WO2022052090A1 - Pet探测器单元、pet探测器 - Google Patents

Pet探测器单元、pet探测器 Download PDF

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WO2022052090A1
WO2022052090A1 PCT/CN2020/115011 CN2020115011W WO2022052090A1 WO 2022052090 A1 WO2022052090 A1 WO 2022052090A1 CN 2020115011 W CN2020115011 W CN 2020115011W WO 2022052090 A1 WO2022052090 A1 WO 2022052090A1
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detector
sub
detectors
array
detector array
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French (fr)
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柳正
杨永峰
郑海荣
刘新
梁栋
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Shenzhen Institute of Advanced Technology of CAS
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Shenzhen Institute of Advanced Technology of CAS
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
    • G01T1/2914—Measurement of spatial distribution of radiation
    • G01T1/2921—Static instruments for imaging the distribution of radioactivity in one or two dimensions; Radio-isotope cameras
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation

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  • the invention belongs to the technical field of PET detection, and in particular relates to a PET detector unit and a PET detector.
  • Positron Emission Tomography is to inject radioisotope-labeled compounds into organisms as tracers, and then measure the radioactivity distribution information in the organism from different angles in vitro, and use modern computers to complete metabolites. 3D imaging techniques for distribution image reconstruction.
  • the main building block of the PET system is the scintillator-based PET detector.
  • the DOI measurement methods include the method of combining multi-layer crystals, the method of reading out the multi-layer detectors separately, the double-end reading method and the method of continuous crystals, etc.
  • the double-ended readout PET detector has better depth resolution and crystal resolution, and is the first choice for research on ultra-high resolution PET detectors.
  • the depth detection capability enables the use of small detector ring diameters and long scintillation crystals. Uniform and high positional resolution across the entire field of view is an important means for PET imaging systems to achieve high efficiency and high definition at the same time.
  • the existing double-end readout DOI-PET detector utilizes photodetectors at both ends to read out the crystal array, and the detector measures the interaction depth according to the energy ratio of the signals measured by the photodetectors at both ends.
  • the area of each detection unit at both ends of the existing detector is the same, and all are small-sized detection units.
  • SiPM Silicon photomultiplier, SiPM for short
  • the unit size of SiPM Sicon photomultiplier, SiPM for short
  • the readout signal is encoded to reduce the readout electronics channel, and the general encoding method (such as resistance net readout code, row and column readout code) will make the time performance of the detector worse.
  • the method of improving the time resolution generally requires 1:1 readout of each detector unit.
  • many electronic readout channels are required, which increases the cost and makes the readout difficult. large, and the power consumption also increases.
  • the technical problem solved by the present invention is: how to reduce the number of reading channels on the basis of maintaining high position resolution and high time resolution.
  • a PET detector unit comprising:
  • a scintillation crystal array including a plurality of scintillation crystals
  • a first detector array comprising a plurality of first sub-detectors, and the first detector array is coupled and connected to the first end of the scintillation crystal array;
  • the second detector array includes 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 first sub-detectors
  • the detection area of the detector 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 first detector array includes M*N first sub-detectors arranged in an array, and the output signals of the first detector array are used to generate time signals and energy signals, where M ⁇ 1 , N ⁇ 1.
  • the second detector array includes m*n second sub-detectors arranged in an array, and the output signals of the second detector array are used to generate a position signal and an energy signal, where m ⁇ 2 , n ⁇ 2.
  • the PET detector unit further includes:
  • the second light coupling layer is sandwiched between the second detector array and the second end.
  • both the first sub-detector and the second sub-detector are silicon photomultiplier tubes.
  • the application also discloses a PET detector, comprising:
  • a first readout circuit unit electrically connected to the first detector array, for converting the output signal of the first detector array into a time signal and a first energy signal;
  • 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.
  • the first readout circuit unit includes:
  • an amplifying circuit for amplifying the output signal of each of the first sub-detectors
  • the time discrimination circuit is used for separately reading the amplified output signal of each of the first sub-detectors to obtain a plurality of time signals.
  • the first readout circuit unit further includes:
  • an OR logic circuit for compressing the multiple time signals obtained by the time discriminating circuit into a predetermined number of time signals.
  • the first readout circuit unit further includes:
  • an energy summation circuit configured to generate a first energy signal of the first detector array according to the amplified output signal of each of the first sub-detectors
  • a first position encoding circuit configured to generate 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 configured to acquire the coordinates of the position to be detected in the second detector array
  • the energy calculation unit is configured 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.
  • the invention discloses a PET detector unit and a PET detector, which have the following technical effects compared with traditional detectors:
  • the PET detector can achieve high temporal resolution, high Under the premise of position resolution and high depth resolution, the back-end electronic channels can be reduced, and the cost of electronic devices can be reduced at the same time.
  • FIG. 1 is a schematic structural diagram of a PET detector unit according to Embodiment 1 of the present invention.
  • Fig. 2 is the principle block diagram of the PET detector of the second embodiment of the present invention.
  • FIG 3 is a schematic diagram of a signal reading process of the first detector array of the PET detector according to the second embodiment of the present invention.
  • the two ends of the PET detector are mostly small-sized detection arrays with a small area and an equal number (there are also large-area detection arrays of the same size). array), although it can maintain a high position resolution, it will cause more reading channels and increase the cost.
  • a first detector array with a large size and a small number is arranged at one end of the scintillation crystal array, and a second detector array with a small size and a large number is arranged at the other end of the scintillation crystal array, and the first detector array is used for independent readout
  • the second detector array is used to output high-resolution position signals, and 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, and the cost can be reduced.
  • 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 the 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 and connected to the second end of the scintillation crystal array 10 opposite to the first end, the first end
  • the detection area of a 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 .
  • the number of scintillation crystals in the scintillation crystal array 10 is not limited, nor is the size of the scintillation crystals.
  • the human whole body PET system adopts the crystal size of 2mm-4mm, and the length of the crystal can be from 10mm to 40mm, which can be adjusted according to the needs of the detection efficiency and cost of the system.
  • LYSO Yttrium Orthosilicate
  • other scintillation crystals can also be used, such as LFS (Lutetium fine silicate crystal, referred to as LFS), GAGG (Cerium-doped gadolinium gallium aluminum garnet, gadolinium gallium aluminum garnet, Referred to as GAGG), BGO (bismuth germanate crystal, Bismuth germanate crystal, referred to as BGO) and so on.
  • LFS Liutetium fine silicate crystal
  • GAGG Cerium-doped gadolinium gallium aluminum garnet, gadolinium gallium aluminum garnet, Referred to as GAGG
  • BGO bismuth germanate crystal, Bismuth germanate crystal, referred to as BGO
  • both the first sub-detector 21 and the second sub-detector 31 are silicon photomultiplier tubes (SiPM).
  • the first detector array 20 includes M*N first sub-detectors 21 arranged in an array, and the output signals of the first detector array 20 are used to generate time signals and energy signals, where M ⁇ 1 and N ⁇ 1.
  • 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-detectors 21 is 4 ⁇ 4 mm 2 or 6 ⁇ 6 mm 2 .
  • the second detector array 30 includes m*n second sub-detectors 31 arranged in an array, and the output signals of the second detector array 30 are used to generate position signals and energy signals, where m ⁇ 2 and 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-detectors 31 is 2 ⁇ 2 mm 2 or 3 ⁇ 3 mm 2 .
  • the PET detector unit further includes a first light coupling layer 40 and a second light coupling layer 50.
  • the first light coupling layer 40 is sandwiched between the first detector array 20 and the first end.
  • Two light coupling layers 50 are sandwiched between the second detector array 30 and the second end.
  • the first detector array 20 independently reads out the signal of each first sub-detector 21 by 1:1, thereby obtaining accurate time signal and energy signal. Once each first sub-detector 21 is read, the number of readout channels required is also smaller.
  • the second detector array 30 reduces the number of readout channels by means of light sharing and coding to provide the position information and energy information of the gamma photons detected by the PET detector.
  • 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 , which can realize the resolution of each 1.5 ⁇ 1.5 mm 2 crystal, especially the crystals at the edge of the array can also be resolved. get a better resolution.
  • the second detector array 30 Since the encoded signal changes greatly and the time performance is poor, the signal readout of the second detector array 30 is mainly used for crystal position resolution and energy measurement of received gamma photons.
  • the measurement methods of the first detector array 20 and the second detector array 30 will be described below through specific embodiments.
  • 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 arranged in an array. 21.
  • 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
  • the detection area of each second sub-detector 31 is 3 ⁇ 3mm 2 .
  • Amplify the signal of each first sub-detector 21 of the first detector array 20 respectively, and encode each amplified signal in one way to obtain the energy signals A 1 , B 1 , C 1 of each first sub-detector 21 , D 1 , the total energy E 1 of the first detector array 20 obtained in this way is E 1 A 1 +B 1 +C 1 +D 1 .
  • Each amplified signal is encoded in another way to obtain energy signals T 1 , T 2 , T 3 , and T 4 of each first sub-detector 21 .
  • X2 is to determine the position of the scintillation crystal in the x-axis direction
  • Y2 is to determine the position of the scintillation crystal in the y-axis direction.
  • a 2 , B 2 , C 2 , and D 2 obtained by the resistance network coding method are the signals in the four directions after the integration of the detector array signal, which can be regarded as the signal is distributed to the four corners, so its x direction and the y-direction positions are divided by the sum of the signals at two different angles and divided by the total signal.
  • the resistance network encoding method is in the prior art, and the specific encoding process is not repeated here.
  • the encoding method is the row-column readout encoding method
  • the calculation method of the crystal resolution map of the second detector array 30 is:
  • X 2 is to determine the position of the scintillation crystal in the x-axis direction
  • Y 2 is to determine the position of the scintillation crystal in the y-axis direction
  • a 2 and B 2 obtained by the row-column readout encoding method are the encoded signals of the row
  • C 2 , D 2 are the coded signals of the column, so the positions in the x-direction and the y-direction are calculated from the coded signals of the row and column respectively.
  • the encoding method for reading out the rows and columns is in the prior art, and the specific encoding process is not described in detail here.
  • the depth action information of the detector is:
  • 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 one in the first embodiment. PET detector unit, so the specific structure of the PET detector unit 100 will not be repeated here, and the description of the first embodiment may be referred to.
  • the first readout circuit unit 60 is electrically connected to the first detector array 20 and 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 used to convert the output signal of the second detector array 30 into a position signal and a second energy signal.
  • the first readout circuit unit 60 includes an amplifying circuit 61 and a time discriminating circuit 62.
  • the amplifying circuit 61 is used to amplify the output signal of each of the first sub-detectors 21, and the time discriminating circuit 62 is used to amplify the output signal of each of the first sub-detectors 21.
  • the amplified output signals of each of the first sub-detectors are respectively read to obtain a plurality of time signals.
  • the first readout circuit unit 60 further includes an OR logic circuit 63, and the OR logic circuit 63 is used for compressing a plurality of time signals obtained by the time discrimination circuit 62 into a predetermined number of time signals.
  • the first readout circuit unit 60 further includes a position encoding circuit 64, and the position encoding circuit 64 is configured to generate the first energy signal and Auxiliary position signal.
  • the first detector array 20 includes 4 ⁇ 4 first sub-detectors 21 arranged in an array, and the signal of each first sub-detector 21 is amplified by the amplifying circuit 61 , and then One signal is read out individually 1:1 through the time discriminating circuit 62 to obtain 16 time signals (T 1 , T 2 , . . . T 15 , T 16 ), which can obtain high-precision time resolution.
  • the 16 channels of time signals can be processed by the OR logic circuit 63 to reduce the number of output channels of the time signals, thereby reducing the number of reading channels.
  • the number of OR logic circuits 63 is 4, and 16 time signals (T 1 , T 2 , ... T 15 , T 16 ) are processed by the OR logic circuit 63 to obtain 4 time signals.
  • the 4-way signals Row1, Row2, Row3, Row4 and the 4-way signals Column1, Column2, Column1, Column2, Column3 and Column4 are encoded respectively to obtain R1, R2, C1, and C2.
  • the first energy signal E R1+R2+C1+C2.
  • Row1, Row2, Row3, and Row4 respectively represent the sum of the signals of the first sub-detectors 21 in each row
  • Column1, Column2, Column3, and Column4 respectively represent the sum of the signals of the first sub-detectors in each column.
  • the coding of R1 and R2 is to convert Row1, Row2, Row3, and Row4 into 2 signals from 4 to 2 signals according to different proportions of electrical signals.
  • C1 and C2 and can be calculated by referring to formulas (3) and (4).
  • the specific coordinates of the position to be detected it should be noted that the specific coordinates of the position to be detected obtained here are used as auxiliary position signals, and a more accurate signal needs to be obtained through the second readout circuit.
  • the number of final readout signals of the first readout circuit unit 60 of the PET detector is: 2 channels + 2 channels + 16 channels, if processed by the OR logic circuit 63, the first readout circuit of the PET detector
  • the number of channels of the final readout signal of the unit 60 is: 2 channels+2 channels+16/or the number of logic circuits.
  • the first readout circuit unit 60 further includes an energy summation circuit, and the first position encoding circuit 64 does not need to be used.
  • the output signals are summed to obtain the first energy signal of the first detector array 20 to form a channel of energy signal.
  • the first readout circuit unit 60 of the PET detector finally reads out the number of signals: 1 channel+16 channels.
  • the second detector array 30 includes 8 ⁇ 8 second sub-detectors 31, the second readout circuit unit 70 includes a second position encoding circuit 71 and an energy calculating unit 72, and the second position encoding circuit 71 is used for Acquire the coordinates of the position to be detected in the second detector array 30, and the second position encoding circuit 71 adopts the discrete positioning method (such as the resistance network readout method) or the charge distribution method (such as the row-column addition readout method).
  • the multi-channel signals of the detector array 30 are encoded into 4-channel signals, and then the signals are collected by the back-end electronics.
  • the specific encoding process refers to the first embodiment, which will not be repeated here.
  • the energy calculation unit 72 sums the four signals output by the second position encoding circuit 71 to obtain the second energy signal.
  • the second detector array 30 generates a smaller number of signals encoded by the second readout circuit unit 70 on the premise of providing precise position resolution, thereby reducing the number of electronic readout channels.
  • the second detector array obtains a more accurate position signal mainly by the second sub-detector with a relatively small size of the array.
  • 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 time signals and energy signals from the second detector array 30 .
  • Accurate position signal and energy signal can be obtained in the first detector array 20, because the number of detectors in the first detector array 20 is small, so on the premise that the PET detector can achieve high time resolution, high position resolution and high depth resolution at the same time, Back-end electronics channels can be reduced.

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Abstract

一种PET探测器单元(100)、PET探测器，PET探测器单元(100)包括：闪烁晶体阵列(10)，包括多根闪烁晶体(11)；第一探测器阵列(20)，包括多个第一子探测器(21)，且第一探测器阵列(20)与闪烁晶体阵列(10)的第一端耦合连接；第二探测器阵列(30)，包括多个第二子探测器(31)，且第二探测器阵列(30)与闪烁晶体阵列(10)的与第一端相对的第二端耦合连接，第一子探测器(21)的探测面积大于第二子探测器(31)的探测面积，且第一子探测器(21)的数量少于第二子探测器(31)的数量。这一PET探测器同时达到高时间分辨率、高位置分辨率、高深度分辨率的前提下，减少后端电子学通道，降低了电子器件的成本。

Description

PET探测器单元、PET探测器 技术领域
本发明属于PET探测技术领域，具体地讲，涉及一种PET探测器单元、PET探测器。
背景技术
正电子发射计算机断层扫描成像技术(Positron Emission Tomography，PET)是将放射性同位素标记的化合物作为示踪剂注入生物体，然后在体外从不同角度测量生物体内的放射性分布信息，利用现代计算机完成代谢物分布图像重建的三维成像技术。而PET系统的主要构成单元就是基于闪烁体的PET探测器。
为了提高PET探测器的探测效率，需要使用比较长的闪烁晶体，但也带来了测量伽马光子作用位置的相互作用深度(Depth of Interaction,DOI)不确定性，DOI不确定性会使成像系统空间分辨率降低，所以高清晰PET探测器需要具有DOI的测量能力。DOI测量的方法包括采用多层晶体结合的方法，多层探测器分别读出的方法，双端读出方法以及连续晶体的方法等等。双端读出PET探测器的深度分辨率和晶体分辨能力较佳，是研究超高分辨率PET探测器的首选，深度探测能力使得可以在使用小探测器环直径和长闪烁晶体的条件下保持全视野均匀高位置分辨率，是PET成像系统同时达到高效率和高清晰的重要手段。
现有的双端读出DOI-PET探测器利用两端的光探测器对晶体阵列进行读出，该探测器根据两端光探测器测量到信号的能量比来测量相互作用深度。为了达到高位置分辨率，现有探测器两端的每个探测单元的面积相同，且均为小尺寸探测单元。例如要达到1mm以下的位置分辨率，SiPM(硅光电倍增管，Silicon photomultiplier，简称SiPM))的单元尺寸需要小于3mm，对于使用小的探测器单元，由于其数量较多，需要进行对探测器的读出信号进行编码来减少读出的电子学通道，而一般的编码方法(如电阻网读出编码，行列读出编码)会使得探测器的时间性能变差。提高时间分辨率的方法一般需要对每个探测器单元进行1：1单独读出，但是由于小面积的探测单元的数量非常多，所需要 的电子学读出通道很多，成本增加、读出难度大、功耗也增加。
发明内容
(一)本发明所要解决的技术问题
本发明解决的技术问题是：如何在保持高位置分辨率和高时间分辨率的基础上，降低读取通道数量。
(二)本发明所采用的技术方案
一种PET探测器单元，包括：
闪烁晶体阵列，包括多根闪烁晶体；
第一探测器阵列，包括多个第一子探测器，且所述第一探测器阵列与所述闪烁晶体阵列的第一端耦合连接；
第二探测器阵列，包括多个第二子探测器，且所述第二探测器阵列与所述闪烁晶体阵列的与所述第一端相对的第二端耦合连接，所述第一子探测器的探测面积大于所述第二子探测器的探测面积，且所述第一子探测器的数量少于所述第二子探测器的数量。
可选择地，所述第一探测器阵列包括M*N个阵列排布的第一子探测器，且所述第一探测器阵列的输出信号用于生成时间信号和能量信号，其中M≥1，N≥1。
可选择地，所述第二探测器阵列包括m*n个阵列排布的第二子探测器，且所述第二探测器阵列的输出信号用于生成位置信号和能量信号，其中m≥2，n≥2。
可选择地，所述PET探测器单元还包括：
第一光耦合层，夹设于所述第一探测器阵列与所述第一端之间；
第二光耦合层，夹设于所述第二探测器阵列与所述第二端之间。
可选择地，所述第一子探测器和所述第二子探测器均为硅光电倍增管。
本申请还公开了一种PET探测器，包括：
上述的PET探测器单元；
第一读出电路单元，与所述第一探测器阵列电性连接，用于将所述第一探测器阵列的输出信号转换为时间信号和第一能量信号；
第二读出电路单元，与所述第二探测器阵列电性连接，用于将所述第二探测器阵列的输出信号转换为位置信号和第二能量信号。
可选择地，所述第一读出电路单元包括：
放大电路，用于对每个所述第一子探测器的输出信号进行放大；
时间甄别电路，用于分别读取每个所述第一子探测器进行放大的输出信号，以得到多个时间信号。
可选择地，所述第一读出电路单元还包括：
或逻辑电路，用于将所述时间甄别电路得到的多个时间信号压缩为预定路数的时间信号。
可选择地，所述第一读出电路单元还包括：
能量求和电路，用于根据每个所述第一子探测器的进行放大后的输出信号生成第一探测器阵列的第一能量信号；
或者包括：第一位置编码电路，用于根据每个所述第一子探测器的进行放大后的输出信号生成辅助位置信号以及生成第一能量信号。
可选择地，所述第二读出电路单元还包括：
第二位置编码电路，用于获取第二探测器阵列中待探测位置的坐标；
能量计算单元，用于根据第二位置编码电路的输出信号的信号强度，计算第二探测器阵列的第二能量信号。
(三)有益效果
本发明公开了一种PET探测器单元、PET探测器，相对于传统的探测器，具有如下技术效果：
(1)通过设置由大尺寸的第一子探测器组成的第一探测器阵列以及小尺寸的第二子探测器组成第二探测器阵列，在使得PET探测器同时达到高时间分辨率、高位置分辨率、高深度分辨率的前提下，可以减少后端电子学通道，同时降低了电子器件的成本。
附图说明
图1为本发明的实施例一的PET探测器单元的结构示意图；
图2为本发明的实施例二的PET探测器的原理框图；
图3为本发明的实施例二的PET探测器的第一探测器阵列的信号读取过程示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
在详细描述本申请的各个实施例之前，首先简单描述本申请的发明构思：现有技术中，PET探测器两端的多为小面积且数量相等的小尺寸探测阵列(也有同尺寸的大面积探测阵列)，虽然能保持较高的位置分辨率，但是会造成较多的读数通道，带来成本上升。本申请通过在闪烁晶体阵列的一端设置大尺寸少数量的第一探测器阵列，在闪烁晶体阵列的另一端设置小尺寸多数量的第二探测器阵列，第一探测器阵列用于单独读出高分辨率的时间信号，第二探测器阵列用于输出高分辨率的位置信号，同时由于第一探测器阵列的探测单元数量较少，可以降低读取通道数量，降低了成本。
实施例一
具体地，如图1所示，本实施例一的PET探测器单元包括闪烁晶体阵列10、第一探测器阵列20和第二探测器阵列30。闪烁晶体阵列10包括多根闪烁晶体11，第一探测器阵列20包括多个第一子探测器21，且所述第一探测器阵列20与所述闪烁晶体阵列10的第一端耦合连接；第二探测器阵列30包括多个第二子探测器31，且所述第二探测器阵列30与所述闪烁晶体阵列10的与所述第一端相对的第二端耦合连接，所述第一子探测器21的探测面积大于所述第二子探测器31的探测面积，且所述第一子探测器21的数量少于所述第二子探测器31的数量。
具体地，闪烁晶体阵列10中闪烁晶体的数量不限定，闪烁晶体的尺寸也 不做具体限定，根据PET扫描系统的需求，高分辨的探测器可以采用0.5mm-1.5mm的晶体尺寸，或者针对人体全身PET系统采用2mm-4mm的晶体尺寸，晶体的长度可以从10mm到40mm，这个根据系统探测效率和成本的需要来调整，晶体可以采用常用的高密度LYSO(硅酸钇镥闪烁晶体，Lutetium Yttrium Orthosilicate，简称LYSO)晶体，也可以采用其他的闪烁晶体，如LFS(镥精细硅酸盐晶体，Lutetium fine silicate crystal，简称LFS)、GAGG(掺铈钆镓铝石榴石，gadolinium gallium aluminum garnet，简称GAGG)、BGO(锗酸铋晶体，Bismuth germanate crystal，简称BGO)等。作为优选实施例，第一子探测器21和第二子探测器31均为硅光电倍增管(SiPM)。
作为优选实施例，所述第一探测器阵列20包括M*N个阵列排布的第一子探测器21，且所述第一探测器阵列20的输出信号用于生成时间信号和能量信号，其中M≥1，N≥1。示例性地，第一探测器阵列20由2×2或4×4个第一子探测器21组成，第一子探测器21的探测面积为4×4mm 2或者6×6mm 2。
作为优选实施例，所述第二探测器阵列30包括m*n个阵列排布的第二子探测器31，且所述第二探测器阵列30的输出信号用于生成位置信号和能量信号，其中m≥2，n≥2。第二探测器阵列30由4×4个或8×8个第二子探测器31组成，第二子探测器31的探测面积为2×2mm 2或者3×3mm 2。
进一步地，PET探测器单元还包括第一光耦合层40和第二光耦合层50，第一光耦合层40夹设于所述第一探测器阵列20与所述第一端之间，第二光耦合层50夹设于所述第二探测器阵列30与所述第二端之间。
其中，第一探测器阵列20通过1：1单独读出每个第一子探测器21的信号，从而得到精确的时间信号和能量信号，由于第一探测器阵列20的数量较少，即使一一读取每个第一子探测器21，所需要的读出通道数目也较少。第二探测器阵列30通过光分享和编码的方法降低读出通道数提供PET探测器探测伽马光子的位置信息和能量信息。例如单个闪烁晶体的晶体尺寸为1.5×1.5mm 2，第二子探测器31的尺寸为3×3mm 2，可以实现对每个1.5×1.5mm 2晶体的分辨，特别是阵列边缘的晶体也能得到比较好的分辨。这样可以对小的晶体单元做出更好的鉴别，同时通过读出信号的编码，在满足区分闪烁晶体阵列的每个晶体单元的前提下使得其读出通道数目降低，第二探测器阵列30由于编码后信号变化大，时间性能较差，所以第二探测器阵列30的信号读出主 要用于进行晶体的位置分辨和接收伽马光子的能量测量。
下面通过具体的实施例来描述第一探测器阵列20和第二探测器阵列30的测量方法。
闪烁晶体阵列10包括阵列排布的8×8根闪烁晶体，每根闪烁晶体的尺寸为1.5×1.5×20mm 3，第一探测器阵列20包括阵列排布的2×2个第一子探测器21，每个第一子探测器21的探测面积为6×6mm 2，第二探测器阵列30包括4×4个第二子探测器31，每个第二子探测器31的探测面积为3×3mm 2。
对第一探测器阵列20的每个第一子探测器21的信号分别放大，每个放大后的信号一路进行编码得到每个第一子探测器21的能量信号A 1、B 1、C 1、D 1，这样得到的第一探测器阵列20的总能量E 1＝A 1+B 1+C 1+D 1。每个放大后的信号另一路进行编码得到每个第一子探测器21的能量信号T 1、T 2、T 3、T 4。
对第二探测器阵列30进行编码网络编码后生成四个能量信号A 2、B 2、C 2、D 2，这样得到的第二探测器阵列30的总能量E 2＝A 2+B 2+C 2+D 2，如果编码方法为电阻网络读出编码方法，则第二探测器阵列30的晶体分辨图的计算方法为：
Figure PCTCN2020115011-appb-000001
Figure PCTCN2020115011-appb-000002
其中，X2为判断闪烁晶体在x轴方向上的位置，Y2为判断闪烁晶体在y轴方向上的位置。具体地来说，电阻网络编码方法得到的A 2、B 2、C 2、D 2为探测器阵列信号整合后四个方向上的信号，可以看成信号分配到四个角，所以其x方向和y方向的位置分别由两个不同角的信号相加除于总信号。电阻网络编码方法为现有技术，具体的编码过程在此不进行赘述。
如果编码方法为行列读出编码方法，则第二探测器阵列30的晶体分辨图的计算方法为：
Figure PCTCN2020115011-appb-000003
Figure PCTCN2020115011-appb-000004
其中，X 2为判断闪烁晶体在x轴方向上的位置，Y 2为判断闪烁晶体在y 轴方向上的位置，行列读出编码方法得到的A 2、B 2为行的编码信号，C 2、D 2为列的编码信号，所以其x方向和y方向的位置分别由行和列的编码信号分别计算。行列读出编码方法为现有技术，具体的编码过程在此不进行赘述。
探测器的深度作用信息为：
Figure PCTCN2020115011-appb-000005
这样，通过第一探测器阵列20和第二探测器阵列30，在使用较少读取通道的情况下获得了较好的晶体分辨图、能量信息、DOI信息、时间信息，使得PET探测器同时达到高时间分辨率、高位置分辨率、高深度分辨率。
实施例二
如图2所示，本实施例二的PET探测器包括PET探测器单元100、第一读出电路单元60和第二读出电路单元70，其中PET探测器单元100优选采用实施例一中的PET探测器单元，因此PET探测器单元100的具体结构在此不进行赘述，参照实施例一的描述即可。第一读出电路单元60与所述第一探测器阵列20电性连接，并用于将所述第一探测器阵列20的输出信号转换为时间信号和第一能量信号。第二读出电路单元70与所述第二探测器阵列30电性连接，并用于将所述第二探测器阵列30的输出信号转换为位置信号和第二能量信号。
作为优选实施例，第一读出电路单元60包括放大电路61和时间甄别电路62，放大电路61用于对每个所述第一子探测器21的输出信号进行放大，时间甄别电路62用于分别读取每个所述第一子探测器进行放大的输出信号，以得到多个时间信号。
进一步地，第一读出电路单元60还包括或逻辑电路63，或逻辑电路63用于将所述时间甄别电路62得到的多个时间信号压缩为预定路数的时间信号。在另一实施例中，所述第一读出电路单元60还包括位置编码电路64，位置编码电路64用于根据每个所述第一子探测器进行放大的输出信号生成第一能量信号和辅助位置信号。
示例性地，如图3所示，第一探测器阵列20包括阵列排布的4×4个第一子探测器21，每个第一子探测器21的信号经过放大电路61进行放大，接着一路信号经过时间甄别电路62被单独1:1读出，得到16路时间信号(T 1、T 2、……T 15、T 16)，可得到高精度的时间分辨率。当然在其他实施方式中，如 果对时间分辨率的要求不高的情况下，16路时间信号可经过或逻辑电路63处理，减少时间信号的输出路数，从而减少读取通道。例如或逻辑电路63的路数为4，16路时间信号(T 1、T 2、……T 15、T 16)经过或逻辑电路63处理之后，得到4路时间信号。
进一步地，16个第一子探测器21的另一路信号经过第一位置编码电路64得到的行读出的4路信号Row1、Row2、Row3、Row4和列读出的4路信号Column1、Column2、Column3、Column4，再分别进行编码得到R1、R2、C1、C2，第一能量信号E＝R1+R2+C1+C2。其中，Row1、Row2、Row3、Row4分别表示每一行第一子探测器21的信号之和，Column1、Column2、Column3、Column4分别表示每一列第一子探测器的信号之和。R1、R2的编码是把Row1、Row2、Row3、Row4按不同比例的电信号分压方式由4变为2个信号，C1、C2同理，并参照公式(3)、(4)可以计算得到待探测位置的具体坐标，需要说明的是，这里得到的待探测位置的具体坐标作为辅助位置信号，更加精确的信号需要通过第二读出电路获取。这样，该PET探测器的第一读出电路单元60最终读出信号的路数为：2路+2路+16路，如果经过或逻辑电路63处理之后，PET探测器的第一读出电路单元60最终读出信号的路数为：2路+2路+16/或逻辑电路路数。
在另一实施例中，第一读出电路单元60还包括能量求和电路，不需要采用第一位置编码电路64，通过能量求和电路将16个第一子探测器21在进行放大之后的输出信号进行求和得到第一探测器阵列20的第一能量信号，形成1路能量信号。这样PET探测器的第一读出电路单元60最终读出信号的路数为：1路+16路。
示例性地，第二探测器阵列30包括8×8个第二子探测器31，第二读出电路单元70包括第二位置编码电路71和能量计算单元72，第二位置编码电路71用于获取获取第二探测器阵列30中待探测位置的坐标，并且第二位置编码电路71采用离散定位法(如电阻网络读出方法)或电荷分配法(如行列相加读出方法)将第二探测器阵列30的多路信号编码为4路信号再通过后端电子学进行信号采集，具体的编码过程参照实施例一，在此不进行赘述。在其他实施方式中，能量计算单元72将第二位置编码电路71输出的4路信号进行求和，得到第二能量信号。第二探测器阵列30在提供精确的位置分辨率的前提下，通过第二读出电路单元70编码生成较少数量的信号，从而减少电子学读取通 道数目。第二探测器阵列获得比较精确的位置信号主要是靠该阵列比较小尺寸的第二子探测器，虽然使用了编码电路，由于其第二子探测器数量多，位置信息更加全面，而且每个单元面积小，所以对晶体的分辨能力更好。
本实施例二提供的PET探测器，利用第一读出电路单元60从第一探测器阵列20中获取精确的时间信号和能量信号，利用第二读出电路单元70从第二探测器阵列30中获取精确的位置信号和能量信号，由于第一探测器阵列20中探测器数量较少，因此在使得PET探测器同时达到高时间分辨率、高位置分辨率、高深度分辨率的前提下，可以减少后端电子学通道。
上面对本发明的具体实施方式进行了详细描述，虽然已表示和描述了一些实施例，但本领域技术人员应该理解，在不脱离由权利要求及其等同物限定其范围的本发明的原理和精神的情况下，可以对这些实施例进行修改和完善，这些修改和完善也应在本发明的保护范围内。

Claims (14)

  1. 一种PET探测器单元，其中，包括：
    闪烁晶体阵列，包括多根闪烁晶体；
    第一探测器阵列，包括多个第一子探测器，且所述第一探测器阵列与所述闪烁晶体阵列的第一端耦合连接；
    第二探测器阵列，包括多个第二子探测器，且所述第二探测器阵列与所述闪烁晶体阵列的与所述第一端相对的第二端耦合连接，所述第一子探测器的探测面积大于所述第二子探测器的探测面积，且所述第一子探测器的数量少于所述第二子探测器的数量。
  2. 根据权利要求1所述的PET探测器单元，其中，所述第一探测器阵列包括M*N个阵列排布的第一子探测器，且所述第一探测器阵列的输出信号用于生成时间信号和能量信号，其中M≥1，N≥1。
  3. 根据权利要求1所述的PET探测器单元，其中，所述第二探测器阵列包括m*n个阵列排布的第二子探测器，且所述第二探测器阵列的输出信号用于生成位置信号和能量信号，其中m≥2，n≥2。
  4. 根据权利要求2所述的PET探测器单元，其中，所述PET探测器单元还包括：
    第一光耦合层，夹设于所述第一探测器阵列与所述第一端之间；
    第二光耦合层，夹设于所述第二探测器阵列与所述第二端之间。
  5. 根据权利要求1所述的PET探测器单元，其中，所述第一子探测器和所述第二子探测器均为硅光电倍增管。
  6. 一种PET探测器，其中，包括：
    闪烁晶体阵列，包括多根闪烁晶体；
    第一探测器阵列，包括多个第一子探测器，且所述第一探测器阵列与所述闪烁晶体阵列的第一端耦合连接；
    第二探测器阵列，包括多个第二子探测器，且所述第二探测器阵列与所述闪烁晶体阵列的与所述第一端相对的第二端耦合连接，所述第一子探测器的探测面积大于所述第二子探测器的探测面积，且所述第一子探测器的数量少于所 述第二子探测器的数量；
    第一读出电路单元，与所述第一探测器阵列电性连接，用于将所述第一探测器阵列的输出信号转换为时间信号和第一能量信号；
    第二读出电路单元，与所述第二探测器阵列电性连接，用于将所述第二探测器阵列的输出信号转换为位置信号和第二能量信号。
  7. 根据权利要求6所述的PET探测器，其中，所述第一读出电路单元包括：
    放大电路，用于对每个所述第一子探测器的输出信号进行放大；
    时间甄别电路，用于分别读取每个所述第一子探测器进行放大的输出信号，以得到多个时间信号。
  8. 根据权利要求7所述的PET探测器，其中，所述第一读出电路单元还包括：
    或逻辑电路，用于将所述时间甄别电路得到的多个时间信号压缩为预定路数的时间信号。
  9. 根据权利要求7所述的PET探测器，其中，所述第一读出电路单元还包括：
    能量求和电路，用于根据每个所述第一子探测器的进行放大后的输出信号生成第一探测器阵列的第一能量信号；
    或者包括：第一位置编码电路，用于根据每个所述第一子探测器的进行放大后的输出信号生成辅助位置信号以及生成第一能量信号。
  10. 根据权利要求6所述的PET探测器，其中，所述第二读出电路单元还包括：
    第二位置编码电路，用于获取第二探测器阵列中待探测位置的坐标；
    能量计算单元，用于根据第二位置编码电路的输出信号的信号强度，计算第二探测器阵列的第二能量信号。
  11. 根据权利要求6所述的PET探测器，其中，所述第一探测器阵列包括M*N个阵列排布的第一子探测器，且所述第一探测器阵列的输出信号用于生成时间信号和能量信号，其中M≥1，N≥1。
  12. 根据权利要求6所述的PET探测器，其中，所述第二探测器阵列包括m*n个阵列排布的第二子探测器，且所述第二探测器阵列的输出信号用于生成位置信号和能量信号，其中m≥2，n≥2。
  13. 根据权利要求6所述的PET探测器，其中，所述PET探测器还包括：
    第一光耦合层，夹设于所述第一探测器阵列与所述第一端之间；
    第二光耦合层，夹设于所述第二探测器阵列与所述第二端之间。
  14. 根据权利要求6所述的PET探测器，其中，所述第一子探测器和所述第二子探测器均为硅光电倍增管。
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