JPH06217963A - X-ray diagnostic device - Google Patents

Abstract

PURPOSE:To provide images at the optimum density even in a variety of diagnosis that causes various brightness distributions by providing a multitude of detection fields in which automatic-exposure control signals are detected, without increasing device cost and dimensions. CONSTITUTION:An X-ray diagnostic device, which irradiates an examine with X-rays from an X-ray tube 1 and forms an X-ray image by detecting the X-rays transmitted through the examine, is provided with a solid image pickup element 13 which detects visible rays, obtained by conversion from at least one part of the transmitted X-rays, and which then supplies a signal indicating the detection to an exposure-control portion 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray diagnostic apparatus having an automatic exposure control device.

[0002]

2. Description of the Related Art Conventionally, this type of X-ray diagnostic apparatus is constructed as shown in FIG.

That is, reference numeral 50 is an X-ray tube which receives high voltage from the X-ray high voltage device 51 and irradiates X-rays.
An image intensifier (II) 52 is arranged to face the X-ray tube 50 with the subject C interposed therebetween. The image intensifier 52 converts the X-rays emitted from the X-ray tube 50 and transmitted through the subject C into visible light, and outputs the visible light to the optical system 53. Image intensifier 5
An attachment / detachment mechanism 55 for attaching / detaching a film holder 54 for attaching an X-ray film is provided on the front surface of 2.

The optical system 53 comprises a condenser lens 56 and an image forming lens 57 arranged in tandem along the optical axis of the visible light, and the visible light output from the image intensifier 52 is transferred to the TV camera 58. The image is formed on the imaging surface of. The output from the TV camera 58 is sent to the TV monitor 59 and is displayed there.

Further, from the condenser lens 56 to the imaging lens 5
A mirror 60 is arranged in a part of the optical path leading to 7 with an inclination of about 45 ° with respect to the optical axis and extracts a part of visible light from the image intensifier 52. An imaging lens 61 is arranged on the optical axis of the extracted visible light,
The photo lens 6 is separated from the imaging lens 61 by a focal length.
2 is placed. The output of the photomultiplier 62 is supplied to the exposure control unit 63, where it is used as a control signal for automatic exposure control. When imaging is performed using the X-ray diagnostic apparatus configured as described above, first, the fluoroscopic mode is selected, and the imaging site and imaging timing are confirmed.

That is, a high voltage is supplied from the X-ray high voltage device 51 to the X-ray tube 50, and a relatively low dose of X-rays is continuously emitted from the X-ray tube 50 toward the subject C. This X
The line is partially absorbed while passing through the subject C, converted into visible light by the image intensifier 52, and imaged on the image pickup surface of the TV camera 58 via the optical system 53. The output from the TV camera 58 is sent to the TV monitor 59 and is displayed there. The operator confirms the imaged region while observing the image displayed on the TV monitor 59 (hereinafter referred to as “transparent image”), and gives an instruction to start the image pickup at an appropriate timing. According to this instruction, the X-ray diagnostic apparatus switches the operation mode from the fluoroscopic mode to the imaging mode.

In this photographing mode, the film holder 54 on which the X-ray film is mounted is mounted on the attachment / detachment mechanism 55. And the X-rays whose dose has been increased to prevent blurring
While passing through the subject C and exposing the X-ray film, it passes through the X-ray film, is converted into visible light by the image intensifier 52, and reaches the mirror 60 provided in the optical system 53. Visible light from the mirror 60 is photo-electrically converted by a photo lens 62 via an imaging lens 61. The output of the photomultiplier 62 is supplied to the exposure control unit 63, where it is used for automatic exposure control.

That is, the exposure control unit 63 time-integrates the output from the photomultiplier 60, and the integrated value (integrated value when the optimum film density is obtained by photographing with a uniform phantom in advance) Hereinafter referred to as "comparison value"). Then, when the integrated value reaches the comparison value, an imaging end signal is output to the X-ray high voltage device 51, and the supply of high voltage from the X-ray high voltage device 51 to the X-ray tube 50 is stopped. The X-ray exposure is stopped and the imaging is terminated. According to such automatic exposure control, a constant density can always be obtained without being affected by variable factors such as the X-ray absorption rate and X-ray intensity of the subject.

[0009]

However, in the conventional X-ray diagnostic apparatus, the mirror 60 is fixed in the optical path, and the input surface of the image intensifier 52 which is projected on the light receiving surface of the photomultiplier is used. Area (hereinafter "detection field"
The size and shape of the
The size of the detection field, its position, its shape, and so on are limited by the fact that it is determined by the focal length of 1 and that it is not possible to equip more than one photomul in order to suppress the cost increase and the size increase of the device. The number is determined at the design stage and significantly narrows the range of adjustments that can be made to obtain appropriate film densities at various postures and diagnostic sites. Therefore,
For example, the X-ray absorptivity of the stomach in contrast imaging of the stomach is greatly different from that of the surrounding tissue, and the detection signal level per unit time greatly changes depending on whether the detection field is in the stomach or in the surrounding tissue, and the imaging time Fluctuates. As a result, the density of the obtained image becomes too high or too low, which causes a problem that an image having an optimum density that can withstand diagnosis cannot be obtained.

The present invention has been made to cope with the above-mentioned circumstances, and an object thereof is to provide a large number of detection fields for detecting a control signal for automatic exposure without increasing the price or increasing the size of the apparatus. Accordingly, it is an object of the present invention to provide an X-ray diagnostic apparatus that can obtain an image with optimum density even in various diagnoses that bring various luminance distributions to an output image of an image intensifier.

[0011]

The present invention relates to an X-ray tube to an X-ray tube.
In an X-ray diagnostic apparatus that irradiates a subject with an X-ray and forms a X-ray image by detecting a transmitted X-ray that has passed through the subject, visible light obtained by converting at least a part of the transmitted X-ray is used. A solid-state image sensor is provided, which detects and supplies the detection signal to an arithmetic means for exposure control.

[0012]

According to the present invention, since the control signal is detected by the solid-state image pickup device for automatic exposure control, the video signal can be supplied to the calculation means for exposure control.

Therefore, in the calculation for the exposure control, the image signal from the solid-state image pickup device is appropriately selected, and the size of the detection field, its position, and the shape and number of the detection field are appropriately set to obtain the optimum density. You will be able to obtain a statue.

[0014]

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

That is, reference numeral 1 denotes an X-ray tube which receives a high voltage from the X-ray high-voltage device 2 and irradiates X-rays. The tensioner (I.I.) 3 is arranged to face each other. The image intensifier 3 is exposed from the X-ray tube 1 and the subject C is exposed.
The transmitted X-rays that have passed through are converted into visible light and output to the optical system 4. The object C and the image intensifier 3
An attaching / detaching mechanism 6 for attaching / detaching the film holder 5 for attaching the X-ray film is provided between the and, and enables film photographing.

The optical system 4 comprises a condenser lens 7 and an image forming lens 8.
And are arranged in tandem along the optical axis of the visible light,
The visible light output from the image intensifier 3 is imaged on the imaging surface of the TV camera 9. The output from the TV camera 9 is sent to the TV monitor 10 and is displayed there.

Further, in the optical path from the condenser lens 7 to the image forming lens 8, a mirror 11 is arranged with an inclination of about 45 ° with respect to the optical axis, and a visible light image from the image intensifier 3 is formed. Reflects the entire area. An imaging lens 12 is arranged on the optical axis of the reflected visible light, and a solid-state image sensor 13 is arranged at a focal distance from the imaging lens 12. As shown in FIG. 2, the imaging lens 12 forms an image so that the entire visible light image B from the image intensifier 3 enters the light receiving area RA of the solid-state image sensor 13.
The solid-state image pickup device 13 picks up the visible light image B and outputs a video signal I in which pixel signals are rearranged one-dimensionally.

Considering that the solid-state image pickup device 13 requires the shortest photographing time of about 10 mS, at least the scanning speed per frame (scanning speed) should be shorter than the shortest photographing time of 10 mS. High-speed solid-state image sensor that realizes automatic exposure control even with the shortest shooting time, such as AMI (Amplified Mos Imager) and CMD.
(Charge Modulation Device) is adopted. Figure 3
It is a top view of CMD of a single output line type. That is,
Reference numeral 15 is a vertical scanning circuit having a plurality of input terminals 16, and 17 is a horizontal scanning circuit having a plurality of input terminals 18. The address line is selected by the vertical scanning circuit 15 and the horizontal scanning circuit 17, and the charges accumulated in the diode 19 are output to the outside via the output line 20. This CMD is
Although not shown, the pixel structure is characterized in that the gate has a ring shape and the drain also serves as an electrical isolation region. The gate potential is uniquely determined by the amount of incident light, and speedup is easy. It has a certain property.

This CMD is suitable for speeding up because it employs electric field driving like the MOS type solid-state image pickup device.
The horizontal scanning frequency can be increased to about 80 MHz. For example, in the case of 300,000 pixel CMD, the horizontal scanning frequency is about 12 MHz at 30 frames / sec of the standard TV system, so if the horizontal scanning frequency is increased to 80 MHz, the scanning time per frame is improved to 5 mS, 20
It is possible to achieve 0 frame / sec, and it is possible to cope with short-time shooting. If a multiple output line type CMD is adopted, the number of frames per second can be further improved. Also, the number of frames per second can be increased by reducing the number of pixels in one frame. For example, if the image is captured with 10,000 pixels, the number of frames that is 30 times as large as the above can be obtained. The high-speed solid-state image pickup device is not limited to these, and may be appropriately selected and used according to cost and required short-time shooting. Returning to FIG. 1, the video signal I from the solid-state image sensor 13 is sent to the exposure control unit 14 and is used there for calculation of the exposure time. The exposure control unit 14 is configured as shown in FIG.

That is, the video signal I from the solid-state image pickup device 13 is transmitted through the television signal conversion circuit 22 to the gate circuit 2
Sent to 3. The gate circuit 23 is a gate control circuit 24.
The passage is opened and closed according to the gate signal from. Therefore, by controlling the opening / closing timing, it is possible to variously change the size, the position, the shape, and the number of the visible light region (hereinafter referred to as “detection field”) used for the automatic exposure control.

The sample hold circuit 25 receives the video signal I'passed through the gate circuit 23, holds the video signal level in accordance with the sample pulse SP from a sample pulse generator (not shown), and responds to the video signal level. Output voltage level v. The voltage level v is converted into a current value i corresponding to the level by the voltage / current conversion circuit 26, and then sent to the capacitor 27 having the capacity C to be charged there. The comparator 28 compares the charging voltage V of the capacitor 27 with the reference voltage V _vef from the reference signal generator (not shown) at any time, and at the timing when the charging voltage V reaches the reference voltage V _vef , the X-ray high voltage device. An imaging end signal EN is output to 2 to terminate the high voltage supply from the X-ray high voltage device 2 to the X-ray tube 1 and terminate the X-ray exposure. Next, the operation of this embodiment will be described.

First, an operator operates a mode selection switch of a console (not shown) to select a fluoroscopic mode, and the fluoroscopic region and radiographic timing are confirmed under the fluoroscopic mode.

That is, the X-ray high voltage device 2 to the X-ray tube 1
A high voltage for fluoroscopy is supplied to the X-ray tube 1, and a relatively low dose of X-rays is continuously emitted from the X-ray tube 1 toward the subject C. This X-ray is partially absorbed while passing through the subject C,
It is converted into visible light by the image intensifier 3 and is imaged on the image pickup surface of the TV camera 9 through the condenser lens 7 and the image forming lens 8 of the optical system 4. The output from the TV camera 9 is sent to the TV monitor 10 where it is displayed and the photographed part and the photographing timing are confirmed. The operator confirms the imaged part while observing the image displayed on the TV monitor 10 (hereinafter referred to as a “transparent image”), and switches the mode selection switch to the image pickup mode at an appropriate timing. At this time, the X-ray film is mounted on the film holder 5 and is installed between the subject C and the image intensifier 3 by the detaching mechanism 6. Then, an instruction to start shooting is given.

Then, the high voltage for imaging is supplied from the X-ray high-voltage device 2 to the X-ray tube 1 this time, and the X-ray tube 1 emits a relatively high dose of X-rays toward the subject C. Be started. This X-ray is partially absorbed while passing through the subject C and then exposed to the X-ray film, and a part of the X-ray passes through the X-ray film and passes through the image intensifier 3 as in the case of fluoroscopy. And is converted into visible light. This visible light reaches the mirror 11 via the condenser lens 7 of the optical system 4 and is reflected. The visible light reflected by the mirror 60 is
An image is formed on the light receiving surface of the solid-state image pickup device 13 by the image forming lens 12, and an image is picked up there. This video signal I is rearranged in one dimension and read at a speed of 200 frames / second,
It is supplied to the exposure control unit 14 and used there for control of automatic exposure control.

That is, the video signal I from the solid-state image pickup device 13 is converted into a TV signal by the TV signal conversion circuit 22 and then sent to the gate circuit 23, where automatic exposure control is performed according to the opening / closing operation of the gate circuit 23. Image signal I corresponding to the visible light region, that is, the detection field
´ is selected. At this time, by adjusting the gate signal from the gate control circuit 24 to control the opening / closing timing of the gate circuit 23, it is possible to variously change the size of the detection field, its position, and further its shape and number. Figure 5
Shows an example of a detection field (hatched line) obtained by this opening / closing timing. This figure shows the case where nine circular detection fields are obtained, but the size, position, shape, and number of these can be changed by controlling the opening / closing timing in accordance with the shape of the region of interest. Good.

The video signal I'is held at the video signal level by the sample and hold circuit 25 and converted into a voltage level v corresponding to the video signal level. This voltage level v
Is converted into a current value i corresponding to the level by the voltage-current conversion circuit 26, and then sent to the capacitor 27 having the capacity C to be charged there.

From time to time, the charging voltage V of the capacitor 27 is sent to the comparator 28 where it is compared with the reference voltage V _vef from the reference signal generator. Then, at the timing when the charging voltage V reaches the reference voltage V _vef , the photographing end signal EN is output from the comparator 28 to the X-ray high voltage device 2. X
The line high voltage device 2 uses the photographing end signal EN from the comparator 28.
When receiving, the high voltage supply to the X-ray tube 1 is terminated, the X-ray exposure is terminated, and the imaging is terminated.

That is, until this time, X-ray irradiation from the X-ray tube 1 is continued, and exposure of the X-ray film is continued. The reference voltage V _vef is set in advance so that an optimum image density can be obtained by, for example, photographing a uniform phantom, so that an image having the optimum density is photographed on the X-ray film.

As described above, in the present embodiment, the solid-state image pickup device is adopted as the detection means for automatic exposure, and the video signal from the solid-state image pickup device is appropriately selected by opening and closing the gate to be used for automatic exposure control. Therefore, it is possible to obtain an image of optimum density by appropriately setting the size and position of the detection field, and the shape and number.

Further, the solid-state image pickup element is cheaper in price and smaller in size than a solid-state image pickup element is attempted to approach the performance such as the number of pixels of the solid-state image pickup element by using a plurality of photomultipliers. It is possible to suppress an increase in size of the device.

In the present embodiment, the number of frames per second is closely related to the shortest photographing time and the stability of density, and the increase of the number of frames per second improves the performance of the shortest photographing time and the stability of density. Next, a second embodiment will be described. The present embodiment is different from the previous embodiment only in the exposure control unit, and the other parts are not different from FIG. 1, so only the exposure control unit will be described and the description of the other parts will be omitted. First, the principle of exposure control according to this embodiment will be described with reference to FIG.

FIG. 6 shows the relationship between the light quantity a per unit time and the shooting time t, with the vertical axis representing the light quantity a incident on the light receiving area of the solid-state image pickup device 13 and the horizontal axis representing the shooting time t. FIG. Note that τ indicates the charge accumulation time of the solid-state image sensor 13, that is, the number of frames per second. Also, S is
It is a time integrated value of the light amount a until the optimum image density is obtained (hereinafter referred to as "optimal light amount integrated value"), and is a known amount obtained in advance by a test.

Here, the output from the solid-state image sensor 13 is
Since the solid-state imaging device 13 is the integrated value of the amount of light incident on the charge storage time τ, it can be expressed by the product of the amount of light a per unit time and the charge storage time τ. Further, since S is an optimum integrated value of the light amount, it can be expressed by the product of the light amount a per unit time and the photographing time t as in the following expression (1). S = a × t (1) When this equation (1) is modified, the following equation (2) is obtained. S = a * t = (a * [tau]) * (t / [tau]) (2) From this equation (2), the shooting time t required to obtain the optimum image density is obtained by the following equation (3). be able to. t = (S × τ) × (a × τ)

As described above, since the output from the solid-state image pickup device 13 is the product of the light amount a per unit time and the charge storage time τ as described above, this output and the optimum light amount integrated value which is a known amount. From S and the charge storage time τ, the shooting time t required to obtain the optimum image density can be calculated when the output is first input from the solid-state image sensor 13.

Returning to the description, FIG. 6 is a block diagram showing the arrangement of the exposure control unit of this embodiment. In FIG. 6, 31
Is a ROM for storing a plurality of types of optimum light amount integrated values S measured in advance for each of various imaged regions, and selectively selects an appropriate optimum light amount integrated value S _n according to an imaged region selection switch from a console (not shown). Output. Reference numeral 32 denotes a ROM that stores various charge accumulation times τ, and an appropriate charge accumulation time τ _n according to an instruction from a console (not shown).
Is selectively output.

