JPS646811Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an X-ray tomography device.
In particular, the present invention relates to a tomography apparatus suitable for imaging parts of a subject having the same absorption coefficient at the same density.

[Prior Art] Conventional tomography equipment uses a wire rope placed between the support and the case to easily perform linear movement of the film inside the case and change the magnification when the support swings. There are those that move the film in parallel using a combination of a pulley and a pulley (for example, see Japanese Patent Application Laid-Open No. 1983-45641), and a combination of a hydraulic cylinder and spring that is the driving part of a conventional one-way tomography device. , a gear clutch mechanism is installed between the drive part and the column, and a configuration that allows reciprocating shooting is obtained that provides the same good resolution as conventional one-way shooting (for example, Japanese Utility Model Publication No. 54-42620 ) are known.

[The problem that the idea attempts to solve]

In all of the above-mentioned conventional tomography devices, the focus of the X-ray tube in the X-ray source, the center of swing of the support, and the center of the film in the case are in a straight line, and the support is oscillated while the X-ray X-rays are irradiated onto the subject, and a tomogram of the subject is taken on film in a plane that includes the center of swing of the support. It is desirable that images of regions having the same absorption coefficient have no difference in density, and it is desirable that each image in divided imaging has uniform image quality.

As a countermeasure for this problem, one-way imaging tomography equipment has been implemented in the past, and the aforementioned tomography equipment that can obtain reciprocating imaging with the same resolution as one-way imaging has been proposed. If the swinging speed of the support is constant during both imaging and reciprocating imaging, the intensity of the X-rays irradiated onto the film through the subject will vary depending on the swinging position of the support. Since the distance through which the beam passes through the object differs, vertical incidence changes depending on whether it is oblique incidence and is no longer constant. For this reason, even if a region having the same X-ray absorption coefficient is photographed, the image will have a difference in density, which is an undesirable problem in terms of photographic analysis.

Furthermore, in a tomography device capable of reciprocating imaging that shortens the imaging time and improves imaging efficiency, in addition to the above-mentioned problem that the swinging speed of the pillar is constant, there is also a difference in the swinging conditions of the left and right pillars. In other words, there are subtle differences in equipment between left-to-right rocking and right-to-left rocking, such as differences in manufacturing dimensions, processing precision, etc., making it difficult to maintain the same rocking conditions. There is also a problem in that the image quality of each pixel in divided photography is not necessarily uniform depending on the direction.

In view of the problems of the prior art described above, the present invention makes it possible to image regions of a subject having the same X-ray absorption coefficient at the same density, and to make each image in divided imaging of uniform image quality. The purpose is to provide a tomography device that can

[Means to solve the problem]

In order to achieve the above object, the tomography apparatus of the present invention includes a base, a support whose middle part is swingably supported by the base, an X-ray source is attached to the upper end, and a box case is attached to the lower end. The film case is attached to the lower end of the pillar so as to be slidable in the longitudinal direction of the pillar, and the film case is made swingable by aligning the center of the film in the film case on an extension of a straight line connecting the X-ray source and the swing center of the pillar. The film horizontally holding means is provided between the support column and the movie case, which moves the movie case supported on the platform in parallel according to the swinging of the column and always holds it horizontally. In a tomography apparatus, a drive for driving the swing speed of the support at a speed that is approximately sinusoidal, with the swing speed of the support being highest when the swing position of the support is at a neutral position, and lowest when the swing position of the support is at the end of swing. It is characterized by having a means.

[Effect]

Now, let the intensity of X-rays incident on the subject be I ₀ , and I ₀
Let I be the intensity of the transmitted X-rays that have passed through the subject, and when I ₀ is constant, the value of I is when the support where the X-rays are almost perpendicular to the subject is in the neutral position. The object passing distance L ₁ of X-rays is different from the object passing distance L ₂ of X-rays at oblique incidence, and L ₂ > L ₁
Therefore, as the support swings toward the neutral position, it increases, reaches a maximum at the neutral position, and then gradually decreases as it moves away from the neutral position. However, since the tomography apparatus of the present invention is configured as described above, the intensity I of the transmitted X-rays has a maximum value due to the relationship with the swinging speed of the column. It is most weakened at the neutral position of the strut, and conversely, it is least weakened at the swing end where the value of I is minimum. As a result, the intensity of the X-rays irradiated onto the film can be averaged to a nearly constant level over the swinging range of the support, making it possible to image areas with the same X-ray absorption coefficient at the same density. Become.

〔Example〕

An embodiment of the tomography apparatus of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 11 indicates a support column. A shaft 12 is provided in the middle of the column 11. By holding the shaft 12 in a bearing on the base 13, the support column 11 can swing on the base 13 with the shaft 12 as the center of swing. The X-ray source 14 includes an X-ray tube and a collimator, and is fixed to the upper end of the column 11. The film holding means, for example, the stick case 15, is attached near the lower end of the support column 11, but there is a mechanism between the stick case 15 and the support column 11 that allows the film to be kept horizontally even if the support column 11 swings. There is a means to do so.

This horizontal holding means includes a lifting platform 16 slidably attached to the column 11 in the longitudinal direction. The elevator platform 16 is provided with a shaft 17, and the bucket case 15 is swingably supported on this shaft 17. The lifting platform 16 swingably supports the film case 15 so that the center of the film in the film case 15 is aligned with the extension of a straight line connecting the focal point of the X-ray tube of the X-ray source 14 and the swing center of the column 11. ing. A weight 18 is slidably attached to the back of the support 11. Two wires 19a, 19
b has one end connected to the weight 18, and
The other end is wrapped around a pulley and then connected to pulleys 21a and 21b fixed to the shaft 17. That is, as shown in FIG.
After the direction of a is changed by the pulleys 22a and 23a on the support 11, it is wrapped around a pulley 24a that is loosely suspended around the shaft 12, which is the center of swing of the support 11, and then it is wrapped around a pulley 25a on the base 13. It is connected to a pulley 21a via a pulley 26a in the case 15. The wire 19b connects to the pulley 2 on the support 11.
2b, 23b, pulley 24b coaxial with pulley 24a,
Pulley 25b on base 13, and Butsuki case 1
5 is wound around the pulley 26b on top of the pulley 26b. The wires 19a, 19b are of fixed length and are constantly tensioned by the weight 18. For this reason, the pillar 11
When the case 15 swings around the shaft 12 at a certain angle, the case 15 swings around the shaft 17 by the same angle in a direction opposite to the swinging direction of the support 11, and is always maintained in a horizontal state. Although not shown, the lifting platform 16 that supports the gun case 15 is connected to an endless chain wrapped around a set of sprocket foils on the support column 11.
By rotating one of the sprocket wheels by the electric motor on the support post 11, the gun case 15 is raised and lowered along the support support 11 together with the elevating table 16, and the photographing magnification is changed.

The table 31 is for resting the subject, and is disposed between the X-ray source 14 and the case 15, and is disposed on the base 13 so as to be movable up and down. The table 31 is fixed to a support plate 32. Guide rails 33 are provided on both sides of the base 13, and rollers 34 are provided on the support plate 32 to sandwich the guide rails 33 from both sides. The table 31 is raised and lowered by an electric motor 35 and a chain 36a.
36b.

Swinging of the support column 11 is performed by an electric motor and a crank mechanism. The electric motor is designated by reference numeral 41 in the drawings and is installed at the bottom of the base 13. The output shaft of the electric motor 41 is connected to the input shaft of a reducer 42 via a belt and a belt pulley, and an arm 43 is attached to the output shaft of the reducer 42. On the other hand, an arm 44 is provided protruding from the vicinity of the shaft 12 of the support 11, and the arms 43 and 44 are connected via a rod 45. The arm 43 is rotated by the rotation of the electric motor 41, but this rotational motion is converted into a linear motion by the rod 45, and the column 11 is swung around the shaft 12 via the arm 44. As the support column 11 swings, the film in the case 15 is moved in a horizontal plane passing through the center of the shaft 12, that is, parallel to the cut section, and the film records the cross section of the object included in the cut section. I can do it. In this embodiment, the swinging of the support column 11 is performed via a crank mechanism, so the speed gradually increases from the swinging end toward the neutral position, reaches the maximum speed at the neutral position, and then swings on the opposite side. The speed gradually decreases as it approaches the moving end. The speed curve during this movement is approximately a sinusoidal curve, and the acceleration curve is also continuous when the swinging direction is changed, so that the support column 11 can swing smoothly and at high speed. In addition, pillar 1
The swinging mechanism of No. 1 is not limited to the above-mentioned crank mechanism, and may be any means capable of driving the pillar 11 so that the swinging speed curve of the pillar 11 becomes a substantially sinusoidal curve. For example, a cam mechanism may be used. good.

On the other hand, the intensity of the X-rays reaching the film can be made substantially constant regardless of the swinging position of the support. That is, in tomography, as shown in FIG. 3, the passing distance L 1 of X-ray x ₁ incident at right angles to the subject P is the passing distance L ₂ of X-ray x ₂ incident obliquely to the subject _P. Since L ₂ > L ₁ , the ratio of the intensity I _of incident X-rays to the intensity I of transmitted X-rays is I/I ₀
When I ₀ is constant, as the column 11 swings toward the neutral position, it gradually increases, reaches a maximum at the neutral position, and then gradually decreases toward the end of the swing. However, in the tomography apparatus according to the present invention, since the velocity curve of the column 11 is a sinusoidal curve as described above, the intensity of transmitted X-rays I
is weakened the most at the neutral position of the support column where the value of I is maximum, and conversely is weakened the least at the swing end where the value of I is minimum. As a result, the intensity of the X-rays that reach the film can be averaged to a nearly constant level over the swinging range of the support, and areas with the same X-ray absorption coefficient can be recorded at the same density on the film. .

In the tomography apparatus of the present invention, imaging is performed only when the column 11 swings in either the right or left direction, the table 31 is moved to change the cross section, and the button case 15 is moved to change the magnification. Shooting preparation operations such as lifting and lowering, moving the mask or film, or both for split shooting, are performed using the support 11.
One-way photography is performed only when the pillar 11 swings in the opposite direction, and by combining the above-mentioned driving means that drives the rocking speed of the pillar 11 at a speed that is approximately a sine curve, compared to the conventional one-way photography, In addition, it is possible to always make each photographed image in divided photographing uniform in image quality.

[Effect of idea]

In the tomographic apparatus of the present invention, as in the embodiments described above, the column is moved sinusoidally and imaging is performed only when the column swings either to the right or to the left. It is possible to image portions having the same line absorption coefficient at the same density, and it is also possible to make the image quality of each captured image uniform in divided imaging.

[Brief explanation of drawings]

The drawings show an embodiment of the tomography apparatus of the present invention, and FIG. 1 is a partially cutaway front view, and FIG.
The figure is an explanatory diagram showing the configuration of means for keeping the film horizontal at all times, and FIG. 3 is a diagram for explaining the relationship between X-rays incident on a subject in tomography and X-rays transmitted therethrough. 11... Support, 12... Shaft, 13... Base, 1
4...X-ray source, 15...butsuki case, 16...
Elevating table, 21-26... means for keeping the film horizontal, 31... table, 41-44... driving means.

Claims (1)

[Scope of utility model registration request] A base, a column whose middle part is swingably supported by the base, an X-ray source is attached to the upper end, and a butsuki case is attached to the lower end, and the column is attached to the lower end of the column so as to be slidable in the longitudinal direction of the column. a lifting platform that swingably supports the shooting case by aligning the center of the film in the shooting case with an extension of a straight line connecting the swinging center of the X-ray source and the support column; In a tomography apparatus that includes a film horizontal holding means disposed between a support that moves in parallel according to the swing of the support and always maintains the support horizontally, and a film case, the swing speed of the support is determined by controlling the swing speed of the support. 1. A tomography apparatus comprising a driving means for driving at a substantially sinusoidal speed that is highest when the swing position is at the neutral position and lowest when the swing position of the support is at the end of swing.