JPH03143430A - Apparatus for x-ray radioscopic tomography - Google Patents

Abstract

PURPOSE:To obtain an optimum X-ray photograph density corresponding to a transfer speed of tomography system without carrying out a test irradiation to a subject before taking photograph by carrying out a radiography of photographing position of the subject and setting up an optimum tomographic condition on referring to a radioscopic tomography condition table, which has been prepared beforehand based on a radioscopic condition for obtaining an image of optimum brightness and a transfer speed of the tomography system. CONSTITUTION:Before carrying out a tomography of a photographing position of a subject M, X-ray is irradiated from an X-ray tube to carry out an X-ray radioscopy of that position. An X-ray image intensifier 3 converts a transmitted X-ray through the photographing position into a light image and outputs to a pick-up face of TV camera 4. The TV camera 4 sends an image signal, which is obtained by picking up that output light image, to a CRT monitor 5 and an X-ray control unit 6. The X-ray control unit 6 compares the image signal level with an optimum brightness level, which has been specified beforehand, and adjusts an application voltage of the X-ray tube so that the two levels coincide with each other and a brightness of transmission image is kept optimum.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application Field The present invention relates to an X-ray fluoroscopic tomography apparatus that irradiates X-rays toward a subject to take a fluoroscopic image and a tomographic image of the subject. In particular, it relates to techniques for obtaining optimal X-ray imaging conditions.

B. Prior art In a normal χ-ray imaging device, automatic control of the X-ray exposure time using a phototimer is known as a method for obtaining optimal X-ray imaging conditions. Fig. 4 shows a schematic configuration of the control mechanism. shows.

X-rays emitted from the X-ray tube 1 enter an XvA image intensifier 3 via an X-ray film mechanism 2. A part of the transmitted X-ray optical image output from the X-ray image intensifier 3 is taken out by the prism 13, converted into a current value according to the brightness value of the optical image by the photomultiplier tube 14, and this current is to charge the capacitor 15. The charging voltage value of the capacitor 15 is given as one input of the comparator 16, and the comparator 16 converts the charging voltage value and the base voltage from the reference voltage generating circuit 17 into a voltage value (so that the X-ray photographic density is optimized). It compares the set (a) and when they match, sends an X-ray blocking quiping signal to the X-ray control unit 6.

In this way, the X-ray exposure time is controlled according to the X-ray dose, and the X-ray photographic density is optimized.

However, the method described above cannot be applied to
When applied to a fluoroscopic N imaging device, the following disadvantages arise. This device includes an imaging system including an X-ray tube 1 that moves in opposite directions centering on an imaging region O of a subject M, an X-ray film mechanism 2, and an X-ray image intensifier that obtains a fluoroscopic image of the subject M. It is equipped with a fluoroscopic system including a viewer 3 and an X-ray television digon (not shown). The X-ray tube 1 is configured to be able to move circularly along the body axis of the subject M, and the X-ray film mechanism 2 and the X-ray image intensifier 3 are movable horizontally along the body axis of the subject M. It is composed of

According to this device, 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-rays are focused only on the tomographic plane of the imaging site O of the subject M. χ-ray imaging is performed while moving in opposite directions. As a result, the tomographic plane of the imaging site ○, which is the center of movement, is clearly imaged because there is no shift due to the movement, and the upper and lower surfaces of the imaging site ○ are blurred due to the shift caused by the movement. In this way, a tomographic image of only the region desired to be imaged is obtained.

The X-ray exposure time in such an X-ray fluoroscopic tomography apparatus is a value determined by the moving speed and distance of the χ-ray tube 1 and the X-ray film mechanism 2, and is a value determined by the moving speed and distance of the It's not something that can be changed. That is, as shown in Fig. 5, when moving the X-ray tube l from position A to position B in order to obtain a tomographic image of the imaging site ○, if the movement of the imaging site ○ is fast, the blurring of the tomographic image will be reduced. In order to reduce this, the moving speed of the X-ray tube 1 and the X-ray film mechanism 2 must be increased. In this case, the X-ray exposure time inevitably becomes shorter and the X-ray photographic density decreases, so it is necessary to increase the energy of the irradiated X-rays to compensate for this decrease.

For this reason, conventionally, before performing X-ray tomography, test irradiation was actually performed on the subject M within an X-ray irradiation time corresponding to a preset moving speed, and the The X-ray tube voltage and tube current values were set to optimize the density of the ray film.

C1 Problems to be Solved by the Invention However, the above-mentioned conventional technology has the following problems.

In order to set the conditions for imaging, a test irradiation is performed on the subject before imaging, so there is a problem in that the subject is exposed to unnecessary radiation.

Furthermore, in order to confirm whether the X-ray photographic density is optimal, the X-ray film subjected to the test exposure is developed, but there is a problem in that extra time is required for the development.

This invention was made in view of these circumstances, and it is possible to set X-ray imaging conditions that optimize the X-ray photographic density according to the moving speed of the X-ray system without performing test exposure. It is an object of the present invention to provide an X-ray fluoroscopic tomography apparatus that can perform

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

That is, the X-ray fluoroscopic tomography IIS imaging 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 mutually opposite directions around the imaging cross section of the subject; In an X-ray fluoroscopic tomography system equipped with an X-ray image intensifier and a fluoroscopic system including an X-ray television camera, a fluoroscopic condition table showing the correspondence between multiple types of phantom thickness and each optimum fluoroscopic condition is prepared in advance. a first storage means for storing therein; and a second storage means for storing in advance a number of imaging condition tables representing the correspondence between the phantom thickness and each optimum imaging condition in a number corresponding to the moving speed of the IT layer imaging system. , an X-ray control means for driving and controlling the X-ray tube, a movement speed setting means for setting the movement speed of the IvI layer imaging system, and optimal X-ray conditions given by the X-ray control means during fluoroscopy of the subject. reads the phantom thickness according to the second storage means from the second storage means, and selects a phantom thickness corresponding to the movement speed set by the movement speed setting means from among a plurality of types of imaging condition tables stored in the second storage means. Select the same imaging condition table, use this imaging condition table to determine optimal imaging conditions corresponding to the phantom thickness read from the first storage means, and apply these to the X-ray control means. The present invention is characterized by comprising a condition setting means.

21 Effects According to the present invention, first, a radiographic region of the subject is fluoroscopically observed and the fluoroscopic conditions are adjusted so that the fluoroscopic image has the optimum brightness, and then the X-ray control means sets the optimum fluoroscopic conditions at this time as the radiographic conditions. send to means. On the other hand, the moving speed setting control means sends to the imaging condition setting means the moving speed information of the tomography system, which is set according to the movement of the imaging region, etc. The imaging condition setting means reads out the phantom thickness corresponding to the given optimal fluoroscopy conditions from the first storage means. Further, the imaging condition setting means selects from the second storage means an imaging condition table corresponding to the moving speed of the tomography system, and uses this imaging condition table to Set the shooting conditions corresponding to the thickness. These optimal imaging conditions are given to the X-ray control means to control the X-ray tube.

F. Example Embodiments of the present invention will be described below based on the drawings.

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

In this figure, the parts indicated by the same reference numerals as those in the conventional FIG. 5 are the same parts, so a description thereof will be omitted here.

In the figure, reference numeral 4 is an X-ray television camera that captures the output optical image of the X-ray image intensifier 3 and outputs a video signal, 5 is a CRT monitor that displays a fluoroscopic image of the subject M, and 6
7 is an X-ray control unit as an X-ray control means, and 7 is a moving speed control unit 10 that specifies the region to be imaged.
An operation console 8 serves as a moving speed setting means for setting the moving speed of the Ir layer imaging system, and reference numeral 8 indicates a tube voltage (hereinafter abbreviated as fluoroscopic tube voltage) applied to the X-ray tube 1 during fluoroscopy that is output from the X-ray control unit 6. ) to a digital signal, 9 is a CPU as an imaging condition setting means, 10 is a movement speed control section of the tomography system, and 11 is a fluoroscopy condition memory as a first storage means. A fluoroscopy condition table representing the correspondence between the fluoroscopy tube voltage value, which is one of the conditions, and the phantom thickness (acrylic thickness in this example) is stored. Reference numeral 12 denotes an imaging condition memory as a second storage means, which stores the tube voltage and tube current (hereinafter referred to as
As many imaging condition tables are stored as the number of settable moving speeds of the tomography system. 1
8 is a D/A converter that converts information output from the CPU 9 into an analog signal and provides it to the X-ray controller 6.

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

First, before performing tomography of the imaging site ○ of subject M,
X-rays are emitted from the radiation tube (■) and XL'AU view of the imaging area O is performed. The xvA image intensifier 3 converts the transmitted X-rays of the imaging site O into an optical image and outputs it to the imaging surface of the television camera 4. The television camera 4 captures the output light image and sends the obtained video signal to the CRT monitor 5 and the X-ray controller 6.

The X-ray control unit 6 compares the video signal level with predetermined optimal brightness level data, automatically adjusts the tube voltage of the X-ray tube 1 so that both are defeated, and adjusts the brightness of the fluoroscopic image. Keep it optimal. The fluoroscopy tube voltage value set as the optimum fluoroscopy condition is given to the A/D converter 8, converted into a digital signal, and then sent to the CPU 9.

On the other hand, when the operation console 7 specifies the imaging region ○ to the movement speed control unit 10, the movement speed control unit 10 sets the movement speed of the tomography system according to the movement of the imaging region 0, and The set moving speed information is sent to the CPU 9.

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

Next, the CPU 9 selects from the photographing condition memory 12 based on the movement speed information given from the movement speed control subsection 10.
A photographing condition table corresponding to the moving speed is selected.

