JP5150219B2 - Radiation position detector - Google Patents

Description

  The present invention relates to a radiation position detector including a scintillator block and an optical sensor.

  The radiation position detector is used in, for example, a PET (Positron Emission Tomography) apparatus. A radiation position detector used in a PET apparatus detects a pair of gamma rays that are generated in association with the annihilation of electrons and positrons in a subject to which a positron emission isotope (RI radiation source) is injected and fly in opposite directions. . The PET apparatus detects a pair of gamma rays by a coincidence method using a plurality of radiation position detectors, accumulates the coincidence information, and creates a histogram. Then, the PET apparatus reconstructs an image representing the spatial distribution of the frequency of occurrence of a pair of gamma rays in the measurement space based on this histogram. This PET apparatus plays an important role in the field of nuclear medicine and the like, and can be used to study, for example, biological functions and higher-order brain functions.

As a radiation position detector suitably used in such a PET apparatus or the like, there is one provided with a scintillator block in which a plurality of scintillator cells are arranged three-dimensionally and an optical sensor (see, for example, Patent Document 1). The scintillator block absorbs incident gamma rays and generates scintillation light. The optical sensors are attached to a plurality of positions on the surface of the scintillator block and detect scintillation light. With such a configuration, the gamma ray incident position and the gamma dose in the scintillator block are specified.
JP 2007-93376 A

  However, in the radiation position detector described in Patent Document 1, the light receiving element (photosensor) is arranged only so as to face the scintillator surface arranged in the lowermost layer. The detection accuracy of the radiation incident position in the Z-axis direction (assuming the XY plane in the orthogonal coordinate system) is low. Further, the detection accuracy of the radiation incident position and the detection sensitivity and accuracy of the radiation dose in the radiation incident from the light receiving element side are low. Therefore, the detection accuracy varies depending on the incident direction of the radiation to the radiation position detector.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a radiation position detector that can suppress variations in the detection accuracy of the radiation incident position and the radiation dose with respect to the radiation incident direction.

In order to solve the above-described problem, the first radiation position detector according to the present invention includes a plurality of scintillator cells that generate scintillation light according to the absorption of radiation and have the same shape as M rows and N columns (however, M and N are integers of 3 or more). A scintillator array arranged two-dimensionally has a K layer so that the surface of the scintillator cell in the upper layer matches the surface of the scintillator cell in the lower layer (where K is 2 or more) (Integer) All scintillator cells comprising stacked polyhedral scintillator blocks and a plurality of optical sensors optically coupled to the surface of the scintillator block, each optical sensor constituting the apex of the polyhedron in the scintillator block at least one is provided within the outer surface, characterized in that it is surface optically coupled to the scintillator cells.

In the second radiation position detector according to the present invention , a plurality of scintillator cells having the same shape and generating scintillation light according to the absorption of radiation have M rows and N columns (where M and N are 3 or more). A polyhedron in which scintillator arrays arranged two-dimensionally in an integer) are stacked in K layers (where K is an integer of 2 or more) such that the surface of the upper layer scintillator cell is aligned with the surface of the lower layer scintillator cell Scintillator block and a plurality of optical sensors optically coupled to the surface of the scintillator block, each optical sensor constituting at least a side of a polyhedron in the scintillator block and not constituting a vertex. It is provided within the range of one outer surface and is optically coupled to the surface of the scintillator cell.

In the first and second radiation position detectors described above, each of the plurality of optical sensors (1) is within the range of at least one outer surface of all scintillator cells constituting the vertex of the polyhedron in the scintillator block. Provided and optically coupled to the surface of the scintillator cell, or (2) at least one of all scintillator cells in which each of the plurality of photosensors constitutes a side of a polyhedron in the scintillator block and does not constitute a vertex. Two outer surfaces are provided, and are optically coupled to the surface of the scintillator cell. By arranging a plurality of photosensors with at least one of these configurations (1) and (2), the photosensors are balanced and efficient not only for the bottom layer of the scintillator block but also for all layers. Therefore, the detection accuracy of the radiation incident position and the radiation dose in the column direction, the row direction, and the stacking direction of the scintillator block can be evenly increased. Therefore, according to the first and second radiation position detectors described above, it is possible to suitably suppress variations in the detection accuracy of the radiation incident position and the radiation dose with respect to the radiation incident direction.

  The configuration (1) has an advantage that the radiation incident position and the radiation dose can be suitably detected by fewer optical sensors than the configuration (2). For example, when the scintillator block is a hexahedron, in the configuration (2), at least 12 photosensors are required corresponding to 12 sides, but in the configuration (1), 8 sensors corresponding to 8 vertices are required. It can be done with an optical sensor. The configuration (2) has an advantage that the radiation beam incident position and the radiation dose can be detected with higher accuracy than the configuration (1). For example, consider a case where the scintillator block is formed by arranging rectangular parallelepiped scintillator cells in three rows, three columns, and three layers. In the above configuration (1), among the surfaces of the scintillator cell that is not optically coupled to the optical sensor (hereinafter referred to as a non-coupled cell; however, excluding the scintillator cell disposed at the center of the scintillator block), the optical sensor and optical The number of surfaces adjacent to the scintillator cell (hereinafter referred to as a combined cell) that is coupled to the other is two, whereas in the configuration (2), the number of surfaces adjacent to the combined cell among the non-bonded cell surfaces Becomes 3 or 4. Therefore, in the configuration (2), the light detection accuracy with respect to the emission of the non-coupled cell is improved as compared with the configuration (1), so that the radiation incident position and the radiation dose can be detected with higher accuracy.

The radiation position detector may further include another optical sensor optically coupled to the outer surface of the scintillator cell that does not constitute the sides of the polyhedron in the scintillator block and does not constitute the apex. As described above, the scintillator cell that does not constitute the vertex or side of the scintillator block is supplementarily provided with a light sensor other than the plurality of light sensors, thereby further improving the detection accuracy of the radiation incident position and the radiation dose. Can do. In this case, it is further preferable that the other optical sensor is optically coupled to the outer surface of the scintillator cell constituting the center of the surface of the polyhedron in the scintillator block.

  The radiation position detector may be characterized in that the scintillator block has a cubic shape. That is, by making the scintillator block dimensions in the row direction, the column direction, and the stacking direction of the scintillator blocks equal to each other, variations in detection accuracy in each direction can be effectively suppressed. In this case, it is more preferable that the plurality of scintillator cells have a cubic shape, so that the number of scintillator cells arranged in the row direction, the column direction, and the stacking direction of the scintillator blocks is equal to each other, and the radiation incident position in each direction is The resolution can be made uniform.

  According to the radiation position detector of the present invention, it is possible to suitably suppress variations in the detection accuracy of the radiation incident position and the radiation dose with respect to the radiation incident direction. In addition, the cost can be reduced because it can be configured with a small number of light receiving elements.

  Embodiments of a radiation position detector according to the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In each figure, an XYZ orthogonal coordinate system is shown for convenience of explanation.

(First embodiment)
First, a first embodiment of the radiation position detector according to the present invention will be described. FIG. 1 is a perspective view showing an appearance of a radiation position detector 1A according to the present embodiment. FIG. 2 is an exploded perspective view of the radiation position detector 1A shown in FIG. The radiation position detector 1A includes a scintillator block 10A, a plurality of optical sensors 20, and a reflector 30.

The scintillator block 10 </ b> A has a polyhedral appearance composed of a plurality of scintillator cells 11. The scintillator block 10A of the present embodiment has a cubic appearance, and three layers of scintillator arrays 12 (see FIG. 2) in which a plurality of cubic scintillator cells 11 are arranged in three rows and three columns are laminated. It is constituted by. Each scintillator cell 11 absorbs radiation such as gamma rays and generates scintillation light having an intensity corresponding to the dose. Such a scintillator cell 11 is preferably composed of, for example, Ce-doped Gd ₂ SiO ₅ (GSO), Lu ₂ SiO ₅ (LSO), or Bi ₄ Ge ₃ O ₁₂ (BGO).

  All surfaces of the plurality of scintillator cells 11 are subjected to mirror polishing or rough polishing. Specifically, as shown in FIG. 2, of the surfaces of the plurality of scintillator cells 11, rough polishing is performed on the bottom, side, or top surface of the scintillator block 10 </ b> A. However, even on the bottom, side, or the surface constituting the top surface of the scintillator block 10A, the part to which the optical sensor 20 described later is attached is subjected to mirror polishing. Of the surfaces of the plurality of scintillator cells 11, the surface facing the adjacent scintillator cells 11 is subjected to mirror polishing. In the present embodiment, no refractive index adjusting material or the like is disposed in the gap between the adjacent scintillator cells 11, and the gap is an air layer.

  The plurality of photosensors 20 are semiconductor photodetecting elements such as MPPC (Multi-Pixel Photon Counter). The MPPC is a photon counting device composed of a plurality of Geiger mode APD (avalanche photodiode) pixels. Each optical sensor 20 is optically coupled to the scintillator block 10A by being mounted on the scintillator block 10A so that its light detection surface faces the surface of the scintillator block 10A. Specifically, each optical sensor 20 is disposed on one surface of a different scintillator cell 11. The scintillator cells 11 in which the optical sensors 20 are arranged are all scintillator cells that constitute the apexes of the polyhedron (cube in the present embodiment) in the scintillator block 10A. One photosensor 20 is arranged for each of these scintillator cells 11 and is optically coupled to one surface of the corresponding scintillator cell 11. In the present embodiment, four photosensors 20 out of the eight photosensors 20 attached to the eight scintillator cells 11 constituting the top of the cube in the scintillator block 10A are one side surface of the cube. The other four optical sensors 20 are arranged on the surface of the scintillator cell 11 constituting the side surface opposite to the one side surface.

Here, among the plurality of scintillator cells 11 constituting the scintillator blocks 10A, X-coordinate, Y-coordinate, and the Z-coordinate is the smallest scintillator cell 11 represents a C _{1, 1, 1,} the C _{1, 1, 1} As a reference, the scintillator cell 11 arranged at the m-th in the X-axis direction, the n-th at the Y-axis direction, and the k-th at the Z-axis direction is expressed as C _{m, n, k.} The sensor 20 includes C _1,1,1 , C _1,1,3 , C _1,3,1 , C _1,3,3 , C _3,1,1 , C _3,1 among the plurality of scintillator cells 11. _{, 3} , C _3,3,1 , and C _3,3,3 are arranged on the surface of each scintillator cell 11. Further, these optical sensors 20 are arranged on a surface along the XZ plane (crossing the Y axis) among the exposed surfaces of each of the scintillator cells 11.

  The reflective material 30 is disposed so as to cover all the portions of the surface of the scintillator block 10A where the optical sensor 20 is not provided. As described above, the surface of the scintillator block 10A where the optical sensor 20 is not provided is subjected to rough polishing, and the reflector 30 prevents the scintillation light that has reached the rough polishing surface from leaking to the outside. .

A radiation incident position and radiation dose detection method using the radiation position detector 1A having the above configuration will be described. FIG. 3 is a side sectional view of the radiation position detector 1A. In FIG. 3, for example, when the scintillation light L is generated at a point O in the scintillator block 10A, the scintillation light L diffuses evenly around. Then, the following three routes are conceivable as the path until the photon of the scintillation light L reaches one of the optical sensors 20.
1. A path where the photon directly reaches the optical sensor 20 without being reflected on the way (path A _{1 in the} figure)

In this case, the number of photons detected in each photosensor 20 depends on the distance from the point O to the photosensor 20, and the photosensor 20 closer to the point O has a higher probability of detecting the photon.
2. A path through which photons diffuse on the rough polishing surface (diffusion surface) of the scintillator cell 11 and reach the optical sensor 20 (path A _{2 in the} figure)

In this case, the direction in which the photons that have reached the diffusing surface are reflected is irregular, but the probability of being detected by the optical sensor 20 closer to the reflected position is increased. As a result, the closer the optical sensor 20 is from the point O, the higher the probability of detecting the photon.
3. A path through which photons totally reflect at the interface between the scintillator cell 11 and the air layer and reach the optical sensor 20 (path A _{3 in the} figure)

  When photons are incident on the interface between the scintillator cell 11 and the air layer at an angle greater than the critical angle, the photons are totally reflected. Thereby, the spread of light is suppressed and the position resolution is improved.

Thus, in the radiation position detector 1A, more photons of the scintillation light L are detected as the optical sensor 20 is closer to the radiation incident position. Therefore, the center-of-gravity calculation shown below is suitable as a method for obtaining the radiation incident position. That is, _{assuming that the} number of photons detected by the optical sensor 20 arranged in a certain scintillator C _{m, n, k} is P _{m, n, k} , the radiation incident position (x, y, z) is
x = {P _3,1,1 + P _3,1,3 + P _3,3,1 + P _3,3,3 } / P
_{y = {P 1,3,1 + P 1,3,3} + P 3,3,1 + P 3,3,3} / P
_{z = {P 1,1,3 + P 1,3,3} + P 3,1,3 + P 3,3,3} / P
(Where P is the total number of photons incident on all photosensors 20)
Is calculated as

In the radiation position detector 1A according to the present embodiment, each of the plurality of optical sensors 20 includes all of the scintillator cells 11 (that is, C _1,1,1 , C _1,1) constituting the vertices of a cube in the scintillator block 10A. _{, 3} , C _1,3,1 , C _1,3,3 , C _3,1,1 , C _3,1,3 , C _3,3,1 , and C _3,3,3 scintillator cells 11 ) And are optically coupled to the surface of the scintillator cell 11. As a result, the photosensors 20 are arranged in a balanced and efficient manner not only on the lowermost layer of the scintillator block 10A but also on all layers, so the row direction (X-axis direction) and column direction (Y-axis direction) of the scintillator block 10A. ) And the detection accuracy of the radiation incident position and the radiation dose in each of the stacking directions (Z-axis direction) can be evenly increased. Therefore, according to the radiation position detector 1A of the present embodiment, it is possible to suitably suppress variations in the detection accuracy of the radiation incident position and the radiation dose with respect to the radiation incident direction.

  Further, as in the present embodiment, the scintillator block 10A is preferably cubic. That is, by making the dimensions of the scintillator block 10A equal to each other in the row direction (X-axis direction), column direction (Y-axis direction), and stacking direction (Z-axis direction) of the scintillator block 10A, variation in detection accuracy in each direction. Can be effectively suppressed. In this case, it is more preferable that the plurality of scintillator cells 11 have a cubic shape. Thereby, the arrangement numbers of the scintillator cells 11 in the row direction (X-axis direction), the column direction (Y-axis direction), and the stacking direction (Z-axis direction) of the scintillator block 10A are equal to each other, and the radiation incident position in each direction is The resolution can be made uniform.

  In the present embodiment, an example in which four photosensors 20 are arranged on one side surface of the scintillator block 10A and the other four photosensors 20 are arranged on the side surface opposite to the side surface will be described. However, the arrangement direction of the optical sensor 20 is not limited to this. For example, a certain optical sensor 20 is on a surface different from the two side surfaces (for example, the radiation position detector 1B shown in FIG. 4 (for example, The scintillator block 10A may be disposed on the top surface or the bottom surface. Even if it is such a form, if each of the some optical sensor 20 is optically couple | bonded with the surface of all the scintillator cells 11 which comprise the vertex of the cube in 10 A of scintillator blocks, the said effect is suitable. Can be played.

(Second Embodiment)
Next, a second embodiment of the radiation position detector according to the present invention will be described. FIG. 5 is a perspective view showing an appearance of the radiation position detector 1C according to the present embodiment. FIG. 6 is an exploded perspective view of the radiation position detector 1C shown in FIG. The radiation position detector 1C includes a scintillator block 10C, a plurality of optical sensors 20, and a reflector 30.

  The difference between the radiation position detector 1C of the present embodiment and the radiation position detector 1A of the first embodiment is the shape of the scintillator block and the number of scintillator cells 11 included in the scintillator block. That is, the scintillator block 10C of the present embodiment has a rectangular parallelepiped appearance, and a scintillator array 13 (see FIG. 6) in which a plurality of cubic scintillator cells 11 are arranged in 4 rows and 3 columns is four layers. It is configured by being laminated. As in the first embodiment described above, of the surfaces of the plurality of scintillator cells 11, the surface constituting the bottom surface, the side surface, or the top surface of the scintillator block 10C is rough polished except for the portion where the optical sensor 20 is attached. The remaining surface is mirror-polished. Further, the point that the gap between adjacent scintillator cells 11 forms an air layer is the same as in the first embodiment.

The plurality of optical sensors 20 are arranged one by one corresponding to all of the scintillator cells 11 constituting the vertex of the rectangular parallelepiped in the scintillator block 10C, and are optically coupled to one surface of the corresponding scintillator cell 11. . That is, the optical sensor 20 of this embodiment includes C _1,1,1 , C _1,1,4 , C _1,3,1 , C _1,3,4 , C _4,1 among the plurality of scintillator cells 11. _{, 1} , C _4,1,4 , C _4,3,1 , and C _4,3,4 are arranged on the surface of each scintillator cell 11. As a result, the photosensors 20 are arranged in a balanced and efficient manner not only on the lowermost layer of the scintillator block 10C but also on all layers, so the row direction (X-axis direction) and column direction (Y-axis direction) of the scintillator block 10C. ) And the detection accuracy of the radiation incident position and the radiation dose in each of the stacking directions (Z-axis direction) can be evenly increased. Therefore, according to the radiation position detector 1C of the present embodiment, it is possible to suitably suppress variations in the detection accuracy of the radiation incident position and the radiation dose with respect to the radiation incident direction.

  Further, the radiation position detector 1C of the present embodiment has the following advantages compared to the radiation position detector 1A of the first embodiment. That is, the number (4) of scintillator cells 11 in the row direction (X-axis direction) and the stacking direction (Z-axis direction) of the scintillator block 10C is larger than the number (3) of the scintillator block 10A of the first embodiment. Nevertheless, the number of photosensors 20 is equal to each other. Therefore, since the ratio of the number of optical sensors 20 required with respect to the volume of the scintillator block is small, the cost can be reduced.

  In contrast, the radiation position detector 1A of the first embodiment has the following advantages compared to the radiation position detector 1C of the present embodiment. That is, since the distance until the scintillation light reaches the optical sensor 20 is shortened as the volume of the scintillator block 10A is small, the detection accuracy of the radiation incident position and the radiation dose can be improved. Further, by making the scintillator block 10A into a cubic shape and having the same dimensions in the row direction, the column direction, and the stacking direction, variations in detection accuracy in each direction can be effectively suppressed. Furthermore, by making the number of arrangements of the scintillator cells 11 in the row direction, the column direction, and the stacking direction of the scintillator block 10A equal, the resolution of the radiation incident position in each direction can be made uniform.

(Third embodiment)
Next, a third embodiment of the radiation position detector according to the present invention will be described. FIG. 7 is a perspective view showing an appearance of the radiation position detector 1D according to the present embodiment. FIG. 8 is an exploded perspective view of the radiation position detector 1D shown in FIG. The radiation position detector 1D includes a scintillator block 10A, a plurality of optical sensors 20, and a reflector 30. The configuration of the scintillator block 10A is the same as that of the first embodiment, and the scintillator block 10A is configured by laminating three layers of scintillator arrays 12 in which a plurality of cubic scintillator cells 11 are arranged in 3 rows and 3 columns. Has been.

  The difference between the radiation position detector 1D of the present embodiment and the radiation position detector 1A of the first embodiment is the arrangement of the optical sensor 20. In other words, in the present embodiment, the plurality of optical sensors 20 are arranged one by one corresponding to each of the scintillator cells 11 that form the sides of the cube in the scintillator block 10A and do not form the vertices. Optically coupled to one of the surfaces. Further, two of these optical sensors 20 are arranged on each side, top and bottom of the scintillator block 10A.

Specifically, optical sensor 20 of the present embodiment, C _{1, 1, 2} of the plurality of scintillator cells _{11, C 1,2,1, C 1,2,3,} C 1,3,2, C _{2,1,1, C 2,3,1, C 2,1,3,} C 2,3,3, C 3,1,2, C 3,2,1, C 3,2,3, and C It is arranged on the face of each scintillator cell 11 _3,3,2. C _{1, 1, 2} and the light sensor 20 arranged on the surface of the C _{3, 1, 2} is disposed on the side facing the negative direction of the Y-axis is along the XZ plane of the side surfaces of the scintillator blocks 10A ing. C _{l, 3,2} and the light sensor 20 arranged on the surface of the C _3,3,2 are arranged on the side facing the positive direction of the Y-axis is along the XZ plane of the side surfaces of the scintillator blocks 10A ing. C _1,2,1 and the light sensor 20 arranged on the surface of the C _{1, 2, 3} is disposed on the side facing the negative direction of the X-axis is along the YZ plane of the side surfaces of the scintillator blocks 10A ing. The photosensors 20 arranged on the surfaces C _3,2,1 and C _3,2,3 are arranged on the side surface of the scintillator block 10A along the YZ plane and facing the positive direction of the X axis. ing. C _2,1,1 and the light sensor 20 arranged on the surface of the C _2,3,1 are arranged on the side facing the negative direction of the Z-axis is along the XY plane of the side surfaces of the scintillator blocks 10A ing. C _{2, l, 3} and the light sensor 20 arranged on the surface of the C _2,3,3 are arranged on the side facing the positive direction of the Z-axis is along the XY plane of the side surfaces of the scintillator blocks 10A ing.

In the radiation position detector 1D according to the present embodiment, each of the plurality of optical sensors 20 includes all the scintillator cells 11 (that is, C _1,1,2) that form the sides of the cube in the scintillator block 10A and do not form the vertices. _{, C 1,2,1, C 1,2,3, C} 1,3,2, C 2,1,1, C 2,3,1, C 2,1,3, C 2,3,3, _{C 3,1,2, C 3,2,1, C 3,2,3} , and are arranged in correspondence with each scintillator cell 11) of the C _3,3,2, the surface of the scintillator cell 11 Optically coupled. As a result, the photosensors 20 are arranged in a balanced and efficient manner not only on the lowermost layer of the scintillator block 10A but also on all layers, so the row direction (X-axis direction) and column direction (Y-axis direction) of the scintillator block 10A. ) And the detection accuracy of the radiation incident position and the radiation dose in each of the stacking directions (Z-axis direction) can be evenly increased. Therefore, according to the radiation position detector 1D of the present embodiment, it is possible to suitably suppress variations in the detection accuracy of the radiation incident position and the radiation dose with respect to the radiation incident direction.

Further, the radiation position detector 1D of the present embodiment has an advantage that the radiation beam incident position and the radiation dose can be detected with higher accuracy than the radiation position detector 1A of the first embodiment. That is, the radiation position detector 1A of the first embodiment and the radiation position detector 1D of the present embodiment both include a scintillator block 10A in which scintillator cells 11 are arranged in three rows, three columns, and three layers. . Then, in the first embodiment, the optical sensor 20 and the optically not coupled unbound cells of the surfaces of (excluding. Scintillator cell C _2,2,2 arranged in the center of the scintillator block 10A), light In contrast to the number of surfaces adjacent to the coupled cell optically coupled to the sensor 20 being 2, in the present embodiment, the number of surfaces adjacent to the coupled cell among the surfaces of the uncoupled cell is 3 or 4. Become. Therefore, according to the present embodiment, the light detection accuracy with respect to the light emission of the non-coupled cell is improved as compared with the first embodiment, so that the radiation incident position and the radiation dose can be detected with higher accuracy.

  On the other hand, the radiation position detector 1A of the first embodiment has an advantage that the radiation incident position and the radiation dose can be suitably detected by the fewer optical sensors 20 than the radiation position detector 1D of the present embodiment. is there. That is, when the scintillator block 10A is a hexahedron as in these embodiments, the radiation position detector 1D of this embodiment requires at least 12 photosensors 20 corresponding to 12 sides. In the radiation position detector 1A of one embodiment, eight optical sensors 20 corresponding to eight vertices can be used.

  In the present embodiment, an example in which two photosensors 20 are arranged on each side, bottom, and top surface of the scintillator block 10A has been described, but the arrangement direction of the photosensors 20 is not limited to this, There may be a bias in the number of optical sensors 20 arranged on the surface. Even in such a form, each of the plurality of optical sensors 20 is optically coupled to the surface of each of all the scintillator cells 11 that form the sides of the cube in the scintillator block 10A and do not form the apex. The above effects can be suitably achieved.

(Fourth embodiment)
Next, a fourth embodiment of the radiation position detector according to the present invention will be described. FIG. 9 is a perspective view showing an appearance of the radiation position detector 1E according to the present embodiment. FIG. 10 is an exploded perspective view of the radiation position detector 1E shown in FIG. The radiation position detector 1E includes a scintillator block 10E, a plurality of optical sensors 20, and a reflector 30.

  The differences between the radiation position detector 1E of the present embodiment and the radiation position detector 1A of the first embodiment are the number of scintillator cells 11 included in the scintillator block and the arrangement of the optical sensors 20. That is, the scintillator block 10E of this embodiment has a cubic appearance, and five layers of scintillator arrays 14 (see FIG. 10) in which cubic scintillator cells 11 are arranged in five rows and five columns are stacked. It is constituted by. As in the first embodiment, among the surfaces of the plurality of scintillator cells 11, the surface constituting the bottom surface, the side surface, or the top surface of the scintillator block 10E is subjected to a rough polishing process except for a portion where the optical sensor 20 is attached. The remaining surface is mirror-polished. Further, the point that the gap between adjacent scintillator cells 11 forms an air layer is the same as in the first embodiment.

The plurality of optical sensors 20 are arranged one by one corresponding to each of all the scintillator cells 11 constituting the cube apex in the scintillator block 10E, and are optically coupled to one surface of the corresponding scintillator cell 11. . That is, the optical sensor 20 of the present embodiment includes C _1,1,1 , C _1,1,5 , C _1,5,1 , C _1,5,5 , C _5,1 among the plurality of scintillator cells 11. _{, 1} , C _5,1,5 , C _5,5,1 , and C _5,5,5 are arranged on the surface of each scintillator cell 11.

In addition, the radiation position detector 1E is provided with an optical sensor 20 that is optically coupled to the surface of the scintillator cell 11 that does not constitute a side of the cube and does not constitute a vertex in the scintillator block 10E as an auxiliary to the plurality of optical sensors 20. In addition. In the present embodiment, the optical sensor 20 is optically coupled to the surface of the scintillator cell 11 that forms the center of the cubic surface of the scintillator block 10E. Specifically, the optical sensor 20, C _1,3,3 among a plurality of scintillator cells _{11, C 3,1,3, C 3,3,1,} C 5,3,3, C 3,5 _{, 3} and C _3,3,5 are arranged on the surface of each scintillator cell 11.

In the present embodiment, each of the plurality of optical sensors 20 includes all the scintillator cells 11 (that is, C _1,1,1 , C _1,1,5 , C _1, C ₎ constituting the cube vertex in the scintillator block 10E _{. 5,1} , C _1,5,5 , C _5,1,1 , C _5,1,5 , C _5,5,1 , and C _5,5,5 scintillator cells 11) And is optically coupled to the surface of the scintillator cell 11. As a result, the photosensors 20 are arranged in a balanced and efficient manner not only on the lowermost layer of the scintillator block 10E but also on all layers, so the row direction (X-axis direction) and column direction (Y-axis direction) of the scintillator block 10E. ) And the detection accuracy of the radiation incident position and the radiation dose in each of the stacking directions (Z-axis direction) can be evenly increased. Therefore, according to the radiation position detector 1E of the present embodiment, it is possible to suitably suppress variations in the detection accuracy of the radiation incident position and the radiation dose with respect to the radiation incident direction.

Furthermore, the radiation position detector 1E of the present embodiment further includes another optical sensor 20 optically coupled to the surface of the scintillator cell 11 that does not constitute a cube side and does not constitute a vertex in the scintillator block 10E. . Thus, by providing the optical sensor 20 to the scintillator cell 11 that does not constitute the apex or side of the scintillator block 10E, the detection accuracy of the radiation incident position and the radiation dose can be further increased. Then, as in this embodiment, the photosensor 20 has a scintillator cell 11 (that is, C _1,3,3 , C _3,1,3 , C _3,3) that forms the center of the cube surface in the scintillator block 10E _{. 3,1,} C _5,3,3, C _3,5,3, and C each scintillator cell 11 _3,3,5) at the surface and being optically coupled in, than against the scintillator block 10E The optical sensor 20 can be arranged with good balance and efficiency.

  FIG. 11 is a diagram conceptually showing measurement by a PET apparatus using the radiation position detector 1E of the present embodiment. In FIG. 11, P is a subject, and Q is a site where positron emission isotopes (RI radiation sources) gather in the subject P. The gamma rays R generated by the annihilation of electrons and positrons in the positron emitting isotope are detected by a plurality of radiation position detectors 1E arranged around the subject. In the conventional PET apparatus, the radiation position detectors are arranged in a ring shape. However, the radiation position detector 1E according to the present embodiment can detect the incident position and dose of radiation from all directions with almost uniform accuracy. The degree of freedom of the placement of the instrument is increased, and the minimum necessary number can be placed at the optimum position for imaging the region of interest. Therefore, it can contribute to the reduction of the number of radiation position detectors in the PET apparatus. The radiation position detectors 1A to 1D of the first to third embodiments described above are not limited to this embodiment, and the same effects can be achieved in the same manner.

  The radiation position detector according to the present invention is not limited to the above-described embodiment, and various other modifications are possible. For example, in each of the embodiments described above, the scintillator cell constituting the scintillator block is exemplified by the case of 3 rows, 3 columns, 3 layers, 4 rows, 3 columns, 4 layers, and 5 rows, 5 columns, 5 layers. Is not limited to these, and the effect of the present invention can be suitably achieved if they are arranged in M rows and N columns and K layers (where M and N are integers of 3 or more and K is an integer of 2 or more). Can play. The shape of the scintillator block is not limited to a cube or a rectangular parallelepiped, and may be another polyhedron. The shape of the scintillator cell is not limited to a cube, and may be a rectangular parallelepiped or another polyhedron.

  Further, in the first, second and fourth embodiments, (1) a mode in which each of a plurality of photosensors is provided corresponding to each of all scintillator cells constituting the vertex of the polyhedron in the scintillator block, In the third embodiment, (2) the configuration in which each of the plurality of photosensors is provided corresponding to each of the scintillator cells that constitute the sides of the polyhedron in the scintillator block and do not constitute the apex is shown. The radiation position detector may be configured by combining form (1) and form (2).

It is a perspective view which shows the external appearance of the radiation position detector which concerns on 1st Embodiment. It is a disassembled perspective view of the radiation position detector shown in FIG. It is a sectional side view of the radiation position detector shown in FIG. It is a figure which shows the form by which a certain optical sensor is arrange | positioned on the surface different from a pair of side surface of a scintillator block (for example, on the upper surface and bottom face of a scintillator block). FIG. 5 is a perspective view showing an appearance of the radiation position detector according to the second embodiment. FIG. 6 is an exploded perspective view of the radiation position detector shown in FIG. FIG. 7 is a perspective view showing an appearance of the radiation position detector according to the third embodiment. FIG. 8 is an exploded perspective view of the radiation position detector shown in FIG. FIG. 9 is a perspective view showing an appearance of the radiation position detector according to the fourth embodiment. FIG. 10 is an exploded perspective view of the radiation position detector shown in FIG. FIG. 11 is a diagram conceptually showing measurement by a PET apparatus using the radiation position detector of the fourth embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A-1E ... Radiation position detector, 10A, 10C, 10E ... Scintillator block, 11 ... Scintillator cell, 12-14 ... Scintillator array, 20 ... Optical sensor, 30 ... Reflective material, L ... Scintillation light, P ... Subject, R: Gamma rays.

Claims (6)

Generates scintillation light in response to absorption of radiation, the plurality having the same shape as each other scintillator cells M rows and N columns (where, M, N is an integer of 3 or more) scintillator arrays arranged two-dimensionally in, above A polyhedral scintillator block formed by laminating K layers (where K is an integer of 2 or more) such that the surface of the scintillator cell of the layer matches the surface of the scintillator cell of the lower layer ;
A plurality of optical sensors optically coupled to the surface of the scintillator block;
Each optical sensor is provided within a range of at least one outer surface of all of the scintillator cells constituting the vertex of the polyhedron in the scintillator block, and is optically coupled to the surface of the scintillator cell. A radiation position detector. Generates scintillation light in response to absorption of radiation, the plurality having the same shape as each other scintillator cells M rows and N columns (where, M, N is an integer of 3 or more) scintillator arrays arranged two-dimensionally in, above A polyhedral scintillator block formed by laminating K layers (where K is an integer of 2 or more) such that the surface of the scintillator cell of the layer matches the surface of the scintillator cell of the lower layer ;
A plurality of optical sensors optically coupled to the surface of the scintillator block;
Each optical sensor is provided within a range of at least one outer surface of all of the scintillator cells that constitute the sides of the polyhedron in the scintillator block and do not constitute the apex, and is optically coupled to the surface of the scintillator cell. A radiation position detector. 3. The apparatus according to claim 1, further comprising another optical sensor optically coupled to an outer surface of the scintillator cell that does not constitute a side of a polyhedron and does not constitute a vertex in the scintillator block. Radiation position detector. The radiation position detector according to claim 3, wherein the another optical sensor is optically coupled to an outer surface of the scintillator cell constituting a center of a polyhedron surface in the scintillator block. .   The radiation position detector according to any one of claims 1 to 4, wherein the scintillator block has a cubic shape. The radiation position detector according to claim 5, wherein the plurality of scintillator cells have a cubic shape.

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