JPS5910038B2 - X Sensouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray apparatus that can control the exposure X-ray dose with high response speed and low power by controlling the X-ray tube voltage using a tetrode vacuum tube. It is.

As is well known, when performing X-ray fluoroscopy or X-ray cinegraphy of a subject using an X-ray device, it is often necessary to move the subject's fluoroscopy or radiography area to obtain X-ray images from various angles. .

In this case, it is required to control the amount of exposed X-rays according to the thickness of each part of the subject, and to keep the output brightness of an X-ray fluorescence intensifier, which is a fluoroscopic display device, for example, constant.

Such control operations are generally ABC (. Au ta
m t ic Brightness Control
: automatic brightness adjustment), and several methods have been put into practical use in the past, and the following two are typical control methods.

(1) A system that automatically controls the primary voltage of a transformer that generates high voltage using a single-turn sliding transformer and a servo motor to control the X-ray tube voltage.

(2) A method that automatically controls the filament current of the X-ray tube and controls the current between the X-ray tubes.

However, both of the above two methods have the disadvantage of slow response speed.

That is, in the above method (1), the response speed of the servo motor is slow, and in the method (2), even if the filament current is changed, the filament heat does not follow the current change, resulting in a time delay.

Furthermore, both of the above two methods have the disadvantage that a large amount of power is required for their control.

Therefore, the present invention was made in view of the above circumstances, and uses a tetrode vacuum tube (hereinafter referred to as a tetrode), which has conventionally been used only as a switching element, as an X-ray exposure switch and X-ray tube voltage control. An object of the present invention is to provide an X-ray apparatus that can increase the control response speed by using the X-ray device as an optical element, enable low-power control, and perform effective ABC operation.

FIG. 1 shows an outline of the device of the present invention, where 1 is a high-voltage generator, and this high-voltage generator 1 is supplied with, for example, a three-phase AC power source (3ψAC), not shown, to its primary winding. It is comprised of a high voltage generation transformer 2 that boosts the voltage, a high voltage rectifier circuit 3 that rectifies the output of the high voltage generation transformer 2, and tetrode control units 4 and 5 whose details will be described later.

Here, the tetrode control units 4 and 5 have exactly the same configuration, and are inserted in series on the anode side and the cand side of the X-ray tube 6, respectively, so that the tetrodes 1 and 8 have an electrical withstand voltage.

Reference numeral 9 denotes a timer circuit (not shown) which receives an X-ray exposure signal and controls the X-ray exposure time, a block diagram of which is shown in FIG.

Reference numeral 10 denotes an automatic bias (Eg2) control circuit for the tetrodes 7 and 8 for controlling the tube voltage of the X-ray tube 6, the details of which will be explained in FIG.

Next, the X-rays emitted from the X-ray tube 6 pass through the subject 11 and enter the X-ray fluorescence multiplier 12 .

A visible light image of the transmitted X-rays is formed on the output fluorescent screen of the X-ray fluorescence multiplier 12, and this visible light image is distributed to a television camera 14 and a cine camera 15 by an optical distributor 13.

On the other hand, the optical distributor 13 has a built-in brightness detector 16 composed of, for example, a photomultiplier tube, and the brightness detector 16 converts the output brightness of the X-ray fluorescence multiplier tube 12 into an electrical signal. The signal is converted and provided to the automatic control circuit 10.

-4, the tetrode control units 4, 5 are constructed as shown in FIG.
5 have the same structure, the same parts are given the same reference numerals and the details will be explained.

The output signal of the timer circuit 9 is introduced into the input terminals A and B, and is appropriately adjusted by the high voltage transformer 17.

In order to improve responsiveness to the X-ray exposure signal from the timer circuit 9, it is appropriate to use a transformer made of a ferrite core as the high voltage transformer 17.

The secondary voltage of the high-voltage transformer 17 is rectified by the full-wave rectifier circuit 18, and is applied as a base current to the switching transistor 21 via a smoothing circuit composed of a resistor 19 and a capacitor 20.

Input terminals C and D are always supplied with a constant voltage, for example, AC 10
0V is applied, and this voltage is applied to the high voltage transformer 22.
It is supplied to the primary winding of the transformer 23 via.

The secondary winding of this transformer 23 includes a first grid bias supply winding 24, a filament voltage supply line 25, and a second grid bias supply winding 24.
It has a grid bias supply winding 26, and the secondary voltage generated in the winding 24 is rectified by a full-wave rectifier circuit 27, and then converted to DC by a smoothing circuit consisting of a resistor 28 and a capacitor 29, and the positive side thereof is connected to the tetrode 7, 8. The negative side of the cathode of the tetrode is connected to the first grid of the tetrode through a resistor 30.

Note that the positive side of the smoothing circuit is also connected to the collector of the transistor 21 and serves as the power supply voltage of this transistor 21.

That is, the transistor 21 is connected between the cathode of the tetrode and the first grid, and is normally in an off state.

When the X-ray exposure signal from the timer circuit 9 is applied to the input terminals A and B, the transistor 21 is turned on, and the tetrode is also turned on to short-circuit between the cathode and the first grid of the tetrode.

Further, the winding 25 is directly connected to the cathodes of the tetrodes 7 and 8, and serves as a filament heating power source.

Further, the voltage generated in the winding 26 is rectified by a full-wave rectifier circuit 27, and is connected to a smoothing circuit composed of a resistor 29 and a capacitor 30 via a transistor 28 inserted in series, and to the terminals 7 and 8. is connected to the second grid of

Further, a silicon photodetecting diode (solar cell) 31 is connected to the base of the transistor 28, and generates a self-electromotive force in response to a light signal from a glass fiber (light guide) 32, which will be described later. The transistor 28 is operated by flowing the current and turning on the transistor 28.

Next, reference numeral 33 denotes a light modulation element composed of, for example, a light emitting diode, which emits light in response to a pulse signal from an automatic control circuit 10 to be described later, and has a structure in which the light passes through the glass fiber 32 and enters the silicon photodetection diode 31.

The light emitting diode 33, glass fiber 32, and silicon photodetection diode 31 are enclosed in an insulating pipe 34 made of vinyl chloride or the like to prevent insulating oil from penetrating.

Next, the operation of the above structure will be explained with reference to FIGS. 4 to 6.

Input terminals G and H are always connected to AC voltage, for example AC I
OOV is applied and is supplied to the primary winding of the transformer 35.

The secondary output of this transformer 35 is rectified by a full-wave rectifier circuit 36 and applied to a constant voltage diode 38 via a resistor 37.

The waveform of the constant voltage diode 38 is shown in the fourth figure B, that is, the zero phase pulse of the AC waveform shown in the fourth figure A.

This zero-phase pulse No. 4 B shown in the figure is led through a resistor 39 to an inverter circuit composed of a transistor 40 and a resistor 41, and becomes a trigger signal for a one-shot multi-circuit 42.

The one-shot multi-circuit 42 oscillates with the time constant of a capacitor 43 and a resistor 44, and has a pulse width control terminal PM, and the pulse width can be adjusted by the signal level applied to the pulse width control terminal PM. be.

The output signal pulse of this one-shot multi-circuit 42 is shown at C in FIG. 4, and is applied to the base of the transistor 45.

The emitter of the transistor 45 is connected to the light emitting diode 33 via output terminals I and J.

That is, the light emitting diode 33 emits light only for the time period of the fourth pulse shown in FIG. 4 whose phase is controlled by the one-shot multi-circuit 42.

On the other hand, the output voltage of the differential amplifier 46 is connected to the pulse width control terminal PM to form a feedback system.

That is, the luminance signal converted by the luminance detector 16 is converted into DC by a smoothing circuit consisting of a resistor 47 and a capacitor 48 via an input terminal K, and is then converted to DC by the differential amplifier 46.
becomes the input signal.

The other input signal to the differential amplifier 46 is from a variable resistor 49 that sets the brightness level.

A voltage D, shown in FIG. 4, representing the difference between the measured brightness detected by the brightness detector 16 and the brightness level set by the variable resistor 49 is fed to the pulse width control terminal PM of the one-shot multi-circuit 42 and output. It operates to vary the pulse width t of the fourth pulse C shown in the figure.

Light emitting diode 3 emitted by pulse No. 4 C shown in FIG.
3 is guided to the silicon photodetector diode 31 through the glass fiber 32 shown in FIG. 2, the transistor 28 is turned on, and the smoothed voltage E shown in FIG. It is being

Therefore, the voltage between the cathodes and the plates of the tetrodes 7 and 8 is controlled according to the voltage value applied to the second grid.

Here, if the circuit shown in FIG. 2 is rewritten equivalently, it will become as shown in FIG. 5.

That is, the transistor 21 shown in FIG. 2, the rectifier circuit 18,
A switching circuit consisting of a resistor 19 and a capacitor 20 is connected to the switch S1, a second grid bias circuit consisting of a winding 26, a rectifier circuit 27, a transistor 28, a resistor 29, and a capacitor 30 is connected to Eg2, and a winding 24 and a rectifier circuit 2
7, the first grid bias circuit consisting of a resistor 28 and a capacitor 29 corresponds to Eg, and the timer circuit 6
When an X-ray exposure signal is given from the grid, the switch S1 is closed, the tetrodes 7 and 8 become conductive, and the internal voltage drop vT is determined by the second grid bias voltage Eg2.

That is, as is well known in the case of a tetrode, if the plate current IP and the first grid voltage Egtt are constant due to its characteristics, the internal voltage drop (T) depends on the second grid voltage Eg2, and therefore the second grid voltage By changing Eg2, the internal voltage drop vT of the tetrode can be controlled.

Therefore, the rectified output voltage of 3 of the high voltage rectifier circuit is
If the tube voltage applied to the wire tube 6 is ■X, then vX=■HT
-2vT.

That is, by controlling the internal voltage drop of the tetrodes 7 and 8, the X-ray tube voltage (Vx) is controlled.

Incidentally, when an X-ray exposure signal is given to the input terminal G, the timer circuit 9 (details shown in FIG. 6) uses this exposure signal as a trigger signal to trigger a one-shot multi-by-break OM.
is driven.

By the way, this one-shot multi-by-break OM is
A pulse signal whose output pulse width is controlled is generated by the exposure time setting device XTS, in which the exposure time is set according to the diagnostic part of the subject currently being imaged, and this pulse signal is given to the gate circuit G. , the gate circuit G is open while said pulse is present.

On the other hand, the output from the sine wave oscillation circuit OS is given to the gate circuit G, and while the gate is open, the output sine wave signal of the oscillation circuit OS is given to the amplifier AP, where it is appropriately amplified and output transformer. The signal is applied to input terminals AB of the control units 4 and 5 via PT.

As described above, according to the present invention, by controlling the second grid voltage of the high voltage tetrode connected in series with the X-ray tube, the voltage of each X-ray tube can be controlled, so the response is faster than that of the conventional method. And it can be controlled with low power.

In addition, by combining the photoconduction mechanism with a combination of light-emitting diodes, glass fibers, and silicon photodetecting diodes, and light-emitting diode control using phase control pulses, voltage control from the low-voltage section to the high-voltage section becomes possible. Compared to systems that use isolation transformers, this method is smaller and has higher insulation.

This can be applied to responsive automatic brightness control in X-ray fluoroscopy or X-ray cine photography.

It should be noted that the present invention is not limited to the above embodiments, and for example, in the above embodiments, a light emitting diode was used as the light emitting element and a silicon photodetection diode (so-called photodiode) was used as the photoelectric element, but a lamp was used as the light generating element. It goes without saying that the present invention may be modified as appropriate without changing the gist, such as replacing the phototransistor with a phototransistor as the photoelectric element.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing one embodiment of the present invention, Fig. 2, Fig. 3
The figure is a configuration diagram showing details of the main parts in Figure 1, Figure 4 is a signal waveform diagram for explaining the operation in Figures 1 to 3, and Figure 5 is an equivalent circuit of the tetrode control units 4 and 5. 6 are block diagrams showing details of the timer circuit 9. FIG. 4, 5... Tetrode control unit, γ, 8...
...Tetrode, 9 ...Timer circuit, 1
0... Automatic control circuit, 31... Silicon light detection diode, 32... Glass fiber, 33... Light emitting diode.

Claims (1)

[Claims] 1. A tetrode vacuum tube connected in series between the output end of a high voltage generator that generates a high voltage to be applied to the X-ray tube and the X-ray tube, and when an X-ray exposure signal is given, the tetrode vacuum tube is electrically connected. a first grid bias circuit that controls the bias voltage of the first grid to control the internal voltage drop of the tetrode vacuum tube; a second grid bias circuit that controls the bias voltage of the second grid to control the internal voltage drop of the tetrode vacuum tube; It is equipped with a light emitting element that emits light according to the amount of X-rays emitted from the tube, and a photoelectric element that photoelectrically converts the amount of light emitted from the light emitting element, and the bias voltage of the second grid bias circuit is controlled by the bias voltage of the photoelectric element. An X-ray device characterized by being controlled by output.