JP2009008560A - Nondestructive inspection method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and easily implement a nondestructive inspection which utilizes positron emission tomography (PET). <P>SOLUTION: While an object to be inspected 15 is irradiated with a high-energy photon beam, a large-area photon detector 19 efficiently detects annihilation γ rays generated on a beam axis. A PET image is obtained from the object to be inspected, by a first-generation CT technology that uses data obtained by rotating and translating a stage 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and apparatus for nondestructively inspecting materials.

  In the non-destructive inspection of industrial products, it is important to inspect the uniformity of the material composition in addition to the presence or absence of cracks and holes at the inspection location. In non-destructive inspection of industrial products using metals, plastics, ceramics, etc., a transmission image photographing method by radiography using X-ray having high transmission power is generally used. In many cases, tomography is performed in combination with a data processing method using computed tomography (CT).

  The amount directly measured by the transmission X-ray CT is an amount obtained by integrating the attenuation along the X-ray track. Based on this, the presence / absence and density of the substance in the tomographic plane are estimated by CT. The first generation CT is classified into the fourth generation CT according to the operation of the X-ray source and CT stage and the data acquisition format. The first-generation CT system developed in 1973 consisted of a straight line of X-rays and a single detector, but in 1975, a fan-shaped X-ray light source and 6 to 30 detectors A second-generation CT system using an instrument was developed. In addition, a third generation CT with a wide angle fan-shaped X-ray beam and several hundred detectors was created. If the X-ray source is fan-shaped and many detectors are used, an image can be taken in a short time. Therefore, since the time required for photographing one image is about 5 seconds in photographing with the third generation CT apparatus, an image in a state where breathing is stopped can be obtained. Since then, there has been further progress in apparatus, and the fourth generation CT apparatus can perform higher-speed scanning and continuous scanning.

  On the other hand, there is a technique for nondestructively inspecting submicron to nanometer order defects in a substance using positrons. Positrons cannot exist stably in matter, and cause annihilation with electrons and emit annihilation gamma rays. When atomic vacancies are formed in the material by the ejection of atoms, positrons can stay in the vacancies for a while. Therefore, the hole size and density can be measured by measuring the lifetime of the positron. Normally, positrons are injected from the outside, so the surface layer defects of the material are known.

  A high-energy photon beam generated by laser Compton scattering has a high directivity equivalent to that of emitted light. Even if it is a thin beam using a collimator, the amount of light does not decrease so much, so a transmission type first generation CT apparatus using this has been developed and used for nondestructive inspection (see Patent Document 1). The collimator usually uses a substance having a high atomic number such as lead and a high density, and has the effect of spatially narrowing the photon beam and the effect of narrowing the energy width of the photon beam.

  When a photon is irradiated onto a material, three interactions occur: photoelectron absorption, Compton scattering, and electron-positron pair production. The probability of each occurrence is roughly proportional to the 4th to 5th power of the atomic number, to the atomic number, and to the square root of the atomic number. If the photon energy is 1.02 MeV or more, which is the static mass energy of the electron / positron pair, an electron / positron pair is formed in the photon beam path inside the irradiated sample. The positron generated by the generation of the electron / positron pair causes pair annihilation with a nearby electron, and generates annihilation γ-ray with energy 511 keV and disappears. The lifetime depends on the surrounding electron density. Furthermore, if the photon energy is 10 MeV or more, most of the interaction is the generation of electron-positron pairs, and many annihilation γ rays are generated from the high energy photon beam axis.

  In recent years, a sample is irradiated with a high-energy particle beam of several MeV or more, such as a laser Compton scattered photon beam or muon, and an electron / positron pair is generated inside. A technique for evaluating defects in a material by measuring the Doppler broadening of the line energy spectrum has been developed (see Patent Document 2).

  A tomography that uses a positron emission tomography (PET) to measure the distribution of annihilation gamma ray generation points by preparing a pair of photon detectors and limiting the generation point of annihilation gamma rays by providing a collimator in front of them. An imaging method has also been developed, and defect distribution measurement is possible. In general, in PET, drugs labeled with radioactive isotopes that generate positrons, such as carbon 11, nitrogen 13, oxygen 15, and fluorine 18, are administered into the living body. I have a diagnosis. Usually, the radioisotope has to be transported to a site where imaging is desired, and PET is considered to be applicable only to living organisms and not to industrial products. However, since high energy particles such as gamma rays and mu particles can be injected into the sample and positrons can be generated inside, it is possible to perform lifetime measurement and nondestructive inspection by PET (see Patent Document 3).

JP 2002-162371 A JP 2004-150851 A JP 2006-177798 A

  In a nondestructive inspection apparatus using PET that uses positrons generated inside by implanting high-energy γ-rays or the like into a sample, only a two-photon annihilation event is selectively measured, so that the object to be inspected is surrounded by 360 degrees. The detector must be placed in Therefore, at least two (a pair) of detectors must be opposed and rotated, or several must be arranged in a ring shape. This method has a difficulty in operating many detectors in conjunction (coincidence).

  In addition, in order to perform high spatial resolution imaging, it is necessary to sufficiently reduce the solid angle expected by the detector, and a collimator must be disposed in front of the detector. This inevitably reduces the counting rate of events, and there is a problem that it takes a long time to measure in order to obtain a good image. At present, the measurement method using mu particles has not been proposed for tomography by PET, but has the same problem.

  The present invention irradiates a test object with a high-energy photon beam, and detects annihilation γ rays generated from the beam axis with a large-area photon detector with high efficiency. A PET apparatus is constructed.

  In PET using only the two-photon annihilation event, it is basically unnecessary to know the irradiation photon beam intensity, but in the present invention, it is necessary to know the irradiation photon beam intensity. For this, when collimating a high-energy photon beam, a method of monitoring the irradiation photon beam intensity in a nondestructive manner by using a scintillation detector for the collimator is effective.

  In the nondestructive inspection of the object to be inspected according to the present invention, the object to be inspected is translated so as to cross the γ-ray beam, and the annihilation of positrons generated inside the object to be inspected at each movement position of the object to be inspected with respect to the γ-ray beam γ The line intensity is measured in one-to-one correspondence with the path of the irradiated γ-ray beam, and the relationship between the path of the irradiated γ-ray beam inside the subject and the detected annihilation γ-ray intensity is obtained.

  Further, in the nondestructive inspection of the inspection object according to the present invention, the inspection object is translated so as to cross the γ-ray beam, and irradiation is performed on the inspection object at each movement position of the inspection object with respect to the γ-ray beam. a step of measuring the γ-ray beam intensity, the transmitted γ-ray intensity transmitted through the object to be inspected, and the positron annihilation γ-ray generated inside the object in a one-to-one correspondence with the irradiation γ-ray beam path; The data is acquired by repeating the rotation step of rotating the object to be inspected with respect to the γ-ray beam by a predetermined angle, and the first of the object to be inspected is based on the data on the irradiation γ-ray beam intensity and the transmitted γ-ray intensity. A tomographic image is formed, and a second tomographic image of the object to be inspected is formed based on data relating to the intensity of annihilation γ rays.

  A non-destructive inspection apparatus for an object to be inspected according to the present invention includes a beam source that generates a high-energy γ-ray beam, a stage that holds the object to be inspected and moves in a direction crossing the irradiated γ-ray beam, and irradiation of γ rays. And an annihilation γ-ray detector that measures, as data corresponding to each coordinate of the stage, the amount of annihilation γ-ray generation of positrons generated inside the inspection object.

  In addition, the non-destructive inspection apparatus for an object to be inspected according to the present invention includes a beam source that generates a high-energy γ-ray beam, and moves the object to be inspected while holding the object to be inspected and designates the object to be inspected. A stage that can be rotated by a predetermined angle, a stage drive unit that drives the stage, a collimator disposed on the optical axis of the irradiation γ-ray between the beam source and the stage, and the optical axis of the irradiation γ-ray beam A transmission γ-ray detector that detects γ-rays that are located above and transmits the object to be inspected, and the amount of positron annihilation γ-rays generated inside the object to be inspected by γ-ray irradiation at each coordinate and angle of the stage. An annihilation γ-ray detector that measures as one corresponding data, an irradiation γ-ray intensity monitor means for monitoring the intensity of γ-rays irradiated to the subject, and a measurement data and an irradiation γ-ray intensity monitor by a transmission γ-ray detector Measurement data by means And a calculation unit for forming the first tomographic image of the inspection object, to form a second tomographic image of the inspection object based on the measured data by the annihilation γ-ray detector based on.

  The collimator preferably includes a scintillation substance, and the irradiation γ-ray intensity monitoring means preferably includes a circuit for detecting the amount of light emitted from the collimator by gamma irradiation. The computing unit can form a PET image of the object to be inspected from the difference between the first tomographic image and the second tomographic image.

  According to the present invention, it is possible to obtain a PET image showing the electron / positron pair generation position distribution in addition to the transmission type γ-ray CT image in a short time with a simplified apparatus configuration. Since two physical quantities with different properties are measured by a single measurement, it is possible to obtain information on density and information on atomic number by calculating their images, greatly expanding the amount of information in nondestructive inspection. . Normally, these pieces of information are extracted based on X-ray CT images of two different colors of energy, but in the present invention, these can be performed by a single γ-ray irradiation.

  Further, the defect density distribution in the material can be found by performing CT using the annihilation γ-ray energy spectrum width as an integral quantity. Therefore, the atomic number, density, and material defects can be examined by a single measurement, and more information can be obtained than the conventional nondestructive inspection.

  Embodiments of the present invention will be described below with reference to the drawings. A case where laser Compton γ rays are used as the high energy photon beam will be described as an example.

  FIG. 1 is a schematic view showing an example of a nondestructive inspection apparatus according to the present invention. When the electron beam 10 accelerated in the electron accelerator 12 is irradiated with laser light from the laser light source 13, laser Compton γ rays 11 having energy of several MeV or more in the direction opposite to the laser light irradiation direction are generated by Compton scattering. The laser Compton γ-ray 11 is characterized by being a quasi-monochromatic line with high transmission power and high directivity. The laser Compton γ-ray 11 is made into a thin beam having a diameter of several millimeters through the collimator 14 and then irradiated to the object 15 to be inspected held on the stage 20. Inside the inspection object 15, electron / positron pairs are generated along the γ-ray beam axis. A thin plastic scintillator is arranged as an irradiation γ-ray intensity monitor 16 in front of the inspected object 15. Transmitted γ-rays that have passed through the object 15 are measured by the γ-ray detector 17. The annihilation γ-ray detector 19 is disposed at an arbitrary position where the inspection object 15 is viewed, and detects annihilation γ-rays generated inside the inspection object.

  Instead of the irradiation γ-ray intensity monitor 16, the irradiation γ-ray intensity may be determined by performing blank measurement by providing regions 18 for monitoring the γ-ray beam irradiation amount on both sides of the object to be inspected. The blank measurement method in the region 18 has an advantage that the irradiation γ-ray intensity can be accurately monitored, although there is a disadvantage that the measurement time is long because it is necessary to move the stage greatly for each measurement. In this case, it is assumed that the γ-ray intensity does not vary greatly while the stage is moved. That is, as the average γ-ray irradiation intensity during the stage movement, a value measured at both ends of the inspection object, that is, the region 18 is used.

  The stage 20 is driven by a stage drive unit 21 and can move the object to be inspected 15 held on the stage 20 in translation in the direction (Y-axis direction) across the optical axis of the laser Compton γ-ray 11 and the stage surface. It can be rotated by any angle around the Z axis perpendicular to. In the measurement, while the stage 20 is moved in the Y-axis direction, the γ-ray intensity transmitted through the inspection object 15 at each position of the stage movement is measured by the γ-ray detector 17, and the irradiation γ-ray in the inspection object is measured. An annihilation γ-ray emitted from the vicinity of the optical path is detected by the annihilation γ-ray detector 19 regardless of the radiation position. At this time, the irradiation γ-ray intensity is also simultaneously measured by the irradiation γ-ray intensity monitor 16. In this way, the irradiation γ-ray intensity, transmitted γ-ray intensity, and annihilation γ-ray intensity are measured at each point of stage movement, and the coordinates of the inspection object 15 on the moving axis of the stage 20 and the γ-ray intensity by each detector are data. To correspond.

  When one measurement by the stage translation is completed, the object 15 is rotated by a predetermined angle around the Z axis, and then the stage 20 is similarly moved in the Y axis direction to irradiate each point of stage movement. γ-ray intensity, transmitted γ-ray intensity and annihilation γ-ray intensity are measured. After rotating the object to be inspected by a predetermined angle, the object to be inspected is moved around the Z axis by measuring the irradiation γ-ray intensity, transmitted γ-ray intensity, and annihilation γ-ray intensity by translating in the Y-axis direction. The measurement data is acquired by repeating until it is rotated 180 degrees or 360 degrees. In this way, the γ-ray beam intensity measured by the irradiation γ-ray intensity monitor 16 is set as the irradiation γ-ray intensity, and the beam attenuation is measured from the transmitted γ-ray intensity detected by the γ-ray detector 17 to thereby obtain the first. A tomogram is obtained by the generation CT method. Specifically, the natural logarithm of the irradiation γ-ray intensity ratio measured by the irradiation γ-ray intensity monitor 16 and the transmission γ-ray intensity ratio measured by the γ-ray detector 17 is imaged using a CT technique. Further, another CT image is constructed by the first generation CT method from the data of the annihilation γ-ray intensity detected by the annihilation γ-ray detector 19.

  The control calculation unit 22 instructs the stage drive unit 21 to control translation and rotation of the stage 20. In addition, measurement signals from the irradiation γ-ray intensity monitor 16, the γ-ray detector 17, and the annihilation γ-ray detector 19 are sequentially input to the control calculation unit 22. The control calculation unit 22 processes the measurement data together with the rotation angle information and translational position information of the stage 20 by the first generation CT method, and calculates a tomographic image including various information. The calculation result is displayed on the display unit 23.

While the γ-ray beam passes through the object to be inspected and generates electron / positron pairs along the path, γ-rays due to positron annihilation are emitted in all directions. In the present invention, the annihilation γ-ray intensity generated when the γ-ray beam 11 passes through the inspection object 15 is detected by the annihilation γ-ray detector 19 installed outside. In this case, the natural logarithm of the intensity ratio of annihilation γ-rays and irradiation γ-rays is expressed as the sum of the linear attenuation coefficient μ _{1 at} which irradiation γ-rays attenuate and the linear attenuation coefficient μ ₂ of annihilation γ-rays generated at a certain depth. The That is, if I ₀ , I ₁ , and I ₂ are the intensity of irradiated γ rays, transmitted γ rays, and annihilation γ rays, respectively, they are expressed as follows.

Therefore, after rotating the object to be inspected by a predetermined angle until the object to be inspected is rotated 180 degrees or 360 degrees, the operation of measuring the irradiation γ-ray intensity, transmitted γ-ray intensity, and annihilation γ-ray intensity while being translated is repeated. Thus, μ ₁ and μ ₂ can be measured by the transmission type first generation CT. The μ ₁ distribution indicates the linear attenuation coefficient in the γ-ray energy, and the μ ₂ distribution indicates the linear attenuation coefficient for the annihilation γ-ray in a form superimposed thereon. Therefore, by taking the difference between the distributions of μ ₂ and μ ₁ , an electron / positron pair generation position distribution, that is, a PET image is obtained.

  According to this method, the transmission image and the PET image can be acquired in exactly the same arrangement, and it is not necessary to align the images, so that highly accurate nondestructive inspection can be performed.

  Of course, the annihilation γ-ray energy spectrum can be measured using the annihilation γ-ray detector 19 and the spectrum width can be used as an integration amount. In this case, information on the defect density distribution in the object to be inspected can be obtained by measuring the energy spectrum at each coordinate and angle and using the half width or standard deviation as an integral amount. For this, a defect measuring method for materials using ordinary positrons can be applied. That is, it is possible to measure the incompleteness of the lattice of the atoms constituting the object to be inspected, that is, the presence or absence of defects, by S-parameter measurement of the annihilation γ-ray energy spectrum, which is a conventionally established technique. Positron annihilation can be broadly divided into annihilation with valence electrons and annihilation with core electrons. Since the former has a small momentum of electrons, the spectrum width of annihilation γ-ray energy due to Doppler broadening is relatively narrow, and the latter has a wide spectrum width because of high electron energy. It is generally known that the energy spectrum width of annihilation γ-rays becomes narrower if there is a defect in the material, because the interaction with the inner shell electrons increases relatively.

  The distribution can be reconstructed by CT using the annihilation γ-ray energy spectrum width as an integral quantity. This distribution represents the defect distribution of the inspection object. For example, when the half-width of the spectrum is the integral amount of the first generation CT, γ-rays are irradiated at an angle at a certain coordinate, the half-width of the annihilation γ-ray energy spectrum generated from that is recorded, and the coordinate and angle are shaken. The defect distribution can be imaged by CT. The feature of this method is that it can be measured simultaneously with the transmission type first generation CT.

According to the present invention, a PET image with annihilation γ rays and a transmission image with high energy γ rays are obtained by one irradiation. This means that a measurement equivalent to simultaneous irradiation of two different colors of γ rays and X rays can be performed by a single irradiation. As a result, the density of the test object and the distribution of the atomic numbers of the constituent atoms of the test object can be independently imaged. That is, the relationship of Expression (3) is obtained by CT using γ-ray transmission of energy E ₁ .

Here, μ ₁ , ρ _A , and Z are the linear attenuation coefficient measured by CT, the atomic density of the test object, and the average atomic number of the test object, respectively. m and n are coefficients representing the atomic number dependence of the linear attenuation coefficient. The interaction cross section normalized by atomic number and atomic density is represented by σ ₀ . That is, σ ₀ does not depend on the atomic number and density. Since high energy X-rays and γ-rays of 511 keV or higher are considered here, the interaction is only Compton scattering and electron / positron pair generation, which are denoted as CMP and PC, respectively. For reference, FIG. 2 and FIG. 3 show σ ₀ calculated for Compton scattering and electron-positron pair production. The calculation was made for aluminum (Al), titanium (Ti), iron (Fe), and tungsten (W), which are the elements of atomic numbers 13, 22, 26, and 74, respectively. M = 0.89 for Compton scattering and n = 1.84 for electron-positron pair production.

Similar to Equation (3), the relationship of Equation (4) is obtained by a PET image using annihilation gamma rays. In this case, E ₂ = 511 keV.

    Rewriting equation (3) to equation (5) and subtracting equation (5) from equation (4) yields equation (6), from which equation (7) is derived.

  By substituting equation (7) into equation (5), equation (8) is obtained, and when it is rewritten, equation (9) is obtained, and thus equation (10) is obtained.

Since σ ₀ , m, and n are known and μ ₁ and μ ₂ are measurement data, a CT image representing the distribution of atomic numbers can be obtained. Further, the following equation (11) is obtained by substituting equation (10) into equation (7).

  Thus, by measuring two physical quantities with a single γ-ray irradiation and reconstructing them independently by CT, an atomic number distribution and an atomic density distribution can be obtained as an image.

  FIG. 4 is a schematic view showing another configuration example of the inspection apparatus according to the present invention. In this embodiment, a scintillation substance having a relatively high atomic number and a high density, such as PWO (lead tungstate), BGO (bismuth oxide / germanium oxide), CsI (cesium iodide), or the like was used for the collimator 14. These scintillation substances were processed into a rectangular parallelepiped of about 10 cm × 10 cm × 20 cm, and a through-hole was provided in the long axis to form a γ-ray collimator 14. That is, the beam of the laser Compton γ-ray 11 is irradiated on the collimator 14 and passed through the through hole, thereby narrowing the γ-ray beam. The diameter of the through hole is arbitrary, but 1 to 2 mm is desirable for performing radiography and the like. The γ-rays that have not passed through the through holes are attenuated by the interaction with the scintillation substance, and the γ-ray beam intensity can be measured by the light emission at that time. That is, since the intensity of the γ-ray beam irradiated on the collimator 14 is substantially uniform, the intensity of the γ-ray beam that has passed through the collimator through-hole is increased by detecting and integrating the light emission amount of the scintillation substance by the scintillation light detection circuit 24. Can be estimated with accuracy.

  In this embodiment, each tomographic image is measured as in the embodiment shown in FIG. 1, but by using the collimator 14 as a γ-ray intensity monitor, the γ-ray intensity monitor 16 in the embodiment shown in FIG. Alternatively, the blank measurement by the region 18 can be omitted. Therefore, the measurement time can be significantly shortened while increasing the measurement accuracy.

  In addition, the annihilation γ-ray detector 19 can be enlarged so as to surround the inspected object 15, or a large number of annihilation γ-rays can be detected by arranging a large number of them, so that the measurement time can be shortened. It is.

  Next, an example of inspection using the inspection apparatus of the present invention will be described. FIG. 5 shows the arrangement of the experimental apparatus. A non-destructive inspection was performed on a sample piece in which a reinforcing bar 34 having a diameter of 1 cm was inserted from the center of a concrete block 33 having a side of 10 cm to an offset of 2.5 cm with respect to one side surface. For convenience, a coordinate axis with the beam axis as the X axis is set, and the beam traveling direction is positive. Assuming that the origin is the front side surface of the concrete block 33, the position where the reinforcing bar 34 is inserted is X = 2.5 cm. The sample was placed on a CT stage 37 that performs translation and rotation, and irradiated with a 20 MeV laser Compton scattered photon beam 31. In this experiment, in order to simplify the data analysis, a normal lead block collimator was used as the collimator 32 without using a scintillation substance. The collimator 32 is provided with a through hole having an inner diameter of 2 mm. The transmission γ-ray detector 35 was made of thallium iodide (NaI). A high-purity germanium detector was used as the annihilation γ-ray detector 36, and an inspection was performed while monitoring the count rate of only the peak at 511 keV.

  FIG. 6 shows the result of examining the correlation between the annihilation γ-ray count rate measured by the annihilation γ-ray detector 36 and the amount of movement by translating the stage 37 along the Y-axis. It can be seen that the count rate of annihilation γ-rays increased at the position where the reinforcing bars were arranged at Y = 0. Here, information on attenuation of X-rays and γ-rays on the Y-axis is obtained, and the presence or absence of reinforcing bars arranged perpendicular to the Y-axis is known.

  FIG. 7 shows the result of CT tomography performed by performing several such measurements. The tomographic image shown in FIG. 7 is a tomographic image of a reinforced concrete block reconstructed from the data of 10 projections, and the position where the reinforcing bar was arranged could be confirmed. An area of 11 cm × 11 cm was displayed so as to include an area of 10 cm square concrete. The region where many annihilation γ rays are emitted is displayed in white, and the region where there are few γ-rays is displayed in black. A spot that appears white and strong at the bottom of the figure represents a reinforcing bar. The other white parts are pseudo-signals (artifacts) due to the fact that the number of projections is small, the annihilation γ-ray intensity change is steep, and the data analysis method cannot model the phenomenon sufficiently accurately. . The concrete is 10 cm × 10 cm, but the boundary with the air layer is not clear because the contrast of the reinforcing bars is emphasized. However, the boundary between the concrete and the air layer can be easily visualized by adjusting the contrast level.

Schematic which shows an example of the nondestructive inspection apparatus by this invention. The figure which shows the photon energy dependence of the Compton scattering cross section normalized by the atomic number and the atomic density. The figure which shows the photon energy dependence of the electron-positron pair production scattering cross section normalized by atomic number and atomic density. Schematic which shows the other structural example of the inspection apparatus by this invention. Layout of nondestructive inspection CT experiment of reinforced concrete block. The figure which shows the relationship between the translation amount of a reinforced concrete block, and the annihilation gamma ray intensity. The tomogram of the reinforced concrete block obtained by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electron beam 11 Laser Compton gamma ray 12 Electron accelerator 13 Laser light source 14 Collimator 15 Inspected object 16 Irradiation gamma ray intensity monitor 17 Gamma ray detector 18 Gamma ray beam monitor area 19 Annihilation gamma ray detector 20 Stage 21 Stage drive part 22 Control calculation unit 23 Display unit 24 Scintillation light detection circuit 31 Laser Compton scattered photon beam 32 Collimator 33 Concrete block 34 Reinforcing bar 35 Transmission gamma ray detector 36 Annihilation gamma ray detector 37 CT stage

Claims (13)

The object to be inspected is translated so as to cross the γ-ray beam, and the annihilation γ-ray intensity of the positron generated inside the object at each movement position of the object to be inspected with respect to the γ-ray beam is paired with the path of the irradiated γ-ray beam. Measuring in association with one,
A non-destructive inspection method for an object to be inspected, comprising a step of obtaining a relationship between a path of an irradiated γ-ray beam inside the object and a detected annihilation γ-ray intensity. The object to be inspected is translated so as to cross the γ-ray beam, and at each movement position of the object to be inspected with respect to the γ-ray beam, the irradiation γ-ray beam intensity irradiated on the object to be inspected and the transmission that has passed through the object to be inspected. A step of measuring data relating to γ-ray intensity and annihilation γ-rays of positrons generated inside the inspected object in one-to-one correspondence with the path of the irradiated γ-ray beam; A process of acquiring data by repeating a rotation process of rotating the angle;
Forming a first tomographic image of the object to be inspected based on the data on the irradiation γ-ray beam intensity and transmitted γ-ray intensity;
And a step of forming a second tomographic image of the object to be inspected based on data on the intensity of the annihilation γ-ray.   3. The nondestructive inspection method according to claim 2, wherein a PET image of the object to be inspected is formed from a difference between the first tomographic image and the second tomographic image of the object to be inspected. Inspection method.   3. The nondestructive inspection method according to claim 2, wherein an image representing a defect density distribution of the inspection object is formed based on data of an energy spectrum width of the annihilation γ-ray. Method.   3. The nondestructive inspection method according to claim 2, wherein the atomic number distribution of atoms inside the object to be inspected is based on the irradiation γ-ray beam intensity, the transmitted γ-ray intensity, and the annihilation γ-ray intensity data. A non-destructive inspection method for an object to be inspected, characterized in that a tomographic image is formed.   The nondestructive inspection method according to claim 2, wherein the tomogram represents an atomic density distribution inside the object to be inspected based on data of the irradiation γ-ray beam intensity, the transmitted γ-ray intensity, and the annihilation γ-ray intensity. A nondestructive inspection method for an object to be inspected, characterized in that an image is formed. A beam source for generating a high energy gamma ray beam;
A stage that holds the object to be inspected and moves in a direction across the γ-ray beam;
an annihilation γ-ray detector that measures, as data corresponding to each coordinate of the stage, the amount of annihilation γ-ray generation of positrons generated inside the inspection object by γ-ray irradiation. Nondestructive inspection equipment. A beam source for generating a high energy gamma ray beam;
A stage capable of holding the object to be inspected and moving in a direction across the γ-ray beam and rotating the object to be inspected by a specified angle;
A stage drive unit for driving the stage;
A collimator disposed on the optical axis of the γ-ray between the beam source and the stage;
A transmission γ-ray detector that is located on the optical axis of the γ-ray beam and detects γ-rays transmitted through the object to be inspected;
An annihilation γ-ray detector that measures the amount of annihilation γ-ray generation of positrons generated inside the object to be inspected by γ-ray irradiation as data corresponding to each coordinate and angle of the stage;
An irradiation γ-ray intensity monitoring means for monitoring the intensity of γ-rays applied to the subject;
A first tomographic image of the object to be inspected is formed based on the measurement data obtained by the transmission γ-ray detector and the measurement data obtained by the irradiation γ-ray intensity monitoring means, and the object to be inspected based on the measurement data obtained by the annihilation γ-ray detector. A non-destructive inspection apparatus for an object to be inspected, comprising: an arithmetic unit that forms a second tomographic image of the body.   9. The non-destructive inspection apparatus according to claim 8, wherein the collimator includes a scintillation substance, and the irradiation γ-ray intensity monitoring means includes a circuit for detecting a light emission amount of the collimator by gamma irradiation. Nondestructive inspection equipment.   The nondestructive inspection apparatus according to claim 8, wherein the arithmetic unit forms a PET image of an object to be inspected based on a difference between the first tomographic image and the second tomographic image.   9. The nondestructive inspection apparatus according to claim 8, wherein the calculation unit displays an image representing a defect density distribution of an inspection object based on energy spectrum width data of the annihilation γ-ray measured by the annihilation γ-ray detector. A non-destructive inspection device for an inspection object characterized by forming.   The nondestructive inspection apparatus according to claim 8, wherein the calculation unit includes an intensity of the irradiated γ-ray beam measured by the irradiation γ-ray intensity monitoring unit, and an intensity of the transmitted γ-ray measured by the transmitted γ-ray detector. A tomographic image representing the atomic number distribution of atoms inside the test object is formed based on the intensity data of the annihilation gamma ray detected by the annihilation gamma ray detector. Inspection device.   The nondestructive inspection apparatus according to claim 8, wherein the calculation unit includes an intensity of the irradiated γ-ray beam measured by the irradiation γ-ray intensity monitoring unit, and an intensity of the transmitted γ-ray measured by the transmitted γ-ray detector. A non-destructive inspection apparatus for an object to be inspected that forms a tomographic image representing an atomic density distribution inside the object to be inspected based on the intensity data of the annihilation γ ray detected by the annihilation γ-ray detector .

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