JPS6254499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray tomography apparatus that irradiates a subject with X-rays from multiple directions around the subject, measures the intensity of the X-rays that have passed through the subject, and
This invention relates to improvements in a computerized tomography scanner (hereinafter referred to as CT scanner) that processes these measured values using a computer to obtain the X-ray absorption coefficient distribution of the tomographic plane of the subject.

Conventional X-ray tomography equipment uses a fan-shaped
A detector consisting of an X-ray tube that emits rays, a large number of detection elements that are placed opposite to the X-ray tube with a subject in between and that are necessary to detect the X-rays emitted from the X-ray tube; a data processing device that converts the intensity of X-rays obtained by the instrument into an electrical signal and processes the electrical signal to obtain an X-ray absorption coefficient distribution of a tomographic plane of the subject; and the X-ray tube and the detector. The operation of rotating the X-ray tube at each step angle, emitting X-rays from the X-ray tube at each step angle, and detecting the X-rays with the detector is performed over an angular range of one rotation or more. It consisted of an X-ray tube, a detector, and a rotation mechanism that mechanically rotates the detector around the subject. Alternatively, a detector consisting of a large number of detection elements arranged in a ring around the subject is fixed,
An X-ray method in which only an X-ray tube that emits fan-shaped X-rays is mechanically rotated around the subject one or more times to obtain the data necessary to determine the X-ray absorption coefficient distribution of the tomographic plane of the subject. A tomography device was also installed.

By the way, in conventional X-ray tomography apparatuses, whether the X-ray tube and the detector are rotated or the X-ray tube alone is rotated, the speed at which the mechanical rotation is performed is, for example, 1. There was a limit of about 30 revolutions per minute. In other words, it takes about 2 rotations for one rotation.
In other words, the X-ray scanning time required to photograph a tomographic plane of the subject was approximately 2 seconds. Therefore, during this time, in the case of a subject such as a human body, the subject moves due to breathing, heartbeat, etc.
There was a drawback that the obtained tomographic image of the subject was unclear.

Furthermore, when photographing a series of various tomographic planes of a subject, conventional X-ray tomography equipment
Since the subject was mechanically moved so that the desired tomographic plane of the subject was at the X-ray irradiation position, there was a drawback that positioning etc. took time. In addition, re-alignment also had the drawback of inaccurate measurements due to difficulty in position reproducibility.

The present invention eliminates the above-mentioned drawbacks of conventional X-ray tomography devices, scans X-rays electromagnetically, and automatically controls the generation position, energy, intensity, etc. of X-rays, allowing accurate imaging at high speed. It is an object of the present invention to provide an X-ray tomography apparatus that can obtain a tomographic image of a specimen.

Hereinafter, the present invention will be explained in detail based on one embodiment. In the drawings of the embodiments, common parts are given the same numbers.

FIG. 1 is a schematic diagram of an X-ray tomography apparatus of the present invention. When an electron beam emitted from an electron gun, which will be described later, collides with a target 1 made of a ring-shaped metal plate, X-rays are emitted from the collision point, that is, the X-ray generation point 2. The X-ray beam 3 emitted from the X-ray generation point 2 has a spread angle sufficient to cover the imaging area 4 of the subject, for example, about 30 degrees, using a collimator placed in a ring shape to be described later. formatted by. The X-ray beam transmitted through the imaging area 4 is passed through a detector 5 consisting of a large number of detection elements arranged in a ring shape.
Detected by. The intensity of the X-ray beam detected by this detector 5 is converted into an electrical signal, and this electrical signal is sent to a data processing device, such as a data acquisition unit 6,
The data is sent to the data processing device 7 and used to obtain a tomographic image of the subject. The data processing device 7
The orbital movement of the X-ray generation point 2 is electromagnetically controlled through the X-ray generation control device 9 so that the X-ray generation point 2 traces a circular orbit 8 on the target 1. This X-ray generation point 2 is controlled to be located on the circular orbit 8 at every predetermined step angle, for example every 1 degree. Further, the X-rays irradiated on the subject at each step angle are detected by the detector 5,
An electrical signal indicating its strength is sent to a data processing device. The data processing device uses image reconstruction methods such as the well-known convolution method based on the measured values of the intensity of X-rays irradiated from all directions around the subject to reconstruct the tomographic plane of the subject. The X-ray absorption coefficient is calculated and the result is displayed on the display device 10.

