JP5700319B1 - Radiation source visualization apparatus and radiation source visualization method - Google Patents

Abstract

A radiation source visualization device and a radiation source visualization method are provided that can achieve both reduction in exposure time and improvement in detection accuracy. A radiation source visualization apparatus 1 for visualizing a distribution of radiation sources, wherein a plurality of apertures 100 are arranged according to a predetermined rule, and an aperture array 101 capable of reconstructing transmitted radiation as an encoded image is a basic pattern. 2 and a plurality of basic patterns 101 arranged adjacent to each other, and the coding mask 10 shown in FIG. 2 and the coding mask 10 are arranged toward the radiation source S, the transmission through the coding mask 10 is performed. Based on the arrangement form of the basic pattern 101 in the coding mask 10 and the detection unit 11 that detects the emitted radiation as the coded image of the optical signal, the radiation source is reconstructed by reconstructing the detected coded image A calculation unit 12 that calculates a radiation dose distribution including S and a display unit 12b that displays the calculated radiation dose distribution. [Selection] Figure 1

Description

  The present invention relates to a radiation source visualization device and a radiation source visualization method, and more particularly to a radiation source visualization device and a radiation source visualization method capable of both reducing an exposure time and improving detection accuracy.

  2. Description of the Related Art Conventionally, there is a radiation distribution measuring device (hereinafter referred to as a gamma camera) using a pinhole method as a device for detecting a gamma ray source from a position far away and visualizing the distribution state.

  In this gamma camera, basically, an aperture having a plurality of pinholes, a detector that detects radiation transmitted through each pinhole as an optical signal, and a distribution process of radiation sources by performing reconstruction processing on the optical signal. And a converter for converting to. By displaying the distribution of radiation sources output from this converter on the display unit of a terminal device such as a personal computer, it is possible to confirm at a glance how much radiation sources are present at what positions. It becomes.

  The gamma camera is suitably used for maintenance work, dismantling work, inspection work, and decontamination work in a radiation environment such as a nuclear power plant.

  However, the reconstruction processing in the conventional gamma camera has a problem that the detection accuracy of the radiation distribution is poor because the distance between the measurement object and the detector is set to infinity.

  In order to solve this problem, Japanese Patent Application Laid-Open No. 9-43359 (Patent Document 1) discloses an aperture in which a large number of pinholes are formed in a shielding plate made of a radiation shielding material, and the aperture through which the pinholes are transmitted. A radiation distribution measuring apparatus including a two-dimensional position detection type radiation detector for detecting radiation to be emitted is disclosed. In this apparatus, there are provided reconstruction means for performing reconstruction processing of the signal counting of the radiation detector and the distribution based on the counted value, and a display device for displaying the result of the distribution, piping and equipment in which a radiation source exists, The distribution of radiation is measured for walls and other structures. Further, the apparatus includes a non-contact type distance meter that measures the distance between the measurement object and the radiation detector, and a means that can input the distance value obtained by the distance meter to the computer online. The radiation distribution is reconstructed based on the distance value. As a result, even if the distance to the detector is unknown, it is possible to perform reconstruction processing accurately in real time using the distance value of the distance meter.

  For visualization (imaging) of X-rays and γ-rays, there is a method called a coded aperture imaging method. In this coded aperture imaging method, the same principle as the above-described pinhole method is used, and a coded aperture mask in which a plurality of small-sized apertures are arranged according to a predetermined rule instead of an aperture having a pinhole (opening). (Also referred to as an encoding mask). Thereby, high angular resolution and signal-to-noise ratio can be obtained.

  As a technique related to this, for example, Japanese Patent Publication No. 2008-542863 (Patent Document 2) discloses a coded aperture image system including a detector array and a reconfigurable coded aperture mask means. This allows imaging at different resolutions across different fields of view without the need for any moving parts or large optical components, and the visible, near infrared, thermal infrared, Alternatively, it can be applied to multifunctional high-resolution images in the ultraviolet wavelength band.

  On the other hand, when reconstruction processing is performed using a coded aperture mask in a gamma camera, the performance is improved, but since there are multiple apertures, various reconstructions (decoding) are possible from the same optical signal. There is a problem that a false radiation source (decoding artifact, ghost image) appears.

  In order to solve this problem, Japanese translations of PCT publication No. 2008-537137 (Patent Document 3) discloses a device that limits the occurrence of decoding artifacts related to a gamma camera having a coding mask. The device comprises a gamma ray detector opposite the coding mask and having a field of view through a region partially encoded by the coding mask, and a detector that does not transmit gamma rays and is referenced to the coding mask. And a concave component disposed on the opposite side of the. The concave part covers the partial coding region of the field of view of the detector and has a thickness that varies over the length of the concave part. This allows gamma photons to be blocked by the same thickness of the material regardless of which path the gamma photon takes between the partial coding region of the field of view and the detector. Can be specified with high accuracy.

Japanese Patent Laid-Open No. 9-43359 Special table 2008-542863 publication Special table 2008-537137

  Here, in a gamma camera using a coding mask, the exposure time required for photographing (visualizing) a measurement object in a predetermined place requires several tens of minutes (for example, 40 minutes), which takes a very long time. There is. Further, a gamma camera using a coding mask still has a problem that a false radiation source (false image) is generated. In this false radiation source, for example, radiation emitted from the ground appears as background noise. Such a problem cannot be solved sufficiently by the techniques described in Patent Documents 1 to 3.

  Therefore, the present invention has been made to solve the above-described problems, and provides a radiation source visualization apparatus and a radiation source visualization method capable of achieving both a reduction in exposure time and an improvement in detection accuracy. Objective.

  As a result of intensive studies, the present inventor has completed a novel radiation source visualization apparatus and radiation source visualization method according to the present invention.

That is, the present invention is a radiation source visualization device for visualizing the distribution of radiation sources, wherein a plurality of apertures are arranged according to a predetermined rule, and an aperture array in which transmitted radiation can be reconstructed as an encoded image is used as a basic pattern. The basic pattern includes four basic patterns, two vertically arranged horizontally, and a mask in which two basic patterns are arranged adjacent to each other in the vertical direction is defined as the first mask. A second mask equivalent to the first mask is arranged adjacent to the right of the first mask, and the second mask has an opening size when viewed from above with respect to the first mask. The unit is shifted upward by one unit, and the portion of the mask that protrudes upward relative to the first mask in the shifted second mask is downward relative to the first mask in the second mask. The part where the mask disappeared A coded mask composed be arranged, the coding mask, when placed toward the radiation source, a detector for detecting the radiation transmitted through the coded mask as an encoded image of the optical signal, By superimposing a plurality of basic encoded images of the optical signal corresponding to the basic pattern included in the detected encoded image based on the arrangement pattern of the basic pattern, each pixel of the basic encoded image An arithmetic unit that calculates the distribution of the radiation dose including the radiation source by increasing the intensity and arranging the radiation dose estimated from the pixel intensity of the enhanced basic encoded image for each pixel; and And a display unit for displaying the calculated radiation dose distribution.

  The calculation unit extracts a radiation dose that is equal to or higher than a lower threshold set by the user from the arranged radiation doses, and extracts all the extracted radiation doses from a region where the radiation dose is high to a low radiation dose. The radiation dose distribution is calculated by dividing the area into a predetermined number of areas and calculating contour lines connecting the boundaries of the divided areas with lines.

  The image processing apparatus further includes a photographing camera that captures a visible image including a radiation source facing the coding mask, and the calculation unit associates a real space position of the coded image with a real space position of the visible image. Then, a process of superimposing the radiation dose distribution and the visible image is executed, and the display unit displays a visible image in which the radiation dose distribution is superimposed. In addition, a laser distance meter capable of irradiating a laser at an arbitrary position in the real space of the visible image and measuring a distance from the irradiated position to the apparatus, the calculation unit is configured to distribute the radiation dose. Of the laser distance meter to a specific position in a real space having a radiation dose equal to or higher than a preset reference radiation dose, and the distance from the apparatus to the specific position. The display unit displays the measured distance at a specific position of the visible image.

The present invention is also a radiation source visualization method for visualizing the distribution of a radiation source, wherein a plurality of apertures are arranged according to a predetermined rule, and an aperture array that can reconstruct the transmitted radiation as an encoded image is used as a basic pattern. The basic pattern includes four basic patterns, two vertically arranged horizontally, and a mask in which two basic patterns are arranged adjacent to each other in the vertical direction is defined as the first mask. A second mask equivalent to the first mask is arranged adjacent to the right of the first mask, and the second mask has an opening size when viewed from above with respect to the first mask. The unit is shifted upward by one unit, and the portion of the mask that protrudes upward relative to the first mask in the shifted second mask is downward relative to the first mask in the second mask. In the part where the mask disappeared The coded mask formed by causing location, the steps of installing toward the radiation source, detecting the radiation transmitted through the coded mask as an encoded image of the optical signal, the detected encoded image The basic encoded image of the optical signal corresponding to the basic pattern included in is superimposed on the basis of the arrangement pattern of the basic pattern to enhance the intensity of each pixel of the basic encoded image, and the enhancement Calculating a radiation dose distribution including the radiation source by arranging a radiation dose estimated from the pixel intensity of the basic encoded image for each pixel; and calculating the calculated radiation dose distribution. And a step of displaying.

  The radiation source visualization apparatus and the radiation source visualization method according to the present invention can achieve both reduction in exposure time and improvement in detection accuracy.

It is the schematic which shows the radiation source visualization apparatus which concerns on this invention. 4 is a specific coding mask according to the present invention. FIG. 3 is a schematic diagram illustrating a specific coding mask according to the present invention. It is the figure which showed the example of the well-known pattern applied to the basic pattern of the specific encoding mask which concerns on this invention. 4 is a block diagram of a radiation source visualization apparatus according to the present invention and a flowchart for illustrating an execution procedure of the radiation source visualization method according to the present invention. It is a photograph of Example 1 of the radiation source visualization device for gamma rays concerning the present invention. It is a photograph which shows the mode of the verification experiment in Example 1 and Comparative Examples 1 and 2. FIG. It is a photograph which shows distribution of the radiation dose calculated and displayed in Example 1 in the distance 10m with the radiation source S of verification experiment 1, and exposure time 10 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in the comparative example 1 in the distance 10m with the radiation source S of the verification experiment 1, and exposure time 10 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in Example 1 in distance 5m with the radiation source S of verification experiment 1, and exposure time 10 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in the comparative example 1 in the distance 5m with the radiation source S of the verification experiment 1, and exposure time 10 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in the comparative example 2 in the distance 5m with the radiation source S of the verification experiment 1, and exposure time 5 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in Example 1 in distance 5m with the radiation source S of verification experiment 2, and exposure time 5 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in the comparative example 1 in the distance 5m with the radiation source S of the verification experiment 2, and exposure time 5 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in the comparative example 1 in the distance 5m with the radiation source S of the verification experiment 2, and exposure time 20 minutes. It is a photograph which shows distribution of the radiation dose calculated and displayed in the comparative example 2 in the distance 5m with the radiation source S of the verification experiment 2, and exposure time 5 minutes.

  Embodiments of a radiation source visualization device and a radiation source visualization method according to the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

<Radiation source visualization device>
The present invention is a radiation source visualization apparatus 1 for visualizing the distribution of a radiation source, and as shown in FIG. 1, a plurality of apertures 100 can be arranged according to a predetermined rule, and transmitted radiation can be reconstructed as an encoded image. An aperture array 101 is used as a basic pattern (unit mask), and the position of the second basic pattern 101 is shifted from the position of the first basic pattern 101 with the size of the opening 100 as a unit, and a plurality of basic patterns 101 are adjacent. When the encoding mask 10 shown in FIG. 2 and the encoding mask 10 are arranged toward the radiation source, the radiation transmitted through the encoding mask 10 is detected as an encoded image of an optical signal. And reconstructing (reconstructing and decoding) the detected encoded image based on an arrangement form of the basic pattern 101 in the encoding mask 10 , An arithmetic unit 12 for calculating the radiation dose distribution, including the radiation source S, characterized in that it comprises a display unit 12b for displaying the distribution of the calculated radiation dose. Thereby, it is possible to achieve both shortening of the exposure time and improvement of detection accuracy.

  That is, the coding mask 10 which is an aperture for shielding radiation has a larger number of openings 100 (multi-pinholes) in order to satisfy the above-mentioned rule than a normal pinhole (one opening) mask. ), The amount of radiation per unit area increases. Therefore, the intensity of the optical signal corresponding to the radiation transmitted through the encoding mask 10 naturally increases, so that the exposure time can be shortened.

  According to the principle of a needle hole camera, with a conventional pinhole mask, the pinhole is narrowed to prevent blurring of the image of the encoded image projected upside down on the detection surface and to sharpen the image outline. However, there is a problem in that the amount of incident radiation is reduced by the aperture of the pinhole, and an encoded image with high intensity cannot be obtained, resulting in a dark encoded image. In the present invention, by using the characteristic encoding mask 10 having a plurality of pinholes (needle holes), a sufficient radiation dose is obtained, the intensity of the encoded image is increased, the exposure time is shortened, and the detection accuracy is increased. It is compatible with improvement.

  In addition, since the plurality of basic patterns 101 are arranged in the encoding mask 10 by shifting the position of the second basic pattern 101 with respect to the position of the first basic pattern 101 with the size of the opening 100 as a unit. Naturally, the encoded image of the optical signal corresponding to the radiation transmitted through the encoding mask 10 includes a plurality of basic encoded images of the optical signal corresponding to the basic pattern 101 repeatedly. Therefore, the intensity (pixel value, etc.) of each pixel of the basic encoded image is enhanced by appropriately overlapping a plurality of basic encoded images included in the encoded image based on the arrangement pattern of the basic pattern 101. In addition, the signal-to-noise ratio can be increased. Therefore, the exposure time required to increase the signal-to-noise ratio of the optical signal pattern can be shortened to several minutes (for example, from 3 minutes to 5 minutes).

  Further, since the position of the basic pattern 101 is shifted in units of the size of the opening 100, the basic encoded images included in the encoded image can be superimposed without being disturbed. Furthermore, by providing this deviation, it is possible to identify which basic pattern 101 a plurality of basic encoded images corresponds to. Therefore, by superimposing a plurality of basic encoded images corresponding to this shift, reconstruction of the radiation dose distribution of the radiation source S depicted by the basic encoded image and a false radiation source (false image) ) Is easy to remove. Therefore, it is possible to obtain a clear radiation image (for example, a gamma image if the radiation is a gamma ray) with a high-precision distribution and resolution of the radiation source S and higher accuracy than before.

  Here, the configuration of the coding mask 10 of the present invention is the coding mask shown in FIG. Specifically, as shown in FIG. 3, the encoding mask 10 is reconstructed with the openings 100 as square holes, the basic pattern 101 as a plurality of openings 100 with a predetermined rule (transmitted radiation as encoded images). An array of apertures arranged according to specific rules possible). Next, a mask in which two basic patterns 101 are arranged adjacent to each other in the vertical direction is defined as a first mask 102 (first basic pattern), and the first mask 102 is set in the left-right direction (for example, right direction). A second mask 103 (second basic pattern) equivalent to the first mask 102 is disposed adjacently. Then, the position of the arranged second mask 103 is shifted in the vertical direction (for example, upward) by shifting the size of the opening 100 by one opening 100 as a unit. Then, the shifted second mask 103 includes a mask 103a that protrudes from the first mask 102 (a mask that protrudes upward) and a portion 103b that does not have a mask (a portion that disappears downward). Therefore, the four portions of the basic pattern 101 are converted into one pattern by translating the protruding portion of the mask 103a in a direction opposite to the direction shifted to the portion 103b where the mask disappears, and the encoding shown in FIG. It can be a mask.

  In addition, the size of the opening 100 is not particularly limited as long as the object of the present invention is not impaired, and is appropriately designed according to the type of radiation. For example, when the radiation is gamma rays, the size of the opening 100 is A range of 5 mm to 10 mm is preferable. The size of the opening 100 shown in FIG. 2 is a square hole of 8 mm in length and width.

  The basic pattern 101 of the coding mask 10 is an improvement of a known basic pattern as shown in FIG. Examples of known basic patterns include URA (Uniform Redundant Array) basic patterns, MURA (Modified URA) basic patterns, HURA (Hexagonal URA: hexagonal URA) basic patterns, and the like. I can do it.

  The shape of the basic pattern 101 is not particularly limited as long as the object of the present invention is not impaired. For example, as shown in FIG. 3, a square pattern with the size of the opening 100 as a unit is preferable.

  The rules constituting the basic pattern 101 are mathematical rules calculated based on the principle of the pinhole camera, and the basic pattern of the coding mask shown in FIG. 2 also follows the mathematical rules.

  Further, as shown in FIG. 3, the deviation of the basic pattern 101 is one opening 101 with respect to a predetermined direction (for example, the vertical direction).

  In addition, as shown in FIG. 3, the entire shape of the coding mask 10 is such that the portion of the mask 103a that protrudes from the shift is moved to the portion 103b where the mask disappears.

  The size of the encoding mask 10 is not particularly limited as long as the object of the present invention is not impaired. However, when the radiation source S is a gamma ray source, a size that generates an encoded image corresponding to gamma rays is preferable. The material of the encoding mask 10 is not particularly limited as long as the object of the present invention is not impaired. For example, the material of tungsten, tungsten alloy, copper, copper alloy, stainless steel, lead, lead alloy, etc. Can be selected.

  The arrangement form of the coding mask 10 and the detection unit 11 is, for example, when the coding mask 10 is arranged on one opened surface of the shielding container 11a that shields radiation, the detection unit 11 It arrange | positions on the other surface facing the said one surface, and is comprised so that the radiation which passed the said encoding mask 10 may be received. This whole shielding container 11a constitutes a measuring device.

  The shielding container 11a is preferably made of a material that shields radiation, such as lead, lead-based alloy, tungsten, tungsten-based alloy, copper, copper-based alloy, and stainless steel. The weight of the entire device can be reduced by using a material that shields radiation weakly, or a material that shields only the surface that faces the ground. good.

The configuration of the detection unit 11 is not particularly limited as long as the object of the present invention is not impaired. For example, the detection unit 11 includes a scintillator, a photocathode, an image intensifier tube, and a charge coupled device (CCD). This scintillator receives photons of radiation emitted from the radiation source S through the encoding mask 10 and converts the radiation into optical signals. As the material of this scintillator, when the radiation is gamma rays, for example, sodium iodide (NaI), thallium activated sodium iodide (NaI (Tl), TI-added NaI), cesium iodide (CsI), thallium activated Cesium iodide (CsI (TI), TI-added CsI), sodium-activated cesium iodide (CsI (Na), Na-added CsI), cadmium telluride (CdTe), zinc cadmium telluride (CdZnTe, Zn-added CdTe, CZT) ), Cerium fluoride (CeF ₃ ), barium fluoride (BaF ₂ ), lead fluoride (PbF ₂ ), europium activated lithium iodide (LiI (Eu), Eu-added LiI), lead tungstate (PbWO ₄ ) , silicic acid gadolinium (GSO, Ce addition of _Gd 2 _SiO 5), germanium Bismuth _{(BGO, Bi 4 Ge 3 O} 12), silicate lutetium (LGO, Ce added _{Lu 2 SiO 5), LYSO (} Cerium doped Lutetium Yttrium Orthosilicate, Lu (2-x) Y x SiO 5: Ce), LGSO _{((Lu, Gd) 2SiO 5} ), corundum _(Al 2 _{O 3} (ruby)), can be mentioned a silicon semiconductor or the like. The photocathode converts the converted optical signal into an electrical signal, the image intensifier tube amplifies the electrical signal, and the charge coupled device includes a predetermined number of pixels, and the amplified electrical signal Are generated and detected as a two-dimensional encoded image.

  The connection between the detection unit 11 and the calculation unit 12 is not particularly limited as long as the object of the present invention is not hindered, and may be wired connection or wireless connection as long as communication is possible.

  The configuration of the calculation unit 12 is not particularly limited as long as the object of the present invention is not impaired. For example, an analysis device 12a such as a personal computer, a notebook computer, a tablet computer, or a mobile terminal device can be employed. . The analysis device 12a includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an HDD (Hard Disk Drive), if necessary. The detected encoded image is reconstructed by using a RAM as a work area, reading a predetermined reconstruction program corresponding to the arrangement form of the basic pattern 101 from a ROM or the like, and executing the reconstruction program. To do.

  Moreover, the method by which the arithmetic unit 12 reconstructs the encoded image is not particularly limited as long as the object of the present invention is not impaired. Basically, a method for reconstructing a needle hole photographer that obtains an encoded image projected on the detection surface by reducing the amount of radiation incident on the needle hole is adopted. Based on the arrangement pattern of the basic pattern 101 (in the encoding mask 10), the calculation unit 12 calculates the basic encoded image of the optical signal corresponding to the basic pattern 101 included in the detected encoded image. By overlapping a plurality of pixels, the intensity of each pixel of the basic encoded image is increased, and the radiation dose estimated from the intensity of the pixel of the increased basic encoded image is arranged for each pixel. Calculate the distribution of quantities. In the case of the encoding mask 10 shown in FIG. 2, since there are four basic patterns 101, four basic encoded images are substantially included in the detected encoded image. By superimposing all the encoded images, one basic encoded image in which the intensity of each pixel is increased can be generated. Thereby, the sensitivity with respect to the radiation source S can be improved, the resolution can be improved, the generation of false images can be prevented, and both the exposure time can be shortened and the detection accuracy can be improved.

  Further, the method for calculating the radiation dose distribution by the calculation unit 12 is not particularly limited as long as the object of the present invention is not impaired. For example, the calculation unit 12 extracts a radiation dose that is equal to or higher than a lower limit threshold set by the user from among the arranged radiation doses, and extracts all the extracted radiation doses from a region where the radiation dose is high. The radiation dose distribution is calculated by dividing the area into a predetermined number of areas and calculating contour lines connecting the boundaries of the divided areas with lines. As a result, the lower limit threshold that can be set by the user can be reflected in the radiation dose distribution, so that the radiation dose distribution is displayed according to the magnitude (strongness) of the radiation dose of the radiation source S. The radiation source S can be clearly displayed by changing. For example, when the radiation dose of the radiation source S in the measurement target is high, the user sets the lower threshold value to a higher value so that the weak radiation dose (fake radiation source) emitted from the ground is changed to the radiation dose. The distribution of the radiation dose of the radiation source S having a high radiation dose can be made to stand out and displayed. On the other hand, when the radiation dose of the radiation source S in the measurement target is low, the user sets a lower threshold value so that weak radiation from the ground is also included in the radiation dose distribution target. The existence of the radiation source S having a low radiation dose can also be clearly displayed.

  Further, for example, if the calculation unit 12 is further provided with a display unit 12b that displays the distribution of the radiation source S as a result of the reconstruction, the user can check the distribution of the radiation source S in real time. It becomes possible.

  Further, the detection unit 11 is further provided with a photographing camera 11b that captures a visible image including a radiation source facing the encoding mask, and the calculation unit 12 includes a position in the real space of the encoded image and a real space of the visible image. A process of superimposing the radiation dose distribution and the visible image in correspondence with the position may be executed, and the display unit 12b may be configured to display the visible image on which the radiation dose distribution is superimposed. Thereby, the user can confirm at a glance at which position of the visible image that can be seen in reality the radiation dose spreads and the radiation source S exists. The photographing camera 11b may be provided at any position as long as the position of the shielding container 11a can correspond to the position of the real space of the encoded image and the position of the real space of the visible image. It is installed on the top surface.

  Further, the detection unit 11 is further provided with a laser rangefinder capable of irradiating a laser at an arbitrary position in the real space of the visible image and measuring the distance from the irradiated position to the apparatus 1 (detection unit 11). The calculation unit 12 irradiates a laser beam of the laser distance meter to a specific position having a radiation dose equal to or higher than a preset reference radiation dose in the visible image in which the radiation dose distribution is superimposed. The distance from the device 1 to the specific position may be measured, and the display unit 12b may display the measured distance at the specific position of the visible image. Thereby, when the radiation source S is specified by the apparatus 1, the user can know the distance to the specific position of the radiation source S. Here, the radiation source S in which radioactive substances are concentrated may be referred to as a hot spot. This hot spot is a radiation source whose spatial radiation dose rate at a height of 1 m is 1 μSv / h higher than the background (surrounding). Means. When searching for a hot spot with this apparatus 1, for example, if the reference radiation dose is set to 1 μSv / h, the specific position corresponds to the hot spot. Therefore, with the above configuration, the distance to the hot spot can be simplified. It becomes possible to know.

  Further, the measurement object corresponding to the radiation dose distribution of the radiation source S is not particularly limited as long as the object of the present invention is not impaired, and examples thereof include peripheral members such as equipment piping, mountainous areas, coasts, and the like. I can do it.

  The analysis device 12a having the calculation unit 12 is further provided with a GPS function, and when the calculation unit 12 calculates the radiation dose distribution, position information by the GPS function is added to the distribution data. You may do it. The analysis device 12a having the calculation unit 12 further includes an environmental information detection sensor for detecting environmental information such as temperature and humidity at the measurement location, and the calculation unit 12 detects the environmental information with respect to the distribution data. You may comprise so that environmental information by may be provided.

<Radiation source visualization method>
Next, a functional block diagram of the radiation source visualization apparatus according to the present invention and an execution procedure of the radiation source visualization method according to the present invention will be described with reference to FIG.

  First, as shown in FIG. 5, the user places the encoding mask 10 of the measuring apparatus 11 a toward the measurement object including the radiation source S and transmits the encoding mask 10 from the radiation source S. It is installed as a radiation aperture (FIG. 5: S101).

  Here, as described above, the encoding mask 10 has a plurality of apertures 100 arranged according to a predetermined rule, and an aperture array 101 that can reconstruct the transmitted radiation as an encoded image as a basic pattern. 2 is a mask shown in FIG. 2 in which a plurality of basic patterns 101 are arranged adjacent to each other by shifting the position of the second basic pattern 101 with respect to the position of the basic pattern 101 with the size of the opening 100 as a unit.

  Next, when the user turns on the analysis device 12a that is communicably connected to the measurement device 11a and inputs a measurement start signal using an interface (for example, a keyboard key) of the analysis device 12a (see FIG. 5: S102 YES), the analysis device 12a receives the measurement start signal and activates the detection unit 11 of the measurement device 11a. Thereby, the detection unit 11 can detect the optical signal of radiation.

  The detection unit 11 detects the radiation transmitted through the encoding mask 10 as an encoded image of the optical signal by directing the encoding mask 10 toward the radiation source S (FIG. 5: S103). Here, as described above, by using the encoding mask 10 shown in FIG. 2, it is possible to obtain an encoded signal having a sufficient signal-to-noise ratio even if the exposure time is several minutes. The detected encoded image is transmitted from the measurement device 11a to the analysis device 12a.

  When receiving the encoded image from the detection unit 11, the arithmetic unit 12 of the analysis device 12 a reconstructs the detected encoded image based on the arrangement pattern of the basic pattern 101 in the encoding mask 10. Thus, the radiation dose distribution including the radiation source S is calculated (FIG. 5: S104). Here, as described above, it is possible to obtain a highly accurate distribution of the radiation source S by using the encoding mask 10 shown in FIG.

  The calculation unit 12 transmits the calculated radiation dose distribution to the display unit 12b as a radiographic image, and the display unit 12b displays the display via a liquid crystal display or the like, for example (FIG. 5: S105). Thereby, the user can confirm a radiation image with high resolution in a short time, and can easily recognize the radiation source S present in the measurement object.

<Examples, comparative examples, etc.>
EXAMPLES Hereinafter, although an Example, a comparative example, etc. demonstrate this invention concretely, this invention is not limited to this.

<Example 1>
The radiation source visualization device for gamma rays shown in FIGS. 1 and 2 was created, and the radiation source visualization device for gamma rays shown in FIG. The detection unit 11 uses a CsI (Tl) crystal as a scintillator and is combined with a photomultiplier tube. As the coding mask 10, a tungsten coding mask shown in FIG. 2 was used as a collimator. The viewing angle of the radiation source visualization apparatus 1 is about 60 degrees, the number of pixels is set to 70 × 70 = 4900 by interpolating 8 × 8 pixels, the detection sensitivity is 900 cps / μSv / h, and the measurement time is The measurement range was 0.04 μSv / h to 30.00 μSv / h depending on the intensity of the gamma ray source and the distance between the gamma ray source and 3 to 10 minutes. The display resolution of the photographing camera 11b is 1240 × 768, the viewing angle is about 60 degrees, and it corresponds to the detection unit 11. The size of the radiation source visualization device 1 is 275 mm × 204 mm × 290 mm, the weight is 20 kg or less, the power source is a lithium battery, the battery driving time is 20 hours or more (when fully charged), and the charging time is 8 hours or less. (In case of main power input).
<Comparative Examples 1 and 2>
A conventional pinhole-type gamma camera was set as Comparative Example 1, and a Compton camera using Compton scattering was set as Comparative Example 2.

<Verification experiment 1>
In a predetermined site in Fukushima Prefecture, in a place where the background air dose rate is 1.5 μSv / h, a region where a hot spot is present is selected and used as the radiation source S of the measurement object, as shown in FIG. As described above, the radiation source visualization apparatus for gamma rays of Example 1, the pinhole type gamma camera of Comparative Example 1, and the Compton camera of Comparative Example 2 were installed. After making the distance from the radiation source S to the apparatus equal to the exposure time (imaging time) to the radiation source S, the radiation dose distributions obtained in Example 1 and Comparative Examples 1 and 2 were compared.

<Verification result 1>
First, assuming that the distance to the radiation source S is 10 m and the exposure time is 10 minutes, the distribution of the radiation dose was calculated (captured) and displayed in Example 1 and Comparative Example 1. As a result, in Example 1, as shown in FIG. 8, the region where the radiation dose as a hot spot is high is narrowly limited, and there are two hot spots, and it is clear where the two hot spots exist. I understand that I understand. On the other hand, in Comparative Example 1, as shown in FIG. 9, it is understood that the region where the radiation dose is high is widened, and the positions where the two hot spots are present are displayed in a wide range.

  Next, at the same place as described above, the distance to the radiation source S was 5 m, the exposure time was 10 minutes, and the radiation dose distribution was calculated and displayed in Example 1 and Comparative Example 1. In Comparative Example 2, the radiation dose distribution was calculated and displayed at the same location as the verification result 1, with the distance from the radiation source S being 5 m and the exposure time being 5 minutes. As a result, in Example 1, as shown in FIG. 10, it is understood that the region where the radiation dose is high is further narrowed and the existence position of the two hot spots can be clearly understood. On the other hand, in Comparative Example 1, as shown in FIG. 11, one hot spot (region with a high radiation dose) of the two hot spots is greatly spread, and the other hot spot is reduced, so that two hot spots. It can be seen that the location of the spot is displayed in a wide range. In Comparative Example 2, the presence of two or more hot spots is confirmed as shown in FIG. Considering the results of Example 1 and Comparative Example 1, the third hot spot is considered to be a false image due to the radiation dose from the background. According to Example 1, it was measured that two hot spots contained cesium 137 of radioactive cesium in an amount of 13 MBq and cesium 134 of radioactive cesium in an amount of 6 MBq.

<Verification experiment 2>
At a site in Fukushima where decontamination has already been completed, in a parking lot with a background radiation dose of 0.4 μSv / h, a 2 MBq cesium 137 sealed standard radiation source is placed near the road cone under the road sign. Is set as the radiation source S of the measurement object, and the devices of Example 1, Comparative Example 1, and Comparative Example 2 are installed in the same manner as described above, the distance from the radiation source S to the device, and the exposure time to the radiation source S The radiation dose distributions obtained in Example 1 and Comparative Examples 1 and 2 were compared.

<Verification result 2>
First, the distance from the radiation source S was set to 5 m, the exposure time was set to 5 minutes, and the radiation dose distribution was calculated and displayed in Example 1, Comparative Example 1, and Comparative Example 2. As a result, in Example 1, as shown in FIG. 13, the region where the radiation dose is high is narrowly displayed near the lower portion of the load cone, and it is understood that the position of the sealed standard radiation source can be clearly seen. On the other hand, in Comparative Example 1, as shown in FIG. 14, the region with a high radiation dose does not concentrate near the lower portion of the load cone, but extends to the upper portion of the load cone, and above (empty) the load cone. It is understood that another region with a high radiation dose occurs. This area is determined to be a false image. Therefore, in Comparative Example 1, when the exposure time is further extended by 15 minutes and the exposure time is 20 minutes at the same place, and the radiation dose distribution is calculated and displayed, as shown in FIG. Although the generated false image is displayed very weakly, it is understood that the false image remains even if the exposure time is extended. In Comparative Example 2, as shown in FIG. 16, the region where the radiation dose is high does not concentrate near the lower portion of the load cone, but extends to the upper portion of the load cone. It can be understood that a false image is generated above.

  Thus, compared with Comparative Examples 1 and 2, Example 1 is superior in sensitivity, detection accuracy, and resolution of the radiation source S, eliminates the problem of false images, and accurately displays the radiation dose distribution. It becomes possible. In particular, in Example 1, it is possible to easily find hot spots that have been left behind in the decontamination work and have been overlooked. It is understood that Example 1 is extremely useful for specifying the position of the hot spot and the magnitude of the radiation dose, for example, at the site of decontamination.

  Thus, the present invention is a radiation source visualization apparatus 1 that visualizes the distribution of radiation sources, and includes the encoding mask 10, the detection unit 11, the calculation unit 12, and the display unit 12 b illustrated in FIG. 2. It is characterized by providing. Thereby, it is possible to achieve both shortening of the exposure time and improvement of detection accuracy. Even with the radiation source visualization method of the present invention, it is possible to obtain the same effect.

  In the first embodiment (gamma ray radiation source visualization apparatus 1), for example, if it is configured to further include an X-ray detector for detecting an X-ray radiation dose, cracks or the like may be formed on the surface of concrete or asphalt. Whether or not there is a radiation source (radioactive cesium) concentrated in a fine gap can be confirmed by using gamma rays and X-rays in combination.

  In addition, if the first embodiment (gamma ray radiation source visualization device 1) is mounted on a flying object such as a helicopter by radio control, a map of the radiation dose distribution of the radiation source (radiocesium) is created from the sky. I can do it. Until now, most of the mountain forests adjacent to residential areas are two-dimensional surface maps. For example, in decontamination work, there has been a need for a map that displays the distribution of radiation dose three-dimensionally. In the first embodiment described above, it is possible to create a three-dimensional map of the radiation dose distribution by incorporating into a flying object by simultaneously reducing the exposure time and improving the detection accuracy.

  When the above-described gamma ray radiation source visualization device 1 is mounted on a flying object, in consideration of weight restrictions (payload) on the flying object, in Example 1, the surface (bottom surface) of the shielding container 11a facing the ground. It is only necessary to reduce the weight of the entire apparatus by removing the shielding material on the other surfaces (side surface, flat surface, etc.) and using only the surface of the shielding container 11a facing the ground as the shielding material.

  Further, in the radiation source visualization apparatus 1 for gamma rays described above, the detection unit 11 is designed to be a semiconductor crystal such as cadmium telluride (CdTe) or zinc cadmium telluride (CZT), and the gamma ray spectrum of the radiation dose distribution is obtained. When configured to analyze, the nuclide of the radiation source S can be identified.

  In addition, as described above, the above-described gamma ray radiation source visualization apparatus 1 can be used for the decontamination work, as well as the identification of the contamination source site in the on-site decommissioning operation in the nuclear power plant, It can also be used for identification of a contamination source location in accident work, transportation of a radiation source S such as an isotope, and identification of a contamination source location in an accident work in nuclear terrorism using the radiation source.

  In the embodiment of the present invention, gamma rays are assumed as radiation, but the same applies to X-rays.

  As described above, the radiation source visualization apparatus and the radiation source visualization method according to the present invention are applied to all fields such as the nuclear field, the medical field, the sanitary field, the food field, the agricultural field, the fishery field, the mining field, the aviation field, and the space field. It is effective as a means for visualizing a radiation source in a radiation source, and is effective as a radiation source visualization device and a radiation source visualization method capable of achieving both shortening of exposure time and improvement of detection accuracy.

DESCRIPTION OF SYMBOLS 1 Radiation source visualization apparatus 10 Encoding mask 11 Detection part 12 Calculation part 12b Display part S Radiation source

Claims (2)

A radiation source visualization device for visualizing the distribution of radiation sources,
A configuration in which a plurality of apertures are arranged according to a predetermined rule, and an aperture array that can be reconstructed by using transmitted radiation as an encoded image is used as a basic pattern, and there are four basic patterns, two vertically and horizontally. The first mask is a mask in which two basic patterns are arranged adjacent to each other in the vertical direction, and a second mask equivalent to the first mask is adjacent to the right of the first mask. When the second mask is viewed from above with respect to the first mask, the second mask is shifted upward by one unit with the opening size as a unit, and the first mask is shifted in the shifted second mask. An encoding mask configured by disposing the mask of the portion protruding upward with respect to the portion of the second mask where the mask disappears downward with respect to the first mask;
A detection unit that detects radiation transmitted through the encoding mask as an encoded image of an optical signal when the encoding mask is disposed toward a radiation source;
By superimposing a plurality of basic encoded images of the optical signal corresponding to the basic pattern included in the detected encoded image based on the arrangement pattern of the basic pattern, each pixel of the basic encoded image An arithmetic unit that calculates the distribution of the radiation dose including the radiation source by increasing the intensity and arranging the radiation dose estimated from the pixel intensity of the enhanced basic encoded image for each pixel ;
A display unit for displaying the calculated radiation dose distribution;
A radiation source visualization apparatus comprising: A radiation source visualization method for visualizing the distribution of radiation sources,
A configuration in which a plurality of apertures are arranged according to a predetermined rule, and an aperture array that can be reconstructed by using transmitted radiation as an encoded image is used as a basic pattern, and there are four basic patterns, two vertically and horizontally. The first mask is a mask in which two basic patterns are arranged adjacent to each other in the vertical direction, and a second mask equivalent to the first mask is adjacent to the right of the first mask. When the second mask is viewed from above with respect to the first mask, the second mask is shifted upward by one unit with the opening size as a unit, and the first mask is shifted in the shifted second mask. An encoding mask configured by disposing a mask that protrudes upward with respect to a portion of the second mask where the mask disappears downward with respect to the first mask; Installed toward And-up,
Detecting radiation transmitted through the encoding mask as an encoded image of an optical signal;
By superimposing a plurality of basic encoded images of the optical signal corresponding to the basic pattern included in the detected encoded image based on the arrangement pattern of the basic pattern, each pixel of the basic encoded image Calculating the radiation dose distribution including the radiation source by increasing the intensity and arranging the radiation dose estimated from the pixel intensity of the enhanced basic encoded image for each pixel ;
Displaying the calculated radiation dose distribution;
A radiation source visualization method comprising: