JP2006314772A - Ct scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CT scanner capable of fast scanning by using plural sets of an X-ray tube and an X-ray detector without a plurality of high voltage generators so as to acquire a clear image. <P>SOLUTION: A plurality of X-ray tubes 2a-2c and X-ray detectors 3a-3c are oppositely arranged. High voltage generated by a high voltage generator 4 is transferred to the X-ray tubes 2a-2c through a high voltage cable CA. Grid control circuits 6a-6c respectively change electric potential of grids provided on the X-ray tubes 2a-2c. A control part 9 controls the grid control circuits 6a-6c so that generation and cease of X-rays could be changed in pulse shape while the X-ray tubes 2a-2c rotate around a subject. Gates 8a-8c enable output signals from the X-ray detectors 3a-3c opposed to the X-ray tubes 2a-2c emitting X-rays, and nullify output signals from the X-ray detectors 3a-3c opposed to the X-ray tubes 2a-2c stopping X-ray emission. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a CT scanner including a plurality of sets of X-ray tubes and X-ray detectors.

  In an RR (Rotate / Rotate) type CT scanner, a set of X-ray tubes and an X-ray detector are arranged opposite to each other on a rotating base. The CT scanner obtains projection data while the X-ray tube and the X-ray detector rotate around the subject, and reconstructs an image inside the subject from the projection data.

  In the diagnosis of an organ that moves rapidly like the heart, it is necessary to complete the scan in a short time in order to obtain a clear image. In order to enable such a scan by the RR method, it is effective to increase the rotation speed of the gantry. However, when the rotational speed of the gantry is increased, the centrifugal force increases in proportion to the square of the rotational speed, so that generally 0.3 seconds / rotation is the limit.

For this reason, Patent Document 1 discloses a technique in which a plurality of sets of X-ray tubes and X-ray detectors are mounted, and these simultaneously collect projection data to shorten the scan time without increasing the rotation speed. It is disclosed.
JP-A-2-52640

  However, when a high voltage device is mounted for each of a plurality of X-ray tubes, the weight of the gantry increases, and the time required for the rotation to stabilize after the gantry starts rotating becomes longer. In addition, since a plurality of high voltage devices are operated simultaneously, the power supplied to the rotating part of the gantry increases, and the life of the slip ring is shortened. In addition, due to variations in output voltages of a plurality of high-voltage devices, a difference occurs in tube voltages of a plurality of X-ray tubes, which may cause artifacts.

  Furthermore, since a plurality of X-ray tubes emit X-rays simultaneously from different directions, the image is blurred due to the influence of scattered rays.

  The present invention has been made in view of such circumstances, and the object of the present invention is to perform a high-speed scan using a plurality of sets of X-ray tubes and X-ray detectors, and a plurality of high-voltage devices. It is an object of the present invention to provide a CT scanner which can be performed without using it and so that a clear image can be obtained.

  In order to achieve the above object, the present invention collects X-ray projection data of a subject by rotating an X-ray tube and an X-ray detector, and generates an image inside the subject from the projection data. A plurality of X-ray tubes that emit X-rays and have a grid for switching generation and stop of the X-rays; and a high-voltage generation unit that generates a high voltage to be supplied to the X-ray tubes; A high-voltage cable that sends the high voltage to each of the plurality of X-ray tubes, a plurality of grid control circuits that respectively change the potentials of grids provided in the plurality of X-ray tubes, and the X-ray tube includes the X-ray tube And a control unit for controlling the grid control circuit so that generation and stop of the X-rays are changed in a pulse shape while rotating around the subject.

  According to the present invention, high-speed scanning using a plurality of sets of X-ray tubes and X-ray detectors can be performed without using a plurality of high-voltage devices so that a clear image can be obtained. It becomes possible.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing the arrangement of X-ray tubes and X-ray detectors in a CT scanner according to this embodiment. FIG. 2 is a block diagram showing an electrical configuration of the CT scanner.

  The CT scanner of this embodiment includes X-ray tubes 2a, 2b, 2c, X-ray detectors 3a, 3b, 3c, a high voltage device 4, high voltage connectors 5a, 5b, 5c, grid control circuits (GCC) 6a, 6b, 6c, filament heating circuits (FHC) 7a, 7b, 7c, gates 8a, 8b, 8c and a control unit 9.

  The X-ray tubes 2a, 2b and 2c, the X-ray detectors 3a, 3b and 3c, the high voltage device 4 and the high voltage connectors 5a, 5b and 5c are all mounted on a rotating gantry. The X-ray tubes 2a, 2b, and 2c are arranged at intervals of 120 degrees on a circumferential rotation trajectory 101 indicated by a one-dot chain line in FIG. The X-ray detectors 3a, 3b, 3c are arranged on the rotary track 101 so as to face the X-ray tubes 2a, 2b, 2c, respectively, with the space 102 at the center of the rotary track 101 interposed therebetween. A subject is placed in the space 102.

  The high voltage device 4 is connected to the high voltage connectors 5a, 5b and 5c by a single high voltage cable CA. X-ray tubes 2a, 2b, and 2c are attached to the high-voltage connectors 5a, 5b, and 5c, respectively. The high voltage device 4 supplies a high voltage to the X-ray tubes 2a, 2b, 2c via the high voltage connectors 5a, 5b, 5c. The grid control circuits 6a, 6b, 6c are built in the high voltage connectors 5a, 5b, 5c. The grid control circuits 6a, 6b and 6c control the grid potentials of the X-ray tubes 2a, 2b and 2c using the high voltage supplied from the high voltage device 4 to the high voltage connectors 5a, 5b and 5c, respectively.

  The gates 8a, 8b, and 8c pass or block the output signals of the X-ray detectors 3a, 3b, and 3c, respectively.

  The control unit 9 controls the grid control circuits 5a, 5b, and 5c so that the X-ray tubes 2a, 2b, and 2c operate in a time division manner. The control unit 9 controls the gates 8a, 8b, and 8c so as to pass only the output signal of the X-ray detector facing the X-ray tube emitting X-rays. Furthermore, the control unit 9 monitors the current flowing into each of the X-ray tubes 2a, 2b, and 2c, and performs control so that the faulty X-ray tube is not used.

  FIG. 3 is a partially broken view showing the external appearance of the X-ray tubes 2a, 2b, 2c and the high-voltage connectors 5a, 5b, 5c. FIG. 4 is a circuit diagram showing the configuration of the X-ray tubes 2a, 2b, 2c and the grid control circuits 5a, 5b, 5c. The X-ray tubes 2a, 2b and 2c have the same configuration, the high voltage connectors 5a, 5b and 5c have the same configuration, and the grid control circuits 6a, 6b and 6c have the same configuration. Therefore, FIGS. 3 and 4 only show the configuration of a pair of X-ray tubes, a high voltage connector, and a grid control circuit. The X-ray tubes 2a, 2b, 2c, the high-voltage connectors 5a, 5b, 5c, and the grid control circuits 6a, 6b, 6c are referred to as the X-ray tube 2, the high-voltage connector 5, and the grid control circuit 6, respectively.

  The X-ray tube 2 includes a grid 21, an anode 22, a cathode 23, an insert tube 24, a filament transformer 25, a high-voltage fuse 26, and a tube container 27.

  The grid 21, the anode 22, and the cathode 23 are accommodated in the insert tube 24. The insert tube 24, the filament transformer 25, and the high voltage fuse 26 are accommodated in a tube container 27.

  The high voltage supplied to the high voltage connector 5 via the high voltage cable CA is guided to the X-ray tube 2 through the inside of the high voltage connector 5. In the X-ray tube 2, a high voltage is applied to the center tap in the secondary winding of the filament transformer 25 via the high voltage fuse 26. As a result, a current is generated in the cathode 23. The anode 22 is grounded, and accelerated electrons are emitted from the cathode 23 toward the anode 22. Then, when the electrons collide with the anode 22, X-rays are emitted from the anode 22. X-rays are emitted from the emission port 28 formed in the tube container 27 to the outside of the tube container 27. The reason why the anode 22 is set to the ground potential and a negative high voltage is applied to the cathode 23 is to increase the cooling efficiency of the anode 22.

  The grid 21 is disposed between the anode 22 and the cathode 23. The grid 21 is turned on / off by application of a negative voltage by the grid control circuit 6. The grid 21 prevents electrons emitted from the cathode 23 from reaching the anode 22 when a negative voltage is applied, thereby turning off X-ray emission.

  The filament transformer 25 is heated by the AC voltage output from the filament heating circuit 7 and controls the current flowing through the cathode 23, that is, the tube current. The high-voltage fuse 26 is blown by an excessive current and interrupts the current to the cathode 23. The high-voltage fuse 26 is configured to obtain a sufficient cut-off voltage in a small space by housing the element in a spiral insulating container.

  The grid control circuit 6 includes a high voltage power supply 61, a capacitor 62, and semiconductor switches 63 and 64.

  The high voltage power supply 61 generates a high voltage negative voltage to be applied to the grid 21 of the X-ray tube 2. The negative voltage is, for example, about -1,000 to -3,000V. The capacitor 62 is connected in parallel to the high voltage power supply 61 and reduces the load applied to the high voltage power supply 61 by the peak current that flows when the X-ray is turned off. The semiconductor switch 63 is turned on during the period in which the X-ray emission is turned off, and applies the output voltage of the high-voltage power supply 61 to the grid 21. The semiconductor switch 64 is turned on during the period when the X-ray emission from the X-ray tube 2 is turned on, and the voltage of the grid 21 is made zero. The semiconductor switches 63 and 64 are turned on / off by a control signal output from the control unit 9. A device that can be used as the semiconductor switches 63 and 64 is typically a power MOS-FET. However, as the semiconductor switches 63 and 64, another type of device such as an IGBT or a bipolar transistor can be applied.

  Next, the operation of the CT scanner configured as described above will be described.

  When the CT scanner scans, the rotation base rotates, so that the X-ray tubes 2a, 2b, 2c and the X-ray detectors 3a, 3b, 3c rotate on the rotation path 101 simultaneously. The rotational speeds of the X-ray tubes 2a, 2b, 2c and the X-ray detectors 3a, 3b, 3c are, for example, about 0.4 second / rotation.

  When the X-ray tubes 2a, 2b, and 2c are rotating, the control unit 9 causes the grid control circuit 6a, so that the X-ray tubes 2a, 2b, and 2c sequentially operate for a certain period as shown in FIG. 6b and 6c are controlled. The grid control circuits 6a, 6b, 6c normally apply a negative voltage to the grid 21 of the X-ray tubes 2a, 2b, 2c to suppress X-ray emission. Then, the grid voltage is set to zero and X-rays are radiated only during a certain period in which the controller 9 is instructed to turn on in the sequence shown in FIG.

  X-rays radiated from the X-ray tube 2a mainly enter the X-ray detector 3a facing the X-ray tube 2a. However, some X-rays (scattered rays) diffusely reflected by the subject placed in the space 102 also enter the other X-ray detectors 3b and 3c. This is the same when the X-ray tube 2b and the X-ray tube 2c are emitting X-rays. These scattered rays cause the sharpness of the reconstructed image to be significantly impaired. Therefore, the control unit 9 controls the gates 8a, 8b, and 8c so that only the output of the X-ray detector facing the X-ray tube being operated is passed. That is, as shown in FIG. 5, for example, when the X-ray tube 2a is operating, the gate 8a is opened and the gates 8b and 8c are closed.

  The pulse rate of the control signal given from the control unit 9 to each of the X-ray tubes 2a, 2b, 2c, that is, the cycle for turning on / off each of the X-ray tubes 2a, 2b, 2c is the projection to be collected per 360 degrees. It is determined according to the number of data (number of views). For example, if the number of views per 360 degrees is 900 views, as shown in FIG. 5, the X-ray tubes 2a, 2b, and 2c are turned on 300 times each while the rotary mount is rotated 1/3. good.

  Now, the X-ray tubes 2a, 2b and 2c continue to discharge at the end of their lifetime. When one of the X-ray tubes 2a, 2b, 2c is in such an abnormal state, the projection data necessary for reconstruction cannot be collected correctly by the above operation. Therefore, it is necessary to replace the X-ray tube in an abnormal state.

  The CT scanner of the present embodiment has a function of continuing the operation using the remaining two X-ray tubes until the X-ray tube that has become abnormal in such a situation is replaced. Hereinafter, the operation by this function will be described.

  In the X-ray tube in the abnormal state as described above, the high-voltage fuse 26 is melted. This prevents the tube current from flowing in the abnormal X-ray tube and prevents abnormal X-ray emission.

  On the other hand, the inflow of current due to the high voltage generated by the high voltage device 4 is eliminated into the X-ray tube in which the high voltage fuse 26 is blown. The controller 9 monitors the current flowing into each of the X-ray tubes 2a, 2b, 2c, and the X-ray tube is in an abnormal state based on the fact that the current stops flowing as described above. It is determined whether it is 2a, 2b, or 2c.

  The control unit 9 always turns off the abnormal X-ray tube and the gate paired with the X-ray tube, and turns on / off the other two X-ray tubes and gates. At this time, the control unit 9 sets the timing for turning on / off the two normal X-ray tubes and the gate to be the same as in the normal state as shown in FIG. FIG. 6 shows the operation timing of the X-ray tubes 2a, 2b, 2c when the X-ray tube 2c is in an abnormal state. In this case, the control of the normal two X-ray tubes and the gate is not different from that at the normal time, so that the processing of the control unit 9 becomes easy. However, since the intervals t1 and t2 of the X-ray radiation are different, the projection data collection interval is uneven, and the resolution may be lowered.

  Therefore, the control unit 9 makes the normal two X-ray tubes and gates turn on / off differently from the normal time so that the intervals t3 and t4 of the X-ray radiation are equal to each other as shown in FIG. May be. In this case, the processing of the control unit 9 is complicated. However, since the projection data collection interval becomes uniform, the resolution does not decrease.

  By the way, during the period in which the rotary mount rotates by 1/3, projection data collected by each of the two normal X-ray tubes remains 300 views and the scan angle also remains 120 degrees. Therefore, only projection data of 600 views for 240 degrees can be collected during this period. Specifically, the first sector, the second sector, and the third sector are defined as shown in FIG. 8 with respect to the positions of the X-ray tubes 2a, 2b, and 2c at a certain point in time, and the X-ray tube 2c enters an abnormal state. Suppose there is. At this time, as shown in FIG. 9, the first sector and the second sector are respectively scanned by the X-ray tubes 2a and 2b during the period PA in which the rotary mount is rotated by 1/3, but the scan relating to the third sector is performed. Is not done.

  However, since the third sector is scanned by the X-ray tube 2b in the period PB in which the rotating platform rotates by 1/3 after the period PA, the output signal of the X-ray detector 3a in the period PA, the period PA, By setting the output signal of the X-ray detector 3b in the period PB as one set, projection data for 360 degrees can be obtained. In the period PC in which the rotary mount rotates by 1/3 after the period PB, the third sector and the first sector are scanned by the X-ray tubes 2a and 2b, respectively, but the scan for the second sector is not performed. However, since the second sector is scanned by the X-ray tube 2a in the period PB, the output signal of the X-ray detector 3a in the period PB and the period PC and the output signal of the X-ray detector 3b in the period PC are 1 By setting it as a set, projection data for 360 degrees can be obtained.

  Thus, 360 degrees of projection data cannot be collected while the rotating base rotates by 1/3 as in the normal state, but 360 degrees of projection data is collected twice while the rotating base rotates once. can do.

  Even when one of the X-ray tubes 2b and 2c is in an abnormal state, it is possible to collect projection data necessary for reconstruction by the same idea as described above.

  As described above, according to the present embodiment, it is possible to acquire projection data for a range of 360 degrees, that is, for one rotation, within the time for which the rotary mount rotates by 1/3. Therefore, the scan time can be shortened to 1/3 of the gantry rotation time, and a high-speed scan can be performed.

  In the present embodiment, since the X-ray tubes 2a, 2b, and 2c are operated in a time-sharing manner, the X-ray tubes 2a, 2b, and 2c are respectively operated by a high voltage output from one high-voltage device 4. Can do. For this reason, various problems associated with the provision of a plurality of high voltage devices can be avoided.

  In this embodiment, since the X-ray tubes 2a, 2b, and 2c are operated in a time-sharing manner, the influence of scattered radiation can be reduced, and effective projection data can be acquired to obtain a clear image. it can. Furthermore, in this embodiment, since the output of the X-ray detector facing the X-ray tube at rest is blocked by the gate, the influence of the scattered radiation can be almost eliminated, and the image can be further refined. Contribute.

  In the X-ray diagnostic apparatus for circulatory organs, pulse X-rays have been generated so far by the method of controlling the grid of the X-ray tube as in the present embodiment, but the pulse rate is 7 About 5 to 30 pulses / second. On the other hand, the pulse rate required in this embodiment is about several thousand pulses / second. When the wiring distance from the grid control circuit 6 to the X-ray tube 2 is long, the grid voltage waveform becomes dull due to the stray capacitance of the wiring, and it is difficult to realize the high pulse rate as described above. However, according to the present embodiment, since the grid control circuit 5 is incorporated in the high-voltage connector 5, the above problems can be avoided and a high pulse rate can be realized. Even if the grid control circuit 5 is arranged in the tube container 24, the same effect can be obtained. However, while the inside of the tube container 24 becomes high temperature, the semiconductor switches 63 and 64 are generally weak against heat, so that the reliability is inferior. Therefore, it is optimal to incorporate the grid control circuit 5 inside the high voltage connector 5 as in the above embodiment.

  On the other hand, a typical X-ray tube does not incorporate a filament transformer. Therefore, a high voltage generated by a filament transformer provided outside the X-ray tube is supplied to the X-ray tube by a high-voltage cable. When such a structure is applied to this embodiment, three pairs of filament transformers and X-ray tubes are provided, so that the high-voltage cable needs to have at least three core wires. However, according to this embodiment, since the filament transformer 25 is built in the X-ray tube 2, the high-voltage cable only needs to have one common core wire for the three X-ray tubes 2a, 2b, and 2c. . According to this embodiment, the diameter of the high-voltage cable CA can be reduced and the structure of the high-voltage connector 5 can be simplified as compared with the case where a multi-core high-voltage cable is used.

  In a typical X-ray tube, since a high voltage is applied to one node of the filament transformer, the other node has a potential corresponding to the filament voltage with respect to the grid, and the grid is opposite to the filament. The same effect as applying a polar voltage occurs. For this reason, the tube current is changed by the filament voltage, causing the X-ray intensity to fluctuate. This fluctuation of the X-ray intensity is averaged when a photograph is taken with an X-ray diagnostic apparatus, or in the case of a CT scanner with a relatively slow data collection speed for generating X-rays continuously from one X-ray tube. It will not be a problem to be converted. However, when pulse X-rays are used and the rate is increased as in this embodiment, fluctuations in X-ray intensity cannot be ignored. In this embodiment, since a high voltage is applied to the center tap provided in the secondary winding of the filament transformer 25, fluctuations in the X-ray intensity due to the influence of the AC voltage output from the filament heating circuit 7 can be reduced.

  Furthermore, according to this embodiment, even if one of the X-ray tubes 2a, 2b, and 2c is in an abnormal state, the operation can be continued.

  This embodiment can be variously modified as follows.

  Two sets or four or more sets of X-ray tubes and X-ray detectors may be provided.

If the output of the X-ray detector facing the resting X-ray tube is not used in the image reconstruction process or its pre-processing, the gates 8a, 8b and 8c can be omitted.
The plurality of X-ray tubes may not be arranged at equal intervals. However, as in the above embodiment, it is desirable for efficient scanning to arrange n X-ray tubes at equal intervals of n / 360 degrees.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

The figure which shows arrangement | positioning of the X-ray tube and X-ray detector in the CT scanner which concerns on one Embodiment of this invention. The block diagram which shows the electrical structure in CT scanner. FIG. 2 is a partially broken view showing the appearance of an X-ray tube and a grid control circuit in FIG. 1. The circuit diagram which shows the structure of the X-ray tube and grid control circuit in FIG. The figure which shows the operation | movement timing of the X-ray tube in FIG. The figure which shows the 1st example of the operation | movement timing of the X-ray tube in FIG. 1 when one of the X-ray tubes in FIG. 1 will be in an abnormal state. The figure which shows the 2nd example of the operation | movement timing of the X-ray tube in FIG. 1 when one of the X-ray tubes in FIG. 1 will be in an abnormal state. The figure which shows the definition of a 1st sector, a 2nd sector, and a 3rd sector. The figure which shows the change of the scanning range of the X-ray tube in FIG. 1 when one of the X-ray tubes in FIG. 1 will be in an abnormal state.

Explanation of symbols

  2, 2a, 2b, 2c ... X-ray tube, 3, 3a, 3b, 3c ... X-ray detector, 4 ... high voltage device, 5, 5a, 5b, 5c ... high voltage connector, 6, 6a, 6b, 6c ... Grid control circuit 7, 7a, 7b, 7c ... Filament heating circuit, 8a, 8b, 8c ... Gate, 9 ... Control part, 21 ... Grid, 22 ... Anode, 23 ... Cathode, 24 ... Insert tube, 24 ... Tube container 25 ... Filament transformer, 26 ... High voltage fuse, 27 ... Tube container, 28 ... Outlet, 61 ... High voltage power supply, 62 ... Capacitor, 63, 64 ... Semiconductor switch.

Claims (15)

A CT scanner that collects X-ray projection data of a subject and generates an image inside the subject from the projection data,
A plurality of X-ray tubes that emit X-rays and have a grid for switching generation and stop of the X-rays;
A high voltage generating unit for generating a high voltage to be supplied to the X-ray tube;
A high-voltage cable for sending the high voltage to each of the plurality of X-ray tubes;
A plurality of grid control circuits that respectively change the potentials of the grids provided in the plurality of X-ray tubes;
A control unit that controls the grid control circuit so that generation and stop of the X-rays change in a pulsed manner while the X-ray tube rotates around the subject;
A plurality of X-ray detectors arranged to face each of the plurality of X-ray tubes;
The output signal from the X-ray detector facing the X-ray tube emitting the X-ray is validated, and the X-ray detector facing the X-ray tube stopping the X-ray is from And a unit for invalidating the output signal.   The CT scanner according to claim 1, wherein the control unit controls the grid control circuit so that at least two of the X-ray tubes do not generate X-rays at the same time.   2. The CT scanner according to claim 1, wherein the high-voltage cable connects a high-voltage input unit of the plurality of X-ray tubes in parallel to an output unit of the high-voltage generation unit. The plurality of X-ray tubes include first to third X-ray tubes,
Furthermore, the high voltage cable
A first cable portion connecting the high voltage generating unit and the first X-ray tube;
A second cable portion connecting the first X-ray tube and the second X-ray tube;
The CT scanner according to claim 1, further comprising a third cable portion that connects the second X-ray tube and the third X-ray tube.   2. The CT scanner according to claim 1, wherein the plurality of grid control circuits are disposed in or near each of the plurality of X-ray tubes. A plurality of high-voltage connectors for connecting the plurality of X-ray tubes to the high-voltage cable,
The CT scanner according to claim 1, wherein the plurality of grid control circuits are built in the plurality of high-voltage connectors, respectively.   The CT scanner according to claim 1, wherein the X-ray tube includes a filament transformer for heating a cathode of the X-ray tube.   The CT scanner according to claim 1, wherein the high-voltage cable has one core wire for transmitting the high voltage, and the plurality of X-ray tubes are all electrically connected to the core wire.   The CT scanner according to claim 1, wherein the high-voltage cable is arranged so that the plurality of X-ray tubes are arranged in order along the high-voltage cable.   The CT scanner according to claim 1, wherein the X-ray tube includes a transformer that applies an AC voltage to a cathode thereof. When the number of the X-ray tubes is expressed as n,
The plurality of X-ray tubes are arranged at an interval of n / 360 degrees;
2. The CT scanner according to claim 1, wherein the control unit generates X-rays in the plurality of X-ray tubes sequentially and the same number of times while the X-ray tube rotates n / 360 degrees.   The CT scanner according to claim 1, wherein the X-ray tube includes a unit that blocks inflow of abnormal current to a cathode thereof.   The control unit detects an abnormality in each of the plurality of X-ray tubes, and constantly stops the abnormal X-ray tubes, and changes the generation and stop of the X-rays in other X-ray tubes in a pulsed manner. The CT scanner according to claim 1, wherein the grid control circuit is controlled so that at least two of the X-ray tubes do not generate X-rays at the same time. A CT scanner that collects X-ray projection data of a subject and generates an image inside the subject from the projection data,
A plurality of X-ray tubes that emit X-rays and have a grid for switching generation and stop of the X-rays;
A high voltage generating unit for generating a high voltage to be supplied to the X-ray tube;
A high-voltage cable for sending the high voltage to each of the plurality of X-ray tubes;
A plurality of grid control circuits that respectively change the potentials of the grids provided in the plurality of X-ray tubes;
A control unit that controls the grid control circuit so that generation and stop of the X-rays change in a pulsed manner while the X-ray tube rotates around the subject.   15. The CT scanner according to claim 14, wherein the control unit controls the grid control circuit so that at least two of the X-ray tubes do not generate X-rays at the same time.

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