JP6656419B2 - Radioactivity distribution measuring device and method - Google Patents

Description

  The present invention relates to a radioactivity distribution measuring device and method for measuring the distribution of radioactive substances contained in an object to be measured.

  As a conventional means for measuring the radioactivity distribution of a radioactive substance, there is a gamma camera for measuring the radioactivity of a radiation source in a measurement target area (for example, see Non-Patent Document 1). The gamma camera measures the radiation (mainly γ-rays and X-rays) coming from the radiation source within the viewing angle by using multiple detectors to identify the direction of the radiation and to determine the three-dimensional radiation source. The distribution was being measured.

  With a general gamma camera, the direction in which the radiation source exists within the viewing angle can be specified, but it is difficult to obtain information in the depth direction. For the measurement in the depth direction, a system for shifting the measurement position and calculating from the parallax is required. However, a plurality of detectors having complicated shapes are required to generate parallax, and the configuration of the measurement device cannot be simplified (for example, see Patent Document 1).

JP 2011-069701 A

Hitachi Aloka Medical Co., Ltd., "Gamma Camera HGD-E1500", [online], searched on November 29, 2016, Internet (URL: http://www.hitachi.co.jp/products/healthcare/products-support) /radiation/gammacamera/index.html) and the Internet (URL: http://www.hitachi.co.jp/products/healthcare/news/ham/pdf/news20140919.pdf)

  In the prior art, the distribution was measured from a plurality of detectors having irregularities and a calculation based on a response function of the radiation detection unit corresponding to the position of the prepared radiation source. Measurement accuracy decreases as the radiation source moves away from the detector. Since the radiation to be detected approaches parallel, it is difficult for a difference depending on the position to appear. Therefore, there is a problem that the structure of the detector becomes more complicated in order to increase the accuracy in the depth direction.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and measure the radioactivity distribution which can measure the three-dimensional distribution of the radiation source with higher accuracy compared to the conventional technology without specially devising the radiation detector itself. It is to provide an apparatus and a method.

According to the radioactivity distribution measuring device according to one aspect of the present invention,
A radiation detection unit that detects the radiation to be measured flying from the radiation source and outputs a detection signal,
A position measurement unit that measures and outputs a measurement position where the radiation detection unit is arranged,
A pulse height calculation unit that calculates a pulse height distribution based on the measured radiation based on the detection signal,
Using a plurality of pulse height distributions respectively calculated for a plurality of predetermined measurement positions, and a plurality of response functions when it is assumed that a radiation source is present at each of the plurality of predetermined positions, the plurality of positions Assuming that a radiation source is present in each of the above, the intensity of the radiation estimated to be emitted from the assumed radiation source is calculated as the predicted intensity, and a predicted intensity distribution indicating the distribution of the predicted intensity with respect to the plurality of positions. Inverse operation unit for calculating and outputting
Using the predicted intensity distribution calculated for the plurality of measurement positions and the position information of the measurement position output from the position measurement unit, a region where the predicted intensity matches is identified, and the three-dimensional distribution of the radiation source is determined. And a distribution reconstruction unit for estimating.

  According to the radioactivity distribution measuring apparatus according to the present invention, it is possible to obtain a predicted intensity distribution in which a radiation source is present without using a radiation detector having a special shape, and to obtain a predicted intensity obtained at a plurality of different measurement positions. By using the distribution, it is possible to measure the three-dimensional distribution of the radiation source including the depth direction with high accuracy compared to the related art without specially devising the radiation detector.

FIG. 1 is a block diagram illustrating a configuration example of a radioactivity distribution measuring device 100 according to Embodiment 1 of the present invention. FIG. 2 is a perspective view showing a predicted intensity distribution of a radiation source obtained by an inverse problem calculation unit 13 and a response function storage unit 14 in FIG. 1. FIG. 2 is a conceptual diagram illustrating an example of an energy spectrum forming a predicted intensity distribution obtained by an inverse problem calculation unit 13 and a response function storage unit 14 in FIG. 1. FIG. 2 is a perspective view illustrating a method of extracting a radiation source distribution from a measurement result in two directions, which is executed by a distribution reconstruction unit 15 of FIG. 1. FIG. 2 is a conceptual diagram illustrating an example of deriving a region where a radiation source exists from two predicted intensities obtained by a distribution reconstruction unit 15 of FIG. 1. FIG. 2 is a perspective view illustrating a method of extracting a radiation source distribution from measurement results in three directions obtained by a distribution reconstruction unit 15 in FIG. 1. 5 is a flowchart illustrating a distribution reconstruction process performed by the distribution reconstruction unit 15 of FIG. 1. 3 is a flowchart illustrating a position measurement process performed by the position measurement unit 3 of FIG. FIG. 2 is a perspective view illustrating a method of measuring a case 1 by the radioactivity distribution measuring apparatus 100 of FIG. 1. FIG. 2 is a perspective view showing a method of measuring a case 2 by the radioactivity distribution measuring device 100 of FIG. 1. FIG. 2 is a perspective view showing a method of measuring a case 3 by the radioactivity distribution measuring device 100 of FIG. 1. FIG. 2 is a perspective view showing a method of measuring a case 4 by the radioactivity distribution measuring device 100 of FIG. 1. FIG. 2 is a block diagram illustrating an example of a hardware configuration of the radioactivity distribution measuring device 100 in FIG. 1. FIG. 5 is a block diagram showing a radioactivity distribution measuring device 200 according to Embodiment 2 of the present invention. FIG. 9 is a block diagram showing a radioactivity distribution measuring device 300 according to Embodiment 3 of the present invention. FIG. 13 is a block diagram showing a radioactivity distribution measuring device 400 according to Embodiment 4 of the present invention. FIG. 15 is a perspective view showing a usage example of the radioactivity distribution measuring device 400 in FIG. 14. It is a conceptual diagram which shows the radioactivity distribution measuring apparatus 500 concerning Embodiment 5 of this invention. FIG. 17 is a longitudinal sectional view showing a range of an incident direction in the radioactivity distribution measuring apparatus 500 of FIG. 16. FIG. 17 is a longitudinal sectional view in the case where the collimator 40 covers the entire side surface and a part of the upper surface of the radiation detection units 2A and 2B in the radioactivity distribution measurement device 500 of FIG. FIG. 17 is a longitudinal sectional view in the case where the collimator 40 covers only the side surfaces of the radiation detection units 2A and 2B in the radioactivity distribution measuring device 500 of FIG. FIG. 16 is a longitudinal sectional view showing a range from a reaction position in the depth direction of the radiation detection units 2A and 2B to an incident direction in the radioactivity distribution measuring device 500.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same components are denoted by the same reference numerals.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration example of a radioactivity distribution measuring device 100 according to Embodiment 1 of the present invention. As shown in FIG. 1, the radioactivity distribution measuring apparatus 100 according to the present embodiment includes a radiation detecting unit 2, a position measuring unit 3, a distribution measuring unit 10, and a display unit 18. Here, the distribution measurement unit 10 includes a signal amplification unit 11, a wave height calculation unit 12, an inverse problem calculation unit 13, a response function storage unit 14, a distribution reconstruction unit 15, and the like. The distribution of the radiation source 1 is estimated from the detection signal of the above and the information of the measurement position from the position measurement unit 3. The display unit 18 is composed of, for example, a liquid crystal display or the like.

  The radiation detecting section 2 detects the radiation 101 to be measured emitted from the radiation source 1 in the substance to be measured and outputs a detection signal to the signal amplifying section 11. The position measurement unit 3 measures information on the measurement position of the radiation detection unit 2 and outputs the information to the distribution reconstruction unit 15. Here, the measurement position means a position where the radiation detection unit 2 is arranged in each measurement. In other words, the measurement position indicates from which position the radiation detection unit 2 starts measuring.

  In the distribution measurement unit 10, the signal amplification unit 11 includes, for example, a preamplifier, a waveform shaping amplifier, and the like. Further, the wave height calculating unit 12 is configured by, for example, a multiplex wave height analyzer or the like. The inverse problem calculation unit 13, the response function storage unit 14, and the distribution reconstruction unit 15 are configured by, for example, a single or a plurality of microprocessors.

  The radiation detection unit 2 includes, for example, a radiation detector that detects the radiation 101 and the like. For example, when the radiation detection unit 2 is a scintillation-type detector, the radiation detection unit 2 has a radiation-sensitive portion made of a scintillation material or the like. The scintillation material is a material that emits fluorescence (scintillation light) when the constituent molecules are excited by the energy given from the radiation and return to the ground state. Such energy is provided by interaction between radiation and the scintillation material, such as photoelectric absorption, Compton effect, and electron pair generation. Therefore, when the radiation 101 emitted from the radiation source 1 of the measurement sample enters the scintillation detector, scintillation light having a wavelength unique to the scintillation material is generated. Further, the scintillation detector has a photocathode (photoelectric conversion unit) for photoelectrically converting the generated scintillation light. Then, the scintillation detector outputs the charge photoelectrically converted by the photoelectric conversion unit as a pulse detection signal.

  Further, for example, when the radiation detection unit 2 is a semiconductor detector, a reverse bias voltage is applied between the n-type semiconductor and the p-type semiconductor forming the electrodes, and a depletion layer generated by the reverse bias voltage causes Is configured. When the radiation 101 emitted from the radiation source 1 is incident on the semiconductor detector, electron-hole pairs are generated by the ionizing action of the radiation. Then, the electrons and holes move to the respective electrodes, and the semiconductor detector outputs a pulse detection signal.

  Next, the operation of the distribution measuring unit 10 will be described.

  First, the signal amplifying unit 11 amplifies the pulse detection signal from the radiation detection unit 2 according to a preset amplification factor, shapes the signal, and outputs the result to the wave height calculation unit 12. The pulse height calculator 12 performs a pulse height analysis on the pulse detection signal from the signal amplifier 11, and calculates a pulse height distribution. Here, the pulse height distribution is a generation distribution of pulses of each pulse height. Specifically, the pulse height calculation unit 12 converts the peak value of the pulse detection signal amplified by the signal amplification unit 11 into a pulse having a peak value equal to or greater than a predetermined value, and outputs the pulse value.

  The calculated pulse height distribution includes not only pure energy information of the radiation 101 emitted from the radiation source 1 but also the radiation 101 and the radiation detection unit 2 and the substances existing from the radiation source 1 to the radiation detection unit 2. , Photoelectric absorption, Compton effect, and electron pair generation. Therefore, in the extracted pulse height distribution, a total absorption peak, a Compton continuous portion, an escape peak, and the like appear. Further, in a process in which the radiation 101 emitted from the radiation source 1 is incident on the radiation detection unit 2 and the applied energy is converted into electric charge, the amount of electric charge generated when the radiation detection unit 2 is applied with energy is calculated. Due to the statistical variation, a statistical spread unique to the radiation detection unit 2 is added. Therefore, the energy resolution (for example, defined by the half width of the peak portion of the pulse height distribution) is reduced. In this case, there arises a problem that the accuracy of identification and quantitative analysis of the radionuclide contained in the radiation source 1 deteriorates.

The pulse crest distribution calculated by the crest calculator 12 is input to the inverse problem calculator 13. The inverse problem calculation unit 13 calls the response function stored in the response function storage unit 14 and performs the inverse problem calculation on the pulse height distribution using the response function. The response function will be described later. By storing a plurality of response functions in the response function storage unit 14, a predetermined response function can be read out at the time of calculation. Here, M is a pulse height distribution, which is a measured value, R _{r, z} (L, E) is a response function, and S _{r, x} is an energy spectrum 34 from which the influence of the interaction of the radiation 101 is eliminated. Equation (1) holds. The inverse problem calculation unit 13 calculates Expression (2), which is the inverse transform of Expression (1) _, and extracts the energy spectrum _{Sr, z} . Here, L is the level of the detection signal from the radiation detector 2, and E is the energy of the incident γ-ray.

M = R _{r, z} (L, E) · S _{r, z} (1)
S _{r, z} = R _{r, z} ⁻¹ (L, E) · M (2)

Here, R _{r, z} ⁻¹ (L, E) is an inverse matrix of the response function R _{r, z} (L, E). The suffix r represents a detection line of the radiation detection unit 2 (generally, a detection centerline of a concentric axis of the radiation detection unit 2 having a coaxial shape or a cylindrical shape. Can be detected.) The detection coordinate origin 2P (the detection line 2L and the detection planes SS1, SS2, and SS3 (for example, see FIG. 2A described later)) intersect on a plane (hereinafter, referred to as a detection plane) parallel to 2L. ) On the detection planes SS1, SS2, and SS3 indicate radial coordinate values r in the radial direction, and z indicates coordinate values z in the depth direction Z parallel to the detection line 2L of the radiation detection unit 2. Show. That is, the position on the detection plane SS1, SS2, SS3 is represented by (r, z) using the coordinate values r, z. The energy spectrum S _{r, z} represents the intensity of radiation emitted from the radiation source 1 at a predetermined position (r, z) for each energy. The intensity of each radiation energy corresponds to the emission (generation) of the radiation.

Here, the response function R _{r, z} (L, E) is, for example, a coordinate value r in the radial direction R on the detection planes SS1, SS2, SS3 from the detection coordinate origin 2P on the detection line 2L of the radiation detection unit 2. From the radiation source 1 on the assumption that the radiation source 1 exists at any one of the positions (r, z) defined by a combination of the coordinate value z in the depth direction Z from the radiation detection unit 2. It is defined from the interaction between the emitted radiation 101 and the radiation detection unit 2. Therefore, the response functions R _{r, z} (L, E) are prepared by the number of positions where the radiation source 1 is assumed to exist. Note that the response function R _{r, z} (L, E) indicates that the plurality of positions where the radiation source 1 is assumed to exist are relative to the origin 30 of the radiation detection unit 2 (or the origin 30 of the position measurement unit 3). Since it is represented by a position, the response function R _{r, z} (L, E) is common even if the measurement position changes. Here, each position (r, z) is defined by a combination of a coordinate value r in the radial direction R on the detection planes SS1, SS2, and SS3 and a coordinate value z in the depth direction Z from the radiation detection unit 2. Can be clearly defined.

For the pulse height distribution serving as the measurement data obtained at any one of the measurement positions of the radiation detection unit 2, the inverse problem _expressed by the equation (2) using all prepared response functions R _{r, z} (L, E). Perform the operation. More specifically, the response function storage unit 14 stores the response function R _{r1, z1} (L, E) when the radiation source 1 exists at the coordinate value r1 in the radial direction R and the coordinate value z1 in the depth direction Z; It is assumed that the radiation source 1 exists at each position (r, z) such as the response function _{Rr2, z2} (L, E) when the radiation source 1 exists at the coordinate value r2 in the radial direction R and the coordinate value z2 in the depth direction. The response function at the time of performing each is stored. The response function R _{r, z} (L, E) may take into account the interaction (attenuation, scattering, etc.) between the substance and the radiation 101 in the path from the radiation source 1 to the radiation detection unit 2.

  FIG. 2A is a perspective view showing a predicted intensity distribution of the radiation source obtained by the inverse problem calculation unit 13 and the response function storage unit 14 of FIG. FIG. 2B is a conceptual diagram showing an example of an energy spectrum forming a predicted intensity distribution obtained by the inverse problem calculation unit 13 and the response function storage unit 14 in FIG.

As shown in FIG. 2A, by solving the above equation (2), from the pulse height distribution M, the detection coordinate origin on the detection line 2L from the origin 30 of the radiation detection unit 2 (or the origin 30 of the position measurement unit 3) is obtained. According to a combination of the response function R _{r, z} (L, E) concerning the position (r, z) defined by the coordinate value r in the radial direction R from 2P and the coordinate value z in the depth direction Z, each position ( r, z), it is possible to extract the energy spectra S _{r, z} of the radiation 101 per unit time emitted from the radiation source 1 when it is assumed that the radiation source 1 exists in the radiation source 1. Note that each position (r, z) does not represent one point, but the coordinate value r in the radial direction R from the detection coordinate origin 2P on the detection line 2L extending from the origin 30 of the radiation detection unit 2. And a relative position (r, z) defined by a coordinate value z in the depth direction Z and a position in an annular region.

As illustrated in FIG. 2B, the influence of the interaction of the radiation detection unit 2 and the influence of the above-described statistical variation are excluded from the plurality of extracted energy spectra S _{r, z} . By the calculation of the above equation (2), the energy information of the radiation 101 can be accurately known, and the accuracy of identification and quantitative analysis of the radioactive substance of the radiation source 1 is improved.

Then, all the extracted energy spectra S _{r, z} are grouped (grouped) for each of the same coordinate values z (for example, a plurality of coordinate values z at predetermined intervals) in the depth direction Z, and The data is output to the distribution reconstruction unit 15 as a group. Each of the energy spectra S _{r, z} obtained for each position (r, z) where the radiation source 1 is assumed to be present is the predicted intensity. The energy spectrum group represents a three-dimensional distribution of the predicted intensity for each position (r, z), and becomes a three-dimensional predicted intensity distribution. As shown in FIG. 2B, the predicted intensity is obtained as an intensity for each energy. Further, the predicted intensity distribution is obtained for each measurement position of the radiation detection unit 2. Here, as described above, the predicted intensity is the intensity of radiation when it is assumed that the radiation source 1 exists at each position. Therefore, the predicted strength can be rephrased as virtual strength. Similarly, the predicted intensity distribution can be rephrased as a virtual intensity distribution.

The response function storage unit 14 stores the response function R _{r, z} (L, E) of the radiation detection unit 2. Alternatively, the response function storage unit 14 may appropriately calculate the response function R _{r, z} (L, E) in advance and store it in a database. Thus, various response functions R _{r, z} (L, E) can be stored in the response function storage unit 14 in advance. Here, for example, the response function storage unit 14 is configured as a memory connected to a microprocessor. Then, the response function storage unit 14 outputs the stored response function R _{r, z} (L, E) in response to the call from the inverse problem calculation unit 13.

The response function R _{r, z} (L, E) indicates the relationship with the radiation detection unit output L output when only the radiation E having a single energy enters the radiation detector of the radiation detection unit 2. The response function R _{r, z} (L, E) is
(1) the position and distribution of the radiation source 1;
(2) the type, size and shape of the radiation detector of the radiation detector 2;
(3) It is determined by the interaction between the radiation 101 emitted from the radiation source 1 such as a measurement system in which the radiation detection unit 2 is installed and the substance that has passed before reaching the radiation detection unit 2. For example, EGS5 (Electron Gamma The response function R _{r, z} (L, E) can be calculated using a Monte Carlo transport calculation code for radiation behavior analysis such as Shower ver. Alternatively, it is also possible to experimentally calculate the response function R _{r, z} (L, E).

Here, as described above, the response function R _{r, z} (L, E) is, for example, the coordinate value r in the radial direction R from the detection coordinate origin 2P on the detection line 2L extending from the origin 30 of the radiation detection unit 2. And the coordinate value z in the depth direction Z, the radiation source 1 is defined as being distributed. Specifically, for each predetermined coordinate value z in the depth direction Z on the detection line 2L of the radiation detection unit 2, Assuming that the radiation source 1 is distributed concentrically or annularly from the detection coordinate origin 2P, the radiation behavior is calculated as described above or experimentally calculated. Note that the detection coordinate origin 2P of the response function R _{r, z} (L, E) can be arbitrarily determined, and may be set to a position other than on the detection line 2L of the radiation detection unit 2. Although the radiation detector 2 is described here assuming that the radiation detector 2 has a cylindrical shape or a coaxial shape, the present invention is not limited to this, and the response function R _{r, z} (L, E) is not limited to this. , The coordinate value r in the radial direction R and the coordinate value z in the depth direction Z can be appropriately selected.

The distribution area of the prepared radiation function R _{r, z} (L, E) of the radiation source 1 can be arbitrarily determined. For example, by increasing the number of divisions of both the coordinate value r in the radial direction R and the coordinate value z in the depth direction Z with respect to the detection line 2L of the radiation detection unit 2, the obtained spatial resolution becomes fine, and conversely The spatial resolution is reduced by reducing the number of divisions. For example, assuming that the distribution region of the radiation source 1 has a maximum length of 1 m in each of the length in the radial direction R and the length in the depth direction Z, and the number of divisions is 100, the response function R _{r, z} (L, E) becomes It is defined corresponding to a total of 10,000 positions (r, z), and the position resolution in the radial direction R and the depth direction Z is 1 cm. Note that the maximum value and the number of divisions of the distribution area may be different in the radial direction R and the depth direction Z.

  The distribution reconstruction unit 15 uses the predicted intensity distribution, which is an energy spectrum group for each combination of the coordinate value r in the radial direction R and the coordinate value z in the depth direction Z, output from the inverse problem calculation unit 13 to measure The three-dimensional distribution of the radiation source 1 existing in the object 33 is estimated, and the position information of the radiation source 1 is output to the display unit 18. The energy spectrum group output from the inverse problem calculation unit 13 is represented by a relative position from the origin 30 of the radiation detection unit 2 (or the position of the origin 30 of the distribution measurement unit 10). Therefore, the distribution reconstruction unit 15 determines the positional relationship between the predicted intensity distributions acquired for each measurement position using the information on the measurement positions of the radiation detection unit 2 acquired by the position measurement unit 3. Further, the distribution reconstruction unit 15 identifies a region where the predicted intensity matches between the aligned predicted intensity distributions, and determines the three-dimensional distribution of the radiation source 1 and the radioactivity based on the three-dimensional distribution of the radiation source 1. Alternatively, estimate the radioactivity concentration.

  Next, the operation of the radioactivity distribution measuring device 100 will be described below. Here, in order to simplify the description, the operation of the radioactivity distribution measuring apparatus 100 will be described with reference to FIGS. 3A and 3B and FIG. 4, which are conceptual diagrams, and FIG. 5 which is a processing flow.

  FIG. 3A is a perspective view showing a method of extracting a radiation source distribution from the measurement results in two directions performed by the distribution reconstruction unit 15 of FIG. 1, and FIG. 3B is obtained by the distribution reconstruction unit 15 of FIG. It is a conceptual diagram showing an example which derives the field where radiation source 1 exists from two prediction intensities. FIG. 4 is a perspective view showing a method of extracting a radiation source distribution from the measurement results in three directions obtained by the distribution reconstruction unit 15 of FIG. FIG. 5 is a flowchart showing the distribution reconstruction processing executed by the distribution reconstruction unit 15 of FIG.

  First, in step S1 of FIG. 5, the distribution reconstruction unit 15 confirms whether information on the coordinates of the origin 30 of the position measurement unit 3 of FIG. 3A has been input from the position measurement unit 3 and set. When the information on the coordinates of the origin 30 has been input (YES in step S1), the process proceeds to step S2, whereas when the information has not been input (NO in step S1), the process returns to step S1 and the position measurement unit 3 Will wait for input from. The operation of the position measuring unit 3 will be described later with reference to FIG.

  In step S2, the movement amount 32 of the position measurement unit 3 from the origin 30 is confirmed. When the movement amount 32 of the position measuring unit 3 from the origin 30 of the position of the position measuring unit 3 measured by the position measuring unit 3 due to the movement of the radiation detecting unit 2 is 0, that is, radiation detection of the position measuring unit 3 If the unit 2 is at the origin 30, the process proceeds to step S3. On the other hand, when the movement amount of the radiation detection unit 2 of the position measurement unit 3 is not 0 and the radiation detection unit 2 is not at the origin 30, the process proceeds to step S4.

In step S3, as shown in FIG. 3A, the origin 30 is determined as the measurement position A of the radiation detection unit 2A, assuming that the radiation detection unit 2A does not move. Next, with respect to the energy spectrum group A extracted by the inverse problem calculation unit 13, the distribution reconstruction unit 15 creates a predicted intensity distribution 31A from the measurement position A which is the origin 30. For example, as shown in FIG. 3A, the distribution reconstructing unit 15 creates a predicted intensity distribution 31A from the origin 30 at a specific depth direction position with the concentric axis of the radiation detection unit 2A. Here, only the method of creating the predicted intensity distribution 31 of the radiation source 1 on the surface in a certain depth direction is described, but the method corresponds to all the depth directions defined by the response function R _{r, z} (L, E). The same processing is performed for the predicted intensity distribution 31 to be created. Here, the radiation detection unit 2A indicates a case where the radiation detection unit 2 is at the measurement position A, and does not mean that a radiation detection unit different from the radiation detection unit 2 is provided, but the radiation detection units 2B and 2C. The same applies to.

  On the other hand, in step S4, as shown in FIG. 3A, at the measurement position B moved with respect to the origin 30, an energy spectrum group B is extracted by the above-described inverse problem calculation unit 13 using the measurement value of the radiation detection unit 2B. I do. Then, a predicted intensity distribution 31B from the measurement position B in consideration of the movement amount 32 from the origin 30 is created, and the process proceeds to step S5. In step S5, as shown in FIG. 3B, for the predicted intensity distribution 31A and the predicted intensity distribution 31B obtained by the above-described method, for example, the intensity of the energy band of interest becomes the same in a certain depth direction. It is determined whether or not an area exists. If the area exists, the process proceeds to step S6. If the area does not exist, the process returns to step S1.

  In step S6, as shown in FIGS. 3A and 3B, when there is a region where the intensities of the predicted intensity distribution 31A and the predicted intensity distribution 31B are the same or within a preset error range, the radiation source 1 is located in that region. After the position information of the radiation source 1 is output to the display unit 18 assuming that the radiation source exists, the process returns to step S1. Here, the preset error is the radiation measurement accuracy of the radiation detection unit 2. Generally, a radiation detector has a precision of about 3% even if it is very accurate, and in a bad case, there is a measurement error of about 30 to 40%.

  Thereafter, as shown in FIG. 4, every time the radiation detecting unit 2 is further moved to the measurement position C, the origin 30 is initialized, or the measurement position of the radiation detecting unit 2 is moved, The signal of 30 or the movement amount 32 is received, and the processing from step S1 to step S6 is repeatedly performed as shown in FIG. Then, the position information of the radiation source 1 and the radioactivity or radioactivity concentration represented by the predicted intensity are output to the display unit 18.

  Next, a method of extracting distribution information of the radiation source 1 by the distribution reconstruction unit 15 will be described for each case with reference to FIGS. 7, 8, 9, and 10.

  FIG. 7 is a perspective view showing a measuring method of the case 1 by the radioactivity distribution measuring device 100 of FIG. Case 1 of FIG. 7 is a case where the radiation source 1 exists on the detection line 2L of the radiation detection unit 2A and on the surface 33S of the measurement target 33.

  In FIG. 7, by moving the radiation detection unit 2 from the measurement position A to the measurement position B and the measurement position C, predetermined coordinates in the depth direction Z are obtained from the measurement data obtained at each of the measurement positions A, B, and C. At the value z, a predicted intensity distribution 31A, a predicted intensity distribution 31B, and a predicted intensity distribution 31C are obtained. In case 1, since the radiation source 1 is on the surface 33S of the measurement target 33 and on the detection line 2L of the radiation detection unit 2A, the measurement target is selected from all the obtained predicted intensity distributions 31. At the center of the predicted intensity distribution 31A on the detection plane of the coordinate value z in the depth direction Z corresponding to the surface 33S of the surface 33, there is a region where the intensity of the predicted intensity distribution 31A, the predicted intensity distribution 31B, and the predicted intensity distribution 31C match. The area where the intensities match is the position where the radiation source 1 is located.

  FIG. 8 is a perspective view showing a measuring method of the case 2 by the radioactivity distribution measuring device 100 of FIG. In the case 2 of FIG. 8, the radiation source 1 is on the detection line 2L of the radiation detection unit 2A, and the radiation source 1 is present on the detection plane in the measurement target 33 and at a specific depth d from the surface 33S. Is the case.

  In FIG. 8, by moving the radiation detection unit 2 from the measurement position A to the measurement position B and the measurement position C, the measurement data obtained at each measurement position can be used to detect the coordinate value z in the depth direction Z on the detection plane. A predicted intensity distribution 31A, a predicted intensity distribution 31B, and a predicted intensity distribution 31C are obtained. In case 2, since the radiation source 1 is inside the measurement target 33 and on the detection line 2L of the radiation detection unit 2A, the measurement target 33 is selected from all the obtained predicted intensity distributions 31. The intensity of the predicted intensity distribution 31A, the predicted intensity distribution 31B, and the predicted intensity distribution 31C coincide at the center of the predicted intensity distribution 31A on the detection plane of the coordinate value z in the depth direction Z corresponding to the specific depth d inside A region exists, and a region where the intensities coincide with each other is a position where the radiation source 1 exists.

  FIG. 9 is a perspective view showing a method of measuring the case 3 by the radioactivity distribution measuring device 100 of FIG. Case 3 in FIG. 9 is a case where the radiation source 1 does not exist on the detection line 2L of any of the radiation detection units 2A, 2B, and 2C, but the radiation source 1 exists on the surface 33S of the measurement target 33.

  In FIG. 9, by moving the radiation detection unit 2 from the measurement position A to the measurement position B and the measurement position C, the measurement data obtained at each measurement position can be used to detect the coordinate value z in the depth direction Z on the detection plane. A predicted intensity distribution 31A, a predicted intensity distribution 31B, and a predicted intensity distribution 31C are obtained. In case 3, since the radiation source 1 is on the surface of the measurement target 33 and is not on the detection line 2L of any of the radiation detection units 2A, 2B, and 2C, all of the obtained predicted intensity distributions 31 In any region (other than the center of the predicted intensity distribution) of the detection plane of the coordinate value z in the depth direction Z corresponding to the surface 33S of the measurement target 33, the predicted intensity distribution 31A, the predicted intensity distribution 31B, and the predicted The intensity of the intensity distribution 31C matches, and the area where the intensity matches is the position where the radiation source 1 is present.

  FIG. 10 is a perspective view showing a measuring method of the case 4 by the radioactivity distribution measuring device 100 of FIG. In the case 4 of FIG. 10, the radiation source 1 does not exist on the detection line 2L of any of the radiation detection units 2A, 2B, and 2C, but on the detection plane at a specific depth d from the surface 33S of the measurement target 33. This is the case where the radiation source 1 is present.

  In FIG. 10, by moving the radiation detection unit 2 from the measurement position A to the measurement position B and the measurement position C, from the measurement data obtained at each measurement position, on the detection plane of the coordinate value z in the depth direction Z, A predicted intensity distribution 31A, a predicted intensity distribution 31B, and a predicted intensity distribution 31C are obtained. In case 3, since the radiation source 1 is inside the measurement target 33 and does not exist on the detection line 2L of any of the radiation detection units 2, the measurement target Inside the object 33 and in any region (other than the center of the predicted intensity distribution) of the detection plane of the coordinate value z in the depth direction Z corresponding to the specific depth d from the surface 33S, the predicted intensity distribution 31A , The intensity of the predicted intensity distribution 31B and the intensity of the predicted intensity distribution 31C match, and the area where the intensities match is the position where the radiation source 1 exists.

  Further, the distribution reconstruction unit 15 uses the count value (intensity) of only a specific energy band from a plurality of energy spectra output by the inverse problem calculation unit 13 to limit the distribution to only a specific radioactive substance. Can measure. As shown in FIG. 2B and the like, the predicted intensity is obtained as an intensity for each energy. Therefore, the predicted intensity distribution is also obtained as an intensity distribution for each energy. When there is a radioactive substance to be noted, the distribution reconstruction unit 15 may estimate the distribution of the radiation source 1 using the predicted intensity of the energy band corresponding to the radioactive substance.

  For example, since the energy of the radiation emitted by the radioactive substance cesium-137 is 662 keV, the count value of only the corresponding energy band is used for the processing of the distribution reconstruction unit 15 from the above-mentioned energy spectrum, so that the cesium-137 is emitted. 137 can be obtained. In addition, by multiplying the count value by the emission ratio corresponding to the energy of the radiation emitted by the radioactive substance, it can be expressed as radioactivity.

  The energy of the radiation emitted by the radioactive material may be stored in advance in the internal memory of the distribution reconstructing unit 15 as a predetermined database. May be used only for the energy band corresponding to. The stored database retrieves data specific to the radionuclide and performs radionuclide identification and quantitative analysis based on the data. The identification and quantitative analysis of the radionuclide are performed by calculating the count value of the energy band corresponding to the data called from the database in the extracted energy spectrum. Here, the database stores data including the energy of the radiation emitted by the radionuclide and the emission ratio. For example, when the radionuclide is cesium-137, data that the energy band of the emitted γ-ray is 662 keV and the emission ratio is 85% are stored. Then, the calculation result of the distribution reconstruction unit 15, that is, the distribution result of each radioactive substance from the radiation source 1 is output to the display unit 18.

  FIG. 6 is a flowchart showing a position measurement process executed by the position measurement unit 3 of FIG. The position measurement unit 3 acquires the position information at the time of starting the measurement by the radiation detection unit 2, and outputs the origin 30 and the movement amount 32 with respect to the origin 30 at the start of the measurement to the distribution reconstruction unit 15. A specific operation flow will be described later with reference to FIG.

In step S11 of FIG. 6, first, the position measuring unit 3 determines whether or not the information of the origin 30 is set in the distribution reconstructing unit 15, and when the information of the origin 30 is set (in step S11). (YES) While proceeding to step S14, if the information of the origin 30 is not set (NO in step S11), for example, the measurement position on the detection line 2L of the radiation detection unit 2 is determined as the origin 30 in step S12. The position information determined in S13 is output to the distribution reconstruction unit 15. Note that the origin 30 does not necessarily have to be on the detection line 2L of the radiation detection unit 2, and the distribution reconstruction unit 15 uses the position information of the radiation detection unit 2 and the response function R _r stored in the response function storage unit 14. _{, Z} (L, E), the origin 30 may be set at an arbitrary position as long as the spatial coordinates are matched.

  Next, in step S14, it is determined whether or not it is necessary to initialize the origin 30, and if it is necessary to initialize (YES in step S14), the process returns to step S11, and the origin 30 is determined again. Set. On the other hand, when it is not necessary to perform initialization (NO in step S14), the movement amount of the radiation detection unit 2 from the origin 30 is measured by the position measurement unit 3 in step S15, and the movement amount from the origin 30 measured in step S16 is measured. The movement amount of the radiation detection unit 2 is output to the distribution reconstruction unit 15, and the position measurement processing ends.

  Here, in obtaining the position information, for example, an image captured by a gyro sensor, an acceleration sensor, an ultrasonic sensor, or a separately prepared laser scanner or camera can be considered, and if the origin coordinates and the movement amount with respect to the origin coordinates can be measured. , Any method may be used. The acquisition of the position information by the position measuring unit 3 may be operated in synchronization with the operation of the radiation detecting unit 2 from the start of measurement to the end of measurement, or may be operated independently.

  Further, in the present embodiment, the distribution of the radioactive substance contained in the measurement target 33 is performed by performing measurement at different measurement positions a plurality of times using the radiation detection unit 2 having no special shape or structure as described above. Information can be obtained.

FIG. 11 is a block diagram showing an example of a hardware configuration of the radioactivity distribution measuring device 100 of FIG. As shown in FIG.
(1) The radiation detector 2 is composed of a radiation detector 2a,
(2) The position measuring unit 3 is constituted by a gyro sensor 3a,
(3) The signal amplifying unit 11 includes an amplifier 11a,
(4) The wave height calculation unit 12, the inverse problem calculation unit 13, and the distribution reconstruction unit 15 are configured by the processor 600,
(5) The display unit 18 is constituted by the display 18a.

  Here, the processor 600 includes, for example, a memory 600b storing programs, data, and the like for processing of the wave height calculation unit 12, the inverse problem calculation unit 13, and the distribution reconstruction unit 15 executed by the CPU 600a, and an external interface (I / F) 600c, 600d, 600e, etc. Further, the parts of the wave height calculating unit 12, the inverse problem calculating unit 13, and the distribution reconstructing unit 15 may be configured by a digital circuit such as an ASIC (Application Specific Integrated Circuit) instead of the processor 600.

Then, a response function R _{r, z} (L, E) for each radiation energy in the response function storage unit 14 necessary for the arithmetic processing, various preset values, etc., are prepared in advance for the radiation measurement. Data, tables, programs, and the like to be stored are stored in the memory 600b in advance. Note that the radioactivity distribution measuring device is in a form that can be carried by a measurer to move the radiation detector 2a.

  As described above, according to the radioactivity distribution measuring apparatus according to the present embodiment, it is possible to obtain a predicted intensity distribution in which the radiation source 1 exists without using a radiation detector having a special shape. By using the predicted intensity distribution obtained at the measurement position, the three-dimensional distribution of the radiation source 1 including the depth direction can be measured with higher accuracy compared to the conventional technology without special measures for the radiation detector It is possible.

  In the above embodiment, the distribution reconstruction unit 15 calculates the predicted intensity using the predicted intensity distribution calculated for the plurality of measurement positions and the position information of the measurement position output from the position measurement unit. A coincident region is identified, and the three-dimensional distribution of the radiation source 1, the radioactivity based on the three-dimensional distribution of the radiation source 1, and the radioactivity concentration are estimated. The present invention is not limited to this. The distribution reconstruction unit 15 uses the predicted intensity distribution calculated for a plurality of measurement positions and the position information of the measurement position output from the position measurement unit to calculate the prediction intensity. May be identified to estimate only the three-dimensional distribution of the radiation source 1. Further, the distribution reconstruction unit 15 may further estimate at least one of the radioactivity based on the three-dimensional distribution of the radiation source 1 and the radioactivity concentration. Thereby, each can be estimated individually.

  According to the above embodiment, a plurality of (one for each of a plurality of measurement positions) predicted intensity distributions on concentric circles for each measurement position obtained by the inverse problem calculation unit 13 are calculated, and the distribution reconstruction unit 15 calculates The three-dimensional distribution of the radiation source 1 can be obtained from the predicted intensity distribution obtained for a plurality of measurement positions. Therefore, it is possible to obtain a three-dimensional distribution of the radiation source 1 without using an uneven radiation detector as in the prior art. Further, by changing the position of the radiation detection unit 2, the difference due to the position of the radiation in the depth direction Z can be measured, and thus a remarkable effect such as improvement in the position resolution particularly in the depth direction Z is achieved.

Embodiment 2 FIG.
FIG. 12 is a block diagram showing a radioactivity distribution measuring device 200 according to Embodiment 2 of the present invention. As shown in FIG. 12, the radioactivity distribution measuring device 200 according to the second embodiment is different from the radioactivity distribution measuring device 100 according to the first embodiment in FIG. Is further provided with a moving unit 4 for mounting and moving. Hereinafter, the difference will be described in detail.

  In FIG. 12, a moving unit 4 uses a remotely controllable vehicle or a small helicopter, an unmanned aerial vehicle, a drone, or the like to move the radiation detecting unit 2 and the position measuring unit 3 to an intended measurement location by a measurer's operation. It is a device that can be moved up to The remote operation may be a wired system or a wireless system. In addition, the moving unit 4 may include not only the radiation detecting unit 2 and the position measuring unit 3 described above, but also a distribution measuring unit 10 and a display unit 18.

  According to the radioactivity distribution measuring device 200 according to the present embodiment configured as described above, the same effect as the radioactivity distribution measuring device 100 according to the first embodiment can be obtained, and the moving unit 4 can detect the radiation. The radiation detection unit 2 and the position measurement unit 3 can be moved to the measurement position intended by the measurer. Therefore, it is possible to perform measurement at a plurality of positions without having to carry the radioactivity distribution measuring device 200 by a measurer in measuring the distribution of radioactivity, and it is possible to measure the position information of the radiation source 1. Furthermore, since only the radioactivity distribution measuring device 200 can be set at the measurement site, the exposure amount of the operator due to the movement and the measurement work can be reduced.

  In other words, by realizing the configuration according to the second embodiment in addition to the effect of the first embodiment, the radioactivity distribution measuring device 200 can be remotely moved without moving the radioactivity distribution measuring device 200 by a measurer. In addition to being able to install the radioactivity distribution measuring device 200 in a place where the measurer cannot enter, the work of the measurer in the area where there is a risk of exposure is eliminated, so that the radiation dose can be reduced. It has the effect of reducing.

Embodiment 3 FIG.
FIG. 13 is a block diagram showing a radioactivity distribution measuring apparatus 300 according to Embodiment 3 of the present invention. As shown in FIG. 13, the radioactivity distribution measuring device 300 according to the third embodiment further includes an imaging unit 5 as compared with the radioactivity distribution measuring device 100 according to the first embodiment of FIG. Features. Hereinafter, the difference will be described in detail.

  In FIG. 13, the imaging unit 5 captures a still image or a moving image of the measurement site including the measurement target 33 at the same time or in advance when performing measurement using the radiation detection unit 2, for example, using an optical digital camera. Then, the obtained image is output to the distribution reconstruction unit 15. In the distribution reconstruction unit 15, the position information where the radiation source 1 exists is collated on the image acquired by the imaging unit 5. For example, at the origin 30, an image of the site is acquired by the imaging unit 5, and the captured image of the site and the obtained position information of the radiation source 1 are superimposed and output to the display unit 18 for display.

  In the above, the radiation detection unit 2 and the position measurement unit 3 collate the obtained position information of the radiation source 1 with the image of the two-dimensional information of the site photographed by the optical camera. However, the present invention is not limited to this. For example, by using a laser scanner, Kinect, or the like, by which the imaging unit 5 can acquire three-dimensional information, the image of the radiation source 1 The position information may be collated, and the position information of the radiation source 1 may be superimposed and displayed on the three-dimensional image of the site.

  According to the radioactivity distribution measuring apparatus 300 according to the present embodiment configured as described above, the same effects as those of the radioactivity distribution measuring apparatus 100 according to the first embodiment can be obtained, and the measurement can be performed using the imaging unit 5. The position information of the radiation source 1 which is output from the distribution measuring unit 10 is compared with spatial information recognized by a person or the like, and the distribution of the radiation source 1 is simultaneously displayed on the display unit 18 by displaying the optically captured image and the distribution of the radioactivity. It is possible to improve the degree of understanding of information for observation. That is, in addition to the effect of the first embodiment, by superimposing and displaying the on-site image and the radioactivity distribution, there is an effect of improving the observation understanding of the radioactivity distribution.

Embodiment 4 FIG.
FIG. 14 is a block diagram showing a radioactivity distribution measuring device 400 according to Embodiment 4 of the present invention. FIG. 15 is a perspective view showing a usage example of the radioactivity distribution measuring device 400 of FIG. As shown in FIG. 14, a radioactivity distribution measuring apparatus 400 according to Embodiment 4 includes a moving unit 4A corresponding to the moving unit 4 according to Embodiment 2 in FIG. 12 and a moving unit 4A according to Embodiment 3 in FIG. It is characterized by having both the imaging unit 5.

  In FIG. 14, the moving unit 4A includes the radiation detecting unit 2, the position measuring unit 3, and the imaging unit 5, and can move the radioactivity distribution measuring device 400 to an intended measuring point by an operation of a measurer, and The position information of the radiation source 1 can be displayed on the image of the measurement site 700 in FIG.

  According to the radioactivity distribution measuring apparatus 400 according to the present embodiment configured as described above, the same effects as those of the radioactivity distribution measuring apparatus 100 according to the first embodiment can be obtained, and the second embodiment and the second embodiment can be implemented. With the combination of mode 3, even if the passage to the measurement site 700 is smaller than the measurer and cannot enter, or even if the radiation dose is so high that the measurer cannot work at the measurement site 700, the moving unit 4A can be remotely controlled. By performing the operation, the image of the measurement site 700 and the distribution information of the radioactivity can be obtained. Therefore, even in a region where the measurer cannot physically enter, when measuring the distribution of radioactivity, the measurement can be performed at a plurality of positions without carrying the radioactivity distribution measuring device 400 with the measurer. The exposure dose of the measurer can be reduced, and the degree of understanding of the distribution information of the radiation source 1 can be improved.

  That is, in addition to the effects according to the first embodiment, by realizing this configuration, the radioactivity distribution measurement device 400 can be remotely moved without the user carrying the radioactivity distribution measurement device 400, and In addition to the fact that the radioactivity distribution measuring device 400 can be installed in a place where no radiation can enter, the work of the measurer in an area where there is a risk of exposure is eliminated, so that the amount of exposure can be reduced. Further, by superimposing and displaying the image of the measurement site 700 and the radioactivity distribution, there is an effect of improving the understanding of the observation of the radioactivity distribution.

Embodiment 5 FIG.
FIG. 16 is a conceptual diagram showing a radioactivity distribution measuring device 500 according to Embodiment 5 of the present invention. The fifth embodiment has a configuration in which an incident direction limiting unit that can obtain direction information of radiation radiating to the radiation detection unit 2 is added to the first to fourth embodiments, as shown in FIG. Further, the range 41 of the incident direction from the radiation source 1 can be limited based on the information on the incident direction of the radiation to be measured that comes to the radiation detection units 2A and 2B. Therefore, the number of times of moving the radioactivity distribution measuring device 500 to obtain the three-dimensional distribution of the radiation source 1 can be reduced, and the time required for measurement can be reduced.

  FIG. 17 is a longitudinal sectional view showing the range of the incident direction in the radioactivity distribution measuring device 500 of FIG. As the incident direction means for limiting the incident direction range 41 of the radiation coming to the radiation detection units 2A and 2B, for example, as shown in FIG. A collimator 40 (having a hole of an arbitrary size) made of heavy metal such as is provided. Thereby, the radiation from other than the hole provided in the collimator 40 may be shielded, and the incident direction range 41 of the radiation incident on the radiation detectors 2A and 2B may be limited.

  As shown in FIG. 17, the limited radiation incident direction range 41 depends on the hole provided in the collimator 40, the thickness of the collimator 40, and the arrangement conditions of the collimator 40 and the radiation detection units 2A and 2B. It becomes a conical shape (infinite height) consisting of the incident direction angle 44 which is determined in a random manner.

  The thickness of the collimator 40 varies depending on the energy of the target radiation, but in the range of general radiation energy (up to 3 MeV), about 10 cm of lead is required.

  FIG. 18A is a longitudinal sectional view in the case where the collimator 40 covers the entire side surface and a part of the upper surface of the radiation detection units 2A and 2B in the radioactivity distribution measuring device 500 of FIG. FIG. 18B is a longitudinal sectional view in the case where the collimator 40 covers only the side surfaces of the radiation detection units 2A and 2B in the radioactivity distribution measuring device of FIG.

  As shown in the vertical cross-sectional views of FIGS. 18A and 18B, the radiation detectors 2A and 2B have a shape that covers the entire side surface and a part of the upper surface to shield radiation from the surroundings, or the radiation detectors 2A and 2B. The shape may be such that only the side surface is covered. As shown in FIGS. 18A and 18B, when covering the entire side surface and a part of the upper surface or only the side surface of the radiation detection units 2A and 2B, the measurement is performed assuming that the radiation source 1 exists in the forward direction of the radiation detection units 2A and 2B. However, shielding the radiation such as γ-rays and scattered rays in the environment from the side faces of the radiation detection units 2A and 2B has an effect of reducing the calculation error of the inverse problem calculation unit 13. The collimator 40 does not have to be always provided during the measurement of radiation.

  Here, information on the incident direction range 41 of the radiation incident on the radiation detection units 2A and 2B is obtained by, for example, a plurality of measurement positions by the distribution reconstruction unit 15 (see FIGS. 1 and 12 to 14). By multiplying the obtained predicted intensity distribution by a correction coefficient that sets the incident direction range 41 to 1 and the other than the incident direction range 41 to 0, the three-dimensional distribution in which the radiation source 1 exists can be changed from the above-described first embodiment. It can be obtained with a smaller number of measurements than in the fourth embodiment.

  FIG. 19 is a longitudinal sectional view showing a range from the reaction position in the depth direction of the radiation detecting units 2A and 2B to the incident direction in the radioactivity distribution measuring device in FIG.

  In addition to providing the collimator 40, for example, a reaction between an anode electrode and a cathode electrode using a difference in electron and hole mobilities as in a CZT (CdZnTe: cadmium zinc telluride) semiconductor detector. If the radiation detecting units 2A and 2B (for example, Non-Patent Document 2) that are generally known to be able to obtain the position are used, as shown in FIG. Since the incident direction range 43 further restricting the incident direction range 41 can be obtained from the incident direction angle 45 restricted from the position 42, the three-dimensional distribution where the radiation source 1 exists can be obtained with a smaller number of measurements. .

  Note that, in the response function storage unit 14 of the fifth embodiment, in consideration of radiation scattering and the like caused by disposing the collimator 40, in order to reduce an error caused by the operation of the inverse problem operation unit 13, the response function storage unit 14 is arranged to The defined response function may be stored.

  As described above, according to the radioactivity distribution measuring apparatus 500 according to the fifth embodiment, the range in which the radiation source exists can be limited based on the direction information in which the radiation source exists. As compared with the fourth embodiment, the distribution of the radiation source can be obtained with a smaller number of measurements.

  As described in detail above, according to the radioactivity distribution measuring apparatus according to the present invention, it is possible to obtain a predicted intensity distribution in which the radiation source 1 exists without using a radiation detector having a special shape, By using the predicted intensity distribution obtained at the measurement position, it is possible to measure the three-dimensional distribution of the radiation source 1 including the depth direction with higher accuracy compared to the conventional technology without using special measures for the radiation detector It is.

  Reference Signs List 1 radiation source, 2, 2A, 2B, 2C radiation detection unit, 2a radiation detector, 2L detection line, 2P detection coordinate origin, 3 position measurement unit, 3a gyro sensor, 4, 4A movement unit, 5 imaging unit, 10 distribution Measuring unit, 11 signal amplifying unit, 11a amplifier, 12 wave height calculating unit, 13 inverse problem calculating unit, 14 response function storing unit, 15 distribution reconstructing unit, 18 display unit, 18a display, 30 origin, 31 predicted intensity distribution, 32 Movement amount, 33 measurement object, 34 energy spectrum, 40 collimator, 41 incident direction range, 42 depth direction reaction position, 43 limited incident direction range, 44 incident direction angle, 45 limited incident direction angle, 100, 200, 300, 400, 500 radioactivity distribution measuring device, 101 radiation, 700 measurement sites, 600 processor, 6 00a CPU, 600b memory, 600c, 600d, 600e Interface (I / F), R radial direction, Z depth direction.

Claims (14)

A radiation detection unit that detects the radiation to be measured flying from the radiation source and outputs a detection signal,
A position measurement unit that measures and outputs a measurement position where the radiation detection unit is arranged,
A pulse height calculation unit that calculates a pulse height distribution based on the measured radiation based on the detection signal,
Using a plurality of pulse height distributions respectively calculated for a plurality of predetermined measurement positions, and a plurality of response functions when it is assumed that a radiation source is present at each of the plurality of predetermined positions, the plurality of positions Assuming that a radiation source is present in each of the above, the intensity of the radiation estimated to be emitted from the assumed radiation source is calculated as the predicted intensity, and a predicted intensity distribution indicating the distribution of the predicted intensity with respect to the plurality of positions. Inverse operation unit for calculating and outputting
Using the predicted intensity distribution calculated for the plurality of measurement positions and the position information of the measurement position output from the position measurement unit, a region where the predicted intensity matches is identified, and the three-dimensional distribution of the radiation source is determined. And a distribution reconstructing unit for estimating the radioactivity distribution.   The radioactivity distribution measuring apparatus according to claim 1, wherein the distribution reconstruction unit further estimates at least one of radioactivity based on a three-dimensional distribution of the radiation source and radioactivity concentration.   The radioactivity distribution measuring apparatus according to claim 1, wherein the plurality of predetermined positions are defined by a combination of a radial direction centering on a position of the radiation detection unit and a depth direction.   The radioactivity distribution measuring device according to any one of claims 1 to 3, further comprising a response function storage unit that stores the plurality of response functions.   The radioactivity distribution measuring apparatus according to any one of claims 1 to 4, further comprising a moving unit that moves a measurement position where the radiation detection unit is arranged for each measurement. An imaging unit that captures an image of a region containing a substance to be measured,
The display device according to claim 1, further comprising a display unit configured to display the three-dimensional distribution of the estimated radiation source and the captured image in a superimposed manner. Radioactivity distribution measurement device.   The radioactivity according to any one of claims 1 to 6, wherein the radiation detection unit includes an incident direction limiting unit that limits an incident direction of the radiation for detecting the flying radiation to be measured. Distribution measuring device. A step of outputting a detection signal by detecting the radiation to be measured flying from the radiation source,
A position measurement unit measures and outputs a measurement position where the radiation detection unit is arranged, and
A step for calculating a pulse height distribution based on the measured radiation, based on the detection signal,
The inverse problem calculation unit uses a plurality of pulse height distributions calculated for a plurality of predetermined measurement positions and a plurality of response functions when it is assumed that a radiation source exists at each of the plurality of predetermined positions. Assuming that a radiation source is present at each of the plurality of positions, calculate the intensity of the radiation estimated to be emitted from the assumed radiation source as the predicted intensity, and calculate the predicted intensity of the predicted intensity for the plurality of positions. Calculating and outputting a predicted intensity distribution indicating the distribution;
The distribution reconstruction unit uses the predicted intensity distribution calculated for the plurality of measurement positions and the position information of the measurement position output from the position measurement unit to identify a region where the prediction intensity matches. Estimating the three-dimensional distribution of the radiation source.   The radioactivity distribution according to claim 8, further comprising the step of the distribution reconstruction unit estimating at least one of radioactivity based on a three-dimensional distribution of the radiation source and radioactivity concentration. Measuring method.   The method according to claim 8, wherein the plurality of predetermined positions are determined by a combination of a radial direction centering on a position of the radiation detection unit and a depth direction. The method according to any one of claims 8 to 10 , wherein the response function storage unit further includes a step of storing the plurality of response functions before the step of outputting by the inverse problem calculation unit. The radioactivity distribution measurement method described. The method according to any one of claims 8 to 11, further comprising , before the step of outputting by the inverse problem calculation unit , moving a measurement position at which the radiation detection unit is arranged for each measurement. The radioactivity distribution measurement method according to any one of the above. Prior to the step of outputting by the inverse problem calculation unit, or simultaneously with the step of outputting by the inverse problem calculation unit, the imaging unit captures an image of a region containing the substance to be measured,
The method according to any one of claims 8 to 12, further comprising a step of displaying a three-dimensional distribution of the estimated radiation source and the captured image in a superimposed manner. The radioactivity distribution measurement method described. The method according to claim 8, further comprising , before the step of outputting a detection signal by the radiation detecting unit, a step of restricting an incident direction of the radiation for detecting the flying radiation to be measured, before the step of outputting a detection signal. 14. The radioactivity distribution measuring method according to any one of the thirteenth aspects.

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