The multiplier 33 multiplies the optimum light amount integrated value S _n supplied from the ROMs 31 and 32 by the charge storage time τ _n . The divider 34 receives the multiplication result S from the multiplier 33.
_n × τ _n is input, and this is input from the solid-state image sensor 13 via the analog-digital (A / D) converter 35 a
It is divided by × τ to calculate the photographing time t required to obtain the optimum image density, and this is supplied to the timer circuit 36.

The timer circuit 36 inputs a photographing start signal ST from a console (not shown), starts subtraction operation of the photographing time t from the divider 34, so-called timer measurement, from this input timing, and the photographing time t becomes zero. When it becomes, X-ray high voltage device 2 outputs a photographing end signal EN, and X
The high voltage supply from the linear high voltage device 2 to the X-ray tube 1 is terminated, and the imaging is terminated.

According to this embodiment, not only the same effects as those of the first embodiment can be obtained, but also the following unique effects can be obtained. That is, even if an error occurs between the calculated shooting time and the actual shooting time, this difference can be utilized for density correction to correct the optimum density.

The present invention is not limited to the above-mentioned embodiments, but can be modified in various ways. For example, the X-ray dose ratio during radiography and fluoroscopy is 20 to several hundred times, so the solid-state image sensor may be saturated during radiography, but in order to solve this problem, the light-receiving region of the solid-state image sensor is An imaging lens provided on the front surface may be provided with a light amount diaphragm mechanism to limit the amount of incident light to prevent saturation, or electronic shutter technology may be used. Further, a solid-state image sensor may be adopted for the TV camera, and this output may be used as a control signal for exposure control. In this case, when seeing through, according to the standard TV system, 3
Operate the solid-state image sensor in the scan mode of 0 frame / second,
Further, it can be easily realized by switching to the high speed scanning mode at the time of photographing. Further, in the above description, the scanning range of the solid-state image sensor is described as the entire area, and the detection field is selected by opening and closing the gate. However, this scanning range may be reduced in advance according to the desired detection field. Good.

[0040]

As described above, according to the present invention, X-rays are radiated from the X-ray tube toward the subject, and transmitted X-rays transmitted through the subject are detected to form an X-ray image. In line diagnostic equipment,

It is characterized in that it comprises a solid-state image pickup device for detecting visible light obtained by converting at least a part of the transmitted X-ray and supplying the detection signal to a calculation means for exposure control. Therefore, since the control signal is detected by the solid-state image sensor for automatic exposure control, the video signal can be supplied to the calculation means for exposure control.

As a result, in the calculation for the exposure control, the image signal from the solid-state image pickup device is appropriately selected, and the size of the detection field, its position, and further the shape and the number are appropriately set.
It becomes possible to obtain an image of optimum density.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an X-ray diagnostic apparatus according to a first embodiment.

FIG. 2 is a diagram showing an image formation range of a visible light image from an image intensifier with respect to a light receiving region of the solid-state image sensor of FIG.

FIG. 3 is a plan view of a single output line type CMD as an example of a high-speed solid-state imaging device.

FIG. 4 is a block diagram of an exposure control unit.

FIG. 5 is a diagram showing an example of a detection field obtained by controlling the opening / closing timing of a gate circuit.

FIG. 6 is a diagram showing a relationship between a light amount per unit time and a photographing time for explaining the principle of exposure control of the second embodiment.

FIG. 7 is a block diagram of an exposure control unit according to the second embodiment.

FIG. 8 is a diagram showing a configuration of a conventional X-ray diagnostic apparatus.

[Explanation of Codes] 1 ... X-ray tube, 2 ... X-ray high voltage device, 3 ... Image intensifier, 4 ... Optical system, 5 ... Film holder, 6 ...
Desorption mechanism, 7 ... Focusing lens, 8, 12 ... Imaging lens, 9
… TV camera, 10… TV monitor, 11… Mirror, 13
... solid-state image sensor, 14 ... Exposure control unit.

Claims (3)

[Claims] 1. An X-ray diagnostic apparatus that irradiates an object with X-rays from an X-ray tube, detects transmitted X-rays that have passed through the object, and forms an X-ray image. An X-ray diagnostic apparatus comprising: a solid-state image sensor that detects visible light obtained by converting at least a part of the converted light and supplies the detection signal to a calculation unit for exposure control. 2. The X-ray according to claim 1, wherein the solid-state imaging device is a high-speed solid-state imaging device in which the scanning speed per frame is at least shorter than the X-ray exposure period. Diagnostic device. 3. The X-ray diagnostic apparatus according to claim 1, wherein the arithmetic means includes gate means for selecting a detection signal from the solid-state image sensor.