Detection collimation unit, detection device and SPECT imaging system

Abstract

The present invention discloses a detection collimation unit, a detection device and a SPECT imaging system. The detection collimation unit includes: a scintillation crystal array for receiving gamma photons emitted by a radiation source in an object to be detected; a plurality of optoelectronic devices for receiving the gamma photons and converting them into digital signals; the scintillation crystal array includes a plurality of scintillation crystals, the plurality of scintillation crystals are substantially parallel and arranged at intervals, each scintillation crystal has an end face and a side face capable of receiving rays emitted by the radiation source; the plurality of optoelectronic devices are coupled to the end faces of the plurality of scintillation crystals. The detection collimation unit of the present invention can be used to replace the heavy metal collimator required in SPECT imaging, reduce the loss of gamma photons, and avoid the absorption of gamma photons by the circuit board and optoelectronic devices in the detection collimation unit, significantly improving the spatial resolution and detection efficiency of SPECT imaging. At the same time, it also avoids the processing difficulty of machining a plurality of small parallel holes or pinholes in the heavy metal collimator, and simplifies the processing process.

Description

Technical Field

[0001] The present invention relates to the field of nuclear medicine imaging technology. In particular, it relates to a detection collimation unit, a detection device containing the detection collimation unit, and a SPECT imaging system. Background Art

[0002] In a SPECT device for single photon emission computed tomography in nuclear medicine imaging diagnosis, it is necessary to include at least the following two components essential for the SPECT imaging function: One is the detector component, which sequentially receives a plurality of gamma photons emitted from within the object to be detected at different times, converts the time information, energy information, and position information of each photon acting on the detector into electrical signals and digitizes them for input into a computer; the other is the collimator component, which is generally located between the object to be detected and the detector component. By absorbing photons emitted from certain specific directions within the object to be detected, photons reaching the detector component cannot be detected when coming from the above directions, or the probability of photons reaching the detector component from certain specific directions is significantly different from the probability of photons coming from other directions, so that the photons received by the detector component also contain incident direction information. All the detection units on the detector component sequentially receive a certain number of gamma photons within an imaging time period and accumulate the number of gamma photons on each detection unit, and input the number information of gamma photons on each detection unit into the image reconstruction algorithm component in the computer. In the image reconstruction algorithm, in the form of a system transfer matrix calculated through a geometric model formula or discretely measured in advance, the probability that gamma photons emitted from each point in the imaging space are received by each detection unit in the detector component is recorded. The image reconstruction algorithm, through the above probability information and the input gamma photon information, performs mathematical operations to solve the distribution information of the radiation source intensity within the object to be detected and forms a digital image for display on the display unit.

[0003] Different from a transmission CT imaging system (whose radiation source is outside the human body and usually uses an X-ray generating device such as an X-ray tube as the radiation source, so the radiation passing through the human body itself has directivity), the radiation source of a SPECT imaging system is a radioactive tracer introduced into the human body by injection, oral administration or inhalation. The tracer emits gamma photons in an isotropic manner, so the gamma photons detected by the SPECT system itself do not carry directivity information. Therefore, a conventional SPECT system needs to use an absorption collimator made of heavy metal, which only allows gamma photons from a specific direction to enter the detector and absorbs gamma photons from other directions, so that the gamma photons received by the detector carry direction information. However, in a SPECT system, the design of the collimator component faces a dilemma: on the one hand, if the collimator component absorbs photons from most directions and only allows photons from a few directions to enter the detector, each photon reaching the detector can carry more effective direction information, which is beneficial to improving the spatial resolution of the imaging system; but the number of photons emitted by the radiation source per unit time follows a Poisson statistical distribution, resulting in relative fluctuations in the number of photons collected on the detection unit, and the relative fluctuation expressed in the form of a standard deviation is inversely proportional to the square root value of the number of photons collected. Therefore, when designing the collimator, it is also necessary to consider allowing more photons to enter the detector, that is, to improve the detection efficiency of the imaging system, so as to increase the number of gamma photons received on each detection unit and correspondingly reduce its relative statistical fluctuations. But this will mean that the collimator needs to allow photons from more directions to enter the detector, thus reducing the effectiveness of the direction information carried by each photon received by the detector, that is, reducing the spatial resolution of the imaging system.

[0004] To ensure the spatial resolution of the SPECT system, the traditional heavy metal collimator tries to reduce the aperture size and spacing along the incident direction of gamma photons. However, this often causes a large number of gamma photons to be attenuated and absorbed by the collimator and cannot be detected by the detector, thus causing a large amount of photon loss and seriously affecting the detection efficiency of the SPECT device.

[0005] Therefore, the existence of the heavy metal collimator component makes it impossible to improve the spatial resolution and detection efficiency of the SPECT system simultaneously.

[0006] On the other hand, in the heavy metal collimator component, to allow gamma photons to pass through, a plurality of parallel straight holes or conical pinholes need to be machined on it. The shape parameters of the holes have a great influence on the performance of the SPECT system, so it is necessary to precisely control its processing dimensions, and the metal processing technology is difficult. Summary of the Invention

[0007] (I) Technical problems to be solved

[0008] To solve at least one of the above problems, an object of the present invention is to provide a detection collimation unit, a detection device, and a SPECT imaging system that improve spatial resolution, and / or improve detection efficiency, and / or reduce the difficulty of metal processing technology.

[0009] (II) Technical solution

[0010] To achieve the above object, according to the first aspect of the present invention, a detection collimation unit is provided, including:

[0011] A scintillation crystal array for receiving gamma photons emitted by a radiation source in an object to be detected;

[0012] A plurality of optoelectronic devices for receiving the gamma photons and converting them into digital signals;

[0013] The scintillation crystal array includes a plurality of scintillation crystals, the plurality of scintillation crystals are arranged substantially parallel and spaced apart, and each scintillation crystal has an end face and a side face that can receive the incidence of rays emitted by the radiation source;

[0014] The plurality of optoelectronic devices are coupled to the end faces of the plurality of scintillation crystals.

[0015] Preferably, the scintillation crystal array is a two-dimensional arrangement array, and the scintillation crystal array includes a plurality of scintillation crystals arranged along the incident direction of gamma rays emitted by the radiation source, and a plurality of scintillation crystals arranged perpendicular to the incident direction of gamma rays emitted by the radiation source.

[0016] Preferably, the scintillation crystal includes an independent scintillation crystal bar and / or a plurality of scintillation crystal bars spliced together.

[0017] Preferably, at least one end face of the scintillation crystal bar is coupled with an optoelectronic device.

[0018] Preferably, in the scintillation crystal array, there is a filler between the spaced scintillation crystals, and the filler includes at least one material of resin, polyethylene plastic, plexiglass, and heavy metal.

[0019] According to the second aspect of the present invention, a detection device is provided, and the detection device includes a plurality of detection collimation units as described in any of the above solutions.

[0020] Preferably, a plurality of the detection collimation units are fixedly connected to form a detection collimation unit layer distributed in any one of a circular, polygonal, arc-shaped, and partial polygonal shape around the object to be detected.

[0021] Preferably, the detection device includes a plurality of detection collimation unit layers arranged at intervals along the incident direction of gamma rays emitted by the radiation source, and the plurality of detection collimation unit layers are arranged in a staggered manner so that there is at least one scintillation crystal on the detection collimation unit of the last detection collimation unit layer, and gamma photons emitted from a point in the imaging field of view can reach the scintillation crystal of the last detection collimation unit layer without passing through any optoelectronic devices or circuit board materials during the transmission path.

[0022] According to a third aspect of the present invention, there is provided a SPECT imaging system, which includes the detection device according to any one of the above solutions, as well as a data processing unit, an image reconstruction unit, and an image display unit;

[0023] The data processing unit is configured to receive the digital signal output by the detection device and perform processing to obtain the incident information of each incident gamma photon;

[0024] The image reconstruction unit is configured to receive the incident information of a plurality of incident gamma photons output by the data processing unit and perform processing to obtain the distribution information of the radiation source in the object to be detected and form a digital image.

[0025] The image display unit is configured to display the digital image and provide the information required for clinical diagnosis.

[0026] Preferably, each detection collimation unit layer of the detection device can be selectively rotated around the object to be detected.

[0027] Preferably, the SPECT imaging system includes at least two detection devices arranged at intervals along the incident direction of gamma rays emitted by the radiation source, and along the incident direction of gamma rays emitted by the radiation source, the distal detection device far from the object to be detected is configured to receive the gamma photons emitted by the radiation source in the object to be detected that pass through one or more proximal detection devices and convert them into digital signals.

[0028] Preferably, according to the spatial resolution and image signal-to-noise ratio required by the SPECT imaging system, the relative position of each detection device in the SPECT imaging system, the distance between adjacent two detection devices, and the number, size, and arrangement mode parameters of the scintillation crystal bars in each detection collimation unit are selected.

[0029] Preferably, a heavy metal collimator with openings is provided between the first detection device close to the object to be detected and the object to be detected, and / or between adjacent two detection devices along the incident direction of gamma rays emitted by the radiation source, and / or between the detection collimation unit layers of each detection device.

[0030] Further, the photon transmittance of the heavy metal collimator is greater than 1%.

[0031] (III) Advantageous Effects

[0032] The present invention has achieved the following technical effects compared with the prior art:

[0033] The present invention provides a detection collimation unit, which includes a plurality of optoelectronic devices and a scintillation crystal array composed of a plurality of substantially parallel and spaced scintillation crystals. The plurality of optoelectronic devices are coupled to the end faces of the plurality of scintillation crystals, so that when gamma photons emitted by a radiation source in an object to be detected enter from the side faces of the scintillation crystals, they do not need to pass through the optoelectronic devices (that is, the optoelectronic devices are arranged substantially parallel to the incident direction of the gamma photons emitted by the radiation source in the object to be detected). This not only achieves the effect of gamma ray direction collimation, but also achieves the purpose of photon detection, and does not affect the image quality. At the same time, compared with the existing imaging system using a heavy metal collimator that does not allow rays to pass through, the detection collimation unit of the present invention can not only avoid the loss of gamma photons, greatly improve the detection efficiency of gamma photons, but also does not affect the image quality of imaging using a SPECT imaging system. At the same time, it also avoids the processing difficulty of machining a plurality of small parallel holes or pinholes in the heavy metal collimator, and simplifies the processing process.

[0034] In addition, the present invention also provides a detection device and a SPECT imaging system including the above detection collimation unit. The detection device and the SPECT imaging system have the same technical effects as the above detection collimation unit, and will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings listed in the present invention are only for better understanding the technical solutions and advantages of the present invention, but do not constitute any limitation to the technical solutions of the present invention. Among them:

[0036] Figure 1 is a schematic structural diagram of a detection collimation unit according to an embodiment of the present invention;

[0037] Figure 2 is a working principle diagram of gamma photons in a human body passing through two detection collimation units according to an embodiment of the present invention;

[0038] Figure 3 is a schematic structural diagram of a detection device according to the first embodiment of the present invention;

[0039] Figure 4 is a schematic structural diagram of a detection device according to the second embodiment of the present invention;

[0040] Figure 5 is a schematic structural diagram of a detection device according to the third embodiment of the present invention;

[0041] Figure 6 It is a schematic structural diagram of the detection device in the fourth embodiment of the present invention;

[0042] Figure 7 It is a schematic structural diagram of the detection device in the fifth embodiment of the present invention;

[0043] Figure 8 It is a schematic structural diagram of the detection device in the sixth embodiment of the present invention;

[0044] Figure 9 It is a schematic structural diagram of the detection device in the seventh embodiment of the present invention;

[0045] Figure 10 It is a schematic structural diagram of the arc detection collimation unit layer in an embodiment of the present invention;

[0046] Figure 11 It is a schematic structural diagram of the circular detection collimation unit layer in an embodiment of the present invention;

[0047] Figure 12 It is a schematic structural diagram of the regular octagon detection collimation unit layer in an embodiment of the present invention;

[0048] Figure 13 It is a structural composition diagram of the SPECT imaging system in an embodiment of the present invention;

[0049] Figure 14 It is a schematic structural diagram of the SPECT imaging system in an embodiment of the present invention. Specific embodiments

[0050] The following further describes the present invention in detail and completely with reference to specific embodiments. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or use.

[0051] Figure 1 It is a schematic structural diagram of the detection collimation unit in an embodiment of the present invention. Figure 2 It is a working principle diagram of gamma photons passing through two detection collimation units in a human body in an embodiment of the present invention. As Figure 1 and Figure 2 described, the detection collimation unit 1 of the embodiment of the present invention can be applied in an SPECT imaging device or system, and includes: a scintillation crystal array 10 and a plurality of optoelectronic devices 20. The scintillation crystal array 10 is used to receive gamma photons emitted by a radiation source in the object 30 to be detected. The plurality of optoelectronic devices 20 are used to receive gamma photons and convert them into digital signals. The aforementioned object 30 to be detected is mostly a target organ or the human body in the human body, and of course, it can also be other objects to be detected.

[0052] Among them, the scintillation crystal array 10 is a two-dimensional arrangement array, including a plurality of scintillation crystals 101. Each scintillation crystal 101 is an independent cuboid scintillation crystal bar 1011, and a plurality of scintillation crystal bars 1011 are arranged in parallel and at intervals. Each scintillation crystal bar 1011 has two end faces and four side faces. The side faces of the scintillation crystal 101 can be used for the gamma rays p emitted by the radiation source in the object to be detected 30 to enter, that is, the side faces of the scintillation crystal 101 serve as the incident surfaces for the gamma rays p emitted by the radiation source. One or more optoelectronic devices 20 are coupled to the same end of all the scintillation crystal bars 1011, and one or more optoelectronic devices 20 are coupled to the other end.

[0053] In the existing low-energy (from dozens of keV to hundreds of keV) nuclide detection units used in SPECT devices, the optoelectronic devices are usually coupled to the gamma photon incident surface (or the exit surface) of the scintillation crystal. This will cause the gamma photons to be easily blocked and attenuated by the optoelectronic devices, the corresponding electronic devices, and the circuit boards when passing through, thereby resulting in the loss of gamma photons and affecting the image quality.

[0054] Based on the design of the detection collimation unit with the above structure of the present invention, when the gamma photons emitted by the radiation source in the object to be detected 30 enter from the side faces of the scintillation crystal bars 1011, they do not need to pass through the optoelectronic devices 20 (that is, the optoelectronic devices 20 are arranged generally parallel to the incident direction of the gamma rays p emitted by the radiation source in the object to be detected 30). This not only achieves the effect of gamma ray direction collimation, but also achieves the purpose of photon detection, and does not affect the image quality. At the same time, compared with the existing imaging systems using heavy metal collimators that do not allow rays to pass through, the detection collimation unit 1 of the present invention can not only avoid the loss of gamma photons, greatly improve the detection efficiency of gamma photons, but also does not affect the image quality of imaging using the SPECT imaging system. At the same time, it also avoids the processing difficulty of machining a plurality of small parallel holes or pinholes in the heavy metal collimator, and simplifies the processing technology.

[0055] Such as Figure 1 and Figure 2 As shown, the arrangement method of the scintillation crystal array 10 of the present invention is not limited. It can be a two-dimensional arrangement array method composed of a plurality of scintillation crystals 101 arranged along the incident direction of the gamma rays p emitted by the radiation source, and several scintillation crystals 101 arranged perpendicular to the incident direction of the gamma rays p emitted by the radiation source, or other two-dimensional arrangement array methods.

[0056] Such as Figure 3As shown in the figure, the first embodiment of the present invention provides a detection device. The detection device 2 in the first embodiment includes a detection collimation unit 1' (which can be used as the front layer of the detection collimation unit because it is close to the object to be detected 30) composed of a row of detection crystals arranged at intervals (each detection crystal includes a scintillation crystal strip 1011 and a coupled optoelectronic device 20), and a detection collimation unit 2' (which can be used as the rear layer of the detection collimation unit because it is far from the object to be detected 30) composed of a row of detection crystals arranged closely. Due to the existence of the detection collimation unit 1', the probabilities of a gamma photon detected at the position of the detection collimation unit 2' coming from different positions 1"-7" in the human body are different. Among them, the probabilities of coming from positions 3" and 5" are relatively large, and the probabilities of coming from 1", 2", 4", 6", and 7" are relatively small. The existence of the detection collimation unit 1' in this embodiment enables the detection collimation unit 2' to have the ability to distinguish the incident direction of gamma photons and the collimation effect.

[0057] The design of the front layer of the above detection collimation unit affects both the detection efficiency of the rear layer of the detection collimation unit and the ability to distinguish the incident direction of gamma photons. The smaller the crystal array arrangement gap of the front layer of the detection collimation unit, the better the ability to distinguish the incident direction of gamma photons in the rear layer of the detection collimation unit, but the detection efficiency will decrease; the greater the thickness of the crystals in the front layer of the detection collimation unit along the photon incident direction, the better the ability to distinguish the incident direction of gamma photons in the rear layer of the detection collimation unit, but the detection efficiency is smaller. Figure 3 An example is a certain cross-section of the scintillation crystal 101 region, and the scintillation crystal strips 101 are arranged along the human body axial direction. By adjusting the crystal spacing distance in the detection collimation unit 1', the collimation effect on the crystals in the detection collimation unit 2' can be changed, and the ability of the crystals in the detection collimation unit 2' to distinguish the incident direction of gamma photons can be adjusted.

[0058] As Figure 4 As shown in the figure, the second embodiment of the present invention provides a detection device. The detection device 2 in the second embodiment is composed of two detection collimation unit layers (equivalent to including a detection collimation unit front layer composed of two rows of staggered detection crystals and a detection collimation unit rear layer composed of a row of closely connected detection crystals). In this embodiment, due to the multi-row crystal effect of the detection collimation unit 1' and the detection collimation unit 2', the probability of photons coming from position 3" is relatively large, and the probabilities of coming from other positions are relatively small. That is, compared with the first embodiment, the ability to distinguish the incident direction of gamma photons in the rear layer of the detection collimation unit is better, but the detection efficiency is relatively smaller. However, the detection efficiency of the front layer of the detection collimation unit has increased, so the total detection efficiency of the detection device has not decreased. Moreover, the proximal row of detection crystals in the detection collimation unit 1' in the front layer of the detection collimation unit also plays a role in photon detection collimation for the distal row of detection crystals.

[0059] In one embodiment of the present invention, when arranging a plurality of scintillation crystals 101 of the scintillation crystal array 10, it is sometimes impossible to make the plurality of scintillation crystals 101 arranged completely parallel. As long as they are generally parallel, that is, some of the scintillation crystals 101 can be inclined, and a slightly smaller inclination angle can be formed with other scintillation crystals 101. For example, any number within the range of 0-15° can be selected as the inclination angle.

[0060] As Figure 5 shown, the third embodiment of the present invention provides a detection device. In the scintillation crystal array 10 that constitutes the detection device of the third embodiment, in addition to filling air between the spaced scintillation crystals 101, there can also be a filler made of a low-density and lightweight material to stabilize the scintillation crystals 101. Optionally, the filler includes at least one of resin, polyethylene plastic, and plexiglass. Further, on the premise of ensuring the structural stability of the scintillation crystal array 10, a hollow design can be adopted or the size of the filler can be changed to reduce the attenuation of gamma photons.

[0061] In another embodiment of the present invention, in the scintillation crystal array 10, a high-density heavy metal material can be filled between the spaced scintillation crystals 101, so that there is a significant difference in the attenuation coefficient of gamma photons between it and the scintillation crystal 101 material. That is: when a plurality of detection collimation units are arranged at intervals along the incident direction of the gamma ray p emitted by the radiation source in the SPECT imaging device, the probability that gamma photons pass through the scintillation crystal strip 1011 area of the proximal detection collimation unit and reach the distal detection collimation unit is significantly different from the probability that gamma photons pass through the filler area of the proximal detection collimation unit and reach the distal detection collimation unit. Furthermore, for the gamma photons detected on the distal detection collimation unit, the probabilities from different directions are significantly different, so that the collimation effect of the proximal detection collimation unit on the distal detection collimation unit can be enhanced. Here, the proximal detection collimation unit and the distal detection collimation unit are both relative concepts. Specifically, taking the object 30 to be detected as a reference, the detection collimation unit close to the object 30 to be detected is called the proximal detection collimation unit, and the detection collimation unit far from the object 30 to be detected is called the distal detection collimation unit.

[0062] As Figure 6 shown, the fourth embodiment of the present invention provides a detection device. In order to enhance the collimation effect, a heavy metal collimator 3' with openings can be added between the first detection device 2 close to the object 30 to be detected (i.e., the detection collimation unit 1' in Figure 6 ), and the object 30 to be detected, and / or between two adjacent detection devices 2 along the incident direction of the gamma ray p emitted by the radiation source (i.e., in Figure 6A heavy metal collimator 3' with openings is additionally provided between the detection collimation unit 1' and the detection collimation unit 2' (in the present invention), and / or a heavy metal collimator 3' with openings is additionally provided between the detection collimation unit layers of each detection device 2 (inside the detection device including multiple detection collimation unit layers and between any two detection collimation unit layers). In addition, the additionally provided heavy metal collimator 3' can also enhance the spatial resolution effect of the rear-end detection collimation unit.

[0063] Further, in order to ensure a certain detection efficiency, the photon transmittance of the heavy metal collimator 3' needs to be greater than 1%, that is, among the photons incident on the front surface of the heavy metal collimator 3', the proportion of photons that can pass through the collimator and exit from the rear surface of the heavy metal collimator 3' is greater than 1%. The openings on the heavy metal collimator 3' can be any one of a slit hole, a square hole, a round hole, a conical hole, etc.

[0064] As Figures 7 - 9 shown, the fifth, sixth, and seventh embodiments of the present invention respectively provide a detection device. Different from the structure of the scintillation crystal array 10 in the above embodiments (each scintillation crystal 101 is an independent scintillation crystal strip 1011), in the scintillation crystal arrays 10 of these three embodiments, each scintillation crystal 101 includes a plurality of scintillation crystal strips 1011 spliced together by an adhesive. Of course, in addition to this, in other embodiments of the present invention, each scintillation crystal 101 can also be composed of an independent scintillation crystal strip 1011 and a plurality of scintillation crystal strips 1011 spliced together.

[0065] As Figure 9 shown, the detection device 2 provided by the seventh embodiment of the present invention is composed of a heavy metal detection collimation unit 3' with an opening rate of 50%, a detection collimation unit 1' arranged to form a front layer of the detection collimation unit, and a detection collimation unit 2' as a rear layer of the detection collimation unit.

[0066] Due to the existence of the heavy metal detection collimation unit 3' and the detection collimation unit 1', the probabilities of a gamma photon detected on the detection collimation unit 2' coming from different positions 1"-7" in the human body are different. In this embodiment, the probability of the photon coming from position 3" is relatively large, and the probabilities of coming from other positions are relatively small. That is: compared with the first embodiment, the resolution ability of the incident direction of gamma photons in the rear layer of the detection collimation unit is better, but the detection efficiency becomes relatively smaller. Compared with the fifth embodiment, due to the existence of the heavy metal detection collimation unit 3', the total detection efficiency of the detection device 2 becomes smaller. However, the heavy metal detection collimation unit 3' also collimates a row of detection crystals of the detection collimation unit 1', so the detection device 2 has better resolution ability for the incident direction of gamma photons.

[0067] In one embodiment of the present invention, the shape of the scintillation crystal bar 1011 is not limited to a cuboid, and it can also be a cylinder or a strip-shaped body in other forms. The present invention can use the scintillation crystal bar 1011 in any one or several of the shapes of a cuboid, a cylinder, and a strip-shaped body in other forms to assemble the scintillation crystal matrix 10.

[0068] In one embodiment of the present invention, the manner in which the plurality of optoelectronic devices 20 are coupled to the end faces of the plurality of scintillation crystal bars 1011 is not limited, as long as at least one end face of the scintillation crystal bar 1011 is coupled with the optoelectronic device 20. It can be that all the optoelectronic devices 20 are coupled to the same end face of all the scintillation crystal bars 1011, and the other end of all the scintillation crystal bars 1011 is a free end; it can be the coupling manner presented in the above first embodiment, that is, some of the optoelectronic devices 20 are coupled to the same end face of all the scintillation crystals 101, and the remaining optoelectronic devices 20 are coupled to the other end face of all the scintillation crystals 101. It can also be that some of the optoelectronic devices 20 are coupled to the same end face of some of the scintillation crystals 101, and the remaining optoelectronic devices 20 are coupled to the other end face of at least one of the scintillation crystals 101 among this part of the scintillation crystals 101 and the other end face of the remaining scintillation crystals 101 other than this part of the scintillation crystals 101, and so on.

[0069] In the first embodiment, the signals output by the two optoelectronic devices 20 coupled to both ends of all the scintillation crystals 101 are jointly used to calculate and determine the three-dimensional spatial position where the gamma photon event acts in the detection collimation unit 1, so that the SPECT imaging device or system can achieve three-dimensional imaging. The specific calculation formula is as follows:

[0070]

[0071] In the formula, DOI represents the three-dimensional spatial position where the gamma photon event acts; E1 and E2 represent the signal amplitudes or areas on the optoelectronic devices coupled to both ends; k and b are fitting coefficients, which are obtained through calibration measurement experiments and fitting. The specific calibration process is as follows:

[0072] 1) Place the collimated radiation source on one side of the detection collimation unit and determine the DOI position where it is incident on the detection collimation unit;

[0073] 2) Collect a plurality of events, and obtain E 1 and E 2 values for each event;

[0074] 3) Calculate the value for each event;

[0075] 4) Perform a first-order polynomial linear fitting according to the DOI value and the value to obtain the fitting coefficients k and b.

[0076] In one embodiment of the present invention, the material of the scintillation crystal bar 1011 can be selected from any one of NaI, CsI, LaBr 3 , CLYC, BGO, LSO, LYSO, GSO, YSO, YAP, GAGG. Of course, the multiple scintillation crystal bars 1011 in the scintillation crystal array 10 can be made of the same material or different materials. When different materials are selected for the scintillation crystal bars 1011, their attenuation ratios for gamma photons will also be different. The length of the scintillation crystal bar 1011 is not limited and can be reasonably selected according to actual application situations.

[0077] In one embodiment of the present invention, the optoelectronic device 20 can be selected from at least one of an avalanche photodiode APD, a silicon photomultiplier SiPM, a photomultiplier tube PMT, a Geiger-mode avalanche photodiode GAPD, and a solid-state photomultiplier SSPM. When multiple detection collimation units are arranged at intervals along the incident direction of the gamma rays p emitted by the radiation source in the detection device, compared with using a PMT device, using any one of the SiPM, APD, GAPD, and SSPM devices can reduce the distance between the detection collimation units, and thus can reduce the size and occupied space of the detection device or the entire SPECT imaging device.

[0078] Figure 10 is a schematic structural diagram of the arc-shaped detection collimation unit layer of one embodiment of the present invention. As Figure 10 shown, the detection device 2 of the embodiment of the present invention includes multiple detection collimation units 1 of any one of the above-mentioned types. The multiple detection collimation units 1 are fixedly connected to form a detection collimation unit layer that is arc-shaped around the object to be detected 20.

[0079] In another embodiment of the present invention, a detection device 2 can include multiple detection collimation unit layers arranged at intervals along the incident direction of the gamma rays p emitted by the radiation source. The multiple detection collimation unit layers are arranged in a staggered manner such that at least one scintillation crystal 101 exists on the detection collimation unit 1 of the last detection collimation unit layer, enabling gamma photons emitted from a point in the imaging field of view not to pass through any optoelectronic device or circuit board material on the transmission path to the scintillation crystal of the last detection collimation unit layer. In this way, when gamma photons are incident on the side of the scintillation crystal bar 1011 in the scintillation crystal array, gamma photon loss can be avoided without affecting the image quality.

[0080] In the embodiment of the present invention, the fixed connection method between the multiple detection collimation units 1 forming the same detection collimation unit layer is not limited. For example, connection can be achieved through an adhesive or a fixing connector.

[0081] In an embodiment of the present invention, the shape in which a plurality of detection collimation units 1 are fixedly connected and distributed around the object to be detected 30 (i.e., the shape of the detection collimation unit layer formed) is not limited to an arc shape, and may also be circular (see Figure 11 ), polygonal (for example, regular hexagon or regular octagon, etc., see Figure 12 ), and partial polygon (i.e., the local shape of a polygon, for example, half of the shape of a regular hexagon or regular octagon), or any one of these shapes.

[0082] Figure 13 is a structural composition diagram of a SPECT imaging system according to an embodiment of the present invention. Figure 14 is a schematic structural diagram of a SPECT imaging system including two detection collimation unit layers according to an embodiment of the present invention. As shown in Figure 13 and Figure 14 , the SPECT imaging system 3 according to the embodiment of the present invention includes a detection device 2 having two detection collimation unit layers, a data processing unit 301, an image reconstruction unit 302, and a display unit 303. Of course, the specific number and structure of the detection collimation unit layers constituting the detection device 2 in the embodiment of the present invention can be designed according to actual application situations.

[0083] In an embodiment of the present invention, each detection collimation unit layer of the detection device 2 can be selectively rotated around the object to be detected 30, for example, rotated circumferentially along the object to be detected 30. Of course, it is not limited thereto. This not only improves the flexibility of the system but also facilitates the detection of objects to be detected 30 with different sizes and structures. Further, in order to further improve the flexibility of system use, the rotation speed and direction of multiple detection collimation unit layers around the object to be detected 30 can be the same or different.

[0084] In another embodiment of the present invention, the SPECT imaging system 3 includes at least two detection devices 2. Adjacent two detection devices 2 are arranged at intervals along the incident direction of the gamma ray p emitted by the radiation source, and along the incident direction of the gamma ray p emitted by the radiation source, the distal detection device far from the object to be detected 30 is used to receive the gamma photons emitted by the radiation source in the object to be detected 30 that pass through one or more proximal detection devices and convert them into digital signals.

[0085] In an embodiment of the present invention, select the relative position of each detection device in the SPECT imaging system 3, the spacing between adjacent two detection devices 2, and the number, size, and arrangement mode parameters of the scintillation crystal bars 1011 in each detection collimation unit 1 according to the spatial resolution and image signal-to-noise ratio required by the SPECT imaging system 3.

[0086] The selection of the above parameters needs to be a trade-off between the spatial resolution and the image signal-to-noise ratio characteristics of the imaging system. It can be calculated optimally through the following steps to determine the final physical structure of the SPECT imaging system.

[0087] 1) Divide the imaging field of view area into discrete image pixel units. According to a set of system design parameter values, calculate the system transfer matrix A = {a ij}, where a ij represents the probability that photons emitted from image pixel unit j in the imaging system are detected by scintillation crystal bar i.

[0088] 2) Define a uniform image vector f covering the field of view, that is: if the i-th element in vector f falls within the field of view, its value is 1, otherwise its value is zero; calculate the expected value of the projection data obtained by the imaging system measuring f:

[0089] y = A·f

[0090] where [·] is the operation of matrix multiplying vector. Assume the system has I detector units and J image units, then A is a matrix of I rows × J columns, f is a column vector of 1 row × J columns, and y is a column vector of 1 row × I columns.

[0091] And calculate the Fisher information matrix F:

[0092]

[0093] where A′ is the transpose of A, is a diagonal matrix of I rows × I columns, whose off-diagonal elements are 0, and the element value on its i-th row and i-th column is the reciprocal of the element value on the i-th column of y.

[0094] 3) Calculate the system local impulse response matrix:

[0095] LIR = F + ·F

[0096] where F + is the Moore-Penrose generalized inverse matrix of F, and LIR is a matrix of J rows × J columns. The J values on the j-th (j = 1,..., J) column represent: when an impulse input is given to the j-th image pixel unit in the field of view space, the image vector values output by the imaging system in response. Ideally, among the J values on the j-th column, only the value on the j-th row is 1, and the rest are 0, and at this time the spatial resolution of the imaging system is the best. When the spatial resolution of the imaging system is limited, the value on the j-th row of the j-th column is a positive integer between 0 and 1, and the smaller its value, the wider the impulse response distribution of the imaging system, indicating that the spatial resolution of the imaging system is worse.

[0097] 4) Take the value of the j-th element on the diagonal of LIR, denoted as R j , representing the spatial resolution characteristics of the imaging system on the j-th pixel unit.

[0098] 5) Traverse the values of LIR on each image pixel unit and calculate the average:

[0099] Use R as the evaluation index for the spatial resolution characteristics of the imaging system.

[0100] 6) Calculate the covariance matrix:

[0101] COV = F + ·F·F +

[0102] Among them, COV is a matrix with J rows × J columns. The value of the j-th element on its diagonal, that is, the value on the j-th (j = 1,..., J) row and the j-th (j = 1,..., J) column of COV, represents: the statistical fluctuation variance of the j-th image pixel unit, representing the noise sensitivity of the imaging system. The smaller its value, the lower the sensitivity of the imaging system to the noise in the measurement data and the better the image quality.

[0103] 6) Take the value of the j-th element on the diagonal of COV, denoted as V j , representing the variance on the j-th pixel unit.

[0104] 7) Traverse the values of COV on each image pixel unit and calculate the average:

[0105] Use V as the evaluation index for the noise sensitivity of the imaging system to the measurement data.

[0106] 8) Take different design parameter values, repeat steps 1)-7), and comprehensively compare the R value and the V value. Take the system design parameter combination with a relatively larger R value and a relatively smaller V value as the output of the optimal design result of the system structure.

[0107] The data processing unit 301 of this embodiment is used to receive the digital signals output by multiple detection devices 2 and process them to obtain the incident information of each incident gamma photon; among them, the information data of each incident gamma photon obtained by the data processing unit 301 includes data such as the position, energy, and time of each incident gamma photon.

[0108] The image reconstruction unit 302 of this embodiment is used to receive the incident information of multiple incident gamma photons output by the data processing unit 301 and process them to obtain the distribution information of the radiation source in the detected object 30 and form a digital image.

[0109] Further, the image reconstruction unit 302 can obtain the distribution information of the radiation source in the object to be detected by using an analytical reconstruction algorithm, an algebraic iterative algorithm, or a statistical iterative reconstruction algorithm.

[0110] Among them, for the analytical reconstruction algorithm, the filtered back-projection formula is as follows:

[0111]

[0112] In the formula, f(x, y) is the reconstructed image, P(ω, θ) is the one-dimensional Fourier transform of the image projection, and |ω| is the high-pass filter.

[0113] The formula of the algebraic iterative algorithm:

[0114]

[0115] In the formula, f k is the image of the k-th iteration, f k+1 is the image of the (k + 1)-th iteration, C is the system transfer matrix of the iteration, representing the contribution of the pixels on the image to the projection, and λ k is the relaxation factor at the k-th iteration.

[0116] The formula of the statistical iterative reconstruction algorithm:

[0117]

[0118] In the formula, represents the pixel value of the j-th pixel on the image at the k-th iteration, and c ij is the value of the i-th row and j-th column in the system transfer matrix, representing the contribution of the j-th point on the image to the i-th detection unit; represents the pixel value of the j-th pixel on the image at the (k + 1)-th iteration, and c ij is the value of the i-th row and j-th column in the system transfer matrix, representing the contribution of the j-th point on the image to the i-th detection unit.

[0119] The display unit 303 of this embodiment is configured to receive and display the digital image formed by the image reconstruction unit 302.

[0120] In addition, an imaging method applying any one of the foregoing SPECT imaging systems provided by an embodiment of the present invention includes the following steps:

[0121] Receiving gamma photons emitted by the radiation source in the object to be detected and converting them into digital signals;

[0122] Receiving the digital signals and processing them to obtain the incident information of each incident gamma photon;

[0123] Receive the incident information of multiple incident gamma photons, process the information, obtain the distribution information of the radiation source in the object to be detected, and form a digital image.

[0124] Receive the digital image formed by the image reconstruction unit 302 and display it.

[0125] In an embodiment of the present invention, multiple detection devices 2 including one or more detection collimation unit layers can receive gamma photons emitted by a radiation source in the object to be detected 30 and convert them into digital signals. The digital processing unit 301 can receive the digital signals output by the multiple detection devices 2 and process each signal one by one to obtain information such as the position, energy, and time of each incident gamma photon. The image reconstruction unit 302 can receive the information such as the position, energy, and time of multiple gamma photons output by the data processing unit 301 within a unit time, and solve it through an image reconstruction algorithm (for example, an analytical reconstruction algorithm, an algebraic iterative algorithm, or a statistical iterative reconstruction algorithm) to obtain the distribution information of the radiation source in the object to be detected 30, and at the same time form a digital image. The display unit 303 is used to finally display the digital image formed by the image reconstruction unit 302.

[0126] An embodiment of the present invention also provides a computer-readable storage medium, on which computer instructions are stored. When the computer instructions run, they execute each step of the above imaging method.

[0127] An embodiment of the present invention also provides a terminal, including a memory and a processor. Computer instructions capable of running on the processor are stored on the memory. When the processor runs the computer instructions, it executes each step of the above imaging method.

[0128] In summary, the detection collimation unit, detection device, and SPECT imaging system provided by the present invention not only achieve the effect of gamma ray direction collimation, but also achieve the purpose of photon detection, and do not affect the image quality. At the same time, compared with the existing imaging system using a heavy metal collimator that does not allow rays to pass through, it can not only avoid the loss of gamma photons, greatly improve the detection efficiency of gamma photons, but also does not affect the image quality of imaging using the SPECT imaging system. At the same time, it also avoids the processing difficulty of machining multiple small parallel holes or pinholes in the heavy metal collimator, and simplifies the processing process.

[0129] In addition, by optimizing the arrangement of the detector part in the existing imaging tradition into the detection device of the present invention, the system sensitivity and resolution are significantly improved simultaneously.

[0130]

[0131] Through the reasonable design of parameters such as the field of view and the size of the scintillating crystal, the SPECT imaging system of the present invention greatly improves the detection efficiency (up to 0.1% to more than 1%) and resolution (less than 0.1 mm to 1 mm) of gamma photons compared with the existing imaging system with a heavy metal collimator (the gamma photon detection efficiency is about 0.01%, and the system imaging resolution is about 12 mm).

[0132] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A detection device, characterized in that, the detection device includes a plurality of detection collimation units, and each detection collimation unit includes: a scintillation crystal array (10) for receiving gamma photons emitted by a radiation source in a detected object (30); a plurality of optoelectronic devices (20) for receiving the gamma photons and converting them into digital signals; wherein, the scintillation crystal array (10) includes a plurality of scintillation crystals (101), the plurality of scintillation crystals (101) are arranged substantially parallel and spaced apart, and each scintillation crystal (101) has an end face and a side face capable of receiving rays emitted by the radiation source; the plurality of optoelectronic devices (20) are coupled to the end faces of the plurality of scintillation crystals (101); wherein, the plurality of detection collimation units are fixedly connected to form a detection collimation unit layer distributed in any one of a circular shape, a polygonal shape, an arc shape, and a partial polygonal shape around the detected object (30); the detection device includes a plurality of detection collimation unit layers arranged at intervals along the incident direction of the gamma rays emitted by the radiation source, and the plurality of detection collimation unit layers are arranged in a staggered manner so that at least one scintillation crystal (101) exists on the detection collimation unit of the last detection collimation unit layer, and gamma photons emitted from a point in the imaging field of view do not pass through any optoelectronic device (20) or circuit board material on the transmission path when incident on the scintillation crystal (101) of the last detection collimation unit layer.

2. The detection device according to claim 1, characterized in that, the scintillation crystal array (10) is a two-dimensional arrangement array, and the scintillation crystal array (10) includes a plurality of scintillation crystals (101) arranged along the incident direction of the gamma rays emitted by the radiation source, and a plurality of scintillation crystals (101) arranged perpendicular to the incident direction of the gamma rays emitted by the radiation source.

3. The detection device according to claim 1 or 2, characterized in that, the scintillation crystal (101) includes at least one independent scintillation crystal strip (1011) and / or a plurality of scintillation crystal strips (1011) spliced together.

4. The detection device according to claim 3, characterized in that, at least one end face of the scintillation crystal strip (1011) is coupled with an optoelectronic device (20).

5. The detection device according to claim 1, characterized in that, in the scintillation crystal array (10), there is a filler between the spaced scintillation crystals (101), and the filler includes at least one material of resin, polyethylene plastic, plexiglass, and heavy metal.

6. A SPECT imaging system, characterized in that, the SPECT imaging system includes the detection device (2) according to any one of claims 1-5, a data processing unit (301), and an image reconstruction unit (302); the data processing unit (301) is configured to receive the digital signal output by the detection device (2) and perform processing to obtain the incident information of each incident gamma photon; The image reconstruction unit (302) is configured to receive the incident information of a plurality of incident gamma photons output by the data processing unit (301), process the information, obtain the distribution information of the radiation source in the object to be detected (30), and form a digital image.

7. The SPECT imaging system according to claim 6, wherein, each detection collimation unit layer of the detection device (2) can be selectively rotated around the object to be detected (30).

8. The SPECT imaging system according to claim 6, wherein, the SPECT imaging system includes at least two detection devices (2) arranged at intervals along the incident direction of the gamma rays emitted by the radiation source, and in the incident direction of the gamma rays emitted by the radiation source, the distal detection device away from the object to be detected (30) is configured to receive the gamma photons emitted by the radiation source in the object to be detected and passing through one or more proximal detection devices, and convert the gamma photons into digital signals.

9. The SPECT imaging system according to claim 6, wherein, the relative position of each detection device in the SPECT imaging system, the spacing between two adjacent detection devices (2), and the number, size, and arrangement parameters of the scintillation crystal bars (1011) in each detection collimation unit are selected according to the spatial resolution and image signal-to-noise ratio required by the SPECT imaging system.

10. The SPECT imaging system according to claim 6, wherein, a heavy metal collimator (3') with openings is provided between the first detection device (2) close to the object to be detected and the object to be detected (30), and / or between two adjacent detection devices (2) along the incident direction of the gamma rays emitted by the radiation source, and / or between the detection collimation unit layers of each detection device (2).

11. The SPECT imaging system according to claim 10, wherein, the photon transmittance of the heavy metal collimator (3') is greater than 1%.

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