JPS6329399B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray imaging apparatus equipped with an automatic imaging tube voltage setting device that automatically sets the tube voltage during imaging.

The configuration of a conventional X-ray imaging apparatus of this type is shown in FIG. 1 and will be described. In the figure, 1 is the X-ray tube, 2 is the subject,
3 is an image intensifier I/I that converts X-rays into a visible light image, 4 is an I/I controller, 5 is a prism, 6 is a photomultiplier that converts the light from the prism 5 into an electrical signal, 7 is an amplifier, 8 is a brightness setting device 9
a comparator for comparing the output of the amplifier 7 with a reference value set by the amplifier 7; 10 is a fluoroscopic tube voltage controller;
Reference numeral 11 designates an imaging tube voltage setting device, 12 a high voltage generator that generates a high voltage to be supplied to the X-ray tube 1, 13 a television camera, and 14 a television monitor. The operation of this device is based on the fluoroscopy tube voltage "ON" signal applied to the fluoroscopy tube voltage controller 10.
0 is activated and is started by supplying the see-through primary voltage to the high voltage generator 12. Then, a high voltage from the high voltage generator 12 is applied to the X-ray tube 1 to generate X-rays, which pass through the object 2. The X-rays that have passed through the object 2 are converted into a visible light image by the I/I 3, and then sent to the prism 5 and the television camera 1.
3. The input light of the television camera 13 is displayed as a television image on the television monitor 14, while the input light of the prism 5 is converted into an electric signal by the photomultiplier 6, amplified by the amplifier 7, and used as a reference for the brightness setting device 9 by the comparator 8. Compared to brightness.
Here, X that passes through object 2 and enters I/I3
If the amount of lines is small and the output light of I/I3 is darker than the reference brightness of the brightness setting device 9, the comparator 8 outputs the transparent light until the output light of I/I3 reaches the standard brightness of the brightness setting device 9. A signal is applied to the tube voltage controller 10 to increase the tube voltage. Conversely, if the amount of X-rays that pass through the object 2 and enter I/I3 is large and the output light of I/I3 is brighter than the reference brightness of the brightness setting device 9, the comparator 8 will output the output of I/I3. A signal is applied to cause the fluoroscopic tube voltage controller 10 to lower the fluoroscopic tube voltage until the light reaches the reference brightness of the brightness setter 9. The brightness is automatically adjusted while repeating such an operation, and when the output light of I/I3 reaches the reference brightness of the brightness setting unit 9, the control operation of the fluoroscopic tube voltage controller 10 is stopped, and in this state This will maintain the fluoroscopy tube voltage. The fluoroscopy tube voltage at this point includes information useful in determining the imaging tube voltage, such as the constitution and body thickness of the subject 2, and the imaging tube voltage is determined based on this fluoroscopy tube voltage. be. That is, in the above configuration, a voltage proportional to the fluoroscopy tube voltage set as described above is extracted from the fluoroscopy tube voltage controller 10 and applied to the imaging tube voltage setting device 11, and the voltage is applied to the imaging tube voltage "ON" signal. Therefore, the primary voltage for imaging is extracted from the imaging tube voltage setting device 11 and supplied to the high voltage generator 12 to perform imaging.

By the way, recently, dual mode I/I (DUAL
MODEI・I) is often used, and a large aperture one is used when photographing a relatively wide area, and a small aperture one is used when partially enlarging the area of interest. It is starting to be used. In this case, there is a problem in that effective photographing tube voltage determination information cannot be obtained because the field of view becomes wide and narrow for the same subject in the case of a large aperture and in the case of a small aperture. For example, if we consider an I/I that can be switched between 9 inches (large aperture) and 5 inches (small aperture), if the I/I lighting field is switched from 9 inches to 5 inches during fluoroscopy, the same subject will be photographed. , under the same transparent tube voltage and tube current conditions, the output light of I and I3 will be darker with 5 inches, and conversely, when switching from 5 inches to 9 inches, the output light of I and I3 will be brighter. It changes like this. In this case, since the apparatus with the above configuration has the automatic brightness adjustment function as described above, the fluoroscopic tube voltage changes every time the aperture is switched.
Therefore, the imaging tube voltage determination information given from the imaging tube voltage controller 10 to the imaging tube voltage setting device 11 is not constant, and as a result, a problem arises in that accurate imaging tube voltage cannot be set.

The present invention has been made in view of the above circumstances, and is designed to always obtain valid imaging tube voltage determination information even if there is a change in the illumination field of I and I during fluoroscopy, thereby setting a constant tube voltage. The object of the present invention is to provide an X-ray imaging apparatus that can perform

The present invention will be specifically explained below using Examples.

FIG. 2 is a block diagram showing an embodiment of the apparatus of the present invention, in which the same parts as those of the conventional apparatus are designated by the same reference numerals. The difference from the conventional device is that I/I3 is set to dual mode I/I, and between the fluoroscopic tube voltage control circuit 10 and imaging tube voltage setting device 11, the dual mode I/I
A correction circuit 15 that operates in conjunction with the lighting field switching operation in step 3 is inserted and connected. This correction circuit 15
For example, the structure is as shown in FIGS. 4a and 4b. That is, the figure a shows the dual mode I/I3.
This is a relay RY that is turned ON when a small diameter (for example, 5 inches) is selected, and a relay switch RYSW that is switched by the operation of this relay is provided in b of the same figure. In the same figure, 1
0 is the fluoroscopic tube voltage controller, and 11 is the imaging tube voltage setter. Also, A ₁ and A ₂ are operational amplifiers (op-amps) connected in parallel, and R ₁ , R ₂ ,
R ₄ and R ₅ are fixed resistances, and R ₃ and R ₆ are variable resistances.
According to such a configuration, relay RY is “OFF”
(i.e., for example, when dual mode I/I3 is used in a large-diameter 9-inch model), the relay switch RYSW is connected to apply voltage to the tube voltage setting device 11 via the operational amplifier _A1 ( If a small diameter 5 inch is selected, the relay contacts are switched (contacts shown as white circles) and the output of the operational amplifier _A2 is transmitted. Here, how to set the output voltage of each operational amplifier will be explained in detail. Note that here, a negative power supply (-15V) is connected to the variable resistor _R6 .

Figure 3 shows the fluoroscopic tube voltage obtained when the I/I output light becomes constant by changing the thickness of the object under the same fluoroscopic tube current condition for the dual mode I/I that can be switched between 9 inches and 5 inches. This is actually measured data. This shows the change in the fluoroscopy tube voltage when V ₁ is selected as 9 inches and V ₂ is selected as 5 inches. Based on the 9 inch waveform V ₁ , the 5 inch waveform V ₂
is higher by the A voltage at the beginning, and the 5-inch waveform V ₂ is suddenly higher at a certain point by an amount corresponding to the B voltage than the 9-inch waveform V ₁ 's parallel movement waveform V ₁ '. Indicates slope. Therefore, in order to match the waveform with the 9-inch waveform V ₁ as a reference, the reference potential of the waveform V ₂ when selecting 5 inches is lowered by an amount equivalent to the A voltage, and the slope is lowered by an amount equivalent to the B voltage. All you have to do is do it like this.

In the circuit shown in FIG. 4, when 9 inches are selected, the upper operational amplifier A ₁ is selected as described above, so the input voltage e ₁ and output voltage e ₂ of the operational amplifier A ₁ and the voltage transmitted to the imaging tube voltage setting device 11 are The relationship of e ₅ is the following formula
It is expressed as (1).

−e ₅ = −e ₂ = e ₁ ……(1) (However, R ₁ = R ₂ ) Next, when selecting 5 inches, the lower operational amplifier
Since A ₂ is selected, the input voltage of op amp A ₂
The relationship among e ₁ , output voltage e ₄ , voltage e ₃ at the output point of variable resistor R ₆ , and voltage e ₅ transmitted to imaging tube voltage setting device 11 is expressed by the following equation (2).

−e ₅ = −e ₄ = R ₄ /R ₃ e ₁ −R ₄ /R ₅ e ₃ ...(2) Here, in the above equation (2), R ₄ /R ₅ ×e ₃ is the operational amplifier A ₂ represents the voltage at the base point of the waveform of the output voltage e ₄ , and R ₄ /R ₃ ×e ₁ represents the slope of this waveform. Therefore, if these two are set as shown in the following equations (3) and (4) in relation to the A voltage and B voltage in _the measured data shown in FIG _. can be matched.

A voltage = R ₄ / R ₅ e ₃ ... (3) B voltage = R ₄ / R ₃ e ₁ ... (4) As a result, even if the sampling field (aperture) of I and I3 changes, it is always 9 inches. Tube voltage determination information when seen through the aperture is applied to the tube voltage setting device 11, and a constant tube voltage is set.

In FIG. 4 showing a specific example of the correction circuit 15,
Using an I/I that can switch between two diameters, 5 inches and 9 inches, the waveform at the small diameter of 5 inches,
This is about the case of matching the waveform of a large diameter 9 inch, but unlike this, for example, an I/I that can be switched between 12 inches (large diameter) and 9 inches (small diameter) is used, and a small diameter A configuration in which a 12-inch waveform is made to match the 9-inch waveform will be described with reference to FIGS. 5 and 6a and 6b. First, FIG. 5 shows data obtained under the same conditions as described above. As is clear from the figure,
Compared to the large diameter 12 inch waveform V ₃ , the small diameter 9 inch waveform V ₄ is higher by voltage A at the reference point, and the 9 inch waveform V ₄ is higher than the parallel displacement waveform V ₃ ' at a certain point. It has a steep slope so that it becomes higher by an amount corresponding to the B voltage. Therefore,
In order to match the waveform with the 9-inch waveform _V4 as a reference, raise the reference potential of the waveform _V3 when selecting the 12-inch by an amount equivalent to the A voltage, and change the slope to the above-mentioned B.
All you have to do is raise it by an amount equivalent to the voltage.

A specific configuration of a correction circuit for performing such an operation may be as shown in FIGS. 6a and 6b. That is, operational amplifier A ₁ , A ₂ , relay switch
The connection relationship between RYSW and resistors R ₁ to R ₆ is exactly the same as in the case of Fig. 4 above, except that the relay RY is configured to be "ON" when 12 inches is selected, and it is connected to variable resistor R ₆ . Connect the power supply to the positive power supply (+
15V). Therefore, if dual mode I/I3 is used with a 9-inch diameter, the voltage based on the operation of the upper stage operational amplifier _A1 .
e ₂ is applied to the tube voltage setting device 11, but if you select a diameter of 12 inches, the relay switch RYSW
is switched, and a voltage _e4 based on the operation of the lower operational amplifier _A2 is applied to the tube voltage setting device 11. Here, the voltage _e5 applied to the tube voltage setting device 11 when the operational amplifier _A1 is selected is:
If the input voltage of operational amplifier A ₁ is e ₁ , then the following formula (5)
It is determined by

-e ₅ = R ₂ / R ₁ e ₁ ...(5) Also, the input voltage e ₅ to the tube voltage setting device 11 when the diameter of 12 inches is selected and the operational amplifier A ₂ is selected based on this. The input voltage of operational amplifier A ₂ is e ₁ , the output voltage is e ₄ , and the voltage of variable resistor R ₆ is e ₃
Then, it is obtained by the following equation (6).

−e ₅ = −e ₄ = R ₄ /R ₃ e ₁ +R ₄ /R ₅ e ₃ ...(6) Here, in the above equation (6), the reference potential of the output voltage of operational amplifier A ₂ is R ₄ / Since R ₅ ×e ₃ and the slope of the waveform are determined by R ₄ /R ₃ ×e ₁ , these are set to values that respectively correspond to the A voltage and B voltage in Fig. 5. Then, the 12-inch waveform V ₃ can be made to match the 9-inch waveform V ₄ .

As a result, even if the illumination field (aperture) of I/I3 changes, the tube voltage determination information when viewed through a 9-inch aperture is always added to the tube voltage setting device 11, and a constant tube voltage is set. become.

The apparatus of the present invention described in detail above has a correction function that operates in conjunction with the switching operation of the lighting field of I and I3 during the transmission of imaging tube voltage determination information from the imaging tube voltage control circuit 10 to the imaging tube voltage setter 11. By providing the circuit 15 and correcting the waveform, fluctuations in the fluoroscopy tube voltage are corrected, and the imaging tube voltage determination information is always the same, regardless of voltage fluctuations that may occur due to the aperture switching operation. This allows the setting of the imaging tube voltage to be constant.

Note that the specific configuration of the correction circuit 15 is not limited to the above embodiment. For example, by pressing the recent switch button, you can continuously change the lighting field (aperture).
A mechanism that can reduce or enlarge the image (called a zoom I.I) is used, but such a zoom I.I.
When using I, the same effect as described above can be obtained by making the variable resistors R ₃ and R ₆ of the correction circuit shown in FIGS. 4 and 6 change in accordance with the continuous change in the aperture. is obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional X-ray imaging device, Fig. 2 is a block diagram showing an embodiment of the device of the present invention, and Fig. 3 uses 5-inch and 9-inch I/I. Actual measurement data showing the relationship between tube voltage and object thickness when Figures 6a and 6b are circuit diagrams showing a modification of the correction circuit used in the apparatus of the present invention. 1...X-ray tube, 2...Subject, 3...I・I,
4... I/I controller, 5... Prism, 6... Photomal, 7... Amplifier, 8... Comparator, 9...
Brightness setting device, 10... Transmission tube voltage controller, 11...
...Photography tube voltage setting device, 12...High voltage generator, 1
3...TV camera, 14...TV monitor, 1
5... Correction circuit, A ₁ , A ₂ ... Operational amplifier, R ₁ ~
_R6 ...Resistance.

Claims (1)

[Claims] 1 It has at least an X-ray-visible light image conversion means having a plurality of apertures that can be selected and switched as appropriate, and a brightness adjustment means configured so that the visible light image obtained by fluoroscopy always maintains a constant brightness. In an X-ray imaging apparatus that performs fluoroscopy of a scheduled imaging site and uses the tube voltage at the time of fluoroscopy as imaging tube voltage determination information,
A correction circuit is provided for correcting fluctuations in the fluoroscopy tube voltage that vary in conjunction with switching of the aperture of the converting means, so that the imaging tube voltage is kept constant regardless of fluctuations in the tube voltage that occur when switching the aperture. An X-ray imaging device characterized by: