Gamma photon detection unit, detection method, PET detection module and PET system

Abstract

The present application relates to a gamma photon detection unit, a gamma photon detection method, a PET detection module, a PET system, and a computer-readable storage medium, wherein the gamma photon detection unit comprises: a digital silicon photomultiplier tube chip dSiPM and a scintillation crystal array; wherein the dSiPM comprises a silicon photomultiplier tube SiPM and a readout circuit, and the SiPM is electrically connected to the readout circuit; the scintillation crystal array comprises a plurality of scintillation crystals, and the scintillation crystal array is coupled to the dSiPM. Through the present application, the problem of low sensitivity of the gamma photon detector in the related art is solved, and the sensitivity of the gamma photon detector is improved.

Description

Technical Field

[0001] The present application relates to the technical field of positron emission tomography, and in particular to a gamma photon detection unit, a gamma photon detection method, a PET detection module, a PET system, and a computer-readable storage medium. Background Art

[0002] PET (Position Emission Tomography) detector is a device used to detect gamma (γ) photons. Its imaging principle is as follows: a positron emitted during the decay of a positron nuclide combines with and annihilates free electrons in human tissue, transforming into two γ photons with opposite directions and energies of 511 KeV each. If the angle is right, the two γ photons will hit the crystal of the PET detector to generate visible light signals, which are converted into electrical signals by photoelectric devices, and then amplified, converted into analog-to-digital signals, and energy and time are identified for compliance judgment.

[0003] In recent years, SiPM (Silicon Photomultiplier) has gradually become a dominant trend in the design and application of PET detectors due to its high gain, good magnetic field compatibility, easy digitization, and small size. However, due to the huge number of signal channels, the readout circuit of SiPM-based PET detectors needs to use ASIC (Application Specific Integrated Circuit). Among them, Philips has integrated SiPM and readout circuit on a chip, launched a fully digital SiPM chip (Digital Photon Counting SiPM, referred to as DPC), and applied it to its PET / CT (Computed Tomography) products.

[0004] Among them, the PET detector readout circuit is used to convert the visible light signal into an electrical signal through a photoelectric converter, and perform amplification, analog-to-digital conversion or time-to-digital conversion. It is worth noting that since the number of photons that pass through the scintillation crystal to reach the photoelectric conversion device is very small, perhaps only a few hundred to thousands, the initial electrical signal is very weak, perhaps only tens to hundreds of millivolts, and is easily affected by noise. Therefore, shortening the front-end analog link is particularly important to ensure signal quality and thus improve system performance.

[0005] At present, there are generally three types of SiPM-based PET detector front-end readout architecture designs from mainstream manufacturers.

[0006] The first is to use SiPM or SiPM array board coupled with block-structured scintillation crystals, and then cooperate with discrete devices to form a multi-channel readout circuit. Since there is still an analog link from SiPM to the readout circuit, signal noise may be introduced, which will have an adverse effect on system performance, especially for discrete device circuits, where the analog link is longer and the possibility of introducing noise is greater. Figure 1 is a schematic diagram of a PET detector readout architecture design according to the related art, such as Figure 1 As shown in the figure, this is a commonly used PET detector readout architecture design, where ReadOut represents the readout circuit, Analog Signal represents the analog signal, Crystal represents the scintillation crystal, and Crystal A, Crystal B, and Crystal C represent three scintillation crystals respectively. This architecture uses a SiPM-based photoelectric converter array to couple with a crystal array to collect visible light signals, and then cooperates with the front-end readout circuit to convert analog signals to digital signals. This readout architecture design is still affected by electronic noise due to the existence of the analog signal transmission path.

[0007] The second is to use ASIC to replace discrete device circuit boards to shorten the length of the front-end analog link, thereby minimizing link noise and increasing the number of channels to achieve the purpose of improving system performance.

[0008] The third is the DPC solution launched by Philips, which highly integrates SiPM with the readout circuit and then couples it with the scintillation crystal array to digitize the visible light signal.

[0009] Integrating SiPM with ASIC can effectively shorten the analog link. However, the one-to-one coupling structure between DPC and crystal currently used by Philips has certain disadvantages in terms of system sensitivity for the following reasons:

[0010] Figure 2 is a schematic diagram of a PET detector readout architecture design 2 according to the related art, such as Figure 2As shown in the figure, the front-end readout structure consists of a DPC and a crystal in a one-to-one form, that is, a DPC is coupled with a scintillation crystal. In this structure, since the analog-to-digital conversion of the front-end signal is completed in the DPC, DPC_1 and DPC_2 cannot transmit information at the analog signal level. Therefore, in order to avoid false triggering, it is generally necessary to perform light shielding between the two scintillation crystals. The solid line in the figure represents the transmission of visible light inside the crystal. Since light shielding or reflection processing is performed between different crystals to ensure that the visible light generated by the deposition of γ light in the scintillation crystal B can only be received by DPC_2, the visible light that originally only needs one reflection to reach the DPC needs to be reflected twice inside the scintillation crystal B before reaching DPC_2. The reflection of visible light will seriously consume the energy of visible light, so that part of the visible light may not reach the DPC. Correspondingly, the signal size and signal certainty obtained by the readout circuit will be affected, which will eventually lead to low sensitivity of the system. This is also a factor affecting the low sensitivity of the current Philips PET / CT system using DPC technology.

[0011] Currently, the gamma photon detector in the related technology has the problem of low sensitivity, and no effective solution has been proposed yet. Summary of the invention

[0012] The embodiments of the present application provide a gamma photon detection unit, a gamma photon detection method, a PET detection module, a PET system, and a computer-readable storage medium to solve the problem of low sensitivity of gamma photon detectors in related technologies.

[0013] In a first aspect, an embodiment of the present application provides a gamma photon detection unit, the gamma photon detection unit comprising: a digital silicon photomultiplier tube chip dSiPM and a scintillation crystal array; wherein,

[0014] The dSiPM includes a silicon photomultiplier tube SiPM and a readout circuit, and the SiPM is electrically connected to the readout circuit;

[0015] The scintillation crystal array includes a plurality of scintillation crystals, and the scintillation crystal array is coupled to the dSiPM.

[0016] In some embodiments, the readout circuit includes a logic processing unit, the SiPM includes a photosensitive element array, and the logic processing unit is electrically connected to the photosensitive element array.

[0017] In some embodiments, a first light shielding layer is disposed between adjacent scintillation crystals in the plurality of scintillation crystals.

[0018] In some of the embodiments, a second light shielding layer is disposed on the outer side of the scintillation crystal array.

[0019] In some of the embodiments, the gamma photon detection unit further comprises: a photoconductive layer, wherein the photoconductive layer is disposed between the one dSiPM and the scintillation crystal array.

[0020] In some of the embodiments, the one dSiPM and the scintillation crystal array are coupled via a light-transmitting coupling agent.

[0021] In some embodiments, a surface of the light-guiding layer coupled to the scintillation crystal array is provided with grooves, and the number of the grooves is consistent with the number of the plurality of scintillation crystals; the plurality of scintillation crystals are respectively embedded in the grooves.

[0022] In some embodiments, the scintillation crystal array includes a plurality of scintillation crystals arranged in an m×m square array, or the scintillation crystal array includes a plurality of scintillation crystals arranged in an m×n square array, wherein m≥2 and n≥1.

[0023] In a second aspect, an embodiment of the present application provides a PET detection module, which includes an annular detector frame and a plurality of gamma photon detection units as described in the first aspect above, wherein the plurality of gamma photon detection units are arranged on the annular detector frame.

[0024] In a third aspect, an embodiment of the present application provides a PET system, comprising a PET detection module and a computer device as described in the second aspect, wherein the computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the computer program is executed by the processor, controls the PET detection module to count coincidence counting events.

[0025] In a fourth aspect, an embodiment of the present application provides a gamma photon detection method, which is applied to the gamma photon detection unit as described in the first aspect above, comprising:

[0026] The dSiPM detects a plurality of photon deposition signals within a preset time window in the scintillation crystal array;

[0027] The dSiPM adds the multiple photon deposition signals to obtain a sum signal;

[0028] The dSiPM determines whether the sum signal is within a preset threshold range;

[0029] When the sum signal is within a preset threshold interval, the dSiPM triggers determination of a preset deposition point position according to the multiple photon deposition signals.

[0030] In some embodiments, the dSiPM triggering to determine a preset deposition point position according to the plurality of photon deposition signals comprises:

[0031] The dSiPM determines the position of the scintillation crystal where energy deposition may occur for each photon deposition signal according to the position of the photosensitive area of ​​each detected photon deposition signal;

[0032] The dSiPM screens out effective photon deposition signals and corresponding scintillation crystal positions where energy deposition may occur from the multiple photon deposition signals according to the scintillation crystal positions where energy deposition may occur for each photon deposition signal and the intensity of each photon deposition signal;

[0033] The dSiPM sends the effective photon deposition signal and the corresponding scintillation crystal position where energy deposition occurs to the logic processing unit, so that the logic processing unit can determine the preset deposition point position.

[0034] In a fifth aspect, an embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the gamma photon detection method as described in the fourth aspect above.

[0035] Compared with the related art, the gamma photon detection unit, gamma photon detection method, PET detection module, PET system, and computer-readable storage medium provided in the embodiments of the present application use a digital silicon photomultiplier tube chip dSiPM and a scintillation crystal array; wherein the dSiPM includes a silicon photomultiplier tube SiPM and a readout circuit, and the SiPM is electrically connected to the readout circuit; the scintillation crystal array includes multiple scintillation crystals, and the scintillation crystal array is coupled to the dSiPM, thereby solving the problem of low sensitivity of the gamma photon detector in the related art and improving the sensitivity of the gamma photon detector.

[0036] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 is a schematic diagram of a PET detector readout architecture design one according to the related art;

[0039] Figure 2 is a schematic diagram of a PET detector readout architecture design 2 according to the related art;

[0040] Figure 3 is a structural schematic diagram of a gamma photon detection unit according to an embodiment of the present application;

[0041] Figure 4 is a schematic diagram of summing up signals detected by a dSiPM according to an embodiment of the present application;

[0042] Figure 5 It is a schematic diagram of a related art in which DPC is triggered when two deposition points appear;

[0043] Figure 6 It is a schematic diagram of response line distribution in the case of two deposition points in the related art;

[0044] Figure 7 is a logic diagram of completing front-end signal comparison in a dSiPM according to an embodiment of the present application;

[0045] Figure 8 is a structural schematic diagram of a gamma photon detection unit according to a preferred embodiment of the present application;

[0046] Fig. 9 is a structural schematic diagram of a gamma photon detection unit with a light shielding layer according to an embodiment of the present application;

[0047] Fig.10 is a structural schematic diagram of a gamma photon detection unit with a photoconductive layer according to an embodiment of the present application;

[0048] Fig.11 is a schematic diagram of the connection between a scintillation crystal and a light-guiding layer according to an embodiment of the present application;

[0049] Fig.12 is a structural schematic diagram of a PET detection module according to an embodiment of the present application;

[0050] Fig.13 is a structural schematic diagram of a PET system according to an embodiment of the present application;

[0051] Fig.14 This is a flow chart of a gamma photon detection method according to an embodiment of the present application. Description of the drawings:

[0053] 301, dSiPM; 302, scintillation crystal array; 3021, first scintillation crystal; 3022, second scintillation crystal; 3023, third scintillation crystal; 303, first light shielding layer; 304, second light shielding layer; 305, optical guide layer; 306, groove; 400, annular detector rack; 500, PET detection module; 600, computer equipment; 601, memory; 602, processor; 603, communication interface; 604, bus. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0055] Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0056] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0057] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation, and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0058] This embodiment provides a gamma photon detection unit, Figure 3 is a structural schematic diagram of a gamma photon detection unit according to an embodiment of the present application, such as Figure 3 As shown, the gamma photon detection unit includes a digital silicon photomultiplier tube chip dSiPM 301 and a scintillation crystal array 302; wherein, the dSiPM 301 includes a silicon photomultiplier tube SiPM and a readout circuit, and the SiPM is electrically connected to the readout circuit; the scintillation crystal array 302 includes a plurality of scintillation crystals, namely a first scintillation crystal 3021, a second scintillation crystal 3022 and a third scintillation crystal 3023, and the scintillation crystal array 302 is coupled to the dSiPM 301.

[0059] The positron annihilation reaction occurs in the scintillation crystal array 302, which converts the 511keV gamma rays generated by the annihilation reaction into thousands of visible photons. The visible photons are reflected multiple times in the scintillation crystal array 302, and are emitted from one side of the scintillation crystal array 302. Some of the visible photons reach the SiPM. The SiPM receives these visible photons, converts them into electrons, and multiplies them to produce electrical signals. The readout circuit obtains the position, time, and energy information of the interacting gamma rays by amplifying the electrical signals.

[0060] This embodiment uses a digital SiPM to shorten the analog link. For a long-axis system with an abnormally large number of sampling channels, the sampling differences between different channels can be reduced, thereby maximizing the time sampling certainty of the long-axis system and avoiding electronic noise problems caused by the introduction of a longer analog link.

[0061] For a gamma photon energy deposition event, when the photosensitive areas at different positions in the scintillation crystal array 302 are illuminated, a SiPM can convert the received visible photons corresponding to each light-emitting area into electrons, multiply and derive electrical signals, and send multiple electrical signals to the readout circuit. The readout circuit receives these multiple electrical signals, sums them up, and then obtains a larger electrical signal, thereby ensuring that the electrical signal can be triggered and recorded as an event for subsequent information processing.

[0062] Figure 4 A schematic diagram of summing up the signals detected by a dSiPM according to an embodiment of the present application is shown, Figure 4 As shown, a gamma photon energy deposition event is generated in the second scintillation crystal 3022, and visible light is emitted. The visible light is refracted and reflected in the multiple scintillation crystals in the scintillation crystal array 302, and is emitted from one of the end faces of the first scintillation crystal 3021, the second scintillation crystal 3022, and the third scintillation crystal 3023 to reach the dSiPM 301. The dSiPM 301 receives multiple optical signals emitted from multiple scintillation crystals, converts them into electrical signals corresponding to the multiple optical signals, and sums them to generate a sum signal corresponding to a gamma photon energy deposition event. After obtaining the sum signal, the dSiPM 301 can compare the sum signal with a preset threshold interval to determine whether the sum signal is within the preset threshold interval; if the sum signal is within the preset threshold interval, the dSiPM 301 triggers the determination of the deposition point position according to the sum signal.

[0063] In the gamma photon detection unit of this embodiment, no matter how many times the visible light in the scintillation crystal array 302 is refracted and reflected, once the visible light is received by the dSiPM 301, it will be converted and summed to generate a sum signal, ensuring that the sum signal can be triggered. Compared with the related art, on the one hand, the gamma photon detection unit in the embodiment of the present application does not need to perform light shielding or reflection processing between the scintillation crystals, so the number of reflections of the visible light in the scintillation crystal array 302 can be reduced, thereby reducing the energy consumption of the visible light, enhancing the signal size and signal certainty obtained by the dSiPM 301, thereby improving the sensitivity of the gamma photon detection unit; on the other hand, for a gamma photon energy deposition event, a dSiPM 301 can convert and sum the received visible photons corresponding to each light-emitting area to obtain a sum signal, ensuring that the electrical signal can be triggered, thereby improving the sensitivity of the gamma photon detection unit.

[0064] Surti et al. studied the impact of event localization algorithms on the performance of whole-body PET scanners using one-to-one coupled detectors. Taking a 3mm*3mm*18mm LYSO (lutetium yttrium silicate) crystal as an example, combined with the attenuation efficiency of gamma light in this type of scintillation crystal, it can be inferred that when a gamma photon is incident on a scintillation crystal obliquely, it has a high probability of passing through the first one or two crystals that it hits, and two deposition points may appear, that is, more than two DPCs will be triggered. Figure 5 FIG. 4 shows a schematic diagram of a related art in which a DPC is triggered when two deposition points appear. Figure 5 As shown, 1 st max represents the maximum deposition energy, 2 nd max represents the next largest deposited energy, Anger represents a logic used to compare two deposited energies, positioning error represents positioning error, and Incident photon represents incident gamma photons. Since there may be two deposited points for one gamma light incident, and particles will produce scattering effects when moving in the crystal, if the visible light signals generated by these two deposits cannot be added together, some events may not be able to complete the triggering results independently. Since the two DPCs in the related technology cannot directly exchange information, it will make SR (Scatter Recovery) work difficult to carry out. In the worst case, these scattering events are discarded, which will also affect the system sensitivity to a certain extent.

[0065] In the case where there are multiple deposition points in the face of a single gamma light incident, the gamma photon detection unit of the embodiment of the present application can directly add the visible light signals generated by the two depositions in one dSiPM to ensure that some events are triggered independently.

[0066] The one-to-one coupling between DPC and crystal has certain disadvantages not only in terms of system sensitivity, but also in terms of spatial resolution. Figure 6 It is a schematic diagram of the distribution of the line of response (LOR) in the case of two deposition points in the related art, such as Figure 6 As shown in the figure, LORs represent multiple response lines. Since two DPCs are triggered, four LORs need to participate in the location calculation of the annihilation event. Since the front-end analog signal cannot be directly transmitted between the front-end DPCs, it is necessary to make a possibility judgment on the deposition point in the back-end processing circuit or algorithm, and then calculate the location of the annihilation event. On the one hand, this method increases the difficulty of back-end data processing. On the other hand, since the judgment of the deposition point is a probabilistic event, not every event strictly completes the main photoelectric effect deposition at the maximum or second largest energy point according to the algorithm. Therefore, this method will introduce a certain spatial resolution calculation error, that is, the accuracy error of the calculation of the annihilation event location information.

[0067] In view of the above problems, in some embodiments, a logic processing unit is provided in the readout circuit, and the logic processing unit is electrically connected to the photosensitive element array in the SiPM. As a specific implementation, the logic processing unit can be a logic unit transistor constructed by FPGA (Field Programmable Gate Array) and built into the readout circuit as a part of the readout circuit.

[0068] Figure 7 FIG. 4 shows a logic diagram of completing front-end signal comparison in a dSiPM. Figure 7 As shown, 1 st max energy represents the maximum deposition energy, which corresponds to the first signal 1 st signal, 2 nd max energy represents the second largest deposition energy, which corresponds to the second signal 2 nd signal, x signal represents a signal that meets the given requirements. That is, through this structure, for different deposition points, dSiPM 301 uses the built-in logic unit to compare 1 st signal and 2 ndsignal, outputs a signal that meets the established requirements. For example, considering the signal amplitude and signal speed, in order to eliminate the large signal caused by noise and other factors, the front-end signal comparison is completed in the dSiPM 301, thereby reducing the corresponding calculation pressure for the back-end data processing and simplifying the back-end processing logic. Among them, the comparison of the front-end signal includes the cross-domain processing of the signal and the corresponding energy position calculation, and the deposition point comparison is performed based on multiple gamma photon deposition signals, so as to give a more accurate recommended deposition point position.

[0069] In addition, since the DPC and the crystal are coupled one-to-one, the cross-sectional size of the crystal needs to be close to the cross-sectional size of the DPC. However, due to chip technology and cost factors, the cross-sectional size of the crystal generally needs to be above 3 mm. The following is the theoretical calculation formula for spatial resolution, where Γ represents the spatial resolution of the system, a represents the reconstruction algorithm coefficient, d represents the size of the scintillation crystal, D represents the PET detector ring diameter, r represents the positron range of the radionuclide, and b represents the decoding deviation of the PET detector. It can be seen that the cross-sectional size of the crystal has a great influence on the spatial resolution of the system. The limitation of the cross-sectional size of the crystal will directly lead to the inability of the system spatial resolution to reach about 3 mm, which also limits the use of PET systems in some clinical scenarios to a certain extent.

[0070]

[0071] To address the above problem, in some preferred embodiments, the scintillation crystal array includes a plurality of scintillation crystals arranged in an m×m matrix, or the scintillation crystal array includes a plurality of scintillation crystals arranged in an m×n matrix, wherein m≥2 and n≥1. Figure 8 is a structural schematic diagram of a gamma photon detection unit according to a preferred embodiment of the present application, such as Figure 8 As shown, the gamma photon detection unit includes a dSiPM 301, and one end face of the dSiPM 301 is coupled to a 6×1 scintillation crystal array 302 composed of 6 scintillation crystals. In this embodiment, a block structure composed of smaller scintillation crystals is coupled to the dSiPM 301 to achieve higher spatial resolution performance requirements.

[0072] Since there may be two deposition points for one incident gamma light, in order to distinguish the light signals emitted by different scintillation crystals, in some embodiments, a first light shielding layer is disposed between adjacent scintillation crystals in the plurality of scintillation crystals. Fig. 9 is a structural schematic diagram of a gamma photon detection unit with a light shielding layer according to an embodiment of the present application, such as Fig. 9As shown, the first shading layer 303 is arranged on the inner side surface of the scintillation crystal array 302. As a specific implementation, the inner side surface of the scintillation crystal array 302 can be processed by a vacuum coating method, and a vacuum film is coated on the surface. The color of the film is black, which prevents light signals from passing through and plays a shading role; or the side surface of the scintillation crystal is processed by a polishing method, so that light is diffusely reflected on the surface, preventing light signals from passing through in a straight line, which plays a shading role; or reflective material, such as a reflective film, is added to the inner side surface of the scintillation crystal array 302, which plays a role of shading and enhancing reflection at the same time.

[0073] In order to prevent the light signal from being emitted from the outer side of the scintillation crystal array, in some embodiments, the outer side of the scintillation crystal array 302 is provided with a second light shielding layer 304, such as Fig. 9 The second light shielding layer 304 can be made of opaque material and wrapped around the outer side of the scintillation crystal array 302 to prevent the light signal from passing through in a straight line, thereby playing a light shielding role.

[0074] For the scintillation crystal at the edge of the gamma photon detection unit, in order to enhance the diffusion of visible photons in the edge crystal, in some embodiments, the optical signal gamma photon detection unit further includes a photoconductive layer 305, referring to Fig.10 , the photoconductive layer 305 is disposed between a dSiPM 301 and the scintillation crystal array 302. The gamma photon detection unit of this embodiment can be replicated to construct a gamma photon detection unit array, and between the edge crystals of these adjacent gamma photon detection units, the photoconductive layer 305 is used to diffuse visible photons, making them easier to be measured by multiple gamma photon detection units. As a specific implementation, the thickness of the photoconductive layer 305 can also be determined according to the cross section of the scintillation crystal and the area of ​​the SiPM, thereby improving the uniformity of the crystal resolution map and the resolution capability of the gamma photon detection unit for edge crystals.

[0075] In some of the embodiments, a dSiPM and a scintillation crystal array are coupled and connected via a light-transmitting coupling agent, wherein the light-transmitting coupling agent may be optical glue for transmitting light.

[0076] like Fig.11 As shown, in some embodiments, a groove 306 is provided on a side of the light guide layer 305 coupled with the scintillation crystal array 302, and the number of the grooves 306 is consistent with the number of the plurality of scintillation crystals; the plurality of scintillation crystals are respectively embedded in the grooves 306. In this embodiment, the light guide layer 305 is engraved with grooves 306, and the grooves 306 divide one surface of the light guide layer 305 into a matrix, and the matrix corresponds to the scintillation crystal array 302 one by one, and each scintillation crystal in the scintillation crystal array 302 is correspondingly embedded in the groove 306, which plays a role in reinforcing the coupling.

[0077] This embodiment also provides a PET detection module. Fig.12 is a schematic diagram of the structure of a PET detection module according to an embodiment of the present application, such as Fig.12 As shown, the PET detection module includes an annular detector frame 400 and a plurality of gamma photon detection units 300 as described above, and the plurality of gamma photon detection units 300 are arranged on the annular detector frame 400 .

[0078] This embodiment also provides a PET system. Fig.13 is a schematic diagram of the structure of a PET system according to an embodiment of the present application, such as Fig.13 As shown, the PET system includes the PET detection module 500 and the computer device 600 described above, wherein the computer device 600 includes a memory 601, a processor 602, and a computer program stored in the memory 601 and executable on the processor 602, and when the computer program is executed by the processor 602, the PET detection module 500 is controlled to count coincidence counting events.

[0079] Specifically, the processor 602 may include a central processing unit (CPU), or a specific integrated circuit, or may be configured to implement one or more integrated circuits of the embodiments of the present application.

[0080] Among them, the memory 601 may include a large capacity memory for data or instructions. For example and not limitation, the memory 601 may include a hard disk drive (HDD), a floppy disk drive, a solid state drive (SSD), a flash memory, an optical disk, a magneto-optical disk, a magnetic tape, or a universal serial bus (USB) drive or a combination of two or more of these. In appropriate cases, the memory 601 may include a removable or non-removable (or fixed) medium. In appropriate cases, the memory 601 may be inside or outside the data processing device. In a specific embodiment, the memory 601 is a non-volatile memory. In a specific embodiment, the memory 601 includes a read-only memory (ROM) and a random access memory (RAM). Where appropriate, the ROM may be a mask-programmed ROM, a programmable ROM (Programmable Read-Only Memory, PROM for short), an erasable PROM (ErasableProgrammable Read-Only Memory, EPROM for short), an electrically erasable PROM (Electrically ErasableProgrammable Read-Only Memory, EEPROM for short), an electrically alterable ROM (ElectricallyAlterable Read-Only Memory, EAROM for short) or a flash memory (FLASH) or a combination of two or more of these. Under appropriate circumstances, the RAM can be a static random access memory (SRAM) or a dynamic random access memory (DRAM), wherein the DRAM can be a fast page mode dynamic random access memory (FPMDRAM), an extended data output dynamic random access memory (EDODRAM), a synchronous dynamic random access memory (SDRAM), etc.

[0081] The memory 601 may be used to store or cache various data files that need to be processed and / or used for communication, as well as possible computer program instructions executed by the processor 602 .

[0082] The processor 602 reads and executes computer program instructions stored in the memory 601 . When the computer program is executed by the processor 602 , the PET detection module 500 is controlled to count coincidence events.

[0083] In some embodiments, the PET system may further include a communication interface 603 and a bus 604. The processor 602, the memory 601, and the communication interface 603 are connected via the bus 604 and communicate with each other.

[0084] The communication interface 603 is used to implement communication between the modules, devices, units and / or equipment in the embodiment of the present application. The communication interface 603 can also implement data communication with other components such as: external devices, image / data acquisition equipment, databases, external storage, and image / data processing workstations.

[0085] The bus 604 includes hardware, software, or both, and couples the components of the PET system to each other. The bus 604 includes, but is not limited to, at least one of the following: a data bus, an address bus, a control bus, an expansion bus, and a local bus. By way of example and not limitation, bus 604 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Extended Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), a Hyper Transport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an InfiniBand interconnect, a Low Pin Count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local Bus (VLB) bus, or other suitable buses or a combination of two or more of these. Where appropriate, bus 80 may include one or more buses. Although embodiments of the present application describe and illustrate a particular bus, the present application contemplates any suitable bus or interconnect.

[0086] The PET system can perform the gamma photon detection method in the embodiment of the present application based on the acquired visible photons, thereby realizing the following combination: Fig.14 Describe the gamma photon detection method.

[0087] This embodiment provides a gamma photon detection method, which is applied to the gamma photon detection unit described above. Fig.14 is a flow chart of a gamma photon detection method according to an embodiment of the present application, such as Fig.14 As shown, the process includes the following steps:

[0088] Step S1401 : the dSiPM detects a plurality of photon deposition signals within a preset time window in a scintillation crystal array.

[0089] In step S1402 , the dSiPM adds up the multiple photon deposition signals to obtain a sum signal.

[0090] Step S1403, the dSiPM determines whether the sum signal is within a preset threshold range.

[0091] Step S1404: when the sum signal is within the preset threshold range, the dSiPM triggers to determine the preset deposition point position according to the multiple photon deposition signals.

[0092] Through the above steps, when the radioactive nuclide decays to produce positrons, the positrons combine with the negative electrons to produce annihilation radiation, generating two gamma photons with 511keV and opposite flight directions. These two photons have the following properties: they are generated at the same time and fly out in almost opposite directions. This makes it possible to use two oppositely placed gamma photon detection units to detect them using coincidence technology. The preset time window can be set between 0ns and 15ns. The dSiPM receives multiple optical signals emitted from multiple scintillation crystals, converts them into electrical signals corresponding to the multiple optical signals, and sums them to generate a sum signal corresponding to a gamma photon energy deposition event. After obtaining the sum signal, the dSiPM can compare the sum signal with the preset threshold interval to determine whether the sum signal is within the preset threshold interval; when the sum signal is within the preset threshold interval, the dSiPM triggers to determine the deposition point position according to the sum signal.

[0093] For a gamma photon energy deposition event, when the photosensitive areas at different positions in the scintillation crystal array are illuminated, a SiPM can convert the received visible photons corresponding to each light-emitting area into electrons, multiply and derive electrical signals, and send multiple electrical signals to the readout circuit. The readout circuit receives these multiple electrical signals, sums them up, and then obtains a larger electrical signal, thereby ensuring that the electrical signal can be triggered and recorded as an event for subsequent information processing.

[0094] Through the above steps, the problem of low sensitivity of the gamma photon detector in the related art is solved, and the sensitivity of the gamma photon detector is improved.

[0095] In view of the fact that there may be multiple deposition points for one gamma light incident, in some embodiments, the dSiPM triggering to determine the preset deposition point position according to multiple photon deposition signals includes the following steps:

[0096] The dSiPM determines the position of the scintillation crystal where energy deposition may occur for each photon deposition signal according to the position of the photosensitive area of ​​each detected photon deposition signal; the dSiPM screens out effective photon deposition signals and the corresponding positions of the scintillation crystal where energy deposition may occur from multiple photon deposition signals according to the position of the scintillation crystal where energy deposition may occur for each photon deposition signal and the intensity of each photon deposition signal; the dSiPM sends the effective photon deposition signals and the corresponding positions of the scintillation crystal where energy deposition occurs to the logic processing unit so that the logic processing unit determines the preset deposition point position, and the preset deposition point position can be selected according to the different deposition point comparison methods adopted, and the deposition point position recommended by the different deposition point comparison methods is selected.

[0097] In the process of determining the preset deposition point position according to multiple photon deposition signals triggered by dSiPM, traditional Compton scattering sequence recovery methods such as "center of gravity method" and "simple energy comparison method" can be used. The specific implementation of these two methods will be introduced below.

[0098] (1) Center of gravity method

[0099] In a gamma photon detection unit, when multiple scintillation crystals generate scintillation light due to collecting Compton scattering deposited energy, the dSiPM covering the entire scintillation crystal array will receive light signals of different intensities, and take the center of gravity position (crystal position) of the energy deposition as the first energy deposition position of the photon. The energy of the gamma photon output by the readout circuit is the sum of the signals of multiple scintillation crystals, and the output position signal is the average position coordinate of multiple scintillation crystal coordinates with the signal amplitude as the weight.

[0100] (2) Simple energy comparison method

[0101] In a gamma photon detection unit, when multiple scintillation crystals generate scintillation light due to the collection of Compton scattering deposited energy, the point of action (crystal position) with the second highest deposited energy is taken as the position where the first scattering occurs. Through the readout circuit, the scintillation light signal intensity of each crystal can be given, and the energy of the gamma photon is still the sum of the signals of several excited crystals; for two action point cases where only one Compton scattering occurs, the action point with less energy deposition is taken as the position where the first scattering occurs; for multiple action point cases where two or more Compton scattering occurs, the action point with the second highest energy deposition is taken as the position where the first scattering occurs, that is, the coordinates of the crystal corresponding to the second largest signal intensity among the several excited crystals.

[0102] Through the above method, when the PET detection module detects two photons belonging to a coincidence event, the annihilation point is on the line between the two scintillation crystal arrays where the flash occurs, forming a response line LOR, and the coincidence is recorded in the memory. Since the two photons have different paths in the scintillation crystal, the time they arrive at their respective gamma photon detection units is also different, so the position of the annihilation point on the coincidence line can be calculated. The coincidence circuit system performs coincidence measurement to generate raw data, and completes data acquisition, system monitoring, attenuation correction, and image reconstruction through the computer system.

[0103] In addition, in combination with the gamma photon detection method in the above embodiments, the present application embodiment may provide a computer-readable storage medium for implementation. The computer-readable storage medium stores computer program instructions; when the computer program instructions are executed by a processor, any one of the gamma photon detection methods in the above embodiments is implemented.

[0104] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A gamma photon detection unit, characterized in that: The gamma photon detection unit comprises: a digital silicon photomultiplier tube chip dSiPM and a scintillation crystal array; wherein, The dSiPM includes a silicon photomultiplier tube SiPM and a readout circuit, and the SiPM is electrically connected to the readout circuit; The scintillation crystal array includes a plurality of scintillation crystals, and the scintillation crystal array is coupled to the dSiPM; wherein the dSiPM is used to receive a plurality of optical signals emitted from the scintillation crystal array, convert them into electrical signals corresponding to the plurality of optical signals, sum the electrical signals, and generate a sum signal corresponding to a gamma photon energy deposition event; when the sum signal is within a preset threshold range, the deposition point position is determined according to the sum signal.

2. The gamma photon detection unit according to claim 1, characterized in that: The readout circuit includes a logic processing unit, the SiPM includes a photosensitive element array, and the logic processing unit is electrically connected to the photosensitive element array.

3. The gamma photon detection unit according to claim 1, characterized in that: A first light shielding layer is arranged between adjacent scintillation crystals in the plurality of scintillation crystals.

4. The gamma photon detection unit according to claim 1, characterized in that: A second light shielding layer is disposed on the outer side of the scintillation crystal array.

5. The gamma photon detection unit according to claim 1, characterized in that: The gamma photon detection unit further comprises: a photoconductive layer, wherein the photoconductive layer is arranged between a dSiPM and the scintillation crystal array.

6. The gamma photon detection unit according to claim 1, characterized in that: The one dSiPM and the scintillation crystal array are coupled and connected via a light-transmitting coupling agent.

7. The gamma photon detection unit according to claim 5, characterized in that: A surface of the optical guide layer coupled with the scintillation crystal array is provided with grooves, and the number of the grooves is consistent with the number of the plurality of scintillation crystals; the plurality of scintillation crystals are respectively embedded in the grooves.

8. The gamma photon detection unit according to any one of claims 1 to 7, characterized in that: The scintillation crystal array includes a plurality of scintillation crystals arranged in an m×m square matrix, or the scintillation crystal array includes a plurality of scintillation crystals arranged in an m×n square matrix, wherein m≥2 and n≥1.

9. A PET detection module, characterized in that: The PET detection module comprises an annular detector frame and a plurality of gamma photon detection units according to any one of claims 1 to 8, wherein the plurality of gamma photon detection units are arranged on the annular detector frame.

10. A PET system, characterized in that: The PET system includes a PET detection module and a computer device as described in claim 9, wherein the computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the computer program is executed by the processor, it controls the PET detection module to count coincidence counting events.

11. A gamma photon detection method, applied to the gamma photon detection unit according to any one of claims 1 to 8, characterized in that include: The dSiPM detects a plurality of photon deposition signals within a preset time window in the scintillation crystal array; The dSiPM adds the multiple photon deposition signals to obtain a sum signal; The dSiPM determines whether the sum signal is within a preset threshold range; When the sum signal is within a preset threshold interval, the dSiPM triggers determination of a preset deposition point position according to the multiple photon deposition signals.

12. The gamma photon detection method according to claim 11, characterized in that: The dSiPM triggering to determine the preset deposition point position according to the multiple photon deposition signals includes: The dSiPM determines the position of the scintillation crystal where energy deposition may occur for each photon deposition signal according to the position of the photosensitive area of ​​each detected photon deposition signal; The dSiPM screens out effective photon deposition signals and corresponding scintillation crystal positions where energy deposition may occur from the multiple photon deposition signals according to the scintillation crystal positions where energy deposition may occur for each photon deposition signal and the intensity of each photon deposition signal; The dSiPM sends the effective photon deposition signal and the corresponding scintillation crystal position where energy deposition occurs to the logic processing unit, so that the logic processing unit can determine the preset deposition point position.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the gamma photon detection method according to any one of claims 11 to 12 is implemented.

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