JPS6229878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diagnostic X-ray apparatus such as an X-ray television apparatus or an X-ray fluoroscopic imaging apparatus, and in particular to a method for keeping the brightness of an X-ray television monitor constant during fluoroscopy regardless of changes in the subject. This invention relates to improvements in the automatic brightness adjustment circuit that controls the fluoroscopy tube voltage during fluoroscopy.

A diagnostic X-ray apparatus such as an X-ray television apparatus used for X-ray diagnosis is generally constructed as shown in FIG. That is, in the figure, reference numeral 1 indicates a power supply for fluoroscopy tube voltage, which is an AC power supply for generating a tube voltage under fluoroscopic conditions, and numeral 2 inputs the output of this power supply 1 for voltage for fluoroscopy tube, and by adjusting the slider 2a. 3 is a relay for switching the output; 4 is a sliding transformer 2 for controlling the voltage of the see-through tube, which is provided via the relay 3; A high voltage generator 5 uses the output as a primary input and generates a high voltage according to its level, and 5 uses the output of this high voltage generator 4 as a tube voltage and generates X-rays with an intensity corresponding to the tube voltage. A tube, 6 is a subject, 7 is an image amplification tube that is provided opposite to the X-ray tube 5 and displays the X-ray image that has passed through the subject 6 and is incident on the output surface as an optical image; 8 is this image amplification tube. A reflecting mirror that branches and guides the output image of the tube 7; 9 is a photomultiplier tube that detects the light branched by this reflecting mirror 8 and converts it into an electrical signal; 10 is an amplifier that amplifies this electronic signal; 11 is a Output resistor of amplifier 10, 1
2 is a variable resistor to which +15V and -15V are applied, and this potential difference is divided and taken out to output a voltage at a level that becomes a reference value for brightness; 13 is a variable resistor that outputs this divided voltage through a resistor 14 and the amplifier. an amplifier into which the outputs of 10 are respectively input via resistors 11;
Zener diodes 15 and 16 are connected between the input and output of the amplifier 13 which are connected in reverse to each other; 17 is a power amplifier that amplifies the output of the amplifier 13; and 18
is a continuator that closes and opens the output of this power amplifier 17;
19 is a motor rotor, and 20 is a motor coil to which the output of the power amplifier 17 is input via the relay 18. Incidentally, the rotation shaft of the motor rotor 19 is connected to the slider 2a of the sliding type transformer 2 for controlling the fluoroscopic tube voltage. Further, 3a and 18a are coils of relays 3 and 18 that are energized when a fluoroscopy command is received.

In a conventional device with such a configuration, the relay 3 is activated by a fluoroscopy command, and the high voltage generated by the high voltage generator 4 is applied as a tube voltage to the X-ray tube 5, and X-rays are emitted from the X-ray tube 5. be done. After the X-rays pass through the subject 6, they are input as an X-ray image into an image intensifier tube 7, where they are converted into visible light.

This X-ray image converted into visible light is transmitted to the image intensifier tube 7
is displayed on the output surface of the camera and sent to the image pickup tube of the X-ray television via an optical system (not shown), but a portion is branched off to a photomultiplier tube 9 by a reflecting mirror 8 installed in this optical system. The light enters the field and undergoes photoelectric conversion.

The minute current signal corresponding to the amount of incident light output from the photomultiplier tube 9 is converted into a voltage signal by an amplifier 10.
It is amplified to Va.

The output Va of the amplifier 10 is connected to the variable resistor 12.
The error is amplified by the voltage V _B outputted by the voltage V B and the comparison circuit constituted by the amplifier 13 and input to the power amplifier 17 . As a result, the power amplifier 17 generates an output power corresponding to the input and applies it to the motor coil to excite it and drive the motor rotor 19. Resistors 11 and 14 are used to determine the voltage division ratio, and when the resistance values are equal, the motor rotor 19 continues sliding of the sliding type transformer 2 for controlling the voltage of the transparent tube until Va - V _B = 0. The output of the sliding type transformer 2 for controlling the voltage of the fluoroscopy tube is adjusted by sliding the child 2a. Then, the high voltage generator 4 generates a tube voltage according to this output, and the X-ray tube 5 emits X-rays under the tube voltage condition.

The problem here is that at the start of fluoroscopy, the rise of the fluoroscopy tube current is delayed as shown in Figure 2, so the X-ray tube 5
The point is that the X-ray output shows a rise almost similar to the fluoroscopic tube current shown in FIG.

That is, if the output of the X-ray tube 5 is D, then D=
kV ⁿ × mA × t (kV = tube voltage, n = multiplier,
mA = tube current, t = time), but in order to keep the output D of the X-ray tube 5 constant and the brightness of the image displayed on the X-ray television monitor constant,
In the configuration shown in Fig. 1, at the start of fluoroscopy, there is a delay in the rise of the fluoroscopy tube current as shown in Fig. 2.
Although the linear energy decreases, since the output of the comparison circuit controls the fluoroscopic tube voltage to correct this, the tube voltage increases excessively in a short period of time.

Therefore, as a result, an unnecessary load was placed on the X-ray tube 5 and the high-pressure system, and the subject (in the case of medical equipment, the human body) was exposed to unnecessary high-energy X-rays, which was a problem. .

That is, the diagnostic X-ray apparatus is capable of performing fluoroscopy and imaging, and during imaging, the film is directly exposed to the transmitted X-rays of the subject 6.
On the other hand, fluoroscopy requires X-rays with a lower energy than the one required for imaging to capture the output image of the image intensifier tube 7 with an image pickup tube and display it on a television monitor. In order to optimize the output of each X-ray during imaging, conditions such as tube voltage, tube current, and exposure time are set.
X-ray exposure is performed under these conditions.

However, in order to make the image displayed on the television monitor easier to observe during fluoroscopy, an automatic brightness adjustment circuit as described above is installed to control the X-ray output according to the subject. This is done by setting the tube current and time to predetermined setting conditions, and turning on the filament current and tube voltage at the same time using a fluoroscopic command in order to perform optimal control using only tube voltage control as described above. During this transition period, the tube voltage is rapidly increased to compensate for the lack of brightness caused by the delay in the rise of the tube current. Therefore, this is also a drawback since X-ray irradiation is started during this transition period.

The present invention has been made in view of the above circumstances, and is capable of controlling the control operation of the automatic brightness adjustment circuit for an arbitrary period of time from the start of fluoroscopy to suppress the transient voltage rise in the automatic brightness adjustment circuit caused by the delay in the rise of the current in the fluoroscopy tube. The purpose of the present invention is to provide a diagnostic X-ray device that prevents unnecessary exposure of high-energy X-rays to a subject by providing a delay, and prevents unnecessary burden on the X-ray tube and high-pressure system. shall be.

An embodiment of the present invention will be described below with reference to FIG. The apparatus is basically the same as that shown in FIG. In order to solve the above-mentioned drawbacks, the present invention is constructed as shown in FIG. 3, but the difference from the conventional construction shown in FIG. 1 is that the relay 3, A delay relay 21 is connected to the circuit of the 18 energizing coils 3a and 18a, so that the automatic brightness adjustment function does not work immediately even if a fluoroscopic command is given.

The operational difference here is that the delay relay 21 delays the time from when the filament current is turned on by a fluoroscopy command and fluoroscopy starts until the automatic brightness adjustment circuit operates.

That is, the delay in the rise of the tube current is caused by the fact that the filament of the X-ray tube 5 is not heated enough to obtain the desired tube current immediately after the fluoroscopy command, and the required amount of thermoelectrons is not emitted. The point is that there are also fluctuations in the filament current until the filament is sufficiently heated.

Therefore, from the start of transmission until the filament current of the X-ray tube 5 stabilizes, the delay relay 21 delays the operation of the relays 3 and 18 and stops the operation of the automatic brightness adjustment circuit, thereby allowing the X-ray exposure to begin. This solves the drawback of the conventional tube current that the rise of the tube current is delayed and the divided tube voltage increases.

If the filament current is stabilized, the tube current necessary to obtain the necessary X-ray output can be secured, so if the relays 3 and 18 are closed at this stable point, the transmitted X-ray intensity of the subject 6 will be the same as that of the X-ray television. Since the tube voltage is controlled to the optimum brightness, it is possible to avoid the sudden rise in tube voltage that occurs during the transition period, which may cause the subject to be exposed to unnecessary high-energy X-rays or cause damage to the high-voltage system or This eliminates the possibility of overloading the X-ray tube.

As detailed above, the light of the output image of the image intensifier tube for converting the X-ray image to the optical image, which converts the X-rays generated by the X-ray tube into light, is detected and compared with the reference value for brightness setting, In an X-ray apparatus that has a brightness control circuit that adjusts a tube voltage according to the differential output, and that captures an output image of the video amplification tube and displays it on a television monitor, We provided a device that supplies filament current to the X-ray tube in response to a command and operates the control circuit after a predetermined time delay when the filament current stabilizes, so that the brightness is adjusted when the filament current stabilizes and the desired tube current is obtained. In order to activate the control circuit and perform X-ray exposure, the X-ray output is maintained at a predetermined value by compensating for the lack of tube current with tube voltage due to the delay in the rise of tube current as in the past. This prevents the occurrence of sudden increases in tube voltage to compensate for this, preventing unnecessary high-energy X-ray exposure to the subject, and also preventing overload on the X-ray tube and high-pressure system. It is possible to provide a diagnostic X-ray apparatus that has excellent features such as not having to give

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with appropriate modifications within the scope without changing the gist thereof.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram for explaining a conventional example, Figure 2 is a circuit diagram for explaining a conventional example.
The figure shows the rise characteristics of tube current, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Power source for fluoroscopic tube voltage, 2...Sliding type transformer for controlling fluoroscopic tube voltage, 2a...Slider, 3, 18...
...Relay, 3a, 18a...Relay coil, 4
... High voltage generator, 5 ... X-ray tube, 7 ... Image amplifier, 8 ... Reflector, 9 ... Photomultiplier tube, 1
0,13...Amplifier, 11,14...Resistor, 1
2...Variable resistor, 17...Power amplifier, 19...
...Motor rotor, 20...Motor coil.

Claims (1)

[Claims] 1. Detects the light output from an image intensifier tube for converting X-ray images to optical images that converts X-rays generated by an X-ray tube into light, compares it with a reference value for brightness setting, and calculates the output according to the difference output. In an X-ray apparatus, the X-ray apparatus has a brightness control circuit that adjusts the tube voltage by using the X-ray apparatus, and is configured to capture an output image of the image intensifier tube and display it on a television monitor. A diagnostic X-ray apparatus, comprising a device that supplies current and operates the brightness control circuit after a predetermined time delay during which the filament current stabilizes.