JPH0510809Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention relates to a detection and display device for tube voltage and tube current in a panoramic X-ray imaging apparatus, particularly an X-ray imaging apparatus for dental diagnosis.

<Prior art> The quality of an X-ray photograph obtained with an X-ray imaging device is determined by the individual characteristics of the person being photographed and the quality of the balance between the tube voltage and tube current of the X-ray tube. It is determined by the degree of blackening (density ratio) on the side. In particular, in X-ray imaging equipment used for panoramic imaging in dental diagnosis, the film feed speed is not constant, and the speed ratio between the anterior tooth region and the molar region is approximately 1:3, and the amount of transmitted X-rays is equivalent to the feed speed. In order to keep the ratio constant, it is necessary to change the amount of transmitted X-rays by three times during imaging even if the thickness of the subject is constant.
Moreover, in reality, there is a large difference in the physique of adults and children, and the amount of X-rays that reach the film varies greatly depending on various imaging conditions such as bone defects and the presence or absence of prosthetics. Setting the tube current requires skill, and if the setting is not done properly, even if good contrast can be obtained at one point on the film, the degree of blackening will be significantly different from the optimum value in other areas and the result will be poor. A situation may occur in which a good contrast cannot be obtained.

For this reason, devices are known that automatically control exposure according to the amount of transmitted X-rays; for example, the one disclosed in Japanese Patent Publication No. 57-46640 is
Automatically controls the tube voltage of the X-ray generator according to the dose,
The one disclosed in Japanese Patent Publication No. 57-12518 is transparent
Tube current is automatically controlled to keep the ratio of dose and film speed constant. In these cases, it is necessary to initially set the tube current or tube voltage, which is not the object of control, and either the value must be fixed or the operator must rely on manual operation.

Furthermore, in Japanese Patent Application No. 58-142045 (Japanese Unexamined Patent Publication No. 60-32300) submitted by the present applicant, both tube current and tube voltage are feedback-controlled at the same time, so initial setting and manual operation of tube current and tube voltage are not necessary. This eliminates the need for reshooting due to setting errors. As mentioned above, this is a great advantage in panoramic X-ray imaging equipment for dental diagnosis, where the imaging conditions change every moment during imaging, and the ratio between the transmitted The control range that can be kept constant is widened, and a single rated device can produce images with good image quality and constant contrast.
This makes it possible to expand the range in which line images can be obtained, that is, the dynamic range.

<Problems to be Solved by the Invention> However, the apparatus having such an automatic exposure control function has the following inconveniences. In other words, if for some reason it is necessary to take an X-ray again with manual settings after taking an X-ray with automatic exposure, or if, for example, there is a significant change in the bone structure due to the removal of the mandible in a subsequent surgery. If you want to take pictures again after this has occurred,
Since there is no data on the tube voltage and tube current from the previous imaging, the surgeon must first take trial shots based on his or her intuition and obtain a rough guide before proceeding with the actual imaging, which is time consuming and costly for both the surgeon and the patient. Both of these methods were burdensome, and there was a risk of unnecessarily increasing the patient's radiation dose.

This invention focuses on these problems and makes it possible to grasp the values of tube voltage and tube current in real time during shooting using automatic exposure control, and is an advantage in devices that automatically control both tube voltage and tube current. The purpose of this invention is to provide a panoramic X-ray imaging device that can perform X-ray imaging with excellent reproducibility while taking full advantage of the above.

<Means for solving the problem> In order to achieve the above purpose, in this invention,
Detects the remaining amount of X-rays that have passed through the subject and the feeding speed of the X-ray film by converting them into electrical outputs.
A panorama configured to automatically control the tube voltage and tube current of the X-ray tube by feeding back the comparison result between the ratio and the reference ratio value to the tube voltage feedback control element and tube current feedback control element of the X-ray tube. In an X-ray imaging device, there is a means for detecting the tube voltage value actually applied to the X-ray tube and the tube current value actually flowing through the X-ray tube, and a means for detecting the tube voltage and tube current values detected by the means in real time. and display means for displaying the information.

<Function> Since both the tube voltage and tube current are feedback-controlled at the same time, there is no need for initial settings by the operator or manual operations during imaging, and good X-ray images can be obtained.
During imaging, the actual tube voltage value actually applied and the tube current value actually flowing through the X-ray tube are displayed in real time, so the data on the tube voltage and tube current required for subsequent manual imaging can be displayed in real time. person can know.

<Example> Next, an illustrated embodiment will be described.

