JP2011064662A - Ct apparatus with table for fluoroscopic observation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CT apparatus capable of easily fluoroscopic photographing a plate-like specimen such as a mounting substrate and fluoroscopic photographing a large number of small electronic parts and the like at once. <P>SOLUTION: The CT apparatus includes: a table 4 for fluoroscopic observation having a horizontal mounting surface 4a; table drive mechanisms 6 and 7 for moving the table 4 for fluoroscopic observation in X-, Y-, and Z-directions; a rotation mechanism 5 for CT fixed to the table 4 for fluoroscopic observation for holding a specimen 10 for CT photographing and performing CT rotations with respect to a CT axis of rotation in parallel with the Y-direction; a mechanism control means 8 for controlling the table drive mechanisms 6 and 7 in such a way as to achieve a desired field of photographing view at the time of fluoroscopic photographing and at the time of CT photographing and for controlling the rotation mechanism 5 for CT to perform CT rotations; and a data processing means 8 for capturing and displaying a fluoroscopic image of a specimen 9 for fluoroscopic observation at the time of fluoroscopic photographing, capturing and reconfiguring a plurality of fluoroscopic images of the specimen 10 for CT photographing outputted by an X-ray detector during the CT rotations at the time of CT photographing to generate and display a cross-sectional image of the specimen 10 for CT photographing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a computed tomography apparatus (hereinafter referred to as a CT (Computed Tomography) apparatus) that captures a cross-sectional image of a subject.

  A so-called RR (Rotate Rotate) (third generation) CT apparatus that performs only rotation irradiates a subject with radiation (X-rays) generated from a radiation source, and the subject is in the direction of the optical axis of the radiation. A radiation detector having a plurality of one-dimensional or two-dimensional detection channels that rotate relative to the radiation at a rotation axis that intersects with respect to the radiation and transmits the radiation transmitted from the subject at each predetermined rotational position during one rotation. Detection is performed, and a cross-sectional image or three-dimensional data of the subject is obtained (tomographic imaging) from the detector output.

  FIG. 9 shows a configuration of a CT apparatus described in Patent Document 1 as a conventional example (FIG. 9A is a plan view and FIG. 9B is a front view). An X-ray tube 101 and an X-ray detector 103 that detects a cone-shaped X-ray beam 102 generated therefrom with two-dimensional resolution are arranged to face each other, and are placed on a table 104 so as to enter the X-ray beam 102. A transmission image (transmission data) of the placed subject 105 is obtained.

  The table 104 is disposed on the XY mechanism 106, and the XY mechanism 106 is disposed on the rotation / lifting mechanism 107. When photographing a cross-sectional image of the subject 105, transmission images are obtained in a number of directions while the table 104 is rotated once by the rotation / lifting mechanism 107 with respect to the rotation axis RA (referred to as scanning). The multiple transmission images are processed by the control processing unit 108 to obtain cross-sectional images (one or many) of the subject 105.

  Here, the XY mechanism 106 is used to move the table 104 in a plane orthogonal to the rotation axis RA with respect to the rotation axis RA and adjust the position so that the target portion of the subject 105 is on the rotation axis RA. .

  Further, the rotation axis RA and the detector 103 can be moved closer to or away from the X-ray tube 101 by the shift mechanism 109, and the imaging magnification (= FDD / FCD) can be changed according to the purpose.

  The cross-sectional image field (or scan area) 110 shown in FIG. 9 is defined as an area included in the X-ray beam 102 that is always measured during one rotation. The cross-sectional image field 110 is a substantially cylindrical region around the rotation axis RA, and is a region where a cross-sectional image can be reconstructed without difficulty.

  The conventional CT apparatus shown in FIG. 9 can be used not only for CT imaging (cross-sectional image imaging) but also for fluoroscopic imaging for observing a transmission image. In the case of fluoroscopic imaging, a transmission image of the subject 105 placed on the table 104 is captured, and the captured transmission image is displayed on the display unit of the control processing unit 108. By using the XY mechanism 106, the rotation raising / lowering mechanism 107, and the shift mechanism 109, a desired position of the subject 105 can be imaged at a desired imaging magnification and a transmission image can be displayed.

JP 2002-310943 A

  The above-described conventional CT apparatus is used as an inspection apparatus for failure analysis and quality control of industrial products. The main inspection object is an electronic component or a mounting board on which the electronic component is mounted. The inspection is performed using both fluoroscopic imaging that can be performed in a short time and CT imaging that can be performed in detail. First, an inspection method is often used in which an outline inspection is performed by fluoroscopic imaging, and CT imaging is performed on a part or part whose details are to be known.

  When the mounting substrate is fluoroscopically imaged with a conventional CT apparatus, a jig needs to be prepared for each type of substrate in order to fix the substrate upright on the table 104. In addition, when a large number of electronic parts such as ICs are photographed at a time, it is necessary to fix a large number of small electronic parts on a plate-shaped jig, which is not convenient.

  The present invention has been made in view of the above, and an object of the present invention is to provide a CT that can easily perform fluoroscopic imaging of a plate-like subject such as a mounting board or fluoroscopic imaging of many small electronic components at once. Is to provide a device.

  In order to achieve the object, the invention according to claim 1 is a fluoroscopic table having a horizontal placement surface, and an X-ray source for irradiating a fluoroscopic subject placed on the fluoroscopic table with an X-ray beam. A two-dimensional X-ray detector that detects the X-ray beam that has passed through the fluoroscopic subject and outputs it as a transmission image; and the X and Y directions perpendicular to the X and Y directions perpendicular to each other in the horizontal plane. A table driving mechanism that moves in the Z direction; a CT rotation means that is fixed to the fluoroscopic table, holds a CT imaging subject, and rotates CT about a CT rotation axis parallel to the Y direction; Controls the table drive mechanism so that a desired portion of the fluoroscopic subject enters the field of view of the transmission image, and during CT imaging, a desired portion of the CT imaging subject enters the field of view of the transmission image. Table drive After controlling the structure, a mechanism control means for controlling the CT rotation means to perform the CT rotation, and at the time of fluoroscopic imaging, capture and display the transmission image of the fluoroscopic subject, and at the time of CT imaging, the CT rotation Data processing means for taking in and reconstructing a plurality of transmission images of the CT imaging object output from the X-ray detector and creating and displaying cross-sectional images of the CT imaging object. The gist.

  With this configuration, by using a fluoroscopic table, in the fluoroscopic imaging of a plate-like subject such as a mounting board or the fluoroscopic imaging of many small electronic components at one time, a jig is not used and it is firmly Therefore, it is possible to easily perform fluoroscopic imaging simply by placing the robot without fixing.

  In addition, the table drive mechanism (XYZ) used for the visual field adjustment operation and the imaging magnification adjustment operation at the time of fluoroscopic imaging, the offset setting (X) of the projection position of the CT rotation axis, the scan area alignment operation (Y), and the imaging at the time of CT imaging. It can be used for the magnification adjustment operation (Z), and it is not necessary to have a dedicated mechanism.

  In order to achieve the above object, according to a second aspect of the present invention, in the CT apparatus according to the first aspect, the fluoroscopic table includes a plate having the horizontal placement surface and a frame fixed around the plate. The CT rotating means is fixed to the frame body.

  With this configuration, since the CT rotating means is fixed to the frame of the fluoroscopic table, the CT rotating means can be firmly fixed, and the portion protruding on the mounting surface of the fluoroscopic table can be reduced. The space for mounting can be widened.

  In order to achieve the above object, according to a third aspect of the present invention, in the CT apparatus according to the first or second aspect, the CT rotating means is attached by selecting one from at least one holding means. The gist is to hold the CT imaging subject through the selected holding means.

  With this configuration, the CT rotating means holds the CT imaging subject via the detachable holding means, so that it is possible to easily hold the CT imaging subject at hand with the holding means removed. Furthermore, the holding means can be removed during fluoroscopic imaging, and the space for placing the fluoroscopic subject can be widened.

  In order to achieve the above object, a fourth aspect of the present invention is the CT apparatus according to any one of the first to third aspects, wherein the CT apparatus is disposed on the fluoroscopic table and parallel to the placement surface. Filter switching means for holding at least one filter plate so as to be independently rotatable about one filter rotation axis, and an arbitrary number of the above-described X-ray beams that pass through the CT imaging subject. The gist is that the filter plate can be rotated and inserted.

  With this configuration, unused filter plates are evacuated, and an arbitrary number of filter plates to be used are inserted by rotating less than 180 ° to fix a plurality of filters to the disc without overlapping. Multi-stage filter switching is possible with a mechanism that rotates this, much less space. For this reason, a space for placing the fluoroscopic subject can be widened, and a more free position can be set by avoiding mechanical interference.

  In order to achieve the above object, according to a fifth aspect of the present invention, in the CT apparatus according to any one of the first to fourth aspects, the data processing means is a planar gap formed by the CT rotating means. A first slice reference line, which is a projection of the gap, is obtained on a transmission image of the gap jig at a reference CT rotation position obtained by rotating the gap jig having CT, and a CT different by 180 ° from the reference CT rotation position A second slice reference line, which is a projection of the gap, is obtained on the transmission image of the gap jig at the rotation position, and the first slice reference line and the second slice reference line are averaged to obtain a slice reference on the transmission image. The gist is to obtain a line and use it in the reconstruction process.

  With this configuration, even if the gap jig is slightly deviated from the perpendicular to the CT rotation axis, this deviation is corrected using the transmission images at the CT rotation positions 0 ° and 180 °, and the slice reference line is accurately obtained. Can be used for reconstruction processing.

  In order to achieve the object, the invention according to claim 6 is the CT apparatus according to any one of claims 1 to 5, wherein the data processing means includes a plurality of the images captured at the time of the CT imaging. The gist is to obtain a projection position on the transmission image of the CT rotation axis from the transmission image of the CT imaging subject, and create a cross-sectional image of the CT imaging subject using the obtained projection position. .

  With this configuration, the projection position on the transmission image of the CT rotation axis is obtained from the transmission images of a plurality of CT imaging subjects captured at the time of CT imaging, and the CT imaging subject is subjected to the CT imaging using this. The reconfiguration process can be performed. Therefore, even if the projection position on the transmission image of the CT rotation axis is shifted when changing the CT imaging position, CT imaging can be performed without calibration with a special jig.

  In order to achieve the above object, a seventh aspect of the present invention is the CT apparatus according to any one of the first to sixth aspects, wherein one or both of the X-ray source and the X-ray detector are used. The gist of the present invention is to have a tilting mechanism that changes the transmission direction of the X-ray beam transmitted through the fluoroscopic subject in a vertical or inclined direction by tilting the X-ray.

  With this configuration, it is possible to perform tilted fluoroscopy that is tilted from the vertical direction during fluoroscopic imaging.

  In order to achieve the above object, the invention according to claim 8 is characterized in that in the CT apparatus according to claim 7, there is provided table rotating means for rotating the fluoroscopic table about a vertical rotation axis.

  With this configuration, it is possible to change the tilt direction of tilted fluoroscopy with respect to the fluoroscopic subject during fluoroscopic imaging.

  According to the present invention, it is possible to provide a CT apparatus that can easily perform fluoroscopic imaging of a plate-like subject such as a mounting substrate or fluoroscopic imaging of many small electronic components at once.

The schematic diagram (front view) which showed the structure of CT apparatus concerning 1st embodiment of this invention. The schematic diagram (front view) which showed the one part detailed structure of CT apparatus which concerns on 1st embodiment. The schematic diagram (front view) which shows 2 types of holders which concern on the modification 3 of 1st embodiment. The schematic diagram which shows the filter switching mechanism which concerns on the modification 4 of 1st embodiment ((a) is a top view, (b) is a front view). The schematic diagram which shows the gap | interval jig | tool which concerns on the modification 5 of 1st embodiment. The figure which shows the permeation | transmission image and slice reference line of the gap | interval jig | tool 15 which concern on the modification 5 of 1st embodiment. The conceptual diagram (front view) explaining the inclination see-through | perspective function which concerns on the modification 8 of 1st embodiment. The conceptual diagram (front view) explaining the inclination azimuth | direction change function which concerns on the modification 9 of 1st embodiment. The schematic diagram which showed the structure of the conventional CT apparatus ((a) is a top view, (b) is a front view).

  Embodiments of the present invention will be described below with reference to the drawings.

(Configuration of the first embodiment of the present invention)
The configuration of the first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic view (front view) showing the configuration of a CT apparatus according to the first embodiment of the present invention.

  The CT apparatus includes an X-ray tube 1 (X-ray source), an X-ray detector 3 that detects an X-ray beam 2 emitted from the X-ray tube 1, and a space between the X-ray tube 1 and the X-ray detector 3. A fluoroscopic table 4 arranged in the X direction, a CT rotating mechanism 5 (CT rotating means) arranged on the fluoroscopic table 4, and an XY mechanism (table driving mechanism) that moves the fluoroscopic table 4 in three axial directions. 6 and a Z mechanism (table drive mechanism) 7, a CT rotation mechanism 5, an XY mechanism 6 and a Z mechanism 7, and a control processing unit (mechanism control) for taking in and processing the output of the X-ray detector 3. Means and data processing means) 8.

  The X-ray tube 1 emits X-rays centered on the vertical direction from the X-ray focal point F, and the X-ray detector 3 is disposed above the X-ray tube 1 with the detection surface 3a facing the X-ray tube 1 and emitted. Then, the pyramid-shaped X-ray beam 2 which is a part of the X-rays transmitted through the fluoroscopic table 4 and the subject (9 or 10) is detected with a two-dimensional resolution and output as a transmission image (transmission data). (X-rays are also emitted outside the X-ray beam 2)

  The X-ray tube 1 uses a microfocus X-ray tube having a focal point F of the generated X-ray beam 2 of about 1 μm, and the X-ray detector 3 is a combination of an X-ray II (Image Intensifier) and a television camera, or X An X-ray flat panel detector (FPD) in which line detection elements are arranged in a two-dimensional matrix is used. The X-ray detector 3 outputs a transmission image as digital data.

  The fluoroscopic table 4 has a horizontal placement surface 4a on which the fluoroscopic subject 9 is placed. Further, the fluoroscopic table 4 holds the CT imaging subject 10 and has a horizontal CT rotation axis HA (Y The CT rotation mechanism 5 that rotates (CT rotation) with respect to (direction) is fixed.

  The XY mechanism 6 moves the fluoroscopic table 4 in the X and Y directions orthogonal to each other in the horizontal direction, and the Z mechanism 7 moves the fluoroscopic table 4 in the vertical Z direction. By this movement, a desired portion of the subject (9 or 10) can enter the field of view of the transmission image (corresponding to the X-ray beam 2) at a desired imaging magnification. Here, referring to FIG. 1, the imaging magnification is FDD / FOD in the case of fluoroscopic imaging, and FDD / FCD in the case of CT imaging. (FDD: distance between focus detection surfaces, FOD: distance between focus objects, FCD: distance between focus CT rotation axes)

  Note that an encoder (not shown) is attached to each mechanism section (CT rotation mechanism 5, XY mechanism 6, Z mechanism 7), and the movement position X, Y, Z (FOD, FCD) and the rotation angle ω by the CT rotation mechanism 5 are read and sent to the control processing unit 8 respectively.

  Further, the X-ray beam 2 intersects only the subjects 9 and 10 and the fluoroscopic table 4 and does not intersect with other mechanical components having strong X-ray absorption. In addition, as components, there are a frame that supports the X-ray tube 1, the X-ray detector 3, the Z mechanism 7, and the like, a shielding box that shields X-rays, and the like, which are not shown.

  FIG. 2 is a schematic diagram (front view) showing a detailed configuration of a part of the CT apparatus according to the first embodiment.

  Referring to FIG. 2, the fluoroscopic table 4 includes a plate 4b having a horizontal mounting surface 4a and a reinforcing frame 4c fixed around the plate 4b. It is fixed to 4c with screws or the like. The plate 4b is made of a material such as carbon or plastic that easily transmits X-rays and is made to have a uniform density and thickness.

  The CT rotation mechanism 5 includes a motor 5a with a reduction gear and a holder (holding means) 5b that can be inserted into a rotary shaft member of the motor 5a and fixed with a single screw. The holder 5b is a spring like a laundry basket. The CT imaging subject 10 is sandwiched between the movable pieces urged in step (1) and fixed near the CT rotation axis HA. The motor 5a rotates the CT imaging object 10 together with the holder 5b with respect to the CT rotation axis HA. The CT rotation mechanism 5 is arranged so that a portion protruding on the placement surface 4a is reduced when the holder 5b is removed.

  Returning to FIG. 1, the control processing unit 8 is a normal computer and includes a CPU, a memory, a disk, a display unit 8a, an input unit (keyboard, mouse, etc.) 8b, a mechanism control board, an interface, and the like.

  The control processing unit 8 receives signals (encoder pulses and the like) of the operation positions of the respective mechanism units (the CT rotation mechanism 5, the XY mechanism 6, and the Z mechanism 7) from the mechanism control board. To control the position of the subject and perform scanning (CT imaging scanning) and the like, and also transmit an imaging command signal of a transmission image to the X-ray detector 3.

  The control processing unit 8 captures a transmission image from the X-ray detector 3 at the time of fluoroscopic imaging, displays the transmission image on the display unit 8a in real time, performs storage and processing, and displays the stored transmission image. In addition, the control processing unit 8 causes the desired portion of the fluoroscopic subject 9 to enter the field of view of the transmission image at a desired imaging magnification in accordance with the input performed by the operator while observing the transmission image displayed in real time during fluoroscopic imaging. The XY mechanism 6 and the Z mechanism 7 are controlled.

  At the time of CT imaging, the control processing unit 8 first transmits a desired portion of the CT imaging subject 10 at a desired imaging magnification according to an input performed by an operator while performing fluoroscopic imaging and observing a transmission image in real time display. After controlling the XY mechanism 6 and the Z mechanism 7 so as to enter the field of view of the image, the CT rotation mechanism 5 is controlled in accordance with a CT imaging start command to perform CT rotation. Further, a plurality of transmission images output by the X-ray detector 3 during CT rotation (scanning) are taken and reconstructed to create and display a cross-sectional image of the CT imaging subject 10.

  In addition, the control processing unit 8 issues a command to an X-ray control unit (not shown) that controls the X-ray tube 1, specifies a tube voltage and a tube current, and instructs X-ray emission and stop. The tube voltage and tube current can be changed according to the subject.

  As shown in FIG. 1, the control processing unit 8 reads the software and functions as a functional block for the CPU to function. The control unit 8c controls the positioning of the subjects 9 and 10 by the mechanism units 6 and 7, and controls CT imaging. A scanning control unit 8d that performs the reconstruction processing of the cross-sectional image, and the like.

(Operation of the first embodiment)
The operation will be described with reference to FIGS.

  When performing fluoroscopic imaging, the operator places a fluoroscopic subject 9 such as a mounting board on the placement surface 4 a of the fluoroscopic table 4, and inputs an X-ray emission start command to the control processing unit 8. The control processing unit 8 starts irradiation with X-rays, captures a transmission image from the X-ray detector 3, and displays it on the display unit 8a in real time.

  When the operator inputs a movement command to the control processing unit 8 so that a desired portion of the fluoroscopic subject 9 enters the field of view of the transmission image at a desired imaging magnification while observing the transmission image displayed in real time, the control processing unit 8 In response to this input, the XY mechanism 6 and the Z mechanism 7 are controlled.

  When the desired portion enters the field of view, the operator observes the transmission image displayed on the display 8a, and stores the image by designating the integrated number as necessary. The control processing unit 8 performs integration and storage of images, and performs image processing, redisplay of stored images, and the like in accordance with instructions from the operator.

  When a large number of electronic parts such as ICs are to be radiographed at a time as the fluoroscopic object 9, the electronic parts are placed directly on the placement surface 4a of the fluoroscopic table 4, or a material that transmits X-rays well. The trays are arranged on the prepared trays, and the trays are placed on the fluoroscopic table 4 to perform fluoroscopic imaging as described above.

  When performing CT imaging, the operator first removes the holder 5b from the CT rotation mechanism 5, holds the CT imaging subject 10 in between, and uses the CT 5 to hold the holder 5b in between. Attached to the rotating mechanism 5.

  Next, when a command for starting X-ray emission is input to the control processing unit 8, the control processing unit 8 starts irradiation of X-rays, captures a transmission image from the X-ray detector 3, and displays it on the display unit 8a in real time.

  As in the case of fluoroscopic imaging, a movement command is given to the control processing unit 8 so that the desired portion of the CT imaging subject 10 enters the visual field of the transmission image at a desired imaging magnification while observing the transmission image displayed in real time. When input, the control processing unit 8 controls the XY mechanism 6 and the Z mechanism 7 in accordance with this input.

  At this time, the projection position of the CT rotation axis HA on the transmission image can be adjusted to the center by X movement (for normal scanning) or offset to the screen edge (for offset scanning), and scanning in the CT rotation axis direction can be performed by Y movement. The area can be adjusted, and the shooting magnification can be adjusted by moving the Z.

  When the desired portion enters the field of view, the operator inputs a command to start CT imaging to the control processing unit 8. The control processing unit 8 controls the CT rotation mechanism 5 in accordance with a CT imaging start command to perform CT rotation, and the X-ray detector 3 outputs a plurality of outputs each time a predetermined angle is rotated during CT rotation (scanning). One or a plurality of cross-sectional images of the CT imaging subject 10 are created and displayed by performing reconstruction processing.

  Here, the CT rotation is 360 ° or more in the normal scan, 180 ° + fan angle (X-ray beam 2 spread angle) or more and less than 360 ° in the half scan. The reconstruction processing is performed by a known method, for example, a filtered back projection method (FBP (Filtered Back Projection) method). Further, when the projection position of the CT rotation axis HA is set at the screen end, a known FBP method reconstruction for offset scanning is performed.

  The control processing unit 8 stores the plurality of captured transmission images and the reconstructed cross-sectional image, and in accordance with an instruction from the operator, the reconfiguration processing is retried, the cross-sectional image is processed, and the image is processed and stored. Redisplay the stored image.

  As described above, an image stored at the time of fluoroscopic imaging or CT imaging can be transferred to a printer to make a hard copy, or transferred to another place through a network.

(Effects of the first embodiment)
According to the first embodiment, by using the fluoroscopic table 4, a jig or the like is used in fluoroscopic imaging of a plate-like subject such as a mounting board or fluoroscopic imaging in which a large number of small electronic components are performed at once. It is possible to easily perform fluoroscopic imaging simply by placing it without using it and without firmly fixing it.

  Further, according to the first embodiment, the table drive mechanism used for the visual field alignment operation (XY) and the imaging magnification adjustment operation (Z) at the time of fluoroscopic imaging is used to set the offset of the projection position of the CT rotation axis (X ), Scan area alignment operation (Y), and imaging magnification alignment operation (Z), and it is not necessary to have a dedicated mechanism.

  In addition, according to the first embodiment, since the CT rotation mechanism 5 is fixed to the frame 4c of the fluoroscopic table 4, the CT rotation mechanism 5 can be firmly fixed and the mounting surface 4a of the fluoroscopic table 4 can be fixed. The portion protruding upward can be reduced, and the space for placing the fluoroscopic subject 9 can be increased.

  In addition, according to the first embodiment, the CT rotation mechanism 5 holds the CT imaging subject 10 via the detachable holder 5b, so that the CT can be easily performed at hand with the holder 5b removed. An operation of holding the imaging subject 10 can be performed. Furthermore, the holder 5b can be removed during fluoroscopic imaging, and the space for placing the fluoroscopic subject 9 can be increased.

  Further, according to the first embodiment, the CT imaging subject 10 can be sandwiched by the movable piece biased by the spring of the holder 5b and can be easily fixed near the CT rotation axis HA.

(Modification of the first embodiment)
In addition, the present invention is not limited to the above-described embodiment, and various modifications and functions can be added without departing from the scope of the invention. The following modifications can be applied in various combinations.

(Modification 1)
In the first embodiment, the CT rotation mechanism 5 is fixed to the fluoroscopic table 4, but it is fixed to the XY mechanism 6 or the Z mechanism 7 so as to be moved in the X, Y, and Z directions. Are the same.

(Modification 2)
In the first embodiment, a mechanism for avoiding the CT rotation mechanism 5 on the fluoroscopic table 4 in a direction far from the placement surface 4a can be provided. The CT rotation mechanism 5 may be detachable from the fluoroscopic table 4. Accordingly, by avoiding or removing the CT rotation mechanism 5 during fluoroscopic imaging, a space for placing the fluoroscopic subject 9 can be widened, and more free position setting is possible by avoiding mechanical interference. Become.

  Further, the fluoroscopic table 4 can be attached to and detached from the XY mechanism 6 and a plurality of fluoroscopic tables 4 are prepared, and the fluoroscopic table 4 with the CT rotating mechanism 5 is provided during CT imaging and normal fluoroscopic imaging. When mounting and mounting a large subject 9 by transmission imaging, or when it is desired to set a more free position by avoiding mechanical interference, the fluoroscopic table 4 without the CT rotation mechanism 5 is mounted. You may do it. In this attachment / detachment method, when a filter switching mechanism 11, a collimator, and the like, which will be described later, are attached to the fluoroscopy table 4, the CT rotation mechanism 5, the filter switching mechanism 11, the collimator, etc. are easily detached from the fluoroscopy table. The whole 4 can be attached and detached.

(Modification 3)
In the first embodiment, the CT rotation mechanism 5 has a detachable holder 5b. However, a plurality of holders may be prepared and an arbitrary one may be attached. According to this, it is possible to perform an operation of holding the next subject while examining one subject.

  Further, one of a plurality of types of holders can be selected and used according to the subject.

  FIG. 3 is a schematic view (front view) showing two types of holders according to Modification 3 of the first embodiment. The holder 5b 'has a holding surface parallel to the CT rotation axis HA, and the CT imaging subject 10 is attached to the holding surface with a double-sided adhesive tape. Alternatively, a single-sided adhesive tape is wound and fixed with the subject placed on the holding surface.

  The holder 5 b ″ has a holding surface perpendicular to the CT rotation axis HA, and the CT imaging subject 10 is attached to the holding surface with a double-sided adhesive tape. Alternatively, a single-sided adhesive tape is wound and fixed with the subject placed on the holding surface.

(Modification 4)
In the first embodiment, a filter switching mechanism (filter switching means) 11 for switching by inserting an X-ray filter into the X-ray beam 2 at the time of CT imaging can be added.

  4A and 4B are schematic views ((a) is a plan view and (b) is a front view) showing a filter switching mechanism according to a fourth modification of the first embodiment.

  The filter switching mechanism 11 is disposed on the fluoroscopic table 4 and can rotate the plurality of filter plates 12 parallel to the placement surface 4a independently around one filter rotation shaft 13 perpendicular to the placement surface 4a. An arbitrary number of filter plates 12 can be manually rotated and inserted or retracted so as to block the X-ray beam 2 transmitted through the CT imaging subject 10.

  As the filter plate 12, for example, four copper-made plates with a thickness of 0.5 mm are used, each of which is independently rotated around the filter rotation shaft 13, and a position (insertion position) where it abuts against the stopper 14 a and a stopper. The position abutted on 14b (retracted position) is switched. This filter switching mechanism 11 allows the operator to switch the filter thickness for the X-ray beam 2 from 0 mm to 2 mm in five steps in 0.5 mm steps by rotating and inserting an arbitrary number of filter plates 12.

  In the case of a conventional filter switching mechanism, the filter is switched by rotating a disk in which five types of filter plates having thicknesses of 0 mm to 2 mm are fixed at the same distance from the filter rotation axis in steps of 0.5 mm. On the other hand, according to the filter switching mechanism 11 of the modified example 4, the unused filter plates are overlapped and retracted, and the arbitrary number of filter plates 12 to be used are inserted after being rotated by less than 180 °. A mechanism for fixing a plurality of filters to a disk without rotating them and rotating them, and multi-stage filter switching can be performed in a much smaller space. For this reason, a space for placing the fluoroscopic subject 9 can be widened, and a more free position can be set while avoiding mechanical interference.

  In Modification 4, four copper-made filter plates 12 having a thickness of 0.5 mm are used, but the material, thickness, and number are not limited thereto. Further, the thicknesses may not be the same, for example, a combination of thicknesses that are powers of 2 times the reference thickness. In this case, for example, three sheets of 0.5 mm, 1 mm, and 2 mm may be used. By combining these three sheets, eight steps can be switched from 0 mm to 3.5 mm in 0.5 mm steps, and the number of switching steps can be increased with a small number of sheets.

  In FIG. 4, the filter switching mechanism 11 is fixed to the frame 4c, but may be fixed to the plate 4b. Furthermore, the filter plate 12 can be switched by rotating it with a motor or the like instead of manually.

(Modification 5)
In the first embodiment, prior to CT imaging, the slice reference line can be calibrated using a gap jig. The slice reference line is a line on the transmission image and is defined as a line on the transmission image corresponding to a line that intersects the detection surface 3a of the X-ray detector 3 with a plane orthogonal to the CT rotation axis HA and passing through the X-ray focal point F. Is done. The reconstruction process is performed with reference to this slice reference line. A line parallel to the slice reference line is defined as a slice line.

  FIG. 5 is a schematic view showing a gap jig according to Modification 5 of the first embodiment. Like the holder 5b, the gap jig 15 can be inserted into the rotating shaft member of the motor 5a of the CT rotation mechanism 5 and fixed with one screw. The gap jig 15 has a planar gap 15a that easily transmits X-rays, and this gap 15a is formed to be perpendicular to the CT rotation axis HA when attached to the CT rotation mechanism 5.

  The calibration of the slice reference line will be described with reference to FIG.

FIG. 6 is a diagram showing a transmission image and a slice reference line of the gap jig 15 according to the fifth modification. First, when the gap jig 15 is inserted into and fixed to the rotating shaft member of the motor 5a to perform fluoroscopic imaging, a transmission image shown in FIG. 6A is obtained. If the X-ray focal point F is deviated from the plane formed by the gap 15a, the transmitted image of the gap 15a is not clear as shown in FIG. Therefore, when the gap jig 15 is moved in the CT rotation axis (Y) direction by the XY mechanism 6 so that the plane of the gap 15a passes through the X-ray focal point F, the projection of the gap 15a is clear as shown in FIG. The straight line that is the projection of this gap is obtained as the slice reference line 16. When the abscissa of the transmission image is n and the ordinate is m, the slice reference line is expressed by the equation m = a · n + b (1)
As obtained.

The above is the principle of calibration. However, in actuality, when the gap jig 15 is inserted into the rotating shaft member of the motor 5a, there is play in the insertion portion, and therefore the gap 15a is usually slightly deviated from the perpendicular to the CT rotating axis HA. Then, calibration is performed to correct this deviation. The calibration corrected for the misalignment is first the first slice reference line as described above at the reference CT rotational position,
m = a1 · n + b1 (2)
Ask for. Next, a second slice reference line is similarly formed at a CT rotation position that is 180 ° different from the reference CT rotation position,
m = a2 · n + b2 (3)
And the first slice reference line and the second slice reference line are averaged to obtain a slice reference line used for the reconstruction process. The average is obtained by, for example, calculating the coefficients of the equations (2) and (3)
a = (a1 + a2) / 2 (4)
b = (b1 + b2) / 2 (5)
And using the averaged coefficient, the slice reference line expressed by Equation (1) is adopted and used for the reconstruction process.

  The correction of the slice line in which the deviation from the vertical is corrected can be expressed as follows when viewed from the control processing means 8.

  The control processing unit 8 is a projection of the gap 15a on the transmission image of the gap jig 15 at the reference CT rotation position obtained by CT rotation of the gap jig 15 having the planar gap 15a by the CT rotation mechanism 5. One slice reference line is obtained, and a second slice reference line that is a projection of the gap 15a is obtained on the transmission image of the gap jig 15 at a CT rotation position that is 180 ° different from the reference CT rotation position. The slice reference lines on the transmission image are obtained by averaging the second slice reference lines and used for the reconstruction process.

  According to this calibration, even if the gap jig is slightly deviated from the perpendicular to the CT rotation axis, this deviation is corrected by using the transmission images at the CT rotation positions 0 ° and 180 °, and the slice reference line is accurately set. And can be used for the reconstruction process.

  As the gap jig 15, the gap 5 can be substituted for the gap 5 by forming a gap in the gap 5 b. Alternatively, the gap jig 15 may be fixedly attached to the rotating shaft member of the motor 5a, and the holder 5b may be attached without removing the gap jig 15.

(Modification 6)
In the first embodiment, the projection position (rotation axis projection position) on the transmission image of the CT rotation axis HA can be obtained from the transmission images of the plurality of CT imaging subjects 10 taken at the time of CT imaging. This is called rotation center calibration. The cross-sectional image of the CT imaging subject 10 is obtained with the obtained rotation axis projection position as a reference. That is, here, the center of rotation is obtained from the transmission image of the subject captured at the time of CT imaging, and the reconstruction processing of the subject taken by the CT imaging is performed using this.

  For example, one of the following three methods can be used as a method of calibrating the center of rotation from a transmission image of the subject itself.

<First rotation center calibration>
Rotation center calibration is performed to find the symmetry center of the projection data obtained by averaging the projection data on the slice reference line of the transmission image or the slice line parallel to the slice reference line by 360 °.

  As disclosed in Japanese Patent No. 3607285, this rotation center calibration is performed by detecting “projection data obtained from the detection channel n of the detector along the imaging tomographic plane (slice reference line) and the (CT) rotation angle φ. The rotation center calibration is performed by obtaining the center of symmetry of the average projection data obtained by averaging 360 degrees of the rotation angle φ for each channel n and setting it as the center channel nc corresponding to the center of rotation.

  Using this rotation center calibration, a rotation axis projection point is obtained on the slice reference line, and a line passing through this point and perpendicular to the slice reference line is obtained as the projection position of the CT rotation axis HA. Alternatively, rotation axis projection points are obtained on a plurality of slice lines parallel to the slice reference line, and a straight line connecting these points is obtained as the projection position of the CT rotation axis HA. <> End

<Second rotation center calibration>
Rotation center calibration is performed to obtain a symmetry center of projection data by correlating on a sinogram formed by projection data on the slice reference line of the transmission image or parallel to the slice reference line.

  As described in Japanese Patent No. 3616928, this rotation center calibration is performed as follows: “Transmission data at a plurality of points and virtual rotation on a sinogram created by a plurality of transmission data (on the slice reference line at the rotation position) of the subject. Correlation between the plurality of points determined by setting the center and transmission data at a plurality of points each forming a reverse X-ray path, and changing the virtual rotation center, the virtual rotation center that gives the best correlation is obtained. This is rotation center calibration, which is obtained as the rotation center position.

  Using this rotation center calibration, a rotation axis projection point is obtained on the slice reference line, and a line passing through this point and perpendicular to the slice reference line is obtained as the projection position of the CT rotation axis HA. Alternatively, rotation axis projection points are obtained on a plurality of slice lines parallel to the slice reference line, and a straight line connecting these points is obtained as the projection position of the CT rotation axis HA. <> End

<Third rotation center calibration>
Center calibration is performed to obtain a symmetrical central axis of an added transmission image obtained by logarithmically converting a plurality of transmission images captured by CT imaging and adding 360 °.

  This rotation center calibration is disclosed in Japanese Patent Application Laid-Open No. 2005-233760. “In a circular tomosynthesis apparatus, each of a plurality of transmission images obtained during one tomosynthesis scanning is converted into a projection image corresponding to an attenuation index, This is a rotation center calibration that uses the fact that the added projection image obtained by adding the plurality of projection images is symmetric with respect to the rotation axis of tomosynthesis, and calculates the rotation axis on the projection image. This rotation center calibration can be applied to not only a circular tomosynthesis apparatus (circular laminograph) but also an RR CT apparatus. Using this rotation center calibration, the projection position of the CT rotation axis HA can be obtained without knowing the slice reference plane.

  In this rotation center calibration, the control processing means 8 logarithmically converts the transmission images of the plurality of CT imaging subjects 10 taken at the time of CT imaging to convert them into images corresponding to attenuation indexes, and then adds and adds them. Create a transmission image (average transmission image), for example, set a virtual straight line on this added transmission image, evaluate the symmetry with respect to this virtual straight line, and tilt and move the virtual straight line with the best symmetry Is obtained as a projection position on the transmission image of the CT rotation axis, and a cross-sectional image of the CT imaging subject 10 is created using the obtained projection position.

  According to this rotation center calibration, the projection position of the CT rotation axis HA can be obtained without knowing the slice reference plane. Furthermore, the direction of the slice line orthogonal to the rotation axis projection position obtained can be obtained. Since the slice line at the center of the screen can be set as the slice reference line, calibration of the slice reference line using the gap jig 15 (Modification 5) becomes unnecessary. <> End

  Thus, the rotation center calibration combining the first to third rotation center calibrations is also possible. For example, first, the slice reference line is obtained by the third rotation center calibration, and then the rotation axis projection point (initial) on the slice reference line is obtained by the first rotation center calibration using the data on the slice reference line. Further, in the third rotation center calibration, the accurate rotation axis projection position (final) can be obtained at a high processing speed by taking the correlation by changing the virtual rotation center around the rotation axis projection point (initial). it can. In addition, the center of rotation can be calibrated without calibrating the slice reference line.

(Modification 7)
In the first embodiment, the X-ray tube 1 is set downward and the X-ray detector 3 is set upward with respect to the fluoroscopic table 4.

  In this case, the X-ray tube 1 emits X-rays to the subjects 9 and 10 on the fluoroscopic table 4 from above to below, and the X-ray detector 3 directs the detection surface toward the X-ray tube 1 for fluoroscopy. X-rays arranged below the table 4 and transmitted through the subjects 9 and 10 are detected.

(Modification 8)
An inclined perspective function can be added to the first embodiment. FIG. 7 is a conceptual diagram (front view) for explaining the tilted perspective function according to the modified example 8 of the first embodiment.

  In contrast to the first embodiment, the CT apparatus that performs oblique fluoroscopy transmits the X-ray beam 2 that transmits the fluoroscopic subject 9 by tilting one or both of the X-ray tube 1 and the X-ray detector 3. A tilting mechanism that changes the direction to a vertical or tilted direction is added. 7A shows a case where the X-ray detector 3 is tilted, FIG. 7B shows a case where the X-ray tube 1 and the X-ray detector 3 are tilted, and FIG. 7C shows a case where the X-ray tube 1 is tilted. Indicates when to do.

  This tilt may be a combination of linear movement and swing motion even in arcuate turning. Further, the tilt direction may be the X direction or the Y direction.

  In addition, when adding a tilt function, the control processing unit 8 may have a tilt follow-up function that calculates the visual field deviation when tilted and moves the fluoroscopic table in XYZ so as to maintain the visual field and the photographing magnification. it can.

(Modification 9)
A tilt azimuth changing function can be further added to the CT apparatus (modification 8) in which the tilt fluoroscopic function is added to the first embodiment.

  FIG. 8 is a conceptual diagram (front view) for explaining the tilt azimuth changing function according to the modification 9 of the first embodiment.

  The CT apparatus for changing the tilt direction adds a table rotating means 17 for rotating the fluoroscopic table 4 with respect to the vertical fluoroscopic rotation axis VA. The table rotating means 17 may rotate the fluoroscopic table 4 and the XY mechanism 6 together as shown in FIG. 8A, or only the fluoroscopic table 4 on the XY mechanism 6 as shown in FIG. 8B. May be rotated. The tilt orientation can be changed when the fluoroscopic subject 9 is tilted through by this rotation.

  Here, when the tilt direction changing function is added, the control processing unit 8 calculates the visual field shift when the fluoroscopic table 4 is rotated, and moves the fluoroscopic table XYZ so as to maintain the visual field and the photographing magnification. A rotation follow-up function can be provided.

(Modification 10)
A lamino imaging function of a circular laminograph can be further added to the CT apparatus (modification 9) in which the tilted perspective function and the tilt direction changing function are added to the first embodiment.

  In laminography, a fluoroscopic subject detected by the X-ray detector 3 at a plurality of rotational positions while rotating the subject around a vertical fluoroscopic rotation axis VA in a perspective state inclined from vertical. 9 transmission images are taken, and the plurality of transmission images are processed to create one or a plurality of cross-sectional images of the fluoroscopic subject 9.

1 ... X-ray tube,
2 ... X-ray beam,
3 ... X-ray detector, 3a ... detection surface,
4 ... see-through table, 4a ... mounting surface, 4b ... plate, 4c ... frame,
5 ... CT rotation mechanism, 5a ... motor, 5b ... holder,
6 ... XY mechanism,
7 ... Z mechanism,
8 ... Control processing unit, 8a ... Display unit, 8b ... Input unit, 8c ... Positioning control unit, 8d ... Scan control unit, 8e ... Reconstruction unit,
9 ... Subject for fluoroscopy,
10 ... CT imaging subject,
11 ... Filter switching mechanism,
12 ... filter plate,
13: Filter rotation shaft,
14a, 14b ... stopper,
15 ... Gap jig, 15a ... Gap,
16 ... slice reference line,
17 ... Table rotating means,
DESCRIPTION OF SYMBOLS 101 ... X-ray tube, 102 ... X-ray beam, 103 ... X-ray detector, 104 ... Table, 105 ... Subject, 106 ... XY mechanism, 107 ... Rotation / lifting mechanism, 108 ... Control processing part, 109 ... Shift mechanism 110: Sectional image field of view

Claims (8)

A fluoroscopic table having a horizontal mounting surface;
An X-ray source for irradiating a fluoroscopic subject placed on the fluoroscopic table with an X-ray beam;
A two-dimensional X-ray detector that detects the X-ray beam that has passed through the fluoroscopic subject and outputs a transmitted image;
A table driving mechanism for moving the fluoroscopic table in an X direction, a Y direction, and a vertical Z direction perpendicular to each other in a horizontal plane;
CT rotation means fixed to the fluoroscopic table, holding a CT imaging object, and performing CT rotation with respect to a CT rotation axis parallel to the Y direction;
At the time of fluoroscopic imaging, the table driving mechanism is controlled so that a desired portion of the fluoroscopic subject falls within the field of view of the transmission image, and at the time of CT radiography, the desired portion of the CT radiographic subject is at the field of view of the transmission image. Mechanism control means for controlling the CT drive means to perform the CT rotation after controlling the table drive mechanism to enter
At the time of fluoroscopic imaging, a transmission image of the fluoroscopic subject is captured and displayed, and at the time of CT imaging, a plurality of transmission images of the CT imaging subject output by the X-ray detector during the CT rotation are captured and reconstructed. Data processing means for creating and displaying a cross-sectional image of the CT imaging subject;
CT apparatus characterized by having. The CT apparatus according to claim 1,
The fluoroscopic table is composed of a plate having the horizontal placement surface and a frame fixed around the plate,
The CT apparatus, wherein the CT rotating means is fixed to the frame. The CT apparatus according to claim 1 or 2,
A CT apparatus characterized in that one of the CT rotation means can be selected and attached from at least one holding means, and the CT imaging subject is held via the selected holding means. The CT apparatus according to any one of claims 1 to 3,
Filter switching means disposed on the fluoroscopic table and holding at least one filter plate parallel to the mounting surface so as to be independently rotatable about one filter rotation axis, A CT apparatus characterized in that an arbitrary number of the filter plates can be rotated and inserted so as to block the X-ray beam passing through the specimen. The CT apparatus according to any one of claims 1 to 4,
The data processing means is a first slice that is a projection of the gap on a transmission image of the gap jig at a reference CT rotation position obtained by rotating the gap jig having a planar gap by CT with the CT rotation means. A reference line is obtained, and a second slice reference line that is a projection of the gap is obtained on a transmission image of the gap jig at a CT rotation position that is 180 ° different from the reference CT rotation position, and the first slice reference line and A CT apparatus characterized in that the second slice reference line is averaged to obtain a slice reference line on a transmission image and used for the reconstruction processing. The CT apparatus according to any one of claims 1 to 5,
The data processing means obtains a projection position on a transmission image of the CT rotation axis from a plurality of transmission images of the CT imaging object captured at the time of the CT imaging, and uses the obtained projection position to calculate the projection position. A CT apparatus for producing a cross-sectional image of a subject for CT imaging. The CT apparatus according to any one of claims 1 to 6,
A tilting mechanism for tilting either one or both of the X-ray source and the X-ray detector to change the transmission direction of the X-ray beam transmitted through the fluoroscopic subject to a vertical or tilted direction; CT apparatus characterized by the above. The CT apparatus according to claim 7,
A CT apparatus comprising table rotation means for rotating the fluoroscopic table with respect to a vertical rotation axis.

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