JP3562449B2 - X-ray CT system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an X-ray CT apparatus.
[0002]
[Prior Art and Problems to be Solved by the Invention]
The X-ray CT device has an X-ray irradiator and a detector provided on a rotating frame attached to a fixed frame, and irradiates the subject sent into the rotating rotating frame with X-rays from the irradiating device, X-rays transmitted through the subject are detected by a detector, so that tomographic image creation data is collected. A collimator located between the subject and the detector is arranged on the rotating frame. The collimator has two blade-shaped X-ray shielding members facing each other via a space forming a slit, and an X-ray passing through the slit is detected by a detector. The width of the slit becomes the slice thickness in tomography.
[0003]
Conventionally, in order to adjust the width and position of the slit, a driving device is provided at both ends of each of the two blades, and both blades are individually driven. However, when the two blades are individually driven, the position and width of the slit cannot be individually adjusted, so that the control of the driving device for the adjustment is complicated. Further, a drive device for each of the two blades is required, which complicates the structure and increases the installation space.
[0004]
In addition, a shim is interposed between the two blades, and both blades are mounted as a unit on a rotating frame via the shim, and the position of the slit is adjusted by changing the mounting position of the unit. ing. However, when adjusting the slit between the two blades as a unit and the mounting position on the rotating frame, it is necessary to adjust the thickness of the shim interposed between the unit and the rotating frame. It is necessary to repeatedly tighten and loosen the bolts and the like for attaching to the rotating frame, which requires labor and time.
[0005]
An object of the present invention is to provide an X-ray CT apparatus that can solve the above problem.
[0006]
[Means for Solving the Problems]
The present invention relates to an X-ray CT apparatus that guides X-rays radiated from an X-ray irradiator and transmitted through a subject to a detector through a slit of a collimator, wherein the collimators mutually communicate through a space forming the slit. It has a pair of opposing X-ray shielding members, and slit width adjusting means for displacing both shielding members so that the width of the slit is changed, and both shielding members and the slit width adjusting means are integrally formed with each other. The slit can be displaced in the width direction of the slit, and the slit width adjusting means displaces both shielding members in the width direction of the slit so that the center position in the width direction of the slit does not change.
According to the configuration of the present invention, even when both shielding members are displaced when adjusting the width of the slit by the slit width adjusting means, the center position in the width direction of the slit does not change. It does not affect position. Further, the position of the slit can be adjusted by displacing the two shielding members and the slit width adjusting means in the width direction of the slit. At this time, since both shield members and the slit width adjusting means are displaced integrally, the position adjustment of the slit does not affect the width of the slit. Thereby, the width adjustment and the position adjustment of the slit can be performed individually without affecting each other. When both the shielding members are driven by the driving device, the control can be easily performed, and the two shielding members are individually driven. Since there is no need, the structure can be simplified and downsized.
[0007]
The slit width adjusting means has a cam that comes into contact with both shielding members via a cam follower, and both shielding members are displaceable in the width direction of the slit such that the width of the slit changes by the operation of the cam. The shape of the cam is preferably determined so that the center position in the width direction of the slit does not change even when both shielding members are displaced by the operation of the cam.
Thus, the width of the slit can be adjusted by displacing the two shielding members only by operating the cam. At this time, even if the two shielding members are displaced by the operation of the cam, the center position in the width direction of the slit does not change, so that the width adjustment of the slit does not affect the position of the slit. Further, the position of the slit can be adjusted by displacing the two shielding members and the cam in the width direction of the slit. At this time, since the two shielding members and the cam are displaced integrally, the position adjustment of the slit does not affect the width of the slit. Thereby, the width adjustment and the position adjustment of the slit can be performed individually without affecting each other. When both the shielding members are driven by the driving device, the control can be easily performed, and the two shielding members are individually driven. Since there is no need, the structure can be simplified and downsized.
It is preferable that a driving device for operating the cam is provided, and the driving device is displaceable in the width direction of the slit integrally with the two shielding members and the slit width adjusting means.
As a result, when adjusting the position of the slit, the driving device for operating the cam is displaced integrally with the two shielding members and the cam, so that an error due to backlash or the like between the driving device and the cam does not occur. Therefore, highly accurate slit position adjustment can be performed.
[0008]
The X-ray CT apparatus of the present invention includes a fixed frame, and a rotating frame rotatably supported by the fixed frame around an axis parallel to the width direction of the slit, and the two shielding members are provided by the rotating frame. And a cam and a driving device are supported via a guide shaft so as to be movable in the width direction of the slit. The cam is sandwiched by the cam followers arranged in parallel along the width direction of the slit, and the width direction of the slit. It is preferable that the dimension of the cam in the rotation axis direction at the contact position with each of the cam followers is changed by the rotation of the cam. .
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The X-ray CT apparatus 1 shown in FIGS. 1 and 2 includes a tomographic image creation data collection unit 2, a bed 6 on which a subject 7 is placed, and a bed driving mechanism 8. The data collection unit 2 includes a gantry-shaped fixed frame 2a, a short cylindrical rotary frame 2b supported by the fixed frame 2a so as to be rotatable about a horizontal axis, and an X-ray attached to the rotary frame 2b. It has an irradiation device 2c and an X-ray detector 2d, and the inside of the rotating frame 2b is a tunnel 2e for arranging a subject. The bed driving mechanism 8 feeds the bed 6 into the tunnel 2e as shown by a two-dot chain line in FIG. While rotating the rotating frame 2b, the subject 7 on the bed 6 is irradiated with X-rays from the X-ray irradiator 2c, and the detector 2d detects X-rays transmitted through the subject 7, thereby detecting the subject. The examiner 7 is scanned to collect data for creating a tomographic image.
[0010]
The rotating frame 2b is provided with a collimator 10 having a slit for guiding the X-rays emitted from the X-ray irradiator 2c and transmitted through the subject 7 to the detector 2d. The rotating frame 2b rotates around an axis parallel to the width direction of the slit. The width of the slit becomes the slice thickness in CT imaging.
[0011]
As shown in FIGS. 3A and 3B, the collimator 10 includes a pair of arched X-ray shielding members 11 and a slit width adjusting means for displacing the shielding members 11 so that the width of the slits changes. And As a slit width adjusting means, there is provided a pair of cams 13 which are in contact with both shielding members 11 via cam followers 12. The two shielding members 11 oppose each other via a space, and the space forms the slit 9. As shown in FIG. 5, each shielding member 11 is configured by attaching a lead shielding material 11b to an aluminum blade 11a. The cam followers 12 are configured by rollers that are rotatably attached to both ends of each shielding member 11.
[0012]
Both shielding members 11 are connected to the rotating frame 2b via a pair of first guide shafts 20, a pair of second guide shafts 21, and a pair of bases 22 so as to be movable in the width direction of the slit 9. Each of the guide shafts 20 and 21 has an axis parallel to the width direction of the slit 9. As shown in FIG. 4, one end of each of the guide shafts 20 and 21 passes through a base 22 fixed to the rotary frame 2b by bolts (not shown), and each of the first guide shafts 20 is a positioning hole 2b 'of the rotary frame 2b. And the second guide shafts 21 are inserted into the guide holes 2b ″ of the rotating frame 2b. Each of the guide shafts 20, 21 is fixed to the base 22 with screws. The other end of the first guide shaft 20 is slidably fitted to the other first guide shaft 20 via a slide bearing 23 in the width direction of the slit 9. As shown in FIG. At each end of both shielding members 11, a spring receiver 25 attached to one shielding member 11 and a spring receiver 25 attached to the other shielding member 11 are connected by a spring 26. Each of the springs 26 exerts an elastic force on the two shielding members 11 to reduce the width of the slit 9. When the two shielding members 11 are pressed against the cam 13 via the cam followers 12 by the elastic force of the springs 26, the width of the slit 9 changes. The shielding members 11, the first guide shafts 20, the second guide shafts 21, and the bases 22 are connected to each other by a jig 50 as shown in FIG. At this time, each of the guide holes 2b "is made larger than the diameter of the second guide shaft 21, and the second guide shaft 21 is inserted into each of the guide holes 2b". As a result, the assembly is roughly positioned with respect to the rotating frame 2b, and then the first guide shafts 20 are inserted into the positioning holes 2b '. Precise positioning with respect to the rotary frame 2b of the assembly is made of, the base 22 is bolted to the rotating frame 2b thereafter.
[0013]
The two shielding members 11 are displaced in the width direction of the slit 9 so that the width of the slit 9 changes by the operation of the cam 13. That is, at one end and the other end of both shielding members 11, the cam follower 12 on one shielding member 11 and the cam follower 12 on the other shielding member 11 are arranged in parallel along the width direction of the slit 9. As shown in (1) to (5) of FIG. 6, each cam 13 is integrated with a support shaft 30 having a rotation shaft 30a parallel to the width direction of the slit 9, and in the present embodiment, the rotation shaft 30a Has an outer peripheral surface 13 ′ along a cylindrical surface centered at. Each of the cams 13 has a first cam contour surface 13 </ b> A contacting a cam follower 12 attached to one shielding member 11 on one end surface outside, and a cam follower 12 attached to the other shielding member 11 on the other end surface outside. The second cam contour surface 13 </ b> B is in contact with the cam follower 12. Each of the cams 13 is operated so as to rotate around the rotation shaft 30a, and the operation changes the contact position with each of the cam followers 12, thereby displacing both the shielding members 11 and changing the width of the slit 9. I do.
[0014]
The dimension of the contact position of each cam 13 with the two cam followers 12 in the direction of the rotating shaft 30 a is changed by changing the contact position by the rotation of the cam 13. That is, each cam 13 of the present embodiment has a constant and maximum first portion 13a in the direction of the rotation axis 30a, which is an interval between the two cam contour surfaces 13A and 13B, and a first portion 13a extending along the rotation direction from the first portion 13a. The second portion 13b gradually becomes smaller, the third portion 13c having the same constant size as the minimum dimension of the second portion 13b, the fourth portion 13d having a certain size smaller than the third portion 13c, and the fourth portion 13d. It has a fifth portion 13e having a fixed size smaller than the four portions 13d, and a sixth portion 13f having a fixed size smaller than the fifth portion 13e. FIG. 7 is an exploded view of a contact portion between the two cam contour surfaces 13A and 13B and the cam follower 12 in each cam 13, and the two cam contour surfaces 13A and 13B are symmetrical to each other with respect to one surface orthogonal to the rotation axis 30a. Shape. Thus, the shape of each cam 13 is determined so that the center position in the width direction of the slit 9 does not change even when the two shielding members 11 are displaced by the operation of the cam 13. That is, the slit width adjusting means displaces both shielding members 11 in the width direction of the slit so that the center position in the width direction of the slit 9 does not change, and the width of the slit 9 is changed even if the width of the slit 9 changes. The centers in the directions are the same. Position adjustment is performed such that the center of the slit 9 in the width direction coincides with the center of the slice thickness in tomography.
[0015]
A pair of driving devices 41 are provided to rotate each cam 13 around the rotation shaft 30a. As shown in (1) to (3) of FIG. 8, each drive device 41 has a motor base 42 and a stepping motor 43 attached to the motor base 42. Each motor base 42 is fitted to the first guide shaft 20 and the second guide shaft 21 so as to be movable in the width direction of the slit 9. The support shaft 30 is supported by the motor base 42 via a bearing, and the output shaft of the stepping motor 43 is connected to one end of the support shaft 30 via the coupling 44 without play. Thereby, the slit width adjusting means including both the shielding members 11 and both the cams 13 and the both driving devices 41 are supported via the first guide shaft 20 so as to be movable in the width direction of the slit 9, and are integrally formed with the slit. 9 can be displaced in the width direction.
[0016]
One end of a male screw 51 is integrated with the other end of each second guide shaft 21, the other end of each second guide shaft 21 and one end of each male screw 51 are covered by a motor base 42, and the other end of each male screw 51 is The female screw member 52 protrudes from the motor base 42 and is screwed to the protruding end. Each male screw 51 has a smaller diameter than the second guide shaft 21, and a spring 53 fitted on the outer periphery thereof is sandwiched between the second guide shaft 21 and the motor base 42. The motor base 42 is pressed against the female screw member 52 by the elastic force of each spring 53. By rotating the female screw member 52 to change the amount of screwing into the male screw 51, the motor base 42, the stepping motor 43, the cam 13, and the shielding member 11 move in the width direction of the slit 9 integrally. Therefore, the position of the slit 9 can be adjusted. A long hole 52a is formed in each female screw member 52 along an arc around the rotation axis, and the female screw member 52 is fixed to the motor base 42 by a bolt (not shown) inserted into the long hole 52a. The rotation can be restricted to position the slit 9, and the female screw member 52 can be rotated by loosening the bolt to adjust the position of the slit 9.
[0017]
A disc 60 is integrated with the other end of each of the support shafts 30, a large number of through holes are formed in the disc 60 at equal intervals along the circumferential direction, and a photo sensor 61 for detecting each of the through holes is a motor base. 42 supported. A detection signal of the through hole by the photo sensor 61 is transmitted as a rotation angle signal of the cam 13 to a control device (not shown) of the stepping motor 43, so that feedback control of the rotation step of the stepping motor 43 is possible.
[0018]
According to the above configuration, the width of the slit 9 can be adjusted by displacing the two shielding members 11 only by operating the cam 13 by rotating the stepping motor 43. At this time, even if the two shielding members 11 are displaced by the operation of the cam 13, the center position in the width direction of the slit 9 does not change, so that the width adjustment of the slit 9 does not affect the position of the slit 9. Further, the position of the slit 9 can be adjusted by displacing the two shielding members 11 and the cam 13 in the width direction of the slit 9. At this time, since the two shielding members 11 and the cam 13 are displaced integrally, the position adjustment of the slit 9 does not affect the width of the slit 9. Thereby, the width adjustment and the position adjustment of the slit 9 can be performed individually without affecting each other. In addition, control when driving both shielding members 11 by the driving device 41 can be easily performed, and since there is no need to individually drive both shielding members 11, the structure can be simplified and downsized. Further, when the position of the slit 9 is adjusted, the driving device 41 for operating the cam 13 is displaced integrally with the two shielding members 11 and the cam 13, so that there is a play between the driving device 41 and the cam 13. Therefore, the position of the slit 9 can be adjusted with high accuracy.
[0019]
The present invention is not limited to the above embodiment. For example, the shape of the cam is not particularly limited as long as the center position in the width direction of the slit is not changed even if both shielding members are displaced by the operation of the cam.
[0020]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the width | variety adjustment and position adjustment of the slit of a collimator can be performed easily and with high precision, and also the X-ray CT apparatus whose structure can be simplified and miniaturized can be provided.
[Brief description of the drawings]
FIG. 1 is a side view of an X-ray CT apparatus according to an embodiment of the present invention. FIG. 2 is a rear view of an X-ray CT apparatus according to an embodiment of the present invention. FIG. (1) is a front view, (2) is a partially broken plan view [FIG. 4] A partially broken plan view of a main part of a collimator in an X-ray CT apparatus according to an embodiment of the present invention [FIG. 5] FIG. 6 is a partially cutaway front view of a main part of the collimator in the X-ray CT apparatus. FIG. 6 is a front view, (2) is a plan view, and (3) is a cam of the collimator in the X-ray CT apparatus according to the embodiment of the present invention. FIG. 7 is a bottom view, (4) is a left side view, (5) is a right side view. FIG. 7 is an explanatory view of a shape of a cam of a collimator in the X-ray CT apparatus according to the embodiment of the present invention. (1) of the collimator driving device in the X-ray CT apparatus shown in FIG. Cutaway side view, (3) back view is [EXPLANATION OF SYMBOLS]
2c X-ray irradiator 2d X-ray detector 9 Slit 10 Collimator 11 Shielding member 12 Cam follower 13 Cam 41 Drive device

Claims (1)

An X-ray CT apparatus that guides an X-ray emitted from an X-ray irradiator and transmitted through a subject to a detector through a slit of a collimator,
A fixed frame, comprising a rotating frame rotatably supported by an axis parallel to the width direction of the slit by the fixed frame,
The collimator has a pair of X-ray shielding members facing each other via a space constituting the slit, and a slit width adjusting unit for displacing both shielding members so that the width of the slit changes,
Both shielding members and slit width adjusting means are integrally displaceable in the width direction of the slit,
The slit width adjusting means displaces both shielding members in the width direction of the slit so that the center position in the width direction of the slit does not change,
The slit width adjusting means has a cam that comes into contact with both shielding members via a cam follower,
Both shielding members are displaceable in the width direction of the slit so that the width of the slit changes by the operation of the cam,
The shape of the cam is determined so that the center position in the width direction of the slit does not change even if both shielding members are displaced by the operation of the cam,
A driving device for operating the cam by rotation of the motor is provided,
The driving device is displaceable in the width direction of the slit integrally with both shielding members and the slit width adjusting means,
By the rotating frame, the two shielding members, the cam and the driving device are supported via a guide shaft movably in the width direction of the slit,
The cam is sandwiched by the cam followers arranged in parallel along the width direction of the slit, and is rotated around a rotation axis parallel to the width direction of the slit,
An X-ray CT apparatus, wherein a dimension of a contact position of the cam with each cam follower in a rotation axis direction is changed by changing the contact position by rotation of the cam.

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