As described above, in order to electromagnetically control the orbital movement of the X-ray generation point 2, the scanning time for rotating the fan-shaped X-ray beam 3 around the object is extremely short, at several milliseconds.
The resulting tomographic image of the subject has reduced image quality degradation due to movement of the subject, resulting in a tomographic image with good image quality. Furthermore, since the position of the X-ray generation point 2 is controlled accurately and quickly, the positioning of the tomographic plane of the subject can also be performed accurately and quickly.

FIG. 2 and the following are concrete configuration diagrams of embodiments of the present invention. FIG. 2 is a cross-sectional view of the X-ray tomography apparatus of the present invention, and FIG. 3 is a cross-sectional view of the X-ray tomography apparatus of the present invention, and FIG.
FIG. 2 is a cross-sectional view of the device of the invention;

In FIG. 2, the electron gun 21 has an opening 22 at one end.
The electron gun 21 is connected to one end of a vacuum vessel 23 at one end thereof. This vacuum container 23
is an exhaust hole 24 provided in the wall of this vacuum container.
The degree of vacuum is maintained at about 10 ^-7 Torr by a vacuum pump 26 through an L-shaped exhaust pipe 25 connected to. A focusing device, ie, a focusing coil 27, and a deflection device, ie, a beam deflection yoke 28, are provided at a narrow constricted portion of the vacuum vessel 23 from the side closer to the electron gun 21. Opening 22 of electron gun 21
The electron beam 29 extracted from the electron beam 29 is focused by the focusing coil 27, deflected by a predetermined angle by the beam deflection yoke 28, and rotated in a cone shape while maintaining the same solid angle.
This electron beam 29 is directed to an auxiliary deflection device provided in a ring shape inside the vacuum container 23, that is, an electrostatic deflection electrode 3.
0, the beam collides with a predetermined point, that is, the X-ray generation point 2, of the target 1 arranged in a ring shape near the other end of the vacuum chamber 23, and an X-ray beam 3 is emitted. A metal pipe 31 is welded to this target 1, and a cooling mechanism (not shown) is provided to flow oil or water into the metal pipe 31 in order to absorb the heat released from the target 1 due to the collision of the electron beam. It is provided.

The vacuum container 23 has a cylindrical cavity 32 with an open hole at one end, into which a subject is inserted. A detector 5 is installed in a ring shape near the open end of the cavity 32, and detects the X emitted from the target 1.
Detect line beam 3. As shown in FIGS. 2 and 3, the ring-shaped detector 5 includes a large number of detection elements 33. As shown in FIGS. Collimators 34 and 35 are installed in a ring shape at positions sandwiching the detector 5 from the inside and outside and at positions concentric with the detector 5. The X-ray beam 3 emitted from the X-ray generation point 2 is scanned along a circular trajectory 8 over the target 1 by electromagnetically controlling the focusing coil 27, beam deflection yoke 28, and electrostatic deflection electrode 30. . This X-ray beam 3 is shaped by a collimator 35 into a fan-shaped beam with a thin beam width and a divergence angle of, for example, about 30 degrees, and irradiates the imaging region 4 of the subject. This X-ray beam 3
is attenuated in accordance with the distribution of the X-ray absorption coefficient depending on the tissue of the subject, and is reshaped by the other collimator 34 installed in a ring shape, and the plurality of specific detection elements 33 arranged in a ring shape ' is incident on a part of the detector 5 consisting of '. The intensity of this incident X-ray beam is converted into an electrical signal indicating the intensity by the detector 5, and processed by the data processing device to obtain a tomographic image of the subject.

Therefore, since scanning of the X-ray beam 3 can be performed electromagnetically using the focusing device, deflection device, etc., high-speed and accurate scanning is possible. Furthermore, the electron beam can be narrowed down by the focusing coil 27, etc., and the size of the X-ray generation point 2 can be reduced, so that a clear image can be obtained.

FIG. 4 shows a cross-sectional view of the electron gun 21.

