JPS6237898A - Automatic exposure control device for x-ray - Google Patents

Abstract

PURPOSE:To reduce the effect of the body thickness and such of the radiographed subject so as to control the exposure properly by rejecting the each output of the detector independently based on the mean signal of several detectors of the X-ray dose and the tube voltage signal at the fluoroscopy. CONSTITUTION:The output of the photo-electric signal conversion circuit 10 provided with several detectors on the suitable locations for the diagnostic purpose in the X-ray field is transferred to the signal averaging circuit 13 to obtain the signal A proportional to the mean output signal of the all detectors. The signal B proportional to the tube voltage at the fluoroscopy or the radiography is obtained from the X-ray high voltage generator 9. And by controlling the circuit 11, each output of the detectors cut of the specified range based on the signal and B is rejected independently, and the residual outputs of the detectors are averaged in the dividing circuit 17, and with which the X-ray conditions are controlled. Therefore the effect of the body thickness of the subject, the contrast agent, and the radiographic method and so on can be reduced to control properly the X-ray conditions of the area of diagnostic interest.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an X-ray automatic exposure control device, and particularly to an X-ray automatic exposure control device suitable for appropriately controlling X-ray conditions during fluoroscopy or imaging in X-ray diagnosis. This invention relates to an automatic exposure control device.

[Background technology]

Although automatic X-ray exposure control devices used in X-ray diagnosis have been devised and improved over the years, it is difficult to set appropriate X-ray conditions due to the influence of contrast agents and bones when the object is transmitted through, making it particularly difficult to use frequently. There is a strong demand for improvements in gastrointestinal diagnosis. As one of the devices, JP-A-57-8869
There is an X-ray automatic exposure control device described in Japanese Patent Application No. 55-166290.

In such an automatic X-ray exposure control device, the tube voltage is varied from approximately 50 KV to 10 KV in order to obtain appropriate X-ray exposure conditions during fluoroscopy or imaging of people of various physiques and constitutions. In order to correct variations in the degree of darkening due to subject thickness characteristics and tube voltage characteristics, which are characteristics of X-ray automatic exposure, the X-ray dose at a predetermined position within the X-ray irradiation field is detected using multiple detectors. A means is required for excluding and correcting the outputs of the detectors whose outputs are underexposed or overexposed.

However, in gastrointestinal diagnosis, for diagnostic purposes,
When various fluoroscopic imaging methods such as a double contrast imaging method and a compression method are used; the means for determining whether the output of each of the conventional detectors is underexposed or overexposed, Since the method did not take this into account, it was insufficient to obtain the desired appropriate X-ray conditions.

[Purpose of the invention]

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

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

[Summary of the invention]

Outline of typical inventions disclosed in this application is as follows.

That is, x and wti at predetermined positions within the X-ray irradiation field are detected by multiple detectors, and a signal A proportional to the average signal of the outputs of all these detectors is generated, and the tube voltage during fluoroscopy or imaging is Generates a signal B proportional to .

Based on these signals A and B, each of the output signals of the detector is independently excluded, the remaining output signals of the detector after exclusion are averaged, and the X-ray conditions are adjusted to the appropriate level using this averaged signal. This is an automatic X-ray exposure control device characterized by controlling the exposure to

[Structure of the invention]

, Hereinafter, the configuration of the present invention will be explained along with examples.

It should be noted that throughout the description of the embodiments, parts having the same functions are denoted by the same reference numerals, and repeated explanations 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 automatic X-ray exposure control device.

In Figure 1, 1 is the X-ray tube device, 2 is the subject, and 3 is the X-ray tube device.
4 is an image intensifier that converts X-rays into light (hereinafter referred to as 1.1.
That's what it means. ), 5 is a lens system, 6 is a spectrometer such as a prism for dispersing the image of the secondary phosphor screen in 1.1.4, 7 is an X-ray television camera, 8 is a condensing lens, 9 is an X-ray height voltage equipment,
Reference numeral 10 denotes an optical-electrical signal conversion circuit in which a plurality of detectors are arranged at positions within the X-ray irradiation field that meet the purpose of diagnosis.

A specific configuration of one detector of this optical-electrical signal conversion circuit 10 is shown in 2v4.

In FIG. 2, IOA is a silicon photodiode that outputs a photocurrent corresponding to the light focused by the condensing lens 8, but since the output photocurrent is a very weak signal current, the amplifier 10B.

It is amplified by 1o1fl to 1012 times by resistor 10C,
The output terminal 10D is connected to the next stage circuit for each detector.

As shown in FIG. 1, 11 is a gate circuit for controlling the stopping and passing of electrical signals output from each detector, and as shown in FIG.
A signal is input from the output terminal 10D of each detector shown in FIG. 2.

This input signal is applied to analog switches IID to II.
It is designed to be outputted to the output terminal 11V-11X via F. The on/off (opening/closing) of the analog switches 11D to 11F is controlled by signals from the latch circuit 11Y. Signals from the turned-on signal lines of these analog switches IID to IIF are output from output terminal groups 11V to IIX. The latch circuit 11Y is, for example, a commercially available semiconductor integrated circuit (I
C) is used. The latch circuit 11Y receives the latch signal 2
4 holds the states of the OR circuits 11Q to IIS.

110 to IIM are comparators, and comparators 11G to IIJ
is a signal for comparing the overlevel signal from the overlevel signal generation circuit 16 (a signal generated by the AS and B signals shown in FIG. 8, and input to the input terminal 11T) and the output voltage of each detector. and outputs a signal that turns off the analog switch of the detector that exceeds the over level.

Comparators 11G to 11J also output an under level signal from an under level signal generating circuit 16' (a signal generated by a2 and b2 shown in FIG. 8, which is input to the input terminal 11U) and the output of each detector. This is for comparison with the voltage. An inverter circuit lIN~11P is connected to the output of the comparator 11 ~IIM, and outputs a signal that turns off the analog switch of the detector that outputs a signal lower than the under level. There is.

12 is an addition circuit for the signals that have passed through the gate circuit 11, and 13 is a signal averaging circuit that calculates the average value of the signals of the entire detector. As shown in FIG. 4, this signal averaging circuit 13 calculates the output voltage of each detector as shown in FIG.
1 to Vn are received at input terminals 13A to 13C, and resistor group 13
D to 13F, and resistor groups 13G to 13J
The output voltage V from the output terminal 13L is obtained by dividing by . It is designed to output .

Here, resistance groups 13D to 13F and resistance groups 13G to 13J
have the same resistance value, and the following equation (1) holds true for the amplifier circuit 13 based on the principle of the amplifier circuit.

Vx+V2- ・ ・ ・ +V port vo=□... (1) In addition, in FIG. 1, the addition circuit 12 and the division circuit 17
Although these are shown as separate blocks for convenience of explanation, they utilize the same principle as the signal averaging circuit 13L.

14.15 This is a direction level output circuit. The specific configuration of the rejection level output circuit 14 is, as shown in FIG. Vo is input, and this voltage is applied to resistor 1
By appropriately selecting voltages 4B and 14E, the voltage is amplified to the required voltage and the output voltage a1 is output to the output terminal 14G. The resistors 14C and 14D are connected to a straight line a in order to obtain a voltage al that meets the purpose (to have a relationship such as the straight line a in FIG. 8).

This is a circuit that moves the . The slope of this constant straight line a1 can be changed by appropriate values of the resistors 14B and 14E.

The constant of the straight line a2 is obtained by configuring the circuit similarly to the above circuit using resistors 14H, 14J, 14L and an operational amplifier 14M.

The rejection level output circuit 15 can also be realized with a configuration similar to 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 as to obtain straight lines b1 and b2.

The specific configuration of the overlevel signal generation circuit 16 that generates 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,
Diode 16E.

16F, the larger value of the voltage is the output terminal 16G
It is designed to be output from.

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

As shown in FIG. 1, 17 is a dividing circuit for obtaining an average value, and the output voltage is connected to a contact 18 that is turned on (closed) during fluoroscopy and a contact 19 that is turned on (closed) during imaging. 20
1 is a fluoroscopic X-ray condition setting circuit that determines fluoroscopic X-ray conditions that make the amount of light to the X-ray television camera 7 appropriate during fluoroscopy, and generally performs control to vary the fluoroscopic tube voltage. 21 is an integrating circuit for a phototimer, and 22 is a comparing circuit. 23 is a signal for correcting the object thickness and tube voltage.

A latch signal 24 holds the state of the gate circuit at that time until the fluoroscopy starts again.

FIG. 7 shows an example of the detector arrangement when used in a digestive system. 25 is 1.1. The secondary phosphor screen 26 shows the shape of the stomach projected thereon, and the shaded area shows the area filled with contrast medium. 27 is a group of silicon photodiodes arranged for digestive organs.

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

In the apparatus shown in Figure 1, fluoroscopy is always performed prior to imaging, and in order to determine the fluoroscopy conditions to obtain appropriate brightness for the X-ray television, the detector of the optical-electrical signal conversion circuit 1O is The output signal is used.

In the case of the image shown in Figure 7, when comparing the output of each detector with a fixed reference value when determining whether the amount of exposure is insufficient or overexposure, the output of the detector in the area without contrast agent is determined to be appropriate. Under fluoroscopic conditions, the detector ■.

It can be stabilized in two states: when the output of ■ is excluded due to underexposure, and when the output of the detector with contrast medium is appropriate, and when detectors ■ to ■ are excluded due to overexposure. It happens. This will not allow us to achieve our goals.

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

In this example, the image shown in FIG. 7 will be explained. In this case, since the number of detectors in the area where there is no contrast agent is large, the average signal output from the signal averaging circuit 13 shows a high value,
The detector injection level also increases accordingly. If such control is performed, the detector signals in the area where the contrast agent is present will be easily excluded, and it will be possible to avoid stabilization with the signals from the detectors ① and ②.

FIG. 9 is a diagram showing the relationship between an image and a detector in the compression method. In this method, diagnosis is made while compressing a limited area of the back, and most of the detectors are placed in the area 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 Figure 7, so with conventional equipment, the X-ray conditions of the part to be diagnosed were not appropriate because the detector was excluded. In this example, as shown in FIG. 8, as the tube voltage increases, the rejection eye level changes to bl and b2, so the detector ■ in the area where there is no contrast medium becomes appropriate, and the detection of the presence of a contrast medium occurs. Vessel ■.

Detectors of ■, ■, ■, ■ are easily excluded. This makes it possible to reduce the effects of the subject's body thickness, contrast agent, imaging method, etc.

Although the present invention has been specifically described above based on examples, it goes without saying that the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof.

For example, although the above-mentioned practical example was exemplified and explained for digestive W diagnosis, this method can also be applied to X-ray automatic exposure for other X-ray diagnosis. Regarding the lid and detector, I, 1. 2
The method described below uses a phosphor screen to collect light, but it is also possible to provide a detector for converting X-rays into light on the front or rear surface of the film.

〔effect〕

As explained above, according to the present invention, the X-ray dose at a predetermined position within the X-ray irradiation field is detected by a plurality of detectors, and a signal A proportional to the average signal of the outputs of all these detectors is generated. generates a signal B proportional to the tube voltage during fluoroscopy or imaging, and independently excludes and excludes each of the output signals of the detector outside the range set based on these signals A and B; The remaining detector output signals were averaged and the X-ray conditions were appropriately controlled using this averaged signal.
The X-ray conditions of the part to be diagnosed can be appropriately controlled, and the effects of the subject's body thickness, contrast agent, imaging method, etc. can be reduced. Moreover, this makes it possible to improve the efficiency of X-ray diagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment in which the present invention is applied to an automatic X-ray exposure control device, and FIG. 3 is a circuit diagram showing a specific configuration of the gate circuit in FIG. 1; FIG. 4 is a circuit diagram showing a specific configuration of the signal averaging circuit in FIG. 1. Figure 5 is a circuit diagram showing a specific configuration of the Noriexigon level output circuit shown in Figure 1. Figure 6 is a circuit diagram showing a specific configuration of an overlevel signal generation circuit that generates an overlevel signal. Schematic diagram. Figure 7 is a diagram showing the positional relationship between the back shape and the installed detector in the filling method, Figure 8 is a diagram showing the subject thickness or tube voltage-comparison voltage and signal voltage characteristics, and Figure 9 is the compression FIG. 3 is a diagram showing the relationship between an image and a detector in the case of a method. In the figure, 1... X-ray tube device, 2... Subject, 3...
Recording medium, 4...1.1. ．． 5... Lens system, 6.
... Spectrometer, 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 circuit, 14.15... Rejection level output circuit, 16... Over level signal generation circuit, 16'... Under level signal generation circuit, 17 . . . Division circuit, 18 . . . Contact that is turned on during fluoroscopy, 19 . . . Contact that is turned on during imaging, 20 . . . Fluoroscopic X-ray condition setting circuit, 21 . It is a circuit.

Claims (1)

[Claims] In an automatic X-ray exposure control device that automatically controls X-ray conditions by collecting light using a signal obtained by converting the amount of X-rays that have passed through an object into light,
Means for detecting the dose with a plurality of detectors, means for generating a signal A proportional to the average signal of the output of all these detectors, and means for generating a signal B proportional to the tube voltage during fluoroscopy or imaging. , means for independently excluding each of the outputs of the detectors outside the range set based on these signals A and B, and means for averaging the output signals of the detectors remaining after exclusion. An automatic X-ray exposure control device characterized by: