JPH01256936A - Computerized tomograph - Google Patents

Abstract

PURPOSE:To maintain geometrical accuracy in the three points of an X-ray tube focus, a cutting center and an image recording medium center as well as to make improvements in the resolving power of an image by deflecting a cutting face frame in a horizontal surface during relative movements of an X-ray tube and a screen imager, and compensating any positional slippage in a fulcrum of the relative movement. CONSTITUTION:A cutting face device 4 is separated to a cutting face frame 15 supporting a column 3 rockably and a moving frame 6 making a cutting face go up or down, while the cutting face frame 15 is shiftably supported on this moving frame 6 in a horizontal surface, and it is made up of installing such a mechanism as deflecting the cutting face frame 15 in this horizontal surface, so that the cutting face frame 15 is deflected in both directions, by way of example, in the horizontal surface during relative movements of an X-ray tube 1 and a screen imager 2, whereby a fulcrum 9 of this relative movement, namely, positional slippage in a cutting center 11 is compensable. For example, when the cutting center 11 is dislocated toward the left as in 11' during the relative movement of the X-ray tube 1 and the screen imager 2, the cutting face frame 15 is deflected toward the right by action of a cam, whereby the cutting center 11 is compensated in the right direction as much as the dislocated value shown in an arrow C. In this connection, a center 14' of an image recording medium 10 is shifted to a position of the original 14.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a means for moving an X-ray tube and an imaging device, which are supported oppositely at the upper and lower ends of a column, relative to each other about a point within a subject located between them. Regarding the X-ray tomography apparatus that performs tomography of the subject, it is possible to improve the resolution of images by maintaining the analytical accuracy of three points, especially the focus of the X-ray tube, the center of cutting, and the center of the image recording medium. The present invention relates to an X-ray tomography device.

[Conventional technology]

As shown in FIG. 5, a conventional X-ray tomography apparatus includes an X-ray tube 1 that emits X-rays to a subject, and an image recording medium that is supported opposite to the X-ray tube 1 with the subject in between. an imaging device 2 that stores the images, a column 3 that supports and connects both at the upper and lower ends, and a column 3 that supports the column 3 in a swingable manner and moves up and down in the vertical direction to obtain a tomographic cross-section of the subject. It was equipped with a cutting section device 4 that moves up and down. The cutting section device 4 includes a middle frame 5 that swingably supports the support column 3, and a movable frame 6 that swingably supports the middle frame 5 inside the frame and is movable up and down. It also consisted of the fifth
In the figure, reference numeral 7 is a table on which a subject (not shown) is placed, and reference numeral 8 is a trajectory generating table for moving the X-ray tube 1 and imaging device 2 relative to each other in synchronization with each other around a fulcrum 9 in opposite directions. It is a mechanism. By this trajectory generating mechanism 8, the xi tube 1 is supported oppositely with the subject in between.
By moving the image device 2 and the imaging device 2 relative to each other around a point inside the subject, based on the principle of rotation, only the image of the desired cross section of the subject can be transferred to an image recording medium such as a film without blurring. It was then possible to take tomographic images by focusing images on the cross-sectional area and blurring other cross-sectional images.

The principle of this tomography will be explained below with reference to FIG. In the figure, the focal point of the X-ray tube 1 is F, the image recording medium stored in the imaging device 2 is 10, and the
Let D be the distance between the focal point F of the ray tube 1 and the fulcrum E of relative motion, and let d be the distance between this fulcrum E and the image recording medium IO. Now, if the X-ray tube 1 and the image recording medium 10 are made to move relative to each other at a constant speed or angular velocity in opposite directions as shown by arrows A and H around the fulcrum E, the image at the fulcrum E will be When the focal point of the ray tube 1 is at position F, the image is projected onto point E' on the image recording medium 10, and when the focal point is at position F', it is projected onto point E'. Here, if another point P is taken on the plane op including the above-mentioned fulcrum E, and the projected images onto the image recording medium 10 corresponding to the two positions of the X-ray tube 1 are respectively P' and P'', ΔFE'P' and ΔF' E
The following relationships hold for 'P'.

E'P' = EP・(D+d) /DE'P' =
EP・(D+d)/D Therefore, E'P' = E"F'. That is, under a certain relationship (D+d)/D, each point on the plane OP such as E, P, etc. The image is always focused on the same point on the recording medium 10.

Next, in the case of a point Q away from the above plane op.

Images are projected as Q' and Q' onto the image recording medium 10 corresponding to two positions of the X-ray tube 1, respectively, but since the projection points of the above point Q onto the plane op are different, ΔFE
'Q' and ΔF'E'Q' clearly E
'Q'≠E'Q'. Therefore, the image of point Q on the image recording medium 10 is E'Q'-E'Q'=Ω
This will result in a deviation of only From this, when the X-ray tube 1 and the image recording medium 10 move relative to each other around the fulcrum E, the above point Q is not projected as a point on the image recording medium 10 but as a line, and the image is In this way, the object on the plane OP containing the fulcrum E is established as a clear image, but (
Such a plane Op is referred to as a "cut plane"), and objects on other planes have large deviations, resulting in blurred images.

Based on this principle, tomography allows only the image of the target cross section (on the cut section) of the subject to be imaged on the image recording medium 10 without blurring, while eliminating images that may obstruct other cross sections. A desired tomographic image is obtained by blurring the image in a circular manner. In order to obtain a tomographic image with high resolution in such tomography, even when the X-ray tube 1 and the imaging device 2 storing the image recording medium 10 are moving relative to each other at a constant speed, the It is necessary that the focal point F of the wire tube 1, the fulcrum (that is, the "cutting center J") E, and the center E' of the image recording medium 10 are always located on a straight line, and the mechanical precision of these three points is must be maintained.

[Problem to be solved by the invention]

However, in the conventional X-ray tomography apparatus shown in FIG. When a heavy object such as the imaging device 2 is moved relative to each other by swinging the support 3, various problems may occur due to backlash, deformation of members, or mechanical precision of the components that occur during the relative movement. It is difficult to maintain the above-mentioned three points of mechanical accuracy due to the addition of errors, and sufficient resolution cannot be obtained.

Furthermore, the above-mentioned resolution is affected by the occurrence of motion artifacts, but in order to suppress these motion artifacts, it is sufficient to shorten the photographing time.

However, in order to achieve this, it is necessary to increase the speed of the relative motion between the X-ray tube 1 and the imaging device 2, but if the relative motion is increased, the acceleration generated in the X-ray tube 1 and the imaging device 2 increases, and the centrifugal The influence of dynamic loads such as force and inertia force becomes large. Therefore, the deformation of the member increases,
Misalignment occurred in the cutting center 11 on the support column 3 shown in FIG. For example, as shown in FIG. 7, ideally, the target part point 13 of the subject 12 located on the cutting center 11 is located on the image recording medium 10 by X-rays emitted from the focal point F of the X-ray tube 1. is projected onto the center 14 of At this time, there is no deviation between the target part point 13 and the cutting center 11.

However, if the relative movement between the X-ray tube 1 and the imaging device 2 is increased and the cutting center 11 is shifted to 11', the image recording medium 1 stored in the imaging device 2 supported at the lower end of the support column 3
Since 0 also shifts to 10', the center 14 of the image recording medium 1o moves to 14', and the image of the target part point 13 of the subject 12 is projected onto a different point on the image recording medium 10'.

Therefore, the image of the target part point 13 becomes blurred.

At this time, the above-mentioned three points of mechanical accuracy were not maintained, and the resolution of the tomographic image was reduced.

To cope with this, the rigidity of the connecting structural members such as the support columns 3 may be increased in order to suppress the deformation of the members, but in this case, the weight and size of the entire device increases.

Therefore, an object of the present invention is to provide an X-ray tomography apparatus that can solve these problems.

[Means to solve the problem]

The above purpose is to provide an X-ray tube that emits X-rays to a subject, an imaging device that is supported opposite to the X-ray tube with the subject in between, and stores an image recording medium, and a video device that stores both at the upper and lower ends. An X-ray tomography apparatus comprising a column that supports and connects the column, and a cross section device that swingably supports the column and moves up and down to raise and lower the cross section of the subject to be photographed, The cutting section device is separated into a cutting section frame that swingably supports the support column and a moving frame that moves the cutting section up and down, and also supports the cutting section frame movably in a horizontal plane with respect to the moving frame. A mechanism for swinging the cut-section frame in a horizontal plane is provided, and the cut-section frame is made to swing in the horizontal plane during the relative movement of the X-ray tube and the imaging device, thereby correcting the positional deviation of the fulcrum of the relative movement. This is achieved by an X-ray tomography apparatus designed to do this.

[For production]

The X-ray tomography apparatus configured in this manner is separated into a cutting section frame that swingably supports the column and a moving frame that raises and lowers the cutting section, and also moves the cutting section frame in a horizontal plane relative to this moving frame. With a cross-section device configured to support the cross-section frame and swing the cross-section frame in a horizontal plane, the cross-section frame is set as an X-ray tube at an arbitrary cross section of the subject. By making the imaging device swing in a horizontal plane during relative motion,
This is to correct the positional deviation of the fulcrum of the relative movement.

As a result, it is possible to maintain the mechanical precision of three points: the focus of the X-ray tube, the center of cutting, and the center of the image recording medium, and improve the resolution of the image.

〔Example〕

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

FIG. 1 is a perspective view showing an embodiment of a cross section device of an X-ray tomography apparatus according to the present invention, and FIG. 2 is a perspective view showing the overall configuration of the X-ray tomography apparatus. This X-ray tomography apparatus takes a tomographic image of an arbitrary cross section of a subject, and as shown in FIG.
and pillar 3.

It comprises a cutting section device 4, a table 7, and a trajectory generating mechanism 8.

The X-ray tube 1 emits X-rays to a subject (not shown) placed on a table 7, which will be described later, and is supported above the table 7, for example. A video device 2 is supported below the table 7. This video device 2 is
A transmitted X-ray image emitted from the X-ray tube 1 and transmitted through the subject is photographed on an image recording medium such as a film. It is supported opposite to the wire tube 1. The X-ray tube 1 and the imaging device 2 are supported by the upper and lower ends of the column 3, respectively. This support column 3 supports and connects both the above-mentioned 1 and 2 at its upper and lower ends, and is swingably provided on one side of the above-mentioned table 7. The middle part of the column 3 is supported by a sectioning device 4. This cutting section device 4
supports the pillar 3 in a swingable manner, and moves up and down in the vertical direction to raise and lower a cross section of the subject to be photographed. A table 7 is provided at an intermediate position where the X-ray tube 1 and the imaging device 2 are supported facing each other.

This table 7 is for placing a subject on its upper surface and is movable in its longitudinal direction. In addition, the above
Above wire tube 1.

A trajectory generating mechanism 8 is provided. This trajectory generating mechanism 8
The X-ray tube 1 and the imaging device 2 are caused to move relative to each other in synchronization with each other in opposite directions about a fulcrum 9.

Here, in the present invention, the cut section device 4 is separated into a cut section frame 15 that swingably supports the support column 3 and a movable frame 6 that raises and lowers the cut section. The cut section frame 15 is supported movably within a horizontal plane, and is provided with a mechanism for swinging the cut section frame 15 within the horizontal plane.

That is, in FIG. 2, a cut-section frame 15 is provided on an extension in a horizontal plane including the fulcrum 9, and its center 16 is located on a line connecting the fulcrum 9 and the support 3. Inside the cut-section frame 15, the middle frame 5 is swingably supported. This middle frame 5 swingably supports a column 3 that connects the X-ray tube 1 and the imaging device 2. On the line connecting the fulcrum 9 of the relative movement of the X-ray tube 1 and the imaging device 2 and the center 16 of the cut section frame 15, there is a swing center when the support 3 swings, that is, a cutting center 11. do. This cutting center 11, the center 16 of the cut section frame 15, and the fulcrum 9 of relative movement are located on a straight line, and a plane including this straight line and parallel to the upper surface of the table 7 becomes the cut section.

In order to change the height of the cut section, a movable frame 6 that supports the cut section frame 15 and can move up and down in a straight line is provided separately from the cut section frame 15. There is. This moving frame 6 moves vertically and reciprocally in a straight line along the pillar 3 to raise and lower the tomographic cross-section of the subject, and as shown in FIG. 1, the moving frame 6 is moved up and down in the vertical direction. It is supported so as to be able to rise and fall by an elevating drive mechanism having a plurality of screws 17, 17 and nuts 18, 18 screwed together with the screws 17 and provided on the moving frame 6, and is capable of being lifted and lowered by the elevating drive mechanism. On the other hand, the positional fluctuation is suppressed by a positional restraining mechanism having rails 19, 20 and rollers 21, 22 which restrain the movement of the moving frame 6 in the front, back, left and right directions within a horizontal plane.

Further, the cut section frame 15 is supported movably in a horizontal plane with respect to the movable frame 6. That is, as shown in FIG. By combining the first guide member 23 and the linear second guide member 24, 24 having a groove that fits and engages, the cut-section frame 15 can be linearly moved, for example, in the left-right direction with respect to the movable frame 6. It is said that

Further, the cut section frame 15 is provided with a mechanism for swinging the cut section frame 15 within a horizontal plane.

That is, as shown in FIG. 1, a motor 25 fixed to the movable frame 6, a pulley 26 fixed to the rotating shaft of the motor 25, and a rectangular shape, for example, bored on both sides of the cut-section frame 15. A first cam 29 and a second cam 30 inserted into the shaped cam holes 27 and 28, pulleys 31 and 32 fixed to the rotating shafts of the first and second cams 29 and 30, and the pulleys Idle pulleys 33, 34, 35° 36 provided as power transmission paths between 26, 31, 32
and a belt 37 as means for transmitting the rotational force of the motor 25 to the pulleys 31 and 32. The motor 25 is designed to rotate in synchronization with the movement of the X-ray tube 1.

Further, the first and second cams 29.30 are each formed, for example, in an elliptical shape, and are inserted into the respective cam holes 27.28 with their major axes being perpendicular to each other, for example. Each pulley 26.3 is rotated by the rotation of the motor 25.
1 to 36 and a belt 37, the rotational force is transmitted and they rotate in synchronization.

Then, at a certain timing, the first cam 29 is inserted into the cam hole 27.
By pushing the inner wall of the cam, the cut section frame 15 is caused to swing linearly, for example, to the left in FIG.
By pressing the inner wall of the cam hole 28, the cut-section frame 15 is caused to swing linearly, for example, to the right due to the shape of the cam. As shown in FIG. 1, screw studs 17, 17 for raising and lowering the movable frame 6 pass through both sides of the cut-section frame 15, and the through holes 3
8.38 is made larger than the diameter of the screw stud 37, so that the cut section frame 15 can move left and right.

In this way, the cutting section device 4 is separated into the cutting section frame 15 that swingably supports the column 3 and the moving frame 6 that raises and lowers the cutting section, and the cutting section frame 15 is separated from the moving frame 6.
is supported movably in a horizontal plane, and its cut-section frame 1
5 in a horizontal plane, the cut section frame 15 is caused to swing in the horizontal plane, for example, in the left-right direction during relative movement between the x4 ray tube 1 and the imaging device 2 shown in FIG. By doing so, the positional deviation of the fulcrum 9 of the relative movement, that is, the cutting center 11, can be corrected.

For example, as shown in FIG.
If the cutting center 11 deviates to the left as indicated by 11' during the relative movement, the cutting frame 15 can be moved to the right by, for example, the operation of the second cam 30 shown in FIG. As shown by arrow C in FIG. 3, the cutting center 11 is corrected to the right by the above-mentioned amount of deviation. At this time, image recording medium 1
The center 14' of 0 moves to the original position of 14. Further, as shown in FIG. 4, if the cutting center 11 is shifted to the right as indicated by 11', the first cam 29 shown in FIG.
By swinging the cutting section frame 15 to the left by the operation, the cutting center 11 is corrected to the left by the amount of deviation as shown by the arrow in FIG. At this time, the center 14' of the image recording medium 10 moves to the original position 14. Note that at this time, the amount of deviation of the cutting center 11 can be known in advance from the weights of the X-ray tube 1 and the imaging device 2, the acceleration caused by their relative movement, and the rigidity of each member. The first and second cams 29, 30 may be determined to have shapes that can compensate for the amount of deviation, and in FIGS. 3 and 4,
Although the correction state is shown when the X-ray tube 1 and the imaging device 2 have moved to both ends of their relative movements and the amount of deviation of the cutting center 11 is at its maximum, the same procedure as above can be made at an intermediate position of their relative movements. Correction can be made in accordance with the amount of deviation at that point.

Although FIG. 1 shows a case in which the X-ray tube 1 and the imaging device 2 move on a linear trajectory and the relative motion thereof is linear motion in the left-right direction, the present invention is not limited to this. The same idea can be applied even when the tube 1 and the imaging device 2 move on a trajectory such as a circular orbit, an elliptical orbit, or a spiral orbit. In this case, the cam holes 27 and 28 shown in FIG.
The shapes of the first and second cams 29, 30 may be determined to be capable of correcting the positional deviation of the cutting center 11 in accordance with the movement on the trajectory thereof. In addition, in Fig. 1,
Although the second guide members 23 and 24 are provided only in one axis direction, when the X-ray tube 1 and the imaging device 2 move on a trajectory such as a circular orbit, an elliptical orbit, or a spiral orbit, the guide members 23 and 24 may be guided in two orthogonal axes directions. What is necessary is just to provide a member. Further, in FIG. 1, the mechanism for swinging the cut section frame 15 in a horizontal plane includes a motor 25, pulleys 26, 31 to 36, and cam holes 27, 28.

Although shown as being composed of the first and second cams 29, 30 and the belt 37, the present invention is not limited to this, and other mechanisms may be used as long as they can be similarly swung in a horizontal plane. You can.

〔Effect of the invention〕

Since the present invention is configured as described above, by swinging the cutting section frame 15 in a horizontal plane during the relative movement of the X-ray tube 1 and the imaging device 2, the position of the fulcrum 9 of the relative movement, that is, the cutting center 11 can be adjusted. Misalignment can always be corrected. Therefore,
Apparently, the cutting center 11 is not moved, and the
It is possible to maintain mechanical accuracy at three points: the focal point F of the wire tube 1, the cutting center 11, and the center 14 of the image recording medium 10.

The target point of the subject is always projected onto the same point on the image recording medium 10 no matter how the Xs tube 1 moves. Further, even if the relative motion between the X-ray tube 1 and the imaging device 2 is increased in speed in order to suppress motion artifacts, it is not possible to effectively correct the positional deviation of the cutting center 11 due to deformation of the members due to this increased speed. Because you can
The above relative motion can actually be sped up, and the occurrence of motion artifacts can be suppressed. For these reasons, the resolution of the obtained tomographic image can be improved. Furthermore, since there is no need to increase the rigidity of the connecting structural members such as the column 3 in order to suppress deformation of one member, it is possible to obtain tomographic images with excellent resolution without increasing the weight or size of the entire device. can.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of a cross section device of an X-ray tomography apparatus according to the present invention, FIG. 2 is a perspective view showing the overall configuration of the X-ray tomography apparatus, and FIGS. 3 and 4 are An explanatory diagram showing the correction operation for the positional deviation of the cutting center, Fig. 5 is a perspective view showing a conventional X-ray tomography apparatus, Fig. 6 is an explanatory diagram showing the principle of tomography, and Fig. 7 shows cutting in the conventional apparatus. FIG. 3 is an explanatory diagram showing a state in which a center positional shift occurs. DESCRIPTION OF SYMBOLS 1... X-ray tube, 2... Imaging device, 3... Support column, 4... Cutting section device 1.5... Middle frame, 6... Moving frame, 9... Relative movement 10... Image recording medium, 11... Cutting center, 14... Center of image recording medium, 15... Cut section frame, 17... Threaded rod, 18... Nut, 23 .24...Guide member, 25...Motor, 26.31-36...Pulley, 27,28...Cam hole, 29.30...Cam, 37...Belt.

Claims (1)

[Claims] An X-ray tube that emits X-rays to a subject, an imaging device that is supported opposite to the X-ray tube and stores an image recording medium with the subject interposed therebetween, and both are supported and connected at the upper and lower ends. In an X-ray tomography apparatus comprising a column, and a cross-section device that swingably supports the column and moves up and down to raise and lower a cross-section of a tomographic image of a subject, the cross-section device comprises: , is separated into a cut section frame that swingably supports the support column and a moving frame that raises and lowers the cut section, supports the cut section frame movably in a horizontal plane with respect to the movable frame, and moves the cut section frame in the horizontal plane. A mechanism is provided to swing the cross-section frame within the horizontal plane during the relative movement of the X-ray tube and the imaging device, thereby correcting the positional deviation of the fulcrum of the relative movement. An X-ray tomography device characterized by: