JP6377370B2 - X-ray tube apparatus and X-ray CT apparatus - Google Patents

Description

  Embodiments described herein relate generally to an X-ray tube apparatus and an X-ray CT apparatus.

  In the dual energy technology of an X-ray image generation apparatus, for example, an X-ray CT apparatus (X-ray computed tomography apparatus), an X-ray tube apparatus capable of irradiating / irradiating two types of energy X-rays in a pulsed manner is used. . The following techniques have been proposed as means for irradiating / irradiating pulsed X-rays at high speed.

(1) The current of the X-ray tube apparatus is directly turned on / off.
(2) X-rays radiated in a direct current are turned on / off in a pulsed manner by a mechanical shutter.
(3) The electron beam in the X-ray tube apparatus is subjected to high-speed deflection switching, so that the X-ray output is changed to pulses.

The following techniques have been proposed and realized as means for simultaneously irradiating two types of energy X-rays.
(4) Two X-ray tube devices / Generator are mounted on an X-ray CT scanner and irradiated with different energy.
(5) With one X-ray tube apparatus / Generator, the generated X-ray energy is switched between high and low for irradiation.

  In order to scan with two energy X-rays in the same trajectory and simultaneous acquisition, the method of switching energy with one tube lacks high-speed response time. That is, the same orbit and simultaneous collection performance by two X-ray energies cannot be maintained. Slow switching means that the angular resolution at the time of collection is also poor. In addition, when switching the tube voltage with one tube, it is difficult to switch in a rectangular wave. Actually, X-rays are irradiated with halfway energy during switching, resulting in poor energy resolution.

JP 2013-31645 A

  The purpose is to switch two energy X-rays in a pulsed manner at high speed (several kHz).

The X-ray tube apparatus according to the present embodiment includes a first electron generation unit that generates a first electron beam, a second electron generation unit that generates a second electron beam having energy different from that of the first electron beam, A target that generates first or second X-rays by irradiation of the first or second electron beam, and an electric or magnetic field arranged in a column between the first and second electron generation units and the target. First and second electron beam deflecting units for deflecting the first and second electron beams, the first electron generating unit, the second electron generating unit, the target, the first electron beam deflecting unit, and the second An X-ray tube apparatus that encloses an electron beam deflection unit, and an X-ray irradiation window formed in the X-ray tube apparatus for outputting the first or second X-ray from the X-ray tube apparatus The first electron beam deflecting unit is configured to provide the first or second electron beam deflecting unit. Is provided for selecting a second electron beam, and the second electron beam deflecting unit is provided for irradiating the selected first or second electron beam on a specific position on the target at a specific angle. The first X-ray beam is output through the X-ray irradiation window when both the first and second electron beam deflecting units are in the OFF state, and when both the first and second electron beam deflecting units are in the ON state. Second X-rays are output through the X-ray irradiation window.

It is a figure which shows the principal part structure of the rotation part of the scanner main body of the X-ray computed tomography apparatus which concerns on this embodiment. It is a figure which shows the controller for switching of the high / low energy X-ray which concerns on this embodiment. It is a figure which shows the track | orbit of the electron beam at the time of the arrangement | positioning of the filament in the X-ray tube apparatus concerning this embodiment, a deflection | deviation part, a target, and deflection | deviation off. It is a figure which shows the track | orbit of the electron beam at the time of the arrangement | positioning of the filament in the X-ray tube apparatus concerning this embodiment, a deflection | deviation part, a target, and a deflection | deviation ON. In this embodiment, it is a figure which compares the profile of a high / low energy X-ray with the profile of the high energy X-ray by the electron beam which does not carry out an orbit correction | amendment. It is a figure which shows the control for switching of the high / low energy X-ray by the controller of FIG.

  Embodiments of an X-ray tube apparatus and an X-ray CT apparatus (X-ray computed tomography apparatus) according to the present invention will be described below with reference to the drawings. An apparatus including an X-ray tube apparatus includes an X-ray diagnostic apparatus, an X-ray computed tomography apparatus, and other apparatuses for generating medical X-ray images. Here, an X-ray computed tomography apparatus will be described as an example.

  FIG. 1 is a diagram showing a main part configuration of a rotating part of a scanner main body of the X-ray computed tomography apparatus according to the present embodiment. The X-ray computed tomography apparatus has an X-ray tube apparatus 1. X-rays are emitted from the irradiation window 17 of the X-ray tube apparatus 1 in the form of a cone beam having a spread in the direction of the body axis of the subject (the rotation axis of the rotating frame 5). The X-ray tube apparatus 1 is mounted on a rotating frame 5 together with a multi-slice type or two-dimensional array type DAS / X-ray detector 4 corresponding to cone beam X-rays. The DAS / X-ray detector 4 faces the X-ray tube apparatus 1. When scanning, the subject is placed between the X-ray tube apparatus 1 and the DAS / X-ray detector 4. A generator 2 and a controller 3 are mounted on the rotating frame 5. The generator 2 is supplied to the deflection unit under the control of the controller 3, the tube voltage applied between both electrodes of the X-ray tube apparatus 1, the filament current supplied to the cathode filament of the X-ray tube apparatus 1. Generating a deflection voltage. The controller 3 controls the generator 2 according to the control of the scan controller for controlling the entire scanning operation (not shown) to generate X-rays, and the detection by the DAS / X-ray detector 4 in synchronization with the generation of X-rays. Processing and analog / digital conversion processing are executed. The output of the DAS / X-ray detector 4 is subjected to correction such as non-channel sensitivity non-uniformity in the preprocessing unit, and is supplied as projection data to the reconstruction processor. The reconstruction processor reconstructs tomographic image data or volume data based on the projection data. The tomographic image is displayed on the display.

  3 and 4 show the configuration of the main part inside the tube of the X-ray tube apparatus 1 of FIG. The X-ray tube apparatus 1 includes a rotating anode (anode target, hereinafter simply referred to as a target) 11 having an umbrella shape inside the tube, and a plurality of, in this case, two types of cathode filaments (electron generation) opposed to the target 11. Part) 15,16. The two types of cathode filaments 15 and 16 are juxtaposed along the radial direction of the target 11. The generator 2 generates a first potential difference (first tube voltage) between the cathode filament 15 and the target 11. The generator 2 generates a second potential difference (second tube voltage) between the cathode filament 16 and the target 11. The generator 2 sets the first potential difference to a lower value than the second potential difference. The cathode filament 15 is hereinafter referred to as a low filament. The cathode filament 16 is hereinafter referred to as a high filament. X-rays generated by irradiating the target 11 with the low energy electron beam (L) generated by the low filament 15 irradiate the target 11 with the high energy electron beam (H) generated by the high filament 16. The energy is lower than the X-rays generated by doing so.

  An electron beam deflecting unit 12 is disposed between the filaments 15 and 16 and the target 11. The electron beam deflecting unit 12 deflects the electron beam by an electric field or a magnetic field. Here, a description will be given by taking an example of deflection by an electric field by a counter electrode, but deflection by a magnetic field by a counter coil may be adopted. The electron beam deflecting unit 12 has a plurality of, here two, deflection electrodes 13 and 14. Each of the deflection electrodes 13 and 14 is made up of a pair of electrodes arranged opposite to each other with the electron beam trajectory in between. The deflection electrodes 13 and 14 are arranged in a column along the trajectory of the electron beam between the filaments 15 and 16 and the target 11. The deflection electrode 13 on the side of the filament 15 functions as a source for selecting one of the filaments 15 and 16 that generate an electron beam that becomes an X-ray source emitted outside through the irradiation window 17. By turning on / off the deflection electrode 13, X-rays generated by irradiating the target 11 with an electron beam derived from one of the filaments 15 and 16 are directly irradiated to the subject via the irradiation window 17. X-rays generated by irradiating the target 11 with the electron beam derived from the other of the filaments 15 and 16 are not directly emitted to the outside through the irradiation window 17.

  The trajectory correcting deflection electrode 14 is disposed between the source selecting deflection electrode 13 and the target 11. When the source selection deflection electrode 13 and the trajectory correction deflection electrode 14 are both off (see FIG. 3), the electron beam generated by the low filament 15 flies linearly and is specified at a specific position on the surface of the target 11. Irradiate at an angle. The angle here is defined as the angle of incidence of the electron beam on the target 11 with respect to a plane perpendicular to the rotation axis of the target 11. The center of the path where the electron beam generated by the low filament 15 linearly flies from the low filament 15 at a specific angle to a specific position of the target 11 with both the source selection deflection electrode 13 and the trajectory correction deflection electrode 14 turned off. The line is here referred to as the trajectory center axis. Low energy X-rays (L) generated at the specific position are emitted from the tube through the irradiation window 17. The electron beam generated by the high filament 16 irradiates the target 11 at other angles other than the specific position. High-energy X-rays (H) generated at the position are generated in directions other than the irradiation window 17.

  When both the source selection deflection electrode 13 and the trajectory correction deflection electrode 14 are on (see FIG. 4), the electron beam generated by the high filament 16 is deflected by the source selection deflection electrode 13 in a direction crossing the trajectory center axis. The The deflected electron beam is changed by the trajectory correcting deflection electrode 14 in the direction opposite to that by the source selecting deflection electrode 13. The voltage applied to the trajectory correction deflection electrode 14 is generated by the high filament 16, and the electron beam deflected in the direction intersecting the trajectory center axis by the source selection deflection electrode 13 is reversed by the trajectory correction deflection electrode 14. It is deflected in the direction and adjusted to fly toward the target 11 along the trajectory center axis. The electron beam (H) from the high filament 16 deflected by the source selection deflection electrode 13 and the trajectory correction deflection electrode 14 is the same as the electron beam (L) from the low filament 15 when the deflection unit 12 is off. The target 11 is irradiated at a specific angle at a specific position on the target 11.

  High energy X-rays (H) generated at the specific position are emitted from the tube through the irradiation window 17. The electron beam (L) generated by the low filament 15 irradiates the target 11 at other angles other than the specific position. Low energy X-rays (L) generated at the position are generated in directions other than the irradiation window 17.

  Thus, both the electron beam (L) generated by the low filament 15 and the electron beam (H) generated by the high filament 16 are irradiated to the same position on the surface of the target 11 at the same angle. Thereby, the X-ray profile of the low energy X-ray (L) and the X-ray profile of the high energy X-ray (H) are as shown in FIG. The X-ray profile refers to an intensity distribution with respect to a change in angle with respect to the central axis of the X-ray flux emitted from the irradiation window.

  When the trajectory correction of the electron beam is not performed, the angle and position at which the electron beam (H) irradiates the target 11 are different from the angle and position at which the electron beam (L) irradiates the target 11. Therefore, when the electron beam trajectory is not corrected, the X-ray profile of the high energy X-ray (H) is deformed as shown by the broken line in FIG. 5 with respect to the X-ray profile of the low energy X-ray (L).

  As is well known, the dual energy technology makes it possible to separate bones and soft tissues from the data obtained by irradiating X-rays with different tube voltages using the fact that the attenuation coefficient of a substance varies depending on the X-ray energy. Technology. Therefore, deformation of the X-ray profile of the high energy X-ray (H) relative to the X-ray profile of the low energy X-ray (L) hinders the realization of the dual energy technology. In the present embodiment, by correcting the trajectory of the electron beam, the angle and position at which the target 11 is irradiated with the high energy electron beam (H) is the angle and position at which the target 11 is irradiated with the low energy electron beam (L). Therefore, the deformation of the X-ray profile is eliminated in principle, thereby greatly improving the feasibility of the dual energy technology with a single X-ray tube device.

  FIG. 6 shows control for switching high / low energy X-rays by the controller 3 of FIG. The controller 3 is supplied with a trigger signal for data collection / radiation synchronization from a scan controller (not shown). The supply of filament current from the generator 2 to both the low filament 15 and the high filament 16 is always continued during the inspection period.

  During the inspection period in which the filament current is constantly supplied to both the low filament 15 and the high filament 16, the source selection deflection electrode 13 and the trajectory correction deflection of the deflection unit 12 are synchronized with the rising edge of the trigger signal. The application of deflection voltage to the electrode 14 is alternately switched on / off. Thereby, high / low energy X-rays are alternately output from the irradiation window of the X-ray tube.

  Under continuous supply of filament currents to a plurality of filaments, voltage application to the deflection unit is switched on / off at regular intervals to alternately and rapidly transmit X-rays having different energies from one X-ray tube apparatus. Irradiation in a pulsed manner becomes possible. Since the pulse is controlled by high-speed switching, the simultaneity and angular resolution of the two energy collection data are improved. Energy resolution is also improved. There is no error in changing time due to one deflecting unit. Since switching of high / low energy X-rays can be controlled by electrical on / off to one deflection unit, it is easy to ensure synchronism with the data collection system.

  Furthermore, by correcting the trajectory of the electron beam, a dual energy technology is applied by irradiating a high / low electron beam at the same angle with respect to the target and at the same focal position on the target, and appropriately adjusting the X-ray profile of the high / low energy X-ray Accuracy can be improved.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... X-ray tube apparatus, 2 ... Generator, 3 ... Controller, 11 ... Rotary anode, 12 ... Electron beam deflection | deviation part, 13 ... Source selection deflection electrode, 14 ... Orbit correction deflection electrode, 15, 16 ... Cathode filament (Electron generator), 17... Irradiation window.

Claims (12)

A first electron generator for generating a first electron beam;
A second electron generator that generates a second electron beam having a different energy from the first electron beam;
A target that generates first or second X-rays by irradiation of the first or second electron beam;
First and second electron beam deflecting units arranged in tandem between the first and second electron generating units and the target and deflecting the first and second electron beams by an electric field or a magnetic field;
An X-ray tube apparatus enclosing the first electron generation unit, the second electron generation unit, the target, the first electron beam deflection unit, and the second electron beam deflection unit;
An X-ray irradiation window formed in the X-ray tube apparatus for outputting the first or second X-ray from the X-ray tube apparatus;
The first electron beam deflection unit is provided to select the first or second electron beam,
The second electron beam deflecting unit is provided to irradiate the selected position on the target with a specific angle with the selected first or second electron beam,
When both the first and second electron beam deflecting units are in an off state, the first X-ray is output through the X-ray irradiation window,
The second X-rays are output through the X-ray irradiation window when both the first and second electron beam deflecting units are in an ON state;
An X-ray tube apparatus characterized by that.   2. The X-ray tube apparatus according to claim 1, wherein the first and second electron beams are constantly generated from the first and second electron generators during an imaging period.   The first and second electron beam deflecting units are alternately switched between an off state and an on state, whereby the first electron beam and the second electron beam are alternately pulsed from the X-ray irradiation window. The X-ray tube apparatus according to claim 1 or 2, wherein   The X-ray tube apparatus according to any one of claims 1 to 3, wherein the second X-ray has higher energy than the first X-ray.   The X-ray tube apparatus according to claim 4, wherein the first and second electron generators are arranged in parallel in a radial direction of the target.   The X-ray tube apparatus according to claim 5, wherein the target has a polyhedral shape. An X-ray tube device;
An X-ray detector arranged with a subject sandwiched between the X-ray tube apparatus;
In an X-ray CT apparatus comprising an image reconstruction unit that reconstructs an image based on the output of the X-ray detector,
The X-ray tube device
A first electron generator for generating a first electron beam;
A second electron generator that generates a second electron beam having a different energy from the first electron beam;
A target that generates first or second X-rays by irradiation of the first or second electron beam;
First and second electron beam deflecting units arranged in tandem between the first and second electron generating units and the target and deflecting the first and second electron beams by an electric field or a magnetic field;
An X-ray tube apparatus enclosing the first electron generation unit, the second electron generation unit, the target, the first electron beam deflection unit, and the second electron beam deflection unit;
An X-ray irradiation window formed in the X-ray tube device for outputting the first or second X-ray from the X-ray tube device;
The first electron beam deflection unit is provided to select the first or second electron beam,
The second electron beam deflecting unit is provided to irradiate the selected position on the target with a specific angle with the selected first or second electron beam,
When both the first and second electron beam deflecting units are in an off state, the first X-ray is output through the X-ray irradiation window,
The second X-rays are output through the X-ray irradiation window when both the first and second electron beam deflecting units are in an ON state;
An X-ray CT apparatus characterized by that.   The X-ray CT apparatus according to claim 7, further comprising a control unit that controls the first and second electron generation units in order to constantly generate the first and second electron beams during an imaging period.   The first and second electron beam deflecting units are alternately switched between an off state and an on state, whereby the first electron beam and the second electron beam are alternately pulsed from the X-ray irradiation window. The X-ray CT apparatus according to claim 7 or 8, wherein   The X-ray CT apparatus according to claim 9, wherein the second X-ray has higher energy than the first X-ray.   The X-ray CT apparatus according to claim 10, wherein the first and second electron generation units are arranged in parallel in a radial direction of the target.   The X-ray CT apparatus according to claim 11, wherein the target has a polyhedral shape.