JPH05152095A - X-ray generating device - Google Patents

Abstract

PURPOSE:To increase the X-ray dose generated for X-ray exposure at one time in a cordless battery type X-ray generating device. CONSTITUTION:A charge voltage detecting circuit 27 for detecting a charge voltage of a capacitor 18 is provided, and a tube current changeover circuit 28 is provided in a filament heating circuit for an X-ray tube 23. The charge voltage detecting circuit 27 detects a drop in a charge current in a capacitor 18 during X-ray exposure. When the charge voltage drops down to a predetermined value, the circuit 27 delivers a detection signal. The tube current change- over circuit 28 receives the detection signal so as to change the tube current to a small value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray generator (also referred to as an X-ray device) for a round, which is mainly used by moving in a hospital.

[0002]

2. Description of the Related Art In recent years, an X-ray apparatus for round trips has been shifting from a conventional capacitor type to an inverter type capable of generating a stable high voltage. Among them, the cordless X-ray device equipped with a battery can be used even in a room without an outlet, so that it is currently the mainstream of X-ray devices for rounds and is widely used. The structure and operation of a conventional cordless inverter type X-ray apparatus for round trip will be described with reference to FIG. First, in a room with a power source, the plug 31 is inserted into an outlet to charge the battery 34. To elaborate on this, the AC voltage (typically 100
V) is boosted to about 600V by the auto transformer 32 of the battery charging circuit 41. The AC current from this is rectified into a DC current by the rectifier circuit 33, and charges the battery 34 in which several tens of unit cells (voltage 12V) are connected in series.

When using this X-ray apparatus for round trip, a DC current supplied from a battery 34 is converted into an AC current by an inverter circuit 35 and input to a high voltage generating transformer 36. 40 generated by high voltage generating transformer 36
A high voltage of about -125 kV is rectified by the rectifier circuit 37 and applied to the X-ray tube 39. During this time, the voltage applied to the X-ray tube 39 is detected by the tube voltage detection circuit 38, fed back to the control circuit 40, and used for controlling the inverter 35.

[0004]

The above X-ray apparatus has a problem that it is impossible to apply a sufficiently large electric power P to the X-ray tube 39 for the following reason. That is, considering the primary side of the high voltage generation transformer 36, the electric power P is the product of the voltage and the current, and therefore, in order to increase the electric power P, it is necessary to increase the primary voltage or the primary current. The X-ray generator for round trip uses the battery 34 as a primary power source for movement, but the battery has a limitation in the electric current that can flow to itself due to its characteristics.

Therefore, the battery voltage must be raised to obtain a large amount of power. However, since the standard battery cell voltage that can be easily obtained is 12 V per cell, in order to obtain the power required for the X-ray apparatus for rounds,
It is necessary to connect dozens of such battery cells in series. Such a round-trip X-ray device is bulky with a battery alone and weighs several hundreds of kilograms, which makes it extremely unwieldy and difficult to operate.

In order to solve such a problem, the inventors of the present invention have proposed an X-ray device in which a capacitor for storing a medium potential of about 600 V is provided between a battery and an X-ray tube (Japanese Patent Application No. Hei 3). -97362).

The structure and operation of this X-ray apparatus will be described with reference to FIG. Before actually using the apparatus, first, in a room with a power source, insert the plug 11 into an outlet and charge the battery 14. The circuit 25 for charging the battery 14 includes the step-down transformer 12 and the rectifier circuit 13 in addition to the plug 11. Unlike the circuit shown in FIG. 2, in the device of FIG. 3, the battery 14 uses only two standard 12V battery cells, so the transformer 12 of the battery charging circuit 25 is a commercial power source.
It is designed to step down 00V.

After the charging of the battery 14 is completed, the X-ray apparatus can be used. Battery 1 when used
The DC current supplied from 4 is converted into AC by the inverter 15.
The voltage is converted into a current and boosted to a medium voltage of about several hundreds V (for example, about 600V) by the insulating transformer 16. The rectifier circuit 17 converts the AC current boosted to about medium pressure into a DC current, and the capacitor 18 is charged thereby. X-rays can be generated when the capacitor 18 is completely charged.

When the operator operates a switch (not shown) to generate X-rays, the control circuit 24 operates the inverter 19. The inverter 19 converts the DC current discharged from the capacitor 18 into an AC current, and the high voltage transformer 20 boosts the voltage to a high tube voltage (for example, 65 kV). This AC current is converted into a DC current again by the rectifier circuit 21 and applied to the X-ray tube 23.

As in the X-ray apparatus of FIG. 2, the tube voltage is monitored by the tube voltage detection circuit 22 and fed back to the control circuit 24. The control circuit 24 is the capacitor charging circuit 2
The inverter 15 of No. 6 and the inverter 19 of the high voltage circuit are controlled so that the high voltage inverter 19 controls the voltage applied to the X-ray tube 23 to a predetermined value based on the monitored tube voltage.

Since the X-ray generator of FIG. 3 does not require such a high voltage for the battery, it has a feature that the volume and weight of the battery can be made very small. However, this apparatus has a problem that the X-ray dose generated by one X-ray exposure is limited by the capacity of the condenser 18. FIG. 4 shows changes in the charging voltage of the capacitor 18 and the tube voltage of the X-ray tube 23 of the X-ray generator shown in FIG. 3 when the X-ray is generated. It goes down like.

This voltage Vc is a value obtained by dividing the X-ray tube voltage Vt by the number of turns n of the high voltage transformer 20 (this is V2).
Otherwise, the predetermined X-ray tube voltage cannot be maintained and control becomes impossible. That is, the occurrence X when the voltage Vc of the capacitor 18 at the end of X-ray exposure is equal to a value V2 obtained by dividing the X-ray tube voltage Vt by the number n of turns of the high-voltage transformer 20.
The dose is the maximum value and no more X-ray dose can be generated.

As a result, when an X-ray photograph of a thick subject is taken, there is a problem that the X-ray dose is insufficient and the photograph has a low density. It is conceivable to increase the capacity of the condenser 18 in order to increase the X-ray dose generated by a single X-ray exposure. However, such a round X-ray apparatus has a large volume and a large weight even with only the condenser. However, it is very unwieldy and has poor operability, which is not practical.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a cordless X-ray generator using a battery,
The purpose is to increase the X-ray dose generated by one X-ray exposure without increasing the volume and weight.

[0015]

SUMMARY OF THE INVENTION In the present invention made to solve the above problems, the electricity stored in a battery is boosted and stored in a capacitor, and the electricity stored in the capacitor is boosted to an X-ray tube. In an X-ray generator that generates X-rays by supplying, a charging voltage detection circuit that detects the charging voltage of a capacitor during X-ray irradiation, and an output signal of this charging voltage detection circuit are used during X-ray irradiation. And a tube current switching circuit for switching the tube current to a small tube current.

[0016]

The charging voltage detection circuit detects the capacitor charging voltage that drops during X-ray irradiation, and outputs an output signal when it reaches a predetermined value. The tube current switching circuit switches the tube current to a small tube current value by the output of the charging voltage detection circuit. Therefore, the drop of the charging voltage of the capacitor is suppressed,
The exposure time at a predetermined tube voltage becomes longer, and the X-ray dose generated by one X-ray exposure can be increased. Also, X
Since the tube current is switched to the small tube current and becomes small, the output current from the battery is sufficiently small, stays within the rated range, and is not overloaded.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a cordless inverter type X-ray apparatus for round trips, which is an embodiment of the present invention. The basic configuration of this embodiment is the same as that of the X-ray apparatus shown in FIG. 3, and the same elements are assigned the same numbers. In the X-ray apparatus of the present embodiment, the plug 11 is inserted into the outlet and the X-ray tube 23
The operation up to applying X-rays by applying a high voltage to is as described above with reference to FIG.

The apparatus of the present embodiment is different from the apparatus of FIG. 3 in that the charging voltage detection circuit 27 connected to both ends of the capacitor 18 and the filament heating circuit of the X-ray tube 23 are provided to switch the X-ray tube current. That is, the tube current switching circuit 28 is provided. The operation of these circuits after the start of X-ray generation (X-ray irradiation) from the X-ray tube 23 will be described below with reference to FIGS. 1 and 4.

When the charging voltage of the capacitor 18 falls below the threshold value V1 during X-ray irradiation, the charging voltage detection circuit 27 sends a detection signal to the control circuit 24. The control circuit 24 receives this detection signal and sends a control signal to the capacitor charging circuit 26 and the tube current switching circuit 28. As a result, the capacitor charging circuit 26 operates and supplies the electric energy of the battery 14 to the X-ray tube. This allows the condenser 18
The charging voltage does not fall below a value V2 obtained by dividing the X-ray tube voltage Vt by the number n of turns of the high voltage transformer 20, and a predetermined tube voltage can be maintained. The tube voltage waveform at this time is shown in d of FIG. At the same time, the tube current switching circuit 28
Operates, and the X-ray tube current becomes a sufficiently small value (for example, switching from 100 mA to 10 mA) after the time Td determined by the thermal inertia of the X-ray tube filament (not shown). Therefore, since the output current from the battery 14 is sufficiently small and stays within the rated range, there is no abnormal heat generation and the life is not shortened.

The threshold value V1 is the time delay T due to thermal inertia.
In consideration of d, the X-ray tube voltage Vt is set to be slightly higher than the value V2 obtained by dividing the number of turns n of the high-voltage transformer 20, so that the charging voltage Vc of the capacitor 18 is V2 during the X-ray exposure.
There is no loss of control due to the action.

In the embodiment, the charging voltage of the capacitor 18 is kept constant during the X-ray irradiation, and the X-ray is kept for a long time at a predetermined tube voltage.
The tube current switching circuit 28 and the capacitor charging circuit 2 are detected by the charging voltage detecting circuit 27 in order to realize the line exposure.
Although both of 6 are operated, only the former may be operated. The voltage Vc of the capacitor 18 in this case
Changes like e in FIG.

[0022]

According to the present invention, the tube current is switched and reduced during X-ray irradiation without increasing the size of the apparatus, so that the drop in the charging voltage of the capacitor is suppressed, and the X-ray voltage at a predetermined tube voltage is suppressed. It is possible to lengthen the radiation exposure time, and as a result, it is possible to increase the X-ray dose generated in one X-ray irradiation.

Further, since the tube current is switched to a small current, overexposure does not occur due to the extension of the exposure time. Further, if the capacitor is charged at the same time as the tube current is switched as in the embodiment, the X-ray dose can be increased and the overload can be prevented.

Furthermore, once the tube current is switched, one X
Since the X-ray dose generated by the radiation exposure is increased, it is not necessary to increase the capacity of the condenser, and as a result, the volume and weight can be reduced, so that the round X-ray apparatus can be made compact. can do.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a cordless inverter type X-ray apparatus for round trips according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional cordless inverter type X-ray apparatus for round trip.

3 is a circuit diagram of a cordless inverter type round-trip X-ray apparatus using a capacitor, which is an improved version of the apparatus of FIG.

FIG. 4 is a diagram showing changes in a capacitor charging voltage and an X-ray tube voltage when an X-ray is generated by the X-ray device.

[Explanation of symbols]

14: Battery 26: Capacitor charging circuit 15, 19: Inverter 27: Charging voltage detection circuit 23: X-ray tube 28: Tube current switching circuit 25: Battery charging circuit

Claims (1)

[Claims] 1. An X-ray generator for generating X-rays by boosting the electricity stored in a battery to charge a capacitor and boosting the electricity stored in the capacitor to supply it to an X-ray tube. A charging voltage detection circuit for detecting the capacitor charging voltage during radiation exposure, and a tube current switching circuit for switching the X-ray tube current to a small tube current during X-ray irradiation by an output signal of the detection circuit. Characteristic X-ray generator.