JP2722730B2 - X-ray fluoroscopy tomography system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray fluoroscopy tomography apparatus that radiates X-rays toward a subject to capture a fluoroscopic image and a tomographic image of the subject. In particular, the present invention relates to a technique for obtaining optimum X-ray imaging conditions.

B. Prior Art In a normal X-ray imaging apparatus, automatic control of an X-ray exposure time by a photo timer is known as a technique for obtaining optimum X-ray imaging conditions, and FIG. 4 shows a schematic configuration of the control mechanism. Is shown.

X-rays emitted from the X-ray tube 1 are transmitted through an X-ray film mechanism 2
Through the X-ray image intensifier 3. A part of the fluoroscopic X-ray light image output from the X-ray image intensifier 3 is taken out by the prism 13 and converted into a current value corresponding to the brightness value of the light image by the photomultiplier tube 14. Charge 15 Capacitor
The charging voltage value of 15 is provided as one input of a comparator 16,
The comparator 16 compares the charged voltage value with a reference voltage value (a value set so as to optimize the radiographic density) from the reference voltage generating circuit 17, and when they match, the X-ray control unit 6 A timing signal for shutting down is transmitted. In this way, the X-ray exposure time is controlled according to the X-ray dose to optimize the X-ray photographic density.

However, when the above-described method is applied to an X-ray fluoroscopy tomography apparatus as shown in FIG. 5, the following inconvenience occurs. The apparatus includes an imaging system including an X-ray tube 1 that moves in opposite directions about an imaging region O of a subject M, an X-ray film mechanism 2, and an X-ray image intensity for obtaining a fluoroscopic image of the subject M. It includes a fire system 3 and a fluoroscopic system including an X-ray television (not shown). The X-ray tube 1 is configured to be able to circularly move along the body axis direction of the subject M, and the X-ray film mechanism 2 and the X-ray image intensifier 3 are horizontally movable along the body axis direction of the subject M. Is configured. According to this apparatus, the X-ray tube 1 and the X-ray film mechanism 2 are moved along the body axis direction of the subject M so that the X-ray is focused only on the tomographic plane of the imaging site O of the subject M. X-ray imaging is performed while moving in the opposite directions. As a result, the tomographic plane of the imaging region O, which is the center of the movement, is sharply captured because there is no displacement due to the movement, and the upper and lower surfaces of the imaging region O are unclear because the displacement occurs due to the movement. In this way, a tomographic image of only a part to be photographed is obtained.

The X-ray exposure time in such an X-ray fluoroscopy tomography apparatus is a value determined by the moving speed and the moving distance of the X-ray tube 1 and the X-ray film mechanism 2. It is not something that can be changed.
That is, as shown in FIG. 5, when the X-ray tube 1 is moved from the position A to the position B in order to obtain a tomographic image of the imaging region O, if the movement of the imaging region O is fast, the tomographic image is blurred. X-ray tube 1 and X-ray film mechanism 2
You have to increase the moving speed. This inevitably shortens the X-ray exposure time and lowers the density of the X-ray photograph. Therefore, it is necessary to increase the energy of the irradiated X-ray in order to compensate for the decrease.

For this reason, conventionally, before performing X-ray tomography, test irradiation is actually performed toward the subject M within an X-ray irradiation time corresponding to a preset moving speed, and X-rays at that time are performed. The X-ray tube voltage and tube current value were set so that the density of the X-ray film became optimal.

C. Problems to be Solved by the Invention However, the above-described related art has the following problems.

When setting the conditions for imaging, test exposure is performed on the subject before imaging, and thus there is a problem in that unnecessary exposure is given to the subject.

Also, in order to check whether the radiographic density is optimal or not,
The X-ray film subjected to the test exposure is developed, but there is a problem that extra time is required for the development.

The present invention has been made in view of such circumstances, and sets an X-ray imaging condition in which an X-ray density is optimum according to a moving speed of an X-ray system without performing test exposure. It is an object of the present invention to provide an X-ray fluoroscopy tomography apparatus capable of performing the above.

D. Means for Solving the Problems The present invention has the following configuration to achieve the above object.

That is, an X-ray fluoroscopy tomography apparatus according to the present invention includes a tomography system that performs tomography of a subject by moving an X-ray tube and an X-ray film in opposite directions about an imaging section of the subject, In an X-ray fluoroscopy tomography apparatus having an X-ray image intensifier and a fluoroscopy system including an X-ray television camera, a fluoroscopy condition table showing correspondences between a plurality of types of phantom thicknesses and respective optimum fluoroscopy conditions is previously stored. A first storage unit for storing, and a photographing condition table indicating a correspondence relationship between the phantom thickness and each of the optimum photographing conditions in advance in a number corresponding to the moving speed of the tomographic system.
Storage means, an X-ray control means for driving and controlling the X-ray tube, a moving speed setting means for setting a moving speed of the tomographic system, and an optimum X-ray value given from the X-ray control means at the time of subject fluoroscopy. A phantom thickness corresponding to a line condition is read from the first storage means, and a moving speed set by the moving speed setting means from a plurality of types of photographing condition tables stored in the second storage means. Is selected, and using this imaging condition table, an optimal imaging condition corresponding to the phantom thickness read out from the first storage means is determined, and is given to the X-ray control means. A photographing condition setting means.

E. Operation According to the present invention, first, fluoroscopy is performed on the imaging region of the subject, and the fluoroscopic conditions are adjusted so that the fluoroscopic image has optimal brightness. Send to condition setting means. On the other hand, the moving speed setting control means sends tomographic condition setting means the moving speed information of the tomographic system set according to the movement of the imaging part. The imaging condition setting means reads the phantom thickness corresponding to the given optimum fluoroscopic condition from the first storage means. Further, the photographing condition setting means selects a photographing condition table corresponding to the moving speed of the tomographic photographing system from the second storage, and uses this photographing condition table to read the phantom thickness read out from the first storage means. Set the shooting conditions corresponding to The optimum imaging conditions are given to the X-ray control means, and the X-ray tube is controlled.

F. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an X-ray fluoroscopy tomography apparatus according to the present invention.

In this figure, the parts denoted by the same reference numerals as those in FIG. 5 according to the related art are the same parts, and the description thereof is omitted here.

In the figure, reference numeral 4 denotes an X-ray television camera that captures an output light image of the X-ray image intensifier 3 and outputs a video signal, 5 denotes a CRT monitor that displays a fluoroscopic image of the subject M, 6
X is an X-ray control unit as X-ray control means, 7 is an operation console as moving speed setting means for setting the moving speed of the tomographic system by designating the imaging site to the moving speed control unit 10, and 8 is Tube voltage applied to the X-ray tube 1 during fluoroscopy output from the X-ray control unit 6 (hereinafter abbreviated as fluoroscopic tube voltage)
An A / D converter for converting the image data into a digital signal; 9, a CPU as imaging condition setting means; 10, a moving speed control unit of a tomography system; 11, a fluoroscopic condition memory as first storage means; A fluoroscopy condition table is stored which shows the correspondence between the fluoroscopy tube voltage value and the phantom thickness (acrylic thickness in this example). Numeral 12 denotes an imaging condition memory as a second storage means, which stores the X-ray tube 1 during tomography.
The imaging condition tables showing the correspondence between the tube voltage and tube current (hereinafter abbreviated as imaging tube voltage and imaging tube current) and the acrylic thickness are stored as many as the number of settable moving speeds of the tomography system. Have been. Reference numeral 18 denotes a D / A converter that converts information output from the CPU 9 into an analog signal and provides the analog signal to the X-ray controller 6.

 Next, the operation of the above-described embodiment apparatus will be described.

First, before performing tomography of the imaging site O of the subject M,
X-rays are emitted from the X-ray tube 1 and X-ray fluoroscopy of the imaging site O is performed. The X-ray image intensifier 3 is a part to be imaged O
Is converted into an optical image and output to the imaging surface of the television camera 4. The television camera 4 sends a video signal obtained by capturing the output light image to the CRT monitor 5 and the X-ray controller 6. The X-ray control unit 6 compares the video signal level with predetermined optimum luminance level data, automatically adjusts the tube voltage of the X-ray tube 1 so that the two coincide, and optimizes the brightness of the fluoroscopic image. To keep. The fluoroscopic tube voltage value set as the optimal fluoroscopic condition is applied to the A / D converter 8, converted into a digital signal, and sent to the CPU 9.

On the other hand, when the imaging site O is designated from the console 7 to the moving speed control unit 10, the moving speed control unit 10 sets the moving speed of the tomographic system according to the movement of the imaging site O, The set moving speed information is sent to the CPU 9.

The CPU 9 supplies the fluoroscopic tube voltage value provided from the X-ray control unit 6 to the fluoroscopic condition memory 11 as an address signal, and reads out the acrylic thickness stored in correspondence with the fluoroscopic tube voltage. An example of information stored in the fluoroscopic condition memory 11 is schematically shown in FIG. In this figure, for example, fluoroscopy tube voltage value if a FV _1, acrylic thickness T ₁ is read out corresponding thereto. The acrylic thickness T ₁ corresponds to the thickness of the subject M that is a photographing target.

Next, the CPU 9 selects a photographing condition table corresponding to the moving speed from the photographing condition memory 12 based on the moving speed information given from the moving speed control unit 10. An example of each photographing condition table is schematically shown in FIGS. 3 (a) to (c). In each figure, the curve indicated by the symbol v indicates the characteristic between the imaging tube voltage and the acrylic thickness, and the curve indicated by the symbol i indicates the characteristic between the imaging tube current and the acrylic thickness. The figure (a) shooting conditions when the moving speed is V = V _1, (b)
The imaging conditions at the time of V = V _i, (c) represents respectively a photographing condition when the V = V _n, a relationship of _{V 1> V i> V n} . When the moving speed is increased, the X-ray exposure time is shortened. Therefore, the initial values of the curves v and i in each figure increase as the moving speed increases. Such image capturing conditions depending on the moving speed from the imaging condition table that stores, for example, when the moving speed was V = V _i, the table shown in (b) is elected.

As the read address signal for the selected table, the acrylic thickness read from the fluoroscopic condition memory 11 is used.
Giving T _1, imaging tube voltage value corresponding to the acrylic thickness T ₁
RV ₁ and the imaging tube current value RI ₁ are read out as optimal imaging conditions.

The read tube voltage RV ₁ and tube current RI ₁ read out
Is supplied to the X-ray controller 6, and the tube voltage value and the tube current value of the X-ray tube 1 are set to these values.

In this way, the X-ray exposure time determined by the moving speed and the optimal imaging tube voltage value and imaging tube current value according to the thickness of the subject M are obtained. The tomography of the subject M is performed.

The present invention can be modified as follows.

In the above-described embodiment, the television camera 4 is provided to take out the luminance level of the output light image of the X-ray image intensifier 3, but this configuration includes the prism 13 as shown in FIG. The light may be extracted using the photomultiplier tube 14.

In the embodiment, the X-ray controller 6 automatically sets the optimum fluoroscopic conditions. However, this may be manually set by the operator while viewing the image on the CRT 5.

G. Effects of the Invention As is clear from the above description, the X-ray fluoroscopic apparatus according to the present invention performs fluoroscopy of the imaging region of the subject, and sets the fluoroscopy conditions and the tomographic system that optimize the brightness of the fluoroscopic image. The optimal imaging conditions are set by referring to the fluoroscopic imaging condition table created in advance based on the moving speed of the tomography system without performing test exposure on the subject before imaging. An optimum radiographic density according to the speed can be obtained.

Therefore, the amount of exposure received by the subject before imaging is based on X-ray fluoroscopy, which is a much smaller amount of X-ray than test exposure for X-ray imaging. Can be reduced.

Further, since the test exposure is not performed, the time for developing the X-ray film before imaging can be omitted, and the time spent for X-ray imaging can be reduced.

[Brief description of the drawings]

1 to 3 relate to an embodiment of the present invention, FIG. 1 is a block diagram showing a schematic configuration of an X-ray fluoroscopy tomography apparatus, and FIG. 2 is stored in a first storage means. FIGS. 3 (a) to 3 (c) are schematic diagrams showing an example of the imaging condition table stored in the second storage means. 4 and 5 relate to a conventional example, FIG. 4 is a block diagram showing a schematic configuration of an X-ray exposure time control mechanism using a photo timer, and FIG. 5 is a schematic diagram of an X-ray fluoroscopic tomography apparatus. It is the front view which showed the structure. 1 X-ray tube 2 X-ray film mechanism 3 X-ray image intensifier 6 X-ray control unit 9 CPU 10 Moving speed control unit 11 Transparent condition memory 12 Photographing Condition memory

Claims (1)

(57) [Claims] 1. A tomography system for performing tomography of an object by moving an X-ray tube and an X-ray film in opposite directions about an imaging section of the object, an X-ray image intensifier, and an X-ray In an X-ray fluoroscopic tomography apparatus including a fluoroscopic system including a television camera, a first storage unit that stores in advance a fluoroscopic condition table representing a correspondence relationship between a plurality of types of phantom thicknesses and respective optimal fluoroscopic conditions, A second storage unit for storing in advance an imaging condition table representing a correspondence relationship between the phantom thickness and each of the optimal imaging conditions in a number corresponding to the moving speed of the tomographic imaging system; and driving control of the X-ray tube. An X-ray control unit, a moving speed setting unit for setting a moving speed of the tomography system, and a phantom thickness according to an optimum X-ray condition given from the X-ray control unit during the fluoroscopy of the subject. Record Means for selecting a photographing condition table corresponding to the moving speed set by the moving speed setting means from a plurality of kinds of photographing condition tables stored in the second storage means. And an imaging condition setting means for determining an optimum imaging condition corresponding to the phantom thickness read out from the first storage means, and providing the same to the X-ray control means. Fluoroscopic tomography equipment.