JP6037968B2 - Radiation measurement apparatus and radiation measurement method - Google Patents

Description

  The present invention relates to a radioactivity analyzer and a radioactivity analysis method for measuring the radioactivity of a measurement object without destroying the measurement object which is a sample to be measured.

  A radioactivity analyzer that analyzes and quantifies radioactive substances contained in food, water, soil, and the like detects radiation from a measurement object that is a sample to be measured, and measures its energy and intensity. That is, analysis and quantification are performed by measuring the intensity of radiation having energy generated by the measurement target nuclide.

  Here, as a method for measuring the energy and intensity of radiation with high accuracy, inverse problem calculation using the response function of the detector can be applied. Specifically, in order to obtain the photon energy spectrum from the measured pulse wave height distribution, inverse problem calculation (unfolding) using the response distribution matrix is performed, and the intensity of the photon energy is measured to quantify the radioactive substance. A measurement method has been proposed (see, for example, Patent Document 1).

  In this spectrophoton dosimetry method, first, a measured object of a certain shape and density is placed at a predetermined measurement location, and the response of a detector fixed at a certain location is simulated in advance. Etc.

  In this spectrophoton dosimetry method, the response function of the detector when the radiation energy is changed to various values is stored in a database as a response distribution matrix, and the measured object is actually measured. The energy and intensity of the incident radiation are obtained by performing an inverse problem calculation using this response distribution matrix on the result.

  In addition, since the output from the detector by the radioactive substance contained in the food depends on the shape of the food, and the shape is indefinite, variation occurs in each measurement. Therefore, in order to reduce the variation in each measurement, the food is crushed and filled into a container having a specific shape such as a marinelli container, and the radioactivity contained by measuring the γ-ray spectrum with a scintillator such as Ge or NaI. It was quantified. For this reason, food was mainly subjected to sampling destructive inspection, and 100% inspection was difficult.

  On the other hand, as a method of quantifying radioactive substances without pulverizing or destroying the object to be measured with an indefinite shape, the measurement range in which the object to be measured is installed is divided into grids, and the individual lattice points are divided. Measure the sensitivity of the detector obtained when a point-like radiation source is placed at the point, integrate the sensitivity of each detector at the lattice points included in the three-dimensional shape of the object to be measured, and integrate the volume There has been proposed a radioactivity measurement method that obtains detection efficiency using space as a volume radiation source (see, for example, Patent Document 2).

Special table 2008-54579 JP 2002-98768 A

However, the prior art has the following problems.
In the spectrophoton dosimetry shown in Patent Document 1, since the response distribution matrix is created on the assumption of the shape, density, and geometric arrangement of the measured object, the shape and density of the measured object are assumed. If it is different from what has been done, there is a problem that the energy and intensity of radiation cannot be measured accurately.

  In other words, when the shape and density of the object to be measured change variously, especially when the accumulation of radioactive material is site-dependent, such as a living body, the energy spectrum obtained by inverse problem calculation (unfolding) There is a problem that the accuracy of quantification of the radioactive material of the target nuclide is significantly reduced.

  In addition, although the radioactivity measurement method disclosed in Patent Document 2 can correct the sensitivity distribution dependence due to the shape, it assumes a uniform source distribution and performs volume integration of only the detection efficiency to obtain a single point. Since it has changed to a representative point, there is a problem that it cannot be applied to a measurement object having a density distribution in a radiation source such that surface contamination or a radiation source is accumulated in a part of a living body.

  In addition, this radiation measurement method cannot be applied to inverse problem calculation, has a problem in energy analysis accuracy, cannot cope with the dependence of the energy spectrum distribution on the source on the source position, and There is also a problem that spectral resolution cannot be improved by problem calculation and sensitivity cannot be improved.

The present invention has been made to solve the above-described problems. An optimum detector response function is calculated even for an object having an indefinite shape for each sample, and this response function is calculated. used by performing arithmetic inverse problem, performs total inspection without destroying the object to be measured, radiation can be measured energy spectrum of the radiation emitted from the object to be measured with high accuracy measuring device and the radiation The purpose is to obtain a line measurement method.

Radiation measuring device according to this invention detects radiation emitted from the object to be measured, and the radiation detecting section for outputting a pulse-height distribution in accordance with the output pulse, the object to be measured for obtaining the shape information of the object to be measured A correction response function that calculates a correction value of a response function corresponding to the shape information of the measurement object as a correction response function based on the information acquisition unit and the shape information of the measurement object acquired by the measurement object information acquisition unit comprising a generator, a, the output pulse height distribution from the radiation detecting unit, by performing the inverse problem calculation using the corrected response function calculated by the corrected response function generating unit, is emitted from the object to be measured The measurement object information acquisition unit includes a three-dimensional shape measuring instrument that measures in real time the three-dimensional shape of at least one measurement object in the examination region. And complement The response function generation unit has a response function of the radiation detection unit for each of the lattice points at a predetermined interval in the space where the measured object can exist, and each of the individual included in the space occupied by the measured object in the examination region The corrected response function is generated by integrating the response functions for the lattice points .

Further, radiation measurement method according to this invention detects radiation emitted from the object to be measured, and the radiation detecting step of outputting a pulse-height distribution corresponding to the output pulse, obtains the shape information of the object to be measured to be Based on the measured object information acquisition step and the measured object information acquisition step, the correction for calculating the correction value of the response function corresponding to the measured object shape information as a corrected response function includes a response function generating step, the relative pulse height distribution outputted from the radiation detecting step, by performing the inverse problem calculation using the corrected response function calculated by the corrected response function generating step, the object to be measured a radiation measuring method for calculating an energy spectrum of the radiation emitted, measured body information acquiring step, three-dimensional least one object to be measured in the inspection area The correction response function generation step uses a three-dimensional shape measuring instrument that measures the shape in real time, and the correction response function generation step is based on the response function used in the radiation detection step for each of the lattice points at predetermined intervals in the space where the measured object can exist. The correction response function is generated by integrating the response functions for the individual lattice points included in the space occupied by the measured object in the inspection region .

According to radiation measurement apparatus and the radiation beam measuring method according to the present invention, the correction response function generating unit (step) is to be obtained by the measured object information acquisition unit that acquires shape information of the object to be measured (step) based on the shape information of the measured sample, the correction value of the response function corresponding to the shape information of the object to be measured, calculated as a correction response function, to detect radiation emitted from the object to be measured, corresponding to the output pulse pulse By performing inverse problem calculation using the corrected response function calculated by the correction response function generation unit (step) on the pulse wave height distribution output from the radiation detection unit (step) that outputs the pulse height distribution, the measurement target Calculate the energy spectrum of radiation emitted from the body.
At this time, the measured object information acquisition unit includes a three-dimensional shape measuring instrument that measures the three-dimensional shape of at least one measured object in the inspection region in real time, and the correction response function generation unit includes the measured object A response function of the radiation detection unit is provided for each of the lattice points at a predetermined interval in the space where the object can exist, and the response functions for the individual lattice points included in the space occupied by the measured object in the inspection region are integrated. Thus, a corrected response function is generated.
The measured object information acquisition step uses a three-dimensional shape measuring instrument that measures the three-dimensional shape of at least one measured object in the inspection region in real time, and the correction response function generation step includes the presence of the measured object. Based on the response function used in the radiation detection step for each of the lattice points at predetermined intervals in the possible space, the response functions for the individual lattice points included in the space occupied by the measured object in the examination region are integrated. Thus, a corrected response function is generated.
For this reason, the optimal detector response function is calculated even for an object with an indefinite shape for each sample, and the inverse function is calculated using this response function without destroying the object. While performing 100% inspection, it is possible to measure the energy spectrum of the radiation emitted from the measurement object with high accuracy.

It is a block diagram which shows the radioactivity analyzer which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the response function distribution in the radioactivity analyzer which concerns on Embodiment 1 of this invention. It is a block diagram which shows the correction | amendment response function production | generation part of the radioactivity analyzer which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows operation | movement of the to-be-measured object information acquisition part of the radioactivity analyzer which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the to-be-measured object information acquisition state of the radioactivity analyzer which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the to-be-measured body information acquisition state of the radioactivity analyzer which concerns on Embodiment 3 of this invention.

  Hereinafter, preferred embodiments of a radioactivity analyzer and a radioactivity analysis method according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals. .

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a radioactivity analyzer according to Embodiment 1 of the present invention. In FIG. 1, the radioactivity analyzer includes a radiation detection unit 10 that detects radiation emitted from the measurement object 1, a measurement object information acquisition unit 20, a correction response function generation unit 30, a radioactivity value calculation unit 40, and A display unit 50 is provided.

  The radiation detection unit 10 includes, for example, a detector 11, an amplifier 12, and a pulse height analyzer 13, detects radiation such as γ rays emitted from the measured object 1, and sets the number of pulses with respect to the pulse height of the output pulse. Count.

  The detector 11 generates a pulse output according to the probability density distribution corresponding to the energy of the incident radiation. For example, in the case of γ-ray measurement using a NaI scintillator, a continuous wave height distribution or the like due to a total absorption peak or Compton scattering occurs. A method of performing inverse calculation using this distribution function and analyzing energy with high accuracy is inverse problem calculation (unfolding). This response function varies depending on the position of the radiation source with respect to the detector 11.

  FIG. 2 is an explanatory diagram showing a response function distribution in the radioactivity analyzer according to Embodiment 1 of the present invention. In FIG. 2, a detection space division grid 2 is defined with respect to the detector 11 in which a region where the measured object 1 is installed is divided into L, M, and N in a grid shape, and a response function is represented by R.

  At this time, the output response function R (E, i, j) of the radiation detection unit 10 obtained by placing a point radiation source with radiation energy E at the lattice point (i, j, k) of the detection space division grating 2. , K) and the output response function R (E, l, m, n) of the lattice point (l, m, n) have different distributions.

  FIG. 3 is a block diagram showing the correction response function generation unit 30 of the radioactivity analyzer according to Embodiment 1 of the present invention. In FIG. 3, a correction response function generation unit 30 includes a detector response function storage unit 31, a measured object distribution calculation unit 32, an integration calculation processing unit 33, a correction response function output unit 34, and a density distribution information storage unit 35 (described later). ) And a radioactive substance content distribution information storage unit 36 (described later).

  The output response function obtained by the radiation detection unit 10 shown in FIG. 2 is stored as Voxel data in the detector response function storage unit 31. On the other hand, in the measured object information acquisition unit 20, as shown in FIG. 4, the shape information of the measured object 1 is acquired by the three-dimensional shape measuring instrument 21 and output to the measured object distribution calculation unit 32.

  The measured object distribution calculation unit 32 weights the lattice points (i, j, k) based on the input shape information of the measured object 1, and calculates weighted data W (i, j, k). . In the simplest case, it is conceivable to input 1 when the lattice point is inside the measured object 1 acquired by the measured object information acquisition unit 20 and 0 when it is outside. You may make it load in the boundary of the measurement body 1 with the occupation rate of the to-be-measured body 1 which exists in the boundary with an adjacent lattice point.

  Next, the integral calculation processing unit 33 combines the weighted data W (i, j, k) calculated by the measured object distribution calculation unit 32 and the Voxel data stored in the detector response function storage unit 31. The calculation represented by the following expression (1) is performed, and the corrected response function output unit 34 outputs the response function R (E) of the measured object 1 calculated by the expression (1).

  The radioactivity value calculation unit 40 responds to the pulse wave height distribution due to the radiation from the measurement object 1 output from the radiation detection unit 10, and the response function R () of the measurement object 1 output from the correction response function output unit 34. E) is used to perform inverse problem calculation using, for example, a successive approximation method, etc. to calculate an energy spectrum and output the result to the display unit 50.

  In addition, the display part 50 is not limited to what displays an energy spectrum itself, You may convert and display it on a becquerel value. Further, in the case of performing screening or the like, it may only be determined and displayed whether or not there is a certain amount of radioactivity, or may be displayed as a processing result of the measured object 1 such as food selection. May be.

  Further, by using a high-speed computer as the measured object information acquisition unit 20, the distribution of the measured object 1 obtained by the three-dimensional shape measuring instrument 21 can be calculated in real time (for example, a conveyor). It can be applied as a 100% inspection system that continuously inspects food.

  Even when a plurality of objects to be measured 1 exist in the detection region, the correction response function can be accurately calculated from the data obtained by the three-dimensional shape measuring instrument 21, and an accurate inspection can be performed. it can.

As described above, according to the first embodiment, the correction response function generation unit is based on the shape information of the measurement target acquired by the measurement target information acquisition unit that acquires the shape information of the measurement target. The correction value of the response function corresponding to the shape information of the measurement object is calculated as a correction response function, and the radioactivity value calculation unit detects the radiation emitted from the measurement object, and calculates the pulse height distribution corresponding to the output pulse. By calculating the inverse problem using the correction response function calculated by the correction response function generation unit for the pulse wave height distribution output from the output radiation detection unit, the amount of radioactivity contained in the measured object is calculated. .
That is, it has a response function of the energy spectrum for the point source, and by inputting the three-dimensional shape information of the object to be measured and the distribution information of the source, the correction value of the response function applied to the inverse problem calculation from the response function Is calculated.
The measured object information acquisition unit includes a three-dimensional shape measuring instrument that measures a three-dimensional shape of at least one measured object in the inspection region in real time, and the correction response function generation unit A response function of the radiation detection unit is provided for each lattice point at a predetermined interval in a space that can exist, and the response function for each lattice point included in the space occupied by the measured object in the examination region is integrated. To generate a corrected response function.
For this reason, the optimal detector response function is calculated even for an object with an indefinite shape for each sample, and the inverse function is calculated using this response function without destroying the object. While performing 100% inspection, the amount of radioactivity contained in the measurement object can be measured with high accuracy.
Further, 100% inspection can be performed on an object to be measured that flows continuously indefinitely without pulverizing the object to be measured.

Embodiment 2. FIG.
For example, like peppers, foods often have non-uniform densities, such as cavities with respect to the outer shape. Therefore, as shown in FIG. 5, when a cavity exists in the device under test 1, it is necessary to calculate the response function R (E) by integration calculation in a region excluding the cavity.

  Therefore, as shown in FIG. 3, the radioactivity analyzer according to Embodiment 2 of the present invention further includes a density distribution information storage unit 35 in the correction response function generation unit 30. The density distribution information storage unit 35 stores the type of the measured object together with the density distribution information by means of a man-machine interface or image recognition as measured object information.

  The measured object distribution calculation unit 32 uses the density distribution information corresponding to the type of the measured object stored in the density distribution information storage unit 35 to calculate the internal state from the outer shape obtained by the measured object information acquisition unit 20. And the measured object distribution data W (i, j, k) are calculated. Further, the integration calculation processing unit 33 calculates a corrected response function by combining the measured object distribution data W (i, j, k) and the Voxel data stored in the detector response function storage unit 31.

As described above, according to the second embodiment, the measured object information acquisition unit includes a three-dimensional shape measuring instrument that measures the three-dimensional shape of at least one measured object in the inspection region in real time. The correction response function generation unit accumulates the response function obtained by multiplying the density at the lattice points with respect to the lattice points included in the space occupied by the measured object in the inspection region, as well as having the density distribution information of the object to be measured. To generate a corrected response function.
Therefore, 100% inspection can be performed on a measurement object having a density distribution without crushing the measurement object.

Embodiment 3 FIG.
For example, in a living body, there are cases where a site for taking in and accumulating radioactive substances is localized, and even if the density is uniform, as shown in FIG. 6, the first radioactive substance concentration region 1a and the second radioactive substance It is divided into a plurality of radioactive substance concentration regions such as the concentration region 1b. Here, the site for accumulating radioactive substances is constant for each species, and the region can be specified if the type and outline are known.

  Therefore, as shown in FIG. 3, the radioactivity analyzer according to Embodiment 3 of the present invention further includes a radioactive substance content distribution information storage unit 36 in the correction response function generation unit 30. The radioactive substance content distribution information storage unit 36 stores area division data relative to the outer shape and weight values as the contents as measured object information.

  The to-be-measured object distribution calculating unit 32 uses the relative region division data for the outer shape stored in the radioactive substance content rate distribution information storage unit 36 and the weight value as the content rate to be measured by the to-be-measured object information acquiring unit 20. The measured object distribution data W (i, j, k) is calculated from the obtained outer shape. Further, the integration calculation processing unit 33 calculates a corrected response function by combining the measured object distribution data W (i, j, k) and the Voxel data stored in the detector response function storage unit 31.

  In the radioactivity analyzer according to Embodiment 3 of the present invention, the radioactive substance content distribution information storage unit 36 may be used in combination with the density distribution information storage unit 35 in Embodiment 2 described above. A more accurate corrected response function can be generated when both the density distribution and the accumulation site are present.

As described above, according to the third embodiment, the measured object information acquisition unit includes the three-dimensional shape measuring instrument that measures the three-dimensional shape of at least one measured object in the inspection region in real time. The correction response function generation unit has the content distribution information of the radioactive material of the measured object, and the content of the radioactive material at the lattice point for the lattice points included in the space occupied by the measured object in the inspection region. A corrected response function is generated by integrating the multiplied response functions.
Therefore, 100% inspection can be performed on the measurement object having a distribution in the content of the radioactive substance without crushing the measurement object.

  DESCRIPTION OF SYMBOLS 1 to-be-measured object, 1a 1st radioactive substance concentration area | region, 1b 2nd radioactive substance concentration area | region, 2 detection space division | segmentation grating | lattice, 10 radiation detection part, 11 detector, 12 amplifier, 13 wave height analyzer, 20 to-be-measured object information acquisition Unit, 21 three-dimensional shape measuring instrument, 30 correction response function generation unit, 31 detector response function storage unit, 32 measured object distribution calculation unit, 33 integral calculation processing unit, 34 correction response function output unit, 35 density distribution information storage Part, 36 radioactive substance content distribution information storage part, 40 radioactivity value calculation part, 50 display part.

Claims (6)

A radiation detector that detects radiation emitted from the measurement object and outputs a pulse height distribution according to the output pulse;
A measured object information acquisition unit that acquires shape information of the measured object;
A correction response function generation unit that calculates a correction value of a response function according to the shape information of the measurement object as a correction response function based on the shape information of the measurement object acquired by the measurement object information acquisition unit and, with a,
By performing inverse problem calculation using the correction response function calculated by the correction response function generation unit on the pulse wave height distribution output from the radiation detection unit, the radiation emitted from the measurement object is measured . a radiation measuring device for calculating the energy spectrum,
The measured object information acquisition unit includes a three-dimensional shape measuring instrument that measures a three-dimensional shape of at least one of the measured objects in an inspection region in real time,
The correction response function generation unit has a response function of the radiation detection unit for each of lattice points at a predetermined interval in a space where the measured object can exist, and a space occupied by the measured object in the inspection region Generating the corrected response function by integrating the response functions for each of the grid points included in
Radiation measurement device . A radiation detector that detects radiation emitted from the measurement object and outputs a pulse height distribution according to the output pulse;
A measured object information acquisition unit that acquires shape information of the measured object;
A correction response function generation unit that calculates a correction value of a response function according to the shape information of the measurement object as a correction response function based on the shape information of the measurement object acquired by the measurement object information acquisition unit and, with a,
By performing inverse problem calculation using the correction response function calculated by the correction response function generation unit on the pulse wave height distribution output from the radiation detection unit, the radiation emitted from the measurement object is measured . a radiation measuring device for calculating the energy spectrum,
The measured object information acquisition unit includes a three-dimensional shape measuring instrument that measures a three-dimensional shape of at least one of the measured objects in an inspection region in real time,
The correction response function generation unit has a density distribution information of the object to be measured, and a response obtained by multiplying the lattice points included in the space occupied by the object to be measured in the inspection region by the density at the lattice points. Generate the corrected response function by integrating the function
Radiation measurement device . A radiation detector that detects radiation emitted from the measurement object and outputs a pulse height distribution according to the output pulse;
A measured object information acquisition unit that acquires shape information of the measured object;
A correction response function generation unit that calculates a correction value of a response function according to the shape information of the measurement object as a correction response function based on the shape information of the measurement object acquired by the measurement object information acquisition unit and, with a,
By performing inverse problem calculation using the correction response function calculated by the correction response function generation unit on the pulse wave height distribution output from the radiation detection unit, the radiation emitted from the measurement object is measured . a radiation measuring device for calculating the energy spectrum,
The measured object information acquisition unit includes a three-dimensional shape measuring instrument that measures a three-dimensional shape of at least one of the measured objects in an inspection region in real time,
The correction response function generation unit has content distribution information of the radioactive substance of the object to be measured, and for the lattice points included in the space occupied by the object to be measured in the inspection region, the radioactivity at the lattice points The corrected response function is generated by integrating the response function multiplied by the substance content rate.
Radiation measurement device . A radiation detection step of detecting radiation emitted from the measurement object and outputting a pulse height distribution according to the output pulse;
Measurement object information acquisition step for acquiring shape information of the measurement object;
A correction response function generating step for calculating a correction value of a response function according to the shape information of the measurement object as a correction response function based on the shape information of the measurement object acquired in the measurement object information acquisition step and, with a,
By performing inverse problem calculation using the correction response function calculated in the correction response function generation step on the pulse wave height distribution output from the radiation detection step, the radiation emitted from the measured object a radiation measuring method for calculating the energy spectrum,
The measurement object information acquisition step uses a three-dimensional shape measuring instrument that measures a three-dimensional shape of at least one of the measurement objects in an inspection region in real time,
In the correction response function generation step, the measurement object occupies the inspection area based on the response function used in the radiation detection step for each of the lattice points at predetermined intervals in the space where the measurement object can exist. The corrected response function is generated by integrating response functions for the individual lattice points included in the space to be
Radiation measurement method . A radiation detection step of detecting radiation emitted from the measurement object and outputting a pulse height distribution according to the output pulse;
Measurement object information acquisition step for acquiring shape information of the measurement object;
A correction response function generating step for calculating a correction value of a response function according to the shape information of the measurement object as a correction response function based on the shape information of the measurement object acquired in the measurement object information acquisition step and, with a,
By performing inverse problem calculation using the correction response function calculated in the correction response function generation step on the pulse wave height distribution output from the radiation detection step, the radiation emitted from the measured object a radiation measuring method for calculating the energy spectrum,
The measurement object information acquisition step uses a three-dimensional shape measuring instrument that measures a three-dimensional shape of at least one of the measurement objects in an inspection region in real time,
In the correction response function generation step, a response obtained by multiplying a density at the grid point with respect to a grid point included in a space occupied by the measured object in the inspection region based on the density distribution information of the measured object. Generate the corrected response function by integrating the function
Radiation measurement method . A radiation detection step of detecting radiation emitted from the measurement object and outputting a pulse height distribution according to the output pulse;
Measurement object information acquisition step for acquiring shape information of the measurement object;
A correction response function generating step for calculating a correction value of a response function according to the shape information of the measurement object as a correction response function based on the shape information of the measurement object acquired in the measurement object information acquisition step and, with a,
By performing inverse problem calculation using the correction response function calculated in the correction response function generation step on the pulse wave height distribution output from the radiation detection step, the radiation emitted from the measured object a radiation measuring method for calculating the energy spectrum,
The measurement object information acquisition step uses a three-dimensional shape measuring instrument that measures a three-dimensional shape of at least one of the measurement objects in an inspection region in real time,
In the correction response function generation step, based on the content distribution information of the radioactive substance of the object to be measured, for the lattice points included in the space that the object to be measured occupies in the inspection area, The corrected response function is generated by integrating the response function multiplied by the substance content rate.
Radiation measurement device .

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