CN106443747B - Method and apparatus for measuring the arrival time of high-energy photons - Google Patents

Method and apparatus for measuring the arrival time of high-energy photons Download PDF

Info

Publication number
CN106443747B
CN106443747B CN201611004839.8A CN201611004839A CN106443747B CN 106443747 B CN106443747 B CN 106443747B CN 201611004839 A CN201611004839 A CN 201611004839A CN 106443747 B CN106443747 B CN 106443747B
Authority
CN
China
Prior art keywords
sensor unit
time
sensor
energy
photons
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201611004839.8A
Other languages
Chinese (zh)
Other versions
CN106443747A (en
Inventor
龚政
赵指向
许剑锋
翁凤花
黄秋
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sino science and Technology (Shenzhen) Co., Ltd.
Original Assignee
Zhongpai S&t Shenzhen Co ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zhongpai S&t Shenzhen Co ltd filed Critical Zhongpai S&t Shenzhen Co ltd
Priority to CN201611004839.8A priority Critical patent/CN106443747B/en
Publication of CN106443747A publication Critical patent/CN106443747A/en
Priority to PCT/CN2017/110864 priority patent/WO2018090900A1/en
Application granted granted Critical
Publication of CN106443747B publication Critical patent/CN106443747B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/003—Scintillation (flow) cells
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/26—Measuring, controlling or protecting

Landscapes

  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Measurement Of Radiation (AREA)

Abstract

The present invention provides a method and apparatus for measuring the arrival time of high energy photons. The method comprises the following steps: acquiring arrival time related to visible photons generated by reaction of high-energy photons with a scintillation crystal, which is a continuous crystal, detected by each sensor unit in a photosensor array, wherein the photosensor array comprises a plurality of sensor units coupled with the scintillation crystal; obtaining a time to be averaged corresponding to each of selected at least some sensor units in the photosensor array, respectively, based on at least an arrival time associated with the optical photon detected by each sensor unit in the photosensor array; and averaging the time to be averaged corresponding to each of at least some of the sensor units, respectively, to obtain the arrival time of the high energy photons. According to the method and the device provided by the embodiment of the invention, higher time resolution can be obtained by averaging the to-be-averaged time obtained by aiming at a plurality of sensor units.

Description

Method and apparatus for measuring the arrival time of high-energy photons
Technical Field
The invention relates to the field of photon measurement, in particular to a method and a device for measuring the arrival time of high-energy photons.
Background
In the field of high-energy photon (e.g., X-ray, gamma photon, etc.) detection, detector systems typically consist of components such as scintillation crystals, photosensors, and readout circuitry. The following description will be made taking a positron emission imaging system as an example. In positron emission imaging systems, scintillation crystals, such as Bismuth Germanate (BGO), yttrium lutetium silicate (LYSO), lanthanum bromide (LaBr3), and the like, can convert gamma photons into visible photon subgroups. Photosensors, such as photomultiplier tubes (PMTs), silicon photomultiplier tubes (sipms), Avalanche Photodiodes (APDs), and the like, can convert optical signals of visible sub-groups into electrical signals. The readout circuit can obtain the energy of the gamma photon and the time of arrival of the gamma photon at the detector system (i.e., the arrival time of the gamma photon) by measuring the electrical signal output by the photosensor.
Depending on the configuration of the scintillation crystal, detector systems can be divided into discrete crystal-based detector systems and continuous crystal-based detector systems. Due to the complexity of readout circuitry, crystal surface treatment, etc., discrete crystal-based detector systems are employed in commercial positron emission imaging systems.
The scintillator layer of a discrete crystal-based detector system consists of an array of discrete crystals. For example, a 10 x 10 array may be formed with 3 mm x 20 mm crystals, with the total size of the crystal array being 30 mm x 20 mm. By designing the corresponding photosensor array and readout circuitry, it can be confirmed into which discrete crystal the gamma photon strikes (called decoding).
The time measurement accuracy of a discrete crystal-based detector system is influenced by factors such as the intrinsic time performance of the crystal, the size of the crystal (gamma photons are converted into visible photon subgroups at different positions in the crystal, and the time for the visible photon subgroups to reach the photosensor is different), the response time stability (jitter) of the photosensor, and the time measurement accuracy of the readout circuit. It has been shown that among the above factors, the most important bottleneck is the response time stability of the photosensor. Due to this bottleneck, the theoretically optimal temporal resolution of a detector system consisting of the most commonly used Lutetium Silicate (LSO) crystals (3 mm x 30 mm) cannot be better than 70 ps. The temporal resolution of practical commercial positron emission imaging systems is typically around 500ps, and optimally no better than 320 ps.
Therefore, there is a need to provide a method for measuring the arrival time of high energy photons to at least partially solve the above-mentioned problems in the prior art.
Disclosure of Invention
To at least partially solve the problems in the prior art, according to one aspect of the present invention, a method for measuring the arrival time of high-energy photons is provided. The method comprises the following steps: acquiring arrival time related to visible photons generated by reaction of high-energy photons with a scintillation crystal, which is a continuous crystal, detected by each sensor unit in a photosensor array, wherein the photosensor array comprises a plurality of sensor units coupled with the scintillation crystal; obtaining a time to be averaged corresponding to each of selected at least some sensor units in the photosensor array, respectively, based on at least an arrival time associated with the optical photon detected by each sensor unit in the photosensor array; and averaging the time to be averaged corresponding to each of at least some of the sensor units, respectively, to obtain the arrival time of the high energy photons.
According to another aspect of the invention, an apparatus for measuring the arrival time of high energy photons is provided. The device includes: the time acquisition module is used for acquiring the arrival time related to the visible photons generated by the reaction of the high-energy photons and the scintillation crystal, which are detected by each sensor unit in the photoelectric sensor array, wherein the scintillation crystal is a continuous crystal, and the photoelectric sensor array comprises a plurality of sensor units coupled with the scintillation crystal; an average time obtaining module, configured to obtain an average time corresponding to each of at least some selected sensor units in the photosensor array based on at least an arrival time associated with the optical photon detected by each sensor unit in the photosensor array; and an averaging module for averaging the time to be averaged corresponding to each of at least some of the sensor units, respectively, to obtain the arrival time of the high-energy photons.
According to the method and the device provided by the embodiment of the invention, higher time resolution can be obtained by averaging the to-be-averaged time which is obtained for a plurality of sensor units and corresponds to the arrival time of the optical photons.
In this summary, a number of simplified concepts are introduced that are further described in the detailed description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The advantages and features of the present invention are described in detail below with reference to the accompanying drawings.
Drawings
The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, there is shown in the drawings,
FIG. 1 shows a schematic diagram of a continuous crystal based detector system according to one embodiment of the present invention;
FIG. 2 shows a schematic flow diagram of a method for measuring the arrival time of high energy photons, according to one embodiment of the invention;
FIG. 3 shows a schematic flow diagram of a method for measuring the arrival time of high energy photons, according to another embodiment of the present invention;
FIG. 4 shows a schematic flow diagram of a method for measuring the arrival time of high energy photons in accordance with yet another embodiment of the present invention;
FIG. 5 is a simulation result of simulating the energy distribution of visible photons detected by a photosensor array based on nine different reaction locations, according to one embodiment of the present invention;
FIG. 6 is a schematic diagram showing waveforms of two different magnitude electrical signals output from a sensor unit and trigger times corresponding to the two electrical signals, respectively, according to an embodiment of the present invention;
FIG. 7 shows a schematic diagram of the distance relationship between the target reaction site of a high energy photon within a scintillation crystal and a sensor cell, according to one embodiment of the invention;
FIG. 8 shows a schematic view of high energy photons and their coincident high energy photons incident on respective scintillation crystals in accordance with one embodiment of the present invention;
FIG. 9 shows a schematic diagram of high energy photons and their coincident high energy photons incident on respective scintillation crystals in accordance with another embodiment of the invention;
FIG. 10 shows a schematic diagram of an improved continuous crystal-based detector system according to one embodiment of the present invention; and
fig. 11 shows a schematic block diagram of an apparatus for measuring the arrival time of high energy photons, according to one embodiment of the present invention.
Detailed Description
In the following description, numerous details are provided to provide a thorough understanding of the present invention. One skilled in the art will recognize, however, that the following description is merely illustrative of a preferred embodiment of the invention and that the invention may be practiced without one or more of these specific details. In addition, some technical features that are well known in the art are not described in order to avoid confusion with the present invention.
To solve the above problems, the present invention proposes a method and apparatus for measuring the arrival time of high-energy photons for an ultra-high time resolution detector system based on continuous crystals. The scintillator layer of a continuous crystal-based detector system may consist of one monolithic continuous crystal. For example, a scintillator layer can be directly formed from a piece of 30 mm by 20 mm crystal. By designing the corresponding photosensor array and readout circuitry, it can be confirmed where in the continuous crystal the gamma photons strike (called decoding).
FIG. 1 shows a schematic diagram of a continuous crystal-based detector system 100 according to one embodiment of the invention. As shown in fig. 1, the detector system 100 includes a continuous crystal 110, a photosensor array 120, readout circuitry 130, and a data processing module 140.
As shown in fig. 1, the photosensor array 120 can be positioned below the continuous crystal 110, coupled to the continuous crystal 110. The other face of the continuous crystal may be covered with a different type of light reflecting material. The photosensor array 120 can also be disposed on any other side of the continuous crystal, as the invention is not limited. The photosensor array 120 can also be a plurality of photosensor arrays disposed on any other one, two, three, four, five, or six sides of the continuous crystal, and the other sides can be covered with different types of reflective materials, as the invention is not limited thereto.
The photosensor array 120 can include a plurality of sensor cells, for example, the photosensor array can be a 4 x 4 array including 16 sensor cells. When high-energy photons (e.g., gamma photons) are incident into the continuous crystal 110, they may react with the continuous crystal 110 to produce a sub-group of visible light of lower energy. The visible light subgroup is directed or reflected onto the photosensor array 120, being received by several sensor cells in the photosensor array 120. When high-energy photons emerge and react with the continuous crystal 110, there is typically more than one sensor unit that detects the optical photons.
Each sensor cell in the photosensor array 120 can convert the optical signal of the detected optical photons to an electrical signal and output the electrical signal to the readout circuitry 130 connected thereto. It will be appreciated that for sensor cells that do not detect optical photons, the electrical signal output may be 0. The readout circuit 130 may read the electrical signals output by the plurality of sensor units in parallel and output the energy and arrival time associated with the optical photons detected by each sensor unit, respectively. It should be understood that the arrival time output by the readout circuit 130 described herein may be an electrical signal containing time information, and the energy output by the readout circuit 130 described herein may be an electrical signal containing energy information.
The readout circuit 130 may output the energy and arrival time associated with the optical photons detected by each sensor unit to a data processing module 140 connected thereto, and the data processing module 140 may perform the calculation of the arrival time of the high energy photons.
Illustratively, the readout circuit 130 may be a stand-alone circuit or may include a plurality of discrete circuits. For example, the readout circuit 130 may be an independent circuit, which is connected to all the sensor units in the photosensor array 120, and can read the electrical signals output by all the sensor units in parallel. For another example, assuming that the photosensor array 120 includes 16 sensor cells, the readout circuitry 130 may include 16 discrete circuits, with 16 discrete circuits being connected in one-to-one correspondence with the 16 sensor cells, each discrete circuit being used to read the electrical signal output by the corresponding sensor cell. Of course, the implementation of the readout circuit 130 is merely an example, and the readout circuit 130 may have any suitable circuit structure, which is not limited in the present invention.
The data processing module 140 may implement the methods described herein for measuring high energy photons. Illustratively, the data processing module 140 may be implemented using any suitable hardware, software, and/or firmware. The method for measuring the arrival time of high-energy photons proposed by the present invention is described below with reference to the accompanying drawings.
FIG. 2 shows a flow diagram of a method 200 for measuring the arrival time of high energy photons, according to one embodiment of the invention. As shown in fig. 2, the method 200 includes the following steps.
In step S210, an arrival time associated with a visible photon generated by a reaction of a high-energy photon with a scintillation crystal, the scintillation crystal being a continuous crystal, detected by each sensor cell in a photosensor array comprising a plurality of sensor cells coupled to the scintillation crystal is obtained.
As described above, the readout circuit 130 may output energy and arrival time associated with the optical photons detected by each sensor unit to the data processing module 140 connected thereto, and the data processing module 140 may receive the energy and time information output by the readout circuit 130.
In step S220, a time to be averaged corresponding to each of the selected at least some sensor units in the photosensor array is obtained based on at least the arrival time associated with the optical photon detected by each sensor unit in the photosensor array.
In one example, the at least some of the sensor units include all of the sensor units in the photosensor array, and the arrival times associated with the optical photons detected by all of the sensor units in the photosensor array may be directly used as the times to be averaged respectively corresponding to each of the at least some of the sensor units in the photosensor array, that is, the arrival times received from the readout circuit are directly averaged without any processing, and the arrival times are subsequently averaged to find the arrival time of the high-energy photon.
In another example, the at least some of the sensor cells include some but not all of the sensor cells in the photosensor array. In this case, the sensor units may be first selected, for example, only the sensor units having an energy associated with the detected light photons that is greater than a predetermined energy may be selected as at least some of the sensor units described herein. Subsequently, in a subsequent step S130, the arrival times associated with the optical photons detected by at least some of the selected sensor units are averaged to obtain the arrival time of the high-energy photon.
In yet another example, the at least some sensor cells include all sensor cells in a photosensor array. In this example, the arrival time associated with the optical photons detected by each sensor unit may be first corrected, and the corrected arrival time may be used as the time to be averaged to participate in the subsequent averaging operation. The manner of correction of the arrival time will be described below.
In yet another example, the at least some of the sensor cells include some but not all of the sensor cells in the photosensor array. In this case, the sensor units may be first selected, for example, only the sensor units having an energy associated with the detected light photons that is greater than a predetermined energy may be selected as at least some of the sensor units described herein. Then, the arrival time associated with the light photons detected by each of the selected sensor units may be first corrected, and the corrected arrival time may be used as the time to be averaged to participate in the subsequent averaging operation. Alternatively, the arrival times associated with the optical photons detected by all the sensor units in the photosensor array may be corrected, and then at least some of the sensor units may be selected from all the sensor units, and the corrected arrival times corresponding to the selected at least some of the sensor units may be averaged to obtain the arrival time of the high-energy photon.
In step S230, the times to be averaged, which correspond to each of at least some of the sensor units, respectively, are averaged to obtain the arrival times of the high-energy photons.
The time to be averaged corresponding to at least part of the sensor units described above may be averaged. The averaging may be by simple arithmetic averaging or weighted averaging.
In the prior art, a single sensor unit is usually used to detect a high-energy photon occurrence event (e.g. a gamma event), and the arrival time associated with the optical photon detected by the sensor unit is regarded as the arrival time of the high-energy photon. In the invention, a plurality of sensor units are adopted to detect the same high-energy photon occurrence event, the readout circuit measures and obtains a plurality of arrival times related to the visible photons according to the electric signals output by the plurality of sensor units, namely measures and obtains a plurality of arrival times of one high-energy photon, and the readout circuit can also be understood as measuring the same high-energy photon for a plurality of times, and obtaining one arrival time in each measurement. The arrival times associated with the light photons detected by the plurality of sensor units may then be averaged, and the time obtained by averaging is taken as the actual arrival time of the high-energy photons. Of course, before averaging, the arrival time associated with the light photons detected by the sensor unit may also be appropriately corrected to improve the accuracy of the arrival time associated with the light photons, and thus the arrival time of the high-energy photons obtained by averaging.
As will be appreciated by those skilled in the art, the error caused by the response time stability of each sensor unit in the photosensor array, and the time measurement error of the readout circuit, are theoretically random variables independent of each other in each measurement of the arrival time of the high-energy photons. Since the arrival times (or corrected arrival times) obtained for the multiple sensor cell measurements in the sensor array are averaged and the amplitude of the signal (i.e. the true arrival time of the high-energy photon) is unchanged, the amplitude of the noise (e.g. response time stability error, or time measurement error of the readout circuit) can be reduced to:
Figure BDA0001153324700000071
in the formula (1), NoisefinalNoise to average, NoisedetectorErrors due to the response time stability of individual sensor cells, or errors in the time measurement of individual readout channels (one sensor cell for each readout channel) of the readout circuit.
Assuming that the error caused by the response time stability of a single sensor unit (each sensor unit is a photosensor) is 50ps, and assuming that the photosensor array comprises 25 sensor units, the measurement error of the arrival time of the high-energy photons is reduced to 10ps after averaging the arrival times of the outputs of the 25 readout channels according to equation (1). That is to say, since the averaging manner is adopted in the embodiment of the present invention to determine the arrival time of the high-energy photon, compared with the prior art, the measurement error of the method 200 provided by the embodiment of the present invention on the arrival time of the high-energy photon is greatly reduced.
From the above, the present invention reduces the influence of the response time stability of the photosensor on the time measurement by using a plurality of sensor units to detect the same high-energy photon occurrence event (equivalent to a plurality of parallel measurements). The method for measuring the arrival time of the high-energy photon provided by the embodiment of the invention (and the device for measuring the arrival time of the high-energy photon described below) has the following main advantages:
(1) time measurement accuracy of 10ps or even higher is possible. The flight distance of photons is only 3 mm within 10 ps. Thus, a temporal measurement accuracy of 10ps means that the annihilation position of a positron annihilation into a pair of oppositely directed gamma photons can be directly positionally imaged without image reconstruction by an image reconstruction algorithm. Therefore, the sensitivity and image signal-to-noise ratio of a 10ps time resolution positron emission imaging system can be improved by a factor of 7 compared to a conventional 500ps time resolution positron emission imaging system. This will have revolutionary profound effects in the field of clinical application of positron emission imaging systems.
(2) The requirements for the photosensor to reduce the effect of response time stability, and for the readout circuit to have accuracy in time measurements, can be substantially reduced, which is advantageous for reducing the cost of the detector system.
According to an embodiment of the present invention, step S220 may include: selecting at least part of the sensor units; and for each of at least some of the sensor units, correcting the arrival time associated with the light photons detected by that sensor unit to obtain the time to be averaged corresponding to that sensor unit.
As described above, at least some of the sensor cells may include some or all of the sensor cells in the photosensor array 120 described above. For example, a part of the sensor units may be selected from all the sensor units of the photosensor array 120 as the at least part of the sensor units as needed. For example, all sensor cells in the photosensor array may be directly used as the at least part of the sensor cells.
After determining at least part of the sensor units participating in the averaging, the arrival time associated with the optical photons detected by each of the at least part of the sensor units may be corrected. Since there are some errors in the time measurement process, such as errors caused by the trigger level used by the readout circuit 130, these errors may be corrected first, and the corrected arrival time is used as the time to be averaged to participate in the subsequent averaging.
Modifying the arrival time associated with the optical photons may improve the accuracy of the arrival time of the high-energy photons obtained by averaging, i.e., may further improve the time measurement accuracy of the method 200.
According to an embodiment of the present invention, before correcting, for each of at least some of the sensor units, the arrival time associated with the optical photon detected by the sensor unit to obtain the time to be averaged corresponding to the sensor unit, the method 200 may further include: acquiring energy associated with the light photons detected by each sensor unit in the photosensor array; for each of at least some of the sensor units, modifying the arrival time associated with the optical photons detected by that sensor unit to obtain the time to be averaged corresponding to that sensor unit may comprise: for each of at least some of the sensor units, the arrival time associated with the light photons detected by the sensor unit is modified at least in accordance with the energy associated with the light photons detected by the sensor unit to obtain a time to be averaged corresponding to the sensor unit.
Fig. 3 shows a flow diagram of a method 300 for measuring the arrival time of high energy photons, according to another embodiment of the invention. Steps S310 and S350 of the method 300 shown in fig. 3 correspond to steps S210 and S230 of the method 200 shown in fig. 2, respectively, and a person skilled in the art can understand the implementation of steps S310 and S350 through the above description about fig. 2, and will not be described again. According to the present embodiment, step S220 shown in fig. 2 may specifically include steps S330 and S340 shown in fig. 3, and before step S340, the method 300 may further include step S320.
Specifically, in step S320, energy associated with the optical photons detected by each sensor unit in the photosensor array is acquired.
The readout circuit 130, after receiving the electrical signal output by each sensor unit, can determine the energy associated with the optical photons detected by the sensor unit according to the magnitude (or called intensity or amplitude) of the electrical signal. Thus, as described above, the readout circuit 130 may output energy associated with the optical photons detected by each sensor cell in addition to the arrival time associated with the optical photons detected by each sensor cell. The data processing module 140 may receive the energy of the light photons.
In step S330, at least a portion of the sensor units are selected. This step can be understood from the above description and will not be described in detail here.
In step S340, for each of at least some of the sensor units, the arrival time associated with the optical photons detected by the sensor unit is corrected at least according to the energy associated with the optical photons detected by the sensor unit to obtain the time to be averaged corresponding to the sensor unit.
Since when the readout circuit 130 measures the arrival time associated with a light photon, the moment at which its received electrical signal exceeds the threshold is typically considered the arrival time of the light photon. However, when a large number of photons of light are generated, the distance between the photons of light and different sensor units is different, and thus the arrival time associated with the photons of light obtained by measurement will be different greatly, i.e. the error is large. Since the energy of the visible photons corresponds to the magnitude of the electrical signal, the time associated with the visible photons can be modified according to the energy associated with the visible photons.
It should be understood that the order of execution of the steps of method 300 shown in fig. 3 is merely exemplary and not limiting, and that method 300 may have other suitable orders of execution. For example, step S320 of method 300 shown in fig. 3 may be performed after step S330, or both.
According to the embodiment of the present invention, step S340 may include: calculating a target reaction position of the high-energy photon in the scintillation crystal according to the energy related to the visible photon detected by all the sensor units in the photoelectric sensor array; for each of at least some of the sensor units, correcting an arrival time associated with a light photon detected by the sensor unit in accordance with an energy associated with the light photon detected by the sensor unit to obtain a corrected time corresponding to the sensor unit; and for each of at least part of the sensor units, correcting the correction time corresponding to the sensor unit according to the target reaction position so as to obtain the time to be averaged corresponding to the sensor unit.
Fig. 4 shows a flow diagram of a method 400 for measuring the arrival time of high energy photons, in accordance with yet another embodiment of the present invention. Steps S410-S430 and S470 of the method 400 shown in fig. 4 correspond to steps S310-S330 and S350 of the method 300 shown in fig. 3, respectively, and a person skilled in the art can understand the implementation of steps S410-S430 and S470 through the above description about fig. 3, and will not be described again. According to this embodiment, step S340 shown in fig. 3 may specifically include steps S440-S460 shown in fig. 4.
In step S440, the target reaction location of the high-energy photons in the scintillation crystal is calculated from the energies associated with the optical photons detected by all the sensor cells in the photosensor array.
The speed of high-energy photons (such as gamma photons) in the scintillation crystal is close to the speed c of vacuum light, and the speed of the generated visible photons after the high-energy photons react with the scintillation crystal is as follows: v ═ c/nr。nrIs the refractive index of the light photons in the scintillation crystal. For example, in an LSO crystal, a light photon having a wavelength of 420nm has a refractive index of about 1.8 and a velocity of 0.56 times the velocity of vacuum light. Therefore, in order to obtain accurate time measurements, it is necessary to compensate for measurement errors caused by the difference in the velocities of the high-energy photons and the light photons in the scintillation crystal. In order to compensate for the errors caused by the speed difference, it is necessary to know the transmission distance of the light photons in the scintillation crystal, which is equal to the distance of the target reaction site of the high-energy photons to the sensor unit that detected the light photons. Thus, the target reaction site for the high-energy photon can be determined first.
The target reaction position of the high-energy photon may be calculated by using energy information obtained based on the electrical signal measurement output from the photosensor array 120. The calculation method of the target reaction position is described below with reference to fig. 5. FIG. 5 is a simulation result of simulating the energy distribution of visible photons detected by a photosensor array based on nine different reaction sites, according to one embodiment of the present invention. The lower left corner of fig. 5 shows the xyz coordinate system used by the simulation.
In the embodiment shown in fig. 5, the parameters of the detector system involved in the simulation are as follows: the scintillation crystal is an LSO crystal, and the size of the scintillation crystal is 60 mm multiplied by 20 mm; the size of the photosensor array is 10 × 10, and the size of the individual sensor units is 6 mm × 6 mm.
FIG. 5 shows simulation results based on nine different reaction sites, each of which may be referred to as an energy profile. The values on the x-axis and y-axis in each energy profile are the lateral and longitudinal numbers of the 10 x 10 photosensor array, respectively, and the z-axis represents the magnitude of the electrical signal read out from each sensor cell in the 10 x 10 photosensor array in units of the number of photons. It should be understood that the magnitude of the electrical signal output by the sensor unit corresponds to the magnitude of the energy associated with the visible photons detected by the sensor unit.
In the 9 energy distribution diagrams shown in fig. 5, the depths of reaction sites of gamma photons in the scintillation crystal are set to 2 mm, 4 mm, 6 mm, … 18 mm, respectively, in order from the upper left corner to the lower right corner. Furthermore, for each energy profile, gamma photons are incident from a position close to the central axis of the scintillation crystal. As can be seen from fig. 5, the reaction positions of gamma photons in the scintillation crystal are different, and the energy distribution (or light distribution) of visible photons measured by the 10 × 10 photosensor array is also different.
Specifically, referring to the first energy distribution diagram at the upper left corner, the depth of the reaction site of the gamma photon is 2 mm, and since the reaction site is far away from the photosensor array below, the generated visible photons are relatively dispersed, and the number of sensor units detecting the visible photons is relatively large. Referring to the last energy profile at the bottom right, the gamma photon reaction site is 18 mm deep, and due to the closer proximity to the underlying photosensor array, the resulting light photons are more concentrated and fewer sensor units detect the light photons. In addition, the energy profiles shown in fig. 5 are all obtained by simulation in the case where gamma photons are incident from a position close to the central axis of the scintillation crystal, and it is understood that if the incident position of a gamma photon is shifted on the xy plane, the energy concentration region of a visible photon also changes following the shift direction of the incident position in the energy profiles. Therefore, the reaction position of the gamma photon in the scintillation crystal can be deduced inversely by the energy distribution of the visible photon, which is called position calculation. The position calculation method may be any existing or future position calculation method that may be implemented, for example, a barycentric method, an artificial neural network, an analytic method, and the like, and the present invention is not limited thereto.
In step S450, for each of at least some of the sensor units, the arrival time associated with the optical photon detected by the sensor unit is corrected according to the energy associated with the optical photon detected by the sensor unit to obtain a corrected time corresponding to the sensor unit.
According to one embodiment of the present invention, the readout circuit 130 may measure the arrival time associated with the optical photons using a constant voltage trigger.
In a detector system, the time measurement circuit of the readout circuit may typically employ two triggering modes, one being a constant ratio triggering mode, the triggering level of which is fixed at a certain proportion (e.g. 10%) of the amplitude of the input signal (i.e. the electrical signal output by the sensor unit); the other is a constant voltage trigger mode, and the trigger level is fixed at a preset voltage.
The constant ratio trigger mode has two disadvantages: (a) the circuit is relatively complex; (b) it is relatively difficult to achieve a low trigger level ratio. Due to the high temporal resolution of the detector system, it is generally required that the triggering occurs at the level of the first few photons of the group of light photons that arrive at the photosensor earliest, i.e. that the triggering level is sufficiently low. Therefore, the constant ratio triggering method is not well suited for use in ultra-high time resolution detector systems.
Compared with a constant ratio trigger mode, the constant voltage trigger mode has the advantages that the trigger level is fixed, so that the required circuit structure is simpler, and the circuit cost is low. Therefore, the time measurement of the optical photons can be realized by adopting a constant voltage triggering mode.
The constant voltage triggering method has the disadvantages that the triggering time is related to the size of the input signal. Fig. 6 is a schematic diagram illustrating waveforms of two different electrical signals output from a sensor unit according to an embodiment of the present invention and trigger times respectively corresponding to the two electrical signals.
As shown in FIG. 6, the electrical signal W2 has a magnitude that is about 20% less than the electrical signal W1. In the case of constant voltage triggering, the actual triggering time of the electrical signal W2 is 45ps later than the electrical signal W1. Therefore, it is necessary to correct (i.e., calibrate) the time measurement obtained by the constant voltage triggering manner so that the time measurement is independent of the magnitude of the input signal.
Illustratively, the modification of the arrival time associated with the visible photon may comprise a polynomial modification, for example a linear modification may be used. The formula for the linear correction is as follows:
TA,k＝Tm,k+αEm,k(2)
in formula (2), TA,kFor a correction time corresponding to the kth sensor cell of at least some of the sensor cells, Tm,kAnd Em,kRespectively, the arrival time and energy associated with the optical photon detected by the kth sensor unit, α is a correction factor.
The correction process in step S450 may be referred to as trigger level correction, the purpose of which is to correct the time measurement corresponding to each sensor unit by the energy measurement corresponding to that sensor unit.
In step S460, for each of at least some of the sensor units, the correction time corresponding to the sensor unit is corrected according to the target reaction position to obtain the time to be averaged corresponding to the sensor unit.
As described above, there is a difference in the velocities of the high energy photons and the light photons in the scintillation crystal, resulting in an error in the time measurement of the readout circuit 130. In order to obtain accurate time measurements, it is necessary to compensate for measurement errors caused by the difference in the velocities of the high-energy photons and the light photons in the scintillation crystal.
FIG. 7 shows a schematic diagram of the distance relationship between the target reaction site of a high energy photon within a scintillation crystal and a sensor cell, according to one embodiment of the invention.
As shown in fig. 7, assuming that the depth of the high-energy photon in the scintillation crystal obtained by position calculation is h, the target reaction position is at a distance d from the center position of a certain sensor unit in the photosensor array. For example, in FIG. 7 the target reaction site is located a distance d from the fourth row of the first column of sensor cells in the photosensor array4,1The distance from the target reaction position to the second row and the fourth column of the sensor units in the photoelectric sensor array is d2,4. The light speed correction can be performed using the following equation:
Figure BDA0001153324700000131
in formula (3), TB,kFor the time to be averaged, n, corresponding to the kth sensor unitrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkIs the distance from the target reaction site to the center position of the kth sensor unit, and h is the depth of the target reaction site.
Formula (2) may be substituted for formula (3) to yield:
Figure BDA0001153324700000132
the correction process in step S460 may be referred to as light speed correction. The trigger level correction and the light velocity correction can be performed simultaneously using equation (4).
Through the trigger level correction and the light velocity correction, the accuracy of the arrival time related to the visible photons is improved, and the arrival time of the high-energy photons obtained through final calculation can be greatly improved.
It is to be noted that the expressions (3) and (4) are obtained assuming that a pair of gamma photons generated after positron annihilation is perpendicularly incident into a continuous crystal (as shown in fig. 8). FIG. 8 shows a schematic diagram of high energy photons and their coincident high energy photons incident on respective scintillation crystals, in accordance with one embodiment of the present invention.
In fact, the situation shown in fig. 8 is only a special case. More often, the continuous crystal detectors are arranged in a geometric configuration, such as along a circle as shown in FIG. 9. FIG. 9 shows a schematic diagram of high energy photons and their coincident high energy photons incident on respective scintillation crystals according to another embodiment of the invention. Assume that position a shown in fig. 9 is the target reaction position for high-energy photon a for which the arrival time needs to be measured, and position B is the reaction position for high-energy photon B coincident with high-energy photon a, i.e., the contralateral reaction position described herein. In the case shown in fig. 9, the target reaction site a and the contralateral reaction site B may be connected after calculating the reaction sites a and B of the two gamma photons a and B in opposite directions in the respective scintillation crystals to obtain the line of response AB of positron annihilation. Subsequently, the response line AB may be extended until reaching the sensor array of the detector system for detecting the high-energy photons a, the length of the extended line (e.g. the length of the extended portion of the sensor array from position a in fig. 9) may be noted as lA. In this case, the formula (3) may be modified as follows:
Figure BDA0001153324700000141
wherein, TB,kFor the time to be averaged, n, associated with the k-th sensor unit of at least some of the sensor unitsrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkThe distance l from the target reaction position to the center position of the kth sensor unit is a length along a line connecting the opposite reaction position of the high-energy photon corresponding to the high-energy photon in the scintillator crystal arranged on the opposite side of the scintillator crystal and the target reaction position, extending from the target reaction position until reaching an extension line of the photosensor array. It is understood that l in the formula (5) represents the above-mentioned lA。
Formula (2) may be substituted for formula (5) to yield:
Figure BDA0001153324700000142
formulas (5) and (6) are more widely used than formulas (3) and (4). The person skilled in the art can select a suitable formula to perform the light speed correction according to the requirement, and of course, the light speed correction can also be performed by combining the two ways.
It should be understood that the order of execution of the steps in the method 400 shown in fig. 4 is merely exemplary and not limiting, and that the method 400 may have other suitable orders of execution. For example, step S440 may be performed before or simultaneously with step S430, and step S440 may also be performed after or simultaneously with step S450.
Although the method 400 of FIG. 4 implements trigger level correction and light speed correction, it should be understood that both correction methods may alternatively be implemented. For example, trigger level correction may be performed only on arrival times associated with at least some of the light photons detected by the sensor unit, and the arrival times obtained through trigger level correction are to-be-averaged times for participating in subsequent averaging operations. For example, the light speed correction may be performed only on the arrival time related to the optical photons detected by at least part of the sensor units, and the arrival time obtained through the light speed correction is the time to be averaged, so as to participate in the subsequent averaging operation. Of course, other suitable modifications may be used to modify the arrival time associated with the optical photons, either individually or in combination, and fall within the scope of the present invention.
According to an embodiment of the present invention, step S230(S350 or S470) may be implemented by the following formula:
Figure BDA0001153324700000143
in formula (7), TfinalIs the arrival time, T, of a high-energy photonB,kIs the kth sensor in at least part of the sensor unitsThe unit corresponds to the average time, and n is the number of at least partial sensor units.
Assuming that at least some of the sensor cells participating in the averaging are all of the sensor cells in the photosensor array, which is an M × N array, equation (7) can be expressed as:
Figure BDA0001153324700000151
the expressions (7) and (8) represent an implementation of averaging the averaging time by an arithmetic mean method, which is relatively simple and requires a small amount of computation.
According to another embodiment of the present invention, step S230(S350 or S470) may be implemented by the following formula:
Figure BDA0001153324700000152
in formula (9), TfinalIs the arrival time, T, of a high-energy photonB,kFor the time to be averaged corresponding to the kth sensor unit of at least some of the sensor units, CkIs the weighting factor associated with the kth sensor unit and n is the number of at least some of the sensor units.
Assuming that at least some of the sensor cells participating in the averaging are all of the sensor cells in the photosensor array, which is an M × N array, equation (9) can be expressed as:
Figure BDA0001153324700000153
equations (9) and (10) represent an implementation of averaging the averaging time by a weighted average method. Compared with the arithmetic mean method, the weighted mean method is more complicated and the calculated arrival time of the high-energy photon is more accurate.
Illustratively, in calculating the arrival time of the high-energy photons using a weighted averaging method, a weight coefficient C associated with each sensor cellkMay be sensed by the sensor unitEnergy E associated with the detected light photonskOr the energy E associated with the light photons detected by the sensor unitkAs a function of (c).
For example, equation (10) may be expressed as:
Figure BDA0001153324700000154
illustratively, in calculating the arrival time of the high-energy photons using a weighted averaging method, a weight coefficient C associated with each sensor cellkIt may be a theoretical value or an empirical value independent of energy. For example, the weighting coefficients respectively associated with all the sensor units in the photosensor array may be initially set to the same value, and then the weighting coefficient associated with each sensor unit may be updated through experiments or the like, and finally an appropriate weighting coefficient associated with each sensor unit may be obtained.
According to an embodiment of the present invention, before selecting at least a part of the sensor units, the method 200 may further include: acquiring energy associated with the light photons detected by each sensor unit in the photosensor array; selecting at least a portion of the sensor cells may include: selecting, as at least part of the sensor units, sensor units from all sensor units in the photosensor array, which have an energy associated with the detected optical photons that is greater than a preset energy.
The energy obtaining step in this embodiment may refer to step S320 of the method 300 shown in fig. 3 or step S420 of the method 400 shown in fig. 4, and is not described herein again. The arithmetic mean (reference formula (7)) or the weighted mean (reference formula (9)) may be obtained only for the time to be averaged of the sensor units in the photosensor array having energy greater than a certain preset value. The light photons may be directed onto the sensor unit while propagating through the scintillation crystal, or may reach the sensor unit after one or more reflections. The arrival time error of the light photons reaching the sensor unit after reflection is large, and the arrival time of the high-energy photons cannot be correctly reflected, so that the arrival time of the light photons can be filtered out, and the light photons do not participate in subsequent averaging operation. This process can reduce the time measurement error due to some sensor units detecting light photons that do not reach the sensor unit directly from the reaction site of the gamma photon.
Although the configuration of the detector system to which the method (and apparatus) for measuring the arrival time of high-energy photons provided by the present invention is applicable is described herein with reference to fig. 1, it is merely an example and not a limitation of the present invention. For example, the method (and apparatus) for measuring the arrival time of high-energy photons provided by the present invention can also be applied to a detector system obtained by improving the detector system shown in fig. 1. Some examples of detector systems obtained by improvement based on the detector system shown in fig. 1 are described below.
In case the method (and apparatus) for measuring the arrival time of high-energy photons provided by the present invention is applied to the detector system shown in fig. 1, when the reaction site of the high-energy photons (e.g. gamma photons) in the continuous crystal 110 is very close to the photosensor array 120, the light photons will be too concentrated on some sensor units in the photosensor array 120. Too much concentration of the light photons may result in a reduction in the number of sensor cells actually participating in the averaging during the operations of equations (7) to (11), thereby reducing the accuracy of the time measurement.
Therefore, in order to improve the accuracy of the time measurement of the method (and apparatus) for measuring the arrival time of high energy photons, the detector system shown in fig. 1 may be improved. The method (and apparatus) for measuring the arrival time of high-energy photons provided by the present invention is applicable to such improved detector systems, and the flow of the method (and corresponding functional blocks of the apparatus) is substantially unchanged, although some changes may be required in the way some data is calculated.
In one example, a light guide may be inserted between the continuous crystal 110 and the photosensor array 120, enabling more uniform distribution of the light photons over the photosensor array 120. The thickness of the light guide may be determined by experimental or simulation methods. For such a detector system, the influence of the light guide needs to be taken into account when applying the method (and the apparatus) for measuring the arrival time of high-energy photons to the detector system. When the method provided by the present invention is described above in connection with the detector system shown in fig. 1, it is assumed that the continuous crystal 110 and the photosensor array 120 are directly coupled, with no gap between them. The way in which the target reaction sites for high-energy photons are calculated as described above needs to be changed if a light guide is inserted between the continuous crystal 110 and the photosensor array 120, since the light guide has a certain thickness that affects the propagation of the light photons. The calculation of the target reaction position in case of inserting the light guide may be performed using algorithms conventional in the art and will not be described in detail herein. Furthermore, equations (3) to (6) also require corresponding changes to be made, taking into account the propagation time of the light photons in the light guide.
In another example, an array of photosensors can be coupled on multiple faces of the continuous crystal 110. For example, an array of photosensors may be coupled on two opposing faces of a continuous crystal. As another example, a photosensor array can be coupled on all six faces of a continuous crystal. FIG. 10 shows a schematic diagram of an improved continuous crystal-based detector system, according to one embodiment of the present invention. As shown in fig. 10, two opposing faces of the continuous crystal (illustratively defined as an upper bottom face and a lower bottom face) are each coupled to a photosensor array. In the case of coupling photosensor arrays on multiple faces of the continuous crystal, the arrival times of the light photons detected by all the photosensor arrays coupled to the multiple faces of the continuous crystal may be measured by a readout circuit, and the arrival times of the light photons detected by all the photosensor arrays coupled to the multiple faces of the continuous crystal may be output to a data processing module. The data processing module implements a method for measuring the arrival time of high-energy photons. That is, all or at least some of the sensor cells in all of the photosensor arrays coupled to multiple facets of the continuous crystal participate in the computation of the arrival times of the high-energy photons.
For the case of coupling the photosensor array on multiple faces of a continuous crystal, the coupling is between and not betweenWhen the photo sensor arrays coupled to the same plane perform the light velocity correction, the depths h (see expressions (3) and (4)) of the target reaction sites are different, and similarly, the lengths l (see expressions (5) and (6)) of the extension lines are also different. Taking the detector system shown in FIG. 10 as an example, for a photosensor array coupled to the top and bottom surfaces of a continuous crystal, the time to average T corresponding to each sensor cell in the photosensor array is calculatedB,kThe depth h of the target reaction position is the vertical distance between the target reaction position of the gamma photon and the upper bottom surface of the continuous crystal; for a photosensor array coupled to the lower bottom surface of a continuous crystal, the time to average T corresponding to each sensor cell in the photosensor array is calculatedB,kThe depth h of the target reaction site is the vertical distance between the target reaction site of the gamma photon and the lower bottom surface of the continuous crystal. The case of l in the formula (5) and the formula (6) is similar to h, and is not described again. Although the detector system shown in fig. 10, which couples the photosensor arrays on two sides of the continuous crystal, is described as an example, the calculation manner of h and l when coupling the photosensor arrays on other number of sides of the continuous crystal can be understood by those skilled in the art with reference to the above description, and will not be described again. In short, in the case of coupling the photosensor arrays on a plurality of surfaces of the continuous crystal, when the light velocity correction is performed for each sensor unit, it is necessary to consider the position of the photosensor array to which the sensor unit belongs with respect to the continuous crystal. According to another aspect of the invention, there is provided an apparatus for measuring the arrival time of high energy photons. Fig. 11 shows a schematic block diagram of an apparatus 1100 for measuring the arrival time of high energy photons, according to one embodiment of the present invention.
As shown in fig. 11, the apparatus 1100 includes a time acquisition module 1110, a time to average acquisition module 1120, and an averaging module 1130.
The time acquisition module 1110 is configured to acquire an arrival time associated with a light photon generated by a reaction of a high-energy photon with a scintillation crystal, which is a continuous crystal, detected by each sensor unit in a photosensor array comprising a plurality of sensor units coupled to the scintillation crystal.
The to-be-averaged time obtaining module 1120 is configured to obtain an to-be-averaged time respectively corresponding to each of at least some selected sensor units in the photosensor array based on at least an arrival time associated with the optical photon detected by each sensor unit in the photosensor array.
The averaging module 1130 is configured to average the time to be averaged corresponding to each of the at least some sensor units, respectively, to obtain the arrival time of the high-energy photon.
For example, the to-be-averaged time obtaining module 1120 may include: a sensor selection submodule for selecting at least some of the sensor units; and a correction submodule for correcting, for each of at least some of the sensor units, an arrival time associated with a light photon detected by that sensor unit to obtain a time to be averaged corresponding to that sensor unit.
Illustratively, the apparatus 1100 may further comprise: an energy acquisition module for acquiring energy associated with the light photons detected by each sensor unit in the photosensor array; the revision submodule may include: and the correction unit is used for correcting the arrival time related to the visible photons detected by the sensor unit at least according to the energy related to the visible photons detected by the sensor unit so as to obtain the time to be averaged corresponding to the sensor unit.
Illustratively, the correction unit may include: a position calculating subunit, configured to calculate a target reaction position of the high-energy photon in the scintillation crystal according to energies associated with the visible photons detected by all the sensor units in the photosensor array; a first correction subunit, configured to, for each of at least some of the sensor units, correct an arrival time associated with a light photon detected by the sensor unit according to an energy associated with the light photon detected by the sensor unit to obtain a correction time corresponding to the sensor unit; and the second correction subunit is used for correcting the correction time corresponding to at least part of the sensor units according to the target reaction position so as to obtain the time to be averaged corresponding to the sensor units.
For example, the first correction subunit may comprise a first correction component for correcting the arrival time associated with the optical photons detected by each of at least some of the sensor units by:
TA,k＝Tm,k+αEm,k，
wherein, TA,kFor a correction time corresponding to the kth sensor cell of at least some of the sensor cells, Tm,kAnd Em,kRespectively, the arrival time and energy associated with the optical photon detected by the kth sensor unit, α is a correction factor.
For example, the second correction subunit may comprise a second correction component for correcting the correction time corresponding to each of at least some of the sensor units by:
Figure BDA0001153324700000191
wherein, TB,kFor the time to be averaged, n, corresponding to the kth sensor unitrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkIs the distance from the target reaction site to the center position of the kth sensor unit, and h is the depth of the target reaction site.
For example, the second correction subunit may comprise a third correction component for correcting the correction time corresponding to each of at least some of the sensor units by the following formula:
Figure BDA0001153324700000192
wherein, TB,kFor the time to be averaged associated with the kth sensor unitM, nrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkThe distance l from the target reaction position to the center position of the kth sensor unit is a length along a line connecting the opposite reaction position of the high-energy photon corresponding to the high-energy photon in the scintillator crystal arranged on the opposite side of the scintillator crystal and the target reaction position, extending from the target reaction position until reaching an extension line of the photosensor array.
For example, the averaging module 1130 may include an averaging submodule for averaging the time to be averaged corresponding to each of at least some of the sensor cells, respectively, by the following equation:
Figure BDA0001153324700000201
wherein, TfinalIs the arrival time, T, of a high-energy photonB,kFor the time to be averaged corresponding to the kth sensor unit of at least some of the sensor units, CkIs the weighting factor associated with the kth sensor unit and n is the number of at least some of the sensor units.
Exemplarily, CkIs the energy associated with the optical photons detected by the kth sensor unit or is a function of the energy associated with the optical photons detected by the kth sensor unit.
Exemplarily, CkIs an empirical value associated with the kth sensor unit.
Illustratively, the apparatus 1100 may further comprise: an energy acquisition module for acquiring energy associated with the light photons detected by each sensor unit in the photosensor array; the sensor selection sub-module may include: and the selection unit is used for selecting the sensor units with the energy related to the detected visible photons, which is greater than the preset energy, from all the sensor units in the photoelectric sensor array as at least part of the sensor units.
A person skilled in the art can understand the embodiments of the apparatus 1100 for measuring the arrival time of high-energy photons disclosed herein, the advantages thereof, etc. according to the above description of the method for measuring the arrival time of high-energy photons and the accompanying fig. 1 to 10, and for the sake of brevity, no further description is provided herein.
In the description herein, "arrival time associated with a light photon" may be replaced with "arrival time of a light photon", both of which represent the same meaning. Similarly, "energy associated with a light photon" may be replaced by "energy of a light photon", both of which are meant to be the same. In case of a "light photon" preceded by a phrase, an alternative expression can be obtained in a similar way as well. For example, "the arrival time associated with the optical photon detected by each sensor unit in the photosensor array" may be replaced with "the arrival time of the optical photon detected by each sensor unit in the photosensor array".
The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical functional division, and there may be other divisions when actually implementing, for example, a plurality of units or components may be combined or integrated into another device, or some features may be omitted, or not implemented.

Claims (16)

1. A method for measuring the arrival time of high energy photons, comprising:
acquiring an arrival time associated with a light photon generated by a reaction of a high-energy photon with a scintillation crystal detected by each sensor unit in a photosensor array, wherein the scintillation crystal is a continuous crystal and the photosensor array comprises a plurality of sensor units coupled to the scintillation crystal;
acquiring energy associated with the detected light photons by each sensor unit in the photosensor array;
obtaining a time to be averaged corresponding to each of selected at least some sensor cells in the photosensor array, respectively, based at least on arrival times associated with the optical photons detected by each sensor cell in the photosensor array; and
averaging the time to be averaged corresponding to each of the at least some sensor units, respectively, to obtain the arrival time of the high energy photons;
wherein said obtaining a time to average corresponding to each of a selected at least some sensor cells in the photosensor array based at least on the arrival time associated with the detected optical photons by each sensor cell in the photosensor array comprises:
selecting the at least part of the sensor units, wherein the selecting the at least part of the sensor units comprises: selecting, as the at least part of sensor units, sensor units having an energy associated with the detected optical photons that is greater than a preset energy from among all sensor units in the photosensor array; and
for each of the at least some sensor units, correcting an arrival time associated with the optical photons detected by that sensor unit to obtain a time to be averaged corresponding to that sensor unit,
wherein, for each of the at least some sensor units, correcting the arrival time associated with the optical photons detected by that sensor unit to obtain the time to be averaged corresponding to that sensor unit comprises:
for each of the at least some sensor units, the arrival time associated with the light photons detected by the sensor unit is modified at least in accordance with the energy associated with the light photons detected by the sensor unit to obtain the time to be averaged corresponding to the sensor unit.
2. The method of claim 1, wherein for each of the at least some sensor units, modifying the arrival time associated with the optical photons detected by the sensor unit based at least on the energy associated with the optical photons detected by the sensor unit to obtain the time to be averaged corresponding to the sensor unit comprises:
calculating a target reaction position of the high-energy photons in the scintillation crystal according to energies related to the light photons detected by all sensor units in the photosensor array;
for each of the at least some of the sensor units,
correcting the arrival time associated with the light photons detected by the sensor unit according to the energy associated with the light photons detected by the sensor unit to obtain a corrected time corresponding to the sensor unit;
and correcting the correction time corresponding to the sensor unit according to the target reaction position to obtain the time to be averaged corresponding to the sensor unit.
3. The method of claim 2, wherein for each of the at least some sensor units, correcting the arrival time associated with the optical photon detected by that sensor unit according to the energy associated with the optical photon detected by that sensor unit to obtain a corrected time corresponding to that sensor unit is performed by:
TA,k＝Tm,k+αEm,k，
wherein, TA,kFor a correction time corresponding to a k-th sensor unit of said at least some sensor units, Tm,kAnd Em,kRespectively the arrival time and the energy associated with the optical photon detected by the kth sensor unit, α is a correction factor.
4. The method of claim 3, wherein for each of the at least some sensor units, the correction time corresponding to the sensor unit is corrected according to the target reaction position to obtain the time to be averaged corresponding to the sensor unit is obtained by the following formula:
Figure FDA0002442180610000021
wherein, TB,kIs the time to average, n, corresponding to the k-th sensor unitrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkIs a distance from the target reaction position to a center position of the kth sensor unit, and h is a depth of the target reaction position.
5. The method of claim 3, wherein for each of the at least some sensor units, the correction time corresponding to the sensor unit is corrected according to the target reaction position to obtain the time to be averaged corresponding to the sensor unit is obtained by the following formula:
Figure FDA0002442180610000031
wherein, TB,kIs the time to average, n, associated with the kth sensor unitrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkAnd l is a length extending from the target reaction position to an extension line of the photosensor array along a connecting line between an opposite side reaction position of the high-energy photon corresponding to the high-energy photon in the scintillation crystal arranged on the opposite side of the scintillation crystal and the target reaction position.
6. The method according to any one of claims 1 to 5, wherein the averaging of the time to be averaged corresponding to each of the at least some sensor units, respectively, to obtain the arrival time of the high-energy photons is performed by the following equation:
Figure FDA0002442180610000032
wherein, TfinalIs the arrival time, T, of the high energy photonB,kIs the time to be averaged corresponding to the kth sensor unit of the at least some sensor units, CkIs a weighting factor associated with the k-th sensor unit, and n is the number of the at least some sensor units.
7. The method of claim 6, wherein C iskIs or is a function of the energy associated with the optical photons detected by the kth sensor unit.
8. The method of claim 6, wherein C iskIs an empirical value associated with the kth sensor unit.
9. An apparatus for measuring the arrival time of high energy photons, comprising:
the time acquisition module is used for acquiring the arrival time related to the visible photons generated by the reaction of the high-energy photons and the scintillation crystal, which are detected by each sensor unit in the photoelectric sensor array, wherein the scintillation crystal is a continuous crystal, and the photoelectric sensor array comprises a plurality of sensor units coupled with the scintillation crystal;
an energy acquisition module for acquiring energy associated with the light photons detected by each sensor unit in the photosensor array;
an average time obtaining module, configured to obtain an average time corresponding to each of at least some selected sensor units in the photosensor array based on at least an arrival time associated with the detected optical photons of each sensor unit in the photosensor array; and
an averaging module, configured to average to-be-averaged time respectively corresponding to each of the at least some sensor units to obtain an arrival time of the high-energy photon;
wherein the to-be-averaged time obtaining module comprises:
a sensor selection submodule for selecting the at least some of the sensor units, wherein the sensor selection submodule comprises: a selection unit, configured to select, as the at least part of sensor units, which have an energy greater than a preset energy and are related to the detected optical photons, from all the sensor units in the photosensor array; and
a correction submodule for correcting, for each of the at least some sensor units, an arrival time associated with a light photon detected by that sensor unit to obtain a time to be averaged corresponding to that sensor unit,
wherein the modification submodule comprises: and the correction unit is used for correcting the arrival time related to the visible photons detected by the sensor unit at least according to the energy related to the visible photons detected by the sensor unit so as to obtain the time to be averaged corresponding to the sensor unit.
10. The apparatus of claim 9, wherein the correction unit comprises:
a position calculating subunit, configured to calculate a target reaction position of the high-energy photon in the scintillation crystal according to energies associated with the light photons detected by all the sensor units in the photosensor array;
a first correction subunit, configured to, for each of the at least some sensor units, correct an arrival time associated with the light photons detected by the sensor unit according to an energy associated with the light photons detected by the sensor unit to obtain a corrected time corresponding to the sensor unit;
and the second correction subunit is used for correcting the correction time corresponding to the sensor unit according to the target reaction position so as to obtain the time to be averaged corresponding to the sensor unit.
11. The apparatus of claim 10, wherein the first correction subunit comprises a first correction component for correcting the arrival time associated with the optical photons detected by each of the at least some sensor units by:
TA,k＝Tm,k+αEm,k，
wherein, TA,kFor a correction time corresponding to a k-th sensor unit of said at least some sensor units, Tm,kAnd Em,kRespectively the arrival time and the energy associated with the optical photon detected by the kth sensor unit, α is a correction factor.
12. The apparatus of claim 11, wherein the second correction subunit comprises a second correction component for correcting the correction time corresponding to each of the at least some sensor units by:
Figure FDA0002442180610000051
wherein, TB,kIs the time to average, n, corresponding to the k-th sensor unitrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkIs a distance from the target reaction position to a center position of the kth sensor unit, and h is a depth of the target reaction position.
13. The apparatus of claim 11, wherein the second correction subunit comprises a third correction component for correcting the correction time corresponding to each of the at least some sensor units by:
Figure FDA0002442180610000052
wherein, TB,kIs the time to average, n, associated with the kth sensor unitrIs the refractive index of the visible photon in the scintillation crystal, c is the vacuum speed of light, dkAnd l is a length extending from the target reaction position to an extension line of the photosensor array along a connecting line between an opposite side reaction position of the high-energy photon corresponding to the high-energy photon in the scintillation crystal arranged on the opposite side of the scintillation crystal and the target reaction position.
14. The apparatus of any one of claims 9 to 13, wherein the averaging module comprises an averaging submodule for averaging the time to be averaged respectively corresponding to each of the at least some sensor units by:
Figure FDA0002442180610000053
wherein, TfinalIs the arrival time, T, of the high energy photonB,kIs the time to be averaged corresponding to the kth sensor unit of the at least some sensor units, CkIs a weighting factor associated with the k-th sensor unit, and n is the number of the at least some sensor units.
15. The apparatus of claim 14, wherein C iskIs or is a function of the energy associated with the optical photons detected by the kth sensor unit.
16. The apparatus of claim 14, wherein C iskIs an empirical value associated with the kth sensor unit.
CN201611004839.8A 2016-11-15 2016-11-15 Method and apparatus for measuring the arrival time of high-energy photons Active CN106443747B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN201611004839.8A CN106443747B (en) 2016-11-15 2016-11-15 Method and apparatus for measuring the arrival time of high-energy photons
PCT/CN2017/110864 WO2018090900A1 (en) 2016-11-15 2017-11-14 Method and apparatus for measuring arrival time of high-energy photons

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201611004839.8A CN106443747B (en) 2016-11-15 2016-11-15 Method and apparatus for measuring the arrival time of high-energy photons

Publications (2)

Publication Number Publication Date
CN106443747A CN106443747A (en) 2017-02-22
CN106443747B true CN106443747B (en) 2020-05-29

Family

ID=58207159

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201611004839.8A Active CN106443747B (en) 2016-11-15 2016-11-15 Method and apparatus for measuring the arrival time of high-energy photons

Country Status (2)

Country Link
CN (1) CN106443747B (en)
WO (1) WO2018090900A1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106443747B (en) * 2016-11-15 2020-05-29 中派科技（深圳）有限责任公司 Method and apparatus for measuring the arrival time of high-energy photons
CN107874773B (en) * 2017-10-16 2020-12-08 中派科技（深圳）有限责任公司 Photon detection method, device, equipment and system and storage medium
EP3732501A4 (en) * 2018-02-13 2021-08-25 Sense Photonics, Inc. Methods and systems for high-resolution long-range flash lidar
CN109507713A (en) * 2018-11-09 2019-03-22 清华大学 Handheld gamma radiation imaging apparatus and method
CN111596302A (en) * 2020-05-21 2020-08-28 深圳市灵明光子科技有限公司 SiPM signal timing point-based distance measurement method and device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102274041A (en) * 2011-05-23 2011-12-14 江苏中惠医疗科技股份有限公司 Fully-digitalized processing device of positron emission tomography imaging electronics system
CN104173070A (en) * 2013-05-21 2014-12-03 上海联影医疗科技有限公司 Method and device for determining PET (Positron Emission Tomography) time of flight
CN105008962A (en) * 2013-03-08 2015-10-28 皇家飞利浦有限公司 Timestamping detected radiation quanta

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6628984B2 (en) * 2000-04-12 2003-09-30 Pem Technologies, Inc. Hand held camera with tomographic capability
WO2009018321A2 (en) * 2007-07-31 2009-02-05 Yu Wang A novel scintillation detector array and associate signal processing method for gamma ray detection with encoding the energy, position, and time coordinates of the interaction
US8816286B2 (en) * 2011-08-01 2014-08-26 Siemens Medical Solutions Usa, Inc. Optical simulation-based time-of-flight compensation and PET system configuration
JP6295265B2 (en) * 2012-11-19 2018-03-14 ピーイーティーエスワイエス−メディカル ピーイーティー イメージング システムズ エスアー Readout device and readout method for measuring energy and time of flight using a silicon photomultiplier tube
WO2014180487A1 (en) * 2013-05-07 2014-11-13 Cern - European Organization For Nuclear Research A detector configuration with semiconductor photomultiplier strips and differential readout
FR3009157B1 (en) * 2013-07-24 2016-12-09 Alain Iltis METHOD FOR DETERMINING THE DEPTH OF AN INTERACTION IN A PIXELIZED RADIATION DETECTOR, DETECTOR AND APPLICATION THEREOF
CN104656115B (en) * 2013-11-19 2018-04-24 苏州瑞派宁科技有限公司 A kind of method and system of time mark combination
CN105769229B (en) * 2014-12-24 2018-08-03 沈阳东软医疗***有限公司 A kind of method, image rebuilding method and device calculating PET system increasing radius value
CN105093258B (en) * 2015-09-30 2018-03-23 中派科技（深圳）有限责任公司 Photon survey front-end circuit
CN106443747B (en) * 2016-11-15 2020-05-29 中派科技（深圳）有限责任公司 Method and apparatus for measuring the arrival time of high-energy photons

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102274041A (en) * 2011-05-23 2011-12-14 江苏中惠医疗科技股份有限公司 Fully-digitalized processing device of positron emission tomography imaging electronics system
CN105008962A (en) * 2013-03-08 2015-10-28 皇家飞利浦有限公司 Timestamping detected radiation quanta
CN104173070A (en) * 2013-05-21 2014-12-03 上海联影医疗科技有限公司 Method and device for determining PET (Positron Emission Tomography) time of flight

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Sub-200 ps CRT inmonolithic scintillator PET detectors using digital SiPM arrays and maximum likelihood interaction time estimation;Herman T van Dam et al.;《Physics in Medicine and Biology》;20130424(第58期);3243-3257 *
Time-based position estimation in monolithic scintillator detectors;Valerio Tabacchini et al.;《Phys.Med.Biol》;20150702(第60期);论文章节1-3 *

Also Published As

Publication number Publication date
CN106443747A (en) 2017-02-22
WO2018090900A1 (en) 2018-05-24

Similar Documents

Publication Publication Date Title
CN106443747B (en) Method and apparatus for measuring the arrival time of high-energy photons
US7709801B2 (en) Nuclear medicine diagnosis equipment
US10877169B2 (en) Apparatus and method for pet detector
US7476864B2 (en) Gamma ray detector with interaction depth coding
Moses et al. Factors influencing timing resolution in a commercial LSO PET camera
US10379228B2 (en) Pet detector scintillator arrangement with light sharing and depth of interaction estimation
US20070270693A1 (en) Timing Calibration for Tof-Pet Scanner
CN107247284B (en) Gain correction device and method for scintillation detector
WO2009018321A2 (en) A novel scintillation detector array and associate signal processing method for gamma ray detection with encoding the energy, position, and time coordinates of the interaction
CN110031884B (en) Detector, ECT system and method for determining occurrence position of scintillation instance
JPH0214666B2 (en)
JP5585094B2 (en) Radiation position detector position calculation method and apparatus
CN107850677A (en) For detecting the Compton camera system and method for gamma radiation
Vinke et al. Optimization of digital time pickoff methods for LaBr 3-SiPM TOF-PET detectors
CN106461797B (en) Method for improving energy resolution of a gamma ray scintillation detector, associated system, component and application
KR101330117B1 (en) Positron emission tomography scanner with multi-channel photo-sensor and gamma-ray energy
CN111221027A (en) Circuit and method for TOF-PET leading edge discrimination to reduce time walk
US10007010B2 (en) Method for determining the depth of an interaction in a pixellated radiation detector, and associated detector and application
JPH0933658A (en) Positron imaging equipment
US20240210575A1 (en) Time-walk correction using multiple energy measurements
US11112511B2 (en) Radiation detector and compton camera
Vinke et al. Thick monolithic scintillation crystals for TOF-PET with depth-of-interaction measurement
Hakamata et al. Development of a depth of interaction detector using a multi-pixel photon counter module for positron emission tomography
WO2009150235A2 (en) Method, device and system for localizing an interaction point
CA2464827A1 (en) Method and system of determining depth of interaction in a scintillation camera

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
C10 Entry into substantive examination
SE01 Entry into force of request for substantive examination
TA01 Transfer of patent application right

Effective date of registration: 20170519

Address after: 518063 Changhong technology building, No. 18 South twelve Road, Nanshan District science and technology, Guangdong, Shenzhen 903

Applicant after: Sino science and Technology (Shenzhen) Co., Ltd.

Address before: The Northeast Industrial Park Dongxin road East Lake Development Zone 430074 Hubei city of Wuhan Province, No. 11, building D C 1-4 layer

Applicant before: WUHAN ZHONGPAI TECHNOLOGY CO., LTD.

TA01 Transfer of patent application right
GR01 Patent grant
GR01 Patent grant