JP2008168056A - Collimator, x-ray detection device, and x-ray computed tomographic apparatus, and method for manufacturing collimator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a collimator capable of attaining light weight and reducing a cost. <P>SOLUTION: The collimator 21 for X-ray computed tomographic apparatus, with X-rays passing therethrough, which are enlarged along the body axial direction F2 of a subject, includes: a plurality of collimator boards 21a respectively aligned by separation thereby so as to remove scattering X-rays and respectively having gradually enlarged shapes along an X-ray advance direction in response to the enlargement of the X-rays, based on a cone angle θ in the body axial direction F2; and a support part 21b for supporting the plurality of collimator boards 21a, so as to allow the X-rays to pass between the respective collimator boards 21a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a collimator, an X-ray detection apparatus including the collimator, an X-ray computed tomography apparatus including the X-ray detection apparatus, and a collimator manufacturing method.

  An X-ray computed tomography apparatus (X-ray CT apparatus) rotates an X-ray irradiation apparatus and an X-ray detection apparatus facing each other around a body axis of a subject such as a patient, This is an apparatus that collects projection data related to a cross section and performs a reconstruction process on the projection data to obtain a cross-sectional image (slice image) representing information inside the subject.

  The X-ray detection apparatus has a fan beam shape having a cone angle, for example, a collimator through which X-rays having a cone shape or a pyramid shape pass, and a plurality of X-ray detections that detect X-rays that are joined to the collimator and pass through the collimator (For example, refer to Patent Document 1). The collimator includes a plurality of collimator plates arranged in an arc shape in the channel direction (the width direction of the spread based on the X-ray fan angle), and a support member called a collimator support that supports the collimator plates. . Each collimator plate is formed in a rectangular shape.

In such an X-ray detection apparatus, the area of the X-ray detection region has been increasing in recent years. As the area increases, the width of the effective detection surface of the X-ray detector increases in the slice direction (the width direction of the spread based on the cone angle: the body axis direction of the subject). Need to be increased. For this reason, the spread of the X-ray in the slice direction is increased, and the incident width of the X-ray in the slice direction on the incident surface of the collimator is greatly different from the emission width of the X-ray in the slice direction on the output surface. This becomes more pronounced as the cone angle of X-rays increases. Therefore, the minimum width of the collimator plate in the slice direction is different between the entrance surface and the exit surface of the collimator.
JP 2003-207575 A

  However, in the above collimator, since each collimator plate is formed in a rectangular shape, the width in the slice direction of each collimator plate on the entrance surface and the exit surface of the collimator is the same, and each collimator plate is unnecessary. Largely formed. For this reason, there is a problem that the collimator is increased in weight and cost.

  The present invention has been made in view of the above, and an object thereof is to provide a collimator, an X-ray detection apparatus, an X-ray computed tomography apparatus, and a collimator manufacturing method capable of realizing weight reduction and cost reduction. It is to be.

  A first feature according to an embodiment of the present invention is to remove scattered X-rays in a collimator for an X-ray computed tomography apparatus through which X-rays extending along the body axis direction of the subject pass. A plurality of collimator plates that are arranged apart from each other and each have a shape that gradually spreads along the traveling direction of the X-rays corresponding to the spread based on the cone angle in the body axis direction of the X-rays; And a support portion that supports a plurality of collimator plates so as to be able to pass between each of the plates.

  A second feature according to the embodiment of the present invention is that an X-ray passes through an X-ray detection apparatus for an X-ray computed tomography apparatus that detects X-rays extending along the body axis direction of a subject. It is provided with the collimator which concerns on a 1st characteristic, and the X-ray detection means which detects the X-ray which passed the collimator.

  A third feature according to the embodiment of the present invention is that, in an X-ray computed tomography apparatus that reconstructs an image inside a subject based on X-ray transmission data, the body axis direction of the subject toward the subject X-ray irradiating means for irradiating X-rays extending along the line, a collimator according to the first feature through which X-rays pass, and X-ray detecting means for detecting X-rays that have passed through the collimator. .

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a collimator for an X-ray computed tomography apparatus through which X-rays extending along the body axis direction of a subject pass. Forming a plurality of collimator plates each having a shape that gradually spreads along the traveling direction of the X-ray corresponding to the spread based on the cone angle in the direction, and the X-rays can pass between each of the plurality of collimator plates Forming a support portion for supporting a plurality of collimator plates and arranging the formed plurality of collimator plates so as to be separated from each other so as to remove scattered X-rays, and attaching to the formed support portion. is there.

  According to the present invention, weight reduction and cost reduction can be realized.

  An embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an X-ray computed tomography apparatus (X-ray CT apparatus) 1 according to an embodiment of the present invention includes a bed 2 on which a subject M such as a patient is placed, and the bed 2. An imaging unit 3 that performs an imaging operation for imaging a medical image of the subject M and a control device 4 that controls driving of the imaging unit 3 are provided. The X-ray computed tomography apparatus 1 is an apparatus for tomographic imaging of a medical image of a predetermined part of a subject M on a bed 2 by an imaging unit 3.

  The couch 2 includes a top plate 2a on which the subject M is placed, and a top plate drive unit 2b that supports the top plate 2a and moves it horizontally and vertically. The couch 2 moves the couchtop 2a by the couchtop drive unit 2b and positions the subject M on the couchtop 2a at a predetermined position.

  The imaging unit 3 includes a rotating frame 3a that is rotatably provided in the housing, a rotation driving unit 3b that rotationally drives the rotating frame 3a, and an X-ray irradiation device 3c that is provided on the rotating frame 3a and emits X-rays. The high voltage generator 3d for supplying a high voltage to the X-ray irradiation device 3c, the X-ray detection device 3e for detecting the X-rays irradiated by the X-ray irradiation device 3c, and the X-ray detection device 3e And a data collection unit 3f that collects projection data.

  The rotating frame 3a is formed in an annular shape, for example. An X-ray irradiation device 3c, an X-ray detection device 3e, and the like are fixed to the rotary frame 3a. Thereby, the X-ray irradiation apparatus 3c and the X-ray detection apparatus 3e rotate around the subject M on the bed 2 (around the body axis of the subject M). The top plate 2a of the bed 2 is inserted into the frame of the rotating frame 3a.

  The rotation driving unit 3b is provided in the housing. The rotation drive unit 3 b controls the rotation drive of the rotation frame 3 a according to the control by the control device 4. For example, the rotation drive unit 3b rotates the rotation frame 3a at a predetermined rotation speed in one direction based on the control signal transmitted from the control device 4.

  The X-ray irradiation apparatus 3 c includes an X-ray tube 11 that emits X-rays and a diaphragm unit 12 that restricts the X-rays emitted from the X-ray tube 11. The X-ray irradiation device 3c emits X-rays by the X-ray tube 11, narrows the X-rays by the diaphragm 12, and forms a fan beam having a cone angle with respect to the subject M on the bed 2, for example, X-rays having a cone shape or a pyramid shape are irradiated. The X-ray irradiation device 3c functions as an X-ray irradiation unit.

  The high voltage generator 3d is provided in the rotary frame 3a. The high voltage generator 3d is a device that generates a high voltage to be supplied to the X-ray irradiation device 3c, boosts and rectifies the voltage supplied from the control device 4, and supplies the voltage to the X-ray irradiation device 3c. . The control device 4 controls various conditions such as the waveform of the voltage applied to the high voltage generator 3d, that is, the amplitude and the pulse width, in order to cause the X-ray irradiation device 3c to generate desired X-rays.

  The X-ray detection device 3e is arranged to face the X-ray irradiation device 3c. The X-ray detection device 3e converts X-ray transmission data obtained from X-rays transmitted through the subject M on the bed 2 into optical information, converts the optical information into an electrical signal, and transmits the electrical signal to the data collection unit 3f. To do. This X-ray detection apparatus 3e is a multi-slice X-ray detection apparatus in which a plurality of X-ray detection element arrays in which X-ray detection elements are arranged in the channel direction are arranged in the slice direction. The slice direction is a direction along the body axis direction of the subject M.

  The data collection unit 3f is provided in the X-ray detection device 3e. The data collection unit 3 f collects the electrical signals transmitted from the X-ray detection device 3 e as projection data and transmits the projection data to the control device 4.

  The control device 4 includes a control unit 4a that controls driving of each unit, an image processing unit 4b that performs image processing including image reconstruction on projection data, a storage unit 4c that stores various data such as medical images, and various programs, An operation unit 4d that receives an input operation by an operator, a display unit 4e that displays an image, and the like are provided. These parts 4a to 4e are electrically connected by a bus line 4f.

  The control unit 4a controls driving of each unit such as the top plate driving unit 2b, the rotation driving unit 3b, and the high voltage generating unit 3d. In addition, the control unit 4a also performs display control for displaying the medical image in the storage unit 4c on the display unit 4e.

  The image processing unit 4b performs image processing including image reconstruction on the projection data transmitted from the data collection unit 3f, and then stores the medical image in the storage unit 4c. For example, an array processor or the like is used as the image processing unit 4b.

  The storage unit 4c is a storage device that stores various programs, various data, and the like, and in particular, is a storage device that stores captured medical images as various data. For example, a ROM, a RAM, a flash memory, and a hard disk are used as the storage unit 4c. The medical image data may be stored in an image server or the like connected to the control device 4 via a network.

  The operation unit 4d is an input unit that is input by an operator. For example, a keyboard or a mouse is used as the operation unit 4d. The operator performs an input operation on the operation unit 4d and performs imaging by the imaging unit 3, or selects and displays a desired medical image from a plurality of reconstructed medical images.

  The display unit 4e is a display device that displays various images such as medical images and operation screens of the subject. As the display unit 4e, for example, a liquid crystal display, a CRT (CRT) display, or the like is used.

  Next, the X-ray detection device 3e will be described in detail.

  As shown in FIG. 2, the X-ray detection device 3e detects a fan beam shape having a cone angle, for example, a collimator 21 through which an X-ray having a cone shape or a pyramid shape passes, and an X-ray that has passed through the collimator 21. The X-ray detector unit 22 is configured. X-rays are emitted from the focal spot S of the X-ray irradiation device 3c.

  The collimator 21 has a plurality of collimator plates 21a arranged in the channel direction (the width direction of the spread based on the X-ray fan angle θ1) F1 and the X-rays can pass between each of the collimator plates 21a. And a support portion 21b for supporting the collimator plates 21a. Here, in the collimator 21, the surface on which the X-rays are incident is the incident surface, and the surface from which the X-rays that have entered and passed through the incident surface are emitted. An X-ray detector unit 22 is provided on the exit surface.

  The X-ray detector unit 22 includes a plurality of X-ray detectors 22a that detect X-rays. Each of these X-ray detectors 22a is composed of a scintillator block in which a plurality of scintillator segments that emit fluorescence upon incidence of X-rays are arranged in a grid, a photoelectric conversion element joined to the scintillator block, and the like. For example, a photodiode is used as the photoelectric conversion element. The X-ray detector 22a converts the fluorescence emitted from each scintillator segment into an electric signal by a photoelectric conversion element. Here, the X-ray detector unit 22 functions as X-ray detection means.

  As shown in FIGS. 2 and 3, each collimator plate 21a is arranged in an arc shape at a predetermined pitch interval in the channel direction F1, and removes scattered X-rays generated when X-rays pass through the subject M. As shown in FIG. As a material of the collimator plate 21a, for example, molybdenum or tungsten is used. These collimator plates 21a guide the X-rays to the X-ray detector unit 22 while removing scattered X-rays.

  Further, as shown in FIG. 4, each collimator plate 21 a corresponds to the spread based on the cone angle θ <b> 2 in the X-ray slice direction F <b> 2 (direction in which the collimator 21 travels from the incident surface to the output surface). ) Are formed in a shape that gradually spreads along the line. For example, these collimator plates 21a are formed in a trapezoidal shape.

  Here, the shape of the collimator plate 21a is such that the cone angle θ2 of the X-ray, the distance L1 between the focal spot S and the effective detection surface of the X-ray detector 22a, and the slice direction of the effective detection surface of the X-ray detector 22a. It is determined based on the length L2. The separation distance L1 between the focal spot S and the effective detection surface is set such that the width of the spread based on the cone angle θ2 of the X-ray is the same as the length L2 of the effective detection surface of the X-ray detector 22a. . Further, when the separation distance L1 between the focal spot S and the effective detection surface is determined due to the limitation due to the apparatus size, the cone angle θ2 of the X-ray is adjusted in accordance with the distance L1.

  As shown in FIGS. 2 and 3, the support portion 21 b includes a pair of support members 31 and 32 that sandwich the collimator plates 21 a and a pair of fixing members 33 and 34 for fixing the support members 31 and 32. And. The pair of support members 31 and 32 are fixed to the pair of fixing members 33 and 34 by fastening members 35 and 36 (see FIG. 3) such as bolts and nuts.

  The pair of support members 31 and 32 are members that hold the collimator plates 21a together from the X-ray slice direction F2. These support members 31 and 32 are curved in a direction away from the focal spot S. For this reason, the incident surface of the collimator 21 is an inner R surface, and its emission surface is an outer R surface.

  Further, as shown in FIG. 4, the pair of support members 31 and 32 have inclined surfaces 31a and 32a, respectively. These inclined surfaces 31a and 32a are formed so as to correspond to the shape of each collimator plate 21a, that is, the cone angle θ2 in the X-ray slice direction F2. In addition, grooves G1 and G2 for attaching the collimator plate 21a are provided on the inclined surfaces 31a and 32a so as to face each other. These grooves G1 and G2 are formed so as to extend from the incident surface side of the collimator 21 to the output surface side. The collimator plate 21a is inserted into the opposing grooves G1 and G2 and fixed to the pair of support members 31 and 32 with an adhesive or the like.

  Next, an imaging operation performed by such an X-ray computed tomography apparatus 1 will be described.

  The X-ray computed tomography apparatus 1 inserts the top plate 2a on which the subject M is placed in the frame of the rotating frame 3a in response to an input operation by the operator to the operation unit 4d, and the subject on the top plate 2a. The specimen M is moved in the slice direction F2 (the body axis direction of the subject M). Along with the movement of the top plate 2a, the X-ray computed tomography apparatus 1 rotates the rotary frame 3a so that the X-ray irradiation device 3c and the X-ray detection device 3e are around the body axis of the subject M on the top plate 2a. While rotating, the X-ray irradiation device 3c irradiates the subject M on the top 2a with an X-ray beam, and the X-ray detection device 3e detects the X-ray beam transmitted through the subject M.

  Thereafter, the X-ray computed tomography apparatus 1 collects electrical signals from the X-ray detection apparatus 3e as projection data by the data collection unit 3f, processes the projection data by the image processing unit 4b, and processes the processed medical image. The data is stored in the storage unit 4c and further displayed on the display unit 4e. At this time, the medical image is displayed on the display unit 4e as a cross-sectional image (slice image).

  Here, the X-ray beam transmitted through the subject M is guided to the X-ray detector unit 22 by the collimator 21 and is incident thereon. At this time, scattered X-rays of the X-ray beam are removed by the collimator 21, and only the X-ray beam that has passed through the collimator 21 enters the X-ray detector unit 22. This makes it possible to obtain a good contrast and obtain a medical image with high accuracy. At this time, in the collimator 21, the width in the slice direction of each collimator plate 21a is the same as the width of the spread based on the cone angle θ2 of the X-ray (see FIG. 4). Accordingly, the collimator plate 21a can be made smaller than the rectangular collimator plate 21a while obtaining a good contrast and obtaining a medical image with high accuracy. In addition, cost reduction can be realized.

  As described above, according to the embodiment of the present invention, the plurality of collimator plates 21a each having a shape that gradually spreads along the X-ray traveling direction corresponding to the spread based on the cone angle θ2 of X-rays. By providing, since each collimator plate 21a becomes small compared with the rectangular-shaped collimator plate 21a, weight reduction is realizable. In addition, since the amount of material used for the collimator plate 21a is also reduced, cost reduction can be realized. In particular, as the material of the collimator plate 21a, a relatively expensive material that is a heavy metal having a high X-ray absorption rate is used. Therefore, the cost reduction can be promoted by reducing the amount of the material used for the collimator plate 21a. .

  Next, a method for manufacturing the collimator 21 will be described.

  In the manufacturing process of the collimator 21, a plurality of collimator plates 21a and support portions 21b are formed, and then each collimator plate 21a is attached to the support portion 21b. Thereby, the collimator 21 is completed. In addition, the process of forming each collimator board 21a and the process of forming the support part 21b may be performed simultaneously, or one may be performed previously.

  In the step of forming each collimator plate 21a, as shown in FIG. 5, punching is performed on the plate material 51 that is a material of each collimator plate 21a by a punching portion 52 having a pair of axially symmetric punching dies 52a and 52b. As a result, each collimator plate 21a is formed. In addition, as the board | plate material 51, a roll-shaped board | plate material etc. are used, for example.

  Here, as shown in FIG. 5, the plate material 51 is conveyed in one direction, and the punched portion 52 slides for each punching in a direction orthogonal to the conveying direction of the plate material 51. Thereby, a pair of punching dies 52a and 52b are used alternately, the plate material 51 is punched, and each collimator plate 21a is formed. In addition, as shown in FIG. 6, the plate material 51 after punching becomes a frame surrounding the shape of each collimator plate 21a. In this way, the plate material 51 is used without waste, and the effective utilization rate of the plate material 51 is improved.

  In the step of forming the support portion 21b, the support portion 21b is formed corresponding to the shape of the collimator plate 21a. Specifically, two arc-shaped prisms that are the material of the support portion 21b are prepared as a pair of support members 31, 32, and a pair of support members corresponding to the shape of the collimator plate 21a, that is, the cone angle θ2 of the X-ray. An inclined surface 31 a is formed on 31 and 32.

  First, as shown in FIG. 7 and FIG. 8, the support member 31 is placed on the mounting table 53, and the mounting table 53 is inclined by a predetermined angle (an angle corresponding to the cone angle θ2) and moves along the arc. However, the processing machine 54 forms the inclined surface 31 a on the support member 31. Thereby, the inclined surface 31 a is formed along the arc shape of the support member 31.

  Next, as shown in FIG. 9, the mounting table 53 is inclined by a predetermined angle in the reverse direction, and a groove processing machine 55 such as a diamond blade is sequentially moved by a predetermined pitch interval, while a plurality of surfaces are provided on the inclined surface 31 a of the support member 31. The groove part G1 is formed. In addition, the inclined surface 32a is formed also in the supporting member 32 by the process similar to the process of processing the supporting member 31, and the several groove part G2 is formed in the inclined surface 32a after that.

  Here, the mounting table 53 is provided so as to be inclined with respect to a horizontal plane and to be movable along an arc. Further, the processing machine 54 includes an end mill 54a for processing, and a rotation driving unit 54b that rotates the end mill 54a. Note that the processing machine 54 may be inclined instead of the mounting table 53, and the processing machine 54 may be moved along an arc instead of the movement of the mounting table 53.

  Thereafter, the pair of support members 31 and 32 are fixed to the pair of fixing members 33 and 34 by the fastening members 35 and 36, and the support portion 21b is assembled (see FIG. 3). Next, the abutting member 56 is attached to the incident surface of the support portion 21b, and an adhesive is applied to each of the grooves G1 and G2.

  Finally, each collimator plate 21a is inserted into each groove G1, G2 from the exit surface side of the support portion 21b, butted against the abutting member 56, and attached to the support portion 21b. Thereby, each collimator plate 21a is spaced apart and arranged in an arc shape in the channel direction F1. After the adhesive is dried, the abutting member 56 is removed, and the collimator 21 is completed. The abutting member 56 is formed in a plate shape and is detachably attached to the incident surface of the support portion 21b.

  As described above, according to the manufacturing method of the embodiment of the present invention, the collimator plate 21a having a shape that gradually spreads along the traveling direction of the X-ray corresponding to the spread based on the cone angle θ2 of the X-ray. By forming and using the collimator plate 21 a for the collimator 21, the collimator 21 can be reduced in weight and cost compared to the case where the rectangular collimator plate 21 a is used for the collimator 21.

  Further, the collimator plate 21a is formed by punching the plate material 51, which is the material of each collimator plate 21a, by alternately using a pair of axially symmetric punching dies 52a and 52b, thereby forming the plate material 51. Is used without waste, so that the effective utilization rate of the plate material 51 can be improved.

  Further, by forming the support portion 21b corresponding to the shape of each collimator plate 21a, it becomes possible to facilitate the attachment of each collimator plate 21a to the support portion 21b, so that the assembly work of the collimator 21 is facilitated. In addition, time reduction can be realized.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

1 is a schematic diagram showing a schematic configuration of an X-ray computed tomography apparatus according to an embodiment of the present invention. It is a perspective view which shows schematic structure of the X-ray detection apparatus with which the X-ray computed tomography apparatus shown in FIG. It is a top view which expands and shows schematic structure of the X-ray detection apparatus shown in FIG. It is A1-A1 sectional view taken on the line shown in FIG. It is a top view for demonstrating the manufacturing method which forms the collimator board of the collimator with which the X-ray detection apparatus shown in FIG. 2 thru | or FIG. 4 is provided. It is a top view which shows the board | plate material after the punching in the manufacturing method of the collimator board shown in FIG. It is a side view for demonstrating the manufacturing method which forms an inclined surface in a pair of support member of the collimator with which the X-ray detection apparatus shown in FIG. 2 thru | or FIG. It is a front view for demonstrating the manufacturing method which forms an inclined surface in a pair of support member of the collimator with which the X-ray detection apparatus shown in FIG. 2 thru | or FIG. 4 is provided. It is a side view for demonstrating the manufacturing method which forms a groove part in a pair of support member of the collimator with which the X-ray detection apparatus shown in FIG. 2 thru | or FIG. 4 is provided. It is sectional drawing for demonstrating the manufacturing method which assembles the collimator with which the X-ray detection apparatus shown in FIG. 2 thru | or FIG. 4 is equipped.

Explanation of symbols

1 X-ray computed tomography apparatus 3c X-ray irradiation means (X-ray irradiation apparatus)
3e X-ray detection device 21 collimator 21a collimator plate 21b support 22 X-ray detection means (X-ray detector unit)
51 Plate material 52a Cavity die 52b Cavity die F2 Body axis direction (slice direction)
M Subject θ2 Cone angle

Claims (6)

In a collimator for an X-ray computed tomography apparatus through which X-rays having a spread along the body axis direction of a subject pass,
A plurality of shapes that are arranged so as to be separated from each other so as to remove scattered X-rays and that gradually spread along the traveling direction of the X-rays corresponding to the spread based on the cone angle in the body axis direction of the X-rays. A collimator plate;
A support portion for supporting the plurality of collimator plates so that the X-ray can pass between each of the plurality of collimator plates;
A collimator comprising: In an X-ray detection apparatus for an X-ray computed tomography apparatus that detects X-rays extending along the body axis direction of a subject,
The collimator according to claim 1, wherein the X-ray passes;
X-ray detection means for detecting the X-ray that has passed through the collimator;
An X-ray detection apparatus comprising: In an X-ray computed tomography apparatus that reconstructs an image inside a subject based on X-ray transmission data,
X-ray irradiation means for irradiating the subject with X-rays extending along the body axis direction of the subject;
The collimator according to claim 1, wherein the X-ray passes;
X-ray detection means for detecting the X-ray that has passed through the collimator;
An X-ray computed tomography apparatus comprising: In a method of manufacturing a collimator for an X-ray computed tomography apparatus through which X-rays having a spread along a body axis direction of a subject pass,
Forming a plurality of collimator plates each having a shape that gradually spreads along the traveling direction of the X-ray corresponding to the spread based on the cone angle in the body axis direction of the X-ray;
Forming a support portion for supporting the plurality of collimator plates so that the X-rays can pass between each of the plurality of collimator plates;
Arranging the plurality of formed collimator plates spaced apart so as to remove scattered X-rays, and attaching to the formed support;
A method for manufacturing a collimator, comprising:   5. The plurality of collimator plates are formed by punching a plate material that is a material of the plurality of collimator plates by alternately using a pair of axially symmetric punching dies. The manufacturing method of the collimator of description.   6. The method of manufacturing a collimator according to claim 4, wherein the support portion is formed corresponding to the shape of the plurality of collimator plates.

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