JPH0324833B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an X-ray fluoroscopic imaging device.

2. Description of the Related Art X-ray fluoroscopic imaging devices that display an X-ray fluoroscopic image on a display device are becoming widely used. An X-ray fluoroscopic imaging device irradiates a subject with X-rays and captures the transmitted X-rays.
The line image is incident on the image intensifier (II), the output image from this II is photographed with a TV camera,
The configuration is such that the video signal is AD converted and displayed on a display device.

When the subject is a human body, the amount of X-rays transmitted through the human body is
It varies greatly depending on the area to be imaged and the imaging conditions (tube voltage, tube current). In the photographing device described above, the video signal from the TV camera is converted into AD by an AD converter, so the accuracy of the AD converter affects the image quality. On the other hand, the camera tube of a TV camera has a usable range with respect to the amount of light, and in terms of signal S/N, the higher the amount of light, the better the S/N. Therefore, it is necessary to adjust the amount of light in front of the TV camera depending on the area to be imaged and the imaging conditions.

Adjustment of the amount of light is generally achieved by using an optical diaphragm. This optical aperture is conventionally
In what is called a test explosion, X-rays are irradiated, and the aperture is manually adjusted based on the captured data. Since this manual operation is time-consuming, the applicant
He invented a line image processing device and applied for it in December 1982.
)

This X-ray image processing device is equipped with an aperture device in front of a television camera, inputs and quantitatively evaluates the peak value of a predetermined video signal in two or more digital stages,
The aperture value is set according to this result, and the aperture device is controlled so as to achieve the set aperture value. The set aperture value is the one obtained during the test firing section, and
The peak value is a peak value within a frame unit.

In this prior application, the peak value is detected within an area equivalent to one screen (frame), so depending on the part of the subject, X may not pass through the subject.
It has the disadvantage that the X-ray itself, that is, the X-ray emitted from the X-ray source, is detected as a peak value. For example, when photographing a human foot, the air around the foot is also included in the measurement space, so the X-rays that have passed through the air around the foot are detected as peak values. As a result, the aperture value is set based on this peak value, and the amount of light in a perspective image that passes through a human body such as a foot becomes extremely small. This may result in failure in photographing.

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray fluoroscopic imaging apparatus that allows the aperture of the amount of light to be adjusted to an appropriate level by adjusting the aperture of the amount of light in accordance with the transmitted X-rays of the measurement site of the subject.

The gist of the present invention is that when setting the amount of light aperture, a shooting range for measuring the amount of light aperture is specified, a peak value is detected within the specified shooting range, and the amount of light aperture is determined based on the detected peak value. The problem lies in the fact that .

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an embodiment of a digital X-ray fluoroscopic imaging device. The X-ray source 1 generates X-rays only when necessary according to instructions from the outside. The image intensifier (II) 3 detects X-rays transmitted through the subject. The TV camera 4 photographs the output image of I.I3. The light quantity diaphragm 20 is installed between the I.I 3 and the TV camera 4, and adjusts the light quantity of the output light of the I.I 3.
The aperture amount of the light amount diaphragm 20 is determined by the peak detection circuit 12,
It is set via the drive circuit 13.

The AD converter 5 takes in the output video signal of the TV camera 4 and performs AD conversion on it. Peak detection circuit 12
The output of the AD converter 5 is discarded within the specified photographing range, and the peak value within that range is detected. The calculation circuit 6 has an addition function and a subtraction function, and performs calculations by selecting either the addition function or the subtraction function depending on the calculation mode at the time. The memory 7 includes an arithmetic circuit 6
The video signal (after AD conversion) is captured and stored in frame units. The output of this memory 7 is sent to the arithmetic circuit 6 and becomes data for addition or subtraction, or becomes input data to the window level setter 8.

The window level setter 8 has a function of contrast enhancement. The DA converter 9 performs DA conversion on the output of setting 8. The mixer 10 mixes the output of the DA converter 9 and the digit display signal from the microcomputer 14. CRT11 is mixer 10
Display the output of This display content becomes a photographed image of the subject.

The microcomputer 14 performs various controls. The control details are as follows.

The microcomputer 14 generates timing signals (horizontal synchronization signal, vertical synchronization signal) for the TV camera 4 and performs scanning control of the TV camera 4.

The microcomputer 14 selects the calculation mode of the calculation circuit 6, either addition or subtraction.

The microcomputer 14 instructs the read/write access mode of the memory 7 and causes one of the operations to be performed.

The microcomputer 14 controls the peak detection circuit 1 to set the peak detection range of the peak detection circuit 12.
Control 2. The peak detection range means the imaging range for detecting peaks. This peak detection range is specified by the operator operating the keyboard of the operating device 15, and is recognized by the microcomputer 14 reading the contents of this instruction.

The microcomputer 14 sends a digit display signal for mixing to the mixer 10 for mixing.

Explain the operation. The X-ray blast from X-ray source 1 is
There are X-ray exposure during the actual imaging period and X-ray exposure during the test period prior to the actual imaging period.
This time chart is shown in Figure 2. The exposure time T ₀ of one X-ray is set to be longer than the minimum time (1/30 second) required for imaging by the TV camera 4.

X-ray exposure during the test period is performed during this one exposure time. Since the image taken by a TV camera obtained in one burst time is called one frame, one frame will be taken during the test period. Peak values are detected from images taken during this test firing section.

The details of the operation up to peak detection during this test period are as follows. The microcomputer 14 instructs the test period. Prior to this period, the measurement site of the subject 2 is positioned. Based on the designation of the test period, the X-ray source 1 irradiates X-rays toward the positioned measurement site of the subject 2 . I.I3 detects transmitted X-rays from the subject 2, outputs them as optical signals, and inputs them to the TV camera 4 via the aperture device 20. The diaphragm device 20 may be set to a reference value or not diaphragm at all. The TV camera 4 photographs the input light as an image. Based on this captured image, the TV camera 4 reads and outputs video signals in accordance with the horizontal-vertical scanning order. This control is performed by the microcomputer 14.

The AD converter 5 performs AD conversion on the video signal from the TV camera 4. The peak detection circuit 12 successively takes in the output of the AD converter 5 and detects a peak value within a set peak detection range. As for the peak detection range, the controller 15 specifies the range, the microcomputer 14 takes in the specified range, and the microcomputer 14
specifies, in terms of timing, the video signal for which peak detection is to be performed according to the specified range. The peak detection circuit 12 performs peak detection within this timing-specific range.

The peak detection circuit 12 sets the amount of light aperture based on the detected peak value. Drive circuit 13
inputs the amount of light aperture, and adjusts the amount of light aperture of the light aperture device 20 to the input amount of light aperture.

Next, actual photography is performed using this adjusted light amount diaphragm device. Four frames are taken for each diagnostic site. As mentioned above, one frame of photographed image is obtained by X-ray bombardment in the interval _T0 , and to obtain four frames, X-ray bombardment is repeated four times. These four images are superimposed to obtain an average value.
To obtain the average value for four frames, first, the first frame is stored directly in the memory 7 via the arithmetic unit 6. Next, shoot the second frame in the same way,
The data is taken into the arithmetic unit 66 via the AD converter 5. On the other hand, at this time, the previous one frame worth of image data from the memory 7 is read out and input to the arithmetic unit 6 under instructions from the microcomputer 14. The arithmetic unit 6 adds both inputs under instructions from the microcomputer 14. This addition is performed for each pixel. The addition result is stored in the memory 7.
Next, the calculation unit 6 executes the third one frame and the sum of the first and second one frames stored in the memory 7. The fourth one-frame addition is similarly executed by the arithmetic unit 6. The total number of frames for these four times is divided by 4 (i.e., achieved by shifting 2 bits to the right)
In some cases, after 4 frames are taken in memory 7,
A captured image showing the average value of the four frames is obtained.

The image obtained by calculating the average value of the four frames becomes one image. The total number of shots is about 10 to 20, and to get 10 to 20 images, it takes 40 to 20 frames.
Requires 80 frames to be shot. The number of frames to be averaged is determined by the accuracy of the image and the diagnosis site, and there are various cases such as cases where averaging is not necessary, cases where an average value of four or more frames is obtained, etc.

The window level setter 8 performs contrast enhancement for each image, and the DA converter 9 performs DA
Perform the conversion. Furthermore, the mixer 10 includes a DA converter 9
The output video signal from the microcomputer 14 is mixed with the digit display signal from the microcomputer 14, and the CRT 11 displays the result. Display on the CRT 11 is performed for each image.

An embodiment centered on the peak detection circuit 12 will be described below. FIG. 3 shows an embodiment of the peak detection circuit 12. The peak detection circuit 12 includes a comparator 12A, a peak latch register 12B, and an AND gate 12.
C, and an intersection setting circuit 12D.

The peak latch register 12B always latches the peak value up to that point. Comparator 12A
sequentially compares the new data obtained from the AD converter 5 with the peak data of the peak latch register 12B, and outputs the latch signal 12a only when the new data is large.
is generated, and the new data that is the output of the AD converter 5 at that time is latched in the latch register 12B.
When the new data is small, the contents of the peak latch register 12B remain unchanged, and the peak value obtained up to that point continues to be latched.

The AND gate 12C receives the clock signal, peak value detection range signal, and latch signal 12a. The microcomputer 14 generates the clock signal and the peak value detection range signal.

The clock signal corresponds to a horizontal synchronizing signal, and the peak value detection range signal, which is clocked 512 times within one horizontal section of 63.5 μsec, is operated by the operator and is controlled by the microcomputer 14 by the controller 15. This is a timing signal corresponding to the peak value detection range that is input to the microcomputer 14 and output from the microcomputer 14.
For example, on the CRT screen 16 shown in FIG.
indicates each peak value detection range. Which peak value range to specify depends on the diagnosis site.

The detection range is specified using the operating device 15 using X and Y coordinates. When specifying a region as a detection range, use the operating device 15 to specify X ₁ <X<X ₆ and Y ₁ <Y<Y ₆ . Similarly, in the area X ₂ <X< ₅ , Y ₂ <Y<
Specify Y ₅ , and in the area X ₃ < X < X ₄ , Y ₃ < Y <
Specify Y ₄ .

The microcomputer 14 takes in this specified area and creates a peak value detection range signal for each area. When specifying an area, a peak value detection range signal is generated that becomes "1" only in the horizontal scanning section where X ₁ <X<X ₆ and the vertical scanning section where Y ₁ <Y<Y ₆ . Similarly,
When specifying an area, set "1" only in the horizontal scanning section where X ₂ < X < X ₅ and the vertical scanning section where Y ₁ < Y < Y ₅ .
A peak value detection range signal is generated. When specifying a region, a peak detection range signal that is "1" only in the section where X ₃ <X < X ₄ and Y ₃ <Y < Y ₄ is generated.

The AND gate 12C is configured such that the above peak detection range signal exists as "1" and the latch signal 12
synchronized with the clock signal only when a exists.
The output data of the AD converter 5 is taken in and latched in the register 12B as a new peak value.

As a result of scanning the entire peak value detection range, the peak value finally obtained in the latch register 12B is:
This is the peak value to be found. The final peak value thus obtained is taken into the aperture amount setting circuit 12D and becomes an appropriate aperture amount, and the drive circuit 13 adjusts the aperture device so that this aperture amount is achieved.

The peak value detection range may be fixed in advance or may be arbitrarily set.
This peak value detection range is preferably set by an operator observing the CRT screen and based on the observation results.

The peak value detection range signal can also be generated by hardware. FIG. 5 shows an embodiment thereof.
The counter 20 is a counter that counts horizontal synchronization clocks H (512 clocks in one horizontal scanning section), and
Specifies the coordinates of the direction. The counter 27 is a counter that counts the vertical synchronization clock V, and indicates the coordinate in the Y direction.

The decoder 21 takes in the count value of the counter 20 and outputs a signal corresponding to the X-direction detection range. The decoder 28 similarly outputs a signal corresponding to the Y direction detection range. The FF 22 generates an output "1" only in the X direction section of the specific area, and the FF 23 generates the output "1" only in the X direction section of the specific area. FF24
Although the input/output relationship is omitted, an output "1" is generated only in the X direction section of the other specific area. at the same time,
The FF 29 generates an output "1" only in the Y-direction section of the specific area, the FF 30 outputs "1" only in the Y-direction section of the specific area, and the same goes for the FF 31.

The AND gate 25 is a gate that receives the outputs of the FF 22 and the FF 29 as input, and its output becomes a signal corresponding to the area of the section. and gate 32
is a gate which inputs the outputs of FF23 and FF30, and provides a signal corresponding to the area of the output section.

The switch 26 is selected using the operating device 15. When the switch 26A is turned on, a timing signal corresponding to the area is obtained, and when the switch 26B is turned on, a timing signal corresponding to the area is obtained. This output is
This becomes the peak value detection range signal.

According to the present invention, it is possible to automatically set an appropriate aperture, thereby reducing the number of cases in which photographing fails.

[Brief explanation of drawings]

Fig. 1 is an embodiment of the present invention, Fig. 2 is its timing chart, Fig. 3 is another embodiment, Fig. 4 is a diagram showing how the peak detection region is set, and Fig. 5 is another example. It is an example figure.

Claims (1)

[Claims] 1. Means for irradiating the subject with X-rays and its transmission
an image intensifier that captures a line image and converts it into an optical signal; a TV camera that captures the output light of the image intensifier; an AD converter that converts the output video signal of the TV camera into an AD converter;
A processing means for processing the output of the AD converter to obtain a screen-compatible signal, and a DA for converting the output of the means from DA to DA.
It consists of a converter and a display means for displaying the video signal output from the DA converter, and a light aperture device is provided between the image intensifier and the TV camera to capture the output of the AD converter. Providing a peak detection means for detecting the peak value obtained during the test firing section, the range for detecting the peak value of the peak detection means is a range determined according to the diagnosis site, and the detection range can be specified from the outside,
The peak detecting means detects a peak in the designated detection range, and the light amount diaphragm of the light amount diaphragm is set and adjusted based on the detected peak value.
Fluoroscopic imaging device.