JPH02224744A - X-ray photographing device - Google Patents

Abstract

PURPOSE:To erase image other than contrast medium completely and enhance the contrast on an image by converting a penetration image created by two monochromatic X-ray beams having different wavelengths, which have penetrated an object to be photographed, into an image signal, and by forming a differential image between penetration images. CONSTITUTION:An electron beam bent by a deflecting electric magnet 83 generates a synchrotron radiative light, which is emitted in the tangential direction to permit taking-out from an SOR takeout port 85. A high frequency accelerative cavity 86 is provided at part of the straight portion of an ultra-high vacuum vessel 82, and high frequency electric power is injected from outside. Rotary discs 12, 14 rotate synchronously under control by a timing control device 7, and a reflex X-ray beam at silicon crystal 11 and a reflex X-ray beam at silicon crystal 13 are generated one after another. The penetration image due to these two X-ray beams is converted by an image converting part 3 into TV image signals. These two TV image signals are sent to an image processing part 4, and upon logarithmic conversion by logarithmic converting circuits 41, 42, such image processings as subtraction, contrast emphasis, etc., are made by an image processing circuit 43.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an X-ray imaging apparatus suitable for angiography and the like.

[Conventional technology]

When performing X-ray contrast imaging, transmission images are obtained using X-rays with energy that is absorbed by the contrast agent and X-rays with energy that is less absorbed, and by obtaining the difference between these images, it is possible to determine the difference between the images. images, usually only blood vessel images. Therefore, conventionally, such so-called X-ray energy subtraction has been carried out using continuous spectrum X-rays, for example, by switching the tube voltage to perform imaging, or by using an exposure plate with a sandwich structure in which the sensor is sandwiched between filters. This is done by taking pictures.

[Problem to be solved by the invention]

However, since monochromatic X-rays are not used conventionally,
There were problems such as the low contrast of the image and the inability to completely erase soft tissues. SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray imaging apparatus that can completely erase images other than a contrast agent, increase the contrast of the image, and obtain an X-ray energy subtraction image with high diagnostic ability.

[Means to solve the problem]

In order to achieve the above object, the X-ray imaging apparatus according to the present invention includes an SOR generating means and the SOR extracted from the SOR generating means being incident on a crystal lattice at different incident angles to generate two monochromatic lights having different wavelengths. A means for creating an X-ray beam and sequentially irradiating the same part of the subject from the same direction; and a means for converting transmitted images created by the two monochromatic X-ray beams of different wavelengths transmitted through the subject into image signals. , the above 2 is achieved by calculation between the image signals.
and means for creating a differential image between images transmitted by the two monochromatic X-ray beams.

[For production]

SOR is synchrotron radiation (SOR).
onOrbital Radiation, abbreviated as 5O
R), which is white light with an unbroken and smooth wavelength spectrum ranging from the radio wave region to the X-ray and gamma ray regions. When this SOR is incident on a crystal lattice, monochromatic X-rays with a wavelength that satisfies Bragg's conditions are obtained as reflected X-rays. Therefore, monochromatic X-ray beams of different wavelengths can be obtained by changing the incident angle. These two monochromatic X-ray beams with different wavelengths are sequentially irradiated onto the same part of the subject from the same direction. Then, two transmitted images of X-rays with different energies are obtained. These two transmitted images are converted into image signals, and by performing calculations between these image signals, a difference image between the two transmitted images can be obtained. If the wavelengths of the two monochromatic X-ray beams are set above and below the absorption edge of the contrast medium, the attenuation caused by the contrast medium will be greatly different between the two transmission images, so the contrast of the contrast medium will be reduced in these difference images. becomes very high and other images are almost erased. Since the transmitted images of the two monochromatic X-ray beams are obtained with very short exposure times, there is no blur caused by the movement of the subject. By performing high-speed continuous shooting with exposure at short time intervals, it is possible to obtain a dynamic subtraction image that represents a temporally moving subject.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, in the X-ray generating section 1, two SOR lights taken out from the SOR light source 8 are incident on a silicon crystal 11 and 13 at incident angles θ1 and θ2, respectively. Since the incident angle is different, the wavelength λ is different from Bragg's condition.
Monochromatic X-ray beams A and λB are obtained, respectively. These two monochromatic X-ray beams are irradiated onto the subject 2 using a rotary shutter 15 made of lead so that unnecessary objects are not irradiated. Here, as shown in FIG. 2, the SOR light source 8 basically consists of an electron injector 81 and an electron storage ring consisting of an ultra-high vacuum container 82 that goes around once in a ring shape. A plurality of bending electromagnets 83 and focusing electromagnets 84 are arranged along the ring of this ultra-high vacuum container 82. The bending electromagnet 83 bends the electron trajectory to form a ring-shaped electron beam trajectory. The electron beam bent by the deflection electromagnet 83 generates synchrotron radiation, which is emitted in the tangential direction and is therefore extracted from the SOR extraction port 85. The converging electromagnet 84 is arranged in a straight line between the deflecting electromagnets 83, and functions as a lens to suppress the divergence of the electron beam and stably circulate the electron beam when the electron beam circulates inside the ultra-high vacuum container 82. . A high frequency acceleration cavity 86 is provided in a part of the straight portion of the ultra-high vacuum vessel 82, and high frequency power is injected from the outside. Further, as shown in FIG. 3, the silicon crystals 11 and 13 are respectively attached to rotating disks 12 and 14, so that the reflected X-rays become X-ray beams in the same direction and along the same path. The rotating disk 14 has a shape that does not interfere with the reflected X-ray beam from the silicon crystal 11, and these rotating disks 12 and 14 rotate synchronously under the control of the timing control device 7. , silicon crystal 11
An X-ray beam reflected by the silicon crystal 13 and an X-ray beam reflected by the silicon crystal 13 are sequentially generated, and these beams travel in the same direction and along the same path. The images transmitted by these two X-ray beams are converted into TV video signals in the image conversion section 3. That is, the X-ray transmitted image is converted into an optical image by the X-ray image intensifier 31, and the output optical image is distributed to the two TV right cameras 3.34 by the half mirror 32. For example, this TV right camera 3.34 is 3.
They are non-interlaced scanning systems with a rate of 0 frames per second, and are each equipped with 35 and 36 optical shutters. The opening/closing operations of the optical shutters 35, 36 and the rotary shutter 15, as well as the rotating operations of the rotating disk 12, 14 holding the silicon crystal 11, 13, are controlled by the timing control device 7 so as to correspond to the TV scanning. . During the period of the TV synchronization signal as shown in FIG. 4A, two rotating shutters 15 are provided in the same amount as shown in FIG. 4B (for example, 2.
rasec open, then 2 m5ec close, then 2m5
ec open) The optical shutters 35, 36 are opened alternately during each open period to pass the X-ray beams λA and λB;
The image transmitted by the X-ray beam of λA is transmitted by the TV right camera 3.
The transmitted images by the B X-ray beam are converted into TV video signals by the TV camera 34, respectively. These TV right camera 3
．． A video signal is generated from 34 as shown in FIG. 4C. These two TV video signals are sent to the image processing section 4,
First, after being logarithmically transformed by logarithmic transformation circuits 41 and 42,
An image processing circuit 43 performs image processing such as subtraction processing and contrast enhancement. The subtraction image thus obtained is displayed by the image display device 5. As shown in Figure 5, the wavelengths λA and λB of these two monochromatic X-ray beams are the absorption edge wavelength (3
3.17 keV>. The wavelengths λA and λB are set as follows. First, Bragg's condition is 2 d hnk sinθ=nλ (n=0.1.2,
.) (hnk) H-plane index dhnk; lattice spacing θ of silicon crystal; incident angle λ; expressed by reflected X-ray wavelength. In this example, silicon crystal (111
) plane is used, n^A=2 d 111 sin θ1 nλB-2dtttsin θ2 Therefore, by adjusting θ1 and θ2, the wavelengths λA and λB can be set to desired values. Next, if the pixel values of images created by monochromatic X-rays with wavelengths λA and λB are Pa and Pb, pa = 1 og [N ex p t −u A
Oxo-u A 1 ・” 11 ] p b = 10g
[N exp'-uBO'xo-uBl ・xl )
]N; X-ray quantum number uAo when there is no contrast agent; mass reduction coefficient uAl of iodine for X-rays with wavelength λA; mass reduction coefficient uBo of soft tissue for Xll of wavelength λA; Mass reduction coefficient uBl; mass reduction coefficient XO of soft tissue for X-rays with wavelength λB; iodine thickness Xl; thickness of soft tissue, so uBl-P a -uAl-P b = (uAl-uBo-uAo -uBl) xo+ (
uBl-uAl) 1ogNz (uAl-uBo-u
Ao・uBl) x. The image processing unit 4 weights 2 by the difference method.
By performing a subtraction operation between the two video signals, the term xl can be eliminated, and an image that depends only on the iodine thickness xo can be obtained.

【Effect of the invention】

According to the X-ray imaging apparatus of the present invention, it is possible to increase the contrast of the differential image, completely erase images other than the contrast agent, and obtain an X-ray energy subtraction image with high diagnostic ability. Moreover, since subtraction images can be obtained with very short exposures, blurring caused by subject movement can be prevented, and high-speed continuous shooting can be performed. This makes it especially suitable for cardiovascular angiography.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a schematic diagram showing the SOR light source, Figure 3 is a schematic perspective view showing the positional relationship of two silicon crystals, and Figure 4 is a schematic diagram showing the positional relationship of two silicon crystals.
Figures A, B, and C are time charts for explaining the operation.
The figure is a graph showing the mass reduction coefficient versus photon energy. 1... X-ray generation part, 11.13... Silicon crystal,
12.14...Rotating disk, 15...Rotating shutter, 2...Subject, 3...Image converter, 31...
・X-ray image intensifier, 32...Half mirror 33, 34...TV right camera 35.36...
Optical shutter, 4... Image processing section, 41, 42...
- Logarithmic conversion circuit, 43... Image processing circuit, 5... Image display device, 7... Timing control device, 8... S
OR light source, 81... Electron injector, 82... Ultra-high vacuum container, 83... Bending electromagnet, 84... Focusing electromagnet, 8
5...SOR extraction boat, 86...High frequency acceleration cavity.

Claims (1)

[Claims] (1) The SOR generation means and the SOR extracted from the SOR generation means are incident on the crystal lattice at different incident angles to create two monochromatic X-ray beams with different wavelengths, and these are applied to the same part of the subject at the same time. means for sequentially irradiating from the direction; means for converting transmitted images created by the two monochromatic X-ray beams having different wavelengths transmitted through the subject into image signals; 1. An X-ray imaging apparatus comprising: means for creating a differential image between images transmitted by a ray beam.