PET detector unit, PET detector

Abstract

The present invention discloses a PET detector unit and a PET detector. The PET detector unit includes: a scintillation crystal array including a plurality of scintillation crystals; a first detector array including a plurality of first sub-detectors, and the first detector array is coupled and connected to a first end of the scintillation crystal array; a second detector array including a plurality of second sub-detectors, and the second detector array is coupled and connected to a second end of the scintillation crystal array opposite to the first end, the detection area of ​​the first sub-detectors is larger than the detection area of ​​the second sub-detectors, and the number of the first sub-detectors is less than the number of the second sub-detectors. The PET detector of the present application can reduce the back-end electronic channels and reduce the cost of electronic devices while achieving high time resolution, high position resolution, and high depth resolution.

Description

Technical Field

[0001] The present invention belongs to the technical field of PET detection, and in particular, relates to a PET detector unit and a PET detector. Background Art

[0002] Positron emission tomography (PET) is a three-dimensional imaging technology that injects radioactive isotope-labeled compounds as tracers into the body, then measures the radioactive distribution information in the body from different angles in vitro, and uses modern computers to reconstruct the metabolite distribution image. The main component of the PET system is the scintillator-based PET detector.

[0003] In order to improve the detection efficiency of PET detectors, relatively long scintillation crystals are needed, but this also brings uncertainty in the depth of interaction (DOI) for measuring the position of gamma photons. DOI uncertainty will reduce the spatial resolution of the imaging system, so high-definition PET detectors need to have the ability to measure DOI. Methods for DOI measurement include the use of multi-layer crystal combination methods, multi-layer detector separate readout methods, double-end readout methods, and continuous crystal methods. Double-end readout PET detectors have better depth resolution and crystal resolution, and are the first choice for studying ultra-high-resolution PET detectors. The depth detection capability allows the full field of view to maintain uniform high position resolution under the conditions of using small detector ring diameters and long scintillation crystals, which is an important means for PET imaging systems to achieve both high efficiency and high definition.

[0004] The existing double-end readout DOI-PET detector uses the light detectors at both ends to read out the crystal array. The detector measures the interaction depth according to the energy ratio of the signals measured by the light detectors at both ends. In order to achieve high position resolution, the area of ​​each detection unit at both ends of the existing detector is the same, and they are all small-sized detection units. For example, to achieve a position resolution below 1mm, the unit size of SiPM (Silicon photomultiplier, SiPM for short) needs to be less than 3mm. For the use of small detector units, due to their large number, it is necessary to encode the readout signal of the detector to reduce the electronic channels for readout, and the general encoding method (such as resistor network readout encoding, row and column readout encoding) will make the time performance of the detector worse. The method of improving the time resolution generally requires a 1:1 separate readout of each detector unit, but due to the large number of small-area detection units, many electronic readout channels are required, which increases the cost, makes the readout difficult, and increases the power consumption. Summary of the invention

[0005] (I) Technical Problems to be Solved by the Present Invention

[0006] The technical problem solved by the present invention is: how to reduce the number of reading channels while maintaining high position resolution and high time resolution.

[0007] (II) Technical solution adopted by the present invention

[0008] A PET detector unit, comprising:

[0009] A scintillation crystal array, comprising a plurality of scintillation crystals;

[0010] A first detector array includes a plurality of first sub-detectors, and the first detector array is coupled to a first end of the scintillation crystal array;

[0011] The second detector array includes multiple second sub-detectors, and the second detector array is coupled to the second end of the scintillation crystal array opposite to the first end, the detection area of ​​the first sub-detector is larger than the detection area of ​​the second sub-detector, and the number of the first sub-detectors is less than the number of the second sub-detectors.

[0012] Preferably, the first detector array comprises M*N first sub-detectors arranged in an array, and the output signal of the first detector array is used to generate a time signal and an energy signal, wherein M≥1 and N≥1.

[0013] Preferably, the second detector array comprises m*n second sub-detectors arranged in an array, and the output signal of the second detector array is used to generate a position signal and an energy signal, wherein m≥2 and n≥2.

[0014] Preferably, the PET detector unit further comprises:

[0015] A first light coupling layer, sandwiched between the first detector array and the first end;

[0016] The second light coupling layer is sandwiched between the second detector array and the second end.

[0017] Preferably, both the first sub-detector and the second sub-detector are silicon photomultiplier tubes.

[0018] The present application also discloses a PET detector, comprising:

[0019] The PET detector unit described above;

[0020] a first readout circuit unit, electrically connected to the first detector array, and configured to convert an output signal of the first detector array into a time signal and a first energy signal;

[0021] The second readout circuit unit is electrically connected to the second detector array and is used for converting the output signal of the second detector array into a position signal and a second energy signal.

[0022] Preferably, the first readout circuit unit comprises:

[0023] an amplifier circuit, used for amplifying the output signal of each of the first sub-detectors;

[0024] The time discrimination circuit is used to read the amplified output signal of each of the first sub-detectors respectively to obtain a plurality of time signals.

[0025] Preferably, the first readout circuit unit further includes:

[0026] An OR logic circuit is used to compress the multiple time signals obtained by the time discrimination circuit into a predetermined number of time signals.

[0027] Preferably, the first readout circuit unit further includes:

[0028] An energy summing circuit, used for generating a first energy signal of a first detector array according to an amplified output signal of each of the first sub-detectors;

[0029] Or it includes: a first position encoding circuit, used for generating an auxiliary position signal and a first energy signal according to the amplified output signal of each of the first sub-detectors.

[0030] Preferably, the second readout circuit unit further includes:

[0031] A second position encoding circuit is used to obtain the coordinates of the position to be detected in the second detector array;

[0032] The energy calculation unit is used to calculate the second energy signal of the second detector array according to the signal strength of the output signal of the second position encoding circuit.

[0033] (III) Beneficial effects

[0034] The present invention discloses a PET detector unit and a PET detector, which have the following technical effects compared with traditional detectors:

[0035] (1) By providing a first detector array consisting of large-sized first sub-detectors and a second detector array consisting of small-sized second sub-detectors, the back-end electronic channels can be reduced while the cost of electronic devices is reduced while the PET detector simultaneously achieves high time resolution, high position resolution, and high depth resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic structural diagram of a PET detector unit according to Embodiment 1 of the present invention;

[0037] Figure 2 This is a principle block diagram of a PET detector according to the second embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of the signal reading process of the first detector array of the PET detector according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail 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 invention and are not used to limit the present invention.

[0040] Before describing the various embodiments of the present application in detail, the inventive concept of the present application is briefly described first: In the prior art, the two ends of the PET detector are mostly small-sized detection arrays with small areas and equal numbers (there are also large-sized detection arrays of the same size). Although they can maintain a high position resolution, they will cause more reading channels and increase costs. The present application sets a large-sized and small-number first detector array at one end of the scintillation crystal array, and sets a small-sized and large-number second detector array at the other end of the scintillation crystal array. The first detector array is used to read out high-resolution time signals separately, and the second detector array is used to output high-resolution position signals. At the same time, since the number of detection units in the first detector array is small, the number of reading channels can be reduced, thereby reducing costs.

[0041] Embodiment 1

[0042] Specifically, Figure 1 As shown, the PET detector unit of the first embodiment includes a scintillation crystal array 10, a first detector array 20 and a second detector array 30. The scintillation crystal array 10 includes a plurality of scintillation crystals 11, the first detector array 20 includes a plurality of first sub-detectors 21, and the first detector array 20 is coupled to a first end of the scintillation crystal array 10; the second detector array 30 includes a plurality of second sub-detectors 31, and the second detector array 30 is coupled to a second end of the scintillation crystal array 10 opposite to the first end, the detection area of ​​the first sub-detector 21 is larger than the detection area of ​​the second sub-detector 31, and the number of the first sub-detectors 21 is less than the number of the second sub-detectors 31.

[0043] Specifically, the number of scintillation crystals in the scintillation crystal array 10 is not limited, and the size of the scintillation crystal is not specifically limited. According to the requirements of the PET scanning system, the high-resolution detector can use a crystal size of 0.5mm-1.5mm, or a crystal size of 2mm-4mm for the human body PET system. The length of the crystal can be from 10mm to 40mm, which is adjusted according to the requirements of the system detection efficiency and cost. The crystal can use a commonly used high-density LYSO (Lutetium Yttrium Orthosilicate, referred to as LYSO) crystal, or other scintillation crystals, such as LFS (Lutetium fine silicate crystal, referred to as LFS), GAGG (Gadolinium gallium aluminum garnet, referred to as GAGG), BGO (Bismuthgermanate crystal, referred to as BGO), etc. As a preferred embodiment, the first sub-detector 21 and the second sub-detector 31 are both silicon photomultiplier tubes (SiPM).

[0044] As a preferred embodiment, the first detector array 20 includes M*N array-arranged first sub-detectors 21, and the output signal of the first detector array 20 is used to generate a time signal and an energy signal, wherein M≥1 and N≥1. Exemplarily, the first detector array 20 is composed of 2×2 or 4×4 first sub-detectors 21, and the detection area of ​​the first sub-detector 21 is 4×4 mm 2 or 6×6mm 2 .

[0045] As a preferred embodiment, the second detector array 30 includes m*n second sub-detectors 31 arranged in an array, and the output signal of the second detector array 30 is used to generate a position signal and an energy signal, wherein m≥2, n≥2. The second detector array 30 is composed of 4×4 or 8×8 second sub-detectors 31, and the detection area of ​​the second sub-detector 31 is 2×2mm 2 or 3×3mm 2 .

[0046] Furthermore, the PET detector unit further includes a first optical coupling layer 40 and a second optical coupling layer 50 . The first optical coupling layer 40 is sandwiched between the first detector array 20 and the first end, and the second optical coupling layer 50 is sandwiched between the second detector array 30 and the second end.

[0047] The first detector array 20 reads out the signal of each first sub-detector 21 individually in a 1:1 manner, thereby obtaining an accurate time signal and energy signal. Since the number of first detector arrays 20 is small, even if each first sub-detector 21 is read one by one, the number of readout channels required is also small. The second detector array 30 reduces the number of readout channels by light sharing and encoding to provide the PET detector with the position information and energy information of the gamma photons detected. For example, the crystal size of a single scintillation crystal is 1.5×1.5 mm 2 The size of the second sub-detector 31 is 3×3 mm 2 , can be achieved for each 1.5×1.5mm 2 Crystal resolution, especially crystals at the edge of the array, can be better resolved. This allows for better identification of small crystal units. At the same time, by encoding the readout signal, the number of readout channels can be reduced while satisfying the requirement of distinguishing each crystal unit in the scintillation crystal array. Since the second detector array 30 has a large signal change after encoding and poor time performance, the signal readout of the second detector array 30 is mainly used for crystal position resolution and energy measurement of received gamma photons.

[0048] The following describes the measurement method of the first detector array 20 and the second detector array 30 through specific embodiments.

[0049] The scintillation crystal array 10 includes 8×8 scintillation crystals arranged in an array, and the size of each scintillation crystal is 1.5×1.5×20 mm. 3 The first detector array 20 includes 2×2 first sub-detectors 21 arranged in an array, and the detection area of ​​each first sub-detector 21 is 6×6 mm 2 The second detector array 30 includes 4×4 second sub-detectors 31, and the detection area of ​​each second sub-detector 31 is 3×3 mm 2 .

[0050] The signal of each first sub-detector 21 of the first detector array 20 is amplified respectively, and each amplified signal is encoded in one path to obtain the energy signal A1, B1, C1, D1 of each first sub-detector 21, so that the total energy E1 of the first detector array 20 is obtained = A1 + B1 + C1 + D1. Each amplified signal is encoded in another path to obtain the energy signal T1, T2, T3, T4 of each first sub-detector 21.

[0051] After the second detector array 30 is encoded by the encoding network, four energy signals A2, B2, C2, and D2 are generated. The total energy E2 of the second detector array 30 obtained in this way is E2=A2+B2+C2+D2. If the encoding method is a resistor network readout encoding method, the calculation method of the crystal resolution map of the second detector array 30 is:

[0052]

[0053]

[0054] Among them, X2 is used to determine the position of the scintillation crystal in the x-axis direction, and Y2 is used to determine the position of the scintillation crystal in the y-axis direction. Specifically, A2, B2, C2, and D2 obtained by the resistor network coding method are the signals in four directions after the detector array signal is integrated. It can be regarded as the signal is distributed to four corners, so the position in the x-direction and y-direction is respectively obtained by adding the signals of two different corners and dividing them by the total signal. The resistor network coding method is a prior art, and the specific coding process is not repeated here.

[0055] If the encoding method is a row-column readout encoding method, the calculation method of the crystal resolution map of the second detector array 30 is:

[0056]

[0057]

[0058] Among them, X2 is used to determine the position of the scintillation crystal in the x-axis direction, Y2 is used to determine the position of the scintillation crystal in the y-axis direction, A2 and B2 obtained by the row-column readout coding method are the row coding signals, and C2 and D2 are the column coding signals, so the positions in the x-direction and y-direction are calculated by the row and column coding signals respectively. The row-column readout coding method is a prior art, and the specific coding process is not described in detail here.

[0059] The depth information of the detector is:

[0060]

[0061] In this way, through the first detector array 20 and the second detector array 30, better crystal resolution images, energy information, DOI information, and time information are obtained while using fewer reading channels, so that the PET detector can simultaneously achieve high time resolution, high position resolution, and high depth resolution.

[0062] Embodiment 2

[0063] like Figure 2As shown, the PET detector of the second embodiment includes a PET detector unit 100, a first readout circuit unit 60 and a second readout circuit unit 70, wherein the PET detector unit 100 preferably adopts the PET detector unit in the first embodiment, so the specific structure of the PET detector unit 100 is not described here, and the description of the first embodiment can be referred to. The first readout circuit unit 60 is electrically connected to the first detector array 20, and is used to convert the output signal of the first detector array 20 into a time signal and a first energy signal. The second readout circuit unit 70 is electrically connected to the second detector array 30, and is used to convert the output signal of the second detector array 30 into a position signal and a second energy signal.

[0064] As a preferred embodiment, the first readout circuit unit 60 includes an amplifier circuit 61 and a time discrimination circuit 62, wherein the amplifier circuit 61 is used to amplify the output signal of each of the first sub-detectors 21, and the time discrimination circuit 62 is used to read the amplified output signal of each of the first sub-detectors respectively to obtain multiple time signals.

[0065] Furthermore, the first readout circuit unit 60 further includes an OR logic circuit 63, which is used to compress the multiple time signals obtained by the time discrimination circuit 62 into a predetermined number of time signals. In another embodiment, the first readout circuit unit 60 further includes a position encoding circuit 64, which is used to generate a first energy signal and an auxiliary position signal according to the output signal amplified by each of the first sub-detectors.

[0066] For example, Figure 3 As shown, the first detector array 20 includes 4×4 first sub-detectors 21 arranged in an array. The signal of each first sub-detector 21 is amplified by an amplifier circuit 61, and then one signal is read out separately by a time discrimination circuit 62 in a 1:1 manner to obtain 16 time signals (T1, T2, ..., T 15 、T 16 ), a high-precision time resolution can be obtained. Of course, in other embodiments, if the time resolution requirement is not high, the 16-channel time signal can be processed by the OR logic circuit 63 to reduce the number of output channels of the time signal, thereby reducing the number of reading channels. For example, the number of channels of the OR logic circuit 63 is 4, and the 16-channel time signal (T1, T2, ... T 15 、T 16 ) After being processed by the OR logic circuit 63, 4 time signals are obtained.

[0067] Furthermore, the other signals of the 16 first sub-detectors 21 are read out by the first position encoding circuit 64 to obtain the 4 signals Row1, Row2, Row3, Row4 and the 4 signals Column1, Column2, Column3, Column4, and then are encoded to obtain R1, R2, C1, C2, and the first energy signal E=R1+R2+C1+C2. Among them, Row1, Row2, Row3, Row4 respectively represent the sum of the signals of the first sub-detectors 21 in each row, and Column1, Column2, Column3, Column4 respectively represent the sum of the signals of the first sub-detectors in each column. The encoding of R1 and R2 is to convert Row1, Row2, Row3, Row4 from 4 to 2 signals according to the electrical signal voltage division method of different proportions, and the same is true for C1 and C2. With reference to formulas (3) and (4), the specific coordinates of the position to be detected can be calculated. It should be noted that the specific coordinates of the position to be detected obtained here are used as auxiliary position signals, and more accurate signals need to be obtained through the second readout circuit. In this way, the number of signal paths that the first readout circuit unit 60 of the PET detector finally reads out is: 2 paths + 2 paths + 16 paths. After being processed by the OR logic circuit 63, the number of signal paths that the first readout circuit unit 60 of the PET detector finally reads out is: 2 paths + 2 paths + 16 / OR logic circuit paths.

[0068] In another embodiment, the first readout circuit unit 60 further includes an energy summing circuit, and the first position encoding circuit 64 is not required. The output signals of the 16 first sub-detectors 21 after amplification are summed by the energy summing circuit to obtain the first energy signal of the first detector array 20, thereby forming one energy signal. In this way, the number of signal paths finally read out by the first readout circuit unit 60 of the PET detector is: 1 path + 16 paths.

[0069] Exemplarily, the second detector array 30 includes 8×8 second sub-detectors 31, and the second readout circuit unit 70 includes a second position encoding circuit 71 and an energy calculation unit 72. The second position encoding circuit 71 is used to obtain the coordinates of the position to be detected in the second detector array 30, and the second position encoding circuit 71 uses a discrete positioning method (such as a resistor network readout method) or a charge distribution method (such as a row-column addition readout method) to encode the multi-channel signals of the second detector array 30 into 4-channel signals and then collect the signals through the back-end electronics. The specific encoding process refers to Example 1 and is not described here. In other embodiments, the energy calculation unit 72 sums the 4-channel signals output by the second position encoding circuit 71 to obtain a second energy signal. The second detector array 30 generates a smaller number of signals through the second readout circuit unit 70 encoding while providing accurate position resolution, thereby reducing the number of electronic reading channels. The second detector array obtains more accurate position signals mainly by using the relatively small second sub-detectors of the array. Although encoding circuits are used, due to the large number of second sub-detectors, the position information is more comprehensive and the area of ​​each unit is small, so the crystal resolution capability is better.

[0070] The PET detector provided in the second embodiment uses the first readout circuit unit 60 to obtain accurate time signals and energy signals from the first detector array 20, and uses the second readout circuit unit 70 to obtain accurate position signals and energy signals from the second detector array 30. Since the number of detectors in the first detector array 20 is relatively small, the back-end electronic channels can be reduced while the PET detector simultaneously achieves high time resolution, high position resolution, and high depth resolution.

[0071] The specific implementation methods of the present invention are described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments can be modified and improved without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents. These modifications and improvements should also be within the scope of protection of the present invention.

Claims

1. A PET detector, characterized in that: The PET detector comprises: A PET detector unit, the PET detector unit comprising a scintillation crystal array, a first detector array, and a second detector array, the scintillation crystal array comprising a plurality of scintillation crystals, the first detector array comprising a plurality of first sub-detectors, and the first detector array is coupled to a first end of the scintillation crystal array, the second detector array comprising a plurality of second sub-detectors, and the second detector array is coupled to a second end of the scintillation crystal array opposite to the first end, the detection area of ​​the first sub-detector is larger than the detection area of ​​the second sub-detector, and the number of the first sub-detectors is less than the number of the second sub-detectors; a first readout circuit unit, electrically connected to the first detector array, and configured to convert an output signal of the first detector array into a time signal and a first energy signal; A second readout circuit unit, electrically connected to the second detector array, and configured to convert an output signal of the second detector array into a position signal and a second energy signal; The first readout circuit unit further includes: An energy summing circuit, used for generating a first energy signal of a first detector array according to an amplified output signal of each of the first sub-detectors; Or it includes: a first position encoding circuit, used for generating an auxiliary position signal and a first energy signal according to the amplified output signal of each of the first sub-detectors; The second readout circuit unit further includes: A second position encoding circuit is used to obtain the coordinates of the position to be detected in the second detector array; The energy calculation unit is used to calculate the second energy signal of the second detector array according to the signal strength of the output signal of the second position encoding circuit.

2. The PET detector according to claim 1, characterized in that: The first detector array includes M×N first sub-detectors arranged in an array, and output signals of the first detector array are used to generate a time signal and an energy signal, wherein M≥1 and N≥1.

3. The PET detector according to claim 1, characterized in that: The second detector array includes m×n second sub-detectors arranged in an array, and output signals of the second detector array are used to generate position signals and energy signals, wherein m≥2 and n≥2.

4. The PET detector according to claim 2, characterized in that: The PET detector unit also includes: A first light coupling layer, sandwiched between the first detector array and the first end; The second light coupling layer is sandwiched between the second detector array and the second end.

5. The PET detector according to any one of claims 1 to 4, characterized in that: The first sub-detector and the second sub-detector are both silicon photomultiplier tubes.

6. The PET detector according to claim 1, characterized in that: The first readout circuit unit comprises: an amplifier circuit, used for amplifying the output signal of each of the first sub-detectors; The time discrimination circuit is used to read the amplified output signal of each of the first sub-detectors respectively to obtain a plurality of time signals.

7. The PET detector according to claim 6, characterized in that: The first readout circuit unit further includes: An OR logic circuit is used to compress the multiple time signals obtained by the time discrimination circuit into a predetermined number of time signals.

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