CN118276150A - Processing circuit for scintillation pulse - Google Patents

Abstract

The application discloses a processing circuit of scintillation pulse. The processing circuit includes: the time sampling circuit and the first amplifying circuit are respectively electrically connected with a plurality of detection channels of the detection unit and are arranged in parallel; the time sampling circuit is used for performing multi-threshold sampling on the scintillation pulse output by the detection channel to acquire time information; the first amplifying circuit is used for amplifying the scintillation pulse to obtain an amplified scintillation pulse; the second amplifying circuit is connected with the first amplifying circuits in series and is used for amplifying the intermediate scintillation pulse added by one or more amplified scintillation pulses to obtain target scintillation pulses; and the energy sampling circuit is connected in series with the second amplifying circuit and is used for performing multi-threshold sampling on the target scintillation pulse to acquire energy information. The application can amplify and add signals and improve the signal-to-noise ratio of the circuit. And meanwhile, a parallel mode of a time sampling circuit and an energy sampling circuit is used, so that the determination of the energy information and the time information is more accurate.

Description

Processing circuit for scintillation pulse

Technical Field

The application relates to the field of hardware circuits, in particular to a scintillation pulse processing circuit.

Background

Positron emission tomography (Positron Emission Tomography, PET for short) is a nuclear medicine image diagnosis technology widely applied in clinic, and by imaging a radioactive tracer injected into a living body, functional information such as metabolism of the living body is provided, and the positron emission tomography plays an important role in clinical diagnosis, curative effect evaluation, basic medicine research and new medicine research and development.

The silicon photomultiplier (Silicon Photomultiplier, siPM) used by detectors in current PET systems is a new type of high performance photodetector. Compared with the traditional photomultiplier, the photomultiplier has the advantages of large gain, low working voltage, small volume, light weight, good process compatibility and insensitivity to magnetic fields, and plays an important role in the fields of weak light detection, radiation detection and the like. Gamma-ray detectors employing sipms as the photoelectric conversion device require the SiPM cells to be combined into an array coupled with a scintillator crystal array due to SiPM size limitations. The direct coupling of 1 to 1 can make the light quantity loss small, the detection speed fast, and can obtain better time performance. However, the data read-out channels corresponding to the sipms are required in data reading, which results in a very complex electronic system and huge power consumption, and greatly increases the cost of the detector. Therefore, how to improve the time resolution of the position sensitive detector can also reduce the cost of the detector, and improving the performance of the detector becomes a technical problem to be solved at present.

Disclosure of Invention

The embodiment of the application aims to solve the technical problem of realizing high-precision and high-sensitivity sampling of scintillation pulse and avoiding false sampling.

In order to solve the problems, the application discloses a processing circuit of scintillation pulse. The processing circuit includes: the time sampling circuit and the first amplifying circuit are respectively electrically connected with a plurality of detection channels of the detection unit and are arranged in parallel; the time sampling circuit is used for performing multi-threshold sampling on the scintillation pulse output by the detection channel to acquire time information; the first amplifying circuit is used for amplifying the scintillation pulse to obtain an amplified scintillation pulse; the second amplifying circuit is connected with the first amplifying circuits in series and is used for amplifying the intermediate scintillation pulse added by one or more amplified scintillation pulses to obtain target scintillation pulses; and the energy sampling circuit is connected in series with the second amplifying circuit and is used for performing multi-threshold sampling on the target scintillation pulse to acquire energy information.

According to some embodiments of the application, the time sampling circuit comprises two first comparators arranged in parallel, a first digital-to-analog converter connected in series with one of the inputs of the first comparators, and a first time-to-digital converter connected in series with the output of the first comparators.

According to some embodiments of the application, the first comparator is implemented by a low voltage differential signal pin of an FPGA chip.

According to some embodiments of the application, the first comparator is implemented by a carry chain of an FPGA chip.

According to some embodiments of the application, the first amplifying circuit includes a first summing resistor, a first operational amplifier, and a first filter capacitor; the first end of the first adding resistor is connected with the detection channel, and the second end of the first adding resistor is connected with the non-inverting input end of the first operational amplifier; the first operational amplifier and the first filter capacitor form a first filter circuit.

According to some embodiments of the application, the first amplifying circuit further comprises a blocking capacitor connecting the detection channel with the first operational amplifier.

According to some embodiments of the application, the second amplifying circuit includes a second summing resistor, a second operational amplifier, and a second filter capacitor; the first end of the second adding resistor is connected with the non-inverting input end of the second operational amplifier due to the fact that the intermediate scintillation pulse is received; the second operational amplifier and the second filter capacitor form a second filter circuit.

According to some embodiments of the application, the energy sampling circuit includes a plurality of second comparators arranged in parallel, a second digital-to-analog converter in series with one of the inputs of the second comparators, and a second time-to-digital converter in series with the output of the second comparators.

According to some embodiments of the application, the second comparator is implemented by a low voltage differential signal pin of an FPGA chip.

According to some embodiments of the application, the second comparator is implemented by a carry chain of FPGA chips.

The processing circuit disclosed by the application can amplify and sum the signals output by the SiPM based on the in-phase addition circuit, reduce bandwidth loss and noise caused by resistance and operational amplifier, and improve the signal-to-noise ratio of the circuit. Meanwhile, a parallel mode of a time sampling circuit and an energy sampling circuit is used, so that the time information is determined more accurately, and the energy is accurately calculated after being amplified by an independent operational amplifier. The circuit structure is simple, and the hardware cost is saved. In addition, the attenuation of the parasitic capacitance of the circuit to the signal is reduced, and the signal bandwidth is ensured.

Drawings

The application will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. The embodiments are not limiting, in which like numerals represent like structures, wherein:

FIG. 1 is an exemplary schematic diagram of a crystal channel of a radiation detection device according to some embodiments of the application;

FIG. 2 is an exemplary schematic diagram of a time sampling circuit shown in accordance with some embodiments of the application;

FIG. 3 is an exemplary schematic diagram of scintillation pulse sampling shown in accordance with some embodiments of the application;

FIG. 4 is an exemplary schematic diagram of a first amplification circuit shown in accordance with some embodiments of the application;

FIG. 5 is an exemplary schematic diagram of a second amplification circuit shown in accordance with some embodiments of the application;

Fig. 6 is an exemplary schematic diagram of an energy sampling circuit according to some embodiments of the application.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

It will be understood that when an element is referred to as being "mounted" to another element, it can be directly mounted to the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.

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 application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" and/or "as used herein includes any and all combinations of one or more of the associated listed items.

Some preferred embodiments of the present application are described below with reference to the accompanying drawings. It should be noted that the following description is for illustrative purposes and is not intended to limit the scope of the present application.

A scintillation crystal (e.g., BGO, PWO, LYSO: ce, GAGG: ce, naI: TI, csI: TI, laBr ₃:Ce、BaF₂, etc.) of a radiation detection device (e.g., scintillation detector) may convert detected high-energy rays (e.g., gamma rays, neutron rays, etc.) into visible light signals, and a photoelectric conversion device (e.g., photomultiplier tube PMT, silicon photomultiplier tube SiPM, etc.) may convert the visible light signals into electrical signals that are output in the form of scintillation pulses through electronics coupled to the photoelectric conversion device.

The scintillation crystal can be an array of crystals. For example, a complete crystal is cut regularly to form a plurality of crystal bars. Each of the crystal bars is independently coupled to a photoelectric conversion device (e.g., a silicon photomultiplier SiPM) to form a crystal channel. Referring to fig. 1, fig. 1 is an exemplary schematic diagram of a crystal channel of a radiation detection device according to some embodiments of the present application. As shown in fig. 1, the scintillation detector is provided with 6×6=36 independent crystal channels. After the energetic particle (e.g., gamma photon) enters a certain crystal channel (e.g., the 10 th crystal channel in fig. 1), energy deposition will occur on the crystal channel. The photoelectric conversion device coupled to the crystal channel generates a scintillation pulse and outputs the scintillation pulse. In the present application, the scintillation detector may also be referred to as a detection unit, and the crystal channel may also be referred to as a detection channel.

When Compton scattering occurs after a gamma photon enters a crystal channel (i.e., after the gamma photon enters the crystal), the energy of the gamma photon changes, and the direction of the gamma photon shifts, so that energy deposits are generated on a plurality of crystal channels, and a plurality of scintillation pulses are output. As shown in fig. 1, compton scattering occurs after gamma photons enter the 10 th crystal channel. Energy deposition occurs in the 15 th, 24 th, and 28 th crystal channels after the direction shift. At this point, one gamma photon will produce 4 scintillation pulses. At the same time, noise signals may be generated due to other causes (e.g., device state changes, background radiation of the scintillation crystal LYSO, etc.). Thus, the capture of one gamma photon may produce multiple pulse signals.

According to the processing circuit for the scintillation pulse, disclosed by the application, the time information of the time event of the scintillation pulse can be accurately measured through the time sampling circuit, and the scintillation pulse is overlapped and recovered through energy addition, so that the energy calculation is more accurate.

Fig. 2 is an exemplary schematic diagram of a time sampling circuit shown in accordance with some embodiments of the application. As shown in fig. 2, the time sampling circuit 200 may include two first comparators 210-1 and 210-2 arranged in parallel. One of the input terminals of the two first comparators is connected in series with a first digital-to-analog converter. For example, one of the input terminals of the first comparator 210-1 is connected in series with the first digital-to-analog converter 220-1 to receive the threshold value set by the first digital-to-analog converter 220-1, the other input terminal of the first comparator 210-1 is connected to the signal output terminal to receive the output pulse signal, one of the input terminals of the first comparator 210-2 is connected in series with the first digital-to-analog converter 220-2 to receive the threshold value set by the first digital-to-analog converter 220-2, the other input terminal of the first comparator 210-2 is connected to the signal output terminal to receive the output pulse signal, and each of the first comparators independently compares the input threshold value with the pulse signal in amplitude. At the same time, the output of each first comparator will be connected in series with two first time data converters. As shown in fig. 2, the output of the first comparator 210-1 is connected to the first time-to-digital converters 230-1 and 230-2, respectively, and the output of the first comparator 210-2 is connected to the first time-to-digital converters 230-3 and 230-4, respectively. The first comparator can be realized through a low-voltage differential signal pin of the FPGA chip, and the first time data converter can be realized through a carry chain of the FPGA chip. CH1 may represent a designation of a crystal channel, denoted herein by way of example as the 1 st crystal channel. SiPM1 may represent a photoelectric conversion device (e.g., a silicon photomultiplier) coupled to the 1 st crystal channel. The blinking pulses output by SiPM1 route the input to two first comparators, e.g., siPM1 outputs, arranged in parallel to one LVDS pin (e.g., P pin) of the FPGA. At the same time, a first digital-to-analog converter (DAC) in parallel with the first comparator will input a trigger threshold, for example by accessing another LVDS pin (e.g., N pin) of the FPGA. The first comparator compares the scintillation pulse with the trigger threshold after receiving the scintillation pulse input by the SiPM1 and the trigger threshold input by the first digital-to-analog converter, so as to output a state jump signal when the scintillation pulse crosses the trigger threshold. The first comparator will generate two state transition signals when the scintillation pulse can cross the trigger threshold. At this time, the two state transition signals are respectively input to a first time-to-digital converter. The first time-to-digital converter will complete the time sampling of the state transition signal and determine the time at which the state transition signal was generated, i.e. the time at which the scintillation pulse crosses the trigger threshold. Of course, when the flicker pulse does not cross a trigger threshold, the first comparator does not output a signal to the first time-to-digital converter.

