Single Photon Emission Tomography

Abstract

The present disclosure provides a single-photon emission tomography device, comprising: a plurality of detector layers, wherein the plurality of detector layers include at least two detector layers arranged along a photon moving direction, wherein the at least two detector layers include a front detector layer and a rear detector layer along the photon moving direction, wherein the front detector layer includes a scintillation crystal array and a silicon photomultiplier device, wherein adjacent scintillation crystal bars in the scintillation crystal array have at least one difference in the number, size and position of coupled silicon photomultiplier devices relative to the scintillation crystal array, so that different gamma photon direction information can be distinguished, so that the probabilities of gamma photons from different directions passing through the front detector layer are different, thereby enabling the front detector layer to have a gamma photon collimation effect on the rear detector layer.

Description

Technical Field

[0001] The present disclosure relates to the field of nuclear technology and application technology, and in particular to a single photon emission tomography device. Background Art

[0002] Single Photon Emission Computed Tomography (SPECT) technology uses radionuclide-labeled tracer drugs to generate gamma photons after being injected into the human body. By detecting the radiation outside the human body, the distribution and changes of the drugs in the human body are obtained, and it is used for the diagnosis and treatment of diseases. SPECT imaging is a typical molecular imaging method that can reflect the physiological, metabolic, functional, and molecular information in the human body, and is one of the current mainstream medical imaging methods.

[0003] Since the process of radioactive nuclides emitting gamma photons is isotropic, if a detector is placed directly outside the human body, the direction of the gamma photons detected by it cannot be determined, that is, it is impossible to know where in the human body they may come from. Therefore, in SPECT imaging, a collimator component needs to be placed between the human body and the detector. The collimator blocks a certain proportion of photons, and the blocking proportions are different for photons from different directions, so that the probability that the photons received by the detector come from different positions in the human body is different, and the image reconstruction algorithm is used to calculate the distribution image of the radioactive nuclides received in the human body.

[0004] Existing collimators are usually absorption collimators made of heavy metals such as tungsten and lead. Through the strong absorption of heavy metals on photons, they are made into specific geometric shapes, such as parallel hole collimators, pinhole collimators, etc., so that photons from certain directions can pass through the collimator completely or have a higher probability of passing through the collimator, while photons from certain directions are completely blocked or have a lower probability of passing through the collimator, thereby achieving the effect of different efficiency of photons from different directions passing through the collimator. Therefore, when each photon is received on a certain detector unit, the probability of it coming from different directions in the human body can be judged. After the detector receives a large number of photons, its statistical information is input into the image reconstruction algorithm, and the spatial distribution image of radionuclides in the human body can be reconstructed. However, since the photons absorbed by the heavy metal absorption collimator cannot be detected by the detector, a large amount of photon loss will be caused, which seriously affects the detection efficiency of SPECT. In addition, the existing single photon emission tomography device also has defects such as large size and poor collimation effect of the collimator. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the above problems, the main purpose of the present disclosure is to provide a single photon emission tomography device to solve at least one of the above problems.

[0007] (II) Technical solution

[0008] In order to achieve the above-mentioned purpose, as one aspect of the present disclosure, a single-photon emission tomography device is provided, comprising: a plurality of detector layers, the plurality of detector layers comprising at least two detector layers arranged along the direction of photon movement, the at least two detector layers comprising a front detector layer and a rear detector layer along the direction of photon movement, the front detector layer comprising a scintillation crystal array and a silicon photomultiplier device.

[0009] Furthermore, the scintillation crystal array includes a plurality of scintillation crystals arranged in an array, each scintillation crystal includes a plurality of spliced ​​scintillation crystal bars; each of the scintillation crystal bars has a plurality of end faces, one or more of the silicon photomultiplier devices are coupled to any one or more of the end faces of one or more of the scintillation crystal bars, forming a fixed relative position relationship with the scintillation crystal bars, or one or more of the silicon photomultiplier devices are separately arranged from the scintillation crystal bars.

[0010] Furthermore, the subsequent detector layer includes a scintillation crystal array, the scintillation crystal array includes a plurality of scintillation crystals arranged in an array, each scintillation crystal includes one or more scintillation crystal bars, the silicon photomultiplier device of the subsequent detector layer includes one or more silicon photomultiplier devices SiPM, and the one or more scintillation crystal bars are selectively connected to the one or more silicon photomultiplier devices SiPM.

[0011] Furthermore, the material of the silicon photomultiplier device is known, and the attenuation and absorption coefficient of photons are known. When the gamma photon passes through the preceding detector layer, it selectively passes through one or more of the scintillation crystal strips and / or selectively passes through one or more of the silicon photomultiplier devices.

[0012] Furthermore, the photons emitted from different positions in the imaging area pass through different numbers of silicon photomultiplier devices and / or different effective optical paths of silicon photomultiplier devices before reaching at least one scintillator crystal bar.

[0013] Furthermore, a distance between the front detector layer and the rear detector layer is greater than or equal to 1 mm.

[0014] (III) Beneficial effects

[0015] It can be seen from the above technical solutions that the single photon emission tomography disclosed in the present invention has at least one of the following beneficial effects:

[0016] (1) Small-volume silicon photomultiplier devices SiPM and APD are used instead of PMT as the photoelectric devices of the front detector layer, reducing the size of the single-photon emission tomography device.

[0017] (2) The rear detector layer of the present invention includes at least one scintillator crystal bar. The photons emitted from different positions in the imaging area pass through different numbers of optoelectronic devices and / or different lengths of optoelectronic devices before reaching the at least one scintillator crystal bar. The absorption effect of optoelectronic devices such as SiPM and APD on photons is further utilized. By arranging different optoelectronic device schemes, the intensity difference of photons from different directions on the rear detector layer after being absorbed by the front scintillator crystal and optoelectronic device is further increased, so that the direction information of different gamma photons can be distinguished, so that the front detector layer has a gamma photon collimation effect on the rear detector layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the single photon emission tomography device according to Embodiment 1 of the present disclosure.

[0019] Figure 2 This is a schematic diagram of the structure of the single photon emission tomography device according to Embodiment 2 of the present disclosure.

[0020] Figure 3 This is a schematic diagram of the structure of the single photon emission tomography device according to Embodiment 3 of the present disclosure.

[0021] Figure 4 This is a schematic diagram of the structure of the single photon emission tomography device according to Embodiment 4 of the present disclosure.

[0022] Figure 5 Schematic diagram of the photon penetration probability disclosed in the present invention.

[0023] <Description of symbols>

[0024] 1-first detector layer, 2-second detector layer, 11, 12, 13, 14, 21, 23, 24-scintillator crystal bars, 15, 16, 17-photoelectric devices (SiPM silicon photomultiplier devices), 22-photoelectric devices (any type of photoelectric devices), 3-human body, P1, P2, P3, P4-gamma photon rays. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0026] The present disclosure provides a single-photon emission tomography device, comprising: a plurality of detector layers, wherein the plurality of detector layers include at least two detector layers arranged along a photon motion direction, wherein the at least two detector layers include a front detector layer and a rear detector layer along the photon motion direction, wherein the front detector layer includes a scintillation crystal array and a silicon photomultiplier device.

[0027] Furthermore, the scintillation crystal array comprises a plurality of discrete scintillation crystal bars and / or a plurality of spliced ​​scintillation crystal bars; each of the scintillation crystal bars has a plurality of end faces, one or more of the silicon photomultiplier devices are coupled to any one or more end faces of one or more of the scintillation crystal bars, forming a fixed relative position relationship with the scintillation crystal bars, or one or more of the silicon photomultiplier devices are separately arranged with the scintillation crystal bars.

[0028] The present disclosure adopts a small-volume silicon photomultiplier device to replace the PMT as the photoelectric device of the front detector layer, thereby reducing the size of the single-photon emission tomography device.

[0029] The material of the silicon photomultiplier device is known, and the attenuation and absorption coefficient of the photons are known. The photons pass through the preceding detector layer and the succeeding detector layer, and play a role in fixing the relative positional relationship between the detector layer and the scintillation crystal in the single photon emission tomography device. When the gamma photons pass through the preceding detector layer, they selectively pass through one or more of the scintillation crystal bars and / or selectively pass through one or more of the silicon photomultiplier devices.

[0030] The photons emitted from different positions in the imaging area pass through different numbers of photoelectric devices and / or different effective optical paths of the photoelectric devices before reaching the at least one scintillation crystal array. Thus, the present disclosure further enhances the photon collimation effect on the subsequent detector layer and improves the detection efficiency of the system.

[0031] The following is combined with Figure 1-5 The embodiments of the present disclosure are described in detail.

[0032] Example 1

[0033] In this embodiment, if Figure 1As shown, the radioactive nuclide in the detected object (such as human body 3) generates gamma photons, and the imaging device includes but is not limited to two detector layers, which are distributed in two layers in the front and back along the gamma photon transmission direction outside the human body, wherein the detector layer in the front along the photon transmission direction is the first detector layer 1, and the detector layer in the back along the photon transmission direction is the second detector layer 2, and the detector layer in the front (first detector layer) is closer to the human body than the detector layer in the back (second detector layer). The first detector layer 1 includes four independent scintillation crystal bars 11, 12, 13, 14 (although the present embodiment is an independent scintillation crystal bar, the number is several, but in fact, spliced ​​scintillation crystal bars or several combinations of the two can also be used) and three SiPM devices 15, 16, 17 (15, 16, 17 can also use APD photoelectric devices), and the second detector layer 2 includes a scintillation crystal bar 21. The scintillation crystal is used to receive the gamma photon signal, and the SiPM device is used to convert the received gamma photon signal into an electrical signal output or to play a collimating role. Two of the four scintillation crystal bars 11 and 13 are scintillation crystal bars of the first type, and the other two scintillation crystal bars 12 and 14 are scintillation crystal bars of the second type, and the two types of scintillation crystal bars are made of different materials. The scintillation crystal bar 11 is coupled to the SiPM device 15, the scintillation crystal bars 12 and 13 are coupled to the SiPM device 17, the scintillation crystal bar 14 is not coupled to the SiPM device, and the SiPM device 16 is not coupled to the scintillation crystal bar.

[0034] The imaging device may further include an image reconstruction module, which receives the electrical signal and uses an image reconstruction algorithm to obtain an image of the distribution of radionuclides in the human body. The image reconstruction algorithm may be, for example, a filtered back-projection analytical reconstruction algorithm, an algebraic iterative algorithm, or a statistical iterative reconstruction algorithm.

[0035] The scintillation crystal strip may be composed of any one or more combinations of NaI, CsI, LaBr3, CLYC, BGO, LSO, LYSO, GSO, YSO, YAP and GAGG.

[0036] Of course, the optoelectronic devices in the first detector layer of this embodiment are not limited to silicon photomultiplier devices SiPM, and may also be avalanche photodiodes APD, Geiger mode avalanche photodiodes GAPD, solid-state photomultiplier devices SSPM, etc. Compared with the use of PMT devices, the use of SiPM, APD, and scintillation crystals as optoelectronic devices in the front detector layer of this embodiment can reduce the distance between the detector layers, thereby reducing the size of the device and the occupied space.

[0037] In addition, the coupling relationship between the SiPM and the scintillation crystal strip is not limited to the coupling relationship in the embodiment. For any one SiPM, it can be coupled with one or more scintillation crystal strips, or it can be not coupled with the scintillation crystal strip (in this case, the SiPM only plays a role in enhancing the collimation effect, and does not play a role in converting the optical signal output by the scintillation crystal strip into an electrical signal). For any one scintillation crystal strip, it can be coupled with one or more SiPMs, or it can be not coupled with the SiPM (in this case, the scintillation crystal strip only plays a role in enhancing the collimation effect, and does not play a role in detecting gamma photons).

[0038] In addition, in the present embodiment, the number of detector layers (preferably, the number of detector layers is 2 to 6 layers to reduce the size of the imaging device and improve the imaging performance of the imaging device), the shape of the scintillator crystals (not limited to strips, for example, it can also be blocks, etc., which does not affect the implementation of the present disclosure, and the same applies to subsequent embodiments), the number of scintillator crystal bars, the type of scintillator crystal bars, the number of optoelectronic devices, etc. are merely exemplary descriptions, and those skilled in the art may make appropriate adjustments as needed.

[0039] Example 2

[0040] In this embodiment, if Figure 2 As shown, the radioactive nuclides in the detected object (such as human body 3) generate gamma photons, and the imaging device includes two detector layers, which are distributed in two layers in front and back along the direction of gamma photon movement outside the human body, wherein the detector layer in front along the direction of photon movement is the first detector layer 1, and the detector layer in the back along the direction of photon movement is the second detector layer 2, and the detector layer in front (first detector layer) is closer to the human body than the detector layer in the back (second detector layer). The first detector layer 1 includes four independent scintillation crystal bars 11, 12, 13, 14 and three SiPM devices 15, 16, 17 (15, 16, 17 can also use APD photoelectric devices), and the second detector layer 2 includes a scintillation crystal bar 21 and a PMT device 22 (22 is not limited to PMT devices, and can be any type of photoelectric device). The scintillation crystal is used to receive gamma photon signals, and the SiPM device and PMT device are used to convert the received gamma photon signals into electrical signal output or play a collimating role.

[0041] Two of the four scintillation crystal bars 11 and 13 are scintillation crystal bars of the first type, and the other two scintillation crystal bars 12 and 14 are scintillation crystal bars of the second type, and the two types of scintillation crystal bars are made of different materials. The scintillation crystal bar 11 is coupled to the SiPM device 15, the scintillation crystal bars 12 and 13 are coupled to the SiPM device 17, the scintillation crystal bar 14 is not coupled to the SiPM device, and the SiPM device 16 is not coupled to the scintillation crystal bar. The scintillation crystal bar 21 is coupled to the PMT device 22.

[0042] The optoelectronic devices included in the first detector layer are not limited to silicon photomultiplier devices SiPM, and avalanche photodiodes APD, Geiger mode avalanche photodiodes GAPD, solid-state photomultiplier devices SSPM, etc. can also be used. By using SiPM, APD, SSPM to replace PMT as the optoelectronic devices of the previous detector layer, the device size and occupied space are reduced. The optoelectronic devices included in the second detector layer are not limited to PMT, and silicon photomultiplier devices SiPM, avalanche photodiodes APD, Geiger mode avalanche photodiodes GAPD, solid-state photomultiplier devices SSPM, etc. can also be used.

[0043] Example 3

[0044] In this embodiment, if Figure 3 As shown, the radioactive nuclides in the detected object (such as human body 3) generate gamma photons, and the imaging device includes two detector layers, which are distributed in two layers in the front and back along the direction of gamma photon movement outside the human body, wherein the detector layer in front along the direction of photon movement is the first detector layer 1, and the detector layer in the back along the direction of photon movement is the second detector layer 2, and the detector layer in front (first detector layer) is closer to the human body than the detector layer in the back (second detector layer).

[0045] The first detector layer is used to block and collimate the photons moving toward the second detector layer, that is, to act as a collimator. Due to its own limitations, conventional SPECT cannot use a collimator with a high penetration ratio. The present disclosure uses the front detector layer as a collimator to collimate the photons on the rear detector layer, thereby improving the detection efficiency.

[0046] Example 4

[0047] In this embodiment, if Figure 4 As shown, the radioactive nuclide in the detected object (such as human body 3) generates gamma photons, and the imaging device includes two detector layers, which are distributed in two layers in front and back along the direction of gamma photon movement outside the human body, wherein the detector layer in front along the direction of photon movement is the first detector layer 1, and the detector layer in the back along the direction of photon movement is the second detector layer 2, and the detector layer in front (first detector layer) is closer to the human body than the detector layer in the back (second detector layer). Preferably, the spacing distance between the first detector layer and the second detector layer is greater than or equal to 1mm to provide a fixed mechanical reserved space, while increasing the photon transmission distance to increase the difference. The first detector layer 1 includes four independent scintillation crystal bars 11, 12, 13, 14 and three SiPM devices 15, 16, 17 (15, 16, 17 can also use APD photoelectric devices), and the second detector layer 2 includes three scintillation crystal bars 21, 23, 24.

[0048] In the above-mentioned embodiment, there is at least one scintillation crystal bar in the second detector layer, and before photons from different directions in the human body enter the scintillation crystal bar, at least one of the number of scintillation crystal bars, the length of the photons passing through the scintillation crystal, and the scintillation crystal material is different. Alternatively, there is at least one scintillation crystal bar in the detectors of the second detector layer, and before photons from different directions in the human body enter the scintillation crystal bar, at least one of the number of SiPMs, and the length of the photons passing through the SiPM is different.

[0049] In general, if N detector layers are arranged outside the detected object, the directions from the direction close to the detected object to the direction far away from the detected object are the first detector layer, the second detector layer, ..., the Nth detector layer, the first detector layer includes k1 scintillation crystal bars, the second detector layer includes k2 scintillation crystal bars, ... and so on, the Nth detector layer includes kN scintillation crystal bars, and the number of scintillation crystal bars included in each detector layer can be any value, without specific limitation, and can be equal or unequal, then there is at least such a scintillation crystal bar in the Nth detector layer, and before photons from different directions in the human body enter this scintillation crystal bar, at least one of the following three factors is different: the number of scintillation crystal bars passed by, the length of the photons passing through the scintillation crystal, and the scintillation crystal material. On this basis, the first to Nth detector layers may also include a certain number of photoelectric devices (such as SiPM), and the number and type of photoelectric devices are not limited. Then there is at least one scintillation crystal bar in the detector of the Nth detector layer, and before photons from different directions in the human body enter this scintillation crystal bar, at least one of the number of photoelectric devices passed by and the length of the photons passing through the photoelectric devices is different.

[0050] The following is combined with Figure 5 The photon penetration probability of the present disclosure is described. Figure 5 As shown, if the attenuation coefficient of the silicon photomultiplier device is μ1, the attenuation coefficient of a single crystal is μ2, μ3..., the effective optical path of the photon is l1, l2..., and through combination, a variety of penetration probabilities of the photon passing through the front detector layer (first detector layer 1) are obtained (the penetration probability of the rear detector layer (second detector layer 2) follows the same rule).

[0051] The probability of a photon passing through a photoelectric device: p1 = 1-e -u1×l1 , where μ1 is the attenuation coefficient of the silicon photomultiplier device and l1 is the effective light path in the photoelectric device.

[0052] The probability that a photon passes through only the first type of scintillation crystal strip is: p2 = 1-e -u2×l2, where μ2 is the attenuation coefficient of a single first-type scintillation crystal, and l2 is the effective light path length in the first-type scintillation crystal bar.

[0053] The probability that a photon passes through both the optoelectronic device and the first type of scintillation crystal strip at the same time: p3 = 1-e -u1×l3′-u2×l3″ , where μ1 is the attenuation coefficient of the silicon photomultiplier device, μ2 is the attenuation coefficient of a single first-type scintillation crystal, l3' is the effective light travel in the photoelectric device, and l3" is the effective light travel in the first-type scintillation crystal strip.

[0054] The probability that a photon passes through both the optoelectronic device and the second type of scintillation crystal strip at the same time: p4 = 1-e -u1×l4′-u3×l4″ , l4' is the effective light path in the optoelectronic device, and l4" is the effective light path in the crystal 2.

[0055] By designing the scintillator crystal arrays and silicon photomultiplier devices in multiple detector layers differently, the probability of gamma photons coming from different directions passing through the front and rear detector layers can be made different, so that the direction information of different gamma photons can be distinguished, so that the front detector layer has a gamma photon collimation effect on the rear detector layer.

[0056] In addition, the above definitions of the various elements and methods are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and those skilled in the art can simply change or replace them.

[0057] It should be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar figure marks. Conventional structures or constructions will be omitted when they may cause confusion in the understanding of the present disclosure. And the shapes and sizes of the components in the figures do not reflect the actual size and proportion, but only illustrate the contents of the embodiments of the present disclosure. In addition, in the claims, any reference symbols between brackets should not be constructed as limitations on the claims.

[0058] Furthermore, the word "comprising" or "including" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0059] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element, or the order in the manufacturing method. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0060] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the following intention: the claimed disclosure requires more features than the features explicitly recited in each claim. More specifically, as reflected in the claims below, the disclosed aspects are less than all the features of the single embodiment disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present disclosure.

[0061] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A single photon emission tomography device, characterized in that: include: A plurality of detector layers, wherein the plurality of detector layers include at least two detector layers arranged along a photon moving direction, wherein the at least two detector layers include a front detector layer and a rear detector layer along the photon moving direction, wherein the front detector layer includes a scintillation crystal array and a silicon photomultiplier device, Wherein, the scintillation crystal array comprises a plurality of scintillation crystals arranged in an array, each scintillation crystal comprises a plurality of spliced ​​scintillation crystal strips; each of the scintillation crystal strips has a plurality of end faces; One or more of the silicon photomultiplier devices are coupled to any one or more of the end faces of one or more of the scintillation crystal bars, forming a fixed relative position relationship with the scintillation crystal bars; one or more of the silicon photomultiplier devices are separately arranged from the scintillation crystal bars; The material of the silicon photomultiplier device is known, and the attenuation and absorption coefficient of photons are known. When a gamma photon passes through the preceding detector layer, it passes through one of the scintillating crystal strips and / or one of the silicon photomultiplier devices.

2. The single photon emission tomography device according to claim 1, characterized in that: The subsequent detector layer includes a scintillation crystal array and a silicon photomultiplier device. The scintillation crystal array includes a plurality of scintillation crystals arranged in an array, each scintillation crystal includes one or more scintillation crystal bars, and the silicon photomultiplier device of the subsequent detector layer includes one or more silicon photomultiplier devices SiPM, and the one or more scintillation crystal bars are selectively connected to the one or more silicon photomultiplier devices SiPM.

3. The single photon emission tomography device according to claim 2, characterized in that: The photons emitted from different positions in the imaging region pass through different numbers of silicon photomultiplier devices and / or different effective optical paths of silicon photomultiplier devices before reaching at least one scintillator crystal strip in the subsequent detector layer.

4. The single photon emission tomography device according to claim 1, characterized in that: The distance between the preceding detector layer and the following detector layer is greater than or equal to 1 mm.

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