CN110780333A - Gamma camera based on double coding plates and method for positioning radioactive substances by using gamma camera - Google Patents
Gamma camera based on double coding plates and method for positioning radioactive substances by using gamma camera Download PDFInfo
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Abstract
The invention discloses a gamma camera based on a double-coding plate and a method for positioning radioactive substances by using the gamma camera, belongs to the field of radiation detection technology and radioactivity monitoring, and can obtain a high-resolution radiation image with the number of pixels higher than that of an array detector. The invention comprises the following steps: the device comprises a first coding plate, a second coding plate, a coding plate switching device, an array detector, a detector position conversion device, a depth camera, a data acquisition and processing system and a shielding structure; the method has the advantages that two coding plates and one array detector are utilized, radioactive images are imaged twice and superposed, a radioactive image with higher resolution can be obtained, meanwhile, the energy spectrum and dose data obtained by the detector are utilized, the distance detection function of a depth camera is combined, the position, the type, the activity and the dose of radioactive substances can be measured, and the multifunctional and multipurpose radioactive position positioning method is realized.
Description
Technical Field
The invention belongs to the fields of radiation detection technology and radioactivity monitoring, and particularly relates to a gamma camera based on a double-coding plate and a method for positioning radioactive substances by using the gamma camera.
Background
With the application of nuclear industry and nuclear technology going deep into various fields of national economic development, the safety supervision of radioactive substances and the emergency capability of nuclear accidents become a problem of special attention in the nuclear safety and security industry. The accurate description of the spatial distribution of the radioactive substances is vital to the promotion of the nuclear safety supervision capability, and the method is widely applied to the fields of safety management of industrial and medical radioactive sources, emergency disposal of nuclear accidents, environmental radiation monitoring, public safety and the like.
The coded aperture gamma ray imaging system is also called a gamma camera, and is a radioactive substance positioning device which adopts a coding plate and an array radiation detector as core devices. After the gamma photons pass through the coding plate arranged in a specific mode, a coding image is formed on the array detector, and the two-dimensional radiation distribution condition of the area to be detected can be restored by decoding the coding image through a special algorithm. The spatial position resolution capability of the traditional gamma camera depends on the number of pixels of the array detector, and the improvement of the spatial position resolution capability of the radioactive image is only required to be realized.
In an actual application scene, it is very important to accurately locate radioactive substances, but the problems that the number of pixels of the existing gamma radiation array detector is small, the aperture of an encoding plate cannot be too small and the like are limited, and the limitation of the number of pixels of the detector on a physical measurement level can not be actually broken through to realize higher-resolution radioactive imaging.
Disclosure of Invention
The invention provides a gamma camera based on a double-coding plate and a radioactive substance positioning method; a high resolution radiation image can be obtained with a higher number of pixels than the array detector.
In order to achieve the purpose, the invention adopts the following technical scheme:
a dual encoding plate based gamma camera comprising: the device comprises a data acquisition and processing system 1, an array detector 2, a detector position conversion device 3, a first coding plate 4, a shielding structure 5, a second coding plate 6, a depth camera 7 and a coding plate switching device 24; the data acquisition and processing system 1, the array detector 2 and the detector position conversion device 3 are all positioned in a hexahedral space enclosed by a shielding structure 5, one front end of six surfaces of the shielding structure 5 is replaced by a coding plate, the detector position conversion device 3 is an integral mechanism for bearing and installing the detector and realizing the position conversion of the detector, can be regarded as a flat plate and fixed to the inner side of the shielding structure 5 and the front end of the data acquisition and processing system 1 through a buckle or a screw, the array detector 2 is fixed to a contact pin on the detector position conversion device 3 through a pin slot, the depth camera 7 is fixed to the lower side of the shielding structure 5 through the buckle and the screw, the coding plate switching device 24 is respectively connected with two side edges of the front end of the shielding structure 5 through a screw or a bonding mode, the coding plate switching device 24 is a hinge structure which is internally provided with a micro motor and can realize automatic opening and closing, the first coding plate 4 and the second coding plate 6 are respectively connected with the shielding structure 5 through a coding plate switching device 24, the data acquisition and processing system 1 is arranged at the rear end of the array detector 2, the array detector 2 is connected to the data acquisition and processing system 1 through a data line, the data acquisition and processing system 1 comprises a data acquisition module, a data transmission module and a data processing module, and the data acquisition and processing system 1 is connected with the array detector 2 through the data transmission module and the data processing device.
In the structure, the first coding plate 4 is a 31-order nested coding plate based on a 16-order coding array, the second coding plate 6 is a 33-order nested array based on a 17-order modified uniform redundant array, the size of the detection unit of the array detector 2 is the same as the size of the aperture unit of the coding plate, and the materials used by the first coding plate 4, the second coding plate 6 and the shielding structure 5 are lead, tungsten, copper, iron or alloys thereof; the array detector 2 is an array radiation detector, the detection material of the array detector 2 comprises an organic scintillation crystal, an inorganic scintillation crystal, a semiconductor or a gas ionization chamber, and the array structure of the array detector 2 is a linear array type, a pixel type or a multilayer resistive plate type; the core component adopted for designing and building the data acquisition, transmission and processing module is one or a combination of more of an ASIC chip, an FPGA chip, a PCB board, an ARM board, a Windows mainboard, a radio frequency module and a GPRS data transmission module.
The method for positioning the radioactive substances by using the dual-coding-plate-based gamma camera comprises the following steps:
step 1: firstly, combining a first coding plate and an array detector at a first position into a first gamma camera to image radioactive substances in a region to be detected, wherein the first position is the central position of a plane where the array detector is located, the first position is parallel to the first coding plate, and a connecting line of central points of the first coding plate and the second coding plate is perpendicular to the detector;
step 2: moving the array detector to a second position, combining a second coding plate and the moved array detector into a second gamma camera, and imaging the radioactive substance in the region to be detected, wherein the second position is the size of a pixel of a detector translated in one of four corners of the plane where the array detector is located, namely the upper left corner, the lower left corner, the upper right corner and the lower right corner;
and step 3: keeping the direction and the position of the gamma camera unchanged, carrying out optical imaging on the region to be measured by using the depth camera and measuring the distance between the region to be measured and the imaging system;
and 4, step 4: superposing the radioactive imaging results obtained by the first gamma camera and the second gamma camera by using a data acquisition and processing system to obtain a high-spatial resolution radioactive imaging result;
and 5: registering the high-spatial-resolution radioactive imaging result obtained in the step (4) with the optical imaging result obtained in the step (3) by using a data acquisition and processing system to obtain a composite image capable of directly indicating the spatial position of the radioactive substance;
step 6: and calculating the nuclide species, the radioactivity and the dose rate of the radioactive substance by using the gamma energy spectrum data measured by the array detector and the distance information measured by the depth camera.
In the above steps, when the first encoding plate and the second encoding plate in step 1 and step 2 are respectively combined with the array detector to form the first gamma camera and the second gamma camera, the positions of the center points of the encoding plates are the same and are both located right in front of the array detector at the first position, the first encoding plate and the second encoding plate are respectively combined with the array detector to form the gamma camera by using a hinge or a hinge device to automatically rotate the encoding plates to the same position in front of the array detector, a mechanism for driving the encoding plates to rotate is an electric motor capable of being operated remotely, the sizes of the encoding plates and the array detector and the distance between the encoding plates and the array detector are further designed according to the use scene of the gamma camera, the required parameters include imaging distance range, field angle size, image spatial resolution and angular resolution requirements, and various parameters of the encoding plates are required to be designed and optimized according to the parameters of the array detector, design parameters to be considered include the material of the collimator, the size and thickness of the collimator, the shape of the holes, the size of the holes;
in step 3, the depth camera is calibrated before use to enable the depth camera to coincide with the center of the field of view of the first gamma camera, so that the gamma camera and the depth camera can image the same region, meanwhile, the optical imaging field of view angle of the depth camera is greater than or equal to that of the gamma camera, so that the optical imaging region is greater than or equal to that of the gamma camera, and the depth camera is one or more of an optical camera, a binocular or multi-view vision system, a structured light vision system and a TOF (time of flight) vision system;
when the radioactive imaging results obtained by the first gamma camera and the second gamma camera are superposed in the step 4, dividing each pixel of the 17-order radioactive image obtained by the second gamma camera and the 16-order image obtained by the first gamma camera into four parts, aligning the four parts according to a central point, and directly performing numerical addition to obtain a new radioactive image;
the method adopted by the image registration in the step 5 is a method based on gray information, a method based on a space transform domain or a method based on image characteristics, and a computing platform adopted by the image registration is an OpenCV computer vision library, ArcGIS or MATLAB;
the method for analyzing the radionuclide species by utilizing the gamma energy spectrum data measured by the array detector in the step 6 comprises a peak searching matching method, a symmetrical zero area method, an artificial neural network method or a machine learning method; the method for reversely deducing the activity and the type of the radioactive nuclide through the dose rate and distance information measured by the array detector is characterized in that the energy of the gamma ray is judged by utilizing a nuclide identification result, and the activity of the radioactive substance and the air dose rate at a distance of one meter are reversely deduced by utilizing the inverse relation between the characteristic gamma ray count and the distance square;
the gamma camera based on the double coding plates is used in the radioactive substance positioning method, and an upper computer lower computer system, a wireless communication module and a GPS positioning system for remotely controlling the gamma camera and the depth camera are also utilized; the upper computer system refers to a software and hardware system used by an operator in remote control and is used for remotely controlling the gamma camera and the depth camera to measure and controlling the detector position conversion device and the coding plate switching device. The lower computer system refers to a software and hardware system which is arranged on the gamma camera and used for receiving a control instruction sent by the upper computer system. The wireless communication module is used for signal transmission and instruction sending, and the GPS positioning system is used for positioning the geographic position of the gamma camera in real time and is arranged on a lower computer system of the gamma camera.
Has the advantages that: the invention provides a gamma camera based on a double-coding plate and a radioactive substance positioning method, which adopt the design of the double-coding plate, utilize an array detector and a twice imaging method, and can more accurately judge the direction and the position of a radioactive substance; the automatic switching method of the double coding boards can be used for remote control operation in a short time, so that the efficiency is improved, the use is convenient, and the irradiation risk of workers is reduced; in addition, the invention adopts a method commonly used by the optical imaging and gamma ray imaging technologies, and can accurately judge the scene position of the radioactive substance by overlapping with the optical image after the radioactive imaging result is obtained; the depth detection method is introduced into a gamma camera system, the nuclide type, the radioactivity and the air dosage rate at a one-meter far position at the radioactive position can be identified while imaging is carried out by utilizing ranging information and a gamma energy spectrum measurement result, and reference is provided for treatment work.
Drawings
FIG. 1 is a schematic diagram of a gamma camera according to the present invention;
FIG. 2 is a flow chart of a radioactive material localization method in the practice of the present invention;
FIG. 3 is a schematic diagram of the arrangement of the apertures of the first code plate and the second code plate in the present invention, wherein 301 is a schematic diagram of the arrangement of the apertures of the first code plate, and 302 is a schematic diagram of the arrangement of the apertures of the second code plate;
FIG. 4 is a schematic diagram of a structural arrangement for moving an array detector from position one to position two in an embodiment of the present invention;
FIG. 5 is a schematic view of a first encoding plate and an array detector forming a first gamma camera and imaging a radiation source at a central location in accordance with an embodiment of the present invention;
FIG. 6 is a schematic view of a second code plate and array detector forming a second gamma camera and imaging a radiation source at a central location in accordance with an embodiment of the present invention;
FIG. 7 is a radiation image which can display the position of a radiation source with higher precision obtained by superimposing the imaging results of the first and second gamma cameras according to the embodiment of the present invention;
in the figure, 1 is a data acquisition system, 2 is an array detector, 3 is a detector position conversion device, 4 is a first encoding plate, 5 is a shielding structure, 6 is a second encoding plate, 7 is a depth camera, 8 is a platform carrying the array detector, 9 is an electromagnet, 10 is a metal shaft, 11 is the middle 4 × 4 pixels a of the array detector, 12 is the middle 3 × 3 units of the first encoding plate, 13 is a radiation source position a, 14 is the middle 4 × 4 pixels b of the array detector, 15 is the middle 3 × 3 units of the second encoding plate, 16 is a 17-order array detector, 17 is a radiation source position b, 18 is a 17-order radiation hotspot image obtained by the second gamma camera, 19 is the upper right corner 16 × 16 hotspot pixels of the 17-order radiation hotspot image obtained by the second gamma camera, 20 is the 16-order radiation hotspot image obtained by the first gamma camera, 21 is the upper right corner 4 × 4 pixels of the 16 × 16 pixels of the upper right corner 16 × 16 hotspot image obtained by the 17-order radiation hotspot image obtained by the second gamma camera, 22 is the middle 4 x 4 pixels of the 16-order radiation hot spot image obtained by the first gamma camera, 23 is the corresponding position of the radiation source on the radiation hot spot image, and 24 is the code plate switching device.
Detailed Description
The invention is described in detail below with reference to the following figures and specific examples:
as shown in fig. 1, includes: the device comprises a data acquisition and processing system 1, an array detector 2, a detector position conversion device 3, a first coding plate 4, a shielding structure 5, a second coding plate 6, a depth camera 7 and a coding plate switching device 24; the data acquisition and processing system 1, the array detector 2 and the detector position conversion device 3 are all positioned in a hexahedral space enclosed by a shielding structure 5, one front end of six surfaces of the shielding structure 5 is replaced by a coding plate, the detector position conversion device 3 is an integral mechanism for bearing and installing the detector and realizing the position conversion of the detector, can be regarded as a flat plate and fixed to the inner side of the shielding structure 5 and the front end of the data acquisition and processing system 1 through a buckle or a screw, the array detector 2 is fixed to a contact pin on the detector position conversion device 3 through a pin slot, the depth camera 7 is fixed to the lower side of the shielding structure 5 through the buckle and the screw, the coding plate switching device 24 is respectively connected with two side edges of the front end of the shielding structure 5 through a screw or a bonding mode, the coding plate switching device 24 is a hinge structure which is internally provided with a micro motor and can realize automatic opening and closing, the first coding plate 4 and the second coding plate 6 are respectively connected with the shielding structure 5 through a coding plate switching device 24, the data acquisition and processing system 1 is arranged at the rear end of the array detector 2, the array detector 2 is connected to the data acquisition and processing system 1 through a data line, the data acquisition and processing system 1 comprises a data acquisition module, a data transmission module and a data processing module, and the data acquisition and processing system 1 is connected with the array detector 2 through the data transmission module and the data processing device.
In the structure, the first coding plate 4 is a 31-order nested coding plate based on a 16-order coding array, the second coding plate 6 is a 33-order nested array based on a 17-order modified uniform redundant array, the size of the detection unit of the array detector 2 is the same as the size of the aperture unit of the coding plate, and the materials used by the first coding plate 4, the second coding plate 6 and the shielding structure 5 are lead, tungsten, copper, iron or alloys thereof; the array detector 2 is an array radiation detector, the detection material of the array detector 2 comprises an organic scintillation crystal, an inorganic scintillation crystal, a semiconductor or a gas ionization chamber, and the array structure of the array detector 2 is a linear array type, a pixel type or a multilayer resistive plate type; the core component adopted for designing and building the data acquisition, transmission and processing module is one or a combination of more of an ASIC chip, an FPGA chip, a PCB board, an ARM board, a Windows mainboard, a radio frequency module and a GPRS data transmission module.
As shown in fig. 2, the above method for positioning radioactive materials by using a dual-encoding-plate-based gamma camera includes the following steps:
step 201: firstly, combining a first coding plate and an array detector at a first position into a first gamma camera to image radioactive substances in a region to be detected, wherein the first position is the central position of a plane where the array detector is located, the first position is parallel to the first coding plate, and a connecting line of central points of the first coding plate and the second coding plate is perpendicular to the detector;
step 202: moving the array detector to a second position, combining a second coding plate and the moved array detector into a second gamma camera, and imaging the radioactive substance in the region to be detected, wherein the second position is the size of a pixel of a detector translated in one of four corners of the plane where the array detector is located, namely the upper left corner, the lower left corner, the upper right corner and the lower right corner;
step 203: keeping the direction and the position of the gamma camera unchanged, carrying out optical imaging on the region to be measured by using the depth camera and measuring the distance between the region to be measured and the imaging system;
step 204: superposing the radioactive imaging results obtained by the first gamma camera and the second gamma camera by using a data acquisition and processing system to obtain a high-spatial resolution radioactive imaging result;
step 205: registering the high-spatial-resolution radioactive imaging result obtained in the step (4) with the optical imaging result obtained in the step (3) by using a data acquisition and processing system to obtain a composite image capable of directly indicating the spatial position of the radioactive substance;
step 206: and calculating the nuclide species, the radioactivity and the dose rate of the radioactive substance by using the gamma energy spectrum data measured by the array detector and the distance information measured by the depth camera.
In the above steps, when the first encoding plate and the second encoding plate in step 1 and step 2 are respectively combined with the array detector to form the first gamma camera and the second gamma camera, the positions of the center points of the encoding plates are the same and are both located right in front of the array detector at the first position, the first encoding plate and the second encoding plate are respectively combined with the array detector to form the gamma camera by using a hinge or a hinge device to automatically rotate the encoding plates to the same position in front of the array detector, a mechanism for driving the encoding plates to rotate is an electric motor capable of being operated remotely, the sizes of the encoding plates and the array detector and the distance between the encoding plates and the array detector are further designed according to the use scene of the gamma camera, the required parameters include imaging distance range, field angle size, image spatial resolution and angular resolution requirements, and various parameters of the encoding plates are required to be designed and optimized according to the parameters of the array detector, design parameters to be considered include the material of the collimator, the size and thickness of the collimator, the shape of the holes, the size of the holes;
in step 3, the depth camera is calibrated before use to enable the depth camera to coincide with the center of the field of view of the first gamma camera, so that the gamma camera and the depth camera can image the same region, meanwhile, the optical imaging field of view angle of the depth camera is greater than or equal to that of the gamma camera, so that the optical imaging region is greater than or equal to that of the gamma camera, and the depth camera is one or more of an optical camera, a binocular or multi-view vision system, a structured light vision system and a TOF (time of flight) vision system;
when the radioactive imaging results obtained by the first gamma camera and the second gamma camera are superposed in the step 4, dividing each pixel of the 17-order radioactive image obtained by the second gamma camera and the 16-order image obtained by the first gamma camera into four parts, aligning the four parts according to a central point, and directly performing numerical addition to obtain a new radioactive image;
the method adopted by the image registration in the step 5 is a method based on gray information, a method based on a space transform domain or a method based on image characteristics, and a computing platform adopted by the image registration is an OpenCV computer vision library, ArcGIS or MATLAB;
the method for analyzing the radionuclide species by utilizing the gamma energy spectrum data measured by the array detector in the step 6 comprises a peak searching matching method, a symmetrical zero area method, an artificial neural network method or a machine learning method; the method for reversely deducing the activity and the type of the radioactive nuclide through the dose rate and the distance information measured by the array detector is to judge the gamma ray energy by using a nuclide identification result and reversely deduct the activity of the radioactive substance and the air dose rate at a distance of one meter by using the inverse relation between the characteristic gamma ray count and the distance square.
The gamma camera based on the double coding plates is used in the radioactive substance positioning method, and an upper computer lower computer system, a wireless communication module and a GPS positioning system for remotely controlling the gamma camera and the depth camera are also utilized; the upper computer system refers to a software and hardware system used by an operator in remote control and is used for remotely controlling the gamma camera and the depth camera to measure and controlling the detector position conversion device and the coding plate switching device. The lower computer system refers to a software and hardware system which is arranged on the gamma camera and used for receiving a control instruction sent by the upper computer system. The wireless communication module is used for signal transmission and instruction sending, and the GPS positioning system is used for positioning the geographic position of the gamma camera in real time and is arranged on a lower computer system of the gamma camera.
The first coding plate is a 31-order nested coding plate based on a 16-order coding array, and the aperture arrangement pattern of the first coding plate is 301 in FIG. 3; the second encoding plate is a 33-order nested array based on a 17-order modified uniform redundant array, the aperture arrangement pattern of the second encoding plate is shown as 302 in fig. 3, wherein the black part represents a shielding material through which rays cannot directly pass, the white part represents a small hole through which rays can directly pass, the number of rows and columns of the array detector is 16, and the size of the detection unit of the array detector is the same as that of the aperture unit of the encoding plate, and both the size and the size are 1 cm.
FIG. 4 is a schematic diagram of a structural device for moving the array detector from the first position to the second position in the embodiment of the present invention, wherein the slot in the front of the platform 8 for carrying the array detector is 16.5 cm, and the length and width of the array detector 2 are 16 cm; 9 is an electromagnet provided with a hole on the platform and arranged around the hole, 10 is a metal shaft connected with the detector, when the array detector 2 is positioned at the lower left of the slot at the front part of the platform 8 for carrying the array detector, the metal shaft 10 is attracted by the lower right of the magnet 9, and the array detector is positioned at the first position in the step 201; when the metal shaft 10 is attracted by the magnet 9 from the upper left, the array detector 2 moves to the upper right of the front slot of the array detector platform 8, i.e. the array detector moves by half a pixel size from the upper right, and the array detector is located at the second position as described in step 202.
The first coding plate and the second coding plate are connected with the shielding structure through electric hinges, and the movement of the coding plates is controlled through software of an external upper computer, so that the coding plates and the array detectors respectively form a first gamma camera and a second gamma camera.
The depth map and the optical image of the detected target area are obtained by using a depth camera, in this embodiment, the depth map and the optical image of the detected target area can be directly obtained by using a commercial depth detection vision product Microsoft Kinect, the optical camera described in step 203 is calibrated before use so that the optical imaging view center coincides with the view center of the first gamma camera, thereby ensuring that the same area is imaged, and meanwhile, the optical imaging view angle is greater than or equal to the view angle of the gamma camera through structural design so that the optical imaging view angle is greater than or equal to the imageable area of the gamma camera, thereby ensuring that the optically imageable area is greater than or equal to the imageable area of the gamma camera.
FIG. 5 is a schematic diagram of the first encoding plate and the array detector constituting the first gamma camera and imaging the radiation source at the central position in the present embodiment, where 4 is the first code plate, 2 array detectors, the solid line squares indicated at 11 represent the middle 4 x 4 pixels of the array detectors 2, the dashed line squares indicated at 12 represent the middle 3 x 3 cells of the first code plate 4, the two black dots indicated at 13 represent the position of the radiation source, the figure is a structural schematic diagram of a first gamma camera viewed from the plane of the radiation source, and it can be seen that the units of the coding plate are not aligned with the pixels of the array detector one by one, the light gray area in the figure represents the radiation hot spot area reflected by the radiation source at the lower left corner in the actual imaging result, and the dark gray area represents the radiation hot spot area reflected by the radiation source at the upper right corner in the actual imaging result.
FIG. 6 is a schematic diagram of the second code plate and the array detector forming the second gamma camera and imaging the radiation source at the central position in this embodiment, where 6 is the second code plate, the position of the second code plate is the same as the position of the first code plate shown in FIG. 5, 2 is the array detector (16 th order), 16 indicates a broken line box which is a 16 th order array detector plus a left column and a lower row of imaginary 17 th order array detectors, in actual operation, the left column and the lower row of data are assigned as the average value of all other pixel values, 14 indicates a solid line box which represents the middle 4 × 4 pixels of the array detector 2, 15 indicates a dashed line box which represents the middle 3 × 3 units of the second code plate, 17 indicates two black dots which represent the position of the radiation source, the position of the radiation source is the same as the position of the radiation source 13 shown in FIG. 5, which is a structural schematic diagram of the second gamma camera viewed from the plane where the radiation source is located, it can be seen that the elements of the code plate are aligned with the pixels of the array detector one by one, that is, the solid line squares indicated by 14 and the dotted line squares indicated by 15 are overlapped, the light gray areas in the figure represent the radiation hot spot areas reflected by the radiation source at the upper right corner in the actual imaging result, and the dark gray areas represent the radiation hot spot areas reflected by the radiation source at the lower left corner in the actual imaging result.
Fig. 7 is a diagram of radiation images obtained by superimposing the imaging results of the first and second gamma cameras in this embodiment, which can display the position of the radiation source with higher precision, the broken line box indicated by 18 is a 17-order radiation hot spot image obtained by the second gamma camera, the thin solid line box indicated by 19 is 16 × 16 pixels at the upper right corner of the 17-order radiation hot spot image obtained by the second gamma camera, the thick solid line box indicated by 20 represents the 16-order radiation hot spot image obtained by the first gamma camera, the broken line box indicated by 21 is 4 × 4 pixels in the middle of the 16 × 16 pixels at the upper right corner of the 17-order radiation hot spot image obtained by the second gamma camera, the solid line box indicated by 22 is 4 × 4 pixels in the middle of the 16-order radiation hot spot image obtained by the first gamma camera, and 23 indicates the corresponding position of the radiation source on the radiation hot spot image; the gray part in the image is the superposition of the imaging results of the radiation hotspots in fig. 5 and fig. 6, each pixel is divided into four parts before pixel value superposition is carried out, then corresponding pixels are sequentially summed according to the positions shown in fig. 7 to obtain a superposed image result, and it can be seen that the actual position of the radioactive source can be more clearly indicated through superposition processing of the imaging results of the first gamma camera and the second gamma camera, the hotspot range is reduced in the pixel where the radioactive source is located, and the image resolution is also doubled.
The periphery of the array detector and the coding plate is made of gamma shielding materials and is in rigid connection with the shell, and the data acquisition and processing system is arranged at the rear end of the array detector and is connected with the image processing device through the signal transmission module.
In the present embodiment, a depth map and an optical image of a probe target region are obtained using a depth detection vision system. In this embodiment, using the commercial depth detection vision product Microsoft Kinect, the depth map and the optical image of the detection target area can be directly obtained by the supporting software system.
And carrying out image registration on the radiation hot spot distribution image, the depth map and the optical image to obtain a composite image which can accurately reflect the radioactive spatial distribution and the surrounding environment characteristics.
And step 5, determining a registration model through a series of experimental settings by adopting a method based on a spatial transform domain and combining an OpenCV computer vision library and MATLAB software, and then registering the radiation hot spot distribution image, the depth map and the optical image in the registration model.
While the invention has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A dual encoding plate based gamma camera, comprising: the device comprises a data acquisition and processing system (1), an array detector (2), a detector position conversion device (3), a first coding plate (4), a shielding structure (5), a second coding plate (6), a depth camera (7) and a coding plate switching device (24); the data acquisition and processing system (1), the array detector (2) and the detector position conversion device (3) are all positioned in a hexahedral space enclosed by the shielding structure (5), one of the six surfaces of the shielding structure (5) is replaced by a coding plate, the data acquisition and processing system (1) is fixed on the inner side of the rear end of the shielding structure, the detector position conversion device (3) is fixed at the front end of the data acquisition and processing system (1), the array detector (2) is fixed on the detector position conversion device (3), the depth camera (7) is fixed at the bottom side of the shielding structure (5), the coding plate switching device (24) is respectively connected with the two side edges of the front end of the shielding structure (5), the first coding plate (4) and the second coding plate (6) are respectively connected with the shielding structure (5) through the coding plate switching device (24), the data acquisition and processing system (1) is arranged at the rear end of the array detector (2), the array detector (2) is connected to the data acquisition and processing system (1) through a data line, the data acquisition and processing system (1) comprises a data acquisition module, a data transmission module and a data processing module, and the data acquisition and processing system (1) is connected with the array detector (2) through the data transmission module and a data processing device.
2. The dual encoding plate based gamma camera of claim 1, wherein the first encoding plate (4) is a 31-order nested encoding plate based on a 16-order encoding array, and the second encoding plate (6) is a 33-order nested array based on a 17-order modified uniform redundant array.
3. The dual encoding plate based gamma camera according to claim 1 or 2, wherein the size of the detection unit of the array detector (2) is the same as the size of the aperture unit of the encoding plate.
4. The gamma camera based on the double encoding plates as claimed in claim 1 or 2, characterized in that the array detector (2) is an array type radiation detector, the detection material of the array detector (2) is organic scintillation crystal, inorganic scintillation crystal, semiconductor or gas ionization chamber, and the array structure of the array detector (2) is linear array type, pixel type or multilayer resistive plate type.
5. The gamma camera based on the double coding boards as claimed in claim 1, wherein the core component adopted for designing and constructing the data acquisition, transmission and processing module is one or a combination of more of ASIC chip, FPGA chip, PCB board, ARM board, Windows motherboard, radio frequency module and GPRS data transmission module.
6. A method for positioning radioactive substances by a gamma camera based on a double-coding plate is characterized by comprising the following steps:
step 1: firstly, combining a first coding plate and an array detector at a first position into a first gamma camera to image radioactive substances in a region to be detected, wherein the first position is the central position of a plane where the array detector is located, the first position is parallel to the first coding plate, and a connecting line of central points of the first coding plate and the second coding plate is perpendicular to the detector;
step 2: moving the array detector to a second position, combining a second coding plate and the moved array detector into a second gamma camera, and imaging the radioactive substance in the region to be detected, wherein the second position is the size of a pixel of a detector translated in one of four corners of the plane where the array detector is located, namely the upper left corner, the lower left corner, the upper right corner and the lower right corner;
and step 3: keeping the direction and the position of the gamma camera unchanged, carrying out optical imaging on the region to be measured by using the depth camera and measuring the distance between the region to be measured and the imaging system;
and 4, step 4: superposing the radioactive imaging results obtained by the first gamma camera and the second gamma camera by using a data acquisition and processing system to obtain a high-spatial resolution radioactive imaging result;
and 5: registering the high-spatial-resolution radioactive imaging result obtained in the step (4) with the optical imaging result obtained in the step (3) by using a data acquisition and processing system to obtain a composite image capable of directly indicating the spatial position of the radioactive substance;
step 6: and calculating the nuclide species, the radioactivity and the dose rate of the radioactive substance by using the gamma energy spectrum data measured by the array detector and the distance information measured by the depth camera.
7. The method for positioning radioactive materials by using a dual-encoding-plate-based gamma camera according to claim 6, wherein in step 1 and step 2, when the first encoding plate and the second encoding plate are combined with the array detector to form the first gamma camera and the second gamma camera, respectively, the central points of the first encoding plate and the second encoding plate are located at the same position and are located right in front of the array detector at the same position.
8. The method for positioning radioactive substances by using a dual-encoding-plate-based gamma camera according to claim 6, wherein the depth camera in step 3 is calibrated before use so that the depth camera coincides with the center of the field of view of the first gamma camera, thereby ensuring that the depth camera and the depth camera image the same region, and simultaneously ensuring that the optical imaging field angle of the depth camera is greater than or equal to the field angle of the gamma camera and the optical imageable region is greater than or equal to the imageable region of the gamma camera.
9. The method according to claim 6, wherein when the radioactive imaging results obtained by the first and second gamma cameras are superimposed in step 4, each pixel of the 17 th-order radioactive image obtained by the second gamma camera and the 16 th-order radioactive image obtained by the first gamma camera is divided into four parts and aligned according to the central point, and the four parts are directly added to obtain a new radioactive image.
10. The method for positioning radioactive substances by using a dual-encoding-plate-based gamma camera according to claim 6, wherein the method for analyzing radionuclide species by using the gamma energy spectrum data measured by the array detector in step 6 comprises a peak-finding matching method, a symmetric zero-area method, an artificial neural network method or a machine learning method; the method for reversely deducing the activity and the type of the radioactive nuclide through the dose rate and the distance information measured by the array detector is to judge the gamma ray energy by using a nuclide identification result and reversely deduct the activity of the radioactive substance and the air dose rate at a distance of one meter by using the inverse relation between the characteristic gamma ray count and the distance square.
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Inventor after: Gong Pin Inventor after: Zhang Rui Inventor after: Tang Xiaobin Inventor after: Cheng Jinxing Inventor after: Wang Qingbo Inventor after: Wen Weiwei Inventor before: Tang Xiaobin Inventor before: Gong Pin Inventor before: Zhang Rui |
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