CN115097511A - Double-end imaging gamma camera of unit-position sensitive detector based on MURA coding mode - Google Patents
Double-end imaging gamma camera of unit-position sensitive detector based on MURA coding mode Download PDFInfo
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- CN115097511A CN115097511A CN202210651294.9A CN202210651294A CN115097511A CN 115097511 A CN115097511 A CN 115097511A CN 202210651294 A CN202210651294 A CN 202210651294A CN 115097511 A CN115097511 A CN 115097511A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/36—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry
- G01T1/362—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry with scintillation detectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
- G01T1/2914—Measurement of spatial distribution of radiation
- G01T1/2921—Static instruments for imaging the distribution of radioactivity in one or two dimensions; Radio-isotope cameras
- G01T1/295—Static instruments for imaging the distribution of radioactivity in one or two dimensions; Radio-isotope cameras using coded aperture devices, e.g. Fresnel zone plates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
- G01T1/2914—Measurement of spatial distribution of radiation
- G01T1/2964—Scanners
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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Abstract
The invention relates to a double-end imaging gamma camera of a unit-position sensitive detector based on a MURA coding mode, which belongs to the technical field of radiation detection and comprises: the positive code plate and the negative code plate are respectively and oppositely arranged on two sides of the array type position sensitive detector, the centers of the positive code plate and the negative code plate are positioned on the same axis, and gamma rays emitted by the radioactive source are modulated by the positive code plate and the negative code plate to form an image about the code plates on the detector; the rear end of the detector is connected with a signal reading module, the signal reading module reads the analog signal in the detector, the analog signal is amplified and filtered and then transmitted to a multi-channel data acquisition card for digital sampling, finally, the energy information and the position information are transmitted to upper computer software, and the distribution image of the radioactive source is restored by using a set algorithm. The gamma camera provided by the invention can double the view field range of the coding camera, so that the imaging of a lost radioactive source can be carried out more quickly.
Description
Technical Field
The invention belongs to the technical field of radiation detection, and particularly relates to a double-end imaging gamma camera of a unit-position sensitive detector based on a MURA (multiple image acquisition) coding mode.
Background
The nuclear radiation detection technology which is mature nowadays comprises a radiation dosimeter and an energy spectrometer which are matched with the numerical value in an acoustic and optical alarm mode, but the modes generally carry out detection under the condition of close distance, the detection efficiency is low, the detection range is small, the time is long, and testers can be subjected to large radiation dose and are not intuitive enough. The ray imaging technology is a new technology in the field of nuclear radiation detection, can remotely detect radioactive substances in a visual field range, gives a two-dimensional distribution image, and is matched with an optical camera to visually indicate the position of a hot spot. According to the energy spectrum of the detected rays, nuclide identification can be carried out so as to determine the category of the radioactive substance.
The FOV (filed of view) of the coded aperture gamma ray imaging system has a certain field angle, so that the scanning efficiency of the environment is improved; the method has better position resolution capability, and can accurately position and distinguish a plurality of nearer radioactive objects; the radioactive substances in a certain energy range can be positioned to deal with a more complex radiation environment; the detection efficiency is higher, and the system sensitivity is improved. However, the imaging FOV of the conventional coded aperture gamma camera is as shown in fig. 1, and the imaging angle is small, so that when the whole radiation field is scanned, the whole radiation field can be scanned by moving the imaging device for many times, and the working efficiency is low.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a double-end imaging gamma camera of a unit-position sensitive detector based on a MURA coding mode, and the gamma camera can increase the visual field range of a coding camera by one time, so that the imaging of a lost radioactive source can be performed more quickly.
In order to achieve the above purposes, the invention adopts a technical scheme that:
the utility model provides a unit puts double-end formation of image gamma camera of sensitive detector based on MURA coding mode, includes positive code board, anti-code board, array type position sensitive detector, signal readout module, multichannel data acquisition card and host computer software, wherein:
the positive code plate and the negative code plate are respectively oppositely arranged at two sides of the array type position sensitive detector, the centers of the positive code plate and the negative code plate are positioned on the same axis, and gamma rays emitted by a radioactive source are modulated by the positive code plate and the negative code plate to form images related to the positive code plate and/or the negative code plate on the array type position sensitive detector;
the array type position sensitive detector transmits received analog signals to the multi-channel data acquisition card connected with the rear end, the multi-channel data acquisition card carries out digital sampling on the input analog signals, and finally energy information and position information of a radioactive source are transmitted to the upper computer software, and the upper computer software recovers the distribution image of the radioactive source by using a set algorithm.
Further, according to the double-end imaging gamma camera of the unit position sensitive detector based on the MURA coding mode, the vertical distances from the positive coding code plate and the negative coding code plate to the array position sensitive detector are equal, so that the imaging angles at two sides are the same.
Further, in the double-end imaging gamma camera of the single-position sensitive detector based on the MURA coding mode, the positive coding code plate and the negative coding code plate both adopt a coding mode of a modified uniform redundant array.
Furthermore, in the above mentioned dual-end imaging gamma camera with a single-end sensitive detector based on the MURA coding scheme, the coding order of the positive coding code plate and the negative coding code plate is 11, and the positive coding code plate and the negative coding code plate are circularly nested to form a circularly nested code plate with 21 × 21 basic units.
Further, according to the double-end imaging gamma camera of the unit-position sensitive detector based on the MURA coding mode, except that the center positions of the positive coding code plate and the negative coding code plate are the same, the other position codes are opposite.
Further, as for the double-end imaging gamma camera of the unit-position sensitive detector based on the MURA coding mode, the positive coding code plate is rotated by 90 degrees around the center of the positive coding code plate to obtain the inverse coding code plate.
Further, as described above, in the double-end imaging gamma camera of the single-position sensitive detector based on the MURA coding method, the optimal angular resolution of the gamma camera is 1/11 of the total angle of the field of view.
Further, in the above mentioned double-end imaging gamma camera of the unit position sensitive detector based on the MURA coding method, the array type position sensitive detector is constructed by coupling a cesium iodide scintillator array with a silicon photomultiplier.
Further, in the above-mentioned double-end imaging gamma camera based on the unit position sensitive detector of the MURA encoding method, the array of the array type position sensitive detector is 22 × 22.
Further, according to the double-end imaging gamma camera of the unit position sensitive detector based on the MURA coding mode, the signal readout module is connected between the array type position sensitive detector and the multichannel data acquisition card, the signal readout module adopts the uniform charge distribution circuit to read the analog signals in the array type position sensitive detector, amplifies and filters the analog signals for imaging, compresses the total number of paths of the analog signals and transmits the compressed analog signals to the multichannel data acquisition card.
The double-end imaging gamma camera of the unit sensitive detector based on the MURA coding mode has the following remarkable technical effects:
the invention can double the imaging FOV by adding the code reflecting plate on the other side of the detector, greatly improves the scanning progress of the gamma camera to the environmental radiation field, and can more quickly search for lost radioactive sources and monitor the radioactive sources. Application value also exists in the fields of decontamination and decommissioning measurement of nuclear facilities, radiation protection optimization and verification of nuclear weapon control treaties.
Drawings
FIG. 1 is a diagram of the FOV of a conventional encoding code plate gamma camera;
FIG. 2 is a diagram of the FOV of a dual-coded gamma camera;
fig. 3 is a schematic structural diagram of a double-end imaging gamma camera of a single-position sensitive detector based on the MURA coding scheme according to an embodiment of the present invention;
fig. 4A and 4B are schematic structural diagrams of a MURA encoding mode 11-order basic code plate and a cyclic nested code plate thereof, respectively;
fig. 5A and 5B are schematic structural diagrams of an 11-order cyclic nested code plate of the MURA coding scheme and a code plate thereof, respectively;
FIGS. 6A and 6B are a three-dimensional image and a planar image of a double-ended radiation source obtained by simulation, respectively;
fig. 7 is a radiation source position diagram.
Detailed Description
The invention is further described with reference to specific embodiments and drawings.
In order to solve the problem that the imaging field of view (FOV) of the conventional coded aperture gamma camera is small, the invention proposes a design idea that the code reflecting plate is added on the other side of the detector, so that the field of view range of the coded camera is doubled, and the imaging of the whole environment can be completed more quickly when the radioactive substance distribution in the environment is imaged, as shown in fig. 2.
Fig. 3 shows a schematic structural diagram of a double-end imaging gamma camera of a unit position sensitive detector provided in an embodiment of the present invention, where the gamma camera mainly includes a positive code plate 1, a negative code plate 2, an array type position sensitive detector 3, a signal readout module 4, a multi-channel data acquisition card 5, upper computer software 6, and a supporting mechanical structure.
The positive code plate 1 and the negative code plate 2 are respectively and oppositely arranged on two sides of the array type position sensitive detector 3, and the centers of the positive code plate and the negative code plate are positioned on the same axis. The gamma rays emitted by the radioactive substance are modulated by the positive code plate 1 and the negative code plate 2, and an image related to the code plate is formed on the array type position sensitive detector 3, and the step is called as a coding process. The rear end of the array type position sensitive detector 3 is connected with a signal reading module 4, the signal reading module 4 is connected with a multi-channel data acquisition card 5, analog signals in the array type position sensitive detector 3 are read through the signal reading module 4, and the analog signals are amplified, filtered and imaged and then transmitted to the multi-channel data acquisition card 5; the multichannel data acquisition card 5 digitally samples the input analog signals, finally transmits the energy information and the position information to the upper computer software 6 for processing, and recovers the distribution image of the radioactive source by using a set algorithm, wherein the step is called a decoding process and is also called image reconstruction.
The positive code plate 1 and the negative code plate 2 are metal plates with small holes distributed in a certain rule. The gamma rays emitted by the radioactive substance pass through each small hole on the code plate and form projections on the array type position sensitive detector 3, and all the projections are superposed together to form an image related to the code plate. If the two sides of the positive code plate 1 and the negative code plate 2 are provided with radioactive sources, superposed images modulated by the positive code plate and the negative code plate can be formed.
The distances from the positive coding code plate 1 and the reverse coding code plate 2 to the array type position sensitive detector 3, namely the focal length of the system, are equal, so that the imaging angles on the two sides are equal. In this embodiment, the imaging angles on both sides are cone angles of 40 °.
The positive code plate 1 and the negative code plate 2 adopt a Modified Uniform Redundant Array (MURA) coding mode. The MURA coding mode has excellent properties in the aspects of aperture ratio, symmetry, autocorrelation function and the like (the aperture ratio is 50%, the autocorrelation function is a delta function, and the MURA coding mode has good symmetry), can improve the sensitivity and the ray collection efficiency of an imaging system, reduces the imaging time of the system, and is more suitable for far-field radioactive source imaging. The selection of the coding order needs to be selected from the requirements of the whole system, and when the coding order is larger, the requirements on the processing and manufacturing of the code plate and the position sensitive detector are high. The encoding order of the MURA encoding scheme is 3, 5, 7, 11, 13, 19, 23, 29, and the like in descending order, and the MURA encoding with the encoding order of 11 is selected in the present embodiment. By utilizing the periodic correlation of the MURA code board, after the 11-order basic code board is subjected to cyclic nesting, a cyclic nested code board with 21 × 21 basic units is obtained, and the size of each basic unit is 30mm × 30mm × 30mm, as shown in FIG. 4. The best angular resolution of the gamma camera is 1/11 of the total angle of its field of view, calculated theoretically.
The positive and negative code plates are relative, namely the position of the original positive code plate is 1 is changed into 0, and the position of the original positive code plate is changed into 1, thus obtaining the negative code plate. For example, if the original code plate matrix is A, the inverse code plate matrix is (1-A). The circularly nested code plate can be obtained by rotating 90 degrees around the center. After the rotation, the codes at the positions of the positive code plate and the negative code plate except the center position are the same and are all opposite, as shown in fig. 5.
The array type position sensitive detector 3 is constructed by cesium iodide (CsI (Tl)) scintillator array coupling silicon photomultiplier (SiPM for short). In this embodiment, the array of the array type position-sensitive detector 3 is 22 × 22, and the effective area is 330mm × 330mm, wherein the size of each crystal bar is 15mm × 15mm × 15mm (the actual size of each crystal is 14.8mm × 14.8mm × 14.8mm, the reflective material between the crystals is TiO2, and the thickness is 0.2 mm). Because the periphery of the crystal array needs a light-blocking material to prevent the light leakage phenomenon, the periphery of the crystal array is pasted by using a black adhesive tape, and the size of the final single small module is 167.5mm multiplied by 15 mm.
In this embodiment, the signal readout module 4 compresses 484(22 × 22) channels of analog signals in the array-type position-sensitive detector 3 into 44(22+22) channels of analog signals by using a uniform charge distribution circuit (SCDC for short), and transmits the analog signals to the multi-channel data acquisition card 5 after amplification, filtering and imaging processes are performed on the analog signals.
Image reconstruction is carried out through upper computer software 6, so that a double-end radioactive source imaging diagram shown in fig. 6 can be obtained, wherein the position of a radioactive source is shown in fig. 7, the distance from the radioactive source on the side of the positive coding code plate 1 to the array type position sensitive detector is 5.2 meters, and the distance is over against the center of the positive coding code plate 1; the source on the side of the anti-code plate 2 is also 5.2 meters from the array-type position sensitive detector, which is offset by 80 cm from the center in the horizontal direction. According to the reconstructed image, the double-end imaging gamma camera provided by the invention can clearly image the double-end radioactive source.
According to the double-end imaging gamma camera of the unit-positioned sensitive detector based on the MURA coding mode, the anti-code plate is additionally arranged on the other side of the detector, so that the imaging FOV can be doubled, the scanning progress of the gamma camera to an environmental radiation field is greatly improved, the gamma camera can more quickly search a lost radioactive source and monitor the radioactive source, and the gamma camera has application values in the fields of decontamination and decommissioning measurement of nuclear facilities, radiation protection optimization and nuclear weapon control convention verification.
The embodiments described above are merely illustrative of the present invention, and the present invention may be embodied in other specific forms or other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the invention should be indicated by the appended claims, and any changes that are equivalent to the intent and scope of the claims are also intended to be included within the scope of the invention.
Claims (10)
1. The utility model provides a unit puts sensitive detector's bi-polar formation of image gamma camera based on MURA coding mode which characterized in that, gamma camera includes just encodes code plate (1), anti-code plate (2), array type position sensitive detector (3), multichannel data acquisition card (5) and host computer software (6), wherein:
the positive coding code plate (1) and the negative coding code plate (2) are respectively and oppositely arranged at two sides of the array type position sensitive detector (3), the centers of the positive coding code plate and the negative coding code plate are positioned on the same axis, and gamma rays emitted by a radioactive source are modulated by the positive coding code plate (1) and the negative coding code plate (2) to form images related to the positive coding code plate (1) and/or the negative coding code plate (2) on the array type position sensitive detector (3);
the array type position sensitive detector (3) transmits received analog signals to the multi-channel data acquisition card (5) connected with the rear end, the multi-channel data acquisition card (5) conducts digital sampling on the input analog signals, finally energy information and position information of a radioactive source are transmitted to the upper computer software (6), and the upper computer software (6) recovers the distribution image of the radioactive source by using a set algorithm.
2. The MURA-based gamma camera with double-end imaging of single-position sensitive detector of claim 1, wherein the vertical distances from the positive code plate (1) and the negative code plate (2) to the array-type position sensitive detector (3) are equal, so as to ensure the same imaging angles at both sides.
3. The MURA-based gamma camera with double-end imaging of single-position sensitive detectors of claim 1, wherein the positive code plate (1) and the negative code plate (2) both adopt a modified uniform redundant array coding method.
4. The MURA-based double-end imaging gamma camera with single-position sensitive detector of claim 3, wherein the coding order of the positive code plate (1) and the negative code plate (2) is 11, and the positive code plate and the negative code plate are circularly nested to form a circularly nested code plate with 21 x 21 basic units.
5. The MURA-based gamma camera with double-end imaging of single-position sensitive detectors of claim 1, wherein the positive code plate (1) and the negative code plate (2) have the same center position and the same position codes are opposite.
6. The MURA-coding-based double-ended imaging gamma camera with single-position sensitive detector according to claim 5, wherein the positive code plate (1) is rotated by 90 ° around its center to obtain the negative code plate (2).
7. The MURA-encoding-based dual-end imaging gamma camera of a single-position sensitive detector according to any of claims 1-6, wherein the optimal angular resolution of the gamma camera is 1/11 of the total angle of the field of view.
8. The MURA-encoding-based double-ended imaging gamma camera with single-position sensitive detector according to claim 1, wherein the array-type position sensitive detector (3) is constructed by coupling cesium iodide scintillator array with silicon photomultiplier.
9. The MURA-encoding-based double-ended imaging gamma camera with single position-sensitive detector according to claim 8, wherein the array of the array-type position-sensitive detectors (3) is 22 x 22.
10. The MURA-based double-end imaging gamma camera with single-position sensitive detector according to claim 8 or 9, wherein a signal readout module (4) is connected between the array-type position sensitive detector (3) and the multi-channel data acquisition card (5), the signal readout module (4) reads the analog signals in the array-type position sensitive detector (3) by using a uniform charge distribution circuit, amplifies and filters the analog signals, compresses the total number of paths of the analog signals, and transmits the compressed analog signals to the multi-channel data acquisition card (5).
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