JP2017146102A - Radioactive ray position specification device, radioactive ray position specification method, and program for radioactive ray position specification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a radioactive ray source planarly spreading to be specified.SOLUTION: A radioactive ray position specification device comprises: a storage unit 22 that stores a plurality of event circle information specifying a plurality of event circles to be created by projecting a Compton cone indicative of an area allowing a ray source of an ionization radiation to exist onto a celestial sphere surface; a creation unit 231 that creates a plurality of segment graphics segmenting the celestial sphere surface into a plurality of segments; a counting unit 232 that counts the number of crossings serving as the number of the event circles crossing respective boundaries of a plurality of segment graphics of the plurality of event circles on the basis of the plurality of event circle information; a calculation unit 233 that calculates an evaluation value of each of the plurality of segment graphics on the basis of the number of crossings counted by the counting unit 232; and a selection unit 234 that selects one or more segment graphics in which the evaluation value satisfies a predetermined condition of the plurality of segment graphics.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a radiation position specifying device, a radiation position specifying method, and a radiation position specifying program for specifying the position of a radiation generation source.

  Since short-wave electromagnetic waves such as γ-rays pass through a substance, a radiation source cannot be specified by an imaging element such as a lens or a reflecting mirror. Therefore, in the astronomical field, a so-called Compton camera is used as a method for specifying the position on the celestial sphere of γ rays generated from pulsars and supernova remnants.

  As disclosed in Patent Document 1, the Compton camera is composed of a plurality of germanium semiconductor detectors in which Compton scattering is caused by incident γ rays. Each germanium semiconductor detector has a plurality of electrodes arranged in a matrix. The incident γ-ray is scattered by electrons in the germanium semiconductor detector, and a signal indicating that the γ-ray has been detected is output from the electrode at a position corresponding to the scattering angle. The Compton scattering angle (Compton scattering angle) can be specified based on the position of the electrode that outputs this signal. Based on the Compton scattering angle measured in one measurement event, one Compton cone is defined that is a cone that indicates the boundary of the region where the source of ionizing radiation may exist.

  The source of ionizing radiation exists at any position on a conical surface called a Compton cone having a shape based on a scattering angle. Therefore, when the celestial sphere is the viewing surface, it can be specified that the radiation source exists on the event circle which is a circle where the celestial sphere and the Compton cone intersect.

  FIG. 13 is a diagram illustrating the relationship between the Compton camera 1 and the Compton cone. The Compton camera 1 shown in FIG. 13 includes a semiconductor detector 11 and a semiconductor detector 12, and γ rays emitted from the γ-ray source S reach the semiconductor detector 12 after reaching the semiconductor detector 11. To do. The Compton camera 1 specifies the scattering angles θ and θ ′ based on the position where the semiconductor detector 11 detects γ rays and the position where the semiconductor detector 12 detects γ rays. Based on the plurality of scattering angles specified in this way, the plurality of Compton cones CN1 and CN2 and the plurality of event circles C1 and C2 corresponding to the positions where the plurality of Compton cones intersect the celestial sphere are specified.

JP 2005-208057 A

  Since the radiation source to be specified in the astronomical field is a point source, the position of the source on the celestial sphere can be specified by obtaining the intersection of a plurality of radiation event circles reaching from the source. That is, when considering the field of view by projecting the celestial sphere onto a plane, the intersection of two event circles is about one or two, and one of these is considered to be a radiation source. Therefore, for example, when a plurality of event circles are displayed in the field of view divided into a plurality of pixels, the number of event circle intersections in the pixel including the radiation source is greater than the number of event circle intersections in the other pixels. As a result, it is possible to easily identify the radiation source by identifying an event circle with a large number of intersections.

  FIG. 14 is a diagram illustrating a method of specifying the position of the point source S based on a plurality of Compton cones. In FIG. 14, three event circles C1, C2, and C3 are depicted. The point source S is included in any of the three event circles C1, C2, and C3. Therefore, when the source S is a point source, it can be specified as the position of the intersection of the three event circles.

However, when a radiation source that spreads in a plane due to a slime containing naturally occurring radioactive material deposited in a separator of an oil mining plant or an artificial radioactive material deposited on the ground due to an accident, etc. is targeted as a specific target The intersections between the event circles are widely distributed inside and outside the source region. Therefore, in the conventional method of counting the intersections between event circles, the position of the radiation source cannot be specified unless a large number of event circles are processed, so that measurement takes time and a large amount of calculation is required. There was a problem.
In addition, even if a large number of event circles are processed, there is also a problem that it is difficult to specify the source region because the intersections of the event circles are widely distributed outside the source region.

  Therefore, an object of the present invention is to provide a radiation position specifying device, a radiation position specifying method, and a radiation position specifying program for specifying a radiation source spreading in a planar shape.

  In the first aspect of the present invention, a memory for storing a plurality of event circle information for specifying a plurality of event circles generated by projecting a Compton cone indicating a region where an ionizing radiation source may be present onto the celestial sphere. And a generation unit that generates a plurality of segmented graphics that divide the celestial sphere into a plurality of segments, and each boundary of the plurality of segmented graphics among the plurality of event circles based on the plurality of event circle information A counting unit that counts the number of event circles that intersect the line, a calculation unit that calculates an evaluation value of each of the plurality of segmented figures based on the number of intersections counted by the counting unit, There is provided a radiation position specifying device comprising: a selection unit that selects one or more segmented graphics for which the evaluation value satisfies a predetermined condition from a plurality of segmented graphics. The above-mentioned divided graphic is, for example, a circle.

  The calculation unit may calculate the evaluation value by correcting the number of intersections based on a circumference of the segmented figure that intersects the event circle. The selection unit may select the one or more segmented graphics based on a plurality of distributions of the evaluation values corresponding to the plurality of segmented graphics.

  The radiation position specifying device further includes a removing unit that removes an event circle that intersects the segmented graphic selected by the selecting unit from among the plurality of event circles, and the counting unit includes the plurality of segmented graphics. You may count the number of event circles which cross | intersect each boundary line and remain after the said removal part removed the said event circle. The removal unit may remove the event circle that intersects one randomly selected segment graphic when there are a plurality of the segment graphics having the same evaluation value.

  In the second aspect of the present invention, a plurality of figure figures are generated by dividing a celestial sphere that generates a plurality of event circles by projecting a Compton cone indicating a region where an ionizing radiation source may exist. And a counting procedure for counting the number of the plurality of event circles crossing each boundary line of the plurality of segment figures based on a plurality of event circle information for specifying the plurality of event circles, Based on the number of the plurality of event circles counted in the counting procedure, a calculation procedure for calculating each evaluation value of the plurality of segment graphics, and a category in which the evaluation value satisfies a predetermined condition from the plurality of segment graphics And a selection procedure for selecting a figure.

  In the third aspect of the present invention, a computer is projected with a Compton cone indicating a region where an ionizing radiation source may exist, and a celestial sphere for generating a plurality of event circles is divided into a plurality of sections. A generation procedure for generating a figure, and a counting procedure for counting the number of the plurality of event circles intersecting each boundary line of the plurality of segmented figures based on a plurality of event circle information for specifying the plurality of event circles A calculation procedure for calculating an evaluation value of each of the plurality of segment graphics based on the number of the plurality of event circles counted in the counting procedure, and the evaluation value is a predetermined condition from the plurality of segment graphics A radiation position specifying program for executing a selection procedure for selecting a segmented figure that satisfies the requirements is provided.

  According to the present invention, there is an effect that it is possible to specify a radiation source extending in a planar shape.

It is a figure for demonstrating the outline | summary of this invention. It is a figure which shows the structure of the radiation position specific device which concerns on 1st Embodiment. It is a flowchart of the operation | movement which pinpoints the position of a radiation source. It is a figure which shows a some division figure. It is a figure for demonstrating the production | generation and evaluation of a division figure. It is a figure for demonstrating the number of intersection of an event circle and a division | segmentation figure. It is a figure which shows the relationship between the evaluation value corresponding to several division figure, and a selection result. It is a figure which shows the state by which the division figure was selected. It is a figure which shows the structure of the radiation position identification apparatus which concerns on 2nd Embodiment. It is a figure which shows the result of having processed the event circle which passes a radiation source, and the event circle which does not pass a radiation source. It is the figure which plotted the evaluation value of the division figure shown in FIG. 11 on the two-dimensional plane. It is a figure which shows the example of the image for specifying a radiation source. It is a figure which shows the relationship between a Compton camera and a Compton cone. It is a figure which shows the principle which pinpoints the position of a point source.

<First Embodiment>
[Summary of Invention]
FIG. 1 is a diagram for explaining the outline of the present invention. In FIG. 1, a plurality of event circles C1, C2, C3, C4, and C5, which are circles in which a Compton cone showing a region where an ionizing radiation source can exist, are intersected with the celestial sphere in the region a on the celestial sphere. It is drawn. The event circle depicted in FIG. 1 is a circle in which the Compton cone generated based on the scattering angle by the radiation emitted from the planar radiation source S intersects the celestial sphere. From the property that the source S is included in any position of each event circle, it is estimated that the source S is in a region where the density of the event circle is high. The present invention is for confirming the existence of the planar radiation source S and specifying the boundary line by using this principle.

  FIG. 2 is a diagram illustrating a configuration of the radiation position specifying device 2 according to the first embodiment. The radiation position specifying device 2 acquires radiation measurement data from the Compton camera 1 and specifies the position of the radiation source S based on the acquired measurement data. The radiation position specifying device 2 includes an acquisition unit 21, a storage unit 22, and a control unit 23.

  The acquisition unit 21 acquires measurement data from the Compton camera 1. The measurement data is, for example, information indicating the position and scattering angle at which radiation is detected in the Compton camera 1. The measurement data may be information indicating the center position and radius of the event circle generated based on the position where the radiation is detected by the Compton camera 1 and the scattering angle. The acquisition unit 21 includes a communication device that acquires information via a communication line such as a LAN controller, or an interface device that acquires information via a storage medium such as a USB interface.

  The storage unit 22 is a storage medium such as a hard disk or a memory. The storage unit 22 stores a program executed by the control unit 23. In addition, the storage unit 22 stores a plurality of event circle information for specifying a plurality of event circles generated by projecting the Compton cone onto the celestial sphere. The event circle information includes the coordinates of the center position of the event circle and the radius of the event circle. The storage unit 22 may store event circle information generated by the Compton camera 1 or may store event circle information generated by the control unit 23 based on measurement data acquired from the Compton camera 1. Moreover, the memory | storage part 22 can memorize | store count object determination information which shows whether an event circle is a count object as information relevant to each event circle.

  The control unit 23 is a CPU that operates the radiation position specifying device 2. The control unit 23 operates as the generation unit 231, the counting unit 232, the calculation unit 233, and the selection unit 234 by executing the program stored in the storage unit 22.

FIG. 3 is a flowchart of an operation for specifying the position of the radiation source S when the control unit 23 operates as the generation unit 231, the counting unit 232, the calculation unit 233, and the selection unit 234. Prior to the processing, the control unit 23 writes information such as the center coordinates and radius of the event circle in the storage unit 22, initializes the count target determination information, sets all event circles as count targets, and then generates the generation procedure S1. The counting procedure S2, the calculation procedure S3, and the selection procedure S4 are sequentially executed.
Hereinafter, with reference to FIGS. 2 and 3, an operation in which the control unit 23 specifies the position of the radiation source S will be described.

First, the generation unit 231 generates a segmented graphic candidate that segments the region a that is the processing target of the celestial sphere (S1).
FIG. 4 is a diagram showing a partitioned graphic generated by dividing the area a on the celestial sphere where the event circle shown in FIG. 1 exists. In FIG. 4, the region a is divided into 27 × 32 meshes in the vertical direction and the horizontal direction, respectively. The segmented figure is a circle, the center coordinate is the center of the mesh, and the radius is quantized to an integral multiple of the radius of the circle inscribed in the mesh. In FIG. 4, as an example, a divided figure corresponding to the size of one section of the upper left mesh is shown.

  FIG. 5 is a diagram for explaining generation and evaluation of a segmented graphic candidate. The generation unit 231 generates a plurality of segmented graphic candidates P01 to P07 having different radii and center coordinates using random numbers so as not to overlap with existing segmented graphics.

  The generation unit 231 may use a circle inscribed in all the meshes obtained by dividing the region a as a divided graphic candidate. Further, in order to determine the intersection with the event circle in the simplest manner, a circle is adopted as the divided figure, but a divided figure such as a hexagon, a square, or a triangle may be generated.

  The counting unit 232 counts the number of intersections, which is the number of event circles that intersect each boundary line of the plurality of segmented figure candidates (S2). Specifically, the counting unit 232 first reads a plurality of event circle information stored in the storage unit 22 from the storage unit 22. Next, the counting unit 232 superimposes a plurality of segmented graphic candidates on a plurality of event circles.

Based on the read event circle information, the counting unit 232 counts the number of intersections, which is the number of event circles that intersect with the boundary lines of the plurality of segment figures, among the plurality of event circles illustrated in FIG. 5.
More specifically, the counting unit 232 selects one segment graphic (for example, the segment graphic P01) from the plurality of segment graphic candidates, and counts the number of event circles that intersect the boundary line of the selected segment graphic. The counting unit 232 sequentially selects one segment graphic (for example, the segment graphic P02, P03,...) From the remaining plurality of segment graphics, and determines the number of event circles that intersect the boundary line of the selected segment graphic. Count.
By adopting a circle as the segment graphic, it is possible to easily calculate the presence / absence of an intersection from the segment graphic candidate, the distance between the centers of each event circle, and the radius of both.

FIG. 6 is a diagram for explaining the number of intersections between an event circle and a segment graphic candidate.
FIG. 6A shows a state where the event circle C1 and the segmented figure P1 do not intersect, and the counting unit 232 counts the number of intersections in this case as zero. FIG. 6B shows a state in which the event circle C1 and the divided figure P2 intersect, and the counting unit 232 counts the number of intersections as 1 in this case. FIG. 6C shows a state where the event circles C1 and C5 intersect with the segmented figure P3, and the counting unit 232 counts the number of intersections in this case as two. For example, the segmented figure candidate P01 in FIG. 5 intersects with the event circles C1, C2, and C3, so the number of event circles that intersect with P01 is three. Similarly, the number of event circles crossing P02 is 1, and the number of event circles crossing P05 is 0.

  Based on the number of intersections counted by the counting unit 232, the calculating unit 233 calculates each evaluation value of the plurality of segmented graphic candidates (S3). Specifically, the calculation unit 233 calculates the evaluation value so that the evaluation value of the segment graphic having a large number of intersecting event circles is larger than the evaluation value of the segment graphic having a small number of intersecting event circles. For example, the calculation unit 233 calculates, as an evaluation value, the number of intersections between each segmented figure and the event circle.

  Here, in FIG. 5, the plurality of segmented graphic candidates for which the evaluation value is calculated include those of different sizes. For this reason, a large segment graphic candidate easily crosses more event circles. Therefore, even if the density of the event circles is the same, the number of intersections with the event circle in the large segment graphic is larger than the number of intersections with the event circle in the small segment graphic, so a fair comparison cannot be made. Accordingly, the calculation unit 233 calculates the evaluation value by correcting the number of intersections with the event circle based on the circumference of the segmented figure that intersects the event circle.

  For example, when the number of intersections with the event circle is the same, the calculation unit 233 corrects the number of intersections of the segment graphic having a circumference of n times the circumference of the segment graphic to be compared to 1 / n times. The evaluation value is calculated. When the segmented figure is a circle, the circumference is proportional to the diameter of the circle. Therefore, the calculation unit 233 may calculate the evaluation value by correcting the number of intersections with the event circle based on the diameter of the segment graphic. If the segmented figure is a rectangle, the perimeter is proportional to the diagonal length of the rectangle. Therefore, the calculation unit 233 may calculate the evaluation value by correcting the number of intersections with the event circle based on the length of the diagonal line of the segment graphic.

  The selection unit 234 selects one or more segment graphics whose evaluation value satisfies a predetermined condition from a plurality of segment graphics (S4). For example, the selection unit 234 selects a segment graphic having an evaluation value equal to or greater than a predetermined threshold as a segment graphic indicating a position corresponding to the radiation source. The selection unit 234 may select one or more segmented graphics based on the distribution of a plurality of evaluation values corresponding to the plurality of segmented graphics.

FIG. 7 is a diagram illustrating a relationship between evaluation values corresponding to a plurality of segmented figures and selection results. In FIG. 7, the evaluation values and the selection results of the seven segment figures (P01 to P07) are shown. The evaluation value indicates the number of intersections between each segment graphic and the event circle, the radius of the segment graphic candidate, and the evaluation value.
In FIG. 7, the divided figure candidates P01 and P03 have the same number of intersections of three. However, when comparing the evaluation values obtained by correcting the number of intersections of the respective segment graphic candidates based on the radius of the segment graphic candidates, it is found that the evaluation value of the segment graphic candidate P01 is the highest. Therefore, the selection unit 234 selects the divided graphic candidate P01.

  FIG. 8 is a diagram in which a segment graphic candidate P01 having the highest evaluation value is selected from a plurality of segment graphic candidates, and this is used as the segment graphic P0. Since the division figure is most likely to be a radiation source, the radiation position specifying device 2 records its coordinates and size, and if necessary, the counted number of intersecting event circles, and meshes the area. By marking on the line, it is possible to visualize the radiation source.

  The radiation position specifying device 2 may include an image generating unit (not shown) that generates colored image data that facilitates specifying the position of the radiation source. Specifically, the image generation unit acquires image data indicating a region where radiation is measured by the Compton camera 1, and divides the image data into a plurality of regions corresponding to a plurality of segmented figures. Then, the image generation unit generates image data in which the image data of the area corresponding to the divided graphic selected by the selection unit 234 is changed to an image having a different color from the image data of the other areas. By doing in this way, it becomes possible to grasp | ascertain visually from which area | region the radiation is radiated | emitted among the area | regions where the Compton camera 1 measured the radiation.

  The radiation position specifying device 2 repeats the above process until the evaluation value of the segmented figure becomes sufficiently small. In addition, as a method for generating a segmented figure candidate and a method for selecting a segmented figure, a so-called random search for randomly generating and selecting a center coordinate and a size of a segmented figure candidate, using a center coordinate and a size of the segmented figure candidate as a gene, A method such as a genetic algorithm that repeats the mating of segmented graphic candidates is exemplified. As described above, according to the first embodiment, the evaluation value calculated based on the number of intersections, which is the number of event circles that intersect with the boundary lines of the plurality of segmented figures among the plurality of event circles, is predetermined. By selecting one or more segmented figures that satisfy the above condition as corresponding to the radiation source, the radiation source can be estimated with high accuracy even when the radiation source is planar.

<Second Embodiment>
FIG. 9 is a diagram illustrating a configuration of the radiation position specifying device 2 according to the second embodiment. The radiation position specifying device 2 is different from the radiation position specifying device 2 according to the first embodiment in that the control unit 23 includes a removing unit 235, and is the same in other points. In the radiation position specifying device 2 according to the second embodiment, after selecting a segment graphic from the segment graphic candidates, an event that intersects the segment graphic selected by the selection unit 234 among the plurality of event circles in the removal unit 235 By removing the circle, the amount of calculation required for specifying the radiation position can be reduced.
That is, in FIG. 8, for the event circles C1, C2, and C3 that intersect with the segment graphic P0, the removal unit 235 rewrites the count target determination information to be counted, so that in the subsequent segment graphic evaluation, Enables determination not to be counted. When the evaluation values of a plurality of segment graphic candidates are the same maximum value, among the segment graphic candidates with the same evaluation value, the count target determination information has already been counted for selection of the segment graphic. Can be counted.

After removing the event circles that intersect the selected segment graphic by the selection unit, the counting unit 232 counts the number of event circles that intersect the remaining segment graphic or some of the segment graphics selected from the remaining plurality of segment graphics. To do. When there are a plurality of segmented figures having the same evaluation value, the removing unit 235 may remove an event circle that intersects one randomly selected segmented figure. By repeating such a procedure, it is possible to reduce the amount of calculation in the counting in the counting unit 232, and the event circle derived from the radiation source that appears with high frequency and the event circle derived from the low frequency environment with a divided figure. It is also possible to determine.

<Example>
FIG. 10 is a diagram illustrating a result of processing 1024 event circles passing through the radiation source and a total of 1101 event circles not passing through the radiation source by the method of the second embodiment. In FIG. 10, the divided figures ID1 to 25 obtained based on the present invention are arranged in the order of processing. The ID corresponds to the order in which the divided figures are obtained, and the X, Y coordinates, the radius R, and the calculated evaluation value are associated with the ID. In the present embodiment, the segmented figure is circular, X in FIG. 11 is the coordinate in the X-axis direction (horizontal direction) of the center of the segmented figure, Y is the coordinate in the Y-axis direction (vertical direction) of the center of the segmented figure, R indicates the radius of the circle of the segmented figure. The “number of passes” indicates the number of event circles that pass through each of the divided figures. The “evaluation value” indicates a value calculated by correcting the number of passages based on a radius proportional to the circumference of the circle of the segmented figure.

  The region a is divided into 0-99 mesh squares in the vertical and horizontal directions, the center coordinates of the segmented figure candidates coincide with the centers of the meshes, and the radius is an integral multiple of the radius of the circle inscribed in the mesh. Is quantized. The method for selecting a segment graphic from the segment graphic candidates is based on a genetic algorithm using the center X coordinate, Y coordinate, and radius as genes, specifically, 1200 sets of random candidates are selected from 600 segment graphic candidates. The process of mating and selecting the top 600 with the highest evaluation value was repeated 600 generations.

  The divided graphic of ID19 has a radius R of 2. Therefore, even though the number of passages of the ID19 partition figure is equal to the number of passages of the ID18 partition figure (radius R is 1), the evaluation value of the ID19 partition figure is two times the evaluation value of the ID18 partition figure. The value is 1. Similarly, the section R of ID23 has a radius R of 3. Therefore, even though the number of passages of the ID23 partition figure is equal to the number of passages of the ID22 partition figure (radius R is 1), the evaluation value of the ID23 partition figure is 3 minutes of the evaluation value of the ID22 partition figure. The value is 1.

  Here, since at least one event circle passes through all the divided graphics shown in FIG. 11, it becomes a problem which selection graphic the selecting unit 234 selects. Therefore, the selection unit 234 selects a segment graphic that is considered to include the radiation source.

  FIG. 11 is a diagram in which the evaluation values of the segmented graphic shown in FIG. 10 are plotted on a two-dimensional plane. The horizontal axis in FIG. 11 indicates the IDs of the segmented figures, which are arranged at equal intervals in descending order of evaluation value. The vertical axis represents the evaluation value of the segmented figure. The selection unit 234 includes a residual sum of squares recording unit (not shown) that selects the obtained segment graphic number n and the segment graphic in order of increasing ID up to the segment point s. The selection unit 234 changes the value of the dividing point s between 2 and n−1, and the first group G1 is selected in order from the smaller ID value, that is, the larger evaluation value. And the second group G2 having a low remaining evaluation value.

  Next, the selection unit 234 generates a first regression line k1 generated based on the first group G1 and a second regression line k2 generated based on the second group G2. G1-k1 residual sum of squares is RSS1, G2-k2 residual sum of squares is RSS2, and total residual sum of squares RSST is RSST = RSS1 + RSS2. (Not shown). The 1st to sminth segmented figures thus obtained are plotted as the source positions. In FIG. 11, n = 25 and smin = 8.

  The selection unit 234 can determine which of the plurality of segment graphics to select based on the first regression line and the second regression line. Specifically, the selection unit 234 obtains the intersection between the first regression line and the second regression line, and identifies the ID of the segmented figure corresponding to the intersection. Then, the selection unit 234 selects a mesh included in the segment graphic having an ID smaller than the segment graphic corresponding to the identified ID, that is, an evaluation value larger than the evaluation value of the segment graphic corresponding to the identified ID. Select as a segmented figure contained in

  In the example shown in FIG. 11, the intersection of the first regression line and the second regression line is between ID7 and ID8. Therefore, the selection unit 234 selects segmented graphics from ID1 to ID7. In this way, it was possible to identify a segmented figure that is considered to have a radiation source.

  FIG. 12 is a diagram illustrating an example of an image for specifying a radiation source. FIG. 12A is an image created by a conventional method of counting the number of intersections of event circles and evaluating a place where the number is large as a radiation source. In FIG. 12A, regions with high evaluation values are widely distributed around the source region, and it is difficult to specify the source region.

  On the other hand, FIG. 12B is an image created using the method according to the present embodiment. In FIG. 12B, since the region having a high evaluation value is limited to the source region, it can be seen that the source region can be clearly identified.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Compton camera 2 Radiation position identification apparatus 3 Threshold value 11 Semiconductor detector 12 Semiconductor detector 21 Acquisition part 22 Storage part 23 Control part 231 Generation part 232 Count part 233 Calculation part 234 Selection part 235 Removal part

Claims (8)

A storage unit for storing a plurality of event circle information for specifying a plurality of event circles generated by projecting a Compton cone indicating a region where an ionizing radiation source may exist, onto a celestial sphere,
A generating unit that generates a plurality of segment figures that divide the celestial sphere into a plurality of segments;
Based on the plurality of event circle information, among the plurality of event circles, a counting unit that counts the number of intersections that is the number of event circles that intersect with each boundary line of the plurality of segmented figures,
Based on the number of intersections counted by the counting unit, a calculation unit that calculates each evaluation value of the plurality of segmented figures,
A selection unit that selects one or more segmented figures for which the evaluation value satisfies a predetermined condition from the plurality of segmented figures,
A radiation localization device comprising: The calculation unit calculates the evaluation value by correcting the number of intersections based on a circumference of the segmented figure that intersects the event circle.
The radiation position specifying device according to claim 1. The selection unit selects the one or more segment graphics based on a plurality of distributions of the evaluation values corresponding to the plurality of segment graphics;
The radiation position specifying device according to claim 1. The segmented figure is circular;
The radiation position specifying device according to any one of claims 1 to 3. A removal unit that removes an event circle that intersects with the divided graphic selected by the selection unit among the plurality of event circles;
The counting unit counts the number of event circles that cross the respective boundary lines of the plurality of segment figures and remain after the removing unit removes the event circles.
The radiation localization apparatus of any one of Claim 1 to 4. When there are a plurality of segmented figures having the same evaluation value, the removing unit removes the event circle that intersects one randomly selected segmented figure,
The radiation position specifying device according to claim 5. A generation procedure for generating a plurality of segment figures, dividing a celestial sphere that generates a plurality of event circles by projecting a Compton cone indicating a region where an ionizing radiation source may exist,
A counting procedure for counting the number of the plurality of event circles crossing each boundary line of the plurality of segmented figures based on a plurality of event circle information identifying the plurality of event circles;
Based on the number of the plurality of event circles counted in the counting procedure, a calculation procedure for calculating each evaluation value of the plurality of segment figures,
A selection procedure for selecting a segment graphic whose evaluation value satisfies a predetermined condition from the plurality of segment graphics;
A radiation localization method comprising: On the computer,
A generation procedure for generating a plurality of segment figures, dividing a celestial sphere that generates a plurality of event circles by projecting a Compton cone indicating a region where an ionizing radiation source may exist,
A counting procedure for counting the number of the plurality of event circles crossing each boundary line of the plurality of segmented figures based on a plurality of event circle information identifying the plurality of event circles;
Based on the number of the plurality of event circles counted in the counting procedure, a calculation procedure for calculating each evaluation value of the plurality of segment figures,
A selection procedure for selecting a segment graphic whose evaluation value satisfies a predetermined condition from the plurality of segment graphics;
A program for specifying the radiation position to execute.