WO2023097776A1 - 一种放射自显影系统及其探测器和成像方法 - Google Patents

一种放射自显影系统及其探测器和成像方法 Download PDF

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WO2023097776A1
WO2023097776A1 PCT/CN2021/137971 CN2021137971W WO2023097776A1 WO 2023097776 A1 WO2023097776 A1 WO 2023097776A1 CN 2021137971 W CN2021137971 W CN 2021137971W WO 2023097776 A1 WO2023097776 A1 WO 2023097776A1
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crystal
detector
array
photoelectric converter
present
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PCT/CN2021/137971
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English (en)
French (fr)
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牛明
杨永峰
邝忠华
柳正
王晓辉
桑子儒
任宁
吴三
丛龙瀚
孙涛
胡战利
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中国科学院深圳先进技术研究院
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Publication of WO2023097776A1 publication Critical patent/WO2023097776A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/202—Measuring radiation intensity with scintillation detectors the detector being a crystal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/208—Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section

Definitions

  • the invention relates to the technical field of medical equipment, in particular to an autoradiography system, a detector and an imaging method thereof.
  • AR autoradiography
  • Traditional autoradiography is a technology that uses radiation emitted by radioactive nuclides to sensitize silver halide in latex to form a latent image, which is then developed and fixed to form a nuclide distribution image.
  • the distribution position and intensity of the radioactive tracer can be accurately judged through image analysis, so as to study the metabolism of active substances in organisms, the distribution of specific antigens, receptors, DNA fragments, etc.
  • AR is a non-vital imaging technique that measures the distribution of radioactivity in a radiolabeled sample.
  • radiotracers are ⁇ - emitting isotopes (such as 3 H, 14 C, 35 S, 32 P, 33 P) and ⁇ + Emitting isotopes (eg, 18 F, 11 C, 15 O, and 13 N) allow quantification of the distribution of drugs labeled with radioisotopes in biological tissues and organs.
  • ⁇ - emitting isotopes such as 3 H, 14 C, 35 S, 32 P, 33 P
  • Emitting isotopes eg, 18 F, 11 C, 15 O, and 13 N
  • the spatial resolution of AR can reach 50-300 ⁇ m.
  • High-resolution AR technology is still a key reference tool for small animal functional neuroimaging, and it also plays a major role in verifying new molecular imaging contrast agents and testing the positioning and quantitative accuracy of PET studies.
  • positron AR is known as the "gold standard” for evaluating the quantitative results of PET imaging.
  • High-resolution small animal PET has been widely used in various preclinical biomedical research studies. In order to verify the quantitative and localization accuracy of small animal PET research, positron AR with higher resolution and higher quantitative accuracy is often used as a small animal Verification and supplementation of PET scans.
  • the traditional manual film autoradiography technology began in the 1950s and 1960s, including the introduction of tracers, specimen preparation, autoradiography preparation, exposure processing, and photo processing. Since then, the use of thin-film plastic scintillators combined with charge-coupled devices (CCD) and avalanche ionization chambers combined with CCD detectors has further improved the resolution of AR. Digital AR based on fluorescent phosphor screen technology has higher sensitivity and faster imaging time than traditional methods. First, the phosphor screen stores the radiation ionization caused by radioactivity, and then the phosphor screen is excited by a laser to generate visible light proportional to the radiation ionization, thereby obtaining high-resolution and high-quantitative-precision images.
  • CCD charge-coupled devices
  • the detector combined with high-density inorganic scintillation crystal and photoelectric conversion device has high detection efficiency for high-energy ⁇ photons, and is the most commonly used detector for PET imaging. Limited by physical effects such as positron range and gamma photon noncollinearity, the spatial resolution of existing whole-body PET imaging instruments is 3-5 mm.
  • the small animal PET imaging system can achieve higher spatial resolution due to the smaller diameter of the detector ring.
  • the spatial resolution of the existing commercial small animal PET imaging system is 1-2 mm.
  • the experimental imaging time is relatively long, manual operation is relatively cumbersome, and the imaging time is long, often up to several days or even months.
  • the spatial resolution that can be obtained in the autoradiography experiment using ⁇ -electron radioisotope nuclides (such as 14 C, 35 S, 32 P, etc.) of the autoradiography instrument using the plastic crystal coupled device CCD is further improved.
  • the instrument uses plastic crystal coupled CCD technology to detect electrons, but the detector has a small dynamic range and low sensitivity.
  • the phosphor screen needs to be cleaned at high temperature. After repeated cleaning, it will lead to problems such as degradation of imaging quality and affect the performance of the instrument.
  • the distance AR can achieve The rate still has a certain distance. That is to say, the sensitivity and resolution of current AR detectors are low, and the resolution cannot approach or reach the physical limit of AR detectors.
  • An object of the present invention is to provide an inventive position resolution approaching or reaching the physical limit of scintillation crystal coupled photoelectric converter type detectors, with high sensitivity, capable of energy measurement, photon counting, real-time display and pulse shape Screening, and the detector does not require refrigeration, suitable for detection and imaging of alpha particles, beta particles and low-energy gamma detectors and autoradiography systems.
  • the present invention provides a detector in one aspect, including a crystal, a light guide, and a photoelectric converter arranged sequentially from bottom to top, the crystal adopts an aluminum gadolinium gallate crystal, and the photoelectric converter adopts a silicon photomultiplier tube array, wherein the crystal is used to interact with radioactive rays to generate fluorescence, the light guide is used to guide the fluorescence to the photoelectric converter, and the photoelectric converter is used to convert the fluorescence into an electrical signal, and use the signal to read The output circuit transmits the electrical signal to the electronic system.
  • the crystal is a continuous crystal or a segmented crystal array
  • the thickness of the continuous crystal and the segmented crystal array is 1-5 mm
  • the width of a single crystal in the segmented crystal array is 0.1-5 mm. 0.3mm.
  • the thickness of the crystal is 1 mm
  • the silicon photomultiplier tube array is composed of a plurality of silicon photomultiplier tubes with an area of (1-3) ⁇ (1-3) mm 2 , so The silicon photomultiplier tube array has a thickness of 1 mm.
  • the size of the continuous crystal is 9.6 ⁇ 9.6 ⁇ 1 mm 3
  • the array of split crystals includes a 60 ⁇ 60 array with a crystal size of 0.11 ⁇ 0.11 ⁇ 1 mm 3 , and the crystal size is 0.19
  • a barium sulfate reflective film with a thickness of 50 mm is used between the crystals of the split crystal array.
  • the surface of the crystal is not polished, polished on both sides or fully polished.
