JPH04200536A - Spectroscopic type x-ray image photographing device - Google Patents

Abstract

PURPOSE:To allow the high-speed continuous photographing necessary for diagnosing the heart disease in particular by using either of two sets of scintillators and TV cameras as a detector for high energy and using the other as a detector for low energy. CONSTITUTION:Quasi monochromatic X-rays 2 transmitted through a subject are first made incident on the detector 4 for high energy and transmit a mirror 13-1. Among the quasi monochromatic X-rays, only the energy component higher than the energy at the absorption end of contrast medium constituting elements is absorbed in the scintillator 10-1 which outputs a high energy visible light image. Among the quasi monochromatic X-rays, only the energy component lower than the energy at the absorption end transmits the scintillator 10-1 and is made incident on the detector 5 for low energy. This component is absorbed in the scintillator 10-27, which outputs a low energy visible light image. The respective visible light images are passed respectively through the mirrors 13, condenser lenses 14, image intensifies 15, and relay lenses 16 and are detected by the TV cameras 11-1, 11-2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to XG imaging using a contrast agent, and particularly to an imaging apparatus suitable for using an energy subtraction method as an imaging method.

[Conventional technology]

The energy subtraction method utilizes the difference in the energy dependence of the X-ray absorption coefficients of contrast agent constituent elements and biological constituent elements, thereby allowing both x-g images with different energy components to be captured.

This is a method of obtaining an image of only the contrast agent by performing arithmetic processing between these images.

When imaging by the energy subtraction method using a contrast agent, there are the following two technical issues. (a) A set of images with different energy components are photographed for a short time so that movement of the living body can be ignored. (b) As the X-rays to be irradiated, two adjacent monochrome X-rays around the absorption edge energy of the contrast agent constituent elements are used. Here, (a) is to avoid motion artifacts and blur caused by the movement of the living body, and (b) is to eliminate tissues other than the contrast agent and obtain an image of only the contrast agent in the energy subtraction method. This is the main point.

As a conventional device, there is a device described in Japanese Unexamined Patent Publication No. 63-95033. This conventional apparatus uses quasi-monochrome X-rays whose energy band spans across the absorption edge energy of the contrast agent constituent elements as the X-rays irradiated to the subject. Further, as a detector, a detector is used that is sensitive to energy changes above and below the absorption edge of the contrast agent constituent elements and can individually sense X-rays of energy components before and after the absorption edge. With an apparatus having such a configuration, it is possible to simultaneously capture xm images of energy components before and after the absorption edge energy, which are close to the absorption edge energy of the contrast agent constituent element. By performing arithmetic processing between these images, it is possible to completely eliminate image components due to living tissue other than the areas containing the contrast agent, resulting in a high-contrast image containing only the desired contrast agent. .

[Problem to be solved by the invention]

In the prior art described above, the detector is composed of a scintillator and a two-dimensional photodiode array, or a scintillator and an X-ray photographic film. However, manufacturing large-area two-dimensional photodiode arrays for medical diagnosis is relatively impractical due to many technical issues. Regarding film, it is possible to use the film currently widely used for medical diagnosis as is, and it is possible to convert it into digital data using film radar and perform various image processing, which is practical, but it does not require film processing. Another problem is that high-speed continuous shooting is not possible.

An object of the present invention is to provide a highly practical apparatus that is capable of high-speed continuous imaging, which is particularly necessary for diagnosis of heart disease.

[Means to solve the problem]

In order to achieve the above object, a TV camera may be used as a photodetector in an image detector composed of a scintillator and a photodetector.

The output signal of the TV camera can be easily converted into a digital signal, and various image processing necessary for medical diagnosis can be performed. Furthermore, since a TV camera is used, high-speed continuous shooting is easily possible. By using one of the two sets of scintillator and camera as a high-energy detector and the other as a low-energy detector, a sensing type detector capable of continuous imaging at island speed can be constructed.

[Effect]

A method for obtaining quasi-monochrome X-rays is to separate high-intensity, broadband synchrotron radiation (synchrotron radiation) obtained from a high-energy electron storage ring into quasi-monochrome X-rays using a spectrometer. Also, as a method using an X-ray tube, it can be obtained by using a filter.

An energy sensitive detector sensitive to the absorption edge energy of the contrast agent constituent elements is composed of a part that senses energy components higher than the absorption edge energy and a part that senses energy components lower than the absorption edge energy.

Among the X-rays incident on the detector, the high-energy sensing section first detects X-rays with energy components higher than the absorption edge energy. Here, the part of the high-energy sensing part that absorbs xm energy is mainly composed of the same element as the contrast agent constituent element or an element with a higher atomic number, and the absorption edge energy of these elements is the same as that of the contrast agent constituent element. It is located at the same or slightly higher energy, and therefore selectively and strongly absorbs X-rays with energy components higher than the absorption edge energy of the contrast agent constituent elements.

Next, the low-energy sensing section absorbs X-rays with energy components lower than the absorption edge energy of the contrast agent constituent elements that were not absorbed by the high-energy sensing section, and senses the low-energy components.

In the high energy sensing section and the low energy sensing section, each scintillator converts the xm image into a visible light image, resulting in visible light images of a high energy image and a low energy image. These visible light images are each taken by an individual TV camera and converted into electrical signals.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

Synchrotron radiation 1 from the high-energy electron storage ring is emitted in the tangential direction of high-energy electrons when their orbits are bent by a magnetic field. The synchrotron radiation 1 has strong directivity and is emitted as a flat fan beam that is wide on the electron orbit deflection plane and has a narrow cross-sectional intensity distribution in the direction perpendicular to this plane. This emitted light 1 is separated into spectra by a spectroscope 3.

Here, by using an asymmetric reflection spectrometer as the spectrometer 3, quasi-monochrome X-rays 2 can be obtained whose energy band width of the X-rays after spectroscopy is wider than that of a normal symmetric reflection spectrometer.
Furthermore, as a result of asymmetric reflection, the beam cross section can be expanded in the vertical direction as shown in Fig. 2, resulting in a cone-shaped beam that can capture two-dimensional images.6 The angle of the spectrometer 3 relative to the emitted light 1 is set to a specific value, and The center of the energy band of the monochrome X-rays 2 is made to coincide with the absorption edge energy of the contrast agent constituent elements, and the object 6 is irradiated with the monochrome X-rays. The X-rays that have passed through the object 6 are first detected by the high-energy detector 4 as an image of xm with energy higher than the absorption edge energy, and then an image of X-rays with lower energy is detected in the energy-sensing detector. It is separated and detected by the low energy detector 5. These image data are processed by the data recording and reproducing processing device W.
7, resulting in a subtraction image containing only the contrast agent.

Next, the configurations of the spectrometer 3 and the energy sensing type detector will be explained.

In FIG. 3, the spectrometer 3 is an asymmetric reflection type spectrometer,
A crystal such as silicon, germanium, or quartz is used, and the structure is processed so that the crystal lattice plane 8, which contributes to X-ray diffraction, is inclined at an angle θ2 with respect to the crystal surface.

Here, the synchrotron radiation 1 is incident on the crystal lattice plane 8 at an angle θ1, and only the X-rays with energy satisfying Black's condition are 0.
Diffracts at an angle of 1. Therefore, at the crystal surface, the synchrotron radiation l incident at an angle of θ knee 02 with respect to the crystal surface is diffracted at an angle of θ1+02 with respect to the crystal surface, thereby making it possible to obtain X-rays 2 with an expanded beam width. . Furthermore, in the case of asymmetric reflection, the energy band width of the diffracted X-ray is wider than that in the case of symmetric reflection (θ2=0)
The line becomes line 2 and spans the adjacent energy region before and after the absorption edge energy of the contrast agent constituent elements.

The basic operation of the energy sensing type detector will be explained using FIG.

The quasi-monochrome X-rays 2 that have passed through the object first enter a high-energy detector 4. This detector is composed of a high energy scintillator 10-1 and an E'V camera 11-1. The high-energy scintillator 10-1 is made of an element whose main component is the same as or has a larger atomic number than the contrast agent constituent element. For example, when the contrast medium is iodine, an iodine compound such as cesium iodide or sodium iodide is used as a scintillator, and when the contrast medium is barium, barium compounds such as various barium halides are used as the scintillator. These compounds have an energy component X higher than the absorption edge energy of the contrast agent constituent elements.
Selectively and strongly absorbs lines.

The energy of the absorbed X-rays is converted into fluorescence by the scintillator, and the TV camera 11-1 detects this to obtain an X-ray image. Next, most of the X-rays having energy components lower than the absorption edge energy of the contrast agent constituent elements pass through the high-energy detector 4 and enter the low-energy detector 5.

This detector is composed of a low energy scintillator 10-2 and a TV camera 11-2.

Since the low energy scintillator 10-2 only absorbs the X-rays that have passed through the high energy detector 4,
There are no particular limitations on the material. The absorbed X-ray energy is converted into fluorescence by the scintillator, and an X-ray image is obtained by detecting this with the TV camera 11-2.

Next, the details of the device configuration will be explained with reference to FIG. In the figure, the front side plates of detectors 4 and 5, the quasi-monochrome X@2 entrance part of detector 4, and the detectors 4 and 5
In Figure 0, some of the partitions are omitted, 13 is a plane mirror, 14 is a condenser that focuses the image on the scintillator 10 reflected by the plane mirror on the input surface of the image intensifier 15. It is a light lens. A relay lens 16 forms an image whose brightness has been amplified by the image intensifier 15 on the imaging surface of the TV camera 11. Images taken by the TV camera 11 are converted into electrical signals and recorded in the data recording/reproduction processing device 7.

During imaging, quasi-monochrome X-rays 2 that have passed through the object first enter the high-energy detector 4, and then are sent to the mirror 13-
Among the quasi-monochrome X-rays, only the energy components higher than the absorption edge energy of the contrast agent constituent elements are absorbed by the scintillator 10-1, and a high-energy visible light image is output. Among the quasi-monochrome X-rays, energy components lower than the absorption edge energy transmit through the scintillator 10-1 and enter the low-energy detector 5. The light is then absorbed by the scintillator 1o-2 and outputs a low-energy visible light image. Each visible light image is transmitted to a mirror 13 within the detector.
．． condenser lens 14, image intensifier 15,
The light passes through the relay lens 16 and is detected by the TV cameras 11-1 and 11-2.

As the TV left camera, either an image pickup tube type or a solid-state image sensor type can be used. Also, instead of the relay lens, the output surface of the image intensifier and the T
Directly connecting the imaging surface of the V left camera with a fiber plate simplifies the optical system and increases practicality. High sensitivity T
If the V left camera is used, an image intensifier and a relay lens are not required, and the image on the scintillator can be directly formed from the condenser lens and itself onto the imaging surface, making the device more practical. The high-sensitivity TV left camera uses an image pickup tube or solid-state image sensor that utilizes the avalanche amplification effect for the photoelectric conversion film.

Next, the structure of the scintillator will be explained.

In the present invention, the scintillator is used as a fluorescent screen that converts a two-dimensional X-ray image into a visible light image. Methods for manufacturing fluorescent screens include a vapor deposition method and a method of forming a thin plate from crystal by polishing. Further, when using a powder scintillator, there are a method of directly applying it and a method of forming a thin plate using a spinner. When using a liquid scintillator, there is a method of sealing it by sandwiching it between glass plates or the like.

As an X-ray source that spectrally specifies synchroton radiation, a multilayer spectrometer is used as a spectrometer. A multilayer spectrometer can freely adjust the energy band width and increase the intensity of quasi-monochrome X-rays after spectroscopy. Further, by forming the multilayer film on a curved surface, the cross-sectional area of the X-ray beam can be expanded, and two-dimensional XM image photography becomes easy.

Regarding the energy band width of quasi-monochrome X-rays, the band width must be 40 K e V or less in order to utilize the change in X-ray absorption rate at the absorption edge energy of a specific element. Furthermore, in order to reduce the intensity of image components of living tissues other than the contrast agent and increase the image intensity of the contrast agent, the band width needs to be 10 KeV or less. Further, in order to almost completely eliminate image components of living tissue and obtain an image containing only a contrast agent, it is desirable that the band width is 5 K e V or less.

As an application of the embodiment of the present invention other than spectroscopic photography, the third example is
In the figure, multiple tomography can be performed by utilizing the fact that two fluorescent screens for detecting X-ray images are juxtaposed.

〔Effect of the invention〕

According to the present invention, it is possible to simultaneously capture a set of images with energy components close to the absorption edge energy before and after the absorption edge energy of the contrast agent constituent element. Therefore, it is possible to obtain an image using the energy subtraction method using only a contrast agent, which is free from motion artifacts and blur caused by the movement of the living body, and in which living tissue other than the contrast agent is almost completely erased.

Furthermore, according to the present invention, selective imaging of specific elements is possible, and wide industrial applications are possible in addition to medical diagnosis.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of an apparatus according to an embodiment of the present invention, and FIG. 2 is a model diagram showing the overall configuration of an apparatus according to an embodiment of the present invention.
Figure 3 shows the structure of the crystal part of a crystal spectrometer. 5 Image inch shift completed / 6 Rishi-Rensu 3rd mouth /

Claims (1)

[Scope of Claims] 1. In an imaging device that performs X-ray photography using a contrast agent, the X-rays irradiated to the subject are X-rays that have an energy band width spanning before and after the absorption edge energy of the contrast agent constituent elements. an X-ray source that emits an 1. A spectroscopic X-ray imaging device comprising: an X-ray detector for detecting . The X-ray detector comprises a scintillator and a TV camera. 2. A spectroscopic X-ray imaging device characterized in that an energy sensing X-ray detector is constructed by using two sets of the X-ray detectors each comprising a scintillator and a TV camera. 3. A spectroscopic X-ray imaging device characterized by converting an X-ray image into a visible light image using a scintillator and focusing the visible light image on the imaging surface of a TV camera using an optical lens. 4. A spectroscopic X-ray imaging device characterized in that the visible light image converted by the scintillator is amplified in brightness by an image intensifier. 5. The visible light image converted by the scintillator is focused on the input surface of an image intensifier using an optical lens, and the output image of the image intensifier is focused on the imaging surface of the TV camera using the optical lens. A spectroscopic X-ray imaging device. 6. A spectroscopic X-ray imaging device characterized in that the output surface of an image intensifier and the imaging surface of a TV camera are optically coupled by a fiber plate. 7. A spectroscopic X-ray imaging device characterized in that synchrotron radiation light is separated into spectra using a curved multilayer film spectrometer. 8. Spectroscopic X-ray imaging according to any one of claims 1 to 7, characterized in that the energy band width of the X-ray is 40 KeV or less, preferably 10 KeV or less, ideally 5 KeV or less. Device.