JP2010027340A - X-ray tube device, and x-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray tube device can carry out switching on/off of X rays irradiated on an inspection object at high speed. <P>SOLUTION: The X-ray tube device is provided with an electron gun 101 emitting electron beams, an electrode for deflection 102 for sending out the electron beams emitted from the electron gun 101 to switch in at least two directions by receiving a control signal, and a target 110 having a first reflection surface 111 irradiating X rays toward a predetermined irradiation field in receipt of electron beams of one direction and a second reflection surface 112 irradiating X rays toward a direction different from the predetermined irradiation field in receipt of electron beams of the other direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an X-ray tube apparatus including a plurality of X-ray irradiation units and an X-ray CT apparatus using the same. More specifically, the present invention relates to an X-ray tube apparatus that alternately emits X-rays from a plurality of X-ray irradiation units and an X-ray CT apparatus that uses the X-ray tube apparatus.

  The X-ray CT apparatus rotates an X-ray tube and an X-ray detector, which are arranged opposite to each other with a subject interposed therebetween, around the subject to expose the X-ray from the X-ray tube toward the subject. The tomographic image of the subject is detected by detecting the X-rays transmitted through the subject with an X-ray detector, and performing reconstruction processing on the projection data generated based on the detected amount of X-rays It is an apparatus which acquires X-ray CT images, such as. For example, the projection data is collected by rotating the X-ray tube and the X-ray detector to 360 ° or (180 ° + fine angle), and the projection data for 360 ° or (180 ° + fine angle) is collected. To obtain an X-ray CT image. This X-ray is several kHz.

  Furthermore, there is a desire to shorten the time required for one scan (scan time) in order to make a detailed diagnosis of a circulatory organ such as the heart. However, to speed up the rotation cycle, an excessive centrifugal force is applied to a rotating portion such as an X-ray tube or an X-ray detector. For this reason, it is technically difficult to meet the demands by advancing the rotation cycle.

  Therefore, a multi-tube X-ray CT system using a set of multiple X-ray tubes and X-ray detectors is proposed in order to collect projection data for the desired number of views in a short time without increasing the rotation period. Has been. In addition, in the multitubular X-ray CT apparatus, it is possible to generate X-ray CT images of different tissues (for example, bones and blood vessels) at a time.

  However, X-rays emitted from the X-ray tube are scattered by X-rays reflected by the bones of the subject and the like, thereby generating scattered rays. In an X-ray CT apparatus provided with a plurality of X-ray tubes, X-rays are continuously generated from the plurality of X-ray tubes. Therefore, not only a set of X-ray detectors but also other X-ray detectors are used. Scattered rays are also detected by the line detector, and the scattered rays affect each other. For example, in an X-ray CT apparatus having two sets of an X-ray tube and an X-ray detector, scattered X-rays emitted from one X-ray tube are detected by the other X-ray detector. become. Such detection of scattered radiation becomes noise, and there is a problem that the image quality of the X-ray CT image is degraded.

  In order to eliminate the influence of scattered rays caused by X-ray tubes other than the paired X-ray tubes, the pulsed X-rays are alternated while shifting the X-ray irradiation timing for each X-ray tube. Reducing mutual effects by exposing to

  Conventionally, as one method for alternately exposing pulsed X-rays, a technique for turning on / off a current (tube current) flowing to an X-ray tube has been proposed (for example, see Patent Document 1). Yes. Another method is to turn on / off the X-rays exposed to direct current with a mechanical shutter (turn a X-ray on by rotating a disk with several holes in front of the X-ray tube. (Including those that turn off / off).

JP 2004-121146 A

  However, in the technique described in Patent Document 1, a rise time that is a time required to reach a current necessary for turning on / off the tube current and a fall time that is a time required to completely stop the current are described. is necessary. In particular, when the exposure dose increases, the tube current increases, the responsiveness of the generator and X-ray tube filament charge-up and disk charge deteriorates, and the number as described above required for the X-ray CT apparatus. It is difficult to irradiate pulsed X-rays at a high speed with a KHz X-ray.

  In addition, it is difficult to turn on / off a mechanical shutter at a speed of several kHz. Furthermore, in the technique of turning on / off X-rays by rotating a disk, two disks are rotated at the same rotation speed. Even if it is possible to rotate, it is difficult to synchronize the rotation with a fixed angle deviation when alternately firing like a two-tube system, and if the amount of X-rays to be irradiated is constant Therefore, it becomes difficult to generate an accurate X-ray CT image.

  The present invention has been made in view of such circumstances, and an X-ray tube apparatus capable of turning on / off X-rays irradiated to a subject at high speed, and scattering using the X-ray tube apparatus. An object of the present invention is to provide an X-ray CT apparatus in which noise caused by lines is reduced.

  To achieve the above object, an X-ray tube apparatus according to claim 1 is configured to switch an electron gun that emits an electron beam and an electron beam emitted from the electron gun in response to a control signal in at least two directions. A deflecting means to be transmitted; a first surface that emits X-rays toward a predetermined irradiation field when receiving the electron beam in one direction; and a predetermined surface when receiving the electron beam in another direction. And a target having a second surface that irradiates X-rays in a direction different from the irradiation field.

  An X-ray tube apparatus according to claim 2, wherein an electron gun that emits an electron beam and an electron beam emitted from the electron gun in response to a control signal are switched to at least two directions of a first direction and a second direction. A deflecting means to be transmitted; a first surface that emits X-rays toward a predetermined irradiation field when receiving the electron beam in one direction; and a predetermined surface when receiving the electron beam in another direction. A first surface that includes a second surface that irradiates X-rays in a direction different from the irradiation field, and is arranged so as to be able to irradiate different irradiation fields for the same subject. Irradiating the electron beam in the first direction with respect to one of the deflecting means in two deflecting means, ie, a radiation means, a second X-ray radiation means, and the first X-ray radiation means and the second X-ray radiation means When letting And control means for transmitting said control signal to irradiate the electron beam in the second direction relative to said deflecting means is characterized in further comprising a.

  The X-ray tube apparatus according to claim 3 switches an electron gun that emits an electron beam and an electron beam emitted from the electron gun in response to a control signal to at least two directions of a first direction and a second direction. A deflecting means to be transmitted; a first surface that emits X-rays toward a predetermined irradiation field when receiving the electron beam in one direction; and a predetermined surface when receiving the electron beam in another direction. Each of the targets having a second surface that irradiates X-rays in a direction different from the irradiation field, and arranged so as to be able to irradiate different irradiation fields for the same subject. 2 ≦ n) X-ray irradiating means and the deflecting means of the n X-ray irradiating means, with respect to the deflecting means of the k (1 ≦ k ≦ n) th X-ray irradiating means. When sending the electron beam in one direction, Control for causing the deflection means of the X-ray irradiation means to emit the electron beam in the second direction, and sequentially changing the k-th X-ray irradiation means from 1 to n. And a control means for transmitting the control signal.

  The X-ray CT apparatus according to claim 6 controls n X-ray irradiation units that irradiate X-rays toward different irradiation fields on the same subject, and X-ray irradiation from the X-ray irradiation units. Control means, an X-ray detector paired with the X-ray irradiation means for detecting X-rays transmitted through the subject, and reconstruction processing is performed on the data based on the detected X-rays to obtain image data. An image generating means for generating, the X-ray irradiating means for emitting an electron beam, and receiving the control signal to emit the electron beam emitted from the electron gun in at least a first direction and a second direction. Deflecting means for switching to two directions and transmitting, a first surface for irradiating X-rays toward a predetermined irradiation field when receiving the electron beam in one direction, and the electron beam in the other direction When pointing in a different direction from the predetermined field A target having a second surface for irradiating X-rays, wherein the control means is the k (1 ≦ k ≦ n) -th X in the deflection means of the n X-ray irradiation means. When the electron beam is sent in the first direction to the deflection means of the beam irradiation means, the electron beam is sent in the second direction to the deflection means of the other X-ray irradiation means. A control signal for controlling the k-th X-ray irradiating means to be sequentially changed from 1 to n.

  According to the X-ray tube apparatus of claim 1, by applying a voltage to the deflecting means and switching the path of the electron beam with respect to the electron beam emitted from the electron gun, the irradiation field can be irradiated with X-rays. ON / OFF can be switched electrically. Thereby, it is possible to perform high-speed X-ray pulse irradiation by turning on / off X-ray irradiation with quick response.

  According to the X-ray tube apparatus of the second and third aspects, the X-ray irradiation means for irradiating the X-ray toward the irradiation field can be quickly switched. Thereby, X-ray irradiation can be performed quickly and alternately from a plurality of X-ray irradiation means.

  According to the X-ray CT apparatus of the sixth aspect, X-ray irradiation is performed alternately from a plurality of X-rays by turning on / off the X-ray irradiation of the responsive and quick X-ray irradiation means. An X-ray CT image can be generated by detecting the irradiated X-rays. Thereby, it is possible to generate an X-ray CT image in which noise due to scattered radiation is reduced. Moreover, since an image can be generated in parallel by a plurality of X-ray irradiation means, it is possible to generate a high-speed image and simultaneously generate an image targeting different tissues.

[First Embodiment]
The X-ray CT apparatus according to the first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing functions of the X-ray CT apparatus according to the present embodiment. 2 and 3 are schematic views of the internal structure of the X-ray irradiation unit 100a and the X-ray irradiation unit 100b. Further, FIG. 2 is a diagram of a state when X-rays are directed toward the irradiation field, and FIG. 3 is a diagram of a state when X-rays are directed in a direction opposite to the irradiation field. Further, FIG. 4 is a schematic diagram showing the configuration of the X-ray detector 001a and the X-ray detector 001b.

  As shown in FIG. 1, the X-ray CT apparatus according to the present embodiment includes two X-ray irradiation units, an X-ray irradiation unit 100a and an X-ray irradiation unit 100b. Since these two X-ray irradiation units have the same configuration, hereinafter, when the X-ray irradiation units are not distinguished from each other, they are simply referred to as “X-ray irradiation unit 100”. This X-ray irradiation unit 100 corresponds to the “X-ray irradiation means” in the present invention. This X-ray irradiation means is generally called an “X-ray tube”. Furthermore, the X-ray CT apparatus according to the present embodiment includes two X-ray detectors, an X-ray detector 001a paired with the X-ray irradiation unit 100a and an X-ray detector 001b paired with the X-ray irradiation unit 100b. Have. Since these two X-ray detectors have the same configuration, hereinafter, when the X-ray detectors are not distinguished from each other, they are simply referred to as “X-ray detector 001”.

  As shown in FIG. 2, the X-ray irradiation unit 100 includes an electron gun 101, a deflection electrode 102, a drive unit 103, an irradiation window 104, and a target 110. The inner wall of the X-ray irradiation unit 100 is covered with copper. Thereby, the X-rays which hit the inner wall of the X-ray irradiation unit 100 are absorbed without being reflected.

  The electron gun 101 includes an inverter, a high voltage transformer, and a filament. The electron gun 101 applies high voltage generated by an inverter and a high-voltage transformer between the filament and the target 110, and generates X-rays by colliding electrons that have jumped out of the filament with the target 110. The electron beam generated and emitted from the electron gun 101 travels straight in the right direction in FIG. 2, that is, toward the first surface 111 of the target 110. At this time, X-rays irradiated from the electron gun 101 pass between the deflection electrodes 102.

  The deflection electrode 102 is composed of two metal plates, and is arranged so that the electron beam emitted from the electron gun 101 passes between the two metals. When a voltage is applied to the deflection electrode 102, one of the metal plates becomes an anode and the other becomes a cathode. In this embodiment, the upper side in FIG. 2 is an anode, and the lower side is a cathode. Hereinafter, a state in which a voltage is applied to the deflection electrode 102 is referred to as ON, and a state in which no voltage is applied to the deflection electrode 102 is referred to as OFF.

  That is, when the deflection electrode 102 is off, the electron beam emitted from the electron gun 101 travels straight in the direction of the first surface 111, and when the deflection electrode 102 is on, the electron emitted from the electron gun 101 The beam is refracted and travels in the direction of the second surface 112. In this way, the deflecting electrode 102 switches the electron beam emitted from the electron gun 101 by turning on / off in two directions and sends it out. This deflection electrode 102 corresponds to the “deflection means” in the present invention. Here, in this embodiment, the electron beam is deflected by applying an electric voltage to the electrode to generate an electric field, but this may be another method, for example, a coil is arranged beside the traveling direction of the electron beam, The electron beam may be changed by applying a magnetic field to the coil.

  This on / off is performed when the deflection electrode 102 receives a control signal from a control unit 002 (see FIG. 1) described later. The deflecting electrode 102 turned on refracts the electron beam passing between the electrodes toward the anode side, and changes the traveling direction of the electron beam. The electron beam whose path has been changed proceeds in the direction of the second surface 112. In the present embodiment, by changing the traveling direction of the electron beam from the electron gun 101, the position where the electron beam strikes the target 110 described later moves 3 mm in the vertical direction in FIG. Here, in the present embodiment, the time required for changing the traveling direction is shortened, and the moving distance on the target 110 is set to 3 mm in order to greatly change the direction of X-rays irradiated from the target 110 described later. The refraction angle of the electron beam is adjusted. However, the smaller the refraction angle, the better the on / off response, but the larger the angle, the easier it is to control the direction of the reflected electron beam. Therefore, this refraction angle is preferably determined in consideration of the on / off response speed and the ease of control of the direction of X-rays irradiated from the target 110. However, when the ON / OFF response speed is too slow, it becomes difficult to perform alternate exposure using pulsed X-ray irradiation by a plurality of X-ray irradiation units 100 described later, and therefore the moving distance on the target 110 is several. It is preferable that it is a millimeter.

  The target 110 is also called an “anode” and is made of copper, aluminum, or the like. The target 110 has a shape in which the upper bottom surface of the truncated cone shape is recessed as shown in FIG. This frustoconical shape corresponds to the “disc shape” in the present invention. Further, the concave portion of the upper bottom surface of the target 110 has a second surface 112 that is a smooth slope with the outer periphery of the upper bottom surface as the top. The outer surface of the truncated cone of the target 110 has a first surface 111 that is a smooth slope with the outer periphery of the upper bottom surface as the top. The first surface 111 corresponds to the “first surface” in the present invention. The second surface 112 corresponds to the “second surface” in the present invention.

  The target 110 is arranged so that the direction in which the electron beam is emitted from the electron gun 101 and the central axis A are parallel.

  Further, the target 110 is arranged so that the electron beam emitted from the electron gun 101 and traveling straight hits the first surface 111. In this embodiment, the first surface 111 corresponds to the lower part in FIG. 2 and is arranged so that X-rays generated on the first surface 111 are irradiated downward in FIG. 2 as shown in FIG. The X-rays generated on the first surface 111 travel toward the irradiation window 104, pass through the irradiation window 104, and are irradiated toward the irradiation field on the subject.

  Further, the target 110 is arranged so that the electron beam emitted from the electron gun 101 and refracted by the deflection electrode 102 hits the second surface 112. That is, in this embodiment, the distance from the position where the electron beam hits the first surface 111 to the position where the electron beam hits the second surface 112 is 3 mm. As shown in FIG. 3, the X-rays irradiated from the second surface 112 travel in a direction substantially opposite to the direction in which the X-rays irradiated from the first surface 111 travel. In addition, the X-rays irradiated from the second surface 112 do not hit a structure in the X-ray irradiation unit 100 (for example, the electron gun 101 or the target 110) and reach the inner wall of the X-ray irradiation unit 100. The angle of the second surface 112 is adjusted to advance.

  Further, the target 110 rotates around the central axis A. This rotation causes the target 110 to melt due to high heat if it continues to be irradiated with an electron beam in one place. Therefore, the position of the target 110 irradiated with the electron beam is changed by rotation, so that the target 110 is melted. It is for prevention.

  The drive unit 103 rotates the target 110 around the central axis A. The driving unit 103 corresponds to “driving means” in the present invention.

  As described above, the first surface 111 receives the advanced electron beam and emits X-rays in the direction of the irradiation window 104, and the second surface 112 receives the advanced electron beam and is substantially opposite to the irradiation window 104. The direction is adjusted so as to irradiate X-rays in a direction that directly hits the inner wall of the X-ray irradiation unit 100. Thereby, when the deflection electrode 102 is off, the electron beam emitted from the electron gun 101 hits the first surface 111 to generate X-rays, and the generated X-rays pass through the irradiation window 104 and are irradiated. Irradiate the field. When the deflection electrode 102 is on, X-rays are generated when the electron beam irradiated from the electron gun 101 hits the second surface 112, and the generated X-rays strike the inner wall of the X-ray irradiation unit 100 and are absorbed. Is done. Therefore, X-rays going outward from the irradiation window 104 can be substantially blocked except when the deflection electrode 102 is on.

  As shown in FIG. 4, the X-ray detector 001 includes a scintillator 401, a photodiode 402, a capacitor 403, a ground switch 404, an amplifier switch 405, and an amplifier 406.

  The scintillator 401 absorbs X-rays that have passed through the subject and generates fluorescence. The photodiode 402 receives the tendency generated in the scintillator 401 and converts it into electrons.

  The X-ray detector 001 receives a control signal from the control unit 002 and turns on / off the ground switch 404 and the amplifier switch 405.

  When the ground switch 404 and the amplifier switch 405 are off, the capacitor 403 stores the electrons generated by the scintillator 401. When the ground switch 404 is on and the amplifier switch 405 is off, the electricity stored in the capacitor 403 is passed to the ground. When the ground switch 404 is off and the amplifier switch 405 is on, the electricity stored in the capacitor 403 is amplified by the amplifier 406 and output to the image generation unit 003. The ground switch 404 and the amplifier switch 405 are turned on / off by the control unit 002, and details of the on / off timing will be collectively described later.

  The control unit 002 emits the electron beam from the electron gun 101 and turns on / off the deflection electrode 102 in the X-ray irradiation unit 100a and the X-ray irradiation unit 100b, and controls the X-ray detector 001a and the X-ray detector 001b. Controls X-ray detection. The control unit 002 corresponds to the “control unit” in the present invention. Hereinafter, each control will be described in detail with reference to FIG. Here, FIG. 5 is a timing chart showing the relationship between the timing pulse in the control unit 002, ON / OFF of the deflection electrode 102, and ON / OFF of X-ray irradiation from each X-ray irradiation unit 100. In this timing chart, the horizontal axis represents time and the vertical axis represents voltage or X-ray irradiation level. 5A is a graph of timing signals in the control unit 002, FIG. 5B is a graph showing the voltage of the deflection electrode 102 of the X-ray irradiation unit 100a, and FIG. 5C is a graph of the X-ray irradiation unit 100a. FIG. 5 (D) is a graph showing the voltage of the deflection electrode 102 of the X-ray irradiation unit 100b, and FIG. 5 (E) is an irradiation field of the X-ray irradiation unit 100b. It is the graph showing the X-ray irradiation amount to.

  The control unit 002 receives an X-ray irradiation start command input from the operator and starts emitting an electron beam from the electron gun 101.

  Further, the control unit 002 generates a timing pulse 500 shown in FIG. The control unit 002 transmits a control signal for turning off the deflection electrode 102 of the X-ray irradiation unit 100a to the X-ray irradiation unit 100a when the timing pulse 500 rises 7n + 1 times. Further, the control unit 002 transmits a control signal for turning on the deflection electrode 102 of the X-ray irradiation unit 100a to the X-ray irradiation unit 100a when the timing pulse 500 rises 7n + 5 times. The control unit 002 transmits a control signal for turning on the deflection electrode 102 of the X-ray irradiation unit 100b to the X-ray irradiation unit 100b when the timing pulse 500 falls by 7n + 1. Further, the control unit 002 transmits a control signal for turning on the deflection electrode 102 of the X-ray irradiation unit 100b to the X-ray irradiation unit 100b when the timing pulse 500 falls 7n + 4 times.

  The deflection electrode 102 that has received the ON control signal from the control unit 002 applies a voltage between the electrodes. As a result, the electron beam emitted from the electron gun 101 is refracted to generate X-rays on the second surface 112, and the generated X-rays hit the inner wall of the X-ray irradiation unit 100, that is, other than the irradiation field. Hereinafter, this state is referred to as an “X-ray off” state. A section 512 in the waveform 510 and a section 531 in the waveform 530 are sections in a state where the deflection electrode 102 is turned on. When the deflection electrode 102 is turned on, the starting points at which the X-ray is turned off are a point 523 on the waveform 520 and a point 541 on the waveform 540. At this time, since the path of the electron beam emitted from the electron gun 101 gradually changes, the falling graphs of the waveform 520 and the waveform 540 are inclined.

Further, the deflection electrode 102 that has received the OFF control signal from the control unit 002 stops the voltage applied between the electrodes. As a result, the electron beam emitted from the electron gun 101 travels straight and generates X-rays on the first surface 111, and the generated X-rays pass through the irradiation window 104 and are irradiated onto the irradiation field. Hereinafter, this state is referred to as an “X-ray on” state. A section 511 in the waveform 510 and a section 532 in the waveform 530 are sections in a state where the deflection electrode 102 is turned off. Then, when the deflection electrode 102 is turned off, the starting point at which the X-ray is turned on is a point 521 on the waveform 520 at time t ₀ and a point 542 on the waveform 540 at time t ₂ . At this time, since the path of the electron beam emitted from the electron gun 101 gradually changes, the rising graphs of the waveform 520 and the waveform 540 are inclined. Then, at the point 522 on the waveform 520 at the time t ₁ and the point 543 on the waveform 540 at the time t ₃ , the switching of the path of the electron beam emitted from the electron gun 101 is completed, and the X-ray is irradiated with a predetermined irradiation It will be in the state of being irradiated accurately toward the field.

By controlling as described above, the deflection electrode 102 of the X-ray irradiation unit 100a is turned off, and the traveling direction of the electron beam emitted from the electron gun 101 in the X-ray irradiation unit 100a is changed from the second surface 112 to the first. The movement toward the surface 111 starts at time t ₀ (point 521), and the movement ends and the X-ray irradiated from the X-ray irradiation unit 100a is accurately irradiated onto the irradiation field (point 522) and the timing (point 541) at which the deflection electrode 102 of the X-ray irradiation unit 100b is turned on and the X-rays irradiated from the X-ray irradiation unit 100a start to deviate accurately from the position where the irradiation field is irradiated. , At time t ₁ . Similarly, when the X-ray irradiated from the X-ray irradiation unit 100b is accurately irradiated to the irradiation field (point 543), the deflection electrode 102 of the X-ray irradiation unit 100a is turned on, and the X-ray is irradiated. timing X-rays irradiated from the irradiation portion 100a starts to shift from the position to be irradiated accurately irradiation field (point 523), but matched at time t _3. This makes it possible to continuously irradiate the subject with X-rays. Further, simultaneous irradiation from both X-ray irradiation units 100 can be prevented, and high-speed pulsed X-rays can be alternately irradiated from each X-ray irradiation unit 100 at an extremely short period.

  The on / off timing of the deflection electrode 102 of the X-ray irradiation unit 100a and the X-ray irradiation unit 100b by the control unit 002 is the same as the time when each deflection electrode 102 is off, As long as the switching of the traveling direction of the electron beam by the other deflection electrode 102 is completed at the timing when one of the deflection electrodes 102 is turned on, the timing other than the present embodiment may be used.

  Also, the control unit 002 sends the X-ray detector 001 to the ground switch 404 and the amplifier switch 405 at the timing when the X-rays from each X-ray irradiation unit 100 are accurately irradiated to the irradiation field. Send off control signal. Thereby, charging of the capacitor 403 is started.

  Further, the control unit 002 transmits a control signal for turning on the amplifier switch 405 to the X-ray detector 001 at a timing when the X-rays from the respective X-ray irradiation units 100 are shifted from the irradiation field. Thereby, the electricity stored in the capacitor 403 is read. This reading ends instantaneously in units of several tenths of a second. For this reason, the influence of noise during this reading is negligible and can be ignored.

  The control unit 002 transmits an off control signal for the amplifier switch 405 and an off control signal for the ground switch 404 to the X-ray detector 001 at the timing when the reading from the capacitor 403 is completed. As a result, the electricity stored in the capacitor 403 from this time to the timing when the X-ray is irradiated from the next X-ray irradiating unit 100 to the irradiation field accurately is passed to the ground, that is, during this time X-ray data detected in (1) is discarded.

The flow of control of the X-ray detector 001 by the control unit 002 will be described along the movement. At time t ₁ (point 522), charging of the capacitor 403 of the X-ray detector 001a is started. Then, charging of the capacitor 403 of the X-ray detector 001a is completed at the timing of time t ₃ (point 523). In other words, the capacitor 403 of the X-ray detector 001a is charged during the interval 524 in the waveform 520. At the same time as the start of charging of the capacitor 403 of the X-ray detector 001a, the readout from the capacitor 403 of the X-ray detector 001b is started at the time t ₁ (point 541). The received X-ray data is discarded. Then, at the timing of time t ₂ (point 542), charging of the capacitor 403 of the X-ray detector 001b is started. Then, the capacitor 403 of the X-ray detector 001b is charged during a section 544 in the waveform 540.

  As described above, the X-ray data from the X-ray irradiation unit 100a and the X-rays from the X-ray irradiation unit 100b are controlled by controlling the operation of the X-ray irradiation unit 100 and the operation of the X-ray detector 001 in synchronization. This data can be obtained alternately with a very short period while removing noise. Therefore, X-ray data irradiated from two different X-ray irradiation units 100 toward different irradiation fields of the subject can be simultaneously acquired, and an image can be generated based on the X-ray data.

  The image generation unit 003 performs sensitivity correction, X-ray intensity correction, and the like on the data input from the X-ray detector 001a and the X-ray detector 001b. Then, the image generation unit 003 reconstructs the data that has been subjected to the above-described processing, and generates image data. Furthermore, the image generation unit 003 performs various image processing on the image data in accordance with an operator instruction input by an input device (not shown). For example, the image generation unit 003 performs volume rendering processing, MPR processing, or the like to generate three-dimensional image data or MPR image data (arbitrary slice image data) and outputs the generated data to the display control unit 004.

  The display control unit 004 displays an image based on the image data input from the image generation unit 003 on a display unit 005 such as a liquid crystal display or a CRT.

  Next, the flow of X-ray irradiation and detection in the X-ray CT apparatus according to the present embodiment will be described with reference to FIG. Here, FIG. 6 is a flowchart showing the flow of X-ray irradiation and detection in the X-ray CT apparatus according to the present embodiment.

  Step S001: The control unit 002 starts emission of electron beams from the electron guns 101 of both the X-ray irradiation unit 100a and the X-ray irradiation unit 100b.

  Step S002: The control unit 002 determines whether the timing pulse generated by itself is rising at 7n + 1 (n = 0, 1, 2,...). If the rising edge is 7n + 1, the process proceeds to step S003. If the rising edge is not 7n + 1, the process proceeds to step S004.

  Step S003: The X-ray irradiation unit 100a receives the control signal from the control unit 002 and turns off the deflection electrode 102. As a result, the X-ray irradiation unit 100a is turned on.

  Step S004: The control unit 002 determines whether the timing pulse generated by itself is falling at 7n + 1 (n = 0, 1, 2,...). If it is 7n + 1, the process proceeds to step S005. If it is not 7n + 1, the process proceeds to step S008.

  Step S005: The X-ray irradiation unit 100b receives the control signal from the control unit 002 and turns on the deflection electrode 102. As a result, the X-ray irradiation unit 100b is in an X-ray off state.

  Step S006: In response to the control signal from the control unit 002, the X-ray detector 001a turns off the ground switch 404 and the amplifier switch 405. As a result, electricity is charged in the capacitor 403 of the X-ray detector 001a.

  Step S007: The X-ray detector 001b turns off the ground switch 404 and turns off the amplifier switch 405. Thereby, reading is performed from the capacitor 403 of the X-ray detector 001b.

  Step S008: The control unit 002 determines whether the timing pulse generated by itself is falling at 7n + 4 (n = 0, 1, 2,...). If it is 7n + 4, the process proceeds to step S009. If it is not 7n + 4, the process proceeds to step S010.

  Step S009: The X-ray irradiation unit 100b receives the control signal from the control unit 002 and turns off the deflection electrode 102. As a result, the X-ray irradiation unit 100b is in the X-ray on state.

  Step S010: The control unit 002 determines whether the timing pulse generated by itself is rising at 7n + 5 (n = 0, 1, 2,...). If the rising edge is 7n + 5, the process proceeds to step S011. If the rising edge is not 7n + 5, the process proceeds to step S014.

  Step S011: The X-ray irradiation unit 100a receives the control signal from the control unit 002 and turns on the deflection electrode 102. As a result, the X-ray irradiation unit 100a is in the X-ray off state.

  Step S012: The X-ray detector 001b receives the control signal from the control unit 002, and turns off the ground switch 404 and the amplifier switch 405. As a result, electricity is charged in the capacitor 403 of the X-ray detector 001b.

  Step S013: The X-ray detector 001a turns off the grounding switch 404 and turns off the amplifier switch 405. Thereby, reading is performed from the capacitor 403 of the X-ray detector 001a.

  Step S014: The control unit 002 confirms whether the reading from the capacitor of the X-ray detector 001a is completed. If completed, the process proceeds to step S015. If not completed, the process proceeds to step S016.

  Step S015: In response to the control signal from the control unit 002, the X-ray detector 001a turns on the ground switch 404 and turns off the amplifier switch 405. As a result, the X-ray data detected by the X-ray detector 001a is discarded.

  Step S016: The control unit 002 confirms whether the reading from the capacitor of the X-ray detector 001b is completed. If completed, the process proceeds to step S015. If not completed, the process proceeds to step S016.

  Step S017: In response to the control signal from the control unit 002, the X-ray detector 001b turns on the ground switch 404 and turns off the amplifier switch 405. As a result, the X-ray data detected by the X-ray detector 001b is discarded.

  Step S018: The control unit 002 determines whether or not the X-ray irradiation ends. If the X-ray irradiation has ended, the process proceeds to step S019. If it is not the end of X-ray irradiation, the process proceeds to step S002.

  Step S018: The control unit 002 stops the emission of electron beams from the electron guns 101 of both the X-ray irradiation unit 100a and the X-ray irradiation unit 100b.

  Moreover, the apparatus which has the control part which controls two X-ray irradiation parts demonstrated above and the X-ray irradiation from the two X-ray irradiation parts corresponds to the X-ray tube apparatus in this invention.

