WO2016203954A1 - Radiation detector and x-ray ct apparatus provided therewith - Google Patents

Radiation detector and x-ray ct apparatus provided therewith Download PDF

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Publication number
WO2016203954A1
WO2016203954A1 PCT/JP2016/066204 JP2016066204W WO2016203954A1 WO 2016203954 A1 WO2016203954 A1 WO 2016203954A1 JP 2016066204 W JP2016066204 W JP 2016066204W WO 2016203954 A1 WO2016203954 A1 WO 2016203954A1
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radiation
ray
dimensional collimator
radiation detector
shielding
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PCT/JP2016/066204
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French (fr)
Japanese (ja)
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佐藤　誠
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株式会社日立製作所
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Priority to JP2017524797A priority Critical patent/JP6523451B2/en
Publication of WO2016203954A1 publication Critical patent/WO2016203954A1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computerised tomographs
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T7/00—Details of radiation-measuring instruments

Definitions

  • the present invention relates to a radiation detector that detects X-rays, ⁇ -rays, and the like, and more particularly to a scattered radiation removing unit provided on the radiation source side of the radiation detector for removing scattered radiation.
  • the present invention also relates to an X-ray CT apparatus provided with a radiation detector provided with such a scattered radiation removal unit.
  • An X-ray CT (Computed Tomography) device which is one of medical diagnostic imaging devices, is an X-ray tube device that irradiates a subject with X-rays, and an X-ray distribution that detects the distribution of the X-ray dose transmitted through the subject as projection data.
  • the tomographic image of the subject is reconstructed using projection data from a plurality of angles obtained by rotating the line detector around the subject, and the reconstructed tomographic image is displayed.
  • a tomographic image acquired by an X-ray CT apparatus describes the shape of an organ in a subject and is used for diagnostic imaging.
  • an indirect conversion type detector having a radiation detection element in which a phosphor element such as a ceramic scintillator and a light detection element such as a photodiode are combined is used. Mainly used. In addition, a direct conversion detector equipped with a semiconductor element as a radiation detection element is being used.
  • any type of radiation detector there is a structure in which a plurality of radiation detection element arrays in which about 1000 radiation detection elements are arranged on an arc centered on the X-ray focal point in the plane of rotation and a plurality of arrays in the direction of the rotation axis. It has been adopted.
  • recent X-ray CT apparatuses there is an apparatus having hundreds of radiation detection element arrays for the purpose of shortening the inspection time, and the radiation detector used is a relatively large size two-dimensional detector.
  • X-rays that have passed through the subject contain scattered rays, and the scattered rays have an adverse effect on the image quality of the tomographic image, so it is desirable to remove the scattered rays from the X-rays incident on the radiation detector as much as possible.
  • a channel direction collimator in which a large number of shielding plates are arranged along the rotation axis direction and a slice direction collimator in which a large number of shielding plates are arranged in parallel with the radiation detection element array are overlapped in the X-ray incident direction.
  • positioned at the X-ray tube apparatus side of the line detector is disclosed.
  • the shield plate is made of a thin metal plate that can sufficiently shield X-rays, and is arranged radially toward the X-ray focal point, so that these shield plates remove scattered radiation in the channel direction and slice direction. .
  • an object of the present invention is to provide a radiation detector in which a scattered radiation removing unit for removing scattered radiation in the channel direction and the slice direction is made compact with a simple structure, and a 4X-ray CT apparatus including the radiation detector.
  • the present invention provides a radiation detection element array in which a plurality of radiation detection elements for detecting radiation generated from a radiation source are arranged in a first direction and a second direction orthogonal to the first direction.
  • a one-dimensional collimator disposed on the radiation source side of the radiation detection element array along the first direction so that a plurality of shielding plates are directed to the radiation source, and a plurality of the collimators along the first direction.
  • a two-dimensional collimator arranged so that the first shielding wall is directed to the radiation source and a plurality of second shielding walls are directed to the radiation source along the second direction, and The one-dimensional collimator and the two-dimensional collimator are overlapped in the radiation incident direction.
  • the present invention it is possible to provide a radiation detector in which the scattered radiation removing unit for removing scattered radiation in the channel direction and the slice direction is made compact with a simple structure and a 4X-ray CT apparatus including the radiation detector.
  • the block diagram which shows the whole structure of the X-ray CT apparatus 1 of this invention
  • the figure explaining the positional relationship between the X-ray focal point 201 and the X-ray detector 106 The perspective view which shows the X-ray detector 106 of 1st embodiment. Sectional drawing which shows the X-ray detector 106 of 1st embodiment.
  • Diagram showing scattering angle ⁇ , ⁇ of scattered radiation The top view which shows the two-dimensional collimator 302 of 3rd embodiment.
  • FIG. 1 is a block diagram showing the overall configuration of the X-ray CT apparatus 1.
  • the X-ray CT apparatus 1 includes a scan gantry unit 100 and an operation unit 120.
  • the scan gantry unit 100 includes an X-ray tube device 101, a rotating disk 102, an irradiation field limiting unit 103, an X-ray detector 106, a data collection device 107, a bed device 105, a gantry control device 108, and a bed A control device 109, an X-ray control device 110, and a high voltage generator 111 are provided.
  • the X-ray tube apparatus 101 is an apparatus that irradiates a subject placed on the bed apparatus 105 with X-rays.
  • the irradiation field limiting unit 103 is a device that limits the radiation range of X-rays emitted from the X-ray tube device 101.
  • the rotating disk 102 includes an opening 104 into which the subject placed on the bed apparatus 105 enters, and is equipped with an X-ray tube device 101 and an X-ray detector 106, and rotates around the subject.
  • the X-ray detector 106 is a device that measures the spatial distribution of transmitted X-rays by detecting X-rays that are disposed opposite to the X-ray tube device 101 and transmitted through the subject. These are two-dimensionally arranged in the circumferential direction in the rotating surface (XY plane) of the rotating disk 102 and the rotating axis direction (direction parallel to the Z axis). Details of the X-ray detector 106, which is an example of a radiation detector, will be described later.
  • the data collection device 107 is a device that collects the X-ray dose detected by the X-ray detector 106 as digital data.
  • the gantry control device 108 is a device that controls the rotation of the rotary disk 102.
  • the bed control device 109 is a device that controls the vertical and horizontal movements of the bed device 105.
  • the high voltage generator 111 is a device that generates a high voltage applied to the X-ray tube apparatus 101.
  • the X-ray control device 110 is a device that controls the output of the high voltage generator 111.
  • the console 120 includes an input device 121, an image calculation device 122, a display device 125, a storage device 123, and a system control device 124.
  • the input device 121 is a device for inputting a subject's name, examination date and time, imaging conditions, and the like, specifically a keyboard or a pointing device.
  • the image calculation device 122 is a device that reconstructs a tomographic image by calculating the measurement data sent from the data collection device 107.
  • the display device 125 is a device that displays a tomographic image created by the image calculation device 122, and specifically, a CRT (Cathode-Ray® Tube), a liquid crystal display, or the like.
  • the storage device 123 is a device that stores data collected by the data collection device 107 and image data of a tomographic image created by the image calculation device 122, and is specifically an HDD (Hard Disk Disk Drive) or the like.
  • the system control device 124 is a device that controls these devices, the gantry control device 108, the bed control device 109, and the X-ray control device 110.
  • the X-ray controller 110 controls the high-voltage generator 111 based on the imaging conditions input from the input device 121, in particular, the tube voltage and the tube current. Power is supplied. With the supplied power, the X-ray tube apparatus 101 irradiates the subject with X-rays according to the imaging conditions.
  • the X-ray detector 106 detects X-rays irradiated from the X-ray tube apparatus 101 and transmitted through the subject with a large number of X-ray detection elements, and measures the distribution of transmitted X-rays.
  • the rotating disk 102 is controlled by the gantry control device 108 and rotates based on the photographing conditions input from the input device 121, particularly the rotation speed.
  • the couch device 105 is controlled by the couch control device 109 and operates based on the imaging conditions input from the input device 121, particularly the helical pitch.
  • X-ray irradiation from the X-ray tube apparatus 101 and transmission X-ray distribution measurement by the X-ray detector 106 are repeated along with the rotation of the rotating disk 102, whereby projection data from various angles is acquired.
  • the projection data is associated with a view representing each angle, a channel (ch) number and a column number that are detection element numbers of the X-ray detector 106.
  • the acquired projection data from various angles is transmitted to the image processing device 122.
  • the image processing device 122 reconstructs a tomographic image by backprojecting the transmitted projection data from various angles.
  • the tomographic image obtained by reconstruction is displayed on the display device 125.
  • the X-ray detector 106 will be described with reference to FIG. Note that the X-ray detector 106 is an example of a radiation detector, and is a device that measures an X-ray dose that is an amount of X-rays that are a kind of radiation.
  • FIG. 2 is a diagram showing the positional relationship between the X-ray focal point 201 which is a radiation source and the X-ray detector 106.
  • the X-ray detector 106 includes a scattered radiation removal unit 202 and a detection element module 203.
  • the scattered radiation removing unit 202 removes scattered radiation generated in the subject or the like.
  • X-rays including scattered radiation are detected by the X-ray detector 106, the X-ray dose attenuated in the subject is detected.
  • the image quality of the reconstructed tomographic image is deteriorated due to incorrect measurement.
  • the detailed structure of the scattered radiation removing unit 202 which is the main part of the present invention, will be described later.
  • the detection element module 203 measures the spatial distribution of X-rays transmitted through the scattered radiation removal unit 202, and is configured by two-dimensionally arranging X-ray detection elements for measuring an X-ray dose on a flat plate. .
  • the X-ray detection element is an example of a radiation detection element.
  • the X-ray detector 106 is provided with a plurality of detection element modules 203 so as to form a polygonal shape formed by a tangent line of an arc centering on the X-ray focal point 201 on the rotating surface (XY plane) of the rotating disk 102. Each detection element module 203 is arranged.
  • the X-ray detection elements are substantially arranged on an arc centered on the X-ray focal point 201.
  • FIG. 2 only seven detection element modules 203 are drawn to simplify the drawing, but the number of detection element modules 203 is not limited to seven.
  • FIG. 3 is a perspective view of the scattered radiation removal unit 202 and the detection element module 203.
  • the scattered radiation removing unit 202 is configured by superimposing a one-dimensional collimator 301 and a two-dimensional collimator 302 in the X-ray incident direction.
  • the detection element module 203 is configured by laminating a scintillator array 303 and a photodiode array 304 in the X-ray incident direction.
  • the one-dimensional collimator 301 is composed of a plurality of shielding plates 301a.
  • the shielding plate 301a is a member that can sufficiently shield X-rays, for example, a heavy metal plate material such as tungsten or molybdenum, and is arranged along the rotation axis direction of the rotating disk 102, that is, along the slice direction (Z direction). They are arranged in the tangential direction of the rotating disk 102, that is, in the channel direction (X direction) so as to be directed to the line focal point 201. Thereby, the scattered radiation in the channel direction that easily affects the image quality can be effectively reduced.
  • the two-dimensional collimator 302 includes a plurality of first shielding walls 302a and a plurality of second shielding walls 302b.
  • the first shielding wall 302a is a member capable of sufficiently shielding X-rays, for example, a heavy metal wall such as tungsten or molybdenum, and is arranged along the slice direction (Z direction) so that each point toward the X-ray focal point 201. Are arranged in the channel direction (X direction).
  • the second shielding wall 302b is also a wall of a member that can sufficiently shield X-rays, and is arranged along the channel direction (X direction), and each slice direction (Z direction) is directed to the X-ray focal point 201. Arranged.
  • FIG. 4 is an XY cross-sectional view of FIG.
  • the one-dimensional collimator 301, the two-dimensional collimator 302, the scintillator array 303, and the photodiode array 304 are arranged in this order from the X-ray focal point 201 side.
  • the scintillator array 303 includes a scintillator element 303a and a reflective material 303b.
  • the scintillator element 303a emits visible light in an amount corresponding to the X-ray dose when X-rays are incident, and a plurality of scintillator elements 303a are two-dimensionally arranged on a plane orthogonal to the X-ray incident direction, that is, the XZ plane.
  • the reflective material 303b reflects visible light emitted from the scintillator element 303a, and covers a surface other than the surface facing the photodiode array 304 of the scintillator element 303a.
  • the photodiode array 304 includes photodiode elements so as to face the scintillator elements 303a.
  • the photodiode element converts visible light emitted from the scintillator element 303a into an electric signal, and sends the electric signal to an AD conversion circuit (not shown).
  • the detection element module 203 described with reference to FIGS. 3 and 4 is an indirect conversion type detector because the scintillator element 303a and the photodiode element constitute an X-ray detection element.
  • the X-ray detection element is a semiconductor element. A direct conversion detector may be used.
  • the X-ray detection element is an example of a radiation detection element.
  • Both the shielding plate 301a of the one-dimensional collimator 301 and the first shielding wall 302a of the two-dimensional collimator 302 are configured by members capable of sufficiently shielding X-rays, and each point toward the X-ray focal point 201 as shown in FIG. Are arranged as follows. With such a structure, most of the direct X-rays that are linearly transmitted through the subject from the X-ray focal point 201 are transmitted through the one-dimensional collimator 301 and the two-dimensional collimator 302 and reach the X-ray detection element.
  • FIG. 5 shows an example of the scattering angle of scattered radiation that can be removed by the scattered radiation removing unit having the structure shown in FIG.
  • the scattering angle is expressed in polar coordinates as shown in FIG. 6, the scattering angle ⁇ is an angle formed by the X-ray incident surface of the X-ray detection element and the scattered radiation, and the scattering angle ⁇ is X of the X-ray detection element. This is the angle between the X-axis and the line on which the scattered radiation is projected onto the line incident surface.
  • the vertical axis is the scattering angle ⁇
  • the horizontal axis is the scattering angle ⁇
  • the total H X of the height of the shielding plate 301a and the height of the first shielding wall 302a is fixed to 15 mm
  • the second shielding The scattering angles ⁇ and ⁇ of scattered radiation that can enter the X-ray detection element when the height H Z of the wall 302b is changed to 0, 5, 10, and 15 mm are shown. That is, it is indicated that the light can be incident on the X-ray detection element if the scattering angle is higher than each broken line in FIG.
  • the scattering angle ⁇ decreases as the scattering angle ⁇ increases, and in particular, scattering occurs when the scattering angle ⁇ is 80 [deg.] Or more.
  • the angle ⁇ decreases rapidly.
  • the scattering angle ⁇ 80 [deg.]
  • the scattering angle ⁇ 72 [deg.]
  • the scattering angle ⁇ 85 [deg.]
  • the manufacturing time can be reduced in a short time.
  • the height of the second shielding wall 302b is low, the shadow caused by the presence of the second shielding wall 302b when the X-ray focal point moves can be reduced as much as possible, and the influence on the image quality of the tomographic image is suppressed. it can.
  • the scattered radiation removal unit 202 of the present embodiment and A plurality of detection element modules 203 may be provided in the rotation axis direction.
  • the alignment irregularities are formed on the detection element module 203 side of the one-dimensional collimator 301 or the X-ray focal point 201 side of the two-dimensional collimator 302. May be provided as appropriate.
  • unevenness for alignment is provided on the detection element module 203 side of the two-dimensional collimator 302 or the X-ray focal point 201 side of the detection element module 203. You may provide suitably.
  • the thickness W1 of the shielding plate 301a of the one-dimensional collimator 301 is made thinner than the thickness W2 of the first shielding wall 302a of the two-dimensional collimator 302.
  • the shielding plate 301a having a height higher than the height of the two-dimensional collimator 302 is warped, deformed by the centrifugal force generated by the rotation of the rotating disk 102, or the mounting position accuracy is not appropriate.
  • the first shielding wall 302a can suppress the shadow of the shielding plate 301a from being applied to the X-ray detection element. That is, it is not necessary to deteriorate the image quality of the tomographic image obtained by the X-ray CT apparatus.
  • FIG. 1 A third embodiment of the present invention will be described.
  • the relationship between the thickness of the shielding plate 301a of the one-dimensional collimator 301 and the thickness of the first shielding wall 302a of the two-dimensional collimator 302 has been described.
  • the relationship between the thickness of the first shielding wall 302a and the thickness of the second shielding wall 302b of the two-dimensional collimator 302 will be described with reference to FIG.
  • FIG. 7 is a plan view of the two-dimensional collimator 302 as seen from the X-ray focal point 201 side.
  • the thickness W2 of the first shielding wall 302a of the two-dimensional collimator 302 is made thicker than the thickness W3 of the second shielding wall 302b.
  • the dose of direct X-rays incident on the X-ray detection element is reduced, and the image quality of the tomographic image obtained by the X-ray CT apparatus is deteriorated.
  • the crosstalk in the rotation plane of the rotating disk 102 has a larger influence on the image quality degradation of the tomographic image than the crosstalk in the rotation axis direction.
  • the thickness W2 of the first shielding wall 302a thicker than the thickness W3 of the second shielding wall 302b as in the present embodiment, the crosstalk in the rotation plane is suppressed and incident on the X-ray detection element. You can increase the direct X-ray dose. That is, it is not necessary to deteriorate the image quality of the tomographic image obtained by the X-ray CT apparatus.
  • the scattered radiation removal unit 202 has a structure in which the one-dimensional collimator 301 and the two-dimensional collimator 302 are stacked in this order from the X-ray focal point 201 side.
  • a structure in which the original collimators 301 are stacked in this order may be employed.
  • X-ray CT device 100 scan gantry unit, 101 X-ray tube device, 102 rotating disk, 103 irradiation field restriction unit, 104 opening, 105 bed device, 106 X-ray detector, 107 data collection device, 108 gantry control device 109, bed control device, 110 X-ray control device, 111 high voltage generation device, 120 console, 121 input device, 122 image calculation device, 123 storage device, 124 system control device, 125 display device, 201 X-ray focus, 202 Scattering ray removal unit, 203 detection element module, 301 one-dimensional collimator, 301a shielding plate, 302 two-dimensional collimator, 302a first shielding wall, 302b second shielding wall, 303 scintillator array, 303a scintillator element, 303b reflector, 304 photo Diode array

Abstract

Provided is an X-ray CT apparatus provided with: a radiation detecting element array including a plurality of radiation detecting elements for detecting radiation generated from a radiation source arranged in a first direction and a second direction perpendicular to the first direction; a one-dimensional collimator including a plurality of shielding plates arranged along the first direction on the side of the radiation detecting element array closer to the radiation source so as to be pointed toward the radiation source; and a two-dimensional collimator including a plurality of first shielding walls arranged along the first direction so as to be pointed toward the radiation source, and a plurality of second shielding walls arranged along the second direction so as to be pointed toward the radiation source, wherein the one-dimensional collimator and the two-dimensional collimator are placed one behind the other in the radiation incident direction.

Description

放射線検出器とそれを備えたＸ線ＣＴ装置Radiation detector and X-ray CT apparatus provided with the same
　本発明は、X線、γ線などを検出する放射線検出器に係り、特に散乱線を除去するために放射線検出器の放射線源側に設けられる散乱線除去部に関する。またそのような散乱線除去部が設けられた放射線検出器を備えたX線CT装置に関する。 The present invention relates to a radiation detector that detects X-rays, γ-rays, and the like, and more particularly to a scattered radiation removing unit provided on the radiation source side of the radiation detector for removing scattered radiation. The present invention also relates to an X-ray CT apparatus provided with a radiation detector provided with such a scattered radiation removal unit.
　医用画像診断装置の一つであるX線CT(Computed Tomography)装置とは、被検体にX線を照射するX線管装置と、被検体を透過したX線量の分布を投影データとして検出するX線検出器と、を被検体の周囲で回転させることにより得られる複数角度からの投影データを用いて被検体の断層画像を再構成し、再構成された断層画像を表示するものである。X線CT装置で取得される断層画像は、被検体の中の臓器の形状を描写するものであり、画像診断に使用される。 An X-ray CT (Computed Tomography) device, which is one of medical diagnostic imaging devices, is an X-ray tube device that irradiates a subject with X-rays, and an X-ray distribution that detects the distribution of the X-ray dose transmitted through the subject as projection data. The tomographic image of the subject is reconstructed using projection data from a plurality of angles obtained by rotating the line detector around the subject, and the reconstructed tomographic image is displayed. A tomographic image acquired by an X-ray CT apparatus describes the shape of an organ in a subject and is used for diagnostic imaging.
　X線CT装置用のX線検出器に代表される放射線検出器では、セラミックシンチレータなどの蛍光体素子と、フォトダイオードなどの光検出素子を組み合わせた放射線検出素子を備えた間接変換型検出器が主に用いられている。また半導体素子を放射線検出素子として備えた直接変換型検出器も用いられつつある。いずれの型の放射線検出器でも、回転面内においてX線焦点を中心とした円弧上に1000個程度の放射線検出素子を並べた放射線検出素子列を、さらに回転軸方向に複数列並べた構造が採用されている。近年のX線CT装置には検査時間の短縮を主たる目的として放射線検出素子列が数百列にも及ぶ装置があり、用いられる放射線検出器は比較的大型サイズの二次元検出器となる。 In radiation detectors typified by X-ray detectors for X-ray CT devices, an indirect conversion type detector having a radiation detection element in which a phosphor element such as a ceramic scintillator and a light detection element such as a photodiode are combined is used. Mainly used. In addition, a direct conversion detector equipped with a semiconductor element as a radiation detection element is being used. In any type of radiation detector, there is a structure in which a plurality of radiation detection element arrays in which about 1000 radiation detection elements are arranged on an arc centered on the X-ray focal point in the plane of rotation and a plurality of arrays in the direction of the rotation axis. It has been adopted. In recent X-ray CT apparatuses, there is an apparatus having hundreds of radiation detection element arrays for the purpose of shortening the inspection time, and the radiation detector used is a relatively large size two-dimensional detector.
　被検体を透過したX線には散乱線が含まれており、散乱線は断層画像の画質に悪影響を与えるので、放射線検出器に入射するX線から散乱線をできるだけ除去することが望ましい。特許文献1には、遮蔽板を回転軸方向に沿って多数配列したチャネル方向コリメータと、遮蔽板を放射線検出素子列と平行に多数配列したスライス方向コリメータとをX線入射方向に重ねて、X線検出器のX線管装置側に配置された散乱線除去部を備えた構成が開示されている。遮蔽板はX線を十分に遮蔽可能な金属の薄板で構成され、X線焦点に向かって放射状に配置されているので、これらの遮蔽板によってチャネル方向及びスライス方向への散乱線が除去される。 X-rays that have passed through the subject contain scattered rays, and the scattered rays have an adverse effect on the image quality of the tomographic image, so it is desirable to remove the scattered rays from the X-rays incident on the radiation detector as much as possible. In Patent Document 1, a channel direction collimator in which a large number of shielding plates are arranged along the rotation axis direction and a slice direction collimator in which a large number of shielding plates are arranged in parallel with the radiation detection element array are overlapped in the X-ray incident direction. The structure provided with the scattered-radiation removal part arrange | positioned at the X-ray tube apparatus side of the line detector is disclosed. The shield plate is made of a thin metal plate that can sufficiently shield X-rays, and is arranged radially toward the X-ray focal point, so that these shield plates remove scattered radiation in the channel direction and slice direction. .
特開平10-5207号公報Japanese Patent Laid-Open No. 10-5207
　しかしながら、特許文献1では、チャネル方向コリメータとスライス方向コリメータとがX線入射方向に重ねられた構成であるので、散乱線を十分に除去するためには各々の遮蔽板の高さを十分に高くする必要があり、そうした場合、散乱線除去部のトータル高さが大きくなり、X線CT装置に放射線検出器を収めることが困難になる。 However, in Patent Document 1, since the channel direction collimator and the slice direction collimator are stacked in the X-ray incident direction, the height of each shielding plate is sufficiently high in order to sufficiently remove scattered radiation. In such a case, the total height of the scattered radiation removal unit becomes large, and it becomes difficult to fit the radiation detector in the X-ray CT apparatus.
　そこで本発明の目的は、チャネル方向及びスライス方向への散乱線を除去する散乱線除去部を簡易な構造でコンパクトにした放射線検出器及びそれを備えた4X線CT装置を提供することである。 Therefore, an object of the present invention is to provide a radiation detector in which a scattered radiation removing unit for removing scattered radiation in the channel direction and the slice direction is made compact with a simple structure, and a 4X-ray CT apparatus including the radiation detector.
　上記目的を達成するために本発明は、放射線源から発生した放射線を検出する複数の放射線検出素子が第1の方向及び第1の方向と直交する第2の方向に配置された放射線検出素子アレイと、前記放射線検出素子アレイの前記放射線源の側に第1の方向に沿って複数の遮蔽板が放射線源を指向するように配置される一次元コリメータと、第1の方向に沿って複数の第一遮蔽壁が放射線源を指向するように配置されるとともに、第2の方向に沿って複数の第二遮蔽壁が放射線源を指向するように配置される二次元コリメータと、を備え、前記一次元コリメータと前記二次元コリメータとが放射線入射方向に重ねられることを特徴とする。 To achieve the above object, the present invention provides a radiation detection element array in which a plurality of radiation detection elements for detecting radiation generated from a radiation source are arranged in a first direction and a second direction orthogonal to the first direction. A one-dimensional collimator disposed on the radiation source side of the radiation detection element array along the first direction so that a plurality of shielding plates are directed to the radiation source, and a plurality of the collimators along the first direction. A two-dimensional collimator arranged so that the first shielding wall is directed to the radiation source and a plurality of second shielding walls are directed to the radiation source along the second direction, and The one-dimensional collimator and the two-dimensional collimator are overlapped in the radiation incident direction.
　本発明によれば、チャネル方向及びスライス方向への散乱線を除去する散乱線除去部を簡易な構造でコンパクトにした放射線検出器及びそれを備えた4X線CT装置を提供することができる。 According to the present invention, it is possible to provide a radiation detector in which the scattered radiation removing unit for removing scattered radiation in the channel direction and the slice direction is made compact with a simple structure and a 4X-ray CT apparatus including the radiation detector.
本発明のX線CT装置1の全体構成を示すブロック図The block diagram which shows the whole structure of the X-ray CT apparatus 1 of this invention X線焦点201とX線検出器106との位置関係を説明する図The figure explaining the positional relationship between the X-ray focal point 201 and the X-ray detector 106 第一の実施形態のX線検出器106を示す斜視図The perspective view which shows the X-ray detector 106 of 1st embodiment. 第一の実施形態のX線検出器106を示す断面図Sectional drawing which shows the X-ray detector 106 of 1st embodiment. 散乱線除去部202により除去可能な散乱線の散乱角Φ、θを示す図The figure which shows the scattering angles (PHI) and (theta) of the scattered radiation which can be removed by the scattered radiation removal part 202. 散乱線の散乱角Φ、θを示す図Diagram showing scattering angle Φ, θ of scattered radiation 第三の実施形態の二次元コリメータ302を示す平面図The top view which shows the two-dimensional collimator 302 of 3rd embodiment.
　以下、添付図面に従って本発明に係るX線CT装置の好ましい実施形態について説明する。なお、以下の説明及び添付図面において、同一の機能構成を有する構成要素については、同一の符号を付けることにより重複説明を省略することにする。また、各図の向きの理解を助けるために、必要に応じて図の左下にXYZ座標系を示す。 Hereinafter, preferred embodiments of the X-ray CT apparatus according to the present invention will be described with reference to the accompanying drawings. In the following description and the accompanying drawings, the same reference numerals are given to constituent elements having the same functional configuration, and redundant description is omitted. In order to help understand the orientation of each figure, the XYZ coordinate system is shown at the bottom left of the figure as needed.
　(第一の実施形態)
　まず、図1を用いて本実施形態の医用画像診断装置の一例であるX線CT装置の全体構成を説明する。図1は、X線CT装置1の全体構成を示すブロック図である。図1に示すようにX線CT装置1は、スキャンガントリ部100と操作ユニット120とを備える。 (First embodiment)
First, the overall configuration of an X-ray CT apparatus which is an example of the medical image diagnostic apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of the X-ray CT apparatus 1. As shown in FIG. As shown in FIG. 1, the X-ray CT apparatus 1 includes a scan gantry unit 100 and an operation unit 120.
　スキャンガントリ部100は、X線管装置101と、回転円盤102と、照射野制限部103と、X線検出器106と、データ収集装置107と、寝台装置105と、ガントリ制御装置108と、寝台制御装置109と、X線制御装置110と、高電圧発生装置111を備えている。X線管装置101は寝台装置105上に載置された被検体にX線を照射する装置である。照射野制限部103はX線管装置101から照射されるX線の放射範囲を制限する装置である。 The scan gantry unit 100 includes an X-ray tube device 101, a rotating disk 102, an irradiation field limiting unit 103, an X-ray detector 106, a data collection device 107, a bed device 105, a gantry control device 108, and a bed A control device 109, an X-ray control device 110, and a high voltage generator 111 are provided. The X-ray tube apparatus 101 is an apparatus that irradiates a subject placed on the bed apparatus 105 with X-rays. The irradiation field limiting unit 103 is a device that limits the radiation range of X-rays emitted from the X-ray tube device 101.
　回転円盤102は、寝台装置105上に載置された被検体が入る開口部104を備えるとともに、X線管装置101とX線検出器106を搭載し、被検体の周囲を回転するものである。X線検出器106は、X線管装置101と対向配置され被検体を透過したX線を検出することにより透過X線の空間的な分布を計測する装置であり、多数のX線検出素子を回転円盤102の回転面(XY面)内の周方向と回転軸方向(Z軸と平行な方向)との二次元に配列したものである。なお、放射線検出器の一例であるX線検出器106の詳細については後述する。 The rotating disk 102 includes an opening 104 into which the subject placed on the bed apparatus 105 enters, and is equipped with an X-ray tube device 101 and an X-ray detector 106, and rotates around the subject. . The X-ray detector 106 is a device that measures the spatial distribution of transmitted X-rays by detecting X-rays that are disposed opposite to the X-ray tube device 101 and transmitted through the subject. These are two-dimensionally arranged in the circumferential direction in the rotating surface (XY plane) of the rotating disk 102 and the rotating axis direction (direction parallel to the Z axis). Details of the X-ray detector 106, which is an example of a radiation detector, will be described later.
　データ収集装置107は、X線検出器106で検出されたX線量をデジタルデータとして収集する装置である。ガントリ制御装置108は回転円盤102の回転を制御する装置である。寝台制御装置109は、寝台装置105の上下左右前後動を制御する装置である。高電圧発生装置111はX線管装置101に印加される高電圧を発生する装置である。X線制御装置110は、高電圧発生装置111の出力を制御する装置である。 The data collection device 107 is a device that collects the X-ray dose detected by the X-ray detector 106 as digital data. The gantry control device 108 is a device that controls the rotation of the rotary disk 102. The bed control device 109 is a device that controls the vertical and horizontal movements of the bed device 105. The high voltage generator 111 is a device that generates a high voltage applied to the X-ray tube apparatus 101. The X-ray control device 110 is a device that controls the output of the high voltage generator 111.
　操作卓120は、入力装置121と、画像演算装置122と、表示装置125と、記憶装置123と、システム制御装置124とを備えている。入力装置121は、被検体氏名、検査日時、撮影条件などを入力するための装置であり、具体的にはキーボードやポインティングデバイスである。画像演算装置122は、データ収集装置107から送出される計測データを演算処理して断層画像を再構成する装置である。 The console 120 includes an input device 121, an image calculation device 122, a display device 125, a storage device 123, and a system control device 124. The input device 121 is a device for inputting a subject's name, examination date and time, imaging conditions, and the like, specifically a keyboard or a pointing device. The image calculation device 122 is a device that reconstructs a tomographic image by calculating the measurement data sent from the data collection device 107.
　表示装置125は、画像演算装置122で作成された断層画像を表示する装置であり、具体的にはCRT(Cathode-Ray Tube)や液晶ディスプレイ等である。記憶装置123は、データ収集装置107で収集したデータ及び画像演算装置122で作成された断層画像の画像データを記憶する装置であり、具体的にはHDD(Hard Disk Drive)等である。システム制御装置124は、これらの装置及びガントリ制御装置108と寝台制御装置109とX線制御装置110を制御する装置である。 The display device 125 is a device that displays a tomographic image created by the image calculation device 122, and specifically, a CRT (Cathode-Ray® Tube), a liquid crystal display, or the like. The storage device 123 is a device that stores data collected by the data collection device 107 and image data of a tomographic image created by the image calculation device 122, and is specifically an HDD (Hard Disk Disk Drive) or the like. The system control device 124 is a device that controls these devices, the gantry control device 108, the bed control device 109, and the X-ray control device 110.
　入力装置121から入力された撮影条件、特に管電圧と管電流などに基づいてX線制御装置110が高電圧発生装置111を制御することにより、高電圧発生装置111からX線管装置101に所定の電力が供給される。供給された電力により、X線管装置101は撮影条件に応じたX線を被検体に照射する。X線検出器106は、X線管装置101から照射され被検体を透過したX線を多数のX線検出素子で検出し、透過X線の分布を計測する。 The X-ray controller 110 controls the high-voltage generator 111 based on the imaging conditions input from the input device 121, in particular, the tube voltage and the tube current. Power is supplied. With the supplied power, the X-ray tube apparatus 101 irradiates the subject with X-rays according to the imaging conditions. The X-ray detector 106 detects X-rays irradiated from the X-ray tube apparatus 101 and transmitted through the subject with a large number of X-ray detection elements, and measures the distribution of transmitted X-rays.
　回転円盤102はガントリ制御装置108により制御され、入力装置121から入力された撮影条件、特に回転速度等に基づいて回転する。寝台装置105は寝台制御装置109によって制御され、入力装置121から入力された撮影条件、特にらせんピッチ等に基づいて動作する。 The rotating disk 102 is controlled by the gantry control device 108 and rotates based on the photographing conditions input from the input device 121, particularly the rotation speed. The couch device 105 is controlled by the couch control device 109 and operates based on the imaging conditions input from the input device 121, particularly the helical pitch.
　X線管装置101からのX線照射とX線検出器106による透過X線分布の計測が回転円盤102の回転とともに繰り返されることにより、様々な角度からの投影データが取得される。投影データは、各角度を表すビュー(View)と、X線検出器106の検出素子番号であるチャネル(ch)番号及び列番号と対応付けられる。取得された様々な角度からの投影データは画像処理装置122に送信される。画像処理装置122は送信された様々な角度からの投影データを逆投影処理することにより断層画像を再構成する。再構成して得られた断層画像は表示装置125に表示される。 X-ray irradiation from the X-ray tube apparatus 101 and transmission X-ray distribution measurement by the X-ray detector 106 are repeated along with the rotation of the rotating disk 102, whereby projection data from various angles is acquired. The projection data is associated with a view representing each angle, a channel (ch) number and a column number that are detection element numbers of the X-ray detector 106. The acquired projection data from various angles is transmitted to the image processing device 122. The image processing device 122 reconstructs a tomographic image by backprojecting the transmitted projection data from various angles. The tomographic image obtained by reconstruction is displayed on the display device 125.
　図2を用いてX線検出器106について説明する。なおX線検出器106は放射線検出器の一例であり、放射線の一種であるX線の量であるX線量を計測する装置である。図2は放射線源であるX線焦点201とX線検出器106との位置関係を示す図である。X線検出器106は散乱線除去部202と検出素子モジュール203とを備えている。 The X-ray detector 106 will be described with reference to FIG. Note that the X-ray detector 106 is an example of a radiation detector, and is a device that measures an X-ray dose that is an amount of X-rays that are a kind of radiation. FIG. 2 is a diagram showing the positional relationship between the X-ray focal point 201 which is a radiation source and the X-ray detector 106. The X-ray detector 106 includes a scattered radiation removal unit 202 and a detection element module 203.
　散乱線除去部202は、被検体等で発生した散乱線を除去するものであり、散乱線を含んだX線がX線検出器106で検出されると、被検体で減弱されたX線量が正しく計測されず、再構成された断層画像の画質が劣化する。本発明の要部である散乱線除去部202の詳細な構造は後述する。 The scattered radiation removing unit 202 removes scattered radiation generated in the subject or the like. When X-rays including scattered radiation are detected by the X-ray detector 106, the X-ray dose attenuated in the subject is detected. The image quality of the reconstructed tomographic image is deteriorated due to incorrect measurement. The detailed structure of the scattered radiation removing unit 202, which is the main part of the present invention, will be described later.
　検出素子モジュール203は、散乱線除去部202を透過したX線の空間的な分布を計測するものであり、X線量を計測するX線検出素子が平板上で二次元に配列されて構成される。X線検出素子は放射線検出素子の一例である。X線検出器106には、複数の検出素子モジュール203が備えられ、回転円盤102の回転面(XY面)においてX線焦点201を中心とする円弧の接線で形成される多角形状をなすように各検出素子モジュール203が配置される。このように各検出素子モジュール203が配置されることにより、X線検出素子はX線焦点201を中心とする円弧上にほぼ配置されることになる。なお、図2では図面を簡略化するために検出素子モジュール203を7つしか描いていないが、検出素子モジュール203の数は7つに限定されるものでない。 The detection element module 203 measures the spatial distribution of X-rays transmitted through the scattered radiation removal unit 202, and is configured by two-dimensionally arranging X-ray detection elements for measuring an X-ray dose on a flat plate. . The X-ray detection element is an example of a radiation detection element. The X-ray detector 106 is provided with a plurality of detection element modules 203 so as to form a polygonal shape formed by a tangent line of an arc centering on the X-ray focal point 201 on the rotating surface (XY plane) of the rotating disk 102. Each detection element module 203 is arranged. By arranging the detection element modules 203 in this way, the X-ray detection elements are substantially arranged on an arc centered on the X-ray focal point 201. In FIG. 2, only seven detection element modules 203 are drawn to simplify the drawing, but the number of detection element modules 203 is not limited to seven.
　図3乃至図5を用いて散乱線除去部202と検出素子モジュール203のより具体的な構造について説明する。 A more specific structure of the scattered radiation removal unit 202 and the detection element module 203 will be described with reference to FIGS.
　図3は散乱線除去部202と検出素子モジュール203の斜視図である。散乱線除去部202は一次元コリメータ301と2次元コリメータ302とがX線入射方向に重ねられて構成される。検出素子モジュール203はシンチレータアレイ303とフォトダイオードアレイ304とがX線入射方向に積層されて構成される。 FIG. 3 is a perspective view of the scattered radiation removal unit 202 and the detection element module 203. FIG. The scattered radiation removing unit 202 is configured by superimposing a one-dimensional collimator 301 and a two-dimensional collimator 302 in the X-ray incident direction. The detection element module 203 is configured by laminating a scintillator array 303 and a photodiode array 304 in the X-ray incident direction.
　一次元コリメータ301は複数の遮蔽板301aによって構成される。遮蔽板301aはX線を十分に遮蔽可能な部材、例えばタングステンやモリブデン等の重金属の板材であり、回転円盤102の回転軸方向、すなわちスライス方向(Z方向)に沿って配置され、各々がX線焦点201を指向するように、回転円盤102の接線方向、すなわちチャネル方向(X方向)に配列される。これにより、画質に影響を及ぼしやすいチャネル方向の散乱線を効果的に低減することができる。 The one-dimensional collimator 301 is composed of a plurality of shielding plates 301a. The shielding plate 301a is a member that can sufficiently shield X-rays, for example, a heavy metal plate material such as tungsten or molybdenum, and is arranged along the rotation axis direction of the rotating disk 102, that is, along the slice direction (Z direction). They are arranged in the tangential direction of the rotating disk 102, that is, in the channel direction (X direction) so as to be directed to the line focal point 201. Thereby, the scattered radiation in the channel direction that easily affects the image quality can be effectively reduced.
　二次元コリメータ302は、複数の第一遮蔽壁302aと複数の第二遮蔽壁302bによって構成される。第一遮蔽壁302aはX線を十分に遮蔽可能な部材、例えばタングステンやモリブデン等の重金属の壁であり、スライス方向(Z方向)に沿って配置され、各々がX線焦点201を指向するように、チャネル方向(X方向)に配列される。第二遮蔽壁302bもX線を十分に遮蔽可能な部材の壁であり、チャネル方向(X方向)に沿って配置され、各々がX線焦点201を指向するように、スライス方向(Z方向)に配列される。 The two-dimensional collimator 302 includes a plurality of first shielding walls 302a and a plurality of second shielding walls 302b. The first shielding wall 302a is a member capable of sufficiently shielding X-rays, for example, a heavy metal wall such as tungsten or molybdenum, and is arranged along the slice direction (Z direction) so that each point toward the X-ray focal point 201. Are arranged in the channel direction (X direction). The second shielding wall 302b is also a wall of a member that can sufficiently shield X-rays, and is arranged along the channel direction (X direction), and each slice direction (Z direction) is directed to the X-ray focal point 201. Arranged.
　図4は図3のXY断面図である。本実施形態ではX線焦点201側から、一次元コリメータ301、二次元コリメータ302、シンチレータアレイ303、フォトダイオードアレイ304の順に配置される。 4 is an XY cross-sectional view of FIG. In the present embodiment, the one-dimensional collimator 301, the two-dimensional collimator 302, the scintillator array 303, and the photodiode array 304 are arranged in this order from the X-ray focal point 201 side.
　シンチレータアレイ303は、シンチレータ素子303aと、反射材303bから構成されている。シンチレータ素子303aはX線が入射するとX線量に応じた量の可視光を発するものであり、X線入射方向と直交する平面、すなわちXZ面上に二次元に複数配置される。反射材303bはシンチレータ素子303aが発する可視光を反射するものであり、シンチレータ素子303aのフォトダイオードアレイ304と対向する面以外の面を覆う。 The scintillator array 303 includes a scintillator element 303a and a reflective material 303b. The scintillator element 303a emits visible light in an amount corresponding to the X-ray dose when X-rays are incident, and a plurality of scintillator elements 303a are two-dimensionally arranged on a plane orthogonal to the X-ray incident direction, that is, the XZ plane. The reflective material 303b reflects visible light emitted from the scintillator element 303a, and covers a surface other than the surface facing the photodiode array 304 of the scintillator element 303a.
　フォトダイオードアレイ304は、各シンチレータ素子303aに対向するようにフォトダイオード素子を備えている。フォトダイオード素子はシンチレータ素子303aが発する可視光を電気信号に変換し、図示しないAD変換回路に電気信号を送る。図3、図4を用いて説明した検出素子モジュール203は、シンチレータ素子303aとフォトダイオード素子とでX線検出素子を構成するので間接変換型検出器であるが、半導体素子でX線検出素子を構成する直接変換型検出器であっても良い。X線検出素子は放射線検出素子の一例である。 The photodiode array 304 includes photodiode elements so as to face the scintillator elements 303a. The photodiode element converts visible light emitted from the scintillator element 303a into an electric signal, and sends the electric signal to an AD conversion circuit (not shown). The detection element module 203 described with reference to FIGS. 3 and 4 is an indirect conversion type detector because the scintillator element 303a and the photodiode element constitute an X-ray detection element. However, the X-ray detection element is a semiconductor element. A direct conversion detector may be used. The X-ray detection element is an example of a radiation detection element.
　一次元コリメータ301の遮蔽板301aと二次元コリメータ302の第一遮蔽壁302aはともに、X線を十分に遮蔽可能な部材で構成され、図4に示すように各々がX線焦点201を指向するように配列されている。このような構造により、X線焦点201から被検体を直線的に透過した直接X線のほとんどは、一次元コリメータ301と二次元コリメータ302を透過してX線検出素子に達する。一方、被検体で散乱され、XY面と平行な方向の成分を有する散乱線のほとんどは一次元コリメータ301又は二次元コリメータ302に吸収されX線検出素子に到達しない。また、YZ面と平行な方向の成分を有する散乱線のほとんどは二次元コリメータ302の第二遮蔽壁302bに吸収されX線検出素子に到達しない。 Both the shielding plate 301a of the one-dimensional collimator 301 and the first shielding wall 302a of the two-dimensional collimator 302 are configured by members capable of sufficiently shielding X-rays, and each point toward the X-ray focal point 201 as shown in FIG. Are arranged as follows. With such a structure, most of the direct X-rays that are linearly transmitted through the subject from the X-ray focal point 201 are transmitted through the one-dimensional collimator 301 and the two-dimensional collimator 302 and reach the X-ray detection element. On the other hand, most of the scattered radiation scattered by the subject and having a component in a direction parallel to the XY plane is absorbed by the one-dimensional collimator 301 or the two-dimensional collimator 302 and does not reach the X-ray detection element. Also, most of the scattered radiation having a component in the direction parallel to the YZ plane is absorbed by the second shielding wall 302b of the two-dimensional collimator 302 and does not reach the X-ray detection element.
　図5に、図3に示した構造の散乱線除去部で除去可能な散乱線の散乱角の一例を示す。なお、散乱角は図6に示すように極座標で表しており、散乱角θはX線検出素子のX線入射面と散乱線とがなす角であり、散乱角ΦはX線検出素子のX線入射面に散乱線が投影された線とX軸とがなす角である。 FIG. 5 shows an example of the scattering angle of scattered radiation that can be removed by the scattered radiation removing unit having the structure shown in FIG. The scattering angle is expressed in polar coordinates as shown in FIG. 6, the scattering angle θ is an angle formed by the X-ray incident surface of the X-ray detection element and the scattered radiation, and the scattering angle Φ is X of the X-ray detection element. This is the angle between the X-axis and the line on which the scattered radiation is projected onto the line incident surface.
　図5に示したグラフは、縦軸が散乱角θ、横軸が散乱角Φであり、遮蔽板301aの高さと第一遮蔽壁302aの高さの合計HXを15mm固定し、第二遮蔽壁302bの高さHZを0、5、10、15mmと変化させた時にX線検出素子へ入射可能な散乱線の散乱角Φおよびθを示している。すなわち、図5中の各折れ線より上の角度の散乱角であればX線検出素子に入射可能であることを示している。 In the graph shown in FIG. 5, the vertical axis is the scattering angle θ, the horizontal axis is the scattering angle Φ, the total H X of the height of the shielding plate 301a and the height of the first shielding wall 302a is fixed to 15 mm, and the second shielding The scattering angles Φ and θ of scattered radiation that can enter the X-ray detection element when the height H Z of the wall 302b is changed to 0, 5, 10, and 15 mm are shown. That is, it is indicated that the light can be incident on the X-ray detection element if the scattering angle is higher than each broken line in FIG.
　図5から明らかなように、第二遮蔽壁302bが存在しないHZ =0mmでは、散乱角Φが大きくなるに従い散乱角θが低下し、特に散乱角Φが80[deg.]以上になると散乱角θが急激に低下し、散乱角Φ＝80[deg.]のとき散乱角θ＝72[deg.]、散乱角Φ＝85[deg.]のとき散乱角θ＝58[deg.]であり、散乱角θの広い範囲に亘って散乱線がX線検出素子に到達することになる。 As is clear from FIG. 5, when H Z = 0 mm where the second shielding wall 302b does not exist, the scattering angle θ decreases as the scattering angle Φ increases, and in particular, scattering occurs when the scattering angle Φ is 80 [deg.] Or more. The angle θ decreases rapidly. When the scattering angle Φ = 80 [deg.], The scattering angle θ = 72 [deg.], And when the scattering angle Φ = 85 [deg.], The scattering angle θ = 58 [deg.] In other words, the scattered radiation reaches the X-ray detection element over a wide range of the scattering angle θ.
　これに対し、第二遮蔽壁302bの高さをHZ =15mmまで増加させると散乱角Φ全範囲に亘って散乱角θが大きな値を保ち、ほとんどの散乱線が除去されることになる。また、HZ =5～10mm程度であれば散乱角Φが80[deg.]以上の範囲でも散乱角θは80[deg.]弱にとどまっており、多くの散乱線が除去されることになる。すなわち本実施形態のように、二次元コリメータ302の高さを低く抑えたとしても、二次元コリメータ302の上に一次元コリメータ301を配置することによって全方向の散乱線を効率良く除去することが可能となる。また二次元コリメータ302の高さを低く抑えている為、散乱線除去部202をコンパクトにすることができる。 On the other hand, when the height of the second shielding wall 302b is increased to H Z = 15 mm, the scattering angle θ maintains a large value over the entire range of the scattering angle Φ, and most of the scattered radiation is removed. Further, if H Z = 5 to 10 mm, the scattering angle θ is only 80 [deg.] Even in the range where the scattering angle Φ is 80 [deg.] Or more, and many scattered rays are removed. Become. That is, even if the height of the two-dimensional collimator 302 is kept low as in this embodiment, the scattered radiation in all directions can be efficiently removed by arranging the one-dimensional collimator 301 on the two-dimensional collimator 302. It becomes possible. Further, since the height of the two-dimensional collimator 302 is kept low, the scattered radiation removal unit 202 can be made compact.
　さらに二次元コリメータ302の高さを低く抑えている為、二次元コリメータ302を積層方式により製造する場合には製造時間を短時間に抑えることができる。また、第二遮蔽壁302bの高さが低いので、X線焦点が移動した際に第二遮蔽壁302bの存在によって発生する影も極力低減させることができ、断層画像の画質への影響を抑制できる。 Furthermore, since the height of the two-dimensional collimator 302 is kept low, when the two-dimensional collimator 302 is manufactured by the lamination method, the manufacturing time can be reduced in a short time. In addition, since the height of the second shielding wall 302b is low, the shadow caused by the presence of the second shielding wall 302b when the X-ray focal point moves can be reduced as much as possible, and the influence on the image quality of the tomographic image is suppressed. it can.
　また、X線CT装置に用いる放射線検出器の多スライス化、すなわち回転円盤102の回転軸方向へのX線検出素子列の多列化を図るために、本実施形態の散乱線除去部202と検出素子モジュール203を回転軸方向に複数個併設させても良い。さらに、一次元コリメータ301と二次元コリメータ302の位置合わせを容易にするために、一次元コリメータ301の検出素子モジュール203側、若しくは二次元コリメータ302のX線焦点201側に、位置合わせ用の凹凸を適宜設けても良い。さらに二次元コリメータ302と検出素子モジュール203の位置合わせを容易にするために、二次元コリメータ302の検出素子モジュール203側、若しくは検出素子モジュール203のX線焦点201側に、位置合わせ用の凹凸を適宜設けても良い。 Further, in order to increase the number of radiation detectors used in the X-ray CT apparatus, that is, to increase the number of X-ray detection element arrays in the rotation axis direction of the rotating disk 102, the scattered radiation removal unit 202 of the present embodiment and A plurality of detection element modules 203 may be provided in the rotation axis direction. Further, in order to facilitate the alignment of the one-dimensional collimator 301 and the two-dimensional collimator 302, the alignment irregularities are formed on the detection element module 203 side of the one-dimensional collimator 301 or the X-ray focal point 201 side of the two-dimensional collimator 302. May be provided as appropriate. Further, in order to facilitate the alignment between the two-dimensional collimator 302 and the detection element module 203, unevenness for alignment is provided on the detection element module 203 side of the two-dimensional collimator 302 or the X-ray focal point 201 side of the detection element module 203. You may provide suitably.
　(第二の実施形態)
　本発明の第二の実施形態について説明する。第一の実施形態では、X線入射方向に一次元コリメータ301と二次元コリメータ302とが重ねられた散乱線除去部202について説明した。本実施形態では、一次元コリメータ301の遮蔽板301aの厚さと、二次元コリメータ302の第一遮蔽壁302aの厚さとの関係について図4を用いて説明する。 (Second embodiment)
A second embodiment of the present invention will be described. In the first embodiment, the scattered radiation removing unit 202 in which the one-dimensional collimator 301 and the two-dimensional collimator 302 are overlapped in the X-ray incident direction has been described. In the present embodiment, the relationship between the thickness of the shielding plate 301a of the one-dimensional collimator 301 and the thickness of the first shielding wall 302a of the two-dimensional collimator 302 will be described with reference to FIG.
　本実施形態では、図4に示すように一次元コリメータ301の遮蔽板301aの厚さW1を二次元コリメータ302の第一遮蔽壁302aの厚さW2よりも薄くする。 In the present embodiment, as shown in FIG. 4, the thickness W1 of the shielding plate 301a of the one-dimensional collimator 301 is made thinner than the thickness W2 of the first shielding wall 302a of the two-dimensional collimator 302.
　このように構成することにより、二次元コリメータ302の高さよりも高い高さを有する遮蔽板301aが反っていたり、回転円盤102の回転によって発生する遠心力によって変形したり、取り付け位置精度が適切でない場合であっても、遮蔽板301aの影がX線検出素子にかかることを、第一遮蔽壁302aによって抑制することができる。すなわち、X線CT装置で得られる断層画像の画質を劣化させずに済む。 With this configuration, the shielding plate 301a having a height higher than the height of the two-dimensional collimator 302 is warped, deformed by the centrifugal force generated by the rotation of the rotating disk 102, or the mounting position accuracy is not appropriate. Even in this case, the first shielding wall 302a can suppress the shadow of the shielding plate 301a from being applied to the X-ray detection element. That is, it is not necessary to deteriorate the image quality of the tomographic image obtained by the X-ray CT apparatus.
　(第三の実施形態)
　本発明の第三の実施形態について説明する。第二の実施形態では、一次元コリメータ301の遮蔽板301aの厚さと、二次元コリメータ302の第一遮蔽壁302aの厚さとの関係について説明した。本実施形態では、二次元コリメータ302の第一遮蔽壁302aの厚さと第二遮蔽壁302bの厚さの関係について図7を用いて説明する。 (Third embodiment)
A third embodiment of the present invention will be described. In the second embodiment, the relationship between the thickness of the shielding plate 301a of the one-dimensional collimator 301 and the thickness of the first shielding wall 302a of the two-dimensional collimator 302 has been described. In the present embodiment, the relationship between the thickness of the first shielding wall 302a and the thickness of the second shielding wall 302b of the two-dimensional collimator 302 will be described with reference to FIG.
　図7は二次元コリメータ302をX線焦点201側から見た平面図である。図7に示すように本実施形態では、二次元コリメータ302の第一遮蔽壁302aの厚さW2を第二遮蔽壁302bの厚さW3よりも厚くする。二次元コリメータ302を用いる場合、二次元コリメータ302を用いない場合に比べ、X線検出素子に入射する直接X線の線量が低下してしまい、X線CT装置で得られる断層画像の画質を劣化させることがある。また、X線CT装置では、回転円盤102の回転面内のクロストークは、回転軸方向のクロストークに比べて断層画像の画質劣化への影響が大きい。 FIG. 7 is a plan view of the two-dimensional collimator 302 as seen from the X-ray focal point 201 side. As shown in FIG. 7, in this embodiment, the thickness W2 of the first shielding wall 302a of the two-dimensional collimator 302 is made thicker than the thickness W3 of the second shielding wall 302b. When using the two-dimensional collimator 302, compared to the case without using the two-dimensional collimator 302, the dose of direct X-rays incident on the X-ray detection element is reduced, and the image quality of the tomographic image obtained by the X-ray CT apparatus is deteriorated. There are things to do. In the X-ray CT apparatus, the crosstalk in the rotation plane of the rotating disk 102 has a larger influence on the image quality degradation of the tomographic image than the crosstalk in the rotation axis direction.
　そこで本実施形態のように第一遮蔽壁302aの厚さW2を第二遮蔽壁302bの厚さW3よりも厚くすることにより、回転面内のクロストークを抑制しつつ、X線検出素子に入射する直接X線の線量を増やすことができる。すなわち、X線CT装置で得られる断層画像の画質を劣化させずに済む。 Therefore, by making the thickness W2 of the first shielding wall 302a thicker than the thickness W3 of the second shielding wall 302b as in the present embodiment, the crosstalk in the rotation plane is suppressed and incident on the X-ray detection element. You can increase the direct X-ray dose. That is, it is not necessary to deteriorate the image quality of the tomographic image obtained by the X-ray CT apparatus.
　なお、上述した実施形態は本発明の構造を限定するためのものではなく、具体的な実施の形態を示す例であり、同一の効果を有する他の形態であっても本発明を実現することは可能である。例えば、上述した実施形態では、散乱線除去部202をX線焦点201側から一次元コリメータ301、二次元コリメータ302の順に重ねた構造としているが、X線焦点201側から二次元コリメータ302、一次元コリメータ301の順に重ねた構造としても良い。 The above-described embodiment is not intended to limit the structure of the present invention, but is an example showing a specific embodiment, and the present invention can be realized in other forms having the same effect. Is possible. For example, in the above-described embodiment, the scattered radiation removal unit 202 has a structure in which the one-dimensional collimator 301 and the two-dimensional collimator 302 are stacked in this order from the X-ray focal point 201 side. A structure in which the original collimators 301 are stacked in this order may be employed.
1　X線CT装置、100　スキャンガントリ部、101　X線管装置、102　回転円盤、103　照射野制限部、104　開口部、105　寝台装置、106　X線検出器、107　データ収集装置、108　ガントリ制御装置、109　寝台制御装置、110　X線制御装置、111　高電圧発生装置、120　操作卓、121　入力装置、122　画像演算装置、123　記憶装置、124　システム制御装置、125　表示装置、201　X線焦点、202　散乱線除去部、203検出素子モジュール、301　一次元コリメータ、301a　遮蔽版、302　二次元コリメータ、302a　第一遮蔽壁、302b　第二遮蔽壁、303　シンチレータアレイ、303a　シンチレータ素子、303b　反射材、304　フォトダイオードアレイ 1 X-ray CT device, 100 scan gantry unit, 101 X-ray tube device, 102 rotating disk, 103 irradiation field restriction unit, 104 opening, 105 bed device, 106 X-ray detector, 107 data collection device, 108 gantry control device 109, bed control device, 110 X-ray control device, 111 high voltage generation device, 120 console, 121 input device, 122 image calculation device, 123 storage device, 124 system control device, 125 display device, 201 X-ray focus, 202 Scattering ray removal unit, 203 detection element module, 301 one-dimensional collimator, 301a shielding plate, 302 two-dimensional collimator, 302a first shielding wall, 302b second shielding wall, 303 scintillator array, 303a scintillator element, 303b reflector, 304 photo Diode array

Claims (6)

  1. 　放射線源から発生した放射線を検出する複数の放射線検出素子が第1の方向及び第1の方向と直交する第2の方向に配置された放射線検出素子アレイと、
    　前記放射線検出素子アレイの前記放射線源の側に第1の方向に沿って複数の遮蔽板が放射線源を指向するように配置される一次元コリメータと、
    　前記第1の方向に沿って複数の第一遮蔽壁が放射線源を指向するように配置されるとともに、前記第2の方向に沿って複数の第二遮蔽壁が放射線源を指向するように配置される二次元コリメータと、を備え、
    　前記一次元コリメータと前記二次元コリメータとが放射線入射方向に重ねられることを特徴とする放射線検出器。     A radiation detection element array in which a plurality of radiation detection elements for detecting radiation generated from a radiation source are arranged in a first direction and a second direction orthogonal to the first direction;
    A one-dimensional collimator arranged such that a plurality of shielding plates are directed to the radiation source along a first direction on the radiation source side of the radiation detection element array;
    A plurality of first shielding walls are arranged to direct the radiation source along the first direction, and a plurality of second shielding walls are arranged to face the radiation source along the second direction. A two-dimensional collimator,
    The radiation detector, wherein the one-dimensional collimator and the two-dimensional collimator are overlapped in a radiation incident direction.
  2. 　請求項1に記載の放射線検出器において、
    　前記一次元コリメータが前記二次元コリメータよりも放射線源側に配置されることを特徴とする放射線検出器。     In the radiation detector according to claim 1,
    The radiation detector, wherein the one-dimensional collimator is disposed closer to a radiation source than the two-dimensional collimator.
  3. 　請求項2に記載の放射線検出器において、
    　前記遮蔽板の厚さが、前記第一遮蔽壁の厚さより薄いことを特徴とする放射線検出器。     In the radiation detector according to claim 2,
    The radiation detector is characterized in that a thickness of the shielding plate is thinner than a thickness of the first shielding wall.
  4. 　請求項1に記載の放射線検出器において、
    　前記第一遮蔽壁の厚さが前記第二遮蔽壁の厚さより厚いことを特徴とする放射線検出器。     In the radiation detector according to claim 1,
    The radiation detector according to claim 1, wherein the first shielding wall is thicker than the second shielding wall.
  5. 　前記放射線源と、前記放射線源に対向配置され被検体を透過した放射線を検出する放射線検出器と、前記放射線源と前記放射線検出器を搭載し前記被検体の周囲を回転する回転円盤と、前記放射線検出器により検出された複数角度からの透過放射線量に基づき前記被検体の断層画像を再構成する画像再構成装置と、前記画像再構成装置により再構成された断層画像を表示する画像表示装置と、を備え、
    　前記放射線検出器が請求項1に記載の放射線検出器であることを特徴とするX線CT装置。     The radiation source, a radiation detector disposed opposite to the radiation source and detecting radiation transmitted through the subject, a rotating disk mounted with the radiation source and the radiation detector and rotating around the subject, An image reconstruction device that reconstructs a tomographic image of the subject based on transmitted radiation doses from a plurality of angles detected by a radiation detector, and an image display device that displays a tomographic image reconstructed by the image reconstruction device And comprising
    2. An X-ray CT apparatus, wherein the radiation detector is the radiation detector according to claim 1.
  6. 　前記第1の方向は、前記回転円盤の回転軸方向であることを特徴とする請求項5に記載のX線CT装置。 6. The X-ray CT apparatus according to claim 5, wherein the first direction is a rotation axis direction of the rotating disk.
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CN112006705B (en) * 2019-05-29 2024-04-23 西门子医疗有限公司 X-ray imaging device comprising a detection unit with a scattered radiation collimator

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