JP2006255066A - X-ray ct equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT equipment where vibration at a micro level can be suppressed. <P>SOLUTION: By imparting vibration of opposite phase to vibration occurring at a rotation stand, the vibration occurring at the rotation stand is canceled. For example, a vibration detector 30 for detecting the vibration occurring at the rotation stand 1 is installed to detect the vibration occurring at the rotation stand 1, and a phase calculation circuit 31 calculates the vibration of the opposite phase to the vibration occurring at the rotation stand 1. Then, the vibration of the opposite phase is imparted to the rotation stand 1 by an electric motor 20 etc. When the vibration waveform of the rotation stand 1 is periodical, vibration waveform corresponding to the rotation angle of the rotation stand is measured in advance and stored in a storage device. Then, a vibration level is obtained from the rotation angle of the rotation stand, and the vibration of the opposite phase to the vibration occurring at the rotation stand 1 is imparted to the rotation stand 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an X-ray CT apparatus, and more particularly, to an X-ray CT apparatus capable of suppressing vibration of a rotary mount (gantry) equipped with an X-ray source and an X-ray detector.

  In general, an X-ray CT apparatus controls an operation of a rotating gantry (gantry) including an X-ray source and an X-ray detector, a bed on which a subject is laid down, a rotating table and a bed, and an X-ray detector. And a control system that reconstructs an image by processing the X-ray projection data collected in this way.

  The rotating gantry usually includes a tilt mechanism for causing X-rays to enter the subject obliquely, and the tilting mechanism can be used to tilt the rotating gantry with respect to the bed. This tilt mechanism tilts the rotating gantry to the bed side or the opposite side with respect to the subject inserted into the opening formed in the rotating gantry, so that the tomography at various angles with respect to the body axis of the subject. Photography is possible (for example, Patent Document 1).

Japanese Patent Publication No. 5-43380

  However, in the X-ray CT apparatus, vibration is generated along with the rotation of the rotating mount due to the imbalance of the rotating mount (gantry) including the X-ray source and the X-ray detector. In the past, a fixed counterweight was installed and its counterbalance was adjusted to balance and suppress vibration.

  However, the counterweight cannot suppress minute vibrations (for example, vibrations in the range of 0.3 to 0.5 mm). With the increase in the number of detectors in the X-ray CT apparatus, the increase in resolution, and the speed of rotation of the rotating gantry (gantry), the minute vibrations are at a level that cannot be ignored. The counterweight cannot suppress minute vibrations that cause displacement between the X-ray source, the X-ray detector, and the diagnostic site, and the image displacement of the tomographic image occurs due to the displacement. However, as a result, the demand for higher resolution cannot be satisfied.

  In addition, since the vibration of the rotating gantry further increases with the rotation of the rotating gantry (gantry), measures for suppressing the increase in the vibration are required. Further, when the rotating cradle is tilted by the tilt mechanism, the center of gravity of the rotating gantry changes, and therefore the vibration is generated in the rotating gantry due to the change in the center of gravity. Similarly, if the wedge in the rotating gantry is switched when changing the diagnosis part, the center of gravity of the rotating gantry changes even when the wedge is switched, and therefore the vibration is generated in the rotating gantry due to the change in the center of gravity. In the X-ray CT apparatus, measures for suppressing these vibrations are also required.

  The present invention solves the above-mentioned problem. By applying a vibration having a phase opposite to that of the rotation of the rotating gantry (gantry) to the rotating gantry to cancel the vibration, a minute amount required for high resolution and the like is required. An object of the present invention is to provide an X-ray CT apparatus capable of suppressing level vibration. In other words, an object of the present invention is to provide an X-ray CT apparatus capable of suppressing a minute vibration and satisfying a demand for high resolution.

  The present invention is an X-ray CT apparatus that cancels vibration generated in a rotating gantry by applying vibration having a phase opposite to that generated in the rotating gantry to the rotating gantry. For example, a detector for detecting the vibration generated in the rotating gantry is installed, the vibration generated in the rotating gantry is sequentially detected, and the vibration having the opposite phase to the vibration is calculated and applied to the rotating gantry. In addition, when the vibration waveform of the rotating gantry is periodic, the vibration waveform corresponding to the rotation angle (phase) of the rotating gantry is measured in advance and stored in the storage device, and the vibration level is calculated from the rotation angle of the rotating gantry. Obtain the vibration and reverse phase of the vibration to the rotating frame. In this way, it is possible to cancel the vibration generated in the rotating gantry by applying the vibration having the opposite phase to the vibration generated in the rotating gantry to suppress the vibration generated in the rotating gantry. Become. Specific embodiments of the present invention will be described below.

  The invention according to claim 1 includes an X-ray source and an X-ray detector, has an opening, and is inserted into the opening while rotating the X-ray source and the X-ray detector. A rotating gantry that irradiates X-rays; a support that supports the rotating gantry in a tiltable manner; a drive unit that is interposed between the support and the rotating gantry and tilts the rotating gantry; An X-ray CT apparatus comprising: an oscillating unit that applies vibrations having a phase opposite to that of the generated vibration to the rotating gantry.

  A second aspect of the present invention is the X-ray CT apparatus according to the first aspect, wherein the detector detects the vibration generated in the rotary mount, and the signal has a phase opposite to that of the vibration detected by the detector. Calculating means, and the excitation means applies vibration to the rotating gantry according to the signal of the opposite phase calculated by the calculating means.

  A third aspect of the present invention is the X-ray CT apparatus according to the second aspect, wherein the detector detects a vibration generated in a tilt direction of the rotary mount, and the excitation means is the rotary mount It is characterized in that vibrations having opposite phases are applied in the tilt direction.

  Invention of Claim 4 is an X-ray CT apparatus in any one of Claim 2 or Claim 3, Comprising: The said detector is installed so that a movement along the rotation direction of the said rotation mount is possible, A vibration at a position where the rotation angle of the rotating gantry is shifted with respect to a rotation angle at which the vibration of the anti-phase is applied to the rotating gantry by the vibrating means is detected.

  A fifth aspect of the present invention is the X-ray CT apparatus according to the second aspect or the third aspect, wherein the excitation means has a timing with respect to a vibration detection timing by the detector. It is shifted and the vibration of an antiphase is given to the said rotation mount frame, It is characterized by the above-mentioned.

  A sixth aspect of the present invention is the X-ray CT apparatus according to the first aspect, further comprising a storage device that stores in advance the vibration generated in the rotary mount in association with the rotation angle of the rotary mount. And the said vibration means gives the vibration of the antiphase in a predetermined | prescribed rotation angle to the said rotation mount according to the said matching.

  A seventh aspect of the present invention is the X-ray CT apparatus according to any one of the first to sixth aspects, wherein the excitation means is applied to the rotary mount according to the rigidity of the rotary mount. It is characterized by changing the magnitude of vibration.

  The invention according to an eighth aspect is the X-ray CT apparatus according to the seventh aspect, wherein the excitation means imparts a larger vibration to a portion having a lower rigidity in the rotary mount. is there.

  A ninth aspect of the present invention is the X-ray CT apparatus according to any one of the first to eighth aspects, wherein the vibration means is used when the vibration of the rotary mount becomes a predetermined level or more. Further, vibrations having an opposite phase are imparted to the rotating gantry.

  According to the first aspect of the present invention, the vibration generated in the rotating gantry is suppressed by applying the vibration having the opposite phase to the vibration generated in the rotating gantry to cancel the vibration generated in the rotating gantry. It becomes possible to do. As a result, it is possible to suppress a minute level of vibration required for high resolution and the like, and to prevent image quality deterioration.

  According to the second aspect of the present invention, the vibration generated in the rotating gantry is detected, and the vibration having the opposite phase to the vibration is applied to the rotating gantry to cancel the vibration generated in the rotating gantry. The generated vibration can be suppressed. As a result, it is possible to suppress a minute level of vibration required for high resolution and the like, and to prevent image quality deterioration.

  According to the third aspect of the present invention, the vibration generated in the tilt direction of the rotating gantry is detected, and the vibration in the tilt direction, which is the main cause of the vibration, is suppressed by applying the anti-phase vibration in the tilt direction. As a result, it is possible to suppress the vibration of the rotary mount.

  According to the fourth aspect of the present invention, the detector is shifted in the rotation direction of the rotating gantry, and the vibration at the position where the rotation angle of the rotating gantry is shifted is detected. It is possible to correct a shift in timing to be applied. Further, according to the invention described in claim 5, it is possible to correct the deviation of the timing of applying the vibration by shifting the timing of applying the anti-phase vibration to the rotating frame with respect to the detection timing of the vibration by the detector. It becomes.

  According to the sixth aspect of the present invention, the vibration generated in the rotating gantry is stored in advance in association with the rotation angle (phase) of the rotating gantry, and the anti-phase vibration at a predetermined rotation angle is stored in the rotating gantry according to the association. By applying and canceling the vibration generated in the rotating gantry, the vibration generated in the rotating gantry can be suppressed. As a result, it is possible to suppress a minute level of vibration required for high resolution and the like, and to prevent image quality deterioration.

  According to the seventh aspect of the present invention, by changing the magnitude of the anti-phase vibration applied to the rotating gantry according to the rigidity of the rotating gantry, the reverse of the level that can cancel the vibration generated in the rotating gantry. It is possible to apply phase vibration. According to the eighth aspect of the present invention, it is possible to appropriately cancel the vibration generated in the rotating gantry by applying a higher level of vibration to a portion having lower rigidity.

  According to the ninth aspect of the invention, when the vibration of the rotating gantry exceeds a predetermined level, the vibration of the rotating gantry can be suppressed by offsetting the vibration having a particularly high level by applying the antiphase vibration. It becomes possible. As a result, high-level vibrations that hinder high resolution and the like can be suppressed, and the demand for high resolution and the like can be satisfied.

  Hereinafter, an X-ray CT apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

(Constitution)
The configuration of the X-ray CT apparatus according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an exploded perspective view showing a configuration of a rotating gantry of an X-ray CT apparatus according to an embodiment of the present invention. FIG. 2 is a rear view of the rotary mount shown in FIG. 3 and 4 are side views of the rotary mount shown in FIG. 1 as viewed from the side.

  The X-ray CT apparatus shown in FIG. 1 to FIG. 3 includes an X-ray source, an X-ray detector, and the like, and includes a rotating mount 1 (gantry) that can be tilt driven. The rotary mount 1 has a main frame 2 that forms the center of the framework. The main frame 2 is integrally attached with a belt-like side plate 2b around an end of a substantially semicircular frame plate 2a, and a hole having a predetermined diameter is formed at the center of the frame plate 2a. It has the structure which attached the housing | casing 2c so that it might guide. The housing 2c forms an opening 3 for inserting the subject while being placed on the bed. The rotating gantry 1 is rotated in the direction of arrow A as shown in FIG. 2 by a control signal from a control device (not shown).

  On the side plate 2b, arc-shaped sector gears 4 and 5 are provided at positions on the lower side (lower side in FIG. 1) of the side surface in the axial direction (the axial direction of the opening 3, that is, the direction along the body axis of the subject). Each is attached integrally. Thus, the sector gears 4 and 5 are extended in the axial direction at the lower ends on both sides of the main frame 2. Gears 4a and 5a are formed in an arc shape on the lower surfaces of the sector gears 4 and 5, respectively. The curvatures of the arcuate gears 4a and 5a are set so that the rotary mount 1 (gantry) can be tilted (tilted) about a predetermined point O with respect to the axial direction.

  On the outside of the sector gears 4 and 5, arc-shaped guides 6 (hereinafter referred to as “R guides 6”) and rails 7 in which the rotation centers of the gears 4 a and 5 a coincide with each other are installed. Each R guide 6 has a structure for guiding the nut portion 6 b along the arc-shaped rail portion 6 a, and the rail portion 6 a is integrally attached to the outer side surface of the sector gear 4. The nut portion 6b is movable along the arcuate direction by the rail 6a.

  The rotating gantry 1 (gantry) is provided with an X-ray source (not shown) for X-ray irradiation and an X-ray detector (not shown) for detecting X-rays transmitted through the subject.

  The rotating gantry 1 (gantry) configured as described above is supported by the support unit 10 so as to be tiltable. The support portion 10 corresponds to the “support portion” of the present invention. The support portion 10 includes a base 11 that forms a rectangular frame, and stands 12 and 13 that stand integrally on both sides in the axial direction of the base 11. Each of the stands 12 and 13 is a plate-like member extending in the axial direction. In this embodiment, a nut portion 6 b of the guide 6 is fixed near the inner upper end of the stand 12. Further, a cam follower 8 is rotatably attached to the inner upper end of the stand 13 along the upper and lower ends of the rail 7. As a result, the stands 12 and 13 receive the weight of the main frame 2 (ie, the rotary base 1) via the guide 6 and the rail 7, and support the main frame 2 (ie, the rotary base 1) in a tiltable manner.

  Furthermore, the base 11 and the stands 12 and 13 are provided with various mechanisms for performing tilt driving. An electric motor 20 that receives a drive signal from a control device (not shown) is provided at the gantry rear end (the front end in FIG. 1) in a direction orthogonal to the axial direction of the base 11.

  A pinion 20b is attached to the output shaft of the electric motor 20, and the pinion 20b meshes with the first gear 21a of the drive shaft 21 that is rotatably supported by both the stands 12 and 13. . That is, the stands 12 and 13 support the drive shaft 21 in a rotatable manner. Second and third gears 21b and 21c are integrally attached to the drive shaft 21 at the positions of both ends thereof. Further, gears 22 and 23 that mesh with each other are attached to the inside of one stand 12, and one of the gears 22 meshes with the second gear 21b of the drive shaft 21, and the other gear 23 is a sector gear. 4 gear 4a. Similarly, gears 24 and 25 that mesh with each other are attached to the inside of the other stand 13, and one of the gears 24 meshes with the third gear 21 c of the drive shaft 21, and the other gear 25 It meshes with the gear 5a of the sector gear 5.

  As a result, the rotation of the electric motor 20 is transmitted to the drive shaft 21, and is transmitted from the drive shaft 21 to the gears 4a and 5a of the sector gears 4 and 5 via the gear systems 21b, 22, 23 and 21c, 24, 25 on both sides. To do. As a result, the electric motor 20 can tilt the main frame 2 (the rotary mount 1) as shown by virtual lines K1 and K2 shown in FIG. 3 with respect to the axial direction. That is, the rotary mount 1 can be tilted in the direction of arrow C shown in FIG. Hereinafter, the direction of the arrow C may be referred to as a tilt direction.

  The drive shaft 21 is provided with a brake 26 that is operated by a control signal from a control device (not shown) at a position outside the stand 13, and the brake 26 can brake the drive shaft 21. ing. The shaft 27 is a shaft with a built-in bearing that rotatably supports the gears 22 and 23, and the bearing 28 is a bearing that rotatably supports the drive shaft 21.

  The vibration detector 30 that detects vibration generated in the rotating gantry 1 (gantry) is installed in a non-contact manner with respect to the upper end of the main frame 2 as shown in the rear view of FIG. The vibration generated in the tilt direction (direction of arrow C shown in FIG. 3) is detected. The vibration detector 30 is composed of, for example, a non-contact sensor using a laser, an ultrasonic wave, an eddy current, etc., and detects the vibration generated in the rotary mount 1 by measuring the distance to the vibration detector 30. To do. Further, by measuring the acceleration of the rotating gantry 1 using an acceleration sensor as the vibration detector 30, the vibration generated in the rotating gantry 1 is detected. This vibration detector 30 corresponds to the “detector” of the present invention.

  Here, a mechanism for suppressing the vibration generated in the rotary mount 1 will be described with reference to FIG. FIG. 4 is a side view of the rotating gantry according to this embodiment, and shows only a mechanism that suppresses vibration by simplifying the rotating gantry shown in FIGS. 1 to 3. In the rotary mount 1 shown in FIG. 4A, as shown in FIGS. 1 to 3, the electric motor 20 rotates the gear system (22, 23, etc.), and the rotation of the gear system is performed by the sector gear 4 (5 ) To rotate the main frame 2 (rotary mount 1) in the tilt direction (direction of arrow C). 4B, the worm gear 32 is rotated by the electric motor 20, and the rotation of the worm gear 32 is transmitted to the sector gear 4 (5) to tilt the main frame 2 (rotary gantry 1). It is rotated in the direction (direction of arrow C).

  Moreover, the rotating gantry 1 shown in FIG.4 (c) is a figure which shows schematic structure in the case of tilting the main frame 2 (rotating gantry 1) with oil_pressure | hydraulic. In the rotating gantry 1 shown in FIG. 4C, the main frame 2 is supported by a support column 35 standing on a stand 36 so as to be tiltable. Further, the main frame 2 (rotary mount 1) is tilted in the direction of arrow C by expanding and contracting the expander 34 in the direction of arrow D by a hydraulic device (hydraulic pump) 33.

  In addition to the electric motor 20 and the hydraulic pump 33, the main frame 2 (rotary mount 1) may be tilted using an electric power cylinder, air pressure, or the like. The electric motor 20, the hydraulic pump 33, and the like correspond to the “drive unit” of the present invention, and further correspond to the “vibration means” of the present invention.

  In FIG. 4, a bed (not shown) on which the subject is placed moves in the direction of arrow B in response to a control signal from a control device (not shown), and enters the opening 3 of the rotary frame 1 and the main frame 2. Inserted.

  As shown in FIG. 4, the vibration detector 30 is installed in a non-contact manner with respect to the upper end portion of the main frame 2. The vibration detector 30 detects vibration for each rotation angle (phase) of the rotary mount 1. A signal indicating the vibration generated in the rotating gantry 1 detected by the vibration detector 30 is output to the phase calculation circuit 31.

  The phase calculation circuit 31 receives a signal indicating vibration generated in the rotating gantry 1 from the vibration detector 30 and performs phase processing on the vibration waveform. For example, the phase calculation circuit 31 performs an inversion process on the vibration waveform of the rotating gantry 1 and extracts an antiphase waveform. At this time, the phase calculation circuit 31 performs calculation so that the amplitude of the vibration of the opposite phase is the same as the amplitude of the original vibration. In the case of the rotary base 1 shown in FIGS. 4A and 4B, the signal subjected to the phase processing by the phase calculation circuit 31 is output to the electric motor 20. When the electric motor 20 receives the signal subjected to the phase processing, the electric motor 20 rotates the gear (worm gear 32) according to the signal. This rotation is transmitted to the sector gear 4, and the main frame 2 (rotary mount 1) performs a rotation operation in a state in which the phase-processed vibration is applied. That is, the rotation operation is performed by applying the vibration of the opposite phase (the amplitude is the same as the original vibration waveform) in the tilt direction of the rotary mount 1. The phase calculation circuit 31 corresponds to “calculation means” of the present invention.

  On the other hand, in the case of the rotating gantry 1 shown in FIG. 4 (c), the signal subjected to the phase processing by the phase calculation circuit 1 is output to the hydraulic pump 33. When the hydraulic pump 33 receives the signal subjected to the phase processing, it expands and contracts the expander 34 in accordance with the signal. This expansion / contraction is transmitted to the sector gear 4, and the main frame 2 (rotary mount 1) rotates in a state in which the phase-processed vibration is applied.

(Operation)
Next, the operation of the X-ray CT apparatus according to the embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a diagram showing a vibration waveform detected by a vibration detector installed in the X-ray CT apparatus according to the embodiment of the present invention.

  For example, when acquiring a tomographic image of a subject by a helical scan, the rotating gantry 1 (gantry) is rotated at a predetermined speed in response to a control signal from a control device (not shown), and further in accordance with the rotation. A bed (not shown) on which the subject is placed is moved in the direction of arrow B shown in FIG. In this way, the rotating gantry 1 is rotated while moving the bed (not shown) in the direction of arrow B. Then, an X-ray detector (not shown) installed at a position opposite to the X-ray source is irradiated with X-rays from an X-ray source (not shown) installed in the rotary mount 1. ) To detect. In this way, X-ray projection data is continuously collected by irradiating X-rays while moving a bed (not shown).

  When collecting a tomographic image of a subject from an oblique direction, for example, a gear is rotated by an electric motor 20 shown in FIG. 4A, and the rotation is transmitted to the sector gear 4 so that the main frame 2 (rotary mount 1) is moved. Tilt in the tilt direction (the direction of arrow C). Thus, by irradiating X-rays from an X-ray source (not shown) with the main frame 2 (rotary mount 1) tilted, a tomographic image of the subject can be collected from an oblique direction.

  When the rotating gantry 1 (gantry) is rotated, the vibration detector 30 starts to detect the vibration generated in the rotating gantry 1. As described above, the distance between the vibration detector 30 and the rotary gantry 1 is measured using a laser, ultrasonic waves, or the like, or the acceleration of the rotary gantry 1 is measured by an acceleration sensor. Vibration generated in the tilt direction (the direction of arrow C) is detected.

  An example of the vibration waveform of the rotating gantry 1 detected by the vibration detector 30 will be described with reference to FIG. In the graph shown in FIG. 5, the horizontal axis indicates the rotation angle (phase) of the rotary mount 1, and the vertical axis indicates the vibration level (amplitude magnitude) of the rotary mount 1. “One cycle (one rotation)” shown in FIG. 5 means that the rotary mount 1 has rotated 360 °. Since the cause of the vibration generated in the rotating gantry 1 is due to the rotation of the rotating gantry 1, the same waveform is repeated every cycle (one rotation: 360 °).

  A signal indicating a vibration waveform as shown in FIG. 5 is output from the vibration detector 30 to the phase calculation circuit 31. When receiving a signal indicating the vibration waveform from the vibration detector 30, the phase calculation circuit 31 performs phase processing on the vibration waveform. For example, the phase calculation circuit 31 performs an inversion process on the vibration waveform, and calculates a waveform having a phase opposite to that of the vibration waveform. At this time, the phase calculation circuit 31 calculates so that the amplitude in the waveform of the opposite phase is the same as the amplitude of the original vibration. A signal indicating the waveform of the antiphase calculated in this way is output to the electric motor 20 or the like.

  In the case of the X-ray CT apparatus shown in FIGS. 4A and 4B, a signal indicating an antiphase waveform calculated by the phase calculation circuit 31 is output to the electric motor 20. When the electric motor 20 receives the signal indicating the waveform of the opposite phase, the electric motor 20 rotates the gear system according to the level of the signal. The rotation by the gear system is transmitted to the sector gear 4, and in the tilt direction (in the direction of arrow C) with respect to the main frame 2 (rotary mount 1), the vibration has the opposite phase to the vibration waveform (the amplitude is the same as the vibration waveform). ) Is given. In this way, by applying a vibration having the opposite phase to the vibration waveform (the amplitude is the same) to the main frame 2 (the rotating mount 1), the vibration of the rotating mount 1 is canceled and the vibration is suppressed. Is possible.

  In the case of the X-ray CT apparatus shown in FIG. 4C, a signal indicating the antiphase vibration calculated by the phase calculation circuit 31 is output to the hydraulic pump 33. When the hydraulic pump 33 receives a signal indicating the vibration in the opposite phase (the amplitude is the same as the vibration waveform), the hydraulic pump 33 expands and contracts the expander 34 according to the level of the signal. Due to the expansion and contraction by the expansion / contraction device 34, vibration having a phase opposite to the vibration waveform is applied to the main frame 2 (rotary mount 1) in the tilt direction (direction of arrow C), as shown in FIGS. 4 (a) and 4 (b). Similar to the X-ray CT apparatus, the vibration of the rotating gantry 1 is canceled and the vibration is suppressed.

  At this time, when vibration at each rotation angle (phase) of the rotating gantry 1 is detected, and vibrations having the opposite phase to the vibration are calculated and applied to the rotating gantry 1, the rotating gantry 1 is equivalent to the time required for the calculation and application. Since the rotation further rotates, an antiphase vibration may be applied to the rotary mount 1 at a rotation angle (phase) different from the rotation angle (phase) to be applied. In other words, the timing of applying the antiphase vibration is delayed by the time of calculation or the like, and the antiphase vibration corresponding to each rotation angle (phase) cannot be appropriately applied, and the rotating mount 1 is appropriately provided. In some cases, it is impossible to cancel the vibration.

  On the other hand, since the cause of the vibration generated in the rotating gantry 1 is due to the rotation of the rotating gantry 1, as shown in FIG. 5, the same waveform is repeated every one cycle (one rotation: 360 °). Thus, since the rotary mount 1 vibrates periodically, it becomes possible to predict the vibration level at a certain rotation angle (phase). In order to perform this prediction, a storage device (not shown) is provided in the X-ray CT apparatus, and the vibration waveform of the rotating gantry 1 detected by the vibration detector 30 is associated with the rotation angle (phase) of the rotating gantry 1. Store in a storage device.

  Since the rotating gantry 1 is rotated under the control of a control device (not shown), the control device (not shown) grasps the rotation angle (phase) of the rotating gantry 1. Therefore, the storage device receives the signal of the rotation angle (phase) of the rotating gantry 1 from the control device, receives the signal of the vibration waveform of the rotating gantry 1 from the vibration detector 30, and associates the vibration waveform with the rotation angle (phase). Remember.

  In this manner, the phase calculation circuit 31 can predict the vibration level at an arbitrary rotation angle (phase) by storing the vibration waveform and the rotation angle (phase) in the storage device in association with each other. It becomes. In other words, the phase is shifted by the time from when the vibration is detected by the vibration detector 30 to when the vibration of the opposite phase is actually applied to the rotary mount 1, and the level of vibration at the shifted phase is stored in the storage device. A vibration having a phase opposite to that of the obtained vibration level is applied to the rotary base 1. In this way, the phase shift corresponding to the time shift from when the vibration is detected to when the vibration having the opposite phase is actually applied is shifted to correct the timing shift.

  The process for correcting the timing will be specifically described with reference to FIG. For example, it is assumed that the vibration detector 30 detects a vibration in the phase A. The level of vibration at this time is assumed to be level C. Then, the phase B is the time when the vibration of the reverse phase is actually applied to the rotary mount 1 due to the timing shift. Since the timing deviation is known in advance from the characteristics of the phase calculation circuit 31 and the electric motor 20, the phase B to which vibration is actually applied is obtained from the phase A. Since the rotating gantry 1 vibrates periodically as described above, the vibration level in the phase B is obtained from the vibration waveform shown in FIG. 5 which is detected in advance and stored in the storage device. For example, as shown in FIG.

  That is, the phase B, which is the timing at which an actually antiphase vibration is applied, is obtained based on the phase A, and the vibration level D at the phase B is obtained from the periodic vibration waveform stored in the storage device. The phase calculation circuit 31 calculates the vibration level D in the phase B, and further obtains vibration having the opposite phase to the vibration level D (the amplitude is the same as that of the original vibration waveform), and sends it to the electric motor 20 or the hydraulic pump 33. A signal indicating antiphase vibration is output. Then, the electric motor 20 or the like can apply vibration to the rotating gantry 1 according to the level of the signal, thereby applying reverse-phase vibration that can cancel the vibration at an appropriate timing. Thus, even when the timing of applying the antiphase vibration is delayed, by predicting the vibration level of the rotary mount 1 from the vibration waveform, the antiphase vibration that can cancel the vibration is appropriately applied. It becomes possible to do.

  In addition, by detecting the vibration of the rotating gantry 1 in advance and storing the vibration in the storage device in association with the rotation angle (phase) of the rotating gantry 1, the vibration detector 30 is installed and sequentially. There is no need to detect the vibration of the rotary mount 1. As described above, the vibration waveform of the rotating gantry 1 is repeated every rotation (one cycle). Therefore, the vibration level at a predetermined rotation angle can be calculated from the rotation angle (phase) of the rotating gantry 1 and the vibration waveform stored in the storage device.

  Information on the rotation angle (phase) of the rotary gantry 1 is output to the phase calculation circuit 31 from a control device (not shown) that controls the rotation of the rotary gantry 1, and the phase calculation circuit 31 is stored in a storage device (not shown). The vibration level at the rotation angle (phase) is obtained based on the rotation angle (phase) information received from the control device with reference to the vibration waveform. Then, an antiphase vibration is calculated from the vibration level, and a signal indicating the antiphase vibration is output to the electric motor 20 or the like. At this time, the phase calculation circuit 1 performs the calculation so that the amplitude of the vibration having the opposite phase is the same as the amplitude of the original vibration waveform. The electric motor 20 or the like applies reverse-phase vibration (the amplitude is the same as the original vibration waveform) to cancel the vibration to the rotary base 1 in accordance with a signal indicating the reverse-phase vibration. By storing the vibration waveform in which the rotation angle (phase) and the vibration are associated with each other in this manner in the storage device, it is possible to apply the reverse phase vibration to the rotating mount 1 at an appropriate timing, and to rotate the rotation appropriately. It becomes possible to cancel the vibration of the gantry 1.

  Further, it is not necessary to detect vibrations in advance by detecting vibrations of the rotating gantry 1 in advance to obtain vibration waveforms and canceling the vibrations using a storage device that stores the vibration waveforms. The need for installing the vessel 30 is eliminated. This eliminates the need to install an expensive vibration detector 30 such as a sensor in the X-ray CT apparatus, thereby reducing the manufacturing cost of the X-ray CT apparatus.

  Further, as a method of correcting the timing difference between the vibration detection and the application of the vibration of the opposite phase, the vibration detector 30 may be installed by being shifted by the timing difference. A mechanism for this correction will be described with reference to FIG. FIG. 6 is a rear view of the rotary mount shown in FIG. 1 as viewed from the rear.

  As shown in FIG. 6, in the embodiment described above, the vibration detector 30 is installed at a position where the rotation angle (phase) of the rotary mount 1 is, for example, “0 °”, and the rotary mount 1 rotates in the direction of arrow A. By doing so, vibration at each rotation angle (phase) is detected.

  On the other hand, in order to correct the timing shift, the vibration detector is installed by shifting the phase from the installation position of the vibration detector 30. For example, when the rotation angle (phase) is shifted by “10 °” from the detection of the vibration generated in the rotating gantry 1 until the actual antiphase vibration is applied, the vibration is detected by shifting by “10 °” in advance. A vibration device is installed, and vibration generated in the rotating gantry 1 is detected by the vibration detector.

  The vibration detector 30a and the vibration detector 30b shown in FIG. 6 are installed at a position shifted by “10 °” from the position where the vibration detector 30 is installed. As a result, the vibration detector 30 a and the vibration detector 30 b detect vibrations having a rotation angle (phase) shifted by “10 °” from the vibration detector 30.

  For example, when the rotating gantry 1 rotates in the direction of the arrow A1, the vibration detector 30a detects the vibration of the rotation angle (phase) “0 °” and the vibration detector 30a has the phase “10 °”. Detecting vibration. When a vibration having the opposite phase to the vibration detected by the vibration detector 30a (the amplitude is the same as the original vibration waveform) is applied to the rotary mount 1, the angle (phase) is shifted by “10 °” until it is applied. For this reason, it is possible to apply vibrations in the opposite phase just at the time of the phase “10 °”.

  Similarly, when the rotating gantry 1 rotates in the direction of the arrow A2, the vibration detector 30b detects the vibration of the rotation angle (phase) “0 °” and the vibration detector 30b 10 ° "vibration is detected. As described above, by applying a vibration having a phase opposite to that detected by the vibration detector 30b to the rotary mount 1, a vibration having a phase opposite to that at the time of the phase “10 °” can be applied. it can.

  As described above, by detecting the vibration by shifting the vibration detector in accordance with the timing deviation that occurs from the vibration detection to the application of the antiphase vibration, the timing deviation that occurs from the detection to the application is detected. It becomes possible to correct. As a result, it is possible to apply vibrations having opposite phases to the rotating gantry 1 at an appropriate timing, and to appropriately suppress vibrations of the rotating gantry 1.

  In addition, vibrations having opposite phases to vibrations may not be applied to the rotating gantry 1 at all rotation angles (phases), and vibrations having opposite phases may be applied partially. For example, when the vibration level at a certain rotation angle (phase E) is high (vibration level F) as in the vibration waveform shown in FIG. 5, the vibration having the opposite phase is rotated only at the rotation angle (phase E). It is given to the gantry 1. When achieving high resolution, etc., anti-phase vibration is not applied to vibrations at a level that can be ignored, but anti-phase vibration is applied to vibrations at a level that affects high resolution. In this way, even if vibrations having a partially opposite phase are applied, it is possible to appropriately suppress vibrations generated in the rotating base.

  For example, a comparison unit (not shown) that receives the level of vibration output from the vibration detector 30 and compares and determines the magnitude of the vibration level (that is, the magnitude of the amplitude) is provided. The comparison unit compares a predetermined level (set value) set in advance with the level of vibration detected by the vibration detector 30. This predetermined level (set value) indicates a level that hinders high resolution and the like. If vibration of a level higher than this predetermined level (set value) occurs in the rotary base 1, it will hinder high resolution and the like. On the other hand, vibrations at a level lower than a predetermined level (set value) will not affect the high resolution even if ignored. This predetermined level (setting value) is obtained in advance, and is stored in a storage device such as a memory.

  When the detected vibration level is greater than or equal to the set value (when the amplitude is greater than or equal to the set value), the comparison unit determines that antiphase vibration is to be applied, and the comparison determination result is used as the phase calculation circuit. To 31. When the phase calculation circuit 31 receives the comparison determination result and determines that the vibration having the opposite phase is applied, the phase calculation circuit 31 obtains the vibration having the opposite phase to the vibration output from the vibration detector 30. At this time, the phase calculation circuit 31 performs calculation so that the amplitude of the antiphase vibration is the same as the amplitude of the original vibration waveform. Then, the phase calculation circuit 31 outputs a signal indicating the antiphase vibration to the electric motor 20 or the like, and the electric motor 20 or the like has the antiphase vibration (the amplitude is the same as the original vibration waveform) as described above. ) Is applied to the rotary mount 1. As a result, vibrations in the rotating gantry 1 are canceled out, and vibrations that affect high resolution and the like can be suppressed, and requirements for high resolution and the like can be satisfied.

  On the other hand, when the vibration level detected by the vibration detector 30 is smaller than the set value, the comparison unit determines that no antiphase vibration is applied, and outputs the comparison determination result to the phase calculation circuit 31. To do. If the phase calculation circuit 31 receives the comparison determination result and determines that no anti-phase vibration is applied, the phase calculation circuit 31 does not calculate the anti-phase and ends the process. As a result, anti-phase vibrations are not applied to the rotary mount 1.

  For example, as shown in FIG. 5, a predetermined level (set value) is set to level G. The comparison unit compares the level G (set value) with the vibration level detected by the vibration detector 30. When the detected vibration level is equal to or higher than the level G (set value), the rotating gantry 1 is given an antiphase vibration (the amplitude is the same as the original vibration waveform), and the detected vibration When the level is smaller than the level G (set value), no antiphase vibration is applied.

  In the example shown in FIG. 5, the level of vibration at phase E is level F, which is equal to or higher than level G (set value). To be granted. On the other hand, the vibration level in phase A is level C, which is smaller than level G (set value), and therefore, in phase A, no anti-phase vibration is applied. Similarly, the vibration level in the phase B is level D, which is smaller than the level G (set value). Therefore, in the transfer B, no antiphase vibration is applied.

  As described above, when a vibration of a predetermined level or higher (a predetermined amplitude or higher) is detected, a vibration having an antiphase is applied to the rotary mount 1 to suppress a vibration that hinders high resolution and the like. This makes it possible to satisfy the demand for higher resolution and the like.

  Further, the rigidity of the rotating gantry 1 to which vibrations having opposite phases are applied varies depending on the location. For example, the rigidity changes and the way in which the force is transmitted differs between the part in which the X-ray source, the X-ray detector, etc. are built, and the other part. Therefore, even if the vibration level is the same, if the rigidity is different, the vibration of the rotating gantry 1 may not be canceled properly. Even at the same vibration level, vibration can be canceled out even if a weak force is applied in a portion with high rigidity, but even if the same force is applied in a portion with low rigidity, the force is not easily transmitted. Therefore, the vibration cannot be canceled out. In addition, if a strong force is applied to a portion having high rigidity, extra vibration is applied to the rotary base 1, and the vibration cannot be offset appropriately. Therefore, even if the vibration level is the same, it is necessary to change the level of vibration applied according to the rigidity of the rotary mount 1.

  For example, weights are applied to the vibrations in the opposite phase of the vibrations detected by the vibration detector 30 and then the vibrations in the opposite phase are applied to the rotary mount 1. The rigidity of the rotating gantry 1 is measured in advance for each location (phase) of the rotating gantry 1, and the rotation angle (phase) and the rigidity are associated with each other and stored in the storage device. After the antiphase vibration is calculated by the phase calculation circuit 31, the antiphase vibration is weighted according to the rigidity at the rotation angle (phase), and the antiphase vibration at the rotation angle (phase) is calculated. Ask for the level. Then, by applying a weighted antiphase vibration to the rotary mount 1, it is possible to apply a vibration corresponding to that portion (phase).

  Specifically, in a portion (phase) with high rigidity, the weighting value is reduced, thereby reducing the level of vibration in the opposite phase and applying it to the rotary base 1. That is, the magnitude of the amplitude of the antiphase vibration is reduced. On the other hand, in the portion (phase) where the rigidity is low, by increasing the weighting value, the level of vibration in the opposite phase is increased and applied to the rotary mount 1. That is, the magnitude of the amplitude of the antiphase vibration is increased. In this way, by weighting the vibration level in the opposite phase in accordance with the rigidity and applying the vibration to the rotating gantry 1, the vibration of the rotating gantry 1 can be canceled appropriately.

