CN108535768B - Gamma camera based on double-detector technology - Google Patents
Gamma camera based on double-detector technology Download PDFInfo
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- CN108535768B CN108535768B CN201810202938.XA CN201810202938A CN108535768B CN 108535768 B CN108535768 B CN 108535768B CN 201810202938 A CN201810202938 A CN 201810202938A CN 108535768 B CN108535768 B CN 108535768B
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Abstract
A gamma camera based on double-detector technology is characterized by comprising an encoding plate, a shielding body, a reading circuit, a data processing circuit and a reconstruction circuit, and further comprising a position sensitive detector, an energy sensitive detector and an optical camera, wherein gamma rays emitted by radioactive substances to a detection area pass through the encoding plate, the position sensitive detector collects projection data and a first energy spectrum data set, the energy sensitive detector collects and generates a second energy spectrum data set, the data processing circuit receives the first energy spectrum data set and the second energy spectrum data set to obtain combined energy spectrum data, the reconstruction circuit obtains a gamma radiation image according to the projection data and the combined energy spectrum data, the optical camera obtains a visible light image, the visible light image is integrated with a two-dimensional radiation image generated by the gamma camera to realize accurate registration and fusion of two modal images, and energy spectrum analysis is carried out by utilizing the combined energy spectrum data, and acquiring a high-resolution energy spectrum, and performing nuclide identification according to a built-in nuclide library.
Description
Technical Field
The invention relates to the field of radioactive substance detection, in particular to a gamma camera based on a double-detector technology.
Background
The positioning, radiation dose measurement, nuclide species identification and activity measurement of radioactive substances are widely applied to the fields of nuclear industry, nuclear safety, environmental protection, industrial and medical radioactive source management, public safety and the like.
The conventional means for detecting radioactive materials mainly include: radioactive dosimeters, gamma spectrometers, and gamma cameras. The gamma camera is a device for detecting radioactive substances by using a radiation detection technology, detects gamma photons from all directions of a target angle plane where the radioactive substances are located, and realizes two-dimensional plane distribution imaging of the radioactive substances. In addition, the gamma camera can also measure the gamma photon energy spectrum of the position of the camera, and the functions of primary gamma photon energy spectrum analysis and nuclide identification are realized.
However, the conventional gamma camera has low accuracy of a radiation image generated by using projection data of a radioactive substance detected by a position sensitive detector, and although a technical scheme of generating a two-dimensional radiation image by using the projection data and energy spectrum data of the radioactive substance detected by the position sensitive detector also exists in the prior art, the accuracy of the generated two-dimensional radiation image is still low because the energy spectrum data acquired by the position sensitive detector is not accurate.
In the prior art, a spectrum sensitive detector is generally adopted to realize a more accurate spectrum analysis function, but the spectrum sensitive detector can only be used for spectrum analysis, cannot realize two-dimensional plane distribution imaging of radioactive substances, is single in use, and generally needs longer detection time for spectrum analysis.
Disclosure of Invention
The invention provides a gamma camera based on a double-detector technology, which can provide a two-dimensional radiation image with higher precision, can also provide a more accurate energy spectrum analysis function and has shorter detection time.
In order to achieve the purpose of the invention, the invention provides a gamma camera based on a double-detector technology, which comprises an encoding plate, a shielding body, a reading circuit, a data processing circuit, a reconstruction circuit, a position sensitive detector, an energy sensitive detector and an optical camera,
after gamma rays of radioactive substances which shoot to a detection area pass through the coding plate, the position sensitive detector collects and generates projection data and a first energy spectrum data set, the energy sensitive detector collects and generates a second energy spectrum data set,
the data processing circuit receives the first and second sets of spectral data, obtains combined spectral data from the first and second sets of spectral data,
a reconstruction circuit receives the projection data and the combined spectral data, obtains a gamma radiation image from the projection data and the combined spectral data,
the optical camera acquires a visible light image, is integrated with a two-dimensional radiation image generated by the gamma camera, realizes the accurate registration and fusion of two modal images,
and performing energy spectrum analysis by using the combined energy spectrum data to obtain an energy spectrum diagram with high resolution, and performing nuclide identification according to a built-in nuclide library.
The specific process of obtaining the combined energy spectrum data according to the first energy spectrum data set and the second energy spectrum data set is as follows:
firstly, a gamma camera detects a standard nuclide sample, a first energy spectrum data set A and a second energy spectrum data set B detected by a position sensitive detector and an energy sensitive detector are respectively obtained, covariance matrixes of the energy spectrum data A and the energy sensitive detector are respectively calculated, a correlation coefficient alpha is calculated according to the covariance matrixes, and then a weight value x corresponding to each energy spectrum data in the first energy spectrum data set A and the second energy spectrum data set B is calculated according to the following formulaiAnd yi：
Wherein N is the number of spectral data of the first spectral data set A or the second spectral data set B,
the data processing circuit calculates the combined power spectrum data C according to the following formula:
C＝xiA+yiB。
wherein the specific process of obtaining the gamma radiation image according to the projection data and the combined energy spectrum data is as follows
Acquiring the total number N of gamma photons detected by a gamma camera according to the projection data, acquiring the photon energy of each gamma photon detected by the gamma camera according to the combined energy spectrum data, wherein the energy of the ith photon is Ei, and then acquiring the average energy of the gamma photons Eave by the following formula:
then, the incident photon energy Epeak is obtained according to the gamma photon average energy Eave through the following formula:
Epeak＝Eave×ae+be
wherein ae and be are fitting coefficients obtained by fitting according to experimental data,
the corresponding transmission matrix is then calculated from the incident photon energy Epeak,
the projection data is reconstructed from the transmission matrix to obtain a gamma radiation image.
The gamma camera based on the double-detector technology can perform high-precision positioning imaging on the radioactive substance and perform energy spectrum analysis on the radioactive substance at higher resolution and shorter time, thereby playing a role in identifying the type of the radioactive substance nuclide.
The features and advantages of the present invention will become apparent by reference to the following drawings and detailed description of specific embodiments of the invention.
Drawings
FIG. 1 is a schematic diagram of a gamma camera according to the present invention;
FIG. 2 shows a schematic block diagram of the working principle of the gamma camera of the present invention.
Detailed Description
The embodiment of the invention provides a gamma camera based on a double-detector technology, which is provided with a position sensitive detector and an energy spectrum sensitive detector, and utilizes the energy spectrum sensitive detector to obtain more accurate energy spectrum data, so that the energy spectrum analysis can be carried out on radioactive substances with higher resolution and shorter time while carrying out high-precision positioning imaging on the radioactive substances.
The technical scheme of the invention is explained in detail in the following with reference to the attached drawings 1-2.
Fig. 1 shows a schematic structural diagram of a gamma camera of the present invention, and fig. 2 shows a schematic block diagram of an operating principle of the gamma camera of the present invention.
The gamma camera 1 includes an encoding plate, a shield, and a readout circuit, a data processing circuit, and a reconstruction circuit, and further includes a position sensitive detector 10, an energy sensitive detector 30, and an optical camera 20.
After gamma rays of radioactive substances which shoot to the detection area pass through the coding plate, the gamma rays are collected by the position sensitive detector, the position sensitive detector converts the obtained detector data into electric signals, the electric signals are collected by the reading circuit, projection data are generated through recombination according to the energy of incident gamma photons and the corresponding detection action positions of the incident gamma photons, and a first energy spectrum data set is generated according to the energy deposited by the incident gamma photons in the detector of the gamma camera.
Meanwhile, the energy sensitive detector detects gamma rays emitted by radioactive substances to the detection area, converts acquired detector data into electric signals, and acquires the electric signals through the reading circuit to generate a second energy spectrum data set.
The data processing circuit receives the first energy spectrum data set and the second energy spectrum data set, and combined energy spectrum data are obtained according to the first energy spectrum data set and the second energy spectrum data set. The specific process is as follows:
firstly, a gamma camera detects a standard nuclide sample, a first energy spectrum data set A and a second energy spectrum data set B detected by a position sensitive detector and an energy sensitive detector are respectively obtained, covariance matrixes of the energy spectrum data A and the energy sensitive detector are respectively calculated, a correlation coefficient alpha is calculated according to the covariance matrixes, and then a weight value x corresponding to each energy spectrum data in the first energy spectrum data set A and the second energy spectrum data set B is calculated by utilizing the correlation coefficient alphaiAnd yiCorrelation coefficient α and weight value xiAnd yiThe relationship of (A) is as follows:
where N is the number of spectral data of the first spectral data set a or the second spectral data set B.
The data processing circuit calculates the combined power spectrum data C according to the following formula:
C＝xiA+yiB
the reconstruction circuit receives the projection data and the combined energy spectrum data, obtains an energy peak of the incident gamma photon according to the combined energy spectrum data, and reconstructs the gamma radiation image according to the projection data and the energy peak of the incident gamma photon. The specific process is as follows:
acquiring the total number N of gamma photons detected by a gamma camera according to the projection data, acquiring the photon energy of each gamma photon detected by the gamma camera according to the combined energy spectrum data, wherein the energy of the ith photon is Ei, and then acquiring the average energy of the gamma photons Eave by the following formula:
then, the incident photon energy Epeak is obtained according to the gamma photon average energy Eave through the following formula:
Epeak＝Eave×ae+be
wherein ae and be are fitting coefficients obtained by fitting according to experimental data.
The corresponding transmission matrix is then calculated from the incident photon energy Epeak. The transmission matrix is a predefined function related to the incident photon energy, i.e. the transmission matrix has a corresponding relation with the incident photon energy, and the corresponding transmission matrix can be obtained according to the incident photon energy Epeak.
The projection data is then reconstructed from the transmission matrix to obtain a gamma radiation image.
According to the invention, the energy spectrum data acquired by the energy spectrum sensitive detector and the energy spectrum data acquired by the position sensitive sensor are utilized to obtain the combined energy spectrum data, so that more accurate photon energy can be obtained compared with the traditional gamma camera which only utilizes the position sensitive sensor to obtain the energy spectrum data, and therefore, a more accurate transmission matrix is obtained, and the radiation image generated by reconstruction can be more accurate.
The optical camera acquires a visible light image, and is integrated with a two-dimensional radiation image generated by the gamma camera, so that accurate registration and fusion of two modal images are realized. According to the invention, the plurality of optical cameras are arranged around the gamma camera, the visible light images are simultaneously acquired, and the obtained plurality of visible light images are analyzed and processed to generate one visible light image without parallax difference with the gamma radiation image, so that the visible light image and the radioactive heat point distribution image can be combined, and the real-time positioning of radioactive substances by workers is facilitated.
On the other hand, the energy spectrum analysis is performed by using the combined energy spectrum data, so that a high-resolution energy spectrum graph can be obtained, and nuclide identification is performed according to a built-in nuclide library. Because the position sensitive detector and the energy sensitive detector are adopted to simultaneously acquire the energy spectrum data, compared with the method of singly acquiring the energy spectrum data by adopting the energy spectrum detector, the method can acquire enough gamma photons only in a shorter time, thereby carrying out high-precision energy spectrum analysis and nuclide identification in a shorter time.
The foregoing is illustrative only, and it is to be understood that modifications and variations in the arrangements and details described herein will be apparent to those skilled in the art, and that any obvious substitutions are within the scope of the present invention without departing from the inventive concepts thereof. It is therefore intended that the scope of the appended claims be limited only by the specific details presented by way of the foregoing description and explanation.
Claims (3)
1. A gamma camera based on double-detector technology is characterized by comprising an encoding plate, a shielding body, a reading circuit, a data processing circuit, a reconstruction circuit, a position sensitive detector, an energy sensitive detector and an optical camera,
after gamma rays of radioactive substances which shoot to a detection area pass through the coding plate, the position sensitive detector collects and generates projection data and a first energy spectrum data set, the energy sensitive detector collects and generates a second energy spectrum data set,
the data processing circuit receives the first and second sets of spectral data, obtains combined spectral data from the first and second sets of spectral data,
a reconstruction circuit receives the projection data and the combined spectral data, obtains a gamma radiation image from the projection data and the combined spectral data,
the optical camera acquires a visible light image, the visible light image is integrated with a gamma radiation image generated by the gamma camera, accurate registration and fusion of two modal images are achieved, energy spectrum analysis is carried out by utilizing combined energy spectrum data, a high-resolution energy spectrum image is obtained, and nuclide identification is carried out according to a built-in nuclide library.
2. The gamma camera of claim 1 wherein the deriving the combined spectral data from the first and second sets of spectral data is as follows:
firstly, a gamma camera detects a standard nuclide sample, a first energy spectrum data set A and a second energy spectrum data set B detected by a position sensitive detector and an energy sensitive detector are respectively obtained, covariance matrixes of the energy spectrum data A and the energy sensitive detector are respectively calculated, a correlation coefficient alpha is calculated according to the covariance matrixes, and then weight values xi and yi corresponding to each energy spectrum data in the first energy spectrum data set A and the second energy spectrum data set B respectively are calculated according to the following formula:
wherein N is the number of spectral data of the first spectral data set A or the second spectral data set B,
the data processing circuit calculates the combined power spectrum data C according to the following formula:
C＝xiA+yiB。
3. the gamma camera of claim 2 wherein the specific process of deriving the gamma radiation image from the projection data and the combined spectral data is as follows
Acquiring the total number N of gamma photons detected by a gamma camera according to the projection data, acquiring the photon energy of each gamma photon detected by the gamma camera according to the combined energy spectrum data, wherein the energy of the ith photon is Ei, and then acquiring the average energy of the gamma photons Eave by the following formula:
then, the incident photon energy Epeak is obtained according to the gamma photon average energy Eave through the following formula:
Epeak＝Eave×ae+be
wherein ae and be are fitting coefficients obtained by fitting according to experimental data,
the corresponding transmission matrix is then calculated from the incident photon energy Epeak,
the projection data is reconstructed from the transmission matrix to obtain a gamma radiation image.
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| CN110780333A (en) * | 2019-09-30 | 2020-02-11 | 南京航空航天大学 | Gamma camera based on double coding plates and method for positioning radioactive substances by using gamma camera |
| CN110796713B (en) * | 2019-11-29 | 2023-06-02 | 北京中科核安科技有限公司 | Radioactive source positioning method and device, electronic equipment and computer readable storage medium |
| CN111308538B (en) * | 2020-03-11 | 2022-03-18 | 江苏超敏科技有限公司 | Detection equipment for simulating radiation environment of space station to damage human body |
| CN113466923B (en) * | 2020-03-31 | 2024-04-12 | 同方威视技术股份有限公司 | Method and apparatus for detecting radioactive substance |
| CN111580149B (en) * | 2020-05-19 | 2022-02-08 | 中国人民解放军国防科技大学 | Fuel assembly energy spectrum imaging method and device |
| CN114001707B (en) * | 2021-10-28 | 2022-07-01 | 中国科学院高能物理研究所 | Method for measuring depth of radiation hotspot based on four-eye coding gamma camera |
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