JPH0251240B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an improvement of an automatic X-ray exposure control device in an X-ray fluoroscopic imaging device, and particularly to a phototimer-type device that automatically sets X-ray imaging conditions from X-ray fluoroscopy conditions. It is about improvement.

BACKGROUND ART FIG. 1 is a diagram showing a schematic configuration of a conventional X-ray automatic exposure type X-ray fluoroscopic imaging apparatus. In the figure, 1 is an X-ray tube, 2 is a subject, 3 is a photographic film, 4 is an image intensifier (hereinafter referred to as II), 5 is a distributor optical system, and 6 is an X-ray automatic exposure control device. It is equipped with a lighting unit and a phototimer that collects the output of II4. 7 is a TV camera, 8
1 is a television monitor, 9 is a control panel, and 10 is a high voltage generator.

In the automatic X-ray exposure operation of this device, the output of the II 4 is collected by the lighting section of the automatic X-ray exposure control device 6, the current or voltage proportional to the amount of light is integrated by the integrating circuit of the phototimer, and the integrated value is The X-ray imaging conditions corresponding to the subject 2 are determined from the X-ray fluoroscopy conditions, and are automatically controlled via the control panel 9 to optimize the amount of X-ray irradiation from the X-ray tube 1.

In such a conventional X-ray automatic exposure control device,
After the X-ray imaging conditions have been set from the X-ray fluoroscopy conditions, the patient 2 may move during the period before the rapid imaging device is ready, and there may be an X-ray, such as a gas part or a direct X-ray, within the field of view of the lighting section. Appropriate X-ray imaging time could not be obtained because areas with low X-ray absorption were intruding, and conversely, areas with high X-ray absorption such as contrast agents were intruding. Furthermore, there were cases in which the mechanical part of the snapshot device entered the field of view for daylighting, reducing the lightness signal and lengthening the X-ray irradiation time.

Purpose of the Invention The purpose of the present invention is to eliminate the drawbacks of the conventional apparatus, automatically set the upper and lower limits of the X-ray imaging time based on the X-ray fluoroscopy conditions, and if the upper and lower limits are within the upper and lower limits, the phototimer To provide an X-ray automatic exposure control device which performs an operation and when the X-ray photographing time by a phototimer is equal to or more than the upper limit time or less than the lower limit time, the X-ray photographing time becomes the set upper limit time or lower limit time, respectively. There is a particular thing.

EXAMPLES Hereinafter, the present invention will be described in detail along with examples.

In addition, in all the figures, the same parts are given the same reference numerals, and the explanations of the overlapping parts are omitted.

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, 11 is a photodetector that collects the output light of II4 and converts it into current or voltage, 12 is a preamplifier that converts and amplifies the output of photodetector 11, and 13 is an X-ray fluoroscopic imaging switch. ,
F is its X-ray fluoroscopy side terminal, and T is its X-ray photography side terminal. Reference numeral 14 denotes a comparator for setting the X-ray fluoroscopy tube voltage, and the output is "0" when the input values are the same. Reference numeral 15 denotes an X-ray fluoroscopy reference voltage setting device for setting a reference voltage corresponding to optimal exposure conditions for X-ray fluoroscopy, and the reference voltage is set in advance from the outside. 16 is an X-ray fluoroscopy tube voltage adjustment motor, and 17 is an X-ray fluoroscopy switching signal input terminal, which generates an X-ray fluoroscopy switching signal at the same time as the X-ray imaging start button is pressed. 1
8 is a phototimer integrating circuit for integrating the output of the preamplifier 12; 19 is a comparison circuit for comparing the output of the integrating circuit 18 with a signal proportional to the X-ray fluoroscopy tube voltage; 20 is an X-ray fluoroscopy tube voltage signal generation circuit , which generates a signal proportional to the optimum fluoroscopy tube voltage. 21 is an X-ray imaging time upper limit setting circuit, which is reset by a reset signal RS at the same time as the start of X-ray irradiation during X-ray imaging, and sets the upper limit of the X-ray imaging time based on a signal proportional to the X-ray fluoroscopy tube voltage. is set, and an X-ray imaging end signal is output after the set time has elapsed. 22 is an X-ray imaging time lower limit setting circuit, which is reset by a reset signal RS at the same time as the start of X-ray irradiation during X-ray imaging, and sets the lower limit of the X-ray imaging time based on a signal proportional to the X-ray fluoroscope tube voltage. is set, and an X-ray imaging end signal is output after the set time has elapsed.
23 is an AND gate circuit which takes the logical product of the output of the comparison circuit 19 and the output of the X-ray imaging time lower limit setting circuit 22; 24 is the logic between the output of the AND gate circuit 23 and the output of the X-ray imaging time upper limit setting circuit 21; An OR gate circuit 25 for calculating the sum is a backup timer circuit for the phototimer, which is generally provided to protect the phototimer. By controlling this back-up timer circuit 25, X-ray irradiation is controlled at an imaging time set to the optimum exposure conditions for the photographic film. 26 is the output of the OR gate circuit 24 and the backup timer circuit 25
This is an OR gate circuit that calculates the logical sum with the output of .
OUT is an X-ray irradiation stop signal output terminal, 27 is an X-ray tube voltage setting circuit, and the X-ray tube voltage is automatically set by setting the X-ray fluoroscopy tube voltage. . 28 is a motor for adjusting the X-ray tube voltage.

Next, the operation of this embodiment will be explained.

In Figure 2, when performing X-ray fluoroscopy,
The fluoroscopy switching device 13 is connected to the X-ray fluoroscopy side terminal F, the X-ray fluoroscopy reference voltage setting device 15 is set to a predetermined value, and the X-ray irradiation start switch (not shown) is turned on. As a result, the subject is irradiated with X-rays, and the transparent X-rays are incident on II4. II４
The output of is detected by the photodetector 11, converted into a current or voltage proportional to the amount of light, and inputted to the preamplifier 12, which is then input to the X-ray fluoroscopy tube voltage comparator 14.
It is input to the X-ray fluoroscopy tube voltage adjustment motor 16 through. As a result, the X-ray fluoroscopy tube voltage adjustment motor 16 is connected to the X-ray fluoroscopy tube voltage regulator (not shown).
Then, the set value of the X-ray fluoroscopy tube voltage signal generation circuit 20 is increased, and when the output of the preamplifier 12 reaches the set reference voltage, the output of the X-ray fluoroscopy tube voltage setting comparator 14 becomes "0". Therefore, the X-ray fluoroscopy tube voltage adjustment motor 16 stops and the optimum X
The line fluoroscopy tube voltage is set. A signal proportional to the set X-ray fluoroscopy tube voltage is generated from the X-ray fluoroscopy tube voltage signal generation circuit 20.

Next, when performing X-ray photography, the X-ray fluoroscopy tube voltage signal generation circuit 20 outputs a signal proportional to the optimal X-ray fluoroscopy tube voltage, and the signal is transmitted to the comparison circuit 19, the X-ray photography time Upper limit setting circuit 21,X
The signal is input to the radiography time lower limit setting circuit 22 and the radiography tube voltage setting circuit 27. The X-ray tube voltage setting circuit 27 drives the X-ray tube voltage adjustment motor 28 to set the X-ray tube voltage based on the optimal X-ray fluoroscopy tube voltage. Then, when the X-ray fluoroscopy switching device 13 is connected to the X-ray imaging side T and the X-ray irradiation start switch is turned on, a reset signal RS is generated, and the integrating circuit 18 and the X-ray imaging time upper limit setting circuit 2
1. At the same time, the output of the photodetector 11 is input to the X-ray imaging time lower limit circuit 22 and the backup tie circuit 25 to reset them.
is input to the integrating circuit 18 and integrated.
The output of this integration circuit 18 is input to a comparator 19, and when this integrated value reaches a signal (comparison reference signal) proportional to the set X-ray fluoroscopy tube voltage, an X-ray imaging end signal _E1 is output. .

On the other hand, a signal proportional to the X-ray fluoroscopic tube voltage is input to the X-ray imaging time lower limit setting circuit 22, which sets the lower limit of the X-ray imaging time based on this signal, and when this time elapses, an X-ray imaging end signal is sent. E ₂ is output.
The AND gate circuit 23 calculates the AND of the X-ray imaging end signals E ₁ and E ₂ , and inputs the output to the OR gate circuit 24 . At this time, if the X-ray imaging time determined by the comparison circuit 19 is shorter than the lower limit value of the X-ray imaging time, the output of the AND gate circuit 23 is the X-ray imaging end signal generated by the X-ray imaging time lower limit setting circuit 22.
Since _E2 is followed, all X-ray imaging end signals become signal _E2 . Furthermore, the output of the AND gate circuit 23, that is, the X-ray imaging end signal E ₂ and the
The OR gate circuit 24 calculates the logical sum with the X-ray imaging end signal _E3 from the radiography time upper limit setting circuit 21,
When both X-ray photography end signals E ₂ and E ₃ are present,
OR is synchronized with the one with the shorter X-ray imaging time between the two.
An X-ray imaging end signal E ₄ is generated from the gate circuit 24 . Then, the OR gate circuit 26 calculates the logical sum of the X-ray imaging end signal E ₅ generated from the backup timer circuit 25 of the phototimer and the X-ray imaging end signal E ₄ , and the An optimal X-ray imaging end signal E ₆ that is not longer than the imaging time is output from the OR gate circuit 26 . This X-ray imaging end signal _E6 is sent to an X-ray irradiation stop signal input terminal (not shown).

FIG. 3 shows the X-ray imaging time upper limit setting circuit 21.
2 is a diagram showing a detailed circuit configuration of an embodiment of the lower limit setting circuit 22. FIG. In the figure, VR ₁ , VR ₂ , VR ₃ ,
VR ₄ is the volume, OP1 and OP3 are the inverting operational amplifiers, OP2 is the voltage floor operational amplifier, OP4
is the buffer operational amplifier, OP5 is the integral operational amplifier, C1 is the comparator, _S1 is the output of the inverting operational amplifier OP1 and the voltage floor operational amplifier OP2.
A selection circuit comprising a diode pair D ₁ which compares the outputs of and selects the larger one, S ₂ is the selection circuit S ₁
SW1 is an analog switch that is turned on by a reset signal _RS that is generated at the same time as X-ray irradiation. , the output of the integrating circuit 18 is set to "0". F.KV is a signal proportional to the X-ray fluoroscopy tube voltage.

4 and 5 are diagrams for explaining the operation of the circuit shown in FIG. 3. FIG. Figure 4 is a diagram showing the relationship between the X-ray fluoroscopy tube voltage and the X-ray imaging time so that the photographic film density remains constant even if the subject changes, and ST is the standard X-ray imaging time curve. , U
is an X-ray imaging time upper limit curve, and D is an X-ray imaging time lower limit curve. Figure 5 shows the input of the circuit shown in Figure 3.
It is a diagram showing output characteristics, and solid line B shows the voltage at point B.

Next, the operation of this circuit will be explained.

The upper limit or lower limit of the X-ray photography time is determined by the X-ray photography time upper limit curve U or the X-ray photography time lower limit curve D in Fig. 4.
To set the volume as shown in
VR ₁ , VR ₂ , VR ₃ are adjusted respectively, and the dashed lines OP1, OP1 and OP2 shown in FIG.
Generate output voltages like OP3 and OP2. Further, in the selection circuit S ₁ with diode pair D ₁ ,
Select the larger of the output of the inverting operational amplifier OP1 and the output of the voltage floor operational amplifier OP2,
The smaller one of the output of the selection circuit _S2 equipped with the diode pair _D2 and the output of the inverting operational amplifier OP3 is selected. The selection signal obtained in this way is
It is input to the integration operational amplifier OP5 through the buffer operational amplifier OP4. This integral operational amplifier OP5 integrates the curve B as shown in Figure 5.
Outputs the voltage of This integrated voltage is the volume
When the constant value set by VR ₄ is reached, the comparator C1 operates and generates an X-ray imaging end signal.

The circuits shown in FIG. 3 are provided as an X-ray imaging time upper limit setting circuit 21 and an X-ray imaging time lower limit setting circuit 22, respectively. The difference between the upper limit setting circuit 21 and the lower limit setting circuit 22 is determined by whether the integral constant is large or small.

Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without changing the gist thereof.

Effects of the Invention As explained above, according to the present invention, the upper and lower limits of the X-ray imaging time are set, the phototimer is operated within the set range, and even if the X-ray imaging time is increased, the upper limit Since the length is set to a lower limit value even if it is short, variations in X-ray photograph density can be reduced compared to conventional apparatuses, and X-ray photographs with more stable image quality can be obtained. In particular,
The present invention is effective in cases where photographic density varies due to the influence of various noises generated during line photography.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a conventional X-ray automatic exposure type X-ray fluoroscopic imaging device, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. FIGS. 4 and 5, which are diagrams showing a detailed circuit configuration of one embodiment of the radiographic time upper limit setting circuit or lower limit setting circuit, are diagrams for explaining the operation of the circuit shown in FIG. 3. 11...Photodetector, 12...Preamplifier, 13
... X-ray fluoroscopy switching device, 14 ... X-ray fluoroscopy tube voltage setting comparator, 15 ... X-ray fluoroscopy reference voltage setting device, 16 ... X-ray fluoroscopy tube voltage adjustment motor, 1
7...X-ray fluoroscopy switching signal input terminal, 18...
Integrating circuit, 19... Comparison circuit, 20... X-ray fluoroscopy tube voltage signal generation circuit, 21... X-ray imaging time upper limit setting circuit, 22... X-ray imaging time lower limit setting circuit,
23...AND gate circuit, 24, 26...OR gate circuit, 25...backup timer circuit,
OUT...X-ray irradiation stop signal output terminal, 27...
X-ray imaging tube voltage setting circuit, 28...X-ray imaging tube voltage adjustment motor.

Claims (1)

[Claims] 1. In an X-ray automatic exposure control device that has a phototimer that controls the X-ray imaging time by controlling a portion of the output of the image intensifier, set the appropriate upper and lower limits of the X-ray imaging time from the X-ray fluoroscopy tube voltage. X-ray imaging time upper limit and lower limit setting circuit, and means for operating the phototimer within the X-ray imaging time range set by the X-ray imaging time upper and lower limit setting circuit. Line automatic exposure control device.