JP5749582B2 - PET equipment - Google Patents

Description

  The present invention relates to a PET apparatus.

  Conventionally, a PET apparatus to which a radiation detector based on DOI (Depth Of Interaction) technology is applied is known (see, for example, Patent Document 1). In such a PET apparatus, a gap may be generated between the radiation detectors arranged in a ring shape. In this case, the gap generated between the radiation detectors becomes a radiation insensitive region, and detection of radiation is performed. There is a risk of lowering sensitivity. In particular, a PET device having a reduced ring diameter for targeting small animals or the like tends to have a higher ratio of insensitive areas.

  In order to reduce the ratio of such insensitive areas, it has been proposed to apply a radiation detector having a tapered phosphor layer that emits light upon incidence of radiation to a PET apparatus (for example, non-patent literature). 1). In such a PET apparatus, the ratio of the insensitive area is lowered by arranging the radiation detectors in a ring shape so that the phosphor layer spreads outward.

International Publication No. 2009/125480

Y. Yang et al, “Tapered LSO arrays for small animal PET”, Phys. Med. Biol., 56 (2011) 139-153.

  However, in a PET apparatus to which a radiation detector having a phosphor layer with a tapered shape is applied, the width of the detection segment constituting the phosphor layer increases toward the outside, so that the resolution (spatial resolution) of the PET apparatus is increased. ) May deteriorate.

  Accordingly, an object of the present invention is to provide a PET apparatus having high radiation detection sensitivity and high resolution.

  The PET apparatus of the present invention has a phosphor layer that emits light by the incidence of radiation emitted from a subject, and a light receiving element layer that detects light emitted from the phosphor layer, with a predetermined line as a center line. And a plurality of radiation detectors arranged on each of a plurality of circumferences having different diameters so that the phosphor layer is on the inner side with respect to the light receiving element layer, and adjacent to each other on any circumference The region between the phosphor layers of the radiation detector is opposed to the phosphor layer of the radiation detector disposed on at least one other circumference on a half line passing through the region starting from the center point of the circumference. doing.

  In such a PET apparatus, the region between the phosphor layers of adjacent radiation detectors on an arbitrary circumference is arranged on at least one other circumference on the above half line. Opposite the layer. Thereby, even if the radiation emitted from the subject passes through the region, it passes through the other phosphor layers, so that the radiation detection sensitivity is increased. Further, a plurality of radiation detectors are arranged in the radial direction. As a result, the detection segment in the radial direction becomes small, and it is not necessary to increase the width of the detection segment in the tangential direction of the circumference, so that the resolution becomes high.

  Here, the region between the phosphor layers of adjacent radiation detectors on an arbitrary circumference is arranged on all other circumferences on a half line passing through the area starting from the center point of the circumference. It is preferable to face the phosphor layer of the radiation detector. According to this, since two or more regions between the phosphor layers of adjacent radiation detectors do not exist on the half line, the radiation detection sensitivity of the entire PET apparatus is further increased.

  In addition, in the tangential direction of the circumference, the width of the phosphor layer is preferably larger as the radiation detector is disposed on the outer circumference. If the width of the phosphor layer can be set according to the radius of the circumference, the distance between the phosphor layers in the circumferential direction can be reduced, and the distance between the phosphor layers in the radial direction can be reduced. Can do. Thereby, the detection sensitivity of radiation is further improved, and the miniaturization of the entire PET apparatus can be achieved.

  According to the present invention, it is possible to provide a PET apparatus with high radiation detection sensitivity and resolution.

It is the schematic of the PET apparatus of one Embodiment of this invention. It is sectional drawing of the gantry of the PET apparatus of FIG. FIG. 3 is a perspective view of a plurality of radiation detectors in FIG. 2. It is a disassembled perspective view of the radiation detector of FIG. FIG. 4 is a virtual perspective view when the plurality of radiation detectors of FIGS. 2 and 3 are aligned so as to expand toward the outside.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same part or an equivalent part, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a schematic view of a PET apparatus according to an embodiment of the present invention. As shown in FIG. 1, a PET apparatus 1 includes a bed (not shown) on which a subject T such as a small animal such as a mouse is placed, a gantry 2 having a circular opening, and a gantry 2. And an image processing unit 3 to which the data detected in (1) is transferred. The PET apparatus 1 is emitted from a subject T to which a drug labeled with a positron emitting nuclide (a radioactive isotope that emits positrons) is administered in order to acquire tomographic images of the subject T at a plurality of slice positions. This is a device for detecting radiation such as gamma rays.

  2 is a cross-sectional view of the gantry of the PET apparatus of FIG. 1, and FIG. 3 is a perspective view of the plurality of radiation detectors of FIG. As shown in FIGS. 2 and 3, the radiation detector 10 includes a phosphor layer 11 that emits light by the incidence of radiation emitted from the subject T, and a light receiving unit that detects light emitted from the phosphor layer 11. An element layer 12 and a support substrate 14 that supports the phosphor layer 11 and the light receiving element layer 12 are provided. Further, a processing circuit 13 is mounted on the support substrate 14. The processing circuit 13 processes the electrical signal output from the light receiving element layer 12 and transfers it to the image processing unit 3. A plurality of the radiation detectors 10 are arranged on the circumference C <b> 1 having the predetermined line L <b> 0 as the center line so that the phosphor layer 11 is inside the light receiving element layer 12.

  The radiation detector 20 includes a phosphor layer 21 that emits light by the incidence of radiation emitted from the subject T, a light receiving element layer 22 that detects light emitted from the phosphor layer 21, a phosphor layer 21, and a light receiving element. And a support substrate 24 that supports the element layer 22. Further, a processing circuit 23 is mounted on the support substrate 24. The processing circuit 23 processes the electrical signal output from the light receiving element layer 22 and transfers it to the image processing unit 3. The radiation detector 20 has a predetermined line L0 as a center line, and the phosphor layer 21 is located on the outer side of the circumference C1 and on the circumference C2 having a diameter different from that of the circumference C1, with respect to the light receiving element layer 22. A plurality are arranged so as to be.

  The radiation detector 30 includes a phosphor layer 31 that emits light by the incidence of radiation emitted from the subject T, a light receiving element layer 32 that detects light emitted from the phosphor layer 31, the phosphor layer 31, and the light reception. And a support substrate 34 that supports the element layer 32. Further, a processing circuit 33 is mounted on the support substrate 34. The processing circuit 33 processes the electrical signal output from the light receiving element layer 32 and transfers it to the image processing unit 3. The radiation detector 30 has a predetermined line L0 as the center line, and the phosphor layer 31 is located on the inner side with respect to the light receiving element layer 32 on the circumference C3 having a diameter different from the circumference C2 outside the circumference C2. A plurality are arranged so as to be.

  The radiation detector 40 includes a phosphor layer 41 that emits light by the incidence of radiation emitted from the subject T, a light receiving element layer 42 that detects light emitted from the phosphor layer 41, the phosphor layer 41, and the light receiving unit. And a support substrate 44 that supports the element layer 42. Further, a processing circuit 43 is mounted on the support substrate 44. The processing circuit 43 processes the electrical signal output from the light receiving element layer 42 and transfers it to the image processing unit 3. The radiation detector 40 has a predetermined line L0 as a center line, and the phosphor layer 41 is disposed on the inner side with respect to the light receiving element layer 42 on a circumference C4 having a diameter different from the circumference C3 outside the circumference C3. A plurality are arranged so as to be.

  Here, the configuration of the radiation detectors 10, 20, 30, and 40 will be described more specifically by taking the radiation detector 10 as an example. FIG. 4 is an exploded perspective view of the radiation detector of FIG. As shown in FIG. 4, the light receiving element layer 12 is an MPPC (Multi-Pixel Photon Counter), an APD (avalanche photodiode), or the like, and includes pixels 16 arranged two-dimensionally. The light receiving element layer 12 is electrically connected to the processing circuit 13 on the support substrate 14. The phosphor layer 11 is a two-dimensional array in which the columnar scintillator single crystals 15 constituting the detection segment correspond to the pixels 16 of the light receiving element layer 12. The light receiving element layer 12 and the phosphor layer 11 are connected to each other either directly or by optical coupling via a refractive index matching material or the like.

  The radiation detectors 20, 30 and 40 are configured in the same manner as the radiation detector 10. However, as shown in FIGS. 2 and 3, in the tangential direction of the circumferences C1, C2, C3, and C4 (hereinafter simply referred to as “tangential direction”), the width of the phosphor layer 21 of the radiation detector 20 is The width of the phosphor layer 11 of the radiation detector 10 is larger. Similarly, in the tangential direction, the width of the phosphor layer 31 of the radiation detector 30 is larger than the width of the phosphor layer 21 of the radiation detector 20, and the width of the phosphor layer 41 of the radiation detector 40 is The width of the phosphor layer 31 of the radiation detector 30 is larger.

