JPS5840800A - X-ray apparatus - Google Patents

Abstract

PURPOSE:To averte light-exposure of an X-ray film due to the unnecessary residual X-ray by shortening to the most the strating-up time of the high-voltage wave form applied onto an X-ray tube by reducing the internal impedance of the X-ray tube immediately after X-ray scanning as far as possible. CONSTITUTION:The heating voltage stabilized by a stabilizer 20 is corrected in the tube voltage by a space-charge compensating transformer 21 and applied onto the heating resistor 22 for selecting the tube current. The standard heating voltage Vf equal to the heating voltage Ve corresponding to the set tube voltage is applied onto a switching device 23, similarly in the concrete example described in the above, and Ve is applied onto the primary side of a filament heating transformer 11 by the timing signal of a timing circuit 24 during heating. The timing circuit 24 consists of a monostable multifilament vibrator circuit and the circuit which is driven so that the switching device 23 applies Vf, switched from Ve, onto the primary side of the filament heating circuit 11 only during the time when the pulse is transmitted from the monostable vibrator circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X1m device that improves the fall characteristics of a high voltage waveform applied to an X-ray tube during X-ray exposure.

Conventionally, in this divine device, especially in large-sized, ordinary diagnostic three-phase The downstream waveforms are significantly different. That is, even if the tube voltage applied to the tXim tube is the same, X @ after the switch is opened.

The falling time for the high voltage waveform to reach substantially zero potential becomes longer as the set tube current becomes smaller and the load becomes lighter. Therefore, under light loads, the unnecessary exposure time of X1s, which is continuously emitted after the Xg switch is opened, becomes longer.

As is well known, the poor falling characteristics of this high voltage waveform are due to the stray capacitance of the high voltage cable (C) and the stray capacitance of the X-ray tube (C).
C";C1>>CI) K is caused by the accumulated nine charges Q discharging through the open-6C X-ray tube of the high voltage circuit. The characteristics of the discharge curve, that is, the falling edge of the high voltage waveform, are the stray capacitance. (C.

The load resistance (R) during discharge is determined as K. Rounding depends on impedance, and changes greatly depending on the magnitude of the set tube current (filament heating current).Therefore,
It is shortest when the maximum allowable tube current is generated by the high voltage waveform.

Diagnostic X-ray equipment generally has an X-ray television system, which observes the diagnosis area using X-ray fluoroscopy to obtain the appropriate imaging angle, and quickly moves the X-ray film from the standby position to the imaging position at high speed. 1. It uses a so-called sniper shooting method. In this case, the above-mentioned
! During the imaging operation, X-ray fluoroscopy and X@film imaging are often repeated alternately. The Xls film starts moving at high speed from the standby position toward the photographing position.

Therefore, in this type of imaging method, X-ray fluoroscopy is performed until just before X-ray film imaging, in which the Xm tube has the lightest load.

When the moving X-ray film begins to enter the imaging area,
Due to the XIm that is continuously irradiated after the fluoroscopy stop command, that is, the residual X-rays due to the stray capacitance, at least the portion of the X-ray film that has begun to invade the imaging area will be exposed to unnecessary light. The exposure of the X-ray film during this movement causes a deterioration in image quality such as blur in the XIm image formed by X1llK for subsequent photographing.

The present invention was made based on the above circumstances, and at least x! immediately after X-ray fluoroscopy! By reducing the internal impedance of the I-tube as much as possible and maximally shortening the fall time of the high voltage waveform applied to the X-ray tube,
An object of the present invention is to provide an X-ray apparatus that can avoid exposure to m-film.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a three-phase X-ray apparatus according to the present invention, in which 1G is an X-ray tube, and 11 is the X-ray tube 10.
filament heating transformer.

12 is a semiconductor heating circuit. In this heating circuit 12, input from a commercial AC power source 13 is controlled and converted by a heating level signal corresponding to a set tube current applied to an input terminal Ps, and is converted into filament heating control power to the filament heating transformer 11. 1 in 0 applied to
゜～几 is a resistor, VR variable resistor, C is a capacitor, D is a diode, 14Fi comparator, N1.

16 is an analog switch, and 17 is a summing amplifier.

When a nine-level heating signal corresponding to the set tube current is applied to the input terminal P, the signal passes through the resistor R1 to the reference heating created by the resistors R, , R4 and the variable resistor VB. The level is compared with the comparator 14, and only the difference in level is inverted and amplified, and the analog switch 1
6 is applied as an input.

Maku, NOR game) N11N! #Resistance R5t Rs t
The circuit constituted by the capacitor C is a monostable multivibrator, which captures the rising edge of the input signal and extracts a pulse output having a width determined by the time constant of C.

Next, the operation of the present invention will be explained with reference to the tie-setting chart of FIG.

First, when a higher X@ exposure signal shown in FIG. 2 Vp is applied to the input terminal P, the edge of this rising edge,
That is, the monostable multivibrator circuit is driven at the tie-setting at the end of the xIII exposure, and generates an output pulse as shown in FIG. 2 Vp4. This signal is applied to the control input of the analog switch 16, and the analog switch 16 is "ON@" only during this pulse width (1, -14).
state, and the output signal of the comparator 14 mentioned above is added to the summing amplifier 1.
7.

Trench 9, P, is a set heating level input terminal of the semiconductor heating circuit, and the filament heating control power applied from the heating circuit 12 to the filament heating transformer 11 is controlled by this input signal. Normally, a heating signal of 9 levels corresponding to the selected tube current is applied (Fig. 2 Vp 1 oVa) After the irradiation is completed, the analog pg switch 16 is turned ON. ``Duration of state (T, -
T4) is the output signal from the comparator 14 (Δ
A signal obtained by adding and amplifying V) by the summing amplifier 17 is applied. In other words, only during this period is light load (during fluoroscopy)
Then, R at the comparator 14 is independent of the selected tube current.
, R4, and the reference level heating signal set at VR is applied to tPs.

Further, a signal for driving the semiconductor heating circuit 12, that is, a signal for controlling the start and end of main heating of the filament for actual imaging, is applied to the input terminal P0.
There are two types of controllers: one in which main heating is performed as long as the nine heating buttons are held down, and the other in which main heating is automatically turned off as soon as X-ray exposure ends. Therefore, Vp in Figure 2
When the heating circuit drive signal is cut off at the same time as the end of X-ray exposure as shown in s, the output of the monostable multivibrator after the end of t The main heating is continued for the width of the pulse signal. (Fig. 2 *Vp@) Further, a control output signal for heating the tube filament from the heating circuit 12, that is, a tube current control signal, is applied to the input terminal P of the filament heating transformer 110. As shown by Vp in FIG. 2, the filament coil of the X-ray tube 10 is initially preheated according to the value of vb-.
The heating level increases to the heating level VC corresponding to the tube current selected at the time tone, that is, the tinging of the main heating start. At the end of X@ exposure (time 1.), the heating level is raised to the reference level Vd regardless of the selected tube current, and at time t, it is returned to the preheating level again for the 9th exposure. wait.

The present invention is not limited to the above-mentioned embodiment.1 For example, even if the heating circuit is resistance heating, the current on the primary side of the filament heating transformer can be changed to the reference level at the timing of the end of exposure. Therefore, it is applicable. A specific example is shown in FIG.

20 is a stabilizer, 21 is a space charge compensation switch,
A timing circuit 24 generates a switching timing signal for the switching device 23.

The heating voltage stabilized by the stabilizer 20 is corrected for tube voltage by a space charge compensation transformer 21,
It is applied to the heating resistor 22 for tube current selection. Switcher 2
A heating voltage Ve corresponding to the set tube current and a reference heating voltage Vf similar to the above-mentioned example are applied to the filament heating transformer 11 . is applied to the primary side of , and ■ is applied at the timing of the end of sunlight.

The timing circuit 24 includes the monostable multivibrator circuit of the above-mentioned specific example, and the switching circuit 23 which is set to V only between its paths.
It consists of a circuit that drives so as to apply Vf from e to the primary side of the filament heating transformer 11.

As described in detail above, according to the present invention, it is possible to provide an X-ray apparatus that can improve the discharge characteristics of the X-ray tube due to differences in tube current and can control the imaging time with high precision.

It should be noted that the present invention is not limited to the one embodiment described above, but can of course be implemented with appropriate modifications within the scope of the present invention without changing the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a block diagram showing an eleventh tie-setting chart, and FIG. 3 is a block diagram showing another embodiment of the present invention. i o ----X-ray tube, 11-...-filament heating transformer, 12-...-semiconductor heating circuit, 13
------ Commercial AC power supply, 14--- Comparator,
15--inverter, 16--analog switch, 17--summing amplifier, 20--stabilizer, 21--space charge compensation transformer, 22--heating resistor for tube current selection, 23-...-switcher, 24-...-
Timing circuit, R4~R, ---resistance, V R--
---Variable resistance, N□~N 5-----No.Gate representative patent attorney Norichika Kensuke and one other person

Claims (1)

[Claims] An X-ray tube, a heating circuit that heats the filament of the X-ray tube, a circuit that applies a heating signal for fluoroscopy connected to this heating circuit via a switch, and heating for imaging. and the circuit that applies the signal. An X-ray device comprising: a circuit that preheats the filament to a certain level when the switch is switched from fluoroscopy to radiography in response to an X-ray exposure signal; and a circuit that controls the timing of the preheating period and the radiography heating period. .