CN116203615A - Autoradiography system, detector and imaging method thereof - Google Patents

Autoradiography system, detector and imaging method thereof Download PDF

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Publication number
CN116203615A
CN116203615A CN202111456927.2A CN202111456927A CN116203615A CN 116203615 A CN116203615 A CN 116203615A CN 202111456927 A CN202111456927 A CN 202111456927A CN 116203615 A CN116203615 A CN 116203615A
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detector
crystal
array
crystals
light guide
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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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Shenzhen Institute of Advanced Technology of CAS
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Shenzhen Institute of Advanced Technology of CAS
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Priority to PCT/CN2021/137971 priority patent/WO2023097776A1/en
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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

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Abstract

The invention relates to an autoradiography system, a detector and an imaging method thereof, wherein the detector comprises crystals, light guides and photoelectric converters which are sequentially arranged from bottom to top, the crystals adopt aluminum gadolinium gallate crystals, the photoelectric converters adopt SiPM arrays, the detector is not required to be refrigerated, and the detector and the autoradiography system are suitable for alpha particle, beta particle and low-energy gamma detection imaging by adopting aluminum gadolinium gallate crystals to couple the SiPM arrays and combining with a mature electronic system in PET and utilizing a CFD (computational fluid dynamics) and digital screening method to screen the difference of the orders of magnitude of the pulse decay time of alpha particles and beta particles, so that the position resolution of the autoradiography system is approximate to or reaches the physical limit of a scintillation crystal coupled photoelectric converter type detector.

Description

Autoradiography system, detector and imaging method thereof
Technical Field
The invention relates to the technical field of medical equipment, in particular to an autoradiography system, a detector and an imaging method thereof.
Background
Conventional Autoradiography (AR) is a technique of forming a latent image by exposing silver halide in emulsion to radiation emitted from a radionuclide, developing and fixing the latent image to form a radionuclide distribution image. By means of the position and the intensity of the photosensitive silver particles, the distribution position and the intensity of the radioactive tracer can be accurately judged through image analysis, so that the metabolism of active substances in organisms, the distribution of specific antigens, receptors, DNA fragments and the like can be studied. AR is a non-living imaging technique that measures the distribution of radioactivity in a radiolabeled sample, a commonly used radiotracer is beta - Transmitting isotopes (e.g 3 H， 14 C， 35 S， 32 P， 33 P) and beta + The isotope is emitted (e.g., 18 F， 11 C， 15 o and 13 n), the distribution of the radioisotope-labeled drug in biological tissues and organs can be quantified. As shown in FIGS. 1 and 2, since the autoradiography technique is a technique of freezing fixed sectionsThe imaging 2D image is carried out, no metabolic change of physiological activities such as respiration, heartbeat, radio markers and the like in a living body exists during scanning, and the scanning time can be increased, so that an image with higher signal-to-noise ratio can be obtained, and high resolution and high quantitative accuracy can be achieved. The spatial resolution of AR can reach 50-300 μm. The high-resolution AR technology is still a key reference tool for functional neuroimaging of small animals, and plays a great role in verifying new molecular imaging contrast agents, checking the positioning and quantitative accuracy of PET research and the like. In small animal brain positron emission tomography (Positron Emission Tomography, PET) imaging studies, positron AR is more known as a "gold standard" for evaluating PET imaging quantification results. High resolution PET for small animals has been widely used in various preclinical biomedical research studies, and positron AR with higher resolution and higher quantitative accuracy is often employed as a test and supplement for PET scanning for small animals in order to verify the quantitative and positional accuracy of PET research for small animals.
In the field of autoradiography, the last five sixties began the traditional manual film autoradiography, which included the steps of tracer introduction, specimen preparation, autoradiography preparation and exposure processing, photo processing, and the like. After that, the thin film plastic scintillator is combined with a charge-coupled device (CCD) and the avalanche ionization chamber is combined with the beginning use of a CCD detector, so that the resolution of AR is further improved. The digital AR based on fluorescent phosphor screen technology has higher sensitivity and faster imaging time than the conventional method. The phosphor screen first stores radiation ionization caused by radioactivity, and then the laser is used for exciting the phosphor screen to generate visible light proportional to the radiation ionization, so that high-resolution and high-quantitative-precision images are obtained.
The detector combined by the high-density inorganic scintillation crystal and the photoelectric conversion device has high detection efficiency on high-energy gamma photons, and is the detector most commonly used for PET imaging. Limited by physical effects such as positron emission range and gamma photon non-collinearity (noncollinearity), the spatial resolution of the existing whole-body PET imaging instrument is 3-5mm. The small animal PET imaging system can achieve higher spatial resolution due to the smaller diameter of the detector ring, and the spatial resolution of the existing commercial small animal PET imaging system is 1-2mm.
In the conventional film autoradiography, the imaging time is longer, the manual operation is more complicated, and the imaging time is longer, often up to days or even months. Autoradiography using a plastic crystal coupling device CCD is performed on a radioisotope nuclide using beta-electrons (e.g.) 14 C， 35 S， 32 P, etc.), the spatial resolution available in the autoradiography experiment is further improved, the instrument adopts a technical mode of coupling plastic crystals with CCDs to detect electrons, but the dynamic range of the detector is smaller, and the sensitivity is lower. The phosphorus screen needs to be cleaned at a high temperature, so that the problems of imaging quality reduction and the like can be caused after the phosphorus screen is cleaned for many times, and the performance of an instrument is affected. In the high resolution small animal PET detectors that have been developed, it is preferable to have been able to resolve 0.5mm crystal units, however, although the physical limit of spatial resolution of the small animal PET imaging system is 0.5mm, there is some distance from the resolution that AR can achieve. That is, current AR detectors have low sensitivity and resolution, which cannot approach or reach the physical limits of the AR detector.
Disclosure of Invention
It is an object of the present invention to provide a detector and autoradiography system that has a position resolution approaching or reaching the physical limits of a scintillation crystal coupled photoelectric converter type detector, has high sensitivity, can perform energy measurement, photon counting, real-time display and pulse shape discrimination, and is suitable for alpha particle, beta particle and low energy gamma detection imaging without requiring refrigeration of the detector.
In one aspect, the invention provides a detector comprising a crystal, a light guide and a photoelectric converter, wherein the crystal, the light guide and the photoelectric converter are sequentially arranged from bottom to top, the crystal adopts aluminum gadolinium gallate crystal, the photoelectric converter adopts a silicon photomultiplier array, the crystal is used for reacting with radioactive rays to generate fluorescence, the light guide is used for guiding the fluorescence to the photoelectric converter, the photoelectric converter is used for converting the fluorescence into an electric signal, and a signal readout circuit is used for transmitting the electric signal to an electronic system.
In one embodiment of the present invention, the crystals are continuous crystals or split crystal arrays, the thickness of the continuous crystals and the split crystal arrays is 1 to 5mm, and the width of individual crystals of the split crystal arrays is 0.1 to 0.3mm.
In one embodiment of the present invention, the crystal has a thickness of 1mm, and the silicon photomultiplier array is formed of a plurality of silicon photomultiplier arrays each having an area of (1-3) × (1-3) mm 2 The thickness of the silicon photomultiplier array is 1mm.
In one embodiment of the invention, the continuous crystals have a size of 9.6X19.6X1 mm 3 The split crystal array includes a crystal size of 0.11×0.11×1mm 3 Is a 60×60 array of (2), the crystal size is 0.19×0.19×1mm 3 40×40 array of (a) and a crystal size of 0.27×0.27×1mm 3 The 24×24 array of the divided crystal array employs a barium sulfate reflective film having a thickness of 50 μm between crystals.
In an embodiment of the present invention, the surface of the crystal is subjected to a non-polishing treatment, a double-sided polishing treatment, or a full polishing treatment.
In an embodiment of the invention, the crystal and the light guide are coupled by silicone oil or optical glue, and the photoelectric converter and the light guide are coupled by silicone oil or optical glue.
In an embodiment of the present invention, the light guide is any one of quartz glass, organic glass, acryl, 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 2-6H.
In one embodiment of the invention, the thickness of the light guide is 1mm, the number of layers is 1, and the hardness is 3H.
In one embodiment of the invention, the signal sensing circuit is a resistive network sensing circuit for counting the number of sensing channels from 64 to 4.
The invention also provides an autoradiography system in another aspect, which comprises the detector, an electronic system electrically connected with the detector, a data acquisition module electrically connected with the electronic system, and an image display module for imaging based on data acquired by the data acquisition module.
In an embodiment of the present invention, the electronic system performs channel multiplexing of the silicon photomultiplier array by using one of a resistive network channel multiplexing method, a transmission line multiplexing method, a row-column sum multiplexing method, a capacitive network multiplexing method, and a coupling radio frequency coil multiplexing method.
A method of imaging an autoradiography system comprising the steps of:
4 paths of signals of the signal reading circuit of the detector are input into the electronic system, and the electronic system performs forming amplification and digital processing on the 4 paths of signals to obtain the numerical value of 4 paths of energy signals;
the electronic system stores 4 paths of energy data to the data acquisition module in a scale mode of the detector, generates a relation scale curve for calculating the position and the actual position of the continuous crystal detector and a crystal lookup table for dividing the crystal array detector, and uploads the result to the electronic system; and
in the imaging stage, the electronic system calculates the preliminary energy and position of each event in the field programmable gate array according to the measured energy signals, and stores the finally obtained event energy and position data in the data acquisition module for further analysis in the later stage through calculating a relation scale curve or a crystal lookup table of the position and the actual position, and simultaneously displays the measured energy and position data in the image display module in real time.
The invention has the following beneficial effects:
(1) The present invention uses gadolinium aluminum gallate crystals (Gd) with a density slightly lower than most commonly used LYSO crystals of PET detectors, but with a light output twice that of LYSO crystals, and without self-emission background 3 Al 2 Ga 3 O 12 Abbreviated as GAGG crystals), the density of GAGG crystals was 6.63g/cm 3 The detection efficiency of the beta, alpha and low-energy X-rays commonly detected by AR is still high, and GAGG crystalsThe light output of the body is 40-60 photons/keV, a high light output being advantageous for ensuring a high resolution of the detector of the invention;
(2) The thicknesses of the array crystal and the continuous crystal are preferably 1mm, so that the position resolution+ of the detector is not affected too much, the detection efficiency is very high for beta and alpha, and the detection efficiency is also certain for low-energy X rays;
(3) The invention adopts SiPM array as photoelectric converter, can realize high integration, is beneficial to reducing the volume of the detector, and has the detection area of 9.6X9.6 mm 2 And the SiPM array is coupled through the aluminum gadolinium gallate crystal, so that the performance of the detector is improved;
(4) The invention uses the mature event energy sampling method of the PET detector, and the mature pulse decay time screening method of the PET detector to screen the pulse of alpha particles and beta particles, so that the traditional constant ratio timing screening (Constant Fraction Discriminator, CFD) method can be used, and the digital screening method can be used for accurately measuring the decay time parameter of the pulse;
(5) The detector provided by the invention adopts the modularized spliced design of the crystal, the light guide and the photoelectric converter, a user can customize the detection area according to actual requirements, the use is more independent, and the detection freedom degree is higher.
Further objects and advantages of the present invention will become fully apparent from the following description and the accompanying drawings.
Drawings
FIG. 1 is a schematic illustration of an autoradiography flow based on CCD detector;
FIG. 2 is an imaging view of a mouse brain slice based on autoradiography of a CCD detector;
FIG. 3 is a schematic view of the structure of the detector according to a preferred embodiment of the present invention;
FIG. 4 is another structural schematic diagram of the crystal of the detector according to the above preferred embodiment of the present invention;
FIG. 5 is a photograph of an SiPM array of the detector according to the above preferred embodiment of the present invention;
FIG. 6 is a schematic diagram of a resistive network readout circuit of the detector according to the above preferred embodiment of the present invention;
FIG. 7 is a schematic view of the structure and workflow of the electronics system of the autoradiography system according to the preferred embodiment of the present invention;
FIG. 8 is a block schematic diagram of the autoradiography system according to the above preferred embodiment of the present invention;
fig. 9 is a graph showing the results of the performance test of the autoradiography system according to the above preferred embodiment of the present invention.
Reference numerals illustrate: an autoradiography system 100; a detector 10; a crystal 11; a light guide 12; a photoelectric converter 13; a signal readout circuit 131; an electronics system 20; a computer 30; a data acquisition module 31; an image display module 32.
Detailed Description
The following description is presented to enable one of ordinary skill in the art to make and use the invention. The preferred embodiments in the following description are by way of example only and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
It will be appreciated by those skilled in the art that in the present disclosure, the terms "vertical," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc. refer to an orientation or positional relationship based on that shown in the drawings, which is merely for convenience of description and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore the above terms should not be construed as limiting the present invention.
It will be understood that the terms "a" and "an" should be interpreted as referring to "at least one" or "one or more," i.e., in one embodiment, the number of elements may be one, while in another embodiment, the number of elements may be plural, and the term "a" should not be interpreted as limiting the number.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically connected, electrically connected or can be communicated with each other; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
The invention provides an autoradiography system with the position resolution approaching or reaching the physical limit of a scintillation crystal coupling photoelectric converter type detector by adopting a continuous crystal detector or a split crystal array (the width of a single crystal is 0.1-0.3 mm) detector and combining with mature electronics in PET. The autoradiography system has the advantages of high sensitivity, capability of carrying out energy measurement, photon counting, real-time display and pulse shape discrimination (alpha and beta), no need of refrigeration, simplicity, low cost and the like, and is suitable for alpha particle, beta particle and low-energy gamma detection imaging.
As shown in fig. 3 to 7, the structure of an autoradiography system 100 and its detector 10 and imaging method according to the present invention is specifically illustrated.
As shown in fig. 3 to 6, the detector 10 includes a crystal 11, a light guide 12, and a photoelectric converter 13 sequentially disposed from bottom to top, the crystal 11 is an aluminum gadolinium gallate crystal, the photoelectric converter 13 is a silicon photomultiplier array, wherein the crystal 11 is used for reacting with radioactive rays to generate fluorescence, the light guide 12 is used for guiding the fluorescence light 12 to the photoelectric converter 13, the photoelectric converter 13 is used for converting the fluorescence light into an electrical signal, and the electrical signal is transmitted to the electronic system 20 by using a signal readout circuit 131.
It should be noted that, silicone oil or optical glue coupling is adopted between the crystal 11 and the light guide 12, and silicone oil or optical glue coupling is also adopted between the light guide 12 and the photoelectric converter 13, that is, the light guide 12 is coupled between the crystal 11 and the photoelectric converter 13.
It will be appreciated that the present invention uses GAGG crystals that have a slightly lower density than the most commonly used LYSO crystals of PET detectors, but twice the light output as LYSO crystals, and no self-emission background. The GAGG crystals had a density of 6.63g/cm 3 Still having high detection efficiency for the beta, alpha and low energy χ rays normally detected by AR, the light output of the GAGG crystal is 40-60 photons/keV, and high light output is advantageous to ensure high resolution of the detector 10.
It will be further appreciated that the present invention introduces the detector mode of the inorganic scintillation crystal array coupled photo-conversion device in the nuclear detector design mode into the field of autoradiography instrument design, and uses the latest photo-conversion device, namely a silicon photomultiplier (SiPM), as the main photo-conversion device, and compared with the conventional autoradiography method, the performance of the detector 10 of the present invention is improved significantly.
That is, the present invention can effectively enhance the performance of the detector 10 by employing an aluminum gadolinium gallate crystal coupled silicon photomultiplier array. The detector 10 of the present invention based on a GAGG crystal and SiPM array can be used for imaging organs such as the heart, kidneys and brain of mice, and the specific application of the detector 10 is not limited by the present invention.
In particular, as shown in fig. 3, in one embodiment of the present invention, the crystal 11 is a continuous crystal, and as shown in fig. 4, in another embodiment of the present invention, the crystal 11 may be a segmented crystal array, that is, the detector 10 of the present invention may be a continuous crystal detector or a segmented crystal array detector, and may perform self-development imaging on a slice having a thickness of 20-100 μm.
Specifically, the thickness h1 of the crystal 11 is 1 to 5mm, preferably 1mm. That is, the thickness of the continuous crystal and the divided crystal array is 1 to 5mm, preferably 1mm.
Preferably, in this particular embodiment of the invention, the width w of the individual crystals of the segmented crystal array is 0.1-0.3 mm.
In particular, in this particular embodiment of the invention, the crystal 11 has a thickness of 1mm, and the silicon photomultiplier array is composed of a plurality of silicon photomultiplier arrays each having an area of (1-3) × (1-3) mm 2 The thickness h3 of the silicon photomultiplier array is 1mm.
That is, the SiPM array is composed of a plurality of unit silicon photomultipliers, as shown in FIG. 5, the unit area of which may be 1X 1mm 2 May be 2X 2mm 2 ，3×3mm 2 The invention is not limited in this regard.
In particular, in this particular embodiment of the invention, the SiPM array may be selected to have a cell size of 1X 1mm 2 Is 8 x 8SiPM array of 9.6x9.6x1 mm in overall size 3 The SiPM array has a minimum detection area, and a minimum dead zone area of only 0.2mm, which is advantageous for ensuring the detection performance of the detector 10.
It will be appreciated that for the detector 10 employing a segmented crystal array, the best detection area for the back-end coupling element is 1X 1mm by using GAGG crystals with a maximum light output (twice LYSO) of 0.1-0.3 mm, 1mm thick 2 The SiPM of the particle detector is matched with a multiplexing resistor network commonly used for PET, and the order of magnitude difference of alpha particle pulse decay time and beta particle pulse decay time is screened by using a CFD (computational fluid dynamics) and digital screening method, so that compared with the traditional autoradiography method of a phosphorus screen and the like, the particle detector has the advantages of high sensitivity, capability of measuring energy, photon counting, real-time display, pulse shape screening (alpha and beta), no need of refrigeration, simplicity, low cost and the like, and is suitable for alpha particle, beta particle and low-energy gamma detection imaging.
It will also be appreciated that in this particular embodiment of the invention, since the thickness of the crystal 11 is selected to be 1mm, i.e., the thickness of both the continuous crystal and the array crystal 11 are selected to be 1mm, the positional resolution of the detector 10 is not significantly affected, there is a high detection efficiency for beta and alpha, and there is some detection efficiency for low energy χ rays.
In addition, because the invention adopts the SiPM array as the photoelectric converter 13, the invention can realize high integration, is beneficial to reducing the volume of the detector 10, and has the detection area of about 9.6X9.6 mm 2 Moreover, the detector 10 adopts the modular and spliced design of the crystal 11, the light guide 12 and the photoelectric converter, so that a user can customize the detection area according to actual requirements, and the detector is more autonomous to use and has higher detection freedom.
It will be appreciated that with a modular design, 9.6X9.6 mm can be used 2 The basic detector modules of the system are spliced into other required sizes for personalized requirement design, and the non-modularized large detector can be used for directly testing, so that the invention is not limited to the method.
In an embodiment of the present invention, the photoelectric converter 13 may be any one of a PSPMT (position sensitive photomultiplier), a PMT (photomultiplier tube, photomultiplier), a CCD (Charge-coupled Device), an APD (Avalanche Photo Diode avalanche photodiode), and a PSAPD (Position sensitive Avalanche Photo Diode position sensitive avalanche photodiode), which is not limited in the present invention.
In some embodiments of the invention, the size of the continuous crystals may be 9.6X1.6X1 mm, depending on the size of the SiPM array 3 . The split crystal array includes a crystal size of 0.11×0.11×1mm 3 Is a 60×60 array of (2), the crystal size is 0.19×0.19×1mm 3 40×40 array of (a) and a crystal size of 0.27×0.27×1mm 3 The 24×24 array of the divided crystal array employs a barium sulfate reflective film having a thickness of 50 μm between crystals.
Further, the surface of the crystal 11 may be subjected to a non-polishing treatment, a double-sided polishing treatment, or a full polishing treatment, to which the present invention is not limited.
It should be noted that, the light guide 12 is used for receiving the crystal 11 and the photoelectric converter 13, and not more than ten layers of light guides can be used for designing, and the thickness of the light guide 12 can also be designed according to specific needs, and the light guide 12 is any one of quartz glass, organic glass, acryl, and optical fiber.
Specifically, the thickness H2 of the light guide 12 is 0.1 to 10mm, the number of layers is 1 to 10, and the hardness is 2 to 6H.
Preferably, in this particular embodiment of the present invention, the thickness of the light guide 12 is 1mm, the number of layers is one, and the hardness is 3H.
As shown in fig. 6, the signal readout circuit 131 is a resistive network readout circuit for changing the number of readout channels from 64 to 4.
In particular, the resistive network readout circuit is a multiplexed resistive network circuit commonly used for PET detectors.
The invention uses the mature event energy sampling method of the PET detector and the mature pulse decay time screening method of the PET detector to screen the pulse of alpha particles and beta particles, and can accurately measure the decay time parameter of the pulse by using the traditional constant ratio timing screening (Constant Fraction Discriminator, CFD) method and the digital screening method.
As shown in fig. 7 and 8, the present invention also provides, in another aspect, an autoradiography system 100, the autoradiography system 100 comprising the detector 10, an electronics system 20 electrically connected to the detector 10, a data acquisition module 31 electrically connected to the electronics system 20, and an image display module 32 for imaging based on data acquired by the data acquisition module 31.
As shown in fig. 7, the imaging method of the autoradiography system 100 includes the steps of:
4 paths of signals of the signal reading 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 paths of signals to obtain values of 4 paths of energy signals;
the electronics system 20 stores 4 paths of energy data to the computer 30 in the scale mode of the detector 10, generates a relationship scale curve for the calculated position and the actual position of the continuous crystal detector and a crystal lookup table for dividing the crystal array detector off-line, and uploads the result to the electronics system 20; and
in the imaging phase, the electronics system 20 calculates the preliminary energy and position of each event in a Field programmable gate array (Field-Programmable Gate Array, FPGA for short) based on the measured energy signals, and stores the resulting event energy and position data in the computer 30 for later further analysis by calculating a relationship scale curve or a crystal look-up table of the position and actual position, while displaying the measured energy and position data on the computer 30 screen in real time.
It should be noted that the computer 30 includes the data acquisition module 31 and the image display module 32, the data acquisition module 31 is configured to store data, and the image display module 32 is configured to image and display images based on the data acquired by the data acquisition module 31.
In addition, it should be noted that the electronic system 20 may perform channel multiplexing of the silicon photomultiplier array by using one of a resistive network channel multiplexing method, a transmission line multiplexing method, a row-column sum multiplexing method, a capacitive network multiplexing method, and a coupled radio frequency coil multiplexing method.
The specific way of calculating the position and energy of the detector 10 is as follows:
specifically, the detector 10 may calculate the position of an event in the crystal resolution map using the following formula:
X＝(B+C)/E,Y＝(C+D)/E；
in the above formula, a, B, C, D are 4 energy signals related to positions read out by the SiPM array resistor network, E is energy of the detector 10, and X and Y are coordinate positions of the event in the crystal resolution diagram; wherein E is calculated by the following formula:
E＝A+B+C+D。
the present invention performed performance testing on the autoradiography system 100, one of which is shown in FIG. 9. In this particular performance test, the autoradiography system 100 employs a splitA segmented crystal array detector having a segmented crystal array of 0.27×0.27×1mm 3 24 x 24 array of (a), i.e. the individual crystal bar areas of the segmented crystal array are 0.27 x 0.27mm 2 Comprises a 24×24 crystal array, and the split crystal array detector adopts a monolithic area of 2×2mm 2 An 8 x 8SiPM array of (c) as a photoelectric converter. FIG. 9 shows the result of the position spectrum, wherein each bright point represents the response of one crystal bar in the autoradiography system 100, and the brightness of the bright point is proportional to the number of rays received on the corresponding crystal bar. From the results, it can be seen that 24×24 crystal bars are clearly discernable in the position spectrum statistics.
The performance test of the autoradiography system 100 is primarily to measure the variation of energy resolution and positional resolution with beta, alpha, and χ ray energy. The energy resolution of the detector 10 is measured by using gamma rays of various energies and alpha particle radiation sources of various energies, and the beta rays are not used for measuring the energy resolution of the system because of continuous spectrum, and the energy resolution of the detector 10 on the beta particles is the same as that of the gamma rays of the same energy. For a continuous crystal detector, the invention estimates the position resolution of the continuous crystal detector by making 5 slits with a width of 0.1mm and a spacing of 2mm, placing beta and alpha radioactive sources at the slits, and measuring the width and the distance of a crystal resolution map. For a split crystal array detector, the invention irradiates the detector from a certain distance by using a gamma ray radiation source, scans the whole surface of the split crystal array detector by using beta and alpha radiation sources, and measures whether particles with different energies can be clearly distinguished from each crystal 11 unit or not by using a crystal resolution diagram. The present invention also uses the same method as a continuous crystal detector to make a detector 10 position resolution measurement.