  More specific description will be given with reference to FIG. For example, the vibration level of the rotary gantry 1 in the phase A is level C, and the vibration level of the rotary gantry 1 in the phase H is also level C. If the rigidity of the rotating gantry 1 in the phase A and the rigidity of the rotating gantry 1 in the phase H are the same, the level of the antiphase vibration to be applied in the phase A and the antiphase vibration to be applied in the phase H The level is the same level. By applying the same level of vibration to the rotating gantry 1 in the phase A and the phase H, the vibration of the rotating gantry 1 can be canceled appropriately in the phase A and the phase H.

  However, when the rigidity of the rotating gantry 1 in the phase A and the rigidity of the rotating gantry 1 in the phase H are different, even if the same level of vibration is applied in the phase A and the phase H, The vibration cannot be canceled. That is, even if vibration having the same amplitude is applied, the vibration of the rotating gantry 1 cannot be canceled. For example, when the rigidity of the rotating gantry 1 in the phase A is higher than the rigidity of the rotating gantry 1 in the phase H, the level of vibration to be applied in the phase H needs to be higher than the level of vibration to be applied in the phase A. There is. That is, it is necessary to make the amplitude of the vibration in the phase H larger than that in the phase A.

  In this case, the rigidity in the phase A and the phase H is obtained in advance, and the vibration level in the opposite phase is weighted according to the rigidity, and the weighted vibration is applied to the rotary mount 1. In this example, by increasing the weighting in the phase H, the level of vibration in the opposite phase is increased and applied to the rotary mount 1. Accordingly, an appropriate vibration for canceling the vibration of the rotating gantry 1 is applied, and the vibration is appropriately canceled.

  In the above-described embodiment, the rotating gantry 1 is tilted using the electric motor 20 or the hydraulic pump 33, and vibrations having a phase opposite to that of the rotating gantry 1 are applied to the rotating gantry 1. Alternatively, an anti-phase vibration may be applied to the rotary mount 1 using an electric power cylinder, air pressure, or the like. Furthermore, in the above-described embodiment, the anti-phase vibration is applied to the rotary mount 1 by using the electric motor 20 or the hydraulic pump 33 that is a means for tilting the rotary mount 1, but the anti-phase vibration is applied. A motor or the like may be provided separately. That is, the electric motor 20 or the like for tilting the rotating gantry 1 may not be used as a means for applying the antiphase vibration, and a motor or the like only for applying the antiphase vibration may be provided separately.

It is a disassembled perspective view which shows the structure of the rotary mount of the X-ray CT apparatus which concerns on embodiment of this invention. It is the rear view which looked at the rotation mount shown in FIG. 1 from back. It is the side view which looked at the rotation mount shown in FIG. 1 from the side surface. It is the side view which looked at the rotation mount shown in FIG. 1 from the side surface. It is a figure which shows the vibration waveform detected by the vibration detector installed in the X-ray CT apparatus which concerns on embodiment of this invention. It is the rear view which looked at the rotation mount shown in FIG. 1 from back.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation stand 2 Main frame 3 Opening part 4 Sector gear 6 R guide 10 Support part 20 Motor 30, 30a, 30b Vibration detector 31 Phase calculation circuit 32 Worm gear 33 Hydraulic device (hydraulic pump)
34 Stretcher

Claims (9)

A rotating gantry including an X-ray source and an X-ray detector, having an opening, and irradiating the subject inserted into the opening while rotating the X-ray source and the X-ray detector; ,
A support portion for tiltably supporting the rotary mount;
A drive unit interposed between the support unit and the rotating gantry to tilt the rotating gantry;
Vibration means for imparting vibration to the rotating gantry in a phase opposite to that generated in the rotating gantry;
An X-ray CT apparatus comprising: A detector for detecting vibrations generated in the rotating mount;
And a calculation means for calculating a signal having a phase opposite to that of the vibration detected by the detector,
2. The X-ray CT apparatus according to claim 1, wherein the excitation unit applies vibration to the rotating mount in accordance with an antiphase signal calculated by the calculation unit. The detector detects a vibration generated in a tilt direction of the rotary mount;
The X-ray CT apparatus according to claim 2, wherein the excitation unit applies a vibration having a phase opposite to the detected vibration in a tilt direction of the rotating gantry.   The detector is installed so as to be movable along the rotation direction of the rotating gantry, and the rotation angle of the rotating gantry is different from the rotation angle at which vibration of the opposite phase is applied to the rotating gantry by the vibration means. The X-ray CT apparatus according to claim 2, wherein vibration at a shifted position is detected.   The said excitation means shifts timing with respect to the detection timing of the vibration by the said detector, and gives the vibration of an antiphase to the said rotation mount frame, The Claim 2 or Claim 3 characterized by the above-mentioned. X-ray CT system. A storage device that stores in advance the vibration generated in the rotating mount in association with the rotation angle of the rotating mount;
2. The X-ray CT apparatus according to claim 1, wherein the excitation unit applies an antiphase vibration at a predetermined rotation angle to the rotating mount according to the association.   The X-ray CT apparatus according to claim 1, wherein the excitation unit changes a magnitude of vibration applied to the rotary mount according to rigidity of the rotary mount.   The X-ray CT apparatus according to claim 7, wherein the excitation unit applies a larger vibration to a portion of the rotating gantry having a lower rigidity. 9. The vibration generator according to claim 1, wherein when the vibration of the rotating gantry becomes a predetermined level or more, the vibration applying unit imparts an anti-phase vibration to the rotating gantry. 10. X-ray CT system.

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