JP2004219224A - Computed tomograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CT scanner for easily setting X-ray geometry, and for obtaining a high-quality cross-sectional image. <P>SOLUTION: A computed tomograph is composed so that it emits radiation beams 2 so that the beams orthogonally cross a rotary shaft 13 of a rotary table 5 for placing a specimen 4. Then, the computed tomograph comprises an x shift mechanism 8 for moving the rotary table 5 in a direction (x) of the radiation beams 2; a y shift mechanism 7 for moving the rotary table 5 in a direction (y) across the radiation beams 2 along the surface of the radiation beams 2; a rotary/rising mechanism 6 for relatively moving the specimen 4 in a direction (z) for crossing the surface of at least the radiation beams 2; and a procedure management part 21 for performing at least one of the successive display and execution of a tomography procedure including x, y, and z movements in a specific procedure. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a computer tomography apparatus used for nondestructive inspection, and more particularly to a high-resolution computer tomography apparatus for inspecting small electronic components and the like with high resolution.
[0002]
[Prior art]
2. Description of the Related Art In recent years, high-resolution industrial computer tomography apparatuses (hereinafter, abbreviated as “CT scanners”) for inspecting small electronic components and the like with high resolution have been developed.
[0003]
For example, a high-resolution CT scanner known in Patent Document 1 or the like detects an X-ray beam generated from an X-ray tube and transmitted through a subject with a two-dimensional X-ray detector to obtain a transmission image of the subject. It is configured as follows. When capturing a cross-sectional image, a number of transmission images are obtained while the subject is rotated once (referred to as scanning). The multiple transmission images are subjected to data processing to obtain cross-sectional images (one to many) of the subject. Reconstruction of a cross-sectional image usually uses a filtered back projection method (FBP: Filtered Back Projection method).
[0004]
FIG. 5 is a conceptual diagram of a general high-resolution CT scanner. This high-resolution CT scanner has a feature that the X-ray geometry can be freely set and can cope with various objects. The rotating table 104 and the X-ray detector 103 for mounting and rotating the subject are moved closer to or farther away from the X-ray tube 101 (X-ray focal point F) (in the x direction) to obtain an imaging distance FCD (Focus to Rotation Center Distance). The detection distance FDD (Focus to Detector Distance) can be continuously changed, and the imaging magnification (enlargement ratio) (= FDD / FCD) can be changed according to the subject. Further, the rotary table 104 can be moved up and down (z direction), and the imaging position of the subject can be changed.
[0005]
In FIG. 5, the scan area (sectional image field) is a circle An centered on the rotation center Cn included in the imaging X-ray beam 102 on the rotation plane, and becomes smaller as the imaging magnification increases. The rotation center Cn is usually slightly deviated from the center due to a mechanical error. However, if the deviation is large, it is not preferable because the scan area becomes narrow (at the same photographing magnification). For this reason, the rotary table is configured to be able to move in the direction (y direction) crossing the X-ray beam along the rotation plane and to adjust the center of rotation.
[0006]
In order to obtain a high-resolution cross-sectional image by performing data processing on a large number of transmission images, it is necessary that the rotation center position on the transmission image is accurately calculated in units smaller than one pixel.
[0007]
In order to accurately calculate the position of the rotation center, the conventional high-resolution CT scanner mounts the subject on a pin-shaped phantom and scans the subject before scanning the subject after completing the geometric setting. Is calibrated (scaled). Calibration is performed by obtaining a detection channel position corresponding to the rotation center and storing the same in the data processing unit. As shown in Patent Document 2, the center of rotation can also be obtained from the scan data of the subject itself, and when this is adopted, calibration of the center of rotation can be omitted.
[0008]
In the case of Patent Document 1, the center of rotation is shifted, and the subject is scanned off one side so that a large subject can be imaged. Such a scan is called an offset scan because the rotation center is set (offset) while being shifted. According to FIG. 5, the scan area (cross-sectional image field) in the offset scan is a circle Aof that is in contact with one side of the imaging X-ray beam about the rotation center Cof on the rotation plane, and is larger than the normal scan in the same FCD.