The performance test result shows that the autoradiography system 100 has higher detection efficiency on beta, alpha and low-energy X rays, and has obviously improved performance compared with the traditional autoradiography method.
In general, the invention adopts aluminum gadolinium gallate crystal coupled SiPM array, combines with mature electronic system in PET, utilizes CFD, digital screening method to screen the order of magnitude difference of alpha particle and beta particle pulse decay time, can make the position resolution of the autoradiography system 100 approach or reach the physical limit of the scintillation crystal coupled photoelectric converter type detector 10, thus the invention provides a detector 10 and an autoradiography system 100 which have high sensitivity and high resolution, can perform energy measurement, photon counting, real-time display, pulse shape screening (alpha and beta), does not need refrigeration, and is suitable for alpha particle, beta particle and low energy gamma detection imaging.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples only represent preferred embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (10)

1. The detector is characterized by comprising a crystal, a light guide and a photoelectric converter, wherein the crystal, the light guide and the photoelectric converter are sequentially arranged from bottom to top, the crystal is an aluminum gadolinium gallate crystal, the photoelectric converter is a silicon photomultiplier array, the crystal is used for reacting with radioactive rays to generate fluorescence, the light guide is used for guiding the fluorescence to the photoelectric converter, the photoelectric converter is used for converting the fluorescence into an electric signal, and a signal readout circuit is used for transmitting the electric signal to an electronic system.
2. The detector of claim 1, wherein the crystal is a continuous crystal or an array of segmented crystals, the continuous crystal and the array of segmented crystals having a thickness of 1 to 5mm, the individual crystals of the array of segmented crystals having a width of 0.1 to 0.3mm.
3. The detector of claim 2, wherein the crystal has a thickness of 1mm, and the silicon photomultiplier array is formed of a plurality of silicon photomultiplier arrays each having an area of (1-3) × (1-3) mm 2 The thickness of the silicon photomultiplier array is 1mm.
4. The detector of claim 2, wherein the continuous crystals have a size of 9.6x9.6x1 mm 3 The split crystal array includes a crystal size of 0.11×0.11×1mm 3 Is a 60×60 array of (2), the crystal size is 0.19×0.19×1mm 3 40×40 array of (a) and a crystal size of 0.27×0.27×1mm 3 The 24×24 array of the divided crystal array employs a barium sulfate reflective film having a thickness of 50 μm between crystals.
5. The detector of claim 1, wherein the surface of the crystal is subjected to a non-polishing treatment, a double-sided polishing treatment, or a full polishing treatment.
6. The detector of claim 1, wherein the crystal and the light guide are coupled using silicone oil or optical glue, and the photoelectric converter and the light guide are coupled using silicone oil or optical glue.
7. The detector of claim 1, wherein the light guide is any one of quartz glass, plexiglas, acryl, optical fiber; the thickness of the light guide is 0.1-10 mm, the number of layers is 1-10, and the hardness is 2-6H.
8. The detector according to any one of claims 1 to 7, wherein the signal readout circuit is a resistive network readout circuit for switching the number of readout channels from 64 to 4.
9. An autoradiography system comprising a detector according to any one of claims 1 to 8, an electronics system electrically connected to the detector, a data acquisition module electrically connected to the electronics system, and an image display module for imaging based on data acquired by the data acquisition module.
10. A method of imaging an autoradiography system according to claim 9, comprising the steps of:
4 paths of signals of the signal reading circuit of the detector are input into the electronic system, and the electronic system performs forming amplification and digital processing on the 4 paths of signals to obtain the numerical value of 4 paths of energy signals;
the electronic system stores 4 paths of energy data to the data acquisition module in a scale mode of the detector, generates a relation scale curve for calculating the position and the actual position of the continuous crystal detector and a crystal lookup table for dividing the crystal array detector, and uploads the result to the electronic system; and
in the imaging stage, the electronic system calculates the preliminary energy and position of each event in the field programmable gate array according to the measured energy signals, and stores the finally obtained event energy and position data in the data acquisition module for further analysis in the later stage through calculating a relation scale curve or a crystal lookup table of the position and the actual position, and simultaneously displays the measured energy and position data in the image display module in real time.
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