JP2005106704A - Nuclear medicine diagnostic equipment and collimator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for nuclear medicine diagnosis improving the sensitivity of detecting elements, and a collimator. <P>SOLUTION: The device includes the collimator 1 having partition walls 11, comprising a plurality of regular hexagonal-shaped radiation passages 12 that are partitioned by the walls 11 and where radiation rays pass; and detectors 2 grid-like arranged along the direction of two-dimensional coordinate, providing a plurality of rectangle semiconductor elements 21 with mutual clearances 22 so that the detectors 2 are arranged so that the semiconductor elements 21 face the radiation passages 12. The pitch of the semiconductor elements 21 in a first (an X axis) coordinate direction is set the same as that of the side facing the partition walls 11 determining the radiation passages 12, and the center 121 of the radiation passages 12 and the center 210a of the semiconductor elements 21 are arranged at the same coordinates, with regard to the first (X-axis) coordinate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a nuclear medicine diagnostic apparatus and a collimator having a structure in which a detection element and a collimator are efficiently arranged.

  Conventionally, what uses a NaI scintillator is known as a radiation detector which detects radiations, such as a gamma ray. As shown in FIG. 9, in a gamma camera (nuclear medicine diagnostic apparatus) equipped with a NaI scintillator, radiation (γ rays) 109 is incident on the scintillator 101 at an angle limited by a collimator 106 and interacts with a crystal of NaI. Wake up and emit scintillation light. This light sandwiches the light guide 102 and reaches the photomultiplier tube 103 to become an electric signal. The electrical signal is shaped by the measurement circuit 104 attached to the measurement circuit fixing board 105 and sent from the output connector 107 to an external data collection system. The scintillator 101, the light guide 102, the photomultiplier tube 103, the measurement circuit 104, the measurement circuit fixing board 105, and the like are all housed in a light shielding shield case 108 to block electromagnetic waves other than external radiation.

  In general, a gamma camera using the scintillator 101 has a structure in which a large photomultiplier tube (also referred to as a photomultiplier) is placed after a single large crystal such as NaI, so that the position resolution is only about 10 mm. Further, since the scintillator 101 performs detection through multi-step conversion from radiation to visible light and from visible light to electrons, it has a problem that the energy resolution is very poor.

As a radiation detector for detecting radiation based on a principle different from that of the scintillator 101, a semiconductor element using a semiconductor material such as CdTe (cadmium telluride), TlBr (thallium bromide), GaAs (gallium arsenide) is provided. There is a semiconductor radiation detector.
In this semiconductor radiation detector, since the semiconductor element converts the electric charge generated by the interaction between the radiation and the semiconductor material into an electric signal, the conversion efficiency to the electric signal is better than that of the scintillator and the size can be reduced. So it is attracting attention.
JP2003-222676 (paragraph 0017)

Some of the semiconductor radiation detectors described above are configured by arranging a plurality of rectangular semiconductor elements in a grid pattern with a gap between each other, as shown in FIG. A collimator having a plurality of radiation paths is arranged in front of the semiconductor element (on the radiation source side), and only radiation incident at a certain angle is transmitted by the collimator and can be detected by a detector. .
However, if a semiconductor radiation detector having a rectangular semiconductor element is appropriately arranged with respect to a collimator having a hexagonal radiation path as shown in FIG. 10, a dead space between the semiconductor elements is disposed in the radiation path. There is a case where the ratio of occurrence of (gap) is increased, and there is a problem that the radiation whose angle is limited by the collimator is incident on the dead space and the detection sensitivity is lowered.
Further, the ratio of the semiconductor elements arranged inside each radiation path is also different, and there is a problem that the sensitivity of the semiconductor elements becomes non-uniform.

  Therefore, an object of the present invention is to provide a nuclear medicine diagnostic apparatus and a collimator that solve the above-described problems and improve the sensitivity of the detection element.

  In order to solve the above-described problems, the present invention provides a regular hexagonal collimator having a partition wall and having a plurality of radiation passages through which radiation passes, and a plurality of rectangular detection elements. And a radiation detector arranged in a lattice shape along a two-dimensional orthogonal coordinate direction, wherein the detector is arranged so that the detection element faces the radiation path. The pitch of the detection elements in the first coordinate direction is set to be the same as the pitch of the opposing sides of the partition walls defining the radiation path, and the center of the radiation path and the center of the detection element are related to the first coordinate. It is characterized by being arranged on the same coordinates.

  According to the present invention, the radiation detector is arranged so that the gap between the detection elements arranged in the first coordinate direction and the partition wall of the collimator efficiently overlap, and the ratio of the detection elements exposed inside each radiation path is increased. it can.

  According to the nuclear medicine diagnostic apparatus of the present invention, the collimator and the detector can be efficiently arranged, and the detection sensitivity can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The nuclear medicine diagnosis apparatus according to the embodiment will be described as SPECT (Single Photon Emission Computer Tomography) which is a radiation imaging apparatus.
In FIG. 1, SPECT 5 includes a pair of semiconductor radiation detection devices 51, a rotation support base 52, a data collection analysis device 53, a data input device 54, and a display device 55. The pair of semiconductor radiation detection devices 51 are disposed on the rotation support base 52 at positions shifted by 180 ° in the circumferential direction. Specifically, each socket board 510 of each semiconductor radiation detection apparatus 51 is attached to the rotation support base 52 at a position 180 degrees apart in the circumferential direction. Each radiation detection unit 511 faces the bed B side. The collimator 1 is installed between the radiation detection unit 511 and the subject P, and the viewing angle from the radiation detection unit 511 is limited. A measurement circuit unit 512 is also installed in each socket board 510. The radiation detection unit 511, the collimator 1 and the measurement circuit unit 512 are housed in the light shielding / electromagnetic shield ES, thereby blocking the influence of electromagnetic waves other than the γ rays S1.

  The bed B on which the subject P to which the radiopharmaceutical is administered is moved, and the subject P is moved between the pair of socket boards 510. Each detector (radiation detector) of the radiation detection unit 511 passes through the radiation path 12 (see FIG. 2) in the collimator 1 and the γ-ray S1 emitted from the accumulation part S in the subject P in which the radiopharmaceutical is accumulated. 2 is incident. The γ-ray detection signal output from the detector 2 is processed by the measurement circuit unit 512. The data collection and analysis device 53 creates image information for the subject P using the information output from the measurement circuit unit 512 and displays this image information on the display device 55. As the rotation support base 52 rotates, each socket board 510 and the radiation detection unit 511 rotate around the subject P. The radiation detection unit 511 outputs a γ-ray detection signal while turning. The rotation control of the rotation support base 52, the control of the distance between the radiation detection unit 511 and the subject P, and the position control of the subject P by the bed B can be performed in the vicinity of SPECT5 by the operation panel 56, and data It is also possible to carry out from a long distance by the input device 54.

(First embodiment)
Next, a first embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
In the present embodiment, a detector arrangement structure for matching the detector 2 with the collimator 1 having the conventional regular hexagonal radiation path 12 in the SPECT 5 described above will be described.

As shown in FIG. 2, in the detector arrangement structure according to the present embodiment, among the γ rays emitted from the γ ray source S, a collimator 1 that transmits only γ rays having a certain angle, and a collimator 1 Is provided with a detector 2 for detecting γ-rays transmitted through the.
In the present embodiment, the direction will be described with reference to the state of FIG. 2 in which the collimator 1 is disposed on the upper surface side of the detector 2.

As shown in FIGS. 2 and 3, the collimator 1 includes a plurality of radiation paths 12 partitioned by partition walls 11 in a honeycomb shape. The radiation path 12 has a predetermined length, and detects only γ-rays S1 incident on the radiation path 12 at a certain limited angle among the γ-rays (radiation) emitted from the γ-ray source S. Guide to vessel 2. The predetermined length can be determined according to the angle of γ rays incident on the detector 2.
As shown in FIG. 3, the radiation path 12 is formed in a regular hexagonal shape in plan view. The spatial resolution is increased as the size of the radiation path 12 is reduced. Here, the side extending in the horizontal direction on the paper surface is 120, and the center of the radiation passage 12 is 121. For convenience of explanation, a line parallel to the direction in which the side 120 extends is set as an X axis (first coordinate), and a vertical line is set as a Y axis (second coordinate).
The partition 11 is made of a material such as lead so as to absorb γ-rays incident from other than a limited angle. The partition wall 11 has a predetermined thickness. Here, the hexagon formed by connecting the center line (one-dot chain line) of the thickness of the partition wall 11 is 13, the distance between opposite sides of the hexagon 13 is A, and the length of one side of the hexagon 13 is B. (See FIG. 4 (a)). The hexagon 13 is a regular hexagon having the same length on each side.

As shown in FIGS. 3 and 4B, the detector 2 is configured by arranging semiconductor elements (detection elements) 21 having a detection surface 210 in a lattice pattern with gaps 22 therebetween. The detection surface 210 of the semiconductor element 21 is formed in a rectangular shape and is arranged so that the detection surface 210 faces the radiation path 12 side of the collimator 1. Here, the center of the detection surface 210 is set to 210a.
Here, if a square formed by connecting the center line (one-dot chain line) of the thickness of the gap 22 is 14, this square 14 is X with a pitch 1.5 times the length B of one side of the hexagon 13. They are arranged in the axial direction and in the Y-axis direction with a pitch of a distance A between opposite sides of the hexagon 13. That is, the semiconductor elements 21 are arranged in the X-axis direction at a pitch that is 1.5 times the length B of one side of the hexagon 13.
The semiconductor element 21 having such a detection surface 210 is made of a semiconductor material such as CdTe (cadmium telluride), TlBr (thallium bromide), GaAs (gallium arsenide), and the angle is limited by the collimator 1. The incident γ rays are incident and can be detected.

Next, a method for arranging the detector 2 with respect to the collimator 1 will be described.
First, the detector 2 is arranged so that the detection surface 210 faces the radiation path 12 of the collimator 1. In a plan view, the side 120 of the radiation path 12 and the row of the detection surface 210 in the X-axis direction are made parallel. The center 210a of the detection surface 210 is located on a straight line connecting the center 121 of the radiation passage 12 in the Y-axis direction. In other words, the center 121 aligned in the Y-axis direction and the center 210a aligned in the Y-axis direction are on the same X coordinate.
In the Y-axis direction, the position of the detector 2 is slightly shifted (see FIG. 3) from the overlap of the gap 11 between the partition 11 of the collimator 1 and the detector 2 (see FIG. 3), preferably the partition in the X-axis direction. It is preferable that the gap 22 in the X-axis direction is located at a position shifted in the Y-axis direction by a quarter from 11 (side 120). This can make the detection sensitivity uniform. This is because the low-sensitivity portion of the detection surface 210 of the detector 2 becomes a bottleneck for statistical errors, and the overall detection sensitivity is improved by the arrangement slightly shifted as shown in FIG.

According to the above, the following effects can be obtained in SPECT5 to which the detector arrangement structure according to the present embodiment is applied.
Since the gap 22 extending in the Y-axis direction of the detector 2 efficiently overlaps the partition wall 11 of the collimator 1, the gap (dead space) in the Y-axis direction is reduced in the detector 2. Therefore, the ratio of the detection surface 21a of the detector 2 exposed in the radiation passage 12 can be increased, and the detection sensitivity can be improved.

  Further, since the detection surfaces 210 are arranged at the same pitch as the length A of the hexagon 13 in the Y-axis direction, the repeated pitches of the hexagon 13 and the detection surfaces 210 in the Y-axis direction are the same. Therefore, the detection sensitivity can be made uniform.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
Since this embodiment is a partial modification of the configuration of the first embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. And

  As shown in FIG. 5, the collimator 1 includes a plurality of radiation paths 12 partitioned by a partition wall 11. Here, the side extending in the horizontal direction on the paper surface is 120, and the center of the radiation passage 12 is 121. For convenience of explanation, a line parallel to the direction in which the side 121 extends is set as an X axis, and a vertical line is set as a Y axis. And the hexagon formed by connecting the center line (one-dot chain line) of the thickness of the partition wall 11 is 13, the distance between opposite sides of the hexagon 13 is A, and the length of one side of the hexagon 13 is B ( (See FIG. 6 (a)). The hexagon 13 is a regular hexagon having the same length on each side.

As shown in FIGS. 5 and 6B, the detector 3 is configured by arranging semiconductor elements (detection elements) 31 having a detection surface 310 in a lattice pattern with gaps 32 therebetween. Here, the center of the detection surface 310 is 310a.
Here, assuming that a square formed by connecting the center line (one-dot chain line) of the thickness of the gap 32 is 15, this square 15 is a square and is 1.5 times the length B of one side of the hexagon 13. Are arranged in the X-axis direction and the Y-axis direction at a pitch of. That is, the semiconductor elements 31 are arranged in the X-axis direction at a pitch that is 1.5 times the length B of one side of the hexagon 13.
The semiconductor element 31 having such a detection surface 310 is made of a semiconductor material such as CdTe (cadmium telluride), TlBr (thallium bromide), GaAs (gallium arsenide), and the angle is limited by the collimator 1. The incident γ rays are incident and can be detected.

Next, a method for arranging the detector 3 with respect to the collimator 1 will be described.
First, the detector 3 is arranged so that the detection surface 310 faces the radiation path 12 of the collimator 1. In the plan view, the side 120 of the radiation path 12 and the row of the detection surface 310 in the X-axis direction are made parallel. Further, the detection surface 310 is arranged so that the center 310a is positioned on a straight line connecting the center 121 of the radiation path 12 in the Y-axis direction.

According to the above, the following effects can be obtained in SPECT5 to which the detector arrangement structure according to the present embodiment is applied.
Since the gap 32 extending in the Y-axis direction of the detector 3 efficiently overlaps the partition wall 11 of the collimator 1, the gap (dead space) in the Y-axis direction is reduced in the detector 3. Therefore, the ratio of the detection surface 21a of the detector 2 exposed in the radiation passage 12 can be increased, and the detection sensitivity can be improved.
In this embodiment, the gap 32 is set to have the same width in the X-axis direction and the Y-axis direction. However, when the dead space can be reduced in either direction, as shown in FIG. The width of the gap 32a parallel to the X-axis direction is reduced. By doing so, the gap 32a exposed in the radiation passage 12 can be reduced and the ratio of the detection surface 31a can be increased, so that the detection sensitivity can be improved.

(Third embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
In the present embodiment, a collimator used in the detector according to the second embodiment described above will be described.

As shown in FIG. 8, the collimator 4 according to the present embodiment includes a plurality of radiation paths 42 partitioned by a partition wall 41. The radiation path 42 has a predetermined length, and detects only γ-rays S1 incident on the radiation path 42 at a certain limited angle among the γ-rays (radiation) emitted from the γ-ray source S. Guide to vessel 3 (see FIG. 2). The predetermined length can be determined according to the angle of γ rays incident on the detector 3.
As shown in FIG. 8, the radiation passage 42 is formed in a substantially square shape in plan view, like the shape and dimensions of the detection surface 310 of the detector 3. As the size of the radiation passage 42 is reduced, the spatial resolution is increased.
Further, the partition wall 41 is made of a material such as lead so as to absorb γ rays incident from other than a limited angle. The partition wall 41 has a predetermined thickness 41a. The predetermined thickness 41 a of the partition wall 41 is the same as the thickness 32 a of the gap 32 of the detector 3.

  As shown in FIG. 8, the collimator 4 configured as described above has the gap 32 between the partition wall 41 of the radiation path 42 and the detector 3 in plan view so that the radiation path 42 faces the detection surface 310. Are arranged to overlap.

According to the above, the following effects can be obtained in the present embodiment.
Since the gap 32 of the detector 3 overlaps the partition wall 41 of the collimator 4 efficiently, the ratio of the detection surface 31a of the detector 3 exposed in the radiation passage 42 can be increased, and the detection sensitivity can be improved. The detection sensitivity can be made uniform.

It is a whole block diagram of SPECT which concerns on embodiment. It is a perspective view of the whole detector arrangement structure used by SPECT. It is a top view which shows a part of detector which has arrange | positioned the collimator on the upper surface. (A) is a figure which shows the dimension of the hexagon which passes along the centerline of a partition, (b) is a figure which shows the dimension of the rectangle which passes along the centerline of a clearance gap. It is a top view which shows a part of detector which has arrange | positioned the collimator on the upper surface. (A) is a figure which shows the dimension of the hexagon which passes along the centerline of a partition, (b) is a figure which shows the dimension of the rectangle which passes along the centerline of a clearance gap. It is a top view which shows a part of detector which has arrange | positioned the collimator on the upper surface. It is a top view explaining arrangement | positioning of a collimator and a detector. It is the figure which showed typically the structure of the principal part of the conventional gamma camera. It is a top view which shows the state which has arrange | positioned the collimator appropriately on the detector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,4 Collimator 2,3 Detector 11,41 Partition 12 Radiation path 21,31 Semiconductor element 22,32 Crevice 42 Radiation path

Claims (5)

A collimator having a regular hexagonal shape and having a plurality of radiation passages through which radiation passes, and a plurality of rectangular detection elements are provided along the two-dimensional orthogonal coordinate direction with a gap therebetween. A radiation detector arranged in a grid, and a nuclear medicine diagnostic apparatus in which the detector is arranged so that the detection element faces the radiation path,
The pitch of the detection elements in the first coordinate direction is set to be the same as the pitch of the opposing sides of the partition walls defining the radiation path;
The nuclear medicine diagnosis apparatus, wherein the center of the radiation path and the center of the detection element are arranged on the same coordinate with respect to the first coordinate. A partition that forms the radiation path and one side of the detection element are arranged in parallel with the first coordinate direction,
The nuclear medicine diagnosis apparatus according to claim 1, wherein the pitch of the detection elements is set to 1.5 times one side of the partition wall forming the radiation path.   The nuclear medicine diagnosis apparatus according to claim 2, wherein the center of the radiation path and the center of the detection element are arranged on the same coordinate with respect to the first coordinate.   One side of each of the detection element and the partition is arranged in parallel with the first coordinate direction, and the center of the radiation path and the center of the detection element are arranged on the same coordinate with respect to the first coordinate. The nuclear medicine diagnostic apparatus according to claim 2. A collimator used in a radiation detector configured by arranging a plurality of detection elements in a grid with a gap therebetween,
A plurality of radiation passages, through which radiation passes, are partitioned by a partition wall, and the radiation passage has a shape that is opposed to and coincides with each of the detection elements, and the partition wall is a gap between the detection elements. Collimator characterized in that it matches the width.

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