JPH0878186A - X-ray fluroscopic photographing device - Google Patents

Abstract

PURPOSE: To automatically control film density to an optimum film density by detecting a divided area off from a standard level to control a shading means, and regulating the standard value of a comparing means or the integrat ing constant of an integrating means. CONSTITUTION: The signal level every divided area of a photomultiplier 12 obtained from a video signal photographed by a TV camera 7 is compared with a standard level by a fluoroscopic processor 20 to detect the divided area off from the standard level. A liquid crystal mask 11 is interruption-controlled so that the light of the detected divided area is never incident to the tube 12, and the standard value of a comparator 15 or the integrating constant of an integrator 13 is regulated. The optical image of the light measuring area which is never shaded is converted into an electric signal by the tube 12, integrated by the integrator 13, and compared with the comparator 15, and when the integrated value reaches the standard value, an X-ray interruption signal is outputted to an X-ray high voltage device 5 to stop the exposure of X-ray. Thus, the X-ray exposing time can be automatically controlled to photograph a subject with a proper film density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray fluoroscopic imaging apparatus, and more particularly to a technique for automatically controlling an X-ray exposure amount associated with X-ray photography to an appropriate value.

[0002]

2. Description of the Related Art Conventionally, an apparatus shown in FIG. 8 is known as an X-ray fluoroscopic apparatus. This is an X-ray tube 100
The subject M is irradiated with X-rays from the subject and the transmitted X-rays from the subject M are converted into an optical image by an image intensifier (hereinafter, simply referred to as II) 101, and this optical image is TV camera 10.
Image is picked up at 2 to generate a video signal. Then, by applying this video signal to the TV monitor 103 via an amplifier or the like, a perspective image of the subject M is displayed on the TV monitor 103. The operator takes an image of the region of interest of the subject M with the image taking device 104 while observing the fluoroscopic image on the TV monitor 103.

When an X-ray image of the subject M is taken on the film F, the X-ray automatic exposure control unit 105 automatically controls the X-ray exposure amount so as to have an appropriate value as follows. II1
A part of the light image converted by 01 is led to a detector (photomal) 106 through a distributor 110 such as a prism lens and converted into an electric quantity, and the electric quantity is integrated by an integrator 107. The integrated charging voltage Vs is compared with the reference voltage Vr by the comparator 108, and when the charging voltage Vs reaches the reference voltage Vr, an X-ray cutoff signal is output to the X-ray high-voltage device 109, whereby X The line exposure is stopped. As a result, the X-ray exposure time is automatically controlled and an X-ray image of the subject M is captured on the film F with an appropriate film density.

[0004]

However, the above-mentioned conventional device has the following problems. That is, since the transmitted X-ray dose varies depending on the imaged site of the subject M, there is a difference in the time for the charging voltage Vs in the integrator 107 to reach the reference voltage Vr. Therefore, insufficient exposure or excessive exposure is caused by variations in X-ray exposure time, and an optimum film density cannot be obtained.

For example, in the case of photographing a stomach containing a contrast agent, as shown in FIG.
Since the amount of light is converted into the amount of electricity, the amount of electricity decreases when the region Aa that does not transmit X-rays containing the contrast agent increases in the photometric region Pa until the charging voltage Vs reaches the reference voltage Vr. Will take time. As a result, the X-ray exposure time becomes long, and a captured image with a high film density and a blurred outline is obtained.

On the other hand, when photographing the area around the esophagus of a subject,
Since the lung part Ab in the photometric region Pb contains air, the X-rays are hardly absorbed and are transmitted, and therefore the amount of light in the photometric region Pb increases and the charging voltage Vs reaches the reference voltage Vr quickly. become. Therefore, the X-ray exposure is completed in a short time, and the captured image has a low film density.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an X-ray fluoroscopic apparatus capable of automatically controlling the optimum film density.

[0008]

In order to achieve such an object, the present invention has the following configuration. That is, an X-ray irradiation unit that irradiates the subject with X-rays, an imaging unit that captures the transmitted X-rays from the subject on a film, and an optical image by detecting the transmitted X-rays from the subject. Convert to X
X-ray detection means, distribution means for extracting a part of the light image converted by the X-ray detection means as a photometric region, and image pickup means for picking up the light image converted by the X-ray detection means and generating a video signal. A detecting means for detecting the amount of light in the photometric region taken out by the distributing means and converting it into an electrical signal; an integrating means for integrating the electrical signals from the detecting means; and an integrated value integrated by the integrating means. By comparing with the reference value,
A comparing means for giving an X-ray blocking signal to the X-ray irradiating means when the integrated value reaches a reference value; and a light-shielding means for dividing the photometric area of the detecting means and shielding the light in each divided area,
By comparing the signal level and the reference level for each divided area of the photometric area obtained from the image signal of the image pickup means,
Based on detecting a divided area deviating from the reference level, the light shielding means is controlled so as to shield the divided area of the light shielding means corresponding to the area, and the reference value of the comparison means or the integration of the integration means is integrated. And a control means for adjusting the constant.

[0009]

According to the structure of the present invention, the following effects are obtained. X-rays are emitted from the X-ray emission means toward the subject,
The transmitted X-rays from the subject are converted into an optical image by the X-ray detection means. This light image is picked up by the image pickup means to generate a video signal, and a part of the light image is guided to the detection means as a photometric region through the distribution means and converted into an electric quantity.

At this time, the control means compares the signal level for each divided area of the detection means obtained from the video signal picked up by the image pickup means with the reference level, and detects the divided area out of the reference level. At the same time, the reference value of the comparison means or the integration constant of the integration means corresponding to the photometric area excluding the area deviating from the reference level is obtained. Then, the control means controls the light-shielding means so that the light in the divided area deviating from the reference level does not enter the detection means, and adjusts the reference value of the comparison means or the integration constant of the integration means.

The light image of the photometric area in which the divided area deviating from the reference level is shielded by the shading means is converted into an electric signal by the detecting means, and this electric signal is integrated by the integrating means. The integrated value is compared with the reference value by the comparison means, and when the integrated value reaches the reference value, the X-ray exposure signal is output to the X-ray exposure means, and the X-ray exposure is stopped. Alternatively, when the integrated value obtained by adjusting the integrating constant of the integrating means reaches a predetermined reference value, an X-ray blocking signal is output to the X-ray irradiating means, and the X-ray exposure is stopped. To be done. Therefore, the X-ray exposure time is automatically controlled, and the fluoroscopic image of the subject is photographed by the photographing means at an appropriate film density.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an X-ray fluoroscopic imaging apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 indicates a top plate on which the subject M is placed, and the X-ray tube 2 and the imaging device 3 (with the subject M placed on the top plate 1 sandwiched therebetween. The photographing means) and the II (image intensifier) 4 (X-ray detecting means) are arranged opposite to each other. An X-ray high-voltage device 5 is connected to the X-ray tube 2, and when an instruction is given to the X-ray high-voltage device 5 at a timing described later, X-ray irradiation of the subject M is stopped. The X-ray tube 2 and the X-ray high voltage device 5 correspond to the X-ray irradiation means in this invention.

A grid 6 is provided between the top plate 1 and the photographing device 3.
Are arranged, and the grid 6 prevents unnecessary scattered X-rays generated in the subject M from entering the imagers 3 and II 4.

The photographing device 3 includes a film F for photographing, a pair of intensifying screens 3a for sandwiching the film F and converting X-rays into light corresponding to the film F, and a pair of intensifying screens 3a for the film F.
And a lead plate 3c for absorbing X-rays transmitted through the film F and preventing reflection. Further, the image capturing device 3 is arranged so as to be able to move back and forth with respect to an image capturing position where X-rays are emitted.

A TV camera 8 (image pickup means) is connected to II4 via a prism 7 (distribution means), and the transmitted X-rays transmitted through the subject M are converted into an optical image by II4. Is picked up by the TV camera 8 and a video signal is generated. The generated video signal is sent to the TV monitor 9 via a fluoroscopic processor described later, and a fluoroscopic image of the subject M is displayed on the TV monitor 9.

The prism 7 sends the light image converted by II4 to the TV camera 9 and distributes a part of the light image (side light area P shown in FIG. 9) to the X-ray automatic exposure control unit 10. It is a guide.