Fig. 3 illustrates an exemplary schematic diagram of sampling of scintillation pulses shown in accordance with some embodiments of the application. The scintillation pulse 300 is shown in fig. 3 as an electrical pulse having a rising edge and a falling edge. The two trigger thresholds output by the first digital-to-analog converter into the first comparator are V ₁ and V ₂. The two first comparators will each be responsible for a trigger threshold to scintillation pulse comparison. For example, the first comparator 210-1 is responsible for comparing the trigger threshold V ₁ to the scintillation pulse and the first comparator 210-2 is responsible for comparing the trigger threshold V ₂ to the scintillation pulse. When the rising edge of the scintillation pulse 300 crosses the trigger threshold V ₁ from bottom to top at time t ₀, the first comparator 210-1 outputs a state transition signal. The first time to digital converter 230-1 coupled to the first comparator 210-1 will time sample the rising edge of the state transition signal to determine t ₀. Meanwhile, when the first comparator 210-1 outputs a state transition signal to the first time-to-digital converter 230-2 when the falling edge of the scintillation pulse 300 crosses the trigger threshold V ₁ from top to bottom, the first time-to-digital converter 230-2 will time sample the falling edge of the state transition signal to determine t ₃. Similarly or similarly, the first comparator 210-2 will output a state transition signal when the rising edge of the scintillation pulse 300 crosses the trigger threshold V ₂ from bottom to top at time t ₁. The first time to digital converter 230-3 coupled to the first comparator 210-2 will time sample the rising edge of the state transition signal to determine t ₁. In addition, the first comparator 210-2 may output a state transition signal to the first time-to-digital converter 230-4 when the falling edge of the scintillation pulse 300 crosses the trigger threshold V ₂ from top to bottom, and the first time-to-digital converter 230-4 will time sample the falling edge of the state transition signal to determine t ₂. Finally, four sampling point data are obtained: (V ₁,t₀)、(V₂,t₁)、(V₂,t₂) and (V ₁,t₃). These sample data may be used to determine time information (e.g., t_s=t ₀), relative energy information (e.g., e_s=t ₂-t₀, the energy of a waveform pulse of a particular shape is characterized by a time difference).

The time sampling circuit requires a preset reference voltage, i.e., a baseline voltage. The SiPM will output a signal, i.e., a scintillation pulse, when the amplitude of the scintillation pulse is greater than the baseline voltage. This can act as an isolation for noise. In some possible embodiments, the baseline voltage may be determined from a priori baseline information of the sampled signal, such as about 625mV, which is common in the PET arts. Thus, the trigger threshold output by the first digital-to-analog converter may be set based thereon. For example, the two trigger thresholds are set to be greater than 10mV-50mV. For example, one trigger threshold is 635mV and the other is 675mV. Thus, noise signals can be filtered out well. Meanwhile, the setting of two trigger thresholds can further avoid false detection of noise signals. Only scintillation pulses crossing two trigger thresholds can be determined as valid pulses, and further the determination of time information can be made based on the sampled data.

In connection with the foregoing description, when high energy particles (e.g., gamma photons) scatter after entering the crystal channels, the energy is dispersed. The scintillation pulses may be superimposed in order to make the energy calculation accurate, and the resulting energy amplitude of the target scintillation pulse may then be the energy summation of the amplitudes of the scintillation pulses. The result of processing the target scintillation pulse will be more accurate. Each scintillation pulse may be amplified before energy addition to improve the signal-to-noise ratio. Thus, even if the noise signal exists in the added scintillation pulse, the proportion of the noise signal is reduced after the amplification. Therefore, the anti-interference capability of the signal can be improved, and the energy calculation is more accurate.

Referring to fig. 4, fig. 4 is an exemplary schematic diagram of a first amplifying circuit according to some embodiments of the present application. As shown in fig. 4, the first amplifying circuit 400 may be disposed in parallel with the time sampling circuit 200 and also connected to the same detection channel (e.g., siPM 1). The first amplifying circuit 400 may include a first summing resistor R _f1, a first operational amplifier 410, and a first filter capacitor (not shown). The first end of the first adding resistor R _f1 is connected with the detection channel, and the second end is connected with the non-inverting input end of the first operational amplifier. The first filter capacitor and the first operational amplifier 410 together form an active filter (high-pass filtering), filtering is performed according to the characteristics of added signal superposition noise, and filtering is mainly aimed at dark count increase caused by multiple SiPM signal outputs, so that compared with direct addition, the filtered signal has higher signal-to-noise ratio, and the accuracy of time discrimination is improved. The first summing resistor R _f1 participates in the negative feedback of the first operational amplifier 410, and the resistances of the feedback resistor R ₁₁ and the first summing resistor R _f1 determine the gain of the operational amplifier. Magnification k ₁＝1+(R_f1/R₁₁). The amplified scintillation pulse is obtained after the scintillation pulse is amplified by the first amplifying circuit, and the energy value of the amplified scintillation pulse becomes k ₁ ×chi assuming that the energy value of the scintillation pulse is CHi (i may represent the channel from which the scintillation pulse is output). While the first summing resistor R _f1 together with the filter capacitance determines the frequency of the high-pass filtering. Therefore, when the first adding resistor R _f1, the first operational amplifier 410 and the first filter capacitor are selected, calculation can be performed according to the characteristics of the signal and the noise, and flexible selection can be achieved. In the present application, the first amplifying circuit 400 may further include a blocking capacitor (not shown). The blocking capacitor connects the detection channel with the first operational amplifier 410. The partition capacitor can isolate the set baseline voltage, so that the situation that the voltage value is overlarge to cause exceeding of the sampling range in the subsequent sampling after the larger voltage value is amplified is avoided, and the accurate detection is facilitated.

Fig. 5 is an exemplary schematic diagram of a second amplification circuit shown in accordance with some embodiments of the application. As shown in fig. 5, the first amplifying circuit corresponding to each detection channel will then be connected in series with the second amplifying circuit. Intermediate scintillation pulses (assuming an energy value of E _n) resulting from energy addition of the amplified scintillation pulse (assuming an energy value of E _n)) The second amplification is performed by the second amplification circuit 500. The second amplifying circuit 500 may include a second summing resistor R _f2, a second operational amplifier 510, and a second filter capacitor (not shown) similar to or identical to the first amplifying circuit 400. The first end of the second summing resistor R _f2 is connected to the non-inverting input of the second operational amplifier 510 due to receiving the intermediate scintillation pulse. The second operational amplifier 510 and the second filter capacitor may form a second filter circuit. The second adding resistor R _f2 participates in the negative feedback of the second operational amplifier 510, and the resistances of the feedback resistor R ₁₂ and the second adding resistor R _f12 determine the gain of the operational amplifier. The amplification factor k ₂＝1+(R_f2/R₁₂ of the second operational amplifier 510). The intermediate scintillation pulse is amplified to obtain the target scintillation pulse (assuming the energy value is) And outputting by F.

The various circuits disclosed by the application can amplify and sum the scintillation pulses and then superimpose the scintillation pulses into one path of scintillation pulse output, so that the threshold value number required to be set in the later adoption process and TDC resources of the FPGA chip required to be consumed can be greatly reduced. Meanwhile, the cost of a large number of DAC chips, a plurality of FPGA chips and other components can be saved, the size and the power consumption (such as the cost of a PCB and the heat dissipation cost) of the PCB are greatly reduced, the structure is more compact and small, and the readout circuit is simple in design, low in power and low in cost.

Meanwhile, energy calculation can be accurate after energy addition, and the performance of the detector is obviously improved. For example, power consumption is reduced, heat can be rapidly dissipated, and the like. Therefore, the influence of temperature on the SIPM gain can be reduced, the performance of the SIPM is improved, and the timing resolution of the position sensitive detector is improved.

In the present application, the target scintillation pulse output by F is input to an energy sampling circuit in series with a second amplification circuit for multi-threshold sampling to determine the energy value of the target scintillation pulse. Referring to fig. 6, fig. 6 is an exemplary schematic diagram of an energy sampling circuit according to some embodiments of the application. As shown in fig. 6, the energy sampling circuit 600 may be similar to a time sampling circuit, including a plurality of second comparators arranged in parallel, a second digital-to-analog converter in series with the second comparators, and a second time-to-digital converter in series with the second comparator outputs. Likewise, the second comparator may be implemented by a low voltage differential signal pin of the FPGA chip, and the second comparator may be implemented by a carry chain of the FPGA chip. As in fig. 6, 8 second comparators, 8 second digital-to-analog converters and 16 second time-to-digital converters are included. The 8 second comparators will each receive the input of the target scintillation pulse and the 8 second digital-to-analog converters will each input a sampling threshold to each of the parallel second comparators. Likewise, the second comparator will output a state transition signal to the connected second time-to-digital converter if a scintillation pulse crossing the sampling threshold occurs when comparing the sampling threshold with the target scintillation pulse, including a rising edge crossing the sampling threshold and a falling edge crossing the sampling threshold. The second time-to-digital converter performs time sampling on the state jump signal to obtain corresponding jump time. Finally, setting of 8 sampling thresholds will result in 16 threshold-time pairs as sampling data. The sampled data may be used to fit the target scintillation pulse. For example, a functional model describing the waveform shape of the target scintillation pulse may first be determined, assuming that y=a×f (x) +b, and the parameters to be fitted may be a and b. The fitting data is constructed with the threshold value in the threshold-time pair comprised by the sampled data as y and the time as x. And performing function fitting through a least square method to determine parameters a and b to be fitted. The expression of the parametric determined functional model may be used to describe the fitted pulse shape of the target scintillation pulse. For example, a curve shape presented in a coordinate system. By integrating the fitted pulse waveform, the resulting integrated value may be the energy value of the target scintillation pulse. I.e. the energy value of the captured energetic particles. After the present application, the combination of the plurality of first amplifying circuits and the second amplifying circuit may also be referred to as a multiple energy adding circuit.

It will be appreciated by those skilled in the art that the time sampling circuit need only acquire the pulse arrival time since no line fitting is required to obtain a precise waveform. Therefore, an amplifying circuit is not required to amplify the pulse signal, and only one baseline voltage which can better distinguish the background noise from the real signal is required to be set. For example, several tens of millivolts, several hundreds of millivolts, such as 625mv as described above, may be set. The signal to noise ratio is improved by directly giving a higher baseline voltage to distinguish noise with background and real signals, and an amplifying element is not needed to be additionally arranged to improve the signal to noise ratio, so that the method is simple and saves cost. The energy calculation requires recovering the waveform of the sampling signal as accurately as possible, and thus the pulse signal needs to be amplified by the in-phase operational amplifier. the impulse signal can better distinguish the noise at the bottom of the book from the real signal after being amplified, thereby improving the signal-to-noise ratio and being not interfered by the noise. And the small signals are easily detected after being amplified, so that all the signals are ensured to be detected, and the detection efficiency and the reliability of the circuit are improved. Therefore, all detected signals participate in energy addition after being amplified, the defect that small signals are not easy to detect is overcome, the added energy is more accurate, the difference between noise signals and real signals is larger after the noise signals and the real signals are amplified, the signal to noise ratio of the added signals is higher, and therefore the waveform obtained by fitting the amplified and added energy sampling data is more accurate, and the energy obtained based on the waveform is more accurate. in view of the need for amplifying the pulse signal, the baseline voltage cannot be larger than the baseline voltage in the time sampling circuit, otherwise, the amplified pulse signal is excessively large and exceeds the detection range when entering the operational amplifier for amplification. At this time, a baseline voltage, such as 69mv, determined based on a priori information, sufficient to distinguish the pulse signal from noise needs to be given. And the minimum of the sampling thresholds may be set at about 50mV-60mV above 69mV. For example, the minimum sampling threshold may be 120mV. In PET detection, the energy of a pair of gamma photons generated by annihilation is 511keV, and the maximum amplitude of the corresponding scintillation pulse is approximately 400mV after amplification. when gamma photons enter the crystal channel, energy deposition occurs, and if no scattering occurs, the maximum amplitude of scintillation pulse generated by the coupled photoelectric conversion device is close to 400mV after amplification. Therefore, the maximum sampling threshold of the plurality of sampling thresholds may be set to approach or equal 400mV to better recover the waveform and energy of the scintillation pulse corresponding to the real single event from the resulting sampled data. The intervals between the set plurality of sampling thresholds may be equal. That is, multiple sampling thresholds may form an arithmetic progression. Assuming that the minimum sampling threshold of the plurality of sampling thresholds is 120mV and the maximum sampling threshold is 400mV, then 8 sampling thresholds may be set at 40mV threshold intervals, 120mV, 160mV, 200mV, 240mV, 280mV, 320mV, 360mV, and 400mV, respectively. the threshold interval may also be other, for example, 10mV, 20mV, 30mV, etc. The spacing between the multiple sampling thresholds may also be unequal. For example, the threshold interval increases with the number of sampling thresholds. For example, the interval between the minimum sample threshold and the next-to-minimum sample threshold is 10mV, the interval between the next-to-minimum sample threshold and the third-to-minimum sample threshold is 20mV, and so on.

Of course, other features of the sampling threshold may be the same as or similar to the trigger threshold. For example, the sampling threshold may also be of a type that is presented as a voltage threshold, a current threshold, a sound intensity threshold, a heat threshold, a pressure threshold, etc., depending on the appearance of the scintillation pulse.

According to the scintillation pulse processing circuit disclosed by the application, scintillation pulses output by each detection channel are equally divided into two paths, one path enters the time sampling circuit to determine time information and relative energy information, and the other path enters the multi-path energy adding circuit to determine energy information and determine corresponding time information based on the energy information. For example, whether the maximum sampling threshold is included in the sampled data obtained by the energy sampling circuit may determine whether the target scintillation pulse corresponds to a true single event. When included may be considered to correspond to a true single event. Or whether the target scintillation pulse corresponds to a true single event may be determined by determining whether the energy value satisfies a preset condition. For example, the energy of a gamma photon is 511keV, and whether to correspond to a real single event is determined by determining whether the energy value is greater than or equal to 511 keV. If so, the real single event can be considered to be corresponded. If it is determined that the target scintillation pulse does not correspond to a true single event, then the relevant data is discarded and no subsequent calculations are made.

After determining that the target scintillation pulse corresponds to the real single event, energy information, time information and position information corresponding to the real single event need to be calculated. The energy information may be an energy value of the target scintillation pulse. The time information may be determined based on the processing results of the time sampling circuits corresponding to the respective scintillation pulses superimposed as the target scintillation pulse. For example, T ₀ corresponding to the earliest t_s or the smallest e_s may be used as the time information. The location information may then be the number information of the probe channel.

The processing circuit of the scintillation pulse disclosed by the application is based on the in-phase addition circuit to amplify and add signals output by the SiPM, reduces bandwidth loss and noise caused by resistance and operational amplifier, and improves the signal-to-noise ratio of the circuit. Meanwhile, a parallel mode of a time sampling circuit and an energy sampling circuit is used, so that the time information is determined more accurately, and the energy is accurately calculated after being amplified by an independent operational amplifier. The circuit structure is simple, and the hardware cost is saved. In addition, the attenuation of the parasitic capacitance of the circuit to the signal is reduced, and the signal bandwidth is ensured.

The processing circuit of the scintillation pulse provided by the application can be applied to positron emission computed tomography (PET), and in a PET system, photon data can be acquired by utilizing the scheme provided by the embodiment of the application and then image reconstruction can be carried out.

Having described the basic concepts herein, it will be apparent to those skilled in the art that the foregoing detailed disclosure is by way of example only and is not intended to be limiting. Although not explicitly described herein, various modifications, improvements, and adaptations to the present disclosure may occur to one skilled in the art. Such modifications, improvements, and modifications are intended to be suggested within this specification, and therefore, such modifications, improvements, and modifications are intended to be included within the spirit and scope of the exemplary embodiments of the present invention.

Meanwhile, the specification uses specific words to describe the embodiments of the specification. Reference to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic is associated with at least one embodiment of the present description. Thus, it should be emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various positions in this specification are not necessarily referring to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of the present description may be combined as suitable.

Furthermore, those skilled in the art will appreciate that the various aspects of the specification can be illustrated and described in terms of several patentable categories or circumstances, including any novel and useful procedures, machines, products, or materials, or any novel and useful modifications thereof. Accordingly, aspects of the present description may be performed entirely by hardware, entirely by software (including firmware, resident software, micro-code, etc.), or by a combination of hardware and software. The above hardware or software may be referred to as a "data block," module, "" engine, "" unit, "" component, "or" system. Furthermore, aspects of the specification may take the form of a computer product, comprising computer-readable program code, embodied in one or more computer-readable media.

Likewise, it should be noted that in order to simplify the presentation disclosed in this specification and thereby aid in understanding one or more inventive embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof. This method of disclosure does not imply that the subject matter of the present description requires more features than are set forth in the claims. Indeed, less than all of the features of a single embodiment disclosed above.

Each patent, patent application publication, and other material, such as articles, books, specifications, publications, documents, etc., referred to in this specification is incorporated herein by reference in its entirety. Except for application history documents that are inconsistent or conflicting with the content of this specification, documents that are currently or later attached to this specification in which the broadest scope of the claims to this specification is limited are also. It is noted that, if the description, definition, and/or use of a term in an attached material in this specification does not conform to or conflict with what is described in this specification, the description, definition, and/or use of the term in this specification controls.

Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments of this specification. Other variations are possible within the scope of this description. Thus, by way of example, and not limitation, alternative configurations of embodiments of the present specification may be considered as consistent with the teachings of the present specification. Accordingly, the embodiments of the present specification are not limited to only the embodiments explicitly described and depicted in the present specification.

Claims (10)

1. A processing circuit for scintillation pulses, the processing circuit comprising:

The time sampling circuit and the first amplifying circuit are respectively electrically connected with a plurality of detection channels of the detection unit and are arranged in parallel; the time sampling circuit is used for performing multi-threshold sampling on the scintillation pulse output by the detection channel to acquire time information; the first amplifying circuit is used for amplifying the scintillation pulse to obtain an amplified scintillation pulse;

the second amplifying circuit is connected with the first amplifying circuits in series and is used for amplifying the intermediate scintillation pulse added by one or more amplified scintillation pulses to obtain target scintillation pulses;

And the energy sampling circuit is connected in series with the second amplifying circuit and is used for performing multi-threshold sampling on the target scintillation pulse to acquire energy information.

2. The scintillation pulse processing circuit of claim 1, wherein the time sampling circuit comprises two first comparators disposed in parallel, a first digital-to-analog converter in series with one of the inputs of the first comparators, and a first time-to-digital converter in series with an output of the first comparators.

3. The scintillation pulse processing circuit of claim 2, wherein the first comparator is implemented via a low voltage differential signal pin of an FPGA chip.

4. The scintillation pulse processing circuit of claim 2, wherein the first comparator is implemented by a carry chain of an FPGA chip.

5. The scintillation pulse processing circuit of claim 1, wherein the first amplification circuit comprises a first summing resistor, a first operational amplifier, and a first filter capacitor; the first end of the first adding resistor is connected with the detection channel, and the second end of the first adding resistor is connected with the non-inverting input end of the first operational amplifier; the first operational amplifier and the first filter capacitor form a first filter circuit.

6. The scintillation pulse processing circuit of claim 5, wherein the first amplification circuit further comprises a blocking capacitor connecting the detection channel with the first operational amplifier.

7. The scintillation pulse processing circuit of claim 1, wherein the second amplification circuit comprises a second summing resistor, a second operational amplifier, and a second filter capacitor; the first end of the second adding resistor is connected with the non-inverting input end of the second operational amplifier due to the fact that the intermediate scintillation pulse is received; the second operational amplifier and the second filter capacitor form a second filter circuit.

8. The scintillation pulse processing circuit of claim 1, wherein the energy sampling circuit comprises a plurality of second comparators arranged in parallel, a second digital-to-analog converter in series with one of the inputs of the second comparators, and a second time-to-digital converter in series with an output of the second comparators.

9. The scintillation pulse processing circuit of claim 8, wherein the second comparator is implemented via a low voltage differential signal pin of an FPGA chip.

10. The scintillation pulse processing circuit of claim 8, wherein the second comparator is implemented by a carry chain of an FPGA chip.