JPH04279153A - Automatic control mechanism of x-ray conditions - Google Patents

Abstract

PURPOSE:To provide an observable image to an operator by keeping visibility of an interest area of an image constant. CONSTITUTION:In an automatically setting mechanism of an X-ray controller, a time constant circuit 16, a latch circuit 17, a D/A converter 18 and a limiter 19 are arranged to switch an increase or decrease in X-ray conditions as well as to switch X-ray conditions and following speed in an automatic exposure control. When an interest area exists at a location other than a lighting field of a sensor, the visibility of the interest area is kept constant, thereby achieving a higher diagnostic performance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic control mechanism for X-ray conditions in an X-ray control device for medical examinations.

0002

[Prior Art] In recent years, X-ray control devices for medical examinations automatically control X-ray conditions according to the situation of the subject in order to improve operability, save labor, and improve image quality. It is essential to obtain the appropriate brightness or the appropriate degree of photographic darkening.

[0003] There are many conventional systems for automatic control of X-ray conditions to obtain the above-mentioned desired results, and FIG. 2 shows a block diagram of the basic configuration.

000
4] The conventional X-ray condition automatic control setting mechanism shown in FIG.
An X-ray tube 1 that irradiates rays, a high voltage generator 2 that generates a predetermined output to be applied to the X-ray tube 1, and the X-ray conditions of voltage [kV], current [mA], and time [s]. ), a central processing unit 3 that controls the brightness reference signal that serves as a reference for the visibility of the X-ray image, and a digital/analog converter ( (hereinafter referred to as a D/A converter) 4, a D/A converter 5 that converts the digital voltage signal output from the central processing unit 3 into an analog signal, voltage [kV], current [mA], and time. It has an X-ray control circuit 6 that controls X-ray conditions by setting input [s].

Furthermore, the object 15 outputted from the X-ray tube 1
an image intensifier (hereinafter referred to as I.I.) 7 that inputs X-rays transmitted through the I.I. and converts it into a visible light image; I. A television camera 8 that converts the visible light image outputted by I.7 into an electrical signal, and I.7. I. A cine camera 9 continuously records visible light images outputted by the I.7 on film as a movie, and I. The output optical image of 7 is sent to the TV camera 8.
and a photo pickup 11 that is built into the video distributor 10 and measures the brightness of a part called a lighting field, converts the degree of brightness into an electrical signal, and outputs it. and has.

A comparator 12 compares the output signal of the photo pickup 11 with the luminance reference signal from the D/A converter 4;
The apparatus includes an adder 13 for adding and subtracting voltage signals from the X-ray apparatus, and a program selection switch 14 for presetting X-ray conditions for each inspection site and calling up the X-ray conditions as necessary.

Next, the operation will be explained. First, the program selection switch 14 is used by the operator to call up the X-ray conditions.
When operated, the corresponding preset voltage [kV] signal is output to the D/A converter 5, the luminance reference signal is output to the D/A converter 4, and the current [mA],
A time [s] signal is output to the X-ray control circuit 6. As a result, when a set predetermined X-ray is irradiated from the X-ray tube 1 controlled by the X-ray control circuit 6, the X-ray is transmitted to the subject 15.
through I. I. 7 is input. I. I. 7 converts the X-rays into visible light images, which are distributed by an image distributor 10 and input to a television camera 8 and a cine camera 9. The signal input to the television camera 8 becomes a television signal for perspective images, and the signal input to the cine camera 9 is used for photographing.

[0008]The X-ray information signal transmitted through the object corresponding to the luminance of the fluoroscopic image and the degree of blackening of the photograph is input to the comparator 12 as an output signal of the photo pickup 11. However, the incident light input to the photo pickup 11 is usually I. I. It is a part of the area inputted in 7,
This area to be taken in is called the lighting field. Furthermore, comparator 1
2, the output signal of the photo pickup 11 is compared with the brightness reference signal, and if the output signal of the photo pickup 11 is larger than the brightness reference signal, the voltage signal is subtracted by the adder 13, so that the output signal of the photo pickup 11 becomes the brightness reference signal. If it is smaller than the reference signal, the adder 13 adds it to the voltage signal.

As described above, the voltage signal corrected by the actual amount of X-ray transmission is input from the adder 13 to the X-ray control circuit 6, and when the X-ray condition is larger than the predetermined X-ray amount determined by the brightness reference signal, The X-ray condition decreases, and when it is small, it increases. As a result, the output signal of the photo pickup 11 is always constant, that is, the X-ray image always looks the same.

The problem here is the difference between the visibility of the image of the region of interest desired by the operator and the visibility of the image created under appropriate X-ray conditions. The human body is a collection of various tissues and organs, and an X-ray image is an image of the difference in the amount of X-ray absorption projected onto a medium such as a film. However,
The optimal appearance of the image is determined by the operator's judgment.

In order to reflect this judgment based on the operator's experience and intuition in the automatic control of X-ray conditions, multiple X-ray sensors are arranged in the irradiation field, and selector switches corresponding to the areas to be imaged are placed on the operating console. There are conventional techniques such as so-called part-specific programming, in which reference parameters for automatic control of X-ray conditions are changed by operating a changeover switch provided on a panel.

0012

The above-mentioned prior art uses a method of automatically controlling the X-ray conditions so that they immediately become appropriate values depending on the X-ray transmission state of the subject.

However, if an area with an extremely large amount of X-ray transmission is placed in the light field of the X-ray sensor compared to other areas, the above-mentioned automatic control mechanism will select the optimal area with a large amount of X-ray transmission. The X-ray dose is controlled to achieve the desired visibility. Therefore, the amount of X-rays transmitted is relatively insufficient for areas other than those areas where the amount of X-rays transmitted is extremely large, so even if the outline of the image can be recognized, the detailed internal state can hardly be recognized or at all. state. Specifically, during cardiac catheterization, when the tip of a catheter is advanced into the heart cavity while being confirmed through X-ray television, if the lungs fall into the light field of the sensor, the lungs become extremely transparent to X-rays. Since the heart is a large area, only the outline of the heart is imaged, and the catheter tip and tissues inside the heart cannot be recognized at all.

[0014] Furthermore, when performing the above automatic control for a moving object, the X-ray conditions immediately follow changes in the amount of transmitted X-rays and operate so that they become appropriate values. Therefore, as the amount of X-ray transmission in the area covered by the sensor's light field changes from moment to moment, the X-ray conditions are controlled from moment to moment so that the area covered by this light field can be seen optimally. . However, if the amount of X-ray transmission changes only in a part including the sensor's lighting field, and the amount of X-ray transmission in the surrounding area hardly changes, the visibility of the changing part will not change. On the contrary, the visibility of the parts that do not change will change, and if the area of interest is outside the sensor's light field where the amount of X-ray transmission does not change, the visibility will change from moment to moment. It was becoming very difficult to see. Specifically, during cardiac catheterization, a contrast medium is injected into the intracardiac cavity to measure the contractile state of the myocardium and blood flow dynamics using X-ray television or movies (cinema).
During observation, the contrast medium passes through the light field of the sensor as the heart expands and contracts, so even though the visibility of the intracardiac cavity remains constant, the overall image, including the myocardium, is synchronized with the expansion and contraction of the heart. There was a problem in that the image changed and became very difficult to see.

[0015] The purpose of the present invention is to
If there is a part with a large amount of radiation transmission, or if there is a part of the image
An object of the present invention is to provide an X-ray apparatus that can obtain images suitable for observation according to an operator's region of interest even when the amount of radiation transmitted changes from moment to moment.

[0016]

[Means for Solving the Problem] In order to achieve the above object, if there is a region with a large amount of X-ray transmission, a lower limit value is set for the X-ray conditions depending on the region to be imaged, and the amount of X-ray transmission increases from moment to moment. When the X-ray conditions change, the response speed of the control of the X-ray conditions, which is feedback-controlled according to the region to be imaged, is intentionally made slower than the time change of the detected values.