[0009]
[Patent Document 1]
JP-A-2002-62268
[0010]
[Patent Document 2]
JP 2000-298105A
[0011]
[Problems to be solved by the invention]
The above-described high-resolution CT scanner has a problem that, although the X-ray geometry can be freely set, the operation procedure is complicated and cannot be easily used by an operator. That is, procedures such as setting the x, y, and z positions of the rotation table for efficiently placing the target portion of the subject in the cross-sectional image field of view, calibrating the center of rotation, and changing the conditions in the middle and repeating the procedure. There was a problem that the procedure was difficult to understand.
[0012]
An object of the present invention is to provide a CT scanner that can easily set the X-ray geometry and can obtain a high-quality cross-sectional image.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is a computer tomography apparatus that emits a radiation beam so as to be orthogonal to a rotation axis of a rotary table on which a subject is mounted,
An x mechanism for moving the rotary table in a direction x of the radiation beam;
A y mechanism for moving the radiation beam in a direction y across the surface of the turntable in a direction traversing the radiation beam;
A z mechanism for relatively moving the subject in a direction z across the plane of rotation,
A tomography procedure including the x, y, and z movements is sequentially provided in a predetermined order, and at least one of the procedure management means is provided.
[0014]
Further, in order to solve the above-described problems, the present invention provides a computed tomography apparatus that integrally rotates a rotating frame that fixes a radiation source and a radiation detector with respect to a rotation axis orthogonal to a direction of a radiation beam.
An x mechanism for moving the radiation source in a direction x of the radiation beam on the rotating frame;
A y mechanism for moving the radiation source in a direction y in which the radiation beam traverses along the plane of rotation;
A z mechanism for relatively moving the subject in a direction z across the plane of rotation,
A tomography procedure including the x, y, and z movements is sequentially provided in a predetermined order, and at least one of the procedure management means is provided.
[0015]
According to such a configuration, a computer tomography apparatus that emits a radiation beam so as to be orthogonal to the rotation axis of a rotary table on which a subject is mounted or a rotating frame in which a radiation source and a radiation detector are fixed is moved in the direction of the radiation beam. The operator can freely set the X-ray geometry in the x, y, and z directions by following the display by the procedure management means in a computer tomography apparatus that rotates integrally with a rotation axis that is orthogonal to.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a configuration diagram of a CT scanner according to the first embodiment of the present invention.
[0017]
The X-ray tube 1 in the present embodiment is a microfocus X-ray tube in which the focus F of the generated X-ray is several to several tens of μm, and the X-ray detector 3 is an X-ray II (image intensifier: image intensifier). Tube) and a television camera.
[0018]
The X-ray tube 1 and the X-ray detector 3 are supported by an x-shift mechanism 8 so as to sandwich the subject 4 therebetween. The subject 4 is placed on a rotary table 5, rotated along an imaging surface 14 (of a cross-sectional image) in the X-ray beam 2 by a rotation / elevation mechanism 6, and vertically moved (z direction) ) Is done.
[0019]
The subject 4 is moved (in the y direction in the drawing) across the X-ray beam 2 by the y-shift mechanism 7 together with the rotary table 5, and is moved between the X-ray tube 1 and the X-ray detector 3 by the x-shift mechanism 8. And the shooting distance FCD is changed. The X-ray detector 3 is moved by the x shift mechanism 8, and the detection distance FDD is changed. C is a rotation center, and D is a detection center.
[0020]
As other components, a data processing unit 19 that processes a transmission image from the X-ray detector 3, a display unit 20 that displays a processing result and the like, and a mechanism that controls the mechanism unit by a command from the data processing unit 19 A control unit 18, an X-ray control unit 17 for controlling a tube voltage and a tube current of the X-ray tube 1, a high voltage generator 16, a part including the X-ray tube 1, the subject 4, and the X-ray detector 3 An X-ray shielding box (not shown) for storing is provided.
[0021]
An encoder (not shown) is attached to the x shift mechanism 8 and the y shift mechanism 7, and the encoder reads the FCD value, the FDD value, and the y value, and sends them to the data processing unit 19 through the mechanism control unit 18.
[0022]
The data processing unit 19 and the display unit 20 are composed of a normal computer, which comprises a CPU, a memory, a disk, a keyboard, an interface, etc., and software for reconstructing a cross-sectional image from tomographic sequences and data. Etc. are stored.
[0023]
The operator operates the data processing unit 19 and the display unit 20 to perform menu selection and condition setting, manual operation of the mechanism unit, start of tomography, reading of the device status, display of a cross-sectional image, analysis of a cross-sectional image, and the like. Do.
[0024]
The data processing unit 19 is, as a functional block of software, a procedure management unit 21 for sequentially displaying / executing a corresponding procedure, a scan control unit 23 for tomography, a rotation center for obtaining a rotation center position on this image from a transmission image. It has a calculating unit 24, an automatic table moving unit 25 for calculating and controlling the shift amount of the rotary table 5, a reconstructing unit 26 for creating a cross-sectional image, and the like.
[0025]
FIG. 2 is a flowchart illustrating a procedure of the procedure management unit 21 in the present embodiment. The operation in the present embodiment will be described with reference to FIG.
[0026]
First, in step S1, a temporary table setting is performed. In the operation window, as screen 1a,
"Place the work on the table and click X-ray ON."
Is displayed. When the operator places the subject 4 on the rotary table 5 and clicks “X-ray ON”, the procedure management unit 21 gives a command to the X-ray control unit 17 in response to this click, and the high-voltage generation unit 16 A high voltage current is applied to the tube 1 to start X-ray irradiation. Thereby, the data from the X-ray detection unit 3 is taken into the procedure management unit 21, whereby the transmission image is displayed on the transmission image window of the display unit 20, and the operation window is the screen 1 b.
"Adjust the magnification and other factors while viewing the transmitted image, and raise and lower the table to adjust the scan position."
Switch to.
[0027]
Next, the operator moves the xyz position of the rotary table 5 and the x position of the X-ray detector 3 by a switch operation, adjusts the magnification so that the target position of the subject 4 falls within the field of view, and sets the target position. Scan position alignment is performed so as to come to the photographing surface 14. When the operator clicks “Next” on the screen 1b, the process proceeds to step S2.
[0028]
In S2, a test scan is performed. In the operation window, as screen 2
"Set the test scan conditions and click start if you like."
Is displayed. The operator sets the number of views, the number of integrated images, the slice thickness, and the like in the condition setting section of the screen. However, the setting can be omitted if the default values are sufficient. Here, the number of views is the number of collection points during one rotation, the number of integrated images is the number of added images at one point, and the slice thickness is the thickness (number of pixels) of one cross-sectional image.
[0029]
When the operator clicks "Start" on the screen 2, a test scan is executed (execution 2). Here, the scan is performed by the scan control unit 23, and the rotation center position on the transmission image is obtained by the rotation center calculation unit 24 using the transmission images for the number of views. The rotation center is obtained from the scan data of the subject as described in Patent Document 2. During scanning, “scanning” on the screen 2 flashes, and the scanning can be interrupted by the operator clicking “stop”. When the scanning is completed, the process automatically proceeds to step S3.
[0030]
In step S3, automatic table movement is performed. In the operation window, as screen 3
"Select Normal / Offset and click Execute Automatic Table Move."
Is displayed. Here, normal scanning is usually performed, and offset is offset scanning. When "execute movement" is clicked by the operator, the rotary table 5 is moved xy by the automatic table moving unit 25 and set to the optimum table position.
[0031]
FIG. 3 is a geometrical diagram of the automatic table movement, and is a diagram when the photographing surface 14 is viewed from above (z direction). In FIG. 3, C is the current position of the rotation center, and A0 is the scan area. Cn is a normal scan rotation center position of the minimum FCD having a scan area of the same size as A0. Cn is the optimal position for normal scanning. Cof is the offset scan rotation center position of the minimum FCD having a scan area of the same size as A0. Cof is the optimum position for the offset scan.
[0032]
The automatic table moving unit 25 calculates the rotation center deviation Δy using the FCD value of the current position and the rotation center position on the transmission image obtained in step S2, and further calculates the amount of movement to the Cn or Cof position. Move the rotary table.
[0033]
While moving, “moving” on the screen flashes, and the operator can interrupt the movement by clicking “stop”. When the movement is completed and “next” is clicked by the operator, the process proceeds to step S4.
[0034]
In step S4, a main scan is performed. As the screen 4 in the operation window, "Set the main scan conditions, and click Start if OK."
Is displayed. The operator sets the number of views, the total number of sheets, the number of slices, the slice thickness, and the like in the condition setting section of the screen. However, if the default values are sufficient, the settings can be omitted. Here, the number of slices is the number of cross-sectional images to be reconstructed in one scan.
[0035]
When "Start" is clicked, the main scan is executed (Execution 4). Here, the scan is performed by the scan control unit 23, and the rotation center position on the transmission image is obtained by the rotation center calculation unit 24 using the transmission images for the number of views. The rotation center is obtained from the scan data of the subject as described in Patent Document 2. Next, a cross-sectional image is reconstructed by the reconstruction unit 26 using the rotation center. One cross-sectional image can be reconstructed for the imaging surface 14, or it can be reconstructed for a specified number of slices over a wide range covered by the X-ray beam 2. During scanning, “Scanning” flashes on the screen, and you can interrupt scanning by clicking “Pause”. When the scanning is completed, the process automatically proceeds to step S5.
[0036]
In step S5, the main scan is completed, the cross-sectional image is displayed in the cross-sectional image window, and the screen 5 is displayed in the operation window.
"Scan completed"
Is displayed. When the operator clicks “close”, the series of flows ends.
[0037]
Note that the operator can click “return” in each of steps S1 to S5 to return to the designated step and repeat. The specification is made by clicking the step name on the screen. (S1, S2, etc. of the screen are omitted, and the step names are actually described.)
As described above, according to the first embodiment of the present invention, operations or setting procedures are sequentially displayed, so that operations can be easily performed. When the condition is changed in the middle and the operation is repeated, the operation can be similarly easily performed.
[0038]
In addition, the automatic table movement makes it possible to easily set the center of rotation for improving the quality of the cross-sectional image. That is, in both the normal scan and the offset scan, the spatial resolution of the cross-sectional image can be increased by setting the maximum magnification without changing the scan area.
[0039]
The invention is not limited to the embodiments described and illustrated. That is, in the first embodiment, the X-ray detector 3 uses an X-ray II (image intensifier tube) and a television camera, but the X-ray detector 3 is arranged along another two-dimensional X-ray detector or the imaging surface 14. It can be easily understood that a one-dimensional X-ray detector arranged in a vertical direction may be used.
[0040]
In the first embodiment, the change of the imaging position of the subject 4 is performed by moving the rotary table 5 up and down. However, another change mechanism may be installed on the rotary table 5 to perform the change. 1 and the X-ray detector 3 may be moved up and down by one body.
[0041]
Further, the X-ray tube 1 and the X-ray detector 3 may be moved by one body for the rotation of the subject 4 and the x- and y-shifts of the rotary table 5 (rotation axis).
[0042]
Further, it is not always necessary to take the z direction in the elevating direction, and the entire apparatus may be inclined in any direction. That is, the present invention is also applied to another mechanism system in which the movement between the X-ray tube 1 (X-ray source), the X-ray detector 3, the subject 4, and the rotating shaft 13 is relatively the same. .
[0043]
Further, in the first embodiment, the automatic table movement is performed so that the maximum enlargement ratio is obtained without changing the scan area. However, the present invention is not limited to this. FIG. 4 is another automatic table movement geometrical diagram. For example, the scan area may be moved to the maximum without changing the enlargement ratio (that is, FCD) as shown in FIG.
[0044]
Further, the flowchart of the procedure management unit 21 in the first embodiment can be variously changed without changing the gist of the present invention. For example, the user can click "return" to return to an earlier step at one time, but only one step before. By clicking "Return" many times, the same operation can be performed after all. Also, for example, adding another display or execution (for example, adding a calibration, adding a cross-sectional image reconstruction of a test scan, adding a primary automatic table movement before a test scan, and adding a reconstruction condition change after a main scan). Repeating only reconstruction without scanning, etc.). Further, the test scan may be a simple one that only obtains the rotation center (for example, data acquisition of several points / 360 °). Various display expressions are possible, and screen division and integration are also possible. Procedures essential as the gist of the present invention include: temporary setting of an x position (magnification ratio) and z position (imaging position) set by an operator; test tomography of a subject as a scan for obtaining a rotation center; At least one of x, y automatic movement for setting an optimum position using the obtained rotation center and main tomography of the subject.
[0045]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a CT scanner that can easily set an X-ray geometry and that can be easily operated.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a CT scanner according to a first embodiment of the present invention.
FIG. 2 is a flowchart of a procedure management unit in the embodiment.
FIG. 3 is a geometric diagram of automatic table movement in the embodiment.
FIG. 4 is a geometric diagram of another automatic table movement in the embodiment.
FIG. 5 is a conceptual diagram of a general high-resolution CT scanner.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... X-ray tube, 2 ... X-ray beam, 3 ... X-ray detector, 4 ... Subject, 5 ... Rotary table, 6 ... Rotation / elevation mechanism, 7 ... Y shift mechanism, 8 ... X shift mechanism, 9, DESCRIPTION OF SYMBOLS 10 ... Support frame, 13 ... Rotating axis, 14 ... Shooting surface, 15 ... Center line, 16 ... High voltage generator, 17 ... X-ray control part, 18 ... Mechanism control part, 19 ... Data processing part, 20 ... Display part , 21: Procedure management unit, 23: Scan control unit, 24: Rotation center rescue unit, 25: Automatic table moving unit, 26: Reconstruction unit

Claims (4)

In a computer tomography apparatus that emits a radiation beam so as to be orthogonal to a rotation axis of a rotary table on which a subject is mounted,
An x mechanism for moving the rotary table in a direction x of the radiation beam;
A y mechanism for moving the turntable in a direction y across the radiation beam along a plane of rotation;
A z mechanism for relatively moving the subject in a direction z across the plane of rotation,
A computer tomography apparatus comprising: a procedure management unit that sequentially displays and executes at least one of the tomographic procedures including the x, y, and z movements in a predetermined order. In a computed tomography apparatus in which a rotating frame fixing a radiation source and a radiation detector is integrally rotated with respect to a rotation axis orthogonal to a direction of a radiation beam,
An x mechanism for moving the radiation source in a direction x of the radiation beam on the rotating frame;
A y mechanism for moving the radiation source in a direction y in which the radiation beam traverses along the plane of rotation;
A z mechanism for relatively moving the subject in a direction z across the plane of rotation,
A computer tomography apparatus comprising: a procedure management unit that sequentially displays and executes at least one of the tomographic procedures including the x, y, and z movements in a predetermined order. 3. The computed tomography apparatus according to claim 1, wherein the procedure management means includes means for permitting an operator to return from one procedure to an earlier procedure. The procedure management means includes: provisional setting of a magnification position defined by an x movement position and a photographing position defined by a z movement position; test tomography of the subject; automatic movement in x and y directions; The computer tomography apparatus according to any one of claims 1 to 3, further comprising: means for sequentially performing at least one of tomography by at least one of display and execution.

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