阅读说明：本技术 一种双读出pet探测器正电子成像方法与系统 (Positron imaging method and system of double-reading PET detector ) 是由 邓贞宙 赵欣 邓宏晟 王怡文 李永绣 洪伟毅 王玉皥 韩春雷 陶凌 王平 赖文升 于 2019-09-26 设计创作，主要内容包括：一种双读出PET探测器正电子成像方法与系统,该系统包括：在晶体条的两端放置光电器件进行耦合；使用光电器件获取晶体中的光信号数据进行闪烁脉冲数据耦合；记录光电器件中测得的脉冲的幅值高度和脉冲的到达时间；计算脉冲到达时间的差值和脉冲的幅值高度,估计伽玛光子在晶体中沉积能量的位置。该方法包括：通过模拟数字转换器由光电探测器获取的闪烁脉冲耦合信号进行数字化处理；根据探测器两端信号振幅的比值计算光子转换相互作用深度的位置；根据获得信号的能量,时间,位置信息,进行交互作用深度信息重建。本发明精确定位光子在晶体中的作用深度并获取作用深度信息,进行视差错误校正,有效降低相互作用深度效应,提高PET成像效果。(A dual readout PET detector positron imaging method and system, the system comprising: photoelectric devices are arranged at two ends of the crystal strip for coupling; using a photoelectric device to obtain optical signal data in the crystal to carry out scintillation pulse data coupling; recording the amplitude height of the pulse and the arrival time of the pulse measured in the photoelectric device; and calculating the difference of the arrival time of the pulse and the amplitude height of the pulse, and estimating the position of the deposition energy of the gamma photon in the crystal. The method comprises the following steps: carrying out digital processing on the scintillation pulse coupling signal acquired by the photoelectric detector through an analog-digital converter; calculating the position of photon conversion interaction depth according to the ratio of the signal amplitudes at two ends of the detector; and reconstructing interaction depth information according to the energy, time and position information of the acquired signals. The invention accurately positions the action depth of photons in the crystal, obtains the action depth information, corrects parallax error, effectively reduces the interaction depth effect and improves the PET imaging effect.)

1. A method of dual readout PET detector positron imaging, the method comprising the steps of:

step S1: the scintillation light is collected by the two detectors and then optically coupled on the two sides of the crystal to obtain scintillation pulse light coupling signals;

step S2: after the PET detector is read out through the two ends, the scintillation pulse optical coupling signal is subjected to multi-path segmentation processing to obtain a scintillation pulse optical coupling signal after data segmentation;

step S3: carrying out digital processing on the scintillation pulse coupling signal acquired by the photoelectric detector through an analog-digital converter;

step S4: acquiring case attribute information of the acquired coupling signal;

step S5: calculating the position of photon conversion interaction depth according to the ratio of the signal amplitudes at two ends of the detector;

step S6: and reconstructing interaction depth information according to the energy, time and position information of the acquired signals.

2. The method for positron imaging of a dual readout PET detector of claim 1 wherein in said step S1, said detector types include SiPM silicon photomultipliers and PMT photomultipliers.

3. The positron imaging method of the dual readout PET detector of claim 1, wherein in the step S2, the multi-path segmentation processing method includes but is not limited to a pulse peak detection method and a first-order differential undershoot zero-crossing segmentation method.

4. The dual readout PET detector positron imaging method of claim 1 wherein the scintillation pulse has an amplitude in the range of 0-hmw, the digital to analog converter has a dynamic range of 0-jhz, and H and J are both positive numbers.

5. The positron imaging method of the dual readout PET detector of claim 1, wherein in the step S3, a conversion frequency of the digital-to-analog converter is set to any value between 0 and jhz.

6. The method for positron imaging with dual readout PET detectors of claim 1, wherein in step S3, the digitizing process is performed in two steps, the first step is time-domain discretization, i.e. sampling in the time domain, and the second step is frequency-domain discretization, i.e. sampling in the frequency domain.

7. The dual readout PET detector positron imaging method of claim 1 wherein J is 5MHz and the frequency is set to 5 MHz.

8. The method for positron imaging by dual readout PET detector of claim 1 wherein in said step S4, said case attribute information includes amplitude, time and position information of scintillation pulse signals.

9. The positron imaging method of the dual readout PET detector of claim 1, wherein in said step S5, the position information of the depth of interaction is calculated according to the ratio of the amplitudes of the signals at the two ends of the detector.

10. The dual readout PET detector positron imaging method as claimed in claim 1 wherein in said step S6, said depth of interaction information reconstruction method includes but is not limited to an analytical reconstruction method and an iterative reconstruction method.

Technical Field

The invention relates to the field of radiation detection and digital imaging, in particular to a positron imaging method and system of a double-reading PET detector.

Background

In the field of medical imaging such as Positron Emission Tomography (PET), Computed Tomography (CT), Single photon emission Tomography (SPECT), and Magnetic Resonance Imaging (MRI), the working modes of the detector mainly include two types: one is that high-energy photons are converted into visible light photons or ultraviolet light photons with lower energy through a scintillator, and then the visible light photons or ultraviolet light photons are converted into electric signals through a photoelectric device; the other is to directly convert high-energy photons into electric signals through semiconductor materials such as Cadmium Zinc Telluride (CZT) and the like. The output of the detector under the above two working modes is an electric signal.

PET is considered one of the most sensitive in vivo molecular imaging modalities, although its spatial resolution is much poorer than that of, for example, CT and MRI. Improving PET detector technology is an active area of research and work has focused on addressing the limitations of spatial resolution and sensitivity achieved in PET.

There are several types of photodetectors available: the first type of photodetector covers a vacuum tube, a photomultiplier tube (hereinafter PMT) having a relatively large detector area of several square centimeters and a multi-anode PMT that provides positional information of several millimeters to allow pixelation in the millimeter range.

A PMT is a type of photodetector commonly used for scintillator readout in numerous applications, including medical imaging. Current PET detectors generally tend to select scintillation crystals with smaller decay time constants and PMTs with faster rise times to achieve superior time and count rate performance. The basic components of a PMT are a vacuum tube consisting of a photocathode, an anode, and a plurality of dynodes.

The second type of photodetector is Silicon-based and includes Avalanche Photodiodes (APD), analog or digital Silicon photomultipliers (SiPM). All silicon photomultipliers allow the design of PET detectors with small pixelation in the millimeter range.

An SiPM is an array of a plurality of avalanche diodes operating in a counting mode. The array of elements in the device is avalanche diodes which can respond rapidly to the photons. Since the number of active photons is greater than 1 in most applications, it is necessary to array avalanche diodes in response to different numbers of photons. The number of response photon bins corresponds monotonically to the desired number of injected photons over a short period of time. According to this correspondence, the number of measurement infinitesimal elements can indirectly reflect the intensity of the incident photon beam.

Sipms for applications in scintillation light detection, weak light detection, quantum physics, and high-energy physics experiments need to mark the start time of a photon beam and the number of active infinitesimal elements over a period of time. Sipms are introduced in PET detectors to address the disadvantages of PMTs to achieve smaller pixelation. New technological advances in the field of semiconductor photodetectors have recently been developed which involve integrating basic processing electronics within the SiPM sensitive area, thereby reducing the need for external processing electronics.

In PET systems, gamma detectors can be used to determine the location of gamma interaction with the detectors in two dimensions, which can cause parallax errors. Parallax is a key limiting factor in image resolution, which reduces the detectability of small lesions in the external field. Depth of interaction (DOI) information is an important parameter when applied to imaging detector geometries where the incident gamma rays strike the crystal in directions other than all of which are substantially perpendicular to the crystal surface. If the incident gamma is assumed to intersect the crystal from a direction non-perpendicular to the crystal, then the depth of action of those gamma-assumed positions within the crystal will cause additional uncertainty in the measured position of action due to parallax effects if the two-dimensional spatial position is calculated only for such absorption events.

PET imaging detectors have some inherent limitations in implementation, and these inherent limitations limit the performance of PET, and DOI effects have a large impact on the performance of PET and the effectiveness of imaging.

Therefore, in view of the above technical problems, there is a need to reconstruct DOI information by using a dual-end readout PET detector positron imaging method and system, which can reduce parallax, to increase the spatial resolution of the system, and provide a gamma action position in three dimensions in space.

Disclosure of Invention

The invention aims to provide a positron imaging method and a positron imaging system for a dual-readout PET (positron emission tomography) detector, which can accurately position DOI (depth of interaction) of photons in a crystal, thereby utilizing DOI information to reduce parallax error, reducing DOI effect, increasing the spatial resolution of the system and realizing data calibration.

To achieve the purpose of the invention, the invention provides a scheme that:

a dual readout PET detector positron imaging system using two photon sensors to detect scintillation light across a scintillator array and to estimate depth of interaction information from a ratio of acquired signals, the system comprising:

the crystal photoelectric module is used for detecting scintillation light signals at two ends of the scintillator array, acquiring the scintillation light signals by using an optical coupling principle, performing photoelectric signal processing on the acquired scintillation light signals and outputting scintillation pulse signals, and comprises a crystal optical module, a photoelectric conversion module and an analog electric signal preprocessing module;

the data acquisition module is connected with the crystal photoelectric module and receives a scintillation pulse signal sent by the crystal photoelectric module, performs signal processing on the obtained scintillation pulse coupling signal and outputs the processed scintillation pulse signal, and the data acquisition module comprises an analog-digital conversion module, a threshold amplification module and a time-digital module;

the depth information reconstruction module is connected with the data acquisition module, receives the scintillation pulse signals output by the data acquisition module, performs correlation attribute calculation on the collected scintillation pulse signals, and estimates 511KeV photon conversion positions according to the ratio of the obtained case attributes, namely the depth information, and comprises a data segmentation module, a case attribute calculation module, a case data encapsulation module and a network module.

Further, the crystal optical module comprises a crystal module, a light guide module, a light reflecting layer module, a light isolating layer module, an optical glue module and a crystal packaging module, and the crystal optical module is connected with the photoelectric conversion module and is placed between two photoelectric detectors in the photoelectric conversion module.

Further, the photoelectric conversion module comprises a photoelectric detector module, a resistor network module, a high-voltage power conversion module and a welding agent module, and the photoelectric conversion module performs photoelectric conversion processing on the scintillation light signals collected by the crystal optical module and outputs the processed scintillation pulse signals.

Further, the analog electrical signal preprocessing module includes an amplifier module and a high-frequency routing module, and a gain calculation formula of an amplifier used by the analog electrical signal preprocessing module is that a ═ R_f/R_iWhere A is the amplifier gain, Rf is the feedback resistance, and Ri is the input resistance of the amplifier.

Further, the case attribute calculation module comprises an amplitude estimation module, an arrival time estimation module and a position calculation module, and is connected with the data segmentation module, receives the scintillation pulse segmentation signals output by the data segmentation module, performs information estimation on the received segmentation signals by adopting an estimation theory, and outputs the required case attribute information.

Furthermore, the optical glue module adopts an adhesive with light transmittance of more than 90%.

Further, the high-voltage power supply conversion module comprises a signal source and a booster circuit, wherein the signal source outputs 5V voltage, and the 5V voltage is converted into 27V power supply voltage required by the photoelectric detector through the booster circuit.

Further, the threshold amplifying module uses a plurality of voltages as the threshold.

Further, the case attribute calculation information includes amplitude, time and position information of the scintillation pulse signal.

Furthermore, the position calculation in the case attribute calculation module adopts a formula

And acquiring the position of the scintillation light on the crystal, wherein E1 and E2 are the energy of the signal, T1 and T2 are the arrival time of two signals, L is the distance between two adjacent crystals, and c is the speed of light.

In order to achieve the purpose of the invention, the invention also provides a scheme that:

a method of dual readout PET detector positron imaging, the method comprising the steps of:

step S1: the scintillation light is collected by the two detectors and then optically coupled on the two sides of the crystal to obtain scintillation pulse light coupling signals;

step S2: after the PET detector is read out through the two ends, the scintillation pulse optical coupling signal is subjected to multi-path segmentation processing to obtain a scintillation pulse optical coupling signal after data segmentation;

step S3: carrying out digital processing on the scintillation pulse coupling signal acquired by the photoelectric detector through an analog-digital converter;

step S4: acquiring case attribute information of the acquired coupling signal;

step S5: calculating the position of photon conversion interaction depth according to the ratio of the signal amplitudes at two ends of the detector;

step S6: and reconstructing interaction depth information according to the energy, time and position information of the acquired signals.

Further, in the above step S1, the detector types include SiPM silicon photomultipliers and PMT photomultipliers.

Further, in the above step S2, the multiple division processing method includes, but is not limited to, a pulse peak detection method and a first-order differential undershoot zero-crossing division method.

Furthermore, the amplitude range of the scintillation pulse is 0-H millivolt, the frequency dynamic range of the digital-to-analog converter is 0-J Hz, and H and J are positive numbers.

Further, in the above step S3, the conversion frequency of the digital-to-analog converter is set to an arbitrary value between 0 and J hz.

Further, in the above step S3, the digitization processing method is divided into two steps, the first step is time-domain discretization, i.e. time-domain sampling, and the second step is frequency-domain discretization, i.e. frequency-domain sampling.

Further, the value of J is 5MHz, and the frequency is set to 5 MHz.

Further, in the above step S4, the case attribute information includes amplitude, time, and position information of the blinking pulse signal.

Further, in the above step S5, the position information of the depth of interaction is calculated according to the ratio of the amplitudes of the signals at the two ends of the detector.

Further, in step S6, the interaction depth information reconstruction method includes, but is not limited to, an analytic reconstruction method and an iterative reconstruction method.

Compared with the prior art, the invention has the following advantages: the depth of action of accurate positioning photon in the crystal effectively acquires the depth of action DOI, carries out parallax error correction, reduces the DOI effect, corrects the time error that leads to because of the action position difference simultaneously, improves the space positioning ability, effectively reduces the cost and the complexity of systems such as PET, SPET, reduces the demand of system to computational resource and time to can effectively improve PET sensitivity under the condition that does not increase the detector volume, thereby improve the PET imaging effect.

Drawings

FIG. 1 is a schematic illustration of a dual readout PET detector positron imaging system in accordance with one embodiment of the invention;

FIG. 2 is a schematic illustration of the crystal array placement of the PET system of the present invention;

FIG. 3 is a system block diagram of an exemplary dual readout PET detector positron imaging system of the present invention;

FIG. 4 is a flow chart of an exemplary dual readout PET detector positron imaging method of the present invention;

FIG. 5 is a schematic structural diagram of a dual readout PET detector positron imaging system in accordance with one embodiment of the present invention;

FIG. 6 is a schematic diagram of a crystal optoelectronic module in a dual readout PET detector positron imaging system in accordance with one embodiment of the invention;

FIG. 7 is a schematic diagram of a crystal photovoltaic module in a dual readout PET detector positron imaging system in accordance with one embodiment of the invention;

reference numerals:

gamma photons	1	Photoelectric detector	2
				Light guide device	3	Crystal	4
Optical glue	5	Light-isolating layer	6

Detailed Description

The present invention will be further described with reference to the following specific examples. It should be understood that the following examples are illustrative only and are not intended to limit the scope of the present invention.

As shown in fig. 1, a schematic diagram of a dual readout PET detector positron imaging system according to an embodiment of the disclosure acquires a scintillation pulse single photon signal in the form of event data, and reconstructs interaction depth information by using a time coincidence and estimation theory.

The schematic diagram of fig. 1 includes gamma photons 1, a photodetector 2, a light guide 3, a crystal strip 4, and optical glue 5, wherein the light guide 3 and the crystal strip 4 are connected by the optical glue 5 and transmit a scintillation light signal; the gamma photon 1 is emitted into the crystal strip, most photons of the scintillation light undergo multiple reflections including total reflection, diffuse reflection and specular reflection in the crystal strip 4, then the scintillation light can generate energy deposition at different positions, pulse heights and pulse arrival times measured by the photoelectric detectors 2 at two ends are different, and the position of the gamma photon deposition energy in the crystal can be estimated by calculating the time difference of the two arrival times and the pulse height.

As shown in fig. 2, the crystal array placement diagram of the PET system disclosed in the present invention shows the crystal bars 4 arranged in an array, the kind of the crystal bars 4 is LYSO 16 × 16, each crystal bar 4 is separated by a light-shielding layer 6, and an optical glue 5 is added between the light guide device 3 and the light-shielding layer 6 to remove air residue between the two to reach the vacuum standard.

FIG. 5 is a schematic structural diagram of a dual readout PET detector positron imaging system in accordance with one embodiment of the present invention; FIG. 6 is a schematic diagram of a crystal optoelectronic module in a dual readout PET detector positron imaging system in accordance with one embodiment of the invention; figure 7 is a schematic diagram of a crystal photovoltaic module in a dual readout PET detector positron imaging system in accordance with one embodiment of the invention. The dual readout PET detector positron imaging method and system of the present invention will be further described in conjunction with figures 5, 6 and 7 by way of several specific embodiments. The parameters, amplifier design, case signal attribute information processing and data acquisition characteristics of the double-reading PET detector positron imaging method and system provided by the invention are adjusted to achieve good time resolution, energy resolution and more accurate interaction depth information.

As shown in fig. 5, the dual readout PET detector positron imaging system in the present invention includes a crystal module 111, a light guide module 112, a light-isolating layer module 114, an optical glue module 115, a crystal packaging module 116, a photodetector module 121, an amplifier module 131, a high-frequency routing module 132, a data acquisition module 200, a case property calculation module 320, a case data packaging module 330, and a network module 340, wherein the light-isolating layer separates the crystals into a single optical compartment; the light guide module, the optical glue module, the light isolating layer module and the crystal module are packaged in a detector device; the optical glue is used for connecting the photoelectric detector, the light guide and the light isolating layer; the amplifier circuit is connected with the photoelectric detector and receives the pulse electric signal output by the photoelectric detector, and the amplification gain A of the amplifier circuit is R_f/R_iWherein, Rf is a feedback resistor, Ri is an input resistor, and the amplified pulse signal is output after passing through an amplifier; the high-frequency wiring module is connected with the amplifier circuit, receives the amplified pulse signal, performs high-frequency processing on the received signal by using high-frequency voltage, and inputs the processed pulse signal to the data acquisition module to realize identification of pulse characteristics; estimating the characteristics of the pulse in a case attribute calculation module to obtain the required pulse amplitude, the required pulse arrival time and the required pulse position; the data acquisition module is connected with the network module for network adaptation.

As shown in fig. 6, the double-end photodetectors 2 in the dual readout system structure of the present invention are SiPM silicon photomultipliers, the crystal strip 4 placement structure in the figure is placed according to a crystal array, a specific model may be 16 × 16 LYSO crystal, and other components include a light-blocking layer 6 on the surface of each crystal strip, an optical glue 5, and a light guide device 3; the optical compartments separated by the light-isolating layer 6 are correspondingly adjusted according to the size of the crystal; the optical glue 5 is an adhesive with light transmittance of more than 90% and is used for connecting the photoelectric detector 2, the light guide device 3 and the light isolating layer 6.

As shown in FIG. 6, with the system shown in FIG. 3, when gamma photons are injected into the crystal strip 4 and energy deposition occurs at different positions, the pulse amplitude A measured by the photodetectors 2 at both ends_mp(+)，A_mp (-), pulse arrival times T1, T2 are all different, using the formula:

(where i is 1,2), the energy E1, E2 of the pulse detected by the photodetectors at both ends is obtained, and the position calculation formula is used:(where E1E2 is the energy of the signal, T1T2 is the arrival time of two signals, L is the distance between two adjacent crystals, and c is the speed of light) to obtain the location of the scintillation light on the crystal.

As shown in fig. 7, the photodetectors 2 in the dual readout system structure of the present invention are a whole photodetector bar at one end and a photodetector array at the other end, wherein the photodetector array includes a plurality of SiPM silicon photomultipliers, which can reduce the need for external processing electronics and ensure enhanced time resolution, and the number of SiPM silicon photomultipliers is adjusted between 36-48 as needed; the shape of the crystal 4 is a crystal strip array, the size of the crystal strip is adjusted between 2.03mm multiplied by 3mm according to the requirement, and the size of the crystal strip array is adjusted according to the number of the SiPM silicon photomultiplier; other components comprise a light isolating layer 6 on the surface of each crystal strip, optical glue 5 and a light guide device 3; optical glue 5 is used to connect the photodetector 2, the light guide 3 and the light-blocking layer 6.

As shown in fig. 7, with the steps shown in fig. 4, scintillation light emitted by gamma photons is irradiated onto a scintillation crystal, scintillation photons at both ends of the scintillation crystal are detected by an SiPM silicon photomultiplier array in a photodetector, and optically coupled at the edge of the crystal, a scintillation pulse signal is amplified by an amplifier circuit, the amplified signal is digitized by an analog-to-digital conversion module, case attribute information of the scintillation pulse signal is calculated, and finally, the position of the interaction depth of 511KeV photons is estimated according to the calculated ratio of the signal amplitudes.

The invention is described in detail below with respect to a dual readout PET detector positron imaging system.

A dual readout PET detector positron imaging system comprising the following modules:

the crystal photoelectric module 100 is used for detecting scintillation light signals at two ends of the scintillator array, acquiring the scintillation light signals by using an optical coupling principle, performing photoelectric signal processing on the acquired scintillation light signals, and outputting scintillation pulse signals;

the crystal photoelectric module 100 comprises a crystal optical module 110, a photoelectric conversion module 120 and an analog electric signal preprocessing module 130;

a crystal optical module 110, wherein the crystal optical module 110 is connected to the photoelectric conversion module 120, is disposed between two photodetectors in the photoelectric conversion module 120, and outputs a scintillation light signal obtained after passing through the crystal optical module 110 by using an optical coupling principle;

the crystal optical module 110 comprises a crystal module 111, a light guide module 112, a light reflecting layer module 113, a light isolating layer module 114, an optical glue module 115 and a crystal packaging module 116;

a crystal module 111 comprising a crystal;

a light guide module 112 including a light guide device, the light guide device being disposed between the crystal and the photodetector in the photodetector module 121 in the photoelectric conversion module 120, the light guide device acquiring a scintillation light signal by using a photoelectric effect, and the acquired scintillation light signal being optically coupled in the crystal module 111 after being collected by the two photodetectors;

the reflective layer module 113 is arranged on the crystal surface and realizes the collection of scintillation light signals on the crystal surface by utilizing the retro-reflection principle of light;

a light-blocking layer module 114 disposed between the respective crystals for preventing an external light source from irradiating the crystals;

the optical glue module 115 is formed by coating optical glue among the photoelectric detector module 121, the light guide module 112 and the light isolating layer module 114, wherein the optical glue adopts an adhesive with light transmittance of more than 90% and is used for exhausting gas among the photoelectric detector, the light guide module 112 and the light isolating layer module 114;

a crystal packaging module 116, wherein all the crystal devices are packaged in a detector device;

the photoelectric conversion module 120 comprises a photodetector, a high-voltage power supply, a resistor network and a welding agent, the photoelectric conversion module 120 is connected with the crystal optical module 110, receives the scintillation light signal output by the crystal optical module 110, performs photoelectric conversion processing on the collected scintillation light signal, and outputs a processed scintillation pulse signal;

the photoelectric conversion module 120 comprises a photoelectric detector module 121, a resistance network module 122, a high-voltage power conversion module 123 and a welding agent module 124;

a photodetector module 121 including photodetectors attached to an outer surface of the light guide for detecting the scintillation light signal, the photodetectors constituting the photodetector module;

the resistance network module 122 comprises a resistance network, the resistance network converts the multi-path signals of the photoelectric detector into four-path signals and amplifies the signals, the amplified signals are used for signal processing at the rear end, and the resistance network forms the resistance network module;

the high-voltage power supply conversion module 123 comprises a signal source and a booster circuit, wherein the signal source outputs 5V voltage, the 5V voltage is converted into power supply voltage 27V required by the photoelectric detector through the booster circuit, and the booster circuit and the signal source form the high-voltage power supply conversion module;

a solder module 124 including solder by which the photodetector is soldered to the front-end circuit, the solder constituting the solder module;

an analog electrical signal preprocessing module 130, which receives the scintillation pulse signal outputted by the photoelectric conversion module 120, and outputs the required scintillation pulse electrical signal after the relevant electrical signal processing;

the analog electrical signal preprocessing module 130 includes an amplifier module 131 and a high-frequency routing module 132;

an amplifier module 131, which includes an amplifier, wherein the amplifier module 131 is connected to the photoelectric conversion module 120, and receives the photoelectric signal output by the photoelectric conversion module 120, and a gain calculation formula of the amplifier is that a ═ R_f/R_iWherein A is amplifier gain, Rf is feedback resistance, Ri is input resistance of amplifier, and the amplifier outputs amplified electrical signal to form amplifier module;

the high-frequency wiring module 132 comprises a high-frequency wiring circuit, wherein two-end signals acquired by the dual-readout system are output through the high-frequency wiring circuit, and the high-frequency wiring circuit forms the high-frequency wiring module;

the data acquisition module 200 is connected with the crystal photoelectric module 100 and receives a scintillation pulse signal sent by the crystal photoelectric module 100, and the data acquisition module 200 performs signal processing on the obtained scintillation pulse coupled signal and outputs the processed scintillation pulse signal;

the data acquisition module 200 comprises an analog-digital conversion module 210, a threshold amplification module 220 and a time-digital module 230;

the analog-digital conversion module 210 includes an analog-digital circuit, the scintillation light signal passes through the crystal photoelectric module 100 to obtain a scintillation pulse coupled analog electrical signal, the obtained scintillation pulse analog electrical signal is converted into a required scintillation pulse signal by the analog-digital circuit, and the analog-digital circuit constitutes an analog-digital conversion module;

a threshold value amplification module 220, wherein the threshold value voltage amplification module 220 is connected to the analog-to-digital conversion module 210, receives the scintillation pulse signal sent by the analog-to-digital conversion module 210, and sets threshold value voltage information, the threshold value voltage information refers to that a plurality of voltages are selected as threshold values so as to obtain a plurality of sampling points, the plurality of sampling points are extracted, processed scintillation pulse information and required time information are obtained, and the process of obtaining the required time information through the threshold values constitutes the threshold value amplification module;

a time digital module 230, wherein the time digital module 230 is connected to the threshold amplification module 220, receives the scintillation pulse signal and the time information processed by the threshold voltage amplification module 220, extracts the time information of the scintillation pulse signal, performs time calibration on the time information, and the process of acquiring the time information constitutes the time digital module;

the depth information reconstruction module 300 is connected with the data acquisition module 200, receives the scintillation pulse signals output by the data acquisition module 200, calculates the correlation attributes of the collected scintillation pulse signals, and estimates 511KeV photon conversion positions according to the ratio of the obtained case attributes, namely the depth information;

the depth information reconstruction module 300 comprises a data segmentation module 310, a case attribute calculation module 320, a case data encapsulation module 330 and a network module 340;

the data segmentation module 310 is used for performing multi-path segmentation processing on the acquired double-end signal information to respectively acquire required segmentation signals, and the process of acquiring the segmentation signals forms the data segmentation module;

the case attribute calculation module 320 is connected to the data segmentation module 310, receives the scintillation pulse segmentation signals output by the data segmentation module 310, performs information estimation on the received segmentation signals by adopting an estimation theory, and outputs required case attribute information, wherein the case attribute information refers to amplitude, time and position information of the scintillation pulse signals, and the process of acquiring the case attribute information constitutes the case attribute calculation module;

the case attribute calculation module 320 comprises a magnitude estimation module 321, a time of arrival estimation module 322, and a location calculation module 323;

the amplitude estimation module 321 comprises an amplitude estimation circuit, the amplitude estimation module 321 is connected with the data segmentation module 310, receives the signal output by the data segmentation module 310, and performs amplitude estimation on the obtained signal through the amplitude estimation circuit, and the amplitude estimation circuit constitutes the amplitude estimation module;

an arrival time estimation module 322, which includes a time calibration circuit, where the arrival time estimation module 322 is connected to the data segmentation module 310, receives the signal output by the data segmentation module 310, and performs arrival time estimation on the acquired signal through the time calibration circuit, and the time calibration circuit constitutes the arrival time estimation module;

a position calculating module 323, wherein the position calculating module 323 is connected to the data dividing module 310, and receives the signal output by the data dividing module 310, and calculates the position according to a position calculation formula:

(where E1, E2 are the energy of the signal, T1, T2 are the arrival times of the two signals, L is the distance between two adjacent crystals, c is the speed of light) obtain the position of the scintillation light on the crystal;

the case data encapsulation module 330 encapsulates the case attributes acquired by the case attribute calculation module 320 to acquire a data packet, wherein the encapsulation process constitutes the case data encapsulation module;

and a network module 340, wherein the detector circuit needs to be connected to a network adapter for network adaptation in a detection process, and the network adaptation process constitutes the network module.

According to one embodiment of the invention, the crystal module may employ LYSO crystals, LSO, YSO and LaBr₃Ce crystal.

According to an embodiment of the invention, the photodetector module can adopt dual sipms or sipms and PMTs, and the position of each crystal can be clearly distinguished by reading optical signals output from two ends of the crystal by using a dual-end photodetector.

According to one embodiment of the invention, the detection conditions of the dual readout system need to be calibrated and the detection conditions may drift due to gain drift of the amplifier or optical coupling degradation of the light guide.

According to one embodiment of the invention, the time calibration process of the dual readout system requires aligning the baseline of the scintillation pulse signal, then performing the leading edge discrimination of the pulse signal, and finally estimating the arrival time of the scintillation pulse.

The invention discloses a positron imaging method of a double-reading PET detector, which comprises the following steps:

step S1: the scintillation light is collected by the two detectors and then optically coupled on the two sides of the crystal to obtain scintillation pulse light coupling signals;

step S2: after the PET detector is read out through the two ends, the scintillation pulse optical coupling signal is subjected to multi-path segmentation processing to obtain a scintillation pulse optical coupling signal after data segmentation;

step S3: carrying out digital processing on the scintillation pulse coupling signal acquired by the photoelectric detector through an analog-digital converter;

step S4: acquiring case attribute information of the acquired coupling signal;

step S5: calculating the position of photon conversion interaction depth according to the ratio of the signal amplitudes at two ends of the detector;

step S6: and reconstructing interaction depth information according to the energy, time and position information of the acquired signals.

In the dual readout PET detector positron imaging method described above, the detector types described in step S1 include SiPM silicon photomultipliers and PMT photomultipliers.

In the above-mentioned positron imaging method of the dual readout PET detector, the methods of the multi-path segmentation processing in step S2 include, but are not limited to, a pulse peak detection method and a first-order differential undershoot zero-crossing segmentation method.

In the positron imaging method of the double-readout PET detector, the amplitude range of the scintillation pulse is 0-H millivolt, the frequency dynamic range of the digital-to-analog converter is 0-J Hz, and H and J are positive numbers.

In the above-described positron imaging method for the dual-readout PET detector, the conversion frequency of the digital-to-analog converter in step S3 is set to an arbitrary value between 0 and J hz.

In the above-mentioned positron imaging method of the dual-readout PET detector, the digitization processing method in step S3 is divided into two steps, the first step is time-domain discretization, i.e., time-domain sampling, and the second step is frequency-domain discretization, i.e., frequency-domain sampling.

In the positron imaging method of the double-readout PET detector, the value of J is 5MHz, and the frequency is set to be 5 MHz.

In the above-described positron imaging method of the dual-readout PET detector, the case attribute information in step S4 includes amplitude, time, and position information of the scintillation pulse signal.

In the above-mentioned positron imaging method using the dual readout PET detector, the position information of the depth of interaction in step S5 is calculated based on the ratio of the amplitudes of the signals at both ends of the detector.

In the dual readout PET detector positron imaging method described above, the method of reconstructing the interaction depth information in step S6 includes, but is not limited to, an analytical reconstruction method and an iterative reconstruction method.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "or/and" includes any and all combinations of one or more of the associated listed items.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.