JPH0634399B2 - X-ray automatic exposure control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an X-ray automatic exposure control device, and more particularly to an X-ray automatic exposure control system for appropriately controlling X-ray conditions during fluoroscopy or radiography in X-ray diagnosis. The present invention relates to an automatic exposure control device.

[Background technology]

The X-ray automatic exposure control device used for X-ray diagnosis has been devised and improved for a long time, but it is difficult to set appropriate X-ray conditions due to the influence of the contrast agent or bone when passing through the subject, and it is especially frequently used. There is a strong demand for the improvement in the digestive system diagnosis that has been performed. As one of the ideas, Japanese Patent Laid-Open No. 57-8869
There is an X-ray automatic exposure control device described in Japanese Patent Application No. 8 (Japanese Patent Application No. 55-166290).

In such an X-ray automatic exposure control device, the tube voltage is changed from approximately 50 KV to 110 KV in order to obtain an appropriate X-ray exposure condition during fluoroscopy or photographing of people of various physiques and constitutions. Then, in order to correct the variation in the blackening degree due to the subject thickness characteristic and the tube voltage characteristic which are the characteristics of the automatic X-ray exposure, the X-ray dose at a predetermined position in the X-ray irradiation field is detected by a plurality of detectors, Measures are taken to exclude and correct the output of the detectors whose respective outputs are underexposed and overexposed.

However, in the diagnosis of the digestive system, for diagnostic purposes,
When various fluoroscopic methods such as double contrast method and compression method are taken, the conventional means for determining whether the output of each detector is underexposed or overexposed is a condition in the various fluoroscopic methods. However, it is not sufficient to obtain the desired proper X-ray conditions.

[Object of the Invention]

The present invention has been made in order to improve the problems of the above-mentioned conventional apparatus, and an object thereof is to provide an X-ray automatic exposure control apparatus used for X-ray diagnosis in which fluoroscopy or radiography is performed. An object of the present invention is to provide an X-ray automatic exposure control device that reduces influences of agents, imaging methods, and the like and always controls appropriate X-ray conditions.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[Outline of Invention]

In order to achieve such an object, the present invention basically disperses the X-rays from the X-ray tube in an area corresponding to an area where an X-ray image obtained by transmitting X-rays to the subject is scattered. Provided with a plurality of detectors, the data defining the appropriate region of the output average value of each detector for the body thickness of the subject, each output from the detector only in the appropriate region of the data In an X-ray automatic exposure control device that controls the tube voltage of the X-ray tube based on the output, in addition to the data, an appropriate region of the tube voltage corresponding to the body thickness of the subject is added, and each appropriate A range within the upper limit value and the lower limit value determined by the larger value from the region is defined as a new proper region, and the tube voltage of the X-ray tube is controlled by using each output of the detector in the new proper region. It is characterized by.

The X-ray automatic exposure control device configured in this way is
The control of the tube voltage of the wire tube is based not only on the data that defines the appropriate region of the output average value of each detector with respect to the body thickness of the subject, but also on that data, it corresponds to the body thickness of the subject. The proper range of the tube voltage is taken into consideration.

Then, the range within the upper limit value and the lower limit value determined by the larger value from each appropriate region is used as a new appropriate region.

By doing so, it becomes possible to properly control the automatic X-ray exposure.

That is, for example, in the imaging of a stomach into which barium is injected, most of the scattered detectors detect barium depending on the arrangement state of the stomach, and as a result,
The average value of the output of each detector is extremely small.

Then, as long as the average value of the output of each detector is within the appropriate range of the average output value of each detector with respect to the body thickness of the subject, each voltage tends to increase, and the barium The output value of the detector positioned in the non-existing region becomes extremely large and is excluded from the target of X-ray control.

From this, the present invention further takes into account the proper region of the tube voltage corresponding to the body thickness of the subject. In other words, the above-mentioned harmful effects caused by the tube voltage controlled by the average value of the output values from the detector becoming unnecessarily small or becoming unnecessarily large should be eliminated. Is.

From the above, the present invention enables more appropriate automatic X-ray exposure control.

[Structure of Invention]

Hereinafter, the configuration of the present invention will be described together with examples.

In all the drawings for explaining the embodiments, parts having the same function are designated by the same reference numerals, and repeated description thereof will be omitted.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment in which the present invention is applied to an X-ray automatic exposure control device.

In FIG. 1, 1 is an X-ray tube device, 2 is a subject, and 3 is an X-ray tube device.
An X-ray image recording medium such as an X-ray film and an image intensifier (hereinafter, referred to as II.
Say. ) 5 is a lens system, 6 is a spectroscope such as a prism for dispersing the image of the secondary phosphor screen of II4, 7 is an X-ray television camera, 8 is a condenser lens, 9 is an X-ray high voltage device, 10
Is an opto-electrical signal conversion circuit in which a plurality of detectors are arranged at positions matching the diagnostic purpose in the X-ray irradiation field.

A specific configuration of one detector of the optical-electrical signal conversion circuit 10 is shown in FIG.

In FIG. 2, 10A is a silicon photodiode, which outputs a photocurrent according to the light condensed by the condenser lens 8. However, since the output photocurrent is a very weak signal current, an amplifier 10 ¹⁰ depending on 10B and resistance 10C
It is amplified 10 ¹² times and output from the output terminal 10D. The output terminal 10D is connected to the next-stage circuit for each detector.

As shown in FIG. 1, reference numeral 11 denotes a gate circuit for controlling stop / passage of electric signals output from the respective detectors. As shown in FIG. 3, input terminal groups 11A to 11C are provided.
A signal is input from the output terminal 10D of each detector shown in FIG. This input signal is output to the output terminals 11V to 11X via the analog switches 11D to 11F.
It is designed to be output to. Analog switch 11
D to 11F are changed by the signal from the latch circuit 11Y.
Its on / off (opening / closing) is controlled. The signal of the signal line that is turned on among these analog switches 11D to 11F is output from the output terminal groups 11V to 11X. As the latch circuit 11Y, for example, a commercially available semiconductor integrated circuit (IC) is used. The latch circuit 1
1Y receives the OR signal 11Q-1Q by the latch signal 24.
It holds the state of 1S.

11G to 11M are comparators, and comparators 11G to 11J
Is a signal for comparing the overlevel signal from the overlevel signal generation circuit 16 (a signal generated by a ₁ and b ₁ shown in FIG. 8 and input to the input terminal 11T) with the output voltage of each detector. And outputs a signal to turn off the analog switch of the detector that exceeds the overlevel.

Further, the comparators 11G to 11J are provided with an under level signal from the under level signal generation circuit 16 '(a signal generated by a ₂ and b ₂ shown in FIG. 8 and input to the input terminal 11U) and each detector. It is for comparing with the output voltage of. Then, the inverter circuits 11N to 11P are connected to the outputs of the comparators 11K to 11M so as to output a signal for turning off the analog switch of the detector outputting a signal lower than the under level. .

Reference numeral 12 is an addition circuit for signals that have passed through the gate circuit 11, and reference numeral 13 is a signal averaging circuit for obtaining an average value of signals of the entire detector. As shown in FIG. 4, the signal averaging circuit 13 outputs the output voltage V of each detector as shown in FIG.
_{1 to} V _n are received at the input terminals 13A to 13C, and the resistance group 13
D to 13F for addition and resistance groups 13G to 13J
The output voltage V ₀ is output from the output terminal 13L by dividing by.

Here, the resistance groups 13D to 13F and the resistance groups 13G to 13J.
Have the same resistance value, and the amplifier circuit 13K
The following equation (1) is established from the principle of the amplifier circuit.

In FIG. 1, the adder circuit 12 and the divider circuit 17
For the convenience of explanation, the blocks are separated, but the same principle as that of the signal averaging circuit 13L is used.

Reference numerals 14 and 15 are rejection level output circuits. As shown in FIG. 5, the concrete structure of the rejection level output circuit 14 is composed of an amplifier circuit using an operational amplifier, and the input terminal 14A has an output voltage from the output terminal 13L shown in FIG. V ₀ is input and this voltage is applied to resistor 1
By properly selecting 4B and 14E, the voltage is amplified to a required voltage and the output voltage a ₁ is output to the output terminal 14G. The resistors 14C and 14D are circuits for translating the straight line a ₁ in order to obtain a voltage a ₁ that matches the purpose (in order to have the relationship of the straight line a _{1 in} FIG. 8). The slope of the straight line a ₁ of this constant is the resistance 14B,
It can be changed by making the value of 14E appropriate.

By forming the resistors 14H, 14J, 14L and the operational amplifier 14M in the same manner as the above circuit, the constant of the straight line a ₂ is obtained.

The rejection level output circuit 15 can also be realized by a configuration similar to that of the circuit shown in FIG.
A signal proportional to the tube voltage from the X-ray high voltage device 9 may be input to 4A and each constant may be set so that the straight lines b ₁ and b ₂ are obtained.

The specific structure of the overlevel signal generating circuit 16 for generating the overlevel signal is as shown in FIG.
Since the output voltages of the rejection level output circuits 14 and 15 are input to the input terminals 16A and 16B, respectively,
The diodes 16E and 16F are adapted to output the larger voltage value from the output terminal 16G.

The under level signal generation circuit 16 'also has the same circuit configuration as the over level signal generation circuit 16.

As shown in FIG. 1, reference numeral 17 is a divider circuit for obtaining an average value, and the output voltage is connected to a contact 18 which is turned on (closed) during fluoroscopy and a contact 19 which is turned on (closed) during photographing. 20
Is a fluoroscopy X-ray condition setting circuit that determines fluoroscopy X-ray conditions that optimize the amount of light to the X-ray television camera 7 during fluoroscopy, and generally performs control to vary the fluoroscopy tube voltage. Reference numeral 21 is an integrating circuit for the photo timer, and 22 is a comparing circuit. Reference numeral 23 is a signal for correcting the subject thickness and the tube voltage.

Reference numeral 24 is a latch signal which holds the state of the date circuit at that time at the end of the fluoroscopy until the fluoroscopy starts again.

FIG. 7 shows an example of the detector arrangement when used in a fire extinguisher. Reference numeral 25 is the secondary fluorescent screen of II, 26 is the shape of the stomach projected on the screen, and the shaded area shows the portion filled with the contrast agent. 27 is a silicon photodiode group arranged for the digestive organs.

Next, the operation of the X-ray automatic control system of this embodiment will be briefly described.

In the apparatus shown in FIG. 1, fluoroscopy is always performed prior to photographing, and the detector of the optical-electrical signal conversion circuit 10 is used to determine fluoroscopy conditions for obtaining proper brightness of the X-ray television. The output signal is used.

In the case of the image shown in FIG. 7, when the exposure amount of each detector is judged to be insufficient or excessive, when compared with a fixed reference value, the output of the detector in the portion without the contrast agent is appropriate. Under the fluoroscopic condition, the output of the detector is excluded due to insufficient exposure, and under the fluoroscopic condition where the output of the detector with the contrast agent is appropriate, the detectors are excluded due to overexposure. It stabilizes at. This cannot achieve the purpose.

FIG. 8 is a diagram showing the subject thickness or tube voltage-comparison voltage and signal voltage characteristics, and the shaded area is the region where the signal of the detector is judged to be appropriate.

In the present embodiment, the image shown in FIG. 7 will be described. In this case, the average signal output from the signal averaging circuit 13 shows a high value because the number of detectors in the portion without the contrast agent is large.
Accordingly, the rejection level of the detector increases. If such control is performed, the signal of the detector in the portion where the contrast agent is present is likely to be excluded, and it is possible to avoid stabilizing the signal of the detector.

FIG. 9 is a diagram showing the relationship between the image and the detector in the case of the compression method. This method diagnoses while squeezing a limited part of the stomach, and most detectors are located in the part where the contrast agent is present. In this case, the tube voltage for fluoroscopy is set to a higher value than in the case shown in FIG. 7, so that in the conventional apparatus, the detector was excluded and the X-ray condition of the portion to be diagnosed was not proper.

However, in this embodiment, as shown in FIG. 8, the rejection level changes to b ₁ and b ₂ as the tube voltage increases, so that the detector in the part without the contrast agent becomes appropriate, and the contrast agent The detectors with ,,,, are easily excluded. As a result, it is possible to reduce the influence of the body thickness of the subject, the contrast agent, the imaging method, and the like.

Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

For example, although the above embodiment has been illustrated and described in the digestive system diagnosis, this method can be applied to X-ray automatic exposure for other X-ray diagnosis. As for the detector, the method of collecting light from the secondary fluorescent screen of II has been described, but a method of providing a detector for converting X-rays into light may be provided on the front surface or the rear surface of the film.

〔effect〕

As described above, according to the present invention, the X-ray dose at a predetermined position in the X-ray irradiation field is detected by a plurality of detectors, and the signal A proportional to the average signal of the outputs of these detectors is generated. However, a signal B proportional to the tube voltage at the time of fluoroscopy or radiography is generated, and each output signal of the detector outside the range set based on these signals A and B is independently excluded and excluded. Since the output signals of the remaining detectors are averaged, and the X-ray conditions are controlled appropriately by this averaged signal, the X-ray conditions of the portion to be diagnosed can be controlled appropriately, and the body thickness of the subject, It is possible to reduce the influence of the contrast agent, the photographing method, and the like. Further, this can improve the efficiency of X-ray diagnosis.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of one embodiment in which the present invention is applied to an X-ray automatic exposure control device, and FIG. 2 is a concrete example of one detector of the optical-electrical signal conversion circuit of FIG. 3 is a circuit diagram showing a specific configuration of the gate circuit of FIG. 1. FIG. 4 is a circuit diagram showing a specific configuration of the signal averaging circuit of FIG. 5 and 5 are circuit diagrams showing a specific configuration of the rejection level output circuit of FIG. 1, and FIG. 6 is a circuit showing a specific configuration of an overlevel signal generating circuit for generating an overlevel signal. Fig. 7 is a diagram showing a positional relationship between a gastric shape and a detector arranged in the filling method, Fig. 8 is a diagram showing subject thickness or tube voltage-comparative voltage and signal voltage characteristics, and Fig. 9 is FIG. 6 is a diagram showing a relationship between an image and a detector in the case of the compression method. In the figure, 1 ... X-ray tube device, 2 ... Subject, 3 ... Recording medium, 4 ... II, 5 ... Lens system, 6 ... Spectroscope, 7 ...
... X-ray television camera, 8 ... Condensing lens, 9 ... X-ray high-voltage device, 10 ... Optical-electrical signal conversion circuit, 11 ... Gate circuit, 12 ... Addition circuit, 13 ... Signal averaging Circuits, 14, 15 ... Rejection level output circuit, 1
6 ... Over-level signal generation circuit, 16 '... Under-level signal generation circuit, 17 ... Division circuit, 18 ... Contact that turns on during see-through, 19 ... Contact that turns on during shooting, 20
...... Fluoroscopic X-ray condition setting circuit, 21 ... Integrating circuit, 22 ...
… Comparison circuit.

Claims (1)

[Claims] 1. A plurality of detectors scatteredly disposed in a region corresponding to a region where an X-ray image obtained by transmitting X-rays from an X-ray tube to a subject, and a body thickness of the subject. The X-ray tube is controlled based on the output of each of the detectors, which has data defining an appropriate region of the output average value, and each output from the detector is in the appropriate region of the data. In the X-ray automatic exposure control device, in addition to the data, an appropriate region of the tube voltage corresponding to the body thickness of the subject is added, and within the upper and lower limit values determined by the larger value from each appropriate region. Is defined as a new proper region, and X is calculated by using each output of the detector in the new proper region.
An X-ray automatic exposure control device characterized by controlling the tube voltage of a ray tube.