When a filament heating power source (not shown) is connected to the coiled filament 41 and energized, a cathode 42 covering the filament 41 is formed.
The electron emitting surface 43 of is heated, and electrons are emitted from this electron emitting surface. Near the front surface of the electron emitting surface 43, a mesh grid 44 is supported by a cylindrical grid support 45 and is electrically insulated from the cathode 42 by an insulator 46.
Furthermore, a funnel-shaped Wehnelt electrode 47 is provided on the front surface of the grid 44. This Wehnelt electrode 47 is supported by a Wehnelt support base 49 which is provided in a concentric cylindrical shape with an insulator 48 interposed between the grid support base 45 and the Wehnelt support base 45 . This Wehnelt support stand 49 is fixed to a fixing member 51 via an insulator 50. The fixed member 51 is
connected to the outer wall of the electron gun 21 (not shown);
On the other hand, an anode 53 is supported via an insulator 52. Although not shown, voltages are applied to the filament, the Wehnelt electrode 47, the anode 53, and the like from respective power sources. The electrons emitted from the electron emitting surface 43 are focused by the Wehnelt electrode 47, and are directed to the anode 53 by a DC voltage or pulsed voltage applied between the cathode 42 and the anode 53.
The electron beam 29 is extracted from a small aperture 54 provided in the electron beam. The beam intensity of this electron beam 29 is controlled by the grid 44, and the energy of the beam is varied by varying the value of the voltage applied between the cathode 42 and the anode 53.

Therefore, the beam intensity and energy of the X-ray beam generated when the electron beam 29 collides with the target 1 can also be controlled. In the X-ray tomography apparatus of the present invention, since the X-ray beam can be rotated around the object many times in a short period of time, parameters such as X-ray energy and beam intensity can be further adjusted by using the electron gun. Many types of data can be obtained in a short period of time by changing the X-ray absorption coefficient of the object. For example, the disadvantage that the X-ray absorption coefficient is a value containing an error because an actual X-ray beam does not have a constant energy but is distributed over a certain energy range can be solved by the present invention. The image becomes clearer.

FIG. 5 is an enlarged view of the detector portion in the sectional view of the apparatus of the present invention shown in FIG.

The electron beam 29 impinges on the target 1, which is provided with a metal pipe 31 for cooling the target 1.
From the collision point, that is, the X-ray generation point 2, the X-ray beam 3
is released. This X-ray beam 3 is detected by a detector 5 consisting of two sets of detectors 5a and 5b. The detectors 5a and 5b control the position of the X-ray generation point 2 so that the X-ray beams 3a and 3b incident on the detectors 5a and 5b have symmetrical beam shapes, or The position is determined by moving the X-ray beam in a direction across the X-ray beam 3. A wedge-shaped X-ray shielding member 55 is provided between the detectors 5a and 5b. Therefore, unnecessary X-ray exposure to the subject is effectively eliminated. Furthermore, since the X-ray beams 3a and 3b are detected simultaneously by the two sets of detectors 5a and 5b, two images of different tomographic planes of the subject can be obtained at the same time.

Note that the X-ray beam 3 incident on the detectors 5a and 5b
To determine whether or not a and 3b are symmetrical to each other, that is, the position of the X-ray generation point 2, a detector 57 located close to the X-ray generation point 2 is used in addition to the detector 56 located far from the X-ray generation point 2. You can also do that.

FIG. 6 is a diagram showing a modification of FIG. 5.

Detectors 61a, 61b, 61c, 61d, 61
e and 61f are arranged at equal intervals. The collision points 2a, 2 of the electron beam 29 on the target 1 are arranged so that the X-ray beams 3 incident on these detectors 61 are symmetrical or have the same beam shape.
The positions of b, 2c, 2d, and 2e are electromagnetically controlled.

Therefore, since a large number of detectors 5 are arranged and the X-ray beam 3 incident on each detector is electromagnetically controlled, a large number of images of different tomographic planes of the subject can be obtained in a short time.

As described above, according to the present invention, since the scanning of the X-ray generation point is electromagnetically controlled, the scanning time for rotating the X-ray beam around the subject is extremely short, and the deterioration of image quality due to the movement of the subject is reduced. A clear tomographic image of the subject can be obtained. Furthermore, by narrowing down the electron beam that generates the X-rays, the size of the X-ray generation point can be reduced, so that a clear tomographic image of the object can be obtained. Furthermore, since the position of the X-ray generation point can be determined accurately and quickly, the positioning of the tomographic plane of the subject can also be accurately and quickly performed.

Furthermore, by changing parameters such as X-ray energy and X
The linear absorption coefficient is obtained. Furthermore, since a plurality of detectors each having a large number of detection elements are arranged and the X-ray beam is electromagnetically scanned, a large number of images of different tomographic planes of the subject can be obtained in a short time.

Furthermore, the target etc. are provided in a single vacuum vessel, and the electron gun that generates X-rays from this target only needs to be connected to one end of the vacuum vessel, which simplifies the structure of the device and makes it easier for the machine to operate. Since a conventional X-ray beam rotation drive device is not required, the device can be made compact.

It should be noted that the present invention is not limited to the embodiments described in this specification, and of course includes modifications included in the scope of the claims. For example, in an electron gun, the cathode may be of the indirectly heated type. A direct heating type may be used, or an electron gun using a plurality of cathodes may be used. Instead of a single metal plate, the target may also include a large number of metal plates arranged side by side in a ring shape.

Further, as a focusing device, an electrostatic electrode may be used for focusing, and the detector may be shaped other than a ring, for example.
They may also be arranged in an arc arranged over an angular range of 180°. Furthermore, in order to facilitate the setting of the object, the electron gun may be mounted eccentrically from the central axis of rotation of the X-ray beam, and the container may be tilted to obtain images of different tomographic planes of the object. It may be a structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the apparatus of the present invention, and FIG.
FIG. 3 is an overall view of an apparatus showing a specific configuration of the present invention. FIG. 4 is a sectional view of an electron gun used in the apparatus of the present invention, FIG. 5 is an enlarged view of a detector portion, and FIG. 6 is a view of a modified example of the detector shown in FIG. 5. DESCRIPTION OF SYMBOLS 1... Target, 2... X-ray generation point, 5... Detector, 6... Data acquisition part, 7... Data processing device, 9
... X-ray generation control device, 10 ... Display device, 21 ... Electron gun, 23 ... Vacuum container, 25 ... L-type exhaust pipe, 26
...Vacuum pump, 27...Focusing coil, 28...Beam deflection yoke, 30...Electrostatic deflection electrode, 31...Metal pipe, 33, 33'...Detection element, 34, 35...Collimator, 41...Filament, 42...Cathode, 44 ...grid, 45...grid support stand, 4
6, 48, 50, 52... Insulator, 47... Wehnelt electrode, 49... Wehnelt support base, 51... Fixing member, 53... Anode, 55... X-ray shielding member, 61
…Detector.

Claims (1)

[Scope of Claims] 1. A target arranged in an arc in an angular range of 360° or less and which irradiates X-rays toward a subject placed approximately at the center of the arc by colliding with an electron beam. , forming a plane parallel to and at a different position from the plane formed by this target, and arranged in an arc shape that is smaller than the radius of the arc shape of the target, opposite to the target, and within an angular range larger than 180°. a first detector for detecting the amount of X-rays transmitted through the subject; a plane parallel to the plane formed by the first detector and sandwiching the plane formed by the target;
Moreover, a second detector is arranged in an arc having the same radius as the first detector, and detects the amount of X-rays that have passed through the subject, and the signals from the first and second detectors are arranged in an arc shape and have the same radius as the first detector. An X-ray tomography apparatus comprising: a data processing unit that reconstructs tomographic images at different positions of the subject based on the subject. 2. The X-ray tomography apparatus according to claim 1, wherein the target is limited to an angular arrangement of 360 degrees. 3. The X-ray tomography apparatus according to claim 1, wherein the detector is limited to a 360° angular arrangement. 4. Claim 1, wherein the distance between the surface formed by the first detector and the surface formed by the target is the same as the distance between the surface formed by the second detector and the surface formed by the target. The X-ray tomography device described in Section 1.