[0017]

[Function] When an area with an extremely high amount of X-ray transmission falls on the sensor's light field, the automatic control mechanism operates to lower the X-ray conditions, but by setting a lower limit here, the predetermined X-ray Do not fall below the conditions. As a result, the visibility of the areas where the amount of X-ray transmission is extremely high will be due to an excessive amount of X-rays, but the visibility of the areas other than the areas where the amount of X-ray transmission is extremely high will be even if the amount of X-ray transmission is slightly insufficient. Able to maintain a level that does not interfere with image recognition.

[0018] Also, the X
When the amount of radiation transmitted changes moment by moment, the automatic control mechanism operates to constantly change the X-ray conditions so that the area covered by the lighting field can be seen optimally, but the response speed of the automatic control is By intentionally taking measures to slow down the speed, even if the amount of X-ray transmission changes rapidly, the automatic control mechanism responds to changes in X-ray conditions at a predetermined speed.

[0019]

[Embodiment] An embodiment of the present invention will be explained below with reference to FIG. The configuration is such that the following elements are added to the conventional X-ray condition automatic setting mechanism described in FIG. That is, in the configuration of FIG. 2, the temporal change dv/d of the output signal of the comparator 12 that compares the output signal of the photo pickup 11 and the luminance reference signal.
A time constant circuit 16 that reduces t, relays 16a to 16d that switch the time constant of the time constant circuit 16, and a central processing unit 3.
A latch circuit 17 that connects or connects one of the relays 16a to 16d with a signal from the central processing unit 3, a D/A converter 18 that converts the digital voltage lower limit signal from the central processing unit 3 into an analog signal, and an output from the adder 13. A limiter 19 is added which replaces the output from the adder 13 with the voltage lower limit signal when the voltage falls below the voltage lower limit signal.

Next, the operation will be explained. First, program selection switch 1 is used by the operator to call up the X-ray conditions.
When a desired switch among 4 is operated, the central processing unit 3
outputs the corresponding preset voltage [kV] signal to the D/A converter 5, and outputs the luminance reference signal to the D/A converter 5.
A current [mA] and time [s] signals are output to the Output to converter 18.

The predetermined X-ray set in this way is
When irradiated from the ray tube 1, the X-rays pass through the subject 15 and enter the I. I. 7 is input. Here I. I. 7 converts the X-rays into a visible light image, and the visible light image is sent to an image distributor 10.
and is input to the television camera 8 and cine camera 9. What is input to the television camera 8 becomes a television signal for displaying a perspective image, and what is input to the cine camera 9 is used for continuous photographing.

[0022] Then, the X-ray information signal transmitted through the object corresponding to the luminance of the fluoroscopic image and the degree of blackening of the photograph is inputted to the comparator 12 as an output signal of the photo pickup 11.
It is compared with a luminance reference signal, and the difference is input to the time constant circuit 16. In the time constant circuit 16, the photo pickup 11
The time rate of change d of the difference signal between the output signal and the luminance reference signal
Since v/dt is made small, when the difference signal fluctuates at a cycle longer than a predetermined time constant, the output of the time constant circuit 16 becomes substantially constant and is input to the adder 13. in this case,
In other words, if the amount of X-ray absorption of the subject in the light field of the photo pickup 11 fluctuates over a predetermined period,
The line conditions do not follow the above-mentioned fluctuations but operate to remain approximately constant.

Furthermore, in the adder 13, as described above,
When the voltage signal corrected by the amount of radiation transmitted is lower than the voltage lower limit signal output from the central processing unit 3 and converted by the D/A converter 18, it is replaced by the voltage lower limit signal by the limiter 19 and X-ray control is performed. Since it is input to circuit 6,
The line condition is a predetermined lower limit value.

According to this embodiment, when the X-ray absorption amount of the subject in the light field of the photo-pickup fluctuates at a predetermined period or more, the X-ray conditions do not follow the fluctuation and remain almost constant. Therefore, when the region of interest is located outside the light field of the photo pickup, the visibility of the region of interest is constant and diagnostic performance is improved.

Since the time constants included in the parameters of the X-ray condition program have various sizes, they can be applied to various moving parts. Also, X
In imaging techniques where the amount of light transmission changes rapidly,
If the time constant is intentionally increased to slowly change the X-ray conditions and images are taken continuously during that time, images in which the appearance of tissues with various amounts of X-ray transmission change continuously can be obtained. Among these, applications such as using only images suitable for the region of interest for diagnosis can be considered.

Furthermore, even if an area with an extremely large amount of X-ray transmission falls on the light field of the photo pickup, the X-ray conditions are suppressed to a predetermined lower limit value and do not become extremely low. Many areas cause halation,
If the region of interest is in another part, that part can be maintained within a range that does not impair diagnostic ability.

Furthermore, since the lower limit value data is included in the parameters of the X-ray condition program, it can be set according to the region to be imaged and the region of interest. For example, if the amount of X-ray transmission in the region of interest is larger than that in the surrounding tissue, the lower limit value is fixed. In addition, as in the embodiment shown in FIG. 3, the output signal of the photo pickup 11 and the
By inputting the X-ray condition signal actually applied to the X-ray tube 1 into the central processing unit 3, it is also possible to perform comparison calculations with the brightness reference signal, time constant calculations, and voltage lower limit calculations in the central processing unit 3. It is.

[0028]

[Effects of the Invention] According to the present invention, even if the X-ray absorption amount of the subject in the light field of the sensor fluctuates over a predetermined period, the X-ray conditions do not immediately follow the fluctuation and remain almost constant. Therefore, when the region of interest is located outside the light field of the sensor, the visibility of the region of interest is constant and diagnostic performance is improved.

For example, when a contrast medium is injected into the intracardial cavity in cardiac catheterization to observe the contractile state of the myocardium and blood flow dynamics, the amount of X-ray transmission periodically changes as the heart expands and contracts. This is particularly effective when the amount of X-ray transmission changes, and by setting the response speed of the automatic control described above to be slower than the period of expansion and contraction of the heart, the visibility of the entire image does not change even if the amount of X-ray transmission changes. It turns out.

Furthermore, since the size of the time constant is included in the parameters of the X-ray conditions, it is possible to deal with various moving parts.

That is, by providing a response speed value for the automatic control for each region of interest of the operator, it is possible to provide an image that does not pose any problem in recognizing the image of the region of interest of the operator.

Furthermore, in the present invention, even when an area with an extremely large amount of X-ray transmission is placed in the light field of the sensor,
Since the X-ray conditions are suppressed to a predetermined lower limit and do not become extremely low, halation will occur in areas with an extremely large amount of X-ray transmission, but if the area of interest is in other areas, the diagnostic ability will be lost in that area. It can be maintained within a certain range.

Furthermore, since the lower limit value data is included in the parameters of the X-ray conditions, it can be set according to the region to be imaged and the region of interest.

That is, by setting a lower limit value of the X-ray conditions for each region of interest of the operator, it is possible to provide an image that does not pose any problem in recognizing the image of the region of interest of the operator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention.

[Figure 2] Block diagram of conventional automatic control circuit for X-ray conditions

[Figure 3
]Block diagram showing an applied circuit of an embodiment of the present invention

[Explanation of symbols]

3 Central processing unit 4 D/A converter 5 D/A converter 6 X-ray control circuit 7 I. I. 10 Video distributor 11 Photo pickup 12 Comparator 13 Adder 14 Program selection switch 16 Time constant circuit 17 Latch circuit 18 D/A converter 19 Limiter

Claims (2)

[Claims] [Claim 1] An automatic X-ray condition control mechanism comprising a sensor that measures the amount of X-rays that have passed through the subject, and a means for feedback controlling the X-ray conditions for irradiating the subject using the output signal of this sensor. means for setting a lower limit value of X-ray conditions that can be set to
An automatic X-ray condition control mechanism, comprising means for setting the X-ray conditions using the lower limit value. 2. An automatic X-ray condition control mechanism comprising: a sensor for measuring the amount of X-rays transmitted through the subject; and means for feedback controlling the X-ray conditions for irradiating the subject using the output signal of the sensor; An automatic X-ray condition control mechanism characterized by comprising means for variably setting the following speed in feedback control of the X-ray conditions.