JPS6329623A - X-ray tomographic imaging apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an X-ray tomography apparatus, which irradiates a subject with X-rays from multiple directions around the subject, for example. , a computed tomography scanner (hereinafter referred to as a CT scanner) that measures the intensity of X-rays that have passed through the object and processes this measurement value with a computer to obtain the X-ray absorption coefficient distribution of the object's tomographic plane. Regarding improvements.

(Prior Art) Conventional X-ray tomography apparatuses emit fan-shaped X-rays that spread sufficiently to cover the imaging area of the subject.
the X-ray tube, which is placed opposite to the X-ray tube with the subject in between;
A detector consisting of a large number of detection elements necessary to detect the X-rays emitted from the ray tube, and a detector that converts the intensity of the X-rays obtained by this detector into an electrical signal and detects the X-rays of the tomographic plane of the subject. a data processing device that processes the electric signal to obtain an absorption coefficient distribution; and a data processing device that rotates the X-ray tube and the detector at each step angle and emits X-rays from the X-ray tube at each step angle; A rotation mechanism unit mechanically rotates the X-ray tube and the detector around the subject so that the detector detects the X-rays over an angular range of one rotation or more. was. Alternatively, a detector consisting of a large number of detection elements arranged in a ring around the subject is fixed, and only the X-ray tube that emits fan-shaped X-rays is mechanically rotated one or more revolutions around the subject. There was also an X-ray tomography apparatus that used a method to obtain the data necessary to determine the X-ray absorption coefficient distribution of the tomographic plane of the subject.

By the way, in conventional X-ray tomography apparatuses, whether the X-ray tube and detector are rotated or the X-ray tube alone is rotated, the mechanical rotation speed has a certain speed, for example, from the viewpoint of speed control. There was a limit of 30 revolutions per minute. That is, about 2 seconds are required for one rotation, and in other words, about 2 seconds are required for the X-ray scanning time required to photograph the tomographic plane of the subject. Therefore, in the case of a subject such as a human body, the subject moves during this time due to breathing, heartbeat, etc., which has the disadvantage that the obtained tomographic image of the subject becomes unclear. Ta.

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

(Problems to be Solved by the Invention) The present invention eliminates the above-mentioned drawbacks of conventional X-ray tomography devices, scans X-rays electromagnetically, and automatically detects the position, energy, intensity, etc. of X-rays. It is an object of the present invention to provide an X-ray tomography apparatus that can be controlled to obtain accurate tomographic images of a subject at high speed.

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 according to 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 that has passed through the imaging area 4 is detected by a detector 5 consisting of a large number of detection elements arranged in a ring shape. 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 and a data processing device 7 to obtain a tomographic image of the subject. used. The data processing device 7 electromagnetically controls the orbital movement of the X-ray generation point 2 through the X-ray generation control device 9 so that the X-ray generation point 2 draws 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.

In addition, the X
The line is detected by a detector 5 and 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 calculate the Calculate the absorption coefficient and display the result on a display device 10
to be displayed.

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 subject is extremely short, at several m5ec, and the obtained tomographic image of the subject is Deterioration in image quality due to movement of the subject is reduced, 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 apparatus of the present invention taken along cutting line ■--■ in FIG.

In FIG. 2, an electron gun 21 has an opening 22 at one end,
At this one end, the electron gun 21 is connected to one end of the vacuum vessel 23 . This vacuum container 23 has an L-shaped exhaust pipe 25 connected to an exhaust hole 24 provided in the wall of the vacuum container.
through the vacuum pump 26 to approximately 10-10 Torr.
It is maintained at a certain degree of vacuum. A focusing device is placed at the narrow constricted part of the vacuum container 23 from the side close to the electron gun 21.
That is, a focusing coil 27 and a deflection device, ie a beam deflection yoke 28, are provided. The electron beam 29 extracted from the aperture 22 of the electron gun 21 is narrowed by the focusing coil 27, then deflected by a predetermined angle by the beam deflection yoke 28, and rotated into a cone shape while maintaining the same solid angle. Ru. This electron beam 29 is
3 is deflected again by an auxiliary deflection device provided in a ring shape in the vacuum chamber 23, that is, an electrostatic deflection electrode 30, to a predetermined point on the target 1 arranged in a ring shape near the other end of the vacuum vessel 23, that is, the X-ray generation point 2. They collide and emit an X-ray beam 3.

A metal vibrator 31 is welded to this target 1, and a cooling mechanism (not shown) is provided to flow oil or water into the metal vibrator 31 in order to absorb the heat released from the target 1 due to the collision of the electron beam. ing.

The vacuum container 23 has a cylindrical cavity 32 with an open hole at one end.
A subject is inserted into this cavity 32. A detector 5 is installed in a ring shape near the open end of the cavity 32 and detects the X-ray beam 3 emitted from the target 1. Second
As shown in the figure and FIG. 3, the ring-shaped detector 5 is made up of a large number of detection elements 33. 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 Xfi beam 3 emitted from the X-ray generation point 2 is scanned along a circular trajectory 8 above 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 according to the distribution of the X-ray absorption coefficient depending on the tissue of the subject, and is sent to the other collimator 3 installed in a ring shape.
The X-ray beam is shaped again in step 4 and enters a part of the detector 5, which is made up of a plurality of specific detection elements 33'' arranged in a ring shape.The intensity of the incident X-ray beam is The data is converted into an electrical signal shown in the figure, and processed by the data processing device to obtain a tomographic image of the subject.

