JPH0125440Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an X-ray apparatus that suppresses fluctuations in the amount of X-ray exposure.

In an X-ray apparatus, it is known that when the power supply voltage fluctuates, the tube voltage and tube current fluctuate, and the rise characteristics of the tube voltage and tube current also change.

Therefore, if only the energization time to the X-ray device is controlled, the amount of X-ray exposure will vary significantly as the power supply voltage fluctuates.

In view of this, an X-ray apparatus has been developed in which the energization of the X-ray apparatus is controlled by the mAs level determined by the product of the tube current of the X-ray tube and time.

Furthermore, the recent development of X-ray film has increased its sensitivity, leading to a reduction in the time required for energizing the X-ray tube, and the mAs level required for X-ray photography has gradually become smaller.

Under such circumstances, it is impossible to accurately control the X-ray exposure amount by simply controlling the X-ray exposure amount by controlling the mAs level.
Even if the mAs level is kept constant and controlled, if the mAs level is small, the amount of X-ray irradiation will fluctuate greatly due to fluctuations in the power supply voltage (see Figure 2). There was an inconvenience that the sharpness, brightness, etc. of the photographed image changed when the camera was used.

The present invention solves the above drawbacks by controlling the current supply to the X-ray tube based on the mAs level and correcting the mAs level by detecting fluctuations in the power supply voltage. This will be explained in detail with reference to the accompanying drawings.

FIG. 1 is an electrical wiring diagram showing the X-ray apparatus of the present invention, in which a high voltage for driving the X-ray tube is connected between both terminals of a commercial alternating power supply 1 via a power switch 2, a fuse 3, a mAs timer 4, and a diode 5. The primary winding of the transformer 6 is connected. Note that 16 is a resistor connected in parallel with the diode 5. The pair of secondary windings of the high-voltage transformer 6 are connected in series via the arrester 7 to apply a secondary high voltage between the anode and cathode of the X-ray tube 8. A relatively low voltage for heater heating, which is obtained by dividing the secondary high voltage, is applied to a certain heater.

Further, while applying the tube current of the X-ray tube 8 to the feedback terminal of the mAs timer 4,
An X-ray exposure switch 10 is provided to conduct the triax 9 in the mAs timer, and a secondary voltage of a transformer 11 whose primary winding is connected between both terminals of the commercial alternating power supply 1 is applied as described below. mAs
The output signal of the level correction device is applied.

Here, the mAs timer 4 is set so that the product (mAs level) of the tube current of the X-ray tube 8 applied to the feedback terminal and time is a predetermined value (determined by the preheating time set to a predetermined value and the type of object to be imaged, etc.). When the time period (sum of the exposure time) is reached, the triax 9 is set to a cutoff state and the power supply to the X-ray tube 8 is cut off.
Since this is a conventionally well-known configuration, details will be omitted.

Furthermore, the mAs level at which the triax 9 is cut off can be set by external operation.

The device for correcting the mAs level that activates the mAs timer 4 when the power supply voltage changes is as follows.

A voltage detector 12 is connected between both terminals of the commercial alternating power supply 1, and the output signal of the voltage detector 12 is applied to a comparator 13, and the output signal of the comparator 13 and the set mAs level are input. , a corrector 14 that calculates a mAs level correction value corresponding to fluctuations in the power supply voltage and applies it to the mAs timer 4;
has been established.

That is, when the power supply voltage is equal to the design value, the change in the X-ray exposure amount depending on the mAs level is as shown by the solid line in Figure 2, and when the power supply voltage is equal to the design value,
The changes in the X-ray exposure amount depending on the mAs level when there is a difference of ±10% are shown in the dotted line and double dotted line in Figure 2, respectively. Therefore, when the power supply voltage is 10% higher than the design value, In this case, the X-ray exposure amount increases by x ₁ , and if the power supply voltage is 10% lower than the design value, the X-ray exposure amount decreases by x ₂ , and in both cases, the X-ray quality decreases. Things will change.

Therefore, in these cases, in order to keep the X-ray exposure amount equal to that at the regular power supply voltage and prevent changes in the X-ray quality, if the power supply voltage is 10% higher than the design value, the mAs level If the supply voltage is 10% lower than the design value, reduce the mAs level by y ₁ .
It is only necessary to increase y ₂ , and in the corrector 14,
By setting y ₁ or y ₂ and correcting the mAs level, the X-ray exposure amount can be kept equal to that of the regular power supply voltage, preventing changes in the X-ray quality and improving the details of the captured image. The brightness, brightness, etc. can be kept constant.

Here, the relationship between X-ray exposure amount and mAs level is
Since it is determined for each power supply voltage,
Once the mAs level is determined, the amount of correction of the mAs level when the power supply voltage fluctuates can be calculated.

The operation of the X-ray apparatus having the above configuration is as follows.

After turning on the power switch 2, set the mAs level at which the mAs timer 4 operates according to the object to be imaged, and then turn on the X-ray exposure switch 10 to emit X-rays as follows. can be done.

When the X-ray exposure switch 10 is turned on, the triax 9 of the mAs timer 4 becomes conductive, and the power supply voltage of the high voltage transformer 6 can be applied.

Therefore, at the same time that a high voltage is applied between the anode and cathode of the X-ray tube 8, the heater 1 of the X-ray tube 8 is
A relatively low voltage for heating is applied to 5.

At the beginning of the conduction of the triax 9, the heater 15 of the X-ray tube 8 is not sufficiently heated.
Since the amount of electron emission is small (tube current is small),
A considerably higher voltage is applied between the anode and cathode than in a stable state. after that,
As the heater 15 heats up, the tube current Ip increases until it reaches a certain level and becomes saturated (see FIG. 4).

Here, the time while the heater 15 is being heated is the preheating time, and the time after the tube current Ip reaches a certain value is the actual X-ray exposure time. It is necessary to set the time plus the time as the mAs level. In the present invention, the preheating time is fixed at a certain time,
This makes it easy to set the mAs level.

However, the actual preheating time is not only affected by fluctuations in the power supply voltage, but also by the rise characteristics of the tube current, etc., so after the power supply voltage is detected by the voltage detector 12, , the comparator 13 determines whether the voltage is close to the design value or not, and the corrector 1 receives the determination output signal from the comparator 13 as input.
By calculating the corrected value of y ₁ or y ₂ in step 4 and increasing or decreasing the set mAs level, the X-ray exposure amount can be maintained optimally (as indicated by the dotted line in Fig. 3). reference).

Then, when the set mAs level or the modified mAs level is reached, the X-ray exposure with the triax 9 cut off is stopped, and even before that, if the X-ray exposure switch 10 is turned OFF,
The triax 9 can be immediately shut off to stop the X-ray exposure.

The above applies to simultaneous ignition type X-ray equipment when the power supply voltage is 90 to 97% of the design value and 104 to 110%.
%, we have described an example in which the mAs level is corrected using correction values corresponding to 90% and 110%, respectively, but it is also possible to finely correct the mAs level for minute changes in the power supply voltage. By doing so, fluctuations in the amount of X-ray exposure can be further suppressed.

In addition, for X-ray devices other than the simultaneous ignition type, there is no need to consider preheating time, but since the power supply voltage may fluctuate during the X-ray exposure operation time, automatic The X-ray exposure amount can be maintained at the set value by correcting the mAs level.

As described above, the present invention provides an X-ray apparatus in which the mAs level is set by assuming a preheating time of a fixed time.
By correcting the mAs level, the X-ray exposure amount is maintained at the set value.
Eliminates the complexity of setting levels,
Also, unlike directly detecting the amount of X-ray exposure,
Since the mAs timer is controlled by changes in the current value flowing through the radiation tube, unlike converting the X-ray optically and then converting this into an electrical signal, the detection unit is damage the durability of the equipment, be affected by the subject, or
It is possible to maintain high performance over a long period of time without causing a decrease in accuracy due to performance deterioration of the equipment that makes up the detection unit due to radiation exposure, and furthermore, it can be easily achieved by incorporating a microcomputer. It is practical, such as being achievable.

[Brief explanation of the drawing]

FIG. 1 is an electrical wiring diagram showing the X-ray apparatus of the present invention.
FIG. 2 is a diagram showing the relationship between X-ray irradiation amount and mAs level. FIG. 3 is a diagram showing the relationship between X-ray irradiation amount and power supply voltage. FIG. 4 is a diagram showing temporal changes in X-ray tube applied voltage and tube current. 1...Commercial alternating power supply, 4...mAs timer,
6... High voltage transformer, 8... X-ray tube, 9... Triax, 10... X-ray exposure switch, 12...
Voltage detector, 13... comparator, 14... corrector.

Claims (1)

[Scope of utility model registration request] An mAs timer is provided on the primary side of the high-voltage transformer for driving the X-ray tube, and the mAs timer that controls the power supply to the high-voltage transformer by a triax is provided, and the voltage applied to the power source is monitored between the mAs timer and the power source. A power supply voltage detector is connected, and a comparator is connected between the power supply voltage detector and the mAs timer to compare the detected value of voltage fluctuation by the detector with the intended design value of the power supply voltage, and a comparator is connected between the power supply voltage detector and the mAs timer. Based on the discrimination signal and the mAs level preset to the mAs timer.
An mAs level correction device for level correction of the mAs timer is provided, and the tube current of the X-ray tube is fed back to the feedback terminal of the mAs timer to constantly detect the mAs level and control the X-ray tube. An X-ray device featuring: