JPH05212028A - Radiation three-dimensional picture photographing device - Google Patents

Abstract

PURPOSE:To provide the information on not only the radiation picture showing the three-dimensional structure of a subject to be photographed but also the material in the three-dimensional structure of the subject by separating and detecting the energy intensity of the Compton scattering radiation from the subject. CONSTITUTION:An X-ray beam 13 from an X-ray generator 11 irradiates a subject 14, and a Compton scattering X-ray 15 generated from the beam 13 and passing through a slit 16 is detected by means of a sensor 17. The output of the sensor 17 is inputted to discriminators 19a and 19b to pass the output with different voltage pulse more than the prescribed level. The passed voltage pulse is counted by counters 20a and 20b. In short, the energy intensity of the Compton scattering X-ray 15 is divided into two energy ranges with the lower and higher energy intensity and detected. The detected information is inputted to a picture processing section 21 to provide the low and high energy picture informations. The ratio of these picture informations are calculated to be displayed on a display section 22 as the contrast of a picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation three-dimensional image capturing apparatus used in an industrial analyzer or medical radiation diagnostic apparatus.

[0002]

2. Description of the Related Art FIG. 5 is a distribution diagram of X-ray scattering directions by Compton scattering. Compton scattering is X-ray or γ
This is because X-rays or γ-rays scatter in a direction different from the incident direction due to interaction between the rays and the electrons of the substance, and an attempt of measurement using this Compton scattering has been made. When the incident X-ray is incident from the left, for example, it is scattered in all directions as shown in FIG. 0 ° is the same direction as the incident direction, and scattering from 0 ° to 90 ° is called forward scattering, and 90 ° to 90 °
The 180 ° direction is the opposite and is called backscattering. By using this backscattering, scattered X-rays from the same direction as the X-ray generator can be detected for the subject. Details of this detection principle are described in the following documents as references. G.HARDING "X-RAY SCATTER IMAGING IN NON-DESTRUCTIV
E TESTING "International Advances in Nondestructive Testing, 1
985, Vol. 11, pp. 271-295 Hereinafter, the above method will be described.

FIG. 6 is a schematic configuration diagram of a conventional radiation three-dimensional image capturing apparatus using backscattering of X-rays. In FIG. 6, X-rays generated from an X-ray generator 1 serving as an X-ray source are focused into a pencil beam-shaped X-ray beam 3 by a slit 2 and the subject 4 is irradiated with this. By detecting the Compton scattered X-rays 5 generated from the X-ray beam 3 applied to the subject 4 through the slit 6 by the X-ray sensor 7,
A tomographic image in the vertical direction inside the subject 4 can be obtained. Further, a three-dimensional image can be obtained by moving the X-ray generator 1 and the X-ray sensor 7 relative to the subject 4.

[0004]

However, with the above-mentioned conventional configuration, although a three-dimensional image of the structure of the subject 4 is obtained, information about the X-ray energy of the subject 4 is not dealt with, and information about the material of the subject 4 is not available. I couldn't get it.

The present invention solves the above conventional problems, and an object of the present invention is to provide a radiation three-dimensional image capturing apparatus capable of obtaining information on the material of an object.

[0006]

In order to solve the above problems, the radiation three-dimensional image capturing apparatus of the present invention detects Compton scattered radiation generated from a radiation beam applied to a subject from a radiation generator. A radiation three-dimensional image capturing apparatus for obtaining a longitudinal tomographic image of the inside of the subject, comprising a radiation detector for detecting the energy intensity of the Compton scattered radiation, and a material constituting the subject by comparing the energy intensities. This is a configuration for obtaining information regarding.

In addition to the above-mentioned structure, the radiation three-dimensional image capturing apparatus of the present invention has, in addition to the above configuration, two sets of discriminators for detecting the energy intensity of Compton scattered radiation by separating it into two energy ranges. And a counter, and image information consisting of energy intensity information of the Compton scattered radiation separated by the two sets of discriminators and counters, using a ratio of low energy image information to high energy image information, or low energy image information. An image processing unit for calculating a ratio between image information obtained by logarithmizing the image information and image information obtained by logarithmizing the high-energy image information to obtain image information is provided.

Further, in addition to the above configuration, the radiation three-dimensional image processing apparatus of the present invention separates the radiation energy intensity generated from the radiation generator into two regions between the radiation generator and the object. (Ta), tungsten (W), platinum (Pt), gold (Au), lead (Pb)
K containing at least one element of the
An edge filter is provided.

[0009]

With the above structure, if the energy intensity information of the Compton scattered radiation generated from the radiation beam applied to the object from the radiation generator is detected as, for example, the contrast of the image, the absorption characteristic due to the photoelectric effect greatly depends on the material. Therefore, as the atomic number of the material increases, the absorption due to the photoelectric effect also increases, so that it is possible to compare the contrasts of the images and obtain information regarding the material forming the subject.

Further, by using image information which is obtained by separating the Compton scattered radiation into two high and low energy ranges and using intensity information for each energy intensity, the ratio of the low energy image information to the high energy image information or the low energy image information is used. If the image information obtained by calculating the ratio of the image information obtained by logarithmizing the information and the image information obtained by logarithmizing the high-energy image information is detected as, for example, the contrast of the image, the contrast becomes clearer and the contrast of the images becomes easier to compare. It is possible to more accurately obtain information about the material that constitutes the subject. At this time, in the case of image information in which the ratio of logarithmized image information is calculated, there is a difference regardless of the material thickness, and therefore more accurate information.

Further, since the K edge filter for separating the radiation energy intensity generated from the radiation generator into two regions is provided between the radiation generator and the object, the energy spectrum of the incident radiation is narrowed and logarithmic scattering is performed. The beam hardening phenomenon in which the radiation information ratio becomes slightly higher as the radiation information ratio becomes thicker is reduced and more accurate information is obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a radiation three-dimensional image capturing apparatus showing an embodiment of the present invention. In FIG.
The X-ray from the X-ray generator 11 is radiated to the subject 14 with the X-ray beam 13 focused into a pencil beam by the slit 12, and the Compton scattered X-ray 15 generated from the X-ray beam 13 passes through the slit 16. The photons of the scattered X-rays 15 are converted into current pulses by a sensor 17 made of CdTe semiconductor. The information converted into the current pulse is converted into a voltage pulse by the amplifier 18 and input to discriminators 19a and 19b which pass different predetermined levels of the voltage pulse, and further from the discriminators 19a and 19b, respectively. Counter 20 that counts output voltage pulses
It is input to a and 20b. In this way, the energy intensity of the Compton scattered X-ray 15 is separated into two energy ranges of a predetermined low energy intensity and a high energy intensity by the two sets of discriminators 19a, 19b and counters 20a, 20b, respectively. To be detected.

These pieces of detection information are input to the image processing unit 21 and stored therein, and then the high energy image information having a high energy intensity or more and the low energy obtained by the difference between the high energy image information and the information having a low energy intensity or more. Energy image information is obtained, and by using these image information, low energy image information or high energy image information is used as image information, or a ratio of low energy image information and high energy image information, or low energy image information is obtained. The image information is calculated by calculating the ratio between the logarithmized image information and the high energy image information logarithmized image information.

After these image information are image-processed by the image processing unit 21, the display unit 22 displays the energy intensity information as the contrast of the image. The contrast of this image is compared and used as information regarding the material forming the subject 14. Above sensor 17, 2 sets of discriminator 19
a, 19b, counters 20a, 20b, an image processing unit 21, and a display unit 22 constitute an X-ray detector 23.
The line generator 11, the slits 12 and 16, and the X-ray detector 23 constitute a radiation three-dimensional image capturing device 24.

The method for obtaining the information regarding the constituent material of the subject 14 will be described in more detail below. First, the interaction between the material forming the subject 14 and the X-ray photons is shown in FIG. The interaction in the energy range centering on the photon energy of 100 keV is mainly absorption by the photoelectric effect and scattering by the Compton effect. In FIG. 2, the photon attenuation coefficient with respect to the photon energy is shown for aluminum and iron. As can be seen from FIG. 2, the characteristic A relating to Compton scattering is not significantly different between aluminum and iron, but the characteristic B relating to absorption due to photoelectric effect is largely dependent on the material in aluminum and iron. The higher the number, the greater the absorption due to the photoelectric effect. This means that scattered X-rays 15 generated by the Compton effect inside the subject 14
It shows that the amount of absorption absorbed before going out depends on the material of the subject 14. Therefore, by measuring the energy dependence of the scattered X-ray 15 scattered light, the subject 14
You can get information about the material.

Therefore, since the X-ray detector 23, which is a CdTe semiconductor detector, has a large atomic number and good absorption efficiency, it is a radiation detector suitable for performing energy analysis in the X-ray energy range (to 200 keV) to be used. Is.
By arranging a plurality of such X-ray detectors 23 and detecting the energy intensity of the scattered X-rays 15, image information in the depth direction having energy information can be obtained. By displaying this image information as the contrast of the image on the display unit 22, it is possible to obtain information about the material forming the subject 14 by comparing the contrasts of the images.

This concrete measurement is performed by setting the X-ray beam 13 to 0.5 mm.
I focused on the diameter of the subject and radiated the subject 14. Subject 14 and slit
The distance between 16 is 1 cm, the distance between the sensor 17 and the slit 16 is 5 cm, and the magnification in the depth direction is 5 times. The sensor 17 has five X-ray detectors 23 arranged at a pitch of 2 mm and has a total length of 10 mm. With this configuration, it is possible to obtain information of 2 mm in the depth direction of the subject 14. Iron and aluminum were used as the subject 14, and the energy intensity of the scattered X-rays 15 generated from the subject 14 was measured separately for two energy bands.
A constant voltage of 150 kV was applied to the X-ray generator 11 to generate X-rays, which were separated by the X-ray detector 23 into two energy bands. When the effective energies of the two energy bands were calculated using the half-value layer of copper, they were approximately 80 keV and 100 keV.

FIG. 3 shows the scattered X-ray transmission intensity ratio in the thickness direction for aluminum and iron. In FIG. 3, the value when the thickness is 0 is normalized as 1. As shown in FIG. 3, in the measurement result C for aluminum, since aluminum has little absorption, there is little attenuation for high energy and low energy. Further, in the measurement result D for iron, it can be seen that the attenuation of low energy is remarkably large for the absorption of high energy. By comparing these high and low energy decay curves, accurate information regarding the materials that make up the subject 14 can be obtained.

FIG. 4 shows the ratio of the values of the scattered X-ray transmission intensity ratio of high energy and low energy, which are logarithmic, and it can be seen that it depends on the type of material, regardless of the thickness of the material. .. As shown in FIG. 4, the logarithmic scattered X-ray information ratio tends to be slightly higher as the thickness increases. This is called a beam hardening phenomenon peculiar to X-rays, and the thickness of the subject 14 is increased. This is because the phenomenon that the effective energy of the transmitted X-rays shifts to the higher side due to the increase in the energy.

A method of reducing the beam hardening phenomenon is to make the energy spectrum of incident X-rays as narrow as possible. This method uses 2 X-rays.
The subject 14 may be illuminated after the energy regions have been separated in advance. As an example, X-ray generator 11 and subject
A K-edge filter 25 utilizing the K-shell absorption edge is provided between 14 and the K-edge filter 25 inserts a material having an absorption edge into the energy to be separated, thereby the X-ray generator.
The X-ray energy intensity generated from 11 can be easily separated into two energy bands. At least one of tantalum (Ta), tungsten (W), platinum (Pt), gold (Au), and lead (Pb) is suitable as the K edge filter used in the scattered X-ray energy region of the present invention.
Filters containing elements, each having an absorption edge at 60 to 80 keV. By using this filter, effective energies of X-rays of about 60 keV and 100 keV can be easily obtained.
Further, to make it easier, it is possible to easily change the X-ray energy by switching the voltage applied to the X-ray generator 11, but in this case, the X-ray spectra overlap. The voltage applied to the X-ray generator 11 is switched to alternately switch the energy of the generated X-rays to irradiate the subject 14, and the Compton scattered X-rays 15 generated from the subject 14 are detected in synchronization with the switching. May be.

[0021]

As described above, according to the present invention, by separately detecting the energy intensity of Compton scattered radiation from a subject, not only the radiation image showing the three-dimensional structure of the subject but also the 3 It is also possible to obtain information on the materials in the dimensional structure.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a radiation three-dimensional image capturing apparatus showing an embodiment of the present invention.

FIG. 2 is a diagram showing attenuation with respect to X-ray photon energy due to interaction between a material forming a subject and X-ray photons.

FIG. 3 is a diagram showing a scattered X-ray transmission intensity ratio in the thickness direction with respect to aluminum and iron.

FIG. 4 is a diagram showing a logarithmized high-energy and low-energy scattered X-ray transmission intensity ratio with respect to a subject thickness.

FIG. 5 is a distribution diagram of X-ray scattering directions by Compton scattering.

FIG. 6 is a schematic configuration diagram of a conventional radiation three-dimensional image capturing apparatus using backscattering of X-rays.

[Explanation of symbols]

 11 X-ray generator 12, 16 Slit 13 X-ray beam 14 Subject 15 Compton scattered X-ray 17 Sensor 19a, 19b Discriminator 20a, 20b Counter 21 Image processing unit 22 Display unit 23 X-ray detector 24 Radiation 3D image capturing Device 25 K edge filter

Claims (3)

[Claims] 1. A radiation three-dimensional image capturing apparatus for obtaining a vertical tomographic image in the subject by detecting Compton scattered radiation generated from a radiation beam applied to the subject by a radiation generator, A radiation detector for detecting the energy intensity of Compton scattered radiation,
A radiation three-dimensional imaging apparatus configured to compare the energy intensities to obtain information about the material forming the subject. 2. A radiation detector, two sets of discriminators and counters for separating and detecting the energy intensity of Compton scattered radiation into two energy ranges, and said two sets of discriminators and counters for separating. Using image information consisting of energy intensity information of Compton scattered radiation, the ratio of low-energy image information to high-energy image information, or image information obtained by logarithmizing low-energy image information and high-energy image information The radiation three-dimensional image capturing apparatus according to claim 1, further comprising: an image processing unit that calculates a ratio of the values to obtain image information. 3. A tantalum (Ta), tungsten (W), which separates the radiation energy intensity generated from the radiation generator into two regions between the radiation generator and the object.
The radiation three-dimensional image capturing apparatus according to claim 2, further comprising a K edge filter including at least one element of platinum (Pt), gold (Au), and lead (Pb) and utilizing a K shell absorption edge.