JPH04150839A - X-ray diagnosing apparatus - Google Patents

Abstract

PURPOSE:To enable the control of an image pickup tube voltage, an image pickup tube current and a photographing time so that a better image taken is obtained by arranging a photographing control auxiliary means which selects a maximum tube current and a minimum photographing time within a range exceeding no rating of an X-ray tube in the combination of the image pickup tube voltage, the image pickup tube current and the photographing time to set that image pickup tube current to the maximum tube current. CONSTITUTION:An X-ray controller 10 controls an X-ray generator 9 so that X rays are irradiated from an X-ray tube 3 by an image pickup tube voltage and an image pickup tube current set with a circuit 12 for setting the image pickup tube voltage automatically or a circuit 13 for correcting the image pickup tube current during a photographing. A photographing time to be set previously is made short so that the photographing time is always short unless the combination of the tube voltage, tube current and photographing time as set with the circuit 12 for setting the image pickup tube voltage automatically exceeds a rating of X rays. when the combination exceeds the X-ray rating, the tube current and photographing time are altered to the maximum tube current and the minimum photographing time within the X-ray rating to set. This enables automatic control of the X-ray tube voltage and current automatically.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) The present invention is an X-ray system that displays a fluoroscopic image obtained by irradiating a subject with X-rays on a monitor and performs spot imaging as necessary. The present invention relates to an X-ray diagnostic apparatus, and particularly relates to an X-ray diagnostic apparatus in which X-ray tube voltage and X-ray tube current are automatically controlled during fluoroscopy and imaging.

(Prior technology) As an X-ray diagnostic device that irradiates X-rays from an X-ray tube to a subject, displays a fluoroscopic image on a monitor, and performs spot imaging as necessary, it automatically adjusts the monitor brightness during fluoroscopy. F-A
B C (Fluoroscopy-Auto Brt
gbtness Control; transparent automatic brightness control)
function and automatic exposure control (Auto Exposur), which consists of a photo timer that keeps the film at a constant density during shooting.
e Contr.

1) F-ATR (Fluoro
Scopy-Auto Tubevoltage Re
There is also a gulator (fluoroscopic automatic tube voltage adjustment) function. Among these functions, the F-ABC function mainly controls tube voltage for ease of control and reduction of exposure dose, and the automatic exposure control function controls imaging time for accuracy, ease of control, and image quality. Each of these functions is configured to be controlled independently.

Figure 5 is a characteristic diagram when the imaging tube voltage is controlled by the F-ATR function when performing fluoroscopy and imaging of a subject, where the vertical axis is the fluoroscopy tube voltage V, [kV], and the left horizontal axis is the imaging tube voltage. VR [
kV], and the right horizontal axis shows the object thickness T [cml].

That is, as the object thickness T increases, the fluoroscopy tube voltage v
The tube voltage is controlled so that P increases sequentially and the imaging tube voltage v11 also increases in proportion to this. Note that the fluoroscopic tube current I,
is set as a parameter, and the figure shows an example of 0.5mA.
.

The case where three types, 1 mA and 2 mA, are selected is shown. According to the imaging tube voltage vR determined as shown in the figure, the imaging time and maximum tube current allowed at this imaging time (tube current that maximizes the X-ray tube capacity) are determined from the X-ray tube rating table.
is selected, and the imaging tube current IR is set to this maximum tube current.

However, in the above-mentioned conventional technology, since the fluoroscopic tube voltage vP and the photography tube voltage vR are different even if the specimen has the same thickness, there are cases where what is seen in the fluoroscopic image is not captured on the photographic film, and the fluoroscopic image and There was a problem in that the photographed images did not match, which caused problems in diagnosis and poor diagnostic efficiency. For example, even if the imaging time is sufficiently shorter than 0°1 second, the maximum tube current when the imaging time is 0.1 seconds is selected from the X-ray rating table as the imaging tube current ■7, and the imaging time is was often longer than necessary. Therefore, there is a problem in that the photographed image has motion blur due to the movement of the subject, which often reduces diagnostic performance.

In order to solve such problems, the imaging tube voltages v, I,
A method has been proposed in which the photo tube current I8 is controlled by the method described below. First, depending on the thickness of the object, the fluoroscopic tube voltage vP
and fluoroscopy tube current 1. is controlled as shown in FIGS. 6 and 7. In other words, within the fluoroscopic tube current range (0.5 mA to 4.0 mA in the figure) set in advance based on an average subject (in the figure, the average subject thickness is 20 cm), the fluoroscope tube voltage vF is constant, and the fluoroscopy tube current is 1. only is changed according to the thickness T of the object to be examined. If the thickness of the subject falls outside the range of the tube current described above, the fluoroscopic tube current I is kept constant, and only the fluoroscopic tube voltage vP is changed in accordance with the thickness T of the subject. Points A and B in Figure 6.7 are values at the boundary between the body thickness range in which only the fluoroscopy tube current I is changed and the body thickness range in which only the fluoroscopy tube voltage V is changed, and point C is the average body thickness. (20
The values are shown in cm). Next, the photographing tube voltage vlI and the photographing tube current 1. is determined according to the following formula.

vRmv, ... (1) IR-αX
l, ... (2) Here, the standard imaging time for the standard body thickness is given in advance, and the coefficient a in the above equation (2) is set in relation to the system sensitivity so that the imaging time becomes the target value. be done. Therefore, since the F-ABC function operates so that the transmitted dose rate is constant, the above (mark)
The imaging tube voltage vR+the imaging tube current IR determined by equation (2) always provides a constant imaging time.

In this control method, since the fluoroscopic tube voltage vP and the imaging tube voltage vR are equal, the fluoroscopic image and the photographed image match, and the photographing time is set to a relatively short time, for example, 0°03 to 0.04 seconds. Therefore, motion blur in the photographed image is reduced. However, if the combination of the imaging tube voltage v11, imaging tube current IR, and imaging time determined by equations (1) and (2) above exceeds the rating of the X-ray tube, the imaging tube current 1R may be changed to Even if the tube current is set to the maximum allowable time and the underexposure is adjusted using a photo timer, there is a problem in that the shooting time becomes longer and the rated value is exceeded, making it unusable.

(Problems to be Solved by the Invention) As described above, in the conventional technology, it is difficult to control the imaging tube voltage, imaging tube current, and imaging time so as to always stay within the X-ray rating and obtain good images. There was a problem.

The present invention was made in order to solve the problems of the prior art, and its purpose is to make the fluoroscopic image and the photographed image coincide, and to obtain a good photographed image that is always within the X-ray rating. An object of the present invention is to provide an X-ray diagnostic apparatus that can control the imaging tube voltage, imaging tube current, and imaging time.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention irradiates a subject with X-rays from an X-ray tube and displays a fluoroscopic image on a display means. In X-ray diagnostic equipment that performs spot imaging as necessary, during fluoroscopy, the X-ray tube voltage is kept constant within the X-ray tube current range preset based on the average subject, and the X-ray tube current is adjusted to the subject thickness. a fluoroscopic control means that changes the tube voltage according to the thickness of the subject while keeping the tube current constant when the thickness of the subject falls outside the range of the tube current; imaging control means that sets the tube current to be the same as the fluoroscopy tube voltage set by the fluoroscopy control means and sets the tube current to a value obtained by multiplying the fluoroscopy tube current set by the fluoroscopy control means by a predetermined coefficient so that imaging is performed in a constant imaging time; , if the combination of the imaging tube voltage, imaging tube current, and imaging time set by the imaging control means exceeds the X-ray tube rating, the maximum tube current and shortest time within the range that does not exceed the X-ray tube rating. The present invention is characterized by comprising a photographing control auxiliary means for selecting the photographing time and setting the photographing tube current to the maximum tube current.

(Function) In the X-ray diagnostic apparatus of the present invention having the above configuration, the fluoroscopic tube voltage is kept constant when the thickness of the subject is within a predetermined range by the fluoroscopy control means, and the fluoroscopic tube voltage is kept constant by the radiography control means. Since the voltage is made equal to the voltage, the fluoroscopic image and the photographed image match.

Further, by determining the fluoroscopy tube voltage and the fluoroscopy tube current by the fluoroscopy control means so that the transmitted dose rate during fluoroscopy is constant, the combination of the fluoroscopy tube voltage and the radiography tube current determined by the radiography control means can be adjusted. It is possible to provide a fixed photographing time, and by making this photographing time relatively short, it is possible to reduce motion blur in the photographed image.

Furthermore, if the combination of the imaging tube voltage, imaging tube current, and imaging time set by the imaging control means exceeds the rating of the X-ray tube, the imaging control auxiliary means Since the maximum tube current and the shortest imaging time are set within a range that does not exceed the ratings, it is possible to always keep the X-ray rating within the X-ray rating, keep the imaging time relatively short, and obtain good images with little motion blur.

(Example) Below, an example of the present invention will be described based on the drawings. 1st
The figure is a block diagram showing the configuration of an X-ray diagnostic apparatus according to an embodiment of the present invention. In the figure, this X-ray diagnostic apparatus 1 includes a tilting table 2 that supports a subject P, an X-ray tube 3 that irradiates X-rays to the subject P, and an X-ray tube 3 arranged opposite to the X-ray tube 3 with the subject P sandwiched between them. and a cassette 4 containing X-ray film for spot imaging, an image intensifier 5 that converts the X-ray image into an optical image, and the image displayed on 1.1.5. A TV camera 6 that takes optical images and a TV monitor 7 that displays perspective images are provided.

The movement of the tilting table 2 is controlled by a tilting controller 8,
The X-ray tube 3 is driven by an X-ray generator 9. The X-ray generator 9 is controlled by an X-ray controller 10.
0 is a fluoroscopy tube voltage automatic setting circuit (F
-ABC) 11. Photographing tube voltage automatic setting circuit 12 as photographing control means for controlling photographing tube voltage V and photographing tube current IR. The X-ray generator 9 is controlled in accordance with the set values of the tube voltage and tube current sent from the imaging tube current correction circuit 13, which serves as imaging control auxiliary means for correcting the imaging tube current. In the figure, 14 is an automatic exposure control circuit (AEC) that keeps the film density constant during photographing, and 15 is a TV camera control circuit.

When performing fluoroscopy on the subject P, the fluoroscopy tube voltage automatic setting circuit 11 sets the fluoroscopy tube voltage vP and the fluoroscopy tube current IF according to the body thickness of the subject P using the sixth control method as described above.
The settings are as shown in FIGS. Here, the X-ray controller 10 takes the average subject into consideration and sets the tube current range in accordance with the body thickness. In other words, the lowest tube current is around the value corresponding to the average body thickness! The maximum tube current I*aX is determined, and the tube current is set so that it changes continuously within this range. Further, the fluoroscopic tube voltage vF is set so that appropriate brightness can be obtained at this center current. In this example, the average body thickness is 20 cm,
The center value of the tube current corresponding to this is 1.5mA, the minimum tube current 1 gin is 0.5mA, the maximum tube current I-ax is 4.
0mA, the fluoroscopic tube voltage corresponding to the center current ■F is 80kV
It was set to

As shown in Figure 6.7, when the body thickness of the subject P is within the range corresponding to point A to point B, the fluoroscopy tube voltage V is fixed at 80 kV, and the fluoroscopy tube current I, is set to vary depending on the body thickness.

When the body thickness is thinner than the thickness corresponding to point A or thicker than the thickness corresponding to point B, the fluoroscopy tube current l.

are fixedly set to 0.5 mA and 4.0 mA, respectively, and the fluoroscopy tube voltage VF is set to vary depending on the body thickness.

The X-ray controller 10 uses the fluoroscopic tube voltage v set as shown here.
The X-ray generator 9 is controlled so that X-rays are emitted from the X-ray tube 3 at F and a fluoroscopic tube current I.