  As described above, in the X-ray CT apparatus according to the present embodiment, pulsed X-rays are alternately irradiated from two X-ray irradiation units toward different irradiation fields in a very short period, and the X-ray CT apparatus The X-rays can be detected separately without being affected by the scattered X-rays of the other X-rays in synchronization with the irradiation of the rays. As a result, X-ray data in two different irradiation fields that are less affected by scattered radiation can be acquired simultaneously, and two different images with less noise can be generated almost simultaneously based on the acquired X-ray data. Become. Therefore, the X-ray CT apparatus according to the present embodiment can generate an X-ray CT image with less noise for different tissues at the same time, and shortens the time for generating one X-ray CT image. The image in that case can also be generated as an image with reduced noise.

  In the present embodiment, the X-ray CT apparatus having two X-ray irradiation units has been described. However, two or more X-ray irradiation units may be provided. In that case, the X-ray irradiation unit irradiated with the X-ray is sequentially changed so that the other X-ray irradiation units do not emit the X-ray to the outside, and the X-ray is irradiated onto the irradiation field. The X-ray detection is performed only by the X-ray detector corresponding to the X-ray irradiation unit.

[Second Embodiment]
The X-ray CT apparatus according to the second embodiment of the present invention will be described below. The X-ray CT apparatus according to the present embodiment is the X-ray CT apparatus according to the first embodiment. The X-ray reflected by the first reflection surface between the first reflection surface and the irradiation window in the X-ray irradiation unit. A shielding member is provided so that scattered rays other than the rays do not enter the irradiation window. Therefore, the shielding member will be mainly described below. The functional configuration of the X-ray CT apparatus according to the present embodiment is also represented by the block diagram of FIG. 1 as in the first embodiment.

  7 and 8 are schematic views of the internal structure of the X-ray irradiation unit 100 in the X-ray CT apparatus according to the present embodiment. Further, FIG. 7 is a diagram of a state when X-rays are directed toward the irradiation field, and FIG. 8 is a diagram of a state when X-rays are directed in a direction opposite to the irradiation field.

  As shown in FIGS. 7 and 8, the X-ray CT apparatus according to the present embodiment has X-rays generated from the electron beam 101 emitted from the electron gun 101 on the first surface 111 inside the X-ray irradiation unit 100. A shielding member 105 is arranged so as to cover the course toward the irradiation window 104. The shielding member 105 is made of a metal that does not transmit X-rays such as lead.

  When the deflection electrode 102 is off, the electron beam emitted from the electron gun 101 hits the first surface 111 and X-rays are generated. As shown in FIG. 7, the X-rays irradiated from the first surface 111 travel along the path covered by the shielding member 105, pass through the irradiation window 104, and are irradiated onto the irradiation field. Thus, the X-rays irradiated from the first surface 111 are advanced to the irradiation window 104 without being blocked by the irradiation field.

  When the deflection electrode 102 is on, the electron beam emitted from the electron gun 101 hits the second surface 112 to generate X-rays. As shown in FIG. 8, the X-rays irradiated from the second surface 112 go to the inner wall of the X-ray irradiation unit 100. Since the inner wall of the X-ray irradiation unit 100 is formed of a material that absorbs X-rays such as copper, most of the X-rays hitting the inner wall are absorbed by the inner wall of the X-ray irradiation unit 100. However, a small amount of X-rays that hit the inner wall of the X-ray irradiation unit 100 is repeatedly reflected inside the X-ray irradiation unit 100 as scattered rays. Then, the scattered radiation may travel toward the irradiation window 104 as indicated by an arrow 800 shown in FIG. In such a case, in the X-ray CT apparatus according to the present embodiment, the scattered radiation is blocked by the shielding member 105 and does not enter the shielding member 105. Therefore, it can be reduced that the scattered radiation passes through the irradiation window 104 and leaks to the outside of the X-ray irradiation unit 100.

  As described above, in the X-ray CT apparatus according to the present embodiment, when the deflection electrode 102 is off, the electron beam emitted from the electron gun 101 hits the first surface 111 to generate X-rays. The generated X-ray passes through the irradiation window 104 and is irradiated to the irradiation field. When the deflection electrode 102 is off, X-rays are generated by the electron beam emitted from the electron gun 101 hitting the second surface 112, and the generated X-rays are generated on the inner wall of the X-ray irradiation unit 100. A part of the light is reflected and becomes scattered radiation, but the scattered radiation is reflected by the shielding member 105 so as not to leak outside the X-ray irradiation unit 100. As a result, only the X-rays emitted from the X-ray irradiation unit 100 that is turned on can be detected by the paired X-ray detector 001, and an image with further reduced noise can be generated. It becomes.

Block diagram of X-ray CT apparatus according to the present invention Schematic of the internal structure of the X-ray irradiation unit in a state when the X-rays according to the first embodiment are directed to the irradiation field Schematic of the internal structure of the X-ray irradiation unit in a state when the X-ray according to the first embodiment is directed in the direction opposite to the irradiation field Schematic showing the configuration of the X-ray detector FIG. 5 is a timing chart showing the relationship between timing pulses in the control unit, deflection electrode on / off, and X-ray irradiation on / off from each X-ray irradiation unit, (A) a timing signal graph in the control unit 002, (B) A graph showing the voltage of the deflection electrode 102 of the X-ray irradiation unit 100a, (C) a graph showing the X-ray irradiation amount to the irradiation field of the X-ray irradiation unit 100a, and (D) the X-ray irradiation unit 100b. A graph showing the voltage of the deflection electrode 102, and (E) a graph showing the X-ray irradiation amount to the irradiation field of the X-ray irradiation unit 100b The figure of the flowchart showing the flow of X-ray irradiation and detection in the X-ray CT apparatus which concerns on 1st Embodiment. Schematic of the internal structure of the X-ray irradiation unit in a state when X-rays according to the second embodiment are directed to the irradiation field Schematic of the internal structure of the X-ray irradiation unit in a state when X-rays according to the second embodiment are directed in the direction opposite to the irradiation field

Explanation of symbols

001a, 001b X-ray detector 002 Control unit 003 Image generation unit 004 Display control unit 005 Display unit 100a, 100b X-ray irradiation unit 101 Electron gun 102 Deflection electrode 103 Drive unit 104 Irradiation window 110 Target (anode)
111 First surface 112 Second surface

Claims (7)

An electron gun that emits an electron beam;
Deflecting means for receiving a control signal and switching and sending out an electron beam emitted from the electron gun in at least two directions;
When receiving the electron beam in one direction, the first surface irradiates X-rays toward a predetermined irradiation field, and when receiving the electron beam in the other direction, in a direction different from the predetermined irradiation field. A second surface that emits X-rays toward the target, and
An X-ray tube apparatus comprising: An electron gun that emits an electron beam; a deflection unit that receives a control signal to switch the electron beam emitted from the electron gun to at least two directions of a first direction and a second direction; and the electron beam in one direction The first surface for irradiating X-rays toward a predetermined irradiation field when received, and irradiating X-rays toward a direction different from the predetermined irradiation field when receiving the electron beam in another direction First X-ray irradiation means and second X-ray irradiation means each provided with a target having a second surface and arranged so as to be able to irradiate different irradiation fields for the same subject.
In the two deflection means of the first X-ray irradiation means and the second X-ray irradiation means, when one of the deflection means is irradiated with the electron beam in the first direction, the other deflection means Control means for transmitting the control signal for irradiating the electron beam in the second direction to the second direction;
An X-ray tube apparatus comprising: An electron gun that emits an electron beam; a deflection unit that receives a control signal to switch the electron beam emitted from the electron gun to at least two directions of a first direction and a second direction; and the electron beam in one direction The first surface for irradiating X-rays toward a predetermined irradiation field when received, and irradiating X-rays toward a direction different from the predetermined irradiation field when receiving the electron beam in another direction N (2 ≦ n) X-ray irradiation means each provided with a target having a second surface and arranged so as to be able to irradiate different irradiation fields for the same subject,
In the deflection means of the n X-ray irradiation means, when the electron beam is sent in the first direction to the deflection means of the k (1 ≦ k ≦ n) th X-ray irradiation means. In this control, the deflecting means of the other X-ray irradiating means emits the electron beam in the second direction, and the kth X-ray irradiating means is sequentially changed from 1 to n. Control means for transmitting the control signal to be controlled;
An X-ray tube apparatus comprising: A driving means for rotating the target;
The target is
It is arranged at a position opposite to the X-ray generating means, is a disc shape rotating around a central axis, and is directed to the X-ray tube side with the upper bottom surface facing away from the central axis with the outer periphery of the upper bottom surface as the top. The upper bottom surface portion is recessed with a second surface that is a smooth inclined surface from the top toward the central axis.
The X-ray tube apparatus according to claim 1.   A shield arranged along a path toward the irradiation field of the X-rays irradiated from the first surface, and suppressing shielding of the scattered rays of the X-rays irradiated from the second surface into the irradiation field. The X-ray tube apparatus according to claim 1, further comprising a member. N X-ray irradiation means for irradiating X-rays toward different irradiation fields on the same subject;
Control means for controlling irradiation of X-rays from the X-ray irradiation means;
An X-ray detector paired with the X-ray irradiation means for detecting X-rays transmitted through the subject;
Image generation means for generating image data by performing reconstruction processing on the data based on the detected X-ray,
The X-ray irradiation means includes
An electron gun that emits an electron beam; a deflection unit that receives a control signal to switch the electron beam emitted from the electron gun to at least two directions of the first direction and the second direction; and the electron in one direction When receiving a beam, the first surface emits X-rays toward a predetermined irradiation field. When receiving the electron beam in another direction, X-rays are directed toward a different direction from the predetermined irradiation field. A target having a second surface to be irradiated, and
The control means includes
In the deflection means of the n X-ray irradiation means, when the electron beam is sent in the first direction to the deflection means of the kth (1 ≦ k ≦ n) th X-ray irradiation means. In this control, the deflecting means of the other X-ray irradiating means emits the electron beam in the second direction, and the kth X-ray irradiating means is sequentially changed from 1 to n. Transmitting the control signal to be controlled,
An X-ray CT apparatus characterized by that.   The control unit controls the pair of X-ray detectors to detect X-rays only while the X-ray irradiation unit irradiates the irradiation field with X-rays. 6. The X-ray CT apparatus according to 6.

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