  • silicon oil or optical glue is used to form the coupling between the crystal and the light guide
  • silicon oil or optical glue is used to form the coupling between the photoelectric converter and the light guide
  • the light guide is any one of quartz glass, plexiglass, acrylic, and optical fiber; the thickness of the light guide is 0.1-10 mm, the number of layers is 1-10, and the hardness is 2-10 mm. 6H.
  • the thickness of the light guide is 1mm
  • the number of layers is 1, and the hardness is 3H.
  • the signal readout circuit is a resistor network readout circuit, and the resistor network readout circuit is used to change the number of readout channels from 64 to 4.
  • the present invention also provides an autoradiography system, comprising the detector, an electronic system electrically connected to the detector, a data acquisition module electrically connected to the electronic system, and a An image display module for imaging data collected by the data collection module.
  • the electronic system adopts one of a resistive network channel multiplexing method, a transmission line multiplexing method, a rank and column sum multiplexing method, a capacitive network multiplexing method, and a coupled radio frequency coil multiplexing method A method for channel multiplexing of the silicon photomultiplier array.
  • An imaging method of an autoradiography system comprising steps:
  • the 4-way signal of the signal readout circuit of the detector is input into the electronic system, and the electronic system performs shaping amplification and digital processing on the 4-way signal to obtain the value of the 4-way energy signal;
  • the electronic system stores 4 channels of energy data to the data acquisition module, and generates a calibration curve and a divided crystal for the relationship between the calculated position and the actual position of the continuous crystal detector a crystal lookup table for the array detector and uploading the results to the electronics system;
  • the electronic system calculates the preliminary energy and position of each event in the field programmable gate array according to the measured energy signal, and the final The obtained event energy and position data are stored in the data acquisition module for further analysis at a later stage, and the measured energy and position data are displayed in the image display module in real time.
  • the present invention adopts the aluminum gadolinium gallate crystal (Gd 3 Al 2 Ga 3 O 12 , GAGG crystal for short), the density of GAGG crystal is 6.63 g/cm 3 , and it still has high detection efficiency for b, a and low-energy c-rays usually detected by AR.
  • the light output of GAGG crystal is 40-60 photons/keV, high The light output is beneficial to ensure the high resolution of the detector of the present invention;
  • the thickness of the array crystal and the continuous crystal of the present invention is preferably 1 mm, which does not affect the position resolution of the detector much, has high detection efficiency for b and a, and has certain protection against low-energy c-rays. Detection efficiency;
  • the present invention uses a SiPM array as a photoelectric converter, which can be highly integrated and is conducive to reducing the volume of the detector.
  • the detection area of the detector is 9.6 ⁇ 9.6 mm 2 , and through aluminum gadolinium gallate A crystal-coupled SiPM array is conducive to improving the performance of the detector;
  • the present invention uses the mature event energy sampling method of the PET detector and the relatively mature pulse decay time discrimination method of the PET detector to discriminate the pulses of ⁇ particles and ⁇ particles, and can use the traditional constant ratio timing Discrimination (Constant Fraction Discriminator, CFD) method, can also use the digital discrimination method to accurately measure the decay time parameters of the pulse;
  • CFD Constant Fraction Discriminator
  • the detector of the present invention adopts the modular splicing design of the crystal, the light guide, and the photoelectric converter, and the user can customize the detection area according to actual needs, so that the use is more autonomous and the detection freedom is higher .
  • Figure 1 is a schematic diagram of the autoradiography process based on a CCD detector
  • Figure 2 is an imaging diagram of a mouse brain slice based on CCD detector autoradiography
  • Fig. 3 is a schematic structural diagram of the detector according to a preferred embodiment of the present invention.
  • Fig. 4 is another schematic structural view of the crystal of the detector according to the above-mentioned preferred embodiment of the present invention.
  • Fig. 5 is a photo of the SiPM array of the detector according to the above-mentioned preferred embodiment of the present invention.
  • FIG. 6 is a schematic diagram of the resistor network readout circuit of the detector according to the above-mentioned preferred embodiment of the present invention.
  • FIG. 7 is a schematic diagram of the structure and workflow of the electronic system of the autoradiography system according to the above-mentioned preferred embodiment of the present invention.
  • Fig. 8 is a schematic block diagram of the structure of the autoradiography system according to the above-mentioned preferred embodiment of the present invention.
  • Fig. 9 is a graph showing the performance test results of the autoradiography system according to the above-mentioned preferred embodiment of the present invention.
  • autoradiography system 100 detector 10; crystal 11; light guide 12; photoelectric converter 13; signal readout circuit 131; electronic system 20; computer 30; data acquisition module 31; image display module 32.
  • the term “a” should be understood as “at least one” or “one or more”, that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element
  • the quantity can be multiple, and the term “a” cannot be understood as a limitation on the quantity.
  • connection should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected, or electrically connected, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation.
  • installation connection
  • connection connection
  • connection should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected, or electrically connected, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction of two components relation.
  • the invention adopts a continuous crystal detector or a split crystal array (the width of a single crystal is 0.1-0.3 mm) detector, combined with the mature electronics in PET, provides an inventive position resolution approaching or reaching the scintillation crystal coupled photoelectric converter type Detectors at the Physical Limits of Autoradiography Systems.
  • the autoradiography system of the present invention has high sensitivity, can perform energy measurement, photon counting, real-time display and pulse shape discrimination ( ⁇ and ⁇ ), the detector does not need refrigeration, is simple and low in cost, and is suitable for ⁇ particles, ⁇ Particle and low energy gamma probe imaging.
  • an autoradiography system 100 As shown in FIG. 3 to FIG. 7 , the structure of an autoradiography system 100 , its detector 10 and an imaging method according to the present invention are specifically illustrated.
  • the detector 10 includes a crystal 11, a light guide 12, and a photoelectric converter 13 arranged sequentially from bottom to top, the crystal 11 adopts an aluminum gadolinium gallate crystal, and the photoelectric converter 13 A silicon photomultiplier tube array is used, wherein the crystal 11 is used to interact with radioactive rays to generate fluorescence, and the light guide 12 is used to guide the fluorescence 12 to the photoelectric converter 13, and the photoelectric converter 13 uses Then convert the fluorescent light into an electrical signal, and use the signal readout circuit 131 to transmit the electrical signal to the electronic system 20 .
  • silicon oil or optical glue is used for coupling between the crystal 11 and the light guide 12
  • silicon oil or optical glue is also used for coupling between the light guide 12 and the photoelectric converter 13, that is, the light guide 12 Coupled between the crystal 11 and the photoelectric converter 13 .
  • the density of the present invention is slightly lower than that of the most commonly used LYSO crystal for PET detectors, but the light output is twice that of the LYSO crystal, and there is no self-emission background of the GAGG crystal.
  • the density of GAGG crystal is 6.63 g/cm 3 , and it still has high detection efficiency for b, a and low-energy c-rays usually detected by AR.
  • the light output of GAGG crystal is 40-60 photons/keV, and the high light output is conducive to ensuring The high resolution of the detector 10.
  • the present invention introduces the detector mode of the inorganic scintillation crystal array coupling photoelectric conversion device in the nuclear detector design mode into the field of autoradiography instrument design, and uses the latest photoelectric conversion device—silicon photomultiplier (SiPM ) is the main photoelectric conversion device, compared with the traditional autoradiography method, the performance of the detector 10 of the present invention is significantly improved.
  • SiPM silicon photomultiplier
  • the present invention can effectively improve the performance of the detector 10 by using an aluminum-gadolinium gallate crystal coupled to a silicon photomultiplier array.
  • the detector 10 based on the GAGG crystal and SiPM array of the present invention can be used for imaging organs such as mouse heart, kidney and brain, and the specific application of the detector 10 is not limited in the present invention.
  • the crystal 11 is a continuous crystal
  • the crystal 11 can also be divided
  • the crystal array that is to say, the detector 10 of the present invention can be two kinds of detectors: a continuous crystal detector and a divided crystal array detector, which can perform autoradiographic imaging on slices with a thickness of 20-100 ⁇ m.
  • the thickness h1 of the crystal 11 is 1-5 mm, preferably 1 mm. That is to say, the thickness of the continuous crystal and the segmented crystal array is 1-5 mm, preferably 1 mm.
  • the width w of a single crystal of the divided crystal array is 0.1-0.3 mm.
  • the thickness of the crystal 11 is 1mm
  • the silicon photomultiplier array is composed of a plurality of silicon Composed of photomultiplier tubes, the thickness h3 of the silicon photomultiplier tube array is 1mm.
  • the SiPM array is composed of multiple unit silicon photomultiplier tubes, as shown in Figure 5, the unit area of the unit silicon photomultiplier tube can be 1 ⁇ 1 mm 2 , or 2 ⁇ 2 mm 2 , 3 ⁇ 3 mm 2 , which is not limited by the present invention.
  • the SiPM array can be an 8 ⁇ 8 SiPM array with a cell size of 1 ⁇ 1 mm 2 , and the overall size of the SiPM array is 9.6 ⁇ 9.6 ⁇ 1 mm 3 ,
  • the SiPM array not only has the smallest detection area, but also has the smallest dead zone area of only 0.2 mm, which is beneficial to ensure the detection performance of the detector 10 .
  • the detector 10 using a split crystal array by using the GAGG crystal with a very large light output (twice as much as LYSO), it is cut to 0.1-0.3 mm, the thickness is 1 mm, and the back-end coupling
  • the SiPM with the best unit detection area of 1 ⁇ 1 mm2 combined with the multiplexing resistor network commonly used in PET, uses CFD and digital screening methods to identify the order of magnitude difference in the decay time of alpha particles and beta particles, compared with traditional phosphor screens, etc.
  • Autoradiography method with high sensitivity, can perform energy measurement, photon counting, real-time display, pulse shape discrimination ( ⁇ and ⁇ ), the detector does not need refrigeration, simple and low cost, suitable for ⁇ particles, ⁇ particles and Low energy gamma detection imaging.
  • the thickness of the crystal 11 is selected as 1 mm, that is, the thickness of the continuous crystal and the array crystal 11 are all selected as 1 mm, neither too much influence
  • the position resolution of the detector 10 has a high detection efficiency for b and a, and also has a certain detection efficiency for low-energy c-rays.
  • the present invention uses a SiPM array as the photoelectric converter 13, it can be highly integrated, which is conducive to reducing the volume of the detector 10.
  • the detection area of the detector 10 is about 9.6 ⁇ 9.6 mm 2 .
  • the detector 10 adopts a modular and splicable design of the crystal 11, the light guide 12, and the photoelectric converter, and the user can customize the detection area according to actual needs, making the use more autonomous and the detection freedom higher.
  • the basic detector module of 9.6 ⁇ 9.6 mm2 can be spliced into other required sizes for individual requirement design, and non-modular large-scale detectors can be used to directly conduct experiments.
  • the present invention There is no limit to this.
  • the photoelectric converter 13 may also be a PSPMT (position-sensitive photomultiplier tube), a PMT (photomultiplier tube, photomultiplier), a CCD (Charge-coupled Device, charge-coupled device), Any one of APD (Avalanche Photo Diode) and PSAPD (Position sensitive Avalanche Photo Diode), which is not limited in the present invention.
  • PSPMT position-sensitive photomultiplier tube
  • PMT photomultiplier tube, photomultiplier
  • CCD Charge-coupled Device, charge-coupled device
  • APD Avalanche Photo Diode
  • PSAPD Position sensitive Avalanche Photo Diode
  • the size of the continuous crystal may be 9.6 ⁇ 9.6 ⁇ 1 mm 3 .
  • the segmented crystal arrays include a 60 ⁇ 60 array with a crystal size of 0.11 ⁇ 0.11 ⁇ 1 mm, a 40 ⁇ 40 array with a crystal size of 0.19 ⁇ 0.19 ⁇ 1 mm, and a 24 -square array with a crystal size of 0.27 ⁇ 0.27 ⁇ 1 mm ⁇ 24 array, the crystals of the split crystal array adopt a barium sulfate reflective film with a thickness of 50 mm.
  • the surface of the crystal 11 may be non-polished, polished on both sides or fully polished, which is not limited in the present invention.
  • the light guide 12 is used to carry the crystal 11 and the photoelectric converter 13, and can be designed with no more than ten layers of light guides, and the thickness can also be designed according to specific needs.
  • the light guide 12 It is any one of quartz glass, plexiglass, acrylic, and optical fiber.
  • the thickness h2 of the light guide 12 is 0.1-10mm, the number of layers is 1-10, and the hardness is 2-6H.
  • the thickness of the light guide 12 is 1 mm, the number of layers is one, and the hardness is 3H.
  • the signal readout circuit 131 is a resistor network readout circuit, and the resistor network readout circuit is used to change the number of readout channels from 64 to 4.
  • the resistor network readout circuit is a multiplexing resistor network circuit commonly used in PET detectors.
  • the present invention utilizes the mature event energy sampling method of the PET detector and the relatively mature pulse decay time discrimination method of the PET detector to discriminate the pulses of ⁇ particles and ⁇ particles, and can use the traditional constant ratio timing discrimination (Constant The Fraction Discriminator (CFD) method can also use a digital discrimination method to accurately measure the decay time parameters of the pulse.
  • CFD Constant The Fraction Discriminator
  • the present invention also provides an autoradiography system 100 in another aspect.
  • the autoradiography system 100 includes the detector 10 , an electronic device electrically connected to the detector 10 An electronic system 20, a data collection module 31 electrically connected to the electronic system 20, and an image display module 32 for imaging based on the data collected by the data collection module 31.
  • the imaging method of the autoradiography system 100 includes steps:
  • the 4-way signals of the signal readout circuit 131 of the detector 10 are input into the electronic system 20, and the electronic system 20 performs shaping, amplification and digital processing on the 4-way signals to obtain the values of the 4-way energy signals;
  • the electronic system 20 stores 4 channels of energy data to the computer 30, and generates off-line the calibration curve and the split crystal for the relationship between the calculated position and the actual position of the continuous crystal detector. a crystal lookup table for the array detector and uploading the results to the electronics system 20; and
  • the electronic system 20 calculates the preliminary energy and position of each event in a field-programmable gate array (Field-Programmable Gate Array, FPGA for short) according to the measured energy signal, by calculating the position and the actual position
  • the relational calibration curve or crystal look-up table store the event energy and position data finally obtained in the computer 30 for further analysis in the later stage, and simultaneously display the measured energy and position data in the computer 30 in real time Screen.
  • the computer 30 includes the data acquisition module 31 and the image display module 32, the data acquisition module 31 is used for storing data, and the image display module 32 is used for The data acquired by module 31 is imaged and displayed.
  • the electronic system 20 can adopt resistive network channel multiplexing method, transmission line multiplexing method, row-column addition and multiplexing method, capacitive network multiplexing method and coupled radio frequency coil multiplexing method A method for channel multiplexing of the silicon photomultiplier array.
  • the detector 10 can use the following formula to calculate the position of the event in the crystal resolution diagram:
  • A, B, C, D are 4 position-related energy signals read out by the SiPM array resistance network
  • E is the energy of the detector 10
  • X and Y are the coordinate positions of the event in the crystal resolution diagram;
  • the present invention has conducted a performance test on the autoradiography system 100 , one of the results is shown in FIG. 9 .
  • the autoradiography system 100 specifically uses a split crystal array detector, and the split crystal array of the split crystal array detector is a 24 ⁇ 24 array of 0.27 ⁇ 0.27 ⁇ 1 mm 3 , that is, the The area of a single crystal strip of the split crystal array is 0.27 ⁇ 0.27 mm 2 , including a 24 ⁇ 24 crystal array, and the split crystal array detector uses an 8 ⁇ 8 SiPM array with a single area of 2 ⁇ 2 mm 2 as a photoelectric converter.
  • FIG. 9 shows the obtained position spectrum results.
  • Each bright spot represents the response of a crystal strip in the autoradiography system 100, and the brightness of the bright spot is proportional to the number of rays received by the corresponding crystal strip. From the results, it can be seen that in this position spectrum statistics, 24 ⁇ 24 crystal strips are clearly distinguishable.
  • the performance test of the autoradiography system 100 is mainly to measure the variation of energy resolution and position resolution with the energy of b, a and c rays.
  • the energy resolution of the detector 10 is measured using g-rays of various energies and a-particle radiation sources of various energies, and b-rays are not used for the measurement of the energy resolution of the system because they are continuum.
  • B particles have the same energy resolution as g rays of the same energy.
  • the present invention places b and a radiation sources at the slits by making five slits with a width of 0.1 mm and a pitch of 2 mm, and by measuring the width and distance of the crystal resolution diagram, the The positional resolution of the continuous crystal detector described above was estimated.
  • the present invention uses g-ray radiation sources to irradiate the detectors from a certain distance, and uses b and a radiation sources to scan the entire surface of the split crystal array detectors to measure particles of different energies, crystals Whether the resolution diagram can make a clear and unmistakable distinction for each crystal 11 unit.
  • the present invention also uses the same method as the continuous crystal detector to measure the position resolution of the detector 10 .
  • the performance test results show that the autoradiography system 100 of the present invention has higher detection efficiency for b, a and low-energy c-rays. Compared with the traditional autoradiography method, the performance is significantly improved.
  • the present invention adopts aluminum-gadolinium gallate crystal coupled SiPM array, combined with the mature electronic system in PET, uses CFD and digital screening method to discriminate the magnitude difference of pulse decay time of ⁇ -particle and ⁇ -particle, which can make autoradiography
  • the inventive positional resolution of the system 100 approaches or reaches the physical limit of scintillation crystal-coupled optoelectronic converter type detectors 10, whereby the present invention provides a high sensitivity and high resolution sensor capable of energy measurement, photon counting, real-time Display, pulse shape discrimination ( ⁇ and ⁇ ), and the detector does not need refrigeration, suitable for the detector 10 and autoradiography system 100 of ⁇ particles, ⁇ particles and low-energy ⁇ detection and imaging.

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Abstract

一种放射自显影系统（100）及其探测器（10）和成像方法，探测器（10）包括自下而上依次设置的晶体（11）、光导（12）以及光电转换器（13），晶体（11）采用镓酸铝钆晶体，光电转换器（13）采用SiPM阵列，通过采用镓酸铝钆晶体耦合SiPM阵列，结合PET中成熟的电子学系统（20），利用CFD、数字化甄别方法甄别α粒子和β粒子脉冲衰变时间的数量级差异，能够使得放射自显影系统（100）的位置分辨率逼近或达到闪烁晶体耦合光电转换器类型探测器（10）的物理极限，提供了一种具有高灵敏度和高分辨率的，可以进行能量测量、光子计数、实时显示以及脉冲形状甄别，且探测器（10）不需要制冷的，适合于α粒子，β粒子和低能γ探测成像的探测器（10）和放射自显影系统（100）。

Description

一种放射自显影系统及其探测器和成像方法 技术领域
本发明涉及医疗设备技术领域，特别是涉及一种放射自显影系统及其探测器和成像方法。
 背景技术
传统放射自显影（autoradiography，简称AR）是一种利用放射性核素发射的放射线，使乳胶中的卤化银感光而形成潜影，经显影和定影，形成核素分布图像的技术。借助感光银颗粒所在的部位和强度，通过影像分析，能准确地判断放射性示踪剂的分布部位和强度，从而研究生物体内活性物质的代谢，特异性抗原、受体、DNA片段等的分布。AR是一种测量由放射性标记的样品中放射性分布的非活体成像技术，常用的放射性示踪剂是β -发射同位素（例如 3H， 14C， 35S， 32P， 33P）和β +发射同位素（例如， 18F， 11C， 15O和 13N），可以量化由放射性同位素标记的药物在生物组织和器官中的分布。如图1和图2所示，由于放射自显影技术是一种对冰冻固定后的切片进行成像的2D影像，扫描期间不存在生理活动如呼吸、心跳、放射标记物等在活体内的代谢变化，可以通过增加扫描时间，从而得到更高信噪比的图像，达到高分辨率和高定量精度。AR的空间分辨率可达50-300μm。高分辨率的AR技术仍然是小动物功能性神经成像的关键参考工具，在验证新的分子影像造影剂和检验PET研究的定位和定量精度等方面也发挥较大作用。在小动物脑部正电子发射断层扫描成像（Positron Emission Tomography, PET）成像研究中，正电子AR更是被称为评价PET成像定量结果的“金标准”。高分辨率小动物PET已广泛应用于各种临床前生物医学研究研究，为了验证小动物PET研究的定量和定位精度，经常采用具有更高分辨率和更高定量精度的正电子AR作为小动物PET扫描的检验和补充。
在放射自显影领域，上个世纪五六十年代便开始了传统的手工胶片自显影技术，其中包括示踪剂的引入、标本制备、自显影制备及曝光处理、照片处理等多个步骤。此后，薄膜塑料闪烁体结合电荷耦合器件（charge-coupled device，简称CCD）以及雪崩电离室结合CCD探测器的开始使用，进一步提高了AR的分辨率。基于荧光磷屏技术的数字AR 比传统方法具有更高的灵敏度和更快的成像时间。首先磷屏存贮由放射性引起的辐射电离，然后采用激光激励磷屏，产生正比于辐射电离的可见光，从而获得高分辨率和高定量精度图像。
高密度无机闪烁晶体和光电转换器件结合的探测器对高能γ光子具有高的探测效率，是PET成像最常用的探测器。受正电子射程和γ光子非共线性（noncollinearity）等物理效应的限制，现有全身PET成像仪器的空间分辨率为 3-5 mm。而小动物PET成像系统由于探测器环直径较小，可以达到更高的空间分辨率，现有商用小动物PET成像系统的空间分辨率为1-2 mm。
 技术问题
在传统胶片放射自显影中，其实验成像时间较长，手工操作，较为繁琐，成像时间较长，经常可达数天甚至数月。使用塑料晶体耦合器件CCD的放射自显影仪器在使用β-电子的放射性同位素核素（如 14C， 35S， 32P等）的放射性自显影实验中可得到的空间分辨率进一步提高，该类仪器采用塑料晶体耦合CCD的技术方式对电子进行探测，但该探测器的动态范围较小，灵敏度较低。磷屏需要高温进行清理，多次清理后会导致成像质量下降等问题，影响仪器的性能。目前已经研发的高分辨率小动物PET探测器中，最好已经可以分辨0.5 mm的晶体单元，然而，虽然小动物PET成像系统的空间分辨率物理极限是0.5 mm，但是距离AR能达到的分辨率还有一定的距离。也就是说，目前的AR探测器的灵敏度和分辨率较低，其分辨率并无法做到逼近或达到AR探测器的物理极限。
技术解决方案
本发明的一目的是，提供一种发明位置分辨率能够逼近或达到闪烁晶体耦合光电转换器类型探测器的物理极限的，具有高灵敏度的，可以进行能量测量、光子计数、实时显示以及脉冲形状甄别，且探测器不需要制冷的，适合于α粒子，β粒子和低能γ探测成像的探测器和放射自显影系统。
本发明在一方面提供了一种探测器，包括自下而上依次设置的晶体、光导以及光电转换器，所述晶体采用镓酸铝钆晶体，所述光电转换器采用硅光电倍增管阵列，其中所述晶体用于与放射性射线作用而产生荧光，所述光导用于将所述荧光导向至所述光电转换器，所述光电转换器用于将所述荧光转换为电信号，并采用信号读出电路将所述电信号传输至电子学系统。
在本发明的一实施例中，所述晶体为连续晶体或分割晶体阵列，所述连续晶体和所述分割晶体阵列的厚度为1～5mm，所述分割晶体阵列的单个晶体的宽度为0.1～0.3mm。
在本发明的一实施例中，所述晶体的厚度为1mm，所述硅光电倍增管阵列由多个面积为（1～3）×（1～3）mm 2的硅光电倍增管组成，所述硅光电倍增管阵列的厚度为1mm。
在本发明的一实施例中，所述连续晶体的尺寸为9.6×9.6×1 mm 3，所述分割晶体阵列包括晶体大小为 0.11×0.11×1 mm 3的60×60阵列，晶体大小为 0.19×0.19×1 mm 3的40×40阵列以及晶体大小为 0.27×0.27×1 mm 3的24×24阵列，所述分割晶体阵列的晶体间采用厚度为50 mm的硫酸钡反射膜。
在本发明的一实施例中，所述晶体的表面进行不抛光处理、两面抛光处理或者全抛光处理。
在本发明的一实施例中，所述晶体和所述光导之间采用硅油或光学胶形成耦合，所述光电转换器和所述光导之间采用硅油或光学胶形成耦合。
在本发明的一实施例中，所述光导为石英玻璃、有机玻璃、亚克力、光纤中的任一种；所述光导的厚度为0.1～10mm，层数为1～10层，硬度为2～6H。
在本发明的一实施例中，所述光导的厚度为1mm，层数为1层，硬度为3H。
在本发明的一实施例中，所述信号读出电路为电阻网络读出电路，所述电阻网络读出电路用于将读出通道数从64将为4。
本发明在另一方面还提供了一种放射自显影系统，包括所述探测器、电连接于所述探测器的电子学系统、电连接于所述电子学系统的数据采集模块以及用于基于所述数据采集模块所采集的数据成像的图像显示模块。
在本发明的一实施例中，所述电子学系统采用电阻式网络通道复用方法、传输线复用方法，行列加和复用方法、电容网络复用方法以及耦合射频线圈复用方法中的一种方法进行所述硅光电倍增管阵列的通道复用。
一种放射自显影系统的成像方法，包括步骤：
所述探测器的信号读出电路的4路信号输入所述电子学系统，所述电子学系统对4路信号进行成型放大和数字化处理，得到4路能量信号的数值；
所述电子学系统在所述探测器的刻度模式下，将4路能量数据存贮到所述数据采集模块，并生成用于连续晶体探测器的计算位置和实际位置的关系刻度曲线和分割晶体阵列探测器的晶体查找表，并将结果上传到所述电子学系统；以及
在成像阶段，所述电子学系统根据测量到的能量信号，在现场可编程门阵列中计算每个事件的初步能量和位置，通过计算位置和实际位置的关系刻度曲线或晶体查找表，将最后得到的事件能量和位置数据存贮于所述数据采集模块，以用于后期的进一步分析，同时将测量到的能量和位置数据实时显示于所述图像显示模块。
 有益效果
本发明具有以下有益效果：
（1）本发明采用密度比PET探测器最常用的LYSO晶体稍低，但光输出为LYSO晶体两倍，并且没有自发射本底的镓酸铝钆晶体（Gd 3Al 2Ga 3O 12，简称GAGG晶体)，GAGG晶体的密度为6.63 g/cm 3，对AR通常探测的b、a和低能c射线依然有高的探测效率，GAGG晶体的光输出为40-60光子/keV，高的光输出有利于确保本发明的所述探测器的高分辨率；
（2）本发明的所述阵列晶体和所述连续晶体厚度优选为1 mm，既不太影响探测器的位置分辨率+，对b和a有很高探测效率，对低能c射线也有一定的探测效率；
（3） 本发明采用SiPM阵列作为光电转换器，能够做到高度集成化，有利于缩小所述探测器的体积，所述探测器的探测面积为9.6 × 9.6 mm 2，而且通过镓酸铝钆晶体耦合SiPM阵列，有利于提升所述探测器的性能；
（4）本发明利用PET探测器的已经成熟的事件能量采样方法， PET探测器的比较成熟的脉冲衰减时间甄别方法，对α粒子和β粒子的脉冲进行甄别，既可以使用传统的恒比定时甄别(Constant Fraction Discriminator，CFD)方法，也可以使用数字化的甄别方法准确的测量出脉冲的衰减时间参数；
（5）本发明的所述探测器采用所述晶体、所述光导以及所述光电转化器的模块化可拼接设计，用户可根据实际需求自定义探测面积，使用更加自主，探测自由度更高。
通过对随后的描述和附图的理解，本发明进一步的目的和优势将得以充分体现。
 附图说明
图1为基于CCD探测器的放射自显影流程示意图；
图2为基于CCD探测器的放射自显影的小鼠脑切片成像图；
图3为根据本发明的一优选实施例的所述探测器的结构示意图；
图4为根据本发明的上述优选实施例的所述探测器的晶体的另一种结构示意图；
图5为根据本发明的上述优选实施例的所述探测器的SiPM阵列的照片；
图6为根据本发明的上述优选实施例的所述探测器的电阻网络读出电路的示意图；
图7为根据本发明的上述优选实施例的所述放射自显影系统的电子学系统的结构和工作流程示意图；
图8为根据本发明的上述优选实施例的所述放射自显影系统的结构示意框图；
图9为根据本发明的上述优选实施例的所述放射自显影系统的性能测试结果图。
附图标号说明：放射自显影系统100；探测器10；晶体11；光导12；光电转换器13；信号读出电路131；电子学系统20；计算机30；数据采集模块31；图像显示模块32。
 本发明的实施方式
以下描述用于揭露本发明以使本领域技术人员能够实现本发明。以下描述中的优选实施例只作为举例，本领域技术人员可以想到其他显而易见的变型。在以下描述中界定的本发明的基本原理可以应用于其他实施方案、形变方案、改进方案、等同方案以及没有背离本发明的精神和范围的其他技术方案。
本领域技术人员应理解的是，在本发明的揭露中，术语“竖向”、“横向”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底” “内”、“外”等指示的方位或位置关系是基于附图所示的方位或位置关系，其仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此上述术语不能理解为对本发明的限制。
可以理解的是，术语“一”应理解为“至少一”或“一个或多个”，即在一个实施例中，一个元件的数量可以为一个，而在另外的实施例中，该元件的数量可以为多个，术语“一”不能理解为对数量的限制。
在本发明的描述中，需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接或可以相互通讯；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本发明中的具体含义。
本发明采用连续晶体探测器或分割晶体阵列（单个晶体宽度为0.1～0.3 mm）探测器，结合PET中成熟的电子学，提供了一种发明位置分辨率逼近或达到闪烁晶体耦合光电转换器类型探测器的物理极限的放射自显影系统。本发明的放射自显影系统具有高灵敏度，可以进行能量测量、光子计数、实时显示以及脉冲形状甄别（α和β），探测器不需要制冷、简单和成本低等优点，适合于α粒子，β粒子和低能γ探测成像。
如图3至图7所示，根据本发明的一种放射自显影系统100及其探测器10和成像方法的结构被具体阐明。
如图3至图6所示，所述探测器10包括自下而上依次设置的晶体11、光导12以及光电转换器13，所述晶体11采用镓酸铝钆晶体，所述光电转换器13采用硅光电倍增管阵列，其中所述晶体11用于与放射性射线作用而产生荧光，所述光导12用于将所述荧光导12向至所述光电转换器13，所述光电转换器13用于将所述荧光转换为电信号，并采用信号读出电路131将所述电信号传输至电子学系统20。
值得一提的是，所述晶体11和所述光导12之间采用硅油或光学胶耦合，所述光导12和所述光电转换器13之间也是采用硅油或光学胶耦合，即所述光导12耦合于所述晶体11和所述光电转换器13之间。
可以理解的是，本发明采用密度比PET探测器最常用的LYSO晶体稍低，但光输出为LYSO晶体两倍，并且没有自发射本底的GAGG晶体。GAGG晶体的密度为6.63 g/cm 3，对AR通常探测的b、a和低能c射线依然有高的探测效率，GAGG晶体的光输出为40-60光子/keV，高的光输出有利于确保所述探测器10的高分辨率。
还可以理解的是，本发明将核探测器设计模式中的无机闪烁晶体阵列耦合光电转换器件的探测器模式引入到放射自显影仪器设计领域，以最新的光电转换器件—硅光电倍增器（SiPM）为主要光电转换器件，相比于传统的放射自显影方法，本发明的所述探测器10的性能提升明显。
也就是说，本发明通过采用镓酸铝钆晶体耦合硅光电倍增管阵列，能够有效提升所述探测器10的性能。本发明的基于GAGG晶体和SiPM阵列的所述探测器10可以用于小鼠心脏、肾和大脑等器官成像，本发明对所述探测器10的具体应用不作限制。
特别地，如图3所示，在本发明的一实施例中，所述晶体11为连续晶体，如图4所示，在本发明的另一实施例中，所述晶体11也可以为分割晶体阵列，也就是说，本发明的所述探测器10可以为连续晶体探测器和分割晶体阵列探测器两种探测器，能对厚度为20-100μm的切片进行自显影成像。
具体地，所述晶体11的厚度h1为1～5mm，优选为1mm。也就是说，所述连续晶体和所述分割晶体阵列的厚度为1～5mm，优选为1mm。
优选地，在本发的这一具体实施例中，所述分割晶体阵列的单个晶体的宽度w为0.1～0.3mm。
特别地，在本发明的这一具体实施例中，所述晶体11的厚度为1mm，所述硅光电倍增管阵列由多个面积为（1～3）×（1～3）mm 2的硅光电倍增管组成，所述硅光电倍增管阵列的厚度h3为1mm。
也就是说，所述SiPM阵列由多个单元硅光电倍增管组成，如图5所示，单元硅光电倍增管的单元面积可以为1×1 mm 2，也可以为2×2mm 2，3×3 mm 2，本发明对此不作限制。
特别地，在本发明的这一具体实施例中，所述SiPM阵列可以选用单元大小为1×1 mm 2的8×8 SiPM阵列，该款SiPM阵列的整体尺寸为9.6×9.6×1mm 3，该款SiPM阵列不仅探测面积最小，而且死区面积也最小，仅为0.2 mm，如此有利于确保所述探测器10的探测性能。
可以理解的是，对于采用分割晶体阵列的所述探测器10来讲，通过利用光输出极大（LYSO两倍）的GAGG晶体，切细到0.1～0.3 mm，厚度在1 mm，后端耦合单元探测面积最好的1×1 mm 2的SiPM，配合PET常用的复用电阻网络，利用CFD、数字化甄别方法甄别α粒子和β粒子脉冲衰变时间的数量级差异，相比于传统的磷屏等放射自显影方法，具有高灵敏度，可以进行能量测量、光子计数、实时显示、脉冲形状甄别（α和β），探测器不需要制冷、简单和成本低等优点，适合于α粒子，β粒子和低能γ探测成像。
还可以理解的是，在本发明的这一具体实施例中，由于所述晶体11的厚度选为1mm，即所述连续晶体和所述阵列晶体11的厚度都选为1mm，既不太影响探测器10的位置分辨率，对b和a有很高探测效率，对低能c射线也有一定的探测效率。
另外，由于本发明采用SiPM阵列作为所述光电转换器13，能够做到高度集成化，有利于缩小所述探测器10的体积，所述探测器10的探测面积约为9.6 × 9.6 mm 2，而且所述探测器10采用所述晶体11、所述光导12以及所述光电转化器的模块化可拼接设计，用户可根据实际需求自定义探测面积，使用更加自主，探测自由度更高。
可以理解的是，利用模块化的设计，可将9.6×9.6 mm 2的基本探测器模块拼接成其他需求的尺寸进行个性化需求设计，可以利用非模块化的大型探测器直接进行试验，本发明对此不作限制。
在本发明的一实施例中，所述光电转换器13也可以为PSPMT（位置敏感型光电倍增管）、PMT（photomultiplier tube，光电倍增器）、CCD（Charge-coupled Device，电荷耦合器件）、APD（Avalanche Photo Diode 雪崩光电二极管）、PSAPD（Position sensitive Avalanche Photo Diode 位置敏感型雪崩光电二极管）中的任一种，本发明对此不作限制。
在本发明的一些实施例中，按照SiPM阵列的尺寸，所述连续晶体的尺寸可以为9.6×9.6×1 mm 3。所述分割晶体阵列包括晶体大小为 0.11×0.11×1 mm 3的60×60阵列，晶体大小为 0.19×0.19×1 mm 3的40×40阵列以及晶体大小为0.27×0.27×1 mm 3的24×24阵列，所述分割晶体阵列的晶体间采用厚度为50 mm的硫酸钡反射膜。
而且，所述晶体11的表面可以进行不抛光处理、两面抛光处理或者全抛光处理，本发明对此不作限制。
值得一提的是，所述光导12用于承接所述晶体11与所述光电转换器13，可使用不多于十层的光导进行设计，厚度亦可根据具体需要进行设计，所述光导12为石英玻璃、有机玻璃、亚克力、光纤中的任一种。
具体地，所述光导12的厚度h2为0.1～10mm，层数为1～10层，硬度为2～6H。
优选地，在本发明的这一具体实施例中，所述光导12的厚度为1mm，层数为一层，硬度为3H。
如图6所示，所述信号读出电路131为电阻网络读出电路，所述电阻网络读出电路用于将读出通道数从64将为4。
特别地，所述电阻网络读出电路为PET探测器常用的复用电阻网络电路。
本发明利用PET探测器的已经成熟的事件能量采样方法， PET探测器的比较成熟的脉冲衰减时间甄别方法，对α粒子和β粒子的脉冲进行甄别，既可以使用传统的恒比定时甄别(Constant Fraction Discriminator，CFD)方法，也可以使用数字化的甄别方法准确的测量出脉冲的衰减时间参数。
如图7和图8所示，本发明在另一方面还提供了一种放射自显影系统100，所述放射自显影系统100包括所述探测器10、电连接于所述探测器10的电子学系统20、电连接于所述电子学系统20的数据采集模块31以及用于基于所述数据采集模块31所采集的数据成像的图像显示模块32。
如图7所示，所述放射自显影系统100的成像方法包括步骤：
所述探测器10的信号读出电路131的4路信号输入所述电子学系统20，所述电子学系统20对4路信号进行成型放大和数字化处理，得到4路能量信号的数值；
所述电子学系统20在所述探测器10的刻度模式下，将4路能量数据存贮到计算机30，并离线生成用于连续晶体探测器的计算位置和实际位置的关系刻度曲线和分割晶体阵列探测器的晶体查找表，并将结果上传到所述电子学系统20；以及
在成像阶段，所述电子学系统20根据测量到的能量信号，在现场可编程门阵列(Field-Programmable Gate Array，简称FPGA)中计算每个事件的初步能量和位置，通过计算位置和实际位置的关系刻度曲线或晶体查找表，将最后得到的事件能量和位置数据存贮于所述计算机30，以用于后期的进一步分析，同时将测量到的能量和位置数据实时显示于所述计算机30屏幕。
值得一提的是，所述计算机30包括所述数据采集模块31和所述图像显示模块32，所述数据采集模块31用于存贮数据，所述图像显示模块32用于基于所述数据采集模块31所采集的数据成像和显示图像。
此外，还值得一提的是，所述电子学系统20可以采用电阻式网络通道复用方法、传输线复用方法，行列加和复用方法、电容网络复用方法以及耦合射频线圈复用方法中的一种方法进行所述硅光电倍增管阵列的通道复用。
所述探测器10的位置和能量计算的具体方式如下：
具体地，所述探测器10可以使用下面公式计算事件在晶体分辨图中的位置：
X=(B+C)/E, Y=(C+D)/E；
上式中，A，B，C，D为 SiPM阵列电阻网络读出的4个和位置相关的能量信号，E为探测器10的能量， X和 Y为事件在晶体分辨图中的坐标位置；其中E由下面公式计算：
E= A+B+C+D。
本发明对所述放射自显影系统100进行了性能测试，其中一个结果如图9所示。在该具体性能测试中，所述放射自显影系统100具体采用分割晶体阵列探测器，所述分割晶体阵列探测器的分割晶体阵列为0.27×0.27×1 mm 3的24×24阵列，即所述分割晶体阵列的单个晶体条面积为 0.27×0.27 mm 2，包含24×24的晶体阵列，而且所述分割晶体阵列探测器采用单片面积2×2 mm 2的8×8SiPM阵列作为光电转换器。图9为得到的位置谱结果，每一个亮点代表所述放射自显影系统100中的一个晶体条的响应，亮点的亮度与对应的晶体条上收到的射线的个数成正比。从结果中，可以看出，在该位置谱统计中，24×24个晶体条均清晰可辨。
所述放射自显影系统100的性能测试主要是测量能量分辨率和位置分辨率随着b、a和c射线能量的变化。所述探测器10的能量分辨率采用各种能量的g射线和各种能量的a粒子放射源测量，b射线由于是连续谱，将不用于系统能量分辨率的测量，所述探测器10对b粒子的能量分辨率和相同能量的g射线一样。对于连续晶体探测器，本发明通过制作5个宽度为0.1 mm间距为2 mm的狭缝，将b和a放射源放置于狭缝处，通过测量到的晶体分辨图的宽度和距离，对所述连续晶体探测器的位置分辨率进行估算。对于分割晶体阵列探测器，本发明采用g射线放射源从一定距离照射探测器，和使用b和a放射源，在所述分割晶体阵列探测器的整个表面扫描，测量对不同能量的粒子，晶体分辨图是否可以对每个晶体11单元做出清楚无误的区分。本发明还采用了和连续晶体探测器相同方法进行探测器10位置分辨率测量。
经性能测试结果表明，本发明的放射自显影系统100对b、a和低能c射线均具有较高的探测效率，相比传统的放射自显影方法，性能提升明显。
总的来讲，本发明采用镓酸铝钆晶体耦合SiPM阵列，结合PET中成熟的电子学系统，利用CFD、数字化甄别方法甄别α粒子和β粒子脉冲衰变时间的数量级差异，能够使得放射自显影系统100的发明位置分辨率逼近或达到闪烁晶体耦合光电转换器类型探测器10的物理极限，以此本发明提供了一种具有高灵敏度和高分辨率的，可以进行能量测量、光子计数、实时显示、脉冲形状甄别（α和β），且探测器不需要制冷的，适合于α粒子，β粒子和低能γ探测成像的探测器10和放射自显影系统100。
以上实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上实施例仅表达了本发明的优选的实施方式，其描述较为具体和详细，但并不能因此而理解为对发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。因此，本发明专利的保护范围应以所附权利要求为准。

Claims (10)

  1. 一种探测器，其特征在于，包括自下而上依次设置的晶体、光导以及光电转换器，所述晶体采用镓酸铝钆晶体，所述光电转换器采用硅光电倍增管阵列，其中所述晶体用于与放射性射线作用而产生荧光，所述光导用于将所述荧光导向至所述光电转换器，所述光电转换器用于将所述荧光转换为电信号，并采用信号读出电路将所述电信号传输至电子学系统。
  2. 根据权利要求1所述的探测器，其特征在于，所述晶体为连续晶体或分割晶体阵列，所述连续晶体和所述分割晶体阵列的厚度为1～5mm，所述分割晶体阵列的单个晶体的宽度为0.1～0.3mm。
  3. 根据权利要求2所述的探测器，其特征在于，所述晶体的厚度为1mm，所述硅光电倍增管阵列由多个面积为（1～3）×（1～3）mm 2的硅光电倍增管组成，所述硅光电倍增管阵列的厚度为1mm。
  4. 根据权利要求2所述的探测器，其特征在于，所述连续晶体的尺寸为9.6×9.6×1 mm 3，所述分割晶体阵列包括晶体大小为 0.11×0.11×1 mm 3的60×60阵列，晶体大小为 0.19×0.19×1 mm 3的40×40阵列以及晶体大小为 0.27×0.27×1 mm 3的24×24阵列，所述分割晶体阵列的晶体间采用厚度为50 mm的硫酸钡反射膜。
  5. 根据权利要求1所述的探测器，其特征在于，所述晶体的表面进行不抛光处理、两面抛光处理或者全抛光处理。
  6. 根据权利要求1所述的探测器，其特征在于，所述晶体和所述光导之间采用硅油或光学胶形成耦合，所述光电转换器和所述光导之间采用硅油或光学胶形成耦合。
  7. 根据权利要求1所述的探测器，其特征在于，所述光导为石英玻璃、有机玻璃、亚克力、光纤中的任一种；所述光导的厚度为0.1～10mm，层数为1～10层，硬度为2～6H。
  8. 根据权利要求1至7中任一项所述的探测器，其特征在于，所述信号读出电路为电阻网络读出电路，所述电阻网络读出电路用于将读出通道数从64将为4。
  9. 一种放射自显影系统，其特征在于，包括根据权利要求1至8中任一项所述的探测器、电连接于所述探测器的电子学系统、电连接于所述电子学系统的数据采集模块以及用于基于所述数据采集模块所采集的数据成像的图像显示模块。
  10. 一种根据权利要求9所述的放射自显影系统的成像方法，其特征在于，包括步骤：
    所述探测器的信号读出电路的4路信号输入所述电子学系统，所述电子学系统对4路信号进行成型放大和数字化处理，得到4路能量信号的数值；
    所述电子学系统在所述探测器的刻度模式下，将4路能量数据存贮到所述数据采集模块，并生成用于连续晶体探测器的计算位置和实际位置的关系刻度曲线和分割晶体阵列探测器的晶体查找表，并将结果上传到所述电子学系统；以及
    在成像阶段，所述电子学系统根据测量到的能量信号，在现场可编程门阵列中计算每个事件的初步能量和位置，通过计算位置和实际位置的关系刻度曲线或晶体查找表，将最后得到的事件能量和位置数据存贮于所述数据采集模块，以用于后期的进一步分析，同时将测量到的能量和位置数据实时显示于所述图像显示模块。
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