JP3265035B2 - Computer tomography equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray generated from an X-ray source.
The present invention relates to a computed tomography apparatus that irradiates a subject with a ray and forms a tomographic image of the subject from X-ray data transmitted through the subject.

[0002]

2. Description of the Related Art Computed tomography apparatuses, so-called CT scanners, have been widely used for medical purposes, but have also been gradually used for industrial purposes in the last ten years.

[0003] In an industrial CT scanner, since the subject to be inspected varies widely, the X-ray source of the X-ray source varies depending on the subject.
The line energy is switched so that the transmission thickness through which X-rays can be transmitted can be varied. For example, Japanese Unexamined Patent Publication
The CT scanner described in Japanese Patent No. 87049 can switch the X-ray energy generated from the X-ray source according to the subject, and also switch the X-ray filter of the comparison detector that measures the change in X-ray intensity. This adjusts the amount of X-rays incident on the comparative detector to obtain a high-quality image.

[0004]

In the above-mentioned conventional CT scanner, the X-ray filter of the comparison detector is switched in accordance with switching of X-ray energy generated from the X-ray source, that is, switching of the X-ray tube voltage. However, there is a problem that the best image cannot be obtained because the filters of the main detector for detecting the X-ray transmitted through the subject are not switched at the same time.

More specifically, an X-ray filter for a main detector is used to remove a soft X-ray component to alleviate a radiation hardening phenomenon and improve the image quality of a cross-sectional image. As the thickness of the filter material is increased, the degree of relaxation is increased. However, if the thickness is too large, the X-ray dose is reduced and the image noise is increased. Therefore, when the X-ray tube voltage is switched,
The appropriate filter thickness will also vary, but the conventional CT
In the scanner, even if the X-ray tube voltage is switched, the filter of the main detector is not switched and one filter is used to make up for the problem. Therefore, even if the X-ray tube voltage is switched, the best image cannot be obtained. There is.

In a CT scanner, an X-ray shutter for shielding X-rays generated from an X-ray source is a filter mechanism.
Since it is provided as another independent mechanism, there is a problem that the mechanism becomes complicated and the space of the mechanism section becomes large, so that the space for placing the subject cannot be increased.

Further, in the conventional CT scanner, the thickness of the comparative detector is relatively large, that is, the thickness of the comparative detector along the X-ray path is large. There is a problem that the distance between them becomes long, and it is not possible to increase the space for placing the subject.

Further, in a conventional CT scanner, a photodiode and a detection circuit, which are photoelectric conversion means constituting a comparison detector, are arranged at a position close to an X-ray path from an X-ray source. There is a problem that the life of the photodiode and the detection circuit is relatively short due to the influence of scattered X-rays.

[0009] The present invention has been made in view of the above,
An object of the present invention is to provide a computed tomography apparatus that can always obtain the best tomographic image even when the X-ray energy generated from the X-ray source is switched according to the subject.

It is another object of the present invention to control a filter mechanism and an X-ray shielding mechanism by the same switching means, to reduce the size of the mechanism, and to increase the space for placing a subject. Is to provide.

Still another object of the present invention is to provide a computed tomography apparatus which has a longer life by making it difficult for scattered X-rays to hit the components of the comparison detector.

[0012]

In order to achieve the above object, a computed tomography apparatus according to the present invention generates X-rays from an X-ray source, irradiates the X-rays toward a subject, and irradiates the subject with the X-rays. The main detector detects the transmitted X-rays, and the comparative detector detects the X-rays from the X-ray source that does not pass through the subject to detect the intensity of the X-rays generated from the X-ray source. A computer tomography apparatus for forming a tomographic image of a subject based on X-ray transmission data detected by the main detector while referring to X-ray intensity data detected by an X-ray source, wherein X-rays generated from the X-ray source are provided. X-ray source switching means for switching X-ray energy, and X-ray doses incident on the main detector and the comparison detector corresponding to the X-ray energy from the X-ray source switched by the X-ray source switching means, respectively. Main filter means and Comparing the filter means, and summarized in that and a filter switching means for switching at the same time each said main filter means and comparing the filter means in accordance with the switching operation of the X-ray source switching means.

Further, the computed tomography apparatus of the present invention generates X-rays from an X-ray source, irradiates the X-rays to a subject, and detects the X-rays transmitted through the subject by a main detector. ,
A computer tomography apparatus configured to form a tomographic image of a subject based on X-ray transmission data detected by the main detector, wherein X-ray source switching means for switching X-ray energy generated from the X-ray source; Main filter means for adjusting the amount of X-ray incident on the main detector in accordance with X-ray energy from the X-ray source switched by the X-ray source switching means; and shielding for shielding X-rays from the X-ray source And a filter switching means capable of switching the main filter means in accordance with a switching operation of the X-ray source switching means and switching the main filter means to the shielding means.

Further, the computed tomography apparatus of the present invention generates X-rays from an X-ray source, irradiates the X-rays toward a subject, and detects the X-rays transmitted through the subject with a main detector. At the same time, in order to detect the intensity of X-rays generated from the X-ray source, X-rays from an X-ray source that does not pass through the subject are detected by a comparative detector, and the X-ray intensity data detected by the comparative detector is referred to. A computer tomography apparatus configured to form a tomographic image of a subject based on X-ray transmission data detected by the main detector, wherein the comparison detector converts X-rays from the X-ray source into visible light The gist of the present invention includes a scintillator, a photoelectric converter for converting visible light from the scintillator into an electric signal, and a light guide for guiding visible light generated from the scintillator to the photoelectric converter.

[0015]

In the computed tomography apparatus of the present invention, the X-rays incident on the main detector and the comparison detector corresponding to the X-ray energy from the X-ray source switched by the X-ray source switching means.
The main filter means and the comparison filter means for respectively adjusting the dose are simultaneously switched according to the switching operation of the X-ray source switching means.

In the computed tomography apparatus according to the present invention, the main filter means for adjusting the amount of X-rays incident on the main detector can be switched according to the switching operation of the X-ray source switching means, and the main filter means can be switched to the X-ray source. X from source
It is possible to switch to shielding means for shielding the line.

Further, in the computed tomography apparatus of the present invention, the comparison detector guides the visible light from the scintillator to the photoelectric conversion means using a light guide.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are a plan view and a front view, respectively, showing a configuration of a computer tomography apparatus according to an embodiment of the present invention. A computed tomography apparatus (hereinafter, referred to as a CT scanner) shown in FIG. 1 is a so-called second generation CT scanner of a traverse / rotation system, and has an X-ray source 1 for generating X-rays. X-rays generated from 1 irradiate the subject 13 as an X-ray fan beam 3 through the primary collimator 2, the filter switching mechanism 8, and the source collimator 5, and the X-rays transmitted through the subject 13 are detected by the detector. Main detector 7 via side collimator 6
, And is detected by the main detector 7.

The subject 13 is placed on a rotary table 10, which can be rotated around a vertical axis by a rotary mechanism 11 provided below the rotary table 10, and also horizontally by a traverse mechanism 12. And traverses the X-ray fan beam 3.

The X-rays generated from the X-ray source 1 are not only formed as an X-ray fan beam 3 by a primary collimator 2 but also an X-ray beam 4 for a comparative detector is taken out.
It is configured to be incident on the comparison detector 9.

The filter switching mechanism 8 includes an X-ray source 1
Between the X-ray source 1 and the collimator 5 on the source side, and are inserted into respective paths of the X-ray fan beam 3 and the X-ray beam 4 for the comparison detector, as described later. Filters are simultaneously switched or X-rays from the X-ray source 1 are blocked.

In the CT scanner shown in FIG. 1, the X-ray control device, console, mechanism control device, data acquisition device (DAS), reconstructing device, CRT display and the like are not shown, but are omitted. Each device of the normal C
It is provided like a T-scanner, whereby, for example, X-ray energy generated from the X-ray source 1 is switched according to the subject 13 by an X-ray controller, and a rotating mechanism 11 and a traverse mechanism are switched by a mechanism controller. While traversing the X-ray fan beam 3 while rotating the subject 13 by controlling the subject 12, the subject transmission data detected by the main detector 7 is supplied to the data collection device, and the subject is further reconstructed by the reconstructing device. Is reconstructed and displayed on a CRT display.

FIGS. 2A and 2B show the structure of a rotary plate 81 constituting the filter switching mechanism 8 and the structure of a mechanism for rotating the rotary plate 81, respectively.

As shown in FIG. 2A, the rotating plate 81 of the filter switching mechanism 8 includes a first filter 8 for the main detector.
3a, a first filter 83b for a comparison detector is provided adjacent to the first filter 83a.
A second filter 84b for comparison detector adjacent to the second filter 84a for main detector is provided on the diagonal line between the first filter 83a and the first filter 83b for comparison detector. Between them, a shutter plate 82a and a shutter plate 82b are provided so as to face each other diagonally.

The first filter 83a for the main detector and the first filter 83b for the comparison detector are used when the tube voltage supplied to the X-ray source 1 is switched to 400 kV. 1 filter 83a is 2
mm for a comparison detector
b is made of a 10 mm steel plate. The second filter 84a for the main detector and the second filter 84b for the comparison detector are used when the tube voltage supplied to the X-ray source 1 is switched to 260 kV. The filter 84a is made of a 1 mm steel plate, and the second filter 84b for a comparative detector is made of a 4 mm steel plate.

Further, the filter switching mechanism 8 is provided in FIG.
As shown in (b), the rotation of the rotary plate 81 is controlled by the motor 86, and the rotational position is
5, the first filter 83a for the main detector, the first filter 83b for the comparison detector, the second filter 84a for the main detector, the second filter 84b for the comparison detector, the shutter plate 82a, the shutter One of the plates 82b filters or shields X-rays generated from the X-ray source 1.

FIG. 3 is a diagram showing the internal configuration of the comparison detector 9. As shown in FIG. As shown in the figure, the comparative detector 9 converts the comparative detector X-ray beam 4 from the X-ray source 1 into, for example, CdWO.
_{4 The} light is received by a scintillator 91 made of a single crystal, converted into visible light, and the visible light from
Leading to 5. Then, the photodiode 95 converts the visible light from the scintillator 91 guided through the light guide 92 into an electric signal, and supplies the electric signal to the detector circuit 96.

The scintillator 91 is joined to one end of the light guide 92 by silicone oil, and the other end of the light guide 92 is joined to the photodiode 95 by a silicon-based transparent adhesive. Detector circuit 96
Is composed of, for example, an amplifier, an integrator, a sample and hold circuit, and the like.

The outer periphery of the scintillator 91 is covered with a reflective light-shielding film 93 made of white paint and an aluminum foil layer, and the outer periphery of the light guide 92 is similarly covered with a reflective light-shielding film 93 made of an aluminum vapor-deposited layer and an aluminum foil layer. ing. An X-ray shield 94 is provided outside these, and the whole is accommodated in a housing 97. In FIG. 3, the holding members for the scintillator 91, the light guide 92, and the detector circuit 96 are omitted.

As described above, using the light guide 92, the comparison detector 9 is provided so that the photodiode 95 and the detector circuit 96 are provided separately from the scintillator 91 and the like.
Makes it difficult for scattered X-rays from the periphery of the path of the X-ray beam such as the structure of the scintillator 91 and the comparison detector 9 to reach the photodiode 95 and the detector circuit 96. The life of the detector circuit 96 can be extended.

The operation of the CT scanner configured as described above will be described below.

As described above, the CT scanner of this embodiment can be used by switching the tube voltage of the X-ray source 1 between two stages of 400 kV and 260 kV. First, when the tube voltage of the X-ray source 1 is switched to 400 kV by a switch of a console (not shown), the 400 kV is set to an X-ray controller (not shown), and the filter switching mechanism 8 is rotated by a mechanism controller (not shown). As a result, the first filter 83a for the main detector and the first filter 83b for the comparison detector are selected and inserted into the path of the X-ray fan beam 3 and the X-ray beam 4 for the comparison detector. As a result, the X-ray fan beam 3 and the X-ray beam 4 for the comparative detector are filtered by the first filter 83a for the main detector and the first filter 83b for the comparative detector corresponding to the tube voltage 400 kV of the X-ray source 1, whereby X An appropriate X through a filter corresponding to the tube voltage of the source 1
A line is provided to the subject.

When the tube voltage of the X-ray source 1 is switched to 260 kV, this 260 kV is set in the X-ray controller, and the rotation of the filter switching mechanism 8 is controlled by the mechanism controller. The second filter 84a and the second filter 84b for comparison detector are selected and inserted into the path of the X-ray fan beam 3 and the X-ray beam 4 for comparison detector.

As described above, when the tube voltage of the X-ray source 1 is set, scanning is started when the operator operates the scan start switch on the console. The scanning is exactly the same as that of a conventional traverse / rotation type CT scanner. As described above, the rotation controller 11 and the traverse mechanism 12 are controlled by the mechanism controller to traverse the X-ray fan beam 3 while rotating the subject 13. X from the X-ray source 1 according to the traversing operation
The main detector 7 detects X-rays transmitted through the subject 13 with X-rays, and detects X-rays not transmitted through the subject 13 from the X-ray source 1 with the comparative detector 9. The X-ray transmission data detected by the main detector 7 is collected by a data collection device while referring to the line intensity data, and supplied to a reconstruction device, thereby forming a tomographic image of the subject 13.

The one shutter plate 82a provided in the filter switching mechanism 8 is used to control the X-ray fan beam 3 and the comparative detection by controlling the filter switching mechanism 8 between scans when performing continuous scanning. The X-ray fan beam 3 and the X-ray beam 4 for the comparison detector are inserted into the path of the dexterous X-ray beam 4, thereby blocking the X-ray beam 4 for the comparison detector from the main detector 7 and the comparison detector 9, respectively. , Is used to collect offset data of the comparison detector 9. What is offset data?
This is output data when X-rays do not enter the detector, and is used for offset correction. Thus, the shutter plate 82a
Can be used to continuously scan without turning off the X-ray source by blocking X-rays to the detector.

Further, the other shutter plate 82b is used when exchanging the subject. When it is desired to perform the examination while exchanging the subject one after another, the filter switching mechanism 8 sets the shutter plate 82b to X. Line fan beam 3
And X-rays from the X-ray source 1 are inserted into the path of the X-ray beam 4 for the comparison detector, thereby cutting off the X-rays from the X-ray source 1 and exchanging the subject in this state, without turning off the X-ray source 1 each time. In addition, the subject can be replaced without the operator being exposed.

FIGS. 4A and 4B are a front view and a side sectional view, respectively, showing the structure of another filter switching mechanism that can be used in the CT scanner of FIG.

The filter switching mechanism shown in FIG.
Near the lower end of the plate-shaped filter holder 31, the first filter 83a for the main detector and the first filter 8 for the comparison detector are arranged.
3b, shutter plate 82a, second filter 84 for main detector
a, a first filter 83aa for the main detector corresponding to the second filter 84b for the comparison detector, and a first filter 83aa for the comparison detector, respectively.
Filter 83bb, shutter plate 82aa, second filter 84aa for main detector, second filter 84b for comparison detector
b, and the filter holder 31 is attached to the guide rail 3
2. The filter and the shutter plate are switched by vertically moving up and down by a base 33, a screw 34, a nut 35, and a motor 36.

[0040]

As described above, according to the present invention,
The main filter means and the comparison filter means for adjusting the X-ray dose incident on the main detector and the comparison detector in accordance with the X-ray energy from the X-ray source switched by the X-ray source switching means, respectively. Switching at the same time in accordance with the switching operation, high-quality tomographic images can be obtained, switching errors are less likely to occur, the structure is simplified, the entire space can be reduced, and the subject can be inspected. The mounting space can be increased.

According to the present invention, the main filter means for adjusting the amount of X-ray incident on the main detector can be switched according to the switching operation of the X-ray source switching means, and the main filter means can be switched from the X-ray source. Can be switched to the shielding means for shielding the X-rays, so that the filter switching mechanism can also serve as the shielding means switching mechanism, so that the entire space can be reduced and the space for placing the subject can be increased. it can. Furthermore, since it is possible to configure the subject to be installed at a position close to the X-ray source,
The resolution of the tomographic image and the defect detection ability can be increased. Furthermore, since the X-ray source can be obtained or the subject can be replaced without turning off the X-ray source by the shielding means, there is no need to wait for the X-ray source to start up or shut down. As a result, the inspection time can be shortened and the life of the X-ray source can be extended.

Further, according to the present invention, since the comparison detector guides the visible light from the scintillator to the photoelectric conversion means using the light guide, the life of the comparison detector can be extended.

[Brief description of the drawings]

FIG. 1 is a plan view and a front view showing a configuration of a computer tomography apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a filter switching mechanism used in the computer tomography apparatus of FIG.

FIG. 3 is a diagram showing a configuration of a comparison detector used in the computer tomography apparatus of FIG. 1;

FIG. 4 is a diagram showing a configuration of another filter switching mechanism that can be used in the computed tomography apparatus of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 X-ray source 3 X-ray fan beam 4 X-ray beam for comparison detector 7 Main detector 8 Filter switching mechanism 9 Comparison detector 10 Rotary table 13 Subjects 82a, 82b Shutter plate 83a First filter for main detector 83b For comparison detector First filter 84a Second filter for main detector 84b Second filter for comparison detector 91 Scintillator 92 Light guide 95 Photodiode 96 Detector circuit

Continuation of front page (56) References JP-A-2-87049 (JP, A) JP-A-5-15519 (JP, A) JP-A-5-27041 (JP, A) JP-A-4-141156 (JP) , A) JP-A-1-301154 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 23/04 A61B 6/03 320

Claims (3)

(57) [Claims] An X-ray source generates X-rays, irradiates the X-rays toward a subject, detects X-rays transmitted through the subject by a main detector, and generates X-rays from the X-ray source. X-rays from an X-ray source that does not pass through the subject are detected by a comparative detector to detect the intensity of the X-rays, and the X-rays detected by the main detector are referred to by referring to the X-ray intensity data detected by the comparative detector. A computer tomography apparatus configured to form a tomographic image of a subject based on X-ray transmission data, comprising: an X-ray source switching unit that switches X-ray energy generated from the X-ray source; X from X-ray source
A plurality of main filter units and a plurality of comparison filter units for adjusting X-rays incident on the main detector and the comparison detector in accordance with a line energy, and the main filter unit and the comparison filter unit are arranged.
Rotating plate or main filter means and comparison filter
A filter holder that tandem orientation means, the times in accordance with the switching operation of the X-ray source switching means
Turn the rolling plate or straighten the filter holder in the column direction.
A computer tomography apparatus, comprising: filter switching means for simultaneously moving the main filter means and the comparison filter means to another main filter means and a comparison filter means by moving a line . 2. The rotary plate or the filter holder.
Is provided with shielding means for shielding X-rays from the X-ray source.
The filter switching means rotates or rotates the rotary plate.
Moves the filter holder linearly,
Switching means and comparison filter means to said shielding means
The computed tomography according to claim 1, wherein
Shadow device. 3. The rotating plate according to claim 1 , wherein the main filter means and the main filter means are provided.
And the comparison filter means are separate main filter means and comparison filter means.
The filter means is disposed diagonally opposite to the filter means, and
A shielding means is arranged diagonally opposite another shielding means
3. The computed tomography according to claim 2, wherein
Shadow device.