The X-ray automatic exposure control unit 10 includes a liquid crystal mask 11 that blocks a predetermined area of the light image distributed by the prism 7.
(Light-shielding means) and a photomultiplier tube 12 (detection means) for detecting an optical image transmitted through the liquid crystal mask 11 and converting it into an electric signal.
And an integrator 13 (integrating means) for charging the electric signal converted by the photomultiplier tube 12, a reference voltage switching circuit 14 for switching the reference voltage Vr, and a charging voltage Vs and a reference voltage Vr for the integrator 13. Then, when the charging voltage Vs reaches the reference voltage Vr, a comparator 15 (comparing means) that outputs an X-ray cutoff signal to the above-mentioned X-ray high voltage device 5 and image processing and X-ray exposure time described later are controlled. And a fluoroscopy processor 20 (control means).

The liquid crystal mask 11 corresponds to a photometric area P as shown in FIG. 9 and is composed of dots obtained by dividing the area into, for example, 80 equal parts. The liquid crystal mask 11 masks each dot according to a signal from the perspective processor 20 to partially block an optical image sent to the photomultiplier tube 12.

As shown in FIG. 2, the perspective processor 20 includes an A / D converter 21 for converting a video signal picked up by the TV camera 8 into a digital signal, and a frame for storing the data of the digitized video signal. A memory 22, a D / A converter 23 for converting a digital video signal passing through the frame memory 22 into an analog signal, and a frame memory 22.
It is composed of a CPU 24 that holds the data in it and outputs a command signal to the liquid crystal mask 11 and the reference voltage switching circuit 14.

The frame memory 22 stores the video signal sent from the TV camera 8, that is, as shown in FIG.
The area corresponding to the photometric area P is a 512 × 512 pixel group, and in the processing by the CPU 24, this pixel group G is divided into 80 equal parts corresponding to the number of dots of the liquid crystal mask 11 and handled.

Next, the X-ray exposure control and the photographing operation are shown in FIG.
This will be described with reference to the flowchart in FIG.

(1) First, the imaging device 3 is retracted (the position shown by the solid line in FIG. 1), the X-ray is irradiated, and the fluoroscopic image of the subject M is displayed on the TV monitor 9, and the region of interest is displayed. Then, the operator operates the imaging switch SW to start X-ray exposure control.

Steps 1 and 2: The CPU 24 judges whether or not the switch SW is turned on. If the switch SW is turned on, the CPU 24 initializes each value described later. That is, the register for setting the address i of the divided area Ai (i = 1 to 80) in FIG. 3 is set to "1", the register for counting the number a of bright areas is set to "0", and the number b of dark areas is counted. The respective registers to be initialized are initialized to "0".

Step 3: Next, the CPU 24 outputs a hold signal to the frame memory 22 to hold the brightness data in the frame memory 22.

Steps 4 to 11: Then, 8 of the pixel group G
The sum Σvi of the data on each pixel is obtained for each area Ai divided into 0 and the sum total value vi of the data is compared with the upper limit reference level V _U. For example, if the data summation value v ₁ of the area A ₁ of the pixel group G is greater than the upper limit reference level V _U, the process proceeds to step 6, as well as one count up the contents of register for counting the number a bright area,
The dots of the liquid crystal mask 11 corresponding to the area A ₁ of the pixel group G are masked. For example, the photometric area Pb shown in FIG.
To block the partial region of the lung part Ab having a large X-ray transmission amount. Here, the upper limit reference level V _U is a value obtained by an experiment and is stored in the CPU 24 in advance. The upper limit reference level V _U may be input from an operation unit (not shown).

When the processing of the area A ₁ is completed, the address i is incremented by one and the process returns to step 4 to repeat the processing of steps 4 and 5 in the next area A ₂ .

[0028] If the data summation value v ₂ of the area A ₂ is smaller than the lower limit reference level V _L, the process proceeds to step 10, to one count up the contents of register for counting the number b of dark areas. Here, the dark area corresponds to, for example, a portion including the contrast agent in the photometric area Pa shown in FIG. 9. Since this portion hardly transmits X-rays, it is not masked by the liquid crystal mask 11.

When the processing of area A ₂ is completed,
The address i is incremented by one, the process returns to step 4, and in the next area A ₃ , the above steps 4 to 10 are performed.
Is repeated.

The area A ₃ of the data summation value v ₃ is the vertical reference level V _U, as long as it is within the range of V _L, the process proceeds to step 11. In this way, the processes of steps 4 to 10 are repeated for each area Ai from the area A ₁ to the area A ₈₀ of the pixel group G.

Step 12: Then, when it is judged that the processing of the area A ₈₀ is completed, for example, the corrected reference voltage V'r which is the correction value of the reference voltage of the comparator 15 is calculated by the following equation. V′r = V _ref − ((a · k + b) / 80) V _ref Here, V _ref is the sum of data of all areas A ₁ to A ₈₀ between the reference levels V _U and V _L. It is a reference voltage when it is at an appropriate level, and k is an experimentally obtained coefficient.

Step 13: Next, the CPU 24 outputs a reference voltage setting signal to the reference voltage switching circuit 14. As a result, the corrected reference voltage V'r obtained by the above equation is set in the reference voltage switching circuit 14.

Step 14: When the corrected reference voltage V'r is set in the reference voltage switching circuit 14, the X-ray photography is started in the following manner based on the instruction from the CPU 24. Here, the operator may start the X-ray imaging by operating the imaging switch SW.

(2) First, after stopping the X-ray irradiation of the X-ray tube 2, the photographing device 3 is moved to the photographing position shown by the chain line in FIG. Then, the crimping mechanism 3b is operated to crimp the pair of intensifying screens 3a so as to be sandwiched between the films F. In this state, the X-ray exposure start signal is output to the X-ray high voltage device 5.

(3) The X-ray high voltage device 5 applies a high voltage to the X-ray tube 2 when the X-ray irradiation start signal is given. As a result, X-rays are emitted from the X-ray tube 2 to the subject M placed on the top plate 1.

(4) The transmitted X-rays that have passed through the subject M are applied to the film F via the intensifying screen 3a to start X-ray exposure. The transmitted X-rays transmitted through the film F are converted into an optical image by II4. Then, a part of this light image is guided to the detector 12 through the prism 9 and converted into an electric quantity.
At this time, as described above, if there is an area larger than the upper limit reference level V _U , the area is masked by the liquid crystal mask 11 and blocked so as not to enter the detector 12. This electric quantity is integrated by the integrator 17. The comparator 15 compares the charged voltage V's with the correction reference voltage V'r, and when the charging voltage V's reaches the correction reference voltage V'r,
By outputting the X-ray cutoff signal to the X-ray high voltage device 5, the X-ray exposure is stopped and the X-ray image capturing on the film F is completed.

Here, the X-ray exposure control will be specifically described. When the periphery of the esophagus of the subject is imaged, as shown in FIG. 9, the lung portion Ab in the photometric region Pb has a large amount of X-ray transmission, and the charging voltage Vs thereof quickly reaches the reference voltage Vr and becomes X.
Since the line exposure is completed in a short time, the X-ray exposure time has to be lengthened.

Therefore, as described above, by removing the lung portion Ab from the photometric region Pb, the light amount is reduced and the charging time of the voltage is reduced. That is, as shown in FIG. 5, the charging voltage Vs becomes the charging voltage V's in the region excluding the lung portion. Further, since the lung portion is removed from the photometric region Pb, as described above, the reference voltage Vr is set to the corrected reference voltage V'r obtained by subtracting the voltage corresponding to the lung portion, and the charging voltage V's and the corrected reference voltage V'r. X by comparing
The line exposure time increases from T to Ta.

On the other hand, when photographing a stomach containing a contrast medium,
The portion containing the contrast agent in the photometric region Pa has almost no X-ray transmission amount, and it takes a long time for the charging voltage Vs to reach the reference voltage Vr.
X-ray exposure must be completed quickly.

The portion containing the contrast agent is not shielded by the liquid crystal mask 11 during X-ray photography, so that the charging voltage Vs does not change, but as described above, the reference voltage Vr
Is set as a correction reference voltage V'r obtained by subtracting a voltage corresponding to a portion including a contrast agent, and the charging voltage Vs and the correction reference voltage V'r are compared to shorten the X-ray exposure time from T to Tb. .

[0041] As described above, the charge voltage V's in the photometric area P 'that shields the area A out of the upper reference level V _U, the upper and lower reference level V _U, are corrected according to the number of the areas out of the V _L When the charging voltage V's reaches the correction reference voltage V'r, X is compared with the correction reference voltage V'r.
Since the line exposure is stopped, X-ray photography can be performed with an appropriate film density even if a contrast agent or an air layer exists in the photometric region.

In the above embodiment, the liquid crystal mask 11 and the frame memory 22 are each divided into 80 equal parts, but the present invention is not limited to this, and they may be divided so that they correspond to each other.

Further, in the above embodiment, the total sum ΣVi of data is obtained for each area Ai and compared with the upper and lower reference levels V _U and V _L , but the present invention is not limited to this. The average value obtained by dividing the total sum ΣVi of data by the number of pixels may be compared with the reference level per pixel.

Further, in the above embodiment, the X-ray exposure time is controlled by correcting the reference voltage, but the present invention is not limited to this. For example, as shown in FIG. A variable resistor 30 is connected to 13 and the correction reference resistance value obtained by the perspective processor 20 is set to the variable resistor 3
The CR time constant may be corrected by setting 0. That is, as shown in FIG.
By correcting the CR time constant of CR0 to CR1, the X-ray exposure time is controlled from T0 to T1 as in the case where the reference voltage of the comparator 15 is corrected.

[0045]

As is apparent from the above description, the X-ray fluoroscopic imaging apparatus of the present invention has the following effects. Comparing the integrated value of the amount of light in the photometry area that shields the area outside the reference level with the corrected reference voltage corrected according to the signal level of each part of the photometry area, or
The amount of light in the photometric area that shields the area outside the reference level is integrated using the corrected integration constant, the integrated value is compared with the reference value, and when the integrated value reaches the reference value, X-ray Since the exposure is stopped, X-ray photography can be performed with an appropriate film density even if a contrast agent or an air layer exists in the photometric area.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a perspective processor.

FIG. 3 is a schematic diagram showing a data configuration of a frame memory.

FIG. 4 is a flowchart of X-ray exposure control.

FIG. 5 is a diagram showing a relationship between a correction reference voltage and a charging voltage.

FIG. 6 is a diagram showing a main part of an apparatus according to another embodiment.

7 is a diagram showing a relationship between a corrected CR time constant and a reference voltage in the device shown in FIG.

FIG. 8 is a block diagram showing a configuration of a conventional device.

FIG. 9 is a diagram illustrating a problem of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Top plate 2 ... X-ray tube (X-ray exposure means) 3 ... Imaging device (imaging means) 4 ... II (image intensifier) (X-ray detection means) 5 ... X-ray high-voltage device (X-ray exposure means) Ejection means 7 ... Prism (distribution means) 8 ... TV camera (imaging means) 10 ... X-ray automatic exposure control section 11 ... Liquid crystal mask (light-shielding means) 12 ... Photomultiplier tube (detection means) 13 ... Integrator (integration) Means) 14 ... Reference voltage switching circuit 15 ... Comparator (comparing means) 20 ... Perspective processor (control means) 22 ... Frame memory 24 ... CPU

Claims (1)

[Claims] 1. An X-ray irradiating means for irradiating an X-ray toward a subject, an imaging means for photographing a transmitted X-ray from the subject on a film, and a transmitted X-ray from the subject are detected. X-ray detection means for converting into a light image, a distribution means for taking out a part of the light image converted by the X-ray detection means as a photometric region, and an image of the light image converted by the X-ray detection means, Image pickup means for generating a video signal, detecting means for detecting the light amount of the photometric region taken out by the distributing means and converting it into an electric signal, accumulating means for accumulating the electric signals from the detecting means, and the accumulating means. By comparing the integrated value integrated by the reference value with the integrated value, the comparison means for giving an X-ray cutoff signal to the X-ray exposure means when the integrated value reaches the reference value, and the photometric area of the detection means. And a light-shielding device that divides the light beam in each divided area, By comparing the signal level for each divided area of the photometric area obtained from the video signal of the step and the reference level, and detecting the divided area deviating from the reference level, the light-shielding means corresponding to the area is detected. An X-ray fluoroscopic imaging apparatus comprising: a control unit that controls the light-shielding unit so as to shield the divided region and adjusts a reference value of the comparison unit or an integration constant of the integration unit.