JPS5923076B2 - X-ray device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray apparatus that controls the imaging tube voltage applied to the X-ray tube using a test load.

Generally, it is ideal for an X-ray automatic exposure cutoff device, a so-called photo timer, an ion timer, etc., to be able to completely cover the thickness of the subject and the voltage of the imaging tube.

However, in reality, there is an appropriate imaging tube voltage that corresponds to the region and thickness of the subject due to the relationship between the radiation quality and the imaging tube voltage, and it is necessary to set this using the X-ray controller before imaging.

For this reason, X-ray technicians require a high degree of skill and experience, which poses a problem for the complete automation of X-ray equipment.
.

Figure 1 is a schematic configuration diagram showing an example of a conventional device of this type, in which 1 is an X-ray controller that controls the tube voltage, filament current, etc., and 2 is a high-voltage generator that boosts the output voltage of the X-ray controller. ,3
is an X-ray tube.

The X-ray controller 1 includes an autotransformer 1a that is supplied with commercial power, a main switch 1b inserted on the secondary side of the autotransformer 1a, and a timer that controls opening and closing of the main switch 1b. 1
c, a voltage stabilizer 1d for stabilizing the commercial power supply, a filament heating adjustment resistor 1e and a filament heating switch 1f inserted on the output side of the voltage stabilizer 1d, and the like are provided.

Note that 1g is a resistor, and 1h is a contact, which is inserted in series with the filament heating adjustment resistor 1e to intentionally worsen the current-voltage characteristics of the filament heating circuit.

The high voltage generator 2 includes a high voltage transformer 2a which is connected to the secondary side of the autotransformer 1a and designed to worsen the current-voltage characteristics, and rectifies the secondary side output of this high voltage transformer 2a. A filament heating transformer 2c is provided which receives the outputs of the rectifier 2b and the voltage stabilizer 1d and supplies the filament current of the X-ray tube 3.

Then, timer 1C closes main switch 1b and
At the same time as the radiation exposure starts, a resistor 1g is inserted into the filament heating circuit by opening the contact 1h.

Therefore, the filament heating current decreases rapidly, that is, the tube current mA decreases according to the thermal cooling curve of the X-ray tube filament, as shown in the graph of the X-ray tube current characteristics shown in FIG. 2a.

Furthermore, since the high voltage transformer 2a has poor current-voltage characteristics, the tube voltage KV rises in response to the change in the heating current, as shown in the X-ray tube voltage characteristics shown in FIG.

Therefore, the tube voltage at the start of shooting can be set to a low voltage and raised over time, making it possible to widen the dynamic range of automatic exposure cutoff control without having to set the tube voltage corresponding to the subject in advance. .

However, in such a device, the current-voltage characteristics of the high-voltage transformer are intentionally worsened to increase the imaging tube voltage, and furthermore, the rise curve of the imaging tube voltage depends on the filament cooling curve of the X-ray tube. Because it is an indirect control, it is not suitable for large-capacity X-ray equipment such as three-phase power supply systems, and faithful tube voltage control is not suitable for short-term imaging where the exposure time is several tens of milliseconds or less. There was a problem that it could not be done.

The present invention has been made in view of the above circumstances, and uses a tetrode to control the X-ray tube voltage.

It is an object of the present invention to provide an X-ray apparatus that can obtain a wide dynamic range and thereby perform reliable control even when a large current is applied for a short time.

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 3 to 5.

FIG. 3 is a block diagram of the above embodiment, and in the figure, 10 is an X-ray controller, 20 is a high pressure generator, and 30 is an X-ray tube.

The X-ray controller 10 includes an autotransformer 11 supplied with three-phase commercial power, an automatic exposure cutoff control circuit 12, and an imaging timer 1.
3, and a tube voltage selection circuit, tube current control circuit, etc. (not shown).

The high-voltage generator 20 also includes a high-voltage transformer 21 that steps up the secondary output of the autotransformer 110, a high-voltage rectifier circuit 22 that rectifies the secondary output of the high-voltage transformer 210, and a pair of high-voltage rectifiers inserted on the secondary side of the rectifier circuit 22. tetro switching unit 2
3,24. A filament heating transformer (not shown) is also provided.

31 is a subject, 32 is an X-ray dose detector placed in the X-ray cone, 32a is a detection element of the X-ray dose detector 32, such as a photomultiplier tube, and 33 is a spot imager, these constitute an imaging system. do.

Furthermore, an actual X-ray diagnostic apparatus is also provided with an image intensifier 34, an optical distributor 35, an X-ray television device 36, etc., but these are not directly related to the present invention, so their explanation will be omitted.

Figure 4 shows a pair of tetrode switching units)23.
24, this switching unit) 23.
24 is composed of exactly the same circuit, so only one of them, 23, will be explained.

In the figure, 23□ is the first high-voltage transformer, and the input terminal to which the X-ray exposure signal is given from the timer unit 13 is connected to the primary side, and the secondary side output is connected to the first full-wave rectifier circuit. 23
2 to rectify.

Note that the first high-voltage transformer 23 is preferably one with good frequency response using a ferrite core or the like.

Then, the positive side output of the first full-wave rectifier circuit 23□ is smoothed by a smoothing circuit consisting of a resistor 233 and a capacitor 234, and is applied to the base of a switching transistor 235.

The negative side is also provided to the first grid of tetrode 236.

And 237 is AC 10 through the input terminal Lm on the primary side.
This secondary side output is applied to the primary side of the transformer 238 by a second high voltage transformer to which a constant voltage such as 0V is applied.

This transformer 238 is connected to the first grid bias supply winding 2.
38a, a filament voltage supply winding 238b and a second grid bias supply winding 238c of the natrode 236 are provided with secondary windings.

Then, the output of the first grid bias supply winding 238a is rectified by a second full-wave rectifier circuit 239, and the resistor 23,
.

After smoothing with a smoothing circuit consisting of a capacitor 23□1, the positive side is applied to the cathode of the tetrode 236, and the negative side is applied to the cathode of the tetrode 236.
3.2 to the first grid of tetrode 236.

Note that the positive side is connected to the collector of the transistor 23, and a power supply voltage is supplied to the transistor 23.

A filament voltage supply winding 238b is also connected to the filament of the tetrode 236 to provide a filament heating current.

Then, the output of the second grid bias supply winding 238c is rectified by a third gold rectifier circuit 2313, and the positive side is smoothed by a smoothing circuit consisting of a capacitor 2314 and a resistor 23.5, and is applied to the collector of the transistor 23□6.

Then, the load of the rectifier circuit 2313 is changed to the tetrode 236.
The slider of the resistor 23.5 is connected to the emitter of the transistor 23.6.

A capacitor 23.7 is interposed between the negative side of the rectifier circuit 23□3 and the emitter of the transistor 2316, and the emitter of the transistor 23.6 is connected to the second grid of the tetrode 236.

Furthermore, a photodetector element, such as a silicon photodetector diode 2318, is connected between the emitter and base of the transistor 23□6.
is inserted, and this silicon photodetecting diode 23□8 provides light from a light emitting element 23□0 controlled by a timer unit via a glass fiber 23.9.

The silicon photodetecting diode 23□7, the glass fiber 2318, and the light emitting element 23□9 are integrally enclosed in an insulating pipe 23□1 made of vinyl chloride, for example, to prevent intrusion of insulating oil from the high-pressure generator 23. ing.

The tetrode 236 of each tetrode switching unit 23, 24 connects the cathode to the X-ray tube 30 and the plate to the high-voltage positive terminal, and the tetrode 246 connects the plate to the X-ray tube 30.
The cand is connected to the high voltage negative terminal on the wire tube.

FIG. 5 is a block diagram showing the imaging timer 3 of the X-ray controller 10, where 131 is a one-shot multivibrator to which an X-ray exposure trigger signal is applied from the outside via the input terminal t, and 13 is the one-shot multivibrator 13.
This is an exposure time setting device that sets the reversal time of .

And 133 is one-shot multivibrator 131
The gate 134 is an oscillation circuit that provides the gate 133 with an oscillation output of a predetermined frequency, for example, 10 KHz.

Further, 135 is an amplifier circuit for amplifying the output of the gate 133, and 136 is an output terminal of the output transformer 136 of the amplifier circuit 135, and is connected to the input terminal j of the tetrode unit 23 and 24 via i.

give to k.

The output of the one-shot multivibrator 13 is applied to the base of the transistor 3□, and the collector output of this transistor 3□ is applied to the input terminal Q of the tetrode unit 23. Make it emit light.

Further, a detection signal from the photomultiplier tube 32a of the X-ray dose detector 32 is applied to the input terminal a of the automatic exposure cutoff control circuit 12.

This automatic exposure cutoff control circuit 12 integrates the detection signal proportional to the X-ray dose, and when this integrated value reaches a predetermined level set in advance, outputs an X-ray cutoff signal to the output terminal, and transmits this output to the above-mentioned imaging timer. The one-shot multivibrator 131 is energized via the input terminal C of No. 20 to stop the X-ray exposure.

With such a configuration, an X-ray exposure trigger signal is first applied from the outside to the input terminal t of the imaging timer 3 to energize the fun shot multi-by-break 131, and this output signal is applied to the gate 133.

In addition, the above one-shot multi-via "L/-12131
The time required for the X-ray exposure to return, that is, the X-ray exposure time, can be arbitrarily set using the exposure time setting device 13□.

Since the oscillation circuit 134 is always in an oscillation state, the output of the gate 133 is a signal obtained by chopping the output of the oscillation circuit 134 using the output of the one-shot multivibrator 131.

This signal is amplified by an amplifier circuit 135, and the X-ray exposure signal shown in FIG.
A predetermined bias voltage is applied to the first grid of the tetrodes 236 and 246 as shown in FIG.
The tetrodes 236 and 246 are made conductive.

In addition, the one-shot multivibrator 13. The output signal is applied from the transistor 137 via the output terminals d and e to the input terminals n and Q of the tetrode units 23 and 24 at a predetermined voltage as shown in FIG.

to emit light.

The light then enters a photodetection element 2318 such as a silicon photodetection diode via the glass fibers 23 and 9, and is converted into an electrical signal again.

The photodetecting element 2318 is a transistor 2316
0 base, so this transistor 231
6 is made conductive and the capacitor 231° on the emitter side is charged.

Therefore, as shown in FIG. 4, the terminal voltage of the capacitor 2317 rises from the divided voltage E2 of the resistor 2315 toward the collector voltage E of the transistor 23□6 at the same time as the start of X-ray exposure, and this voltage applied to the second grid to control its internal voltage drop.

In this case, the terminal voltage of the capacitor 231□ increases almost linearly because the collector current of the transistor is constant through the base due to its characteristics depending on the base current.

Here, FIG. 6 shows an equivalent circuit of the tetrode switching unit shown in FIG.
, a rectifier circuit 23□, a resistor 233, and a capacitor 234. The switching circuit of the first grid is S shown in FIG.
, corresponds to .

In addition, in FIG. 4, the secondary winding 238c, the rectifier circuit 23
13. A power supply consisting of a capacitor 2314 is connected to a power supply E shown in FIG.
, E2, and the transistor 23.6 corresponds to the switch S2.

When the X-ray exposure signal from the timer unit 13 is applied here, the switch S1 is closed, the tetrode 236 becomes conductive, the high voltage vbt is applied to the X-ray tube 30, and X-rays are emitted.

- the second grid bias of the force tetrode 236 is given the voltage E2 when the switch S2 is open;
At the same time as switch S1 is closed, switch S2 is also closed.

Then, charging starts to the capacitor 231□, and this second
The grid bias voltage increases approximately linearly from E2 to E.

That is, in the case of a tetrode, in general, if the plate current ■p1 and the first grid voltage Eg1 are kept constant, the internal voltage drop Vt
will depend on the second grid voltage Eg2.

Therefore, by changing the second grid voltage Eg2, the internal voltage drop Vt of the tetrode can be controlled.

Therefore, if the output voltage of the voltage rectifier circuit 22 is yhζ and the internal voltage drop at each tetrode 236, 246 is Vt, then the tube voltage Vx of the X-ray tube 30 is expressed by the following equation 1).

Vx=Vht-2Vt・・・・・・・・・
・・・・・・・・・・・・・・・1) That is, Tetrode 236
, 246, the X-ray tube voltage can be controlled.

Therefore, the second grid bias of the tetrodes 236, 246 increases directly as shown in FIG. It gradually rises as shown in FIG. 7e.

- The signal detected by the detection element 32a of the force X-ray dose detector 32 is applied to the input terminal a of the automatic exposure cutoff control circuit 12.

This automatic exposure cutoff control circuit integrates the current L1 applied to the input terminal a, that is, the output current of the photomultiplier tube that is proportional to the X-ray dose, and when this value reaches a predetermined value, the output terminal An X-ray cutoff signal is output as shown in FIG. 7f.

Then, this X-ray cutoff signal is sent to terminal C of the timer unit 13.
The one-shot vibrator 131 is reversed and returned to its original position to stop X-ray exposure.

Therefore, since the X-ray tube voltage is gradually increased, imaging can be performed without setting a special imaging tube voltage, and a wide dynamic range can be obtained by controlling the X-ray tube voltage using a tetrode. I can do it.

As detailed above, the present invention connects a tetrode in series with an X-ray tube to apply tube voltage, and performs switching control by bias control of the first grid of this tetrode.
Since the tube voltage is controlled by bias control of the second grid, it is possible to provide an X-ray apparatus that has good responsiveness, can obtain a wide dynamic range, and can particularly easily automate X-ray photography.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram showing an example of a conventional X-ray device, Figure 2
The figure is a graph showing changes in the tube current and tube voltage of the X-ray apparatus, FIGS. 3 to 7 are diagrams showing one embodiment of the present invention, FIG. 3 is a block diagram, and FIG. 5 is a block diagram showing the photographing timer, FIG. 6 is an equivalent circuit of the tetro switching unit, and FIG. 7 is a time chart explaining the operation of the above embodiment. . 10... X-ray controller, 12... Automatic exposure cutoff control circuit, 13... Shooting timer, 20...
...High voltage generator, 21...High voltage transformer,
22...High voltage rectifier circuit, 23.24...
・Tetro switching unit, 236.246・
...Tetrode, 30...X-ray tube.

Claims (1)

[Claims] 1 A tetrode inserted between a high-voltage generator and an X-ray tube, a first grid switching circuit that controls and switches the first grid bias voltage of the tetrode, and a second grid bias voltage of the tetrode. An X-ray apparatus comprising a second grid bias variable circuit that gradually increases the X-ray tube voltage immediately after the start of X-ray exposure.