An example of each imaging condition table is schematically shown in FIGS. 3(a) to 3(C). In each figure, the curve indicated by the symbol V shows the characteristic between the imaging tube voltage and the acrylic thickness, and the curve indicated by the symbol i shows the characteristic between the imaging tube current and the acrylic thickness. In the same figure, (a) shows the shooting conditions when the moving speed is V-ν1, (b) shows the shooting conditions when V=V, and (C) shows the shooting conditions when the moving speed is V-ν1.
= V, respectively, represents the shooting conditions when V,
＞Vi＞V.

There is a relationship between Since the X-ray exposure time is shortened as the moving speed increases, the initial values of curves ■ and curve I in each figure increase as the moving speed increases.

From the photographing condition table that stores photographing conditions according to the movement speed, for example, if the movement speed is v=V
, the chifur shown in fb) of the same figure is selected.

The acrylic thickness TI read from the fluoroscopic condition memory 11 is given as a read address signal to this selected table, and the imaging tube voltage value RV and imaging tube current value 1?corresponding to this acrylic thickness T1 are given. I, is read out as the optimum imaging condition.

The read-out camera tube pressure value RV and camera tube current value R
1+ is given to the X-ray control unit 6, and the tube voltage value and 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 determined, and based on the obtained tube voltage value and tube current value, Tomography of the subject M is performed.

Note that this invention can be modified as follows.

In the above-described embodiment, the TV camera 4 is provided to extract the brightness level of the output light image of the X-ray image intensifier 3, but this includes a prism I3 as shown in FIG. The photomultiplier tube 14 may be used to take out the electrons.

Further, in the embodiment, the optimum fluoroscopy conditions are automatically set by the X-ray control unit 6, but they may be set manually by the operator while viewing the image on the CRT 5.

Effects of the G0 Invention As is clear from the above explanation, the X-ray fluoroscopic imaging apparatus according to the present invention performs fluoroscopy of the imaged part of the subject, and sets the fluoroscopic conditions and tomography system to optimize the brightness of the fluoroscopic image. Since the optimal imaging conditions are set by referring to a pre-created fluoroscopic imaging condition table based on the movement speed, the movement of the tomography system can be easily Optimal radiographic density can be obtained depending on the speed.

For this reason, the amount of radiation that the subject receives before imaging is significantly less than the test exposure for X-ray imaging.
Since it is based on fluoroscopy, the amount of radiation exposure can be significantly reduced compared to conventional methods.

Furthermore, since test exposure is not performed, the time required to develop the X-ray film before imaging can be omitted, and the time spent on X-ray imaging can be shortened.

[Brief explanation of the drawing]

1 to 3 relate to one embodiment of the present invention, in which FIG. 1 is a bronch diagram showing the +11 schematic configuration of an X-ray fluoroscopic tomography apparatus, and FIG. Fig. 3 (a) is a schematic diagram showing an example of a perspective condition table stored in a
1 to c) are schematic diagrams showing an example of a photographing condition table stored in the second item 0 means. 4 and 5 relate to nine conventional examples, FIG. 4 is a block diagram showing a schematic configuration of an X-ray exposure time control mechanism using a phototimer, and FIG. 5 is a block diagram of an X-ray fluoroscopic tomography apparatus. FIG. 2 is a front view showing a schematic configuration. l...X-ray tube 2...X-ray film mechanism 3...X-ray image intensifier 6...χ-ray control unit 9...CPU 10...Movement speed control roller unit 11...fluoroscopy Condition memory 12... Shooting condition memory

Claims (1)

[Claims] (1) A tomography system that performs tomography of a subject by moving an X-ray tube and an X-ray film in opposite directions around the cross section of the subject, an X-ray image intensifier, and an X-ray television camera. In the X-ray fluoroscopic tomography apparatus, the X-ray fluoroscopic tomography apparatus includes a fluoroscopic tomography apparatus that stores in advance a fluoroscopic condition table representing a correspondence relationship between a plurality of types of phantom thicknesses and respective optimum fluoroscopic conditions; a second storage means for storing in advance imaging condition tables representing correspondence relationships between thicknesses and respective optimum imaging conditions in a number corresponding to the moving speed of the tomography system; and an X-ray tube for driving and controlling the X-ray tube.
a ray control means, a movement speed setting means for setting a movement speed of the tomography system, and a phantom thickness in accordance with the optimum X-ray conditions given by the X-ray control means during fluoroscopy of a subject. The photographing condition table is read from the means, and a photographing condition table corresponding to the moving speed set by the moving speed setting means is selected from among a plurality of types of photographing condition tables stored in the second storage means. and an imaging condition setting means for determining optimal imaging conditions corresponding to the phantom thickness read from the first storage means and applying the optimal imaging conditions to the X-ray control means. Linear fluoroscopic tomography device.