In addition to the ring shape, the detector may also be arranged in an arc shape arranged in an angular range of 180 degrees, for example.

In this way, since the X-ray beam 3 can be scanned electromagnetically by 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 xi (not shown) is connected to the coiled filament 41 and energized, the electron emitting surface 43 of the cathode 42 covering the filament 41 is heated, and electrons are emitted from this electron emitting surface. Near the front surface of the electron emission surface 43, a mesh-like grid 44 is supported by a cylindrical grid support 45, and an insulator 4
6 is electrically insulated from the cathode 42.

Furthermore, a funnel-shaped Wehnelt electrode 47 is provided on the front surface of this grid 44. This Wehnelt electrode 4
7 is a Wehnelt support base 49 which is provided in a concentric cylindrical shape with an insulator 48 in between, which is different from the grid support base 45;
Supported.

This Wehnelt support base 49 is fixed to a fixing member 51 via an insulator 50. The fixing member 51 is connected to an outer wall of the electron gun 21 (not shown), and is connected to an insulator 52.
The anode 53 is supported via the anode 53. 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 emitted from the small aperture 54 provided in the anode 53 by the DC voltage or pulsed voltage applied between the cathode 42 and the anode 53. It becomes an electron beam 29 and is extracted.

The beam intensity of this electron beam 29 is
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 ray beam can be rotated around the object many times in a short period of time, by using the electron gun, it is possible to obtain many types of data in a short period of time by changing parameters such as X-ray energy and beam intensity. These data can be used to obtain more accurate X-ray absorption coefficients of the tomographic plane of the subject. For example, the present invention can alleviate the disadvantage that the X-ray absorption coefficient becomes 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. 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 collides with the target 1 provided with a metal vibrator 31 for cooling the target 1 .

An X-ray beam 3 is emitted from the collision point, that is, the X-ray generation point 2. This X-ray beam 3 is detected by a detector 5 consisting of two sets of detectors 5a and 5b. The detectors 5a, 5b are arranged so that the X-ray beams 3a, 3 are incident on the detectors 5a, 5b.
Either control the position of the X-ray generation point 2 or move the detector 5 so that the X-ray beam 3 has a symmetrical beam shape.
The position is determined by moving in the transverse direction.

A wedge-shaped X-ray shielding member 55 is provided between the detectors 5a and 5b. Therefore, unnecessary X to the subject
Radiation exposure has the effect of being removed. Two more sets of detectors 5
X-ray beams 3a, 3b simultaneously by a, 5b, respectively
In order to detect this, two images of different tomographic planes of the subject can be obtained at the same time.

Note that the X-ray beams 3a and 3b incident on the detector 5as5b
To determine whether the X-ray generation point 2 is 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 may be used in addition to the detector 56 located far from the X-ray generation point 2. I can do it.

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

Detectors 61a, 61b, 61c, 61d, 61e, 61
f are arranged at equal intervals. The target 1 of the electron beam 29 is adjusted so that the X-ray beams 3 incident on these detectors 61 are symmetrical or have the same beam shape.
The positions of the impact points 2a%2b, 2c, 2d, 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 of the X-ray beam is extremely short.
Deterioration in image quality due to specimen movement is reduced, and a clear tomographic image of the specimen can be obtained. In addition, 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 The X-ray 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, a target etc. are provided in a single vacuum container,
In addition, the electron gun that generates X-rays from this target only needs to be connected to one end of the vacuum chamber, which simplifies the structure of the device.Also, there is no need for a mechanical X-ray beam rotation drive device, making the device easy to use. can be made small.

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. The target may also include a plurality of metal plates arranged side by side in a ring shape instead of one metal plate.

Further, as a focusing device, an electrostatic electrode may be used for focusing, and the detector may also be arranged in an arc shape, for example, in an angular range of 180'' instead of in a ring shape. In order to facilitate this, the electron gun may be mounted eccentrically from the central axis of rotation of the X-ray beam, or the container may be tilted to obtain images of different tomographic planes of the subject.

[Effects of the Invention] According to the present invention, since the scanning of the X-ray generation point is electromagnetically controlled, the scanning time of the X-ray beam is extremely short, the deterioration of image quality due to the movement of the subject is reduced, and the subject can be examined clearly. tomographic images can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the apparatus of the present invention, and FIGS. 2 and 3 are overall views of the apparatus showing a specific configuration of the present invention. FIG. 4 is a sectional view of the electron gun used in the device of the present invention, and FIG.
The figure is an enlarged view of the detector portion, and FIG. 6 is a diagram showing a modified example of the detector shown in FIG. 5.

Claims (3)

[Claims] (1) A target that is arranged in an arc shape within an angle range of 360° or less and irradiates X-rays toward a subject placed approximately in the center of the arc by colliding with an electron beam; a plane parallel to the plane formed by the target, and arranged in an arc shape smaller than the radius of the arc shape of the target, opposite to the target and within an angular range larger than 180°; An X-ray tomography apparatus comprising: a detector that detects the amount of X-rays that have passed through a subject; and a data processing unit that reconstructs a tomographic image of the subject based on signals from the detector. . (2) The X-ray tomography apparatus according to claim 1, wherein the target is arranged at an angle of 360°. (3) The X-ray tomography apparatus according to claim 1, wherein the detector is arranged at an angle of 360°.