  The radiation detectors 10, 20, 30, and 40 configured as described above have the same number (here, 12) so as to form a ring shape substantially along the circumferences C1, C2, C3, and C4. Has been placed. Here, as shown in FIG. 3, these radiation detectors 10, 20, 30, and 40 are respectively phosphor layer 11 and light receiving element layer 12, phosphor layer 21 and light receiving element layer 22, phosphor layer 31 and The light receiving element layer 32, and the phosphor layer 41 and the light receiving element layer 42 are accommodated in the light shielding cases 51, 52, 53, and 54, respectively. The light shielding case 50 prevents ambient light from entering the radiation detectors 10, 20, 30, and 40.

  In the PET apparatus 1, the radiation detectors 10, 20, 30, and 40 accommodated in the light shielding cases 51, 52, 53, and 54 in this way have their center positions in the tangential direction set to the circumferences C1, C2, and C3. , C4 are shifted in the circumferential direction. That is, a region between phosphor layers of adjacent radiation detectors on an arbitrary circumference C1, C2, C3, C4 is a half passing through the region starting from the center point O of the circumference C1, C2, C3, C4. On the straight line, the radiation detectors 10, 20, 30, and 40 are arranged so as to face the phosphor layers of the radiation detectors arranged on other circumferences, respectively.

  Specifically, as shown in FIG. 2, the region R1 between the phosphor layers 11 and 11 of the adjacent radiation detectors 10 and 10 on the circumference C1 starts from the center point O of the circumference C1. On the half line L1 passing through the region, the phosphor layers 21, 31, 41 of the radiation detectors 20, 30, 40 arranged on the other circumferences C2, C3, C4 are respectively opposed.

  Similarly, the region R2 between the phosphor layers 21 and 21 of the radiation detectors 20 and 20 adjacent to each other on the circumference C2 starts on the center line O of the circumference C2 and is on a half line L2 passing through the region. Opposite to the phosphor layers 11, 31, 41 of the radiation detectors 10, 30, 40 arranged on the other circumferences C1, C3, C4, respectively.

  Similarly, a region R3 between the phosphor layers 31 and 31 of the radiation detectors 30 and 30 adjacent to each other on the circumference C3 starts on the half line L3 passing through the region starting from the center point O of the circumference C3. The phosphor layers 11, 21, 41 of the radiation detectors 10, 20, 40 disposed on the other circumferences C 1, C 2, C 4 are opposed to each other.

  Similarly, a region R4 between the phosphor layers 41 and 41 of the radiation detectors 40 and 40 adjacent to each other on the circumference C4 starts on the center line O of the circumference C4 and on a half line L4 passing through the region. The phosphor layers 11, 21, 31 of the radiation detectors 10, 20, 30 disposed on the other circumferences C 1, C 2, C 3 are opposed to each other.

  FIG. 5 shows that the radiation detector spreads outward in the radial direction of the circumferences C1, C2, C3, and C4 (hereinafter simply referred to as “radial direction”) for explaining the mutual positional relationship. It is a virtual perspective view at the time of aligning like this. In this embodiment, each of the 12 radiation detectors 10, 20, 30, and 40 existing in such a way as to spread outward in the radial direction in the PET apparatus 1 and in the radial direction. Are aligned so as to be substantially line symmetric with respect to a line extending in the direction of the straight line (for example, the above-described half straight lines L1 to L4), the extension line of the side surface of the divergent shape, that is, the extension line extending in the radial direction, , C3, C4 at the center point O, and the angle formed is 30 degrees. The angle formed by the extension line extending in the radial direction is generally 360 degrees / (the number of radiation detectors in the circumferential direction).

  In the PET apparatus 1, there are 12 sets of these groups of radiation detectors 10, 20, 30, and 40. Here, the radiation detectors 10, 20, 30, and 40 in the present embodiment have their respective center positions in the tangential direction at an angle of 7.5 degrees with respect to the center point O from the state shown in FIG. 5. Arranged in a staggered manner. The radiation detectors 10, 20, 30, and 40 are similarly shifted and arranged for each of the 12 sets, so that the arrangement of the radiation detectors 10, 20, 30, and 40 is the same as that shown in FIGS. Become. In addition, the angle which mutually shifts the said center position of a radiation detector with respect to the center point O was calculated | required by calculation of (the angle which the extended line extended in radial direction makes) / (the number of steps of the radiation detector in radial direction).