Then, the X-ray image formed by the X-rays emitted from the X-ray tube 3 and transmitted through the subject P is 1. It is converted into an optical image by I, 5, and this optical image is converted into an electrical signal within the TV camera 6. This signal is sent to T via the TV right camera control circuit 15.
The subject P is sent to the V monitor 7 and displayed on the screen of the TV monitor 7.
A transparent image is displayed. The operator performs spot imaging as necessary while observing the fluoroscopic image.
X from the X-ray tube 3 with the imaging tube voltage vR and imaging tube current IR set by
The X-ray controller 10 controls the X-ray generator 9 so that the radiation is emitted.
control.

Similarly to the control method described above, the imaging tube voltage automatic setting circuit 12 sets the imaging tube voltage vl according to equations (1) and (2).
1 and the photo tube current ■R. In this case, as described above, the imaging time is a constant time set in advance as a target value. However, the set imaging tube voltage V8. The combination of imaging tube current IR + set imaging time may exceed the rating of the X-ray tube, and in this case, the imaging tube current correction circuit 13
As explained below, a combination of maximum tube current and shortest imaging time within a range that does not exceed the X-ray tube rating is selected at the set imaging tube voltage V3 at this time, and the imaging tube current I is
, is corrected and set to this maximum tube current.

Regarding this correction method, the imaging tube voltage vR1 set by the imaging tube voltage automatic setting circuit 12 + the imaging tube current IR + the set imaging time are 80 kV, 500 mA, and 0.03 seconds, respectively, and the imaging tube voltage vR is 60 kV, 70 kV, and 80 kV.
An explanation will be given by taking as an example a case where the relationship between the imaging time and the maximum imaging tube current I3 within the X-ray rating is as shown in FIG. 2. In this case, (set photo tube current I.

x imaging time) (hereinafter referred to as mAs) is equal to the area of the rectangle DEFG shown in Figure 2, and the maximum mAs within the X-ray rating is equal to the area of the rectangle HKFG, so the set mAs
, that is, the mAs required to obtain a good captured image is
It is larger than the maximum mAs within the line rating.

Here, FIG. 3 is a diagram showing the relationship between the imaging time within the X-ray rating and the maximum mAs. In this case, the required mAs is 500
[mA] xO, 03 [sec] - 15 [mA·sec], and from FIG. 3, when the imaging tube voltage V7 is 80 kV, the imaging time at which the maximum mAs becomes 15 [mA·sec] is 0.06
It turns out that seconds. And the shooting time is 0.06'
The maximum imaging tube current within the X-ray rating is 15[: mA
・sec]+0.06'[sec] -250[mA].

That is, the camera tube voltage V is 80 kV, and the camera tube current IR is
If you set it to 250mA, the shooting time will be 0.06 seconds, and at this time, the shooting tube current IR-250mA and the shooting time 0.
．． The combination of 0.06 seconds is a combination of the maximum imaging tube current and the shortest imaging time within the X-ray rating when the imaging tube voltage V8 is 80 kV.

In addition, in this case, as shown in FIG. 4, the imaging tube voltage vR
The combination of the maximum imaging tube current and the shortest imaging time may be determined from a graph showing the relationship between the imaging time within the X-ray rating and the maximum imaging tube current when is 80 kV. That is, first, a photographing time t2 slightly longer than the set photographing time t-0.03C seconds is selected, and the maximum photographing tube current A2 at this time is determined from the graph. The above setting shooting tube current (500mA
) is Ao, and if Ao/A2 < t2 /11, then mA S mA2 X t2 is the required m
As−AoXt1 or more, A2, A2 requires X
Maximum imaging tube current and shortest imaging time within the line rating.

If Ao/A2 > t2 /12, the imaging time t3. is slightly longer than t2. Select the maximum photo tube current A3 at this time, and if A o /A 3≦t3 /lj, then A3. t3 is the maximum tube current and shortest imaging time required. If AO/A3 > t3, / is electric, then a photographing time t4 slightly longer than t3 is selected, and the same comparison as above is made. By repeating this process one after another within a range that does not exceed the backup mAs set in the device,
The combination of the maximum imaging tube current and the shortest imaging time within the X-ray rating when the imaging tube voltage vR is 80 kV can be determined.

