Detection imaging method and device for accurately obtaining depth of gamma photons

Abstract

The invention provides a detection imaging method and device for accurately obtaining the depth of gamma photons, and relates to the field of radiation detection.The method comprises the steps that after gamma rays enter a segmented scintillation crystal strip, the signal intensities of the two ends of the segmented scintillation crystal strip are obtained through the double-end reading technology, and a DOI factor is calculated based on the difference of the signal intensities of the two ends, a plurality of adjacent crystal sections in the scintillation crystal strip are designed into scintillation crystals with different decay time constants; a waveform discrimination technology is introduced, and a PSD factor is calculated according to output waveform differences of crystals at different decay times; and constructing a two-dimensional statistical graph according to the DOI factor and the PSD factor, carrying out classification discrimination on the gamma event through different areas in the two-dimensional statistical graph, determining a crystal segment where the gamma event occurs, and further obtaining the depth position of the crystal segment. According to the invention, the double-end reading technology and the waveform discrimination technology are combined, and the limit DOI resolution of the scintillation crystal detector can be further improved by comparing the difference between the signals at the two ends and combining the waveform characteristics of the signals.

Description

Technical Field

[0001] The present application relates to the field of radiation detection, and particularly to a detection imaging method and device for accurately obtaining the depth of gamma photons. Background Art

[0002] In a scintillation crystal detector with three-dimensional position localization ability, improving the detection accuracy of the photon interaction depth position (Depth of Interaction, DOI) has always been a research hotspot. Especially in the design of gamma locators, Compton cameras, small animal PETs, and organ-level PET systems, there is an urgent need to improve their spatial resolution performance. Currently, scintillation crystals can achieve a planar position localization ability of 0.35 mm, but in the depth direction, there is still a lack of a practical way to improve the resolution ability to the submillimeter level.

[0003] Currently, the methods for obtaining DOI by scintillator detectors are mainly divided into two types.

[0004] The first approach is in the spatial dimension: through spectroscopic design, controlling the distribution of scintillation photons detected by events at different DOIs to be different, and determining the DOI by discriminating this difference in light distribution.

[0005] The second approach is in the time dimension: stacking multiple crystals to form a detector. Different types of scintillation crystals have different light emission time decay constants, corresponding to different pulse waveforms for the detected signals. The DOI is determined by pulse shape discrimination (PSD) to determine in which crystal the event occurs. Currently, this method can achieve the discrimination of 3 crystals.

[0006] However, all current methods extract DOI information from parameters in one dimension and it is difficult to achieve submillimeter DOI resolution. The current solutions that can achieve submillimeter DOI resolution increase the number of SiPMs by at least 3 times compared to other solutions, greatly increasing the scale of signal processing and also restricting the spatial arrangement of the detector. Summary of the Invention

[0007] The present application aims to solve the problem that the current DOI resolution in radiation detection devices is difficult to reach the submillimeter level, and at least solve one of the technical problems in the related art to a certain extent.

[0008] To this end, the first object of the present application is to propose a detection imaging method for accurately obtaining the depth of gamma photons.

[0009] The second object of the present application is to propose a detection imaging device for accurately obtaining the depth of gamma photons.

[0010] The third object of the present application is to propose an electronic device.

[0011] The fourth object of the present application is to propose a computer-readable storage medium.

[0012] The fifth object of the present application is to propose a computer program product.

[0013] To achieve the above object, an embodiment of the first aspect of the present application proposes a detection imaging method for accurately obtaining the depth of gamma photons, including:

[0014] After gamma rays are incident on the segmented scintillation crystal bar, the signal intensities at both ends of the segmented scintillation crystal bar are obtained by using the double-ended readout technology, and the DOI factor is calculated based on the difference in signal intensities at both ends, wherein a plurality of adjacent crystal segments in the scintillation crystal bar are designed as scintillation crystal types with different decay time constants;

[0015] The waveform discrimination technology is introduced, and the PSD factor is calculated according to the difference in the output waveforms of crystals with different decay times;

[0016] A two-dimensional statistical graph is constructed according to the DOI factor and the PSD factor, and gamma events are classified and discriminated through different regions in the two-dimensional statistical graph to determine the crystal segment where the gamma event occurs, and then its depth position is obtained.

[0017] Optionally, the step of obtaining the signal intensities at both ends of the segmented scintillation crystal bar by using the double-ended readout technology and calculating the DOI factor based on the difference in signal intensities at both ends includes:

[0018] The signal intensities of the SiPMs at both ends of the segmented scintillation crystal bar are obtained by using the double-ended readout technology, and are respectively denoted as S 1 and S 2 ; wherein, the calculation formula for the signal intensity S of a certain end SiPM is:

[0019] S = ∫Wdt

[0020] wherein, W is the waveform obtained by amplifying the signal generated by a certain end SiPM;

[0021] Based on the difference between the signal intensities S 1 and S 2 , the DOI factor is calculated, and the formula is:

[0022]

[0023] wherein, DOI is the DOI factor.

[0024] Optionally, the step of introducing the waveform discrimination technology and calculating the PSD factor according to the difference in the output waveforms of crystals with different decay times includes:

[0025] According to the characteristics of the waveform after summing at both ends, the PSD factor is calculated.

[0026] Optionally, the calculating the PSD factor according to the characteristics of the waveform after summing at both ends includes:

[0027] Calculating the PSD factor by dividing the sum of the signal intensities at both ends by the maximum value of the sum of the signals at both ends;

[0028] Or, calculating the PSD factor by dividing the integral value of a partial waveform by the integral value of the overall waveform.

[0029] Optionally, the calculating the PSD factor by dividing the sum of the signal intensities at both ends by the maximum value of the sum of the signals at both ends includes:

[0030]

[0031] Wherein, PSD is the PSD factor, W 1 and W 2 are the signals of the SiPMs at both ends respectively.

[0032] To achieve the above object, an embodiment of the second aspect of the present application provides a detection imaging device for accurately obtaining the depth of gamma photons, including:

[0033] A first calculation module, configured to, after gamma rays are incident on a segmented scintillation crystal bar, use a double-ended readout technique to obtain the signal intensities at both ends of the segmented scintillation crystal bar, and calculate the DOI factor based on the difference in the signal intensities at both ends, wherein a plurality of adjacent crystal segments in the scintillation crystal bar are designed as scintillation crystal types with different decay time constants;

[0034] A second calculation module, configured to introduce a waveform discrimination technique and calculate the PSD factor according to the difference in the output waveforms of crystals with different decay times;

[0035] A classification and discrimination module, configured to construct a two-dimensional statistical graph according to the DOI factor and the PSD factor, classify and discriminate gamma events through different regions in the two-dimensional statistical graph, determine the crystal segment where the gamma event occurs, and further obtain its depth position.

[0036] To achieve the above object, an embodiment of the third aspect of the present application provides an electronic device, including: a processor, and a memory communicatively connected to the processor;

[0037] The memory stores computer execution instructions;

[0038] The processor executes the computer execution instructions stored in the memory to implement the method according to any one of the above first aspects.

[0039] To achieve the above object, an embodiment of the fourth aspect of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, they are used to implement the method described in any one of the above first aspects.

[0040] To achieve the above object, an embodiment of the fifth aspect of the present application provides a computer program product, including a computer program, which when executed by a processor implements the method described in any one of the above first aspects.

[0041] The technical solutions provided by the embodiments of the present application at least bring the following beneficial effects:

[0042] Compared with other methods for estimating DOI information in a scintillating crystal, the main advantage of the present application is the introduction of new estimation parameters. Different from other methods that obtain DOI information through a single path, the present application combines information from two dimensions of intensity distribution and time distribution to jointly estimate DOI information, thereby being able to further improve the ultimate DOI resolution of the scintillating crystal detector. Verification experiments show that the joint gamma photon depth position estimation method of double-ended readout plus waveform discrimination can achieve sub-millimeter DOI resolution, and the formed array can also achieve sub-millimeter three-dimensional position resolution ability.

[0043] Compared with the published pixelated detector structures with single-ended or double-ended readout, the present application further improves the DOI resolution, enabling the scintillator to achieve three-dimensional sub-millimeter resolution performance.

[0044] Compared with the proposed six-sided readout structure, the present application can reduce the number of electronics readout channels by at least three times while achieving a similar DOI resolution, thus being more convenient for cost savings and reducing the amount of data.

[0045] In addition, the present application performs three-dimensional pixelization on the crystal array, simplifying the detector calibration process.

[0046] At the same time, the present application has a high degree of freedom in crystal type selection and crystal segment design, and can be flexibly designed according to actual needs.

[0047] Additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and / or additional aspects and advantages of the present application will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0049] Figure 1Schematic flowchart of a detection imaging method for accurately obtaining the depth of gamma photons provided by an embodiment of the present application;

[0050] Figure 2 Statistical chart of DOI factors obtained when a radiation source is used for general field irradiation on the side of a crystal bar provided by an embodiment of the present application;

[0051] Figure 3 Schematic diagram of the cyclic arrangement structure of a segmented crystal composed of multiple decay time crystals provided by an embodiment of the present application;

[0052] Figure 4 Design schematic diagram of a scintillation crystal bar composed of crystals with different decay time constants provided by an embodiment of the present application;

[0053] Figure 5 Waveform schematic diagram of signals generated by crystals with different decay time constants provided by an embodiment of the present application;

[0054] Figure 6 PSD-DOI schematic diagram provided by an embodiment of the present application;

[0055] Figure 7 Physical schematic diagram of a 12×12 crystal array composed of multiple crystal bars provided by an embodiment of the present application;

[0056] Figure 8 For the present application embodiment provided Figure 7 PSD-DOI schematic diagram of all events obtained by testing the crystal array shown;

[0057] Figure 9 Position statistical chart drawn according to events of each crystal layer provided by an embodiment of the present application;

[0058] Figure 10 Schematic flowchart of a detection imaging device for accurately obtaining the depth of gamma photons provided by an embodiment of the present application. Detailed implementation manners

[0059] The embodiments of the present application are described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application.

[0060] Currently, the methods for obtaining DOI by scintillation detectors are mainly divided into two types.

[0061] The first approach is in the spatial dimension: Through spectroscopic design, the distribution of scintillation photons detected for events at different DOIs is controlled to be different, and the DOI is determined by discriminating this difference in light distribution. The specific methods under this approach are as follows:

[0062] (1) A whole crystal is coupled to an array of silicon photomultiplier (SiPM) devices at a single end. The distribution of photons on the SiPM array at different three-dimensional detection positions within the crystal is different, resulting in different signal distributions. This method can achieve a DOI resolution of approximately 3 mm for crystals with a thickness of no less than 15 mm.

[0063] (2) A crystal module composed of multiple layers of crystal wafers is coupled to the SiPM array at a single end. At this time, the DOI on each crystal wafer is determined by the broadening of the photon distribution in the continuous direction of the crystal. This method can currently achieve a DOI resolution of approximately 1.5 mm for a 1 mm × 37.6 mm × 20 mm thick crystal.

[0064] (3) A two-dimensional crystal array composed of slender crystal bars is coupled to the SiPM array at a single end, and light sharing is performed at the crystal pixels (such as through a special reflective film design or adding a light transmission channel at the top), so that the local light distribution is sensitive to DOI changes. This method can achieve a resolution of 2.52 mm for a 20 mm thick crystal.

[0065] (4) A crystal array composed of crystal bars is coupled to SiPM arrays at both ends, and the DOI information is determined by comparing the signal differences at both ends. This method can achieve a DOI resolution of 1.67 mm for a 1 mm × 1 mm × 20 mm crystal unit.

[0066] (5) A three-dimensional crystal array composed of crystal cubes is read out on all six sides, and the crystal cube in which the event occurs is obtained by analyzing the signal distribution on the six sides. This method can currently achieve a DOI resolution of 0.77 mm for a 13.1 × 13.1 mm × 13.1 mm crystal module.

[0067] The second approach is in the time dimension: Multiple types of crystals are stacked to form a detector. Different types of scintillation crystals have different light emission time decay constants, corresponding to different pulse waveforms for the detected signals. The DOI is determined by means of pulse shape discrimination (PSD) to determine in which crystal the event occurs. This method can currently achieve the discrimination of 3 types of crystals.

[0068] To solve the problem that the current DOI resolution is difficult to reach the sub - millimeter level, the embodiments of the present application provide a detection imaging method for accurately obtaining the depth of gamma photons. By comparing the signal differences at both ends and combining the signal waveform characteristics, a higher DOI resolution can be achieved compared to the current single - way method of obtaining DOI information. Moreover, the detector designed based on this new DOI estimation method can be applied to the design of gamma locators, Compton cameras, small - animal PETs, and organ - level PET systems, improving their spatial resolution performance.

[0069] Figure 1 It is a schematic flow chart of a detection imaging method for accurately obtaining the depth of gamma photons provided by the embodiments of the present application. As Figure 1 shown, the method includes the following steps:

[0070] Step 101, after gamma rays are incident on the segmented scintillation crystal bar, use the double - end readout technology to obtain the signal intensities at both ends of the segmented scintillation crystal bar, and calculate the DOI factor based on the difference in signal intensities at both ends. Among them, multiple adjacent crystal segments in the scintillation crystal bar are designed as scintillation crystal types with different decay time constants.

[0071] For the existing double - end readout method, for a segmented scintillation crystal bar, if the specific crystal segment where the gamma event occurs can be determined, the event position can be restricted to a local area within the crystal bar. Therefore, the minimum length of the distinguishable crystal segments determines the DOI resolution of the segmented crystal bar. Generally, the double - end readout estimates the DOI by calculating a parameter value, which is defined as the DOI factor in the embodiments of the present application to reflect the actual event position.

[0072] In the embodiments of the present application, first, use the double - end readout technology to obtain the signal intensities of the SiPMs at both ends of the segmented scintillation crystal bar, denoted as S 1 and S 2 . The double - end readout technology arranges SiPMs (silicon photomultiplier devices) at both ends of the crystal bar to read the scintillation light signals caused by incident gamma rays respectively. The calculation formula for the signal intensity S of each SiPM is:

[0073] S = ∫Wdt

[0074] where W is the waveform obtained after amplifying the signal generated by the SiPM at one end. In the embodiments of the present application, the waveform signal is the scintillation light signal generated after the photons in the scintillation crystal bar interact with the crystal, and is detected by the SiPM array and converted into an electronic signal.

[0075] Next, the present application calculates the DOI factor based on the difference between the signal intensities S 1 and S 2 . The calculation formula for the DOI factor is as follows:

[0076]

[0077] Among them, DOI is the DOI factor.

[0078] It should be noted that, due to the existence of an interface with discontinuous optical properties between the crystal segments of the segmented crystal, the DOI factor values within each crystal segment are relatively close, and there are differences in the DOI factors between crystal segments due to the existence of the interface. The conventional calibration method is to perform a general field irradiation on the side of the crystal strip using a radiation source. At this time, the statistical chart of the DOI factor obtained is as Figure 2 shown, which can be regarded as the superposition of the event distributions of each crystal segment. When the number of crystal segments is small, the responses of adjacent crystal segments are far apart, and obvious peak structures corresponding to each crystal segment can be seen on the DOI factor curve at this time. Increasing the number of crystal segments will make the responses of adjacent crystal segments closer and closer until the two peaks are superimposed and indistinguishable. At this time, this detector structure reaches the DOI resolution limit. Currently, the limit DOI resolution of the segmented crystal double-ended readout for a 1mm×1mm×20mm crystal strip is 1.67mm.

[0079] To solve the problem that adjacent crystal segments cannot be distinguished, the present application introduces a pulse shape discrimination technology (PSD) to distinguish adjacent crystal segments, and designs multiple adjacent crystal segments in the scintillating crystal strip as scintillating crystal types with different decay time constants. The specific content will be described in step 102.

[0080] Step 102, introduce the pulse shape discrimination technology, and calculate the PSD factor according to the output waveform differences of crystals with different decay times.

[0081] As described in step 101, to solve the problem that adjacent crystal segments cannot be distinguished, the present application introduces a pulse shape discrimination technology (PSD) to distinguish adjacent crystal segments. Specifically, the crystal segments in the scintillating crystal strip are distinguished by designing them as scintillating crystal types with different decay time constants, and these crystal segments are arranged in a certain structure within the crystal strip. In an embodiment of the present application, three adjacent crystal segments in the crystal strip are designed as scintillating crystal types with different decay time constants, and these crystal segments are arranged in a structure of three crystals in a cyclic arrangement, as Figure 3 shown.

[0082] The advantage of this design is that, through the difference in decay time constants between different crystal segments, the photon output waveforms of each crystal segment can show obvious different characteristics, so that the position where the event occurs can be estimated more accurately. Especially under the requirement of high DOI resolution, using crystal types with different decay time constants can effectively avoid the cross-interference of the responses of adjacent crystal segments, thereby improving the accuracy of DOI estimation.

[0083] Under this structure, the parameters for estimating the DOI position increase to two: one is the DOI factor of the signal intensity difference obtained through the double-ended readout technique, and the other is the difference in the output waveforms of crystals with different decay times, which is characterized by the waveform discrimination parameter (PSD factor). The core purpose of introducing the PSD factor is to further improve the DOI positioning accuracy at high resolution. Especially when the signal characteristics of adjacent crystal segments are close, the PSD factor can effectively distinguish adjacent crystal segments and avoid the resolution degradation caused by signal overlap in traditional methods.

[0084] In the embodiment of the present application, the PSD factor is obtained by analyzing the signal waveform amplified by the SiPM. There are two calculation methods:

[0085] The first calculation method calculates the PSD factor by dividing the sum of the signal intensities at both ends by the maximum value after adding the signals at both ends. The advantage of this method is that it can make full use of the difference in the signal waveforms at both ends and is suitable for distinguishing different types of crystals.

[0086] The second calculation method calculates the PSD factor by dividing the integral value of the partial waveform signals at both ends by the integral value of the overall waveform. This method pays more attention to the change of the overall signal and is relatively suitable for analyzing the global characteristics of the waveform.

[0087] In an embodiment of the present application, the first method is used to calculate the PSD factor, and the formula is as follows:

[0088]

[0089] where PSD is the PSD factor, W 1 and W 2 are the signals of the SiPMs at both ends respectively.

[0090] It can be understood that by introducing the PSD factor, when estimating the DOI position of an event, the PSD factor and the DOI factor can be combined for joint estimation. Specifically, the PSD factor is mainly used to distinguish adjacent crystal segments. It can effectively distinguish crystal segments with different decay time constants through waveform feature differences, while the DOI factor is used to determine the depth position where the event occurs. The combined use of the two can effectively avoid interference between adjacent crystal segments when the DOI resolution is high, improving the positioning accuracy of the system.

[0091] For example, although crystal segments with different decay times may exhibit some overlap in signal intensity, due to their waveform differences, the PSD factor can effectively distinguish these overlapping signals, thereby accurately locating the position where the event occurs. Compared with traditional methods, the joint estimation method of this application significantly improves the DOI resolution. Especially in high-resolution detector structures, it can achieve sub-millimeter-level accuracy.

[0092] Step 103: Construct a two-dimensional statistical graph based on the DOI factor and the PSD factor, classify and discriminate gamma events through different regions in the two-dimensional statistical graph, determine the crystal segment where the gamma event occurs, and further obtain its depth position.

[0093] To further improve the accuracy of DOI estimation, this application constructs a two-dimensional statistical graph (PSD-DOI graph) by combining the DOI factor and the PSD factor. The construction of this graph utilizes the variation characteristics of the DOI factor and the PSD factor in space and time. Through the distribution of these two factors in the two-dimensional plane, the distribution law of different gamma events can be intuitively reflected, and then the gamma events can be accurately classified.

[0094] Specifically, the two-dimensional statistical graph (PSD-DOI graph) uses the DOI factor and the PSD factor as coordinate axes to form a two-dimensional coordinate system. In this graph, different regions represent different crystal segments and their depth positions. By analyzing this graph, the classification and discrimination of gamma events can be carried out in different regions, so as to determine the specific crystal segment where the gamma event occurs and its depth position.

[0095] By introducing the two-dimensional statistical graph, this application can achieve the accurate classification of gamma events while ensuring the DOI resolution. This method makes full use of the multi-dimensional information brought by the DOI factor and the PSD factor, overcoming the limitations of traditional methods that rely on a single parameter for positioning. By analyzing different regions in the PSD-DOI graph, adjacent crystal segments can be effectively distinguished, and accurate judgments can also be made at different depth positions of the same crystal segment.

[0096] The advantage of this method is that it provides an intuitive and easy-to-understand way to process complex signal information in a scintillation crystal detector. Through the classification and discrimination of different regions, the performance of the detector in a complex environment can be significantly improved, making the estimation of the depth position of gamma photons more accurate.

[0097] By combining the DOI factor and the PSD factor, the present application can significantly improve the ultimate DOI resolution of the scintillation crystal detector. Adjacent crystal units are mainly distinguished by the PSD factor, while crystal segments of the same crystal type that are far apart are distinguished by the DOI factor. Such a design effectively improves the resolution ability of the detector in complex situations, especially in application scenarios that require extremely high spatial resolution. The method of the present application has high adaptability and flexibility and can be widely applied to detectors that require high-precision gamma photon positioning, such as PET scanners, gamma cameras, etc.

[0098] In addition, the scintillator detector designed according to the present application has many aspects that can be selected and optimized for specific scenarios:

[0099] (1) Selection of crystal types. When designing a scintillator detector, it is very important to select different types of scintillation crystals. In the embodiments of the present application, there should be a certain difference in the decay constants of different types of crystals selected. At the same time, the maximum decay time constant should not be too long, as this will affect the ultimate count rate of the detector.

[0100] It should be noted that the crystal types selected are not limited to the three types shown in the above embodiments. As long as there are two or more crystals with different decay times, they are applicable to the present application.

[0101] (2) Sorting of crystals. The sorting of crystals does not need to be arranged in a strict sequential cycle, but can be optimized according to performance preferences. In specific applications, especially detectors operating under high count rate conditions, the sorting of crystals can be customized according to regional performance requirements. For example, crystals with shorter decay times can be selected for the crystals near the imaging area, which can effectively reduce the dead time during the detection process, ensure efficient detection, and improve the real-time response ability of the signal.

[0102] (3) Selection of crystal sizes. Since the detector structure designed in the present application can achieve high resolution for small crystal segments, it can be compatible with scintillation crystals of various size ranges. The number of crystal segments and the three-dimensional size of a single crystal segment can be adjusted according to design requirements. This flexibility enables the detector to adapt to different working scenarios and target requirements. In addition, this design method also supports the combination of crystal segments of different lengths, enabling the detector to be customized more personalized and flexibly to meet diverse application needs.

[0103] (4) Selection of crystal surface treatment. The surface treatment process of the crystal segment has an important impact on the transmission characteristics of the scintillation light, and thus affects the resolution performance of the crystal segment on the PSD-DOI diagram. The surface treatment method also affects the light output amount at different positions in the detector, thereby affecting the energy resolution of each crystal segment. Common surface treatment processes include polishing and rough grinding, and rough grinding can adjust the surface roughness according to the particle size. Selecting an appropriate surface treatment process can improve the detection efficiency of the detector and ensure that the detector can perform optimally in different application scenarios.

[0104] (5) Reflective film wrapped outside the crystal. To reduce the leakage of scintillation light, a reflective film is usually added outside the crystal strip. Reflective materials are mainly divided into two categories: specular reflection type and diffuse reflection type. The specular reflection type of reflective film (such as ESR film) can achieve efficient light reflection and is suitable for application scenarios that require concentrated reflection of light; diffuse reflection materials (such as powders of MgO, Al 2 O 3 , BaSO 4 etc., or Teflon film) are suitable for diffusing reflected light and can provide better performance in occasions that require a more uniform light distribution. By selecting a suitable reflective film, the utilization rate of scintillation light can be effectively improved, light loss can be reduced, and the overall performance of the detector can be optimized.

[0105] Based on the above design method, this application also designed a scintillation crystal strip and evaluated its performance through experiments. Specifically, the crystal strip selects gadolinium gallium aluminum garnet (GAGG:Ce) crystals doped with cerium with three decay time constants. The densities and reflectivities of the three GAGG:Ce are the same, and the decay times are from short to long, which are approximately 50 ns, approximately 140 ns, and approximately 200 ns, respectively, denoted as GAGG-50, GAGG-140, and GAGG-200. The crystal strip is composed of 25 cubic crystal segments, and the size of each crystal segment is 0.8 mm. All crystal segments are bonded with optical glue to form a crystal strip with a size of 0.8 mm × 0.8 mm × 20 mm. The outer ends of the crystal strip are wrapped with reflective materials, and SiPMs are coupled at both ends for double-end readout. Its design diagram is as Figure 4 shown.

[0106] Among them, the waveforms of the signals generated by GAGG-50, GAGG-140, and GAGG-200 are as Figure 5 shown, and the differences in the waveform shapes can be clearly observed.

[0107] Further, all crystal segments of the crystal bar are numbered #1, #2, …, #25 from left to right. The side of the crystal is irradiated with a 22Na exemption source (the main gamma ray energy is 511 keV, which is the same as the nuclide energy used in positron emission tomography in nuclear medicine), and sufficient event data is collected through a data acquisition system, and finally PSD-DOI is obtained. Figure 6 As shown. It can be seen that all numbered crystal segments can be clearly distinguished in the PSD-DOI diagram, and the crystal segments with the same decay time constant are all on the same row. This result proves that the combined gamma photon depth position estimation method of double-ended readout plus waveform discrimination can achieve a DOI resolution of 0.8 mm in the actual test of a single crystal bar.

[0108] It should be noted that this application is not only applicable to the design of a single crystal. By forming a two-dimensional array of multiple crystal bars, this method can provide three-dimensional high-position positioning capabilities. In a certain embodiment, this application simultaneously designs a 12×12 crystal array composed of the above crystal bars, and its physical diagram is as Figure 7 shown.

[0109] Using the same experimental conditions to test the Figure 7 shown crystal array, and obtaining the PSD-DOI of all events as Figure 8 shown.

[0110] It can be seen that the responses of all 25 layers of crystals can be clearly distinguished. The events of each crystal layer are selected and their position statistical charts are drawn as shown in Figure 9. The 12×12 crystal segments of all crystal layers can be distinguished on the position statistical chart, and the detector designed according to this method can achieve a three-dimensional position resolution of 0.8 mm.

[0111] In addition, this application can also be applied to the design of other scintillation detectors that require high DOI resolution, and can improve the DOI limit resolution of the detector in a wide energy range.

[0112] To implement the above embodiments, this application also proposes a detection imaging device for accurately obtaining the depth of gamma photons. Figure 10 This is a schematic structural diagram of a detection imaging device for accurately obtaining the depth of gamma photons provided by an embodiment of this application. As Figure 10 shown, the device includes:

[0113] A first calculation module, configured to, after gamma rays are incident on a segmented scintillation crystal bar, use double-ended readout technology to obtain the signal intensities at both ends of the segmented scintillation crystal bar, and calculate a DOI factor based on the difference between the signal intensities at both ends, where multiple adjacent crystal segments in the scintillation crystal bar are designed as scintillation crystal types with different decay time constants;

[0114] A second calculation module, configured to introduce a waveform discrimination technique and calculate a PSD factor based on the output waveform differences of crystals with different decay times.

[0115] A classification and discrimination module, configured to construct a two-dimensional statistical chart based on the DOI factor and the PSD factor, classify and discriminate gamma events through different regions in the two-dimensional statistical chart, determine the crystal segment where the gamma event occurs, and further obtain its depth position.

[0116] To implement the above embodiments, the present application also provides an electronic device, including: a processor, and a memory communicatively connected to the processor; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory to implement the method provided in the foregoing embodiments.

[0117] To implement the above embodiments, the present application also provides a computer-readable storage medium storing computer-executable instructions, which are used to implement the method provided in the foregoing embodiments when executed by a processor.

[0118] To implement the above embodiments, the present application also provides a computer program product including a computer program, which implements the method provided in the foregoing embodiments when executed by a processor.

[0119] The collection, storage, use, processing, transmission, provision, and disclosure of the user's personal information involved in the present application are all in compliance with the provisions of relevant laws and regulations and do not violate public order and good customs.

[0120] It should be noted that personal information from users should be collected for legal and reasonable purposes and should not be shared or sold outside of these legal uses. In addition, such collection / sharing should be carried out after obtaining the user's informed consent, including but not limited to notifying the user to read the user agreement / user notice and signing an agreement / authorization including authorizing relevant user information before the user uses the function. In addition, any necessary steps should be taken to protect and safeguard access to such personal information data and ensure that others with access to personal information data comply with their privacy policies and procedures.

[0121] The present application is expected to provide an implementation scheme for users to selectively block the use or access of personal information data. That is, the present disclosure is expected to provide hardware and / or software to prevent or block access to such personal information data. Once personal information data is no longer needed, the risk can be minimized by restricting data collection and deleting data. In addition, when applicable, personal identifiers are removed from such personal information to protect the privacy of users.

[0122] In the description of the foregoing embodiments, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0123] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0124] Any process or method description in the flowchart or otherwise described herein may be understood to represent a module, segment, or portion of code including one or more executable instructions for implementing a customized logic function or process, and the scope of the preferred embodiments of the present application includes additional implementations, where the functions may be performed in a substantially simultaneous manner or in a reverse order according to the functions involved, rather than in the order shown or discussed, which should be understood by those skilled in the art to which the embodiments of the present application pertain.