  As described above, in the PET apparatus 1, the regions R1, R2, R3, and R4 are the radiation detectors disposed on at least one other circumference on the half lines L1, L2, L3, and L4, respectively. Opposite the phosphor layer. Thereby, even if the radiation emitted from the subject passes through the region, it passes through the other phosphor layers, so that the radiation detection sensitivity is increased. That is, data with improved quantitativeness can be obtained as compared with the conventional PET apparatus. Furthermore, a plurality of radiation detectors 10, 20, 30, 40 are arranged in the radial direction. As a result, the detection segment in the radial direction becomes small, and it is not necessary to increase the width of the detection segment in the tangential direction of the circumference, so that the resolution becomes high. According to the PET apparatus 1 having these configurations, when the subject T is relatively large, the advantage of the DOI technique in which the resolution around the visual field is difficult to be reduced is exhibited.

  In the PET apparatus 1, in the tangential direction, the width of the phosphor layer is larger as the radiation detector is arranged on the outer circumference. Thus, since the width of the phosphor layer can be set according to the radius of the circumference, the distance between the phosphor layers in the circumferential direction can be reduced, and the distance between the phosphor layers in the radial direction Can be narrowed. Thereby, the detection sensitivity of radiation is further improved, and the miniaturization of the entire PET apparatus can be achieved.

  In the PET apparatus 1, the light receiving element layers 12, 22, 32, and 42 are composed of elements having a small atomic number, and therefore do not absorb γ rays, and the radiation detectors are assembled in multiple stages as in this embodiment. Also, deterioration of the radiation detection sensitivity is prevented.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, although the embodiment in which the radiation detectors are stacked in four stages in the radial direction has been described in the above embodiment, the number of stages in which the radiation detectors are stacked is not particularly limited, and may be smaller or larger than four.

  Further, in the example shown in FIG. 2, the radiation detectors 10, 20, 30, and 40 are configured such that the widths of the phosphor layers in the tangential directions are different from each other, but the tangential directions are all on the circumference. A radiation detector having the same phosphor layer may be used, or a radiation detector having a smaller phosphor layer width on the outer circumference than the phosphor layer width on the inner circumference may be used. Good.

  In the above embodiment, the radiation detectors 10, 20, 30, and 40 are arranged with their center positions in the circumferential direction shifted from each other by an angle of 7.5 degrees with respect to the center point O. It may be an angle. In the above embodiment, the same number (12) of radiation detectors is arranged on each circumference, but the number of radiation detectors on each circumference may be different from each other.

  DESCRIPTION OF SYMBOLS 1 ... PET apparatus 10, 20, 30, 40 ... Radiation detector 11, 21, 31, 41 ... Phosphor layer, 12, 22, 32, 42 ... Light receiving element layer, C1, C2, C3, C4 ... Circle Circumference, L0 ... predetermined line, L1, L2, L3, L4 ... half line, O ... center, R1, R2, R3, R4 ... region, T ... subject.

Claims (4)

A phosphor layer that emits light upon incidence of radiation emitted from a subject; and a light-receiving element layer that detects light emitted from the phosphor layer, the predetermined line being a center line, and diameters of each other On each of a plurality of different circumferences, a plurality of radiation detectors are arranged so that the phosphor layer is inside with respect to the light receiving element layer,
The region between the phosphor layers of the radiation detectors adjacent to each other on the circumference is at least one other circumference on a half line passing through the area starting from the center point of the circumference. A PET apparatus facing the phosphor layer of the arranged radiation detector.   The regions between the phosphor layers of the radiation detectors adjacent to each other on any of the circumferences are arranged on all other circumferences on a semi-line that starts from the center point of the circumference and passes through the area. The PET device according to claim 1, wherein the PET device faces the phosphor layer of the radiation detector. A phosphor layer that emits light upon incidence of radiation emitted from a subject; and a light-receiving element layer that detects light emitted from the phosphor layer, the predetermined line being a center line, and diameters of each other On each of a plurality of different circumferences, a plurality of radiation detectors are arranged so that the phosphor layer is inside with respect to the light receiving element layer,
The region between the phosphor layers of the radiation detectors adjacent to each other on the circumference is at least one other circumference on a half line passing through the area starting from the center point of the circumference. Facing the phosphor layer of the arranged radiation detector,
In the tangential direction of the circumference, the width of the phosphor layer is greater as the radiation detector located outside of said circumferentially, P ET device. The regions between the phosphor layers of the radiation detectors adjacent to each other on any of the circumferences are arranged on all other circumferences on a semi-line that starts from the center point of the circumference and passes through the area. The PET device according to claim 3, wherein the PET device faces the phosphor layer of the radiation detector.

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