FIG. 1 shows a schematic configuration of an embodiment of the apparatus, in which high-voltage equipment such as a high-voltage transformer 1, a filament transformer 2, and an X-ray tube 3 are housed in an X-ray irradiation head. An X-ray film 4 is placed corresponding to this head,
A low-speed tachometer 5 that detects the feed speed of the film 4 and outputs it as an electrical signal; a fluorescent screen 6 that emits light from the X-rays that have passed through the film 4;
A photoelectric conversion device 7 that outputs an electrical signal corresponding to the luminance of the fluorescent screen 6 is provided. As is well known, the X-ray irradiation head and the X-ray film 4 are mounted on an arm (not shown) that rotates around the subject.
The X-ray head is placed at both ends of the
A ray beam is emitted, and the X-ray beam is transmitted sequentially through the dental arch of the person to be imaged, and at the same time an X-ray film 4 is
to create a panoramic X on the X-ray film 4.
Line photographs are now being taken.

Reference numeral 8 denotes a circuit for amplifying the output signal of the photoelectric conversion device 7 using amplifiers 8a and 8b, and the output of the low-speed tachometer 5 and the output of the photoelectric conversion device 7 that have passed through the amplifier circuit 8 are input to an arithmetic circuit 9. , and the arithmetic circuit 9 outputs a ratio signal Z=y/x of both signals. on the other hand,
On the head side, the primary side of the high voltage transformer 1 and the primary side of the filament transformer 2 are each connected to an AC power source 10 via a power on/off switch 11. A transistor 12 and a current feedback control transistor 13 are provided on the primary side of the filament transformer 2, respectively.

The output of the arithmetic circuit 9 is sent to a tube voltage control comparator 14 and a tube current control comparator 15, respectively, and the outputs of the comparators are sent to transistors 12 and 13 via comparators 16 and 17 in the next stage. As a result, the base bias of each transistor is adjusted, and feedback control is applied to the high voltage transformer 1 and the filament transformer 2. 18 and 19 are reference ratio setters for the ratio signal Z, and 20 and 21 are Zener diodes as limiters for setting the voltage range. Further, the comparators 16 and 17 are inputted with the output of the previous stage comparator, while the tube voltage actually applied to the X-ray tube 3 is inputted to the detection voltage obtained through the voltage dividing resistors R ₁ and R ₂ . , a detected voltage corresponding to the tube current actually flowing through the X-ray tube 3 taken out from the secondary side point P of the high-voltage transformer 1 is inputted.

27 and 28 are display devices, in which the detected voltages corresponding to the tube voltage and tube current described above are digitized by A/D converters 23 and 24, respectively, and inputted via display device drive circuits 25 and 26. Also,
Reference numerals 31 and 32 are memories, and 33 and 34 are arithmetic circuits, which are appropriately provided as necessary.These circuits constitute data detection and display means 29 and 30, respectively. Display device 27, 2
As 8, for example, a CRT display, a printer, etc. are used.

This embodiment has the configuration described above and operates as follows.

During imaging, when the X-ray tube 3 is activated, X-rays pass through the teeth of the person to be imaged 22, expose the film 4, and form an image of the teeth on the film 4.
On the other hand, the remaining amount of X-rays transmitted through the film 4 causes the fluorescent screen 6 to
emits light, and the luminance of this emission is proportional to the X-ray intensity, so the photoelectric conversion device 7 outputs an electrical signal corresponding to the X-ray intensity, which is input to the arithmetic circuit 9 via the amplifier circuit 8. At the same time, a film 4 is being fed by a feed mechanism (not shown) for panoramic photography, and a low-speed tachometer 5 detecting this feeding speed outputs an electrical signal, which is input to an arithmetic circuit 9. This circuit 9 inputs a signal Z=y/x based on the ratio of both input signals to comparators 14 and 15, and these comparators 14 and 15 input the ratio value input from the calculation circuit 9 and the reference ratio setter 18, 19
The output is compared with a predetermined reference ratio value, and the output is sent to the next-stage comparators 16 and 17 so that they match.

The comparator 16 uses the output of the comparator 14 as a reference signal for comparison with the tube voltage of the X-ray tube 3, and the comparator 17 uses the output of the comparator 15 as a reference signal for comparison with the tube current of the X-ray tube 3. The feedback signal obtained changes the base bias of the transistors 12 and 13 for feedback control, and the inputs of the high voltage transformer 1 and the filament transformer 2 are adjusted. As a result, the voltage applied to the X-ray tube 3 and the filament current are feedback-controlled, and the output Z=y/x of the arithmetic circuit 9 is kept constant. In addition, in the comparators 16 and 17, when the actual tube voltage and tube current increase or decrease due to fluctuations in the power supply voltage, etc., the feedback signals from the comparators 14 and 15 are compensated, and the X-ray imaging results are adjusted to the power supply voltage. Perform control so that it is not affected by fluctuations.

Note that the control range of the tube voltage and tube current has a certain limit, and cannot be increased or decreased without limit. That is, the upper limit of the control range is determined by the maximum rating of the apparatus, and the lower limit is determined by the limit on the exposure of the person to be imaged by soft X-rays.

The detected voltages corresponding to the actual tube voltage and tube current used for such control are A/D converters 23 and 24 and display device drive circuits 25 and 26, respectively.
The tube voltage and tube current are input to the display devices 27 and 28 via the display devices 27 and 28, and the tube voltage and tube current are displayed in real time. Therefore, the operator can read the current values and changing states of tube voltage and tube current while looking at the CRT display, or input the data into a printer and record it as necessary, and store the data in the memory 31, 32, and after the completion of X-ray imaging, the data can be processed by the arithmetic circuits 33 and 34 to extract, for example, the maximum value, minimum value, average value, etc., and these data can be used as a reference during subsequent manual imaging. This makes it possible to set shooting conditions.

Note that it is also possible to set a constant relationship between the tube voltage and tube current, and display only either the tube voltage or the tube current. That is, the setting devices 18 and 19 are set so that the tube voltage and tube current change while maintaining a constant relationship, such that when the tube voltage is 60 kV, the tube current is 5 mA, and when the tube voltage is 80 kV, it is 10 mA. Adjust it. In this way, the tube voltage and tube current are feedback-controlled simultaneously, and the output Z = y/x of the arithmetic circuit 9 is kept constant, which not only makes it possible to maintain the image quality in an optimal state, but also allows the tube voltage and tube current to be controlled simultaneously. Since the tube current changes in a constant relationship, the value of either the tube voltage or the tube current can be easily determined from the displayed value of the other.

In the above embodiment, the transistor 1 is used as a tube voltage feedback control element and a tube current feedback control element.
Although elements 2 and 13 are used, it is also possible to use elements such as thyristors 121 and 131 and triaxes 122 and 132 as shown in FIGS. 2 and 3, for example.

Furthermore, this invention is not limited to the device with the circuit configuration shown in the figure, but can be applied to any device that performs automatic exposure using feedback control, and can be applied to any device that performs automatic exposure using feedback control. The method of taking it out is not limited to that shown in the drawings.

<Effects of the invention> As is clear from the description of the above-mentioned embodiments, according to this invention, the tube voltage and tube current of the X-ray tube can be simultaneously controlled based on the ratio between the remaining amount of transmitted X-rays and the film feed speed. In a panoramic X-ray imaging apparatus equipped with an automatic exposure control function that performs feedback control, the values of the tube voltage actually applied to the X-ray tube and the tube current actually flowing can be detected and displayed in real time. Therefore, since both tube current and tube voltage are feedback-controlled at the same time, there is no need for initial settings or manual operations by the surgeon, and the advantage is that the dynamic range for obtaining good imaging results is expanded. It is now possible to perform X-ray imaging with excellent reproducibility based on the data and records from the previous imaging, for subsequent imaging using manual settings or imaging after changes in the patient's bone structure, while still utilizing the X-ray imaging technology. This makes it possible to reduce the burden on the person to be imaged and the operator, and to reliably avoid the dangers associated with increased radiation doses.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of this invention, and FIGS. 2 and 3 are diagrams showing other examples of a tube voltage feedback control element and a tube current feedback control element. 1...High voltage transformer, 2...Filament transformer, 3...X-ray tube, 4...X-ray film, 5...
...Low speed tachometer, 7...Photoelectric conversion device, 9...Arithmetic circuit, 12...Voltage feedback control transistor, 1
3... Current feedback control transistor, 14, 15
and 16, 17... comparator, 18, 19... ratio setter, 23, 24... A/D converter, 2
5, 26... Display device drive circuit, 27, 28...
Display device, 29, 30... detection display means, 31,
32...Memory, 33, 34...Arithmetic circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] 1) A means for detecting the residual amount of X-rays transmitted through the subject by replacing it with an electrical output, and a means for detecting the X-ray film feeding speed by replacing it with an electrical output. and a tube voltage feedback control element interposed on the primary side of the high voltage transformer, a tube current feedback control element interposed on the primary side of the filament transformer, and means for calculating the ratio of output signals from both of the above detection means. , means for comparing the output of the calculation means with a preset reference ratio value, and the output of the comparison means is fed back to the tube voltage feedback control element and the tube current feedback control element to control the X-ray tube. In a panoramic X-ray imaging apparatus configured to automatically control tube voltage and tube current, means for detecting a tube voltage value actually applied to the X-ray tube and a tube current value actually flowing through the X-ray tube; 1. A panoramic X-ray imaging apparatus, comprising display means for displaying in real time the tube voltage value and tube current value detected by the means. 2) The panoramic X-ray imaging apparatus according to claim 1, wherein the detection and display means includes a printer for recording tube voltage values and tube current values. 3) The detection display means detects at least one of the maximum value, minimum value, and average value of the tube voltage value and tube current value.
2. A panoramic X-ray imaging apparatus according to claim 1 or 2, which comprises a memory and an arithmetic circuit for calculating the number of points.