In the apparatus of this embodiment, as described above, the fluoroscopic tube voltage v
Since P and the imaging tube voltage V are equal, the fluoroscopic image and the photographed image match, improving diagnostic efficiency. In addition, by setting the above-described preset imaging time to a short time, the imaging time will be as long as the combination of tube voltage, tube current, and imaging time set by the imaging tube voltage automatic setting circuit 12 does not exceed the X-ray rating. is always a short time, and if the above combination exceeds the X-ray rating, the tube current, and the maximum tube current while the imaging time is within the X-ray rating.

Since the shortest imaging time is changed and set, imaging can always be performed within the X-ray rating and in a relatively short time. Therefore, motion blur in the photographed image is reduced and the required mAs
Since the image can be photographed with the camera, it is possible to obtain a good photographed image. Therefore, diagnostic ability can be improved.

In addition, in this embodiment, the imaging tube voltage automatic setting circuit 12
If mAs when the imaging tube voltage VR9 and imaging tube current IR are set is smaller than mAs obtained from the set imaging time and the maximum imaging tube current within the X-ray rating at this time, the imaging is performed as before. The tube current JR is never set to a value greater than the set value, and photography is performed at the set photography time, so the photography time will not be extremely short and exceed the control range of the photo timer. . Therefore, the reliability of the device can be improved.

Although the embodiments of the present invention have been described above, the values of the tube voltage, tube current, etc. given as examples in the above embodiments can be arbitrarily set depending on the purpose, application, etc. Further, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made.

[Effects of the Invention] The X-ray diagnostic apparatus of the present invention has the above-described configuration and function, and matches the fluoroscopic image and the photographed image, always within the X-ray rating, and
Moreover, the X-ray tube voltage and tube current can be automatically controlled so as to obtain a good photographic image with less motion blur. Therefore, the diagnostic efficiency 9 can be improved. Furthermore, since imaging is prevented from taking an extremely short imaging time, the reliability of the apparatus can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an X-ray diagnostic apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the imaging time and the maximum imaging tube current within the X-ray rating in the same embodiment, and FIG. Figure 3 shows the relationship between the imaging time and the maximum mAs within the X-ray rating in the same example, and Figure 4 shows the method for determining the combination of the maximum imaging tube current and the shortest time within the X-ray rating in the same example. FIG. 5 is a diagram for explaining an example, and FIG. 6 is a characteristic diagram for explaining a tube voltage control method during conventional fluoroscopy and imaging. FIG. 7 is a characteristic diagram for explaining a method of controlling the tube voltage and tube current so that the fluoroscopy tube voltage and the imaging tube voltage become equal. DESCRIPTION OF SYMBOLS 1... X-ray diagnostic device 3... X-ray tube 11... Fluoroscopic tube voltage automatic setting circuit (fluoroscopy control means) 12... Imaging tube voltage automatic setting circuit (imaging control means) 13... Imaging Tube current correction circuit (imaging control auxiliary means) P...subject

Claims (1)

[Scope of Claims] An X-ray diagnostic apparatus that irradiates an object with X-rays from an The X-ray tube voltage is kept constant within the range of the X-ray tube current set based on the X-ray tube current, and the X-ray tube current is changed according to the thickness of the subject.If the thickness of the subject is outside the range of the tube current, the tube current is A fluoroscopic control means that keeps the tube voltage constant and changes it according to the thickness of the subject, and during imaging, the tube voltage is made the same as the fluoroscopic tube voltage set by the fluoroscopic control means and the tube current is controlled to be the same as the fluoroscopic tube voltage set by the fluoroscopy control means. A photographing control means that sets the value obtained by multiplying the tube current by a predetermined coefficient and performs photographing for a constant photographing time, and a combination of the photographing tube voltage, the photographing tube current, and the photographing time set by the photographing control means. If the X-ray tube's rating is exceeded, an imaging control auxiliary means is provided that selects the maximum tube current and shortest imaging time within a range that does not exceed the X-ray tube's rating and sets the imaging tube current to this maximum tube current. An X-ray diagnostic device comprising: