiving surface of a fourth light receiving element adjacent to the first light receiving element in the light receiving element array;
a bottom surface of the second scintillator of the fourth scintillator unit is optically connected to a light receiving surface of a fifth light receiving element adjacent to the first light receiving element in the light receiving element array;
2. The scintillator array of claim 1.
ことを特徴とする請求項１に記載のシンチレータアレイ。A portion of the roughened side surface of the first scintillator and a portion of the roughened side surface of the second scintillator are optically connected.
2. The scintillator array of claim 1.
前記第１シンチレータにおいて粗面加工されている側面は、前記第２シンチレータと光学接続される第１側面、及び、該第１側面に隣接する第２側面であって、前記第１シンチレータと光学接続された受光素子の外縁上に位置する第２側面であり、
前記第２シンチレータにおいて側面加工されている側面は、前記第１シンチレータと光学接続される第３側面、及び、該第３側面に隣接する第４側面であって、前記第２シンチレータと光学接続された受光素子の外縁上に位置する第４側面である、
ことを特徴とする請求項４に記載のシンチレータアレイ。The first scintillator and the second scintillator have two side surfaces roughened,
the side surfaces of the first scintillator that are roughened include a first side surface that is optically connected to the second scintillator, and a second side surface that is adjacent to the first side surface and is located on an outer edge of a light receiving element that is optically connected to the first scintillator;
The side surfaces of the second scintillator that are processed include a third side surface that is optically connected to the first scintillator, and a fourth side surface that is adjacent to the third side surface and is located on an outer edge of a light receiving element that is optically connected to the second scintillator.
5. The scintillator array of claim 4.
ことを特徴とする請求項１に記載のシンチレータアレイ。In the first scintillator and the second scintillator, the side surfaces that are not roughened are mirror-finished.
2. The scintillator array of claim 1.
ことを特徴とする請求項１に記載のシンチレータアレイ。The first scintillator and the second scintillator have non-roughened sides chemically etched;
2. The scintillator array of claim 1.
前記受光素子アレイと、を備えている、
ことを特徴とする放射線検出装置。A scintillator array according to any one of claims 1 to 7;
The light receiving element array,
A radiation detection device comprising:
前記受光素子アレイからの出力信号を処理する信号処理装置と、を備え、
前記信号処理装置は、前記受光素子アレイにおいて蛍光を検出した２つの受光素子の組合せに基づいて、放射線が入射したシンチレータユニットを特定する第１特定処理と、
前記２つの受光素子の各々が検出した蛍光強度の比に基づいて、前記放射線が入射したシンチレータ、及び、該シンチレータにおける該放射線の入射位置を特定する第２特定処理と、を実行する、
ことを特徴とする陽電子放出断層撮影装置。The radiation detection device according to claim 8 ;
a signal processing device for processing an output signal from the light receiving element array,
the signal processing device performs a first identification process of identifying a scintillator unit into which radiation is incident based on a combination of two light receiving elements in the light receiving element array that detect fluorescence;
and performing a second identification process to identify the scintillator on which the radiation is incident and the incident position of the radiation on the scintillator based on a ratio of the fluorescence intensities detected by the two light receiving elements.
A positron emission tomography apparatus comprising:
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