JPH04168883A - X-ray fluoroscopy equipment - Google Patents

Abstract

PURPOSE:To reduce (correct) a shade image due to noise resulting from the structure of an X-ray image intensifier by storing a picture due to noise resulting from the structure of the X-ray image intensifier as a correction picture and applying division processing to the correction picture and an image of a reagent. CONSTITUTION:A phantom 17 is place on a bed 18 in place of a reagent M, a command of a correction picture is given to a control section 12 from a console 13 and an X-ray radiates from an X-ray tube 1. The X-ray transmits through the phantom 17 and is made incident in a light incidence face of an X-ray I.I2, in which the X-ray is converted into a visual light image as a picture representing only a structural noise and stored in a correction picture memory 7. Then the reagent M is placed on the bed 18 and a pickup command of a reagent picture is given to the control section 12 from the console 13. The X-ray image transmitted through the reagent M is converted sequentially into a digital density data by an A/D converter 4 and the control section 12 reads the density data in the correction picture memory 7 synchronously with a sampling timing of a reagent image data by the A/D converter 4.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention is capable of transmitting an X-ray image transmitted through a subject using an X-ray television camera or a CCD camera, and displaying it on a monitor display. The present invention relates to an X-ray fluoroscopic imaging device.

B. Prior Art Fluoroscopic imaging using this type of X-ray fluoroscopic imaging apparatus is performed as follows.

X-rays are emitted from the X-ray tube toward the subject, and an X-ray image intensifier placed opposite the X-ray tube transmits the X-ray image through the subject. Changes in X-ray intensity are interpreted as changes in brightness. Convert to a visible light image. An X-ray television camera (or
A CCD camera) captures the visible light image, converts it into a video signal, and sends it to an image processing system.

The image processing system uses an A/D converter to digitize the output video signal from the Xia TV camera and stores it in the image memory, converts it into an analog video signal using the D/A converter, and displays the transparent image on a monitor. When displaying 0 on the screen, image processing such as edge enhancement and contrast enhancement is performed to make it easier for the surgeon to interpret the image.

In addition, while maintaining the opposing postures of the X-ray tube and the XwA image intensifier, they are moved in opposite directions along the body axis of the subject, and the fluoroscopic images taken during the movement process are electrified. In some cases, a tomographic image of the area at the center of movement may be taken.

C9 Problems to be Solved by the Invention However, various noises described below are present in images obtained by the above-mentioned xastix imaging device.

(]) Quantum noise: Noise that occurs when the amount of X-rays irradiated is small, and appears on the image as noise whose brightness changes over time.

[2) TV noise: The X-ray television camera temporarily stores the visible light image output from the X-ray image intensifier.
This is converted into a video signal by scanning it with an electron beam, but this noise is generated when the scanning of this electron beam is disturbed by the electrical noise generated in the XL TV camera.Similar to (1), On the image, it appears as noise whose brightness changes over time.

(3) Structural noise: Noise that appears due to non-uniformity in the deposited film, such as Cs1, which forms the input fluorescence surface of the X-ray image intensifier. This results in non-uniformity in the luminance of the emitted light, which appears as uneven brightness on the image. If the non-uniformity of the vapor deposition film formation is extreme, granular black dot noise may be mixed into the image corresponding to that part.

Among the above noises, quantum noise (1) can be reduced by increasing the X-ray dose, and TV noise (2) can be reduced by performing integral calculation processing on image data, which has already been done. , (3) is often not performed to reduce structural noise. this is,
The noise that appears on the image is dominated by (1) quantum noise and (2) TV noise, and (3) structural noise is caused by errors in the manufacturing process of the X-ray image intensifier. However, since there are differences in how noise is generated depending on the individual X!! image intensifiers, it is generally difficult to reduce the noise.

However, if edge enhancement processing such as that described in the prior art is applied without attempting to reduce structural noise, the noise itself will be emphasized, and even though quantum noise and TV noise are dominant, structural Noise cannot be ignored,
This results in significant image quality deterioration.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an X-ray fluoroscopic imaging apparatus that can reduce structural noise and obtain high-quality images.

04 Means for Solving the Problems The present invention has the following configuration to achieve the above object.

That is, the present invention includes an X-ray tube for XII exposure, an XL image intensifier that converts a transmitted X-ray image into a visible light image, and an imaging means that captures the visible light image to generate a video signal. an A/D converter that converts the video signal into digital data, and digital data of a correction image obtained by imaging a subject having a uniform X-ray transmission coefficient. A correction image memory to store, digital data of the patient image obtained by imaging the patient,
The present invention is characterized by comprising a divider that performs division processing with the corresponding digital data in the correction image memory, and an output means that outputs the image after the division processing to the image reader. .

80 Effects According to this invention, before photographing a subject, -W
A correction image is captured by transmitting an object having a radiation transmission coefficient and an X-ray image intensifier. The correction image is converted into digital data by an A/D converter and stored in a correction image memory.

At this time, if the input fluorescence surface of the X-ray image intensifier is formed non-uniformly and structural noise is present, an image taken of a subject with a uniform X-ray transmission coefficient will be
The resulting image is caused by that structural noise.

After the close-up of the correction image, an X-ray image of the subject is taken. As before, structural noise exists in the image transmitted through the subject, and the density data of that part is different from that of the subject. X exposed to
It is obtained by multiplying the line intensity by the density value of the "structural noise portion" of the correction image.

The divider performs a division process between the density data of the correction image stored in the correction image memory and the density data of the subject image corresponding thereto. This process eliminates structural noise data located at the same position in the subject image and the correction image (
correction).

The output means outputs the corrected high-quality image to the image interpreter.

F. Example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an X-ray fluoroscopic imaging device.

In the figure, numeral 1 is an X-ray tube that emits X-rays toward the subject M, and 2 is a translucent tube! ! X-ray image intensifier (X&i11.I) that converts an X-ray image into a visible light image, 3 is X11
．． This is an X-ray television camera that captures the output light image from I2 and outputs a video signal.

The X-ray tube 1 is configured to be movable in the body axis direction of the subject M by the swinging motion of a support arm (not shown).
．． 12 and the X-ray television camera 3 can be moved in the opposite direction along the body axis of the subject M while maintaining the position facing the X-ray tube 1 by horizontal movement of a moving mechanism (not shown). It is configured.

The above configuration is the same as the conventional one, and not only fluoroscopic imaging but also tomography is possible.

Reference numeral 4 denotes A that converts the output video signal from the X-ray television camera 3 into a digital signal, that is, multivalued density data.
/D converter, the digital density data is sent to a divider 5 for correcting structural noise and a switch S by a switch SWI.
The output light is configured to be switched to W2.

The switch SWt has four input/output terminals C and D.

E and F, and the input terminal C is the switch SW
+, the input terminal is connected to the divider 5, the output terminal E is connected to the correction image memory 7 via the integrator 6, and the output terminal F is connected to the image memory 8.

The integrator 6 is added mainly to reduce the above-mentioned TV noise. The correction image memory 7 stores an image of an arbitrary subject used for structural noise correction (
This is a memory that temporarily stores the density data of the correction image). Therefore, the image for correction is captured with the input terminal C of the switch SW O connected to the output terminal E, and the image after structural noise correction is obtained with the input terminal 1 and the output terminal F connected. , is configured to be captured into the image memory 8.

The divider 5 includes two logarithmic conversion daples 9A and 9B, a differentiator 10, and an anti-logarithm conversion table 11. The logarithmic conversion table 9A is given the digital electric power data transmitted through the subject M by switching the switch SWI, and the logarithmic conversion table 9B is given the digital density of the correction image stored in the correction image memory 7. The data is configured to be given. Anti-log conversion table 11
The output data (corrected image data) of the switch S
W2.

The controller 12 controls the switching between the switches SW and SWt, and controls the reading of the correction image memory 7, and the doctor (or X-ray technician) gives commands to the controller 12. This is the console 13 operated by.

Reference numeral 14 denotes an image processing unit that performs image processing desired by the reader, such as edge enhancement processing and contrast enhancement processing, on the corrected image, and 15 refers to a D/A conversion unit that converts digital density data into an analog video signal. A monitor display 16 serves as an output means and displays the image to the reader. In addition, as the output means, a device that outputs an image as a printed matter, such as a laser printer, may be used.

Further, reference numeral 17 denotes a phantom as an object having a uniform X-ray transmission coefficient, which is used to collect correction images, and is made of a uniform material such as an acrylic plate or a copper plate. Note that it is also possible to collect correction images without using this phantom 17. In that case, "air" as a uniform substance existing in the X-ray irradiation area corresponds to an object having a uniform X-ray transmission coefficient. However, it is preferable to use the phantom 17 because it is possible to collect a correction image in a state closer to that of the subject M.

Next, correction of structural noise by the X-ray fluoroscopic imaging apparatus having the above-described configuration will be explained.

Typically, an X-ray tube 1 and an X-ray 1. + 2. When the X-ray television camera 3 is set at the photographing position, the subject M is photographed. J2
An image (correction image) from which structural noise has been extracted is photographed. That is, if a uniform object is photographed in the presence of structural noise, an image will be obtained in which the density value changes only in the structural noise area. Therefore, a phantom 17 is placed on the head 18 instead of the subject M, and a correction image command is given to the control unit 12 from the console 13.

The control unit 12 switches the switch SW to the output terminal A side, and switches the switch SWt so that the input terminal C and the output terminal E are connected. In this state, X-rays are emitted from the X-ray tube l. In addition, in order to reduce quantum noise,
Here, irradiation is performed with a relatively high dose of X-rays.

After xm passes through the phantom 17, it enters the incident plane of the X-rays 1.12 and is converted into a visible light image. The X-ray television camera 3 scans the visible light image with an electron beam and outputs the generated one-dimensional video signal to the A/D converter 4. A
The /D converter 4 samples continuous analog density values of the video signal at a predetermined period, and converts them into multi-value digital density data expressed by, for example, 8 points. The 7-bit sequence of density data output from the A/D converter 4 is input to the integration Fi6 through the A terminal of the switch SW, the C terminal, and the E terminal of the switch SW. The integrator 6 performs integral calculation processing on the input density data, and then stores the data in the correction image memory 7. Therefore, the correction image memory 7
The image stored in is an image in which quantum noise and TV noise have been reduced, that is, an image in which only the structural noise of X-rays [12] appears.

FIG. 2(a) shows the density value distribution of the photographed correction image.

Here, an example will be given in which granular black spots appear in an image as structural noise. In the figure, X! corresponds to pixel number Pi! %
11. It is set that a black spot exists on the input fluorescent surface of I2, and the density value is extremely high only there. This density value changes depending on the intensity of the irradiated X-rays, and is generally expressed by a multiplication formula of the XM intensity. For example, if the X-ray intensity is 1 and the density value of the noise part is D, then rD=α
It is represented by XIJ. The sign α is a multiplication coefficient.

Therefore, in order to correct structural noise, it is effective to divide the density data of an image obtained by photographing the subject M by the density data of an image from which structural noise has been extracted.

Therefore, after collecting the correction images as described above, photographing of the subject M is started.

That is, the phantom 17 is removed from the bed 18, the patient M is placed on the bed 18, and a command to photograph the patient's image is given to the control unit 12 from the console 13.

The control unit I2 switches the switch SW to the B terminal side,
The switch SWt is switched to connect the input terminal 1 and the output terminal F. In this state, from XwA tube 1 to
Emits a ray.

The X-ray image transmitted through the subject M is sequentially converted into digital density data by the A/D converter 4, and is applied to the logarithmic conversion daple 9A via the switch SWl.

Here, an example of the density distribution of an X-ray photographed image of a subject is shown in Fig. 2 et al. As shown in this figure, the density value D' of the subject's image corresponding to the sunspot noise position is the X-ray intensity at that point multiplied by the density value D of the sunspot noise (see figure (a)). become.

Therefore, in order to correct this black spot noise, the control unit 12
starts sequentially reading the density data from the correction image memory 7 in synchronization with the sampling timing of the subject image data by the A/D converter 4. The bit string of density data output from the correction image memory 7 is applied to a logarithmic conversion daple 9B. In the same way, A/D
The bit string of the density data of the subject's image outputted from the converter 4 is also sequentially applied to the logarithmic conversion daple 9A.

The density data of the subject's image and the density data of the correction image that have been simultaneously logarithmically transformed (LOG-converted) by the logarithmic conversion table 9A and the logarithmic conversion table 9B are subjected to power reduction processing in the subtractor 10, and then subjected to anti-logarithm conversion. It is inverse logarithmically transformed in Table 11 and then subjected to division processing.

As a result, the X11. The black spot noise of I2 is corrected, and only the density data transmitted through the subject M is stored in the image memory 8.

The density data stored in the image memory 8 is sequentially read out and given to the image processing section 14, where it is subjected to image processing desired by the image interpreter, such as edge enhancement and contrast enhancement processing, and then processed by the D/A. The converter 15 converts the signal into an analog video signal and displays it on the monitor display 16.

In the above-mentioned embodiment, a simple X-ray fluoroscopic image was explained, but structural noise can be corrected in the same way when a tomographic image of the subject M is taken using this device. .

That is, in taking a tomographic image, X-ray photography is performed while moving the X-ray tube 1, the X-ray 1.12, and the X-ray television camera 3 in opposite directions along the body axis of the subject M. Therefore, the correction images are also photographed in the same manner, and the correction images from which structural noise has been extracted at each photographing position are stored in a plurality of correction image memories 7. Then, an image of the subject is photographed, and the above-mentioned division process is performed between the correction image corresponding to each photographing position and the subject image to correct structural noise. By adding the images after each correction, a clear tomographic image of the movement center region can be obtained. The present invention is particularly effective in such tomography. That is, when a plurality of images are added as in tomography, structural noise is also emphasized, so the X-ray fluoroscopic imaging apparatus of the present invention that corrects structural noise can obtain particularly clear tomographic images.

Further, in the above-described embodiment, reading of data from the correction image memory 7 is started in synchronization with the sampling timing of the A/D converter 4, and structural noise is corrected in real time. A new patient image memory is provided to store the examiner's image, and after imaging, a division process is performed between the data in the patient image memory and the data in the correction image memory 7 to correct structural noise. You may also do so.

Effects of the G0 Invention As is clear from the above explanation, the X-ray fluoroscopic imaging apparatus according to the present invention is capable of capturing an image obtained by photographing a subject having a uniform X-ray transmission coefficient in advance, that is, an X-ray image. Since the image caused by the structural noise of the intensifier is stored as a correction image, and the correction image and the patient image are divided, the structural noise of the X-ray image intensifier can be Reduce (correct) unnecessary shadow images caused by
can do.

Therefore, the image outputted to the image reader by the output means is a high-quality image with reduced structural noise, which can contribute to accurate image diagnosis.

In particular, when performing image processing related to image diagnosis, such as image distortion enhancement processing, structural noise is corrected, which suppresses deterioration of image quality and expands the scope of application of image processing related to diagnosis. can do.

Also, the brightness decreases at the periphery of the input phosphor surface of the X-ray image intensifier (the shape of the input phosphor surface is generally not flat, but has a slightly concave shape at the periphery, and the brightness decreases in this area). There is also an effect that the above-mentioned division process can correct the decrease (decreased).

[Brief explanation of the drawing]

Figures 1 and 2 relate to an embodiment of the present invention, with Figure 1 being a block diagram showing the schematic configuration of an X-ray fluoroscopic imaging device, and Figure 2(a) showing the density distribution of a correction image. FIG. 1B is an example of the density distribution of the image of the subject. 1... X-ray tube 2... X-ray image intensifier 3... X-ray television camera 4... A/D converter 5... Divider 7... Image memory for correction 15 ...D/A converter 16...Monitor display Figure 1 Figure 2 (b) L pixel

Claims (1)

[Claims] (1) An X-ray tube for X-ray exposure, an X-ray image intensifier that converts a transmitted X-ray image into a visible light image, and an imaging means that captures the visible light image and generates a video signal. The X-ray fluoroscopic imaging device includes an A/D converter that converts the video signal into digital data, and stores digital data of a correction image obtained by imaging a subject having a uniform X-ray transmission coefficient. and a divider that performs a division process between digital data of a subject image obtained by imaging the subject and corresponding digital data in the correction image memory. 1. An X-ray fluoroscopic imaging apparatus comprising: an output means for outputting an image after the division process to an interpreter.