JPS5818760B2 - Pulse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides
Pulsed X-ray triggering performs X-ray fluoroscopy by intermittently emitting pulsed X-rays to reduce radiation exposure.

This invention relates to an automatic brightness adjustment device that is optimal for the device.

Conventional X-ray television equipment performs rapid reading during fluoroscopic observation.
The output of an X-ray fluorophore multiplier tube, which converts the X-ray image transmitted through the subject into visible light, is continuously provided.

The automatic brightness adjustment device that always keeps the fluoroscopic image at the best brightness receives the continuous output of this fluorescent multiplier tube with a photomultiplier tube, converts it into an electrical signal, and adjusts it to the best brightness. The X-ray exposure conditions such as tube voltage are automatically adjusted depending on the magnitude of the comparison with the corresponding reference value to maintain the best conditions.

On the other hand, in pulsed X-ray fluoroscopy, which is performed by intermittently emitting extremely short pulsed X-rays several times per second, the output of the X-ray fluorophore tube is intermittent depending on the ratio of the exposed X-rays. Moreover, since the X-ray pulse width is very short compared to the X-ray exposure period, the period during which the X-rays are interrupted, that is, the output from the fluorescence multiplier tube is zero, is long.

Therefore, it is impossible to automatically adjust the brightness using the same method as in the case of continuous X-ray fluoroscopy.

In view of the above problems, the present invention seeks to provide an automatic brightness adjustment device that can stably perform automatic brightness adjustment in pulsed X-ray fluoroscopy in the same manner as the conventional automatic brightness adjustment device for continuous X-ray fluoroscopy. It is something.

The present invention will be described below with reference to embodiments shown in the drawings.

In the block diagram shown in FIG. 1, the automatic brightness adjustment device is used not only for continuous X-ray fluoroscopy, in which X-rays are continuously emitted during fluoroscopy, but also for pulsed X-ray fluoroscopy, in which pulsed X-rays are intermittently irradiated. In order to make the automatic brightness adjustment operation effective even in the case of pulse X-ray fluoroscopy, a control circuit according to the present invention is constructed so that a switch S can be used as a part of the control system.

Therefore, when the on/off switch S is turned to the A side, the control system C functions as a known automatic brightness adjustment device for continuous X-ray fluoroscopy.

In this state, X-rays are continuously irradiated from the X-ray tube 13 to the subject 14 during fluoroscopic observation, and a part of the visible X-ray image amplified by the X-ray fluorescence multiplier tube 15 is transmitted to the mirror 16. It is extracted as a luminance signal and detected by the photomultiplier tube 1.

This signal is compared with the reference value B from the reference signal generator 3 corresponding to the best brightness in the comparator circuit 2, and the servo amplifier circuit 4 and servo motor 5 are driven based on the result to drive the X-ray high voltage equipment. The ray tube voltage regulator 6 is operated to automatically adjust the X-ray exposure conditions.

In the figure, 11 is an image pickup tube, and 18 is a monitor cathode ray tube.
3 to 18 constitute the X-ray television system.

In pulsed X-ray fluoroscopy, the output of the fluorescence multiplier tube 15, that is, the input of the photomultiplier tube 1, can be obtained only when pulsed X-rays are being irradiated as described above, so the selector switch S is set to the In the state where the control system C is tilted down, the control operation by the control system C becomes impossible. Therefore, when the changeover switch S is switched to the open side and the control circuit 7 provided according to the present invention is interposed in the control system C, the control system C becomes as follows. The present invention is suitable for pulsed X-ray fluoroscopy.

Operates as an automatic brightness adjustment device.

In this case, the pulsed X-ray controller 19 shown in the figure is activated to intermittently irradiate the subject 14 with pulsed X-rays from the X-ray tube 13, and as a result, the photomultiplier tube 1 is exposed to X-rays. An intermittent signal synchronized to this is detected.

The signal is converted into a step-like signal by a signal holding circuit provided in the control circuit 7 and sent to the comparison circuit 2.

In addition, in the case of this pulsed X-ray fluoroscopy, the image storage device 20 having a configuration function is also activated, and the pulsed X-rays i.

A transmitted X-ray image of the subject 14 caused by the X-ray exposure is stored, and this stored image is displayed on the monitor cathode ray tube 18 while the X-rays are suspended until the next X-ray exposure.

Next, the configuration of the control@circuit 7 which forms the main part of the present invention is shown in FIG. 2 together with the operating waveform diagram shown in FIG. 3.

explain.

When the X-ray tube 13 emits the pulsed X-rays shown in FIG. A signal shown in FIG. 3 is detected.

The peak value of this signal is held by a holding circuit 8, and this holding circuit 8 is reset before a new input is received by a reset signal synchronized with the exposure X-ray pulse.

The output waveform of the holding circuit 8 is shown in FIG. 3 (■), and the reset signal is shown in FIG. 3 as a waveform (■).

On the other hand, the gate drive circuit 9 is operated by the reset signal, and the state in which the gate 10 was closed and the gate 11 was open up to that point is reversed.

As a result, the output of the holding circuit 8 appears at the output terminal and becomes the input of the comparator circuit 2 of FIG.

After the time set in the gate drive circuit 9, the open/close states of the gates 10 and 11 are reversed again, and the reference value B from the reference signal generator 12 appears at the output terminal.

Note that the reference value B from the reference signal generator 12 is exactly the same value as the reference value B from the reference signal generator 3.

To further explain the time setting in the gate drive circuit 9, when the exposure X-ray pulse period is long such as 1 pulse/second or 1 pulse/2 seconds, the above-mentioned held signal ( (Figure 3 waveform ■) (Continuing the control operation will result in over-correction due to the long operation time,
There is a high possibility that the optimum state may be exceeded.8 Since stable operation cannot be performed in this case, it is necessary to limit the control operation time when the exposure cycle is long.

Therefore, in the present invention, the gate drive circuit 9 is configured to be able to set the control operation time for automatic brightness adjustment, and when the set time is over, the gate drive circuit 9
0 is closed, the gate 11 is opened, and the reference value B from the reference signal generator 12 appears at the output terminal, and at that point, the first
The output of comparison circuit 2 in the figure becomes zero, and servo motor 5
is stopped and control operations are disabled.

FIG. 4 shows each operation waveform when the exposure period is long.

In the figure, ■ indicates an X-ray output waveform, ■ indicates an output waveform of the photomultiplier tube 1, ■ indicates an output waveform of the control circuit 7 in FIG. 2, and ■ indicates a reset signal.

In the signal waveform ■, A indicates the peak value of the waveform ■ held in the holding circuit 8, B indicates the reference value of the reference signal generator 12, and T indicates the signal from the holding circuit 8 set by the gate drive circuit 9. The control operation period supplied to the comparator circuit 2 is t
indicates a period in which the reference B from the reference signal generator 12 is supplied to the comparator circuit 2 and control operation is disabled.

The gate drive circuit 9 performs exactly the same operation even when the exposure cycle is short, but compared to this cycle, the control operation setting time is actually longer, for example, about 0.5 seconds; Even after the set time is over, there is a reset input immediately, so the gate 10 remains open and the gate 11 remains closed, so the output terminal of the above 1 has the following conditions:
A stepped waveform (■) in FIG. 31 appears.

Therefore, the operation of a servo motor is almost the same as that of continuous human power.

FIG. 5 is a circuit diagram showing an example of the electrical circuit diagram of the block diagram shown in FIG.

In this circuit, the peak value of the human power is held by the capacitor C1t, and this holding circuit is reset by the transistor (FET) Tr1 every time a reset input is made.

On the other hand, transistors Tr5+Tr6, resistors R2 to R,,
, iW resistor VR4, and -17 capacitor C2, Tr6 changes from 'OFF' to 'ON' state by the reset input, and the base of Tr2 + Trs forming the gate circuit. The current is cut off and Tr2tTr3 becomes "OFF".

At the same time, one transistor Tr4 is also turned off, so transistor Tr4, diode D4, variable resistor VR3
The reference voltage B created by and appearing at the output terminal
is cut off, and the output of amplifier A2 appears at output terminal f.

Note that the time for driving the gate circuit constituted by Tr2 + Tr3 II is set by the variable resistor vR4 of the mechanically stable multi-by-break circuit.

When this set time ends, Tr6 is turned "OFF" again, and Tr2, 'rr3 and Tr4 are set to 4 (O
N? +, and the reference voltage B from T r4 , VH2, and D4 appears at the output terminal.

As described in detail above, in the present invention, the control system of the automatic brightness adjustment device in the case of radiography A using conventional continuous X-rays is changed to A holding circuit that holds the peak value of transmitted X-ray output, a circuit that synchronizes with the pulsed X-ray exposure E and resets the holding circuit immediately before the X-ray exposure, and a control operation of the control system. By simply interposing a control circuit including a time setting circuit, the pulse
An automatic brightness adjustment device that can perform effective automatic brightness adjustment operations also in fluoroscopy can be obtained, and by holding and resetting input values, it is stable and has a fast response, and moreover, when the exposure cycle is long. In the case of fluoroscopy using pulsed X-rays, stable automatic brightness adjustment without damage correction is possible by limiting the control operation time (this is the case).

In the above description, a method of controlling the X-ray tube voltage has been described, but a method of controlling the X-ray tube current in the same manner is also possible.

Furthermore, although the case has been described in which a signal from a photomultiplier tube is used as an input, it is also possible to use a video signal from a television device as an input.

Furthermore, the monostable multi-break variable resistor VR4 in FIG. 5, which sets the control operation time of the control system, is replaced with a selector (not shown) for selecting the pulse period in the pulsed X-ray controller 19 in FIG. If they are linked, it will be useful for handling and operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the automatic brightness adjustment device of the present invention, FIG. 2 is a block diagram showing the configuration of the main parts of FIG. 1, and FIGS. 3 and 4 are the operations shown in FIGS. 1 and 2. An explanatory waveform diagram, FIG. 5, is a circuit diagram showing an example of the electric circuit of FIG. 2. 1...Photometer multiplier tube, 2...Comparison circuit, 3...Reference signal generator, 4...Servo amplifier circuit, 5... ... Servo motor, 6...
...X-ray tube voltage regulator, 1... Control circuit, 8.
...Holding circuit, 9...Data drive circuit, 10.11...Gate, 12...Reference signal generator, S...・Choice switch, 13...
...X-ray tube, 14... Subject, 15...
...Photoelectric 7 multiplier tube, 16...Mirror, 17.
...Photography tube, 18...Cathode ray tube for monitor, 19...Pulse X-ray controller, 20...
...Image storage device.

Claims (1)

[Claims] 1. A detector that detects the intensity of transmitted X-rays of a subject due to intermittent irradiation of pulsed X-rays, a holding circuit that holds the output peak value of this detector until just before the next pulsed An X-ray output control circuit is provided that has a comparison circuit that compares a held value of the circuit with a target value and controls X-ray output based on the output of the comparison circuit, and also disables the control operation of the X-ray output control circuit. a signal generator for generating a signal equal to the target value; and a signal generator for supplying the signal of the signal generator to the comparison circuit for a predetermined period in synchronization with the pulsed X-ray exposure in place of the held value. An automatic brightness adjustment device for a pulsed X-ray fluoroscope, characterized in that a control circuit is provided, and a period of X-ray output control operation by the X-ray output control circuit is limited within a period in which pulsed X-rays are suspended. .