[0125] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or in conjunction with these instruction execution systems, apparatuses, or devices. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or otherwise processing as appropriate, and then storing it in a computer memory.

[0126] It should be understood that various parts of the present application can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0127] Those of ordinary skill in the art of this technology can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0128] In addition, each functional unit in various embodiments of the present application may be integrated into a processing module, or each unit may exist physically alone, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0129] The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disc, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present application.

[0130] It should be understood that various forms of the processes shown above may be used, reordering, adding or deleting steps. For example, the steps described in the present application may be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution of the present application can be achieved. There is no limitation herein.

[0131] The above specific embodiments do not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A detection imaging method for accurately acquiring the depth of gamma photons, characterized in that: The following steps are involved: After the gamma ray enters the segmented scintillation crystal strip, the signal strength at both ends of the segmented scintillation crystal strip is obtained by using a double-end readout technology, and the DOI factor is calculated based on the difference in the signal strength at both ends, wherein the adjacent multiple crystal segments in the scintillation crystal strip are designed to be scintillation crystal types with different decay time constants; Waveform discrimination technology is introduced to calculate the PSD factor based on the output waveform differences of crystals with different decay times; A two-dimensional statistical graph is constructed according to the DOI factor and the PSD factor, and gamma events are classified and identified through different areas in the two-dimensional statistical graph to determine the crystal segment where the gamma event occurs, thereby obtaining its depth position.

2. The method according to claim 1, characterized in that: The method of obtaining the signal strength at both ends of the segmented scintillation crystal strip by using the dual-end readout technology and calculating the DOI factor based on the difference in the signal strength at both ends includes: The signal strength of the SiPM at both ends of the segmented scintillation crystal strip is obtained by a dual-end readout technique, which are respectively denoted as S1 and S2; wherein the calculation formula for the signal strength S of the SiPM at one end is: S=∫Wdt Wherein, W is the waveform obtained by amplifying the signal generated by SiPM at one end; Based on the difference between the signal strengths S1 and S2 at both ends, the DOI factor is calculated using the formula: Among them, DOI is the DOI factor.

3. The method according to claim 2, characterized in that The waveform discrimination technology is introduced to calculate the PSD factor according to the output waveform difference of crystals with different decay times, including: A plurality of crystal segment structures are formed in the segmented scintillation crystal strip by using scintillation crystal types with different decay time constants to generate signal waveforms at both ends; The PSD factor is calculated based on the characteristics of the waveform after the two ends are added together.

4. The method according to claim 3, characterized in that The PSD factor is calculated based on the characteristics of the waveform after the two ends are added together, including: The PSD factor is calculated by dividing the sum of the signal strengths at both ends by the maximum value of the sum of the signals at both ends. Alternatively, the PSD factor is calculated by dividing the integral value of a portion of the waveform by the integral value of the entire waveform.

5. The method according to claim 4, characterized in that The PSD factor is calculated by dividing the sum of the signal strengths at both ends by the maximum value of the sum of the signals at both ends, including: Wherein, PSD is the PSD factor, W1 and W2 are the signals of SiPM at both ends respectively.

6. A detection imaging device for accurately acquiring the depth of gamma photons, characterized in that: include: A first calculation module is used for obtaining the signal strength at both ends of the segmented scintillation crystal bar by using a double-end readout technology after the gamma ray enters the segmented scintillation crystal bar, and calculating the DOI factor based on the difference in the signal strength at both ends, wherein the adjacent multiple crystal segments in the scintillation crystal bar are designed to be scintillation crystal types with different decay time constants; The second calculation module is used to introduce waveform discrimination technology and calculate the PSD factor according to the output waveform difference of crystals with different decay times; The classification and discrimination module is used to construct a two-dimensional statistical graph according to the DOI factor and the PSD factor, classify and discriminate gamma events through different areas in the two-dimensional statistical graph, determine the crystal segment where the gamma event occurs, and then obtain its depth position.

7. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 5 when executed by a processor.

9. A computer program product, characterized in that The invention comprises a computer program, which implements the method according to any one of claims 1 to 5 when being executed by a processor.

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